Communication method, relay device, remote terminal, and communication system

Abstract

A communication method, a communication device, and a communication system. The communication method comprises: a first relay device receiving a first announcement message sent by a second relay device, wherein the first announcement message comprises a first hop count and identification information of the second relay device; verifying the first announcement message; on the basis of the verification result and whether a link is present between the first relay device and the second relay device, determining to broadcast a second announcement message or to discard the first announcement message, wherein the second announcement message comprises a second hop count and / or identification information of the first relay device, and the second hop count is a hop count obtained by adding one to the first hop count. In this way, a transmission mechanism between a remote UE and a U2N relay is further enhanced.

Description

Communication methods, relay equipment, remote terminals and communication systems Technical Field

[0001] This disclosure relates to the field of communication technology, and in particular to a communication method, relay device, remote terminal and communication system. Background Technology

[0002] To support communication between terminals outside network coverage and the network, Proximity-based Services (ProSe) were introduced. An intermediate relay is a ProSe UE located on the path between a remote UE and a U2N relay (UE-to-Network Relay), providing support for 5G ProSe remote UEs to connect to the network, thus supporting multi-hop U2N relay services.

[0003] Currently, it is necessary to improve the existing transmission mechanism between remote UEs and U2N relays to support multi-hop U2N relay services.

[0004] Summary of the Invention

[0005] This disclosure provides a communication method, relay device, remote terminal, and communication system to further enhance the transmission mechanism between the remote UE and the U2N relay.

[0006] In a first aspect, embodiments of this disclosure provide a communication method, executed by a first relay device, the method comprising:

[0007] Receive a first notification message sent by a second relay device; wherein the first notification message includes: a first hop count and identification information of the second relay device;

[0008] Verify the first notification message;

[0009] Based on the verification results and whether there is a link between the first relay device and the second relay device, determine whether to broadcast the second announcement message or discard the first announcement message;

[0010] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0011] Secondly, embodiments of this disclosure also provide a communication method, executed by a second relay device, the method comprising:

[0012] Send the first notification message to the first relay device;

[0013] The first notification message includes: the first hop count and the identification information of the second relay device.

[0014] Secondly, embodiments of this disclosure also provide a communication method executed by a remote terminal, the method comprising:

[0015] Receive the second announcement message broadcast by the first relay device;

[0016] Wherein, the second notification message is sent by the first relay device when the first notification message is verified and a link exists between the first relay device and the second relay device; the first notification message is sent by the second relay device;

[0017] The first notification message includes: the first hop count and the identification information of the second relay device;

[0018] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0019] Fourthly, embodiments of this disclosure also provide a relay device, the relay device including a first relay device, comprising:

[0020] The first receiving module is configured to receive a first notification message sent by the second relay device; wherein the first notification message includes: a first hop count and identification information of the second relay device;

[0021] The processing module is used to verify the first announcement message; and, based on the verification result and whether there is a link between the first relay device and the second relay device, determine whether to broadcast the second announcement message or discard the first announcement message.

[0022] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0023] Fifthly, embodiments of this disclosure also provide a relay device, the relay device including a second relay device, comprising:

[0024] The sending module is used to send a first notification message to the first relay device;

[0025] The first notification message includes: the first hop count and the identification information of the second relay device.

[0026] Sixthly, embodiments of this disclosure also provide a remote terminal, including:

[0027] The second receiving module is used to receive the second announcement message broadcast by the first relay device;

[0028] Wherein, the second notification message is sent by the first relay device when the first notification message is verified and a link exists between the first relay device and the second relay device; the first notification message is sent by the second relay device;

[0029] The first notification message includes: the first hop count and the identification information of the second relay device;

[0030] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0031] In a seventh aspect, embodiments of this disclosure also provide a relay device, the relay device including a first relay device, comprising:

[0032] One or more processors;

[0033] The first relay device is used to execute the communication method described in the first aspect of the embodiments of this disclosure.

[0034] Eighthly, embodiments of this disclosure also provide a relay device, the relay device including a second relay device, comprising:

[0035] One or more processors;

[0036] The second relay device is used to execute the communication method described in the second aspect of the embodiments of this disclosure.

[0037] Ninthly, embodiments of this disclosure also provide a remote terminal, including:

[0038] One or more processors;

[0039] The remote terminal is used to execute the communication method described in the third aspect of the embodiments of this disclosure.

[0040] This disclosure also provides a communication system, including a first relay device and a second relay device; wherein the first relay device is configured to implement the communication method described in this disclosure, and the second relay device is configured to implement the communication method described in this disclosure.

[0041] This disclosure also provides a storage medium storing instructions that, when executed on a communication device, cause the communication device to perform the communication method as described in this disclosure.

[0042] In this embodiment, a first relay device receives a first notification message sent by a second relay device. The first notification message includes a first hop count and the identification information of the second relay device. After verifying the first notification message, based on the verification result and whether a link exists between the first and second relay devices, a decision is made to broadcast a second notification message or discard the first notification message. The second notification message includes a second hop count and / or the identification information of the first relay device. The second hop count is the number of hops obtained by adding one to the first hop count. Thus, based on the verification result of the first notification message and the link establishment result between the first and second relay devices, it is determined whether a second notification message can be broadcast. This allows the second relay device to be safely discovered through the first relay device, ensuring the security of the forwarded notification message, improving the security and reliability of the discovery and transmission process, and further perfecting the transmission mechanism between the remote UE and the U2N relay.

[0043] Additional aspects and advantages of embodiments of this disclosure will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of this disclosure. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings required for the description of the embodiments are introduced below. The following drawings are only some embodiments of this disclosure and do not impose specific limitations on the protection scope of this disclosure.

[0045] Figure 1 is an exemplary schematic diagram of the architecture of the communication system provided in an embodiment of this disclosure;

[0046] Figure 2 is one of the exemplary interaction diagrams of the communication method provided in the embodiments of this disclosure;

[0047] Figure 3a is a second exemplary interactive schematic diagram of the communication method provided in the embodiments of this disclosure;

[0048] Figure 3b is a third exemplary interactive schematic diagram of the communication method provided in this disclosure embodiment;

[0049] Figure 4a is a fourth exemplary interactive schematic diagram of the communication method provided in the embodiments of this disclosure;

[0050] Figure 4b is a fifth exemplary interactive schematic diagram of the communication method provided in this embodiment of the present disclosure;

[0051] Figure 5 is a flowchart illustrating one of the communication methods provided in this embodiment of the present disclosure;

[0052] Figure 6a is a second schematic flowchart of the communication method provided in an embodiment of this disclosure;

[0053] Figure 6b is a third schematic flowchart of the communication method provided in this embodiment of the present disclosure;

[0054] Figure 7 is a fourth schematic flowchart of the communication method provided in the embodiments of this disclosure;

[0055] Figure 8 is a fifth flowchart illustrating the communication method provided in this embodiment of the present disclosure;

[0056] Figure 9 is a schematic diagram of the structure of the first relay device proposed in an embodiment of this disclosure;

[0057] Figure 10 is a schematic diagram of the structure of the second relay device proposed in the embodiment of this disclosure;

[0058] Figure 11 is a schematic diagram of the structure of the remote terminal proposed in an embodiment of this disclosure;

[0059] Figure 12 is a schematic diagram of the structure of the terminal proposed in the embodiment of this disclosure;

[0060] Figure 13 is a schematic diagram of the chip structure proposed in the embodiments of this disclosure. Detailed Implementation

[0061] This disclosure provides a communication method, a relay device, a remote terminal, and a communication system.

[0062] In a first aspect, embodiments of this disclosure provide a communication method executed by a first relay device, the method comprising:

[0063] Receive a first notification message sent by a second relay device; wherein the first notification message includes: a first hop count and identification information of the second relay device;

[0064] Verify the first notification message;

[0065] Based on the verification results and whether there is a link between the first relay device and the second relay device, determine whether to broadcast the second announcement message or discard the first announcement message;

[0066] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0067] In the above embodiments, the transmission mechanism between the remote UE and the U2N relay has been further improved. Based on the verification result of the first announcement message and the link establishment result between the first relay device and the second relay device, it is determined whether the second announcement message can be broadcast. The second relay device can be discovered securely through the first relay device, ensuring the security of the forwarded announcement message and improving the security and reliability of the discovery and transmission process.

[0068] In conjunction with some embodiments of the first aspect, in some embodiments, determining whether to broadcast the second announcement message or discard the first announcement message based on the verification result and whether a link exists between the first relay device and the second relay device includes at least one of the following:

[0069] If the first notification message fails verification, then the first notification message is discarded.

[0070] If the first notification message is verified and a link exists between the first relay device and the second relay device, then it is determined that the second notification message will be broadcast.

[0071] If the first notification message passes verification and there is no link between the first relay device and the second relay device, then the first notification message is discarded.

[0072] In the above embodiments, the specific method for determining whether to broadcast the second announcement message can be determined by combining the verification result of the first announcement message and the link establishment result between the first relay device and the second relay device. Based on the verification result of the received first announcement message and the link establishment result between the first relay device and the second relay device, the processing method for the received first announcement message can be determined.

[0073] In conjunction with some embodiments of the first aspect, in some embodiments, if a link exists between the first relay device and the second relay device, then determining to broadcast the second announcement message includes:

[0074] If there is no link between the first relay device and the second relay device, a link establishment request is sent to the second relay device.

[0075] Receive a first response message sent by the second relay device; wherein the first response message indicates that the second relay device accepts the link establishment request;

[0076] If a link is successfully established with the second relay device, the second announcement message is broadcast.

[0077] In the above embodiments, if there is no link between the first relay device and the second relay device, it can be determined whether a link can be successfully established between the first relay device and the second relay device, and if it is determined that a link can be successfully established between the first relay device and the second relay device, a second announcement message can be broadcast.

[0078] In conjunction with some embodiments of the first aspect, in some embodiments, if there is no link between the first relay device and the second relay device, then it is determined that the first notification message will be discarded, including:

[0079] Send a link establishment request to the second relay device;

[0080] If the second response information sent by the second relay device is received, it is determined that the first notification message should be discarded.

[0081] The second response information indicates that the second relay device rejects the link establishment request.

[0082] In the above embodiments, if there is no link between the first relay device and the second relay device, it can be determined whether a link can be successfully established between the first relay device and the second relay device. If it is determined that a link cannot be successfully established between the first relay device and the second relay device, the first announcement message can be discarded.

[0083] In conjunction with some embodiments of the first aspect, in some embodiments, the first notification message further includes an RSC (relay service code) and the PLMN ID (Public-Land-Mobile-Network identification) of the second relay device.

[0084] The verification of the first notification message includes:

[0085] The first notification message is securely verified based on the RSC and the PLMN ID of the second relay device;

[0086] Determine whether the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition; wherein, the third hop count is the hop count obtained by adding one to the first hop count.

[0087] In the above embodiments, the first notification message can be verified based on the RSC, PLMN ID of the second relay device, identification information of the second relay device, and third hop count carried in the first notification message, thus laying the groundwork for securely discovering the second relay device through the first relay device.

[0088] In some embodiments of the first aspect, the first notification message passes security verification, and the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition.

[0089] In the above embodiments, the first notification message is determined to have passed security verification based on the RSC and the PLMN ID of the second relay device carried in the first notification message; and if the RSC, the identification information of the second relay device, and the third hop count meet the first condition, the first notification message can be determined to have passed verification.

[0090] In conjunction with some embodiments of the first aspect, in some embodiments, the step of performing security verification on the first notification message based on the RSC and the PLMN ID of the second relay device includes:

[0091] Among the discovery security materials acquired by the first relay device, the discovery security materials associated with the RSC and the PLMN ID of the second relay device are identified;

[0092] Based on the identified secure materials, the first notification message is subjected to security verification.

[0093] In the above embodiments, it can be determined whether the discovery security material obtained by the first relay device includes discovery security material associated with the RSC and the PLMN ID of the second relay device; and if the discovery security material obtained by the first relay device includes discovery security material associated with the RSC and the PLMN ID of the second relay device, it can be determined whether the first notification message passes the security verification through the discovery security material associated with the RSC and the PLMN ID of the second relay device, thus laying the groundwork for the secure discovery of the second relay device by the first relay device.

[0094] In conjunction with some embodiments of the first aspect, in some embodiments, the first condition includes:

[0095] The third hop count is less than the first hop count threshold; and any of the following:

[0096] The information list stored by the first relay device does not store a first information entry including the RSC, or does not store a second information entry including the identification information of the second relay device, or does not store a sixth information entry including both the RSC and the identification information of the second relay device;

[0097] The information list stored in the first relay device contains a third information entry that includes the RSC and the identification information of the second relay device, and the third hop count is less than the hop count in the third information entry.

[0098] In the above embodiments, the relationship between the third hop count and the first hop count threshold, and whether the storage list of the first relay device contains a first information entry including the RSC; or whether the storage list of the first relay device contains a second information entry including the identification information of the second relay device; or whether the storage list of the first relay device contains a sixth information entry including the RSC and the identification information of the second relay device; or whether the storage list of the first relay device contains a third information entry including the RSC and the identification information of the second relay device, and the third hop count is less than the hop count in the third information entry, can be used to determine whether the RSC, the identification information of the second relay device, and the third hop count meet the first condition, thus laying the groundwork for how to verify the first notification message.

[0099] In conjunction with some embodiments of the first aspect, in some embodiments, after determining the broadcast of the second announcement message, the method further includes:

[0100] The third information entry is updated based on the third hop count; or,

[0101] Store the fourth information entry.

[0102] In the above embodiments, after determining the broadcast of the second announcement message, the hop count information in the third information entry is updated directly according to the third hop count, or the fourth information entry is directly stored in the information list stored by the first relay device, laying the groundwork for subsequent verification of the received announcement message.

[0103] In conjunction with some embodiments of the first aspect, in some embodiments, the fourth information entry includes at least one of the following:

[0104] The RSC, the identification information of the second relay device, the third hop count, the layer 2 ID of the second relay device, and the identification information of the link between the first relay device and the second relay device.

[0105] In the above embodiments, when the fourth information entry is directly stored in the information list stored by the first relay device, at least one of the following information entries can be stored as the fourth information entry: RSC, identification information of the second relay device, third hop count, layer 2 ID of the second relay device, and identification information of the link between the first relay device and the second relay device.

[0106] In conjunction with some embodiments of the first aspect, in some embodiments, the second notification message also includes identification information of the second relay device.

[0107] In the above embodiments, when forwarding the second notification message, the identification information of the second relay device can be specifically carried in the second notification message; in this way, the recipient of the second notification message can determine the source of the notification message and the relay device that forwarded the notification message based on the notification message currently received, thus laying the groundwork for safely discovering the second relay device through the first relay device.

[0108] In conjunction with some embodiments of the first aspect, in some embodiments, the method further includes:

[0109] If the link between the first relay device and the second relay device is released, then the fifth information entry associated with the link information in the information list stored by the first relay device is deleted.

[0110] The fifth information entry is an information entry that includes the identification information of the RSC and the second relay device.

[0111] In the above embodiments, when the link between the first relay device and the second relay device is released, it indicates that it is temporarily impossible to connect to the second relay device through the link. By further deleting the fifth information entry associated with the link information in the information list stored by the first relay device, the storage space of the information list of the first relay device can be saved.

[0112] In conjunction with some embodiments of the first aspect, in some embodiments, the first notification message further includes the RSC and the PLMN ID of the second relay device.

[0113] The verification of the first notification message includes:

[0114] The first notification message is securely verified based on the RSC and the PLMN ID of the second relay device;

[0115] Determine whether the third hop count satisfies the second condition.

[0116] In the above embodiments, the first notification message can be verified based on the RSC, the PLMN ID of the second relay device, and the third hop number carried in the first notification message, thus paving the way for the secure discovery of the second relay device through the first relay device.

[0117] In conjunction with some embodiments of the first aspect, in some embodiments, if the first notification message passes security verification and the third hop count satisfies the second condition, then the first notification message passes verification.

[0118] In the above embodiments, if the first notification message passes security verification based on the RSC and the PLMN ID of the second relay device carried in the first notification message, and the third hop count meets the second condition, it can be determined that the first notification message has passed verification.

[0119] In conjunction with some embodiments of the first aspect, in some embodiments, the second condition includes: the third hop count is less than the second hop count threshold.

[0120] In the above embodiments, the third hop count can be determined based on the relationship between the third hop count and the second hop count threshold, according to the defined second condition.

[0121] Secondly, embodiments of this disclosure provide a communication method executed by a second relay device, the method comprising:

[0122] Send the first notification message to the first relay device;

[0123] The first notification message includes: the first hop count and the identification information of the second relay device.

[0124] In conjunction with some embodiments of the second aspect, in some embodiments, the method further includes:

[0125] Receive the link establishment request sent by the first relay device.

[0126] In conjunction with some embodiments of the second aspect, in some embodiments, the method further includes:

[0127] Send a first response message to the first relay device; wherein the first response message indicates that the second relay device accepts the link establishment request; or,

[0128] Send a second response message to the first relay device; wherein the second response message indicates that the second relay device rejects the link establishment request.

[0129] Thirdly, embodiments of this disclosure propose a communication method executed by a remote terminal, the method comprising:

[0130] Receive the second announcement message broadcast by the first relay device;

[0131] Wherein, the second notification message is sent by the first relay device when the first notification message is verified and a link exists between the first relay device and the second relay device; the first notification message is sent by the second relay device;

[0132] The first notification message includes: the first hop count and the identification information of the second relay device;

[0133] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0134] Fourthly, embodiments of this disclosure also provide a relay device, the relay device including a first relay device, including at least one of a first receiving module and a processing module; wherein the first relay device is used to perform an optional implementation of the first aspect.

[0135] Fifthly, embodiments of this disclosure also provide a relay device, the relay device including a second relay device including a transmitting module; wherein the second relay device is used to execute an optional implementation of the second aspect.

[0136] In a sixth aspect, embodiments of this disclosure also provide a remote terminal, the remote terminal including a second receiving module; wherein the remote terminal is used to execute an optional implementation of the third aspect.

[0137] In a seventh aspect, embodiments of this disclosure also provide a relay device, the relay device including a first relay device, comprising:

[0138] One or more processors;

[0139] The first relay device is used to execute the optional implementation of the first aspect.

[0140] Eighthly, embodiments of this disclosure also provide a relay device, the relay device including a second relay device, comprising:

[0141] One or more processors;

[0142] The second relay device is used to implement the optional implementation of the second aspect.

[0143] Ninthly, embodiments of this disclosure also provide a remote terminal, including:

[0144] One or more processors;

[0145] The remote terminal is used to execute the optional implementation of the third aspect.

[0146] In a tenth aspect, embodiments of this disclosure also provide a communication system, including a first relay device, a second relay device, and a remote terminal; wherein the first relay device is configured to perform an optional implementation as described in the first aspect, the second relay device is configured to perform an optional implementation as described in the second aspect, and the remote terminal is configured to perform an optional implementation as described in the third aspect.

[0147] Eleventhly, embodiments of this disclosure also provide a storage medium storing instructions that, when executed on a communication device, cause the communication device to perform the optional implementations described in the first, second, or third aspects.

[0148] In a twelfth aspect, embodiments of this disclosure provide a program product that, when executed by a communication device, causes the communication device to perform the method as described in the optional implementations of the first, second, or third aspects.

[0149] In a thirteenth aspect, embodiments of this disclosure provide a computer program that, when run on a computer, causes the computer to perform the methods described in alternative implementations of the first, second, or third aspects.

[0150] In a fourteenth aspect, embodiments of this disclosure provide a chip or chip system. The chip or chip system includes processing circuitry configured to perform the methods described according to the first aspect, the second aspect, or an optional implementation by a third party.

[0151] It is understood that the aforementioned relay devices, remote terminals, communication systems, storage media, program products, computer programs, chips, or chip systems are all used to execute the methods proposed in the embodiments of this disclosure. Therefore, the beneficial effects they can achieve can be referred to the beneficial effects in the corresponding methods, and will not be repeated here.

[0152] This disclosure provides embodiments of a communication method, a relay device, a remote terminal, and a communication system. In some embodiments, the terms "communication method" and "signal transmission method," "wireless frame transmission method," etc., can be used interchangeably, as can the terms "information processing system" and "communication system."

[0153] This disclosure is not exhaustive, but merely illustrative of some embodiments, and is not intended to limit the scope of protection of this disclosure. Unless otherwise specified, each step in a particular embodiment can be implemented as an independent embodiment, and the steps can be arbitrarily combined. For example, a solution after removing some steps in a particular embodiment can also be implemented as an independent embodiment, and the order of the steps in a particular embodiment can be arbitrarily interchanged. Furthermore, the optional implementation methods in a particular embodiment can be arbitrarily combined; moreover, the embodiments can be arbitrarily combined, for example, some or all steps of different embodiments can be arbitrarily combined, and a particular embodiment can be arbitrarily combined with the optional implementation methods of other embodiments.

[0154] In each of the disclosed embodiments, unless otherwise specified or in case of logical conflict, the terminology and / or descriptions of the embodiments are consistent and can be referenced by each other. Technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0155] The terminology used in the embodiments of this disclosure is for the purpose of describing particular embodiments only and is not intended to limit the scope of this disclosure.

[0156] In the embodiments disclosed herein, "multiple" refers to two or more.

[0157] In some embodiments, the terms “at least one of”, “one or more”, “a plurality of”, “multiple”, etc., may be used interchangeably.

[0158] In some embodiments, the notation "at least one of A and B", "A and / or B", "A in one case, B in another", "in response to one case A, in response to another case B", etc., may include the following technical solutions depending on the situation: in some embodiments, A (execute A regardless of B); in some embodiments, B (execute B regardless of A); in some embodiments, execution is selected from A and B (A and B are selectively executed); in some embodiments, A and B (both A and B are executed). The same applies when there are more branches such as A, B, C, etc.

[0159] In some embodiments, the notation "A or B" may include the following technical solutions, depending on the situation: in some embodiments, A (execution of A regardless of B); in some embodiments, B (execution of B regardless of A); in some embodiments, execution is selected from A and B (A and B are selectively executed). The same applies when there are more branches such as A, B, C, etc.

[0160] The prefixes "first," "second," etc., used in the embodiments of this disclosure are merely for distinguishing different descriptive objects and do not impose restrictions on the position, order, priority, quantity, or content of the descriptive objects. The description of the descriptive objects is found in the claims or the context of the embodiments, and the use of prefixes should not constitute unnecessary restrictions. For example, if the descriptive object is a "field," the ordinal numbers preceding "field" in "first field" and "second field" do not restrict the position or order of the "fields." "First" and "second" do not restrict whether the "fields" they modify are in the same message, nor do they restrict the order of "first field" and "second field." Similarly, if the descriptive object is a "level," the ordinal numbers preceding "level" in "first level" and "second level" do not restrict the priority between "levels." Furthermore, the number of descriptive objects is not limited by ordinal numbers and can be one or more. For example, in "first device," the number of "devices" can be one or more. Furthermore, the objects modified by different prefixes can be the same or different. For example, if the object being described is "device", then "first device" and "second device" can be the same device or different devices, and their types can be the same or different. Similarly, if the object being described is "information", then "first information" and "second information" can be the same information or different information, and their content can be the same or different.

[0161] In some embodiments, “including A,” “containing A,” “for indicating A,” and “carrying A” can be interpreted as directly carrying A or indirectly indicating A.

[0162] In some embodiments, the terms “in response to…”, “in response to determining…”, “in the case of…”, “when…”, “if…”, “if…”, etc., can be used interchangeably.

[0163] In some embodiments, the terms “greater than,” “greater than or equal to,” “not less than,” “more than,” “more than or equal to,” “not less than,” “higher than,” “higher than or equal to,” “not lower than,” and “above” can be used interchangeably, as can the terms “less than,” “less than or equal to,” “not greater than,” “less than,” “less than or equal to,” “not more than,” “lower than,” “lower than or equal to,” “not higher than,” and “below”.

[0164] In some embodiments, the apparatus and device may be interpreted as physical or virtual, and their names are not limited to the names recorded in the embodiments. In some cases, they may also be understood as "equipment", "device", "circuit", "network element", "node", "function", "unit", "section", "system", "network", "chip", "chip system", "entity", "body", etc.

[0165] In some embodiments, "network" can be interpreted as devices included in the network, such as access network devices, core network devices, etc.

[0166] In some embodiments, "access network device (AN device)" may also be referred to as "radio access network device (RAN device)," "base station (BS)," "radio base station," or "fixed station." In some embodiments, it may also be understood as "node," "access point," "transmission point (TP)," "reception point (RP)," "transmission / reception point (TRP)," "panel," "antenna panel," "antenna array," "cell," "macro cell," "small cell," "femto cell," "pico cell," "sector," "cell group," "serving cell," "carrier," "component carrier," or "bandwidth part (BWP)."

[0167] In some embodiments, "terminal" or "terminal device" may be referred to as "user equipment (UE)," "user terminal," "mobile station (MS)," "mobile terminal (MT)," "subscriber station," "mobile unit," "subscriber unit," "wireless unit," "remote unit," "mobile device," "wireless device," "wireless communication device," "remote device," "mobile subscriber station," "access terminal," "mobile terminal," "wireless terminal," "remote terminal," "handset," "user agent," "mobile client," "client," etc.

[0168] In some embodiments, the acquisition of data, information, etc., may comply with the laws and regulations of the country where the location is situated.

[0169] In some embodiments, data, information, etc., may be obtained with the user's consent.

[0170] Furthermore, each element, each row, or each column in the table of this disclosure can be implemented as an independent embodiment, and any combination of any element, any row, or any column can also be implemented as an independent embodiment.

[0171] Figure 1a is a schematic diagram of the architecture of a communication system according to an embodiment of the present disclosure.

[0172] As shown in Figure 1a, the communication system 100 includes a remote terminal (i.e., a remote UE; a terminal is also known as a UE (User Equipment)) 101, a relay device 102 (for example, it may include two relay devices, such as a first relay device 1021 and a second relay device 1022; the number of relay devices is not limited in this embodiment), a relay terminal 103, and a network device 104.

[0173] In some embodiments, the first relay device 1021 may be, for example, an intermediate relay device, and the name of the first relay device is not limited herein.

[0174] In some embodiments, the second relay device 1022 may be, for example, an intermediate relay device or a U2N relay device. The name of the second relay device is not limited herein.

[0175] In some embodiments, the remote terminal 101 and the relay terminal 103 include, for example, at least one of the following: mobile phone, wearable device, Internet of Things device, car with communication function, smart car, tablet computer, computer with wireless transceiver function, virtual reality (VR) terminal device, augmented reality (AR) terminal device, wireless terminal device in industrial control, wireless terminal device in self-driving, wireless terminal device in remote medical surgery, wireless terminal device in smart grid, wireless terminal device in transportation safety, wireless terminal device in smart city, and wireless terminal device in smart home, but are not limited thereto.

[0176] In some embodiments, a sidelink (SL) communication method, also known as proximity-based services (ProSe), is introduced to support communication between terminals outside network coverage and the network. A UE can communicate with network devices (such as base stations) without directly connecting to them, but through a relay of another UE. The communication interface between the UEs is the PC5 interface. The UE not connected to the network device is called the remote UE, and the UE providing relay functionality is called the relay UE. The remote UE and the relay UE communicate via a sidelink; this architecture is called U2N (UE to NW, terminal device to network) relay. A multi-hop U2N relay architecture can include a remote UE, a relay UE (hereinafter referred to as a U2N relay), and relay devices (i.e., intermediate relays) between the remote UE and the U2N relay.

[0177] In some embodiments, network device 104 may include at least one of access network device and core network device.

[0178] In some embodiments, the access network device is, for example, a node or device that connects a terminal to a wireless network. The network device may include, but is not limited to, at least one of the following in a 5G communication system: evolved Node B (eNB), next-generation eNB (ng-eNB), next-generation Node B (gNB), node B (NB), home node B (HNB), home evolved node B (HeNB), wireless backhaul device, radio network controller (RNC), base station controller (BSC), base transceiver station (BTS), base band unit (BBU), mobile switching center, base station in a 6G communication system, open RAN, cloud RAN, base station in other communication systems, and access node in a wireless fidelity (WiFi) system.

[0179] In some embodiments, the technical solutions of this disclosure can be applied to the Open RAN architecture. In this case, the interfaces between or within network devices involved in the embodiments of this disclosure can be transformed into internal interfaces of Open RAN. The processes and information interactions between these internal interfaces can be implemented by software or programs.

[0180] In some embodiments, the access network device may be composed of a central unit (CU) and a distributed unit (DU). The CU may also be called a control unit. The CU-DU structure can separate the protocol layer of the network device. Some of the protocol layer functions are centrally controlled by the CU, while the remaining part or all of the protocol layer functions are distributed in the DU and centrally controlled by the CU. However, this is not the only possibility.

[0181] In some embodiments, the access network device may be a single device, multiple devices, or a group of devices, including all or part of a first network element, a second network element, etc. Network elements may be virtual or physical. Network devices may include, for example, at least one of an Evolved Packet Core (EPC), a 5G Core Network (5GCN), and a Next Generation Core (NGC).

[0182] In some embodiments, a core network device may be a single device comprising one or more network elements, or it may be multiple devices or a group of devices, each comprising all or part of the aforementioned one or more network elements. Network elements may be virtual or physical. The core network may include, for example, at least one of an Evolved Packet Core (EPC), a 5G Core Network (5GCN), or a Next Generation Core (NGC).

[0183] In some embodiments, network device 104 may include core network elements, such as at least one of PKMF, DDNMF, UDM, and PCF. PKMF (ProSeKey Management Function) is the key management function for 5G Proximity-based Service (ProSe). DDNMF (Direct DiscoveryName Management Function) is the name management function for proximity communication services. UDM (Unified Data Management) is the unified data management function, responsible for managing user identifiers, subscription data, authentication data, and user service element registration management. PCF (Policy Control Function) is the policy control function, providing policy rules for network entities.

[0184] It is understood that the communication system described in this disclosure is for the purpose of more clearly illustrating the technical solutions of this disclosure, and does not constitute a limitation on the technical solutions proposed in this disclosure. As those skilled in the art will know, with the evolution of system architecture and the emergence of new business scenarios, the technical solutions proposed in this disclosure are also applicable to similar technical problems.

[0185] The following embodiments of this disclosure can be applied to the communication system 100 shown in FIG1a, or to some of the main bodies, but are not limited thereto. The main bodies shown in FIG1a are illustrative. The communication system may include all or some of the main bodies in FIG1a, or it may include other main bodies outside of FIG1a. The number and form of each main body are arbitrary. The connection relationship between the main bodies is illustrative. The main bodies may not be connected or may be connected. The connection can be in any way, it can be a direct connection or an indirect connection, it can be a wired connection or a wireless connection.

[0186] The embodiments disclosed herein can be applied to Long Term Evolution (LTE), LTE-Advanced (LTE-A), LTE-Beyond (LTE-B), SUPER 3G, IMT-Advanced, 4th generation mobile communication system (4G), 5th generation mobile communication system (5G), 5G new radio (NR), Future Radio Access (FRA), New-Radio Access Technology (RAT), New Radio (NR), New radio access (NX), Future generation radio access (FX), Global System for Mobile communications (GSM), CDMA2000, Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), and IEEE 802.20, Ultra-Wideband (UWB), Bluetooth (a registered trademark), Public Land Mobile Network (PLMN) networks, Device-to-Device (D2D) systems, Machine-to-Machine (M2M) systems, Internet of Things (IoT) systems, Vehicle-to-Everything (V2X) systems, systems utilizing other communication methods, and next-generation systems built upon them, etc. Furthermore, multiple systems can be combined (e.g., a combination of LTE or LTE-A with 5G).

[0187] As shown in Figure 1b, a PC5 connection is established between the remote UE and the intermediate relay, a PC5 connection is established between the intermediate relay and the U2N relay, a Uu connection is established between the U2N relay and the core network, and an N6 connection is established between the core network and the data network.

[0188] Currently, single-hop relay discovery, selection, authorization, connection establishment, and data transmission for ProSe UE to network relay have been resolved. With the development of communication technology, there is a need to support multi-hop U2N relays on the PC5 reference point. An intermediate relay is a ProSe UE located on the path between the remote UE and the U2N relay (UE-to-Network Relay), providing support for 5G ProSe (Proximity-based Services) remote UEs to connect to the network.

[0189] In some embodiments, the remote UE and the relay device establish a PC5 connection through a pre-configured RSC (relay service code). This can be understood as the RSC configured locally by the remote UE being the same as, or equivalent to, the relay service code pre-configured locally by the relay device, or equivalent information between the two being obtained through specific encryption / decryption algorithms. For example, the relay service code used by the remote UE is the same as, or corresponds to, the same application identifier.

[0190] To implement the new feature of multi-hop U2N relay, it is necessary to study how to support the discovery of multi-hop U2N relays. For the Model A discovery process, the U2N relay sends an announcement message, and intermediate relays forward the announcement message. Based on the received announcement message, the remote UE can select a path to establish a connection to the network.

[0191] However, there are currently no relevant security protection schemes to ensure the security of multi-hop U2N relay discovery. Without security protection, attackers can impersonate intermediate relays and publish false information about U2N relays, preventing remote UEs from discovering potential U2N relays and thus causing them to be unable to connect to the network. Therefore, the security protection of the multi-hop U2N relay discovery process is an urgent problem to be solved.

[0192] In response to this, the embodiments of this disclosure further improve the transmission mechanism between the remote UE and the U2N relay. The proposed communication method, by verifying the announcement messages between the remote UE and the U2N relay, can securely discover the second relay device, ensure the security of the forwarded announcement messages, and improve the security and reliability of the transmission process.

[0193] Based on the aforementioned wireless communication system, various embodiments of the communication method proposed in this disclosure will be described in detail below.

[0194] Figure 2 is one of the interactive schematic diagrams of a communication method according to an embodiment of the present disclosure. As shown in Figure 2, the method includes:

[0195] Step 201: The second relay device broadcasts a first announcement message. Correspondingly, the first relay device receives the first announcement message sent by the second relay device.

[0196] The first notification message includes: the first hop count and the identification information of the second relay device.

[0197] Optionally, the first notification message may be a real notification message or a fake notification message, that is, a fake notification message issued by an attacker. Therefore, in this embodiment of the disclosure, after the second relay device receives the first notification message, it can verify the identity of the first notification message and the broadcaster of the first notification message (e.g., the second relay device) based on the information carried in the first notification message.

[0198] Optionally, by verifying the identity of the second relay device, it can be determined whether the second relay device is an intermediate relay device or a U2N relay, and this embodiment of the present disclosure does not impose any limitations on this. Optionally, the intermediate relay device is an intermediate relay device on the path between the remote UE and the U2N relay that supports U2N relay services, used to transmit communication information between the remote UE and the U2N relay, including but not limited to announcement messages.

[0199] Alternatively, an announcement message can also be described as a declaration message or a notice message, but the name of the message is not limited to these.

[0200] Optionally, in this embodiment of the disclosure, the first notification message is protected by discovery security material associated with the pre-configured RSC (relay service code) and the HPLMN ID of the second relay device.

[0201] In some embodiments, RSC stands for Relay Service Code, which can be used to identify the proximity services provided by 5G ProSe Relay. Each ProSe service has a corresponding RSC.

[0202] In some embodiments, the discovery of security materials can be used to protect or verify the notification and request / response messages of the U2N discovery process.

[0203] In some embodiments, the discovery security material can be described as key material or discovery security parameters.

[0204] Optionally, remote UEs, U2N relays, and intermediate relay devices can all acquire discovery security materials in advance.

[0205] As an example, assuming the transmission equipment from the U2N relay to the remote UE sequentially includes the U2N relay, intermediate relay 1, intermediate relay 2, and the remote UE, the U2N relay can pre-obtain the discovery security materials (also referred to as discovery security parameters, which are not limited in this embodiment) associated with the RSC and the HPLMN ID (Home PLMN, Public Land Mobile Network) of the U2N relay. Intermediate relay 1 can pre-obtain the discovery security materials associated with the RSC and the HPLMN of intermediate relay 1, as well as multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay. Intermediate relay 2 can pre-obtain the discovery security materials associated with the RSC and the HPLMN of intermediate relay 2, as well as multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay, and multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential intermediate relay 1. The remote UE can obtain multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay, multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential intermediate relay 1, and multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential intermediate relay 2.

[0206] Step 202: The first relay device verifies the first notification message.

[0207] Optionally, in this embodiment of the disclosure, the first notification message further includes an RSC and the PLMN ID of the second relay device, and the first relay device can verify the first notification message based on the RSC and the discovery security material associated with the PLMN ID of the second relay device.

[0208] In this embodiment of the disclosure, the first notification message can be verified in two ways:

[0209] (Method 1)

[0210] Optionally, in this embodiment of the disclosure, in method one, verifying the first notification message includes:

[0211] The first notification message is securely verified based on the RSC and the PLMN ID of the second relay device;

[0212] Determine whether the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition; wherein, the third hop count is the hop count obtained by adding one to the first hop count.

[0213] Optionally, in this embodiment of the disclosure, if the first notification message passes security verification, and the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition, then the first notification message passes verification.

[0214] Optionally, in this embodiment of the disclosure, the step of performing security verification on the first notification message based on the RSC and the PLMN ID of the second relay device includes:

[0215] Among the discovery security materials acquired by the first relay device, the discovery security materials associated with the RSC and the PLMN ID of the second relay device are identified;

[0216] Based on the identified secure materials, the first notification message is subjected to security verification.

[0217] Optionally, the first relay device can use the RSC and the PLMN ID of the second relay device as an index to query multiple sets of discovery security materials obtained by the first relay device, and filter out the discovery security materials associated with the RSC and the PLMN ID of the second relay device from the discovery security materials obtained by the first relay device.

[0218] For example, if the first relay device has pre-acquired discovery security material 1 associated with the HPLMN of the RSC and the second relay device, and multiple sets of discovery security materials 2 associated with the HPLMN of the RSC and the potential U2N relay, the first relay device can use the PLMN IDs of the RSC and the second relay device as indexes to query the multiple sets of discovery security materials (i.e., discovery security material 1 and discovery security material 2) acquired by the first relay device. From the discovery security materials acquired by the first relay device, the first relay device can filter out the discovery security material 1 associated with the PLMN IDs of the RSC and the second relay device, and perform security verification on the first notification message based on the discovery security material 1.

[0219] Optionally, in this embodiment of the disclosure, the first condition includes:

[0220] The third hop count is less than the first hop count threshold; and any of the following:

[0221] The information list stored by the first relay device does not store a first information entry including the RSC, or does not store a second information entry including the identification information of the second relay device, or does not store a sixth information entry including both the RSC and the identification information of the second relay device;

[0222] The information list stored in the first relay device contains a third information entry that includes the RSC and the identification information of the second relay device, and the third hop count is less than the hop count in the third information entry.

[0223] Optionally, the first relay device may, after performing security verification on the first notification message based on the discovery security material associated with the RSC and the PLMN ID of the second relay device, and if the first notification message passes the security verification, further determine whether the identification information of the RSC, the second relay device, and the third hop number meet the first condition.

[0224] Optionally, in some embodiments, the first hop count threshold may be preset, specified by the protocol, or configured by higher-layer signaling, but is not limited to these.

[0225] As an example, suppose the first hop count threshold is 5, and the first hop count in the first notification message is 1. Then the third hop count is 2. Since 2 is less than 5, it can be determined that the third hop count is less than the first hop count threshold.

[0226] Optionally, the information list stored in the first relay device can be associated with and stored as RSC, identification information of the second relay device, link identifier between the first and second relay devices, hop count, and Layer 2 ID of the second relay device.

[0227] Optionally, if the first relay device determines that the third hop count is less than the first hop count threshold, it can use the RSC and the identification information of the second relay device as indexes to query the information list stored by the first relay device to determine whether the information list stores a first information entry including the RSC, a second information entry including the identification information of the second relay device, a sixth information entry including the RSC and the identification information of the second relay device, and a third information entry including the RSC and the identification information of the second relay device.

[0228] Optionally, if the first relay device determines that in its stored information list, ① it does not store a first information entry including RSC; or ② it does not store a second information entry including the identification information of the second relay device; or ③ it does not store a sixth information entry including RSC and the identification information of the second relay device; or ④ it stores a third information entry including RSC and the identification information of the second relay device, and the third hop number is less than the hop number in the third information entry, then the first relay device determines that RSC, the identification information of the second relay device, and the third hop number satisfy the first condition.

[0229] Optionally, if the first relay device determines that the third hop count is less than the first hop count threshold, it can use the RSC in the first announcement message as an index to query the information list stored in the first relay device to determine whether the information list stores a first information entry that includes the RSC of the first announcement message.

[0230] As an example, if the information list stored in the first relay device contains information entry 1 (RSC2, link identifier between the first and second relay devices, fourth hop count, and layer 2 ID of the seventh relay device) and information entry 2 (RSC2, identification information of the fourth relay device, link identifier between the fourth and fifth relay devices, fifth hop count, and layer 2 ID of the fifth relay device), the RSC (e.g., RSC1) in the first announcement message can be used as an index to determine that RSC1 does not exist in either information entry 1 or information entry 2, thereby determining that the information list stored in the first relay device does not store a first information entry including RSC1.

[0231] Optionally, if the first relay device determines that the third hop count is less than the first hop count threshold, the identification information of the second relay device can be used as an index to query the information list stored in the first relay device to determine whether the information list stores a second information entry that includes the identification information of the second relay device.

[0232] As an example, if the information list stored in the first relay device contains information entry 3 (identification information of the fourth relay device, sixth hop count) and information entry 4 (fourth hop count, identification information of the seventh relay device, layer 2 ID of the seventh relay device), the identification information of the second relay device can be used as an index to determine that the identification information of the second relay device does not exist in information entry 3 or information entry 4. Therefore, it can be determined that the information list stored in the first relay device does not contain a second information entry that includes the identification information of the second relay device.

[0233] Optionally, if the first relay device determines that the third hop count is less than the first hop count threshold, it can use the RSC in the first notification message and the identification information of the second relay device as an index to query the information list stored by the first relay device to determine whether the information list stores a sixth information entry that includes the RSC and the identification information of the second relay device.

[0234] As an example, if the information list stored in the first relay device contains information entry 5 (RSC2, identification information of the seventh relay device, seventh hop count, layer 2 ID of the seventh relay device) and information entry 6 (RSC2, link identifier between the first relay device and the second relay device, fourth hop count, identification information of the fourth relay device), the RSC (e.g., RSC1) and the identification information of the second relay device in the first announcement message can be used together as an index to determine that neither information entry 5 nor information entry 6 contains both RSC and identification information of the second relay device. Therefore, it can be determined that the information list stored in the first relay device does not contain a sixth information entry that includes the identification information of the second relay device.

[0235] Optionally, if the first relay device determines that the third hop count is less than the first hop count threshold, the RSC, the identification information of the second relay device, and the hop count can be used as an index to query the information list stored by the first relay device to determine whether the information list stores a third information entry including the RSC and the identification information of the second relay device. If it is determined that the information list stores a third information entry, it can be further determined whether the third hop count is less than the hop count in the third information entry.

[0236] As an example, if the information list stored in the first relay device contains information entry 7 (RSC1, identification information of the second relay device, link identifier between the first and second relay devices, eighth hop count, layer 2 ID of the second relay device, and the eighth hop count is greater than the third hop count) and information entry 8 (RSC2, identification information of the second relay device, link identifier between the first and second relay devices, and layer 2 ID of the second relay device), the RSC (e.g., RSC1) in the first announcement message and the identification information of the second relay device can be used together as an index to determine that information entry 7 contains both RSC1 and the identification information of the second relay device, and that the eighth hop count in information entry 7 is greater than the third hop count (i.e., the third hop count is less than the hop count in the third information entry). Therefore, it can be determined that the information list stored in the first relay device contains a third information entry that includes RSC and the identification information of the second relay device, and that the third hop count is less than the hop count in the third information entry.

[0237] (Method 2)

[0238] Optionally, in this embodiment of the disclosure, in method two, verifying the first notification message includes:

[0239] The first notification message is securely verified based on the RSC and the PLMN ID of the second relay device;

[0240] Determine whether the third hop count satisfies the second condition.

[0241] Optionally, in this embodiment of the disclosure, if the first notification message passes security verification and the third hop count satisfies the second condition, then the first notification message passes verification.

[0242] Optionally, in this embodiment of the disclosure, the step of performing security verification on the first notification message based on the RSC and the PLMN ID of the second relay device includes:

[0243] Among the discovery security materials acquired by the first relay device, the discovery security materials associated with the RSC and the PLMN ID of the second relay device are identified;

[0244] Based on the identified secure materials, the first notification message is subjected to security verification.

[0245] Optionally, the first relay device can filter out discovery security materials associated with the RSC and the PLMN ID of the second relay device from the discovery security materials obtained by the first relay device based on the RSC and the PLMN ID of the second relay device.

[0246] Referring to the example above, if the first relay device has pre-acquired discovery security material 1 associated with the HPLMN of the RSC and the second relay device, and multiple sets of discovery security materials 2 associated with the HPLMN of the RSC and the potential U2N relay, the first relay device can filter out the discovery security material 1 associated with the HPLMN ID of the RSC and the second relay device from the discovery security materials acquired by the first relay device according to the PLMN ID of the RSC and the second relay device, and perform security verification on the first notification message based on the discovery security material 1.

[0247] Optionally, in this embodiment of the disclosure, the second condition includes: the third hop count is less than the second hop count threshold.

[0248] Optionally, the first relay device may perform security verification on the first notification message based on the discovery security material associated with the RSC and the PLMN ID of the second relay device, and if the first notification message passes the security verification, further determine whether the third hop count meets the second condition, i.e., whether the third hop count is less than the second hop count threshold.

[0249] Optionally, in some embodiments, the second hop count threshold may be preset, protocol-specified, or configured by higher-layer signaling, but is not limited to these.

[0250] Optionally, the second hop count threshold can be the same as the first hop count threshold.

[0251] As an example, suppose the second hop count threshold is the same as the first hop count threshold, both being 5. If the first hop count in the first notification message is 1, then the third hop count is 2. Since 2 is less than 5, it can be determined that the third hop count is less than the second hop count threshold.

[0252] Step 203: The first relay device determines whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether there is a link between the first relay device and the second relay device.

[0253] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0254] Optionally, if the first relay device determines that the first announcement message has been successfully verified, it may further determine whether to broadcast the second announcement message or discard the first announcement message based on whether there is a link between the first relay device and the second relay device; if it determines that the first announcement message has not been successfully verified, it may discard the first announcement message.

[0255] Optionally, in this embodiment of the disclosure, if the first notification message is verified using method one, then if the first notification message passes the security verification, and the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition, then the first notification message passes the verification.

[0256] Optionally, in this embodiment of the disclosure, if the first notification message is verified using method two, then if the first notification message passes the security verification and the third hop count satisfies the second condition, then the first notification message passes the verification.

[0257] Optionally, the first relay device may refer to the following logic to determine whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether a link exists between the first relay device and the second relay device:

[0258] ① After verifying the first notification message using either method one or method two above and obtaining the verification result of the first notification message, if the verification result of the first notification message is that the first notification message has failed verification, proceed to ②; if the verification result of the first notification message is that the first notification message has passed verification, proceed to ③.

[0259] ② Discard the first announcement message;

[0260] ③ Determine whether a link already exists between the first and second relay devices corresponding to the RSC; for example, there is a PC5 link between the first and second relay devices, and the PC5 link corresponds to the RSC in the first announcement message; wherein, if a link already exists between the first and second relay devices corresponding to the RSC, proceed to ④; if no link exists between the first and second relay devices corresponding to the RSC, proceed to ⑤.

[0261] ④ Broadcast the second announcement;

[0262] ⑤ Initiate a link establishment request to the second relay device (i.e., send a link establishment request to the second relay device), and receive a response message from the second relay device to the second relay device; wherein, if the response message indicates that the second relay device accepts the link establishment request (i.e., the first response message is the first response message), execute ⑥; if the response message indicates that the second relay device rejects the link establishment request (i.e., the first response message is the second response message), execute ②.

[0263] ⑥ During the link establishment process, the identity of the second relay device is verified; if the second relay device is successfully authenticated and returns a first response message, indicating that the link between the first and second relay devices has been successfully established, proceed to step ④; if the second relay device fails to authenticate or returns a second response message, indicating that the link between the first and second relay devices has failed to be established, proceed to step ②.

[0264] Referring to the above logic, the method for determining whether a second announcement message can be broadcast based on the verification result of the first announcement message and the link establishment result between the first relay device and the second relay device will be explained below:

[0265] Optionally, in this embodiment of the disclosure, determining whether to broadcast the second announcement message or discard the first announcement message based on the verification result and whether a link exists between the first relay device and the second relay device includes at least one of the following:

[0266] If the first notification message fails verification, then the first notification message is discarded.

[0267] If the first notification message is verified and a link exists between the first relay device and the second relay device, then it is determined that the second notification message will be broadcast.

[0268] If the first notification message passes verification and there is no link between the first relay device and the second relay device, then the first notification message is discarded.

[0269] Optionally, after verifying the first notification message using either method one or method two, and obtaining the verification result of the first notification message, if the verification result of the first notification message is that the first notification message fails verification, then the first notification message is discarded; if the verification result of the first notification message is that the first notification message passes verification, then by further verifying whether there is a link between the first relay device and the second relay device, the source of the first notification message can be further verified to ensure the security of the message forwarding process.

[0270] Specifically, if the first notification message passes verification and there is a link between the first relay device and the second relay device, then the second notification message is broadcast; if the first notification message passes verification and there is no link between the first relay device and the second relay device, then the first notification message is discarded.

[0271] Optionally, determining the existence of a link between the first relay device and the second relay device can include two methods: First, when the verification result of the first notification message is that the first notification message has passed verification, a link already exists between the first relay device and the second relay device; second, when the verification result of the first notification message is that the first notification message has passed verification, a link does not exist between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through the link establishment process. In this embodiment of the disclosure, either method can be considered as indicating the existence of a link between the first relay device and the second relay device.

[0272] In one example, when the verification result of the first notification message is that the first notification message has passed verification, there is no link between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through the link establishment process. The details are as follows:

[0273] Optionally, in this embodiment of the disclosure, if a link exists between the first relay device and the second relay device, then determining to broadcast the second announcement message includes:

[0274] If there is no link between the first relay device and the second relay device, a link establishment request is sent to the second relay device.

[0275] Receive a first response message sent by the second relay device; wherein the first response message indicates that the second relay device accepts the link establishment request;

[0276] If a link is successfully established with the second relay device, the second announcement message is broadcast.

[0277] Optionally, if there is no link between the first relay device and the second relay device, the link establishment process can be re-initiated, that is, a link establishment request can be sent to the second relay device.

[0278] Optionally, the link establishment process can be a direct communication establishment process or a U2N communication establishment process, and this disclosure does not limit this.

[0279] Optionally, if the second relay device accepts the link establishment request, that is, if the second relay device agrees to establish a link with the first relay device, the second relay device may send a first response message to the first relay device. Accordingly, the first relay device may receive the first response message sent by the second relay device and determine that the second relay device accepts the link establishment request.

[0280] Optionally, if the second relay device rejects the link establishment request, that is, if the second relay device cannot establish a link with the first relay device, the second relay device may send a second response message to the first relay device. Accordingly, the first relay device may receive the second response message sent by the second relay device and determine that the second relay device has rejected the link establishment request.

[0281] Optionally, after the first relay device receives the first response message sent by the second relay device, the first relay device may establish a link with the second relay device.

[0282] Optionally, during the link establishment process between the first relay device and the second relay device, the identity of the second relay device can be verified. If the information list stored by the first relay device contains a third information entry including the RSC and the identifier information of the second relay device, and the third hop count is less than the hop count in the third information entry; or if the information list stored by the first relay device does not contain a sixth information entry including the RSC and the identifier information of the second relay device, then the identity of the second relay device is verified, and the link between the first and second relay devices is successfully established. Otherwise, if the identity of the second relay device fails verification, the link between the first and second relay devices cannot be successfully established, meaning the link establishment between the first and second relay devices fails.

[0283] Optionally, after the first relay device receives the second response message sent by the second relay device, the first relay device terminates the link establishment with the second relay device, that is, the link establishment between the first relay device and the second relay device fails.

[0284] Optionally, if a link is successfully established between the first relay device and the second relay device, the first relay device may broadcast a second announcement message. In other words, the first intermediate relay can only further broadcast the first announcement message after the link between the first relay device and the second relay device is established.

[0285] Optionally, determining that no link exists between the first relay device and the second relay device may include: when the verification result of the first notification message is that the first notification message passes verification, there is no link between the first relay device and the second relay device, and the link establishment process still fails to successfully establish a link between the first relay device and the second relay device. This situation is explained in detail below:

[0286] Optionally, in this embodiment of the disclosure, if there is no link between the first relay device and the second relay device, then determining to discard the first notification message includes:

[0287] Send a link establishment request to the second relay device;

[0288] If the second response information sent by the second relay device is received, it is determined that the first notification message should be discarded.

[0289] The second response information indicates that the second relay device rejects the link establishment request.

[0290] Optionally, if the second relay device rejects the link establishment request, that is, if the second relay device does not agree to establish a link with the first relay device, the second relay device may send a second response message to the first relay device. Accordingly, the first relay device may receive the second response message sent by the second relay device and determine that the second relay device has rejected the link establishment request.

[0291] Optionally, if the first relay device receives the second response message sent by the second relay device and determines that it cannot establish a link with the second relay device, then the first relay device terminates the link establishment with the second relay device, that is, the link establishment between the first relay device and the second relay device fails, and there is no link between the first relay device and the second relay device.

[0292] Optionally, if a link cannot be successfully established between the first relay device and the second relay device, the first relay device may discard the first announcement message. In other words, if a link cannot be established between the first intermediate relay and the second intermediate relay (e.g., the link establishment between the first intermediate relay and the second intermediate relay fails), the first intermediate relay ignores the first announcement message.

[0293] Optionally, in this embodiment of the disclosure, if method one is used to verify the first notification message, then after determining that the second notification message will be broadcast, the method further includes:

[0294] The third information entry is updated based on the third hop count; or,

[0295] Store the fourth information entry.

[0296] Optionally, when updating the third information entry based on the third hop count, the hop count stored in the third information entry can be directly updated to the third hop count.

[0297] As an example, suppose the third information entry includes RSC, the identification information of the second relay device, the link identifier between the first relay device and the second relay device, the eighth hop number, and the Layer 2 ID of the second relay device, and the eighth hop number is greater than the third hop number. When updating the third information entry based on the third hop number, the eighth hop number in the third information entry can be directly updated to the third hop number.

[0298] Optionally, when determining the storage of the fourth information entry, the fourth information entry associated with the third hop number can be stored in the information list stored by the first relay device.

[0299] Optionally, after storing the fourth information entry in the information list stored by the first relay device, the third information entry can also be deleted.

[0300] Optionally, when storing the fourth information entry in the information list stored by the first relay device, the content of the fourth information entry may include the following:

[0301] Optionally, in embodiments of this disclosure, the fourth information entry includes at least one of the following:

[0302] The RSC, the identification information of the second relay device, the third hop count, the layer 2 ID of the second relay device, and the identification information of the link between the first relay device and the second relay device.

[0303] Optionally, in this embodiment of the disclosure, the second notification message may also include the identification information of the second relay device.

[0304] Optionally, in some embodiments, when broadcasting the announcement message, the announcement message may carry the identification information of the current relay device (i.e., the relay device that forwards the announcement message) and the identification information of each intermediate relay (including the U2N relay) from the U2N relay to the current relay device. In this way, the recipient of the announcement message (e.g., the remote UE and the relay devices from the current relay device to the remote UE) can trace the transmission path of the announcement message based on the identification information of each relay device carried in the announcement message.

[0305] As an example, when the first relay device broadcasts the second announcement message, it can carry the identification information of the first relay device and the identification information of the second relay device in the second announcement message. In this way, the recipient of the second announcement message can obtain the transmission path of the second announcement message based on the identification information of the first relay device and the identification information of the second relay device.

[0306] Optionally, in this embodiment of the disclosure, if method one is used to verify the first notification message, the method further includes:

[0307] If the link between the first relay device and the second relay device is released, then the fifth information entry associated with the link information in the information list stored by the first relay device is deleted.

[0308] The fifth information entry is an information entry that includes the identification information of the RSC and the second relay device.

[0309] Optionally, when it is determined that the link between the first relay device and the second relay device has been released, the link identifier between the first relay device and the second relay device can be used as an index to query the information list stored in the first relay device, determine the fifth information entry including the link identifier between the first relay device and the second relay device, and delete the fifth information entry.

[0310] Optionally, when it is determined that the link between the first relay device and the second relay device has been released, the identification information of the RSC and the second relay device can be used as an index to query the information list stored in the first relay device, determine the fifth information entry including the identification information of the RSC and the second relay device, and delete the fifth information entry.

[0311] In some embodiments, if the link between the first relay device and the second relay device is released, i.e., the historical notification messages (e.g., the first notification message in this embodiment) transmitted by the first relay device and the second relay device through the link are invalid, then the fifth information entry associated with the link information of the link in the information list stored by the first relay device can be deleted.

[0312] Step 204: When the first relay device determines that it is broadcasting the second announcement message, it broadcasts the second announcement message.

[0313] Optionally, if a direct PC5 connection can be established between the first relay device and the remote terminal, the remote terminal can receive the second announcement message broadcast by the first relay device. Optionally, the remote terminal can be a remote UE.

[0314] Optionally, when the first relay device and the remote terminal are connected via a third relay device, the third relay device may also receive the second announcement message broadcast by the first relay device, and broadcast a third announcement message after verifying the second announcement message (the verification method is described above and will not be repeated here) and determining that a link exists between the first relay device and the third relay device. Accordingly, the remote terminal may receive the third announcement message broadcast by the third relay device.

[0315] Figure 3a is a second interactive schematic diagram of a communication method according to an embodiment of the present disclosure.

[0316] As shown in Figure 3a, the above method includes:

[0317] Step 3101: The second relay device sends a first notification message to the first relay device; correspondingly, the first relay device receives the first notification message sent by the second relay device.

[0318] The first notification message includes: the first hop count and the identification information of the second relay device.

[0319] Optionally, the first notification message may be a real notification message or a fake notification message, that is, a fake notification message issued by an attacker. Therefore, in this embodiment of the disclosure, after the second relay device receives the first notification message, it can verify the identity of the first notification message and the broadcaster of the first notification message (e.g., the second relay device) based on the information carried in the first notification message.

[0320] Optionally, by verifying the identity of the second relay device, it can be determined whether the second relay device is an intermediate relay device or a U2N relay, and this embodiment of the present disclosure does not impose any limitations on this. Optionally, the intermediate relay device is an intermediate relay device on the path between the remote UE and the U2N relay that supports U2N relay services, used to transmit communication information between the remote UE and the U2N relay, including but not limited to announcement messages.

[0321] Alternatively, an announcement message can also be described as a declaration message or a notice message, but the name of the message is not limited to these.

[0322] Optionally, in this embodiment of the disclosure, the first notification message is protected by discovery security material associated with the pre-configured RSC (relay service code) and the HPLMN ID of the second relay device.

[0323] As an example, assuming the transmission equipment from the U2N relay to the remote UE sequentially includes the U2N relay, intermediate relay 1, intermediate relay 2, and the remote UE, the U2N relay can pre-obtain the discovery security materials (also referred to as discovery security parameters, which are not limited in this embodiment) associated with the RSC and the HPLMN ID (Home PLMN, Public Land Mobile Network) of the U2N relay. Intermediate relay 1 can pre-obtain the discovery security materials associated with the RSC and the HPLMN of intermediate relay 1, as well as multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay. Intermediate relay 2 can pre-obtain the discovery security materials associated with the RSC and the HPLMN of intermediate relay 2, as well as multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay, and multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential intermediate relay 1. The remote UE can obtain multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay, multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential intermediate relay 1, and multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential intermediate relay 2.

[0324] Step 3102: The first relay device performs security verification on the first notification message based on the RSC and the PLMN ID of the second relay device;

[0325] Determine whether the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition; wherein, the third hop count is the hop count obtained by adding one to the first hop count.

[0326] Optionally, in this embodiment of the disclosure, the step of performing security verification on the first notification message based on the RSC and the PLMN ID of the second relay device includes:

[0327] Among the discovery security materials acquired by the first relay device, the discovery security materials associated with the RSC and the PLMN ID of the second relay device are identified;

[0328] Based on the identified secure materials, the first notification message is subjected to security verification.

[0329] Optionally, the first relay device can use the RSC and the PLMN ID of the second relay device as an index to query multiple sets of discovery security materials obtained by the first relay device, and filter out the discovery security materials associated with the RSC and the PLMN ID of the second relay device from the discovery security materials obtained by the first relay device.

[0330] For example, if the first relay device has pre-acquired discovery security material 1 associated with the HPLMN of the RSC and the second intermediate relay, and multiple sets of discovery security materials 2 associated with the HPLMN of the RSC and the potential U2N relay, the first relay device can use the PLMN IDs of the RSC and the second relay device as indexes to query the multiple sets of discovery security materials (i.e., discovery security material 1 and discovery security material 2) acquired by the first relay device. From the discovery security materials acquired by the first relay device, the first relay device can filter out the discovery security material 1 associated with the PLMN IDs of the RSC and the second relay device, and perform security verification on the first notification message based on the discovery security material 1.

[0331] Optionally, in this embodiment of the disclosure, the first condition includes:

[0332] The third hop count is less than the first hop count threshold; and any of the following:

[0333] The information list stored by the first relay device does not store a first information entry including the RSC, or does not store a second information entry including the identification information of the second relay device, or does not store a sixth information entry including both the RSC and the identification information of the second relay device;

[0334] The information list stored in the first relay device contains a third information entry that includes the RSC and the identification information of the second relay device, and the third hop count is less than the hop count in the third information entry.

[0335] Optionally, the first relay device may, after performing security verification on the first notification message based on the discovery security material associated with the RSC and the PLMN ID of the second relay device, and if the first notification message passes the security verification, further determine whether the identification information of the RSC, the second relay device, and the third hop number meet the first condition.

[0336] Optionally, in some embodiments, the first hop count threshold may be preset, specified by the protocol, or configured by higher-layer signaling, but is not limited to these.

[0337] As an example, suppose the first hop count threshold is 5, and the first hop count in the first notification message is 1. Then the third hop count is 2. Since 2 is less than 5, it can be determined that the third hop count is less than the first hop count threshold.

[0338] Optionally, if the first relay device determines that the third hop count is less than the first hop count threshold, it can use the RSC and the identification information of the second relay device as indexes to query the information list stored by the first relay device to determine whether the information list stores a first information entry including the RSC, a second information entry including the identification information of the second relay device, a sixth information entry including the RSC and the identification information of the second relay device, and a third information entry including the RSC and the identification information of the second relay device.

[0339] Optionally, if the first relay device determines that in its stored information list, ① it does not store a first information entry including RSC; or ② it does not store a second information entry including the identification information of the second relay device; or ③ it does not store a sixth information entry including RSC and the identification information of the second relay device; or ④ it stores a third information entry including RSC and the identification information of the second relay device, and the third hop number is less than the hop number in the third information entry, then the first relay device determines that RSC, the identification information of the second relay device, and the third hop number satisfy the first condition.

[0340] Optionally, if the first relay device determines that the third hop count is less than the first hop count threshold, it can use the RSC in the first announcement message as an index to query the information list stored in the first relay device to determine whether the information list stores a first information entry that includes the RSC of the first announcement message.

[0341] As an example, if the information list stored in the first relay device contains information entry 1 (RSC2, link identifier between the first and second relay devices, fourth hop count, and layer 2 ID of the seventh relay device) and information entry 2 (RSC2, identification information of the fourth relay device, link identifier between the fourth and fifth relay devices, fifth hop count, and layer 2 ID of the fifth relay device), the RSC (e.g., RSC1) in the first announcement message can be used as an index to determine that RSC1 does not exist in either information entry 1 or information entry 2, thereby determining that the information list stored in the first relay device does not store a first information entry including RSC1.

[0342] Optionally, if the first relay device determines that the third hop count is less than the first hop count threshold, the identification information of the second relay device can be used as an index to query the information list stored in the first relay device to determine whether the information list stores a second information entry that includes the identification information of the second relay device.

[0343] As an example, if the information list stored in the first relay device contains information entry 3 (identification information of the fourth relay device, sixth hop count) and information entry 4 (fourth hop count, identification information of the seventh relay device, layer 2 ID of the seventh relay device), the identification information of the second relay device can be used as an index to determine that the identification information of the second relay device does not exist in information entry 3 or information entry 4. Therefore, it can be determined that the information list stored in the first relay device does not contain a second information entry that includes the identification information of the second relay device.

[0344] Optionally, if the first relay device determines that the third hop count is less than the first hop count threshold, it can use the RSC in the first notification message and the identification information of the second relay device as an index to query the information list stored by the first relay device to determine whether the information list stores a sixth information entry that includes the RSC and the identification information of the second relay device.

[0345] As an example, if the information list stored in the first relay device contains information entry 5 (RSC2, identification information of the seventh relay device, seventh hop count, layer 2 ID of the seventh relay device) and information entry 6 (RSC2, link identifier between the first relay device and the second relay device, fourth hop count, identification information of the fourth relay device), the RSC (e.g., RSC1) and the identification information of the second relay device in the first announcement message can be used together as an index to determine that neither information entry 5 nor information entry 6 contains both RSC and identification information of the second relay device. Therefore, it can be determined that the information list stored in the first relay device does not contain a sixth information entry that includes the identification information of the second relay device.

[0346] Optionally, if the first relay device determines that the third hop count is less than the first hop count threshold, the RSC, the identification information of the second relay device, and the hop count can be used as an index to query the information list stored by the first relay device to determine whether the information list stores a third information entry including the RSC and the identification information of the second relay device. If it is determined that the information list stores a third information entry, it can be further determined whether the third hop count is less than the hop count in the third information entry.

[0347] As an example, if the information list stored in the first relay device contains information entry 7 (RSC1, identification information of the second relay device, link identifier between the first and second relay devices, eighth hop count, layer 2 ID of the second relay device, and the eighth hop count is greater than the third hop count) and information entry 8 (RSC2, identification information of the second relay device, link identifier between the first and second relay devices, and layer 2 ID of the second relay device), the RSC (e.g., RSC1) in the first announcement message and the identification information of the second relay device can be used together as an index to determine that information entry 7 contains both RSC1 and the identification information of the second relay device, and that the eighth hop count in information entry 7 is greater than the third hop count (i.e., the third hop count is less than the hop count in the third information entry). Therefore, it can be determined that the information list stored in the first relay device contains a third information entry that includes RSC and the identification information of the second relay device, and that the third hop count is less than the hop count in the third information entry.

[0348] Step 3103: The first relay device determines whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether there is a link between the first relay device and the second relay device.

[0349] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0350] Optionally, if the first relay device determines that the first announcement message has been successfully verified, it may further determine whether to broadcast the second announcement message or discard the first announcement message based on whether there is a link between the first relay device and the second relay device; if it determines that the first announcement message has not been successfully verified, it may discard the first announcement message.

[0351] Optionally, in this embodiment of the disclosure, if the first notification message passes security verification, and the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition, then the first notification message passes verification.

[0352] Optionally, the first relay device may refer to the following logic to determine whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether a link exists between the first relay device and the second relay device:

[0353] ① After verifying the first announcement message using the above method (i.e., performing security verification on the first announcement message based on the RSC and the PLMN ID of the second relay device; determining whether the RSC, the identification information of the second relay device, and the third hop count meet the first condition), and obtaining the verification result of the first announcement message, if the verification result of the first announcement message is that the first announcement message fails verification, proceed to ②; if the verification result of the first announcement message is that the first announcement message passes verification, proceed to ③.

[0354] ② Discard the first announcement message;

[0355] ③ Determine whether a link already exists between the first and second relay devices corresponding to the RSC; for example, there is a PC5 link between the first and second relay devices, and the PC5 link corresponds to the RSC in the first announcement message; wherein, if a link already exists between the first and second relay devices corresponding to the RSC, proceed to ④; if no link exists between the first and second relay devices corresponding to the RSC, proceed to ⑤.

[0356] ④ Broadcast the second announcement;

[0357] ⑤ Initiate a link establishment request to the second relay device (i.e., send a link establishment request to the second relay device), and receive a response message from the second relay device to the second relay device; wherein, if the response message indicates that the second relay device accepts the link establishment request (i.e., the first response message is the first response message), execute ⑥; if the response message indicates that the second relay device rejects the link establishment request (i.e., the first response message is the second response message), execute ②.

[0358] ⑥ During the link establishment process, the identity of the second relay device is verified; if the second relay device is successfully authenticated and returns a first response message, indicating that the link between the first and second relay devices has been successfully established, proceed to step ④; if the second relay device fails to authenticate or returns a second response message, indicating that the link between the first and second relay devices has failed to be established, proceed to step ②.

[0359] Referring to the above logic, the method for determining whether a second announcement message can be broadcast based on the verification result of the first announcement message and the link establishment result between the first relay device and the second relay device will be explained below:

[0360] Optionally, in this embodiment of the disclosure, determining whether to broadcast the second announcement message or discard the first announcement message based on the verification result and whether a link exists between the first relay device and the second relay device includes at least one of the following:

[0361] If the first notification message fails verification, then the first notification message is discarded.

[0362] If the first notification message is verified and a link exists between the first relay device and the second relay device, then it is determined that the second notification message will be broadcast.

[0363] If the first notification message passes verification and there is no link between the first relay device and the second relay device, then the first notification message is discarded.

[0364] Optionally, after verifying the first notification message using the above method and obtaining the verification result of the first notification message, if the verification result of the first notification message is that the first notification message fails verification, then the first notification message is discarded; if the verification result of the first notification message is that the first notification message passes verification, then by further verifying whether there is a link between the first relay device and the second relay device, the source of the first notification message can be further verified to ensure the security of the message forwarding process.

[0365] Specifically, if the first notification message passes verification and there is a link between the first relay device and the second relay device, then the second notification message is broadcast; if the first notification message passes verification and there is no link between the first relay device and the second relay device, then the first notification message is discarded.

[0366] Optionally, determining the existence of a link between the first relay device and the second relay device can include two methods: First, when the verification result of the first notification message is that the first notification message has passed verification, a link already exists between the first relay device and the second relay device; second, when the verification result of the first notification message is that the first notification message has passed verification, a link does not exist between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through the link establishment process. In this embodiment of the disclosure, either method can be considered as indicating the existence of a link between the first relay device and the second relay device.

[0367] In one example, when the verification result of the first notification message is that the first notification message has passed verification, there is no link between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through the link establishment process. The details are as follows:

[0368] Optionally, in this embodiment of the disclosure, if a link exists between the first relay device and the second relay device, then determining to broadcast the second announcement message includes:

[0369] If there is no link between the first relay device and the second relay device, a link establishment request is sent to the second relay device.

[0370] Receive a first response message sent by the second relay device; wherein the first response message indicates that the second relay device accepts the link establishment request;

[0371] If a link is successfully established with the second relay device, the second announcement message is broadcast.

[0372] Optionally, if there is no link between the first relay device and the second relay device, the link establishment process can be re-initiated, that is, a link establishment request can be sent to the second relay device.

[0373] Optionally, the link establishment process can be a direct communication establishment process or a U2N communication establishment process, and this disclosure does not limit this.

[0374] Optionally, if the second relay device accepts the link establishment request, that is, if the second relay device agrees to establish a link with the first relay device, the second relay device may send a first response message to the first relay device. Accordingly, the first relay device may receive the first response message sent by the second relay device and determine that the second relay device accepts the link establishment request.

[0375] Optionally, if the second relay device rejects the link establishment request, that is, if the second relay device cannot establish a link with the first relay device, the second relay device may send a second response message to the first relay device. Accordingly, the first relay device may receive the second response message sent by the second relay device and determine that the second relay device has rejected the link establishment request.

[0376] Optionally, after the first relay device receives the first response message sent by the second relay device, the first relay device may establish a link with the second relay device.

[0377] Optionally, during the link establishment process between the first relay device and the second relay device, the identity of the second relay device can be verified. If the information list stored by the first relay device contains a third information entry including the RSC and the identifier information of the second relay device, and the third hop count is less than the hop count in the third information entry; or if the information list stored by the first relay device does not contain a sixth information entry including the RSC and the identifier information of the second relay device, then the identity of the second relay device is verified, and the link between the first and second relay devices is successfully established. Otherwise, if the identity of the second relay device fails verification, the link between the first and second relay devices cannot be successfully established, meaning the link establishment between the first and second relay devices fails.

[0378] Optionally, after the first relay device receives the second response message sent by the second relay device, the first relay device terminates the link establishment with the second relay device, that is, the link establishment between the first relay device and the second relay device fails.

[0379] Optionally, if a link is successfully established between the first relay device and the second relay device, the first relay device may broadcast a second announcement message. In other words, the first intermediate relay can only further broadcast the first announcement message after the link between the first relay device and the second relay device, which is the second intermediate relay, is established.

[0380] Optionally, in this embodiment of the disclosure, if there is no link between the first relay device and the second relay device, then determining to discard the first notification message includes:

[0381] Send a link establishment request to the second relay device;

[0382] If the second response information sent by the second relay device is received, it is determined that the first notification message should be discarded.

[0383] The second response information indicates that the second relay device rejects the link establishment request.

[0384] Optionally, if the second relay device rejects the link establishment request, that is, if the second relay device cannot establish a link with the first relay device, the second relay device may send a second response message to the first relay device. Accordingly, the first relay device may receive the second response message sent by the second relay device and determine that the second relay device has rejected the link establishment request.

[0385] Optionally, if the first relay device receives the second response message sent by the second relay device and determines that it cannot establish a link with the second relay device, then the first relay device terminates the link establishment with the second relay device, that is, the link establishment between the first relay device and the second relay device fails, and there is no link between the first relay device and the second relay device.

[0386] Optionally, if a link cannot be successfully established between the first relay device and the second relay device, the first relay device may discard the first announcement message. In other words, if a link cannot be established between the first intermediate relay and the second intermediate relay (e.g., the link establishment between the first intermediate relay and the second intermediate relay fails), the first intermediate relay ignores the first announcement message.

[0387] Step 3104: After the first relay device determines that the second announcement message has been broadcast, it updates the third information entry according to the third hop count; or,

[0388] Store the fourth information entry.

[0389] Optionally, when updating the third information entry based on the third hop count, the hop count stored in the third information entry can be directly updated to the third hop count.

[0390] As an example, suppose the third information entry includes RSC, the identification information of the second relay device, the link identifier between the first relay device and the second relay device, the eighth hop number, and the Layer 2 ID of the second relay device, and the eighth hop number is greater than the third hop number. When updating the third information entry based on the third hop number, the eighth hop number in the third information entry can be directly updated to the third hop number.

[0391] Optionally, when determining the storage of the fourth information entry, the fourth information entry associated with the third hop number can be stored in the information list stored by the first relay device.

[0392] Optionally, after storing the fourth information entry in the information list stored by the first relay device, the third information entry can also be deleted.

[0393] Optionally, when storing the fourth information entry in the information list stored by the first relay device, the content of the fourth information entry may include the following:

[0394] Optionally, in embodiments of this disclosure, the fourth information entry includes at least one of the following:

[0395] The RSC, the identification information of the second relay device, the third hop count, the layer 2 ID of the second relay device, and the identification information of the link between the first relay device and the second relay device.

[0396] Optionally, in this embodiment of the disclosure, the second notification message may also include the identification information of the second relay device.

[0397] Optionally, in some embodiments, when broadcasting the announcement message, the announcement message may carry the identification information of the current relay device (i.e., the relay device that forwards the announcement message) and the identification information of each intermediate relay (including the U2N relay) from the U2N relay to the current relay device. In this way, the recipient of the announcement message (e.g., the remote UE and the relay devices from the current relay device to the remote UE) can trace the transmission path of the announcement message based on the identification information of each relay device carried in the announcement message.

[0398] As an example, when the first relay device broadcasts the second announcement message, it can carry the identification information of the first relay device and the identification information of the second relay device in the second announcement message. In this way, the recipient of the second announcement message can obtain the transmission path of the second announcement message based on the identification information of the first relay device and the identification information of the second relay device.

[0399] Optionally, in embodiments of this disclosure, the method further includes:

[0400] If the link between the first relay device and the second relay device is released, then the fifth information entry associated with the link information in the information list stored by the first relay device is deleted.

[0401] The fifth information entry is an information entry that includes the identification information of the RSC and the second relay device.

[0402] Optionally, when it is determined that the link between the first relay device and the second relay device has been released, the link identifier between the first relay device and the second relay device can be used as an index to query the information list stored in the first relay device, determine the fifth information entry including the link identifier between the first relay device and the second relay device, and delete the fifth information entry.

[0403] Optionally, when it is determined that the link between the first relay device and the second relay device has been released, the identification information of the RSC and the second relay device can be used as an index to query the information list stored in the first relay device, determine the fifth information entry including the identification information of the RSC and the second relay device, and delete the fifth information entry.

[0404] In some embodiments, if the link between the first relay device and the second relay device is released, i.e., the historical notification messages (e.g., the first notification message in this embodiment) transmitted by the first relay device and the second relay device through the link are invalid, then the fifth information entry associated with the link information recorded by the curtain can be deleted from the information list stored by the first relay device.

[0405] Step 3105: When the first relay device determines that it is broadcasting the second announcement message, it broadcasts the second announcement message.

[0406] Optionally, in the case of a direct connection between the first relay device and the remote terminal, the remote terminal may receive a second announcement message broadcast by the first relay device. Optionally, the remote terminal may be a remote UE.

[0407] Optionally, when the first relay device and the remote terminal are connected via a third relay device, the third relay device may also receive the second announcement message broadcast by the first relay device, and broadcast a third announcement message after verifying the second announcement message (the verification method is described above and will not be repeated here) and determining that a link exists between the first relay device and the third relay device. Accordingly, the remote terminal may receive the third announcement message broadcast by the third relay device.

[0408] The communication method involved in the embodiments of this disclosure may include the foregoing steps and at least one of the embodiments. For example, step 3101 may be implemented as an independent embodiment, step 3102 may be implemented as an independent embodiment, step 3103 may be implemented as an independent embodiment, step 3104 may be implemented as an independent embodiment, and step 3105 may be implemented as an independent embodiment; the combination of step 3101 and step 3102 may be implemented as an independent embodiment, the combination of step 3101, step 3102 and step 3103 may be implemented as an independent embodiment, the combination of step 3101, step 3102, step 3103 and step 3104 may be implemented as an independent embodiment, and the combination of step 3101, step 3102, step 3103, step 3104 and step 3105 may be implemented as an independent embodiment, but is not limited thereto.

[0409] In some embodiments, other alternative implementations may be described before or after the specification corresponding to FIG3a.

[0410] Figure 3b is a third interactive schematic diagram of a communication method according to an embodiment of the present disclosure.

[0411] As shown in Figure 3b, the above method includes:

[0412] Step 3201: The second relay device sends a first notification message to the first relay device; correspondingly, the first relay device receives the first notification message sent by the second relay device.

[0413] The first notification message includes: the first hop count and the identification information of the second relay device.

[0414] Optionally, the first notification message may be a real notification message or a fake notification message, that is, a fake notification message issued by an attacker. Therefore, in this embodiment of the disclosure, after the second relay device receives the first notification message, it can verify the identity of the first notification message and the broadcaster of the first notification message (e.g., the second relay device) based on the information carried in the first notification message.

[0415] Optionally, by verifying the identity of the second relay device, it can be determined whether the second relay device is an intermediate relay device or a U2N relay, and this embodiment of the present disclosure does not impose any limitations on this. Optionally, the intermediate relay device is an intermediate relay device on the path between the remote UE and the U2N relay that supports U2N relay services, used to transmit communication information between the remote UE and the U2N relay, including but not limited to announcement messages.

[0416] Alternatively, an announcement message can also be described as a declaration message or a notice message, but the name of the message is not limited to these.

[0417] Optionally, in this embodiment of the disclosure, the first notification message is protected by discovery security material associated with the pre-configured RSC (relay service code) and the HPLMN ID of the second relay device.

[0418] As an example, assuming the transmission equipment from the U2N relay to the remote UE sequentially includes the U2N relay, intermediate relay 1, intermediate relay 2, and the remote UE, the U2N relay can pre-obtain the discovery security materials (also referred to as discovery security parameters, which are not limited in this embodiment) associated with the RSC and the HPLMN ID (Home PLMN, Public Land Mobile Network) of the U2N relay. Intermediate relay 1 can pre-obtain the discovery security materials associated with the RSC and the HPLMN of intermediate relay 1, as well as multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay. Intermediate relay 2 can pre-obtain the discovery security materials associated with the RSC and the HPLMN of intermediate relay 2, as well as multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay, and multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential intermediate relay 1. The remote UE can obtain multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay, multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential intermediate relay 1, and multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential intermediate relay 2.

[0419] Step 3202: The first relay device performs security verification on the first notification message based on the RSC and the PLMN ID of the second relay device;

[0420] Determine whether the third hop count satisfies the second condition.

[0421] Optionally, in this embodiment of the disclosure, the step of performing security verification on the first notification message based on the RSC and the PLMN ID of the second relay device includes:

[0422] Among the discovery security materials acquired by the first relay device, the discovery security materials associated with the RSC and the PLMN ID of the second relay device are identified;

[0423] Based on the identified secure materials, the first notification message is subjected to security verification.

[0424] Optionally, the first relay device can filter out discovery security materials associated with the RSC and the PLMN ID of the second relay device from the discovery security materials obtained by the first relay device based on the RSC and the PLMN ID of the second relay device.

[0425] As an example, if the first relay device has pre-acquired discovery security material 1 associated with the HPLMN of the RSC and the second relay device, and multiple sets of discovery security materials 2 associated with the HPLMN of the RSC and the potential U2N relay, the first relay device can filter out the discovery security material 1 associated with the HPLMN ID of the RSC and the second relay device from the discovery security materials acquired by the first relay device according to the PLMN ID of the RSC and the second relay device, and perform security verification on the first notification message based on the discovery security material 1.

[0426] Optionally, in this embodiment of the disclosure, the second condition includes: the third hop count is less than the second hop count threshold.

[0427] Optionally, in some embodiments, the second hop count threshold may be preset, protocol-specified, or configured by higher-layer signaling, but is not limited to these.

[0428] Optionally, the second hop count threshold can be the same as the first hop count threshold.

[0429] Optionally, the first relay device may perform security verification on the first notification message based on the discovery security material associated with the RSC and the PLMN ID of the second relay device, and if the first notification message passes the security verification, further determine whether the third hop count meets the second condition, i.e., whether the third hop count is less than the second hop count threshold.

[0430] As an example, suppose the second hop count threshold is the same as the first hop count threshold, both being 5. If the first hop count in the first notification message is 1, then the third hop count is 2. Since 2 is less than 5, it can be determined that the third hop count is less than the second hop count threshold.

[0431] Step 3203: The first relay device determines whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether there is a link between the first relay device and the second relay device.

[0432] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0433] Optionally, in this embodiment of the disclosure, if the first notification message passes security verification and the third hop count satisfies the second condition, then the first notification message passes verification.

[0434] Optionally, the first relay device may refer to the following logic to determine whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether a link exists between the first relay device and the second relay device:

[0435] ① After verifying the first announcement message using the above method (i.e., performing security verification on the first announcement message based on the RSC and the PLMN ID of the second relay device; determining whether the RSC, the identification information of the second relay device, and the third hop count meet the first condition), and obtaining the verification result of the first announcement message, if the verification result of the first announcement message is that the first announcement message fails verification, proceed to ②; if the verification result of the first announcement message is that the first announcement message passes verification, proceed to ③.

[0436] ② Discard the first announcement message;

[0437] ③ Determine whether a link already exists between the first and second relay devices corresponding to the RSC; for example, there is a PC5 link between the first and second relay devices, and the PC5 link corresponds to the RSC in the first announcement message; wherein, if a link already exists between the first and second relay devices corresponding to the RSC, proceed to ④; if no link exists between the first and second relay devices corresponding to the RSC, proceed to ⑤.

[0438] ④ Broadcast the second announcement;

[0439] ⑤ Initiate a link establishment request to the second relay device (i.e., send a link establishment request to the second relay device), and receive a response message from the second relay device to the second relay device; wherein, if the response message indicates that the second relay device accepts the link establishment request (i.e., the first response message is the first response message), execute ⑥; if the response message indicates that the second relay device rejects the link establishment request (i.e., the first response message is the second response message), execute ②.

[0440] ⑥ During the link establishment process, the identity of the second relay device is verified; if the second relay device is successfully authenticated and returns a first response message, indicating that the link between the first and second relay devices has been successfully established, proceed to step ④; if the second relay device fails to authenticate or returns a second response message, indicating that the link between the first and second relay devices has failed to be established, proceed to step ②.

[0441] Referring to the above logic, the method for determining whether a second announcement message can be broadcast based on the verification result of the first announcement message and the link establishment result between the first relay device and the second relay device will be explained below:

[0442] Optionally, in this embodiment of the disclosure, determining whether to broadcast the second announcement message or discard the first announcement message based on the verification result and whether a link exists between the first relay device and the second relay device includes at least one of the following:

[0443] If the first notification message fails verification, then the first notification message is discarded.

[0444] If the first notification message is verified and a link exists between the first relay device and the second relay device, then it is determined that the second notification message will be broadcast.

[0445] If the first notification message passes verification and there is no link between the first relay device and the second relay device, then the first notification message is discarded.

[0446] Optionally, after verifying the first notification message using the above method and obtaining the verification result of the first notification message, if the verification result of the first notification message is that the first notification message fails verification, then the first notification message is discarded; if the verification result of the first notification message is that the first notification message passes verification, then by further verifying whether there is a link between the first relay device and the second relay device, the source of the first notification message can be further verified to ensure the security of the message forwarding process.

[0447] Specifically, if the first notification message passes verification and there is a link between the first relay device and the second relay device, then the second notification message is broadcast; if the first notification message passes verification and there is no link between the first relay device and the second relay device, then the first notification message is discarded.

[0448] Optionally, determining the existence of a link between the first relay device and the second relay device can include two methods: First, when the verification result of the first notification message is that the first notification message has passed verification, a link already exists between the first relay device and the second relay device; second, when the verification result of the first notification message is that the first notification message has passed verification, a link does not exist between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through the link establishment process. In this embodiment of the disclosure, either method can be considered as indicating the existence of a link between the first relay device and the second relay device.

[0449] In one example, when the verification result of the first notification message is that the first notification message has passed verification, there is no link between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through the link establishment process. The details are as follows:

[0450] Optionally, in this embodiment of the disclosure, if a link exists between the first relay device and the second relay device, then determining to broadcast the second announcement message includes:

[0451] If there is no link between the first relay device and the second relay device, a link establishment request is sent to the second relay device.

[0452] Receive a first response message sent by the second relay device; wherein the first response message indicates that the second relay device accepts the link establishment request;

[0453] If a link is successfully established with the second relay device, the second announcement message is broadcast.

[0454] Optionally, if there is no link between the first relay device and the second relay device, the link establishment process can be re-initiated, that is, a link establishment request can be sent to the second relay device.

[0455] Optionally, the link establishment process can be a direct communication establishment process or a U2N communication establishment process, and this disclosure does not limit this.

[0456] Optionally, if the second relay device accepts the link establishment request, that is, if the second relay device agrees to establish a link with the first relay device, the second relay device may send a first response message to the first relay device. Accordingly, the first relay device may receive the first response message sent by the second relay device and determine that the second relay device accepts the link establishment request.

[0457] Optionally, if the second relay device rejects the link establishment request, that is, if the second relay device cannot establish a link with the first relay device, the second relay device may send a second response message to the first relay device. Accordingly, the first relay device may receive the second response message sent by the second relay device and determine that the second relay device has rejected the link establishment request.

[0458] Optionally, after the first relay device receives the first response message sent by the second relay device, the first relay device may establish a link with the second relay device.

[0459] Optionally, during the link establishment process between the first relay device and the second relay device, the identity of the second relay device can be verified. If the information list stored by the first relay device contains a third information entry including the RSC and the identifier information of the second relay device, and the third hop count is less than the hop count in the third information entry; or if the information list stored by the first relay device does not contain a sixth information entry including the RSC and the identifier information of the second relay device, then the identity of the second relay device is verified, and the link between the first and second relay devices is successfully established. Otherwise, if the identity of the second relay device fails verification, the link between the first and second relay devices cannot be successfully established, meaning the link establishment between the first and second relay devices fails.

[0460] Optionally, after the first relay device receives the second response message sent by the second relay device, the first relay device terminates the link establishment with the second relay device, that is, the link establishment between the first relay device and the second relay device fails.

[0461] Optionally, if a link is successfully established between the first relay device and the second relay device, the first relay device may broadcast a second announcement message. In other words, the first intermediate relay can only further broadcast the first announcement message after the link between the first relay device and the second relay device, which is the second intermediate relay, is established.

[0462] Optionally, in this embodiment of the disclosure, if there is no link between the first relay device and the second relay device, then determining to discard the first notification message includes:

[0463] Send a link establishment request to the second relay device;

[0464] If the second response information sent by the second relay device is received, it is determined that the first notification message should be discarded.

[0465] The second response information indicates that the second relay device rejects the link establishment request.

[0466] Optionally, if the second relay device rejects the link establishment request, that is, if the second relay device cannot establish a link with the first relay device, the second relay device may send a second response message to the first relay device. Accordingly, the first relay device may receive the second response message sent by the second relay device and determine that the second relay device has rejected the link establishment request.

[0467] Optionally, if the first relay device receives the second response message sent by the second relay device and determines that it cannot establish a link with the second relay device, then the first relay device terminates the link establishment with the second relay device, that is, the link establishment between the first relay device and the second relay device fails, and there is no link between the first relay device and the second relay device.

[0468] Optionally, if a link cannot be successfully established between the first relay device and the second relay device, the first relay device may discard the first announcement message. In other words, if a link cannot be established between the first intermediate relay and the second intermediate relay (e.g., the link establishment between the first intermediate relay and the second intermediate relay fails), the first intermediate relay ignores the first announcement message.

[0469] Step 3204: When the first relay device determines that it is broadcasting the second announcement message, it broadcasts the second announcement message.

[0470] Optionally, in the case of a direct connection between the first relay device and the remote terminal, the remote terminal may receive a second announcement message broadcast by the first relay device. Optionally, the remote terminal may be a remote UE.

[0471] Optionally, when the first relay device and the remote terminal are connected via a third relay device, the third relay device may also receive the second announcement message broadcast by the first relay device, and broadcast a third announcement message after verifying the second announcement message (the verification method is described above and will not be repeated here) and determining that a link exists between the first relay device and the third relay device. Accordingly, the remote terminal may receive the third announcement message broadcast by the third relay device.

[0472] The communication method involved in the embodiments of this disclosure may include the foregoing steps and at least one of the embodiments. For example, step 3201 may be implemented as an independent embodiment, step 3202 may be implemented as an independent embodiment, step 3203 may be implemented as an independent embodiment, and step 3204 may be implemented as an independent embodiment; the combination of step 3201 and step 3202 may be implemented as an independent embodiment, the combination of step 3201, step 3202 and step 3203 may be implemented as an independent embodiment, and the combination of step 3201, step 3202, step 3203 and step 3204 may be implemented as an independent embodiment, but is not limited thereto.

[0473] In some embodiments, other alternative implementations may be described before or after the specification corresponding to FIG3b.

[0474] In some embodiments, the names of information, etc., are not limited to the names described in the embodiments. Terms such as "information", "message", "signal", "signaling", "report", "configuration", "indication", "instruction", "command", "channel", "parameter", "domain", "field", "symbol", "codepoint", "bit", "data", "program", and "chip" can be used interchangeably.

[0475] In some embodiments, terms such as “moment,” “point in time,” “time,” and “time location” can be used interchangeably, as can terms such as “duration,” “segment,” “time window,” “window,” and “time.”

[0476] In some embodiments, terms such as wireless access scheme and waveform can be used interchangeably.

[0477] In some embodiments, terms such as "certain," "preset," "default," "set," "indicated," "a certain," "any," and "first" can be used interchangeably. "Certain A," "preset A," "default A," "set A," "indicated A," "a certain A," "any A," and "first A" can be interpreted as A pre-defined in a protocol or the like, or as A obtained through setting, configuration, or instruction, or as specific A, a certain A, any A, or first A, but are not limited thereto.

[0478] In some embodiments, the determination or judgment can be made by a value represented by 1 bit (0 or 1), or by a true or false value (boolean), or by a comparison of numerical values ​​(e.g., a comparison with a predetermined value), but is not limited thereto.

[0479] In some embodiments, "not expecting to receive" can be interpreted as not receiving on time domain resources and / or frequency domain resources, or as not performing subsequent processing on the data after receiving it; "not expecting to send" can be interpreted as not sending, or as sending but not expecting the receiver to respond to the sent content.

[0480] Referring to the above, during message transmission between the remote UE and the U2N relay, two verification methods can be used to verify the messages transmitted between the remote UE and the U2N relay. Verification method one: if the transmitted message (e.g., the first announcement message) passes security verification, and the RSC, the identification information of the second relay device (the sender of the first announcement message), and the third hop count (the hop count obtained by adding one to the hop count in the first announcement message) meet the first condition, then the first announcement message passes verification. Verification method two: if the first announcement message passes security verification, and the third hop count meets the second condition, then the first announcement message passes verification. The following, in conjunction with specific embodiments, explains the verification methods using different verification approaches during message transmission between the remote UE and the U2N relay. Specifically:

[0481] (i) Referring to Figure 4a, when using verification method one to verify the messages transmitted between the remote UE and the U2N relay, the specific message transmission process may include the following steps:

[0482] Optionally, in Figure 4a, the U2N relay has acquired discovery security materials (also referred to as discovery security parameters, which are not limited in this embodiment) associated with the RSC and the HPLMN ID of the U2N relay. The intermediate relay has acquired discovery security materials associated with the RSC and the HPLMN of the intermediate relay, as well as multiple sets of discovery security materials associated with the HPLMN of the potential U2N relay or the HPLMN of the potential intermediate relay. The remote UE has acquired multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay or the HPLMN of the potential intermediate relay.

[0483] Step 411: U2N relay broadcast announcement message (i.e., first announcement message) (for example, intermediate relay 1 and intermediate relay 2 can both receive the U2N relay broadcast announcement message). The announcement message includes RSC, first hop count, and U2N relay user information ID.

[0484] Optionally, the notification message is protected by the RSC (relay service code) and discovery security material associated with the HPLMN ID of the U2N relay.

[0485] Optionally, the notification message may also include the PLMN ID in plaintext (e.g., the HPLMN ID of a U2N relay).

[0486] Optionally, relay device 1 can receive a U2N relay broadcast announcement message (411a). Relay device 2 can also receive a U2N relay broadcast announcement message (411b).

[0487] Step 412, the intermediate relay (intermediate relay 1 or intermediate relay 2) performs security verification on the notification message by using discovery security material associated with the PLMN ID and RSC of the U2N relay.

[0488] If the security verification of the notification message passes, the first hop count in the notification message is incremented by one to obtain the third hop count; if the third hop count is less than the first hop count threshold (the Hop-Limit value), then Rule 1 is applied to verify the notification message.

[0489] Principle 1: ① The new RSC or user information of the new U2N trunk in the notification message is not stored in the information entry of the intermediate trunk (i.e., the first information entry including the RSC is not stored in the information list stored by the first trunk device, or the second information entry including the identification information of the second trunk device is not stored). Alternatively, ② The RSC and user information of the U2N trunk in the notification message are stored in the information entry of the intermediate trunk, and the third hop count is less than the hop count stored by the intermediate trunk (i.e., the third information entry including the RSC and the identification information of the second trunk device is stored in the information list stored by the first trunk device, and the third hop count is less than the hop count in the third information entry).

[0490] Optionally, if the intermediate relay determines that the announcement message satisfies principle 1, then it is further determined whether a link exists between the intermediate relay and its parent relay (e.g., a U2N relay or other intermediate relay). If the intermediate relay determines that the announcement message does not satisfy principle 1, then the announcement message is ignored.

[0491] Optionally, if there is a link between the intermediate relay and its parent relay, the intermediate relay determines to broadcast a further announcement message and determines to update the stored information entries.

[0492] Optionally, if no link exists between an intermediate relay and its parent relay, the intermediate relay initiates a link establishment process (i.e., sends a link establishment request to its parent relay). Only after a link is established between the intermediate relay and its parent relay can the intermediate relay further broadcast announcement messages and update stored information entries. In other words, if a link cannot be established between the intermediate relay and its parent relay (e.g., link establishment between the intermediate relay and its parent relay fails), the intermediate relay ignores the announcement message.

[0493] Optionally, the link establishment process can be a direct communication establishment process or a U2N communication establishment process, and this disclosure does not limit this.

[0494] Optionally, relay device 1 can verify the announcement message and determine whether a connection has been established between relay device 1 and the U2N relay (412a). Relay device 2 can also verify the announcement message and determine whether a connection has been established between relay device 2 and the U2N relay (412b).

[0495] Step 413: The intermediate relay updates the stored information entries.

[0496] Optionally, the information entries stored in the intermediate relay may include RSC, user information of the U2N relay, user information of the parent relay of the intermediate relay (optional), hop count, Layer-2 ID of peer UE (i.e., Layer-2 ID of the parent relay of the intermediate relay), and link identifier (optional).

[0497] Optionally, when there is a link between an intermediate relay and its parent relay, the information entries stored in the intermediate relay include a link identifier, that is, the identification information of the link between the intermediate relay and its parent relay; when there is no link between the intermediate relay and its parent relay, the information entries stored in the intermediate relay do not include a link identifier, that is, they do not include the identification message of the link between the intermediate relay and its parent relay.

[0498] Optionally, if the link between the intermediate relay and its parent relay is released, the intermediate relay deletes the information entry corresponding to the link's identification information.

[0499] Optionally, relay device 1 can update the stored information entry (413a). Relay device 2 can also update the stored information entry (413b).

[0500] Step 414: The intermediate relay further broadcasts an announcement message (i.e., a second announcement message). For example, the intermediate relay may broadcast the announcement message to nearby UEs that support the proximity service function. For instance, the intermediate relay may broadcast the announcement message to a remote UE, or the intermediate relay may broadcast the announcement message to nearby intermediate relays.

[0501] Optionally, the notification messages further broadcast by the intermediate relay are protected by the discovery security material associated with the RSC and the intermediate relay's HPLMN ID.

[0502] Optionally, the announcement message further broadcast by the intermediate relay may include RSC, the second hop count, user information of the U2N relay, and user information of the intermediate relay. The second hop count is the hop count obtained by incrementing the first hop count by one.

[0503] Optionally, the announcement message further broadcast by the intermediate relay may also include the PLMN ID in plaintext (e.g., the HPLMN ID of the intermediate relay).

[0504] Optionally, in the above example, the remote UE can receive announcement messages sent by intermediate relays with different hop numbers (for example, the remote UE can receive announcement messages broadcast by intermediate relay 1 or intermediate relay 2).

[0505] Optionally, the remote UE can select one of the intermediate relays for subsequent communication after verifying the received notification message.

[0506] (ii) Referring to Figure 4b, when using verification method two to verify the messages transmitted between the remote UE and the U2N relay, the specific message transmission process may include the following steps:

[0507] Optionally, in Figure 4b, the U2N relay has acquired discovery security materials (also referred to as discovery security parameters, which are not limited in this embodiment) associated with the RSC and the HPLMN ID of the U2N relay. The intermediate relay has acquired discovery security materials associated with the RSC and the HPLMN of the intermediate relay, as well as multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay or the RSC and the HPLMN of the potential intermediate relay. The remote UE has acquired multiple sets of discovery security materials associated with the RSC and the HPLMN of the potential U2N relay or the RSC and the HPLMN of the potential intermediate relay.

[0508] Optionally, relay device 1 can receive a U2N relay broadcast announcement message (421a). Relay device 2 can also receive a U2N relay broadcast announcement message (421b).

[0509] Step 421: U2N relay broadcast announcement message (i.e., the first announcement message) (for example, intermediate relay 1 and intermediate relay 2 can both receive the U2N relay broadcast announcement message). The announcement message includes RSC, the first hop count, and the user information ID of the U2N relay.

[0510] Optionally, the notification message is protected by the RSC (relay service code) and discovery security material associated with the HPLMN ID of the U2N relay.

[0511] Optionally, the notification message may also include the PLMN ID in plaintext (e.g., the HPLMN ID of a U2N trunk (Home PLMN, Public Land Mobile Network)).

[0512] Optionally, relay device 1 can verify the announcement message and determine whether a connection has been established between relay device 1 and the U2N relay (422a). Relay device 2 can also verify the announcement message and determine whether a connection has been established between relay device 2 and the U2N relay (422b).

[0513] Step 422, the intermediate relay (intermediate relay 1 or intermediate relay 2) performs security verification on the notification message by using discovery security material associated with the PLMN ID and RSC of the U2N relay.

[0514] If the security verification of the notification message passes, the first hop number in the notification message is incremented by one to obtain the third hop number; if the third hop number is less than the first hop number threshold (the Hop-Limit value), it is further determined whether there is a link between the intermediate relay and its parent relay (e.g., U2N relay or other intermediate relay).

[0515] Optionally, if there is a link between the intermediate relay and its parent relay, the intermediate relay determines to broadcast a further announcement message and determines to update the stored information entries.

[0516] Optionally, if no link exists between an intermediate relay and its parent relay, the intermediate relay initiates a link establishment process (i.e., sends a link establishment request to its parent relay). Only after a link is established between the intermediate relay and its parent relay can the intermediate relay further broadcast announcement messages and update stored information entries. In other words, if a link cannot be established between the intermediate relay and its parent relay (e.g., link establishment between the intermediate relay and its parent relay fails), the intermediate relay ignores the announcement message.

[0517] Optionally, the link establishment process can be a direct communication establishment process or a U2N communication establishment process, and this disclosure does not limit this.

[0518] Step 423: The intermediate relay further broadcasts an announcement message (i.e., a second announcement message). For example, the intermediate relay may broadcast the announcement message to its sub-relays, or the intermediate relay may broadcast the announcement message to the remote UE.

[0519] Optionally, the notification messages further broadcast by the intermediate relay are protected by the discovery security material associated with the RSC and the intermediate relay's HPLMN ID.

[0520] Optionally, the announcement message further broadcast by the intermediate relay may include an RSC, a second hop count, and additional information about the intermediate relay (e.g., user information of the intermediate relay). The second hop count is the hop count obtained by incrementing the first hop count by one.

[0521] Optionally, the announcement message further broadcast by the intermediate relay may also include the PLMN ID in plaintext (e.g., the HPLMN ID of the intermediate relay).

[0522] Optionally, in the above example, the remote UE can receive announcement messages sent by intermediate relays with different hop numbers (for example, the remote UE can receive announcement messages broadcast by intermediate relay 1 or intermediate relay 2).

[0523] Optionally, the remote UE can select one of the intermediate relays for subsequent communication after verifying the received notification message.

[0524] Figure 5 is a flowchart illustrating one of the communication methods according to an embodiment of the present disclosure.

[0525] As shown in Figure 5, the above method is performed by the first relay device, and the method includes:

[0526] Step 501: The first relay device receives a first notification message sent by the second relay device; wherein the first notification message includes: a first hop count and the identification information of the second relay device.

[0527] Step 502: The first relay device verifies the first notification message.

[0528] In this embodiment of the disclosure, the first relay device can verify the first notification message in two ways:

[0529] (Method 1)

[0530] Optionally, in this embodiment of the disclosure, in method one, verifying the first notification message includes:

[0531] The first notification message is securely verified based on the RSC and the PLMN ID of the second relay device;

[0532] Determine whether the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition; wherein, the third hop count is the hop count obtained by adding one to the first hop count.

[0533] Optionally, in this embodiment of the disclosure, if the first notification message passes security verification, and the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition, then the first notification message passes verification.

[0534] Optionally, in this embodiment of the disclosure, the step of performing security verification on the first notification message based on the RSC and the PLMN ID of the second relay device includes:

[0535] Among the discovery security materials acquired by the first relay device, the discovery security materials associated with the RSC and the PLMN ID of the second relay device are identified;

[0536] Based on the identified secure materials, the first notification message is subjected to security verification.

[0537] Optionally, in this embodiment of the disclosure, the first condition includes:

[0538] The third hop count is less than the first hop count threshold; and any of the following:

[0539] The information list stored by the first relay device does not store a first information entry including the RSC, or does not store a second information entry including the identification information of the second relay device, or does not store a sixth information entry including both the RSC and the identification information of the second relay device;

[0540] The information list stored in the first relay device contains a third information entry that includes the RSC and the identification information of the second relay device, and the third hop count is less than the hop count in the third information entry.

[0541] (Method 2)

[0542] Optionally, in this embodiment of the disclosure, in method two, verifying the first notification message includes:

[0543] The first notification message is securely verified based on the RSC and the PLMN ID of the second relay device;

[0544] Determine whether the third hop count satisfies the second condition.

[0545] Optionally, in this embodiment of the disclosure, if the first notification message passes security verification and the third hop count satisfies the second condition, then the first notification message passes verification.

[0546] Optionally, in this embodiment of the disclosure, the step of performing security verification on the first notification message based on the RSC and the PLMN ID of the second relay device includes:

[0547] Among the discovery security materials acquired by the first relay device, the discovery security materials associated with the RSC and the PLMN ID of the second relay device are identified;

[0548] Based on the identified secure materials, the first notification message is subjected to security verification.

[0549] Optionally, in this embodiment of the disclosure, the second condition includes: the third hop count is less than the second hop count threshold.

[0550] Step 503: The first relay device determines whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether there is a link between the first relay device and the second relay device.

[0551] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0552] Optionally, if the first relay device determines that the first announcement message has been successfully verified, it may further determine whether to broadcast the second announcement message or discard the first announcement message based on whether there is a link between the first relay device and the second relay device; if it determines that the first announcement message has not been successfully verified, it may discard the first announcement message.

[0553] Optionally, in this embodiment of the disclosure, if the first notification message is verified using method one, then if the first notification message passes the security verification, and the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition, then the first notification message passes the verification.

[0554] Optionally, in this embodiment of the disclosure, if the first notification message is verified using method two, then if the first notification message passes the security verification and the third hop count satisfies the second condition, then the first notification message passes the verification.

[0555] Optionally, the first relay device may refer to the following logic to determine whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether a link exists between the first relay device and the second relay device:

[0556] ① After verifying the first notification message using either method one or method two above and obtaining the verification result of the first notification message, if the verification result of the first notification message is that the first notification message has failed verification, proceed to ②; if the verification result of the first notification message is that the first notification message has passed verification, proceed to ③.

[0557] ② Discard the first announcement message;

[0558] ③ Determine whether a link already exists between the first and second relay devices corresponding to the RSC; if a link already exists between the first and second relay devices corresponding to the RSC, proceed to step ④; if no link exists between the first and second relay devices corresponding to the RSC, proceed to step ⑤.

[0559] ④ Broadcast the second announcement;

[0560] ⑤ Initiate a link establishment request to the second relay device (i.e., send a link establishment request to the second relay device), and receive a response message from the second relay device to the second relay device; wherein, if the response message indicates that the second relay device accepts the link establishment request (i.e., the first response message is the first response message), execute ⑥; if the response message indicates that the second relay device rejects the link establishment request (i.e., the first response message is the second response message), execute ②.

[0561] ⑥ During the link establishment process, the identity of the second relay device is verified; if the second relay device is successfully authenticated and returns a first response message, indicating that the link between the first and second relay devices has been successfully established, proceed to step ④; if the second relay device fails to authenticate or returns a second response message, indicating that the link between the first and second relay devices has failed to be established, proceed to step ②.

[0562] Referring to the above logic, the method for determining whether a second announcement message can be broadcast based on the verification result of the first announcement message and the link establishment result between the first relay device and the second relay device will be explained below:

[0563] Optionally, in this embodiment of the disclosure, determining whether to broadcast the second announcement message or discard the first announcement message based on the verification result and whether a link exists between the first relay device and the second relay device includes at least one of the following:

[0564] If the first notification message fails verification, then the first notification message is discarded.

[0565] If the first notification message is verified and a link exists between the first relay device and the second relay device, then it is determined that the second notification message will be broadcast.

[0566] If the first notification message passes verification and there is no link between the first relay device and the second relay device, then the first notification message is discarded.

[0567] Optionally, determining the existence of a link between the first relay device and the second relay device can include two methods: First, when the verification result of the first notification message is that the first notification message has passed verification, a link already exists between the first relay device and the second relay device; second, when the verification result of the first notification message is that the first notification message has passed verification, a link does not exist between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through a link establishment process. In this embodiment of the disclosure, either method can be considered as indicating the existence of a link between the first relay device and the second relay device.

[0568] In one example, when the verification result of the first notification message is that the first notification message has passed verification, there is no link between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through the link establishment process. The details are as follows:

[0569] Optionally, in this embodiment of the disclosure, if a link exists between the first relay device and the second relay device, then determining to broadcast the second announcement message includes:

[0570] If there is no link between the first relay device and the second relay device, a link establishment request is sent to the second relay device.

[0571] Receive a first response message sent by the second relay device; wherein the first response message indicates that the second relay device accepts the link establishment request;

[0572] If a link is successfully established with the second relay device, the second announcement message is broadcast.

[0573] Optionally, in this embodiment of the disclosure, if there is no link between the first relay device and the second relay device, then determining to discard the first notification message includes:

[0574] Send a link establishment request to the second relay device;

[0575] If the second response information sent by the second relay device is received, it is determined that the first notification message should be discarded.

[0576] The second response information indicates that the second relay device rejects the link establishment request.

[0577] Optionally, in this embodiment of the disclosure, if method one is used to verify the first notification message, then after determining that the second notification message will be broadcast, the method further includes:

[0578] The third information entry is updated based on the third hop count; or,

[0579] Store the fourth information entry.

[0580] Optionally, when updating the third information entry based on the third hop count, the hop count stored in the third information entry can be directly updated to the third hop count.

[0581] As an example, suppose the third information entry includes RSC, the identification information of the second relay device, the link identifier between the first relay device and the second relay device, the eighth hop number, and the Layer 2 ID of the second relay device, and the eighth hop number is greater than the third hop number. When updating the third information entry based on the third hop number, the eighth hop number in the third information entry can be directly updated to the third hop number.

[0582] Optionally, when determining the storage of the fourth information entry, the fourth information entry associated with the third hop number can be stored in the information list stored by the first relay device.

[0583] Optionally, after storing the fourth information entry in the information list stored by the first relay device, the third information entry can also be deleted.

[0584] Optionally, when storing the fourth information entry in the information list stored by the first relay device, the content of the fourth information entry may include the following:

[0585] Optionally, in embodiments of this disclosure, the fourth information entry includes at least one of the following:

[0586] The RSC, the identification information of the second relay device, the third hop count, the layer 2 ID of the second relay device, and the identification information of the link between the first relay device and the second relay device.

[0587] Optionally, in this embodiment of the disclosure, the second notification message may also include the identification information of the second relay device.

[0588] Optionally, in this embodiment of the disclosure, if method one is used to verify the first notification message, the method further includes:

[0589] If the link between the first relay device and the second relay device is released, then the fifth information entry associated with the link information in the information list stored by the first relay device is deleted.

[0590] The fifth information entry is an information entry that includes the identification information of the RSC and the second relay device.

[0591] Step 504: When the first relay device determines that it is broadcasting the second announcement message, it broadcasts the second announcement message.

[0592] The communication method involved in the embodiments of this disclosure may include the foregoing steps and at least one of the embodiments. For example, step 501 may be implemented as an independent embodiment, step 502 may be implemented as an independent embodiment, step 503 may be implemented as an independent embodiment, and step 504 may be implemented as an independent embodiment; the combination of step 501 and step 502 may be implemented as an independent embodiment, the combination of step 501, step 502 and step 503 may be implemented as an independent embodiment, the combination of step 501 and step 502 may be implemented as an independent embodiment, and the combination of step 501, step 502, step 503 and step 504 may be implemented as an independent embodiment, but is not limited thereto.

[0593] In some embodiments, other optional implementations described before or after the specification corresponding to Figure 5 may be referred to.

[0594] Figure 6a is a second schematic flowchart illustrating a communication method according to an embodiment of the present disclosure.

[0595] As shown in Figure 6a, the above method is performed by the first relay device, and the method includes:

[0596] Step 6101: The first relay device receives a first notification message sent by the second relay device; wherein the first notification message includes: a first hop count and the identification information of the second relay device.

[0597] Step 6102: The first relay device performs security verification on the first notification message based on the RSC and the PLMN ID of the second relay device;

[0598] Determine whether the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition; wherein, the third hop count is the hop count obtained by adding one to the first hop count.

[0599] Optionally, in this embodiment of the disclosure, the step of performing security verification on the first notification message based on the RSC and the PLMN ID of the second relay device includes:

[0600] Among the discovery security materials acquired by the first relay device, the discovery security materials associated with the RSC and the PLMN ID of the second relay device are identified;

[0601] Based on the identified secure materials, the first notification message is subjected to security verification.

[0602] Optionally, in this embodiment of the disclosure, the first condition includes:

[0603] The third hop count is less than the first hop count threshold; and any of the following:

[0604] The information list stored by the first relay device does not store a first information entry including the RSC, or does not store a second information entry including the identification information of the second relay device, or does not store a sixth information entry including both the RSC and the identification information of the second relay device;

[0605] The information list stored in the first relay device contains a third information entry that includes the RSC and the identification information of the second relay device, and the third hop count is less than the hop count in the third information entry.

[0606] Step 6103: The first relay device determines whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether there is a link between the first relay device and the second relay device.

[0607] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0608] Optionally, if the first relay device determines that the first announcement message has been successfully verified, it may further determine whether to broadcast the second announcement message or discard the first announcement message based on whether there is a link between the first relay device and the second relay device; if it determines that the first announcement message has not been successfully verified, it may discard the first announcement message.

[0609] Optionally, in this embodiment of the disclosure, if the first notification message passes security verification, and the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition, then the first notification message passes verification.

[0610] Optionally, the first relay device may refer to the following logic to determine whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether a link exists between the first relay device and the second relay device:

[0611] ① After verifying the first announcement message using the above method (i.e., performing security verification on the first announcement message based on the RSC and the PLMN ID of the second relay device; determining whether the RSC, the identification information of the second relay device, and the third hop count meet the first condition), and obtaining the verification result of the first announcement message, if the verification result of the first announcement message is that the first announcement message fails verification, proceed to ②; if the verification result of the first announcement message is that the first announcement message passes verification, proceed to ③.

[0612] ② Discard the first announcement message;

[0613] ③ Determine whether a link already exists between the first and second relay devices corresponding to the RSC; if a link already exists between the first and second relay devices corresponding to the RSC, proceed to step ④; if no link exists between the first and second relay devices corresponding to the RSC, proceed to step ⑤.

[0614] ④ Broadcast the second announcement;

[0615] ⑤ Initiate a link establishment request to the second relay device (i.e., send a link establishment request to the second relay device), and receive a response message from the second relay device to the second relay device; wherein, if the response message indicates that the second relay device accepts the link establishment request (i.e., the first response message is the first response message), execute ⑥; if the response message indicates that the second relay device rejects the link establishment request (i.e., the first response message is the second response message), execute ②.

[0616] ⑥ During the link establishment process, the identity of the second relay device is verified; if the second relay device is successfully authenticated and returns a first response message, indicating that the link between the first and second relay devices has been successfully established, proceed to step ④; if the second relay device fails to authenticate or returns a second response message, indicating that the link between the first and second relay devices has failed to be established, proceed to step ②.

[0617] Referring to the above logic, the method for determining whether a second announcement message can be broadcast based on the verification result of the first announcement message and the link establishment result between the first relay device and the second relay device will be explained below:

[0618] Optionally, in this embodiment of the disclosure, determining whether to broadcast the second announcement message or discard the first announcement message based on the verification result and whether a link exists between the first relay device and the second relay device includes at least one of the following:

[0619] If the first notification message fails verification, then the first notification message is discarded.

[0620] If the first notification message is verified and a link exists between the first relay device and the second relay device, then it is determined that the second notification message will be broadcast.

[0621] If the first notification message passes verification and there is no link between the first relay device and the second relay device, then the first notification message is discarded.

[0622] Optionally, determining the existence of a link between the first relay device and the second relay device can include two methods: First, when the verification result of the first notification message is that the first notification message has passed verification, a link already exists between the first relay device and the second relay device; second, when the verification result of the first notification message is that the first notification message has passed verification, a link does not exist between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through a link establishment process. In this embodiment of the disclosure, either method can be considered as indicating the existence of a link between the first relay device and the second relay device.

[0623] In one example, when the verification result of the first notification message is that the first notification message has passed verification, there is no link between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through the link establishment process. The details are as follows:

[0624] Optionally, in this embodiment of the disclosure, if a link exists between the first relay device and the second relay device, then determining to broadcast the second announcement message includes:

[0625] If there is no link between the first relay device and the second relay device, a link establishment request is sent to the second relay device.

[0626] Receive a first response message sent by the second relay device; wherein the first response message indicates that the second relay device accepts the link establishment request;

[0627] If a link is successfully established with the second relay device, the second announcement message is broadcast.

[0628] Optionally, in this embodiment of the disclosure, if there is no link between the first relay device and the second relay device, then determining to discard the first notification message includes:

[0629] Send a link establishment request to the second relay device;

[0630] If the second response information sent by the second relay device is received, it is determined that the first notification message should be discarded.

[0631] The second response information indicates that the second relay device rejects the link establishment request.

[0632] Step 6104: After the first relay device determines that the second announcement message has been broadcast, it updates the third information entry according to the third hop count; or,

[0633] Store the fourth information entry.

[0634] Optionally, in this embodiment of the disclosure, the second notification message may also include the identification information of the second relay device.

[0635] Optionally, in embodiments of this disclosure, the method further includes:

[0636] If the link between the first relay device and the second relay device is released, then the fifth information entry associated with the link information in the information list stored by the first relay device is deleted.

[0637] The fifth information entry is an information entry that includes the identification information of the RSC and the second relay device.

[0638] Step 6105: When the first relay device determines that it is broadcasting the second announcement message, it broadcasts the second announcement message.

[0639] The communication method involved in the embodiments of this disclosure may include the foregoing steps and at least one of the embodiments. For example, step 6101 may be implemented as an independent embodiment, step 6102 may be implemented as an independent embodiment, step 6103 may be implemented as an independent embodiment, step 6104 may be implemented as an independent embodiment, and step 6105 may be implemented as an independent embodiment; the combination of step 6101 and step 6102 may be implemented as an independent embodiment, the combination of step 6101, step 6102 and step 6103 may be implemented as an independent embodiment, the combination of step 6101, step 6102, step 6103 and step 6104 may be implemented as an independent embodiment, and the combination of step 6101, step 6102, step 6103 and step 6104 may be implemented as an independent embodiment, but is not limited thereto.

[0640] In some embodiments, other alternative implementations may be described before or after the specification corresponding to FIG6a.

[0641] Figure 6b is a third schematic flowchart illustrating a communication method according to an embodiment of the present disclosure.

[0642] As shown in Figure 6b, the above method is performed by the first relay device and includes:

[0643] Step 6201: The first relay device receives a first notification message sent by the second relay device; wherein the first notification message includes: a first hop count and the identification information of the second relay device.

[0644] Step 6202: The first relay device performs security verification on the first notification message based on the RSC and the PLMN ID of the second relay device;

[0645] Determine whether the third hop count satisfies the second condition.

[0646] Optionally, in this embodiment of the disclosure, the step of performing security verification on the first notification message based on the RSC and the PLMN ID of the second relay device includes:

[0647] Among the discovery security materials acquired by the first relay device, the discovery security materials associated with the RSC and the PLMN ID of the second relay device are identified;

[0648] Based on the identified secure materials, the first notification message is subjected to security verification.

[0649] Optionally, in this embodiment of the disclosure, the second condition includes: the third hop count is less than the second hop count threshold.

[0650] Step 6203: The first relay device determines whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether there is a link between the first relay device and the second relay device.

[0651] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0652] Optionally, the first relay device may refer to the following logic to determine whether to broadcast the second announcement message or discard the first announcement message based on the verification result of the first announcement message and whether a link exists between the first relay device and the second relay device:

[0653] ① After verifying the first announcement message using the above method (i.e., performing security verification on the first announcement message based on the RSC and the PLMN ID of the second relay device; determining whether the third hop count meets the second condition) and obtaining the verification result of the first announcement message, if the verification result of the first announcement message is that the first announcement message fails verification, proceed to ②; if the verification result of the first announcement message is that the first announcement message passes verification, proceed to ③.

[0654] ② Discard the first announcement message;

[0655] ③ Determine whether a link already exists between the first and second relay devices corresponding to the RSC; if a link already exists between the first and second relay devices corresponding to the RSC, proceed to step ④; if no link exists between the first and second relay devices corresponding to the RSC, proceed to step ⑤.

[0656] ④ Broadcast the second announcement;

[0657] ⑤ Initiate a link establishment request to the second relay device (i.e., send a link establishment request to the second relay device), and receive a response message from the second relay device to the second relay device; wherein, if the response message indicates that the second relay device accepts the link establishment request (i.e., the first response message is the first response message), execute ⑥; if the response message indicates that the second relay device rejects the link establishment request (i.e., the first response message is the second response message), execute ②.

[0658] ⑥ During the link establishment process, the identity of the second relay device is verified; if the second relay device is successfully authenticated and returns a first response message, indicating that the link between the first and second relay devices has been successfully established, proceed to step ④; if the second relay device fails to authenticate or returns a second response message, indicating that the link between the first and second relay devices has failed to be established, proceed to step ②.

[0659] Referring to the above logic, the method for determining whether a second announcement message can be broadcast based on the verification result of the first announcement message and the link establishment result between the first relay device and the second relay device will be explained below:

[0660] Optionally, in this embodiment of the disclosure, determining whether to broadcast the second announcement message or discard the first announcement message based on the verification result and whether a link exists between the first relay device and the second relay device includes at least one of the following:

[0661] If the first notification message fails verification, then the first notification message is discarded.

[0662] If the first notification message is verified and a link exists between the first relay device and the second relay device, then it is determined that the second notification message will be broadcast.

[0663] If the first notification message passes verification and there is no link between the first relay device and the second relay device, then the first notification message is discarded.

[0664] Optionally, determining the existence of a link between the first relay device and the second relay device can include two methods: First, when the verification result of the first notification message is that the first notification message has passed verification, a link already exists between the first relay device and the second relay device; second, when the verification result of the first notification message is that the first notification message has passed verification, a link does not exist between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through a link establishment process. In this embodiment of the disclosure, either method can be considered as indicating the existence of a link between the first relay device and the second relay device.

[0665] In one example, when the verification result of the first notification message is that the first notification message has passed verification, there is no link between the first relay device and the second relay device, but a link can be successfully established between the first relay device and the second relay device through the link establishment process. The details are as follows:

[0666] Optionally, in this embodiment of the disclosure, if a link exists between the first relay device and the second relay device, then determining to broadcast the second announcement message includes:

[0667] If there is no link between the first relay device and the second relay device, a link establishment request is sent to the second relay device.

[0668] Receive a first response message sent by the second relay device; wherein the first response message indicates that the second relay device accepts the link establishment request;

[0669] If a link is successfully established with the second relay device, the second announcement message is broadcast.

[0670] Optionally, in this embodiment of the disclosure, if there is no link between the first relay device and the second relay device, then determining to discard the first notification message includes:

[0671] Send a link establishment request to the second relay device;

[0672] If the second response information sent by the second relay device is received, it is determined that the first notification message should be discarded.

[0673] The second response information indicates that the second relay device rejects the link establishment request.

[0674] Step 6204: When the first relay device determines that it is broadcasting the second announcement message, it broadcasts the second announcement message.

[0675] The communication method involved in the embodiments of this disclosure may include the foregoing steps and at least one of the embodiments. For example, step 6201 may be implemented as an independent embodiment, step 6202 may be implemented as an independent embodiment, step 6203 may be implemented as an independent embodiment, and step 6204 may be implemented as an independent embodiment; the combination of step 6201 and step 6202 may be implemented as an independent embodiment, the combination of step 6201, step 6202 and step 6203 may be implemented as an independent embodiment, and the combination of step 6201, step 6202, step 6203 and step 6204 may be implemented as an independent embodiment, but is not limited thereto.

[0676] In some embodiments, other alternative implementations may be described before or after the specification corresponding to FIG6b.

[0677] Figure 7 is a fourth schematic flowchart illustrating a communication method according to an embodiment of the present disclosure.

[0678] As shown in Figure 7, the above method is executed by the second relay device and includes:

[0679] Step 701: The second relay device sends a first notification message to the first relay device; wherein the first notification message includes: a first hop count and the identification information of the second relay device.

[0680] Step 702: The second relay device receives the link establishment request sent by the first relay device.

[0681] Step 703: The second relay device sends a response message to the first relay device in response to the link establishment request.

[0682] Optionally, the second relay device sends a first response message to the first relay device; wherein the first response message indicates that the second relay device accepts the link establishment request; or,

[0683] The second relay device sends a second response message to the first relay device; wherein the second response message indicates that the second relay device rejects the link establishment request.

[0684] Optionally, if the second relay device accepts the link establishment request, that is, if the second relay device agrees to establish a link with the first relay device, the second relay device may send a first response message to the first relay device, instructing the second relay device to accept the link establishment request through the first response message.

[0685] Optionally, if the second relay device rejects the link establishment request, that is, if the second relay device does not agree to establish a link with the first relay device, the second relay device may send a second response message to the first relay device, instructing the second relay device to reject the link establishment request.

[0686] The communication method involved in the embodiments of this disclosure may include the foregoing steps and at least one of the embodiments. For example, step 701 may be implemented as an independent embodiment, step 702 may be implemented as an independent embodiment, and step 703 may be implemented as an independent embodiment; the combination of step 701 and step 702 may be implemented as an independent embodiment, the combination of step 702 and step 703 may be implemented as an independent embodiment, and the combination of step 701, step 702 and step 703 may be implemented as an independent embodiment, but is not limited thereto.

[0687] In some embodiments, other optional implementations described before or after the specification corresponding to FIG7 may be referred to.

[0688] Figure 8 is a fifth schematic flowchart illustrating a communication method according to an embodiment of the present disclosure.

[0689] As shown in Figure 8, the above method is executed by a remote terminal and includes:

[0690] Step 801: The remote terminal receives the second announcement message broadcast by the first relay device;

[0691] Wherein, the second notification message is sent by the first relay device when the first notification message is verified and a link exists between the first relay device and the second relay device; the first notification message is sent by the second relay device;

[0692] The first notification message includes: the first hop count and the identification information of the second relay device;

[0693] The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0694] This disclosure also provides an apparatus for implementing any of the above methods. For example, an apparatus is provided that includes units or modules for implementing the steps performed by the terminal in any of the above methods. Alternatively, another apparatus is provided that includes units or modules for implementing the steps performed by a network device (e.g., an access network device, a core network functional node, a core network device, etc.) in any of the above methods.

[0695] It should be understood that the division of units or modules in the above device is only a logical functional division. In actual implementation, they can be fully or partially integrated into a single physical entity, or they can be physically separated. Furthermore, the units or modules in the device can be implemented by a processor calling software: for example, the device includes a processor connected to a memory containing instructions. The processor calls the instructions stored in the memory to implement any of the above methods or to implement the functions of the units or modules in the above device. The processor can be, for example, a general-purpose processor, such as a Central Processing Unit (CPU) or a microprocessor, and the memory can be internal or external to the device. Alternatively, the units or modules in the device can be implemented in the form of hardware circuits. The functionality of some or all of the units or modules can be achieved through the design of these hardware circuits, which can be understood as one or more processors. For example, in one implementation, the hardware circuit is an application-specific integrated circuit (ASIC). The functionality of some or all of the units or modules is achieved through the design of the logical relationships between the components within the circuit. In another implementation, the hardware circuit can be implemented using a programmable logic device (PLD). Taking a field-programmable gate array (FPGA) as an example, it can include a large number of logic gates. The connection relationships between the logic gates are configured through configuration files, thereby achieving the functionality of some or all of the units or modules. All units or modules of the above device can be implemented entirely through processor-called software, entirely through hardware circuits, or partially through processor-called software with the remaining parts implemented through hardware circuits.

[0696] In this embodiment, the processor is a circuit with signal processing capabilities. In one implementation, the processor can be a circuit with instruction read and execute capabilities, such as a Central Processing Unit (CPU), a microprocessor, a graphics processing unit (GPU) (which can be understood as a microprocessor), or a digital signal processor (DSP). In another implementation, the processor can implement certain functions through the logical relationships of hardware circuits. The logical relationships of the aforementioned hardware circuits are fixed or reconfigurable. For example, the processor is a hardware circuit implemented using an application-specific integrated circuit (ASIC) or a programmable logic device (PLD), such as an FPGA. In a reconfigurable hardware circuit, the process of the processor loading a configuration document and configuring the hardware circuit can be understood as the process of the processor loading instructions to implement the functions of some or all of the above units or modules. Furthermore, it can also be a hardware circuit designed for artificial intelligence, which can be understood as an ASIC, such as a Neural Network Processing Unit (NPU), a Tensor Processing Unit (TPU), or a Deep Learning Processing Unit (DPU).

[0697] Figure 9 is a schematic diagram of the structure of the first relay device proposed in an embodiment of this disclosure. As shown in Figure 9, the first relay device 900 may include at least one of a first receiving module 901, a processing module 902, etc.

[0698] In some embodiments, the first receiving module 901 is configured to receive a first notification message sent by the second relay device; wherein the first notification message includes: a first hop count and identification information of the second relay device; the processing module 902 is configured to verify the first notification message; and, based on the verification result and whether a link exists between the first relay device and the second relay device, determine whether to broadcast a second notification message or discard the first notification message; wherein the second notification message includes: a second hop count and / or identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0699] Optionally, the first receiving module 901 is used to execute at least one of the transmit / receive steps (e.g., steps 201, 204, 3101, 3105, 3201, 3204, 501, 504, 6101, 6105, 6201, 6204, but not limited thereto) performed by the first relay device in any of the above methods, which will not be elaborated here. The first receiving module 901 is also used to execute the communication steps (e.g., steps 202, 203, 3102, 3103, 3104, 3202, 3203, 502, 503, 6102, 6106, 6104, 6202, 6206, but not limited thereto) performed by the first relay device in any of the above methods.

[0700] Figure 10 is a schematic diagram of the structure of the second relay device proposed in an embodiment of this disclosure. As shown in Figure 10, the second relay device 1000 may include: a transmitting module 1001.

[0701] In some embodiments, the sending module 1001 is configured to send a first notification message to the first relay device; wherein the first notification message includes: a first hop count and identification information of the second relay device.

[0702] Optionally, the above-mentioned sending module 1001 is used to execute at least one of the sending and receiving steps (such as steps 201, 3101, 701, 702, and 703, but not limited thereto) executed by the second relay device 102 in any of the above methods, which will not be described in detail here.

[0703] Figure 11 is a schematic diagram of the structure of a remote terminal according to an embodiment of this disclosure. As shown in Figure 11, the remote terminal 1100 may include: a second receiving module 1101.

[0704] In some embodiments, the second receiving module 1101 described above is used to receive a second announcement message broadcast by the first relay device;

[0705] Wherein, the second notification message is sent by the first relay device when the first notification message is verified and a link exists between the first relay device and the second relay device; the first notification message is sent by the second relay device; the first notification message includes: a first hop count and the identification information of the second relay device; the second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

[0706] Optionally, the second receiving module 1101 is used to execute at least one of the communication steps (e.g., steps 204, 3105, 3204, and 801, but not limited thereto) performed by the remote terminal in any of the above methods, which will not be described in detail here.

[0707] Figure 12 is a schematic diagram of the structure of a terminal 1200 (e.g., a user equipment) proposed in an embodiment of this disclosure. The terminal 1200 may be a chip, chip system, or processor that supports network devices in implementing any of the above methods, or it may be a chip, chip system, or processor that supports a terminal in implementing any of the above methods. The terminal 1200 can be used to implement the methods described in the above method embodiments; for details, please refer to the descriptions in the above method embodiments.

[0708] As shown in Figure 12, terminal 1200 includes one or more processors 1201. Processor 1201 can be a general-purpose processor or a dedicated processor, such as a baseband processor or a central processing unit (CPU). The baseband processor can be used to process communication protocols and communication data, while the CPU can be used to control communication devices (e.g., base stations, baseband chips, terminal devices, terminal device chips, DUs or CUs, etc.), execute programs, and process program data. Terminal 1200 is used to execute any of the above methods.

[0709] In some embodiments, terminal 1200 further includes one or more memories 1202 for storing instructions. Optionally, all or part of the memories 1202 may also be located outside of terminal 1200.

[0710] In some embodiments, terminal 1200 further includes one or more transceivers 1204. When the terminal 1200 includes one or more transceivers 1204, the transceiver 1204 performs at least one of the communication steps such as sending and / or receiving in the above method (e.g., steps 201, 204, 3101, 3105, 3201, 3204, 501, 504, 6101, 6105, 6201, 6204, 701, 702, 703, 801, but not limited thereto), and the processor 1201 performs at least one of other steps (e.g., steps 202, 203, 3102, 3103, 3104, 3202, 3203, 502, 503, 6102, 6106, 6104, 6202, 6206, but not limited thereto).

[0711] In some embodiments, a transceiver may include a receiver and / or a transmitter, which may be separate or integrated. Optionally, the terms transceiver, transceiver unit, transceiver, transceiver circuit, etc., may be used interchangeably; the terms transmitter, transmitting unit, transmitter, transmitting circuit, etc., may be used interchangeably; and the terms receiver, receiving unit, receiver, receiving circuit, etc., may be used interchangeably.

[0712] In some embodiments, terminal 1200 may include one or more interface circuits 1203. Optionally, interface circuit 1203 is connected to memory 1202, and interface circuit 1203 can be used to receive signals from memory 1202 or other devices, and can be used to send signals to memory 1202 or other devices. For example, interface circuit 1203 can read instructions stored in memory 1202 and send the instructions to processor 1201.

[0713] The terminal 1200 described in the above embodiments can be a user equipment or other communication device, but the scope of the terminal 1200 described in this disclosure is not limited thereto, and the structure of the terminal 1200 may not be limited by FIG12. The communication device may be an independent device or a part of a larger device. For example, the communication device may be: (1) an independent integrated circuit IC, or chip, or chip system or subsystem; (2) a set of one or more ICs, optionally, the IC set may also include storage components for storing data and programs; (3) an ASIC, such as a modem; (4) a module that can be embedded in other devices; (5) a receiver, terminal device, smart terminal device, cellular phone, wireless device, handheld device, mobile unit, vehicle device, network device, cloud device, artificial intelligence device, etc.; (6) others, etc.

[0714] Figure 13 is a schematic diagram of the structure of the chip 1300 proposed in an embodiment of this disclosure. For cases where the terminal 1200 can be a chip or a chip system, please refer to the schematic diagram of the chip 1300 shown in Figure 13, but it is not limited thereto.

[0715] Chip 1300 includes one or more processors 1301, which are used to perform any of the above methods.

[0716] In some embodiments, chip 1300 further includes one or more 1303s. Optionally, interface circuitry 1303 is connected to memory 1302, and interface circuitry 1303 can be used to receive signals from memory 1302 or other devices, and interface circuitry 1303 can be used to send signals to memory 1302 or other devices. For example, interface circuitry 1303 can read instructions stored in memory 1302 and send the instructions to processor 1301.

[0717] In some embodiments, the interface circuit 1303 performs at least one of the communication steps such as sending and / or receiving in the above method (e.g., steps 201, 204, 3101, 3105, 3201, 3204, 501, 504, 6101, 6105, 6201, 6204, 701, 702, 703, 801, but not limited thereto), and the processor 1301 performs at least one of other steps (e.g., steps 202, 203, 3102, 3103, 3104, 3202, 3203, 502, 503, 6102, 6106, 6104, 6202, 6206, but not limited thereto).

[0718] In some embodiments, the terms interface circuit, interface, transceiver pin, transceiver, etc., can be used interchangeably.

[0719] In some embodiments, chip 1300 further includes one or more memories 1302 for storing instructions. Optionally, all or part of the memories 1302 may be located outside of chip 1300.

[0720] This disclosure also proposes a storage medium storing instructions that, when executed on terminal 1200, cause terminal 1200 to perform any of the above methods. Optionally, the storage medium is an electronic storage medium. Optionally, the storage medium is a computer-readable storage medium, but not limited thereto; it may also be a storage medium readable by other devices. Optionally, the storage medium may be a non-transitory storage medium, but not limited thereto; it may also be a temporary storage medium.

[0721] This disclosure also proposes a program product that, when executed by terminal 1200, causes terminal 1200 to perform any of the above methods. Optionally, the program product is a computer program product.

[0722] This disclosure also proposes a computer program that, when run on a computer, causes the computer to perform any of the above methods.

Claims

1. A communication method, characterized in that, Performed by a first relay device, the method includes: Receive a first notification message sent by a second relay device; wherein the first notification message includes: a first hop count and identification information of the second relay device; Verify the first notification message; Based on the verification results and whether there is a link between the first relay device and the second relay device, determine whether to broadcast the second announcement message or discard the first announcement message; The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

2. The communication method according to claim 1, characterized in that, The step of determining whether to broadcast the second announcement message or discard the first announcement message based on the verification result and whether a link exists between the first relay device and the second relay device includes at least one of the following: If the first notification message fails verification, then the first notification message is discarded. If the first notification message is verified and a link exists between the first relay device and the second relay device, then it is determined that the second notification message will be broadcast. If the first notification message passes verification and there is no link between the first relay device and the second relay device, then the first notification message is discarded.

3. The communication method according to claim 2, characterized in that, If a link exists between the first relay device and the second relay device, then it is determined that the second announcement message will be broadcast, including: If there is no link between the first relay device and the second relay device, a link establishment request is sent to the second relay device. Receive a first response message sent by the second relay device; wherein the first response message indicates that the second relay device accepts the link establishment request; If a link is successfully established with the second relay device, the second announcement message is broadcast.

4. The communication method according to claim 2, characterized in that, If there is no link between the first relay device and the second relay device, then the first notification message is discarded, including: Send a link establishment request to the second relay device; If the second response information sent by the second relay device is received, it is determined that the first notification message should be discarded. The second response information indicates that the second relay device rejects the link establishment request.

5. The communication method according to any one of claims 2 to 4, characterized in that, The first notification message also includes the relay service code RSC and the public land mobile network (PLMN) ID of the second relay device. The verification of the first notification message includes: The first notification message is securely verified based on the RSC and the PLMNID of the second relay device; Determine whether the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition; wherein the third hop count is the hop count obtained by adding one to the first hop count.

6. The method according to claim 5, characterized in that, If the first notification message passes security verification, and the RSC, the identification information of the second relay device, and the third hop count satisfy the first condition, then the first notification message passes verification.

7. The method according to claim 5 or 6, characterized in that, The step of performing security verification on the first notification message based on the RSC and the PLMN ID of the second relay device includes: Among the discovery security materials acquired by the first relay device, the discovery security materials associated with the RSC and the PLMN ID of the second relay device are identified; Based on the identified secure materials, the first notification message is subjected to security verification.

8. The method according to any one of claims 5 to 7, characterized in that, The first condition includes: The third hop count is less than the first hop count threshold; and any of the following: The information list stored by the first relay device does not store a first information entry including the RSC, or does not store a second information entry including the identification information of the second relay device, or does not store a sixth information entry including both the RSC and the identification information of the second relay device; The information list stored in the first relay device contains a third information entry that includes the RSC and the identification information of the second relay device, and the third hop count is less than the hop count in the third information entry.

9. The method according to any one of claims 5 to 8, characterized in that, After determining the broadcast second announcement message, the method further includes: The third information entry is updated based on the third hop count; or, Store the fourth information entry.

10. The method according to claim 9, characterized in that, The fourth information entry includes at least one of the following: The RSC, the identification information of the second relay device, the third hop count, the layer 2 ID of the second relay device, and the identification information of the link between the first relay device and the second relay device.

11. The method according to any one of claims 5 to 10, characterized in that, The second notification message also includes the identification information of the second relay device.

12. The communication method according to claims 1 to 11, characterized in that, The method further includes: If the link between the first relay device and the second relay device is released, then the fifth information entry associated with the link information in the information list stored by the first relay device is deleted. The fifth information entry is an information entry that includes the identification information of the RSC and the second relay device.

13. The communication method according to any one of claims 2 to 4, characterized in that, The first notification message also includes the relay service code RSC and the Public Land Mobile Network Identifier (PLMNID) of the second relay device. The verification of the first notification message includes: The first notification message is securely verified based on the RSC and the PLMNID of the second relay device; Determine whether the third hop count satisfies the second condition; wherein the third hop count is the hop count obtained by adding one to the first hop count.

14. The communication method according to claim 13, characterized in that, If the first notification message passes security verification and the third hop count satisfies the second condition, then the first notification message passes verification.

15. The communication method according to claim 13 or 14, characterized in that, The second condition includes: the third hop count is less than the second hop count threshold.

16. A communication method, characterized in that, Performed by a second relay device, the method includes: Send the first notification message to the first relay device; The first notification message includes: the first hop count and the identification information of the second relay device.

17. The communication method according to claim 16, characterized in that, The method further includes: Receive the link establishment request sent by the first relay device.

18. The communication method according to claim 17, characterized in that, The method further includes: Send a first response message to the first relay device; wherein the first response message indicates that the second relay device accepts the link establishment request; or, Send a second response message to the first relay device; wherein the second response message indicates that the second relay device rejects the link establishment request.

19. A communication method, characterized in that, The method, executed by a remote terminal, includes: Receive the second announcement message broadcast by the first relay device; Wherein, the second notification message is sent by the first relay device when the first notification message is verified and a link exists between the first relay device and the second relay device; the first notification message is sent by the second relay device; The first notification message includes: the first hop count and the identification information of the second relay device; The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

20. A relay device, characterized in that, The relay equipment includes a first relay equipment, comprising: The first receiving module is configured to receive a first notification message sent by the second relay device; wherein the first notification message includes: a first hop count and identification information of the second relay device; The processing module is used to verify the first announcement message; and, based on the verification result and whether there is a link between the first relay device and the second relay device, determine whether to broadcast the second announcement message or discard the first announcement message. The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

21. A relay device, characterized in that, The relay equipment includes a second relay equipment, comprising: The sending module is used to send a first notification message to the first relay device; The first notification message includes: the first hop count and the identification information of the second relay device.

22. A remote terminal, characterized in that, include: The second receiving module is used to receive the second announcement message broadcast by the first relay device; Wherein, the second notification message is sent by the first relay device when the first notification message is verified and a link exists between the first relay device and the second relay device; the first notification message is sent by the second relay device; The first notification message includes: the first hop count and the identification information of the second relay device; The second notification message includes: a second hop count and / or the identification information of the first relay device; the second hop count is the hop count obtained by adding one to the first hop count.

23. A relay device, characterized in that, The relay equipment includes a first relay equipment, comprising: One or more processors; The first relay device is used to perform the communication method according to any one of claims 1 to 15.

24. A relay device, characterized in that, The relay equipment includes a second relay equipment, comprising: One or more processors; The second relay device is used to perform the communication method according to any one of claims 16 to 18.

25. A remote terminal, characterized in that, include: One or more processors; The second relay device is used to perform the communication method of claim 19.

26. A communication system, characterized in that, The device includes a first relay device, a second relay device, and a remote terminal; wherein the first relay device is configured to implement the communication method of any one of claims 1 to 15, the second relay device is configured to implement the communication method of any one of claims 16 to 18, and the remote terminal is configured to implement the communication method of claim 19.

27. A storage medium storing instructions, characterized in that, When the instruction is executed on the communication device, the communication device performs the communication method as described in any one of claims 1 to 15, or the communication method as described in any one of claims 16 to 18, or the communication method as described in claim 19.

28. A program product, characterized in that, When the program product is executed by a communication device, the communication device performs the communication method as described in any one of claims 1 to 15, or the communication method as described in any one of claims 16 to 18, or the communication method as described in claim 19.

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