Mechanism for falling back from a first random access mode to a second random access mode

Abstract

Embodiments of the present disclosure relate to a mechanism for a first random access mode to fall back to a second random access mode. According to an embodiment of the present disclosure, the fallback to the second random access mode is indicated in message B, and the user equipment only needs to monitor message B for the quick mode on the downlink control signal addressed to the identifier. For the second random access mode, the user equipment does not need to monitor the downlink control channel. In this way, the user equipment is allowed to fall back to the second random access mode without additional retries of the quick mode, thereby reducing overload and delay.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to the field of communications, and in particular to a method, device, apparatus, and computer-readable storage medium for falling back from a first random access mode to a second random access mode. Background Art

[0002] In recent communication networks, the Random Access Channel (RACH) is shared by terminal devices to request access to the network for call establishment and burst data transmission. Since the RACH is shared, there may be two or more terminal devices transmitting at the same time and their transmissions may conflict. This is called contention. If the user equipment does not get a response, it performs a random access request again. This transmission conflict may cause undesirable random access failures and unexpected delays in transmission. Summary of the invention

[0003] In general, embodiments of the present disclosure relate to a contention resolution method for a random access procedure and a corresponding communication device. According to some aspects, the subject matter of the independent claims is provided. Some further aspects are defined in the dependent claims.

[0004] In a first aspect, a device for communication is provided. The device includes at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured to, together with the at least one processor, cause the device to send a first request for a random access procedure in a first random access mode to another device. The device is also caused to monitor a response to the first request on a downlink control channel. The device is also caused to determine the first random access mode or the second random access mode for the random access procedure in response to receiving a response indicating that the first request failed. The user equipment is also caused to send a second request for a random access procedure in the determined random access mode to another device.

[0005] In a second aspect, an apparatus for communication is provided. The apparatus includes at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured to, together with the at least one processor, cause the apparatus to receive a first request for a random access procedure in a first random access mode from a user equipment. The network device is also caused to generate a response indicating failure in response to determining that the request failed. The response also includes information about determining the first random access mode or the second random access mode. The network device is also caused to send a response to the first request on a downlink control channel.

[0006] In a third aspect, a method implemented at a user equipment is provided. The method includes sending, at the user equipment, a first request for a random access procedure in a first random access mode to a network device. The method also includes monitoring a response to the first request on a downlink control channel. The method also includes determining, in response to receiving a response indicating that the first request failed, the first random access mode or the second random access mode for the random access procedure. The method also includes sending, to the network, a second request for a random access procedure in the determined random access mode.

[0007] In a fourth aspect, a method implemented at a network device is provided. The method includes receiving, at the network device, a request for a random access procedure in a first random access mode from a user equipment. The method also includes, in response to determining that the request failed, generating a response indicating failure. The response also includes information about determining the first random access mode or the second random access mode. The method also includes sending a response to the first request on a downlink control channel.

[0008] In a fifth aspect, a device is provided, comprising a component for sending a first request for a random access procedure in a first random access mode to a network device at a user device; a component for monitoring a response to the first request on a downlink control channel; a component for determining the first random access mode or the second random access mode for the random access procedure in response to receiving a response indicating that the first request failed; and a component for sending a second request for the random access procedure to the network device, the second request including a second preamble code for the selected RA mode.

[0009] In a sixth aspect, a device is provided, comprising a component for receiving, at a network device, a request for a random access procedure in a first random access mode from a user equipment; a component for generating a response indicating a failure in response to determining that the request failed, the response also comprising information about determining the first random access mode or the second random access mode; and a component for sending a response to the request on a downlink control channel.

[0010] In a seventh aspect, a non-transitory computer-readable medium is provided, the non-transitory computer-readable medium comprising program instructions for causing an apparatus to at least perform a method according to any one of the third and fourth aspects above.

[0011] It should be understood that the summary is not intended to identify the key or essential features of the embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0013] Figure 1 A schematic diagram showing a conventional four-step RACH process;

[0014] Figure 2 A schematic diagram showing a conventional two-step RACH process;

[0015] Figure 3 A schematic diagram of a media access control (MAC) protocol data unit (PDU) is shown;

[0016] Figure 4 A schematic diagram of a communication system according to an embodiment of the present disclosure is shown;

[0017] Figure 5 A schematic diagram showing interactions between devices according to an embodiment of the present disclosure;

[0018] Figure 6 A flow chart of a method implemented at a communication device according to an embodiment of the present disclosure is shown;

[0019] Figure 7 A flow chart of a method implemented at a communication device according to an embodiment of the present disclosure is shown;

[0020] Figure 8 A schematic diagram showing an apparatus according to an embodiment of the present disclosure; and

[0021] Fig. 9 A block diagram of an example computer-readable medium is shown in accordance with some embodiments of the present disclosure.

[0022] Throughout the drawings, the same or similar reference numerals refer to the same or similar elements. DETAILED DESCRIPTION

[0023] The principle of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described only for the purpose of illustrating and helping those skilled in the art to understand and realize the present disclosure, without any limitation to the scope of the present disclosure. The disclosure described herein can be realized in various other ways except as described below.

[0024] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0025] References in this disclosure to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment must include the particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is considered to be within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0026] It should be understood that although the terms "first" and "second" etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the exemplary embodiment, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0027] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments. As used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It will be further understood that the terms "comprise", "including", "having", "having", "including" and / or "comprising" when used herein specify the presence of the features, elements and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0028] As used in this application, the term "circuitry" may refer to one, more, or all of the following:

[0029] (a) pure hardware circuit implementation (such as implementation in analog and / or digital circuitry only), and

[0030] (b) a combination of hardware circuitry and software such as (where applicable):

[0031] (i) a combination of analog and / or digital hardware circuitry and software / firmware, and

[0032] (ii) any portion of a hardware processor (including a digital signal processor) with software, software and memory that work together to cause a device (such as a mobile phone or server) to perform various functions, and

[0033] (c) Hardware circuits and / or processors, such as a microprocessor or portion of a microprocessor, that require software (e.g., firmware) to operate, but which may not be present when not required for operation.

[0034] This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers (for example and if applicable to a particular claim element) a baseband integrated circuit or processor integrated circuit of a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0035] As used herein, the term "communication network" refers to a network that complies with any suitable communication standard, such as Long Term Evolution (LTE), Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), High Speed ​​Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), etc. In addition, the communication between the user equipment and the network equipment in the communication network can be performed according to any suitable generation communication protocol, including but not limited to the first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, future fifth generation (5G) communication protocol, and / or any other protocol currently known or developed in the future. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communication, of course, there will also be communication technologies and systems that can be used to embody future types of the present disclosure. The scope of the present disclosure should not be limited to the above-mentioned systems.

[0036] As used herein, the term "network device" refers to a node in a communication network via which a user equipment accesses the network and receives services therefrom. A network device may refer to a base station (BS) or an access point (AP), for example, a NodeB (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also known as a gNB), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, a low power node (such as a femto, a pico), etc., depending on the terminology and technology applied.

[0037] The term "terminal device" refers to any terminal device capable of wireless communication. As an example and not limitation, the terminal device may also be referred to as a communication device, a user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS) or an access terminal (AT). The terminal device may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a voice over IP (VoIP) phone, a wireless local loop phone, a tablet computer, a wearable terminal device, a personal digital assistant (PDA), a portable computer, a desktop computer, an image acquisition terminal device (such as a digital camera), a game terminal device, a music storage and playback device, a vehicle-mounted wireless terminal device, a wireless terminal, a mobile station, a laptop embedded device (LEE), a laptop mounted device (LME), a USB dongle, a smart device, a wireless client device (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head mounted display (HMD), a vehicle, a drone, medical equipment and applications (e.g., remote surgery), industrial equipment and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain environments), consumer electronic devices, equipment operating on commercial and / or industrial wireless networks, etc. In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

[0038] As mentioned above, several RACH mechanisms have been proposed. For example, a four-step RACH process has been proposed. Figure 1 As shown, for a four-step RACH procedure, a RACH transmission opportunity is defined as a time-frequency resource on which a PRACH message 1 is transmitted using a configured PRACH preamble format. A user equipment (UE) 110 may transmit 1010 a RACH preamble on a PRACH resource mapped to a RA-RNTI, and a network device may decode the preamble and obtain the RA-RNTI based on the PRACH resource on which the preamble is received. The gNB 120 may transmit 1020 a message 2, which may indicate a transmission resource for a message 3. Specifically, the gNB 120 may transmit a RA response, which is scheduled using a PDCCH addressed to a RA-RNTI calculated based on a PRACH resource (e.g., time and / or frequency allocation). The UE 110 may decode the RA response and obtain a transmission resource for the message 3. The UE 110 may transmit 1030 a radio resource control (RRC) connection request as the message 3 scrambled by the T-CRNTI obtained from the RA response (message 2). The gNB 120 may respond 1040 with the contention resolution ID (containing the UL CCCH SDU in msg3) in message 4 scrambled by the T-CRNTI obtained from the RA response (message 2), and the T-CRNTI is considered as C-RNTI by the UE upon receipt of message 4.

[0039] In recent studies, two-step RACH has also been proposed, such as Figure 2 As shown. UE 210 sends 2010 message A or msgA to gNB 220, and gNB 220 sends 2020 message B or msgB to UE 210. Compared to the traditional four-step RACH with preamble, RAR, message 3, and contention resolution message, two-step RACH combines the transmission of the preamble and message 3 payload into message A, and combines the RAR and contention resolution message into message B. For two-step RACH, message A is a signal for detecting UEs, while the second message is contention resolution for CBRA with possible payload. Message A will include at least the equivalent information transmitted in message 3 of the four-step RACH.

[0040] As a baseline, all triggers for four-step RACH also apply to two-step RACH; however, further analysis of the request and BFR and how to obtain the timing advance and grant for message A is required.

[0041] Contention resolution in two-step RACH may be performed by including a UE identifier in the first message, which is encoded in the second message. Fallback from two-step RACH to four-step RACH may be supported. Fallback after Message A transmission is only feasible if UE detection is possible without decoding of the payload and therefore relies on such support at the physical layer. If two-step RACH is used for initial access, the parameters of the two-step RACH procedure, including the resources of Message A, will be broadcast.

[0042] Fallback operation has been discussed which proposes using RAR for a four-step RACH scheduled by a PDCCH addressed to the RA-RNTI to indicate fallback. Figure 3 Schematic diagram of MAC PDU 300 is shown. MAC PDU may include MAC sub-PDU 310-1, MAC sub-PDU 310-2, MAC sub-PDU 310-3, MAC sub-PDU 310-4, ..., MAC sub-PDU 310-M (where M is an integer). Figure 3 As shown, MAC sub-PDU 310-1 has an E / T / R / BI sub-header 320, MAC sub-PDU 310-2 has an E / T / R / RAPID sub-header 330-1, and MAC sub-PDU 310-3 has an E / T / R / RAPID sub-header 330-2 and a MAC RAR 340. Figure 3As shown, this requires the UE to monitor both the RAR from the four-step RACH and the message B from the two-step RACH addressed to the CR-RNTI (contention resolution RNTI). In some embodiments, the RA-RNTI design can be reused for the four-step RACH as well as for the CR-RNTI, just with different terminology as an abbreviation of "RA-RNTI for msgB of two-step RACH" to distinguish it from the RA-RNTI for RAR of the four-step RACH. This not only increases the monitoring work, but another problem is that the windows are different. If the traditional starting point and window length for RAR are retained, it is too late to schedule RAR after the gNB decodes PUSCH, because the gNB can only decide on contention resolution or fallback after decoding the PUSCH payload.

[0043] According to an embodiment of the present disclosure, the fallback to the second random access mode is indicated in message B, and the user equipment only needs to monitor the fast mode of message B on the downlink control signal addressed to the identifier. For the second random access mode, the user equipment does not need to monitor the downlink control channel. In this way, the user equipment is allowed to fall back to the second random access mode without another retry of the fast mode, thereby reducing overload and delay.

[0044] Figure 4 A schematic diagram of a communication system 400 in which embodiments of the present disclosure may be implemented is shown. The communication system 400, as part of a communication network, includes a terminal device 410-1, a terminal device 410-2, ..., a terminal device 410-N (collectively referred to as "terminal device 410", where N is an integer). The communication system 400 includes one or more network devices, such as a network device 420. It should be understood that the communication system 300 may also include other elements omitted for clarity. It should be understood that Figure 4 The number of terminal devices and network devices shown is given for illustrative purposes and does not represent any limitation. Network device 420 can communicate with terminal device 410.

[0045] It should be understood that the number of network devices and terminal devices is only for illustration purposes and does not represent any limitation. System 400 may include any suitable number of network devices and terminal devices suitable for implementing the embodiments of the present disclosure.

[0046] The communication in the communication system 400 can be implemented according to any appropriate communication protocol, including but not limited to cellular communication protocols of the first generation (1G), second generation (2G), third generation (3G), fourth generation (4G) and fifth generation (5G), wireless local area network communication protocols (such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, etc.), and / or any other protocol currently known or developed in the future. In addition, the communication can use any appropriate wireless communication technology, including but not limited to: code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), frequency division duplex (FDD), time division duplex (TDD), multiple input multiple output (MIMO), orthogonal frequency division multiplexing (OFDM), discrete Fourier transform spread OFDM (DFT-s-OFDM), and / or any other technology currently known or developed in the future.

[0047] Figure 5 A schematic diagram of an interaction 500 according to an embodiment of the present disclosure is shown. The interaction 500 may be implemented at any suitable device. For illustrative purposes only, the interaction 500 is described as being implemented at the user equipment 410-1 and the network device 420. For illustrative purposes only, the embodiments of the present disclosure are described with reference to two-step RACH as the first random access mode and four-step RACH as the second random access mode. It should be noted that the embodiments of the present disclosure may be applied to any suitable type of RACH.

[0048] The user equipment 410-1 sends 505 a first request (also referred to as "message A") to the network device 420 to access a random access channel in a first random access mode. The first request includes a first preamble for the first random access mode. The first preamble is sent on a random access channel (e.g., a physical random access channel (PRACH)). In some embodiments, the user equipment 410-1 may determine the PRACH and the preamble based on a predetermined configuration. For example, the user equipment 410-1 may be configured with information indicating the PRACH and / or the preamble for the first random access mode.

[0049] In addition, the first request includes identification information. The identification information may be transmitted on a physical uplink shared channel (PUSCH). In other embodiments, if the user equipment 410-1 has a cell radio network temporary identifier (C-RNTI), for example, the user equipment 410-1 may be in connected mode, the identification information may be the C-RNTI. The request may include a C-RNTI media access control (MAC) control element (CE).

[0050] The network device 420 may be configured with information indicating a set of predetermined preambles for the first random access mode. If the preamble belongs to the set of predetermined preambles, the network device 420 may determine that the first request is for the first random access mode.

[0051] The network device 420 may obtain 506 identification information and a first preamble from the first request. The identification information may be used to scramble a physical downlink control channel. The first preamble indicates that the random access is in a first random access mode. The network device 420 determines 508 whether the random access procedure in the first random access mode is successful based on the capacity of the random access channel. For example, if the random access channel is overloaded, the network device 420 determines that the UE should be backed off before attempting the next attempt.

[0052] The network device 420 generates 510 a response to the first request (message B). In some embodiments, responses to multiple terminal devices may be multiplexed into the same data unit. For example, the network device 420 may receive another request for a random access procedure in the first random access mode. The network device may also generate another response to another request and transmit the other response together with the response in the same PDU.

[0053] The random access response may indicate whether the random access procedure in the first random access mode is successful. In this way, the user equipment is prevented from monitoring both the CR-RNTI of the first random access mode and the RA-RNTI of the second random access mode. The response may include a field for indicating whether the first random access mode is successful. The response may include one of the following: a backoff indication (backoff indicator), a backoff response indication or a contention resolution indication, and padding. Table 1 below shows an example of a response (message B). It should be noted that the values ​​and numbers shown in Table 1 are examples only and are not limiting.

[0054] Table 1

[0055]

[0056] As shown in Table 1, "00" in this field indicates that the back-off value follows the 4-bit BI. "01" in this field indicates that the contention resolution for a user equipment without C-RNTI follows: 12-bit TA, 48-bit contention resolution ID (CCCH) and 16-bit allocated C-RNTI.

[0057] The "10" in this field indicates that the fallback format is as follows: a random access preamble identifier (RAPID) for the first random access mode, a RACH opportunity (RO) for the first random access mode (if not unique via RNTI), and a random access response (RAR) payload for the second random access mode. If the RO is not uniquely indicated via the CR-RNTI, the RO is indicated in the fallback response. In some embodiments, if the response includes multiple BIs, the RO can be indicated for the BI. The number of bits required for the RO depends on the CR-RNTI, which is intended to indicate part of the information not implied by the CR-RNTI. For example, if the current RA-RNTI and other information are indicated in the DCI or RAR / message B, the RO field indicates the lost information. If there is a common CR-RNTI for the first random access mode, the RO field indicates the RO used to transmit the preamble. If the time domain information is uniquely indicated by the CR-RNTI, the RO only needs to indicate the frequency domain information. The "11" in this field can be reserved or used for contention resolution for terminal devices with C-RNTI, or to indicate padding. Alternatively, padding can be indicated by "00" in this field, followed by another bit indicating padding or BI.

[0058] The network device 420 sends 515 a random access response (also referred to as "message B") to the user equipment 310-1. In some embodiments, the network device 420 may determine a physical downlink control channel for sending the random access response. The downlink control channel is scrambled using the identification information.

[0059] The identification information may be common to requests received on different random access channels. Alternatively, the identification information may also be common to all requests received on the random access channel. In an example embodiment, one common specific RNTI, the contention resolution RNTI (CR-RNTI), may be configured for transmitting the random access response, rather than linking the response to the PRACH opportunity at which the preamble for the first request was sent.

[0060] In some embodiments, the downlink control channel is scrambled using the CR-RNTI. In other embodiments, if the network device 420 knows the C-RNTI of the user equipment 310-1, the downlink control channel is scrambled using the C-RNTI.

[0061] The user equipment 410-1 monitors 520 a response to the first request on the downlink control channel, the response being scrambled with the identification information.The user equipment 410-1 may monitor the downlink control channel during a configured window time (eg, a contention resolution window).

[0062] If the request indicates that random access in the first random access mode failed, the user equipment 410-1 determines 525 a random access mode to use for the random access procedure. As described above, the response may include a field for indicating whether the first random access mode was successful.

[0063] In some embodiments, the response may include a backoff indication, which indicates that the user equipment that did not successfully complete the random access applies a backoff before the next attempt. In this way, the enabling / disabling of the backoff to the second random access mode can be dynamically indicated in the response. The user equipment 110-1 can derive a random value between 0 and the backoff indication as its backoff value and compare the backoff value with a threshold. The threshold can be configured via radio resource control (RRC) signaling. If the backoff value is greater than the threshold, it indicates that the resources used for the first random access mode are overloaded and a longer delay will be introduced. The user equipment 110-1 can determine that the second random access mode is used to access the random access.

[0064] Alternatively, if the backoff value is less than the threshold, the user equipment 110-1 may select the first random access mode for random access. In other embodiments, the response may include one backoff indication for the first random access mode and one backoff indication for the second random access mode. If the backoff value for the first random access mode is greater than the backoff value for the second random access mode, the user equipment 110-1 may determine the second random access mode. If the derived backoff value for the first random access mode is less than the derived backoff value for the slow mode, the user equipment 110-1 may determine the first random access mode.

[0065] In some embodiments, the response may indicate the need to fall back to the second random access mode. For example, if the field in the response shows "10", it indicates the need to fall back to the second random access mode. User equipment 110-1 may continue msg3 transmission using the uplink grant indicated in the RAR and start a contention resolution timer in the second random access mode.

[0066] In some embodiments, if the user equipment 410-1 determines that the response includes a random access preamble identifier for the first request and a random access channel opportunity for the first request, the user equipment 410-1 determines that it is necessary to fall back to the second random access mode. The user equipment 410-1 can also obtain a random access response payload for the second random access mode from the response.

[0067] The user equipment 410-1 sends 530 a second request for random access. The second request includes a preamble for the selected mode. In this way, the user equipment is allowed to fall back to the second random access mode without an additional retry of the quick mode, thereby reducing overload and delay.

[0068] Figure 6 A flow chart of a method 600 according to an embodiment of the present disclosure is shown. The method 600 may be implemented at any suitable device. For illustration purposes only, the method 600 is described as being implemented at the user device 410-1.

[0069] At block 610, user equipment 410-1 sends a first request (also referred to as "message A") for a random access procedure in a first random access mode to network device 420. The first request includes a first preamble for the first random access mode. The preamble is sent on a random access channel (e.g., a physical random access channel (PRACH)). In some embodiments, user equipment 410-1 may determine the PRACH and preamble based on a predetermined configuration. For example, user equipment 410-1 may be configured with information indicating the PRACH and / or preamble for the first random access mode.

[0070] In addition, the first request includes identification information of the user equipment 310-1. The identification information may be transmitted on a physical uplink shared channel (PUSCH). In other embodiments, if the user equipment 410-1 has a cell radio network temporary identifier (C-RNTI), for example, the user equipment 410-1 may be in a connected mode, the identification information may be the C-RNTI. The request may include a C-RNTI media access control (MAC) control element (CE).

[0071] At block 620, user equipment 410-1 monitors a response to the first request on a downlink control channel. The downlink control channel is scrambled using identification information. The identification information may be common to requests received on different random access channels. Alternatively, the identification information may also be common to all requests received on the random access channel. In an example embodiment, a common specific RNTI, i.e., a contention resolution RNTI (CR-RNTI), may be configured for transmitting a random access response, rather than linking the response to a PRACH opportunity at which a preamble for the first request was sent.

[0072] In some embodiments, the downlink control channel is scrambled using the CR-RNTI. In other embodiments, if the network device 420 knows the C-RNTI of the user equipment 310-1, the downlink control channel is scrambled using the C-RNTI.

[0073] At box 630, if the request indicates that the first request failed, the user equipment 410-1 determines the RA mode for the random access process. In some embodiments, the response may include a backoff indication, which indicates that the user equipment has not successfully completed the random access under the first random access mode and needs to apply a backoff for its next attempt. In this way, the enabling / disabling of the backoff to the second random access mode can be dynamically indicated in the response. The user equipment 110-1 can derive a random value between 0 and the backoff indication as its backoff value and compare the backoff value with a threshold. The threshold can be configured via radio resource control (RRC) signaling. If the backoff value is greater than the threshold, it indicates that the resources used for the first random access mode are overloaded and a longer delay will be introduced. The user equipment 110-1 can determine the second random access mode for random access.

[0074] Alternatively, if the backoff value is less than the threshold, the user equipment 110-1 may determine the first random access mode for the random access procedure. In other embodiments, the response may include one backoff indication for the first random access mode and one backoff indication for the second random access mode. If the derived backoff value for the first random access mode is greater than the derived backoff value for the second random access mode, the user equipment 110-1 may determine the second random access mode. If the backoff value for the first random access mode is less than the backoff value for the slow mode, the user equipment 110-1 may determine the first random access mode.

[0075] In some embodiments, if the user equipment 410-1 determines that the response includes a random access preamble identifier for the first request and a random access channel opportunity for the first request, the user equipment 410-1 determines that it needs to fall back to the second random access mode. The user equipment 410-1 can also obtain a random access response payload for the second random access mode from the response.

[0076] At block 640, user equipment 410-1 sends a second request for a random access procedure in the determined random access mode to network device 420. The second request includes a preamble of the selected mode. In this way, the user equipment is allowed to fall back to the second random access mode without additional retries of the fast mode, thereby reducing overload and delay.

[0077] Figure 7 A flow chart of a method 700 according to an embodiment of the present disclosure is shown. The method 700 may be implemented at any suitable device. For illustration purposes only, the method 700 is described as being implemented at the network device 420.

[0078] At block 710, the network device 420 receives a request for a random access procedure in a first random access mode. The request may include a first preamble for the first random access mode. The preamble is sent on a random access channel (e.g., a physical random access channel (PRACH)). In some embodiments, the user equipment 410-1 may determine the PRACH and the preamble based on a predetermined configuration. For example, the user equipment 410-1 may be configured with information indicating the PRACH and / or preamble for the first random access mode.

[0079] In addition, the first request includes identification information of the user equipment 410-1. The identification information may be transmitted on a physical uplink shared channel (PUSCH). In other embodiments, if the user equipment 410-1 has a cell radio network temporary identifier (C-RNTI), for example, the user equipment 410-1 may be in a connected mode, the identification information may be the C-RNTI. The request may include a C-RNTI media access control (MAC) control element (CE).

[0080] In some embodiments, at block 730, the network device 420 may obtain identification information and a preamble from the request. The identification information may be used to scramble a physical downlink control channel. The preamble indicates that the random access is in a first random access mode.

[0081] The network device 420 may determine whether the request is successful based on the capacity of the random access channel. For example, if the random access channel is overloaded, the network device 420 may determine that the first random access mode has failed.

[0082] At block 720, if the network device 420 determines that the request failed, the network device 420 generates a response indicating the failure. In some embodiments, responses to multiple terminal devices may be multiplexed into the same data unit. In this way, it is avoided that the user equipment monitors both the CR-RNTI of the first random access mode and the RA-RNTI of the second random access mode. The response may include a field for indicating whether the first random access mode is successful. The response may include one of the following: a backoff indication (backoff indicator), a fallback response indication or a contention resolution indication, or padding.

[0083] In some embodiments, "00" in this field indicates that the backoff indication follows the 4-bit BI. "01" in this field indicates that contention resolution for UEs without C-RNTI follows the 12-bit Time Advance (TA), 48-bit Contention Resolution ID (Common Control Channel CCCH) and 16-bit allocated C-RNTI.

[0084] In some embodiments, a "10" in this field indicates that the fallback format is as follows: a random access preamble identifier (RAPID) for the request, a RACH opportunity (RO) for the request (if not unique via RNTI), and a random access response (RAR) payload for the second random access mode. If the RO is not uniquely indicated via the CR-RNTI, the RO is indicated in the fallback response. In some embodiments, if the response includes multiple BIs, the RO can be indicated for the BI. The number of bits required for the RO depends on the CR-RNTI, which is intended to indicate part of the information not implied by the CR-RNTI. For example, if the current RA-RNTI and other information are indicated in the DCI or RAR / message B, the RO field indicates the lost information. If there is a common CR-RNTI for the first random access mode, the RO field indicates the RO used to transmit the preamble. If the time domain information is uniquely indicated by the CR-RNTI, the RO only needs to indicate the frequency domain information. The "11" in this field can be reserved or used for contention resolution for terminal devices with C-RNTI.

[0085] In some embodiments, the network device 420 may indicate a fallback indication for a certain random access preamble identifier (RAPID) transmitted by the user equipment 410-1 and a contention resolution identifier of the user equipment 410-1. For example, this may occur when two random access preambles are mapped to the same data resource when the terminal device transmits message A / msgA and the network device 420 is only able to decode one of the data resources transmitted by the terminal device. Therefore, in some embodiments, the contention resolution identifier of the terminal device is multiplexed by the network device 420 before the fallback indication in the message B / msgB. When the user equipment 410-1 decodes the received message B / msgB, it will first find its contention resolution identifier and can determine that the first random access is successful. In some embodiments, for example, if there is no fixed order for contention resolution and fallback indication, the terminal device ignores the fallback indication when its contention resolution identifier is found.

[0086] At block 730, the network device 420 transmits a response to the first request. In some embodiments, the network device 420 may determine a physical downlink control channel for transmitting the random access response. The downlink control channel is scrambled using the identification information.

[0087] The identification information may be common to requests received on different random access channels. Alternatively, the identification information may also be common to all requests received on the random access channel. In an example embodiment, one common specific RNTI, the contention resolution RNTI (CR-RNTI), may be configured for transmitting the random access response, rather than linking the response to the PRACH opportunity at which the preamble for the first request was sent.

[0088] In some embodiments, the downlink control channel is scrambled using the CR-RNTI. In other embodiments, if the network device 420 knows the C-RNTI of the user equipment 310-1, the downlink control channel is scrambled using the C-RNTI.

[0089] In some embodiments, an apparatus for executing method 600 (e.g., user equipment 410-1) may include corresponding components for executing corresponding steps in method 600. These components may be implemented in any suitable manner. For example, it may be implemented by a circuit system or a software module.

[0090] In some embodiments, the apparatus includes: a component for sending, at a user equipment, a first request for a random access procedure in a first random access mode to a network device; a component for monitoring a response to the first request on a downlink control channel; a component for determining, in response to receiving a response indicating that the first request failed, the first random access mode or the second random access mode for the random access procedure; and a component for sending a second request for a random access procedure in the determined random access mode to the network.

[0091] In some embodiments, the component for determining the first random access mode or the second random access mode for a random access channel includes: a component for determining a backoff value for the first random access mode based on a backoff indication in response to the response including a backoff indication; a component for comparing the backoff value to a threshold; and a component for determining the second random access mode for the random access procedure in response to the backoff value exceeding the threshold.

[0092] In some embodiments, the means for determining the first random access mode or the second random access mode for a random access channel includes: means for determining a backoff value based on a backoff indication in response to the response including a backoff indication; means for comparing the backoff value to a threshold; and means for determining the first random access mode for the random access procedure in response to the backoff value being lower than the threshold.

[0093] In some embodiments, the component for determining the first random access mode or the second random access mode for a random access channel includes: a component for determining a first backoff value for the first random access mode and a second backoff value for the second random access mode based on the response in response to the response including a backoff indication; a component for comparing the first backoff value with the second backoff value; and a component for determining the second random access mode for the random access procedure in response to the first backoff value exceeding the second backoff value.

[0094] In some embodiments, the means for determining the first random access mode or the second random access mode for the random access channel comprises: means for determining the second random access mode for the random access channel in response to the response indicating a need to fall back to the second random access mode.

[0095] In some embodiments, the apparatus further comprises: means for obtaining a random access response payload for a second random access mode from the response in response to determining that the response includes at least one of a random access preamble identifier for the first request and a random access channel opportunity for the first request.

[0096] In some embodiments, the identification information includes a preamble and identification information of a user equipment, and the apparatus further comprises: a component for determining that the first random access mode fails in response to failure to find the identification information and / or the identification of the first preamble in the response.

[0097] In some embodiments, an apparatus for executing method 700 (e.g., network device 120) may include corresponding components for executing corresponding steps in method 700. These components may be implemented in any suitable manner. For example, it may be implemented by a circuit system or a software module.

[0098] In some embodiments, the apparatus includes: a component for receiving a request for a random access procedure from a user equipment; a component for generating a response indicating failure in response to determining that the request failed, the response also including information about the user equipment determining a first random access mode or a second random access mode; and a component for sending a response to the request on a downlink control channel.

[0099] In some embodiments, the request includes at least one of: a backoff indication, a contention resolution indication, or an indication of a second random access mode.

[0100] In some embodiments, if the response includes an indication of a backoff value, the response also includes at least one of: a first backoff value for the first random access mode, or a second backoff value for the second random access mode.

[0101] In some embodiments, if the response includes an indication of contention resolution, the response also includes at least one of: a timing advance for the terminal device, a contention resolution identifier for the user equipment, a cell radio network temporary identifier for the user equipment, or a contention resolution cell radio network temporary identifier media access control (MAC) control element for the user equipment.

[0102] In some embodiments, if the response includes an indication of the second random access mode, the response also includes at least one of: a random access preamble identifier for the request, a random access channel opportunity for the request, or a random access response payload for the second random access mode.

[0103] In some embodiments, the apparatus further comprises: means for receiving another request for a random access procedure from another user equipment; means for generating another response to the another request; and means for transmitting the response and the further response on a downlink control channel.

[0104] Figure 8 800 is a simplified block diagram of a device 800 suitable for implementing an embodiment of the present disclosure. The device 800 may be used to implement a communication device, such as Figure 1 The network devices 120-1, 120-2 or user equipment 110-1 are shown. As shown, the device 800 includes one or more processors 810, one or more memories 820 coupled to the processors 810, and one or more communication modules (e.g., transmitters and / or receivers (TX / RX)) 840 coupled to the processors 810.

[0105] The communication module 840 is used for two-way communication. The communication module 840 has at least one antenna to facilitate communication. The communication interface may represent any interface required to communicate with other network elements.

[0106] Processor 810 may be of any type suitable for the local technology network, and may include, as non-limiting examples, one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 800 may have multiple processors, such as application specific integrated circuit chips that are time slaved to a clock synchronized with a main processor.

[0107] The memory 820 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 824, electrically programmable read-only memory (EPROM), flash memory, hard disks, compact disks (CDs), digital video disks (DVDs), and other magnetic storage and / or optical storage devices. Examples of volatile memories include, but are not limited to, random access memory (RAM) 822 and other volatile memories that do not persist over the duration of a power outage.

[0108] The computer program 830 includes computer executable instructions that are executed by the associated processor 810. The program 830 may be stored in the ROM 824. The processor 810 may perform any suitable actions and processes by loading the program 830 into the RAM 822.

[0109] The embodiments of the present disclosure may be implemented by a program 830, so that the device 800 may execute the Figures 2 to 6 Any process of the present disclosure discussed. The embodiments of the present disclosure may also be implemented by hardware or a combination of software and hardware.

[0110] In some embodiments, the program 830 may be tangibly embodied in a computer-readable medium that may be included in the device 800 (such as in the memory 820) or in other storage devices accessible to the device 800. The device 800 may load the program 830 from the computer-readable medium to the RAM 822 for execution. The computer-readable medium may include any type of tangible non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Fig. 9 An example of a computer readable medium 900 in the form of a CD or DVD is shown. The computer readable medium has a program 830 stored thereon.

[0111] Generally, various embodiments of the present disclosure may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are shown and described as block diagrams, flow charts, or using some other graphical representations, it should be understood that the block diagrams, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general hardware or controllers or other computing devices, or some combination thereof.

[0112] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer executable instructions, such as computer executable instructions included in a program module, which are executed in a device on a target real or virtual processor to perform the above reference Figure 2-6 Methods 500 and 600 described herein. Typically, program modules include routines, programs, libraries, objects, classes, components, data types, etc. that perform specific tasks or implement specific abstract data structures. The functions of program modules can be combined or split between program modules as needed in various embodiments. Machine executable instructions for program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in local and remote storage media.

[0113] The program code for executing the method of the present disclosure can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device, so that these program codes cause the functions / operations specified in the flow chart and / or block diagram to be implemented when executed by the processor or controller. The program code can be executed completely on the machine, partially on the machine, executed as an independent software package, partially on the machine and partially on a remote machine, or completely on a remote machine or server.

[0114] In the context of the present disclosure, computer program codes or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform various processes and operations as described above. Examples of carriers include signals, computer readable media, etc.

[0115] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer readable medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared or semiconductor systems, devices or equipment, or any suitable combination thereof. More specific examples of computer readable storage media include an electrical connection with one or more wires, a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0116] In addition, although the operations are depicted in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown or in a continuous order or to perform all the operations shown to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although the above discussion includes several specific implementation details, these details should not be interpreted as limitations on the scope of the present disclosure, but should be interpreted as descriptions of features that may be specific to a particular embodiment. Certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented in multiple embodiments or in any suitable sub-combination, respectively.

[0117] Although the disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A device for communication, comprising: at least one processor; as well as at least one memory including computer program code; The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to: sending a first request for a random access procedure in a first random access mode to another device; as well as monitoring a response to said first request on a downlink control channel, wherein: In case fallback to a second random access mode is required, the response includes a fallback response indication, wherein the first random access mode is a fast mode compared to the second random access mode; In a case where there is no need to fall back to the second random access mode, the response includes a backoff indication or an indication of contention resolution, and wherein: In response to the response including the backoff indication, a backoff value is determined based on the backoff indication; In response to the response including the indication of contention resolution, the apparatus proceeds with contention resolution.

2. The apparatus according to claim 1, wherein the apparatus is further configured to: In response to the response including the backoff indication: comparing the backoff value to a threshold; and In response to the backoff value exceeding the threshold, determining the second random access mode for the random access procedure.

3. The apparatus according to claim 1, wherein the apparatus is further configured to: In response to the response including the backoff indication: comparing the backoff value to a threshold; and In response to the backoff value being lower than the threshold, determining the first random access mode for the random access procedure.

4. The apparatus according to claim 1, wherein the apparatus is further configured to: In response to the response including the backoff indication, determining a first backoff value for the first random access mode and a second backoff value for the second random access mode based on the backoff indication; comparing the first backoff value with the second backoff value; In response to the first backoff value exceeding the second backoff value, determining the second random access mode for the random access procedure.

5. The apparatus according to claim 2 or 4, wherein the apparatus is further configured to: In response to determining that the response includes at least one of a random access preamble identifier for the first request and a random access channel opportunity for the first request, obtaining a random access response payload for the second random access mode from the response.

6. The apparatus according to claim 1, wherein the response comprises a first preamble and identification information of the apparatus, and the apparatus is further caused to: In response to failure to find the identification information and / or the identification of the first preamble in the response, it is determined that the first request has failed.

7. A device for communication, comprising: at least one processor; as well as at least one memory including computer program code; The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to: receiving, from a user equipment, a request for a random access procedure in a first random access mode; Generates a response where: In case fallback to a second random access mode is required, the response includes a fallback response indication, wherein the first random access mode is a fast mode compared to the second random access mode; In case fallback to the second random access mode is not required, the response includes a backoff indication or an indication of contention resolution, and wherein: a backoff value can be determined based on the backoff indication; or contention resolution can be determined based on the indication of contention resolution; and The response to the request is sent on a downlink control channel.

8. The apparatus of claim 7, wherein the backoff indication comprises at least one of: a first backoff indication for said first random access mode, or A second backoff indication for the second random access mode.

9. The apparatus of claim 7, wherein if the response includes the indication of the contention resolution, the response further includes at least one of: a time advance for said user equipment, a contention resolution identifier for the user equipment, a cell radio network temporary identifier for the user equipment, or A contention resolution cell radio network temporary identifier medium access control (MAC) control element for the user equipment.

10. The apparatus of claim 7, wherein if the response includes the backoff response indication, the response further includes at least one of: a random access preamble identifier for the request, a random access channel opportunity for the request, or A random access response payload for the second random access mode.

11. The apparatus of claim 7, wherein the apparatus is further configured to: receiving another request for the random access procedure from another user equipment; generating another response to the another request; and The response and the further response are sent on the downlink control channel.

12. A method for communication, comprising: Sending, at a user equipment, to a network device, a first request for a random access procedure in a first random access mode; as well as monitoring a response to said first request on a downlink control channel, wherein: In case fallback to a second random access mode is required, the response includes a fallback response indication, wherein the first random access mode is a fast mode compared to the second random access mode; In a case where there is no need to fall back to the second random access mode, the response includes a backoff indication or an indication of contention resolution, and wherein: In response to the response including the backoff indication, a backoff value is determined based on the backoff indication; In response to the response including the indication of contention resolution, the user equipment proceeds with contention resolution.

13. The method according to claim 12, further comprising: In response to the response including the backoff indication: comparing the backoff value to a threshold; as well as In response to the backoff value exceeding the threshold, determining the second random access mode for the random access procedure.

14. The method according to claim 12, further comprising: In response to the response including the backoff indication: comparing the backoff value to a threshold; as well as In response to the backoff value being lower than the threshold, determining the first random access mode for the random access procedure.

15. The method according to claim 12, further comprising: In response to the response including the backoff indication, determining a first backoff value for the first random access mode and a second backoff value for the second random access mode based on the response; comparing the first backoff value with the second backoff value; In response to the first backoff value exceeding the second backoff value, determining the second random access mode for the random access procedure.

16. The method according to claim 13 or 15, further comprising: In response to determining that the response includes at least one of a random access preamble identifier for the first request and a random access channel opportunity for the first request, obtaining a random access response payload for the second random access mode from the response.

17. The method according to claim 12, wherein the response comprises a first preamble and identification information of the user equipment, and the method further comprises: In response to failure to find the identification information and / or the identification of the first preamble in the response, it is determined that the first request has failed.

18. A method for communication, comprising: receiving, at a network device, from a user equipment, a request for a random access procedure in a first random access mode; Generates a response where: In case fallback to a second random access mode is required, the response includes a fallback response indication, wherein the first random access mode is a fast mode compared to the second random access mode; In case fallback to the second random access mode is not required, the response includes a backoff indication or an indication of contention resolution, and wherein: a backoff value can be determined based on the backoff indication; or contention resolution can be determined based on the indication of contention resolution; and The response to the request is sent on a downlink control channel.

19. The method of claim 18, wherein if the response includes an indication of the backoff value, the response further includes at least one of: a first backoff value for said first random access mode, or A second backoff value for the second random access mode.

20. The method of claim 18, wherein if the response includes the indication of the contention resolution, the response further includes at least one of: a time advance for said user equipment, a contention resolution identifier for the user equipment, a cell radio network temporary identifier for the user equipment, or A contention resolution cell radio network temporary identifier medium access control (MAC) control element for the user equipment.

21. The method of claim 18, wherein if the response includes the backoff response indication, the response further includes at least one of: a random access preamble identifier for the request, a random access channel opportunity for the request, or A random access response payload for the second random access mode.

22. The method of claim 18, further comprising: receiving another request for the random access procedure from another user equipment; generating another response to the another request; as well as The response and the further response are sent on the downlink control channel.

23. An apparatus for communication, comprising: means for sending, at a user equipment, to a network device, a first request for a random access procedure in a first random access mode; as well as means for monitoring on a downlink control channel for a response to said first request, wherein: In case fallback to a second random access mode is required, the response includes a fallback response indication, wherein the first random access mode is a fast mode compared to the second random access mode; In a case where there is no need to fall back to the second random access mode, the response includes a backoff indication or an indication of contention resolution, and wherein: In response to the response including the backoff indication, a backoff value is determined based on the backoff indication; In response to the response including the indication of contention resolution, the apparatus proceeds with contention resolution.

24. An apparatus for communication, comprising: means for receiving, at a network device, from a user equipment, a request for a random access procedure in a first random access mode; A component used to generate a response, where: In case fallback to a second random access mode is required, the response includes a fallback response indication, wherein the first random access mode is a fast mode compared to the second random access mode; In case fallback to the second random access mode is not required, the response includes a backoff indication or an indication of contention resolution, and wherein: a backoff value can be determined based on the backoff indication; or contention resolution can be determined based on the indication of contention resolution; and Means for sending said response to said request on a downlink control channel.

25. A computer readable medium having stored thereon instructions which, when executed by at least one processing unit of a machine, cause the machine to perform the method according to any one of claims 12 to 17.

26. A computer readable medium having stored thereon instructions which, when executed by at least one processing unit of a machine, cause the machine to perform the method according to any one of claims 18 to 22.

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