Cooperative random access for cell-free networks

Abstract

The invention relates to a cell-less network. A network device is provided that maintains a first data set indicating neighboring network devices and a second data set indicating one or more user IDs, respectively. One second data set is associated with the network device, and each of the other second data sets is associated with a neighboring network device of the first data set. The network device receives signals from user equipment, where each signal includes a respective user ID and a respective payload of one user equipment. The network device separates one or more signals to obtain the respective user ID and payload and sends first exchange information to each neighboring network device associated with a second data set comprising at least one obtained respective user ID in the first data set. The transmitted first exchange information includes at least one acquired respective user ID and a respective payload.

Description

Technical Field

[0001] The present invention relates to communication networks and systems, and in particular, to a cell-free communication network. The present invention provides a network device for a cell-free wireless communication network, and a method for operating the network device. Background Art

[0002] A cell-free network consists of multiple network devices (e.g., access points (APs)), which provide services to multiple user devices (e.g., UEs), where the user devices are not attached to a specific network device.

[0003] Traditional cell-free networks operate based on the assumption of a multi-access scenario, where the active user devices are known and pilot sequences are allocated to these active user devices in a coordinated manner (i.e., traditional cell-free networks are not license-free). Therefore, the uplink (UL) communication of user devices is divided into two steps: the first step is channel estimation, where the pilot sequence is transmitted by the user device; the second step is communication, where the user device transmits the message of the user device. The random access scheme in traditional cell-free networks also performs an activity detection step based on preambles.

[0004] It should be noted that "license-free" means that in a network, one or more transmitting devices (in UL, UEs) send messages to one or more receiving devices (in UL, APs) without any prior resource request or authorization. Further, "random access" means that a random number of transmitting devices in the network are simultaneously active. License-free and random access communications are typical applications in large-scale Internet of Things (IoT) scenarios.

[0005] One problem is that for communication networks and systems where activity detection and decoding will be jointly (cooperatively) performed by network devices, the above activity detection method of traditional cell-free networks is not applicable. Therefore, a new scheme for cooperative random access in cell-free networks is needed. Summary of the Invention

[0006] In summary, the present invention relates to cell-free networks and random access. The object of the present invention is to achieve cooperative random access in a cell-free (wireless) network. A specific object is to achieve cooperative decoding of signals sent from multiple user devices to multiple network devices in a cell-free network.

[0007] These and other objects are achieved by the present invention described in the appended independent claims. Advantageous implementations are further defined in the dependent claims.

[0008] A first aspect of the present invention provides a network device for a cell-free wireless communication network, the network device being configured to: maintain a first data set indicating one or more neighboring network devices; maintain a plurality of second data sets respectively indicating one or more user IDs, wherein one of the plurality of second data sets is associated with the network device, and each of the other second data sets in the plurality of second data sets is associated with one of the one or more neighboring network devices in the first data set; receive a plurality of signals from a plurality of user devices within a first interval, wherein each signal includes a corresponding user ID of one of the user devices and a corresponding payload of one of the user devices; separate one or more of the plurality of signals within the first interval to obtain the corresponding user ID and the corresponding payload of the one or more signals; send first exchange information to each neighboring network device within the first interval, each neighboring network device being in the first data set and associated with a second data set including at least one of the obtained corresponding user IDs; wherein the sent first exchange information includes at least one of the obtained corresponding user IDs and at least one of the obtained corresponding payloads.

[0009] By maintaining the first data set and the second data sets and by sending the first exchange message to the neighboring network devices (the neighboring network devices can also maintain the first data set and the second data sets), the network device of the first aspect supports the cooperative separation (decoding) of the plurality of signals sent by the plurality of user devices to the network device and the neighboring network devices. Therefore, the network device of the first aspect supports cooperative random access in a cell-free network (e.g., a cell-free wireless / mobile network).

[0010] In an implementation of the first aspect, if a specific user ID among the obtained corresponding user IDs is not in the second data set associated with the network device, the network device is configured to send second exchange information to each neighboring network device within the first interval, each neighboring network device being in the first data set and associated with a second data set that does not include the specific user ID; wherein the second exchange information includes the specific user ID but does not include the corresponding payload corresponding to the specific user ID.

[0011] This can reduce the signaling overhead of the cooperative random access method.

[0012] In an implementation of the first aspect, the network device is further configured to: receive first exchange information from an adjacent network device within the first interval, where the received first exchange information includes at least one corresponding user ID of the plurality of signals and at least one corresponding payload of the corresponding payloads; further separate one or more signals of the plurality of signals based on the separated signals and the corresponding payloads in the received first exchange information within the first interval.

[0013] Accordingly, the network device may exchange first exchange messages with an adjacent network device to implement cooperative separation (decoding) of a plurality of signals transmitted by multiple users.

[0014] In an implementation of the first aspect, the network device is further configured to send the second exchange information to each adjacent network device in the first data set within a second interval.

[0015] In an implementation of the first aspect, the network device is further configured to: perform separation of one or more signals of the plurality of signals within the first interval without prior knowledge of the corresponding user IDs and the corresponding payloads of the one or more signals.

[0016] Therefore, random access in a cell-free network is supported.

[0017] In an implementation of the first aspect, the first exchange information received from the adjacent network device includes one or more corresponding user IDs and one or more corresponding payloads, and the one or more corresponding user IDs and the one or more corresponding payloads are different from the corresponding user IDs and the corresponding payloads in the sent first exchange information.

[0018] In an implementation of the first aspect, in the further separation of one or more signals of the plurality of signals within the first interval, the network device is configured to perform interference cancellation.

[0019] Therefore, the separation of multiple signals is improved.

[0020] In an implementation of the first aspect, the network device is further configured to: update the second data set associated with the network device based on the one or more separated signals and the one or more further separated signals, and / or update one or more second data sets associated with the one or more adjacent network devices based on the first exchange information received from the one or more adjacent network devices.

[0021] Accordingly, the network device of the first aspect (which can also be done by adjacent network devices in a similar manner) maintains up-to-date information about the connections in the cell-free network.

[0022] In one implementation of the first aspect, the network device is used to update the second dataset associated with the network device and / or the one or more second datasets associated with the one or more adjacent network devices by at least one of the following: adding one or more user IDs to the second dataset associated with the network device; adding one or more user IDs to the one or more second datasets associated with the one or more adjacent network devices; deleting one or more user IDs from the second dataset associated with the network device; deleting one or more user IDs from the one or more second datasets associated with the one or more adjacent network devices.

[0023] In one implementation of the first aspect, the network device is further used to associate a timestamp with any user ID added to the second dataset.

[0024] In one implementation of the first aspect, the network device is further used to: if the timestamp associated with the user ID is earlier than a threshold, delete any user ID from the second dataset.

[0025] In one implementation of the first aspect, the network device is further used to adjust the threshold based on at least one of network conditions and upper-layer configurations.

[0026] In one implementation of the first aspect, the network device is further used to: if the user ID of the separated signal is not yet in the second dataset of the network device, add the user ID of the separated signal or the user ID of the further separated signal to the second dataset of the network device; and / or if the user ID in the first exchange information is not yet in the second dataset of the adjacent network device, add the user ID in the first exchange information received from the adjacent network device to the second dataset of the adjacent network device.

[0027] A second aspect of the present invention provides a method for a network device in a cell-free wireless communication network, the method comprising: maintaining a first data set indicating one or more neighboring network devices; maintaining a plurality of second data sets respectively indicating one or more user IDs, wherein one of the plurality of second data sets is associated with the network device, and each of the other second data sets in the plurality of second data sets is associated with one of the one or more neighboring network devices in the first data set; receiving a plurality of signals from a plurality of user devices within a first interval, wherein each signal includes a corresponding user ID of one of the user devices and a corresponding payload of one of the user devices; separating one or more of the plurality of signals within the first interval to obtain the corresponding user ID and the corresponding payload of the one or more signals; sending first exchange information to each neighboring network device within the first interval, each neighboring network device being in the first data set and associated with a second data set including at least one of the obtained corresponding user IDs; wherein the first exchange information includes at least one of the obtained corresponding user IDs and at least one of the obtained corresponding payloads.

[0028] The implementation manner of the method in the second aspect may correspond to the implementation manner of the network device in the first aspect. The method in the second aspect and its possible implementation manners achieve the same advantages as the network device in the first aspect and its corresponding implementation manners described above.

[0029] A third aspect of the present invention provides a computer program, the computer program comprising instructions that, when the program is executed by a computer, cause the computer to execute the method according to the second aspect and its possible implementation manners.

[0030] A fourth aspect of the present invention provides a non-transitory storage medium that stores executable program code, which, when executed by a processor, causes the method according to the second aspect and its possible implementation manners to be executed.

[0031] According to the above aspects and implementation manners, the present invention solves the collaborative separation of signals sent by multiple user devices (e.g., multiple UEs) to multiple network devices (e.g., multiple APs) in a cell-free wireless network.

[0032] The present invention proposes a first data set, the content of which can be represented by a connected graph, and the connected graph indicates the understanding of the connection between a user equipment and a network equipment. Each network equipment can maintain such a first data set. The first data set can be used to exchange signals (first exchange information and second exchange information) between network equipments sharing the same user equipment. Then, these exchanged signals can be used by the network equipments to perform interference cancellation, thereby improving the decoding performance. The method for constructing and using the first data set in a distributed manner is illustrated in the present invention. Specifically, the understanding of the first data set at each network equipment can be simplified to the understanding of a second data set. The content of the second data set can be represented by an adjacent graph, and the adjacent graph includes the first-order and second-order adjacent network equipments of the corresponding network equipment.

[0033] It should be noted that all the devices, elements, units and apparatuses described in this application can be implemented in software or hardware elements or any combination thereof. All the steps performed by the various entities described in this application and the functions to be performed by the various entities described are intended to mean that the corresponding entities are used to perform the corresponding steps and functions. Although in the description of the following specific embodiments, the specific functions or steps to be performed by external entities are not reflected in the description of the specific detailed elements of the entities performing the specific steps or functions, those skilled in the art should understand that these methods and functions can be implemented by the corresponding software or hardware elements or any combination thereof. Brief Description of the Drawings

[0034] Combined with the accompanying drawings, the description of the following specific embodiments will elaborate on the above aspects and their implementation manners. In the drawings:

[0035] Figure 1 The network equipment for a cell-free network provided by the present invention is shown.

[0036] Figure 2 An (a) exemplary connected graph and (b) exemplary adjacent graph are shown.

[0037] Figure 3 An (a) information encoding at a user equipment and (b) example of an encoder of the user equipment are shown.

[0038] Figure 4 Two consecutive decoding time axes are shown, wherein the decoding is performed by the network equipment provided by the present invention.

[0039] Figure 5 An (a) separation of signals of multiple user equipments in a first decoding step and (b) example of information decoding at a network equipment are shown.

[0040] Figure 6 An exemplary scheme for exchanging information of each decoded user equipment between adjacent network equipments is shown.

[0041] Figure 7 Shows the further separation of the signals of multiple user equipments in the second decoding step.

[0042] Figure 8 Shows an illustrative example of a decoding scheme with four intervals proposed by the present invention.

[0043] Figure 9 Shows the first interval of this example.

[0044] Figure 10 Shows the second interval of this example.

[0045] Figure 11 Shows the third interval of this example.

[0046] Figure 12 Shows the fourth interval of this example.

[0047] Figure 13 Shows the method of a network device for a cell-free network provided by the present invention. Detailed implementation

[0048] Figure 1 Shows network device 100 for a cell-free wireless communication network. This communication network can be a mobile communication network. For example, the mobile communication network can be the fifth generation (5 th generation, 5G), new radio (NR) or other next-generation mobile networks. The network device can be an AP, a base station (BS), a gNodeB or other types of network access devices.

[0049] Network device 100 is used to maintain a first data set 101, and the first data set 101 indicates one or more adjacent network devices 100 of network device 100. The adjacent network devices 100 can be the first-order adjacent network devices 100 of network device 100, or the second-order adjacent network devices 100. It should be noted that each adjacent network device 100 can be configured like the network device 100.

[0050] Network device 100 is also used to maintain multiple second data sets 102. Each second data set 102 indicates one or more user IDs. One of the second data sets 102 in the second data sets 102 is associated with network device 100, and each of the other second data sets 102 in the second data sets 102 is associated with one of the one or more adjacent network devices 100 indicated in the first data set 101.

[0051] The network device 100 is further configured to receive a plurality of signals 103 from a plurality of user devices 110 within a first interval. Each user device 110 may be a UE or a terminal device. Each of the plurality of signals 103 includes a corresponding user identification (ID) of one of the user devices 110 in the user device 110, and includes a corresponding payload (message) of one of the user devices 110 in the user device 110. It should be noted that the plurality of signals 103 from the user device 110 may also be received by one or more adjacent network devices 100. That is to say, the adjacent network devices 100 of the network device 100 may be devices that can potentially receive and decode user device signals that the network device 100 can also receive and decode.

[0052] The network device 100 is configured to separate one or more of the plurality of signals 103 within the first interval to obtain the corresponding user ID and the corresponding payload of these one or more signals. That is to say, for each separated signal, the network device 100 can obtain the corresponding user ID and the corresponding payload.

[0053] Then, the network device 100 is configured to send first exchange information 104 to each adjacent network device 100 within the first interval, and each adjacent network device 100 is indicated in the first data set 101 and associated with a second data set 102 including at least one of the obtained corresponding user IDs. The sent first exchange information 104 includes at least one of the obtained corresponding user IDs and at least one of the obtained corresponding payloads.

[0054] In addition, the network device 100 may also receive similar first exchange information 104 from at least one of the adjacent network devices 100 within the first interval. The received first exchange information 104 includes at least one of the corresponding user IDs of the plurality of signals 103 and at least one of the corresponding payloads. The first exchange information 104 received from at least one adjacent network device 100 may include one or more corresponding user IDs and one or more corresponding payloads, and the one or more corresponding user IDs and the one or more corresponding payloads are different from the corresponding user IDs and the corresponding payloads in the sent first exchange information 104. Accordingly, the network device 100 and its adjacent network devices 100 may exchange the first exchange information 104.

[0055] The network device 100 can also be used to further separate one or more signals 103 from among the multiple signals 103 within a first interval based on the (previous) separated signals and based on the respective payloads included in the received first switching information 104. In this sense, the first switching information 104 is used to further separate the signals, and this can be done at each network device 100. Thus, the network device 100 and the adjacent network device 100 can cooperate to separate the signals.

[0056] It should be noted that the separation and further separation of the signals from among the multiple signals 103 can be regarded as decoding steps. Thus, the network device 100 can participate in the cooperative decoding of signals sent by multiple user devices (to the network device 100 and the adjacent network device 100), especially in a cell-free wireless network.

[0057] Each network device 100 can include a processor or processing circuitry (not shown) for performing, conducting, or initiating the various operations of the network device 100 described herein. The processing circuitry can include hardware and / or the processing circuitry can be controlled by software. The hardware can include analog circuitry or digital circuitry, or both analog circuitry and digital circuitry. The digital circuitry can include components such as an application-specific integrated circuit (ASIC), a field-programmable array (FPGA), a digital signal processor (DSP), or a general-purpose processor. Each network device 100 can also include a memory circuit that stores one or more instructions that can be executed by the processor or processing circuitry, especially under software control. For example, the memory circuit can include a non-transitory storage medium that stores executable software code that, when executed by the processor or processing circuitry, can cause the various operations of the network device 100 to be performed. In one embodiment, the processing circuitry includes one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory can carry executable program code that, when executed by the one or more processors, can cause the network device 100 to perform, conduct, or initiate the operations or methods described herein.

[0058] Further considerations and details of the above-described solution of the present invention will be described below.

[0059] Within the region of interest, a communication network or system may include a set of network devices 100 (e.g., APs), including the aforementioned network devices 100, their neighboring network devices 100, and optionally other network devices, and may include a set of user devices 110 (e.g., UEs). To represent such a communication network or system, for example, a first data set 101 and a plurality of second data sets 102 maintained separately at each network device 100 may be used. The contents of these data sets 101, 102 can be represented by two graphs: a connectivity graph as shown in Figure 2 (a) and an adjacent graph as shown in Figure 2 (b). These graphs can specifically show the contents of all data sets 101, 102.

[0060] The connectivity graph can have two types of nodes: network devices 100 (e.g., APs used in the figures) and user devices 110 (e.g., UEs used in the figures). The connectivity graph is a bipartite graph that describes the connectivity between user devices 110 and network devices 100. This means that a network device node can only be connected to one or more user device nodes of the graph. Similarly, a user device node can only be connected to one or more network device nodes of the graph. The edges in the connectivity graph between network devices 100 and user devices 110 indicate that the messages transmitted by user devices 110 have been recently decoded by network devices 100.

[0061] The adjacent graph has only one type of node, namely network devices 100. This graph (i.e., the data represented by the graph) may be known in advance by network devices 100. Two network devices 100 can be connected in the adjacent graph if they can potentially decode a common user device message. The following exemplary criteria can be used to determine whether two network devices 100 are connected in the adjacent graph: (i) Propagation characteristics ensure sufficient received signal strength at the two network devices 100; (ii) Geometric considerations of the geographical scenario, e.g., the distance between the two network devices 100 and the user device 110 is below a certain threshold; (c) The distance between the two network devices 100 is below a certain threshold; (d) Backhaul network architecture characteristics.

[0062] It should be noted that the illustration of the adjacent graph is an overview of the set of network devices 100. In contrast, each network device 100 may only have partial knowledge of the graph in the sense that each network device 100 may only know its neighboring network devices 100 (that is, the respective second data sets can be maintained by network devices 100).

[0063] Figure 2The two figures are for illustrative purposes only. Knowledge of these figures can be obtained through the following two objects locally stored and maintained by each network device 100: (i) a list of adjacent network devices 100 (an example of the first data set 101); (ii) for each network device 100 in the list of adjacent network devices 100 and the local network device 100 itself, a list of user devices 110 connected to the network device 100 (an example of the second data set 102), where any list can be empty if the network device 100 under consideration has no connected user devices 110. The present invention also refers to these lists as user ID lists or UID lists. Each element of the user ID list can be tagged with a timestamp.

[0064] In the present invention, taking UL communication as an example, where the user device 110 and the network device 100 are a transmitter and a receiver respectively. This UL communication is carried out over multiple time intervals. In each interval, a subset of user devices 110 (denoted as active user devices 110) can transmit a payload (message) consisting of a bit sequence. The network device 100 is unaware of the fact whether the user device 110 is active or inactive. Since a cell-free network is configured in the present invention, each user device 110 is not attached to a specific network device 100, and the payload of the user device 110 can be decoded by any network device 100.

[0065] Taking the single-input multiple-output block fading multiple access channel (SIMO-BF-MAC) as an example, it can be assumed that in each interval, the user device 110 and the network device 100 are synchronized in time such that the signal received by the network device 100 is the sum of the contributions of each user device 110. Under these assumptions, at a specific network device l with N l receiving antennas (where the index l can refer to the identifier of the network device 100), within an interval of length T, the baseband received signal from K l active user devices 110 can be expressed as

[0066]

[0067] where, is the transmission signal of user device k, is the channel vector between user device k and network device l, is the additive noise term. Correspondingly, the signal Y l can be the above-mentioned multiple signals 103.

[0068] Each user equipment 110 can encode its signal as a vector symbol s selected from a common vector constellation C k . The vector constellation can be characterized as a set of 2 B complex vectors:

[0069]

[0070] It should be noted that the constellation can be common to all user equipments 110 and can be known to all user equipments 110 and network device 100. The signal transmitted in each interval can consist of a user ID and payload bits. Figure 3 (a) shows an example of a transmission scheme that can be used in the present invention.

[0071] An example of the encoder is as shown in Figure 3 (b) and can be configured as follows. The user ID and payload bits can be concatenated, and the concatenated bit sequence can be converted into an integer index corresponding to an element of the constellation C having elements (thus, B = B1 + B2).

[0072] The network device 100 proposed by the present invention processes the signal sent by the user equipment 110 according to the following four steps: (i) the first decoding step, (ii) the exchange step, (iii) the second decoding step, (iv) the update step. Figure 4 Shows the decoding steps for two consecutive intervals (i.e., the first interval 401 and the second interval 402).

[0073] For example, steps (i), (iii), and (iv) can be independently executed at each network device 100 based on the current knowledge of the local UID list (i.e., an example of the second data set 102 maintained by the network device 100). These local UID lists can change over time in each step (iv). The processing described in the present invention is distributed because it does not involve a central network device or node that fully understands the transmitted signal and does not use a fully connected graph of the network.

[0074] In the first decoding step, without prior knowledge of the user ID or payload, each network device 100 separates the received signal 503 from the multiple signals 103 of multiple user equipments 110. Figure 5 (a) describes the input and output of this step, which can be completed by the receiver 501 of the network device 100, where is the recovered signal 503 of user equipment k, represents the number of active user equipments decoded by network device l.

[0075] The user ID and payload of each separated signal 503 can be recovered by a constellation demapper 502 as shown in Figure 5 (b).

[0076] The signal separation step is actually a step of demixing multiple transmitted signals 103. For example, for a SIMO-BF-MAC channel, this step can be achieved by solving the following optimization problem (where ).

[0077]

[0078] In the exchange step, the network device 100 can then exchange two types of information: (i) the user ID of the separated user equipment signal 503 (denoted as UID) (the second exchange information); or (ii) if the relevant user equipment 110 has been decoded in the first decoding step of the current interval 401, the index of the transmitted signal s in the constellation C of the separated user signal 504 (denoted as SIDX). SIDX includes the user ID and its payload and can be the above-mentioned first exchange information 104.

[0079] Then, adjacent network devices 100 can use the exchanged information to improve their performance in the next decoding step or within the next interval 402. It should be noted that the exchange step can depend on the results of the second decoding step of the previous interval and the first decoding step of the current interval 401.

[0080] In the exchange step, the network device 100 sends the UID or SIDX of its decoded user equipment 110 to its adjacent network device 100 according to the Figure 6 flowchart shown.

[0081] Specifically, at block 601, the network device 100 determines whether the user equipment 110 has been decoded in the first decoding step of the current interval (referred to here as the "resource block"). If so, then at block 602, the network device 100 determines whether the user equipment 100 belongs to the second data set 102 maintained at the network device 100, that is, whether the user ID of the user equipment 110 is in the second data set. If so, then at block 604, the network device sends the first exchange information 104 to the adjacent network device 100 that is in the first data set 101 and is associated with the second data set 102 including the user ID. If not, then at block 605, the network device 100 sends the first exchange information 104 to the adjacent network device 100 and sends the second exchange information to the remaining adjacent network devices 100 in the first data set 101 that are associated with the second data set 102 including the user ID.

[0082] If, at block 601, the answer is no, then at block 603, network device 100 determines whether user device 100 has decoded in the second decoding step of a previous interval. If so, then at block 606, network device sends the second exchange information to all neighboring network devices 100 in the first data set 101. If so, then network device 100 does not perform any operation.

[0083] In the second decoding step, network device 100 performs a second separation of the received plurality of signals 103, taking into account the previously decoded signals 503 (in the first decoding step) and the received SIDX of the user devices 110 decoded on neighboring network devices 100 (the first exchange information 104 received in the exchange step). At a given network device 100, let K′ l <K l be the total number of successfully decoded user signals 503 resulting from both the first decoding step and the exchange step. For example, for SIMO - BF - MAC, the received signal Y l can be re - defined as shown in Figure 7 (A).

[0084] Figure 7 (b) Denote the number of active user devices 110 (i.e., the signals 703 of user devices 110 separated in further separation) decoded by network device l at the end of the second decoding step as

[0085] The interference cancellation (SIC) receiver 501 is an example of a decoder that can be applied here, as it uses previously decoded signals to decode unknown signals. In the case of SIMO - BF - MAC, it can be achieved by solving the following optimization problem.

[0086]

[0087] It should be noted that in the case of random access with joint activity detection and payload decoding, this type of receiver (interference cancellation) is used in many detection schemes.

[0088] In the updated set, the user ID list (the second data set 102) is updated based on the results of both the first decoding step of the current interval 401 and the second decoding of the previous interval.

[0089] In this update step, the user ID list can be updated by maintaining useful connections (so that the list does not become too large) and adding newly connected user devices 110 after the newly connected ones. This update can be done based on locally separated signals 503, 703 and information received from adjacent network devices 100. Since each network device 100 performs the update process of its own subgraph (i.e., the local update of the second data set 102), the connected graph can be updated in a distributed manner. In this step, the network device 100 can: (i) add the user device 110 to the "local" network device UID list (the second data set 102 associated with the network device 100) of the user devices 110 whose signals 503, 703 have been locally decoded, and mark the edge with a timestamp; (ii) add the user device 110 to the adjacent network device UID list (the second data set 102 associated with the adjacent network device 100) when this information has been transmitted in the exchange step, and mark the edge with a timestamp; (iii) prune the UID list elements whose associated timestamps are earlier than the threshold (timeout).

[0090] This threshold can be set according to network conditions and can be updated by the upper layer of the network. For example, the timeout threshold can be dynamically adjusted to have an optimized connected subgraph on each network device 100. This can prevent the UID list from being too large (useless entries) or too small (insufficient amount of information exchanged).

[0091] In the following illustrative example, three APs are considered as network devices 100 and five UEs are considered as user devices 110. This example goes through four time intervals (also called four macro time snapshots). Within each interval, the timeline is represented according to the four main steps of the proposed scheme above. Figure 8 Summarizes the four intervals of this example.

[0092] In the first interval (see also Figure 9 ), AP1, AP2, and AP3 have successfully separated the following signals (s1, s3), (s4), and (s3) respectively. After the exchange step, there are no remaining signals to be separated in the second decoding step, and the connected graph is updated accordingly; only new edges are added here: (AP1-UE1), (AP1-UE3), (AP3-UE3), and (AP2-UE4).

[0093] In the second interval (see Figure 10), AP1, AP2, and AP3 successfully separated the following signals (s1), (s2), and (s3, s4), respectively. After the exchange step, for AP2 and AP3, there are no remaining signals to be separated in the second decoding step, but at AP1, the set (s1) still needs to be separated in the second decoding step. Then, the connectivity graph is updated accordingly; only the following new edges are added: (AP1-UE5), (AP2-UE2), and (AP3-UE4).

[0094] In the third interval (see Figure 11 ), AP1, AP2, and AP3 successfully separated the following sets (s1, s3), (s4), and (s3), respectively. After the exchange step, for AP1 and AP2, there are no remaining signals to be separated in the second decoding step, but at AP3, the set (s5) still needs to be separated in the second decoding step. Here, no new connections need to be added to the connectivity graph.

[0095] In the fourth interval (see Figure 12 ), AP1 and AP3 successfully separated the following sets (s5) and (s3), respectively. It should be noted here that AP3 transmits information about the ID of UE5 because it has been decoded in the second decoding step of the previous time interval. After the exchange step, there are no remaining signals to be separated in the second decoding step. The connectivity graph is updated accordingly; the connection (AP3-UE5) is added accordingly, and the connections (AP1-UE1), (AP1-UE3), and (AP3-UE3) are deleted due to timeout.

[0096] Figure 13 A method 1300 of a network device 100 for a cell-free wireless communication network is shown. The method 1300 can be executed by any of the above network devices 100.

[0097] The method 1300 includes step 1301: maintaining a first data set 101 indicating one or more adjacent network devices 100, and step 1302: maintaining a plurality of second data sets 102 respectively indicating one or more user IDs. One of the plurality of second data sets 102 is associated with the network device 100, and each of the other second data sets 102 in the plurality of second data sets 102 is associated with one of the one or more adjacent network devices 100 in the first data set 101.

[0098] The method 1300 further includes step 1303: receiving a plurality of signals 103 from a plurality of user devices 110 in a first interval 401, wherein each signal 503, 703 includes a corresponding user ID of one of the user devices 110 in the user devices 110 and a corresponding payload of one of the user devices 110 in the user devices 110.

[0099] Method 1300 further includes step 1304 (corresponding to the first decoding step described above): separating one or more signals 503 from the plurality of signals 103 within the first interval 401 to obtain the corresponding user ID and the corresponding payload of the one or more signals 503.

[0100] Method 1300 further includes step 1305 (corresponding to the exchange step described above): sending first exchange information 104 to each adjacent network device 100 within the first interval 401, each adjacent network device 100 being in the first data set 101 and associated with a second data set 102 including at least one of the corresponding user IDs obtained. The first exchange information 104 includes at least one of the corresponding user IDs obtained and at least one of the corresponding payloads obtained. In step 1305, first exchange information 104 may also be received from the adjacent network device 100, wherein the received first exchange information 104 includes at least one of the corresponding user IDs of the plurality of signals 103 and at least one of the corresponding payloads.

[0101] Method 1300 may further include the following steps (corresponding to the second decoding step described above): further separating one or more signals 703 from the plurality of signals 103 within the first interval 401 based on the previously separated signals 503 and the corresponding payloads in the received first exchange information 104.

[0102] Method 1300 may further include the following steps (corresponding to the update step described above): updating the second data set 102 associated with the network device 100 based on one or more separated signals 503 and one or more further separated signals 703, and / or updating one or more second data sets 102 associated with one or more adjacent network devices 100 based on the first exchange information 104 received from one or more adjacent network devices 100.

[0103] In summary, the present invention proposes a cooperation process in a random access scenario, which includes structuring and updating data sets 101, 102 that indicate the network device to user device connections (e.g., AP-UE connections) at each network device 100 in a set of network devices 100. This is done to exchange separated signals 503, 703 between network devices 100 based on the learned local data set 102.

[0104] The present invention has been described by way of example in conjunction with various embodiments and implementation manners. However, upon study of the drawings, the present invention, and the independent claims, those skilled in the art will be able to understand and implement other variations when implementing the claimed subject matter. In the claims as well as in the specification, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items described in the claims. The fact that certain measures are recited in mutually different dependent claims does not by itself indicate that a combination of these measures cannot be used in an advantageous implementation.

Claims

1. A network device (100) for a cell-free wireless communication network, characterized in that, The network device (100) is configured to: Maintain a first data set (101) indicating one or more neighboring network devices (100); Maintain a plurality of second data sets (102) respectively indicating one or more user IDs, wherein one of the plurality of second data sets (102) is associated with the network device (100), and each of the other second data sets (102) in the plurality of second data sets (102) is associated with one of the one or more neighboring network devices (100) in the first data set (101); Receive a plurality of signals (103) from a plurality of user devices (110) within a first interval (401), wherein each signal (503, 703) includes a corresponding user ID of one of the plurality of user devices (110) and a corresponding payload of one of the plurality of user devices (110); Separate one or more signals (503) among the plurality of signals (103) within the first interval (401) to obtain the corresponding user ID and the corresponding payload of the one or more signals (503); Send first exchange information (104) to each neighboring network device (100) within the first interval (401), each neighboring network device (100) being in the first data set (101) and associated with a second data set (102) including at least one of the obtained corresponding user IDs; Wherein the sent first exchange information (104) includes at least one of the obtained corresponding user IDs and at least one of the obtained corresponding payloads.

2. The network device (100) according to claim 1, characterized in that, If a specific user ID among the obtained corresponding user IDs is not in the second data set (102) associated with the network device (100), the network device (100) is configured to: Send second exchange information to each neighboring network device (100) within the first interval (401), each neighboring network device (100) being in the first data set (101) and associated with a second data set (102) not including the specific user ID; Wherein the second exchange information includes the specific user ID but does not include the corresponding payload corresponding to the specific user ID.

3. The network device (100) according to claim 1 or 2, characterized in that, The network device (100) is further configured to: Receive first exchange information (104) from a neighboring network device (100) within the first interval (401), wherein the received first exchange information (104) includes at least one of the corresponding user IDs of the plurality of signals (103) and at least one of the corresponding payloads; Further separate one or more signals (103) among the plurality of signals (103) within the first interval (401) based on the corresponding payloads in the separated signals (503) and the received first exchange information (104).

4. The network device (100) according to claim 2 or 3, characterized in that, The network device (100) is further configured to: Transmit the second exchange information to each adjacent network device (100) in the first data set (101) within the second interval (402).

5. The network device (100) according to any one of claims 1 to 4, characterized in that, For: Perform the separation of the one or more signals (503) among the plurality of signals (103) within the first interval (401) without prior knowledge of the corresponding user IDs and the corresponding payloads of the one or more signals (503).

6. The network device (100) according to any one of claims 3 to 5, characterized in that, The first exchange information (104) received from the adjacent network device (100) includes one or more corresponding user IDs and one or more corresponding payloads, which are different from the corresponding user IDs and the corresponding payloads in the transmitted first exchange information (104).

7. The network device (100) according to any one of claims 1 to 6, characterized in that, In the further separation of the one or more signals (703) among the plurality of signals (103) within the first interval (401), the network device (100) is used to perform interference cancellation.

8. The network device (100) according to any one of claims 3 to 7, characterized in that, Also for: Update the second data set (102) associated with the network device (100) based on the one or more separated signals (503) and the one or more further separated signals (703), and / or update one or more second data sets (102) associated with the one or more adjacent network devices (100) based on the first exchange information (104) received from the one or more adjacent network devices (100).

9. The network device (100) according to claim 8, wherein For updating the second data set (102) associated with the network device (100) and / or the one or more second data sets (102) associated with the one or more adjacent network devices (100) by at least one of the following: Add the one or more user IDs to the second data set (102) associated with the network device (100); Add the one or more user IDs to one or more second data sets (102) associated with one or more adjacent network devices (100); Delete one or more user IDs from the second data set (102) associated with the network device (100); Delete one or more user IDs from the one or more second data sets (102) associated with the one or more adjacent network devices (100).

10. The network device (100) according to claim 9, characterized in that, Also for associating a timestamp with any user ID added to the second data set (102).

11. The network device (100) according to claim 9 or 10, characterized in that, Also for: If the timestamp associated with the user ID is earlier than a threshold, delete any user ID from the second data set (102).

12. The network device (100) according to claim 11, characterized in that, Also for adjusting the threshold based on at least one of network conditions and upper layer configurations.

13. The network device (100) according to any one of claims 9 to 12, characterized in that, Also for: If the user ID of the separated signal is not yet in the second data set (102) of the network device (100), add the user ID of the separated signal or the user ID of the further separated signal to the second data set (102) of the network device (100); and / or If the user ID in the first exchange information (104) is not yet in the second data set (102) of the adjacent network device (100), add the user ID in the first exchange information (104) received from the adjacent network device (100) to the second data set (102) of the adjacent network device (100).

14. A method (1300) for a network device (100) in a cell-free wireless communication network, characterized in that, The method (1300) includes: maintaining (1301) a first data set (101) indicating one or more adjacent network devices (100); maintaining (1302) a plurality of second data sets (102) respectively indicating one or more user IDs, wherein one of the plurality of second data sets (102) is associated with the network device (100), and each of the other second data sets (102) in the plurality of second data sets (102) is associated with one of the one or more adjacent network devices (100) in the first data set (101); receiving (1303) a plurality of signals (103) from a plurality of user devices (110) within a first interval (401), wherein each signal (503, 703) includes a corresponding user ID of one of the plurality of user devices (110) and a corresponding payload of one of the plurality of user devices (110); separating (1304) one or more signals (503) from the plurality of signals within the first interval (401) to obtain the corresponding user ID and the corresponding payload of the one or more signals (103); sending (1305) first exchange information (104) to each adjacent network device (100) within the first interval (401), each adjacent network device (100) being in the first data set (101) and associated with a second data set (102) including at least one of the obtained corresponding user IDs; wherein the first exchange information (104) includes at least one of the obtained corresponding user IDs and at least one of the obtained corresponding payloads.

15. A computer program, characterized in that, The computer program includes instructions which, when the program is executed by a computer, cause the computer to perform the method (1300) according to claim 14.

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