A regionalized unlicensed random access method for large-scale terminal communication

Abstract

The application discloses a regionalized unlicensed random access method for large-scale terminal communication, and establishes an uplink unlicensed random access network for large-scale terminal communication, wherein the uplink unlicensed random access network comprises a plurality of access points, a central processing unit and a plurality of terminals, the plurality of access points are distributedly arranged in a coverage area of the uplink unlicensed random access network and are connected with the central processing unit; the same pilot usage between different access areas is determined as inter-area pilot multiplexing in the method, and according to large-scale channel parameters between each access area and each access point, inter-area equivalent pollution and inter-area pollution budget are determined, so that whether different areas are suitable for multiplexing the same pilot is judged; compared with a global unified pilot pool or a random pilot selection mode without distinguishing spatial relationship in the prior art, the method can control inter-area pilot pollution and improve pilot resource multiplexing efficiency.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, specifically relating to a regionalized unlicensed random access method for large-scale terminal communication. Background Technology

[0002] With the development of the Internet of Things (IoT), the Industrial Internet, smart cities, and large-scale sensing and monitoring services, large-scale communication scenarios involve a vast number of widely distributed terminals with unpredictable access times. These terminals are typically used for services such as status sensing, environmental monitoring, industrial control, smart metering, and anomaly alarms. Their uplink data is characterized by short data packets, low power consumption, intermittency, and random activation. In these scenarios, terminals do not continuously transmit online but randomly access the network based on service events, sampling periods, or alarm triggering conditions. Therefore, the network needs to support low-overhead uplink access from a large number of terminals within a short period of time.

[0003] Traditional authorized access methods typically require terminals to first send a scheduling request, then wait for the network to allocate radio resources before uplink data transmission can begin. For a massive number of terminals, if each terminal follows this process, it will generate a large amount of control signaling interaction, resulting in high access latency and resource scheduling overhead, making it difficult to adapt to the characteristics of short packets, bursts, and random activation in large-scale terminal communication. Unauthorized random access allows terminals to directly select a pilot and send uplink data after random activation, thereby reducing scheduling requests and resource authorization processes, lowering control signaling overhead and access latency, and making it more suitable for uplink random access scenarios with a large number of terminals.

[0004] However, during unlicensed random access, pilot collisions are prone to occur because multiple terminals may randomly activate and select the same pilot within the same access slot. When multiple terminals in the same area select the same pilot, the receiver struggles to distinguish the channel and data of the corresponding terminal, typically leading to access failure for that terminal. Furthermore, with limited pilot resources, different spatial regions often need to reuse the same pilot; while reusing the same pilot across different regions can improve pilot resource utilization, it also introduces inter-regional pilot pollution, affecting the channel estimation and data detection performance of the access point and central processing unit.

[0005] Existing unlicensed random access methods typically employ a globally unified pilot pool for terminal-oriented random pilot selection, rarely considering the non-uniform spatial distribution characteristics of terminals, i.e. Figure 1 The diagram shown illustrates the structure of an uplink unlicensed random access network in an existing terminal-oriented random pilot selection method using a globally unified pilot pool. Figure 1The uplink transmission in the diagram represents the active terminal sending pilot signals and uplink data to the access point. In real-world large-scale terminal communication scenarios, terminal density, service activation probability, and access load may vary significantly across different areas. Some hotspot areas may experience a large number of terminals accessing simultaneously within a short period, while low-load areas have relatively lower pilot resource requirements. If a unified pilot pool or averaged pilot configuration is still used, it can easily lead to severe pilot collisions in hotspot areas and may also cause unnecessary inter-regional pilot reuse pollution, thereby reducing the overall system access success rate and the worst-case access reliability. Therefore, existing unlicensed random access methods still struggle to simultaneously address intra-regional collision suppression, inter-regional pollution control, and access reliability in scenarios with limited pilot resources, uneven terminal spatial distribution, and the coexistence of inter-regional pilot reuse. Summary of the Invention

[0006] The purpose of this invention is to address the problems raised in the background art by proposing a regionalized unlicensed random access method for large-scale terminal communication.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention proposes a regionalized unlicensed random access method for large-scale terminal communication, comprising:

[0009] An uplink unlicensed random access network for large-scale terminal communication is established, and the uplink unlicensed random access network includes multiple access points, a central processing unit and multiple terminals. The multiple access points are distributed and deployed within the coverage area of ​​the uplink unlicensed random access network and are connected to the central processing unit.

[0010] The coverage area of ​​the uplink unlicensed random access network is divided into multiple access areas, and the active load of each access area is determined.

[0011] Determine the pilot requirements for each access area based on the active load of each access area;

[0012] Based on the large-scale channel parameters between each access area and each access point, determine the equivalent pollution amount between areas and the pollution budget between areas;

[0013] Based on the pilot requirements of each access area, the equivalent pollution amount between areas, and the pollution budget between areas, a corresponding set of target pilots is configured for each access area.

[0014] The central processing unit sends the target pilot set of each access area to the access point of the corresponding access area. The access point broadcasts to all terminals. The activated terminal selects a pilot from the target pilot set of its access area according to its access area. Each terminal sends the selected pilot during the pilot transmission phase of the current unlicensed random access time slot, and then sends uplink data during the data transmission phase of the current unlicensed random access time slot.

[0015] After receiving the pilot signal and uplink data, the access point sends a signal to the central processing unit, which then determines whether the terminal's unauthorized random access to the local area was successful.

[0016] Preferably, all pilots in the uplink unlicensed random access network constitute a pilot set, and any two different pilots in the pilot set are orthogonal to each other.

[0017] Preferably, the coverage area of ​​the uplink unlicensed random access network is divided into multiple access areas, and the active load of each access area is determined, including:

[0018] The coverage area is divided into multiple non-overlapping access areas according to the preset area size;

[0019] Acquire spatial distribution information and random activation information of terminals in each access area. The spatial distribution information of terminals represents the distribution density of terminals at different locations, and the random activation information represents the probability of a terminal being activated in an unauthorized random access time slot. Activated terminals are called active terminals, and inactive terminals are called potential terminals.

[0020] The active load of each access area is calculated based on the spatial distribution information of active terminals within each access area, and the calculation formula is as follows:

[0021] ;

[0022] in, For the first Active load in each access area For position Spatial distribution information of active terminals Indicates the first One access area.

[0023] Preferably, determining the pilot requirements of each access area based on the active load of each access area includes:

[0024] The number of pilots in the access area is calculated as follows: The probability that no co-pilot collision occurs within the access area is given by the following formula:

[0025] ;

[0026] in, For the first The probability of no co-pilot collision occurring within an access area, and Greater than or equal to a preset threshold;

[0027] The minimum number of pilots whose probability of no co-pilot collisions within the access area meets the preset threshold requirement is determined as the number of pilots. Pilot requirements for each access area;

[0028] When multiple active terminals in the same access area select the same pilot signal, the multiple active terminals are determined to have experienced a pilot collision within the area.

[0029] When active terminals in different access areas select the same pilot, the use of the same pilot between different access areas is determined as inter-area pilot reuse.

[0030] Preferably, determining the equivalent pollution levels between regions and the pollution budget between regions includes:

[0031] Inter-regional equivalent contamination is used to represent the intensity of pilot contamination caused to channel estimation and data detection when different access areas reuse the same pilot. The formula for calculating inter-regional equivalent contamination is as follows:

[0032] ;

[0033] in, Indicates the first The access area in the first Equivalent contamination between regions on each pilot frequency Indicates the first Does the first access area use the first...? The pilot, i.e. the first pilot... Does the first access area use the first...? The region-pilot assignment variable for each pilot is set to 1 when in use and 0 otherwise. Indicates the first Does the first access area use the first...? The pilot, i.e. the first pilot... Does the first access area use the first...? Region-pilot assignment variable for each pilot, Indicates the first Active load in each access area Indicates the first Pilot requirements for each access area Indicates the first The access area for the first Inter-regional pollution coefficient of each access area It is the set consisting of all access areas;

[0034] The formula for calculating pollution budgets between regions is as follows:

[0035] ;

[0036] in, Indicates the first The pollution budget between access areas is expressed as a preset reliability parameter. Next, the The maximum inter-region equivalent contamination level that each access area can tolerate on any assigned pilot, and , This represents the upper bound that satisfies the conditions within the curly braces. For the first The equivalent pollution level between the receiving areas for each access area is: The probability of successful inter-region pilot reuse at that time. Indicates the first The inter-regional pilot reuse reliability threshold corresponding to each access area.

[0037] Preferably, based on the pilot requirements of each access area, the equivalent pollution level between areas, and the pollution budget between areas, a corresponding set of target pilots is configured for each access area, including:

[0038] With the optimization objective of maximizing the probability of successful unlicensed random access in each access area, the target pilot set of each access area is configured, and the probability of successful unlicensed random access in each access area is expressed as the product of the probability of no collision between the same pilot within the access area and the probability of successful pilot reuse between areas.

[0039] The optimization objective is transformed into setting preset reliability parameters. The feasibility assessment problem is whether there exists a region-pilot allocation matrix such that the probability of successful unlicensed random access in each access region is greater than or equal to a preset reliability parameter. ;

[0040] The feasibility assessment problem is transformed into three constraints: the first constraint is that each access area obtains the number of pilots that meet the corresponding pilot requirements; the second constraint is that the equivalent pollution amount between areas in each access area on each pilot does not exceed the corresponding pollution budget; and the third constraint is that the area-pilot allocation variable is a binary variable.

[0041] The central processing unit configures a corresponding set of target pilots for each access area to solve the area-pilot allocation matrix.

[0042] Preferably, the central processing unit configures a corresponding set of target pilot signals for each access area, including:

[0043] Step 1: For each access area, calculate the remaining pilot demand, candidate pilot set, and pollution correlation degree of each access area. Based on the remaining pilot demand, candidate pilot set, and pollution correlation degree of each access area, calculate the configuration priority index of each access area and select the access area with the highest priority index as the current access area to be configured. When multiple access areas have the same configuration priority index, the access area with the highest active load is selected as the current access area to be configured.

[0044] Step II: For the current access area to be configured, the central processing unit selects pilot candidates from the pilot set and configures them to the current access area to be configured. When configuring each candidate, the newly added pollution cost is calculated. The central processing unit selects the minimum pollution cost from all pollution costs corresponding to the current access area to be configured and configures the pilot corresponding to the minimum pollution cost to the current access area to be configured. Steps I-II are repeated until the number of pilots configured in all access areas reaches the corresponding pilot requirements, and the pilots configured in each access area constitute the target pilot set of the current access area, thus obtaining the area-pilot allocation matrix.

[0045] Preferably, the central processing unit determines whether the terminal's unauthorized random access to the localized area is successful by:

[0046] The central processing unit first determines whether the terminal's current unlicensed random access to the region is due to a pilot collision within the region or pilot reuse between regions. If it is a pilot collision within the region, the terminal's current unlicensed random access to the region fails. If it is pilot reuse between regions, the unit combines channel estimation and data detection metrics to determine whether the terminal's current unlicensed random access to the region is successful.

[0047] The channel estimation and data detection metrics are based on the received signal-to-interference-plus-noise ratio (SINR). The SINR is compared with a preset threshold. When the SINR is greater than or equal to the preset threshold, it indicates that the terminal has successfully performed unauthorized random access in the current region. When the SINR is less than the preset threshold, it indicates that the terminal has failed to perform unauthorized random access in the current region.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0049] 1. This regionalized unlicensed random access method for large-scale terminal communication determines the use of the same pilot between different access areas as inter-regional pilot reuse. Based on the large-scale channel parameters between each access area and each access point, it determines the equivalent pollution amount and pollution budget between regions, thereby determining whether different regions are suitable for reusing the same pilot. Compared with the existing methods of globally unified pilot pool or random pilot selection without distinguishing spatial relationships, this method can improve the pilot resource reuse efficiency while controlling inter-regional pilot pollution.

[0050] 2. This regionalized unlicensed random access method for large-scale terminal communication can adaptively determine pilot requirements based on the active load of each access area, and configure the target pilot set under the constraints of equivalent pollution levels and pollution budgets between areas. This improves the worst-case access reliability and average access success rate under conditions of hotspot load (i.e., a large number of terminals) and limited pilot resources. This method demonstrates effectiveness in suppressing intra-area pilot collisions, controlling inter-area pilot reuse pollution, and improving overall access reliability in large-scale unlicensed random access scenarios.

[0051] 3. This regionalized unlicensed random access method for large-scale terminal communication determines the active load based on the spatial distribution information and random activation information of terminals in each access area, so that the pilot configuration can reflect the differences in active load between different areas, and avoid the area with many active terminals becoming a reliability bottleneck due to insufficient pilot resources. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the uplink unlicensed random access network structure in the terminal-oriented random pilot selection method using a globally unified pilot pool in the existing technology.

[0053] Figure 2 This is a flowchart illustrating the regionalized unlicensed random access method for large-scale terminal communication according to the present invention.

[0054] Figure 3 This is a schematic diagram of the uplink unlicensed random access network in this invention;

[0055] Figure 4 This is a topological schematic diagram of the normalized load density coefficient under the uniform load coverage area of ​​the present invention.

[0056] Figure 5 This is a topological schematic diagram of the normalized load density coefficient under the central hotspot coverage area of ​​the present invention.

[0057] Figure 6 This is a topological schematic diagram of the normalized load density coefficient under the strong hotspot coverage area of ​​the present invention.

[0058] Figure 7This is a topological schematic diagram of the normalized load density coefficient under the edge hotspot coverage area of ​​the present invention;

[0059] Figure 8 This is a schematic diagram comparing the worst-case success probability of the method of the present invention with that of four existing methods under a uniform load coverage area, as the active load scaling factor changes.

[0060] Figure 9 This diagram illustrates the comparison of the worst-case success probability of the method of the present invention with that of four existing methods under the coverage area of ​​a central hotspot, as the active load scaling factor changes.

[0061] Figure 10 This diagram illustrates the comparison of the worst-case success probability of the method of the present invention and four existing methods under strong hotspot coverage areas with variations in the active load scaling factor.

[0062] Figure 11 This is a schematic diagram comparing the worst-case success probability of the method of the present invention with that of four existing methods under the edge hotspot coverage area as the active load scaling factor changes;

[0063] Figure 12 This is a schematic diagram comparing the performance decomposition results of the method of the present invention with four existing methods under a uniform load coverage area.

[0064] Figure 13 This is a schematic diagram comparing the performance decomposition results of the method of the present invention with four existing methods in the central hotspot coverage area;

[0065] Figure 14 This is a schematic diagram comparing the performance decomposition results of the method of the present invention with four existing methods in a strong hotspot coverage area.

[0066] Figure 15 This diagram illustrates a comparison of the performance decomposition results of the method of the present invention and four existing methods in the edge hotspot coverage area. Detailed Implementation

[0067] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0068] Unless otherwise defined, 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 invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0069] In one embodiment, such as Figures 2-15 As shown, a regionalized unlicensed random access method for large-scale terminal communication is provided, including:

[0070] Step 1: Establish an uplink unlicensed random access network for large-scale terminal communication. The uplink unlicensed random access network includes multiple access points, a central processing unit, and multiple terminals. The multiple access points are distributed and deployed within the coverage area of ​​the uplink unlicensed random access network and are connected to the central processing unit (through the fronthaul link).

[0071] The network coverage area is denoted as , In a two-dimensional real space, in this embodiment, the network coverage area has a side length of... A square area (where all terminals are also distributed within the network's coverage area); a set of multiple access points is represented as: ,in, Indicates the first One access point.

[0072] In this context, all pilots in the uplink unlicensed random access network constitute the pilot set, and the pilot set is represented as follows: , Indicates the first There are 1 pilots, and any two different pilots in the pilot set are orthogonal to each other.

[0073] Terminals are classified into potential terminals and active terminals, and the probability of a terminal being activated during an unauthorized random access time slot is determined by the following criteria: In order to characterize the randomness of the spatial distribution of large-scale terminal access scenarios and the spatial non-uniformity of service load, the spatial distribution of terminals is modeled as a non-uniform Poisson point process, and the activated terminals are called active terminals, while the inactive terminals are called potential terminals.

[0074] The total length of an unlicensed random access slot is denoted as It includes a pilot transmission phase and a data transmission phase, wherein the length of the pilot transmission phase is denoted as . The length of the data transmission phase is denoted as .

[0075] Step 2: Divide the coverage area of ​​the uplink unlicensed random access network into multiple access areas, and determine the active load of each access area, including:

[0076] Step 2.1: Divide the coverage area into multiple non-overlapping access areas according to a preset area size. All access areas constitute an access area set, represented as... , Indicates the first One access area;

[0077] In this embodiment, the network coverage area has a side length of [missing information]. A square region, with a side length of If the square access area is divided into equal areas, then the number of access areas in each spatial dimension is expressed as: The total number of access areas is expressed as Multiple access areas constitute a non-overlapping division of the network's coverage area, that is... (That is, the sum of all access areas constitutes the network coverage area), and for any different access areas and ,satisfy Each terminal is distributed across its respective access area.

[0078] like Figure 3 As shown, the coverage area is divided into 9 access areas, and in Figure 3 The regions are sequentially represented as region 1, region 2, region 3, region 4, region 5, region 6, region 7, region 8, and region 9. Figure 3 The example of pilot signals is given in the text (e.g.) Figure 3 (example of pilot label in the text), and , , , and The first pilot, second pilot, third pilot, fourth pilot, and fifth pilot are represented in sequence. Using the same pilot in different areas is called pilot reuse.

[0079] Step 2.2: Obtain the spatial distribution information and random activation information of terminals in each access area (the specific method of obtaining this information is well known in the art and will not be described in detail). The spatial distribution information of terminals represents the distribution density of terminals at different locations, and the random activation information represents the probability of a terminal being activated in an unauthorized random access time slot.

[0080] Step 2.3: Calculate the active load of each access area based on the spatial distribution information of active terminals within each access area, and the calculation formula is as follows:

[0081] ;

[0082] in,

[0083] ;

[0084] in, For the first Active load in each access area For position Spatial distribution information of active terminals Indicates the first One access area, Indicates position Spatial distribution information of potential terminals.

[0085] Step 3: Determine the pilot requirements for each access area based on the active load of each access area, including:

[0086] First, it should be noted that when multiple active terminals in the same access area select the same pilot, the multiple active terminals are judged to have experienced a pilot collision within the area, and the unauthorized random access of the terminal that experienced the pilot collision within the area is judged to have failed.

[0087] When active terminals in different access areas select the same pilot, the use of the same pilot between different access areas is determined as inter-area pilot reuse.

[0088] Step 3.1: Calculate the number of pilots in the access area. The probability that no co-pilot collision occurs within the access area is given by the following formula:

[0089] ;

[0090] in, For the first Each access area has a pilot number of When randomly selecting pilots, the first The probability of no co-pilot collision occurring within an access area, and Greater than or equal to a preset threshold;

[0091] Step 3.2: Determine the minimum number of pilots required to meet the preset threshold (collision reliability threshold within the area) for which no co-pilot collisions occur within the access area. The pilot requirements for each access area are as follows:

[0092] Definition of the first The collision reliability threshold within the region corresponding to each access region is: ,and The minimum number of candidate pilots required to ensure that the probability of no collisions with the same pilot within the region meets the collision reliability threshold requirement within the region is determined as the number of pilots. Pilot requirements for each access area ,Right now ,in, Indicates the first Number of candidate pilot signals required for each access area Let represent the set of positive integers, where is the set of all integers that can make the _i_i = _i_i. The probability of no co-pilot collision within the access area is not less than Among the candidate pilot requirements, the smallest one is selected as the first. Pilot requirements for each access area , can be obtained .

[0093] Step 4: Based on the large-scale channel parameters between each access area and each access point, determine the equivalent pollution amount between areas and the pollution budget between areas (where the equivalent pollution amount between areas is...). Pollution levels and inter-regional pollution budgets are only in the first The first access area and the first The access area uses the first (Only exists when there is a pilot signal), including:

[0094] Step 4.1: The inter-regional equivalent pollution level is used to represent the intensity of pilot pollution caused to channel estimation and data detection when different access areas reuse the same pilot. The formula for calculating the inter-regional equivalent pollution level is as follows:

[0095] ;

[0096] in,

[0097] ;

[0098] ;

[0099] in, Indicates the first The access area in the first Equivalent contamination between regions on each pilot frequency Indicates the first Does the first access area use the first...? The pilot, i.e. the first pilot... Does the first access area use the first...? The region-pilot assignment variable for each pilot, when used... Select 1 if the value is 1, otherwise select 0. Indicates the first Does the first access area use the first...? The pilot, i.e. the first pilot... Does the first access area use the first...? The region-pilot assignment variable for each pilot, when used... Select 1 if the value is 1, otherwise select 0. Indicates the first Active load in each access area Indicates the first Pilot requirements for each access area Indicates the first The access area for the first Inter-regional pollution coefficient of each access area The set comprises all access areas. In this embodiment, a block fading channel model is adopted, meaning that the channel remains unchanged within an unlicensed random access slot. Indicates the first The number of active terminals in the access area to the first Large-scale channel parameters between access points Indicates the location active terminals and the first Large-scale channel parameters for each access point Indicates the first The set of access points corresponding to each access area, and ;

[0100] Where for formula The molecule represents the first Active terminals within the access area in the first The average received signal strength generated at the set of access points in the access area, where the denominator represents the average received signal strength at the set of access points in the access area, is given by the denominator. The average reception strength generated by active terminals within a given access area at the corresponding set of access points (the larger this ratio, the stronger the reception strength of the first access point). The first access area and the first The more dangerous it is for multiple access areas to reuse the same pilot signal; the smaller this ratio, the safer it is for them to reuse the same pilot signal.

[0101] Step 4.2, the formula for calculating the pollution budget between regions is as follows:

[0102] ;

[0103] in,

[0104] ;

[0105] ;

[0106] ;

[0107] in, Indicates the first The pollution budget between access areas is expressed as a preset reliability parameter. Next, the The maximum inter-region equivalent contamination level that each access area can tolerate on any assigned pilot, and , This represents the upper bound that satisfies the conditions within the curly braces. For the first The equivalent pollution level of each access area is as follows: The probability of successful inter-region pilot reuse at that time. This indicates an indicator function that returns 1 if the condition within the curly braces is true, and 0 otherwise. Indicates the first Inter-region pilot reuse reliability threshold for each access area Indicates position The active terminal is in the The equivalent useful channel strength over the set of access points corresponding to each access area. Indicates the SINR threshold. Indicates position The maximum inter-regional equivalent pollution level that an active terminal can withstand while meeting the SINR threshold requirements.

[0108] Step 5: Based on the pilot requirements of each access area, the equivalent pollution level between areas, and the pollution budget between areas, configure the corresponding target pilot set for each access area, including:

[0109] Step 5.1: With the optimization objective of maximizing the minimum unlicensed random access success probability in each access area, configure the target pilot set for each access area. The probability of successful unlicensed random access in each access area is expressed as the product of the probability of no collision between the same pilot within the access area and the probability of successful pilot reuse between areas. That is, the optimization objective is expressed as:

[0110] ;

[0111] in,

[0112] ;

[0113] in, The matrix formed by the area-pilot allocation variables between all access areas and all pilots is called the area-pilot allocation matrix. In the context of the region-pilot allocation matrix, the first... The probability of successful unauthorized random access in each access zone. In the context of the region-pilot allocation matrix, the first... The probability of successful inter-area pilot reuse in an access area.

[0114] The optimization objective is transformed into setting preset reliability parameters. The feasibility assessment problem is whether there exists a region-pilot allocation matrix such that the probability of successful unlicensed random access in each access region is greater than or equal to a preset reliability parameter. :

[0115] That is, to facilitate the solution, a preset reliability parameter is introduced. Transform the optimization objective into a given The next feasibility determination problem is to determine whether a region-pilot allocation matrix exists such that all access regions satisfy the following:

[0116] ;

[0117] The feasibility assessment problem is transformed into three constraints: the first constraint is the number of pilots obtained by each access area to meet the corresponding pilot requirements; the second constraint is that the equivalent inter-regional pollution amount of each access area on each pilot does not exceed the corresponding pollution budget; and the third constraint is that the region-pilot allocation variable is a binary variable, which can be expressed by the following formula:

[0118]

[0119] satisfy:

[0120] (1);

[0121] (2);

[0122] (3);

[0123] Wherein, formulas (1), (2), and (3) represent the first constraint, the second constraint, and the third constraint, respectively. Represents solving the matrix , Indicates the preset reliability parameters Next, the Pilot requirements for each access area In the context of the region-pilot allocation matrix, the first... The access area in the first Equivalent contamination between regions on each pilot frequency.

[0124] To solve the region-pilot allocation matrix, the central processing unit configures a corresponding set of target pilots for each access region, including:

[0125] Step 1: For each access area, calculate the remaining pilot demand, candidate pilot set, and pollution correlation degree of each access area. Based on the remaining pilot demand, candidate pilot set, and pollution correlation degree of each access area, calculate the configuration priority index of each access area and select the access area with the highest priority index as the current access area to be configured. When multiple access areas have the same configuration priority index, the access area with the highest active load is selected as the current access area to be configured.

[0126] The formula for calculating the configuration priority indicator is as follows:

[0127] ;

[0128] in,

[0129] ;

[0130] ;

[0131] ;

[0132] in, Indicates the first Configuration priority indicators for each access zone , and The weighting coefficients are, in order, the remaining pilot demand, the candidate pilot set, and the contamination correlation degree. The value is a preset positive number to avoid the denominator being zero. For the first Remaining pilot requirements for each access area For the first Pollution correlation of each access area This represents the maximum value among all access areas for pollution correlation, used to evaluate the th... Pollution correlation of individual access areas Normalize, This indicates that under the current region-pilot allocation matrix, the first... Candidate pilot set for each access area Number of pilots in Indicates the first Pilot requirements for each access area Indicates the first The access area for the first The inter-regional pollution coefficient of each access area, and ; , This indicates that under the current region-pilot allocation matrix, the first... The pilot candidate is assigned to the first After the first access area, the first The equivalent amount of pollution received by each access area across regions This indicates that under the current region-pilot allocation matrix, the first [pilot] has already been used. A set of access areas for each pilot. , This indicates that under the current region-pilot allocation matrix, the first... The pilot candidate is assigned to the first After the first access area, the first one was already in use. The first pilot frequency The equivalent amount of inter-regional contamination received by each access area;

[0133] Among them, the central processing unit meets all the requirements. Among the access areas, select the access area with the highest priority index as the current access area to be configured. This can be expressed by the formula: .

[0134] Step II: For the current access area to be configured, the central processing unit sequentially selects pilot candidates from the pilot set and configures them to the current access area. When configuring each candidate, the newly added pollution cost is calculated. The central processing unit selects the minimum pollution cost from all pollution costs corresponding to the current access area to be configured and configures the pilot corresponding to the minimum pollution cost to the current access area to be configured. Steps I-II are repeated until the number of pilots configured in all access areas reaches the corresponding pilot requirements, and the pilots configured in each access area constitute the target pilot set of the current access area (each target pilot set contains specific pilots), thus obtaining the area-pilot allocation matrix.

[0135] The formula for calculating the additional pollution cost is as follows:

[0136] ;

[0137] in, Indicates the first The pilot is assigned to the first When accessing a single area, the additional pollution cost, It means that for all satisfying Access area Perform summation;

[0138] Among them, the first The set of target pilots corresponding to each access area is represented as follows: .

[0139] By using the above methods, each access area can meet its own pilot requirements while controlling the equivalent pollution between different access areas caused by the reuse of the same pilot. This allows for both pilot collision suppression within the area and pilot reuse pollution control between areas under the condition of limited pilot resources.

[0140] This regionalized unlicensed random access method for large-scale terminal communication constrains the pilot selection range of terminals within the same access area by using a target pilot set, thereby reducing the probability of collisions between the same pilots within the area. At the same time, it determines whether the reuse relationship of the same pilot between different access areas can be retained by verifying the equivalent pollution amount between areas. This allows areas that meet the preset access reliability conditions to reuse the same pilot, while the reuse relationship that does not meet the conditions is adjusted, thereby improving the overall reliability of unlicensed random access.

[0141] Step 6: The central processing unit sends the target pilot set of each access area to the access point of the corresponding access area. The access point broadcasts to all terminals. The activated terminal selects a pilot from the target pilot set of its access area according to its access area. Each terminal sends the selected pilot during the pilot transmission phase of the current unlicensed random access time slot, and then sends uplink data during the data transmission phase of the current unlicensed random access time slot.

[0142] Step 7: After receiving the pilot signal and uplink data, the access point sends a signal to the central processing unit (this signal indicates that the access point has received the pilot signal and uplink data). The central processing unit determines whether the terminal's unlicensed random access to the localized area was successful, including:

[0143] The central processing unit first determines whether the terminal's unauthorized random access within a region is a pilot collision within the region or pilot reuse between regions (i.e., when multiple active terminals within the same access region select the same pilot, the multiple active terminals are determined to have experienced a pilot collision within the region; when active terminals in different access regions select the same pilot, the use of the same pilot between different access regions is determined to be pilot reuse between regions), specifically:

[0144] Statistics on unauthorized random access slots within the current time slot belonging to the first The access area is selected and the first one is chosen. The number of active terminals for each pilot is expressed as ,in The set consisting of all active terminals. Indicates the first One active terminal, Indicates the first The access area to which each active terminal belongs. Indicates the first Pilot selected by each active terminal This indicates an indicator function that returns 1 if the condition within the curly braces is true, and 0 otherwise; When, determine the first Within the access area, in the first Pilot collisions occur within a region on a pilot, when When, determine the first Within the access area, in the first No pilot collisions occurred within the area on the pilot (when it is neither a pilot collision nor pilot reuse, that is, a pilot is used by only one terminal in one access area, the judgment process for whether the access is successful is the same as that for pilot reuse).

[0145] When a pilot collision occurs within a region, the terminal's current unlicensed random access fails. When pilot reuse occurs between regions, the success of the terminal's current unlicensed random access is determined by combining channel estimation and data detection metrics (this process references the capture effect and effective access determination concepts in unlicensed random access, the corresponding existing literature being Performance Analysis and Optimization of Grant-Free Random Access With Capture Effect for Cell-Free Massive MIMO). MIMO (Multiple Input Multiple Output) refers to...

[0146] The channel estimation and data detection metrics are the received signal-to-interference-plus-noise ratio (SINR). The SINR is compared with a preset threshold. When the SINR is greater than or equal to the preset threshold, it indicates that the terminal has successfully performed unlicensed random access in the current region. When the SINR is less than the preset threshold, it indicates that the terminal has failed to perform unlicensed random access in the current region.

[0147] It should be noted that existing research has shown that in distributed access point cooperative access or cell-free massive MIMO networks, the differences in received power distribution or spatial distribution of different terminals at multiple access points can be used to distinguish and mitigate collisions between terminals accessing the same pilot. The corresponding literature is: Fixed Cluster-Based Collision Resolution Random Access for Cell-Free Massive MIMO. Therefore, in this method, pilot reuse between regions is different from pilot collision within regions. It does not directly lead to terminal access failure, but is determined based on channel estimation and data detection indicators.

[0148] In another embodiment, the method is further validated using specific experimental results to characterize the non-uniformity of terminal spatial distribution and active load in large-scale terminal communication. The experiments were implemented using Python 3.10 and run on a computer equipped with an Intel(R) Core(TM) i7-10510U CPU and 16GB of memory. The simulation experiments set up four different coverage areas (referred to as uniform load, central hotspot, strong hotspot, and edge hotspot), with different normalized active load distributions within each coverage area. Figures 4-7In this context, the normalized active load is represented by the normalized load density coefficient, and the normalization method used for the active load is proportional normalization, which maps to the 0-1 interval.

[0149] like Figures 4-7 The diagram shows topological illustrations of normalized load density coefficients for four coverage areas: uniform load, central hotspot, strong hotspot, and edge hotspot. Figures 4-7 Each grid represents a defined access area, and the background color intensity of each access area indicates the magnitude of the normalized load density coefficient. A higher normalized load density coefficient indicates a more concentrated concentration of active terminals within the corresponding access area, resulting in higher pilot frequency contention pressure. Figures 4-7 It can be seen that the distribution of normalized load density coefficients varies among access areas under different coverage areas. The normalized load density coefficients of some areas in the central hotspot, strong hotspot, and edge hotspot are significantly higher than those in other areas. Using a globally unified pilot pool or an averaged pilot configuration can easily lead to an increased probability of pilot collisions within hotspot areas and a decrease in the access reliability of the worst-performing access area. Therefore, this method can improve this problem. Specifically, in Figures 4-7 In the table, z1, z2, z3, z4, z5, z6, z7, z8, z9, z10, z11, z12, z13, z14, z15, z16, z17, z18, z19, z20, z21, z22, z23, z24, and z25 represent 25 access areas, and the values ​​in each access area represent their respective normalized load density coefficient values.

[0150] like Figures 8-11 The diagram illustrates a comparison of the success probability of the proposed method versus four existing methods across different coverage areas, focusing on the access area with the lowest success probability as the active load scaling factor changes. The active load scaling factor is the factor that amplifies or reduces the active load in each access area. Figures 8-11 The corresponding coverage areas are, in order, uniform load, central hotspot, strong hotspot, and edge hotspot; the success probability of the access area with the lowest probability of successful access (i.e., the worst area) is... ,exist Figures 8-11 The probability of success in the worst-case region is used to represent this, and the four existing methods are as follows:

[0151] Global random multiplexing method: It does not distinguish between different access areas, nor does it configure independent target pilot sets for different access areas; active terminals randomly select pilots from the pilot set, which is used to measure the performance of unlicensed random access under the traditional global random pilot selection method;

[0152] Uniform slicing method: The pilot resources are divided into uniform or approximately uniform sections according to the access area, so that each access area obtains the same or approximately the same number of pilots.

[0153] Load-aware configuration method: Determine the corresponding pilot demand based on the active load of each access area, and prioritize allocating more pilot resources to access areas with high active loads to reduce the probability of pilot collisions;

[0154] Graph coloring configuration method: Construct a conflict graph based on the adjacency or pollution relationship between different access areas, and configure pilot resources for access areas based on graph coloring method, so that access areas with strong conflict relationship can avoid reusing the same pilot as much as possible.

[0155] from Figures 8-11 It can be seen that as the active load scaling factor increases, the worst-case region success probability of each method generally decreases, indicating that increased active load exacerbates pilot collisions within the region and pilot reuse pollution between regions. Compared with existing methods, this method maintains a higher worst-case region success probability under uniform load, strong hotspots, central hotspots, and edge hotspots, indicating that this method can effectively improve the reliability and load carrying capacity of the worst-case region. Further analysis shows that the global random reuse method does not distinguish between the access region and the target pilot set, which easily leads to strong competition for the same pilot in hotspot regions (i.e., regions with high normalized load density coefficients); the uniform slicing method, although introducing a regionalized pilot pool, allocates approximately the same number of pilots to different regions, making it difficult to adapt to the high load demand of hotspot regions; the load-aware configuration method can alleviate pilot collisions within the region, but does not fully consider pilot reuse pollution between regions; the graph coloring configuration method can suppress pilot reuse between some strongly polluted regions, but its characterization of regional load differences and directional pollution intensity is still insufficient. In contrast, this method considers regional active load, inter-regional pollution coefficient, inter-regional equivalent pollution amount, and inter-regional pollution budget simultaneously, thus enabling it to balance intra-regional collision suppression and inter-regional reuse pollution control under conditions of limited pilot resources.

[0156] like Figures 12-15 As shown, the performance decomposition results of our method and four existing methods are presented in different coverage areas. The performance decomposition results include the pilot-free collision probability in the worst-case region (in...). Figures 12-15 The probability of no collision within a region is represented by the lowest probability (in the worst-case scenario, the probability of successful inter-region pilot reuse under the condition of no pilot collision within the region). Figures 12-15 The probability of successful inter-region pilot reuse is represented by the lowest probability of successful unlicensed random access in the worst-case region. Figures 12-15 The numbers represent the worst-case probability of successful access and the average probability of successful unlicensed random access across all access areas within the coverage area. Figures 12-15 The value in is the average success probability of access; where... Figures 12-15 The corresponding coverage areas are, in order, uniform load, central hotspot, strong hotspot, and edge hotspot; from Figures 12-15It can be seen that the proposed method has a high probability of no collisions within the area under four different coverage areas, indicating that determining pilot demand based on active load can effectively reduce pilot collisions within the same area. At the same time, the probability of successful pilot reuse between areas remains at a high level, indicating that reuse control based on equivalent pollution amount and pollution budget between areas can avoid reuse of the same pilot in areas with excessive pollution. In terms of the probability of successful access in the worst area and the probability of successful access on average, the proposed method is superior to existing methods, especially in the coverage areas of central hotspots and edge hotspots.

[0157] Therefore, according to Figures 4-15 Simulation results demonstrate that the proposed method can adaptively determine pilot requirements based on the active load of each access area and configure the target pilot set under the constraints of equivalent pollution levels and pollution budgets between areas. This improves the worst-case access reliability and average access success rate under conditions of hotspot load (i.e., a large number of terminals) and limited pilot resources. These results validate the effectiveness of the proposed method in suppressing intra-area pilot collisions, controlling inter-area pilot reuse pollution, and improving overall access reliability in large-scale unlicensed random access scenarios.

[0158] This regionalized unlicensed random access method for large-scale terminal communication classifies the use of the same pilot between different access areas as inter-regional pilot reuse. Based on large-scale channel parameters between each access area and each access point, it determines the equivalent pollution level and pollution budget between areas, thereby judging whether different areas are suitable for reusing the same pilot. Compared to existing methods that use a globally unified pilot pool or random pilot selection without distinguishing spatial relationships, this method can improve pilot resource reuse efficiency while controlling inter-regional pilot pollution. This regionalized unlicensed random access method for large-scale terminal communication can adaptively determine pilot requirements based on the active load of each access area and configure the target pilot set under the constraints of equivalent pollution level and pollution budget between areas. This improves the worst-case access reliability and average access success rate under conditions of hotspot load (i.e., a large number of terminals) and limited pilot resources. This method demonstrates effectiveness in suppressing intra-regional pilot collisions, controlling inter-regional pilot reuse pollution, and improving overall access reliability in large-scale terminal unlicensed random access scenarios. This regionalized unlicensed random access method for large-scale terminal communication determines the active load based on the spatial distribution information and random activation information of terminals in each access area, so that the pilot configuration can reflect the differences in active load between different areas and avoid the area with many active terminals becoming a reliability bottleneck due to insufficient pilot resources.

[0159] It should be understood that, although Figure 2The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 2 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0160] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0161] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A regionalized unlicensed random access method for large-scale terminal communication, characterized in that: An uplink unlicensed random access network for large-scale terminal communication is established, and the uplink unlicensed random access network includes multiple access points, a central processing unit and multiple terminals. The multiple access points are distributed and deployed within the coverage area of ​​the uplink unlicensed random access network and are connected to the central processing unit. The coverage area of ​​the uplink unlicensed random access network is divided into multiple access areas, and the active load of each access area is determined. Determine the pilot requirements for each access area based on the active load of each access area; Based on the large-scale channel parameters between each access area and each access point, determine the equivalent pollution amount between areas and the pollution budget between areas; Based on the pilot requirements of each access area, the equivalent pollution amount between areas, and the pollution budget between areas, a corresponding set of target pilots is configured for each access area. The central processing unit sends the target pilot set of each access area to the access point of the corresponding access area. The access point broadcasts to all terminals. The activated terminal selects a pilot from the target pilot set of its access area according to its access area. Each terminal sends the selected pilot during the pilot transmission phase of the current unlicensed random access time slot, and then sends uplink data during the data transmission phase of the current unlicensed random access time slot. After receiving the pilot signal and uplink data, the access point sends a signal to the central processing unit, which then determines whether the terminal's unauthorized random access to the local area was successful. This includes determining the equivalent pollution levels and pollution budgets between regions, including: Inter-regional equivalent contamination is used to represent the intensity of pilot contamination caused to channel estimation and data detection when different access areas reuse the same pilot. The formula for calculating inter-regional equivalent contamination is as follows: ； in, Indicates the first The access area in the first Equivalent contamination between regions on each pilot frequency Indicates the first Does the first access area use the first...? The pilot, i.e. the first pilot... Does the first access area use the first...? The region-pilot assignment variable for each pilot is set to 1 when in use and 0 otherwise. Indicates the first Does the first access area use the first...? The pilot, i.e. the first pilot... Does the first access area use the first...? Region-pilot assignment variable for each pilot, Indicates the first Active load in each access area Indicates the first Pilot requirements for each access area Indicates the first The access area for the first Inter-regional pollution coefficient of each access area It is the set consisting of all access areas; The formula for calculating pollution budgets between regions is as follows: ； in, Indicates the first The pollution budget between access areas is expressed as a preset reliability parameter. Next, the The maximum inter-region equivalent contamination level that each access area can tolerate on any assigned pilot, and , This represents the upper bound that satisfies the conditions within the curly braces. For the first The equivalent pollution level between the receiving areas for each access area is: The probability of successful inter-region pilot reuse at that time. Indicates the first The inter-regional pilot reuse reliability threshold corresponding to each access area.

2. The regionalized unlicensed random access method for large-scale terminal communication as described in claim 1, characterized in that: In the uplink unlicensed random access network, all pilots constitute a pilot set, and any two different pilots in the pilot set are orthogonal to each other.

3. The regionalized unlicensed random access method for large-scale terminal communication as described in claim 2, characterized in that: The coverage area of ​​the uplink unlicensed random access network is divided into multiple access areas, and the active load of each access area is determined, including: The coverage area is divided into multiple non-overlapping access areas according to the preset area size; Acquire spatial distribution information and random activation information of terminals in each access area. The spatial distribution information of terminals represents the distribution density of terminals at different locations, and the random activation information represents the probability of a terminal being activated in an unauthorized random access time slot. Activated terminals are called active terminals, and inactive terminals are called potential terminals. The active load of each access area is calculated based on the spatial distribution information of active terminals within each access area, and the calculation formula is as follows: ； in, For the first Active load in each access area For position Spatial distribution information of active terminals Indicates the first One access area.

4. The regionalized unlicensed random access method for large-scale terminal communication as described in claim 3, characterized in that: The step of determining the pilot requirements for each access area based on the active load of each access area includes: The number of pilots in the access area is calculated as follows: The probability that no co-pilot collision occurs within the access area is given by the following formula: ； in, For the first The probability of no co-pilot collision occurring within an access area, and Greater than or equal to a preset threshold; The minimum number of pilots whose probability of no co-pilot collisions within the access area meets the preset threshold requirement is determined as the number of pilots. Pilot requirements for each access area; When multiple active terminals in the same access area select the same pilot signal, the multiple active terminals are determined to have experienced a pilot collision within the area. When active terminals in different access areas select the same pilot, the use of the same pilot between different access areas is determined as inter-area pilot reuse.

5. The regionalized unlicensed random access method for large-scale terminal communication as described in claim 1, characterized in that: Based on the pilot requirements of each access area, the equivalent pollution level between areas, and the pollution budget between areas, a corresponding set of target pilots is configured for each access area, including: With the optimization objective of maximizing the probability of successful unlicensed random access in each access area, the target pilot set of each access area is configured, and the probability of successful unlicensed random access in each access area is expressed as the product of the probability of no collision between the same pilot within the access area and the probability of successful pilot reuse between areas. The optimization objective is transformed into setting preset reliability parameters. The feasibility assessment problem is whether there exists a region-pilot allocation matrix such that the probability of successful unlicensed random access in each access region is greater than or equal to a preset reliability parameter. ; The feasibility assessment problem is transformed into three constraints: the first constraint is that each access area obtains the number of pilots that meet the corresponding pilot requirements; the second constraint is that the equivalent pollution amount between areas in each access area on each pilot does not exceed the corresponding pollution budget; and the third constraint is that the area-pilot allocation variable is a binary variable. The central processing unit configures a corresponding set of target pilots for each access area to solve the area-pilot allocation matrix.

6. The regionalized unlicensed random access method for large-scale terminal communication as described in claim 5, characterized in that: The central processing unit configures a corresponding set of target pilot signals for each access area, including: Step 1: For each access area, calculate the remaining pilot demand, candidate pilot set, and pollution correlation degree of each access area. Based on the remaining pilot demand, candidate pilot set, and pollution correlation degree of each access area, calculate the configuration priority index of each access area and select the access area with the highest priority index as the current access area to be configured. When multiple access areas have the same configuration priority index, the access area with the highest active load is selected as the current access area to be configured. Step II: For the current access area to be configured, the central processing unit selects pilot candidates from the pilot set and configures them to the current access area to be configured. When configuring each candidate, the newly added pollution cost is calculated. The central processing unit selects the minimum pollution cost from all pollution costs corresponding to the current access area to be configured and configures the pilot corresponding to the minimum pollution cost to the current access area to be configured. Steps I-II are repeated until the number of pilots configured in all access areas reaches the corresponding pilot requirements, and the pilots configured in each access area constitute the target pilot set of the current access area, thereby obtaining the area-pilot allocation matrix. The formula for calculating the pollution correlation degree is as follows: ； in, For the first Pollution correlation of each access area Indicates the first Pilot requirements for each access area Indicates the first Pilot requirements for each access area Indicates the first The access area for the first Inter-regional pollution coefficient of each access area; The formula for calculating the additional pollution cost is as follows: ； in, Indicates the first The pilot is assigned to the first When accessing a single area, the additional pollution cost, It means that for all satisfying Access area Perform summation.

7. The regionalized unlicensed random access method for large-scale terminal communication as described in claim 5, characterized in that: The central processing unit determines whether the terminal's unauthorized random access to the localized area was successful, including: The central processing unit first determines whether the terminal's current unlicensed random access to the region is due to a pilot collision within the region or pilot reuse between regions. If it is a pilot collision within the region, the terminal's current unlicensed random access to the region fails. If it is pilot reuse between regions, the unit combines channel estimation and data detection metrics to determine whether the terminal's current unlicensed random access to the region is successful. The channel estimation and data detection metrics are based on the received signal-to-interference-plus-noise ratio (SINR). The SINR is compared with a preset threshold. When the SINR is greater than or equal to the preset threshold, it indicates that the terminal has successfully performed unauthorized random access in the current region. When the SINR is less than the preset threshold, it indicates that the terminal has failed to perform unauthorized random access in the current region.

Images