Enhanced Multi-Cell Cellular Networking Method for D2D Communication with Spectrum Efficiency Optimization

Abstract

The present invention discloses a method for enhancing multi - cell cellular networking of D2D communication with optimized spectral efficiency, belonging to the field of wireless communication technology. The present invention provides a D2D communication - enhanced multi - cell cellular networking method that takes into account the load difference between the cellular uplink and downlink, can be carried out across cells, and optimizes spectral resources. It provides a method that allows cellular base stations to support D2D communication within the cell, and establishes a performance index for comprehensively evaluating the networking effect among users in a multi - cell cellular network. The method in the present invention has low computational complexity, can complete networking relatively quickly, and saves the time - frequency resources consumed during the networking process. The present invention can minimize the usage of time - frequency resources on the premise of meeting the service requirements of all CUEs, achieve optimized spectral efficiency, so as to meet the needs of massive device access or improve network throughput.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication, and specifically relates to a multi-cell cellular network networking method for enhancing D2D communication. Background Art

[0002] In a traditional cellular network, cellular users cannot directly communicate with each other without the base station. The centralized working mode controlled by the base station facilitates resource management and interference control, but there is still room for improvement in the utilization rate of spectrum resources. Driven by the fifth-generation mobile communication technology, the number of intelligent terminals has increased rapidly, and the mobile data traffic and network load have exploded. As a result, the transmission load pressure of the base station has increased sharply, and the time-frequency resources have become more scarce. This makes D2D communication, which can effectively reduce the base station load pressure, more prominent in the cellular network. The D2D communication technology consists of a variety of seamlessly integrated wireless access technologies, aiming to support direct communication between user devices in various ways. Currently, it has been widely considered as an important supplementary form under the cellular network.

[0003] Under the condition of limited time-frequency resources, the cellular network urgently needs more advanced technologies to reduce the resource consumption of the network. The introduction of D2D communication technology under the cellular network divides cellular users in a conventional cellular network into two categories: one is cellular users working in the cellular mode, and the other is D2D users whose data transmission does not pass through the base station.

[0004] D2D communication allows devices to directly communicate with each other in the authorized frequency band or the unlicensed frequency band. Since the interference environment in the unlicensed frequency band is uncontrollable, the reliability of data transmission is usually not as good as that in the authorized frequency band, and it is not convenient for the base station to perform centralized control. Therefore, a common integration method is to let D2D users reuse the authorized channel resources of cellular users for data transmission. This method can significantly optimize the spectrum utilization rate, but sharing channel resources brings a series of problems such as mutual interference control, bringing additional scheduling pressure and cost overhead to the base station, and also bringing more challenges to solving the above problems. Summary of the Invention

[0005] Aiming at the problem of scarce spectrum resources, the main purpose of the present invention is to provide a D2D communication enhanced multi-cell cellular networking method that takes into account the load difference between the cellular uplink and downlink, can cross cells, and optimizes spectrum resources.

[0006] Another object of the present invention is to provide a method that allows a cellular base station to support D2D communication within a cell.

[0007] Another object of the present invention is to establish a performance index for comprehensively evaluating the networking effect between users in a multi-cell cellular network.

[0008] Technical Solution:

[0009] The model of the present invention is established under a multi - cell cellular network. By default, all users in the network use mutually orthogonal time - frequency resources, or reuse time - frequency resources when the interference between them is negligible. To achieve the above - mentioned purpose, a networking method is provided in which users under a network establish D2D direct transmission and D2D relay under the control of the base station according to service traffic requirements. The main methods include: a method for differentiating the service traffic of cellular users; a method for establishing networking performance indicators between Cellular User Equipments (CUEs); a method for completing D2D direct - transmission establishment between CUEs; and a method for completing D2D relay establishment between CUEs. Specifically:

[0010] S1, a method for differentiating the service traffic of cellular users;

[0011] In S1, denote the set of all users in the cellular network as U = {1, 2, …, i}, and the transmission rate requirement of cellular user i ∈ U is where, respectively represent the average uplink and downlink transmission rate requirements of the cellular network. For the D2D direct - transmission establishment process, the direct - transmission requirements of users will all be regarded as uplink direct - transmission requirements, and the feedback data that appears at the direct - transmission receiver will also be regarded as its uplink direct - transmission requirements. However, the establishment of direct - transmission will affect the cellular downlink requirements of the receiver.

[0012] Before the networking starts, for the transmission rate requirement of any user i, according to the actual uplink - downlink load difference, it can be determined that:

[0013]

[0014] i i represents the ratio relationship of the uplink - downlink load difference.

[0015] During the direct - transmission establishment process, cellular user i ∈ U will search for potential (with direct - transmission requirements and not yet established direct - transmission) direct - transmission receivers d within its maximum D2D communication range to attempt to establish direct - transmission. Assume that the set of users that finally establish direct - transmission with user i is D i .

[0016] If D i = φ, then That is φ represents the empty set.

[0017] If D i ≠ φ, assume that D i has n (n ∈ N + ) elements, then there are n values respectively, and their relationship is:

[0018]

[0019] When the direct transmission is successfully established, the present invention will be specifically divided into:

[0020]

[0021]

[0022] which respectively represent the D2D direct transmission demand rate and the cellular demand rate of user i.

[0023] And there is the following expression:

[0024]

[0025]

[0026] S2, a method for establishing the networking performance index among CUEs;

[0027] The said S2 includes:

[0028] S2.1 calculates the number of physical (time-frequency) resource blocks (Physical Resource Block, PRBs) required to provide services for the uplink and downlink transmissions of all CUEs. Specifically:

[0029] Denote the set of all cellular base stations, CUEs, and the CUEs served by base station k as B = {1, 2,..., k}, U = {1, 2,..., i},

[0030] On the transmission path from sender i to receiver j, the channel capacity of each PRB is:

[0031]

[0032] where W is the bandwidth of a PRB, is the signal-to-noise ratio (SNR) of the signal received at j from i, and j is arbitrarily from the set B or U. is the transmit power, v ∈ {u, d}, representing the uplink frequency band and the downlink frequency band respectively. N0 is the average power of narrowband Gaussian white noise, N0 = n0B0, n0 is the power spectral density of white noise, and B0 is the equivalent bandwidth of the noise.

[0033] From here on, for the sake of clear expression, denote For user i, define its uplink and downlink total traffic and define the unit time T sWhen not using the networking method proposed by the present invention, the number of PRBs required to provide services for the uplink and downlink transmissions of all CUEs is N u and N d respectively, where:

[0034]

[0035]

[0036] In the above formula, respectively represent the uplink and downlink transmission rate requirements of user i.

[0037] S2.2 After completing the networking using the present invention, calculate the number of PRBs required to meet the communication requirements of all users. S2.2 should be based on S1. Specifically:

[0038] Define the base station association matrix X |U|×|B| (x i,k ∈{0, 1}), the intra-cluster relay matrix Y |U|×|U| (y i,j ∈{0, 1}), and the D2D direct transmission matrix Z |U|×|U| (z i,l ∈{0, 1}). They respectively represent whether user i is directly connected to base station k, whether user i uses user j as a relay to connect to the base station, and whether user i has established a D2D direct transmission with user l. If so, the value is 1; otherwise, the value is 0. Then, the number of PRBs required to meet the communication requirements of all users after the networking is completed is

[0039]

[0040] In the above formula, i i represents the ratio relationship of the uplink and downlink load differences of user i,

[0041] S2.3 Calculate the networking gain among CUEs. Specifically:

[0042] The present invention further defines the networking gain of the networking method of the present invention as follows, which is also applicable to other networking methods with the same idea.

[0043]

[0044] S3, The networking method for achieving spectrum efficiency optimization among CUEs;

[0045] The networking method given by the present invention includes two parts: D2D direct transmission establishment and D2D relay establishment. The constraints for this method in networking are as follows:

[0046] After networking, each device works in at least one of the following modes: directly connected to the base station, relayed to the base station, and D2D direct transmission; after the user equipment finds the relay equipment, it no longer connects directly to the base station; only single-hop and one-way relay are allowed; there is at least one user directly connected to the base station under each base station.

[0047] Furthermore, the specific process of the above method S3 includes:

[0048] S3.1 First, complete the establishment of D2D direct transmission. The method is as follows:

[0049] Consider the establishment of feasible D2D direct transmission between CUEs and nearby users. Assume that for user i ∈ U k The set of users with potential D2D direct transmission requirements is P i = {1, 2, …, m}, and the corresponding direct transmission demand rate sets are A i = {R i1 , R i2 , …, R im}, then determine the establishment of D2D direct transmission with the D2D direct transmission gain G (D) :

[0050]

[0051] In the above formula, b is the base station connected to m. Calculate G (D)im for all users i ∈ U. If G (D)im > 0, then z i,m = 1; otherwise, z i,m = 0.

[0052] After the D2D direct transmission is established, part of the service traffic of the CUE is transmitted to the destination CUE through the D2D direct transmission link.

[0053] S3.2 Complete the establishment of D2D relay. The method is as follows:..

[0054] Consider the relay establishment between user i ∈ U and adjacent users. Assume that the set of users within the relay range of user i ∈ U is Q i = {1, 2, …, n}, then determine the establishment of D2D relay with the D2D relay gain G (R) :

[0055]

[0056] In the above formula, b ′ is the base station associated with n′. Calculate G (R)in for all users i ∈ U. (1) If the maximum value of G (R)in ≤ 0, then x i,k = 1; (2) If the maximum value of G (R)in > 0, denote the user corresponding to the maximum value as n * , if Then Otherwise, replace user n with the user having the second - largest value * , repeat (2); (3) After traversing all values greater than 0 in (2), x i,k = 1.

[0057] After the D2D relay is established, the CUE will connect to the relay - node user through the D2D relay link, and then the relay node will directly connect to the base station to complete the communication between the CUE and the base station. The remaining or all traffic will be transmitted through this link.

[0058] Advantages of the present invention:

[0059] 1. In the present invention, various methods, especially the calculation complexity of S3, is low, which can complete network formation quickly and save the time - frequency resources consumed during network formation.

[0060] 2. The present invention can minimize the usage of time - frequency resources and optimize the spectrum efficiency to meet the requirements of massive device access or increase network throughput under the premise of meeting the service requirements of all CUEs. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 is an example diagram of a multi - cell cellular network system model.

[0062] Figure 2 is an example diagram of the system model after user - to - user network formation using the method of the present invention.

[0063] Figure 3 is a flowchart of the steps that the cellular base station needs to execute in the present invention.

[0064] Table 1 is Figure 3 the pseudo - code diagram for performing ① D2D direct transmission establishment in

[0065] Table 2 is Figure 3 the pseudo - code diagram for performing ② D2D relay establishment in DETAILED DESCRIPTION OF THE EMBODIMENTS

[0066] The present invention will be further described below with reference to the drawings.

[0067] For the sake of more concise and clear description in the following, it is hereby declared that certain nouns in the following text are replaced by their English abbreviations: cellular base station (BS), user equipment (UE), cellular user equipment (CUE), physical resource block (PRB).

[0068] In the concept of the present invention, Figure 1 , Figure 2 all devices in do not have structural differences and belong to the same type of typical mobile communication UE, and are only in different working modes due to different communication links.

[0069] The present invention will be further described below in conjunction with the accompanying drawings. Refer to Figure 1 , an example of a multi-cell cellular network scenario according to an embodiment of the present invention. After the user-to-user networking is completed by the method of the present invention, a network structure will be as Figure 2 shown. Figure 3 These are the necessary execution steps of each base station when performing user-to-user networking by the method of the present invention.

[0070] In the present invention, for Figure 1 the complete steps of performing user-to-user networking for this type of network are as follows:

[0071] Step 1, the BS measures the number of PRBs occupied by serving all CUEs under the current network structure, and the specific implementation is as follows.

[0072] The BS should first measure the average channel capacity of the uplink and downlink of each channel in each frequency band allocated by the cellular network

[0073]

[0074] where W is the bandwidth of a PRB, is the signal-to-noise ratio (SNR) of the signal received at j from i, i is a certain CUE, and j can be the BS or other CUEs. P is the transmit power. v ∈ {u, d} respectively represent the uplink frequency band and the downlink frequency band. N0 = n0B0, n0 is the power spectral density of white noise, and B0 is the equivalent bandwidth of the noise.

[0075] The BS counts the total uplink and downlink traffic Q u , Q d , sets the unit time (which can be taken as 1 ms) T s , and then it can be calculated that the number of PRBs required to provide services for the uplink and downlink transmissions of all CUEs are N u 、N d :

[0076]

[0077]

[0078] Step 2, the BS attempts to find D2D direct transmission establishment objects for all CUEs, and the specific implementation is as follows.

[0079] The BS checks the packet headers sent by each CUE and continuously looks for potential D2D data flows. If the distance between the data source device i and the data destination device m is within the maximum D2D communication range, it is considered that UE i has a D2D uplink direct transmission requirement for UE m. A UE set P is established for all D2D uplink direct transmission requirement objects of UE i i ={1, 2, …, m}, and a set A is established for the corresponding direct transmission requirement rates i ={R i1 , R i2 , …, R im}.

[0080] Step 3, the BS attempts to establish D2D direct transmissions for all CUEs and their D2D direct transmission objects, and the specific implementation is as follows.

[0081] The BS processes the D2D uplink direct transmission requirements of each CUE. For the UE set P i 、A i corresponding to UE i, according to the service demand volume of UE i and the measured channel capacity calculate If then establish a D2D direct transmission for UE i and UE m, otherwise, do not allow the establishment of a direct transmission. Or when P i = φ, ignore this UE i.

[0082] Wherein:

[0083]

[0084] In the above formula, b is the base station connected to m. The execution pseudocode of this step is shown in Table 1. The z i in Table 1 represents all elements in the i-th row of the matrix Z. By solving through the algorithm in Table 1, the D2D direct transmission matrix Z can be obtained.

[0085] Table 1

[0086] ① Direct transmission establishment

[0087]

[0088] Step 4, the BS differentiates the service demand volumes of all CUEs, and the specific implementation is as follows.

[0089] The BS determines according to the actual cellular uplink and downlink load differences:

[0090]

[0091] And after the direct transmission establishment is completed, the service demand volume of UE i is specifically differentiated into:

[0092]

[0093] R i(D2D) and R i(CE) respectively represent the D2D direct transmission demand rate and the cellular demand rate of user i.

[0094] Step 5, the BS attempts to find D2D relay objects for all CUEs, and the specific implementation is as follows.

[0095] The BS checks other CUEs within the maximum D2D communication range of each CUE and establishes the UE set Q i = {1, 2,..., n}.

[0096] Step 6, the BS attempts to establish D2D relays between all CUEs and their D2D relay objects, and the specific implementation is as follows.

[0097] For each UE i and UE n from Q i = {1, 2,..., n}, the BS also calculates according to and the measured channel capacity to calculate for D2D relay establishment.

[0098] 1) If Q i = φ, then no D2D relay is established for UE i.

[0099] 2) If Q i ≠ φ, for all UEs within the Q i set, calculate

[0100] a) If all values < 0, then no D2D relay is established for UE i.

[0101] b) If there are values > 0, form a sequence of these values

[0102] i. Denote the UE corresponding to the maximum value as n*; if UE n* is directly connected to the BS, then UE i and UE n* establish a D2D relay, otherwise replace UE n with the UE corresponding to the second maximum value * , and repeat step i.; if no D2D relay is established after traversing all UEs corresponding to , then no D2D relay is established for UE i.

[0103] The execution pseudocode for this step is shown in Table 2. In Table 2, represents the set of users with the maximum value greater than 0, In this, b is n * Connect to BS.

[0104] Table 2 ② Relay establishment

[0105]

[0106] The above is all the steps to complete user - to - user networking in a multi - cell cellular network in the embodiments of the present invention. All operations regarding BS in the steps should be shared by all BSs in the network. The necessary execution steps for each base station are summarized in the appendix Figure 3 。

[0107] The above is only a description of the operation steps of the present invention for this kind of embodiment. The applicable scope of the present invention is not limited to multi - cell cellular networks and is also applicable to single - cell cellular networks. Operations carried out without departing from the fundamental idea of the present invention are within the protection scope of the present invention.

[0108] The series of detailed descriptions listed above are only specific descriptions of the feasible implementation manners of the present invention. They are not used to limit the protection scope of the present invention. Any equivalent manners or changes that do not depart from the technology created by the present invention should be included in the protection scope of the present invention.

Claims

1. An enhanced multi-cell cellular networking method for D2D communication with spectrum efficiency optimization, characterized in that The steps include: Step 1: The BS calculates the number of PRBs occupied by all CUEs in the current network structure. Step 2: BS searches for D2D direct transmission establishment objects for all CUEs; Step 3: The BS establishes D2D direct transmission for all CUEs and their D2D direct transmission targets; The specific process of step 3 includes the following: The BS processes the D2D uplink direct transmission requirements of each CUE. For the UE set P corresponding to UEi i and A i , P i represents the UE set of all D2D uplink direct transmission requirement objects of UEi, and A i represents the set of direct transmission requirement rates corresponding to all D2D uplink direct transmission requirement objects of UEi. According to the service demand volume of UEi and the measured channel capacity u and d represent uplink and downlink respectively, and calculate the direct transmission gain If then establish D2D direct transmission between UEi and UEm, otherwise do not allow the establishment of direct transmission, or when ignore this UEi; where: In the above formula, b is the base station connected by user m; R im represents the direct transmission rate of user m, who has a potential D2D direct transmission requirement with user i; φ represents the reciprocal of the channel capacity, where its subscripts i and k correspond to user i and base station k, and the subscripts b, m corresponds to base station b and user m, subscripts i and m correspond to user i and user m, and superscripts u and d correspond to uplink and downlink; Step 4: BS differentiates the service demands of all CUEs; Step 5, the BS finds D2D relay objects for all CUEs; the BS checks other CUEs within the maximum D2D communication range of each CUE and establishes a UE set Q i ={1, 2, …, n}; Step 6: BS establishes D2D direct transmission for all CUEs and their D2D relay objects; The specific process of step 6 includes the following: BS for each UEi and UEn from Q i ={1, 2, …, n}, according to and the measured channel capacity calculate the relay gain for D2D relay establishment; the specific situation is as follows: 1) If then UEi does not establish a D2D relay; 2) If for all UEs in the Q i compute In the above formula, b′ is the base station associated with n′; γ i represents the ratio relationship of the uplink and downlink load differences of user i, and γ i ≥ 1; represents the uplink transmission rate requirement of user i; 0 ≤ α i ≤ 1; 0 < β i ≤ 1; φ represents the reciprocal of the channel capacity, where its subscript represents the user number and base station number, and the superscripts u and d represent uplink and downlink; a) If all values < 0, UEi does not establish a D2D relay; b) If there are values > 0, form a sequence of these values i. Denote The UE corresponding to the maximum value is n * ; If UE n * is directly connected to the BS, then UE i and UE n * establish a D2D relay. Otherwise, replace UE n with the UE corresponding to the second maximum value * , and repeat step i.; If all UEs corresponding to are traversed and no D2D relay is established, then UE i does not establish a D2D relay.

2. The method for enhancing multi-cell cellular networking of spectrum efficiency optimized D2D communication according to claim 1, wherein The specific process of step 1 includes the following: BS first measures the average channel capacity of the uplink and downlink of each channel in each frequency band allocated by the cellular network where W is the bandwidth of a PRB, is the signal-to-noise ratio (SNR) of the signal received at j from i, where i is a certain CUE and j can be the BS or another CUE, P is the transmit power, v ∈ {u, d}, where u and d represent the uplink frequency band and the downlink frequency band respectively, N0 = n0B0, n0 is the power spectral density of white noise, and B0 is the equivalent bandwidth of the noise; BS statistically calculates the total uplink and downlink traffic volume Q of each CUE u , Q d , set the unit time T S , then the calculated number of PRBs required to provide services for the uplink and downlink transmissions of all CUEs are N u , N d : In the formula, k represents the base station number k, B represents the set of all cellular base stations, and U k represents the set of CUEs served by base station k, respectively represent the uplink and downlink transmission rate requirements of user i.

3. The method for optimizing the spectrum efficiency of D2D communication enhanced multi-cell cellular networking according to claim 1, wherein The specific process of step 2 includes the following: The BS continuously checks the packet headers sent by each CUE to search for potential D2D data flows. If the distance between the data source device i and the data destination device m is within the maximum D2D communication range, it is considered that UEi has a D2D uplink direct transmission requirement for UEm. A UE set P is established for all D2D uplink direct transmission requirement objects of UEi i ={1, 2, …, m}, and a set A is established for the corresponding direct transmission requirement rates respectively i ={R i1 , R i2 , …, R im}.

4. The method for enhancing multi-cell cellular networking of spectrum efficiency optimized D2D communication according to claim 1, wherein The specific process of step 4 includes the following: Let the set of all users under the cellular network be \(U = \{1, 2, \ldots, i\}\), and the transmission rate requirement of cellular user \(i\in U\) is where represent the average uplink and downlink transmission rate requirements respectively. For the D2D direct transmission establishment process, the direct transmission requirements of users will all be regarded as uplink direct transmission requirements, and the backhaul data that appears at the direct transmission receiver will also be regarded as its uplink direct transmission requirement; Before the network formation starts, for the transmission rate requirement of any user i Based on the actual uplink and downlink load differences, it can be determined that: During the direct transmission establishment process, cellular user i ∈ U will search for potential direct transmission receivers d within its maximum D2D communication range and attempt to establish direct transmission. Suppose the set of users that finally establish direct transmission with user i is D i , If then i.e. If Suppose D i has n elements, then there are n values respectively and their relationship is: When the direct transfer is successfully established, Specifically, it is divided into: R i(D2D) and R i(CE) respectively represent the D2D direct transmission required rate and the cellular required rate of user i; And there are the following expressions:

5. The method for enhancing multi-cell cellular networking of spectrum efficiency optimized D2D communication according to claim 1, characterized in that The networking method is applicable to a single-cell cellular network.

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