CN102970758B - Straight-through self-adaptive resource distribution method for cellular communication system terminal - Google Patents

Abstract

The invention discloses a straight-through self-adaptive resource distribution method for a cellular communication system terminal, which is specifically a resource distribution method for device-to-device (D2D) communication based on an orthogonal frequency division multiplexing system. Based on the characteristic of low transmission power of D2D users, and with consideration of the multiplex of same resources of two groups of D2D pairs, when cellular user resources are distributed to the D2D pairs, path attenuation, interference channel gains of cellular users on the D2D users and channel gains between the D2D users are considered at the same time, so that the resources with maximum equivalent channel gains are distributed to the matched D2D pairs in a self-adaptive manner so as to maximize a throughput capacity. The straight-through self-adaptive resource distribution method has the advantages that the capacity of a D2D system can be greatly improved, and an algorithm is relatively simple.

Description

Cellular communication system terminal direct adaptive resource allocation method

technical field

The invention relates to a resource allocation method based on D2D (device-to-device) communication under an orthogonal frequency division multiplexing system, and belongs to the technical field of resource allocation in mobile communication.

Background technique

Resource allocation is the key to the normal communication of the mobile communication system. Since the spectrum resources available for mobile communication are very limited, it is necessary to use spectrum resources more efficiently, and D2D technology emerges as the times require. Judging from the current D2D resource allocation methods, most of the methods reuse the spectrum resources of different cellular users for each group of D2D pairs, and there is almost no mention of two or more groups of D2D pairs that reuse the same cellular user resources. method, and using two or more groups of D2D pairs to multiplex the same cellular user resources can greatly improve spectrum efficiency; at the same time, when selecting multiplexed resources for D2D pairs, it is not limited to all resources of a single cellular user, these resources There may be good and bad, if all multiplexing may cause restrictions on D2D communication. Therefore, resources that are good for D2D users are selected from each cellular user for multiplexing, that is, the starting point is to consider subcarriers rather than cellular users to better utilize channel frequency selection and multi-user diversity gain. When allocating resources, we adopt an adaptive subcarrier allocation method, that is, each subcarrier is allocated to the user with the largest equivalent channel gain on it. The equivalent channel here is the channel between D2D and interference channel , The interference power is considered uniformly. Based on the above content, the capacity of the D2D system is greatly improved.

Contents of the invention

Technical problem: The purpose of the present invention is to provide a cellular communication system terminal direct adaptive resource allocation method, mainly for the situation where a large number of D2D pairs need to allocate resources, reduce the interference of cellular users to D2D users, and greatly improve System capacity and spectrum utilization of D2D systems.

Technical method: the cellular communication system terminal direct adaptive resource allocation method of the present invention is:

1) According to the distance area, the cell is divided into inner ring and outer ring (using D2D mode in the outer ring can obtain better performance);

2) Divide the outer ring into an even number of equal areas, and determine the two areas facing the center of the circle as a matching set of areas;

3) Randomly find a pair of D2D pairs in the two matching areas as a matching set of D2D pairs, as shown in Figure 2;

4) The base station calculates the equivalent channel gain between D2D users based on the interference channel gain, path fading, and channel gain between D2D users from cellular users to D2D users at the current moment where H _d is the equivalent channel gain between D2D users, h _d is the actual channel gain between D2D users, P _{I, CiD} is the interference power of cellular users to D2D users, h _CiD is the interference channel between cellular users and D2D users gain;

5) Let N, V be used to represent the number of subcarriers allocated to each D2D pair and the equivalent channel gain, and its initial value is set to 0;

6) For all the subcarriers that can be allocated, select a group of matching D2D pairs with the largest average equivalent channel gain on the subcarriers, allocate the subcarriers to this group of matching D2D pairs, and assign the N Add 1 to the corresponding item until it meets the required number of subcarriers, then no subcarriers will be allocated to it, and record the allocated equivalent channel gain with V;

7) Repeat step 6) until all subcarriers are allocated;

This cellular system terminal direct adaptive pairing resource allocation method greatly improves the system capacity and spectrum efficiency by allowing D2D pairs in different areas to match and reuse the same cellular user resources, and considers subcarriers when allocating resources. Bad subcarriers, and considering equivalent channels can better meet the requirements of improving D2D user capacity. Among them, allowing two groups of D2D pairs to match and reuse the same cellular user resources can be directly applied to many methods of allocating different cellular user resources for each group of D2D pair users, thereby obtaining great performance gains.

Beneficial effect:

1. Introduce the concept of equivalent channel gain, comprehensively consider the factors that affect the capacity of the D2D system, avoid separate consideration of interference power and interference channel gain, and effectively improve the capacity of the D2D system.

2. Using subcarrier-based resource allocation as a unit avoids allocating spectrum resources with poor conditions for D2D users to D2D users.

3. Two sets of D2D pairs in different areas are used to multiplex the same cellular user resources, which greatly improves the capacity and spectrum efficiency of the D2D system while controlling the interference between D2D pairs.

The method of allowing two groups of D2D pairs to match and reuse the same cellular user resources proposed by the present invention can be directly applied to many methods of allocating different cellular user resources for each group of D2D pair users, thereby obtaining a great performance gain.

The present invention mainly considers how to reduce the interference of cellular users to D2D users and improve the capacity of the D2D system in the process of allocating resources through the cellular system.

Description of drawings

Figure 1 is a system model diagram, assuming that users using D2D mode are evenly distributed on the outer ring of the cell, and cellular users are randomly allocated in the cell.

Fig. 2 is a schematic diagram of D2D pair matching in the present invention.

Fig. 3 is a flowchart of a resource allocation method.

Detailed ways

Assuming that the number of subcarriers contained in an OFDM symbol is M, and the numbers of cellular users and D2D pairs are N _C and N _D respectively, D2D users can communicate directly under the coordination of the base station, and D2D users multiplex the cellular user's resource.

We assume that the power of all cellular users arriving at the base station is controlled at the same level _PCB , namely

$P_{\mathrm{CB}}=P_{\mathrm{Ci}}\&Center\; Dot;{\left(d_{\mathrm{Ci}}\right)}^{-a},\∀i$ [formula one]

P _CB is a constant, P _Ci is the transmission power of the i-th cellular user, and d _Ci is the distance from the cellular user to the base station. Then the interference power of cellular users to D2D can be written as

$P_{I,\mathrm{CiD}}=P_{\mathrm{Ci}}{\left(d_{\mathrm{CiD}}\right)}^{-a},\∀i$ [formula two]

d _CiD is the distance from the cellular user to the D2D receiving user, and the interference power of D2D to the base station is strictly limited to δ _B , that is, P _D ·(d _DB ) ^-a /P _CB ≤ δ _B , to ensure that there will be no interference to the base station Interference P _D is the transmission power of the D2D user, and d _DB is the distance from the D2D user to the base station. The channel capacity of D2D users can be obtained from the Shannon formula:

$C_d={\log }_2(1+\frac{P_{\mathrm{D.}}\&Center\; Dot;{\left(d_{\mathrm{D.}}\right)}^{-a}\&Center\; Dot;h_d}{P_{I,\mathrm{CiD}}\·h_{\mathrm{CiD}}+P_{{\mathrm{D.}}^{\′}}{\left(d_{{\mathrm{dd}}^{\′}}\right)}^{-a}{h}_{d^{\′}d}+{\mathrm{no}}_0})$ [formula three]

P _D' is the transmission power of another pair of D2D users who reuse the same cellular user resources, h _dd' is the channel gain between two pairs of D2D users who reuse the same cellular user resources, d _dd' is the two pairs of D2D users who reuse the same resources For the distance between D2D pairs, n ₀ is the one-sided power spectral density of the noise. Under the condition that D2D users adopt the maximum transmission power, that is, P _D =(d _DB ) ^a ·δ _B ·P _CB , let P _CB =c ·n ₀ , and c is a constant, then the interference power and noise between D2D pairs can be obtained ratio of power;

$\frac{P_{\mathrm{D.}}\&Center\; Dot;{\left(d_{{\mathrm{DD}}^{\′}}\right)}^{-a}}{{\mathrm{no}}_0}=\frac{{(d_{\mathrm{DB}}/d_{{\mathrm{DD}}^{\′}})}^a\&Center\; Dot;{\mathrm{\δ}}_B\·P_{\mathrm{CB}}}{{\mathrm{no}}_0}=\frac{{(d_{\mathrm{DB}}/d_{{\mathrm{DD}}^{\′}})}^a\&Center\; Dot;{\mathrm{\δ}}_B\&Center\; Dot;c\&Center\; Dot;{\mathrm{no}}_0}{{\mathrm{no}}_0}={(d_{\mathrm{DB}}/d_{{\mathrm{DD}}^{\′}})}^a\·{\mathrm{\δ}}_B\·c$ [formula four]

And this formula can easily reach the situation of far less than 1 by appropriately and feasiblely taking the value of the distance.

The specific allocation method implementation steps are as follows:

1. The base station divides the cell into an inner ring and an outer ring (better performance can be obtained by using the D2D mode in the outer ring);

2. Divide the outer ring into an even number of equal areas, and determine the two areas facing the center of the circle as a matching set of areas, as shown in Figure 2;

3. The base station randomly finds a pair of D2D pairs in the two matching areas as a matching set of D2D pairs;

4. The base station calculates the equivalent channel gain between D2D users based on the interference channel gain, path fading, and channel gain between D2D users from cellular users to D2D users at the current moment where H _d represents the equivalent channel gain between D2D users, h _d represents the actual channel gain between D2D users, P _I,CiD represents the interference power of cellular users to D2D users, and h _CiD represents the interference channel between cellular users and D2D users gain;

5. Initialize N and V, which are respectively used to represent the number of subcarriers allocated to each group of D2D pairs and the equivalent channel gain, and the initial value is set to 0;

6. For all the subcarriers that can be allocated, the base station selects a group of matching D2D pairs with the largest average equivalent channel gain on the subcarrier in turn, allocates the subcarriers to this group of matching D2D pairs, and assigns the N Add 1 to the corresponding item until it meets the required number of subcarriers, then no subcarriers will be allocated to it, and record the allocated equivalent channel gain with V;

7. Repeat step 6 until all subcarriers are allocated;

Finally, the average capacity of the D2D system is calculated according to the channel capacity formula. Compared with the traditional allocation method, the invention can greatly improve the D2D user capacity.

In short, this method is a new and efficient D2D resource allocation method. Its purpose is to improve the D2D system capacity and spectrum utilization, reduce the interference of cellular users to D2D users, so as to meet the high data rate service requirements of D2D users.

Claims (1)

1. A cellular communication system terminal direct adaptive resource allocation method, characterized in that the resource allocation method is: 1) According to the distance, the cell is divided into an inner ring and an outer ring, and the D2D mode can be used in the outer ring to obtain better performance; 2) Divide the outer ring into an even number of equal areas, and determine the two areas facing the center of the circle as a matching set of areas; 3) Randomly find a pair of D2D pairs in the two matching areas as a matched set of D2D pairs; 4) The base station calculates the equivalent channel gain between D2D users based on the interference channel gain, path fading, and channel gain between D2D users from cellular users to D2D users at the current moment where H _d is the equivalent channel gain between D2D users, h _d is the actual channel gain between D2D users, P _I,CiD is the interference power of cellular users to D2D users, h _CiD is the interference channel between cellular users and D2D users gain; 5) Let N, V be used to represent the number of subcarriers allocated to each D2D pair and the equivalent channel gain, and its initial value is set to 0; 6) For all the subcarriers that can be allocated, select a group of matching D2D pairs with the largest average equivalent channel gain on the subcarriers, assign the subcarriers to this group of matching D2D pairs, and assign the N Add 1 to the corresponding item until it meets the required number of subcarriers, then no subcarriers will be allocated to it, and record the allocated equivalent channel gain with V; 7) Step 6) is repeated until all subcarriers are allocated.