WO2014170750A2

WO2014170750A2 - Method and apparatus for allocating resources for multiple device-to-device communications

Info

Publication number: WO2014170750A2
Application number: PCT/IB2014/000655
Authority: WO
Inventors: Yanli XU; Yong Liu; Dong Li; Kai Yang
Original assignee: Alcatel Lucent
Priority date: 2013-04-15
Filing date: 2014-03-25
Publication date: 2014-10-23
Also published as: CN104105217A; WO2014170750A3; TW201505468A; CN104105217B

Abstract

The invention provides a scheme to allocate resources in a communication system so as to accommodate multiple simultaneous D2D communications. Firstly an eNB sends a predetermined neighbor distance to all of D2D UEs in a cell; the respective D2D UEs determines their respective neighbor information based upon the received predetermined neighbor distance and send their respective neighbor information to the eNB; the eNB determines respective neighbor information of all of D2D pairs according to the received respective neighbor information from all the D2D UEs; then a receiving D2D UE in a D2D pair determines its value of tolerant interference degree and sends the determined value to the eNB; and the eNB takes the received value of tolerant interference degree of the receiving D2D UE as a value of tolerant interference degree of the D2D pair to which the receiving D2D UE belongs; and finally the eNB divides all the D2D pairs into several groups according to the respective neighbor information and values of tolerant interference degree of all the D2D pairs and based upon a greedy algorithm and allocates a different resource for each of the groups, and then notifies each of the D2D pairs a resource allocated for the each D2D pair.

Description

Method and Apparatus for Allocating Resources for Multiple Device-to-Device Communications

Field of the invention

The present disclosure relates to a communication system and particularly to a method and apparatus for, in the communication system, allocating resources for respective Device-to-Device (D2D) pairs to accommodate multiple simultaneous Device-to-Device (D2D) communications.

Background of the invention

Device-to-Device (D2D) communication is a very promising technique in which User Equipments (UEs) with a good communication channel may construct a D2D pair, enabling them to communicate directly with each other without relaying by a cellular evolved Node B (eNB). Thereby the performance (such as throughput and transmission delay) of an LTE cellular network can be improved. Because of the aforementioned advantage, many companies and research institutions are trying to introduce D2D communication into the LTE cellular network to improve the efficiency of system. In the recent 3 GPP RAN meeting #58, D2D communication has been approved as a study item for the LTE cellular network.

The coexistence of D2D and cellular UEs usually has two ways, i.e., (1) D2D shares resources with the cellular UEs, and (2) D2D communicates via dedicated resources allocated by the cellular eNB, which are orthogonal with those of the cellular UEs. The latter coexistence way makes D2D communication bring profits without interference to the existing cellular UEs. However, these D2D pairs may interfere with each other if they share the same resources, leading to the offset of a throughput gain they bring. On the other hand, resources shortage will be severer if all these D2D pairs use orthogonal resources.

Currently a few existing schemes consider an application scenario of the second aforementioned coexistence scenario. For example, for an application scenario of the second coexistence scenario, a scheme (referred hereafter to simply as a freedom degree scheme) is proposed by " Xiaogang R., Gaohui T. and Zhongpei Z., The research of IMT-A_3GPP_12108 on D2D grouping algorithm (in Chinese), Proc. 33th conference of IMT-A promoting group of 3GPP project, Beijing, 2012, 1-8. " to make it possible for multiple D2D pairs to transmit simultaneously. In this scheme, D2D pairs with a fixed link distance are divided into multiple groups and each group uses a resource. The D2D pairs are ranked by their freedom degrees (i.e., the number of neighbors of a D2D pair) and each pair is allocated a resource orderly. The number of allocated resources was minimized based on the coloring algorithm.

However, there are some disadvantages of this scheme:

1. Low data rates of most of the D2D pairs. This scheme causes the majority of the D2D pairs to be divided into a first group. Thereby, interference is maximal in the first group where D2D links are more possibly in outage, leading to a low throughput.

2. Sum-interference is not considered. It may fail to achieve a target data rate for D2D communication since an interference graph is drawn by a pairwise model and an aggregated effect of interference from all other transmitting links is ignored.

3. The distances of the D2D links are assumed to be all equal. In a realistic wireless environment, the distances of the D2D links are usually different from each other and qualities of the links are affected by their distances. Thus a better scheme needs to take their distances and link qualities into consideration.

Another scheme is a random scheme in which each resource tends to accommodate the same number of D2D pairs. Thus this scheme will achieve a better throughput if individual link qualities of the D2D pairs are not considered. However this random scheme consumes a larger number of resources.

Thus how to introduce D2D communication effectively into a cellular network, that is, achieve a higher throughput via less dedicated resources, is a problem highly desirable to be addressed.

Summary of the invention

The invention is intended to propose a scheme to accommodate multiple simultaneous D2D communications in an LTE-A cellular network.

The cellular cell of the invention is assumed where multiple UEs are deployed randomly. The UEs communicating with each other constitute a D2D pair if a radio link between them is good enough. D2D pairs transmit data via resources allocated by an eNB and two UEs in a D2D pair will not send data simultaneously. Hence, we can regard each D2D pair as a vertex, and its location is assumed to be determined by the transmitting UE in this pair. UEs in the cell, which are not selected as D2D pairs are called cellular UEs, transmitting data via resources orthogonal to those of the D2D pairs. Hence, an impact of the cellular UEs on the performance of the D2D pairs will be ignored in this invention.

A scheme of this invention is intended to achieve the following two objects: (1) a resource efficiency of these D2D pairs is maximized, i.e., a throughput of the multiple D2D pairs per resource is maximized; and (2) each D2D pair can satisfy a requirement of a Signal to Interference and Noise Ratio (SINR) to thereby achieve a certain Quality of Service (QoS).

To achieve the foregoing objects, according to an aspect of the invention, there is provided a method of allocating a resource in a base station of a communication system, wherein a coverage area of the base station includes a plurality of D2D pairs, each of which includes two D2D user equipments, and the method includes the steps of: i. sending a predetermined neighbor distance to all the D2D user equipments in the coverage area of the base station; ii. receiving respective neighbor information from all the D2D user equipments; iii. determining respective neighbor information of the plurality of D2D pairs according to the respective neighbor information of all the D2D user equipments; iv. obtaining values of respective tolerant interference degrees of the plurality of D2D pairs; v. dividing the plurality of D2D pairs into several groups according to the respective neighbor information and the values of respective tolerant interference degrees of the plurality of D2D pairs and based upon a greedy algorithm, and allocating a different resource for each group, wherein D2D pairs divided into the same group are not a neighbor of each other; and vi. notifying each of the plurality of D2D pairs of a resource allocated for the each D2D pair.

Advantageously after the step i and before the step iv, the method further includes the steps of: - receiving from one or more of all the D2D user equipments an inquiry message about a D2D partner of the one or more D2D user equipments; and - notifying the one or more D2D user equipments of information about the D2D partner of the one or more D2D user equipments.

Advantageously the step iv includes the steps of: - obtaining from a receiving D2D user equipment of each of the plurality of D2D pairs a value of tolerant interference degree of the receiving D2D user equipment; and - taking the value of tolerant interference degree of the receiving D2D user equipment as a value of tolerant interference degree of a D2D pair to which the receiving D2D user equipment belongs;

wherein the value of tolerant interference degree of the receiving D2D user equipment is obtained by:

- calculating the value tf j of tolerant interference degree of the receiving D2D user equipment in the equation of:

wherein P_td- represents receiving power of a useful signal received by the receiving D2D user equipment from its transmitting D2D user equipment, 7₀ represents receiving power of a signal received by the receiving D2D user equipment from its nearest non-neighbor D2D pair, No represents thermal noise, y_th represents an SINR threshold value, and a represents a path loss factor; and

- quantizing the calculated value K _¾- of tolerant interference degree in the equation of:

M tf ₍ > M

K;= I «,<I ,

|_K J Otherwise to obtain a quantized value , of tolerant interference degree,

wherein M represents the number of D2D pairs in the coverage area of the base station, and |_ J represents rounding down.

Advantageously the step iv includes the steps of: - obtaining from a receiving D2D user equipment of each of the plurality of D2D pairs a value of tolerant interference degree of the receiving D2D user equipment, and obtaining from a transmitting D2D user equipment a value of tolerant interference degree of the transmitting D2D user equipment; and - taking a lower one of the value of tolerant interference degree of the receiving D2D user equipment and the value of tolerant interference degree of the transmitting D2D user equipment as a value of tolerant interference degree of a D2D pair to which the receiving D2D user equipment and the transmitting D2D user equipment belong;

- calculating the value of tolerant interference degree of the receiving D2D user equi ment in the equation of:

wherein P_td. represents receiving power of a useful signal received by the receiving D2D user equipment from its transmitting D2D user equipment, 7₀ represents receiving power of a signal received by the receiving D2D user equipment from its nearest non-neighbor D2D pair, No represents thermal noise, y_th represents an SINR threshold value, and a represents a path loss factor; and

M K . > M

1 < 1

|_K J Otherwise to obtain a quantized value , of tolerant interference degree,

wherein M represents the number of D2D pairs in the coverage area of the base station, and |_ J represents rounding down; and

wherein the value of tolerant interference degree of the transmitting

D2D user equipment is obtained by:

- calculating the value tf j of tolerant interference degree of the transmitting D2D user e uipment in the equation of:

wherein P_td- represents receiving power of a useful signal received by the transmitting D2D user equipment from its receiving D2D user equipment, 7₀ represents receiving power of a signal received by the transmitting D2D user equipment from its nearest non-neighbor D2D pair, No represents thermal noise, and y_th represents the SINR threshold value; and - quantizing the calculated value K _¾- of tolerant interference degree in the equation of:

M > M

1 < 1

|_K J Otherwise to obtain a quantized value , of tolerant interference degree,

Advantageously the step v includes the steps of: vl . arranging the plurality of D2D pairs in a non-descending order of the values of tolerant interference degrees of respective D2D pairs among the plurality of D2D pairs to generate an ordered set of D2D pairs; v2. creating a group, putting a first D2D pair in the ordered set of D2D pairs into the group, and removing the first D2D pair from the ordered set of D2D pairs to update the set of D2D pairs; v3. selecting sequentially from the updated set of D2D pairs a D2D pair which is not a neighbor of any member in the group, putting the selected D2D pair into the group, removing the selected D2D pair from the set of D2D pairs to update the set of D2D pairs, and decreasing a value of tolerant interference degree of each member in the group by 1 ; v4. repeating the step v3 until a value of tolerant interference degree of at least one member in the group is below or equal to zero; v5. arranging remaining D2D pairs in the updated set of D2D pairs in a non-descending order of values of tolerant interference degree of the remaining D2D pairs to generate an ordered set of D2D pairs; v6. repeating the steps v2 to v5 until the set of D2D pairs is null; and v7. allocating a different resource for each of the plurality of created groups.

According to another aspect of the invention, there is proposes a method, in a receiving D2D user equipment of a communication network, of assisting a base station in allocating a resource, wherein the method includes the steps of: I. receiving a predetermined neighbor distance from the base station; II. determining neighbor information of the receiving D2D user equipment based upon the received predetermined neighbor distance; IV. sending the determined neighbor information of the receiving D2D user equipment to the base station; IV. determining a value of tolerant interference degree of the receiving D2D user equipment, and sending the determined value of tolerant interference degree of the receiving D2D user equipment to the base station; and V. receiving resource allocation information from the base station.

Advantageously after the step I and before the step IV, the method further includes the steps of: - judging whether the receiving D2D user equipment has a knowledge of its D2D partner; - if not, then sending an inquiry message to the base station to inquire about a D2D partner of the receiving D2D user equipment; and - receiving from the base station information about the D2D partner of the receiving D2D user equipment.

Advantageously the step IV includes the steps of:

- calculating the value tf j of tolerant interference degree of the receiving D2D user equi ment in the equation of:

M > M

1 < 1

|_K J Otherwise to obtain a quantized value , of tolerant interference degree,

According to another aspect of the invention, there is proposes a method, in a transmitting D2D user equipment of a communication network, of assisting a base station in allocating a resource, wherein the method includes the steps of: A. receiving a predetermined neighbor distance from the base station; B. determining neighbor information of the transmitting D2D user equipment based upon the received predetermined neighbor distance; C. sending the determined neighbor information of the transmitting D2D user equipment to the base station; and E. receiving resource allocation information from the base station.

Advantageously after the step A and before the step E, the method further includes the steps of: - judging whether the transmitting D2D user equipment has a knowledge of its D2D partner; - if not, then sending an inquiry message to the base station to inquire about a D2D partner of the transmitting D2D user equipment; and - receiving from the base station information about the D2D partner of the transmitting D2D user equipment.

Advantageously after the step C and before the step E, the method further includes the step of: D. determining a value of tolerant interference degree of the transmitting D2D user equipment, and sending the value of tolerant interference degree of the transmitting D2D user equipment to the base station.

Advantageously the step D includes the steps of:

wherein P_td. represents receiving power of a useful signal received by the transmitting D2D user equipment from its receiving D2D user equipment, 7₀ represents receiving power of a signal received by the transmitting D2D user equipment from its nearest non-neighbor D2D pair, No represents thermal noise, and y_th represents the SINR threshold value; and

M tf ₍ > M

5

|_K J Otherwise to obtain a quantized value , of tolerant interference degree,

In the scheme according to the foregoing embodiments of the invention, since neighbors of respective D2D pairs in a cellular cell are divided into different groups, interference between the D2D pairs can be well controlled. Moreover in the inventive scheme, a feedback, i.e., a Tolerant Interference Degree (TID), is newly defined to make it easy to evaluate the sum interference of the D2D pairs. Furthermore the use of the TID can lower a signaling overhead and power consumption.

With an application of the scheme according to the foregoing embodiments of the invention, firstly simultaneous communication over multiple D2D links can occupy a lower number of resources. Secondly an SINR of each D2D pair satisfy a demand for communication. Thirdly the cellular cell is provided with higher resource efficiency.

According another aspect of the invention, there is provided a method of allocating a resource in a base station of a communication system, wherein a coverage area of the base station includes a plurality of D2D pairs, each of which includes two D2D user equipments, and the method includes the steps of: a. sending a predetermined partner distance and a predetermined interference distance to all the D2D user equipments in the coverage area of the base station; b. receiving respective partner sets and interference source sets from all the D2D user equipments; c. creating an interference graph of the plurality of D2D pairs according to the respective partner sets and interference source sets of all the D2D user equipments; and d. dividing the plurality of D2D pairs into several groups based upon the interference graph of the plurality of D2D pairs and a greedy algorithm and according to saturation degrees of the plurality of D2D pairs, and allocating a different resource for each group, wherein for a D2D pair, its saturation degree represents the number of D2D pairs, among its neighbors, for which a resource has been allocated; and e. notifying each of the plurality of D2D pairs of a resource allocated for the each D2D pair.

According another aspect of the invention, there is provided a method, in a D2D user equipment of a communication network, of assisting a base station in allocating a resource, wherein the method includes the steps of: receiving a predetermined partner distance and a predetermined interference distance from the base station; determining a partner set and an interference source set of the D2D user equipment based upon the received predetermined partner distance and predetermined interference distance; sending the determined partner set and the determined interference source set of the D2D user equipment to the base station; and receiving resource allocation information from the base station.

In the scheme according to the foregoing embodiments of the invention, since mutual interference sources are divided into different groups, interference between D2D pairs can be well controlled based upon interference source sets. Furthermore a D2D candidate partner set is defined to narrow a search range for an eNB and to ensure D2D link qualities. Thus the eNB can adjust this set so that D2D communication satisfies an application demand without consuming a considerate signaling overhead. With an application of the scheme according to the foregoing embodiments of the invention, firstly simultaneous communication over multiple D2D links can occupy a lower number of resources. Secondly each resource is allocated to a similar number of D2D pairs, so the allocation of the resource is more uniform. Thirdly an SINR of a D2D pair is greatly improved.

The respective aspects of the invention will become more apparent from the following description of particular embodiments thereof. Brief description of drawings

The foregoing and other features of the invention will become more apparent upon review of the following detailed description of non-limiting embodiments taken with reference the drawings in which:

Fig. l illustrates a schematic diagram of communication of multiple D2D pairs in a cellular cell according to an embodiment of the invention;

Fig.2 illustrates an example of a neighbor relationship of a UE according to an embodiment of the invention;

Fig.3 illustrates an example of a neighbor relationship of a D2D pair according to an embodiment of the invention;

Fig.4 illustrates a flow chart of a method of allocating a resource according to an embodiment of the invention;

Fig.5 illustrates an example of a neighbor graph of a cell according to an embodiment of the invention;

Fig.6 illustrates a schematic diagram of resource allocation according to an embodiment of the invention;

Fig.7 illustrates a schematic diagram of comparison of the number of resources used for the inventive scheme and the two prior schemes;

Fig.8 illustrates a schematic diagram of comparison of throughput for the inventive scheme and the two prior schemes;

Fig.9 illustrates a schematic diagram of comparison of resource efficiency for the inventive scheme and the two prior schemes; Fig.10 illustrates an example of an interference relationship of a UE, where interference sources of the UE are located in a circular area;

Fig.11 illustrates an example of an interference relationship of a D2D pair;

Fig.12 illustrates a flow chart of a method of allocating a resource according to another embodiment of the invention;

Fig.13 illustrates an example of an interference graph of a cell including 100 D2D pairs;

Fig.14 illustrates a schematic diagram of an example of allocating resources for multiple D2D pairs in a cell;

Fig.15 illustrates a schematic diagram of comparison of uniformity for the inventive scheme and the two prior schemes at an interference distance of 100m;

Fig.16 illustrates a schematic diagram of comparison of a signal to interference and noise ratio for the inventive scheme and the two prior schemes at an interference distance of 100m;

Fig.17 illustrates a schematic diagram of comparison of a signal to interference and noise ratio for the inventive scheme and the two prior schemes at an interference distance of 150m; and

Fig.18 illustrates a schematic diagram of comparison of the used number of resources for the inventive scheme and the two prior schemes at an interference distance of 100m.

Identical or similar reference numerals in the drawings denote identical or similar components.

Detailed description of embodiments

Embodiments of the invention will be described below with reference to the drawings.

Referring to Fig. l , we assume a cellular cell including multiple cellular UEs (which transmit data in a traditional way) and multiple D2D pairs (which transmit directly with resources allocated by an eNB). Since the cellular UEs and the D2D pairs use separate resources, their mutual interferences can be ignored here. In D2D communication, the communication link is usually short, making it possible for the multiple D2D pairs to transmit simultaneously. On the other hand, interference among the D2D pairs may exist due to the characteristic of wireless broadcast. Thus we need to control the interference and guarantee a demand of communication for introducing the multiple D2D pairs to a cellular network efficiently.

To this end, the SINR y_v at a random D2D link v should be beyond a given threshold y_th to provide a specified QoS. In addition, the resource efficiency is targeted to be maximized. These considerations can be modeled as follows:

C "',throughput

max r_eff

^resource ^ )

Where r_eff represents the resource efficiency, C_th_r0ughput is the total throughput of multiple D2D pairs set Ψ , and N_resource is the corresponding amount of used resources. The optimal problem above can be converted to a sub-optimal problem which maximizes the throughput while minimizing the amount of used resources.

To maximize the throughput, interference among the D2D pairs needs to be controlled. In a wireless environment, each UE has direct links (the channel between UEs is above a threshold) to a certain number of UEs, which are defined as its neighbors. Usually, interference of a UE is assumed to come from its neighbors. Here, we assume that for two random UEs i and j, they will be neighbors for each other if the distance between them d_y is less than a pre-defined neighbor distance d_nei_g, i.e., d..≤d (2) i/_neig is a priori value stored at the eNB side, whose value is usually larger than the distance of a practical communication link to control interference. Fig.2 shows an example of a neighbor relationship of a UE whose neighbors are located in the circle as illustrated. Since there is only one UE transmitting at a time in each D2D pair, interference to a D2D link comes from transmitting UEs in other D2D pairs. Thus we regard each D2D link as a whole, denoted by a vertex for simplicity, since the link distance of a D2D pair is short. If two UEs are neighbors, then two D2D pairs to which they belong are also neighbors. Fig.3 shows an example of a neighbor relationship of a D2D pair.

Referring to Fig.4, in the inventive scheme, firstly in the step S41, an eNB broadcasts a predetermined neighbor distance d_ne[_g to all of D2D pairs (all of D2D UEs) in a cell, and then in the step S42, each of the D2D UEs in the D2D pairs determines its respective neighbor information of the D2D UE according to the above equation of (2) based upon the received predetermined neighbor distance i/_neig. In practice, the UE j can be regarded as a neighbor of the UE i if the inequality below of (3) is satisfied:

Pd > Pd

Where P_r is transmission power of a UE, a is a path loss factor, and

Pd ^a

' " is receiving power of a signal received by the UE i from the UE j. That is, in a practical application, whether the two UEs are neighbors of each other can be judged according to the receiving power instead of the distance.

Each D2D UE feeds its own neighbor information back to the eNB in the step S43 after determining its own neighbor information.

Since not every D2D UE knows its D2D partner, advantageously before or after the step S42 above, the step S42' can be further included in which each D2D UE judges whether it know its respective D2D partner; and if not, then it sends an inquiry message to the eNB in step S42 a' to inquire about its D2D partner; and the eNB notifies the D2D UE of information about the D2D partner of the D2D UE in response to the received inquiry message in the step S42b' . The eNB determines respective neighbor information of all the D2D pairs in the cell according to the respective neighbor information of all the D2D UEs in the step S44 upon reception of the respective neighbor information from all the D2D UEs. For example, the eNB can determine the neighbor of a D2D pair according to the following criterion: if any D2D UE in a D2D pair is the neighbor of one D2D UE in another D2D pair, then these two D2D pairs are neighbors. Fig.5 shows an example of a neighbor graph of a cell including 100 D2D pairs, where each D2D pair is represented by a star and neighbors are connected by edges.

Since the neighbor graph of the cell conveys information of interference among the D2D pairs to some extent, we can also call the neighbor graph of the cell an interference graph of the multiple D2D pairs. To accommodate simultaneous communications of these D2D pairs, the eNB allocates different resources for the neighbors. To achieve high resource efficiency, the eNB also needs to know the sum interference, the link quality and the Signal-Interference-Noise Ratio (SINR) threshold γ_ώ of each D2D pair. However, so many feedbacks lead to a significant signaling overhead. In view of this, we propose a new metric, i.e., a Tolerant Interference Degree (TID), where for a vertex i (i.e., a D2D pair i), its tolerant interference degree is represented as 3Λ _e-. To make the SINR of each D2D link satisfy the SINR requirement for communication, namely, satisfy the constraint in the above equation of (1), the following expression needs to be satisfied:

Where ^]≡ψ/ψί is the sum-interference at the vertex i, d_t is the distance of a D2D link, ^< is a neighbor set of the vertex i and N₀ is thermal noise. To satisfy the inequality of (4), we have: -a

L≤ -N,

(5)

From (5) we can see that the sum-interference at a D2D pair shall be below a threshold which is determined by its link quality (such as a link distance and a fading factor). Thus, the sum-interferences of the D2D pairs need to be controlled based on their respective link qualities.

According to the results of the previous research work (see Mordachev, V. and Loyka, S., On node density-outage probability tradeoff in wireless networks, IEEE Journal on Selected Areas in Communications, vol.27, 2009, 1120- 1131.), dominating interference to a node comes from one node at the nearest distance from the node, while interference from other nodes can be ignored. Here we approximate interference from other non-neighbor vertices by thermal noise N₀ and assume that interference from the nearest non-neighbor vertex is 7₀. Then, we define the TID as follows to indicate the tolerant number of vertices coexisting with the vertex i.

In the equation of (6), P_td:^a represents receiving power of a useful signal received by a receiving D2D UE in a D2D pair from its transmitting D2D UE, and 7₀ represents receiving power of a signal received by a receiving D2D UE in a D2D pair from its nearest non-neighbor vertex.

That is, in the inventive scheme, after the D2D UE determines its neighbor information and obtains the information about its D2D partner, furthermore in the step S45, the receiving D2D UE in the D2D pair calculates its value of tolerant interference degree , according to the above equation of (6), and then in the step S46, the receiving D2D UE quantizes the calculated value of tolerant interference degree i _t according to the equation of:

to obtain a quantized value , of tolerant interference degree

Where M represents the number of D2D pairs in the cell, and |_ J represents rounding down. That is, when the calculated value of tolerant interference degree i , is above M, M is taken as a resultant value of tolerant interference degree; when the calculated value of tolerant interference degree it , is below 1 , 1 is taken as a resultant value of tolerant interference degree; and when the calculated value of tolerant interference degree i , is above or equal to 1 and below or equal to M, the calculated value of tolerant interference degree it ,- is rounded down and then taken as a resultant value of tolerant interference degree.

The receiving D2D UE sends the determined value of tolerant interference degree to the eNB, for example, over a PUSCH or EPDCCH channel, in the step S47 after determining its value of tolerant interference degree. The eNB takes the value of tolerant interference degree of the receiving D2D UE in the D2D pair as a value of tolerant interference degree corresponding to the D2D pair to which the receiving D2D UE belongs in the step S48 upon reception of the value of tolerant interference degree of the receiving D2D UE.

In another example, the receiving D2D UE and the transmitting D2D UE in the D2D pair determine their respective values of tolerant interference degree respectively and provide the eNB with their respective values of tolerant interference degree. The eNB takes a lower one of these two values of tolerant interference degree as a value of tolerant interference degree of the D2D pair.

After the eNB obtains the respective values of tolerant interference degree of all the D2D pairs in the cell, in the step S49, the eNB divides all the D2D pairs into several groups according to the respective neighbor information and the respective values of tolerant interference degree of all the D2D pairs and based upon a greedy algorithm, and allocates a different resource for each group, wherein D2D pairs divided into the same group are not a neighbor of each other, as illustrated in Fig.6. Then in the step S410, the eNB notifies each of the D2D pairs of a resource allocated for the each D2D pair. The resources allocated by the eNB for the respective D2D pairs can be broadcasted, for example, to the respective D2D pairs. The respective D2D pairs can receive information about the resource allocated thereto over a PDSCH or an EPDCCH, for example.

In this greedy algorithm, all the vertices (i.e., D2D pairs) in the cell are ranked non-decreasingly according to their respective values of tolerant interference degree, and then these vertices are put orderly into different groups. After s times of loops, all the vertices are divided into s groups ( G_l G_s ), where each group is allocated a resource, that is, resources allocated to the respective groups among the s groups are different from each other. In this algorithm, vertices which are neighbors with each other will not be put in the same group. And we put non-neighbor vertices orderly in a group until there is a D2D pair at which the sum of interference is not tolerant any more. That is, the values of tolerant interference degree ^< of respective vertices in each group satisfy the equation of:

K,≥0 ₍₈)

We denote the number of vertices in the s^th group by ^N^ whose initial value is zero. The inventive greedy algorithm is listed as follows.

Given ⁼ '

Input: The set Ψ^ν^^••••v_M ] of all the D2D pairs, the neighbor graph {ψ_ί }._{=1 M} , and the set of TIDs _l ={^χ _ι,^χ ₂ · -^■ -x_M }

Output: Groups G_l G_s Repeat

1) In the s* loop, make non-decreasing ordering of respective vertices in the vertex set (that is, the D2D pairs set) according to TIDs of the respective vertices, T_s = , where N(£)reprents the number

of vertices in a group G_k . Then obtain an ordered vertice set

2) Set up a group G_s and put the first vertex v_sl in the vertex set into this group, i.e., G =v_sl . In the mean time, remove v_sl from Ψ_ί5 i.e., Ψ^Ψ,Νν^.Ι^ί N(s)=N(s)+l.

3) Select ordinally a vertex which is not the neighbor of members of G_s and put it into G_s.

Repeat

i. Select a vertex v_si with the maximum TID which is not a neighbor of the members of G_s and put it into G_s i.e., G_s={G_s,v_{s i}). In the mean time, remove v_SI from Ψ_^,ί.ε., Ψ^Ψ^ν_^.. ii. Update the value of TIDs for the members in G_s, i.e.,

T_G =T_G -1. And update the number of vetices in group s, i.e., N(s)=N(s)+l .

Until there is at least a vertex in G_s whose TID is not greater than zero, i.e., V_/eG,, T,<0.

4) s=s+l

Until there is no vertex left, i.e., Ψ,= .

In the inventive scheme, by using the TID feedback, the eNB does not need to know the location and interference of each UE. Thereby, the signaling overhead and complexity is reduced.

To further evaluate the scheme according to the foregoing embodiments of the invention, we carried out relevant simulations and compared it with the freedom degree scheme and the random scheme. Simulation parameters are as depicted in Table 1 below.

Table 1

Fig.7 shows that the number of resources used by the inventive scheme is greatly lowered as compared with the number of resources used by the random scheme (about 94%). This is because the number of D2D pairs sharing the same resource tends to be equal in the random scheme, while resources in the inventive scheme are allocated greedily, which is similar to the freedom degree scheme.

Fig.8 shows that the throughput of the cell for the inventive scheme is greatly improved as compared with the freedom degree scheme (from 135% to 220%). This is because the sum-interference and the link quality for each D2D pair are considered in the inventive scheme. In addition, since interference is well controlled in the inventive scheme, its throughput is similar to that of the random scheme, while resources used by random scheme are quite more.

Fig.9 shows that the inventive scheme has better resource efficiency which is about up to 4 times larger than the freedom degree scheme and 17 times larger than the random scheme. This is because the inventive scheme has a significant improvement on throughput while a lower number of resources are used. An embodiment of the invention has been described in details above. In another embodiment of the invention, referring to Fig.l again, if there are data to be transmitted between two proximal UEs which have good enough link quality, the eNB will choose them as a D2D pair. We use a distance as a metric for defining this partner relationship here. We assume that for a random UE j, it will be a D2D partner candidate of a UE i if the distance between them d_y is below a predefined partner distance d_pa∑tnei, i.e.,

Since D2D links are often short and are of a good quality, simultaneous transmission over the multiple D2D links will become possible. On the other hand, interference among D2D pairs may exist due to the characteristic of wireless broadcast. Thus we need to control interference and guarantee an SINR requirement in order for efficient D2D communication. To this end, UEs with intolerant mutual interference need to be allocated different resources. In a wireless environment, a communication link is typically only interfered by transmission signals of UEs within a certain range due to a path loss. Within this range, channels between the UEs are better than a threshold, and here we call these UEs mutual interference sources. According to the research work "Mordachev, V. and Loyka, S., On node density-outage probability tradeoff in wireless networks, IEEE Journal on Selected Areas in Communications, vol.27, 2009, 1120-1131", interference between UEs decreases rapidly as their distance increases. That is, we can assume that dominant interference to a specific UE comes from UEs within a certain range. Hence, mutual interference sources will be allocated different resources in the inventive scheme to control interference.

Here, we assume that for two random UEs i and j, they will be mutual interference sources for each other if the distance between them d_y is less than a predefined distance ^interference, i.e.,

dij ≤ interference (10) where interference is a priori value stored at the eNB side which is usually larger than d_paitaei to restrict interference. Fig.10 shows an example of this interference relationship of a UE whose interference sources are located in a circular area.

Since there is only a UE transmitting at a time in a D2D pair, interference to the link of a D2D pair comes from transmitting UEs in other D2D pairs. Thus we regard each D2D pair as a whole, denoted by a vertex. If two UEs are interfering with each other, then two D2D pairs to which they belong are also considered to interfere with each other. Fig.11 shows an example of an interference relationship of a D2D pair.

We assume that D2D pairs are divided into different groups and D2D pairs in the same group share the same resource. We define a metric σ to judge how uniform resource allocation is. With the number of D2D pairs in a group being represented by a random variable M, σ can be expressed as follows:

Where μ denotes the mean value of M, M_t denotes the number of members in the group i, and N is the number of groups. The smaller σ is, the more uniform the resource allocation scheme is. In the following, we will elaborate this scheme step by step.

As illustrated in Fig.12, firstly in the step S I 201, the eNB broadcasts a D2D partner distance d_paitnei and an interference distance

In practice, the eNB can regulate reception signals and interference at receiving UEs by setting values of d_paitnei and

Their values can be determined based on empirical values, UE deployment from rough estimation of TAs (Timing Advance) or other information (such as transmission power, transmission distances and so on) fed back by the UEs.

The UE sends a packet containing information of its identity in a random channel or an allocated channel in a timeslot upon reception of the partner distance d_paitnei and the interference distance interference from the eNB; and in another timeslot, it listens to information from other UEs. Then the UE decodes the received packet and estimates the distance between the UE and a UE transmitting the packet. Then in the step SI 202, the UE obtains the two sets above according to the equations of (9) and (10). In practice, the UE can alternatively make this judgement based on receiving power. A UE j can be regarded as a partner candidate of a UE i if receiving power of the transmission signal of the UE j at the UE i satisfies the inequality below of (12):

^ ≥¾L_er (i2)

Where P_r is transmission power of a UE, a is a path loss factor and P_td ^a is receiving power at the UE i from the UE j. Similarly, interference sources of the UE i can be determined by the following expression of:

P ¹ td^U _1] > - P ¹ [d"interference ( V 13) /

After these comparisons, the UE can obtain its partner candidate set _p and interference source set Φ_ι . In general, the partner set belongs to the interference set, i.e., Φ_Ρ £ Φ_: because _partner < 4_nterference .

Then in the step S I 203, each UE feeds its partner candidate set and interference source set back to the eNB. Since Φ_ρ and Φ_ι are partially overlapped, the UE only needs to feed back Φ_ρ and Φ_Τ/Φ_Ρ where the UE is only in the interference source set. By using the partner candidate set Φ_ρ , the eNB can determine that the UE transmits information in a traditional way or via D2D. This set can help the eNB decide the transmission mode of the UE and narrow the D2D partner search range. Thus the signalling overhead will be reduced. Given a UE, if another UE is its target receiver and also belongs to it partner candidate set, then these two UEs will constitute a D2D pair and can transmit information directly. By using the interference set Φ_ι , the eNB can get an interference graph of all the UEs. In the step SI 204, based on these feedbacks from the UEs, the eNB can construct an interference graph of all the D2D pairs. Fig.13 shows an example of an interference graph of a cell including 100 D2D pairs, where a vertex is represented by a star and interference sources are connected by edges. Then in the step S I 205, the eNB allocates resources to these D2D pairs according to a greedy colouring method. Each D2D pair is regarded as a vertex and these vertices are ranked non-increasingly according to their respective freedom degrees. They are put into different groups based on saturation degrees. Given a D2D pair, the saturation degree is defined as the number of vertices, which have been allocated resources, among its neighbours. After s times of loops, the vertices are divided into N groups

( G₁ G_N where D2D pairs in each group share a resource. In this procedure, D2D pairs which interfere with each other are put in different groups by using Φ_Γ . The group with the least number of members has the highest priority to accommodate a new D2D pair. This greedy algorithm is particularly as follows:

CD The eNB constructs an interference graph, where each D2D pair is denoted by a vertex, based on Φ_ι and Φ_ρ .

(D Calculate the freedom degree of each vertex and make non-decreasing ordering of the vertices according to their freedom degrees.

(3) Colour the first vertex by a random colour and calculate saturation degrees of the other vertices.

(D Select a vertex with the highest saturation degree. In the case of vertices with the same saturation degree, select any of them.

(D Colour the selected vertex with a colour which has been used for the least number of times in a currently available colour set Φ_Α . Φ_Α includes a set of all of used colours except colours used by interference sources of this vertex. Create a new colour if Φ_Α Ϊ8 empty. Update the saturation degrees of the interference sources of this vertex.

(D Return to step (D until all the vertices are coloured.

After the above procedure, each vertex is allocated a colour, as shown in Fig.14. D2D pairs with the same colour share the same resource. The number of colours is equal to the number of allocated resources. With this greedy algorithm, the number of allocated resource is minimized. At the same time, each resource accommodates a similar number of D2D pairs. Finally in the step SI 206, the eNB notifies each of the D2D pairs of the resource allocated for the each D2D pair. Then each D2D pair transmits data with the allocated recourse.

To further evaluate the scheme according to the foregoing embodiments of the invention, we carries out relevant simulations and compared the inventive scheme with both the freedom degree scheme and the random scheme. Simulation parameters are depicted in Table 2.

Table 2

Fig.15 compares the uniformity for the three schemes. As can be apparent from this figure, we can see that the random scheme has the best uniformity as a benchmark, while the freedom degree scheme has the worst uniformity. In addition, as compared with the freedom degree scheme, the value of σ is reduced by about 50% by the inventive scheme. That is, the inventive scheme performs better than the freedom degree scheme in term of uniform resource allocation.

Fig.16 shows that there is a probability of 50% for the very low SINR of the freedom degree scheme, which may not satisfy a practical communication requirement. The reason is that most of D2D pairs in this scheme are allocated to a first group, i.e., most of D2D pairs share the same resource. To make the SINR satisfy the practical requirement, an interference distance needs to be enlarged, leading to a higher cost of resources. In the inventive scheme, the SINR is improved up to a double because this scheme allocates resources more uniformly and interference can also be controlled by the interference set.

Fig.17 shows that the SINR of the inventive scheme is close to that of the random scheme. This is because as an interference distance increases, mutual interference sources are more possible to be allocated different resources in the inventive scheme, while the random scheme only allocates resources equally without considering interferences among D2D pairs. Furthermore, the SINR of the freedom degree scheme is improved up to 6 times by the inventive scheme. That is, the advantage of the proposed scheme becomes more significant with the interference distance is larger and Φ_ι is lower because a gain as a result of uniform resource allocation becomes more obvious.

Fig.18 shows that the inventive scheme occupies a similar number of resources with the freedom degree scheme although the inventive scheme has a much better SINR than the latter. In addition, the random scheme achieves the best SINR at the cost of significantly consumed resources.

Those skilled in the art shall appreciate that the invention apparently will not be limited to the foregoing exemplary embodiments and can be embodied in other specific forms without departing from the spirit or essence of the invention. Accordingly the embodiments shall be construed anyway to be exemplary and non-limiting. Any reference numerals in the claims shall not be construed as limiting the scope of the invention. Moreover apparently the term "comprising" will not preclude another element(s) or step(s), and the term "a" or "an" preceding an element will not preclude a plurality of this element. A plurality of elements stated in an apparatus claim can alternatively be embodied as a single element in software or hardware. The terms "first", "second", etc., are intended to designate a name but not to suggest any specific order.

Claims

1. A method of allocating a resource in a base station of a communication system, wherein a coverage area of the base station includes a plurality of D2D pairs, each of which includes two D2D user equipments, and the method comprises the steps of:

1. sending a predetermined neighbor distance to all the D2D user equipments in the coverage area of the base station;

ii. receiving respective neighbor information from all the D2D user equipments;

iii. determining respective neighbor information of the plurality of D2D pairs according to the respective neighbor information of all the D2D user equipments;

iv. obtaining values of respective tolerant interference degrees of the plurality of D2D pairs;

v. dividing the plurality of D2D pairs into several groups according to the respective neighbor information and the values of respective tolerant interference degrees of the plurality of D2D pairs and based upon a greedy algorithm, and allocating a different resource for each group, wherein D2D pairs divided into the same group are not a neighbor of each other; and

vi. notifying each of the plurality of D2D pairs of a resource allocated for the each D2D pair.

2. The method according to claim 1 , wherein after the step i and before the step iv, the method further comprises the steps of:

- receiving from one or more of all the D2D user equipments an inquiry message about a D2D partner of the one or more D2D user equipments; and

- notifying the one or more D2D user equipments of information about the D2D partner of the one or more D2D user equipments.

3. The method according to claim 1 , wherein the step iv comprises the steps of:

- obtaining from a receiving D2D user equipment of each of the plurality of D2D pairs a value of tolerant interference degree of the receiving D2D user equipment; and

- taking the value of tolerant interference degree of the receiving D2D user equipment as a value of tolerant interference degree of a D2D pair to which the receiving D2D user equipment belongs;

- calculating the value tf j of tolerant interference degree of the receiving D2D user equipment in the e uation of:

wherein P_td ^a represents receiving power of a useful signal received by the receiving D2D user equipment from its transmitting D2D user equipment, 7₀ represents receiving power of a signal received by the receiving D2D user equipment from its nearest non-neighbor D2D pair, N₀ represents thermal noise, y_th represents an SINR threshold value, and a represents a path loss factor; and

- quantizing the calculated value tf j of tolerant interference degree in the equation of:

ise to obtain a quantized value , of tolerant interference degree,

4. The method according to claim 1 , wherein the step iv comprises the steps of:

- obtaining from a receiving D2D user equipment of each of the plurality of D2D pairs a value of tolerant interference degree of the receiving D2D user equipment, and obtaining from a transmitting D2D user equipment a value of tolerant interference degree of the transmitting D2D user equipment; and

- taking a lower one of the value of tolerant interference degree of the receiving D2D user equipment and the value of tolerant interference degree of the transmitting D2D user equipment as a value of tolerant interference degree of a D2D pair to which the receiving D2D user equipment and the transmitting D2D user equipment belong;

- calculating the value of tolerant interference degree of the receiving D2D user equipment in the e uation of:

wherein P_td-^a represents receiving power of a useful signal received by the receiving D2D user equipment from its transmitting D2D user equipment, 7₀ represents receiving power of a signal received by the receiving D2D user equipment from its nearest non-neighbor D2D pair, N₀ represents thermal noise, _th represents an SINR threshold value, and represents a path loss factor; and

- quantizing the calculated value of tolerant interference degree in the equation of:

M tf ₍ > M

|_K J Otherwise to obtain a quantized value , of tolerant interference degree,

wherein the value of tolerant interference degree of the transmitting D2D user equipment is obtained by:

- calculating the value tf j of tolerant interference degree of the transmitting D2D user equipment in the e uation of:

wherein P_td ^a represents receiving power of a useful signal received by the transmitting D2D user equipment from its receiving D2D user equipment, 7₀ represents receiving power of a signal received by the transmitting D2D user equipment from its nearest non-neighbor D2D pair, N₀ represents thermal noise, and y_th represents the SINR threshold value; and - quantizing the calculated value tf j of tolerant interference degree in the equation of:

ise to obtain a quantized value , of tolerant interference degree,

5. The method according to claim 1, wherein the step v comprises the steps of:

vl . arranging the plurality of D2D pairs in a non-descending order of the values of tolerant interference degrees of respective D2D pairs among the plurality of D2D pairs to generate an ordered set of D2D pairs;

v2. creating a group, putting a first D2D pair in the ordered set of D2D pairs into the group, and removing the first D2D pair from the ordered set of D2D pairs to update the set of D2D pairs;

v3. selecting sequentially from the updated set of D2D pairs a D2D pair which is not a neighbor of any member in the group, putting the selected D2D pair into the group, removing the selected D2D pair from the set of D2D pairs to update the set of D2D pairs, and decreasing a value of tolerant interference degree of each member in the group by 1 ;

v4. repeating the step v3 until a value of tolerant interference degree of at least one member in the group is below or equal to zero;

v5. arranging remaining D2D pairs in the updated set of D2D pairs in a non-descending order of values of tolerant interference degree of the remaining D2D pairs to generate an ordered set of D2D pairs;

v6. repeating the steps v2 to v5 until the set of D2D pairs is null; and v7. allocating a different resource for each of the plurality of created groups.

6. A method of allocating a resource in a base station of a communication system, wherein a coverage area of the base station includes a plurality of D2D pairs, each of which includes two D2D user equipments, and the method comprises the steps of:

a. sending a predetermined partner distance and a predetermined interference distance to all the D2D user equipments in the coverage area of the base station;

b. receiving respective partner sets and interference source sets from all the D2D user equipments;

c. creating an interference graph of the plurality of D2D pairs according to the respective partner sets and interference source sets of all the D2D user equipments; and

d. dividing the plurality of D2D pairs into several groups based upon the interference graph of the plurality of D2D pairs and a greedy algorithm and according to saturation degrees of the plurality of D2D pairs, and allocating a different resource for each group, wherein for a D2D pair, its saturation degree represents the number of D2D pairs, among its neighbors, for which a resource has been allocated; and

e. notifying each of the plurality of D2D pairs of a resource allocated for the each D2D pair.

7. The method according to claim 6, wherein the step d comprises the steps of:

dl . calculating respective freedom degrees of the plurality of D2D pairs, and arranging the plurality of D2D pairs in a non-ascending order of the respective freedom degrees of the plurality of D2D pairs to generate an ordered set of D2D pairs;

d2. coloring a first D2D pair in the ordered set of D2D pairs with a random color, and calculating saturation degrees of remaining D2D pairs in the ordered set of D2D pairs;

d3. selecting a D2D pair with a highest saturation degree from the remaining D2D pairs;

d4. coloring the selected D2D pair with a color with a least times of being used in a set of currently available colors, wherein the set of currently available colors includes a set of all colors except for colors used by the D2D pair of interference sources; and if the set of currently available colors is null, then creating a new color;

d5. updating a saturation degree of the D2D pair of interference sources; and

d6. returning the step d3 until all the D2D pairs are colored.

8. A method, in a receiving D2D user equipment of a communication network, of assisting a base station in allocating a resource, wherein the method comprises the steps of:

I. receiving a predetermined neighbor distance from the base station;

II. determining neighbor information of the receiving D2D user equipment based upon the received predetermined neighbor distance;

IV. sending the determined neighbor information of the receiving D2D user equipment to the base station;

IV. determining a value of tolerant interference degree of the receiving D2D user equipment, and sending the determined value of tolerant interference degree of the receiving D2D user equipment to the base station; and

V. receiving resource allocation information from the base station.

9. The method according to claim 8, wherein after the step I and before the step IV, the method further comprises the steps of:

- judging whether the receiving D2D user equipment has a knowledge of its D2D partner;

- if not, then sending an inquiry message to the base station to inquire about a D2D partner of the receiving D2D user equipment; and

- receiving from the base station information about the D2D partner of the receiving D2D user equipment.

10. The method according to claim 8, wherein the step IV comprises the steps of:

M tf ₍ > M

|_K J Otherwise to obtain a quantized value , of tolerant interference degree,

11. A method, in a transmitting D2D user equipment of a communication network, of assisting a base station in allocating a resource, wherein the method comprises the steps of:

A. receiving a predetermined neighbor distance from the base station;

B. determining neighbor information of the transmitting D2D user equipment based upon the received predetermined neighbor distance;

C. sending the determined neighbor information of the transmitting D2D user equipment to the base station; and

E. receiving resource allocation information from the base station.

12. The method according to claim 11, wherein after the step A and before the step E, the method further comprises the steps of:

- judging whether the transmitting D2D user equipment has a knowledge of its D2D partner;

- if not, then sending an inquiry message to the base station to inquire about a D2D partner of the transmitting D2D user equipment; and

- receiving from the base station information about the D2D partner of the transmitting D2D user equipment.

13. The method according to claim 11, wherein after the step C and before the step E, the method further comprises the step of:

D. determining a value of tolerant interference degree of the transmitting D2D user equipment, and sending the value of tolerant interference degree of the transmitting D2D user equipment to the base station.

14. The method according to claim 13, wherein the step D comprises the steps of:

- calculating the value of tolerant interference degree of the transmitting D2D user equipment in the e uation of:

wherein P_td ^a represents receiving power of a useful signal received by the transmitting D2D user equipment from its receiving D2D user equipment, 7₀ represents receiving power of a signal received by the transmitting D2D user equipment from its nearest non-neighbor D2D pair, N₀ represents thermal noise, and y_th represents the SINR threshold value; and

ise to obtain a quantized value , of tolerant interference degree,

15. A method, in a D2D user equipment of a communication network, of assisting a base station in allocating a resource, wherein the method comprises the steps of:

- receiving a predetermined partner distance and a predetermined interference distance from the base station;

- determining a partner set and an interference source set of the D2D user equipment based upon the received predetermined partner distance and predetermined interference distance;

- sending the determined partner set and the determined interference source set of the D2D user equipment to the base station; and

- receiving resource allocation information from the base station.

16. An apparatus for allocating a resource in a base station of a communication system, wherein a coverage area of the base station includes a plurality of D2D pairs, each of which includes two D2D user equipments, and the apparatus comprises:

a first sending unit configured to send a predetermined neighbor distance to all the D2D user equipments in the coverage area of the base station;

a first receiving unit configured to receive respective neighbor information from all the D2D user equipments;

a first determining unit configured to determine respective neighbor information of the plurality of D2D pairs according to the respective neighbor information of all the D2D user equipments;

an obtaining unit configured to obtain values of respective tolerant interference degrees of the plurality of D2D pairs;

a resource allocating unit configured to divide the plurality of D2D pairs into several groups according to the respective neighbor information and the values of respective tolerant interference degrees of the plurality of D2D pairs and based upon a greedy algorithm, and to allocate a different resource for each group, wherein D2D pairs divided into the same group are not a neighbor of each other; and

a second sending unit configured to notify each of the plurality of D2D pairs of a resource allocated for the each D2D pair.

17. An apparatus, in a receiving D2D user equipment of a communication network, for assisting a base station in allocating a resource, wherein the apparatus comprises:

a second receiving unit configured to receive a predetermined neighbor distance from the base station;

a second determining unit configured to determine neighbor information of the receiving D2D user equipment based upon the received predetermined neighbor distance;

a third sending unit configured to send the determined neighbor information of the receiving D2D user equipment to the base station;

a third determining unit configured to determine a value of tolerant interference degree of the receiving D2D user equipment, and to send the determined value of tolerant interference degree of the receiving D2D user equipment to the base station; and

a third receiving unit configured to receive resource allocation information from the base station.

18. An apparatus for, in a transmitting D2D user equipment of a communication network, of assisting a base station in allocating a resource, wherein the method comprises the steps of:

a fourth receiving unit configured to receive a predetermined neighbor distance from the base station;

a fourth determining unit configured to determine neighbor information of the transmitting D2D user equipment based upon the received predetermined neighbor distance;

a fourth sending unit configured to send the determined neighbor information of the transmitting D2D user equipment to the base station; and a fifth receiving unit configured to receive resource allocation information from the base station.

19. An apparatus for allocating a resource in a base station of a communication system, wherein a coverage area of the base station includes a plurality of D2D pairs, each of which includes two D2D user equipments, and the apparatus comprises:

a fifth sending unit configured to send a predetermined partner distance and a predetermined interference distance to all the D2D user equipments in the coverage area of the base station;

a sixth receiving unit configured to receive respective partner sets and interference source sets from all the D2D user equipments;

a creating unit configured to create an interference graph of the plurality of D2D pairs according to the respective partner sets and interference source sets of all the D2D user equipments; and

an allocating unit configured to divide the plurality of D2D pairs into several groups based upon the interference graph of the plurality of D2D pairs and a greedy algorithm and according to saturation degrees of the plurality of D2D pairs, and to allocate a different resource for each group, wherein for a D2D pair, its saturation degree represents the number of D2D pairs, among its neighbors, for which a resource has been allocated; and

a sixth sending unit configured to notify each of a plurality of D2D pairs of the resource allocated for the each D2D pair.

20. An apparatus, in a D2D user equipment of a communication network, of assisting a base station in allocating a resource, wherein the apparatus comprises:

a seventh receiving unit configured to receive a predetermined partner distance and a predetermined interference distance from the base station; a fifth determining unit configured to determine a partner set and a interference source set of the D2D user equipment based upon the received predetermined partner distance and predetermined interference distance;

a seventh sending unit configured to send the determined partner set and the determined interference source set of the D2D user equipment to the base station; and

an eighth receiving unit configured to receive resource allocation information from the base station.