CN113660065B - A multicast retransmission method and system in D2D communication - Google Patents

Abstract

The present invention relates to a multicast retransmission method in D2D communication, the method comprising: a base station multicasts data to all UEs in a D2D cluster, a cluster head receives the multicast data reception status fed back by all non-cluster head UEs, and judges the status of all D2D links according to the reception status; the cluster head determines a retransmission scheme according to the status of all D2D links, and feeds back the retransmission scheme to the base station; the base station allocates resources for retransmission according to the retransmission scheme, and sends a signal to the UEs participating in the retransmission so that the UEs participating in the retransmission retransmit the multicast data. The present invention summarizes the D2D multicast ACK status and the link quality within the cluster by the cluster head, thereby avoiding the problem of too much uplink reporting signaling overhead in the centralized scheme. At the same time, by letting the cluster head decide the retransmission scheme and then reporting to the base station, the resource waste problem caused by the reserved resources in the distributed retransmission scheme is avoided.

Description

Multicast retransmission method and system in D2D communication

Technical Field

The invention belongs to the technical field of communication, and particularly relates to a multicast retransmission method in D2D communication of an electric power Internet of things, and a multicast retransmission system in D2D communication of the electric power Internet of things.

Background

In order to meet the trend of the fusion development of the energy revolution and the digital revolution, china proposes to build the ubiquitous electric power Internet of things as a supplement to a strong intelligent power grid, and is also an important content for building the energy Internet. In order to realize the panoramic sensing and ubiquitous access of various devices and personnel in the ubiquitous electric power Internet of things, a high-performance electric power communication network is required to be used as an important support, and extensive researches are carried out on students at home and abroad. The fifth generation mobile communication (5G) is favored by various industries because of the advantages of high bandwidth, low time delay, low power consumption and the like, and is also deeply fused with the ubiquitous electric power Internet of things. Part of the prior art analyzes the application scene of the 5G communication in the ubiquitous electric power Internet of things. Typical services of the 5G power Internet of things are generally divided into two main types, namely control and acquisition, the acquisition type comprises low-voltage centralized meter reading, intelligent power grid large video application of scenes inside and outside a station, and the like, future acquisition objects tend to be multimedia, acquisition contents tend to be video and high-definition, acquisition frequency tends to be quasi-real-time, and the system evolves from unidirectional acquisition to bidirectional interaction.

To meet these trends, new technologies for 5G communication are needed. The device-to-device (D2D) communication is a potential performance enhancement technology, and can support applications of ubiquitous internet of things on mass measurement, audio and video dimension inspection operation, even power virtual reality, and the like. D2D is an important technical approach for solving the problems of shortage of frequency spectrum resources, increased network load and the like caused by rapid increase of wireless network data volume, and the method does not need a base station as a relay, so that the terminals can directly communicate through multiplexing the wireless resources of the base station. The advantages of D2D technology are mainly the reduction of base station load, the increase of network throughput, the provision of more reliable and larger capacity data transmission channels, etc.

In D2D multicasting, the base station may multicast the same data packets to all cluster terminals at a higher rate that does not have to ensure proper reception by all terminals within the cluster. The terminals in the cluster that successfully receive may retransmit the data packet to the terminals that did not successfully receive in a direct communication manner. Therefore, the multicast throughput can be greatly increased, and the high-rate retransmission can be supported due to the fact that the short-distance link has better channel quality, so that the frequency spectrum efficiency of multicast transmission is greatly improved.

For intra-cluster terminals that fail to correctly receive data, the corresponding data needs to be retransmitted. The specific retransmission flow is as follows: ① The base station multicasts and transmits a group of data to the ad hoc network terminal in the corresponding area; ② A terminal that does not correctly receive the multicast data feeds back NACK (Negative Acknowledgement ) to the base station, and a terminal that correctly receives the multicast data feeds back ACK (Acknowledgement) to the base station; and the terminal feeding back ACK to the base station is referred to as an ACK terminal, and the terminal feeding back NACK to the base station is referred to as a NACK terminal. ③ And retransmitting the required data packet to the terminal feeding back NACK by the cluster head.

The problems involved in the above-mentioned D2D intra-cluster retransmission are: whether all ACK equipment terminals in the cluster participate in retransmission or only the cluster head retransmits data to the NACK terminal; and selecting only one ACK terminal to retransmit to the NACK terminal or a plurality of ACK terminals to cooperatively retransmit to the NACK terminal, and the like. For example, a plurality of terminals may be selected to employ space-time coding or network coding to increase retransmission success rate.

In the prior art, in the dynamic and semi-static scheduling modes in the LTE standard, the signaling overhead of a centralized retransmission scheme is too large in D2D multicast retransmission, and the distributed retransmission scheme also has the problem of reserved resource waste.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, provides a multicast retransmission method in D2D communication, and solves the technical problems that the signaling overhead of a centralized retransmission scheme is too large and reserved resources are wasted in a distributed retransmission scheme in the prior art.

In order to solve the technical problems, the invention provides the following technical scheme.

In a first aspect, the present invention provides a multicast retransmission method in D2D communication, including the following procedures:

The base station multicasts data to the UE in the D2D cluster, wherein the UE in the D2D cluster comprises a cluster head UE and a non-cluster head UE

The base station receives a retransmission scheme fed back by the cluster head UE, wherein the retransmission scheme is determined by the cluster head UE according to a receiving state fed back by the non-cluster head UE;

And the base station sends signaling to the UE participating in retransmission according to the retransmission scheme, so that the UE participating in retransmission retransmits the multicast data.

Optionally, the receiving state includes: the data state is correctly received and the data state is not correctly received, if the acknowledgement ACK is fed back by the non-cluster-head UE, the data state is considered to be the correct data state, and if the acknowledgement NACK and the channel quality information CQI are fed back by the non-cluster-head UE, the data state is considered to be the incorrect data state. .

Optionally, the retransmission scheme includes a retransmission transceiving terminal bitmap, where the retransmission transceiving terminal bitmap is used to specify a retransmission sender UE.

Optionally, the retransmission transceiving terminal bitmap is represented by a bitmap with the same number of bits as the number of all UEs in the D2D cluster, and each bit value in the bitmap specifies whether the corresponding UE is the sender UE of the retransmission.

Optionally, in the retransmission transceiving terminal bitmap, if a certain bit value is 1, the corresponding UE is designated as a sender of retransmission.

Optionally, the retransmission scheme includes a retransmission mode, where the retransmission mode is mode 2: the bitmap is needed, and the retransmission mode is that the ACK terminal specified by the bitmap performs D2D intra-cluster retransmission.

Optionally, the retransmission mode further includes a mode 0 and a mode 1; wherein:

the mode 0: the bitmap is not needed, and the retransmission mode is that all ACKs do not need to be retransmitted;

the mode 1: no bitmap is needed and the retransmission is such that all NACKs require base station retransmissions.

Optionally, the base station sends signaling to the UE participating in retransmission through a physical downlink control channel PDCCH.

In a second aspect, the present invention also provides a multicast retransmission method in D2D communication, including the following procedures:

the method comprises the steps that cluster head UE and non-cluster head UE in a D2D cluster respectively receive multicast data;

the cluster head UE receives a receiving state fed back by the non-cluster head UE;

and the cluster head UE determines a retransmission scheme according to the receiving state fed back by the non-cluster head UE and feeds back the retransmission scheme to the base station.

In a third aspect, the invention also provides a multicast retransmission system in D2D communication of the electric power internet of things, which comprises a D2D cluster consisting of a base station and a plurality of UEs, wherein the UEs in the D2D cluster comprise cluster head UEs and non-cluster head UEs; the base station is in connection communication with the UE through a physical control channel;

The base station is used for multicasting data to the UE in the D2D cluster and receiving a retransmission scheme fed back by the cluster head UE, and sending signaling to the UE participating in retransmission according to the retransmission scheme so that the UE participating in retransmission retransmits the multicasting data;

the cluster head UE is used for receiving the receiving state fed back by the non-cluster head UE, determining a retransmission scheme according to the receiving state of the multicast data fed back by the non-cluster head UE, and feeding back the retransmission scheme to the base station.

Optionally, the retransmission scheme includes a retransmission transceiving terminal bitmap, where the retransmission transceiving terminal bitmap is used to specify a retransmission sender UE.

The system in the present invention is used for executing the above method, and the specific processing procedure is referred to the above method, and will not be described herein.

Compared with the prior art, the invention has the following beneficial effects: the invention avoids the problem of overlarge uplink reporting signaling overhead in a centralized scheme by summarizing the D2D multicast ACK state and the intra-cluster link quality by the cluster head. Meanwhile, the cluster head determines the retransmission scheme and then reports the retransmission scheme to the base station, so that the problem of resource waste caused by reserved resources in the distributed retransmission scheme is avoided. The invention has certain reference significance for designing the 5G network D2D transmission technology.

Drawings

FIG. 1 is a schematic diagram of a scene of a field dimension inspection operation supported by a 5G network D2D technology according to an embodiment;

fig. 2 is a schematic diagram of a signaling procedure of centralized retransmission in the prior art according to an embodiment;

FIG. 3 is a schematic diagram of a signaling process of distributed retransmission in the prior art according to an embodiment;

Fig. 4 is a schematic signaling process diagram of a retransmission scheme according to the present invention according to an embodiment;

Fig. 5 is a schematic flow chart of a multicast retransmission method in D2D communication of the power internet of things according to an embodiment;

FIG. 6 is a diagram illustrating the signaling overhead of the present invention versus a centralized scheme according to an embodiment;

FIG. 7 is a comparison diagram of resource consumption performance according to one embodiment;

fig. 8 is a diagram illustrating comparison of retransmission times according to an embodiment.

Detailed Description

The invention is further described below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and are not intended to limit the scope of the present invention.

In a field maintenance operation scenario shown in fig. 1, a team of field maintenance staff is provided with an audio and video communication terminal, and in a maintenance field area, the team of field maintenance staff forms a D2D cluster, and is provided with team members serving as cluster heads, wherein the team members can directly communicate with each other by adopting a D2D technology, and the team members (the cluster heads) can be responsible for collecting state information of a D2D link in the cluster and reporting the state information to a base station. The maintenance staff is under the coverage of a 5G base station, is connected with a control center in the intelligent power grid application platform through a dedicated channel configured in the 5G base station and a 5G core network, reports the site condition to the control center through an audio and video communication terminal, and receives the remote command and the operation guidance of a maintenance expert of the control center.

In the above scenario, the transmission of audio-video data requires a lot of bandwidth, and it is suitable to use multicast/broadcast to transmit control center data to each dimension inspector in the D2D cluster.

D2D multicast retransmission is a resource scheduling problem, and 2 scheduling modes based on LTE, namely dynamic and semi-static scheduling modes, and from the perspective of retransmission decision, the corresponding retransmission scheme has 2 types of centralized and distributed retransmission.

In centralized retransmission, the decision and resource allocation of retransmission are handled centrally by the base station, and the signaling procedure is shown in fig. 2. The cluster head or the UEs in the cluster report ACK/NACK and CQI (Channel Quality Indication, channel quality information) to the base station, based on which the intra-base station decides the intra-cluster D2D retransmission mode. The base station allocates retransmission resources for D2D and informs all UEs through PDCCH (Physical Downlink Control Channel ). The method has the advantages that the control channels of the cellular network can be multiplexed, and D2D is compatible with the UE of the cellular network; in addition, the signaling delay is very small. But the base station needs the UEs of the D2D cluster to provide ACK/NACK status of each UE, CQI between each pair of UEs, which is a great burden on the cellular network uplink signaling. Let the D2D cluster have N UE, the cluster head collects CQI and ACK/NACK state of the D2D link and reports to the base station, presume that ACK/NACK state is represented by 1 bit, CQI is represented by 3 bits. The number of bits required for D2D signaling and cellular network signaling is shown in table 1.

Table 1 signalling overhead for centralized retransmission

Signaling type	Signaling of	Number of bits
			D2D signaling	ACK/NACK	N-1
D2D signaling	D2D link CQI	3·N(N-1)/2
			Cellular network uplink signaling	ACK/NACK	N-1
Cellular network uplink signaling	D2D link CQI	3·N(N-1)/2

In distributed retransmission, the UE in the cluster reports ACK/NACK and CQI information to the cluster head, and the cluster head decides the retransmission mode, and the signaling process is shown in fig. 3. The advantage of this scheme is that no additional cellular uplink signaling is required. However, this solution has 2 main disadvantages: ① An additional control channel is needed between the cluster head and the UE in the cluster; ② Whether or not retransmission is necessary, the base station reserves resources for D2D retransmission, resulting in serious resource waste. Retransmission is not needed if all the multicasting is successful, and the base station is needed to re-multicast if all the multicasting is failed, so that reserved resources are not necessary. More importantly, since D2D retransmission resources are not allocated according to ACK/NACK and CQI information of D2D links, MCS for D2D retransmission should be decided according to the worst D2D link to ensure retransmission success. For example, D1, D2, and D3 are 3 terminals within a cluster, D1 and D2 are ACK terminals, D3 is a NACK terminal, and D2D retransmission can only occur on D1-D3 or D2-D3 links provided that the D1-D2 link is worst. Then the MCS (Modulation Coding Scheme, modulation coding strategy) determined by D1-D2 obviously results in a loss of transmission efficiency.

Aiming at the problems that the signaling overhead of a centralized retransmission scheme is too large and the reserved resource is wasted in a distributed retransmission scheme in the prior art, the invention provides a multicast retransmission method in D2D communication of the electric power Internet of things, which is recorded as a new scheme. The new scheme considers the link state in the D2D cluster, the cluster head determines the corresponding retransmission scheme, and feeds back the preselected retransmission scheme to the base station for retransmission, and the signaling flow of the newly proposed scheme is shown in fig. 4.

The multicast retransmission method in D2D communication according to the embodiment of the present invention, with specific steps referring to fig. 5, includes the steps of:

s100, a control base station multicasts data to all UE in a D2D cluster, wherein the UE comprises: cluster head UE and non-cluster head UE;

S200, the non-cluster-head UE feeds back a receiving state to the cluster-head UE, wherein the UE which correctly receives data feeds back Acknowledgement (ACK), and the UE which does not correctly receive data feeds back Negative Acknowledgement (NACK) and Channel Quality Information (CQI);

s300, the cluster head UE judges the states of all D2D links according to feedback of all non-cluster head UEs;

s400, the cluster head UE determines a retransmission scheme according to the states of all the D2D links.

S500, the cluster head UE feeds back a retransmission scheme to the base station.

S600, the base station allocates resources for retransmission according to a retransmission scheme fed back by the cluster head UE, and sends signaling to the UE participating in retransmission through a physical downlink control channel PDCCH. And the UE participating in retransmission retransmits the multicast data according to the command.

The cluster head determines a retransmission scheme and feeds back a selection result to the base station through an uplink control channel of the cellular network. The retransmission scheme specifically includes 3 items of content: retransmission mode, retransmission MCS, and retransmission transceiving terminal bitmap. The details of the scheme are as follows.

Wherein the retransmission MCS is an index of the MCS format at the time of retransmission, which can be represented by 5 bits in the LTE system.

The retransmission transceiving terminal bitmap is used to designate the sender UE of the retransmission. Represented by a bitmap comprising N bits, where N is the number of terminal UEs in the D2D cluster. The n-th bit value is 1, which indicates that the n-th terminal UE is designated as the sender of the retransmission to retransmit the multicast data. For example, in a D2D cluster having 6 UEs, UE1 is a cluster head, UEs 1 to UE3 are ACK terminals, and UEs 4 to UE6 are NACK terminals. If the UE2 retransmits the multicast data to the UEs 4 to 6, the corresponding retransmission receiving and transmitting terminal bitmap is '010000', that is, the UE2 is designated as the retransmission sender, the UEs 4 to 6 are taken as the retransmission receiver, and the retransmission sender and the retransmission receiver are collectively called as the retransmission participating UEs.

In this embodiment, the base station and the cluster head maintain a retransmission mode table, where each retransmission mode in the table has a corresponding index value, and keep the tables of both sides completely the same. When the cluster head feeds back the retransmission mode to the base station, the feedback is the retransmission mode index, and the receiving side of the retransmission is determined.

In the scheme, 4 retransmission modes are defined, namely mode 0, mode 1, mode 2 and mode 3; the specific retransmission pattern definition is shown in table 2. Wherein:

the mode 0: the bitmap is not needed, and the retransmission mode is that all ACKs do not need to be retransmitted;

The mode 1: the bitmap is not needed, and the retransmission mode is that all NACK needs to be retransmitted by the base station;

the mode 2: the bitmap is needed, and the retransmission mode is that the ACK terminal appointed by the bitmap performs D2D intra-cluster retransmission;

the mode 3: the bitmap is needed and its retransmission is reserved for expansion.

Table 2 retransmission mode definition

Retransmission mode	Retransmission scheme	Whether or not a bitmap is required
			0	All ACKs need not be retransmitted	Does not need
1	All NACKs require base station retransmission	Does not need
			2	D2D intra-cluster retransmission by bitmap-designated ACK terminal	Needs to be as follows
3	Reservation, available for expansion	Needs to be as follows

The multicast retransmission scheme in the present invention selects mode 2. The receiver of the retransmission is designated by the retransmission receiving terminal bitmap, and the receiver of the retransmission is a NACK terminal.

Particularly, in step S400, the cluster head may perform global optimization configuration on retransmission parameters in the cluster according to the link state fed back by each UE, adaptively select an optimal transmission node according to the D2D link quality, and avoid transmission bottlenecks by reasonably selecting parameters such as a retransmission mode, a retransmission MCS, a retransmission transceiver terminal, and the like, and fully utilize diversity gain of multiple channels in the cluster, thereby further improving retransmission efficiency.

Compared with a distributed mode, the method and the device have the advantages that the cluster head performs link self-adaption of the D2D retransmission, resources are not required to be allocated for the D2D retransmission in advance, and resource waste is avoided. In addition, the base station performs resource scheduling through the cellular network control signaling without designing additional signaling between the D2D cluster head and the UE. Compared with a centralized method, the extra cost of the scheme is that a retransmission mode table is required to be maintained by the base station and the cluster head, and the table size is small, so that the memory is hardly affected. The method has the greatest advantage of greatly reducing the uplink signaling of the cellular network. The signaling overhead pairs for the new scheme and the centralized retransmission are shown in table 3.

Table 3 signalling overhead comparison

The D2D signaling overhead required for the 2 schemes is the same, and is used for the terminal UE to aggregate the ACK status and the link status to the cluster head. Because the cluster head feeds back parameters such as retransmission modes and the like to the base station, the uplink signaling overhead of the cellular network of the new scheme is greatly reduced compared with that of the centralized retransmission scheme. In the centralized scheme, the bit number of the uplink signaling of the cellular network is in direct proportion to the square of the node number in the cluster, while the uplink signaling overhead of the cellular network of the new scheme is in direct proportion to the node number in the cluster, and the more the node number in the cluster is, the more obvious the advantage of the new scheme on the signaling overhead is.

The cellular network signaling overhead pairs for the new scheme and the centralized scheme are shown in fig. 6. For example, the uplink signaling in a centralized manner when n=4 requires 22 bits, while the new scheme requires only 11 bits, and the overhead is only half of the centralized scheme. If n=8, the signaling overhead of the centralized scheme is 92 bits, while the new scheme is only 15 bits, which is only 16% of the centralized scheme. If n=10, the signaling overhead of the centralized scheme is 145 bits, while the new scheme is only 17 bits, which is only 12% of the centralized scheme. The more nodes in the cluster, the more obvious the signaling overhead advantage of the new scheme.

In order to verify retransmission efficiency of the new scheme, matlab was used for simulation experiments. Without loss of generality, assuming that all terminals are uniformly distributed in a D2D cooperative cluster, small-scale fading of a D2D link is a slow-to-flat Rayleigh fading model, and D2D communication among the terminals adopts an adaptive coding modulation technology to fully utilize channel capacity; the coded modulation format is divided into 15 levels altogether.

In the simulation, the sizes of the D2D cooperative clusters are set to 4, 6, 10 and 16, respectively, to observe the influence of the cooperative cluster sizes on the algorithm performance. For each simulated cluster size, the D2D collaborative cluster (including terminal position and link quality) was randomly generated 10,000 times, counting performance parameters.

The performance index of retransmission efficiency is normalized resource consumption, and is defined as the time-frequency resource quantity required by completing successful retransmission of 1bit information to all NACK terminals in a cluster, and the unit is Hz.S. The resource consumption performance of the 3 retransmission schemes is 10 nodes in the cluster as shown in fig. 7. The abscissa is the proportion of terminals feeding back NACK at the time of base station multicasting, and varies from 10% to 90%. As can be seen from fig. 7, the new method proposed by the present invention is significantly better than the centralized and distributed 2 retransmission schemes. With the increase of NACK terminals, the resource consumption increases more due to the larger data volume to be reported in a centralized manner, and the resource consumption also increases with the increase of the number of terminals feeding back NACK due to the influence of reserved resources in a distributed scheme. The method overcomes the main factor of resource consumption in centralized and distributed mode, so the resource consumption is the least in 3 schemes. In addition, since the proposed scheme can adaptively select the optimal retransmission parameters in step S400 of the present embodiment, the present embodiment further improves the retransmission efficiency.

The average retransmission times (average retransmission times when 100 data packets are transmitted) of the 3 retransmission schemes when the nodes in the cluster are 4, 6, 10 and 16 respectively are as shown in fig. 8, and it can be seen that the centralized retransmission times are the most and the distributed retransmission times are the least. The method has the advantages of higher resource utilization rate, reduced signaling overhead, and improved retransmission success rate and overall reduced retransmission times by means of better links between D2D nodes. As can be seen from fig. 8, as the number of nodes in the cluster increases, the number of retransmissions correspondingly decreases, which represents an advantage of D2D communication. In addition, the average transmission delay and the number of retransmissions of the 3 schemes have the same trend, which is not easily understood from the relationship between the average transmission delay and the number of retransmissions.

In summary, the method provides a new retransmission mode pre-selection scheme by analyzing the advantages and the disadvantages of the centralized and distributed 2 retransmission schemes of the D2D transmission, and the problem of too high uplink reporting signaling overhead in the centralized scheme is avoided by summarizing the D2D multicast ACK state and the intra-cluster link quality by the cluster head. Meanwhile, the cluster head determines the retransmission scheme and then reports the retransmission scheme to the base station, so that the problem of resource waste caused by reserved resources in the distributed retransmission scheme is avoided. In addition, the cluster head of the method fully considers the D2D link difference, and can adaptively select the optimal transmission node according to the D2D link quality, thereby fully utilizing the multi-channel diversity gain of the D2D link. The theoretical analysis and computer simulation of the method verify the effectiveness of the scheme in the aspects of signaling overhead, transmission efficiency, average retransmission times and transmission delay, and have certain reference significance for designing the 5G network D2D transmission technology.

Example 2

Based on the same inventive concept as that of embodiment 1, the multicast retransmission system in D2D communication of the electric power Internet of things comprises a D2D cluster formed by a base station and a plurality of UE, wherein all the UE in the D2D cluster are divided into cluster heads and non-cluster head UE; the base station is in connection communication with the UE through a physical control channel;

the base station is used for multicasting data to all the UE in the D2D cluster, distributing resources for retransmission according to a retransmission scheme, and sending signaling to the UE participating in retransmission so that the UE participating in retransmission retransmits the multicasting data;

the non-cluster-head UE is used for feeding back a multicast data receiving state to the cluster head;

the cluster head UE is used for determining a retransmission scheme according to the multicast data receiving states fed back by all the non-cluster head UEs and feeding back the retransmission scheme to the base station.

Optionally, the retransmission scheme includes a retransmission transceiving terminal bitmap, where the retransmission transceiving terminal bitmap is used to specify a retransmission sender UE.

The system in the present invention is used for executing the above method, and its functions and technical effects are referred to the above method, and will not be described herein.

For a specific implementation of the system according to the present invention, reference is made to the specific implementation of the method in embodiment 1.

It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

The foregoing is merely a preferred embodiment of the present invention, and it should be noted that it will be apparent to those skilled in the art that modifications and variations can be made without departing from the technical principles of the present invention, and these modifications and variations should also be regarded as the scope of the invention.

Claims (4)

1. A multicast retransmission method in D2D communication, characterized by comprising the following process: The base station multicasts data to UEs in the D2D cluster, where the UEs in the D2D cluster include cluster head UEs and non-cluster head UEs; The base station receives a retransmission scheme fed back by the cluster head UE, where the retransmission scheme is determined by the cluster head UE according to a reception state fed back by the non-cluster head UE; The base station sends a signaling to the UE participating in the retransmission according to the retransmission scheme, so that the UE participating in the retransmission retransmits the multicast data; The receiving state includes: a state of correctly receiving data and a state of incorrectly receiving data. If the non-cluster head UE feeds back an ACK, it is considered to be a state of correctly receiving data. If the non-cluster head UE feeds back a NACK and channel quality information CQI, it is considered to be a state of incorrectly receiving data. The retransmission scheme includes: retransmission mode, retransmission MCS and retransmission transceiver terminal bitmap; The retransmission transceiver terminal bitmap is used to specify the retransmission sender UE; The retransmission transceiver terminal bitmap is represented by a bitmap with the same number of bits as the number of all UEs in the D2D cluster, and each bit value in the bitmap specifies whether the corresponding UE is the retransmission sender UE; In the retransmission transceiver terminal bitmap, if a certain bit value is 1, it indicates that the corresponding UE is designated as the sender of the retransmission; The retransmission mode includes mode 0, mode 1 and mode 2; wherein: Mode 0: no bitmap is required, and the retransmission mode is that all ACKs do not need to be retransmitted; Mode 1: does not require a bitmap, and its retransmission method is that all NACKs need to be retransmitted by the base station; Mode 2: A bitmap is required, and the retransmission method is that the ACK terminal specified by the bitmap performs intra-D2D cluster retransmission. 2. A multicast retransmission method in D2D communication according to claim 1, characterized in that the base station sends signaling to the UE participating in the retransmission through a physical downlink control channel PDCCH. 3. A multicast retransmission method in D2D communication, characterized in that it includes the following process: The cluster head UE and non-cluster head UE in the D2D cluster receive multicast data respectively; The cluster head UE receives the reception status fed back by the non-cluster head UE; The cluster head UE determines a retransmission scheme according to the reception status fed back by the non-cluster head UE, and feeds back the retransmission scheme to the base station; The receiving state includes: a state of correctly receiving data and a state of incorrectly receiving data. If the non-cluster head UE feeds back an ACK, it is considered to be a state of correctly receiving data. If the non-cluster head UE feeds back a NACK and channel quality information CQI, it is considered to be a state of incorrectly receiving data. The retransmission scheme includes: retransmission mode, retransmission MCS and retransmission transceiver terminal bitmap; The retransmission transceiver terminal bitmap is used to specify the retransmission sender UE; The retransmission transceiver terminal bitmap is represented by a bitmap with the same number of bits as the number of all UEs in the D2D cluster, and each bit value in the bitmap specifies whether the corresponding UE is the retransmission sender UE; In the retransmission transceiver terminal bitmap, if a certain bit value is 1, it indicates that the corresponding UE is designated as the sender of the retransmission; The retransmission mode includes mode 0, mode 1 and mode 2; wherein: Mode 0: no bitmap is required, and the retransmission mode is that all ACKs do not need to be retransmitted; Mode 1: does not require a bitmap, and its retransmission method is that all NACKs need to be retransmitted by the base station; Mode 2: A bitmap is required, and the retransmission method is that the ACK terminal specified by the bitmap performs intra-D2D cluster retransmission. 4. A multicast retransmission system in D2D communication of electric power Internet of Things, characterized by comprising a D2D cluster consisting of a base station and a plurality of UEs, wherein the UEs in the D2D cluster include cluster heads and non-cluster head UEs; the base station is connected and communicated with the UEs through a physical control channel; The base station is used to multicast data to UEs in the D2D cluster, receive a retransmission scheme fed back by the cluster head UE, and send signaling to UEs participating in the retransmission according to the retransmission scheme, so that the UEs participating in the retransmission retransmit the multicast data; The cluster head UE is used to receive the reception status fed back by the non-cluster head UE, determine a retransmission scheme according to the reception status fed back by the non-cluster head UE, and feed back the retransmission scheme to the base station; The receiving state includes: a state of correctly receiving data and a state of incorrectly receiving data. If the non-cluster head UE feeds back an ACK, it is considered to be a state of correctly receiving data. If the non-cluster head UE feeds back a NACK and channel quality information CQI, it is considered to be a state of incorrectly receiving data. The retransmission scheme includes: retransmission mode, retransmission MCS and retransmission transceiver terminal bitmap; The retransmission transceiver terminal bitmap is used to specify the retransmission sender UE; The retransmission transceiver terminal bitmap is represented by a bitmap with the same number of bits as the number of all UEs in the D2D cluster, and each bit value in the bitmap specifies whether the corresponding UE is the retransmission sender UE; In the retransmission transceiver terminal bitmap, if a certain bit value is 1, it indicates that the corresponding UE is designated as the sender of the retransmission; The retransmission mode includes mode 0, mode 1 and mode 2; wherein: Mode 0: no bitmap is required, and the retransmission mode is that all ACKs do not need to be retransmitted; Mode 1: does not require a bitmap, and its retransmission method is that all NACKs need to be retransmitted by the base station; Mode 2: A bitmap is required, and the retransmission method is that the ACK terminal specified by the bitmap performs intra-D2D cluster retransmission.