CN102740236B - Method for cooperative multicast among users based on energy efficiency - Google Patents

Abstract

The invention aims to reduce the energy consumption and improve the energy efficiency of a system through selection of cooperative relay users and the distribution of relay power under the condition that the throughput capacity of the system is ensured. The invention discloses a method for cooperative multicast among users based on the energy efficiency. The method comprises the following steps of: dividing the multicast process into two stages, and at the first stage, multicasting data to all the users at a high speed by a base station, ensuring that a part of the users with good channel conditions correctly decode the data, estimating channel state information between the remaining users with bad channel conditions and the users correctly decoding the data, finding a user who has the best channel condition and correctly decodes the data relative to each user with a bad channel condition, and using the user correctly decoding the data as a relay; and at the second stage, reasonably distributing the power of each relay by using the estimated channel state information between the relay users and the remaining users with the bad channel conditions, and multicasting data to the remaining users with the bad channel conditions by using selected relays.

Description

A kind of cooperation among users multicasting method based on efficiency

Technical field

The invention belongs to wireless communication technology field, the multiple users achieved as channel quality is different carry out reliable and effective transmission, and reduce the energy consumption of system, improve the efficiency of system.

Background technology

Multimedia broadcast multi-broadcasting business (MBMS) is a kind of point-to-multipoint transport service pattern defined in 3GPP R6 specification, the basis not changing network configuration can realize network resources locating, and effectively improve wireless resource utility efficiency.The user receiving identical services in multicast network belongs to same multicast group, due to the user distribution diverse location in the cell in a multicast group, experience different large scale declines and multipath fading, the channel condition difference of different user is very large, the capacity constraint of a multicast group is in the poorest user of channel condition, if transmission rate is too high, the poor user of channel condition can not correct decoding data; If transmission rate meets the poorest user of channel condition, good fairness can be realized like this, but wireless resource utility efficiency is too low.Traditional cooperation multicast transmission is a kind of method effectively eliminating subscriber channel decline, effectively can improve power system capacity, but increasing along with number of users, the energy consumption of system is also considerable.

Summary of the invention

The power system capacity that the object of the invention is to solve multicast group is limited to the poorest user of channel condition, though and tradition cooperation multicast can improve power system capacity and increase the large problem of system energy consumption along with number of users.The present invention reduces system energy consumption while can be implemented in and ensureing throughput of system, improves efficiency.The present invention is achieved through the following technical solutions:

The present invention is a kind of cooperation among users multicasting method based on efficiency, and by the selection of cooperating relay user and the distribution of relay power, the energy consumption reducing system improves efficiency.Its special character is in following steps:

1) multicast process is divided into two stages, all user's multi-case datas are given with higher speed in first stage base station, ensure user's correct decoding that a part of channel condition is good, estimate the channel condition information between the user of residue bad channel conditions to correct decoding user, find the user of a correct decoding best with the subscriber channel condition of each bad channel conditions, and using the user of this correct decoding as relaying.

2) in second stage, utilize the trunk subscriber estimated to residue bad channel conditions user between channel condition information, carry out reasonable distribution to the power of each relaying, the relaying that recycling is selected is to the user's multi-case data remaining bad channel conditions.The object that the energy consumption reducing system while ensureing throughput of system improves efficiency is reached with this.

In technique scheme, step 1) concrete operations as follows:

1-1) multicast process is divided into two stages, first stage base station transmitting power P _b, in first stage community, the Received signal strength of any user i is:

$y_i^{\mathrm{bd}}=\sqrt{P_b{l}_i^{-\mathrm{\η}}}{h}_{i}x+n_i$

The received signal to noise ratio of user i is:

1-2) suppose that the multicast transmission speed of first stage is υ ₁, then the signal-noise ratio threshold of this signal of correct decoding is when the received signal to noise ratio of user then represent that this user can correct decoding.Descending is pressed to the received signal to noise ratio of first stage all users, composition signal to noise ratio vector assuming that the ratio C shared by first stage correct decoding user, then before in signal to noise ratio vector, N*C user can correct decoding data.The set G of first stage correct decoding user, the set B of the user of residue bad channel conditions, channel condition information between the user of estimation N* (1-C) individual bad channel conditions and correct decoding user, for the user of i-th bad channel conditions, find the correct decoding user that best with its channel condition, using the user of this correct decoding as relaying, and this correct decoding user corresponding numbering in set G is placed in set Relay, delete repeat element in Relay, then in Relay, each element is selected relaying.

In technique scheme, step 2) concrete operations as follows:

Second stage, the total transmitting power P of all relayings _r, the user that the power division of each relaying directly affects bad channel conditions in B correctly receives the transmission rate that data are supported, transmission rate is larger, and the time that cooperating relay user participates in cooperating is shorter, and the energy of consumption is fewer.Therefore in order to make the user of bad channel conditions correctly receive, transmission rate that data support is large as far as possible, the cooperating relay user that utilization has estimated is to the channel condition information of the user of bad channel conditions, obtain the overall channel state information of the user of each relaying and bad channel conditions, with this, dynamic assignment is carried out to relay power, reach reduction energy consumption, improve the object of efficiency.

The present invention has following beneficial effect: the present invention is in the first stage of multicast process, utilize the channel condition information of base station and user, one is selected relatively much higherly to broadcast rate multicast data, ensure user's correct decoding data that a part of channel condition is good, and according to the channel status between correct decoding user and non-correct decoding user, select the correct decoding user best with non-correct decoding subscriber channel condition as cooperating relay, decrease the number of users as cooperating relay.Second stage utilizes the overall channel situation of the user of cooperating relay and bad channel conditions to carry out reasonable distribution to relay power, the user that improve bad channel conditions correctly receives the transmission rate that data can be supported, ensure that the throughput of system, decrease the time that relaying participates in cooperation, reduce energy consumption, improve efficiency.

Accompanying drawing explanation

Fig. 1 is system model figure of the present invention;

Fig. 2 is overall algorithm flow chart of the present invention;

Fig. 3 is the multicast system efficiency (C=90%, α=0.6, N=100) under different base station launches signal to noise ratio;

Fig. 4 is the multicast system efficiency (C=90%, α=0.6, Base Transmitter signal to noise ratio is 100db) under different user number;

Fig. 5 is the multicast efficiency (C=90%, N=100, Base Transmitter signal to noise ratio is 100db) under different base station power accounts for gross power ratio;

Fig. 6 is that first stage different correct decoding user accounts for always by the multicast efficiency (N=100, α=0.6, Base Transmitter signal to noise ratio is 100db) under ratio.

Embodiment

Below in conjunction with accompanying drawing and concrete embodiment, the present invention is described in further detail.

Core concept of the present invention is the channel condition information utilized between user, reduce the trunk subscriber number participating in cooperation, and utilize the channel condition information between user, reasonable distribution is carried out to relay power, improve multicast data transmission speed, reduce system energy consumption and improve efficiency.The present invention proposes a kind of cooperation among users multicasting method based on efficiency, the method is divided into two stages multicast process, all user's multi-case datas are given with higher emission rate in first stage base station, ensure that user that a part of channel condition is good can correct decoding, estimate the channel condition information between correct decoding user and the user remaining bad channel conditions, select the correct decoding user best with the subscriber channel condition of each bad channel conditions as cooperating relay, which reduce the number of users participating in cooperation.Second stage utilizes the trunk subscriber estimated to the channel condition information of the user of bad channel conditions, obtain the overall channel state information of the user of each relaying and all bad channel conditions, carry out reasonable distribution to relay power again, the user that improve bad channel conditions correctly receives the transmission rate that data are supported.

The present invention is for multiple users of different channels condition provide the cooperation among users multicasting method of identical multimedia service, ensures throughput of system, reduce energy consumption and improve efficiency by the selection of trunk subscriber and the distribution of relay power.Its content comprises:

1) multicast process is divided into two stages, all user's multi-case datas are given with higher speed in first stage base station, ensure user's correct decoding that a part of channel condition is good, estimate the channel condition information between the user of residue bad channel conditions to correct decoding user, find the user of a correct decoding best with the subscriber channel condition of each bad channel conditions, and using the user of this correct decoding as relaying.

1-1), the present invention considers a cellular cell scene, and there is a base station this community as shown in Figure 1, the user of the identical multicast service of N number of acceptance.Multicast process is divided into two stages, first stage base station transmitting power P _b, the total transmitting power P of all relayings of second stage _r, meet P _b+ P _r=P, P _b=α P, long data packet is B _o.Then in first stage community, the Received signal strength of any user i is: $y_i^{\mathrm{bd}}=\sqrt{P_b{l}_i^{-\mathrm{\η}}}{h}_{i}x+n_i$

X is transmitting of base station, n _iadditive white Gaussian noise, variance N ₀, channel fading comprises path loss and Rayleigh fading, then the received signal to noise ratio of user i is:

${\mathrm{SNR}}_i^{\mathrm{bd}}=\frac{P_b{\left|h_i\right|}^2{l}_i^{-\mathrm{\η}}}{N_0};$

1-2) suppose that the multicast transmission speed of first stage is υ ₁, then the signal-noise ratio threshold of this signal of correct decoding is when the received signal to noise ratio of user represent that this user can correct decoding.Descending is pressed to the received signal to noise ratio of first stage all users, composition signal to noise ratio vector the ratio C of definition shared by first stage correct decoding user, then the set G={1 of first stage correct decoding user, 2,3 ..., N*C}, the set B of the user of residue bad channel conditions=N*C+1, N*C+2 ..., N}, then the multi-case data speed of first stage is time first stage is channel condition information between the user of estimation N* (1-C) individual bad channel conditions and correct decoding user

$H_{i,j}={\left|h_{\mathrm{ij}}^{\′}\right|}^2=l_{\mathrm{ij}}^{-\mathrm{\η}}{\left|h_{\mathrm{ij}}\right|}^2$ {i∈B;j∈G}；

${\left(l_{\mathrm{ij}}\right)}^2=l_i^2+l_j^2-{2l}_i*l_j*\cos ({\mathrm{\θ}}_i-{\mathrm{\θ}}_j)$

H ' _ijbe the user of i-th bad channel conditions to the channel coefficients between a jth correct decoding user, H _{i, j}for channel coefficients h ' _ijmodulus value square, l _ijbe the user of i-th bad channel conditions to the distance between a jth correct decoding user, h _ijbe the Rayleigh fading of user on earth between j correct decoding user of i-th bad channel conditions.For the user of i-th bad channel conditions, find the correct decoding user that best with its channel condition, i.e. maximum H _{i, j}corresponding j, using the user of this correct decoding as relaying, and this correct decoding user corresponding numbering in set G be placed in set Relay, delete repeat element in Relay, then in Relay, each element is selected relaying, and relaying number is N _r.

2) in second stage, utilize the trunk subscriber estimated to residue bad channel conditions user between channel condition information, carry out reasonable distribution to the power of each relaying, the relaying that recycling is selected is to the user's multi-case data remaining bad channel conditions.

2-1) second stage, utilizes the cooperating relay user estimated to the channel condition information of the user of bad channel conditions, obtains relay power and distribute normalized vector

${\mathrm{\β}}_j=\frac{H_j}{\underset{i=1}{\overset{N_r}{\mathrm{\Σ}}}{H}_i}=\frac{{|{h^{\′}}_{1j}+{h^{\′}}_{2j}+...+{h^{\′}}_{N*(1-C)j}|}^2}{\underset{i=1}{\overset{N_r}{\mathrm{\Σ}}}{|{h^{\′}}_{1i}+{h^{\′}}_{2i}+...+{h^{\′}}_{N*(1-C)i}|}^2}$

H _jfor the channel coefficients modulus value square of the user of cooperating relay j and all bad channel conditions, reflect the overall channel state of the user of relaying j and all bad channel conditions.The power division of each like this relaying not only takes full advantage of the overall channel state information of the user of this relaying and all bad channel conditions, have also contemplated that the overall channel state information of the user of other relaying and all bad channel conditions, even cooperating relay is better to the overall channel condition of the user of all bad channel conditions, and this relaying is with regard to the more power of distribution ratio; If a cooperating relay is bad to the overall channel condition of the user of all bad channel conditions, this relaying just distributes less power.

The Received signal strength that 2-2) user of second stage i-th bad channel conditions utilizes cooperating relay to obtain is: subscript ' rd ' represents that relaying sends out data to user

The received signal to noise ratio that 2-3) user of second stage i-th bad channel conditions receives from trunk subscriber is: ${\mathrm{SNR}}_i^{\mathrm{rd}}=\frac{P_r*{\left|\underset{j}{\mathrm{\Σ}}\sqrt{{\mathrm{\β}}_j*l_{\mathrm{ij}}^{-\mathrm{\η}}}{h}_{\mathrm{ij}}\right|}^2}{N_0}=\frac{P*(1-\mathrm{\α})*{\left|\underset{j}{\mathrm{\Σ}}\sqrt{{\mathrm{\β}}_j*l_{\mathrm{ij}}^{-\mathrm{\η}}}{h}_{\mathrm{ij}}\right|}^2}{N_0}$

Maximum-ratio combing mode is utilized to obtain the received signal to noise ratio of user i after first stage and second stage merge of bad channel conditions:

$\begin{array}{c}{\mathrm{SNR}}_i={\mathrm{SNR}}_i^{\mathrm{bd}}+{\mathrm{SNR}}_i^{\mathrm{rd}}=\frac{P_b{\left|h_i\right|}^2{l}_i^{-\mathrm{\η}}+P_r{\left|\underset{j}{\mathrm{\Σ}}\sqrt{{\mathrm{\β}}_j*l_{\mathrm{ij}}^{-\mathrm{\η}}}{h}_{\mathrm{ij}}\right|}^2}{N_0}\\ =\frac{P*\mathrm{\α}*{\left|h_i\right|}^2{l}_i^{-\mathrm{\η}}+P*(1-\mathrm{\α})*{\left|\underset{j}{\mathrm{\Σ}}\sqrt{{\mathrm{\β}}_j*l_{\mathrm{ij}}^{-\mathrm{\η}}}{h}_{\mathrm{ij}}\right|}^2}{N_0}\end{array}$ In order to ensure

The user of all bad channel conditions of second stage can correctly receive and decoding data, gets the multicast rate v that the receivable data rate of the minimum user of second stage received signal to noise ratio is second stage ₂=Blog ₂(1+min (SNR _i)).Second stage required time is then the efficiency of two stage whole multicast process systems is:

$E=\frac{{\mathrm{NB}}_o}{P_b{T}_1+P_r{T}_2}=\frac{{\mathrm{NB}}_o}{P*\mathrm{\α}*T_1+P*(1-\mathrm{\α})*T_2}.$

Claims (1)

1., based on a cooperation among users multicasting method for efficiency, for a cellular cell, this cellular cell comprises a base station, N number of multicast users, and the bandwidth that multicast takies is B, it is characterized in that:

1) multicast process is divided into two stages, all user's multi-case datas are given in first stage base station, ensure user's correct decoding that a part of channel condition is good, estimate the channel condition information between the user of residue bad channel conditions to correct decoding user, find the user of a correct decoding best with the subscriber channel condition of each bad channel conditions, and using the user of this correct decoding as relaying;

Described step 1) concrete grammar as follows:

1-1) multicast process is divided into two stages, first stage base station transmitting power P _b, P _b=α P, P are the gross power that whole multicast process base station and relaying consume, and α is the ratio that base station transmitting power accounts for gross power, and long data packet is B _o; Then the first stage is arranged in community (l _i, θ _i) Received signal strength of user i of position is:

$y_i^{\mathrm{bd}}=\sqrt{P_b{l}_i^{-\mathrm{\η}}}{h}_{i}x+n_i$

X is transmitting of base station, and subscript ' bd ' represents that data are sent out to user in base station, l _irepresent the distance between user i and base station, θ _ifor the phase angle of user i and base station, η is path loss coefficient, h _ithe multipath fading suffered by user i, h _i~ CN (0,1) is namely the multiple Gaussian random variable of zero mean unit variance, n _iadditive white Gaussian noise, variance N ₀, then the received signal to noise ratio of user i is:

${\mathrm{SNR}}_i^{\mathrm{bd}}=\frac{P_b{\left|h_i\right|}^2{l}_i^{-\mathrm{\η}}}{N_0};$

1-2) descending is pressed to the received signal to noise ratio of first stage all users, composition signal to noise ratio vector the ratio C of definition shared by first stage correct decoding user, then the set G={1 of first stage correct decoding user, 2,3 ..., N*C}, the set B of the user of residue bad channel conditions=N*C+1, N*C+2 ..., N}, the multi-case data speed of first stage is required time is channel condition information between the user of estimation N* (1-C) individual bad channel conditions and correct decoding user:

$H_{i,j}={\left|h_{\mathrm{ij}}^{\′}\right|}^2=l_{\mathrm{ij}}^{-\mathrm{\η}}{\left|h_{\mathrm{ij}}\right|}^2,\{i\∈B;j\∈G\};$

${\left(l_{\mathrm{ij}}\right)}^2=l_i^2+l_j^2-2l_i*l_j*\cos ({\mathrm{\θ}}_i-{\mathrm{\θ}}_j)$

H ' _ijfor the user for i-th bad channel conditions is to the channel coefficients between a jth correct decoding user, H _i,jfor channel coefficients h ' _ijmodulus value square, l _ijbe the user of i-th bad channel conditions to the distance between a jth correct decoding user, h _ijbe that the user of i-th bad channel conditions is to the Rayleigh fading between a jth correct decoding user; For the user of i-th bad channel conditions, find the correct decoding user that best with its channel condition, i.e. maximum H _i,jcorresponding j, using the user of this correct decoding as relaying, and this correct decoding user corresponding numbering in set G be placed in set Relay, delete repeat element in Relay, then in Relay, each element is selected relaying, and relaying number is N _r;

2) in second stage, utilize the trunk subscriber estimated to residue bad channel conditions user between channel condition information, carry out reasonable distribution to the power of each relaying, the relaying that recycling is selected is to the user's multi-case data remaining bad channel conditions;

Described step 2) concrete steps as follows:

2-1) second stage, utilizes the channel condition information between the user of the bad channel conditions estimated and correct decoding user, obtains relay power and distributes normalized vector

${\mathrm{\β}}_j=\frac{H_j}{\underset{i=1}{\overset{N_r}{\mathrm{\Σ}}}{H}_i}=\frac{{|h_{1j}^{\′}+h_{2j}^{\′}+...+h_{N*(1-C)j}^{\′}|}^2}{\underset{i=1}{\overset{N_r}{\mathrm{\Σ}}}{|h_{1i}^{\′}+h_{2i}^{\′}+...+h_{N*(1-C)i}^{\′}|}^2}$

H _jfor the channel coefficients modulus value square of the user of relaying j and all bad channel conditions, reflect the overall channel state of the user of relaying j and all bad channel conditions;

The Received signal strength that 2-2) user of second stage i-th bad channel conditions utilizes relaying to obtain is: p _rbe the total transmitting power of all relayings of second stage, meet P _b+ P _r=P, subscript ' rd ' represents that relaying sends out data to user;

The received signal to noise ratio that 2-3) user of second stage i-th bad channel conditions receives from trunk subscriber is: ${\mathrm{SNR}}_i^{\mathrm{rd}}=\frac{P_r*{\left|\underset{j}{\mathrm{\Σ}}\sqrt{{\mathrm{\β}}_j*l_{\mathrm{ij}}^{-\mathrm{\η}}}{h}_{\mathrm{ij}}\right|}^2}{N_0}=\frac{P*(1-\mathrm{\α})*{\left|\underset{j}{\mathrm{\Σ}}\sqrt{{\mathrm{\β}}_j*l_{\mathrm{ij}}^{-\mathrm{\η}}}{h}_{\mathrm{ij}}\right|}^2}{N_0}$

Maximum-ratio combing mode is utilized to obtain the received signal to noise ratio of user i after first stage and second stage merge of bad channel conditions:

${\mathrm{SNR}}_i={\mathrm{SNR}}_i^{\mathrm{bd}}+{\mathrm{SNR}}_i^{\mathrm{rd}}=\frac{P_b{\left|h_i\right|}^2{l}_i^{-\mathrm{\η}}+P_r{\left|\underset{j}{\mathrm{\Σ}}\sqrt{{\mathrm{\β}}_j*l_{\mathrm{ij}}^{-\mathrm{\η}}}{h}_{\mathrm{ij}}\right|}^2}{N_0}$

In order to ensure can correctly to receive and decoding data the user of all bad channel conditions of second stage, the receivable data rate getting the minimum user of second stage received signal to noise ratio is the multicast rate v of second stage ₂=Blog ₂(1+min (SNR _i)), wherein, min (SNR _i) be received signal to noise ratio corresponding to user that second stage received signal to noise ratio is minimum.