CN106209335A - A kind of pilot multiplex method for D2D communication system - Google Patents

Abstract

The invention discloses a kind of pilot multiplex method for D2D communication system, the method finds D2D pair that suffered potential interference is maximum from the D2D user of unallocated pilot tone every time, the pilot tone interfering minimum will be distributed to it by this D2D, until all D2D are to being assigned to pilot tone.The present invention makes full use of slowly varying large scale fading coefficients, define describe two D2D between the parameter that interferes, the algorithm using complexity relatively low achieves the pilot tone distribution in the case of multiplexed pilot between D2D user, can effectively reduce pilot pollution.

Description

A kind of pilot multiplex method for D2D communication system

Technical field

The present invention relates to the D2D communications field, particularly relate to a kind of pilot multiplex method for D2D communication system.

Background technology

In recent years, along with the rapid growth of wireless traffic, frequency spectrum resource worsening shortages, D2D (Device-to-Device) Communication technology can be with the availability of frequency spectrum of significant increase system, so beening proposed in the 5th Generation Mobile Communication System employing.D2D Communication allows neighboring user directly to communicate, and without through base station, and D2D user can provide with the frequency of multiplexing phone user Source.Therefore, D2D communication has raising band efficiency, reduces propagation delay time, the advantage reducing energy expenditure.

In honeycomb and D2D hybrid communication system, phone user is generally of higher priority, and phone user Number is typically smaller than the number of D2D pair.So, it can be assumed that in single cell scenario, phone user uses mutually orthogonal pilot tone sequence Row carry out channel estimation.In order to reduce the length of pilot frequency sequence, between D2D user, there is pilot frequency multiplexing, namely D2D user can use The number of pilot set less than the number of D2D pair.In order to reduce D2D subscriber channel estimation difference, need the one can be effective Reduce the method for pilot pollution between D2D user.

This patent gives a kind of method of pilot frequency multiplexing in honeycomb and D2D hybrid communication system, and this method can have Effect reduce D2D between Pilot Interference problem.

Summary of the invention

Goal of the invention: the present invention is directed to the problem that prior art exists, it is provided that a kind of pilot tone for D2D communication system is multiple By method, the method be applicable to honeycomb and D2D hybrid communication system, can effectively reduce D2D between Pilot Interference ask Topic.

Technical scheme: the pilot multiplex method for D2D communication system of the present invention, including:

S1, obtain all D2D between large scale fading coefficients；

S2, according to large scale fading coefficients, calculate any two D2D between potential interference；

S3, from the D2D of unallocated pilot tone to set being chosen by maximum D2D pair of potential interference；

S4, from pilot resources, choose pilot tone ω_mDistribute to D2D pair chosen, and the D2D chosen is divided to adding to Join the D2D of pilot tone in set；Wherein, ω_mRepresent m-th pilot tone in pilot resources, m be distributed D2D pair of pilot tone Number；

S5, judge to have distributed the number of D2D pair of pilot tone whether less than the number of pilot resources；The most then it is back to S3； If it is not, perform S6；

S6, calculate the potential pilot tone of D2D pair of each unallocated pilot tone；

S7, choose from the D2D of unallocated pilot tone gathers by maximum D2D pair of potential interference；

S8, distribute to the D2D chosen corresponding potential pilot tone to choose D2D pair, and by the D2D chosen to adding to Distribute the D2D of pilot tone in set；

S9, judge whether all D2D to having distributed pilot tone, if it is not, then return step S6, the most then complete pilot tone Distribution.

Further, the computing formula of the potential interference in described step S2 is:

${\mathrm{\β}}_{ik}=\left\{\begin{array}{cc}0,& i=k\\ ln(1+\frac{v_{ik}^2}{v_{kk}^2}+\frac{v_{ki}^2}{v_{ii}^2}),& i\≠k\end{array}\right.$

In formula, β_ikRepresent D2D to i and D2D between k use same pilot time potential interference, i, k represent D2D pair Numbering,K represents the number of D2D pair, v_·*Represent D2D to and D2D the large scale between * is declined Fall coefficient.

Further, the potential pilot tone in described step S6 is to causing the minimum pilot tone of potential interference to D2D；Wherein, D2D is numbered n to the potential pilot tone of k_kPilot tone,In formula, N is for leading Frequently the number of resource, pilot matrix isλ_iRepresenting and distribute to the D2D pilot frequency sequence to i, Λ is Distribute the D2D of pilot tone to set.

Further, the computing formula of k ' is by the D2D maximum by potential interference in described step S7

$k^{\′}=\arg \underset{k\∈K\backslash \mathrm{\Λ}}{max}\left\{\underset{i\∈K\backslash \mathrm{\Λ}}{\Σ}{\mathrm{\β}}_{ik}+\underset{\left\{i|{\mathrm{\λ}}_i={\mathrm{\ω}}_{n_k}\right\}}{\Σ}{\mathrm{\β}}_{ik}\right\}.$

Beneficial effect: compared with prior art, its remarkable advantage is the present invention: the present invention makes full use of slowly varying big Yardstick fading coefficients, define describe two D2D between the parameter that interferes, the algorithm using complexity relatively low achieves In the case of multiplexed pilot, the pilot tone between D2D user is distributed, and can effectively reduce pilot pollution, have certain practicality.This Bright core concept is every time find suffered potential interference maximum from the D2D user of unallocated pilot tone D2D pair, will be to this The pilot tone interfering minimum is distributed to it by D2D, until all D2D are to being assigned to pilot tone.The present invention realizes simply, and Emulation proves that it has good performance.

Accompanying drawing explanation

Fig. 1 is the scene schematic diagram of the D2D communication system that this present embodiment relates to；In Fig. 1, BS is base station, D2D-Tx and D2D-Rx represents the D2D transmitter and receiver to x respectively, and solid arrow represents useful pilot signal, and dotted arrow represents leads Frequency interference signal；

Fig. 2 is the schematic flow sheet of the present embodiment；

Fig. 3 be the present invention provide pilot tone allocation algorithm (Proposed Scheme), random assortment pilot tone (RPA) and The comparison diagram of pilot tone not multiplexing (NPR)；Consider to have the communication system of 20 D2D pair, abscissa represent D2D user can lead Frequently number, vertical coordinate represents the Mean Speed of each D2D pair.

Detailed description of the invention

The network of the present embodiment as it is shown in figure 1, communication system has K single antenna D2D to and a base station, D2D pair Set is denoted asThe N number of orthogonal guide frequency of D2D user's multiplexing carries out channel estimation.All transmitters use identical Running time-frequency resource sends signal.The pilot matrix of pilot resources is denoted asPilot frequency sequence is standard Orthogonal vectors, namely Ω^HΩ=I_N.For reducing the length of pilot frequency sequence, D2D user multiplexed pilot set { ω₁,…,ω_N, N < K.The pilot signal that then D2D receiver k receives is

Wherein, p_iIt it is the pilot power of D2D transmitter i；It it is the channel of D2D transmitter i to D2D receiver k Gain, wherein, v_ikRepresent large scale decline,Represent multipath fading；λ_i∈{ω₁,…,ω_NRepresent distribution To the D2D pilot frequency sequence to i；Represent additive white noise.Then channel gain g_ikMMSE can represent For

Wherein,Represent with i is used the D2D of same pilot sequence to gather by D2D.Channel estimation errors is denoted asThenAccording to MMSE estimate character it is recognised thatWithSeparate, and meet

Wherein,

ε_ik=v_ik-δ_ik

In order to reduce pilot pollution, the mean square error minimizing the estimation of D2D link channel obtains following optimization problem

Wherein,Represent pilot tone allocation strategy.Above-mentioned optimization problem is a combinatorial optimization problem, it is possible to use The method of exhaustive search finds optimal solution, but the complexity of exhaustive search is with number of users exponential increase.Use for this with lower section Method carries out pilot tone distribution.

As in figure 2 it is shown, the pilot multiplex method for D2D communication system of the present embodiment, comprise the following steps:

S1, obtain all D2D between large scale fading coefficientsWherein, v_.*Represent D2D to D2D is to the large scale fading coefficients between *.

S2, according to large scale fading coefficients, calculate any two D2D between potential interference.

Wherein, the computing formula of potential interference is:

${\mathrm{\&beta;}}_{ik}=\left\{\begin{array}{cc}0,& i=k\\ ln(1+\frac{v_{ik}^2}{v_{kk}^2}+\frac{v_{ki}^2}{v_{ii}^2}),& i\&NotEqual;k\end{array}\right.$

In formula, β_ikRepresent D2D to i and D2D between k use same pilot time potential interference, i, k represent D2D pair Numbering,

S3, from the D2D of unallocated pilot tone to set being chosen by the maximum D2D of potential interference k^.

Wherein,

S4, from pilot resources, choose pilot tone ω_mThe D2D distributing to choose is to k^{^}, ω_mRepresent that in pilot resources, m-th is led Frequently, m is the number of D2D pair that has distributed pilot tone；And by the D2D that chooses to k^{^}Add the D2D distributing pilot tone to set Λ In, i.e.

λ_k^=ω_m, Λ=Λ ∪ k^{^}。

S5, judge to have distributed the number of D2D pair of pilot tone whether less than number N of pilot resources；The most then it is back to S3；If it is not, perform S6.

S6, calculate the potential pilot tone of D2D pair of each unallocated pilot tone.

Wherein, potential pilot tone is to causing the minimum pilot tone of potential interference to D2D；Concrete, the D2D potential pilot tone to k For n numbered in pilot matrix_kPilot tone,

S7, choose from the D2D of unallocated pilot tone gathers by maximum D2D pair of potential interference.

Wherein, by the D2D that potential interference is maximum to the computing formula of k ' it is

$k^{\&prime;}=\arg \underset{k\&Element;K\backslash \mathrm{\&Lambda;}}{max}\left\{\underset{i\&Element;K\backslash \mathrm{\&Lambda;}}{\&Sigma;}{\mathrm{\&beta;}}_{ik}+\underset{\left\{i|{\mathrm{\&lambda;}}_i={\mathrm{\&omega;}}_{n_k}\right\}}{\&Sigma;}{\mathrm{\&beta;}}_{ik}\right\}.$

S8, distribute to the D2D chosen corresponding potential pilot tone to choose D2D pair, and by the D2D chosen to adding to Distribute the D2D of pilot tone in set, it may be assumed thatΛ=Λ ∪ k '..

S9, judge whether all D2D to having distributed pilot tone, if it is not, then return step S6, the most then complete pilot tone Distribution.

Said method being carried out simulating, verifying, has 20 D2D pair in the community of radius 500 meters, path loss obeys ginseng Number is the exponential of 3.7, shadow fading be standard deviation be the logarithm normal distribution of 8dB, pilot transmission power is 20mW.Result Fig. 3, it is shown that compared with random assortment pilot tone, the scheme that the present invention proposes can be effectively improved user rate；With The scene (namely each D2D is to using different pilot tones) of pilot tone not multiplexing is compared, and the scheme that the present invention proposes can effectively subtract The length of little pilot frequency sequence, promotes spectrum efficiency.

Above disclosed only one preferred embodiment of the present invention, it is impossible to limit the right model of the present invention with this Enclose, the equivalent variations therefore made according to the claims in the present invention, still belong to the scope that the present invention is contained.

Claims (4)

1. the pilot multiplex method for D2D communication system, it is characterised in that the method includes:

S1, obtain all D2D between large scale fading coefficients；

S2, according to large scale fading coefficients, calculate any two D2D between potential interference；

S3, from the D2D of unallocated pilot tone to set being chosen by maximum D2D pair of potential interference；

S4, from pilot resources, choose pilot tone ω_mDistribute to D2D pair chosen, and the D2D chosen is led adding to distribute The D2D of frequency is in set；Wherein, ω_mRepresenting m-th pilot tone in pilot resources, m is the number of D2D pair that has distributed pilot tone；

S5, judge to have distributed the number of D2D pair of pilot tone whether less than the number of pilot resources；The most then it is back to S3；If No, perform S6；

S6, calculate the potential pilot tone of D2D pair of each unallocated pilot tone；

S7, choose from the D2D of unallocated pilot tone gathers by maximum D2D pair of potential interference；

S8, distribute to the D2D chosen corresponding potential pilot tone to choose D2D pair, and the D2D chosen is divided to adding to Join the D2D of pilot tone in set；

S9, judge whether all D2D to having distributed pilot tone, if it is not, then return step S6, the most then complete pilot tone distribution.

2. the pilot multiplex method for D2D communication system as claimed in claim 1, it is characterised in that: in described step S2 The computing formula of potential interference be:

${\mathrm{\&beta;}}_{ik}=\left\{\begin{array}{cc}0,& i=k\\ ln(1+\frac{v_{ik}^2}{v_{kk}^2}+\frac{v_{ki}^2}{v_{ii}^2}),& i\&NotEqual;k\end{array}\right.$

In formula, β_ikRepresent D2D to i and D2D to potential interference when using same pilot between k, i, k represent the numbering of D2D pair,K represents the number of D2D pair, υ_·*Represent D2D to and D2D between * large scale decline system Number.

3. the pilot multiplex method for D2D communication system as claimed in claim 2, it is characterised in that: in described step S6 Potential pilot tone be to causing the minimum pilot tone of potential interference to D2D；Wherein, D2D is numbered n to the potential pilot tone of k_kLead Frequently,In formula, N is the number of pilot resources, and pilot matrix isλ_iRepresenting and distribute to the D2D pilot frequency sequence to i, Λ is that the D2D having distributed pilot tone is to set.

4. the pilot multiplex method for D2D communication system as claimed in claim 3, it is characterised in that: in described step S7 The D2D maximum by potential interference to the computing formula of k ' be

$k^{\&prime;}=\arg \underset{k\&Element;K\backslash \mathrm{\&Lambda;}}{max}\left\{\underset{i\&Element;K\backslash \mathrm{\&Lambda;}}{\&Sigma;}{\mathrm{\&beta;}}_{ik}+\underset{\left\{i\right|{\mathrm{\&lambda;}}_i={\mathrm{\&omega;}}_{n_k}\}}{\&Sigma;}{\mathrm{\&beta;}}_{ik}\right\}.$