CN102291684B - Method for selecting unicast channel and multicast channel in multicast communication system - Google Patents

Abstract

The invention discloses a method for selecting a unicast channel and a multicast channel in multicast communication system. The method comprises the following steps: 1) setting K users and N cells in a single-frequency network, and setting R as the multicast transmission rate, arranging the fed-back signal-to-noise ratio of each user in an ascending order; and setting the arrangement result as set B: B=[SNR1, SNR2,..., SNRK], wherein SNRk is the signal-to-noise ratio of the received signal of the kth user, and k is a natural number; and a user set corresponding to the set B is: A=[1, 2, 3,..., K]; and 2) calculating the spectral efficiency under each condition of the (K+1) conditions as the number of users participating in unicast is 0, 1,..., K and totally (K+1) conditions exists;finding the maximum spectral frequency [epsilon]k; and determining the first k users in the set A as unicast users and other users as multicast users. The method disclosed by the invention can effectively reduce influence on the weakest user in multicast service in the case of relatively low complexity, and increase the spectral efficiency of the cell system so as to improve the performance of the entire system.

Description

A kind of system of selection of unicast tunnel and Multicast Channel for multi-casting communication system

Technical field

The invention belongs to wireless communication technology field, the unicast tunnel in especially a kind of multi-medium multi-packet broadcasting system (MBMS, Multimedia Broadcast Multicast Service) and the system of selection of Multicast Channel.The method can improve the spectrum efficiency of system, improves systematic function.

Background technology

Along with the development of wireless communication technology, the continuous growth of people to multimedia service (video traffic, downloading service) demand, make the MBMS business play the part of more and more important effect in communication system.In MBMS, there are two kinds of transmission modes available: p-t-m (point-to-multipoint) and p-t-p (point-to-point).P-t-p refers to base station and only to a user, sends data, and p-t-m refers to base station and sends data to several users simultaneously.Unicast user is defined as selects the user of p-t-p as transmission means, multicast users to be defined as the user of selection p-t-m as transmission means.Traditional multicast service has limited the throughput of communication system multi-medium multi-packet broadcasting service and the lifting of spectrum efficiency greatly, because the performance of traditional multicast service whole system is limited to the poorest user of channel condition, its transmission rate the user the poorest by channel condition determine, the user that channel condition is good like this can not take full advantage of the capacity of its channel.Therefore how to make the minimum or channel capacity that how to take full advantage of other users of the poorest customer impact become the emphasis of a lot of literature research.

In fact, the poor especially user for some channel condition, we can consider to go transmission (with large bandwidth or power, guaranteeing transmission rate) with unicast tunnel, thus the spectrum efficiency of raising whole system.We can be suitable the selection multicast service in p-t-m user and p-t-p user's ratio, target is to make spectrum efficiency maximize.

Unicast tunnel at present commonly used and the selection strategy of Multicast Channel are as follows: in the situation that known signal to noise ratio user's signal to noise ratio probability density function, can be in the hope of best signal-noise ratio threshold, when certain user's signal to noise ratio is greater than this thresholding, adopt Multicast Channel, adopt unicast tunnel while being less than this thresholding, and then can obtain optimum system spectral efficiency.But the acquisition of user's signal to noise ratio probability density function has certain difficulty in practice, be achieved by a variety of factors, so the method practicality is poor.

Summary of the invention

The object of the invention is to overcome the shortcoming of above-mentioned prior art, a kind of system of selection of unicast tunnel and Multicast Channel for multi-casting communication system is provided, the method is in the situation that complexity is less, can effectively reduce the poorest user's impact in multicast service, improve the spectrum efficiency of cell system, thereby improve the performance of whole system.

The objective of the invention is to solve by the following technical programs:

This kind, for the system of selection of unicast tunnel and the Multicast Channel of multi-casting communication system, comprises the following steps:

1) establish in single frequency network K user arranged, N community, R is multicast transmission speed, and each user's of feeding back signal to noise ratio is arranged by ascending order, establishing rank results is set B:

B＝[SNR ₁，SNR ₂，...，SNR _K] (1)

In set, SNR _kbe the signal to noise ratio of k user's acknowledge(ment) signal, k is natural number;

User's set corresponding to set B is: A=[1,2,3......K];

2) number of participation unicast user is 0,1 ..., K, one have (K+1) kind situation, calculates the spectrum efficiency in every kind of situation:

When the unicast user number is 0,1 ..., during K-1, spectrum efficiency ε _kfor: k gets 0～K-1;

${\mathrm{\ϵ}}_k=\frac{\mathrm{KR}}{\frac{\mathrm{NR}}{\log (1+{\mathrm{SNR}}_{i+1})}+\underset{j=1}{\overset{i}{\mathrm{\Σ}}}\frac{R}{\log (1+{\mathrm{SNR}}_j)}}---\left(2\right)$

When the number of unicast user is K, spectrum efficiency ε _kfor:

${\mathrm{\ϵ}}_K=\frac{\mathrm{KR}}{\underset{i=1}{\overset{K}{\mathrm{\Σ}}}\frac{R}{\log (1+{\mathrm{SNR}}_i)}}---\left(3\right)$

Find out maximum spectrum efficiency ε _k, and front k user in definite set A be unicast user, all the other users are multicast users.

The present invention also proposes the system of selection of another kind of unicast tunnel and Multicast Channel for multi-casting communication system, comprises the following steps:

1) establish in single frequency network K user arranged, N community, R is multicast transmission speed, and each user's of feeding back signal to noise ratio is arranged by ascending order, establishing rank results is set B:

B＝[SNR ₁，SNR ₂，...，SNR _K] (1)

In set, SNR _kbe the signal to noise ratio of k user's acknowledge(ment) signal, k is natural number.User's set corresponding to set B is: A=[1,2,3......K];

2) user of first from set A starts, and calculates respectively and the spectrum efficiency while comparing each user for clean culture or multicast; If spectrum efficiency when during clean culture, user's spectrum efficiency is greater than multicast, just select this user for unicast user, and more next user, if arrived last user, all users are unicast user, and algorithm finishes; Spectrum efficiency when if during multicast, user's spectrum efficiency is greater than clean culture, the user of back has not just compared so, and from this user, later user, comprise this user, is all multicast users, and algorithm finishes.

The system of selection of above-mentioned unicast tunnel and Multicast Channel for multi-casting communication system is characterized in that:

The number of 1), establishing unicast user in optimal algorithm is K _opt, obtain K _optthe relation curve of the signal to noise ratio of/K and transmitting terminal signal;

2), use multinomial (4) with the above-mentioned curve obtained of least square fitting;

$f\left(x\right)=\frac{a_0}{x}+a_{1}x+a_2---\left(4\right)$

Obtain coefficient a in formula (4) ₀, a ₁, a ₂;

3), using the signal to noise ratio of transmitting terminal as independent variable, bring in formula (4), and obtain the value of function f (x), and to make k be from the nearest integer of f (x) * K, before then selecting in set A, k user is as unicast user, and all the other users are as multicast users.

The system of selection of above-mentioned unicast tunnel and Multicast Channel for multi-casting communication system, it is characterized in that, step 3) in, find out three nearest integers from f (x) * K, the spectrum efficiency when these three integers represent respectively the unicast user number relatively, the integer of the spectrum efficiency maximum of selecting to send as an envoy to is as the number of unicast user.

The present invention has following beneficial effect:

The present invention selects optimum situation to determine that the user is p-t-p user or p-t-m user in all situations, and when number of users is more, algorithm complex is higher.The present invention adopts another kind of sub-optimal algorithm, although its performance and optimal algorithm slightly have gap, its algorithm complex reduces a lot.The statistical forecast algorithm be data that a certain special scenes is drawn according to lot of experiments to concrete certain once realize being predicted, therefore in the situation that the very low effect preferably that obtained of algorithm complex, but because system realizes existing randomness each time, so proposed again improved statistical forecast algorithm, on the basis of statistical forecast algorithm, go around the integer obtained from the statistical forecast algorithm to find to make the unicast user number that spectrum efficiency is larger, therefore from algorithm complex or performance, all obtain effect preferably.

The accompanying drawing explanation

Fig. 1 signal to noise ratio and K _optthe relation (N=10, K=50) of/K;

Fig. 2 real data and matched curve (N=10, K=50);

The flow chart of Fig. 3 optimal algorithm;

The flow chart of Fig. 4 sub-optimal algorithm;

The flow chart of Fig. 5 statistical forecast algorithm;

The flow chart of the improved statistical forecast algorithm of Fig. 6.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail:

In the single frequency network multicast system, single frequency network wherein means to carry out synchronous transmission with same frequency in a plurality of communities at one time.Use this transmission means can save frequency resource, improve the availability of frequency spectrum.This multiple sectors at same keeps pouring in defeated brought diversity and can solve the problems such as blind area covering simultaneously, strengthens the reliability received, and improves coverage rate.The performance of traditional multicast system is limited to the poorest user of channel condition, and the present invention is that the user selects unicast or multicast mode to be transmitted by certain method, reduces the impact of the user of bad channel conditions on whole system, promotes the whole system spectrum efficiency.

Suppose in single frequency network to have K user, N community, R is multicast transmission speed, and each user's signal to noise ratio that will feed back from receiving terminal is arranged by ascending order, and establishing rank results is set B:

B＝[SNR ₁，SNR ₂，...，SNR _K] (1)

In set, SNR _kbe the signal to noise ratio of k user's acknowledge(ment) signal, k is natural number;

User's set corresponding to set B is: A=[1,2,3......K];

The speed that i user can reach is

R _i＝B _ilog(1+SNR _i) (2)

In MBMS, the definition spectrum efficiency

$\mathrm{\ϵ}=\frac{R_{\mathrm{total}}}{B_{\mathrm{total}}}=\frac{B_{\mathrm{total}}}{B_{\mathrm{multi}}+B_{\mathrm{uni}}}---\left(3\right)$

R wherein _totaltotal speed of expression system, B _totalmean the total bandwidth that multicast service takies, B _multiand B _unirepresent respectively multicast and the shared bandwidth of unicast user in multicast service.No matter be unicast user or multicast users, use without exception identical transmission rate, the user that the separate channel condition is poor, can improve transmission rate by the mode that increases bandwidth.

While carrying out the selection of certain user's transmission means (p-t-p or p-t-m), comprise following method:

1), optimal algorithm, concrete steps are as follows:

1-1), come to K user, the number of participating in so unicast user can only be 0,1 ..., K that is to say situation in one total (K+1), calculates the spectrum efficiency in every kind of situation:

When the unicast user number is 0,1 ..., during K-1, spectrum efficiency is

${\mathrm{\ϵ}}_k=\frac{\mathrm{KR}}{\frac{\mathrm{NR}}{\log (1+{\mathrm{SNR}}_{i+1})}+\underset{j=1}{\overset{i}{\mathrm{\Σ}}}\frac{R}{\log (1+{\mathrm{SNR}}_j)}}---\left(2\right)$

K gets 0～K-1;

When the number of unicast user is K (all users are clean cultures)

${\mathrm{\ϵ}}_K=\frac{\mathrm{KR}}{\underset{i=1}{\overset{K}{\mathrm{\Σ}}}\frac{R}{\log (1+{\mathrm{SNR}}_i)}}---\left(3\right)$

1-2) find out maximum spectrum efficiency ε _k(k=0,1 ..., K), and front k user in definite set A be unicast user (p-t-p), all the other users are multicast users (p-t-m).

2), sub-optimal algorithm, concrete steps are as follows:

If K user arranged in single frequency network, N community, R is multicast transmission speed, and each user's of feeding back signal to noise ratio is arranged by ascending order, establishing rank results is set B:

B＝[SNR ₁，SNR ₂，...，SNR _K] (1)

In set, SNR _kbe the signal to noise ratio of k user's acknowledge(ment) signal, k is natural number.User's set corresponding to set B is: A=[1,2,3......K];

2-1), the user of first from set A starts, calculate respectively and the spectrum efficiency of more some users during for clean culture or multicast: if spectrum efficiency a) during clean culture is higher, just selecting this user is p-t-p user, and more next user, if arrived last user, all users use the p-t-p mode to transmit, and algorithm finishes; B) if spectrum efficiency during multicast is high, the user of back has not just compared so, and from this user, later user, comprise this user, all uses the p-t-m mode, and algorithm finishes.

3), the statistical forecast algorithm, comprise the following steps:

The number of 3-1), establishing p-t-p user in optimal algorithm is K _opt, obtain K _optthe relation curve of the signal to noise ratio of/K and signal transmitting terminal (drawing by a large amount of tests);

3-2), with a certain curve, remove this curve of matching, select multinomial (4) with least square fitting here;

$f\left(x\right)=\frac{a_0}{x}+a_{1}x+a_2---\left(4\right)$

By least square method, data and curve are carried out to matching, obtain coefficient a ₀, a ₁, a ₂, the test data in a kind of situation and matched curve are as shown in figure (1) and figure (2)

3-3), bring function (4) into using the signal to noise ratio of system transmitting terminal as independent variable, and obtain the value f (x) of function.And to make k be from the nearest integer of f (x) * K, before then selecting in set A, k user is as unicast user, and all the other users are as multicast users.

4), improved statistical forecast algorithm, comprise the following steps:

4-1) with 3-1) identical;

4-2) with 3-2) identical;

4-3), bring (4) into using the signal to noise ratio of system transmitting terminal as independent variable, and obtain the value f (x) of function.Find out three nearest integers from f (x) * K, the spectrum efficiency when these three integers represent the unicast user number relatively respectively, select the integer that makes the spectrum efficiency maximum number as unicast user.

Fig. 1 is the relation curve that unicast user that a large amount of emulation draws accounts for total user's ratio and signal to noise ratio, Fig. 2 is tried to achieve fit equation and the relation between real data, and Fig. 3 to Fig. 6 is to be respectively the flow chart of optimal algorithm, sub-optimal algorithm, statistical forecast algorithm and improved statistical forecast algorithm.

Claims (4)

1. the system of selection for unicast tunnel and the Multicast Channel of multi-casting communication system, is characterized in that, comprises the following steps:

1) establish in single frequency network K user arranged, N community, R is multicast transmission speed, and each user's of feeding back signal to noise ratio is arranged by ascending order, establishing rank results is set B:

B=[SNR ₁,SNR ₂,...,SNR _K] (1)

In set, SNR _kbe the signal to noise ratio of k user's acknowledge(ment) signal, k is natural number;

User's set corresponding to set B is: A=[1,2,3 ... K];

2) number of participation unicast user is 0,1 ..., K, one have (K+1) kind situation, calculates the spectrum efficiency in every kind of situation:

When the unicast user number is 0,1 ..., during K-1, spectrum efficiency ε _kfor:

${\mathrm{\ϵ}}_k=\frac{\mathrm{KR}}{\frac{\mathrm{NR}}{\log (1+{\mathrm{SNR}}_{i+1})}+\underset{j=1}{\overset{i}{\mathrm{\Σ}}}\frac{R}{\log (1+{\mathrm{SNR}}_j)}}---\left(2\right)$

K gets 0～K-1, and i is number of users, and i=k;

When the number of unicast user is K, spectrum efficiency ε _kfor:

${\mathrm{\ϵ}}_K=\frac{\mathrm{KR}}{\underset{i=1}{\overset{K}{\mathrm{\Σ}}}\frac{R}{\log (1+{\mathrm{SNR}}_i)}}---\left(3\right)$

Find out maximum spectrum efficiency ε _k, and front k user in definite set A be unicast user, all the other users are multicast users.

2. the system of selection for unicast tunnel and the Multicast Channel of multi-casting communication system, is characterized in that, comprises the following steps:

1) establish in single frequency network K user arranged, N community, R is multicast transmission speed, and each user's of feeding back signal to noise ratio is arranged by ascending order, establishing rank results is set B:

B=[SNR ₁,SNR ₂,...,SNR _K] (1)

In set, SNR _kbe the signal to noise ratio of k user's acknowledge(ment) signal, k is natural number; User's set corresponding to set B is: A=[1,2,3 ... K];

2) user of first from set A starts, and calculates respectively and the spectrum efficiency while comparing each user for clean culture or multicast; If spectrum efficiency when during clean culture, user's spectrum efficiency is greater than multicast, just select this user for unicast user, and more next user, if arrived last user, all users are unicast user, and algorithm finishes; Spectrum efficiency when if during multicast, user's spectrum efficiency is greater than clean culture, the user of back has not just compared so, and from this user, later user, comprise this user, is all multicast users, and algorithm finishes.

3. the system of selection of unicast tunnel and Multicast Channel for multi-casting communication system according to claim 1 is characterized in that:

The number of 1), establishing unicast user in optimal algorithm is K _opt, obtain K _optthe relation curve of the signal to noise ratio of/K and transmitting terminal signal;

2), use multinomial (4) with the above-mentioned curve obtained of least square fitting;

$f\left(x\right)=\frac{a_0}{x}+a_{1}x+a_2---\left(4\right)$

Obtain coefficient a in formula (4) ₀, a ₁, a ₂;

3), using the signal to noise ratio of transmitting terminal as independent variable, bring in formula (4), and obtain the value of function f (x), and to make k be from f(x) the nearest integer of * K, before then selecting in set A, k user is as unicast user, all the other users are as multicast users.

4. the system of selection of unicast tunnel and Multicast Channel for multi-casting communication system according to claim 3, it is characterized in that, in step 3), find out from f(x) three nearest integers of * K, the spectrum efficiency when these three integers represent respectively the unicast user number relatively, the integer of the spectrum efficiency maximum of selecting to send as an envoy to is as the number of unicast user.

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