CN103108361A - Method for setting down-link adaptive parameters in base station of wireless communication network - Google Patents

Abstract

The invention provides a method for setting down-link adaptive parameters in a base station of a wireless communication network. The method includes the following steps: judging whether downlink user transmission power density on a downlink data shared channel of the base station needs to be calculated; and determining the downlink user transmission power density on the downlink data shared channel of the base station based on signal to interference plus noise power ratio between the base station and the user terminal under the base station and interference of the base station on an adjacent area when the downlink user transmission power density needs to be calculated.

Description

The method that down link self adaption parameter in wireless communications network base station arranges

Technical field

The present invention relates to cordless communication network, relate in particular to the method that the down link self adaption parameter in the base station of cordless communication network arranges.

Background technology

In order to improve systematic function, heterogeneous network (Heterogeneous networks, HetNet) is discussed in further deep Long Term Evolution (Long Term Evolution-Advanced, LTE-A) job widely.In heterogeneous network, except traditional macro base station (macro eNB, MeNB), also comprise other little base station, pico for example, femto and relaying eNodeB, these little base stations are not planned well and are disposed and optimize.More interference will be brought for system in these little base stations, thereby these base stations will become the factor of performance limitations.At present, under the situation that only has macro base station to dispose, in order to simplify configuration, be physical data shared channel (Physical Downlink Shared Channel, PDSCH) the identical through-put power of each Resource Block configuration, this is for the communication environment of high interference, for example, the HetNet scene is obviously inapplicable.Under the HetNet scene, the PDSCH through-put power should carefully be distributed, to configure optimum transformation parameter, for example modulate and coded system, and to obtain at receiving data rate, the particularly compromise of the optimum between Cell Edge User and interference.On the other hand, logical overpowering distribution and the adaptive link adjustment that reaches can utilize power resource fully, thus improve the efficient of system and reduce the needed through-put power of every bits per second, thus environmental protection more.

In the environment of many residential quarters, the main purpose of power division is that how maximum system performance and minimum power adjustment are disturbed user's impact on common channel.The most algorithm of research and development is to process this problem in the centralized mode at present, perhaps processes this problem in the mode of mutual extra channel information between neighbor cell.Yet above-mentioned mode can produce a large amount of signaling consumptions, and needs a large amount of effort of plot planning.In HetNet, flat system architecture is not because exist CPU, thereby centralized power division mode can't realize.And in the situation that there is a large amount of pico base stations in network, if adopt the mode of mutual signaling between adjacent base station, can bring a large amount of signaling consumptions.Therefore, need a kind of intelligence, automatic power allocation scheme with less information interaction or cooperation, thereby pare down expenses.

In existing scheme, for all Resource Block provide identical power density.Because the coverage of macro base station is very large, under the situation that only has macro base station to dispose, this scheme is suitable, and due to user terminal mean allocation in network normally, may not can lose a lot of performances.But under the scene for HetNet, the covering of pico base station is less.Therefore, due to the network environment of complexity, different pico position for example, different pico numbers, and different user distributions, identical power density scheme will make whole system be operated in state away from optimization work point.

Centralized multi-user water injection power allocative decision can realize optimum systematic function, yet this scheme needs a large amount of information interactions, thereby because need central control node, and be not suitable for flat system architecture.In order to reduce feedback and complexity, distributed waterflood project has also been proposed in prior art, wherein, power is distributed based on the Signal to Interference plus Noise Ratio (Signal-to-Interference plus Noise Ratio, SINR) that the user receives in each base station.But this scheme is in interference-limited system, and for example, in 3GPP LTE system, performance is unsatisfactory, because should the adjustment scheme not consider that the power adjustment was disturbed the impact of residential quarter on common channel.The method might be brought following result, because cell power increases, the interference of neighbor cell is also strengthened, thereby total cell data rate does not improve.

Summary of the invention

According to a first aspect of the invention, a kind of transmission parameter regulation means that is used for carrying out down link self adaption in the base station of cordless communication network is provided, has comprised the following steps: need to have judged whether the downlink user through-put power density on the downlink data shared channel of calculating book base station; When needs calculate described downlink user through-put power density, according to the interference to neighbor cell of the Signal to Interference plus Noise Ratio between this base station and this base station jurisdiction user terminal, this base station, determine the downlink user through-put power density on the downlink data shared channel of described this base station.

Adopt the solution of the present invention, through-put power density and modulation coding mode (Modulation and Coding Scheme in the PDSCH configuration, MCS) can automatically be upgraded to improve the performance of system and the utilization ratio of resource in the mode of intelligence by each base station, only need to transmit limited signaling consumption by X2 interface between the macro base station pico base station adjacent with it.In addition, the present invention also is not limited to the scene of HetNet, and it also can be used for only comprising the scene of macro base station.

Description of drawings

Read following detailed description to non-limiting example by the reference accompanying drawing, further feature of the present invention, purpose and advantage will be more obvious.

Fig. 1 shows the network topology structure of example and disturbs the schematic diagram of scene;

Fig. 2 shows the systems approach flow chart according to a specific embodiment of the present invention;

Fig. 3 shows the analogous diagram according to the cumulative distribution function of the throughput of a specific embodiment of the present invention.

Wherein, same or analogous Reference numeral represents same or analogous steps characteristic or device/module.

Embodiment

In order to tackle the problems referred to above, the present invention proposes a kind of adaptive link parameter and adjust mode, the solution of the present invention optimally based on channel circumstance with to the disturbed condition of serviced user terminal, is adjusted the transmission link parameter, comprises through-put power, modulation and coded system (MCS).In the present invention, at first the base station is that all serviced user terminals are preserved main interference source base station separately, and corresponding path gain.Then, after base station measurement and reporting channel quality information, user terminal will based on the theory of games rule, upgrade relevant power density functions when user terminal.This new power density functions will be used to follow-up PDSCH (Physical Downlink Shared Channel, Physical Downlink Shared Channel) to the transmission of this user terminal.

At first, optimum power division will be calculated.Table one shows the implication of the symbol that uses.

Table one

In order to realize distributed method, used game theoretic design here.Can form a kind of game G=[N of non-cooperation, { P ⁿ* A ⁿ, { u _n], (1)

Wherein, N={1,2 ..., N} is the player of this game, is the base station in this example, { P ⁿ* A ⁿThe policy space of each base station, u _nIt is utility function.

Then, should can be formulated as for the Noncooperative game of power division:

$\underset{p^n\∈P^n}{\max }{u}_n(p^n,P^{-n},A^n),\mathrm{for\; all\; n}\∈N---\left(2\right)$

For in the n of base station, be scheduled in the user k on Physical Resource Block m, its attainable SINR (Signal to Interference plus Noise Ratio) can be calculated as

${\mathrm{\γ}}_{m,k}^n\left(P\right)=\frac{G_{m,k}^n{p}_m^n}{\underset{l=1,l\≠n}{\overset{N}{\mathrm{\Σ}}}{G}_{m,k}^l{p}_m^l+{\mathrm{\σ}}^2}---\left(3\right)$

Then, attainable data transfer rate can be calculated as

$R_{m,k}^n\left(P\right)=\frac{B}{M}\·\log (1+\frac{{\mathrm{\γ}}_{m,k}^n\left(P\right)}{\mathrm{\Γ}})---\left(4\right)$

Total attainable data transfer rate of user k is

$R_k(P,A^n)=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{a}_{m,k}^n{R}_{m,k}^n\left(P\right)---\left(5\right)$

In this case, the target of power distribution method is maximum system throughput and minimizes interference to other users, therefore, utility function (utility function) u can be set _nFor

$u_n(P,A^n)=\underset{k\∈U_n}{\mathrm{\Σ}}{\mathrm{\μ}}_k{R}_k(P,A^n)-\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{c}_m^n{p}_m^n---\left(6\right)$

Wherein,

Represent that power adjustments is subjected to the impact of common-channel interference UE to other, larger

Mean and be subjected to common-channel interference UE to the sensitivity more of the power adjustments on this Resource Block.

The through-put power vector that can maximize this utility function in policy space is called as by the selected optimal response to the through-put power vector in other base stations.Make r _n(P ^-n) represent that base station n is to given interference power vector P ^-nOptimal response.In formal expression, optimal response is corresponding r _n: P ^-n→ p ⁿ

Theoretical according to optimal response, the Nash Equilibrium on the power division problem can obtain by using Lagrangian method.Therefore, the optimal response of base station n on Resource Block m is

${\left[r_n\left(P^{-n}\right)\right]}_m={[\frac{B{\mathrm{\μ}}_{k_m^{*n}}}{c_m^{n}M\ln 2}-\frac{\mathrm{\Γ}(\underset{l=1,l\≠n}{\overset{N}{\mathrm{\Σ}}}{G}_{{\mathrm{mk}}_m^{*n}}^l{p}_m^l+{\mathrm{\σ}}^2)}{G_{{\mathrm{mk}}_m^{*n}}^n}]}^{+}---\left(7\right)$

Below, we will illustrate as an example of typical scene example implementation of the present invention.This scene has been disposed 2 pico base stations as shown in Figure 1 in each macrocell.At first, suppose that the number of residential quarter is N, comprise macrocell and pico residential quarter.Then, the number of serviced user terminal is expressed as K in each residential quarter _i(i=1,2 ..., N).Wherein, straight line represents to wish signal, and dotted line represents to disturb.Fig. 2 shows the systems approach flow chart according to a specific embodiment of the present invention.Wherein, this base station (eNB) comprises macro cell base station, also comprises the pico cell base station.

At first, in step S21, initialization is carried out in the base station

A) for each user terminal, its serving BS is preserved group of base stations, and this group of base stations comprises the main interference source for this user terminal, also,

IS _n，k＝{eNB _i|eNodeB i is the interference source for UE k in cell n} (a)

This information can and be upgraded by the adjacent R SRP report acquisition in the RRC signaling.In addition, according to the information of base station's transmission power, we can obtain the corresponding path gain between user terminal and their main interference source, and this gain can be expressed as:

G _n，k＝{g _i|eNodeB i is the interference source for UE k in cell n} (b)

Above-mentioned information is used for each base station after calculating new power density, recomputates Signal to Interference plus Noise Ratio, and upgrades link parameter and set as code modulation mode.

B) for each user terminal, its serving BS also can be safeguarded two variablees relevant to power information, and this can be expressed as＜c variable, PD 〉, wherein, c represents that this through-put power density meter is shown PD for the variable of the through-put power density of calculating this user terminal.When user terminal entered the RRC-connection mode, c was initialized to 0, PD and is initialized to the identical value with CRS (cell-specific reference signal, cell specific reference signal).

Then, in running, in step S22, UE informs serving BS with its channel quality.

Then, in step S23, this base station will upgrade be used for this UE a pair of＜c, PD 〉, as follows:

A) variable c will upgrade according to following formula

Definition ${\mathrm{SINR}}_{\mathrm{eff}}=\frac{\mathrm{PD}\×g_s}{\mathrm{PD}\left(\mathrm{CRS}\right)}\×\mathrm{SINR}\left(\mathrm{org}\right)$

And c (new)=min (max (c (new), c _min), c _max)

Wherein, Δ _cBe one greater than 1 constant.PD (CRS) is the power density of using on CRS.SINR (org) is that UE measures the channel quality of reporting based on CRS.g _sIt is the path gain between UE and serving BS.The cost coefficient that once calculates before c (old) expression; The cost coefficient that c (new) expression is upgraded.

The new value c (new) of above-mentioned c adopts fuzzy logic algorithm (fuzzy rule) to draw.More generally, fuzzy logic algorithm can be expressed as following table two:

Table two

Wherein, the power of the every bit of each Resource Block is relevant to SINR, and wherein the increase of cost coefficient or reduction have represented the variation tendency of cost coefficient.

B) use new c, the base station can judge need to recomputate PD, thereby according to new c, downlink user transmission (Tx) power density PD (new) that the base station can make new advances, also namely, expression is for the downlink transmission power of the base station of unique user terminal, and is as follows

$\mathrm{PD}\left(\mathrm{new}\right)={[\frac{\mathrm{RB\; Bandwidth}}{c\×\ln 2}-\frac{\mathrm{PD}\left(\mathrm{CRS}\right)}{\mathrm{SINR}\left(\mathrm{org}\right)}]}^{+}$

C) newer downlink user transmission (Tx) power density PD (new) and front old transmission (Tx) the power density PD (old) that once calculates in base station, if | PD (new)-PD (old) | 〉=Δ _Threshold, in step S24, the base station will be triggered RRC and be reshuffled the signalling process, and UE will use this new Tx power density, i.e. PD=PD (new) to the follow-up transmission of this UE with notice.Otherwise, PD=PD (old).Wherein, this Δ _ThresholdIt is the first predetermined threshold.The power density of all calculating is all to use for the later data frame transfer of several ms, old through-put power density, the through-put power density that once calculates before being also, can be understood as the through-put power density for the former frame data setting, can be also in the enterprising row iteration of same frame on the result that obtains of iteration once.

Alternatively, if | PD (new)-PD (old) | 〉=Δ _Threshold, in step S24, the E-PDCCH channel also can be used in the base station, and the power density PD that this is new (new) notifies to user terminal, to substitute the RRC signaling.

Alternately, the base station also can comprise the difference between PD (new) and PD (old) in RRC signaling or E-PDCCH channel information, to substitute the absolute value of PD (new).

In addition, in step S25, the average T x power density of UE of its service for all will be calculated in each base station

${\mathrm{PD}}_{\mathrm{average}}=\frac{\underset{j=1}{\overset{K_i}{\mathrm{\Σ}}}{\mathrm{PD}}_j}{K_i}$

And, the downlink user through-put power density average value P D that the base station is newer _Average(new) with the front old downlink user through-put power density average value P D that once calculates _Average(old) difference

Δ _PD＝PD _average(new)-PD _average(old)

If | Δ _PD| 〉=Ψ _Threshold, in step S26, the base station will be by the x2 interface with this difference DELTA _PDNotify its adjacent base station.Herein, Ψ _ThresholdIt is the second predetermined threshold.It will be understood by those skilled in the art that the first predetermined threshold delta _ThresholdWith the second predetermined threshold Ψ _ThresholdCan be identical, also can be set to different values.The concrete value of above-mentioned threshold value relates to the specific implementation problem, does not repeat them here.

Then, in step S27, in each subframe, serving BS is after the average T x power density of having collected from adjacent base station, the channel quality that serving BS can be reported based on the user terminal of being served by this base station of before having received is this user terminal predicted channel quality.For example, the channel quality of UE j can upgrade as follows

$\mathrm{SINR}\left(\mathrm{org}\right)=\frac{\mathrm{PD}\left(\mathrm{CRS}\right)\×g_s}{I\left(\mathrm{old}\right)+{\mathrm{\δ}}^2}\→I\left(\mathrm{old}\right)=\frac{\mathrm{PD}\left(\mathrm{CRS}\right)\×g_s}{\mathrm{SINR}\left(\mathrm{org}\right)}-{\mathrm{\δ}}^2$

$\mathrm{SINR}\left(\mathrm{new}\right)=\frac{\mathrm{PD}\left(\mathrm{new}\right)\×g_s}{I\left(\mathrm{old}\right)+\underset{i\∈{\mathrm{IS}}_{k,n}}{\mathrm{\Σ}}({\mathrm{\Δ}}_{\mathrm{PD}}\left(i\right)\×g\left(i\right))+{\mathrm{\δ}}^2}$

Wherein, SINR (old) be the last UE based on the channel quality of CRS measurement report, and g _sBe the path gain between UE and serving BS, I represents the interference of main interference source.

(4) MCS upgrades

Then, in step S28, the SINR that upgrades is used in the base station, according to new Tx power density and disturbance regime, resets modulation and coded system (Modulation and Coding Scheme, MCS).

Simulation result

Below, we compare the performance of the present invention and traditional impartial power distribution method (as benchmark).Here we illustrate the example that a MeNB (macro base station) under 3GPP LTE-A heterogeneous network framework adds Pico (small-cell) deployment.Detailed simulation parameter is listed in following table three.UE received power descending according to the best is linked into MeNB or PeNB.Except transfer of data, HARQ retransmits also and is considered in Performance Evaluation.For fear of the significantly variation of Tx power density, we have defined the effective range that is used for the PD value, i.e. [PD _L, PD _H], wherein, And PD _H=2 * PD _CRS

Fig. 3 shows corresponding to baseline and C.D.F. (Cumulative Distribution Function, cumulative distribution function) curve of the present invention, the UE receiving data rate.Table four has been described the comparison of user's receiving data rate of the 5%-ile in Fig. 3 (cell edge) and average (the UE residential quarter is average).Can find out from simulation result, the present invention for cell edge and average UE receiving data rate respectively than benchmark high 6.35% and 17.66%.

Table three

Table four

Wherein, ile is the abbreviation of Percentile, and the meaning of 5%-ile is 5% point in figure.

Above embodiments of the invention are described, but the present invention is not limited to specific system, equipment and concrete agreement, those skilled in that art can make various distortion or modification within the scope of the appended claims.

The those skilled in the art of those the art can be by research specification, disclosed content and accompanying drawing and appending claims, understanding and enforcement other changes to the execution mode of disclosure.In the claims, word " comprises " element and the step of not getting rid of other, and wording " one " is not got rid of plural number.In the present invention, " first ", " second " only represent title, do not represent orbution.In the practical application of invention, the function of a plurality of technical characterictics of quoting during a part possibility enforcement of rights requires.Any Reference numeral in claim should not be construed as the restriction to scope.

Claims (13)

1. method that is used for carrying out down link self adaption in the base station of cordless communication network comprises the following steps:

A. need to judge whether the downlink user through-put power density on the downlink data shared channel of calculating book base station;

B. when needs calculate described downlink user through-put power density, according to the interference to neighbor cell of the Signal to Interference plus Noise Ratio between this base station and this base station jurisdiction user terminal, this base station, determine the downlink user through-put power density on the downlink data shared channel of described this base station.

2. method according to claim 1 wherein, also comprises before described steps A:

The main interference source base station of the described user terminal of-initialization and corresponding path gain, and the initial downlink user through-put power density of initialization initial cost coefficient and described base station.

3. method according to claim 1, wherein, described steps A also comprises:

When the channel quality indication that gets by the report of described user terminal, need to determine the downlink user through-put power density on the downlink data shared channel of calculating book base station.

4. method according to claim 3, wherein, described step B also comprises:

B1. according to described channel quality indication and the front cost coefficient that once calculates, calculate the cost coefficient that upgrades, to obtain this base station to the interference of neighbor cell;

B2. according to the cost coefficient of described renewal and the described initial downlink user through-put power density of described base station, calculate the downlink user through-put power density on described downlink data shared channel.

5. method according to claim 4, wherein, described step B 1 also comprises:

-according to the variation tendency of Signal to Interference plus Noise Ratio and the trend of downlink user through-put power variable density, in conjunction with fuzzy logic algorithm, estimate the variation tendency of described cost coefficient, and according to the variation tendency of described cost coefficient and described before the cost coefficient that once calculates upgrade cost coefficient.

6. method according to claim 1, wherein, described steps A also comprises:

When the triggering signaling that gets from neighbor cell, this triggers signaling and is used for triggering when calculating downlink user through-put power density, need to determine the average downlink user through-put power density on the downlink data shared channel of calculating book base station.

7. method according to claim 6, wherein, described triggering signaling comprises the average downlink user through-put power density of the current calculating of this neighbor cell and the difference of the front average downlink user through-put power density of once calculating.

8. method according to claim 6, wherein, described step B also comprises:

-according to the variation tendency of Signal to Interference plus Noise Ratio and the trend of downlink user through-put power variable density, in conjunction with fuzzy logic algorithm, estimate the variation tendency of described cost coefficient, and according to the variation tendency of described cost coefficient and described before the cost coefficient that once calculates upgrade cost coefficient.

9. method according to claim 1 wherein, also comprises after described step B:

C. whether the difference of the downlink user through-put power density on the current downlink user through-put power density on the downlink data shared channel of more described this base station and the front downlink data shared channel that once calculates is greater than the first predetermined threshold;

D. when described difference during greater than described the first predetermined threshold, to described user terminal notify described current downlink user through-put power density value or and described before difference between the value once calculated.

10. method according to claim 9, wherein, described step D realizes by following any mode:

-with radio resource control signaling to described user terminal notify described current downlink user through-put power density or and described before difference between the value once calculated; Or

-notify to described user terminal on the Physical Downlink Control Channel that strengthens described current downlink user through-put power density or and described before difference between the value once calculated.

11. method according to claim 1 wherein, also comprises after described step B:

C. whether the difference of the downlink user through-put power density on the current downlink user through-put power density on the downlink data shared channel of more described this base station and the front downlink data shared channel that once calculates is greater than the second predetermined threshold;

D. during greater than described the second predetermined threshold, notify described current downlink user through-put power density difference to adjacent base station when described difference.

12. method according to claim 11, wherein, described step D realizes in the following manner:

-notify described difference with X2 interface message to described adjacent base station.

13. method according to claim 1 wherein, also comprises after described step B:

-according to described downlink user through-put power density, determine corresponding modulation coding mode.

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