CN1589053A - Relay selecting and power distribution method for double bounce honeycomb system - Google Patents

Abstract

The invention discloses a relay selection and power allocation method for a two-hop cellular system, comprising the steps of: setting a plurality of relay stations in the cellular system according to the requirements of network planning; initializing the working parameters of these relay stations, And obtain the path information from the base station to each relay station; according to the user information and combined with the working parameters of the relay station, measure the path loss from the base station to each relay station and from each relay station to each user; use the measured path loss to select for each user Make the relay station whose sum of the two-hop path loss is the smallest as its serving relay station; detect the multi-cell system interference of its communication link when the user uses the relay station whose sum of the two-hop path loss is the smallest as its serving relay station; based on the selected The serving relay station and the detected multi-cell system interference use an adaptive power allocation method to set the power of the signal sending end and the selected serving relay station.

Description

A kind of relay selection and power distribution method that is used for the two-hop cellular system

Technical field

The present invention relates to a kind of relay selection and power distribution method that is applicable to the two-hop cellular system.

Background technology

Future broadband wireless communication systems will be devoted to develop higher rate, the more multiple business of great dynamic range, enlarge network coverage area simultaneously, improves spectrum efficiency and strengthen the robustness of system.In the non-relay system of cellular network, power division is only finished at signal sending end, by the detection to channel information, can finish the self adaptation adjustment of information source end transmitting power, satisfies service quality (QoS) index of different user.Because the communication of the non-relay system of cellular network directly builds between base station (BS) and the user, the problem that does not exist relay station (RS) to select correspondingly also just need not and be transmitted between the RS and carry out adaptive power division at signal sending end.

In existing wireless cellular network, use " relaying " strategy, utilize the relay transmission of RS, can overcome the fading characteristic of wireless channel, introduce diversity gain, improve the covering and the capacity of wireless network, guarantee the QoS of variety classes business simultaneously better, strengthen every performance of wireless system.In the two-hop cellular relay system, because the introducing of RS, need in the RS of some, select communicating by letter between suitable service RS support BS and the user on the one hand; Owing to the restriction of transmitting power and the demand of user QoS, network also will be adjusted the power division ratio adaptively according to the decline and the interfere information of current system between signal sending end and RS on the other hand.Like this, selection of relay stations and adaptive power assignment problem just become research contents important in the relay system.

Select the service RS can be based on path loss (PL), also can be based on signal interference ratio (SIR).RS selection algorithm based on SIR can be under same power condition, for the user provides better communication quality, but because the time variation of network interferences and this algorithm are to transmit power allocations result's dependence, its algorithm complex is higher, and need a large amount of mutual of network signal, can the emphasis network load.

For power distribution algorithm, generally be divided into adaptive power and distribute (OPA) and average power allocation (UPA).When adopting the UPA algorithm, the transmitting power of signal sending end and service RS equates.Though the UPA algorithm is simple relatively,, lacks adaptivity, thereby greatly reduced usage factor of system resource system because algorithm itself is not considered user's each opposite sex in network.

In addition, because relay station is selected and power distribution algorithm generally is an independent studies, so do not consider mutual coordination and optimization between the algorithm.At different relay station selection strategy and power distribution algorithms, can carry out joint study to its combination, in the optimization system performance, reduce design cost as much as possible, obtain perfect performance cost ratio.Angle from theory analysis, adaptive power based on SIR distributes (SIR_OPA) can obtain maximized instantaneous channel capacity, but, it calculates because introducing a large amount of power division in the selection course of RS, increased the complexity of computing greatly, increased the weight of the network signal load, thereby realizability is lower.And other algorithms as based on the average power allocation algorithm (PL_UPA) of PL with based on the average power allocation algorithm (SIR_UPA) of SIR, owing to divide equally power, can not adaptively satisfy user's business demand, thereby resource utilization ratio are lower.

Therefore, design a kind of new method that relay station is selected and adaptive power distributes, as far as possible rationally, effectively utilize limited system resource, the optimization system configuration, improve transmission rate, communication quality and network capacity, become a right basic problem of two-hop cellular relay system demand side.

Summary of the invention

Demand and problems of the prior art at network development, the present invention proposes a kind of method that relay station is selected and adaptive power distributes that is applicable to the two-hop cellular relay system, when guaranteeing transmission quality, obtained higher transmission rate, improved resource utilization, and greatly reduce algorithm complex and network signal load, performance cost has stronger practicality than high.

According to the present invention, a kind of relay selection and power distribution method that is used for the two-hop cellular system is provided, comprise step:

(1) according to the requirement of the network planning, a plurality of relay stations is set in described cellular system;

(2) running parameter to these relay stations carries out initialization, and obtains the routing information of base station to each relay station;

(3), measure the path loss of base station to each relay station and each relay station to each user according to user profile and in conjunction with the running parameter of relay station;

(4) utilize measured path loss, for each user select to make its double bounce path loss sum for minimum relay station as its service relay stations;

(5) detect the multi-cell system interference that described user is the relay station of minimum its communication link during as its service relay stations with double bounce path loss sum;

(6) disturb based on selected service relay stations and detected multi-cell system, utilize the adaptive power distribution method to come the power of setting signal transmitting terminal and selected service relay stations.

In the present invention, by uniting with path loss is the relay station selection strategy of foundation and adaptive power allocative decision corresponding to different RS types, not only obtain the higher system capacity, improved transmission quality, and the implementation complexity and the network signal that greatly reduce algorithm are loaded, by adopting adaptive power to distribute, make finite wireless resources obtain effective utilization simultaneously.

Description of drawings

Further describe the present invention with reference to the accompanying drawings and in conjunction with the embodiments.Wherein:

Fig. 1 shows and realizes that relay station of the present invention is selected and the block diagram of adaptive power distribution method;

Fig. 2 show according to associating relay station of the present invention select and adaptive power allocation algorithm (PL_OPA) and other three kinds of related algorithms (SIR_OPA, SIR_UPA is PL_UPA) with the channel capacity performance curve of RRS number of variations in the system;

Fig. 3 show according to associating relay station of the present invention select and adaptive power allocation algorithm (PL_OPA) and other three kinds of related algorithms (SIR_OPA, SIR_UPA is PL_UPA) with the channel capacity performance curve of NRRS number of variations in the system.

Embodiment

Describing relay station of the present invention below in conjunction with Fig. 1 selects and the adaptive power distribution method.

The first step according to the requirement of the network planning, is a Master Control Center with the base station in cellular system, and N relay station (RS) is set in its service area, these relay stations be positioned at described base station around, and the relay station of this sub-district is served the user who is connected to this sub-district.

According to the processing mode difference of relay station for received signal, be divided into regenerative relay station (RRS) and non-regenerative relaying station (NRRS), wherein RRS carries out transmitting behind the decoding and reconstituting for received signal again, and NRRS transmits after amplifying for received signal again.

Second step, add up the essential information such as position, working method, Power Limitation of these RS, and the initiation parameter of these RS is sent to the network control center, for its configuration information tabulation, can obtain the routing information of BS by the network control center to each RS by this table.

In the 3rd step, obtain the current relevant information U={U that needs M user of service _m, 1≤m≤M} comprises customer location, business demand, and power condition etc. after the parameter of contrast RS, measure BS to each RS, and each RS are to each user's path loss values.Like this, system need set up communication service for M user, and each user is corresponding to N information on path loss L={L _Mn, 1≤m≤M, 1≤n≤N}, here, L _MnDouble bounce path loss sum when to be m user by n RS link to each other with this cell base station.

In addition, measured path loss values except signal the propagation loss of free space, also considered to comprise the various factors that signal is influenced to some extent that exist in the radio transmission processes such as antenna gain, multipath fading and shadow fading.

The 4th step, utilize the path loss measurement result, to m user, select to make the RS of its double bounce path loss sum minimum, $n_m^{\mathrm{PL}}=\arg \underset{\mathrm{al}\ln \∈N}{\min }\left(L_{\mathrm{mn}}\right)),$ As its service RS, i.e. n _m ^PLBe m user's selecting according to the minimal path loss service RS.Here be example only, but other all usefulness adopt identical processing mode per family with m user.

In the 5th step, on the basis of RS selection result, detect m user with n _m ^PLThe multi-cell system of two-hop link disturbs during for service RS.Wherein first jump to disturb co-channel signal transmitting terminal from other sub-districts to n _m ^PLInterference, second jump to disturb the interference to the signal receiving end of supporting m user from the cochannel RS of other sub-districts; If this signal receiving end is also handled direct signal from this subscriber signal transmitting terminal, except above-mentioned two-hop link, interferometry also comprises from the interference of the corresponding co-channel signal transmitting terminal in other sub-districts to the path that direct transfers of m user's signal receiving end so.

The 6th the step, obtain the said system interfere information after, at n _m ^PLType, promptly be RRS or NRRS, it is that the adaptive power of optimizing criterion distributes that m user's communications link carried out with the channel capacity, finishes the power setting that comprises signal sending end and RS.

If RRS, as majorized function, then power distribution result is with channel capacity:

Wherein $a_i=\frac{L_i}{{\mathrm{\σ}}_i^2+I_i}>0(i=\mathrm{0,1,2}),$ L _iBe the path loss that i jumps, σ _i ²Be the noise power that i jumps, I _iBe that i jumps the interference that is subjected to.Here, first jumping refers to signal sending end to RS, and second jumping refers to RS to signal receiving end, and the DCL between BS and user is jumped with the 0th and represented.After finishing power division, the power setting of signal sending end is P ₁, the power setting of service RS is P ₂, the two satisfies Power Limitation P ₁+ P ₂=P ₀, P ₀Transmission power limit decision by signal sending end and service RS.

If NRRS, equally with channel capacity as majorized function, then power distribution result is:

Wherein

Here, all the situation with RRS is consistent for the implication of each parameter and measurement, P ₀Set according to the network design needs too.

Above power distribution result has certain restrictive condition, is a for RRS ₁＞a ₀And a ₂＞a ₀, for NRRS be This is to transmit trigger condition by the relaying of RS itself to cause.If this condition does not satisfy, will adopt directly transmission so, i.e. direct communication between BS and the user is because user's the link-quality that direct transfers can be with the QoS that guarantees that it is professional at this moment.

Fig. 2 shows scheme for combining PL_OPA of the present invention and theoretical optimization algorithm SIR_OPA, and other two kinds of related algorithm SIR_UPA and PL_UPA be with the channel capacity performance curve of RRS number of variations in the system, and this emulation is based on the TDMA cellular system.The channel capacity here refer to unit bandwidth, transmission per unit of time amount of information (unit: bps/Hz), i.e. spectrum efficiency.If system transmission bandwidth is B, according to Shannon capacity formula C/B=log ₂(1+SIR), can obtain m the corresponding channel capacity C/B of user, this capacity is the maximum channel capacity after transistroute is selected.

With m user is example, counts this user's sir value according to power distribution result, just can obtain corresponding channel capacity.Both handled signal from service RS when this user's signal receiving end, when handling directly the signal from signal sending end again, corresponding to the service RS of RRS, user's SIR is:

${\mathrm{SIR}}_m^{\mathrm{RRS}}=a_0{P}_1+a_2{P}_2=\frac{a_1{a}_2{P}_0}{a_1+a_2-a_0}.$

If service RS is NRRS, then user's SIR is:

${\mathrm{SIR}}_m^{\mathrm{NRRS}}=\frac{a_1{a}_2{P}_1{P}_2}{a_1{P}_1+a_2{P}_2+1}+a_0{P}_1$

$={\left[\frac{a_1{a}_2{P}_0+a_2{a}_0{P}_0+a_0}{\sqrt{a_1{a}_2(a_1{P}_0+1)}+\sqrt{(a_1{a}_2+a_2{a}_0-a_1{a}_0)(a_2{P}_0+1)}}\right]}^2.$

As can be seen from Figure 2, though the RS number constantly changes in the system, scheme for combining PL_OPA of the present invention is better than SIR_UPA and PL_UPA algorithm all the time on performance, near theoretical optimal algorithm SIR_OPA.Fig. 3 has provided the situation when RS is NRRS, and this moment, scheme for combining PL_OPA of the present invention as can be seen still was only second to theoretical optimal algorithm SIR_OPA on performance.

Table 1 shows according to associating relay station of the present invention and selects and adaptive power allocation algorithm (PL_OPA) and other three kinds of related algorithms (SIR_OPA, SIR_UPA, Signalling exchange amount PL_UPA) and the contrast of algorithm complex statistics.Weigh the superiority of an algorithm, should be from its performance cost than assessing.Therefore, on the basis of channel capacity, also adopt Signalling exchange amount (needing to measure the also number of links of feedback channel information) and algorithm complex (number of times that rated output distributes) as performance index.

Table 1

Algorithm PL_OPA SIR_OPA SIR_UPA PL_UPA

Signalling exchange amount N+2 N * 2+1 N * 2+1 N+2

Algorithm complex 1 N N 1

In table 1, N is the number of RS in the system.The Signalling exchange amount measures with needs and the number of links of feedback channel information is an evaluation criteria, and algorithm complex is an evaluation criteria with the number of times that rated output distributes.

For scheme for combining PL_OPA of the present invention, because there is the information of each RS in the network control center, and the present invention program is carrying out only needing information on path loss when RS selects, do not need interference statistics, therefore carrying out RS when selecting, needing to measure and what feed back to system is channel information between user and N RS; Behind the selected service RS,, also need to add up between user and the BS for realizing power division, and this user's double bounce interfere information, wherein the link between user and the service RS only need feed back once.So the Signalling exchange amount of scheme for combining of the present invention is N+2.And for theoretical optimal algorithm SIR_OPA, because its RS selects based on SIR, so the algorithm realization depends on user and all RS links, and the interferometry of all RS and BS link statistics, therefore the Signalling exchange amount is N * 2+1, and wherein " 1 " is meant the link information between user and BS.Similarly, can obtain the Signalling exchange amount of other two kinds of algorithm SIR_UPA and PL_UPA, as shown in table 1.

From algorithm complex, mainly be the number of times that adopts the adaptive power Distribution Calculation.For scheme for combining of the present invention, because power division is to finish on the basis of RS selection result, so only need an adaptive power Distribution Calculation to finish.For theoretical optimal algorithm SIR_OPA, the power division that needs before its RS selects N RS simulated is calculated, and just can choose RS that the highest SIR is provided then as serving RS, so its algorithm complex is N.Same, table 1 has also been listed the complexity statistics of other two kinds of algorithms.The data that comparison sheet 1 is listed, in conjunction with above-mentioned analysis as can be known, the performance advantage of SIR_OPA depends on a large amount of Signalling exchanges and complicated calculations, and scheme for combining of the present invention greatly reduces the complexity of mutual amount of network signal and optimized Algorithm, is convenient to realize.

It is to be noted, though emulation at be tdma system, but, therefore during the cellular system under being applied to other working methods, still can embody the present invention program's superiority because algorithm and formula itself that scheme for combining of the present invention adopts have certain generality.

Cross plot as seen, scheme for combining PL_OPA of the present invention not only makes system obtain higher channel capacity (near theoretical optimal algorithm SIR_OPA), improved transmission quality, and the implementation complexity and the network signal that greatly reduce algorithm are loaded, by adopting adaptive power to distribute, make finite wireless resources obtain effective utilization simultaneously.

Although the present invention has been described with reference to preferred embodiment, those skilled in the art can make various modifications and replacement to the present invention by reference specification embodiment and accompanying drawing, and can not deviate from the spirit and scope of the present invention.Therefore these modifications and replacement all should fall within protection scope of the present invention.

Claims (8)

1. A relay selection and power distribution method for a two-hop cellular system, comprising steps: (1) According to the requirements of network planning, a plurality of relay stations are set in the cellular system; (2) Initialize the working parameters of these relay stations, and obtain the path information from the base station to each relay station; (3) Measure the path loss from the base station to each relay station and from each relay station to each user according to the user information and in combination with the operating parameters of the relay station; (4) Utilizing the measured path loss, for each user, select the relay station whose sum of the two-hop path losses is the minimum as its serving relay station; (5) detecting the multi-cell system interference of the user's communication link when the relay station whose sum of the two-hop path losses is the smallest is used as the serving relay station; (6) Based on the selected serving relay station and the detected multi-cell system interference, an adaptive power allocation method is used to set the power of the signal transmitting end and the selected serving relay station. 2. The method according to claim 1, wherein the relay station set in step (1) takes the base station as the main control center and is located around the base station, and the relay station of this cell serves the users connected to this cell. 3. The method according to claim 1, wherein the relay station includes a regenerative relay station and a non-regenerative relay station, wherein the regenerative relay station decodes and reconstructs the received signal before retransmitting, and the non-regenerative relay station performs retransmission on the received signal Repost after zooming in. 4. The method according to claim 1, wherein the operating parameters of the relay station include the position of the relay station, the mode of operation, and the power limit, and step (2) further includes the step of transmitting the initialization parameters of the relay station to the network control center. 5. The method according to claim 1, wherein the multi-cell system interference detected in step (5) includes first-hop interference and second-hop interference, and the first-hop interference comes from co-channel signal transmission of other cells The terminal interferes with the selected serving relay station, and the second-hop interference comes from the interference of co-channel relay stations of other cells to the signal receiving terminal supporting the user. 6. The method according to claim 1, wherein if the signal receiving end also processes signals directly from the signal transmitting end of the user, the multi-cell system interference measured in step (5) also includes signals from other cells Corresponding co-channel signal transmitting end interferes with the direct transmission path of the user's signal receiving end. 7. The method according to claim 1, wherein in step (6), when the selected serving relay station is a regenerative relay station, the power P ₁ of the signal transmitting end and the power P ₂ of the selected serving relay station are set by the following formula :

a ₁ >a ₀ and a ₂ >a ₀ in $a_i=\frac{L_i}{{\mathrm{\σ}}_i^2+I_i}>0(i=\mathrm{0,1,2}),$ L _i is the path loss of the i-th hop, σ _i ² is the noise power of the i-th hop, I _i is the interference received by the i-th hop, "i=0" means the communication path between the user signal sending end and the signal receiving end , Moreover, the power limit P ₁ +P ₂ =P ₀ is satisfied, and P ₀ is determined by the transmit power limit of the signal sending end and the serving relay station. 8. The method according to claim 1, wherein in step (6), when the selected serving relay station is a non-regenerative relay station, the power _P of the signal transmitting end and the power P of the selected serving relay station are set by the following formula ₂ : in in $a_i=\frac{L_i}{{\mathrm{\σ}}_i^2+I_i}>0(i=\mathrm{0,1,2}),$ L _i is the path loss of the i-th hop, σ _i ² is the noise power of the i-th hop, I _i is the interference received by the i-th hop, "i=0" means the communication path between the user signal sending end and the signal receiving end , Moreover, the power limit P ₁ +P ₂ =P ₀ is satisfied, and P ₀ is determined by the transmit power limit of the signal sending end and the serving relay station.

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