CN103281170B - Resource allocation methods in local mapping formula single carrier-frequency division multiple access system - Google Patents

Abstract

The invention belongs to wireless communication technology field, be specifically related to the resource allocation methods in a kind of local mapping formula single carrier-frequency division multiple access system, comprise that base station obtains the up-to-date channel condition information between itself and each user, and call the transmitted data rates average of sub-channel assignment procedure in early stage after carrying out; Divide sub-band according to channel coherence bandwidth, be chosen at the user on sub-band with larger direct ratio fairness weights, and for they determine the original position of subchannel; Consider the subchannel adjacent limits of local single carrier frequency division multiple access, distribute to one by one user remaining subchannel, in every sub-distribution, taking maximize direct ratio fairness weights and increment as target, carry out the pairing of user and subchannel; Final updating user's transmitted data rates average, for distribute foundation be provided next time. The present invention takes into full account that subchannel distributes adjacent limits, and introduces the direct ratio fairness doctrine, compared with traditional algorithm, can promote the fairness between user, and improve the availability of frequency spectrum of system.

Description

Resource allocation methods in local mapping formula single carrier-frequency division multiple access system

Technical field

The invention belongs to wireless communication technology field, be specifically related in a kind of local mapping formula single carrier-frequency division multiple access systemResource allocation methods.

Background technology

Along with the fast development of society, people are more next for the bandwidth of wireless communication system and the requirement of data rateHigher. How in system of broadband wireless communication, to carry out efficient resource distribution, in improving system spectrum utilization rate, hold concurrentlyTurn round and look at the fairness between user, become the important subject of wireless communication field.

Single-carrier frequency division multiple access (singlecarrierfrequencydivisionmultipleaccess, SC-FDMA) be except OFDM (orthogonalfrequencydivisionmultipleaccess, OFDMA) itOuter a kind of multiple access technique that is applicable to wide-band mobile communication. SC-FDMA and OFDMA have similar overall performance andComputation complexity. But because SC-FDMA adopts single-carrier modulated, the power PAR of its transmitted signal is lower, therefore SC-FDMA is more suitable for being used to up-link. SC-FDMA is by third generation partner program-Long Term Evolution (3rd at presentGenerationPartnershipProject-LongTermEvolution, 3GPP-LTE) and LTE-AdvancedStandard is adopted as uplink multi-address access scheme.

Adopt the SC-FDMA system (singlecarrierlocalized of local formula channel mapping modeFrequencydivisionmultipleaccess, SC-LFDMA) multi-user diversity can be provided. But in this system,User can only be assigned with adjacent multiple subchannels (as shown in Figure 1), therefore obtains the complexity of this system resource allocation optimal solutionSpend very high. The optimal algorithm that the people such as I.C.Wong propose, taking maximum system throughput as target, divides original resourceJoin problem and be converted into set partitioning problem, and use for reference its related algorithm in operational research and obtain optimal solution (referring to document " I.C.Wong,O.Oteri,andW.McCoy.OptimalResourceAllocationinUplinkSC-FDMASystems[J],IEEETransactionsonWirelessCommunications.2009,8(5):2161-2165. ") although this algorithm has the very high availability of frequency spectrum, computation complexity is very high, and can not ensure to useFairness between family.

In order to ensure the fairness between user, the people such as S.-B.Lee propose direct ratio fair algorithm to be applied in SC-LFDMAIn system (referring to document " S.-B.Lee, I.Pefkianakis, A.Meyerson, S.Xu, S.Lu.ProportionalFairFrequency-DomainPacketSchedulingfor3GPPLTEUplink[C],ProceedingsofIEEEINFOCOM’09.RiodeJaneiro,Brazil:IEEEPress,2009:2611-2615 ". ) their exploratory algorithm of greediness of proposing to be to maximize the logarithmic utility function of systemFor orderMark, had both ensured throughput of system, considered again the fairness between user, but this algorithm was vulnerable to the shadow that frequency domain changes among a small circleRing, cannot reach the desirable availability of frequency spectrum. For the deficiency of above-mentioned algorithm, it is greedy that they propose again a kind of follow-on packet typeGreedy algorithm, its basic thought is that adjacent multiple subchannels are merged into subchannel grouping. But in this algorithm, subchannel groupingQuantity equal number of users, therefore, along with the increase of number of users, the performance of this algorithm moves closer to traditional greedy algorithm. AndBecause the length of subchannel grouping is fixed, therefore assigning process lacks flexibility.

Summary of the invention

The present invention is directed to prior art above shortcomings, provide the resource in a kind of SC-LFDMA system to divide formulaMethod, is ensureing that under the condition of direct ratio fairness, flexible and efficient ground allocated sub-channels, finally promotes the fairness between user, and carryThe availability of frequency spectrum of high system.

Resource allocation methods in SC-LFDMA system provided by the invention, concrete steps are as follows:

Step 1: base station obtains the up-to-date channel condition information between itself and each user, and call early stage subchannel and distributedTransmitted data rates average after Cheng Zhihang.

Described channel condition information is: user is to the channel gain of base station, wherein:Represent user's orderNumber,Represent user's set, M is total number of users,Represent subchannel sequence number,Represent available sets of sub-channels, K is subchannel sum.

Transmitted data rates average after described sub-channel assignment procedure in early stage is carried out refers to: hold by before this sub-distributionEach user's that the sub-channel assignment procedure of row obtains transmitted data rates average。

Step 2: sub-band is divided according to channel coherence bandwidth in base station, is chosen at and on sub-band, has the fair power of larger direct ratioHeavy user, and for they determine the original position of subchannel.

Described direct ratio fairness weights is:

Wherein,For the instantaneous transmission data rate of user m on subchannel k, can be expressed as:

Wherein, B is system transmission bandwidth,Represent the transmitting power of user m on subchannel k, N is every sub-channelsOn noise power.

Base station is Q the sub-band that size is identical according to channel coherence bandwidth W by whole frequency band division. Wherein

Wherein,Represent to be less than or equal to the maximum integer of real number x. Every sub-frequency bands comprisesIndividual adjacent sonChannel. If K is not the integral multiple of C, so remaining K-QC sub-channels will be retained, and distribute to user in step 3.

Calculate the direct ratio fairness weights of each user on each sub-band and, and they are stored in to oneSquareIn battle array V. The direct ratio fairness weights of user m on sub-band q and, in matrix the capable q of m row be, itsInFor the sets of sub-channels in sub-band q.

Find the maximum V in matrix V_ij, the direct ratio fairness weights of user i on sub-band j and be maximum. By sonFrequency band j and user i match, and then all items relevant with sub-band j to user i in matrix V are removed, by matrix VIn the item that lists of the item of i on capable and j replace with-1. Repeat above process until all users match (if) or all sub-bands match (if）。

After user and sub-band have matched, the subchannel of direct ratio fairness weights maximum in every sub-frequency bands is distributed to and joinedRight user, and in this sub-band, remaining C-1 sub-channels will be retained, and distribute to user in step 3.

By above process, base station be the individual user assignment with larger direct ratio fairness weights of min (M, Q) firstSubchannel, has determined these users' subchannel original position.

Step 3: consider the subchannel adjacent limits of SC-LFDMA, residue subchannel is distributed to user one by one. At every turnIn distribution, taking maximize direct ratio fairness weights and increment as target, carry out the pairing of user and subchannel.

First, for each user determines all assignable candidate sub-channel. Due in SC-LFDMA system, Mei GeyongFamily can only be assigned with adjacent multiple subchannels, therefore in the time that a user has been assigned with one or more subchannel, only have withThe subchannel that allocated sub-channels is adjacent can be assigned to this user. And for the user who is not assigned with subchannel, allThe subchannel not being assigned with can be distributed to this user.

Determine after each user's candidate sub-channel, calculate that system is being just after candidate sub-channel k is assigned to respective user mThan fairness weights and increment,

Wherein,Represent to have distributed to the sets of sub-channels of user m.

In all possible distribution, obtain user and the subchannel pairing of weight limit and incrementWin thisDistribution once, by subchannelDistribute to user。

Group channel allocation is complete, when all subchannels are all distributed to user, enters step 4, otherwise continues to divideGamete channel.

Step 4: upgrade user's transmitted data rates average, for distribute foundation is provided next time.

After this subchannel is assigned, should upgrade transmitted data rates average according to user's instantaneous transmission speed,That is:

Wherein,The transmitted data rates average that represents user m after upgrading, T represents to complete distribution number of times.

The present invention has realized the resource of SC-LFDMA system and has distributed. First divide sub-band according to channel coherence bandwidth, choosingBe taken at the user on sub-band with larger direct ratio fairness weights, and the original position of determining subchannel for them, be in advanceThese users have divided optimum range of distribution. In ensuing subchannel distributes, consider subchannel adjacent limits, and withLargeization direct ratio fairness weights and increment be target, carry out the pairing of user and subchannel. After subchannel distribution finishes, also needAccording to this allocation result, upgrade user's average transmission data rate, as the foundation of distributing next time.

The invention has the advantages that: in following GSM, the public affairs between the availability of frequency spectrum and the user of systemLevelling is indispensable, and the introducing of the direct ratio fairness doctrine can reach balance between the two well. The present invention proposes oneMethod, first divides sub-band according to channel coherence bandwidth, has avoided packet type greedy algorithm to cause because number of users increasesHydraulic performance decline. Then the original position of determining subchannel for having the user of larger direct ratio fairness weights is these use in advanceOptimum range of distribution has been divided at family, has reduced the impact that frequency domain changes among a small circle. Meanwhile, in sub-band, remaining subchannel willBe retained, make other users that are not assigned with also have an opportunity to obtain some resources, improved fairness between user and distributionFlexibility. This algorithm has lower computation complexity, ensureing under the prerequisite of the direct ratio fairness doctrine, has obviously improved systemThe availability of frequency spectrum.

Brief description of the drawings

Figure 1 shows that the subchannel adjacent limits schematic diagram of SC-LFDMA.

Figure 2 shows that in embodiments of the invention, adopt single sector uplink network model schematic diagram of SC-LFDMA technology.

Figure 3 shows that the schematic flow sheet of resource allocation methods of the present invention.

Figure 4 shows that SC-LFDMA system spectrum utilization rate schematic diagram.

Detailed description of the invention

Below embodiments of the invention are elaborated, the present embodiment carries out under taking technical solution of the present invention as prerequisiteImplement, provided detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following enforcementExample.

What as shown in Figure 2, this example adopted is single sector uplink network of a multi-user SC-LFDMA system. System bandWide is 5MHz, is divided into 48 sub-channels. User is evenly distributed in radius Wei250 meter community. User emission power is10mW, the power spectral density of additive white Gaussian noise is-160dBm/Hz.

Path loss index is 3.5, and the variance of shadow loss is 8dB. Small scale multipath channel has been modeled as 20 pathsTypical urban channel, as shown in table 1.

Table 1 typical urban channel model

This example is specifically realized by following steps:

Step 1: single sector uplink network of multi-user SC-LFDMA system as shown in Figure 2. Base station obtains itself and each userBetween up-to-date channel condition information, the instantaneous transmission data rate of user m on k sub-channels is:

Wherein, system transmission bandwidth B=5MHz, number of subchannels K=48,Represent the transmitting merit of user m on subchannel kRate, N is the noise power on every sub-channels. In the present embodiment, all sub-channel transmission merits of distributing to same userRate is identical, and each user's sub-channel transmission power sum equals the maximum transmitting power 10mW that allows of user.

Then the long-term transmitted data rates average of the user R of storage is called in base station_m, utilizeCalculateGo out the direct ratio fairness weights of user m on subchannel k.

Step 2: in this example according to coherence bandwidth empirical equation, whereinThe root mean square of channelTime delay expansion, the coherence bandwidth that can obtain urban channel is W=400kHz. In the present invention, do not limit the definition that uses otherMode is obtained above-mentioned coherence bandwidth. Base station is Q=12 the son frequency that size is identical according to coherence bandwidth by whole frequency band divisionBand, comprises C=4 adjacent subchannel in every sub-frequency bands.

Calculate the direct ratio fairness weights of each user on each sub-band and, and they are stored in to oneSquareIn battle array V, M is total number of users. The direct ratio fairness weights of user m on sub-band q and, in matrix the capable q of m row be, whereinFor the sets of sub-channels in sub-band q,。

Find the maximum V in matrix V_ij, it represent user i on sub-band j, have maximum direct ratio fairness weights and.Sub-band j and user i are matched, then all items relevant with sub-band j to user i in matrix V are removed, by squareThe item that in battle array V, the item of i on capable and j list replaces with-1. Repeat above process until all users have matched or instituteThere is sub-band to match.

After user and sub-band have matched, the subchannel of direct ratio fairness weights maximum in every sub-frequency bands is distributed to and joinedRight user, and in this sub-band, remaining 3 sub-channels will be retained, and distribute to user in step 3.

By above process, base station be have larger direct ratio fairness weights user assignment first subchannel, trueDetermine these users' subchannel original position, in advance for they have divided optimum range of distribution. In subsequent step, will divideJoin remaining subchannel.

Step 3: in SC-LFDMA system, each user can only be assigned with adjacent multiple subchannels. And through upper oneStep, certain user has been assigned with a sub-channels, so only the subchannel on the allocated sub-channels left side and the right canBe assigned to this user. And for the user who is not assigned with subchannel, all subchannels that are not assigned with can be distributed toThis user.

Determine after each user's candidate sub-channel, calculate that system is being just after candidate sub-channel k is assigned to respective user mThan fairness weights and increment,

Wherein,Represent to have distributed to the sets of sub-channels of user m.

In all possible distribution, find have weight limit and user and subchannel pairing, by sonChannelDistribute to user。

Calculate the subchannel number being assigned with, if subchannel allotment reaches 48, show that subchannel distributesFinish, enter step 4; Otherwise return to step 3, continue allocated sub-channels.

Step 4: after this subchannel is assigned, can obtain user's instantaneous transmission speed, now average transmission dataSpeed is updated to:

Wherein, T represents to complete distribution number of times,The transmitted data rates average of user m after representing to upgrade, using asThe foundation of next time distributing.

Above-mentioned steps has completed the resource of SC-LFDMA system distributes, and idiographic flow as shown in Figure 3.

For the superiority of the present embodiment is described, compare four kinds of schemes here: the algorithm of the present embodiment, greedy exploratoryAlgorithm, packet type greedy algorithm, optimal algorithm.

Fig. 4 has provided number of users and has been respectively 8,12, the availability of frequency spectrum of 16,20 o'clock systems. For more each more intuitivelyThe direct ratio fairness of individual scheme, table 2 has provided by four kinds of schemes and has carried out the logarithmic utility function that resource is distributed rear system。

Table 2 system logarithmic utility function

Can be found out by Fig. 4 and table 2, take the algorithm of the present embodiment can obviously improve the availability of frequency spectrum of system, simultaneouslyEnsure the fairness between user.

Table 3 has provided the computation complexity of greedy exploratory algorithm, packet type greedy algorithm and the present embodiment algorithm. CanFind out, in the time that number of users is larger, the algorithm of the present embodiment is compared other two kinds of greedy algorithms and is had lower computation complexity.

Table 3 computation complexity

The present embodiment has solved the resource allocation problem of SC-LFDMA system, and has introduced the direct ratio fairness doctrine, both improvesThe availability of frequency spectrum of system, ensured again the fairness between user. Divide sub-band according to channel coherence bandwidth, avoided pointGroup formula greedy algorithm increases the hydraulic performance decline causing because of number of users. Determine by the user for thering is larger direct ratio fairness weightsThe original position of subchannel, for these users have divided optimum range of distribution, has both overcome traditional greediness exploratory in advanceAlgorithm is easily changed the shortcoming of deception among a small circle by frequency domain, reduced again the complexity of subsequent allocations. Meanwhile, retain in sub-band and remainRemaining subchannel makes other users that are not assigned with also have an opportunity to obtain some resources, has improved the fairness between user and has dividedThe flexibility of joining. The performance of this algorithm has been approached optimal algorithm, but has much lower computation complexity.

Although content of the present invention has been done detailed introduction by above preferred embodiment, will be appreciated that above-mentionedDescribe and should not be considered to limitation of the present invention. Read after foregoing those skilled in the art, for of the present inventionMultiple amendment and substitute will be all apparent. Therefore, protection scope of the present invention should be limited to the appended claims.

Claims (5)

1. the resource allocation methods in local mapping formula single carrier-frequency division multiple access system, is characterized in that, comprising:

Step 1, base station obtain the up-to-date channel condition information between itself and multi-user, and call early stage sub-channel assignment procedure and holdTransmitted data rates average after row;

Step 2, base station are divided sub-band according to channel coherence bandwidth, are chosen at and on sub-band, have larger direct ratio fairness weightsUser, and for they determine the original position of subchannel, taking in advance as these users divide optimum range of distribution;

The subchannel adjacent limits of step 3, consideration local single carrier frequency division multiple access, distributes to use one by one residue subchannelFamily, in every sub-distribution, taking maximize direct ratio fairness weights and increment as target, carry out the pairing of user and subchannel;

Step 4, final updating user's transmitted data rates average, for distribute foundation be provided next time;

In described step 1, described channel condition information is: user is to the channel gain H of base station_m,k, wherein: m ∈ M tableShow user's sequence number, M={1 ..., m ..., M} represents that user gathers, and M is total number of users, and k ∈ K represents subchannel sequence number, K=1 ..., k ..., K} represents available sets of sub-channels, K is subchannel sum;

Transmitted data rates average after described sub-channel assignment procedure in early stage is carried out refers to: by what carry out before this sub-distributionEach user's that sub-channel assignment procedure obtains transmitted data rates average R={R₁,...,R_m,...,R_M},m∈M；

In described step 2, base station is Q the sub-band that size is identical according to channel coherence bandwidth by whole frequency band division;Calculate the direct ratio fairness weights of each user on each sub-band and, and they are stored in the matrix V of a M × Q; UserThe direct ratio fairness weights of m on sub-band q and, in matrix the capable q of m row beWhereinS_qFor the sets of sub-channels in sub-band q, q=1 ..., Q;

Described direct ratio fairness weights is:

λ_m,k＝r_m,k/R_m

Wherein, r_m,kFor the instantaneous transmission data rate of user m on subchannel k;

Find the maximum V in matrix V_ij, the direct ratio fairness weights of user i on sub-band j and be maximum; By sub-bandJ and user i match, and then all items relevant with sub-band j to user i in matrix V are removed, by i in matrix VThe item that item on row and j list replaces with-1; If M≤Q, repeats above process until all users match, or,If M > is Q, repeat above process until all sub-bands match;

After user and sub-band have matched, the subchannel of direct ratio fairness weights maximum in every sub-frequency bands is distributed to pairingUser, and in this sub-band, remaining C-1 sub-channels will be retained, and in step 3, distribute to user;

By above process, base station has been the individual user assignment with larger direct ratio fairness weights of min (M, Q) first son letterRoad, has determined these users' subchannel original position.

2. resource allocation methods as claimed in claim 1, is characterized in that,

In step 2, the instantaneous transmission data rate r of user m on subchannel k_m,k, be expressed as:

$r_{m,k}=\frac{B}{K}{\log }_2(1+\frac{P_{m,k}|H_{m,k}{|}^2}{N})$

Wherein, B is system transmission bandwidth, P_m,kRepresent the transmitting power of user m on subchannel k, N is on every sub-channelsNoise power.

3. resource allocation methods as claimed in claim 2, is characterized in that,

In step 2, base station is Q the sub-band that size is identical according to channel coherence bandwidth W by whole frequency band division; Wherein

Wherein,Represent to be less than or equal to the maximum integer of real number x; Every sub-frequency bands comprisesIndividual adjacent son letterRoad; If K is not the integral multiple of C, so remaining K-QC sub-channels will be retained, and distribute to user in step 3.

4. resource allocation methods as claimed in claim 3, is characterized in that,

In step 3, for each user determines all assignable candidate sub-channel, that is, one or more subchannels are distributedUser, it is the subchannel adjacent with this user allocated sub-channels that its candidate sub-channel is merely able to; Be not assigned with subchannelUser, its candidate sub-channel is selected the subchannel from being not yet assigned with;

Determine after each user's candidate sub-channel, calculate system direct ratio public affairs after candidate sub-channel k is assigned to respective user mEqual rights heavy and increment,

${\mathrm{\Δ\λ}}_{m,k}=\underset{j\∈K_m\∪k}{\mathrm{\Σ}}{\mathrm{\λ}}_{m,j}-\underset{j\∈K_m}{\Σ}{\mathrm{\λ}}_{m,j}$

Wherein, K_mRepresent to have distributed to the sets of sub-channels of user m;

In all possible distribution, obtain user and the subchannel pairing (m of weight limit and increment^*,k^*) win this timeDistribute, by subchannel k^*Distribute to user m^*；

Group channel allocation is complete, when all subchannels are all distributed to user, enters step 4, otherwise continues a point gameteChannel.

5. resource allocation methods as claimed in claim 4, is characterized in that,

In step 4, after this subchannel is assigned, upgrade transmitted data rates according to user's instantaneous transmission speed equalValue, that is:

Wherein,The transmitted data rates average that represents user m after upgrading, T represents to complete distribution number of times.