CN100581074C - Real-time service resource distribution method of orthogonal frequency division multisystem - Google Patents

Abstract

This invention relates to a distribution method for real-time service resources of the OFDM system characterizing that a dispatch module divides a packet into multiple priorities and decides the packet dispatch sequence based on the feedback information, the channel states of users, queue state, demand on service quality and the head packet time delay of a power combined algorithm, sub-carriers and the power combined distribution module distribute sub-carriers for the packets of high priorities first, then distribute them for packets of low priorities based on the sequence result provided by the dispatch module, information of user channel state and packet numbers in the user queue and meeting the needs of certain error bit rate so as to reduce steps for distributing sub-carrier waves and the sub-carrier exchange unit is turned on if necessary to maintain the system volume and its release unit is turned on to minimize the packet drop-out rate.

Description

A kind of real-time service resource distribution method of ofdm system

Technical field:

The invention belongs to OFDM (OFDM) mobile communication technology field, particularly the resource allocation methods in the ofdm communication system.

Background technology:

Traditional OFDM resource allocation research concentrates on Bit Allocation in Discrete and two aspects of power division, " international electronics communicate by letter the selected topic magazine " (IEEE J.on Select Areas.Commun for example with The Institution of Electrical Engineers, Volume 17, No 10,1999, pp 1747-1758) a kind of Multi User Adaptive subcarrier, bit and the power distribution algorithm mentioned in.Because these algorithms consider that in assigning process the professional stochastic behaviour that arrives, Subscriber Queue state, user are to service quality (Quality of Service, requirement QoS) etc., thereby be difficult to provide satisfied service for the user.

" international communication conference " (International Conference on Communications, Volume 5,2004, the method of a kind of resource allocation of mentioning pp2949-2953), do not treat the constraint of time delay owing to consider grouping equity in the Subscriber Queue, thereby increased the packet loss of real time business, reduced power system capacity; In addition, this method hypothesis Subscriber Queue infinite in length is big, but real system is always limited, has a long way to go with this hypothesis.

Summary of the invention:

The present invention proposes a kind of resource allocation methods of ofdm system, considered that the professional stochastic behaviour that reaches, requirement that professional equity treats time delay, Subscriber Queue state, user are to the restriction to Subscriber Queue length of the requirement of service quality and system, adopt and earlier the grouping in the Subscriber Queue is divided into a plurality of priority, carry out the method for resource allocation then, can reduce the packet loss of real time business, improve power system capacity, and provide satisfied service for the user.

The real-time service resource distribution method of ofdm system of the present invention, described ofdm system comprise scheduler module and adaptive subcarrier and power associating distribution module; The base station provides the formation of finite length for each user, queue length is the peak value arrival rate of grouping and the product of sustainable maximum wait time delay, the base station is also set up for each user's service queue and is safeguarded that label, label write down the wait time delay and the sustainable maximum wait time delay of dividing into groups of corresponding user identifier, packet identifier, subcarrier identifier that the user is assigned to, the number of packet in the Subscriber Queue, each grouping; The base station is input to each user independently in the formation with the data of real time business, and the SO service order that divides into groups in the formation is First Come First Served; The base station end carries out channel estimating by the user of number of packet non-zero in the broadcast channel notification queue; The user reports channel estimation results to the base station by the feedback channel of zero defect; The every frame of the resource allocation algorithm of base station side is carried out once, only gives a user with a subcarrier allocation in each assigning process, and each subcarrier adopts identical modulation system; In the initial moment of a frame, scheduler module is user's ordering, and the user identifier sequence after will sort and the grouping in the Subscriber Queue offers adaptive subcarrier and power is united distribution module; Adaptive subcarrier and power associating distribution module earlier according to the channel condition information of user feedback with user's subcarrier according to the gain sort descending, obtain each user's subcarrier gains descending series, user identifier sequence that provides according to scheduler module and the grouping information in the Subscriber Queue are the packet allocation subcarrier in the Subscriber Queue again, and the number of packet that each user can be launched feeds back to scheduler module;

It is characterized in that:

Described scheduler module produces high priority packet user identifier sequence and low-priority packet user identifier sequence, comprise: initialization unit initial moment of every frame according on once the resource allocation feedback that finishes back adaptive subcarrier and power associating distribution module abandon of the grouping of wait time delay more than or equal to this sustainable maximum wait time delay of dividing into groups, the subcarrier identifier that the user is assigned to carries out zero clearing, for new packet identifier is set up in the grouping that previous frame arrived in the time, the wait time delay of statistics remaining number of packet of Subscriber Queue and the grouping of recording user head of the queue, and will wait for that the head of the queue group markups that time delay equals the difference of sustainable maximum wait time delay of this user grouping and frame length is designated as " being in the grouping that is dropped the edge ", is designated as " ordinary groups " with other group markups; The scheduling factor calculating unit is according to formula $G_k=J(T_{P_{\mathrm{fk}}},{\left|h^k\right|}^2)$ Calculate the scheduling factor of the user k of packets remaining quantity non-zero in each formation, in the formula The grouping P that arrives at first in the expression Subscriber Queue _FkThe time delay of having waited for, ${\left|h^k\right|}^2=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{\left|h_n^k\right|}^2,$ H wherein _n ^kThe amplitude of representing the channel gain of k user on n subcarrier, N is the system subcarrier sum; After calculating end, sequencing unit obtains user's the scheduling factor sort descending user and dispatches factor descending series; Taxon is opened up high priority packet user identifier sequence and two empty sequences of low-priority packet user identifier sequence earlier, to dispatch in the factor descending series user identifier again and put into high priority packet user identifier sequence successively with " being in the grouping that is dropped the edge ", the user identifier that will have " ordinary groups " is put into low-priority packet user identifier sequence successively, enters adaptive subcarrier and power associating assigning process then; Adaptive subcarrier and power associating distribution module comprises: the subcarrier sequencing unit is according to the channel condition information of user feedback, and the user's of number of packet non-zero subcarrier according to the gain sort descending, is obtained each user's subcarrier gains descending series; High priority packet subcarrier and power associating allocation units are followed successively by the idle sub-carrier in this user's subcarrier gains descending series of head of the queue packet allocation of the user in the high priority packet user identifier sequence, write down the identifier of the subcarrier that each user is assigned to, calculate and write down the transmitting power of distributing to these subcarriers, up to there not being head of the queue grouping to be launched, or be zero up to system's idle sub-carrier number; Then, the ordinary groups that low-priority packet subcarrier and power associating allocation units are followed successively by the user in the low-priority packet user identifier sequence is distributed the idle sub-carrier in this user's subcarrier gains descending series, write down the identifier of the subcarrier that each user is assigned to, calculate and write down the transmitting power of distributing to these subcarriers, need be launched up to grouping not, or be zero up to system's idle sub-carrier number; Distribute after the end, the total emission power computing unit will obtain total emission power and send into decision unit distributing to the transmitting power accumulative total summation of each subcarrier; If the decision value that decision unit is received limits greater than the base station gross power, then iteration subcarrier crosspoint is started working, described iteration subcarrier crosspoint is for any a pair of user (k in the system, k '), the subcarrier identifier that is assigned at them the subcarrier set of being write down is fallen into a trap and is calculated the power save factor of each subcarrier at first respectively, obtains the power save factor set of user k after the descending

Power save factor set with user k '

M represents the position of subcarrier in set; Then, find all to satisfy $({\mathrm{\ΔS}}_{n,m}^{k^{\′},k}+{\mathrm{\ΔS}}_{n^{\′},m}^{{k,k}^{\′}})>0\∀m\∈\min (N_k,N_{k^{\′}})$ Subcarrier right, exchange also more is newly assigned to the transmitting power of each subcarrier; Wherein, N _kBe the sub-carrier number of distributing to k user, N _{K '}Be the sub-carrier number of distributing to the individual user of k ', Δ S _n ^{K, k '}Be the power save factor of n subcarrier, Δ S _n ^{K ' k '}, k is the power save factor of the individual subcarrier of n '; Upgrade sub-carrier allocation results again, distribute to the user subcarrier identifier and distribute to the transmitting power of each subcarrier; After the subcarrier exchange finished, the total emission power computing unit recomputated total emission power and sends into decision unit; If the decision value that decision unit is received still limits greater than base station transmitting power, then the subcarrier releasing unit is assigned to the grouping of subcarrier from last, according to the backward of packet allocation to the precedence of subcarrier, discharge the subcarrier of distributing to each grouping successively, after the subcarrier of the selected grouping of carrying has been released, upgrade the identifier of the subcarrier that the user is assigned under the selected grouping and will distribute to the transmitting power zero clearing of these subcarriers, the decision value of receiving up to decision unit is no more than the restriction of base station gross power; At last, the statistics feedback unit writes down the result of this resource allocation, and the number of packet that each user can launch is fed back to the initialization unit of scheduler module.

For any user k, the described scheduling factor $G_k=J(T_{P_{\mathrm{fk}}},{\left|h^k\right|}^2),$ Satisfy constraints ${\∂G}_k/{\∂T}_{P_{\mathrm{fk}}}\≥0,$ $\∂G_k/\∂{\left|h^k\right|}^2\≥0,$ And can be expressed as and comprise: the scheduling sequence between the user is by the expression formula of waiting for the time delay decision $G_k=T_{P_{\mathrm{fk}}},$ Expression formula G by the channel quality decision _k=| h ^k| ²Or by the expression formula of channel quality with the product decision of waiting for time delay $G_k=T_{P_{\mathrm{fk}}}\·{\left|h^k\right|}^2$ In interior various ways.

The operation principle of described scheduler module is as follows:

For having the grouping of waiting for delay constraint, if the grouping time-delay has surpassed the sustainable maximum wait time delay of this grouping, these groupings will be dropped.In order to reduce the packet loss of system, need give " being in the grouping that is dropped the edge " higher priority.Because, if being grouped in this resource allocation process, these can not be launched away, will be dropped because the wait time delay is long, increase system's packet loss.Therefore, this patent is divided into two priority with user's grouping: be in the grouping that is dropped the edge, have higher priority P1; Ordinary groups has lower priority P2.On this basis, the user's who is belonged to dividing into groups priority comes the priority between the identical grouping of grade is divided further.The user's lower with respect to priority ratio grouping is for higher priority is given in the higher user's of priority ratio ad eundem grouping.

Described scheduler module is used the priority at scheduling factor table requisition family, and the user gradation that the scheduling factor values is big more is high more.Here, two aspects have been considered in the definition of the scheduling factor: the one, and medium insert the service delay characteristic of sublayer, if promptly the time delay of user grouping is big more, its possibility that is scheduled is also big more; Because time delay is important performance index of real time business, also be an important parameter weighing the satisfaction of the service that the user provides system; Wait for that the long more user of time delay is low more to the satisfaction of system; Otherwise, satisfied more to the service that system provides; The 2nd, the channel condition information of physical layer that is to say, if user's channel condition is good more, this user's grouping is just possible is more launched by the base station priority scheduling; In the total emission power limited systems, the user's that priority scheduling send channel condition is good grouping can improve the resource utilization and the power efficiency of system.Therefore, user's the scheduling factor is based on the nondecreasing function of user's time delay and channel gain, has taken all factors into consideration layer characteristic of striding of medium access sublayer and physical layer.

Like this, described scheduler module can obtain two sequences, and one is that to have priority be P ₁The high priority packet user of grouping dispatch factor descending series Another is that to have priority be P ₂The low-priority packet user of grouping dispatch factor descending series

The information of utilizing scheduler module to provide not only is provided described adaptive subcarrier and power associating distribution module, dispatches factor descending series as the high priority packet user Low priority user scheduling factor descending series

High priority packet and low-priority packet etc., and allocation result to be fed back to scheduler module.Its operation principle is as follows:

Adaptive subcarrier and power associating distribution module are earlier

Middle user's head of the queue packet allocation subcarrier is again

Middle user's packet allocation subcarrier, when the transmitting power of needs during greater than the maximum transmission power of base station limits, exchange the total emission power that unit of sub-carriers reduces needs by opening iteration, if still can't satisfy the restriction of base station after the iteration exchange to maximum transmission power, the subcarrier releasing unit just by discharging the method for subcarrier, reaches and satisfies the purpose of base station to maximum transmit power limit.Its advantage is, when channel condition is relatively good, reduces the subcarrier allocation step guaranteeing to satisfy under the condition of base station transmitting power constraint as far as possible; When channel condition is poor, method by iteration commutator carrier wave, on the basis that the received signal to noise ratio that guarantees receiving terminal satisfies the demands, reduced the transmitting power of distributing to each subcarrier, reached the purpose that guarantees that system emission number of packet in iteration exchange front and back remains unchanged, thereby the service of satisfaction is provided for the user; When channel condition is very poor, under the prerequisite that the transmitting power of distributing to each subcarrier has been minimized, guarantee to have only, just emission " ordinary groups " when not having " being in the grouping that is dropped the edge " in the time of need being launched, thereby reduced system's packet loss, improved power system capacity.This is because when channel quality is relatively good, does not need iteration subcarrier crosspoint and the work of subcarrier releasing unit can satisfy all constraintss, thereby reduced the subcarrier allocation step; When channel quality is poor, iteration subcarrier crosspoint can minimize the transmitting power of distributing to each subcarrier on the basis that the received signal to noise ratio that guarantees receiving terminal satisfies the demands, thereby do not need to discharge subcarrier and can satisfy all constraintss, the number of packet of system's emission is not reduced before and after iteration commutator carrier wave like this, and the service of satisfaction is provided for the user; Very poor and need reduce transmitting power by the method that discharges subcarrier the time when channel quality, the order that the subcarrier releasing unit discharges subcarrier is: be assigned to the grouping of subcarrier from last, according to the backward of packet allocation to the precedence of subcarrier, discharge the subcarrier of distributing to each grouping successively, be not more than the maximum transmission power of base station limits up to total emission power.Because " being in the grouping that is dropped the edge " arrives subcarrier than " ordinary groups " priority allocation, therefore have only when the subcarrier that not have to carry " ordinary groups " can be released and still can't satisfy the base station to the restriction of maximum transmission power, just understand the subcarrier that releasing bearing " is in the grouping that is dropped the edge ".

The algorithm of adaptive subcarrier and power associating distribution module, can describe with following formula:

$S=\min \underset{k=1}{\overset{K}{\mathrm{\Σ}}}{S}_i^k---\left(1\right)$

Its constraints is: $A_{i,n}^k=1,A_{i,n}^{k^{\′}}=0,\∀k\≠k^{\′},n\∈[1,N]---\left(2\right)$

$\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{A}_{i,n}^k=N_k---\left(3\right)$

S≤S _max (4)

Wherein, K is the system user number; $A_{i,n}^k=1$ Represent that k user has been assigned to n subcarrier at the i frame; Because the recipient can't detect a plurality of user's data from same subcarrier simultaneously, so for the norator carrier wave n, when $A_{i,n}^k=1$ The time, have $A_{i,n}^{k^{\′}}=0,\∀k^{\′}\≠k{k}^{\′}\∈[1,K];$ S _MaxMaximum transmission power for base station limits; Formula (2) guarantees only to give a user with a subcarrier allocation in each OFDM symbol; Formula (3) guarantees that the sub-carrier number that the user is assigned to satisfies business need; Formula (4) guarantees that system's total emission power is no more than the maximum transmission power of base station limits; S _i ^kBe illustrated in the i frame and distribute to k user's transmitting power, it calculates as shown in Equation (5):

$S_i^k=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{S}_{i,n}^k---\left(5\right)$

S wherein _{I, n} ^kRepresent that the i frame distributes to k user's the transmitting power on n subcarrier, it calculates as shown in Equation (6):

$S_i^k=\frac{f\left(b\right)}{{\left|h_{i,n}^k\right|}^2}\·A_{i,n}^k\·{\mathrm{\σ}}_n^2---\left(6\right)$

Wherein, h _{I, n} ^kRepresent the amplitude of k user, σ at the channel gain on n subcarrier of the initial moment estimation of i frame _n ²Be the noise power on each subcarrier, b is an information bit that the OFDM symbol carries, and f (b) represents for given bit error rate requirement, the needed received signal to noise ratio of receiving terminal, and it calculates as formula (7):

$b={\log }_2(1+\frac{f\left(b\right)}{\mathrm{\Γ}})---\left(7\right)$

Wherein, for the QPSK modulation, Γ can use

Approximate.

If n subcarrier is not assigned to Any user, then S _n=0.

Compared with prior art, the present invention has considered the requirement to service quality of the stochastic behaviour, Subscriber Queue state, user of professional arrival in resource allocation process, and taken into full account the long characteristic that will be dropped of real time business packet awaits time delay, in scheduler module, user's grouping is divided into a plurality of priority, and uses the priority between the grouping identical of priority with the scheduling factor table requisition family of striding layer characteristic with grade according to the relation between packet awaits time delay and its sustainable maximum wait time delay; On this basis, adaptive subcarrier and power associating distribution module are the packet allocation subcarrier of high priority earlier, be the packet allocation subcarrier of low priority again, thereby reduced the step of subcarrier allocation, and reach and do not reduce power system capacity and for the user provides the purpose of satisfactory service by opening iteration subcarrier crosspoint where necessary, reach the purpose of minimization system packet loss by opening the subcarrier releasing unit.So the present invention can reduce the packet loss of real time business, improve power system capacity, and provide satisfied service for the user.

Description of drawings:

Fig. 1 is the theory diagram of the resource allocation methods of ofdm system of the present invention.

Fig. 2 is the simulation curve of number of users and normalization packet delay.

Embodiment:

Embodiment below in conjunction with description of drawings this method.

Embodiment 1:

The present embodiment utilized bandwidth is that 20MHz, data subcarrier number are 512 OFDM transmission system.Channel adopts COST207 six footpath models, and maximum multipath time delay is 10us, and six footpaths are spacedly distributed in 0～10us, and the power spectral density in each footpath satisfies common Jake model.Maximum Doppler frequency offset is 50Hz.Every frame is made of an OFDM symbol.

The service source model adopts ON-OFF two condition markov Markov process.Separate and obeys index distribution (the Efficiency of packet reservation multiple access of active period and quiet period, IEEE Trans.on Veh.Technol., 1991, vol.40:170-176. with Performance of PRMA:A packet voice protocol for cellular systems, IEEE Trans.on Veh.Technol., 1991, vol.40:584-598.).Transition probability from the active period to the quiet period is γ=1-exp (T _f/ t ₁), the transition probability from the quiet period to the active period is u=1-exp (T _f/ t ₂), T wherein _fBe frame length, t ₁And t ₂Be respectively the average of active period and quiet period.

Select for use the real time business parameter to be: t ₁=5.0s, t ₂=4.05s, BER=10 ^-6, T _Max=5ms, active period data rate are 2.56Mbps, and each grouping comprises 256 information bits.

For the performance of striding the layer self-adapting resource allocation algorithm is described, defined the expression-form of three kinds of scheduling factors in the emulation:

1. the scheduling sequence between the user is by the expression formula of waiting for the time delay decision: $G_k=T_{P_{\mathrm{fk}}};$

2. the scheduling sequence between the user is by the expression formula of channel quality decision: G _k=| h ^k| ²

3. the scheduling sequence between the user is by channel quality with wait for the expression formula of the product decision of time delay: $G_k=T_{P_{\mathrm{fk}}}\·{\left|h^k\right|}^2$ The definition of this expression formula has embodied channel quality and has waited for the fairness that time delay acts on each other.

Accompanying drawing 1 has provided the theory diagram of the resource allocation methods of ofdm system of the present invention: the base station end, in the initial moment of every frame, initialization unit 1 is upgraded the label that respectively inserts Subscriber Queue, comprise that the number of packet signal 23 that can launch according to each user who adds up feedback unit 22 feedbacks after the last resource allocation end abandons the grouping of wait time delay more than or equal to this sustainable maximum wait time delay of dividing into groups, the subcarrier identifier that the user is assigned to carries out zero clearing, for new packet identifier is set up in the grouping that previous frame arrived in the time, the remaining number of packet of statistics Subscriber Queue, the wait time delay of recording user head of the queue grouping, and will wait for that the head of the queue group markups that time delay equals the difference of sustainable maximum wait time delay of this user grouping and frame length is designated as " being in the grouping that is dropped the edge ", other group markups are designated as " ordinary groups ", and mark is sent initialization end signal 2 after finishing; Initialization end signal 2 beginnings that scheduling factor calculating unit 3 is sent according to initialization module are dispatched the formula that embodies of the factor in conjunction with described user, according to the user's of the wait time-delay calculation number of packet non-zero of subscriber channel results estimated and the grouping of user's head of the queue the scheduling factor; The initialization end signal 2 that user's subcarrier sequencing unit 10 is sent according to initialization module begins user's subcarrier to obtain each user's subcarrier gains descending series according to the gain sort descending; After calculating end, scheduling factor sequencing unit 4 obtains user's the scheduling factor sort descending user and dispatches factor descending series { G _k} _K=1 ^KTaxon 5 is opened up high priority packet user identifier sequence earlier

With low-priority packet user identifier sequence

Two empty sequences will be dispatched in the factor descending series user identifier with " being in the grouping that is dropped the edge " more successively and put into successively

The user identifier that will have " ordinary groups " is put into successively

Then with sequence

Be signal 6 Hes

Be that signal 7 is sent into high priority packet subcarrier and power associating allocation units 8 and low-priority packet subcarrier and power associating allocation units 11 respectively; High priority packet subcarrier and power associating distribution module 8 subcarrier gains descending series according to each user of storage in the high priority packet user identifier sequential signal of sending into 6 and the user's subcarrier order module 10, from the head of the queue user, under the prerequisite that meets constraints formula (2) and formula (3), be followed successively by the idle sub-carrier in " being in the grouping that is dropped the edge " the distributing user subcarrier gains descending series in the Subscriber Queue, write down the identifier of the subcarrier that each user is assigned to, by formula (6) and formula (7) dispensed is given the transmitting power of these subcarriers and is preserved, up to not having " being in the grouping that is dropped the edge " to be launched or system's idle sub-carrier number is zero, and the identifier of the subcarrier that will distribute is that signal 9 is sent into the low-priority packet subcarrier and united distribution module 11 with power; Low-priority packet subcarrier and power associating distribution module 11 are according to the low-priority packet user identifier sequence signal 7 of input, each user's of storage subcarrier gains descending series in the identifier signal 9 of the subcarrier that has been assigned with and the user's subcarrier order module 10, from the head of the queue user, be followed successively by idle sub-carrier in " ordinary groups " distributing user subcarrier gains descending series in the Subscriber Queue in the prerequisite that meets constraints formula (2) and formula (3), write down the identifier of the subcarrier that each user is assigned to, by formula (6) and formula (7) dispensed is given the transmitting power of these subcarriers and is preserved, up to not having " ordinary groups " to be launched or system's idle sub-carrier number is zero; Distribute after the end, total emission power computing unit 12 calculates the total emission power that needs according to the transmitting power of distributing to each subcarrier according to formula (5) and formula (1), and result of calculation is admitted to transmitting power decision unit 13; Power decision unit 13 judges whether the decision value of receiving satisfies constraints (4), when not satisfying, produces triggering signal 14 and sends into release subcarrier decision unit 16, when this unit receives triggering signal 14 first, sends triggering signal 17; Triggering signal 17 triggers 19 work of iteration subcarrier crosspoint, upgrade the identifier of the subcarrier that each user is assigned to, and the transmitting power of distributing to each subcarrier after will upgrading is that signal 21 is sent into total emission power computing module 12, and the power signal of distributing to each subcarrier 21 of total emission power computing module 12 after according to the iteration exchange recomputates the total emission power of needs; If the decision value that transmitting power decision unit 13 is received still can't satisfy constraints (4), triggering signal 14 triggers release subcarrier decision unit 16 and sends triggering signal 18; Triggering signal 18 triggers subcarrier releasing unit 20 and starts working, be assigned to the grouping of subcarrier from last, according to the backward of packet allocation to the precedence of subcarrier, discharge the subcarrier of distributing to each grouping successively, after the subcarrier of the selected grouping of carrying has been released, upgrade the identifier of the subcarrier that the user is assigned under this grouping and will distribute to the transmitting power zero clearing of these subcarriers, the decision value of receiving up to transmitting power decision unit 13 satisfies constraints (4), just produce the transmitting power that signal 15 triggers the identifier of the subcarrier that statistics feedback units 22 each user of record are assigned to and distributes to each subcarrier, and be that signal 23 feeds back to initialization module 1 number of packet that each user can launch.

Accompanying drawing 2 is the simulation curve of number of users and normalization packet delay, and curve α, curve β and curve γ are respectively the scheduling factor and adopt expression formula $G_k=T_{P_{\mathrm{fk}}},$ $G_k=T_{P_{\mathrm{fk}}}\·{\left|h^k\right|}^2$ With expression formula G _k=| h ^k| ²The time simulation result.When adopting expression formula G _k=| h ^k| ²The time system number of users supported maximum; When adopting expression formula $G_k=T_{P_{\mathrm{fk}}}$ The time system number of users supported minimum.

Can see from the simulation curve of Fig. 2: along with the increase of number of users, the normalization packet delay increases; When the scheduling factor adopts expression formula G _k=| h ^k| ²The time power system capacity maximum, adopt expression formula $G_k=T_{P_{\mathrm{fk}}}\·{\left|h^k\right|}^2$ The time power system capacity take second place, adopt expression formula $G_k=T_{P_{\mathrm{fk}}}$ The time power system capacity minimum.This is because the scheduling factor adopts expression formula G _k=| h ^k| ²The time, the priority between the user is determined that by channel quality having reduced priority so on the one hand is P ₁The transmitting power that consumes of grouping, can be beneficial to the multi-user diversity gain on the frequency domain on the other hand more fully, sending more priority is P ₂Grouping, thereby improved power system capacity, reduced packet delay.Adopt expression formula $G_k=T_{P_{\mathrm{fk}}}$ The time, the priority between the user can't be beneficial to channel information and be reduced the transmitting power that single grouping consumes by user's wait time delay decision, and priority is P like this ₁Grouping might consume a large amount of transmitting powers, thereby reduced the number of packet of emission in the OFDM symbol time, increased packet delay.Adopt expression formula $G_k=T_{P_{\mathrm{fk}}}\·{\left|h^k\right|}^2$ The time, the priority between the user is determined jointly by user's wait time delay and channel quality, so performance is between above-mentioned two kinds of algorithms.

The present invention is a starting point with the satisfaction that improves the user, has provided a kind of layer resource allocation algorithm of striding that is used for ofdm system down link real time business.This scheme has taken into full account the long characteristic that will be dropped of real time business packet awaits time delay, and the realization of its algorithm comprises scheduler module and adaptive subcarrier and power associating distribution module two parts.Scheduler module is divided into a plurality of priority with user's grouping, the ordering of grouping had both considered that medium such as the wait time delay, quene state of user's head of the queue grouping, professional delay requirement, random packet arrival insert the characteristic of sublayer, had considered the time-varying characteristics of physical layer wireless channel etc. again in the same priority; Adaptive subcarrier and power associating distribution module are the packet allocation subcarrier of high priority earlier, be the packet allocation subcarrier of low priority again, thereby reduced the step of subcarrier allocation, and reach and do not reduce power system capacity and for the user provides the purpose of satisfactory service by opening iteration subcarrier crosspoint where necessary, reach the purpose of minimization system packet loss by opening the subcarrier releasing unit.So the present invention can reduce the packet loss of real time business, improve power system capacity, and provide satisfied service for the user.

Claims (2)

1, a kind of real-time service resource distribution method of ofdm system, described ofdm system comprise scheduler module and adaptive subcarrier and power associating distribution module; The base station provides the formation of finite length for each user, queue length is the peak value arrival rate of grouping and the product of sustainable maximum wait time delay, the base station is also set up for each user's service queue and is safeguarded that label, label write down the wait time delay and the sustainable maximum wait time delay of dividing into groups of corresponding user identifier, packet identifier, subcarrier identifier that the user is assigned to, the number of packet in the Subscriber Queue, each grouping; The base station is input to each user independently in the formation with the data of real time business, and the SO service order that divides into groups in the formation is First Come First Served; The base station end carries out channel estimating by the user of number of packet non-zero in the broadcast channel notification queue; The user reports channel estimation results to the base station by the feedback channel of zero defect; The every frame of the resource allocation algorithm of base station side is carried out once, only gives a user with a subcarrier allocation in each assigning process, and each subcarrier adopts identical modulation system; In the initial moment of a frame, scheduler module is user's ordering, and the user identifier sequence after will sort and the grouping in the Subscriber Queue offers adaptive subcarrier and power is united distribution module; Adaptive subcarrier and power associating distribution module earlier according to the channel condition information of user feedback with user's subcarrier according to the gain sort descending, obtain each user's subcarrier gains descending series, user identifier sequence that provides according to scheduler module and the grouping information in the Subscriber Queue are the packet allocation subcarrier in the Subscriber Queue again, and the number of packet that each user can be launched feeds back to scheduler module;

It is characterized in that:

Described scheduler module produces high priority packet user identifier sequence and low-priority packet user identifier sequence, comprise: initialization unit initial moment of every frame according on once the resource allocation feedback that finishes back adaptive subcarrier and power associating distribution module abandon of the grouping of wait time delay more than or equal to this sustainable maximum wait time delay of dividing into groups, the subcarrier identifier that the user is assigned to carries out zero clearing, for new packet identifier is set up in the grouping that previous frame arrived in the time, the wait time delay of the packets remaining quantity of statistics Subscriber Queue and the grouping of recording user head of the queue, and will wait for that the head of the queue group markups that time delay equals the difference of sustainable maximum wait time delay of this user grouping and frame length is designated as " being in the grouping that is dropped the edge ", is designated as " ordinary groups " with other group markups; The scheduling factor calculating unit is according to formula $G_k=J(T_{P_{\mathrm{fk}}},{\left|h^k\right|}^2)$ Calculate the scheduling factor of the user k of the packets remaining quantity non-zero in each formation, in the formula

The grouping P that arrives at first in the expression Subscriber Queue _FkThe time delay of having waited for, ${\left|h^k\right|}^2=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{\left|h_n^k\right|}^2,$ H wherein _n ^kThe amplitude of representing the channel gain of k user on n subcarrier, N is the system subcarrier sum; After calculating end, sequencing unit obtains user's the scheduling factor sort descending user and dispatches factor descending series; Taxon is opened up high priority packet user identifier sequence and two empty sequences of low-priority packet user identifier sequence earlier, to dispatch in the factor descending series user identifier again and put into high priority packet user identifier sequence successively with " being in the grouping that is dropped the edge ", the user identifier that will have " ordinary groups " is put into low-priority packet user identifier sequence successively, and adaptive subcarrier and power associating distribution module is carried out adaptive subcarrier and power associating assigning process then; Adaptive subcarrier and power associating assigning process comprises: the subcarrier sequencing unit is according to the channel condition information of user feedback, and the user's of number of packet non-zero subcarrier according to the gain sort descending, is obtained each user's subcarrier gains descending series; High priority packet subcarrier and power associating allocation units are followed successively by the idle sub-carrier in this user's subcarrier gains descending series of head of the queue packet allocation of the user in the high priority packet user identifier sequence, write down the identifier of the subcarrier that each user is assigned to, calculate and write down the transmitting power of distributing to these subcarriers, up to there not being head of the queue grouping to be launched, or be zero up to system's idle sub-carrier number; Then, the ordinary groups that low-priority packet subcarrier and power associating allocation units are followed successively by the user in the low-priority packet user identifier sequence is distributed the idle sub-carrier in this user's subcarrier gains descending series, write down the identifier of the subcarrier that each user is assigned to, calculate and write down the transmitting power of distributing to these subcarriers, need be launched up to grouping not, or be zero up to system's idle sub-carrier number; Distribute after the end, the total emission power computing unit will obtain total emission power and send into decision unit distributing to the transmitting power accumulative total summation of each subcarrier; If the decision value that decision unit is received limits greater than the base station gross power, then iteration subcarrier crosspoint is started working, described iteration subcarrier crosspoint is for any a pair of user (k in the system, k '), the subcarrier identifier that is assigned at them the subcarrier set of being write down is fallen into a trap and is calculated the power save factor of each subcarrier at first respectively, obtains the power save factor set of user k after the descending

Power save factor set with user k '

M represents the position of subcarrier in set; Then, find all to satisfy $(\mathrm{\Δ}{S}_{n,m}^{k^{\′},k}+\mathrm{\Δ}{S}_{n^{\′},m}^{k,k^{\′}})>0\∀m\∈\min (N_k,N_{k^{\′}})$ Subcarrier right, exchange also more is newly assigned to the transmitting power of each subcarrier; Wherein, N _kBe the sub-carrier number of distributing to k user, N _{K '}Be the sub-carrier number of distributing to the individual user of k ', Δ S _n ^{K, k}' be the power save factor of n subcarrier, Δ S _{N '} ^k' ^{, k}It is the power save factor of the individual subcarrier of n '; Upgrade sub-carrier allocation results again, distribute to the user subcarrier identifier and distribute to the transmitting power of each subcarrier; After the subcarrier exchange finished, the total emission power computing unit recomputated total emission power and sends into decision unit; If the decision value that decision unit is received still limits greater than base station transmitting power, then the subcarrier releasing unit is assigned to the grouping of subcarrier from last, according to the backward of packet allocation to the precedence of subcarrier, discharge the subcarrier of distributing to each grouping successively, after the subcarrier of the selected grouping of carrying has been released, upgrade the identifier of the subcarrier that the user is assigned under the selected grouping and will distribute to the transmitting power zero clearing of these subcarriers, the decision value of receiving up to decision unit is no more than the restriction of base station gross power; At last, the statistics feedback unit writes down the result of this resource allocation, and the number of packet that each user can launch is fed back to the initialization unit of scheduler module.

2, the real-time service resource distribution method of ofdm system according to claim 1 is characterised in that for any user k the described scheduling factor $G_k=J(T_{P_{\mathrm{fk}}},{\left|h^k\right|}^2),$ Satisfy constraints $\∂G_k/\∂T_{P_{\mathrm{fk}}}\≥0,$ $\∂G_k/\∂{\left|h^k\right|}^2\≥0,$ And can be expressed as: the scheduling sequence between the user is by the expression formula of waiting for the time delay decision $G_k=T_{P_{\mathrm{fk}}},$ Expression formula G by the channel quality decision _k=| h ^k| ²Or by the expression formula of channel quality with the product decision of waiting for time delay $G_k=T_{P_{\mathrm{fk}}}\·{\left|h^k\right|}^2.$

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