CN100550842C - A kind of control method of radio local network block transmission delay - Google Patents

Abstract

A kind of control method of radio local network block transmission delay, a kind of performance analysis models of IEEE 802.11 WLAN (wireless local area network) under more actual " unsaturated state " is provided, thereby and then has proposed a kind of by regulating the method that each sends terminal minimum competition window size control radio local network block transmission delay.Utilize this delay control method, wireless communication terminal can detect by the dynamic real-time to network traffic, adjusts its " minimum competition window size " adaptively, thereby satisfies predetermined block transmission delay.The present invention realizes simply, can be used as the part of wireless network card firmware or realized as the part of NIC driver, supports full distributed working method, can be locked on certain target mean packet delay with higher precision sending terminal.

Description

A kind of control method of radio local network block transmission delay

(1) technical field

The present invention relates to communication technical field, particularly a kind of transfer control method that is applied to WLAN (wireless local area network).

(2) background technology

Current I EEE 802.11 standards have become the generally acknowledged international standard of WLAN (wireless local area network) access technology.Mainly defined two kinds of multiple access access protocols in IEEE 802.11 standards: first distributed coordination function (DCF), another one are point coordination function (PCF).Wherein, DCF is inserted standard by the multiple access of industry-wide adoption, and a kind of multiple access that is based on carrier sense and collision avoidance mechanism is access strategy at random.Below give concise and to the point introduction to the basic functional principle of DCF in IEEE 802.11 standards.

Along with Development of Multimedia Technology, people need consider how to support multiple business on the net at the wireless local based on IEEE 802.11, and for different business provides different service quality, as different block transmission delay etc. is provided.Regrettably in IEEE 802.11 standards, and reckon without effective support to multiple business.That is to say that the packet of all Business Streams all is equal to be treated.Such mode of operation obviously can not adapt to the requirement of multimedia service.The key that addresses this problem is to make DCF have the tenability of " differential service ".The tenability of so-called differential service just is meant that network provides different service quality to different business, such as different block transmission delays.In the IEEE 802.11E standard of finishing recently, people have proposed by giving different different " the minimum competition windows " of terminal distribution that send, and come to provide for different transmission terminals the thought of different service quality.Based on the operation principle of DCF, can know if send terminal to have less " minimum competition window ", this terminal will be than the easier access wireless channel of other terminal.That is to say that less " minimum competition window " will bring less packetization delay.Yet, how according to the variation of network traffic, adaptive adjustment " minimum competition window ", thus the specific implementation technology that satisfies predetermined packeting average transmission delay does not provide in standard.Address this problem, the major technology difficult point just is in the deep performance evaluation of IEEE 802.11 WLAN (wireless local area network).Because have only the inherent law of having grasped IEEE 802.11 WLAN (wireless local area network), could effectively go the performance of Control Network.People such as G.Bianchi professor and professor E.Gregori have proposed two kinds of theoretical models about IEEE 802.11 wireless local performance evaluations respectively, yet these analyses all are based on the hypothesis of system works under " saturation condition ".Under saturation condition, send terminal after sending a grouping, just have the next one to be grouped in transmit queue medium to be sent at once.Such hypothesis has made things convenient for theory analysis, but because and real system operating state not consistent (real system mainly is to be operated under the unsaturated state), so these analytical models are difficult to be applied to and go to control transmission packets in the actual system and postpone.

(3) summary of the invention

In order to overcome the effectively defective of control data block transmission delay of prior art, the invention provides a kind of performance analysis models of IEEE 802.11 WLAN (wireless local area network) under more actual " unsaturated state ", thereby and then proposed a kind of by regulating the method that each sends terminal minimum competition window size control radio local network block transmission delay.Utilize this delay control method, wireless communication terminal can detect by the dynamic real-time to network traffic, adjusts its " minimum competition window size " adaptively, thereby satisfies predetermined block transmission delay.

The present invention is based on the performance evaluation of 802.11 WLAN (wireless local area network) of IEEE under the unsaturated state obtainedly, described controlling party rule is based on the specific implementation that these theoretical analysis result put forward.

Consider that having H in the WLAN (wireless local area network) sends terminal.Each sends terminal and all carries a Business Stream.For narrate convenient for the purpose of, we send terminal to H and are numbered, from No. 1 up to H number.Business Stream is made up of packet, and the transmission time of the payload of each packet on wireless channel is T _LIn addition, and i (i=1 ..., H) the arrival equispaced between the packet of individual Business Stream is T _{P, i}(i=1 ..., H).The data throughput that all transmission terminals are contributed in the system is designated as S.By i (i=1 ..., H) data throughput contributed of individual Business Stream is s _i(i=1 .., H).

Below in conjunction with i (i=1 ..., H) individual transmission terminal provides the concrete steps that realize this delay control method:

Step 1: at moment t _k, i (i=1 ..., H) individual transmission terminal successfully send it k the grouping after, data estimator throughput S and s _i(i=1 ..., H).Consider to be numbered the transmission terminal of i.At moment t _kThis terminal has successfully sent its k grouping.This transmission terminal all is recorded in D the pairing delivery time of grouping that its success recently sends in the buffer memory.t _K-j(j=0 ..., D; D 〉=1) corresponding k-j is divided into groups the successfully moment of transmission.Like this at moment t _k, this transmission terminal can be estimated as its data throughput of contributing $s_i\≈\frac{D\·T_L}{t_k-t_{k-D}}.$ Simultaneously, this transmission terminal is also noted at moment t _K-pTo t _kDuring this time, be numbered j (the transmission terminal of j ≠ i) the packet count N that sends of success _iLike this, at moment t _k, we can be estimated as the data throughput that other each transmission terminal is contributed $s_j\≈\frac{N_j\·T_L}{t_k-t_{k-1)}}.$ Estimate all and send the data throughput s that terminal is contributed _j(j=1,2 ..., H), so total data throughput can be estimated as $S=\underset{j=1}{\overset{H}{\mathrm{\Σ}}}{s}_j.$ Notice that the D value is big more, it is just slow more to the reaction of the dynamic change of network traffic to send terminal.Therefore, parameter D suggestion value is 10 to 20.Need to prove that in addition in IEEE 802.11 WLAN (wireless local area network), certain packet that sends the terminal transmission can be received by other terminal.Send the multiple access access address (being MAC Address) that this transmission terminal is arranged in the packet that terminal sent, whose transmission other-end just can identify this packet by by this address.

Step 2: based on the data throughput S and the s that estimate to obtain _i(i=1 ..., H), calculate ${\mathrm{\θ}}_{1,i}=T_L\·\underset{j=1}{\overset{H}{\mathrm{\Σ}}}\frac{s_j}{s_i}(i=1,...,H),$ ${\mathrm{\θ}}_{2,i}=T_s\·\underset{j=1}{\overset{H}{\mathrm{\Σ}}}\frac{s_j}{s_i}(i=1,...,H)$ With ${\mathrm{\θ}}_{3,i}=T_c\·\underset{\underset{j\≠k}{1\≤j,k\≤H}}{\mathrm{\Σ}}\frac{s_j\·s_k}{{s_i}^2}(i=1,...,H).$ T wherein _cAnd T _sCan calculate according to following formula:

T _s＝PHY _headr+MAC _header+T _L+SIFS+ACK+DIFS (1)

T _c＝PHY _header+MAC _header+T _L+DIFS (2)

In the formula, PHY _HeaderThe Channel Transmission time of expression physical packet of data head; MAC _HeaderThe Channel Transmission time of representing many toes Access Layer data packet header; ACK represents to confirm Channel Transmission time of dividing into groups; SIFS and DIFS are the preset parameter of stipulating in IEEE 802.11 standards.These parameters all can obtain with reference to the regulation of IEEE 802.11.

Step 3: according to formula (3) calculating parameter τ _i(i=1 ..., H).

${\mathrm{\τ}}_i=\frac{({\mathrm{\θ}}_{1,i}-S{\mathrm{\θ}}_{2,i})-\sqrt{{({\mathrm{\θ}}_{1,i}-S{\mathrm{\θ}}_{2,i})}^2-4\mathrm{\σ}{\mathrm{\θ}}_{3,i}{S}^2}}{2S{\mathrm{\θ}}_{3,i}}---\left(3\right)$

In the formula, σ represents the length of an idle time slot in the backoff procedure.This value has clearly regulation in IEEE 802.11 standards.

Step 4: according to formula (4) calculating parameter p _i(i=1 ..., H).

$p_i=1-\underset{j=1,j\≠i}{\overset{H}{\mathrm{\Π}}}(1-{\mathrm{\τ}}_j)---\left(4\right)$

Step 5: calculate the desired value of " minimum competition window size " according to formula (5), and finish to " minimum competition window size " W _iAdjustment.

$W_i=\frac{{\hat{T}}_{d,i}-\frac{T_s}{1-p_i}}{(\frac{T_L}{s_i}-\frac{T_s}{1-p_i})\·\frac{(1-p_i)\·{\mathrm{\τ}}_i}{2(1-2p_i)}}---\left(5\right)$

In the formula

Be i (i=1 ..., H) the target mean packet delay of individual transmission terminal; W _iBe i (i=1 ..., H) " the minimum competition window size " of individual transmission terminal.In order to reach

W _iShould set according to formula 5.

Step 6: the desired value that sends " minimum competition window size " that terminal calculates according to formula (5) is provided with the W of himself _i, and go to control its backoff procedure according to the regulation of IEEE 802.11 standards with this new " minimum competition window size ", concrete backoff procedure is carried out according to standard code fully.Go to carry out the backoff procedure of IEEE 802.11 prescribed by standard with this " minimum competition window size " that calculates, will produce mean packet delay and approximate desired value

Actual packet postpone.

Above-mentioned steps has provided the method that sends terminal " minimum competition window size " thereby reach control block transmission delay purpose by regulating.Concrete WAP (wireless access protocol), i.e. DCF can be with reference to the regulation of IEEE 802.11 standards.

The present invention realizes simply, can be used as the part of wireless network card firmware or realized as the part of NIC driver, supports full distributed working method.Need not the intervention of master controller.The present invention can guarantee to send terminal and reach its target mean packet delay separately Can be locked on certain target mean packet delay with higher precision sending terminal.And, along with the dynamic change of Network, can accomplish that adaptive adjustment sends " the minimum competition window size " of terminal, thereby guarantee that the packetization delay that reaches does not change with the dynamic change of network traffic.Below, by simulation result, provide the technique effect that this method can reach.

Having H=15 l-G simulation test that sends the WLAN (wireless local area network) of terminal with one is example, and each sends terminal and all carries a Business Stream.T _L=0.0014545 (s), T _{P, i}=0.043636 (s) (i=1,2 ..., 15), D=10, other parameter is all according to the standard code setting of IEEE 802.11b.0 arrive 20 (s) constantly constantly, only be numbered 5 transmission terminal transmission data of 1 to 5., be numbered 6 to 15 transmission terminal and join in the system and send data to the moment 60 (s) from 20 (s) constantly.The target mean packet delay that is numbered 1 to 5 transmission terminal is 10 milliseconds.The target mean packet delay that is numbered 6 to 15 transmission terminal is 30 milliseconds.Locate at the moment 20 (s) like this, the traffic carrying capacity of system just exists a saltus step.Because this method can be adjusted " minimum competition window size " W of corresponding transmission terminal according to the variation self adaptation of network traffic _i, guaranteed that therefore each grouping transmission lag that sends terminal remains unchanged, and be locked on the desired value.Fig. 1 has provided each contrast that sends the target mean packet delay of terminal and utilize the mean packet delay that this method finally reaches.As can be seen, use this method can well the lock onto target packetization delay.Fig. 2 has provided from 0 (s) constantly to constantly 60 (s), " minimum competition window size " W of No. 1 transmission terminal ₁Situation about constantly adjusting with the dynamic change of network traffic.Notice that 20 (s) locate in the moment, owing to there are 10 new transmission terminals to join in the network, the traffic carrying capacity of network is suddenlyd change to some extent, at this moment W ₁Adjust to certain value fast, thereby the assurance packetization delay is not subjected to the variation of network traffic and is affected thereupon yet.

(4) description of drawings

1, accompanying drawing 1 postpones and the actual packetization delay comparison diagram that reaches for targeted packets of the present invention.

2, accompanying drawing 2 carries out self adaptation adjustment figure for " minimum competition window size " with the variation of network traffic.

(5) embodiment

This method can be used as firmware and realizes in IEEE 802.11 wireless access network interface cards on the whole, or is implemented in the driver of wireless access network interface card.Realization to each step is described in detail below.

Consider that having H in the WLAN (wireless local area network) sends terminal.Each sends terminal and all carries a Business Stream.For narrate convenient for the purpose of, we send terminal to H and are numbered, from No. 1 up to H number.Business Stream is made up of packet.The transmission time of the payload of each packet on wireless channel is T _LHere the payload of indication refers to the valid data from the communication protocol upper strata that carried in the grouping of multiple access Access Layer.The data throughput that all transmission terminals are contributed in the system is designated as S.By i (i=1 ..., H) data throughput contributed of individual Business Stream is s _i(i=1 .., H).

Below, in conjunction with instantiation this method is illustrated.Consider that having H=2 in the WLAN (wireless local area network) sends terminal.Each sends terminal and all carries a Business Stream.We send terminal to H=2 and are numbered (No. 1 and No. 2).The payload of each packet is 16000 bits.Here we are illustrated in conjunction with the regulation of IEEE 802.11b.In IEEE 802.11b, the message transmission rate of wireless channel is the 11M bits per second.Therefore, we can calculate the Channel Transmission time T of valid data _LFor $T_L=\frac{16000\mathrm{bit}}{11000000\mathrm{bit}/s}=0.0014545s.$ Next, we to consider to send terminal 1 as how to realize its " minimum competition window size " regulated according to our method.If send the targeted packets average retardation of terminal 1 be ${\hat{T}}_{d,i}=0.010s.$

Step 1: at moment t _k=0.020s, send for No. 1 terminal k that successfully sends it divide into groups after, data estimator throughput S and s _i(i=1,2).Send terminal for No. 1 at moment t _kThis terminal of=0.020s has successfully sent its k grouping.This transmission terminal all is recorded in D=2 the pairing delivery time of grouping that its success recently sends in the buffer memory.If t _K-2=0.005s and t _K-1=0.015s.Like this at moment t _k=0.020s, sending the data throughput that terminal contributes for No. 1 can be estimated as $s_1\≈\frac{D\·T_L}{t_k-t_{k-2}}=\frac{2*0.0014545}{0.020-0.005}=0.19393.$ Simultaneously, sending terminal for No. 1 also notes at moment t _K-2To t _kDuring this time, send the packet count N of terminals institute success transmission for No. 2 ₂=3.Like this, at moment t _k, we can be estimated as the data throughput that No. 2 transmission terminals are contributed $s_2\≈\frac{N_2\·T_L}{t_k-t_{k-2}}=\frac{3*0.0014545}{0.020-0.005}=0.29090.$ Total data throughput can be estimated as S=s ₁+ s ₂=0.48483.

Step 2: based on the data throughput S and the s that estimate to obtain _i(i=1,2) calculate θ _1,1, θ _2,1, θ _3,1, θ _1,2, θ _2,2And θ _3,2At first according to formula (1) and (2) calculating parameter T _cAnd T _sAccording to the regulation of IEEE 802.11b, we have following parameter setting: PHY _Header+ MAC _Header=0.0002167s, ACK=0.0002022s, SIFS=0.00001s, DIFS=0.00005s, σ=0.00002s.Like this

T _s＝PHY _header+MAC _header+T _L+SIFS+ACK+DIFS

＝0.0002167+0.0014545+0.00001+0.0002022+0.00005

＝0.0019334s

T _c＝PHY _header+MAC _header+T _L+DIFS

＝0.0002167+0.0014545+0.00005

＝0.0017212s

T has been arranged _cAnd T _s, we can obtain:

${\mathrm{\θ}}_{\mathrm{1,1}}=T_L\·\underset{j=1}{\overset{2}{\mathrm{\Σ}}}\frac{s_j}{s_1}=0.0014545*(1.0+1.5)=0.0036363$

${\mathrm{\θ}}_{\mathrm{2,1}}=T_s\·\underset{j=1}{\overset{2}{\mathrm{\Σ}}}\frac{s_j}{s_1}=0.0019334*(1.0+1.5)=0.0048335$

${\mathrm{\θ}}_{\mathrm{3,1}}=T_c\·\underset{\underset{j\≠k}{1\≤j,k\≤2}}{\mathrm{\Σ}}\frac{s_j\·s_k}{{s_1}^2}=0.0017212*1.5=0.0025818$

${\mathrm{\θ}}_{1,2}=T_L\·\underset{j=1}{\overset{2}{\mathrm{\Σ}}}\frac{s_j}{s_2}=0.0014545*(1.0+0.6666)=0.0024242$

${\mathrm{\θ}}_{2,2}=T_s\·\underset{j=1}{\overset{2}{\mathrm{\Σ}}}\frac{s_j}{s_2}=0.0019334*(1.0+0.6666)=0.0032223$

${\mathrm{\θ}}_{3,2}=T_c\·\underset{\underset{j\≠k}{1\≤j,k\≤2}}{\mathrm{\Σ}}\frac{s_j\·s_k}{{s_2}^2}=0.0017212*0.6666=0.0011475$

Step 3: each sends the pairing τ of terminal according to formula (3) calculating parameter _i(i=1,2).

${\mathrm{\τ}}_1=\frac{({\mathrm{\θ}}_{\mathrm{1,1}}-S{\mathrm{\θ}}_{\mathrm{2,1}})-\sqrt{{({\mathrm{\θ}}_{\mathrm{1,1}}-S{\mathrm{\θ}}_{\mathrm{2,1}})}^2-4\mathrm{\σ}{\mathrm{\θ}}_{\mathrm{3,1}}{S}^2}}{2S{\mathrm{\θ}}_{\mathrm{3,1}}}=0.0075557$

${\mathrm{\τ}}_2=\frac{({\mathrm{\θ}}_{1,2}-S{\mathrm{\θ}}_{2,2})-\sqrt{{({\mathrm{\θ}}_{1,2}-S{\mathrm{\θ}}_{2,2})}^2-4\mathrm{\σ}{\mathrm{\θ}}_{3,2}{S}^2}}{2S{\mathrm{\θ}}_{3,2}}=0.011334$

Step 4: each sends the pairing p of terminal according to formula (4) calculating parameter _i(i=1,2).

p ₁＝1-(1-τ ₂)＝0.011334

p ₂＝1-(1-τ ₁)＝0.0075557

Step 5: the desired value of calculating " minimum competition window size " according to formula (5).

$W_1=\frac{{\hat{T}}_{d,1}-\frac{T_s}{1-p_1}}{(\frac{T_L}{s_1}-\frac{T_s}{1-p_1})\·\frac{(1-p_1)\·{\mathrm{\τ}}_1}{2(1-2p_1)}}$

$=\frac{0.010-\frac{0.0019334}{1.0-0.01133354}}{(\frac{0.0014545}{0.1939333}-\frac{0.0019334}{1.0-0.01133354})*\frac{(1.0-0.01133354)*0.00755574}{2.0*(1.0-2.0*0.01133354)}}$

$=379.66$

Like this, No. 1 transmission terminal is set to 380 (noticing that " minimum competition window size " must round numerical value) with its " minimum competition window size " and can guarantees that the average retardation of its packet reaches ${\hat{T}}_{d,1}=0.010s.$ Determined that this transmission terminal is just carried out in strict accordance with the back off algorithm of IEEE 802.11 prescribed by standard after the value of " minimum competition window size ".Please refer to IEEE 802.11 standards about back off algorithm.When this transmission terminal is every successfully send a grouping after, just can repeat by the process of step 1, thereby constantly adjust its " minimum competition window size ", and packetization delay is remained on to step 5 ${\hat{T}}_{d,1}=0.010s.$

Step 6: new " the minimum competition window size " of using formula (5) to calculate goes to control the backoff procedure (referring to the standard code of IEEE 802.11) that sends terminal.

Claims (1)

1, a kind of control method of radio local network block transmission delay is characterized in that concrete steps are:

Step 1: at moment t _k, i (i=1 ..., H) individual transmission terminal successfully send it k the grouping after, data estimator throughput S and s _i(i=1 ..., H), wherein, H sends number of terminals;

Step 2: based on the data throughput S that estimates to obtain and by i (i=1 ..., H) the data throughput s that contributes of individual Business Stream _i(i=1 ..., H), calculate ${\mathrm{\θ}}_{1i}=T_l\·\underset{l=1}{\overset{H}{\mathrm{\Σ}}}\frac{s_l}{s_i}(i=1,...,H),$ ${\mathrm{\θ}}_{2,i}=T_s\·\underset{l=1}{\overset{H}{\mathrm{\Σ}}}\frac{s_l}{s_i}(i=1,...,H)$ With ${\mathrm{\θ}}_{3i}=T_c\·\underset{\underset{i\≠k}{1\≤\mathrm{ik}\≤H}}{\mathrm{\Σ}}\frac{s_i\·s_k}{{s_i}^2}(i=1,...,H),$ Wherein, T _lBe the transmission time of payload on wireless channel of each packet,

T _c＝PHY _header+MAC _header+T _l+DIFS；

In the formula, PHY _HeaderThe Channel Transmission time of expression physical packet of data head; MAC _HeaderThe Channel Transmission time of expression multiple access Access Layer data packet header; ACK represents to confirm Channel Transmission time of dividing into groups; SIFS and DIFS are the preset parameter of stipulating in IEEE 802.11 standards;

Step 3: each sends the pairing τ of terminal calculating parameter _i(i=1 ..., H),

${\mathrm{\τ}}_i=\frac{({\mathrm{\θ}}_{1i}-{\mathrm{S\θ}}_{2i})-\sqrt{{({\mathrm{\θ}}_{1i}-{\mathrm{S\θ}}_{2i})}^2-{4\mathrm{\σ\θ}}_{3i}{S}^2}}{2{\mathrm{S\θ}}_{3i}},$

Wherein σ represents the length of an idle time slot in the backoff procedure;

Step 4: each sends the pairing p of terminal calculating parameter _i(i=1 ..., H);

$p_i=1-\underset{l=1,l\≠i}{\overset{H}{\mathrm{\Π}}}(1-{\mathrm{\τ}}_i)$

Step 5: calculate the desired value of " minimum competition window size ", and finish to " minimum competition window size " W _iAdjustment, $W_i=\frac{{\hat{T}}_{\mathrm{di}}-\frac{T_s}{1-p_i}}{(\frac{T_l}{S_i}-\frac{T_s}{1-p_i})\·\frac{(1-p_i)\·{\mathrm{\τ}}_i}{2(1-{2p}_i)}},$ Wherein,

Be i (i=1 ..., H) the target mean packet delay of individual transmission terminal;

Step 6: new " the minimum competition window size " of using step 5 to calculate goes to control the backoff procedure that sends terminal.

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