CN101442778A - Scheduling method of high speed wireless personal network protocol based on channel - Google Patents

Abstract

The invention relates to a dispatching method based on channel in high speed wireless personal web protocol. In real time and non-real time data transmission in high speed wireless personal network based on IEEE 802.15.3 protocol, channel status information is fed back and collected for every data stream of user by modifying protocol; data stream is ranked by integrative balancing according to QoS request of every data stream and endowed with different dispatching priority, thereby effectively overcoming channel fading influence to network performance and promoting channel utilization rate of system.

Description

In the high speed wireless personal network protocol based on the dispatching method of channel

Technical field

The present invention relates to the correlative technology field of wireless personal network, specifically in the high speed wireless personal network protocol based on the dispatching method of channel.

Background technology

Based on adopting time-division multiplexing multiple access mode and centralized channel allocation mechanism that transfer of data between the multi-user is provided in the high speed wireless personal network network agreement of IEEE 802.15.3.In this standard, the most basic time structure is superframe (as Fig. 1), comprises in each superframe that some channel time slots distribution (CTA) are in order to the specified data transfer between devices of this CTA.CTA is distributed according to specific dispatching algorithm by net control device (PNC).This allocation result is broadcasted in the beacon frame (Beacon) that each superframe begins by net control device.Management channel time slot allocation (MCTA) is special CTA, is used for the Signalling exchange between the network equipment and the net control device.Need carry out the equipment of data transmission and be responsible for, insert quantity and the needed schedule information of channel resource allocation that sends the channel resource of asking in period (CAP) to net control device corresponding to the competition in each superframe in Random Access Channel.

IEEE 802.15.3 physical layer is operated between the 2.4GHz to 2.4835GHz that does not need licence, the transmission rate of physical layer has five kinds of 11Mbps, 22Mbps, 33Mbps, 44Mbps and 55Mbps, the symbol transmission speed of system's regulation is 11Mbps, be respectively Trellis-coded modulation (Trellis Coded Modulation, TCM) QPSK, DQPSK, TCM16QAM, TCM32QAM and TCM64QAM with five kinds of corresponding code modulation modes of speed.By the self adaptation adjustment of transmission rate, can effectively improve the throughput and the bit error rate performance of system.

Because IEEE 802.15.3 agreement is not made regulation to the dispatch channel resource algorithm, the dispatching algorithm of traditional regular length time slot can't make full use of channel resource again, and this just provides prerequisite and Practical significance for the application based on the dispatching algorithm of channel status efficiently.

Dispatching algorithm based on channel extensively is used in cdma2000 1xEV-DO, HSDPA, and EVDO in the systems such as 4G, and does not propose as yet in the IEEE802.15.3 high speed wireless personal network and adopts.The dispatching algorithm based on channel of extensive concern has 1 at present) the MAX-RATE algorithm; 2) PROP-FAIR algorithm; 3) M-LWDF algorithm; 4) EXP algorithm.

The basic way of MAX-RATE algorithm is according to the transmission rate that the current channel conditions of data flow is supported it to be sorted from big to small, and data stream is carried out the distribution of channel resource according to this order.Its formulate is as follows:

$j=\arg \underset{i}{\max }{\mathrm{\μ}}_i\left(t\right)---\left(1\right)$

μ wherein _i(t) be corresponding to the current message transmission rate of supporting of the wireless channel of data flow i.

The PROP-FAIR algorithm once adopted in cdma2000 1xEV-DO (data optimized), and at the shortcoming of fairness difference in the MAX-RATE algorithm, it has redefined other computational methods of data flow service priority:

$j=\arg \underset{i}{\max }\frac{{\mathrm{\μ}}_i\left(t\right)}{{\stackrel{\‾}{\mathrm{\μ}}}_i\left(t\right)}---\left(2\right)$

μ wherein _i(t) refer at current time t certain hour window T _CThe average transmission rate that the data flow of interior statistics is supported, promptly

${\stackrel{\‾}{\mathrm{\μ}}}_i(t+1)=(1-\frac{1}{T_C}){\stackrel{\‾}{\mathrm{\μ}}}_i\left(t\right)+\frac{1}{T_C}{\mathrm{\μ}}_i\left(t\right)---\left(3\right)$

The M-LWDF algorithm adopts following formula to select the data flow of the allocation of channel resources may of wanting.

$j=\arg \underset{i}{\max }{\mathrm{\γ}}_i{\mathrm{\μ}}_i\left(t\right)W_i\left(t\right)---\left(4\right)$

W wherein _i(t) refer to stand-by period of HOL (the head of line) packet in the t data flow i buffering area formation constantly, γ _iExpression formula as follows:

γ _i＝α _i/μ _i，α _i＝-log(δ _i)/T _i (5)

T wherein _iBe meant the network lifetime (deadline) of packet among the data flow i, δ _iThe qos parameter that refers to data flow i can be seen as the probability that the packet awaits time surpasses the maximum delay restriction, and there is following relation in above parameter:

P(W _i>T _i)≤δ _i (6)

The EXP class of algorithms is similar to the M-LWDF algorithm, and it also is that time delay with each data flow takes into account, and it is as follows to provide other computing formula of data flow service priority:

$j=\arg \underset{i}{\max }{\mathrm{\γ}}_i{\mathrm{\μ}}_i\left(t\right)\exp \left(\frac{a_i{W}_i\left(t\right)-\stackrel{\‾}{W}}{1+\sqrt{\stackrel{\‾}{W}}}\right)---\left(7\right)$

Wherein $\stackrel{\‾}{W}=\frac{1}{N}\underset{i}{\mathrm{\Σ}}{a}_i{W}_i\left(t\right)$ , for treating the weighted average stand-by period of the HOL packet in the formation of service data streambuf.γ _iWith α _iValue identical with the M-LWDF algorithm.

M-LWDF and EXP algorithm have fully taken into account the requirement for QoS of channel conditions under the different pieces of information flow transmission and data flow.M-LWDF algorithm and EXP algorithm all have been proved to be and have been throughput-optimal, that is to say, under the hypothesis for the traversal stationary random process, these two kinds of algorithms have maximum system stability zone in data flow arrival process and channel variation.As can be seen, α in these two kinds of dispatching algorithms _iBe priority parameters, give certain data flow higher α _iValue can make it obtain bigger throughput and littler time delay, but the too high priority that certain bar data flow is set diminishes the fairness between data flow and cause the entire system performance to descend, and therefore, needs rationally to be provided with and to adjust α _iValue, with the qos requirement of all data flow of As soon as possible Promising Policy.

Be subjected to factor affecting such as network topology structure and data flow feature, in some cases, multi-medium data transmission as high load capacity, we find performance existence to a certain degree the loss of simple employing based on the IEEE802.15.3 high speed wireless personal network network system of the dispatching algorithm of channel, have therefore introduced the robustness of following two kinds of cross-layer optimizing controlling mechanisms with enhanced system.

BTED (Burst transfer eligibility decision) mechanism is responsible for judging to send whether each packet can transmit in the data flow before it is overtime.If can not, then abandon this packet.This mechanism can effectively reduce the channel resource that causes owing to the unnecessary burst that is transmitted in its network lifetime packet that can not transmission success wastes.When adopting M-LWDF and EXP algorithm, this mechanism can effectively improve the throughput performance of system under high load capacity.

FDA (frame-decodability aware) mechanism designs for mpeg data stream specially.The video mpeg encoded is the video coding mode that extensively adopts at present.Mpeg data stream can be compressed into continuous GOP (Group of Picture) structure when coding, be illustrated in figure 2 as (12,3) gop structure, comprise I among the GOP, P, three kinds of data of different types frames of B, because different compression ratios makes the size of three kinds of frames that very big difference be arranged, usually the I frame is maximum, secondly is the P frame, and minimum is the B frame.The dependence of Code And Decode is a key character of mpeg data stream between the different types of data frame, shown in arrow among the figure.Have only correct and other Frames that it relied on of data frame transfer all to be correctly decoded, this Frame is only and can separates.

FDA mechanism can abandon the channel resource waste of determining that unsolvable mpeg frame brings to reduce these intangibility frames of transmission at transmitting terminal.As mentioned above, MPEG will rely on other frame in decode procedure.If the error of transmission of I frame then can be determined whole GOP intangibility, transmitting terminal can be lost whole GOP, and is same, and the GOP after P frame error of transmission meeting causes abandons.Compare the mechanism with BTED, FDA mechanism prevents indirect admission control (intangibility).

The dispatching method at IEEE 802.15.3 high speed wireless personal network network agreement that has proposed does not take into full account the requirement for QoS of channel information and data flow.The shortcoming of doing like this is mainly:

1) can not make full use of channel resource.The fading characteristic that the time-varying characteristics of radio communication channel and multipath transmisstion cause makes that the message transmission rate that can provide between the equipment in the network is different, and asynchronous fast change at random.Particular moment, the received signal to noise ratio of certain data flow may be very low, makes this data flow can only adopt lower speed rates, and transmitting identical data volume needs more time.Often can reduce average throughput and the system's delay performance that network can be supported greatly for such data flow channel resource allocation.Good dispatching method should be able to utilize these characteristics of channel, selects other data flow to transmit when certain data flow Channel Transmission situation is bad.For the channel of rapid fading, the pace of change of channel is very fast, data flow also can not occur and can not get the situation of serving for a long time.Therefore, thus improve channel utilization in the wireless personal network based on the harmful effect that the dispatch channel resource method of channel can be good at overcoming channel fading.

2) can not adapt to the requirement of different types of data flows for QoS.Because different types of data flows has different qos requirements, the lower system's time delay of transmission requirement of real-time voice and video stream, the transmission of general data then requires less frame error rate.Traditional dispatching method is not considered the QoS difference between the different data streams, and this causes real time data stream may have bigger system's time delay, but not the frame error rate of real time data stream also can not get reducing.

Summary of the invention

The purpose of this invention is to provide in the high speed wireless personal network protocol dispatching method based on channel, solved existing method and can not make full use of channel resource and can not adapt to the problem of different types of data flows, overcome the influence of channel fading network performance for the requirement of QoS.

For achieving the above object, the present invention has adopted following technical scheme:

The invention discloses in a kind of high speed wireless personal network protocol based on the dispatching method of channel, scheduling process is specific as follows:

1) after the network equipment is finished data flow registration work, net control device (PNC) is according to the priority parameters initial value of priority (Priority) (referring to Table A 1 in [1]) the specified data stream scheduling of channel resource request control domain in the channel resource requested data block in channel resource request (Channeltime request) signaling.As for video stream data, we get the δ in (5) formula _i=0.01, T _i=100ms.For audio data stream, get δ _i=0.01, T _i=10ms.Above-mentioned parameter can be used as default parameter and designs with simplified system, but this priority parameters can be carried out system function optimization according to the adjustment of transfer of data situation.

2) network equipment application BTED and FDA (when the transmission mpeg data stream) mechanism sends or filters sending data flow before to net control device (PNC) transmission schedule information in data according to current data packet formation and channel information.For BTED mechanism, the network equipment adopts HOL packet residue length and current channel condition μ _i(t) calculate the required expection residue transmission time of this packet, and compare, if the transmission time greater than the rest network life span, then abandons this packet with this packet rest network life span.For BTED mechanism, then adopt the interframe dependence to judge whether present frame can be separated, and abandon and be judged as unsolvable frame according to the transmission result of frame before this GOP of record.The packet that is dropped is defined as bust this, the notice upper-layer protocol.

3) each network equipment is responsible for sending the required relevant information of dispatch channel resource of its transmitting data stream of signaling net control device (PNC).This signaling can be at competition access channel (corresponding to the CAP time slot in the superframe), the CTA of this data flow, or send among the open MCTA of PNC specific assigned.The signaling format design is as follows:

octets：1	1	1	2	2
					Waiting Time	Queue Lenght	Transmission Rate	Length(＝3)	Command Type

Command Type is Scheduling information update, corresponding to retention of signaling type in the IEEE802.15.3 standard, as 0 x 001D.

According to the IEEE802.15.3 standard, Length is a signaling length, is 3bytes at this.

The message transmission rate that Transmission Rate will adopt at next superframe corresponding to corresponding data flow, desirable 0 x 00-0 x 05.This data flow of 0 x 00 expression is crossed reason such as low and is not carried out transfer of data at next superframe owing to received power, and 0 x 01-0 x 05 corresponds respectively to IEEE802.15.3 physical layer 11-55Mbps message transmission rate.

Queue Length is the data packet queue length of corresponding data flow.This length is unit with the data fragmentation number, and value is 0-255.

Waiting Time is made as the stand-by period of first packet in the data flow, and unit is the superframe number.

PNC is responsible for safeguarding the schedule information of each data flow.At first, the distribution MCTA in net control device (PNC) cycle is not so that there is the data flow of channel resource allocation its schedule information that can upgrade in time for a long time.The message transmission rate of relevant data stream, length of data queue, the information of packet stand-by period is by Scheduling information update signaling update, if through not receiving the information updating signaling of certain data flow behind the superframe, then the Waiting Time of this data stream scheduling information adds 1 in the net control device (PNC), Queue Length and Transmission Rate remain unchanged, after Waiting Time surpasses data flow network life span, Waiting Time, Queue Length and Transmission Rate zero clearing wait signaling to be updated.The μ that uses in the dispatching algorithm _iUpgrade according to (3) formula when (t) receiving Scheduling information update signaling by PNC

4) net control device sorts to each data flow according to (8) formula when each superframe begins, in the formula definition of each parameter identical with the 4th joint, come from data flow priority parameters and schedule information that net control device (PNC) is safeguarded.After the ordering, by the needed channel resource of this order assignment data flow, allocated length can obtain according to Transmission Rate in the data stream scheduling information of net control device (PNC) and Queue Length calculation of parameter, finishes or does not have data to need transmission up to current superframe channel resource allocation.

${\mathrm{\γ}}_i{\mathrm{\μ}}_i\left(t\right)\exp \left(\frac{a_i{W}_i\left(t\right)-\stackrel{\‾}{W}}{1+\sqrt{\stackrel{\‾}{W}}}\right)$

5) net control device is broadcasted the channel allocation result in beacon frame.

6) each equipment carries out transfer of data in the CTA that is distributed.If CTA still has residue after the transfer of data, can send the schedule information of this data flow of Scheduling Information Update signaling update.

Characteristics of the present invention are:

1) will introduce in the high speed wireless personal network to improve the channel utilization and the overall performance of network based on the dispatching method of channel conditions.

2) the reasonable disposition scheduling parameter is to optimize network performance.

3) design of feedback mechanism makes each bar data stream scheduling information needed can accurately and timely be sent to net control device (PNC).

Description of drawings

Fig. 1 is based on the superframe structure schematic diagram that adopts in the high speed wireless personal network network agreement of IEEE 802.15.3;

Fig. 2 is the gop structure schematic diagram;

Fig. 3 is based on the system schematic of the dispatching method of channel.

Embodiment

Below in conjunction with drawings and Examples the present invention is further described.

Based on the dispatching method of channel, its range of application is in the high speed wireless personal network protocol: based on the transmission of the real-time and non-real-time data in the high speed wireless personal network network of IEEE 802.15.3 agreement.Its prerequisite is: 1) transmission of each bar data flow can be carried out the self adaptation adjustment of transmission rate, and this can realize by add feedback mechanism in the ACK frame; 2) net control device (PNC) of informing that each bar data flow can be real-time is dispatched desired parameters.

In the IEEE 802.15.3 high speed wireless personal network protocol proposed by the invention based on the dispatching method system design of channel as shown in Figure 3.Scheduling process is specific as follows:

1) after the network equipment is finished data flow registration work, net control device (PNC) is according to the priority parameters initial value of priority (Priority) (referring to Table A 1 in [1]) the specified data stream scheduling of channel resource request control domain in the channel resource requested data block in channel resource request (Channeltime request) signaling.As for video stream data, we get the δ in (5) formula _i=0.01, T _i=100ms.For audio data stream, get δ _i=0.01, T _i=10ms.Above-mentioned parameter can be used as default parameter and designs with simplified system, but this priority parameters can be carried out system function optimization according to the adjustment of transfer of data situation.

2) network equipment application BTED and FDA (when the transmission mpeg data stream) mechanism sends or filters sending data flow before to net control device (PNC) transmission schedule information in data according to current data packet formation and channel information.For BTED mechanism, the network equipment adopts HOL packet residue length and current channel condition μ _i(t) calculate the required expection residue transmission time of this packet, and compare, if the transmission time greater than the rest network life span, then abandons this packet with this packet rest network life span.For BTED mechanism, then adopt the interframe dependence to judge whether present frame can be separated, and abandon and be judged as unsolvable frame according to the transmission result of frame before this GOP of record.The packet that is dropped is defined as bust this, the notice upper-layer protocol.

3) each network equipment is responsible for sending the required relevant information of dispatch channel resource of its transmitting data stream of signaling net control device (PNC).This signaling can be at competition access channel (corresponding to the CAP time slot in the superframe), the CTA of this data flow, or send among the open MCTA of PNC specific assigned.The signaling format design is as follows:

octets：1	1	1	2	2
					Waiting Time	Queue Lenght	Transmission Rate	Length(＝3)	Command Type

Command Type is Scheduling information update, corresponding to retention of signaling type in the IEEE802.15.3 standard, as 0 x 001D.

According to the IEEE802.15.3 standard, Length is a signaling length, is 3bytes at this.

The message transmission rate that Transmission Rate will adopt at next superframe corresponding to corresponding data flow, desirable 0 x 00-0 x 05.0x00 represents that this data flow crosses reason such as low and do not carry out transfer of data at next superframe owing to received power, and 0 x 01-0 x 05 corresponds respectively to IEEE802.15.3 physical layer 11-55Mbps message transmission rate.

Queue Length is the data packet queue length of corresponding data flow.This length is unit with the data fragmentation number, and value is 0-255.

Waiting Time is made as the stand-by period of first packet in the data flow, and unit is the superframe number.

PNC is responsible for safeguarding the schedule information of each data flow.At first, the distribution MCTA in net control device (PNC) cycle is not so that there is the data flow of channel resource allocation its schedule information that can upgrade in time for a long time.The message transmission rate of relevant data stream, length of data queue, the information of packet stand-by period is by Scheduling information update signaling update, if through not receiving the information updating signaling of certain data flow behind the superframe, then the Waiting Time of this data stream scheduling information adds 1 in the net control device (PNC), Queue Length and Transmission Rate remain unchanged, after Waiting Time surpasses data flow network life span, Waiting Time, Queue Length and Transmission Rate zero clearing wait signaling to be updated.The μ that uses in the dispatching algorithm _iUpgrade according to (3) formula when (t) receiving Scheduling information update signaling by PNC

4) net control device basis when each superframe begins Each data flow is sorted, in the formula definition of each parameter identical with previous narration, come from data flow priority parameters and schedule information that net control device (PNC) is safeguarded.After the ordering, by the needed channel resource of this order assignment data flow, allocated length can obtain according to Transmission Rate in the data stream scheduling information of net control device (PNC) and Queue Length calculation of parameter, finishes or does not have data to need transmission up to current superframe channel resource allocation.

5) net control device is broadcasted the channel allocation result in beacon frame.

6) each equipment carries out transfer of data in the CTA that is distributed.If CTA still has residue after the transfer of data, can send the schedule information of this data flow of Scheduling Information Update signaling update.

By a large amount of performance simulations, we verify the validity of the method that proposed.Emulation is to adopt network simulation instrument ns-2.In the emulation, it is the MPEG real time data of (12,3) that data flow adopts gop structure, and every streaming rate is 5Mbps, and the Frame network lifetime is 33ms, and the time started of data flow is independently of one another.Channel adopts the Rayleigh fading modeling.All devices is distributed in the zone of 10m * 10m, moves at random with the speed that is no more than 0.5m/s.Other simulation parameters see the following form.For the sake of simplicity, ignore CAP and signaling the transmission time and suppose the beacon frame transmissions zero defect.Simulation process continues 120s.

Throughput of system (unit is Mbps) is with the number of data streams variation relation under BTED and the FDA mechanism in order to adopt for following table, and system noise is-80dBm.As can be seen from the table, the EXP of consideration data flow qos requirement and M-LWDF algorithm performance are apparently higher than other algorithms.The performance of these two kinds of algorithms is not subjected to the influence of high network load, and (8-9 bar data flow) still can keep good performance when the total speed of data flow surpasses power system capacity.The performance of other algorithms is relatively approaching.

Claims (4)

1, in the high speed wireless personal network protocol based on the dispatching method of channel, it is characterized in that comprising following scheduling step:

1) after the network equipment is finished the data flow registration, net control device is according to the priority of channel resource request control domain in the channel resource requested data block in the channel resource demand signalling, and specified data flows the priority parameters initial value of scheduling;

2) network equipment application BTED and FDA mechanism send or filtered sending data flow before net control device sends schedule information in data according to current data packet formation and channel information;

3) each network equipment sends the required relevant information of dispatch channel resource of its transmitting data stream of signaling net control device; Net control device manages channel time slot periodically and distributes, more the schedule information of new data stream;

4) net control device priority parameters and schedule information according to data flow when each superframe begins sorts to each data flow, flow needed channel resource by this clooating sequence distribute data again, up to current superframe channel resource allocation finish or do not have data need the transmission;

5) net control device is broadcasted the channel allocation result in beacon frame;

6) each network equipment carries out transfer of data in the channel time slot of being distributed.

2, by in the described high speed wireless personal network protocol of claim 1 based on the dispatching method of channel, it is characterized in that: the signaling that each network equipment described in the step 3 sends comprises message transmission rate, length of data queue, packet stand-by period and this signaling length and the type field of its data flow.

3, by in the described high speed wireless personal network protocol of claim 1 based on the dispatching method of channel, it is characterized in that: the net control device described in the step 4 is concrete basis when each superframe begins ${\mathrm{\γ}}_i{\mathrm{\μ}}_i\left(t\right)\exp \left(\frac{a_i{W}_i\left(t\right)-\stackrel{\‾}{W}}{1+\sqrt{\stackrel{\‾}{W}}}\right)$ Sort;

μ wherein _i(t) be corresponding to the current message transmission rate of supporting of the wireless channel of data flow;

W _i(t) refer to t stand-by period of first packet in the data stream buffer sector row constantly;

${\mathrm{\γ}}_i=a_i/{\stackrel{\‾}{\mathrm{\μ}}}_i,a_i=-\log \left({\mathrm{\δ}}_i\right)/T_i,$ Wherein, T _iBe meant the network lifetime of packet among the data flow i, δ _iThe qos parameter that refers to data flow i;

$\stackrel{\‾}{W}=\frac{1}{N}\underset{i}{\mathrm{\Σ}}{a}_i{W}_i\left(t\right),$ For treating the weighted average stand-by period of first packet in the formation of service data streambuf.

4, by in the described high speed wireless personal network protocol of claim 1 based on the dispatching method of channel, it is characterized in that: in the described step 6, if the channel time slot of being distributed after the transfer of data still has residue, then send the schedule information of this data flow of Scheduling InformationUpdate signaling update.

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