CN100553359C - In the BWA based on measuring and the acceptance controlling method of QoS - Google Patents

Abstract

The invention reside in acceptance controlling method field in the BWA, it is characterized in that judging type of service, the business of doing one's best is allowed to insert; Whether the non-real-time polling service of the non-application of the 1st priority being authorized business and the 3rd priority is judged less than the given bandwidth of system by professional actual bandwidth and system dedicated bandwidth sum; To the real-time polling service of the 2nd priority, screen as described above by professional actual bandwidth earlier, secondly, again by whether being that the GPC pattern is judged, if the GPC pattern is then judged by professional time-delay.The present invention adopts actual bandwidth and the admission control scheme that time-delay combines simultaneously, has improved quality of real-time service, has optimized systematic function.

Description

In the BWA based on measuring and the acceptance controlling method of QoS

Technical field

The present invention relates to admit in a kind of broadband wireless access (BWA) system the algorithm of control, belong to wireless communication technology field based on IEEE 802.16.

Background technology

IEEE 802.16 standards are air interface specification of wireless MAN, and crucial meaning and wide application prospect are arranged in the broadband wireless access in future.802.16 standard not only allows non line of sight to connect, supports large-capacity user, and can provide carrier-class QoS assurance, the application of the multimedia service that support voice, video, data etc. are abundant comprehensively.

The effective QoS guarantee system must carry out reasonable distribution to Radio Resource, and especially at the complex environment under the wireless communications environment, the QoS system of wireless access system faces a lot of challenges.802.16 standard has been implemented a series of mechanism at the MAC layer.Admittance control is the Critical policies in the BWA QoS guarantee system.By admitting control, system can estimate system resource and traffic performance before formal communication, at the QoS of survice that can satisfy new access with do not influence under the prerequisite of the QoS of survice that has inserted and allow service access, and refusal does not satisfy the business of admittance condition.

There is the business of four kinds of different grades of service in IEEE 802.16 systems, be respectively that business (unsolicited grantservice is authorized in non-application, UGS), real-time polling service (real-time polling service, rtPS), non-real-time polling service (non-real-timepolling service, nrtPS), the business of doing one's best (best effort service, BE).

The existing acceptance method of admitting strategy to be based on bandwidth, its concrete realization flow is as follows:

The bandwidth B of can use for fixed system is established when new business arrives, and the already used bandwidth of system is B _Used, establishing the professional required bandwidth of UGS is b _UGS, the professional required minimum bandwidth of rtPS and nrtPS is b _Min, maximum bandwidth is b _Max

If new business is the UGS business, if B then _Used+ b _UGS＜B allows the UGS service access system and distributes b _UGSBandwidth reserved, otherwise the refusal;

If new business is the rtPS business, if B then _Used+ b _Max＜B allows service access and distributes b _MaxBandwidth reserved, otherwise the refusal;

If new business is the nrtPS business, if B then _Used+ b _Min＜B allows service access and distributes b _MinBandwidth reserved, otherwise the refusal;

The BE business is all allowed to insert, but do not distribute bandwidth reserved.

Because the required bandwidth of rtPS and nrtPS business is at (b _Min, b _Max) between distribute, so judge whether that with maximum or minimum bandwidth admittance is not very reasonable at every turn.Such as to the rtPS business, if the rtPS business that arrives does not need maximum bandwidth, but judge access according to maximum bandwidth, then can cause the rtPS business block rate bigger, contrast other business and lose fairness.

Simultaneously, for real-time rtPS business, existing acceptance controlling method has only adopted the method for bandwidth control, does not consider the parameter of the time-delay, packet loss etc. of real time business, therefore, also can't guarantee the service quality of real time business.A good acceptance algorithm need be taken all factors into consideration QoS parameters such as bandwidth, time-delay, packet loss, could guarantee for communication system provides QoS.

Summary of the invention

The objective of the invention is to propose in a kind of IEEE of being applied in 802.16 BWA based on measuring the admission control algorithm that guarantees with QoS, can under the situation that does not influence the system bandwidth resource utilization, effectively reduce the packet loss of real time business, improve service quality, obtain better system performance.

The invention is characterized in, contain following steps successively:

Step (1), when new business arrives, the type of new business is judged in the base station of described BWA based on IEEE 802.16, system all allows to insert to Best-Effort service, other business are carried out priority classification, and the wherein non-application business of authorizing is classified the 1st priority as, and real-time polling service is classified the 2nd priority as, non-real-time polling service is classified the 3rd priority as, handles according to the following steps at different types of service respectively;

Step (2), for the business of doing one's best, this base station allows to insert, and changes step (6);

Step (3) is authorized business for non-application, and this base station judges that whether the given available bandwidth B of system is greater than the already used bandwidth B of system _UsedWith the required bandwidth B of new business _UGSSum if the available bandwidth more given than system is big, then allows to insert, and change step (6), otherwise refusal inserts;

Step (4), for non-real-time polling service, carry out according to the following steps this base station:

Step (4.1) is measured the actual bandwidth b of described business _m

Adopt the time window method of measurement, step is as follows:

A time window is divided into 10 sampling periods, in each cycle, calculates the average utilized bandwidth of each class service

Sampling time is S, upgrades the value of estimated bandwidth below under 4 kinds of situations: 1. when time window finishes, get maximum

As estimated bandwidth; 2. when inserting new stream, upgrade estimated bandwidth, and restart time window; 3. work as

When surpassing estimated bandwidth, with

As estimated bandwidth; 4. when first-class leaving, upgrade estimated bandwidth, and restart time window; The more new formula of estimated bandwidth is as follows:

Wherein, b _mBe the estimated bandwidth that upgrades, i.e. Ye Wu actual measurement bandwidth;

Be the average utilized bandwidth among the S;

r ^pFor business information produces speed;

β is that bandwidth reduces the factor, when stream finishes deviated from network, needs to reduce the estimated value of utilized bandwidth, and the bandwidth of minimizing equals the equivalent bandwidth of this stream, should determine different values according to the β that is not all of stream, for shortcut calculation, can get β=1;

Whether step (4.2) judge gives bandwidth B that fixed system can use greater than the actual bandwidth b of already used bandwidth of system and described business _mSum if the bandwidth B that system can use for big, then allows to insert, change step (6), otherwise refusal inserts;

Step (5), for real-time polling service, carry out according to the following steps the base station:

Step (5.1) is measured the actual bandwidth b of described business _m, the same step of method of measurement (4.1);

Step (5.2) judges that whether the available bandwidth B of system is greater than system dedicated bandwidth B _UsedWith described actual bandwidth sum; If the available bandwidth B of system is big, then enter step (5.3);

Otherwise just refusal inserts;

Step (5.3) judges whether described business is the GPC pattern, and this pattern is meant that the base station is that each connects distribution setting bandwidth;

If the GPC pattern is just judged:

p _i＜P _iNot, p _i＜P _iIn time, allow to insert, otherwise the refusal access,

Wherein, p _iPacket loss for described professional i is calculated as follows:

$p_i=\frac{{\mathrm{\λ}}_i}{{\mathrm{\μ}}_i}{e}^{-({\mathrm{\μ}}_i-{\mathrm{\λ}}_i)(D_i-\mathrm{Ts})}$

λ _iBe the Poisson parameter that bag arrives, this value is by measuring;

μ _iBe the complex exponential distributed constant of service time of bag, this value is by measuring;

D _iMaximum delay for professional i permission tolerance is the default index parameter;

Ts is the frameing time compensation, is system default parameter;

P _iBe the maximum packet loss of setting according to Service Quality Metrics, be the default index parameter;

If not the GPC pattern is undertaken by next step;

Step (5.4) is pressed the GPSS pattern and is carried out, and this pattern is meant the bandwidth that the base station is set for each terminal distribution, and terminal is redistributed bandwidth in its several connections;

W is judged in this base station ₂＜D not,

${\mathrm{<figure-callout\; id="2"\; label="W"\; filenames="C20061011277500132.png"\; state="\{\{state\}\}">W</figure-callout>}}_2=\frac{T_1}{(1-{\mathrm{\&rho;}}_1-{\mathrm{\&rho;}}_2)\&times;(1-{\mathrm{\&rho;}}_1)}$

T ₁Be the time of waiting for that information desk is vacated, ${\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="C20061011277500121.png,C20061011277500122.png"\; state="\{\{state\}\}">T</figure-callout>}}_1=\mathrm{\&Sigma;}\frac{{\mathrm{\&lambda;}}_i}{2}({\mathrm{<figure-callout\; id="2"\; label="h\; i"\; filenames="C20061011277500132.png"\; state="\{\{state\}\}">h</figure-callout>}}_i^{}+{\mathrm{\&sigma;}}_i^2),$ λ _iBe the Poisson parameter that the bag of the i priority that measures arrives, h _iBe the mean value of bag service time of i priority, σ _i ²Be variance service time;

ρ ₁=λ ₁h ₁, ρ ₂=λ ₂h ₂, λ, h are as described above;

D is the maximum delay that real-time polling service allows, and is the default index parameter;

W ₂It is the time-delay of real-time polling service;

If judged result is W ₂＜D just allow to insert, otherwise refusal inserts;

Step (6), the base station assigns bandwidth reserved.

The present invention introduces measurement mechanism, can obtain system's relevant parameter in real time, adopts bandwidth and the admission control scheme that time-delay combines simultaneously, can improve quality of real-time service, optimizes the BWA performance.

Description of drawings

The QoS guarantee system of Fig. 1 .IEEE 802.16 systems;

Fig. 2. existing admission control algorithm flow chart;

Fig. 3. the admission control algorithm flow chart that the present invention proposes;

Fig. 4. introduce the blocking rate contrast of measurement mechanism front and back: Fig. 4 a is each business block rate of existing algorithm, and its cathetus is that the service blocking rate curve is authorized in non-application, and the asterisk line is a real time business blocking rate curve, and line of dots is a non-real-time service blocking rate curve; Fig. 4 b is the service blocking rate of the algorithm behind the introducing measurement mechanism, and its cathetus is that the service blocking rate curve is authorized in non-application, and the asterisk line is a real time business blocking rate curve, and line of dots is a non-real-time service blocking rate curve;

Fig. 5. introduce the professional packet loss contrast of rtPS that time delay is admitted the control front and back;

Fig. 6. adopt the resource utilization ratio contrast of the present invention front and back.

Embodiment

For realizing the technical problem to be solved in the present invention, the present invention adopts a kind of two-layer admittance hierarchy of control based on bandwidth and time-delay of introducing measurement mechanism, comprises the steps:

At all business, at first carry out admission judgment according to bandwidth, if the total bandwidth that the bandwidth sum of already used bandwidth of system and new business can provide less than system then allows service access, otherwise refusal.In order to guarantee real-time, adopt method of measurement to obtain the bandwidth of rtPS and nrtPS business, carry out the bandwidth admission judgement to measure bandwidth.

At real-time rtPS business, after the bandwidth in having carried out (1) is judged, the judgement of delaying time again.According to the parameter of the Business Stream that measures, carry out modeling with the correlation technique of queuing theory, obtain the time-delay of rtPS business or the measurement of packet loss, whether compare with corresponding QoS parameter allows the judgement of admitting.Allow to insert if i.e. time-delay of real time business or packet loss index satisfy quality of service requirement, otherwise refusal inserts.

Below the specific embodiment of the present invention is further described.

Fig. 3 is the flow chart of admission control algorithm of the present invention, specifies as follows:

After new business arrives, at first carry out judging based on the admittance control of bandwidth.The bandwidth B of can use for fixed system is established when new business arrives, and the already used bandwidth of system is B _Used, establishing the professional required bandwidth of UGS is b _UGS, the professional actual bandwidth of rtPS that measures and nrtPS is b _mAdmit control module at first to judge type of service.

If new business is the UGS business, if B then _Used+ b _UGS＜B allows the UGS service access system and distributes b _UGSBandwidth reserved, otherwise the refusal;

If new business is the rtPS business, if B then _Used+ b _m＜B begins the admission judgment of delaying time, otherwise refusal;

If new business is the nrtPS business, if B then _Used+ b _m＜B allows to insert and distribute b _mBandwidth reserved, otherwise the refusal;

The BE business is all allowed to insert, but do not distribute bandwidth reserved.

For the rtPS business that enters the time-delay admission judgment in (2), carry out admission judgment according to the time-delay admission control algorithm.

802.16 MAC two kinds of patterns are arranged, a kind of is GPC (Grant Per Connection) pattern, be that the base station is that each connects the certain bandwidth of distribution, a kind of is GPSS (Grant Per Subscriber Station) pattern, be that the base station is the certain bandwidth of each terminal distribution, terminal is redistributed bandwidth in its several connections.

Which kind of for the rtPS business that enters the time-delay admission judgment in (2), at first judge to belong to MAC pattern.

If the GPC pattern then adopts the time-delay control strategy based on the GPC pattern.

The admission judgment condition is: if p _i＜P _i, then allow the rtPS service access, otherwise refusal.

Wherein, p _iBe the packet loss of professional i, P _iBe maximum packet loss, be preset parameter as Service Quality Metrics.

The packet loss p of professional i _iComputational process as follows:

Suppose the arrival obedience Poisson distribution of business packet, obey negative exponent the service time of bag and distribute, then the approximate modeling of the buffer memory of SS end is become the M/M/1 formation.

The Poisson parameter that measures the business packet arrival is λ _i, the negative exponent distributed constant is μ _i

According to the conclusion of queuing theory, the stand-by period W of bag is distributed as:

$G\left(w\right)=1-\frac{{\mathrm{\&lambda;}}_i}{{\mathrm{\&mu;}}_i}{e}^{-({\mathrm{\&mu;}}_i-{\mathrm{\&lambda;}}_i)w}$

Packet loss that then can computing service i is:

$p_i=p(W>(\mathrm{Di}-\mathrm{Ts}))$

$=1-G(\mathrm{Di}-\mathrm{Ts})$

$=\frac{{\mathrm{\&lambda;}}_i}{{\mathrm{\&mu;}}_i}{e}^{-({\mathrm{\&mu;}}_i-{\mathrm{\&lambda;}}_i)(\mathrm{Di}-\mathrm{Ts})}$

Wherein, D _iBe the maximum delay that professional i can tolerate, Ts is the frameing time compensation.

The packet loss p of professional i then _iCan be in the hope of, the judgment expression p that admits according to time delay then _i＜P _iCarry out the professional judgement that whether inserts.

If be the GPSS pattern, then adopt time-delay control strategy based on the GPC pattern.

The condition of admission judgment is: if W ₂＜D then allows to insert, otherwise refusal.

Wherein, W ₂Be the professional time-delay of rtPS, D is the maximum delay that business can allow.

W ₂Computational process as follows:

Under the GPSS pattern, priority criteria is satisfied in the scheduling of SS end, and promptly in the service queue of four grades that SS holds, the bag that priority is high sends to wireless channel earlier, and the bag that priority is low only just can send when high-priority queue is sky.

Modeling becomes priority query.Wherein, UGS is the 1st priority, and rtPS is the 2nd priority, and nrtPS is the 3rd priority.

If the Poisson parameter that the i level bag that measures arrives is λ _i, average service time is h _i, variance is σ _i ², system's total traffic is ρ=∑ λ _ih _i, W is established in ρ＜1 _iIt is the stand-by period of i level bag.

According to priority queue's theory, establish and wait for that the time that information desk is vacated is T ₁, W is then arranged ₁=T ₁/ (1-ρ ₁), the average latency that recursion obtains k level bag is:

$W_k=W_{k-1}(1-\underset{i=1}{\overset{k-2}{\mathrm{\&Sigma;}}}{\mathrm{\&rho;}}_i)/(1-\underset{i=1}{\overset{k}{\mathrm{\&Sigma;}}}{p}_i)$

$=\frac{T_1}{(1-\underset{i=1}{\overset{k}{\mathrm{\&Sigma;}}}{\mathrm{\&rho;}}_i)(1-\underset{i=1}{\overset{k-1}{\mathrm{\&Sigma;}}}{\mathrm{\&rho;}}_i)}$

Therefore, the average latency of rtPS bag is:

${\mathrm{<figure-callout\; id="2"\; label="W"\; filenames="C20061011277500132.png"\; state="\{\{state\}\}">W</figure-callout>}}_2=\frac{T_1}{(1-{\mathrm{\&rho;}}_1-{\mathrm{\&rho;}}_2)\&times;(1-{\mathrm{\&rho;}}_1)}$

Wherein, ${\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="C20061011277500121.png,C20061011277500122.png"\; state="\{\{state\}\}">T</figure-callout>}}_1=\mathrm{\&Sigma;}\frac{{\mathrm{\&lambda;}}_i}{2}({\mathrm{<figure-callout\; id="2"\; label="h\; i"\; filenames="C20061011277500132.png"\; state="\{\{state\}\}">h</figure-callout>}}_i^{}+{\mathrm{\&sigma;}}_i^2),$ ρ _i＝λ _ih _i。

Then the time-delay admission judgment expression formula under the GPSS pattern is

W ₂＜D

Then can admit expression formula W according to time-delay again in the hope of the time-delay of rtPS business under the GPSS pattern ₂＜D judges, satisfies condition and then inserts, otherwise refusal.

In order to contrast the effect of the invention process front and back, algorithm of the present invention has been carried out emulation with Matlab, simulation parameter adopts B=2000kbps, b _UGS=32kbps, b _Min=32kbps, b _Max=32kbps, the Poisson parameter of three kinds of Business Streams is identical, and the value of itself and λ is from 1-10, and distributed constant service time of three kinds of business is 3.05.Suppose that rtPS that actual measurement is arrived and nrtPS service bandwidth evenly distribute the business time-delay of actual measurement and the positive correlation of λ size, and obeys index distribution in that (32,128) kbps is last.

Fig. 4 has represented the contrast of each service blocking rate before and after the introducing measurement mechanism, can see original admittance strategy because the professional maximum bandwidth that adopts of rtPS judges whether to admit, make the rtPS business block rate greater than other business block rate, and behind the introducing measurement mechanism, rtPS business block rate and other professional equilibriums.Corresponding to the audio frequency and video business of rtPS in the Radio Access Network in future in occupation of consequence, can effectively improve professional fairness so introduce measurement mechanism.

Fig. 5 has shown the professional packet loss contrast of the rtPS that adopts time-delay admittance front and back, behind the professional admission control scheme of introducing based on time-delay of rtPS, can see that the packet loss of real time business obviously descends, and along with the increase of system loading, it is stable that packet loss keeps.Simultaneously, because the restriction of time-delay control, the rtPS business block rate can increase.

Fig. 6 is the contrast of adopting the system bandwidth resource utilization of the present invention front and back.Because the admittance strategy that combines bandwidth and time-delay control can reduce the packet loss of real time business effectively, guarantee professional QoS, also increased simultaneously the blocking rate of real time business to a certain extent, and the measurement mechanism of introducing can reduce the blocking rate of real time business, therefore, we contrast the resource utilization ratio of the new algorithm that acceptance algorithm original in 802.16 systems and the present invention propose.In Fig. 6, can see employing

The resource utilization of system changes not quite after the algorithm of the present invention, and basic and original resource utilization ratio maintains an equal level, but has obviously improved the service quality of real-time rtPS business simultaneously, therefore, has improved the performance of system.

Claims (2)

1, in the BWA based on measuring and the acceptance controlling method of QoS, it is characterized in that, contain following steps successively:

Step (1), when new business arrives, the type of new business is judged in the base station of described BWA based on IEEE 802.16, system all allows to insert to Best-Effort service, other business are carried out priority classification, and the wherein non-application business of authorizing is classified the 1st priority as, and real-time polling service is classified the 2nd priority as, non-real-time polling service is classified the 3rd priority as, handles according to the following steps at different types of service respectively;

Step (2), for the business of doing one's best, this base station allows to insert, and changes step (6);

Step (3) is authorized business for non-application, and this base station judges that whether the given available bandwidth B of system is greater than the already used bandwidth B of system _UsedWith the required bandwidth B of new business _UGSSum if the available bandwidth more given than system is big, then allows to insert, and change step (6), otherwise refusal inserts;

Step (4), for non-real-time polling service, carry out according to the following steps this base station:

Step (4.1) is measured the actual bandwidth b of described business _m

Adopt the time window method of measurement, step is as follows:

A time window is divided into 10 sampling periods, in each cycle, calculates the average utilized bandwidth of each class service

Sampling time is S, upgrades the value of estimated bandwidth below under 4 kinds of situations: 1. when time window finishes, get maximum

As estimated bandwidth; 2. when inserting new stream, upgrade estimated bandwidth, and restart time window; 3. work as

When surpassing estimated bandwidth, with

As estimated bandwidth; 4. when first-class leaving, upgrade estimated bandwidth, and restart time window; The more new formula of estimated bandwidth is as follows:

Wherein, b _mBe the estimated bandwidth that upgrades, i.e. Ye Wu actual measurement bandwidth;

Be the average utilized bandwidth among the S;

r ^pFor business information produces speed;

β is that bandwidth reduces the factor, when stream finishes deviated from network, needs to reduce the estimated value of utilized bandwidth, and the bandwidth of minimizing equals the equivalent bandwidth of this stream, should determine different values according to the β that is not all of stream;

Whether step (4.2) judge gives bandwidth B that fixed system can use greater than the actual bandwidth b of already used bandwidth of system and described business _mSum if the bandwidth B that system can use for big, then allows to insert, change step (6), otherwise refusal inserts;

Step (5), for real-time polling service, carry out according to the following steps the base station:

Step (5.1) is measured the actual bandwidth b of described business _m, the same step of method of measurement (4.1);

Step (5.2) judges that whether the available bandwidth B of system is greater than system dedicated bandwidth B _UsedWith described actual bandwidth sum; If the available bandwidth B of system is big, then enter step (5.3);

Otherwise just refusal inserts;

Step (5.3) judges whether described business is the GPC pattern, and this pattern is meant that the base station is that each connects distribution setting bandwidth;

If the GPC pattern is just judged:

p _i＜P _iNot, p _i＜P _iIn time, allow to insert, otherwise the refusal access,

Wherein, p _iPacket loss for described professional i is calculated as follows:

$p_i=\frac{{\mathrm{\&lambda;}}_i}{{\mathrm{\&mu;}}_i}{e}^{-({\mathrm{\&mu;}}_i-{\mathrm{\&lambda;}}_i)(D_i-\mathrm{Ts})}$

λ _iBe the Poisson parameter that bag arrives, this value is by measuring;

μ _iBe the complex exponential distributed constant of service time of bag, this value is by measuring;

D _iMaximum delay for professional i permission tolerance is the default index parameter;

Ts is the frameing time compensation, is system default parameter;

P _iBe the maximum packet loss of setting according to Service Quality Metrics, be the default index parameter;

If not the GPC pattern is undertaken by next step;

Step (5.4) is pressed the GPSS pattern and is carried out, and this pattern is meant the bandwidth that the base station is set for each terminal distribution, and terminal is redistributed bandwidth in its several connections;

W is judged in this base station ₂＜D not,

$W_2=\frac{T_1}{(1-{\mathrm{\&rho;}}_1-{\mathrm{\&rho;}}_2)\&times;(1-{\mathrm{\&rho;}}_1)}$

T ₁Be the time of waiting for that information desk is vacated, $T_1=\mathrm{\&Sigma;}\frac{{\mathrm{\&lambda;}}_i}{2}(h_i^2+{\mathrm{\&sigma;}}_i^2),$ λ _iBe the Poisson parameter that the bag of the i priority that measures arrives, h _iBe the mean value of bag service time of i priority, σ _i ²Be variance service time;

ρ ₁=λ ₁h ₁, ρ ₂=λ ₂h ₂, λ, h are as described above;

D is the maximum delay that real-time polling service allows, and is the default index parameter;

W ₂It is the time-delay of real-time polling service;

If judged result is W ₂＜D just allow to insert, otherwise refusal inserts;

Step (6), the base station assigns bandwidth reserved.

2, in the BWA according to claim 1 based on measuring and the acceptance controlling method of QoS, it is characterized in that described β=1.

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