CN1917708A - Reception contro method based on measurement and QoS in broadband radio access system - Google Patents

Abstract

The invention features to estimate the service type and does its best to allow the service to access; for the non-application authorized service of first priority and the nonreal time polling service, according to the sum of their actual bandwidth and the system-used bandwidth, giving a bandwidth decision; for the real time polling service of second priority, firstly according to its actual bandwidth, giving a bandwidth decision, and then according to whether or not it is a GPC mode, giving a decision; if it is a GPC mode, then giving decision according to service delay.

Description

Admission control method based on measurement and QoS in broadband wireless access system

Technical Field

The invention relates to an algorithm of admission control in a Broadband Wireless Access (BWA) system based on IEEE 802.16, belonging to the technical field of wireless communication.

Background

The IEEE 802.16 standard is an air interface specification of a wireless metropolitan area network, and has very important meaning and wide application prospect in future broadband wireless access. The 802.16 standard not only allows non-line-of-sight connection and supports high-capacity users, but also can provide carrier-grade QoS guarantee and comprehensively support the application of rich multimedia services such as voice, video, data and the like.

An effective QoS guarantee system must reasonably allocate radio resources, and particularly, for a complex environment in a wireless communication environment, the QoS system of a wireless access system faces many challenges. The 802.16 standard implements a series of mechanisms at the MAC layer. Admission control is an important policy in the QoS guarantee architecture of broadband wireless access systems. Through admission control, the system can estimate system resources and service characteristics before formal communication, allow service access on the premise of meeting newly accessed service QoS and not influencing the accessed service QoS, and reject services which do not meet admission conditions.

The IEEE 802.16 system has four services of different service classes, which are respectively non-application granted service (UGS), real-time polling service (rtPS), non-real-time polling service (nrtPS), and best effort service (BE).

The existing admission strategy is a bandwidth-based admission method, and the specific implementation flow is as follows:

given the bandwidth B available to the system, let B be the bandwidth already used by the system when a new service arrives_usedLet the bandwidth required by UGS service be b_UGSThe minimum bandwidth required for rtPS and nrtPS services is b_minMaximum bandwidth is b_max。

If the new service is a UGS service, then if B_used+b_UGS< B, allowing UGS service to access system and assigning B_UGSIf not, refusing;

if the new service is rtPS service, if B_used+b_max< B, service Access allowed and assignment B_maxIf not, refusing;

if the new service is nrtPS service, then if B_used+b_min< B, service Access allowed and assignment B_minIf not, refusing;

access is allowed to BE made to BE traffic, but reserved bandwidth is not allocated.

Since the required bandwidth of rtPS and nrtPS services is (b)_min，b_max) And so it is not reasonable to use the maximum or minimum bandwidth at a time to decide whether to admit or not. For example, for rtPS service, if the incoming rtPS service does not need the maximum bandwidth, but judges access according to the maximum bandwidth, it will lead to the connectionThe blocking rate of rtPS service is larger, and the fairness is lost compared with other services.

Meanwhile, for the real-time rtPS service, the existing admission control method only adopts a bandwidth control method, and does not consider parameters such as delay, packet loss rate and the like of the real-time service, so that the service quality of the real-time service cannot be ensured. A good admission algorithm needs to comprehensively consider the service quality parameters such as bandwidth, delay, packet loss rate, etc. to provide QoS guarantee for the communication system.

Disclosure of Invention

The invention aims to provide an admission control algorithm based on measurement and QoS guarantee, which is applied to an IEEE 802.16 broadband wireless access system, can effectively reduce the packet loss rate of real-time services under the condition of not influencing the utilization rate of system bandwidth resources, improves the service quality and obtains better system performance.

The invention is characterized by comprising the following steps in sequence:

step (1), when a new service arrives, the base station of the broadband wireless access system based on IEEE 802.16 judges the type of the new service, and lists the non-application granted service as the 1 st priority, the real-time polling service as the 2 nd priority and the non-real-time polling service as the 3 rd priority, and processes the following steps respectively aiming at different service types;

step (2), for the best-effort service, the base station allows access, and step (6) is switched;

step (3), for non-application grant service, the base station judges whether the given system available bandwidth B is larger than the bandwidth B already used by the system_usedBandwidth required for new service B_UGSIf the sum is larger than the available bandwidth given by the system, allowing access, and turning to the step (6), otherwise, rejecting access;

and (4) for the non-real-time polling service, the base station performs the following steps:

step (4.1) of measuring the actual bandwidth b of said traffic_m；

The method for measuring the time window comprises the following steps:

dividing a time window into 10 sampling periods, and calculating the average used bandwidth of each type of service in each period(sampling time is S), the value of the estimated bandwidth is updated in the following 4 cases: taking the maximum value when the time window is finished

As an estimated bandwidth; updating the estimated bandwidth and restarting the time window when a new flow is accessed; ③ when

When the estimated bandwidth is exceeded, toAs an estimated bandwidth; fourthly, when a flow leaves, updating the estimated bandwidth and restarting the time window; the update formula of the estimated bandwidth is as follows:

wherein, b_mIs the updated estimated bandwidth, i.e. the actual measured bandwidth of the traffic;

average used bandwidth in S;

r^pgenerating a rate for the traffic information;

beta is a bandwidth reduction factor, when a flow leaves the network after finishing leaving, the estimated value of the used bandwidth needs to be reduced, the reduced bandwidth is approximately equal to the equivalent bandwidth of the flow, different values can be determined for beta according to different flows, and the value of beta can be 1 in order to simplify the algorithm;

step (4.2), judging to giveWhether the bandwidth B available for the system is larger than the bandwidth already used by the system and the actual bandwidth B of the service_mIf the available bandwidth B of the system is large, allowing access, turning to the step (6), otherwise refusing access;

and (5) for the real-time polling service, the base station performs the following steps:

step (5.1) of measuring the actual bandwidth b of said traffic_mThe measuring method is the same as the step (4.1);

step (5.2), judging whether the available bandwidth B of the system is larger than the used bandwidth B of the system_usedThe sum of the actual bandwidth;

if the available bandwidth B of the system is large, entering the step (5.3);

otherwise, access is refused;

step (5.3), judge whether the said business is GPC mode, the mode means the base transceiver station distributes and sets up the bandwidth for each connection;

if the mode is GPC mode, judge:

p_i＜P_ino, p_i＜P_iWhen the access is allowed, otherwise the access is refused,

wherein p is_iCalculating the packet loss rate of the service i according to the following formula:

<math> <mrow> <msub> <mi>p</mi> <mi>i</mi> </msub> <mo>=</mo> <mfrac> <msub> <mi>&lambda;</mi> <mi>i</mi> </msub> <msub> <mi>&mu;</mi> <mi>i</mi> </msub> </mfrac> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mrow> <mo>(</mo> <msub> <mi>&mu;</mi> <mi>i</mi> </msub> <mo>-</mo> <msub> <mi>&lambda;</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mrow> <mo>(</mo> <msub> <mi>D</mi> <mi>i</mi> </msub> <mo>-</mo> <mi>Ts</mi> <mo>)</mo> </mrow> </mrow> </msup> </mrow> </math>

λ_imeasuring the acquired known value for the Poisson parameter of the service packet;

μ_imeasuring the obtained known value for the average service time of the service packet;

D_isetting a value for the maximum delay allowed to be tolerated by the service i;

ts is a framing time compensation and set value;

p_ia maximum packet loss rate set according to the service quality index;

if not, the method comprises the following steps;

step (5.4), executing in GPSS mode, where the base station allocates the set bandwidth for each terminal, and the terminal reallocates the bandwidth among several connections;

the base station determines W₂If the number < D is not greater than the preset value,

<math> <mrow> <msub> <mi>W</mi> <mn>2</mn> </msub> <mo>=</mo> <mfrac> <msub> <mi>T</mi> <mn>1</mn> </msub> <mrow> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <msub> <mi>&rho;</mi> <mn>1</mn> </msub> <mo>-</mo> <msub> <mi>&rho;</mi> <mn>2</mn> </msub> <mo>)</mo> </mrow> <mo>&times;</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <msub> <mi>&rho;</mi> <mn>1</mn> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow> </math>

T₁time vacated for waiting service desk，λ_iFor the measured poisson parameter, h, of the arrival of the ith priority packet_iIs the average value, σ, of packet service time of ith priority_i ²Is the service time variance;

ρ₁＝λ₁h₁，ρ₂＝λ₂h₂λ, h are as already mentioned above;

d is the maximum delay allowed by the real-time polling service, and is set;

W₂is the delay of the real-time polling service;

judging if W is the result₂If D, the access is allowed, otherwise, the access is refused;

and (6) the base station allocates reserved bandwidth.

The invention introduces a measuring mechanism, can obtain the relevant parameters of the system in real time, and simultaneously adopts an admission control strategy combining bandwidth and time delay, thereby improving the quality of real-time service and optimizing the performance of the broadband wireless access system.

Drawings

FIG. 1 is a QoS guarantee architecture for an IEEE 802.16 system;

FIG. 2 is a flow chart of a prior art admission control algorithm;

FIG. 3 is a flow chart of an admission control algorithm proposed by the present invention;

fig. 4. comparison of blocking rate before and after introduction of the measurement mechanism: fig. 4a is a congestion rate of each service in the existing algorithm, in which a straight line is a non-application granted service congestion rate curve, an asterisk line is a real-time service congestion rate curve, and a dot line is a non-real-time service congestion rate curve; fig. 4b is a service blocking rate of the algorithm after introducing the measurement mechanism, wherein a straight line is a non-application granted service blocking rate curve, an asterisk line is a real-time service blocking rate curve, and a dot line is a non-real-time service blocking rate curve;

fig. 5 shows packet loss ratio comparison of rtPS services before and after introducing delay admission control;

FIG. 6 is a comparison of system resource utilization before and after the present invention is employed.

Detailed Description

In order to solve the technical problem, the invention adopts a two-layer admission control system which introduces a measurement mechanism and is based on bandwidth and time delay, and the two-layer admission control system comprises the following steps:

and for all services, firstly carrying out admission judgment according to the bandwidth, if the sum of the bandwidth already used by the system and the bandwidth of the new service is less than the total bandwidth which can be provided by the system, allowing the service to be accessed, and if not, rejecting the service. In order to ensure real-time performance, the bandwidth of rtPS and nrtPS services is obtained by a measurement method, and bandwidth admission judgment is carried out by measuring the bandwidth.

And (3) for the real-time rtPS service, after the bandwidth judgment in the step (1) is carried out, the delay judgment is carried out. And modeling by using a relevant method of a queuing theory according to the measured parameters of the service flow to obtain the measurement of the delay or the packet loss rate of the rtPS service, and comparing the measurement with the corresponding service quality parameters to judge whether the admission is allowed or not. That is, if the delay or packet loss rate index of the real-time service meets the service quality requirement, the access is allowed, otherwise, the access is refused.

The following further describes embodiments of the present invention.

Fig. 3 is a flow chart of an admission control algorithm of the present invention, which is specifically described as follows:

when a new service arrives, the admission control judgment based on the bandwidth is firstly carried out. Given the bandwidth B available to the system, let B be the bandwidth already used by the system when a new service arrives_usedLet the bandwidth required by UGS service be b_UGSThe actual bandwidth of rtPS and nrtPS services measured is b_m. The admission control module first determines the traffic type.

If the new service is a UGS service, then if B_used+b_UGS< B, allowing UGS service to access system and assigning B_UGSIf not, refusing;

if the new service is rtPS service, if B_used+b_mIf the result is less than B, starting to perform delay admission judgment, otherwise, rejecting;

if the new service is nrtPS service, then if B_used+b_m< B, Access allowed and Allocation B_mIf not, refusing;

access is allowed to BE made to BE traffic, but reserved bandwidth is not allocated.

And (3) for the rtPS service entering the delay admission judgment in the step (2), carrying out admission judgment according to a delay admission control algorithm.

The MAC of 802.16 has two modes, one is a gpc (grant Per connection) mode, in which the base station allocates a certain bandwidth to each connection, and the other is a gpss (grant Per Subscriber station) mode, in which the base station allocates a certain bandwidth to each terminal, and the terminal reallocates the bandwidth among several connections.

For the rtPS service entering the delay admission judgment in (2), it is first judged which MAC mode belongs to.

If the mode is GPC mode, a time delay control strategy based on GPC mode is adopted.

The admission judgment conditions are as follows: if p is_i＜P_iThe rtPS service is allowed to be accessed, otherwise, the rtPS service is refused.

Wherein p is_iIs the packet loss rate, P, of service i_iThe maximum packet loss rate is used as a service quality index and is a fixed parameter.

Packet loss rate p of service i_iThe calculation process of (2) is as follows:

and assuming that arrival of service packets obeys Poisson distribution and service time of the packets obeys negative exponential distribution, the cache of the SS end is approximately modeled into an M/M/1 queue.

The Poisson parameter of the arrival of the service packet is measured to be lambda_iNegative exponential distribution parameter is mu_i。

According to the conclusion of the queuing theory, the packet latency W is distributed as:

<math> <mrow> <mi>G</mi> <mrow> <mo>(</mo> <mi>w</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>1</mn> <mo>-</mo> <mfrac> <msub> <mi>&lambda;</mi> <mi>i</mi> </msub> <msub> <mi>&mu;</mi> <mi>i</mi> </msub> </mfrac> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mrow> <mo>(</mo> <msub> <mi>&mu;</mi> <mi>i</mi> </msub> <mo>-</mo> <msub> <mi>&lambda;</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mi>w</mi> </mrow> </msup> </mrow> </math>

then, the packet loss rate of the service i may be calculated as:

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

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

<math> <mrow> <mo>=</mo> <mfrac> <msub> <mi>&lambda;</mi> <mi>i</mi> </msub> <msub> <mi>&mu;</mi> <mi>i</mi> </msub> </mfrac> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mrow> <mo>(</mo> <msub> <mi>&mu;</mi> <mi>i</mi> </msub> <mo>-</mo> <msub> <mi>&lambda;</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mrow> <mo>(</mo> <mi>Di</mi> <mo>-</mo> <mi>Ts</mi> <mo>)</mo> </mrow> </mrow> </msup> </mrow> </math>

wherein D is_iFor the maximum delay that service i can tolerate, Ts is framing time offset.

Packet loss rate p of service i_iCan be solved, then according to the judgment expression p of the time delay admission_i＜P_iAnd judging whether the service is accessed.

If the mode is GPSS mode, a time delay control strategy based on GPC mode is adopted.

The conditions for admission judgment are as follows: if W is₂If < D, the access is allowed, otherwise, the access is refused.

Wherein, W₂Is rtPS service delay, D is the maximum delay that the service can allow.

W₂The calculation process of (2) is as follows:

in the GPSS mode, scheduling at the SS end meets a priority criterion, i.e., in the four classes of service queues at the SS end, a packet with a high priority is sent to a wireless channel first, and a packet with a low priority can be sent only when the high priority queue is empty.

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

Let the measured poisson parameter of the ith-level packet arrive be lambda_iThe average service time is h_iVariance is σ_i ²The total traffic of the system is rho ═ Σ λ_ih_iRho < 1, W_iIs the latency of the ith level of packets.

According to the priority queuing theory, the time for waiting for the vacation of the service desk is T₁Then there is W₁＝T₁/(1-ρ₁) And recurrently obtaining the average waiting time of the kth-level packet as follows:

<math> <mrow> <msub> <mi>W</mi> <mi>k</mi> </msub> <mo>=</mo> <msub> <mi>W</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mrow> <mi>k</mi> <mo>-</mo> <mn>2</mn> </mrow> </munderover> <msub> <mi>&rho;</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mo>/</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>k</mi> </munderover> <msub> <mi>&rho;</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> </mrow> </math>

<math> <mrow> <mo>=</mo> <mfrac> <msub> <mi>T</mi> <mn>1</mn> </msub> <mrow> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>k</mi> </munderover> <msub> <mi>&rho;</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msub> <mi>&rho;</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow> </math>

thus, the average latency of an rtPS packet is:

<math> <mrow> <msub> <mi>W</mi> <mn>2</mn> </msub> <mo>=</mo> <mfrac> <msub> <mi>T</mi> <mn>1</mn> </msub> <mrow> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <msub> <mi>&rho;</mi> <mn>1</mn> </msub> <mo>-</mo> <msub> <mi>&rho;</mi> <mn>2</mn> </msub> <mo>)</mo> </mrow> <mo>&times;</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <msub> <mi>&rho;</mi> <mn>1</mn> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow> </math>

wherein, <math> <mrow> <msub> <mi>T</mi> <mn>1</mn> </msub> <mo>=</mo> <mi>&Sigma;</mi> <mfrac> <msub> <mi>&lambda;</mi> <mi>i</mi> </msub> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msubsup> <mi>h</mi> <mi>i</mi> <mn>2</mn> </msubsup> <mo>+</mo> <msubsup> <mi>&sigma;</mi> <mi>i</mi> <mn>2</mn> </msubsup> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math> ρ_i＝λ_ih_i。

the delay admission judgment expression in the GPSS mode is

W₂＜D

Then the delay of rtPS service in GPSS mode can be obtained, and then the expression W is admitted according to the delay₂If the judgment result is less than D, the access is carried out if the condition is met, otherwise, the access is rejected.

In order to compare the effects before and after the implementation of the invention, Matlab is used for simulating the algorithm of the invention, and B is 2000kbps and B is adopted as simulation parameters_UGS＝32kbps，b_min＝32kbps，b_maxThe poisson parameters of the three traffic flows are the same at 32kbps, the sum lambda of the poisson parameters ranges from 1 to 10, and the service time distribution parameters of the three traffic flows are all 3.05. Assuming that the actually measured rtPS and nrtPS traffic bandwidths are uniformly distributed over (32, 128) kbps, the actually measured traffic delay is positively correlated with the size of λ and follows an exponential distribution.

Fig. 4 shows the comparison of the blocking rates of the services before and after the measurement mechanism is introduced, and it can be seen that in the original admission strategy, since the rtPS service adopts the maximum bandwidth to determine whether to admit, the blocking rate of the rtPS service is greater than the blocking rates of other services, and after the measurement mechanism is introduced, the blocking rate of the rtPS service is balanced with other services. The audio and video service corresponding to rtPS occupies an important position in a future wireless access network, so that the fairness of the service can be effectively improved by introducing a measurement mechanism.

Fig. 5 shows the comparison of the packet loss rates of the rtPS services before and after the delay admission is adopted, and after the admission control strategy based on the delay is introduced for the rtPS service, it can be seen that the packet loss rate of the real-time service is obviously reduced, and the packet loss rate is kept stable with the increase of the system load. Meanwhile, due to the limitation of delay control, the blocking rate of rtPS service may increase.

Fig. 6 is a comparison of system bandwidth resource utilization before and after the present invention is employed. Because the admission strategy integrating bandwidth and delay control can effectively reduce the packet loss rate of the real-time service, ensure the QoS of the service, and increase the blocking rate of the real-time service to a certain extent, and the introduced measurement mechanism can reduce the blocking rate of the real-time service, the resource utilization rate of the system of the original admission algorithm in the 802.16 system and the new algorithm provided by the invention is compared. The use of which can be seen in fig. 6

The resource utilization rate of the system after the algorithm of the invention is not changed greatly, and is basically equal to the original system resource utilization rate, but the service quality of real-time rtPS service is obviously improved, thereby improving the performance of the system.

Claims (1)

1. An admission control method based on measurement and QoS in a broadband wireless access system is characterized by comprising the following steps in sequence:

step (1), when a new service arrives, the base station of the broadband wireless access system based on IEEE 802.16 judges the type of the new service, and lists the non-application granted service as the 1 st priority, the real-time polling service as the 2 nd priority and the non-real-time polling service as the 3 rd priority, and processes the following steps respectively aiming at different service types;

step (2), for the best-effort service, the base station allows access, and step (6) is switched;

step (3), for non-application grant service, the base station judges whether the given system available bandwidth B is larger than the bandwidth B already used by the system_usedBandwidth required for new service B_UGSIf the sum is larger than the available bandwidth given by the system, allowing access, and turning to the step (6), otherwise, rejecting access;

and (4) for the non-real-time polling service, the base station performs the following steps:

step (4.1) of measuring the actual bandwidth b of said traffic_m；

The method for measuring the time window comprises the following steps:

dividing a time window into 10 sampling periods, and calculating the average used bandwidth of each type of service in each period

The sampling time is S, and the value of the estimated bandwidth is updated in the following 4 cases: taking the maximum value when the time window is finished

As an estimated bandwidth; updating the estimated bandwidth and restarting the time window when a new flow is accessed; ③ when

When the estimated bandwidth is exceeded, to

As an estimated bandwidth; fourthly, when a flow leaves, updating the estimated bandwidth and restarting the time window; the update formula of the estimated bandwidth is as follows:

wherein, b_mIs the updated estimated bandwidth, i.e. the actual measured bandwidth of the traffic;

average used bandwidth in S;

r^pgenerating a rate for the traffic information;

beta is a bandwidth reduction factor, when a flow leaves the network after finishing leaving, the estimated value of the used bandwidth needs to be reduced, the reduced bandwidth is approximately equal to the equivalent bandwidth of the flow, different values can be determined for beta according to different flows, and the value of beta can be 1 in order to simplify the algorithm;

step (4.2), judging whether the available bandwidth B of the given system is larger than the used bandwidth of the system and the actual bandwidth B of the service_mIf the available bandwidth B of the system is large, the access is allowed, and the step (6) is carried out, otherwise, the access is refused;

and (5) for the real-time polling service, the base station performs the following steps:

step (5.1) of measuring the actual bandwidth b of said traffic_mThe measuring method is the same as the step (4.1);

step (5.2), judging whether the available bandwidth B of the system is larger than the used bandwidth B of the system_usedThe sum of the actual bandwidth;

if the available bandwidth B of the system is large, entering the step (5.3);

otherwise, access is refused;

step (5.3), judge whether the said business is GPC mode, the mode means the base transceiver station distributes and sets up the bandwidth for each connection;

if the mode is GPC mode, judge:

p_i＜P_ino, p_i＜P_iWhen the access is allowed, otherwise the access is refused,

wherein p is_iCalculating the packet loss rate of the service i according to the following formula:

<math> <mrow> <msub> <mi>p</mi> <mi>i</mi> </msub> <mo>=</mo> <mfrac> <msub> <mi>&lambda;</mi> <mi>i</mi> </msub> <msub> <mi>&mu;</mi> <mi>i</mi> </msub> </mfrac> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mrow> <mo>(</mo> <msub> <mi>&mu;</mi> <mi>i</mi> </msub> <mo>-</mo> <msub> <mi>&lambda;</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mrow> <mo>(</mo> <msub> <mi>D</mi> <mi>i</mi> </msub> <mo>-</mo> <mi>Ts</mi> <mo>)</mo> </mrow> </mrow> </msup> </mrow> </math>

λ_imeasuring the obtained known value for the coming Poisson parameter of the package;

μ_imeasuring the obtained known value for the complex exponential distribution parameter of the service time of the packet;

D_isetting a value for the maximum delay allowed to be tolerated by the service i;

ts is a framing time compensation and set value;

p_ia maximum packet loss rate set according to the service quality index;

if not, the method comprises the following steps;

step (5.4), executing in GPSS mode, where the base station allocates the set bandwidth for each terminal, and the terminal reallocates the bandwidth among several connections;

the base station determines W₂If the number < D is not greater than the preset value,

<math> <mrow> <msub> <mi>W</mi> <mn>2</mn> </msub> <mo>=</mo> <mfrac> <msub> <mi>T</mi> <mn>1</mn> </msub> <mrow> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <msub> <mi>&rho;</mi> <mn>1</mn> </msub> <mo>-</mo> <msub> <mi>&rho;</mi> <mn>2</mn> </msub> <mo>)</mo> </mrow> <mo>&times;</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <msub> <mi>&rho;</mi> <mn>1</mn> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow> </math>

T₁in order to wait for the time vacated by the service station, <math> <mrow> <msub> <mi>T</mi> <mn>1</mn> </msub> <mo>=</mo> <mi>&Sigma;</mi> <mfrac> <msub> <mi>&lambda;</mi> <mi>i</mi> </msub> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msubsup> <mi>h</mi> <mi>i</mi> <mn>2</mn> </msubsup> <mo>+</mo> <msubsup> <mi>&sigma;</mi> <mi>i</mi> <mn>2</mn> </msubsup> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math> λ_ifor the measured poisson parameter of the arrival of the ith priority packet,h_iis the average value, σ, of packet service time of ith priority_i ²Is the service time variance;

ρ₁＝λ₁h₁，ρ₂＝λ₂h₂λ, h are as already mentioned above;

d is the maximum delay allowed by the real-time polling service, and is set;

W₂is the delay of the real-time polling service;

judging if W is the result₂If D, the access is allowed, otherwise, the access is refused;

and (6) the base station allocates reserved bandwidth.

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