CN103491599B - The forecast Control Algorithm of TDMA agreement - Google Patents

Abstract

The invention discloses the forecast Control Algorithm of a kind of TDMA agreement, for solving the technical problem of existing TDMA protocol communication weak effect.Technical scheme is to use feedforward and feedback to combine, and is primarily based on real-time queue theory model, it was predicted that the permission arrival rate of tdma communication system, completes the feedforward；Then pass through feedback control and correct the inaccuracy of the complicated real-time communication system of feed forward models modeling further.The method avoids the peak flow problem in tdma communication system effectively, makes node access the rapidest, and system communication is the most sane.Owing to dynamically carrying out the congestion control of TDMA agreement, when communication node detects congested generation, distribute, to the data slot resource of node, the method using call access control, receive or refuse new business, thus effectively avoided instantaneous peak flow and network congestion.Owing to the method can make node access the rapidest, communication resources utilization ratio is higher.

Description

The forecast Control Algorithm of TDMA agreement

Technical field

The present invention relates to the forecast Control Algorithm of a kind of TTDMA agreement.

Background technology

In real-time Communication for Power environment, because base station and mobile station scale are unstable or unpredictable, i.e. mobile station goes out the frequency that networks Numerous, send quantity of information burst change big, dynamic TDMA call access control is more attractive.This agreement can be according to complexity In network, the change of subscriber signal transmission demand, redistributes time interval resource in real time, has control flexibly, time interval resource The feature that utilization rate is high.

Document 1 " research of dynamic TDMA resource allocation methods with realize. Yan Zhong etc. mobile communication, 2010 (6): 41-44 " Disclose a kind of dynamic TDMA agreement based on mini-slot.The method, in the case of not interrupt network operates, respectively saves Point applies for time slot according to the practical situation of information traffic volume and the situation of change of interstitial content, dynamically changes slot length, To adapt to change in topology and to improve the efficiency of transmission of system.

Document 2 " U.S. patent Nos of the US6810022B1 of patent publication No. " discloses one and is applicable to mobile many Jump the TDMA call access control agreement of Ad-Hoc network, i.e. unify slot assignment protocol (USAP).USAP considers The autonomous behavior of mobile node, it is allowed to node selects one or more time slot from unappropriated time slot, by each adjacent Between node, distribution information is reached double bounce scope by statement and confirmation to time slot distribution.

Document 3 " RFC5352/RFC5356 " discloses a kind of self adaptation time slot distributorship agreement (ASAP).The method root According to the nodes in the range of double bounce, dynamically change frame length, decrease untapped timeslot number, improve channel utilization. Meanwhile, ASAP also provides for having the packet transmission of different frame length internodal Lothrus apterus, is effectively utilized channel width.

But, above-mentioned dynamic TDMA agreement is gone back when solving the heavy duty tdma communication with clear and definite off period demand Have the disadvantage that (1) in the dynamic TDMA agreement of mini-slot, when multiple business message arrive beyond letter During the design load in road, time interval resource can scarcity, due to instantaneous peak flow, be likely to result in the congested of communication network； (2) in USAP agreement, the access delay of node is relatively big, and it uses the method arranging peak flow to gather around in addition Plug controls, and again because congested less generation, this method ensures tdma communication system with dividing, and resource utilization is low； (3) ASAP agreement does not support that multiple node applies for time slot simultaneously, is only applicable to the network that business is constant；And it uses Based on the congestion control policy directly inferred, there are the biggest randomness and anthropic factor, easily produce error of transmission and lose Lose；And it is unsuitable for Accurate Analysis and improves further.

Summary of the invention

In order to overcome the deficiency of existing TDMA protocol communication weak effect, the present invention provides the pre-of a kind of TDMA agreement Survey control method.The method uses feedforward and feedback to combine, and is primarily based on real-time queue theory model, it was predicted that TDMA The permission arrival rate of communication system, completes the feedforward；Then pass through feedback control and correct feed forward models modeling further The inaccuracy of complicated real-time communication system.The peak flow that the method can effectively be avoided in tdma communication system is asked Topic, makes node access the rapidest, and system communication is the most sane.

The technical solution adopted for the present invention to solve the technical problems: the forecast Control Algorithm of a kind of TDMA agreement, its Feature is to comprise the following steps:

The feedforward unit being made up of real-time queue predictor and feedforward controller, by congestion detector, feedback control The feedback control unit of device and timeslot resource management device composition realizes；

To business arrival, service time and the hypothesis below of off period:

A () business arrives obeys a renewal process, and arrival interval is distributed by average 1/ λ and standard deviation sigma_aDetermine；

B () business has a Random Service Annual distribution, by average 1/ μ and standard deviation sigma_sDetermine；

C () each business has a relative stochastic deadline, obey G distribution.Off period meansigma methods is obtained by theory of probabilityA standard knots opinion $\stackrel{\‾}{D}={\∫}_0^{\∞}(1-G\left(x\right))\mathrm{dx};$

(d) business interval time of advent, separate between service time and off period.

Orderρ=λ/μ, real-time queueing theory give the earliest the off period preferentially weight Approximation deadline missing ratio under loading condition:

$M_{\mathrm{EDF}}=e^{-\mathrm{\θ}\stackrel{\‾}{D}}---\left(1\right)$

Assuming that the service rate μ of tdma communication system is a definite value, arrival rate λ λ is from the exponential of λ, to formula (1) Derive, obtain off period meansigma methodsWith miss rate M_EDFMeet following relation:

$M_{\mathrm{EDF}}=e^{-(\frac{2}{\mathrm{\λ}}{\mathrm{\μ}}^2-2\mathrm{\μ})\×\stackrel{\_}{D}}---\left(2\right)$

Accordingly, in known off period meansigma methodsRate M is missed with reference system_EDFOn the premise of, real-time queue predictor under One arrival rate controlling periodic system permission is predicted:

${\mathrm{\λ}}^{\′}=\frac{2}{2-\frac{\ln M_{\mathrm{EDF}}}{\stackrel{\‾}{D}{\mathrm{\μ}}^2}}---\left(3\right)$

And regulate arrival rate λ accordingly, complete system is missed the feedforward of rate.

Congestion detector real-time sampling system misses rate the most reallySystem after the above-mentioned feedforward is wrong Cross rateRate M is missed with reference_EDFBetween deviation delta M_EDFTo not be 0.

Feedback controller calculates and truly misses rateRate M is missed with reference_EDFBetween deviation delta M_EDFCalculate again The regulated quantity Δ λ of arrival rate, so that this deviation is close in zero.Because the feedforward is by the state of communication system Within being adjusted to the effective range of feedback control, so considering Δ M during feedback control_EDFAnd the direct mathematics between Δ λ Relation.It is the probability distribution of a stochastic process in view of arrival rate λ controlled, when main influence factor is to arrive Between be spaced T_a, i.e.Therefore perform in field of events, i.e. reach the change Delta T of time interval_aTo missing rate change ΔM_EDFControl.Obtain the interval time of advent and the relation of missing between rate by the following method:

1) uncontrolled algorithm, directly change the interval time of advent thus obtain system miss rate；

2) Dynamic simulation program, obtain corresponding system misses rate；

3) and then obtain the interval and the mathematical relationship of missing between the rate time of advent of system:

$T_a=0.0339M_{\mathrm{EDF}}^{-0.1275}---\left(4\right)$

The change Delta T that the time of advent is spaced_aWith miss rate changes delta M_EDFBetween relation as follows:

$\mathrm{\Δ}{T}_a\left(n\right)=-0.00432225\×M_{\mathrm{EDF}}{(n-1)}^{-1.1275}\×\mathrm{\Δ}{M}_{\mathrm{EDF}}(n-1)---\left(5\right)$

N-th time period was controlled by the state using (n-1) time period.

Because rate of missing only takes on the occasion of with zero, this allows for feedback control is a monotonous process, if i.e. missed, The arrival rate of system reduces.Not havinging negative value owing to missing rate, the arrival rate of system will not rise all the time, when causing Gap utilization rate will be more and more lower.To this, then add a slot efficiency control to system, i.e. utilize when the time slot of system When rate is more than a upper limit 0.96, no matter either with or without missing, all admission control mechanism above will be used to carry out control system Utilization rate.

Timeslot resource management device uses a saturation block, to above-mentioned calculated arrival rateLimit:

${\mathrm{\&lambda;}}_q=\left\{\begin{array}{cc}0& \mathrm{\&lambda;}<0\\ \mathrm{\&lambda;}& 0\&le;\mathrm{\&lambda;}\&le;a\\ a& \mathrm{\&lambda;}>a\end{array}\right.---\left(6\right)$

In formula, λ_qFor allowing arrival rate, a is new mobile station number of request；Then by λ_qAs the response of communication system, send To mobile station；Work as λ_qWhen=0, mobile station does not obtains data transmission route, works as λ_qWhen ≠ 0, it is thus achieved that the shifting of data transmission route Dynamic platform is according to allowing time interval λ_qRegulate emission rate.

The invention has the beneficial effects as follows: the method uses feedforward and feedback to combine, and is primarily based on real-time queue theory model, The permission arrival rate of prediction tdma communication system, completes the feedforward；Then pass through before feedback control corrects further The inaccuracy of feedback model modeling complexity real-time communication system.The method can effectively avoid the stream in tdma communication system Amount spike problem, makes node access the rapidest, and system communication is the most sane.

(1) dynamically carry out the congestion control of TDMA agreement with cybernetic method, gather around when communication node detects When plug occurs, distribute, to the data slot resource of node, the method using call access control, receive or refuse new business, Thus effectively avoided instantaneous peak flow and network congestion.

(2) use queueing theory to predict the control input of approximation, detect when the arrival rate of business has a greater change, In advance the permission arrival rate of system is controlled, to ensure that the feedback controller of system always works in its effective model Within enclosing.It is the rapidest that this method can make node access, and communication resources utilization ratio is higher.

(3) for isomerism, complexity and the unpredictability of communication system, it is possible to provide closed-loop fashion control model. And in the case of the weight traffic, the queuing behavior of standard has good behavior to define, simultaneously remaining time off period Distribution also converges to the form defined.Therefore cybernetics combines with queueing theory and can accurately manage the congested of system Opinion is analyzed, and makes real-time communication system more healthy and stronger.

With detailed description of the invention, the present invention is elaborated below in conjunction with the accompanying drawings.

Accompanying drawing explanation

Fig. 1 is the tdma communication system Feedforward-feedback control structure based on real-time queueing theory that institute of the present invention method uses.

Fig. 2 is the tdma communication system group network model that the inventive method is used.

Fig. 3 be to lose rate and the time of advent interval between graph of a relation.

Fig. 4 is that system is added the most in the same time encourages schematic diagram.

When Fig. 5 is without controlling, system misses rate schematic diagram.

Fig. 6 is without controlling slot efficiency schematic diagram.

Fig. 7 is to miss rate comparison diagram under different control system.

Fig. 8 is slot efficiency comparison diagram under different control system.

Fig. 9 is that when controlling with/without slot efficiency, system misses rate comparison diagram.

Detailed description of the invention

The present invention is described in detail with reference to Fig. 1-9.

The forecast Control Algorithm of a kind of TDMA agreement, it is mainly made up of real-time queue predictor and feedforward controller Feedforward unit and the feedback control unit composition of congestion detector, feedback controller and timeslot resource management device composition；

Call access control process realizes the feedforward of the forecast Control Algorithm of TDMA agreement, feedback, feedforward compensation feedback control Deng three kinds of call access control modes.

Use this model of OPNET tool modeling and emulate.The network model that emulation is set up is by a base station sum Ten mobile stations are constituted.Using channel data transmission speed during emulation is 30000bps, and simulation time is 12h, and node produces Raw data packet length is 512bit, and the discharge model that each base station produces obeys exponential, and service time is one Constant, application time slot thresholding is set to the 100% of queue utilization.Emulation uses high traffic on base station, and by number According to contracting for fixed output quotas, raw speed average is set to 10pkt/s.

Because heavy duty tdma communication system has clear and definite off period demand, with reference to real-time queueing theory, business is arrived, Service time and the hypothesis below of off period:

(1) business arrives and obeys a renewal process, and arrival interval is distributed by average 1/ λ and standard deviation sigma_aDetermine；

(2) business has a Random Service Annual distribution, by average 1/ μ and standard deviation sigma_sDetermine；

(3) each business has a relative stochastic deadline, obeys G distribution.The off period can be obtained average by theory of probability ValueA standard knots opinion $\stackrel{\&OverBar;}{D}={\&Integral;}_0^{\&infin;}(1-G\left(x\right))\mathrm{dx};$

(4) the business interval time of advent, separate between service time and off period.

Orderρ=λ/μ, it is preferential (EDF) that real-time queueing theory gives the off period the earliest Approximation deadline missing ratio in the case of heavy duty:

$M_{\mathrm{EDF}}=e^{-\mathrm{\&theta;}\stackrel{\&OverBar;}{D}}---\left(1\right)$

Assuming that the service rate μ of tdma communication system is a definite value, arrival rate λ obeys the exponential of λ, to formula (1) Derive, obtain off period meansigma methodsWith miss rate M_EDFMeet following relation:

$M_{\mathrm{EDF}}=e^{-(\frac{2}{\mathrm{\&lambda;}}{\mathrm{\&mu;}}^2-2\mathrm{\&mu;})\&times;\stackrel{\&OverBar;}{D}}---\left(2\right)$

Accordingly, in known off period meansigma methodsRate M is missed with reference system_EDFOn the premise of, real-time queue predictor under One arrival rate controlling periodic system permission is predicted:

${\mathrm{\&lambda;}}^{\&prime;}=\frac{2}{2-\frac{\ln M_{\mathrm{EDF}}}{\stackrel{\&OverBar;}{D}{\mathrm{\&mu;}}^2}}---\left(3\right)$

And regulate arrival rate λ accordingly, complete system is missed the feedforward of rate.

Congestion detector real-time sampling system misses rate the most reallyOwing to queue theory model modeling is complicated real Time communication system inaccuracy, the system after the above-mentioned feedforward misses rateRate M is missed with reference_EDFBetween Deviation delta M_EDFTo not be 0.

Feedback controller calculates and truly misses rateRate M is missed with reference_EDFBetween deviation delta M_EDF, then calculate The regulated quantity Δ λ of arrival rate, so that this deviation is close in zero.Because the feedforward is by the state of communication system Within being adjusted to the effective range of feedback control, so considering Δ M during feedback control_EDFAnd the direct mathematics between Δ λ Relation.It is the probability distribution of a stochastic process in view of arrival rate λ controlled, when main influence factor is to arrive Between be spaced T_a, i.e.Therefore perform in field of events, i.e. reach the change Delta T of time interval_aTo missing rate change ΔM_EDFControl.Obtain the interval time of advent and the relation of missing between rate by the following method:

1) uncontrolled algorithm, directly change the interval time of advent thus obtain system miss rate；

2) Dynamic simulation program, obtain corresponding system misses rate；

3) and then can obtain the interval and the mathematical relationship of missing between the rate time of advent of system:

$T_a=0.0339M_{\mathrm{EDF}}^{-0.1275}---\left(4\right)$

So, the change Delta T that the time of advent is spaced_aWith miss rate changes delta M_EDFBetween relation as follows:

ΔT_a(n)=-0.00432225 × M_EDF(n-1)^-1.l275×ΔM_EDF(n-1) (5)

N-th time period was controlled by the state using (n-1) time period.

Because rate of missing only takes on the occasion of with zero, this allows for feedback control is a monotonous process, if i.e. missed, The arrival rate of system reduces.Not havinging negative value owing to missing rate, the arrival rate of system will not rise all the time, when causing Gap utilization rate will be more and more lower.To this, then add a slot efficiency control to system, i.e. utilize when the time slot of system When rate is more than a upper limit 0.96, no matter either with or without missing, all admission control mechanism above will be used to carry out control system Utilization rate.

Timeslot resource management device uses a saturation block, to above-mentioned calculated arrival rateLimit:

${\mathrm{\&lambda;}}_q=\left\{\begin{array}{cc}0& \mathrm{\&lambda;}<0\\ \mathrm{\&lambda;}& 0\&le;\mathrm{\&lambda;}\&le;a\\ a& \mathrm{\&lambda;}>a\end{array}\right.---\left(6\right)$

In formula, λ_qFor allowing arrival rate, a is new mobile station number of request；Then by λ_qAs the response of communication system, send To mobile station；Work as λ_qWhen=0, mobile station does not obtains data transmission route, works as λ_qWhen ≠ 0, it is thus achieved that the shifting of data transmission route Dynamic platform is according to allowing time interval λ_qRegulate emission rate.

From figure 5 it can be seen that when approximating, to one, the step that saturated system adds 30% again, uncontrolled In the case of, system will soon be saturated, and owing to having little time the message in processing system queue, the rate of missing of system will The highest, reach 100%, cause system congestion.

From fig. 6 it can be seen that reaction is on slot efficiency, system the most quickly reaches the most saturated, causes system congestion.

It can be seen from figure 7 that when only adding the feedforward, corresponding to feedforward part, i.e. assume tdma communication system Service rate μ be a definite value, arrival rate λ obey λ exponential, the feedforward is given based on real-time queueing theory Off period preferential (EDF) off period meansigma methods in the case of heavy duty the earliestWith miss rate M_EDFBetween approximation relation:

$M_{\mathrm{EDF}}=e^{-(\frac{2}{\mathrm{\&lambda;}}{\mathrm{\&mu;}}^2-2\mathrm{\&mu;})\&times;\stackrel{\_}{D}}$

Known reference system misses rate M_EDF, and obtain off period meansigma methods by real-time monitor and communication system, real-time queue Predictor controls the arrival rate of periodic system permission and is predicted the next one:

${\mathrm{\&lambda;}}^{\&prime;}=\frac{2}{2-\frac{\ln M_{\mathrm{EDF}}}{\stackrel{\&OverBar;}{D}{\mathrm{\&mu;}}^2}}$

And regulate arrival rate λ accordingly.With without compared with controlling, it is very significantly improved through the performance of feedforward control system, but Due to the inexactness of forecast model, cause the simple feedforward not ideal enough.

Feedback controller is proportional integral (PI) controller, under periodic control interval h, utilizes buoy to lead to What communication system was surveyed misses rateWith reference value M_EDFBetween difference DELTA M_EDF, according to following discrete time Regular new arrival rate λ (kh) calculating the kh moment of control:

$\mathrm{\&lambda;}\left(\mathrm{kh}\right)=\mathrm{K\&Delta;}{M}_{\mathrm{EDF}}\left(\mathrm{kh}\right)+\underset{i=0}{\overset{k-1}{\mathrm{\&Sigma;}}}\frac{K}{T_i}\mathrm{\&Delta;}{M}_{\mathrm{EDF}}\left(\mathrm{ih}\right)$

By Digital PID Controller Ziegler-Nichols method, utilize Matlab can obtain the parameter of PI controller: K=16, T_i=1.8.Because simple feedback controller be by the accumulation of error in the past, communication system behavior in the future is controlled so Certainly having certain delay, and control effect when there being big step the most undesirable, maximum is missed rate and is reached 50%.

Feedforward and feedback are combined, utilize the feedforward to carry out the state of prognoses system, adjust system mode in time, Within the state of communication system is adjusted to the effective range of feedback control, directly utilize the mathematics pass that formula (5) is set up System, by the change Delta T being spaced the time of advent_aTo missing rate changes delta M_EDFCarry out feedback control so that having step Time feedback control time delay less, meanwhile, feedback control compensate for again the inexactness of the feedforward.

As can be seen from Figure 8, the slot efficiency ratio of feedback control is relatively low, its reason be to lose rate be one special Variable, it only takes on the occasion of with zero.This allows for feedback control is a dull process, if i.e. missed, system Arrival rate reduce, do not have negative value owing to missing rate, the arrival rate of system will not rise all the time, cause time slot profit More and more lower by rate.So, the rate of missing the most only using feedback control to carry out control system is infeasible.

It can be seen in figure 9 that due to the defect of feedback control self, just can be controlled after the most only missing, Rate of so missing has in some little fluctuations, i.e. Fig. 7 certainly with the presence of some burrs.Hereinafter one is added to system again Slot efficiency controls to make systematic function more preferably.Specific practice is: when the slot efficiency of system is more than on one In limited time (in experiment, it is determined as 0.96), no matter either with or without missing, all the admission control mechanism using above is controlled be The utilization rate of system.Can be seen that the fluctuation of the rate of missing having added the system that slot efficiency controls is obviously reduced.

Claims (1)

1. the forecast Control Algorithm of a TDMA agreement, it is characterised in that comprise the following steps:

The feedforward unit being made up of real-time queue predictor and feedforward controller, the feedback control unit being made up of congestion detector, feedback controller and timeslot resource management device realizes；

To business arrival, service time and the hypothesis below of off period:

A () business arrives obeys a renewal process, and the time of advent is spaced apart by average 1/ λ and standard deviation sigma_aDetermine；

B () business has a Random Service Annual distribution, by average 1/ μ and standard deviation sigma_sDetermine；

C () each business has a relative stochastic deadline, obey G distribution；Off period meansigma methods is obtained by theory of probabilityA standard knots opinion

(d) business interval time of advent, separate between service time and off period；

Orderρ=λ/μ, real-time queueing theory gives the reference preferentially in the case of heavy duty of off period the earliest and misses rate:

Assuming that the service rate μ of tdma communication system is a definite value, arrival rate λ obeys the exponential of λ, derives formula (1), obtains off period meansigma methodsRate M is missed with reference_EDFMeet following relation:

Accordingly, in known off period meansigma methodsRate M is missed with reference_EDFOn the premise of, real-time queue predictor controls the arrival rate of periodic system permission and is predicted the next one:

And regulate arrival rate λ accordingly, complete system is missed the feedforward of rate；

The rate of truly missing that congestion detector real-time sampling system is currentRate of truly missing after the above-mentioned feedforwardRate M is missed with reference_EDFBetween deviation delta M_EDFTo not be 0；

Feedback controller calculates and truly misses rateRate M is missed with reference_EDFBetween deviation delta M_EDF, then calculate the regulated quantity Δ λ of arrival rate, so that this deviation is close in zero；Because within the state of communication system is adjusted to the effective range of feedback control by the feedforward, so considering Δ M during feedback control_EDFAnd the direct mathematical relationship between Δ λ；Being the probability distribution of a stochastic process in view of arrival rate λ controlled, main influence factor is to be spaced T the time of advent_a, i.e.Therefore perform in field of events, the change Delta T that the time of advent is spaced_aTo deviation delta M_EDFControl；Obtain the interval time of advent and the relation of missing between rate by the following method:

1) uncontrolled algorithm, directly change the interval time of advent thus obtain system miss rate；

2) Dynamic simulation program, obtain corresponding system misses rate；

3) and then obtain the interval and the mathematical relationship of missing between the rate time of advent of system:

The change Delta T that the time of advent is spaced_aWith miss rate changes delta M_EDFBetween relation as follows:

ΔT_a(n)=-0.00432225 × M_EDF(n-1)^-1.1275×ΔM_EDF(n-1) (5)

N-th time period was controlled by the state using (n-1) time period；

Because rate of missing only takes on the occasion of with zero, this allows for feedback control is a monotonous process, if i.e. missed, the arrival rate of system reduces；Not havinging negative value owing to missing rate, the arrival rate of system will not rise all the time, causes the slot efficiency will be more and more lower；To this, then add slot efficiency to system and control, i.e. when the slot efficiency of system is more than a upper limit 0.96, no matter either with or without missing, all the admission control mechanism using above is come the utilization rate of control system；

Timeslot resource management device uses a saturation block, to above-mentioned calculated arrival rateLimit:

In formula, λ_qFor allowing arrival rate, a is new mobile station number of request；Then by λ_qAs the response of communication system, it is sent to mobile station；Work as λ_qWhen=0, mobile station does not obtains data transmission route, works as λ_qWhen ≠ 0, it is thus achieved that the mobile station of data transmission route is according to allowing arrival rate λ_qRegulate emission rate.