A Hierarchical Model for Bandwidth Management and Admission Control in

Integrated IEEE 802.16&802.11 Wireless Networks

Dusit Niyato and Ekram Hossain

IEEE Wireless Communications and Networking Conference (WCNC), March 2007

報告者：李宗穎

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Outline

Introduction System Model and Assumptions Bandwidth Allocation Admission Control Performance Evaluation Conclusion

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Introduction

This paper present a hierarchical bandwidth management and admission control framework for integrated IEEE 802.16/802.11 wireless networks

Related works considered connections only from standalone subscriber stations

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Network Model

two-level hierarchical model first level a bargaining game between the set of

standalone SSs and the WLAN APs second level, connections corresponding to the

different service types in the standalone SSs

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IEEE 802.11/16 AP/wireless router

Paper assume that the dual radio interface at a 802.11/802.16 AP/wireless router uses different frequency bands

Data packets corresponding to local and Internet traffic are stored in separate queues

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Uplink Transmission in the IEEE 802.16 Air Interface Paper consider a single BS with multiple connecti

ons from SSs using the TDMA/TDD access mode

Bi : burst sizeRi : transmission rate for any connection i in a frameC : channel bandwidthIn : the number of transmitted bits per symbol for AMC state nPrn : the probability of using AMC state nF : frame size

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Hierarchical Model for Bandwidth Management

Paper use sigmoid utility function which represents quantitatively the satisfaction on received transmission rate R

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Bargaining Game (1/3) The average transmission rate for the group

s of standalone SS and WLAN connections can be obtained from

γSS, γWL, NSS, NWL denote the average SNR and the total number of standalone SSs and WLAN APs/routers

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Bargaining Game (2/3)

The utilities for these groups of connections φSS(ΣBSS) = U(RSS(ΣBSS))

φWL(ΣBWL) = U(RWL(ΣBWL))

If an agreement between both the players in the game cannot be reached, the utility that the players will receive is given by the threat point

is the threat point for this bargaining game

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Bargaining Game (3/3)

The equilibrium strategy of this game refers to the set of strategies for which all the players are satisfied with their received payoff

[8] S. Chae and P. Heidhues, “A group bargaining solution, ” Elsevier Mathematical Social Sciences, vol. 48, no. 1, pp. 37-53, 2005.

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N-Person Game in Coalition Form (1/2)

define a finite set A of players (i.e., A = {UGS,PS,BE})

the required burst size for service type (i.e., player) j can be obtained from

λ(j) is the bandwidth requirementN(j) is the number of connections in service type j from standalone SSs

SS

SS

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N-Person Game in Coalition Form (2/2)

A coalition S is defined as a subset of A, S ⊂ A

The coalition form of an N-person game is defined by the pair (A, ν) where ν is a characteristic function of the game

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Shapley Value

the value function φ(ν) as the worth or value of player j in the game with characteristic function ν

The Shapley value φ = [φ1,…,φi,…,φn] can be computed as follows

[9] L. S. Shapley, “A value for N-Person game, ” Annals of Mathematics Studies, Princeton University Press, vol. 2, pp. 307-317, 1953

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Admission Control of Connections in Standalone SSs (1/2)

For connections in service type j, the burst size allocated to connection k depends on the channel quality as follows

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Admission Control of Connections in Standalone SSs (2/2)

a new connection in service type j arrives, the 802.16 BS decides whether this connection can be accepted or not by considering the change in total utility

a new connection is accepted only when the total utility increases, and rejected otherwise

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Admission Control of WLAN Nodes

This WLAN initial message contains the bandwidth requirement of the new connection

If the link between the AP and the 802.16 BS lacks sufficient bandwidth, the BS performs bandwidth reallocation among standalone SSs and WLAN APs

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Transmission Rate in WLAN

in the saturated case, the estimated received bandwidth is obtained as follows

λ(j) (k) : the bandwidth requirement of connection k in WLAN j, CWL : the channel rate in the WLANPs : the measured probability of successful transmission

WL

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Formulation of the Admission Control Game for WLAN (1/2)

The burst size allocated to WLAN connection j depends on the channel quality as follows

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Formulation of the Admission Control Game for WLAN (2/2)

The payoff for the case when a new connection is accepted can be obtained as follows

A new connection from node k in WLAN j is accepted if for WMAN and WLAN the pure strategy (accept, accept) is a Nash equilibrium

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Parameter Setting

Transmission Mode TDMA

Transmission bandwidth 25 MHz

Frame size 1 ms

Cell size 5 km

Average receive SNR 7 ~ 26 dB

UGS, PS, BE 400/500/300 kbps

WLAN channel rate 10 Mbps

WLAN cell radius 50 meters

WLAN bandwidth 400 kbps

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Variation of Allocated Bandwidth Under Different Channel Qualities

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Variation of Total Utility of Standalone SSs

the number of PS and BE connections is 15 and 20

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Performance of Admission Control Method for WLANs

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Conclusions

A bargaining game has been used to determine the optimal burst size for WMAN and WLAN connections

The Shapley value has been used to obtain the solution of the bandwidth allocation problem for different types of WMAN connections

An admission control scheme based on variation in total utility has been presented