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An Adaptive Call Admission Control in WiMAX Networks with Fair
Tradeoff Analysis
R.K. MANGANG
OUTLINE
Introduction IEEE 802.16 and WiMAXCall Admission Control(CAC)Adaptive Bandwidth Degradation CAC (ABD-CAC)Trade off analysisConclusion
INTRODUCTIONBackground and Motivation
Broadband Wireless Access(BWA)Promising solution for last mile accessHigh speed internet access in residential as well as small
and medium sized enterprise sectorFill the gap between high data rate wireless LAN and very
mobile cellular networks. Advantages of BWA Ease of deployment and installation Capacity can be increased by installing more base stations Challenges for BWA Price Performance Interoperability issues IEEE 802.16 standard is the first industry based standard for BWA
IEEE 802.16 Overview • Family of standards for wireless metropolitan area
networks (WMAN)• Provide broadband (i.e., voice, data, video) connectivity• Specifies the air interface, including the medium access
control (MAC) layer and multiple physical layer specifications
• promises to provide different kinds of services with guaranteed QoS.
Evolution of IEEE 802.16 Standards
802.16 802.16a 802.16-2004(Fixed WiMAX)
802.16e-2005(Mobile WiMAX)
Date Completed
December 2001
January 2003
June 2004 December 2005
Spectrum 10-66 GHz < 11 GHz < 11 GHz < 6 GHz
Operation LOS Non-LOS Non-LOS Non-LOS and Mobile
Bit Rate 32-134 Mbps
Up to 75 Mbps
Up to 75 Mbps
Up to 35 Mbps
Cell Radius 1-3 miles 3-5 miles 3-5 miles 1-3 miles
Service Flows supported in WiMAX
Service Flow Designation Defining QoS Parameters Application Examples
Unsolicited Grant Service (UGS)Maximum Sustained Rate(MSR)Maximum Latency ToleranceJitter Tolerance
Voice over IP (VoIP) without silence supression
Extended Real-time Polling Service (ertPS)
(included in IEEE 802.16e)
Minimum Reserved Rate (MRR)Maximum Sustained Rate(MSR)Maximum Latency ToleranceJitter ToleranceTraffic Priority
VoIP with silence suppression
Real-time Polling Service (rtPS)
Minimum Reserved Rate(MRR)Maximum Sustained Rate(MSR)Maximum Latency ToleranceJitter Tolerance
Streaming audio and video, MPEG (Motion Picture Expert Group) encoded
Non Real-time Polling Service (nrtPS)
Minimum Reserved Rate (MRR)Maximum Sustained Rate MSR)
File Transfer Protocol (FTP)
Best Effort Service (BE)Maximum Sustained Rate(MSR) Web browsing, data transfer
Basics of Call Admission Control (CAC) WHAT IS CAC ? A QoS mechanism that decides whether a new session
(connection) can be established. WHY CAC ? This mechanism will ensure that existing sessions’ QoS will not be degraded and the new session will be provided QoS support. HOW ?A connection is admitted if
There is enough bandwidth to accommodate the new connection The new admitted connection will receive QoS guarantees QoS of existing connections is maintained.
CAC ALGORITHMS
I. Reservation Based CAC
II. Non-Reservation Based CAC
No Bandwidth Degradation
Bandwidth Degradation
Adaptive Bandwidth Degradation-CAC Scheme [6]
Features Non-Reservation Based CAC Modified from FBD-CAC[5]
Bandwidth guarantee to all the connections Delay guarantee to rtPS connections Excellent Bandwidth Utilization
Fixed Bandwidth Degradation-CAC (FBD-CAC)[19]
In this scheme the bandwidth of lower priority connections are degraded to accommodate more connections.
The degradation is done in steps with an initially assigned step size (delta). Degradation is performed on rtPS and nrtPS connections to allow more
handoff calls. To allow more new UGS connections the degraded bandwidth from nrtPS
connections is also allocated to UGS connections.
Example :-Let B= 10240 kbpsBUGS= 256 kbps
BRTPSMAX = 1024 kbps; BRTPSMIN=512 kbpsBNRTPSMAX= 1024 kbps; BNRTPSMIN=512 kbpsLet at any instant the numbers calls admitted in the system as
given below :-Nu=8; Nr=3; Nn=5Total used bandwidth=Nu*BUGS+Nr*BRTPSMAX+Nn*BNRTPSMAX =10240 kbps.
• When a new UGS call arrives degradation will be performed on nrtPS connections• After degradation the Bandwidth available for nrtPS connection is given by
Bn=BNRTPSMAX-delta Let delta=256 kbps
Therefore Bn =768 kbps.NowTotal used bandwidth=(Nu+1)*BUGS+Nr*BRTPSMAX+Nn*Bn =9216 kbpsTotal bandwidth degraded = Nn*delta =5*256 =1280 kbps.
Disadvantage of FBD-CAC Scheme
Degradation more than necessaryStep size initially assigned arbitrarilyAvailable bandwidth for rtPS and nrtPS
connections are lessComputation time is longer because of the
degradation loopBandwidth utilization of the system is greatly
affected.
Adaptive Bandwidth Degradation(ABD)-CAC scheme
No fixed step size degradation.No need to assigned initial step size.Instead calculate the minimum required
bandwidth and then degrade.The degradation is adaptive to the required
bandwidth.
Example :- When a new UGS connection arrives degradation is performed to obtain the minimum required bandwidth as follows:
delta= [{(Nu+1)*BUGS+Nr*BRTPSMAX+Nn*BRTPSMAX} – B]/Nn =51.2 kbps.Available bandwidth of nrtPS connections = BNRTPSMAX-delta =1024-51.2 = 972.8 kbps Total bandwidth degraded = 5*51.2 = 256 kbps.Now,Total used bandwidth=(Nu+1)*BUGS+Nr*BRTPSMAX+Nn*Bn =10240 kbps.
Simulation Setup
Simulation was performed in MATLAB environment. The parameters taken for the simulation are:
B=10240 kbps. f=1 ms
TRAFFIC LOAD CONFIGURATION
g is defined as service request parameter
Simulation results
Fig. 1: Comparison NCBP and HCDP of UGS Connections Fig 2: Comparison NCBP and HCDP of rtPS Connections
Fig 3: Comparison NCBP and HCDP of nrtPS Connections Fig 4: Comparison of Bandwidth Utilization
Simulation results
Average Bandwidth Allocated to different services
TRADE OFF ANALYSIS
Design a tradeoff between HCDP and NCBPWHY?Giving more priorities to hand off calls
deprived the new incoming new calls from its own cell.
NCBP may be beyond an acceptable limit
APPROACH Define Two metrics1. Grade of Service (GoS)GoSk=NCBPk+bk.HCDPk, k ε {u, r, n} Where u, r, n denotes UGS, rtPS and nrtPS connections
respectively.bk= penalty weight for handoff calls relative to new calls >>1** Small GoS means better performance2. Cost function (CF) CF=w1*GoSu+w2*GoSr+w3*GoSn
Where w1+w2+w3=1 and different w1, w2 and w3 means different priority of the services. Therefore the weights are selected such that w1>w2>w3.
Define a Degradation threshold variable Bth which is optimized according to the minimum cost function.
Basic Steps
• For a particular arrival rate vary Bth in the interval 0 < Bth < Bmin
• For every value of Bth Calculate CF.
• The value Bth that gives the smallest CF is the optimal value of Bth for that arrival rate.
Simulation results
Fig 5 : Comparison of NCBP of UGS connections Fig 6 : Comparison of NCBP of rtPS connections
Fig 7 : Comparison of NCBP of nrtPS connections Fig 8 : Comparison of HCDP of UGS connections
Simulation results
Fig 9 : Comparison of HCDP of rtPS connections Fig 10 : Comparison of HCDP of nrtPS connections
Simulation results
Fig 11: The Optimal value of degradation variable Bth
Simulation results
CONCLUSIONAdaptive Bandwidth Degradation-CAC is further
extended to achieve fairness among new calls and handoff calls.
The proposed scheme has shown improvement in NCBP without affecting the HCDP.
The bandwidth utilization remains unaffected as obtained in ABD-CAC.
Tuning of the parameters used in tradeoff analysis is required which may be done using robust optimization techniques.
REFERENCE1. IEEE Standard: Air Interface for Fixed Broadband Wireless Access System. IEEE STD 802.16 – 2004,
October, 2004.2. IEEE Standard: Air Interface for Fixed and Mobile Broadband Wireless Access System. IEEE
P802.16e/D12, February, 2005.3. Fen Hou, Pin-Han Ho, and Xuemin (Sherman) Shen: Performance Analysis of Reservation Based
Connection Admission Scheme in IEEE 802.16 Networks. Global Telecommunications Conference, GLOBECOM’06, November 2006, pp. 1-5.
4. Xiang Chen, Bin Li, and Yuguang Fang: A Dynamic Multiple-Threshold Bandwidth Reservation (DMTBR) Scheme for QoS Provisioning in Multimedia Wireless Networks. IEEE Trans. on Wireless Communications, vol. 4, no. 2, pp. 583-592, March 2005.
5. Kalikivayi Suresh, Iti Saha Misra and Kalpana Saha (Roy): Bandwidth and Delay Guaranteed Connection Admission Control Scheme for QoS Provisioning in IEEE 802.16e Mobile WiMAX. proc. IEEE GLOBECOM 2008.
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7. D. S. Shu'aibu, S. K. Syed Yusof, N. Fisal et al: Fuzzy Logic Partition-Based Call Admission Control for Mobile WiMAX. ISRN Communications and Networking, vol. 2011, Article ID 171760, 2011.
8. Sabari Ganesh.J, Bhuvaneswari P.T.V.: Enhanced Call Admission Control for WiMAX Networks. IEEE-International Conference on Recent Trends in Information Technology, ICRTIT 2011, Chennai. June 3-5, 2011, pp 33-36.
9. Wan Kim and Hwang Jun S.: QoS-aware joint working packet scheduling and call admission control for video streaming service over WiMAX network. Wirel. Netw. 17, 4 (May 2011), 1083-1094.
10. Shengdong Xie, Meng Wu: Optimized Call Admission Control in Wireless Networks. proc. International Conference on Advanced Infocomm Technology 2008.