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Multi-level Bandwidth Adaptation for QoS
Provisioning in Wireless Networks
Mostafa Zaman Chowdhury1
, Yeong Min Jang1, and Zygmunt J. Haas2
1Department of Electronics Engineering, Kookmin University, Seoul, Korea.
2Wireless Networks Lab, Cornell University, Ithaca, NY, 14853, U.S.A
E-mail: mzceee@yahoo.com, yjang@kookmin.ac.kr, zhaas@cornell.edu
Abstract. In this paper we propose a bandwidth adaptation scheme that release
multi-level of bandwidth from the existing calls. The amount of released
bandwidth is based on the priority of requesting traffic call. This priority
scheme does not reduce the bandwidth utilization. Moreover, the bandwidth
adaptation policy provides significantly reduced call blocking probability for
the higher priority traffic calls.
Keywords: Bandwidth adaptation, traffic class, and call blocking probability.
1 Introduction
The quality of service (QoS) adaptability has been used by several schemes (e.g., [1],
[2]]) to reduce the call blocking probability. The adaptive QoS schemes [3], [4]
proved more flexible and efficient in guaranteeing QoS than the guard channel
schemes [1]. In this paper, we present a scheme which allows reclaiming some of the
allocated bandwidth from already admitted bandwidth adaptive traffic calls, as to
accept higher priority calls, when the system’s resources are running low.
Consequently, the scheme can reduce the overall forced call termination probability
significantly as well as provides significantly reduced call blocking probability for the
higher priority traffic calls. Our scheme reserves some releasable bandwidth to accept
higher priority calls by providing multi-level bandwidth adaptation.
2 Proposed Bandwidth Adaptation
The basic idea for the proposed scheme is shown in Fig. 1. A call of m-th class traffic
can be allocated by different level of bandwidth. The bandwidth allocation scheme is
characterized by bandwidth degradation factors γm and γm,p, respectively, are defined
for each class m traffic, as: the fraction of the bandwidth that has been already
degraded of an admitted call, the maximum fraction of the bandwidth of an admitted
call that can be degraded to accept a call of class p type (p=0 represents the handover
calls of any types of traffic). Therefore, to accept p-th priority call, the existing m-th
class traffic call can be degraded to the maximum limit of the γm,p portion.
m,0
g
m, p
g
m,1
g
m,M 1
g
-
m,M
g
Fig. 1. System model for the proposed multi-level bandwidth adaptation scheme.
From the Fig. 1 it can be stated that,
, , , ,m 0 m 1 m m m M
1 0
g g g g
> ³ ³ ×× ³ ³ × × ³ ³
(1)
Equation (1) indicates that the proposed scheme offers more degradation of the
existing m-th class bandwidth adaptive traffic calls to accept a higher priority traffic
call compared to the lower priority traffic calls.
3 Performance Analysis
In this section we present the performance of our proposed scheme. The ratio of the
number of requested calls (voice: web-browsing: video: background) is considered as
3:3:1:2. Considering the average call duration of 120 sec during condition of no
bandwidth degradation, the average cell dwell time is found to be 240 sec. During the
bandwidth degraded condition, we considered the average call duration is state
dependent i.e., more than 120 sec. We assume that the system capacity is 6 Mbps. For
p=1 to 4, we consider γm,p=0.95 γm,p-1.
Fig. 2 shows that the proposed scheme provides negligible handover call dropping
probability even for high call arrival rate. The provision of maximum level of
bandwidth adaptation without the priority of calls cannot provide acceptable handover
call dropping probability and new call blocking probability of the higher priority
traffic calls. Our scheme provides almost equal forced call termination probability
compared to the adaptive non-priority scheme. Therefore, our proposed scheme offers
priority for the higher priority calls without reducing the resource utilization.
0.6 0.8 1.0 1.2 1.4 1.6 1.8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
New call blocking probability
Handover call dropping probability
Overal forced call termination Probability
New call arrival rate (calls/sec)
Handover (Proposed scheme)
New voice (Proposed scheme)
New web-browsing (Proposed scheme)
New video (Proposed scheme)
New background (Proposed scheme)
Overall forced (Proposed scheme)
New/Handover (Adaptive non-priority scheme)
Overall forced (Adaptive non-priority scheme)
Fig. 2. A comparison of new call blocking probability, handover call dropping probability, and
overall forced call termination probability.
4 Conclusions
The proposed scheme offers more bandwidth degradation of the calls to support
higher priority traffic calls over lower priority calls. Therefore, our proposed scheme
provides priority of traffic calls as well as bandwidth adaptation. As a result, to give
the priority of traffic calls, the overall forced call termination probability is not
increased significantly.
Acknowledgments. This work was supported by the IT R&D program of MKE/KEIT
[10035362, Development of Home Network Technology based on LED-ID].
References
1. Vergados, D. D.: Simulation and Modeling Bandwidth Control in Wireless Healthcare
Information Systems. SIMULATION. 83(4), 347–364 (2007)
2. Zhuang, W., Bensaou, B., Chua, K. C.: Adaptive Quality of Service Handoff Priority
Scheme for Mobile Multimedia Networks. IEEE Trans. Veh. Technol. 49(2), 494-505
(2000)
3. Sheu, T.-L., Huang, K.-C.: Adaptive Bandwidth Allocation Model for Multiple Traffic
Classes in IEEE 802.16 Worldwide Interoperability for Microwave Access Networks. IET
Communications. 5(1), 90-98 (2011)
4. Nasser, N.: Service Adaptability in Multimedia Wireless Networks. IEEE Trans.
Multimedia. 11(4), 786-792, (2009)
