A Low-Complexity Source Encoding Assisted Multiple Access Protocol for Voice/Data Integrated Networks
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A Low-Complexity Source Encoding Assisted Multiple Access Protocol for Voice/Data Integrated Networks Andres Kwasinski Department of Electrical and Computer Engineering and The Institute for Systems Research, University of Maryland, College Park, MD 20742, USA Email: [email protected]
Mehdi Alasti Department of Electrical and Computer Engineering and The Institute for Systems Research, University of Maryland, College Park, MD 20742, USA Email: [email protected]
K. J. Ray Liu Department of Electrical and Computer Engineering and The Institute for Systems Research, University of Maryland, College Park, MD 20742, USA Email: [email protected]
Nariman Farvardin Department of Electrical and Computer Engineering and The Institute for Systems Research, University of Maryland, College Park, MD 20742, USA Email: [email protected] Received 22 August 2003; Revised 19 May 2004 We present and evaluate the performance of a reduced complexity variation to the source encoding assisted multiple access (SEAMA) protocol for integrating voice and data over a wireless network. This protocol, denoted as slow movable-boundary SEAMA (SMB-SEAMA), uses the same embedded and multistate voice encoder used in the original SEAMA protocol. However, in SMB-SEAMA, the movable voice/data boundary is not set based on the frame-by-frame bandwidth demand of the voice subsystem, but on the number of ongoing voice calls and the acceptable average distortion level. This results in a protocol that, at the network layer, is packet switched for both voice and data; however, from the data traffic point of view, the voice looks like circuit switched. Analytical results show that SMB-SEAMA is a very efficient MAC protocol and presents a model for analyzing the performance of queuing systems with a variable number of servers, each with a constant service time. Consequently, while reducing the refreshing rate of the movable boundary by three orders of magnitude, simulation results demonstrate that SMBSEAMA does not significantly degrade the system performance (less than 8% reduction in throughput) and it still performs better than packet reservation multiple access (PRMA), the other known packet-switched scheme, which updates the boundary during every transmit frame. Keywords and phrases: TDMA, embedded voice coding, packet-switched wireless network, voice-data boundary setting, voicedata integration.
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INTRODUCTION
In a resource-limited wireless network, the medium access control (MAC) protocol design plays an essential role in integrating different services (e.g., voice and data) and satisfying each service demands while providing high network utilization. While end-users evaluate network performance in terms of the perceived quality (regardless of how it is defined), network operators and designers face the conflicting need to satisfy end-users’ demands and assure high network
utilization. At the root of this problem is the need to consider the design problem at two different layers of the communication link: the application layer and the network layer. Because of these inhere
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