Institute for Systems Research
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Item An Adaptive Hybrid FEC/ARQ Protocol Using Turbo Codes for Multi-Media Transmission of ATM over Wireless Networks(1997) Chan, Wai-Chung; Geraniotis, Evaggelos A.; ISR; CSHCNThis paper describes a type-II adaptive hybrid FEC/ARQ protocol using turbo codes for both voice and data services.Recently, a powerful family of error correcting codes using parallelconcatenated convolutional codes is introduced. Near-Shannon-limitis achievable by such codes. For example, a bit error rateof $10^{-5}$ can be achieved at $E_b/N_o =$ 0.7~dB using a rate1/2 code or at about 2.5~dB if fewer iterations are used in decoding.Given the promising performance of the codes, it is expected thatthe performance of an adaptive FEC/ARQ protocol employingturbo codes will be better than protocols using other error correcting codes.Rate compatible turbo codes are used in the protocol. Extra parity bitscorresponding to a lower rate turbo code will betransmitted if the previous transmission leads to a decoding error.For real-time services, the number of retransmissions is limited to one soas to limit the delay. For data services, the number of retransmissions is unlimited to provide a reliable communication link.Results in terms of throughput are obtained for the adaptive FEC/ARQ protocol using compatible rate 1/2 and rate 1/4 turbo codes.Item A Methodology for Modeling, Performance Analysis, and Control of ATM Networks with Multi-Media Traffic(1997) Chou, Chih-Hsien; Chan, Wai-Chung; Geraniotis, Evaggelos A.; ISR; CSHCNIn this paper we review recent advances in developing a methodology for traffic modeling, performance evaluation, and control of ATM networks that can be used to support several aspects of Task 4.3 of the ATIRP project. Our methodology includes model matching and validation for multi-media traffic, analytical approximation techniques for time-efficient and accurate evaluation of end-to-end as well as intermediate node performance measures of multi-hop networks, and optimization of control (resource allocation) schemes.Item Medium Access Protocols for Interconnecting ATM and Wireless Networks(1997) Chan, Wai-Chung; Geraniotis, Evaggelos A.; ISR; CSHCNThe current trend in modern telecommunication is that most of the traffic (CBR, VBR and ABR, real-time and delay-insensitive) in the fixed broadband networks will be carried by fixed-length packets. It is desirable to extend the services to wireless networks as well. However, one major difficulty in wireless networks is the limited spectrum available. Another difficulty is that the bit error rate (BER) of the wireless channel is typically much higher than that of the channels of the wireline broadband networks. The latter problem is amplified for military wireless networks that experience substantial link interference (e.g., multipath fading, other-user interference jamming). Therefore, we can only expect that the same services are being carried in a similar fashion but with a lower source rate. In this paper, a medium access protocol for interconnecting ATM and wireless networks is discussed, followed by some alternatives, and other issues pertaining to guaranteeing low BER. This research was conducted in support of Task 1.1 of the ATIRP project during FY 96 and continues under Task 4.3 for FY 97.