WSEAS CONFERENCES. WSEAS, Unifying the Science

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Oct. 2007, Nov. 2007, Dec. 2007, 2008


Issue 11, Volume 6, November 2007
Print ISSN: 1109-2742
E-ISSN: 2224-2864








Title of the Paper:  Adaptive Link-Weight Routing Protocol using Cross-Layer Communication for MANET


Authors: A.N. Al-Khwildi, S. Khan, K.K. Loo, H.S. Al-Raweshidy

Abstract: Routing efficiency is one of the challenges offered by Mobile Ad-hoc Networks (MANETs). This paper proposes a novel routing technique called Adaptive Link-Weight (ALW) routing protocol. ALW adaptively selects an optimum route on the basis of available bandwidth, low delay and long route lifetime. The technique adapts a cross-layer framework where the ALW is integrated with application and physical layer. The proposed design allows applications to convey preferences to the ALW protocol to override the default path selection mechanism. The results confirm improvement over AODV in terms of network load, route discovery time and link reliability.

Keywords: Reliable Routing Protocol, Mobile Ad Hoc Network (MANET), Adaptive Routing, QoS

Title of the Paper: Design of a Modified Bi-Directional SOVA


Authors: Kingsley Oteng-Amoako, Saeid Nooshabadi

Abstract: In this paper, a directional bi-directional Soft-Output Viterbi algorithm (SOVA) based Turbo decoder architecture is proposed. By performing an extra pass through the decoder trellis, effectively bi-directional decoding, decoder performance can be improved. The bi-directional decoding results in a 60% increase in operations over the conventional SOVA decoder, while incurring no significant increase in architecture size. The paper also proposes the use of extrinsic information in selecting the SOVA algorithm, resulting in improved decoding performance. The use of the extrinsic information as a reliability measure does not introduce any inherent latency and requires a negligible increase in hardware. Following both architecture proposals, the paper discusses practical implementation using finite precise arithmetic. Simulation results show that by combining both proposed techniques, an extra coding gain of 0.4dB can be obtained over the conventional SOVA decoder in an Additive White Gaussian Noise (AWGN) channel.

Keywords: Information rate, adaptive modulation, adaptive coding, fading channels, concatenated coding

Title of the Paper: Limitations of Current 4G Systems and Its Substitute Schemes with TDD/TDMA


Authors: Lu Zhaogan, Shen Xiaodong, Li Xiaohe, Zhang Taiyi

Abstract: In current 4G system given in recent literatures, channel estimation overhead and complexity of multi-user detectors (MUD), may lead to bad performance in fast fading channel scenarios when large number of users exists. So, a novel 4G system with TDD/TDMA as duplex and wireless access is designed to reduce channel estimation spending and avoid MUD, as only one user can be active to communicate with base station. Under the requirement of 4G systems, radio frame structure is elaborately designed to fit for fast fading channel scenarios. Construction of training sequences for channel estimation is also detailed together with a novel eigenmodes coupled universal space-time codes. The system architecture with consideration of link adaptations is given and evaluated for performance of TDD/TDMA 4G systems. Results show the proposed TDD/TDMA 4G can meet the requirement of 4G system under the classical ITU channel profiles.

Keywords: MIMO, OFDM, orthogonal eigenmodes, 4G, link adaptation

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