46 research outputs found
ATM networks Traffic control, interworking with CAN, and end station NIC architecture
SIGLEAvailable from British Library Document Supply Centre-DSC:DXN020777 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Short Message Service Link for Automatic Vehicle Location Reporting
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Joint Source-Adaptive Vector Quantisation and Index Assignment with Embedded Redundancy
A new vector encoder-decoder (VED) design that is jointly adaptive to source statistics and optimised for noisy channels is proposed. The vector encoder consists of a source-adaptive vector quantiser (AVQ) and a structured index assignment with embedded redundancy (IAER) scheme to provide error-protection capability for noisy channels. The AVQ and IAER processes are combined together resulting in a very effective source-adaptive and channel-optimised VED design. The joint algorithm is designed and evaluated for the non-stationary Wiener process, modelling the source, and for two noisy channels, the binary symmetric channel and the more practical wireless flat-fading Rayleigh channel. It is shown that the proposed technique gives substantial signal-to-noise ratio gains over the separate design of the source AVQ and the IAER in both channel conditions without any additional online computational complexity. In addition, it is suitable for different applications of varying source and channel environments
Particle Swarm Optimization for Resource Allocation in OFDMA
Particle Swarm Optimization (PSO) is a well-known technique in Artificial Intelligence (AI) for n-dimensional optimization problems. In this paper we extend the application of PSO to physical layer of communication systems and propose a simple target-customized PSO algorithm that could be used in centralized iterative optimization techniques. It is applied here for the sub-carrier allocation in OFDMA and shown that to significantly reduce the computation complexity and increases the flexibility compared with conventional techniques
Adaptive Multi-Carrier Cooperative Communication Technique
In this paper, we propose adaptive multi-carrier cooperative communication (MCCC) technique for multi-path fading channels. In the proposed system, the nodes cooperatively transmit data over adaptively allocated sub-carriers to maximize the spectral efficiency while improving the bit error rate performance. Two adaptive sub-carrier allocation strategies are introduced. In the first strategy, the sub-carriers are selected solely based on the channel gain while in the second strategy the sub-carriers are allocated using both channel gains and distance measure between the nodes. It is shown that the proposed technique has a better bit error rate performance and spectral efficiency compared with adaptive and none adaptive OFDM systems
Performance of Cooperative CDMA with Successive Interference Cancellation
We investigate the BER and achievable rate of user cooperation schemes in practical uplink CDMA channels with multiple access interference (MAI). It is shown that when the system loading increases, cooperation alone becomes less effective if simple matched filters (MF) followed by combining from each partners' signals are employed for obtaining decision variables. By performing successive interference cancellation (SIC) for each received signals from the partners and then using the maximum ratio combining technique, the diversity gain and hence the uplink capacity is enhanced. We further analyse the output decision variable signals and also provide a simplified bound on achievable rate based on Gaussian Approximation of MAI signals. Illustrative simulation results are given, which confirm that the proposed scheme using SIC achieves much improved diversity and error performance under high system loading and near far conditions