Browsing by Author "Suraweera, ND"

Now showing 1 - 3 of 3

item: Thesis-Abstract
Beamforming techniques for the downlink of space-frequency coded decode-and-forward MIMO-OFDM relay systems
Suraweera, ND; Wavegedara, Dr. KCB; Ekanayake, Prof. EMN
Multiple-input multiple-output (MIMO) techniques can be used to achieve diversity gain, multiplexing gain and/or array gain. Particularly, diversity cod- ing techniques (e.g. Space-Time (ST), Space-Frequency (SF) coding) have re- ceived tremendous attention as e ective means of achieving spatial diversity gain in MIMO systems. However, in the presence of spatial correlations the diversity gain of ST/SF coding diminishes. Beamforming techniques can be used to achieve array gains in MIMO systems. Hence, in correlated channels beamforming tech- niques can be combined with ST/SF coding to further improve the performance. In this thesis, we develop beamforming techniques relying on statistical channel state information at the transmitter (CSIT) for space-time (ST) / space-frequency (SF) coded MIMO systems to minimize the pair-wise error probability. We pro- pose beamforming techniques for SF coded MIMO-OFDM systems in correlated frequency-selective Rician fading channels. We propose two novel beamforming techniques for this channel model. Furthermore, distributed beamforming techniques are developed for correlated Rayleigh at-fading channels, relying on full-instantaneous CSIT as well as sta- tistical CSIT. Moreover, we extend these techniques for SF coded MIMO-OFDM relay networks in correlated Rician fading channels and propose optimal beam- forming techniques relying on full-instantaneous CSIT. Also, suboptimal beam- forming techniques relying on statistical CSIT are developed. The variation of error performance is thoroughly investigated and the simulation results con rm that all the proposed beamforming techniques achieve signi cant performance ad- vantages over MIMO systems using ST or SF coding only.
item: Conference-Extended-Abstract
Transmit beamforming for space-frequency coded MIMO-OFDM cystems operating in a correlated ricean fading channel
(2010) Suraweera, ND; Wavegedara, KCB
In highly spatially-correlated channels the diversity gain obtained by diversity coding schemes (such as Space-frequency (SF) coding or Space-Time (ST) coding) is considerably low. Combining beamforming with SF/ST coding help to improve the system performance in spatially correlated channels. In this paper, we propose two beamforming technique for SF coded MIMO-OFDM systems in a frequence-selective Rician-fading channel to minimize the pair-wise error probability (PEP). The proposed beamforming techniques are based on the channel mean and spatial correlation statistics. In Technique, 1. all the eigenmodes of the channel spatial correlation and mean matrices taken in to consideration, where in Technique 2. Only the strongest egimodes of the channel spatial correlation and mean matrices is considered. Simulation results demonstrate that Technique 2 offers a substantial performance improvement over SF coding without beamforming in highly spatially-correlated channels. Furthermore, considerable performance improvements can be obtained using Technique 1 overSF coding only in low correlated channels with a high Ricean K factor.
item: Conference-Abstract
ZigBee based local communication system for high noise environments
(2008) Silva, KVR; Suraweera, ND; Talagala, DS; Thilakarathna, DK; Dias, D
In a very high noise environment, conventional communication means suffer from significant degradation due to the external noise which can drown out the desired speech signal. Environments such as industrial complexes, manufacturing plants, battle fields are examples of extremely noisy environments. Mobility is also crucial requirement for communication in such environments frequently. The paper describes the design and implementation of a mobile wireless communication system which can operate in such an environment using effective noise cancellation techniques.