Investigations on improved channel estimation technique of multiple input multiple output for cooperative mimo and wireless sensor networks systems

Abstract

The rapid development in mobile data applications has increased the requirement for wireless systems that offer improved reliability, high throughput and wide coverage range. The major challenges faced in designing such systems are bandwidth scarcity, reduced transmission power and the impairments of the wireless channels resulting in fading and interference. To meet these demands, Multiple-Input Multiple-Output (MIMO) system is considered to be one of the favorable wireless technologies. MIMO system plays a major role in the fourth generation wireless systems to provide high data rates and reliable transmission. With multiple antennas employed at both the transmitter and receiver, MIMO offers increased channel capacity. The major problem encountered in communication system is the Inter Symbol Interference (ISI) imposed on the signal transmitted owing to multipath effects and band limiting effect of the channel. The widely used technique to combat the ISI effect is to utilize linear channel equalizer. This equalizer gives an approximate inverse of the channel response. Generally, ue to unknown channel characteristics or variation over time, the equalizer needs to be made adaptive. Traditional equalizers utilize predetermined time slot through which a training sequence, known prior to the receiver is transmitted. At the receiver, the coefficients of the equalizer are adapted using various adaptive algorithms such that the equalizer output closely matches the training sequence. However, frequently transmitting the training sequence is an overhead which negatively impacts the throughput of the system. To overcome this bottleneck, adaptation algorithms like blind equalization are preferred. In blind equalization, the inverse of the channel is estimated using one or more properties of the transmitted data signal newline