Effective Channel State Information (csi) Feedback for Mimo Systems in Wireless Broadband Communications

Multiple Input Multiple Output (MIMO) is seen as one of the key technologies in wireless communication industry that offers significant increase in data throughput and link range without additional bandwidth or increased transmit power. Such systems have the potential to spread the same total transmit power over the antennas to achieve an array gain that improves the spectral efficiency and/or to achieve a diversity gain that improves the link reliability. The availability of Channel State Information (CSI) at the transmitter end in MIMO system has been a popular research topic in recent years. The knowledge of accurate and timely CSI at the transmitter is becoming increasingly important in wireless communication systems. While it is often assumed that the receiver needs to know the channel for accurate power control, scheduling, and data demodulation, it is now known that the transmitter (especially, the base station) can also benefit greatly from this information. The CSI makes it possible to adapt transmissions to current channel conditions, which is crucial for achieving reliable communication with high data rates in multi antenna systems. The channel capacity of MIMO system increases linearly with the increase in the number of antenna pairs between transmitter and receiver. In addition, several works have shown that the capacity in MIMO can be further improved if the forward Channel State Information (CSI) is made available at the transmitter. Basically, there are two methods that allow the transmitter to obtain CSI from the receiver. The first one is based on the channel reciprocity principle and the second one uses feedback from the receiver. This research has analysed both reciprocity and feedback mechanisms and has presented the basis of an effective CSI feedback mechanism that efficiently provides the transmitter with minimum CSI to allow the accurate knowledge of a rapidly changing channel. The simulations have been conducted using MATLAB to measure the performance degradation when the channel is imperfectly estimated at the receiver in a 2 X 2 MIMO systems and compared to the case of perfect channel knowledge at the receiver. The simulation results show that with 8 pilot symbols for each 100 symbols of data, channel estimation causes about a 1 dB degradation in performance for the selected Eb/No range when compared to feedback CSI at the transmitter end. Also the channel estimation causes about a 2.45 dB degradation in performance for the selected Eb/No range as compared to the feedback channel …