Channel or spectral estimation is a ground-breaking feature in wireless communication systems as it helps in obtaining information about a wireless channel at any state of time. Employing this can help in reducing the intensity of noise and bit error rate (BER). Here, images are processed, channels are estimated and image restoration is being done. Orthogonal Frequency Division Multiplexing (OFDM) is looked upon as a very popular multiplexing cum modulation technique used in wireless communication systems and so, it is selected to play a cardinal role in channel estimation. The LMS algorithm is preferred in this technique since it is a simpler technique and provides results which are desirable. To simulate realistic conditions, OFDM signal is passed through Additive White Gaussian Noise (AWGN) and also a multipath fading channel. In this paper, an FFT based OFDM, adopting several digital modulation techniques like BPSK, QPSK, 8PSK and 16QAM is being implemented on images. The values of BER is observed for different values of SNR and a comparison is drawn out for the aforementioned modulation techniques. Results prove that BPSK provides the least BER for a particular value of SNR and hence, it can be observed to give the best performance.

No abstract

No abstract

In a wireless communication system, the transmitted signal is exposed to various surfaces where it bounces and results in several delayed versions of the same signal at the receiver end. The delayed signals are in the form of electromagnetic waves that are diffracted and reflected from the various object surfaces. These result in co-channel interferences for wireless systems. MIMO has proven to be a striking solution for the new generation of wireless systems. MIMO-OFDM system with QPSK modulation is considered as the wireless system for studying the performance of interference cancellation techniques. The BER performance is studied in channels such as Rayleigh and Rician Fading Channels. The effects of interference are reduced to a certain extent by the inclusion of CDMA (spread spectrum technique) as Technique 1. The effects of interference on this system have been further reduced using the LMS filter as Technique 2. Hence, to show better performance in MIMO-OFDM systems, it is recommended to employ both CDMA and LMS filters to decrease the effects of co-channel interference. It is observed that the parameter BER reduces as the SNR increases for both these channels. Doi: 10.28991/esj-2021-01313 Full Text: PDF