Abstract:The era of entirely wireless, mobile communication is rapidly approaching.Increasingly; users are demanding versatile and convenient modes of communication along with high-speed broadband and technology in the premise of guaranteeing certain quality of communication without losing performance and efficiency. The challenges are to give users high-speed, high-performance in different channel conditions. So, Orthogonal Frequency Division multiplexing (OFDM) has been recognized as one of the most promising techniques to meet these challenges. Space Time block Coding (STBC) has drawn much attention in 4G wireless technologies just because of its decoding simplicity. This paper presents the performance evaluation of STBC-OFDM systems covering channel model and coding scheme, it includes Rayleigh fading channels by which it is observed that Bit Error Rate(BER) is reduced to achieve the high data rate.In this work, a performance criterion such as bit error rates for low SNR is analyzed. The BER for OFDM system over Rician fading channel is observed to be 0.1273.It has been reduced to 0.03919 over Rayleigh fading channel with Line of Sight (LOS) for the same Signal to noise ratio (SNR).

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Abstract:The basic function of the digital IC tester is to test digital IC for correct logical functioning as described in the truth table. It can test digital ICs having 14 pins. This model applies the necessary signals to the inputs of the IC, monitoring the outputs at each stage and comparing them with the outputs in the truth table. Any discrepancy in the functioning of the IC results in a fail indication through LEDs. The testing procedure is accomplished with the help of keys present on the main board. At this stage we had completed to test the most common used digital IC's used in our laboratories, mainly belonging to the 74TTL series. This tests various types of ICs like AND, OR, EX-OR, NAND, NOR and EX-NOR gates.

Abstract:In current 4G systems growing demand of multimedia services and the growth of internet related contents lead to increasing interest to high speed communications. One indispensable problem of the wireless channel is fading, which can be mitigated by diversity. There are various coding methods to achieve high reliability for Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems earlier. Recently, Space Time Block Codes (STBC) have gained much attention as an effective transmit diversity technique to provide reliable transmission with high peak data rates to increase the speed and performance of wireless communication systems. This paper presents the performance evaluation of OFDM system, in which fading is reduced by using diversity techniques along with coding methods under various fading channels such as Rician and Rayleigh fading channels. In this work, a performance criterion such as Bit Error Rate (BER) for low Signal to Noise Ratio (SNR) ranging from 10dB to 20dB is analyzed. The BER for OFDM system without including STBC is 1.776x10 -3 and including STBC is 1.621x10 -3 over Rician Channel. Whereas, over Rayleigh channel the BER for OFDM system without including STBC is 1.834x10 -5 and including STBC, it is reduced to 6.345x10 -6 for the same SNR of 14dB. Thus, OFDM system with STBC provide high data rate with good reliability.