Performance Analysis of MIMO–OFDM System with Relaying Techniques in Rayleigh Fading Channel
Shivi Tikko, Shweta Pandit, Pradeep Kumar · International Journal of Engineering and Technology · 2017
A relay network is a wide class of network configuration which is often used in wireless networks, where the source node and destination node cannot communicate directly and are interlinked with the help of some nodes.The different methods by which the relay networks are implemented in the system are known as relaying techniques.In this paper, we have presented the spectral efficiency and BER performance analysis of the MIMO-OFDM wireless system with different relaying techniques in Rayleigh fading channel.The simulated results for different modulation schemes are presented.The obtained results have shown that the hybrid relaying technique provides better spectral efficiency and bit error rate (BER) performance as compared to the other relaying techniques.Keyword-MIMO-OFDM, relaying techniques, decode and forward, amplify and forward, hybrid decode and amplify forward, Rayleigh fading, spectral efficiency, BER. I. INTRODUCTIONThe use of diverse number of antennas at the transmitter and receiver side in wireless system is known as Multiple Input and Multiple Output technology or MIMO technology that has achieved popularity over the past years because of its powerful performance enhancing capabilities over single input single output or SISO antenna system.MIMO antenna technology exploits the spatial domain property of fading channels to bring noteworthy performance improvements to wireless communication systems.Typical MIMO systems require both the transmitter and receiver of a communication link to be equipped with multiple antennas and have potential for increased capacity [1-3].In addition, MIMO system improves SNR, range and coverage area of a wireless network [4].It also improves the quality and reliability of reception and is resistant to noise [5].Further, in OFDM (Orthogonal Frequency Division Multiplexing) system, large amount of closely spaced orthogonal subcarrier signals carry data on various data channels or data streams.Each sub-carrier signal is modulated by suitable modulation scheme like QAM, PSK or FSK at a low symbol rate, thus maintaining the total data rate same as that of standard single carrier modulation scheme for the same bandwidth.OFDM is advanced form of FDM (Frequency Division Multiplexing) where all subcarrier data signals are orthogonal to one another.The signals whose integral of the products for their common (fundamental) period is zero are known as orthogonal signals [6].The main advantage of OFDM system is that it makes competent use of the spectrum by enabling the overlapping of signals and divides the broadband frequency selective channel into various narrowband flat fading channels.Hence, as compared to single carrier systems, OFDM is more impervious to frequency selective fading.All wireless linkage are mainly affected by three typical parameters which are speed, range and reliability.These characteristics of wireless system are tied to each other by strict regulations.Speed could be enhanced only by neglecting the range and reliability of the system.Range could be widen at the loss of reliability and speed.And at last, reliability could be reinforced by deflating range and speed.Only MIMO-OFDM gives everything in one set by offering optimal values of speed, range and reliability simultaneously.In OFDM, an individual channel within a spectrum band can be segmented into large number of small sub carrier signals that can transmit information simultaneously without any kind of interference.Since in MIMO technology many smaller antennas are linked up to work as one, so they can transmit and receive these multiple OFDM sub signals.This allows the substantial increment of bandwidth for each user as required.Thus, combining these two technologies results in a wireless system that has characteristics like good spectral coverage, more reliable transmission in highly perverse surrounding, with high data rates [7,8].Since MIMO serves the spatial diversity whereas OFDM uses multiplexing technique like frequency division duplex (FDD) or time division duplex (TDD); therefore in the spatial domain, MIMO provides greater capacity.Further in the time domain, the