Communications and Signal Processing Lab (ComSP)

Title	Performance of SC-FDMA with diversity techniques over land mobile satellite channel
State	Finished
Author	Jyoti Ramesh Gangane
Director/s	Mª Carmen Aguayo Torres ,  Juan Jesús Sánchez Sánchez
University	Universidad de Málaga
Center	Escuelta Técnica Superior de Ingeniería de Telecomunicación
Department	Ingeniería de Comunicaciones
Reading date	08/07/2016
File	PDF

The major expansion seen in wireless technologies over last two decades is a direct result of the increasing demand for high data rate transmissions. Third Generation Partnership (3GPP) developed Long Term Evolution (LTE) mobile communication to meet high data rate requirement. Besides cellular communications, Land Mobile Satellite (LMS) systems is a significant part of the wireless systems. The LMS system provides services that are not feasible via Land Mobile Terrestrial (LMT) systems over a wide area of the network with low cost. Next generation of wireless systems is expected to be formed by the convergence of what now are considered independent systems.

The demand for high data rate results in significant Inter-Symbol Interference (ISI) for single carrier systems over bandwidth and power limited channels. Overcoming the time and frequency selective nature of the propagation channel requires the use of powerful signal processing techniques. Recent examples include different transmitter/receiver diversity techniques for high data rate transmissions as well as including multiple antennas at transmitter/receiver known as Multiple-Input Multiple-Output (MIMO). Multiple antenna communication technologies provide significant advantages over single antenna systems. These advantages include extended range, improved reliability in fading environments and higher data throughputs. In certain environments (such as the uplink of a mobile link) usually only one antenna is available at the transmission. Thus, only Single-Input-Single-Output (SISO) or Single-Input Multiple-Output (SIMO) transmissions are feasible.

Orthogonal Frequency-Division Multiplexing (OFDM) has been a more widely used modulation technique due to its robustness against frequency selective fading channels, scalability, and MIMO compatibility. However, it suffers from a high Peak-to-Average Power ratio (PAPR) which may be particularly troublesome in uplink cellular and satellite downlink transmissions as costly high-power linear amplifiers are needed for transmitting terminals.

Single Carrier Frequency-Division Multiple access (SC-FDMA) has become an alternative to OFDM techniques, specifically used as the uplink multiple access schemes in 3GPP LTE. It is able to reduce the PAPR in the transmission, resulting in a relaxation of the constraints regarding power efficiency needed in user terminals and satellite units. The SC-FDMA can be described as a version of OFDMA in which pre-coding and inverse pre-coding stages are included at the transmitter and receiver ends respectively, thus symbols are transmitted in time but after processing in the frequency. Even with the use of OFDMA or SC-FDMA, inter-symbol interference has to be compensated by equalization, which is usually performed in frequency domain.

The aim of this dissertation is to provide a mathematical analysis of the performance of SC-FDMA over land mobile satellite channel. For this purpose, the channel will be modelled as a shadowed Rice channel such that its Line Of Sight (LOS) follows Nakagami distribution. We first describe OFDMA and SC-FDMA multicarrier modulation techniques. Then we undertake an analysis of OFDMA and SC-FDMA based on enhanced complex noise at the detector stage. We evaluate the Bit Error Rate (BER) and spectral efficiency performance of SC-FDMA for different depths of shadowing. Finally, SC-FDMA performance with receiver diversity techniques, such as Maximal Ratio Combining (MRC) and Equal Gain Combining (EGC), is also evaluated.