A Zadoff-Chu Matrix Transform Precoding Based Orthogonal Frequency Division Multiplexing System

Orthogonal-frequency-division-multiplexing (OFDM) schemes are most popular in
the literature due to their ability to combat frequency selective fadingwhile providing
high data-rate transmission. Today,OFDM has become part of several
telecommunication standards that includes, among others, theupcoming 4G standards
like long-term-evolution-advanced (LTE-A) and mobile worldwide interoperability
for microwave access (Mobile-WiMAX).However, OFDM is not without some
drawbacks.Major among them is the high peak-to-average power ratio (P APR) in the
transmitted OFDM signals. High PAPR decreases the signal-to-quantization noise
ratio (SQNR) of analog-to-digital converter (ADC)and digital-to-analog converter
(DAC) while degrading the efficiency of the high-power-amplifier (HPA) in the
transmitter. PAPR problem gets more severe in the uplink communications, since
theefficiency of HPA is critical due to the limited battery power in a mobile terminal.
The literature is replete with a large number of P APR reduction techniques.
Among them, schemes like constellation shaping, phase optimization, nonlinear
companding transforms, tone reservation (TR) and tone injection (TI), clipping and
filtering, partial transmit sequence (PTS), selective mapping (SLM), and precoding
based techniques are popular. The precoding based techniques, however, show great
promise as they are simple linear techniques to implement without the need of any
complex optimizations. Usually, the autocorrelation of the input sequence at OFDM
modulator is related to the PAPR at its output. Use of precoder before the OFDM
modulator affects that favourably.