Novel Equalization Techniques for OQPSK
Akbar, Md Navid
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In this thesis, three different equalizers for the offset quadrature phase-shift keying (OQPSK) signaling are presented. At first, the use of a real-only equalizer (ROE) is proposed. ROE acts on real signals derived from the received OQPSK symbols. For the same fading channel, it is proven that both ROE and the popular widely linear equalizer (WLE) yield equivalent outputs, under both known and estimated channel state information. Hence, they exhibit the same performance. Presented complexity analysis finds that depending on the frame length, ROE can be computationally less complex, and save significant signal processing time over WLE. Secondly, implementation of ROE in the adaptive normalized least mean square (NLMS) is also designed. ROE in NLMS performs better with reduced complexity than its WLE counterpart, for a given number of pilot bits. Finally, a symbol spaced equalizer (SSE) is also developed under the widely linear criteria. Numerical studies indicate that it provides an identical performance, while operating at half the speed but with higher complexity compared to WLE.