Chapter 10: Diversity Techniques

Learning Objectives

• Explain why deep fades create error floors and how diversity changes the error-probability slope from SNR^{-1} to SNR^{-L}
• Compare selection combining, equal-gain combining, and maximal-ratio combining in terms of performance, complexity, and CSI requirements
• Derive the MRC output SNR as the sum of branch SNRs and compute BER for BPSK in Rayleigh fading with L-branch MRC
• Describe the Alamouti scheme for transmit diversity and prove it achieves full diversity order 2 at rate 1
• State the rate constraints of orthogonal space-time block codes for more than two transmit antennas
• Explain how interleaving and wideband transmission provide time and frequency diversity, and state the rank and determinant criterion for space-time code design
• Distinguish macrodiversity from microdiversity and describe the role of CoMP and soft handover in modern cellular networks