Chapter 19: Multiple Access Techniques

Learning Objectives

• Classify FDMA, TDMA, and OFDMA as orthogonal multiple access schemes and prove that orthogonal partitioning of the resource space incurs a sum-rate penalty relative to the capacity region
• Explain power-domain NOMA with successive interference cancellation and show that it achieves the boundary of the Gaussian MAC capacity region
• Describe direct-sequence CDMA, derive the processing gain, and analyse performance degradation due to multiple-access interference and the near-far problem
• Derive the throughput of pure and slotted ALOHA, prove the 1/e maximum-throughput result, and contrast random access with scheduled access
• Compare FDD and TDD duplexing in terms of CSI overhead, channel reciprocity, and spectral efficiency as functions of the number of antennas and users
• Analyse the near-far effect in spread-spectrum systems and explain how power control mitigates performance degradation
• Relate multi-user capacity concepts to practical multiple access design choices in LTE, 5G NR, and Wi-Fi systems