Prerequisites

Before You Begin

This chapter applies the theoretical foundations of earlier chapters to the concrete designs of LTE and 5G NR. It requires familiarity with MIMO (Chapter 7), channel coding (Chapter 12), OFDM (Chapter 14), diversity techniques (Chapter 15), space-time coding (Chapter 16), MIMO capacity and precoding (Chapter 17), and massive MIMO (Chapter 18).

MIMO spatial multiplexing and diversity(Review ch07)
Self-check: Can you explain the difference between spatial multiplexing and transmit diversity, and describe the SVD-based precoding model $\mathbf{H} = \mathbf{U}\mathbf{\Sigma}\mathbf{V}^H$ ?
Channel coding: turbo codes, LDPC, and polar codes(Review ch12)
Self-check: Can you describe the encoding and decoding principles of LDPC codes (used in NR data channels) and polar codes (used in NR control channels)?
OFDM: subcarrier spacing, cyclic prefix, and resource grid(Review ch14)
Self-check: Can you draw the OFDM time-frequency resource grid and explain how cyclic prefix length relates to channel delay spread?
Diversity techniques: MRC, STBC, frequency diversity(Review ch15)
Self-check: Can you derive the diversity order of maximal ratio combining with $L$ branches and explain how OFDM exploits frequency diversity through interleaving across subcarriers?
Space-time block codes: Alamouti scheme(Review ch16)
Self-check: Can you write the Alamouti code matrix and show that it achieves full transmit diversity of order 2 with rate 1?
MIMO capacity and precoding design(Review ch17)
Self-check: Can you state the MIMO capacity with water-filling $C = \sum_i \log_2(1 + \lambda_i p_i)$ and explain codebook-based precoding using DFT beams?
Massive MIMO: array gain, channel hardening, pilot contamination(Review ch18)
Self-check: Can you explain channel hardening in massive MIMO and describe the pilot contamination problem in multi-cell TDD systems?

Chapter 24 Notation

Key symbols introduced or heavily used in this chapter.

Symbol	Meaning	Introduced
$\mu$	Numerology index in 5G NR ( $\mu = 0,1,2,3,4$ )	s02
$\Delta f$	Subcarrier spacing: $\Delta f = 2^\mu \times 15$ kHz	s02
$N_{\text{RB}}$	Number of resource blocks in the channel bandwidth	s01
$T_{\text{slot}}$	Slot duration: $T_{\text{slot}} = 1/(2^\mu)$ ms	s02
$L_{\text{SSB}}$	Number of SSB beams in a beam sweep	s03
$\mathbf{W}_{1}, \mathbf{W}_{2}$	Type II CSI feedback: wideband and subband precoding matrices	s03
$BWP$	Bandwidth part: a contiguous set of RBs with a single numerology	s02
$CORESET$	Control resource set for PDCCH in NR	s02
$R_{\text{target}}$	Reliability target (e.g., $1 - 10^{-5}$ for URLLC)	s04
$CA / DC$	Carrier aggregation / dual connectivity	s05

← Ch 23 LTE Physical Layer