Prerequisites & Notation
Before You Begin
This chapter is the information-theoretic culmination of Part III. It takes the MIMO outage analysis of Chapter 10 and the pairwise-error analysis of space-time codes from Chapter 11 and binds them into a single, tight asymptotic identity β the Zheng-Tse diversity-multiplexing tradeoff. To follow the proof the reader needs the outage-probability / ergodic-capacity distinction, the distribution of the eigenvalues of (Wishart), the rank and determinant criteria for space-time codes, and the Gallager-style random-coding argument in its high-SNR / error-exponent flavour. A working familiarity with exponential-equality asymptotics () as used in the large-deviations literature is strongly recommended.
- MIMO outage probability and ergodic capacity(Review ch10)
Self-check: Can you write the outage probability for an i.i.d. Rayleigh channel at target rate , and distinguish it operationally from the ergodic capacity ?
- Wishart-eigenvalue distribution of (Review ch10)
Self-check: Can you state the joint density of the nonzero eigenvalues of when is with i.i.d. entries? And identify the Vandermonde factor that drives the DMT exponent?
- Rank and determinant criteria for space-time codes(Review ch11)
Self-check: Can you state the rank criterion ( implies diversity ) and the determinant criterion ( controls coding gain) for the codeword error matrix ?
- Alamouti scheme and V-BLAST (ZF and ML) receivers(Review ch11)
Self-check: Can you compute the diversity order of Alamouti on an -receive channel (), and of zero-forcing V-BLAST on an channel with ()? And explain why the latter is so much smaller than ?
- Gallager random-coding exponent and exponential equality(Review ch13)
Self-check: Can you state iff , and describe why additive terms β constants, polylog prefactors β are invisible to this notation?
- Outage exponent of a scalar Rayleigh channel(Review ch11)
Self-check: Can you show that for a scalar Rayleigh channel at fixed rate , (diversity order 1)? And extend this to Alamouti on an -receive channel ()?
Notation for This Chapter
Symbols specific to the DMT analysis. The Chapter 10β11 MIMO notation (channel matrix , codeword matrix , SNR , noise ) continues to apply and is not repeated here.
| Symbol | Meaning | Introduced |
|---|---|---|
| Multiplexing gain, | s01 | |
| Diversity gain, | s01 | |
| The diversity-multiplexing tradeoff (DMT) curve; maximum achievable diversity at multiplexing gain | s02 | |
| Exponential equality: iff | s01 | |
| Codeword difference (error) matrix, , size | s04 | |
| Number of transmit and receive antennas | s01 | |
| Space-time codeword block length (number of channel uses per block). Also written in some texts. | s05 | |
| Tx spatial correlation matrix (Hermitian positive-semidefinite, size ) | s05 | |
| Target rate at SNR , scaling as | s01 | |
| -th eigenvalue of Hermitian , ordered | s02 | |
| Spatial degrees of freedom; the maximum achievable multiplexing gain | s01 |