Layered space-time (LST) transmissions employing continuous phase modulations (CPM) are well motivated for both bandwidth- and power-limited multiantenna communications. However, one of the major challenges for LST-CPM is the high complexity it incurs with maximum likelihood (ML) detection. In this paper, we develop reduced complexity LST-CPM receivers. First, we consider single antenna systems. Specifically, we study a reduced complexity Viterbi receiver for binary CPM. Based on this design, we introduce differential encoding for a class of CPM signals and analyze its performance gain both theoretically and with simulations. Second, we focus on multiantenna LST systems with minimum shift-keying (MSK)-type modulations. With group milling-canceling (NC) and low-complexity linear equalization, we convert a coded multiuser detection problem into an uncoded one with small equalization loss. We also find that the combination of sphere decoding with hard-decision iterative processing is effective in boosting performance with a controllable complexity increase. Both analytical and simulated performance confirm that the novel LST-MSK receiver exhibits markedly unproved performance relative to conventional NC detectors with moderate complexity increase.
Bibliographical noteFunding Information:
Manuscript received February 26, 2003; revised July 22, 2003 and January 7, 2004; accepted January 22, 2004. The editor coordinating the review of this paper and approving it for publication is A. F. Molisch. This work was supported by the ARO/CTA under Grant DAAD19-01-2-0011. This work was presented in part at the 37th Conference on Information Sciences and Systems (CISS), Baltimore, Maryland, March 12–14, 2003.
- Continuous phase modulation (CPM)
- Fading channel
- Minimum shift keying (MSK)
- Multiuser detection
- Performance analysis
- Space time