Differential encoding is known to simplify receiver implementation because it by-passes channel estimation. However, over rapidly fading wireless channels, extra transceiver modules are necessary to enable differential transmission. Relying on a basis expansion model for time and frequency selective (doubly selective) channels, we derive such a generalized block-differential (BD) codec and prove thal it achieves maximum Doppler and multipath diversity gains, while affording low-complexity maximum-likelihood decoding. We further show that existing BD systems over frequency-selective or time-selective channels follow as special cases of our novel system. Simulations using the widely accepted Jakes' model corroborate our theoretical analysis.
Bibliographical noteFunding Information:
Paper approved by X. Dong, the Editor for Modulation and Signal Design of the IEEE Communications Society. Manuscript received September 23, 2004; revised April 18, 2005. Work in this paper was prepared through collaborative participation in the Communications and Networks Consortium sponsored by the U.S. Army Research Laboratory under the Collaborative Technology Alliance Program, Cooperative Agreement DAAD19-01-2-0011. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation thereon. The work of the second author was supported by the Army Research Office under Grant W911NF-04-1-0338. The work of the third author was supported in part by the Italian Minister of University and Research under PRIN 2002 Project “MC-CDMA: An air interface for the 4th generation of wireless systems.” This paper was presented in part at the International Conference on Communications, Seoul, Korea, May 2005.
- Differential encoding
- Doubly selective channels