A novel multiuser-interference (MUI)-free code division multiple access (CDMA) transceiver for frequency-selective multipath channels is developed in this paper. Relying on chip-interleaving and zero padded transmissions, orthogonality among different users' spreading codes is maintained at the receiver even after frequency-selective propagation. As a result, deterministic multiuser separation with low-complexity code-matched filtering becomes possible without loss of maximum likelihood optimality. In addition to MUI-free reception, the proposed system guarantees channel-irrespective symbol detection and achieves high bandwidth efficiency by increasing the symbol block size. Filling the zero-gaps with known symbols allows for perfectly constant modulus transmissions. Important variants of the proposed transceivers are derived to include cyclic prefixed transmissions and various redundant or nonredundant precoding alternatives. (Semi-) blind channel estimation algorithms are also discussed. Simulation results demonstrate improved performance of the proposed system relative to competing alternatives.
Bibliographical noteFunding Information:
Paper approved by W. A. Krzymien, the Editor for Multicarrier and Spread Spectrum Systems of the IEEE Communications Society. Manuscript received August 31, 2000; revised June 9, 2001. This work was supported by the National Science Foundation under Wireless Initiative Grant 99-79443 and NSF Grant 0105612. This paper was presented in part at the 38th Allerton Conference, University of Illinois at U-C, Monticello, IL, October 4–6, 2000, and at the 35th Conference on Information Sciences and Systems, the Johns Hopkins University, Baltimore, March 21–23, 2001.
- Block spreading
- Channel estimation
- Chip inter-leaving
- Code division multiple access (CDMA)
- Multiuser interference