Time dispersion equalizer receiver with a time-reversal structure for TDMA ...

United States Patent m

Ariyavisitakul et al.

[ii] Patent Number: [45] Date of Patent:

5,155,742 Oct. 13, 1992

[54] TIME DISPERSION EQUALIZER RECEIVER WITH A TIME-REVERSAL STRUCTURE FOR TDMA PORTABLE RADIO SYSTEMS

[75] Inventors: Sirikiat Ariyavisitakul, Eatontown;

Hamilton W. Arnold, Middletown, both of N.J.

[73] Assignee: Bell Communications Research, Inc.,

Livingston, N.J.

[21] Appl. No.: 695,460
[22] Filed: May 3,1991

[51] Int. C1.5 H04B 3/04

[52] U.S. Q 375/13; 333/18;

375/14

[58] Field of Search 375/12, 13, 14, 101;

333/18, 28; 364/724.2; 370/95.3

[56] References Cited

U.S. PATENT DOCUMENTS

2,933,702 4/1960 Bogert 333/18

4,849,991 7/1989 Arnold et al 375/84

4,937,841 6/1990 Chuang et al 375/94

4,941,155 7/1990 Chuang et al 375/84

5,050,186 9/1991 Gurcan et al 375/14

OTHER*PUBLICATIONS

"Portable Digital Radio Communications-An Approach to Tetherless Access", D. C. Cox, IEEE Communications Magazine, Jul. 1989, vol. 27, No. 7, pp. 30-40.

"Universal Digital Portable Radio Communications", D. C. Cox, Proceedings of the IEEE, vol 75, No. 4, Apr. 1987, pp. 436-477 pp. 436-477.

"Adaptive Equalization", S. U. H. Qureshi, Proceedings of the IEEE, vol. 73, No. 9 Sep. 1985, pp. 1349-1387.

Primary Examiner—Benedict V. Safourek

A receiver for use in the port or portable units in a TDM/TDMA digital radio communications system is disclosed which incorporates an equalizer (107) to compensate for channel distortion due to multipath delay spread. Each received burst of information is oversampled at a multiple of the symbol rate and stored in a buffer memory (105). A joint estimator (106) processes the stored burst by operating on a known training sequence of bits within the burst to determine burst timing (where the burst actually begins) and the symbol timing (the optimum sample per oversampled symbol to be used for detection purposes). The estimator also determines whether the stored burst should be processed in a time-forward or time-reversed order. The joint estimator includes plural training equalizers (201), each of which is associated with an assumed burst location and each of which attempts to converge on the known training sequence as the stored sequence is circulated plural times through the equalizers in both the time-forward and the time-reversed order. Burst and symbol timing and the optimum processing order are determined from the location of the training equalizer which converges with the minimum mean-square error. The determined burst and symbol timing, and the selected processing order, are passed to the buffer storage for read-out, in that selected direction, of the stored burst information to the input of the main receiver equalizer (107). The main and training equalizers can be either conventional fractionally-spaced decision feedback equalizers or phase equalizers, which operate on the received phase angle.

2 Claims, 8 Drawing Sheets

106