DocumentCode :
1231426
Title :
Joint blind equalization, carrier recovery and timing recovery for high-order QAM signal constellations
Author :
Jablon, Neil K.
Author_Institution :
AT&T Bell Lab., Holmdel, NJ, USA
Volume :
40
Issue :
6
fYear :
1992
fDate :
6/1/1992 12:00:00 AM
Firstpage :
1383
Lastpage :
1398
Abstract :
Two existing blind equalization tap update recursions for 64-point and greater QAM (quadrature amplitude modulation) signal constellations are studied, along with existing and novel carrier and timing recovery techniques. It is determined that the superior tap update recursion is the one known as the constant modulus algorithm. Carrier recovery requires a modified second-order decision-directed digital phase-locked loop. An all-digital implementation of band-edge timing recovery is used. With 14.4 kb/s outbound transmission using CCITT V.33 trellis-coded 128-QAM signals having 12.5% excess bandwidth, a prototype blind retrain procedure is developed to demonstrate the feasibility of the techniques for high-speed multipoint modems. A WE DSP32-based real-time digital signal processor was employed to test the retrain over a set of severely impaired channels. For each channel in the set, the retrain succeeded at least 90% of the time
Keywords :
amplitude modulation; equalisers; phase-locked loops; 14.4 kbit/s; CCITT V.33 trellis-coded 128-QAM signals; WE DSP32-based real-time digital signal processor; band-edge timing recovery; blind equalization tap update recursions; blind retrain procedure; carrier recovery; constant modulus algorithm; excess bandwidth; high-order QAM signal constellations; high-speed multipoint modems; outbound transmission; quadrature amplitude modulation; second-order decision-directed digital phase-locked loop; severely impaired channels; Bandwidth; Blind equalizers; Constellation diagram; Digital signal processors; Modems; Phase locked loops; Prototypes; Quadrature amplitude modulation; Signal processing algorithms; Timing;
fLanguage :
English
Journal_Title :
Signal Processing, IEEE Transactions on
Publisher :
ieee
ISSN :
1053-587X
Type :
jour
DOI :
10.1109/78.139243
Filename :
139243
Link To Document :
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