DocumentCode :
1382795
Title :
Channel estimation and equalization for M-QAM transmission with a hidden pilot sequence
Author :
Mazzenga, Franco
Author_Institution :
Dipt. di Ingegneria Elettronica, Rome Univ., Italy
Volume :
46
Issue :
2
fYear :
2000
fDate :
6/1/2000 12:00:00 AM
Firstpage :
170
Lastpage :
176
Abstract :
Blind equalization techniques are useful to counteract multipath effects in radio local loop (RLL) and in general for wireless point to multipoint transmissions. One of the main drawbacks of blind equalization is the slow convergence time of the equalizer. Another major problem of blind equalization is the possible convergence toward wrong solutions. When these two main disadvantages cannot be tolerated it is necessary to adopt trained channel estimation and/or equalization techniques to counteract multipath. The training sequence is usually time division multiplexed with the informative sequence. This solution reduces the bandwidth efficiency and can be unusable when too frequent updating of the communications parameters need to be performed in the receiver. It is shown that bandwidth efficiency can be preserved at the expense of an increase in the transmitted power. The additional transmitted power is used to send a known pilot sequence hidden into the informative sequence. The hidden sequence is superimposed onto the symbols to be transmitted before waveform modulation. Thus each pilot symbol has the same period of the informative symbol so that no bandwidth spreading is necessary. High spectral efficiency M-QAM modulation is considered but the technique can be easily extended to any type of digital modulation format. We analyze the problems of channel estimation and of equalization based on the hidden pilot sequence. To prove the effectiveness of the proposed technique simulation results are provided. It is observed that in the case of equalization a pilot recovery subsystem should be used before using the pilot to train the equalizer
Keywords :
equalisers; least mean squares methods; multipath channels; parameter estimation; quadrature amplitude modulation; sequences; M-QAM transmission; MMSE equalization; bandwidth efficiency; blind equalization; channel equalization; communications parameters updating; digital modulation format; hidden pilot sequence; multipath; multipath effects; pilot recovery subsystem; radio local loop; simulation results; time division multiplexing; trained channel estimation; training sequence; transmitted power; waveform modulation; wireless point to multipoint transmissions; Bandwidth; Blind equalizers; Channel estimation; DSL; Demodulation; Digital modulation; Partial transmit sequences; Spread spectrum communication; Time division multiplexing; Wideband;
fLanguage :
English
Journal_Title :
Broadcasting, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-9316
Type :
jour
DOI :
10.1109/11.868934
Filename :
868934
Link To Document :
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