Dual direction channel estimator

Details Dual direction channel estimator Dual direction channel estimator

2000-11-20

2003-06-24

Chin, Stephen (Department: 2634)

Pulse or digital communications

Equalizers

Automatic

C375S324000, C375S340000, C708S305000, C370S252000, C370S321000

Reexamination Certificate

active

06584150

ABSTRACT:

The present invention relates to a method for improving the working of mobile telephone communications particularly in the Global System for Mobile Communication (GSM).
GSM is a digital system which will give a higher quality of service than analogue systems and has a higher capacity for users than in an analogue system.
In GSM the communication has a burst structure and it is necessary to estimate the channel impulse response (CIR). There is a problem in estimating the CIR in the current GSM system. In the current GSM equaliser, the overall channel impulse response (CIR) is estimated by cross-correlating the received signals in the midamble portion with the known midamble sequence. Based on the assumption of a static channel during the time slot, the estimated CIR taps are used throughout the entire burst. It has found that the performance of the current channel estimation techniques suffers at least 2 dB degradation when compared with the benchmark, defined as the performance when ideal CIR taps are available at the equaliser.
The degradation can easily be seen with the following example. If a car is travelling at 120 kilometres per hour, its Doppler frequency shift will be about 100 Hz at the current radio frequency. The period of the Doppler frequency is 10 ms. On the other hand, the GSM burst is about 0.577 ms, thus it takes about one-eighth the half Doppler frequency period. Future personal land mobile telecommunication systems (IMT-2000)/UMTS) will use 2 GHz, so the Doppler frequency shift will be 220 Hz at 120 kilometres per hour. This means that during the burst the fading could vary from nearly maximum to minimum. Therefore, the assumption of a (quasi) channel is not true and tracking the CIR estimation during the data mode will be compulsory.
SUMMARY OF THE INVENTION
We have devised a system for reducing or overcoming this problem.
According to the invention there is provided a method for estimating the CIR in GSM a system in which method two channel estimators are started up using the midamble and channel estimations are obtained by channel estimators using the midamble with split burst, the two estimations are then cross-correlated to obtain the estimated CIR.
In an alternative embodiment of the invention an unbiased estimation method can be used in place of a cross-correlator to obtain the CIR.
The current channel estimation method can be used to fast start-up the two channel estimators and RLS algorithms can be used to track the changes of the channel and update the CIR during the data mode.


REFERENCES:
patent: 5065411 (1991-11-01), Muto
patent: 5293401 (1994-03-01), Serfaty
patent: 5303226 (1994-04-01), Okanoue et al.
patent: 5633860 (1997-05-01), Hagmanns
patent: 5903610 (1999-05-01), Skold et al.
patent: 5995499 (1999-11-01), Hottinen et al.
patent: 6330294 (2001-12-01), Ansbro et al.
patent: 6418175 (2002-07-01), Pukkila et al.
patent: 0520969 (1992-06-01), None
patent: 2751815 (1996-07-01), None
W. Liu et al., “Adaptive Channel Equalization for High-Speed Train,” Proceedings of the Vehicular Technology Conference, Stockholm, vol. 1, No. Conf. 44, pp. 225-229 (1994).
Y. Liu et al., “A Soft-Output Bidirectional Decision Feedback Equalization Technique for TDMA Cellular Radio,” IEEE Journal on Selected Areas in Communications, vol. 11, No. 7, pp. 1034-1045 (1993).
Wu et al., “A New Adaptive Equalizer with a Channel Estimator for Mobile Radio Communications,” Proceedings of the Conf. on Communications, Seattle, vol. 2, pp. 998-1002 (1995).
English translation of FR 2,751,815.

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