H - Electricity – 04 – L
Patent
H - Electricity
04
L
H04L 27/01 (2006.01) H03M 13/41 (2006.01) H04B 7/005 (2006.01)
Patent
CA 2478539
In a digital signal transmission system, a receiver (14) receives a signal (R(T)), wherein the signal bandwidth of the system exceeds the system symbol rate. A correlation and sampling circuit (15) receives a baseband signal (y(T)), samples (21) the signal eight times (y(k/8)) per symbol time (TS), correlates (23), generates a channel estimate (H~F) and down-samples the sampled signal (y(k/8)) to form an observed signal (y(k/2)). This signal is filtered in a prefilter (26), whose output is sampled at symbol rate (27, TS/1) and the obtained signal (z(k)) is delivered to a channel equalizer (17) which performs a viterbi algorithm with non-quadratic metric calculation and generates estimated symbols (S~ D(k)). A channel estimation filter (31) receives a symbol sequence which contains alternate zero-value symbols (.OMEGA.) and the estimated symbols (S~ D(k)) and generates an estimated signal (y~(k/2)). An error signal (e(k/2)=y(k/2)-y~(k/2)) is generated and used to adapt (34) the channel estimate (H~(k/2)) and also to generate (35) weight factors (.alpha.(k/2)). The coefficients (G~(k/2)) of the prefilter (26) are generated as a function of the channel estimate (H~(k/2)) and the weight factors (.alpha.(k/2)). Coefficients are generated in a metric calculation filter (39, W~(k)) by convoluting the channel estimate (H~(k/2)) with the prefilter (G~(k/2)) and are used to generate the estimated symbols (S~ D(k)). The transmisson channel, excluding the prefilter (26), is estimated explicitly so as to enable fast channel changes to be followed. The use of the weight factors (.alpha.(k/2)) enables a short channel estimate to be used. The insertion of the zero-value symbols (.OMEGA.) simplifies adaptation (34) of the channel estimate (H~(k/2)).
Brismark Gustav
Gudmundson Bjorn
Jamal Karim
Marks & Clerk
Telefonaktiebolaget Lm Ericsson
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