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US 2001/0017883 A1Published application
Rake receiver
AssigneeNokia Networks Oy
InventorsEsa Tiirola, Juha Ylitalo
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AssigneeNokia Networks Oy
InventorsEsa Tiirola, Juha Ylitalo
Estimating the term…
The invention relates to a Rake receiver of a CDMA system using IRC. The Rake receiver comprises at least two antenna branches, at least one Rake finger, and a delay estimator. The delay estimator comprises a despreader and an allocator for selecting at least one delay, and allocating a Rake finger for processing the signal component found by informing the Rake finger of the delay found. The delay estimator further comprises: a channel estimator, an interference estimator for generating an interference signal, a weighting coefficient part for providing each antenna branch with weighting coefficients maximizing the Signal-to-Interference-and-Noise Ratio, a multiplier for multiplying the pilot part by a weighting coefficient, and an antenna branch summer for combining the despread pilot parts, received via the separate antenna branches and multiplied by the weighting coefficient, to one combined pilot signal, on which combined pilot signal the selection is based in the allocator.
A Rake receiver comprising at least two antenna branches (232A, 232B) for receiving a radio signal, at least one Rake finger (270A, 270B) connected to the antenna branches (232A, 232B) for processing a multipath propagated signal component of the radio signal, and a delay estimator (290A) connected to the antenna branches (232A, 232B), the delay estimator (290A) comprising:
A Rake receiver according to any preceding claim, characterized in that the interference estimator (292) uses as an input the despread pilot part (274A) included in the multipath propagated signal component by using a known spreading code by a delay.
A Rake receiver according to any preceding claim, characterized in that the interference estimator (292) generates an interference signal by subtracting from the received radio signal a desired regenerated radio signal.
A Rake receiver according to any preceding claim, characterized in that the interference estimator (292) generates an interference signal by using multi-user detection, whereby the signals of other users form the interference signal.
A Rake receiver according to any preceding claim, characterized in that the impulse response of the channel generated by the channel estimator (292) is averaged coherently by a first filter structure connected to the channel estimator (292).
A Rake receiver according to any preceding claim, characterized in that the despread pilot part multiplied by the weighting coefficient is non-coherently filtered by a second filter structure connected between the multiplier (294A, 294B) and the antenna branch summer (298) in each antenna branch (232A, 232B).
A Rake receiver according to any preceding claim, characterized in that the combined pilot signal is averaged non-coherently by a third filter structure connected between the antenna branch summer (298) and the allocator (264).
A Rake receiver according to any preceding claim, characterized in that the despreader (296A, 296B) is replaced by a matched filter (262A, 262B) for each antenna branch (232A, 232B) for performing a predetermined number of parallel correlation calculations for the received radio signal by different delays, whereby the pilot part included in the received radio signal is despread in correlation calculation by a known spreading code at a predetermined delay.
A Rake receiver according to any preceding claim, characterized in that, to provide antenna gain, the antenna branches (232A, 232B) form an antenna array, by which an antenna beam is formed in the desired direction by phasing separate antenna signals.
A Rake receiver according to any preceding claim, characterized in that the antenna branches (232A, 232B) are diversity branches.
A Rake receiver according to any preceding claim, characterized in that the channel estimator (272) performs the channel estimation on the optimal Maximum Likelihood principle.
A Rake receiver according to any preceding claim, characterized in that weighting coefficients maximizing the signal-to-interference-and-noise ratio are formed for each antenna branch (232A, 232B) by multiplying an inverse matrix of a covariance matrix, generated of an interference signal of the antenna branches (232A, 232B), by an estimated impulse response of the channel.
A Rake receiver according to any preceding claim, characterized in that the interference signal generated by the interference estimator (272) comprises interference caused by the adjacent frequency band of the desired channel, i.e. adjacent channel power.
Dependencies are inferred from the claim text.