Telefonaktiebolaget Lm Ericsson (Publ)

Karin Engdahl

Andres Reial

Bo Göransson

Lennart Andersson

Respective residual frequency offsets of de-spread correlated signals derived from a received communication signal are determined and used to improve receiver performance in high-velocity situations. The knowledge of the residual frequency offsets of the respective fingers can be used for adaptive AFC combining, improved velocity estimation, and adaptive residual frequency offset compensation.

Residual frequency offset exploitation

A subset of modeled impairment correlation terms are selected for use in received signal processing. According to one embodiment, a subset of modeled impairment correlation terms is selected and a composite impairment correlation term is determined based on the subset of modeled impairment correlation terms. The composite impairment correlation term may be determined by scaling the modeled impairment correlation terms included in the subset by respective model fitting parameters. The scaled modeled impairment correlation terms are then combined to form the composite impairment correlation term. The subset of modeled impairment correlation terms may be selected based on their respective model fitting parameters. In one embodiment, the modeled impairment terms having a model fitting parameter that satisfy a threshold are included in the subset while those that do not are excluded. The composite impairment correlation term may be used for received signal processing, e.g., demodulation or signal-to-interference estimation.

Method and apparatus for selecting a subset of modeled impairment correlation terms for use in received signal processing

A wrap-around event in an automatic frequency control (AFC) in a receiver in a communication system can be detected by performing AFC-like operations on one or more additional channel estimates of the strongest communication path. Once a wrap-around event is detected, a correct frequency reference can be restored by forcing the AFC into a high-speed mode of operation, which gives the AFC a chance to restore the correct frequency reference, or by applying a momentary frequency reference change.

AFC wrap-around detection

Whether relative velocity between a transmitter and a receiver is higher than a predetermined amount is detected. This involves using a Doppler estimation technique to generate an estimate of Doppler spread, {circumflex over (f)}, based on a received signal, and using an alternative velocity estimation technique to generate an estimate of velocity, {circumflex over (v)}, based on the received signal, wherein the alternative velocity estimation technique differs from the Doppler estimation technique. A plurality of estimates, including at least the estimate of Doppler spread and the estimate of velocity, are used to detect whether the relative velocity between the transmitter and the receiver is higher than the predetermined amount. The alternative velocity estimation technique may, for example, be a second Doppler estimation technique that differs from the other Doppler estimation technique.

Growing community of inventors

Staffanstorp, Sweden

Karin Engdahl