Mobile terminals using cellular networks often experience interference from various sources or due to various causes, such as interference caused by the same signal arriving at the mobile terminal at slightly different times after having propagated along different paths, i.e. so-called multipath interference. As is known, it is often possible to cancel interfering signals at a receiver, and the prior art teaches various methods of interference cancellation (IC), both at mobile terminals and at base stations. Mobile terminals often implement so-called single antenna interference cancellation (SAIC) algorithms, since physical constraints make it difficult to use more than one antenna in providing IC. A SAIC algorithm estimates and removes the effect of interference from a received signal.
In using a SAIC algorithm in a receiver of a mobile telephone, it is often (when using a non-blind method) necessary to estimate parameters that characterize the communication channel over which the mobile is communicating. Estimates of the channel parameters (i.e. the so-called channel impulse response components) made according to the prior art are significantly degraded in the presence of interference, and so receiver performance suffers. Clearly, to the extent that interference can be suppressed, performance is improved. In other words, if the parameters that characterize the communication channel (i.e. the channel impulse response components) can be selected so as to suppress one or another component of interference, receiver performance will be improved.
Interference sometimes includes as a component (besides noise) an interfering signal (from a radio, i.e. as opposed to noise). To handle such interference, radio receivers may include what is called a CM-SAIC (constant modulus-single antenna interference cancellation) equalizer, which is provided with the above-mentioned communication channel parameters by a channel estimator also included in the receiver. The prior art does teach algorithms for a channel estimator suitable for a CM-SAIC equalizer, but the estimates are somewhat inaccurate, and so what is needed is an improved procedure (algorithm) for estimating the communication channel parameters (channel impulse response components) so as to be suitable for use in a CM-SAIC equalizer.
USPTO Backgrounds
USPTO Backgrounds