Signal-to-interference + noise ratio estimator and method, mobile terminal having this estimator
The SINR (signal-to-interference+noise ratio) estimator comprises a low-pass filter ( 66 ) to filter a variance σκ computed from the received pilot symbol amplitude to obtain an estimated variance σκ with a reduced bias, wherein the low-pass filter has an adjustable coefficient and the estimator comprises an electronic controller able to adjust the value of the adjustable coefficient according to the number of pilot symbols received during a timeslot.
1. An estimator to estimate a signal-to-interference plus noise ratio SINR from the amplitude of known pilot symbols received from a base station within a wireless communication system, said pilot symbols being received during a timeslot according to {circumflex over (θ)} K =(Ŷ K ) 2 /{circumflex over (σ)} K wherein {circumflex over (θ)} K is SINR estimation, and Y K 2 is a mean amplitude estimation of pilot symbols, the estimator comprising a low-pass filter to filter an interference plus noise variance σ K computed from the received pilot symbol amplitudes to obtain an estimated variance {circumflex over (σ)} K with a reduced bias, wherein the low-pass filter has an adjustable coefficient and the estimator comprises an electronic controller able to adjust the value of the adjustable coefficient according to the number N P of received pilot symbols being received during the timeslot wherein the low-pass filter comprises a feedback loop so that the estimated variance {circumflex over (σ)} K for the k th timeslot depends also on an estimated variance {circumflex over (σ)} K−1 of the previous (k−1) th timeslot.
2. The estimator according to claim 1 , wherein the low-pass filter is able to obtain the estimated variance {circumflex over (σ)} K as the result of the following relation:
{circumflex over (σ)} K =aσ K +b{circumflex over (σ)} K−1
wherein:
σ K is the variance computed only from pilot symbols received during the k th timeslot,
{circumflex over (σ)} K−1 is the estimated variance for the (k−1) th timeslot,
a is a predetermined coefficient, and
b is the adjustable coefficient.
3. The estimator according to claim 2 , wherein coefficient a is equal to a predetermined value α and the coefficient b value is adjusted so that:
b
=
1
-
α
+
α
N
P
wherein N p is the number of pilot symbols received during the k th timeslot.
4. The estimator according to claim 1 , wherein the low-pass filter is an IIR (Infinite Impulse Response) filter.
5. The estimator according to claim 1 , wherein the controller is able to receive the number of N p of received pilot symbols from a wireless emitter of a wireless telecommunication system.
6. Mobile terminal comprising an estimator according to claim 1 to estimate the SINR used in signal processing.
7. A method to estimate a signal-to-interference plus noise ratio SINR from the amplitude of known pilot symbols received from a base station within a wireless communication system, said pilot symbols being received during a timeslot according to {circumflex over (θ)} K =(Ŷ K ) 2 /{circumflex over (σ)} K wherein {circumflex over (σ)} K is SINR estimation, and Y K 2 is a mean amplitude estimation of pilot symbols, the method comprising:
a step of filtering, using a low-pass filter, an interference plus noise variance σ K computed from the amplitudes of the received pilot symbols to obtain an estimated variance {circumflex over (σ)} K with a reduced bias, and
a step of automatically adjusting a coefficient of the low-pass filter according to the number N p of received pilot symbols being received during the timeslot wherein the low-pass filter comprises a feedback loop so that the estimated variance {circumflex over (σ)} K for the k th timeslot depends also on an estimated variance {circumflex over (σ)} K−1 of the previous (k−1) th timeslot.
8. The method according to claim 7 , wherein the method comprises the step of receiving the number N p of received pilot symbols from a wireless emitter of a wireless telecommunication system.