Method and apparatus for channel estimation and equalization
AssigneeInstituto de Pesquisas Eldorado
InventorEduardo Rodrigues de Lima
Life of this patent
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Abstract
An inverse channel estimation method includes receiving a modulated signal with a pilot. A local reference pilot, matching the received pilot as it was prior to transmission, is divided by a scaled version of the received pilot's power. The division result is scaled again and multiplied with a conjugate value of the received pilot signal, to obtain the inverse channel estimate. Scaling may be performed using bit shifting. The division is performed using a CORDIC algorithm. If multiple pilots are received, interpolation can be performed to provide channel estimates for time and/or frequencies in between. Interpolation can be based on the Farrow method. The received signal may be equalized by multiplying it with the inverse channel estimate.
Claims14
A method for inverse channel transfer function estimation in a radio receiver, comprising:
- in the radio receiver, receiving a modulated signal including a received pilot and storing a frequency-domain representation of the modulated signal in a buffer;
- in a digital processing unit included in the radio receiver, calculating a value representing a power of the received pilot;
- determining a bit-shift value;
- left-shifting the value representing the received pilot's power by the bit-shift value;
- using a CORDIC algorithm to divide a local reference pilot value by the left-shifted value representing the received pilot's power, obtaining a division result;
- left-shifting the division result by the bit-shift value;
- and
- multiplying the left-shifted division result with a conjugate value of the received pilot to obtain an inverse channel transfer function estimate.
An apparatus for inverse channel estimation, comprising:
- a buffer configured for storing a frequency-domain representation of a modulated signal including a pilot;
- a pilot power calculator coupled with the buffer and operationally configured to calculate a power of a pilot value by squaring an absolute value of the pilot value;
- a conjugate value calculator coupled with the buffer and operationally configured to calculate a conjugate of the pilot value by inverting a sign of an imaginary part of the pilot value;
- a first left-shift circuit with an input coupled with an output of the first processing unit;
- a CORDIC unit operationally configured to perform a division on a numerator input signal and a denominator input signal, wherein the numerator input is configured for receiving a local reference pilot signal, and wherein the denominator input is coupled with the left-shift module output;
- a second left-shift circuit with an input coupled with an output of the CORDIC unit;
- and
- a first multiplier including a real input and a complex input, wherein the real input is coupled with a second left-shift module output, and the complex input is coupled with a second processing unit output, and including an output configured to provide an output signal that is a multiplication of a first signal on the real input and a second signal on the complex input.
A system for channel estimation, comprising a digital signal processor coupled with a program memory and coupled with a data memory, the digital signal processor configured to control a read address of the program memory and to control a read and a write address of the data memory, wherein the digital signal processor is operatively configured to read and execute software instructions stored in the program memory, the software instructions comprising:
- receiving a modulated signal including a received pilot and storing a frequency-domain representation of the modulated signal in at least one of a data memory and a buffer;
- calculating a value representing a power of the received pilot;
- determining a bit-shift value;
- left-shifting the value representing the received pilot's power by the bit-shift value;
- using a CORDIC algorithm to divide a local reference pilot value by the left-shifted value representing the received pilot's power, obtaining a division result;
- left-shifting the division result by the bit-shift value;
- and
- multiplying the left-shifted division result with a conjugate value of the received pilot to obtain an inverse channel transfer function estimate.
Dependencies are inferred from the claim text.