RFID system with low complexity implementation and pallet coding error correction

1. An RFID receiver configured to decode a data signal modulated onto a carrier wave, where the phase and timing of the data signal is ambiguous, comprising:

an analyzer and equalizer configured to filter an input signal;

an estimation block configured to obtain a baseband representation of the modulated data signal by mixing the filtered input signal with the carrier wave; and

a coherent detector configured to perform phase and timing recovery on the modulated data signal in the presence of noise and to determine a sequence of data symbols;

wherein the data signal is channel coded;

wherein the coherent detector comprises:

a soft metric estimator;

a de-interleaver;

a soft input soft output (SISO) decoder;

an interleaver; and

a channel code decoder;

wherein the soft metric estimator is configured to calculate initial soft metrics using the data signal and a fixed phase value, timing value and channel state estimated by the channel code decoder during a previous iteration;

wherein the de-interleaver is configured to de-interleave an input generated by subtracting the output generated by the interleaver in a previous iteration from the initial soft metrics;

wherein the SISO decoder is configured to generate updated soft metrics using the output of the de-interleaver;

wherein the interleaver is configured to interleave an input generated by subtracting the output of the de-interleaver from the updated soft metrics;

wherein the channel code decoder is configured to estimate a phase value, a timing value and channel state from the output of the interleaver; and

wherein the coherent detector is configured to iterate until the initial soft metrics and the updated soft metrics converge.

2. The receiver of claim 1 , wherein:

the coherent detector determines the maximum soft metric and outputs the maximum soft metric; and

coherent detector uses predetermined probabilities to augment at least some of the maximum soft metrics.

3. The receiver of claim 1 , wherein the channel code decoder includes a soft input soft output forward error correction decoder.

4. An RFID receiver configured to decode a data signal modulated onto a carrier wave, where the phase and timing of the data signal is ambiguous, comprising:

an analyzer and equalizer configured to filter an input signal;

an estimation block configured to obtain the data signal by extracting the carrier wave from the filtered input signal; and

a non-coherent detector configured to perform timing recovery on the modulated data signal in the presence of noise and to determine a sequence of data symbols;

wherein the non-coherent detector includes a non-coherent decoder that selects from the set of all possible symbol combinations for a short sequence the symbol combination that maximizes a non-coherent combining relation;

wherein the non-coherent combining relation determines the data symbols by selecting the values for x 1,i , and x 2,i , that maximize the following metric:

Metric

=



∑

i

=

k

-

N

+

2

k

+

1

⁢

⁢

(

r

2

,

i

-

1

⁢

x

2

,

i

-

1

+

r

1

,

i

⁢

x

1

,

i

)



where:

r 1,i is the received component in the first half of a symbol interval after removal of an estimate of the DC value of the received signal; and

r 2,i is the received component in the second half of a symbol interval after removal of an estimate of the DC value of the received signal

x 1,i is a hypothesis for the waveform of the first half of a symbol interval resulting from the modulation of the data value i using the modulation scheme used to modulate the data signal onto the carrier wave; and

x 2,i is a hypothesis for the waveform of the second half of a symbol interval resulting from the modulation of the data value i using the modulation scheme used to modulate the data signal onto the carrier wave.