Rate adaptation using error vector magnitude

1. A method of adapting a rate for a radio frequency device, the method comprising:

in a radio frequency device computing an average signal-to-noise ratio (SNR) from a plurality of error vector magnitude (EVM) values; and

using the average SNR and a (SNR, rate) lookup table to determine an optimized rate,

wherein computing the average SNR includes:

computing a bit error rate (BER) for each EVM value;

computing an average BER for all EVM values; and

determining an SNR corresponding to the average BER,

wherein determining the average BER includes computing a local average BER for a de-interleaved bit sequence using a sliding window format.

2. The method of claim 1 , wherein the EVM values include at least one of pilot EVM values and data EVM values.

3. A method of adapting a rate for a radio frequency device, the method comprising:

in a radio frequency device computing error vector magnitude (EVM) values for a current packet;

determining an average bit error rate (BER) using the EVM values for each data rate;

determining an average signal-to-noise ratio (SNR) from the average BER;

for each data rate, determining a predicted packet error rate (PER) using the average SNR and a PER versus SNR curve;

for each data rate, computing a predicted throughput using the data rate and the predicted PER; and

selecting a rate having a high predicted throughput,

wherein determining the average BER includes computing a local average BER for a de-interleaved bit sequence using a sliding window format.

4. The method of claim 3 , further including generating PER versus SNR curves, which comprises:

simulating PER versus SNR curves for an additive white Gaussian noise (AWGN) channel for all data rates; and

saving the PER versus SNR curves.

5. The method of claim 3 , wherein the PER versus SNR curve is generated from an additive white Gaussian noise (AWGN) channel.

6. The method of claim 5 , wherein determining the average BER includes averaging a BER over all bins with EVM values, thereby providing a global average BER.

7. The method of claim 6 , wherein the EVM values include at least one of pilot EVM values and data EVM values.

8. The method of claim 5 , wherein computing the local average BER comprises:

for each data bin, computing a BER of each data bit using data EVM values, a modulation type, and a bit position;

de-interleaving all BER values; and

computing the local average BER in a the sliding window format using de-interleaved BER values.

9. A method of adapting a rate for a radio frequency device, the method comprising:

in a radio frequency device for each rate, mapping an error vector magnitude (EVM) to a packet error rate (PER);

computing a throughput for each data rate and PER; and

selecting a data rate with a high throughput,

wherein mapping the EVM to the PER includes:

estimating EVMs of pilots for each data symbol in a packet;

computing an average EVM per pilot across all data symbols in the packet;

estimating a mean EVM and a standard deviation for each stream;

computing the mean EVM and the standard deviation for all streams;

computing an effective EVM; and

using a lookup table to map the EVM to the PER.