Adaptive signal decompression
View Patent ↗The adverse effects of RF and baseband circuits are mitigated using a post-compensation method wherein a transfer function that would un-distort or complement a distorted waveform is parameterized to a relatively small number of degrees of freedom; and the parameters are estimated in a feedback loop. The error function of the feedback loop is generated by comparing some relatively low-order statistics that are known a priori or can be computed with relative certainty from the decided output waveform—to the statistics of the corrected signal.
1. A method of decompressing a distorted signal, the method comprising:
converting an analog signal to a digital signal, wherein the analog signal is distorted via nonlinearities of at least one of a receiver or a transmitter of the analog signal;
determining a peak-to-average power ratio (PAR), wherein the determined PAR is based on observations of the digital signal for one or more symbol periods;
remapping the digital signal to generate a modified digital signal via a decompression function; and
adaptively adjusting the decompression function based at least in part on an error between the determined PAR and an expected PAR.
2. The method of claim 1 , wherein a value for the expected PAR is generated based at least in part on how many symbol periods are observed for the determined PAR.
3. The method of claim 1 , wherein remapping comprises maintaining a lookup table that holds the decompression function, and wherein adaptively adjusting comprises updating the lookup table.
4. The method of claim 1 , wherein the analog signal is modulated with symbols via orthogonal frequency division multiplexing (OFDM).
5. The method of claim 1 , wherein determining the peak-to-average power ratio (PAR) comprises determining the PAR for a predetermined number of symbol periods, and wherein the expected PAR is based at least in part on the predetermined number.
6. The method of claim 1 , wherein adaptively adjusting the decompression function comprises adaptively adjusting a gain of a variable gain amplifier.
7. An apparatus for decompressing a compressed signal, the apparatus comprising:
an analog to digital converter (ADC) for converting an analog signal to a digital signal, wherein the analog signal is compressed via nonlinearities of at least one of a receiver or a transmitter of the analog signal;
a computation circuit configured to observe one or more symbol periods of the digital signal and to determine a peak-to-average power ratio (PAR);
a remapping circuit configured to remap the digital signal to generate a modified digital signal via a decompression function; and
an adaptive adjustment circuit configured to adaptively adjust the decompression function of the remapping circuit based at least in part on an error between the determined PAR and an expected PAR.
8. The apparatus of claim 7 , further comprising a memory table, wherein a value for the expected PAR is retrieved from the memory table based at least in part on how many symbol periods are observed by the computation circuit for the determined PAR.
9. The apparatus of claim 7 , wherein the remapping circuit comprises a lookup table that holds the decompression function, and wherein the adaptive adjustment circuit is configured to update the lookup table.
10. The apparatus of claim 7 , wherein the analog signal is modulated with symbols via orthogonal frequency division multiplexing (OFDM), and wherein the apparatus is embodied in an OFDM receiver.
11. An apparatus for decompressing a distorted signal, the apparatus comprising:
a means for converting an analog signal to a digital signal, wherein the analog signal is distorted via nonlinearities of at least one of a receiver or a transmitter of the analog signal;
a means for determining a peak-to-average power ratio (PAR), wherein the determined PAR is based on observations of the digital signal for one or more symbol periods;
a means for remapping the digital signal to generate a modified digital signal via a decompression function; and
a means for adaptively adjusting the decompression function based at least in part on an error between the determined PAR and an expected PAR.
12. The apparatus of claim 11 , wherein the analog signal is modulated with symbols via orthogonal frequency division multiplexing (OFDM).