System And Method For Fast Acquisition Of Ultra Wideband Signals

Abstract

An ultra wideband system employing a threshold to detect signal quality during acquisition wherein the threshold is adjusted based on signal characteristics such as packet traffic rate, packet loss rate, and packet loss fraction. In one embodiment, the threshold is adjusted by adjusting the gain of a variable gain stage ahead of the threshold. In another embodiment, gain and threshold are adjusted in a coordinated manner wherein gain is adjusted for low signal levels and threshold is adjusted for high signal levels. In one embodiment, packet traffic rate is evaluated over an interval based on maximum packet length, number of monitor packets, and inter-packet delay. In a further embodiment, multiple ramp builders are operated in parallel at multiple code offset values to generate signal statistics to compare with the threshold. Embodiments are disclosed wherein the thresholds are adaptively adjusted based on signal performance characteristics or the multipath environment.

1 . An ultra wideband transceiver system comprising:
 an ultra wideband transmitter;   an ultra wideband antenna coupled to the uwb transmitter;   an ultra wideband receiver coupled to the uwb antenna for receiving an input signal, said ultra wideband receiver further comprising:   a sampling stage for sampling the input signal and generating a sampled signal;   a summation stage for summing a plurality of sampled signals and generating a sum signal;   an evaluation stage for evaluating one or more sum signals to generate an evaluation result;   a threshold comparator to compare the evaluation result with a threshold;   wherein the threshold is varied based on a performance criterion.   
   
   
       2 . The system of  claim 1  wherein the timing is adjusted to receive signals synchronous with a different frame offset value and a new set of sampled signals is generated and evaluated. 
   
   
       3 . The system of  claim 1  further including multiple parallel ramp builders to generate a plurality of concurrently generated sum signals wherein said plurality of concurrently generated sum signals is evaluated to generate the evaluation result. 
   
   
       4 . The system of  claim 1  wherein the input signal includes packet sequence information and the receiver utilizes said packet sequence information for setting said threshold. 
   
   
       5 . A network of UWB transceivers having a protocol, said protocol including packet count information, said network comprising;
 at least one transmitter sending a plurality of packets;   at least one receiver receiving a portion of said plurality of packets;   wherein said at least one transmitter includes said packet count information in at least one packet and said receiver uses said packet count information to adjust at least one threshold.   
   
   
       6 . The network of  claim 5  wherein said packet count information is a packet sequence number. 
   
   
       7 . An ultra wideband receiver comprising:
 an ultra wideband antenna;   an ultra wideband receiver coupled to the uwb antenna for receiving an input signal, said ultra wideband receiver further comprising:   a sampling stage for sampling the input signal and generating a sampled signal;   a summation stage for summing a plurality of sampled signals and generating a sum signal;   an evaluation stage for evaluating one or more sum signals to generate an evaluation result;   a threshold comparator to compare the evaluation result with a threshold;   wherein the threshold is varied based on a performance criterion.   
   
   
       8 . The receiver of  claim 7  wherein the timing is adjusted to receive signals synchronous with a different frame offset value and a new set of sampled signals is generated and evaluated. 
   
   
       9 . The receiver of  claim 7  wherein the receiver includes a single correlator. 
   
   
       10 . The receiver of  claim 7  further including a memory, wherein the receiver receives the signal from a given transmitter a plurality of times, the threshold parameters associated with the given transmitter are stored and retrieved from the memory and utilized to search for the given transmitter. 
   
   
       11 . The receiver of  claim 7  wherein said receiver receives a plurality of packets wherein the number of missed packets can be estimated; wherein said receiver adjusts at least one threshold based on said number of missed packets 
   
   
       12 . An ultra wideband receiver comprising:
 an ultra wideband antenna;   an ultra wideband receiver coupled to the uwb antenna for receiving an input signal, said ultra wideband receiver further comprising:   a sampling stage for sampling the input signal and generating a sampled signal;   a summation stage for summing a plurality of sampled signals and generating a sum signal;   a first evaluation stage for evaluating one or more sum signals to generate an evaluation result;   a threshold comparator to compare the first evaluation result with a threshold;   a plurality of subsequent evaluation stages for comparing one or more sum signals to generate a evaluation results;   wherein data is demodulated after all of the thresholds are satisfied.   
   
   
       13 . The receiver of  claim 12  wherein the threshold of the first evaluation stage is varied based on the success or failure rates of the evaluations in the subsequent stages. 
   
   
       14 . The receiver of  claim 12  wherein a plurality of the thresholds are adjusted based on the success rates of one or more of the evaluation stages. 
   
   
       15 . The receiver of  claim 12  further including a memory, wherein the receiver receives the signal from a given transmitter a plurality of times, the threshold parameters associated with the given transmitter are stored and retrieved from the memory and utilized to search for the given transmitter. 
   
   
       16 . An ultra wideband receiver comprising:
 an ultra wideband antenna;   an ultra wideband receiver coupled to the uwb antenna for receiving an input signal, said ultra wideband receiver further comprising:   a sampling stage for sampling the input signal and generating a sampled signal;   a summation stage for summing a plurality of sampled signals and generating a sum signal;   a gain control loop having a gain setting, said gain control loop for compressing the dynamic range of the sum signal;   an evaluation stage for evaluating one or more sum signals to generate an evaluation result;   a threshold comparator to compare the evaluation result with a threshold;   wherein the threshold is adjusted based on said gain setting.   wherein data is demodulated after the threshold is satisfied.   
   
   
       17 . The receiver of  claim 16  wherein gain is varied based on a long term average of the maximum ramp value. 
   
   
       18 . The receiver of  claim 17  wherein the gain control loop has a gain limit and the threshold is varied when the gain limit is reached. 
   
   
       19 . A method for receiving an ultra wideband signal, said method comprising:
 sampling said ultra wideband signal to generate a sampled signal;   summing a plurality of sampled signals to generate a sum signal;   generating an evaluation criteria based on at least one said sum signal;   comparing said evaluation criteria with a predetermined threshold value;   proceeding with further processing when the threshold is met;   generating a performance criterion relating to the threshold value;   adjusting the threshold value based on the performance criteria;   
   
   
       20 . The method of  claim 19  wherein the receiving includes a short code receiving process and the threshold value relates to receiving short code signals. 
   
   
       21 . The method of  claim 19  wherein the receiving includes a long code receiving process and the threshold value relates to receiving long code signals. 
   
   
       22 . The method of  claim 19  wherein the sampling step includes sampling by multiple correlators. 
   
   
       23 . The method of  claim 19  wherein the summing step includes summing by multiple parallel ramp builders. 
   
   
       24 . The method of  claim 19  wherein the generating step is based on multiple sum signals. 
   
   
       25 . The method of  claim 19  wherein the performance criterion is based on packet received rate. 
   
   
       26 . The method of  claim 19  wherein the performance criterion is based on a packet loss rate. 
   
   
       27 . A method of acquiring an ultra wideband signal, comprising the steps of:
 (a) establishing an acquisition threshold;   (b) obtaining a template signal;   (c) receiving the ultra wideband signal;   (d) comparing the received ultra wideband signal and the template signal to produce a comparison result;   (e) determining whether the comparison result satisfies the acquisition threshold; and   (f) if the comparison result fails to satisfy the acquisition threshold, varying the acquisition threshold based on a performance criteria and returning to step (b), and if the comparison result satisfies the acquisition threshold, locking on the received ultra wideband signal.   
   
   
       28 . A method of acquiring an ultra wideband signal, comprising:
 varying the timing of a generated template signal until a comparison of the template signal and the ultra wideband produces a comparison result that satisfies an acquisition threshold, wherein the acquisition threshold is varied in accordance with a performance criteria.   
   
   
       29 . A method of acquiring an ultra wideband signal, comprising:
 satisfying each of a plurality of thresholds wherein at least one of said plurality of thresholds is adjusted based on a performance criteria.