System and method for fast acquisition of ultra wideband signals

• US 7,436,876 B2
• Filed: 09/30/2004
• Issued: 10/14/2008
• Est. Priority Date: 11/15/2002
• Status: Expired due to Fees

• Current Assignee: Humatics Corporation
• Original Assignee: Time Domain Corporation (Humatics Corporation)
• Inventors: Roberts, Mark, Richards, James, Dodoukh, Irina, Brethour, Vernon R., Fisher, Teresa E., Rolin, Jennifer P.
• Primary Examiner(s): Payne; David C.
• Assistant Examiner(s): Bolourchi; Nader
• Application Number:
  US10/955,118
• Publication Number:
  US 20050089083A1
• Time in Patent Office: 1,475 Days
• Field of Search: 375/130, 375/144
• US Class Current: 375/130
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/7183 Synchronisation
• CPC Class Codes: H04B 1/719 Interference-related aspects
• CPC Class Codes: H04L 25/4902 Pulse width modulation; Pulse position modulation

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.

Claims

1. An ultra wideband receiver comprising:

an ultra wideband antenna;

an ultra wideband receiver coupled to the ultra wideband 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, wherein the evaluation stage and threshold comparator utilize a plurality of ramps in accordance with one or more of the following relationships;

Number Threshold Equation 0 MaxR >

C 1 N * MaxR / MA_meanV >

C 2 MaxR / NextR >

C 3 Logic AND of equation 1 and 2 4 Logic OR of equation 1 and 2 5 N * MaxR / MaxV >

C 6 N * (MaxR / MA_meanV) * (MinV / MaxV) >

C 7 N * (MaxR / MA_meanV) * [FORCE_ZERO(MinV −

MA_MinV) / FORCE_ONE(MaxV −

MA_MinV)] >

C 8 N * (MaxR −

NextR) / MA_meanV >

C 9 N * [(MaxR −

NextR) / MA_meanV] * (MinV / MaxV) >

C.

wherein N represents the acquisition integration length, C is some programmable constant, and the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.

2. The receiver of claim 1 wherein two or more of the relationships are combined by a logical AND.

3. The receiver of claim 1 wherein two or more of the relationships are combined by a logical OR.

4. The receiver of claim 1 wherein the selection of the one or more relationship is made in response to a criterion of the received signal.

5. The receiver of claim 4 wherein the criterion comprises a performance measure.

6. The receiver of claim 4 wherein the criterion comprises an application characteristic.

7. The receiver of claim 1 wherein the selection of the one or more relationship is made in response to the success or failure rates of the threshold decision.

8. The receiver of claim 1 wherein at least two of the plurality of ramps are generated serially.

9. The receiver of claim 8 wherein at least two of the plurality of ramps are generated in sequence.

10. The receiver of claim 1 wherein the plurality of ramps is generated in parallel.

11. 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, 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, wherein said plurality of packets have a known traffic rate over a time period;

wherein said receiver estimates said number of missed packets by comparing the number of received packets with said known traffic rate over said time period

wherein the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.

12. The receiver of claim 11 wherein said known traffic rate is based on packet length, number of monitor packets, and inter packet delay.

13. An ultra wideb and 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, 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, wherein at least one packet of said plurality of packets includes packet count information and wherein said number of missed packets is estimated by comparing said packet count information with the number of received packets

wherein the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.

14. The receiver of claim 13 wherein the packet count information is a packet sequence number.

15. 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;

wherein the receiving includes a quick check process and the threshold value relates to receiving quick check signals

wherein the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.

16. 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;

wherein the receiving includes a delimiter receiving process and the threshold value relates to receiving delimiter signals.

wherein the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.

17. 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;

wherein the receiver includes a memory, wherein the ultrawideband signal is from a particular transmitter among a plurality of transmitters, said method further including the steps of;

associating at least one threshold value with said particular transmitter;

storing said at least one threshold value in memory;

restoring from memory said at least one threshold value for comparing with signals relating to said particular transmitter

wherein the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.

18. 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;

further including the step of determining at least one threshold value based on optimization information received from a remote unit

wherein the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.

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;

wherein threshold criteria peaks are observed as signal space is scanned over a range of frame offset values and the threshold is set to recieve the strongest signal and reject the next strongest signal

wherein the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.

20. 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;

wherein the threshold is set to receive the strongest signal and reject the next strongest reflection based on a prior scan of the multipath environment

wherein the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.

21. 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;

wherein the performance criterion is based on a packet loss rate, wherein the packet loss rate is derived, at least in part, from packet size, or monitor packet rate, or inter packet delay

wherein the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.

22. 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;

further including an initial detection stage and a quick check stage wherein the quick check false alarm rate is used to adjust the initial detection threshold

wherein the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.

23. 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;

further including a quick check stage and wherein the receiver scans a frame offset modulo;

wherein the quick check threshold is adjusted based on the time required to scan the frame offset modulo

wherein the performance criterion is described as the following;

Quantity Description MaxR 1^st largest acquisition ramp NextR 2^nd largest acquisition ramp MaxV Maximum correlator variance MinV Minimum correlator variance MeanV Mean correlator variance MA_MeanV Moving (historical) average of the mean correlator varience MA_MinV Moving (historical) average of the minimum correlator varience Logic_1 Constant value 1 Logic_0 Constant value 0.