Battery-conserving transmission and encoding method for wireless ad hoc networks

• US 7,155,263 B1
• Filed: 02/27/2004
• Issued: 12/26/2006
• Est. Priority Date: 02/27/2004
• Status: Active Grant

• Current Assignee: Raytheon BBN Technologies Corp. (Rtx Corporation)
• Original Assignee: BBN Technologies (Rtx Corporation)
• Inventors: Bergamo, Marcos A.
• Primary Examiner(s): Feild, Joseph
• Assistant Examiner(s): SMITH, SHEILA B
• Application Number:
  US10/787,215
• Time in Patent Office: 1,033 Days
• Field of Search: 455/574, 455/343.5, 455/343.1, 455/522, 455/500
• US Class Current: 455/574
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A burst of data in a wireless network includes a preamble [502], a postamble [504] and one or more blocks of data [506]. A low or no power receiving device [102] receives the preamble [502]. When the preamble [502] includes an ID of the receiving device, structural information of the burst is derived from the preamble [502], indicating when at least one component of the device is to be powered on to receive the at least one block of data [506] included in the burst. The at least one component [306, 308, 310] is powered on at a first time period in order to receive the data in the one or more blocks of data. The at least one component [306, 308, 310] is powered off at a specific time period from a beginning of the first time period. The powering on and off are repeated for each of the one or more blocks of data [506] in the burst.

Claims

1. A method for conserving power in a wireless ad hoc network, comprising:

receiving, in a device, a burst via the wireless network, the burst including a preamble, a postamble and one or more blocks of data, the device being in one of a low power state and a powered off state at a time when the preamble is received;

determining whether the preamble of the burst includes data indicating an ID of the receiving device;

when the determining determines that the preamble includes the data indicating the ID of the receiving device, performing;

deriving, from the preamble, information indicating a time for powering on one or more components of the device to receive the one or more blocks of data included in the burst;

powering on the one or more components at a first time period based on the derived information in order to receive the data in a block of the one or more blocks;

powering off the one or more components at a specific time period from a beginning of the first time period based on the derived information;

repeating the powering on and the powering off for each of the one or more blocks of data in the burst; and

processing the received one or more blocks of data.

2. The method of claim 1, wherein the processing comprises:

powering on a second component of the receiving device after a second time period occurs after a beginning of reception of the postamble.

3. The method of claim 2, wherein the second component includes a digital signal processor configured to process the received one or more blocks of data.

4. The method of claim 1, wherein the one or more components include an analog-to-digital converter configured to convert a received one of the blocks of data from analog to digital form.

5. The method of claim 1, further comprising:

powering on a low noise amplifier simultaneously with a first execution of the powering on of the one or more components for the received burst; and

powering off the low noise amplifier after reception of a last one of the blocks of data of the received burst.

6. The method of claim 1, wherein the network includes a plurality of devices, the method further comprising synchronizing the plurality of devices.

7. The method of claim 6, wherein the deriving, the powering on, the powering off, the repeating and the processing are performed when the determining determines that the preamble includes the data indicating the ID of the receiving device and the burst is received within a narrow window within a time slot, including a narrow time window of a time slot boundary.

8. The method of claim 6, wherein the deriving, the powering on, the powering off, the repeating and the processing are performed when the determining determines that the preamble includes information indicating the ID of the receiving device, and the burst is received within a narrow time window of a time slot and a collision-free reception occurred.

9. The method of claim 1, further comprising:

deriving from the preamble, information regarding interference; and

deriving from at least one of the one or more data blocks, the information regarding interference; and

when the information regarding interference indicates an occurrence of an unacceptable level of interference, aborting the receiving of the burst.

10. The method of claim 1, further comprising:

generating a wake-up signal when the determining determines that the preamble includes the data indicating the ID of the receiving device, wherein

the deriving occurs responsive to the generating of the wake-up signal.

11. The method of claim 1, wherein the burst is a direct-sequence spread spectrum transmitted burst.

12. The method of claim 11, wherein the received burst was transmitted with a superposition of direct-sequence spread spectrum cyclic-shifted codes, wherein each of the direct-sequence spread spectrum cyclic-shift codes is a cyclic-shift of a base code, including a pseudo-random noise sequence having a sequence of a plurality of chips, each chip having a value that is one of a binary number, an integer-valued number, a real-valued number, and a complex-valued number.

13. The method of claim 12, wherein each of the cyclic shift codes is multiplied by one of a bit and a modulated-data-symbol.

14. The method of claim 13, wherein each of the modulated-data-symbols conveys information of at least one or more bits.

15. The method of claims 14, wherein a multi-code sub-burst is received, by the device, with a filter matched to a base code.

16. The method of claim 14, wherein:

a multi-code sub-burst is received, by the device, with a cyclic correlator matched to a base code, and

after being sampled and stored, the received sub-burst is correlated with all cyclic codes included in a multi-code sub-burst.

17. The method of claim 15, wherein the filter includes Surface Acoustic Wave technology at a convenient intermediary frequency or a radio frequency.

18. The method of claim 15, wherein a signal at an output of the filter, after being down-converted from radio frequency to baseband frequency, results in a sequence of modulated data symbols that, in an absence of noise, reproduces a sequence of modulated data symbols used, by the transmitter, to multiply the cyclic codes included in the each of multi-code sub-bursts.

19. The method of claim 15, wherein the preamble detected at the output of the filter is used as a wake-up signal comprising two pulses at a distance of M+K chip-times from each other, where M is a number of bits or modulated-data-symbols included in each of the subsequent data sub-bursts, and K is a number of chip times required to flush out the filter.

20. The method of claim 19, wherein a value, M+K, is used to power on a low noise amplifier simultaneously with a first execution of the powering on of the one or more components, including the powering on of devices performing sample-and-hold (S/H) and analog to digital (A/D) conversion, and a memory device used to store sampled data.

21. The method of claim 16, wherein the cyclic correlator is implemented in one of hardware and software using Fast Fourier Transform techniques.

22. The method of claim 18, wherein each cyclic shift of a received multi-code sub-burst corresponds to one chip time of the signal at the output of the filter.

23. The method of claim 18, wherein a time-domain signal detected at the output of the filter reproduces the sequenced transmission of the modulated-data-symbols of the each of the multi-code sub-bursts over a channel between a transmitter and a receiver, with a transmission being performed at a rate of one modulated data symbol per chip time, including one chip-time of guard-time for each unused cyclic shift-code in the each of the multi-code sub-bursts.

24. The method of claim 23, wherein the postamble detected at the output of the filter is used as an end-of-burst signal comprising two pulses at a distance of K chip times apart, where the value K is a number of chip times required to flush out the filter.

25. The method of claim 24, wherein the end-of-burst signal is used to power off a low noise amplifier simultaneously with a last execution of the powering off of a last received block of data in the burst, including powering off of devices performing sample-and-hold (S/H) and analog to digital (A/D) conversion, and a temporary memory device used to store sampled data.

26. The method of claim 24, wherein the end-of-burst signal is used to power on a Direct-to-Memory Access device used for transferring the data from the temporary memory to another memory.

27. The method of claim 24, wherein a processor is powered on when or after a last block of data in the burst is transferred from the temporary memory to another memory.

28. The method of claim 24, wherein, at the end-of burst signal, a value, K, is used to reassemble the received burst from the received data sub-bursts.

29. The method of claim 24, wherein a processor is powered off or put on a low power mode after assembling and processing a received burst.

30. The method of claim 13, wherein each of the cyclic-shift codes, after being multiplied by the bit or the modulated data symbol, are added together forming a multi-code block.

31. The method of claim 30, wherein the first of the cyclic-shift codes is cyclically-padded at an end by at least as many chips as a number of cyclic-shift codes included in the multi-code block, including unused cyclic-shift codes.

32. The method of claim 30, wherein the last of the cyclic-shift codes is cyclically-padded at a beginning by at least as many chips as a number of cyclic-shift codes included in the multi-code block, including unused cyclic-shift codes.

33. The method of claim 30, wherein respective intermediated ones of the cyclic-shift codes are cyclically padded at an end and at a beginning by as many chips as a relative position of the respective intermediated ones of the cyclic-shift codes in the multi-code sub-burst.

34. The method of claim 30, wherein the cyclic-shift codes include cyclic-padding having additional chips at an end and at a beginning to accommodate signal extensions that occur due to the non-zero length of an impulse response of a channel between a transmitter and a receiver.

35. The method of claim 13, wherein information is transmitted in bursts, each burst composed of consecutive multi-code sub-bursts, including a preamble sub-burst with at least two cyclic-codes, one or more data sub-bursts, each with one or more cyclic-codes, and postamble sub-bursts with at least two cyclic-codes.

36. The method of claim 35, wherein at least one of an amplitude, a phase of the modulated data symbols, and a cyclic-shift separation between consecutive ones of the cyclic-shift codes in the preamble conveys structural information regarding a time composition of a remaining portion of the burst.

37. The method of claim 36, wherein the preamble includes two cyclic shift codes at M+K cyclic-shifts apart, where M is a number of modulated data symbols transmitted per data sub-burst and K is a total length of an impulse response of a channel between a transmitter and a receiver measured in chip times.

38. The method of claim 35, wherein at least one of an amplitude, a phase, and a cyclic-shift separation between consecutive ones of the cyclic-shift codes in the postamble conveys additional structural information about a time composition of a preceding portion of the burst.

39. The method of claim 38, wherein the postamble includes two cyclic shift codes at K cyclic-shifts apart, where K is a total length of an impulse response of a channel between a transmitter and a receiver measured in a number of chips.

40. The method of claim 35, wherein the one or more data sub-bursts are encoded using one or more cyclic-codes with consecutive cyclic-shifts, each of the one or more data sub-bursts of a burst includes an equal number of cyclic-codes.

41. The method of claim 35, wherein the cyclic-codes in the preamble, the data sub-bursts, and the postamble sub-bursts are generated from a common base sequence.

42. The method of claim 35, wherein different bursts transmitted from a transmitting device use different base sequences and include a different number of data sub-bursts per burst.

43. The method of claim 35, wherein data sub-bursts of different bursts use modulation constellations with a different number of bits per modulated-data-symbol.

44. The method of claim 12, wherein multiple devices transmit simultaneously and each transmission is to one of a specific device, a group of devices, and broadcast to all receiving devices in the network.

45. The method of claim 44, wherein a base code is uniquely-assigned to each of the devices, and the uniquely-assigned base code indicates a unique ID for the each of the devices.

46. The method of claim 45, wherein a base code, distinct from any of the uniquely-assigned base codes, is assigned to the group of devices, and the assigned base code indicates a unique group ID or multicast ID for a group of devices.

47. The method of claim 46, wherein a base code, distinct from any of the uniquely-assigned base codes, and also distinct from any of the group ID base codes assigned to groups of devices, is assigned to all devices in the network, and the assigned base code indicates a network broadcast ID.

48. The method of claim 12, wherein a base code is uniquely-assigned to the device, and the uniquely-assigned base code indicates a unique ID for the receiving device.

49. The method of claim 12, wherein a receiving device having a broadcast ID is equipped with at least a filter or a cyclic correlator that is matched to a base code indicating a network broadcast ID.

50. The method of claim 49, wherein the network broadcast ID is used by a transmitting device to inform one or more neighbor receiving devices of their own node unique ID and an eventual group ID.

51. The method of claims 12, wherein a receiving device having a group ID is equipped with a filter or a cyclic correlator that is matched to a base code indicating a receiving device group ID.

52. The methods of claim 12, wherein the device has a unique ID and is equipped with a filter or a cyclic correlator that is matched to a base code indicating the unique ID of the device.

53. The method of claim 52, wherein the matching base code for the cyclic correlator is programmable.

54. The method of claim 52, wherein operations of the filter are performed by hardware, software, or combination thereof.

55. The method of claim 52, wherein an input signal for the filter or the cyclic correlator is sampled and stored, and correlating operations are made consecutively and as required to check for matches with a base code indicating either a network broadcast ID, a receiving device group ID, or the unique ID of the device.

56. The method of claims 1, wherein the burst includes a base code indicating one of a broadcast ID and a group ID that includes information indicating a first of a plurality of cyclic codes used in the preamble, the block of data or the postamble.

57. The method of claim 56, wherein the first of the cyclic codes indicates a number of chip-times from a start of time-slot in which a first data symbol used in each of the data blocks is detected.

58. The method of claim 1, wherein:

the burst includes a cyclic code from a base sequence indicating a broadcast ID, and

the device measures a timing event indicating a start of burst time relative to a start of a closest time-slot.

59. The method of claim 58, further comprising:

using transmission and reception times to determine a signal propagation time, including delays related to signal filtering operations performed at a transmitter and at a receiver.

60. The method of claim 1, wherein the derived information includes an indication of a duration for powering on one or more components of the device to receive the one or more blocks of data included in the burst.

61. The method of claim 60 wherein the powering on of the one or more components continues for a first duration of time based on the derived information.