IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0085242
(2011-04-12)
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등록번호 |
US-8660013
(2014-02-25)
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발명자
/ 주소 |
- Yonge, III, Lawrence W.
- Katar, Srinivas
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출원인 / 주소 |
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
10 인용 특허 :
198 |
초록
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A waveform communicated from a first station to a second station over the shared medium may be communicated at a time that is based on a shared time reference shared by the first and second stations. The waveform may include at least a first symbol, having a predetermined symbol length, comprising a
A waveform communicated from a first station to a second station over the shared medium may be communicated at a time that is based on a shared time reference shared by the first and second stations. The waveform may include at least a first symbol, having a predetermined symbol length, comprising a first set of frequency components at predetermined carrier frequencies modulated with preamble information and a second set of frequency components at predetermined carrier frequencies modulated with frame control information. The carrier frequencies of the first and second sets of frequency components may be integral multiples of a frequency interval determined by the inverse of the symbol length. The first symbol of the waveform may be demodulated in response to detecting a series of values sampled based on the shared time reference.
대표청구항
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1. A method comprising: monitoring a shared medium at a second station, before receiving a waveform from a first station, to detect a start of a first symbol of the waveform at one of multiple time slot boundaries, the monitoring including, after each of multiple time slot boundaries, periodically s
1. A method comprising: monitoring a shared medium at a second station, before receiving a waveform from a first station, to detect a start of a first symbol of the waveform at one of multiple time slot boundaries, the monitoring including, after each of multiple time slot boundaries, periodically sampling a series of values received over the shared medium starting at a beginning of a most recent time slot boundary and processing the sampled values to generate a metric value that indicates whether the start of the first symbol of the waveform has been detected;receiving the waveform from the first station over the shared medium at a time that is based on a shared time reference shared by the first station and the second station, the waveform including at least the first symbol, having a predetermined symbol length, comprising a first set of frequency components at predetermined carrier frequencies modulated with preamble information and a second set of frequency components at predetermined carrier frequencies modulated with frame control information, with the carrier frequencies of the first and second sets of frequency components being integral multiples of a frequency interval determined by an inverse of the symbol length; andin response to detecting the start of the first symbol of the waveform, demodulating, at the second station, the first symbol of the waveform from values sampled based on the shared time reference. 2. The method of claim 1 wherein the multiple time slot boundaries are boundaries of contention resolution slots used for resolving contention in carrier sense multiple access (CSMA). 3. The method of claim 2 wherein the shared medium is monitored after a detected collision. 4. The method of claim 1 wherein the multiple time slot boundaries are boundaries of slots within a time division multiple access (TDMA) allocation. 5. The method of claim 4, wherein the shared medium is monitored after missing an initial frame within the allocation. 6. The method of claim 1 further comprising calculating an offset from a time slot boundary determined relative to the shared time reference, wherein the offset is calculated based on a propagation delay between the first station and the second station. 7. The method of claim 6, wherein the offset is calculated at one of the first station and the second station. 8. The method of claim 1 wherein the shared time reference is determined based on a synchronization signal transmitted from a master station, wherein the synchronization signal can be detected without a determination of the shared time reference. 9. The method of claim 1, wherein the shared time reference is determined based on synchronizing a time base at the first station or the second station to a master time base maintained at a third station. 10. The method of claim 1, wherein a first portion of the waveform comprises the first symbol and a second portion of the waveform comprises a segment that is correlated with at least an initial segment of the first portion of the waveform. 11. The method of claim 10, wherein receiving the waveform includes receiving the second portion followed in time by the first portion over the shared medium. 12. The method of claim 11 further comprising receiving, at the second station, the first portion of the waveform, and storing data representative of the received first portion. 13. The method of claim 12, further comprising receiving, at the second station, the second portion of the waveform, and detecting a correlation between the stored data representative of the received first portion and data representative of an initial segment of the received second portion. 14. The method of claim 13, further comprising, in response to detecting the correlation, demodulating a symbol having a predetermined symbol length from the received second portion. 15. The method of claim 13, wherein the correlation is in a time domain. 16. The method of claim 15, wherein detecting the correlation is performed after passing the received waveform through a frequency selective filter. 17. The method of claim 13, wherein the correlation is in an frequency domain. 18. The method of claim 1, wherein the predetermined symbol length of the first symbol is greater than a time duration between adjacent slot boundaries. 19. The method of claim 1, wherein the first symbol is preceded by a prefix representing a cyclic extension of a terminal portion of the first symbol. 20. The method of claim 1, wherein the first symbol is followed by a suffix representing a cyclic extension of an initial portion of the first symbol. 21. A system for communicating between stations over a shared medium, the system comprising: a first station that transmits a waveform over the shared medium at a time that is based on a shared time reference shared by multiple of the stations, the waveform including at least a first symbol, having a predetermined symbol length, comprising a first set of frequency components at predetermined carrier frequencies modulated with preamble information stored in a second station and a second set of frequency components at predetermined carrier frequencies modulated with frame control information to be communicated to at least one station, with the carrier frequencies of the first and second sets of frequency components being integral multiples of a frequency interval determined by an inverse of the symbol length; andat least a second station that monitors the shared medium before transmission of the waveform from the first station, to detect a start of the first symbol of the waveform at one of multiple time slot boundaries, the monitoring including, after each of multiple time slot boundaries, periodically sampling a series of values received over the shared medium starting at a beginning of a most recent time slot boundary and processing the sampled values to generate a metric value that indicates whether the start of the first symbol of the waveform has been detected, andin response to detecting the start of the first symbol of the waveform, demodulates the first symbol of the waveform from values sampled based on the shared time reference. 22. A method comprising: transmitting a waveform from a first station over a shared medium to a second station at a time that is based on a shared time reference shared by the first station and the second station, the waveform including at least a first symbol, having a predetermined symbol length,wherein the first symbol comprises a first set of frequency components at predetermined carrier frequencies modulated with preamble information and a second set of frequency components at predetermined carrier frequencies modulated with frame control information, with the carrier frequencies of the first and second sets of frequency components being integral multiples of a frequency interval determined by an inverse of the symbol length. 23. The method of claim 22, further comprising forming a first portion of the waveform comprising the first symbol and a second portion of the waveform comprising a segment that is correlated with at least an initial segment of the first portion of the waveform. 24. The method of claim 23, wherein transmitting the waveform includes transmitting the second portion followed in time by the first portion over the shared medium. 25. The method of claim 22, further comprising adapting which frequency components are included in one or more of the first and second sets of frequency components to conditions on the shared medium. 26. The method of claim 22, further comprising adapting the symbol length to conditions on the shared medium. 27. The method of claim 22, wherein transmitting the waveform comprises transmitting the waveform at one of multiple time slot boundaries, wherein the multiple time slot boundaries are boundaries of contention resolution slots used for resolving contention in carrier sense multiple access (CSMA) or wherein the multiple time slot boundaries are boundaries of slots within a time division multiple access (TDMA) allocation. 28. The method of claim 22, further comprising calculating an offset from a time slot boundary determined relative to the shared time reference, wherein the offset is calculated based on a propagation delay between the first station and the second station. 29. The method of claim 22, wherein the shared time reference is determined based on a synchronization signal transmitted from a master station, wherein the synchronization signal can be detected without a determination of the shared time reference. 30. The method of claim 22, wherein the shared time reference is determined based on synchronizing a time base at the first station or the second station to a master time base maintained at a third station. 31. The method of claim 22, wherein a first portion of the waveform comprises the first symbol and a second portion of the waveform comprises a segment that is correlated with at least an initial segment of the first portion of the waveform. 32. The method of claim 31, wherein transmitting the waveform includes transmitting the second portion followed in time by the first portion over the shared medium. 33. The method of claim 32, wherein a correlation exists between the transmitted first portion and an initial segment of the second portion. 34. The method of claim 33, wherein the correlation is in a time domain or a frequency domain. 35. The method of claim 22, wherein the predetermined symbol length of the first symbol is greater than a time duration between adjacent slot boundaries. 36. The method of claim 22, wherein the first symbol is preceded by a prefix representing a cyclic extension of a terminal portion of the first symbol. 37. The method of claim 22, wherein the first symbol is followed by a suffix representing a cyclic extension of an initial portion of the first symbol. 38. An apparatus in a first station, the apparatus comprising: a transmitter suitable to transmit a waveform over a shared medium to a second station at a time that is based on a shared time reference shared by the first station and the second station, the waveform including at least a first symbol, having a predetermined symbol length,wherein the first symbol comprises a first set of frequency components at predetermined carrier frequencies modulated with preamble information and a second set of frequency components at predetermined carrier frequencies modulated with frame control information, with the carrier frequencies of the first and second sets of frequency components being integral multiples of a frequency interval determined by an inverse of the symbol length. 39. The apparatus of claim 38, wherein the transmitter comprises modules for implementing a physical (PHY) layer, the modules including at least an encoding module, a mapping module, and a modulation module configured to prepare the waveform including at least the first symbol. 40. An apparatus in a second station, the apparatus comprising: a receiver suitable to monitor a shared medium before receiving a waveform from a first station, to detect a start of a first symbol of the waveform at one of multiple time slot boundaries, the monitoring including, after each of multiple time slot boundaries, periodically sampling a series of values received over the shared medium starting at a beginning of a most recent time slot boundary and processing the sampled values to generate a metric value that indicates whether the start of the first symbol of the waveform has been detected;the receiver suitable to receive the waveform from the first station over the shared medium at a time that is based on a shared time reference shared by the first station and the second station, the waveform including at least the first symbol, having a predetermined symbol length, comprising a first set of frequency components at predetermined carrier frequencies modulated with preamble information and a second set of frequency components at predetermined carrier frequencies modulated with frame control information, with the carrier frequencies of the first and second sets of frequency components being integral multiples of a frequency interval determined by an inverse of the symbol length; andthe receiver suitable to demodulate the first symbol of the waveform from values sampled based on the shared time reference in response to detecting the start of the first symbol of the waveform. 41. A non-transitory computer readable medium storing computer program code, the computer program code comprising instructions which when executed by a processor of a device cause the device to perform operations comprising: monitoring a shared medium at a second station, before receiving a waveform from a first station, to detect a start of a first symbol of the waveform at one of multiple time slot boundaries, the monitoring including, after each of multiple time slot boundaries, periodically sampling a series of values received over the shared medium starting at a beginning of a most recent time slot boundary and processing the sampled values to generate a metric value that indicates whether the start of the first symbol of the waveform has been detected;receiving the waveform from the first station over the shared medium at a time that is based on a shared time reference shared by the first station and the second station, the waveform including at least the first symbol, having a predetermined symbol length, comprising a first set of frequency components at predetermined carrier frequencies modulated with preamble information and a second set of frequency components at predetermined carrier frequencies modulated with frame control information, with the carrier frequencies of the first and second sets of frequency components being integral multiples of a frequency interval determined by an inverse of the symbol length; andin response to detecting the start of the first symbol of the waveform, demodulating, at the second station, the first symbol of the waveform from values sampled based on the shared time reference. 42. A non-transitory computer readable medium storing computer program code, the computer program code comprising instructions which when executed by a processor of a device cause the device to perform operations comprising: transmitting a waveform from a first station over a shared medium to a second station at a time that is based on a shared time reference shared by the first station and the second station, the waveform including at least a first symbol, having a predetermined symbol length,wherein the first symbol comprises a first set of frequency components at predetermined carrier frequencies modulated with preamble information and a second set of frequency components at predetermined carrier frequencies modulated with frame control information, with the carrier frequencies of the first and second sets of frequency components being integral multiples of a frequency interval determined by an inverse of the symbol length.
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