Timing drift compensation in wireless packet-based systems
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
H04Q-007/00
H04J-003/06
출원번호
US-0994944
(2001-11-28)
발명자
/ 주소
Davidsson,Stefan
Pauli,Mathias
Schramm,Peter
Wenger,Fabian
Wachsmann,Udo
Walther,Roger
출원인 / 주소
Telefonaktiebologet LM Ericsson (publ)
대리인 / 주소
Nixon &
인용정보
피인용 횟수 :
20인용 특허 :
12
초록▼
A radio receiver system (30) comprises a radio receiver (41), a receiver sample clock (60), which is used for sampling a modulated base-band signal; and a timing correction unit (100). The timing correction unit (100) performs, in the frequency domain, a timing drift compensation between a transmitt
A radio receiver system (30) comprises a radio receiver (41), a receiver sample clock (60), which is used for sampling a modulated base-band signal; and a timing correction unit (100). The timing correction unit (100) performs, in the frequency domain, a timing drift compensation between a transmitter sample clock (66) and the receiver sample clock (60). In one example context of implementation, the plural modulated radio frequency carriers have been modulated using Orthogonal Frequency Division Multiplexing (OFDM).
대표청구항▼
What is claimed is: 1. A radio receiver system comprising: a radio receiver which receives plural modulated radio frequency carriers and produces therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accorda
What is claimed is: 1. A radio receiver system comprising: a radio receiver which receives plural modulated radio frequency carriers and produces therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; a receiver sample clock which is used for sampling the modulated base-band signal; a timing correction unit which performs in the frequency domain a timing drift compensation between the transmitter sample clock and the receiver sample clock; a demodulation section which comprises the timing correction unit, and wherein the dcmodulation section further comprises: a frequency offset estimation unit which outputs a frequency offset estimation; frequency correction unit which receives the modulated base-band signal and outputs a frequency corrected modulated base-band signal; a fast Fourier transform (FFT) unit which receives the frequency corrected modulated base-band signal and outputs a frequency domain modulated subcarrier signal; a channel estimation unit which uses the frequency corrected modulated base-band signal to generate a frequency domain channel estimate which is applied to the timing correction unit; wherein the timing correction unit generates a time corrected channel estimate; a demodulator which uses the frequency domain modulated subcarrier signal and the time corrected channel estimate to generate a demodulated signal. 2. The apparatus of claim 1, wherein the plural modulated radio frequency carriers have been modulated using Orthogonal Frequency Division Multiplexing (OFDM). 3. The apparatus of claim 1, wherein the timing correction unit performs the timing drift compensation using a frequency estimation and frequency domain channel estimation. 4. The apparatus of claim 1, wherein the timing correction unit estimates a timing drift value and compensates for the timing drift value in the frequency domain by applying an appropriate phase factor to a subcarrier to update the channel estimate and thereby provide the time corrected channel estimate. 5. The apparatus of claim 4, wherein the timing correction unit updates the channel estimate using a relationship description="In-line Formulae" end="lead"H m[k]=exp(j쨌φm,k)쨌H m[0]description="In-line Formulae" end="tail" wherein: Hm[k] is the time corrected channel estimate for a time index measured in data symbols k; Hm[0] is the frequency domain channel estimate for the data symbol k; φm,k is the phase factor; and wherein m is a subcarrier index for used subcarriers. 6. The apparatus of claim 5, wherein the phase factor φm,k is defined by the following expression: wherein: m is the subcarrier index; k is the time index measured in data symbols; Ts is a symbol time; T is a sample time; Tinit is a time between a reference time and a first data symbol; and t0 is the timing drift value. 7. The apparatus of claim 6, wherein the timing drift value t0 is derived from the following relationship: wherein foff is an absolute frequency offset estimate in Hz, and fc is a carrier frequency in Hz. 8. The apparatus of claim 1, wherein the frequency offset estimation unit is a preamble directed frequency offset estimation unit which receives the modulated base-band signal. 9. The apparatus of claim 8, further comprising a decision directed frequency offset estimation unit which is connected to receive respective inputs from the demodulation unit, the timing correction unit, and the fast Fourier transform (FFT) unit. 10. The apparatus of claim 1, wherein the frequency offset estimation unit is a decision directed frequency offset estimation unit which is connected to receive respective inputs from the demodulation unit, the timing correction unit, and the fast Fourier transform (FFT) unit. 11. The apparatus of claim 1, wherein updating of the channel estimate for the timing drift compensation occurs every Mth symbol. 12. The apparatus of claim 11, wherein a value for M is selected based on a particular link adaptation mode. 13. A radio receiver system comprising: a radio receiver which receives plural modulated radio frequency carriers and produces therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; a demodulation section which comprises the timing correction unit, and wherein the demodulation section further comprises: a frequency offset estimation unit which outputs a frequency offset estimation; a frequency correction unit which receives the modulated base-band signal and outputs a frequency corrected modulated base-band signal; a fast Fourier transform (FFT) unit which receives the frequency corrected digital complex modulated base-band signal and outputs, for each subcarrier, a frequency domain modulated subcarrier signal which is applied to the demodulator; a channel estimation unit which uses the frequency corrected modulated base-band signal and generates a frequency domain channel estimate; wherein the timing correction unit receives the frequency offset estimation and the frequency domain modulated subcarrier signal to generate a time corrected frequency domain modulated subcarrier signal; a demodulator which uses the time corrected frequency domain modulated signal and the frequency domain channel estimate to generate a demodulated signal. 14. The apparatus of claim 13, wherein the timing correction unit estimates a timing drift value and compensates for the timing drift value in the frequency domain by applying an appropriate phase factor to a subcarrier to update the frequency domain modulated subcarrier signal and thereby provide a time corrected frequency domain modulated signal. 15. The apparatus of claim 14, wherein the timing correction unit updates the frequency domain modulated signal using a relationship description="In-line Formulae" end="lead"R TD,m[k]=exp(-jφm,k)쨌RFFT, m[k]description="In-line Formulae" end="tail" wherein: RTD,m[k] is the time corrected frequency domain modulated frequency domain signal of an mth subcarrier of a k th data carrying symbol; RFFT,m[k] is the frequency domain modulated signal as output by the fast Fourier transform (FFT) unit of the mth subcarrier of the kth data carrying symbol; and φ m,k is the phase factor; and wherein m is a subcarrier index for used subcarriers. 16. The apparatus of claim 15, wherein the phase factor φm,k is defined by the following expression: wherein: m is the subcarrier index; k is the time index measured in data symbols; Ts is a symbol time; T is a sample time; Tinit is a time between a reference time and a first data symbol; and t0 is the timing drift value. 17. The apparatus of claim 16, wherein the timing drift value t0 is derived from the following relationship: wherein foff is an absolute frequency offset estimate in Hz, and fc is a carrier frequency in Hz. 18. The apparatus of claim 13, wherein the frequency offset estimation unit is a preamble directed frequency offset estimation unit which receives the modulated base-band signal. 19. The apparatus of claim 18, further comprising a decision directed frequency offset estimation unit which is connected to receive respective inputs from the demodulation unit, the timing correction unit, and the channel estimation unit. 20. The apparatus of claim 13, wherein the frequency offset estimation unit is a decision directed frequency offset estimation unit which is connected to receive respective inputs from the demodulation unit, the timing correction unit, and the channel estimation unit. 21. A radio receiver system comprising: a radio receiver which receives plural modulated radio frequency carriers and produces therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; a receiver sample clock which is used for sampling the modulated base-band signal; a timing correction unit which performs in the frequency domain a timing drift compensation between the transmitter sample clock and the receiver sample clock; wherein the timing correction unit uses a frequency offset to determine a timing drift value, wherein the subcarrier signal comprises a stream of data symbols, further comprising: a frequency offset estimation unit which calculates: an estimated phase offset for each data symbol as a function of the data symbol; a predicted phase offset for each data symbol as a function of the estimated phase offset thereof and an estimated phase offset of a preceding one of the data symbols in the stream; a predicted sample phase offset for each data symbol as a function of a predicted phase offset of a corresponding one of the data symbol; and the frequency offset as a function of the predicted sample phase offset for each data signal sample. 22. The apparatus of claim 21, wherein the frequency offset calculation unit comprises: a phase locked loop for generating the predicted phase offset; a phase discrimination unit for generating an estimated phase offset for each data signal as a function thereof; a filter for receiving estimated phase offsets and generating the predicted phase offset for each data symbol as a function of the estimated phase offset thereof and the estimated phase offset of a preceding one of the data symbols. 23. A method of operating radio receiver system comprising: receiving plural modulated radio frequency carriers and producing therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; sampling the modulated base-band signal in accordance with a receiver sample clock; performing in a frequency domain a timing drift compensation between the transmitter sample clock and the receiver sample clock; generating a frequency offset estimation; generating a frequency corrected modulated base-band signal; using a fast Fourier transform (FFT) unit to generate a frequency domain modulated subcarrier signal using the frequency corrected modulated base-band signal; using the frequency corrected modulated base-band signal to generate a frequency domain channel estimate; generating a time corrected channel estimate using the frequency domain channel estimate; using the frequency domain modulated subcarrier signal and the time corrected channel estimate to generate a demodulated signal. 24. The method of claim 23, wherein the plural modulated radio frequency carriers have been modulated using Orthogonal Frequency Division Multiplexing (OFDM). 25. The method of claim 23, further comprising performing the timing drift compensation using a frequency estimation and frequency domain channel estimation. 26. The method of claim 23, further comprising estimating a timing drift value and compensating for the timing drift value in the frequency domain by applying an appropriate phase factor to a subcarrier to update the channel estimate and thereby provide a time corrected channel estimate. 27. The method of claim 26, wherein the channel estimate is updated using a relationship description="In-line Formulae" end="lead"H m[k]=exp(j쨌φm,k)쨌H m[0]description="In-line Formulae" end="tail" wherein: Hm[k] is the time corrected channel estimate for a time index measured in data symbols k; Hm[0] is the frequency domain channel estimate for the data symbol φm,k is the phase factor; and wherein m is a subcarrier index for used subcarriers. 28. The method of claim 27, wherein the phase factor φm,k is defined by the following expression: wherein: m is the subcarrier index; k is the time index measured in data symbols; Ts is a symbol time; T is a sample time; Tinit is a time between a reference time and a first data symbol; and t0 is the timing drift value. 29. The method of claim 28, wherein the timing drift value t0 is derived from the following relationship: wherein foff is an absolute frequency offset estimate in Hz, and fc is a carrier frequency in Hz. 30. The method of claim 23, wherein the frequency offset estimation is obtained from a preamble directed frequency offset estimation unit which receives the modulated base-band signal. 31. The method of claim 23, wherein the frequency offset estimation is obtained from a decision directed frequency offset estimation unit. 32. The method of claim 23, wherein updating of the channel estimate for the timing drift compensation occurs every Mth symbol. 33. The method of claim 32, wherein a value for M is selected based on a particular link adaptation mode. 34. A method of operating radio receiver system comprising: receiving plural modulated radio frequency carriers and producing therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; sampling the modulated base-band signal in accordance with a receiver sample clock; generating a frequency offset estimation; generating a frequency corrected modulated base-band signal; using the frequency corrected digital modulated base-band signal and generating, for each subcarrier, a frequency domain modulated subcarrier signal; using the frequency corrected modulated base-band signal to generate a frequency domain channel estimate; performing in a frequency domain a timing drift comprising between the transmitter sample clock and the receiver sample clock by using the frequency offset estimation and the frequency domain modulated subcarrier signal to generate a time corrected frequency domain modulated subcarrier signal; using the time corrected frequency domain modulated signal and the frequency domain channel estimate to generate a demodulated signal. 35. The method of claim 34, wherein the timing correction unit estimates a timing drift value and compensates for the timing drift value in the frequency domain by applying an appropriate phase factor to a subcarrier to update the frequency domain modulated subcarrier signal and thereby provide a time corrected frequency domain modulated signal. 36. The method of claim 35, further comprising updating the frequency domain modulated signal using a relationship description="In-line Formulae" end="lead"R TD,m[k]=exp(-jφm,k)쨌RFFT, m[k]description="In-line Formulae" end="tail" wherein: RTD,m[k] is the time corrected frequency domain modulated frequency domain signal of an mth subcarrier of a k th data carrying symbol; RFFT,m[k] is the frequency domain modulated signal as output by the fast Fourier transform (FFT) unit of the mth subcarrier of the kth data carrying symbol; and φ m,k is the phase factor; and wherein m is a subcarrier index for used subcarriers. 37. The method of claim 36, wherein the phase factor φm,k is defined by the following expression: wherein: m is the subcarrier index; k is the time index measured in data symbols; Ts is a symbol time; T is a sample time; Tinit is a time between a reference time and a first data symbol; and t0 is the timing drift value. 38. The method of claim 37, wherein the timing drift value t0 is derived from the following relationship: wherein foff is an absolute frequency offset estimate in Hz, and fc is a carrier frequency in Hz. 39. The method of claim 34, wherein the frequency offset estimation is obtained from a preamble directed frequency offset estimation unit which receives the modulated base-band signal. 40. The method of claim 34, wherein the frequency offset estimation is obtained from a decision directed frequency offset estimation unit. 41. A method of operating radio receiver system comprising: receiving plural modulated radio frequency carriers and producing therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; sampling the modulated base-band signal in accordance with a receiver sample clock; performing in a frequency domain a timing drift compensation between the transmitter sample clock and the receiver sample clock; using a frequency offset to determine a timing drift value, wherein the subcarrier signal comprises a stream of data symbols, further comprising calculating: an estimated phase offset for each data symbol as a function of the data symbol; a predicted phase offset for each data symbol as a function of the estimated phase offset thereof and an estimated phase offset of a preceding one of the data symbols in the stream; a predicted sample phase offset for each data symbol as a function of a predicted phase offset of a corresponding one of the data symbol; and the frequency offset as a function of the predicted sample phase offset for each data signal sample. 42. The method of claim 41, further comprising: generating the predicted phase offset; generating an estimated phase offset for each data signal as a function thereof; receiving estimated phase offsets and generating the predicted phase offset for each data symbol as a function of the estimated phase offset thereof and the estimated phase offset of a preceding one of the data symbols.
Cupo, Robert Louis; Karim, Muhammad R., In-band-on-channel (IBOC) system and methods of operation using orthogonal frequency division multiplexing (OFDM) with timing and frequency offset correction.
Yu, Nicholas K.; Easton, Kenneth David; Sankuratri, Raghu, Method and apparatus for activating a high frequency clock following a sleep mode within a mobile station operating in a slotted paging mode.
Wallace, Mark S.; Tiedemann, Jr., Edward G.; Wheatley, III, Charles E.; Walton, J. Rod; Howard, Steven J., Method and apparatus for providing wireless communication system synchronization.
Castelain, Damien, Method of transmitting data on multiple carriers from a transmitter to a receiver and receiver designed to implement the said method.
Lamkin Allan B. ; Blakely Michael ; Nouri Richard ; Killen Katherine A., TDMA system timer for maintaining timing to multiple satellite simultaneously.
Atungsiri,Samuel Asangbeng; Wilson,John Nicholas, Apparatus and associated method of symbol timing recovery using coarse and fine symbol time acquisition.
Kao, Kai Pon; Ma, ChinGwo, Method and circuit for frequency offset estimation in frequency domain in the orthogonal frequency division multiplexing baseband receiver for IEEE 802.11A/G wireless LAN standard.
Kao, Kai-Pon; Ma, ChinGwo, Method and circuit for frequency offset estimation in frequency domain in the orthogonal frequency division multiplexing baseband receiver for IEEE 802.11a/g wireless LAN standard.
Thadasina, Nivedan; Csapo, John; Gilliland, Paul, Method and system for synchronizing a clock for an adjacent network to a clock for an overlay network.
Gardner, James; Jones, IV, Vincent K.; van Nee, D. J. Richard, Modified preamble structure for IEEE 802.11A extensions to allow for coexistence and interoperability between 802.11A devices and higher data rate, MIMO or otherwise extended devices.
van Zelst, Albert; van Nee, D. J. Richard; Jones, Vincent K., Modified preamble structure for IEEE 802.11A extensions to allow for coexistence and interoperability between 802.11A devices and higher data rate, MIMO or otherwise extended devices.
※ AI-Helper는 부적절한 답변을 할 수 있습니다.