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US 8,428,001 B2Granted
Timing corrections in a multi carrier system and propagation to a channel estimation time filter
AssigneeQUALCOMM Incorporated
InventorsBojan Vrcelj, Ashok Mantravadi, Fuyun Ling, Krishna Kiran Mukkavilli
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Abstract
Systems and methods are provided for determining and applying timing corrections in a digital communications system. In an aspect, a timing correction method is provided for a multi-carrier system. This includes aligning two or more symbols with respect to each other from a symbol subset in order to account for timing differences between the symbols. The symbol alignment is first carried out to generate channel estimates for data demodulation. The channel estimates, thus generated, along with the timing alignment information are in turn used for determining timing corrections-to be applied to future symbols.
Claims61
A timing correction method for a communication system, comprising:
- determining channel observations of two or more symbols modulated on different frequencies;
- aligning symbol timing of the channel observations of the two or more symbols, included in a symbol subset, with respect to each other to account for timing differences between the channel observations of the two or more symbols;
- obtaining a channel estimate based on the channel observations of the two or more symbols from the symbol subset, where the channel observations of the two or more symbols have been aligned in time;
- and
- demodulating one of the symbols in the symbol subset based on the channel estimate while concurrently correcting the timing for another channel observation of another symbol in the symbol subset based on the timing differences between the channel observations of the two or more symbols.
2 more elements
A timing correction method for a communication system, comprising:
- determining channel observations of symbols;
- aligning symbol timing of channel observations of two or more symbols, included in a symbol subset, with respect to each other to account for timing differences between said two or more symbols;
- and
- obtaining a channel estimate based on the channel observations of the two or more symbols from the symbol subset, where two or more received channel observations of symbols have been aligned in time;
- performing a channel estimate of length 2P, where P is an integer number of pilot carriers;
- and
- demodulating one of the symbols in the symbol subset based on the channel estimate while concurrently correcting the timing for another channel observation of another symbol in the symbol subset based on the timing differences between the channel observations of the two or more symbols.
4 more elements
A wireless receiver comprising:
- a processor;
- a memory coupled to the processor, the memory configured to store the following components for execution by the processor:
- a time filter component to process channel observations of a received symbol subset received in a broadcast network, wherein the symbols in the subset are modulated on different frequencies;
- and
- an alignment component to adjust timing between the channel observations of the symbols in the channel observations of the received symbol subset and to adjust timing of at least one channel observation for a received symbol with respect to other channel observations of received symbols in the subset based on a timing difference between the at least one channel observation of the received symbol and the other channel observations of the received symbols in the subset while concurrently demodulating a current symbol from the symbol subset.
2 more elements
A wireless receiver comprising:
- a processor;
- a memory coupled to the processor, the memory configured to store the following components for execution by the processor:
- a time filter component to process channel observations of a received symbol subset received in a broadcast network;
- an alignment component to adjust timing between the channel observations of the symbols in the received symbol subset and to adjust timing of at least one channel observation of a received symbol with respect to other channel observations of received symbol members in the subset while demodulating a current symbol;
- and
- at least three time domain filter taps to generate channel estimate data demodulation and timing correction, wherein the taps are set to values of {0.25, 0.5, and 0.25 respectively}.
3 more elements
A wireless receiver comprising:
- a processor;
- a memory coupled to the processor, the memory configured to store the following components for execution by the processor:
- a time filter component to process channel observations of a symbol subset received in a broadcast network, wherein symbols in the symbol subset are modulated on different frequencies;
- an alignment component to adjust timing between the channel observations of the symbols in the symbol subset and to adjust timing of at least one channel observation of a symbol with respect to other channel observations of symbols in the subset based on a timing difference between the at least one channel observation of the symbol and the other channel observations of the symbols in the subset while concurrently demodulating a current symbol from the symbol subset;
- and
- a component to optimize a data to pilot energy ratio based on the symbols in the symbol subset.
3 more elements
A time correction component for a wireless receiver, comprising:
- means for determining channel observations of a symbol subset in an OFDM broadcast;
- means for filtering the channel observations of the symbol subset;
- means for aligning channel observations of symbols within the channel observations of the symbol subset;
- and
- means for aligning one or more channel observations of symbols in view of a current demodulation of one of the symbols of the symbol subset.
2 more elements
A memory unit having processor executable code stored thereon, comprising:
- code for controlling a processor to determine channel observations of a symbol subset in a wireless network, wherein symbols in the symbol subset are modulated on different frequencies;
- code for controlling the processor to assign at least three non-causal filter tap structures to align symbol timing of channel observations of symbols within the symbol subset by adjusting for timing differences within the channel observations of the symbol subset;
- and
- code for controlling the processor to decodes at least one current symbol while adjusting the timing of another channel observation of another symbol in the symbol subset.
1 more element
A wireless communications apparatus, comprising:
- a memory that includes a component to determine time corrections for channel observations of a received symbol subset, wherein symbols in the symbol subset are modulated on different frequencies;
- and
- at least one processor associated with a receiver that decodes at least one current symbol while adjusting the timing of another channel observation of another symbol in the symbol subset, to align symbol timing of two or more channel observations of symbols in the symbol subset.
A method to perform time synchronization in a communications environment, comprising:
- determining timing corrections to be applied to channel observations with operations based on the relative early or late sampling of OFDM symbols;
- and
- performing a sampling correction, to align symbol timing of two or more channel observations of received OFDM symbols, based in part on the early or late sampling of the OFDM symbols and timing of a currently demodulated OFDM symbol, wherein the sampling correction is performed by a cyclic shift of one or more samples of the early or late sampling of the OFDM symbols followed by a constant complex multiplication applied on a portion of the one or more samples.
A method to perform time synchronization in a communications environment, comprising:
- determining timing corrections to be applied with operations based on the relative early or late sampling of OFDM symbols;
- and
- performing a sampling correction based in part on the early or late sampling of the OFDM symbols,
- at least one of the following equations being used to perform the sampling correction:
- early sampling correction:
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100 more elements
An apparatus to perform time synchronization in a communications environment, comprising:
- a first hardware module for determining timing corrections to be applied to channel observations with operations based on the relative early or late sampling of OFDM symbols;
- and
- a second hardware module for performing a sampling correction, to align symbol timing of two or more channel observations of received OFDM symbols, based in part on the early or late sampling of the OFDM symbols and timing of a currently demodulated OFDM symbol, wherein the sampling correction is performed by a cyclic shift of one or more samples of the early or late sampling of the OFDM symbols followed by a constant complex multiplication applied on a portion of the one or more samples.
An apparatus to perform time synchronization in a communications environment, comprising:
- a first hardware module for determining timing corrections to be applied with operations based on the relative early or late sampling of OFDM symbols;
- and
- a second hardware module for performing a sampling correction based in part on the early or late sampling of the OFDM symbols, using at least one of the following equations:
- early sampling correction:
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98 more elements
An apparatus to perform time synchronization in a communications environment, comprising:
- means for determining timing corrections to be applied to channel observations with operations based on the relative early or late sampling of OFDM symbols;
- and
- means for performing a sampling correction, to align symbol timing of two or more channel observations of received OFDM symbols, based in part on the early or late sampling of the OFDM symbols and timing of a currently demodulated OFDM symbol, wherein the sampling correction is performed by a cyclic shift of one or more samples of the early or late sampling of the OFDM symbols followed by a constant complex multiplication applied on a portion of the one or more samples.
An apparatus to perform time synchronization in a communications environment, comprising:
- means for determining timing corrections to be applied with operations based on the relative early or late sampling of OFDM symbols;
- and
- means for performing a sampling correction, to align symbol timing of two or more received OFDM symbols, based in part on the early or late sampling of the OFDM symbols,
- wherein said means for performing a sampling correction uses at least one of the following equations for performing the sampling correction:
- early sampling correction:
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- n
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- late sampling correction:
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- .
99 more elements
A memory unit including processor executable code, the memory unit comprising:
- code for causing a processor to determine timing corrections to be applied to channel observations with operations based on the relative early or late sampling of OFDM symbols;
- and
- code for causing the processor to perform a sampling correction, to align symbol timing of two or more channel observations of received OFDM symbols, based in part on the early or late sampling of the OFDM symbols and timing of a currently demodulated OFDM symbol, wherein the sampling correction is performed by a cyclic shift of one or more samples of the early or late sampling of the OFDM symbols followed by a constant complex multiplication applied on a portion of the one or more samples.
An apparatus to perform time synchronization in a communications environment, comprising:
- at least one processor configured to:
- determine timing corrections to be applied to channel observations with operations based on the relative early or late sampling of OFDM symbols;
- and
- perform a sampling correction, to align symbol timing of two or more channel observations of received OFDM symbols, based in part on the early or late sampling of the OFDM symbols and timing of a currently demodulated OFDM symbol, wherein the sampling correction is performed by a cyclic shift of one or more samples of the early or late sampling of the OFDM symbols followed by a constant complex multiplication applied on a portion of the one or more samples.
1 more element
A timing correction method for a communication system, comprising:
- receiving symbols;
- aligning symbol timing of two or more received symbols included in a symbol subset, with respect to each other to account for timing differences between said two or more received symbols;
- obtaining a channel estimate based on the received symbols from the symbol subset, where two or more received symbols have been aligned in time;
- aligning symbol timing of two or more received symbols included in a second symbol subset, with respect to each other to account for timing differences between said two or more received symbols in the second symbol subset, said second symbol subset including at least one symbol which is different from symbols included in said first symbol subset and at least one symbol which is included in the first symbol subset;
- and
- obtaining a second channel estimate based on the received symbols from the second symbol subset, wherein two or more received symbols in the second symbol subset have been aligned in time.
3 more elements
Dependencies are inferred from the claim text.