Joint timing offset, frequency offset, and channel estimation
A receiver receives signals from a transmitter in subframes on subcarriers having orthogonal frequencies. A subset of the subframes include reference signals. The receiver generates a first channel estimate for a target subframe based on reference signals in the target subframe. The receiver also generates one or more second channel estimates for one or more other subframes based on one or reference signals in the other subframes. The receiver combines the first channel estimate and the one or more second channel estimates based on a frequency offset between the receiver and the transmitter to form a channel estimate of the target subframe. In some cases, the receiver performs joint estimates of a timing offset, a frequency offset, and a channel for the target subframe based on the reference signals, selected candidate timing offsets, selected candidate frequency offsets, and selected candidate channel estimates.
1 . A method comprising:
receiving, at a receiver device from a transmitter device, signals in subframes on subcarriers having orthogonal frequencies, wherein a subset of the subframes comprise reference signals;
generating a first channel estimate for a target subframe based on at least one reference signal in the target subframe;
generating at least one second channel estimate for at least one other subframe based on at least one reference signal in the at least one other subframe; and
combining the first channel estimate and the at least one second channel estimate based on a frequency offset between the receiver and the transmitter to form a channel estimate of the target subframe.
2 . The method of claim 1 , wherein generating the at least one second channel estimate comprises generating a preceding channel estimate based on reference signals in a subframe that precedes the target subframe and a succeeding channel estimate based on reference signals in a subframe that succeeds the target subframe.
3 . The method of claim 2 , wherein the preceding subframe and the succeeding subframe are substantially symmetric about the target subframe or a span of target subframes.
4 . The method of claim 2 , wherein the preceding subframe and the succeeding subframe are broadcast channel subframes and the target subframe is a data channel subframe or a control channel subframe.
5 . The method of claim 2 , wherein the preceding subframe and the succeeding subframe comprise synchronization signals for a data channel subframe or a control channel subframe.
6 . The method of claim 2 , wherein the preceding subframe and the succeeding subframe bracket a set of subframes that includes blocks of data channel subframes or control channel subframes and at least one broadcast channel or synchronization signal.
7 . The method of claim 6 , wherein the preceding subframe and the succeeding subframe are defined by a sliding window so that each broadcast channel or synchronization signal is chosen as both the preceding subframe and the succeeding subframe for different target subframes.
8 . The method of claim 1 , further comprising:
jointly estimating a timing offset, the frequency offset, and a channel of the target subframe.
9 . The method of claim 8 , wherein jointly estimating the timing offset, the frequency offset, and the channel comprises:
generating a candidate set of timing offsets and frequency offsets;
generating channel estimates based on the candidate set of timing offsets and frequency offsets; and
performing the joint estimation of the timing offset, frequency offset, and channel based on the candidate set and the corresponding channel estimates.
10 . A wireless communication device comprising:
a receiver configured to receive signals from a transmitter in subframes on subcarriers having orthogonal frequencies; wherein a subset of the subframes comprises reference signals;
a memory configured to store data representing the signals; and
a processor configured to execute instructions stored by the memory to:
generate a first channel estimate for a target subframe based on at least one reference signal in the target subframe;
generate at least one second channel estimate for at least one other subframe based on at least one reference signal in the at least one other subframe; and
combine the first channel estimate and the at least one second channel estimate based on a frequency offset between the receiver and the transmitter to form a channel estimate of the target subframe.
11 . The wireless communication device of claim 10 , wherein the processor is further configured to generate a preceding channel estimate based on reference signals in a subframe that precedes the target subframe and a succeeding channel estimate based on reference signals in a subframe that succeeds the target subframe and to combine the first channel estimate, the preceding channel estimate, and the succeeding channel estimate based on the frequency offset to form the channel estimate of the target subframe.
12 . The wireless communication device of claim 11 , wherein the preceding subframe and the succeeding subframe are substantially symmetric about the target subframe or a span of target subframes.
13 . The wireless communication device of claim 11 , wherein the preceding subframe and the succeeding subframe are broadcast channel subframes and the target subframe is a data channel subframe or a control channel subframe.
14 . The wireless communication device of claim 11 , wherein the preceding subframe and the succeeding subframe comprise synchronization signals for a data channel subframe or a control channel subframe.
15 . The wireless communication device of claim 11 , wherein the preceding subframe and the succeeding subframe bracket a set of subframes that includes blocks of data channel subframes or control channel subframes and at least one broadcast channel or synchronization signal.
16 . The wireless communication device of claim 15 , wherein the preceding subframe and the succeeding subframe are defined by a sliding window so that each broadcast channel or synchronization signal is chosen as both the preceding subframe and the succeeding subframe for different target subframes.
17 . The wireless communication device of claim 10 , wherein the processor is further configured to:
jointly estimate a timing offset, the frequency offset, and a channel of the target subframe.
18 . The wireless communication device of claim 17 , wherein the processor is further configured to:
generate a candidate set of timing offsets and frequency offsets;
generate channel estimates based on the candidate set of timing offsets and frequency offsets; and
perform the joint estimation of the timing offset, frequency offset, and channel based on the candidate set and the corresponding channel estimates.