Low complexity intercarrier interference (ICI) compensation algorithm: cyclic block phase tracking reference signal (PTRS) sequence design
A method, system and apparatus for low complexity intercarrier interference (ICI) compensation algorithms and cyclic block phase tracking reference signal (PTRS) sequence design are disclosed. According to one aspect, a method in a network node includes generating a PTRS, having a PTRS sequence that is configured to lower a complexity of an ICI compensation algorithm. According to another aspect, a method in a wireless device (WD) includes determining an ICI compensation algorithm based at least in part on a PTRS having a PTRS sequence, and applying the determined ICI compensation algorithm to compensate for ICI.
1 . A method in a transmitter of one of a network node and a wireless device (WD), the method comprising:
determining, for a receiver, a cyclic block phase tracking reference signal (PTRS) sequence by cyclically extending a base sequence;
performing, based at least in part on the PTRS sequence, an inter-carrier interference (ICI) compensation algorithm of a specified level of complexity; and
transmitting the PTRS.
2 . The method of claim 1 , wherein determining the PTRS includes determining a different PTRS for each of a plurality of clusters.
3 . The method of claim 2 , wherein the PTRS for each cluster is based at least in part on cyclically shifting the PTRS of a first cluster of the plurality of clusters.
4 . The method of claim 3 , wherein cyclically shifting the PTRS includes shifting by an amount that is based at least in part on at least one of a resource block index, an orthogonal frequency division multiplex (OFDM) symbol index, a WD identification and a cell identification.
5 . The method of claim 2 , wherein a PTRS for a cluster is determined based at least in part on an element-wise product in the frequency domain of a base sequence common to all of the plurality of clusters and a cluster-specific sequence.
6 . The method of claim 5 , wherein the cluster-specific sequence is based at least in part on a complex exponential of a phase step times an index.
7 . The method of claim 5 , wherein the cluster-specific sequence is based at least in part on a scrambling sequence.
8 . The method of claim 7 , wherein the scrambling sequence is selected to minimize a peak to average power ratio of the transmitted PTRS.
9 . The method of claim 1 , wherein cyclically extending the base sequence includes appending a cyclic prefix and a cyclic postfix to the base sequence.
10 . The method of claim 1 , wherein cyclically extending the base sequence includes appending a last L−1 symbols of the base sequence to a beginning of the base sequence, L being a filter length of the ICI compensation algorithm.
11 . A transmitter for one of a network node and a wireless device (WD), the transmitter comprising:
processing circuitry configured to:
determine, for a receiver, a cyclic block phase tracking reference signal, (PTRS) sequence by cyclically extending a base sequence; and
perform, based at least in part on the PTRS sequence, an inter-carrier interference (ICI) compensation algorithm of a specified level of complexity; and
a radio interface in communication with the processing circuitry and configured to transmit the PTRS.
12 . The transmitter of claim 11 , wherein determining the PTRS includes determining a different PTRS for each of a plurality of clusters.
13 . A method in a receiver of one of a network node and a wireless device, WD, the method comprising:
receiving a phase tracking reference signal (PTRS), having a PTRS sequence;
determining intercarrier interference (ICI) compensation filter coefficients based at least in part on a circulant matrix of known PTRS sequences, a PTRS sequence being formed by cyclically extending a base sequence; and
applying a filter having the determined ICI compensation filter coefficients to the received PTRS sequence.
14 . The method of claim 13 , wherein determining a set of ICI filter coefficients is further based in part on a channel equalization applied to the received PTRS.
15 . The method of claim 13 , wherein the received PTRS includes a plurality of PTRS sequences, each PTRS sequence corresponding to a different cluster.
16 . The method of claim 13 , wherein determining the ICI filter coefficients includes determining a vector of ICI filter coefficients that minimizes a residue sum of squares of terms involving the circulant matrix times an ICI filter coefficient vector minus an equalized received PTRS vector.
17 . The method of claim 16 , wherein determining the vector of ICI filter coefficients that minimizes the residue sum of squares includes multiplying the circulant matrix by a Hermitian transpose of the circulant matrix.
18 . The method of claim 13 , wherein determining the ICI filter coefficients includes multiplying an equalized received PTRS vector by an inverse of the circulant matrix.
19 . A receiver for one of a network node and a wireless device (WD), the receiver comprising:
a radio interface configured to receive a phase tracking reference signal (PTRS), and
processing circuitry in communication with the radio interface and configured to:
determine intercarrier interference (ICI) compensation filter coefficients based at least in part on a circulant matrix of known phase tracking reference signal (PTRS) sequences, a PTRS sequence being formed by cyclically extending a base sequence; and
apply a filter having the determined ICI compensation filter coefficients to a received PTRS sequence.
20 . The receiver of claim 19 , wherein determining a set of ICI filter coefficients is further based in part on a channel equalization applied to the received PTRS.