PUSCH Reference Signal Design for High Doppler Frequency
A method is provided for communication in a wireless telecommunication system. The method comprises transmitting, by a UE, a DMRS, wherein REs carrying the DMRS are separated into a plurality of portions, each of the portions occupying a different OFDM symbol in a single slot of a radio subframe. In one aspect, a new PUSCH DMRS format may provide accurate channel estimates, increased RS density in the time domain at the expense of relaxed PAPR, and/or a symmetric pattern to ease the channel estimation algorithm. The PUSCH DMRS format may provide sufficient RS density in the time domain to enable accurate channel estimation for high Doppler scenarios.
1 . A method for communication in a wireless telecommunication system, the method comprising:
transmitting, by a user equipment (UE), a demodulation reference signal (DMRS), wherein resource elements (REs) carrying the DMRS are separated into a plurality of portions, each of the portions occupying a different orthogonal frequency division multiplexing (OFDM) symbol in a single slot of a radio subframe.
2 . The method of claim 1 , wherein, in an OFDM symbol occupied by one of the portions, REs not used for carrying the DMRS are used for carrying data.
3 . The method of claim 1 , wherein, in the OFDM symbol occupied by one of the portions, the data symbols are Discrete Fourier Transform (DFT) precoded and subsequently mapped on to the REs that are not used for carrying the DMRS.
4 . The method of claim 3 , wherein the length of the DFT is equal to the number of data symbols.
5 . The method of claim 1 , wherein the REs carrying the DMRS are separated into two portions with six REs in each portion, and wherein REs in a first portion occupy even numbered subcarriers in the slot and REs in a second portion occupy odd numbered subcarriers in the slot, and wherein OFDM symbols carrying the DMRS are separated by at least one OFDM symbol.
6 . The method of claim 1 , wherein the REs carrying the DMRS are separated into two portions with six REs in each portion, and wherein REs in each portion occupy the same subcarriers, and wherein the subcarriers carrying the DMRS are separated by a subcarrier carrying data, and wherein OFDM symbols carrying the DMRS are separated by at least one OFDM symbol.
7 . The method of claim 1 , wherein the REs carrying the DMRS are separated into three portions with four REs in each portion, and wherein all of the REs carrying the DMRS occupy different subcarriers, and wherein OFDM symbols carrying the DMRS are separated by at least one OFDM symbol.
8 . The method of claim 1 , wherein the REs carrying the DMRS are separated into four portions with three REs in each portion, and wherein all of the REs carrying the DMRS occupy different or same subcarriers, and wherein OFDM symbols carrying the DMRS are separated by at least one OFDM symbol.
9 . The method of claim 1 , wherein a DMRS sequence has a length of half of the number of subcarriers of a physical uplink shared channel (PUSCH).
10 . The method of claim 1 , wherein a cyclic shift α λ in a slot n s to generate a DMRS sequence is given as α λ =2πn cs,λ /6 with n cs,λ =(n DMRS (1) +n DMRS,λ +n PN (n s ))mod 6.
11 . The method of claim 1 , wherein an orthogonal cover code (OCC) is applied to the plurality of portions in the slot.
12 . The method of claim 11 , wherein the same OCC is repeated in a second slot of the subframe.
13 . The method of claim 1 , wherein the UE receives information regarding a pattern of the plurality of portions via one of:
radio resource control signaling; and
a Layer 1 resource grant; and
a medium access control (MAC) control element.
14 . The method of claim 13 , wherein, when the UE receives the information regarding the pattern of the plurality of portions via radio resource control signaling, the information is received in a parameter in a PUSCH-ConfigDedicated information element.
15 . The method of claim 13 , wherein the parameter is one of:
a single-bit parameter specifying whether a pre-defined pattern of the plurality of portions is used; and
a multiple-bit parameter specifying which one of a plurality of patterns of the plurality of portions is used.
16 . A user equipment (UE) comprising:
a transmitter configured to transmit a demodulation reference signal (DMRS), wherein the DMRS occupies at least two orthogonal frequency division multiplexing (OFDM) symbols in a single slot of a radio subframe, and wherein each of the at least two OFDM symbols comprises resource elements (REs) carrying the DMRS interleaved in the frequency domain with REs carrying data.
17 . The UE of claim 16 , wherein, in an OFDM occupied by one of the portions of the DMRS, the data are Discrete Fourier Transform (DFT) precoded and subsequently mapped on to the REs that are not used for carrying the DMRS.
18 . The UE of claim 16 , wherein the length of the DFT is equal to the number of data symbols.
19 . The UE of claim 16 , wherein the REs carrying the DMRS are separated into two portions with six REs in each portion, and wherein REs in a first portion occupy even numbered subcarriers in the slot and REs in a second portion occupy odd numbered subcarriers in the slot, and wherein OFDM symbols carrying the DMRS are separated by at least one OFDM symbol carrying data.
20 . The UE of claim 16 , wherein the REs carrying the DMRS are separated into two portions with six REs in each portion, and wherein REs in each portion occupy the same subcarriers, and wherein the subcarriers carrying the DMRS are separated by a subcarrier carrying data, and wherein OFDM symbols carrying the DMRS are separated by at least one OFDM symbol carrying data.
21 . The UE of claim 16 , wherein the REs carrying the DMRS are separated into three portions with four REs in each portion, and wherein all of the REs carrying the DMRS occupy different subcarriers, and wherein OFDM symbols carrying the DMRS are separated by at least one OFDM symbol carrying data.
22 . The UE of claim 16 , wherein the REs carrying the DMRS are separated into four portions with three REs in each portion, and wherein all of the REs carrying the DMRS occupy different or same subcarriers, and wherein OFDM symbols carrying the DMRS are separated by at least one OFDM symbol carrying data.
23 . The UE of claim 16 , wherein the UE performs N/2-point fast Fourier transform (FFT) on data to be transmitted, where N is the number of physical uplink shared channel subcarriers, and wherein the UE multiplexes the data with the DMRS, and wherein the UE performs M-point inverse FFT (IFFT) on the multiplexed data and DMRS, where M is an IFFT size corresponding to a system bandwidth.
24 . The UE of claim 16 , wherein, when the UE possesses information indicating that the UE is moving at a high speed, the UE transmits a request to use a DMRS that occupies at least two OFDM symbols in a single slot of a radio subframe.
25 . A network element comprising:
a receiver configured to receive a plurality of resource elements (REs) carrying a demodulation reference signal (DMRS), wherein the plurality of REs are received in a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a single slot of a radio subframe.
26 . The network element of claim 25 , wherein the plurality of REs are interleaved in the frequency domain with REs carrying data.
27 . The network element of claim 25 , wherein the network element transmits the information regarding the pattern of the plurality of REs to a user equipment (UE) when the network element possesses information indicating that the UE is moving at a high speed.
28 . The network element of claim 25 , wherein the network element transmits the information regarding the pattern of the plurality of REs to a user equipment (UE) in a handover Command message when the network element possesses information indicating that the UE is being handed over to another network element.
29 . The network element of claim 25 , wherein the network element transmits the information regarding the pattern of the plurality of REs of a user equipment (UE) to another network element when the network element possesses information indicating that the UE is being handed over to another network element.