Collision management of LTE NR reference signals
Embodiments of methods in a base station and a UE are disclosed. In some embodiments, a method implemented in a network node includes any one or more of: selectively puncturing transmission of LTE CRS symbols that overlap NR DMRS symbols in a downlink transmission time interval; selectively puncturing transmission of NR DMRS symbols that overlap LTE CRS symbols in the downlink transmission time interval; and selectively reducing a number of NR DMRS symbols transmitted to the UE in the downlink transmission time interval. In some embodiments, a method implemented in a UE includes identifying, in a downlink channel, subchannels containing NR DMRS symbols that are corrupted due to collision with LTE CRS symbols. For each identified subchannel: a respective time averaged channel estimate is determined based on NR DMRS symbols that are not corrupted due to collision with the LTE CRS symbols; and a respective MMSE weight is determined using the time averaged channel estimate.
1. A method implemented in a network node, the method comprising any one or more of:
selectively puncturing transmission of LTE CRS symbols that overlap NR DMRS symbols in a downlink transmission time interval;
selectively puncturing transmission of NR DMRS symbols that overlap LTE CRS symbols in the downlink transmission time interval; and
selectively reducing DMRS signaling to the UE to avoid overlap with LTE CRS symbols.
2. The method as claimed in claim 1 , wherein the network node is configured to transmit LTE and NR symbols in respective different physical resource blocks, PRBs, and wherein selectively puncturing transmission of LTE CRS symbols that overlap NR DMRS symbols in a downlink transmission time interval comprises puncturing transmission of LTE CRS in PRBs allocated for NR symbols.
3. The method as claimed in claim 2 , wherein puncturing transmission of LTE CRS in PRBs allocated for NR symbols comprises:
generating ( 902 ) a reference signal sequence;
mapping ( 908 ) the reference signal sequence to complex valued modulation symbols used as reference symbols; and
puncturing ( 910 ) the complex valued modulation symbols by setting symbol values that overlap NR DMRS symbols to zero.
4. The method as claimed in claim 1 , wherein selectively reducing DMRS signaling to avoid overlap with LTE CRS symbols comprises using a single symbol DMRS pattern without any additional DMRS positions.
5. The method as claimed in claim 4 , further comprising transmitting a tracking reference signal.
6. A network node comprising processing circuitry configured to implement a method including any one or more of:
selectively puncturing transmission of LTE CRS symbols that overlap NR DMRS symbols in a downlink transmission time interval;
selectively puncturing transmission of NR DMRS symbols that overlap LTE CRS symbols in the downlink transmission time interval; and
selectively reducing DMRS signaling to the UE to avoid overlap with LTE CRS symbols.