5G-NR TRS (Tracking Ref Signal) Mapping on Physical Resource Grid

5G-NR TRS (Tracking Ref Signal) Mapping on Physical Resource Grid

Why is TRS required?

  • TRS is Tracking Reference Signal, which is also a kind of CSI-RS.
  • When the UE receives downlink data transmission, it needs to constantly track and compensate for the time and frequency offset's (deviations). TRS is used to perform this function.
  • The UE tracks time/frequency deviation by measuring CSI-RS configured for TRS.

Time-Frequency Resource Characteristics of TRS

For FR1(B6G), TRS has the following characteristics (38.214-5.1.6.1.1 CSI-RS for tracking):

  • It is a NZP-CSI-RS-Resource Set composed of 4 periodic nzp-CSI-RS resources, and this resource set will be configured with the parameter "trs-Info true"
  • The UE may be configured with a NZP CSI-RS set, where a NZP-CSI-RS-ResourceSet consists of four periodic NZP CSI-RS resources in two consecutive slots
  • . Two CSI-RS resources are mapped in each slot, and the time domain interval is a fixed 4 symbols (l∈{4,8}, l∈{5,9}, or l∈{6,10} for FR 1)
  • Each CSI-RS resource is 1-port and density-3

For FR2 (A6G), TRS has the following characteristics (38.214-5.1.6.1.1 CSI-RS for tracking):

  • It is a NZP-CSI-RS-Resource Set composed of either 2 or 4 periodic nzp-CSI-RS resources, and this resource set will be configured with the parameter "trs-Info true"
  • The UE may be configured with a NZP CSI-RS set, where a NZP-CSI-RS-ResourceSet consists of two CSI-RS resources in one slot
  • Or with a NZP-CSI-RS-ResourceSet of four NZP CSI-RS resources in two consecutive slots with two NZP CSI-RS resources in each slot.?
  • Two CSI-RS resources are mapped in one slot or two slots, and the time domain interval is a fixed 4 symbols (l∈{0,4},l∈{1,5},l∈{2,6},l∈{3,7},l∈{7,11},l∈{8,12},l∈{9,13} for FR 12
  • Each CSI-RS resource is 1-port and density-3


Below is an example of FR2 TRS RE's Mapping on a Physical Grid where The UE is configured with a NZP CSI-RS set that consists of two CSI-RS resources in one slot.

No alt text provided for this image

From above example TRS Periodicity=160slots & SCS is 120Khz.

For 120Khz SCS One Radio Frame has 80 slots, hence periodicity of TRS is 20ms(160 slots).

In every 20ms, prbs from 0 to 68 with density of 3( three REs) will have TRS with?(nzp-CSI-RS-ResourceId 0 & nzp-CSI-RS-ResourceId 1) Time-Frequency resources located as shown in the picture.


Pappu Kumar Chaurasia

Test Manager | 5G SA/NSA | LTE | NB-IoT | UE (L1,L2,L3) LOG ANALYSIS | Device Protocol Testing

10 个月

Naveen Chelikani can you pls help me to understand how you have taken k0=1. From frequencyDomainAllocation row1 : 0010, It value seems to be 2 in decimal. Or its just position index we need to take from 0010.

Venkatesh Thalluri

NR SmallCell || 5GNR Option 6 & 7 || L1Phy Layer Optimization/Dev Avx512/C/C++/STL || FH Interface eCpri || ORAN M-Plane || Qxdm/Fapi/IQ Logs Analysist ll BLER/Throughput/UE Attach/Config Issues Debugger || URLLC

1 年

Naveen Chelikani already 5G has channel dmrs to correct time and frequency deviation right.....why we need TRS specially ??.....can you please tell

回复
Suresh Majjara

Senior RF Engineer @ T-Mobile

1 年

Nicely written

Susanta Bose

Lead Engineer at Radisys Corporation

1 年

Thanks Naveen Chelikani . Keep posting such informative articles

Venkatesh Thalluri

NR SmallCell || 5GNR Option 6 & 7 || L1Phy Layer Optimization/Dev Avx512/C/C++/STL || FH Interface eCpri || ORAN M-Plane || Qxdm/Fapi/IQ Logs Analysist ll BLER/Throughput/UE Attach/Config Issues Debugger || URLLC

1 年

Thanks Naveen Chelikani......for your valuable post....please post more on Phy layer

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