Explain the differences between RedCap device and baseline NR device (legacy UE) capabilities in 5G?
Differences between RedCap device and baseline NR device capabilities:
1-Maximum device bandwidth: A baseline NR device is required to support 100 MHz in frequency range 1 (FR1), and 200 MHz in FR2, for transmission and reception. For RedCap, these requirements are reduced to 20 MHz and 100 MHz, respectively. Such bandwidth reductions however still allow all the physical channels and signals specified for initial acquisition to be readily reusable for RedCap devices, therefore minimizing the impact on network and device deployment when introducing RedCap to support the new use cases.
2-Minimum number of device receive branches: The number of receive branches is related to the number of receive antennas. Reducing the number of receive branches therefore results in a reduction in the number of receive antennas and cost saving. The requirements on the minimum number of receive branches depends on frequency bands. Some frequency bands (most of the FR1 frequency-division duplex (FDD) bands, a handful of FR1 time-division duplex (TDD) bands, and all FR2 bands) require a baseline NR device to be equipped with two receive branches, whereas some other frequency bands, mostly in the FR1 TDD bands, require the device to be equipped with four receive branches.
3-Maximum number of downlink MIMO layers: The maximum number of downlink MIMO layers for a RedCap device is the same as the number of receive branches it supports. This is a reduction compared to the requirements for a baseline device.
4-Maximum downlink modulation order: A baseline NR device is required to support 256QAM in the downlink in FR1. For a RedCap device, the support of downlink 256QAM is optional. For FR1 uplink and FR2, both downlink and uplink, a RedCap device is required to support 64QAM, same as the requirement for a baseline device.
5-Duplex operation: Regarding duplex operations, the only relaxation is for operations in FDD bands. A baseline NR device is required to support a full duplex (FD) operation in an FDD band, i.e., transmitting and receiving on different frequencies at the same time. A typical full-duplex device incorporates a duplex filter to isolate the interference between the device’s transmit and receive paths. In practice, the same device may need to support multiple FDD bands; therefore, multiple duplex filters may be needed to support the FD-FDD operation.
