# Compatibility Analysis Between RedCap Non-Public Networks and 5G NR in TDD FR1 and FR2 Bands
## 3 Key Limitations of RedCap's Technological Capabilities  
RedCap technology, also known as NR-Light, represents a breakthrough in creating low-cost, simplified IoT devices. It extends the benefits of 5G NR to battery-powered  
Figure 1: Standardization plans of RedCap technology. applications while maintaining efficiency and reducing complexity. Pioneering a departure from the preceding reliance on extant 4G technologies such as NB-IoT or LTE-M for IoT services on 5G NR networks, RedCap technology introduces technical advancements primarily manifested at the Radio Resource Control (RRC) [TS 38.331] and Packet Data Convergence Protocol (PDCP) layers of the 5G NR network, with discernible implications for Internet of Things (IoT) and massive machine-type communication (mMTC) services. An exploration of the principal innovations within RedCap technology reveals nuanced modifications affecting the throughput, receiving channels, Multiple Input Multiple Output (MIMO) levels in the downlink, downlink modulation order, and duplex operation modes of the subscriber device. In terms of maximum throughput, the NR basic subscriber device, operating within frequency channels up to 100 MHz wide in the FR1 sub-band (410-7125 MHz) and up to 200 MHz in the FR2 sub-band (24.250-52.600 GHz) for transmission and reception, undergoes a reduction in RedCap technology to 20 MHz and 100 MHz, respectively. This reduction, while constraining frequency channel width, accommodates the reuse of physical channels and signals specified for initial data collection, thereby mitigating adverse impacts on network and device deployments. RedCap technology minimizes the number of receiving channels required, reducing reliance on antennas and lowering equipment costs. The maximum number of MIMO levels in the downlink for a RedCap subscriber unit aligns with the number of receiving channels it supports (2 \(\times\) 2 MIMO DL and 1 UL SISO), deviating from the more expansive capabilities of a basic 5G NR subscriber device. This reduction in MIMO levels is underscored by a comparative analysis against the conventional requirements for a basic 5G NR subscriber device, which may support up to eight levels of Single-User (SU) MIMO. Considering downlink modulation orders, the RedCap device introduces flexibility by rendering the support for 256 QAM in the downlink optional, in contrast to the mandatory requirement for the NR base unit. The uplink for both FR1 and FR2 mandates 64 QAM support for the RedCap device, mirroring the baseline device. In the realm of duplex operation modes, the focal simplification pertains to RedCap's operation in Frequency Division Duplex (FDD) bands. Unlike the 5G NR base subscriber device, which must support full duplex (FD) operation, including simultaneous transmission and reception at distinct duplex frequencies, the RedCap device exhibits streamlined operation within the FDD bands. This simplification arises from the elimination of the need for simultaneous transmission and reception, resulting in a more straightforward operational framework for RedCap technology in FDD bands. The nuanced intricacies of full-duplex devices, involving the utilization of duplex filters to mitigate interference, are notably alleviated in RedCap's operational context. The forthcoming investigations in Release 18 aim to refine the specifics of RedCap devices in frequency bands mandating at least four receive channels, addressing ongoing considerations related to the number of required receiving channels in this context. The abovementioned limitations are similar to those that existed in LTE IoT standards such as NB-IoT or LTE-M; at the same, time there is another issue that arose particularly for RedCap since 5G NR, unlike LTE, is a more Time Division Duplex (TDD)-focused technology. In TDD, it is important to distribute time slots between DL and UL and to synchronize it to avoid inter-link interference between different networks [10] due to the advent of extended MTC in non-public networks (NNNs) within industrial settings.