1=1+1, Smart Duplex Empowers Private 5G with high cost efficiency

Large-scale commercialization of 5G speeds across the world, and is extending 5G’s reach into more industry verticals, including manufacturing, energy, education and transportation. Further, 5G is to be applied in the core sectors of industries to accelerate digital transformation, such as cloud PLC, Cloud AGV and machine vision. Different from consumers’ service requirements, these applications require support for stringent performance of uplink capacity and end-2-end latency.

However, Private 5G networks are still in the early stage. To monetize 5G networks and release 5G value, operators must find the solutions to balance the increasingly service requirements of enterprises and high deployment costs.

Smart Duplex Empowers 1=1+1 by breaking through the limitation of TDD and FDD

Frequency division duplex (FDD) and time division duplex (TDD) are widely used in 4G and 5G networks. The fixed allocation of time/frequency resources of TDD/FDD has both advantages and limitations. With continuous time domain resources but divided frequency domain for downlink and uplink, FDD is characterized by lower latency, lower throughput and scattered spectrum bands. In TDD mode, the time domain resource is split between downlink and uplink, which leads to higher latency.

To meet the requirements for large uplink and low latency of B2B applications, operators usually adopts FDD+TDD dual band networks, that is, FDD for low latency services and TDD for large UL capacity. But this also means higher cost for multi-layer 5G network deployment.

To cope with the technical and economic challenges, ZTE releases Smart Duplex solution to enable 1=1+1 to achieve the low delay of FDD and large capacity of TDD on a single frequency carrier.

Smart Duplex is a promising enhancement to the limitations of conventional duplex operation to improve spectrum flexibility and network efficiency. By embedding FDD mechanism into TDD slots, Smart Duplex allows gNodeB to perform simultaneous transmission and reception at the same time. As shown in the figure, FDD mechanism is introduced in slot1/2/3 within a single carrier by splitting the carrier into sub-bands for downlink and uplink separately.

By combine the advantages of FDD and TDD, Smart Duplex can achieve higher uplink throughput and lower end-to-end latency simultaneously.

Two Smart capabilities make Smart Duplex serve Private 5G networks better

In fact, Smart Duplex extends the traditional duplex division mode from frequency domain or time domain to time-frequency domain. Therefore, it is necessary to introduce the “Smart” capability in frame structure design and radio resource scheduling to improve performance and compatibility.

• Smart Frame Structure with Flexible Slot to enhancecompatibility with 5G Legacy UEs

ZTE has designed the smart and flexible frame structure for Smart Duplex in order to be compatible with 5G legacy UEs. Slots with simultaneous TX/RX are configured as “flexible slot”. In flexible slot, gNodeB can serve different UEs with flexible UL and DL transmission based on service requirement.

• Smart Scheduling to improve spectrum flexibility for excellent performance

Based on the flexible frame structure, gNB can flexibly schedule the DL/UL resources as required. For high-bandwidth UL services, the radio resources in Flexible slot and Uplink slot can all be scheduled. For low-latency services, with DL/UL resources available in every slot, the DL or UL latency can be lowered to about 1 ms. In addition, gNB can also meet the needs of both large UL capacity and low latency through the cross-subband scheduling.

In addition, gNodeB uses UE-level radio resource scheduling mechanisms to be compatible with legacy UEs of half duplex mode.

In 2022, ZTE has released industry’s first smart duplex RRU prototype and achieved an uplink throughput of over 1.4 Gbps for a single carrier while reducing the end-to-end latency to 4 ms in TDD band with 100MHz bandwidth, reaching the best level in the industry. In the inter-operability test, commercial UEs can operate in smart duplex cells properly, including identifying the flexible frame structure, accessing the system properly, and implementing large uplink services and low-latency services simultaneously.

For 5G-Advanced and beyond, full duplex of simultaneous transmission on downlink and uplink is set as the main research direction to further enhance 5G capability with extended use cases, and sub-band full duplex is the key milestone on full duplex evolution. ZTE’s Smart Duplex is based on sub-band full duplex technology. As the evolution to 5G-Advanced accelerates, ZTE will focus on verifying the interworking capability of smart duplex cells with macro cells for public service with cross-link interference suppression schemes to further facilitate private 5G deployment more cost-effectively.

Source: Mobile World Live