ZTE FDD Assisted Super TDD 5G Solution (FAST) to Build the Superior Network - Mobile World Live

ZTE FDD Assisted Super TDD 5G Solution (FAST) to Build the Superior Network

27 FEB 2020


5G Rollout Facing Challenges

5G is the fastest-adopted mobile generation with nearly 10% of all LTE operators deployed 5G by the end of 2019. In 2020, 5G is expected to fast approach for mass-market launch, despite some concerns over coverage and uplink throughput capabilities.

The mid-range bands around 3.5GHz is the prime spectrum for 5G commercial network. Compared to legacy FDD-LTE frequency band (1.8 GHz /2.1 GHz), this new spectrum band means higher path loss and penetration loss, especially in indoor deep coverage scenarios, which brings coverage gap between 5G and 4G network. So 5G is facing the challenge to fulfill coverage requirements in the early stages of network rollout. Another challenge comes from UHD Video and VR/AR, the biggest drivers of mobile data traffic growth in the 5G era, which expect 5G to provide significantly faster mobile broadband speeds and lower latencies than previous generations, especially on the uplink.

To address the above problems, ZTE launched FDD Assisted Super TDD 5G Solution (FAST) to facilitate 5G commercialization.

ZTE FAST Briefing

The 5G cellular network of the mid-range bands around 3.5GHz is based on Time Division Duplex (TDD) mode, which means that base stations and end-user devices transmit using the same channel at different times, while the lower-bands of 5G NR (including 700MHz, 1.8GHz and 2.1GHz) are based on Frequency Division Duplex (FDD) mode. With deep coordination in both time and frequency domain, FDD Assisted Super TDD 5G Solution (FAST) enabled harmonized spectrums to boost 5G system performance.

  • FDD Supplementing TDD to Expand Coverage: FAST enables FDD coordination with TDD, which expands uplink coverage to fill TDD coverage gap. The contiguous coverage of 5G networks can be ensured with FDD and TDD co-sited.
  • FDD Aggregating TDD to Enhance Capacity: FAST deepens FDD and TDD spectrum aggregation capability by maximizing the number of data streams in both downlink and uplink.

For UE with 2Tx (transmit channels) in uplink, with the introduction of innovative TDM (Time Division Mode) CA (Carrier Aggregation), FAST can combine the advantages of TDD and FDD. In TDD uplink time slots UE can send data on TDD spectrum, and in other time slots, UE is switched to FDD spectrum for data sending. By making full utilization of time-frequency resources, uplink throughput is enhanced.

  • FDD Coordinating TDD to Reduce Latency: FAST integrates the advantages of FDD and TDD to reduce service latencies. After receiving base station’s data, UE flexibly selects proper slot of TDD or FDD to send acknowledgement.

With ZTE FAST solution, 5G networks guarantee superior coverage and capacity.

ZTE FAST Boost 5G performance

With deep aggregation and cooperation in high and low spectrum bands and FDD/TDD duplex modes, FAST enhances 5G system capabilities in the following ways:

  • Strongest Radio Resources Scheduling Capability: FAST schedules terminals to transmit data on both FDD and TDD spectrum with multi-stream to maximize spectrum efficiency. It is a unique solution in industry that supports three streams data transmitting from the terminal to base station.
  • Best Compatibility with All Terminals: Taking full consideration of terminals’ implementation differences (supporting 3GPP R15 or R16), the solution can flexibly match terminal’s multi-band and multi-stream capability with resource scheduling algorithms to maximize system performance.
  • Widest Spectrum Aggregation Capability: FAST strengthens high and low spectrum cooperation so that in the weak coverage area of high-band, terminals can transmit data on low-band with uplink coverage expansion, while downlink capacity can still benefit from high and low spectrum aggregation to further improve the throughput.
  • Fastest System Coordination Capability: FDD and TDD integration flexibly adapts duplex modes to service latency requirements. If downlink data is sent with TDD for ultra-fast speed, uplink can use FDD for instant acknowledgement instead of restricting to TDD mode. By decoupling the duplex modes, the minimum service latency is reduced.

Progress of FAST

China Telecom, the major Chinese telecom operators, is aiming to build a nationwide 5G network and keep promoting the research and deployment of 5G network and applications. With deepened 5G cooperation with ZTE, China Telecom took FAST as key 5G solution to support 5G ever-growing data traffic and fulfill requirements of increasing applications, including environmental governance, intelligent education and other industries, thus to facilitate the intelligent transformation and upgrade of traditional industries.

With joint verification conducted by China Telecom and ZTE, it was proved that FAST can improve downlink throughput by 15% and uplink throughput by 16% in cell center with TDM CA, expand the coverage by 24.5% and reduce latency by 20%.(*the test result is based on the 2.1GHz and 3.5GHz)


By enhancing the throughput in both downlink and uplink and expanding the coverage of 5G network, FAST surmounts the challenges of 5G deployment and ensures a smooth, cost-efficient way to deploy the 5G network.



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