Telecom Review Asia secured an exclusive interview with Mr. Yuan Zhigui, senior network architect at ZTE Corporation to discuss the company’s FDD Assisted Super TDD (FAST) 5G technology and why it is a fundamental ingredient to the success of operators and their businesses.

Could you please explain what ZTE FAST technology is all about?

ZTE FAST (FDD Assisted Super TDD) solution is based on traditional Carrier Aggregation framework with innovative uplink TDM scheduling. Based on standalone (5G SA) New Radio architecture, with close collaboration of FDD low band (n1/n3/n28) and TDD middle band (n78), FAST solution not only improves UL coverage, but also is the only solution to benefit downlink and uplink capacity and the unique solution to boost network capacity and coverage.

FAST deepens the coordination of FDD-NR and TDD-NR in the following ways;

a)Mid-low-band coordination to expand coverage: FAST enables FDD to coordinate with TDD to expand the uplink coverage by 31%.

b)Flexible mid-low-band aggregating and scheduling to enhance capacity: FAST deepens the FDD and TDD spectrum aggregation capability and introduces innovative TDM scheduling to unleash the spectrum potential. With FAST, uplink throughput is improved by over 33% and downlink throughput is improved by over 25%.

c)Coordinating duplex mode of FDD and TDD to reduce latency: With duplex mode coordination, the uplink time slot is 100% available to reduce data transfer latency by 30% compared to 5G TDD mode.

d)Flexible pairing and cross-sector implementation: Based on the standard carrier aggregation framework, FAST can support inter-sector scheduling and coordination flexibly. Compared with other uplink enhancement technologies which can only be used in the same sector, FAST can guarantee the user's mobility experience.

Please note that the above data is based on the scenarios of TDD 3.5GHz (bandwidth 100MHz, frame structure of 2.5ms single)

In terms of 5G deployment and commercialisation, how can ZTE FAST technology make a difference?

3.5GHz band has been widely adopted for initial 5G deployment, but its uplink coverage is weaker than traditional FDD band such as 1.8GHz or 2.1GHz because of its higher propagation loss, higher penetration loss, and less uplink ratio. Therefore, with only mid-range spectrum around 3.5GHz, it is challenged to deploy an evolution-oriented 5G SA network leveraging top-quality and low cost.

ZTE innovatively proposed FAST solution, which combines middle band TDD carrier with low band FDD carrier in accordance with the framework of carrier aggregation (CA), with the addition of innovative UL Time Division Mode (TDM) CA mode. FAST solution can not only enhance UL coverage, but also improve capacity and reduce latency.

FAST solution can be flexibly applied to different scenarios. In the first scenario, operators get the mid-range band of 3.5GHz for NR deployment, and already deployed FDD-LTE network. With FAST solution, first upgrade part of FDD spectrums to LTE/NR with Dynamic Spectrum Sharing (DSS) technology to realize quick and seamless NR coverage with the FDD and TDD co-sited deployment; by combining this FDD band with 3.5GHZ TDD band, NR network performance is further enhanced with uplink and downlink capacity enhanced.

In the second scenario, operators get the mid-range band of 3.5GHz for NR deployment, and acquire new FDD band directly for NR, such as 700MHz in Europe. With FAST solution combining 3.5GHz and 700MHz, operators can build SA overlay networks with contiguous coverage without the help of 4G anchor and without impact to existing networks. With 5G SA networks, operators can explore new business mode with E2E slicing and other 2B service.

FAST unlocks bottleneck of 5G network deployment from the initial launch of 5G. With FAST, operators can deploy a top-quality 5G SA New Radio network with contiguous coverage, low latency and high DL/UL capacity, and avoid the network evolution complexity from NSA to SA.

Have you faced any challenges trying to introduce ZTE FAST to the industry? If so, how are you approaching these issues?

As the innovative 5G solution, FAST confronts the challenge of end-to-end support of ecosystem from terminals to RAN.

First, ZTE has partnered with the main operators, device and terminal manufacturers to push forward the standardization of FAST solution in 3GPP Release 16.

Second, with close collaboration with ZTE, Qualcomm and Media Tek are already list FAST functions in chipset plans and work together for further interoperability tests.

And, by taking full consideration of the difference on terminal antenna implementation, FAST can accommodate all type of terminals by flexibly aggregating and coordinating FDD and TDD in time and frequency domain to enable spectrum to reach its full potential.

ZTE is strive to push forward the ecosystem for wider players, and take full consideration of system compatibility.

Could you tell us a little bit more about the progress of your partnership with China Telecom? Are there any more similar partnerships on the horizon?

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 takes 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.

In Nov 2019, China and ZTE have conducted the first joint verification of FAST. It is 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)

As the main solution for performance enhancement, the domestic and overseas operators are already pay attention on FAST and have the deep technical discussions with ZTE.

ZTE keeps actively promote the research, standardization, compatibility and product realization of the innovative FAST solutions.

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