Based on standalone (5G SA) NR 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 improve downlink and uplink capacity simultaneously, and the only solution to boost network capacity and coverage in the same time.
Scenarios and Challenges
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. So 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.
- Scenario 1: Operators get the Mid-range band of 3.5GHz for NR deployment, and already deployed FDD-LTE network. With FAST solution, upgrade one FDD band to LTE/NR with DSS technology to realize quick and seamless NR coverage.
- Scenario 2: 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 4G anchor and impact to existing networks.
Advantages and Highlights
ZTE innovatively proposed FAST solution, which deeply combines middle band TDD carrier with low band FDD carrier to boost 5G system performance of coverage, capacity and latency.
- Mid-low-band coordination to expand coverage: FDD coordinates with TDD to expand the uplink coverage.
- 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, improve uplink and downlink throughput.
- 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.
- Flexible pairing and cross-sector implementation: Based on the standard carrier aggregation framework, FAST can support inter-sector scheduling and coordination flexibly, guarantee user mobility experiences.
Based on the standard carrier aggregation framework which is already widely applied in 4G networks, FAST represents the mainstream solution of 5G NR which supports the flexible coordination of FDD and TDD among inter-cell and inter-site. Furthermore, by taking full consideration of the terminal implementing differentiation and the network strategies of operators, FAST can flexibly aggregate and coordinate FDD and TDD in time and frequency domain to enable spectrum to reach its full potential.
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.