5G: Full Spectrum Access, New Architecture, New Air Interface
5G will bring about brand-new applications and experiences, triggering the mobile Internet of Everything. 5G will have the following significant characteristics:
- Peak rate of 10 Gbps
- Ultra-low latency of 1 ms
- 100 billion connections
These characteristics require more spectrum, and more importantly, revolutionary innovations in air interface technologies and network architecture. Huawei started researching 5G in 2009 and has now achieved a comprehensive breakthrough in key technologies, including full spectrum, new architecture, and new air interface.
1. Full Spectrum
5G will use the frequency bands below 6 GHz as its primary working band. As supplementary spectral resource, the bands above 6 GHz will be deployed in hotspots and indoor areas. The 5G network, choosing sub-6 GHz as primary frequency, will require no extra construction to roll out. The launch of 5G will need only upgrade of the existing mobile network infrastructures, which are working on low frequency bands, thus protecting investment by reusing sites and increasing spectral efficiency. On the other hand, networking based on high bands is technically insufficient to support wide area networks.
Huawei has demonstrated the world's first 5G testbed working on bands below 6 GHz. Its peak rate reaches 10.32 Gbps. Huawei has also released a millimeter wave system with a peak rate of 115 Gbps, the highest peak rate in the world.
2. New Architecture
5G will support multiple services covering enhanced mobile broadband and vertical industries, which bring about highly diverse requirements. To meet such requirements, the 5G network architecture must accommodate different services. The new architecture proposed by Huawei is based on SDN and NFV technologies, meaning a physical network can connect to hundreds of industries using virtual network slicing technology. The new architecture of 5G has the following highlights:
Industry Defined Network Slicing
Will one or multiple physical networks be used to meet service requirements in different industries in the 5G era? Huawei believes that we should use one single physical network to meet all these requirements by using the virtual network slicing technology.
Service-Oriented Cloud Formation
Based on SDN and NFV technologies, the service-oriented cloud formation emerges. 5G, with existing hardware, is able to implement centralized resource allocation and network functions virtualization. The network is simplified by logically separating the control plane from the user plane. Functions needed by different services are deployed on the relevant physical nodes by using software. For example, the control plane and user plane of the network slice that operates autonomous automobiles are located closest to users to ensure milliseconds-class latency.
Internet Architectural Operation
The 5G network is flat and needs an Internet-based operating system thanks to the separation of software and hardware, as well as the separation of control plane and user plane. With the introduction of Internet-based operating system, end users, developers, operators, and partners can access the same operating system simultaneously. 5G network operators can efficiently deploy different functions to meet various customer requirements from different industries.
3. New Air Interface
The air interface is the key distinction between generations of mobile communication technologies. Like in 3G and 4G, revolutionary air interface technology is also introduced in 5G. With new air interface technologies, 5G can meet differentiated service requirements and maximize the spectrum efficiency.
Huawei has achieved a comprehensive breakthrough in terms of the air interface:
1) Basic Wave Form -- Filtered Orthogonal Frequency Division Multiplexing (F-OFDM)
The subcarrier interval of OFDM in 4G is fixed as 15 KHz. The subcarriers of F-OFDM are more adaptable to various services and maximize the spectrum utilization.
Applying this technology will enable the 5G system to use different waveforms, multiple access modes, and frame structures according to the application scenarios and service requirements. F-OFDM can support various transmission waveforms and OFDM parameter configurations. Different sub-band filters divide the OFDM subcarriers into several groups, which adopt different subcarrier intervals, symbol lengths, and guard time intervals. With the flexibility of simultaneously supporting multiple groups of parameter configurations, F-OFDM provides better parameter choices and resource configurations for each service group to efficiently improve the spectral efficiency of the entire system.
2) Channel Coding -- Polar Code
Polar code is now the only code that is proven to reach the Shannon capacity. When the code blocks are large enough, Polar Code can use encoders and successive-cancellation decoders to reach the Shannon capacity. In 5G air interface design, Polar Code is one of the best candidate coding technologies to encode the forward error correction code (FEC). It outperforms the channel coding currently used in the 4G system. Polar Code is especially suitable for the short code scenarios.
3) Multiple Access Technology -- Sparse Code Multiple Access (SCMA)
SCMA is a new multiple access technology for the 5G new air interface. Its core purpose is to implement a new non-orthogonal multiple access mode. Because the sparse code is introduced in SCMA on the basis of OFDMA, the number of connections can increase by 300%. In addition, Grant Free, the multiuser blind detection receiving technology is introduced in the receiving terminal of SCMA to implement "arrive to go", that means zero latency between sending and receiving. The multiple access technology of SCMA can support massive connections, reduce transmission latency, and save UE power consumption.
In 4G, there are two duplex modes: frequency division duplex (FDD) and time division duplex (TDD). In an FDD system, the uplink and downlink use different frequencies. In a TDD system, the uplink and downlink use different timeslots. In a full-duplex system, the uplink and downlink use the same frequency and timeslot, which increases system capacity and spectral efficiency. The theoretical gain is nearly 100%.
Based on FDD and TDD, a new generation of TDD and full duplex technology will be introduced to 5G.
5) Massive MIMO
The Massive-MIMO technology uses the dense array of antenna space domain to increase the number of physical sites by deploying a massive antenna array on the network side and terminal side, and significantly improves the spectral efficiency.
According to the test result released by Huawei, Huawei 5G new air interface technology can improve spectral efficiency by three times without adding antennas and sites. If the Massive MIMO technology is also used, spectral efficiency will be improved by far more than three times.