Huawei’s unified air interface
Huawei is another company looking to influence the outcome with its own R&D. Earlier this year, it said it had created a “unified” air interface which draws on several approaches at once and allows different sub-bands, within the baseband, to be configured individually for different purposes.
Its design is based on three key concepts – Filtered OFDM (fOFDM), Sparse Code Multiple Access (SCMA) and polar code. Each has a contribution to make to a standard which can be adaptable without compromising on the performance requirements, says Huawei.
- fOFDM enables a flexible OFDM interface in which sub-bands are "filtered" so that they can be configured differently from one another to support different use cases with different demands on the network. It can also, according to Huawei, provide twice the system throughput of LTE’s OFDM interface.
- SCMA supports huge numbers of connections and also boosts system throughput by optimizing power allocation across multiple SCMA layers. Huawei said that, in its test, SCMA delivered three times more uplink connections per link and increased downlink system throughput by 80%.
- Meanwhile, polar code is a new coding scheme which claims to deliver increased gain, compared to the turbocoding used in LTE. Polar techniques claim to support channel coding of any code rate with an appropriate code construction to fit any future service requirements.
Huawei says it has trialled these three concepts in early-stage tests on outdoor macrocells in China, which also used two of the most hotly tipped technologies to underpin 5G – advanced multiuser MIMO and full duplex radio (the latter allowing for simultaneous transmit and receive on the same frequency, doubling spectral efficiency). The MU-MIMO implementation supported up to 24 users, and up to 24 parallel layers of transmission on the same time-frequency resources.
And at the NGMN conference in Germany this week, Huawei and partner Vodafone said they have demonstrated that filtered-OFDM, SCMA and polar code work in a stable manner with massive multiuser MIMO (MU-MIMO) antenna technology. They announced that, in a large-scale field trial of macro coverage in a dense urban environment, using the prototype 5G New Radio, they had used the three technologies with MU-MIMO to achieve three times the spectral efficiency of LTE, with air interface latency of 0.5ms in the user plane.
Huawei also claimed a breakthrough on channel coding for 5G networks during a field trial in China, achieving download speeds of 27 Gbps. This further makes the case for polar code, it said, claiming this made that approach the leading candidate for channel coding of 5G communications.
It claimed spectrum efficiency is three times greater with polar coding than with current RAN coding technologies and was appropriate for many 5G use cases and behaviors, including high speed and ultra-low latency wireless communications, and very large device volumes.
“Polar code provides an efficient channel coding technology for 5G allowing significantly higher spectrum efficiency than today’s cellular accesses. It has the practical decoding ability of linear complexity in order to minimise the implementation cost of coming 5G equipment,” Huawei said in a statement.
It added that this technique can optimize channel activity to the point it is running at close to its maximum transfer rate, or Shannon limit, on the encoding side. It also allows close-to-optimal performance on the decoding side, with less complex implementation, it said.
Many players believe the IoT use cases will require a new waveform. Alan Carlson, European head of InterDigital, wrote earlier this year: “The third high capacity solution will be provided in the so-called mmWave bands that start around 30 GHz. This is probably where the most industry debate is going on at this time. This radio may or may not be based on OFDM. A single carrier-based approach is more likely to be selected.
“Simply stated, in moving to higher frequencies and narrower beams, many of the benefits of OFDM such as MIMO integration and higher order QAM schemes diminish and further PAPR (peak to average power ratio) becomes a handicap. So, it is fair to expect something new here as well.”
New trials in millimetre wave spectrum
- AT&T has revealed it will be using the 70 GHz to 80 GHz spectrum band in its trials for point-to-point millimetre wave wireless and wireline networks, to bring fixed-line speeds of 100Mbps to homes outside its wireline footprint in 21 states. These tests will complement its pre-5G trials in 28 GHz and 39 GHz, but will not use a pre-5G radio at this stage. The 70 GHz and 80 GHz bands have mainly been used, to date, for backhaul and proprietary P2P wireless fibre links, and regulations do not currently permit mobility.
The carrier announced trials in Minneapolis last week, using small antenna systems on rooftops to distribute high internet speeds from a fibre-connected property to its neighbours, in the lightly licensed 70 GHz to 80 GHz bands. These signals are then converted into wired internet connections using existing wiring.
Residents in apartment buildings will also be able to receive AT&T’s DirecTV service, by sending a video signal to a single satellite dish on the building which goes to a centralized distribution system in the apartment building.
These very high bands require unobstructed line of sight, and the short wavelengths are susceptible to atmospheric conditions such as rain and fog. However, new antenna arrays are being developed to mitigate these effects, so that millimetre waves do not have to be lined up like microwave P2P communication, and to enable links with a lower degree of precision, which will reduce cost.
AT&T says this trial is not using a 5G radio protocol, unlike its tests with pre-standard 5G in the 28 GHz to 39 GHz licensed bands.
Ed Balcerzak, SVP of commercial and connected communities at AT&T, said: “If successful, this will give us the ability to offer a combination of internet, DirecTV and wireless services to apartment complexes and multifamily communities in additional metro areas.”
- At the NGMN Industry Conference and Exhibition in Germany this seek Huawei and Vodafone tested mobile and fixed services in two emerging 5G spectrum bands. The companies demonstrated a 1.5km cell in the lower C-band (3.7-4.2 GHz for the downlink and 5.925-6.425 GHz for the uplink) and 5 Gbps peak throughput for a single user in the high band. The pair claimed it is the world’s first 5G large-scale mobility field test of macro coverage in dense urban city scenarios.
Huawei and Vodafone signed a 5G strategic memorandum of understanding (MoU) in 2015 and a 5G Technologies Acceleration MoU in 2016.
- Adam Koeppe of Verizon told the NGMN event that field trials in 28 GHz had been positive, using a 100 MHz bandwidth, which has the potential to be aggregated up to 800 MHz. With beamforming and tracking experiments under way, Koeppe thinks some advances can also be taken forward to full mobile 5G, including modelling channel properties and propagation.
- Anritsu was showing channel modelling in 77 GHz for in-building coverage, and also modelling RF distortion and propagation over fiber, alongside VPI Photonics, an area that may be of increasing importance as Cloud-RAN architectures are deployed.
- US Cellular has tested fixed wireless in 28 GHz band, working with Nokia’s AirScale platform. Six simultaneous 4K videos were streamed outdoors at US Cellular's technology centre in Illinois, with data speeds reaching 5 Gbps. Researchers set up a clear line of sight between the base station and user equipment, before obscuring the hardware among trees and foliage, as well as placing obstacles such as dry walls, windows and metal panels along the path.
- Telia and Ericsson have completed a 5G trial on a live network in Europe, achieving peak rates of 15 Gbps and latency of less than 3ms in 800 MHz of spectrum in the 15 GHz band. Telia said the trial, in Kista, in Sweden, marked an “important milestone” in its work with Ericsson to launch 5G services in Stockholm and in Estonian capital Tallinn, in 2018.
Mats Svärdh, head of networks & IT infrastructure for Telia Global Services & Operations, said: “The standardization and development of 5G has just started. Our knowledge and learning from testing in a real outdoor environment will be crucial to understand and develop the 5G technology and networks needed to meet our customers’ future requirements on our services in a digital society.”
* OFDM reduces interference from neighbouring cells and LTE enables a very fast soft hand-off between cells, reducing the signalling load on the network.
Copyright © 2016, Wireless Watch
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