How to overcome high latency in the 5G era?
Low latency is a challenge to be overcome in the 5G era
Higher latency or “ping time” means that in Fortnite you’ll find yourself “killed” before you’ve ever seen your opponent; in a game of FIFA, you’ve conceded a goal before you’ve seen the ball kicked. High latency renders games unplayable, causes people to talk over each other in video conferences, and risks killing the market for consumer applications such as Virtual and Augmented reality (VR and AR) that many hope will be major 5G revenue opportunities but are highly latency sensitive.
In the standards for 5G many innovations have been included with the target of reducing latency by 10 or 20 times compared to 4G. The degree to which these are delivered on will in a large part come down to whether we, as an industry, let latency get in the way of a supercharged future.
Channel coding as a latency challenge
As mobile devices of all shapes, sizes and form factors communicate with fixed infrastructure, wireless communications are susceptible to noise and interference. If uncorrected this will lead to the received message differing to the transmitted message and therefore requesting a retransmit.
To address this, before sending a message, transmitters use a channel encoder to protect the communication from these transmission errors by adding additional bits, which enable the receiver decoding the transmitted signal to recompile the message correctly, a process sometimes called forward error correction.
Different types of channel codes exist, each coming with its own benefits and challenges. For 5G, Low Density Parity Check (LDPC) coding has been chosen for the data channel, where the user’s information is transmitted, and Polar Coding has been chosen for the control channel, where the mobile and the base station exchange control information.
Delivering channel coding performance
Although the coding schemes themselves have been standardised, it’s the implementation techniques and algorithms of these channel codes, which are outside of the standardisation process, that can greatly reduce latency and improve Quality of Service (QoS).
Overcoming the latency challenge and unlocking the full power of 5G is the focus of a growing band of channel coding experts, combining in-depth knowledge with unique insights as to the approach the industry should implement when it comes to LDPC and Polar coding.
This expertise is critical because, whilst LDPC codes have been used in Wi-Fi and satellite communications in the past, 5G has adopted the most flexible and most capable LDPC code ever standardised. This flexibility is key to allowing New Radio to meet the requirements of the diverse range of 5G use cases but presents its own challenges.
4G has a fixed timing for the radio whereas 5G supports up to 5 timing options (referred to as numerologies). 5G also supports a much wider range of frequencies, including those above 30HGz referred to as mmWave, and throughputs up to 20X those of LTE. The channel coders and decoders must deliver the required performance for all these different options.
For the industry to go forward and unlock 5G’s full potential, the channel coding challenges of LDPC and Polar have to be overcome if we are to solve the 5G latency challenge. Implementing flexible, high performance decoders is possible – but it requires a fresh approach.
For example, LDPC decoders have to have many elements working in parallel to meet the performance requirements and there are two different established architectures. One of these can efficiently achieve the throughput requirements, but at relatively high latency whereas the other achieves lower latency with reduced efficiency at some throughputs. AccelerComm has developed a unique approach that efficiently delivers on both requirements.
Compared with LDPC codes, Polar codes are far less mature and a conventional approach to their implementation has not yet emerged. The encoder and decoder of a Polar code have regular but intricate structures. AccelerComm’s patented solutions deliver a highly efficient complete 3GPP compliant solution to simplify integration.
Integrating the channel coding building blocks
You can’t build a “one size fits all” when trading off latency, area, throughput and power for multi-market solutions from handset modems, small cell and vRAN infrastructure development. Channel coding has to be addressed with configurability at the design stage to enable optimal cost-effective design choices across not only FPGA and ASIC implementations, but also software-only virtualised network infrastructure.
Innovation in this area includes patented encode and decode IP for both Polar and LDPC coding. For example, AccelerComm has collaborated with Intel to develop a new, highly optimised LDPC decoder in software for its FlexRAN Reference Software. This reference architecture can be implemented in software-based radio stations, which can sit on any part of the wireless networks from edge to core.
Integrating LDPC codes within a FlexRAN-based software-based radio station can increase throughput by up to 3X whilst increasing network power efficiency and reducing latency – ultimately delivering a better user experience and potentially reducing system costs. The same designs also deliver market leading performance when implemented in FPGA and ASIC.
Taking a new look at channel coding
McKinsey has forecast that low latency 5G networks in healthcare could free up additional investment capacity in the sector and generate $250 billion to $420 billion in global GDP impact by 2030, while in manufacturing they see ultra-reliable and low-latency communications (uRLLC) 5G networks potentially having a GDP impact of $400 billion to $650 billion by the decade’s end. At the most recent count, published by the Global mobile Suppliers Association (GSA) at the end of March, 70 operators have now launched commercial 5G services in 40 countries. However, this is just the tip of the iceberg, with 381 operators in 123 countries now investing in 5G.
In a research note published in December 2019, Gartner forecast that by 2021, investments in 5G NR network infrastructure will account for 19% of the total wireless infrastructure revenue of communications service providers (CSPs), up from 6% in 2019. While early 5G applications will focus on fixed wireless access (FWA) and enhanced mobile broadband (eMBB), the analyst firm is expecting first uRLLC private networks and then massive machine-type communications (mMTC) to be deployed between 2021-2025. These later use cases will really stretch the flexibility of 5G.
As more 5G networks are deployed, devices launched, and services commercialised, so the pressure to deliver on the 5G subscriber promise will become more acute. Low latency is not a ‘nice to have’ or something that is the sole preserve of niche ultra-low latency use cases. Rather, it is critical for both today’s mass market applications and tomorrow’s future use cases, be they autonomous vehicles, remote surgery or smart manufacturing. With a relentless downward pressure on revenue and margins, performance must be delivered efficiently.
By addressing latency at the design stage and integrating the latest channel coding technologies and innovations into both physical and software-defined network elements, mobile operators and equipment manufacturers can design-in low latency performance that is fit for the 5G era.
About the author:
Robert Barnes is VP Sales and Marketing at Accelercomm – www.accelercomm.com
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