The 5G NR (new radio) standard was completed in June 2018. Although this was an announcement that industry personnel across the board agreed was an enormous tick in the box, and one that was a long time coming, this latest standard specification presents some significant challenges for systems designers transitioning from 4G to 5G. For instance, compared to 4G, 5G will use different operate on different radio spectrum frequencies, connect many more devices to the internet, minimise delays, and deliver ultra-fast speeds.
Achieving more with 5G
5G brings with it an increased data rate and increased mobile broadband network capacity. To achieve this goal, 5G will use higher frequencies, which will require different baseband algorithms and radio architectures to contain cost and accomplish performance goals.
5G NR introduces significant changes to the physical layer of mobile communication systems requiring baseband modems to implement flexible algorithms to achieve the high-speed, high-capacity, and low-latency goals of 5G. These changes affect the design of the receivers in base stations and mobile devices, and they have a large impact on the testing strategy for all components in a 5G NR system.
Because 5G requires operation at higher millimetre wave (mmWave) frequencies, it necessitates dramatic changes to the architecture of the radio front end, including massive MIMO (multiple input, multiple output) antenna arrays and beamforming techniques to overcome high frequency propagation losses. The proficiency required to design the highly integrated 5G radio technology includes RF, antenna, DSP (Digital Signal Processing), control logic, hardware, and software – as well as a working knowledge of the new standard specifications. 5G system and design engineers need the latest methods to verify that components will work together and eliminate the problems that lead to expensive hardware failures and delays to project run-times.
5G design engineers must avoid approaches that are too siloed with different methodologies and different teams, as this will cause issues further down the line. Engineering organisations that have separate workflows for doing baseband, RF front end, and antenna design will likely struggle to keep pace with their peers. For example, achieving power efficiency and linear performance across wide bandwidths in the RF front-end, including power amplifiers is another obstacle that needs to be overcome. This requires adaptive DSP techniques such as DPD (digital predistortion), which often must be designed and verified in simulation before the RF hardware is even available.
Looking to FPGA prototypes and test beds
The increased complexity of 5G NR is prompting development teams to look to FPGA (field-programmable gate array) prototypes and test beds to validate their designs. This is a significant hurdle for many teams that lack experience with FPGA development workflows and RTL (register-transfer level) implementation of signal processing and communications algorithms. For a typical R&D group that consists of engineers with strong signal processing and algorithm development backgrounds but relatively little experience with hardware implementation, it is often difficult to implement these radio prototypes and testbeds without outside assistance.
But that’s not all the wireless networks community need to be aware of. 5G radio and network designs also need to account for several effects as a result the use of mmWave frequencies. These now make it essential for designers to characterise RF signal propagation channels in various outdoor and indoor scenarios early in the R&D process. While higher frequencies are essential to transmitting information at ultra-fast rates, unfortunately there is an unwanted side-effect that they don’t travel as far and are easily absorbed by the atmosphere, terrain, and other objects.
Getting investment right first time
As is abundantly clear, the journey to 5G success is not all smooth-sailing – the technologies that enable 5G to function can drive up the cost of development and create a strong incentive to get the implementation right the first time. To successfully transition from 4G to 5G and create a totally new mobile network that works, it is crucial for designers to utilise tools that enable modelling and simulation of the critical 5GNR technologies and ensure conformance to the standard specification.
Fortunately, there are new tools available that help engineers efficiently explore algorithms and architectures, optimise system performance, identify critical problems in simulation, and automate hardware implementation and testing on COTS (Commercial Off-The-Shelf) or custom hardware.
Furthermore, software that provides 5G-compliant waveforms, algorithms, and end-to-end reference models can simplify the process of design space exploration, design verification, and conformance testing. This will be especially useful to engineers working in all aspects of 5G development as they will all need a means to ensure that their design conforms to the 5G standard.
New modelling software can also provide multi-domain simulation that permits full-system verification of digital, RF, and antenna design, technology key for engineers designing new massive MIMO antenna arrays and RF front end architectures. Previously, these different domains were typically designed separately, using different specialist tools for each component, but now they can be planned and simulated in unison, resulting in more precise results and quicker design cycles.
This approach is being used successfully by engineers designing various 5G technologies, such as digital predistortion & CFR (crest factor reduction) algorithms, which require fast simulation of accurate RF models together with compensating DSP algorithms. Another example includes hybrid beamforming for massive MIMO systems, where the number of digital receiver paths can be limited by partitioning beamforming across analogue and digital parts of the system. The strategy is also of use when it comes to future antenna architectures where the tightly coupled nature of the system requires antenna, RF and digital ICs to be considered as an integrated system.
What if you have limited hardware experience?
For engineers with limited hardware experience to create and deploy hardware test beds, all is not lost. Fortunately, the latest model-based design techniques enable those engineers to take algorithms all the way from concept to 5G testbeds, and then on to production-quality IP implementations for future 5G ASICs (application-specific integrated circuits). This is particularly suited for prototyping and proof-of-concept projects with tight design schedules. Engineers are no longer dependent on specialised hardware experts.
As opposed to a traditional process, this approach has several benefits. First, using a single model for simulation and code generation greatly simplifies the process and eliminates handoffs between system design and implementation teams. Second, models can be interfaced to a range of commercially available RF test and SDR equipment from different vendors. This enables flexible, cost-effective design verification with live RF signals. And third, Once the model has been verified, it is ready for FPGA implementation. Iteration cycles for design changes are much shorter, enabling the engineering team to respond quickly to changes in specifications or standards. The generated HDL (hardware description language) code is hardware-independent and can be deployed to COTS and custom testbed hardware.
Modelling and simulation key
Harnessing modelling and simulation is key to smarter 5G design practice, something engineers should be doing not only because it will save organisations time and money, but also for the simple fact that it will make 5G engineers lives easier! The fundamental benefit though is that as the specifications and engineering changes are coming in to the design teams, they can iterate on their designs quickly. They’re able to ensure that their designs can support the new changes. And then to validate it, they can quickly take the new version of what they are working on and deploy it in a radio test bed.
Modelling tools allow designers to verify their projects using simulation, rather than waiting for expensive and time-consuming lab and field tests. The models can be used as a golden reference for implementation and can help to automate testing in order to verify that designs function correctly throughout the development process.
Instead of waiting for expensive and time-consuming lab and field tests, modelling tools allow designers to verify their projects using simulation. The models become something of a blueprint for implementation, and they can help verify that designs function correctly throughout the development process via automated testing.
Ken Karnofsky, Senior Strategist for Signal Processing Applications, MathWorks
Image Credit: O2
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