Open Modular-Based Radio: The Trade-Off Between Flexibility and Performance

Field Programmable Gate Array (FPGA) is an integrated circuit designed for designers or customers to flexibly configure the hardware to realize certain processing functionalities after manufacturing. According to a standard processing hardware development procedure, once the performance requirements are well understood, the designed functions are hardened onto Application-Specific Integrated Circuit (ASIC) for high-speed, cost-effective, and large volumes market provisioning. Such historical strategy works well for most applications that require optimization and high volumes, including radio network deployments of previous wireless generations, such as 4G/3G/2G. However, with the advent of 5G, the rapid growth of data traffic and various service requirements may force network operators and their ecosystem partners to look for a new way to design these systems. As network operators are under pressure to speed up their 5G deployments, there are many new technologies being considered, especially on the radio side—such as beamforming, bandwidth support, and processing requirements—that are still evolving.

With the market learning what 5G can truly offer, flexibility is definitely one of the key focuses, especially for radio units. Recent market activities show that many chipset suppliers and equipment vendors have been aware of the market trend and are working hard to develop new products to balance radio flexibility design and high-performance connectivity with lower cost. Xilinx recently published its Zynq RFSoC DFE adaptable radio platform that hardens the Digital Front End (DFE) for massive MIMO radio and a wide range of other applications. Built on an adaptive single-chip platform integrating all DFE IPs along with programmable logic, the solution leverages the technology to offer flexibility, scalability and fast deployment benefits for a potential market presence. Similarly, Marvell announced its 5G O-RAN platform that consists of silicon, software, and hardware reference design spanning the whole gamut of radio functions. Qualcomm also introduced a full portfolio of 5G infrastructure semiconductor platform to accelerate the cellular ecosystem transition toward Open vRAN driven by 5G. TIP’s OpenRAN Whitebox RU sub-group, a collaboration with leading vendor partners, harmonizes different requirements to develop Whitebox radio based on an open interface and modular approach.

The initial 5G network deployment, under the 3rd Generation Partnership Project (3GPP) standard guideline, mainly focused on enhanced Mobile Broadband (eMBB), aiming to provide improved data rate performance, especially in the consumer market. The market adaptation of the 5G solution was quick and successful. However, this achievement does not show that the deployed network solutions have been optimized completely. From a technology perspective, the implementation of existing massive MIMO technology still needs significant improvements. With the advent of Artificial Intelligence (AI)/Machine Learning (ML) technology, MIMO beamset components can be further optimized to offer high-qualitty granular user-level service assurance. Moreover, the delayed 5G spectrum auctions in certain geographical regions and the promotion of RAN sharing strategy show that more flexible communication bandwidth and hardware processing supports are required to capitalize on radio performance.

With these considerations, open modular-based radio design offers great opportunities to allow key stakeholders, including chipset suppliers, hardware and software vendors, and system integrators to work together to address new market and service needs. This innovative approach can provide network operators and many other customers with cost-effective radio solutions and reduce time to market. Specifically, by hardening the individual radio functions with ASIC-like optimization and integrating them on a System on Chip (SoC), the radio's power consumption can be significantly reduced. Moreover, to provide more flexibility, adaptable software logic can leverage existing hardened radio functions by adding more logic in parallel or bypassing any existing blocks by inserting replaced radio functions. For any application-specific functions, such as timing and synchronization, adaptable software logic can be presented to adapt to future requirements, offering a trade-off between flexibility and deployment cost.

The combination of standard-compliant hardened radio functions and adaptable software logic offers customers a balanced radio to adapt to various connectivity requirements. Moreover, in comparison to ASIC-based solutions, it also has minimal impact on performance loss. When considering the Total Cost of Ownership (TCO) and many other impacts (such as adaptability for unknown market requirements) this open modular-based radio solution may be the most sensible choice in the future, especially when considering geopolitical restrictions, supply chain diversity, and the need for new innovation in the market.

For the purpose of accessing the development and deployment benefits of open modular-based radio design, several challenges faced by network operators and their ecosystem partners should be adequately addressed:

• With the rapid growth of data traffic and stringent service requirements, processing hardware (especially for layer one and radio layers) requires extremely high computational capabilities and flexibility for both real-time and near-real-time applications. In this way, chipset suppliers and equipment vendors should proactively test and trial their solutions to learn from their customers about specific connectivity requirements.
• Allowing the third-party radio functions to interconnect with the pre-built radio hardware platform may create a multi-vendor interoperable complexity problem. Without a clear understanding of the interfaces and all radio functions, radio performance will be most likely affected. This accentuates the value of creating common implementation frameworks.
• The coexistence of open modular radio networks with conventional networks is another concern. The capability of coordinatively serving a mobile user using both open modular-based radio units and the incumbent vendors' infrastructure will be necessary for the foreseeable future.

The study of open modular-based radio is arguably a long-term initiative. As more commercial open radio solutions are ready for market and the ecosystem gets stronger, network operators and many other players will gradually become more confident about investing in the solution.