5G’s Departure from Its Predecessors
In each move from 1G to 4G people became accustomed to seeing the new generation as primarily offering increased bandwidth and efficiency. It would be a mistake to view the transition to 5G along these same lines. 5G takes Radio Area Networks (RANs) from a use model primarily for cell phone communications to a service supporting multiple use models that can support industrial IoT, machine to machine, even real time applications such as automotive navigation and more. 5G comes with more new operational bands and modes that work in environments from rural to dense urban areas.
The 5G Evolution
The increased sophistication of 5G means major shifts in how mobile network operators (MNOs) build out and deploy their networks. An informative white paper by Achronix, a leading supplier of FPGA components and eFPGA IP, discusses the changes coming in 5G and how they will affect every aspect of its architecture. The paper is titled “Enabling the Next Generation of 5G Platforms”. Indeed, 5G is still in the processes of being specified. 3GPP, the organization that is developing the specifications, is currently on Rel-18, with plans for specification releases up to Rel-21 in 2028. Each release includes new features that add essential functionality.
Three New 5G Use Cases
5G adds three new use cases to the existing 4G fixed broadband implementation. The Achronix white paper describes them as follows:
- Massive machine type communication (mMTC) supports machine to machine connections, with an eye towards large numbers of IoT devices requiring high efficiency, low cost, and deep indoor coverage.
- Enhanced mobile broadband (eMBB) aims to meet the new requirements for interactive applications on mobile devices. The focus is on 8K streaming video, augmented reality and other high bandwidth uses.
- Ultra-reliable low latency communication (URLLC) is the third use case focusing on high performance low latency real-time connectivity. It will be used for things like vehicle control, remote medical and time critical factory automation.
Because of the number of devices that will be connected and the new use models, the existing monolithic base station and backhaul building blocks will create bottle necks and limit flexibility. A new split architecture consisting of centralized units (CU), distributed units (DU) and radio units (RU) will be used. This change allows coordination for performance features, load management, and real-time performance optimization, which all enable adaptation to various use cases. DU, CU and RU elements can be collocated or physically distributed to accommodate the needs of the workloads and environment. This shift requires more intelligence in each type of equipment and the development of standard interfaces to allow a high level of interoperability.
Where CPUs Fall Short, FPGAs Provide More Processing Power
It’s more than simply disaggregation that is driving the need to more intelligence and processing power within all elements of the 5G network. The white paper offers an excellent example of this on the expanding need for beam forming in the RU. Bandwidth is going from 20Mhz to 100MHz, transmission intervals are moving to 0.5ms and antenna arrays will grow to 64 by 64 elements. Future 5G releases will include AI/ML processing in the RU to improve signal quality. All of this will require significant processing power.
While it is tempting for the MNOs to fall back on virtualization of network functions running on traditional CPUs, the reality is that for systems far from the central office the requirements for power, cooling and size quickly begin to rule out multi-CPU solutions. With an evolving specification for 5G equipment, designing custom ASICs for DUs, CUs and RUs is not feasible. The Achronix white paper points out that FPGAs offer an excellent middle ground for these systems. They offer programmability and also provide high performance with very efficient power consumption.
FPGAs will allow upgrades on installed systems as new revisions are ratified. One additional way that Achronix offers to improve power and system size is by adding an embedded FPGA fabric to an ASIC. This eliminates costly and inefficient IO conversions between processing elements. Achronix eFPGA is fully configurable to specific system requirements, which means that no unused extra silicon real estate gets wasted. Furthermore, Achronix offers AI/ML processing units as part of their core functionality.
Every stage in the 5G radio area network (RAN) can benefit from the features offered by Achronix FPGA and eFPGA. The Achronix white paper dives deeper than I can in this article to illustrate the changes coming in 5G, both now and in future releases, and how Achronix FPGA and eFPGAs can effectively address them. The full white paper is available for download on the Achronix website.
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