Enabling architectural diversity: Dealing with the aftermath of the RAN “Big Bang” and its ongoing expansion
Dr Doug Pulley, Chief Solutions Architect, Picocom
Much discussion surrounds the need to diversify the supply base in radio access networks (RANs). The move to more open disaggregated RAN architectures, together with standardised, interoperable interfaces (such as Small Cell Forum’s nFAPI and O-RAN Alliance’s Open Fronthaul) between network elements, opens up the choice of best-in-class equipment at each network node. However, the benefits of this architectural approach extend to flexibility in network deployment to meet the diverse challenges of real-world environments.
The last four decades of cellular have seen extraordinary growth in the demands placed upon radio access networks and a concurrent expansion in the resources made available to try to meet those requirements.
This RAN “Big Bang” started from a start point where there was one type of service (voice) and one cell size (macrocell) with its accompanying radio environment challenges. To satisfy these needs, there was one standard (TACS/NMT/AMPS), one frequency band per network (typically 900MHz) with one channel bandwidth (e.g. 25kHz).
The expansion (or increase in “entropy” or disorder) of demand sources and mitigation choices has been extraordinary. Driven by enormous growth in users and the variety of services they use, the traffic demands placed on the RAN have become exponentially more extensive and more diverse with time. To meet these challenges, a bewildering list of frequency bands has been made available to mobile operators, and five generations of ever more intricate standards have been designed to deliver services over a wide range of channel bandwidths and, ultimately, a bewildering array of combinations of those channels, frequency bands and standards which typically varies from network to network and country to country.
Even with new tools provided by standards evolution and the availability of new spectrum, the physical embodiment of the RAN must also be tailored far more closely to the environment than in the early stages of the “Big Bang” to maximise coverage and capacity.
If you zoom in to a dense urban centre using a mapping app with satellite imaging turned on, you’ll see a diverse range of buildings and environments. As you scroll north, south, east, or west, you’ll find offices, malls, stadia, parks, public transport infrastructure, etc. As you zoom out, you’ll see the variation in these environments between dense-urban, urban, suburban and rural areas. You’ll even see variations between environments of the same type.
This rich diversity of scenarios demands a matching diversity of RAN architecture options to be effective in network cost, performance and fundamental deployability across the range of challenges presented. However, the targeted network element cost and power consumption points cannot be met without chips optimised to meet the processing and transport needs of a high-performance 5G NR network and be flexible enough to span the range of use cases.
Small cells are at the leading edge of many of these capacity and coverage deployment challenges to locate the antennas as advantageously as possible while exploiting the available fronthaul and backhaul technologies to most effectively use those antennas. The disaggregation of the RAN enables small cell network architectures that are sufficiently flexible to be moulded to fit these many and varied demands rather than force a ‘one size fits all’ approach.
Original Source Small Cell World Summit (SWCS) 2022 event brochure.