Virtually all types of electronic equipment have evolved – often in quite disruptive stages – from very big and discrete to very small embedded form factors. Tracking Moore's law, large mainframe computers have evolved to mini computers, then to PCs, on to laptops, and recently to web tablets. Today's smartphones put more crunching power in your hands than could fit into an entire room just little more than a decade ago.
Why is it, then, that mobile base stations still look essentially the same as they did 10 years ago ─ a rack full of equipment with line cards, a common shelf, backhaul equipment, UPS, air conditioning and more?
The main reason is the rapidly increasing capacity of mobile base stations (BTSs), driven by the evolving radio technology, as it is indeed approaching the limits of Shannon's theorem. A decade ago, user traffic was measured in terms of mobile voice sessions using less than 16 kbps of capacity. Today we are entering the data-centric era of 4G services, with ITU Advanced requiring up to 1 Gbps per subscriber.
While Moore's Law predicts a continuous cycle of miniaturization, Shannon's Law describes an inherent capacity boundary for the amount of data that can be transmitted using a given swath of spectrum. 4G technology is closely approaching these limits described by Shannon's Law. This means that we have essentially reached an inevitable physical limit of total wireless capacity per each cell site.
In practicality, the consequence of approaching Shannon's boundary is quite simple. Operators must install more cells - many more cells at the current rate of mobile data explosion. The industry can no longer get by just adding more spectrum to existing cells to keep pace with exploding mobile data demand. If the industry continues in the current fashion, we are headed for a tremendous 4G capacity gap in 2014/15.
Next-generation Compact BTS equipment will enable mobile operators to cope with the data explosion. It only stands to reason that the industry take advantage of Moore's Law and produce smaller, lighter weight, and much more compact equipment with much lower power consumption – equipment that can easily, and at a sustainable cost, be installed in these new cell sites. Shedding the tremendous physical and operational cost overhead of today's BTS equipment, Compact BTS equipment uses highly integrated System-on-Chip (SoC) silicon platforms.
The reason it took so long to make SoC-based Compact BTS equipment available ─ even though the market obviously requires them for 3G and 4G networks ─ goes back to the complex nature of mobile base station functionality. Mobile base stations are comprised of low-level analog RF transmission and digital modem technology, signal, frame and packet processing layers, as well as end-to-end network control layers and backhaul.
This tremendous scope of functionality requires a multitude of optimized processor types, each of which needs to be augmented with powerful task-specific co-processors to cope with the exploding data rates.
From a silicon design standpoint, multiple layers of task-specific processor cores must be integrated in 4G SoC platforms to handle this complex stack of functionality – even multiple cores of each processor type. Next, these need to be assisted by layer-specific hardware acceleration cores, off-loading software-centric processors, so next-generation SoCs can handle the tremendous throughput.
In order to take advantage of Moore's Law, i.e., harnessing the full impact of silicon technology for the miniaturization on the product level, various radio access network processing layers must be integrated to form a new SoC platform architecture suitable for 4G infrastructure applications - multi-layer, multi-core SoCs are required for high-capacity mobile 4G network equipment.
Only recently has the framework for 4G infrastructure SoCs become a viable technology option with massive advancements in both, underlying silicon process technology (as described by Moore's Law) and the ability to integrate multiple layers of complex multi-core SoC sub-systems within a single chip.
A new category of mobile base station equipment – Compact BTSs – is targeting the evolution of the 3G and 4G RAN infrastructure, enabled by the latest generation of 4G SoC platforms. Compact BTSs are by no means femtocells; they are powerful, carrier-grade infrastructure equipment, performance limited only by available spectrum and cell size.
Compact BTSs are miniaturized versions of existing base station equipment – a natural evolution predicted by Moore's Law. They are a disruptive step in the evolution of base station equipment, driving a fundamental paradigm shift. What used to be comprised of an entire rack of equipment is now integrated in a single silicon chip that can fit in the palm of your hand, next to your smartphone.
Compact BTSs couldn't have arrived at a more perfect time. With substantially reduced cost, size, weight and power consumption, Compact BTS take full advantage of Moore's Law. They are the only cost-effective solution for operators, helping to overcome the limits of Shannon's Law to handle the 4G capacity gap.
Joachim Hallwachs is vice president of marketing at DesignArt Networks.