Cloud RAN Small Cells Emerging to Fill Wireless Vacuum

Date:   Tuesday , May 19, 2015

Headquartered in Massachusetts, Airvana is a provider of small cells and femtocells.

Vendors have been promoting macro Cloud RAN, or C-RAN products for several years. But C-RAN is also relevant to small cells, in particular enterprise small cells. In 2014, the Small Cell Forum announced an effort to understand how small cells fit into C-RAN, and the first commercial C-RAN small cell products were announced. These moves signal an important shift in the way indoor wireless coverage is delivered.

What is a C-RAN Small Cell?

C-RAN Small Cells can be broadly defined as having a centralized baseband that is pooled across distributed access points. This provides management and SON benefits compared to a cluster of standalone small cells. However, some C-RAN small cells go beyond this, and support these other key attributes:

  1. Coordination between Radios - While the baseband processing is centralized, some intelligence also must reside in the radios for coordination between multiple radios that serve the same user. This is in contrast to Remote Radio Head or DAS systems that have no such coordination.

  2. Ethernet Fronthaul - C-RAN for Small Cells can leverage standard, inexpensive Ethernet switches and cabling for front-haul. This is in contrast to Macro C-RAN approaches which typically use costly CPRI over fiber connections.

  3. Single Cell Operation - The radio points act as one large cell, which eliminates handovers and simplifies interactions with the macro network.

Solving Key Problems for LTE in the Enterprise

C-RAN Small Cells have advantages for enterprise small cell deployments. The creation of a single cell ensures a superior user experience by eliminating border interference. In side-by-side tests, eliminating small cell borders has been shown to increase data throughput by up to 10X, while reducing latency by a factor of five, which is critical for VoLTE quality.

Implemented properly, C-RAN Small Cells are simple and economical to deploy. The elimination of cell borders simplifies radio frequency planning since there is no concern about interference between access points. C-RAN also simplifies frequency coordination the outdoor macro network. The use of standard Ethernet LANs reduces both material and installation costs. C-RAN is also a multi-operator friendly architecture.

Finally, C-RAN Small Cells can provide a high degree of investment protection. Standalone small cells are typically optimized for low cost, and upgradeability is limited by their chipsets. With a C-RAN approach, the functionality is concentrated in the more powerful, upgradeable baseband controller.

Why C-RAN Small Cells Now?

Several factors have recently converged to make C-RAN small cells both viable and necessary.
Silicon keeps getting faster, making it now possible to pack the power of a macro base station into a 1U-sized central controller.

The rapid deployment of LTE is another factor. C-RAN maximizes LTE air link performance and capacity, and it supports LTE-Advanced features like distributed MIMO and Coordinated Multipoint (CoMP). VoLTE is also being rapidly deployed and this too would be difficult to support in large indoor spaces using traditional small cell architectures, due to the inherent interference and latency issues mentioned previously.

All of these things are happening against the backdrop of continuing growth in mobile data consumption. According to the Cisco Visual Networking Index, mobile data usage will grow 67 percent from 2014 to 2015, and continue at this pace for the foreseeable future. C-RAN Small Cells will emerge as an important tool to help operators to respond to this insatiable demand.