Last week at The Small Cells Summit in London, Small Cell Forum announced their release 5.1 document suite which is the first phase of its work on small cell virtualisation. Alongside the Forum’s own work to assess the technical benefits of the virtualising of small cells in cellular networks, Real Wireless examined the key cost elements in deploying and operating small cells in urban areas that would be most sensitive to a move to a more virtualised network architecture. Core to this assessment was understanding both wireline and wireless transport options to small cell sites and considering how these options reduce and costs potentially increase as architectures move from traditional distributed RAN (DRAN) LTE networks today towards classical cloud RAN (CRAN) architectures with remote radio heads and CPRI interfaces at the network extremes with strict latency requirements in the order of 250us and bandwidths in the order of 2.5Gbps.
Key findings from the study were:
- Our results challenge the traditional view that dark fibre is prohibitively expensive. On a five-year TCO basis dark fibre costs can be commensurate with managed fibre given recent falls in dark fibre prices.
- Most transport options today can meet bandwidth and latency requirements up to and including a MAC/PHY split with latency requirements of 2 to 6ms if the centralised processing is done at a local macrocell.
- The CPRI/ORI case of the most challenging virtualisation split considered is supported only by Sub-6 GHz and dark fibre in 2015 but could be supported by all other transport options by as early as 2020 (except copper). However, we note that most wireless options will only support these requirements over short links and with good line of sight and that managed fibre products do need to evolve from packetised services offered today.
- Across the transport options surveyed, the cost increase for supporting CPRI split beyond a MAC/PHY split was most dramatic for managed fibre and microwave (assuming these will support CPRI by 2020).
- Across the transport options surveyed, the lowest five-year TCO for a CPRI split was found for Sub-6 GHz with $32k versus a managed fibre CPRI of $95k in 2020.
- The virtualisation cost, although very sensitive to whether NFV is done at a macrocell or data centre, is still a very small cost in the bigger scheme of the total TCO of a small cell site and has only a marginal impact compared with the transport connection to the small cell site.
- The power cost is also very small (in the range of $100/year) and has little impact on the overall TCO and has little variation between transport options.
The full report is available at: http://scf.io/en/documents/158_-_Business_case_elements_for_small_cell_virtualization.php