TheVirtual Base Station (vBTS) is a deployment of the Sooktha SBS on the Freescale vAccess Platform that allows a virtualized LTE access network deployment. This solution demonstrates the portability and deployment flexibility of the SBS software.

Solution Overview

The vBTS involves a split between the Layer 2 and Layer 1. The Layer 1 is deployed in the distributed radio nodes. The rest of the BTS functions are centralized. They execute on a VM to allow virtualization. The standard FAPI interface is used between the Layer 2 and the Layer 1. This interface is implemented using a low latency and light weight FAPI transport layer to meet the 1ms subframe constraint. The radio nodes have a corresponding FAPI transport module that is derived from the PHY_IF module in the SBS solution.

The use of the standard FAPI interface, a low-latency and light-weight UDP/IP transport layer, and proven eNodeB software, mean that the Sooktha vBTS on the Freescale vAccess platform can be used to significantly accelerate the virtualization of LTE access network solutions.

Hardware/Platform Overview

The vBTS is implemented on the Freescale vAccess platform, which allows NFV/SDN style deployment of base station functions and allows orchestration using OpenStack. The vBTS executes on a Linux VM hosted on a Freescale T4240 RDB. The vAccess platform also uses an iNIC for advanced networking. The radio nodes are implemented using the Freescale BSC9131 RDB.

Virtualization Options

The Sooktha SBS solution also allows different splits in addition to the split between Layer 2 and Layer 1. This allows the solution to balance the constraints of the available Fronthaul transport network with the requirements for centralization and virtualization. A split is possible between:
  • L1 baseband and the radio transceiver – using a standard CPRI interface
  • MAC and RLC – using a proprietary interface encapsulated in UDP
  • RLC and PDCP – using a proprietary interface encapsulated in UDP and/or
  • Control plane and data path – using a proprietary interface encapsulated in UDP

In addition to the modularity in software required to allow the above splits, there is an optimization of implementation required to allow distributed execution. Sooktha has analyzed the distributed execution requirements and built-in the necessary optimization in the SBS components.

Virtualization Benefits

The benefit of virtualization and supporting orchestration is that more than one split (from the possibilities above) may be employed allowing a tighter low-latency transport network and time critical functions to be implemented closer to the actual radio sites and the transport network requirements to be relaxed and more functions to be centralized and virtualized towards to the core network.