A Software Defined Radio Lab

Network Slicing Prototype for C-RAN architecture

The logic architecture of our  prototype is based on the C-RAN architecture implemented by the OAI software [1] and on the SDN controller  provided by FlexRAN [2]. Our prototype is in line with the NGFI C-RAN architecure [1], wherein the baseband processing functions are carried out at the Remote Cloud Center (RCC) node, which in turns  sends I/Q samples to the Radio Remote Unit (RRU) via a  fronthaul interface. Note that the protoype utilizes an ethernet based fronthaul, i.e. the link between the RCC and the RRU,  as described in [1]. The C-RAN architecture is based on the IF4p5 splitting [1] implemented by OAI, which refers  to the split-point at the input (TX) and output (RX) of the OFDM symbol generator. More details on the C-RAN splitting solutions implemented in OAI are provided in [1].

In our prototype the RRU consists of an Ettus USRP B2100 card [3] which is connected to an Ubuntu Desktop computer via an USB 3.0 interface. The RCC, which implements the remaining levels of the LTE protocol stack, is executed in an Ubuntu laptop with an Intel I7 processor and 8 GB RAM.  Moreover the laptop hosts a VMware Ubuntu virtual machine (VM) where all the functionalities of the Core Network are  implemented by the OAI software. The laptop hosts also a FlexRAN controller, which consists of two main entities: the Master Controller and the Agent. The Master Controller is connected to the Agent, i.e. a software module built within the software of the OAI eNB. The FlexRAN Agent is the entity that separates the control plane and data plane of the OAI software and acts as a southbound interface (SBI) between the control plane, which is moved at the Master Controller side, and the dataplane which remains at the eNB side. By means of such an SBI, the Master Controller can interact with the Agent and collect information about the network state of the RAN. Moreover, the Master Controller offers a northbound interface (NBI) which can let a northbound application to implement an algorithm for configuring some RAN parameters in an  abstracted way. The implementation details of the FlexRAN Controller are provided in [2]

We propose a network slicing solution for sharing the  spectrum among multiple slices, which utilizes an SDN approach to manage the creation of each slice and dynamically configure the size of each slice on-demand, in accordance to some specific SLA constraints. More specifically, we focus on the real-time allocation of the bandwidth resources and we propose a slicing scheduling algorithm that is driven by a centralized SDN controller. The logic architecture of the the slicing scheduler is depicted in the above figure (right side), while the left part of this figure describes the scheduler architecture in a legacy LTE eNB.
The OTT providers can communicate  a service request to the an SDN controller, named SDN  Multi-tenant Controller, via a Northbound Interface, which  is based on an HTTP interface provided by the FlexRAN  Master Controller. For instance, the OTT provider could ask  to the SDN Multi-tenant Controller to execute a service with a  specific QoS target, for a number of users, which are located in  a specific area, while respecting an average system throughput  target. Accordingly, the SDN Multi-tenant Controller performs  firstly an admission control, i.e. it verifies that the service  request is in line with the pre-established SLA agreements  and that the required QoS can be matched according to the  real-time network state. Secondly, it allocates a slice to the OTT, by setting the following parameters:
  • size, i.e. the total number of RBs to be used from that slice
  • duration of the slice, expressed in number of Transmission Time Interval (TTIs)
  • QoS target, e.g. the throughput target for aggregate traffic within the slice
Once the slice is configured, the SDN Multi-tenant Controller sends a command to the Slice Manager function, which  is employed at the Agent side at the eNB, via the SBI interface provided by FlexRAN. The Slice Manager finally  instantiates the slices by reserving an appropriate portion of  the bandwidth to each OTT provider according to the slicing  scheduler decision taken by the SDN Multi-Tenant Controller.

The configuration of the slices can be done manually for testing purposes, via a web GUI, but also dynamically. In fact the input values of the Slicing App can also come from a complex slicing allocation algorithm.

Demo of Network Slicing Prototype


In the following video we present a demo of the network slicing prototype. The aim of this demo is to show the feasibility of the prototype in handling the creation and configuration of network slices on-demand, taking into account some inputs that are elaborated from an SDN-based slicing application.


  2. X. Foukas, N. Nikaein, M. M. Kassem, M. K. Marina and K. Kontovasilis, FlexRAN: A Flexible and Programmable Platform for Software-Defined Radio Access Networks,ACM CoNEXT, California, USA, 12-15 Dec. 2016
  3. USRP B200/B210 Specification Sheet, avalaible online at 
  4. S. Costanzo, I. Fajjari, N. Aitsaadi and R. Langar, "A Network Slicing Prototype for a Flexible Cloud Radio Access Network", 15th IEEE Annual Consumer Communications Networking Conference (CCNC), Las Vegas, NV, USA, 12-15 Jan. 2018.
  5. S. Costanzo, I. Fajjari, N. Aitsaadi and R. Langar, "DEMO: SDN-based Network Slicing in C-RAN", 15th IEEE Annual Consumer Communications Networking Conference (CCNC), Las Vegas, NV, USA, 12-15 Jan. 2018.