Experimental Demonstration of SDN-controlled Variable-rate Fronthaul for Converged LTE-over-PON

A Variable Rate Fronthaul Scheme for Cloud Radio Access Networks

“…Furthermore, it also takes care of the latency encountered by the SDN controller to configure between different CPRI rates. For example, if the latency for reconfiguration between different CPRI rates is somewhere between 500ms (this is a value we experimented in our dynamicbandwidth SDR testbed implementation [16]) to 5seconds (this is the average value taken to completely reboot the SDR BBU) and if we consider normalized traffic load (for example a = 0.2) per RRU then we can write, a = λ/Kµ = 0.2 =⇒ λ = 0.2 × K × µ = 10µ (K = 50 → maximum number of users supported) Now, if we consider a moderate traffic scenario, with λ = 10 calls/min (e.g., in terms of number of users joining the cell) and µ = 1 calls/min, this means that one call, two calls and three calls are expected to arrive, within the reconfiguration window (0.5 seconds), respectively, with probabilities (p) = 0.0767, 0.0032 and 8.8739 × 10 −5 . Therefore, if we choose F l − R l < 2 (say for example F l − R l = 1), then while the SDN controller is triggering a transition to a lower CPRI rate, it is highly probable that one or more calls might arrive.…”

“…As a result, it coordinates operations with the BBU and RRU to dynamically adapt the wireless bandwidth and fronthaul rate. Recently, in [16], we have experimentally demonstrated the practical feasibility of our variable rate fronthaul concept using a software LTE BBU connected to its RRU (implemented using a USRP board [17]) via a fronthaul link operating over a PON.…”

Coordinated fibre and wireless spectrum allocation in SDN-controlled wireless-optical-cloud converged architecture

“…The BBU part of the wireless LTE system is implemented through the open source srsLTE library 9 , which provides the building blocks for implementing LTE prototypes in SDR. In our previous publication 5 we only made use of the LTE physical layer, because the MAC layer had not yet been released as open source. In this current experiment, we make use of the full-stack LTE system, e.g., including the MAC, enabling full endto-end communication.…”

“…In 5 , we demonstrated the concept of adaptive variable-rate fronthaul, which is enabled by Software Defined Network (SDN) and statistical Time Division Multiplexing (TDM). There, the SDN controller interacted with the BBU to monitor the cell usage, and in response adapted the cell wireless bandwidth.…”

Optical and wireless network convergence in 5G systems – an experimental approach

“…The fronthaul bandwidth for transmitting the wireless I/Q samples is adapted to foreground traffic load, by changing the LTE sampling rate on the RRH. We have also implemented an SDN controller based on RYU [4] to control the integration of background traffic and foreground traffic, using an event-triggered scheme shown in Fig. 2.…”