Cloud Radio Access Network

FluidNet: A Cloud RAN Architecture with a Reconfigurable Backhaul

Small cells have become an integral component in meeting the increased demand for cellular network capacity. Cloud radio access networks (C-RAN) have been proposed as an effective means to harness the capacity benefits of small cells at reduced capital and operational expenses. With the baseband units (BBUs) separated from the radio access units (RAUs) and moved to the cloud for centralized processing, the backhaul between BBUs and RAUs forms a key component of any C-RAN. In this work, we argue that a one-one mapping of BBUs to RAUs is highly sub-optimal, thereby calling for a functional decoupling of the BBU pool from the RAUs. Further, the backhaul architecture must be made re-configurable to allow the mapping between BBUs and RAUs to be changed dynamically so as to not just optimize RAN performance but also energy consumption in the BBU pool. Towards this end, we design and implement the first OFDMA-based C-RAN test-bed with a reconfigurable backhaul that connects 4 BBUs with 4 RAUs using radio-over-fiber technology.

We demonstrate the feasibility of our system over a 10 km separation between the BBU pool and RAUs. Further, real world experiments with commercial off-the-shelf WiMAX clients reveal the performance benefits of our reconfigurable backhaul in catering effectively to heterogeneous user (static and mobile clients) and traffic profiles, while also delivering energy benefits in the BBU pool.

The video shows the FluidNet architecture and the need for a logical reconfigurable backhaul to execute different wireless transmission strategies (eg. DAS, FFR, CoMP) for both improved end-user performance as well as energy savings in the baseband pool.

TRINITY: A System Tailored to use Heterogeneous Transmission Strategies based on User and Traffic Profiles

The proliferation of smartphones and tablet devices is changing the landscape of user connectivity and data access from predominantly static users to a mix of static and mobile users. While significant advances have been made in wireless transmission strategies (e.g., network MIMO) to meet the increased demand for capacity, such strategies primarily cater to static users. To cope with growing heterogeneity in data access, it is critical to identify and optimize strategies that can cater to users of various profiles to maximize system performance and more importantly, improve users’ quality of experience. Towards this goal, we first show that users can be profiled into three distinct categories based on their data access (mobility) and channel coherence characteristics. Then, with real-world experiments, we show that the strategy that best serves users in these categories varies distinctly from one profile to another and belongs to the class of strategies that emphasize either multiplexing (eg., netMIMO), diversity (eg., distributed antenna systems) or reuse (eg., conventional CSMA). Two key challenges remain in translating these inferences to a practical system, namely: (i) how to profile users, and (ii) how to combine strategies to communicate with users of different profiles simultaneously. In addressing these challenges, we have designed TRINITY - a practical system that effectively caters to a heterogeneous set of users spanning multiple profiles simultaneously.



Relevant Publications

FluidNet: A Flexible Cloud-based Radio Access Network for Small Cells
The 19th Annual International Conference on Mobile Computing and Networking (MobiCom 2013)
pp. 99-110, 2013
Karthikeyan Sundaresan, Mustafa Y. Arslan, Shailendra Singh, Sampath Rangarajan, Srikanth V. Krishnamurthy

The Case for Re-configurable Backhaul in Cloud-RAN based Small Cell Networks
IEEE Infocom 2013
pp. 1148-1156, 2013
Cheng Liu, Karthikeyan Sundaresan, Meilong Jiang, Sampath Rangarajan, Gee-Kung Chang

One Strategy Does Not Serve All: Tailoring Wireless Transmission Strategies to User Profiles
ACM HotNets 2012
ACM 978-1-4503-1776-4, pp. 1-6, 2012
Shailendra Singh, Karthikeyan Sundaresan, Mohammad A. Khojastepour, Sampath Rangarajan, Srikanth V. Krishnamurthy