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SoftRAN : Software Defined RAN. Aditya Gudipati † , Daniel Perry † , Li Erran Li * , Sachin Katti † Stanford University † , Bell Labs *. LTE - Radio Access Network. High C apacity , Uniform C overage W ide-Area W ireless Network. I N T E R N E T. S-Gateway 1. Client1.
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SoftRAN : Software Defined RAN AdityaGudipati†, Daniel Perry†, Li Erran Li*, SachinKatti† Stanford University†, Bell Labs*
LTE - Radio Access Network High Capacity, Uniform Coverage Wide-Area Wireless Network I N T E R N E T S-Gateway 1 Client1 BS1 P-Gateway BS2 Client2 Client3 BS3 S-Gateway 2 Core Network Client4 Radio Access Network
RAN Actions: Radio Resource Management 1. Assign each client to a base station Flow 1 Flow 2 dB dB time time dB dB dB frequency frequency 3. Assign transmit powers to be used for each resource block 2. Assign resource blocks (time-frequency slots) to each flow
RAN Challenges • Increasing demand on wireless resources • Dense deployments of small cells Radio Resource Management gets coupled across base stations
Coupled Radio Resource Management: Interference • Power used by BS1 affects interference at Client 2 • Interference at Client 2 affects power reqd. at BS2 BS2 BS1 Client1 Client2
Coupled Radio Resource Management: Mobility • Dense deployments • Higher frequency of handovers • More candidate base stations • Coordinating handovers critical BS2 BS1 Client1 Client1
In dense deployments, Radio Resource Management needs to be tightly coordinated
LTE-RAN: Current Architecture • Distributed control plane • Tight coordination becomes infeasible with density • Huge demands on the backhaul network • Inefficient radio resource management • Hard to manage in a dense network
SoftRAN: Big Base Station Abstraction Big Base Station Radio Element 1 time controller frequency Radio Element 2 Radio Element 3 time time time frequency radio element frequency frequency
SoftRAN Architecture CONTROLLER RAN Information Base Periodic Updates Controller API • Bytes • Rate • Queue • Size Network Operator Inputs RADIO ELEMENTS QoS Constraints Interference Map Flow Records 3D Resource Grid Radio Resource Management Algorithm Radio Element API Time Radio Element POWER FLOW Frequency
SoftRAN: SDN Approach to RAN Coordination : X2 Interface Control Algo Control Algo OS OS Packet Tx/Rx Control Algo Packet Tx/Rx OS Packet Tx/Rx BS1 BS3 Control Algo Control Algo BS5 OS OS Packet Tx/Rx Packet Tx/Rx BS2 BS4
SoftRAN: SDN Approach to RAN Control Algorithm Operator Inputs Network OS Packet Tx/Rx Packet Tx/Rx Packet Tx/Rx BS1 BS3 BS5 Packet Tx/Rx Packet Tx/Rx BS2 BS4
SoftRAN: SDN Approach to RAN • Efficient use of wireless resources • Global view on interference and load • Simplified network management • Plug-and-play control algorithms
Challenges: Backhaul Latency controller time radio element frequency
Challenges: Backhaul Latency • Refactor control plane based on latency • Low latency ( < 1 ms) => No refactoring • Principles for refactoring: • Controller manages global network state • Radio Elements leverage frequently varying local network state
Implementation • Incrementally deployable on current infrastructure • No modification to Base Station – client interface • New API definitions for Base Station • Femto API: Standardized interface between scheduler and L1 * *http://www.smallcellforum.org/resources-technical-papers
Future Vision • Expand SoftRAN to include 3G and Wifi networks • Coordinated management of all available radio resources THANKS !
