OpenRadio: Taking Control of Wireless

1. OpenRadio: Taking Control of Wireless Sachin Katti Assistant Professor EE&CS, Stanford University

2. Three Dissatisfied Parties Applications Carriers Users

3. Frustrated Users

4. LTE Femtocell 3G WiFi Paradoxically, surrounded by wireless APs (WiFi, 3G, 4G, picocells, femtocells, whitespace ….)

5. LTE Femtocell 3G WiFi Why cant I seamlessly connect me to the best AP available?

6. LTE Femtocell 3G WiFi Why cant I seamlessly connect to multiple APs if I want more speed?

7. Applications’ Perspective

8. LTE Femtocell 3G WiFi User experience with rich cloud services over mobile wireless is poor

9. LTE Femtocell 3G WiFi • To cope, resort to reverse engineering • Probe for bandwidth/latency • Resort to hacks (e.g. multiple TCP connections, …)

10. LTE Femtocell 3G WiFi Why cant applications directly ask the network its current state, or directly request the connectivity they need?

11. LTE Femtocell 3G WiFi More generally, why isn't the network a partners for apps rather than an opaque bit pipe? • Network knows user location, connectivity, billing …. • Well positioned to host & enhance applications

12. Carrier’s Perspective

13. Carrier’s Dilemma Exponential Traffic Growth Limited Capacity Gains Exponential growth + Limited spectrum/capacity gains  Poor wireless connectivity

14. Cooper’s Law Capacity Improvements come from increasing cell density

15. Capacity  Dense/Chaotic Deployments Dense  Higher SNR/user  Higher Capacity • Femtocells, dense WiFi deployments etc

16. Dense & Chaotic  Hard to Manage • Limited spectrum + Dense  Intercell Interference • Many, chaotic cells  Variable Load & Backhaul • Operators need to dynamically manage how their traffic is routed, scheduled and encoded on a per packet level to manage inter-cell interference & variable load in a chaotic infrastructure  Hard to build at scale

17. Everyone is Dissatisfied! Underlying Cause: Lack of control Infrastructure does not scalably expose state • Hard or infeasible to find available APs, their speeds, user locations, fine-grained network/load information etc Infrastructure does not provide granular control • Hard or infeasible to granularly control traffic E2E across all layers and network infrastructure

18. What does it take to….. Open the wireless infrastructure to provide users, applications and carriers control over their traffic across all layers end to end across the entire infrastructure?

19. OpenRadio: Taking Control of Wireless Wireless network architecture that provides unified software interfaces to: • Query wireless networks about availability, quality, location, spectrum, interference … • Control granularly how individual user or application traffic is handled by the network across the entire stack

20. OpenRadio: Control Interface Match/Action interface for the entire stack Match: Identify and tag flows of individual users and/or applications Action: Control how packets are routed, what speeds & priorities they get, and how they are scheduled/encoded at the AP

21. OpenRadio: Architecture Control Program Control Program Global Network View Wireless Network OS Open interface to heterogeneous wireless infrastructure If pkt = x: forward to LTE AP If pkt = y: forward to LTE AP and allocate speed 1Mbps X X If pkt = x: schedule low priority If pkt = y: schedule high priority and allocate 40% airtime WiFi AP 3G LTE

22. E.g: Seamless Connectivity to the best APs Connectivity/Mobility Control Program Global Network View Wireless Network OS X X LTE WiFi AP 3G Control program to automatically route user traffic to the best available AP

23. E.g: Dynamic High Speed Pipe for Video Netflix/CDN Connectivity/Mobility Global Network View Wireless Network OS X X WiFI AP LTE 3G Applications stitch a high speed pipe from available APs for HD video streams

24. Connectivity CDN Load Mgmt Internet of Things …… Global Network View Wireless Network OS X X WiFI AP LTE 3G Complex network services as pieces of software running on the network OS

25. OpenRadio: Design • Data Plane: Access, backhaul & core network • Can we build a programmable data plane using merchant silicon? • Control Plane: Modular software abstractions for building complex network applications • What are the right abstractions for wireless?

26. OpenRadio: Radio Access Dataplane

27. OpenRadio: Access Dataplane OpenRadio APs built with merchant DSP & ARM silicon • Single platform capable of LTE, 3G, WiMax, WiFi • OpenFlow for Layer 3 • Inexpensive ($300-500) Forwarding Dataplane Control CPU Baseband & Layer 2 DSP Exposes a match/action interface to program how a flow is forwarded, scheduled & encoded RF RF RF

28. Design goals and Challenges Programmable wireless dataplane using off-the-shelf components • At least 40MHz OFDM-complexity performance • More than 200 GLOPS computation • Strict processing deadlines, eg. 25us ACK in WiFi • Modularity to provide ease of programmability • Only modify affected components, reuse the rest • Hide hardware details and stitching of modules

29. Wireless Basebands OFDM Demod Demap(BPSK) Deinterleave Viterbi Decode Descramble CRC Check Hdr Parse OFDM Demod OFDM Demod Demap(BPSK) Demap(64QAM) Demap(BPSK) Demap(64QAM) Deinterleave Deinterleave (UEP) Deinterleave (WiFi) Decode (1/2) Decode (3/4) Decode (1/2) Decode (3/4) Descramble CRC Check Hdr Parse Descramble Descramble CRC Check Hdr Parse Hdr Parse WiFi 6mbps WiFi 6, 54mbps WiFi 6, 18mbps and UEP

30. Modular declarative interface Composing ACTIONS A A A A A B C C Inserting RULES OFDM Demod A B E D D Demap(BPSK) C F G G F B Demap(64QAM) H H H C H B D E D I I I D Deinterleave (UEP) Deinterleave (WiFi) Blocks J J J J F G F Decode (3/4) Decode (1/2) Data flow F G H H J I I Descramble Hdr Parse CRC Check Control flow J H 6M, 54M UEP 6M 54M 6M I Actions: DAGs of blocks Rules: Branching logic J

31. State machines and deadlines • Rules and actions encode the protocol state machine • Rules define state transitions • Each state has an associated action • Deadlines are expressed on state sequences Start decoding Finish decoding F B A D G C H I deadline J

32. Design principle IJudiciously scoping flexibility • Provide just enough flexibility • Keep blocks coarse • Higher level of abstraction • High performance through hardware acceleration • Viterbi co-processor • FFT co-processor • Off-the-shelf heterogeneous multicore DSPs • TI, CEVA, Freescale etc.

33. Design principle IIProcessing-Decision separation A • Logic pulled out to decision plane • Blocks and actions are branch-free • Deterministic execution times • Efficient pipelining, algorithmic scheduling • Hardware is abstracted out A B C B D 60x C D E F F G H 6M, 54M I J

34. Prototype • COTS TI KeyStone multicore DSP platform (EVM6618, two chips with 4 cores each at 1.2GHz, configurable hardware accelerators for FFT, Viterbi, Turbo) • Prototype can process 40MHz, 108Mbps 802.11g on one chip using 3 of 4 cores I/Q base- band samples RF signal (Analog) (Digital) Baseband-processor unit (BBU) Antenna chain(AX) Radio front end (RFE) Layer 1 & 2 Layer 0 & 1 Layer 0

35. Software architecture BBU RFE AX (Digital) (Analog) OR Wireless Decision Plane protocol state machine, flowgraph composition, block configurations, knowledge plane, RFE control logic monitor & control OR Runtime System compute resource scheduling, deterministic execution ensuring protocol deadlines are met OR Wireless Processing Plane deterministic signal processing blocks, header parsing, channel resource scheduling, multicore fifo queues, sample I/O blocks data in data out Bare-metal with drivers

36. OpenRadio: Current Status • OpenRadio APs with full WiFi/LTE software on TI C66x DSP silicon • OpenRadio commodity WiFi APs with a firmware upgrade • Network OS under development

37. To Conclude… OpenRadio: Taking control of wireless through SDN Provides programmatic interfaces to monitor and program wireless networks • High performance substrate using merchant silicon Complex network services as software apps

38. Our Vision: Virtualized Wireless Networks Verizon AT&T Wireless Network OS Open interface to heterogeneous wireless infrastructure X X Shared physical wireless infrastructure decoupled from network service 3G WiFi AP LTE