Transcript OpenRadio Software Defined Wireless Infrastructure

OpenRadio: Taking Control of Wireless
Sachin Katti
Assistant Professor
EE&CS, Stanford University
Three Dissatisfied Parties
Applications
Carriers
Users
Frustrated Users
LTE
Femtocell
3G
WiFi
Paradoxically, surrounded by wireless APs (WiFi,
3G, 4G, picocells, femtocells, whitespace ….)
4
LTE
Femtocell
3G
WiFi
Why cant I seamlessly connect me to the best
AP available?
5
LTE
Femtocell
3G
WiFi
Why cant I seamlessly connect to multiple APs if I
want more speed?
6
Applications’ Perspective
LTE
Femtocell
3G
WiFi
User experience with rich cloud services
over mobile wireless is poor
8
LTE
Femtocell
3G
WiFi
To cope, resort to reverse engineering
• Probe for bandwidth/latency
• Resort to hacks (e.g. multiple TCP
connections, …)
9
LTE
Femtocell
3G
WiFi
Why cant applications directly ask the
network its current state, or directly
request the connectivity they need?
10
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
11
Carrier’s Perspective
Carrier’s Dilemma
Exponential Traffic Growth
Limited Capacity Gains
8
350000
300000
6
250000
200000
4
150000
100000
Shannon
Shannon (3dB)
4G
2
50000
0
0
2010 2011 2012 2013 2014 2015
-15 -10 -2.5 2.5
7.5 12.5 17.5
Exponential growth + Limited spectrum/capacity gains
 Poor wireless connectivity
Cooper’s Law
PHY Improvements
Increasing Spectrum
Shrinking Cell Sizes
Capacity Improvements come from
increasing cell density
Capacity  Dense/Chaotic Deployments
Dense  Higher SNR/user  Higher Capacity
• Femtocells, dense WiFi deployments etc
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
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
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?
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OpenRadio: Taking Control of Wireless
Wireless network architecture that provides
unified software interfaces to:
1. Query wireless networks about availability,
quality, location, spectrum, interference …
2. Control granularly how individual user or
application traffic is handled by the network
across the entire stack
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
OpenRadio: Architecture
Control Program
Control Program
Global Network View
Wireless Network OS
Open interface to heterogeneous
wireless infrastructure
X
X
3G
If pkt = x: forward to LTE AP
If pkt = y: forward to LTE AP
and allocate speed 1Mbps
If pkt = x: schedule low priority
If pkt = y: schedule high priority
and allocate 40% airtime
WiFi AP
LTE
E.g: Seamless Connectivity to the best APs
Connectivity/Mobility
Control Program
Global Network View
Wireless Network OS
X
X
LTE
3G
WiFi AP
Control program to automatically route
user traffic to the best available AP
E.g: Dynamic High Speed Pipe for Video
Connectivity/Mobility
Netflix/CDN
Global Network View
Wireless Network OS
X
X
3G
WiFI AP
LTE
Applications stitch a high speed pipe
from available APs for HD video
Connectivity
CDN
Load Mgmt
Internet of Things
Global Network View
Wireless Network OS
X
X
3G
WiFI AP
LTE
Complex network services as pieces of
software running on the network OS
……
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?
OpenRadio: Radio Access Dataplane
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
&RFencoded
RF
RF
Design goals and Challenges
Programmable wireless dataplane using off-theshelf 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
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Wireless Basebands
OFDM Demod
OFDM Demod
OFDM Demod
Demap
(BPSK)
Deinterleave
Viterbi Decode
Demap
(BPSK)
Decode
(1/2)
Descramble
CRC Check
CRC Check
Hdr Parse
Hdr Parse
Demap
(BPSK)
Deinterleave
(WiFi)
Deinterleave
Descramble
WiFi 6mbps
Demap
(64QAM)
Decode
(3/4)
WiFi 6, 54mbps
Decode
(1/2)
Descramble
Demap
(64QAM)
Deinterleave
(UEP)
Decode
(3/4)
Descramble
CRC Check
Hdr Parse
Hdr Parse
WiFi 6, 18mbps and UEP
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Modular declarative interface
Composing ACTIONS
E
D
C
B
A
Deinterleave
(UEP)
Deinterleave
(WiFi)
Demap
(64QAM)
Demap
(BPSK)
OFDM
Demod
J
I
H
Decode
(3/4)
Decode
(1/2)
A
B
D
F
G
H
H
H
H
I
I
I
J
J
H
C
E
G
6M
C
A
D
F
B
F
C
D
A
B
D
Blocks
A
A
CRC Check
Descramble
G
F
Hdr Parse
Inserting RULES
54M
J
J
I
F
G
Data
flow
H
I
J
UEP
Actions: DAGs of blocks
6M
J
6M, 54M
Control
flow
Rules: Branching logic
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
B
A
Finish
decoding
F
D
H
I
G
C
deadline
J
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Design principle I
Judiciously 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.
Algorithm
WiFi
LTE
3G
DVB-T
FIR / IIR
√
√
√
√
Correlation
√
√
√
√
Spreading
√
FFT
√
√
Channel
Estimation
√
√
√
√
QAM
Mapping
√
√
√
√
Interleaving
√
√
√
√
Convolution
Coding
√
√
√
√
√
√
Turbo Coding
√
Randomization
√
√
√
CRC
√
√
√
√
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A
Design principle II
Processing-Decision separation
B C
D
• Logic pulled out to decision plane
• Blocks and actions are branch-free
F G
H
I
J
– Deterministic execution times
– Efficient pipelining, algorithmic
scheduling
– Hardware is abstracted out
Regular compilation
OpenRadio scheduling
Instructions
Atomic processing blocks
Heterogeneous functional units
Heterogeneous cores
Known cycle counts
Predictable cycle counts
Argument data dependency
FIFO queue data dependency
6M, 54M
A
B
C
D
60x
E
F
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Prototype
I/Q baseband
samples
RF signal
(Analog)
(Digital)
Baseband-processor unit (BBU)
Layer 1 & 2
Radio front end (RFE)
Layer 0 & 1
Antenna chain(AX)
Layer 0
• 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
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Software architecture
BBU
RFE
(Digital)
protocol state machine, flowgraph
composition, block configurations,
knowledge plane, RFE control logic
OR Wireless Processing Plane
i
n
(Analog)
OR Wireless Decision Plane
monitor
&
co
ntr
ol
data
AX
data
o
u
t
deterministic signal processing blocks,
header parsing, channel resource
scheduling, multicore fifo queues,
sample I/O blocks
OR Runtime System
compute resource
scheduling,
deterministic execution
ensuring protocol
deadlines are met
Bare-metal with drivers
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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
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
Our Vision: Virtualized Wireless Networks
AT&T
Verizon
Wireless Network OS
Open interface to heterogeneous
wireless infrastructure
X
X
Shared physical
wireless infrastructure
3G
WiFi decoupled
AP
from network
service
LTE