Cognitive Radio Solutions Beyond DSA MobiCom 2011

The information presented herein is confidential and subject to change without notice. xG® and xMax® are

registered trademarks of xG Technology, Inc. Copyright 2010, All Rights Reserved.

www.xgtechnology.com 1

MobiCom 2011 Rick Rotondo, xG Technology

“Cognitive Radio

Solutions:

Moving Beyond DSA”




Cognitive Technology

►Cognitive radio is a paradigm for wireless

communication in which either a network or a

wireless node changes its transmission or reception

parameters to communicate efficiently avoiding

interference with licensed or unlicensed users.

Cognitive techniques have been almost exclusively focused on DSA (running away from interference)

http://en.wikipedia.org/wiki/Cognition

http://en.wikipedia.org/wiki/Wireless

http://en.wikipedia.org/wiki/Communication

http://en.wikipedia.org/wiki/Computer_network

http://en.wikipedia.org/wiki/Wireless

http://en.wikipedia.org/wiki/Node_(networking)

http://en.wikipedia.org/wiki/Transmission_(telecommunications)

http://en.wikipedia.org/wiki/Reception

http://en.wikipedia.org/wiki/Parameter




White Spaces?

Unused Spectrum – White Spaces

Very Light Use – Off-White Spaces

Heavy use – Dark Gray Spaces

Active Jamming – Black Spaces

Wh

ite

Sp

aces

Is there such a thing as

White Spaces???

No! it is all gray space to

some degree

(or worse!)

Average Use – Light Gray Spaces

TIM

E

Getting

hard to

find…




► Able to identify spectrum that is not being used

► Dynamically tunes to those frequencies (within 30 ms)

► Instantly find other spectrum if interference is detected

► Adapt power, modulation, channel plan, network protocol, etc.

► Dynamically maximize throughput (or range) and minimize interference to other devices

Traditional view of Cognitive Radios

The Focus on running away from interference (DSA) does a poor job of optimizing all available spectrum resources i.e.

Gray/Black Spaces




► Able to identify spectrum that is not being fully used

► Dynamically tunes to those frequencies (within 30 ms)

► Mitigate interference to the extent possible to extend “dwell time” on the current frequency

► Employ DSA techniques if interference is overwhelming and performance falls below set thresholds

► Adapt power, modulation, channel plan, network protocol, etc.

► Dynamically maximize throughput (or range) and minimize interference

xG’s take on Cognitive Radios

xG radios dynamically optimize spectrum utilization through use of all available spectrum resources




xMax Cognitive Technology

xMax Layered Cognitive Approach:

– Spectrum sensing: Interference based detection of transmitters.

– Spatial processing: MIMO technologies allow resistance to interferers. Optimize SNR using multiple antenna processing.

– Spectrum sharing: Able to operate in crowed shared spectrum (ISM UNI II etc.). Detect interferers, mitigate them, or avoid them by changing operating parameters or frequencies.

– Spectrum management: Capture the most available spectrum. Terminals and Base Station can change operating frequencies dynamically.

– Spectrum mobility: Use spectrum dynamically. Mobile user stations and base stations can decide to change bands where they operate.




xMax Interference Processing

►Dependably operate on “gray and black spaces”

►Mitigate narrow/wideband, burst/continuous interference.

Short bursts of tens/hundred of microseconds typical to

cordless phones and other frequency hoppers are

removed by identifying the location of error in the time

domain and applying xMax adaptive interference error

correction.

Longer bursts of several hundred microseconds and

longer are removed by spatial multi-antenna, multi-

algorithm error processing.

T

I

M

E

Frequency





►Spatial processing to remove interference.

xMax

• xMax samples the arriving RF wave

front using 4 antennas.

• Interferers can be located by position

• Algorithms can be used in the receive

chain to mitigate this energy

• The xMax system sends known

training signals that are measured

and used to calibrate the receivers

• Spatial processing removes

interference that is longer than 800

microseconds.

• Shorter interference is removed by

redundant coding.





►Multi-layer interference mitigation system.

Receiver algorithm 1

(MRC)


(Spacial projection)


(Time diversity,

nonlinear combining)


(Time diversity,

nonlinear combining)

Select

correctly

decoded

data

based on

CRC.





►Redundant coding to remove burst interference.

Data is

Transmitted

twice.

Error free symbols

are identified Interference randomly

destroys OFDM symbols.

Error free version

is reassembled How do we know what pieces of a received signal are

erroneous before error correction coding and CRC?

With 20 redundant pieces there are 1048576 possible

ways to assemble them. Not feasible unless we can

identify interference symbol by symbol.





►How do we tell what received bits are interfered with?

(If we know exactly what bits are wrong we could just

invert them!)

0 20 40 60 80 100 1201

1.2

1.4

1.6

1.8x 10

6

0 20 40 60 80 100 1200.5

1

1.5

2x 10

6

xMax calculates estimate of OFDM

symbol being interfered based on statistics

computed for the whole data packet.

By computing statistics for two redundant

packets the system can assemble an error

free packet. It is like an error correction

coder on top of error correction coder telling

what pieces of the signal the coder should use.

80µs error burst.




xMax Interference Processing Simulation Results

0 10 20 30 40 50 60 70 80 90 1000

1

2

3

4

5

6

7

1.4 MHz wide xMax with GSM-

like jammer.

0 10 20 30 40 50 60 70 80 90 1000

0.5

1

1.5

1.4 MHz wide xMax signal after

Spatial processing.

-4 -2 0 2 4 6 8 10 12 1410

-6

10-5

10-4

10-3

10-2

10-1

100

SNR

BE

R

Xmax OFDM BER

BPSK

QPSK

16QAM

64QAM

THEOR. 16QAM

THEOR. QPSK

-4 -2 0 2 4 6 8 10 12 1410

-6

10-5

10-4

10-3

10-2

10-1

100

SNR

BE

R

Xmax OFDM BER

BPSK

QPSK

16QAM

64QAM

THEOR. 16QAM

THEOR. QPSK




xMax Wireless Network

Public or

Private

Internet

xMSC

xMax Cognitive Radio Network (C-RAN) Core Network Public Network

VoIP CORE

POTS calling

SMS service

Wi-Fi

Network

xMSC has COTs

equipment for

network

management,

firewall , SIP

Proxy, and SMS

server

xMod is a mobile

seamless bridge

between WiFi and

xMax networks Smart Phones,

Laptops or any

device with WiFi

can connect to the

xMod

xAPs provide wired

network to xMax

network conversion.

They can be vehicle

or tower mounted.

xAPs are Ethernet IP

connected.

WiFi Network

SMS

server

xMax Overview




► Dynamic Spectrum Access (DSA) is a key aspect of CR

► But Cognitive Networks Must Leverage More Than DSA! – Parallel Receiver Processing Chains (MIMO)

– Interference Mitigation Algorithms

– Adaptive Antennas, Beam Forming

– Adaptive Architecture (Point to Multipoint, Mesh, etc.)

– Application Aware QoS (VoIP, Throughput, Latency, Priority)

– Automatic & Dynamic Channel Planning

– Intelligent Modulation Adaptation

– Real-time Link Optimization

– Transmit Power Adjustment

Beyond DSA Summary




Thank You

Cognitive Radio Solutions Beyond DSA MobiCom 2011

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Transcript of Cognitive Radio Solutions Beyond DSA MobiCom 2011