1 cooperative mimo paradigms for cognitive radio networks wei chen & liang hong college of...

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Cooperative MIMO Paradigms for Cognitive Radio

Networks

Wei Chen & Liang Hong

College of EngineeringTennessee State University

Dr. Liang [email protected]

(615) 963-5364


APDCM 2013 Boston, MA, May 20, 2013

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Outline

• Introduction• Problem Statement• Cooperative MIMO Network Model and

Communication Schemes • Cooperative MIMO Paradigm for Overlay Systems• Cooperative MIMO Paradigm for Underlay Systems• Numerical Analysis and Experiments• Conclusions

Cooperative MIMO Paradigms for Cognitive Radio Networks


(615) 963-5364College of EngineeringTennessee State University

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Introduction


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T×1

T×2

T×M R×M

R×1

R×2

T×1

T×2

T×M R×M

R×1

R×2

Wireless MIMO network

MIMO Technology−Multiple antennas transmit same data streams simultaneously: it can be used to reduce energy, or extending communication range and error rate. −Multiple antennas transmit different data streams simultaneously: it can be used to provide higher data rate (multiplexing gain)

multiplexing gaindiversity gain

MIMO transceiver

However, it is unrealistic to equip multiple antennas to small and inexpensive wireless devices (e.g., wireless sensor nodes).


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Cooperative Communication MIMO Technology

– Distributed individual single-antenna nodes cooperating on information transmission and reception as a multiple antenna array

First hop Other hops

MIMO LinkMISO LinkSIMO LinkSISO Link

MIMO links

Cooperative MIMO Schemes

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Cognitive radio A promising paradigm in wireless communication that enables efficient use of frequency resources

− Coexistence of licensed primary users (PUs) and unlicensed secondary users (SUs) in the same frequency band

− Cognitive capabilities

Basic approaches: (1) spectrum overlay, (2) underlay, and (3) interweave


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A cooperative SIMO link

A cooperative MISO link

Secondary Users

PT PR

an mt×mr cooperative MIMO link

SRST

Primary Users

Overlay Underlay Interweave

time

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• Existing overlay schemes require the relay SUs to be in the convenient location, typically halfway between source and destination

• Existing underlay schemes cannot guarantee that the aggregated interference generated by SUs is maintained below the threshold


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Problem Statement

This Research

Develop energy efficient cooperative MIMO paradigms that can maximize the diversity gain and significantly improve the performance of both overlay and underlay systems.

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Network Model and Communication Schemes


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Underlying network: Network G = (V,E) of single-antenna radio nodes.

d-Clustering: the distance between two nodes in a cluster ≤ d. d-clusters are called Cooperative MIMO nodes, and the nodes of G are called primary nodes.

D-Cooperative-MIMO links: Let A and B be two d-clusters, and A’ and B’ be the subsets of A and B, respectively. Suppose there are mt nodes in A’ and mr nodes in B’. If the largest distance between any node of A’ and any node of B’ is not larger than D, a D-mt×mr virtual MIMO transmission link can be defined between A and B.

Heterogeneity: The size and the diameter of a cluster, and the length of virtual MIMO links can be different.

3×2 MIMO link

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Cooperative MIMO Paradigm for Overlay System


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A cooperative SIMO link A cooperative MISO link

− Step 1: data transmission from the

primary transmitter to m SUs via 1×m

SIMO link

− Step2: data transmission from m SUs

to the primary receiver via a m×1

MISO link



Optimization (at SUs)•Maximize the distance that the secondary users can be away from the primary users.•Minimize the energy usage at the secondary users.

SUs assistant PUs’ communication: (SUs can use the PUs channel when PUs’ communication completed)

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Cooperative MIMO Paradigm for Underlay System


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Secondary Users

PT PR

mt×mr cooperative MIMO link

SRST

Primary Users



SUs utilize PUs’ channel obliviously: SUs share the PUs’ frequency resource without any knowledge about the PUs’ signals and under the strict constraint that the spectral density of their transmitted signals fall below the noise floor at the primary receivers

Optimization at SUs•Maximize the communication performance (minimize error rate)•Minimize the energy usage at the secondary users.

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Energy Model

− Energy consumption per bit at each primary node for local/intra data

transmission

− Energy consumption per bit at each primary node for local/intra

reception

LtC

LtPA

Lt eee

22 )21(4

ln3

)12)(1(4 fd

b

bb

LtPA NG

bPbe

nTPbBPe trsynctLtC /)/(

nTPbBPe trsyncrLr /)/(



Numerical Analysis and Experiments

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− Energy consumption per bit at each primary node for data transmission in long-haul mt

× mr cooperative MIMO link

− Energy consumption per bit at each primary node for data reception in long-haul mt ×

mr cooperative MIMO link

MIMOtC

MIMOtPA

MIMOt eemrmte ),(

flrt

bbMIMOtPA NM

GG

D

b

mrmtbPee

2

2)4(

3

),,,()1(

bBPPe synctMIMOtC /)(

)/()( bBPPe syncrMIMOr



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− Parameters

Pct = 48.64 mw Pcr = 62.5 mw

Psyn = 50 mw Nf = 10 dB

Ttr = 5 μs σ2 = N0/2 = -174 dBm/Hz

GtGr = 5 dBi λ = 0.1199

Gd = G1dkMl (G1 = 10 mw, k = 3.5, Ml = 40 dB)

)12(35.0

)12(3

b

b

2for ,1

3

2

11

42/

b

M

bQ

bp b

bHb

1for ,2 bQp bHb bM 2

mtN

mrmybpeH bbFb

0

2),,,(

tscoefficien channel :H



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Numerical analysis in Overlay System


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− Step 1: data transmission from the

primary transmitter to m SUs via 1×m

SIMO link

− Step2: data transmission from m SUs

to the primary receiver via a m×1

MISO link

),1( mee MIMOtPt MIMOr

sr ee

)1,(mee MIMOtSt MIMOree Pr



given are and whendistanceslargest thefind .2

energy minimizingby of valueoptimal thefind .1

nodesprimary the tonodes SU thefrom distanceslargest theDetermine

SPA

SrStS

EE

EEEb

Secondary Users

PT PR


SRST

Primary Users

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Numerical Analysis in Underlay System


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Since only transmission energy brings

interference from SUs to primary receiver,

only the transmission energy is considered

−Intra/local transmission

−Long-haul transmission

LtPA

Lt ee

MIMOtPASt emte

),max( MIMOtPA

LtPAPA emteE



PAEb minimizingby of valueoptimal theFinding

Secondary Users

PT PR


SRST

Primary Users

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Numerical Analysis Results


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In overlay systems the SUs can assist/relay the PUs’ transmission even when SUs are far away from primary transmitter (Pt) and primary receiver (Pr)



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In underlay systems the SUs are able to share the PUs’ frequency resource without any knowledge about the PUs’ signals and under the strict constraint that the spectral density of their transmitted signals fall below the noise floor at the primary receivers.




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System Evaluation in Real Wireless Environment Build a cooperative cognitive testbed using the universal software radio peripheral (USRP) platform and GNU Radio

−Each node consists: an USRP motherboard + RFX2400 daughterboard −signal processing module implemented in GNU Radio running in a general purpose computer under Ubuntu operating system −BPSK modulation and demodulation is used for all experiments

Underlay System Overlay System

Licensed Primary Transmitter

Licensed Primary Receiver

unlicensed Secondary Transmitter

unlicensed Secondary Cooperative Transmitter

unlicensed Secondary Receiver

unlicensed Secondary Users as Relay



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Multiple Relays Coop.(Node Distance: 30 ft)

Single Relay Cooperation

Without Cooperation

2.93% 2.21% 9.13%


Overlay System Underlay System

(Bit error rate performance) (Packet error rate performance)

•Single-relay Cooperation

•Multiple-relay cooperation

Trial(Node distance: 2 m)

With Cooperation

Without Cooperation

1 2.21% 9.13%

2 2.27% 12.73%

3 2.89% 10.76%

Average 2.46% 10.87%

Amplitude With Cooperation

Without Cooperation

800 0 24.85%

600 6.12% 70.28%

400 13.72% 97.1%

Average 6.61% 64.08%


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Conclusions

• Proposes energy efficient cooperative MIMO paradigms for cognitive radio networks.

• In overlay systems, SUs can relay the primary transmissions even when they are far away from the primary users

• In underlay systems, SUs are able to share the primary users’ frequency resources without any knowledge about the PUs’ signals, even when they are close to the primary receivers

• Performance evaluation in real wireless environment verified the advantage of the proposed paradigms.


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Thank you!

Questions?



1 cooperative mimo paradigms for cognitive radio networks wei chen & liang hong college of...

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