Cooperative Communication Protocol on Software Defined Radio

Howard T. HuangProf. Hamid JafarkhaniProf. Homayoun Yousefi’zadehLun Dong (Postdoctoral)

SURF-IT 2010

Multipath fading

Diversity Schemes

Diversity schemes mitigate effects of multipath fading

Transmit redundant signals over independent channels

Well known schemes:MIMO – multi-input multi-outputCooperative Communication

Cooperative Communication

Trans

mitte

d sig

nal

Transmitted signal

Retransmitted signal

relay

destinationsource

Differences From Repeaters

Repeaters are dedicated base stations (infrastructure)Have “unlimited” power resources

Relay radios belong to other usersAre generally mobile and run on batteriesHave their own data to transmit

SURF-IT Project

Implementation and Testing of A Cooperative Communication Protocol on a Software-Defined Radio Platform

Verify performance of cooperative protocol by measuring bit error rate (BER) and packet error rate (PER)

What is Software-Defined Radio? Software-Defined Radio (SDR) is programmable

by…software! Can be easily reconfigured to users’ needs Example: Qualcomm’s Gobi SDR can switch between

HSPA (AT&T) and EV-DO (Verizon)

Traditional radios can only operate as one type of radio Function is hard-coded and cannot be changed Example: AT&T phones (GSM) do not work on

Verizon network (CDMA2000)

Our SDR Test Platform

GNU Radio Software on regular PC’s running Linux + Universal Software Radio Peripheral (USRP)

GNU Radio is open source softwareDoes bulk of signal processing

USRP contains only ADC/DAC converters and RF frontendDoes only baseband processing

GNU Radio + USRP

Photo by Jason Tran, SURF-IT 2009

The USRP

Photo by Jason Tran, SURF-IT 2009

Transmission Errors

Bit error

Sent: 01101101|01101101|00101110Received: 01111101|01101001|01001100Errors: X X XX X

Packet error Any bit error in the packet results in packet error

Sent: 01101101|01101101|00101110Received: 01111101|01101101|00101110Errors: X

Results: BER vs. Transmit Power

0

1

2

3

4

5

6

7

2.5 3 3.5 4 4.5 5 5.5 6

Tx power (mW)

BE

R (

%)

Direct Tx Coop

Conclusions & Future Work Cooperative protocol is actually extension of

Load-Adaptive MAC protocol (LA-MAC) proposed earlier MAC protocols allow devices to share a transmission

medium (the air) LA-MAC is designed to improve efficient usage of

wireless medium

Part of larger project using GNU Radio/USRP as MANET (mobile ad-hoc network) testbed for developing network protocols and algorithms

Acknowledgements

Prof. Hamid Jafarkhani (mentor)Prof. Homayoun Yousefi’zadeh (mentor)Lun Duong (Postdoctoral)Xiaofang Liu (MSEE graduate)Weihong Hu (Ph.D candidate)Jason Tran (SURF-IT 2009 fellow)

And of course the SURF-IT sponsors, Calit2 and UROP

And the Boeing Corporation

Questions?