Title: Energy Efficiency of MIMO Transmissions in Wireless Sensor Networks with Diversity and Multiplexing Gains
1Energy Efficiency of MIMO Transmissions in
Wireless Sensor Networks with Diversity and
Multiplexing Gains
Wenyu Liu, Xiaohua (Edward) Li and Mo Chen
Department of Electrical and Computer
Engineering State University of New York at
Binghamton hyusa_at_hyig.com, xli,
mchen0_at_binghamton.edu, http//ucesp.ws.binghamton
.edu/xli
2Abstract
- Energy efficiencies of some MIMO transmission
schemes in wireless sensor networks are analyzed
considering the trade-off between diversity and
multiplexing gains - Optimal energy efficiency requires both
diversity and multiplexing gain - Cooperative MIMO are potential for enhancing
energy efficiency
3Outline
- Introduction
- MIMO Transmission Schemes
- Energy Efficiency of non-cooperative MIMO
- Energy Efficiency of cooperative MIMO
- Simulations
- Conclusions
4- Introduction
- Cooperative transmissions in sensor networks
exploit the collaborative nature of sensors - Cooperative STBC to improve energy efficiency
depending on transmission distance - Overheads
- Circuitry energy consumption increases
- Cooperation overhead reduces energy efficiency
- Cooperative MIMO Is it better for energy
efficiency? - Even higher overheads
- There is a fundamental trade-off between the
diversity gain and the multiplexing gain.
52. MIMO Transmission Schemes
- non-cooperative MIMO
Physical antenna array in Rx
Physical antenna array in Tx
b) one-side, half-cooperative MIMO
Physical antenna array in Rx
A cluster of sensors forming an virtual array at
Tx
6c) two-side, cooperative MIMO
A cluster of sensors forming an virtual array at
Rx
A cluster of sensors forming an virtual array at
Tx
General Cooperative MIMO Description
Cooperative transmission The primary head sensor
first broadcasts to the secondary head sensors
the data to be transmitted. Then at the next time
slot, all the heads (the primary and secondary)
perform cooperative transmission.
Cooperative receiving All the secondary heads
forward their received signals to the primary
head, where the MIMO signal detection is
performed.
7MIMO Signal Model
Mt x 1 transmitted Signal, zero mean, ss
Mr x Mt channel matrix
power adjuster
Mr x 1 AWGN, zero mean, sv
Mr x 1 received signal
The received signal-to-noise ratio (SNR) at each
antenna
83. Energy Efficiency of Non-cooperative MIMO
3.1, Transmission Energy Efficiency
Bit Error Rate
Transmission Date Rate
- Diversity Gain Improve energy efficiency
- Multiplexing Gain Achieve higher rate ? higher
trans. power - Reduce
time ? enhance energy efficiency
9Trade off between dr and r for some MIMO schemes
10Transmission Energy
Total data to be transmitted
Large scale path loss with exponent n
N/-logPe
Cs2v
Transmission energy depends on both diversity
gain dr and multiplexing gain r
11Circuitry Energy
Circuit Energy Constant
Overall transmission and circuitry energies
12Non Cooperative MIMO energy efficiency (Jtc/Ktc
109)
MtMr2, Pe0.001, n 2 and d 10
meters Et100pJ / 249 and Ec50 nJ
134. Energy Efficiency of Cooperative MIMO
With either cooperative or half-cooperative
MIMOs, there is energy consumption in
cooperative overhead.
Primary heads chooses Mt -1 secondary heads
Step 1
(Overhead is small, and can be skipped)
(Major overhead broadcasting of the N data bits)
14Total Energy Consumption
The data rate of broadcasting from the primary
head to the secondary head
Scale factor due to the fact that the symbol
alphabet of broadcast may be different from
cooperative transmission
Signal noise ratio to broadcasting
15Step 4
The Mr-1secondary heads
quantize their received samples, and transmit
them as new symbol sequences to the primary head,
where MIMO receiving is performed to recover the
original N bits
Composite result of quantization and symbol
mapping
16Overall energy consumption of the cooperative
MIMO transmission
Overall energy consumption of the
half-cooperative MIMO transmission
The cooperative or half cooperative MIMO energy
efficiency can be optimized as
17Cooperative MIMO energy efficiency (Ja/Ktc 109)
MtMr2, Pe0.001, n 2 and d 100 meters,
Et100pJ / 249 and Ec50 nJ
18Half-cooperative MIMO energy efficiency (Jh/Ktc
109)
MtMr2, Pe0.001, n 2 and d 100 meters,
Et100pJ / 249 and Ec50 nJ
195. Simulation
Compare the simulated transmission energy
consumption with the theoretical values
206. Conclusion
- Derived energy consumption representations for
MIMO and cooperative MIMO - Cooperative overheads were considered in
addition to transmission energy efficiency - The MIMO tradeoff between diversity and
multiplexing was exploited for transmission
energy efficiency optimization - MIMO and cooperative MIMO were shown beneficial
to sensor network energy efficiency