An Image Processing Approach to Distributed Access for Multiantenna Cognitive Radios

Mauro Biagi, Valentina Polli, Jose Alberto Andrade Freitas

Dept. of Information, Electr. and Comm. Eng., “Sapienza” University of Rome

September 21, 2010

International Symposium on Wireless Communication Systems

ISWCS’10 York, United Kingdom

Outline

• Introduction and Related Works

• System Model

• Spectrum Occupancy and Image Processing

• Time - Frequency Access

•Numerical Results

•Conclusions

Introduction and Related Works

Conventional wireless medium management has always been basedon exclusive bandwidth usage in order to prevent mutual interference

1

Introduction and Related Works

Need for new technologies to face the evergrowing demand for bandwidth and the inefficient employment of the licensed

spectrum across space, time and frequency

Conventional wireless medium management has always been basedon exclusive bandwidth usage in order to prevent mutual interference

1

Introduction and Related Works

Need for new technologies to face the evergrowing demand for bandwidth and the inefficient employment of the licensed

spectrum across space, time and frequency

Conventional wireless medium management has always been basedon exclusive bandwidth usage in order to prevent mutual interference

Cognitive Radio

leveraging on system capabilities (observe, decide, act, learn) to develop

dynamic, flexible and autonomous spectrum access

1

Introduction and Related Works

Cognitive Access

- spectrum sensing

- spectrum access

2

Introduction and Related Works

Cognitive Access

- spectrum access

- spectrum sensing • energy detection

• matched filter detection

• cyclostationary detection

2

Introduction and Related Works

Cognitive Access

- spectrum access

- spectrum sensing • energy detection

• matched filter detection

• cyclostationary detection

simplicity

2

Introduction and Related Works

Cognitive Access

- spectrum access

- spectrum sensing • energy detection

• matched filter detection

• cyclostationary detection

simplicity

accuracy

2

Introduction and Related Works

Cognitive Access

- spectrum sensing • energy detection

• matched filter detection

• cyclostationary detection

simplicity

accuracy

- spectrum access • probability of occupancy

• optimization

2

Introduction and Related Works

Cognitive Access

- spectrum sensing • energy detection

• matched filter detection

• cyclostationary detection

simplicity

accuracy

- spectrum access • probability of occupancy

• optimization

common features Sensing : spectrum as a collection of channels (mostly carriers) Access : suitability criterion for secondary users transmissions

2

• Access performed through :

Introduction and Related Works

SIGNAL SHAPING

* Biagi, Baccarelli, Cordeschi, Pelizzoni, Polli, “Collision erasure and generalized access in MIMO

cognitive ad-hoc networks”. Wireless Communication Systems. 2008. ISWCS’ 08.

Cognitive Generalized Access *

- Time- Frequency- Code

• Channel as a resource available in

3

• Access performed through :

Introduction and Related Works

SIGNAL SHAPING

* Biagi, Baccarelli, Cordeschi, Pelizzoni, Polli, “Collision erasure and generalized access in MIMO

cognitive ad-hoc networks”. Wireless Communication Systems. 2008. ISWCS’ 08.

Cognitive Generalized Access *

- Time- Frequency- Code

• Channel as a resource available in

1. Interference acquisition - TL

3

freq

uen

cy

time

• Access performed through :

Introduction and Related Works

SIGNAL SHAPING

* Biagi, Baccarelli, Cordeschi, Pelizzoni, Polli, “Collision erasure and generalized access in MIMO

cognitive ad-hoc networks”. Wireless Communication Systems. 2008. ISWCS’ 08.

Cognitive Generalized Access *

- Time- Frequency- Code

• Channel as a resource available in

1. Interference acquisition - TL

2. Channel estimation - TE

3

freq

uen

cy

time

• Access performed through :

Introduction and Related Works

SIGNAL SHAPING

* Biagi, Baccarelli, Cordeschi, Pelizzoni, Polli, “Collision erasure and generalized access in MIMO

cognitive ad-hoc networks”. Wireless Communication Systems. 2008. ISWCS’ 08.

Cognitive Generalized Access *

- Time- Frequency- Code

• Channel as a resource available in

1. Interference acquisition - TL

2. Channel estimation - TE

3. Data transmission - TPAY

3

freq

uen

cy

time

• Access performed through :

Introduction and Related Works

SIGNAL SHAPING

Cognitive Generalized Access *

- Time- Frequency- Code

• Channel as a resource available in

Biagi, Baccarelli, Cordeschi, Pelizzoni, Polli, “Collision erasure and generalized access in MIMO cognitive ad-hoc networks”. Wireless Communication Systems. 2008. ISWCS’ 08.

*

Interference shape affects spectrum availability

3

• Access performed through :

Introduction and Related Works

SIGNAL SHAPING

Cognitive Generalized Access *

- Time- Frequency- Code

• Channel as a resource available in

Biagi, Baccarelli, Cordeschi, Pelizzoni, Polli, “Collision erasure and generalized access in MIMO cognitive ad-hoc networks”. Wireless Communication Systems. 2008. ISWCS’ 08.

*

Interference shape affects spectrum availability

Find solutions to fill up the ”holes”

3

System Model

Cognitive MIMO radio

( ) (r t)i j kf H

Cognitive radios

- power-limited

- multiantenna

- noncooperative

Channel

- Multiple Input Multiple Output (MIMO)

- additive Multiple Access Interference (MAI)

- block fading

(t r)

maxP

4

Spectrum Occupancy and Image Processing

Spectrum Imaging

Interference acquisition:

primary users communications organized on a time frequency grid

received signal

5

Spectrum Occupancy and Image Processing

Spectrum Imaging

Interference acquisition:

primary users communications organized on a time frequency grid

received signal

Wigner-Ville Transform (WVT)

5

Spectrum Occupancy and Image Processing

Spectrum Imaging

Interference acquisition:

primary users communications organized on a time frequency grid

received signal

time

frequency

2D representation of spectrum occupancy

Wigner-Ville Transform (WVT)

5

Spectrum Occupancy and Image Processing

time

frequency

Edge Detection

6

Marking occupied/free zones and select transmission opportunities

Spectrum Occupancy and Image Processing

time

frequency

Edge Detection

Canny processing

Good detection

Good localization

Single response

6

Marking occupied/free zones and select transmission opportunities

Spectrum Occupancy and Image Processing

time

frequency

Edge Detection

Canny processing

Good detection

Good localization

Single response

6

Marking occupied/free zones and select transmission opportunities

Time-Frequency Slot (TFS)

Spectrum Occupancy and Image Processing

time

frequency

Edge Detection

Canny processing

Good detection

Good localization

Single response

Marking occupied/free zones and select transmission opportunities

Evaluation of free-area indicators

Sorting

6

Time - Frequency Access

Signal Shaping

Slot partitioning

7

Interference slope analysis

Time - Frequency Access

Signal Shaping

Slot partitioning

Mask definition

7

Interference slope analysis

Time - Frequency Access

Signal Shaping

Slot partitioning

Mask definition

mask compliance criterion

constraints

7

Interference slope analysis

Time - Frequency Access

Signal Shaping

mask compliance criterion

constraints

Slot partitioning

Mask definition

Parks McClellan Algorithm

7

Interference slope analysis

Time - Frequency Access

Algorithm

8

Shaping computed through a simple iterative algorithm

Time - Frequency Access

Algorithm

8

Shaping computed through a simple iterative algorithm

MIMO Channel State Information to optimize power allocation among transmit antennas (Water-Filling)

Time - Frequency Access

Algorithm

8

Shaping computed through a simple iterative algorithm

Interference slope analysis to optimize mask definition

Numerical Results

Chirp-like Interference

*

-6

max

200 kbps 50 kHz

1 s = 10 (BER 10 )

0.01 Ws

C B

T

P

Simulation parameters

9

Numerical Results

Chirp-like Interference

*

-6

max

200 kbps 50 kHz

1 s = 10 (BER 10 )

0.01 Ws

C B

T

P

Simulation parameters

primary user occupancy

9

Numerical Results

Chirp-like Interference

*

-6

max

200 kbps 50 kHz

1 s = 10 (BER 10 )

0.01 Ws

C B

T

P

Simulation parameters

secondary user allocationprimary user occupancy

9

Numerical Results

Generic-shaped Interference

*

-6

max

200 kbps 50 kHz

1 s = 10 (BER 10 )

0.01 Ws

C B

T

P

Simulation parameters

central high energy signal components usually preclude secondary user access

10

Numerical Results

Generic-shaped Interference

*

-6

max

200 kbps 50 kHz

1 s = 10 (BER 10 )

0.01 Ws

C B

T

P

Simulation parameters

central high energy signal components usually preclude secondary user access

allocation on unemployed portions of the spectrum

10

Numerical Results

Performance Analysis

Time-Frequency vs Cognitive Generalized Access

11

MORE accessing usersemploying LESS antennas

Numerical Results

Performance Analysis

Time-Frequency vs Cognitive Generalized Access

MORE accessing usersemploying LESS antennas

11

Conclusions

Main features of the proposed access strategy are:

the simplicity of the algorithm;

the capability to understand the interference slope and suitably adapt the emission masks;

the new availability criterion which allows to widen the transmission possibilities and enhance spectrum utilization;

the adaptivity to several performance measures.

12