NeXt Generation Wireless
Networks: Smart Radios
Suzan Bayhan
bayhan@boun.edu.tr
http://satlab.cmpe.boun.edu.tr
http://www.cmpe.boun.edu.tr//~bayhan
1/37
NETLAB Seminar 7 March 2007
Outline
Problem Definition & Motivation
Software Defined Radio + Cognitive Radio
Standardization
What about Satellites?
Conclusion and References
2/37
NETLAB Seminar 7 March 2007
Motivation
Going wireless more and more...
Lack of interoperability bw. different technologies
Lack of spectrum (???)
3/37
NETLAB Seminar 7 March 2007
Spectrum Facts
 Fixed Spectrum Assignment
 Bandwidth is expensive and good
frequencies are taken
 Recent measurements by the
FCC in the US show 70% of the
allocated spectrum is not utilized
 Time scale of the spectrum
occupancy varies from msecs to
hours
SOLUTION
More clever radio
Frequency Agility----SPECTRUM SHARING
4/37
NETLAB Seminar 7 March 2007
Solution
Joseph Mitola 1992
Joseph Mitola 1999
Software Defined Radio(SDR)
Cognitive Radio(CR)
radio primarily defined in
software, which supports a broad range of
frequencies, and its initial configurations can be
modified for user requirements.
SDR + Intelligence
5/37
NETLAB Seminar 7 March 2007
Outline
Problem Definition & Motivation
Software Defined Radio + Cognitive Radio
Standardization
What about Satellites?
Conclusion and References
6/37
NETLAB Seminar 7 March 2007
SDR properties
Reconfigurable
Easily Upgradeable
Responds to the changes in the operating environment
Lower maintenance cost
7/37
NETLAB Seminar 7 March 2007
If SDR technology is properly applied...
it will facilitate this single platform design, and will also
provide a path towards the realization of concepts such
as
Reconfigurability (single platform concept)
run-time reconfiguration (run-time bug fixes)
and eventually self-governed learning (cognitive)
radio.
8/37
NETLAB Seminar 7 March 2007
FINAL GOAL...
UNIVERSAL WIRELESS DEVICE
that can seamlessly handle a range of frequencies,
modulation techniques, and encoding schemes.
9/37
NETLAB Seminar 7 March 2007
Some definitions
Primary User (Licensed User)
the user which has an exclusive right to a certain spectrum band.
In other words, the license holders...
No need to be aware of cognitive users
No additional functionalities or modifications needed
Secondary User (Unlicensed User)
Cognitive-radio enabled users
Lower priority than PUs
10/37
NETLAB Seminar 7 March 2007
SPECTRUM HOLE
A spectrum hole is a band of frequencies assigned to a
primary user, but, at a particular time and specific
geographic location, the band is not being utilized by that
user.
11/37
NETLAB Seminar 7 March 2007
Definition (1)
In the 1999 paper that first coined the term “cognitive
radio”, Joseph Mitola III defines a cognitive radio as
“A radio that employs model based reasoning to
achieve a specified level of competence in radiorelated domains.”
12/37
NETLAB Seminar 7 March 2007
Definition (2)
Simon Haykin defines a cognitive radio as “An intelligent wireless
communication system that is aware of its surrounding environment
(i.e., outside world), and uses the methodology of understanding-bybuilding to learn from the environment and adapt its internal
states to statistical variations in the incoming RF stimuli by making
corresponding changes in certain operating parameters (e.g.,
transmit-power, carrierf requency, and modulation strategy) in realtime, with two primary objectives in mind:
· highly reliable communications whenever and wherever needed;
· efficient utilization of the radio spectrum.
13/37
NETLAB Seminar 7 March 2007
Properties
Cognitive radio requirements
co-exists with legacy wireless systems
uses their spectrum resources
does not interfere with them
Cognitive radio properties
RF technology that "listens" the spectrum
Knowledge of primary users’ spectrum usage as a function
of location and time
Rules of sharing the available resources (time, frequency,
space)
Embedded intelligence to determine optimal transmission
(bandwidth, latency, QoS) based on primary users’ behavior
14/37
NETLAB Seminar 7 March 2007
Main Cognitive Functions
Spectrum Sensing
Spectrum Management
Spectrum Mobility
Spectrum Sharing
15/37
NETLAB Seminar 7 March 2007
But...
Hard to design a radio front end in software...
A single antenna with good gain across a wide
range of frequencies.
16/37
NETLAB Seminar 7 March 2007
9 levels of CR functionality
17/37
NETLAB Seminar 7 March 2007
How Does a Cognitive Radio Get So Smart?
External
Intelligence
Sources
Orient
Establish Priority
Infer on Context Hierarchy
Plan
Pre-process
Immediate
Urgent
Parse
Observe
Receive a Message
Read Buttons
Outside
World
Normal
Learn
New
States
Save Global
States
Prior
States
Act
Send a Message
Set Display
Register to Current Time
Decide
Alternate Resources
Initiate Process(es)
(Isochronism Is Key)
The Cognition Cycle
OBSERVE-ORIENT-DECIDE-ACT
18/37
NETLAB Seminar 7 March 2007
Generate Alternatives
(Program Generation)
Evaluate Alternatives
OODA loop
19/37
NETLAB Seminar 7 March 2007
SPECTRUM SENSING
Goal: Reliably detect presence of a Primary User
Different Primary Users have different sensitivity
thresholds
Three possible approaches:
1. Matched Filter
2. Energy detector
3. Cyclostationary Feature detector
Local Spectrum Sensing
– Each user makes decision on a Primary User presence
based on its local sensing measurements
Cooperative Spectrum Sensing
20/37
NETLAB Seminar 7 March 2007
Outline
Introduction
Software-defined radio-Cognitive Radio
Standardization
Research Issues
References
21/37
NETLAB Seminar 7 March 2007
Standardization efforts
IEEE 802.22 WRAN
SDR Forum
GNU Radio Project
DARPA xG
JTRS
22/37
North R., Browne N., Schiavone L., Joint Tactical Radio System- Connecting the GIG to the
tactical Edge, MILCOM 2006, 23-25 Oct, 2006, Washington, DC. USA.
NETLAB Seminar 7 March 2007
FCC approves first software-defined
radio...2004
The Vanu Software Radio GSM
Base Station from Vanu can support
multiple cellular technologies and
frequencies at the same time and can
be modified in the future without any
hardware changes.
GSM + CDMA waveforms
Written in C++, running under the
Linux OS.
IEEE Spectrum, January 2007
23/37
NETLAB Seminar 7 March 2007
Challenges and Research Issues
Hardware
Learning Mechanisms
Routing and Upper layer Issues (Networking, QoS)
Developing spectrum sharing behaviors
Sensitive detection
Frequency assignment negotiation
Resource allocation
Security (Unintentional config..)
Integration with “spectrum market”
24/37
NETLAB Seminar 7 March 2007
Cross-layer design
Routing, System
Management, QoS and other
upper layer issues...
Application Layer
Transport Layer
Network Layer
• Optimize transmission
parameters
• Adapt rates through feedback
• Negotiate or opportunistically
use resources
MAC Layer
Physical Layer
OFDM transmission
Spectrum monitoring
Dynamic frequency selection,
modulation, power control
25/37
Analog impairments compensation
NETLAB Seminar 7 March 2007
Some SDR platforms
26/37
NETLAB Seminar 7 March 2007
Outline
Problem Definition & Motivation
Software Defined Radio + Cognitive Radio
Standardization
What about Satellites?
Conclusion and References
27/37
NETLAB Seminar 7 March 2007
What about satellites!!!
How can satellites take role in the game?
Or can they?
Satellite knowledge chunk in Mitola’s book (2000)
Software Radio in Space Segment by Catherine Morlet,
European Space Agency (ESA), 2006.
28/37
NETLAB Seminar 7 March 2007
WAND (softWare rAdio techNology in
space segment stuDy)
Software Radio in Space Segment Final Report v1.1
20 April 2006
Alcatel Alenia Space France (FR)
Alcatel Alenia Space Espana (SP)
Atos Origin (SP)
Carlo Gavazzi (IT)
The introduction of Software Radio Technology at the satellite level has particular
interest for:
• Improving the functionalities of a payload/repeater.
• Introducing standard updates.
• Modifying the mission of a payload/repeater.
• Introducing new concepts (e.g. adaptative coding and modulation).
29/37
NETLAB Seminar 7 March 2007
Satellite Lifetime ~ 10-15 years
Standards and associated algorithms are going to
evolution during this period putting the satellite in risk of
obsolescence during its lifetime period.
30/37
NETLAB Seminar 7 March 2007
Other issues
Intelligence in satellite
Spectrum Manager(!)  Can it be logical?
Policy Updates by satellites (Broadcasts)
31/37
NETLAB Seminar 7 March 2007
Simulation Scenario
A 1000 m X 1000 m area
Some WLAN users
Some SUs (mobile)
High Altitude Platform
decides on frequency and
other transmission
parameters based on feedback from the SUs and the
policies from LEO or
Command Center.
32/37
NETLAB Seminar 7 March 2007
Performance Evaluation
Effect of number of SUs
Overall Throughput
SU Throughput
Interference by SUs
Spectrum Utilization
RESULTS COMING SOON!
33/37
NETLAB Seminar 7 March 2007
To conclude...
More efficient use of spectrum (may decrease cost of the
services like GSM calls)
Flexibility (Interoperability)
Dreaming of a universal device!
34/37
NETLAB Seminar 7 March 2007
References
S. Haykin, "Cognitive radio: brain-empowered wireless communications," IEEE Journal Selected
Areas in Communications, vol. 23, no. 2, pp. 201 - 220, 2005.
J. Mitola III, “Software radios survey, critical evaluation and future directions,” IEEE AES Systems
Magazine, Vol. 8, No. 4, pp. 25-36, Apr. 1993.
I.F. Akyıldız, W-Y.Lee, M.C. Vuran, S.Mohanty,”NeXt generation/dynamic spectrum
access/cognitive radio wireless networks: A survey”, Computer Networks Journal (Elsevier), vol.
50, pp. 2127-2159, September 2006.
David Scaperoth, Cognitive Software Defined Radio: Applications of Cognitive SDR using the
GNU Radio and the USRP, 09/09/05.
http://www.cognitiveradio.wireless.vt.edu/dokuwiki/doku.php?id=research:radio_hw_sw
http://web.syr.edu/~ejhumphr/
http://bwrc.eecs.berkeley.edu/Research/Cognitive/publications.htm
Neli Hayes, JTRS Specification: The past, the present, and the future..., MILCOM 2005.
J. Powell, “Public safety perspectives on cognitive radio–Potential and pitfalls,” presented at the
Conf. Cognitive Radios, Technology Training Corporation, Las Vegas, NV, Mar. 15–16, 2004.
J. D. Shilling, “FCC rulemaking proceeding on cognitive radio technologies,” presented at the
Conf. Cogn. Radios, Technol. Training Corp., Las Vegas, NV, Mar. 15–16, 2004.IEEE Spectrum,
January 2007.
35/37
NETLAB Seminar 7 March 2007
Thank You!
Questions?
bayhan@boun.edu.tr
www.satlab.cmpe.boun.edu.tr
36/37
NETLAB Seminar 7 March 2007