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