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Mis term paper Mis term paper Document Transcript

  • 1 TERM PAPER ON COGNITIVE RADIO By Rahul Mahajan (10BM60066) MBA 1st year, 2010-2012 batch Vinod Gupta School of Management IIT Kharagpur rahulsm.27@gmail.com
  • 2 ABSTRACT The pervasive use of wireless technology has created an ever-increasing demand for more and more spectrum. However the most recent studies highlight the fact that the current spectrum allocation method is inefficient as the bands are underutilized. There have been many technological developments to increase the efficiency of spectrum utilization. This concentrated mainly on increasing the number of users in a frequency band. These developments are evolutionary as such they evolve from the exiting technologies. However cognitive radio is one of recent revolutionary advancement that promises to govern the future wireless world. It is considered to have a profound effect the way we will mange, utilize and share radio spectrum in future. In this paper the implications of cognitive radio for future management of spectrum is discussed. INTRODUCTION Currently in wireless communication, all around the world, the availability of spectrum is governed by regulatory and licensing bodies. This is called as Static spectrum allocation. In this, the spectrum available is divided into fixed bands and each band is dedicated for a particular service or wireless technology. This dedicated allocation of spectrum to particular services leads to inefficient utilization of spectrum. However the growing need for more and more bandwidth is resulting in spectrum scarcity. Cognitive radio is the most promising solution which can address this problem. What is cognitive radio? The term cognitive radio (CR) was coined by Mitola in 1999 .Quoting the definition of cognitive radio in his words as “the point in which wireless personal digital assistants (PDAs) and the related networks are sufficiently computationally intelligent about radio resources and related computer-to-computer communication to: (a) detect user communications needs as a function of user context and (b) to provide radio resources and wireless services most appropriate to those needs”. A cognitive radio can be considered as a system which continuously interacts with its environment to evaluate the availability of resources and needs of users so as to efficiently utilize the spectrum available. It does so by changing its operation parameters like frequency of operation, modulation and coding technique etc
  • 3 In essence the two most important features of cognitive radio are 1. Intelligent awareness - Being aware of the surrounding environment and continuously learning from the user and environment needs 2. Re-configurability - Ability to make changes in the operating parameters like transmission or reception in real time. AN ANOLOGY The current spectrum allocation can be considered analogous in the way road traffic is controlled with definite lanes and electronic signals, controlling and restricting the flow. The cognitive radio can be considered analogous to a more distributed and self managed- regulated pedestrian traffic. Why cognitive radio? Globally wireless networks are increasingly facing bandwidth crisis .The spectrum available has become a scarce resource. Today mobile communications are allowed only certain frequencies which are getting crowded. As demand for new enhanced services like music, videos and internet are increasing day by day requirement for bandwidth is far more then currently available. Hence fundamental problem facing future wireless communication systems is where to find suitable carrier frequencies and bandwidths to meet the predicted demand of future services. However if one scans the radio spectrum, it would be found that  Some frequencies are unutilized for most of the time  Some frequencies are partially utilized  Some frequencies are heavily loaded for most of the time Thus the available spectrum is inefficiently utilized. HOW One can identify a range of frequencies dedicated to a particular user, but at a particular time and place this frequencies are not being utilized. Cognitive radio exploits this to efficiently utilize the available spectrum. With cognitive radio technology one can use all available frequency even those dedicated to TV and Satellite. Intelligent devices will negotiate with each other in order to utilize the whole spectrum available in the most efficient way.
  • 4 A cognitive radio thus would require the following core capabilities 1. FLEXIBILITY AND AGILITY: Ability to dynamically change the operational parameters. Full flexibility would be possible if cognitive radios are built on top a software-defined radio. An SDR is a radio in which the transmission properties such as signal bandwidth, carrier frequency, modulation, and network access are defined by software. In addition to SDR, another important requirement to achieve flexibility is reconfigure-ability and wideband antenna technologies. 2. SENSING: Ability to scan the RF environment and measure the current state of the environment, including spectral occupancy. Sensing is necessary if the device has to change its operation based on its current knowledge of environment. 3. LEARNING: Ability to make sense out of what is being sensed and learn from it. 4. ADAPTABILITY: Ability to modify internal operational behavior based on the resultant analysis of the new situation, 5. LOCATION AWARENESS: Ability to respond to spatially variant regulatory policies or spatially variant spectrum availabilities. Advantages Cognitive radios thus results in  Proper utilization of available spectrum  Giving precedence to high priority communication  Optimum power consumption  Providing new services
  • 5 KEY DRIVERS FOR COGNITIVE RADIO DSA (DYNAMIC SYSTEM ALLOCATION) Currently Static allocation model is deployed in which the portion of spectrum for a particular service is always dedicated. This procedure ensures simplicity, guaranteed access to the licensee and better quality of services. However deployment of cognitive networks call for a model in which if the licensee called the primary user is not utilizing the band at a particular time then the secondary user can opportunistically use the spectrum. This deployment called Dynamic Spectrum Access would open up vast amount of spectrum. The challenge lies in developing models that significantly improve spectrum efficiency without compromising on the benefits of Static Allocation Model. How one would develop polices that would ensure that the rights of licensee and quality of services are maintained. Also it must be economically viable for manufactures to deploy DSA. The deployment of DSA possesses much technology, spectrum policy and economic challenges. CRN-(COGNITIVE RADIO NETWORKS) Devices employing cognitive radios need to operate smoothly in multiple frequency bands. In addition they must be able to decide which frequency band to use and configure the network appropriately. Specifically, the devices need to agree on how to realize various physical, link, and network layer functions in a way that makes best use of the available spectrum, while also satisfying the policy constraints that apply in the selected band.
  • 6 Cognitive Radio Networks (CRNs) are networks that would be able to sense their RF environment and adapt themselves to achieve optimum efficiency. Wifi already use cognitive optimization (in terms of rate adaptation) and spectrum agility. However the use is very restricted. For deployment of CR more robust and aggressive adaptation techniques such as across wider spectrum band and radical runtime protocol optimizations would be required. SDR (Software Defined Radio) Most of the radios today implement all the processing and protocol functions in hardware thereby limiting runtime adaptability to very small changes. CRN would require a wireless device that is very flexible in changing various protocol functions during runtime. For this SDR present an ideal platform.SDR would enable deployment of several standards on the same hardware by reprogramming the software. In SDR conversion of analog signal to digital signal takes place as early as possible at the front end while conversion of digital signal to analog signal is done as late as possible at the back end. Hence much of the processing takes place in the digital domain. Processing in digital domain is easy and enhances devices flexibility and adaptability However, due to the limitations of analog/digital converters, digital processing capacity and power constraints, SDR are still not fully deployed. The flexibility offered by SDRs is very attractive, especially when prototyping and evaluating cognitive networking technology. TECHNOLOGICAL TECHNIQUES 1. Signal processing - The signal processing problems that would be typical in CR would be making inference about the transmitted information base on received signals in an unknown and dynamically changing environment. Conventional processing methods are computationally complex. However the recently emerged Bayesian signal processing promises a simpler solution 2. Dynamic programming- Dynamic programming broadly refers to solve large complex problem by breaking them down into simpler steps. In cognitive environment dynamic programming would suffer from exponentially increased computational algorithm and resource requirements. 3. Learning machines with feedback- One of the key aspects that will be development of techniques that can learn from the information collected in the past and present .There are techniques currently deployed to fine tune radio parameters but these are in very nascent stage. A lot of research needs to be done on learning , reasoning and resulting intelligence in CR networks 4. Cross-layer protocol design. Currently in wireless network protocol design each layer is designed and operated independently. In cross-layer protocol design adaptivity and optimization across multiple layers of the protocol stack are needed. Each layer responds to variations local to that layer and information from other layers with the aim of joint optimization of all protocol layers.
  • 7 PRESENT SCENARIO –KEY PLAYERS DISA- US Defense Information Systems Agency The US Defense Information Systems Agency (DISA) is moving into the age of dynamic spectrum access (DSA), which is the key near-term contribution of cognitive radio. DISA's Defense Spectrum Organization (DSO) is the DoD center of excellence for spectrum management. The key DSO elements are Global Electromagnetic Spectrum Information System Program Management Office (GEMSIS PMO) Global Electromagnetic Spectrum Information System (GEMSIS) is the joint program of record that will transform spectrum operations from a pre-planned and static frequency assignment into a dynamic, responsive, and agile capability. GEMSIS is focused on increasing the efficiency of DoD spectrum use by eliminating inefficient preplanned and static frequency assignment. Joint Spectrum Center (JSC) JSC is a source of engineering expertise and services dedicated to ensuring effective use of the electromagnetic spectrum. JSC provides services such as spectrum- planning guidance, system integration, system vulnerability analysis, environmental analysis, test and measurement support, operational support and spectrum management software development. NOKIA Nokia a market leader with the aim of improving user experiences for more innovative and integrated telecommunication has already adapted cognitive radio within allocated spectrum bands to manage heterogeneous more efficiently. Nokia research center is working extensively in this field COGNITIVE ACCESS TO TV BANDS In UK digital switchover is expected to be completed by 2012 that would require the TV stations to convert from analogue to digital transmission. After the switchover a portion of TV analogue channels would become vacant which be auctioned off by regulators to other services. In addition there will be a number of TV channels in a given area that would not be used by DTV station because such stations would not be able to operate without interference to adjacent channels. However low power unlicensed device can operate on these vacant spaces that could not be used by DTV due to interferences. These vacant TV channel care called white spaces. The proposed new rules would, in principle allow the operation of both fixed and portable broadband devices on a non-interference basis in this white spaces. A preliminary study by Ofcom indicates that “at any one location, around 100 MHz on average is not being used by DTT (Digital Terrestrial Television) and could, in principle be used by license-exempt devices”
  • 8 PROMOSING APPLICATION OF COGNITIVE Cognitive radio has the potential to drastically alter the way we would mange our communication in the future. Some of the promising applications are 1. Emergency Services Use of Cognitive Radio The public safety users have direct application for cognitive radios. In conditions of emergency need for quality of service and interoperability among various standards becomes vital. CR with there inherent ability to adapt and adjust to different standards would help in such situation. 2. Low Cost Internet Access .The dynamic spectrum access model approach would enable broadband access on the unused spectrums, thereby enabling lower Internet access cost by drastically reducing cost component associated with purchase of spectrum. 3. Rural connectivity By deploying smart mesh CRN systems remote rural areas can be provided connectivity. 4. New services Radio based advertising in which the user gets only relevant information Application in public safety: Consider a situation during an emergency. Emergency situation generally require great deal of co ordination of between different relief workers, fire brigade, police and other concerned person. Chances of communication breakdown both internally and externally increase due to lack of common standards and overburden of emergency bands. Cognitive radio would help in such situation by prioritizing such communication and enabling communication all standards. Application in security: Imagine a situation in which a soldier has to only turn on the device which he is carrying. Once engaged the cognitive radio will determine what spectrum to use, sense any disruptions in the environment (jamming) and adjust accordingly. Application in daily life: A flight entering into the borders of another country. Currently the radio parameters need to be set by the pilot with the help of ground controllers as the standards for communication are different in different countries With cognitive radios no human involvement would be required
  • 9 ECONOMIC APPROACHES FOR IMPLEMENTATION OF COGNITIVE RADIO NETWORKS For implementation of CRN we need to understand the feasibility of various economic approaches as well as the associated technical challenges. The licensed users are called primary users and the users of the CRN are called secondary users. For peaceful existences of both accurate information of the usage of spectrum is required .There are two different approaches that can be followed OPPORTUNISTIC SPECTRUM ACCESS: Secondary users scan the primary user spectrum to determine any vacant spectra. Sensing becomes a critical issue. RESOURCE TRADING: Primary user explicitly provides any relevant information to secondary users. By allowing some monetary to primary users can get some monetary benefits by allowing secondary users to use spectrum In opportunistic spectrum access since there is no motivation for primary user it becomes difficult to guarantee a peaceful coexistence of both. Hence a resource trading based approach is a better option A combination of different economic approaches can be applied in order to have a resource trading based spectrum sharing. These approaches are briefly described next GAME THEORY It’s the study of cooperation and conflict among individuals or groups. It provides an analytical framework for decision making based on this. It aims at maximum optimization of all resources at same time protecting the interest of primary users. PRICE THEORY For resource trade based spectrum sharing appropriate schemes for setting up the price of the spectrum, formulating models that maximizes payoff to both primary users in terms of monetary value and secondary users in terms of service is an important issue MARKET THEORY -Stability would be required overall in order to have a feasible model
  • 10 CHALLENGES IN DEPLOYMENT OF COGNITIVE RADIO LEGAL HURDLES Cognitive radio is an advanced technology. Successful implementation of such revolutionary technologies in an economy and policy regime thrives heavily upon how and where it return value that too without impeding other technologies or innovation. Thus the success of cognitive radios would greatly depend on what policy changes would be required throughout the world and corresponding consequences. Research would be required to support any proposed policy reform. Demonstration of improved performance over the other technology is a must. Improved spectrum utilization and cost effectiveness must be visible to the policy makers. Implementation of cognitive radio requires a model with following requirements  Sharing among equals, or giving some wireless systems primary rights and others secondary status.  Cooperation among systems from different administration domains,  Assumptions that systems are licensed or unlicensed or a mix of the two. A proper research addressing critical issues such as how devices would operate in a given band, what are the levels of risk involved in case of harmful interference, possibility of congestion and interferences under different regulatory approaches, what be the role and responsibility of standard bodies, industry and user groups, what would be the social and economic benefits and potential impact on business and technological strategies would be required. SECURITY RELATED ISSUE Security would be one of the major concerns while deploying cognitive radio. In a system where radios can decide how to use the available spectral resources proper identification and authentication is must. Rouge player trying to cause major communication disruption would flourish. Mechanism would be required to develop to identify such systems and deactivate or block them. Hence proper and successful implementation of robust security measures becomes vital while deploying cognitive radios. TECHNOLOGY HURDLES Being aware of the environment cognitive radio chooses the best available option based on certain performance parameters such as carrier frequency, type of modulation, antenna, power bandwidth etc. This means that the radio would have to deal with different RF spectrum and baseband varieties at the same time, thus requiring a more robust, efficient and reconfigurable hardware architecture. Clearly, the introduction of this revolutionary paradigm poses many challenges across all layers of a cognitive radio system design like spectrum sensing, interference management, resource allocation, RF design and implementation issues.
  • 11 1. SPECTRUM SENSING TECHNIQUES One of the most important functions of cognitive radio is to sense its environment accurately and thereby choose its operation parameter. Spectrum sensing has been identified as a key enabling cognitive radio to not interfere with primary users, by reliability detecting primary user’s signals. And sensing is not merely enough. Making sense out of what it being sensed is another all together different issue. Sensing techniques available today are susceptible to changing levels of interference and noise levels. Also these techniques can only detect the presence or absence of signal. They are not able to differentiate whether the detected signal is a noise, interference or information carrying signal. The hurdle lies in developing fast low-cost detecting techniques that are able to detect weak signals and also differentiate between them. 2. HARDWARE DESIGN Another major hurdle is designing of a flexible hardware that can be used for wideband sensing and multiband communication purposes. Conventionally, in the design of RF circuit for radio certain assumptions regarding interferes and worst case scenarios can be made fairly. This greatly eased the design of hardware for a desired performance. However cognitive radio operates in a dynamic environment. Additionally not having prior information on the frequency of operation bandwidth and other operation parameters greatly complicates the situation. If one follows the conventional approach it would lead to design of excessive circuit blocks thereby increasing space, cost and complexity. Designing a flexible circuit giving a minimal level of performance under all expected and unexpected scenarios becomes a challenge 3. ON CHIP IMPLEMENTATION Designing the digital baseband processing of such a complex system also posses an uphill task. The power usage would increase significantly due to increase in functionality. Also the memory requirement would increase significantly due to operation in an unknown dynamically changing environment. 4. PROTOCOL ARCHITECTURES The extreme flexible requirements of cognitive radios involve redesigning of network algorithms and protocols. In particular cross layer algorithms that adapt to changes in quality, network structure, and physical link availability would require an advanced management framework. Design of network protocols that can enable cognitive devices to exchange key information like frequency coordination network configuration transmission parameters would be critical.
  • 12 THE WAY FORWARD CURRENT SCENARIO FUTURE SCENARIO  Cognitive radio would enable interaction between all types of radio devices  A simple embedding of a radio in any object could mean interaction of all objects!!  Verify and control your identity, online and offline all at the same time  All time connectivity not only through network cells but also through formation of spontaneous networks  New marketing strategy - Radio enabled advertising sends customized information to your phone in your language SUMMARY In this paper we examined how cognitive radio can impact the way spectrum will be managed and regulated in future. The concept of cognitive radio is promising to improve the utilization of spectrum. With technological advancement in device cognitive and re-configurability capabilities we may see current static spectrum management model completely disappear. Spectrum would be managed by a society of intelligence cognitive devices which on behalf of their user would be continuously involved in communication negotiation cooperation and trading. This would require the need of formation of new regulation in the future. Many key technological, economical and legal issue need to be explored before cognitive radios are fully deployed. Significant new research is required to address these challenges. The potential for cognitive radio to make a significant difference to wireless communications is immense. The key issue in the final evolution of cognitive radio for any application would be- • Trust by the users of cognitive radio; • Trust by all other users who might be interfered with.
  • 13 References 1. Radio electronics.com: Future of Cognitive Radio - an interview with Dr Joseph Mitola 2. Maziar Nekovee : Impact of Cognitive Radio on Future Management of Spectrum 3. Cristian Ianculescu: Cognitive radio and dynamic spectrum sharing 4. Dr. Bruce Fette, Ph.D. Cognitive radios: The future of SDR technology 5. Joseph Mitola Cognitive Radio: Making Software Radios More Personal 6. Sabita Maharjan · Yan Zhang · Stein Gjessing: Economic Approaches for Cognitive Radio Networks 7. Angsuman Rudra Cognitive radio: An evolution from software radio 8. Nokia research center: http://research.nokia.com/