Viji Seminar 2

Embed Size (px)

Citation preview

  • 7/30/2019 Viji Seminar 2

    1/25

    COGNITIVE RADIO

    1

    CHAPTER 1

    INTRODUCTION

    Interest is rapidly growing in lowering barriers to spectrum access and

    improving spectrum efficiency. The introduction of software-defined radios

    and the realization that new levels of computational performance applied to

    radios creates exciting new possibilities for wireless devices. This has resulted

    in explosive growth in interest in cognitive radios. The term cognitive radio

    was first used by Joe Mitola. The concept and the term cognitive radio quickly

    caught the interest of many in the communications field.

    Cognitive radio technology enables a number of capabilities to

    improve the usefulness and effectiveness of wireless communications. Those

    functions include:

    Exploit locally vacant or unused radio channels, or ranges of radiospectrum, to provide new paths to spectrum access.

    Roam across borders and perform self-adjustment to stay incompliance with all local radio operations and emissions

    regulations.

    Negotiate as a broker on behalf of the radio user with multiple serviceproviders to give network access best matched to the user needs at the

    lowest cost.

    Adapt itself without user intervention to save battery power or toreduce interference to other users.

    Make use of location awareness to ensure that radio emissionsdo not interfere with licensed broadcasters.

    Understand and follow the actions and choices taken by theirusers to become more responsive and anticipate user needs over

    time.

    Formulate and issue queries, one radio to another. Execute commands sent by another radio. Fuse contradictory or complementary information.

  • 7/30/2019 Viji Seminar 2

    2/25

    COGNITIVE RADIO

    2

    This proliferation of the term cognitive radio is validation of the strong

    interest in the industry and government for communications systems that can

    operate with more intelligence and improved performance. This interest leads

    to a need for a common terminology for manufacturers, regulators,researchers, and users all to be able to advance the development of cognitive

    radios.

  • 7/30/2019 Viji Seminar 2

    3/25

    COGNITIVE RADIO

    3

    CHAPTER 2

    DEFINITION

    Tautologically, a cognitive radio could be defined as A radio that is

    cognitive.In the absence of a turing test for radios, applying this definition is

    nontrivial and implies a level of functionality that many researchers consider

    excessive. Indeed, while many researchers and public officials agree that

    upgrading a software radios control processes will add significant value to

    software radio, there is currently some disagreement over how much

    cognition is needed which results in disagreement over the precise definition

    of a cognitive radio. The following provides some of the more prominently

    offered definitions of cognitive radio.

    In the 1999 paper that first coined the term cognitive radio, Joseph

    Mitola defines a cognitive radio as A radio that employs model based

    reasoning to achieve a specified level of competence in radio-related

    domains.However, Simon Haykin defines a cognitive radio as An intelligent

    wireless communication system that is aware of its surrounding environment,

    and uses the methodology of understanding-by-building to learn from theenvironment and adapt its internal states to statistical variations in the

    incoming RF stimuli by making corresponding changes in certain operating

    parameters in real-time, with two primary objectives in mind:

    Highly reliable communications whenever and wherever needed; Efficient utilization of the radio spectrum.

    Cognitive radio (CR) is type of wireless communication which is used

    to receive and identify the channels of communication sharply that which

    channels can be operated or which cannot be operated. It progress immediately

    into available channels although preventing occupied anyone. This radio-

    frequency (RF) spectrum is available for the optimistic users and decreasing

    the interference to another client.

    Cognitive radio is capable to identify its geological area, recognize and

    approve its user, encode and decode the signals, awareness of connecting the

  • 7/30/2019 Viji Seminar 2

    4/25

    COGNITIVE RADIO

    4

    wireless devices in process and manage the power of output and intonation

    components.

    2.1. Types of cognitive radio (CR)

    Depending on the set of parameters taken into account in deciding on

    transmission and reception changes, and for historical reasons, we can

    distinguish certain types of cognitive radio. The main two are:

    Full Cognitive Radio: Radio in which every possible parameterobservable by a wireless node or network is taken into account. Also

    known as Mitolas Radio.

    Spectrum Sensing Cognitive Radio: Radio in which only the radiofrequency spectrum is considered.

    Also, depending on the parts of the spectrum available for cognitive

    radio, we can distinguish:

    Licensed Band Cognitive Radio: cognitive radio which is capableof using bands assigned to licensed users, apart from unlicensed bands,

    such as U-NII band or ISM band.

    Unlicensed Band Cognitive Radio: Cognitive radio which canonly utilize unlicensed parts of radiofrequency spectrum.

  • 7/30/2019 Viji Seminar 2

    5/25

    COGNITIVE RADIO

    5

    CHAPTER 3

    FUNCTIONS

    3.1. Spectrum Sensing

    Spectrum sensing refers to the action of a wireless device measuring

    characteristics of received signals, which may include RF energy levels as part

    of the process of determining if a particular section of spectrum is occupied.

    Sensing in the spectrum domain is the detection of some signal

    features indicating the presence (or absence) of other users/services. These can

    include signal energy, periodic features (pilots, preambles, and chip rates),

    likely identity of the other users/services, estimation of interference-tolerance

    capabilities and estimation of the duration of spectrum occupancy.

    Spectrum sensing techniques is divided into three components:-

    1. Transmitter detection: The capability must be in cognitive radio

    to identify the signals which come from basic transmitter either is nearby in

    specific spectrum. There are many accesses are suggested:

    Coordinated filter recognition Force or power recognition Cyclostationary characteristics recognition2. Cooperative detection: it specifies the methods of spectrum

    sensing at which information is included to detect the main user from multiple

    users of cognitive radio.

    3. Interference based detection.

    3.2. Spectrum Management

    Capturing the finest accessible spectrum to fulfill the communication

    needs of the user. Cognitive radio must have the capability to settle on the

    finest spectrum band to fulfill the needs of quality of advantage over the

  • 7/30/2019 Viji Seminar 2

    6/25

    COGNITIVE RADIO

    6

    accessible spectrum bands, although spectrum authority affairs are necessary

    for Cognitive radios. These management affairs can be divided as:

    Spectrum/Range analysis Spectrum/Range decision

    3.3. Spectrum Mobility

    When cognitive radio user interacts the frequency of process is called

    spectrum mobility. The main objective of cognitive radio networks is to use in

    energetic manner as a spectrum that will be available from the radio stations to

    process in finest frequency band, retain faultless communication needsthroughout the switch to improved spectrum.

    3.4. Spectrum Sharing

    Spectrum sharing is the method where spectrum that has been assigned

    to a license holder is made available to other users on a secondary, non-

    interfering basis. The secondary users may have arrangements with the license

    holders that are arrived at through some kind of cooperation agreement. Thesecondary users may, by following a set of rules designed to prevent the

    possibility of interference, access the spectrum either with the cooperation

    of, or alternatively without the knowledge of license holders depending

    on the relevant policies and protocols.

  • 7/30/2019 Viji Seminar 2

    7/25

    COGNITIVE RADIO

    7

    CHAPTER 4

    LEVELS OF FUNCTIONALITY

    The differences in the definitions for cognitive radio can be largely

    attributed to differences in the expectations of the functionality that a

    cognitive radio will exhibit. Joseph Mitola considers the nine levels of

    increasing cognitive radio functionality shown in the table 4.1, ranging from a

    software radio to a complex self-aware radio.

    Table 4.1: Levels of cognitive radio functionality.

    LEVEL CAPABILITY COMMENTS

    0 Pre-programmed A software radio

    1 Goal Driven Choose waveform according

    to goal. Requires

    environment awareness

    2 Context Awareness Knowledge of what the User

    is trying to do

    3 Radio Aware Knowledge of radio and

    network components,

    Environment Models

    4 Capable of Planning Analyze situation(level2&3)

    to determine

    goals(QoS,power), Follows

    prescribed plans

    5 Conducts Negotiations Settle on a plan with another

    radio

    6 Learn Environment Autonomously determines

    structure of environment

  • 7/30/2019 Viji Seminar 2

    8/25

    COGNITIVE RADIO

    8

    7 Adapts Plans Generates new goals

    8 Adapts Protocols Proposes and negotiates

    new protocols

    As a reference for how a cognitive radio could achieve these levels of

    functionality, Mitola introduces the cognition cycle, shown in Figure 4.1, as a

    top-level control loop for cognitive radio. In the cognition cycle, a radio

    receives information about its operating environment (Outside world) through

    direct observation or through signaling. This information is then evaluated

    (Orient) to determine its importance. Based on this valuation, the radio

    determines its alternatives (Plan) and chooses an alternative (Decide) in a way

    that presumably would improve the valuation. Assuming a waveform change

    was deemed necessary, the radio then implements the alternative (Act) by

    adjusting its resources and performing the appropriate signaling. These

    changes are then reflected in the interference profile presented by the

    cognitive radio in the Outside world. As part of this process, the radio uses

    these observations and decisions to improve the operation of the radio (Learn),

    perhaps by creating new modeling states, generating new alternatives, or

    creating new valuations.

  • 7/30/2019 Viji Seminar 2

    9/25

    COGNITIVE RADIO

    9

    Figure 4.1: Cognition Cycle

  • 7/30/2019 Viji Seminar 2

    10/25

    COGNITIVE RADIO

    10

    CHAPTER 5

    ARCHITECTURE

    Cognitive radios are capable of making decisions and selecting or

    modifying the operating parameters of a radio. In the most abstract view of the

    Cognitive Radio Working Group, there are two major subsystems in a

    cognitive SDR radio; a cognitive unit that makes decisions based on various

    inputs and a flexible SDR unit whose operating software provides a range of

    possible operating modes.

    The Cognitive Radio Working Group developed a conceptual model

    that uses a layered architecture where the SDR radio is at the base and is

    closest to the physical RF channel. The cognitive layer is above the SDR

    layer and below the application layer. One goal of this architecture is to hide

    the complexity of the SDR radio from the applications. The combination of a

    cognitive "engine" and the SDR together comprise a "cognitive radio" or a

    cognitive SDR radio. The cognitive layer acts to optimize or control the SDR

    with minimal user interaction or oversight. In this model the cognitive engine

    accepts inputs, makes decisions and inferences from a pool of current and

    historical contextual knowledge and issues control or configuration

    commands to the flexible-architecture SDR radio.

    The basic function of a cognitive radio is matching the radio link

    requirements of a higher layer application or user need with the available

    device, spectral and infrastructure resources. The cognitive layer could also

    be aware of the data rates and quality of service requirements of the

    application.

    The cognitive layer would be aware of the radios hardware resources

    and capabilities. It would store an inventory of the software modulation

    schemes available and the capabilities and characteristics of these

    modulation and spectrum access schemes. The cognitive layer could know

    the measurement utilities available to allow it to collect information to feed the

    decision process.

  • 7/30/2019 Viji Seminar 2

    11/25

    COGNITIVE RADIO

    11

    In this model the rules or decision algorithms are stored separately

    from the engines to enable them to be updated easily. The cognitive function

    is further separated into two parts as shown in the block diagram in Figure 5.1

    below. The first labeled the cognitive engine tries to find a solution oroptimize a performance goal based on inputs received from other parts of the

    radio. These other parts can supply information that is the basis for

    awareness as described above.

    The second engine is the policy engine and is used to ensure that the

    solution is in compliance with regulatory rules and other policies external to

    the radio. Each of these engines has a separate rule-set or algorithm-set. The

    reason we have shown them separately is that these subsystems perform two

    different tasks. The policy engine isolates policy or regulatory rules from the

    operational capability rules of the radio as regulatory policies apply to all

    radios. The purpose of the policy engine is to veto, if necessary,

    adaptation choices made by the cognitive engine.

    Cognitive rules are likely to be written to be compatible with the

    specific capabilities of a particular radio.

    The cognitive engine strives to find ways to adapt the radio to best

    meet a goal or a set of priorities based in awareness of both internal and

    external conditions. This view is a conceptual one and implementations may in

    practice share processing hardware and memory.

    The cognitive layer, using the available radio resources, could monitor

    RF environment and gain awareness of external users and the presence of

    unused spectrum. It could monitor and be aware of the presence of relay

    nodes or infrastructure access points that the radio could use. It could also

    utilize other criteria in the decision process, such as whether to maximize

    battery life or minimize operating expense.

    It is envisioned that in the future, advanced cognitive SDR radios could

    learn and innovate, meaning they test new hypotheses, store and recall

    adaptations that resulted in successful outcomes in addition to those that may

    not have improved performance in future, similar situations.

  • 7/30/2019 Viji Seminar 2

    12/25

    COGNITIVE RADIO

    12

    The inputs come from both the lower SDR layer and from the upper

    application layers. The SDR, or special monitoring subsystems, provide inputs

    including the status and current capabilities of the radio and the results of

    spectrum scans. The upper layers will provide inputs including informationabout the desired data rates, QoS and inputs from other sensors such as GPS

    based location.

    The decisions can be simple or complex. The decision making activity

    can also make use of some memory along with the external inputs. This makes

    it possible for the radio to learn and possibly improve the quality or speed of

    its decisions. Decisions can be derived using declarative languages combined

    with inference engines. In other systems, decision systems can be

    implemented using game theoretic or genetic algorithms. Of course, simple if-

    then-else decision trees can be implemented in imperative languages such as C

    or Java.

    Figure 5.1: Conceptual view of Cognitive Radio Architecture

  • 7/30/2019 Viji Seminar 2

    13/25

    COGNITIVE RADIO

    13

    A less flexible hardware radio may have some degree of cognitive

    ability but will be limited by the ability of hardware to adapt to different

    frequencies and modulations. A radio that can operate on only a handful of

    channels in a single band using a single modulation will have limitedinterference avoidance ability if all the channels are occupied. A radio that

    can only connect to a single radio network cannot change modes to avoid

    congestion.

    To the extent allowed by the RF hardware a cognitive SDR radio may

    be capable of multitasking and can simultaneously receive and spectrum scan.

    The interface between the cognitive layer and the application layer can

    be a simple known list or array of available modes or a highly abstracted

    interface. The abstracted interface of the cognitive layer would appear to

    applications in terms of a client requesting a communications service

    possibly with particular latencies or data rates.

  • 7/30/2019 Viji Seminar 2

    14/25

    COGNITIVE RADIO

    14

    CHAPTER 6

    FEATURES

    6.1. Energy (battery) awareness

    Refers to including knowledge or awareness of the remaining amount

    of energy in a radios power supply(e.g. available battery charge) to influence

    decisions about which operating mode or frequency to use.

    6.2. Spatial awareness

    A very significant role for a CR may be viewed as personal assistant.One of its key missions is facilitating communication over wireless links. The

    opposite key mission is impending communication when appropriate. As an

    example most people do not want to be disturbed while in church, in an

    important meeting. A CR could learn to classify its situation into user

    interruptible and user non interruptible. The radio accepting aural inputs

    can classify a long running exchange in which only one person is speaking at a

    time as a meeting or classroom and autonomously put itself into vibration only

    mode. If the radio senses its primary user is speaking continuously or even

    50% of time, it may autonomously turn off the vibration mode.

    6.3. Self-correction, Fault tolerance

    Refers to the ability of a radio to discover that, for some reason,

    something is wrong, and that it can reconfigure itself and thereby recover and

    re-establish communications.

    6.4. Recovery after incorrect decision, error condition sensing

    It is expected that cognitive radios will in some situations adapt their

    operating characteristics in a way that worsens performance or possibly

    increases the likelihood of causing interference. Decisions should be

    followed up with checks where possible to detect these situations and initiate

    corrective action. Awareness of error conditions could be part of the input set

    of the cognitive engine.

  • 7/30/2019 Viji Seminar 2

    15/25

    COGNITIVE RADIO

    15

    6.5. Negotiation

    Negotiation refers to radios that can adapt to new operating

    characteristics based not only on knowledge of their own priorities and goals

    and environmental state. Radios and networks that can share knowledge and

    negotiate with each other to select mutually optimal operating characteristics

    may perform better. A negotiation language that can express the concepts of

    and offer and counter-offer may prove useful

  • 7/30/2019 Viji Seminar 2

    16/25

  • 7/30/2019 Viji Seminar 2

    17/25

    COGNITIVE RADIO

    17

    Unrestricted roaming for consumers using different types of wireless

    services such as GSM, CDMA, and WCDMA in addition to WLAN networks

    could become more common with the introduction of cognitive radios and

    systems. These consumer radios could listen for the presence of accessnetworks and select the carrier that best meets a users needs.

    Management of identity and authentication are also important aspects

    of interoperability. The identity of the users of radios who wish to join a

    network needs to be assured. Authentication that the devices themselves are

    suitable and authorized for use on a network is critical. The SDR Forum

    Public Safety SIG has explored some of these issues in greater detail and has

    published a document describing improvements in interoperability.

    7.2. Reduced demand on user, reduced user control burden

    Another potential benefit of cognitive radios is the reduction and

    simplification of the tasks needed to set up and use a radio. Cognitive radios

    aware of a users goals and priorities, and capable of independently acting,

    could simplify the operation of radios. A flexible SDR radio needs some form

    of input or command to set the operating frequency, power level, modulation,

    bandwidth, and possibly many other radio parameters. For example, filters

    may need to be tuned and different subsystems may need to be switched in to

    enable certain operating modes. Software routines may need to be selected,

    loaded and run to facilitate operation using a new waveform. Enhanced

    flexibility in a wireless device offers a greater number of possible

    options and settings. There is value in significantly reducing the burden of

    technical knowhow on the part of the user using cognitive functionality. Usersshould be able to utilize the capability of the radio with a minimum level of

    detail over radio operating parameters, with the radio making appropriate

    choices among options.

    7.3. Greater spectrum efficiency through improved access

    The term spectrum efficiency, as used in the SDR Forum Cognitive

    Radio Working Group, refers to increasing the efficiency of how spectrum isassigned and used to support one or more wireless services in one or more

  • 7/30/2019 Viji Seminar 2

    18/25

    COGNITIVE RADIO

    18

    geographical locations in either a concurrent or time-based manner. New

    methods provide ways of accessing spectrum that would have been excluded

    by regulatory policy and licensing rules in the past. One scenario involves

    use of licensed spectrum by unlicensed users using protocols and etiquettes tominimize the potential for interference to licensed users.

    Wireless devices that are aware of their spectral environment provide

    benefits by being able to access previously unused, unavailable, or restricted

    spectrum segments that may be available for usage in other geographical areas

    or under other regulatory regimes. Spectral awareness may enable the use of

    this spectrum without causing interference to the radios originally operating in

    the spectrum. Radio spectrum is perceived to be a scarce resource: there may

    be a shortage of spectrum available for dedicated allocation without displacing

    current users. Interest is high to find ways to use spectrum more efficiently.

    Utilization levels vary widely between services and geographic areas, with

    some having substantial amounts of white space, or unused spectrum

    segments at any point in time. Radios capable of exploiting unused or lightly-

    used spectrum without introducing interference will improve efficiency of

    spectrum utilization.

    Figure 7.1: Opportunistic spectrum utilization

    To improve spectrum utilization, opportunistic spectrum utilization has

    been proposed wherein devices occupy spectrum that has been left vacant. An

    illustrative example of opportunistic spectrum utilization is shown in Figure

    7.1. In the left half of the figure, a pair of transmitted carrier signals is presentin the lower frequency bands while a random access system and a TDMA

  • 7/30/2019 Viji Seminar 2

    19/25

    COGNITIVE RADIO

    19

    system are operating in the upper bands. After observing the spectrum holes -

    points in time and frequency where spectrum is underutilized opportunistic

    devices could fill in these holes to support concurrent services as illustrated in

    the diagram on the right.

    7.4. Improved application interface for communications tasks

    A Cognitive radio can provide communications services that allow

    users to designate a priority or a value for each particular communications

    task. For example, email might be given a higher priority than streaming

    video. Cognitive radios could be aware of the requirements that different

    applications on a radio have for data throughput rates, latencies, and quality ofservice (QoS) levels. These services become increasingly important as users

    multiplex applications (e.g. streaming audio and video while simultaneously

    text messaging) and executing applications in parallel. The cognitive SDR can

    support communications by using prioritized connection use rules (i.e. drop

    streaming audio if incoming call), time of transmission optimization (i.e. batch

    low priority uploads/downloads until low cost, high bandwidth connections),

    appropriate channel bandwidth to match endpoint coding/decoding schemes,

    and adaptive compression to balance bandwidth usage (i.e. increase

    compression in voice over IP (VOIP) conference call scenario). The cognitive

    radio can also gracefully degrade the supplied services according to

    environmental conditions such as link quality changes, interference, and

    energy-source degradation in order to help maximize the useful operating

    lifetime of the device

    7.5. Dynamic Regulatory Compliance

    Radios that are aware of their locations and current regulatory

    jurisdiction can update and maintain compliance with local regulations. This is

    important for radios that are likely to cross borders. This awareness combined

    with the ability to update a radios knowledge of regulatory rules could

    allow regulations to adapt more quickly to new technologies.

  • 7/30/2019 Viji Seminar 2

    20/25

    COGNITIVE RADIO

    20

    7.6. Radio performance optimization

    A radio that is aware of its internal state can improve its performance

    compared to a traditional radio. For example, a radio aware of its remaining

    energy level could adapt its data rates or modulation type to maximize its

    operating time. A radio that was aware that its decoder was operating near the

    limits of its abilities may adapt its data rate or bandwidth to increase the

    operating margins of the communications link.

    7.7. User based Cognitive Adaptation

    An additional level of cognition may be the radios awareness of its

    user. Soft biometrics enables a CR node to recognize user identity. Sensors for

    medical triage and first responder health may indicate to a wearable CR the

    health of its user, enabling the radio to adjust even its physical layer (power)

    or network layer (routing parameters from forwarding to flooding) to call for

    help if a first responder is in need. The robotics industry is developing robots

    for health care, and these robots will have different priorities for use of

    wireless services for various forms of service and assistance. Although the

    radio itself would not take on the job of assessing the state of the user, the

    cognitive radio that is user-aware may autonomously adjust air interface,

    application, and protocol stack agility to provide the most appropriate mode of

    communications on a scale of assured connectivity to better bandwidth

    without the user having to explicitly program or control the SDR.

  • 7/30/2019 Viji Seminar 2

    21/25

    COGNITIVE RADIO

    21

    CHAPTER 8

    DISADVANTAGES

    With any emerging technology there are drawbacks that can potentially

    affect the development of the system. Key problems that arise for CR include:

    Encompasses the same drawbacks as software defined radio Loss of control Regulatory concerns Significant research remains to be done to realize commercially

    practical cognitive radios

    With any software define radio based technology there are always

    complexity drawbacks. Since the core of CR resided with software defined

    radio, CR inherits most of the same problems associated with software defined

    radio. Some of the drawbacks associated with software defined radio are:

    Security Software reliability Keeping up with higher data ratesThe process of CRs sense, learns, and adapt cycle changes the outside

    world for other cognitive radios with each cycle. This can potentially result in

    loss of control if a group of radios interact with each other causing chaotic

    networks. As far as regulatory concerns apply to CR the current FCC

    regulations are not specified or designed for CR use. The fear is that

    regulations will retard the development of cognitive radio or actually reduce

    available spectrum. The concept of CR is still evolving and there are many

    research areas that need to be addressed for the systems. This includes:

    information collection and modeling; decision processes; learning processes;

    hardware support

  • 7/30/2019 Viji Seminar 2

    22/25

    COGNITIVE RADIO

    22

    CHAPTER 9

    FUTURE OF COGNITIVE RADIO

    Today engineers are trying to make further adaptable operating

    capacity to upcoming radios, mobiles and other wireless communication

    accessories. In future, it will be permitted that cognitive radio technology

    almost wireless networking that will use to establish and to connect to any

    nearby accessible unused radio spectrum that facilitates the customer.

    Cognitive radio technology can improve interoperability by enabling

    devices to bridge communications between jurisdictions using different

    frequencies and modulation formats. Such interoperability is crucial to

    enabling public safety agencies to do their jobs. Example: National Public

    Safety Telecommunications Council (NPSTC) supported by U.S. DOJs

    AGILE Program for the public safety.

    Planning applications are one of the new attractive technologies that

    CR will enable. Navigation using databases and GPS signals will increase.

    Some of the planning applications envisioned are:

    Route planning Battery Management Noise Discipline Light Discipline Management of Information Flow Role Assignment as a function of the operators skills Talk Group Assignment Smart Calibration Smart Bridge (recognize the need for two or more legacy to

    communicate and connect them through a bridge)

  • 7/30/2019 Viji Seminar 2

    23/25

    COGNITIVE RADIO

    23

    CHAPTER 10

    CONCLUSION

    We have discussed a number of different considerations of the use of

    Cognitive Radio technology. The challenge is to understand its implications,

    and make use of its capabilities to specify, design, and operate

    communications systems that provide users with capabilities they need,

    enhance their applications, and make them more effective. Gaining more

    utility from existing spectrum or minimizing the acquisition cost of additional

    spectrum for additional services is shown to have a huge monetary

    value. And in the commercial world, time is also critical. Systems must

    complete their communications tasks within an acceptable time frame to suit

    the users purposes. All of these goals are substantially enabled by cognitive

    radio capabilities.

  • 7/30/2019 Viji Seminar 2

    24/25

    COGNITIVE RADIO

    24

    CHAPTER 11

    REFERENCES

    1. Kwang-Cheng Chen, Peng-Yu Chen, Neeli Prasad, Ying-Chang Liang, SumeiSun, Trusted Cognitive Radio Networking, Wireless Communications and

    Mobile Computing, Wiley, 2009

    2. S. Srinivasa and S. A. Jafar, ``The throughput potential of cognitive radio: atheoretical perspective,'' IEEE Commun. Mag., vol. 45, pp. 73-79, May 2007

    3. Ghasemi and E. S. Sousa, ``Spectrum sensing in cognitive radio networks: thecooperation-processing tradeoff,'' Wireless Communications and Mobile

    Computing, vol. 7, no. 9, pp. 1049-1060, Nov. 2007.

    4. G. Ganesan and Y. G. Li, Cooperative spectrum sensing in cognitive radio:Part I: two user networks, IEEE Trans. Wireless Commun., vol. 6, pp. 2204-

    2213, June 2007M.

    5. Gandetto and C. Regazzoni, ``Spectrum sensing: A distributed approach forcognitive terminals,'' IEEE J. Select. Areas Commun., vol. 25, pp. 546-557,

    Apr. 2007.

    6. Hasari Celebi and Huseyin Arslan "Enabling Location and EnvironmentAwareness in Cognitive Radios," Elsevier Computer Communications-Special

    Issue on Advanced Location-Based Services, vol. 31, no. 6, pp. 1114-1125,

    April 2008.

    7. Hasari Celebi and Huseyin Arslan "Cognitive Positioning Systems," IEEETransactions on Wireless Communications, vol. 6, no. 12, pp.4475-4483, Dec.

    2007.

    8. Hasari Celebi and Huseyin Arslan "Utilization of Location Information inCognitive Wireless Networks," IEEE Wireless Communications Magazine-

    Special Issue on Cognitive Wireless Networks, vol. 14, no. 4, pp. 6-13, Aug.

    2007.

  • 7/30/2019 Viji Seminar 2

    25/25

    COGNITIVE RADIO

    9. E. Adamopoulou, K. Demestichas and M. Theologou, Enhanced estimationof configuration capabilities in cognitive radio, IEEE Commun. Mag., vol.

    46, no. 4, pp. 56-63, April 2008

    10.IEEE JSAC, Mar. 2007.11.IEEE JSAC, Nov. 2008.12.IEEE Wireless Mag., Nov. 2007. .13.IEEE Signal Processing Mag., Nov. 2008.