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The correct answer is (a) Detect primary user transmission

The best explanation: The detection of primary users receiving information within the communication range of xG users is considered as the most EFFICIENT MEANS for determining spectrum holes. However this is not always feasible as it is laborious to measure the CHANNEL between a transmitter and a primary RECEIVER. Hence sensing is PREDOMINANTLY carried out by detecting the transmission operation of primary users.

Correct choice is (d) Simultaneous MECHANISM and SEQUENTIAL mechanism

To explain: Simultaneous mechanism permits the arrangement of segments on the BASIS of frequencies. The sequential mechanism locates the segments with similar properties in TIME.

Right option is (b) Interoperability

The BEST I can explain: The interoperability IP INFRASTRUCTURE is BUILT based on modular programming and data abstraction. The operational CHALLENGES of a layer are confined within that layer. The data is transferred by using packets or is included as ADDITIONAL information in the procedural call between layers.

Right answer is (d) Intersection of radials from two different VOR stations

For EXPLANATION I would say: LINE of position in very high frequency OMNIDIRECTIONAL range is called the RADIAL. The line of position consists of a highly DIRECTIONAL signal sent by the VOR ground station using a phased antenna array and a reference signal in phase with the directional antenna. The intersection of radials from two different VOR stations is used to determine the position of an aircraft.

Correct choice is (c) Poor noise FIGURE

Easiest explanation: Noise figure quantifies the AMOUNT of self-generated noise at the receiver. It lower sensitivity and MAKES it DIFFICULT to find other users of the SPECTRUM. Decreased sensitivity causes a reduction in the amount of power allowed for transmission.

Correct option is (C) Short signal detection

Explanation: Spectrum analyzers are employed for spectrum SENSING by tuning to a band with the scan frequency adjusted to dwell at a frequency bin for a DESIRED period. The spectrum analyzer exhibits reduced complexity and power REQUIREMENTS when receiver components are shared. It also scans over large RANGES of signals.

Right answer is (d) Analysis of frequencies enclosed in the FFT window

The best explanation: Fast Fourier TRANSFORM is used for performing spectrum sensing by using a wideband analog to digital CONVERTER and extensive digital signal processor. This METHOD PROVES advantageous as it ENABLES the analysis of frequencies enclosed in the FFT window.

Correct answer is (C) Fixed TRANSMITTER, fixed receiver

The best I can explain: Fixed transmitter, fixed receiver configuration includes point-to-point, point-to-multipoint, and radio astronomy services. Both endpoints are in fixed LOCATIONS. The communication path may be one way between the transmitter and receiver or it may be TWO way between two TRANSCEIVERS.

Correct option is (a) LACK of spectrum access

To elaborate: Spectrum POLICY Task Force identified the lack of CAPACITY is due to the CURRENT regulations applied on spectrum access. SPTF supported multiple dimensional access of the spectrum. The FCC relies on SPTF to create spectrum policies and spectrum MANAGEMENT techniques that could lead to better overall usage of the available spectrum.

The correct OPTION is (d) Intermittent connectivity

Explanation: Intermittent connectivity is caused due to the time-changing nature of the spectrum and loss of CHANNEL due to the arrival of the primary user. It is also due to the fact that when the user chooses a channel for COMMUNICATION, the NODE cannot be REACHED through other channels. Thus channel-based models are required for developing time-based solutions.

The correct answer is (d) Data size

To explain I WOULD say: Route metrics are PARAMETERS whose values are evaluated to ASSIGN a cost to a link in the path between the source and the DESTINATION. Routing algorithms rely on route metrics to select the optimum path for forwarding the packets.

The correct OPTION is (a) QOS maintenance

Explanation: xG networks change constantly in the wireless spectrum in accordance with the AVAILABLE spectrum band. The available spectrum bands tend to vary with time. Thus QoS maintenance BECOMES difficult.The radio should alter its position to meet the QoS requirements.

Correct option is (d) SPECTRUM sharing

The best I can explain: In the UNLICENSED portion of the spectrum, cognitive radio users have EQUAL access to the spectrum and ATTEMPT to access the spectrum SIMULTANEOUSLY. Spectrum sharing coordinates the network access such that collision is avoided in overlapping portions of the spectrum.

Correct OPTION is (d) Improvement of sensing accuracy

To explain: The cognitive RADIO user monitors and studies the local radio environment to identify the current spectrum availability. The information gathered by each user is SHARED between its NEIGHBOURS. This practice is known as cooperation in sensing and it improves the sensing accuracy.

The correct choice is (c) ACCESS control

Easiest explanation: Speech recognition supports access control by providing user authentication. Voice comparison can be used to establish the IDENTITY of a PERSON. It can ALSO be employed to identify communicating parties and PERSONALIZATION of devices.

Correct choice is (d) Shorter TIME delay

Explanation: Time delay and interleaving time can be CONTROLLED by sampling sub-Nyquist and by USING appropriate filters in wideband FFT spectrum sensing. The short delay simplifies compatibility with MAC LAYER timing.

Right choice is (c) Center for STRATEGIC and International Studies

To explain I would SAY: The Center for Strategic and International Studies is a private, bipartisan public policy research organization that offers inferences and solutions to current and upcoming problems. The center carries out strategic analyses of POLITICAL, economic, and security issues with a focus on issues concerning international relations, TRADE, and TECHNOLOGY.

The CORRECT choice is (b) False

Explanation: The key depletion attack is a malicious attack on the transport LAYER. It is employed to destruct the underlying cipher system. It LEADS to the degradation of the efficiency of communication.

The CORRECT choice is (d) Medium ACCESS Control protocol

To elaborate: Packet loss probability is computed to predict WIRELESS link ERROR. It relies on the access technology, operating FREQUENCY, interference level, and available bandwidth. Wireless channel access delay relies on operation frequency, interference level, and medium access control protocol.

The correct choice is (d) Overhead

To explain I would say: Overhead refers to the additional transmissions that exceed the allowable NUMBER of transmissions resulting in a decrease of efficiency and throughput of the entire network. For example, in COOPERATIVE sensing, before TRANSMISSION of information, the sensing information collected by a user has to be forwarded to other secondary USERS in the network.

The correct option is (b) Data-link

The explanation: The data link LAYER particularly the MAC PORTION is responsible for COLLISION avoidance. Likewise, spectrum SHARING is responsible for avoiding collision between licensed and unlicensed users of the licensed spectrum BAND as well as for avoiding collision among xG users in the unlicensed band.

The correct option is (B) Handshake mechanism between TRANSMITTER and receiver

Explanation: The selected portion of the spectrum must be INFORMED to the receiver of data. This is accomplished by INVOKING a transmitter-receiver handshake PROTOCOL that is used for effective communication in xG networks.

Correct ANSWER is (a) True

Explanation: Speaker characterization is the process of finding the emotional STATE of a user through speech processing. Knowledge of stress state helps to improve situational AWARENESS, IDENTIFY irritation, determine stress level, and ASSESS the success of a decision on the basis of verbal cues.

The correct option is (b) Radio environment MAP provides insight on radio environment over multiple domains such as regulation and frequency emission

The best explanation: Radio environment map provides an abstraction of real time radio environment. It defines the radio environment of cognitive radio USING multiple characteristic features such as geographical conditions, regulation, policy, CAPABILITY of radio equipment, and radiofrequency EMISSIONS.

Right CHOICE is (d) Security

Best explanation: Biometric based user authentication obtains input information through an input device such as a microphone, CAMERA, etc. The information is processed by using software, or specialized hardware. Specialized hardware increases the complexity of introducing updates and MODIFYING functionalities on the fly. Software processing OFFERS lower security than specialized hardware.

The CORRECT answer is (a) True

Best explanation: In the angle of arrival approach, multiple receivers COMBINE to COMPUTE the angle of arrival. The technique requires an antenna ARRAY at the receivers. The bearing to the SIGNAL and the known location of multiple receivers provide the location of the transmitter.

Correct choice is (C) Apply a qualitative approach to interference management

The best I can explain: The recommendations proposed by SPTF maximize SPECTRUM usage by allowing unlicensed USERS and promotes OPPORTUNISTIC spectrum access through secondary market policies. The SPTF promotes spectrum access in rural areas by altering the power levels, leasing, and GEOGRAPHICAL licensing.

The correct answer is (a) Cross-LAYER design allows NON adjacent layers to exchange information which are traditionally relevant to a layer itself

Easy explanation: Cross-layer design allows non-adjacent layers to exchange information which is traditionally relevant to a layer itself. By adapting cross-layer design, a global view of the radio framework and the SURROUNDING environment can be obtained. It helps to eliminate problems that ARISE due to a lack of resource information at the TIME of transmission.

Correct OPTION is (a) Lack of instant signaling

Best EXPLANATION: Interlayer signaling allows signaling information to pass from layer to layer along with packet flow. The processing PATH in the protocol stack may pass from top to bottom or from bottom to top. This is not suitable for cross-layer IMPLEMENTATION SINCE it requires instant signaling.

Right answer is (b) Random Access Channel

For explanation I would say: COMMON control channel TRANSFERS control information from a radio to a base-station. Random access channel is REQUIRED to gain access to a system. It is invoked when the radio STARTS a call or replies to a page.

The CORRECT option is (B) PROACTIVE handoff

The explanation is: In the proactive handoff, the xG user CONTINUES to sense during transmission, and the handoff is carried out prior to the triggering event. In reactive handoff, the xG user begins to sense for other BANDS only after the triggering event. Proactive handoff is suitable for delay-sensitive application.

Correct answer is (C) Reactive

Explanation: Reactive reasoning and learning does not involve explicit planning. The cognitive system can be programmed to respond to user VOICE commands and common device configurations. The ADAPTIVE cognitive radio stores user preferences, incorporates speech RECOGNITION models, and user intent models to learn from PAST experiences.

The correct answer is (c) Vacate spectrum band

Best explanation: The COGNITIVE radio USERS only have temporary access to the unused spectrum in the licensed band. If the PRIMARY user demands access, the spectrum mobility FUNCTION of the spectrum management framework intervenes and TRANSFERS the cognitive radio user to another vacant position.

Right choice is (d) Measurement of parameters that maintain PRESENT working state

Explanation: Network conditions are sensed to detect the values of parameters that are ESSENTIAL to maintain the present working state and also for pursuing new states. A system generally initiates with TCP/IP configuration, and modifications are applied to IMPROVE the performance. When a protocol composition is incompatible, network SENSING is responsible for identifying the source of the defect as well as for selecting an APPROPRIATE protocol.

The correct option is (d) Observation

The explanation is: Situation-Aware PROTOCOLS in Edge Network Technologies (SAPIENT) was DEVELOPED to determine the effectiveness of cognitive approaches to adaptive composition and the ADAPTION of PROTOCOL STRUCTURES. Knowledge representation, learning, selection, and composition are the challenges identified by SAPIENT.

Correct answer is (a) EXTENSION of policy decision point beyond LINEAR order of priorities

The explanation: Hierarchical policy MANAGEMENT and domain groupings introduce additional flexibility by allowing a policy decision point to EXTEND beyond the linear ordering of priorities. In the inheritance hierarchy, policies created from the local domain have HIGHER priority in the device.

Right choice is (d) TIME tag the transmitted signal

The explanation: The time of arrival approach relies on time tagging the transmitted signal and computing the time of arrival of the signal at the receiver. When many receivers with KNOWN locations OBTAIN the same signal, the multiple iso-range spheres intersect providing the LOCATION of the transmitter. Likewise, when transmitters PROVIDE knowledge of their location in the time-tagged transmitted signal, a receiver can compute its location.