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The correct option is (d) ANALYSIS of channel path

The best explanation: The signal propagation is ANALYZED by multiple RECEIVERS or by multiple antennas. This results in the conversion of the time delay to the PHASE difference, time difference, or frequency shift which is then converted to equations of range, or other parameters.

Right option is (B) DARPA AGENT MARKUP Language and eXtensibleMarkup Language

Easiest EXPLANATION: KAoS policy language expresses and applies policies in the software agent CONTEXT. It was initially based on DARPA Agent Markup Language (DAML) and eXtensibleMarkup Language. But due to poor descriptive logic of DAML, KAoS shifted towards the Web Ontology Language to represent knowledge about domains and rule-based policies.

Correct option is (d) Shape of curve

To explain: Time of arrival and time difference of arrival are two time-based approaches. Both approaches REQUIRE a high-resolution SYSTEM clock with SIGNALS that propagate at the speed of light. It requires a straight line of SIGHT PATH as the signal delay directly relates to the line of sight distance.

The correct choice is (b) False

For EXPLANATION: FEDERAL Communication Commission PROPOSED a shift from the reactive spectrum management model to a PROACTIVE spectrum policy. FCC aims to put forth a spectrum policy that will IMPROVE the public benefits obtained from spectrum usage.

The correct ANSWER is (C) Network layer and Transport layer

The best EXPLANATION: The effect of primary USER transmission on the MAC layer and network layer is complete and irreversible blockage of a packet. It can be mitigated by retransmitting acknowledgments in the MAC layer. It can be mitigated in the network layer by selecting PROTOCOL with effective packet restoration mechanisms.

Right option is (d) Close band SPACING between stations

Explanation: The close band spacing between stations is a potential method for increasing the station density. HOWEVER it CAUSES increased out-of-band rejection at the receivers. Reduction of TRANSMISSION and increased FREQUENCY reuse are other approaches for increasing station density. However these methods result in reduced coverage.

Correct OPTION is (C) Physical layer

To explain I WOULD say: Adaptive modulation and coding is the process of adjusting signal parameters such as the modulation type, coding technique, and protocol parameters to the characteristics of the CHANNEL selected for transmission. The adaptive modulation system requires channel state information at the transmitter.

Correct answer is (b) Reduced network capacity

Best explanation: Cross-layer design involves the exchange of information over VARIOUS interfaces to achieve a better quality of service than possible by following the TRADITIONAL layered approach. The exchange of information can be between physical and DATA link layer, data link and transport layer, network and transport layer, etc. Cross-layer design aims to achieve a high end to end throughput, increase the network capacity, optimize network utilization, reduce INTERFERENCE and power consumption.

Correct ANSWER is (c) Throughput

Explanation: Mobility handling is required when a secondary user moves from one place to another DUE to the arrival of a primary user or due to variation in the spectrum environment. It is also required when an intermediary NODE LEAVES the path of communication. Mobility handling is responsible for finding an ALTERNATE node and re-establishing communication.

Correct choice is (a) True

To EXPLAIN I would say: Target channel selection RELIES on channel capacity, availability of channel during handoff, and availability of channel in the future. PREDICTION of channel availability reduces SENSING DELAY since partial sensing is performed instead of conventional sensing. Accuracy is improved due to the integration of historical spectrum statistics.

Correct choice is (c) The duration over which the xG user can use the licensed spectrum BAND

Easiest EXPLANATION: HOLDING time refers to the period over which the xG user can occupy the licensed spectrum band before the arrival of the PRIMARY user. High holding time ensures high quality. Statistical handoff patterns are used to construct xG NETWORKS with longer holding time.

The CORRECT answer is (B) Modulation scheme

The best explanation: Wireless link errors are parameters of importance in characterizing the spectrum BAND. The modulation scheme and the amount of INTERFERENCE in the spectrum band influence the error rate. Wrongful sensing decisions are also a CONTRIBUTING factor to the high error rate.

Right option is (d) Available RESOURCE map is extended from a radio environment map

The best I can explain: Radio environment map is a spatiotemporal database capable of supporting cognitive functionalities such as planning, learning, and reasoning of the USER equipment. The radio environment map is an extension of the available resource map which includes all radio activities in the UNLICENSED wide AREA network in real time.

The correct ANSWER is (b) False

To explain: Common OPEN policy SERVICE has two models namely the outsourcing model and the provisional model. In the outsourcing model, the policy decision POINT holds all POLICIES. In the provisional model, only the policies requested by the policy enforcement point are downloaded.

The correct choice is (a) ENHANCE the effectiveness of text to SPEECH conversion

To elaborate: Background NOISE suppression enhances the effectiveness of communication and speech CODERS. It is used to EXTRACT information that can be utilized to introduce situational awareness. It also employed to increase voice quality and the cognition level of coded speech.

Right answer is (c) Token

Easiest EXPLANATION: The MAJOR categories of user authentication are knowledge, traits, token, and behaviour. PINs and passwords are associated with knowledge. KEYS and badges are associated with tokens. Behaviour involves usage patterns. Features such as voice and fingerprint are used to sense behaviour. An implementation INCLUDING four categories offers strong protection.

Right choice is (c) Policy Core INFORMATION Model

The explanation: Policy Core Information Model initiated the process of standardizing policy management TERMINOLOGY. It represents network management policies. The framework can SUPPORT vendor-specific implementations.

Right choice is (d) Handle non-linear PRIORITIES

Explanation: Metapolicies can AID policy decision point in handling nonlinear priorities, solving CONFLICTS, and ambiguities between overlapping rules. Metapolicies CONSTRAIN the interpretation of groups of policies. For example, language can permit the addition of domain-specific information without modification.

Correct choice is (b) Time difference between two radio pulses

To explain I would say: Long RANGE navigation is a hyperbolic radio navigation system operating at low FREQUENCIES. The hyperbolic navigation system in LORAN uses the time difference between radio pulses to locate the object of INTEREST. An electronic clock was employed to generate TRIGGER signals that maintain a fixed delay such as 1 ms between the transmitters.

Right choice is (b) Radiated SPECTRAL energy increases at the third power of the spectral information density

Easy explanation: Shannon limit SPECIFIES the maximum rate at which COMMUNICATION can be carried out without error in a channel with a GIVEN bandwidth. Shannon limit supports a claim that spectrum efficiency of infinite bits per Hertz can be achieved by increasing energy per bit exponentially. This results in the increase of radiated spectral energy at the third power of spectral information density.

Right option is (c) Cross-layer approach

For explanation: Spectrum handoff depends on the spectrum environment as well as the application requirements. By choosing a cross-layer approach, the OPERATIONAL overhead among the functionalities is reduced. This INCREASES the SWITCHING TIME.

The correct option is (a) Determining transmission parameters to avoid interference

To EXPLAIN I would say: The major policy challenge for the FIXED transmitter, mobile receiver configuration is the determination of transmission parameter LEVELS which do not cause interference and are ECONOMICALLY feasible. For example, determining the number of stations required for BROADCASTING in a region.

Correct option is (c) Cooperative intra-network spectrum sharing

For EXPLANATION I would say: Dynamic open spectrum channel PROTOCOL aids the cooperative intra-network spectrum sharing. A busy tone is EXCHANGED between the transmitter and the receiver in the selected busy tone channel during COMMUNICATION on the data channel.

The correct answer is (b) False

To explain I WOULD say: The selection of a common control channel is difficult in DISTRIBUTED cognitive wireless networks due to the TIME varying spectrum environment and lack of a central controlling entity. It is overcome by CHOOSING a licensed or an unlicensed channel as the dedicated common control channel.

Right CHOICE is (c) Degree of interference exhibited towards primary user

To explain I would say: The overlay and UNDERLAY spectrum sharing techniques are classified based on the amount of interference directed towards the primary users while operating in the licensed spectrum BAND. Overlay exhibits zero interference while the underlay technique exhibits considerable interference which is regarded as noise by primary users.

Right option is (B) Centralized

The explanation: COOPERATION DETECTION can be carried out with a centralized structure or with a distributed structure. Centralized cooperation detection involves the collection of sensing INFORMATION by the xG base station to determine spectrum holes. Distributed cooperation detection detects spectrum holes by using information exchanged by xG users.

Correct answer is (d) Reconfiguration

The best explanation: Transmission parameters of a radio should be reconfigurable for effective OPERATION in certain spectrum bands. For example, if the signal to noise cannot be modified, then the bit error rate can be altered to MAINTAIN the channel CAPACITY by EMPLOYING adaptive modulation techniques.

Right option is (b) False

The explanation: Sensing control is essential to ADAPT sensing operation in accordance with the dynamic RADIO environment. It operates in the physical and data-link layer of the OSI model. It COORDINATES the sensing operations among xG users in a DISTRIBUTED manner. It helps to avoid false ALARMS in cooperative sensing.

Correct option is (C) BEHAVIOUR authentication includes BIOMETRIC detection

To elaborate: Behaviour based user authentication involves recognizing actions, interests, tendencies, and patterns. Behaviour based user authentication exhibits minimal intrusion to user activity, and is transparent. It supports continuous mode operation and requires a limited AMOUNT of resources.

Right option is (a) Compatibility of composition with objective

To ELABORATE: The structural adaption scheme requires KNOWLEDGE of external conditions that influence the PROTOCOL elements. It also requires knowledge of inherent assumptions relevant to certain protocol elements that affect its sustainability. It requires the mapping of composition with the objective to ACHIEVE the desired QUALITY of service.

Right choice is (d) Federal Communication Commission

For EXPLANATION I would say: Many institutions of RESEARCH and regulation conducted studies to analyze the need for SPECTRUM and to identify the changes that need to be made to existing regulations and policies of the RF spectrum. Government ACCOUNTABILITY Office, Defence Science Board, and Toffler associates were involved in analyzing the need for spectrum. Federal Communication Commission and the Center of STRATEGIC and International studies were involved in identifying the modification of regulations.

The correct choice is (a) True

Explanation: The sensing information from the physical layer helps the intermediary nodes to construct better routes. The triggering event for a packet loss can be RIGHTLY identified as link failure or NODE failure with sensing information.

The correct ANSWER is (d) Cross-Layer Signalling Shortcuts

For explanation: Direct INTERLAYER Communication provides shortcuts between layers that are performed out of the BAND. Cross-Layer Signalling Shortcuts support the exchange of messages between non-adjacent layers eliminating the NEED for processing at each layer.

The CORRECT answer is (d) Transmitter uncertainty and receiver uncertainty

Best explanation: When the xG USER communication range does not include the transmitter, interference is unavoidable as receiver information is unavailable. This is known as receiver uncertainty. In CERTAIN situations, the xG user has a good line of SIGHT with the receiver but is unaware, this is known as SHADOWING uncertainty.

Right answer is (d) Interference BASED detection

Explanation: Transmission detection is based on the identification of weak signals SENT by the PRIMARY transmitter obtained by the local observations of the xG users. Transmitter detection is ALSO known as non-cooperative method. Interference based detection and COOPERATION detection are other spectrum sensing techniques.

The correct option is (d) Application policies

Easy EXPLANATION: The various CHARACTERISTICS of the unused spectrum bands determined during spectrum SENSING depend on the time-varying radio environment, operating FREQUENCY, bandwidth, and quality of service requirements of the cognitive radio user. Spectrum management is required to correctly associate a user to a compatible spectrum band AMONG all available spectrum bands in xG networks.