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Correct choice is (b) Establish research consortium to support the government and PRIVATE sectors

The explanation: The research consortium sets goals for spectrum innovation research. It is responsible for solving technical conflicts that tend to arise with the change in technology. CSIS also recommended the FORMATION of an organization comprising of the White House, NATIONAL Security Council, National Economic Council, and spectrum advisory BOARD.

The CORRECT choice is (d) Loss of message packet cannot be identified

For explanation I would say: ICMP protocol has a large protocol header and protocol processing overhead. It is limited to request-response actions. However, cross-layer DESIGN demands for ASYNCHRONOUS COMMUNICATION. This can be overcome by creating a call BACK function with a procedure suited to the needs of the layers under consideration.

The correct choice is (a) Random access TECHNIQUES

Explanation: Non-cooperative intra-network spectrum sharing is a rule based spectrum access approach. When more than ONE CLOSELY located nodes access the same channel, random access techniques are used to resolve contention. The RULES help to reduce COMMUNICATION overhead.

Correct option is (b) Resolve SPECTRUM access contention

For EXPLANATION: The primary user does not INTERACT or coordinate with the secondary user. Therefore the secondary user must be made transparent for the primary user. DSAP should avoid collision between primary users and secondary users by introducing power constraints. The spectrum should be allocated such that AVERAGE network throughput is increased.

The correct answer is (d) Maintenance of MULTIPLE handoffs

The explanation is: Connection MANAGEMENT initially selects the best available spectrum band using algorithms that analyze the channel characteristics and the application requirements. Further challenges for connection management are the ESTIMATION of ACCURATE latency, and reduction of delay and loss during spectrum handoff.

Right option is (a) STORAGE of PACKETS

To explain I would say: Connection management in spectrum mobility enforces protocols with respect to the application for MAINTAINING COMMUNICATION. FTP requires protocols to store packets that are transmitted during handoff. But real-time applications do not REQUIRE storage of packets as the information is obsolete for the corresponding application.

Correct answer is (c) CONTIGUOUS spectrum band

The best I can explain: xG users can transmit packets on multiple spectrum bands provided the AVAILABLE spectrum meets the quality of service REQUIREMENTS and the spectrum policies required for communication. However it does not require the multiple spectrum bands to be contiguous. This exhibits a VAST improvement in communication quality during the spectrum HANDOFF.

The correct choice is (a) True

For explanation I would SAY: Spectrum decisions are AFFECTED by the co-location of data transmission and SENSING function. This problem is overcome by developing a separate sensor NETWORK for cooperative spectrum sensing while an operational network is constructed for data transmission.

Correct option is (c) Fast discovery

Easy EXPLANATION: Out-of-BAND sensing computes the TIME duration required by a cognitive radio user to detect a completely available spectrum band for transmission. Sensing order and STOPPING rule are factors that overlook out-of-band sensing.

Correct option is (d) RAPID attainment of HIGH processing gain

For explanation I would say: The primary advantage of using cyclostationary feature detection is its ability to DIFFERENTIATE noise signals from modulated signals. This is due to incorporated REDUNDANCY in modulated signals. HOWEVER cyclostationary feature detection is computationally intensive and demands long observation time.

The CORRECT choice is (d) Reduce interference

To explain I would SAY: xG networks allow the selection of intermediate frequency bandwidth, and compatible modulation and coding techniques. It is CAPABLE of adapting to the changing radio environment of a BATTLEFIELD. xG networks ALSO carry out secure spectrum handoff.

Correct option is (d) MVNO MIGHT operate with mobile virtual network enabler

Easy explanation: Mobile Virtual Network Operator does not own wireless network infrastructure. It PURCHASES network services from a mobile network operator. In this method, the primary network provides opportunistic access to licensed SPECTRUM. This is an example of LEASED network implementation in xG architecture.

The correct answer is (C) Null hypothesis

Easy explanation: The following equation REPRESENTS the basic hypothesis model for transmitter detection,

s(t) = n(t)[U1]

s(t) = a*i(t) + n(t)[U2]

where s(t) is the signal available at the xG user, i(t) is the signal transmitted by the primary user, n(t) is the AWGN, and a is the AMPLITUDE GAIN of the channel.

U1 is the null hypothesis which indicates the absence of signals from the licensed USERS in the spectrum band. U2 is termed alternate hypothesis which indicates the presence of signals from the licensed users in the spectrum band.

The CORRECT answer is (b) EMISSION of sound to CANCEL noise

To EXPLAIN: Active noise SUPPRESSION mitigates the noise experienced by a user by producing a sound to compensate for the undesired noise field. It can reduce the damage inflicted by exposure to high noise levels and reduce the Lombard effect.

Correct choice is (d) Phonetic translation

Easy explanation: Phonetic transcription is a traditional method for language identification. Phones are the subunits of BASIC SOUNDS of speech. The relation between the OCCURRENCES of phones in different language is analyzed to develop a STATISTICAL model for each language for identification.

Correct option is (d) Memory optimization

Easiest EXPLANATION: The ponder policy management framework consists of a policy language with a set of tools and SOURCE code available FREELY on the internet. The tools can ADMINISTRATE domain HIERARCHIES, allow positive and negative authorization policies, delegate policies, and support event-triggered condition-action rules.

The correct option is (c) Expand communication bandwidth

To explain I would say: The DARPA NeXt Generation radio communication program aims to DEVELOP a radio with technology that can dynamically REDISTRIBUTE the AVAILABLE spectrum in radio networks, THEREBY making the best use of available communication bandwidth. The spectrum should be sensed automatically. The selected operating mode should maximize the survivability of communication networks and reduce the amount of interference to other users of the spectrum.

Correct choice is (C) Hyperbola

The EXPLANATION: The time difference of arrival approach involves computing the time difference between the reception of a signal at one LOCATION and the reception of the same signal at a DIFFERENT location. The plot of time difference of arrival produces a hyperboloid surface with its foci at the two receivers.

Correct answer is (b) False

Explanation: Very High Frequency Omnidirectional Range begins with transmission of amplitude modulated signal with a CONSTANT frequency. The transmitted signal passes through a SET of antenna in a circle introducing frequency modulated Doppler onto the received signal. The RELATIVE phase angle between amplitude modulated signal and frequency modulated signal is employed to find the location of the SOURCE.

Right choice is (c) VOR is intolerant of diffraction

For explanation I WOULD say: Very high frequency omnidirectional RANGE is a radio navigation system incorporated in AIRCRAFTS to stay on route with the help of radio signals transmitted by a network of ground radio beacons. A PROMINENT feature of VOR is that the bearing from the station to the aircraft is UNAFFECTED by wind and orientation of the aircraft.

Right choice is (b) Inbuilt rules

Explanation: Peer to peer cognitive radio RELY on SPECTRUM usage information from local neighbours but is mostly controlled by a SET of comprehensive rules which are provided by the MANUFACTURER. This reduces the amount of overhead in communication but leads to reduced efficiency. Decisions are TAKEN by combining local spectrum awareness and inbuilt rules.

Right option is (b) Spectrum SHARING Innovation Test bed and Spectrum MANAGEMENT TOOLS

The best explanation: Spectrum Sharing Innovation Testbed and Spectrum Management Tools are the recommendations proposed in the Spectrum Policy INITIATIVE created in 2003. Most of the recommendations pertained to the modification of the spectrum management infrastructure. The initiative states that technological advances can be exploited to overcome spectrum scarcity by spectrum sharing.

Correct ANSWER is (d) Better performance during spectrum handoff

The explanation: Cross-layer design improves the accuracy and the productivity of algorithms by extending the amount of information at hand. Cross-layer design helps to adjust in ACCORDANCE with the varying resource availability. It eliminates COMPUTATIONS that are PERFORMED due to a lack of communication between the LAYERS of the protocol stack.

The correct answer is (a) CROSS-layer intra hub module

The EXPLANATION: Cross design involves the SHARING of information among different LAYERS of the protocol stack. For example, spectrum occupancy information gathered in the physical layer must be accurately transferred to the MAC layer through a proper interface. The units required to implement the cross-layer design are interfaces, controllers, schedulers, and inter hubs.

The correct choice is (b) HANDLE multiple interfaces

Best EXPLANATION: An XG terminal USES multiple interfaces to interact with multiple nodes. Queue management is responsible for finding an interface best SUITED for the traffic in the spectrum environment. Queues are generated after evaluating each interface with each traffic type.

Right choice is (c) Spectrum knowledge

To EXPLAIN: The routing LAYER REQUIRES information about the spectrum for determining the PATH of communication. The consolidation of information obtained by sensing and by characterization operations of the physical layer is a challenge as it is difficult to decide which information should be stored. The user requires local as well as GLOBAL knowledge of the spectrum.

Right answer is (a) Spectrum MOBILITY involves seamless channel SWITCHOVER

To explain I would say: Spectrum mobility involves performing seamless channel switchover while MAINTAINING the PERFORMANCE of current secondary user communication. Spectrum mobility is required when degradation of the current channel CONDITION is observed or when the primary user arrives in the licensed band.

Right choice is (a) Intra-cell/Intra-pool handoff

The explanation: When an xG user SWITCHES from ONE spectrum band to another in the same spectrum pool without selecting an ALTERNATE base station, it is termed as intra-cell/intra-pool handoff. A cell is a unit of coverage area. Spectrum pool is a set of contiguous LICENSED spectrum BANDS.

Right choice is (c) Minimum latency

For explanation I would say: Emergency NETWORKS require minimum latency, and a large radio SPECTRUM to accommodate a high VOLUME of traffic including voice, video, and DATA. Since xG networks do not rely entirely on fixed infrastructure for communication and are capable of utilizing unused spectrum bands, they are used for reliable communication under emergency conditions.

Correct ANSWER is (d) Interference temperature measurement

To explain: xG users should not cause interference to primary user communication. The HANDOFF to a different spectrum band upon arrival of the primary user should be seamless. The dynamic spectrum ENVIRONMENT and quality of service REQUIREMENTS should be analyzed and managed for effective communication.

Right choice is (B) Detect spectrum holes

The best I can explain: A cognitive radio should be aware of its surrounding radio environment. Spectrum sensing allows a radio to find the unused spectrum in the radio environment. In out-of-band sensing, cognitive radio USERS FOCUS on the identification of spectrum holes over a WIDE frequency range to transmit their information.

The correct answer is (b) False

To explain: Primary users do not undergo any MODIFICATION to support xG base-stations and xG users. The operation of the primary USER should not be hindered by unlicensed users. SIMILARLY the xG users OPERATING on the licensed band should not affect other primary users.

Right choice is (b) Primary user and primary base-station

The EXPLANATION is: Primary USERS are licensed users of the spectrum. Primary base-station refers to the FIXED infrastructure network component with a spectrum license. The primary base-station contains LEGACY protocols and xG protocols for supporting communication through xG networks.

The correct option is (c) Primary network has a dedicated spectrum band

To ELABORATE: The currently available fixed infrastructure wireless network represents a primary network. It POSSESSES the rights of a dedicated spectrum band. Cellular NETWORKS and TV BROADCAST networks are examples of the primary network.

Correct choice is (a) Interference at nearby primary users

The explanation is: The amount of primary users prone to interference caused by xG users in UNUSED spectrum holes of licensed spectrum band DETERMINES the channel CAPACITY of spectrum holes. Interference avoidance with primary users is an important criterion in the DESIGN of xG architecture.

Right answer is (B) Intelligent spectrum access NETWORK

Easiest explanation: The xG network is ALSO known as the secondary network, UNLICENSED network, cognitive radio network and dynamic spectrum access network. The xG does not have an exclusive right to use any spectrum band. xG networks aim to make use of temporarily UNUSED spectrum bands.

Correct choice is (d) Existing wireless networks EXHIBIT heterogeneity in the spectrum policies and the communication technologies

The explanation is: The currently AVAILABLE wireless networks express heterogeneity in both spectrum policies and communication technologies. For the effective incorporation of communication protocols, a clearly DEFINED XG architecture model is required.

Correct ANSWER is (d) Spectrum HANDOFF

Easy explanation: If a primary USER returns to a spectrum band currently being used by an xG user, the xG user should remove itself from the spectrum and continue operating in a different spectrum band immediately. This is referred to as spectrum handoff.

Right CHOICE is (b) Detection of the presence of PRIMARY USERS

The explanation: An xG user should ensure that the primary user is not affected by the operations of the xG users. The primary user does not have the capability to DETECT the presence of the primary user and request for termination of the connection. Hence the xG user listens for the ARRIVAL of the primary user.

The CORRECT option is (a) xG user has equal rights to access the spectrum

To explain I would SAY: In the UNLICENSED spectrum band, each user has the same right to access the spectrum bands. The xG users PRESENT in one particular area MAY use the same portion of the spectrum band for communication.

Right choice is (a) Single hop for XG USERS

Easy explanation: xG base-station is capable of PROVIDING single hop connection for xG users accessing the licensed portion of the SPECTRUM. It is similar to a primary base-station with fixed NETWORK infrastructure network components however it has additional xG capabilities.

The correct answer is (c) Capacity of OPEN spectrum access

Easiest explanation: FACTORS such as the capacity of open spectrum access and quality of SERVICE rely on the ability of a radio to efficiently allocate radio spectrum. xG network architecture aims for EFFECTIVE USE of unlicensed spectrum band which have multiple heterogeneous networks.

Correct option is (d) xG spectrum access

To elaborate: xG network access refers to the communication established VIA xG base-station on licensed and UNLICENSED spectrum band. xG ad hoc access refers to communication among xG USERS using an ad hoc connection on licensed and unlicensed spectrum band. Primary network access refers to the communication CARRIED out using primary base-station on licensed spectrum band.

The correct answer is (a) Licensed band and UNLICENSED band

The explanation is: xG ARCHITECTURE exists in a mixed spectrum environment with licensed and unlicensed bands. Wideband ACCESS technology allows xG users to OPERATE on both bands. xG users can communicate by using a base-station or by opting for a multi-hop connection.