This set of Cognitive Radio Question Bank focuses on “The xG Network Architecture – 2”.
1. What is the function of the xG network in the licensed band?
a) Exploit unused spectrum holes
b) Route xG users
c) Route primary users
d) Manage information for primary users
Explanation: The xG users on the xG network exploit the unused spectrum holes that are available for a limited time in the licensed spectrum band. This may be carried out by applying various cognitive communication techniques.
2. Which among the following is an additional function carried out xG users in the licensed band?
a) Route primary users
b) Detection of the presence of primary users
c) Detection of the presence of secondary users
d) Route secondary users
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.
3. Which among the following affects the channel capacity of spectrum holes?
a) Interference at nearby primary users
b) Interference at nearby xG users
c) Distance between the xG user and primary base-station
d) Distance between the xG user and xG base-station
Explanation: 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.
4. What is the terminology used to refer to the transfer of users from one spectrum to another spectrum?
a) Spectrum routing
b) Mobile routing
c) Mobile handoff
d) Spectrum handoff
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.
5. Which among the following relies on efficient allocation of spectrum?
a) Effective multiplexing
b) Effective modulation
c) Capacity of open spectrum access
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.
6. Which among the following is true about xG users in an unlicensed spectrum band?
a) xG user has equal rights to access the spectrum
b) xG user vacate the spectrum band upon arrival of the primary user
c) xG user vacate the spectrum band upon arrival of another xG user
d) xG users compete for the position of primary user
Explanation: 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.
7. Which among the following is required for effective use of spectrum in an unlicensed spectrum band?
a) Spectrum sharing algorithms
b) Scheduling algorithms
c) Planning algorithms
d) Decision-making algorithms
Explanation: xG users compete to access the unlicensed spectrum band since every user has an equal right to access the spectrum. Intelligent spectrum sharing algorithms ensure effective spectrum usage and good quality of service. If many xG networks are present, impartial sharing on a network level is required.
8. Which among the following may not be achieved by using xG networks for military applications?
a) Select intermediate frequency bandwidth
b) Improve security
c) Select compatible modulation scheme
d) Reduce interference
Explanation: 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.
9. Which among the following is a requirement of emergency networks?
a) Quality of service
b) Determine of charges for usage
c) Minimum latency
d) Parsing incoming information
Explanation: 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.
10. Which among the following is a requirement of a cognitive mesh network?
a) Large spectrum
b) Quality of service
d) Effective modulation scheme
Explanation: Cognitive mesh networks require high capacity to support applications that require high throughput. xG networks are capable of accessing large portions of the spectrum and can support the demand generally present in dense urban areas. Cognitive mesh networks are used for providing broadband connectivity.
11. Which among the following is not true about Mobile Virtual Network Operator?
a) MVNO owns wireless infrastructure
b) MVNO purchases infrastructure at retail price
c) MVNO is a form of leased network
d) MVNO might operate with mobile virtual network enabler
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.
12. xG networks allow usage of spectrum band without a fixed infrastructure.
Explanation: xG networks allow usage of spectrum band without a fixed infrastructure by maintaining communication priority and response time. It is also capable of adding a temporary or permanent spectrum to infrastructure links that are used for relaying traffic.
13. What type of network is depicted in the following diagram?
a) xG ad hoc access
b) xG network access
c) Primary network access
d) Secondary network access
Explanation: The diagram depicts xG network access connection. xG network access refers to the communication established via xG base-station on the licensed and unlicensed spectrum band. xG base station is a fixed infrastructure network component that provides single hop connection to xG users.
Sanfoundry Global Education & Learning Series – Cognitive Radio.
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