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SRM UNIVERSITYRamapuram Campus

Department of Computer ApplicationsPCA15E07- ADHOC WIRELESS NETWORKS

QUESTION BANK

UNIT I

PART-A (2 marks)

1.Draw electromagnetic spectrum.

2.write about three propagation mechanism.

• Reflection: When the propagating radio wave hits an object which is very large compared to its wavelength (such as the surface of the Earth, or tall buildings), the wave gets reflected by that object. Reflection causes a phase shift of 180 degrees between the incident and the reflected rays. • Diffraction: This propagation effect is undergone by a wave when it hits an impenetrable object. The wave bends at the edges of the object, thereby propagating in different directions. This phenomenon is termed as diffraction.The dimensions of the object causing diffraction are comparable to the wavelength of the wave being diffracted. The bending causes the wave to reach places behind the object which generally cannot be reached by the line-of-sight transmission. The amount of diffraction is frequency-dependent, with the lower frequency waves diffracting more. • Scattering: When the wave travels through a medium, which contains many objects with dimensions small when compared to its wavelength, scattering occurs. The wave gets scattered into several weaker outgoing signals. In practice, objects such as street signs, lamp posts, and foliage cause scattering.

3. what is doppler shift? The Doppler shift is defined as the change/shift in the frequency of the received signal when the transmitter and the receiver are mobile with respect to each other. If they are moving toward each other, then the frequency of the received signal will be higher than that of the transmitted signal, and if they are moving away from each other, the frequency of the signal at

PCA15E07- ADHOC WIRELESS NETWORKS QUESTION BANK

the receiver will be lower than that at the transmitter. The Doppler shift fd is given by where v is the relative velocity between the transmitter and receiver, and λ is the wavelength of the signal.

4. write about nyquist theorem? The signaling speed of a transmitted signal denotes the number of times per second the signal changes its value/voltage. The number of changes per second is measured in terms of baud. The baud rate is not the same as the bit rate/data rate of the signal since each signal value may be used to convey multiple bits.

5. write about shannon’s theorem? Noise level in the channel is represented by the SNR. It is the ratio of signal power (S) to noise power (N), specified in decibels, that is, SNR = 10 log10(S/N). One of the most important contributions of Shannon was his theorem on the maximum data rate possible on a noisy channel.

6. what are the techniques of analog modulation? Analog modulation techniques are used for transmitting analog data. The analog data signal is superimposed on a carrier signal. This superimposition is aimed at altering a certain property (amplitude or frequency) of the carrier signal. Some of the commonly used analog modulation techniques are amplitude modulation, frequency modulation, and phase modulation.

7.What are techniques of digital modulation?

Digital modulation schemes are used for transmitting digital signals that consist of a sequence of 0 and 1 bits. As in analog modulation, digital modulation also changes a certain property of the carrier signal. The main difference between analog and digital modulation is that while the changes occur in a continuous manner in analog modulation, they occur at discrete time intervals in digital modulation. The number of such changes per second is known as the baud rate of the signal. Some of the basic digital modulation techniques such as Amplitude shift keying, frequency shift keying, and phase shift keying. 8.Draw the illustration of SDMAC?

9.Define quantisation & sampling?


The quantization phase, the amplitudes of the PAM pulses are measured and each pulse is assigned a numerical value. In order to avoid having to deal with an infinite number of values for thePAM pulses, a fixed number of amplitude levels are used. This distortion is also known as quantization error. But at the same time, since only a fixed number of amplitude levels are used, only a fixed number of numerical values need to be transmitted. The codec converts the analog speech signal to its digital representation by sampling the signal at regular intervals of time. The higher the sampling rate, that is, the shorter the time interval between successive samples, the better the description of the voice signal. The frequency of the samples to be taken, such that quality of the voice signal is preserved, is given by the sampling theorem.10. Define binary encoding?

In this final phase, the quantized PAM pulses are encoded into the binary format which forms the final output of the analog to digital conversion process. The number of bits used to represent each amplitude level is based on the total number of amplitude levels that need to be represented.11.Define vocoder? The PCM mechanisms described above echniques in high bit rates. Eg. If a sampling rate of 8000 samples/sec is used and each sample is encoded in 8 bits then corresponding rate would be 64 hours.

Part B (16 Marks)

1. Define in detail about electromagnetic spectrum?

- Radio waves - Frequency waves -Micro waves - Infrared waves -Spectrum allocation 2. write brief about characteristics of wireless channel?

Path loss Fading Interference Doppler shift Transmission rate constraints Nyquist theorem Shannon’s theorem 3.Explain the following multiple access techniques in detail?

FDMA Illustration of FDMA Orthogonal frequency division multiplexing TDMA Illustration of TDMA SDMA


Illustration of SDMA4.Describe in detail about code division multiple access? FHSS DSSS Illustration of DSSS.5.Explain briefly about voice coding?

Pulse code modulation Sampling Quantization Binary encoding6.Write briefly about modulation techniques?

Analog modulation Amplitude modulation Angle modulation Frequency modulation Phase modulation Digital modulation Amplitude shift keying Frequency shift keying Phase shift keying


Unit – II

PART-A(2 marks)

1. Differentiate wireless and wired transmission?

Address is not equivalent to physical location Dynamic topology and restricted connectivity Medium boundaries are not well-defined Error-prone medium2. What are the uses of WLAN?

Users would be able to surf the Internet, check e-mail, and receive Instant Messages on the move. • In areas affected by earthquakes or other such disasters, no suitable infrastructure may be available on the site. WLANs are handy in such locations to set up networks on the fly. • There are many historic buildings where there has been a need to set up computer networks. In such places, wiring may not be permitted or the building design may not be conducive to efficient wiring. WLANs are very good solutions in such places.3. Define access points?

Infrastructure networks contain special nodes called access points(AP) which are connected via existing networks.4. what are the components in typical IEEE802.11?

The set of stations that can remain in contact (i.e., are associated) with a given AP is called a basic service set (BSS). The coverage area of an AP within which member stations (STAs or MTs) may remain in communication is called the basic service area (BSA). A BSS is the basic building block of the network. BSSs are connected by means of a distribution system (DS) to form an extended network. 5. Differentiate infrastructure based versus Adhoc LANS?

Infrastructure networks contain special nodes called access points which are connected via existing networks. Aps are special in the sense that they can interact with wireless nodes as well as with the existing wired network.adhoc lans do not need any fixed infrastructure.6.What are the various services offered by typical IEEE802.11 network?

Association, reassociation, disassociation, distribution,integration, authentication, deauthentication, privacy, data delivery.7.What are the two modes that mobile terminal can operate?

Infrastructure mode in which MTs can communicate with one or more Aps which are connected to a WLAN. Adhoc mode, in which MTS can communicate directly with each other without using an AP.8.What is IFS & mention its types?

Inter-frame spacing refers to the time interval between the transmission of two successive frames by any station. There are four types of IFS: SIFS, PIFS, DIFS, and EIFS, in order from


shortest to longest. They denote priority levels of access to the medium. Shorter IFS denotes a higher priority to access the medium, because the wait time to access the medium is lower. The exact values of the IFS are obtained from the attributes specified in the physical layer management information base (PHYMIB) and are independent of the station bit rate.9. Write the objective of PCF?

It is the waiting time whose value lies between SIFS and DIFS. This is used for real time services.10. Define roaming

Roaming refers to providing uninterrupted service when the user walks around with a wireless station. When the station realizes that the quality of the current link is poor, it starts scanning for another AP. This scanning can be done in two ways: active scanning and passive scanning. Active scanning refers to sending a probe on each channel and waiting for a response. Passive scanning refers to listening into the medium to find other networks.11.List all four standards defined for wireless network by the ETSI?

12.Write a note L2CAP?

13.Draw the operational state of bluetooth?

14. What are the various bluetooth modes of operation during connection state?

• Active mode: In this mode, the Bluetooth unit actively participates in thepiconet. Various optimizations are provided to save power. For instance, if the


master informs the slave when it will be addressed, the slave may sleep until then. The active slaves are polled by the master for transmissions. • Sniff mode: This is a low-power mode in which the listening activity of the slave is reduced. TheLMP in the master issues a command to the slave to enter the sniff mode, giving it a sniff interval, and the slave listens for transmissions only at these fixed intervals. • Hold mode: In this mode, the slave temporarily does not support ACL packets on the channel (possible SCO links will still be supported). In this mode, capacity is made available for performing other functions such as scanning, paging, inquiring, or attending another piconet. • Park mode: This is a very low-power mode. The slave gives up its active member address and is given an eight-bit parked member address.

Unit – II

PART-B (16 marks)

1.Explain the following i)Fundamentals of WLANS.

Technical issues Differences between wireless and wired transmissions. Uses of WLANs Design goals Security Safety requirementsIi) Network architecture

Infrastructure based vs adhoc LANs Components in a typical IEEE 802.11 network.2.Explain CSMA/CA mechanism in IEEE 802.11 standard?

The medium access mechanism. Contention window size Acknowlwdgements RTS-CTS mechanism How RTS-CTS Works MAC as a state machine Other MAC layer functionalities.3.Explain HIPERLAN/1 in detail?

The physical layer The MAC layer The CAC sublayer EY-NPMA Prioritization Contention Transmission Power conservation issues


Failure of HIPERLAN/14.Briefly about HYPERLAN/2?

The physical layer The cl layer The DLC Layer The RLC sublayer The MAC sublayer Security issues5.Explain the following transport protocol group in bluetooth specification

i)Radio layer ii)Baseband layer6.Explain

i)Link manager protocol ii)logical link control and adaption protocol(L2CAP) iii)host controller interface iv)middleware protocol groups.


Unit – III

PART-A (2 marks)

1. Define cluster?A cluster is a group of cells which uses the entire radio spectrum. The cluster size N is the number of cells in each cluster. No two cells within a cluster use channels of the same frequency. Cluster in ensures that cells which use the same frequency are separated by a minimum distance, called the reuse distance D.

2. Define Handoff or Handover?An important concept that is essential for the functioning of cellular networks is handoffs, also called handovers. When a user moves from the coverage area of one BS to the adjacent one, a handoff has to be executed to continue the call. There are two main parts to the handoff procedure: the first is to find an uplink-downlink channel pair from the new cell to carry on the call, and the second is to drop the link from the first BS.

3. Define HLR and VLR? In the current location management scheme, each user is permanently associated with the home location register (HLR) in his/her subscribed cellular network. This HLR contains the user profile consisting of the services subscribed by the user(such as SMS and paging), billing information, and location information.The visitor location register (VLR) maintains the information regarding roaming users in the cell. VLRs download the information from the users' respective HLRs. The number and placement of the VLRs vary among networks. Registration of an MT in a new cell entails updates of its HLR, and the VLRs of its old and new cells.

4. What are the three broad categories of control channels in GSM?1) The broadcast control channel(BCCH)2) The dedicated control channel (DCCH) 3) common control channel(CCCH)5. Define virtual home environment? A virtual home environment, formally defined as a uniform and continuous presentation of services, independent of location and access. This means that the user must be able to access the services that he/she has subscribed to, from anywhere in the world, irrespective of his/her method of access, as if he/she were still at home.

6.Name the commonly used fixed wireless system which are typically used for high speed internet access?Two commonly used fixed wireless systems, which are typically used for high-speed Internet access, are local multipoint distribution service (LMDS) and multichannel multipoint distribution service (MMDS). These can be regarded as metropolitan area networks (MANs).7.List out various parameters needed to classify the services in order to minimize the AAL protocol?


• Timing relationship between source and destination• Bit rate (constant or variable)• Type of connection (connection-oriented or connection-less)

8.write a small notes on different situation of backward handoff? A backward handoff can occur in one of the following three situations:1. Intra AP: In this case, the source and destination radio BSs belong to the same AP. The EMAS-E merely finds out the resource availability at the new BS and forwards the response to the MT. The issues involved in an Intra-AP handoff decision are similar to those in cellular networks.2. Inter AP/Intra EMAS-E: In this case, the BSs belong to different APs connected to the same EMAS-E. The EMAS-E inquires about the availability of resources at the destination AP and forwards the response to the MT.3. Inter EMAS-E: In this case, the BSs belong to different EMAS-Es. This is the most complicated of the handoffs. The MT asks the Destination EMAS-E for the availability of resources. The Destination EMAS-E in turn queries the corresponding AP and the response is sent back. The source EMAS-E now requests that the destination EMAS-E reserve resources and the handoff is performed.9.What is the location management?In a WATM network, the MTs are mobile and move from one BS to another over a period of time. Therefore, in order to enable communication with them some methods need to be developed to keep track of their current locations. This process comes under the purview of location management (LM). The following are some of the requirements of an LM system [29]:1. Transparency: The LM system should be developed in such a manner that the user should be able to communicate irrespective of mobility.2. Security: The system must guard against unauthorized access to the database of MT addresses and MT locations.3. Unambiguous identification: The LM system should be capable of uniquely identifying MTs and their locations. 4. Scalability: The system must be scalable to various sizes of networks. For doing this efficiently, it should harness the advantages of the hierarchical nature of networks.

PART-B (16 marks)

1.Explain cellular concept & capacity enhancement in detail?

Cell-Splitting Sectorization Power Control 2.Explain channel allocation algorithms & handoff in detai? Issues Involved in Handoffs Handoff Quality Improved Handoff Strategies

3.GSM in detail?

Data over voice channel


GSM evolution of data services Other 2g standards4.Explain data over voice channel & GSM evaluation of dataservices in detail?

Short messaging service High speed circuit switched data(HSCSD) General packet radio service(GPRS) Enhanced data rate for GSM Evolution(EDGE) Cellular digital packet data(CDPD)5.Describe 3G cellular system in detail?

3G standards. The problems with 3g systems.6.Explain WLL technologies in detail?

Generic WLL architecture. WLL technologies Broadband wireless access7.Explain wireless ATM in detail?

ATM-an overview Motivation for WATM Generic reference model MAC layer for WATM Handoff issues in WATM Location management


Unit – IV

PART-A (2 marks)

1. Differentiate cellular and adhoc networks.

2. Listout the applications of adhoc wireless networks.Ad hoc wireless networks, due to their quick and economically less demanding deployment, find applications in several areas. Some of these include: military applications, collaborative and distributed computing, emergency operations, wireless mesh networks, wireless sensor networks,and hybrid wireless network architectures.3. What are the issues in adhoc wireless networks.

Gateways Address mobility Routing Transport layer protocol Load balancing


Pricing/billing Provisioning of security QoS support Service, address, and location discovery4. What are the classification of energy management. Transmission power management: Battery energy management: Processor power management: Devices power management:5. What are the deployment advantages of wireless networks.Low cost of deploymentIncremental deploymentShort deployment timeReconfigurabilityScenario of deploymentMilitary deploymentEmergency operations deploymentCommercial wide-area deploymentHome network deploymentRequired longevity of networkArea of coverageService availabilityOperational integration with other infrastructureChoice of protocols6. Draw MCN architecture.

7. What are the major issues considered in designing a mac protocol.Bandwidth EfficiencyQuality of Service SupportSynchronizationHidden and Exposed Terminal ProblemsError-Prone Shared Broadcast Channel


Distributed Nature/Lack of Central CoordinationMobility of Nodes8. What are the major challenges that a routing protocol faces.MobilityBandwidth ConstraintError-Prone Shared Broadcast Radio ChannelHidden and Exposed Terminal ProblemsResource ConstraintsCharacteristics of an Ideal Routing Protocol for Ad Hoc Wireless Networks

Unit – IVPART-B (16 marks)

1. Explain in detail about the applications of adhoc wireless networks.2. Explain in detail about cellular and adhoc wireless networks and differentiate the same.3. Describe the following in detail. i)MAC

Distributed operationSynchronizationExposed terminals:Hidden terminalsThroughputAccess delayFairnessReal-time traffic supportResource reservation:Ability to measure resource availabilityCapability for power controlAdaptive rate control:Use of directional antennas

II)ROUTINGMobilityBandwidth constraintError-prone and shared channelLocation-dependent contentionOther resource constraintsMinimum route acquisition delayQuick route reconfigurationLoop-free routingDistributed routing approachMinimum control overheadScalability:Provisioning of QoS:Support for time-sensitive trafficSecurity and privacy


4. Expalin in detail about the following.i)multicasting

RobustnessEfficiency:Control overheadQuality of serviceEfficient group management:ScalabilitySecurity

ii) transport layer protocolsiii)pricing schemeiv)QOS provisioning

QoS parametersQoS-aware routingQoS framework

5. Expalin deployment consideration of adhoc wireless networks. Low cost of deployment Incremental deployment Short deployment time Reconfigurability Scenario of deployment Military deployment Emergency operations deployment Commercial wide-area deployment Home network deployment Required longevity of network Area of coverage Service availability Operational integration with other infrastructure Choice of protocols

6. Explain adhoc wireless internet in detail. Gateways Address mobility Routing Transport layer protocol Load balancing Pricing/billing Provisioning of security QoS support Service, address, and location discovery


Unit – V

PART-A (2 Marks)

1. Write short notes on hidden and exposed terminal problem?2. What are the design goals of a MAC protocol for adhoc wireless networks? The operation of the protocol should be distributed.

• The protocol should provide QoS support for real-time traffic.• The access delay, which refers to the average delay experienced by any packet to gettransmitted, must be kept low.• The available bandwidth must be utilized efficiently.• The protocol should ensure fair allocation (either equal allocation or weighted allocation) ofbandwidth to nodes.• Control overhead must be kept as low as possible.• The protocol should minimize the effects of hidden and exposed terminal problems.• The protocol must be scalable to large networks.• It should have power control mechanisms in order to efficiently manage energy consumption ofthe nodes.• The protocol should have mechanisms for adaptive data rate control (adaptive rate controlrefers to the ability to control the rate of outgoing traffic from a node after taking intoconsideration such factors as load in the network and the status of neighbor nodes).• It should try to use directional antennas which can provide advantages such as reducedinterference, increased spectrum reuse, and reduced power consumption.• Since synchronization among nodes is very important for bandwidth reservations, the protocolshould provide time synchronization among nodes..

3. Draw the classification of MAC protocol?

4.Draw the packet exchange in MACAW?


5. Draw transmission in BTMA?

7. Draw packet transmission in DBTMA?


8. Draw packet transmission in RI-BTMA?

9.What are the two basic principle needed for CATA operation?The operation of CATA is based on two basicprinciples:

• The receiver(s) of a flow must inform the potential source nodes about the reserved slot on which it is currently receiving packets. Similarly, the source node must inform the potential destination node(s) about interferences in the slot.• Usage of negative acknowledgments for reservation requests, and control packet transmissions at the beginning of each slot, for distributing slot reservation information to senders of broadcast or multicast sessions.

PART-B (16 marks)

1. Explain media access control in wireless LAN in detail.MACA ProtocolMACAW Protocol

2. Explain i)CATA ii)HRMA


3. Explain i)SRMA/PA ii)FPRP

a. Reservation request phase:b. Collision report phase:c. Reservation confirmation phase:d. Reservation acknowledgment phase:e. Packing/elimination (P/E) phase:

4. Explain MACA with piggy backed reservation in detail.5. Explain content based MAC protocol with scheduling mechanism.

Distributed Priority Scheduling and Medium Access in Ad Hoc Networks Distributed Wireless Ordering Protocol Distributed Laxity-Based Priority Scheduling Scheme

6. Explain MAC protocol that are use in directional antennas in detail.I. MAC Protocol Using Directional Antennas

II. Directional Busy Tone-Based MACProtocolIII. Directional MAC Protocols for Ad Hoc Wireless Networks


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