EC 8004 wireless networks -Two marks with answers
- 1. EC 8004 - WIRELESS NETWORKS UNIT - I: WIRELESS LAN 1. What is infrared (IR) transmission? Infrared light transmission is one ofthe important technologies used in wireless LAN. It is based on the transmission of infrared light at 900 nm wavelength. 2. What is the principle behind infrared technology? Infrared technology uses diffuse lightreflected atwalls, furniture etc. Or directed lightwhen line of sight(LOS) exists between sender and receiver. 3. What are the advantages ofinfrared technology? Shielding is easy and no need for license for infrared technology. Electrical devices do notinterfere with infrared transmission. 4. What are the disadvantages ofinfrared transmission? Low bandwidth Cannot penetrate through walls or other obstacles. 5. Define – Spread Spectrum Spread spectrum involves spreading the bandwidth needed to transmit data. The main advantage of using spread spectrum is the resistance to narrow interference. 6. What are the spread spectrum techniques? There are two basic methods for spread spectrum transmissions. Direct Sequence Spread Spectrum (DSSS) Frequency Hopping Spread Spectrum (FHSS) 7. What is the principle behind FHSS? Frequency Hopping Spread Spectrum is evolved in order to avoid jamming. Hence in this method, the transmitter shifts the center frequency of transmitted signal. The shifts in frequency or frequency hops, occur according to a random pattern is known only to the transmitter and receiver. 8. What are the major issues in WLAN? Two major issues in WLAN are as follows Hidden station problem Exposed stationproblem 9. List out the applications of WLAN. Transfer ofmedical images
- 2. Remote access to patient records Remote monitoring of patients Remote diagnosis ofpatients at home or in an ambulance In telemedicine Surveillance Internet supporting database. 10. What is IEEE 802.11? The IEEE 802.11 is the first WLAN standard that has secured the market in large extent. The primary goal ofthe standard was the specification of a simple and robust that offers time bounded and asynchronous services. 11. Define - Short Inter Frame Space (SIFS) Short IFS is the shortest IFS used for the high priority frames like acknowledgement frames, CTS frames, poll response etc. 12. Define - Distributed coordination function Inter Frame Space (DIFS) DCF-IFS is used for transmitting data frames. It is equal to SIFS plus two time slots and is the longest inter frame gap. 13. What are the functions of MAC layer in IEEE 802.11? The functions of MAC layerare Media Access Control Reliable delivery ofdata units Management functions Authentication encryption 14. What is the need for WATM? WATM systems had to be designed for transferring voice, classical data, video, multimedia etc. 15. What is HIPERLAN? The HIPERLAN stands for High PERformance Radio LAN is an initiation of RES-10 group of the ETSI as a PAN European standard for high speed wireless local networks. 16. Give any two requirements ofHIPERLAN. Data rates of 23.529 Mbps Multi-hop and Ad-hoc networking Supportoftime bounded services 17. What are the three phases in channel access in HIPERLAN-1? Prioritization phase
- 3. Contention phase Transmission phase 18. Give any three differences between HIPERLAN 1 and HIPERLAN 2. HIPERLAN 1 HIPERLAN 2 Application Wireless LAN Access to ATM fixed networks Range 50 m 50 – 100 m Data rate 23.5 M bits/ sec > 20 M bits / s 19. What is meant by BRAN? The BRAN (Broadband Radio Access Networks (BRAN) is standardized by the European Telecommunications Standards Institute (ETSI). Primary motivation of BRAN is the deregulation and privatization of the telecommunication sector. BRAN technology is independent from the protocols of the fixed network. BRAN can be used for ATM and TCP/IP networks. 20. List the functional requirements ofHIPERLANS. Data rates of 23.529 Mbps Supportboth synchronous and asynchronous traffic Power saving support Video at2 Mbps, 100 ns latency and audio at 32 Kbps, 10 ns latency To coverage multihub features Low mobility of1.4 m/s Supportoftime bound services Asynchronous file transfer at 13.4 Mbps 21. What is Bluetooth? Bluetooth is an inexpensive personal area Ad-hoc network operating in unlicensed bands and owned by the user. It is an open specification for short range wireless voice and data communications that was developed for cable replacement in PAN (Personal Area Network). 22. What is the advantage of piconet /scatternet. ? The advantage of the Piconet / Scatternet scheme is that it allows many devices to share the same physical area and make efficient use ofbandwidth. 23. What are the states of Bluetooth? Bluetooth specifies four states, they are Master-M , Slave- S Standby- S SBParked- S 24. List the two major states in the operation ofBluetooth.
- 4. The major states in the operation ofBluetooth are Standby state Connection state 25. What is Piconetand Scatternet? Bluetooth specification defines a small cell called as piconet which has upto 8 devices grouped together. Two or more piconets grouped together know as scatternet. 26. What type ofmodulation used in Bluetooth? Bluetooth uses Gaussian-shaped Frequency Shift Keying (GFSK) modulation with a nominal modulation index of K = 0.3 27. What is the data rate of Bluetooth? The maximum data rate is 721Mbps for asymmetric mode. 28. List the logical channels provided by L2CAP. L2CAP provides three types oflogical channels. They are: Connectionless Connection riented Signaling 29. What is the need for WIMAX? The main reason for the developmentof WIMAX( World Interoperability Microwave Access ) is the demand ofhigh data rates not only the faster downloading but also for the use of new applications like VoIP, Video, streaming multimedia conferencing and interactive gaming. 30. What is WIMAX? WIMAX is the air interface for the actual radio interface network, where both fixed and mobile users can have access to the network. Its specification is IEEE 802.16. 31. Write the throughput feature in WIMAX. WIMAX supports throughput up to 63 Mbps on the downlink and 28 Mbps on the uplink, assuming a 10 MHZ bandwidth channel with TDD frames and with 64 QAM 5/6 as modulation scheme. 32. What are the frequency bands ofIEEE 802.16? The 802.16 standard defines a number of air interfaces that can be divided into, 10-66 GHz licensed band Below 11 GHz licensed bands Below 11 GHZ unlicensed bands
- 5. UNIT II : MOBILE NETWORK LAYER 1. What is a Mobile IP? Mobile IP is a protocol developed to allow internetwork mobility for wireless nodes without them having to change their IP addresses. 2. What are the entities of Mobile IP? Mobile Node (MN) Correspondent Node (CN) Home Network (HN) Foreign Network (FN) Foreign Agent (FA) Home Agent(HA) 3. What are the benefits ofMobile IP? The major benefit of Mobile IP is that it frees the user from a fixed location. Mobile IP makes invisible the boundaries between attachment points, it is able to track and deliver information to mobile devices without needing to change the device’s long-term Internet Protocol (IP) address. 4. What is Care-Of Address (COA)? The Care of Address defines the currentlocation of the MN from an IP pointof view. All IP packets sent to the MN are delivered to the COA, not directly to the subnet. 5. What is agent advertisement? Home Agent (HA) and Foreign Agent (FA) advertise their presence periodically using agent advertisementmessages. These advertisementmessages can be seen as a beacon broadcastinto the subnet. 6. What is the need for registration? The main purpose of the registration is to inform the HA of the current location for correct forwarding of packets. 7. Define – Encapsulation and Decapsulation Encapsulation is the mechanism of taking a packet consisting of packet header and data and putting it into the data part of a new packet. The reverse operation, taking a packet out of the data part of another packet, is called decapsulation. 8. What is triangular routing? Tunneling in its simplest form has all packets to Home Network and then sent to MN via a tunnel. The inefficient behavior of a non-optimized mobile IP is called triangular routing. 9. What is DHCP?
- 6. The Dynamic Host Configuration Protocol (DHCP) is based on the bootstrap protocol (BOOTP), which provides the framework for passing configuration information to hosts on a TCP/IP network. DHCP adds the automatically allocate reusable network addresses and configuration options to internet hosts. 10. What is SIP? The Session Initiation Protocol (SIP) is an application-layer control (signaling) protocol for creating, modifying and terminating sessions with one or more participants. It is a IETF (Internet Standard) RFC 3261 protocol. 11. What are the functions of Session Initiation Protocol (SIP)? SIP has following major functions SIP allows for the establishmentofuser location SIP provides a mechanism for call management SIP provides feature negotiation, so that all the parties in the call can agree to the features supported among them. 12. What are the characteristics ofMANET? Dynamic Topologies Bandwidth Constraints and Variable Capacity Links Energy Constrained Operations Limited Physical Security 13. Differentiate an ad hoc network and a cellular network with respectto a) Bandwidth usage b) Cost effectiveness PARAMETER CELLULAR NETWORK AD HOC NETWORK Bandwidth usage Easier to employ bandwidth reservation Bandwidth reservation requires complex medium access control protocols Guaranteed bandwidth (designed for voice traffic) Shared radio channel (more suitable for best-effort data traffic) Cost effectiveness Cost ofnetwork maintenance is high (backup power source, staffing, etc.) Self-organization and maintenance properties are built into the network. Hence the cost of network maintenance is less. 14. What are the challenging issues in ad hoc network maintenance? Medium accessscheme, Routing Multicastrouting
- 7. TransportlayerprotocolPricingSchemes Qualityof Service Provisioning Self-Organization Security Addressing and Service Discovery EnergyManagement Scalability & Deploymentconsiderations 15. Why are ad hoc networks needed? Ad hoc networking is often needed where an infrastructure network cannot be deployed and managed. The presence ofdynamic and adaptive routing protocols enables quick formation of ad hoc networks and is suitable for emergency situations like natural disasters, spontaneous meetings or military conflicts. 16. List out the applications ofad hoc networks. Ad hoc networks are widely used in Military applications and battlefields Collaborative and distributed computing Emergency search and rescue operations Wireless sensor and mesh networks 17. Give the classifications of routing protocol in MANET. The classifications of routing protocol in MANET are a) Proactive protocols: This protocol attempt to evaluate continuously the routes within the network, so that when a packetneeds to be forwarded, the router is already known and can be immediately used. b) Reactive protocols: This protocol invokes a route determination procedure only on demand. The routing protocols may also be categorized as follows: Table-driven protocols. Source-initiated on-demand protocols. 18. List the Source-initiated On-Demand Routing Protocols. The Source-initiated On-Demand Routing Protocols are Ad-hoc On-Demand Distance Vector Routing (AODV) Dynamic Source Routing (DSR) Temporarily Ordered Routing Algorithm (TORA) Associatively Based Routing (ABR) Signal Stability Based Routing (SSR) 19. Differentiate proactive and reactive routing protocols. Write examples for each.
- 8. S.No. Proactive Reactive 1 Route is pre-established Route establishmentis on-demand 2 Continuously discover the routes Route discovery by some global search 3 Updates topology information(table) periodically No information update is done 4 No latency in route discovery longer delay due to latency ofroute discovery 5 Large capacity is needed to update network information Large capacity is not needed 6 A lot of routing information may never be used May not be appropriate for real-time communication 7 Eg: DSDV, WRP Eg: AODV, ABR 20. What is DSDV? Distance-Vector Routing (DSDV) is a table driven routing scheme for ad-hoc mobile networks. The main contribution ofthe algorithm was to solve the routing loop problem. 21. List out the advantages and disadvantages ofDSDV routing protocols. Advantages Less Delay is involved in route setup process. DSDV protocol guarantees loop free paths. Incremental updates with sequence number tags make the existing wired network protocols adaptable to ad-hoc wireless networks. Count to infinity problem is reduced in DSDV. Path Selection: DSDV maintains only the best path instead ofmaintaining multiple paths to every destination. With this, the amount ofspace in routing table is reduced. Disadvantages Updates due to broken links lead to heavy control overheadduring mobility. The control overhead is directly proportional to the number ofnodes. Small network with high mobility or large network with low mobility can choke the available bandwidth. Wastage ofbandwidth due to unnecessary advertising ofrouting information even if there is no change in the network topology. Delay in obtaining information abouta node could resultin stale routing at the nodes. 22. What is IOT?
- 9. The Internet of things (IoT) is a system of interrelated computing devices, mechanical and digital machines provided with unique identifiers (UIDs) and the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction. 23. What is the use of IOT? IoT is essentiallya platform whereembeddeddevicesareconnectedto the internet, so theycan collect and exchange data with each other. It enables devices to interact, collaborate and, learn from each other's experiences just like humans do 24. Define COAP. Constrained Application Protocol (CoAP) is a specialized Internet Application Protocol for constrained devices, as defined in RFC 7252.CoAP is a service layer protocol that is intended for use in resource- constrained internet devices, such as wireless sensor network nodes. 25. How does CoAP work? CoAP enablesdevicesto communicateoverthe Internet.CoAP are a simplificationofthe HTTP protocol running on UDP that helps save bandwidth. The Internet Engineering Task Force Constrained REST ful environments (IETF CoRE) Working Group has done the major standardization work for CoAP
- 10. UNIT V: 4G & Beyond Part – A (2 Marks) 1. What are the main features of 4G? 1. Support interactive multimedia, voice, video, wireless internet and other broadband services. 2. High speed, high capacity and low cost per bit. 3. Global mobility, service portability, scalable mobile networks. 4. Seamless switching, variety of services based on Quality of Service (QoS) requirements 5. Better scheduling and call admission control techniques. 6. Ad hoc networks and multi-hop networks. 2. Write down the Challenges of4G networks Security of the network is a major Multi-access interfaces, recovery and timing. Seamless Roaming and seamless transfer of services. The various issues in the interface with Ad-hoc network should be sorted out. This new 4G network is expected to interact with various other networks such as hiperlan, Bluetooth, IEEE802.11b etc. The Digital to Analog conversation at high data rates, multi-user detection, smart antennas and complex error control techniques provide dynamic routing. 3. Write down the Visions of4G networks • Fully converged services • Ubiquitous mobile access • Diverse user devices • Autonomous networks • Software dependency 4. What is meant by MIMO? MIMO means Multiple Input and Multiple Output that represents multiple individual, parallel data streams that are carried on the air interface. 5. What are the benefits ofSmart Antenna Technology? a. Reduction in Co – Channel Interference b. Range Improvement c. Increase in Capacity d. Reduction in Transmitted Power e. Reduction in Handoff 6. What is meant by receiver diversity? The Single Input Multiple Output (SIMO) configuration of the radio channel is known as receiver diversity. The input the channel is single transmitter signal that feeds two receiver paths. Depending on multipath fading and the correlation between two receiver gain is achieved in the form of fading resistance.
- 11. 7. What is Smart Antenna? A Smart Antenna is a multi- elementantenna where the signals received ateach antenna elementare intelligently combined to improve the performance ofthe wireless system. 8. Define Multi Carrier Modulation (MCM) Multi Carrier Modulation (MCM) is a baseband process thatuses parallel equal bandwidth sub channels to transmit information and is normally implemented with Fast Fourier Techniques (FFT) techniques. 9. What are the types ofMCM that are likely preferred for 4G? The two different types ofMCM that are likely preferred for 4G are: a. Multi Carrier Code Division Multiple Access b. Orthogonal Frequency Division Multiplexing (OFDM) using TDMA 10. What are the advantages of MCM? a. Better performance in the Inter Symbol Interference environment b. Avoidance ofsingle frequency interference 11. What are the technologies used in 4G? a. Multi Carrier Modulation (MCM) b. Smart Antenna Techniques c. OFDM – MIMO Systems d. Adaptive Modulation and Coding with Time Slot Scheduler e. Cognitive Radio 12. List out the applications of4G technologies. a. Virtual Presence b. Virtual Navigation c. Tele-Medicine d. Tele-Geo-Processing applications e. Gaming f. Cloud Computing g. Crisis detection and prevention h. Education 13. What are the techniques to improve network survivability in different layers? a. Prevention ,b. Network design and capacity allocation,c.Traffic Management and restoration
- 12. 14. What are the challenges of 4G? a. Multimode user terminals b. Wireless System Discovery and Selection c. Terminal Mobility d. Network Infrastructure and QoS Support e. Security and Privacy f. Fault tolerance and Survivability g. Multiple Operators and Billing Systems h. Personal Mobility 15. What are the main issues in terminal mobility of4G? The two main issues in terminal mobility are a. Location Management b. Handoff Management With location management, the system tracks and locates a mobile terminal fir possible connection Handoff managementmaintains ongoing communications when the terminal roams. 16. Define 4G 4G can defined as MAGIC MAGIC a. Mobile Multimedia b. Anytime Anywhere c. Global Mobility Support d. Integrated Wireless Solution e. Customized Personal Services f. Also known as Mobile Broadband Everywhere 17. What are the goals of 4G? The ambitious goal of 4G is to allow everyone to access the Internet anytime and everywhere. The provided connection to Internet will allow users to access all types of services including text, databases and multimedia. Unlike 3G, 4G is IP based, that is every user connected to the Internet will have an IP address. 18. Compare 3G with 4G.
- 13. Technology 3G 4G Frequency Band 1.8 - 2.5GHz 2 - 8GHz Bandwidth 5-20MHz 5-20MHz Data Rates Up to 2Mbps 100Mbps moving - 1Gbps stationary Access W-CDMA VSF-OFCDM and VSF-CDMA FEC Turbo-codes Concatenated codes Switching Circuit/Packet Packet 19. What are the features of 4G Wireless Systems? a. Supportinteractive multimedia, voice, video, wireless internetand other broadband services. b. High speed, high capacity and low costper bit. c. Global mobility, service portability, scalable mobile networks d. Seamless switching, variety ofservices based on Quality ofServices requirements. 20. Write a short note on security challenges in 4G. The security challenges with IP network is one of the most significant factors that slows down the further adoption ofnetwork technologies.An end to end system approach to security is required in next generation wireless networks, including: a. Platform hardening b. User/Operator authentication, authorization and auditing c. Secure protocols,communication and data storage d. Software and configuration integrity