MCC Question Bank

PRATHMESH GUNJGUR 1

Chapter 1 : Introduction to Mobile Computing Q1. Explain GPRS architecture reference model and show the protocol architecture of the transmission plane for GPRS. [10M] Q2. Show the typical satellite system for global mobile telecommunication and describe the basic applications for satellite communication. [10M] Q3. Explain localization of user in satellite network. [10M] Q4. Explain different methods used to increase the capacity of analog cellular system without increasing the number of antenna sites. [10M] Q5. Compare Iridium, Globalstar, ICO and Teledesic. [10M] Q6. Explain the various wideband modulation techniques employed in cellular technologies. [10M] Q7. Explain w.r.t satellite systems : (i) Inclination Angle (ii) Elevation Angle. [4M] Q8. What are the hidden terminal and exposed terminal problem ? Identify methods to overcome these. [5M / 10M] Q9. Write short note on : 1) Near and Far terminals 2) Hidden and exposed terminal. [10M] Q10. Explain need for wireless communication with its special applications. [6M / 10M] Q11. Write a short note on Mobile and Wireless devices. [7M / 10M] Q12 Which components are new in GPRS as compared to GSM ? What is their purpose? [5M] Q13. What is the simple scheme to solve hidden terminal problem in wireless network? [5M] Q14. Draw and explain architecture of GPRS system. [10M] Q15. Name basic applications of satellite communication and describe the trends. [5M] Q16. What are the general problems of satellite signals travelling from a satellite to a receiver? [5M] Q17. Describe the Mobile satellite systems (LEO and MEO) OR (LEO and GEO). [10M] Q18. Write a note on GPRS. [5M] Q19. Write about types of antennas and their radiation pattern? [10M]

MCC Question Bank

PRATHMESH GUNJGUR 2

Q20. What are the various types of satellites are used ? Describe their functionality and also explain the concept of localization, routing and handover in them. [10M] Q21. What is Spread Spectrum? [5M] Q22. What is frequency reuse concept in cellular communication? [5M] Q23. Compare MEO and GEO satellite systems. [10M] Q24. In wireless communication, multiplexing can be carried out in four dimensions i.e space, time, frequency and code. Explain [10M] Q25. What are the main benefits of spread spectrum ? How can spreading be achieved ? How can DSSS system benefit from multipath propagation? [10M] Q26. Draw the block diagram of FHSS transmitter and receiver. Differentiate between slow hopping and fast hopping. [10M] Q27. Explain the need of spreading the spectrum. Explain different types of spreading the spectrum. [10M] Q28. Explain what is spread spectrum. How can spreading be achieved ? What are the merits of spread spectrum technique ? [10M] Q29. What are the different types of mobility in mobile communication? [5M] Q30. What are the main characteristics of communication devices. [5M] Q31. What is cellular system? [5M] Q32. What are the advantages and limitations of cellular systems? [10M] Q33. What characteristics do the different orbits have ? What are the pros and cons? [10M] Chapter 2 : GSM Cellular Telephony Architecture and System Aspects Q1. Write a short note on GSM. [7M / 10M] Q2. Explain the system architecture of GSM. [7M / 10M] Q3. Explain signaling protocol architecture of GSM system. [10M] Q4. Explain typical call flow in GSM addressed to the following features :

(1) Mobile call origination (2) Mobile call termination. [10M] Q5. Elaborate on security handling in wireless / mobile networks. [10M]

MCC Question Bank

PRATHMESH GUNJGUR 3

Q6. Explain the security algorithms used in GSM. [10M] Q7. What are the reasons for delay in GSM system for packet data traffic ? Draw and explain the protocol architecture of GPRS. [10M] Q8. How much of the original GSM network does GPRS need ? Which elements of the network perform data transfer? [10M] Q9. Draw a neat diagram of GSM architecture and explain with different types of interfaces. [10M] Q10. Describe how data encryption is done in GSM system, with diagram explaining the role of SIM, A3, A5 and A8 algorithm. [10M] Q11. What are the modifications required to an existing GSM system network to be upgraded to GPRS ? Explain with the help of diagram. [10M] Q12. What are the functions of authentication and encryption in GSM ? How is the system security maintained ?[10M] Q13. What is the use of HLR and VLR registers in Mobile computing ? [5M] Q14. Describe the call initiation and call termination procedure in GSM systems. [10M] Q15. Explain the channels used by the GSM system. [10M] Q16. What is radio burst? Explain the different types of radio bursts in GSM system. [5M] Q17. Write a note on GSM Time hierarchy. [5M] Q18. Describe the call set-up procedure in GSM system. [10M] Q19. What is handover? Explain types of handover within a GSM system. [5M / 7M / 10M] Q20. Explain how we can ensure the privacy and authentication of mobile user. [10M] Q21. What is handover mechanism in cellular system ? Differentiate hard handover from soft handover. [7M / 10M] Q22. What strategies can be followed to detect the presence of a handoff? [5M] Q23. Compare GSM 900 and DCS 1800. [5M] Q24. List and explain GSM services. [5M] Q25. What is handoff ? What is roaming ? How do you perform handoff during roaming? [5M] Q26. Explain handoff management technique used in cellular system. [10M]

MCC Question Bank

PRATHMESH GUNJGUR 4

Chapter 3 : Mobile Network Q1. Explain the following entities in brief : i) Foreign Agent (FA) ii) Home Agent (HA) iii) Care of Address (CoA) iv) Mobile Node (MN) v) Correspondent Node (CN). [5M] Q2. Explain packet flow if two mobile nodes communicate. [5M / 6M] Q3. List the entities of mobile IP and describe packet delivery to and from the mobile node. [10M] Q4. Explain how tunneling works for mobile IP using IP-in-IP, minimal and generic routing encapsulation respectively. Discuss the advantages and disadvantages of these three methods. [10M] Q5. What are the general problems of mobile IP regarding security and quality of service? [10M] Q6. Write a note on Mobile IP. [5M / 10M] Q7. Explain what is meant by tunneling and encapsulation. How does it work in IP-in-IP, minimal and generic routing encapsulation? Show schematically. [10M] Q8. How and why does I-TCP isolate problems on wireless link ? What are main drawbacks of this solution? [10M] Q9. Write a short note on I-TCP, S-TCP, M-TCP. [10M] Q10. Explain the errors in wireless networks that degrades the performance of TCP. [10M] Q11. Write a note M-TCP. [10M] Q12. Write detailed note on Indirect TCP (I-TCP) including its merits and demerits over Snooping TCP and Mobile TCP. [10M] Q13. Explain various types of various types transmission errors in wired networks and wireless networks. [10M] Q14. Explain S-TCP with is advantages and disadvantages. [10M] Q15. Explain the errors in wireless networks that degrades the performance of TCP and How TCP snooping can improve the situation. [10M] Q16. What are the general problems of Mobile IP regarding the support of quality of service? [5M] Q17. Why traditional TCP is not suitable for mobile environment? Discuss about strengths and weakness of Indirect-TCP, Snooping-TCP and M-TCP. [10M]

MCC Question Bank

PRATHMESH GUNJGUR 5

Q18. What is tunneling mechanism of Mobile IP using IP-in-IP, minimal and generic routing encapsulation respectively. Discuss pros and cons of these three methods. [10M] Q19. What is Mobile IP? Describe it in detail. [10M] Q20. Discuss Mobile Transport Layer. [10M] Q21. Explain snooping TCP and mobile TCP and their merits and demerits. [10M] Q22. Explain the following w.r.t mobile IP. i) IP packet delivery ii) Agent Discovery iii) Registration iv) Tunneling and encapsulation [10M] Q23. Compare and contrast I-TCP, Snooping TCP and Mobile TCP. [10M] Q24. List the entities of mobile IP and describe data transfer from a mobile node to a fixed node and vice versa. [5M] Q25. Explain IP-in-IP, minimal and generic encapsulation. Also discuss their merits and Demerits. [10M] Q26. Write a note on mobile agents. [5M] Q27. Explain I-TCP and M-TCP in detail. [10M] Q28. Explain tunneling and encapsulation in mobile IP. [10M] Q29. Explain merits and demerits of snooping TCP and indirect TCP ? [10M] Q30. Describe the terms binding request, binding update, binding acknowledgement and binding warning in the context of route optimization. [5M] Q31. Write a note on : i) Fast Retransmit / Fast Recovery ii) Time-out Freezing iii) Selective Retransmission iv) Transaction oriented TCP [5M each] Q32. Write a note on reverse tunneling. [5M] Q33. Compare and contrast various TCP enhancements. [10M] Q34. What is mobile agent ? What are the application domain in which Mobile Agent have potential development ? [5M] Chapter 4 : Third and Fourth Generation Systems Q1. Explain the system architecture of W-CDMA. [10M] Q2. Explain the system architecture of CDMA 2000. [10M]

MCC Question Bank

PRATHMESH GUNJGUR 6

Q3. Compare W-CDMA and CDMA 2000. [5M / 10M] Q4. Explain the quality of services in 3G. [5M / 10M] Q5. What do you mean by near far problem in CDMA system? [5M] Q6. Describe Wireless Local Loop (WLL) in detail. [10M] Q7. Explain the major components of WLL architecture. [10M] Q8. State the deployment issues in WLL development. [5M / 10M] Q9. Explain the WLL technologies. [5M / 10M] Q10. Explain TR-45 service description. [5M / 10M] Q11. Write a note on UMTS. [10M] Q12. Explain the system architecture of UMTS. [10M] Q13. Draw and explain the frame structure of UTRA-FDD (W-CDMA). [10M] Q14. Explain UMTS basic architecture and frame structure for UMTS-FDD mode. [10M] Q15. Explain UMTS architecture and its domains. [10M] Q16. Write a note on WLL. [5M] Q17. Explain main features of 3G mobile phone system. How do they achieve higher capacities and higher data rates? [10M] Q18. What is IMT-2000? OR Discuss IMT 2000 system. [10M] Q19. Draw and explain the UMTS core network together with a 3G RNS and 2G BSS. [10M] Q20. Explain UTRA FDD TDD mode in detail ? [10M] Q21. Compare : i) 2G vs 3G OR i) 3G vs 4G [5M / 10M] Q22. Describe TETRA system architecture. [10M] Q23. Describe 4G architecture in detail. [10M] Chapter 5 : Mobility Management Q1. What is co-channel interference? [5M] Q2. What are the main causes of co-channel interference? [5M]

MCC Question Bank

PRATHMESH GUNJGUR 7

Q3. What are the measures taken to reduce co-channel interference ? [5M] Q4. What is mobility management ? [5M] Q5. Explain in brief handoff management in mobile communication. [5M / 10M] Q6. What are the different types of handoffs in mobile communication ? [5M / 10M] Q7. Explain the intra-system handoff strategy. [5M] Q8. Explain the inter-system handoff strategy. [5M] Q9. What is location management ? What are the primary issues faced in location Management ? [5M] Q10. What are the different schemes in which location management is performed ? [5M / 10M] Q11. Describe cellular IP in mobile communication. [5M / 10M] Q12. What are the basic principles with which cellular IP is designed ? [5M] Q13. What are the different handoff techniques in mobile networks that utilize cellular IP? [5M] Q14. Describe PSTN in context of mobile communication. [5M] Q15. Describe two distinct hierarchies of PSTN. [5M] Q16. What are the main factors that determines the access to the PSTN services? [5M] Q17. What is mechanism of call processing in PSTN? [5M] Q18. Write a short note on PSTN. [5M] Q19. Explain Handoff Management Technique used in cellular system. [10M] Q20. What is the purpose of using HLR and VLR in mobile computing environment? [10M] Q21. Elaborate on various handover mechanisms in cellular system. [10M] Chapter 6 : Wireless Local Area Networks Q1. What are the advantages and disadvantages of WLAN ? [5M / 10M] Q2. Explain types of WLAN ? [5M / 10M]

MCC Question Bank

PRATHMESH GUNJGUR 8

Q3. Compare 802.11 a, b, g. [10M] Q4. How does IEEE 802.11 solve the hidden terminal (station) problem. [5M / 10M] Q5. What is hidden station problem? How can you rectify it? [5M] Q6. What is hidden terminal problem in wireless network? And what types of possible solutions can be taken to solve it? [5M / 10M] Q7. What is RTS / CTS in 802.11, what services does it provide and how is it implemented? [5M] Q8. Explain power management in IEEE 802.11 infrastructure networks and ad-hoc networks. [10M] Q9. Describe about HIPERLAN Type 1. [10M] Q10. Explain IEEE 802.11 MAC packet structure. Also explain the various fields in the frame control of MAC. [10M] Q11. Discuss the MAC protocols for wireless LANs such as IEEE 8022.11 or HIPERLAN. [8M /10M] Q12. What are the different tasks a MAC layer handles in 802.11? Explain the basic access mechanisms defined for IEEE 802.11 in detail. Q13.Explain in detail IEEE 802.11 protocol architecture. [10M] Q14. Discuss MAC protocol for IEEE 802.11. [10M]

Q15. Explain similarities between HIPERLAN and 802.11. [10M] Q16. Explain HIPERLAN 2 basic structure and handover scenarios. [10M] Q17. Write a short note on Bluetooth. [10M] Q18. Explain Bluetooth protocol stack with a neat diagram. [10M] Q19. Compare IEEE 802.11, HIPERLAN and Bluetooth with regards to their ad-hoc capabilities, where is the focus of these technologies? [10M] Q20. Compare IEEE 802.11 and HIPERLAN2. [10M] Q21. The channel access control sublayer of HIPERLAN offers a connectionless data transfer service to the higher MAC layer. Justify the above statement with related references. [10M] Q22. Give the physical specification summary of the DSSS and FHSS used by the IEEE 802.11. [5M]

MCC Question Bank

PRATHMESH GUNJGUR 9

Q23. Discuss PHY frame format of an IEEE 802.11 using the spread spectrum technique which separates by code. [10M] Q24. List and explain the applications of ad-hoc networks. [6M] Q25. What is Bluetooth? Describe some of its user scenarios. [5M / 10M] Chapter 7 : Introduction to Android Q1. Explain Android layered architecture. [10M] Q2. Describe Android SDK features. [10M] Q3. What is Android? [5M] Q4. Explain the role of Linux kernel in Android architecture. [5M] Q5. Enlist some native Android libraries used in Android architecture. [5M] Q6. Describe the major android application components. [5M] Chapter 8 : Security issues in Mobile Computing Q1. Describe the security concerns in mobile communication. [5M] Q2. Describe the traditional issues in security management in mobile communication. [5M / 10M] Q3. What is the use of authentication credentials in mobile computing and communication explain it? [5M / 10M] Q4. Write a note on Encryption. [5M / 10M] Q5. Describe the characteristics of SIM. [5M] Q6. Discuss about the primary security threats and issues with mobile computing Q7. Write short note on : i) Digital Signature ii) Digital Certificate iii) Threats and Security issues in Mobile computing iv) Cryptographic Attacks v) Cryptographic Tools [5M each]

MCC Question Bank

PRATHMESH GUNJGUR 10

Problems : Q1. If a total of 33 MHz of bandwidth is allocated to a particular FDD cellular telephone system which uses two 25 kHz simplex channels to provide full duplex voice and control channels, compute the number of channels available per cell if a system uses (a) 4-cell reuse (b) 7-cell reuse (c) 12-cell reuse. If 1 MHz of the allocated spectrum is dedicated to control channels, determine an equitable distribution of control channels and voice channels in each cell for each of the three systems. Solution : Given: Total bandwidth=33 MHz Channel bandwidth=25 KHz x 2 simplex channels = 50 kHz/duplex channel. Total available channels = 33,000/50 = 660 channels. (a) For N=4, total number of channels available per cell = 660/4 =165 channels. (b) For N=7, total number of channels available per cell = 660/7 =95 channels. (c) For N=12, total number of channels available per cell = 660/12 = 55 channels. A 1 MHz spectrum for control channels implies that there are 1000/50 = 20 control channels out of the 660 channels available. To evenly distributes the control and voice channels, simply allocate the same number of voice channels in each cell wherever possible. Here, the 660 channels must be evenly distributed to each cell within the cluster. In practice, only the 640 voice channels would be allocated, since the control channels are allocated separately as 1 per cell. (a) For N=4, we can have 5 control channels and 160 voice channels/cell. In practice, however, each cell only needs a single control channel (the control channels have a greater reuse distance than the voice channels). Thus, one control channel and 160 voice channels would be assigned to each cell. (b) For N=7, 4 cells with 3 control channels and 92 voice channels, 2 cells with 3 control channels and 90 voice channels, and 1 cell with 2 control channels and 92 voice channels could be allocated.

MCC Question Bank

PRATHMESH GUNJGUR 11

In practice, however, each cell would have 1 control channel, 4 cells would have 91 voice channels, and 3 cells would have 92 voice channels. (c) For N=12, we can have 8 cells with 2 control channels and 53 voice channels, and 4 cells with 1 control channel and 54 voice channels each. In an actual system, each cell would have 1 control channel, 8 cells would have 53 voice channels and 4 cells would have 54 voice channels. Q2. If a Signal-to-Interference ratio of 15 dB is required for satisfactory forward channel performance of a cellular system, What is the frequency re-use factor and cluster size that should be used for maximum capacity if the path loss exponent is, (a) n=4 (b) n=3 Assume that there are 6 co-channel cells in the first tier and all of them are at the same distance from the mobile. Use suitable approximations. Solution : (a) n=4 First, let us consider a 7-cells re-use pattern. The co-channel re-use ratio, Q=D/R = 4.583.

The signal-to-noise interference ratio is given by,

00

)3()/(iN

iRD

IS nn

S/I = (1/6)(4.583)4 = 75.3 =18.66 dB

Since this is greater than the maximum required S/I, N=7 can be used. (b) n=3 First, let us consider a 7-cells re-use pattern. The signal-to-interference ratio is given by, S/I = (1/6)(4.583)3 =16.04 = 12.05 dB

Since this is less than the minimum required S/I, we need to use a larger N. Using equation (N=i2+ij+j2), the next possible value of N is 12, (i=j=2). The corresponding co-channel ratio is given by, Q = D/R =6.0

MCC Question Bank

PRATHMESH GUNJGUR 12

The signal-to-interference ratio is given by, S/I = (1/6)(6)3 = 36 = 15.56 dB Since this is greater than the minimum required S/I, N=12 is used. Q3. How many users can be supported for a 0.5% blocking probability for the following number of trunked channels in a blocked calls system? (a) 1, (b) 5, (c) 10, (d) 20, (e) 100. Assume each user generates 0.1 Erlangs for traffic. Solution : From Table 2.4 or F2.6 we can find the total capacity in Erlangs for the 0.5% GOS for different numbers of channels. By using the relation A = UAu , we can obtain the total number of users that can be supported in the system. (a) Given C = 1, Au = 0.1, GOS (Grade of Service) = 0.005 From Erlang B formula, we obtain A = 0.005. ( Because

10

11

!005.0

k kA

A A

A 1005.0 0.995A=0.005 A=0.005 )

Therefore, total number of users, U = A/ Au = 0.005/0.1 = 0.05 users. But, actually one user could be supported on one channel. So, U = 1. And 1 user can be supported by 1 channel. (b) Given C = 5, Au = 0.1, GOS = 0.005 From Table 2.4 or Figure 2.6, we obtain A = 1.13. Therefore, total number of users, U = A/Au = 1.13/0.1 = 11 users. The number of user per channel: Uc = U/C = 11/5 = 2.2 user/channel (c) Given C = 10, Au = 0.1, GOS = 0.005 From Figure 2.6, we. obtain A = 3.96. Therefore, total number of users, U = A/ Au = 3.96/0.1 = 39 users. The number of user per channel: Uc = U/C = 39/10 = 3.9 user/channel (d) Given C = 20, Au = 0.1, GOS = 0.005 From Figure 2.6, we obtain A = 11.10 . Therefore, total number of users, U =A/Au = 11.1/0.1 = 110 users. The number of user per channel: Uc = U/C = 110/20 = 5.5 user/channel (e) Given C = 100, Au = 0.1, GOS = 0.005 From Figure 2.6, we obtain A = 80.9. Therefore, total number of users, U =A/Au = 80.9/0.1 = 809 users. The number of user per channel: Uc = U/C = 809/100 = 8.09 user/channel

MCC Question Bank

PRATHMESH GUNJGUR 13

Q4. An urban area has a population of two million residents. Three competing trunked mobile networks (systems A, B and C) provide cellular service in this area. System A has 394 cells with 19 channels each, System B has 98 cells with 57 channels each, and System C has 49 cells, each with 100 channels. Find the number of users that can be supported at 2% blocking if each user averages two calls per hour at an average call duration of 3 minutes. Assuming that all 3 trunked systems are operated at maximum capacity, compute the percentage market penetration of each cellular provider. Solution : System A Given : Probability of blocking = 2% =0.02 Number of channels per cell used in the system, C=19 Traffic intensity per user, Au = H = 2 (3/60) = 0.1 Erlangs For GoS =0.02, and C = 19, from the Erlang B chart, the total carried traffic, A, is obtained as 12.33 Erlangs. Therefore, the number of users that can be supported per cell is U=A/Au =12.33/0.1 = 123. Since there are 394 cells, the total number of subscribers that can be supported by system A is equal to 123 394 = 48,462. System B Given : Probability of blocking = 2% =0.02 Number of channels per cell used in the system, C=57 Traffic intensity per user, Au = H = 2 (3/60) = 0.1 Erlangs For GoS =0.02, and C = 57, from the Erlang B chart, the total carried traffic, A, is obtained as 46.82 Erlangs. Therefore, the number of users that can be supported per cell is U=A/Au = 46.82/0.1 = 468. Since there are 98 cells, the total number of subscribers that can be supported by system A is equal to 468 98 = 45,864. System C Given : Probability of blocking = 2% =0.02 Number of channels per cell used in the system, C=100 Traffic intensity per user, Au = H = 2 (3/60) = 0.1 Erlangs For GoS =0.02, and C = 57, from the Erlang B chart, the total carried traffic, A, is obtained as 87.97 Erlangs.

MCC Question Bank

PRATHMESH GUNJGUR 14

Therefore, the number of users that can be supported per cell is U=A/Au = 87.97/0.1 = 879. Since there are 49 cells, the total number of subscribers that can be supported by system A is equal to 879 49 = 43,071. Therefore, total number of cellular subscribers that can be supported by these three systems are 48,462+45,864+43,071 = 137,397 users. Since there are 2 million residents in the given urban area, System As market penetration = 48,462/2,000,000 = 2.42% System Bs market penetration = 45,864/2,000,000 = 2.29% System Cs market penetration = 43,071/2,000,000 = 2.15% Total market penetration of the three systems = 6.87% Q5. A certain city has an area of 1,300 square miles and is covered by a cellular system using a seven-cell reuse pattern. Each cell has a radius of 4 miles and the city is allocated 40 MHz of spectrum with a full duplex channel bandwidth of 60 MHz. Assume a GoS of 2% for an Erlang B system is specified. If the offered traffic per user is 0.03 Erlangs, compute (a) the number of cells in the service area, (b) the number of channels per cell (c) traffic intensity of each cell (d) the maximum carried traffic (e) the total number of users that can be served for 2% GoS (f) the umber of mobiles per unique channel (where it is understood that channels are reused) (g) the theoretical maximum number of users that could be served at one time by the system. Solution : (a) Given: Total coverage area = 1,300 sq.miles and cell radius = 4 miles The area of a cell (hexagon) can be shown to be , 2.5981R2 thus each cell covers 2.5981 x (4x4) = 41.57 sq.mi. Hence, the total number of cells are Nc = 1300/41.57 = 31 cells. (b) The total number of channels per cell (C) = allocated spectrum/ (channel width x frequency reuse factor) = 40,000,000/(60,000 x 7) = 95 channels/cell. (c) Given: C=95 and GoS = 0.02, from the Erlang B chart, we have traffic intensity per cell A=83.13 Erlangs/cell. (d) Maximum carried traffic = number of cells x traffic intensity per cell = 31 x 83.13 = 2,577 Erlangs.

MCC Question Bank

PRATHMESH GUNJGUR 15

(e) Given traffic per user = 0.03 Erlangs, Total number of users = Total traffic / traffic per user = 2,577/0.03 = 85,901 users. (f) Number of mobiles per channel = number of users/number of channels = 85,901/666 = 129 mobiles/channel. (g) The theoretical maximum number of served mobiles is the number of available channels in the system (all channels occupied) = C x Nc = 95 x 31 = 2,945 users, which is 3.4% of the customer base. Q6. A Hexagonal cell within 4-cell system has a radius of 1.387 km. A total of 60 channels are used within the entire system. If the load per user is 0.029 Erlangs, and = 1 call/hour, compute the following for an Erlang C system that has a 5% probability of a delayed call: (a) How many users per square kilometer will this system support? (b) What is the probability that a delayed call will have to wait for more than 10 seconds? (c) What is the probability that a call will be delayed for more than 10 seconds? Solution : Given: Cell radius, R=1.387 km, Area covered per cell is 2.5981 (1.387)2 = 4.9981 i.e 5 sq.km. Number of cells per cluster = 4 Total number of channels = 60 Therefore, number of channels per cell = 60/4 = 15 channels. (a) From Erlang C chart, for 5% probability of delay with C = 15, traffic intensity = 9.044 Erlangs. Therefore, number of users = total traffic intensity/traffic per user = 9.044/0.029 = 311 users = 311 users/5 sq.km = 62 users/sq.km (b) Given , = 1 holding time H = Au/ = 0.029 hour = 104.4 seconds The probability that a delayed call will have to wait longer than 10s is Pr [delay > t | delay] = exp(-(C-A)t/H) = exp(-(15-9.0)10/104.4) = 56.29% (c) Given Pr[delay > 0] = 5%=0.05 Probability that a call is delayed more than 10 seconds, Pr[delay > 10] = Pr[delay > 0] Pr[delay > t | delay] = 0.05 x 0.5629 = 2.81%

MCC Question Bank

PRATHMESH GUNJGUR 16

Q7. (a) What is the maximum system capacity (total and per channel) in Erlangs when providing a 2% blocking probability with 4 channels, with 20 channels, with 40 channels? (b) How many users can be supported with 40 channels at 2% blocking? Assume H=105s, =1 call/hour. Solution : (a) GOS=2% C=4 from Erlang B formula , The total system traffic intensity (capacity) A= 1.2 Erlangs, The traffic intensity per channel Ac = A/C= 1.2/ 4 = 0.3 Erlangs. C=20 from Erlang B formula , The total system traffic intensity (capacity) A= 11 Erlangs, The traffic intensity per channel Ac = A/C= 1.2/ 4 = 0.5 Erlangs. C=40 from Erlang B formula , The total system traffic intensity (capacity) A= 30.1 Erlangs, The traffic intensity per channel Ac = A/C= 1.2/ 4 = 0.75 Erlangs. (b) Given: H=105s = 0.03 Hour, = 1 call/Hour, C=40, GOS= 2 % = 0.02, From Erlangs B Formula , A=30.1 A=UAu = UH So, The number of the users:

103203.01.30

HAU