B.E./B. Tech DEGREE EXAMINAION, MAY/JUNE 2009
Electronics and Communication Engineering
EC 1013 - WIRELESS NETWORKS
Time : Three hours Maximum: 100 marks
Answer ALL questions
PART A- (10*2=20 marks)
1. What are the advantages of UWB pulse transmission?
2. Write short notes on OOK modulation.
3. What is meant by overlaid cell concept in cell splitting?
4. Mention the circumstances that prefer temporary channel borrowing in cellular networks.
5. Is CDMA an access method or an air-interface? Justify your answer.
6. What is meant by 'capacity on demand' principle in GPRS networks?
7. How does IEEE 802.11a PHY layer differ from that of IEEE 802.11 PHY layer?
8. State the relationship between HYPERLAN-2 and WATM.
9. Mention the role played by L2CAP in Bluetooth networks.
10. What is the difference between TDOA and TOA in GPS?
PART B -- (5*16=80 marks)
11. (a) (i) Explain the multicarrier, multisymbol, multirate OFDM Modulation followed in broadband modems for higher speeds. [ 8]
(ii) Illustrate Frequency Hopping Spread Spectrum and Direct Sequence Spread Spectrum with suitable examples. 
(b) (i) Discuss the modulation schemes followed in high speed modems for spread spectrum technology. 
(ii) Explain the time diversity techniques of DSSS and the RAKE receiver. 
12. (a) Assume that we wanted to deploy an analog FM AMPS system with half band of 15KHz rather than the existing 30KHz. Also assume that in analog FM,the carrier - to - interference ratio (C/I) requirement is inversely proportional to the square of the bandwidth (4 time increase in C/I for dividing the band into two).
(i) What is the required C/I in dB for the 15MHz channel if the required C/I for the 30KHz systems in 18dB? 
(ii) Determine the frequency reuse factor N needed for the implementation of this 15KHz per user analog cellular system. [ 4]
(iii) If a service provider had a 12.5MHz band in each direction (up link and downlink) and it would install 30 antenna sites to provide its service, what would be the maximum number of simultaneous users (capacity) that the system could support in all cells? Neglect the channel that are used for control signaling. [ 4]
(iv) If we use the same antenna sites but a 30KHz per channel system with N=7 (instead of the 15KHz) what would be the capacity of the new system? [ 4]
(b) We have installed cellular system with 100 sites, a frequency reuse factor of N=7, and 500 overall two-way channels :
(i) Give the number of channels per cell, total number of channels available to the service provider, and the minimum carrier-to-interference ratio (C/I)of the system in dB [Marks 4]
(ii) To expand the network, we decide to create an underlay-overlay system where the new system uses a frequency reuse factor of K=3. Give the number of cells assigned to inner and outer cells to keep a uniform traffic density over the entire coverage area. [Marks 4]
Answer the above two questions with N=12. 
13. (a) (i) Explain the GSM services and the reference architecture of GSM cellular networks. 
(ii) Explain the registration mechanism to support a mobile environment. 
(b) (i) Explain the IS-95 CDMA forward channel in detail. 
(ii) Explain the IS-95 CDMA reverse channel in detail. [ 10]
14. (a) (i) Explain the MAC management sublayer in terms of handoff and power management. 
(ii) Explain the reference model and protocol entities of WATM. 
(b) (i) Discuss the HIPERLAN-1 PHY and MAC layers in detail. [ 8]
(ii) Discuss the DLC layer of HIPERLAN-2 in detail. [ 8]
15. (a) (i) Explain the frame format in Bluetooth technology. 
(ii) Discuss the connection management followed in Bluetooth technology. 
(b) (i) Explain the wireless geolocation system architecutre. [Marks 8]
(ii) Discuss the performance measures for geolocation systems. [Marks 8]