Wireless And Mobile Communication Question Paper of 3rd Semester M.Tech(ECE) Download Previous Years Question Paper 4

Roll no.                                                                                                                      Total no. of pages: 02                                                                                                                            Total no. of questions: 08

M.TECH(PE) (Sem.  3^rd)

WIRELESS AND MOBILE COMMUNICATION

Subject code: EC-520

Paper ID: [E0577]

Time: 3 Hrs.                                                                                                 Max Marks:  100

INSTRUCTIONS TO CANDIDATE:

1.     Attempt any five question of eight questions

2.    Each  questions carry TWRNTY marks

Q1.

a)     IPV6 supports resource allocation. Explain hoe this is achieved.

b)    What are the functions performed by router.

c)     What are some advantages and disadvantages to layering as seen in the TCP/IP architecture?

Q2.

a)     Calculate the rms excess delay,  rms  delay spread and the maximum excess delay (10db) for  the multipath profile given in the figure below.  Estimate the 50% coherence bandwidth of the channel, would this channel be suitable for AMPS or GSM service without the use of an equalizer

b)       Demonstrate that the codes in an 8X8   Walsh are orthogonal to each other by showing that multiplying any code by any other code produces a result of zero.

c)     Explain the difference between slow FHSS.

Q3.

a)     What are the three factors that limit the number of sub channels that can be provided within a satellite channel via FDMA.

b)    What are the relative advantages  of MMDS compared to LMDS?

c)     What are the principle advantages an d disadvantages of millimeter wave transmission compared to transmission at longer wavelengths.

Q4.

a)     What is the difference between a single-cell and multiple-cell wireless LAN?

b)    Explain briefly GSM control channels.

c)     What characteristics of a wireless LAN present unique security challenges not present in wired LANs

d)    Briefly define IEEE 802.11 services.

Q5.

a)     In a normal GSM time slot, why would the 26 equalizer traning bitebe placed in the middle of the frame that at the beginning? What is the reason for having an 8.25 bit guard period after the data bursts?

b)    Explain the various interface used in GSM system architecture.

c)     List and brifly define different perfomance metricsthat may be used tomake the handoff decisions.

Q6.

a)     What mechanisms would cause breakdown in the reverse link of an  IS-95 CDMA systems as the numberof users in a sector approaches the theoretical limit.

b)    Derive an expression for the number of mobile users in a  single cel  CDMA system employing a voice activity factor of a and a three sector antenna. How dose the capacity change for a multi cell CDMA system.

c)     Ecplain the encoding and decoding methds for cyclic codes giving proper block diagram.

Q7.

a)     List for significant factors which influence the choice of speech coder in mobile communication systems. Elaborate on the tradeoff which is caused by each factor. Rank order  the factors based on your personal view point and defend your position.

b)    Conside a sub band   spech coder that allocates 5 bits for the audiosoectrum between 225 hz and 500hz bits for 500hz to 1200hz and 2 bits for  frequencies between 1300 hz and 3khz, assume that the sub  band coder point output is then applited to a ¾  convolution coder. Determine the data ratye out of the channel coder.

Q8.

a)     What are the principle advantages of WLL over a wired subsriber loops?

b)    What are the p[rinciple advantages of OFDM?

c)     What are the key differences among  IEEE802.16, IEEE802.16.2, and IEEE802.165.3?

d)    What are the key difference between satellite based and terrestrial wireless communications?