CS547 Wireless Networking

a) The function f (t) = (10 cos t)²

b) The frequency of a telephone line which is 3kHz

3) (10 pts) A communication channel is designed to have a capacity of 300 Mbps with a bandwidth of 3 MHz. Calculate the Signal-to-Noise ratio that is required to achieve this data rate.

N = Number of hops between two end-point stations

L = Message length in bits B = data rate in bits per second (bps)

P = Fixed packet size in bits H = header size for each packet in bits

S = Call setup time (for circuit switching) in seconds

D = Propagation delay per hop in seconds

For N=4, L=3200, B=9600, P=1024, H=16, S=0.2, D=0.001, compute the end-to-end delay for circuit switching and datagram packet switching. Assume that there are no acknowledgements and that the processing delay at each node is negligible.

5) (10 pts) Differentiate between a virtual channel and a virtual path.

6) (10 pts) IP and UDP all discard a packet that arrives with a checksum error and do not attempt to notify the source. Why?

7)(10 pts) Describe the advantage of a parabolic reflective antenna.

a) Express the transmit power in units of dBm and dBW

b) If the transmitter’s power is applied to a unity gain antenna with a 900-MHz carrier frequency, what is the received power in dBm at a free space distance of 100 m?

c) Repeat (b) for a distance of 10 km.

d) Repeat (c) but assume a receiver antenna gain of 2.