## CS718 Wireless Networks Assignment No. 1 Evolution of Wireless Networks Fall 2014

CS718 Wireless Networks Assignment No. 1 Evolution of Wireless Networks Fall 2014 Due Date: Dec 12, 2014

The purpose of this assignment is to give you hands on practice. It is expected that students will solve the assignments themselves. Following rules will apply during the evaluation of assignment.Cheating from any source will result in ZERO marks in the assignment.If the assignment of any two students is found same then ZERO marks will awarded to both students.No assignment after due date will be accepted. It really means. Do not send assignment through email. Only the assignments will be accepted on VULMS.If account of a student is blocked please get unblocked your account before the
due date; as no assignment will be accepted through email even within the due
date.
Read all attached Research Papers very carefully
Numerical Part (30 Points)
1. A hexagonal cell within a four-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 l = 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 kilometre will this system support? (5
points)
b. What is the probability that a delayed call will have to wait for more
than 10 seconds? (5 points)
c. What is the probability that a call will be delayed for more than 10
seconds? (5 points)
2. If a signal-to-interference ratio of 15 dB is required for satisfactory forward
channel performance of a cellular system, what is the frequency reuse factor
and cluster size that should be used for maximum capacity if the path loss
exponent is n = 4 and n = 3 ? Assume that there are six co-channel cells in the
first tier, and all of them at the same distance from the mobile. Use suitable
approximations. (5 + 5 points)
3. Suppose a signal encoding technique requires that Eb/No = 8.4 dB for a bit
error rate of 10-4 (one bit error out of every 10,000). If the effective noise
Department of Computer Science, Virtual University of Pakistan
temperature is 290oK (room temperature) and the data rate is 2400 bps, what
received signal level is required to overcome thermal noise. (5 points)
Theoretical Part (20 Points)
1. Why OFDMA signal is considered worse in uplink coverage? Discuss the
major weaknesses of OFDM in context of 4G wireless technology as discussed
in the paper [1].Elaborate the role of cross-layer design mechanism in 4G
networks and how this affects its quality of service [1]? (10 points)
2. Do you think that the scheduling scheme presented in the paper [2], can
perform poor than CSMA-CA protocol? If yes, please give one scenario. (10
points)
List of Research Papers:
[1] Road Map and Challenges in 4G Wireless System
[2] Adaptive Topology-Transparent Distributed Scheduling in Wireless
Networks