1) Multiaccess communications:
a) Explain multi-access techniques used in these technologies

i) Wi-Fi
ii) WiMax

b) Give an intuitive explanation of why the maximum throughput, for small β, is approximately the same for CSMA slotted Aloha and FCFS splitting with CSMA.

c) Assume the number of packets n in a slotted Aloha system at a given time is a Poisson random variable with mean n ≥ 1. Suppose that each packet is independently transmitted in the next slot with probability 1/n.

i) Find the probability that the slot is idle.
ii) Show that the a posteriori probability that there were n packets in the system, given an idle slot, is Poisson with mean n-1.
iii) Find the probability that the slot is successful.

2) Routing in data networks;
a) What is the difference between Dijkstra's algorithm and Bellman-Ford's algorithm (explain based on a graph which shows simple network topology)

b) Find the shortest path tree from every node to node 1for the graph of following figure using Bellman-Ford and Dijkstra algorithm.

c) Assume that there is a wireless mesh network (IEEE 802.16) with few base stations and certain coverage area;

i) Highlight four main routing challenges, which are needed to solve by implementing routing algorithm.

ii) Select one of the challenges based on your answer in part "i", and then give a solution in a pseudocode format.

d) Answer to one of the following questions:

i) Categorise routing protocols based on at least three criterions and disclose a sample for each category.

ii) List and explain at least three characteristics of routing algorithms.