Question:

(a) Explain how a Mobile Terminating call, from a PSTN phone, is processed in a GSM network. Illustrate your answer with a diagram.

(b) Top-Net, a new telecommunication service provider, wants to implement a 3G cellular network in Mauritius. They decide on using the chipping code 101101 for the code division multiplexing.

(i) Assuming no scrambling code is used, what are the chipping sequences that can be derived from the original chipping code in order to encode four different data streams in a Top-Net 3G cell?

(ii) Assuming the data rate if the original chipping code is used is 512kbit/s and assuming a constant chipping rate of 3.84Mchip/s, what will be the new data rate for each of the four chipping sequences you calculated above?

(iii) Discuss on the result of question (ii) above; is the resulting data rate a reasonable value for typical 3G networks?

(iv) The Engineers at Top-Net are new to 3G as they have primarily worked on GSM networks before. They are worried about effects such as cell breathing, multi-path propagation and shadowing. Explain each of these effects briefly.

(v) What property of the architecture of 3G networks, inherently take care of the problems mentioned in question (iv) above? Describe this property briefly.

(vi) Why is a 3G network typically more expensive to set up as compared to GSM or GPRS networks? How can the setting up costs be alleviated?