Wireless and mobile communication

QUESTION ONE [Total: 20 Marks] a. What do you understand by call roaming in mobile telephony? Explain the condition that will occasion this feature and also explain the security feature on the mobile switch that handles this facility. U [7Marks] b. Explain briefly the operation of GPS. U [5 Marks] c. You are presented with the cellular topology as shown in figure 1; explain the interconnections between the various mobile generations. Data (IP) Network Voice (PSTN) Network P-GW EPC Core Network GGSN SGSN MSC S-GW MME RNC BSC Access Network RNS BSS ()) Node B (oh) (3) BTS eNodeb ho Air Interface 2G 2.5G UE UE MS 3G 4G Fig 1 U (8Marks]