Describe the steps involved in making a phone call from a mobile phone to another mobile phone in a different town.

a) When you make a phone call from your mobile phone to a friend in another town, the communication proceeds through a mobile voice network in these steps:

1. Call Initiation: Your mobile phone converts your voice into digital signals and transmits them as radio waves to the nearest base station (BTS).
2. Network Routing (Sender's Side): The base station receives these signals and forwards them to a Base Station Controller (BSC). The BSC then routes the call to the Mobile Switching Center (MSC) in your area.
3. Call Setup and Authentication: Your MSC authenticates your phone and checks your location information. It then determines the location of your friend's phone, potentially by querying a Home Location Register (HLR) or Visitor Location Register (VLR).
4. Inter-Network Routing: Since your friend is in another town, your MSC routes the call through the core network, possibly involving other MSCs or the Public Switched Telephone Network (PSTN), to reach the MSC serving your friend's location.
5. Network Routing (Receiver's Side): Your friend's MSC locates their phone via their current base station controller and base station.
6. Call Delivery: The friend's base station sends a signal to their mobile phone, causing it to ring.
7. Voice Channel Establishment: Once your friend answers, a dedicated voice channel is established, allowing real-time two-way communication. Your voice travels through the network to their phone, and their voice travels back to yours.

b) Here are the identified components:

1. Sender: Your mobile phone.
2. Receiver: Your friend's mobile phone.
3. Transmission medium:
   • Wireless (radio waves) between your phone and the base station, and between your friend's phone and their base station.
   • Wired (fiber optic cables, copper cables) within the core mobile network infrastructure, connecting base stations, controllers, and switching centers.
4. Type of network used: A mobile cellular network (e.g., GSM, 3G, 4G, or 5G network).

c) Here is a description of the call flow:

Your Mobile Phone $\leftrightarrow$ Your Base Station (BTS) $\leftrightarrow$ Your Base Station Controller (BSC) $\leftrightarrow$ Your Mobile Switching Center (MSC) $\leftrightarrow$ Core Network / Other MSCs / PSTN $\leftrightarrow$ Friend's Mobile Switching Center (MSC) $\leftrightarrow$ Friend's Base Station Controller (BSC) $\leftrightarrow$ Friend's Base Station (BTS) $\leftrightarrow$ Friend's Mobile Phone