Topics : Evolution of Mobile Communication, Basic Cell Fundamentals, Introduction to Cellular Telephone Systems: 1G, 2G, 3G, 4G and 5G, Comparison of these systems.
Que. 1 : Explain in brief Basic Cell Fundamentals in wireless communication ?
- The early mobile radio systems achieved a large coverage area by using a single, high-powered transmitter with an antenna mounted on a tall tower.
- This approach achieved very good coverage, but it was impossible to reuse the frequencies.
- The cellular concept offered very high capacity in a limited spectrum by reusing frequencies.
- In cellular system the coverage area is divided into (conceptually hexagonal) cells. A low power transmitter provides coverage to a cell. The actual radio coverage of a cell is known as the footprint and is amorphous in nature.
- Each base station is allocated a portion of the total number of channels available to the entire system. Nearby base stations are assigned different groups of channels to reduce interference. All the available channels are assigned to a small number (called cluster size) of neighboring base stations.
- The channel groups may be reused as many times as necessary, as long as the interference between co-channel stations is kept below acceptable levels.
- As the demand for service increases (i.e., as more channels are needed within a particular market), the number of base stations may be increased (along with a corresponding decrease in transmitter power to avoid added interference), thereby providing additional radio capacity without additional radio spectrum. Any regular polygon, such as an equilateral triangle, a square or a hexagon can be used
for cell design.
Criteria for shape of a cell: –- Area without overlap
- Geometric shape and
- Area of cell
- The hexagon is used for two reasons:
- First a hexagonal layout requires fewer cells and therefore, fewer transmitter sites and
- Second a hexagonal cell layout is less expensive compared to square andtriangular cells.
Que 2: Explain the following terms used in wireless communication ?
- Mobile Station (MS): A mobile station or simply mobile is a radio terminal that may be attached to a high speed mobile platform (e.g. a cell phone in a fast moving vehicle). It is also called User Equipment (UE).
- Subscriber: A mobile or a portable user.
- Cell: The area of coverage is divided into cells. Each cell has a base station usually located at its center or at the edge.
- Control Channel: Radio channels used for transmission of call setup, callrequest and call initiation. Control channels intended to carry signaling and
- synchronization data between base station and mobile user.
- •Forward Channel (downlink): Radio channel used for transmission of
- information from the base station to the mobile.
- •Reverse Channel (uplink): Radio channel used for transmission of
- information from the mobile to the base station.
- •Base Station
- A base station is a common term used in telecommunications for a radio
- receiver with one or more antennae. While the base station has many other
- applications, it’s often used for mobile telephony, wireless communications, and
- even wireless computer networking.
- A base station works as the main communication point for one or more wireless
- mobile devices. It is a fixed transceiver capable of sending and receiving wireless
- signals via the radio frequency (RF) base station antennas to transmit RF signals
- to other devices.
