Cell

The smallest physical entity that allows access to mobile entities.

Cell ≠ point-to-point connection.

Associated with the physical mechanism of information transfer (radio technologies or infrared).

Cell:

• Terminal oriented or

• Defined by a base station.

There is an overlapping of different cells in a wireless network.

Public cellular network

Access the network with a radio link.

• Space is divided into cells with a base station.

• Mobile Node (MN) can work when changing between cells.

The cell coverage size is:

• Highly variable.

• Depends on the technology.

• Depends on the number of users.

Cells

Coverage size:

• 100m to 35 km (GSM).

• Microcells: closed spaces.

• Hat cell: a set of cells

  • Avoid frequent handoffs in critical places.

Format:

• Theoretically analyzed as a hexagon.

• Reality: it depends on the place.

BS positioning:

• Cell centrally excited.

  • BS in the center of the cell, with an omnidirectional antenna.

• Cell side excited.

  • BSs in the vertices (in three).

  • Directional antennas.

Advantages

• + Capacity.

• + users.

• - power.

• + robustness (distributed system).

Each cell locally takes care of interference, coverage area, etc...

Disadvantages

• Uses a cabled network between cells.

• Many handovers.

• Interference between cells.

Fundamental

Cell dimensioning.

• Length of the cell.

• Frequency re-utilization.

• Channel reservation.