TELECOMMUNICATION AN OVERVIEW

Telecommunication

Ø  Communication system is a point-to-point system composed of two connected parties or devices that can communicate with one another in both directions, simultaneously.

Ø  There are three types of communication:

Ø  Simplex

Ø  Half-duplex

Ø  Full- duplex

Simplex:

Ø  A pager is a wireless telecommunications device that receives and displays numeric or text messages, or receives and announces voice messages. One-way pagers can only receive messages,

 

 

HALF-DUPLEX

Ø  A half-duplex (HDX) system provides communication in both directions, but only one direction at a time (not simultaneously).

Ø  Typically, once a party begins receiving a signal, it must wait for the transmitter to stop transmitting, before replying (antennas are of trans-receiver type in these devices, so as to transmit and receive the signal as well).

Ø  An example of a half-duplex system is a two-party system such as a walkie-talkie, wherein one must use "Over" or another previously designated command to indicate the end of transmission, and ensure that only one party transmits at a time, because both parties transmit and receive on the same frequency.

FULL – DUPLEX

Ø  A full-duplex (FDX), or sometimes double-duplex system, allows communication in both directions, and, unlike half-duplex, allows this to happen simultaneously. Land-line telephone networks are full-duplex, since they allow both callers to speak and be heard at the same time, the transition from four to two wires being achieved by a hybrid coil. A good analogy for a full-duplex system would be a two-lane road with one lane for each direction.

Ø  In full-duplex mode, data you transmit does not appear on your screen until it has been received and sent back by the other party.

HANDOVER

•       Between 1 and 2 – Inter BTS / Intra BSC

•       Between 1 and 3 –    Inter BSC/ Intra MSC

•       Between 1 and 4 –     Inter MSC

CLUSTER CONCEPT

Cluster size

Frequency reuse

Cell splitting technique

Ø  MACRO CELL – their coverage is large (aprox. 6 miles in diameter); used in remote areas, high-power transmitters and receivers are used

Ø  MICROCELL – their coverage is small (half a mile in diameter) and are used in urban zones; low-powered transmitters and receivers are used to avoid interference with cells in another clusters

Ø  PICOCELL – covers areas such as building or a tunnel

Ø  handover = moving a call from one zone (from the transmitter-receiver from one zone) to another zone due to subscriber’s mobility