Relay

Basic information

Relay is a transmission channel between two points, both of which are usually exchange center. Trunks are carrying multiple logical link of a physical connection. Along with the science and technology development, relay concept is not only applied in wireless communication, network communication switch trunk can also call a relay.

principle

The basic principle of relief theory is at the end of the 19th century mathematicians Erlang proposed, Danish study how he devoted himself to the limited service capacity for a lot of customer service. Now, use his name as traffic intensity of the unit. A Erlang said a fully occupied in a channel traffic intensity (i.e. unit hours or unit minutes of call duration). For example, a in one hour occupied a 30-minute channel traffic for 0.5 Erlang.

Wireless communications, relay concept refers to allow large number of users in a village in relatively small number of Shared channel, namely from available channel repository to give each user on-demand channel.

In relay wireless systems, each user just in a call when it allocate a channel, once call terminated, originally occupied by the channel immediately return to available channel repository.

According to user behaviour statistics, relay make fixed number of channels or lines can be a quantity greater, random user community service. Telephone company according to relay theory to decide which has hundreds of thousands sets telephone office building of the number needed distribution circuit. Relay theory is also used in cellular wireless systems design, in the available telephone lines in a contact number and peak no lines are available between the possibility of a compromise. When the telephone lines declined, for a specific user, all line busy all the possibility of bigger. In relay of the mobile wireless systems, when all wireless channels are occupied and users and, when they occur to request service call obstruction or system refuse access. In some systems, may use queuing ways to keep is asking conversation user information, until one channel so far.

Basic term definition

Relay theory used in basic terms definition:

Build time:

Give the user is asking to allocate a relay radio channel of time required

Obstruction call:

Because of congestion cannot finish in the request of the call, also called loss call

Keep time:

A typical call the average time to maintain, expressed as H (in seconds for the unit)

Traffic intensity:

Characterization channel availability, efficiency, and the average occupancy rate for channel to Erlang for the unit. It is a dimensionless value, usable to represent the single or multiple channel availability. Expressed as A

Load:

The whole system of traffic strength to Erlang for the unit

Service level (GOS) :

The amount of characterization congestion level, defined as a call blocking probability (expressed as B, the unit is Erlang), or delay time more than one particular time of the probability (expressed as C, the unit is Erlang)

Request rate:

Unit time average call requested times. Expressed as l/SEC

The stock of the rise in relief

Banker in pull litre share price, discover cast dish is overweight, to cleanse them from these float to prepare, need a wash dish finishing process, in K line represents a box-like finishing shape, in share price on expression is fluctuate and we put the finishing form called up relay form.