Network delay

Delay ( engl. Delay), latency, or latency, occurs in telecommunications as

  • The time interval by which an event is delayed;
  • The time between the occurrence of an event and the occurrence of an expected event sequence;
  • In radar technology as the electronic delay of the start of the time base, which is used to select a particular segment of the whole.

The events and their relationships should be precisely specified. A total delay can be demonstrated by means of the impulse response of a device or system. In analog systems, the total delay is given by functions in the frequency domain (delay time).

Types of delay

Delay can occur in various ways. These are divided into four classes:

  • The algorithmic delay is caused by characteristics of the algorithm used for the processing or transmission of the signal. They can only be influenced by changing the algorithm. Examples: package way voice communication or interleaving of data transfer.
  • The processing delay is determined by the time required for processing of the signal period. It can be reduced by the use of more processing power. Example: computation time of an MPEG encoder.
  • The Serialisierungsverzögerung is the time that is necessary to send a data unit to the complete medium. The following applies: Serialisierungsverzögerung = amount of data / data rate.
  • The propagation delay caused by signal delays in the wires or air. By selecting a different route this can be influenced within limits. The following applies: propagation delay = distance in the medium / propagation speed. For the speed of propagation can be assumed as a general rule 5 microseconds per kilometer.

Delays in language communication

The delay of the speech signal in the telephone network is with the echo, so the attenuated reflected signal travels back from the receiver to the transmitter, an essential quality parameters for speech intelligibility. For this reason, several guidelines have been established.

National landline

For national fixed networks the delay in Germany was set to a value of 25 ms end-to- end, since up to this value according to ITU -T Recommendation G.131 "Control of talker echo" no active echo control measures are necessary. The 25 ms were divided so that the terminals allowed to consume each 5 ms and 15 ms network (5 ms 15 ms 5 ms = 25 ms).

International landline

For international connections due to the greater maturity of the use of " echo suppressor " according to ITU -T Recommendation G.164 or "Echo Canceller " in accordance with ITU -T Recommendation G.165 is necessary.

Internet

In the Internet telephony technology, the delay due to longer and therefore the quality can be significantly worse. Depending on the codec used packaging or already take depacketing 20-25 ms. Then there are the transfer times for the IP packets on the network.

In accordance with ITU -T Recommendation G.114 is no more real-time communication is not possible, above a one-way running period of 400 ms.

  • Communication technology
  • Period of time
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