8.4 Normalized network parameters

Attenuation distribution

The norms of attenuation distribution are approved by the provisions for network design [14]. In fig. 8.9 shows the attenuation distribution for various options for building urban networks and connection routes.

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Fig. 8.9. Attenuation distribution on GTS

The maximum attenuation between two telephone sets should not exceed 28 dB. In this case, the attenuation of subscriber lines should not exceed 4.5 dB. For a station quadrupole attenuation, the allowable attenuation value is much less: for the RATS, it should not exceed 1 dB per RATS and 0.5 dB at the AIS or UHS during two-wire switching. In four-wire switching, the attenuation of the station quadrupole AIS and UWS is assumed to be 0. The attenuation of the station quadrupole when switching from a two-wire to a four-wire path is 1.0 dB.

The attenuation distribution on the intrazone network is shown in Fig. 8.10. The attenuation from the telephone to the station, where the transition to the four-wire path (AMTS, UVS, UIS) is carried out, should not exceed 9.5 dB.

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Fig. 8.10. Attenuation distribution on an intrazonal network

Distribution of losses on GTS

The quality of telephone call service on the urban telephone network is determined by the probability of loss or denial of service due to the lack of free and accessible switching devices and channels. The actual or actual losses on calls to the CTA are estimated by the ratio of the number of calls lost per hour (CNN) to the total number of calls received. Estimated loss rates in CNI at various sections of the CTA are used in determining the volumes of equipment in the CTA.

The total estimated losses for GTS subscribers should not exceed 0.030, when communicating with the suburban area and private PBXs - 0.040, and when communicating with PBXs with telephone stations - 0.005.

Estimated loss rates at GTS stations are given in Table 8.1.

Connection steps are considered:

1. from the moment of raising the tube;

2 and 3. from the moment of acceptance of the address information sufficient for establishing a connection;

4 and 5. from the moment the call arrived at the station entrance.

The probability of losses includes the probability of occupancy of the inputs of switching equipment, control devices, devices for receiving and transmitting signals, internal blocking of devices of lines and channels. When using detours in the long-distance communication, these norms are used to calculate the number of devices per site of the last choice (between UAK1-UAK1).

In case of losses due to waiting beyond the allowable time, the same standards can be adopted by setting the maximum waiting time.

Routing Synchronization of digital communication networks. Networking

Routing Objects included in the routing system

Earlier, in other courses of lectures, a part of the problem was already considered concerning the work of the station in terms of number analysis and direction selection. Now consider the network aspects of routing. In fig. 8.11 shows the basic concepts that make up the routing definition.

Fig. 8.11. Basic Network Routing Concepts

End point This is the goal where the connection is directed.

Endpoint code. This is the number assigned in accordance with the numbering rules.

The following concepts are associated with this code:

1. The charging zone is a number that indicates the level of the tariff relative to the outgoing connection point. The level is set in relative units, specific payments depend on the price of a unit, determined in accordance with commercial and other offers and calculated separately in the settlement center.

   When assigning tariffing there may be cases when different substations of one station or PBX of one node belong to different tariff zones. Such requirements may arise due to the specific geographical location of these stations. Requirements are also possible, due to which the substations of different stations can be assigned to one tariff zone.

   It should be noted especially that the code of the intelligent network, as a rule, can be marked not by stations, but by services.

   When fixing the code, it is also necessary to determine the possible end station responses that may affect the operation of the original station.

   These can be the following:

   1. the ability to request the number of the outgoing subscriber;
   2. Reverse number forwarding;
   3. request for retransmission of the code;
   4. request for additional subscriber number (frequency method).

   For each endpoint with a code, the time constraints (time-outs) are specified:

   1. connection establishment time;
   2. subscriber response time;
   3. talk time;
   4. the buzzer listening time is “busy” for any non-connection.

   Obviously, each of these restrictions must be set to "not set."

   Setup completion can also be programmed. Sign of the end of the establishment of the connection can be:

   1. control signal;
   2. timeout after signal transmission;
   3. a logical combination of the connection stage and the last signal.

   The above actions and restrictions can be set on a combination of a code point and a selected route.
2. Route - a set of possible ways to establish a connection to the end point.

   When creating a route, you should define:

   1. How many digits of the end point code can determine the route;
   2. from which character of the dialed number you can start establishing a connection;
   3. How many characters from the beginning must be skipped to establish a connection (for example, the transition to 18-digit numbering is currently underway, but it will not be immediately entered on communication networks);
   4. from which sign the information transfer should be started;
   5. What sign should be replaced in order to continue the connection (and should it be done) in case of emergency replacement of the number on the route section.
3. Direction or group of channels (lines). Represents a group of channels or lines directly connecting adjacent stations.

   It (direction) is characterized by:

   • Physical transmission medium:
     1. analog lines;
     2. digital channels;
     3. frequency-compressed channels.
   • Signaling method:
     1. channel (interaction signals along two-wire, three-wire, and other lines);
     2. dedicated frequency channels (codes "2 out of 5", "2 out of 6", methods of transferring "shuttle", "non-stop code");
     3. frequency transmission of control signals;
     4. dedicated channels in digital systems;
     5. separate channel alarm.
   • Communication direction:
     1. outgoing;
     2. incoming;
     3. bilateral.

   Also, the direction characteristic can be a limitation on the type of communication, which is essential when traffic is regulated in case of overload.

   It:

   1. local communication;
   2. long distance;
   3. international.

   This category can be assigned by an operator or system for a specific time.

   Combinations of these connections are possible or the introduction of the inverse characteristic "permission to a type of communication", which opens a closed direction for a certain type of communication. In the general case, the direction can be composed of channels that have various of the listed characteristics, but this complicates the programs for managing them.

   Channel search method:

   1. Ascending numbers towards.
   2. Descending numbers in the direction.
   3. +1 number after each channel selection.
   4. Random way.

   Most preferred is the third option.

   The first two methods are called "constant priority search".

   As is known, damage control is not absolute, that is, it cannot determine (foresee) all network errors, station equipment and environmental behavior. And if one of the channels is damaged or has a degraded quality that is not detected by the control, then the constant priority leads to the LEAST load in an hour of communication failure - since the subscriber chooses the same faulty channel and all the time gets a failure until some other subscriber takes faulty line. Such an event is unlikely with a small load and more likely with a large one. In addition, the constant priority leads to the priority occupation of lines that have a higher priority. This also has its negative consequences (for example, the wear of mechanical elements in the most used devices).
4. A channel (line) is devices and lines that provide the physical medium between stations. They have the same characteristics as the directions. At the same time for each channel (line) can be assigned timeouts. These timeouts limit either the connection establishment time, or the general occupation or idle time without receiving a response signal.