European E1 Digital Hierarchy

The E1 hierarchy is identified in a similar manner as the DS1 hierarchy. E1 (30 voice channels) is the primary multiplex; E2 is the second level and is derived from four E1s.

Hierarchy Frame
Figure 6.15 Makeup of a DS2 frame.

Thus E2 contains 120 equivalent digital voice channels. E3 is the third level and it is derived from four E2 inputs and contains 480 equivalent voice channels. E4 derives from four E3 formations and contains the equivalent of 1920 voice channels. International digital hierarchies are compared in Table 6.2. Table 6.3 provides the basic parameters for the formation of the E2 level in the European digital hierarchy.

CCITT Rec. G.745 (Ref. 6) recommends cyclic bit interleaving in the tributary (i.e., E1 inputs) numbering order and positive/zero/negative justification with two-command control.10 The justification control signal is distributed and the Cjin bits (n = 1, 2, 3; see Table 6.3) are used for justification control bits.

Positive justification is indicated by the signal 111, transmitted in each of two consecutive frames. Negative justification is indicated by the signal 000, also transmitted in each of two consecutive frames. No-justification is indicated by the signal 111 in one frame and 000 in the next frame. Bits 5, 6, 7, and 8 in Set IV (Table 6.3) are used for negative justification of tributaries 1, 2, 3, and 4, respectively, and bits 9 to 12 for positive justification of the same tributaries.

Table 6.2 Higher-Level PCM Multiplex Comparison

Level

Table 6.2 Higher-Level PCM Multiplex Comparison

Level

System Type

1

2

3

4

5

North American T/D type

1

2

3

4

Number of voice channels

24

96

672

4032

Line bit rate (Mbps)

1.544

6.312

44.736

274.176

Japan

Number of voice channels

24

96

480

1440

5760

Line bit rate (Mbps)

1.544

6.312

32.064

97.728

400.362

Europe

Number of voice channels

30

120

480

1920

Line bit rate (Mbps)

2.048

8.448

34.368

139.264

10Positive/zero/negative justification. This refers to stuffing to compensate for input channel bit rates that are either too slow, none necessary, or too fast.

10Positive/zero/negative justification. This refers to stuffing to compensate for input channel bit rates that are either too slow, none necessary, or too fast.

Table 6.3 8448-kbps Digital Multiplexing Frame Structure Using Positive/Zero/Negative Justification

Tributary bit rate (kbit/s) 2048

Number of tributaries 4

Frame Structure

Bit Number

Set I

Frame-alignment signal (11100110)

1 to 8

Bits from tributaries

9 to 264

Set II

Justification control bits Cj1 (see Note)

1 to 4

Bits for service functions

5 to 8

Bits from tributaries

9 to 264

Set III

Justification control bits Cj2 (see Note)

1 to 4

Spare bits

5 to 8

Bits from tributaries

9 to 264

Set IV

Justification control bits Cj3 (see Note)

1 to 4

Bits from tributaries available for negative justification

5 to 8

Bits from tributaries available for positive justification

9 to 12

Bits from tributaries

12 to 264

Frame length

1056 bits

Frame duration

125 M-S

Bits per tributary

256 bits

Maximum justification rate per tributary

8 kbps

Note: Cjn Indicates nth justification control bit of the jth tributary.

Source: Table 1/G.745, CCITT Rec. G.745, p. 437, Fascicle III.4, IXth Plenary Assembly, Melbourne, 1988 (Ref. 6).

Note: Cjn Indicates nth justification control bit of the jth tributary.

Source: Table 1/G.745, CCITT Rec. G.745, p. 437, Fascicle III.4, IXth Plenary Assembly, Melbourne, 1988 (Ref. 6).

Besides, when information from tributaries 1, 2, 3, and 4 is not transmitted, bits 5, 6, 7, and 8 in Set IV are available for transmitting information concerning the type of justification (positive or negative) in frames containing commands of positive justification and intermediate amount of jitter in frames containing commands of negative justification.11 The maximum amount of justification rate per tributary is shown in Table 6.3.

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Responses

  • joshua
    What is frame structure in european hierarchy contains?
    5 years ago
  • anton
    How much slots contains in frame structure in european hierarchy?
    5 months ago

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