2G/GSM

 

 

 

System Information Type 1

 

System Information Type1 carries some important information as follows

  • Cell Channel Description : Cell Channel (Frequency) that UE is allowed to use in specical format called Cell Channel Description. This data format varies depending on GSM band.

  • RACH Control Parameter : Parameters related to RACH transmission

    • Max retrans
    • Tx-integer
    • CELL_BAR_ACCESS
    • Call reestablishment allowed
      • 'Not Allowed' means that Call Restablishement is not allowed even after losing TCH
      • 'Allowed' means that if an MS using a TCH looses contact with the network, it is allowed to attempt to re-establish the contact using the old TCH within a certain interval
    • Access Control Class C15-C11  
      • 0 in the bit map indicates 'Not Barred'
      • 1 'in the bit map indicates 'Barred'
    • Emergency Call allowed
      • 0 means that all MSs are allowed to make emergency calls,
      • 1 means that only MSs belonging to priority classes 11-15 are allowed to make emergency calls.
    • Access Control Class C9-C0
      • 0 in the bit map indicates 'Not Barred'
      • 1 'in the bit map indicates 'Barred'
  • Band Indicator

 

 

Example 01 >

 

NAS:RR,System Information Type 1

System Information Type 1 ::= DIVISION

  +-L2 Pseudo Length ::= V

  | +-L2 Pseudo Length value ::= INT (0..63) [21]

  | +-N(SD)or0_1 ::= FIX [0]

  | +-N(SD)or0_2 ::= FIX [1]

  +-Skip Indicator ::= V

  | +-Skip Indicator ::= FIX [0]

  +-RR management Protocol Discriminator ::= V

  | +-Protocol Discriminator ::= PD [6]

  +-System Information Type 1 Message Type ::= V

  | +-Message Type ::= MSG [19]

  +-Cell Channel Description ::= V

  | +-Octet1-16 ::= DIVISION

  |   +-Format-ID bit128-127 ::= SWITCH [bit map 0]

  |   +-(Format-ID bit128-127)=0 ::= BRANCH

  |     +-spare ::= FIX [0]

  |     +-Cell Allocation Absolute RF Channel Number bit124-121 ::= INT (0..15) [0]

  |     +-Cell Allocation Absolute RF Channel Number bit120-001 ::= OCTETARRAY SIZE(15..15)

                                                                 [000000000000000000000000000000]

  +-RACH Control Parameter ::= V

  | +-Octet1 ::= DIVISION

  | | +-Max retrans ::= CHOICE [Maximum 1 retransmission]

  | | +-Tx-integer ::= CHOICE [3 slots used to spread transmission]

  | | +-CELL_BAR_ACCESS ::= CHOICE [The cell is not barred]

  | | +-Call reestablishment allowed ::= CHOICE [Call Reestablishment not allowed in the cell]

  | +-Octet2-3 ::= DIVISION

  |   +-Access Control Class C15-C11 ::= INT (0..31) [0]

  |   +-Emergency Call allowed ::= CHOICE [Emergency call allowed in the cell to all MSs]

  |   +-Access Control Class C9-C0 ::= INT (0..1023) [0]

  +-SI 1 Rest Octets ::= V

    +-flg0 ::= SWITCH [L]

    +-Band indicator ::= CHOICE [ARFCN indicates 1800 band]

    +-spare padding ::= PAD SIZE(23..23) [2B]

 

 

Example 02 >

 

GSM CCCH - System Information Type 1

L2 Pseudo Length

0101 01.. = L2 Pseudo Length value: 21

.... 0110 = Protocol discriminator: Radio Resources Management messages (0x6)

.... 0110 = Protocol discriminator: Radio Resources Management messages (0x6)

0000 .... = Skip Indicator: No indication of selected PLMN (0)

Message Type: System Information Type 1

Cell Channel Description

00.. 000. = Format Identifier: bit map 0 (0x00)

List of ARFCNs =

RACH Control Parameters

00.. .... = Max retrans: Maximum 1 retransmission (0)

..00 00.. = Tx-integer: 3 slots used to spread transmission (0)

.... ..0. = CELL_BARR_ACCESS: The cell is not barred (0)

.... ...1 = RE: Call Reestablishment not allowed in the cell (1)

0000 0000 0000 0000 = ACC: 0x0000

SI 1 Rest Octets

L... .... = NCH position: Not Present

.L.. .... = Band Indicator: 1800

Padding Bits: default padding