EQ-Project / Long Entry

MTP - SIGNALLING LINK

SIGNALLING LINK: Reliable transfer of signalling messages (signal(ling) units - SU)-s between two directly connected signalling points. Basic SU formats: FISU, LSSU, MSU

Functions:

SU delimitation (flag)
SU alignment (acceptance)
error detection (CRC-16)
error correction (retransmission)
processor outage
initial alignment
signalling link error monitoring (SU error rate monitor, alignment error rate monitor)
flow control - (LSSU messages)


   -----------+        MSU        +------RC-------+ SU  +----DAEDR----+  +--------------
              |<------------------|               |<----|    DAEDT    |  |
              |   +---LSC----+LSSU| Reception     |     |    AERM     |  |
              |   |   IAC    |<---|  part         |     |    SUERM    |  |
              |   |   POC    |-CI-| Impl.         |--I--|             |  |
              |   |          |    +---------------+     |             |  |
              |   |          |      +----CC----+        | Error       |  | Signalling
    Signalling|   |Link state|      |Congestion|        | detection   |  | data
    network   |   |control   |      |  control |        | delimitation|  | link
    functions |   |part      |      |  part    |        | and         |  | (Level1)
    (Level3)  |   |Impl.     |      +----------+        | alignment   |  |
              |   |          |    +------TC-------+     |             |  |
              |   |          |-CI-|               |<----| Impl.
              |   +----------+    | Transmission  |     |             |  |
              |-------------------|  part         |     |             |  |
              |--------MSU------->|               |-SU->|             |  |
    ----------+                   +---------------+     +-------------+  +-------------

      C - Control
      I - Indication

Automaták:

Link State Control (LSC)
- Link state control states:
  - Power off, Out of service, Initial alignment, Aligned not ready, Aligned ready, Aligned already ???, In service, Processor outage
- Events:
  - Power on, Start, Stop, Aligned not possible, Link failure, Alignment complete FISU, MSU, SIPO, Local processor outage, SIO, SIOS, Local processor recovered, SIN, SIE, No processor outage,
- Transmitted signals: - SIOS, SIPO, FISU, MSU
Initial Alignment Control (IAC)
Első inicalizáláskor, link hiba visszaálláskor. Complelled exchange of status information between the two signalling points.
Processor Outage Control (POC)
A vett jelzésüzenetek nem továbbítódnak a 3-as és 4-es rétegek felé. Adás: LSSU "PO" Vétel: MSU-k eldobása. Csak a 3. réteg képes kihozni ebből az állapotból.
Delimitation, Alignment and Error Detection (Receiving) (DAEDR)
Delimitation, Alignment and Error Detection (Transmitting) (DAEDT)
Basic Transmission Control (TC)
Basic Reception Control (RC)
Preventive Cyclic Retransmission - Transmission Control (PCR-TC)
Preventive Cyclic Retransmission - Reception Control (PCR-RC)
Alignment Error Rate Monitor (AERM)
Signal Unit Error Rate Monitor (SUERM)
Congestion Control Part (CC)