In any telecommunication system, signaling is required to coordinate the necessarily distributed functional entities of the network. In GSM networks signaling information transforms according to the OSI model.
• Layer 1:Physical Layer
– Radio Transmission
• Layer 2:Data Link Layer(DLL)
– Provides error-free transmission between adjacent entities, based on the ISDN’s LAPD protocol for the Um and Abis interfaces, and on SS7’s Message Transfer Protocol (MTP) for the other Layer interfaces
• Layer 3: Networking or Messaging Layer
– Responsible for the communication of network resources, mobility, code format and call-related management messages between various network entities
Figure: Simplified ISDN reference model
Logical channels are at the Service Access Point of Layer 1 (physical layer), where they are visible to the upper layers as transmission channels of the physical layer
User Plane - User data are transmitted in GSM across the air interface over traffic channels (TCH) from a subscriber or a data channel.
Controlling/ Signaling Plane - Handles subscriber access to the network and the control of the user plane
…To be continued
Reference :
1. J .Eberspächer et. al., GSM-Architecture, Protocols and Services (3rd Ed.)
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