GSM Radio Stack

Intro GSM Stack

MS to BTS Protocols

Based on the interface, the GSM signaling protocol is assembled into three general layers −

• Layer 1 − The physical layer. It uses the channel structures over the air interface.

• Layer 2 − The data-link layer. Across the Um interface, the data-link layer is a modified version of the Link access protocol for the D channel (LAP-D) protocol used in ISDN, called Link access protocol on the Dm channel (LAP-Dm). Across the A interface, the Message Transfer Part (MTP), Layer 2 of SS7 is used.

• Layer 3 − GSM signalling protocol’s third layer is divided into three sublayers −

  • Radio Resource Management (RR),

  • Mobility Management (MM), and

  • Connection Management (CM).