Mobile communication and computing GSM protocol stack and frame formatting.pdf

GSM Protocol Stack and Frame Formatting
www.rsmangrulkar.com
January 24, 2018
www.rsmangrulkar.com GSM Protocol Stack and Frame Formatting

Physical Layer Radio Transmission (BTS – MS)

Data Link Layer Provides errorfree transmission
between adjacent entities based on ISDN’s LAPD
Protocol for the Um and Abis Interface.

Data Link Layer Provides errorfree transmission
between adjacent entities based on ISDN’s LAPD
Protocol for the Um and Abis Interface.
Networking or Messaging Layer Responsible for
communication between various network resources,
mobility, code format and call related management
messages between various network entities.

Physical Layer
Handles all radiosp. functions
Creates burst according to 5 different formats
multiplexing of burst into TDMA frame
Idle channel detection and quality measurement
Channel coding and error detection.
voice activity detection (VAT)

Data Link Layer
LAPD channel of ISDN
LAPDm light weight LAPD (Eliminates synchronization
flags and error detection)
LAPDm offers
Resequencing of data frames
Flow Control
Segmentation and Reassembly of data
Ack / UnAck of data
Data tr. used PCM(64 kbps channels)
contains A interface leased lines with 2.048Mbps capacity
Channel coding and error detection.
voice activity detection (VAT)

Network Layer
Radio Resource Management.
Call Setup , Maintenance and release of radio channel.
Mobility Management
RAIL(Registration, Authentication, Identification,
Location updating)
Provision for TMSI(Temorary Mobile Subscription
Identity)
Call Management
Call Control, Short Messaging Service, Supplementary
services

Additional Protocols: Signaling System 7
Signaling System 7 (SS7) is an international
telecommunications standard that defines how network
elements in a public switched telephone network (PSTN)
exchange information over a digital signaling network.
Nodes in an SS7 network are called signaling points.

Three kinds of network points signaling points: Service
Switching Points (SSPs), Signal Transfer Points (STPs),
and Service Control Points (SCPs).

Three kinds of network points signaling points: Service
Switching Points (SSPs), Signal Transfer Points (STPs),
and Service Control Points (SCPs).
Traffic on the SS7 network is routed by packet switches
called STPs.

Figure 4: GSM Overview

* Interfacing the PSTN, the MSC performs call signalling
functions using the Telephone User Part (TUP), or interfacing
the ISDN, the ISDN User Part (ISUP).
* Between the MSC and the BSC, the Base Station System
Management Application Part (BSSMAP) is used.
The Direct Transfer Application Part (DTAP) is used to send
messages between the MSC and the mobile (MS). MAP is
used between the MSC and the VLR, EIR, and HLR.

BSSAP Base Station System Application Part
BSSMAP Base Station System Management Application Part
DTAP Direct Transfer Application Part
ISUP ISDN User Part
MAP Mobile Application Part
SCCP Signalling Connection Control Part
TUP Telephone User Part
TCAP Transaction Capabilities Application Part

The physical channel is the medium over which the
information is carried.
The logical channel consists of the information carried over the
physical channels.

A Physical Channel (a TS, defined by a fixed position (0 to 7) on a given TDMA frame) may be used to
broadcast messages containing different kinds of information:
traffic messages for speech and data,
signaling messages for different procedures and supplementary services,
synchronization messages for temporal and logical synchronization between the mobile stations and the
BTS,
measurements messages for uplink report of the downlink measurements,
control messages to manage the access to the network.
All these kinds of messages are classified in Logical Channels. Depending on the quantity of information to
transmit and on their consistency,
several logical channels may be mapped onto one physical channel, in order to use its successive Time
Slots as much as possible (optimization of the resources number by maximizing the occupancy duration of
each).
As a conclusion: Physical Channel : information container Logical Channel : specification of the
information global content

Mobile communication and computing GSM protocol stack and frame formatting.pdf

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Mobile communication and computing GSM protocol stack and frame formatting.pdf