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GSM Protocol Analyzer


The Global System for Mobile communications is a digital cellular communications system. GSM standards are used to provide the interface between the various entities in GSM network.

GSM networks presently operate in three different frequency ranges,

  • GSM 900 (operates in the 900 MHz frequency range; is used in most parts of the world -Europe, most of Asia, Australia, Africa, Middle East),
  • GSM 1800 or DCS 1800 (operates in the 1800 MHz frequency range; is found in a number of countries including France, Germany, Switzerland, the UK, and Russia)
  • PCS 1900 or DCS 1900 - ( used in the United States and Canada).

The differences between these appear to be minor and mainly confined to power levels, frequency, and minor changes in signaling.

User's Guide
Product Brochure
GSM-R Protocol Analyzer Brochure
GSM Protocol Tutorial
Sample Messages
View Presentation

GL's GSM Analyzer is used to analyze GSM protocols, a switching and signaling telecommunication protocol between MSC & BSC, BSC & BTS, MSC & SMLC, UMA & MS,. and so on. GSM analyzer also supports decoding proprietary 'Mobis' Interface (Motorola equivalent of the GSM A-bis interface) with additional license XX151 between BSC (Base Station Controller) - BTS (Base Transceiver Station) and BSC (Base Station Controller) - PCU (Packet Controller Unit).

Other interfaces supported include Ls / Lb / Lp Interface (Interface between MSC and SMLC), and Up (Interface between UNC (UMA network controller) and MS).

HDLC frames are parsed according to Q.921, SS7 information parsing is based on ANSI and ITU standards: T1.111, T1.112, T1.113, Q.703, Q.704, Q.708, Q.723, Q.763 & GSM information parsing is based on 3GPP TS 08.08 3GPP TS 24.008, 03.40, 3GPP TS 04.11, 3GPP TS 08.58, 3GPP TS 04.18. MTP2 is parsed according to ANSI-ITU standards and the higher GSM layer information parsing depends on the user's selection of GSM 900, DCS 1800 & PCS 1900 according GSM variants.

GL Communications supports the following types of GSM analyzers:

  • Real-time GSM Analyzer (Pre-requisites: GL's field proven E1 or T1 internal cards or USB Laptop E1 or T1 external units, required licenses and Windows XP (or higher) Operating System)
  • Offline GSM Analyzers(Pre-requisites: Hardware Dongles and Windows XP (or higher) Operating System)

In addition the following GSM applications are supported that further help in emulating GSM protocol over A & Abis interfaces:

GL’s GSM Protocol Analyzer supports complete analysis, decode and monitoring of GSM-R (GSM-Railway) - an international wireless communications standard for railway communication and applications. For more information, click on GSM-R Analyzer.

GSM Analyzer Main Features

  • Interfaces supported are A (Interface b/w BSC and MSC), A-bis (Interface b/w BSC and BTS), Mobis (Motorola Proprietary Interface b/w BSC and BTS and also b/w BSC and PCU), Gs (Interface between SGSN and MSC), Ls / Lb / Lp Interface (Interface between MSC and SMLC), Up (Interface between UNC (UMA network controller) and MS).
  • Displays Summary, Detail, Hex-dump, Statistics, and Call Trace Views, the contents of this view can also be copied to clipboard.
  • Summary View displays MTP2, MTP3 information, GSM Message types, information about various channels used during the call, frequency hopping and so on in a tabular format.
  • Detail View displays decodes of a user-selected frame from the Summary View.
  • Decoding of many RR layer non-transparent messages such as "System Information", "Measurement Result", "Immediate Assignment" etc.
  • Statistics View displays statistics based on frame count, byte count, frames/sec, bytes/sec etc for the entire captured data.
  • Call Detail View displays call statistics such as number of active/completed calls, durations of the completed calls, Type of Call (e.g. SMS/Location Update/Authentication/Speech Call), IMSI/TMSI associated with each call.
  • Call Detail Recording feature includes data link groups that help in defining the direction of the calls in a given network and form logical groups comprised of unidirectional (either 'Forward' or 'Backward') data links.
  • Hex dump view displays raw frame data as hexadecimal and ASCII octet dump, the contents of this view can also be copied to clipboard.
  • Search and filtering capabilities.
  • Exports Summary View information to a comma delimited file for subsequent import into a database or spreadsheet.
  • Capability to export detailed decode information to an ASCII file.
  • Any protocol field can be added to the summary view, filtering, and search features providing users more flexibility to monitor required protocol fields.
  • Remote monitoring capability using GL's Network Surveillance System.

Additional features supported by real time GSM analyzer are

  • Streams can be captured on the selected time slots (contiguous or non-contiguous), sub-channels or full bandwidth.
  • Real-time filtering based on the frame length.
  • Supports decoding of frames with FCS of 16 bits and 32 bits, or none.
  • Recorded trace files can be played back using HDLC Playback application.
  • Multiple streams of GSM traffic on various T1/E1 channels can be simultaneously decoded with different GUI instances.
  • Frames can be transmitted or captured in either, n x 64 kbps, or n x 56 kbps data channels.
  • The variations accommodated in the software are inverted or non-inverted data, and byte reversal or non-reversal.

Additional features supported by Offline GSM Analyzer:

  • Trace files for analysis can be loaded through simple command-line arguments.
  • Multiple trace files can be loaded simultaneously with different GUI instances for offline analysis.

The supported protocol interfaces in GSM analyzer are A-Interface, Abis-Interface, Gs-Interface, Up-Interface, Lb,Ls,Lp-Interfaces, Mobis Interface.

Supported Protocols:

Supported Protocols Specification Used
IP RFC 791
MAC IEEE 802.3
MTP2 Q.703, ITU-T Blue Book / ANSI T1.111-1996
MTP3 Q.704, ITU-T Blue Book / ANSI T1.111-1996
SCCP Q.713, CCITT (ITU-T) Blue Book / ANSI T1.112-1996
BSSMAP / DTAP 3GPP TS 48.008 10.0.0
SMS 3GPP TS 03.40 V7.5.0 & 3GPP TS 04.11 V7.1.0 GSM 03.38 version 7.2.0 Release 1998
Test & Network Management Messages (ITU) ITU-T Q.703, Q.704
Test & Network Management Messages (ANSI) ANSI T1.111.4, ANSI T1.111.7
MM 3GPP TS 04.08 V7.17.0
CC 3GPP TS 04.08 V7.17.0
BTSM 3GPP TS 08.58 V8.6.0
RR 3GPP TS 04.18 V8.13.0
BSSAP+ 3GPP TS 29.018 V6.0.0
RRLP 3GPP TS 44.031 V 7.5.0
BSSLAP 3GPP TS 48.071 V 7.2.0
SMLCPP 3GPP TS 48.031 V 6.6.0
LLP 3GPP TS 44.071 V 6.0.0
Mobis Layer 3 BSC-BTS: Motorola GSM Base Station System BSC to BTS Interface Design Specification. Document ID: GSD-GSM_NRS-MULTI_FA-IDS-001. BSC-PCU: Motorola GSL External Interface Specification - GSR9. Document ID: GSD-GSR9-GSL-EIS-001.
UMA Protocols (Stage 3) R1.0.4 TS 24.008, Mobile radio interface layer 3 specification, Core Network Protocols - Stage 3
TS 25.331, RRC Protocol Specification
TS 44.018, Mobile radio interface layer 3 specification
TS 48.018, Base Station System (BSS) - Serving GPRS Support Node (SGSN)
TS 48.008, BSS GPRS Protocol (BSSGP)
TS 45.008, Radio subsystem link control
GCC (Group Call Control) 3GPP TS 44.068 V9.0.0
BCC (Broadcast Call Control) 3GPP TS 44.069 V9.0.0

Click here to view the protocol glossary page for more information

Summary, Detail and Hex dump View

The GSM analyzer application is invoked from the main menu of GL's T1/E1 Analyzer for real-time analyzer. The offline GSM analyzer is invoked from the installation directory of the offline GSM Analyzer. The analyzer displays Summary, Detail and Hex dump View in different panes. The Summary View displays Frame Number, Time, Length, BSN, BIB, FSN, FIB, SLC, OPC, DPC, SSN and Type of GSM Messages for all the frames. User can select a frame in Summary View to analyze and decode each frame in the Detail View. The Hex dump View displays the frame information in HEX and ASCII format.

Screen Shot of Summary, Detail and Hex dump View

Real-time and Offline Analysis

Users can capture and analyze multi GSM links in real-time and record all or filtered traffic into trace file. The recorded trace file can be used for offline analysis or exported to a comma-delimited file, or ASCII file.

Real-time capturing requires (except for Up Interface) user to specify timeslots, bit inversion, octet bit reversion, user/network side, FCS, and data transmission rate. Recorded trace file can be opened later for offline analysis and can then transmit using HDLC playback file application.

Screen Shot of Real-time and Offline Analysis

Filtering and Search

Users can record all or filtered traffic into a trace file. Filtering and search capabilities adds another powerful feature to the GSM Analyzer. This features isolate the required frames from captured frames in real-time as well as off-line. Users can specify custom values for frame length to filter frames during real-time capture. The frames can also be filtered after completion of capture according to Frame Number, Time, Length, Error, BSN, BIB, FSN, type of GSM Message and more. Similarly, search capability helps user to search for a particular frame based on specific search criteria.

Screen Shot of Setting the Filtering Criteria

Call Detail Record and Statistics View

Important call specific parameters like status of each call (i.e. active/completed), duration of completed call, Call status, Call Type (e.g. SMS/Location Update/Authentication/ Speech Call), IMSI/TMSI associated with each call, Call OPC, DPC etc., are displayed in the Call Detail Record View. Call traces can also be logically grouped, with each group comprised of unidirectional (either 'Forward' or 'Backward') data links. Additionally, users are provided with the option to search for a particular call detail record from the captured traces.

Statistics is an important feature available in GSM analyzer and can be obtained for all frames both in real-time as well as offline mode. Numerous statistics can be obtained to study the performance and trend in the GSM network and it is based on protocol fields and different parameters.

Screen Shot of Statistics and Call Detail Record View

Enhanced Trace Saving Options

Users can control the captured trace files by saving the trace using different conventions such as trace files with user-defined prefixes, trace file with date-time prefixes, and slider control to indicate the total number of files, file size, frame count, or time limit. This feature also allows the captured frames to be saved into a trace file based on the filtering criteria set using display filter feature.

Screen Shot of Enhanced Trace Saving Options

Save/Load All Configuration Settings

Protocol Configuration window provides a consolidated interface for all the GUI and Protocol settings required in the analyzer. This includes various options such as protocol selection, startup options, filter/search criteria and so on. Any protocol field can be added to the summary view, filtering, and search features from this GUI providing the users more flexibility to monitor required protocol fields. All the configuration settings done in any of these options can be saved to a file, loaded from a configuration file, or user may just revert to the default values using the default option.

Screen Shot of Save/Load All Configuration Settings

Scripted GSM Emulation over A & Abis interfaces using MAPS™

GL's GSM A Interface Emulator is an advanced protocol simulator/tester for GSM simulation over A Interface that can simulate network elements MSC and BSC by generating and receiving BSSMAP and DTAP messages. The signaling specification conforms to ITU-T and 3GPP standards. For more details, click here.

GL's GSM Abis Interface Emulator is an advanced protocol simulator/tester for GSM simulation over Abis Interface that can simulate network elements BTS and BSC by generating and receiving BTSM messages. The signaling specification conforms to 3GPP standards. For more details, click here.

GSM-R Protocol Analyzer

GSM-R is a proven mobile communications standard of ERTMS (European Rail Traffic Management System), the European standard for railway operations. It is used to carry railway-specific voice and data services. It is an extension of the standard GSM signaling protocol and uses frequencies specifically reserved for railway operations.

GSM Protocol Analyzer adds GSM-R features such as VGCS, VBS, eMLPP, Emergency numbering and Functional numbering etc. GSM Protocol Analyzer also adds an User to User Information IE to GSM CC, BCC and GCC protocols to support GSM-R features according to EIRENE specification (H 22 T 0001 2) and ETSI TS 102 610.  A GSM-SS layer decode is also added to existing GSM protocol stack to support all the Supplementary Services.

GSM-R Services supported by GL’s GSM Analyzer

  • Alerting of a Controller (User-to-User Signaling  - UUS)
  • Presentation of a Functional Number – UUS
  • Multi driver Communication – (Multi Party - MPTY)
  • Registration and Deregistration of Functional Numbers – (Unstructured Supplementary Services Data - USSD)
  • DSD Alarm Notification – UUS
  • Enhanced Location Dependent Addressing – UUS
  • Shunting – MPTY, SCD, VGCS, FA
  • Functional Addressing – Follow Me
  • Confirmation of High Priority Calls –  UUS
  • Railway Emergency Calls – MPTY
  • Voice Broadcast Service (VBS)
  • Voice Group Call Service (VGCS)
  • Enhanced Multi-Level Precedence & Pre-emption (eMLPP)
  • Line identification services like CLIP, CLIR etc
  • Call Forwarding, Call Waiting, and Call Hold
  • Closed User Group
  • Advice of Charge
  • Call Barring and Call Deflection
  • User-to-user signaling
  • Follow Me (Based on USSD and CF)
  • Location Services, USSD and more

Typical Users

  • Railway operators
  • Railway system integrators

Typical Applications

  • Complete end-to-end surveillance of the GSM-R Network
  • Surveillance of specific tracks and high speed lines
  • Roll-out, and verification railway specific applications

Supported Standards:

Standards Specifications
GSM A 3GPP TS 24.080
3GPP TS 04.08 V7.17.0 (2002-02) (SS Layer)
GSM-R ETSI TS 102 610
  EIRENE H 22 T 0001 2
  FRS (Functional Requirements Specification) 7.1
  SRS (System Requirements Specification) 15.1

Bridge and Monitor Connections

Buyer's Guide:

Please Note: The XX in the Item No. refers to the hardware platform, listed at the bottom of the Buyer's Guide, which the software will be running on. Therefore, XX can either be ETA or EEA (Octal/Quad Boards), PTA or PEA (tProbe Units), UTA or UEA (USB Units), HUT or HUE (Universal Cards), and HDT or HDE (HD cards) depending upon the hardware.

Item No. Item Description
XX150 T1 or E1 Real-time GSM Protocol Analyzer
OLV150 Offline T1 or E1 GSM Protocol Analyzer
XX151 GSM Motorola Mobis option
  Related Software
XX692 GSM A Interface Emulator
XX693 MAPS™ GSM Abis Interface Emulator
XX090 HDLC Capture and Playback Software (T1 or E1)
XX120 Real-time SS7 Analyzer (T1 or E1)
XX153 TRAU Analyzer
XX155 GPRS Protocol Analyzer
  Related Hardware
PTE001 tProbe™ Dual T1 E1 Laptop Analyzer with Basic Analyzer Software
HDT001/HDE001 Legacy HD T1 or E1 (PCI) Cards with Basic Analyzer Software
HTE001 Universal T1/E1 Card with Basic Analyzer Software
UTE001 Portable USB based Dual T1 or E1 Laptop Analyzer with Basic Analyzer Software

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