Overview
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 and is the most common in Europe and rest of the world),
- GSM 1800 or DCS 1800 (operates in the 1800 MHz frequency range and is found in a rapidly-increasing number of countries
including France, Germany, Switzerland, the UK, and Russia)
- PCS 1900 or DCS 1900 - the only frequency used in the United States and Canada for GSM).
Between these, the only differences so far seem to be the power levels, frequency & some small changes in signaling.
GL's GSM Analyzer is used to analyze GSM protocols, a switching and signaling telecommunication protocol between MSC & BSC,
BSC & BTS, MSC & HLR, MSC & VLR, VLR and HLR, MSC & SMLC, UMA & MS,. and so on.
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 2000/XP Operating System)
- Offline GSM Analyzers(Pre-requisites: Hardware Dongles and Windows 2000/XP Operating System)
GSM Analyzer Main Features
- Interfaces supported are A (Interface b/w BSC and MSC), A-bis (Interface b/w BSC and BTS), B (Interface b/w the MSC and its
associated VLR), C (Interface b/w the HLR and the MSC), D (Interface b/w the HLR and the VLR), E (Interface b/w MSCs),
F (Interface b/w MSC and EIR), H (Interface between HLR and AuC), J (Interface b/w the HLR and the gsmSCF), 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.
- Summary View displays MTP2, MTP3 information, GSM Message types, information about various channels used during the call,
frequency hopping etc.
- Detailed View displays easy to understand decodes of user-selected frame.
- 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 trace 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 HDLC frame data as a hexadecimal and ASCII octet dump.
- Search and filtering capabilities.
- Exports detailed and summary information to a comma delimited file for subsequent import into a database or spreadsheet.
- 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.
- Recorded trace files can be played back using HDLC playback option
- Multiple streams of GSM traffic on various T1/E1 channels can be simultaneously decoded with different GUI instances
- Frames can be transmitted/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
- 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
Supported Protocols:
- A Interface (variants GSM 900, DCS 1800, PCS 1900) – MTP2, MTP3, SCCP, BSSMAP, MM, CC, SMS
- Abis Interface (variants GSM 900, DCS 1800, PCS 1900) - LAPD, BTSM, RR, MM, CC, SMS
- Gs Interface (variants GSM 900, DCS 1800, PCS 1900) – MTP2, MTP3, SCCP, BSSAP+, RRLP, BSSLAP, SMLCPP, LLP, BSSAP-LE
(BSSMAP-LE/DTAP-LE), SCCP, MTP3, MTP2
- Up Interface – UMA, TCP, UDP, IP, MAC
Summary, Detail and Hexdump 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
hexdump view in different panes. The summary pane 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 Hexdump 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 then be analyzed offline and exported to ASCII file, or printed.
Real-time capturing requires (except for Up Interface) user to specify timeslots, bit inversion, octet bit reversion,
user/network side, 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 Realtime and Offline Analysis
Filtering and Search
Users can record all or filtered traffic into a trace file. Filtering and search capability adds another powerful feature to the
GSM Analyzer. This feature can isolate 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 Trace and Statistics View
Call trace defining 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. Call traces can also be logically grouped, with each group comprised of unidirectional (either
'Forward' or 'Backward') data links (applicable for A1 interface only)
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 e.g. Use Type (Key/Total/Field), Statistic type (Frame count, Byte count,
Frames/Sec) and patterns like Range List, Wild card etc.
Screen Shot of Statistics and Call Trace 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 important settings required in the analyzer.
This includes various options such as protocol selection, startup options, stream/interface selection, filter/search criteria
and so on. 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
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 DPT, DPE, PCT, PCE, HDT, HDE, DLT, DLE or UTE depending
upon the hardware.
Back to Protocol Analysis Index Page
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