MAPS™ GSM Abis Interface Emulator
(Scripted GSM Abis Interface Emulation)
Background
GSM stands for Global System for Mobile Communication and is an open, digital cellular technology used for
transmitting mobile voice and data services.
A GSM network is made up of multiple functional entities and interfaces that facilitate sending and receiving of
signaling and traffic messages. It is a collection of transceivers, controllers, switches, routers, and registers.
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The GSM network can be divided into following broad parts.
- The Mobile Station (MS)
- The Base Station Subsystem (BSS)
- The Network Switching Subsystem (NSS)
- The Operation Support Subsystem (OSS)
The MS and the BSS communicate across the Um interface, also known as the air interface or radio link. BTS and BSC
will communicate across Abis interface and The BSS communicates with the Network Service Switching center across the
A interface.
The Abis interface is used between the BTS and BSC. At this level, the radio resources at the lower portion of Layer
3 are changed from the RR to the Base Transceiver Station Management (BTSM). The BTS management layer is a relay
function at the BTS to the BSC.
The RR protocols are responsible for the allocation and reallocation of traffic channels between the MS and the BTS.
These services include controlling the initial access to the system, paging for MT calls, the handover of calls between cell
sites, power control, and call termination. The RR protocols provide the procedures for the use, allocation, reallocation,
and release of the GSM channels. The BSC still has some radio resource management in place for the frequency
coordination, frequency allocation, and the management of the overall network layer for the Layer 2 interfaces.
Overview
GL’s GSM Abis Interface Emulator is an advanced protocol simulator/tester for GSM simulation over Abis Interface that
can simulate BTSM messages and signaling specification as defined by 3GPP standards. The tester supports
testing network elements BTS and BSC, Error tracking, regression testing, conformance testing, load testing/call
generation and generation of high volumes of GSM traffic. It is able to run pre-defined test scenarios against GSM Abis
interface test objects in a controlled & deterministic manner.
GSM Abis Interface Emulator supports powerful utilities like Message Editor, Script Editor and
Profile Editor which allow new scenarios to be created or existing scenarios to be modified using BTSM messages
and parameters.
GL also provides an independent GUI based GSM protocol analyzer (optional
application – XX150) for online capture and decode of the signaling in real-time both during tests and as a stand-alone
tracer for live systems.
Supported Protocol Standards
GSM Abis Interface Protocol Standards
| Available Standards |
Supported Protocols |
Standard / Specification Used |
| GSM Abis 900 |
BTSM |
3GPP TS 08.58 V8.6.0 |
| |
MM |
3GPP TS 04.08 V7.17.0 |
| |
CC |
3GPP TS 04.08 V7.17.0 |
| |
RR |
3GPP TS 04.18 V8.13.0 |
| |
SMS |
3GPP TS 03.40 V7.5.0 &
3GPP TS 04.11 V7.1.0 GSM 03.38 version 7.2.0 Release 1998 |
Main Features
- GSM Abis Interface simulation over TDM (E1/T1)
- Simulates BSC and BTS nodes
- Supports transmission and detection of TDM traffic - digits, voice file, single /dual tones
- Multiple E1/T1 line interfaces supported
- User-friendly GUI for configuring the LAPD Layer
- Supports DCM, RLM, CCM message groups.
- Configure AGCH, ACCH, SDCCH, BCCH and other logical channels.
- Supports all Call Control, Mobility Management, and Radio Resource messages.
- Access to all BTSM Message Parameters like CM Service Request, Paging, call Control messages like Release messages, and more.
- User controlled access to optional parameters such as timers.
- Supports Authentication, TMSI Reallocation, Encryption and other optional procedures.
- Ready scripts for Mobile Originating, Mobile terminating and Location Updating procedures.
- Logging of all messages in real time.
Test Configuration
The test configuration window allows users to configure the necessary parameters in order to establish communication between MAPS™
and the DUT. It includes the T1/E1 (GL) server and LAPD Task parameters along with LAPD signaling parameters. Once the LAPD layer is configured properly,
BTSM messages can be transmitted and received over LAPD layer.
Screenshot of Testbed Setup
Call Generation
Call Generation option allows the user to simulate outgoing communications where an outgoing call is initiated by sending call control messages using
proper scripts and profiles. The profile allows necessary parameters of call control messages to be changed during runtime.
The GSM Abis Interface Emulator simulates BTSM signaling and call control messages between the BTS and BSC nodes. In this document, we are
considering the call flow between the BTS and BSC nodes for Mobile Originating Call (MOC), Mobile Terminating Call (MTC), and Location Updating (LU).
Hence, three different scenarios have been illustrated for MOC, MTC, and LU call flows.
Testing BSC (Mobile Originating Call (MOC) Flow)
Mobile Originating Call (MOC) Call Flow Scenario
MAPS™ GSM Abis interface includes inbuilt scripts (*.gls) that allows itself to act as BTS initiating Mobile Originating Call and test BSC in the network.
The MAPS™ GSM ABis sends Channel Required message to the BSC in the network. The DUT (BSC) on receipt of a Channel Required message, sends a
Channel activation and channel activation acknowledgement message in response. Also, simulates the complete call flow as in Mobile Originating Call (MOC)
call flow.
MOC Call Generation at BTS Node
Testing MSC (Location Updating Call (LUC) Flow)
The MAPS™ GSM Abis is considered to act as Base Transceiver Station (BTS) and initiating the call flow by sending Location Updating Request to the
BSC (Base Station Controller). The DUT (BSC) on receipt of a LOCATION UPDATING REQUEST message initiates authentication process by sending
AUTHENTICATION REQUEST. Also, simulates the complete call flow as in Location Updating Call (LUC) call flow.
LUC Call Flow
LUC Call Generation at BTS Node
Testing BTS (Mobile Terminating Call (MTC) Flow)
MTC Call Flow
MAPS™ GSM ABis is located at the network as Base Station Controller (BSC) initiating the call flow by sending the Paging message to the
Mobile Station (BTS). The DUT (BTS) on receipt of a Paging message, sends a Paging Response message back to BSC. This can be observed in Call
Reception window at BSC node. Also, simulates the complete call flow as in Mobile Terminating Call (MTC) call flow.
MTC at BSC Node
Call Reception
Call generated from other entity can be automatically detected in call reception window by pre-setting the required scripts in the
Incoming Call Handler window.
Testing BTS (MOC Call Flow)
This test is performed to ensure that the MAPS™ (BSC) on receipt of a Channel Required message from BTS, sends a Channel Activation
message in response. And also simulates the complete call flow as in Mobile OriginatingCall (MOC) call flow.
MOC Call Reception Flow at BSC Node
Testing BTS (LUC Call Flow)
This test is performed to ensure that the MAPS™ (BSC) on receipt of a Channel Required message from BTS, sends a Channel Activation
message in response and Also MAPS™ (BSC) simulates the complete call flow as in Location Updating call.
LUC Call Reception Flow at BSC Node
Testing BSC (MTC Call Flow)
At reception of a paging Command message, the BTS shall respond with the PAGING RESPONSE message. Also, MAPS™ (BSC) simulates the
complete call flow as in Mobile Terminating call.
MTC Call Reception at BTS Node
Bulk Call Simulation
MAPS™ supports Bulk Call Simulation and Stress/Load Testing capabilities through Load Generation feature. Load Generation window helps
users configure Stress/Load Testing parameters such as Call per second (CPS) or Busy hour call attempts (BHCA), Max Simultaneous Calls and Burst
parameters.
Screenshot of Load Generation Parameters
Customization of Call Flow and Messages Using Pre-Processing Tools
- Script Editor - The script editor allows the user to create / edit scripts and to define variables for the protocol fields. The script uses
pre-defined message templates to build call flow and perform send and receive actions. Script editor provides options to run the test for multiple
iterations in sequential or random flow. Commands allow retransmission of messages with specific interval
Screenshot of Script Editor
- Profile Editor - Profiles are used to provide the user configured values to the fields in the Messages (i.e Message Template in MAPS™)
through variables which are going to change during the course of a call.
Screenshot of Profile Editor
- Message Editor - The Message Template is a *.HDL file that comprises of protocol encoding parameters with preset values. It is required to
create a message template for every message in a protocol. The message templates are called within the scripts to perform scenario based testing.
Screenshot of Message Editor
Call Flow & Script Execution Control
Message Sequence - MAPS™ provides protocol trace with full message decoding, custom trace, and graphical ladder diagrams of
call flow with time stamp while simulation is running. Call flow graph allows to easily verifying the messages exchanged between MAPS™ and DUT.
See Call Generation and Call Reception for details
Script Contents & Script Flow - The Scripts Contents window displays the contents of the script selected for call generation or reception.
The Script Flow window displays the set of statements successfully executed by MAPS™ to help users in troubleshooting a particular the call scenario.
Events & Event Profile Editor - User-defined events allow redirection of script execution on-the-go. The custom parameters in the events
can also be changed during script execution using Event Profiles.
Screenshot of Script Contents and Script Flow
Screenshot of Event Config
Call Statistics, Events, Link Status
Call Statistics & Status - By default, all call handling scripts (irrespective of the type of the functions) are assessed by MAPS™ to
provide statistical information about total calls, active calls, completed calls, passed calls, and failed calls. It is also possible to characterize the
statistical information under different groups of call handling scripts under a unique heading.
In addition, Call Generation and Call Reception windows provide useful call status & script execution results.
Screenshot of Call Statistics and Status
Events Reporting – MAPS™ provides Event Log, Error Events, and Captured Errors windows that log the captured events and
errors encountered during the progress of the call.
Screenshot of Event Log
Buyer's Guide:
Specifications are subject to change without notice.
Back to Message Automation & Protocol Simulation
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