MAPS™ GSM A Interface Emulator(Scripted GSM A Interface Emulation)

MAPS™ GSM A Interface Emulator
(Scripted GSM A Interface Emulation)

Background

GSM is a globally accepted standard for digital cellular communications. 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 A-bis interface and The BSS communicates with the Network Service Switching center across the A interface.

At the MSC, the information is mapped across the A interface to the MTP Layers 1 through 3 from the BSC. Here the equivalent set of radio resources is called the BSS MAP. The BSS MAP/DTAP and the MM and CM are at the upper layers of Layer 3 protocols. This completes the relay process. Through the control-signaling network, the MSCs interact to locate and connect to users throughout the network. Location registers are included in the MSC databases to assist in the role of determining how and whether connections are to be made to roaming users.

Overview

GL’s MAPS™ GSM A Interface Emulator is an advanced protocol simulator/tester for GSM simulation over A Interface that can simulate BSSMAP and DTAP messages and signaling specification as defined by 3GPP standards. The tester supports testing network elements MSC 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 A interface test objects in a controlled & deterministic manner.

GSM A 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 BSSMAP and DTAP 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 A Interface Protocol Standards

Available Standards	Supported Protocols	Standard / Specification Used
GSM A 900	SCCP	Q.713, CCITT (ITU-T) Blue Book
	MTP3	ITU-T Q.704
	BSSMAP / DTAP	3GPP TS 08.08 V8.9.0
	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 A interface simulation over TDM (E1/T1)
Simulates BSC and MSC 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 MTP Layers
User Configurable Signaling Links
Supports all Call Control, Mobility Management, and Radio Resource messages
Access to all BSSMAP and DTAP Message Parameters like CM Service Request, Paging, call Control messages, 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
Impairments can be applied to messages to simulate error conditions
Supports customization of call flows and message templates using Script editor and Message editor.
Supports scripted call generation and automated call reception.
Provides protocol trace with full message decoding, and graphical ladder diagrams of call flow with time stamp
Script based & protocol independent software architecture.
Provides call statistics with associated captured events and error events during call simulation
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 MTP server parameters along with MTP signaling parameters (Source Point Code (SPC) and a Destination Point Code (DPC), Signaling Link Code). Once the MTP layer is configured properly, BSSMAP and DTAP messages can be transmitted and received over MTP 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 A Interface Emulator simulates BSSMAP and DTAP signaling and call control messages between the MSC and BSC nodes. In this document, we are considering the call flow between the MSC 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 MSC (Mobile Originating Call Flow)

Mobile Originating Call (MOC) Call Flow

The MAPS™ GSM A acts as Base Station Controller (BSC) and initiates the Mobile Originating Call flow by sending CM Service Request to the DUT (MSC). The DUT on receipt of a CM SERVICE REQUEST message should send a CC connection confirm message in response as shown in the figure below. Also, simulates the complete call flow as in Mobile Originating Call (MOC) call flow.

MOC Call Generation at BSC Node

Testing MSC (Location Updating Call Flow)

LUC Call Flow

The MAPS™ GSM A can also act as Base Station Controller (BSC) initiating the Location Updating Call flow by sending Location Updating Request to the Network (MSC). The DUT on receipt of a LOCAION UPDATING REQUEST message sends a CC connection confirm message in response as shown in the figure below. Also, simulates the complete call flow as in Location Updating Call (MOC) call flow.

LUC Call Generation at BSC Node

Testing BSC (Mobile Terminating Call)

MTC Call Flow

MAPS™ GSM A acts as Mobile Station Controller (MSC) processing the call flow by receivingIinitiating the Paging message to from the Mobile Station (BSC). The DUT (BSC) on receipt of a Paging message, sends a Paging Response message back to MSC. Also, simulates the complete call flow as in Mobile Terminating Call (MTC) call flow.

MTC at MSC 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 BSC (MOC)

This test is performed to ensure that the MAPS™ (MSC) on receipt of a CM SERVICE REQUEST message from BSC, sends a CC connection confirm message in response. And also simulates the complete call flow as in Mobile OriginatingCall (MOC) call flow.

MOC Call Reception at MSC Node

Testing BSC (LUC Call Flow)

This test is performed to ensure that the MAPS™ (MSC) on receipt of a LOCATION UPDATING REQUEST message from BSC, replies with CC connection confirm message as depicted in the figure. Also, MAPS™ (MSC) simulates the complete call flow as in Location Updating Call.

LUC Call Reception at MSC Node

Testing MSC (MTC Call Flow)

This test is performed to ensure that the MAPS™ (MSC) on receipt of a PAGING RESPONSE Message from BSC, replies with CC connection confirm message as depicted in the figure. Also, MAPS™ (MSC) simulates the complete call flow as in MTC call flow.

MTC Call Reception at BSC 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

Link Status - Link Status window indicates transport related information of the protocol, for example, if SCTP is used as transport, it indicates if the Association is up or Down in the Link Status window.

Screenshot of Link Status

Buyer's Guide:

Item No.	Item Description
XX600	Basic Client/Server Scripted Control Software
XX692	GSM A Interface Emulator
XX610 XX620	TDM Traffic Options File based Record/Playback (requires xx600) Transmit/Detect digits (Place Call/ Answer Call) (requires xx600)
	Related Software
XX647	MAPS™ ISUP Conformance Test Suite (Test Scripts)
XX648	MAPS™ ISDN Emulator
XX649	MAPS™ ISUP Emulator
XX693	MAPS™ GSM Abis Interface Emulator
XX120	SS7 Analyzer Software
OLV120	Offline/ Remote SS7 Analyzer Software
XX150	T1 or E1 Real-time GSM Protocol Analyzer
OLV150	Offline T1 or E1 GSM Protocol Analyzer
PKS124	MAPS™ MGCP Emulator
	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

Specifications are subject to change without notice.

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