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Software Modules

All of the supported protocol and simulation support packages are available as optional software modules, in order to allow the customer to precisely tailor the instrument capabilities to the test environment where it is to be used; or to keep it up to date as the requirements evolve or new projects start.
All packages support concurrent operation of more clients, that can use different packages or create multiple instances of the same protocol stack.

ATM AAL2 Module

Functional diagram

Main features:
  • Up to 8 ATM channels on PCM are supported.
  • The ATMVC protocol layer allows several clients to use different VC.
  • Several client concurrent operations are supported.
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Drop-Insert Module

Functional diagram

Drop-Insert message loop

The Drop Insert module allows to modify the content of some specific messages that are exchanged between two real network elements. The function works with any HDLC based protocols (LAPx, SS7, Frame Relay, etc) and channel rate. A special syntax has been defined to identify specific message and to describe related modification rules. Main features:

  • Specified message content can be modified.
  • Real system behaviour checking when protocol exceptions occur.
  • Any communication protocol based on HDLC (LABx, SS7, Frame Relay) is supported.
  • Any channel rate is supported.
  • A particular language syntax allows to identify messages and to describe the modification rules related to them.
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GPRS Modules

this is agroup of four modules:

  • GPRS Gb SGSN Simulation Base Module (Frame Relay, NS, BSSGP)
  • GPRS Gb SGSN Simulation Extension Module (LLC, SNDCP)
  • GPRS Gb BSC Simulation Base Module (Frame Relay, NS, BSSGP)
  • GPRS Gb BSC Simulation Extension Module (LLC, SNDCP) 
These modules provide the Gb-Interface protocol stack that allows the LSU+ to simulate the SGSN or a suite of BSCs. The Base Module supports testing of signalling, while the Extension Module is required when the simulation involves user data transfer towards real mobiles of the SGSN.
On the top of the SNDCP, the optional UDG (User Data Generator) function can be added in order to build powerful test bed that includes the simulation and the qualitative verification of user data flows. 
The Frame Relay implementation supports multiple physical links with variable rate. Each physical link can accommodate multiple permanent virtual circuits (PVC) that are mapped to the NSVC (NS Virtual circuits). 
The user can allocate multiple instances of the Network Service, associated to related BSSGP layers. The LLC/SNDCP layers support up to 10.000 MSs. 
The current implementation does not support encryption and data compression. The following figure shows the full protocol stack of the Gb interface including the UDG.

Functional diagram

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User Data Generator

The GPRS UDG consists of two co-operating modules that simulate the IP data flow on both user and network side.
The UDG User module works on top of Abis GPRS protocol stack, or the Gb BSC Simulation Extended Package, or with the LSU+ GPRS mobile commander.
The UDG Network module  works on top of Gi Interface package.
These two processes work per mobile basis and exchange test parameters through in-band IP signalling in the assigned channels. The test parameters allow to configure the Quality of Service and other options to vary packet length and data rate gradient. It supports client with multiple active PDP contexts. A set of primitives allows to control UDG operation from the user side only, and a timer driven "Suspend- Resume" logic provides network originated data when the MS could be in MM_READY or MM_STANDBY mobility management state. The UDG reports the results of the test to its client, including counters of transmitted and dropped packets and statistics about data transfer, activation latency and packet travelling times. 

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GPRS Gi-interface Modules

Fuctional diagram

Main features:
  • The UDG/Net module works in cooperation with the UDG/User one to verify and to mesure the data flow performances in GPRS through MS and Gi.
  • The two cooperative modules exchange the test parameters with the IP in-band signalling into the assigned channels.
  • Ethernet connection or Frame Relay with multiple PVC.
  • Frame Relay link set with a rate up to 2048 Kb/s.
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GPRS Gi Module IP Interface Simulation — This module provides the Gi protocol stack that simulates the operations of the IP packet data network at the GiIP reference point of the GSM/GPRS Network in case of transparent access. In case of Frame Relay connections, it can handle a pool of physical links at different rates.The implementation supports multiple PVCs. Optionally this layer can be handled through an additional Ethernet connection according to IEEE-802 (an additional network card on the PPU must be added), and the LSU+ will behave as a TCP/IP gateway for the simulated IP traffic. On top of the Gi Packages typically resides the optional UDG/Net module.
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GPRS Abis-interface Module

Functional diagram

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GPRS Abis BTS/MS Simulation PCU FRAMES — This protocol layer transports user data and in-band signalling between the BSC and the BTS related to GPRS traffic channels. As it is not specified by GSM Recommendations, the various manufactures have adopted proprietary solutions. The LSU+ development team can customise this module in conformity with the specific proprietary interface specifications.
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GPRS Abis BTS/MS Simulation RLC/MAC Module — It provides implementation of RLC/MAC protocol of a set of BTS and a population of up to 10.000 mobiles that are using up to 128 PCU frame channel on a PPU, according to GSM 04.60, and specifically including the procedures: 

- TBF establishment initiated by the MS on PCCCH;.
- TBF establishment initiated by the Network on PCCCH;
- TBF establishment initiated by the MS on CCCH;
- TBF establishment initiated by the Network on CCCH;
- Packet PDCH release;
- Paging on PCCCH sub-channel;
- Paging on CCCH sub-channel;
- Transfer of RLC data blocks (acknowledged mode);
- Transfer of RLC data blocks (unacknowledged mode);
- Segmentation and Re-assembly of LLC PDUs;
- Re-assembly of RLC/MAC control messages and the following control messages:
* Packet Access Reject
* Packet Channel Request
* Packet Resource Request
* Packet Uplink Assignment
* Packet Downlink Assignment
* Packet TBF Release
* Packet Paging Request
* Packet Downlink Ack/Nack
* Packet Uplink Ack/Nack
* Packet Control Acknowledgement
* Packet Downlink Dummy Control Block
* Packet Uplink Dummy Control Block
* Packet PDCH Release
* Packet Polling Request
* Packet System Info 1, 2, 3, 3 bis, 5, 13.
The implementation has two operations modes: debug and automatic. In debug mode the MAC function handling is demanded to the client application, conversely in automatic mode the client application handles MAC internally and it interfaces to the upper layer with the standard GRR-* primitives (GSM 04.07).
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GPRS Abis BTS/MS Simulation LLC, SNDCP Module — This module provides the remaining upper protocol layers to complete the GPRS Abis protocol stack. The implementation supports up to 10.000 simulated mobiles. It suits an outline of the Abis GPRS protocol stack including UDG.
Main features:
  • Multiple clients can work in concurrent manner.
  • Up to 256 physical links supported.
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GPRS Mobile Commander (RS-232, GSM 07.07, PPP) — This module manages up to 128 real GPRS mobiles, connected to the LSU+ through separate RS-232 ports. It requires the installation of additional multiple RS-232 cards in the PPUs. The software controls the mobiles through the AT command set, and it handles packet data transfer through the PPP protocol (IETF STD 51). On top of PPP the UDG/User can be used to generate and control user data traffic.

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