R&S^®PTW70 WLAN Protocol Tester

Hardware: Measurement unit

Fig. 2 provides a schematic view of the modules of the R&S® PTW 70 measurement unit. Using a standard PC architecture, the R&S® PTW 70 measurement unit can simultaneously carry out measurements, record measured data and, in the background, send the data to to the detached controller. The baseband architecture is oriented to the realtime requirements of the PHY layer and the MAC layer. The baseband board is designed to support future requirements of the WLAN standards by installing software updates. The RF frontend covers the currently used frequency spectrum for WLAN systems. The RF frontend can be set to receive selected frequency bands or channel bandwidths to match the internal settings of the mixer stages or external devices that are connected. Featuring trigger signal inputs and outputs, an I/Q output and configurable RF connectors, the R&S® PTW 70 measurement unit can easily be integrated into more complex test setups.

Fig. 2: R&S® PTW 70 modules

Software concept

The R&S® PTW 70 uses three operating systems. All time-critical processes run on the OSE realtime operating system and are executed by accessing a reliable Rohde & Schwarz protocol stack model. The PC of the measurement unit runs on the Linux operating system, which is also used to communicate with the controller. The user interface is designed for 32-bit Microsoft Windows operating systems.

Three tools are available to enable optimal configuration of the R&S® CPTW 70 for a given measurement task (see Fig. 3).The user interface consists of the following elements:

• Graphical script editor: the direct way to measurement results
• Script-based programming interface: time-saving in automatic tests
• C++ library: error simulation for quality assurance at all stages of development

Fig. 3: R&S® PTW 70 programming environment

The graphical script editor (see Fig. 4, background) is installed on the controller. Featuring a predefined set of control commands and 802.11-specific protocol vocabulary, the editor supports the fast and guided generation of test scenarios. The graphical user interface is a very convenient means of setting variables and protocol parameters as well as branching to program sections or repeating selected sequences.Test scenarios can also be created as texts through direct access to the script engine command interface (see Fig. 3) (feature currently in the planning stage). The measurement unit processes both graphical and text scripts. With no more than a mouseclick, the scripts are available for processing after going through an executability check.The protocol SAP interface (see Fig. 3) provides unrestricted access to the R&S® PTW 70 protocol stack. The interface, which is implemented as a C++ library, enables the user to manipulate the time sequence of events, modify baseband processes (for example by changing the header or checksum of a protocol message) and insert test sequences. The graphical analyzer (see Fig. 4, foreground) displays the protocol-based communication between the DUT and the R&S® PTW 70 in detail and with high time resolution. Analysis is facilitated by various protocol views displaying, for example, a decoded protocol message in detail, a single protocol layer, or a complete protocol sequence. In addition, an extensive range of filter and event functions is available to support systematic fault and error analysis and correction. Since it supports controlled error simulation in the protocol sequence, manipulation of test sequences, realtime analysis and complete documentation of results, the WLAN Protocol Tester R&S® PTW 70 is an indispensable tool in the development, integration and verification of wireless LAN systems.

Fig. 4: R&S® PTW 70 graphical script editor and analyzer