CSIT Group - Research Areas


Software Defined Radio techniques for test and verification of wireless systems


In the last few years, the development of new wireless standards has imposed the adoption of modular and flexible systems for test and verification during manufacturing. Two main testing solutions are available: customized and general-purpose ones. While the former solution is cost-optimized but it not flexible enough to handle multi-standard applications, the latter may be employed in different testing scenarios being based on the Virtual Instrumentation paradigm. However, both families suffer from inherent off-line behavior, for their inability to cope with real-time requirements of the new wireless standards.

Evolutionary 3G/3.5G standards (e.g., UMTS/HSPA, WiMAX, LTE) pose a threat to the Virtual Instrumentation approach since these standards required full bi-directional real-time capabilities. Off-line testing solution is not the answer and only real-time systems may be flexible enough to meet the time constraints defined by these new standards. Therefore, the traditional Virtual Instrumentation approach must be enhanced to support Real-time Virtual Instruments.

The generic hardware/software architecture that supports these features includes at least a programmable logic device (FPGA – Field Programmable Gate Array), a programmable signal processor (DSP – Digital Signal Processor) and a wideband RF interface (e.g., I/Q Transceiver). While the FPGA implements the physical layer (i.e., PHY) processing blocks, the DSP runs the upper layers of the protocol stack (i.e, MAC and IP networking) and the tester application.

The proposed hardware/software architecture based on National Instruments boards, is able to support different wireless standards. Radio broadcasting standards such as AM/FM, RDS/RDBS, DAB/DAB+/DMB and DVB-S/DVB-T, are very simple ones and they can be easily implemented with this architecture. Of course, they require only the downlink protocol.

The proposed hardware/software solution is well suited also for more intricate wireless standards. For instance, the Mobile WiMAX (IEEE802.16e) protocol is considered the most complex wireless standard up to date. Unlike the radio broadcasting one, the complexity of its uplink and downlink protocols introduces several issues in the PHY design: i) the required processing power, ii) the size of the FPGA, iii) the optimization/standardization of the base-band processing blocks and iv) the time frame constraint (e.g., 5 ms). In addition, the MAC layer requires real-time capabilities to meet the tight frame time constraints as well. Nevertheless, the proposed hardware/software architecture fits well even into the Mobile WiMAX constraints and a prototype of a Mobile WiMAX Base Station Emulator (BSE) is currently under test. Preliminary results show that the BSE is able to setup a direct communication with a commercially available Subscriber Station.


Related Publications:

•    V. Rampa; WiMAX scalable testing technologies; 802.16e Taiwan WiMAX Forum, Taipei (ROC), Invited Presentation, Mar. 5th 2007.
•    V. Rampa, M. Arigossi; Il Test dei Sistemi di Telecomunicazione: Sfida in Tempo Reale; Atti del Forum Tecnologico NIDays09, 25 Feb. 2009, Milano, Pag. 155-156.
•    A. Giudici, V. Rampa; Metodo e Apparato per la compensazione a larga banda dello sbilanciamento I/Q nei ricetrasmettitori in fase e quadratura; Brevetto depositato, Mar. 2010.