Software-Defined Radio Testbed for the Physical Layer of Wireless LANs

This paper presents a software-defined radio testbed for the physical layer of wireless LAN standards. All baseband physical layer functions have been successfully mapped on a Pentium~4 processor that performs these functions in real-time. This has been tested in combination with a CMOS integrated wideband analog front-end containing a low noise amplifier, downconversion mixers and filters. The testbed consists of both a transmitter and a receiver. The transmitter contains a PC with a DAC board, an Agilent E4438C generator for upconversion and an antenna. The receiver consists of an antenna, a wideband analog front-end and a PC with an ADC board. On this testbed we have implemented two different types of standards, a continuous-phase-modulation based standard, Bluetooth in the 2.4 GHz band and an OFDM based standard, HiperLAN/2 in the 5 GHz band. However, as all baseband processing is performed by software, our testbed can easily be extended to other standards. To validate the SDR testbed we describe RF experiments for both Bluetooth and HiperLAN/2. In HiperLAN/2 mode, some sub-carriers are more noisy than others which is probably introduced by non-linearities in the analog frontend for example, non-linearities in the power amplifier. To investigate this effect, we have performed simulations in HiperLAN/2 mode to study these effects.