Virtual Prototype of a wireless sensor node using VHDL-AMS

Wireless sensor networks (WSN's) have evolved since their first inception and have a wide range of applications. Senor nodes which constitute WSN's need to support increased computation and communication capabilities, while being limited in size and energy. These requirements demand that the design of sensor nodes cohabit multiple functionalities such as mixed (analog / digital) signal processing in one chip. In this work, we present such an implementation using VHDL-AMS which is acronym for Very High Speed Integrated Circuit Hardware Description Language - Analog and Mixed Signal extensions. The implementation presented in this paper is a virtual prototype of the communication architecture of a sensor node which cohabits mixed signal design. The functionality of the communication module of a sensor node is broadly divided into two main parts - baseband and radio frequency (RF). Baseband processing involves data encoding followed by spectrum spreading using direct sequence spread spectrum (DS-SS). The spread spectrum signal subsequently undergoes several functions such as modulation, amplification and filtering which are implemented in the RF domain before final transmission over a channel. The baseband processing constitutes digital functionality and the RF processing constitutes analog functionality. The virtual prototype is modelled as an implementation on a Virtex 4 FPGA board and the validity of the prototype is verified by comparing bit error rate (BER) curves obtained using the virtual prototype with the theoretical results for BPSK and BFSK) signals transmitted over Additive White Gaussian Noise (AWGN) channel as well as Rayleigh channel.