Wideband Communication using ergodic chaos

Henry Leung (U Galgary)


Abstract

	In recent years, there has been an increasing interest in 
applying chaos theory to communication system design. Chaotic 
dynamical systems possess many properties that are appealing for 
communication system design, in particular wideband communications. 
However, most of schemes developed are sensitive to noise, 
propagation environment and achieve a performance improvement 
at the expense of increased symbol energy and reduced data rate.  
In this presentation, we introduce a novel chaos based wideband 
communication that has a better performance compared to conventional 
communication systems. The developed scheme relies on ergodic 
properties of the underlying chaotic system for signal demodulation. 
It is inherently simple and can be implemented using simple monolithic 
circuits. System complexity is further reduced since the proposed 
scheme is basically non-coherent which eliminates the synchronization 
procedure. In addition, the developed scheme has a novel multipath 
mitigation technique, which has low implementation complexity and 
improved performance. Using theoretical and simulation analysis, 
it was shown that the developed system could achieve a better 
performance over conventional communication system.

	The above-mentioned advantages of the proposed ECPM scheme 
have motivated further investigation into practical implementation 
of a ECPM Transceiver for wideband applications. The basic definition 
of the digital ECPM scheme calls for an implementation in the digital 
domain. However, a digital transceiver suffers from limitations on 
supportable data rate, higher power consumption and increased cost of 
implementation. Hence, there is a need for analog transceiver design. 
A possible solution to an analog transceiver design lies in the use of 
chaos signal generated by wideband continuous-time dynamical systems 
such as the Colpitts oscillator and additional tuning circuits to make 
the mean value of the resulting chaos signal monotonic with a control 
parameter. The limitation on the data rate is relaxed since the 
Colpitts oscillator can generate chaos with a high bandwidth (300MHz~1GHz). 
In addition, the elimination of A/D and D/A allows for considerable power 
savings. The proposed approach in implementing the ECPM scheme in analog 
domain has been successfully verified through simulations in CircuitMaker 
2000. The current design relies on the use of just two Opamps, two 
comparators, along with a few passive components, which is very suitable 
for both breadboard implementation and integration. In addition, a 
digital design for the ECPM Transceiver in VHDL has also been simulated 
using nclaunch and ncsim tools and verified for functionality. 
It is currently under synthesis using a Stratix DSP Development 
Kit form Altera.