Investigations on construction of Walsh hadamard like codes and their Applications in a DS CDMA system and Underlay cognitive radio system

Abstract

In recent years efficient utilization of radio frequency spectrum newlineresources has received much attention This necessitates the need for highly newlineflexible and intelligent terminals that can support different standards in different newlinefrequency bands Software Defined Radio SDR is a technology that aims at newlinedesigning a reconfigurable hardware platform which can support multiple air newlineinterfaces such as Code Division Multiple Access CDMA Orthogonal newlineFrequency Division Multiplexing OFDM and Multi Carrier CDMA newline MC CDMA This is achieved by a change in the software without modifying newlinethe hardware Cognitive Radio CR an enhancement of SDR is an emerging newlinetechnology that enables flexible and efficient utilization of spectrum resources by newlineallowing unlicensed Secondary Users SU to share the spectrum of licensed newlinePrimary User PU by using dynamic spectrum allocation without degrading the newlineQuality of Service at the PU end The spectrum sharing approach based on newlinehierarchical access model can be classified into two categories namely underlay newlineapproach and overlay approach In an overlay system SU cancels the newlineinterference of PU by sensing PU s message whereas in the underlay approach newlinethere is no sharing of information between PU and SU and the spectrum newlineresources are shared concurrently newline newline