Cognitive Radio withUltra-Wide Bandwidth Location-capable Nodes
Davide Dardari, Riccardo Minutolo · 2007
In thispaperwe introduce thebasicconcepts underlying Cognitive Radio(CR)asanemerging approach fora moreflexible usageoftheprecious radiospectrum resources. Afterthedefinition ofa possible scenario, we discuss Ultra- WideBandwidth (UWB)technology asoneofthetransmission techniques suitable forimplementing aCR system. We thenre- viewsomerecent results concerning interference andcoexistence betweennarrowband (NB)andUWB communication systems. Finally, weshowthegreatpotential oftheUWB technology in adapting thetransmitted spectrum tocounteract NB interference andatthesametimetoguarantee lowspectral emissions over existing NB communications. I.INTRODUCTION Theformidable development ofwireless communication systems hasledtoaprogressive definition ofrules forac- cessing totheradio spectrum, posing several tasks intheor- ganization andsharing strategies forsuchaprecious resource. Traditionally theradio spectrum canbedivided intwocat- egories: licensed andunlicensed bands. Inunlicensed bands, users canfreely transmit. However, theamountofinterference introduced byatransmission system operating inthose bands mustbelimited inorder toavoid impairments toother users' communications. Thus, somelimitations onthepowerspectral density areusually introduced. Nevertheless, atoolarge num- berofusers transmitting onthesameunlicensed band(inthe samearea), canberesponsible ofanhighoverall aggregated interference, sufficient toprevent communications. Licensed services areinstead designed toefficiently utilize thespectrum, withtheaimofguaranteing arequired quality ofservice (QoS) tousers. Thereisanemerging communications concept knownas Cognitive Radio(CR)thatprovides a moreefficient and flexible usageofthespectrum. Thebasic ideaisthat aCR terminal cansenseitsenvironment andlocation andthen adapt someofitsfeatures (aspower, frequency, modulation, etc.) allowing thedynamic reuseoftheavailable spectrum (1)-(6). Thiscould, intheory, leadtoa multidimensional reuse ofspectrum inspace, frequency andtime, exceeding the severe limitations inthespectrum andbandwidth allocations thathaveslowed downbroadband wireless communications development.