Citation Context

...ion wireless networks. Within the Cognitive Radio (CR) context [3], fixed spectrum allocation policy could be replaced by innovative forms of dynamic use, referred to as Dynamic Spectrum Access (DSA) =-=[4]-=-. Among the DSA options it is of great interest the so-called Hierarchical Access model (HAM) [5], according to which an unlicensed secondary CR user (SU) can access the spectrum licensed to a primary...

Citation Context

...licensed secondary CR user (SU) can access the spectrum licensed to a primary user (PU), provided that harmful interference is avoided. In the literature, mainly two HAM approaches have been proposed =-=[6]-=-: “Spectrum Underlay”, also called horizontal sharing since based on spreading signals transmitted by SUs, for example by means of Ultra Wide Band (UWB) techniques; “Spectrum Overlay”, also known as O...

Citation Context

...lt does not comply with the general belief that the available spectrum resources are not sufficient to meet the needs of the next generation wireless networks. Within the Cognitive Radio (CR) context =-=[3]-=-, fixed spectrum allocation policy could be replaced by innovative forms of dynamic use, referred to as Dynamic Spectrum Access (DSA) [4]. Among the DSA options it is of great interest the so-called H...

Citation Context

... considering the AND decision rule, that is a PU is considered idle only if an available band is detected out of all sensing data, the detection probability associated to the CCN decision is given by =-=[14]-=-: PD(k) = 1− (1− pd)k+1 , k ≥ 0 (11) where k is the number of sensing data collected from the single CCN, which corresponds to the number of SUs within its coverage, while pd is the detection probabil...

Citation Context

...mary systems. Keywords - Cognitive Radio; Opportunistic Spectrum Access; Ultra-wideband; Control Channel. I. INTRODUCTION A lot of experimental studies prove the inefficient use of the radio spectrum =-=[1]-=-, [2]. This result does not comply with the general belief that the available spectrum resources are not sufficient to meet the needs of the next generation wireless networks. Within the Cognitive Rad...

Citation Context

...or realizing OSA among SUs. More in general, a coordination among SUs is needed to improve the performance in terms of detection probability of PUs by means of cooperative spectrum sensing techniques =-=[8]-=-. Such methods assume particular relevance for detecting the spectrum occupancy when wireless channels are affected by shadow fading [9]. For these reasons the CC plays a fundametal role in OSA networ...

Citation Context

...lity of PUs by means of cooperative spectrum sensing techniques [8]. Such methods assume particular relevance for detecting the spectrum occupancy when wireless channels are affected by shadow fading =-=[9]-=-. For these reasons the CC plays a fundametal role in OSA networks. Nevertheless, typically an interference-free CC is unrealistically assumed in the literature. Indeed, the allocation of a separate f...

Citation Context

...SD of DS-UWB devices and the ratio between the bandwidths of PUs and UWB SUs, respectively. This latter parameter is defined since the flat spectrum approximation, valid for narrowband PU, is assumed =-=[13]-=-. In (7) Ith is the allowable interference threshold. It is directly derived from the Signal-to-Noise Ratio (SNR) degradation, r, expressed as [13]: r = η + IUWB η (9) This parameter measures the impa...

Citation Context

...ssumed in the literature. Indeed, the allocation of a separate fixed CC for exchanging information on spectrum opportunities is very likely unavailable on PU networks with fast varying spectrum usage =-=[10]-=-, and anyway it can entail waste of spectrum resources only for signalling data. An interesting promising solution is represented by the usage of an underlay UWB channel for sharing spectrum sensing i...

Citation Context

...systems. Keywords - Cognitive Radio; Opportunistic Spectrum Access; Ultra-wideband; Control Channel. I. INTRODUCTION A lot of experimental studies prove the inefficient use of the radio spectrum [1], =-=[2]-=-. This result does not comply with the general belief that the available spectrum resources are not sufficient to meet the needs of the next generation wireless networks. Within the Cognitive Radio (C...

Citation Context

...waste of spectrum resources only for signalling data. An interesting promising solution is represented by the usage of an underlay UWB channel for sharing spectrum sensing information, as proposed in =-=[11]-=-. Usually signalling channels require low bit-rates and this feature permits to extend the UWB radio coverage even for low transmission power. This satisfies the double target of ensuring as wide sign...

Citation Context

...icy could be replaced by innovative forms of dynamic use, referred to as Dynamic Spectrum Access (DSA) [4]. Among the DSA options it is of great interest the so-called Hierarchical Access model (HAM) =-=[5]-=-, according to which an unlicensed secondary CR user (SU) can access the spectrum licensed to a primary user (PU), provided that harmful interference is avoided. In the literature, mainly two HAM appr...