Hybrid underlay/overlay cognitive radio system with hierarchical modulation in the presence of channel estimation error

Dynamic interference‐limited relay sharing in cognitive radio networks by using hierarchical modulation

“…For average BER, we need to integrate (22) and 23 Since the integrals for the expectation operations in (24) and (25) cannot be calculated analytically, we provide high-SNR approximate expressions in Section 5 to calculate these error probabilities.…”

“…In [21], we utilised HM in radio cognitive context in order to improve secondary user's (SU's) performance and compensate the degradation of primary users' (PUs') performance and even improve it by allowing the existing relay to send information data of both PU and SU. In addition, in [22] we considered a scenario in which the information sender has two types of data with two different levels of priority; i.e. the less important bits mapped onto the second layer and the most important ones mapped onto the first layer of constellation.…”

“…Typically in a CR system, transmission happens in one of the underlay or overlay sharing methods or a combination of which that is called the hybrid underlay/overlay spectrum sharing [22,24,25]. In the underlay method, the SU utilises the licensed spectrum with a proper level of power, in order to keep the level of interference imposed to the PU under a given threshold that is tolerable by it.…”

BER performance of an MRT‐HQAM system over Rayleigh fading channels with channel estimation errors and feedback delay

“…In general, ICSI contains channel estimation error (CEE) and feedback delay (FD). The effects of the CEE on systems employing HM have been studied in [6–8]. In [6,7], the impact of the CEE on the BER performance of the HM systems with receiver diversity or MRC was studied.…”

Sub-nyquist sampling techniques for cognitive radio applications

“…4.1 Introductionthe trade-off between the sensing duration against the SU's transmission throughput performance is a convex problem. More recent studies on CR's transmission performance focus on the influences of the channel state information[98,99] and energy efficiency[100].…”