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Ongoing developments of the LTE standard will allow for device-to-device (D2D) communications, which will enable direct connection of user equipments (UEs). Since UEs are becoming increasingly more powerful both in computational power and in the role they have in the network, a concrete threat is that a hand-held D2D-enabled device could be deployed to jam intentionally ongoing transmissions of other...
In this paper we present the concept of cognitive satellite terrestrial radios (CSTR) for hybrid satellite-terrestrial systems (HSTS). The cognitive radio (CR) technology is being motivated by the radio regulatory bodies for efficient utilization of the radio spectrum. The future satellite ground terminals therefore need to integrate and co-exist with the spectrally crowded terrestrial wireless systems...
This paper details the current work status of the ETSI Reconfigurable Radio Systems (RRS) Technical Committee (TC) and gives an outlook on the future evolution. While previous publications have presented an overview of ETSI RRS' main working axes related to i) Cognitive Radio System Aspects, ii) Radio Equipment Architecture (including a Cognitive Pilot Channel (CPC) proposal and a Functional Architecture...
In this paper we consider cooperative spectrum sensing to detect incumbent spectrum users (ISU) in cognitive radio (CR) networks. We propose a time-divisional cooperative periodic spectrum sensing (TD-CPSS) technique and analyze the detection performance based on the blind energy based detection scheme. The CR detects the presence of the ISU by means of TD-CPSS and opportunistically uses the spectrum...
In this paper we consider the spectrum sensing performance and requirements for detecting legacy users (LU) in cognitive radios (CR) with periodic scanning. The performance and requirements are studied based on the temporal spectral occupancy statistics of the LU and the sensing signal to noise ratio levels in order to achieve a certain level of detection probability. We model the temporal statistics...
In this paper we present the spectrum sensing performance for detecting the IEEE 802.11n Wi-Fi terminals for ultrawideband (UWB) based cognitive radio (CR) systems. The 802.11 n WiFi system lies in the 5 GHz un-licensed frequency band and is subjected to interferences from the UWB transmissions. The UWB based CR terminals perform secondary communications by opportunistically utilizing the available...
Most critical component of the cognitive radio paradigm is spectrum sensing and accordingly, detection of primary users. Recently proposed cooperative spectrum sensing methods do not consider errors occurring during the transmission of local cognitive radio decisions to the cognitive base station. However, perfect communication is clearly not the case in realistic cooperative spectrum sensing scenarios...
In this paper we present a time divisional and a time-frequency divisional cooperative spectrum sensing technique suitable for cognitive radio (CR) networks. The two methods are well suited for very high bandwidth CR networks, such as UWB networks, where the individual nodes need to scan a wide range of spectrum which is a time consuming process. With the time divisional and the time-frequency divisional...
Cooperative spectrum sensing for cognitive radio networks is recently being studied to simultaneously minimize uncertainty in primary user detection and solve hidden terminal problem. Sensing wideband spectrum is another challenging task for a single cognitive radio due to large sensing time required. In this paper, we introduce a technique to tackle both wideband and cooperative spectrum sensing...
In this paper we consider cooperative localization and tracking of primary users (PU) in a cognitive radio network using Bayesian techniques. We use particle filtering methods to track the location of a PU in the network using cooperative localization techniques and present some results for noisy measurements. The cognitive radio (CR) nodes estimate the information related to the geographical position...
A hyperbolic arctan based digital tanlock loop (D-TLL) operating with complex signals at base-band or intermediate frequencies in high Doppler environments is treated here. The arctan based loop, known as the tanlock loop (TLL), is used in software defined radio architectures for frequency acquisition and tracking. The hyperbolic nonlinearity intentionally introduced within the phase detector extends...
In this paper, we analyze the performance of a non-data aided near maximum likelihood (NDA-NML) estimator for symbol timing recovery in binary digital communications. The analysis of the estimator is performed for an additive noise only channel and the simulation results are extended to a flat fading channel. The probability distribution of the timing estimates is derived, presented and compared with...
Cognitive radio has emerged as an innovative approach able to cope with the spectral limitations. Cognitive radio networks rely on detecting whether a particular segment of the radio spectrum is currently in use and to exploit the temporarily unused spectrum rapidly without interfering with the transmissions of other users. Thus, one of the most important and critical components of the cognitive radio...
The high demand in providing broadband mobile services for 3G+ systems motivates researchers and engineers to design, implement and test highly efficient and scalable high speed communication systems. With similar motivations, in this paper, we present a high speed base-band processing unit implemented in software targeting high speed hardware devices for advanced communication receiver design. The...
In this paper we present a Digital Phase Locked Loop (D-PLL), based on an arctan phase detector for complex signals, implemented on a Field Programmable Gate Array (FPGA) together with its performance analysis. The work is motivated by the requirement of signal synchronisation in Software Defined Radios (SDR) for high speed communication receivers. The theoretical model for the D-PLL and its corresponding...
Nonlinear system design is a common practice in communication engineering for improved performances in advanced receivers. Here we look into a logarithmic based nonlinear loop for a second order arctan based digital phase locked loop (D-PLL) for frequency synchronisation. The steady state and the acquisition performances of the loop are analyzed. The logarithmic nonlinearity is intentionally introduced...
In this paper, we investigate the SNR and BER performance of an OFDM system under imperfect synchronization which is caused due to noise, Doppler shift and frequency selective fades in the channel. An analytical expression for BER is derived assuming BPSK modulation and numerical results are presented to show the effect and extent of the above channel impairments in OFDM downlinks.
The presence of frequency offsets in the received signal for an orthogonal frequency division multiplexing (OFDM) based multicarrier system leads to inter carrier interferences (ICI). The degradation in the performance of an OFDM system is severe when there is frequency error, which is caused by the loss of orthogonality in the received carrier frequencies. Here, we look into the correction of frequency...
The treatment of phase locked loops (PLL) has been heavily looked into over the past several decades on its performances and analysis, and is a very old topic. However the usage of it has never been reduced with the rapid evolvement of various open loop and closed loop systems. In this paper we analyse the performance of an arctan based digital phase locked loop (DPLL) with a hyperbolic nonlinearity...
A statistical analysis of the single-delay multiplication based frequency estimator is treated here. The single-delay multiplication frequency estimator for complex single sinusoid signals is a phase averaged estimator, which is similar to the Kay's estimator. Here we provide a study on the statistical distribution of the frequency estimates made by the estimator, and verify the analytical results...
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