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Interference and delay are considered as the main reasons limiting the capacity and increasing the new call blocking probability in the cellular systems. The Probability of handover failure is considered a common criterion for performance evaluation of handovers in cellular systems. In this paper we discuss and analyze cognitive radio handover managements based on social agent technology in cellular...
This paper investigates the adjacent channel interference (ACI) resistance of a multi-Gbps single carrier wireless personal area network (WPAN) operating in the 60 GHz millimeter-wave band. The significance of performance degradation due to ACI is investigated corresponding to varying factors such as types of modulation and radio frequency (RF) hardware impairments. The level of modulation scheme...
The novel frequency rotation techniques for suppressing the path interference and increasing the frequency diversity gain are proposed in uplink IFDMA system. In IFDMA, the path interference in multipath fading channel and the reduction of frequency diversity gain degrades the error rate performance, especially more significantly as the number of simultaneous access users becomes large. For suppressing...
UMTS has been designed as the next platform for mobile mass market communication. After a slow start, the usage of UMTS in terms of subscribers and volume is picking up momentum. Following the initial coverage-driven phase, network capacity is moving into focus. During network planning and optimization, cell capacity can be improved by explicitly designing for minimal interference. This article introduces...
We present 60 GHz OFDM hardware demonstrators developed so far and outline design considerations for future developments. OFDM schemes have been developed to combat multi-path interferences in indoor wireless environments and further optimized for multi-gigabit data transmission in 60 GHz-band. RF and IF analogues front-ends (AFEs) have been developed with high-speed SiGe BiCMOS technologies. Future...
The increasing demand for radio spectrum along with inefficient usage of the licensed bands has led the regulatory bodies to consider opening up the under-utilized licensed frequency bands for dynamic access by unlicensed users. Such dynamic spectrum access is envisioned to resolve the spectrum scarcity by allowing unlicensed users to opportunistically utilize the white spaces across the licensed...
In an OFDM system, known symbols referred to as pilot are transmitted across the time-frequency plane for the receiving device to estimate the channelpsilas time-frequency response in order to perform coherent demodulation of data symbols. The placement of these pilot symbols largely falls into two categories, namely, the regular and irregular patterns. Inspired by synchronization techniques used...
In this paper we develop a cellular cognitive radio network based on MC-CDMA, which is able to coexist with a number of legacy RANs in a shared band. Using the simple-to-obtain knowledge of RF environment, namely the bandwidth and frequency location of each legacy system, the cognitive MC-CDMA transmitter mitigates the interference in the corresponding receivers by adaptive transmission. We will develop...
The Internet of Things, emerging pervasive and sensor networks are low data-rate wireless networks with, a priori, no specific topology and no fixed infrastructure. Their primary requirements are twofold: first, low power consumption and, due to environmental concerns, low emitted power. Second, robustness to poor propagation environments and multi-user interference. Impulse-radio ultra-wide band...
Due to small sideband power leakage, filter bank multicarrier techniques are considered as interesting alternatives to traditional OFDMs for spectrum pooling cognitive radio. In this paper, we propose an oversampled filter bank multicarrier system for cognitive radio. The increased spacing between adjacent subcarriers in the oversampled filter bank multicarrier system largely reduce the intercarrier...
Coordinating the reception and transmission of signals across spatially distributed base stations has been shown to improve sum-rate performance by mitigating the effects of intercell interference in Multiple-Input-Multiple-Output (MIMO) cellular networks. Relying on recent results on the freeness of certain non-Gaussian random matrices, we provide an information theoretic analysis of cooperative...
Recently, a multiuser MIMO system has attracted much attention. In the downlink of the multiuser MIMO system, since the base station simultaneously transmits signals to terminals, there is inter-user interference (IUI) at each terminal. Block diagonalization, which can achieve perfect IUI suppression, has been extensively studied to solve the issue. However, with the scheme we cannot obtain extra...
In this paper we analyze low complexity turbo equalization that combines interference canceling and soft-input soft-output (SISO) decoding. We derive a new, exact MMSE solution for the equalization part taking into account the cross-correlation between the linear equalizer output and the soft decisions in the turbo equalization feedback loop as well as the auto-correlation function of the decoder...
In this paper, we studied the method that improves the downlink performance of cellular relay system in multiple-cell environment by using cognitive radio. When relay stations in the network have spectrum agility, they can establish downlink channels which are orthogonal to downlink of base station. In this way, interference between base station and relay station can be reduced and spectral resource...
In this paper, we present an effective phase precoding diversity scheme to mitigate intersymbol interference from multiple transmissions in hybrid automatic repeat request (HARQ) protocols over slowly time varying frequency-selective channels. For each HARQ transmission, only the phases of modulated symbols are changed according to a periodic pattern. This diversity scheme results in a spectrum thinning...
Multi-carrier Modulation (MCM) and especially Orthogonal Frequency Division Multiplexing (OFDM) are currently used in many radio transmission standards. Among these modulations, OFDM/OQAM is an interesting alternative to OFDM. However, a simple one-tap Zero Forcing (ZF) equalization of OFDM/OQAM modulation may cause a performance floor problem, while the transmission meets a requirement of high order...
The stack algorithm is a promising tree-search algorithm with relatively low computation complexity for multi-input multi-output (MIMO) systems. Recent researches show that it obtains low detection complexity at the price of performance degradation. To achieve a better compromise between computational complexity and detection performance, a sphere constraint stack detection algorithm (SC-Stack) is...
In this work we present a demonstrator for coherent linear amplify-and-forward (AF) relaying. Two source/destination pairs communicate with the help of three half-duplex relays in a two-hop manner. We implemented a coherent gain allocation scheme that suppresses inter-user interference at each destination and does not require a global phase reference at the relays. In order to assess the performance...
A continuously increasing demand for higher spectral efficiencies in mobile communications will require next generation cellular systems to employ a very dense reuse of spectrum in combination with smart interference mitigation or cancellation schemes. Recent publications have revealed a large potential in terms of spectral efficiency and system fairness of multi-cell cooperative schemes, where e...
In this paper, we propose a low complexity MIMO detection method for double space-time block (D-STBC) coded OFDM system. The proposed MIMO detector involves two step decoding process to efficiently de-correlate spatially-multiplexed / space-time-coded signals. The proposed MIMO detector collects feedback information from interfering spatial domain. Then, interference cancellation is applied once to...
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