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New VLC based wireless backhaul technologies are studied for high data-rate access. In this paper, we summarize the latest progress on VLC systems including pre-/post-equalization hardware, electrical differential receivers, bitloading OFDM, and MRC, which supporting VLC Gigabit capacity over long-range free-space transmission.
The ranging and positioning accuracy of an impulse radio (IR) 60 GHz system is investigated. The corresponding Cramér-Rao lower bound (CRLB) over an additive white Gaussian noise (AWGN) channel is analyzed. The signal parameters which may affect the accuracy are examined. Performance results over AWGN and indoor residential channels are presented. In particular, the indoor residential channel models...
This paper discusses the signal to noise ratio (SNR) improvement at the antenna receiver system output using non-Foster matching. High mismatch loss in an antenna reduces the external noise power below the internal noise floor which results in a lower SNR than expected appearing at the input of the receiver. Non-Foster matching can minimize the mismatch loss but also adds its own noise to the receiver...
With the increasing bandwidth of communication signals, the challenges on the feedback path used for digital predistortion (DPD) of power amplifiers are getting significantly stringent. A subband approach has been recently proposed by the authors in order to relax the design constraints on the feedback path ADC. This paper presents a new step toward a practical implementation of the concept with LTE...
Owing to the decline of recognition rate of speech recognition system in noisy environments. In signal space, the speech enhancement algorithm which combines the Priori Signal-to-Noise Ratio (SNR) with Auditory Masking Effect can effectively remove the noise of the speech signal. In feature space, improved non-uniform spectral perceptual compression feature extraction algorithm can effectively compress...
High expectations are tied to the millimeter wave (mmWave) technology and device to device (D2D) communications to leverage the capacity and the spectrum efficiency in 5th generation (5G) systems. In this context, we carry out a resource allocation scheme designed to enable D2D communications underlay cellular network in the E-band. The proposed scheme aims to enhance the system throughput and alleviate...
In this paper we explore uplink connection performances in a LTE Heterogeneous Network (HetNet). We perform a set of experiments in two different LTE HetNet configurations and focus on uplink coverage and capacity within an office building. The current results are obtained in single user equipment (UE) environment but the recommendation is valid also for multi-UE environment. The analysis is based...
Emerging wireless network and mobile computing enable user-generated mobile video streaming to be shared and consumed in a novel manner. The feature of shared wireless medium, multihop data forwarding, and time-varying channel quality seriously limits the quality of experience (QoE), partially owing to the lack of mechanisms for effectively utilizing multi-rate channel resources. However, the existing...
Energy efficiency (EE) and spectral efficiency (SE) have become the key performance indicators for wireless communication systems. In this paper, EE and SE, efficiency metrics, of a digital communication system with M-QAM modulation technique are introduced. The upper bounds on the efficiency metrics over generalized-K fading channel are derived in closed form. These efficiency metrics are analyzed...
The huge increase of high bandwidth demanding applications like interactive gaming, video streaming etc. over wireless channel and exponential growth of average mobile user population raise need of higher spectral density and cell capacity. The 4th Generation (4G) wireless network standardized as Long Term Evolution (LTE) utilizes advantages Orthogonal Frequency Division Multiple Access (OFDMA), where...
Device-to-Device (D2D) communication is a promising technology in the next generation (5G) cellular network as it can significantly improve the system performance by leveraging the proximity of communications and reusing cellular frequency resources. However, this benefit may not be fully exploited if the co-channel interference among D2D users (DUE) and cellular users (CUE) is not properly tackled...
A hybrid scheme of femtocell and distributed antenna system (DAS) is proposed that utilizes a subband dedicatedly assigned to each of multiple femtocells for system capacity gain and a subband shared for DAS simulcasting for cell-edge interference reduction. This paper presents a fundamental downlink performance evaluation and analysis of the in-building wireless system. Proportional fair (PF) scheduling...
Cooperative communication is a promising technique, which can greatly improve the performance and extend the coverage of cellular networks. In this paper, the resource allocation problem is investigated for multi-carrier amplify-and-forward (AF) relay assisted multi-access networks with multiple users and subcarriers. The joint relay selection and subcarrier allocation problem is formulated as a combinatorial...
This paper introduces an ultra-low voltage open loop VCO-based ADC with background calibration for ultra-low power applications. A novel calibration scheme is proposed to calibrate the nonlinear voltage-to-frequency tuning curve of the VCO. A replica VCO is used to compute the correction coefficients and the corrected values are stored in a lookup table. The proposed calibration method is at least...
A time-modulated antenna array (TMAA) provides similar beamforming capability as a phased antenna array. The main difference is generation of sideband components. Such components limit allowable bandwidth of digitally modulated signals transmitted over the TMAA. Nevertheless, the time-modulation allows spatial filtration of mutually interfering signals. In this paper two experimental studies are presented...
Radar signal design in spectrally dense environments is a very challenging and topical problem. This paper deals with the synthesis of waveforms optimizing radar performance while satisfying multiple spectral compatibility constraints. Unlike some counterparts available in the open literature, a specific control on the interference energy radiated on each shared bandwidth is enforced. To tackle the...
It has been well-established that Device-to-device (D2D) communication underlying cellular networks can improve network radio resource efficiency and provide higher transmission data rates to devices in proximity. In this work, we propose a cooperative system model. Three relay selection schemes are compared under such model. The Distance-based Relay Selection considers only distance for optimal relay...
In this paper, we propose a novel resource allocation (RA) scheme based on interference minimization (IM) for cognitive radio networks (CRN). In the approach, we focus on an efficient scheme of subchannels assignment, power allocation and access control for the orthogonal frequency division multiple access (OFDMA)-based secondary users (SUs), accessing licensed spectrums of primary users (PUs) with...
A newer technique in the field of direction finding (DF) is the use of time modulated array (TMA) switching harmonics to detect angle of arrival. A switch is used to introduce harmonics to an incoming signal, which are measured and compared to determine angle of arrival (AoA). The work done on this technique has been mostly theoretical and effects such as signal modulation, symbol rate and signal...
Inter-cell interference (ICI) is one of the most important problems facing the planning of cellular networks which depends on Orthogonal Frequency-Division Multiple Access (OFDMA). Mainly, it affects the throughput performance of the cellular system. Many schemes are adopted to mitigate ICI. This paper deals with the co-channel interference (CCI) coordination and avoidance method defined as Fractional...
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