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In this paper, we present a novel hybrid orthogonal frequency division multiplexing (H-OFDM) for visible light communication (VLC). H-OFDM uses a combination of DC-bias optical OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM (ACO-OFDM) techniques. In this hybrid technique, the absolute value of bipolar DCOOFDM signal is used to carry amplitude information in the first block, while the ACO-OFDM...
Aiming at allocating resources to eliminate inter-femtocell collision interference, a spectrum allocation strategy SAC (spectrum allocation based on clustering) for OFDMA (orthogonal frequency division multiple access) downlink femtocell networks was proposed. In SAC, a cluster was taken as the unit for frequency reuse among femtocells and the FGW (femto gateway) was responsible for clustering and...
Heterogenous networks (HetNets) consisting of both macrocells and small cells are capable of improving system capacity and user throughput significantly. However, the deployment of various small cells may result in frequent handover between the macrocell and small cells, and between small cells, and the possible handover failure (HoF) may severely affect system performance and user quality of service...
In the frequency-limited cellular networks, the underlaying Device-to-Device (D2D) communications is an efficient way to enhance the user access probability and network capacity performance. To satisfy the communication requirements for users in different network sizes, a cooperative transmission strategy based on multi-relay D2D communications is proposed. Specifically, to increase the serving users...
Assignment of Physical Cell Identity (PCI) is an important work in TD-LTE network optimization, and the reasonable PCI allocation helps to eliminate the interference and improve the quality of service of networks. In the practical large-scale TD-LTE networks, how to properly reuse PCIs among a large number of cells is challenging. In this paper, we propose a multiobjective optimization model for PCI...
In this paper, we investigate the combination of Orthogonal Frequency Division Multiplexing with Offset Quadrature Amplitude Modulation (OFDM/OQAM) with spread spectrum Code Division Multiple Access (CDMA) transmission scheme as an alternative to classical Multicarrier-CDMA (MC-CDMA) system over multipath fading channel. The performance of real CDMA-OFDM/ OQAM transmission system with Walsh Hadamard...
In Long Term Evolution (LTE) systems, some subcarriers at the borders of the allocated bandwidth are known as virtual subcarriers which are not used for data transmission. Conventional DFT-based channel estimation methods encounter performance degradation due to low SNR and the edge effect caused by virtual subcarriers. Adding virtual carrier frequency responses (VCFR) properly at receivers is proved...
In this paper, we consider a Generalized Joint Channel Network Coding (GJCNC) applied to Physical Layer Network Coding (PLNC) for Two Way Relay Channel (TWRC). For this purpose, two correlated sources A and B desire to exchange information with each other by the help of a relay R. PLNC allows the relay to decode the combined information of both sources from the superimposed information. A Low Density...
As the energy consumption of network has become an increasingly important issue, traffic grooming on Internet protocol over wavelength division multiplexing (IP-WDM) networks has been widely used for energy-efficient optical network. Traffic grooming can reduce the number of installed light paths and corresponding IP router line cards at the cost of traffic processing overhead. However, traditional...
Wireless Body Area Network (WBAN) is considered as a special type of WSN. It consists of low-power wireless sensor nodes, which are placed on or implanted in the body for continuous health monitoring. MAC protocol is responsible for conflict detection, processing, priority control, timeslot assignment, transmission order etc. So the design of MAC protocol plays an important role in the reliability...
A stochastic model for joint optimal congestion control and power allocation in multi-channel multi-radio wireless mesh networks is proposed. The design problem characterizes the stochastic traffic of the network data flows and the capacity of radio channels in multi-channel multi-radio wireless mesh networks as some random variables. The corresponding design problem is formulated as the stochastic...
In the existing distributed cooperative spectrum sensing schemes, cooperation based on consensus algorithms is a research hotspot. However, the existing methods haven't embodied the reliability difference among cognitive radio users, so there is an enormous scope to improve the accuracy. In this paper, we propose a weighted average consensus-based distributed compressive spectrum sensing (PE-WDCS)...
In this paper, we investigate the subcarrier allocation and power adjustment to maximize the sum data rate of the secondary users with limited interference to the primary users in OFDM-based cooperative cognitive networks. A fixed common relay is introduced to forward the data of the secondary users by adopting two-way amplify-and forward (AF) relay. By categorizing the subcarriers into 2 classes,...
In this paper, we investigate the problem of locating the indoor objects with the help of the received Wi-Fi signal strength fingerprints. Many Wi-Fi RSS based positioning techniques have been developed recently for indoor positioning purposes, but the positioning accuracy faces various challenges, including the high noise to signal ratio. In this paper, we consider two typical elements affecting...
The micro-Doppler effect on a flying spinning target, introduced by the rotation, would modulate the receiving signal with SFM (Sinusoidal Frequency Modulation), and we usually use some TF (Time-Frequency) analysis methods with complex calculation to estimate the frequency. As to the issue of the complexity of the classic TF method, a method based on the piecewise FFT was proposed in this paper. With...
The objective of the proposed work is to find the effects on the reading performance of 900 MHz radio frequency identification system (RFID) under the wireless interference. Experiments were carried out in full anechoic chamber avoiding the influence of wireless signal produced by the reflection. In order to simplify the analysis of the process of performance, single tone signal was selected as the...
A dual passbands filter with the function of varactor tuned is proposed in this paper, which has a wide stopband. Stepped impedance resonators (SIRS) are used at the filter. The varactor is loaded on the T-shaped resonators, while changing the bias voltage across the varactor, the second passband frequency is tuned from 1.56 GHz to 2.25 GHz; the first passband's center frequency is fixed at 1.02 GHz...
Cyclic Delay Diversity (CDD) is a simple approach to provide spatial diversity for Orthogonal Frequency Division Multiplexing (OFDM) system. CDD provides not only the multipath diversity without channel coding but also a sample receiver structure. Discrete Hartley transform (DHT) as a linear precoding based OFDM outperforms the OFDM based on discrete Fourier transform (DFT) for it intrinsic frequency...
Binary offset carrier (BOC) modulation signals have been widely adopted in global navigation satellite systems (GNSSs) such as Galileo and modernized global positioning system [1] [2]. Although this kind of modulation offers excellent performances, a main drawback of BOC modulation is that ambiguous acquisition and biased tracking for its multi-peak autocorrelation function (ACF). This article presents...
In this paper a new coding scheme is proposed to accomplish unequal error protection (UEP) for distributed rateless codes. This coding scheme can be applied when multi-sources symbols share a single relay and the relay has no knowledge about their importance levels. We design this coding scheme by encoding the symbols with a second LT process at the relay. UEP property is provided via several equal...
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