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Vehicular ad hoc networks (VANETs) drive new challenging research issues at different layers of the protocol pillar, from physical to application. Focusing on the medium access layer, one of the most promising and not yet fully explored option is the adoption of orthogonal frequency division multiple access (OFDMA). Besides guaranteeing high spectral efficiency and effective resource allocation, it...
Several studies have revealed that OFDM is outperformed in several areas by the filter bank based multicarrier (FBMC) modulation thanks to pulse shaping techniques. Nevertheless, the combination of FBMC with multi-antenna architectures is nontrivial. Aiming at making progress towards this direction we study MIMO precoding techniques for the MISO broadcast channel (MISO-BC). Due to its superior performance...
A major constraint in deployments of resource-limited networks is the energy consumption related to the battery lifetime of the network nodes. To this end, power efficient digital modulation techniques such as On-Off keying (OOK) are highly attractive. In this paper, a novel complete probabilistic description of the Direct Sequence — Coded Division Multiple Access (DS-CDMA) system with random signatures...
In a typical cognitive radio network (CRN), secondary users can only access the channel when they do not harmfully interfere with the primary users. Therefore, an accurate estimation or prediction of interference from secondary users to primary users is essential. In this paper, we tackle the problem of interference estimation in a channel in presence of one PU and multiple SUs. We solve this problem...
Power line communication (PLC) systems are one of the most popular technologies for smart grids due to their cost efficiency. This paper presents bit error rate (BER) performance of traditional interleave-division multiple access (IDMA) systems over broadband (BB) indoor PLC channels. The BB PLC channels considered in this paper are proposed by Cañete and others. Subsequently, simulation results are...
In this work, a novel particle swarm optimization (PSO) assisted Joint Channel Estimation and Partial Parallel Interference Cancellation (PSO-JCEPPIC) detector is adopted for multiuser Multiple-Input Multiple-Output /Space Division Multiple Access (MIMO-SDMA) Orthogonal Frequency Division Multiplexing (OFDM) systems. The proposed PSO-PPIC scheme tries to reduce the cancellation error in Conventional...
This paper studies detecting matrices in random dense and sparse Code Division Multiple Access (CDMA) systems. Detecting matrices were originally introduced in the coin weighing problem. Such matrices can be used in CDMA systems in over-loaded scheme where the number of users is greater than the number of chips. We drive some conditions in the large system limit for binary and bipolar random CDMA...
Carrier Sense Multiple Access protocols are the most widely used methods for collision avoidance in Wireless Sensor Networks (WSNs). These protocols are prone to suffer from the hidden and exposed terminal problems, which lead to inefficiency and unfairness in the communications. Both problems are particularly significant in applications with massive traffic requirements, commonly found in WSNs. The...
Quick growth in the amount of wireless subscribers coupled with the necessity to provide desired level of user experience for broadband, stimulates mobile operators to improve the efficiency of their limited air resources by using different technologies. This paper discusses the study on Single Frequency Network (SFN) based multipoint-to-point transmission scheme as a possible way to improve the usage...
This paper proposes an enhancement to the performance of a Direct Sequence Code Division Multiple Access (DS-CDMA) system by utilizing an adaptive filter in the presence of different jamming techniques. In order to combat the impact of such jamming, the adaptive filter utilizes three adaptive algorithms which are the Variable Step-Size Affine Projection (VSS-APA) algorithm, the Generalized Normalized...
Radio networks using array processing or Single-Input Multiple-Output (SIMO); Multiple-Input Multiple-Output (MIMO) with and without Channel State Information (CSI) feedback; and Multi-User Detection (MUD) were all compared to baseline Single-Input Single-Output (SISO) networks to estimate possible improvements to area-spectral-efficiency. Two scenarios were investigated, a Mobile Ad-Hoc Network (MANET)...
The central issue in direct-sequence code-division multiple-access (DS-CDMA) ad hoc networks is the prevention of a near-far problem. This paper considers two types of guard zones that may be used to control the near-far problem: a fundamental exclusion zone and an additional CSMA guard zone that may be established by the carrier-sense multiple-access (CSMA) protocol. In the exclusion zone, no mobiles...
Retrieval process of original symbols of a spread spectrum based communication system is tried to be improved by Gradient Algorithm (GA) and Blind Source Separation (BSS) principles. Two simple schemes, based on two energy functions are presented. Time correlation properties of the channel are used as advantages in developing the filter coefficients for the receiver. Direct Sequence - Code Division...
The wavelength-time modified double weight (MDW) optical division multiple access (OCDMA) scheme to reduce multiple access interference (MAI) and compensate bit error rate (BER) and phase-induced intensity noise (PIIN) in incoherent OCDMA systems is proposed. The analysis permits thorough understanding of PIIN, shot and thermal noises effect on 2-Dimensional (2-D) MDW OCDMA system performance. PIIN...
Multiple-Input Multiple-Output (MIMO) systems are capable of simultaneously capturing more than one packet. Such capability is known as Multi-Packet Reception (MPR), which is new way to improve performance of Ad Hoc Networks. In order to effectively enhance throughput of Ad Hoc Networks, a novel MAC protocol (MIMO-MAC) with MIMO links that takes into account MPR is proposed. It can receive more than...
This paper proposes an autonomous grouping in subsystem band for spectrum sharing with the aid of selfish dynamic spectrum control (S-DSC) for asynchronous private wireless networks. When S-DSC, in which each transmitter maps its original spectrum to spectrum with higher channel gain of a system band in a selfish manner, is employed in each link of a shared band, and their transmission timing is asynchronous,...
This paper presents a flexible Programmable Gain Amplifier (PGA) with DC Offset Cancellation (DOC) for reconfigurable direct-conversion receiver. This circuit is designed for reconfiguration of GPS/Galileo and WCDMA dual mode receiver in order to reduce power consumption, because it consumes different current and provides different bandwidths in different working conditions. This PGA consists of one-stage...
In the context of green technology, we propose in this work1 a new channel access method for wireless systems to reduce energy consumption. This method uses the concept of Cross Layer Design and cognitive radio blind sensing techniques to formulate a unified framework for congestion and fading analysis as well as Backoff exponent computation. It allows to acquire from the physical layer the information...
A method to traceably calibrate Wideband Code Division Multiple Access (WCDMA) Error Vector Magnitude (EVM) contributions of a source or receiver is described using a Real-Time Digital Oscilloscope as the reference receiver. The results and uncertainties are presented for a receiver calibrated using four WCDMA sources from different manufacturers. The weighted mean EVM of the receiver at 900 MHz is...
Code division multiple access (CDMA) systems are being counted to provide the necessary infrastructure to implement future 3G systems. The CDMA is uniquely featured by its spread spectrum (a random) process employing a pseudo random noise (PN) sequence, thus it is called the spread spectrum multiple access (SSMA). The CDMA can eliminate the data transfer latency variations by sharing the data communication...
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