Azizollah Jamshidi - Academia.edu (original) (raw)

Papers by Azizollah Jamshidi

IEEE Communications Letters, 2007

Distributed spatial diversity systems utilize multiple communication nodes to create independent ... more Distributed spatial diversity systems utilize multiple communication nodes to create independent signal replicas that are combined at the destination. Practical diversity receivers often employ simple combining techniques especially if comparable performance to more complex optimum combining can be achieved. The performance of decode-and-forward relaying that uses selection combining is investigated. In particular, a closed- form expression for the outage probability

MILCOM 2009 - 2009 IEEE Military Communications Conference, 2009

ABSTRACT

Applied Soft Computing, 2016

Nowadays, the development of classification algorithms gives the ability to improve Automatic Mod... more Nowadays, the development of classification algorithms gives the ability to improve Automatic Modulation Recognition (AMR) effectively. This paper presents a novel modulation recognition algorithm based on clustering approach. Generally, we aim to distinguish multicarrier modulation OFDM from singlecarrier modulations. In this regard, two statistics of the amplitude of the received signal are calculated at the output of a quadrature mixer as key features. The extracted features of training data points are submitted to the clustering algorithm, then, centroids for single-carrier and multicarrier modulations are assessed. Afterwards, each point of testing dataset is dedicated to its nearest centroid based on Euclidian distance and the recognition is accomplished. Simulation results demonstrate that the algorithm is beneficial in a wide range from low to high SNRs.

The Journal of the Acoustical Society of Korea, 2013

Rcent measurements suggest the possibility of sharing spectrum among different parties subject to... more Rcent measurements suggest the possibility of sharing spectrum among different parties subject to interferenceprotection constraints. In order to enable access to an unused licensed spectrum, a secondary user has to monitor licensed bands and opportunistically transmit whenever no primary signal is detected. In this paper, we study spectrum-sharing between a primary licensee and a group of secondary users. The structure of an asymptotically optimum detector based on the measurements of all secondary users is derived and the effect of the quantization error in such a system is evaluated. The results show the superiority of the proposed detector to other schemes.

Molecular Communication via Diffusion (MCvD) is one of the most prominent approaches to interconn... more Molecular Communication via Diffusion (MCvD) is one of the most prominent approaches to interconnect the nanomachines which can do some simple communication functions. In this paper, Pulse Position Modulation is studied. We proposed two techniques in order to design the receiver for this modulation. These detection methods called ML and MAX detector. The performances of the proposed detection algorithms are discussed in the different ISI values. It is seen that two detection methods can achieve the same performance in bit error probability for some practical cases. While the MAX detector is simpler than ML detector.

—Molecular Communication via Diffusion (MCvD) is one of the most prominent approaches to intercon... more —Molecular Communication via Diffusion (MCvD)
is one of the most prominent approaches to interconnect the
nanomachines which can do some simple communication functions. In this paper, Pulse Position Modulation is studied. We
proposed two techniques in order to design the receiver for
this modulation. These detection methods called ML and MAX
detector. The performances of the proposed detection algorithms
are discussed in the different ISI values. It is seen that two
detection methods can achieve the same performance in bit error
probability for some practical cases. While the MAX detector is
simpler than ML detector

Internet traffic classification plays an important role for network management. In fact, operator... more Internet traffic classification plays an important role for network management. In fact, operators need to better predict future traffic behavior to identify anomalous situations. We present here an approach for traffic classification using Hidden Naive Bayes model and a supervised discretization scheme. This approach can achieve an appropriate performance on a range of application types with accessing only the information that remains unchanged after encryption. At first, we use a supervised method based on idea behind Holte's 1R algorithm for discretization of continuous features derived from packet headers. Then, in order to assign flows to their respective classes, we utilize Hidden Naive Bayes (HNB) model. Finally, we test our scheme using a subset of two data sets and compare it to Tree-Augmented Naive Bayes (TAN) algorithm. Various performance measures namely Accuracy (Auc) and Trust are used for quantitative analysis of our results. Experimental results reveal that our proposed modeling approach based on HNB not only achieves a higher performance in terms of both measures in comparison to TAN algorithm but also learns very well even with a small number of training flows.

The characteristics of the underwater acoustic communication such as large propagation delay, hig... more The characteristics of the underwater acoustic communication such as large propagation delay, high bit error rate and halfduplex, bring challenges to traditional automatic repeat request (ARQ) schemes. In this paper, we propose cooperative ARQ protocols based on relay selection in wireless sensor networks. These protocols use cooperative relays that provide an alternative path along a specific source-to-destination route. This alternative path has higher channel quality than that of the direct source-destination path. The main advantage of our methods is that we do not need to be aware of the relays locations. In fact, the relays will be organized by creating a time table at the destination. Furthermore, we evaluate the proposed schemes by comparing them with conventional stop and wait (S&W) ARQ and some other works in terms of throughput efficiency. Analytical and computer simulation results show that the proposed cooperative retransmission protocols can significantly improve the throughput even in a network with a few cooperative relay nodes.

arXiv (Cornell University), Apr 2, 2018

Molecular Communications via Diffusion (MCvD) is a promising paradigm which enables nano-machines... more Molecular Communications via Diffusion (MCvD) is a promising paradigm which enables nano-machines to communicate with each other. However, the reliability of existing systems degrades rapidly as the distance between the transmitters and the receivers grows. To solve this issue, relaying schemes must be implemented in practice. In this paper, we study two relaying schemes: In the first case, the relay node decodes the incoming signal symbol and forwards it to the receiver using a different type of molecule. Then, the receiver detects the information bits by only considering the molecules from the relay node. In the second case, the receiver considers both the types of molecules sent from the transmitter and the relay node. For these two scenarios, the optimal location of the relay node are obtained. We assume Quadruple Concentration Shift Keying (QCSK) modulation in which the signal is encoded into the four level concentrations of molecules emitted by the nano-machines. Our simulation results indicate that adding a relay improves the performance by 10dB and 15dB in the first and the second schemes, respectively.

IET Nanobiotechnology, 2019

Forthcoming applications for molecular communications (MC) such as drug-delivery and health monit... more Forthcoming applications for molecular communications (MC) such as drug-delivery and health monitoring will require robust receiver capabilities to mitigate channel memory and inter symbol interference caused by previous transmitted symbols. Here, the authors introduce an adaptive weighted algorithm to reduce the influence of these factors. This novel signal detection is deployed on to a concentration-based MC system with absorbing receiver which is based on the so-called first passage time concept. The proposed detector has low complexity and does not require explicit channel knowledge. To evaluate authors' proposed algorithm, a theoretical approach is developed to derive the bit error rate (BER). Numerical results also carried out to verify the accuracy of these formulations and establish that the new detector will achieve better performance in comparison with other common low-complex detectors under certain scenarios. Additionally, the authors propose a simple pre-coding technique to combat the sequence of consecutive ones in low ISI scenarios. Also a comparison between detectors is given, which is based on the variation of distance, symbol period, signal-to-noise ratio (SNR), and number of molecules.

IET Communications, 2017

In this paper, the authors show that using physical layer network coding (PNC) in wireless relay ... more In this paper, the authors show that using physical layer network coding (PNC) in wireless relay systems does not always increase throughput performance, and to achieve maximum throughput, PNC should be exploited intelligently regarding to the channel conditions. In this study, they propose a selective PNC (SPNC) scheme in bidirectional relay systems for binary phase shift keying. In the proposed scheme, the relay chooses either to detect network-coded data from superimposed signal by PNC scheme or single source data by a so-called single node detection (SND) scheme, based on which offers more end-toend throughput for current channel realisation. They analytically determine the region of channel state plane in which SPNC selects SND scheme. Also, they obtain expressions for instantaneous bit error rates (BERs) of PNC and SND protocols. Moreover, they derive upper bounds in closed-form for average BERs of PNC and SND schemes during multiple access phase at the relay. Then, they investigate SPNC with high-order modulations. Simulations and analytical results confirm that SPNC achieves considerable throughput gain over PNC in Rayleigh fading channels.

Abstract– When channel is severely frequency selective, Orthogonal Frequency Division Multiplexin... more Abstract– When channel is severely frequency selective, Orthogonal Frequency Division Multiplexing (OFDM) is a suitable candidate for high rate communications. In multipath fading channels like harsh underwater channels, due to Inter Carrier Interference (ICI) and Carrier Frequency Offset (CFO) the performance of this technique is dramatically decreased. Therefore, these effects must be alleviated to overcome the performance degradation. To do that, first the CFO’s must be estimated. In this paper, we consider an underwater channel with three sets of paths and we assume that the paths in each set have similar Doppler scale factor. For minimum transmission power, Zero Padded OFDM (ZP-OFDM) is considered. We propose a new method based on MUltiple SIgnal Classification (MUSIC) technique that facilitates the estimation of multiple CFO’s in Under Water Acoustic (UWA) channel and compare it with the derived Maximum Likelihood (ML) estimator algorithm. Simulation results show that the prop...

IEEE Transactions on Wireless Communications, 2009

This paper investigates the fundamental capacity limits of opportunistic spectrum-sharing channel... more This paper investigates the fundamental capacity limits of opportunistic spectrum-sharing channels in fading environments. The concept of opportunistic spectrum access is motivated by the frontier technology of cognitive radio which offers a tremendous potential to improve the utilization of the radio spectrum by implementing efficient sharing of the licensed spectrum. In this spectrum-sharing technology, a secondary user may utilize the primary user's licensed band as long as its interference to the primary receiver remains below a tolerable level. Herein, we consider that the secondary user's transmission has to adhere to limitations on the ensuing received power at the primary's receiver, and investigate the capacity gains offered by this spectrum-sharing approach in a Rayleigh fading environment. Specifically, we derive the fading channel capacity of a secondary user subject to both average and peak received-power constraints at the primary's receiver. In particular, considering flat Rayleigh fading, we derive the capacity and optimum power allocation scheme for three different capacity notions, namely, ergodic, outage, and minimum-rate, and provide closed-form expressions for these capacity metrics. Numerical simulations are conducted to corroborate our theoretical results.

Proceedings of the 8th ACM international workshop on Mobility management and wireless access - MobiWac '10, 2010

Direct Sequence Spread Spectrum (DSSS) techniques are widely used due not only to their inherent ... more Direct Sequence Spread Spectrum (DSSS) techniques are widely used due not only to their inherent interference rejection and multiple access capability, but also to their relative immunity from multipath effects, which are encountered in UWA channels. In code division multiple access (CDMA) technology signals from different users are distinguished by means of pseudo noise (PN) codes that are used for spreading the user messages. To overcome the severe impact of ISI in the point to point UWA communications, we propose a novel multiple pseudo noise (PN) sequences DSSS scheme and analyze its performance in sparse underwater acoustic channels. To further alleviate the ISI effect, we propose a simple ISI reduction algorithm.

2013 21st Iranian Conference on Electrical Engineering (ICEE), 2013

In this paper a new strategy of fountain code transmission over cooperative relay networks is pro... more In this paper a new strategy of fountain code transmission over cooperative relay networks is proposed. The rateless characteristic of fountain codes makes them suitable for sending data over erasure channels. In addition, the presence of relay nodes can help to improve the performance. Until now, traditional rateless codes, rarely use feedback communication channels between receivers and broadcasters, a feature that is available in many wireless settings and helps to have better performance. Thus, in this paper we provide a feedback channel between the destination and the relay in order to help the relay to have more efficient transmissions. It ends to decrease the overall overhead in transmission over erasure channels. Thereby, significant savings in time and energy are obtained.

IET Communications, 2009

Collaborative spectrum sensing is regarded as a key technology for tackling the challenges of the... more Collaborative spectrum sensing is regarded as a key technology for tackling the challenges of the practical implementation of cognitive radio (CR). However, most of the proposed solutions require infinite bits or several bits exchanging per each CR to make the final decision to indicate the absence or presence of a primary user. It is well known that if N CRs employ energy detector with the same threshold and then send individual decision bits to a fusion centre, the OR-rule (1-out-of-N rule) will be optimal under Neyman-Pearson criterion. To decrease the average number of exchanging bits, we propose novel schemes while they perform as well as the OR-rule, our analytical and simulation results show that the proposed schemes has two important advantages over previously proposed schemes: (1) the average number of exchanging bits for N CRs always is 1/N bits per CR in perfect control channels; however, it is much higher than 1/N for the other proposed methods, e.g. it is 1 bit for the OR-rule and (2) the proposed method is very robust against the errors of imperfect control channels, specially, in low signal-to-noise ratio (SNR) regimes. Furthermore, the average number of reporting bits do not change considerably under the imperfect control channels.

IET Communications, 2012

A cognitive radio (CR) network is formed by allowing the secondary users to opportunistically acc... more A cognitive radio (CR) network is formed by allowing the secondary users to opportunistically access the frequency bands that are idle in time or frequency whenever the primary users (PUs) are not using these bands. In fact, this new technology tries to solve the spectrum scarcity. In this study, with the assumption that the CR users operate in a wideband communication system, first the bandwidth of the system is divided into some equal parts that are larger than the coherent bandwidth of the channel, and then the capacity of the channel by considering the CR user's outage capacity criteria is compared in two structures: one with the use of frequency diversity technique and the other without the use of frequency diversity. After that, the authors will evaluate the total interference power in the primary system and its statistical characterisation. Finally, the permissible ranges of the CRs transmit power by considering the outage probability and interference probability constraints will be obtained in these two structures.

IEEE Transactions on Vehicular Technology, 2008

In this paper, we present two physical layer cooperative protocols for heterogeneous sensor netwo... more In this paper, we present two physical layer cooperative protocols for heterogeneous sensor networks. There is one cooperator near the transmitter and a second cooperator (as a relay) near the receiver. Although the focus is on heterogeneous sensor networks, the methods can be applied to homogeneous sensor networks as well. Analytical and simulation results show that, under an additive white Gaussian noise channel assumption for the links between the transmitter and its partner and between the receiver and its partner, the proposed protocols achieve a diversity order of three or four by using the amplify-and-forward cooperation strategy and maximal ratio combining in the receiver. In addition, the proposed methods outperform the noncooperative single-hop transmission in the clustered heterogeneous sensor network and save a considerable amount of energy relative to the noncooperative transmission. Index Terms-Amplify-and-forward (AF) cooperation, cooperative diversity, heterogeneous sensor networks, maximal ratio combining. I. INTRODUCTION S ENSOR networks are composed of a large number of nodes that sense certain phenomena in the area of interest and communicate their observations to other nodes or a central base station, such as a cluster head or a gateway for further processing. Due to the large number of sensing nodes and their computing and communication capabilities, many different applications for the home, military, habitat monitoring, and healthcare industry have become possible (for more details, see [1] and references therein). Sensor networks are categorized as homogeneous and heterogeneous networks [2], [3]. In a homogeneous sensor network, the sensor nodes are identical in terms of computing, sensing and communication capabilities, and power supplies, whereas, in a heterogeneous sensor network, the nodes have different capabilities and/or power supplies [2]. In a homogeneous sensor network, data can be relayed using a multihop transmission or a cluster-based transmission. For example, in a data gathering application, multihop links are utilized to relay information to a sink, which is the ultimate destination of the data. In the clusterbased transmission, the cluster head gathers the information

Arabian Journal for Science and Engineering, 2013

ABSTRACT Wireless sensor networks are composed of many small distributed battery–powered sensor n... more ABSTRACT Wireless sensor networks are composed of many small distributed battery–powered sensor nodes, so reducing the energy consumption in each node to increase network lifetime is essential. One method that significantly reduces the energy consumption in each node is cooperative communication. In this paper, we investigate power allocation to one source node and partner node(s) in two scenarios for an energy efficient cooperative communication. In both of them, we use a cluster of partners and we want to minimize energy consumption. In the first scenario, we use two partners and allocate power to them according to a search based optimization problem and compare its performance with the case of using one partner. In the second one, we select one partner according to its channel gain to reduce packet failure ratio. It is also shown that using two partners instead of one can often increase the performance of the system in the first scenario. Furthermore, it is shown that increasing cluster size can decrease packet failure ratio, significantly.