Papers by Alireza Keshavarz-Haddad
Wireless networks, Feb 28, 2024
Millimeter-Wave (mmWave) communication is susceptible to blockages, which can significantly reduc... more Millimeter-Wave (mmWave) communication is susceptible to blockages, which can significantly reduce the signal strength at the receiver. Mitigating the negative impacts of blockages is a key requirement to ensure reliable and high throughput mmWave communication links. Previous research on blockage mitigation has introduced several model and protocol based blockage mitigation solutions that focus on one technique at a time, such as handoff to a different base station or beam adaptation to the same base station. In this paper, we address the overarching problem: what blockage mitigation method should be employed? and what is the optimal subselection within that method? To address the problem, we developed a Gated Recurrent Unit (GRU) model that is trained using periodically exchanged messages in mmWave systems. We gathered extensive amount of simulation data from a commercially available mmWave simulator, show that the proposed method does not incur any additional communication overhead, and that it achieves outstanding results in selecting the optimal blockage mitigation method with an accuracy higher than 93%. We also show that the proposed method significantly increases the amount of transferred data compared to several other blockage mitigation policies. CCS CONCEPTS • Networks → Network performance evaluation; • Computing methodologies → Machine learning.
Wireless Networks, Oct 5, 2023
Vehicular Ad Hoc Network (VANET) is a key component in the Intelligent Transportation System (ITS... more Vehicular Ad Hoc Network (VANET) is a key component in the Intelligent Transportation System (ITS) with a number of applications for safety, traffic management, emergency services, entertainment, and so on. These applications are implemented by exchanging data among the nodes in an open, dynamic, and distributed fashion, and hence VANETs are vulnerable to different network attacks. For examples, DoS and black-hole attacks can be easily executed in VANETs, and strongly affect the routing protocol and its functionality. Through the nature of VANETs, trust management is considered one of the practical means to secure these networks. In this paper, we propose an up-to-date dynamic entity-centric trust model for VANETs, called T-AODV. We use social science techniques to apply weight and fuzzy logic theory and identify the malicious nodes. Our NS2 simulation results indicate that T-AODV can be more resists in contact with black-hole attacks by boosting the security of AODV routing protoco...
We present the design and implementation of F D 2 , a directional full-duplex (FD) communication ... more We present the design and implementation of F D 2 , a directional full-duplex (FD) communication system for indoor wireless networks. An F D 2 AP uses directional transmit and receive antennas to reduce self-interference, and to combat AP-AP and client-client interferences that arise due to FD operation in multi-cell networks. F D 2 addresses the joint problem of scheduling and beam selection by proposing efficient practical algorithms. F D 2 is implemented on the WARP platform, and its performance is compared against CSMA/CA and other FD and directional communication systems. Our experimental results reveal that: (i) Simple application of FD to multi-cell networks can result in significant loss of capacity due to high FD induced interference, while F D 2 can effectively overcome the problem and provide an average gain of ninefold; (ii) F D 2 's performance depends on the hardware capture properties and the corresponding rate table, and increases when packets can be captured at lower SINR margins, or when dynamic range of the rate table is high; and (iii) F D 2 's uplink and downlink performances are susceptible to channel dynamics, and are impacted differently due to mobility. However, we show that training F D 2 's rates according to traffic direction, mobility, and feedback rate, increases its robustness to channel dynamics.
Iet Communications, May 26, 2022
IEEE Transactions on Mobile Computing, 2014
ABSTRACT In this paper, we explore fundamental limitations of the benefit of network coding in mu... more ABSTRACT In this paper, we explore fundamental limitations of the benefit of network coding in multihop wireless networks. We study two well-accepted scenarios in the field: single multicast session and multiple unicast sessions. We assume arbitrary but fixed topology and traffic patterns for the wireless network. We prove that the gain of network coding in terms of throughput and energy saving of a single multicast session is at most a constant factor. Also, we present a lower bound on the average number of transmissions of multiple unicast sessions under any arbitrary network coding. We identify scenarios under which network coding provides no gain at all, in the sense that there exists a simple flow scheme that achieves the same performance. Moreover, we prove that the gain of network coding in terms of the maximum transport capacity is bounded by a constant factor of at most $(pi)$ in any arbitrary wireless network under all traditional Gaussian channel models. As a corollary, we find that the gain of network coding on the throughput of large homogeneous wireless networks is asymptotically bounded by a constant. Furthermore, we establish theorems which relate a network coding scheme to a simple routing scheme for multiple unicast sessions. The theorems can be used as criteria for evaluating the potential gain of network coding in a given wired or wireless network. Based on these criteria, we find more scenarios where network coding has no gain on throughput or energy saving.
Deterministic, timer-based broadcast schemes not only guarantee full reachability over an idealis... more Deterministic, timer-based broadcast schemes not only guarantee full reachability over an idealistic lossless MAC layer, they also stand out for their robustness against node failure as well as more general changes in the network topology. This paper proposes the first broadcast schemes in this class which provably perform within a factor of the optimal efficiency (in terms of number of rebroadcasts). To the best of our knowledge no other deterministic timer-based scheme possesses this property. NS-2 simulations employing the 802.11b MAC protocol confirm our analysis. The factor can be estimated to be quite small. Novel to the proposed schemes is also their hybrid backbone consisting of a given, static Dominating Set (DS) and a dynamically computed set of connecting nodes. As an additional contribution, this paper studies the trade-off of timer settings (and thus latency) against the number of rebroadcasts, as well as the robustness of the proposed algorithms. To the best of our knowledge, no prior study of these issues in the context of broadcast exists.
International journal of computer applications, Feb 18, 2015
SCADA systems are essential for the critical infrastructures, such as electric power, oil, and ga... more SCADA systems are essential for the critical infrastructures, such as electric power, oil, and gas production and distribution systems. Hence, incapacitation or destruction of SCADAs would have a debilitating impact on the defence or economic security of organizations and states. In this paper, we study fifteen SCADA cyber security standards and also assess the security of ten widely-used SCADA systems. Our investigation leads to a comprehensive categorized list of security solutions for SCADAs. This list is used to evaluate and compare security of the SCADA systems; also it will be used as model to improve the security of new SCADA systems.
In this paper, we study network coding for a single multicast session in wireless networks based ... more In this paper, we study network coding for a single multicast session in wireless networks based on "deterministic channel model" introduced recently in [2], [3]. We propose a network coding scheme for acyclic deterministic wireless network which can achieve the well-known cutset upper bound for such networks. While the original approach in [3] first proves the achievability of cutset upper bound for the layered networks and then extends the result to acyclic networks, we provide a short and direct proof for acyclic networks which trivially includes the layered networks.
... Network Ali Akbar Safavi, Alireza keshavarz-Haddad, Sahar Khoubani, Sajjad Mosharraf-Dehkordi... more ... Network Ali Akbar Safavi, Alireza keshavarz-Haddad, Sahar Khoubani, Sajjad Mosharraf-Dehkordi, Alireza Dehghani Pilehvarani, Fatemeh sadat Tabei Electrical and Computer Engineering School Shiraz University Shiraz, Iran [email protected] ...
IEEE ACM Transactions on Networking, 2017
This paper addresses the dynamics of broadcast flooding in random wireless ad hoc networks. In pa... more This paper addresses the dynamics of broadcast flooding in random wireless ad hoc networks. In particular, we study the subset of nodes covered by a flood as well as timing issues related to the first (latency) and the last time (duration of back-chatter) at which a broadcast is received by a fixed node. Notably, this analysis takes into account the MAC-layer as well as background traffic which both are often neglected in related studies. Assuming a protocol model for the transmission channel which accounts for carrier sensing and interference, we find bounds for the probability of survival of the flood and for its coverage probabilities. Moreover, under certain conditions on the parameters, we establish asymptotical linear bounds on the latency as the distance from the origin of the flood increases and show that the duration of the back-chatter is stochastically bounded. The analytical results are compared to simulation.
Mobile malware has become a serious security challenge in the world. Google Android dominated the... more Mobile malware has become a serious security challenge in the world. Google Android dominated the global Smart-phone market in 2014. This popularity makes it easier for the attackers to target larger community of devices. In this paper, we study the dynamics of infection propagation of mobile malware over mobile phones. We construct a framework for simulating peer-to-peer malware infection among mobile users in a community such as students in a campus. Also, we propose a distributed patching scheme for controlling and protecting users in a community against rapid propagation of mobile malware. This technique is effective especially in the underdeveloped countries with expensive and limited mobile Internet services. Using our framework, we simulate the infection rate and performance of patching techniques for a campus area. Our simulation results verify that under certain conditions immunization rate (reaching 90% immunization in the community) in our scheme is 3.5 times faster than the classic centralized scheme. Also, using our scheme would reduce infected devices population in the early stages of malware spreading four times faster.
We present the design and implementation of PAFD, a design methodology that enables full-duplex (... more We present the design and implementation of PAFD, a design methodology that enables full-duplex (FD) in hybrid beamforming systems with constant amplitude phased array antennas. The key novelty in PAFD's design is construction of analog beamformers that maximize the beamforming gains in the desired directions while simultaneously reducing the selfinterference (SI). PAFD is implemented on the WARP platform, and its performance is extensively evaluated in both indoor and outdoor environments. Our experimental results reveal that (i) PAFD sacrifices a few dB in beamfomring gain to provide large amounts of reduction in SI power; (ii) the reduction in SI is dependent on the number of phased array antennas and increases as the number of antennas increases; and (iii) finally, PAFD significantly outperforms half-duplex (HD) for small cells even in presence of high interference caused by uplink clients to the downlink clients. The gains increase with a larger array size or less multipath in the propagation environment.
arXiv (Cornell University), Jun 1, 2019
Heterogeneity in wireless network architectures (i.e., the coexistence of 3G, LTE, 5G, WiFi, etc.... more Heterogeneity in wireless network architectures (i.e., the coexistence of 3G, LTE, 5G, WiFi, etc.) has become a key component of current and future generation cellular networks. Simultaneous aggregation of each client's traffic across multiple such radio access technologies (RATs) / base stations (BSs) can significantly increase the system throughput, and has become an important feature of cellular standards on multi-RAT integration. Distributed algorithms that can realize the full potential of this aggregation are thus of great importance to operators. In this paper, we study the problem of resource allocation for multi-RAT traffic aggregation in HetNets (heterogeneous networks). Our goal is to ensure that the resources at each BS are allocated so that the aggregate throughput achieved by each client across its RATs satisfies a proportional fairness (PF) criterion. In particular, we provide a simple distributed algorithm for resource allocation at each BS that extends the PF allocation algorithm for a single BS. Despite its simplicity and lack of coordination across the BSs, we show that our algorithm converges to the desired PF solution and provide (tight) bounds on its convergence speed. We also study the characteristics of the optimal solution and use its properties to prove the optimality of our algorithm's outcomes.
IEEE Transactions on Wireless Communications, Feb 1, 2018
Bounds on the capacity of wireless networks often rely on simplifying assumptions and are given i... more Bounds on the capacity of wireless networks often rely on simplifying assumptions and are given in terms of coarse network parameters such as the number of nodes. While useful due to their simplicity such bounds can significantly overestimate the achievable capacity in real world situations, ignoring actual network topology and traffic patterns. The results of this paper improve such analytical results on network capacity in several ways. At the heart of our methodology lies the concept of transmission arenas which indicate the presence of active transmissions near any given location in the network. This novel space-based approach is well suited to untangle the interactions of simultaneous transmissions. Avoiding a graph-based model of the network it opens new avenues of studying capacities. For homogeneous networks we recover classical bounds. However, our methodology applies to arbitrary networks and can, thus, inform placing and activating of nodes also in the presence of clustering. Our method works with all classical channel models and dimensions. It provides bounds on the transport capacity which involve only high level knowledge of node locations, such as the length of Euclidean Minimum Spanning Tree. As an additional novelty we establish bounds on wireless unicast and multicast capacities.
In this paper, we propose a new scheme for detecting Sybil attacks and the attackers in vehicular... more In this paper, we propose a new scheme for detecting Sybil attacks and the attackers in vehicular ad hoc networks (VANETs) based on roadside units (RSUs) support. Due to the differences of moving dynamics among vehicles, having two vehicles passing by multiple RSUs at the same time is considered a rare coincidence. In the other hand, observation of two different identities (IDs) in the vicinity of two distinct RSUs provides strong evidence that the IDs belong to different vehicles. We use these two facts to determine if the Sybil attack is taking place. The proposed scheme uses routine communications among the nodes and RSUs to detect the attackers. Our simulation results indicate that the scheme outperforms the existing solutions in terms of detection rate, false positive rate, and system requirements.
Signal Processing, Aug 1, 2017
Cognitive radio has emerged as a solution to the problem of spectrum scarcity in recent years. Sp... more Cognitive radio has emerged as a solution to the problem of spectrum scarcity in recent years. Spectrum sensing is a key task in cognitive radio systems that can be performed collaboratively. Although collaboration enhances the performance of spectrum sensing, it can put the cognitive network in a vulnerable position. The cognitive users may send falsified reports, hence degrade the performance of spectrum sensing. In this paper, we propose a flexible structure which enables the attacker to reconfigure the attack parameters based on the defense strategy employed at the fusion center (FC) adaptively. In particular, we consider a cognitive network in which the cognitive users send their observations in a quantized format. It is assumed that a soft-decision-based defense strategy is employed at FC to detect the attackers. The attacker maps its quantized observations onto the other quantization levels probabilistically and reports them to FC. The attacker's objective is to perform probabilistic mapping such that the performance of FC degrades as much as possible. At the same time, the attacker considers the attack costs. We demonstrate that the proposed attack method leads to a convex linear programming problem. A low complexity algorithm is proposed to solve the problem. Simulation results are presented to show the effectiveness of the proposed scheme.
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Papers by Alireza Keshavarz-Haddad