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Aamir Hasan

Bio: Aamir Hasan is an academic researcher from Air University (Islamabad). The author has contributed to research in topics: Wireless ad hoc network & Mobile ad hoc network. The author has an hindex of 8, co-authored 19 publications receiving 477 citations. Previous affiliations of Aamir Hasan include National University of Sciences and Technology & University of Texas at Austin.

Papers
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Journal ArticleDOI
TL;DR: This paper introduces the concept of a guard zone, defined as the region around each receiver where interfering transmissions are inhibited, using stochastic geometry to derive the guard zone size that maximizes the transmission capacity for spread spectrum ad hoc networks.
Abstract: In ad hoc networks, it may be helpful to suppress transmissions by nodes around the desired receiver in order to increase the likelihood of successful communication. This paper introduces the concept of a guard zone, defined as the region around each receiver where interfering transmissions are inhibited. Using stochastic geometry, the guard zone size that maximizes the transmission capacity for spread spectrum ad hoc networks is derived - narrowband transmission (spreading gain of unity) is a special case. A large guard zone naturally decreases the interference, but at the cost of inefficient spatial reuse. The derived results provide insight into the design of contention resolution algorithms by quantifying the optimal tradeoff between interference and spatial reuse in terms of the system parameters. A capacity increase relative to random access (ALOHA) in the range of 2 - 100 fold is demonstrated through an optimal guard zone; the capacity increase depending primarily on the required outage probability, as higher required QoS increasingly rewards scheduling. Compared to the ubiquitous carrier sense multiple access (CSMA) which essentially implements a guard zone around the transmitter rather than the receiver - we observe a capacity increase on the order of 30 - 100%

330 citations

Proceedings ArticleDOI
13 Oct 2003
TL;DR: A network topology with high network awareness via a broadcast CSMA channel is developed, and the resulting system increases network throughput and overcomes existing problems with IEEE 802.11.
Abstract: This paper develops a system design for clustered wireless ad hoc networks, combining CSMA and CDMA to enable spatial reuse and simultaneous transmissions. Typically, CDMA networks require fine-tuned power control, but here that requirement is eliminated through a combination of open loop power control, user ordering, and successive interference cancellation (SIC). A network topology with high network awareness via a broadcast CSMA channel is developed. The resulting system increases network throughput and overcomes existing problems with IEEE 802.11.

34 citations

Proceedings ArticleDOI
29 Nov 2004
TL;DR: It is shown that the size of this exclusion zone has a large impact on the transmission capacity of ad hoc networks, and an optimal critical radius is found using stochastic geometry.
Abstract: In ad hoc networks, it is necessary to suppress transmissions by nodes around the desired receiver in order to achieve successful communication. This minimum separation, the critical radius, has important implications on carrier sensing and other MAC-level protocols. Previously, the critical radius has not been well understood. The critical radius is investigated in CDMA ad hoc networks, with non-spread spectrum ad hoc networks being a special case where the spreading gain is unity. It is shown that the size of this exclusion zone has a large impact on the transmission capacity of ad hoc networks, and an optimal critical radius is found using stochastic geometry.

19 citations

Journal ArticleDOI
TL;DR: This paper reviews connectivity issues in VANET with emphasis on routing, and offers comprehensive literature review on state of the art inVANET routing, with its detailed classifications.
Abstract: Human safety considerations linked with rapidly growing auto mobile market has given special attention to the Intelligent Transportation System (ITS). ITS provides a set of stan- dards for inter vehicular communication with emphasis on safety, traffic efficiency and infotain- ment related applications. In ITS, the vehicles acting as mobile nodes, form a specialized ad hoc network, known as Vehicular Ad-hoc Network (VANET). Although, VANET and ITS are under intense research since last decade, technology still lacks large scale deployment. Vehicle to Ve- hicle (V2V) and Vehicle to Infrastructure (V2I) communications are the main research goals of ITS. High relative node velocity and high active node density has presented peculiar challenges to connectivity within VANET. VANET connectivity and routing requirements range from the time critical safety applications, to the time and space hovering, delay tolerant and infotainment applications. This paper reviews connectivity issues in VANET with emphasis on routing, and offers comprehensive literature review on state of the art in VANET routing, with its detailed classifications. It also compares some standard architectures of VANET from MAC, routing and management perspective, i.e., WAVE by IEEE, CALM by ISO, C2CNet by C2C consortium / GeoNet.

17 citations

Proceedings ArticleDOI
06 Aug 2008
TL;DR: An improved Nonce construction scheme is proposed for the AES CCMP to effectively prevent Initial Counter Prediction and the possibility of a subsequent TMTO attack.
Abstract: IEEE 802.11i standard offers arguably uncompromised confidentiality and integrity services by utilizing advance encryption standard in counter with cipher block chaining message authentication code protocol (AES CCMP). However the Nonce construction mechanism employed in the standard is weak, leading to Initial Counter prediction. Resultantly, the effective Key Length used for encryption is reduced from 128 to 85 bits and Time Memory Trade Off (TMTO) attack becomes a possibility. In this paper, an improved Nonce construction scheme is proposed for the AES CCMP to effectively prevent Initial Counter Prediction and the possibility of a subsequent TMTO attack. The proposed technique involves randomization of the Nonce value to make it unpredictable. The devised technique can be easily employed as a software upgrade in the existing 802.11i based Wireless Local Area Network (WLAN) devices, without any requirement of hardware up gradation.

15 citations


Cited by
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Proceedings Article
01 Jan 1991
TL;DR: It is concluded that properly augmented and power-controlled multiple-cell CDMA (code division multiple access) promises a quantum increase in current cellular capacity.
Abstract: It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

2,951 citations

Journal ArticleDOI
TL;DR: This tutorial article surveys some of these techniques based on stochastic geometry and the theory of random geometric graphs, discusses their application to model wireless networks, and presents some of the main results that have appeared in the literature.
Abstract: Wireless networks are fundamentally limited by the intensity of the received signals and by their interference. Since both of these quantities depend on the spatial location of the nodes, mathematical techniques have been developed in the last decade to provide communication-theoretic results accounting for the networks geometrical configuration. Often, the location of the nodes in the network can be modeled as random, following for example a Poisson point process. In this case, different techniques based on stochastic geometry and the theory of random geometric graphs -including point process theory, percolation theory, and probabilistic combinatorics-have led to results on the connectivity, the capacity, the outage probability, and other fundamental limits of wireless networks. This tutorial article surveys some of these techniques, discusses their application to model wireless networks, and presents some of the main results that have appeared in the literature. It also serves as an introduction to the field for the other papers in this special issue.

1,893 citations

Journal ArticleDOI
TL;DR: This article presents a comprehensive survey on the literature related to stochastic geometry models for single-tier as well as multi-tier and cognitive cellular wireless networks, and discusses the open research challenges and future research directions.
Abstract: For more than three decades, stochastic geometry has been used to model large-scale ad hoc wireless networks, and it has succeeded to develop tractable models to characterize and better understand the performance of these networks. Recently, stochastic geometry models have been shown to provide tractable yet accurate performance bounds for multi-tier and cognitive cellular wireless networks. Given the need for interference characterization in multi-tier cellular networks, stochastic geometry models provide high potential to simplify their modeling and provide insights into their design. Hence, a new research area dealing with the modeling and analysis of multi-tier and cognitive cellular wireless networks is increasingly attracting the attention of the research community. In this article, we present a comprehensive survey on the literature related to stochastic geometry models for single-tier as well as multi-tier and cognitive cellular wireless networks. A taxonomy based on the target network model, the point process used, and the performance evaluation technique is also presented. To conclude, we discuss the open research challenges and future research directions.

1,065 citations

Book
13 Nov 2009
TL;DR: For certain classes of node distributions, most notably Poisson point processes, and attenuation laws, closed-form results are available, for both the interference itself as well as the signal-to-interference ratios, which determine the network performance.
Abstract: Since interference is the main performance-limiting factor in most wireless networks, it is crucial to characterize the interference statistics. The two main determinants of the interference are the network geometry (spatial distribution of concurrently transmitting nodes) and the path loss law (signal attenuation with distance). For certain classes of node distributions, most notably Poisson point processes, and attenuation laws, closed-form results are available, for both the interference itself as well as the signal-to-interference ratios, which determine the network performance. This monograph presents an overview of these results and gives an introduction to the analytical techniques used in their derivation. The node distribution models range from lattices to homogeneous and clustered Poisson models to general motion-invariant ones. The analysis of the more general models requires the use of Palm theory, in particular conditional probability generating functionals, which are briefly introduced in the appendix.

976 citations