Ossama Younis

An energy-aware distributed clustering protocol in wireless sensor networks using fuzzy logic

Clustering is an effective approach for organizing a network into a connected hierarchy, load balancing, and prolonging the network lifetime. On the other hand, fuzzy logic is capable of wisely blending different parameters. This paper proposes an energy-aware distributed dynamic clustering protocol (ECPF) which applies three techniques: (1) non-probabilistic cluster head (CH) elections, (2) fuzzy logic, and (3) on demand clustering. The remaining energy of the nodes is the primary parameter for electing tentative CHs via a non-probabilistic fashion. A non-probabilistic CH election is implemented by introducing a delay inversely proportional to the residual energy of each node. Therefore, tentative CHs are selected based on their remaining energy. In addition, fuzzy logic is employed to evaluate the fitness (cost) of a node in order to choose a final CH from the set of neighboring tentative CHs. On the other hand, every regular (non CH) node elects to connect to the CH with the least fuzzy cost in its neighborhood. Besides, in ECPF, CH elections are performed sporadically (in contrast to performing it every round). Simulation results demonstrate that our approach performs better than well known protocols (LEACH, HEED, and CHEF) in terms of extending network lifetime and saving energy.

Cooperative adaptive spectrum sharing in cognitive radio networks

The cognitive radio (CR) paradigm calls for open spectrum access according to a predetermined etiquette. Under this paradigm, CR nodes access the spectrum opportunistically by continuously monitoring the operating channels. A key challenge in this domain is how the nodes in a CR network (CRN) cooperate to access the medium in order to maximize the CRN throughput. Typical multichannel MAC protocols assume that frequency channels are adjacent and that there are no constraints on the transmission power. However, a CRN may operate over a wide range of frequencies, and a power mask is often enforced on the transmission of a CR user to avoid corrupting the transmissions of spectrum-licensed primary-radio (PR) users. To avoid unnecessary blocking of CR transmissions, we propose a novel distance-dependent MAC protocol for CRNs. Our protocol, called DDMAC, attempts to maximize the CRN throughput. It uses a novel probabilistic channel assignment mechanism that exploits the dependence between the signals attenuation model and the transmission distance while considering the traffic profile. DDMAC allows a pair of CR users to communicate on a channel that may not be optimal from one users perspective, but that allows more concurrent transmissions to take place, especially under moderate and high traffic loads. Simulation results indicate that, compared to typical multichannel CSMA-based protocols, DDMAC reduces the blocking rate of CR requests by up to 30%, which consequently improves the network throughput.

Energy-Efficient Clustering/Routing for Cooperative MIMO Operation in Sensor Networks

Employing multi-input multi-output (MIMO) links can improve energy efficiency in wireless sensor networks (WSNs). Although a sensor node is likely to be equipped with only one antenna, it is possible to group several sensors to form a virtual MIMO link. Such grouping can be formed by means of clustering. In this paper, we propose a distributed MIMO-adaptive energy-efficient clustering/routing scheme, coined cooperative MIMO (CMIMO), which aims at reducing energy consumption in multi- hop WSNs. In CMIMO, each cluster has up to two cluster heads (CHs), which are responsible for routing traffic between clusters (i.e., inter-cluster communications). CMIMO has the ability to adapt the transmission mode and transmission power on a per-packet basis. The transmission mode can be one of four transmit/receive configurations: 1 times 1 (SISO), 2 times 1 (MISO), 1 times 2 (SIMO), and 2 times 2 (MIMO). We study the performance of CMIMO via simulations. Results indicate that our proposed scheme achieves a significant reduction in energy consumption, compared to non-adaptive clustered WSNs.

Cognitive MANET design for mission-critical networks

For mobile ad hoc networks used in network-centric operations, there is a growing need for a systematic methodology for analyzing/predicting the performance of the network over the mission duration. With the advance in cognitive networking as a possible means of exploiting unused spectrum, there is now a growing need to study how to design a cognitive network using an automated methodology. In this article we study the concepts and challenges for automatic design/ reconfiguration of cognitive MANETs. We describe the design objectives, imposed constraints, and involved parameters in MANETs. We describe how cognitive techniques can be employed to exploit the unused spectrum in military architectures. We then discuss the challenges facing the design/reconfiguration of a cognitive network and their implications at different network layers. We also describe possible implementation options for designing MANETs that employ cognitive features at all layers.

Distance- and Traffic-Aware Channel Assignment in Cognitive Radio Networks

The scarcity of unlicensed spectrum has triggered great interest in cognitive radio (CR) technology as a means to improve spectrum utilization. An important challenge in this domain is how to enable nodes in a CR network (CRN) to access the medium opportunistically. Multi-channel MAC protocols for typical ad hoc networks assume that frequency channels are adjacent and that there are no strict constraints on the transmission power. However, a CRN may occupy a wide range of frequencies. In addition, a power mask is often enforced on the transmission power of a CR user to avoid corrupting the transmissions of spectrum-licensed primary-radio (PR) users. Obviously, CR users operating in different licensed bands will be subject to different PR-to-CR interference conditions. To avoid unnecessary blocking of CR transmissions under these constraints, we propose a novel distance-dependent MAC protocol for CRNs (DDMAC) that attempts to maximize the CRN throughput. DDMAC introduces a novel suboptimal probabilistic channel assignment algorithm that exploits the dependence between the signals attenuation model and the transmission distance while considering the traffic profile. The protocol allows a pair of CR users to communicate on a channel that may not be optimal from one users perspective, but that allows more transmissions to take place simultaneously, especially under moderate to high traffic loads. Simulation results indicate that compared to typical multi-channel CSMA-based protocols, DDMAC decreases the connection blocking rate of CR transmission requests by up to 30%, which improves the network throughput at no additional cost in energy consumption. On the whole, our protocol is simple yet effective. It can be incorporated into existing multi-channel systems with little extra processing overhead.

Network science based approaches to design and analyze MANETs for military applications

Mobile ad hoc networks have become the basis of the militarys network-centric warfare (NCW) approach. However, for NCW to be successful, it is imperative that the networks be designed in a robust manner with the capability to produce consistent predictable results despite the uncertainties of the underlying environment. This underscores the need for formal systematic methodologies to design and predict performance of such networks. The challenges of mobile ad hoc networking combined with those associated with the stringent requirements posed by NCW systems, however, are daunting, and thus no systematic design techniques for NCW system design exist. To address this problem, a joint project was initiated between CERDEC and Telcordia Technologies to develop the Network Engineering Design Analytic Toolset (NEDAT) - a toolset that applies network-science-based approaches to design MANETs for use in NCW. Rooted in formal/analytic techniques, NEDAT can be used to design MANETs for use in NCW given information about available resources and performance objectives, analyze performance of a given NCW network, and understand design trades.

Throughput-oriented MAC for mobile ad hoc networks: A game-theoretic approach

The conservative nature of the 802.11 channel access scheme has instigated extensive research whose goal is to improve the spatial reuse and/or energy consumption of a mobile ad hoc network. Transmission power control (TPC) was shown to be effective in achieving this goal. Despite their demonstrated performance gains, previously proposed power-controlled channel access protocols often incur extra hardware cost (e.g., require multiple transceivers). Furthermore, they do not fully exploit the potential of power control due to the heuristic nature of power allocation. In this paper, we propose a distributed, single-channel MAC protocol (GMAC) that is inspired by game theory. In GMAC, each transmitter computes a utility function that maximizes the links achievable throughput. The utility function includes a pricing factor that accounts for energy consumption. GMAC allows multiple potential transmitters to contend through an admission phase that enables them to determine the transmission powers that achieve the Nash equilibrium (NE). Simulation results indicate that GMAC significantly improves the network throughput over the 802.11 scheme and over another single-channel power-controlled MAC protocol (POWMAC). These gains are achieved at no extra energy cost. Our results also indicate that GMAC performs best under high node densities and large data packet sizes.

Cognitive tactical network models

Unlike commercial MANET applications, tactical networks are typically hierarchical and involve heterogeneous types of radio communications. Future tactical networks also require cognitive functions across the protocol stack to exploit scarce spectrum and dynamically adapt functions and configuration settings. In this work we highlight the need for novel design tools for cognitive tactical networks. We define a system design model that will provide the foundation for generic network design problem formulations via the use of cognitive techniques covering both dynamic frequency adaptations and machinelearning- related aspects of cognition. We use the system model to identify several potential cognitive design knobs and describe how the different design knobs can potentially be adjusted at different timescales of operation. These knobs are used in formulating a cognitive network design problem. Finally, we discuss how a network designer can potentially benefit from the proposed model result, a cognitive network design toolset we have recently developed.

C-NEDAT: A cognitive network engineering design analytic toolset for MANETs

Future force networks of the types envisioned for the network centric warfare (NCW) paradigm will be highly diverse, with the diversity spanning a wide range of (a) requirements (e.g., need for capacity, connectivity, survivability), (b) resources (e.g., radios with widely different capabilities and ‘smart’ (e.g., Software Defined Radios (SDRs)), and (c) environments (e.g., urban, rural). The need to facilitate robust and adaptable communications in such networks has in turn triggered research in the area of cognitive networks that have the ability to ‘learn’ and generate real-time control actions to adapt to the wide diversity of requirements, resources and environments. However, the combination of diversity and “smart” networking exacerbates the problem of generating reliable and robust network designs. We present in this paper, our work on the use of cognitive mechanisms to assist with the design and analysis of robust NCW-like networks. Based on formal network-science based approaches, our Cognitive Network Engineering Design Analytic Toolset (C-NEDAT) provides for a systematic way to design, analyze and maintain robustness of future force MANETs. We provide in this paper an overview of the key functional modules and design capabilities of C-NEDAT and present example results.

NEDAT- a toolset to design and analyze future force networks

The Department of Defense has developed the over-arching concept of Net-Centric Warfare (NCW) to incorporate the technological advancements of the information age into the U.S. military. Mobile ad hoc networks (MANETs) are a vital component to realizing the NCW concept. To ensure the success of the NCW concept, there is a critical need for systematic techniques based on formal approaches to designing and predicting performance of MANETs. This paper presents a Network Engineering Design Analytic Toolset (NEDAT) that applies network science based approaches to the design and analysis of NCW-like networks. It is the result of a joint project between CERDEC and Telcordia Technologies.