Wireless Sensor Networks (WSNs) provide a valuable capability to autonomously monitor remote activities. Their limited resources challenge WSN medium access control (MAC) layer designers to adequately support network services while conserving limited battery power. This paper presents an energyadaptive WSN MAC protocol, Gateway MAC (G-MAC), which implements a new cluster-centric paradigm to effectively distribute cluster energy resources and extend network lifetime. G-MAC’s centralized cluster management function offers significant energy savings by leveraging the advantages of both contention and contention-free protocols. A centralized gateway node collects all transmission requirements during a contention period and then schedules their distributions during a reservation-based, contention-free period. With minimal overhead, the gateway duties are efficiently rotated based upon available resources to distribute the increased network management energy requirements among all of the nodes. 1.

As mobile computing platforms make dynamic collaborative environments more common, the need for access control becomes more imperative. Centralized access control determination fails to work in unstructured networks, as the information necessary for pre-configuration is not available. This situation is exacerbated by the dynamic nature of the environment's membership, so that the time and resources expended in off-line management are largely wasted. This paper presents a decentralized access control system that implements sociological trust constructs in a quantitative system to evaluate potential associates for collaborative interaction. A distributed, node-centric approach to trust management processes behavior grades into a reputation that nodes use to determine trustworthiness their peers before establishing associations. The application of a reputation against a dynamic risk assessment gives a measure of expectation of a peer's behavior, based on past performance and current the network environment. These safeguards work together to make a safer dynamic collaborative environment

With the progression of computer networks extending boundaries and joining distant locations, wireless sensor networks (WSNs) emerge as the new frontier in developing opportunities to collect and process data from remote locations. WSNs rely on hardware simplicity to make sensor field deployments both affordable and long-lasting without maintenance support. WSN designers strive to extend network lifetimes while meeting application-specific throughput and latency requirements. Effective power management places sensor nodes into one of the available energy-saving modes based upon the sleep period duration and the current state of the radio. The newest generation of sensor platform radios with a 250 kbps data rate does not provide adequate time to completely power off the radio during overheard 128-byte constrained IEEE 802.15.4 transmissions. This paper proposes a new radio power management (RPM) algorithm which optimizes radio sleep capabilities by transitioning nodes to intermediate power level states. Additionally, the experimental work characterizes the radio power levels, state transition times, and state transition energy costs of an IEEE 802.15.4 compliant sensor platform for improved accuracy in simulating WSN energy consumption

Behavior grading is crucial to the operation of a mobile ad-hoc network (MANET). Our Key Management System project has established a behavior grading and tracking mechanism through the use of X.509 v3 certificates with appropriate extensions. Our distributed, node-centric approach to reputation management processes nodal behavior feedback and provides a reputation index that nodes use to determine trustworthiness of their peers before establishing IPsec security associations. Behavior feedback is "aged" in a three-window weighted average, which emphasizes current behavior while conservatively approximating behavior trends over time. The windowed approach maintains non-reputable evidence, which supports the reputation calculation and facilitates the exchange of behavior information with new nodes as they join the network.

This paper proposes an early warning system via a host-based form of intrusion detection that can alert security administrators to protect their corporate network(s). This innovative technique operates through the implementation of battery-based intrusion detection (B-bid) on mobile devices by correlating attacks with their impact on device power consumption using a rules-based host intrusion detection engine (HIDE). HIDE monitors power behavior to detect potential intrusions by noting irregularities of power consumption.

This paper focuses on characterizing the overhead of IP security (IPSec) for email and Web applications using a set of test bed configurations. The different configurations are implemented using both wireline and wireless network links. The testing considers different combinations of authentication algorithms and authentication protocols. Authentication algorithms include Hashed Message Authentication Code-Message Digest 5 (HMAC-MD5) and Hashed Message Authentication Code-Secure Hash Algorithm 1 (HMAC-SHA1). Authentication protocols include Encapsulating Security Payload (ESP) and Authentication Header (AH) protocols. Triple Digital Encryption Standard (3DES) is used for encryption. Overhead is examined for scenarios using no encryption and no authentication, authentication and no encryption, and authentication and encryption. A variety of different file sizes are considered when measuring the overhead The results present a thorough analysis of the overhead of different IPSec configurations and provide practical guidance for choosing the IPSec configuration needed in a network environment.

Emerging third generation (3G) wireless standards promise a "last-mile" solution capable of supporting mobile, wireless Internet service. The Third Generation Partnership Proposal (3GPP) wideband code division multiple access (WCDMA) standard will support data rates up to 2 Mbit/s with orthogonal variable spreading factor (OVSF) codes. These variable spreading factor codes provide a means of bandwidth allocation in a CDMA system. This paper presents a dynamic OVSF code assignment algorithm that efficiently shares a WCDMA downlink between data traffic sources with different quality of service (QoS) requirements. Both analytic and simulation results for bursty traffic sources demonstrate that our dynamic code assignment algorithm offers significant improvement in channel utilization over dedicated code assignment schemes.

Emerging third generation (3G) wireless standards promise a "last-mile" solution capable of supporting mobile, wireless Internet service. The Third Generation Partnership Proposal (3GPP) wideband code division multiple access (WCDMA) standard will support data rates up to 2 Mbit/s with orthogonal variable spreading factor (OVSF) codes. This paper presents a dynamic OVSF code assignment algorithm that efficiently shares a WCDMA downlink between data traffic sources with different QoS requirements. Our simulation results verify that the algorithm functions as desired. The QoS guarantees for high QoS traffic are protected, and best effort traffic is able to utilize available bandwidth.

We develop and analyze an elegant, opportunistic medium access control (MAC) protocol based on the proposed MAC standard for wireless local area networks (WLAN)-IEEE 802.11. Our adaptation of 802.11 is called CATER (code adapts to enhance reliability) and allows communicating stations to reconfigure their transceivers to use a longer pseudonoise (PN) code when retransmissions are unsuccessful over a degraded channel. Results show that our protocol continues to function, permitting up to 14 percent normalized aggregate throughput, at times when IEEE 802.11 fails. In addition, throughput experiences only a small decrease due to protocol overhead during periods when stations experience a good channel and few bit errors.

Metamodeling is demonstrated as a methodology to accurately and concisely characterize the behavior of parallel processing interconnection networks. A set of mathematical metamodels are derived from a discrete event simulation model and then used to predict and compare the performance of interconnection networks. To illustrate the development and the application of metamodels, models for the multistage cube network, the single stage cube network (hypercube), and the llliac IV mesh-type network are formulated. These models, validated using empirical data from earlier studies, provide compact mathematical relations between packet delay time, message load, and switch size for each interconnection architecture. This approach provides insight into the complexities of network performance and uses simulation as the experimental vehicle for theoretical development. We show the comparison of network performance and conclude that the use of simulation as a means to estimate mathematical models is beneficial and consistent with experimental evidence. Our metamodels for performance prediction establish a basis for future comparisons that can be directly applied by other researchers. The models give the designer of a parallel processing system additional insight for choosing the interconnection network which best suits the application needs. INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.

Abstract This paper discusses efforts to develop parallel algorithms that can be used to solve large‐scale assignment problems typical of military battle management systems. Attempts to parallellze the classical Hungarian method are explored. Drawing on experimental data, a regresslon model is derived that relates the Hungarian method's run time to a cubic function of the number of parallel processors used in the solution. Four parallel heuristics for solving the assignment problem are developed and analysed. Two of them perform well in a parallel environment. The first, based on Vagel's approximation, can be used to identify a feasible, near‐optimal assignment. The second algorithm partitions the assignment problem into independent subproblems across the parallel array. The resulting solution, although infeasible in the strict definition of the assignment problem, is seen to be reasonably good and can be obtained very rapidly. Either of these two heuristics are of potential use in the stringent computing environment of a real‐time resource management system.

An integral part of any parallel processing system is its interconnection network.These networks have been the objects of intense research in recent years.Existing Markov chain analysis techniques for circuit switched, generalized cube interconnection networks will be extended to allow the performance modeling of partitionable SIMD/MIMD systems.Based on both analysis and simulation data, the relationship between the network performance, the partitioning scheme employed, and the conflict resolution algorithm used within the network will be enumerated.It will be shown that "input partitioning" coupled with the use of the "hold" conflict algorithm produces the best network operation in terms of the time to establish a circuit switched path through the network.Additionally, it will be shown that the performance of partitioned subnetworks is generally better than the performance of comparable sized random groupings of network resources.

One class of networks suitable for use in parallel processing systems is the multistage cube network. The authors focus on fault location procedures suitable for use in networks that use distributed routing control through the use of routing tags and message transmission protocols. Faults occurring in the data lines can corrupt message routing tags transmitted over them and thereby cause misrouting of messages. Protocol lines (used in handshaking between network sources and destinations), if faulty, can prevent a message path from being established or can cause the path to `lock up' once transmission of data has begun. These faults have more pronounced effects on the network performance than faults previously considered for centralized routing control systems. The single-fault location procedures presented form a logical superset to those of the centralized control systems (where message routing is dictated by the actions of a global control unit) and can be adapted for use in both circuit and packet switching networks.