Joseph Kabara

MAC Protocols Used by Wireless Sensor Networks and a General Method of Performance Evaluation

Many researchers employ IEEE802.15.4 as communication technology for wireless sensor networks (WSNs). However, medium access control (MAC) layer requirements for communications in wireless sensor networks (WSNs) vary because the network is usually optimized for specific applications. Thus, one particular standard will hardly be suitable for every possible application. Two general categories of MAC techniques exist: contention based and schedule based. This paper explains these two main approaches and includes examples of each one. The paper concludes with a unique performance analysis and comparison of benefits and limitations of each protocol with respect to WSNs.

Next generation wireless LAN system design

An important issue in the widespread deployment of infrastructure based wireless local area networks (WLANs) is the network design. In this paper, we propose a new WLAN design approach that focuses on assuring sufficient data rate capacity to meet expected user demand in the coverage area, while still satisfying signal coverage and interference level requirements. Noting the low cost of WLAN access points, we formulate a novel mathematical network design model within the framework of constraint satisfaction problems. Our model is termed the capacity based WLAN constraint satisfaction problem (Cap-WLAN CSP). The solution of the Cap-WLAN CSP model yields a network design based on data rate demand by providing the access point locations, the frequency channel allocation, and power levels required for the WLAN to meet expected user demands. Our numerical results illustrate that the capacity based approach is more appropriate for the design of WLAN systems than those of traditional coverage based designs.

Measuring Energy Consumption in Wireless Sensor Networks Using GSP

The energy consumption rate for sensors in a wireless sensor network vary greatly depending on the protocols the sensors use for communication. The gossip-based sleep protocol (GSP) (X. Hou et al., 2004) is an example of a protocol that implements routing and some MAC functions in an effort to conserve energy. Simulations show that GSP can conserve energy. We expand on this effort by building a prototype system and measuring energy consumption rates. GSP was implemented on the Mica2 platform and measurements were conducted to determine energy consumption. The measurements were then used to build an energy consumption model for GSP

Security in wireless residential networks

The installation rate of residential networks is expected to accelerate in the next few years with wireless networking being by far the technology of choice due to attractive features such as ease of use. A wide variety of traditional computing devices and embedded Internet appliances will be networked in homes. However, due to the broadcast nature of these networks and the heterogeneity of devices on these networks, new security problems will arise since the different types of devices have different security requirements and capabilities. We provide an overview of wireless residential networks, security issues for these networks and security in current wireless technologies such as IEEE 802.11 and Bluetooth. We then suggest a security architecture based on a classification of security services, containment and algorithm agility that will be suitable for wireless residential networks.

The Effect of Physical Topology on Wireless Sensor Network Lifetime

Wireless sensor networks must measure environmental conditions, such as temperature, over extended periods and therefore require a long system lifetime. The design of long lifetime networks in turn requires efficient sensor node circuits, algorithms, and protocols. Protocols such as GSP (Gossip-based Sleep Protocol) have been shown to mitigate energy consumption in idle listening and receiving, by turning off the receiver circuit. However, previous studies of network lifetime have been based on physical topologies in which nodes were placed on a square grid or randomly distributed throughout the service area. This paper shows that the lifetime of a sensor network depends on the physical topology of the sensor nodes. The lifetime of a sensor network varies as a function of both the size of the network and the transmission range of individual nodes.

Security architecture for wireless residential networks

Adoption of residential networking is expected to accelerate in the next few years with wireless networking being by far the most popular technology because of its attractive features, such as ease of use. However, easy access to the transmitted information and the heterogeneity of devices on the network result in security problems since the devices have diverse security requirements and employ a variety of protocols. In this paper, we provide an overview of security issues in wireless residential networks and suggest a security architecture based on a classification of security services, containment and algorithm agility.

A QoS-based indoor wireless data network design for VoIP applications

Multiple factors are contributing to the surge in the demand for wireless LAN (WLAN): laptop penetration, increased user mobility, ubiquitous access to the Internet and intranets, and newly introduced voice over IP (VoIP) capabilities. Today almost all popular wireless LAN applications such as Web access, E-mail processing, telnet, FTP, and database access are using a client-server architecture. However, the number of supported mobile nodes depends on the type of application the user employs. Thus, evaluation of the number of voice users supported by a wireless LAN access point is beginning to attract the attention of those involved in deployment of wireless LAN. Currently, most commercial wireless data networks are arbitrarily installed. The only optimization, if any, is that for the area covered by an access point. However the coverage aspect of the network design is only suitable for the initial installation phases wherein the capacity of users and the channel utilization is low. We investigate QoS parameters necessary to support voice and the implications these parameters have on WLAN design.

MAC Protocols for GSP in Wireless Sensor Networks

The Gossip-based Sleep Protocol (GSP) is a routing protocol designed to save energy in Wireless Sensor Networks. This work presents two MAC protocols designed to complement the characteristics of GSP: MACGSP1 and MACGSP2 were evaluated in combination with GSP on square grids of 100, 400 and 900 simulated nodes. Both protocols show increased energy savings compared to GSP by itself. MACGSP1 provided the greatest energy savings, however MACGSP2 exhibited the best trade off between overhead, delay and packet reception probability. MACGSP2 reduces the duplicate packets generated by GSP, with no significant difference in end-to end delay and a reduced GSP packet reception probability of 10%.

On survivability of IEEE 802.11 WLAN

In this paper, we address the problem of enhancing the survivability of IEEE 802.11 wireless local area networks focusing on tolerating access point-AP failures. We develop a simple fault detection approach, based on response timeout, which promises to be more cost-effective to identify failures due to lack of energy to an AP or problems with the wired link to an AP. In particular, we focus on the problem of overcoming these APs failures working with reconfiguration of the remaining APs by changing parameters such as power level and frequency channels. Our approach consists of two main phases: design and fault response. In design phase, we deal with quantifying, placement and setting up of APs according to both area coverage and performance criteria. In fault response phase we consider the reconfiguration of active APs in order to deal with AP fault in the service area. Finally, describe one of the major characteristics of the proposed system, which is a simple implementation in concordance with established IEEE 802.11 standards and related management systems

Reduction of location estimation error using neural networks

The objective of this work is to estimate the locations of Bluetooth enabled devices. Collecting received signal strength from a device may help with estimating its location. However, for indoor environments, the signal attenuation model becomes complex and difficult to represent concisely due to multi-path and small-scale fading effects. The flexible modeling and learning capabilities of neural networks provide lower errors in determining the position even in the presence of these destructive effects. A standard backpropagation learning algorithm was employed to minimize the error between target and estimated locations in order to find the weights of the links of the neural network. Simulation results show that a neural network with three input units and 8 hidden layer units and two output units can provide 75cm root mean square (RMS) error.