Ivan Howitt

IEEE 802.15.4 low rate - wireless personal area network coexistence issues

IEEE 802.15.4 is a proposed standard addressing the needs of low-rate wireless personal area networks or LR-WPAN with a focus on enabling wireless sensor networks. The standard is characterized by maintaining a high level of simplicity, allowing for low cost and low power implementations. Its operational frequency band includes the 2.4 GHz industrial, scientific and medical band providing nearly worldwide availability; additionally, this band is also used by other IEEE 802 wireless standards. Coexistence among diverse collocated devices in the 2.4 GHz band is an important issue in order to ensure that each wireless service maintains its desired performance requirements. This paper presents a brief technical introduction of the IEEE 802.15.4 standard and analyzes the coexistence impact of an IEEE 802.15.4 network on the IEEE 802.11b devices.

WLAN and WPAN coexistence in UL band

Wireless local- and personal-area networks provide complimentary services in the same unlicensed (UL) radio frequency band of operation. As the mutual benefits of utilizing these services become increasingly apparent, the likelihood of mutual interference may also increase. A method was developed for examining wireless services coexistence in order to evaluate the impact that interference may have on network performance. The methodology for the analysis was centered on deriving a closed-form solution for the probability of collision Pr[C] in terms of the network and radio propagation parameters. In addition, a set of measures of performance was derived based on Pr[C]. In this fashion, the network performance was investigated in regards to the presence of interference. The approach was then illustrated by examining the coexistence between 802.11b and Bluetooth UL band wireless services and summarizing the impact on network performance.

Bluetooth performance in the presence of 802.11b WLAN

Both Bluetooth and 802.11b wireless communication technology are poised to make a significant impact in many applications. The complementary nature of the two technologies leads to applications enhanced by their collocation and simultaneous operation. Thus heightening the need for understanding the coexistence issues between the two technologies. A method was developed for evaluating the impact an 802.11b network will have on the Bluetooth piconet performance. A three step process was used in this development: characterize the 802.11b interference in a stationary environment, characterize the Bluetooth performance in the presence of a single 802.11b interferer and characterize the Bluetooth performance in an arbitrary 802.11b network environment. Empirical results were used to develop and substantiate the analytical model. The root-mean-square (RMS) difference between the single interferer empirical test results and the analytical model results was 2%. Analysis results, based on a specific range of radio propagation parameters and 802.11b network parameters, are presented.

Cognitive Radio Resource Management Using Multi-Agent Systems

This paper investigates cooperative radio resource management for multiple cognitive radio networks in interference environments. The objective of this research is to manage shared radio resources fairly among multiple non- cooperative cognitive radio networks to optimize the overall performance. We emphasize the underlying predictability of network conditions and promote management solutions tailored to different interference environments. A multi-agent-system- based approach is proposed to achieve information sharing and decision distribution among multiple cognitive radio networks in a distributed manner. We address the distributed constraint optimization problem (DCOP) in cognitive radio networks and study the effectiveness of DCOP algorithms to find the optimal radio resource assignment through communications between distributed agents.

Wireless industrial sensor networks: framework for QoS assessment and QoS management.

This paper presents a framework that addresses Quality of Service (QoS) for industrial wireless sensor networks as a real-time measurable set of parameters within the context of feedback control, thereby facilitating QoS management. This framework is based on examining the interaction between the industrial control processes and the wireless network. Control theory is used to evaluate the impact of the control/communication interaction, providing a methodology for defining, measuring, and quantifying QoS requirements. An example is presented illustrating the wireless industrial sensor network (WISN) QoS management framework for providing dynamic QoS control within WISN. The example focuses on WISN operating in a time-varying RF interference environment in order to manage application-driven QoS latency constraints.

Mutual interference between independent Bluetooth piconets

The Bluetooth wireless communication technology provides wireless solutions applicable for a number of communications needs. In addition, multiple independent piconets are possible and likely to occur within the same location, either intentionally or by chance. Bluetooth devices utilize frequency hopping and independent piconets operate on different hopping sequences. Although the use of independently selected hopping sequences reduces the likelihood of mutual interference, as the number of colocated piconets increases, mutual interference becomes more likely. Mutual interference is also dependent on the performance requirements dictated by the application utilizing Bluetooth technology as well as the environment in which the piconet is operating. A method for analytically evaluating mutual interference for Bluetooth technology is presented. Models were developed for a single Bluetooth interferer as well as multiple interfering Bluetooth piconets operating in an arbitrary environment. The analytical models are based on two sets of parameters: Bluetooth interference and radio propagation. Empirical tests have been conducted to both support the derivation of the analytical models as well as to substantiate the analytical model results. The analytical results fall within the 95% confidence bounds of the empirical test results. Mutual interference analysis is presented based on evaluating the analytical model over a wide range of the multidimensional parameter space. The analytical model presented is a general approach well suited for evaluating mutual interference for applications using Bluetooth for data communications.

Extended energy model for the low rate WPAN

Energy efficiency is a major concern in wireless sensor networks (WSNs) and as such power control policies play an essential component in maximizing a networks lifetime. Optimal power control policies provide the correct trade-off in balancing packet transmission reliability within the operational environment with expanded energy based on the wireless transceiver characteristics. In this paper, an extension of an energy model previously developed for the Chipcon CC2420, an IEEE802.15.4trade device, is presented. The approach provides an extended energy model taking into account transitions energy cost between the Chipcon CC2420 operational states. The empirical testbed used to obtain the measured data is presented along with a summary of the measurements. A comparison is made between the extended model and the previous model to illustrate the importance of incorporating the transition energy requirements

Design considerations for a wireless sensor network for locating parking spaces

This paper considers the design of a real time parking space locating system using a network of wireless sensor nodes that are equipped with magnetic sensors. Considerations for designing a reliable detection scheme for cars using magnetic signatures obtained by the wireless sensors are presented. All design considerations are derived from experimental data obtained from a campus parking garage. Results indicate that the proposed detection algorithm can effectively detect a wide range of passing vehicles with small error probability.

IEEE 802.11-Based Mobile IP Fast Handoff Latency Analysis

Mobile IP is a solution for mobility support in the global Internet. However, it suffers from long handoff delay. Many solutions have been proposed to reduce the handoff delay of Mobile IP. Among these solutions, Fast Handovers for Mobile IPv6 (FMIPv6) and Hierarchical Mobile IPv6 (HMIPv6) are actively developed by the Internet Engineering Task Force for future IPv6 networks. A majority of the research on performance analysis of Mobile IP handoff latency either adopts a simulation approach or is based on experimental testbeds. This paper focuses on the analytical modeling of handoff latency for the two Mobile IPv6 fast handoff protocols, FMIPv6 and HMIPv6, using IEEE 802.11-based wireless local area networks as the wireless access networks. Different from other previously proposed analytical models for handoff latency analysis, our model considers comprehensive factors from both link layer and network layer which influence the Mobile IP handoff delay. Individual analytical models for each of these factors affecting the handoff latency are developed. The outcome of this research is the probability distribution of the handoff latency occurring within a certain range based on the offered traffic load and network conditions.

Energy efficient power control policies for the low rate WPAN

Energy efficiency is a major concern in large scale wireless sensor networks. Transmit power control can provide an effective mechanism for improving energy efficiencies. In this paper, an alternative approach to power management is presented which is applicable to wireless sensor networks. The approach is based on developing power control policies which take into account the sensor networks deployment characteristics and the RF environment in which the sensor network is deployed. The method developed in the paper can be applied, in general to packet based transceivers, but the energy models developed for optimizing the transmit power are based on IEEE802.15.4/spl trade/ devices, specifically the Chipcon CC2420. As illustrated in the paper, the approach provides a straight forward method for evaluating the feasibility of a networks deployment strategy as well as provide insight into the modifications to the wireless network design to obtain greater energy efficiencies.