No abstract

For ad-hoc home networks without central coordinator, IEEE 802.11 systems merely support service differentiation. In many usage scenarios of a typical home network with applications requiring a strict quality of service (QoS), this MAC functionality is not sufficient. In order to counteract this problem, we developed in previous works a modified MAC scheme based on the IEEE 802.11 enhanced distributed channel access (EDCA) function. This paper describes enhancements of the modified MAC scheme enforcing prioritized medium access for strict QoS applications. For the first time, the established concept is realized in a distributed way with in-band signaling. Our enhanced MAC is embedded into a comprehensive IEEE 802.11n reference application to demonstrate its effectiveness in combination with the latest amendments like frame aggregation. The reference application is modeled in SystemClick, a framework for describing and evaluating packet processing applications on resource constraint network nodes. This enables functional validation and provides a path to future, cost-efficient implementations on programmable devices. On this basis, the paper presents simulation results substantiating the significant improvement of QoS parameters like delay and throughput. Besides enforcing strict priorities, collisions can be reduced to zero and the average waiting time can be decreased by up to 33 % for typical usage scenarios.

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The presented work aims at development of a management evaluation system (condition monitoring) in the event of an explosion using a network of wireless sensors. The flow of information in the situation assessment system is made possible with the applied energy autonomous and energy-efficient wireless sensor nodes. Through this evaluation system, we will be able to do a real time assessment on the state of the damaged infrastructure through which we will be able to react to the situation in the area in a timely manner. We will show a new wireless sensor network topology and develop new rules for self-synchronization for energy efficient and collision free communication which is capable of data transmission in the event of an emergency situation

The operation range and reliability of single-carrier wireless transmission systems are limited due to effects of the indoor multipath propagation environment. Multichannel systems can exploit frequency diversity and increase the reliability. Common frequency-hopping protocols change the channel continuously without consideration of the actual channel quality and require regular frame exchange for synchronization. However, in residential application scenarios, control data traffic occurs only very sporadic. In this letter, we describe an asynchronous wireless multichannel system, which utilizes good channels and avoids unnecessary overhead, but at the same time is able to change the frequency in case of a deep fade. The optimal protocol for the initial connection setup is extended for efficient long-term operation. The hopping sequences are modified based on successful transmissions in the past. The method is evaluated and simulated.Index Terms-Dynamic frequency selection, frequency hopping, frequency agility, multichannel MAC, wireless sensor networks.