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In this paper, the RT-WiFi architecture is proposed to handle real-time (RT) communication in infrastructured IEEE 802.11 networks operating in high density industrial environments. This architecture is composed of a time division multiple access (TDMA)-based coordination layer that schedules the medium access of RT traffic flows, and an underlying traffic separation mechanism that is able do handle the coexistence of RT and non-RT traffic sources in the same communication environment. The simulation assessment considers an overlapping basic service set (OBSS), where a set of RT and non-RT stations share the same frequency band. The performance assessment compares the behaviour of the RT-WiFi architecture vs. the behaviour of standard distributed coordination function (DCF), point coordination function (PCF), enhanced distributed channel access (EDCA), and hybrid coordination function (HCF) controlled channel access (HCCA) medium access control mechanisms. A realistic error-prone model has been used to measure the impact of message losses in the RT-WiFi architecture. It is shown that the proposed RT-WiFi architecture offers a significantly enhanced behaviour when compared with the use of IEEE 802.11 standard mechanisms, in what concerns average deadline misses and average access delays. Moreover, it also offers an almost constant access delay, which is a relevant characteristic when supporting RT applications.

Wireless sensor networks (WSNs) can be used to support monitoring activities in a wide range of applications and communication environments. Its usage in extreme conditions, in what concerns pressure, temperature, and humidity, must be carefully assessed before the network deployment. In particular, the temperature variations have a direct impact upon the behavior of WSNs through the batteries of sensor nodes. These electrochemical devices are highly susceptible to temperature variations, which modifies the offered effective charge capacity. In this context, it is difficult to estimate the behavior of batteries over time, impairing the extraction of relevant information for energy-aware approaches. Such information, particularly battery state of charge, voltage, and lifetime, is often used by WSN simulators to predict the communication behavior in different scenarios. Nevertheless, WSN simulators generally use simplistic battery models, causing significant deviations in simulation results when compared with actual WSN deployments. This paper describes the implementation of the Temperature-Dependent Kinetic Battery Model (T-KiBaM) in the Castalia simulator, which enables a considerable improvement of the accuracy of simulations in communication environments with different temperature conditions. An experimental assessment has been performed with temperature variations over time to validate the usage of the T-KiBaM battery model. The experimental results indicate that the T-KiBaM model is quite accurate when estimating battery behavior under both different temperature set points and different temperature variations.

This paper proposes a real-time communication scheme for wireless local area network (WLAN) infrastructure. This strategy was called Group Sequential Communication (GSC). The GSC has the main goal to reduce the network overhead due to the Polling, Ack and QoS Null Frames of Hybrid Coordination Function Controlled Channel Access (HCCA) in IEEE 802.11e, because it uses a Virtual Token Passing procedure to priority the real-time communication over WLAN. In order to improve the confiability of the new scheme is presented a fault-tolerant mechanism based on Block-Ack strategy to avoid missing real-time messages. The GSC was implemented in NS2 and simulation results have proved the superior performance of GSC in comparison with HCCA for real-time industrial communications.

Currently, there is a trend towards the implementation of industrial communication systems using wireless networks. However, keeping up with the timing constraints of real-time traffic in wireless environments is a hard task. The main reason is that real-time devices must share the same communication medium with timing unconstrained devices. The VTP-CSMA architecture has been proposed to deal with this problem. It considers an unified wireless system in one frequency band, where the communication bandwidth is shared by real-time and non-real-time communicating devices. The proposed architecture is based on a virtual token passing (VTP) procedure that circulates a virtual token among real-time devices. This virtual token is complemented by an underlying traffic separation mechanism that prioritizes the real-time traffic over the non-real-time traffic. This is one of the most innovative aspects of the proposed architecture, as most part of real-time communication approaches are not able to handle timing unconstrained traffic sharing the same communication medium. A ring management procedure for the VTP-CSMA architecture is also proposed, allowing real-time stations to adequately join/leave the virtual ring.