The draft IEEE 802.11 wireless local area network (WLAN) specification is approaching completion. In this article, the IEEE 802.11 protocol is explained, with particular emphasis on the medium access control sublayer. Performance results are provided for packetized data and a combination of packetized data and voice over the WLAN. Our performance investigation reveals that an IEEE 802.11 network may be able to carry traffic with time-bounded requirements using the point coordination function. However, our findings suggest that packetized voice traffic must be handled in conjunction with an echo canceler.

In recent years, wireless multimedia sensor networks (WMSNs) have emerged as a prominent technique for delivering multimedia information such as still images and videos. Being under the great spotlight of research communities, however, multimedia delivery over resource- constraint WMSNs poses great challenges, especially in terms of energy efficiency and quality-of-service (QoS) guarantees. In this paper, recent developments in techniques for designing highly energy-efficient and QoS-capable WMSNs are surveyed. We first study the unique characteristics and the relevantly imposed requirements of WMSNs. For each requirement we also summarize their existing solutions. Then we review recent research efforts on energy-efficient and QoS-aware communication protocols, including MAC protocols, with a focus on their prioritization and service differentiation mechanisms and disjoint multipath routing protocols.

Analysis of the draft IEEE 802.11 wireless local area network (WLAN) standard is needed to characterize the expected performance of the standard's ad hoc and infrastructure networks. The performance of the medium access control (MAC) sublayer, which consists of distributed coordination function (DCF) and point coordination function (PCF), is determined by simulating asynchronous data traffic in a 1 Mbps ad hoc network, and asynchronous data and packetized voice traffic in a 1 Mbps infrastructure network. The simulation models incorporate the effect of burst errors, packet size, RTS threshold and fragmentation threshold on network throughput and delay. The results show that the IEEE 802.11 WLAN can achieve a reasonably high efficiency when the medium is almost error-free, but may degrade appreciably under harsh fading. The results also show that time-sensitive traffic such as packet voice can be supported together with other intensive traffic such as packet data. However, an echo canceller is required for packet voice systems.

This letter presents a novel anti-collision algorithm for radio frequency identification (RFID) systems that drastically improve throughput performance via an intelligent access control for capture inducement. In order to induce the capture, our protocol attempts to divide tags into multiple groups depending on received signal strength, and allow only a selected pair of groups to join the contention process, in which the outcome of contention is more likely to lead to capture due to a significant difference in their signal strengths. Numerical results show that our proposed algorithm significantly outperforms the existing approaches in terms of throughput.

With the advent of the Internet of Things (IoT) era, a wide array of wireless sensors supporting the IoT have proliferated. As key elements for enabling the IoT, wireless sensor nodes require minimal energy consumption and low device complexity. In particular, energy-efficient resource scheduling is critical in maintaining a network of wireless sensor nodes, since the energy-intensive processing of wireless sensor nodes and their interactions is too complicated to control. In this study, we present a practical deep Q-network (DQN)-based packet scheduling algorithm that coordinates the transmissions of multiple IoT devices. The scheduling algorithm dynamically adjusts the connection interval (CI) and the number of packets transmitted by each node within the interval. Through various experiments, we verify how effectively the proposed scheduler improves energy efficiency and handles the time-varying nature of the network environment. Moreover, we attempt to gain insight into the optimized packet scheduler by analyzing the policy of the DQN scheduler. The experimental results show that the proposed scheduling algorithm can further prolong a network’s lifetime in a dynamic network environment in comparison with that in other alternative schemes while ensuring the quality of service (QoS).