The rise of social media platforms makes it a valuable information source of recent events and users’ perspective towards them. Twitter has been one of the most important communication platforms in recent years. Event detection, one of the information extraction aspects, involves identifying specified types of events in the text. Detecting events from tweets can help to predict real-world events precisely. A serious challenge that faces Arabic event detection is the lack of Arabic datasets that can be exploited in detecting events. This paper will describe FloDusTA, which is a dataset of tweets that we have built for the purpose of developing an event detection system. The dataset contains tweets written in both Modern Standard Arabic and Saudi dialect. The process of building the dataset starting from tweets collection to annotation by human annotators will be present. The tweets are labeled with four labels: flood, dust storm, traffic accident, and non-event. The dataset was tested for classification and the result was strongly encouraging.

This paper proposes a novel distributed multi-channel medium access control (MAC) protocol using fast and slow hopping sequences with dual radio interfaces. Specifically, one interface follows fast hopping and is primarily for transmission, and the other interface follows slow hopping and is generally for reception. The proposed protocol, which is in line with the IEEE 802.11 MAC strategies, is based on the multiple rendezvous approach and able to enhance the network performance and resolve the congestion. An analytical model is developed to evaluate the network performance in terms of the aggregate throughput. Furthermore, the maximum saturation throughput and the upper achievable throughput are computed. Simulations using network simulator-2 (ns-2) are conducted to validate the analytical model and demonstrate the significant enhancement of the proposed protocol in single- and multi-hop networks.

In this paper, we investigate the deficiency of uncontrolled asymmetrical transmission power over multiple channels in ad hoc environments. We further propose a novel distributed transmission power control protocol called the distributed power level DPL protocol for multi-channel ad hoc networks without requiring clock synchronization. Specifically, different transmission power levels are assigned to different channels, and nodes search for an idle channel on the basis of the received power so that the maximum allowable power of the preferred data channel is larger than or equal to the received power. If the most preferred channel of the least maximum power is busy, the nodes are able to select the next channel and so forth. As a result, interference is reduced over channels because the nodes that require higher transmission power are separated from interfering with the nodes that require lower transmission power. Two transmission power control modes are introduced for DPL: symmetrical and asymmetrical. For the symmetrical DPL protocol mode, nodes transmit at the same power level assigned to the selected channel. On the other hand, for the asymmetrical DPL protocol, nodes are allowed to transmit at a lower or equal power level that is assigned to the selected channel. Extensive ns-2-based simulation results are presented to demonstrate that the proposed protocols can enhance the network throughput compared with the existing uncontrolled asymmetrical transmission power protocol. Copyright © 2012 John Wiley & Sons, Ltd.

ABSTRACT In this paper, we study the multichannel exposed terminal problem in multihop wireless networks. We propose a multichannel medium access control (MAC) protocol, called multichannel MAC protocol with hopping reservation (MMAC‐HR), to resolve the multichannel exposed terminal problem. MMAC‐HR uses two radio interfaces; one interface is fixed over the control channel, and the other interface switches dynamically between data channels. The fixed interface supports broadcast information and reserves a data channel for any data transmission. The switchable interface, on other hand, is for data exchanges and follows independent slow hopping without requiring clock synchronization. In addition, the proposed protocol is a distributed one. By using the ns‐2 simulator, extensive simulations are performed to demonstrate that MMAC‐HR can enhance the network throughput and delay compared with existing multichannel MAC protocol. Copyright © 2011 John Wiley & Sons, Ltd.

This paper proposes a novel multi-channel medium access control (MAC) protocol using fast and slow hopping sequences with dual radio interfaces. Specifically, one interface follows fast hopping and is primary for transmission, and the second interface follows slow hopping and is mainly responsible for reception. In addition, the new protocol follows the IEEE 802.11 MAC strategy. Moreover, the new protocol is based on the multiple rendezvous approach that has been proven to enhance the network performance and resolve the congestion of the single rendezvous approach. Also, an analytical model is developed to evaluate the network performance in terms of the aggregate throughput. Computer simulations using network simulator-2 (ns-2) are conducted to validate the analytical model and demonstrate the enhancement of the proposed protocol.

Transmitting request-to-send (RTS)/clear-to-send (CTS) packets at the maximum power and data/ACK packets at the minimum power creates a asymmetrical link which has been proven to increase the collision probability. In this paper, we first discuss the deficiency of uncontrolled asymmetrical transmission power in multi-channel environments. We then propose a symmetrical power control for multi-channel multi-hop networks. Specifically, we allocate different transmission powers to different channels to create symmetrical links. Nodes select a channel based on the received power and then transmit at the power that has been assigned to the selected channel. Simulation results are given to demonstrate that the proposed scheme can significantly enhance the network performance.

In this paper, we study the multi-channel exposed terminal problem in multi-hop wireless networks. We first explain how the multi-channel exposed terminal problem occurs. We then propose a multi-channel MAC protocol, called multi-channel MAC with hopping reservation (MMAC-HR), to resolve the multi-channel exposed terminal problem. The proposed MMAC-HR protocol has the following features: 1) it does not require clock synchronization; 2) it uses channel hopping without exchanging information; 3) it is distributed; and 4) it is based on CSMA/CA for all channels. Simulation results by using the ns-2 simulator are given to demonstrate the performance of the proposed multi-channel MAC protocol.

In this paper, a credit-based user authentication scheme is proposed for delay tolerant mobile wireless networks. The proposed authentication scheme isolates the uncertain network condition in the high-delay wireless backhaul with high error rate, and accelerates the overall authentication process when the mobile terminal roams in the visited network. The performance evaluation demonstrates that the proposed credit-based authentication scheme is secure and effectively reduces the overall delay and overhead in user authentication for delay tolerant mobile wireless networks.