Zhongjiang Yan

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Wireless sensor networks (WSNs) are widely used for various applications. In some applications, it is very likely that the number of sensors is limited, the initial deployment is random, and deployment “holes” (i.e., subareas where there is no sensor) may exist. Therefore, a major challenge in WSNs is to improve the network coverage. A viable solution is to(More)
Recently, IEEE drew up a new task group named TGax to draft out the standard IEEE 802.11ax for next generation WLANs. However, the average throughput is very low due to the current medium access control (MAC) protocol. A promising solution for this problem is to draw Orthogonal Frequency Division Multiple Access (OFDMA) into IEEE 802.11ax to enable(More)
In a 1-D linear vehicular ad hoc network (1-DL-VANET), some vehicles may leave the network (e.g., at highway exits), which may make the 1-DL-VANET disconnected. Thus, it is important to analyze the connectivity of the 1-DL-VANET. When removal of any (k− 1) arbitrary nodes from a network does not disconnect the network, the network is said to be k-connected.(More)
The physical (PHY) layer peak rate of the wireless local area network (WLAN) has been almost exponentially improved over the past 15 years since 1999. However, it is proved that the throughput is very low comparing to the PHY peak rate, and the media access control (MAC) efficiency is very low in the current WLANs specification, especially in dense(More)
Location estimation is an essential issue for wireless sensor networks (WSN). In this paper a new localization estimation algorithm for WSN is proposed which is based on the Grid-Scan method. In the proposed algorithm, the node collects its 1-hop and 2-hop anchors before the localization algorithm is waked up. Firstly, it obtains the intersection region of(More)
For a wireless ad hoc network to achieve fault-tolerance, it is desired that the network is bi-connected. This means that each pair of nodes in the network have at least two node-disjoint paths between them, and thus, failure at any single node does not partition the network. In other words, in a bi-connected network, there is no cut-node (defined as a node(More)
We study fast data collection in linear duty-cycled wireless sensor networks. We first present a benchmark algorithm that can achieve optimality in a general case (i.e., in non-dutycycled case). Then based on the insights obtained in the general case, we propose an optimal algorithm for the case when each sensor only works at one slot in a cycle in the(More)
In the past few decades, the world has witnessed a rapid growth in mobile communication and reaped great benefits from it. Even though the fourth generation (4G) mobile communication system is just being deployed worldwide, proliferating mobile demands call for newer wireless communication technologies with even better performance. Consequently, the fifth(More)
The multi-channel MAC protocols have been proposed recently to improve the network capacity by accommodating more concurrent transmissions. In this paper, we propose a distributed multi-channel MAC protocol using reliable multiple channel reservation with only a single transceiver. Specifically, the control handshake information is reserved to be(More)
In a vehicular delay tolerant network, the problem of scheduling the traffic from a roadside unit to passing-by vehicles is studied. A cost function is associated with a scheduled transmission. And if a delay bound is violated, a penalty cost is charged. The optimal stopping theory is applied to decide when the roadside unit should schedule its accumulated(More)