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1.
Wireless Networks - In a mobile sensor network with a mobile sink, choosing the next hop depends on the current location of the sink. This necessitates a frequent update of routing paths within the...  相似文献   
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Guaranteeing end-to-end data security in wireless sensor networks (WSNs) is important and has drawn much attention of researchers over past years. Because an attacker may take control of compromised sensor nodes to inject bogus reports into WSNs, enhancing data authenticity becomes a necessary issue in WSNs. Unlike PCREF (Yang et al. in IEEE Trans Comput 64(1):4–18, 2015) (LEDS, Ren et al. in IEEE Trans Mobile Comput 7(5):585–598, 2008), digital signature rather than message authentication polynomials (message authentication codes) is adopted by our protocol in en-route filtering. Keeping the advantages of clusters in PCREF and overcoming the drawbacks in LEDS, an enhanced and efficient cluster-based security protocol is proposed in this paper. The proposed protocol can guarantee end-to-end data authentication with the aid of digital signature and exhibits its effectiveness and efficiency through security analysis and performance analysis. Our analytical results show that the proposed protocol significantly outperforms the closely related protocols in the literature in term of security strength and protocol overhead.  相似文献   
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In this paper, we propose an efficient algorithm, called CMP-Miner, to mine closed patterns in a time-series database where each record in the database, also called a transaction, contains multiple time-series sequences. Our proposed algorithm consists of three phases. First, we transform each time-series sequence in a transaction into a symbolic sequence. Second, we scan the transformed database to find frequent patterns of length one. Third, for each frequent pattern found in the second phase, we recursively enumerate frequent patterns by a frequent pattern tree in a depth-first search manner. During the process of enumeration, we apply several efficient pruning strategies to remove frequent but non-closed patterns. Thus, the CMP-Miner algorithm can efficiently mine the closed patterns from a time-series database. The experimental results show that our proposed algorithm outperforms the modified Apriori and BIDE algorithms.  相似文献   
5.
A movement based location update (MBLU) scheme is an LU scheme, under which a user equipment (UE) performs an LU when the number of cells crossed by the UE reaches a movement threshold. The MBLU scheme suffers from ping-pong LU effect. The ping-pong LU effect arises when the UE that moves repetitively between two adjacent cells performs LUs in the same way as in the case of straight movement. To tackle the ping-pong LU effect encountered by the original MBLU (OMBLU) scheme, an improved MBLU (IMBLU) scheme was proposed in the literature. Under the IMBLU scheme, the UE performs an LU when the number of different cells, rather than the number of cells, visited by the UE reaches the movement threshold. In this paper we develop an embedded Markov chain model to calculate the signaling cost of the IMBLU scheme. We derive analytical formulas for the signaling cost, whose accuracy is tested through simulation. It is observed from a numerical study based on these formulas that 1) the signaling cost is a downward convex function of the movement threshold, implying the existence of an optimal movement threshold that can minimize the signaling cost, and that 2) the reduction in the signaling cost achieved by the IMBLU scheme relative to the OMBLU scheme is more prominent in the case of stronger repetitiveness in the UE movement. The model developed and the formulas derived in this paper can guide the implementation of the IMBLU scheme in wireless communication networks.  相似文献   
6.
Focusing on a large-scale wireless sensor network with multiple base stations (BS), a key management protocol is designed in this paper. For securely relaying data between a node and a base station or two nodes, an end-to-end data security method is adopted by this protocol. Further employing a distributed key revocation scheme to efficiently remove compromised nodes then forms our key management protocol celled multi-BS key management protocol (MKMP). Through performance evaluation, we show that MKMP outperforms LEDS Ren et al. (IEEE Trans Mobile Comput 7(5):585–598, 2008) in terms of efficiency of resilience against the node capture attack. With the analysis of key storage overheads, we demonstrate that MKMP performs better than mKeying Wang et al. (A key management protocol for wireless sensor networks with multiple base stations. In: Procceedings of ICC'08, pp 1625–1629, 2008) in terms of this overhead.  相似文献   
7.
How to guarantee both quality of service (QoS) and fairness in wireless local area networks (WLANs) is a challenging issue. To touch this issue, a fair medium access control (MAC) scheme called fair round robin binary countdown (FRRBC) adopting the eminent concepts of allowance and binary countdown is proposed in this paper. FRRBC can guarantee QoS for both audio and video with the aid of adaptive adjustment on system parameters and some extra rules designed according to delay bounds. Using multiple mapping functions from allowances to fixed-bit binary numbers to indicate different priorities, FRRBC not only provides guaranteed system performance but also achieves good fairness. Finally, we demonstrate that FRRBC can significantly outperform the enhanced distributed channel access (EDCA) (IEEE 802.11 WG in IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. Amendment 8: Medium Access Control (MAC) Quality of Service Enhancements, 2005) and the synchronized medium access control (SYN-MAC) (Wu HY et al. in Mobile Netw Appl 11:627–637, 2005) because of its superiority to offer guaranteed QoS for both audio and video, low delay jitter, low blocking ratio, and good fairness. Of course, FRRBC can be illustrated to be a better choice than the enhanced distributed elastic round robin (EDERR) (Ferng HW, Liau HY in IEEE Trans Mobile Comput 8(7):880–894, 2009).  相似文献   
8.
Abstract

Settlement–time behaviors in the last stage of consolidation are studied both in the laboratory and in the field. It is shown that the long-term settlement–time curves observed in the field are linear with the logarithm of time and the rate of the long-term settlement are analogous to the rate of secondary compression measured in a laboratory. The finite difference consolidation analyses for cohesive soils exhibiting large amounts of secondary compression during primary consolidation provide fairly good predictions of the settlement–time curves observed in the laboratory and in the field. In this paper, the applicability of the secondary compression model established in the laboratory is examined in in situ conditions. The initial rate of secondary compression used in this paper has a predominant influence on the settlement–time curve with different drainage distances. It is emphasized that the assumption for unknown secondary compression behaviors during the primary consolidation has a predominant influence on the settlement–time curve.  相似文献   
9.
Three predictive and dynamic sleep time planning (PDSTP) energy-efficient mechanisms are proposed in this paper to simultaneously improve energy efficiency and packet delay for IEEE 802.16e. To estimate the time instant when a mobile station (MS) should wake up for receiving downlink packets, a prediction method is designed. With the predicted time instant, an MS is then allowed to sleep as much as possible using multiple maximum sleep intervals followed by a smaller sleep interval before the predicted time instant. After the predicted time instant, a few smaller sleep intervals with a trend of constant level (CL), exponential decrease (ED), or linear decrease (LD) can be further arranged. To react to the outlier of prediction, exponential increase for sleep intervals can be extended. The combination of the aforementioned designs then forms our three proposed mechanisms, namely, PDSTP-CL, PDSTP-ED, and PDSTP-LD. Via simulations, we show that PDSTP-CL not only performs better than PDSTP-ED and PDSTP-LD under general situations but also outperforms the standard sleep mode operation of the type-I power saving class (PSC-I) in IEEE 802.16e and the exponential sleep time backoff mechanism (ESTBM) in the literature in terms of energy efficiency and packet delay.  相似文献   
10.
It was shown that the hybrid coordination function control channel access (HCCA) is capable of guaranteeing quality of service in wireless local area networks. However, there is still no comprehensive analytical model for HCCA. Therefore, novel modeling of pure HCCA based on the cyclic-service queueing system is provided in this paper. Our model is general enough to accept a wide range of schedulers and various types of traffic under the finite buffer policy. Via comparisons with simulations, high accuracy of the analytical model is exhibited. Furthermore, some valuable insights and recommendations on how to improve the HCCA performance are revealed by investigating the HCCA mode through the proposed model.  相似文献   
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