A Distributed Query Protocol in Wireless Sensor Networks

In wireless sensor networks, query execution over a specific geographical region is an essential function for collecting sensed data. However, sensor nodes deployed in sensor networks have limited battery power. Hence, the minimum number of connected sensor nodes that covers the queried region in a sensor network must be determined. This paper proposes an efficient distributed protocol to find a subset of connected sensor nodes to cover the queried region. Each node determines whether to be a sensing node to sense the queried region according to its priority. The proposed protocol can efficiently construct a subset of connected sensing nodes and respond the query request to the sink node. In addition, the proposed protocol is extended to solve the k-coverage request. Simulation results show that our protocol is more efficient and has a lower communication overhead than the existing protocol.     

Energy efficient routing protocols for mobile ad hoc networks

Although establishing correct and efficient routes is an important design issue in mobile ad hoc networks (MANETs), a more challenging goal is to provide energy efficient routes because mobile nodes' operation time is the most critical limiting factor. This article surveys and classifies the energy‐aware routing protocols proposed for MANETs. They minimize either the active communication energy required to transmit or receive packets or the inactive energy consumed when a mobile node stays idle but listens to the wireless medium for any possible communication requests from other nodes. Transmission power control approach and load distribution approach belong to the former category, and sleep/power‐down mode approach belongs to the latter category. While it is not clear whether any particular algorithm or a class of algorithms is the best for all scenarios, each protocol has definite advantages/disadvantages and is well suited for certain situations. The purpose of this paper is to facilitate the research efforts in combining the existing solutions to offer a more energy efficient routing mechanism. Copyright © 2003 John Wiley & Sons, Ltd.     

A Power-Aware Multicast Routing Protocol for Mobile Ad Hoc Networks With Mobility Prediction

A mobile ad hoc network (MANET) is a dynamically reconfigurable wireless network that does not have a fixed infrastructure. Due to the high mobility of nodes, the network topology of MANETs changes very fast, making it more difficult to find the routes that message packets use. Because mobile nodes have limited battery power, it is therefore very important to use energy in a MANET efficiently. In this paper, we propose a power-aware multicast routing protocol (PMRP) with mobility prediction for MANETs. In order to select a subset of paths that provide increased stability and reliability of routes, in routing discovery, each node receives the RREQ packet and uses the power-aware metric to get in advance the power consumption of transmitted data packets. If the node has enough remaining power to transmit data packets, it uses the global positioning system (GPS) to get the location information (i.e., position, velocity and direction) of the mobile nodes and utilizes this information to calculate the link expiration time (LET) between two connected mobile nodes. During route discovery, each destination node selects the routing path with the smallest LET and uses this smallest link expiration time as the route expiration time (RET). Each destination node collects several feasible routes and then selects the path with the longest RET value as the primary routing path. Then the source node uses these routes between the source node and each destination node to create a multicast tree. In the multicast tree, the source node will be the root node and the destination nodes will be the leaf nodes. Simulation results show that the proposed PMRP outperforms MAODV (Royer, E. M. & Perkins, C. E. (1999). In Proceedings of the ACM MOBICOM, pp. 207–218, August 1999.) and RMAODV (Baolin, S. & Layuan, L. (2005). In Proceeding of the 2005 IEEE International symposium on microwave antenna, propagation and EMC technologies for wireless communications, Vol. 2, pp. 1514–1517, August 2005.).     

Active query forwarding in sensor networks

While sensor networks are going to be deployed in diverse application specific contexts, one unifying view is to treat them essentially as distributed databases. The simplest mechanism to obtain information from this kind of a database is to flood queries for named data within the network and obtain the relevant responses from sources. However, if the queries are (a) complex, (b) one-shot, and (c) for replicated data, this simple approach can be highly inefficient. In the context of energy-starved sensor networks, alternative strategies need to be examined for such queries.We propose a novel and efficient mechanism for obtaining information in sensor networks which we refer to as ACtive QUery forwarding In sensoR nEtworks (ACQUIRE). The basic principle behind ACQUIRE is to consider the query as an active entity that is forwarded through the network (either randomly or in some directed manner) in search of the solution. ACQUIRE also incorporates a look-ahead parameter d in the following manner: intermediate nodes that handle the active query use information from all nodes within d hops in order to partially resolve the query. When the active query is fully resolved, a completed response is sent directly back to the querying node.We take a mathematical modelling approach in this paper to calculate the energy costs associated with ACQUIRE. The models permit us to characterize analytically the impact of critical parameters, and compare the performance of ACQUIRE with respect to other schemes such as flooding-based querying (FBQ) and expanding ring search (ERS), in terms of energy usage, response latency and storage requirements. We show that with optimal parameter settings, depending on the update frequency, ACQUIRE obtains order of magnitude reduction over FBQ and potentially over 60–75% reduction over ERS (in highly dynamic environments and high query rates) in consumed energy. We show that these energy savings are provided in trade for increased response latency. The mathematical analysis is validated through extensive simulations.     

基于深度学习的域名查询行为向量空间嵌入

提出一种新的分析DNS查询行为的方法,用深度学习机制将被查询域名和请求查询的主机分别映射到向量空间,域名或主机的关联分析转化成向量的运算。通过对2组真实的校园网DNS日志数据集的处理,发现该方法很好地保持了关联特性,使用降维处理以及聚类分析,不仅可以让人直观地发现隐含的关联关系,还有助于发现网络中的异常问题如botnet等。     

Using Heterogeneity to Enhance Random Walk-based Queries

It is a well-known property of random walks that nodes with higher degree are visited more frequently. Based on this property, we propose the use of cluster-heads (high-degree nodes) together with a simple push-pull mechanism to enhance the performance of random walk-based querying: events are pushed towards high-degree nodes (cluster-heads) and pulled from the cluster-heads by a random-walk originated at the sink. Following this simple mechanism, we show that having even a small percentage of cluster-heads (degree-heterogeneity) can provide significant improvements in query performance. For linear topologies, we use connections between random walks and electrical resistances to prove that placing uniformly a fraction of 4/5k cluster-heads (where 2k is the degree of each cluster-head), can reduce querying costs from Θ(n ²) to Θ(n ²/k ²), an improvement of Θ(k ²). For more realistic two-dimensional topologies, we use Markov chain analysis and simulations to show a similar trend—using about 10% of the nodes as cluster-heads provides a query cost improvement between 30% and 70% depending on the coverage of the high-degree nodes.     

GMZRP: Geography-aided Multicast Zone Routing Protocol in Mobile Ad Hoc Networks

This paper presents the design and evaluation of a highly efficient on-demand multicast routing protocol for mobile ad hoc networks (MANETs). The protocol, called Geography-aided Multicast Zone Routing Protocol (GMZRP), eliminates as much as possible duplicate route queries by using a simple yet effective strategy for propagating the multicast route request (MRREQ) packets. GMZRP is the first hybrid multicast protocol taking the advantages of both topological routing and geographical routing. It partitions the network coverage area into small zones and guarantees that each geographic zone is queried only once. GMZRP maintains a multicast forwarding tree at two levels of granularities, i.e., the zone granularity and the node granularity. By doing this, it can easily handle route breakage since the zone level information can help recover the link failure at the node level. The results of the performance evaluation of GMZRP using simulation show that, comparing with the well-known multicast protocol ODMRP (On-Demand Multicast Routing Protocol), GMZRP has much lower protocol overhead in terms of query packets and, meanwhile, achieves competing packet delivery ratio and shorter delivery latency.

Query routing mismatch alleviation architecture for P2P file lookup in MANETs

A cross-layer optimized query routing mismatch alleviation(QRMA)architecture is proposed to mitigate the problem of query routing mismatch(QRM)phenomenon between the structured peer to peer(P2P)overlay and the routing layer in mobile Ad-hoc networks(MANETs),which is an important issue that results in the inefficiency of lookup process in the system.Explicated with the representative Chord protocol,the proposal exploits the information of topologic neighbors in the routing layer of MANETs to find if there is any optimized alternative next hop in P2P overlay during conventional lookup progress.Once an alternative next hop is detected,it will take the shortcut to accelerate the query procedure and therefore alleviate the QRM problem in scalable MANETs without any assistance of affiliation equipments such as GPS device.The probability of finding out such an alternative node is formulated and the factors that could increase the chance are discussed.The simulation results show that the proposed architecture can effectively alleviate the QRM problem and significantly improve the system performance compared with the conventional mechanism.     

Secure multicast routing protocols in mobile ad‐hoc networks

A mobile ad‐hoc network (MANET) is a collection of autonomous nodes that communicate with each other by forming a multi‐hop radio network. Routing protocols in MANETs define how routes between source and destination nodes are established and maintained. Multicast routing provides a bandwidth‐efficient means for supporting group‐oriented applications. The increasing demand for such applications coupled with the inherent characteristics of MANETs (e.g., lack of infrastructure and node mobility) have made secure multicast routing a crucial yet challenging issue. Recently, several multicast routing protocols (MRP) have been proposed in MANETs. Depending on whether security is built‐in or added, MRP can be classified into two types: secure and security‐enhanced routing protocols, respectively. This paper presents a survey on secure and security‐enhanced MRP along with their security techniques and the types of attacks they can confront. A detailed comparison for the capability of the various routing protocols against some known attacks is also presented and analyzed. Copyright © 2013 John Wiley & Sons, Ltd.     

Feature Selection Based Correlation Attack on HTTPS Secure Searching

Search engine plays an irreplaceable role in web information organizing and accessing. It is very common for Internet users to query a search engine when retrieving web information. Sensitive data about search engine user’s intentions or behavior can be inferred from his query phrases, the returned results pages, and the webpages he visits subsequently. In order to protect contents of communications from being eavesdropped, some search engines adopt HTTPS by default to provide bidirectional encryption. This only provides an encrypted channel between user and search engine, the majority of webpages indexed in search engines’ results pages are still on HTTP enabled websites and the contents of these webpages can be observed by attackers once the user click on these links. Imitating attackers, we propose a novel approach for attacking secure search through correlating analysis of encrypted search with unencrypted webpages. We show that a simple weighted TF–DF mechanism is sufficient for selecting guessing phrase candidates. Imitating search engine users, by querying these candidates and enumerating webpages indexed in results pages, we can hit the definite query phrases and meanwhile reconstruct user’s web-surfing trails through DNS-based URLs comparison and flow feature statistics-based network traffic analysis. In the experiment including 28 search phrases, we achieved 67.86% hit rate at first guess and 96.43% hit rate within three guesses. Our empirical research shows that HTTPS traffic can be correlated and de-anonymized through HTTP traffic and secured search of search engines are not always secure unless HTTPS by default enabled everywhere.     

In‐band bootstrapping in database‐driven multi‐hop cognitive radio networks

Database‐driven approach has emerged recently as an alternative or supplement for spectrum sensing for cognitive radio networks (CRNs). Within database‐driven CRNs, master devices obtain spectrum information by direct connection to a spectrum database, while slave devices can only access spectrum information indirectly via masters. The in‐band approach completely based on primary spectrum channels can be used, which eliminates the need for out‐of‐band connections and eases the adoption of the database‐driven spectrum sharing. In this paper, we study the in‐band bootstrapping process for database‐driven multi‐hop CRNs, where master/slave devices form a multi‐hop networks, and slaves need multi‐hop communications to obtain spectrum information from the master during bootstrapping. We start with the basic design of in‐band bootstrap protocol, whose performance is unsatisfactory of protocol overhead and bootstrap time. Then we propose 2 enhancements: first, we incorporates the recursive fractional spectrum information query scheme to reduce protocol overhead; then we propose the prefetch scheme to reduce the bootstrap time. According to the analysis and simulation results, our proposed protocols can greatly improve the performance: the recursive fractional spectrum information query enhancement reduces up to 40% of the overhead, the prefetch enhancement reduces more than 20% of the bootstrap time.     

Load-Balanced Location Management for Cellular Mobile Systems Using Quorums and Dynamic Hashing

This paper presents a new distributed location management strategy for cellular mobile systems. Its salient features are fast location update and query, load balancing among location servers, and scalability. The strategy employs dynamic hashing techniques and quorums to manage location update and query operations. The proposed strategy does not require a home location register (HLR) to be associated with each mobile node. Location updates and queries for a mobile node are multicast to subsets of location servers, which change with time depending on the location of mobile node/querying node and load on the servers. Simulation experiments demonstrate that such dynamism prevents situations of heavy load on some location servers when mobile nodes are not uniformly distributed in space, or when some mobile nodes have their location updated or queried more often than others. Also, queries return the latest location information of a mobile node with a very high probability. The proposed scheme requires at most one unicast and two rounds of message multicasting for location update and query operations. All multicast messages have a small payload and are restricted to the high bandwidth wired part of the mobile network resulting in low communication overhead. Moreover, if a quorum of location servers gets overloaded, part of its load can be transferred to another lightly loaded quorum using dynamic hashing techniques.     

Indexing and encoding based image feature representation with bin overlapped similarity measure for CBIR applications

In Content Based Image Retrieval (CBIR) system, the exhaustive search for a given query image to find the relevant images in the database are non-scalable. In this paper, we propose indexing, coding technique and similarity measure to address the above mentioned problem. We consider the color histogram of the image and its bin values are analyzed to understand the color information in the image. The histogram dimension is reduced by removing trivial bins and only those bins that represent color information significantly are considered. Based on the dimensions of the histogram, it is clustered and indexed. The Golomb–Rice (GR) coding is used to encode the indexed histograms. The Bin Overlapped Similarity Measure (BOSM) is proposed to compute the distance values between query and database image histograms. The performance of proposed approach is evaluated on benchmark datasets and found that the performance of the proposed approach is encouraging.     

Bandwidth‐satisfied routing in multi‐rate MANETs by cross‐layer approach

Previous quality‐of‐service (QoS) routing protocols in mobile ad hoc networks (MANETs) determined bandwidth‐satisfied routes for QoS applications. Since the multi‐rate enhancements have been implemented in MANETs, QoS routing protocols should be adapted to exploit them fully. However, existing works suffer from one bandwidth‐violation problem, named the hidden route problem (HRP), which may arise when a new flow is permitted and only the bandwidth consumption of the hosts in the neighborhood of the route is computed. Without considering the bandwidth consumption to ongoing flows is the reason the problem is introduced. This work proposes a routing protocol that can avoid HRP for data rate selection and bandwidth‐satisfied route determination with an efficient cross‐layer design based on the integration of PHY and MAC layers into the network layer. To use bandwidth efficiently, we aim to select the combination of data rates and a route with minimal bandwidth consumption to the network, instead of the strategy adopted in the most previous works by selecting the combination with the shortest total transmission time. Using bandwidth efficiently can increase the number of flows supported by a network. Copyright 2010 John Wiley & Sons, Ltd.     

Cross‐layer design for topology control and routing in MANETs

A mobile ad hoc network (MANET) is a self‐organized and adaptive wireless network formed by dynamically gathering mobile nodes. Since the topology of the network is constantly changing, the issue of routing packets and energy conservation become challenging tasks. In this paper, we propose a cross‐layer design that jointly considers routing and topology control taking mobility and interference into account for MANETs. We called the proposed protocol as Mobility‐aware Routing and Interference‐aware Topology control (MRIT) protocol. The main objective of the proposed protocol is to increase the network lifetime, reduce energy consumption, and find stable end‐to‐end routes for MANETs. We evaluate the performance of the proposed protocol by comprehensively simulating a set of random MANET environments. The results show that the proposed protocol reduces energy consumption rate, end‐to‐end delay, interference while preserving throughput and network connectivity. Copyright © 2010 John Wiley & Sons, Ltd.     

A novel efficient power‐saving MAC protocol for multi‐hop MANETs

Following recent advances in the performance of ad hoc networks, the limited life of batteries in mobile devices poses a bottleneck in their development. Consequently, how to minimize power consumption in the Medium Access Control (MAC) layer of ad hoc networks is an essential issue. The power‐saving mode (PSM) of IEEE 802.11 involves the Timing Synchronization Function to reduce power consumption for single‐hop mobile ad hoc networks (MANETs). However, the IEEE 802.11 PSM is known to result in unnecessary energy consumption as well as the problems of overheating and back‐off time delay. Hence, this study presents an efficient power‐saving MAC protocol, called p‐MANET, based on a Multi‐hop Time Synchronization Protocol, which involves a hibernation mechanism, a beacon inhibition mechanism, and a low‐latency next‐hop selection mechanism for general‐purpose multi‐hop MANETs. The main purposes of the p‐MANET protocol are to reduce significantly the power consumption and the transmission latency. In the hibernation mechanism, each p‐MANET node needs only to wake up during one out of every N beacon interval, where N is the number of beacon intervals in a cycle. Thus, efficient power consumption is achieved. Furthermore, a beacon inhibition mechanism is proposed to prevent the beacon storm problem that is caused by synchronization and neighbor discovery messages. Finally, the low‐latency next‐hop selection mechanism is designed to yield low transmission latency. Each p‐MANET node is aware of the active beacon intervals of its neighbors by using a hash function, such that it can easily forward packets to a neighbor in active mode or with the least remaining time to wake up. As a consequence, upper‐layer routing protocols can cooperate with p‐MANET to select the next‐hop neighbor with the best forwarding delay. To verify the proposed design and demonstrate the favorable performance of the proposed p‐MANET, we present the theoretical analysis related to p‐MANET and also perform experimental simulations. The numerical results show that p‐MANET reduces power consumption and routing latency and performs well in extending lifetime with a small neighbor discovery time. Copyright © 2011 John Wiley & Sons, Ltd.     

Brands电子现金系统的改进

Brands电子现金系统为防止重复使用电子现金,主要通过查询银行存储的电子现金数据来识别重复花费的用户,极大地增加了银行服务器的数据存储量和查询负载。把电子现金的提取时间嵌入到电子现金以及银行对电子现金的签名中,只需要存储未过期的电子现金数据,这样大大地减少了银行存储的数据量,并且按照提取时间进行数据库索引,可以有效地提高数据查询效率,较好地解决了银行瓶颈问题。     

Efficient and distributed access control for sensor networks

Sensor networks are a promising computing paradigm for monitoring the physical environment and providing observations for various uses. In hostile situations, it is critical to enforce network access control to ensure the integrity, availability, and at times confidentiality of the sensor data. A natural idea is to adopt a centralized design where every access request from users goes through a trusted base station. However, this idea is not practical due to the cost and efficiency issues. This paper proposes two efficient and distributed access control methods, uni-access query and multi-access query. The uni-access query uses only symmetric cryptographic operations; it allows (1) a user to directly access the data on any sensor node in the network without going through the base station and (2) a sensor to protect its data so that only authorized users can access. Compared to existing solutions, this scheme is much more flexible and efficient. In addition, this scheme can also support privilege delegation, which allows a user to delegate all or part of its privilege to others without using the base station. The multi-access query applies public key cryptography to provide an additional feature, which allows a user to access the data on many sensor nodes via a single query. Compared to existing solutions that require a user to send at least one request for every sensor node to be queried, the multi-access query reduces the communication overhead significantly. The theoretical analysis and simulation evaluation show that the proposed schemes are practical for access control in sensor networks.     

Adaptive zone routing protocol for ad hoc network nodes with non‐uniform mobilities

In recent years, a variety of new routing protocols for mobile ad hoc wireless NETworks (MANETs) have been developed. Performance evaluation and comparison of many of these routing protocols have been performed using detailed simulation models. Zone routing protocol (ZRP) is one of these routing protocols, which is a hybrid routing protocol that proactively maintains routing information for a local neighbourhood (routing zone), while reactively acquiring routes to destinations beyond the routing zone. The studies on ZRP have assumed homogeneous scenarios where all mobile nodes have uniform mobility and are statistically identical, lacking the studies on heterogeneous scenarios where mobile nodes move with non‐uniform mobilities in the same network. In this paper, we study the performance of ZRP in such scenarios. We propose an efficient scheme for ZRP to adapt to the non‐uniform mobilities scenario and study its performance for different mobility scenarios, network loads and network sizes. Copyright © 2003 John Wiley & Sons, Ltd.