MOTIVATION: Error detection/correction codes play an important role to reduce writing and/or reading costs in DNA data storage. Sequence analysis algorithms also make a crucial effect on error correction but have been executed independently from the decoding of error correction codes. In conventional sequence analysis, low-quality reads are usually discarded. For DNA data storage, low-quality reads can be constructively used to sequence analysis with the assistance of error detection/correction codes. RESULTS: We obtained the low-quality reads which failed to pass the chastity filter in Illumina NGS sequencing. We confirmed the effectiveness of the extra low-quality reads by providing error statistics and performing decoding with them. We proposed a sequence clustering algorithm for various-length reads and a consensus algorithm based on probabilistic majority and error detection to efficiently exploit the extra reads. The proposed methods reduced the reading cost by 6.83% on average and up to 19.67% while maintaining the writing cost. AVAILABILITY AND IMPLEMENTATION: https://github.com/PParkJy/SAD-DNAstorage (10.5281/zenodo.15571858).

MOTIVATION: DNA-based data storage is one of the most attractive research areas for future archival storage. However, it faces the problems of high writing and reading costs for practical use. There have been many efforts to resolve this problem, but existing schemes are not fully suitable for DNA-based data storage, and more cost reduction is needed. RESULTS: We propose whole encoding and decoding procedures for DNA storage. The encoding procedure consists of a carefully designed single low-density parity-check code as an inter-oligo code, which corrects errors and dropouts efficiently. We apply new clustering and alignment methods that operate on variable-length reads to aid the decoding performance. We use edit distance and quality scores during the sequence analysis-aided decoding procedure, which can discard abnormal reads and utilize high-quality soft information. We store 548.83 KB of an image file in DNA oligos and achieve a writing cost reduction of 7.46% and a significant reading cost reduction of 26.57% and 19.41% compared with the two previous works. AVAILABILITY AND IMPLEMENTATION: Data and codes for all the algorithms proposed in this study are available at: https://github.com/sjpark0905/DNA-LDPC-codes.

Videos contain visual and auditory information. Visual information in a video can include images of people, objects, and the landscape, whereas auditory information includes voices, sound effects, background music, and the soundscape. The audio content can provide detailed information on the story by conducting a voice and atmosphere analysis of the sound effects and soundscape. Metadata tags represent the results of a media analysis as text. The tags can classify video content on social networking services, like YouTube. This paper presents the methodologies of speech, audio, and music processing. Also, we propose integrating these audio tagging methods and applying them in an audio metadata generation system for video storytelling. The proposed system automatically creates metadata tags based on speech, sound effects, and background music information from the audio input. The proposed system comprises five subsystems: (1) automatic speech recognition, which generates text from the linguistic sounds in the audio, (2) audio event classification for the type of sound effect, (3) audio scene classification for the type of place from the soundscape, (4) music detection for the background music, and (5) keyword extraction from the automatic speech recognition results. First, the audio signal is converted into a suitable form, which is subsequently combined from each subsystem to create metadata for the audio content. We evaluated the proposed system using video logs (vlogs) on YouTube. The proposed system exhibits a similar accuracy to handcrafted metadata for the audio content, and for a total of 104 YouTube vlogs, achieves an accuracy of 65.83%.

In this paper, we propose a newly constructed binary code to correct one deletion and one insertion error that simultaneously occur at any position in a codeword. We first investigated all cases of one deletion and one insertion error. Three constraints in the proposed construction were used for determining the bit values and positions of all error cases. Furthermore, we propose the decoding procedure with two parallel decoding algorithms and explain the specific decoding procedure. To the best of the authors’ knowledge, our work is the first trial to provide an efficient code construction design to correct one deletion and one insertion error occurring in a codeword.

For ultra-reliable low-latency communications (URLLC), low error floors are required for channel codes. In this paper, we propose a method of adding some edges to the protograph of the protograph-based raptor-like (PBRL) low-density parity-check (LDPC) codes. The added edges play a role of boosting up the reliability of weak variable nodes so that the code with edge addition can achieve low error floors. The edge addition is applied to an instance of 5G new radio (NR) LDPC code and it is shown that the edge addition lowers the error floor of the 5G NR LDPC code. Since the edge addition does not change the existing edge connections in the protograph, an adaptive use with/without edge addition have an effect of implementing two PBRL LDPC codes for enhanced mobile broadband (eMBB) and URLLC in an efficient way while keeping the system compatible with the original PBRL LDPC code.

In this study, an automatic end-to-end speech recognition system based on hybrid CTC-attention network for Korean language is proposed. Deep neural network/hidden Markov model (DNN/HMM)-based speech recognition system has driven dramatic improvement in this area. However, it is difficult for non-experts to develop speech recognition for new applications. End-to-end approaches have simplified speech recognition system into a single-network architecture. These approaches can develop speech recognition system that does not require expert knowledge. In this paper, we propose hybrid CTC-attention network as end-to-end speech recognition model for Korean language. This model effectively utilizes a CTC objective function during attention model training. This approach improves the performance in terms of speech recognition accuracy as well as training speed. In most languages, end-to-end speech recognition uses characters as output labels. However, for Korean, character-based end-to-end speech recognition is not an efficient approach because Korean language has 11,172 possible numbers of characters. The number is relatively large compared to other languages. For example, English has 26 characters, and Japanese has 50 characters. To address this problem, we utilize Korean 49 graphemes as output labels. Experimental result shows 10.02% character error rate (CER) when 740 hours of Korean training data are used.

In this paper, we propose an optimization method for protograph-based spatially coupled low-density parity-check (SC-LDPC) codes under window decoding (WD). Previous works on constructing SC-LDPC codes for WD typically focused on optimizing asymptotic performance metrics such as the WD threshold. However, in this paper, it is observed that the WD threshold is not an appropriate metric to sufficiently explain the finite-length behavior of SC-LDPC codes under WD. Thus, we propose a new performance metric, called the window mean parameter, based on a scaling analysis to capture the WD performance more accurately and formulate a code optimization algorithm that optimizes the proposed performance metric. Since the proposed metric depends on the window size, the optimization algorithm can provide a code family of SC-LDPC codes optimized for various target window sizes. Simulation results confirm that the improvement in the proposed metric leads to a finite-length performance improvement, resulting in one to two orders of the frame error rate gain over the conventional SC-LDPC codes for a wide range of window sizes. Furthermore, we investigate structural characteristics of the proposed codes to provide a supplementary explanation for the performance improvement, which also promotes a better understanding of SC-LDPC codes for WD.

Energy-efficient optimal power allocation (OPA) has always been an essential optimization for multi-user cooperative diversity systems. However, most of the existing works have mainly focused on optimizing the system’s overall energy efficiency (EE) while neglecting to maximize the EE of each user jointly which is an inherent demand for multi-user systems. To this end, in this letter, we investigate the quality-of-service constrained EE-OPA to maximize the EE for each user simultaneously in a multi-user decode-and-forward cooperative system by a multi-objective optimization approach. This constrained multi-objective optimization problem (MOOP) is solved by jointly leveraging the weighted Tchebycheff method and the Dinkelbach method, however, with a considerably high computational complexity. In order to reduce the computational complexity while still obtaining near-optimal solutions, we further proposed a machine learning approach to solve the MOOP. Specifically, we setup an Elman neural network to model and learn the multi-objective EE-OPA (MO-EE-OPA) for a given multi-user DF cooperative network. Numerical results show that the Elman network can output near-optimal solutions with dramatically low computational complexity.

MOTIVATION: In DNA storage systems, there are tradeoffs between writing and reading costs. Increasing the code rate of error-correcting codes may save writing cost, but it will need more sequence reads for data retrieval. There is potentially a way to improve sequencing and decoding processes in such a way that the reading cost induced by this tradeoff is reduced without increasing the writing cost. In past researches, clustering, alignment and decoding processes were considered as separate stages but we believe that using the information from all these processes together may improve decoding performance. Actual experiments of DNA synthesis and sequencing should be performed because simulations cannot be relied on to cover all error possibilities in practical circumstances. RESULTS: For DNA storage systems using fountain code and Reed-Solomon (RS) code, we introduce several techniques to improve the decoding performance. We designed the decoding process focusing on the cooperation of key components: Hamming-distance based clustering, discarding of abnormal sequence reads, RS error correction as well as detection and quality score-based ordering of sequences. We synthesized 513.6 KB data into DNA oligo pools and sequenced this data successfully with Illumina MiSeq instrument. Compared to Erlich's research, the proposed decoding method additionally incorporates sequence reads with minor errors which had been discarded before, and thus was able to make use of 10.6-11.9% more sequence reads from the same sequencing environment, this resulted in 6.5-8.9% reduction in the reading cost. Channel characteristics including sequence coverage and read-length distributions are provided as well. AVAILABILITY AND IMPLEMENTATION: The raw data files and the source codes of our experiments are available at: https://github.com/jhjeong0702/dna-storage.

Deep neural networks (DNNs) have become increasingly effective in difficult machine learning tasks, such as image classification, speech recognition, and natural language processing. Face recognition (FR) using DNNs shows high performance and is widely used in various domains such as payment systems and immigration inspection. However, DNNs are vulnerable to adversarial examples generated by adding a small amount of noise to an original sample, resulting in misclassification by the DNNs. In this study, we attempt to deceive state-of-the-art FR by attaching noise markers on a face in the real world. To deceive an FR model in the real world, we address challenges in the attack process, including selection of locations of noise markers, the differences between colors of digital noise markers and those of noise markers after printing, the differences between the colors of noise markers that are attached to the face and those of noise markers after a picture is taken, and the differences between the locations of digital noise markers and those of noise markers that are attached to the face. In experiments, we generate noise markers considering these challenges and show that state-of-the-art FR can be deceived by attaching a maximum of 10 noise markers to a face. This can cause a security risk for FR models using DNNs.

Irregular quasi-cyclic (QC) low-density parity-check (LDPC) codes with the block dual-diagonal (BDD) parity structure are widely adopted in many communication standards because the BDD structure supports an efficient encoding and many degree-2 variable nodes inside are adequate for the construction of mid- to high-rate codes. However, we observe that low-rate irregular QC LDPC codes with the BDD parity structure inherently contain too many degree-2 variable nodes and suffer from error floors in high signal-to-noise ratio (SNR) region. In this paper, a generalized BDD structure including double-weight circulants as well as circulant permutation matrices is proposed for low-rate irregular QC LDPC codes with low error floors which is achieved with a little bit giving up error performance in the waterfall region. When constructing the parity part of a code with the generalized BDD structure, the portion of double-weight circulants is variable so that the resulting LDPC code can achieve a desired degree distribution including degrees 2 and 3 while supporting the efficient encoding. We show that low-rate QC LDPC codes constructed with the proposed BDD structure have better theoretical properties and lower error floor than those with the conventional BDD structure.

A low-complexity coding scheme is developed to achieve the rate region of maximum likelihood decoding for interference channels. As in the classical rate-splitting multiple access scheme by Grant, Urbanke, and Whiting, the proposed coding scheme uses superposition of multiple codewords with successive cancellation decoding, which can be implemented using standard point-to-point encoders and decoders. Unlike rate-splitting multiple access, which is not rate-optimal for multiple receivers, the proposed coding scheme transmits codewords over multiple blocks in a staggered manner and recovers them successively over sliding decoding windows, achieving the single-stream optimal rate region as well as the more general Han–Kobayashi inner bound for the two-user interference channel. The feasibility of this scheme in practice is verified by implementing it using commercial channel codes over the two-user Gaussian interference channel.

In this paper, we propose new design algorithms of irregular spatially-coupled low-density parity-check (SC-LDPC) codes with non-uniform degree distributions using linear programming (LP). In general, irregular SC-LDPC codes with non-uniform degree distributions are difficult to design with low complexity because their density evolution equations are multi-dimensional. To overcome this problem, proposed design algorithms are based on three main ideas: a local design of degree distributions, pre-computation of the input/output message relationship, and selection of a proper objective function. These ideas make it possible to design degree distributions of irregular SC-LDPC codes by solving low-complexity LP problems over the binary erasure channel (BEC). It is shown that the proposed irregular SC-LDPC codes designed by the proposed algorithms are superior to regular SC-LDPC codes in terms of both asymptotic and finite-length performances over the BEC. We also confirm that the proposed irregular SC-LDPC code achieves better performance compared with an optimized irregular block LDPC code in the same blocklength, which implies that the proposed design algorithms also provide a new way to construct capacity-approaching block LDPC codes.

This paper proposes an address authentication method based on the user's location history. For address authentication, existing studies discover the user's regular locations called location of interest (LOI) from the location history by using clustering algorithms. They authenticate an address if the address is contained in one of the LOIs. However, unnecessary LOIs which are unrelated to the address may lead to false authentications of illegitimate addresses, i.e. other users' addresses or feigned addresses. The proposed method tries to reduce the authentication error rate by eliminating unnecessary LOIs with the distinguishing properties of address. In other words, only few LOIs that satisfy the properties (long duration, high density, and consistency) are kept and utilized for address authentication. Experimental results show that the proposed method decreases the authentication error rate compared with previous approaches using time-based clustering and density-based clustering.

In this study, the authors propose a new two‐stage decoding scheme for low‐density parity‐check codes to lower the error‐floor, which consists of the conventional belief propagation (BP) decoding algorithm as the first‐stage decoding and the re‐decodings with manipulated log‐likelihood ratios (LLRs) of variable nodes as the second‐stage decoding. In the first‐stage decoding, an early stopping criterion is proposed for early detection of decoding failure and the candidate set of the variable nodes are determined, which can be partly included in the small trapping sets. In the second‐stage decoding, the scores of the variable nodes in the candidate set are computed by the proposed unreliable path search algorithm and the variable nodes are sorted in ascending order by their scores for the re‐decoding trials. Each re‐decoding trial is performed by BP decoding algorithm with manipulated LLR of a selected variable node in the candidate set one at a time with the second early stopping criterion. The parallel unreliable path search algorithm is also proposed for practical application of the proposed algorithm. Numerical results show that the proposed early stopping criteria and the proposed decoding algorithms for the second‐stage decoding can correct most of the unsuccessfully decoded codewords by the first‐stage decoding in the error‐floor region.

In this paper, two classes of fountain codes, called batched zigzag fountain codes and two-phase batched zigzag fountain codes, are proposed for the symbol erasure channel. At a cost of slightly lengthened code symbols, the involved message symbols in each batch of the proposed codes can be recovered by low complexity zigzag decoding algorithm. Thus, the proposed codes have low buffer occupancy during decoding process. These features are suitable for broadcasting to receivers with limited hardware resources. We also propose a method to obtain degree distributions of code symbols for the proposed codes via ripple size evolution by taking into account the released code symbols from the batches. We also show that the proposed codes outperform Luby transform codes and zigzag decodable fountain codes with respect to intermediate recovery rate and coding overhead when message length is short, symbol erasure rate is low, and available buffer size is limited.

Generally, various traffic requirements in wireless sensor network are mostly dependent on specific application types, that is, event-driven, continuous, and query-driven types. In these applications, real-time delivery is one of the important research challenges. However, due to harsh networking environment around a node, many researchers usually take different approach from conventional networks. In order to discuss and analyze the advantage or disadvantage of these approaches, some comprehensive survey literatures were published; however they are either out of date or compiled for communication protocols on single layer. Based on this deficiency, in this paper, we present the up-to-date research approaches and discuss the important features related to real-time communications in wireless sensor networks. As for grouping, we categorize the approaches into hard, soft, and firm real-time model. Furthermore, in all these categories, research has been focused on MAC and scheduling and routing according to research area or objective in second level. Finally, the article also suggests potential directions for future research in the field.

The sliding-window superposition coding scheme aims to mitigate intercell interference at the physical layer by achieving the simultaneous decoding performance with point-to-point channel codes, low- complexity decoding, and minimal coordination overhead. The associated sliding-window coded modulation (SWCM) scheme can be readily implemented using standard off-the-shelf codes, such as the standard LTE turbo code, and tracks the information-theoretical performance guarantee of sliding-window superposition coding. This paper investigates how the basic SWCM scheme performs for the Ped-B fading interference channel model and proposes several improvements in transceiver design, such as soft decoding, input bit-mapping and layer optimization, and power control. Our enhanced SWCM scheme achieves the rates higher than those of the basic SWCM scheme by 10% to 20%, which already shows a significant gain over existing schemes that ignore modulation or coding information of interfering signals. This result confirms the potential of SWCM as a basic building block for physical-layer interference management in 5G and subsequent generations of cellular networks.

In this paper, a new class of (N, K) near-optimal partial Hadamard codebooks is proposed. The construction of the proposed codebooks from Hadamard matrices is based on binary row selection sequences, which are generated by quadratic have parameters N = pnand K = (p - 1/2 p)(N + √N) + 1 for an odd prime p and an even positive integer n. We prove that the maximum magnitude of inner products between the code vectors of the proposed codebooks asymptotically achieves the Welch bound equality for sufficiently large p and derive their inner product distribution.

In this paper, we study the process of information diffusion in a microblog service developing Galton-Watson with Killing (GWK) model. Microblog services offer a unique approach to online information sharing allowing microblog users to forward messages to others. We describe an information propagation as a discrete GWK process based on Galton-Watson model which models the evolution of family names. Our model explains the interaction between the topology of the social graph and the intrinsic interest of the message. We validate our model on dataset collected from Sina Weibo and Twitter microblog. Sina Weibo is a Chinese microblog web service which reached over 100 million users as for January 2011. Our Sina Weibo dataset contains over 261 thousand tweets which have retweets and 2 million retweets from 500 thousand users. Twitter dataset contains over 1.1 million tweets which have retweets and 3.3 million retweets from 4.3 million users. The results of the validation show that our proposed GWK model fits the information diffusion of microblog service very well in terms of the number of message receivers. We show that our model can be used in generating tweets load and also analyze the relationships between parameters of our model and popularity of the diffused information. To the best of our knowledge, this paper is the first to give a systemic and comprehensive analysis for the information diffusion on microblog services, to be used in tweets-like load generators while still guaranteeing popularity distribution characteristics.

In wireless sensor networks, the existing real-time routing protocols for stationary sinks exploit a spatiotemporal approach, utilizing the delivery speed based on the end-to-end distance to fulfill the desired time deadline. This approach cannot be directly applied to a mobile sink since the distance can be varied depending on its movement. That is, the delivery speed cannot be determined without knowing the intermediate sensors to know the current location update of the mobile sink and control their transmission speeds. We focus on the real-time protocol for slowly varying mobile sink compared to transmission speed, which may be the most common case. By the slowly varying constraint, the movable area of a sink can be determined by the two factors: its moving distance and initial location. The movable area could provide the maximum transmission distance between a source and a mobile sink. This letter proposes a real-time data dissemination protocol for mobile sinks utilizing the movable area concept. Simulation results show the proposed protocol provides high success ratio of real-time requirement.

In wireless sensor networks (WSNs), real-time service is one of the important issues. Typically, existing studies for the service are relied on beacons. Recently, beaconless routing has been proposed to overcome control overhead for resource constrained environment of WSNs. Thus, real-time communication based on the beaconless scheme could give great advantages with less energy consumption. To do that, however, it brings new challenges. For the real-time communication, each node needs to be aware of single hop delay for data forwarding within desired time. In conventional approaches, it is based on delay in neighbor information through beacons. An appropriate next forwarder is selected by a sender. However, in the beaconless scheme, a sender could not select a next forwarder since that is determined by a receiver after transmitting data. Also, contention delay is included in single hop delay for beaconless routing. Thus, the delay estimation principle should be renovated. In this paper, we present a receiver-based beaconless routing for real-time services. We design a novel delay estimation strategy. The single hop delay from a sender to a receiver could be calculated by a receiver but not a sender. Therefore, the receiver itself makes a decision whether desired time requirement is satisfied. Simulation experiments show that the strategy achieves higher performance in terms of energy consumption.

In this paper, we propose an opportunistic real-time data dissemination protocol in order to solve the transmission failure problem in error-prone WSNs. Retransmission is well-known for recovery of transmission failure, however, this may cause the severe time delay possibly to violate the real-time requirement. To solve the problem, our protocol exploits both broadcasting nature and temporal opportunity concept. In a radio-range of a sensor node, there may be multiple neighbor nodes to satisfy the real-time requirement. By broadcasting property, all neighbors can receive a data from a node, and only each satisfying neighbor decides its relay toward the destination by using temporal selection function. The temporal function is related to the tolerable time period to be able to satisfy the real-time requirement. By giving the priority to the node with smaller tolerable time, we have more opportunities to forward toward the destination. That is, even if a node with a long tolerable time waits for the longer period of time, it still has a chance to forward with the real-time requirement. In summary, the proposed protocol attains the high reliability and real-time requirement by removing data retransmission and multiple opportunities with temporal consideration. Simulation results show that the proposed protocol is superior to the existing real-time protocols in terms of real-time data dissemination and energy consumption.

For a high-rate case, it is difficult to randomly construct good low-density parity-check (LDPC) codes of short and moderate lengths because their Tanner graphs are prone to have short cycles. Also, the existing high-rate quasi-cyclic (QC) LDPC codes can be constructed only for very restricted code parameters. In this paper, based on special classes of cyclic difference families, we propose a new construction method of high-rate regular QC LDPC codes having parity-check matrices consisting of a single row of circulants with column-weight 3 or 4. The proposed QC LDPC codes can be constructed for various code rates and lengths including the minimum achievable length for given column-weight and design rate under girth 6. It is observed that the parity-check matrices of the proposed QC LDPC codes have full rank for column-weight 3 and just one redundant row for column-weight 4. It is shown that the error correcting performance of the proposed QC LDPC codes of short and moderate lengths is almost the same as that of the existing ones through numerical analysis.

There have been lots of efforts on the construction of quasi-cyclic (QC) low-density parity-check (LDPC) codes with large girth. However, most of them focus on protographs with single edges and little research has been done for the construction of QC LDPC codes lifted from protographs with multiple (i.e., parallel) edges. Compared to single-edge protographs, multiple-edge protographs have benefits such that QC LDPC codes lifted from them can potentially have larger minimum Hamming distance. In this paper, all subgraph patterns of multiple-edge protographs, which prevent QC LDPC codes from having large girth by inducing inevitable cycles, are fully investigated based on a graph-theoretic approach. By using combinatorial designs, a systematic construction method of multiple-edge protographs is proposed for regular QC LDPC codes with girth at least 12 and another method is proposed for regular QC LDPC codes with girth at least 14. Moreover, a construction algorithm of QC LDPC codes based on certain liftings of multiple-edge protographs is proposed and it is shown that the resulting QC LDPC codes have larger upper bounds on the minimum Hamming distance than those lifted from single-edge protographs. Simulation results are provided to compare the performance of the proposed QC LDPC codes with progressive edge-growth (PEG) LDPC codes and with PEG QC LDPC codes.

Geographic multipath routing is one of the most appropriate approaches which can improve the end-to-end reliability via multiple paths for the wireless sensor networks that have frequent network dynamics such as both node and link failures. It has been focused on how to construct a node-disjoint multipath that an intermediate node should be belonged by only a single path. It is because that if two or more paths share one intermediate node, the node may be congested by multiple traffics. Even it might bring multiple path failures if the shared node fails. However, if the node-disjoint multipath schemes are used, there might be another significant problem such as transmission failure or corrupted packet reception due to collisions between adjacent paths. Therefore, we propose a radio-disjoint geographic multipath scheme to avoid the collisions, which allow multiple paths to keep a certain distance between each other. Unfortunately, this simple idea still remains inevitable interference regions, i.e., both source side and destination side. So we eliminate the interferences in these regions by using local scheduling algorithms. We demonstrate that the proposed protocol shows better performance than the previous studies via extensive simulation in terms of end-to-end packet delivery ratio and the end-to-end delay.

In wireless sensor networks (WSNs), the real-time data dissemination protocols exploit the spatiotemporal communication approach which forwards data at the delivery speed calculated with the desired time deadline and the end-to-end distance. However, the protocols do not focus on the reliable communication. Recently, MMSPEED is proposed for both reliable and real-time data delivery based on multipath. For construction of the multipath in MMSPEED, the relay nodes branch off by local decision. Namely, in order to improve the reliability, the protocol locally chooses branch nodes among neighbor nodes which fulfill the real-time constraints and have the better reach ability to the sink. However, since the paths are branched off blindly, the branched paths have no information of each other. So, the paths could be merged each other. The end-to-end reliability of multipath could decrease due to the failure of the merged path. Moreover, as the reach ability to the sink is not estimated but calculated, the value could not be applied for reliability in real world. In this paper, we propose a reliable and real-time service protocol with geographical parallel track concept. The parallel track concept provides the information of each path to all paths. In the proposed protocol, the branch of multipath occurs only by real-time constraint. Simulation results show that the proposed protocol is superior to the related studies in terms of successful data delivery in desired time deadline.

The block dual-diagonal (BDD) parity structure is widely adopted in many practical irregular quasi-cyclic (QC) low-density parity-check (LDPC) codes. These QC LDPC codes have good error-correcting performance in waterfall region but usually show relatively high error floors in low error rate region. In this paper, by using multi-weight circulants, a new BDD structure is proposed for the parity part of irregular QC LDPC codes to lower error floors and support efficient encoding. Since the parity part of parity-check matrices has flexible degree distribution with the aid of multi-weight circulants, QC LDPC codes with the proposed BDD structure can have large minimum Hamming distance compared to those with the conventional BDD structure, especially, in the low-rate case. Simulation results show that QC LDPC codes with the proposed BDD structure have lower error floor than those with the conventional BDD structure.

For tracking a continuous object, mass communications are generated in the sensor field because of their huge scale and extensive diffusing property. Due to the severe resource constraints of sensor nodes, the redundant information and communications should be reduced in order to prolong the life time of WSNs. Although there have been numerous studies on continuous object tracking, most of the proposed schemes have focused on reducing the redundant boundary nodes and control messages through static/dynamic clustering in space domain. However, it is not enough to reduce the redundancy only with space domain. Redundantly sampled reporting packets could be a cause of generating redundant long range transmission, which is an important source of energy consumption. For reducing the redundancy, we need to consider not only the method to reduce the redundancy in space domain but also an adaptive sampling scheme in time domain. However, adaptive sampling is difficult to design in continuous object tracking because local sensor nodes hard to figure out how far the continuous object is diffused. To solve this problem, we suggest a new scheme which picturizes the diffusing object by dividing the sensor field into several cells like a pixel on TV and samples reporting time based on pixel image. In addition, we use pictured image of diffusing object for selecting the boundary information of diffusing object in space domain to reduce the redundant boundary information. To present the sensor field as an image, we adopt a virtual grid which divides the sensor field into several cells under the static clustering WSN architecture. The performance of proposed scheme is verified with simulation and the results show that the total number of control messages, reporting packets and boundary nodes can be reduced.

In order to find a completely disjointed multiple routes, traditional multipath strategies try to get global topology information by using frequent flooding or end-to-end signaling. It is very useful, but too much expensive to directly adapt to the resource constrained wireless sensor networks. Thus, recently there has been proposed an energy-efficient localized multipath scheme (EDM), which exploits geographic information for multipath discovery and routing. However, EDM has a significant limitation that it does not consider the case of simultaneous transmission between adjacent paths. Because of the path interferences, the transmission fails or corrupted packet receptions might be frequently occurred even if EDM has made completely disjointed multiple paths. Therefore we propose an interference-free geographic multipath protocol by allowing the paths to separate each other. To implement that, we utilize a logical multipath pipeline approach. Each pipeline has to keep a certain distance between each other, and a route can be allowed to be made within a pipeline.

In order to disseminate data to a mobile sink by location-based routing, it is important to provide location information of the sink altering continuously with a source in wireless sensor networks. Fundamentally, it could send directly location information message to a source whenever the sink moves. On the other hand, some schemes without additional cost for location update are proposed recently. The schemes could learn location information by utilizing overhearing of broadcasting nature in wireless transmission environments. Transmission path is turned steadily to the new location at an intermediate node hop by hop per packet along the reverse path. However, if the sink moves frequently while the path is being changed, new location information of the sink exists on the other previous paths rather than on the current path. Therefore, the information might not be propagated to a source securely. Namely, it could not guarantee reachability. In this paper, we propose a novel implicit location service scheme, which guarantees the reachability. With this scheme, we exploit location information of static sensor node as destination information instead of actual location of the dynamic sink. Then, packets are delivered toward one sensor node so the packets could be delivered to the destination. We provide the proof of its reachability and simulation result shows that the proposed scheme has improved than previous works in terms of reliability.

The real-time data dissemination schemes exploit the spatiotemporal communication approach which forwards data at the delivery speed calculated with the desired time deadline and the end-to-end distance in wireless sensor networks (WSNs). However, the schemes do not focus on the reliable communication. Recently, MMSPEED is a well-known scheme for both reliable and real-time data delivery based on multipath. For construction of the multipath in MMSPEED, the relay nodes branch off by local decision. Namely, in order to improve the reliability, MMSPEED locally chooses branch nodes among neighbor nodes which fulfill the real-time constraints and have the better reachability to the sink. However, since the paths are branched off blindly, the branched paths have no information of each other. So, the paths could be merged each other. The end-to-end reliability of multipath could decrease due to the failure of the merged path. Moreover, as the reachability to the sink is not estimated but calculated, the value could not be applied for reliability in real world. In this paper, we propose a reliable and real-time service protocol with geographical parallel track concept. The parallel track concept provides the information of each path to all paths. In the proposed protocol, the branch of multipath occurs only by real-time constraint. Simulation results show that the proposed protocol is superior to the related studies in terms of successful data delivery in desired time deadline.

A principal issue for wireless sensor networks is energy efficiency, which is necessary for prolonging applications to track continuous object, such as wild fire and poison gas. Selective wakeup approach is an effective way to save energy in such networks. However, most previous studies on selective wakeup schemes have concentrated on individual objects, such as intruders and tanks, and they cannot be applied for tracking continuous objects. This is because the continuous object is pretty flexible and dynamic due to its sensitiveness to surrounding natural effects so that movable area cannot be correctly estimated by the just spatiotemporal mechanism. Therefore, we propose a grid-based protocol for applying the efficient and accurate selective wakeup technique to tracking continuous objects. When an object is detected in some specific area which tightly surrounds the object, a pre-designated area where the target may move is activated to prepare the target without any complex calculations. Moreover, our protocol is simple and asynchronous, which makes it more suitable for wireless sensor networks.

In this letter, a new performance measure for compressed sensing matrices is proposed. This new measure is based on thek-set correlation vectors whose components consist of the correlation values between two columns in thek-column submatrices of a sensing matrix. This measure is highly related to the restricted isometry property (RIP). And the proposed measure has less computational complexity than the condition number approach which is a typical approach for performance prediction with RIP check. It is shown by simulation that the proposed scheme works well as a performance measure for the compressed sensing matrices.

In wireless sensor applications such as disaster recovery and military actions, the behavior of mobile sinks is characterized by group features. A number of mobile sinks move together in a group manner, and mobile sinks in the group stay closely and randomly move within a geographically restricted region. Recently, many communication schemes have been suggested to reflect the properties of the mobile sink group to effectively support the group communications. These schemes calculate the group region and disseminate the source's data to the calculated region in a certain discrete-time. However, as they ignore the continuous movement behavior of the group, they might have a serious reach ability problem that some mobile sinks cannot receive the source's data. Also, the periodic calculation of the region and propagation of data extrinsic to the movement of the group cause a waste of network resources. In this paper, we propose a novel data dissemination scheme for mobile sink group considering continuous movement of the group, which could resolve the problems of reach ability and inefficiency faced by the previous schemes. The proposed scheme allows the sink group to receive the source's data from virtual grid infrastructure when the group moves out from a local grid. Simulation results show that the proposed scheme is superior to previous ones in terms of transmission success ratio and node energy consumption.

In wireless sensor networks, many studies on data dissemination to individual mobile sinks traditionally rely on a strategy that consists of a virtual infrastructure to serve current location of the mobile sinks and a per-sink foot-print chaining mechanism to support local mobility after location update. To adapt the strategy for supporting mobile sink groups, it may be simply considered to exploit a representative per a mobile sink group in order to representatively register location of the mobile sink group and representatively make a foot-print chain of the sink group. However, the representative manner may lead to considerable problems with respect to efficiency and robustness of data dissemination: inefficient data collection problem, needless location update problem, and relay path loss problem. These problems could be caused from dependency between the group and the representative, i.e. a member sink. Therefore, we propose a novel protocol for data dissemination decoupled with any member sink of a mobile sink group. In order to independently deal with a mobile sink group, the protocol is composed of three major mechanisms: 1) representative location update, 2) distributed data collection, and 3) per-group foot-print chaining.

Geocasting has been known as the appropriate scheme for providing effective data dissemination from a source to all nodes in a geographically restricted region. However, since the geocasting typically assumes the restricted region is stationary, it is hard to directly adopt the traditional geocasting in order to offer effective data delivery to mobile sink groups that have geographically collective mobility. Hence, this paper proposes a novel geocasting, called M-Geocasting (Mobile Geocasting) to support mobile sink groups. M-Geocasting provides the representative location information of a sink group to sources. The location information contains information in terms of a restricted region in which all member sinks of the group exist. A source disseminates data to the closest node in the region; then, the node restrictedly floods the data only within the region. Also, to support local movement of member sinks toward out of scope of the region, some nodes on boundary of the region maintain the data and offer it to member sinks out of scope of the region. We have evaluated M-Geocasting performance through simulation experiments, and our results show that M-Geocasting effectively supports mobile sink groups that have geographically collective mobility.

In wireless sensor networks, reliable event detection is one of the most important research issues. For the reliable event detection, existing studies usually assume that events are individual objects such as tanks, people, and animals. The existing studies estimate detection reliability of an individual object by the ratio of the number of successfully received data packets at a sink to the number of data packets determined by applications for reliable detection. Recently, detection of the other one kind of events, called the continuous object, such as wild fire and bio-chemical material has been receiving increased attention. Unlike the individual objects, a continuous object might cover a wide area and it could dynamically alter its own shape according to physical environments, e.g. wind, geographical features, and so on. Hence, the continuous object detection reliability can not be estimated by the indicator for the individual objects. In this paper we newly define the reliability indicator for continuous object detection. Then, we propose error recovery and revision scheme based on the estimation result from the novel indicator. Simulation results prove that the proposed scheme provides high reliability with respect to continuous object detection.

For reliable event detection in wireless sensor networks, a sink requires collective information reported by sensor nodes sensing an event. In other words, the sink has to receive a certain amount of data dealing with the event for reliable event detection. Existing studies propose quantity-based event reliability protocols that improve event reliability by increasing the number of data successfully transmitted by controlling transport process. These studies present diverse schemes to successfully transmit as many reporting data as possible such as diversification of routing path for congestion avoidance and control of data reporting frequency rate for transport error compensation. However, since it frequently happens that wireless sensor networks with restricted capacity cannot deliver more than required amount of data due to data collision and congestion, the quantity-based event reliability protocols have limitation to raise the possibility of event detection. In this paper, we proposes a Quality-based Event Reliability Protocol (QERP) utilizing a property that the reporting data from sensor nodes are different in the contribution degree (CD) for event detection according to their environmental conditions. QERP selects sensor nodes to send their reporting data according to CD, and differentially transports them by CD-based buffer management and load balancing. Simulation results show that QERP detect more reliably and energy-efficiently an event than quantity-based event reliability protocols.

For WSNs, many data dissemination protocols have been proposed for mobile sink groups, in which sinks are spatially apart each other in their close proximity and move together according to group mobility. Most previous works cannot be directly applied to mobile sink groups due to the control overhead caused by the individual mobility in the group. M-geocasting protocol considers both of data dissemination and group mobility, but regional flooding leads to energy inefficiency. Energy consumption is increased in proportion to the spatial size of the group. In addition, the more frequent events generated in a source have more potential of broadcast storms and failures in data reception in some sinks exist in the group. In the paper, we propose an energy efficient scheme for data dissemination called Pipe Based Data Dissemination (PBDD), in which flooding combines with a virtual pipe, preventing the problems in flooding and data loss in group mobility. The virtual pipe is a unit of data storage for stable data dissemination, while flooding is utilized only for location discovery. Simulation results show that the PBDD outperform the existing protocols in terms of energy consumption and successful delivery rate.

In this paper, all subgraph patterns of protographs which prevent quasi-cyclic (QC) low-density parity-check (LDPC) codes from having large girth are searched in allowance with multiple edges based on graph theoretic approach. A systematic construction of protographs with multiple edges using combinatorial design is proposed for designing QC LDPC codes with girth greater than or equal to 14.

There have been proposed many data dissemination protocols which use routing structures dependent on sinks or events in wireless sensor networks. However, as many mobile sinks and events exist in the network, such protocols are not energy-efficient due to frequent reconstructions of routing structures. Thus, in this paper, to provide the scalability and mobility of sinks and events, we propose new independent structure-based data dissemination protocol which exploits a k-level Independent Grid Structure (IGS) for data dissemination from sources detecting the events to sinks. The proposed protocol needs not to construct any routing structure irrespective of the number and the movement of both sinks and events. The proposed protocol also allows query or report packets to be sent to only a few grid headers in the k-level IGS and provides aggregation and multicasting of report packets by the k-level IGS. Simulation results show that the proposed protocol is superior to other protocols.

In wireless sensor networks, there have recently been studies on mobile sinks groups such as groups of soldiers on battlefields, which are characterized by geographically collective movement. Although the existing protocols for individual mobile sinks can support the mobile sinks groups, they suffer from high congestion and control overhead due to location updates by each sink in the groups. To solve the location update problem by individual sinks, a protocol, called M-Geocasting only updates the region information of the mobile sink groups to sources. However, since M-Geocasting uses the flooding within the group regions for data delivery to member sinks, it excessively consumes the energy of sensor nodes in the group region. Moreover, the flooding potentially causes broadcast storms within the group region when many events exist. Thus, in this paper, we propose an efficient data dissemination protocol which can avoid the flooding within the group region for supporting mobile sink group. The proposed protocol introduces a virtual pipe in the group region for data dissemination as data storage. In the proposed protocol, a source sends data to the pipe and member sinks retrieve data directly from the pipe. Simulation results show that the proposed protocol is superior to the existing protocols in terms of the energy consumption and the data delivery ratio.

Wireless sensor networks consist of a large number of sensor nodes, recharging them is often infeasible. The failure of sensor nodes caused by energy exhaustion or physical destruction may lead to the reduction of sensor areas. In wireless sensor networks, holes can be formed due to void areas in sensor nodes deployment, destruction of sensor nodes, or uneven energy consumption. In such a network, geographic routing is very strong energy-efficient routing scheme without consideration of global network topology. But the hole problem becomes another difficult issue faced by geographic routing. Moreover, the holes make more serious obstacles in multipath routing, that is, multiple paths are eager to bypass the holes simultaneously. It results in more energy consumption or data collision on the edge of holes by the right hand rule and finally cannot construct disjoint multipath. In this paper, we propose the hole detouring strategy to handle the hole problem in disjoint multipath routing. Then our robust disjoint multipath routing scheme based on the hole detouring strategy can efficiently construct disjoint multipath preventing the hole problem and avoiding data collision on the edge of holes. Simulation results present our protocol is superior to the previous works in terms of energy consumption, average delivery delay and show reliable disjoint multipath construction under the hole flexibly.

The mobility model of a mobile sink group typically consists of two movement behaviors as follows: a micro-level movement behavior and a macro-level one. In the micro-level, mobile sinks randomly move within a geographically restricted region while all the member sinks in the macro level collectively and slowly move together toward with similar direction. Recently, a group communication protocol has been proposed to support the mobile sink group. It exploits both data dissemination by restricted flooding within the group region for the micro-level movement and periodical updates of the group region to the source for the macro-level movement. However, such mechanism might causes the excessive energy consumption of sensor nodes due to the frequent flooding for both location requests of a leader sink for the group region calculation and data dissemination within the group. Also, since it calculates the group region through current location of member sinks, the group region might be moved in the macro-level even if only a sink moves in the micro-level in practice. It might bring frequent updates of the group information to the long-distance source. In this paper, we propose an energy-efficient group communication protocol that disseminates data without both the flooding and the group region calculation. In the proposed protocol, data of the source is only disseminated to grid headers of virtual grid structure in the group instead of all sensor nodes in the group, and then each member sink directly gets the data from the closest grid header. As the group region update performs locally in grid- level, the communication cost would be significantly reduced. Simulation results demonstrate that the proposed protocol has lower energy consumption than the previous one.

Due to the severe resource constraints of sensor hardware, energy efficiency is a principal factor for detecting and tracking the movement of the large-scale phenomena such as wild fire, poison gas and hazardous bio-chemical material, denoted by continuous objects. In order to save the energy, the selective wakeup approach is effective way in the wireless sensor networks. However, most previous researches concentrated on individual objects such as intruders, tanks, and animals cannot be applied to the continuous object tracking because it is hard to expect that the diffusion of continuous object has the uniform velocity or acceleration. Recently, a prediction-based selective wakeup algorithm, denoted by PRECO is proposed. Nevertheless, this mechanism is still not acceptable. First, its prediction result is very inaccurate because a sensor node calculates next boundary line with only a few data while the continuous objects are pretty flexible and vicissitudinous. Second, its prediction tasks among current boundary nodes should be operated at the same time but it is a hard problem for the nodes to have synchronization in the wireless sensor networks. Therefore, we propose a novel prediction and selective wakeup scheme for energy efficient and accuracy continuous object tracking by using structured clustering. Hence, when objects are detected in some specific area, appointed areas where the target may move activate to keep guard without any complex calculations. Moreover, our scheme is asynchronous so that it is suitable for the sensor networks.

In wireless sensor networks (WSNs), the studies that support sink mobility without location information of sensor nodes traditionally establish a cluster-based virtual infrastructure. The cluster-based infrastructure consists of clusters involving sensor nodes and a shared tree organized by the cluster heads. In the studies, data dissemination from a source node to a mobile sink is performed via the shared tree. The mobile sink makes connection from the current standing cluster into the root of the shared tree; the source transmits data to the root; and the root delivers the data to the mobile sink. Namely, the data from a source may always be detoured to a mobile sink via the shared tree. According to a change of the current standing cluster, the mobile sink could frequently remake connection into the root; thus, excessive energy consumption by the detour problem might seriously happen. In this paper, we propose a communication protocol that provides the shortest path from a source to a sink by exchanging a routing table between neighboring cluster heads. The routing table contains the cluster ID of a neighbor cluster and hop-count from the neighbor cluster to the other clusters. A sink registers the cluster ID of the current standing cluster into the root of the shared tree, and a source then obtains the cluster ID. Thus, the source can deliver data directly to the current standing cluster of the mobile sink. Simulation results show that the proposed protocol is superior to the existing protocol.

Real-time data delivery to a multicast group may be defined as data dissemination to each member in the multicast group within the desired time deadline. The hardest part of this mission is to enforce this real-time constraint in the communication between a source and the furthest member since an end-to-end delay is proportional to a physical distance in wireless sensor networks. We may call it the critical distance. This must be most important constraint for real-time multicasting. That is, the delivery distance from a source to each member must not be longer than the critical distance even by any reason. However, since the traditional multicasting protocols lay the strong emphasis only on communication cost rather than distance, they may violate the real-time constraint related to the critical distance. In this paper, we propose a novel multicasting scheme satisfying the real-time constraint.

In wireless sensor networks, a mobile sink group have geographically collective movement and member sinks of the group try to get same data to execute a communal mission. In order to support the mobility for such groups, it is needed to get the current location of a mobile sink group and then to offer the location to a source. Previous works for mobile sink groups provide region information of a sink group to a source. To provide the information, the previous works calculate a region including all member sinks by flooding; then, it notifies this region information to a source. However, flooding and location updates are periodically performed regardless of the group movement so that it causes considerable overhead in terms of energy consumption. In this paper, we propose an energy-efficient scheme supporting mobile sink groups without periodic flooding and location update. The proposed scheme calculates a location of a group without large energy consumption due to flooding. It exploits the inherent property of mobile sink groups which could approximate entire group movement by only partial member sinks movement. Also, the scheme learns group location by back-propagation learning method through exploiting overhearing feature in wireless communication environment. Our simulation studies show that the proposed scheme significantly improves in terms of energy consumption compared to the previous work.

There have been many geographic multicasting protocols proposed for wireless sensor networks (WSNs). These protocols tend to exploit a SOurce-initiated Geographic Multicasting (SOGM) approach which consists of three phases: first, a source collects the position information of all sink nodes; second, the source constructs a multicast tree through the position information; third, the source forwards data down the multicast tree. However, if a multicast group contains many mobile sinks, frequent movement of the sinks cause a huge number of link failures of the multicast tree. To fix them, the SOGM approach requires a great deal of delivery of position registration and update messages to the source, thus leads to significant energy consumption of the sensor nodes in the vicinity of the source. Moreover, since each sink asynchronously updates one's new position to the source, it is difficult for the source node to find an opportune time for reconstructing the multicast tree. In this paper, we propose a SInk-initiated Geographic Multicasting (SIGM) protocol for WSNs which can avoid these problems faced by the SOGM approach. The SIGM allows sinks to construct their own data delivery paths to a source, and a multicast tree is automatically constructed by merging the data delivery paths. Simulation results show that the proposed protocol is superior to other protocols in term of average energy consumption, it thus prolongs the network lifetime.

In wireless sensor networks, with respect to a desired time deadline real-time data dissemination schemes achieve that by a spatiotemporal communication approach forwarding data from a source to a destination with a delivery speed. The delivery speed is typically obtained from both the static distance from the source to the destination and the interval of the time deadline. However, in case of real-time routing to a mobile sink, since the mobile sink randomly moves around, the distance from a source to the mobile sink would be dynamically changed. Hence, we propose a new real-time routing scheme considering the dynamic distances by the mobile sink. In the scheme, the source calculates an expected area of the mobile sink by the moving speed of the sink; then, the data delivery speed is obtained from the worst case distance from the source to the farthest position on the area. The source transmits data to expected area with the delivery speed, and the first sensor node within the area then floods in the area to deliver the data to the mobile sink that is dynamically located within the area.

There have been proposed many geographic multicasting protocols for wireless ad hoc sensor networks. Most of these protocols tend to exploit a Source-initiated Geographic Multicasting (SGM) approach which consists of three phases: first, a source collects the position information of all destination nodes; second, the source constructs a multicast tree through the position information; third, the source forwards data down the multicast tree. However, if a multicast group contains many mobile destinations, the SGM approach may cause a great deal of delivery of position registration and update messages to the source, thus lead to significant energy consumption of the sensor nodes in the vicinity of the source. In addition, high data delivery latency is another problem since the data delivery is triggered after the source obtains the position of all destinations and constructs a geographic multicast tree. Moreover, since each destination asynchronously updates one's new position to the source, the source node in the SGM approach is difficult to find an opportune time for reconstructing the multicast tree. In this paper, we propose a Destination-initiated Geographic Multicasting (DGM) protocol which can avoid these problems faced by the SGM approach. The DGM allows destinations to construct their own data delivery paths to a source, and a multicast tree is automatically constructed by merging the data delivery paths, and then, the source node forwards data to them down the multicast tree. In the DGM, we also propose a round-based virtual infrastructure with a radial shape for increasing the merging probability of data delivery paths and reducing reconstruction ratio of the multicast tree due to mobility. Simulation results show that the proposed protocol is superior to other protocols in term of average data delay and average energy consumption.

Twitter, a microblogging service less than three years old, commands more than 41 million users as of July 2009 and is growing fast. Twitter users tweet about any topic within the 140-character limit and follow others to receive their tweets. The goal of this paper is to study the topological characteristics of Twitter and its power as a new medium of information sharing.

Twitter offers an explicit mechanism to facilitate information diffusion and has emerged as a new medium for communication. Many approaches to find influentials have been proposed, but they do not consider the temporal order of information adoption. In this work, we propose a novel method to find influentials by considering both the link structure and the temporal order of information adoption in Twitter. Our method finds distinct influentials who are not discovered by other methods.

Geographic routing has been considered as an efficient, simple, and scalable routing protocol for wireless sensor networks since it exploits pure location information instead of global topology information to route data packets. Geographic routing requires the source nodes to be aware of the location of the sink nodes. How source nodes efficiently obtain the sink location information has been merely studied yet. In this paper, we propose a Sink Location Service via Inner Rectangular in Wireless Sensor Networks. A source node and a sink node send location queries and location announcement messages to specified direction respectively by geographic routing; thus, a sink location query path and a sink location announcement path is generated. The node located on a crossing point of these two paths informs the source node about the sink location information. Then the source node sends data to the sink node by geographic routing. The proposed scheme constructs a virtual restricted linear flooding zone inside the network to guarantee the existence of the crossing point. Simulation results show that proposed scheme is reliable and efficient than the existing protocols.

In delay-tolerant wireless sensor networks, reporting data from a source node to a sink may be delayed to satisfy certain criterions, for example, high energy-efficiency, low algorithm complexity and so on. Sensed data in such networks accumulate on a sensor node during time delayed. It means that even a single failed node may cause a massive-data loss. This paper proposes a backup scheme to minimize data losses caused by failed nodes in wireless sensor networks using the delayed report. The proposed scheme can safely preserve data and consume less energy by backuping a single data to multiple nodes that exist in the one-hop distance from the source node. Multiple backup nodes do not only store and recover backup data but also distributedly report their backup data to the sink instead of the source node. As a result, the energy consumption for data report is not concentrated to the source node and is distributed to backup nodes. Such approach suggests the new potentiality of a backup scheme in error-scarce network.

Typical multicasting saves efficiently both bandwidth and energy in static wireless sensor networks. Such benefits make the research of multicast which is a transmission from a data source to multiple destinations (sinks), actively. Most of these researches focused on the way how to make efficient multicast tree only, they are weak for supporting mobile sinks. In practical applications, sinks move around and collect information from a sensor field. If the mobile sinks apply to these approaches, frequent entire multicast tree reconstructions are needed to support mobile sinks. Unfortunately, it leads to exhaustion of sensors' limited power supply, consequently it reduces whole network lifetime. In this paper, we propose an energy-efficient multicast protocol to support multiple mobile sinks by the local multicast tree reconstruction, called Local Updated-based geographic Multicasting for Mobile sinks (LUMM) for wireless sensor networks. A value of BOD (benefit of distance) used a standard from a local multicast tree reconstruction with minimal overhead. Our simulation results show that LUMM support the mobility of sinks efficiently.

Geographic routing has been considered as a scalable approach in ad-hoc and sensor networks since it exploits pure position information of neighbors and a destination node instead of global topology information to route data packets. To obtain the position information of the neighbors, many geographic routing protocols assume that each node exchange periodically its own position information with its neighbors. However, these periodically position exchanges in regions without packet forwarding make nodes consume unnecessary energy. In addition, given that the nodes have mobility, when a node forwards a packet, the position information of its neighbor nodes may be invalid. Hence, in these mobile networks, it is more efficient that a mobile node collects the position information of its neighbors when it needs to forward a packet. Because every sender node in geographic routing also selects the nearest neighbor node to the destination node as the receiver node, obtaining the position information of only closer neighbor nodes to the destination node can save more wireless resources than obtaining that of all neighbor nodes. In large-scale networks, because many wireless collisions can happen due to position exchanges of many neighbor nodes, they should share limited wireless resources. Therefore, we propose a mechanism to solve these issues of geographic routing in large-scale mobile networks. Simulation results show that the proposed mechanism has better performance than the existing geographic routing protocols.

In many sensor applications such as intruder tracking, reliable data dissemination is necessary. Existing studies in ad hoc networks generally apply end-to-end control for reliability. This approach however could not adapt to wireless sensor networks (WSNs). Existing studies in WSNs generally apply multi-path approach for reliability. This approach however only increases probability but could not assure data dissemination. In typical WSNs, data are delivered from a source node to a destination node on routing path that is fixed within a certain period of time. This routing path is well-matched with notion of virtual circuit. Approaches based on virtual circuit traditionally use hop-by-hop control for reliable data dissemination. In this paper, we apply notion of virtual circuit to WSNs and propose hop-by-hop control for reliable data dissemination. The proposed scheme consists of three major functionalities: virtual circuit construction, hop-by-hop control, and virtual circuit management. Virtual circuit construction make sure constructing fixed routing path by routing table. Hop-by-hop control guarantees data transmission between two nodes, i.e. one hop, on virtual circuit by error detection and retransmission. Virtual circuit management prevents disconnecting circuit by reconstructing circuit. Simulation results show that the proposed scheme is efficient in terms of data delivery ratio and energy consumption.

In large scale Internet network, the research in area of event detection and report publish/subscribe communications paradigm is being progressed. Data-centric is the basic characteristic of data transmission mode of the publish/subscribe communications paradigm. Such characteristic coincides with the wireless sensor network. The publish/subscribe communications paradigm performs task in manner of space, time and synchronous decoupling. The publish/subscribe communications paradigm with such property is tend to be applied to the wireless sensor network. However, existing algorithms do not satisfy the three decoupling modes in wireless sensor network. Therefore, this paper applies the publish/subscribe communications paradigm to the wireless sensor network and proposes a model to solve the energy consumption problem. The proposed communication model satisfies the three decoupling modes by using Embedded Grid Structure (EGS) in the wireless sensor network. Simulation results show that proposed model is energy-efficient compared with other protocols.