Band-based geocasting for mobile sink groups in wireless sensor networks

Virtual tube storage scheme for supporting mobile sink groups in wireless sensor networks

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.

HashQuery, a Hash-area-based data dissemination protocol, was designed in wireless sensor networks. Using a Hash function which uses time as the key, both mobile sinks and sensors can determine the same Hash area. The sensors can send the information about the events that they monitor to the Hash area and the mobile sinks need only to query that area instead of flooding among the whole network, and thus much energy can be saved. In addition, the location of the Hash area changes over time so as to balance the energy consumption in the whole network. Theoretical analysis shows that the proposed protocol can be energy-efficient and simulation studies further show that when there are 5 sources and 5 sinks in the network, it can save at least 50% energy compared with the existing two-tier data dissemination(TTDD) protocol, especially in large-scale wireless sensor networks.

Active data dissemination for mobile sink groups in wireless sensor networks

Communications for mobile sink groups such as rescue teams or platoons bring about a new challenging issue for handling mobility in wireless sensor networks. Recently, a group region-based approach has been proposed to send data to a mobile sink group. However, it uses flooding for discovering and notifying group region information and flooding or long distance forwarding for disseminating data. Thus, it causes high energy consumption and data delivery failure. Moreover, its per-sink mobility supporting scheme makes energy consumption and data delivery failure more serious. Thus, this letter proposes an Energy-efficient and Reliable Mobile Group communication protocol (ERMG) to support a mobile sink group, which exploits a virtual grid structure. For the group region discover and notification and the data dissemination, ERMG uses communications with only cell heads of grid cells that manages group sinks. ERMG also uses a per-grid based scheme to support sink mobility. Simulation results show that ERMG has better performance than the existing protocols.

무선 센서 네트워크에서 구조대나 군 소대와 같은 이동 싱크 그룹을 위한 통신은 군집 이동 특성에 의해 이동성 지원 측면에서 새로운 도전 과제를 야기한다. 최근에 그룹 영역 기반의 이동성 지원 접근법이 제안되었지만, 접근법에서 제시하는 3 단계(싱크 그룹 영역 발견, 영역 정보 통지, 데이터 전달)의 과정은 과도한 플러딩(flooding)을 요구한다. 따라서 많은 에너지 소모와 혼잡 및 간섭으로 인한 데이터 전달 실패를 야기한다. 더욱이, 이는 개별 싱크 단위의 이동성을 지원하기 때문에 앞의 문제를 심화시킨다. 따라서, 본 논문은 가상 격자 구조를 활용한 에너지 효율적이고 신뢰성있는 이동 싱크 그룹 통신 방안(Energy-efficient and Reliable Mobile Group communication protocol, ERMG)을 제안한다. ERMG는 그룹 영역의 발견과 영역 정보 통지, 데이터 전달을 위해 오직 싱크 그룹을 관리하는 격자 셀의 대표(cell heads)와의 통신만을 요구한다. 또한, ERMG는 효율적인 이동성 지원을 위해 격자 단위의 이동성 지원 방안을 사용한다. 시율레이션 결과는 ERMG가 기존 방안들에 비해 에너지 소모량이 평균 30% 감소하였고, 전달 요구 시간 내 성공률이 평균 6% 증가하였음을 보인다. Communications for mobile sink groups such as rescue teams or platoons bring about a new challenging issue for handling group mobility in wireless sensor networks. Recently, a group region-based approach has been proposed to send data to a mobile sink group. However, it uses excessive flooding for 3 steps (group region discovery, region information notification, and data dissemination) to support mobile sink group. Thus, it causes high energy consumption and data delivery failure. Moreover, its per-sink mobility supporting scheme makes energy consumption and data delivery failure more serious. Thus, this paper proposes an Energy-efficient and Reliable Mobile Group communication protocol (ERMG) to support a mobile sink group, which exploits a virtual grid structure. For the group region discover and notification and the data dissemination, ERMG uses communications with only cell heads of grid cells that manages group sinks. ERMG also uses a per-grid based scheme to support sink mobility. Simulation results show that ERMG has 30% less energy consumption and 6% more desired delivery deadline success ratio than the existing protocols.

Data dissemination from multiple sources to mobile sinks is fundamental and challenging in WSN applications due to limited energy supply of sensor nodes and sink mobility. Previous data dissemination protocols either rely on an energy-consuming coordinate system or build an inefficient backbone. In this paper, we propose a hierarchical role-based data dissemination (HRDD) protocol in wireless sensor networks. In HRDD, a small number of sensor nodes are assigned to serve as cluster heads and agents to form the data dissemination backbone and mitigate unnecessary query forwarding. In addition, HRDD designs an efficient data delivery mechanism that provides shorter paths to accelerate data delivery as well as reduce the number of data transmissions. An adaptive backbone maintenance mechanism is also introduced for low-energy cluster heads and agents to reduce their load, thereby prolonging the network lifetime. The experimental results show that HRDD achieves the longer network lifetime, the shorter delay, and the high success ratio compared to the prior work.

Recently, group mobility support of mobile sinks has received increasing interest, and several mechanisms have been proposed. The mechanisms typically follow a strategy that simply adopts flooding. The strategy detects the currently located region of a mobile sink group in flooding, registers the current region to a source, and performs data flooding in the region to disseminate data to the sink group. However, this strategy might cause serious problems in terms of reachability and communication overhead. In the first, although a group could continuously move toward a target point for its own mission, the strategy discretely performs detecting the group region and updating the region information. Namely, data may be delivered the previously current region, i.e. already updated but changed the region. Moreover, in order to obtain the region information of the group, flooding is frequently fulfilled as well as the strategy utilizes flooding for data delivery to the group every time. Therefore, we propose a novel strategy for reachability and low overhead, called X-Geocasting. X-Geocasting merely finds out the region of a group when the group changes direction or movement velocity. Also, instead of fully flooding in group regions, X-Geocasting predictively and flexibly determines the restricted flooding area according to direction and movement velocity. Simulation results prove this proposed group mobility support strategy provides reachability and high energy-efficiency.

The advantages of deploying mobile sinks (MSs) in wireless sensor networks (WSNs) have attracted tremendous attention recently, because mobility of a sink provides an efficient method to improve data gathering performance in WSNs. However, in such kind of WSN, the efficiency of data dissemination is obviously affected by the trajectory of the MS. Therefore, optimal moving schemes of the MS have been studied in many researches. Nevertheless, in many cases, the trajectory of the MS is not able to change ideally as previous studies assumed but depending on the environmental conditions. In this paper, we focus on the efficiency of data gathering in WSN with a MS whose trajectory cannot change ideally and propose a new data diffusion scheme - implementing a new Pre-Diffusion Algorithm (PDA) in a hierarchical WSN aimed at improving data gathering efficiency. This hierarchical WSN is composed of several clusters, and datatransmission is done by higher powered cluster head (CH) node. Our scheme predetermines the cluster area where the MS is going to arrive in most probability in next period of time. MS fulfills data converging in the cluster head (CH)whose distance to the MS may the smallest compared with other CHs when data gathering starts. Thus more data can be collected with less trajectory length of MS. Simulation results show that our proposed scheme improves data gathering efficiency as compared to conventional scheme.

Achieving efficient data dissemination to a mobile sink moving is one of the main challenges in wireless sensor networks. In this paper, we describe DHA, a data Dissemination protocol based on Home agent and Access node. DHA introduces the home agent and access node concepts to represent the mobile sink in sensor networks. The movement of the mobile sink affects only the access nodes and home agent, and the sensor nodes can transfer data to the fixed home agent without knowing the position of mobile sink. All the sensor nodes except the home agent and access node don't need to be updated in the direction of forwarding future data. DHA provides reliable and efficient data delivery to a mobile sink with minimum overheads. Our result shows that DHA increases the reliability of data delivery to the mobile sink and reduces the number of broadcast packets, thereby increasing the lifetime of sensor networks.

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.

Life time and Energy Efficiency are important factors in the design of wireless sensor network. A critical issue during data collection is the formation of energy holes near the sink. Sensors near the sink have to participate in relaying data on behalf of other sensors and thus their energy will be depleted very quickly. The mobile sink movement yields the significant performance gained through decreasing the amount of energy consumption. In this study, we propose a Grid Based approach for Data Disseminating to the Mobile Sink in Wireless Sensor Network. Mapping the position of nodes and sink to virtual grid infrastructure construct our main contribution. So that the data which is buffered by nodes could be disseminated to the mobile sink to the optimal manner. Finally, comprehensive simulation reveals the superiority of proposed algorithm in various scenarios.

Lifetime and energy efficiency are important factors in the design of wireless sensor network. A critical issue during data collection is the formation of energy holes near the sink. Sensors which are located near the sink have to participate in relaying data on behalf of other sensors and thus their energy will be depleted very quickly. Mobile sink movement yields the significant performance gained by decreasing the amount of energy consumption. In this paper, we propose an Intelligent Grid Based Data Disseminating protocol for mobile sink in wireless sensor networks. We have utilized a virtual grid as the protocol's substructure. In our proposed method, cell heads (CHs) will be selected based on the locations of virtual cross points (CPs) and CPs selection is needless to transfer any required data between neighbor nodes. We have optimized CPs selection using linear programming technique in order to increase network lifetime. By selecting the CHs based on our proposed algorithm, data will be disseminated toward the sink. Our data dissemination protocol is simple and has low overhead to construct and maintain. Also, we have presented a new method for sink location update which leads to the least cost in data transfer. Simulation results illustrate that by utilizing hierarchical functionality and selecting appropriate CPs and consequently selecting CHs, energy consumption will be decreased in comparison with other presented methods which directly lead to network lifetime increment. Also by determining an optimal cell size, packet delivery rate will be improved noticeably.

Network coding and schedule-based flooding trees have been widely deployed to improve the performance of a flooding process in low-duty-cycle wireless sensor networks (WSNs). However, the conventional schemes induce too long flooding delay because there is only one static sink node as a single source. In this paper, we use a mobile sink to travel around the monitoring area. When the mobile sink travels to a position, it serves as a new source. Since multiple sources can simultaneously forward data packets, flooding speed can be accelerated. We investigate the new problems when both a mobile sink and network coding are integrated with a schedule-tree-based flooding scheme. We model the process to deliver multiple encoded packets from the source to a node as a Markov process, and we theoretically investigate how to minimize the total expected flooding delay with a mobile sink by considering all the possible traveling orders of the branches. We propose a heuristic algorithm to obtain an appropriate trajectory by accounting for the effect of traveling delay of the mobile sink. Simulation results show that our proposed flooding scheme with a mobile sink can significantly reduce the flooding delay.

We investigate a broadcast scenario that a mobile sink disseminating broadcast packets while moving in asynchronous wireless sensor networks (WSNs), to prolong the network lifetime and reduce the broadcast delay. Such a scenario may yield multiple logical sink nodes in WSNs and the moving speed and trajectory of the mobile sink have the significant impact on the speed and efficiency of the broadcast. Thus, the conventional broadcast protocols may not fit for the mobile sink scenario. We propose a fast and efficient broadcast (FEB) protocol with a mobile sink in asynchronous WSNs. We analyze the moving pattern as well as the travel speed of the mobile sink. We jointly consider the broadcast process, the node location, and the neighbor coverage information within two-hops and then propose an efficient broadcast scheme together with a heuristic moving strategy for the mobile sink. The proposed broadcast scheme needs to exchange node coverage information before the transmission begins, thus to avoid redundant packet transmissions, and the proposed moving pattern strategy decreases the network broadcast delay by moving the mobile sink to monitoring areas, where fewer nodes are covered by the broadcast process. The simulation results show that our proposed protocol significantly reduces the broadcast delay and energy consumption.