Periodic Messages Research Articles

PETAL: A fully distributed location service for wireless ad hoc networks

Location service is an essential prerequisite for mobile wireless ad hoc networks (MANETs) in which the underlying routing protocol leverages physical location information of sender and receiver nodes. Fulfillment of this requirement is challenging partly due to the mobility and unpredictability of nodes in MANETs. Moreover, scalability and location information availability under various circumstances are also substantial factors in designing an effective location service paradigm. By and large, utilizing centralized or distributed location servers responsible for storing the location information of all, or a subset of participant mobile devices, is a method employed in a significant portion of location service schemes. However, from the fairness point of view, it is more suitable to employ a location service scheme that treats participant nodes fairly, without mandating an unlucky subset to undertake the responsibility of serving as location server(s). In this work, we propose a scalable and fully decentralized location service scheme (PETAL) in which the burden of location update and inquiry tasks is almost evenly distributed among the nodes, resulting in an improvement in resilience against individual node failures. PETAL does not require hashing which results in more complexity, it is resilient against swarm mobility pattern, it requires minimal periodic location update messages when nodes do not move, and finally it does not require too many parameter configurations on all nodes. Our simulation results reveal that PETAL performs efficiently, particularly in environments densely populated by wireless devices.

Expected Completion Time Aware Message Scheduling for UM-BUS Interconnected System

Predictable message transmission is the primary requirement in networked safety critical embedded systems design. In these systems, delay jitter has been proven to be a critical factor that must be considered. For periodic messages, minimizing the delay jitter means messages should be transmitted at the expected time in every period. In this paper, we investigate the scheduling problem to reduce the delay jitter for periodic messages in networked safety critical embedded systems. Our approach is empirically assigning an expected completion time as a baseline for the periodic messages and minimizing the total deviation to them. It can be applied either in centralized control buses or in synchronized ones. This paper selects a novel bus protocol and UM-BUS, to evaluate the effectiveness of the proposed algorithm. UM-BUS is a multi-master bus with the capability of multi-lane concurrent transmission. Aiming at different operation mode of UM-BUS, we implemented two sets of experiments by configuring different parameters to change the bus utilization. The results show that the heuristic algorithm works effectively and can achieve a deviation within 0.35%, which is significantly smaller comparing with the existing scheduling algorithms.

Organizing message transmission in AFDX networks

In this paper, a problem of periodical message transmission in the onboard networks based on the Avionics Full Duplex Ethernet (AFDX) standard is formalized and an algorithm for solving this problem is proposed. The algorithm combines the greedy approach with the limited exhaustive search and consists of several procedures to solve the problem step by step with respect to the constraints imposed. The results of the experimental research aimed at investigating the effectiveness of the proposed algorithm are presented.

A Randomized Controlled Trial of Assisted Intention Monitoring for the Rehabilitation of Executive Impairments Following Acquired Brain Injury

Background. Acquired brain injury (ABI) can impair executive function, impeding planning and attainment of intentions. Research shows promise for some goal-management rehabilitation interventions. However, evidence that alerts assist monitoring and completion of day-to-day intentions is limited. Objective. To examine the efficacy of brief goal-directed rehabilitation paired with periodic SMS text messages designed to enhance executive monitoring of intentions (assisted intention monitoring [AIM]). Methods. A randomized, double-blind, controlled trial was conducted. Following a baseline phase, 74 people with ABI and executive problems were randomized to receive AIM or control (information and games) for 3 weeks (phase 1) before crossing over to either AIM or no intervention (phase 2). The primary outcome was change in composite score of proportion of daily intentions achieved. A total of 59 people (71% male; 46% traumatic brain injury) completed all study phases. Results. Per protocol crossover analysis found a significant benefit of AIM for all intentions [F(1, 56) = 4.28; P = .04; f = 0.28; 3.7% mean difference; 95% CI = 0.1%-7.4%] and all intentions excluding a proxy prospective memory task [F(1, 55) = 4.79; P = .033; f = 0.28, medium effect size; 3% mean difference; 95% CI = 0.3%-5.6%] in the absence of significant changes on tests of executive functioning. Intention-to-treat analyses, comparing AIM against control at the end of phase 1 revealed no statistically significant differences in the attainment of intentions. Conclusion. Combining brief executive rehabilitation with alerts may be effective for some in improving achievement of daily intentions, but further evaluation of clinical effectiveness and mechanisms is required.

MESSAGE SCHEDULING ON CAN BUS FOR SHIP ENGINE SYSTEMS

This paper reports novel algorithm for handling real time message scheduling on CAN bus which consider buffer occupancy and message type (alarm, periodic real time and non real time). This algorithm is derived to reduce burden of the distributed control unit (DCU) which have obligation to deliver message within strict time and also manage buffer storage occupancy. The algorithm works by changing the message priority which is attached in the identifier field of message frame. The priority adjustment is performed by online calculation prior to send the message on the CAN bus. Finally, this proposed algorithm is applied on ship engine systems which consist of certain number of DCUs. In this networked control system, the proposed algorithm can decrease buffer overflow. Furthermore, the important message alarm and periodic real time message can be delivered within the deadline.Keywords: CAN Bus, message scheduling, DCU

ECPR: Environment-and context-aware combined power and rate distributed congestion control for vehicular communications

Safety and efficiency applications in vehicular networks rely on the exchange of periodic messages between vehicles. These messages contain position, speed, heading, and other vital information that makes the vehicles aware of their surroundings. The drawback of exchanging periodic cooperative messages is that they generate significant channel load. Decentralized Congestion Control (DCC) algorithms have been proposed to minimize the channel load. However, while the rationale for periodic message exchange is to improve awareness, existing DCC algorithms do not use awareness as a metric for deciding when, at what power, and at what rate the periodic messages need to be sent in order to make sure all vehicles are informed. We propose an environment- and context-aware DCC algorithm combines power and rate control in order to improve cooperative awareness by adapting to both specific propagation environments (e.g., urban intersections, open highways, suburban roads) as well as application requirements (e.g., different target cooperative awareness range). Studying various operational conditions (e.g., speed, direction, and application requirement), ECPR adjusts the transmit power of the messages in order to reach the desired awareness ratio at the target distance while at the same time controlling the channel load using an adaptive rate control algorithm. By performing extensive simulations, including realistic propagation as well as environment modeling and realistic vehicle operational environments (varying demand on both awareness range and rate), we show that ECPR can increase awareness by 20% while keeping the channel load and interference at almost the same level. When permitted by the awareness requirements, ECPR can improve the average message rate by 18% compared to algorithms that perform rate adaptation only.

Exploring the Practical Limits of Cooperative Awareness in Vehicular Communications

We perform an extensive study of cooperative awareness in vehicular communication based on periodic message exchange. We start by analyzing measurements collected on four test sites across Europe. To measure cooperative awareness, we use three metrics: 1) neighborhood awareness ratio; 2) ratio of neighbors above range; and 3) packet delivery rate. Using the collected data, we define a simple model for calculating neighborhood awareness given packet delivery ratio for a given environment. Finally, we perform realistic, large-scale simulations to explore the achievable performance of cooperative awareness under realistic transmit power and transmit rate constraints. Our measurements and simulation results show that: i) above a certain threshold, there is little benefit in increasing cooperative message rate to improve the awareness; higher transmit power and fewer messages transmissions are a better approach, since message delivery is dominated by shadowing. ii) the efficacy of cooperative awareness varies greatly in different environments on both large scale (e.g., 90\% awareness is achievable up to 200~m in urban and over 500~m in highway) and small scale (e.g., vehicles in nearby streets can have significantly different awareness); iii) V2V and V2I communication have distinct awareness patterns; iv) each location has a distinct transmit power that achieves high awareness; and v) achieving high awareness levels results in increased reception of potentially unwanted messages; therefore, a balance needs to be found between awareness and interference, depending on the specific context. We hope our results will serve as a starting point for designing more effective periodic message exchange services for cooperative awareness.

Can Intraoperative Text Messages Reduce Parental Anxiety of Children Undergoing Posterior Spinal Fusion Surgery for Adolescent Idiopathic Scoliosis?

A prospective, nonrandomized study. To evaluate the effectiveness of periodic intraoperative text messages (SMS) in reducing parental anxiety level during posterior spinal fusion (PSF) surgery for adolescent idiopathic scoliosis (AIS) patients. No studies have reported the use of intraoperative SMS to reduce level of anxiety in parents of patients who are undergoing AIS corrective surgery. Parents of 50 AIS patients were studied at two centers. Group 1 did not receive any SMS whereas those in Group 2 received periodic SMS. Parents' anxiety were assessed using a validated Visual Analog Scale for anxiety (VAS-A) and the anxiety component of the Hospital Anxiety Depression Score (HADS). The assessment was carried out at five different periods: (P1) 6 hours before the surgery; (P2) at separation in the operation theatre; (P3) 1 hour after commencement of surgery; (P4) immediately after completion of surgery; (P5) 1 day postsurgery. A total of 96 parents (47 fathers, 49 mothers) were involved in this study. Both groups were comparable in terms of demographics and education level. The mean VAS for Group 1 peaked at P2 and the HADS scores peaked at P3. The anxiety level of Group 1 remained high at P2, P3, and P4. There was a steady decline in parental anxiety in Group 2 from P1 to P5. There were significantly lower mean VAS score and HADS score for both father and mother in Group 2 during P3 and P4. The mean HADS scores for parents in Group 1 at P2 and P3 were higher than 8, which indicate abnormal anxiety. The anxiety levels of parents receiving the SMS were significantly lower than parents who did not receive any messages. Thus, intraoperative SMS is an effective intervention to decrease parental anxiety of AIS patients undergoing PSF surgery. 3.

Gambling warning messages: The impact of winning and losing on message reception across a gambling session.

Gambling warning messages have been shown to lead to prevention and modification of risk-taking behaviors. Laboratory studies have shown messages can increase a player's knowledge about gambling specific risks, modify their gambling-related cognitive distortions, and even change play. In the present laboratory study, participants were randomly assigned to a winning or losing slot machine gambling experience where they either viewed periodic warning messages or not. It was hypothesized that those in the message conditions would place smaller bets, spend more time considering bets, and spend less time gambling than those in the control conditions. We also hypothesized participants would play differently across the contexts of winning or losing. The results showed those who received warning messages while winning made the fewest number of spins and did not speed up their bet rate over the course of play as much as those in other conditions. Players who received warning messages while losing decreased the size of their bets over the course of play compared to those who received messages while winning. Despite receiving warning messages, losing players did not decrease their number of spins or rate of betting. Winning or losing during slot machine play appears to have significant consequences on the impact of a warning message. Whereas a message to change gambling behavior may encourage a winning gambler to stop play, the same message for a losing player may lead to a small minimization in harm by helping them to decrease bet size, though not their rate of betting. (PsycINFO Database Record

Sink-to-Sink Coordination Framework Using RPL: Routing Protocol for Low Power and Lossy Networks

RPL (Routing Protocol for low power and Lossy networks) is recommended by Internet Engineering Task Force (IETF) for IPv6-based LLNs (Low Power and Lossy Networks). RPL uses a proactive routing approach and each node always maintains an active path to the sink node. Sink-to-sink coordination defines syntax and semantics for the exchange of any network defined parameters among sink nodes like network size, traffic load, mobility of a sink, and so forth. The coordination allows sink to learn about the network condition of neighboring sinks. As a result, sinks can make coordinated decision to increase/decrease their network size for optimizing over all network performance in terms of load sharing, increasing network lifetime, and lowering end-to-end latency of communication. Currently, RPL does not provide any coordination framework that can define message exchange between different sink nodes for enhancing the network performance. In this paper, a sink-to-sink coordination framework is proposed which utilizes the periodic route maintenance messages issued by RPL to exchange network status observed at a sink with its neighboring sinks. The proposed framework distributes network load among sink nodes for achieving higher throughputs and longer network’s life time.

Geographic scheduling of directional transmission for periodic safety messages in IEEE WAVE

It is typically assumed that safety communication will use omnidirectional broadcast in vehicle-to-vehicle environments. However, in the IEEE Wireless Access in Vehicular Environment standard, some safety application messages will have directional semantics. For example, messages in the cooperative adaptive cruise control application are relevant to vehicles following the transmitter. In this paper, we investigate the impacts of using directional communication that is tailored to such applications. In particular, we show that the directional transmission indeed improves the message delivery probability by reducing message spillover in unnecessary directions. However, we also find that such benefit is not automatically obtained. Analysis reveals that it is crucial that the temporal ordering of the transmission is aligned with the vehicles’ spatial ordering to minimize the hidden terminal losses and fully garner the benefits of directional communication. For a method to ensure that the alignment takes place, we propose an application-level message scheduling solution that utilizes vehicle position information, and demonstrate that it leads to both lower channel utilization and higher message delivery rates than omnidirectional transmission.

Network-Aware Double-Layer Distance-Dependent Broadcast Protocol for VANETs

Dissemination of traffic information over multiple hops in vehicular networks requires scalability measures that prevent network congestion and avoid wasting network capacity with unnecessary information forwarding. This issue is even more important if such traffic information coexists with critical safety information. In particular, a viable solution for traffic information dissemination is piggybacking compressed information over periodic basic safety messages. Leveraging this technique, we propose a network-aware double-layer distance-dependent protocol for fast broadcasting of aggregated traffic information over multiple hops. The first distance-dependent layer uses a message size control scheme and a probabilistic approach to ensure that the forwarding within each hop is as fast as possible. The second layer progressively decreases the forwarding rate of subsequent hops as the distance from the source increases. Jointly, the two layers considerably reduce the overall latency of information while also improving the scalability and robustness of the system. We evaluate the performance of the algorithm and compare it with the existing methods, using ns-3 simulations. The results confirm that significant improvement in performance is possible without complicating the forwarding algorithm.

Risk Factor–tailored Small Group Education for Patients with First-time Acute Coronary Syndrome

The purpose of this study was to evaluate the effects of a risk factor-tailored small group education on anxiety and depressive symptoms, self-efficacy and self-care compliance in patients with first-time acute coronary syndrome (ACS) for 12-month follow-up. A quasi-experimental pretest and post-test design was used. Patients were recruited from a national university hospital from 2010 to 2011 in Korea. The group education consisted of a 60-minute long video developed using multimedia contents including voice-recorded texts, flash animation, and video clips, with nurses' dialogue. The intervention group (n = 34) participated in group education using the multimedia video in a small group of patients with similar risk factors, and received periodic telephone counseling and text messages. The control group (n = 40) received usual care and counseling upon request. Depressive symptoms decreased, and self-efficacy and self-care compliance in the areas of medication, exercise, and healthy diet practice significantly increased in patients in the intervention group, compared with those in the control group. Risk factor-tailored small group education and periodic text message were an effective strategy for decreasing depression, and increasing self-efficacy and long-term compliance with lifestyle changes in patients with first-time ACS. We suggested that risk factor-tailored small group education need to be given for first-time ACS patients for psychological support and behavioral change in clinical practice. It is also comparable to individual approach to encourage psychological and behavioral change.

Integration of congestion and awareness control in vehicular networks

Cooperative vehicular networks require the exchange of positioning and basic status information between neighboring nodes to support vehicular applications. The exchange of information is based on the periodic transmission/reception of 1-hop broadcast messages on the so called control channel. The dynamic adaptation of the transmission parameters when broadcasting such messages will be key for the reliable and efficient operation of vehicular networks. To this aim, vehicular networks utilize congestion control protocols to control the channel load, typically through the adaptation of the transmission parameters based on certain channel load metrics. Awareness control protocols are also required to adequately support cooperative vehicular applications. These protocols typically adapt the transmission parameters of periodic broadcast messages to ensure each vehicle's capacity to detect, and possibly communicate, with the relevant vehicles and infrastructure nodes present in its local neighborhood. To date, congestion and awareness control protocols have been normally designed and evaluated separately, although both will be required for the reliable and efficient operation of vehicular networks. In this context, this paper proposes and evaluates INTERN, a new control protocol that integrates two congestion and awareness control processes. The simulation results obtained for three different scenarios demonstrate that INTERN is able to satisfy the applications’ requirements of all vehicles, while effectively controlling the channel load. The results obtained highlight the challenges ahead with emerging automated vehicles.

Schemes for inter-domain lightpath establishment based on PCE architecture

Despite the research advances in intra-domain lightpath provisioning in Wavelength Division Multiplexing networks, efficient and practical schemes for path computation and resource advertisement in multi-domain mesh networks still need to be developed. Most of the solutions proposed in the literature lacks the ability to convey optical network-specific Traffic Engineering information and are based on a periodic message flooding technique. This paper proposes three novel solutions for inter-domain lightpath provisioning in WDM circuit switched mesh networks. Two routing advertisement schemes and two path and wavelength selection criteria for the PCE architecture are proposed. The solutions provide a complete inter-domain routing and wavelength solution. Simulation experiments show the effectiveness of the proposed solutions which significantly reduce the total amount of message exchanged as well as overall call blocking.

Studying the effectiveness of an aggregation procedure for virtual links in onboard switched networks design

The problem of organizing periodical message transmission for onboard networks based on the Avionics Full Duplex Ethernet (AFDX) standard is considered, and an approach to solving it is proposed. An important stage of solving this problem is the aggregation procedure, in which a virtual link, via which several messages from one partition are transmitted, is formed. The aggregation procedure is described in detail, and the results from experimental studies of its effectiveness are presented.

Load Balanced Fuzzy Control based Adaptive Gateway Discovery for Ubiquitous Internet Access in MANET

Integrating MANETs (Mobile Ad-hoc Networks) nodes to the Internet require either a connection to the Internet or they can connect to the Internet through the Internet gateways. For the second case if a node in a MANET has discover the gateway to connect to the fixed hosts in the Internet and it can be done either by broadcasting a gateway discovery request message initiated by nodes itself or by broadcasting periodic gateway advertisement messages from the gateways. End to end packet delay and throughput are strongly dependent on the time needed to discover the gateways.Nodes in a MANET use number of hops as metric to select a path to a gateway, if all the nodes select its nearest gateway to access the Internet then there may be situations when the network performance degrades because some nodes along the path have too many packets waiting in the queue.This paper presents a novel solution to access internet through mobile nodes in ad hoc network. Here the gateway replies with an advertisement message which is broadcasted to the whole network instead of sending a unicast reply to the requesting node. The traffic load taken into account along a path in addition with minimum hop count to select an efficient gateway. The AODV routing protocol has been used for routing in the MANET domain.A new strategy of gateway discovery was investigated and impact of new metric on the gateway selection in NS-2 was observed. Simulation results show that the proposed scheme outperforms over the existing scheme with high throughput and lower end to end delay.

MANET환경에서 Interrupt Message와 Backup path 기법에 기반한 AODV의 성능개선

MANET 환경에서 빈번한 경로 단절은 반복된 경로 탐색으로 인해 제어 패킷 오버헤드와 패킷 손실을 증가시킨다. AODV-I는 event driven방식을 이용하여 주기적인 Hello 메시지를 제거함으로써 AODV의 성능을 개선하였다. Hello 메시지와 달리 각 이벤트마다 전송되는 인터럽트 메시지는 이웃노드의 상태를 알 수 있어 링크 단절을 탐지 및 예측도 할 수 있다. 따라서 AODV-I의 성능은 각 인터럽트 메시지 종류에 따라 처리 절차를 추가함으로써 더욱 개선될 수 있고, 또한 AODV의 단일경로로 인한 문제를 백업 경로기법을 추가하여 개선하는 것도 가능하다. 본 연구에서는 경로 탐색 수와 전송 지연을 줄이기 위해 개선된 백업 경로방식과 인터럽트 메시지 방식을 결합한 AODV-IB를 제안한다. AODV-IB는 각 인터럽트 메시지마다 링크 단절 예측과 탐지에 대한 처리 절차를 추가하여 AODV-I를 개선한다. 또한 추가적인 제어 패킷 없이 지연을 최소화하도록 개선한 백업 경로 방식도 구현한다. QualNet 5.0을 사용하여 구현한 시뮬레이션 결과는 AODV-I에 비해 제안하는 AODV-IB가 더 좋은 성능을 나타낸다. In MANET, frequent route breaks lead to repeated route discovery process and this increases control packet overhead and packet drop. AODV-I improves performance of AODV by using the event driven approach which removes periodic Hello message. Unlike the Hello message, Interrupt message which is sent for each event can detect and predict the link failure because it allows node to know the status of the neighbor node. From this characteristics of Interrupt message, performance of AODV-I can be further improved by adding a processing procedures for each type of Interrupt message and it is also possible to improve AODV-I by adding the Backup path scheme because it originally has problems due to a single path of AODV. In this paper, we propose AODV-IB that combines improved Backup path scheme and Interrupt message approach of AODV-I in order to reduce transmission delay and the number of route discoveries. AODV-IB improves AODV-I by adding proper processing procedures for the link failure prediction and detection for each Interrupt message. We also implement improved Backup path strategy in AODV-IB by minimizing delay without additional Control packet. Simulation results, using the simulator QualNet 5.0, indicate that proposed AODV-IB performs better than AODV-I.

Message scheduling for real-time interprocessor communication

Optimization of periodic message scheduling in a real-time multiprocessor system.Use of the space-sharing concept for a many-core architecture on a single chip.An efficient heuristic based on a generalized graph coloring model.Experiments on realistic scenarios show the effectiveness of the algorithm. In this paper an efficient algorithm is proposed which optimizes periodic message scheduling in a real-time multiprocessor system. The system is based on a many-core single-chip computer architecture and uses a multistage baseline network for inter-core communication. Due to its basic architecture, internal blockings can occur during data transfers, i.e. the baseline network is not real-time capable by itself. Therefore, we propose a scheduling algorithm that may be performed before the execution of an application in order to compute a non-blocking schedule of periodic message transfers. Additionally, we optimize the clock rate of the network subject to the constraint that all data transfers can be performed in a non-blocking way. Our solution algorithm is based on a generalized graph coloring model and a randomized greedy approach. The algorithm was tested on some realistic communication scenarios as they appear in modern electronic car units. Computational results show the effectiveness of the proposed algorithm.

A novel context-aware variable interval MAC protocol to enhance event-driven message delivery in IEEE 802.11p/WAVE vehicular networks

Vehicular Ad hoc NETworks (VANETs) are the key to the future of Intelligent Transportation Systems (ITS). In VANETs, event driven safety messages, generated for example when an abnormal condition or an imminent danger is detected, have stringent requirements on delay. However, due to the inherent drawbacks of CSMA which is used in VANETs, such messages will not be able to meet the timing constraints in dense traffic scenarios. In this paper, we introduce a Context Aware Variable Interval MAC (CAVI-MAC) protocol for IEEE 802.11p/WAVE VANETs which utilizes multichannel access scheduling in a novel way. We differentiate between event driven and periodic messages by assigning priorities and also suggest a probabilistic model for addressing interference from hidden terminals. We also use a novel atomic model to analyze the propagation of event driven messages. Extensive simulations over lower Manhattan city scenario for a variety of metrics indicate that CAVI-MAC provides better performance (packet delivery ratio) than any of the existing protocols.