Showing papers on "Transmission delay published in 2012"

Packet routing and switching device

Abstract: A method for routing and switching data packets from one or more incoming links to one or more outgoing links of a router. The method comprises receiving a data packet from the incoming link, assigning at least one outgoing link to the data packet based on the destination address of the data packet, and after the assigning operation, storing the data packet in a switching memory based on the assigned outgoing link. The data packet extracted from the switching memory, and transmitted along the assigned outgoing link. The router may include a network processing unit having one or more systolic array pipelines for performing the assigning operation.

An IEEE 802.11p-Based Multichannel MAC Scheme With Channel Coordination for Vehicular Ad Hoc Networks

Abstract: In recent years, governments, standardization bodies, automobile manufacturers, and academia are working together to develop vehicular ad hoc network (VANET)-based communication technologies. VANETs apply multiple channels, i.e., control channel (CCH) and service channels (SCHs), to provide open public road safety services and the improve comfort and efficiency of driving. Based on the latest standard draft IEEE 802.11p and IEEE 1609.4, this paper proposes a variable CCH interval (VCI) multichannel medium access control (MAC) scheme, which can dynamically adjust the length ratio between CCH and SCHs. The scheme also introduces a multichannel coordination mechanism to provide contention-free access of SCHs. Markov modeling is conducted to optimize the intervals based on the traffic condition. Theoretical analysis and simulation results show that the proposed scheme is able to help IEEE 1609.4 MAC significantly enhance the saturated throughput of SCHs and reduce the transmission delay of service packets while maintaining the prioritized transmission of critical safety information on CCH.

Packet capture for error tracking

Abstract: A method of tracking network traffic anomalies in a computing system, comprises receiving an ingress network packet at a configurable logic device (CLD), associating a timestamp with the packet, identifying at least one anomaly based on the contents of the packet, and storing the anomalous packet and the timestamp in a persistent memory.

Communication method of content router to control traffic transmission rate in content-centric network(ccn), and content router

Abstract: A communication apparatus and method of a content router control a traffic transmission rate in a content-centric network (CCN), and the content router. In the communication method and the content router, a congestion of a network may be predicted, a warning signal indicating the congestion may be added to an interest packet, and the interest packet with the warning signal may be transmitted. Additionally, a traffic transmission rate may be controlled by adjusting a data packet transmission time based on a value of a marked field of a PIT. The PIT is set by receiving an interest packet to which a warning signal is added. Thus, the communication apparatus and method thereof provide reachability, while maintaining stability of network routing.

A Reliable Transmission Protocol for ZigBee-Based Wireless Patient Monitoring

Abstract: Patient monitoring systems are gaining their importance as the fast-growing global elderly population increases demands for caretaking. These systems use wireless technologies to transmit vital signs for medical evaluation. In a multihop ZigBee network, the existing systems usually use broadcast or multicast schemes to increase the reliability of signals transmission; however, both the schemes lead to significantly higher network traffic and end-to-end transmission delay. In this paper, we present a reliable transmission protocol based on anycast routing for wireless patient monitoring. Our scheme automatically selects the closest data receiver in an anycast group as a destination to reduce the transmission latency as well as the control overhead. The new protocol also shortens the latency of path recovery by initiating route recovery from the intermediate routers of the original path. On the basis of a reliable transmission scheme, we implement a ZigBee device for fall monitoring, which integrates fall detection, indoor positioning, and ECG monitoring. When the triaxial accelerometer of the device detects a fall, the current position of the patient is transmitted to an emergency center through a ZigBee network. In order to clarify the situation of the fallen patient, 4-s ECG signals are also transmitted. Our transmission scheme ensures the successful transmission of these critical messages. The experimental results show that our scheme is fast and reliable. We also demonstrate that our devices can seamlessly integrate with the next generation technology of wireless wide area network, worldwide interoperability for microwave access, to achieve real-time patient monitoring.

Generalized two-hop relay for flexible delay control in MANETs

Abstract: The available two-hop relay protocols with out-of-order or strictly in-order reception cannot provide a flexible control for the packet delivery delay, which may significantly limit their applications to the future mobile ad hoc networks (MANETs) with different delay requirements. This paper extends the conventional two-hop relay and proposes a general group-based two-hop relay algorithm with packet redundancy. In such an algorithm with packet redundancy limit $f$ and group size $g$ (2HR- $(f,g)$ for short), each packet is delivered to at most $f$ distinct relay nodes and can be accepted by its destination if it is a fresh packet to the destination and also it is among $g$ packets of the group the destination is currently requesting. The 2HR- $(f,g)$ covers the available two-hop relay protocols as special cases, like the in-order reception ones $(f\geq 1,g=1)$ , the out-of-order reception ones with redundancy $(f>1,g=\infty)$ , or without redundancy $(f=1,g=\infty)$ . A Markov chain-based theoretical framework is further developed to analyze how the mean value and variance of packet delivery delay vary with the parameters $f$ and $g$ , where the important medium contention, interference, and traffic contention issues are carefully incorporated into the analysis. Extensive simulation and theoretical results are provided to illustrate the performance of the 2HR- $(f,g)$ algorithm and the corresponding theoretical framework, which indicate that the theoretical framework is efficient in delay analysis and the new 2HR- $(f,g)$ algorithm actually enables both the mean value and variance of packet delivery delay to be flexibly controlled in a large region.

Packet processing for logical datapath sets

Abstract: Some embodiments provide a method that processes network data through a network. The method receives a packet destined for a network host associated with a logical datapath set implemented by a set of managed edge switching elements and a set of managed non-edge switching elements in the network. The method determines whether the packet is a known packet. When the packet is a known packet, the method forwards the packet to a managed switching element in the set of managed edge switching elements for forwarding to the network host. When the packet is not a known packet, the method forwards the packet to a managed switching element in the set of managed non-edge switching elements for further processing.

Transparent acceleration of software packet forwarding using netmap

Abstract: Software packet forwarding has been used for a long time in general purpose operating systems. While interesting for prototyping or on slow links, it is not considered a viable solution at very high packet rates, where various sources of overhead (particularly, the packet I/O mechanisms) get in the way of achieving good performance.

Event-based control with communication delays and packet losses

Abstract: Event-based control aims at reducing the information exchange over the communication network in feedback-control systems. This article extends a state-feedback approach to event-based control to cope with communication delays and packet losses in the feedback link. The main result is a bound for the maximum tolerable communication delay, which guarantees that the event-based state-feedback loop is stable in the sense that its state remains in a bounded surrounding of the state of a continuous-time state-feedback loop. This result is extended to communication links with additional packet losses. Simulation studies and experimental results illustrate the performance of the event-based control loop.

Provisioning QoS controlled media access in vehicular to infrastructure communications

Abstract: The emerging IEEE 802.11p standard adopts the enhanced distributed channel access (EDCA) mechanism as its Media Access Control (MAC) scheme to support quality-of-service (QoS) in the rapidly changing vehicular environment. While the IEEE 802.11 protocol family represents the dominant solutions for wireless local area networks, its QoS performance in terms of throughput and delay, in the highly mobile vehicular networks, is still unclear. To explore an in-depth understanding on this issue, in this paper, we develop a comprehensive analytical model that takes into account both the QoS features of EDCA and the vehicle mobility (velocity and moving directions). Based on the model, we analyze the throughput performance and mean transmission delay of differentiated service traffic, and seek solutions to optimally adjust the parameters of EDCA towards the controllable QoS provision to vehicles. Analytical and simulation results are given to demonstrate the accuracy of the proposed model for varying EDCA parameters and vehicle velocity and density.

Distributed event-triggered control with network delays and packet losses

Abstract: This paper presents a distributed event-based control approach to cope with communication delays and packet losses affecting a networked dynamical system consisting of N linear time-invariant coupled systems. Two communication protocols are proposed to deal with these communication effects. It is shown that both protocols preserve the system stability in the sense that the state of every subsystem converges to a small region around the origin if the delay and the number of packet losses are bounded. Analytical expressions for the delay bound and the maximum number of consecutive packet losses are derived. Simulations illustrate the results.

Optimized Packet Size Selection in Underwater Wireless Sensor Network Communications

Abstract: In this paper, we investigate the effect of packet size selection on the performance of media access control (MAC) protocols for underwater wireless sensor networks, namely, carrier sense multiple access (CSMA) and the distance-aware collision avoidance protocol (DACAP). Our comparative analysis, conducted via ns-2 simulations, considers scenarios with varying, nonzero bit error rate (BER) and interference. We investigate metrics such as throughput efficiency (the ratio between the delivered bit rate and the offered bit rate), end-to-end packet latency, measured “per meter” to allow for different sizes of deployment areas, and the energy consumed to correctly deliver an information bit to the network collection point. Our results show the dependence of these metrics on the packet size, indicating the existence of an optimum. The optimum packet size is found to depend on the protocol characteristics, the bit rate, and the BER. For each protocol and scenario considered, we determine the packet size that optimizes throughput performance, and we show its effect on the normalized packet latency and on energy consumption.

Wireless communication apparatus and wireless communication method using bluetooth

Abstract: A wireless communication apparatus which is capable of communicating with a first wireless terminal holding a first data packet by Bluetooth includes a search unit, a first transceiver transmitting, a first controller, and a scheduling unit. The search unit reserves a search, and executing the search. The first transceiver transmits the first and second control packets, and receives the first data packet and a second data packet. The first controller reserves a transmission of the second control packet to the first wireless terminal, the first controller giving instructions to transmit the second control packet to the first transceiver. The scheduling unit accepts the reservation from the first controller and the search unit, the scheduling unit preferentially allowing a transmission of the second control packet compared with the search, and allowing the search when no reservation of the transmission of the second control packet is made.

Method and apparatus for managing packets in a packet switched network

Abstract: Methods and apparatus for managing packets in a packet switched network include, in at least one aspect, a device including: an input to receive a packet from one of a plurality of network devices, the plurality of network devices configured to communicate with one or more others of the network devices using a plurality of packets; and circuitry configured to control packet switching of the plurality of packets, at least one packet including: a switch tag including a tag portion embedded with switching information and an extended tag portion embedded with additional switching information, the switching information and the additional switching information configured to control a switching pattern associated with the at least one packet.

Medium for storing packet conversion program, packet conversion apparatus and packet conversion method

Abstract: Upon obtaining a packet including a broadcast/multicast MAC address from a virtual machine, a packet conversion apparatus obtains, based on first association information, a subnet identifier corresponding to the MAC address of the obtained packet, also obtains, based on second association information, a packet type identifier corresponding to the MAC address of the obtained packet, converts the packet to be transmitted to a different computer via a network into a multicast packet by setting the subnet identifier obtained based on the first association information and the packet type identifier obtained based on the second association information in a field of the MAC address of the packet to be transmitted, and transmits the packet to be transmitted, which is obtained by being converted, to the different computer via the network.

Delay and Throughput Oriented Continuous Spectrum Sensing Schemes in Cognitive Radio Networks

Abstract: Periodic spectrum sensing over the entire primary user (PU) band always interrupts the secondary user (SU) data transmission in the sensing interval, which may degrade the quality of service of the SU. To alleviate this problem, we divide the PU band into two subbands, one for opportunistic SU data transmission, and the other for continuous spectrum sensing. Based on the PU band division, we propose a delay oriented continuous spectrum sensing (DO-CSS) scheme for delay sensitive SU services. In the DO-CSS scheme, the average SU transmission delay is reduced by selecting the proper bandwidth for spectrum sensing within each frame. Since different SUs may have different requirements on their quality of services, we further propose a throughput oriented continuous spectrum sensing (TO-CSS) scheme. In the TO-CSS scheme, the achievable average SU throughput is maximized by choosing the optimal sensing bandwidth within multiple adjacent frames. Both theoretical analyses and simulation results show that compared with the conventional periodical spectrum sensing scheme, the average transmission delay of the SU is reduced without degradation in the maximum achievable throughput by using the proposed DO-CSS scheme, and both the delay performance and achievable SU throughput are further improved by using the proposed TO-CSS scheme.

Buffer-aware network coding for wireless networks

Abstract: Network coding, which can combine various traffic flows or packets via algebraic operations, has the potential of achieving substantial throughput and power efficiency gains in wireless networks. As such, it is considered as a powerful solution to meet the stringent demands and requirements of next-generation wireless systems. However, because of the random and asynchronous packet arrivals, network coding may result in severe delay and packet loss because packets need to wait to be network-coded with each others. To overcome this and guarantee quality of service (QoS), we present a novel cross-layer approach, which we shall refer to as Buffer-Aware Network Coding, or BANC, which allows transmission of some packets without network coding to reduce the packet delay. We shall derive the average delay and power consumption of BANC by presenting a random mapping description of BANC and Markov models of buffer states. A cross-layer optimization problem that minimizes the average delay under a given power constraint is then proposed and analyzed. Its solution will not only demonstrate the fundamental performance limits of BANC in terms of the achievable delay region and delay-power tradeoff, but also obtains the delay-optimal BANC schemes. Simulation results will show that the proposed approach can strike the optimal tradeoff between power efficiency and QoS.

On playback delay in streaming communication

Abstract: We consider the problem of minimizing playback delay in streaming over a packet erasure channel with fixed bandwidth. When packets have to be played in order, the expected delay inherently grows with time. We analyze two cases, namely no feedback and instantaneous feedback. We find that in both cases the delay grows logarithmically with the time elapsed since the start of transmission, and we evaluate the growth constant, i.e. the pre-log term, as a function of the transmission bandwidth (relative to the source bandwidth). The growth constant with feedback is strictly better that the one without, but they have the same asymptotic value in the limit of infinite bandwidth.

Switch for clock synchronization over a switched fabric

Abstract: Devices and methods for synchronizing devices over a switched fabric. A switch receives a request packet from a device, transmits a completion packet to the device, determines an in-switch delay, and stores the in-switch delay. Another switch receives a packet from a first device, forwards the packet to a second device, determines an in-switch delay of the packet, and stores the in-switch delay. Storing of in-switch delays may include adding an in-switch delay to values in one or more transaction delay fields of a packet. Storing of in-switch delays may include storing the delays in a storage element of a switch. In-switch delay may be determined as a difference between a receiving time corresponding to reception of a packet and a forwarding or transmittal time corresponding to forwarding or transmitting of a packet.

Development of an Autonomous Distributed Control System for Optical Packet and Circuit Integrated Networks

Abstract: In this paper, we describe an autonomous distributed control system that we have been developing for an optical packet and circuit integrated network, and we experimentally evaluate its performance. Colored (i.e., multi-wavelength) optical packet-switched links transfer both control signals for circuit switching (e.g., signaling and routing) and best-effort packet data. We successfully transmitted high-definition uncompressed real-time video signals on two lightpaths established by our control system without degradation of video quality, simultaneously with other optical packet data transferred on the same optical fibers. Our developed control system not only achieved autonomous distributed signaling and routing but also has a function that can adjust wavelength resources for optical packet and circuit switching autonomously in each link at each node. Controllers achieved lightpath establishment within approximately 360 ms and dynamic resource adjustment within approximately 454 ms, in the best possible case in our experimental setup.

Self-Adaptive On-Demand Geographic Routing for Mobile Ad Hoc Networks

Abstract: It has been a big challenge to develop a routing protocol that can meet different application needs and optimize routing paths according to the topology changes in mobile ad hoc networks. Basing their forwarding decisions only on local topology, geographic routing protocols have drawn a lot of attentions in recent years. However, there is a lack of holistic design for geographic routing to be more efficient and robust in a dynamic environment. Inaccurate local and destination position information can lead to inefficient geographic forwarding and even routing failure. The use of proactive fixed-interval beaconing to distribute local positions introduces high overhead when there is no traffic and cannot capture the topology changes under high mobility. It is also difficult to preset protocol parameters correctly to fit in different environments. In this work, we propose two self-adaptive on-demand geographic routing schemes which build efficient paths based on the need of user applications and adapt to various scenarios to provide efficient and reliable routing. To alleviate the impact due to inaccurate local topology knowledge, the topology information is updated at a node in a timely manner according to network dynamics and traffic demand. On-demand routing mechanism in both protocols reduces control overhead compared to the proactive schemes which are normally adopted in current geographic routing protocols. Additionally, our route optimization scheme adapts the routing path according to both topology changes and actual data traffic requirements. Furthermore, adaptive parameter setting scheme is introduced to allow each node to determine and adjust the protocol parameter values independently according to different network environments, data traffic conditions, and node's own conditions. Our simulation studies demonstrate that the proposed routing protocols are more robust and outperform the existing geographic routing protocol and conventional on-demand routing protocols under various conditions including different mobilities, node densities, traffic loads, and destination position inaccuracies. Specifically, the proposed protocols could reduce the packet delivery latency up to 80 percent as compared to GPSR at high mobility. Both routing protocols could achieve about 98 percent delivery ratios, avoid incurring unnecessary control overhead, have very low forwarding overhead and transmission delay in all test scenarios.

Analytical Modeling for Delay-Sensitive Video Over WLAN

Abstract: Delay-sensitive video transmission over IEEE 802.11 wireless local area networks (WLANs) is analyzed in a cross-layer optimization framework. The effect of delay constraint on the quality of received packets is studied by analyzing “expired-time packet discard rate”. Three analytical models are examined and it is shown that M/M/1 model is quite an adequate model for analyzing delay-limited applications such as live video transmission over WLAN. The optimal MAC retry limit corresponding to the minimum “total packet loss rate” is derived by exploiting both mathematical analysis and NS-2 simulations. We have shown that there is an interaction between "packet overflow drop" and "expired-time packet discard" processes in the queue. Subsequently, by introducing the concept of virtual buffer size, we will obtain the optimal buffer size in order to avoid "packet overflow drop". We finally introduced a simple and yet effective real-time algorithm for retry-limit adaptation over IEEE 802.11 MAC in order to maintain a loss protection for delay-critical video traffic transmission, and showed that the average link-layer throughput can be improved by using our adaptive scheme.

Use of test packets by packet switches in computer networks

Abstract: A packet switch receives a management packet sent for discovery on a data flow's path through a network. The switch creates a test packet (310T) which looks like a packet belonging to the data flow of interest. The test packet is processed by the switch like the data flow of interest except that the test packet is not necessarily transmitted. The processing results may include the egress ports for the test packet, and if the ports are part of a LAG or ECMP group, the results provide the group and the group members associated with the egress ports. Firewall actions and other information can be included. The switch may forward the results to the originator of the management packet. The switch may insert the results into the management packet and forward the management packet on the ports determined as egress ports for the test packet. Other features are also provided.

Modeling and stabilization of a wireless network control system with packet loss and time delay

Abstract: The problem of modeling and stabilization of a wireless network control system (NCS) is considered in this paper, where packet loss and time delay exist simultaneously in the wireless network. A discrete-time switched system with time-varying delay model is first proposed to describe the system closed by a static state feedback controller. A sufficient criteria for the discrete-time switched system with time-varying delay to be stable is proposed, based on which, the corresponding state feedback controller is obtained by solving a set of linear matrix inequalities (LMIs). Numerical examples show the effectiveness of the proposed method.

Two level packet distribution with stateless first level packet distribution to a group of servers and stateful second level packet distribution to a server within the group

Abstract: A method, in one or more network elements that are in communication between clients that transmit packets and servers, of distributing the packets among the servers which are to process the packets. Stickiness of flows to servers assigned to process them is provided. A packet of a flow is received at a static first level packet distribution module. A group of servers is statically selected for the packet of the flow with the first level module. State that assigns the packet of the flow to the selected group of servers is not used. The packet of the flow is distributed to a distributed stateful second level packet distribution system. A server of the selected group is statefully selected with the second level system by accessing state that assigns processing of packets of the flow to the selected server. The packet of the flow is distributed to the selected server.

Joint coding and scheduling optimization in wireless systems with varying delay sensitivities

Abstract: Throughput and per-packet delay can present strong trade-offs that are important in the cases of delay sensitive applications. We investigate such trade-offs using a random linear network coding scheme for one or more receivers in single hop wireless packet erasure broadcast channels. We capture the delay sensitivities across different types of network applications using a class of delay metrics based on the norms of packet arrival times. With these delay metrics, we establish a unified framework to characterize the rate and delay requirements of applications and to optimize system parameters. In the single receiver case, we demonstrate the trade-off between average packet delay, which we view as the inverse of throughput, and maximum inorder inter-arrival delay for various system parameters. For a single broadcast channel with multiple receivers having different delay constraints and feedback delays, we jointly optimize the coding parameters and time-division scheduling parameters at the transmitter. We formulate the optimization problem as a Generalized Geometric Program (GGP). This approach allows the transmitter to adjust adaptively the coding and scheduling parameters for efficient allocation of network resources under varying delay constraints. In the case where the receivers are served by multiple non-interfering wireless broadcast channels, the same optimization problem is formulated as a Signomial Program, which is NP-hard in general. We provide approximation methods using successive formulation of geometric programs and show the convergence of approximations.

A dynamic traffic-aware duty cycle adjustment MAC protocol for energy conserving in wireless sensor networks

Abstract: Wireless sensors are battery-limited sensing and computing devices. How to prolong the lifetime of wireless sensors becomes an important issue. In order to reduce the energy consumptions when nodes are in idle listening, duty-cycle-based MAC protocols are introduced to let node go into sleep mode periodically or aperiodically. The long duty cycle makes sensors increase the transmission throughput but consumes more energy. The short duty cycle makes sensors have low energy consumption rate but increases the transmission delay. In this paper, a dynamic traffic-aware MAC protocol for energy conserving in wireless sensor networks is proposed. The proposed MAC protocol can provide better data transmission rate when sensors are with high traffic loading. On the other hand, the proposed MAC protocol can save energy when sensors are with low traffic loading. Simulation results show that the proposed protocol has better data throughput than other duty-cycle-based MAC protocols, for example, S-MAC and U- MAC. We also developed a set of comprehensive experiments based on the well-known OMNET++ simulator and revealed that our proposed TA-MAC performs significantly outstanding than related schemes under various situations.

Markov-Chain-Based Output Feedback Control for Stabilization of Networked Control Systems with Random Time Delays and Packet Losses

Abstract: This paper proposes an output feedback method to stabilize and control networked control systems (NCSs). Random time delays and packet losses are treated separately when an NCS is modeled. The random time delays in the controller-to-actuator and sensor-to-controller links are modeled with two time-homogeneous Markov chains, while the packet losses are treated by the Dirac delta functions. An asymptotic mean-square stability criterion is established to compensate for the network-induced random time delays and packet losses in both the controller-to-actuator and sensor-to-controller links simultaneously. An algorithm to implement the asymptotic mean-square stability criterion is also proposed. Further, a DC-motor speed-control test bed with Ethernet using User Datagram Protocol (UDP) is constructed and employed for experimental verification. Two sets of experiments, with and without 10% packet losses in the links, are conducted on this NCS. Experimental results illustrate the effectiveness of the proposed output feedback method compared to conventional controllers. This method could compensate for the effects of the random time delays and packet losses and guarantee the system performance and stability. The integral time and absolute error (ITAE) of the experiments without packet losses is reduced by 13% with the proposed method, and the ITAE of experiments with 10% packet losses, by 30%. The NCS can track the reference command faithfully with the proposed method when random time delays and packet losses exist in the links, whereas the NCS fails to track the reference command with the conventional control algorithms.

Online Adaptive Compression in Delay Sensitive Wireless Sensor Networks

Abstract: Compression, as a popular technique to reduce data size by exploiting data redundancy, can be used in delay sensitive wireless sensor networks (WSNs) to reduce end-to-end packet delay as it can reduce packet transmission time and contention on the wireless channel. However, the limited computing resources at sensor nodes make the processing time of compression a nontrivial factor in the total delay a packet experiences and must be carefully examined when adopting compression. In this paper, we first study the effect of compression on data gathering in WSNs under a practical compression algorithm. We observe that compression does not always reduce packet delay in a WSN as commonly perceived, whereas its effect is jointly determined by the network configuration and hardware configuration. Based on this observation, we then design an adaptive algorithm to make online decisions such that compression is only performed when it can benefit the overall performance. We implement the algorithm in a completely distributed manner that utilizes only local information of individual sensor nodes. Our extensive experimental results show that the algorithm demonstrates good adaptiveness to network dynamics and maximizes compression benefit.