Showing papers on "Transmission delay published in 2006"

On Delay Performance Gains From Network Coding

Abstract: This paper analyzes the gains in delay performance resulting from network coding. We consider a model of file transmission to multiple receivers from a single base station. Using this model, we show that gains in delay performance from network coding with or without channel side information can be substantial compared to conventional scheduling methods for downlink transmission.

Packet processors and packet filter processes, circuits, devices, and systems

Abstract: A packet filter (2500) for incoming communications packets includes extractor circuitry (2510) operable to extract data from a packet, and packet processor circuitry (2520) operable to concurrently mask (3010) the packet data from the extractor circuitry (2510), perform an arithmetic/logic operation (3020) on the packet to supply a packet drop signal (DROP), and perform a conditional limit operation and a conditional jump operation (3030).

Method and apparatus for improved multicast streaming in wireless networks

Abstract: The invention includes a method and apparatus for providing media content. The method includes duplicating each packet of an original packet stream for which an associated importance level satisfies an importance condition, inserting each duplicate packet within the original packet stream to form thereby a modified packet stream, and transmitting the modified packet stream toward a wireless terminal adapted for processing the modified packet stream for presenting the media content conveyed by the original packet stream. The duplicate packets may be inserted within respective windows associated with the duplicate packets, wherein each window is determined according to an original packet position associated with the original packet from which the duplicate packet is formed.

Transmission Delay Line Based ID Generation Circuit for RFID Applications

Abstract: A transmission delay line based ID generation circuit is presented for radio frequency identification (RFID) applications. The ID generation circuit has been designed using microstrip transmission lines as delay lines for its operation at ultra high frequency (UHF: 915MHz). The layout has been realized on a flexible substrate using photolithography based fabrication techniques. The circuit has been tested with an on-off-key (OOK) modulated input signal and different combinations of 4bit ID code have been generated. Obtained results confirm the concept and its use in RFID applications

Rate-distortion optimized distributed packet scheduling of multiple video streams over shared communication resources

Abstract: We consider the problem of distributed packet selection and scheduling for multiple video streams sharing a communication channel. An optimization framework is proposed, which enables the multiple senders to coordinate their packet transmission schedules, such that the average quality over all video clients is maximized. The framework relies on rate-distortion information that is used to characterize a video packet. This information consists of two quantities: the size of the packet in bits, and its importance for the reconstruction quality of the corresponding stream. A distributed streaming strategy then allows for trading off rate and distortion, not only within a single video stream, but also across different streams. Each of the senders allocates to its own video packets a share of the available bandwidth on the channel in proportion to their importance. We evaluate the performance of the distributed packet scheduling algorithm for two canonical problems in streaming media, namely adaptation to available bandwidth and adaptation to packet loss through prioritized packet retransmissions. Simulation results demonstrate that, for the difficult case of scheduling nonscalably encoded video streams, our framework is very efficient in terms of video quality, both over all streams jointly and also over the individual videos. Compared to a conventional streaming system that does not consider the relative importance of the video packets, the gains in performance range up to 6 dB for the scenario of bandwidth adaptation, and even up to 10 dB for the scenario of random packet loss adaptation.

Subnet scoped multicast/broadcast packet distribution mechanism over a routed network

Abstract: In one embodiment, receiving a data packet in a data forwarding domain, encapsulating a header to the received data packet, and routing the encapsulated data packet in the data forwarding domain over a distribution tree are provided.

Optimal Throughput–Delay Scaling in Wireless Networks—Part II: Constant-Size Packets

Abstract: In Part I of this paper, the optimal throughput-delay tradeoff for static wireless networks was shown to be D(n)=Theta(nT(n)), where D(n) and T(n) are the average packet delay and throughput in a network of n nodes, respectively. While this tradeoff captures the essential network dynamics, packets need to scale down with the network size. In this "fluid model, " no buffers are required. Due to this packet scaling, D(n) does not correspond to the average delay per bit. This leads to the question whether the tradeoff remains the same when the packet size is kept constant, which necessitates packet scheduling in the network. In this correspondence, this question is answered in the affirmative by showing that the optimal throughput-delay tradeoff is still D(n)=Theta(nT(n)), where now D(n) is the average delay per bit. Packets of constant size necessitate the use of buffers in the network, which in turn requires scheduling packet transmissions in a discrete-time queuing network and analyzing the corresponding delay. Our method consists of deriving packet schedules in the discrete-time network by devising a corresponding continuous-time network and then analyzing the delay induced in the actual discrete network using results from queuing theory for continuous-time networks.

Temperature compensation via power supply modification to produce a temperature-independent delay in an integrated circuit

Abstract: A method and circuitry for adjusting the delay of a variable delay line (VDL) in a delay locked loop (DLL) or other delay element or subcircuit on an integrated circuit is disclosed. Such delay circuitry will inherently have a delay which is a function of temperature. In accordance with embodiments of the invention, such temperature-dependent delays are compensated for by adjusting the power supply voltage of the VDL, delay element, or subcircuit. Specifically, a temperature sensing stage is used to sense the temperature of the integrated circuit, and hence the VDL, delay element, or subcircuit. Information concerning the sensed temperature is sent to a regulator which derives the local power supply voltage from the master power supply voltage, Vcc, of the integrated circuit. If the temperature sensed is relatively high, which otherwise would increase the delay though the VDL, delay element, or subcircuit, the regulator increases the local power supply voltage, thus decreasing the delay and offsetting the increase in delay due to temperature. Through this scheme, and assuming the temperature sensing stage is properly tuned, temperature-dependent delays can be reduced to approximately zero.

Rate limiting per-flow of traffic to CPU on network switching and routing devices

Abstract: A network device for use in a networking system. The network device includes a packet processor adapted to receive control packets at a network port of the network device. The packet processor is also adapted to assign a CPU code to the control packets. The network device also includes a CPU in communication with the packet processor and a lookup table indexed by the CPU code and in communication with the packet processor. According to embodiments of the present invention, one or more entries in the lookup table define a rate limit in accordance with which packets characterized by the CPU code are delivered from the packet processor to the CPU.

Translating between a switching format and a transport format

Abstract: This invention includes methods and packet switches that translate a packet between a switching format and a transport format. One packet switch receives a packet intended for a destination port of a packet switch from a switching fabric of the packet switch and determines, based on the destination port, a treatment to be applied to the packet. The packet switch then applies the treatment to the packet prior to forwarding the packet to the destination port. The treatment may include adding a transport identifier to the packet.

Data transmitting/receiving system and method thereof

Abstract: A data transmitter transmitting a data packet containing identifier information including a kind of data, a sequence of data, and/or a packet generating sequence A receiver extracting a packet number and the identifier information for an error-receipt occurring data packet based upon the identifier information recorded in a header of the packet, generating retransmission control information, such as retransmission times and priority, based on the extracted packet number and the identifier information and transmitting the retransmission control information to the transmitter of the packet The retransmitting the error-occurring data packet according to the received retransmission control information The number of retransmissions and the retransmission priority can be varied according to characteristics of the transmitted data, so that retransmissions is suitable for the characteristics of the data and to more stably receive the data that is more influential to the restoration of the data

Analysis of the Total Delay of IEEE 802.11e EDCA and 802.11 DCF

Abstract: A packet sent from an upper-layer protocol or application over IEEE 802.11 [1] will first be placed in a transmission queue. The packet delay caused by waiting here is referred to as the queueing delay. When the packet reaches the head of the queue it will start contending for channel access until it is successfully transmitted over the medium (or finally dropped). The delay associated with the medium access is referred to as the MAC delay. The majority of analytical work on the delay performance of IEEE 802.11 focuses on predicting only the mean MAC delay, although higher layer applications and protocols are interested in the total performance of the MAC layer. The main contribution of this paper opposed to other works is that it provides analytical predictions of the total delay, which also includes the queueing delay. The analyses presented apply to the priority schemes of the Enhanced Distributed Channel Access (EDCA) mechanism of the IEEE 802.11e standard [2]. However, by using an appropriate parameter setting, the results presented are also applicable to the legacy 802.11 Distributed Coordination Function (DCF) [1]. The model predictions are calculated numerically and validated against simulation results.

Enhanced channel interleaving for optimized data throughput

Abstract: In a transmission scheme wherein multi-slot packet transmissions to a remote station can be terminated by an acknowledgment signal from the remote station, code symbols can be efficiently packed over the multi-slot packet so that the remote station can easily decode the data payload of the multi-slot packet by decoding only a portion of the multi-slot packet. Hence, the remote station can signal for the early termination of the multi-slot packet transmission, which thereby increases the data throughput of the system.

On the capacity of mobile ad hoc networks with delay constraints

Abstract: Previous work on ad hoc network capacity has focused primarily on source-destination throughput requirements for different models and transmission scenarios, with an emphasis on delay tolerant applications. In such problems, network capacity enhancement is achieved as a tradeoff with transmission delay. In this paper, the capacity of ad hoc networks supporting delay sensitive traffic is studied. First, a general framework is . proposed for characterizing the interactions between the physical and the network layer in an ad hoc network. Then, CDMA ad hoc networks, in which advanced signal processing techniques such as multiuser detection are relied upon to enhance the user capacity, are analyzed. The network capacity is characterized using a combination of geometric arguments and large scale analysis, for several network scenarios employing matched filters, decorrelators and minimum-mean-square-error receivers. Insight into the network performance for finite systems is also provided by means of simulations. Both analysis and simulations show a significant network capacity gain for ad hoc networks employing multiuser detectors, compared with those using matched filter receivers, as well as very good performance even under tight delay and transmission power requirements

Designing Energy-Efficient Wireless Sensor Networks with Mobile Sinks

Abstract: Mobile enable Wireless Sensor Network (mWSN) has been proposed to realize large-scale information gathering via networking wireless sensors and mobile sinks. Some fundamental design parameters in mWSN have been investigated in this article, such as cluster size, sink velocity, transmission range, and packet length. Our contributions include: 1) We propose to use multihop forwarding to form a cluster around the expected position of a mobile sink, in order to guarantee packet delay and minimize energy consumption. 2) Sink velocity should be carefully chosen, in order to make a compromise between sink-sensor meeting delay and message delivery delay. 3) Large transmission range and short packet length are both of benefit to lower the outage probability of packet transmission. Extensive simulations have been designed to evaluate the performance of mWSN in terms of packet delay, energy consumption and outage probability.

Interleaved processing of dropped packets in a network device

Abstract: A network device for processing packets includes at least one ingress module for performing switching functions on a packet, a memory management unit for storing the packet and at least one egress module for transmitting the packet to at least one port. The at least one egress module is configured to maintain multiple queues for the at least one port, including a purge queue, and to store the packet in the purge queue when an error condition is determined when the end of the packet is received by the at least one ingress module.

Performance Evaluation of Scheduling in IEEE 802.16 Based Wireless Mesh Networks

Abstract: we propose an efficient centralized scheduling algorithm in IEEE 802.16 based Wireless Mesh Networks (WMN) to provide high qualified wireless multimedia services. Our algorithm takes special attention on the relay function of the mesh nodes in a transmission tree which is seldom studied in previous research. Some important design metrics, such as fairness, channel utilization and transmission delay are considered in this scheduling algorithm. IEEE 802.16 employs TDMA and the selection policy for scheduled links in a time slot will definitely impact the system performance. We evaluated the proposed algorithm with four selection criteria through extensive simulations and the results are instrumental for improving the performance of IEEE 802.16 based WMNs in terms of link scheduling.

Method and apparatus for retransmission management for reliable hybrid ARQ process

Abstract: A method for transmitting a packet from a transmitter to a receiver in a wireless communication system begins by building a packet by a transport format combination (TFC) selection process, and the packet is transmitted from the transmitter to the receiver. If the transmitter receives an indication that the packet was not successfully received at the receiver, the packet is retransmitted via a hybrid automatic repeat request (HARQ) procedure. If the HARQ procedure did not successfully transmit the packet, then the packet is retransmitted via a retransmission management (RM) procedure. If the RM procedure did not successfully transmit the packet, then the packet is discarded by the transmitter.

Optimal estimation in networked control systems subject to random delay and packet loss

Abstract: In this paper we study optimal estimation design for sampled linear systems where the sensors measurements are transmitted to the estimator site via a generic digital communication network. Sensor measurements are subject to random delay or might even be completely lost. We present two time-invariant estimator architectures and, surprisingly, we show that stability does not depend on packet delay but only on the packet loss probability. Finally, algorithms to compute critical packet loss probability and estimators performance in terms of their error covariance are given and applied to some numerical examples.

Recovery from burst packet loss in internet protocol based wireless networks using staggercasting and cross-packet forward error correction

Abstract: A method and apparatus for staggercasting are described including encoding and compressing a first data sequence, packetizing the compressed encoded data sequence to form a data packet, performing forward error correction (FEC) encoding on the data packet in order to generate a second data sequence related to the first data sequence, appending FEC control information as padding to the end of payload data of the data packet, packetizing the second data sequence to form a packet, multicasting the data packet to a first multicast group, multicasting the packet formed using the second data sequence delayed by an offset time to a second multicast group.

Communications method for a packet-switched network and network employing the method

Abstract: A communications method for a packet-switched network includes: a) receiving at a routing module operating in a low layer of a layered model defining communications on the network, a packet including an identifier associated to a protocol to be employed at a high layer of the model which is higher than the low layer; b) inspecting the received packet at an inspection module so as to identify the protocol associated to the identifier; c) selecting at a selection module a first device, operating in the high layer associated with the identified protocol; d) sending the packet toward the first device; e) processing the packet by applying at the first device a procedure of the high layer to produce a processed packet; f) sending the processed packet from the first device to the routing module; and g) transmitting the processed packet from the routing module toward the network.

Synchronous data communication

Abstract: A data packet is provided that includes a synchronization field and an acknowledgement field indicative of an acknowledgement of receipt of a prior data packet. The data packet also includes a response field that includes information indicative of a system fault, a header field, and a sequence number field that includes a number assigned to the data packet. The data packet further includes a data field, an end of packet field, and an error-checking field. Methods and computer program products are provided that, in some implementations, include retransmitting packets if the acknowledgement field in a received data packet is a no acknowledgement (NAK) and/or placing a node into a safe state in response to a fault signal that is included in the received data packet.

Internet-Based Bilateral Teleoperation Based on Wave Variable With Adaptive Predictor and Direct Drift Control

Abstract: In a conventional bilateral teleoperation, transmission delay over the Internet can potentially cause instability. A wave variable algorithm guarantees teleoperation stability under varying transmission delay at the cost of poor transient performance. Adding a predictor on the master side can reduce this undesirable side effect, but that would require a slave model. An inaccurate slave model used in the predictor as well as variations in transmission delay, both of which are likely under realistic situations, can result in steady-state errors. A direct drift control algorithm is used to drive this error to zero, regardless of the source of the error. A semi-adaptive predictor that can distinguish between free space and a rigid contact environment is used to provide a more accurate force feedback on the master side. A full adaptive predictor is also used that estimates the environmental force using recursive least squares with a forgetting factor. This research presents the experimental results and evaluations of the previously mentioned wavevariable-based methods under a realistic operation environment using a real master and slave. The algorithm proposed is innovative in that it takes advantage of the strengths of several control methods to build a promising bilateral teleoperation setup that can function under varying transmission delay, modeling error, and changing environment. Success could lead to practical applications in various fields, such as space-based remote control, and telesurgey.

The Packet Loss Effect on MPEG Video Transmission in Wireless Networks

Abstract: The purpose of this paper is to study the packet loss effect on MPEG video transmission quality in wireless networks. First, we consider the distribution of packet losses in wireless network, including distributed and burst packet losses. Besides, we also discuss the additional packet drops by the play-out buffer at the received end, and the effect of the transmission packet size on the video delivered quality. From the results, we find that the effect of burst packet losses on the video delivered quality is less than distributed packet losses in the same packet loss rate. Moreover, the smaller size of the play-out buffer leads to more packet drops and worse video quality. Finally, if there is no video recovery for video transmission, the video delivered quality of the larger packet size will be better than smaller packet size.

Apparatus and method of variable bandwidth multi-codec QoS control

Abstract: An apparatus and method of variable bandwidth multi-codec quality of service (QoS) control are provided. The apparatus for controlling the QoS of a variable bandwidth multi-codec includes: a network state detection unit detecting a network state including at least one of a packet loss ratio, a packet loss interval, and a packet delay time based on an RTP packet transmitted to and received from a destination for which a call connection is established; and a codec control unit updating a transmission rate by comparing the detected resultant value with an already set reference value and increasing or decreasing the transmission rate, and controlling the variable bandwidth multi-codec to code data with the updated transmission rate. According to the apparatus and method, data can be coded with a codec transmission rate suitable for a network state identified during a voice call after the call is set up.

Delay circuit and delay synchronization loop device

Abstract: A delay circuit includes a first delay line circuit having a plurality of stages of delay units, a second delay line circuit having a plurality of stages of delay units, a plurality of transfer circuits provided in association with respective stages of the delay units of the first delay line circuit, the transfer circuits controlling the transfer of the outputs of the delay units of the first delay line circuit to associated stages of the delay units of the second delay line circuit. The delay units of respective stages of the first delay line circuit inverting input signals. Each stage delay unit of the second delay line circuit includes a logic circuit receiving an output signal of the transfer circuit associated with the delay unit in question and an output signal of a preceding stage to send an output signal to a following stage. The duty ratio is rendered variable by independently selecting the rising edge of the input signal and a propagation path of the falling edge.

Method and devices for installing packet filters in a data transmission

Abstract: A method is described for associating a data packet (DP) with a packet bearer (PB) in a user equipment (UE1) of a communication network. The data packet is sent in a data flow from an application function of the user equipment, the packet bearer (PB) is established with the user equipment to transmit the data packet (DP) over the communication network towards a further entity, and the user equipment is adapted to establish different packet bearers. The method comprises the steps of identifying the flow with the data packet in a control entity of the communication network, determining the packet bearer for association with said flow from the different packet bearers in a policy function of the control entity, determining a routing level identification of the further entity, instructing the user equipment to install a packet filter based on the routing level identification, wherein the packet filter associates data packets comprising the routing level identification of the further entity with the determined packet bearer, providing the routing level identification to the application function, including the routing level identification into the data packet, and forwarding the data packet (DP) on the determined packet bearer (PB). A corresponding network, control entity, monitoring entity and computer program are also described.