Showing papers on "Transmission delay published in 1982"

A variation on CSMA/CD that yields movable TDM slots in integrated voice/data local networks

Abstract: A variation on the carrier-sense, multiple-access/collision-detection (CSMA/CD) protocol for local-area, random-access broadcast networks is presented. The new protocol supports any mix of voice and data traffic, and has an upper bound on the delay of periodic traffic. In conventional CSMA/CD systems, statistical fluctuations in the transmission delay may cause disruptions in reconstructed voice waveforms. This does not occur with the new protocol. With this protocol, data sources use conventional CSMA/CD techniques to access the channel, while voice sources use a subset of these protocols, and appear to acquire a time-division multiplexed (TDM) slot. As in TDM systems, the entire system capacity can be used by the periodic sources. Unlike TDM systems, periodic slots are repositioned when other transmissions interfere with them, timing discrepancies between sources can be tolerated, and a centralized controller is not required to assign slots. Simulations are used to compare the delays in this system with those in conventional CSMA/CD systems. It is shown that at link utilizations of 0.9, voice sources can operate in a time-assignment, speech-interpolation mode. The effect of periodic traffic on conventional CSMA/CD protocols is also determined.

Loop transmission system

Abstract: In a loop transmission system in which packet communications are made among a plurality of transmission/reception terminals which are connected in a loop, a higher degree of priority is given to a real time signal packet, while a lower degree of priority is given to a data packet. A communication path in each terminal is controlled according to the degree of priority such that a packet having a higher degree of priority will not be delayed when it passes through the terminal. Further, a transmission request command signal having an intermediate degree of priority is sent for effecting a real time signal transmission as well as full dual communication. In a modified embodiment, a traffic quantity detector is provided for sending out a real time information message. In another modification, an activity control circuit is added for controlling sending out of the voice packet according to a detected traffic quantity.

Distributions of packet delay and interdeparture time in slotted ALOHA and carrier sense multiple access

Abstract: Packet communication systems of the multiaccess/broadcast type, in which all communicating devices share a common channel that is multiaecessed in some random fashion, are considered. Among the various muhraecess schemes known, two prominent ones are considered: slotted ALOHA and Carrier Sense Multiple Access (CSMA). Existing analysis of these schemes has led to the determination of the average channel performance m terms of average throughput and average packet delay. This was achieved by formulating Markovian models for these channels with finite populations of users, each with a single packet buffer. Unfortunately, average performance is not adequate when designing communication systems intended for real-tune applicauons, such as digitized speech, or when analyzing multihop packet radio networks, and the analysis has to be extended so as to provide delay distributions. Using the same Markovian models, the distributions of packet delay and interdeparture time for slotted ALOHA and CSMA channels are derived, and expressions for their moments are given.

Speech packet switching method and device

Abstract: In a speech packet switching system, an input speech signal to a speech packet transmitting station is converted to a digital signal to form speech data blocks, which are discriminated to talkspurt blocks and silence blocks, and only the talkspurt speech blocks are packetized and transmitted through a speech packet switching network. In a receiving station, a series of speech packets received in one talkspurt period are temporarily stored in a variance absorbing buffer to compensate for a variance of transmission delay times resulting from the transmission through said speech packet switching network to add variance absorbing times to the speech packets depending on the transmission delay times of the respective speech packets. Then the speech packets are sequentially reproduced. A size of the variance absorbing buffer is determined by a variance of the transmission delay times of the speech packets received in one talkspurt period and the size of the variance absorbing buffer for the next talkspurt period is dynamically changed based on the determined size. A constant speech quality is assured to a change of the variance of the transmission delay times of the speech packets due to a change of traffic in the speech packet switching network.

Performance Evaluation Methods for an Integrated Voice/Data Link

Abstract: This paper presents an approximation method for estimating the average number of data packets in a SENET-concept integrated voice and data system. The method is simple to use and its estimates are found to be in good agreement with simulation results. In general, the method applies to any system that integrates packet traffic with a more slowly varying traffic class that can preempt a portion of the packet transmission capacity.

Packet switching loop-around network and facilities testing

Abstract: A communication method and packet switching system in which packets comprising logical addresses and voice/data information are communicated through the system by packet switching networks which are interconnected by high-speed digital trunks with each of the latter being directly terminated on both ends by trunk controllers. During initial call setup of a particular call, central processors associated with each network in the desired route store the necessary logical to physical address information in the controllers which perform all logical to physical address translations on packets of the call. Each network comprises stages of switching nodes which are responsive to the physical address associated with a packet by a controller to communicate this packet to a designated subsequent node. The nodes provide for variable packet buffering, packet address rotation techniques, and intranode and internode signaling protocols. Each packet has a field which is automatically updated by the controllers for accumulating the total time delay incurred by the packet in progressing through the networks. Each processor has the capability of doing fault detection and isolation on the associated network, trunks, and controllers by the transmission of a single test packet. The testing is done solely in response to the test packet and no preconditioning of controllers or networks is necessary.

Analysis of a Finite Storage System with Batch Input Arising out of Message Packetization

Abstract: A Markovian queueing model with finite waiting space is developed for the communications controller which buffers the flow of packets from a host computer to its associated packet switch. The segmentation of messages into packets by the host is modeled by a batch input to the communications controller. The probabilities of state are determined by numerical recursion and subsequently used in expressions developed for the blocking probabilities and waiting-time distribution as a function of two proposed batch acceptance strategies. Representative numerical results as would be useful in the dimensioning and performance analysis of the communications controller are presented. A more general non-Markovian model is investigated by means of simulation, showing that the initial Markovian model is very accurate in determining the system performance.

Stream Traffic Communication in Packet Switched Networks: Destination Buffering Considerations

Abstract: In this paper we consider the problem of sending a stream of data (speech, for example) through a packet-switched network which introduces variable source-to-destination delays for different packets of the stream Ideally, this delay difference should be smoothed so as to preserve the continuity of the stream We investigate an adaptive destination buffering scheme which may be used to achieve the smoothing of the output stream The scheme uses delay information, measured for previous streams, in order to compute destination buffering information Specifically, of the last m packet delays, one discards the largest k and then the range of this partial sample is used for the destination wait time D We obtain a rule of thumb for choosing m and k , and demonstrate its applicability on some empirical delay distributions from ARPANET measurements It is, in general, necessary to deal with discontinuities which occur even after smoothing To this end, we consider two possible playback schemes: method E (time expanded in order to preserve information) and method I (late data ignored in order to preserve timing) The two methods are at opposite ends of a continuum of possible playback schemes We study the implication of methods E and I on the choice of smoothing parameters and establish a foundation for evaluating all schemes in this continuum

Analysis of a Hybrid Access Scheme for Buffered Users-Probabilistic Time Division

Abstract: A new multiple access scheme is proposed and evaluated. The proposed scheme combines desirable features of the ordinary time-division (TDMA) and the random access (RA) schemes. It is shown that by adjusting the value of a single parameter a, the proposed access method can vary continuously from one extreme (TDMA) to the other (RA). The average delay per packet and the throughput can be improved for intermediate values of the load factor. Furthermore, the method can control the channel instability.

A Study of Fairness in Packet-Switching Networks

Abstract: The use of channel scheduling to improve a measure of fairness in packet-switching networks is investigated. This fairness measure is based on mean end-to-end delays derived from Kleinrock's classical model. The network designer can incorporate any desired relative delay among user classes into this fairness measure. It is found that scheduling is helpful in reallocating delay among user classes and can be used to improve the fairness of a network. It is also shown that a parameterized queueing discipline can be used to further improve fairness. A conservation theorem characterizing the effects of scheduling on overall mean end-to-end delay is established. The results are applicable to both fixed and random routing and are found to be relatively insensitive to fluctuations in traffic.

Method and apparatus of packet switching

Abstract: It is efficient to detect a data error, which is produced in a packet switching network, in a range between final users of data. A packet including data for detecting a data error is formed for a data unit made up of a series of data packets sent to a packet mode terminal, and send to the packet mode terminal. A data error is detected by the data for detecting a data error each time the above-mentioned series of data packets are received.

Minimizing Packet Waiting Time in a Multibeam Satellite System

Abstract: In this paper, we examine the problem of time-slot assignment in an SS/TDMA system operating in a packet-switched environment. We seek to assign time slots in order to minimize average packet waiting time and in order to maximize transponder utilization. We show that an assignment which achieves both objectives exists and develop a branch-and-bound algorithm to find it. In addition, we suggest several heuristics which require much less computational effort and give very close to optimal results. We derive theoretical bounds on the performance of these heuristics and perform simulation trials to show that, on average, the heuristics are very much better than their bounds suggest, and are, in fact, extremely close to optimal.

Optimal fixed frame multiplexing in integrated line- and packet-switched communication networks

Abstract: Recently, emphasis has been placed on integrated communication facilities capable of handling both line-switching and packet-switch-ing digital traffic. The problem of dynamically allocating the bandwidth of a trunk to both types of traffic is formulated as a Markovian decision process. Line switching is modeled as a time division multiplexing loss scheme over a varying portion of a fixed time frame. Packet-switching traffic is served through the remaining portion of the frame and requires queueing at the multiplexer-concentrator. Two different cost criteria are examined involving probability of blocking for line switching and average queueing delay for packets. The corresponding optimization problems are presented under reasonable simplifying assumptions. The movable boundary scheme suggested for commercial implementation of integrated multi-plexers is shown to offer optimal or near-optimal performance.

System for resolving collision in local network

Abstract: The invention provides a method for resolving a data packet collision in a local network where a plurality of nodes which respectively comprise processors and terminal equipment utilize a single transmission line in accordance with a contention system. A contention phase is initiated unless a collision occurs. When a collision occurs, a resolution phase is initiated. The nodes which have been performing transmission immediately stop transmission. They discriminate their positions on the transmission line before a time interval (2×maximum transmission delay time interval) elapses from the start of transmission. If no signal is received by a given node from the left, the given node is regarded as the leftmost node among the conflicting nodes. The leftmost node immediately starts transmitting a packet. Other nodes except for the leftmost node stop retransmitting the packets. The nodes which have performed retransmission are stopped until the resolution phase is completed. The nodes except for the leftmost node receive retransmitted packets and immediately send out short reservation signals to the right. A node which does not receive the reservation signal from any other node during the reservation signal transmission is the leftmost node among the nodes which may not perform retransmission, and performs retransmission immediately after the reservation signal is sent out. Retransmission of the packet and transmission of the reservation signal are repeated. When the final conflicting node finishes retransmission, all of the nodes complete transmission. Each node continuously monitors the transmission line. When a nonsignalling period continues for more than a given time period (2×maximum propagating delay time interval), another contention phase is initiated.

Performance Analysis of Hybrid Switching Concepts for Integrated Voice/Data Communications

Abstract: This paper describes and evaluates variations of a generic hybrid switching concept for integrated voice and data communications. Concepts examined include the Slotted ENvelope NETwork approach, the enhanced hybrid (SENET with time assignment speech interpolation/time assignment data interpolation), the flexible hybrid, and the variable length frame/packet approach. Primary criteria used to evaluate the concepts are transmission throughput efficiency and delay versus information throughput. Other criteria, such as voice continuity and routing/flow control, were also applied. It is seen that several of the hybrid approaches perform very Well in comparison with circuit and packet switching techniques, in terms of their ability to service different traffic mixtures both efficiently and effectively.

Time division switching system for circuit mode and packet mode channels

Abstract: The switching network included in the system is connected to circuit mode and/or packet mode mono- or multi-channel digital lines via connection modules. These modules enable the system connections to be standardized and accept thus any number of multiplexed channels in the lines and any transmission mode, namely duplex or half-duplex. The flag/packet transition in a packet mode channel is detected in a connection module and is transmitted as a particular word in a predetermined time interval of the outgoing multiplex of this module, at the same time as the address of the channel, thereby precluding the use of purpose-built links.

Packet Satellite System with Multiuplinks and Priority Discipline

Abstract: The performance of a packet satellite system with multiple uplink channels using priority service discipline for successful packets on the uplinks is analyzed in this paper. The satellite is assumed to provide either no on-board storage or an infinite buffer for successful packets on the uplinks. The delay-throughput characteristics for each priority as well as the entire system have been obtained. Expression for the z -transform of the system state at equilibrium has been derived for the case of infinite buffer. As expected, it is demonstrated through examples that packets with lower priorities have lower throughput and suffer longer delay.

Packet Switching:Tomorrow's Communications Today

Abstract: One What is a Packet?.- 1. To Switch or Not to Switch.- What Is Packet Switching?.- Why Use a Switched Network?.- Summary.- Suggested Readings.- 2. Packet Switching in a Telephone World.- Switching through the Telephone.- Transparent and Transactional Switching.- Approaches to Switching Compared.- Data Communications versus Voice Communications.- Data Call Statistics.- The Why and Where of Packet Switching.- Summary.- Suggested Readings.- 3. Circuit Switching/Message Switching/Packet Switching-A Quick Comparison.- Circuit Switching.- Message Switching.- Packet Switching.- Circuit Switching of Data-Advantages and Disadvantages.- Message Switching of Data-Advantages and Disadvantages.- Packet Switching of Data-Advantages and Disadvantages.- Summary 38 Suggested Readings.- 4. Getting Started with Network Basics.- The Network Environment.- The Example of the Public Telephone Network.- The Network User and the Network Supplier-Two Sides of the Coin.- Design Considerations.- Summary.- Suggested Readings.- 5. What Is an Erlang? An Introduction to Telecommunications Traffic Engineering.- Statistical Behavior of Network Users.- Traffic and User Satisfaction.- Blocking, Lines, and Erlangs.- Networks with Storage and Delay Instead of Blocking.- Capacity of Networks-Some Examples.- Summary.- Suggested Readings.- 6. Quantitative Tradeoffs-Packet, Circuit, and Message Switching.- Packet Switching-Operational Detail and Possible Faults.- Packet Switching-Overhead Structure Fundamentals.- Delay Comparison-Ideal Case.- Data Traffic Impact on Processor Loading.- Overhead in Circuit Switching and Packet Switching.- A Nationwide Data Network.- Summary.- Suggested Readings.- Two Operational Protocols-Packet Switching In Networks.- 7. Protocol Structures in Packet Switched Networks.- Types of Network Protocols.- The International Standards Organization (ISO) Protocol Hierarchy.- The ARPANET Approach to Protocols.- Virtual Circuit.- Datagrams.- Two Classes of Terminals.- Summary.- Suggested Readings.- 8. The User-Network Interface-The X.25 Standard.- The Packet-Switched Network User's Perspective.- The X.25 Protocol-Level 3 Features and Facilities.- User Actions under the X.25 Protocol.- Summary.- Suggested Readings.- 9. Control and Monitoring in a Network-Some Considerations.- The Role of Control.- Network Control Centers for Packet Networks.- Summary.- Suggested Readings.- Three Packet Networks in the Real World-Topology, Routing, Robustness, and Some Lucky Guesses.- 10. Topological Principles-Some Tricks to Make Packet Switching Work Better.- Alternative Topological Structures.- The General Topological Design Problem.- Desirable Topological Features for Packet Switching.- Summary.- Suggested Readings.- 11. Network Design Case Example-Even a Bad Guess Is Better Than None.- The Network Design Requirements.- The Impact of Topology and Data Rate on Network Resources.- Detailed Requirements and Bad Guesses.- Summary.- Suggested Readings.- 12. Routing in Packet Networks.- Alternative Routing Methods.- Advantages and Disadvantages of Routing Methods.- Approaches to Adaptive Directory Routing.- Summary.- Suggested Readings.- Four Packet Switching Without Packet Switches.- 13. Resource Sharing and Multiple Access Techniques.- The General Problem of Communications Resource Sharing.- The Satellite-Based ALOHA Technique.- The Network Aspect of the Packet Broadcast Channel.- Capacity and Delay of the ALOHA Channel.- ALOHA Channel Delay Characteristics.- Summary.- Suggested Readings.- 14. Improvements on the Basic ALOHA Channel-Slots and Reservations.- Increasing the Capacity of the Packet Broadcast Channel.- The Slotted ALOHA Channel.- Slotted ALOHA Channel with Capture.- Packet Broadcast Channels with Capacity Reservation.- Highlight Comparison of Multiple Access Techniques.- Summary.- Suggested Readings.- 15. Terrestrial Packet Radio Systems.- Terrestrial Repeaters and Local Networks.- Carrier Sense Multiple Access-Listen Before You Send.- Summary.- Suggested Readings.- 16. Combination of Satellite and Terrestrial Connectivity-The General Optimization Problem.- Serving Users without Dedicated Earth Stations-The General Problem.- Deriving the Optimum Value of the Number of Earth Stations.- Applications and Examples of the Random Network Analysis.- Summary.- Suggested Readings.- Five Data Networks, Packet Switching, and the Common Carriers.- 17. The Carrier Marketplace.- Common Carrier Services and Facilities.- Common Carriers in the United States.- Summary.- Suggested Readings.- 18. Value-Added Networks (VANs) and Packet Switching.- Public Networks and the Role of VANs.- The Telenet Packet Switched Network.- The Tymnet Nationwide Data Network.- Worldwide Packet Switching Services.- Summary.- Suggested Readings.- 19. A Tariff for Every Occasion.- A Sample of Common Carrier Communications Tariffs.- A Current and Future Tariff Cost Model.- Summary.- Suggested Readings.- 20. Some New Common Carrier Prospects.- Some Proposed New Telecommunications Services.- AT&T's Advanced Communications Service (ACS).- The Nationwide Network of Satellite Business Systems (SBS).- The Xerox Telecommunications Network (XTEN).- ACS, SBS, and STEN Compared.- Summary.- Suggested Readings.- Six Integrated Networks and the Future of Packet Switching.- 21. Hybrid Techniques: Combining Circuit and Packet Switching.- Classification of Information and Switching Techniques.- Approaches to Integrating Circuit and Packet Switching.- The Master Frame Approach to Integrated Switching.- Summary.- Suggested Readings.- 22. Integrated Services Networks.- Voice Digitization.- General Structure of Integrated Services Packet Switched Networks.- Cost/Performance Analysis.- Summary.- Suggested Readings.- 23. The Outlook for Packet Switching-And What to Do about It.

On a hybrid network system of circuit switching and packet switching

Abstract: This paper describes the architecture of a hybrid switching network employing both circuit switching and packet switching. The network usually operates in a packet switching mode, but, depending on the traffic conditions, it can use special control packets to temporarily change certain lines to a circuit switching mode. The change between the two switching modes is performed dynamically depending on the traffic load of the network. Also described in this paper is the concept of metapacket which can be employed in some relatively small-scale networks to average the load of packets and to reduce data transmission time.

Digital data transmission system with time division/packet transformation function

Abstract: A digital data transmission system with a transmultiplexer arrangement for interconnection of a time division multiplex line and a packet multiplex line. The transmultiplexer has a section which converts data for each of a plurality of terminals on the time division multiplex line in the unit of a packet, for allocation on the packet multiplex line, and a section which identifies the time position of each data unit on the time division multiplex line, prepares a specific packet containing the position information and allocates the specific packet before the data packet on the packet multiplex line. The transmultiplexer also has a section which periodically allocates data on the packet multiplex line allotted with a specific packet containing position information of a terminal before a data packet corresponding to the terminal on the time division multiplex line in accordance with the position information of the terminal.

Control system for plurality of lines

Abstract: PURPOSE:To optimize a transmission scheduling, by taking into consideration data length of transmission data, transmission speed and transmission delay time of each communication line and selecting the line in use so that the utilization factor and transmission time of each communication line can be constant. CONSTITUTION:A communication system 1 is provided with communication system HDLC control sections 61, 62... connecting communication systems using a pluraity of lines connected to a plurality of communication lines 51, 52... via MODEMs 31, 32... and a scheduling control section 10, and a transmission data Ds is inputted and stored to a first-in/first-out FIFO CUE14 sequentially for storage, and if a transmission waiting CUE12 of the HDLC section 61... corresponding to each line 51... is vacant, the line number is stored in a vacant display latch 18, a gate 15 is opened by it, a transmission data is picked up from a open CUE14 and inputted to a data length detection/share section 16. The data length is measured, the line in use is selected by using a delay time of each line, the data is inputted to the transmission waiting CUE12 in the HDLC control section of the said line via a switching device 17 and transmission is made.

Circuit and method for correcting distortion in a digital audio system

Abstract: A circuit and method are provided to compensate for the non-linear delay characteristics of a digital audio system introduced by the systems anti-aliasing filter. The circuit and method provide for introducing time delay to the digital system at the low and mid range frequencies, and adding decreasing amounts of time delay at the high frequency ranges to produce an overall composite time delay for the digital system which is relatively constant over its operating frequency range. The delay equalizer used to achieve such delay compensation is made up of active delay equalizer sections which are non-interactive, and which are independently tunable in terms of each sections center frequency and Q. An active delay equalizer section with a second order bandpass transfer functions has been devised to achieve this capability. It is comprised of an operational amplifier having input resistance and feedback resistance connected to its inverting input and a twin-T network connected in its non-inverting input. The twin-T is a driven twin-T for variable Q, and provides a delay equalizer wherein the time delay of each section can readily be tailored to the designers requirements.

Method for transmitting of voice packet

Abstract: PURPOSE:To obtain a packet communication system with high quality even if the delay of a voice packet is varied, by adding sound starting information to the voice packet to process the voice packet. CONSTITUTION:A start information generator SPG adds starting information to a packet. Receiving a control signal S119 in each voice data block, the SPG supervises a control signal S118 outputted from a voice detecting circuit VDET to detect a voice data block corresponding to voice starting out of respective voice data blocks. The starting informatiin dlt is supplied to a voice packet transmitting circuit PVT through a data line 115 and used for the assembling of the starting information field of the voice packet. In a voice data block discriminated as voice, a transmission control signal tpt is supplied to a packet transmitting circuit PUT and the corresponding voice data vdt, sequential- number sqt and starting information dlt are supplied to the PVT and assembled as a voice packet to be sent to a data line 111.

Control system of packet switching batch communication

Abstract: PURPOSE:To reduce the number of logical channels which are used at a terminal and the number of terminal sent packets by transmitting and receiving a call request packet or data packet at the terminal in a bundle by one packet. CONSTITUTION:A terminal 1 sends the call request packet 5 which consists of pieces of terminal identification information 9 and 10 on terminals 3 and 4 and an additional logical channel CH number 8 to an exchange 2. The exchange 2 sends the incoming call packet 6 which consists of originating terminal identification information 11 and an additional logical CH number 12 to the terminal an d the incoming call packet 7 which consists of the information and an additional logical CH number 13 to the terminal 14. The exchange 2 waits the arrive of incoming-call acceptance packets from the terminals 3 and 4 for a specific time, and edits and sends a connection completion packet 16 to the terminal 1 once receiving the incoming-call acceptance packet 14 and 15. The pieces of identification information 9 and 10 on the terminals which return the incoming-call acceptance packets are added to the packet 16, so the originating terminal knows the party terminals which finish call setting normally.