Showing papers on "Transmission delay published in 1985"

Transmitting sequence numbers of information in a packet data transmission system

Abstract: In a packet data transmission system, correctly received information packets are acknowledged by piggybacking their sequence numbers onto information packets being transmitted. The control field of each information packet includes a bit which indicates whether or not there is a piggybacked acknowledgement. Acknowledgements can also be transmitted separately in control packets having no information field. Each acknowledgement consists of not only the sequence number of a correctly received information packet, but also the acknowledgement status of a plurality of preceding information packets whereby these can be negatively acknowledged if necessary. The sequence numbers can have any one of three different sizes, for efficient transmission of sequence numbers on transmission links of arbitrary transmission speed and length (and hence delay), The sequence number size which is used on any particular transmission link is determined on set-up of the link in dependence upon the transmission speed and the round-trip delay of the link.

Idle period signalling in a packet switching system

Abstract: Trunk controllers (131) at each end of a trunk (118) of a packet switching system (Figs. 1 and 2) include an idle packet generator (1419) and an idle packet detector (1420). During idle periods, when packets are not available for transmission, the transmitter of each idle trunk controller generates and transmits a continuous sequence of flags (801/810) on the trunk. Periodically during the idle periods, the idle packet generator generates and provides to the transmitter (1403) for transmission an idle packet (800). An idle packet is structured like a normal packet. However, it is marked as an idle packet by the packet identification (PID) field (804) and contains pseudo-random bits in the data field (806). The receiver (1402) of the other trunk controller receives the idle code and packets including idle packets, discards the idle code, and sends all packets to the idle packet detector. The detector identifies idle packets by their PID field and discards them - blocks them from propagating further - while allowing other packets to pass therethrough.

Self-routing packets with stage address identifying fields.

Abstract: A multi-stage packet switching network comprising a plurality of packet switch nodes for communicating broadcast and non-broadcast packets each comprising stage identification information and sets of routing information. Each node responsive to receipt of one of the packets for decoding the stage identification information to determine if the packet is a broadcast or a non-broadcast packet. If a broadcast packet has been received, the switch node transmits this packet to the next sequential stage on all output links interconnecting the switch node to the next sequential stage. If the packet is of the non-broadcast type, the switch node decodes the stage identification field to determine which of the sets of the routing information is to be used for routing the non-broadcast packet to the next sequential stage. Before routing the non-broadcast packet to the next sequential stage, the switch node increments the stage identification field. The switch node contains the necessary circuits for performing the incrementing of the stage identification field of a non-broadcast packet and for bypassing the adder circuit for a non-stage identification information portions of the packet and for bypassing the adder circuit for stage indentification field of the broadcast packet.

Packet switching system

Abstract: In a packet switching system of the present invention, a packet handler is facilitated for each incoming circuit to the switching system. The packet handler analyzes the header of each incoming packet from the correspondent circuit and decides the outgoing route of the packet. The packet is then sent out to an outgoing circuit of the decided route, the rest of it including the data field not being stored in the switching system, through a conventional cross-point switch for circuit-switching. Thus, elimination of storing the whole packet raises the efficiency of packet processing and shortens the processing delay. The use of a cross-point switch enables the functional sharing of the system by circuit-switched calls and packet-switched calls.

Lockup detection and recovery in a packet switching network

Abstract: A self-routing packet switching network (100) in which packets are communicated through stages of the network in response to self-contained addresses (Fig. 2) and in which a packet is discarded if a packet cannot be transferred to a subsequent stage of the network within a predefined amount of time. In addition, upon a packet being discarded, a maintenance message is transmitted over a maintenance channel (140) to the processor (149) controlling the network. Each network comprises stages of switching nodes which are responsive to the physical address in a packet to communicate the packet to a designated subsequent node (100-15). The nodes provide for variable packet buffering, packet address rotation techniques, and inter-node and intra-node signaling protocols. Each node comprises a timer (531) which commences timing for a predefined amount of time upon receipt of a packet. If the timer times out, the packet is discarded and a maintenance message is transmitted to the processor controlling the network. The maintenance message includes the physical address plus an address identifying the network entry point of the packet. By discarding packets after a predefined amount of time, the problem of a self-routing network locking up is avoided when one switching node within the network fails or is experiencing overload traffic conditions.

Mean Packet Queueing Delay in a Buffered Two-User CSMA/CD System

Abstract: We consider a system of two users of slotted CSMA-CD (carrier-sense multiple-access with collision detection). The two users are assumed to have independent identical packet arrival streams, the identical randomizing policy for retransmission, and an infinite capacity for storing queued packets. The mean packet delay (including the queueing and retransmission delays) is derived explicitly.

Delay analysis of interval-searching contention resolution algorithms

Abstract: The intelligent design of a random multiple-access communication system involves analyzing the tradeoffs among throughput rate, transmission delay, and stability subject to additional restrictions imposed by distributed processing requirements. Interval-searching contention resolution algorithms have been found to achieve high throughput, and simulations have shown that they also possess short average delay. A general approach to the delay analysis of interval-searching contention resolution is proposed based on solving an integral equation for the distribution of a quantity called the transmission lag. For a certain multibit feedback algorithm, this analytical technique leads to exact determination of the throughput-delay characteristic. For the celebrated " 0.487 " algorithm, the method yields upper and lower bounds to the curve of expected delay versus throughput that are in close agreement with simulation results.

System for adjusting signal transmission timing in time-division multiplexing signal transmission

Abstract: A time-division multiplexing communication network comprising a central station (1) and a plurality of local stations (2a to 2n), in which information signals (Dl1 to Dln) are transmitted from the local stations to the central station on a time-division multiplexing basis, and the central station transmits information signals (001 to DOn) to the local stations on a time-division multiplexing basis. The central station sequentially requests that local stations transmit a test signal in order to prevent collision of transmission signals from the local stations. Each local station, of which a test signal transmission is requested, transmits the test signal to the central station. The central station sends back the test signal to the local station which transmitted this test signal. The local station measures transmission delay time from transmission to reception of the test signal, and adjusts transmission timing of the information signal to be transmitted to the central station based on the measured delay time.

Packet-based telecommunication system

Abstract: Multiservice packet telecommunication network in which each packet has inserted in an address field thereof a sequence of addresses respectively assigned to the successive switching network included in a route from a packet sender station to a packet receiver station and defining in these networks groups or bundles of outgoing channels. In each bundle the seizure of an outgoing channel is made by scanning and searching a free channel in the bundle.

Priority Access Schemes Using CSMA-CD

Abstract: Some CSMA-CD schemes for multiple priority message classes are suggested. For all the schemes, an approximate analytic technique for calculating the mean packet delay (for each priority) at the stable operating point of the system has been developed. The analytic results are tested against computer simulation. A Poisson packet arrival process and a general packet length distribution are considered. The mean packet retransmission delay is a general function of priority and the number of unsuccessful attempts. There is a variation in delay differences among priorities for the different schemes. This allows one to single out the particular scheme that is optimal for a given system delay requirement. Some of the priority schemes possess the desirable property of having less average delay compared to a corresponding nonpriority system.

Packet transmission system

Abstract: A multiaccess packet transmission system for transmitting both bursty and periodical packets. A packet detection circuit detects the arrival of a first periodical packet and predicts the time of arrival of the next periodical packet for reserving the transmission path at the predicted time. Bursty packets are transmitted only when the transmission path is idle and not reserved.

Distributed Switching for Data Transmission over Two-Way CATV

Abstract: Most of tile present approaches to two-way interactive CATV focus on the centralized approach, in which all traffic must travel to the CATV head end. In this paper, we present a distributed approach, in which intelligent store-and-forward packet switches are to be installed at various locations on the cable. The analysis emphasizes three main criteria: the maximum traffic flow on the cable, the throughput of each switch, and the average message delay. Two possible schemes are compared. In one, the switches appear on the main trunk only. In the second, switches are used at branch locations as well.

Optical communication system

Abstract: The optical communication system of the invention comprises an optical transmission line, optical coupling devices, each having a varying coupling ratio, connected to the transmission line, and stations connected to the optical coupling devices; wherein the coupling ratio of the device is changed to a predetermined value by a control signal applied by its associated station, depending on the state of transmission and reception, level of received signal, operating state of the station, and the like, to thereby provide high reliability, reduced transmission delay and low error rate, as well as to thereby decrease the amount of attenuation between transmitting and receiving stations

Packet transmission and reception via a shared DMA channel

Abstract: A DMA channel is shared by transmit and receive ports via which data packets are transmitted and received using a bit oriented protocol such as HDLC. For the transmission of each packet, an abort signal of the protocol is initially transmitted, and the packet is transmitted when the DMA channel is free after a delay equal to the packet transmission turnaround time. In response to receipt of the abort signal, the DMA channel is reserved for reception of a packet within a time-out period. The DMA channel adopts a receive state in response to the abort signal either immediately if it is free, or at the end of transmission if a packet is currently being transmitted.

Asynchronous packet switch

Abstract: In this switch, the incoming packet is received by incoming circuit assemblies (GCE) and transmitted to packet memory assemblies (GMP) permitting the storing of the packet in memory once reception starts, the analysis of the header of the said packet during reception, and the despatching of its characteristics to the outgoing circuit assemblies (GCS) once reception ends. The despatching of the packet over an outgoing circuit (CS) is done through a three space-domain stage (SSS) packet transfer network (RTP), once the despatching of the previous packet has ended, the route within the packet transfer network being connected up before the end of the previous packet. The invention applies in particular to automatic packet switches for multi-service networks including visual communication.

Mobile packet radio networks: State-of-the-art

Abstract: MUCH WORK HAS been done in the areas of packet switching, packet radio, and random communication channels. However, efforts combining these areas are not as plentiful. There are several reasons for this. One reason is, the packet communications area is relatively young. Much of the research into packet communications has been accomplished by computer scientists rather then communications engineers, with a resulting emphasis on architecture, protocols, software, and so on. Even the development of packet radio has not fostered extensive examination of link effects on system performances. The UHF line-of-sight links and SHF satellite links have been assumed to be perfect with packet collisions as the dominant error source, which is a good assumption under normal circumstances. However, abnormal circumstances including ionospheric scintillations and multipath fading are another source of error on degraded packet radio links, which characterize Mobile Packet Radio Networks (MPRNET). In this paper we define and discuss Mobile Packet Radio Networks and presend their channel characteristics. The performance avaluation of some channel access protocols for a Mobile Packet Radio Network link, which is a typical example of a degraded packet radio channel, is descirbed.

Speech transmission capacity of standard ethernet systems

Abstract: This paper is concerned with the estimation of the speech traffic capacity of a standard ethernet system by simulation techniques. The particular interest in this work is the possible trade-off of speech coding rate against number of simultaneous users during peak traffic conditions. The results of simulation studies are given and it is concluded that the decisive factor in such a trade-off is the maximum transmission delay which may be accepted and also the percentage loss of transmitted information which occurs as a result.

System for informing detection of transmission line fault section

Abstract: PURPOSE: To specify the presence of a fault on a loop transmission line and a faulty section by receiving packet data at a sender and applying operation it with a specific constant in the own equipment. CONSTITUTION: When a packet sender sends a packet #i, a specific constant M is set to a control section CTL provided at the outside of operation object of the packet #i and the result is sent. In a data transfer device Ni other than the sender connected in a loop, the packet #i is received and only when an error is detected, operation is applied to the content of the control section CTL. Then the transmission of the packet to the data transfer device Ni of the next rank is repeated, the sender receives the said packet data #i to apply operation with the specific constant N in the own device. Thus, the presence of a fault and the faulty section on the loop transmission line are specified. Thus, even when the loop transmission line consists of many transmission line sections, a faulty section of the transmission line is located easily. COPYRIGHT: (C)1986,JPO&Japio

A hybrid FARA/CSMA-CD protocol for voice-data integration

Abstract: A new hybrid packet switching protocol for voice-data integration is proposed and analysed The protocol adapts to the changing traffic conditions of both voice and data Network control is distributed over all nodes, thus eliminating the need for central switching or multiplexing Voice users follow a modified version of FARA, whereas CSMA-CD is adopted by data users for their channel access policy The analysis is based on the solution of a 2-state Markovian chain, after which the voice blocking probability, data packets delay and network throughputs are determined

Timepiece control system

Abstract: PURPOSE:To adjust slave clock time with high precision by using evaluation information on time information transmission delay time from a master clock to a slave clock as slave clock time adjustment information. CONSTITUTION:The time when the slave clock SCL sends a time information request signal TMD is denoted as T'O, the time when the master clock MCL receives the TMD and sends a time information annunciation signal TMI is denoted as T1, and the time on the SCL when CL receives the TMI from the MCL and make a time adjustment is denoted as T's. At this time, the transmission delay time DLTM on the SCL as to the MCL is evaluated from an equation I . The SCL uses time information and evaluated transmission delay time from the MCL to make a time adjustment by regarding the time equation II obtained by adding the delay time based upon the equation I to the time T1 of the time information as new time.

Switching Strategies in Shuffle-Exchange Packet-Switched Networks

Abstract: This correspondence investigates some methods for improving the performance of single-stage shuffle-exchange networks (SSN's) in a packet communication environment where the modules in a computer system communicate by sending fixed size packets. The three new switching strategies proposed use extra buffers to enhance performance, while preventing deadlocks. An intuitive criterion for determining the applicability of approximate analysis techniques is discussed.

Signal Delay In RC Trees With Charge Sharing Or Leakage

Abstract: A single value for delay, based upon the delay of Elmore, is derived for two types of RC tree networks In one type of network, there is no driving source: this undriven situation causes static charge sharing among nodes An expression for delay is obtained by straightforward analysis of this network In our second case, an RC tree which is driven by at least one source has leaky capacitors We show how to calculate delays for such trees by a linear time algorithm A simple MOS circuit with a leakage path to ground is analyzed using the method presented in this paper The result is compared with that of SPICE

Data block transfer system

Abstract: PURPOSE: To prevent missing of packet from being caused even if a fault of a communication line is encountered without causing transfer delay in a data by giving a serial number to one and the same packet and transferring the result to all of plural communication lines. CONSTITUTION: A data transmitter 2 gives serial numbers 0, 1, 2, 3 to packets to be sent and transmits the result to both data communication lines 50 and 51. When a transmitter 2 receives a packet from the lines 50, 51, the transmitter detects the said serial numbers, discriminates whether or not the number is received already, and when the number is received already, the transmitter abolishes the packet, and when the packet is not received yet, the transmitter eliminates the serial number from the received packet and sends the result to a data processor 4. If the line 51 has a fault, the transmitter receives packets C,D received from the line 50. COPYRIGHT: (C)1986,JPO&Japio

Packet priority transfer system

Abstract: PURPOSE: To attain priority transfer by controlling an exchange so as to apply priority transmission when a packet of call request designating priority transfer of the packet from a terminal device and the data packet is received to a logical channel relating to the packet. CONSTITUTION: When a terminal device 5A applying priority transfer designation makes call request similarly to a terminal device 5C to start a packet exchange 2A, a call request packet CR is sent. The priority transfer facility of the packet CR represents the priority transfer designation. The exchange 2A stores the information to a storage device 3A. The information is used to identify the processing of the priority transfer as to a packet relating to the said logical channel. The packet CR is sent to the exchange 2C via an exchange 2B, where the packet is converted into an incoming packet and reaches the terminal 5C. COPYRIGHT: (C)1986,JPO&Japio

Voice packet communication system

Abstract: PURPOSE: To set properly and simply a minimum recovery queue time suppressing an abolition rate to a prescribed value or below by transmitting a voice packet only added with header information, calculating the abolition rate of each packet at each prescribed time and controlling the recovery queue time of a received packet variably. CONSTITUTION: A voice/silence discrimination section 16 discriminates whether a voice packet generated by a packet composing section 14 from an input voice is a voice packet or a silence packet and a packet transmission control section 15 sends only the voice packet according to the result of discrimination. A packet reception section 2 stores the reception packet by a transmission control section 21 to a buffer memory 22 once, and it is extracted by a packet decomposing section 23 after a prescribed waiting time elapses and the result is decoded by a decoder 24 and the voice is outputted from a D/A converter 25 via a voice output section 26. Then a packet abolition rate discrimination section 27 inputs header information and calculates the abolition rate of the transmission packet at each prescribed time. COPYRIGHT: (C)1987,JPO&Japio

Duplicated loop communication system

Abstract: PURPOSE:To prevent a transmission delay time at fault from being increased by constituting the system so that each node receives a signal from one of active and spare transmission lines and the signal is transmitted to both the active and spare transmission lines. CONSTITUTION:Five nodes 11-15 are connected by the active loop transmission line 16 and the spare loop transmission line 17. Each node receives a signal from a reception section able to receive a carrier in an active reception section R connected to the active loop transmission line 16 and a spare reception section R' connected to the spare loop transmission line 17, regenerates it and transmits respectively it to the active loop transmission line 16 and the spare loop transmission line 17 from both an active transmission section S and a spare transmission section S'. When no fault takes place in the loop transmission lines 16, 17, each node selects the active reception section R as the reception use.