Showing papers on "Transmission delay published in 1984"

The Spatial Capacity of a Slotted ALOHA Multihop Packet Radio Network with Capture

Abstract: In this paper we determine throughput equations for a packet radio network where terminals are randomly distributed on the plane, are able to capture transmitted signals, and use slotted ALOHA to access the channel. We find that the throughput of the network is a strictly increasing function of the receiver's ability to capture signals, and depends on the transmission range of the terminals and their probability of transmitting packets. Under ideal circumstances, we show the expected fraction of terminals in the network that are engaged in successful traffic in any slot does not exceed 21 percent.

Self-routing packet switching network with intrastage packet communication

Abstract: A communication method and packet switching network in which self-routing packets are communicated through the network by intra-communication of the packets within stages of the network as well as inter-communication of the packets among stages. The stages each having a plurality of pairs of switch nodes with each pair having an intra-node link between the pair of nodes. Each of the switch nodes comprises input controllers and output controllers. The input controller of a node is responsive to the receipt of a packet for interrogating the address field of the packet to determine the destination of the packet. The input control on the basis of the destination determination commmunicates the packet towards the destination via either an inter-stage link or an intra-node link on the basis of availability of the links and an internal control circuit. If a packet is transmitted via an intra-node link to the paired node the latter then transmits the packet via its output controller to the next stage via an inter-stage link. If both the intra-node link and the inter-stage link are available, the internal control circuit then determines which link should be utilized in communicating the packet. The internal destination circuit performs this designating function on the basis of a random number generator.

Adaptive preferential flow control for packet switching system

Abstract: Flow control of data packets through a packet switching network (20) to reduce congestion is controlled by an adaptive preferential permit packet (APP) processing from an originating data terminal (10) through each packet switch node of the network to a destination data terminal (11). APP requires less buffer storage capacity at each switch node, and enables data packets to enter the network only when there is a permit packet indication that the data packets are likely to reach, and be accepted by, their destination. The permit packet is sent node to node (16-19, 25, 28) prior to a transmission of a bulk of data packets. Each node is equipped to queue buffer (12-15, 21-24) a permit packet on a preferential basis ahead of data packets. The node discards the permit packet if the number of packets awaiting transmission from that node exceeds a prescribed threshold. This is throttling process, since the originating port times out and resends a permit packing if a permit-return packet is not received within a predetermined time. Permit-return packet processing, adaptive time-out controls, and preferential treatment of permit packets are disclosed.

Packet Switching Networks for Multiprocessors and Data Flow Computers

Abstract: Most packet switched multistage networks have been proposed to use a unique path between any source and destination. We propose to add a few extra stages to create multiple paths between any source and destination. Connection principles of such multipath networks for packet switching are presented. Performance of such networks is analyzed for possible use in multiprocessor systems or in data flow computers.

A simulation-based comparison of voice transmission on CSMA/CD networks and on token buses

Abstract: Digitized speech can be transmitted over a variety of digital media. An interesting choice is the use of a Local-Area Network (LAN), for which digitized speech is packetized at the transmitter and depacketized at the receiver. Many local-area networks exhibit good throughput but poor delay characteristics; variable or excessive transmission delay can become noticeable and objectionable to the users of such a voice system. A number of simulations were performed to assess the delay characteristics of a Carrier Sense Multiple Access/Collision Detection (CSMA/CD) LAN and of a similar token bus LAN. A comparison of the results shows that the token bus performs somewhat better. The CSMA/CD LAN's performance was characterized by carrying voice well until a point of collapse is reached; the token bus's performance degraded more continuously. In either case, throughput close to the theoretical capacity of the LAN was found achievable with appropriate techniques.

Multiple paths in a self-routing packet and circuit switching network

Abstract: A communication method and self-routing switching network interconnecting a plurality of interface controllers for communicating packets and circuit switched information via multiple paths within the self-routing switching network. The latter comprises stages of switch nodes that are grouped into pairs. The stages are interconnected by links and each pair of switch nodes shares the same set of input links from the preceding stage. In response to receipt of address information from a destination interface controller transmitted via a link, a pair of nodes determines one of a multitude of paths through the switching network by one of the pair responding to the address information to communicate the address information to the next sequential stage after establishing a path through that particular switch node. Once a path has been established through the switching network, an acknowledge signal is transmitted back through the network to the destination trunk controller indicating that the path has been established. The path remains established until the end field of the packet is detected or the proper end information is transmitted after transmission of the circuit switched information. The architecture of the switching network is such that no additional switch nodes are required beyond what would be required in a conventional self-routing network.

System for digitized voice and data with means to compensate for variable path delays

Abstract: In a communications system in which voice is transmitted as packets of digitized samples, a receiving station (Fig 3) delays the output of the first packet in a way that compensates for wide variations in the intervals at which successive packets are received According to one feature of this system, a first packet is transmitted at a higher priority so that a greater delay can be used without encounter problems that arise from the uncertainty in the delay in transmitting this packet In another feature of this system, the arrival times of the first few packets of a conversation are detected and the delay is readjusted in case the first packet has been unusually delayed

Ring communications system

Abstract: A communications network including a plurality of terminals coupled together to provide a unidirectional communications ring. Each of the terminals is adapted to transmit (at an associated fixed data rate) a digital signal to the next downstream terminal on the ring. Each terminal is adapted to receive a digital signal at the data rate associated with the next upstream terminal. In each local terminal, there is a detector for detecting the received synchronization packets and associated data packets are generated for transmission to the next downstream terminal on the ring at a predetermined fixed data rate associated with the local terminal. The data of each transmitted data packet matches bit for bit the data of the corresponding received data packet. The number of bits in the transmit synchronization packet differs from the number of bits in the associated received synchronization packet in a manner so that the data rate for the composite packet formed by the transmitted data packet and associated synchronization data packet corresponds to the transmit data rate for the terminal. The difference varies between predetermined minimum and maximum limits, and may be zero for two terminals having substantially the same transient bit rate.

Scheme for reducing transmission delay following collision of transmissions in communication networks

Abstract: In a contention type of communication network, the collision backoff time period during which retransmission of collided messages may not be attempted is computed as a multiple of a time slot S, such that B+2A

Contention-type data communication system

Abstract: A contention-type data communication system such as an optical star-configured network comprises a plurality of stations (121, 122) connected with one another through data bus (13). To detect a signal collision quickly, each of the stations is arranged to transmit a collision-detecting packet which has a predetermined time length T1 and a predetermined pulse pattern, and then transmit a data packet after a time interval T2. The number or pattern of pulses received during a time period T + T2 from the start of reception of a collision-detecting packet is compared with that of the self-transmitted collision-detecting packet so that the signal collision is detected when noncoincidence occurs.

Method for operating a packet bus for transmission of asynchronous and pseudo-synchronous signals

Abstract: Data transactions and voice communications are facilitated in a packet switching system including a group of ports each of which is capable of exchanging inter-destined and intra-destined information signals via a packet bus. The packet bus is operated under the direction of a bus controller which communicates with the ports to arbitrate access to the packet bus for packet transmission. Arbitrating access to the packet bus for pseudo-synchronous and asynchronous signal communications includes the steps of polling the ports within a period of time for high and low priority, transmission requirements. In response to each high priority requirement transmission over a predetermined number of consecutive bus cycles is granted by the bus controller within a predetermined period of time for pseudo-synchronous transmission of signals from each of the corresponding ports one after another. In response to each lower priority requirement, transmission over an indefinite number of consecutive bus cycles is granted by the bus controller for asynchronous transmission of signals from at least one of the corresponding ports. The preceding steps are repeated with a frequency such that high priority grants occur at a uniform rate that is consistent with a sampling rate of digitized voice communications being divided by one less than the predetermined number of consecutive bus cycles.

Data packet transmission using shared channel

Abstract: In a data communication system an interface unit connects a device to a common communications channel shared with other devices using e.g. a carrier-sense multiple-access protocol. Individual bytes for a predetermined destination device are supplied by the device to communications controller 6 without any grouping into packets. They are then stored in a RAM 8 under control of a microcomputer 5. As soon as a byte is received, the interface unit attempts to transmit a packet; when the right to transmit is won the interface unit transmits a packet containing that and any subsequent bytes. The length of the packet therefore depends on the delay before a packet can be transmitted, and hence on the loading on the channel.

ARQ transmission system

Abstract: A facsimile communication system equipped with an ARQ function for transmitting data in the form of a block between a transmitter and a receiver through a transmission route having a relatively large time delay, such as a submarine cable and communications satellite, is provided. In the system, prior to transmission of image data, a time delay in transmission of data through a selected transmission route is measured and the number of bits of data block is determined in accordance with the thus measured time delay.

Method and apparatus for the detection and regeneration of a lost token in a token based data communications network

Abstract: A token-passing, ring-based data communications network provides a distributive method and apparatus for detecting and regenerating a lost token. The method includes, after detection of the loss of the token, transmitting at a detecting node a data packet not including a token, the data packet uniquely identifying the transmitting node as the data source. Simultaneously, the transmitting node, after transmitting the tokenless data packet, strips all incoming data from the network. If the transmitted packet is successfully received by the transmitting node, a new token is generated by the node. If the packet is not received, the node defers to an arbitration method which includes delaying a next data packet transmission for a probabilistically determined period of time. The mean time upon which the probabilistic approach is based increases with each unsuccessful data packet transmission attempt.

Integrated delay circuit for digital signals

Abstract: A delay circuit provides adjustable delay in constant increments. In order to achieve adjustable but constant delay times of a chain of inverter pairs, each pair is completed by a capacitor, a third inverter, and a transfer transistor the gate of which is fed by a voltage controlling the pair delay time. This voltage is generated by a control circuit measuring the actual delay time of the chain with respect to the period of a constant clock signal.

Method for adjustment of variable delay line

Abstract: This invention aims to provide a method of adjustment for a variable delay line which is provided with two delay line elements of dissimilar delay times and switch means capable of selectively switching from one to the other of the two delay line elements and adapted to enable the delay time to be digitally increased or decreased by the delay time difference produced by the selective switching between the delay time elements. This method allows the delay time to be finely adjusted with high accuracy of the order of 1 to some tens of ps by changing the delay time of either of the two delay line elements which has a smaller delay time than the other.

Packet communication systems

Abstract: In a packet communication system of a multiaccess type in which a single communication medium is used commonly and divided into a plurality of channels, respective users observe states of the channels and the probability of packet transmission to respective channels is controlled in accordance with observed information, respective users are assigned parameters corresponding to respective channels and the probability of packet transmission onto the channels is controlled according to the parameters, a dummy packet is continuously transmitted for a predetermined time at in channels having low utilization factors, for data requiring immediate transmission. In a modification, a setup packet is sent for data requiring immediate transmission. All the users determine whether the received packet is the setup packet and the set the stored parameters. Accordingly, in another modification, a setup packet is transmitted for data requiring immediate transmission and a dummy packet is continuously transmitted in a channel for which the origination setting packet is successful.

Performance Evaluation of a Packetized Voice System--Simulation Study

Abstract: Introduction of the packet switching technique into digitized voice communication may afford great advantages in efficient use of the channel, compared to both circuit-switched and DSI systems. Detailed characteristics, however, have not been obtained because of difficulty in the exact analysis. Hence, simalation models are developed in this paper for the packetized voice transmission system, and various characteristics such as tranmission delays and loss probability of voice packets are obtained. We further evaluate three types of voice packet reassembly strategy at the receiving terminal, and obtain the optimal packet length, which keeps both overall packet transmission delay and packet loss probabilty less than a certain permissible value. Comparison among three strategies is also stated.

Packet exchange data transmission system

Abstract: At least two packet exchangers are interconnected through an external transmission line to transmit a data packet. Each packet exchanger comprises a main controller for processing the data packet sent from a packet terminal, in a data link level and a packet level, and a connecting unit for sending the data packet sent from the main controller to the external transmission line and sending the data packet sent from the external transmission line to the main controller.

Quasi cut-through: New hybrid switching technique for computer communication networks

Abstract: A novel hybrid switching technique for computer networks is proposed and analysed in this paper. This hybrid switching technique combines packet switching and cut-through switching. Partial cuts are introduced to improve the performance of a network from a practical point of view. Messages are segmented into packets using a threshold-based segmentation rule. A method to calculate reassembly delay for noisy channels is described and has been used in the analysis of the hybrid switching. Several numerical results are reported at the end which depict the practical versatility of the proposed hybrid switching. Some simulation results are also reported in order to verify the analytical formulation.

Communications control circuit with adaptive timing

Abstract: A communications control circuit including a monitor circuit for receiving transmissions of a first and second frequency from a base radio station to other radio stations and measuring several time intervals, each time interval being the time from the end of a first frequency transmission to the end of a second frequency transmission The two frequency transmissions are a portion of the signal protocol required by the base radio station to establish a communications link between a radio station and a base radio station The control circuit further includes logic circuitry for computing an estimated delay time used in delaying the transmission of an identification code to the base station to establish the communication link after the end of the first frequency transmission The estimated delay time is computed from monitoring other successful radio station protocol exchanges with the base station and measuring similar delay times and adjusting the delay time iteratively based upon the monitored delay times and any deviation between these monitored delay times and the estimated delay time

The Behavior of a Finite Queue with Batch Poisson Inputs Resulting from Message Packetization and a Synchronous Server

Abstract: This paper studies the behavior of a packet switch which provides finite waiting space and receives packetized messages. The arrivals of the messages constitute a Poisson process. Each message consists of a random number of packets. The number of packets contained in a message is assumed to be an integer-valued random variable which may follow any arbitrary probability distribution. All packets residing in the buffer receive service from a single output transmitter operating synchronously at a constant rate. Each packet receives the same fixed service time from the transmitter and then leaves the system. Upon the arrival of a message, if the remaining buffer space is not enough to accommodate all packets of the message, then the entire message is completely rejected. Results such as message blocking probability, packet blocking probability, throughput, and mean delay have been obtained. Two different approaches, minislot approximation and the application of the residue theorem, are used to obtain these results. Especially, this combinatorially very complex problem is successfully solved by the residue theorem in a recursive manner. These results are useful in evaluating the performance of a packet switch. They are also useful for design purposes.

Performance evaluation of a protocol for packet radio network in mobile computer communications

Abstract: The need to provide computer network access to mobile terminals and computer communications in the mobile environment has stimulated and motivated the current developments in this area. Packet radio technology has developed over the past decade in response to the need for real-time, interactive communications among mobile users and shared computer resources. In computer communication systems we have a great need for sharing expensive resources among a collection of high peak-to-average (i.e., bursty) users. Packet radio networks provide an effective way to interconnect fixed and mobile resources. The results of an attempt to study the performance of the mobile packet radio network for computer communications over degraded channels are presented. We develop a model under fading conditions and derive a protocol for evaluating the performance of the mobile packet radio network (MPRNET) in terms of the packet error rate, packet delay, throughput and average number of retransmitted packets per cycle. The analytical results are presented and numerical examples are given to illustrate the behavior of these performance criteria as a function of packet transmission rate, packets transmitted per cycle, packet size, and vehicle speed with the help of appropriate plots.

A Multisubscriber Variable-Rate Sampling HCDM System with Dynamic Buffer Control

Abstract: In this paper we present a multisubscriber variable-rate sampling hybrid companding delta modulation (HCDM) system for simultaneous transmission of several speech signals. This system employs both the statistical multiplexing and variable-rate sampling schemes. It transmits speech signals synchronously at a fixed rate using a buffer. In this system the sampling rate of each subscriber is varied according to the speech activity and the status of buffer occupancy, and only the speech portion is coded for transmission. To optimize the system performance within the allowed maximum transmission delay (300 ms), an efficient dynamic buffer control algorithm is proposed. When the number of subscribers is six and the transmission rate for each subscriber is 16 kbits/s, the proposed system yields a performance improvement of about 10 dB over the conventional single-subscriber HCDM system. The buffer delay in this case is 150 ms, which gives a perceptually negligible effect.

A Loop-Structured Switching Network

Abstract: This paper describes a novel loop-structured switching network (LSSN) intended for highly parallel processing architectures. With L loops, it can connect up to N = L* log2 L pairs of transmitting and receiving devices using only N/2 two-by-two switching elements; thus, it is very cost-effective in terms of its component count. Its topology resembles that of the indirect binary n-cube network, but a much higher device-to-switch ratio is achieved because all the links between the switches could be used as both transmitting and receiving stations. It has the advantage of incremental extensibility, and-it could avoid store-and-forward deadlocks (SFD) which prevail in other recirculating packet-switched networks. Our simulation studies show that the average throughput rate and delay of LSSN are close to that of other designs despite its relatively low component count.

Ultrasonic diagnostic apparatus

Abstract: PURPOSE:To accurately display the ultrasonic image within a region of concern with uniform resolving power and to reduce the lowering of a frame rate by selecting delay data on the basis of an indicated region and the number of focus points and setting the transmission caliber control data of a probe and controlling a transmission circuit on the basis of both data CONSTITUTION:An F-number capable of realizing uniform resolving power and the max focus is calculated on the basis of the number of focus stages and the size of a region of concern and converted to caliber element number data on the basis of the element pitch data of a fine vibrator 2 Next, the delay data at the position of a focus point performing transmission is read from a ROM 7 to be inputted to a transmission delay control circuit 6 along with the calculated caliber element number data The transmission delay control circuit 6 outputs a trigger signal to a transmission pulser 4 on the basis of the delay data and caliber element number data from a CPU 8 The transmission pulser 4 outputs an ultrasonic pulse on the basis of the trigger signal to perform the transmission driving of the fine vibrator 2