Loop transmission system

• US 4,500,987 A
• Filed: 11/23/1982
• Issued: 02/19/1985
• Est. Priority Date: 11/24/1981
• Status: Expired due to Term

• Current Assignee: Nippon Electric Company Limited (NEC Corporation)
• Original Assignee: Nippon Electric Company Limited (NEC Corporation)
• Inventors: Hasegawa, Satoshi
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Scutch, III, Frank M.
• Application Number:
  US06/443,876
• Time in Patent Office: 819 Days
• Field of Search: 370/60, 370/94, 370/86, 370/89, 340/825.05, 340/825.5
• US Class Current: 370/462
• CPC Class Codes: H04L 12/433 with asynchronous transmission, e.g. token ring, register insertion
• CPC Class Codes: H04L 12/64 Hybrid switching systems

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.

Claims

1. In a loop transmission system of the type including a plurality of transmission/reception terminals and a control terminal which are connected in a loop so as to perform packet communications among respective transmission/reception terminals, the improvement wherein said control terminal includes means for periodically sending out a signal indicative of a leading position of a packet, and means for establishing a loop synchronization such that a transmission line delay created while the packet circulates once through the loop will be an integer multiple of a length of said packet, wherein there is provided means which gives a degree of priority to information signal from each of said transmission/reception terminals in accordance with the type of said information signal, and wherein said transmission/reception terminal comprises first accumulating means for storing and retiring an input packet from an input transmission line;

second accumulating means for accumulating a transmission packet sent out from information generating means connected to said transmission/reception terminal, and means for comparing degrees of priorities of said input packet, a delayed packet and said transmission packet for sending out a packet having the highest degree of priority.

2. A loop transmission system of the type including a plurality of transmission/reception terminals and a control terminal which are connected in a loop to effect packet communications among respective transmission/reception terminals, the improvement wherein said control terminal includes means for periodically sending out a signal indicative of a leading position of the packet, and means for establishing synchronization of said loop such that a transmission line delay created while the packet circulates once through the loop will be an integer multiple of a length of said packet, and wherein there are provided means for imparting a first degree of priority to a real time signal among information signals outputted from said transmission/reception terminals, for imparting a second degree of priority to a command packet utilized at a time of starting exchange of said real time signal, and for imparting a third and lesser degrees of priority to data;

means provided at a transmitting terminal of said transmission/reception terminals for sending out a transmission request command packet at a time when a request for transmitting said real time signal occurs;

means provided at a receiving side terminal for receiving said transmission request command packet and inserting a reply command packet in the same packet position as said transmission request command packet so as to send back said reply command packet;

means provided at said transmission side terminal for inserting said real time signal packet in the same packet position as said reply command packet when the same is received within a predetermined interval after sending out said transmission request command packet; and

means provided at said receiving side terminal for inserting said real time signal packet in the same packet position as the real time signal packet transmitted from said transmission side terminal and for sending back said real time signal packet, thereby effecting a full dual transmission of said real time signal.

3. In data transmission/reception apparatus for use in a loop transmission system of the type including a plurality of transmission/reception terminals and a control terminal which are connected in a loop, the improvement which comprises means extracting header information from an input packet sent over an input transmission line;

address collation means for comparing a received address of said input packet in the header information with an address assigned to said terminal;

converter means for converting said input packet into information signal suitable for various apparatus and devices connected to said terminal;

input accumulating means for storing and retiring said input packet;

packeting means for packeting information signals from said apparatus and devices;

output accumulating means supplied with an output from said packeting means;

priority selection means comparing degree of priorities of said input packet, of a delayed packet being stored and retired in said output accumulating means, and of a transmission packet sent out from said output accumulating means; and

switch means for sending out either one of said input packet, said delayed packet and said transmission packet to an output transmission line;

said priority selection means producing a signal that controls the storage and retirement of said input packet, controls delivery of said delayed packet being stored and retired, controls delivery of said transmission packet and controls selection of said switch.

4. A real time signal transmission/reception system for use in a loop transmission system of the type including a plurality of transmission/reception terminals and a control terminal which are connected in a loop for performing packet communications among respective transmission/reception terminals, the improvement which comprises means for extracting header information from an input packet sent over an input transmission line;

address collation means for comparing a received address of said input address in said header information with an address assigned to said terminal;

converting means for converting said input packet into information signal suitable for real time signal generating device connected to said terminal;

input accumulating means for storing and retiring said input packet;

packeting means for packeting said real time information signal from said real time signal generating device;

output accumulating means for accumulating outputs from said packeting means;

command packet generating means for generating a transmission request and a reply command packet;

a priority selection circuit which compares degrees of priorities of said input packet, of a delayed packet being stored and retired in said input accumulating means, of a transmission packet sent out from said output accumulating means and of said transmission request and reply command packets;

means for judging the type of said command packet based on said header information;

a timer for sending a time out signal to said real time signal devices by calculating an interval between sending out of said transmission request signal and reception of said reply command packet; and

switch means for sending out to an output transmission line either one of said input packet, said delayed packet, said transmission packet and said command packet;

said priority selection means and said command packet judging means producing output signals that control storage and retirement of said input packet, delivery of a delayed packet being stored and retired in said input accumulating means, delivery of said transmission packet and selection of said switch.

5. In a loop transmission system of the type including a plurality of transmission/reception terminals and a control terminal which are connected in a loop so as to perform packet communications among respective transmission/reception terminals, the improvement wherein said control terminal includes means for periodically sending out a signal indicative of a leading position of a packet, and means for establishing a loop synchronization such that a transmission line delay created while the packet circulates once through the loop will be an integer multiple of a length of said packet, wherein there is provided means which gives a first higher degree of priority to a real time information packet from said transmission/reception terminal which is required to have a real time property, and gives a second lower degree of priority to an information packet not required to have the real time property, and wherein said transmission/reception terminal comprises first accumulating means for storing and retiring an input packet from an input transmission line, second accumulating means for accumulating a transmission packet sent out from information generating means connected to said transmission/reception terminal;

means for comparing degrees of priorities of said input packet, of a delayed packet outputted from said first accumulating means and of said transmission packet so as to send out a packet having the highest degree of priority to an output transmission line;

means which when real time information constituted by a plurality of real time information packets having the first higher degree of priority is sent out from a first transmission/reception terminal, prior to sending out a real time message, detects traffic quantities of the real time information and the data packets in accordance with the number of real time information packets and the data packets passing through said first transmission/reception terminal during a repetition period of sending out said real time information packet; and

means, which when said detected traffic quantities satisfy a predetermined condition, begins to send out said real time information message.

6. The loop transmission system according to claim 5 wherein said traffic quantity detecting means comprises a first counter counting the number of the voice packets, a second counter counting the number of the data packets which pass through a terminal in a period of sending out the voice packet, a latch circuit latching outputs of said first and second counters, and a judging circuit which judges whether the voice signal can be sent out or not in accordance with the output of said latch circuit.

7. In a loop transmission system of the type including a plurality of transmission/reception terminals and a control terminal which are connected in a loop so as to perform packet communications among respective transmission/reception terminals, the improvement wherein said control terminal includes means for periodically sending out a signal indicative of a leading position of a packet, and means for establishing a loop synchronization such that a transmission line delay created while the packet circulates once through the loop will be an integer multiple of a length of said packet, wherein there is provided means which gives a first higher degree of priority to an information packet from said transmission/reception terminal which is required to have a real time property, and gives a second lower degree of priority to an information packet not required to have the real time property, and wherein said transmission/reception terminal comprises first accumulating means for storing and retiring an input packet from an input transmission line;

second accumulating means for accumulating a transmission packet sent out from information generating means connected to said transmission/reception terminal;

means for comparing degrees of priorities of said input packet, of a delayed packet outputted from said first accumulating means and of said transmission packet so as to send out a packet having the highest degree of priority to an output transmission line;

means which when a real time information message constituted by a plurality of real time information packets is sent out from a first transmission/reception terminal, prior to sending out said real time information message, sends out a control packet;

means provided for a transmission reception terminal which is sending out the first information packet among the transmission/reception terminals included in the loop, for increasing by one a value of a first control field in said control packet when the control packet passes through said transmission/reception terminal sending out said first information packet;

means provided for another transmission/reception terminal sending out a second information packet, for increasing a value of a second control field in said control packet by an amount corresponding to a transmission speed when said control packet passes through said another transmission/reception terminal;

means for detecting activities of the real time information packet and the data packet based on the first and second control fields of said control packet when the same returns back to said first transmission/reception terminal after the control packet has circulated once through said loop; and

means for causing said first transmission/reception terminal to begin to send out said real time information message when said detected activities satisfy a predetermined condition.