Multiple-access control for a communication system with order pad passing

Claim 2

Method in accordance with claim 1, comprising the following further steps: - assigning identifying node labels (NOD-LBL) to all nodes in ascending order; - providing in each said order pad, besides a cycle number (CYC-NUM) and a field for said request count (REQ-LEN), a field for a furthest destination node label (DST-MAX), and a field for a requested maximum (REQ-MAX); - in each node which wants to reserve time slots for data transmission: (a) if the furthest destination node label (DST-MAX) in a received order pad is less than or equal to the own local node label, setting a local restart indication (REU-FLG), and restarting the request count (REQ-LEN) in said order pad; (b) updating, in a received order pad, the request count (REQ-LEN) by adding the locally required number of time slots (ORD-LEN), and updating said furthest destination node label by inserting the selected destination node label (ORD-DST) for the local data to be transmitted if the latter is greater than the furthest destination node label received in the order pad; and (c) transferring the resulting request count (REQ-LEN) into the field for the requested maximum (REQ-MAX) if the contents of the latter is smaller than the resulting request count.

Claim 3

Multiple-access control method for a communication system comprising nodes attached to a transmission bus and headend means for generating time slots and order pads for numbered cycles; each said order pad comprising a cycle number (CYC-NUM), and a request count (REQ-LEN) which each node can amend by a requested time slot number (ORD-LEN); each node using after start of the respective operation cycle the requested number of free time slots; and each node being identified by a label (NOD-LBL) indicating its position; said method comprising the following steps: providing in each said order pad, fields for a furthest destination node label (DST-MAX) and for a requested maximum (REQ-MAX), the contents of said fields being initially zero; in each node intending to request time slots for transmitting local data to a selected destination: (1) comparing said furthest destination node label (DST-MAX) with the own node label (NOD-LBL); and either (a) if the furthest destination node label is equal to said own node label or identifies an upstream node: - replacing the furthest destination node label (DST-MAX) by the selected destination node's label (ORD-DST); - replacing the current request count (REQ-LEN) by the requested time slot number (ORD-LEN); - storing a local restart indication (REU-FLG) for the respective operation cycle in the requesting node; or (b) if the furthest destination node label identifies a downstream node: - replacing the furthest destination node label (DST-MAX) by the selected destination node's label (ORD-DST) if the latter is greater; - amending the current request count (REQ-LEN) by the requested time slot number (ORD-LEN); and (2) replacing the requested maximum (REQ-MAX) by the resulting request count (REQ-LEN) if the latter is greater.

Claim 4

Method in accordance with claim 3, characterized in that each order pad is returned to its originating headend means, and that the value of the requested maximum (REQ-MAX) contained in the returning order pad, is stored together with the respective operation cycle number (CYC-NUM) in an entry of a global reservation queue maintained in said headend means.

Claim 5

Method in accordance with claim 2 or 3, characterized in that said local restart indication (REU-FLG) is stored, together with a respective cycle number (CYC-NUM) and the number of the requested time slots (ORD-LEN), in an entry of a local reservation queue maintained in each node.

Claim 6

Method in accordance with claim 2 or 3, for use in a system where each time slot comprises a busy/free indication which is set to busy when a node enters data into the slot, and in which each operation cycle is started by a numbered cycle start command, characterized in that a node containing a local restart indication (REU-FLG) for any specific cycle, after detecting the cycle start command for that cycle uses the first slots following the cycle start command for transmitting its local data, and then resets the busy/free indication in all following time slots to free until it detects the next cycle start command.

Claim 7

Method in accordance with claim 2 or 3, for use in a system in which each said order pad is distributed over the control fields of plural consecutive time slots; characterized in that the field for said furthest destination node label (DST-MAX) is contained in the first one of said control fields.

Claim 8

Method in accordance with claim 2 or 3, characterized in that for assigning node labels in ascending order to said nodes, a label command is issued, containing a node number (NOD-NUM) initially being zero; that each node receiving the label command increases the node number (NOD-NUM) by one unit and then stores the new value of the node number as its own node label (NOD-LBL) and transmits the label command to the next node.

Claim 9

Apparatus for allowing multiple use of time slots in a communication system comprising a unidirectional transmission medium (11; Fig.1), several nodes (19-1 ... 19-N) connected to it, and a headend means (15) for generating transmission time slots and control information passing on said transmission medium; an order pad being passed for each of plural numbered operation cycles, comprising a request count (REQ-LEN) which each node can amend by a requested time slot number (ORD-LEN); each node using after start of the respective operation cycle the requested number of free time slots; and each node being identified by a label (NOD-LBL) indicating its position; said apparatus comprising: in said headend means - means for generating order pads (Fig.6; A, B, C) including, besides a cycle number (CYC-NUM) and a field for said request count (REQ-LEN), further fields for a furthest destination node label (DST-MAX) and for a requested maximum (REQ-MAX), respectively; and in each said node, - means (51; Fig.10) for storing a local node label (NOD-LBL); - means (39) for storing the label (ORD-DST) of a selected destination node to which local data are to be transmitted; - means (57) for comparing the furthest destination node label in a received order pad with the local node label; - means (33, 35, 61) for storing the cycle number together with a reuse flag (REU-FLG), if the furthest destination node label is less than or equal to the local node label, and means (31, 47, 73, 75) for inserting the selected destination node's label into the furthest destination node label (DST-MAX) field of the order pad; and - means (31, 95, 97, 99, 101) for making available, after start of a respective operation cycle for which the node has stored a reuse flag, all time slots of that respective operation cycle for use by the respective node or by other nodes further downstream.

Claim 10

Apparatus in accordance with claim 9, characterized in that each node further comprises: - means (91) for comparing the requested maximum (REQ-MAX) in a received order pad with the current request count (REQ-LEN); and - means (31, 85, 93) for replacing the requested maximum by the current request count if the latter is greater.

Claim 11

Apparatus in accordance with claim 9, characterized in that each node further comprises. - means (45) for storing a requested number of slots (ORD-LEN); - means (45, 61, 83, 85, 87) for replacing the current request count (REQ-LEN) in a received order pad by the requested number of slots (ORD-LEN) if the furthest destination node label (DST-MAX) is less than or equal to the local node label (NOD-LBL), but to add the requested number of slots to the current request count if the furthest destination node label is greater than the local node label.