Communications systems

Claim 2

A communications system for carrying encoded messages, comprising a plurality of locations (10) for storing information to be carried in message blocks on a link (11), characterised in that said messages may be delay sensitive and non-delay sensitive, and each location (10) has an allocation of d blocks and provided d is greater than zero, each location is entitled to transmit one block onto the link (11) whenever a block is waiting at that location, but if d blocks are transmitted onto the link (11) from a location (10), that location loses its entitlement to transmit further blocks until a further allocation is received, wherein said further allocation is received following a test of all locations (10) for loss of entitlement and wherein no location (10) is in a preferential position with regard to the interval of time between successive allocations.

Claim 3

A system as claimed in claim 1, characterised in that a maximum allowable interval for receipt of a further allocation is set according to delay requirements for delay sensitive message blocks.

Claim 4

A system as claimed in claim 2, characterised in that a counter for each location (10) is provided, wherein the counters are reset when every location (10) is inhibited or empty.

Claim 5

A system as claimed in claim 3, characterised in that prior to accepting a new delay sensitive call, the interval between resets is compared with the maximum allowable interval between resets to determine whether the call can be accepted without the reset interval rising above the maximum allowable interval, and on acceptance of the call, increasing the allocation d for its location.

Claim 9

A communications network comprising a plurality of stations (10) which can communicate via a ring (11), information in digital form being transmitted from one station (10) to another in message blocks which circulate around the ring (11), each message block comprising a first group of control bits (20) and a second group of data bits (21), each station (10) when it requires to transmit assuming an active state in which it inserts digitally encoded information into empty blocks for transmission to a destination station (10), characterised in that if said station (10) has inserted information into d blocks, it enters a state in which it cannot gain access to empty blocks for the transmission of information until it is reset in response to recognition of an empty block having travelled at least once around the ring (11), said resets being issued to all stations (10) so that no station (10) is in a preferential position with regard to the rate of reception of resets.

Claim 10

A communications network comprising a plurality of stations (10) which can communicate via a ring (11), information in digital form being transmitted from one station (10) to another in message blocks which circulate around the ring (11), each message block comprising a first group of control bits (20) and a second group of data bits (21), each station (10) when it requires to transmit assuming an active state in which it inserts digitally encoded information into empty blocks for transmission to a destination station (10), characterised in that if said station (10) has inserted information into d blocks, it enters a state in which it cannot gain access to empty blocks for the transmission of information until it is reset in response to recognition of an empty block having travelled at least once around the ring (11), said resets being issued to all stations (10) so that no station (10) is in a preferential position with regard to the rate of reception of resets.

Claim 11

A communications network as claimed in claim 8, characterised in that the control bits of each block include a bit which when that block is empty can be set to a particular state by an inhibited station (10).

Claim 12

A communications network as claimed in claim 9, characterised in that each station which senses an empty block having a said bit which is set is arranged to set a further control bit, a block which has said two control bits set operating to carry out said resetting of stations (10).

Claim 13

A communications network as claimed in any one of claims 8 to 10, characterised in that means are provided at each station for controlling the value for d, wherein for determining whether an increase in insertion rate of data information can be accommodated, said controlling means is responsive to the interval between resets to increase the value of d provided this interval is less than a predetermined value.

Claim 14

A communications multiplexer comprising a plurality of queues (31, 32, 33) for message blocks to be transmitted onto a communications link (40) characterised in that, control means (42) is provided to give an allocation of d blocks to each queue, wherein if d blocks are transmitted onto the link (40) from a queue, that queue is inhibited from transmitting further blocks until a further allocation is received.

Claim 15

A communications multiplexer comprising a plurality of queues (31, 32, 33) for message blocks to be transmitted onto a communications link (40) characterised in that, control means (42) is provided to give an allocation of d blocks to each queue, wherein if d blocks are transmitted onto the link (40) from a queue, that queue is inhibited from transmitting further blocks until a further allocation is received.

Claim 16

A multiplexer as claimed in claim 12, characterised in that the control means (42) comprises a counter for each queue (31, 32, 33) and the counters are reset when every queue is inhibited or empty.

Claim 17

A multiplexer as claimed in claim 13, characterised in that a maximum allowable interval between resets is set according to delay requirements for message blocks for time sensitive services.

Claim 18

A multiplexer as claimed in claim 14, characterised in that respective queues are provided for time sensitive services having different maximum delay intervals, and the maximum allowable interval between resets is no greater than the maximum delay interval for the queue having the smallest such interval.

Claim 19

A multiplexer as claimed in claim 14 or claim 15, characterised in that prior to accepting a new time-sensitive service call, the number of resets per maximum allowable interval between resets is used to determine whether the call can be accepted without the reset interval rising above the maximum, and m acceptance of the call, increasing the allocation d for its queue.

Claim 20

A multiplexer as claimed in any one of claims 12 to 16, characterised in that each queue (31, 32, 33) has an assigned priority and the control means (42) polls the queues (31, 32, 33) in priority order.

Claim 21

A multiplexer as claimed in any one of claims 12 to 17, characterised in that a queue (31) is provided for non-time sensitive services, said queue having a small, fixed allocation d.