Local area communication system for integrated services based on a token-ring transmission medium
First Claim
1. A communications system having at least one transmission facility in which data are transmitted in asynchronously circulating frames, in which access to said at least one transmission facility is regulated by a token, and in which a priority token for marking a priority frame is released at quasi-regular intervals by a synchronous bandwidth manager (SBM) unit provided for said at least one transmission facility,characterized in that for transmission and switching of information blocks requiring synchronous transfer:
- a common time division multiplex (TDM) switching unit is provided and is connected to the transmission facility by a SBM unit (57);
saidSBM unit includes means (61 . . . 73, 79 . . .
89) for extracting all information blocks from each priority frame and for inserting them into buffers (75) readable by said TDM switching unit, and for extracting information blocks from buffers (77) writable from said TDM switching unit and inserting them into priority frames it transmits on its associated transmission facility, each said priority frame having a plurality of time slots (V1 . . . Vn) for information blocks; and
thateach station which participates in the exchange of information blocks requiring synchronous transfer, has means (101 . . .
109) for receiving such an information block from, and transmitting such an information block in, at least one predetermined slot of each said priority frame.
1 Assignment
0 Petitions
Accused Products
Abstract
In a local area communication system comprising token rings (11) with synchronous bandwidth managers SBM (15) for issuing priority tokens for quasi-synchronous frames at regular intervals, the rings are interconnected by a time division muliplex PBX unit (21) via their SMB units. Buffers are provided in each SBM for synchronous information blocks transferred from and to the ring, and the TDM control (31) can independently access these buffers for TDM switching of the individual bytes of said information blocks. Besides this PBX interconnection for synchronous information or voice, the rings are also interconnected by a backbone bus or ring for transfer of asynchronous data between rings. A special slot rearrangement procedure is provided to improve the filling of time slots in the quasi-synchronous frames that are no longer used after release of a connection, to allow for adapting the frame length (number of issued slots) to the number of existing connections.
-
Citations
14 Claims
-
1. A communications system having at least one transmission facility in which data are transmitted in asynchronously circulating frames, in which access to said at least one transmission facility is regulated by a token, and in which a priority token for marking a priority frame is released at quasi-regular intervals by a synchronous bandwidth manager (SBM) unit provided for said at least one transmission facility,
characterized in that for transmission and switching of information blocks requiring synchronous transfer: -
a common time division multiplex (TDM) switching unit is provided and is connected to the transmission facility by a SBM unit (57);
saidSBM unit includes means (61 . . . 73, 79 . . .
89) for extracting all information blocks from each priority frame and for inserting them into buffers (75) readable by said TDM switching unit, and for extracting information blocks from buffers (77) writable from said TDM switching unit and inserting them into priority frames it transmits on its associated transmission facility, each said priority frame having a plurality of time slots (V1 . . . Vn) for information blocks; and
thateach station which participates in the exchange of information blocks requiring synchronous transfer, has means (101 . . .
109) for receiving such an information block from, and transmitting such an information block in, at least one predetermined slot of each said priority frame. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 12)
-
-
10. A communication system comprising at least one token ring (11) which is interconnected to a PBX unit (21) by a synchronous bandwidth manager (SBM) unit (57) issuing priority frames for synchronous information transfer at quasi-synchronous intervals, and in which system information blocks for each specific connection are inserted in and extracted from at least one predetermined slot in each priority frame by the SBM unit (57) and the respective station (13) involved, characterized in that the SBM unit and each station comprise means (151 . . . 159;
- 169 . . .
187) for using temporarily two slots in each said priority frame for transferring the same synchronous information block in duplicate, for comparing the information blocks received in both said slots, and for changing transmission and reception of information blocks from the one of said slots which was previously used for the respective connection, to the other slot when information blocks were received identically in both slots a predetermined number of times. - View Dependent Claims (11)
- 169 . . .
-
13. A method of slot rearrangement in a system in which information for a specific connection is transmitted between first and second units in predetermined slots of transmission frames comprising the steps of:
-
transmitting and receiving identical information from units using the last slot in a transmission frame, said identical information transmitted and received in both said last slot and a free slot wherein said free slot results from the release of a connection; testing whether identical information is received in both said slots for a predetermined number of times; switching said first and second units so as they use only said free slot wherein said last slot of each transmission frame remains unused and future transmission frames can be issued with a reduced length. - View Dependent Claims (14)
-
Specification