TDM data communications network wherein each data frame is divided into respective lower rate sub-frames for respective sets of substations, and main station and substation for use therein

• US 5,509,003 A
• Filed: 07/11/1994
• Issued: 04/16/1996
• Est. Priority Date: 07/09/1993
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Van Grinsven, Petrus A. M., Snijders, Wilfred A. M.
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US08/273,529
• Time in Patent Office: 645 Days
• Field of Search: 370/54, 370/58.1, 370/58.2, 370/58.3, 370/60, 370/79, 370/80, 370/82, 370/83, 370/84, 370/94.1, 370/94.2, 370/95.1, 370/95.3, 370/99, 370/100.1, 370/103, 370/105.1 , 370/105.3, 370/105.4, 370/106, 370/110.1, 370/112, 370/24, 370/29, 370/85.7, 455/51.1, 455/53.1, 455/54.1, 455/67.1, 455/132, 455/137, 455/139, 375/354, 375/356, 375/362, 375/364, 375/365, 375/368, 375/371
• US Class Current: 370/294
• CPC Class Codes: H04J 3/1694 Allocation of channels in TDM/TDMA networks, e.g. distributed multiplexers Passive Optical Networks H04Q11/0062

Abstract

Telecommunications passive optical networks are known which employ a TDMA frame structure for transmission between a main station and a number of substations. Due to increased capacity demands and still further service demands, there is a need for higher bit rates over such networks. The invention provides a high bit rate passive optical network wherein the substations operate at only a fraction of the network bit rate, and so are hardly more complex than in lower bit rate networks. That is achieved by formation by the main station of sub-frames of the data intended for transmission to a number of the substations, and bit interleaving the sub-frames to form a data frame which is transmitted over the optical fiber cable. Each substation is adjusted to only listen to the sub-frame to which it is assigned. In one embodiment the substations are automatically adjusted to only listen to a particular phase in the interleaved bit stream, which is identified by phase adjustment data transmitted by the main station in a housekeeping time slot of the data frame.

Claims

1. A telecommunications network comprising a main station which is coupled by a transmission channel to a plurality of substations, the main station receiving a plurality of data messages addressed to respective substations and combining the data messages for transmission over the transmission channel;

characterized in that;

the main station comprises

interface means for combining the data messages by time division sampling to form a series of time division multiplex input data frames, each input data frame having time slots assigned to respective ones of said substations, the time slots having a predetermined bit rate;

frame splitting means coupled to said interface means for splitting each input data frame into a plurality n of sub-frames;

where n≧

2;

each sub-frame having 1/n-th the number of time slots in an input data frame, so that each sub-frame has a bit rate which is 1/n-th said predetermined bit rate, any given sub-frame of each frame including the time slots assigned to a given set of said substations;

sub-frame assembling means coupled to said frame splitting means for combining the n sub-frames by bit interleaving, thereby forming a series of bit interleaved downstream data frames, and including in each downstream data frame characterizing information identifying the substations assigned to each of the sub-frames in said downstream data frame; and

means for transmitting said series of downstream data frames over said transmission channel for reception therefrom by each of said substations; and

each substation comprises means for adjusting the substation to receive data from each downstream data frame only during a sub-frame thereof to which said substation is assigned, as signified by the substation characterizing information included in the downstream data frame;

whereby each substation receives data from a downstream data frame at the bit rate of a sub-frame therein to which said substation is assigned, which bit rate is 1/n-th of said predetermined bit rate.

2. A telecommunications network as claimed in claim 1, wherein for transmission of data messages to the main station a substation transmits in a time slot assigned thereto in a sub-frame of each of a series of upstream data frames established by the main station, each upstream data frame comprising a plurality of bit interleaved sub-frames;

the assigned time slot being at a position in a sub-frame of an upstream data frame corresponding to the position of the time slot assigned to said substation in a sub-frame of a downstream data frame; and

wherein for reception of data messages from the substations the main station further comprises;

means for dis-assembling a received upstream data frame to recover therefrom bit interleaved sub-frames included therein; and

combining means coupled to said dis-assembling means for combining the recovered sub-frames to form composite frames of data messages transmitted by said substations, the composite frames of data messages frames being supplied to said interface means for de-multiplexing to recover individual data messages therefrom.

3. A telecommunications system as claimed in claim 2, wherein said sub-frame assembling means and said means for dis-assembling operate at 1/nth of said predetermined bit rate, and said frame splitting means and said combining means operate at said predetermined bit rate.

4. A telecommunications system as claimed in claim 2, wherein said sub-frame assembling means, said means for dis-assembling, said frame splitting means and said combining means are all comprised in an integrated circuit which operates at said predetermined bit rate.

5. A telecommunications network as claimed in claim 2, wherein each substation adjusts to receive data during a particular phase of each downstream data frame on the basis of phase adjustment data provided by the main station in a housekeeping time slot of said downstream frame.

6. A telecommunications network as claimed in claim 1, wherein the substation characterizing information comprises a general synchronization word followed by a substation type identifier signifying a particular sub-frame of a data frame.

7. A telecommunications network as claimed in claim 1, wherein n=2 and the substation characterizing information comprises a first synchronization word for substations assigned to a first sub-frame of a data frame, and a second synchronization word for substations assigned to a second sub-frame of a data frame;

the second synchronization word being the inverse of the first synchronization word.

8. A main station for use in a telecommunication network wherein said main station is coupled by a transmission channel to a plurality of substations, data messages addressed to respective substations being received by said main station for transmission to said substations;

comprising;

interface means for combining the data messages by time division sampling to form a series of time division multiplex input data frames, each input data frame having time slots assigned to respective ones of said substations, the time slots having a predetermined bit rate;

frame splitting means coupled to said interface means for splitting each input data frame into a plurality n of sub-frames, where n≧

2;

each sub-frame having 1/n-th the number of time slots in an input data frame, so that each sub-frame has a bit rate which is 1/n-th said predetermined bit rate, any given sub-frame of each frame including the time slots assigned to a given set of said substations;

sub-frame assembling means coupled to said frame splitting means for combining the n sub-frames by bit interleaving, thereby forming a series of bit interleaved downstream data frames, and including in each downstream data frame characterizing information identifying the sub-stations assigned to each of the sub-frames in said downstream data frame; and

means for transmitting said series of downstream data frames over said transmission channel for reception of the respective sub-frames therein by the respective sets of sub-stations assigned to said sub-frames.

9. A substation for use in a telecommunications network comprising a main station coupled by a transmission channel to a plurality of substations, communication of data messages from the main station to the substations being affected in time division multiplex data frames which comprise a plurality of bit interleaved sub-frames, respective sets of substations being assigned to time slots in respective sub-frames of each data frame, the main station providing in each data frame substation characterizing information which includes a general synchronization word followed by a substation type identifier signifying the sets of substations which are assigned to respective sub-frames of a data frame;

said substation comprising;

means responsive to the synchronization word in a received data frame for synchronizing the substation to said data frame; and

phase adjusting means for adjusting the substation to a correct receiving phase for a particular sub-frame of a received data frame, as signified by the sub-frame identifier relevant to said substation in the received data frame;

whereby each substation only monitors a received data frame during the sub-frame thereof to which said substation is assigned.