Timeslot management method, a related network terminator, a related line terminator and an upstream signal frame structure for a time division multiple access system

Abstract

A time slot management method for use in a time division multiple access system that couples a line terminator via a tree-like network to a plurality of network terminations is provided. At least one grant is transmitted by the line terminator towards a network terminator in order to allocate at least one adjacent subsequent corresponding upstream time-slot to the network terminator. The grant is received by the network terminator from the line termination, and it is recognized if the at least one grant is associated to the network termination. Upon recognition of the at least one grant being associated to the network termination by the network terminator, overhead data in the first time slot of the at least one time slot and payload data in each potential adjacent subsequent time slot of at least one time-slot allocated to said network terminator is transmitted.

Claims

1. A time slot management method of a time division multiple access system that couples a line terminator via a tree-like network to a plurality of network terminators, said method comprising: transmitting, by said line terminator, at least one grant towards a network terminator in order to allocate a plurality of adjacent subsequent upstream time-slots to said network terminator, respectively, wherein each of said plurality of time-slots corresponds to each of said at least one grant, respectively; receiving said at least one grant by said network terminator from said line terminator; recognizing if said at least one grant is associated to said network terminator, and in response to recognizing that said at least one grant is associated to said network terminator, transmitting, in a data burst, overhead data in a first time slot of said plurality of time-slots and payload data in each adjacent subsequent time-slot of said plurality of time-slots allocated to said network terminator, wherein the overhead data in the first time-slot is a combined overhead data of the each adjacent subsequent time-slot, and wherein said network terminator receives said at least one grant for transmitting the data burst at least once per buffer reporting cycle.

2. A time slot management method according to claim 1, wherein said overhead data comprises status reporting information and Operation and Maintenance information.

3. A time slot management method according to claim 1, wherein said payload data comprises payload data in combination with additional management information.

4. A time slot management method according to claim 1, wherein said payload data comprises Asynchronous Transfer Mode cells.

5. A time slot management method according to claim 1, wherein said payload data comprises Ethernet cells.

6. A time slot management method according to claim 1, wherein each network terminator of said plurality of network terminators is allocated at least one time-slot for transmitting data each buffer reporting interval.

7. A network terminator of a time division multiple access system that couples a line termination via a tree-like network to a plurality of network terminations, said network terminator comprising: a receiver which receives at least one grant forwarded by said line termination; a recognition part which recognizes if said at least one grant is associated with said network terminator; and a transmitter which, in response to recognizing that said at least one grant is associated to said network terminator, transmitting, in a data burst, overhead data in a first time slot of a plurality of time-slots and payload data in each adjacent subsequent time-slot of said plurality of time-slots allocated to said network terminator, wherein the overhead data in the first time-slot is a combined overhead data of the each adjacent subsequent time-slot, and wherein said network terminator receives said at least one grant for transmitting the data burst at least once per buffer reporting cycle.

8. A line terminator of a time division multiple access system that couples a line terminator via a tree-like network to a plurality of network terminators, said line terminator comprising: a grant transmitting module which transmits at least one grant towards a network terminator in order to allocate a plurality of corresponding upstream time-slots to said network terminator, respectively, wherein each of said plurality of time-slots corresponds to each of said at least one grant, respectively; and a detector which detects overhead data in a first time-slot of the plurality of time-slots transmitted in a data burst and allocated to said network terminator based on said grants transmitted to said network terminator, wherein the overhead data in the first time-slot is a combined overhead data of each adjacent subsequent time-slot of said plurality of time-slots, and wherein said network terminator receives said at least one grant for transmitting the data burst at least once per buffer reporting cycle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other objects and features of the invention will become more apparent and the invention itself will be best understood by referring to the following description of an embodiment taken in conjunction with the accompanying drawings wherein:

(2) FIG. 1 shows a block scheme of an embodiment of a time division multiple access network wherein the method of the invention is used; and

(3) FIG. 2 shows an upstream timeslot format used by a time division multiple access network according to the prior art; and

(4) FIG. 3 shows a sequence of upstream time-slots within one buffer reporting interval used by a time division multiple access network according to the present application; and

(5) FIG. 4 presents a proposed structure of a first time-slot containing overhead data of each data frame of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

(6) The time division multiple access network includes a line terminator LT and a plurality of network terminators NT1, NT2, NT3, . . . , NT31, NT32. The line terminator LT is coupled to each network terminator NT1, NT2, NT3, . . . , NT31, NT32 via the cascade connection of a common transmission link Lc and an individual user link L1, L2, L3, . . . , L31, L32.

(7) The time division multiple access network is an optical network transporting for instance asynchronous transfer mode ATM cells over optical fibers from the line terminator LT to the network terminators NT1, NT2, NT3, . . . , NT31, NT32. The time division multiple access network broadcasts network terminator identities or grants in downstream information packets from the line terminator LT to the plurality of network terminators NT1, NT2, NT3, . . . , NT31, NT32. Upon detection of its own identity a network terminator is allowed to transfer a predetermined amount of upstream information packets in predetermined upstream timeslots to the line terminator LT. For example: upon detection of network terminator NT3 of its own identity, network terminator NT3 is allowed to send to the line terminator upstream information packets in predetermined timeslots.

(8) Each network terminator, whereof only network terminator NT2 is shown in detail in order not to overload the figure, includes a receiver REC for receiving the grants forwarded by the line termination LT, a recognition part RP that is able to recognise if the grant is associated to the network termination NT2, and a transmitter TR that is able to transmit upon recognition of a multi-slot grant being associated to the network termination NT2 by the network terminator NT2, overhead data in the first time-slot of a multi-slot burst and data in each adjacent subsequent multi-slot data burst time slot allocated to the network terminator.

(9) The line terminator LT allocates the time slots in a flexible and dynamic way. Indeed the upstream transfer capacity of the time division multiple access network is shared amongst the network terminators NT1, NT2, NT3, . . . , NT31, NT32 based on their needed and requested upstream bandwidth to transmit upstream information. This needed upstream bandwidth is requested by the network terminators NT1, NT2, NT3, . . . , NT31, NT32 to the line terminator LT. The requested bandwidth is translated by the line terminator LT in a number of allocated timeslots. This is realised by creating according the requested bandwidth of the network terminators NT1, NT2, NT3, . . . , NT31, NT32 a stream of grants (as shown in FIG. 3). It has to be remarked that the detailed working of this allocation goes beyond the scope of this invention and is therefore not described. The aim is the use of the grants to inform the network terminators NT1, NT2, NT3, . . . , NT31, NT32 of the allocated timeslots. It is further assumed that the grants are dealt with as presented in FIG. 3 where each network terminator is granted multi-slots for forwarding databursts.

(10) Such a Line terminator LT comprises a grant transmitting part GTP that is adapted to transmit at grants towards a network terminator in order to allocate corresponding upstream time-slot to the network terminator and a detector DET for detecting overhead data in a first timeslot of a multi-slot data burst.

(11) Following this embodiment the stream of grants is provided to the receiver REC of each network terminator.

(12) The receiver REC in each network terminator terminators NT1, NT2, NT3, . . . , NT31, NT32 (only shown for NT2) is included to receive a grant from the line terminator LT within the downstream information; and the transmitter TR which is coupled to this receiver, is included to transmit, upon recognition by the network terminator of its grant as being associated to itself, an upstream data packet in an upstream timeslot. In the cited prior art, the upstream data packet comprises an overhead in front of a payload. However, in contrast to this cited prior art, in the present invention the entire first timeslot is filled with overhead data, and for each adjacent subsequent grant being associated to the same network terminator the network terminator fills the corresponding adjacent subsequent time-slot with payload. This results in a data burst of a network terminator towards the line terminator LT wherein the data is forwarded using a sequence of one or more adjacent subsequent timeslots wherefrom in any case a first timeslot only comprises overhead data.

(13) In order to explain the subject method, it is supposed that network terminator NT2 is a higher order network terminator, e.g. a network terminator transmitting at 1.24416 Gigabit/sec.

(14) At reception of a first grant that is associated to network terminator NT1 by the receiver of network terminator NT1, the transmitter of network terminator NT1 fills the corresponding upstream time-slot with overhead data. Further there are two additional grants associated to network terminator NT1 (as is shown in FIG. 3) received by the receiver of network terminator NT1, allocating two time-slots to network terminator NT1. Consequently, the transmitter of network terminator NT1 fills two timeslots subsequent to the timeslot dedicated to overhead (See FIG. 3). A subsequent grant is associated to network terminator NT2, as is shown in FIG. 3. The receiver of network terminator NT2 receives this grant and subsequently the transmitter NT2 fills the corresponding upstream time-slot with overhead data. Further there are nine additional grants associated to network terminator NT2 received by the receiver of network terminator NT2, allocating nine time-slots to network terminator NT2. Consequently, the transmitter of network terminator NT2 fills nine timeslots subsequent to the timeslot dedicated to overhead (See FIG. 3).

(15) The network termination NT3 is the next network terminator in the cycle of 32 network terminators NT1, NT2, NT3, . . . , NT31, NT32 that is granted the opportunity to forward data towards the line termination LT. So at reception of a first grant that is associated to network terminator NT3 by the receiver of network terminator NT3, the transmitter of network terminator NT3 fills the corresponding upstream time-slot with overhead data. However, no further grant is associated to network termination NT3. Hence no further timeslots on behalf of network terminator NT3 are filled with payload. Then this procedure is continued by granting bandwidth to the subsequent network terminators NT4 up to NT32.

(16) The first time slot of each data-frame forwarded by any of the network terminators NT1, NT2, NT3, . . . , NT31, NT32 containing overhead data may have the content as presented in FIG. 4.

(17) It is to be remarked that the order wherein each of the network terminations is granted time-slots within one buffer reporting cycle is of no relevance. Of only relevance is that each network terminator is granted at least one burst per buffer reporting cycle.

(18) A further remark is that the Line terminator LT receives a frame consisting of a first time-slot containing overhead data and potential subsequent timeslots containing payload data and consequently the line terminator has to accept the data contained in this first time slot as being overhead data. The structure of such overhead data is presented in FIG. 4.

(19) The proposed structure of the overhead data comprises a first group of bytes being used for providing a sufficient guard time, for the delimiter, for the preamble and possibly for other physical layer related fields. A second part of the structure is used for operating and maintenance information (OAM) and for dynamic bandwidth allocation (DBA) reporting. Then a third part of the structure comprises an additional number of bytes for operating and maintenance information (OAM) and for dynamic bandwidth allocation (DBA) reporting.

(20) The detecting of overhead data in a first timeslot of at least one time-slot allocated to the network terminator is done based on the grants transmitted to the network terminator.

(21) Another remark is that the system may be an ATM based PON, wherein ATM cells are transported. The length of each such ATM cells is 53 bytes, excluding possible Forward Error Correction bits.

(22) A final remark is that embodiments of the present invention are described above in terms of functional blocks. From the functional description of these blocks, given above, it will be apparent for a person skilled in the art of designing electronic devices how embodiments of these blocks can be manufactured with well-known electronic components. A detailed architecture of the contents of the functional blocks hence is not given.

(23) While the principles of the invention have been described above in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention, as defined in the appended claims.