Multiplex communications – Channel assignment techniques – Using time slots
Reexamination Certificate
1998-07-01
2002-10-08
Ton, Dang (Department: 2661)
Multiplex communications
Channel assignment techniques
Using time slots
C370S442000
Reexamination Certificate
active
06463075
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method to assign upstream timeslots to a plurality of network terminals, in a communications network wherein a central station is coupled to the plurality of network terminals via the cascade connection of a common link and respective individual links and wherein the network terminals transmit upstream information to the central station in a time multiplex way over the common link using the upstream timeslots. It is also directed to an arrangement to be used in a network terminal to perform this method, wherein a central station is coupled to the plurality of network terminals via the cascade connection of a common link and respective individual links and wherein the network terminals transmit upstream information to the central station in a time multiplexed way over the common link using the upstream timeslots of a communications network an arrangement to be used in a network terminal.
The invention is further directed to an arrangement to be used in a central station of a communications network to perform this method, wherein a central station is coupled to a plurality of network terminals via the cascade connection of a common link and respective individual links and wherein the network terminals transmit information to the central station in a time multiplexed way over the common link using upstream timeslots assigned by the central station.
BACKGROUND OF THE INVENTION
Such a method is already known in the art, e.g. from the proposal to the FSAN-OAN (Full Service Access Network—Optical Access Network) Workgroup entitled ‘Short Slot Proposal’. This proposal is written by the authors Mark Bridger, Dan Donovan, Paul Welton, and Mike Haynes, and dated Apr. 22-23, 1997. Therein, the central station of a passive optical network (PON) with point-to-multipoint architecture regularly broadcasts so called PLOAM (Physical Layer Operation Administration and Maintenance) cells containing identifiers of the network terminals which are allowed to send a burst in the upstream timeslots of an upstream frame. The central station in the optical network of the mentioned proposal is called the OLT (Optical Line Termination), whereas the network terminals are named ONU's (Optical Network Units). The contents of such a PLOAM cell as proposed by Mark Bridger et al. is shown in a figure on page 4 of the just cited proposal. The 30 grant messages therein each contain an ONU identifier. Each ONU identified in the PLOAM cell is permitted to occupy one timeslot. By downstream broadcasting this message, all ONU's in the network become aware of the order wherein they are allowed to occupy upstream timeslots for transmission of data bursts towards the OLT. The upstream timeslots may be standard full size upstream slots with a length of 56 bytes or short slots with a length of 7 bytes. Schemes of the contents of such a short slot and such a standard full size slot are drawn in the figures on pages 2 and 3 of the proposal.
Broadcasting for each upstream timeslot an identifier of the network terminal that is allowed to send an upstream burst in it inevitably involves a high downstream bandwidth occupancy by grant messages. Especially the upstream transmission of short bursts in short timeslots requires a relatively high downstream bandwidth capacity for transfer of overhead information. In networks such as the passive optical network in the cited proposal, the length and transmit rate of PLOAM cells are fixed, and thus the bandwidth available for downstream transmission of grant messages is fixed and limited. Applying the known method for assigning timeslots to network terminals in such networks puts a severe limit on the number of timeslots within an upstream frame, irrespective of the length of these timeslots.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method to assign upstream timeslots to a plurality of network terminals and related arrangements of the above known type, but wherein the downstream bandwidth occupancy to assign a certain amount of upstream timeslots is reduced or, in other words, wherein the amount of timeslots that can be assigned with a certain downstream bandwidth capacity is increased.
According to the invention, this object is achieved by a method to assign upstream timeslots to a plurality of network terminals in a communications network wherein a central station is coupled to the plurality of network terminals via the cascade connection of a common link and respective individual links and wherein the network terminals transmit upstream information to the central station in a time multiplexed way over the common link using the upstream timeslots, wherein the central station downstream broadcasts a group identifier to assign a plurality of the upstream timeslots in a predefined order to network terminals of a group of the plurality of network terminals, the group having a predefined composition and being identified by the group identifier.
The object is also achieved by an arrangement to be used in a network terminal of a communications network wherein a central station is coupled to a plurality of network terminals via the cascade connection of a common link and respective individual links and wherein the network terminals transmit information to the central station in a time multiplexed way over the common link using upstream timeslots assigned by the central station, the plurality of network terminals comprising the network terminal, wherein the arrangement comprises: comparison means, adapted to compare a group identifier, downstream broadcasted by the central station to assign a plurality of the upstream timeslots in a predefined order to network terminals of a group of the plurality of network terminals, the group being identified by the group identifier, with group identifiers of groups of network terminals whereof the network terminal forms part; and control means, coupled between the comparison means and a transmitting part of the network terminal and adapted to control, in case the group identifier downstream broadcasted matches one of the group identifiers, the transmitting part to transmit an upstream burst in a thereby assigned upstream timeslot and to respect the predefined order.
The object is still further achieved by an arrangement to be used in a central station of a communications network wherein the central station is coupled to a plurality of network terminals via the cascade connection of a common link and respective individual links and wherein the network terminals transmit information to the central station in a time multiplexed way over the common link using upstream timeslots assigned by the central station, where the arrangement comprises: selection means adapted to select a precomposed group of network terminals; message generating means, to an input of which the selection means is coupled and which is adapted to generate a broadcast message including a group identifier of the precomposed group of network terminals; and a transmitting part, to an input of which the message generating means is coupled, the transmitting part being adapted to broadcast the broadcast message to the plurality of network terminals to thereby assign a plurality of the upstream timeslots in a predefined order to the network terminals of the precomposed group.
Indeed, no more bandwidth than that used in the known method to assign a timeslot to a single terminal, is used according to the present invention to assign a plurality of timeslots to a plurality of terminals. More precisely, as many timeslots are assigned as there are network terminals in a group. The amount of downstream bandwidth needed thereto is that for transmission of a group identifier and may be considered equal to that needed for transmission of a terminal identifier in the known method. As a result, the downstream bandwidth occupancy to assign an equal amount of timeslots to terminals is reduced with a factor equal to the number of network terminals that composes one group. If, on the other hand, the downstream bandwid
Alcatel
Ton Dang
LandOfFree
Time multiplexing method, and related arrangements to be... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Time multiplexing method, and related arrangements to be..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Time multiplexing method, and related arrangements to be... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2927646