Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1998-10-29
2001-10-02
Olms, Douglas (Department: 2661)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S442000
Reexamination Certificate
active
06298049
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a method to assign an upstream timeslot to a network terminal, an arrangement adapted to perform this method, and a communication system wherein the method is used.
2. Discussion of Related Art
Such a method and related arrangement are already known in the art, e.g. from the U.S. Pat. No. 5,539,743, entitled ‘Multiple Access System for Communication Network’. Therein, a communications system is disclosed wherein a plurality of network terminals, named substations, are coupled to a main station via a network with multipoint-to-point architecture. A substation upon request is assigned an upstream timeslot that is used for transmission of an upstream data burst towards the main station. This is done by the main station which downstream broadcasts so called data transmission enable signals (TENO) or grant messages that define for each upstream timeslot to which substation it is assigned. The main station keeps track of a time table or grant table wherein the different substations occupy entries based on their requests for upstream bandwidth. This table is scanned at regular time intervals and the substation whose identifier is stored in the scanned entry is assigned a timeslot via a grant message. As indicated in column 11, lines 30-37, of the cited United States Patent, the main station gives authority to an arbitrary substation to occupy an upstream timeslot if the scanned table entry is empty.
The solution known from U.S. Pat. No. 5,539,743 lacks an optimal decision criterion for selecting the substation which is given the allowance to send an upstream burst in case the scanned entry in the time table is empty. In the known method, an arbitrary substation is given the allowance. This arbitrary selected substation however may have no data available for upstream transmission whereas other substations which do not get access to the free upstream timeslots have lots of data waiting to be transferred.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and related equipment of the above known type, but wherein the substations which are assigned an upstream timeslot in case of absence of substation identifiers in the grant table, are selected in a more efficient way.
According to a first aspect of the invention, a method to assign an upstream timeslot to a network terminal via a grant message, said method for use in a communication network wherein a main station is coupled to a plurality of network terminals via a cascade connection of a common link and respective individual links, and wherein said network terminals transmit upstream bursts towards said main station in a time division multiplexed way over said common link in upstream timeslots assigned thereto, comprises the steps of scanning in said main station an entry of a grant table wherein a list of terminal identifiers is memorized, generating said grant message and embedding therein a terminal identifier memorized in said entry of said grant table, and downstream broadcasting said grant message, wherein said method further comprises the steps of reading, if said entry of said grant table is empty, a terminal identifier from an exceptional grant queue, and embedding said terminal identifier read from said exceptional grant queue in said grant message before it is broadcasted.
In accordance with a second aspect of the invention, an arrangement adapted to assign an upstream timeslot to a network terminal via a grant message, said arrangement for use in a communications network wherein a main station is coupled to a plurality of network terminals via a cascade connection of a common link and respective individual links, said network terminals for transmitting upstream bursts towards said main station in a time division multiplexed way over said common link in upstream timeslots assigned thereto, comprises at least one grant table memory, for memorizing a list of terminal identifiers, scanning means to at least one input of which outputs of said at least one grant table memory are coupled, said scanning means for scanning an entry of said at least one grant table memory and for applying a terminal identifier read from said entry to an output thereof, grant message generating means, to an input of which said output of said table scanning means is coupled, said grant message generating means for generating said grant message and for embedding said terminal identifier received from said scanning means in said grant message, transmitting means, coupled to said grant message generating means, for broadcasting said grant message, and at least one exceptional grant queue memory, for memorizing terminal identifiers of network terminals that request exceptional additional bandwidth, wherein said scanning means is equipped with at least one additional input whereto outputs of said at least one exceptional grant queue are coupled, said scanning means for scanning an entry of said at least one exceptional grant queue memory if said entry of said grant table memory is empty, and for providing a terminal identifier read from said entry of said exceptional grant queue memory to said grant message generation means.
According to a third aspect of the invention, a communication system comprises a main station and a plurality of network terminals coupled to said main station via a cascade connection of a common link and respective individual links, said network terminals for transmitting upstream bursts towards said main station in a time division multiplexed way over said common link in upstream timeslots assigned thereto by said main station, and said main station for assigning an upstream timeslot to a network terminal via a grant message, whereby said main station comprises at least one grant table memory for memorizing a list of terminal identifiers, scanning means to at least one input of which outputs of said at least one grant table memory are coupled, said scanning means for scanning an entry of said at least one grant table memory and for applying a terminal identifier read from said entry to an output thereof, grant message generating means, to an input of which said output of said table scanning means is coupled, said grant message generating means for generating said grant message and for embedding said terminal identifier received from said scanning means in said grant message, and transmitting means, coupled to said grant message generating means, for broadcasting said grant message, and at least one exceptional grant queue memory, for memorizing terminal identifiers of network terminals that request exceptional additional bandwidth, wherein said scanning means is equipped with at least one additional input whereto outputs of said at least one exceptional grant queue are coupled, said scanning means for scanning an entry of said at least one exceptional grant queue memory if said entry of said grant table memory is empty, and for applying a terminal identifier read from said entry of said exceptional grant queue memory to said grant message generation means.
In this way, by providing an exceptional grant queue that is consulted each time an empty entry is scanned in the grant table, assignment of upstream timeslots is managed so that network terminals with the highest needs for exceptional additional bandwidth receive most exceptional grant messages. In case a network terminal needs a single sequence of grant messages for exceptional transmission of a data packet, its terminal identifier may be written in subsequent entries of the exceptional grant queue, so that a sequence of upstream timeslots that would be assigned at random to network terminals in the known method, becomes now assigned to this network terminal with special needs. The request of a network terminal for exceptional additional bandwidth, i.e. bandwidth that supersedes the negotiated minimum bandwidth to be delivered to a network terminal, can be handled in a similar way via the exceptional grant queue. Concluding, the exceptional grant queue allows to assig
VanHoof Harry Franciscus Ludovica
Wolters Robert
Alcatel
Olms Douglas
Vanderpuye Ken
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