Multiplex communications – Channel assignment techniques – Combining or distributing information via time channels...
Reexamination Certificate
1998-06-19
2003-05-27
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Channel assignment techniques
Combining or distributing information via time channels...
C370S337000
Reexamination Certificate
active
06570886
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a time slot management method for use in a time division multiple access network which includes a main station coupled to each of a plurality of substations via the cascade connection of a common transmission link and an individual user link, the management method including broadcasting substation identities in downstream information packets from the main station to the plurality of substations to allow each one of the plurality of substations upon detection of its own substation identity to transfer a predetermined amount of upstream information packets in predetermined upstream timeslots to the main station. The invention also relates to a main station and a substation realizing such a method.
BACKGROUND OF THE INVENTION
Such a time slot management method, main station and substation are already known in the art, e.g. from the published European patent application with publication number 0 544 975 A1. Therein, a time slot management system is described which includes a time division multiple access system with a main station connected to a plurality of substations by means of a tree like network. Substation identities are broadcasted in downstream information packets from the main station to the substations in order to thereby allow each one of the substations upon detection of its own substation identity to transfer upstream information in upstream information packets in predefined upstream timeslots. This time slot management system allocates the time slots in a flexible and dynamically way. The needed bandwidth to transmit upstream information is requested by the substations to the main station and the substations are informed by the main station of the allocated timeslots.
A feature of the described time slot management system is that the downstream information packets are including a predetermined number of blocks each of which include a header part and an information part. In order to reduce the overhead of the downstream information packets a first step is realized to distribute the stream of substation identities over the header parts of this predetermined number of blocks and a second step is realized to performe only one error check for this predetermined number of blocks and to distribute the error check information bits over the header parts of the predetermined number of blocks. In this way, the overhead of one information packet is a reduced number of bits.
It has to be remarked that in order to keep a maximum transfer capacity between the main station and the substations it is desirable to keep the number of bits of the overhead of the information packets as low as possible.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a time slot management method of the above known type but wherein the overhead of one information packet is further reduced.
According to the invention, this object is achieved due to the fact that the time slot management method of the invention includes embedding at least part of the substation identities in a physical layer operation and maintenance part. Such a physical layer operation and maintenance part is a predefined part of one of the downstream information packets which is anyway broadcasted from the main station to the plurality of substations in order to transport operation and maintenance information packets related to operation and maintenance functions.
Indeed, by embedding substation identities in unused fields of physical layer operation and maintenance parts, which are a predefined part of one of the downstream information packets and which are broadcasted anyway on a predefined regular base the number of bits of the overhead of one information packet is a reduced number of bits. This method is a time slot management method for use in a time division multiple access network which includes a main station coupled to each of a plurality of substations via the cascade connection of a common transmission link and an individual user link, the management method including broadcasting substation identities in downstream information packets from the main station to the plurality of substations to allow each one of the plurality of substations upon detection of its own substation identity to transfer a predetermined amount of upstream information packets in predetermined upstream timeslots to the main station, wherein the time slot management method additionally includes embedding at least part of the substation identities in a physical layer operation and maintenance part, the physical layer operation and maintenance part being a predefined part of one of the downstream information packets broadcasted from the main station to the plurality of substations to transport operation and maintenance information packets related to operation and maintenance functions.
In addition, the present invention is directed to a main station for inclusion in a time division multiple access network wherein the main station is to be coupled to each of a plurality of substations via the cascade connection of a common transmission link and an individual user link, the main station including a packet formatting module to insert substation identities in downstream information packets in order to broadcast the information packets from the main station to the plurality of substations to thereby allow each one of the plurality of substations upon detection of its own substation identity to transfer a predetermined amount of upstream information packets in predetermined upstream timeslots to the main station, wherein the main station includes inserting means to insert at least part of the substation identities in a physical layer operation and maintenance cell, the physical layers in one of the downstream information packets broadcasted from the main station to the plurality of substations to transport operation and maintenance information packets related to operation and maintenance functions.
Furthermore, the present invention is directed to a substation for inclusion in a time division multiple access network, the time division multiple access network including a main station being coupled to each of a plurality of substations including the substation via the cascade connection of a common transmission link and an individual user link, substation identities of the plurality of substations being broadcasted in downstream information packets from the main station to the substations in order to allow each one of the plurality of substations upon detection of its own substation identity to transfer a predetermined amount of upstream information packets in predetermined upstream timeslots to the main station, wherein the substation includes detecting means to detect in a physical layer operation and maintenance cell its own substation identity inserted by the main station in the physical layer operation and maintenance cell, the physical layer operation and maintenance cell being a predefined part included in one of the downstream information packets broadcasted from the main station to the plurality of substations to transport operation and maintenance information packets related to operation and maintenance functions.
It has to be remarked that operation and maintenance functions for e.g. an Asynchronous Transfer Mode layered model are described in e.g. the book
Asynchronous Transfer Mode: Solution for Broadband ISDN
written by Martin de Prycker, and more particular in Chapter 3: Description of ATM according to CCITT from page 97 to page 124, published in 1991 by Ellis Horwood Limited, ISBN 0-13-053513-3.
Also the scope of the Recommandation ITU-TI.610, March /1993, previously CCITT Recommandation described in paragraph 1.2, page 1 thereof, is to identify the minimum set of functions required to operate and maintain the Physical Layer and Asyncronous Transfer Mode ATM Layer aspects of the Broadband Integrated Services Digital Network B-ISDN user network interface. Five phases are considered in specifying the operation and maintenance OAM functions of the Broadband—Integrated Services
Bert De Groote Jan Lieven
Van De Voorde Ingrid Zulma Benoit
Alcatel
Hsu Alpus H.
Nguyen Toan D.
Ware Fressola Van Der Sluys & Adolphson
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