Multiplex communications – Channel assignment techniques – Combining or distributing information via time channels...
Reexamination Certificate
1996-04-24
2001-11-20
Vu, Huy D. (Department: 2663)
Multiplex communications
Channel assignment techniques
Combining or distributing information via time channels...
C370S461000
Reexamination Certificate
active
06320869
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a telecommunication network comprising a primary station and a plurality of secondary stations, the secondary stations being linked to the primary station via a transmission medium which is at least partly in common for a number of secondary stations.
The invention also relates to stations for use in such network and to a communication method for such networks.
2. Description of the Related Art
A telecommunication network according to the preamble is known from the conference paper “Network Evolution for End User Access to Interactive Digital Services” by C.-J. L. van Driel and W. A. M. Snijders, Proceedings of “The Last Mile of the Information Superhighway”, IBC conference, Sydney, August 1994.
Such telecommunication networks are used for communication between several secondary stations and a primary station, via a transmission channel being, at least partially, common to some of the secondary stations. Such transmission channel can comprise an optical fibre, a coaxial cable, or a radio link. Application of such transmission systems can be passive optical networks, cable TV systems, local area networks, systems for satellite communication and mobile radio systems.
In transmission systems utilising a common channel for some secondary stations it must be ensured that no interference is caused by secondary stations simultaneously transmitting information to the primary station. However, to ensure an adequate service for the secondary stations, it is also required that efficiency of the data transport over the network be high, particularly under heavy load conditions.
There exist various different access protocols, such as Aloha and slotted Aloha, for such type of networks. However these protocols suffer from a very low efficiency under heavy load conditions.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a telecommunication network according to the preamble having a high efficiency under high load conditions.
Therefor the telecommunication network is characterised in that the secondary stations comprise request transmitting means for transmitting a transmission request signal to the primary station, the primary station comprises allocation transmitting means for transmitting an allocation signal to the secondary stations in response to transmission request signals received, the secondary stations comprise payload transmitting means for transmitting in response to the allocation signal payload data in turn to the primary station, and the request transmitting means are arranged to transmit a transmission request signal to the primary station immediately after transmission of payload data by the secondary stations.
By having the secondary stations which have payload data to be transmitted to the primary station to transmit a transmission request signal, the primary station is informed of the secondary stations which have payload data for the primary station. Thereafter the primary station transmits to the secondary stations an allocation signal indicating timeslots they may use. Subsequently the secondary stations transmit their payload data to the primary station in the timeslots assigned to them. After the transmission of payload data by a secondary station has been completed, the secondary station transmits its next request signal for the next transmission cycle if it has further data to transmit. It is also conceivable that the next transmission request signals are transmitted after a predetermined amount of payload data has been transmitted by the secondary stations. This can lead to more efficient operation, because it is not required that all the secondary stations have to wait for the allocation signal before transmitting their payload data.
Under high load conditions the transmission path from secondary stations to the primary station will be mostly filled with payload data from the secondary stations, leading to a high efficiency.
An additional advantage is that the delay a substation encounters when it wishes to transmit data to the primary station is bounded to some maximum value. This is because the substations transmitting a transmission request signal are granted a timeslot shortly thereafter. The actual transmission interval available for each secondary station depends on the transmission load of the network.
It is observed that the book “Computer Networks” by A. S. Tanenbaum, published by Prentice-Hall, 1989, ISBN 0-13-166836-6 pp 130-131 discloses a protocol having a high efficiency under heavy load conditions, and having a upperbound to the delay. However in this protocol there is no primary station which receives transmission request signals from the secondary stations and issues allocation signals to them.
A further embodiment of the invention is characterised in that the request transmitting means of a secondary station are arranged for transmitting the transmission request signal during a timeslot associated to said secondary station.
An easy way of distinguishing the transmission request signals from different secondary stations is associating a particular timeslot to said secondary station wherein said secondary station has to transmit its transmission request signal.
A further embodiment of the invention is characterised in that the allocation transmitting means are arranged for transmitting the transmission request signals as received by the primary station, as an allocation signal.
Retransmission of the received transmit request signals as an allocation signal is a simple way of providing an allocation signal. The secondary station receiving said allocation signal then know all the other secondary stations that have payload data to be transmitted to the primary station. Having this information they can determine a time slot number they can transmit in. This can for example be done by allowing transmission by the secondary stations in an order determined by a rank number associated with each of the secondary stations.
A further embodiment of the invention is characterised in that the payload transmitting means are arranged for transmitting in a predetermined number of symbol intervals a integer plurality of short information cells, or one single synchronous transfer mode cell.
Arranging the payload transmission means for transmitting a number of short information cells or one single ATM cell results in a network allowing the transmission of several types of signals during one predetermined time interval. This is advantageous for higher level protocols that only have to cope with one predetermined time interval of transmission by each secondary stations.
A first choice for the size of the short information cells is characterised in that the short information cells have a size of sixteen bytes, and in that the predetermined number of short information cells is equal to four. Using four short information cell of 16 bytes results in 64 bytes in total, which can also carry one ATM cell (53 bytes) plus some additional overhead information.
A second choice for the size of the short information cells is characterised in that the short information cells have a size of nine bytes, and in that the predetermined number of short information cells is equal to six. Using six short information cell of 9 bytes results in 54 bytes in total, which can also carry one ATM cell (53 bytes) plus one additional overhead byte.
REFERENCES:
patent: 4646345 (1987-02-01), Zdunek et al.
patent: 4999835 (1991-03-01), Lagoutee
patent: 5327432 (1994-07-01), Abedeen et al.
patent: 5384777 (1995-01-01), Ahmadi et al.
“Network Evolution for End User Access to Interactive Digital Services”, By C.J.L. Van Driel et al, “The Last Mile of the Information Superhighway”, IBC Conference, Sydney, Aug. 1994.
“Computer Networks”, By A.S. Tanenbaum, Prentice-Hall, 1989, ISBN 0-13-166836, pp. 130-131.
Van Driel Carel J. L.
Van Grinsven Petrus A. M.
Gross Russell
U.S. Philips Corporation
Vu Huy D.
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