Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1998-03-03
2001-10-02
Cangialosi, Salvatore (Department: 2661)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C375S267000
Reexamination Certificate
active
06298052
ABSTRACT:
The field of the invention is that of transmitting data in a shared resource transmission system. To be more precise, the present invention concerns an ALOHA type shared resource transmission system that can be used to set up transmission between a calling station and a called station, for example via satellite. In the case of transmission via satellite the stations are typically earth stations.
Consider first the context of transmitting data in packets via a shared resource for setting up a call between a calling station and a called station. Call set-up is a phase preceding communication proper and its function is to allocate a resource reserved to the call in question.
The random ALOHA access system is used prior to call set-up. This system entails a calling station sending a data packet called the access packet for the attention of a called station using for this purpose a resource shared with other stations. The shared resource is typically a carrier frequency. The various stations share the resource without any prior reservation of time slots and without any temporal synchronization of the stations. Because there is no reservation, collisions can occur between access packets sent by different stations. To compensate this risk of collision a station sending a first access packet that does not receive any acknowledgement message from the called station sends a second access packet via the shared resource after a particular time-delay starting from sending the first access packet.
Assuming that there is no correlation between the sending of access packets by the various stations, in other words that the sending of the packets obeys Poisson's law, the probability P of a collision between access packets occurring is equal to:
P=1−e
−2RT
where R is the average number of packets transmitted per second and T is the duration of a packet. The digit 2 indicates that a collision occurs if two packets of duration T are transmitted within a time window of duration 2T.
To overcome this drawback it has been decided to provide time windows of duration T during which stations are authorized to send access packets. In this case the various stations are temporally synchronized. This system is known as the slotted ALOHA system. In this case the probability P of a collision between access packets occurring is equal to:
P=1−e
−2RT
Accordingly, the number r of access packets transmitted without repetition is generally written:
r=R*e
−kRT
with k=1 for the slotted ALOHA system and k=2 for the random ALOHA system.
The main drawback of these two types of access system is the high number of repetitions of access packets, which commensurately increases call set-up time. This problem is serious in the case of transmission via satellite because of the distance traveled by the access packets between the sending station and the station to which the access packets are addressed.
Packets of data can also be transmitted using ALOHA systems, slotted or otherwise. In this case the packets are not access packets but packets of data as such used for the call between the calling station and the called station. The data packets convey alarm, supervisory, etc data. The same problem arises for these data packets as that which has previously arisen for access packets.
One aim of the present invention is to solve these problems.
To be more precise, one aim of the invention is to reduce the number of collisions between data packets transmitted by a station in a system where the senders of such packets use the same resource.
This aim and others that will become apparent hereinafter are achieved by a method of communication used in a shared resource transmission system characterized in that it consists in sending at least two identical data packets without waiting for an acknowledgement of reception between sending said data packets.
The above method is advantageously used to set up a call and in this case the aforementioned data packets are access packets.
The above method is advantageously employed in a satellite transmission system either for call set-up or for communication proper.
The data packets preferably each include data for detecting a collision between the data packets transmitted on the shared resource.
The packets can be transmitted with a temporal spacing and/or on different carrier frequencies and/or using code-division multiple access (CDMA).
The invention applies to a slotted or otherwise ALOHA type shared resource transmission system.
REFERENCES:
patent: 3906445 (1975-09-01), Beckmann et al.
patent: 4133504 (1979-01-01), Dobler et al.
patent: 4400811 (1983-08-01), Brown et al.
patent: 4518947 (1985-05-01), Poston et al.
patent: 4621368 (1986-11-01), Onoe et al.
patent: 4841527 (1989-06-01), Raychaudhuri et al.
patent: 4908828 (1990-03-01), Tikalsky
patent: 5034966 (1991-07-01), Hochstein
patent: 5109390 (1992-04-01), Gilhousen et al.
patent: 5138631 (1992-08-01), Taylor
patent: 5142533 (1992-08-01), Crisler et al.
patent: 5168510 (1982-12-01), Hill
patent: 5457678 (1995-10-01), Goeldner
patent: 5663990 (1997-09-01), Bolgiano et al.
patent: 5883581 (1999-03-01), Dorenbosch et al.
patent: 2029170 (1980-03-01), None
patent: 61 043850 (1986-03-01), None
patent: 62 131636 (1987-06-01), None
patent: 08 032596 (1996-02-01), None
Bousquet Jacques
Dehaene Jean-Pierre
Alcatel
Cangialosi Salvatore
Sughrue Mion Zinn Macpeak & Seas, PLLC
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