France Telecom

Orange

Patrick Tortelier

Raphaël Visoz

Christophe Delesalle

Muhammad Moazam Azeem

Didier Le Ruyet

A system for transmitting data packets includes at least one access point and at least one terminal. The access point receives data packets transmitted by the terminal in compliance with a multiple access protocol including carrier detection, and transmits to the terminal at least the width of the contention window that the terminal is to observe for transmitting a packet. The transmitted packets are coded using an erasure code and the access point is further adapted to decode the received packets. The system may be applied to networks such as WLANs.

System for transmitting data packets according to a multiple access protocol

The invention concerns a method for jointly decoding and equalizing a digital signal protected by a trellis-defined code and transmitted though a channel. The method consists in carrying out a maximum likelihood estimate of each current bit xby minimizing the quadratic error between the observed symbol Vand the current symbol in the channel output z, the quadratic error being calculated () from the set of observed symbols based on the branch metric of the last transition e(X)&#x2192;e(X) according to the relationship (I); wherein k represents the rank of the coefficients of transverse filtering introduced by the radioelectric channel. The branch metric is calculated by backtracking through the successive states and the error propagating process is inhibited () while backtracking through the successive states by storing at each node S survivors and by updating each survivor at the next time. The final survivor of the least metric is determined () and the sequence of bits is read by backtracking through the successive nodes. The invention is applicable to ATM radio transmission.

Method for decoding and of joint equalization of a digital signal protected by a code defined by a trellis

The interfacing device handles asynchronous/synchronous adaptation and rate control between the ATM flows and the flows transmitted on the wireless interface. It transposes the ATM cells (53 octets) into packets which can be transmitted directly on the wireless interface (40 octets in the case of DECT). Similarly, at the receiving end, it reconstructs the original ATM cell flow on the basis of the packets received. In order to guarantee a certain transmission quality at the level of the wireless link, the device uses a data acknowledgement and retransmission mechanism adapted to the characteristics of the synchronous wireless channel. In order to fulfil the quality of service requirements of the various applications in terms of error rates and transmission delays, the device allows the data protection mechanism to be set for each ATM connection depending on the characteristics of the service.

Interface device between an ATM equipment and a transmission channel having a synchronous wireless link

A method of detecting, blind, the coding mode used to encode digital data, for data transmitted in frames of n bits, partially subjected to a convolutional coding. A soft syndrome value is calculated over a sequence of bits representative of a transmission error probability in these bits, and a likelihood value V(&agr;,&bgr;), where &agr;, &bgr; denote the number of coded bits and non-coded bits respectively, is then calculated on the basis of the mean value m and the variance &sgr; of the distribution of the absolute soft syndrome values. The likelihood value V(&agr;,&bgr;) is maximised as a function of &agr; or &bgr; which makes it possible to determine the coding mode used on the basis of the corresponding values &agr; or &bgr;.

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Clichy, France

Patrick Tortelier