Abstract: This application relates to a method of performing wireless communications between a hub station and a plurality of user terminals. The method comprises transmitting radio signals to subsets of user terminals among the plurality of user terminals with sets of active beams, wherein the active beams have beam centers that are determined based on locations of the user terminals. The method further comprises, for each of a plurality of radio resource blocks: selecting a subset of user terminals among the plurality of user terminals; for each user terminal among the subset of user terminals, determining a beam center based on a location of the respective user terminal; and transmitting, using the respective radio resource block, radio signals to the user terminals among the selected subset of user terminals, in beams corresponding to the determined beam centers.

Abstract: A method of transmitting data packets from a terminal (T) to a gateway receiver (GWR) over a channel shared with other terminals using an unslotted spread spectrum random access protocol, characterized in that transmission is performed at a transmit power level given by the sum of a deterministic term, function of a communication link budget, and of a random term, following a predetermined probability distribution. A method of operating a communication system, based on the method of transmitting data packets. A communication system and a terminal for implementing the methods.

Abstract: A method of transmitting data packets over a transmission channel shared by transmitters on the basis of a first unit of transmission of fixed length subdivided into second units of transmission of fixed length, includes: associating, at a first transmitter, for each packet to be transmitted at least two packet replicas with respective second units within a current first unit; generating, at the first transmitter, the replicas, in each of which signaling information is included, the signaling information indicating relative positions of the other replicas of the same packet within the current first unit with respect to the given replica; setting, at the first transmitter, a start timing for beginning transmission of the current first unit independently of the other transmitters of the transmitters sharing the transmission channel; and transmitting the replicas at respective timings in accordance with their association with the respective second units within the current first unit.

Abstract: A satellite communication system including a multibeam satellite for generating a plurality of feeder beams and a plurality of user beams over a region of interest, a plurality of spatially-separated gateway stations for providing feeder links to said multibeam satellite via respective feeder beams; and a control for operating said gateway stations and multibeam satellite such that: in nominal conditions, NGW gateway stations exchange data with K user beams, each of the gateway stations allocating a fraction of its bandwidth to each of the user beams; and in case of fading, data are switched from faded to unfaded gateway stations, whereby none of said user terminals experiences service outage. A method of performing satellite communication using the satellite communication system, and a multibeam communication satellite payload for carrying out the method are provided.

Abstract: A method of transmitting data packets over a transmission channel shared by transmitters on the basis of a first unit of transmission of fixed length subdivided into second units of transmission of fixed length, includes: associating, at a first transmitter, for each packet to be transmitted at least two packet replicas with respective second units within a current first unit; generating, at the first transmitter, the replicas, in each of which signaling information is included, the signaling information indicating relative positions of the other replicas of the same packet within the current first unit with respect to the given replica; setting, at the first transmitter, a start timing for beginning transmission of the current first unit independently of the other transmitters of the transmitters sharing the transmission channel; and transmitting the replicas at respective timings in accordance with their association with the respective second units within the current first unit.

Abstract: A method of transmitting data packets from a terminal (T) to a gateway receiver (GWR) over a channel shared with other terminals using an unslotted spread spectrum random access protocol, characterized in that transmission is performed at a transmit power level given by the sum of a deterministic term, function of a communication link budget, and of a random term, following a predetermined probability distribution. A method of operating a communication system, based on the method of transmitting data packets. A communication system and a terminal for implementing the methods.

Abstract: A satellite communication system including a multibeam satellite for generating a plurality of feeder beams and a plurality of user beams over a region of interest, a plurality of spatially-separated gateway stations for providing feeder links to said multibeam satellite via respective feeder beams; and a control for operating said gateway stations and multibeam satellite such that: in nominal conditions, NGW gateway stations exchange data with K user beams, each of the gateway stations allocating a fraction of its bandwidth to each of the user beams; and in case of fading, data are switched from faded to unfaded gateway stations, whereby none of said user terminals experiences service outage. A method of performing satellite communication using the satellite communication system, and a multibeam communication satellite payload for carrying out the method are provided.

Abstract: A first aspect of the invention is a method of transmitting data packets over a transmission channel shared by a plurality of users, based on the time and/or frequency diversity slotted Aloha technique, in which at least two replicas of each packet to be transmitted are sent over said transmission channel, wherein each replica transports signaling information enabling the other replica(s) of the same packet to be located in the time and/or frequency domain. A second aspect of the invention is a method of recovering packets in the receiver, the method exploiting said signaling information to execute an interference cancellation algorithm for recovering packets corrupted by collisions caused by access conflicts. Other aspects of the invention are a transmitter equipment and a receiver packet recovery equipment adapted to use said methods.

Abstract: A method of receiving data packets asynchronously transmitted by a plurality of user terminals using a spread-spectrum medium access protocol, comprises a step of cancelling interferences between colliding packets according to an innovative “sliding window” processing algorithm. A gateway receiver is adapted for carrying out interference cancellation using this algorithm. Asynchronous packet transmission from a user terminal is controlled by estimating a parameter indicative of the quality of information transmission through a communication channel; and inhibiting or allowing data transmission depending on a comparison between said estimated parameter and an adaptively varying threshold. A user terminal comprises transmission control means adapted for carrying out such a method.

Abstract: A method of receiving data packets asynchronously transmitted by a plurality of user terminals using a spread-spectrum medium access protocol, comprises a step of cancelling interferences between colliding packets according to an innovative “sliding window” processing algorithm. A gateway receiver is adapted for carrying out interference cancellation using this algorithm. Asynchronous packet transmission from a user terminal is controlled by estimating a parameter indicative of the quality of information transmission through a communication channel; and inhibiting or allowing data transmission depending on a comparison between said estimated parameter and an adaptively varying threshold. A user terminal comprises transmission control means adapted for carrying out such a method.

Abstract: A process for providing a phase synchronization of a pilot aided carrier of an input digital signal z(k), the signal z(k) having signal fields of Ls symbol signals, namely a block of LP pilot symbol signals ZP(k) and a data field of (Ls?LP) data symbol signals Zd(k), and characterized for each signal field (l) by: extracting the pilot symbol signals ZP(k) and calculating an unwrapped phase estimate {circumflex over (?)}(lLs) over the pilot block of said signal field (1) and: interpolating said unwrapped phase estimates of successive signal fields (l, +1 . . .

Abstract: Providing a pilot aided phase recovery of a carrier of an input digital signal Zk having signal fields of Ls symbol signals, LP pilot symbol signals ZP(k) and (Ls?LP) data symbol signals Zd(k), by for each signal field: calculating an unwrapped pilot phase estimate {circumflex over (?)}f(P)(l); initiating with {circumflex over (?)}f(P)(l) a first digital phase locked loop implementing a phase estimate algorithm and calculating a forward phase trajectory {circumflex over (?)}F(k) from Zd(k), ks varying between 1 and Ls?LP over the data field (l), {circumflex over (?)}F(P)(l) having Ls?LP forward phase estimates {circumflex over (?)}F(ks); and initiating with {circumflex over (?)}(P)f(l+1) a second digital phase locked loop, implementing a phase estimate algorithm and calculating a backward phase trajectory {circumflex over (?)}B(ks) from Zd(k), ks varying between Ls?LP and 1 over said data field (l), {circumflex over (?)}B(ks) having Ls?LP backward phase estimates {circumflex over (?)}B(ks); and from said p

Abstract: A new class of 16-ary Amplitude and Phase Shift Keying (APSK) coded modulations, called double-ring APSK modulation, based on an amplitude and phase shift keying constellation in which the locations of the digital signals to be encoded are placed on two concentric rings of equally spaced signal points. The APSK constellation parameters are optimised so as to pre-compensate the impact of non-linearities. The new modulation scheme is suited for being used with different coding schemes. It is shown that, for the same coding scheme, pre-distorted double-ring APSK modulation significantly outperforms classical 16-QAM and 16-PSK over a typical satellite channel, due to its intrinsic robustness against the high power amplifier non-linear characteristics. The proposed coded modulation scheme is shown to provide a considerable performance advantage for future satellite multi-media and broadcasting systems.

Abstract: A new class of 16-ary Amplitude and Phase Shift Keying (APSK) coded modulations, called double-ring APSK modulation, based on an amplitude and phase shift keying constellation in which the locations of the digital signals to be encoded are placed on two concentric rings of equally spaced signal points. The APSK constellation parameters are optimised so as to pre-compensate the impact of non-linearities. The new modulation scheme is suited for being used with different coding schemes. It is shown that, for the same coding scheme, pre-distorted double-ring APSK modulation significantly outperforms classical 16-QAM and 16-PSK over a typical satellite channel, due to its intrinsic robustness against the high power amplifier non-linear characteristics. The proposed coded modulation scheme is shown to provide a considerable performance advantage for future satellite multi-media and broadcasting systems.

Abstract: A first aspect of the invention is a method of transmitting data packets over a transmission channel shared by a plurality of users, based on the time and/or frequency diversity slotted Aloha technique, in which at least two replicas of each packet to be transmitted are sent over said transmission channel, wherein each replica transports signaling information enabling the other replica(s) of the same packet to be located in the time and/or frequency domain. A second aspect of the invention is a method of recovering packets in the receiver, the method exploiting said signaling information to execute an interference cancellation algorithm for recovering packets corrupted by collisions caused by access conflicts. Other aspects of the invention are a transmitter equipment and a receiver packet recovery equipment adapted to use said methods.

Abstract: The Invention relates to a process for providing a pilot aided phase recovery of a carrier of an input digital signal, said signal Zk comprising signal fields comprised of Ls symbol signals, namely a block of LP pilot symbol signals ZP(k) and a data field of (Ls?LP) data symbol signals Zd(k), and characterized in that it comprises for each signal field (l) calculating an unwrapped pilot phase estimate {circumflex over (?)}f(P)(l). initiating with {circumflex over (?)}f(P)(l) a first digital phase locked loop (DPLLF) implementing a phase estimate algorithm and calculating a forward phase trajectory {circumflex over (?)}F(k) from the data symbol signals Zd(k) of the data field, ks varying between 1 and Lx?LP over said data field (l), said forward phase trajectory {circumflex over (?)}F(P)(l) being comprised of Ls?LP forward phase estimates {circumflex over (?)}F(ks).

Abstract: A new class of 16-ary Amplitude and Phase Shift Keying (APSK) coded modulations, called double-ring APSK modulation, based on an amplitude and phase shift keying constellation in which the locations of the digital signals to be encoded are placed on two concentric rings of equally spaced signal points. The APSK constellation parameters are optimised so as to pre-compensate the impact of non-linearities. The new modulation scheme is suited for being used with different coding schemes. It is shown that, for the same coding scheme, pre-distorted double-ring APSK modulation significantly outperforms classical 16-QAM and 16-PSK over a typical satellite channel, due to its intrinsic robustness against the high power amplifier non-linear characteristics. The proposed coded modulation scheme is shown to provide a considerable performance advantage for future satellite multi-media and broadcasting systems.

Abstract: An adaptive signal receiver comprising at least one blind detection unit arranged to be robust to asynchronous multiple access interference (MAI). The useful signal is detected using a user signature sequence comprised of a fixed term and a complex adaptive part having a length that extends over a number of samples within a defined observation window. Provision is made for updating automatically and periodically the complex adaptive part of the signature sequence.

Abstract: The invention relates to the recognition of a spread spectrum data signal transmitted in code division multiple access communication systems. The invention provides a receiver whose code acquisition and detection circuit includes circuitry configured for detecting the signal received by using an audio adaptive detection threshold generated locally from the output signal of the detection circuit itself. The invention is used for example, in terrestrial or satellite radio communication systems.

Abstract: A communication system comprising a master control station and user terminals (100), in which synchronization in the outward link is achieved by transmitting a master code (MC) with the same clock frequency and carrier as the communication signals, wherein the master code (MC) is transmitted continuously and with greater power than that of the return link signals, and wherein the user voice activated message transmission carrier is broken during the pauses in a message. The invention relates in particular to a mobile satellite communications system.