195 results about "Satellite channel" patented technology

A mobile wireless terminal (MWT) receives IP packets destined for a ground network in a predetermined sequence order. The MWT fragments each of the IP packets into many smaller packet fragments, appends identifying information to each of the packet fragments, and transmits the packet fragments in parallel with one another over concurrently operating satellite channels. A receiving station receives the packet fragments transmitted by the MWT. The receiving station forwards the received packet fragments to a ground controller over a network connection, based on the identifying information appended to the packet fragments. The ground controller combines the packet fragments into reconstructed IP packets based on the identifying information appended to the fragments. The ground controller also sequences the reconstructed IP packets in the predetermined sequence order based on the identifying information. The ground controller forwards the reconstructed IP packets in the correct sequence order to the destination ground network. The same sequence of events occur in the opposite direction as well i.e., from the ground controller to the MWT.

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. A communication system comprises a plurality of mobile user terminal communicating with a gateway through a satellite channel using an asynchronous spread-spectrum medium access protocol without closed-loop power control, wherein the user terminals and said gateway are of the kind described above.

The invention discloses a satellite network simulation system and belongs to the technical field of satellite communication simulation. The system comprises a main control computer, a real-time satellite channel simulator and a plurality of service simulation node computers; the main control computer is provided with a satellite network simulation software system which can achieve establishment of a satellite network simulation scene, can select a routing algorithm, set link parameters and achieve the information management of the simulation satellite network, and is connected with the real-time satellite channel simulator by an RS232 bus; the service simulation node is provided with a service simulation software which achieves simulation of a transmission process of the satellite network service, and is connected with the real-time satellite channel simulator by an Ethernet port. The satellite network simulation system can truly and comprehensively simulate topological changes of the satellite network, channel characteristics of an inter-satellite link and a satellite-to-earth link, and the transmission process of the satellite network service under the laboratory condition.

An enhanced Base Transceiver Stations (BTS) includes a satellite receiver for use in receiving video and/or data signals. Since most video services (and many data services) are updated relatively infrequently, and since most such services require that the majority of traffic be sent from the core to the client (as opposed to from the client to the core), delivering such services over a satellite channel advantageously provides an opportunity to offer broadcast services, for example, with minimal use of the existing backhaul network, thereby advantageously eliminating the bottleneck typically created by the limited bandwidth of the backhaul network which is conventionally used to supply such video and/or data signals.

The invention discloses a bandwidth reservation-based very small aperture terminal (VSAT) satellite communication system bandwidth distribution method, and relates to the technical field of satellite communication. In the method, different applications are endowed with different priorities based on the conventional bandwidth reservation-based dynamic bandwidth distribution method, and the high-priority application can occupy the bandwidth section occupied by the low-priority application, vice is not; and in actual distribution, when the bandwidth section corresponding to the application has no enough idle bandwidth, and the bandwidth sections with low priorities are searched in turn from high priorities to low priorities. The method keeps the advantages of the conventional bandwidth reservation-based dynamic bandwidth distribution method such as simple implementation, few channel fragments and high distribution speed, coordinates different QoS (quality of service) demands and application scenes, realizes effective management of channel resources, improves the utilization rate of satellite channel resources in a network environment of multiple service types, meanwhile, simplifies star-earth interaction and reduces the time delay caused by bandwidth distribution.

The invention discloses a high dynamic satellite channel simulator, belonging to the field of satellite communications. The satellite channel simulator comprises a channel parameter generation unit, a channel simulation unit and a radio frequency unit. The whole system has the following working principle: a computer operates satellite channel simulation software, a satellite channel model, a communication frequency point, orbit parameters, terminal parameters and environmental parameters are configured, and a simulation program is started after configuration is completed. In the operating process of the simulation program, generated channel parameters are transmitted to the satellite channel simulation unit via the Ethernet network, the simulation unit loads the satellite channel parameters to a signal sent by a satellite communication device, the realization of channel simulation is completed, and finally, the radio frequency unit modulates the signal to radio frequency. The invention has the main goal of accurately and timely simulating a satellite channel under laboratory conditions, and a channel simulator with controlled cost and strong operability is provided for the development of the satellite communication device.

Provided is an apparatus and method for transmitting/receiving multiband broadcasting using scalable video coding, which can solve a limitation of a transmission band in a multichannel satellite broadcasting service and increase availability of a satellite broadcasting service by scalably encoding video data and transmitting the data using a different transmission band for each layer. The apparatus for transmitting multiband broadcasting using scalable video coding includes: a scalable video encoder for scalably encoding video data to generate a scalable video stream having multiple layers; a multiplexer for multiplexing the scalable video elementary stream having multiple layers, a compressed audio elementary stream, and program specification information to generate a transport stream (TS); and a multiband transmitter for separating packets of the TS into multiple TSs according to pre-given priority information and transmitting the packet streams using a different transmission band.

The invention discloses a satellite signal simulator and a satellite signal simulation method. The satellite signal simulator comprises a channel parameter generation unit used for calculating channel feature parameters according to satellite channel model parameters, communication frequency points, orbit parameters, terminal parameters and environment parameters; a radio frequency input unit used for converting intermediate-frequency signals of a satellite down to baseband signals; a channel simulation unit used for, according to the channel feature parameters, respectively performing Doppler frequency shift, multipath shadow fading, additive white noise and amplification filtering processing on the baseband signals; and a radio frequency output unit used for converting the signals output by the channel simulation unit into radio frequency signals for output. According to the invention, the simulated channel model types are enabled to be more diversified, the operation is convenient and visual, and the work accuracy and the data reliability of the satellite signal simulator are improved.

Disclosed is a method and apparatus for multipath mitigation using an antenna array. An antenna array made up of a plurality of antennas is used to receive satellite signals from satellites. Various configurations of antenna arrays is disclosed, including a linear vertical antenna array and a horizontal antenna array in which the antenna elements are located in a horizontal plane. A switch sequentially connects each of the antenna outputs to a single processing path to generate a common additive signal. The common additive signal is provided to satellite channel processors, each of which processes the signals from an associated satellite. A phase shift correction signal associated with each of the antennas is generated and synchronously applied to a carrier phase reference signal. A blocking signal may be applied to the satellite channel processors in order to block the processing of signals from an unwanted satellite.

The invention discloses a satellite mobile voice communication system with an extra-low speed, and relates to the satellite technology. The satellite mobile voice communication system with the extra-low speed based on a forwarding type satellite navigation system can be built by taking advantages of GEO (geostationary orbit) communication satellite resources (or other satellite resources) in the current forwarding type satellite navigation system, adopting a speech compression coding with the extra-low speed and a ground mobile voice communication network technology, and determining a communication system, signal characteristic and a system composition of the satellite mobile voice communication through an optimized design of satellite channel, a microminiature satellite terminal and an optimized design of ground network control technology. The system provided by the invention has the advantages of system resource sharing, flexible and effective network and combined navigation and communication capability, and can provide a low-cost voice communication application service and can be applied to an air-ground emergency communication system and a measurement system with small data volume demand.

A method for removing distortions in a transmitted signal transmitted by a high power amplifier in a satellite communications system. The method characterizes the high power amplifier to define a series of Volterra coefficients and uses those coefficients in an equalizer in a receiver in the communications system to remove the distortions. The equalizer is a non-linear soft interference cancellation and minimum mean square error equalizer that employs three processing operations including parallel soft interference cancellation, minimum mean square error filtering and a priori log-likelihood ratio calculations.

The character of the invention are as follows. The response mechanism of the TCP protocol is changed to the choice passive response. The sending ned only retransmits the data frames that the receiving end requests for re-transmitting definitely. The following measures change the conservative congestion control mechanism of TCP protocol to the active congestion control mechanism. The size of the slide window is set up as 32bit. When the congestion being detected, the decrement of the congestion window is 2/3 in TCP. In the congestion elusion stage, the congestion window takes on the non-linear growth. The rearward facing explicit congestion indicator is adopted so that the router informs the data-sending end directly that the network is about to be congested.

The invention provides a self-adaption covert communication method based on satellite channel coding, and directing at different channel encoding algorithms of block codes, RS codes, convolutional codes, serial concatenated code and the like, provides a capacity self-adaption method for secrete information embedding; further provides a channel encoding information embedding and extracting algorithm based on m sequences. By the utilization of the self-adaption covert communication method, the capacity of covert channels can be determined in a self-adaption mode according to different used channel encoding algorithms and different used communication environments; normal use of carriers containing secretes is not influenced, and main steganalysis attacks such as chi-square analysis attacks and RS analysis attacks can be resisted; under the condition that the satellite channel bit error rate is 10-3-10-5, quasi error-free transmission of secrete information can be realized.

The invention discloses a tour guide and safety control method based on satellite equipment. The method comprises the steps of: (1) acquiring longitude and latitude coordinates by connecting a satellite through a positioning module, by a mobile terminal; (2) judging whether to use a GPRS (General Packet Radio Service) or 3G (The 3rd Generation Telecommunication) communication channel or a Beidou satellite channel; (3) sending information containing the longitude and latitude coordinates to a communication server by a mobile terminal; (4) establishing persistent link with the mobile terminal through a communication server; (5) transmitting information sent by the mobile terminal to an application server through a communication server; and (6) carrying out various business logic calculations by the application server based on a data cloud service center, returning a calculation result to the mobile terminal, and by utilization of the mobile terminal, a satellite, the communication server and the application server, partially or completely completing the following operations: verifying the communication channel and recording the coordinate information and weather and disaster conditions of a current city in real time; performing navigation for lost; intelligently searching positions of accompanying partners; and automatically prompting on dangerous areas around according to user position to facilitate evasion of a user.

The invention discloses an outbound resource scheduling method and device of an outbound capacity restricted asymmetric satellite channel. The device comprises a buffer unit, a business type parameter configuration unit, a user parameter configuring unit, a prior scheduling acknowledgement unit, a non-prior scheduling acknowledgement unit and a resource allocation unit. Outbound messages are classified according to outbound beams; the data businesses belonging to the same outbound beam are classified according to business priorities; the data businesses belonging to the same business type K are arranged according to a first-in first-out sequence; with respect to the data business queue of any one outbound beam, users of [delta]T<k,i> <N*T <subframe > are selected out from the outbound queues of various current business types k as ''emergency users''; the ''emergency users'' are arranged according to [delta]T<k,i>; the outbound data with low [delta]T<k,i> are transmitted preferentially; if there is no ''emergency user'', all outbound users are ranked according to a weighted proportional fair algorithm; and the users with high priories are transmitted firstly. According to the method and the device provided by the invention, the quality of service demands of various businesses of the users and the system performance are ensured.

The invention relates to a DVB_RCS satellite channel dynamic distribution method based on predicating of a wavelet neural network. In terms of the multiple-scale features of satellite network flow, firstly, a wavelet neural network flow predicating algorithm is used for predicating real-time arrived flow of user stations of the next cycle and sending the real-time arrived flow to a gateway station; secondly, the gateway station performs distribution as needed according to the real-time access data rate of all the user stations in each channel application distribution cycle. The access data rate in the next cycle predicated by all the user stations serves as weight allocation residual capacitance. The DVB_RCS satellite channel dynamic distribution method based on predicating of the wavelet neural network is characterized in that in terms of the multiple-scale features of satellite service flow such as long relevance, self similarity and the multiple fractal property, the flow of the next moment is predicated with the wavelet neural network, the predication accuracy of the flow is improved, service time slots are reasonably distributed, service time delay is effectively shortened, the service quality of the users is ensured and the channel resource utilization rate is improved.

A channel encoding system and a channel decoding system for use in transmitting multiple high definition television programs in a single satellite channel. The channel encoding system may comprise a frame formatter that may be configured to format a transport stream to produce a block stream. An error correction encoder may be configured to encode the block stream to produce an error protected block stream. An interleave module may be configured to interleave the error protected block stream to produce a data stream. A turbo encoder may be configured to encode the data stream to produce an encoded stream. A bit-to-symbol mapper may be configured to map the encoded stream to produce a symbol stream capable of at least eight different symbols. Finally, a modulator may be configured to modulate the symbol stream.

The invention provides a Ka-band satellite channel modeling method integrated with meteorological factors and aims at solving the problems that data classification is lack of theoretical basis and simulation data are difficult to obtain in a traditional Ka-band satellite channel modeling process. The method comprises the following steps of: firstly, analyzing the propagation characteristic of a Ka-band satellite channel and the influences of multipath propagation, rainfall, atmospheric absorption, atmospheric scintillation and other factors to satellite channel modeling; and secondly, establishing a multistate Markov model of the Ka-band satellite channel by using a principal component analysis and fuzzy clustering analysis method. Through comparing the electrical level crossing-over rate and the average decay time of the established model with the electrical level crossing-over rate and the average decay time of a former model, the accuracy and the effectiveness of the channel model are checked, the theoretical basis is provided for resisting the rain attenuation of the Ka-band satellite channel, and meanwhile, Ka-band satellite channel modeling method has great practical significance in technical research on the aspects of signal modulation, coding mode and power control of Ka-band satellite communication.

The invention discloses a global navigation satellite system (GNSS)/inertial/navigation system (INS) ultra-tight combination navigation apparatus and a relative navigation system thereof. On the basis of the traditional GNSS/INS ultra-tight combination navigation apparatus, the provided GNSS/INS ultra-tight combination navigation apparatus uses a distributed filtering structure. Slave filters are used for carrying out pretreatment on I,Q signals of all satellite channels; and the processed information is sent to a combined filter. Meanwhile, the GNSS/INS ultra-tight combination navigation apparatus is also applied to a relative navigation system; while the navigation state and the inertia measurement of a carrier itself are received, navigation information and a carrier phase of another carrier are also received; with a dual-different carrier phase and inertia measurement, recursion filtering resolving is carried out by using an optimal kalman filter and an optimal relative position and a relative speed between each two carriers among multiple carriers are estimated.