141 results about "Optical wireless" patented technology

In a free space communication network in which different communication nodes are linked together by directed beams, a method for dynamically configuring the topology of the network allows the transmission directions of the communication nodes to be autonomously changed to communicate with a new node as dictated by the needs of the network. Moreover, the nodes can be switched from directional to broadcast and back again on an as-needed basis. The network consists of a topology that can be rapidly and physically reconfigured as required to provide multiple connectivity, a desired quality of service, or to compensate with the loss of communication links between nodes. The loss of direct communication between any two nodes in an optical network can occur because of obscuration of the atmospheric path between the two nodes. The directed beam which provides the communication channel between the two nodes can, in this situation, be steered to direct its energy towards another accessible node.

A wireless communication method between mobile terminals using visible light and a mobile terminal therefore are disclosed. The method includes: periodically transmitting device discovery signals for searching for a visible light communication device when there is a request for a visible light communication; transmitting only reference clock signals between the device discovery signals; and connecting a link to a receiving terminal to transmit data when a response signal for the device discovery signal is received from the receiving terminal.

Certain implementations of the disclosed technology may include systems, methods, and apparatus for carrier-embedded optical radio-over-fiber (RoF) communications. Example embodiments of the method may include modulating a baseband signal with and an intermediate frequency (IF) and a radio frequency (RF) carrier signal to produce a RF modulated optical signal, transmitting the RF modulated optical signal to a remote access point with an optical fiber, and detecting the transmitted RF modulated optical signal. The method may also include receiving a RF uplink signal and mixing a harmonic of the RF carrier signal with the received RF uplink signal to down-convert the received RF uplink signal to an IF uplink signal. The method may include modulating a second optical source with the IF uplink signal to produce an IF uplink optical signal, transmitting the IF uplink optical signal via an optical fiber, and detecting the IF uplink optical signal.

A technique for synchronizing the servo control systems between two optical wireless links (OWLs) that are in communication with one another. This synchronization allows the alignment in time of the various tasks to be assigned in a desired time period. The synchronization is not intended to synchronize the two OWLs down to the processor clock level, but rather at the servo sampling level, preferably to within a few percent of the servo sampling time. This synchronization may be advantageous in improving processor efficiency and control loop performance, and or improving system calibrations.

The invention provides a 60GHz millimeter wave-based optical wireless fusion video transmission system and method. According to the system, at a junction center, a single-arm Mach-Zehnder intensity modulator is adopted to generate optical millimeter waves through an optical carrier suppression manner, wherein the frequency of the optical millimeter waves is twice of that of radio frequency signals; then, downlink baseband data signals, i.e. high-definition television data stored in a DVD (Digital Video Disk), are modulated to the optical millimeter waves by using another electro-optical Mach-Zehnder modulator; the downlink signals are transmitted to a base station unit through an optical fiber link, and 60GHz electrical millimeter waves are generated from optical-millimeter-wave signals by a high-speed photolectric transducer, are amplified, and then are sent out by an antenna; and the optical-millimeter-wave signals received through the antenna by a user unit are reconstructed into downlink video baseband data signals by using coherent demodulation. According to the system, the radio frequency signals with the frequency of 29GHz are adopted to generate the optical millimeter waves with the frequency of 58GHz, the video transmission rate is 500Mb/s, the transmission distance for data in a downlink in monomode optical fiber at the transmission rate of 500Mb/s is 200m, and the wireless transmission distance can reach 5m.

A service providing system comprising a server device, a terminal device, and a service providing device in combination with an optical wireless tag device to achieve transmitting of ID, password, or other service information stored in the service providing device in a non-contact and non-broadcasting manner, thus enabling highly secured and reliable services.

An optical wireless network includes an optical coupler for diverting received millimeter-wave signals comprised of an optical carrier and second order sidebands into multiple transmission paths; a downstream optical path being one of the multiple transmission paths and including an optical filter for filtering passing through the optical carrier with a single sideband, a converter for converting the optical carrier and single sideband to a corresponding electrical signal for amplification and broadcast transmission from an antenna; and an upstream path being one of the multiple transmission paths and having a filter for passing through the optical carrier only from the mm-wave signals and an intensity modulator driven by data received over the antenna to modulate the optical carrier for optical transmission to a receiving destination.

A system and method is disclosed for mitigating the scintillation and fading effects of baseband wireless, radio frequency wireless, optical wireless and satellite communication links. The system uses a space-time channel model to derive an optimal processing architecture for signal recovery through a scintillation channel. The signal power is collected by space-time sampling within the four dimensional volume of the spatial and temporal spread. Consequently, the space-time equalizer can effectively recover the lost signal power induced by the spreading effects of atmospheric scintillating medium. The advantages of this invention include a decrease in link outages resulting in higher link availability and more reliable data network services.

Optical wireless links automatically align themselves using feedback information that is transmitted over the light beams being aligned. Each link performs an acquisition routine in which its light beam is swept through a pre-defined pattern while transmitting its beam alignment information. When a link receives beam alignment information from a remote link, it updates its transmission to include the alignment information received from the remote link. At some point during the acquisition routine, the remote link will receive its own alignment information “echoed back” from the first link and will re-align its beam accordingly. At some point, each link will have received its own alignment information echoed back from the other link and will have aligned itself to that position. Data communication can begin at that point, or a more refined alignment step can then be performed. The alignment information can be based upon position, sample number, or time transmitted.

In an optical wireless network, where light beams are transmitted over-the-air, reflections of the transmitted light beams may cause a receiver of an optical wireless device to detect and subsequently lock onto the signal that it transmitted. By doing so, the network is effectively broken. A method and apparatus to detect the reception of reflected signals using minimal additional hardware and data is presented. Should a reflected signal be detected, the receiver is prevented from locking onto the signal, allowing the receiver to detect and subsequently lock onto light beams originating from other optical wireless devices.

The invention relates to a multi-user visible light communication method and a multi-user visible light communication system. The method comprises the steps of generating a plurality of chaotic sequences for identifying different users in a multi-user visible light communication system; performing CSK modulation on bit information input by each user of a transmitting end, thus obtaining a three-dimensional transmission vector, including RGB information, corresponding to each user; modulating the transmission vectors for the second time by using the chaotic sequences corresponding to the users, thus obtaining transmission matrixes corresponding to the users, and transmitting the transmission matrixes to a receiving end via an optical wireless channel; receiving the matrixes transmitted by the optical wireless channel by the receiving end, demodulating the matrixes by using the chaotic sequences corresponding to the users, thus obtaining the three-dimensional transmission vectors, including RGB information, corresponding to the users; and demodulating each three-dimensional transmission vector to obtain the bit information transmitted by the corresponding user. According to the multi-user visible light communication method, the interference among users can be reduced, the reliability and security of the system can be improved, and the system capacity can be increased.