245 results about "Radio over fiber" patented technology

A radio-over-fiber (RoF) wireless picocellular system adapted to form an array of substantially non-overlapping individual picocells by operating adjacent picocells at different frequencies is operated to form one or more combined picocells. The combined picocells are formed from two or more neighboring picocells by the central head-end station operating neighboring picocells at a common frequency. Communication between the central head-end station and a client device residing within a combined picocell is enhanced by the availability of two or more transponder antenna systems. Thus, enhanced communication techniques such as antenna diversity, phased-array antenna networks and multiple-input/multiple-output (MIMO) methods can be implemented to provide the system with enhanced performance capability. These techniques are preferably implemented at the central head-end station to avoid having to make substantial changes to the wireless picocellular system infrastructure.

Optical transmitters for radio over fiber systems are disclosed. More particularly, the optical transmitters include optically-injection-locked vertical cavity surface-emitting laser devices (OIL VCSELS). The transmitters include a master laser, at least one slave laser injection-locked by the master laser, and an equalizer/filter unit that enables the ratio of the carrier power to the sideband power in the output signal of the transmitter to be varied and optimized independently of the injection ratio of the transmitter.

A radio-over-fiber (RoF) system and method for controlling a transmission time is provided. In a Time Division Duplex (TDD) wireless communication system comprising a Base Station (BS) having a donor and a remote connected thereto via am optical fiber, upstream and downstream Radio Frequency (RF) signals are transmitted and received, and by reliably transmitting a switch control signal to the remote and simultaneously compensating for a transmission time delay occurring in the optical cable, time synchronization of the upstream and downstream RF signals transmitted and received via antennas of the BS and the remote is controlled, thereby efficiently increasing the performance of a TDD wireless service system.

A Fiber-wireless uplink consists of a wireless channel followed by a radio-over-fiber (ROF) link. Typically, nonlinear distortion of the ROF link is the major concern when the radio frequency is only a few GHz. This especially severe in the uplink, because of the multipath fading of the wireless channel. A Hammerstein type decision feedback equalizer is described for the fiber wireless uplink, that compensates for nonlinear distortion of the ROF link as well as linear dispersion of the wireless channel. Since the linear and nonlinear parts of the receiver are separated, tracking the fast changing wireless channel is virtually independent of compensating for the relatively static nonlinearity. Analytical results show that the receiver provides excellent compensation with notably less complexity.

A radio over fiber link apparatus for transmitting/receiving radio frequency up/downlink signals in a TDD mobile communication system. The radio over fiber link apparatus includes a center site for receiving radio frequency signals from an access point of the mobile communication system. The center site has a first electro-optic converter for converting the radio frequency signals into optical signals, bias control of the first electro-optic converter being performed based on the switching of TDD signals; and a remote for transmitting the radio frequency signals to a mobile communication terminal through an antenna. The remote site has a first photoelectric converter for converting the optical signals transmitted through an optical fiber from the center site into radio frequency signals.

Disclosed is an all-optical frequency upconverter in a radio-over-fiber system that outputs upconverted optical radio frequency (RF) signals using an optical intermediate frequency signal and an optical local oscillation signal. The all-optical frequency upconverter includes a semiconductor optical amplifier that mixes the optical intermediate frequency signal with the optical local oscillation signal through four wave mixing, and an optical filter that filters a plurality of frequency component signals, which are generated through the four wave mixing, to extract optical RF signals. According to the invention the system configuration can be made simple, and wide LO and IF frequency bandwidths can be provided.

A radio-over-fiber (RoF) optical fiber cable system with transponder diversity for a RoF wireless picocellular system that includes at least one optical fiber cable. The at least one optical fiber cable supports one or more groups of two or more transponders, wherein the transponders in a given group are arranged to form substantially co-located picocells. The transponders in each transponder group may also have one of two orthogonal antenna polarizations. A diversity combiner optically coupled to each transponder determines respective signal strengths from each transponder in each transponder group. The transponder with the greatest signal strength in a given transponder group is selected to form the picocell for the given group. This allows for the optical fiber cable system to adjust to changes in the signal strength of each picocell, such as caused by a transponder obstruction or failure.

An apparatus includes multiple signal paths for optically converting an optical signal to multiples of the optical signal at different respective carrier frequencies for reducing interference between wireless transmissions of the multiples of the optical signal. Preferably, the converting includes a first modulator for modulating the optical signal into a first optical carrier and an initial first-order sideband signal with a frequency spacing twice that of the first optical carrier and a first interleaver for separating the first optical carrier and the initial first-order sideband signal. The converting also includes a second phase modulator for modulating the first optical carrier into a second optical carrier and a second first-order sideband signal with a frequency spacing twice that of the second optical carrier.

An optical fiber radio transmission system is provided which is capable of considerably improving the received dynamic range of radio signals and, in addition, is capable of optically transmitting radio signals while preventing the deterioration of transmission performance and the loss of linearity of an input signal more easily. A received level detection section 111 detects which one of predetermined levels, i.e., Level I, Level II, and Level III, the received level of a radio signal received by an antenna 400 falls under. A signal control section 112 performs an amplification/attenuation process on the radio signal in accordance with the detected level. A control information sending section 113 superimposes control information indicating the detected level on a primary signal obtained after the amplification/attenuation process. This signal is converted to an optical signal and transmitted. An optical to electrical conversion section 211 converts the optical signal received from a transmitting unit to an electrical signal. A control information extraction section 212 extracts the level from the control information, which has been superimposed on the primary signal. A signal control section 213 performs an amplification/attenuation process on the primary signal in accordance with the extracted level.

A radio-over-fiber (RoF) hybrid wired/wireless transponder is disclosed that is configured to provide both wireless and wired communication between a hybrid head-end and one or more client devices. The hybrid transponder includes optical-to-electrical (O/E) and electrical-to-optical (E/O) conversion capability and is configured to frequency multiplex/demultiplex electrical “wired” signals and electrical “wireless” signals. The electrical wireless signals are wirelessly communicated to the client device(s) via a multiple-input/multiple-output (MIMO) antenna system within a cellular coverage area. The electrical wired signals are communicated to the client device(s) via a wireline cable that plugs into a wireline cable port on the transponder. The hybrid RoF system includes a hybrid head-end capable of transmitting and receiving wired and wireless optical signals, and an optical fiber cable that is optically coupled to the hybrid head-end and to at least one hybrid transponder. Drop-down transponder configurations that allow for easy wired and wireless connectivity between the client device(s) to the transponder(s) are also disclosed.

A multi-port accumulator apparatus for a radio-over-fiber (RoF) wireless picocellular system that includes a housing that supports a tail cable port and a number of RoF transponder ports. The tail cable port is optically coupled to the RoF transponder ports so as to provide for optical transmission of uplink and downlink optical signals between the tail cable port and each of the transponder ports. The tail cable port is also electrically coupled to each transponder port so as to provide electrical power to each of the plurality of transponder ports. The multi-port accumulator supports two or more RoF transponders, one at each RoF transponder port. Each RoF transponder includes a directional antenna system that forms a picocellular coverage sub-area, with the combined sub-areas constituting a picocellular coverage area for the multi-port accumulator. The multi-port accumulator allows for the quick installation and deployment of large numbers of RoF transponders without having to individually connect each RoF transponder to a pair of downlink and uplink optical fibers carried by an optical fiber RF communication link.

Transponder systems and methods for radio-over-fiber (RoF) wireless picocellular system are disclosed. One type of transponder system includes a RoF transponder used in combination with at least one radiation-reflector assembly to provide for enhanced antenna directivity of the transponder. Another type of transponder system is a transponder node assembly, wherein two or more transponders are integrated into a single assembly, thereby reducing cost while facilitating RoF wireless picocellular system deployment. Another type of transponder system provides one or more transponders in a RoF wireless picocellular system with radio-frequency identification (RFID) tags, and uses an RFID tag reader to locate and read information from the transponders, as well as to perform transponder mode selection. Another type of transponder system is directed to a tether cable assembly that includes a dispensible/retractable coiled tether cable housed in a protective housing for connecting the tether cable to a transponder.

Communication devices, systems, and methods for dynamic cell bonding (DCB) for Radio-over-Fiber (RoF)-based networks and communication systems are disclosed. In one embodiment, a method of operating an optical fiber-based wireless communication system is provided. The method includes determining a first plurality of remote units in a cloud bonded to a Radio-over-Fiber (RoF) communication session. The method also includes measuring a received signal strength from each of the first plurality of remote units. The method also includes measuring a received signal strength from each of a second plurality of remote units in the cloud not bonded to the RoF communication session. At least one of the second plurality of remote units is dynamically bonded to the RoF communication session if the measured received signal strength of the one of the second plurality of remote units is greater than the measured received signal strength of the first plurality of remote units.

A radio base station for a mobile radio network, includes a set of remote units connected with the radio base station, preferably via a radio over fibre arrangement. Each remote unit provides radio cell coverage by means of a set of communication channels, and is equipped with a respective set of antenna elements. The communication channels are distributed over the antenna elements according to an assignment scheme that is dynamically variable.

The invention discloses a wireless terminal transceiver of a 60GHz RoF (Radio over Fiber) access system. Secondary subharmonic frequency mixing is adopted, and the frequency of a needed local oscillation signal is reduced in a frequency multiplication frequency mixing way, so that the problem of leakage of the local oscillation signal to an antenna, i.e., a radiofrequency transmitting end in the conventional wireless terminal transceiver scheme is solved, and the circuit modulation performance is improved. Meanwhile, a downlink medium frequency analog signal obtained after secondary subharmonic down-conversion is subjected to downlink medium frequency digital signal processing after ADC (Analog to Digital Conversion) to obtain a needed downlink digital baseband signal; and an uplink digital baseband signal is subjected to uplink medium frequency digital signal processing to obtain an uplink medium frequency digital signal. A series of medium frequency digital signal processing such as odd-even extraction or interpolation, symbol modulation, delay filtering, demodulation or modulation and the like is performed in a digital domain, so that the problem of IQ orthogonal mismatch caused by 90-degree phase change on a local oscillation signal for obtaining two paths of analog signals in an analog frequency domain of the conventional receiver is solved.

Wired/wireless optical signal modulation and demodulation apparatuses and methods using an intensity modulation/direct detection method and an orthogonal frequency division multiplexing (OFDM) method are provided. A unipolar OFDM symbol frame is generated by determining the polarity of each of a plurality of sub-frames of a bipolar OFDM symbol frame which comprises both a plurality of positive pulses and a plurality of negative pulses, inverting the polarity of the sub-frames which are determined to be negative, delaying one of the positive sub-frame and a positive sub-frame obtained through the inversion by the duration of the sub-frames, and multiplexing the result of the delaying and whichever of the positive sub-frame and the positive sub-frame obtained through the inversion is not the result of the delaying. The unipolar OFDM symbol frame can guarantee high power amplification efficiency and high transmission power efficiency, and is robust against a multi-path channel environment. Therefore, the unipolar OFDM symbol frame can be used in various optical signal modulation/demodulation methods for wireless indoor broadband optical transmission devices, wired broadband optical transmission devices using multi-mode optical fibers, and radio-over-fiber devices which transmit baseband analog signals as optical signals.

The invention discloses a device and method for generating eight frequency multiplication millimeter waves by utilizing a Mach-Zehnder modulator, and the device and method are mainly used for the generation of the optical millimeter waves in a radio over fiber (ROF) access network. The method is shown in attached figures: optical millimeter wave signals, the frequency of which is eight times as large as that of local oscillator signals, are generated by utilizing nonlinear characteristics and interference superposition characteristics of two parallelly-connected double-parallel lithium niobate Mach-Zehnder modulators (DPMZM) and under the condition of an appropriate DC bias voltage, thereby greatly reducing equipment frequency index required for generating high frequency/ extremely high frequency signals, and reducing the system cost. According to the device and method, specific phase modulation index is not needed, and radio-frequency signals can be flexibly adjusted, so that the requirement for radio-frequency power is lowered; and meanwhile, stray sideband can be well restrained.

The invention relates to a serial-parallel connection modulation optical frequency multiplication millimeter-wave RoF (Radio Over Fiber) system and a QPSK (Quadrature Phase Shift Keying)/16QAM (Quadrature Amplitude Modulation) modulation method thereof. The system comprises a central station, a base station and fiber connection thereof, wherein the central station comprises a single longitudinal mode laser, a double-electrode Mach-Zehnder optical modulator, an IQ optical modulator, two microwave signal sources, a pi phase shifter, a pi/2 phase shifter and an erbium doped fiber amplifier; and the base station comprises an optical detector, a front low-noise amplifier, two millimeter-wave bandpass filters, two millimeter-wave amplifiers, a millimeter-wave duplexer and a millimeter-wave antenna. In the method, the cascading of the double-electrode Mach-Zehnder optical modulator and the IQ optical modulator is adopted, and a balanced optical waveguide structure formed by integrating the two optical modulators avoids the influence of optical source phase interference noise caused by support arm optical delay inequality on modulation signals.

An optically-switched fiber optic communication system, such as a Radio-over-Fiber (RoF) based optical fiber link system, may be used to increase the range of peer-to-peer communications. The optically-switched fiber optic communication system may include a head-end unit (HEU) having an optical switch bank. Fiber optic cables comprising optical fibers optically couple the HEU to one or more remote access points in different coverage areas. The optical switch bank in the HEU provides a link between the remote access points in the different coverage areas such that devices in the different cellular coverage areas can communicate with each other over the optical fibers through the HEU. By using the optically-switched fiber optic communication system, the range and coverage of communication between devices may be extended such that devices in different coverage areas and devices using different communication protocols can communicate.