In order to solve problems arising when a communication system such as a wireless LAN is constructed as a decentralized distributed type network without a relationship of control station and controlled stations such as a master station and slave stations, in a wireless communication system composed of a plurality of communication stations without a relationship of control station and controlled stations, respective communication stations transmit beacons with information concerning a network written thereon with each other to construct the network, and it becomes possible to make sophisticated judgment such as communication states of other communication stations by those beacons.

Wireless communication system, wireless communication apparatus and wireless communication method and computer program

A method of and wireless communications unit (WCU) for providing service in a mesh network (200) includes a receiver for receiving a first signal from a first WCU (201) in the mesh network; a directional antenna (427) system for coupling the signal to the receiver, the signal arriving from a first selected one of a first plurality of directions; a controller (413) to control the directional antenna system such that the signal is coupled to the receiver according to a local predetermined pattern of the first plurality of directions; and a transmitter to send a second signal in a second selected one of the first plurality of directions, where the controller interrupts the local predetermined pattern and selects the second direction.

Method and apparatus for increasing service efficacy in an ad-hoc mesh network

A wireless router access point for use with a mesh network employing a mesh protocol and a point-to-multipoint network employing a point-to-multipoint protocol, and a multimedia system employing the same. In one embodiment, the wireless router access point includes a mesh access point subsystem configured to translate between a point-to-multipoint protocol and a mesh protocol to communicate with the mesh network. The wireless router access point also includes a point-to-multipoint access point subsystem configured to translate between a mesh protocol and a point-to-multipoint protocol to communicate with a user of the point-to-multipoint network.

Method and system for providing broadband multimedia services

The invention is related to methods and apparatus for controlling and adapting a digital predistortion linearizer for amplification of bandlimited signals using non-linear amplifiers. The control method advantageously permits the predistortion function applied by a predistortion entity to provide a relatively constant gain. This attribute is advantageous for operation within cellular radio systems, which often employ digital power control systems. However, the disclosed techniques can also be applicable to virtually any type of digital predistortion for which an input signal or reference signal to be amplified is predistorted in a manner that is complementary to the distortion induced by a non-linear amplifier. Embodiments of the invention advantageously enhance the practicality of using digital linearization and predistortion amplification techniques. Embodiments of the invention can automatically adjust the characteristics of a predistorted signal so that a deviation from overall linearity is compensated and subsequently reduced while maintaining a nearly constant gain attribute.

Constant gain digital predistortion controller for linearization of non-linear amplifiers

A digital communications transmitter (100) includes a digital linear-and-nonlinear predistortion section (200, 1800, 2800) to compensate for linear and nonlinear distortion introduced by transmitter-analog components (120). A direct-digital-downconversion section (300) generates a complex digital return-data stream (254) from the analog components (120) without introducing quadrature imbalance. A relatively low resolution exhibited by the return-data stream (254) is effectively increased through arithmetic processing. Distortion introduced by an analog-to-digital converter (304) may be compensated using a variety of adaptive techniques. Linear distortion is compensated using adaptive techniques with an equalizer (246) positioned in the forward-data stream (112). Nonlinear distortion is then compensated using adaptive techniques with a plurality of equalizers (226) that filter a plurality of orthogonal, higher-ordered-basis functions (214) generated from the forward-data stream (112). The filtered-basis functions are combined together and subtracted from the forward-data stream (112).

Transmitter predistortion circuit and method therefor

A method for an adaptive equalization apparatus (500) in a multiple-link hopping radio system includes hopping among a plurality of radio links to receive variable-length bursts of radio signals on the plurality of radio links and equalizing amplitude and phase variations of a slow channel for each radio link from a received burst on the radio link. Further, the method includes storing the estimated tap coefficients pertinent to each radio link and using the tap weights of the current burst of the radio link to reliably pre-compensate the channel amplitude and phase distortion of a next received burst on the radio link.

Adaptive equalizer system for short burst modems and link hopping radio networks

A method for a combined adaptive digital pre-distorter and pre-equalizer apparatus in single- and/or multiple-link hopping radio systems including hopping among a plurality of radio links to transmit variable-length bursts of radio signals on the plurality of radio links. Further, pre-distorting amplitude and phase of transmitted signal constellations based on the inverse AM-to-AM and AM-to-PM characteristics and the operating conditions of the high-power amplifier, respectively. Further, pre-equalizing amplitude and group-delay variations of the transmit RF radio using the pre-stored estimated complex tap coefficient of the pre-equalizer under different frequency bands.

Combined digital adaptive pre-distorter and pre-equalizer system for modems in link hopping radio networks

A method for a carrier phase recovery apparatus in a multiple-link hopping radio system includes hopping among a plurality of radio links to receive bursts of radio signals on the plurality of radio links and determining channel information for each radio link from a received burst on the radio link. Further, the method includes storing the determined channel information and using the determined channel information for the radio link to reliably recover the carrier phase of a next received burst on the radio link.

Jun Lu

Papers

Adaptive equalizer system for short burst modems and link hopping radio networks

Combined digital adaptive pre-distorter and pre-equalizer system for modems in link hopping radio networks

Carrier phase recovery system for adaptive burst modems and link hopping radio networks