Tellabs Operations, Inc.

Nec Usa, Inc.

Other

Samir Kapoor

Daniel J Marchok

Ravi Chandran

Richard C Younce

George Cherian

Santosh Paul Abraham

Peerapol Tinnakornsrisuphap

Jouni Kalevi Malinen

Rolf De Vegt

Peter J W Melsa

Slobodan Nedic

Peter Jw Melsa

Prashant Choudhary

A method includes, at a first device while the first device is connected to a wireless local area network (WLAN) and a second device is unconnected to the WLAN, establishing a secure channel to the second device using an EAP exchange. The method also includes sending at least one credential associated with the WLAN to the second device via the secure channel to enable the second device to connect to the WLAN.

Using a mobile device to enable another device to connect to a wireless network

A method and apparatus for interference suppression in wireless communication systems, especially Orthogonal Frequency Division Multiplexed (OFDM) systems, is presented. The array apparatus includes a two-tier adaptive array system, which provides for both spatial diversity and beamforming at the uplink and includes sub-arrays spaced at a distance sufficient to provide spatial diversity and support beamforming or scanning. A Direction of Arrival (DOA) of signals impinging upon the array can be calculated by comparing signals from sub-array elements. Each sub-array can be filtered or beamformed to provide high gain to desired signals received from the DOA (which may be a multipath signal) while simultaneously dampening-out undesired signals, such as co-channel interference (CCI) in the frequency band of operation. The DOA is also used for allocating frequency bins for data signals, such as in an OFDM system, to provide weighted guidelines for bin allocation to maximize received signal power.

Method and apparatus for interference suppression in orthogonal frequency division multiplexed (OFDM) wireless communication systems

A multi-point communications system is set forth herein. The communications system includes a transmitter for transmitting OFDM/DMT symbols over a predetermined number of bins across a transmission medium. The OFDM/DMT symbols are generated using at least one timing signal. At least one of the predetermined number of bins includes a pilot tone sub-symbol having a frequency corresponding to a clock signal. The communications system may also include a receiver for receiving the OFDM/DMT symbols via the transmission medium. The receiver demodulates the received symbols using at least one timing signal.

Apparatus and method for clock synchronization in a multi-point OFDM/DMT digital communications system

A multi-point communications system is set forth herein. The communications system comprises a transmitter for transmitting OFDM/DMT symbols over a predetermined number of bins across a transmission medium. The OFDM/DMT symbols are generated using at least one timing signal. At least one of the predetermined number of bins includes a pilot tone sub-symbol having a frequency corresponding to the clock signal. The communications system also includes a receiver for receiving the OFDM/DMT symbols from the transmission medium. The receiver demodulates the received symbols using at least one timing signal. The receiver has a first pilot tone search mode of operation in which the receiver adjusts its timing signal to scan the frequency range of the predetermined number of bins looking for the pilot tone sub-symbol and identifies the bin including the pilot tone sub-symbol. The receiver further has a subsequent second pilot tone acquisition mode in which the receiver adjusts the timing signal to receive the identified bin containing the pilot tone sub-symbol and measures phase differences between successive pilot tone sub-symbols to thereby perform a further adjustment of the timing signal so that the pilot tone sub-symbol is received within a frequency range sufficient for subsequent phase locked loop processing thereof.

A method and apparatus for interference suppression in wireless communication systems, especially Orthogonal Frequency Division Multiplexed (OFDM) systems. The array apparatus includes a two-tier adaptive array system which provides for both spatial diversity and beamforming at the uplink. The adaptive array is comprised of sub-arrays spaced at a distance sufficient to provide spatial diversity, ideally 5 to 15 wavelengths at the frequency of operation. Each sub-array is composed of at least two antenna elements spaced in proximity sufficient to provide effective beamforming or scanning, ideally less then one-half of one wavelength at the frequency of operation. The Direction of Arrival (DOA) of signals impinging upon the array can be calculated by comparing signals from sub-array elements. Each sub-array can then be filtered or beamformed so as to provide high gain to desired signals received from the DOA (which may be a multipath signal) while at the same time damping out undesired signals such as co-channel interference (CCI) in the frequency band of operation. The DOA is also used in a method of allocating frequency bins for data signals, such as in an OFDMA system, to provide weighted guidelines for bin allocation to maximize received signal power.

A receiver for improving the performance of conventional Discrete Multitone Modulation (DMT) based Asymmetric Digital Subscriber Line (ADSL) modems, in the presence of noise and/or interference. A demodulator having an FFT followed by a single-tap-per-bin frequency-domain equalizer is augmented by an additional data-path utilizing windowing or pulse shaping. Windowing is done independently for each symbol over the orthogonality interval and efficiently in the time domain or frequency domain. A decision feedback equalizer at the output of the windowed data-path cancels inter-bin-interference created by windowing.

Receiver for discrete multitone modulated signals having window function

A multi-point communication system that comprises a head end unit disposed at a primary site and a plurality of receivers disposed at remote sites. The head end unit includes a transmitter for transmitting OFDM/DMT symbols over a predetermined number of bins across a transmission medium. The OFDM/DMT symbols are transmitted in periodically occurring formatted symbol frames. The cyclic prefix includes a predetermined periodic signal superimposed thereon. The receivers receive the OFDM/DMT symbols over a subset of the predetermined number of bins from the transmission medium and use the superimposed signals to attain symbol alignment. In accordance with a further aspect of the present invention, the receivers apply a predetermined incremental phase shift to received samples corresponding to the received OFDM/DMT symbols to thereby compensate for phase shifts.

Apparatus and method for symbol alignment in a multi-point OFDM/DMT digital communications system

Communication system clock synchronization techniques

A communications system includes a transmitter that generates symbols in a plurality of bins using a first timing signal and generates a reference signal by using the first timing signal. The transmitter transmits the symbols and the reference signal carried by a first signal, which is frequency multiplexed with a second signal from another transmission source. A demultiplexer frequency demultiplexes the first signal, which is downconverted in response to a control signal to generate a frequency downconverted signal, and a processing circuit is responsive to the frequency downconverted signal to identify the predetermined bin and to generate the control signal in response to the identification of the predetermined bin.

Communication system signal synchronization techniques

A method and apparatus for allocating bits to subchannels in a discrete multitone environment. The method employs the use of precalculated and prestored look-up tables which take into account a desired bit error rate, signal-to-noise ratio gap for a particular coding scheme, and gain scaling factor. This eliminates the need for the communication device to conduct complex and time consuming calculations. During the training sequence portion of data communication channel establishment, the measured signal-to-noise ratio for each subchannel is compared with values in the precalculated look-up tables to determine the bit allocation for that subchannel. The bit allocation value is stored in a data structure in the communication device. A gain scaling factor for each subchannel is then determined and stored as a data structure. The bit allocation and gain scaling data can then be transmitted to a partner communication device in order to instruct the transmitter how to load each subchannel.

Method and apparatus for discrete multitone communication bit allocation

An apparatus for receiving a discrete multi-tone signal over a communications channel having an impulse response h(n), energy of the impulse response being substantially concentrated in a first band of samples, the apparatus including: a receiver for receiving the discrete multi-tone signal; and a T coefficient finite impulse response time-domain equalizer included in the receiver, the time-domain equalizer having an output additive noise signal, the T coefficients of the time-domain equalizer being provided such that: (a) energy of an effective impulse response h (n) of at least the communications channel combined with the time-domain equalizer is substantially concentrated in a second band of V&plus;1 samples, whereby the second band of samples is shorter than the first band of samples; and (b) a variance in a frequency spectrum of the output additive noise signal of the time-domain equalizer is controlled.

DMT time-domain equalizer algorithm

A multi-point communications system that comprises a head end unit disposed at a primary site and a plurality of receivers disposed at remote sites. The head end unit includes a transmitter for transmitting OFDM/DMT symbols over a predetermined number of bins across a transmission medium. The OFDM/DMT symbols are transmitted in periodically occurring formatted symbol frames. The cyclic prefix includes a predetermined periodic signal superimposed thereon. The receivers receive the OFDM/DMT symbols over a subset of the predetermined number of bins from the transmission medium and use the superimposed signals to attain symbol alignment. In accordance with a further aspect of the present invention, the receivers apply a predetermined incremental phase shift to received samples corresponding to the received OFDM/DMT symbols to thereby compensate for phase shifts. The multi-point communications system may include a similar system for aligning symbols transmissions from a remote service unit having a transmitter. Such a system includes a plurality of remote service units each including a transmitter for transmitting OFDM/DMT symbols over a predetermined number of bins across a transmission medium. Each of the plurality of remote service units is operable in a symbol alignment mode in which the transmitter transmits a broad band periodic signal. The head end unit includes a receiver for receiving the OFDM/DMT symbols, including the broad band periodic signal, from the transmission medium. The head end unit uses the time position of the broad band periodic signal to align the symbol transmissions of the remote service unit.

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South Bend, IN, United States of America

Samir Kapoor