Other

Agere Systems Inc.

Lucent Technologies Inc.

Agere Systems Guardian Corp.

Intel Mobile Communications Gmbh

Xiao-an Wang

Steven P Pekarich

Jens Berkmann

Richard Adam Cesari

Sameer V Ovalekar

Roger A Fratti

Mohit Kishore Prasad

Thomas Baker

David G Martin

Eliahou Arviv

Yi-Chen Li

Oliver Ridler

Stanley Reinhold

Robert L Lang

Dwane A Bell

Multipoint broadcasting relying on channel reciprocity in a TDD network requires that the broadcasters be calibrated. In the cases where the relative amplitude profiles and nonlinear phases are time-invariant or slow-varying, broadcaster calibration reduces to phase synchronization. Methods and apparatus are described that provide broadcaster calibration and phase synchronization with terminal feedback and overcome the drawbacks of self-calibration. The methods and apparatus are capable of calibrating hundreds of broadcaster antennas in massive antenna applications while maintaining an extremely low overhead. Applications of the described methods and apparatus include multipoint broadcasting in wireless networks, also known as coordinated multipoint transmission, or CoMP, in LTE-A (long-term evolution, advanced) networks, and distributed MIMO, massive MIMO, massive beamforming, etc., in other networks including 5G and 802.11. Applications also include frequency and phase synchronization of a cluster of wireless devices.

Phase synchronization and channel reciprocity calibration of antennas via terminal feedback

Methods and apparatus of channel estimation using time-domain parameter extraction are disclosed. The wireless channel can be modeled by a multipath model with a limited number of parameters in the continuous time domain. Extracting the time-domain parameters and then reconstructing the channel yields channel estimates that have better accuracy. Time-domain parameter extraction also has lower computational complexity than existing methods.

Channel estimation by continuous time-domain parameter extraction

Methods and apparatus of channel estimation using time-domain parameter extraction are disclosed. The wireless channel can be modeled by a multipath model with a limited number of parameters in the continuous time domain. In the discrete time domain, the multipath model leads to channel impulse responses that have a limited number of channel taps with non-negligible energy. Extracting the time-domain parameters and then reconstructing the channel yields channel estimates that have better accuracy. Time-domain parameter extraction also has lower computational complexity than existing methods.

Channel estimation by time-domain parameter extraction

Large-dimension MIMO and multipoint broadcasting in new generation of wireless networks create high demand for various types of pilots in transmission signals for channel estimation, data demodulation, synchronization, etc. More pilots, as in existing networks, use more resources and thus diminish the network capacity. Methods and apparatus of heterogeneous pilots are disclosed. A heterogeneous pilot has its own signal characteristics that are different from the primary information-bearing signals in the network. Heterogeneous pilots can be spread-spectrum signals in an OFDM-based wireless network. Heterogeneous pilots use no network resources, and can be as many as desired, and can be designed to have versatile utilities. Also described are methods and apparatus of heterogeneous pilot cancellation that minimizes the interference of heterogeneous pilots on the primary information-bearing signals. Applications of the described methods and apparatus include OFDM-based wireless cellular networks, such as LTE-advanced and Wireless LAN.

Heterogeneous pilots

MU-MIMO and CoMP have potentials to increase the cell capacity by many folds. Interferences and channel feedback overhead, however, severely limits such potentials. Method of reference signal-based grid of beams (RS-GOB) is described. RS-GOB distributes the effective antennas of a base station into multiple beams, thereby significantly reducing the feedback overhead of CoMP and making effective use of CoMP to turn the interferences into cooperating useful signals. RS-GOB also reduces the need for small HetNet cells, which mitigates the interferences of small HetNet cells on macro cells.

Coordinated multi-point transmission and multi-user MIMO

A description is given of an apparatus that includes a division unit configured to receive a data stream and to divide the received data stream into a plurality of data segments. The apparatus further includes a plurality of first CRC check units, wherein each of the first CRC check units is configured to perform a first CRC check of a respective one of the plurality of data segments, the plurality of first CRC checks being performed concurrently, and wherein each of the first CRC check units is configured to perform a second CRC check based on an output of the respective first CRC check unit.

Method and apparatus for performing a CRC check

Most wireless channels are sparse, so sparse channel-based methods can be used for channel estimation and feedback with much better estimation accuracy and much lower feedback overhead. However, certain wireless channels can be non-sparse, for which sparse channel-based methods may cause degraded estimation quality and increased feedback overhead. Means of detecting the channel sparseness are described that provide simple and effective channel sparseness indicators and safeguard against the mismatch between non-sparse channels and sparse channel-based methods. Various fallback options can be used under non-sparse channels such that estimation degradation and feedback overhead are both minimized. Fake multipath removal in continuous time-domain parameter extraction, a sparse channel-based method, is also described that further improves estimation quality and reduces feedback overhead.

Sparse channel detection, estimation, and feedback

Methods and apparatus of channel feedback are disclosed. In OFDM systems, the channel is acquired in the frequency domain. A generic multipath model for wireless channels, however, reveals that the time-domain parameters of the channel require much smaller data than the frequency-domain representation of the channel. Means to extracting the time-domain parameters from the frequency-domain channel samples are described for both the continuous time domain and the discrete time domain. Refinements of the time-domain parameters via minimizing a frequency-domain matching error are also described, which further improve the quality of the channel feedback and reduce the feedback overhead. Channel feedback with the time-domain parameters requires only a small fraction of the feedback overhead that is needed by existing channel feedback schemes, and maintains consistently superior performances over wireless channels of various delay spreads, short or long.

Channel feedback in OFDM systems

Methods and apparatus are described that provide carrier-phase difference (CPD) acquisition via signaling protocols between communicating devices. The random CPD between two disjoint devices can be measured by the signaling protocols described herein. With the availability of the CPD, a device is also able to acquire its outgoing channel (transmit channel) information, thus avoiding the channel information feedback that is being considered and/or practiced in some wireless communications systems. Also described are methods and apparatus that use the CPD to synchronize the clocks of two or more devices and that track the time-variations of the CPD for reliable CPD measurement and tracking loop operations. Applications of the described methods and apparatus include wireless multipoint broadcast systems, also known as coordinated multipoint transmission, or CoMP, in LTE (long-term evolution)-advanced systems, point-to-point wireless MIMO systems, and general wireless device networks.

Carrier-phase difference detection and tracking in multipoint broadcast channels

Methods and apparatus are described that provide efficient detection of the carrier-phase difference (CPD) between communicating devices over the entire signal bandwidth. The CPD detection utilizes the linear structure of the CPD, which eliminates most of the feedback overhead. Both feedback mechanisms, compact digitized feedback, and feedback via fast signaling protocols, are described. The CPD can be decomposed into a fixed/slow-changing portion and a fast-varying portion, with the former being pre-calibrated and communicated prior to communications sessions, thus further reducing the feedback overhead and improving the CPD detection accuracy. The nonlinearity in the TX/RX chains can also be pre-calibrated, allowing CPDs with more general structures to be detected by methods that detect CPDs with linear structures. Applications of the described methods and apparatus include wireless multipoint broadcast systems, also known as coordinated multipoint transmission, or CoMP, in LTE-A (long-term evolution, advanced) systems, and frequency and phase synchronization of a cluster of base stations.

Carrier-phase difference detection with mismatched transmitter and receiver delays

A method is described that enables maximum-likelihood (ML) demodulation for MIMO communications over frequency-selective channels. An equalizer is typically employed to suppress inter-symbol interference (ISI) due to frequency-selectiveness of the channel, but the noise of the equalizer output can be highly correlated such that standard ML-MIMO demodulations cannot directly apply. The method comprises first constructing equivalent post-equalization MIMO channel and noise covariance matrix, and then de-correlating the equalizer output so that ML or near-ML MIMO demodulations can be applied to improve the performance. Additionally, successive ISI cancellation (SIC) is described for further performance improvement.

Maximum-likelihood MIMO demodulation for frequency-selective channels

A wireless telecommunication device conducts base station pages at large intervals, such as 30 seconds, rather than the more conventional 0.5 to 4 seconds. The network processes calls placed to that telecommunication device in accordance with an SMS (Short Messaging Service) type protocol rather than a conventional voice call protocol. Particularly, the network sends an SMS to the telephone indicating that a third party is calling (hereinafter termed a 'pre-call SMS'). The pre-call SMS indicates the telephone number of the third party. The user of the telephone may call the third party back. In accordance with this protocol, the need to page at very short intervals so as to permit a telephone call to be established in 'real-time' is eliminated. Therefore, the paging interval can be increased substantially, thereby substantially prolonging battery charge lifetime of the telephone. In accordance with another aspect of the invention, when a cellular telephone sends a pre-call SMS, it temporarily decreases its paging interval to a more conventional interval such as 0.5 seconds for a predetermined period of time (e.g., 1-5 minutes) after placing a call so that, if the called party returns the call, the calling party will receive the return call in real-time and be able to answer the incoming call and establish a voice call.

Method and apparatus for prolonging battery charge life in a mobile communication device using a text messaging type protocol for calls

Multipoint broadcasting requires that the downlink-channel information be available at collaborating base stations. Methods and apparatus for wideband analog channel feedback are described that provide downlink-channel information feedback from mobile users to base stations via uplink channels, and that use very few or no resources of the RAT of the wireless cellular network. Also described are methods and apparatus that perform channel-feedback signal cancellation at base stations to reduce its interference on the uplink-traffic signal. Wideband analog channel feedback is adaptable to the feedback bandwidth in uplink, and it offers frequency diversity to combat the deep fading in feedback channels. Wideband analog channel feedback is also applicable to uplink channel-information feedback. Applications of the described methods and apparatus include multipoint broadcasting in a wireless cellular network, and more generally, channel feedback between two communicating devices in a communications network.

Wideband analog channel information feedback

Multipoint broadcasting requires the base stations to be phase-synchronized. Methods and apparatus are described that provide phase synchronization of base stations with the downlink-channel phase feedback by mobile users. Also described are methods and apparatus that make phase synchronization of base stations independent of multipoint-broadcast sessions, thus reducing the synchronization overhead and improving network capacity. The methods and apparatus utilize model-based downlink-channel phase feedback that reduces most of the feedback overhead. Applications of the described methods and apparatus include wireless multipoint broadcast systems, also known as coordinated multipoint transmission, or CoMP, in LTE-A (long-term evolution, advanced) systems, and frequency and phase synchronization of a cluster of base stations, or more generally, of a cluster of wireless devices.

Phase synchronization of base stations via mobile feedback in multipoint broadcasting

A method and apparatus are disclosed for detecting a pilot signal in a wireless receiver using coherent combining/noncoherent detection techniques. Coherent combining/noncoherent detection techniques are used to detect the pilot signal whenever the receiver is already frequency locked, or otherwise known to have a small frequency offset Conventional noncoherent combining/noncoherent detection techniques are utilized to initially acquire the timing of the forward channel. Once the receiver is frequency locked, coherent combining/noncoherent detection techniques may be used to continuously detect the pilot signals. After the receiver is frequency locked, the residue frequency error is small over several consecutive correlator outputs The correlator outputs can thus be combined coherently (since the frequency error is known to be small), and the phase dependency is then eliminated by noncoherent detection.

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Allentown, PA, United States of America

Xiao-an Wang