Collision Communications, Inc.

Sagar Dhakal

Brandon P Hombs

Joseph Farkas

Sayak Bose

Seyedmehdi S Nokhodberiz

Methods and systems for performing compressed time domain joint channel estimation in a multi-user MIMO wireless network include receiving data corresponding to transmission of training signals from a plurality of users to a base station over a MIMO wireless network, determining a limited data set by limiting the received data in a time domain according to an estimated maximum delay spread, forming a well-conditioned low rank training matrix by identifying a channel model, estimating an active tap from the formed well-conditioned low rank training matrix, and subtracting a contribution of the selected active tap from the limited data set.

Method and system for compressed sensing joint channel estimation in a cellular communications network

Methods and systems for performing compressed time domain joint channel estimation in a multi-user MIMO wireless network include receiving training signals from a plurality of users, estimating a maximum delay spread for the received data according to a coherence bandwidth of the received data, limiting the received data in the time domain to the estimated maximum delay spread, selecting and estimating an active tap from the limited data set, and subtracting a contribution of the selected active tap from the reduced data set. These steps can be repeated until the residual signal falls below a specified minimum. The network can be a C-RAN network. The training data can be SRS or DMRS data. Limiting the received data ensures that only a few significant taps are analyzed, so that the system is not under determined and can be analyzed for accurate channel estimation using any of several existing algorithms.

Methods and systems for obtaining improved joint channel estimates for a multi-user, frequency-multiplexed data transmission such as SC-FDMA or OFDM begins by estimating separate contributions of users (and/or other signal sources) to the received signal based on joint frequency domain channel estimates. A reduced data set is obtained by subtracting contributions of one or more users from the received data, leaving only the estimated contributions of the remaining users, with noise and residual estimation error signal. Time domain joint channel estimation is then performed on the reduced data set, which is feasible because the number of users has been reduced. In exemplary embodiments, the reduced data set includes only one estimated user contribution. This process is repeated to obtain channel estimates for all of the users. The method can be repeated by using the channel estimates to re-estimate the user contributions and calculate revised channel estimates.

Reduced dimension channel estimation in a wireless communication network

Methods and systems are described for calibrating amplitude hardware-induced distortion in a communications system. A power status indication is received by a base station (BS) of a communications system from a user equipment (UE) communicating in the communications system. A downlink pathloss associated with communications to the UE from at least one other BS is estimated by the at least one other BS of the communication system based on the received power status indication. Downlink power allocation is performed based on the downlink pathloss estimate from at least one other BS.

Methods, systems, and computer program products for calibrating amplitude hardware-induced distortion in a long term evolution (LTE) communications system

Methods and systems are described for calibrating hardware-induced distortion in a communication system. In one aspect, a calibration signal is transmitted from a base station (BS) to a user equipment (UE). A corresponding amplified version of the transmitted calibration signal is received by the BS from the UE. A composite downlink-uplink channel state information (CSI) is estimated based on the received corresponding amplified version of the transmitted calibration signal. Uplink CSI is estimated based on a reference signal received from the UE. At least one of a phase hardware-induced distortion and an amplitude hardware induced distortion is determined based on the estimated composite downlink-uplink CSI and the estimated uplink CSI.

Methods, systems, and computer program products for calibrating hardware-induced distortion in a communication system

Methods and systems are described for calibrating phase hardware-induced distortion in a cellular communications system. In one aspect, an estimate of a phase difference at a user equipment (UE) between downlink channels including signals sent over two or more BS transmitter chains is obtained. A phase difference between uplink channels including signals received over two or more BS receiver chains is determined. A relative phase distortion induced by two or more BS transceiver chains is determined based on the received estimate of phase difference between downlink channels and the determined phase difference between uplink channels.

Methods, systems, and computer program products for calibrating phase hardware-induced distortion in a cellular communications system

Methods and systems for obtaining improved joint channel estimates for a multi-user, frequency-multiplexed data transmission such as SC-FDMA or OFDM begins by estimating separate contributions of users (and/or other signal sources) to the received signal based on joint frequency domain channel estimates. A reduced data set is obtained by subtracting contributions of one or more users from the received data, leaving only the estimated contributions of the remaining users, with noise and residual estimation error signal. Time domain joint channel estimation is then performed on the reduced data set, which is feasible because the number of users has been reduced. In exemplary embodiments, the reduced data set includes only one estimated user contribution. This process is repeated to obtain time domain estimates for all of the users. The method can be repeated by using the TD channel estimates to re-estimate the user contributions and calculate revised TD channel estimates.

Reduced dimension time domain channel estimation in a wireless communication network

Methods and systems for performing compressed time domain joint channel estimation in a multi-user MIMO LTE wireless network include receiving training signals from a plurality of users, estimating a maximum delay spread for the received data according to a coherence bandwidth of the received data, limiting the received data in the time domain to the estimated maximum delay spread, selecting and estimating an active tap from the limited data set, and subtracting a contribution of the selected active tap from the reduced data set. These steps can be repeated until the residual signal falls below a specified minimum. The network can be a C-RAN network. The training data can be SRS or DMRS data. Limiting the received data ensures that only a few significant taps are analyzed, so that the system is not under determined and can be analyzed for accurate channel estimation using any of several existing algorithms.

Method and system for compressed sensing joint channel estimation in an LTE cellular communications network

Methods and systems are described for calibrating amplitude hardware-induced distortion in a long term evolution (LTE) communications system. In one aspect, a power status indication is received at a base station (BS) associated with a centralized radio access network (C-RAN) of an LTE communications system from a user equipment (UE) communicating in the LTE communications system. A downlink pathloss associated with communications to the UE is estimated based on the received power status indication. Downlink power allocation is performed at the C-RAN based on the downlink pathloss estimates of one or more UEs.

Methods systems, and computer program products for calibrating amplitude hardware-induced distortion in a long term evolution (LTE) communications system

Methods and systems are described for calibrating phase hardware-induced distortion in a long term evolution (LTE) communications system. In one aspect, an estimate of a phase difference at a user equipment (UE) between downlink channels including signals sent over two or more BS transmitter chains is received from the UE in an LTE communications system. A phase difference between uplink channels including signals received over two or more BS receiver chains is determined at a BS. A relative phase distortion induced by two or more BS transceiver chains is determined based on the received estimate of phase difference between downlink channels and the determined phase difference between uplink channels.

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Bedford, NH, United States of America

Sagar Dhakal