Chester Park

Evolution of uplink MIMO for LTE-advanced

The evolution of LTE uplink transmission toward MIMO has recently been agreed in 3GPP, including the support of up to four-layer transmission using precoded spatial multiplexing as well as transmit diversity techniques. In this article, an overview of these uplink MIMO schemes is presented, along with their impact on reference signals and DL control signaling. Receivers suitable for uplink MIMO are presented, and their link performances are compared.

Towards an integrated circuit design of a compresssed sampling wireless receiver

In this paper, we investigate the extension of previous work on compressed sampling receivers from mathematical abstractions and proof of concept work into a system that directly competes with more traditional receivers in standard CMOS integrated circuit technology. As developed in the literature, the Modulated Wideband Converter shows great promise as a compressed sampling receiver due to its flexibility and inherent spectral agility. We propose several modifications to the system that improve its usability and performance in real-world scenarios. Then, using standard LTE receivers as a basis for comparison, we propose a set of target specifications for the Modulated Wideband Converter, discuss the associated circuit challenges, and evaluate potential solutions that build upon prior work in integrated circuit and system design.

MIMO Layer Shifting for LTE-Advanced Uplink

Abstract-In this paper, multiple-input multiple-output (MIMO) layer shifting with cubic metric (CM) preserving precoder and downlink control signal sharing is proposed as a uplink transmission scheme for 3GPP Long Term Evolution (LTE). The design criteria for CM preserving precoder are presented and uplink precoder is designed accordingly. By sharing MCS (modulation and coding scheme) and/or HARQ (hybrid automatic repeat request) among codewords, downlink control signal sharing reduces the control signal overhead at the expense of performance degradation, which motivates this paper. The proposed MIMO layer shifting on a per SC-FDMA (single-carrier frequency division multiple access) symbol basis eliminates the discrepancy of channel quality among codewords, and thus improves the performance in the presence of MCS and/or HARQ sharing. Simulation results show that layer shifting is beneficial to both minimum mean square error (MMSE) and successive interference cancellation (SIC) receivers.

Impact of Gain/Phase Variation on MIMO Precoder Selection for LTE UL

In this paper, the MIMO precoder selection of LTE uplink (UL) is evaluated taking into account the gain/phase variation between SRS and PUSCH. The gain/phase variation introduced by radio impairment is modeled and the impact on precoding gain is analyzed. The simulation results show that gain variation has a stronger impact on the precoding gain than phase variation. Specifically, a gain variation of 9 dB costs 5 dB in performance.

On Soft Decision Value Calculation for Linear-Dispersion Codes with SC-FDMA

The capability of error correction codes is largely dependent on the calculation of soft decision values. In this letter, linear-dispersion (LD) code is applied to single-carrier frequency-division multiple access (SC-FDMA) and the closed-form expression of soft decision values is derived. It is shown that the calculation of soft decision values generally depends on both time and space within an SC-FDMA symbol, as opposed to single-antenna transmission. In addition, a sufficient condition to guarantee the independence from time and space is presented.