Optimal Reference Signal Design for Phase Noise Compensation in Multi-carrier Massive MIMO Systems
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Millimeter-wave and Terahertz frequencies, while promising high throughput and abundant spectrum, are highly susceptible to hardware non-idealities like phase-noise, which degrade the system performance and make transceiver implementation difficult. In this paper, a novel reference-signal (RS) aided low-complexity and low-latency technique is proposed to mitigate phase-noise in high-frequency multi-carrier massive multiple-input-multiple-output systems. Unlike in existing methods, the proposed RS is transmitted in each symbol and occupies adjacent sub-carriers separated from the data by null sub-carriers. The receiver uses the received RS to estimate and compensate for the dominant spectral components of the phase-noise at each symbol. While the null sub-carriers reduce the interference between the RS and data, the frequency compactness of the RS decouples phase-noise estimation from channel equalization, reducing error propagation. A detailed theoretical analysis of the technique is presented and correspondingly, throughput-optimal designs for the RS sequence, RS bandwidth, power allocation and the number of nulled sub-carriers and estimated spectral components, are derived. A hitherto unexplored interplay between oscillator phase-locked loop design and the performance of phase-noise compensation is also studied. Simulations, performed under 3GPP compliant settings, suggest that the proposed scheme, while achieving better performance than several existing solutions, also effectively compensates for oscillator frequency offsets.
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