45 research outputs found
Remarks on Bounds for Quantum Codes
We present some results that show that bounds from classical coding theory
still work in many cases of quantum coding theory
Correction of Data and Syndrome Errors by Stabilizer Codes
Performing active quantum error correction to protect fragile quantum states
highly depends on the correctness of error information--error syndromes. To
obtain reliable error syndromes using imperfect physical circuits, we propose
the idea of quantum data-syndrome (DS) codes that are capable of correcting
both data qubits and syndrome bits errors. We study fundamental properties of
quantum DS codes and provide several CSS-type code constructions of quantum DS
codes.Comment: 2 figures. This is a short version of our full paper (in preparation
Sectoring in Multi-cell Massive MIMO Systems
In this paper, the downlink of a typical massive MIMO system is studied when
each base station is composed of three antenna arrays with directional antenna
elements serving 120 degrees of the two-dimensional space. A lower bound for
the achievable rate is provided. Furthermore, a power optimization problem is
formulated and as a result, centralized and decentralized power allocation
schemes are proposed. The simulation results reveal that using directional
antennas at base stations along with sectoring can lead to a notable increase
in the achievable rates by increasing the received signal power and decreasing
'pilot contamination' interference in multicell massive MIMO systems. Moreover,
it is shown that using optimized power allocation can increase 0.95-likely rate
in the system significantly