Abstract
In Constant Envelope Symbol Level Precoding (CESLP), the transmitted signals by the antennas have constant amplitude regardless of the channel realization and the conveyed information symbols. Such solutions enable the use of power-efficient components, i.e. non-linear power amplifiers and thus, are suitable for systems based on large-scale antenna arrays. In the latter systems, the hardware complexity and power consumption can be limiting factors since each antenna element requires dedicated hardware components. These components include the Digital-to-Analog Converters (DACs) that have exponential complexity and power consumption with the number of the supported resolution. To that end, in this paper, a CESLP precoding technique is presented for Multi-User Multiple Input-Multiple Output (MU-MIMO) systems with low resolution DACs. The case of a multi-carrier system employing the well-known Orthogonal Frequency Division Multiplexing (OFDM) technique is considered. The precoding design problem is formulated as a mixed discrete-continuous least-squares optimization one which is NP-hard. An efficient low complexity solution is developed based on the Cyclic Coordinate Descent (CCD) optimization framework. Simulations show that the proposed solution is able to achieve very close performance to the one of the infinite resolution CESLP precoding counterpart even though, it is based on DACs that have resolution of only a few bits.
Highlights
Cellular systems based on a Base-Station (BS) equipped with a Large-Scale Antenna Array (LSAA) exhibit significantly improved spectral efficiency, reliability and coverage compared to the traditional ones that are employing antenna arrays of few elements
Their performance is compared to the ones of a) the existing literature solution [51], b) the Constant Envelope Symbol Level Precoding (CESLP) precoding for infinite resolution Digital-to-Analog Converters (DACs) for which an efficient solution can be found in [23] and c) the well-known Zeroforcing (ZF) precoder when quantized such that the output signals are of constant envelope and can support the resolution of the employed DACs, i.e., lie in the set X in (4) [57]
In this paper, a Symbol-Level Precoding techniques (SLP) solution was presented for constant envelope systems with low resolution DACs
Summary
Cellular systems based on a Base-Station (BS) equipped with a Large-Scale Antenna Array (LSAA) exhibit significantly improved spectral efficiency, reliability and coverage compared to the traditional ones that are employing antenna arrays of few elements. The proposed solution achieves better performance compared to the one in [51] which considers the CESLP problem design for an OFDM-based system based on low resolution DACs. The approach in [51] extends the results in [48] to a system that employs the OFDM technique to combat frequency selectivity. The approach in [51] extends the results in [48] to a system that employs the OFDM technique to combat frequency selectivity It is based on a different problem formulation and solution to the one that is developed in the present paper. The subset of a set A, B is denoted by B ⊂ A
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