Energy-Efficient Transceiver Design for Hybrid Sub-Array Architecture MIMO Systems

Abstract

Millimeter-wave (mmWave) communication operated in frequency bands between 30 and 300 GHz has attracted extensive attention due to the potential ability of offering orders of magnitude greater bandwidths combined with further gains via beamforming and spatial multiplexing from multi-element antenna arrays. MmWave system may exploit the hybrid analog and digital precoding to achieve simultaneously the diversity, array and multiplexing gain with a lower cost of implementation. Motivated by this, in this paper, we investigate the design of hybrid precoder and combiner with sub-connected architecture, where each radio frequency chain is connected to only a subset of base station (BS) antennas from the perspective of energy efficient transmission. The problem of interest is a non-convex and NPhard problem that is difficult to solve directly. In order to address it, we resort to design a two-layer optimization method to solve the problem of interest by exploiting jointly the interference alignment and fractional programming. First, the analog precoder and combiner are optimized via the alternatingdirection optimization method (ADOM) where the phase shifter can be easily adjusted with an analytical structure. Then, we optimize the digital precoder and combiner based on an effective multiple-input January 9, 2017 DRAFT Index TermsMillimeter-wave communication, multiple-input multiple-output (MIMO) system, analog precoding and combining, interference alignment, energy efficiency. I. INTRODUCTIONRecently, data traffic has suffered an exponential growth due to the rapid proliferation of wireless devices, which are creating a spectrum crisis at the current wireless frequency bands. A variety of communication and signal processing techniques are currently being pursued for improvement of wireless rate and efficient use of the available spectrum, such as multiple-input multiple-output (MIMO) technolo-. Despite these efforts, meeting the dramatically increasing data demands of wireless devices and applications is still a tremendous challenge for sub-6 Gigabit Hertz wireless communications [7].Millimeter Wave (mmWave) wireless communication systems, operating in the frequency bands from 30 − 300 GHz, are emerging as a promising technology for the exploding bandwidth requirements by enabling multi-Gpbs speeds [8]- [12]. Recently, the advance in mmWave hardware has encouraged studying and applying mmWave for outdoor cellular networks and short distance communication. However, the shortcoming is that mmWave signal may experience an order of magnitude increase in free-space path-loss due to the ten-fold increase in carrier frequency compared to sub-6 GHz frequency bands.Fortunately, the decrease in wavelength leads to a dramatic increase of the number of antenna elements within a given antenna size such that large arrays can provide narrow and high-gain beams to overcome the path-loss [13]- [20]. Furthermore, large arrays may significantly improve the spectrum efficiency by transmitting simultaneously multiple data streams [21]- [25...

Millimeter Wave Communications for Future Mobile Networks

“…More recently, the energy efficiency optimization was studied and a solution was proposed in [165]. Since the subconnected architecture adopts a subarray structure, it is natural to solve the complicated hybrid precoding problem by decomposing it into several subproblems and optimizing them in an alternating manner.…”

“…The hybrid precoding problem with energy efficiency as the objective is more complicated. In [165], this optimization problem is solved by jointly exploiting the interference alignment and fractional programming. First, the analog precoder and combiner are optimized via the alternating direction optimization method.…”

Hybrid beamforming for single-user MIMO with partially connected RF architecture

“…For a practical implementation of a mm-wave massive MIMO system, the fully connected structure may be too complex to be used due to very challenging and lossy RF signal division and combining processes. A more practical solution is to use partially connected RF architecture, in which each RF chain is connected only to a subset of the antenna array, called a sub-array [14], [15].…”

Iterative Multiuser Equalization for Subconnected Hybrid mmWave Massive MIMO Architecture

“…The authors of [33] proposed a two-step algorithm for single-user narrowband systems that iteratively optimizes the hybrid precoder for spectral efficiency maximization, obtaining an extra data stream via the index of the active antenna set without any extra RF chain. Fixed subconnected hybrid architectures were addressed in [34][35][36][37]. In [34], precoder and combiner schemes for narrowband singleuser systems are proposed, where a two-layer optimization method jointly exploiting the interference alignment and fractional programming was employed.…”

“…Fixed subconnected hybrid architectures were addressed in [34][35][36][37]. In [34], precoder and combiner schemes for narrowband singleuser systems are proposed, where a two-layer optimization method jointly exploiting the interference alignment and fractional programming was employed. First, the analog precoder and combiner are optimized via the alternatingdirection optimization method, and then the digital precoder and combiner are optimized based on an effective channel matrix.…”