Power Efficient Scheduling and Hybrid Precoding for Time Modulated Arrays

Abstract

We consider power efficient scheduling and precoding solutions for multiantenna hybrid digital-analog transmission systems that use Time-Modulated Arrays (TMAs) in the analog domain. TMAs perform beamforming with switches instead of conventional Phase Shifters (PSs). The extremely low insertion losses of switches, together with their reduced power consumption and cost make TMAs attractive in emerging technologies like massive Multiple-Input Multiple-Output (MIMO) and millimeter wave (mmWave) systems. We propose a novel analog processing network based on TMAs and provide an angular scheduling algorithm that overcomes the limitations of conventional approaches. Next, we pose a convex optimization problem to determine the analog precoder. This formulation allows us to account for the Sideband Radiation (SR) effect inherent to TMAs, and achieve remarkable power efficiencies with a very low impact on performance. Computer experiments results show that the proposed design, while presenting a significantly better power efficiency, achieves a throughput similar to that obtained with other strategies based on angular selection for conventional architectures.<br>

A Time Modulated Array With Polarization Diversity Capability

“…4(b).Additionally, Table2indicates the gain at each sideband for the first scenario. The corresponding DG at each sideband can be easily calculated using(14). The DG is more than 1.93 for all of the sidebands, very close to the full diversity gain.…”

“…In addition, in [12] the capability of TMA to reject unwanted interference in a Global Positioning System (GPS) receiver is demonstrated. The considerations of sending data through a TMA structure is investigated in [3] and recently, Furthermore, TMA is proposed as a low-cost and simple architecture for beamforming for the emerging mm-wave communication systems [13], [14]. Although beamforming helps to direct the beam toward the receiver, the wireless Exploiting diversity techniques helps to overcome the propagation issues.…”

Rank Constrained Precoding for the Downlink of mmWave Massive MIMO Hybrid Systems

“…Algorithm 2 summarizes the steps of the proposed algorithm based on the trace constraint. At each iteration , the algorithm updates the matrices { u ( )} U u=1 by using the uplink-downlink duality, and computes the matrices U( ) by applying the eigen-decomposition in (22) to the uplink covariance matrices obtained in the previous iteration, i.e., {S u ( )} U u=1 . Next, ( 21) is solved with a semi-definite program solver to update the uplink covariance matrices, i.e, α( + 1) = β( )α( )…”

“…Next, the baseband matrices are optimized to maximize the considered metric [17]- [21]. This strategy relies on the baseband precoders to cancel the interference and performs poorly in certain scenarios since the degrees of freedom available for removing the interference are limited [22].…”

“…Finally, the digital baseband precoder is designed according to the Zero-Forcing criterion. As aforementioned, this solution is unfeasible for some scenarios [22].…”