Hybrid LISA Precoding for Multiuser Millimeter-Wave Communications

Abstract

Millimeter-wave (mmWave) communications plays an important role for future cellular networks because of the vast amount of spectrum available in the underutilized mmWave frequency bands. To overcome the huge free space omnidirectional path loss in those frequency bands, the deployment of a very large number of antenna elements at the base station is crucial. The complexity, power consumption and costs resulting from the large number of antenna elements can be reduced by limiting the number of RF chains. This leads to hybrid precoding and combining, which, in contrast to the traditional fully digital precoding and combining, moves a part of the signal processing from the digital to the analog domain. This paper proposes new algorithms for the design of hybrid precoders and combiners in a multiuser scenario. The algorithms are based on the previously proposed Linear Successive Allocation method developed for the traditional fully digital version. It successively allocates data streams to users and suppresses the respective interstream interference in two stages, which perfectly matches the hybrid architecture. Furthermore, a low-complexity version is developed by exploiting the typical structure of mmWave channels. The good performance of the proposed method and its low-complexity version is demonstrated by simulation results. Index TermsMultiuser communications, mmWave communications, hybrid precoding, linear successive allocation method, structured mmWave channels.The authors are with Methods of Signal Processing,

Hybrid LISA for Wideband Multiuser Millimeter-Wave Communication Systems Under Beam Squint

“…2, we plot the achievable sum rates obtained with different strategies and bandwidths B = 800 MHz and B = 3200 MHz. We take as a benchmark the results obtained with the LISA scheme applied individually at each subcarrier [3]. This strategy allows us to allocate a maximum of N RF streams at each subcarrier, though neglecting the rank constraint imposed by the frequency flat analog PS network.…”

“…As previously stated the total number of LISA iterations is always smaller than or equal to the number of RF chains at the transmitter, i.e., i ≤ N RF . Hence, the extension to the hybrid scenario is similar to that for the narrowband scenario [3], [20]. Therein, after algorithms convergence, the matrix Q i is substituted by its projection onto the feasible set for analog precoding as…”

Hybrid Precoding for Massive MIMO With Low Rank Channels: A Two-Stage User Scheduling Approach

“…The transmitter treats the reconstructed channel statistics as the real ones, thus, from (20), the baseband precoder design problem is formulated as…”

“…Most previous works on hybrid precoding design the analog and digital precoders based on the assumption of full CSIT (see e.g., [17]- [20]). However, the acquisition of perfect CSIT in hybrid precoding imposes substantial challenges in both TDD and FDD systems.…”

Hybrid Beamforming: Where Should the Analog Power Amplifiers Be Placed?

“…The authors in [4] study the optimal analog and digital beamforming design in hybrid P2P-MIMO systems. Moreover, the authors in [5] provide an algorithm for obtaining the sub-optimal digital and analog beamforming solutions in cellular downlink. These works consider the analog amplifiers right after the D2A converters.…”