Time-to-Space Division Multiplexing for Tb/s Mobile Cells

Abstract

Space division multiplexing increases the capacity of mobile cells by reusing the frequencies in various directions. Yet, today's concepts scale badly to millimeter wave and therefore cannot provide Tb/s capacity. In this paper, we introduce timeto-space division multiplexing as a novel scheme to steer multiple beams simultaneously to different users. The main benefit of the proposed method relies in the fact that simple hardware can be used to generate the beams. In other words, it provides the advantages of space division multiplexing without relying on the complex array feeders that are usually required. Thanks to this advantage, the proposed technique can be easily combined with millimeter Wave systems as recently demonstrated.

Development Challenges of Millimeter‐Wave 5G Beamformers

“…A sub-version of the scheme is implemented and tested on 40-nm CMOS technology with 16 beams and 8 simultaneous uses. Other variations of time-to-space division multiplexing (like (Bonjour, Welschen and Leuthold, 2018)) are also found to enable multiple beam steering serving multiple users. The most prominent benefit is that it requires simpler hardware compared to counterparts which need complex antenna feeding and relaying.…”

MmWave Hybrid Array with More Users than RF Chains

“…Techniques for solving or mitigating this problem are left for future study. Possible solutions may be to include passband filters at the antennas or employ pulses of duration less than a symbol as in [19].…”

“…For the distortion of SbS precoding to be negligible in comparison to hybrid or digital beamforming, it should be an order of magnitude below other types of interferences. We derive expressions for the signal gain and interference power from the formula in (19). Precisely, let g k,k be the (k, k )-th entry of matrix Ĝ, then the gain for the k-th user is g k,k and the inter-beam interference from user k to user k is g k,k , and the signal-to-interference-plus-distortion ratio (SIDR) averaged for all users is defined as…”

“…To break the limit on the maximum number of transmitted streams in the case of a phase shifting network, some architectural changes are required. In [18], [19], the base station (BS) time-multiplexes multiple streams of data and transmits them through a single RFC. Then, it performs symbol-by-symbol beam steering in order to direct the beam of each symbol into a different direction.…”