Millimeter Wave Beamforming for Wireless Backhaul and Access in Small Cell Networks

Abstract

Recently, there has been considerable interest in new tiered network cellular architectures, which would likely use many more cell sites than found today. Two major challenges will be i) providing backhaul to all of these cells and ii) finding efficient techniques to leverage higher frequency bands for mobile access and backhaul. This paper proposes the use of outdoor millimeter wave communications for backhaul networking between cells and mobile access within a cell. To overcome the outdoor impairments found in millimeter wave propagation, this paper studies beamforming using large arrays.However, such systems will require narrow beams, increasing sensitivity to movement caused by pole sway and other environmental concerns. To overcome this, we propose an efficient beam alignment technique using adaptive subspace sampling and hierarchical beam codebooks. A wind sway analysis is presented to establish a notion of beam coherence time. This highlights a previously unexplored tradeoff between array size and wind-induced movement. Generally, it is not possible to use larger arrays without risking a corresponding performance loss from wind-induced beam misalignment. The performance of the proposed alignment technique is analyzed and compared with other search and alignment methods.The results show significant performance improvement with reduced search time. Index Terms

5G Position and Orientation Estimation through Millimeter Wave MIMO

“…When the MS is within one meter of the BS, REB values range from 0.0014 rad in the 3 In particular A 0 ≈ 8 × 10 −3 I and A 2 ≈ 6.6 × 10 −4 I, obtained by generating white Gaussian signals. 4 Here [J −1 η ] 1:2,1:2 denotes the 2 × 2 block from the first two rows and first two columns of the inverse of the FIM Jη . direction π/5, over 0.05 rad in the direction −π/3, up to 0.2 rad outside any of the beams.…”

Channel Models and Beamforming at Millimeter-Wave Frequency Bands

“…The beamforming capability is at the same time a required feature for mm-wave radios in order to compensate for the high losses of radio propagation and the human blockage [160]- [163]. What makes the beamforming more relevant for future cellular applications is its potential for dense spatial frequency reuse; pointing a narrow, so-called pencil beams towards the intended user keeps interference to other users minimal, making multiple concurrent wireless data transfers feasible in a confined area [164], [165].…”

“…For outdoor cellular scenarios, [71] indicates that an antenna with wide beamwidth at a ground level may lead to robust link budget in their rooftop-to-ground channel at 28 GHz, given the rich scattering and lack of beam tracking at the rooftop. Flattening antenna beams is proposed in [163] to cope with small variations of directional antenna orientation incurred by wind for mast-mounted outdoor backhaul links. Design of the hybrid beamforming under the presence of various losses and channel time-variation is of a practical interest for mm-wave devices.…”

Compressed sensing based multi-user millimeter wave systems: How many measurements are needed?

“…To overcome the hardware limitations, analog beamforming solutions were proposed in [6][7][8][9][10], which rely on controlThis work is supported in part by the National Science Foundation under Grant No. 1218338 and 1319556, and by a gift from Huawei Technologies, Inc. ling the phase of the signal transmitted by each antenna via a network of analog phase shifters.…”