Cover story: 50 GHz optical true time delay beamforming in hybrid optical/mm-wave access networks with multi-core optical fiber distribution
At: 2018/6/11 10:27:50 by admin

The tremendous growth of worldwidedata traffic over the past years means that the future access network architectures will be revised.The flexibility of wireless links, compared with wired ones, makes them moreadequate and cost efficient in several scenarios. Consequently, high-capacitywireless interfaces must be integrated with optical networks without imposing acapacity bottleneck. The millimeter-wave (30–300 GHz) band is postulated as themain candidate to extend the capacity of wireless interfaces because of highlyavailable bandwidth resources. However, a high-gain directive antenna with beamsteering capabilities must be used in this spectrum region to overcome largefree space attenuation.

Researchers from EindhovenUniversity of Technology, The Netherlands and Tektronix AB, Sweden proposedthat the optical true time delay beamforming technique is the best candidate toprovide beam steering capabilities to an antenna array at millimeter-wavefrequencies within a hybrid millimeter-wave/photonic system. This scheme offersbroadband operation, low loss, and straightforward integration into opticaldistribution networks. Traditionally, the beamformer network is situated at theantenna unit. This work proposes a scheme that shifts this functionality to a central entityto control the beamforming configuration remotely. A multicore fiber is used totransmit different replicas of the signal to each array element keeping therelative time delay between different cores. This system is validated by an experimentaldemonstration and the measurement of the relative delay after the transmissionover 2 km of the multicore fiber. This work has been published in ChineseOptics Letters, Volume 16, No. 4, 2018 (álvaro Morales et al., 50 GHz optical true time delay beamformingin hybrid optical/mm-wave access networks with multicore optical fiber distribution).

The shift of the beamformer networkto a remote central entity is completelydifferent from common approaches. The main advantages are the centralmanagement of the beamformer configuration for different antenna units and thereduction in the deployment costs of new base stations. The results serve as engineeringguidelines for the design of a hybrid optical/millimeter-wave access networkwith centralized beamforming capabilities.

“Most researches agree that newparadigms for the next generation of radio access networks will rely on thedeployment of a large number of radio stations, multi-antenna systems, andmillimeter-wave communications,” said Prof. Idelfonso Tafur Monroy from Eindhoven University of Technology, “The ideas proposed in this work are in accordancewith this philosophy.”

Further work will be focused on the end-to-enddesign of the radio frequency segment and the reconfigurability of thebeamformer to make the proposed system suitable for implementations.

Graphic Description:

A) Hybrid optical/mm-wave access network with beamforming capabilities. B) Principle of optical true time delay beamforming in a linear phased antenna array with multicore optical fiber distribution. C) Schematic diagram of the experimental setup.

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