Mirror Mirror on the Ceiling: Flexible Wireless Links for Data Centers
Xia Zhou
Zengbin Zhang
Yibo Zhu
Yubo Li
Saipriya Kumar
Amin Vahdat
Ben Y. Zhao
Haitao Zheng
Proceedings of ACM SIGCOMM 2012
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Paper Abstract
Modern data centers are massive, and support a range of distributed applications across potentially hundreds of server racks. As their utilization and bandwidth needs continue to grow, traditional methods of augmenting bandwidth have proven complex and costly in time and resources. Recent measurements show that data center traffic is often limited by congestion loss caused by short traffic bursts. Thus an attractive alternative to adding physical bandwidth is to augment wired links with wireless links in the 60 GHz band.
We address two limitations with current 60 GHz wireless
proposals. First, 60 GHz wireless links are limited by
line-of-sight, and can be blocked by even small obstacles. Second,
even beamforming links leak power, and potential interference will
severely limit concurrent transmissions in dense data centers. We
propose and evaluate a new wireless primitive for data centers, 3D beamforming, where 60 GHz signals bounce off data center
ceilings, thus establishing indirect line-of-sight between any two
racks in a data center. We build a small 3D beamforming testbed to
demonstrate its ability to address both link blockage and link
interference, thus improving link range and number of concurrent
transmissions in the data center. In addition, we propose a simple
link scheduler and use traffic simulations to show that
these 3D links significantly expand wireless capacity compared to
their 2D counterparts.