Reconfigurable wireless data center network using free-space optics

Patent metadata

Field	Value
Publication number	US-2018294877-A1
Application number	US-201816010191-A
Country	US
Kind code	A1
Filing date	Jun 15, 2018
Priority date	Nov 6, 2014
Publication date	Oct 11, 2018
Grant date	—

Abstract

A reconfigurable free-space optical inter-rack network includes a plurality of server racks, each including at least one switch mounted on a top thereof, where each top mounted switch includes a plurality of free-space-optic link connector, each with a free-space optical connection to a free-space-optic link connector on another top-mounted switch, a single ceiling mirror above the plurality of server racks that substantially covers the plurality of server racks, wherein the single ceiling mirror redirects optical connections between pairs of free-space-optic link connectors to provide a clear lines-of-sight between each pair of connected free-space-optic link connectors, and a controller that preconfigures a free-space optical network connecting the plurality of server racks by establishing connections between pairs of free-space-optic link connectors, and that reconfigures connections between pairs of free-space-optic link connectors in response to network traffic demands and events.

First claim

What is claimed is:

1 . A reconfigurable free-space optical inter-rack network, comprising:
a plurality of server racks, each including at least one switch mounted on a top thereof; wherein each top-mounted switch includes a plurality of free-space-optic link connector, each with a free-space optical connection to a free-space-optic link connector on another top-mounted switch; a plurality of ceiling mirrors above the plurality of server racks, wherein each of the plurality of ceiling mirrors has an area that is smaller than an area of the top of a server rack, wherein each single ceiling mirror redirects optical connections between one or more pairs of free-space-optic link connectors to provide a clear lines-of-sight between each pair of connected free-space-optic link connectors; and a controller that preconfigures a free-space optical network connecting the plurality of server racks by establishing connections between pairs of free-space-optic link connectors, and that reconfigures connections between pairs of free-space-optic link connectors in response to network traffic demands and events.

2 . The network of claim 1 , wherein the free-space-optic link connector is a liquid crystal switchable mirror (SM) that is electrically controllable to switch between a reflection mode and a transparent mode.

3 . The network of claim 2 , wherein the controller preconfigures an alignment of each SM to maximize a number of pairs of racks that have at least one candidate link therebetween in a set of all candidate links, and minimizing a total area of rectangular overhead mirrors, wherein a total number of mirrors is less than a predetermined constant r.

4 . The network of claim 2 , wherein the controller preconfigures an alignment of each SM by
creating a random simple graph over racks wherein each rack has mk links, wherein m is a number of top-mounted switches per rack and k is the number of SMs per top-mounted switch, mapping each pair of server racks to its reflection polygon, wherein a reflection polygon is, for any pair of racks R a and R b , a convex hull of reflection points of all possible assigned candidate links connecting a top-rack switch on R a to a top-rack switch on R b , wherein reflection point for an assigned candidate link connecting two top mounted switches a and b is the point p on a ceiling wherein a, b, and p are on the same vertical plane, and p is equidistant from a and b, clustering the reflection polygons by stabbing the reflection polygons using a minimum number of points, wherein a point stabs a polygon if it lies inside the polygon, wherein a set of polygons that are stabbed by a same point are assigned to a same cluster.

5 . The network of claim 4 , wherein if a polygon is stabbed by multiple points, said polygon is randomly assigned to one of the corresponding clusters.

6 . The network of claim 4 , further comprising
randomly selecting a link (R a , R b ) from a set of unassigned links E that has not been already selected, and assigning said selected link to a best pair of top mounted switches on racks R a and R b , while ensuring that no top mounted switch is assigned more than a maximum number of links allowed per top-mounted switch, wherein a best pair of top-mounted switches is one that results in a minimum increase of an area of an overhead mirror currently being used to cover the reflection points of already-assigned links in the cluster of (R a , R b ), wherein said steps of randomly selecting a link and assigning said selected link to a best pair of top mounted switches are repeated until all links in set E are assigned.

7 . The network of claim 6 , wherein if (R a , R b ) is the first link being considered from its cluster, then the assignment to FSOs is randomly performed.

8 . The network of claim 6 , wherein if a number of clusters exceeds the predetermined number of top-mounted switches, pairs of mirrors are found that minimizes an increase in the total area, and merged.

9 . The network of claim 1 , wherein the free-space-optic link connector is a mirror galvanometer configured to rotate around the axis on a plane of the mirror in response to an electric signal.

10 . The network of claim 9 , wherein the controller preconfigures an orientation of each GM to create a set of candidate links with near-optimal performance over a network of said links while minimizing usage of the overhead mirrors, wherein there is an orientation of a GM at each top-mounted switch so that all assigned links at said top-mounted switch are covered by the GM.

11 . The network of claim 9 , wherein the controller preconfigures an orientation of each GM by creating a complete simple graph over the plurality of server racks and assigning as many links as possible that connect pairs of top-mounted racks, wherein a number of assigned links is less than or equal to a maximum possible number of links,
partitioning the plurality of server racks into disjoint blocks, wherein each block of server racks is co-located and sufficiently small to be covered by an appropriately oriented GM on any top-mounted switch in the data center, creating a random block-level matching, for each edge (B 1 , B 2 ) in a matching, orienting a GM on each rack of block B 1 towards a GM on a rack of block B 2 , wherein each GM selected for orientation minimizes a sum of distances between reflection points of candidate links in a same matching, wherein a reflection point for a candidate link connecting two top mounted switches a and b is the point p on a ceiling wherein a, b, and p are on the same vertical plane, and p is equidistant from a and b, and covering the reflection points on the ceiling with a number of overhead mirrors using a greedy approach wherein the minors are shaped as rectangles, a number of rectangles can be chosen of order p/A, wherein p is a number of uncovered reflection points covered by a rectangle under consideration and A is an area of the rectangle, wherein mirrors have an appropriate minimum size based on the density of the points to cover.

12 . A reconfigurable free-space optical inter-rack network, comprising:
a plurality of server racks, each including at least one tower mounted on a top thereof; a plurality of switches attached to each tower, wherein each switch includes a plurality of free-space-optic link connectors, each with a free-space optical connection to a free-space-optic link connector on another switch; wherein the plurality of free-space-optic link connectors for each switch is attached to the switches for each tower, wherein the plurality of free-space-optic link connectors are spaced apart from each other; and a controller that preconfigures a free-space optical network connecting the plurality of server racks by establishing connections between pairs of free-space-optic link connectors, and that reconfigures connections between pairs of free-space-optic, link connectors in response to network traffic demands and events.

13 . The network of claim 12 , wherein the free-space-optic link connector is a liquid crystal switchable mirror (SM) that is electrically controllable to switch between a reflection mode and a transparent mode.

14 . The network of claim 13 , wherein the controller preconfigures an alignment of each SM by generating a random simple graph over racks with a maximum possible number of assigned links,
determining locations of towers on the server racks by selecting a location. that is ranked based on a total number of already placed towers that are visible from a location under consideration, while ensuring that only a given number of towers are placed on any par

Assignees

• Univ New York State Res Found

Inventors

• Gupta Himanshu
• Hamedazimi Navid
• Das Samir Ranjan
• Longtin Jon
• Sekar Vyas
• Curran Max

Classifications

• H04B10/11 Primary

  Arrangements specific to free-space transmission, i.e. transmission through air or vacuum · CPC title

• H04L41/0803

  Configuration setting · CPC title

• H04B10/1149 Primary

  Arrangements for indoor wireless networking of information · CPC title

• H04Q2011/0026

  using free space propagation (e.g. lenses, mirrors) · CPC title