U.S. patent application number 14/614017 was filed with the patent office on 2015-05-28 for inter-node communication system and method.
The applicant listed for this patent is The Research Foundation for The State University of New York. Invention is credited to Samir Ranjan DAS.
Application Number | 20150146591 14/614017 |
Document ID | / |
Family ID | 44146186 |
Filed Date | 2015-05-28 |
United States Patent
Application |
20150146591 |
Kind Code |
A1 |
DAS; Samir Ranjan |
May 28, 2015 |
INTER-NODE COMMUNICATION SYSTEM AND METHOD
Abstract
Provided is a system for data transmission in a wireless network
including a plurality of sets of directional antennas with each set
of directional antennas rotatably mounted on a common axis and each
antenna of each set of directional antennas focused in a different
sector emanating from a respective common axis, and a memory
includes routing information identifying aligned sectors of
adjacent sets of directional antennas. Detection of rotation of a
set of directional antennas beyond a threshold amount identifies a
changed alignment of adjacent sectors. Upon identification of the
changed alignment of the adjacent sectors, revised routing
information is provided to the plurality of sets of directional
antennas. Upon identification of the changed alignment of the
adjacent sectors, a data packet is rebroadcast between adjacent
sets of directional antennas utilizing directional antennas
identified by the revised routing information.
Inventors: |
DAS; Samir Ranjan;
(Melville, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Research Foundation for The State University of New
York |
Albany |
NY |
US |
|
|
Family ID: |
44146186 |
Appl. No.: |
14/614017 |
Filed: |
February 4, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13492352 |
Jun 8, 2012 |
8989090 |
|
|
14614017 |
|
|
|
|
Current U.S.
Class: |
370/310 |
Current CPC
Class: |
H04W 40/18 20130101;
H04W 16/28 20130101; H01Q 3/04 20130101; H04W 40/06 20130101 |
Class at
Publication: |
370/310 |
International
Class: |
H04W 16/28 20060101
H04W016/28; H01Q 3/04 20060101 H01Q003/04 |
Claims
1. A system for data transmission in a wireless network, the system
comprising: a plurality of sets of directional antennas, wherein
each set of directional antennas of the plurality of sets of
directional antennas is rotatably mounted on a common axis, with
each antenna of the each set of directional antennas focused on an
adjacent sector emanating from a respective common axis; and a
memory including routing information identifying aligned sectors of
adjacent directional antennas, wherein detection of rotation of a
set of directional antennas beyond a threshold amount identifies a
changed alignment of adjacent sectors, wherein, upon identification
of the changed alignment, revised routing information is provided
to the plurality of sets of directional antennas, and wherein, upon
identification of the changed alignment, a data packet is
rebroadcast between adjacent sets of directional antennas utilizing
directional antennas identified by the revised routing
information.
2. The system of claim 1, wherein the adjacent sectors do not
overlap.
3. A data transmission method comprising: detecting rotation of a
set of directional antennas; identifying, when the detected
rotation exceeds a threshold amount, a changed alignment of
adjacent sectors of a plurality of sets of directional antennas
each having a set of directional antennas rotatably mounted on a
common respective axis; upon identification of the changed
alignment, providing revised routing information to the plurality
of sets of directional antennas; and upon identification of the
changed alignment, rebroadcasting a data packet between adjacent
sets of directional antennas utilizing directional antennas
identified by the revised routing information.
4. The method of claim 3, wherein the adjacent sectors do not
overlap.
Description
PRIORITY
[0001] This application is a continuation application claiming
priority to U.S. patent application Ser. No. 13/492,352, which was
filed with the U.S. Patent and Trademark Office on Jun. 8, 2012,
and is a National Phase application of International Application
No. PCT/US2010/059759, filed with the U.S. Patent and Trademark
Office on Dec. 9, 2010, and claims priority to U.S. Provisional
Application No. 61/285,069, filed Dec. 9, 2009, the contents of
which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The disclosed method relates generally to wireless network
communication techniques and, in particular, to a method and system
for network-wide broadcast via hopping between nodes equipped with
directional antennas, with rebroadcast restricted based on node
location and yawing position.
[0004] 2. Background of the Related Art
[0005] Conventional wind farms have multiple wind turbines. Each
turbine typically has a nacelle located at an upper portion
thereof, onto which turbine blades are rotatably connected. Each
nacelle of each wind turbine in the wind farm will yaw about a
vertical axis, to position the nacelle and turbine blades into the
wind for maximum power production. See U.S. Publ. No. 2005/0196280
A1 to Gonzalez et al. and U.S. Publ. No. 2010/0109327 A1 to Nielson
et al., the contents of which are incorporated herein by
reference.
[0006] The need for each of the multiple turbines in the wind farm
to wirelessly communicate is well recognized, for reasons that
include but are not limited to efficient and reliable propagation
of aircraft approach alert signals to activate an anti-collision
warning light located on each nacelle.
[0007] Wireless communication protocols are well known.
Conventional protocols include a random access protocol, such as
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA).
See IEEE 802.11 Wireless Local Area Network ("WLAN") standard and
U.S. Pat. Nos. 5,761,431 and 6,680,950, the contents of which are
incorporated herein by reference.
[0008] In such conventional methods, a same wireless communication
channel is typically utilized for all nodes in a network, avoiding
the need to coordinate between the transmitter and receiver of a
link to select a communication channel. A multi-hop wireless
routing is needed when source and destination nodes are not
connected by a direct link. Multi-hop routing is typically achieved
by relaying packets over multiple links, i.e. hops that involve
intermediate nodes. Such routing can be unicast or broadcast.
[0009] For unicast routing, a source node sends the packet to a
specific destination node located one or more hops away. A routing
protocol at the network layer determines a next hop node to forward
the packet via a link layer transmission.
[0010] For broadcast routing, a source node sends the packet to all
nodes in the network.
[0011] Broadcast routing, sometimes referred to `flooding`, is
typically used to distribute network wide control or management
information, as described in U.S. Pat. No. 7,369,512, the contents
of which are incorporated herein by reference.
[0012] Omni-directional antennas are typically used to facilitate
flooding since all neighboring nodes will receive the packet using
a single link layer broadcast and will relay the packet by link
layer broadcast. For example, in a naive flooding broadcast method
a source node broadcasts a packet via a single link layer
broadcast. Any other node, upon receiving a packet for the first
time, rebroadcasts the packet via a single link layer broadcast.
When a node receives the rebroadcast of same packet, a duplicate,
i.e. rebroadcast, packet is ignored to prevent endless rebroadcast
throughout the network.
[0013] To recognize duplicate packets, a unique signature is
typically provided in a packet header. The originating or source
node inserts the signature in the packet header. In this example
method of naive flooding, every node in a network having `N` number
of nodes will transmit via a broadcast transmission at the link
layer each unique packet only once, resulting in N number of
transmissions of each packet.
[0014] However, naive flooding is inefficient since nodes having
links that are linked to more than one other node will receive the
same packet more than once. Accordingly, to improve network
efficiency and to reduce packet loss due to packet collisions in a
shared wireless channel, there is a need to achieve network-wide
broadcast utilizing less than N packet transmissions.
[0015] For wireless communication between wind farm turbines, it
has been proposed to use directional antennas instead of
omni-directional antennas. In a directional antenna, wireless
communication is restricted to a sector for reasons that include
reduction of interference and providing longer transmission range.
However, conventional use of directional antennas fails to account
for yawing of the wind turbine and also fails to provide a method
to reduce congestion of a shared transmission channel.
SUMMARY OF THE INVENTION
[0016] The disclosed method overcomes the above shortcomings by
providing a system for data transmission in a wireless network
including a plurality of sets of directional antennas with each set
of directional antennas rotatably mounted on a common axis and each
antenna of each set of directional antennas focused in a different
sector emanating from a respective common axis, and a memory
includes routing information identifying aligned sectors of
adjacent sets of directional antennas. Detection of rotation of a
set of directional antennas beyond a threshold amount identifies a
changed alignment of adjacent sectors. Upon identification of the
changed alignment of the adjacent sectors, revised routing
information is provided to the plurality of sets of directional
antennas. Upon identification of the changed alignment of the
adjacent sectors, a data packet is rebroadcast between adjacent
sets of directional antennas utilizing directional antennas
identified by the revised routing information.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The above and other objects, features and advantages of
certain embodiments of the present invention will be more apparent
from the following detailed description taken in conjunction with
the accompanying drawings, in which:
[0018] FIGS. 1A and 1B depict a wind farm having four nodes,
showing varied packet transmission after yaw of a nacelle of a
first node; and
[0019] FIG. 2 is flowchart of a method of the disclosed method.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] The following detailed description of preferred embodiments
will be made in reference to the accompanying drawings. In the
description provided herein, an explanation of related functions or
constructions known in the art are omitted for the sake of clarity
to avoid obscuring the invention with unnecessary detail.
[0021] In the disclosed method, restrictions on rebroadcast of
network messages are established based on static factors of network
topography and established positions of nodes therein, and a
dynamic factor of present yaw angle, thereby improving network
efficiency, and reducing packet loss due to shared transmission
channel collisions.
[0022] FIGS. 1A and 1B provide a simplified plan view of a four
node network, i.e. Nodes A, B, C and D. In a preferred embodiment,
each of Nodes A through D includes a three (3) sector directional
antenna, for transmission and reception of respective sectors, e.g.
sectors A-1, A-2, A-3, emanating from each node. Each node may
further include a computer embedded within a nacelle of a wind
turbine. In the network depicted in FIGS. 1A and 1B, Node D is
positioned beyond transmission range of Node A, with Node D relying
on rebroadcast via Node B and/or Node C, as described below.
[0023] FIG. 1A shows Nodes A through D in first yaw positions. FIG.
1B shows Nodes B-D, each in the first yaw position and Node A
having moved to a second yaw position that exceeds a threshold
amount, which in a preferred embodiment is a rotation angle greater
than five degrees (5.degree.) but will vary depending on empirical
values obtained during network training, relative node positions
and transmission characteristics. The threshold amount is
preferably reduced as the number of antennas and sectors for a node
is increased.
[0024] In a preferred embodiment, transmission from Node A, as an
originator node, is performed based on routing information stored
in a memory, i.e. preferred link transmissions, which can be stored
and calculated in a central location. Updated routing information
is provided to the nodes upon detection of node yaw beyond a
threshold amount. In wind farm and similar applications it is
recognized that yaw movement is often controlled and typically does
not occur at a rapid pace, reducing the number of database updates
provided to the nodes.
[0025] The provided preferred link broadcast, i.e. routing
information, is computed such that the total number of
transmissions is reduced while ensuring that transmission is made
to all nodes in the network, effectively eliminating redundant
transmissions. In the preferred embodiment, where the database,
list, or memory is centrally located, a central controller node is
responsible for computing and updating this database. This
controller receives updated yaw angles from the nodes upon
detection of yaw beyond the specified threshold amount.
[0026] In a preferred embodiment, a system is provided for data
transmission via a multi-node wireless network that is provided in
a geographic area 100 having more than two nodes, as shown in FIGS.
1A and 1B. Each node is stationary, having a set geographic
position stored in a list, database or memory, preferably in values
of latitude and longitude.
[0027] The data transmission is typically in a data packet format
for wireless communication between non-adjacent nodes by
rebroadcast via adjacent nodes. As described herein, rebroadcast
occurs over preferred link transmissions of certain adjacent nodes,
thereby reducing redundant transmissions.
[0028] A plurality of antennas is affixed to each node, typically
by fixing the antennas to a nacelle that rotates about a vertical
axis, i.e., yaws. Each node, while being fixed in a geographic
location, includes a component that rotates about the vertical
axis, with such rotation typically being of a nacelle occurring
independent of rotation of nacelles of other nodes. As used herein,
each node is associated with a nacelle of a wind turbine, and the
geographic area refers to a wind farm.
[0029] Each node includes a minimum of two directional antennas,
e.g. 111-1, 111-2, that each performs transmit/receive function of
data packets for that node. The data packets are transmitted
throughout the network via hopping between adjacent nodes.
[0030] The directional antennas 111-1, 111-2 are positioned to
cover different sectors, each emanating from and providing radio
frequency coverage around each node, preferably with sectors that
do not overlap. The database that stores node position information
also communicates to each node preferred link transmissions of
aligned sectors of adjacent nodes.
[0031] As known to those of skill in the art, a compass or similar
detector is included to detect a degree of yaw of the nacelle
relative to the tower on which the nacelle is rotatably mounted.
When a node is detected to rotate beyond the threshold amount, a
changed alignment is identified and an identification of revised
preferred link transmissions is provided to each node in the
geographic area 100, with such detection being made either at the
node or by a central controller. Based on the preferred link
transmissions, the data packet is re-transmitted to one or more
specifically identified antennas of each transmitting node.
[0032] As shown in FIG. 1A, Node A, acting as an originating source
for network-wide broadcast of a message (O), transmits the data
packet in second and third sectors via directional second and third
antennas (111-2, 111-3), which is received by Nodes B and C.
[0033] In some embodiments, rebroadcast of the message (R) by Nodes
B and C is contingent on permissions provided via routing
information provided in the database. For the first yaw position
shown in FIG. 1A, the routing information for messages originating
from source Node A is set forth in Table 1.
TABLE-US-00001 TABLE 1 Tx Node Ant. 1 Ant. 2 Ant. 3 A No Yes Yes B
No No Yes C No No No D No No No
[0034] FIG. 1B shows Node A having rotated to the second yaw
position. When in such position, the revised routing information
for messages originating from source Node
[0035] A is set forth in Table 2.
TABLE-US-00002 TABLE 2 Tx Node Ant. 1 Ant. 2 Ant. 3 A No No Yes B
No No Yes C No No No D No No No
[0036] In FIG. 1A, the network message is propagated to all nodes
in three transmissions. In FIG. 1B, the network message is
propagated to all nodes in two transmissions. In comparison,
conventional, naive flooding broadcast protocol propagates the
message in twelve (4.times.3) transmissions, since each antenna on
each node must transmit once. Accordingly, channel congestion is
reduced, particularly for networks having four or more nodes. One
of ordinary skill in the art will recognize that the nodes can also
be configured with two or more sectors emanating from each
node.
[0037] As will be noted from the above, the antennas identified by
the routing information will transmit on sectors corresponding to
known coordinate values of adjacent nodes. Also, the message packet
will typically include in a header thereof an identifier of the
originator node (Node A). Based on the known positions of each node
in the network, Node D will recognize that no further rebroadcast
is needed.
[0038] In a preferred embodiment, geographical positions of each
node corresponding to a turbine in the wind farm are mapped, and
the mapped positions are stored in a list or memory of a
database.
[0039] As described above, at least two directional antennas are
mounted on each turbine and each directional antenna is focused on
a different sector emanating from the node. A predetermined
preferred link transmission table that identifies directional
antennas aligned with an adjacent node is provided to each node.
The yaw of each turbine is determined. When yaw of the turbines is
within the threshold amount, data packets are wirelessly
communicated between adjacent nodes using directional antennas
identified in the preferred link transmission table. When the yaw
of any turbine is determined to exceed the threshold amount, a
revised preferred link transmission table is calculated based on
the determined yaw, and the revised preferred link transmission
table is transmitted for use by each node. Thereafter, subsequent
data packet transmission is only performed by those directional
antennas identified in the revised predetermined preferred link
transmission table.
[0040] FIG. 2 is a flowchart depicting an operation of a preferred
embodiment. In step 201, the system is in a quiescent state,
waiting for timer expiry or receipt of a signal indicating that one
or more nodes have experienced yaw in excess of the threshold
amount set for that respective node of the network.
[0041] If in step 203 it is determined that an excessive yaw has
not been received or occurred, a determination is made of whether
the timer has expired in step 205. If in step 205 it is determined
that the timer has not expired, the system returns to the quiescent
state of step 201.
[0042] If in step 205 it is determined that the timer has expired,
in step 207 a controller, preferably centrally located, that
manages the database sends a heartbeat message to the nodes. Upon
receipt of the heartbeat message, each node responds to the
controller by providing a current yaw position, which the
controller compares to maintained prior positions to confirm
accuracy of the preferred link identifications previously provided
to the nodes. In a preferred embodiment, if a node does not receive
the heartbeat message within one or more timer intervals, the node
will default to a conventional transmission protocol and retransmit
any received data packets via transmit antennas, rather than only
the antenna(s) identified by the preferred link identifications,
thereby operating in a failsafe mode.
[0043] If in step 203 it is determined that an excessive yaw has
been received, a recalculation is performed in step 209 based on
the new yaw angle that is in excess of the threshold amount, with
the calculation utilizing database information including the
position of each node, and the previously reported yaw angles of
nodes not reported to have exceeded their respective threshold
amount.
[0044] In step 211 the recalculated information is transmitted to
the nodes as revised preferred link identifications for use by each
node. The method then returns to step 201.
[0045] While the disclosed method has been shown and described with
reference to certain embodiments thereof, it will be understood by
those skilled in the art that various changes in form and details
may be made therein without departing from the spirit and scope of
the present invention as defined by the appended claims and
equivalents thereof.
* * * * *