Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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[0001] METHOD AND SYSTEM FOR UTILIZING SMART ANTENNAS IN
ESTABLISHING A BACKHAUL NETWORK
[0002] FIELD OF INVENTION
[0003] The present invention is related to wireless communications. More
particularly, the present invention is a method and system which utilizes
smart
antennas in establishing a backhaul network.
[0004] BACKGROUND
[0005] One of the most important issues in a wireless communication system
is to increase of capacity of the system by decreasing interference. Array
antennas
(also known as smart antennas) have been developed to improve capacity and to
reduce interference. A smart antenna uses a plurality of antenna elements to
generate a directional beam radiating signals only toward a particular
direction in
azimuth, and selectively detects signals transmitted from a particular
direction.
With a smart antenna, a wireless communication system is able to increase
capacity and reduce interference since signals are radiated to a narrow region
in a
coverage area. This increases overall system capacity since a transmitter may
increase the transmission power level of the directional beam without causing
excessive interference to other transmitters and receivers, such as wireless
transmit/receive units (WTRUs) and base stations.
[0006] A wireless communication system generally comprises a plurality of
nodes, such as base stations and radio network controllers, or the like. The
nodes
are typically connected to each other with wired connections, such as a mesh
network or a cellular network. The nodes communicate with each other and
transmit messages, such as backhaul messages.
[0007] However, there is a disadvantage with wired connections for
establishing a backhaul network in that wired connections are expensive, time
consuming, and inflexible for modification or change of the network. In
particular,
mesh networking requires nodes to be connected with each other. When a new
node is added to the mesh network, there is a large burden (in terms of both
cost
and time) for establishing new connections to the new node for backhauling.
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[0008] Therefore, there is a need for a cost effective, less time consuming,
and flexible method and system for establishing a backhaul network.
[0009] SUMMARY
[0010] The present invention is a. method and system for utilizing a smart
antenna in establishing a backhaul network. The present invention is directed
to using smart antennas in for improving in-cell communications, increasing
throughput and forming at least a portion of a flexible backhaul network for
conveying backhaul data. The present invention is implemented in a wireless
communication system which includes a plurality of nodes, and wherein each
node is connected together in a mesh network. At least a portion of the nodes
are
provided with one or more smart antennas which are configured to generate a
plurality of directional beams. Each node having one or more smart antennas
maintains a list of other nodes having smart antennas and beam direction and
configuration information to be used in transmission of messages to those
other
nodes. When a source node is required to transmit backhaul data to a target
node, the source node retrieves the beam direction and configuration
information
for the target node and transmits the messages with a directional beam
directed
to the target node.
[0010a] According to a first broad aspect of the present invention there is
disclosed a wireless communication system comprising: a plurality of nodes,
wherein each node is connected to at least one neighbor node and is configured
to
transmit beacon signals carrying a beacon message to neighboring nodes, the
beacon message including a power level, a traffic level, an interference
level, a
priority of access, security, identification, and other access control and
security
control information; each node comprising: a smart antenna for generating a
plurality of directional beams; a memory for storing a list of neighbor nodes
having connections and beam configuration information to be used in
transmission of messages to the neighbor nodes; and a controller for selecting
a
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particular directional beam for transmitting a particular message to another
node while independently controlling each of said plurality of directional
beams;
wherein at least one of the plurality of nodes comprises a wired connection.
[0010b] According to a second broad aspect of the present invention there is
disclosed a method for utilizing smart antennas in a wireless communication
system comprising a plurality of nodes, at least two of the plurality of nodes
each having a smart antenna which generates at least one directional beam for
connection to at least one neighbor node, the method comprising: each node
transmitting a beacon signal carrying a beacon message to neighbor nodes,
wherein the beacon message includes a power level, a traffic level, an
interference level, a priority of access, security, identification, and other
access
control and security information; measuring and storing a list of neighbor
nodes
having connections and beam direction and configuration information to be used
in transmission of messages to the neighbor nodes; generating a directional
beam for transmitting a particular message to a target node in accordance with
the beam direction and configuration information; and transmitting the message
to the target node with the generated directional beam; wherein at least one
of
the plurality of nodes comprises a wired connection.
[0011] BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 is a block diagram of a network of a plurality of nodes in
accordance with the present invention.
[0013] Figure 2 is a block diagram of a node made in accordance with the
present invention.
[0014] Figure 3 is a flow diagram of a process of utilizing smart antennas
in transmission of messages between nodes in accordance with the present
invention.
[0015] Figure 4 is a diagram of an example of a beam pattern generated
by a node in accordance with the present invention.
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[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] The present invention is applicable to any wireless communication
system including, but not limited to, Time Division Duplex (TDD), Frequency
Division Duplex (FDD), and Time Division Synchronous Code Division Multiple
Access (TD-SCDMA), as applied to a Universal Mobile Telecommunications
System (UMTS), CDMA2000, CDMA in general, Global System For Mobile
Communications (GSM), General Packet Radio System (GPRS), and Enhanced
Data Rates For GSM Evolution (EDGE).
[0018] Hereafter, the terminology "WTRU" includes but is not limited to a
user equipment, a mobile station, a fixed or mobile subscriber unit, a pager,
or any
other type of device capable of operating in a wireless environment. When
referred
to hereafter, the terminology "node" includes but is not limited to a base
station, a
Node-B, a site controller, an access point or any other type of interfacing
device in
a wireless environment.
[0019] Figure 1 is a block diagram of a network 100 of a plurality of nodes
102a-n in accordance with the present invention. At least one of the nodes,
graphically shown as 102n, is connected to a core network 110. The operation
of a
core network of a wireless communication system is well known to those of
skill in
the art and is not central to the present invention. Accordingly, the core
network
110 will not be explained in detail herein.
[0020] Each node 102a-n serves one or more WTRUs (not shown) which are
located within the coverage area of the nodes 102a-n. The network 100 may be a
mesh network or a cellular network. In the context of the present invention,
both
mesh networks and cellular networks transmit backhaul information, but there
is
a fundamental difference. Cellular networks typically have fixed network
infrastructures and backhaul connections. These connections are typically
point-
to-point and they do not change. One node transmits the backhaul data to
another
node at another location in the network, and to that location only.
[0021] In the case of a mesh network, the connections between nodes change,
and therefore the backhaul data may be transmitted to different nodes at
different
times for further routing. Particularly in the case of mesh networks, since
the
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backhaul connection can change from time to time, it is important to be able
to
adjust the smart antennas so that a connection to a different node can be
achieved
without creating undue interference to other nodes.
[0022] At least a portion of the nodes 102a-n are provided with at least one
smart antenna (as will be explained in detail hereinafter) and utilize the
smart
antenna in transmission of backhaul data to other nodes 102a-n in addition to
regular download transmissions to WTRUs and upload receipts from WTRUs.
These nodes 102a-n are capable of generating a plurality of directional beams
and
steering the beams to any direction in azimuth.
[0023] It is expected that the network 100 will include nodes with wired
connections as well as those with wireless backhaul connections that use smart
antennas. Since connections established using smart antennas can be
reconfigured
and directed to different nodes, they increase the flexibility of the system.
However, at least one of the nodes will have both a wired connection to the
core
network 110 and wireless connections to other nodes in order to provide a
connection between the group of wireless nodes and the core network that is
essentially wired. At least a portion of the nodes 102a-n may also be provided
with
the capability to transmit backhaul information over a wired or dedicated
connection. A node (shown as node 102n) having both wired and wireless
backhaul
connections, (hereinafter referred to as a hybrid node), will be the
connection to the
wired core network 110. In other words, as nodes transmit backhaul information
wirelessly with the help of smart antennas, this backhaul information will be
routed eventually to the core network 110 through the hybrid node 102n.
Therefore, the hybrid node 102n can receive and send backhaul information to
the
nodes with wireless backhaul connections while it receives and sends backhaul
information to the core network 110, thereby forming a bridge.
[0024] In one embodiment, a node 102a-n has a plurality of predetermined
beams 109a-h as shown in Figure 4, and selects one among the plurality of
beams
109a-h in order to direct a transmission or reception. Figure 4 shows eight
beams
in azimuth that may be generated by each node 102a-n. It should be noted that
the beams shown in Figure 4 are provided just as an example and any number of
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beams, beam patterns, or any other type of pattern may be implemented.
[0025] In an alternative embodiment, each beam 109a-h may be generated
and directed in real time, rather than chosen from a set of predetermined
positions.
[0026] A node 102a-n selects a beam 109a-h direction, either dynamically or
among a plurality of available positions, that provides the best performance
in
terms of system capacity, data throughput, interference, or the like. Nodes
102a-n
are generally fixed in a particular location. Therefore, once a beam 109a-h
and
configuration between two nodes 102a-n is set, the direction and configuration
may be stored and used thereafter without change. Each node 102a-n may be
capable of providing more than one beam 109a-h for connection to other nodes
102a-n, since the radio environment and the traffic load may change on a long-
term basis. Therefore, each node 102a-n monitors signals received from other
nodes 102a-n in order to determine the radio environment, and dynamically
adjusts the beam direction and signal configuration to optimize the
performance of
the system.
[0027] One example of the operation of the system is as follows: a first
selected node, such as node 102a, generates a beam and steers it towards
another
selected node, such as node 102b. This can be done by adjusting the complex
weights applied to the antenna array elements as is typically done with beam
forming antenna arrays. At the same time, node 102a measures the quality of
the
link A to node 102b. The quality of the link A may be measured as signal-to-
noise
ratio, bit or frame error rate, or some other measurable quality indicator.
The
transmitting node 102a finds the best antenna beam direction, the best
combination of weights to maximize the link quality in this case, and stores
both
the link quality measure and the corresponding beam direction (weights). The
transmitting node 102a does this for all nodes that are in the vicinity and
stores
the corresponding quality and beam information.
[0028] Any node 102a-n can be flexibly and wirelessly connected or
disconnected to other nodes 102 a-n by selectively directing one or more beams
at
the other nodes 102 a-n. In Figure 1, the first node 102a transmits messages
to
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the second node 102b using a directional beam A, and to a fourth node 102d
using
a directional beam B. The directional beams A and B are independently
controlled
and can be transmitted simultaneously. Since each directional beam A and B is
radiated only toward a particular direction, it does not cause excessive
interference
to other nodes 102a-n or WTRUs.
[0029] Figure 2 is a block diagram of a node 202 in accordance with the
present invention. The node 202 comprises a smart antenna 204, a controller
206,
a memory 208 and an optional wired link 210. The wired link 210 may be a link
to
the core network 110 or to another node. The node 202 implements a signal
processing algorithm to adapt to user movement, changes in the radio-frequency
environment and multipath along with co-channel interference. A radio resource
management (RRM) function implemented by the controller 206 decides how radio
resources should be allocated in the node 202.
[0030] The smart antenna 204 comprises a plurality of antenna elements
(not shown) to generate a plurality of directional beams under the control of
the
controller 206. Each beam functions as a wireless connection between the node
202 and other nodes. As aforementioned, since the node 202 is typically fixed
in a
particular location, a beam direction and configuration between two nodes can
be
predetermined and stored in the memory 208. The memory 208 maintains a list of
other nodes and beam direction and configuration information for each of those
other nodes. When the node 202 is required to transmit messages, such as
backhaul data, to another node, the controller 206 retrieves corresponding
beam
direction and configuration information from the memory 208 and generates a
directional beam steered to a particular direction and transmits the messages
using the beam.
[0031] In the case of a hybrid node 102n, this process is followed in
establishing wireless connections to other nodes with the help of the smart
antenna 204. When the hybrid node 102n establishes a backhaul connection to
the
core network 110, or another node, there is no configuration information or no
beam selection since the wired link 210 is physically fixed and will always
provide
a connection between the same two nodes.
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[0032] In accordance with the present invention, the smart antenna 204
preferably has a multi-beam capability, in which each beam can be used
independently. A node 202 generates more than one directional beam to transmit
backhaul data to a plurality of other nodes at the same time. Since the same
frequency may be reused for more than one directional beam in the same
coverage
area, the system capacity is substantially increased.
[0033] Several nodes may be coupled together with several beams. This
makes it convenient to change connections and dynamically adapt to changes in
the radio environment. For example, two beams may be provided for connection
between two nodes. If one beam suffers from excessive interference, then the
nodes may switch to another beam for transmission of messages.
[0034] The use of smart antennas enables the formation of flexible backhaul
links between nodes. Since each node is configured to generate a plurality of
directional beams and is capable of steering the directional beams to any
direction
in azimuth, when a new node is added to the network 100, existing nodes may
establish new connections to the new node by simply setting a new beam
direction
and configuration directed to the new node. In addition, when an existing node
is
removed from the network 100, nodes may simply delete beam direction and
configuration information for the removed node from memory 208. The present
invention makes additional installation or removal of facilities unnecessary
for
establishing or removing connections between nodes. It should be noted that
the
present invention may be implemented either in a mesh network or in a cellular
network.
[0035] One of the strengths of mesh networking is the ability to create new
links and delete other links between nodes depending on a plurality of
factors,
including a traffic load, interference, and individual node performance. As
shown
in Figure 1, a plurality of nodes 102a-n are coupled to each other using smart
antennas. The lines between the nodes 102a-n in Figure 1 indicate possible
links
A-F. Control may be centralized, whereby at least one node functions as a
controlling node to control the connection between nodes, or may be
decentralized,
where control is distributed over several nodes or all nodes. If one node is
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designated as a controlling node, the controlling node collects information
regarding traffic conditions and performances in each node, and determines the
best traffic route for transmission of messages from one node to another node.
[0036] Each node 102a-n preferably transmits one or more beacon signals in
its one or more beams, which provide information useful for network operation.
For example, the beacon signals may transmit current power levels, traffic
levels,
interference levels, and other parameters. Beacon signals may also include
priority of access, security, identification, and other varying types of
access control
and security control information. The beacon signals are measured periodically
or
non-periodically, and the parameters are utilized as the basis for adjusting
connections between nodes in order to find the most efficient traffic routes.
Forming at least a portion of the backhaul connections wirelessly by using
smart
antennas in accordance with the present invention allows flexibility and
reduces
unnecessary cost and time for establishing and adjusting connections between
nodes.
[0037] For example, as shown in Figure 1, if the traffic load between the
second node 102b and the fourth node 102d is too heavy, other nodes recognize
the
traffic conditions between the two nodes 102b, d by reading the beacon signals
of
the nodes 102 b, d, as will be described in detail hereinafter. If the first
node 102a
desires to route traffic to the fifth node 102e, it will avoid, if possible,
the second
and fourth nodes 102 b, d and will alternatively route traffic through the Nth
node
102n.
[0038] The present invention not only has the advantage of providing a
flexible, wireless mesh network, but also the backhaul information (which is
typically sent via a wired line) may now be sent via the same flexible links
through
the smart antenna. Implementation of this type of dual-use smart antenna
scheme in accordance with the present invention results in significant
advantages
over current wireless communication systems.
[0039] Figure 3 is a flow diagram of a process 300 of utilizing smart
antennas in transmission of messages between nodes in accordance with the
present invention. At least a portion of the nodes are provided with at least
one
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smart antenna, which is configured to generate a plurality of directional
beams
and to steer then independently in azimuth (step 302). Each beam is used as a
wireless connection to other nodes in addition to regular traffic of downloads
to
WTRUs and uploads from WTRUs. Each node maintains a list of other nodes and
beam direction and configuration information to be used for transmission to
the
other nodes (step 304). It should be noted that steps 302 and 304 are
typically
performed upon setting up a system or reconfiguring the system to accept or
delete
nodes, and will not typically have to be formed during normal operation. When
a
source node is required to transmit to a target node, the source node
retrieves
beam direction and configuration information for the target node from the
memory, and generates a directional beam using the beam direction and
configuration information (step 306). Once a node is selected for transmission
of
backhaul data, based on link quality and other considerations such as traffic
density, the transmitting node selects the beam direction (weights) from the
list
and applies it to the antennas.
[0040] The process for measuring the quality of links and storing relevant
information may need to be done periodically since the environment may change
and adjustment of beam directions may be necessary. The source node then
transmits to the target node with the generated directional beam (step 308).
[0041] In an optional step, a change in the network may occur whereby a
new node may be added to the network, an existing node may be removed from the
network, or radio frequency or other conditions may change. In response to the
change, other nodes update the list of beam direction and configuration
information to reflect the change (step 310).
[0042] Although the features and elements of the present invention are
described in the preferred embodiments in particular combinations, each
feature or
element can be used alone without the other features and elements of the
preferred embodiments or in various combinations with or without other
features
and elements of the present invention.
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