NO343968B1 - Method and system for utilizing smart antennas to establish a background transport network - Google Patents

Description

The present invention relates to wireless communications. More specifically, the present invention relates to a method and system that uses smart antennas to establish a background transport network. Where traditional wireless communication systems use wire-based connections, such as a mesh network or cellular network, to establish a background network, the present invention can wirelessly transmit background communication using a plurality of nodes where each node has a smart antenna that generates at least one directional beam for to connect to at least one neighboring node.

One of the most important issues in a wireless communication system is to increase the capacity of the system to reduce interference. Directional 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 that radiates signals only toward a specific direction in azimuth, and selectively detects signals sent from a specific direction. With a smart antenna, a wireless communication system will be able to increase capacity and reduce interference since signals are radiated to a narrow area in a coverage area. This increases overall system capacity since a transmitter can increase the transmit power level of the directional beam without causing excess interference in other transmitters and receivers, such as wireless transceiver units (WTRUs) and base stations.

A wireless communication system generally includes a plurality of nodes, such as base stations and radio network controllers, or the like. The nodes are typically connected to each other via wire-based connections, such as a mesh network or a cellular network. The nodes communicate with each other and send messages, such as background transport messages.

However, there is a disadvantage of wire-based connections for establishing a background transport network in that wire-based connections are expensive, time-consuming, and inflexible when modifying or changing the network. Especially in the mesh network, nodes are required that are connected to each other. When a new node is added to the mesh network, a large task (in both cost and time) is used to establish new connections to the new node for background transport.

Therefore, there is a need for a cost-effective, less time-consuming and flexible method and system for establishing a background transport network.

US 2003/0109285 describes a wireless communication device for providing a service in a mesh network. Each of the units has a directional antenna.

The article "Coexistence Study for the introduction of FWA in the 5.8 GHz band (5725-5875 MHz)", page 1- 63, 01/05/2003, describes a mesh communication system.

EP 1401151 relates to hybrid wired/wireless networks, and describes a method and system for providing a mesh network using a plurality of wireless access points.

The present invention is a method and system for using a smart antenna to establish a background transport network. The present invention is directed to using smart antennas to improve intra-cell communications, increase throughput, and to form at least part of a flexible background transport network to convey background data. The present invention is implemented in a wireless communication system that includes a plurality of nodes, and where each node is connected in a mesh network. At least a portion of the nodes are provided with one or more smart antennas configured to generate a plurality of directional beams. Each node has one or more smart antennas that maintain a list of other nodes that have smart antennas and beam direction and configuration information that is used in sending messages to these other nodes. When a source node is required to send background data to a target node, the source node retrieves the beam direction and configuration information of the target node and sends the message with the directional beam aimed at the target node.

The invention is defined by the independent claim.

Figure 1 is a block diagram of a network with a plurality of nodes according to the present invention.

Figure 2 is a block diagram of a node made according to the present invention.

Figure 3 is a flow diagram of a process that uses smart antennas in sending messages between nodes according to the present invention.

Figure 4 is a diagram of an example of a beam pattern generated by a node according to the present invention.

The present invention is applicable in 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 form, global system for mobile communications (GSM), general packet radio system (GPRS), and enhanced data rates for GSM evolution (EDGE).

Hereinafter, the term "WTRU" will include, but not be 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 term "node" will include, but not be limited to, a base station, a Node-B, a site controller, an access point or any other type of interface device in a wireless environment.

Figure 1 is a block diagram of a network 100 with a plurality of nodes 102a-ni according to the present invention. At least one of the nodes, graphically shown as 102a, is connected to a core network 110. The operation of a core network in a wireless communication system is well known to one skilled in the art and is not central to the present invention. Accordingly, the core network 110 will not be explained in detail here.

Each node 102a-n serves one or more WTRUs (not shown) that 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 will send background information, but there is a fundamental difference. Cellular networks typically have fixed network infrastructures and background transport connectivity. These connections are typically point to point and they do not change. A node sends background data to another node in another location in the network, and only to this location.

In the case of a mesh network, the connections between the nodes will change, and therefore background data may be sent to different nodes at different times for further routing. Especially in the case of mesh networks, since the background connection can change from time to time, it is important to be able to adjust the smart antennas so that a connection to another node can be achieved without creating unnecessary interference to other nodes.

At least some of the nodes 102a-ner provided with at least one smart antenna (which will be explained in detail hereinafter) and use the smart antenna in transmitting background data to other nodes 102a-ni in addition to regular download transmissions to the WTRU and upload reception from WTRU. These nodes 102a are capable of generating a plurality of directional beams and directing the beam to any direction in azimuth.

It is expected that the network 100 will include nodes with wired connections as well as those with wireless background connections using smart antennas. Since connections established using smart antennas can be reconfigured and routed to different nodes, these 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 to provide a connection between the group of wireless nodes and the core network that is substantially wired. At least some of the nodes 102a may also be provided with the ability to send background information over a wired or dedicated connection. A node (shown as node 102n has both wired and wireless background connections, (hereafter referred to as a hybrid node), which will be the connection to the wired core network 110. In other words, since the nodes transmit background information wirelessly using smart antennas, this the background information is ultimately routed to the core network 110 through the hybrid node 102n. Therefore, the hybrid node 102n can receive and send background information to the nodes with wireless background connections while receiving and sending background information to the core network 110, thus forming a bridge.

In one embodiment, a node 102a-net has a plurality of predetermined beams 109a-k as shown in Figure 4, and selects one among the plurality of beams 109a-h to control a transmission or reception. Figure 4 shows eight rays in azimuth which can be generated by each node 102a-n. It should be noted that the beams shown in Figure 4 are provided as an example only and any number of bars, beam patterns, or any other type of pattern may be implemented.

In an alternative embodiment, each beam 109a could be generated and controlled in real time, rather than being selected from a set of predetermined positions.

A node 102a selects a beam 109a direction, either a dynamic one or among a plurality of available positions, which provides the desired performance in terms of system capacity, data throughput, interference, or the like. Node 102a is generally fixed at a particular location. Therefore, once a beam 109a-hog configuration between two nodes 102a-ners is set, the direction and configuration can be stored and used thereafter without change. Each node 102a-n may be able to provide more than one beam 109a-h for connection to other nodes 102a-n, since the radio environment and traffic load may change on a long-term basis. Therefore, each node 102a-n will monitor signals received from other nodes 102a-n to determine the radio environment, and dynamically adjust the beam direction and signal configuration to optimize the performance of the system.

An example of the operation of the system is as follows: a first selected node, such as node 102a, generates a beam and directs it towards another selected node, such as node 102b. This can be done by adjusting the complex weights applied to the antenna array elements, which is typically done by beamforming in antenna arrays. At the same time, the node 102a can measure the quality of the link A to the node 102b. The quality of link A can be measured as signal to noise ratio, bit or frame error rate, or some other measurable quality indicator. The transmitting node 102finds 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 nearby nodes and stores the corresponding quality and beam information.

Any node 102a can be flexible and wirelessly connected or disconnected to other nodes 102a-n by selectively directing one or more beams to the other nodes 102a-n. In Figure 1, the first node 102a sends messages to the second node 102b using a directional beam A, and to a fourth node 102d using a directional beam B.

Directional beams A and B are independently controlled and can be sent simultaneously. Since each directional beam A and B is beamed only towards a specific direction, this causes excessive interference in other nodes 102a or WTRU.

Figure 2 is a block diagram of a node 202 according to the present invention. The node 202 includes 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 another node. The node 202 implements a signal processing algorithm to adapt to user movement, changes in radio frequency environment and multipath along with co-channel interference. A radio resource manager (RRM) function implemented by the controller 206 determines how radio resources should be allocated in the node 202.

The smart antenna 204 includes a plurality of antenna elements (not shown) to generate a plurality of directional beams under the control of the controller 206. Each beam acts as a wireless link between the node 202 and other nodes. As mentioned earlier, since node 202 is typically fixed in a particular location, a beam direction and configuration between two nodes will be predetermined and stored in memory 208. Memory 208 maintains a list of other nodes and beam directions and configuration information for each of these other nodes. When the node 202 is required to send messages, such as background data, to other nodes, the controller 206 receives the corresponding beam direction and configuration information from the memory 208 and generates a directional beam directed to a particular direction and sends the message using the beam.

In the case of a hybrid node 102n, this process is followed in establishing wireless connections to other nodes using the smart antenna 204. When the hybrid node 102n establishes a background connection to the core network 110, or another node, there is no configuration information or no beam selection since the wire-based link 210 is typically fixed and will always provide a connection between the same two nodes.

According to the present invention, the smart antenna 204 will preferably have a multi-beam option, where each beam can be used independently. A node 202 generates more than one directional beam to send background data to a plurality of other nodes at the same time. Since the same frequency can be reused on more than one directional beam in the same coverage area, the system capacity is significantly increased.

Multiple nodes can be connected with multiple beams. This makes it appropriate to change connections and dynamically adapt to changes in the radio environment. For example, two rays may be provided for connection between two nodes. If a beam suffers from excess interference, then the nodes will be able to switch to other beams for sending messages.

The use of smart antennas enables the formation of flexible background links between nodes. Since each node is configured to generate a plurality of directional beams and is capable of steering directional beams to any direction in azimuth, when a new node is added to the network 100, existing nodes can establish new connections to the new node by simply setting new beam direction and configuration directed to the new node. In addition, when an existing node is removed from the network 100, nodes can easily remove beam direction and configuration information for the removed node from memory 208. The present invention makes additional installation or removal of facilities unnecessary to establish or remove connections between nodes. It should be noted that the present invention can be implemented either in a mesh network or in a cellular network.

One of the strengths of mesh networks is the ability to create new links and to remove other lines between nodes depending on a multitude of factors, including traffic load, interference, and individual node performance. As shown in Figure 1, a majority of nodes 102a will be connected to each other using smart antennas. The lines between the nodes 102a-9 in Figure 1 indicate possible links a-f. Control can be centralized, whereby at least one node acts as a controlling node controlling the connection between nodes, or can be decentralized, where control is distributed over several nodes or all nodes. If a node is designated as a controlling node, the controlling node collects information regarding traffic conditions and performance in each node, and determines the best traffic route for sending messages from one node to another node.

Each node 102a preferably transmits one or more guiding signals in its one or more beams, which provide information that is appropriate for network operation. For example, the conductor signals may transmit current power levels, traffic levels, interference levels, and other parameters. Guidance signals may also include priority for access, security, identification, and other varying types of access control and security control information. The guidance signals are measured periodically or non-periodically, and the parameters are used as a basis for adjusting connections between nodes to find the most efficient traffic routes. Shaping at least part of the background connections wirelessly using smart antennas according to the present invention allows flexibility and reduces unnecessary costs and time to establish and adjust connections between nodes.

For example, as shown in figure 1, if the traffic load between the second node 102b and the fourth node 102 is too great, other nodes will recognize the traffic conditions between the two nodes 102b,d by reading the control signals from the node 102b,d, which will be described in detail hereafter. If the first node 102a wants to route traffic to the fifth node 102e, it will avoid, if possible, the second and fourth nodes 102b, d and will alternatively route traffic through the Nth node 102n.

The present invention not only has the advantage of providing a flexible wireless mesh network, but also background traffic information (which is typically sent via a wire-based line) which can now be sent via the same flexible lines through the smart antennas. Implementation of this type of dual use of smart antenna plans according to the present invention results in significant advantages over current wireless communication systems.

Figure 3 is a flow diagram of a process 300 that uses smart antennas in sending messages between nodes according to the present invention. At least some of the nodes are provided with at least one smart antenna, which is configured to generate a plurality of directional beams and steer them independently in azimuth (step 302). Each beam is used as a wireless connection to other nodes in addition to regular traffic with downloads to the WTRU and uploads from the WTRU. Each node maintains a list of other nodes and beam directions and configuration information that is used for transmission to the other nodes (step 304). It should be noted that steps 302 and 304 are typically performed when setting up a system or reconfiguring the system to accept or remove nodes, and will not typically be performed 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 memory, and generates a direction node using the beam direction and configuration information (step 306). Once the node is selected for sending background data, based on link quality and other considerations such as traffic density, the sending node selects the beam direction (weights) from the list and applies it to the antennas.

The process of 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 sends to the target node the generated directional beam (step 308).

In a selected free step, a change in the network can occur whereby a new node can be added to the network, an existing node can be removed from the network, or the radio frequency or other conditions can be changed. In response to the change, other nodes update the list of beam direction and configuration information to reflect the change (step 310):

Although the scope of the features and elements of the present invention is defined by the claims, each feature or element may be used alone with or without the other features and elements in the preferred embodiments or in various combinations with or without other features and elements according to present invention.

Claims (7)

Patent claims 1. Wireless communication system that uses at least one smart antenna to establish a background network where the system includes: a plurality of nodes (102a-n), where each node is connected to at least one neighboring node, where at least one of the plurality of nodes is a hybrid node (102n) which further includes a wire-based background connection to a core network a first node includes: a smart antenna (204) configured to generate a plurality of directional beams, a memory (208) configured to store a list of neighbor nodes having connections and beam configuration information used in sending messages to the neighbor nodes, and a controller (206) configured to update the list stored in the memory by monitoring signals received from the neighboring nodes and determining configurations for sending data to the neighboring nodes, and selecting a particular directional beam to send a particular beam-shaped message to another node by using the updated list stored in the memory; wherein the controller is further configured to send and receive background data over a wireless cellular connection to a second node; wherein the controller is further configured to receive wireless beamforming background data from the second node and transmit wireless beamforming background data to a third node; and wherein the controller is further configured to change a beam to the third node in response to the measured conditions. 2. System according to claim 1, characterized in that the hybrid node according to claim 1 further includes a wire-based background connection to the at least one neighboring node. 3. System according to claim 1, characterized in that the generated majority of directional rays are selected from a set of predefined positions. 4. System according to claim 1, characterized in that the generated majority of directional beams are dynamically selected and controlled in real time. 5. System according to claim 1, characterized in that the directional beams are configured to provide the best possible performance in terms of system capacity, data throughput, and interference. 6. System according to claim 1, characterized in that the majority of nodes include a mesh network. 7. System according to claim 1, characterized in that the majority of nodes comprise a cellular network.