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DYNAMIC WIRELESS BACKHAUL
BACKGROUND OF THE INVENTION
1. Field of the Invention 5 The present invention generally relates to wireless communication systems and, more particularly, to implementation of wireless backhauls.
2. Background of the Invention
Contemporary wireless communication systems often 10 include one or more access points communicatively linked to backhaul sites to provide a communication path between a communication device and a communications network. Oftentimes an access point will communicate with a backhaul site using a wireless backhaul. Use of the wireless backhaul 15 eliminates the need to install wire or fiber optic cables between the access point and the communications network, thereby reducing network installation and maintenance costs.
Although it is desirable that wireless backhauls be very reliable, this is not always possible. Adverse propagation 20 effects, such as those due to adverse weather conditions and electromagnetic interference, oftentimes degrade signal characteristics. In addition, co-channel interference, for example interference caused by groundlink communications that also may be supported on an access point or backhaul site, can 25 contribute to signal degradation.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention relates to a method of communicating data. The method can include dynamically selecting a first backhaul site from a plurality of backhaul sites that are each configured to wirelessly communicate with a particular access point. At least one transmission parameter used to communicate a first backhaul data stream between the access 35 point and the first backhaul site can be dynamically configured.
In one aspect of the invention, at least a second backhaul site also can be selected from the plurality of backhaul sites. The first backhaul data stream can be derived from a source data stream and can be wirelessly communicated between the access point and the first backhaul site. A second backhaul data stream also can be derived from the source data stream and wirelessly communicated between the access point and the second backhaul site. The first backhaul data stream can be combined with the second backhaul data stream.
The present invention also relates to a communication system. The communication system can include an access point and a first backhaul site configured to wirelessly communi- 5Q cate with the access point. The communication system further can include a controller that dynamically configures at least one transmission characteristic of a backhaul data stream communicated between the access point and the first backhaul site.
FIG. 4 depicts another arrangement of the wireless communication system of FIG. 1; and
FIG. 5 depicts a flowchart presenting a communication method that is useful for understanding the present invention.
While the specification concludes with claims defining features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the description in conjunction with the drawings. As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of the invention.
The inventive arrangements disclosed herein relate to dynamic backhaul configuration in a communication system that includes an access point and one or more backhaul sites with which the access point wirelessly communicates. For example, characteristics of a backhaul signal transmission can be dynamically controlled to provide optimum signal quality while minimizing use of network bandwidth. In addition, transmission of a source data stream can be dynamically allocated to one or more spatially diverse backhaul channels. Data received over the various backhaul channels can be combined to generate a replica of the source data stream. Transmitting the source data stream in this manner provides greater immunity to noise and interference in comparison to transmitting the source data stream over a backhaul channel in a conventional manner.
FIG. 1 depicts a communication system 100 that is useful for understanding the present invention. The communication system 100 can communicatively link one or more communication devices 110 to a communications network 105. The communication system 100 can include at least one access point 115, a plurality of geographically separated backhaul sites 120, 125, and a combination/distribution site 130.
The access point 115 can communicate with the communication devices 110 via a wired connection or via groundlinks 135. As used herein, a "groundlink" is a wireless communication link between a network infrastructure node and a wireless communication device that is not part of the network infrastructure. For example, the communication devices 110 can be mobile telephones, mobile computers, personal digital assistants (PDAs), network appliances, or any other communication devices which are not part of the network infrastructure.
The access point 115 can communicate with the plurality of backhaul sites 120, 125 via respective wireless backhaul channels 140,145. As used herein, a "backhaul channel" is a communication link between two network infrastructure nodes. Although two backhaul sites 120, 125 and two backhaul channels 140, 145 are depicted, the invention is not so limited and any number of backhaul sites can be configured to communicate with the access point 115. In this regard, any number of backhaul channels can be implemented for communicating with each of the backhaul sites 120,125. Further, in addition to supporting backhaul communications, one or more of the backhaul sites 120, 125 can be configured with
access point functionality to support groundlink communications directly with communication devices 110.
The spatial diversity of the geographically separated backhaul sites 120, 125 can be utilized to spatially diversify the backhaul channels 140, 145. In one arrangement, known 5 beam forming techniques can be used to transmit RF signals over the backhaul channels 140,145. Accordingly, each of the backhaul channels 140, 145 can operate in the same frequency spectrum, thereby conserving network bandwidth. Moreover, the backhaul channels 140,145 also can operate in 10 the same frequency spectrum used for the groundlinks 135, thus further conserving network bandwidth. Nonetheless, each backhaul channel also may operate in an exclusively dedicated frequency spectrum. Furthermore, a variety of multiple access modulation techniques can be implemented for 15 the various backhaul channels to achieve signal separation. Examples of suitable modulation techniques are frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), wideband code division multiple access (WCDMA), 20 orthogonal frequency division multiple access (OFDMA), and the like.
In operation, the communication system 100 can dynamically configure the manner in which backhaul communications are used to propagate data through the communications 25 network 100. The dynamic configuration can be performed by a controller contained in the access point 115, a controller contained in the combination/distribution site 130, and/or any other controller(s) associated with the communications network 100. For example, the dynamic configuration can be 30 performed by a base station controller (BSC). Regardless of where the system configuration occurs, suitable control signals for implementing the selected configuration can be provided to the access point 115, backhaul sites 120,125 and/or the combination/distribution site 130. 35
In response to the communication device 110 propagating a source data stream 150 to the access point 115, one or more backhaul sites 120, 125 can be dynamically selected for receiving a backhaul data stream, such as the data stream 155 or the data stream 160. For example, the communication 40 system 100 can evaluate measured or determined network parameters to select one or more of the backhaul channels 140, 145 over which to transmit a backhaul data stream 155 and/or the backhaul data stream 160. The communication system 100 can, for instance, estimate the reliability of each 45 of the backhaul channels 140, 145 by measuring receive signal parameters at each of the backhaul sites 120, 125. Examples of such receive signal parameters are signal strength, bit error rate, signal to interference ratio and signal to noise ratio. The communication system 100 also can mea- 50 sure or determine other operational aspects of the system 100. For example, backhaul loading on a particular backhaul site can be determined. If the backhaul site is also operating as an access point, groundlink loading also can be determined. Still, other signal parameters or aspects of system operation 55 can be measured or determined, and the invention is not limited in this regard.
In another aspect of the invention, the backhaul sites 120, 125 that are dynamically selected can be those backhaul sites that minimize the number of serial backhaul links between 60 the access point 115 and the node of the communications network 105 where the source data stream 150 is to be communicated. For example, a central controller (not shown) can monitor the topology of the communications network 105 and indicate to the access point 115 which backhaul sites 120, 65 125 are preferable to use to communicate the backhaul data stream(s) 155, 160. The controller can provide such indica
tion based on a distributed protocol based approach that leverages adjacency of infrastructure sites. One example of such a protocol is the Open Shortest Path First (OSPF) protocol. The controller can forward updated indications to the access point 115 in response to changes in network topology.
In one arrangement, the access point 115 can communicate a first portion of the source data stream 150 to the first backhaul site 120. The first portion of the source data stream 150 can be transmitted as the first backhaul data stream 155. A second portion of the source data stream 150 can be transmitted to the second backhaul site 125 as the second backhaul data stream 160. Accordingly, each of the backhaul data streams 155,160 can be derived from the source data stream 150.
The respective data streams 155,160 can be communicated from the backhaul sites 120,125 to the combination/distribution site 130 in a suitable manner. The combination/distributionsite 130 can combine, or merge, the data streams 155,160 to generate a data stream 165 that replicates the source data stream 150. The replicated data stream 165 can be propagated from the combination/distribution site 130 via the communications network 105.
The first and second backhaul data streams 155,160 can be approximately equal in size, or the source data stream 150 can be allocated disproportionably to the first and second backhaul data streams 155,160. For example, if the second backhaul site 125 currently is carrying a greater signal load (e.g. backhaul signal load and/or groundlink signal load) than the first backhaul site 120, the source data stream 150 can be allocated such that the first backhaul data stream 155 carries more data than the second backhaul data stream 160. If the second backhaul site 125 is currently at maximum capacity, the entire source data stream 150 can be allocated to the first backhaul data stream 155.
Data pertaining to the loading of the respective backhaul sites 120, 125 can be communicated to the appropriate controller in any suitable manner. For instance, in response to receiving a signal containing data from the access point 115, each of the backhaul sites 120,125 can be configured to send a response to the access point 115 that indicates the amount of bandwidth that is available for use by the access point 115 over the respective backhaul channels 140,145. The available bandwidth can be all unused bandwidth of a respective backhaul site 120, 125, or a portion of the bandwidth. The available bandwidth of each of the backhaul sites 120,125 also can be periodically communicated to the access point 115, for example in a control signal.
In another arrangement, the source data stream 150 can be directed to the backhaul site that has greater visibility to the access point 115, is experiencing better signal reception, and/ or is experiencing the least interference. For instance, if the second backhaul site 125 has greater visibility to the access point 115 than the first backhaul site 120, the entire source data stream 150 can be allocated to the second backhaul data stream 160. The visibility from each of the backhaul sites 120, 125 to the access point 115 can be at least partially dependent on changing environmental conditions, for instance weather, pollution, etc., and can be determined by evaluating measured receive signal parameters (e.g. signal strength, bit error rate, signal to interference ratio and/or signal to noise ratio). The visibility also can be determined in any other suitable manner and the invention is not limited in this regard.
Each of the backhaul data streams 155, 160 also can contain data sets that are substantially identical (hereinafter "identical", although the data sets may contain differences due to data errors and/or adverse propagation effects). For