HK1155021B - Wireless network synchronization - Google Patents

Description

Wireless network synchronization

Claiming priority based on 35U.S.C. § 119

This patent application claims priority to provisional application No.61/025,661, entitled "method and apparatus FOR SYNCHRONIZATION IN WIRELESS network," filed on 1/2/2008, which is assigned to the assignee of the present application and is expressly incorporated herein by reference; and claim priority to provisional application No.61/091,096 entitled "TREE-BASED NETWORK SYNCHRONIZATION" filed on 22.8.2008, assigned to the assignee of the present application and expressly incorporated herein by reference.

Technical Field

The present disclosure relates generally to wireless communications, and more specifically to synchronizing wireless nodes.

Background

Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. A typical wireless communication system may be a multiple-access system capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple access systems may include: code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, and the like. Further, the system may comply with specifications such as: third generation partnership project (3GPP), 3GPP Long Term Evolution (LTE), Ultra Mobile Broadband (UMB), and/or multicarrier wireless specifications such as evolution-data optimized (EV-DO), one or more modified versions thereof, and/or the like.

Generally, a wireless multiple-access communication system can simultaneously support communication for multiple mobile devices. Each mobile device may communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations. Moreover, communications between mobile devices and base stations can be established through single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, multiple-input multiple-output (MIMO) systems, and so forth. Further, mobile devices can communicate with other mobile devices (and/or base stations with other base stations) in peer-to-peer wireless network configurations.

MIMO systems typically use multiple (N)_T) A transmitting antenna and a plurality of (N)_R) And the receiving antennas are used for data transmission. The antennas may be associated with both base stations and mobile devices, allowing, in one example, two-way communication between devices on a wireless network. In addition, the base station and the mobile device may communicate over a channel defined by a fractional frequency over a fractional time. In this way, synchronizing the mobile device and the base station can facilitate efficient and substantially accurate communication. In addition, synchronizing the base stations can ensure substantially accurate timing across the associated wireless networks so that the mobile device can communicate with multiple base stationsThe base stations communicate without requiring large adjustments to the timing of the mobile device.

Disclosure of Invention

The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of all contemplated embodiments, and is intended to neither identify key or critical elements of all embodiments nor delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

In accordance with one or more aspects and corresponding disclosure thereof, various embodiments are described in connection with facilitating synchronization of wireless nodes (e.g., access points and/or access terminals) in a wireless communication network. In particular, the wireless nodes may form a synchronization tree in which the nodes may be associated with quality metrics. In this way, wireless nodes with lower quality metrics may be timing synchronized with nodes with higher quality metrics. For example, there may be one or more root nodes, with the lower nodes ultimately depending on the tree. In one example, the root node may be synchronized using Global Positioning System (GPS) technology, such that substantially all slave nodes may be substantially synchronized with GPS for timing, regardless of whether the slave nodes are GPS equipped.

According to related aspects, a method for synchronizing wireless nodes in a wireless communication network is provided. The method includes receiving quality metrics related to surrounding wireless nodes over a backhaul link. The method further includes selecting the surrounding wireless node for synchronization with respect to one or more different surrounding wireless nodes and timing synchronization with the surrounding wireless nodes based at least in part on the quality metric.

Another aspect relates to a wireless communications apparatus. The wireless communications apparatus can include at least one processor configured to determine quality metrics corresponding to a plurality of wireless nodes received over a backhaul link. The at least one processor is further configured to select at least one of the plurality of wireless nodes to synchronize and to synchronize with timing of the at least one wireless node based at least in part on the corresponding quality metrics. The wireless communications apparatus also includes a memory coupled to the at least one processor.

Another aspect relates to an apparatus comprising means for receiving quality metrics corresponding to one or more wireless nodes over a backhaul link. The apparatus may also include means for selecting at least one of the wireless nodes to synchronize based at least in part on the corresponding quality metric, and means for timing synchronization with the at least one wireless node.

Another aspect relates to a computer program product, which can include a computer-readable medium. The computer-readable medium includes code for causing at least one computer to receive quality metrics related to surrounding access points over a backhaul link. The computer-readable medium can further comprise code for causing the at least one computer to select one or more different surrounding access points with respect to which to synchronize based at least in part on the quality metric. Further, the computer-readable medium can comprise code for causing the at least one computer to perform timing synchronization with the surrounding access points.

Yet another aspect relates to an apparatus. The apparatus may include a wireless node evaluator to receive a quality metric related to a wireless node over a backhaul link. The apparatus also includes a wireless node selector that selects the wireless node for synchronization with respect to one or more disparate wireless nodes based at least in part on the quality metric, and a timing synchronizer that is timing synchronized with the wireless node.

According to another aspect, a method of timing synchronization in wireless communications is provided. The method includes detecting timing of the wireless node and a disparate wireless node. The method further includes comparing the timing of the wireless node to the timing of the disparate wireless node and sending a timing correction message to the wireless node based on the comparison.

Another aspect relates to a wireless communications apparatus. The wireless communications apparatus can include at least one processor configured to determine timing of a wireless node. The at least one processor is further configured to determine a timing of a disparate wireless node and to transmit a timing correction message to the wireless node based on the timing of the disparate wireless node. The wireless communications apparatus also includes a memory coupled to the at least one processor.

Another aspect relates to an apparatus comprising means for comparing a timing of a wireless node to a timing of a disparate wireless node, and means for transmitting a timing correction message to the disparate wireless node based at least in part on the comparing.

Another aspect relates to a computer program product having a computer-readable medium. The computer-readable medium includes code for causing at least one computer to detect timing of a wireless node and a disparate wireless node. The computer-readable medium can further comprise code for causing the at least one computer to compare the timing of the wireless node to the timing of the disparate wireless node. Moreover, the computer-readable medium can comprise code for causing the at least one computer to transmit a timing correction message to the wireless node based on the comparison.

Yet another aspect relates to an apparatus. The apparatus may include a synchronization information receiver that obtains timing of the wireless node and the disparate wireless node. The apparatus further comprises a synchronization information provider that sends a timing correction message to the wireless node based at least in part on a comparison of the timing of the wireless node and the timing of the disparate wireless node.

To the accomplishment of the foregoing and related ends, the one or more embodiments comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the one or more embodiments. These aspects are indicative, however, of but a few of the various ways in which the principles of various embodiments may be employed and the described embodiments are intended to include all such aspects and their equivalents.

Drawings

Fig. 1 is an illustration of a wireless communication system in accordance with various aspects set forth herein.

Fig. 2 is an example of a wireless communication system that supports timing synchronization between wireless nodes.

Fig. 3 is an example of an exemplary communications apparatus for use within a wireless communication environment.

Fig. 4 is an example of an exemplary wireless communication system that implements timing synchronization between wireless nodes.

Fig. 5 is an example of an exemplary state diagram for tracking timing synchronization of a wireless node with a Global Positioning System (GPS) or a target wireless node.

Fig. 6 is an example of an example methodology that facilitates timing synchronization with a selected wireless node based on one or more associated quality metrics.

Fig. 7 is an example of an example methodology that facilitates selecting a wireless node for timing synchronization.

Fig. 8 is an example of an example methodology that facilitates timing synchronization with a wireless node based on a signal-to-noise ratio (SNR).

Fig. 9 is an example of an exemplary mobile device that facilitates receiving and providing synchronization information from/to various wireless nodes.

Fig. 10 is an example of an example system that performs timing synchronization with one or more wireless nodes.

Fig. 11 is an example of an exemplary wireless network environment that can be employed in connection with the various systems and methods described herein.

Fig. 12 is an example of an example system that facilitates timing synchronization with one or more surrounding wireless nodes.

Fig. 13 is an example of an example system that facilitates timing synchronization at one or more wireless nodes.

Detailed Description

Various embodiments are now described with reference to the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident, however, that such embodiment(s) may be practiced without these specific details.

As used herein, the terms "component," "module," "system," and the like are intended to include a computer-related entity, such as, but not limited to: hardware, firmware, a combination of hardware and software, or software in execution. For example, a component may be, but is not limited to: a process running on a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be a component. One or more components can reside within a process and/or thread of execution and a component can be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the internet with other systems by way of the signal).

Furthermore, various embodiments are described in connection with a terminal, which may be a wired terminal or a wireless terminal. A terminal can also be called a system, device, subscriber unit, subscriber station, mobile device, remote station, remote terminal, access terminal, user terminal, communication device, user agent, user device, or User Equipment (UE). A terminal may be a cellular telephone, a satellite telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device having wireless connection capability, a computing device, or other processing device connected to a wireless modem. Furthermore, various embodiments are described herein in connection with a base station. A base station may be utilized for communicating with wireless terminal(s) and may also be referred to as an access point, node B, or some other terminology.

Furthermore, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless otherwise indicated, or otherwise clear from context, the phrase "X employs A or B" is intended to mean any of the natural inclusive permutations. That is, any of the following examples satisfies the phrase "X employs A or B": x is A; b is used as X; or X employs both A and B. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from context to be directed to a singular form.

The techniques described herein may be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other systems. The terms "system" and "network" are often used interchangeably. A CDMA system may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), CDMA2000, etc. UTRA includes wideband CDMA (W-CDMA) and other variants of CDMA. Further, cdma2000 covers IS-2000, IS-95 and IS-856 standards. TDMA systems may implement wireless technologies such as global system for mobile communications (GSM). The OFDMA system may implement wireless technologies such as evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) is a version of UMTS that uses E-UTRA, which uses OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE, and GSM are described in documents of the organization entitled "third Generation partnership project" (3 GPP). Further, cdma2000 and UMB are described in documents of an organization named "third generation partnership project 2" (3GPP 2). Further, such wireless communication systems may additionally include peer-to-peer (e.g., mobile-to-mobile terminal) ad hoc network systems that often use unpaired unlicensed spectrum, 802.xx wireless LANs, BLUETOOTH, and any other short or long range wireless communication technologies.

Various aspects or features will be presented in terms of systems that may include a number of devices, components, modules, and the like. It is to be understood and appreciated that the various systems may include additional devices, components, modules, etc. and/or may not include all of the devices, components, modules etc. discussed in connection with the figures. Combinations of these schemes may also be used.

Referring now to fig. 1, a wireless communication system 100 is shown in accordance with various embodiments of the present application. System 100 comprises a base station 102, which base station 102 can comprise multiple antenna groups. For example, one antenna group can include antennas 104 and 106, another group can include antennas 108 and 110, and an additional group can include antennas 112 and 114. Two antennas are shown for each antenna group, however, more or fewer antennas may be utilized for each group. Base station 102 can additionally include a transmitter chain and a receiver chain, each of which can in turn comprise a plurality of components associated with signal transmission and reception (e.g., processors, modulators, multiplexers, demodulators, demultiplexers, antennas, etc.), as will be appreciated by one skilled in the art.

Base station 102 can communicate with one or more mobile devices (e.g., mobile device 116 and mobile device 122); however, it should be appreciated that base station 102 can communicate with substantially any number of mobile devices similar to mobile devices 116 and 122. For example, mobile devices 116 and 122 can be cellular phones, smart phones, laptops, handheld communication devices, handheld computing devices, satellite radios, global positioning systems, PDAs, and/or any other suitable device for communicating over wireless communication system 100. As depicted, mobile device 116 is in communication with antennas 112 and 114, where antennas 112 and 114 transmit information to mobile device 116 over a forward link 118 and receive information from mobile device 116 over a reverse link 120. In addition, mobile device 122 is in communication with antennas 104 and 106, where antennas 104 and 106 transmit information to mobile device 122 over a forward link 124 and receive information from mobile device 122 over a reverse link 126. In a Frequency Division Duplex (FDD) system, forward link 118 can utilize a different frequency band than that used by reverse link 120, and forward link 124 can utilize a different frequency band than that used by reverse link 126, for example. Further, in a Time Division Duplex (TDD) system, forward link 118 and reverse link 120 can utilize a common frequency band and forward link 124 and reverse link 126 can utilize a common frequency band.

Each group of antennas and/or the area in which they are designed to communicate is often referred to as a sector of base station 102. For example, antenna groups can be designed to communicate to mobile devices in a sector of the areas covered by base station 102. In communication over forward links 118 and 124, the transmitting antennas of base station 102 can utilize beamforming to improve signal-to-noise ratio (SNR) of forward links 118 and 124 for mobile devices 116 and 122. Likewise, when base station 102 employs beamforming to transmit to mobile devices 116 and 122 scattered randomly through an associated coverage, less interference is caused to mobile devices in neighboring cells as compared to a base station transmitting through a single antenna to all its mobile devices. Further, mobile devices 116 and 122 can communicate directly with each other using peer-to-peer or ad hoc technology (not shown).

According to an example, system 100 can be a multiple-input multiple-output (MIMO) communication system. Moreover, system 100 can utilize substantially any type of duplexing technique to divide communication channels (e.g., forward link, reverse link …), such as FDD, FDM, TDD, TDM, CDM, and the like. Further, the communication channels may be orthogonalized to enable simultaneous communication with multiple devices; in one example, OFDM may take advantage of this. In any case, the communication techniques used may be based, at least in part, on time, such that synchronization between base station 102 and mobile devices 116 and 122 may facilitate efficient communication. For example, mobile devices 116 and 122 can share common timing-based resources when synchronizing with base station 102. Further, synchronization between base stations, such as base station 102 and other base stations (not shown), for example, may also be beneficial in providing efficient communication over an associated wireless network. As described herein, it should be understood that a base station or access point can refer to a macrocell base station, a femtocell, a mobile base station, a wireless base station, a mobile device operating in a peer-to-peer mode to accept communications from other mobile devices, and/or substantially any access point that provides wireless communications to one or more devices. Further, these devices, which may be referred to herein as wireless nodes, may comprise substantially any wireless communication device.

According to one example, if a Global Positioning System (GPS) is equipped, the base station 102 can be timing synchronized with the GPS. It should be appreciated that while GPS is explicitly mentioned herein, it may refer to substantially any global timing source or satellite-based timing system, a terrestrial transmitter-based system (e.g., long-range assisted navigation (LORAN), etc.), an atomic clock-based timing source, another radio access technology, a synchronization signal, a terrestrial broadcast signal, and/or substantially any standard timing source. In another example, as described in further detail below, if base station 102 is not equipped with a GPS, it may also synchronize with one or more different base stations. In one example, base station 102 can evaluate surrounding base stations to determine a base station with a high quality metric. Base station 102 can evaluate surrounding base stations Over The Air (OTA), over a backhaul link, and/or the like based at least in part on information received from mobile devices 116 and/or 122 associated with disparate base stations. For example, a backhaul link may refer to one or more communication links between base station 102 and an underlying wireless network (not shown). For example, the backhaul link may be wired or wireless. Further, the base station 102 can receive and respond to requests from different base stations to, for example, synchronize timing when the base station 102 has a desired quality metric with respect to the different base stations. As described in further detail below, the quality metric may be a metric or structure assigned by the wireless network based on one or more aspects of the base station, a measured SNR, or the like.

Referring to fig. 2, an exemplary wireless communication network 200 that facilitates wireless node timing synchronization is illustrated. Network 200 includes a plurality of wireless nodes 202, 204, and 206. A wireless node may be an access point, a mobile device, and/or substantially any device that communicates with other wireless devices. In one example, wireless nodes 202 and 206 may be timing synchronized with wireless node 204. Thus, in one example, wireless node 204 may be GPS equipped or may otherwise have a higher quality metric than wireless nodes 202 and 206. As described, the quality metric may relate to one or more aspects of the wireless node and may be received and/or calculated by a different wireless node. For example, the quality metric for wireless node 204 may be the SNR measured by wireless nodes 202 and 206, and in fact, in this example, the SNR for wireless node 204 is higher than for wireless nodes 206 and 202, otherwise wireless node 202 would synchronize with wireless node 202.

In another example, the quality metric may be specified by the underlying wireless network based at least in part on one or more aspects of the associated wireless node. For example, a GPS-equipped wireless node may have a higher quality metric than an unassembled GPS wireless node. Additionally or alternatively, the quality metric may relate to the following factors: the wireless node's normal operating time or reliability, the number of devices communicating with the wireless node, the period of time the wireless node has been GPS equipped, GPS signal quality, synchronization source, the number of wireless nodes synchronized, etc. Using the quality metrics, the wireless nodes 202, 204, and 206 may form a synchronization tree such that the wireless node 204 is the root and the wireless nodes 202 and 206 may be children of the wireless node 204. It should be understood that the wireless node 204 may synchronize with a different wireless node having a higher quality metric, which may then be the root of a tree, and so on. Likewise, wireless nodes 202 and/or 206 may be used for synchronization by slave wireless nodes, which become children of lower levels of the expanded tree, and so on.

According to an example, wireless node 202 may discover wireless nodes 204 and/or 206 for synchronization upon power-up, reboot, or other initialization. Discovery may include detecting wireless nodes 204 and/or 206 through OTA signaling (e.g., analyzing a superframe preamble, etc.), a backhaul link, etc. In another example, the wireless node may utilize mobile device 208 or another device (e.g., a different wireless node) to receive information about wireless node 204 (and/or 206, although not shown), such as signal strength, timing offset, and the like. Thus, in this way, mobile device 208 may act as a gateway to synchronize wireless node 202 and wireless node 204, or provide information regarding synchronization. When wireless node 202 discovers different wireless nodes 204 and/or 206, it may receive quality metrics about wireless nodes 204 and/or 206, as described. It should be appreciated that in one example, wireless node 202 may receive the quality metric as part of discovery. Further, the quality metrics may similarly be received OTA or over a backhaul link from the wireless nodes 204 and/or 206 or underlying network components or the like. As indicated, in the depicted example, wireless node 204 may have a higher quality metric than wireless node 206 relative to wireless node 202; thus, wireless node 202 may select wireless node 204 for synchronization.

As depicted, wireless node 202 may synchronize with wireless node 204 either OTA or through a backhaul link; in one example, timing can be obtained from wireless node 204 using a similar mechanism as a mobile device. In another example, as mentioned, mobile device 208 may act as a gateway to achieve synchronization when wireless node 202 is unable to effectively communicate with wireless node 204 for one or more reasons (e.g., a bad connection, strong interference, a backhaul link failure, inability to communicate with other wireless nodes, etc.), etc. As such, mobile device 208 or another device (e.g., a base station or other wireless node in a wireless network) may send a timing correction message to wireless node 202. In one example, mobile device 208 can send a correction message based on evaluating the timing of access point 202 and access point 204 and detecting an inconsistency between the timing. In one example, the timing correction message can include the timing of the access point 204, a difference between the timings, and/or other timing information related to synchronizing with the access point 204.

Further, wireless node 202 may maintain synchronization after initial setup. In this way, wireless node 202 may continue to receive and evaluate quality metrics for surrounding wireless nodes, such as wireless nodes 204 and/or 206. For example, when wireless node 204 is initially equipped with GPS, it may also lose GPS signals, shut down, reboot, etc., in which case its quality metric may be modified. Wireless node 202 may synchronize with wireless node 206 or a different wireless node in the event that wireless node 204 is bad or no longer has the highest quality metric of the discovered wireless nodes. In one example, wireless node 202 may become the root node (e.g., wireless node 206 may synchronize with wireless node 202) if no surrounding wireless nodes have a higher quality metric than wireless node 202. In another example, if after wireless node 202 synchronizes with wireless node 204, a new wireless node (not shown) is powered on and has a higher quality metric, wireless node 202 may instead synchronize with the new wireless node as part of maintaining synchronization.

In another example, the wireless nodes 204 and 206 may specify a root parameter (e.g., using a quality metric, etc.) that indicates a root node of the respective trees. Wireless node 202 may evaluate the root node of wireless nodes 204 and/or 206, as well as other nodes on the path, during the maintenance of synchronization to prevent synchronization with the node that caused the synchronization ring. Further, it should be appreciated that sequential synchronization using quality metrics may prevent frequent hopping (e.g., ping-pong effect) between synchronizations when other wireless nodes are present. The quality metric may allow priority-based wireless node selection such that the node may select the synchronization node with the highest quality metric to allow formation of a tree.

Referring to fig. 3, illustrated is a communications apparatus 300 that facilitates employment within a wireless communications environment. The communications apparatus 300 can be a base station or a portion thereof, a mobile device or a portion thereof, or substantially any communications apparatus that communicates over a wireless network. The communications apparatus 300 can include a wireless node finder 302, a quality metric analyzer 304, a wireless node selector 306, a timing synchronizer 308, and a wireless node monitor 310. Wireless node finder 302 can detect the presence of one or more surrounding wireless nodes, quality metric analyzer 304 can receive and evaluate one or more quality metrics related to at least one surrounding wireless node, wireless node selector 306 can determine a wireless node for timing synchronization based at least in part on the related quality metrics, timing synchronizer 308 can adjust timing of communications apparatus 300 to substantially match timing of the wireless node, and wireless node monitor 310 can continuously evaluate surrounding wireless nodes to ensure communications apparatus 300 is synchronized with the wireless node having the highest quality metric.

According to an example, the communications apparatus 300 can require or desire timing synchronization with one or more wireless nodes operating in a synchronous wireless network. If GPS is equipped, the communications device 300 may synchronize with the GPS. The communications apparatus 300 can additionally or alternatively be timing synchronized with one or more disparate wireless nodes in a wireless network. To this end, the wireless node finder 302 may determine that there are surrounding wireless nodes that may be timing synchronized with the communications apparatus 300. As described, the wireless node finder 302 can detect surrounding wireless nodes using OTA signaling (e.g., using mechanisms similar to mobile devices), backhaul links, information from underlying network components, and so forth. Further, as described, the wireless node finder 302 can communicate with the mobile device to receive information related to surrounding wireless nodes, such as signal strength, timing offsets, and the like.

Further, the quality metric analyzer 304 may receive at least one quality metric related to one or more surrounding wireless nodes. In one example, the quality metrics may be received during a wireless node discovery period, or later requested by the quality metric analyzer 304 over OTA or over a backhaul link, etc., as described. The quality metric may be measured by quality metric analyzer 304, such as an SNR associated with communicating with surrounding wireless nodes. Quality metrics may also be calculated and assigned to surrounding wireless nodes based on various factors, such as the uptime of the wireless node, the uptime of the associated GPS device, the signal strength of the GPS signal, the number of wireless nodes synchronized, and the like. According to another example, the quality metrics may be stored in a synchronization structure associated with the wireless node. In one example, the synchronization structure may be received by the wireless node finder 302 and the quality metric analyzer 304 may determine the quality metric and other related metrics in the synchronization structure.

It should be appreciated that the structure of a GPS-equipped wireless node may be different, for example, relative to a wireless node that is not GPS-equipped. In one example, the synchronization structure for a GPS-equipped wireless node may be arranged as follows:

field(s)	Size and breadth
		Type (B)	1
Quality of	64
		Hop count	8

Where type indicates whether a wireless node is equipped with GPS, quality refers to a quality metric, and hop count refers to the number of wireless nodes between the associated wireless node and the root in the tree. In the case of a GPS equipped wireless node, for example, the hop count may typically be zero since in most cases the GPS equipped wireless node may be synchronized with GPS. In one example, the synchronization structure of a wireless node that is not equipped with GPS may be arranged as follows:

field(s)	Size and breadth
		Type (B)	1
Quality of	64
		RootANID	64
Hop count	8

Where type indicates whether the wireless node is equipped with GPS, quality refers to a quality metric, a root access node identifier (RootANID) is associated with the wireless node that is the root of the tree (which may be synchronized with GPS in one example), and hop count indicates the number of wireless nodes between the associated wireless node and the root. The above arrangement is only one example of a synchronization structure.

The wireless node selector 306 may evaluate the quality metrics and/or parameters in the structure (as determined by the quality metric analyzer 304 for surrounding wireless nodes) to select candidate nodes for synchronization. For example, the wireless node selector 306 may compare the quality metrics to determine the highest metric and select the corresponding wireless node for synchronization. Wireless node selector 306 may also compare the quality metric to a quality metric associated with communication apparatus 300 to ensure that communication apparatus 300 should synchronize with another wireless node-where communication apparatus 300 has a higher quality metric than substantially all surrounding wireless nodes, e.g., it may be a root node. Further, as described, if the communication device 300 is equipped with a GPS, it can perform timing synchronization with its GPS and can be a root node. In one example, the wireless node selector 306 may jointly evaluate parameters of the synchronization structure. Thus, for example, the wireless node selector 306 may evaluate the quality metric and hop count of a wireless node that is not equipped with GPS to determine whether to select the wireless node. The wireless node selector 306 may determine that a different wireless node with a lower quality metric but with a fewer number of hops is a more desirable choice.

When the wireless node selector 306 determines a wireless node, the timing synchronizer 308 may adjust the timing of the communications apparatus 300 to substantially match the selected wireless node. For example, the timing may relate to actual time, time slot and/or frame number, etc. based on GPS. In one example, this can be performed using a mechanism similar to a mobile device to perform synchronization and/or acquisition with a wireless node (e.g., evaluating pilot signals, system information blocks, utilizing a common channel configuration such as a Random Access Channel (RACH), etc.). Further, as described, the timing synchronizer 308 can synchronize with a selected wireless node, relay, etc., based at least in part on a message from a mobile device connected with the selected wireless node. For example, the timing synchronizer 308 may adjust the timing of the communication device 300 by rotating the time in steps to accommodate the wireless node, by adjusting the time in a process, and so on. The wireless node monitor 310 may continuously monitor surrounding wireless nodes to determine if there are candidates with higher quality metrics for synchronization.

According to an example, the wireless node monitor 310 may continue to receive information related to surrounding wireless nodes like the wireless node finder 302; in fact, wireless node monitor 310 may utilize wireless node finder 302 to implement this functionality. As described, the wireless node monitor 310 may additionally utilize the quality metric analyzer 304 to receive and/or determine quality metrics related to surrounding wireless nodes. When a wireless node with a more desirable metric than the currently connected wireless node for synchronization occurs (and/or the current wireless node loses GPS signal, fails, reboots, or otherwise becomes inaccessible), a new surrounding wireless node may be selected for synchronization using the wireless node selector 306, as described, and the timing synchronizer 308 may adjust the timing of the communications apparatus 300 accordingly.

It should be appreciated that in one example, the current wireless node used for timing synchronization may fail and the wireless node monitor 310 does not detect other wireless nodes having a threshold or desired quality metric. In this case, the communication apparatus may become a root node. In another example, if other wireless nodes are detected, the wireless node monitor 310 may evaluate the RootANID of the synchronization structures associated with the newly discovered wireless node (e.g., if GPS is not equipped) to ensure that they do not have the same root. If so, wireless node selector 306 may select other wireless nodes that meet the desired quality metric; if not, the communications apparatus 300 can become the root node in the synchronization tree, as described. This prevents, for example, cyclic synchronization within the tree. Further, similar to the initialization process described above, the wireless node monitor 310 may preferably synchronize with a GPS equipped wireless node, a wireless node with a higher quality metric and a fewer number of hops, and the like.

According to one example as described above, if the quality metric relates to the SNR measured by the quality metric analyzer 304, the wireless node selector 306 may decide to synchronize with the wireless node with the highest SNR. This may be regardless of whether the wireless node has GPS. Thus, a synchronization tree may be formed at the root node having the highest SNR. Thus, even if the communication apparatus 300 is equipped with GPS, it can become a child node of a wireless node of higher SNR for the purpose of synchronization. Indeed, when the communication device is GPS-equipped, in one example, the timing synchronizer 308 can send synchronization commands to higher SNR wireless nodes and/or root nodes so that these wireless nodes can be GPS-synchronized despite possibly not being GPS-equipped.

Referring now to fig. 4, illustrated is a wireless communication system 400 that facilitates synchronizing wireless node timing. Tracking wireless node 402 and/or target wireless node 404 may be mobile devices (e.g., including not only stand-alone power supplies, but also modems), base stations, and/or portions thereof, or substantially any wireless device. Further, system 400 can be a MIMO system and/or can conform to one or more wireless network system specifications (e.g., EV-DO, 3GPP2, 3GPP LTE, WiMAX, etc.). Likewise, in one example, the components and functions shown and described below in tracking wireless node 402 may also be present in target wireless node 404, and vice versa; for ease of explanation, the described configuration does not include these components.

Tracking wireless node 402 includes a wireless node evaluator 406, a wireless node selector 408, a timing synchronizer 410, and a synchronization structure updater 412. Wireless node evaluator 406 can discover and receive timing information related to one or more surrounding wireless nodes, such as target wireless node 404, wireless node selector 408 can determine a wireless node for timing synchronization, timing synchronizer 410 can adjust timing of a tracking wireless node based on the determination, and synchronization structure updater 412 can modify a synchronization structure or other quality metric related to tracking wireless node 402 to reflect timing synchronization. The target wireless node 404 may include a synchronization structure specifier 414 and a timing information transmitter 416. The synchronization structure designator 414 sends a synchronization structure or other quality parameter to one or more wireless nodes, such as the tracking wireless node 402, and the timing information transmitter 416 may broadcast information related to the timing of the targeted wireless node 404. This may be, for example, system acquisition information related to a common channel (e.g., RACH), a pilot signal with a frame preamble, etc.

According to an example, wireless node evaluator 406 can determine a quality metric and/or synchronization structure associated with one or more surrounding wireless nodes, such as target wireless node 404. In one example, wireless node evaluator 406 can receive the information from synchronization structure specifier 414 or other component of target wireless node 404 that transmits the structure (e.g., OTA, over a backhaul link, using one or more devices as a gateway, etc.). In one example, the synchronization structure may be a quality metric or a structure including a quality metric, such as the structural format described with reference to the previous figures. Wireless node selector 408 may compare the synchronization structure or quality metric to synchronization structures or quality metrics received from different wireless nodes to determine a wireless node for timing synchronization. In the depicted example, wireless node selector 408 may select target wireless node 404 for synchronization. As such, timing synchronizer 410 may adjust the timing of tracking wireless node 402 based on the timing parameters received from timing information transmitter 416. As described above, this can be performed OTA, using backhaul, utilizing the mobile device as a gateway, and so forth. As described, the timing synchronizer 410 may rotate the timing to gradually adjust over a period of time and/or may perform instantaneous synchronization. When synchronizing with a wireless node, tracking wireless node 402 may become part of a synchronization tree and may have different tracking wireless nodes (not shown) rely on it for timing synchronization.

In one example, as described, wireless node selector 408 may compare measured quality metrics, such as SNRs, of various wireless nodes to determine a wireless node for timing synchronization. As noted, in this example, the wireless node with the highest SNR can be the root node, such that substantially all surrounding wireless nodes within range can synchronize with the root node. However, in this example, the root node need not be equipped with a GPS. For example, in this example, the target wireless node 404 may be a root node. If the target wireless node 404 is not equipped with GPS and the tracking wireless node 402 is equipped with GPS, the timing synchronizer 410 may send timing synchronization information (e.g., a synchronization signal) to the target wireless node 404, allowing the target wireless node 404 to synchronize with the tracking wireless node.

In another example, wireless node selector 408 may compare synchronization structure parameters (e.g., quality metrics, hop count, RootANID, access node identifier) of the entire path of the synchronization tree from target wireless node 404 to the root node, i.e., the synchronization source (e.g., GPS, access point, mobile device, etc.) when the wireless node is GPS-equipped or not, to determine the wireless node to use for synchronization. As described, for example, wireless node selector 408 may ensure that the selected wireless node for synchronization has a different RootANID than tracking wireless node 402 to prevent loops in the synchronization tree. In one example, wireless node selector 408 may also compare the quality metric, hop count, etc. of tracking wireless node 402 to the quality metrics, hop counts, etc. of surrounding wireless nodes to ensure that a lower quality metric wireless node is not selected for synchronization. Thus, in this example, target wireless node 404 may have a higher quality metric than tracking wireless node 402 and/or other surrounding wireless nodes, causing selection by wireless node selector 408. Thus, for example, strict priority may be enforced based on quality metrics for wireless nodes selected for synchronization. Further, for example, hop counts may be estimated to select between wireless nodes having the same or similar quality metrics. In another example, as depicted, the target wireless node 404 may be a root node in a synchronization tree.

According to an example, the tracking wireless node 402 can be timing synchronized with the target wireless node 404, and the target wireless node 404 can experience a change in the quality metric, as described. For example, the target wireless node 404 may fail, restart, lose, or experience degradation of the GPS signal, etc., which may degrade its quality metric. Wireless node evaluator 406 may continuously monitor target wireless node 404 and other surrounding wireless nodes to detect such changes in the quality metric to ensure that it is synchronized with the desired candidate wireless node. Thus, the quality metric of the target wireless node 404 may decrease, causing the wireless node selector 408 to select another wireless node for timing synchronization (if there is a wireless node with a higher quality metric). However, in addition, one or more surrounding wireless nodes may have a higher quality metric than the target wireless node 404 (e.g., due to the presence of new or recovered wireless nodes, the addition or acquisition of GPS signals, etc.). In this case, wireless node selector 408 may detect and select surrounding wireless nodes for synchronization. Likewise, as the quality metric increases such that the target wireless node 404 becomes the wireless node with the highest quality metric or other more desirable synchronization structure parameter, the wireless node selector 408 can reselect the target wireless node 404 for timing synchronization.

According to another example, tracking changes on the wireless node 402 may affect timing synchronization. For example, the tracking wireless node 402 may acquire GPS functionality or discover GPS signals. The quality metric of the tracking wireless node 402 may be increased above the target wireless node 404 so that the tracking wireless node 402 synchronizes with itself or with other GPS equipped wireless nodes using GPS signals, in one example. In one example, as described above, although not shown, target wireless node 404 may act as a tracking wireless node and may be timing synchronized with tracking wireless node 402 as the quality metric of tracking wireless node 402 increases. In one example, it is to be appreciated that the tracking wireless node 402 and/or surrounding wireless nodes can substantially silence transmissions within a common time period to find a desired target wireless node for timing synchronization.

Referring now to fig. 5, an exemplary state diagram 500 is shown illustrating tracking wireless node states and associated transition events. The state diagram begins with establishing timing synchronization 502 with one or more wireless nodes. As noted, such establishment can occur by receiving quality metrics for one or more target wireless nodes via an OTA, backhaul link, or the like. As previously mentioned, the quality metrics may relate to SNR, synchronization structure or related parameters, uptime of the wireless node, GPS signal strength, and the like. However, if a GPS signal is detected at the tracking wireless node, such establishment is not necessary and the tracking wireless node may enter a GPS synchronized state 504 in which the tracking wireless node adjusts its timing to conform to the timing of GPS. In state 504, for example, the tracking wireless node may maintain synchronization with the GPS by continuously monitoring for timing inconsistencies. Further, the tracking wireless node may set its synchronization parameters to reflect GPS synchronization (e.g., GPS = true, target node = null, hop count =0, etc.). Thus, other tracking wireless nodes may utilize this information to determine whether to synchronize timing with the tracking wireless node of this example. In one example, the tracking wireless node may be a root node and may set a root node synchronization structure parameter to its own identifier.

If the GPS fails (e.g., the signal becomes jammed, the device itself fails), the establish synchronization state 502 may be entered to determine the target wireless node for timing synchronization, as described above. In one example, a target wireless node may be selected from a set of wireless nodes by evaluating one or more quality metrics associated with the set of wireless nodes, as described above. For example, the tracking wireless node may select a target node equipped with GPS. If there is more than one target node, the target node with the earliest time, the highest quality metric, and/or the least number of hops may be selected. If there are no target nodes equipped with GPS, the tracking wireless node may select the target node or nodes with the highest quality metrics. If there is more than one node with the same highest quality metric, the target wireless node may, for example, select one or more with the largest node identifier and/or the fewest number of hops. In one example, if not, the target wireless node may select the target node with the least number of hops. When a node is selected, timing synchronization may be performed as described above. Further, the tracking wireless node may set its synchronization parameters to reflect the target node synchronization (e.g., GPS ═ false, target node ═ target node identifier, root node ═ root node of target node, quality metric ═ quality metric of target node, hop count ═ hop count of target node +1, etc.). Thus, other tracking wireless nodes may utilize this information to determine whether to synchronize timing with the tracking wireless node in this example. If the target node is not determined, then the tracking wireless node may also be the root node in this case, as described above (e.g., the exemplary parameters described above may be GPS-false, target node-tracking node identifier, hop-count 0, etc.).

When synchronization is complete, the tracking wireless node may move to a monitor wireless node state 506 in which the target wireless node is continuously monitored and evaluated to detect a higher quality metric. If a wireless node with a higher quality metric is detected, the tracking wireless node may instead synchronize with these nodes, reset the synchronization structure parameters or quality metrics (if available) as described above, and remain in the monitor wireless node state 506. When the higher quality metric node is the current target node, the tracking wireless node may, for example, increase its quality metric to match. However, if the target node for synchronization fails, the tracking wireless node may enter the establish synchronization state 502 to determine another target wireless node to perform timing synchronization. Further, while in the monitor wireless node state 506, the tracking wireless node may also monitor for GPS signals. As described above, if such a condition is detected (e.g., GPS is re-available after a failure to synchronize with the target wireless node), the tracking wireless node may enter the synchronize with GPS state 504.

Referring to fig. 6-8, methodologies relating to timing synchronization between wireless nodes in a wireless communication network are illustrated. While, for purposes of simplicity of explanation, the methodologies are shown and described as a series of acts, it is to be understood and appreciated that the methodologies are not limited by the order of acts, as some acts may, in accordance with one or more aspects, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a methodology in accordance with one or more aspects.

Referring to fig. 6, an exemplary methodology 600 that facilitates selecting a wireless node for synchronization in a wireless network is illustrated. At step 602, quality metrics associated with surrounding wireless nodes are received over a backhaul. As noted, in one example, the quality metric may be used as a priority for selecting the wireless node, and thus the wireless node with the highest quality to synchronize. For example, the quality metric may relate to whether the wireless node is equipped with GPS, GPS signal strength, uptime, quality of timing source, combinations thereof, and the like. At step 604, the surrounding wireless nodes may be selected for timing synchronization with respect to one or more different wireless nodes based on the metric. Thus, as described, the wireless node with the most desirable metric may be selected. As described above, in one example, the metrics may also relate to one or more parameters (e.g., root node, target node, hop count, etc.) in the synchronization structure, which may be jointly evaluated. At step 606, timing synchronization may be performed with surrounding wireless nodes, which may include rotating time, setting time in one adjustment, and so forth.

Referring to fig. 7, an exemplary methodology 700 that facilitates selecting a wireless node for timing synchronization is illustrated. At step 702, it is determined whether a GPS-equipped node is detected; as previously mentioned, GPS equipped nodes may be synchronized with the timing of GPS. If no GPS node is detected, then at step 704, a cluster of nodes with the highest quality metric may be selected. In one example, the group may include one or more wireless nodes having similar root nodes. As noted, the quality metrics may relate to SNR, GPS capability, GPS signal strength, uptime, quality of timing source, synchronization structure parameters, and the like. Further, the quality metric may be specified by the wireless node, obtained OTA from other devices, received over a backhaul link to one or more network components, and so forth. At step 706, it is determined whether there is more than one cluster with the highest quality metric. If so, then at step 708, the cluster with the largest node identifier may be selected. At step 710, the wireless node in the group having the smallest number of hops may be selected.

If there is only one cluster with the highest quality metric at step 706, then the wireless node in the cluster with the smallest number of hops may be selected at step 712. If a GPS equipped node is detected at step 702, then a cluster having the earliest time among the other GPS metrics detected may be selected at step 714. At step 716, the cluster with the highest quality metric may be selected from the clusters with the earliest GPS time. At step 718, the wireless node in the group having the smallest number of hops may be selected for synchronization. It should be appreciated that if more than one node in the above example has the same hop count, other metrics may be evaluated to determine which node to select for timing synchronization. Again, this is merely one example of selecting a wireless node relative to other nodes. It should be understood that many other examples are possible based on the quality metrics described herein.

The wireless node is selected for timing synchronization based on the SNR. At step 806, timing synchronization can be performed with the wireless node. For example, as described, this may include rotating the timing to match the wireless node over a span of time, synchronizing the timing in one adjustment, and so on. Further, as previously described, the wireless node may be a node in a synchronization tree, where the synchronization tree has a root node and a plurality of nodes are timing synchronized with the root node and/or one or more associated child nodes. In one example, the selected wireless node may be a root node.

At step 808, it is determined whether a synchronized node is detected. If so, at step 810 a root node of the synchronization tree may be identified. In one example, the wireless node may indicate the root node in a transmitted synchronization structure or the like. At step 812, GPS timing (e.g., from the synchronized node) can be sent to the root node to synchronize the root node with GPS. In this example, the root node of the synchronization tree may have the largest SNR among the nodes of the tree. As noted, for example, the root node may maintain its own timing, may maintain timing with GPS if equipped, and/or may receive GPS timing from one or more child nodes in the tree.

It is to be appreciated that, in accordance with one or more aspects described herein, inferences can be made regarding quality metrics and/or synchronization structure value relationships to determine a desired wireless node for timing synchronization, as described. As used herein, the term to "infer" or "inference" refers generally to the process of reasoning about or inferring states of the system, environment, and/or user from a set of observations as captured via events and/or data. Inference can be employed to determine a specific context or action, or can generate a probability distribution over states, for example. The inference can be probabilistic-that is, the computation of a probability distribution over states of interest based on a consideration of data and events. Inference can also refer to techniques employed for composing higher-level events from a set of events and/or data. Such inference can constitute a new event or action from a set of observed events and/or stored event data, whether or not the events are correlated in close temporal proximity, and whether the events and data come from one or more event and data sources.

Fig. 9 is an example of a mobile device 900 that facilitates providing synchronization information to one or more access points. Mobile device 900 comprises a receiver 902, e.g., receiver 902 receives one or more signals on one or more carriers from a receive antenna (not shown), performs typical actions on (e.g., filters, amplifies, and downconverts, etc.) the received signal, and digitizes the conditioned signal to obtain samples. Receiver 902 can comprise a demodulator 904 that can demodulate received symbols and provide them to a processor 906 for channel estimation. Processor 906 can be a processor dedicated to analyzing information received by receiver 902 and/or generating information for transmission by a transmitter 916, a processor that controls one or more components of mobile device 900, and/or a processor that both analyzes information received by receiver 902, generates information for transmission by transmitter 916, and controls one or more components of mobile device 900.

Mobile device 900 can additionally comprise memory 908 that is operatively coupled to memory 906 and that can store data to be transmitted, received data, information regarding available channels, data associated with analyzed signal and/or interference strength, information regarding allocated channels, power, rate, or the like, as well as any other suitable information for estimating a channel and transmitting via the channel. Memory 908 may also store protocols and/or algorithms associated with estimating and/or using a channel (e.g., performance based, capacity based, etc.).

It will be appreciated that the data store (e.g., memory 908) described herein can be either volatile memory or nonvolatile memory, or can include both volatile and nonvolatile memory. By way of example, and not limitation, nonvolatile memory can include Read Only Memory (ROM), Programmable ROM (PROM), Electrically Programmable ROM (EPROM), Electrically Erasable PROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM), which acts as external cache memory. By way of example, and not limitation, RAM may be available in a variety of forms such as Synchronous RAM (SRAM), Dynamic RAM (DRAM), Static DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), Enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and Direct Rambus RAM (DRRAM). The memory 908 of the subject systems and methods is intended to comprise, without being limited to, these and any other suitable types of memory.

The processor 906 may be further operatively coupled to a synchronization information receiver 910 and a synchronization information provider 912. The synchronization information receiver 910 can obtain timing synchronization related information from an access point and the synchronization information provider 912 can provide timing synchronization information to a disparate access point. For example, as described, the synchronization information receiver 910 can receive quality metrics related to one or more target access points from previous communications with the target access points, other mobile devices, and/or the like. As described, the synchronization information provider 912 may specify the quality metric to be transmitted to the tracking access point. In another example, the synchronization information receiver 910 can receive timing information from one or more target access points. In this example, the synchronization information provider 912 can send information, such as timing correction messages, to the different tracking access points to facilitate timing synchronization with the desired target access point. Further, as described in one example, the synchronization information provider 912 can transmit information regarding discovered access points to tracking access points to facilitate subsequent quality metric determination and selection for synchronization. Mobile device 900 further comprises a modulator 914 and a transmitter 916, e.g., modulator 914 and transmitter 916 respectively modulate and transmit signals to a base station, another mobile device, etc. Although depicted as being separate from the processor 906, it is to be understood that the synchronization information receiver 910, the synchronization information provider 912, the demodulator 904, and/or the modulator 914 can be part of the processor 906 or multiple processors (not shown).

Fig. 10 is an example of a system 1000 that facilitates timing synchronization with nodes in a wireless communication network. System 1000 includes a base station 1002 (e.g., access point …), with base station 1002 having a receiver 1010 and a transmitter 1026. Receiver 1010 receives signals from one or more mobile devices 1004 via a plurality of receive antennas 1006 and transmitter 1026 transmits to the one or more mobile devices 1004 via a transmit antenna 1008. Receiver 1010 can receive information from receive antennas 1006 and is operatively associated with a demodulator 1012 that demodulates received information. The analysis of the demodulated symbols by processor 1014 can be similar to that described above with respect to fig. 9, and processor 1014 can be coupled to a memory 1016, memory 1016 storing information related to estimating signal (e.g., pilot) strength and/or interference strength, data to be transmitted to or received from mobile device 1004 (or a disparate base station (not shown)), and/or any other suitable information related to performing the various acts and functions described herein. The processor 1014 is further coupled to a wireless node evaluator 1018, a wireless node selector, and a timing synchronizer 1022, the wireless node evaluator 1018 analyzing one or more wireless nodes to determine a quality metric associated therewith, the wireless node selector selecting a wireless node for timing synchronization based at least in part on the metric, the timing synchronizer 1022 adjusting the timing of the base station 102 to substantially match the timing of the selected wireless node.

According to an example, wireless node evaluator 1018 can receive quality metrics related to one or more wireless nodes, where the quality metrics can relate to SNR, GPS capabilities, synchronization structure, and/or the like of the wireless nodes, as described. Wireless node selector 1020 may compare the quality metrics to select a wireless node for synchronization. It should be appreciated that substantially any comparison algorithm may be used, such as selecting the wireless node with the greatest SNR, selecting the wireless node equipped with GPS, selecting the wireless node with the least number of hops, any combination of the preceding, and so forth, as described. As described, timing synchronizer 1022 can adjust the timing of base station 1002 based on the timing of the selected wireless node. Further, although depicted as being separate from the processor 1014, it is to be understood that the wireless node evaluator 1018, wireless node selector 1020, timing synchronizer 1022, demodulator 1012, and/or modulator 1024 can be part of the processor 1014 or multiple processors (not shown).

Fig. 11 illustrates an exemplary wireless communication system 1100. The wireless communication system 1100 depicts one base station 1110 and one mobile device 1150 for sake of brevity. However, it is to be appreciated that system 1100 can include more than one base station and/or more than one mobile device, wherein other base stations and/or mobile devices can be substantially similar or different from example base station 1110 and mobile device 1150 described below. Moreover, it is to be appreciated that base station 1110 and/or mobile device 1150 can employ the systems (fig. 1-4 and 9-10), state diagrams (fig. 5), and/or methods (fig. 6-8) described herein to facilitate wireless communication there between.

At base station 1110, traffic data for a number of data streams is provided from a data source 1112 to a Transmit (TX) data processor 1114. According to an example, each data stream can be transmitted over a respective antenna. TX data processor 1114 formats, codes, and interleaves each traffic data stream based on a particular coding scheme selected for that data stream to provide coded data.

The coded data for each data stream can be multiplexed with pilot data using Orthogonal Frequency Division Multiplexing (OFDM) techniques. Alternatively or additionally, the pilot symbols may be Frequency Division Multiplexed (FDM), Time Division Multiplexed (TDM), or Code Division Multiplexed (CDM). The pilot data is typically a known data pattern that is processed in a known manner and can be used at mobile device 1150 to estimate channel response. The multiplexed pilot and coded data for each data stream can be modulated (e.g., symbol mapped) based on a particular modulation scheme (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM), etc.) selected for that data stream to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions performed or provided by processor 1130.

The modulation symbols for the data streams can be provided to a TX MIMO processor 1120, and the modulation symbols can be further processed by TX MIMO processor 1120 (e.g., for OFDM). TX MIMO processor 1120 then forwards to N_TN are provided by transmitters (TMTR)1122a through 1122t_TA stream of modulation symbols. In various embodiments, TX MIMO processor 1120 applies beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted.

Each transmitter 1122 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (e.g., amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. Then, N from transmitters 1122a through 1122t_TThe modulated signals are respectively from N_TThe antennas 1124a through 1124t transmit.

At mobile device 1150, by N_RThe transmitted modulated signals are received by antennas 1152a through 1152r and the received signal from each antenna 1152 is provided to a respective receiver (RCVR)1154a through 1154 r. Each receiver 1154 conditions (e.g., filters, amplifies, and downconverts) a respective signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

RX data processor 1160 receives and processes data from N based on particular receiver processing techniques_RN of receivers 1154_RA stream of received symbols to provide N_TA "detected" symbol stream. RX data processor 1160 can demodulate, deinterleave, and decode each detected symbol stream to recover the traffic data for the data stream. The processing by RX data processor 1160 is complementary to that performed by TX MIMO processor 1120 and TX data processor 1114 at base station 1110.

A processor 1170 can periodically determine which precoding matrix to use as discussed above. Further, processor 1170 can formulate a reverse link message comprising a matrix index portion and a rank value portion.

The reverse link message may comprise various types of information regarding the communication link and/or the received data stream. The reverse link message may be processed by a TX data processor 1138 (TX data processor 1138 also receives traffic data for a number of data streams from a data source 1136), modulated by a modulator 1180, conditioned by transmitters 1154a through 1154r, and transmitted back to base station 1110.

At base station 1110, the modulated signals from mobile device 1150 are received by antennas 1124, conditioned by receivers 1122, demodulated by a demodulator 1140, and processed by a RX data processor 1142 to extract the reverse link message transmitted by mobile device 1150. Processor 1130 can then process the extracted message to determine which precoding matrix to use for determining the beamforming weights.

Processors 1130 and 1170 can direct (e.g., control, coordinate, manage, etc.) operation at base station 1110 and mobile device 1150, respectively. Respective processors 1130 and 1170 can be associated with memory 1132 and 1172 that store program codes and data. Processors 1130 and 1170 can also perform computations to derive frequency and impulse response estimates for the uplink and downlink, respectively.

It is to be understood that the embodiments described herein may be implemented by hardware, software, firmware, middleware, microcode, or any combination thereof. For a hardware implementation, the processing units may be implemented within one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.

When the embodiments are implemented in software, firmware, middleware or microcode, program code or code segments, they may be stored in a machine-readable medium, such as a storage component. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, any combination of instructions, a data structure, or a program statement. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.

For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described. The software codes may be stored in memory units and executed by processors. The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.

Referring to fig. 12, illustrated is a system 1200 that facilitates timing synchronization with one or more wireless nodes in a wireless communication network. For example, system 1200 can reside at least partially within a base station, mobile device, etc. It is to be appreciated that system 1200 is represented as including functional blocks, which can be functional blocks that represent functions implemented by a processor, software, or combination thereof (e.g., firmware). System 1200 includes a logical grouping 1202 of electrical components that can act in conjunction. For instance, logical grouping 1202 can include an electrical component for receiving quality metrics corresponding to one or more surrounding wireless nodes over a backhaul link 1204. For example, as noted, the quality metric may relate to one or more aspects of the wireless node (e.g., SNR, GPS information, uptime, synchronization structure parameters (e.g., root node, hop count, etc.) that may be used to select the node for timing synchronization relative to other nodes. Further, logical grouping 1202 can include an electrical component for selecting at least one surrounding wireless node for synchronization based at least in part upon a corresponding quality metric 1206.

As described, for example, electrical component 1206 may compare quality metrics of surrounding wireless nodes to determine a wireless node for synchronization, e.g., may make the determination based on which node has the highest quality metric. In another example, one or more parameters of the quality metric may be evaluated in connection with selecting a wireless node, for example. Moreover, logical grouping 1202 can include an electrical component for timing synchronization 1208 with at least one surrounding wireless node. As described above, this may be accomplished by rotating the timing based on the timing of the wireless node, adjusting the timing in a single step, and so forth. Moreover, logical grouping 1202 can include an electrical component for monitoring disparate surrounding wireless nodes to determine whether a disparate wireless node has a higher quality metric than the surrounding wireless nodes 1210. For example, other wireless nodes may be continually evaluated to detect when a wireless node with a higher quality metric is present. This may occur, for example, when the quality metrics of surrounding wireless nodes are degraded, as previously described. Further, when a wireless node with a higher quality metric is detected, in one example, electrical component 1206 can perform timing synchronization with the new wireless node. Additionally, system 1200 can include a memory 1212 that retains instructions for executing functions associated with electrical components 1204, 1206, 1208, and 1210. While electrical components 1204, 1206, 1208, and 1210 are shown as being external to memory 1212, it is to be understood that one or more of electrical components 1204, 1206, 1208, and 1210 can exist within memory 1212.

Referring to fig. 13, illustrated is a system 1300 that facilitates timing synchronization at one or more wireless nodes in a wireless communication network. For example, system 1300 can reside at least partially within a base station, mobile device, etc. It is to be appreciated that system 1300 is represented as including functional blocks, which can be functional blocks that represent functions implemented by a processor, software, or combination thereof (e.g., firmware). System 1300 includes a logical grouping 1302 of electrical components that can act in conjunction. For instance, logical grouping 1302 can include an electrical component that compares a timing of one wireless node to a timing of a disparate wireless node 1304. The timing may be received by evaluating the wireless node, requesting timing, etc. Comparing the timing may indicate whether an inconsistency exists and/or whether the inconsistency should be corrected. Further, logical grouping 1302 can comprise an electrical component for transmitting a timing correction signal to a disparate wireless node based at least in part upon the comparing 1306. Thus, when the timing deviates from a specified threshold, a message may be sent to at least one wireless node to inform the node of the inconsistency. Additionally, system 1300 can include a memory 1308 that retains instructions for executing functions associated with electrical components 1304 and 1306. While electrical components 1304 and 1306 are shown as being external to memory 1308, it is to be understood that one or more of electrical components 1304 and 1306 can exist within memory 1308.

The various illustrative logics, logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with the following components: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other similar configuration. Further, at least one processor may comprise one or more modules operable to perform one or more of the steps and/or actions described above.

Further, the steps and/or actions of a method or algorithm described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium may be coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. In addition, in some aspects, the processor and the storage medium may reside in an ASIC. Additionally, the ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal. Additionally, in some aspects, the steps and/or actions of a method or algorithm may reside as one or any combination or set of codes and/or instructions in a machine readable medium and/or computer readable medium, which may be incorporated into a computer program product.

In one or more aspects, the functions described may be implemented as hardware, software, firmware, or any combination thereof. If implemented as software, the functions may be one or more instructions or code stored or transmitted on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are also included in the definition of medium. Disk and disc, as used in this application, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks (disks) usually reproduce data magnetically, while discs (discs) usually reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

While the foregoing disclosure discusses illustrative aspects and/or embodiments, it should be noted that various changes and modifications could be made herein without departing from the scope of the aspects and/or embodiments as defined by the appended claims. Furthermore, although elements of the described aspects and/or embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any aspect and/or embodiment may be utilized with all or a portion of any other aspect and/or embodiment, unless stated otherwise. Furthermore, to the extent that the term "includes" is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in a claim. Furthermore, although elements of the described aspects and/or aspects may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any aspect and/or embodiment may be utilized with all or a portion of any other aspect and/or embodiment, unless stated otherwise.

Claims (30)

1. A method of synchronizing wireless nodes in a wireless communication network, comprising:

receiving quality metrics related to at least one surrounding wireless node over a backhaul link;

selecting a wireless node of the at least one surrounding wireless node for synchronization with respect to one or more different wireless nodes based at least in part on the quality metric; and

timing synchronization with the wireless node, wherein the wireless node is synchronized to at least one different wireless node in a wireless node tree having a root node, wherein all wireless nodes in the wireless node tree are synchronized with the root node, and wherein the quality metric comprises a synchronization metric identifying the root node, and timing synchronization is based at least in part on the identified root node.

2. The method of claim 1, wherein timing synchronization is based at least in part on an over-the-air synchronization signal transmitted to or received from the wireless node.

3. The method of claim 1, wherein the timing synchronization comprises: the time slots and/or frame numbers are synchronized.

4. The method of claim 1, wherein the timing synchronization comprises: synchronizing with the wireless node or transmitting a synchronization signal to the wireless node.

5. The method of claim 4, further comprising:

the timing is set to the timing received from the global timing source,

wherein the timing synchronization comprises: transmitting timing from the global timing source to the wireless node over a backhaul link.

6. The method of claim 5, wherein the global timing source is a Global Positioning System (GPS), another radio access technology, a synchronization signal, or a terrestrial broadcast signal.

7. The method of claim 1, wherein the quality metric comprises an indication of a priority of the wireless node.

8. The method of claim 1, wherein the wireless node is selected based at least in part on a received over-the-air (OTA) signal.

9. The method of claim 1, wherein the wireless node is selected based at least in part on a receiver signal strength or a signal-to-noise ratio of an OTA signal.

10. The method of claim 1, wherein the quality metric relates to whether the wireless node is synchronized with a global timing source.

11. The method of claim 10, wherein the global timing source is a Global Positioning System (GPS), another radio access technology, a synchronization signal, or a terrestrial broadcast signal.

12. The method of claim 1, wherein the quality metric relates to uptime of the wireless node.

13. The method of claim 1, wherein the quality metric is received from one or more mobile devices.

14. The method of claim 1, further comprising: different neighboring wireless nodes are monitored to determine if a different neighboring wireless node has a higher quality metric than the wireless node.

15. The method of claim 1, wherein the backhaul link is a wireless link.

16. An apparatus for synchronizing wireless nodes in a wireless communication network, comprising:

means for receiving quality metrics corresponding to one or more surrounding wireless nodes over a backhaul link;

means for selecting at least one of the one or more surrounding wireless nodes for synchronization based at least in part on the corresponding quality metrics; and

means for timing synchronization with the at least one wireless node, wherein the wireless node is synchronized to at least one different wireless node in a wireless node tree having a root node, wherein all wireless nodes in the wireless node tree are synchronized with the root node, and wherein the quality metric comprises a synchronization metric that identifies the root node, and the timing synchronization is based at least in part on the identified root node.

17. An apparatus for synchronizing wireless nodes in a wireless communication network, comprising:

a wireless node evaluator to receive quality metrics related to at least one surrounding wireless node over a backhaul link;

a wireless node selector to select a wireless node of the at least one surrounding wireless node for synchronization with respect to one or more different wireless nodes based at least in part on the quality metric; and

a timing synchronizer to timing synchronize with the wireless node, wherein the wireless node is synchronized to at least one different wireless node in a wireless node tree having a root node, wherein all wireless nodes in the wireless node tree are synchronized with the root node, wherein the quality metric comprises a synchronization metric identifying the root node, and the timing synchronizer is to timing synchronize with the wireless node based at least in part on the root node.

18. The apparatus of claim 17, wherein the timing synchronizer adjusts timing based at least in part on an over-the-air synchronization signal transmitted to or received from the wireless node.

19. The apparatus of claim 17, wherein the timing synchronizer adjusts timing based on a time slot and/or frame number of the wireless node.

20. The apparatus of claim 17, wherein the timing synchronizer transmits a timing synchronization signal to the wireless node.

21. The apparatus of claim 20, wherein the timing synchronizer synchronizes timing of the apparatus with timing received from a global timing source and sends the timing to the wireless node in the timing synchronization signal over a backhaul link.

22. The apparatus of claim 21, wherein the global timing source is a Global Positioning System (GPS), another radio access technology, a synchronization signal, or a terrestrial broadcast signal.

23. The apparatus of claim 17, wherein the wireless node selector selects the wireless node based at least in part on a received over-the-air (OTA) signal.

24. The apparatus of claim 17, wherein the wireless node selector selects the wireless node based at least in part on a receiver signal strength or a signal-to-noise ratio of an OTA signal.

25. The apparatus of claim 17, wherein the quality metric relates to whether the wireless node is synchronized with a global timing source.

26. The apparatus of claim 25, wherein the global timing source is a Global Positioning System (GPS), another radio access technology, a synchronization signal, or a terrestrial broadcast signal.

27. The apparatus of claim 17, wherein the quality metric relates to uptime of the wireless node.

28. The apparatus of claim 17, wherein the wireless node evaluator receives the quality metric from one or more mobile devices.

29. The apparatus of claim 17, further comprising a synchronization monitor that monitors different neighboring wireless nodes to determine if a different neighboring wireless node has a higher quality metric than the wireless node.

30. The apparatus of claim 17, wherein the backhaul link is a wireless link.