US20060251017A1 - Self synchronized beacon - Google Patents

Self synchronized beacon Download PDF

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US20060251017A1
US20060251017A1 US11417732 US41773206A US2006251017A1 US 20060251017 A1 US20060251017 A1 US 20060251017A1 US 11417732 US11417732 US 11417732 US 41773206 A US41773206 A US 41773206A US 2006251017 A1 US2006251017 A1 US 2006251017A1
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radio
beacon
beacon signal
radios
network
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US11417732
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Donald Bishop
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Wavestar Communications Systems LLC
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MediaCell Licensing Corp
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATIONS NETWORKS
    • H04W56/00Synchronisation arrangements
    • H04W56/001Synchronization between nodes
    • H04W56/0015Synchronization between nodes one node acting as a reference for the others
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/24Radio transmission systems, i.e. using radiation field for communication between two or more posts
    • H04B7/26Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
    • H04B7/2662Arrangements for Wireless System Synchronisation
    • H04B7/2671Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
    • H04B7/2678Time synchronisation
    • H04B7/2687Inter base stations synchronisation
    • H04B7/2693Centralised synchronisation, i.e. using external universal time reference, e.g. by using a global positioning system [GPS] or by distributing time reference over the wireline network
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATIONS NETWORKS
    • H04W48/00Access restriction; Network selection; Access point selection
    • H04W48/08Access restriction or access information delivery, e.g. discovery data delivery
    • H04W48/10Access restriction or access information delivery, e.g. discovery data delivery using broadcasted information
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATIONS NETWORKS
    • H04W48/00Access restriction; Network selection; Access point selection
    • H04W48/08Access restriction or access information delivery, e.g. discovery data delivery
    • H04W48/12Access restriction or access information delivery, e.g. discovery data delivery using downlink control channel
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATIONS NETWORKS
    • H04W36/00Handoff or reselection arrangements
    • H04W36/16Performing reselection for specific purposes
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATIONS NETWORKS
    • H04W56/00Synchronisation arrangements
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATIONS NETWORKS
    • H04W74/00Wireless channel access, e.g. scheduled or random access
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATIONS NETWORKS
    • H04W84/00Network topologies
    • H04W84/02Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10Small scale networks; Flat hierarchical networks
    • H04W84/12WLAN [Wireless Local Area Networks]
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATIONS NETWORKS
    • H04W84/00Network topologies
    • H04W84/18Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

A system and method for communicating on a network having multiple radios by substantially simultaneously transmitting a beacon signal from the radios. When a first radio receives a beacon signal from another radio, the first radio determines if the received beacon signal contains a priority designator. If the received beacon signal has a higher priority than that of the first radio, the first radio synchronizes subsequent transmission of its beacon signals to the other radio's beacon signal. In a network environment, radios may continuously adapt their beacon signals to transmit substantially simultaneously. Additionally, radios in a congested environment may coordinate beacon signals to minimize overhead use of bandwidth.

Description

    CROSS REFERENCE TO RELATED APPLICATIONS
  • This application claims priority to and the benefit of U.S. provisional patent application Ser. No. 60/677,626 entitled “Externally Sourced Synchronized Beacon” filed May 4, 2005 by Donald M. Bishop, and U.S. provisional patent application Ser. No. 60/677,625 entitled “Self Synchronizing Beacon” filed May 4, 2005 by Donald M. Bishop, both of which are hereby expressly incorporated by reference. This application is related to and simultaneously filed with application Ser. No. ______ entitled “Externally Sourced Synchronized Beacon” by Donald M. Bishop and being commonly assigned, the entire contents of which are hereby expressly incorporated by reference.
  • BACKGROUND OF THE INVENTION
  • a. Field of the Invention
  • The present invention pertains generally to communication networks and specifically to networks having multiple radios.
  • b. Description of the Background
  • Wireless communications networks are being widely deployed. In order to ensure subscriber coverage, a wireless network may have several radio transceivers positioned so that the coverage areas of the radios overlap. As radio coverage areas overlap, some interference and undesirable cross-communication between radios may occur. Such interference may decrease available bandwidth, which diminishes the number and quality of potential subscriber connections.
  • Many wireless protocols have a feature whereby a device can sense if another device is using the specific frequency or band, and the first device will refrain from transmitting. In some protocols, the first device may retry the transmission at a later time, which may be a randomly generated time. Such a feature aims to minimize one device ‘talking over’ another device and preventing both device's transmissions from getting through. This collision detection feature is widely used in many different protocols, including standard wired Ethernet and wireless Ethernet-based protocols such as IEEE 802.11 wireless protocols.
  • A distinct problem with such protocols is that the bandwidth is inherently underutilized and throughput for each device can be much less than optimal, especially when many devices are communicating on the network. When many devices attempt to communicate on the band simultaneously, the collision detection and avoidance procedures begin to occupy much of the communication bandwidth.
  • It would therefore be advantageous to provide a system and method for providing improved use of the available bandwidth for communication networks having several radios.
  • SUMMARY OF THE INVENTION
  • The present invention provides a system and method for communicating on a network having multiple radios by substantially simultaneously transmitting a beacon signal from the radios. When a first radio receives a beacon signal from another radio, the first radio determines if the received beacon signal contains a priority designator. If the received beacon signal has a higher priority than that of the first radio, the first radio synchronizes subsequent transmission of its beacon signals to the other radio's beacon signal. In a network environment, radios may continuously adapt their beacon signals to transmit substantially simultaneously. Additionally, radios in a congested environment may coordinate beacon signals to minimize overhead use of bandwidth.
  • An embodiment may include a network comprising: a plurality of radio terminals, each of the plurality of radios being adapted to establish at least one two-way data communication session, adapted to delay sending a transmission when another ongoing transmission is detected, and adapted to broadcast a beacon signal; wherein each of the plurality of radios being adapted to transmit the beacon signal substantially simultaneously by the method of identifying a second beacon signal from a second of the plurality of radios and synchronizing the transmission of the beacon signal based on the second beacon signal.
  • Another embodiment may include a radio comprising: a transmitter; and a receiver; wherein the radio is adapted to establish at least one two-way data communication session, adapted to delay sending a transmission when another ongoing transmission is detected, adapted to broadcast a beacon signal, adapted to transmit the beacon signal substantially simultaneously by the method of receiving a second beacon signal from a second radio capable of two-way communications with the radio, determining a beacon rhythm from the second beacon signal, and transmitting the beacon signal using the beacon rhythm.
  • Yet another embodiment may include a method comprising: establishing at least one two-way communication session; delay sending a transmission when another ongoing transmission is detected; transmitting a beacon signal on a first beacon rhythm; receiving a beacon signal having a second beacon rhythm from a second radio capable of two-way communication; adjusting the first beacon rhythm to be substantially synchronous with the second beacon rhythm to; and transmitting the beacon signal substantially simultaneously with the second beacon rhythm.
  • Still another embodiment may include a radio communications protocol comprising: performing two-way communications with a second radio; detecting an ongoing transmission from a third radio and delaying transmitting a signal during the ongoing transmission; broadcasting a beacon signal on a repeated basis; receiving a second beacon signal from a third radio; synchronizing the beacon signal to the second beacon signal; and transmitting the beacon signal regardless of any ongoing transmissions from another radio.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • In the drawings,
  • FIG. 1 is a diagrammatic illustration of an embodiment showing a wireless network with overlapping coverage areas.
  • FIG. 2 is a diagrammatic illustration of an embodiment showing a wireless access point having multiple radios.
  • FIG. 3 is a flowchart illustration of an embodiment showing a method for self-synchronizing by a radio.
  • FIG. 4 is a flowchart illustration of an embodiment showing a method for analyzing beacon signals received while in synchronization mode.
  • FIG. 5 is a timeline illustration of an embodiment showing a sequence for synchronizing beacon signals when grossly out of synchronization.
  • FIG. 6 is a timeline illustration of an embodiment showing a sequence for fine tuning synchronizing beacon signals when in synchronization mode.
  • FIG. 7 is a plan view illustration of a residential neighborhood having wireless access service.
  • DETAILED DESCRIPTION OF THE INVENTION
  • Specific embodiments of the invention are described in detail below. The embodiments were selected to illustrate various features of the invention, but should not be considered to limit the invention to the embodiments described, as the invention is susceptible to various modifications and alternative forms. The invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims. In general, the embodiments were selected to highlight specific inventive aspects or features of the invention.
  • Throughout this specification, like reference numbers signify the same elements throughout the description of the figures.
  • When elements are referred to as being “connected” or “coupled,” the elements can be directly connected or coupled together or one or more intervening elements may also be present. In contrast, when elements are referred to as being “directly connected” or “directly coupled,” there are no intervening elements present.
  • The invention may be embodied as devices, systems, methods, and/or computer program products. Accordingly, some or all of the invention may be embodied in hardware and/or in software (including firmware, resident software, micro-code, state machines, gate arrays, etc.) Furthermore, the present invention may take the form of a computer program product on a computer-usable or computer-readable storage medium having computer-usable or computer-readable program code embodied in the medium for use by or in connection with an instruction execution system. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
  • The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media.
  • Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by an instruction execution system. Note that the computer-usable or computer-readable medium could be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, of otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.
  • Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Combinations of the any of the above should also be included within the scope of computer readable media.
  • When the invention is embodied in the general context of computer-executable instructions, the embodiment may comprise program modules, executed by one or more systems, computers, or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically, the functionality of the program modules may be combined or distributed as desired in various embodiments.
  • Throughout this specification, the term “comprising” shall be synonymous with “including,” “containing,” or “characterized by,” is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. “Comprising” is a term of art which means that the named elements are essential, but other elements may be added and still form a construct within the scope of the statement. “Comprising” leaves open for the inclusion of unspecified ingredients even in major amounts.
  • FIG. 1 illustrates an embodiment 100 showing a wireless network with overlapping coverage areas. A network controller 102 is connected to a network backbone 104. Connected to the backbone 104 are radio transceivers 106, 108, 110, and 112. Each radio transceiver has an antenna, such as antenna 109 connected to transceiver 108. Transceiver 106 has a coverage area 114. Similarly, transceivers 108, 110, and 112 have coverage areas 116, 118, and 120, respectively. A wireless device 122 is located in an overlapping coverage area 124. In the area 124, radio transmissions from transceivers 106, 108, and 112 all overlap.
  • In embodiment 100, two or more of the transceivers 106, 108, 110, and 112 may simultaneously transmit a beacon signal. By simultaneously transmitting a beacon signal, bandwidth is freed up that would otherwise be dedicated to transmitting and receiving beacon signals from transceivers with overlapping coverage areas.
  • Radio transceivers 106, 108, 110, and 112 may periodically transmit a beacon signal. Such a signal may identify the transceiver and provide information such that other devices in the area may begin communications. In many embodiments, the beacon signal may provide a unique identifier for the radio, as well as an identifier for the network and transmission parameters so that another device may successfully initiate communications.
  • In many cases, radios that communicate with digitized or other forms of data communication, in a similar way as human operated audio radio communication, are able to listen on the communication band, determine that the band is quiet, then begin a transmission. If another device is transmitting, the radio is able to wait until the band is quiet before attempting another transmission. This technique prevents two radios from simultaneously transmitting and distorting each other's signals.
  • Many standards have been developed for automated data transmission over wireless airwaves. Examples are cellular phone networks, wireless data standards such as IEEE 802.11, various spread spectrum and time division multiple access standards, and many others.
  • As more devices are attempting to communicate in a certain geographical area, the available bandwidth decreases. Especially after a certain number of devices is reached, the available bandwidth and data throughput decreases exponentially as more devices are added.
  • One reason for the decrease in bandwidth is the communications overhead associated with each device. For example, fixed base stations may transmit a beacon signal on a periodic basis. In a typical prior art application, when one radio transmits a beacon signal, another radio within the area would be thereby forced to wait to transmit its beacon signal or any other signal. In an area where many radio coverage areas overlap, a significant portion of the bandwidth might become cluttered with the repeated transmission of beacon signals of the transceivers from overlapping coverage areas. This is because as each radio transmits its own beacon signal, all other devices typically refrain from transmitting.
  • In the embodiment 100, two or more of the transceivers may simultaneously transmit beacon signals. The coordinated transmission of beacon signals may eliminate much of the transmission overhead on a channel or frequency that is shared by all the transceivers. The coordination and synchronization of the beacon signals may be accomplished using many methods. In one method, a broadcast transmitter 126 may broadcast a signal that may be interpreted as having a timing component used to synchronize several of the radios at one time.
  • In some embodiments, every transceiver having overlapping coverage area with another transceiver may transmit synchronized beacon signals, whereas in other embodiments two or more transceivers may do so. In particularly busy areas, synchronized beacon signals are especially useful, since the bandwidth can be at a premium in congested areas.
  • Some radio transmission schemes have a base and remote architecture. In such a scheme, the base stations have a defined transmission scheme that may include a repeated beacon signal. The remote devices in such a scheme may or may not transmit a beacon signal and may or may not be able to communicate directly from one remote device to another. Examples of such schemes include IEEE 802.11 and the various cellular phone architectures. In many cases, the base stations are connection points for other networks such as the Internet, cable television, or POTS phone system.
  • In contrast, other schemes have a peer to peer architecture. In such a scheme, each device operates in the same manner as all the other devices in the area and any device is able to transmit to any other device in the area.
  • One purpose of a beacon signal is to alert other devices in the area of a station's presence. In situations where a remote device is in the area of a base station, the remote device may be capable of listening for a base station's beacon signal, interpreting the signal, and establishing connections.
  • For example, the device 122 is located within the transmission coverage areas of radio transceivers 106, 108, and 112. The area 124 is highlighted showing the overlapping coverage areas. If the beacon signals of the transceivers 106, 108, and 112 were asynchronously transmitting beacon signals, each transceiver 106, 108, and 112 would wait until the other transceivers had completed their beacon signals before transmitting a beacon signal of its own. This process would take up at least three times the bandwidth of a single beacon signal. In some instances, since some devices may delay more than others after detecting that another device was transmitting, the bandwidth used up by the beacon signals may be four or more times the bandwidth consumed by a single beacon signal.
  • When the transceivers 106, 108, and 112 simultaneously transmit a beacon signal, the device 122 may be able to detect and decode at least one of the beacon signals. In practice, it is likely that the device 122 may detect and decode the beacon signal from the nearest transceiver. In this example, the device 122 may be able to detect and decode the beacon signal from transceiver 108 because the signal to noise ratio for the beacon signal from transceiver 108 may be greater than either of the simultaneous beacon signals from transceivers 106 and 112. In some situations, the device 122 may detect the beacon signals from one of the transceivers 106 or 112, depending on the relative signal strength of the particular beacon signal.
  • Overlapping coverage areas are typical of many wireless networks where a full coverage is desired over a specific area. For example, a wireless data network may provide coverage in a large building, shopping mall, or airport using multiple radio transceivers with overlapping coverage areas. Similarly, a school campus or residential neighborhood may be blanketed by various wireless networks for data, voice, or other communications.
  • For the purposes of this specification, the terms “radio,” “radio transceiver,” “wireless access point,” “transceiver,” and similar terms are used interchangeably. Similarly, the terms “backbone,” “network,” “network backbone,” etc. are also used interchangeably.
  • In some embodiments, the radio transceivers may have a mode by which all transmissions, including beacon signals are delayed when the radio detects that another transmission is occurring. The radio transceivers may have a second mode which forces the beacon signals to be transmitted at the synchronized time, regardless if another device is transmitting.
  • Many network architectures comprise a network backbone with several wireless transceivers attached to the backbone. For example, a wireless service provider may connect several wireless access points using digital subscriber line (DSL) connections to a central access point. In another example, a cable television and internet connection service may be provided through a hybrid fiber/coax (HFC) network with wireless subscriber connections mounted on utility poles or utility pedestals in a neighborhood.
  • The network backbone 104 may be any type of hardwired or wireless connection between the various transceivers. In some configurations, the backbone 104 may be fiber optic cable, coaxial cable, twisted pair, or some other directly connected communication path. In other configurations, microwave communications or other radio frequency may be used to connect various portions of the network. In still other configurations, any combination of connection may be used.
  • The controller 102 may be any type of device in communication with one or more of the transceivers. In some configurations, the controller 102 may be a centralized computer, hub, switch, gateway, headend, Cable Modem Termination System (CMTS), Digital Subscriber Line Access Multiplexer (DSLAM), or any other device that communicates along the backbone 104. In some configurations, the controller 102 may provide connection between the backbone 104 and the Internet, telephone network, or another outside network.
  • In some configurations, the controller 102 may be a dedicated device that provides a synchronization function for the transceivers. In still other configurations, one of the transceivers may have a controller function enabled and function as both a transceiver as well as the controller 102.
  • The controller 102 may provide various sorts of communications in order to set up and control the radio functions of the various transceivers. For example, the controller 102 may send commands to the radio transceivers to initiate sequences for synchronizing or for setting the mode from normal to synchronous beacon transmittal. In many cases, the controller 102 may additionally monitor the performance of the radio transmitters.
  • FIG. 2 illustrates an embodiment 200 of a wireless access point having two radio transceivers. The wireless access point 202 contains radio transceivers 204 and 206. Directional antennas 207 and 208 are connected to transceivers 204 and 206, respectively. A network interface 210 connects the transceivers to the network 214. The directional antenna 207 has a coverage area 218. Similarly, the directional antenna 208 has a coverage area 220. The overlapping coverage area 222 is the area where both antenna signals overlap.
  • The wireless access point 202 may be a single device that is fixedly mounted in an area for wireless communications. For example, the wireless access point 202 may be mounted in an airport terminal, a coffee shop, a residential neighborhood, an office building, or any other area where it is desired to service the area with two or more radio transceivers. In many cases, a single radio transceiver may be overwhelmed by the communications, so it may be desirable to service the area by using multiple radios with directional antennas to cover specific sectors. In some cases, the sectors may overlap, while in other cases the sectors may not overlap.
  • In some configurations, the proximity of the antennas 207 and 208 may cause some interference between the two radio systems. In such cases, it is possible that the beacon signal from one antenna may be received by the other antenna, causing the receiving transceiver to become quiet while the other transceiver is transmitting in some modes of operation.
  • The beacon signals of the two radio transceivers 204 and 206 may be synchronized by having one radio listen to the beacon signal of the other and synchronizing subsequent beacon signals. The radio may synchronize to another radio's beacon signal by a predetermined protocol. In some cases, the protocol may include determining that the other radio has a higher priority and thus the first radio must adopt the higher priority radio's beacon rhythm.
  • During normal operations prior to synchronizing, a radio may normally refrain from transmitting when another radio is broadcasting. This may also apply when the second radio is broadcasting a beacon signal. When the radio adopts the beacon rhythm of the second radio, the first radio may broadcast a beacon signal that indicates it is in a synchronized beacon mode. Such a beacon signal may cause the second radio to continue to broadcast its beacon signal on rhythm.
  • In the embodiment 200, where two radios are located in close proximity, the radios may be operable independently of each other. However, the operations of one radio may interfere with that of the other. In order to synchronize the beacon signals of the two radios, radio 204 may be given a higher priority than radio 206. When the access point 202 is started, both radios 204 and 206 may be in normal operation mode where each radio refrains from transmitting while another radio is transmitting. The controller 210 may send a command to one or both of the radios 204 and 206 to enter self-synchronized beacon mode. In such a mode, each radio may listen for the other radio's beacon signal, determine if the beacon signal has a higher priority, and synchronize further beacon signals.
  • In another embodiment, two radios may begin normal operations. During the operations, each radio may receive beacon signals from the other repeatedly. After a certain number of repetitions, one radio may initiate a synchronization routine wherein the radio transmits a synchronization command to the other radio, one of the radios is determined to be the primary radio, and the other radio adopts a beacon rhythm from the primary radio. In such an embodiment, the radios are capable of determining that the beacon signals may be synchronized, initiating the synchronization sequence, arbitrating the primary rhythm, and entering a synchronized beacon sequence.
  • Beacon signal synchronization may occur just between the two radios 204 and 206, but may also occur between other radios within communication range of the radios 204 and 206. In some cases, synchronization may occur with radios outside the network. For example, if two separate networks were covering the same area, all of the radios in the space may listen to each other's beacon signal and begin to transmit beacon signals substantially simultaneously. In a very large network situation, the beacon signals may start out as random intervals, but as the radios begin to synchronize to each other, the network may adapt to producing synchronized beacons.
  • In many configurations, the radio transceivers 204 and 206 may be independent devices having separate processors and capable of operating independently from each other. Such a configuration may allow each transceiver 204 or 206 to conduct separate communications with devices within its coverage area. Each transceiver 204 and 206 may have a dedicated input line or be otherwise adapted to receive commands from the controller 210 or from each other.
  • The network interface/controller 210 may perform several functions, including transmitting communications between the network 214 and the radio transceivers 204 and 206. In some configurations, the network interface/controller 210 may have a processor or state machine that is independent from the radio transceivers 204 and 206.
  • The embodiment 200 illustrates an example of a multiple radio transceiver system where the radio transceivers are located in very close proximity. Some configurations may have three or more radio transceivers. In some configurations, the system may have the wireless access point 202 located in one location, with the directional antennas 207 and 208 located remotely. For example, a wireless access point 202 may be located on one floor of a multistory building while the various directional antennas may be each located on a different floor of the building. The directional antennas in such an example may have a horizontal coverage area that covers one floor of the building.
  • The embodiment 200 functions in a similar manner as the embodiment 100, with multiple radios having a synchronized beacon signal. In the case of embodiment 200, the ‘backbone’ may be a communication path through the controller 210.
  • In a specific configuration of embodiment 200, a wireless access point 202 may be mounted in a single box with the directional antennas 207 and 208 mounted on the outside surface of the box. Such a configuration may be mounted on an interior wall of a building, whereas a weather tight configuration may be mounted on a utility pole, utility pedestal, or on an exterior wall of a building.
  • The network 214 may be any type of communication network. For example, the network 214 may be a cable television network, a twisted pair digital subscriber line (‘DSL’) network, Ethernet, or other type of wired connection. In other examples, the network may be a wireless network designed to not interfere with the radio transmitters 204, 206, or 224. In still other examples, the network may be a fiber optic network or other optical communication medium. Any type of communication medium and any protocol may be used to communicate via the network 214.
  • FIG. 3 illustrates an embodiment 300 of a method for self-synchronizing. When a radio receives a beacon signal in block 302, it determines if the incoming beacon signal has a higher priority in block 304. If the incoming beacon signal has a higher priority, the radio's beacon signal rhythm is adjusted to correspond with the incoming beacon signal in block 306. If the incoming beacon signal has a lower priority in block 304, the radio's beacon signal rhythm is not adjusted and the radio transmits a beacon signal on the unchanged beacon signal rhythm in block 308. If the beacon signal rhythm is adjusted, the transmission of block 308 would be using the newly adjusted beacon signal rhythm.
  • During some beacon signal transmissions, the radio may refrain from transmitting in block 310 and receive a beacon signal from another radio in block 302. In such a case, the radio's beacon signal rhythm may be readjusted to synchronize. Such an action may be a fine tuning of the rhythms as they may drift over time with respect to each other.
  • The embodiment 300 illustrates how a radio may monitor a second radio's beacon signal and synchronize thereto. The radio may periodically fine tune the beacon signal rhythm at various intervals to account for any shift or drift in a recurring beacon signal.
  • When the radio receives a beacon signal, it may determine if the incoming beacon signal has a higher priority in block 304. The priority may be determined by any imaginable means. In some embodiments, the beacon signal received may include an identifier of the transmitting radio. The identifier may be a hardware address such as an IP address, MAC address, radio transmitter identifier, or any other similar unique identifier. In other situations, the identifier may be a network node ID or other identifier.
  • In some configurations, the identifier used to determine priority may be a predetermined identifier that is determined when a network is arranged and deployed. For example, in a network configuration such as in FIG. 1, the various radio transmitters may be given identifiers that have some relationship to the distance of the radio transmitter to the controller.
  • In other configurations, the identifier used to determine priority may be a unique identifier but may be otherwise randomly assigned. For example, a MAC address, IP address, or other hardware address of a device may be unique to the device and may serve as a priority number.
  • In still other configurations, an identifier may be a value generated by the transmitting radio. The value may be static or may change from time to time. For example, an identifier may be some measure of performance such as an average signal to noise ratio for incoming signals to a radio, the data throughput of the radio, or the number of average transmissions over a period of time. In another example, the identifier may be a randomly generated identifier that may be used for encryption purposes in addition to determining priority.
  • The identifier may be a number, text string, binary sequence, or any other transmission that may be transmitted for another purpose but also used for determining priority. For example, if a beacon signal contains a unique radio identifier, the identifier may be used for prioritization purposes.
  • When a prioritization method is used, the beacon signal rhythm may propagate across a network until all of the radios are transmitting a beacon signal substantially simultaneously. As new radios are added to the network, the new radios may adapt to the existing signal beacon rhythm or the nearby radios may adapt to the new radio, and each radio across the network may adjust the beacon signal rhythm to be synchronized with the new radio.
  • If a radio is removed from a synchronized network, there may be no changes to the synchronized beacon signal rhythm.
  • In many cases, the priority determination may be arbitrary. One radio's beacon signal rhythm may not be any better than that of a second radio. In such a case, the priority determination may serve as an arbitrary tie breaker when choosing one radio's beacon signal over another. In other cases, the priority determination may be selected so that a specific, coordinated beacon signal rhythm is distributed over the network.
  • FIG. 4 is a flowchart illustration of an embodiment 400 of a method for analyzing beacon signals received while in synchronized mode. A beacon signal is transmitted in block 402. The loop of block 404 may wait for the next pulse of the beacon signal rhythm to occur. At the end of the beacon signal rhythm of block 404, the radio may decide to transmit, wherein it returns to block 402, or to receive a beacon signal from a neighbor radio in block 408. After receiving the beacon signal in block 408, it may compare the beacon signal received to previous beacon signals in block 410. If the beacon rhythm needs to be adjusted in block 412, it is done so in block 414. If the previous neighbor beacon signal is missing or some other problem is detected in block 416, a technician may be altered in block 418. Otherwise, the process returns to block 404.
  • Embodiment 400 illustrates a method by which a radio may automatically synchronize its beacon signal rhythm as well as perform some auxiliary functions and network monitoring. A radio may periodically refrain from transmitting a beacon signal on the beacon signal rhythm and instead receive one or more beacon signals from other radios in its vicinity. An incoming beacon signal may be used to re-synchronize the beacon signal rhythm and may also be used to update a list of neighboring radios. If a problem is detected from neighboring beacon signals, or lack thereof, an alert condition may be issued.
  • Many radios are not able to simultaneously transmit and receive messages. Thus, during a normal time for a beacon transmission, a radio may instead receive beacon messages from other radios. By doing this on a periodic basis, the beacon signal rhythm may be updated and re-synchronized. Also, some diagnostic procedures may be used to determine some performance parameters of the network.
  • The listen or transmit decision of block 406 may be made on a fixed periodic basis or on a randomized basis. In some instances, the beacon signal may be transmitted every 99 out of 100 times, 9 out of 10 times, 2 out of 3 times, or any other predetermined frequency.
  • A randomized listen interval may be useful for instances where several radios are in the same vicinity and there may concern that two or more radios may be on the same sequence of receiving during beacon rhythms and thus not receiving a beacon signal from each other. When a randomized sequence of transmitting and receiving beacon signals is used, there is a possibility that two radios may both be receiving at the same time and thus may determine that the other radio is not properly functioning. Such a situation may be avoided by determining that an error condition exists only after two or more repeated events when a beacon signal was not detected.
  • Error conditions and diagnostic data may be detected by evaluating the history of beacon signals sent from another radio. In some cases, signal to noise ratio, power levels, bit error rate, or other data may be measured from the incoming beacon signal. In other cases, the beacon signal may include performance data such as available bandwidth, number of ongoing communication sessions, and other statistics relating to the workload of that radio.
  • The history of beacon signals may include one or more parameters from one or more previous beacon signals. The parameters may include any type of statistic, including numerical data, textual data, Boolean data, or any other type of data, including combinations of data types.
  • Various errors or diagnostic determinations may be made by analyzing the historical data from previous beacon signals. For example, if a beacon signal has not been detected for one or more cycles of listening for the beacon signal, it may be determined that the neighboring radio is out of service or has malfunctioned. Similarly, if the signal to noise ratio has changed at an amount more than expected, a malfunction or other problem may be assumed.
  • When an error or problem occurs, especially when the error is a potential outage, the radio that detects the problem may send a message to an administrator or technician. In some cases, performance statistics of the various radios may be transmitted to a central controller or database for ongoing performance monitoring of the network.
  • FIG. 5 is a timeline representation of an embodiment 500 showing gross synchronization and propagation of synchronized beacons through a series of radios. Each timeline 502, 504, 506, and 508 represent the actions of four separate radios. Before time 510, each radio is broadcasting a beacon signal at different intervals from the other radios. At time 510, radio 508 listens and synchronizes to radio 506. At the next beacon signal of radio 506, both radios 506 and 508 transmit a beacon signal simultaneously. At time 514, radio 506 listens and synchronizes to radio 504. At time 516, both radios 504 and 506 are synchronized, but radio 508 listens and synchronizes to radio 506. At time 518, all three radios 504, 506, and 508 are synchronized. At time 520, radio 504 listens and synchronizes to radio 502. At time 522, radio 506 listens and synchronizes to radio 504.
  • The embodiment 500 illustrates how the synchronization of beacon signals may propagate through a series of radios. In many instances, each radio may not be in communication with every other radio, but each radio may have overlapping coverage areas with at least one or two other radios. In such instances, the synchronization of beacon signals may take several cycles and some time to propagate throughout the system.
  • The embodiment 500 assumes that the radios are arranged in order of priority with radio 502 being the highest priority and radios 504, 506, and 508 being lower priority.
  • In some embodiments, one or more cycles of beacon signals may occur before a beacon signal is synchronized. Such an embodiment may be useful when mobile and fixed radios are used in a network. When fixed and mobile radios are present, the beacon signal rhythm may be determined by one of the fixed radios rather than one of the mobile radios, otherwise the beacon signal rhythm might be adjusted when various mobile radios enter and leave the network. In cases where the beacon signal rhythm is quickly adjusted, such a requirement may not be necessary.
  • FIG. 6 is a timeline illustration of embodiment 600 of a sequence for refining the beacon signal rhythm due to small drifts in the rhythm by one or more radios. Each timeline 602, 604, 606, and 608 represents the actions of a separate radio. At time 610, radio 604 begins its beacon signal. Shortly thereafter at time 612, radios 602 and 608 begin their beacon signal, and shortly thereafter again at time 614, radio 606 begins its beacon signal. At time 616, radio 604 begins a period of listening and synchronizing to a neighbor radio. At time 618, radio 604 has successfully synchronized to radios 602 and 608. Similarly at time 620, radio 606 begins a period of listening and synchronizing to a neighbor radio, and is fully synchronized at time 622 with the remaining radios.
  • Embodiment 600 illustrates one sequence where several radios may have drifted out of synchronization with each other but are able to resynchronize by periodically listening to a neighbor radio's beacon signal. Using such a method, many radios in a large network may be able to keep synchronized periodically and automatically.
  • FIG. 7 illustrates an embodiment 700 of a sequence for entering into a synchronization mode by two radios, radio 702 and radio 704. In block 706, radio 702 transmits a normal beacon signal. Similarly, radio 704 transmits a normal beacon signal in block 708. Again radio 702 transmits a beacon signal in block 710. After receiving several beacon signals from radio 702, radio 704 requests beacon signal synchronization from radio 702. In blocks 714 and 716, both radios negotiate the priority for the beacon signal. After determining which radio's beacon signal rhythm will prevail, both radios enter a synchronization beacon mode in blocks 718 and 720. In blocks 722 and 724, both radios simultaneously transmit a beacon signal and again in blocks 726 and 728.
  • Embodiment 700 illustrates a sequence where two radios each have a normal mode of operation and a synchronized mode. Synchronization mode may be similar to normal mode except that during synchronization mode each radio may transmit a beacon signal regardless if another radio is transmitting.
  • Embodiment 700 also illustrates how one radio may begin the process of synchronization after receiving several beacon signals from a neighbor radio. Once a threshold of repeated beacon signals is reached, be it two cycles of beacon signals, 200, or any other value, one of the radios may send a request to the other radio to begin the synchronization process. The communication between radios may be through the radio channels or through another channel such as a network backbone. In some cases, the communications between the radios may be through a combination of channels. For example, the synchronization request may be made through a radio channel with the priority negotiation through a separate channel.
  • FIG. 8 illustrates a plan view of an embodiment 800 showing wireless access points deployed in a residential area. A road 802 is shown with several houses 804. Wireless access points 806, 808, and 810 are shown with their respective coverage areas 812, 814, and 816 that blanket the residential complex. The network backbone 818 runs along the main road 802 and has a junction 820 that connects the wireless access points 806, 808, and 810 along the branch line.
  • Embodiment 800 is an application for wireless connectivity in a residential area. The wireless access points 806, 808, and 810 may provide various communications to and from the homes 804, such as internet data connections, voice telephony, video services, and any other communication. In many applications, the wireless access points may use a standardized radio communications protocol, such as those defined by IEEE 802.11 specification. In other applications, different radio communications protocols, including custom or non-standard protocols, may be used.
  • The wireless access points 806, 808, and 810 may be mounted on utility poles for areas that have overhead utility lines. In areas with underground utilities, the wireless access points may be mounted on utility pedestals that are short stanchions connected to the underground cabling. The utility pedestals may also be used for making various connections with the underground cabling.
  • Each wireless access point 806, 808, and 810 may contain one or more radios. For example, directional antennas may be used to subdivide the coverage are 814 into several smaller sectors, with each sector being covered by at least one two way radio and an associated directional antenna.
  • The network backbone 818 may be a coaxial cable, fiber optic, twisted pair, or other communications cable. In some configurations, the network backbone 818 may be similar to a conventional cable television plant using DOCSIS or other communication protocols connected to a cable modem termination system (‘CMTS’). In other configurations, the network backbone 818 may be twisted pair digital subscriber line (‘DSL’) lines that are connected using a digital subscriber line area manager (‘DSLAM’). In still other configurations, the network may be an Ethernet or Ethernet-type network.
  • The wireless access points 806, 808, and 810 may be configured such that the beacon signals from all of the wireless access points are broadcast substantially simultaneously. The coordination and synchronization of the beacon signal may be performed by various methods, including the methods described in embodiments 300, 400, 500, 600, and 700 and variations of such methods.
  • The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.

Claims (31)

  1. 1. A network comprising:
    a plurality of radio terminals, each of said plurality of radios being adapted to establish at least one two-way data communication session, adapted to delay sending a transmission when another ongoing transmission is detected, and adapted to broadcast a beacon signal;
    wherein each of said plurality of radios being adapted to transmit said beacon signal substantially simultaneously by the method of identifying a second beacon signal from a second of said plurality of radios and synchronizing the transmission of said beacon signal based on said second beacon signal.
  2. 2. The network of claim 1 wherein said method further comprises:
    determining a priority for said second beacon signal; and
    comparing said priority to a predetermined value.
  3. 3. The network of claim 2 wherein said predetermined value comprises an address.
  4. 4. The network of claim 1 wherein one of said radios is further adapted to receive and not transmit during a beacon interval to receive beacon signals from one or more of said plurality of radio transmitters.
  5. 5. The network of claim 4 wherein said beacon interval is a randomly selected beacon interval.
  6. 6. The network of claim 1 wherein at least one of said radios is adapted to receive a synchronize command, said synchronization command adapted to initiate a sequence within said at least one of said radios comprising receiving rather than transmitting for one or more beacon rhythms.
  7. 7. The network of claim 1 wherein said plurality of radios are connected through a secondary communication path.
  8. 8. The network of claim 7 wherein said secondary communication path comprises at least one from a group comprising a coaxial connection, a fiber optic connection, and a twisted pair connection.
  9. 9. The network of claim 7 wherein said secondary communication path comprises at least one from a group composed of: a cable television distribution network, a digital subscriber line distribution network, an Ethernet network, and a second wireless communications path.
  10. 10. The network of claim 1 wherein at least one of said radios is adapted to operate in substantial compliance with at least a portion of IEEE 802.11.
  11. 11. A radio comprising:
    a transmitter; and
    a receiver;
    wherein said radio is adapted to establish at least one two-way data communication session, adapted to delay sending a transmission when another ongoing transmission is detected, adapted to broadcast a beacon signal, adapted to transmit said beacon signal substantially simultaneously by the method of receiving a second beacon signal from a second radio capable of two-way communications with said radio, determining a beacon rhythm from said second beacon signal, and transmitting said beacon signal using said beacon rhythm.
  12. 12. The radio of claim 11 wherein said method further comprises:
    determining a priority for said second beacon signal; and
    comparing said priority to a predetermined value.
  13. 13. The radio of claim 12 wherein said predetermined value comprises an address.
  14. 13. The radio of claim 11 wherein said beacon signal comprises an identifier specific to said each of said plurality of radios.
  15. 14. The radio of claim 11 wherein one of said radios is further adapted to receive and not transmit during a beacon interval to receive beacon signals from one or more of said plurality of radio transmitters.
  16. 15. The radio of claim 14 wherein said beacon interval is a randomly selected beacon interval.
  17. 16. The radio of claim 11 wherein at least one of said radios is adapted to receive a synchronize command, said synchronization command initiating a sequence within said at least one of said radios comprising receiving rather than transmitting for one or more beacon rhythms.
  18. 17. The radio of claim 11 wherein said plurality of radios are connected through a secondary communication path.
  19. 18. The radio of claim 17 wherein said secondary communication path comprises at least one from a group comprising a coaxial connection, a fiber optic connection, and a twisted pair connection.
  20. 19. The radio of claim 17 wherein said secondary communication path comprises at least one from a group composed of: a cable television distribution network, a digital subscriber line distribution network, an Ethernet network, and a second wireless communications path.
  21. 20. The radio of claim 11 wherein at least one of said radios is adapted to operate in substantial compliance with at least a portion of IEEE 802.11.
  22. 21. A method comprising:
    establishing at least one two-way communication session;
    delay sending a transmission when another ongoing transmission is detected;
    transmitting a beacon signal on a first beacon rhythm;
    receiving a beacon signal having a second beacon rhythm from a second radio capable of two-way communication;
    adjusting said first beacon rhythm to be substantially synchronous with said second beacon rhythm to; and
    transmitting said beacon signal substantially simultaneously with said second beacon rhythm.
  23. 22. The method of claim 21 further comprising:
    determining a priority for said second beacon signal; and
    comparing said priority to a predetermined value.
  24. 23. The method of claim 21 wherein said beacon signal comprises an identifier specific to said each of said plurality of radios.
  25. 24. The method of claim 21 further comprising receiving and not transmitting during said transmitting said beacon signal and receiving at least one beacon signal from said second radio.
  26. 25. The method of claim 24 wherein said beacon interval is a randomly selected beacon interval.
  27. 26. The method of claim 21 further comprising:
    receiving a synchronize command, said synchronization command initiating a sequence comprising: receiving rather than transmit for one or more beacon rhythms; and receiving at least one beacon signal.
  28. 27. The method of claim 21 further comprising communicating through a secondary communication path.
  29. 28. The method of claim 27 wherein said secondary communication path comprises at least one from a group comprising a coaxial connection, a fiber optic connection, and a twisted pair connection.
  30. 29. The method of claim 27 wherein said secondary communication path comprises at least one from a group composed of: a cable television distribution network, a digital subscriber line distribution network, an Ethernet network, and a second wireless communications path.
  31. 30. The method of claim 21 wherein at least a portion of said transmission is in substantial compliance with at least a portion of IEEE 802.11.
US11417732 2005-05-04 2006-05-04 Self synchronized beacon Abandoned US20060251017A1 (en)

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US20060252378A1 (en) 2006-11-09 application
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WO2006119452A1 (en) 2006-11-09 application
EP1884071A1 (en) 2008-02-06 application
CA2607154A1 (en) 2006-11-09 application
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US8315573B2 (en) 2012-11-20 grant

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