Patent Publication Number: US-2023144370-A1

Title: Leap frog techniques for transmitting back haul data in a mesh wireless local area network and related access points

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application Ser. No. 63/276,816, filed Nov. 8, 2021, the entire content of which is incorporated herein by reference herein. 
    
    
     BACKGROUND 
     The present invention generally relates to radio communications and, more particularly, to communications in mesh wireless local area networks. 
     A wireless local area network (“WLAN”) refers to a network that operates in a limited area (e.g., within a home, school, store, campus, shopping mall, etc.) that interconnects two or more electronic devices using wireless radio frequency (“RF”) communications. Electronic devices belonging to users (“clients”) of a WLAN, such as smartphones, computers, tablets, printers, appliances, televisions, lab equipment and the like (herein “client devices”), can communicate with each other and with external networks such as the Internet over the WLAN. Since wireless communications are used, portable client devices can be moved throughout the area covered by the WLAN and remain connected to the network. Most WLANs operate under a family of standards promulgated by the Institute of Electrical and Electronics Engineers (IEEE) that are referred to as the IEEE 802.11 standards. WLANs operating under the IEEE 802.11 family of standards are commonly referred to as WiFi networks. Client devices that include a networking subsystem that includes a WiFi network interface can communicate over WiFi networks. 
     A WiFi network includes one or more access points (also referred to as hotspots) that are typically installed at fixed locations throughout the area covered by the WiFi network. The WiFi network can include a single access point that provides coverage in a very limited area or may include tens, hundreds or even thousands of access points that provide in-building and/or outdoor coverage to a large campus or region. Client devices communicate with each other and/or with wired devices that are connected to the WiFi network through the access points. The access points may be connected to each other and/or to one or more controllers through wired and/or wireless connections. The Win network typically includes one or more gateways that may be used to provide Internet access to the client devices and/or access to other external networks. 
     Many WiFi networks are implemented in whole or part as so-called mesh networks. A mesh network has one or more root nodes as well as a plurality of additional nodes, which are typically implemented as access points. The root node(s) provide wired backhaul to external networks. A root node may, for example, comprise an access point that is connected to one or more gateways via wired connections or may comprise another electronic device such as a router. In a mesh WiFi network, at least some of the access points (herein “mesh access points”) do not include a wired connection to a root node, but instead communicate with one or more root nodes via wireless connections through other access points. Thus, a “source” mesh access point will transmit uplink mesh backhaul communications to a root node through one or more intervening access points, and the root node will transmit downlink mesh backhaul communications through one or more intervening access points to each “destination” mesh access point. In many cases, a mesh access point will be capable of communicating with multiple other mesh access points, and hence multiple communications paths may exist between each mesh access point and a given root node. 
     Mesh WiFi networks typically self-configure to automatically select the communications path(s) used for each uplink and downlink wireless backhaul communication. For the non-root access points of a mesh network, backhaul refers to communications between a non-root access point and a root node that are associated with communications between the non-root access point and client devices that are associated with the non-root access point. The backhaul from the non-root access points constitute wireless communications. The backhaul communications may flow in both the upstream direction (i.e., from the non-root access point to the root node) and in the downstream direction (i.e., from the root node to the non-root access point). Each backhaul communication may travel through one or more “hops,” where each hop comprises a wireless communication link between two nodes on the communication path between the root node and the source/destination access point. A first access point along such a communication path is “downstream” of a second access point if the first access point is in between the second access point and the source/destination access point. Conversely, a first access point along such a communication path is “upstream” of a second access point if the second access point is in between the first access point and the source/destination access point. Mesh networks may cost effectively extend the wireless coverage of a WiFi network. 
     Early WiFi standards supported communication in the 2.401-2.484 GHz frequency range (herein “the 2.4 GHz frequency band”). Later WiFi standards supported communication in the 5.170-5.835 GHz frequency range (herein “the 5 GHz frequency band”) Most modern access points support communications in both the 2.4 GHz and 5 GHz frequency bands, and have a radio for each frequency band. Recently, the United States Federal Communications Commission voted to open spectrum in the 5.935-7.125 GHz frequency range, which is referred to herein as “the 6 GHz frequency band,” for use in WiFi applications, and many other countries are likewise in the process of allowing WiFi networks to operate in the 6 GHz frequency band. 
     SUMMARY 
     Embodiments of the present invention provide methods of transmitting mesh backhaul data in a WiFi network. Pursuant to these methods, the mesh backhaul data is transmitted between a root node and a first intervening mesh access point via a wireless communication in a first frequency band. The mesh backhaul data is then transmitted between the first intervening mesh access point and a second mesh access point via a wireless communication in a second frequency band. 
     In some embodiments, the mesh backhaul data is downlink mesh backhaul data, and the second mesh access point is a destination for the downlink mesh backhaul data. In other embodiments, the mesh backhaul data is downlink mesh backhaul data and the second mesh access point is a second intervening mesh access point. In such embodiments, the method may further comprise transmitting the downlink mesh backhaul data between the second intervening mesh access point and a third mesh access point via a wireless communication in the first frequency band. 
     In some embodiments, the mesh backhaul data is uplink mesh backhaul data, and the second mesh access point is a source of the uplink mesh backhaul data. In other embodiments, the mesh backhaul data is uplink mesh backhaul data and the second mesh access point is a second intervening mesh access point. In such embodiments, the method may further comprise transmitting the uplink mesh backhaul data between the second intervening mesh access point and a third mesh access point via a wireless communication in the first frequency band, wherein the uplink mesh backhaul data is first transmitted from the third mesh access point to the second intervening mesh access point, and then is transmitted from the second intervening mesh access point to the first intervening mesh access point, and then is transmitted from the first intervening mesh access point to the root node. 
     In some embodiments, a second portion of the mesh backhaul data is transmitted between the first mesh intervening access point and the second mesh access point at the same time that a first portion of the mesh backhaul data is transmitted between the root node and the first intervening mesh access point. 
     In some embodiments, the first frequency band is one of a 5.170-5.835 GHz frequency band and a 5.935-7.125 GHz frequency band, and the second frequency band is the other of the 5.170-5.835 GHz frequency band and the 5.935-7.125 GHz frequency band. 
     In some embodiments, the first frequency band is one of a 5.170-5.330 GHz frequency band and a 5.490-5.835 GHz frequency band, and the second frequency band is the other of the 5.170-5.330 GHz frequency band and the 5.490-5.835 GHz frequency band. 
     In some embodiments, the first intervening mesh access point selects the first frequency band for exchanging mesh backhaul data with the root node, and advertises the selection of the first frequency band in a beacon. 
     In some embodiments, the second mesh access point selects the second frequency band for exchanging mesh backhaul data with the first intervening mesh access point based on the advertisement of the selection of the first frequency band in the beacon. 
     According to further embodiments of the present invention, methods of operating an access point are provided. Pursuant to these methods, a first wireless local area network is enabled for mesh downlink traffic, where the first wireless local area network supports wireless communication in a first frequency band. A second wireless local area network is enabled for mesh downlink traffic, where the second wireless local area network supports wireless communication in a second frequency band that is different from the first frequency band. Downlink mesh backhaul data is received over the first wireless local area network. The downlink mesh backhaul data is transmitted over the second wireless area network. 
     In some embodiments, a first portion of the downlink mesh backhaul data is transmitted over the second wireless local area network at the same time that a second portion of the downlink mesh backhaul data is received over first wireless local area network. 
     In some embodiments, the first frequency band is one of a 5.170-5.835 GHz frequency band and a 5.935-7.125 GHz frequency band, and the second frequency band is the other of the 5.170-5.835 GHz frequency band and the 5.935-7.125 GHz frequency band. In other embodiments, the first frequency band is one of a 5.170-5.330 GHz frequency band and a 5.490-5.835 GHz frequency band, and the second frequency band is the other of the 5.170-5.330 GHz frequency band and the 5.490-5.835 GHz frequency band. 
     In some embodiments, the method may further include selecting one of the first frequency band and the second frequency band for uplink mesh backhaul data communication. 
     In some embodiments, the method may further include enabling a third wireless local area network for mesh downlink traffic, where the third wireless local area network supports wireless communication in the first frequency band. 
     According to further embodiments of the present invention, access points are provided. These access points include at least one antenna and an interface circuit that is coupled to the at least one antenna and configured to enable a first wireless local area network in a first frequency band for mesh backhaul data, enable a second wireless local area network in a second frequency band for mesh backhaul data, receive mesh backhaul data on the first wireless local area network, and transmit the mesh backhaul data on the second wireless local area network. 
     In some embodiments, the interface circuit is further configured so that the access point can receive mesh backhaul data on the first wireless local area network while simultaneously transmitting the mesh backhaul data on the second wireless local area network. 
     In some embodiments, the first wireless local area network supports uplink communications and the second wireless local area network supports downlink communications. 
     In some embodiments, the first frequency band is one of a 5.170-5.835 GHz frequency band and a 5.935-7.125 GHz frequency band, and the second frequency band is the other of the 5.170-5.835 GHz frequency band and the 5.935-7.125 GHz frequency band. In other embodiments, the first frequency band is one of a 5.170-5.330 GHz frequency band and a 5.490-5.835 GHz frequency band, and the second frequency band is the other of the 5.170-5.330 GHz frequency band and the 5.490-5.835 GHz frequency band. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram illustrating an example of a simplified WiFi network in which the communication techniques according to embodiments of the present invention may be practiced. 
         FIG.  2 A  is a schematic block diagram of a mesh WiFi network. 
         FIG.  2 B  is a schematic block diagram of another mesh WW 1  network. 
         FIG.  3    is a schematic diagram illustrating a mesh backhaul communication path in a conventional mesh WiFi network. 
         FIG.  4    is a schematic diagram illustrating a communications technique according to embodiments of the present invention. 
         FIG.  5    is a schematic diagram illustrating a communications technique according to further embodiments of the present invention 
         FIG.  6    is a block diagram of a mesh access point according to embodiments of the present invention. 
         FIG.  7    is a flow chart illustrating a method of transmitting mesh backhaul data in a WiFi network according to embodiments of the present invention. 
         FIG.  8    is a flow chart illustrating a method of operating an access point according to embodiments of the present invention. 
         FIG.  9    is a schematic representation of a portion of a mesh WiFi network that illustrates a communications technique according to embodiments of the present invention. 
         FIG.  10    is a block diagram of an access point according to embodiments of the present invention. 
     
    
    
     Like reference numerals refer to corresponding parts throughout the drawings. Moreover, multiple instances of the same part may be designated by a common prefix separated from an instance number by a dash. 
     DETAILED DESCRIPTION 
     As discussed above, WiFi networks are now authorized to operate in the 5.935-7.125 GHz frequency range, which is referred to herein as “the 6 GHz frequency band.” With the opening of the 6 GHz frequency band for WiFi communications, so-called “tri-band” WiFi access points are being developed that will include a first radio that operates in the 2.401-2.484 GHz frequency range (herein “the 2.4 GHz frequency band”), a second radio that operates in the 5.170-5.835 GHz frequency range (herein “the 5 GHz frequency band”) and a third radio that operates in the 6 GHz frequency band. 
     In conventional WiFi networks, mesh backhaul communications are supported in a single frequency band, which is usually the 5 GHz frequency band. One disadvantage of this approach is that the radio supporting mesh backhaul communications in an intervening mesh access point cannot simultaneously receive and transmit mesh backhaul communications. Thus, for example, an intervening mesh access point that is receiving a downlink communication (i.e., a communication flowing in the direction from the root node toward a client device) cannot forward that downlink communication to another downstream mesh access point (either another intervening mesh access point or the destination access point) at the same time. The inability to both receive 5 GHz communications from the root node while simultaneously transmitting 5 GHz communications to the next downstream access point can reduce backhaul throughput by as much as 50%. 
     Pursuant to embodiments of the present invention, WiFi networks are provided in which mesh backhaul communications are supported in at least two different frequency bands. This allows an intervening mesh access point to receive mesh backhaul communications using a first frequency band radio and to simultaneously transmit the received mesh backhaul communications using a second frequency band radio. In other words, the intervening access point does not need to buffer received mesh backhaul communications until the full mesh backhaul communication is received prior to transmitting the received mesh backhaul communication to the next node along the communication path to the destination access point. This may increase throughput by up to nearly a factor of two over conventional approaches. 
     In some embodiments, each access point along the communication path between the root node and the source/destination access point may be configured to automatically select which frequency band to use for the mesh backhaul communications based on which frequency band will provide the highest throughput. In such embodiments, adjacent nodes on the mesh backhaul communications path will almost always alternate between the two frequency bands for two reasons. First, as discussed above, if a node receives mesh backhaul communications over a first frequency band link, it will almost always be advantageous to forward those backhaul communications over a second frequency band link, as that allows the forwarding transmissions to start as soon as the access point processes the received communication, since the second and frequency band radio can transmit signals while the first frequency band radio is still receiving signals. Second, the mesh backhaul communications received in the first frequency band at the intervening access point will typically appear as interference to any mesh backhaul communications that are transmitted by the intervening access point in the first frequency band, due to the fact that there is overlap between many of the channels in each WiFi frequency band. No such overlap exists between channels in different WiFi frequency bands, and hence having adjacent hops on the communication path use different frequency bands will typically maximize throughput. In light of this, in some embodiments the root node (for downlink communications) may select between the first and second frequency bands based on some criteria (e.g., throughput) and then subsequent links in the communication path may simply alternate between frequency bands. 
     In some embodiments of the present invention, methods of transmitting mesh backhaul data in a WiFi network are provided. Pursuant to these methods, the mesh backhaul data is transmitted between a root node and a first intervening mesh access point via a wireless communication in a first frequency band. The mesh backhaul data is then transmitted between the first intervening mesh access point and a second mesh access point via a wireless communication in a second frequency band. 
     In other embodiments, methods of operating an access point are provided. Pursuant to these methods, a first wireless local area network is enabled for mesh downlink traffic, where the first wireless local area network supports wireless communication in a first frequency band. A second wireless local area network is enabled for mesh downlink traffic, where the second wireless local area network supports wireless communication in a second frequency band that is different from the first frequency band. Downlink mesh backhaul data is received over the first wireless local area network. The downlink mesh backhaul data is transmitted over the second wireless area network. 
     In still other embodiments, access points are provided. These access points include at least one antenna and an interface circuit that is coupled to the at least one antenna and configured to enable a first wireless local area network in a first frequency band for mesh backhaul data, enable a second wireless local area network in a second frequency band for mesh backhaul data, receive mesh backhaul data on the first wireless local area network, and transmit the mesh backhaul data on the second wireless local area network. 
     Embodiments of the present invention will now be described in further detail with reference to the figures. 
       FIG.  1    is a block diagram illustrating a simplified WiFi network  100  in which the communications techniques according to embodiments of the present invention may be used. As shown in  FIG.  1   , the WiFi network  100  may include one or more access points  110 , one or more client devices  120  (such as cellular telephones, computers, tablets, printers and a wide range of other WiFi-capable electronic devices), and one or more optional controllers  130 . The access points  110  may communicate with one or more of the client devices  120  using wireless communication that is compatible with an IEEE 802.11 standard. At least some of the access points  110  may be tri-band access points that include three access point radios. The access point radios may include first access point radios  112  that operate in the 2.4 GHz frequency band, second access point radios  114  that operate in the 5 GHz frequency band, and third access point radios  116  that operate in the 6 GHz frequency band. The client devices  120  may also include one or more client radios  122 ,  124 ,  126 . The client radios may include first client radios  122  that operate in the 2.4 GHz frequency band, second client radios  124  that operate in the 5 GHz frequency band, and third client radios  126  that operate in the 6 GHz frequency band. Some client devices  120  may only include fewer than all of the first, second and third client radios  122 ,  124 ,  126 , as shown in  FIG.  1    (i.e., client device  120 - 2  only includes a 2.4 GHz client radio  122 - 2  and a 5 GHz client radio  124 - 2 ). 
     The access points  110  may also communicate with the one or more optional controllers  130  via a network  140 , which may comprise, for example, the Internet, an intra-net and/or one or more dedicated communication links. It will also be appreciated that some access points  110  may only be connected to the network  140  through other access points  110  (e.g., in a mesh network implementation), as will be discussed in greater detail below. 
     Note that the optional controllers  130  may be at the same location as the other components in WiFi network  100  or may be located remotely (e.g., cloud based controllers  130 ). The access points  110  may be managed and/or configured by the controllers  130 . The access points  110  may communicate with the controller(s)  130  or other services using wireless communications and/or using a wired communication protocol, such as a wired communication protocol that is compatible with an IEEE 802.3 standard (which is sometimes referred to as “Ethernet”), e.g., an Ethernet II standard. The access points  110  may provide the client devices  120  access to the network  140 . The access points  110  may be physical access points or may be virtual access points that are implemented on a computer or other electronic device. While not shown in  FIG.  1   , the WiFi network  100  may include additional components or electronic devices, such as, for example, a router. 
     The access points  110  and the client devices  120  may communicate with each other via wireless communication. The access points  110  and the client devices  120  may wirelessly communicate by: transmitting advertising frames on wireless channels, detecting one another by scanning wireless channels, exchanging subsequent data/management frames (such as association requests and responses) to establish a connection and configure security options (e.g., Internet Protocol Security), transmit and receive frames or packets via the connection, etc. 
     As described further below with reference to  FIG.  10   , the access points  110 , client devices  120  and/or the controllers  130  may include subsystems, such as a networking subsystem, a memory subsystem and a processor subsystem. The networking subsystems of the access points  110  may include the above-described access point radios  112 ,  114 ,  116 , and the networking subsystems of the client device  120  may include the above-described client radios  122 ,  124 ,  126 . 
     As can be seen in  FIG.  1   , wireless signals  128  (represented by a jagged line) are transmitted from one of the radios  122 - 1 ,  124 - 1 ,  126 - 1  in client device  120 - 1 . These wireless signals  128  are received by the corresponding radio  112 - 1 ,  114 - 1 ,  116 - 1  in at least one of the access points  110 , such as access point  110 - 1 . The wireless signals  128  may comprise frames or packets that are received by access point  110 - 1 . It will be appreciated that wireless signals  128  may flow in both directions, namely from a client device  120  to an access point  110 , and from an access point  110  to a client device  120 . 
     As discussed above, some WiFi networks are implemented in whole or part as so-called mesh networks.  FIG.  2 A  is a schematic block diagram of such a mesh WiFi network  200 . The Wifi network includes at least one root node  202 . In the example of  FIG.  2 A , three root nodes  202 - 1  through  202 - 3  are shown. Each root node  202 . may comprise, for example, an access point or another electronic device such as a router. Each root node  202  may be coupled to one or more external networks via a wired connection to provide wired backhaul to such networks (the external network is not shown in  FIG.  2 A , but is shown as external network  140  in  FIG.  1   ). The mesh WiFi network  200  further includes a plurality of access points  210 , which may also be referred to herein as “nodes.” A total of twelve access points  210 - 1  through  10 - 12  are shown in the example of  FIG.  2 A . Each access point  210  is capable of communicating; with at least one other access point  210  and/or with a root node  202 . Each access point  210  may communicate with one or more client devices  120  (see  FIG.  1   ) in the manner described above with reference to  FIG.  1   . Five example client devices  220 - 1  through  220 - 5  are depicted in  FIG.  2 A . 
     In some cases, all of the access points  210  in mesh WiFi network  200  are only connected to other access points  210  via respective wireless connections. Herein, an access point that is only connected to other access points  210  and root nodes  202  via wireless connections is referred to as a “mesh access point.” In other embodiments, some of the access points  210  may be connected to other access points  210  via wired connections, while other of the connections between access points  210  may be wireless connections. In the example of  FIG.  2 A , the access points  210  are only connected to each other and to the root nodes  202  via wireless connections. 
     Each access point  210  may communicate with one or more of the client devices  220  using wireless communication that are compatible with an IEEE 802.11 standard. For example, a client device (e.g., client device  220 - 5 ) may associate with a particular access point (e.g., access point  210 - 8 ). The client device  220 - 5  may communicate with other client devices  220  and/or with external networks  140  via the access point  210 - 8 . 
     As shown in  FIG.  2 A , each access point  210  is only connected to a subset of the other access points  210  and root nodes  202 . This is typical in mesh WiFi networks, as each access point only has a limited transmission range, and hence can typically only communicate with a few other access points  210  and/or root nodes  202  that are in close proximity. 
     The mesh WiFi network  200  may operate as follows. A client device such as client device  220 - 5  may associate with one of the access points  210  (here access point  210 - 8 ). The client device  220 - 5  may then communicate with one or more external networks (e.g., the Internet, a cellular telephone network, etc.) and/or other client devices  220  via access point  220 - 8 . Access point  210 - 8  receives communications from client device  220 - 5  and forwards these communications to a root node  202 . In the discussion that follows, it will be assumed that the mesh network routing algorithms connect access point  210 - 8  to root node  202 - 3  for mesh backhaul traffic. Root node  202 - 3  may, for example, route these communications to the one or more external networks  140 , and may receive responsive communications from the external networks  140  that are forwarded back to access point  210 - 8  and then provided to client device  220 - 5 . 
     The data that is sent from access point  210 - 8  to root node  202 - 3  in response to receiving communications from client device  210 - 5 , as well as the data forwarded from the root node  202 - 3  to access point  210 - 8  for provision to client device  220 - 5 , is referred to as backhaul data. As can be seen in  FIG.  2 A , many different potential communication paths exist over which the backhaul data may be passed between access point  210 - 8  and root node  202 - 3 . For example, access point  210 - 8  could forward mesh backhaul data to access point  210 - 9 , and access point  210 - 9  could then forward this mesh backhaul data to root node  202 - 3 . Alternatively, access point  210 - 8  could forward mesh backhaul data to access point  210 - 7 , and access point  210 - 7  could then forward this mesh backhaul data to root node  202 - 3 . While the above two communication paths appear to be the most direct communication paths between access point  210 - 8  and root node  202 - 3 , other communication paths exist. For example, access point  210 - 8  could forward mesh backhaul data to access point  210 - 7 , and access point  210 - 7  could then forward this mesh backhaul data to access point  210 - 5 , and access point  210 - 5  could then forward the backhaul data to root node  202 - 3 . Many other communication paths exist. Herein, a mesh access point  210  that forwards mesh backhaul data received from an associated client device  220  to a root node  202  is referred to as a “source” mesh access point  210 . A mesh access point  210  that receives mesh backhaul data that is addressed to a client device  220  that is associated with the mesh access point  210  is referred to as a “destination” mesh access point  210 . A mesh access point  210  that is along a communication path between a root node  202  and a source mesh access point  210  or a destination mesh access point  210  is referred to as an “intervening” mesh access point  210 . 
     A wireless communication link between an access point and another access point or a root node may be referred to herein as a “hop.” Since access point  210 - 8  is not directly connected to root node  202 - 3  via a wireless communication link (see  FIG.  2 A ), the mesh backhaul data passing between access point  210 - 8  and root node  202 - 3  will necessarily be transmitted over at least a two-hop communication path. Mesh WiFi networks are typically designed to self-configure so that the mesh WiFi network automatically selects the communications path(s) used for each wireless backhaul communication. Thus, for example, access point  210 - 8  may self-determine whether to forward mesh backhaul communications to access point  210 - 7  or  210 - 9  based on, for example, estimates of mesh backhaul capability of access points  210 - 7  and  210 - 9  that are provided to access point  210 - 8 . Upon receiving mesh backhaul data from access point  210 - 8 , access point  210 - 7  (or  210 - 9 ) will then determine the best path for forwarding this mesh backhaul data to root node  202 - 3 . The best path may or may not be the direct path between access point  210 - 7  (or  210 - 9 ) and root node  202 - 3  depending upon the throughput capabilities of the various different single hop and multi-hop communications links that connect access point  210 - 7  (or  210 - 9 ) to root node  202 - 3 . 
     As described above, most existing WiFi networks support WiFi communications in two frequency bands, namely the 2.4 GHz frequency band and the 5 GHz frequency band. In conventional mesh WiFi networks, backhaul data is transmitted solely in either the 2.4 GHz frequency band or the 5 GHz frequency band. Typically, the default is to transmit mesh backhaul communications in the 5 GHz frequency band, given that the 5 GHz frequency band typically supports higher throughputs and often is subject to less congestion. However, mesh WiFi networks may, for example, be manually configured to transmit backhaul communications in the 2.4 GHz frequency band. Typically, when such manual configuration is performed, all of the access points in a given zone will be configured to transmit backhaul communications in the 2.4 GHz frequency band. 
     It will be appreciated that  FIG.  2 A  illustrates a mesh WiFi network that has a star topology in which many of the non-root access points  210  have multiple upstream paths to a root node  202 . In many cases, mesh networks may instead be implemented to have a tree topology in which non-root access points  210  may each only have one upstream path to a root node  202 . The use of the tree topology may advantageously avoid loops. A mesh network  200 ′ having such a tree topology is illustrated in  FIG.  2 B . The communication techniques according to embodiments of the present invention that are described herein may be performed on either mesh network topology. 
       FIG.  3    is a schematic diagram illustrating a mesh backhaul communication path in the conventional mesh WiFi network  200  of  FIG.  2 A . As shown in  FIG.  3   , client device  220 - 1  is associated with access point  210 - 1 . Access point  210 - 1  may transmit first backhaul data associated with client device  220 - 1  to an intervening access point  210 - 2  over a first wireless communication link  230 - 1 . The first wireless communications link  230 - 1  may be established in a channel in the 5 GHz frequency band. Intervening access point  210 - 2  may transmit the first backhaul data received from access point  210 - 1  to root node  202 - 1  over a second wireless communication link  230 - 2 . The second wireless communications link  230 - 2  may also be established in a channel in the 5 GHz frequency band. Root node  202 - 1  may be connected to an external network  140 . Root node  202 - 1  may transmit the first backhaul data to the external network  140  over, for example, a wired connection. 
     Root node  202 - 1  may also receive second backhaul data from the external network  140  that is addressed to client device  220 - 1 . For example, client device  220 - 1  may request a web page, and the first backhaul data may comprise this request for the web page. The second backhaul data may comprise the web page, and may be transmitted from external network  140  to root node  202 - 1  over the above-referenced wired connection. Root node  202 - 1  may forward the second backhaul data to intervening access point  210 - 2  over the second wireless communications link  230 - 2 , and intervening access point  210 - 2  may forward the second backhaul data to access point  210 - 1  over the first wireless communications link  230 - 1 . Access point  210 - 1  may then wirelessly transmit the second backhaul data to client device  220 - 1 . 
     As shown in  FIG.  3   , both the first and second communications links  230 - 1 ,  230 - 2  are established as channels in the 5 GHz frequency band. While different channels  230  in the 5 GHz frequency band may be used to establish the first and second communications links  230 - 1 ,  230 - 2 , the same radio (namely the 5 GHz radio) in intervening access point  210 - 2  will be used to receive the first backhaul data over communications link  230 - 1  and to transmit the first backhaul data over communications link  230 - 2 . Since the 5 GHz radio in intervening access point  210 - 2  cannot simultaneously receive and transmit data, the first backhaul data cannot be forwarded from intervening access point  210 - 2  to root node  202 - 1  at the same time that the first backhaul data is being received at access point  210 - 2  from access point  210 - 1 . This limitation can limit the uplink throughput for backhaul data by as much as 50%. Likewise, the second backhaul data cannot be forwarded from intervening access point  210 - 2  to access point  210 - 1  at the same time that the second backhaul data is being received at access point  210 - 2  from root node  202 - 1 . This limitation can similarly limit the downlink throughput for backhaul data by as much as 50%. 
     As discussed above, pursuant to embodiments of the present invention, communications techniques are provided for transmitting mesh backhaul data in a WiFi network.  FIG.  4    is a schematic diagram illustrating such a communications technique according to embodiments of the present invention. As shown in  FIG.  4   , the client device  220 - 1  again is associated with access point  210 - 1 . Access point  210 - 1  transmits first backhaul data associated with client device  220 - 1  to intervening access point  210 - 2  over a first wireless communication link  230 - 1  that is in a first frequency band. Access point  210 - 1  may select the first frequency band for implementing the first wireless communication link  230 - 1  based on, for example, information indicating that the first frequency band can support higher capacity communications between source access point  210 - 1  and intervening access point  210 - 2 . The intervening access point  210 - 2  may receive the first backhaul data received from access point  210 -land may simultaneously start transmitting this first backhaul data to root node  202 - 1  over the second wireless communication link  230 - 2 . The second wireless communication link  230 - 2  may be established in a channel in a second frequency band that is different from the first frequency band. For example, if the first frequency band is the 6 GHz frequency band, then the second frequency band may be the 5 GHz frequency band. Alternatively, if the first frequency band is the 5 GHz frequency band, then the second frequency band may be the 6 GHz frequency band. Root node  202 - 1  is connected to external network  140 . Root node  202 - 1  may transmit the first backhaul data to external network  140  over, for example, a wired connection 
     Root node  202 - 1  may also receive second backhaul data from external network  140  that is addressed to client device  220 - 1 . Root node  202 - 1  may forward the second backhaul data to intervening access point  210 - 2  over the second wireless communications link  230 - 2 , and intervening access point  210 - 2  may start to forward the second backhaul data received from root node  202 - 1  to access point  210 - 1  over the first wireless communications link  230 - 1 . Such simultaneous communication is possible since intervening access point  210 - 2  is receiving the second backhaul data from root node  202 - 1  using a first radio and transmitting this second backhaul data to destination access point  210 - 1  using a second radio. Access point  210 - 1  may wirelessly transmit the second backhaul data to client device  220 - 1 . 
     As shown in  FIG.  4   , intervening access point  210 - 2  receives backhaul data in a first frequency band using a first radio and retransmits the received backhaul data in a second (different) frequency band using a second radio. As such, intervening access point  210 - 2  can receive backhaul data over a first hop of a backhaul communications path while simultaneously retransmitting the received backhaul data over the next hop in the communications path since different radios are used for each hop. This may increase the throughput on the backhaul communications path. Additionally, since intervening access point  210 - 2  transmits and receives the first or second backhaul data in different frequency bands, the transmission of the backhaul data over the second hop does not cause substantial interference with the reception of the backhaul data over the first hop. 
       FIG.  5    is a schematic diagram illustrating backhaul communications over a three hop backhaul communications path using the communications technique according to embodiments of the present invention. The example of  FIG.  5    is very similar to the example of  FIG.  4   , except in  FIG.  5    the communications paths between source/destination access point  210 - 1  and root node  202 - 1  includes a second intervening access point  210 - 3  that is on the communications path between the first intervening access point  210 - 2  and the root node  202 - 1  (see  FIG.  2   ). As shown in  FIG.  5   , since intervening access point  210 - 3  receives the first backhaul data from intervening access point  210 - 2  in the 5 GHz frequency band, it forwards the first backhaul data to root node  202 - 1  over a wireless communications link in the 6 GHz frequency band. Similarly, since intervening access point  210 - 3  receives the second backhaul data from root node  202 - 1  in the 6 GHz frequency band, it forwards the second backhaul data to the first intervening access point  210 - 2  over a wireless communications link in the 5 GHz frequency band. If additional intervening access points  210  are provided, they may continue to alternate between the 5 GHz and 6 GHz frequency bands so that each adjacent hop in the communications path is transmitted in a different frequency band. 
     In the examples of  FIGS.  4  and  5   , adjacent hops for both downlink and uplink communications are transmitted in different frequency bands. It will be appreciated, however, that embodiments of the present invention are not limited thereto. For example, in other embodiments, only adjacent hops in the downlink direction may be transmitted in different frequency bands, whereas uplink hops are all transmitted in the same frequency band. In still other embodiments, only adjacent hops in the uplink direction are transmitted in different frequency bands, whereas downlink hops are all transmitted in the same frequency band. Other implementations are also possible. 
     While embodiments of the present invention have been discussed above with respect to implementing an alternating or “leap frog” technique for mesh backhaul communications using the 5 GHz and 6 GHz frequency bands, it will be appreciated that embodiments of the present invention are not limited thereto. For example, WiFi access points may be deployed that have a first radio that supports communication in the 2.4 GHz frequency band, a second radio that supports communication in the 5 GHz frequency band, and a third radio that supports communication in both the 6 GHz frequency band as well as at least a portion of the 5 GHz frequency band. Access points having such capabilities may be deployed so that they initially use one radio in the 2.4 GHz frequency band and two radios in the 5 GHz frequency band (e.g., a first radio that operates in the 5.170-5.330 GHz frequency band and a second radio that operates in the 5.490-5.835 GHz frequency band), but later can be configured to use one radio in each of 2.4 GHz, 5 GHz and 6 GHz frequency bands. This design may be beneficial for use in jurisdictions where WiFi service in the 6 GHz frequency band has not yet been authorized or in situations where few if any 6 GHz client devices are deployed. When access points having the above capabilities are deployed and configured to use one radio to support communications in the 5.170-5.330 GHz frequency band (the lower 5 GHz frequency band) and another radio to support communications in the 5.490-5.835 GHz frequency band (the upper 5 GHz frequency band), the above described communications techniques may be used where the mesh backhaul alternates between the lower and upper 5 GHz frequency bands. 
       FIG.  6    is a schematic block diagram of an access point  300  according to embodiments of the present invention. As shown in  FIG.  6   , the access point  300  includes a first frequency band radio  314  (e.g., a 5 GHz radio) and a second frequency band radio  316  (e.g., a 6 GHz radio). The first frequency band radio  314  and the second frequency band radio  316  may be part of an interface circuit of a networking subsystem of the access point (see  FIG.  10   ). As described above, when the communications techniques according to embodiments of the present invention are enabled, control logic  320  in access point  300  may be configured to automatically select the “best” (e.g., highest capacity) frequency band (e.g., either the 5 GHz frequency band or the 6 frequency band) for uplink mesh backhaul communications. If the first frequency band is selected (e.g., the 5 GHz frequency band), then the control logic will create a first WLAN  331  for supporting the uplink mesh backhaul communications. If the second frequency band is instead selected (e.g., the 6 GHz frequency band), then the control logic will create a second WLAN  332  for supporting the uplink mesh backhaul communications. In either case, the control logic  320  may also be configured to automatically create a third WLAN  333  for supporting downlink mesh backhaul communications in the first frequency band and a fourth WLAN  334  for supporting downlink mesh backhaul communications in the second frequency band. The backhaul data flow through access point  300  is shown by the dashed line. 
       FIG.  7    is a flow chart illustrating a method of transmitting mesh backhaul data in a WiFi network according to embodiments of the present invention. As shown in  FIG.  7   , operations may begin with mesh backhaul data being transmitted between a root node and a first intervening mesh access point via a wireless communication in a first frequency band (Block  400 ). The first frequency band may be, for example, one of the 5 GHz frequency band or the 6 GHz frequency band. The mesh backhaul data may then be transmitted between the first mesh access point and a second mesh access point via a wireless communication in a second frequency band (Block  410 ). The second frequency band may be, for example, the other of the 5 GHz frequency band and the 6 GHz frequency band. It should be noted that the steps of Blocks  400  and  410  may partially overlap so that a second portion of the mesh backhaul data may be is transmitted between the first mesh access point and the second mesh access point at the same time that a first portion of the mesh backhaul is transmitted between the root node and the first mesh access point. 
     In some cases, the mesh backhaul data may be downlink mesh backhaul data. In this situation, the second mesh access point may be a destination access point for the downlink mesh backhaul data, or may be a second intervening mesh access point. In other cases, the mesh backhaul data may be uplink mesh backhaul data. In this situation, the second mesh access point may be a source access point for the uplink mesh backhaul data, or may be a second intervening mesh access point. In cases where the second mesh access point is a second intervening mesh access point, then the mesh backhaul data (uplink or downlink) may further be transmitted between the second intervening mesh access point and a third mesh access point via a wireless communication in the first frequency band (Block  420 ). 
       FIG.  8    is a flow chart illustrating a method of operating an access point according to further embodiments of the present invention. Pursuant to this method, a first wireless local area network is enabled for mesh downlink traffic, where the first wireless local area network supports wireless communication in a first frequency band (Block  500 ). A second wireless local area network is enabled for mesh downlink traffic, where the second wireless local area network supports wireless communication in a second frequency band that is different from the first frequency band (Block  510 ). Downlink mesh backhaul data is received over the first wireless local area network (Block  520 ). The received downlink mesh backhaul data is transmitted over the second wireless area network (Block  530 ). A first portion of the downlink mesh backhaul data may be transmitted over the second wireless local area network at the same time that a second portion of the downlink mesh backhaul data is received over first wireless local area network. In example embodiments, the first frequency band may be one of the 5.170-5.835 GHz frequency band and a 5.935-7.125 GHz frequency band, and the second frequency band may be the other of the 5.170-5.835 GHz frequency band and the 5.935-7.125 GHz frequency band. 
       FIG.  9    is a schematic representation of a portion of a mesh WiFi network  600 . The illustrated portion of the WiFi network  600  includes a root node  602  and four access points  610 - 1  to  610 - 4 . A client device  620  is associated with access point  610 - 1 . The leap frog backhaul communications techniques according to embodiments of the present invention may be implemented in WiFi network  600  as follows. 
     First, access point  610 - 4  may select one of the 5 GHz and 6 GHz frequency bands for backhaul communications with the root access point  602 . The selected frequency band will be used for both uplink and downlink backhaul communications between access point  610 - 4  and root access point  602 . Access point  610 - 4  may selects between the 5 GHz and 6 GHz frequency bands based on an estimate as to which frequency band will support greater backhaul throughput to root access point  602 . For purposes of this example, it is assumed that the 5 GHz frequency band was selected by access point  610 - 4  for all backhaul communications with the root access point  602 . After making this selection, access point  610 - 4  may advertise the selection of the 5 GHz frequency band for upstream backhaul communications in an information element field of its beacon. Access point  610 - 4  may also enable a 5 GHz WLAN for supporting upstream backhaul communications with root access point  602 , and may enable both a 5 GHz WLAN and a 6 GHz WLAN for supporting backhaul communications with downstream access points (here access points  610 - 2 ,  610 - 3 ). 
     Access point  610 - 2  may then select one of the 5 GHz and 6 GHz frequency bands for its uplink and downlink backhaul communications with access point  610 - 4 . As described above, in some embodiments, access point  610 - 2  may select between the 5 GHz and 6 GHz frequency bands based on an estimate as to which frequency band will support greater throughput, while in other embodiments access point  610 - 2  may select the frequency band that was not selected by access point  610 - 4 . In practice, the selected frequency band will almost always be the opposite of the frequency band used by access point  610 - 4  for its backhaul communications with Root access point  602 . Thus, in this example, access point  610 - 2  selects the 6 GHz frequency band for its upstream backhaul communications. Access point  610 - 2  advertises in the information element field of its beacon that it will use the 6 GHz frequency band for its upstream backhaul communications, and also enables a 6 GHz WLAN for supporting upstream backhaul communications with the root access point  602 , and enables both a 5 GHz WLAN and a 6 GHz WLAN for supporting backhaul communications with downstream access point  610 - 1 . Access point  610 - 3  may also perform each of the same steps performed by access point  610 - 2 . 
     Access point  610 - 1  selects one of access points  610 - 2  and  610 - 3  for backhaul communications based on, for example, an estimation as to which access point  610 - 2 ,  610 - 3  is deemed to have a higher backhaul capacity to root access point  602 . Here, it is assumed that access point  610 - 3  is selected. Access point  610 - 1  then selects one of the 5 GHz and 6 GHz frequency bands for its uplink and downlink backhaul communications with access point  610 - 3  in, for example, the same manner that access point  610 - 3  makes this selection, as described above. In this example, access point  610 - 1  selects the 5 GHz frequency band for its upstream backhaul communications so that adjacent hops for the backhaul communications alternate between the 5 GHz and 6 GHz frequency bands. 
     At some point, client device  620  associates with access point  610 - 1  and transmits a request thereto (e.g., a request for a web page) that requires uplink backhaul communications. Access point  610 - 1  forwards the request for the web page to access point  610 - 3  over a first 5 GHz channel, access point  610 - 3  forwards the request for the web page to access point  610 - 4  over a first 6 GHz channel, and access point  610 - 4  forwards the request for the web page to the root access point  602  over a second 5 GHz channel. Root access point  602  requests the web page from an external network  140  and then forwards the retrieved web page to access point  610 - 4  over the second 5 GHz channel. Access point  610 - 4  then forwards the retrieved web page to access point  610 - 3  over the first 6 GHz channel, access point  610 - 3  forwards the retrieved web page to access point  610 - 1  over the first 5 GHz channel, and access point  610 - 1  forwards the retrieved web page to client device  620 . 
       FIG.  10    is a block diagram illustrating an access point  900  in accordance with some embodiments. The access point  900  includes a processing subsystem  910 , a memory subsystem  912 , and a networking subsystem  914 . Processing subsystem  910  includes one or more devices configured to perform computational operations. Memory subsystem  912  includes one or more devices for storing data and/or instructions. In some embodiments, the instructions may include an operating system and one or more program modules which may be executed by processing subsystem  910 . 
     Networking subsystem  914  includes one or more devices configured to couple to and communicate on a wired and/or wireless network (i.e., to perform network operations), including: control logic  916 , an interface circuit  918  and one or more radiating elements  920 . Thus, electronic device  900  may or may not include the one or more radiating elements  920 . Networking subsystem  914  includes at least a networking system based on the standards described in IEEE 802.11 (e.g., a Wi-Fi networking system). 
     Networking subsystem  914  includes processors, controllers, radios/radiating elements, sockets/plugs, and/or other devices used for coupling to, communicating on, and handling data and events for each supported networking system. Note that mechanisms used for coupling to, communicating on, and handling data and events on the network for each network system are sometimes collectively referred to as a “network interface” for the network system. Access point  900  may use the mechanisms in networking subsystem  914  for performing simple wireless communication, e.g., transmitting frames and/or scanning for frames transmitted by other electronic devices. 
     Processing subsystem  910 , memory subsystem  912 , and networking subsystem  914  are coupled together using bus  928 . Bus  928  may include an electrical, optical, and/or electro-optical connection that the subsystems can use to communicate commands and data among one another. 
     The operations performed in the communication techniques according to embodiments of the present invention may be implemented in hardware or software, and in a wide variety of configurations and architectures. For example, at least some of the operations in the communication techniques may be implemented using program instructions  922 , operating system  924  (such as a driver for interface circuit  918 ) or in firmware in interface circuit  918 . Alternatively or additionally, at least some of the operations in the communication techniques may be implemented in a physical layer, such as hardware in interface circuit  918 . 
     Embodiments of the present invention have been described above with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (i.e., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and/or groups thereof. 
     Aspects and elements of all of the embodiments disclosed above can be combined in any way and/or combination with aspects or elements of other embodiments to provide a plurality of additional embodiments.