Patent Publication Number: US-11659446-B2

Title: Systems and methods for providing LTE-based backhaul

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of, and claims the benefit of an earlier filing date under 35 U.S.C. § 120 based on, U.S. patent application Ser. No. 16/220,960, filed on Dec. 14, 2018, entitled “Systems and Methods for Providing LTE-Based Backhaul”, which is a continuation of, and claims the benefit of an earlier filing date under 35 U.S.C. § 120 based on, U.S. patent application Ser. No. 15/202,496, filed on Jul. 5, 2016, entitled “Systems and methods for Providing LTE-Based Backhaul”, which itself is a continuation in part of, and claims the benefit of an earlier filing date under 35 U.S.C. § 120 based on, U.S. patent application Ser. No. 14/453,365, filed on Aug. 6, 2014, entitled “Systems and Methods for Providing LTE-Based Backhaul,” which itself claims priority to the following U.S. Provisional patent applications: U.S. Provisional Patent Application No. 61/862,688, filed Aug. 6, 2013 entitled “Uplink and Downlink Role Reversal,” and U.S. Provisional Pat. App. No. 61/926,675, filed Jan. 13, 2014 and also entitled “Uplink and Downlink Role Reversal,” each of which are hereby incorporated by reference herein in their entirety for all purposes. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to wireless base stations and mesh networks. More specifically, this disclosure relates to the use of asymmetric uplink and downlink connections to and from base stations in a wireless mesh network. 
     BACKGROUND 
     Wireless networks are typically architected with multiple base stations, each with a coverage area. Within each coverage area, mobile nodes, such as mobile phones or user equipments (UEs), may attach to the base stations and may be said to be associated with the base stations to which they are attached. Communications between base stations and attached UEs may provide access capability to attached UEs, and may be asymmetric, i.e., having different downlink and uplink speeds. 
     Wireless networks may also be architected with base stations organized in a mesh network. Such mesh base stations may connect to one another wirelessly to route traffic from mesh base stations that are stationed far from a high-bandwidth core network connection to mesh base stations that are closer to such connections. The use of such routing functionality among mesh base stations may thus be used to provide backhaul, i.e., connectivity to a core network and/or the public Internet, using a backhaul connection that is shared among multiple mesh base stations. When the mesh base stations are configured to be mobile or vehicle-mounted, a complete ad-hoc wireless network may be created in a short time, without the time and expense required for a typical fixed wireless network deployment, by using mobile mesh base stations configured to route traffic to the mesh base station with the shared backhaul connection. 
     However, there is a need for more-efficient wireless protocols for communication between mesh base stations that are designed for shared backhaul connections. 
     SUMMARY 
     Systems and methods are disclosed for enabling a mesh network node to switch from a base station role to a user equipment role relative to a second mesh network node, and vice versa. By switching roles in this manner, the mesh network node may be able to benefit from increased uplink or downlink speed in the new role. This role reversal technique is particularly useful when using wireless protocols such as LTE that are asymmetric and allow differing throughput on uplink and downlink connections. Methods for determining whether to perform role reversal are disclosed, and methods for using role reversal in mesh networks comprising greater than two nodes are also disclosed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic diagram of a first network configuration depicting the use of a wireless network for backhaul, in accordance with some embodiments. 
         FIG.  2    is a schematic diagram of a second network configuration depicting the use of a wireless network for backhaul, in accordance with some embodiments, 
         FIG.  3    is a schematic diagram of a third network configuration depicting a role reversal along with the use of a wireless network for backhaul, in accordance with some embodiments. 
         FIG.  4    is a block diagram of an exemplary base station, in accordance with some embodiments. 
         FIG.  5    is a signaling diagram depicting an exemplary message flow, in accordance with some embodiments. 
         FIG.  6    is a flowchart depicting an exemplary method for operating the hardware depicted in  FIG.  5   , in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Mesh Networks 
     The present application is related to mesh networks. A mesh network is a network in which each node of the network contributes to the formation of a network by routing network traffic to the appropriate node. A mesh network may be enhanced by the use of heterogeneous network nodes that each incorporate multiple radio access technologies (RATs). Additionally, a mesh network may be enhanced by the use of network nodes that self-organize without the coordination of a master node. 
     A mesh network may be used to provide cellular voice and data capabilities by using base stations that are also mesh network nodes. Cellular data terminals and cellular phones (collectively “user equipments,” or UEs) may connect to the base stations to obtain services. The connected UEs need not be mesh network nodes. Allowing UEs to attach to, or associate with, a base station is also known as access functionality, because the base stations are capable of providing access for the attached UEs to the broader network. 
     Mesh network nodes may be connected together to provide network services to each other, such as for peer-to-peer services or voice calls among handsets within the mesh network. However, it is common for mesh network nodes to also have a connection to another network, such as the public Internet, or to a private telecom operator&#39;s network, enabling UEs connected to the mesh network nodes to establish connections with UEs on other networks. A connection to such an outside network is called a backhaul connection. 
     Mesh networks have many advantages. One advantage is resiliency; when the mesh network nodes are capable of independently performing routing, no single node is indispensable for providing network services. Another advantage is flexibility; the network may be reconfigured by adding or subtracting mesh network nodes to meet various usage scenarios. Another advantage is ease of setup, particularly for self-organizing nodes; since all nodes are involved in routing, no specific configuration of routes, links, or backhaul connections need be put into place before the establishment of a mesh network. Various topologies may be contemplated for mesh network nodes in the field, including a daisy chain (nodes are connected to two other nodes in a chain) or web topology. A mesh network wherein each of the mesh network nodes is mobile offers all of the above advantages, with the additional advantage that such a mesh network may be rapidly deployed by sending mobile mesh base stations into the field. 
     Such a mesh network may be used to provide Long Term Evolution (LTE) voice and data services, in some embodiments. When providing LTE services, the mesh network nodes may provide evolved NodeB (eNB or eNodeB) base station functionality, and the user equipments (UEs) may be LTE UEs. A mesh network providing LTE services may include several mesh network nodes, each with eNodeB functionality. When combined with the SON and mobile base station aspects described above, a LTE network may be rapidly deployed in an area without cellular coverage by positioning several vehicle-mounted mesh network nodes throughout the area as needed. 
     A backhaul connection is typically needed to provide connectivity to an Evolved Packet Core (EPC) in order to provide full LTE access functionality. The backhaul connection may be provided via a wired network connection, such as a fiber, Ethernet, or cable-based network connection. Alternately, the backhaul connection may be provided by a wireless connection, such as a line-of-sight (LOS) microwave or radio frequency (RF) connection, a Wi-Fi connection, or an LTE connection. A single backhaul connection may be shared among all mesh network nodes, in some embodiments. Some methods for sharing a backhaul connection are described below, in accordance with some embodiments. 
     The LTE Protocol 
     The LTE protocol is an air interface protocol and network stack defined by the 3 rd  Generation Partnership Project (3GPP). Different global regions and wireless operators are assigned different usable frequency bands. LTE is an Internet protocol (IP)-based architecture, and incorporates standards for user equipments (UEs) and eNodeB base stations, as well as the functionality and architecture of the core network. Typically, within the core network are the mobility management entity (MME) for managing UEs, the packet gateway (PGW) for providing IP-based access to different packet data networks, the serving gateway (SGW) for serving as a mobility anchor, the home subscriber server (HSS) for storing authentication and user-related information, and other entities. The PGW typically provides limited access to the public Internet. Further information about LTE may be found in the 3GPP standard, Release 8 and following. 
     LTE bands assigned to carriers are paired, such that each carrier uses a downlink band and a paired uplink band, each of equal bandwidth. The LTE air interface uses access control protocols, including orthogonal frequency division multiple access (OFDMA) for downlink, and single-carrier frequency division multiple access (SC-FDMA) for the uplink, to conserve power. Two duplexing schemes, frequency division duplexing (FDD) and time division duplexing (TDD), are also used in conjunction with these access control schemes. As OFDMA is a multi-carrier transmission scheme and SC-FDMA is a single-carrier transmission scheme, it follows that, given the same amount of power for a given carrier, the LTE air interface is asymmetric, i.e., it provides greater bandwidth for downlink communications relative to uplink communications. The differentiation between downlink and uplink is informed by the assumption that unlike mobile devices that are limited in processing power and radio output power, cellular base stations have orders of magnitude more processing power, in many cases more than one antenna, and the ability to broadcast at higher power, such that higher speeds on the downlink channel are possible within the downlink frequency band. Current versions of LTE may provide up to 150 Mbps downlink and 75 Mbps at peak. However, while the LTE air interface is described, other asymmetric network connections may also be used with the methods disclosed herein. 
     When a UE is activated, it may perform a sniffing procedure to search for a broadcast message from a nearby eNodeB to connect to. This broadcast message typically includes radio resource configuration information, including identification of a radio frequency used between the broadcasting eNodeB and UEs attached to the eNodeB. Once an appropriate eNodeB is identified, the UE may send an attach request message to the eNodeB, including identifying information such as an international mobile station equipment identity (IMEI). The eNodeB determines whether it is capable of accepting the attach request, and if so, it connects to the MME and SGW to authenticate the user and set up IP connectivity. The MME is responsible for accessing the user information in the HSS for authentication purposes. IP connectivity is granted to a UE by the SGW, which creates and stores UE contexts and IP bearers for the UE, and indicates to the core network that IP traffic for the UE may be sent to the particular eNodeB. Once the UE is authenticated and the bearer is set up, the eNodeB sends a confirmatory response to the attach request to the UE, resulting in a completed connection. The UE may periodically send measurement reports to the base station subsequent to connection, indicating the radio frequency strength of the base station&#39;s signal (and other base stations&#39; signals). Further information regarding UE attach behavior is available in 3GPP TS 23.401 and other 3GPP technical standards. 
     Asymmetric Connections Between Mesh Nodes 
     In the context of this disclosure, for a data terminal using a wireless modem, the uplink direction is defined to mean the direction from a data terminal to a base station, and the downlink direction to mean the direction from the base station to the data terminal. An LTE data terminal may be a user equipment (UE), and an LTE base station may be an eNodeB. This corresponds with the usage of these terms in the LTE specification, as well as with a typical usage scenario in which a user “downloads” data from the network to his or her handset, and “uploads” data such as email attachments from his or her handset to the network. In the case of a role reversal, the source and destination nodes for the “uplink” and “downlink” connections may change, but the terminology will be used as described in this paragraph. Note that in many cases, the devices described herein may be mobile and may include both a data terminal and a base station functionality. 
     While a UE and an eNodeB are typically considered to be specific hardware devices, in some embodiments of this disclosure, the functionality embodied within the UE and eNodeB may be considered to be “roles.” By inclusion of both UE and eNodeB hardware, software, and/or functionality within a single mesh network node, a given node may be enabled to use two roles at the same time, or to use either role as needed. Switching between roles may also be enabled. 
       FIG.  1    is a schematic diagram of a first network configuration depicting the use of a wireless network for backhaul, in accordance with some embodiments. In the case where the mesh network node  102  is connected to another, second mesh network node  104  via an LTE connection  110 , and the first mesh network node is also connected to a wired fiber backhaul connection  106 , such as a fiber-optic connection, it follows that the second mesh node should share the fiber-optic backhaul of the first mesh node. In the case that the second mesh node  104  has a number of UEs  108  attached to it, and that these UEs are requesting primarily downloads, the second mesh node  104  requires greater bandwidth in the downlink direction. In this case, the LTE connection  110  between the first mesh node  102  and the second mesh node  104  should be set up to prioritize data traffic from the first mesh node to the second mesh node (i.e., downloads). 
     First mesh network node  102  includes UE functionality  102   a  and eNodeB functionality  102   b . Second mesh network node  104  also includes UE functionality  104   a  and eNodeB functionality  104   b . The aforementioned download prioritization may be achieved by using the second mesh node&#39;s UE functionality  104   a  to connect to the first mesh node&#39;s eNodeB functionality  102   b , which results in a higher-bandwidth downlink channel and a lower-bandwidth uplink channel being created as shown by LTE connection  110 . Data requests from the UEs  108  are forwarded from the second mesh node  104  to the first mesh node  102  and serviced via the fiber backhaul connection  106 . The asymmetric nature of the LTE connection results in greater download capacity than upload capacity for the UEs. 
       FIG.  2    is a schematic diagram of a second network configuration depicting the use of a wireless network for backhaul, in accordance with some embodiments. In the case where a first mesh network node  202  is connected to UEs  208  and to a second mesh network node  204 , and fiber backhaul  206  is connected to the second mesh network node, the first mesh node may connect as a UE using UE functionality  202   a  to the second mesh node&#39;s eNodeB functionality  204   b  to share the second mesh node&#39;s backhaul on behalf of UEs  208 , with the LTE connection  210  being faster in the downlink direction from the second mesh node to the first mesh node. 
       FIG.  3    is a schematic diagram of a third network configuration depicting a role reversal along with the use of a wireless network for backhaul, in accordance with some embodiments. In the case where a first mesh network node  102  is connected to a second mesh network node  104 , and fiber backhaul  106  is connected to the first mesh network node, and UEs  308  are connected to the second mesh node, as in the first example, but where instead the attached UEs require greater uplink traffic than downlink traffic, the direction of the LTE connection  310  may be reversed. For example, if all the UEs  308  are simultaneously sending email attachments, it may be useful to have greater uplink bandwidth than downlink bandwidth. In this case, the first mesh node  102  may use its UE functionality  102   a  to connect to the eNodeB functionality  104   b  of the second mesh node  104  to set up an asymmetric LTE connection  310  that is faster in the uplink direction. The first mesh network&#39;s backhaul  106  is still used to connect to the outside network. In the case that LTE connection  310  is now set up in the opposite direction, this may be described as a role reversal, in accordance with some embodiments. 
     In some embodiments, more than one of these cases may occur within a brief time period. To provide prioritization for both upload and download traffic at different times, either the first or the second mesh node may be enabled to dynamically switch between the two roles based on traffic conditions at a given time. In the present disclosure, the UE functionality and the eNodeB functionality may be considered to be roles that may be simultaneously adopted by a single mesh node, and that may be subject to switching and coordination. Additionally, combinations with more than two functionalities may be supported, in some embodiments, e.g., multiple eNodeB functionalities may be provided for a single network node. 
     In further embodiments, another network configuration may be supported in which LTE relay functionality is supported by one or both of nodes  102  and  104 . Relay functionality is described in 3GPP TS 36.216, Release 10, which is hereby incorporated herein in its entirety. Either LTE relay functionality or the paired UE-eNodeB method described herein, or both, may be used to provide backhaul, in some embodiments. 
     Previous implementations separated radio resources allocated to access and backhaul, and did not allow them to be reallocated. By contrast, this method may provide increased flexibility for the mesh nodes, allowing them to be used with greater efficiency in a number of different situations, and with a variety of backhaul configurations. Reduction of resource use and tunneling cost may also be achieved throughout, which may be substantial when considered over a plurality of mesh network nodes. 
     Physical Device 
     A physical device for use with the methods described herein is disclosed in connection with  FIG.  4   . 
       FIG.  4    depicts a block diagram of an exemplary base station, in accordance with some embodiments. Mesh network base station  400  may include processor  402 , processor memory  404  in communication with the processor, baseband processor  406 , and baseband processor memory  408  in communication with the baseband processor. Base station  400  may also include first radio transceiver  410  and second radio transceiver  412 , internal universal serial bus (USB) port  414 , and wired backhaul connection  416 . A subscriber information module card (SIM card)  418  may be coupled to USB port  414 . In some embodiments, the second radio transceiver  412  itself may be coupled to USB port  414 , and communications from the baseband processor may be passed through USB port  414 . A mini-evolved packet core (EPC) module  420  may also be included for authenticating users and performing other EPC-dependent functions when no backhaul link is available at all. Other elements and/or modules may also be included, such as a home eNodeB, a local gateway (LGW), a self-organizing network (SON) module, or another module. Additional radio amplifiers, radio transceivers and/or wired network connections may also be included. Device  400  may also be identified as a converged wireless station (CWS) or unified radio access network (UniRAN), in some embodiments. 
     Processor  402  and baseband processor  406  are in communication with one another. Processor  402  may perform routing functions, and may determine if/when a switch in network configuration is needed. Baseband processor  406  may generate and receive radio signals for both radio transceivers  410  and  412 , based on instructions from processor  402 . In some embodiments, processors  402  and  406  may be on the same physical logic board. In other embodiments, they may be on separate logic boards. 
     The first radio transceiver  410  may be a radio transceiver capable of providing LTE eNodeB functionality, and may be capable of higher power and multi-channel OFDMA. The second radio transceiver  412  may be a radio transceiver capable of providing LTE UE functionality. Both transceivers  410  and  412  are capable of receiving and transmitting on one or more LTE bands. In some embodiments, either or both of transceivers  410  and  412  may be capable of providing both LTE eNodeB and LTE UE functionality. Transceiver  410  may be coupled to processor  402  via a Peripheral Component Interconnect-Express (PCI-E) bus, and/or via a daughtercard. As transceiver  412  is for providing LTE UE functionality, in effect emulating a user equipment, it may be connected via the same or different PCI-E bus, or by a USB bus, and may also be coupled to SIM card  418 . 
     SIM card  418  may provide information required for authenticating the simulated UE to the evolved packet core (EPC). When no access to an EPC is available, a mini-EPC within device  400  may be used, or a mini-EPC located within the confines of the mesh network. This information may be stored within the SIM card, and may include one or more of an international mobile equipment identity (IMEI), international mobile subscriber identity (IMSI), or other parameter needed to identify a UE. Special parameters may also be stored in the SIM card or provided by the processor during processing to identify to a target eNodeB that device  400  is not an ordinary UE but instead is a special UE for providing backhaul to device  400 . 
     In some embodiments, one or both radio transceivers may be modems on daughtercards that snap into the main device, henceforth referred to as UE modules. The UE modules may be Peripheral Component Interconnect Express Mini (PCI Express Mini) card modules, or may be M.2 form factor modules. The UE modules may plug into a PCI Express Mini interface electrically connected to processor  402  and baseband processor  406 . 
     The UE modules may include dual-carrier or single-carrier support. Frequency division duplex (FDD), time division duplex (TDD), or both may be supported on each UE module. 2G quad-band, 3G wideband code division multiple access (WCDMA), Enhanced Data Rates for GSM Evolution (EDGE), or other 2G, 3G, 4G, or 5G standards may be supported. 
     Each UE module may support one or more frequency bands. For example, one UE module may provide LTE band  3  support and another UE module may provide LTE band  14  support. UE modules may be mixed and matched by a manufacturer or operator or reseller to provide different band support. As the LTE UE modules interoperate to a single standard, only minor configuration changes may be required to perform the methods described herein using UE modules on different LTE bands. 
     The UE modules may each provide a SIM card interface for enabling each modem to authenticate as a UE to the core network. Each UE module may independently handle UE functionality, requiring little support or processing from the baseband processor  406 , and only requiring configuration using, for example, an AT command set protocol. 
     In some embodiments, one or both of the UE modules may be configured to support LTE-Advanced carrier aggregation. Using carrier aggregation, multiple bands or carriers may be ganged together to provide a single, higher-speed connection. For example, a UE module may support 2×10 MHz carrier aggregation (CA) or 2×20 MHz CA, providing double the performance. CA may be used on the uplink or the downlink. CA may be used in particular for a backhaul modem. CA may be used in particular for increasing downlink performance in the situation described herein wherein two base stations determine that increased downlink performance is required; CA may be used in place of the method described herein, in some embodiments, or CA may be used in addition to the method described herein (as CA stacks cumulatively with the approach described herein). CA may be used for FDD or TDD bands. 
     In some embodiments, the modules may include global positioning system (GPS), global navigation satellite system (GLONASS), or other positioning functionality in silicon, to be connected to antennas on the exterior of the base station. In some embodiments, the base stations may include a timing source for providing synchronization to the base station with respect to the core network; in some embodiments the timing source may be IEEE 1588 compliant, or may be a GPS module used as a timing source. 
     Wired backhaul  416  may be an Ethernet-based backhaul (including Gigabit Ethernet), or a fiber-optic backhaul connection, or a cable-based backhaul connection, in some embodiments. Additionally, wireless backhaul may be provided in addition to wireless transceivers  410  and  412 , which may be Wi-Fi 802.11a/b/g/n/ac, Bluetooth, ZigBee (used for low speed communications between mesh nodes), microwave (including line-of-sight microwave), or another wireless backhaul connection. Any of the wired and wireless connections may be used for either access or backhaul, according to identified network conditions and needs, and may be under the control of processor  402  for reconfiguration. 
     Operation 
     In operation of device  400 , processor  402  may identify the appropriate network configuration, and may perform routing of packets from one network interface to another accordingly. Processor  402  may use memory  404 , in particular to store a routing table to be used for routing packets. Baseband processor  406  may perform operations to generate the radio frequency signals for transmission or retransmission by both transceivers  410  and  412 . Baseband processor  406  may also perform operations to decode signals received by transceivers  410  and  412 . Baseband processor  406  may use memory  408  to perform these tasks. 
       FIG.  5    is a signaling diagram depicting an exemplary message flow in accordance with some embodiments. Signals between user equipment  502 , a first mesh node  504 , a second mesh node  506 , a backhaul evolved packet core (EPC)  508 , and a user equipment EPC  510  are described below. Signals are indicated as “Uu” to represent signals on the radio interface between the UE and an eNodeB functionality, as “S1-AP” for signals that are according to the 51 protocol between an eNodeB and an MME carrying control plane traffic, or as “GTP-U” for signals that are according to the GTP-U protocol between an eNodeB and a serving gateway (SGW) carrying user plane traffic. Steps may be omitted in the following discussion for clarity. 
     At step  512 , user equipment  502  sends an attach request to first mesh node  504 . Specifically, UE  502  sends this attach request to an eNodeB functionality at node  504 . Node  504 , however, has both a UE functionality and an eNodeB functionality. Second mesh node  506  also has a UE functionality and an eNodeB functionality. Node  504  relies on second mesh node  506  for backhaul, and specifically relies on an LTE connection with second mesh node  506 . In order to establish this backhaul LTE connection, node  504 , from its UE functionality, sends an attach message to the eNodeB functionality of node  506 . 
     Node  506  receives the attach message and is then responsible for setting up the backhaul connection using the UE credentials of node  504 . In order to do this, at step  516 , node  506  acts as an eNodeB and forwards the attach request from node  504  to an MME in EPC  508 , which will be called the backhaul EPC. The backhaul EPC may be a different EPC than the one intended for use by UE  502 . Backhaul EPC may be an EPC of a service provider, such as AT&amp;T, Verizon, or another LTE service provider. Backhaul EPC  508  may authenticate node  504  using the UE credentials of node  504 , e.g., by using a home subscriber server (HSS) with a record of these credentials. The details of this authentication may be performed according to the LTE standard. At step  518 , a successful authentication message is sent from EPC  508  to node  506 , which passes this message along to node  504 . At this point, the credentials of UE  502  have not yet been sent over the network. 
     At steps  524  and  526 , a global packet radio service tunneling protocol (GTP) tunnel  522  is created between node  504  and backhaul EPC  508 . This tunnel also passes through node  506 . The tunnel includes user plane bearer  524  and control plane bearer  526 . User plane bearer  524  provides a connection to the public Internet through a packet gateway (PGW) at backhaul EPC  508 . This bearer is used to provide backhaul for node  504 . 
     Once tunnel  522  and bearers  524  and  526  are established, node  504  is configured with a routing table as follows. For all traffic that should be sent to UE EPC  510 , or to any external packet network (i.e., not to other UEs accessible from nodes  504  and  506 , or other mesh network nodes, such as node  506 ), a route is created in the routing table on node  504  that places any such IP traffic onto bearer  524 . In the case that multiple UEs are connected to node  504 , any external IP traffic from any of those UEs may be placed onto bearer  524 , including connection requests intended for EPC  510 , such as request  512 . The route may be identified or distinguished in the routing table using, in some embodiments, one or more of the GTP ID of the bearer, a hardware identifier for the LTE UE network interface at node  504 , or another identifier. 
     Once the backhaul bearer  524  is established, first mesh node  504  may use this bearer to reach EPC  510 , to provide access services to UE  502 . At step  528 , the attach message  512  received by node  504  is now forwarded to EPC  510 , and authentication takes place within EPC  510 . At step  530 , confirmation of the authentication is returned to the eNodeB functionality of node  504 , and at step  532 , this is forwarded to UE  502 . UE  502  is now enabled to access UE EPC  510 . 
     At steps  536  and  538 , a GTP tunnel  534  is created between node  504  and UE EPC  510 , for encapsulating traffic to and from UE  502 . UE EPC  510  may be a private EPC, or it may be another EPC of a service provider, or it may be the same EPC as backhaul EPC  508 . Bearer  536  may be created between UE  502  and at least an MME (not shown) in UE EPC  510 , for transferring control plane data, and bearer  538  may be created between UE  502  and at least an SGW (not shown) in UE EPC  510 , for transferring user plane data. In some embodiments, tunnel  534  may be secured using Internet protocol security (IPSEC). In some embodiments, tunnel  534  may use IPv4, IPv6, or point-to-point protocol for transferring data. When using PPP, node  504  is enabled to provide authentication and other information needed for establishing the PPP connection. 
       FIG.  6    is a flowchart depicting an exemplary method for operating the hardware depicted in  FIG.  5   , in accordance with some embodiments. Method  600  includes an initial attach  600   a  and a role switch  600   b , each shown from the perspective of first mesh network node  102  in  FIGS.  1  and  3   . Not shown are attach and detach steps relating to the association and dissociation of UEs  108  with network node  102 , which may occur at any time during the process shown, but it is assumed that there is at least one UE attached to network node  102 . 
     At step  602 , network node  102  is turned on and performs initial configuration. During step  602 , node  102  may perform a network sniffing or scanning operation, to determine what other networks and mesh network nodes are in its vicinity. Sniffing or scanning may include receiving and interpreting timing and synchronization messages from eNodeBs according to the LTE standard, as well as radio resource control (RRC) information that is broadcast from eNodeBs for identifying available radio frequency bands. Sniffing or scanning may use either or both of network node  102 &#39;s two radio interfaces. 
     After sniffing or scanning, node  102  may provide the output of the scan to network selection code for selecting a given mesh node in its vicinity to attempt connection. In some embodiments, the initial network selection code may look for the network node with the lowest cost backhaul route, taking into account parameters that may include latency, received signal strength indications (RSSIs), and other parameters. A low latency and a high RSSI may be preferred. In the case of network node  102  as shown in  FIG.  1   , it identifies second mesh network node  104  for connection at step  603 , as it is nearby and as it has a reliable, low-latency backhaul connection. In some embodiments, the network node is selected based on information received from a cloud coordination server (UniCloud). 
     At step  604 , node  102  processes the broadcast information from the eNodeB received at step  602  and assesses whether to join as a UE or as an eNodeB. The determination performed in step  604  may be based on a number of parameters, which may include: the total aggregate uplink and downlink bandwidth used by all UEs attached to node  102 ; the total aggregate bandwidth within a particular time window or averaged over a particular time window; latency characteristics of all links, including all backhaul links known to node  102 ; load characteristics of node  102 , including processor  502  load; load characteristics of any links that are visible to node  102 ; load characteristics of other nodes or links that are known; time of day and day of week, which may affect load; specific UE identifiers for providing improved or degraded service to particular individuals; or other factors. If it is determined that greater total bandwidth (based on aggregate bandwidth over a particular time window) is desired for downlink than for uplink, at step  606 , node  102  will attempt to join as a UE, and will create and send an attach message to eNodeB  104  using UE functionality built into node  102 . 
     At step  610 , the attach message is received by eNodeB  104 , which returns an attach accept message and a RRC configuration message. The eNodeB may, in some embodiments, authenticate node  102  using the IMEI and IMSI stored in the UE transceiver&#39;s SIM card. In some embodiments, authentication may first be attempted via the backhaul connection to the EPC, or alternately, or in the case that authentication fails, authentication can be performed on a limited basis using a local EPC cache. At step  612 , an LTE connection between node  102  and  104  has been established with the path from node  104  to node  102  (downlink) being faster than the path from node  102  to node  104  (uplink). This is helpful in this case because node  104  has the backhaul connection, so that all downloads from destinations on the other side of the backhaul connection will be faster than uploads thereto. 
     If, however, at step  606 , node  102  determines that greater bandwidth is desired for uplink, at step  608 , node  102  prepares to join as an eNodeB, and to potentially take over one or more of the UEs attached to eNodeB  104 ; it does not send an attach message from the UE circuit, and instead may begin sending broadcast messages to other nodes, including eNodeB  104  and all UEs, as shown, indicating its role as an eNodeB. At step  614 , node  102  receives an attach request from node  104  (and possibly from other UEs previously connected to node  102 ), and adds node  104  to the network. At step  616 , an LTE connection between node  102  and  104  has been established with the path from node  102  to node  104  (downlink) being faster than the path from node  104  to node  102  (uplink). 
     At step  618 , node  102  repeatedly performs monitoring of the load criteria described above, which may be continuous, polled at intervals, or any other method. Load may refer to network load, processor load, baseband processor load, radio resource load, or any other type of load, and may refer to load that is on node  102 , or on an air link connected to node  102 , or load on another resource. Step  618  may take place on the mobile device itself, in some embodiments, or on a remote network node or cloud server, or it may connect to a UniCloud server device to obtain approval from the central coordination server. Step  618  identifies, in particular based on desired aggregate uplink and downlink bandwidth, as described above with respect to step  604 , whether role reversal is currently desired. At step  620 , it has been identified that role reversal is desired, which may cause the existing LTE connection between node  102  and  104  to be torn down, and which may cause a new LTE connection to be established according to either of steps  612  or  616 . 
     ALTERNATIVE EMBODIMENTS 
     In some embodiments, coordination may be performed between mesh nodes, so that when one node (or a cloud server) determines that a role reversal is needed, both nodes may immediately perform the role reversal. Coordination may be provided by a direct control channel or control connection between the nodes, in some embodiments, which may be a channel according to the 3GPP X2 protocol, or in a preferred embodiment, by an out-of-band X2 connection to a coordination node, which may be identified as UniCloud. UniCloud may perform other coordination functions, such as coordinating radio spectrum allocation and signal strength among mesh network nodes. Each mesh network node may have its own X2 connection to UniCloud, and UniCloud may send instructions to the mesh network nodes to cause them to be reconfigured. UniCloud is valuable in that it may be enabled to coordinate among more than two nodes, and may thus facilitate the formation of a mesh network more quickly than a mesh network that relies purely on cooperative configuration strategies, like voting. The UniCloud may perform coordination by specifically sending instructions to one or more network nodes to initiate a network change, by approving requests sent by one or more network nodes, or a combination of both. 
     An example of the utility of the UniCloud is as follows. In a network configuration where more than one mesh node has attached UEs, it may be more difficult to determine whether role reversal is desired because each mesh node has information about throughput (uplink/downlink data) demands of each of its own UEs, but not of UEs attached to other mesh nodes. A UniCloud implementation can determine an improved network flow based on aggregating throughput over all connected UEs throughout the mesh network. 
     Another example of the utility of the UniCloud is as follows. When more than one network node has a backhaul connection, it can be difficult for a plurality of self-organizing network nodes to determine an efficient routing that attempts to maximize use of all backhaul connections. UniCloud may be able to do so by splitting the mesh network into zones and instructing particular network zones to use routing algorithms to share the particular backhaul connection closest to that zone, including a role reversal if necessary. 
     In some embodiments, UniCloud may help identify which nodes should use local breakout, which is defined as the use of a backhaul connection by a mesh network node without routing traffic to other mesh network nodes. Local breakout may be used without UniCloud as well, in some embodiments, and algorithms may be implemented on each network node to determine when local breakout should be used. Characteristics that could be used for determining whether to use local breakout may include route, load, traffic type (e.g., voice or video), or other factors. However, UniCloud may assist by splitting the mesh network into zones, as above, so that local breakout becomes a special case of the shared backhaul scenario described in the previous paragraph. In some embodiments, UniCloud may divide bandwidth between backhaul and access uses, or may broker bandwidth negotiations between mesh nodes if negotiation is being used in a self-organizing network. 
     In some embodiments, frequency interworking may be provided using the two included LTE radio transceivers within the device  400 . While in the preceding disclosure, it has been assumed that both the eNodeB radio transceiver and the UE radio transceiver may be using the same designated LTE frequency band (such as LTE Band  14  for public safety, or LTE Band  13  for U.S.-based Verizon Wireless deployments), it is not necessary for the same band to be used. As an example of the use of two different bands, it is contemplated that a mesh network may be formed by a network node with the eNodeB transceiver on LTE Band  14  for a public safety application, such that all UEs are attached on Band  14 , but with the UE transceiver in the same network node set to use LTE Band  13  to connect to a Verizon Wireless LTE eNodeB for providing backhaul to the Band  14  network. Data flowing on such a secondary LTE backhaul link may be secured, in order to avoid interception while passing through the commercial LTE network&#39;s radio access network and packet core before reaching the UniCloud and/or the desired EPC core. Other frequency interworking combinations are also contemplated. 
     In some embodiments, it may be possible to reduce the likelihood that the LTE UE being used to create a backhaul connection connects to an LTE eNodeB found in the same base station that is being used for access by other UEs, or an LTE eNodeB in another mesh base station that will not be useful for establishing a backhaul connection. One technique for doing so is as follows. The LTE UE has an identifier, which may be a built-in international mobile subscriber identity (IMSI), as a result of the use of a standard UE with SIM card. The identifier may be used to determine which UEs are being used for creating a backhaul connection. In some embodiments, other identifiers, such as international mobile equipment identities (IMEIs) or global unique temporary identifiers (GUTIs), may be used. 
     When the LTE UE connects to an eNodeB, the UE sends its MEI or IMSI to the eNodeB in the initial attach message. The eNodeB may determine, based on the MEI or that the UE is a special UE, and may then cause the UE to be released without performing the steps involved in an ordinary attach procedure. For example, instead of sending the UE attach request to the MME, the eNodeB may respond to the UE attach message with a radio resource control (RRC) connection release message to the UE. 
     Prior to use, the IMEIs or other identifiers may be registered at a mesh node. In some embodiments, the mesh node may include a home subscriber server as part of a mini-evolved packet core (mini-EPC), which may be used to register the identifier. Upon an attach request, the IMEI will be queried at the HSS, which will result in a profile being retrieved from the HSS and propagated by the MME to the eNodeB functionality of the mesh network node. This profile may result in disconnection if the IMEI is determined to be an undesirable IMEI, e.g., if the UE in question should attempt to connect to another eNodeB, not the eNodeB at the particular mesh network node. 
     When the LTE UE connects to an eNodeB, the UE sends its MEI or IMSI to the eNodeB in the initial attach message. The eNodeB may determine, based on the MEI or that the UE is a special UE, and may then cause the UE to be released without performing the steps involved in an ordinary attach procedure. For example, instead of sending the UE attach request to the MME, the eNodeB may respond to the UE attach message with a radio resource control (RRC) connection release message to the UE. 
     The RRC connection release message may include the following information elements (IEs): (i) Redirection carrier information, about which frequency the special UE should use to connect to another, more-appropriate connection for the backhaul connection; (ii) New cell selection priorities in a FreqPriorityListX, listing either specific eNodeBs or tracking areas, such that the UE does not attempt to connect to another access functionality of the same or another mesh network node, but instead attempts to connect to a node providing backhaul; and (iii) increase the T320 timer such that the configuration sent in (i) and (ii) is valid for a relatively long period, such as a few hours, before the UE attempts to connect again to the LTE eNodeB of the same base station. This technique may thus be called backhaul persistence, in some embodiments. This technique may also be used to reduce such connections between backhaul-type UEs and any other eNodeBs deemed to not provide an effective backhaul path. 
     In some embodiments, the HSS and MME in the commercial operator&#39;s network may be used to provision this information. In other embodiments, the IMEI may be used directly, without provisioning a profile from an HSS to an MME. In some embodiments, the policy may include an information element with a particular secret value. Any arbitrary value could be chosen. For example, the information element “download/upload max rate limit” may be set to the value “1234567” to cause automatic disconnection of the UE. 
     In some embodiments, attach messages from a UE may be encrypted and may not be detectable at an eNodeB without decryption. However, when the IMSI is not detectable by the eNodeB functionality of the mesh network node, a timeout could be used to cause the UE to re-send an attach message that is not encrypted. In another embodiment, a keep-alive ping or other technique could be used to prevent a UE from going IDLE, thereby avoiding the encrypted attach messages. In another embodiment, special UE configuration may cause attach requests to be made non-encrypted when the mesh node UE is performing an attach. 
     In some embodiments, new cells that may form the access side for a backhaul UE can be configured or detected through a network monitor mode (NMM mode). NMM mode is a mode that may be supported by some eNodeBs that permits cell RF configuration, carrier and cell ID selection, querying of carrier signal strength, listing of carriers or cells, and other configuration operations to be performed by the eNodeB. NMM mode may be used on the mesh network node with the eNodeB functionality to detect new cells as they appear, in some embodiments. The detected new cells may be used by the eNodeB to create an appropriate frequency priority list for the UE, as described above. 
     In other embodiments, NMM mode may be used to scan for bands that are not in use, and then to set up a particular eNodeB on such a band. The backhaul UE may be enabled to select these particular eNodeBs instead of the eNodeB built into the co-located mesh network node itself, in some embodiments, either by identification of these eNodeBs in a FreqPriorityListX information element as described above or using other methods. In other embodiments, the backhaul UE may be configured to avoid mesh network node eNodeBs via prior configuration, via a connection from a cloud configuration server, via hard-coding, e.g., to avoid the single eNodeB with the strongest signal strength, or via another means. In other embodiments, the specific tracking area of the particular eNodeB to be avoided may be added to the list of forbidden tracking areas for roaming, as described in further detail in 3GPP TS 23.122 § 3.1. 
     In some embodiments, the software needed for implementing the methods and procedures described herein may be implemented in a high level procedural or an object-oriented language such as C, C++, C#, Python, Java, or Perl. The software may also be implemented in assembly language if desired. Packet processing implemented in a network device can include any processing determined by the context. For example, packet processing may involve high-level data link control (HDLC) framing, header compression, and/or encryption. In certain embodiments, the software is stored on a storage medium or device such as read-only memory (ROM), programmable-read-only memory (PROM), electrically erasable programmable-read-only memory (EEPROM), flash memory, or a magnetic disk that is readable by a general or special purpose-processing unit to perform the processes described in this document. The processors can include any microprocessor (single or multiple core), system on chip (SoC), microcontroller, digital signal processor (DSP), graphics processing unit (GPU), or any other integrated circuit capable of processing instructions such as an x86 microprocessor. 
     Although the present disclosure has been described and illustrated in the foregoing example embodiments, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the details of implementation of the disclosure may be made without departing from the spirit and scope of the disclosure, which is limited only by the claims which follow. Other embodiments are within the following claims. For example, the out-of-band channel may be implemented over a virtual channel over the public Internet.