Patent Publication Number: US-2023164755-A1

Title: Band agile mobile broadband radio, system and methods of operation

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Non-Provisional Application No. 16/805,780, filed Mar. 1, 2020, which claims the benefit of priority under 35 U.S.C. § 119 to U.S. Provisional Application No. 62/812,640, filed Mar. 1, 2019, in the United States Patent and Trademark Office, the entire contents of which are hereby incorporated by reference. 
    
    
     FIELD 
     The present disclosure relates to the incorporation of multiple communication modes and network services in a single self-contained unit. More particularly, the present disclosure relates to a single device that is capable of hosting and operating network services and multiple communications devices which transmit and receive over various communication modalities. 
     BACKGROUND 
     Wireless broadband communications for mobile devices provide convenient and reliable means of communications. For example, LONG-TERM EVOLUTION(TM) (LTE) communication systems are used to provide voice and data communications between various users and allow applications running on mobile devices to access data and/or other applications and programs. 
     Cellular base stations are used to establish communication links or channels between a mobile device and a baseband radio of the cellular base station. Cellular base stations can provide multiple radio channels to establish communication links with multiple mobile devices located within the coverage area of the cellular base station (e.g., the cell cite or macrocell of the cellular base station). 
     Cellular base stations are often fixed to a radio mast (or cell tower) which in turn fixes the coverage area of the cellular base station. Mobile devices configured for communications with a particular wireless broadband communication network are thus constrained for communications limited to the coverage area provided by cellular base stations of the network. 
     To extend service coverage of a communication network, additional cellular base stations may be added. However, providing additional macrocells may be impractical in many situations, such as due to cost, environmental concerns, etc. To extend and/or supplement coverage at discrete smaller locations (such as in a home, small business, geographically challenged coverage locations), a small cell, such as a microcell, picocell or femtocell may be used. Such microcells are formed from a small, low-power cellular base station and allow service provides to extend service coverage indoors or at the edges of a macrocell. Microcell base stations provide wireless broadband communications with the same communication network system and may use the same licensed spectrum of the cellular system of the mobile network communications provider. Microcell base stations must thus avoid interference with neighboring macrocells and are typically limited in power and communication range, often limiting use to a small number of mobile devices. Further, microcells may require installation of an access point and thus are unsuitable for providing mobility of the network coverage area. 
     The variety of communications systems used may also require network services to bridge connectivity, monitor equipment and communication status, and provide updates and repairs. 
     SUMMARY 
     Exemplary embodiments of the disclosure provide a mobile broadband communication system with band agility. A mobile cellular base station (e.g., portable and/or mountable on a vehicle) is provided with several MIMO RF front end modules operating at different RF carrier frequencies. The mobile cellular base station may use a selected subset (e.g., one) of the RF front end modules to provide communication links to multiple users using standard mobile devices (e.g., cell phones or other handheld devices) and establish communications therebetween. Switching between the RF front end modules may be done automatically or by a user. Further, the MIMO RF front end modules may be detachable so that different RF carrier families may be used with the same baseband radio to support use within different environments. 
     In some exemplary embodiments, the present disclosure is directed to a method of operating a mobile wireless communication station comprising an edge server, a digital broadband radio, and a plurality of radio frequency (RF) front end modules detachably connected to the digital broadband radio, each of the plurality of RF front end modules having a different operating frequency band, the method comprising: identifying a first RF front end module of the plurality of RF front end modules for establishing a first wireless communication link at a first RF frequency band with a user device; receiving, by the digital broadband radio, first data for transmission to the user device; converting, by the digital broadband radio, the first data into first digital transmission data; sending the first digital transmission data to the first RF front end module; converting, by the first RF front end module, the first digital transmission data to first RF transmission data at the first RF frequency band; and transmitting, by the first RF front end module, the first RF transmission data to the user device via the first wireless communication link. 
     In some exemplary embodiments, the present disclosure is directed to a wireless communication station for wireless communication, comprising: a housing; an edge server configured to establish a wireless connection with a backend network and receive first data from the backend network for wireless transmission to a user device; a baseband radio configured to receive the first data from the edge server and convert the first data to first digital transmission data; a plurality of radio frequency (RF) front end modules removably attached to the baseband radio, each of the plurality of RF front end modules operable in respectively different frequency bands, the plurality of RF front end modules including a first RF front end module configured to receive the first digital transmission data from the baseband radio, convert the first digital transmission data to first RF transmission data, and transmit the first RF transmission data to the user device; and a plurality of RF antennas respectively corresponding to the plurality of RF front end modules, wherein the edge server, the baseband radio, and the plurality of RF front end modules are provided in the housing. 
     In some exemplary embodiments, the present disclosure is directed to a wireless communication station for wireless communication, the wireless communication station comprising: a housing; an edge server configured to establish a wireless connection with a backend network and receive first data and second data from the backend network for wireless transmission to a user device; a baseband radio configured to receive the first data from the edge server, convert the first data to first digital transmission data, receive the second data from the edge server, convert the second data to second digital transmission data; a first radio frequency (RF) front end module removably attached to the baseband radio and operable in a first frequency band, the first RF front end module configured to receive the first digital transmission data from the baseband radio, convert the first digital transmission data to first RF transmission data, and transmit the first RF transmission data to the user device; and a second RF front end module removably attached to the baseband radio and operable in a second frequency band, the second RF front end module configured to receive the second digital transmission data from the baseband radio, convert the second digital transmission data to second RF transmission data, and transmit the second RF transmission data to the user device, wherein the edge server, the baseband radio, and the first and second RF front end modules are provided in the housing, and wherein the first frequency band is different from the second frequency band. 
     The mobile cellular base station may be deployed to quickly establish an edge broadband communications network within a corresponding cell formed by the mobile cellular base station. Connection to an access point may be unnecessary in certain implementations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Example embodiments will be more clearly understood from the following brief description taken in conjunction with the accompanying drawings. The accompanying drawings represent non-limiting, example embodiments as described herein. 
         FIG.  1    is a perspective illustration of an exemplary portable cellular base station, according to certain example embodiments; 
         FIG.  2    is a block diagram of the exemplary portable cellular base station of  FIG.  1   , according to certain example embodiments; 
         FIGS.  3 A and  3 B  provide exemplary details of RF front end modules usable with the portable cellular base station, according to certain example embodiments; 
         FIGS.  4 A- 4 C  diagrams illustrating operations in an exemplary communication system including the portable cellular base station, according to certain example embodiments; and 
         FIG.  5    is a flowchart illustrating an exemplary connection and communication process in a multi-modal communication system, according to certain example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. These example embodiments are just that — examples — and many implementations and variations are possible that do not require the details provided herein. It should also be emphasized that the disclosure provides details of alternative examples, but such listing of alternatives is not exhaustive. Furthermore, any consistency of detail between various examples should not be interpreted as requiring such detail — it is impracticable to list every possible variation for every feature described herein. The language of the claims should be referenced in determining the requirements of the invention. 
     It will be appreciated that the use of the same or similar reference numerals indicates the same or similar structure and thus associated description is typically relevant to all such same/similar structure. Use of suffixes for reference numerals (e.g., “a” for reference numeral “ 100 - a ”) is used when several similar structures are provided and/or variations are implemented between similar structures. Generic use of a reference numeral without a suffix (e.g., just “ 100 ”) may refer individually to all such structures (e.g., each of  100 - 1 ,  100 - 2  ...  100 - n ). 
     In the drawings, different figures show various features of exemplary embodiments, these figures and their features are not necessarily intended to be mutually exclusive from each other. Rather, certain features depicted and described in a particular figure may also be implemented with embodiment(s) depicted in different figures, even if such a combination is not separately illustrated. Referencing such features/figures with different embodiment labels (e.g. “first embodiment”) should not be interpreted as indicating certain features of one embodiment are mutually exclusive of and are not intended to be used with another embodiment. 
     Unless the context indicates otherwise, the terms first, second, third, etc., are used as labels to distinguish one element, component, region, layer or section from another element, component, region, layer or section (that may or may not be similar). Thus, a first element, component, region, layer or section discussed below in one section of the specification (or claim) may be referred to as a second element, component, region, layer or section in another section of the specification (or another claim). 
     It will be understood that when an element is referred to as being “connected,” “coupled to” or “on” another element, it can be directly connected / coupled to / on 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, or as “contacting” or “in contact with” another element, there are no intervening elements present. 
     As is traditional in the field of the disclosed technology, features and embodiments are described, and illustrated in the drawings, in terms of functional blocks, units and/or modules. Those skilled in the art will appreciate that these blocks, units and/or modules are physically implemented by electronic (or optical) circuits such as logic circuits, discrete components, microprocessors, hard-wired circuits, memory elements, wiring connections, and the like, which may be formed using semiconductor-based fabrication techniques or other manufacturing technologies. In the case of the blocks, units and/or modules being implemented by microprocessors or similar, they may be programmed using software (e.g., microcode) to perform various functions discussed herein and may optionally be driven by firmware and/or software. Alternatively, each block, unit and/or module may be implemented by dedicated hardware, or as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. 
       FIG.  1    shows a perspective view and  FIG.  2    is a block diagram representing an exemplary portable cellular base station (PCBS)  100 , according to some embodiments. The PCBS  100  may be a cellular base station having a smaller form factor, such that it is capable of being easily moved or transported from one location to another. 
     The PCBS  100  may include a baseband radio  10 , a plurality of RF front end modules  20 , and an embedded edge server  30 . The plurality of RF front end modules  20  each may comprise a MIMO (multi-input multi-output) RF transceiver, and may operate at different RF carrier frequencies from one other. The RF front end modules  20  may be detachably connected to the baseband radio  10  to provide signal communications therebetween in the form of binary digital data (which may form a voice signal between two end users, or application data, etc.). 
     As shown in  FIG.  2   , baseband radio  10  may comprise a baseband processor  12  and busses  14   a ,  14   b , and  14   c  formed on a printed circuit board  18 . Each RF front end module  20  may include signal processing circuitry  22 , bus  23 , an RF waveguide  24  (e.g., coaxial cable), and a printed circuit board  26 . In addition, the PCBS  100  may include one or more RF antennas  25  corresponding to each RF front end module  20 . For example, in  FIGS.  1  and  2   , RF front end modules  20   a  and  20   b  are each provided with one RF antenna  25 . 
     The signal processing circuitry  22 , bus  23 , and RF waveguide  24  may be mounted on and/or be formed as elements of the printed circuit board  26 . Signal processing circuitry  22  of each RF front end module  20  may exchange binary digital data with baseband processor  12  of baseband radio  10 . More specifically, each RF front end module  20  may receive I and Q signals in digital binary form from the baseband processor  12 , and may convert the same to an RF electrical signal which is then used to drive antenna  25  to emit an RF electromagnetic wave. In addition, each RF front end module  20  may receive an RF electromagnetic wave from one or more external sources via antenna  25 , and may convert the same to an RF electrical signal, which is then converted to I and Q signals in digital binary form and transmitted to the baseband processor  12 . The transmitted and received RF electromagnetic waves may form a plurality of wireless links to a plurality of user devices (e.g., in the form of an OFDM RF electromagnetic signal). 
     The baseband processor  12  may be a processor that converts data, which is input from the edge server  30 , into signals that can be used to modulate the carrier frequency for transmission. In addition, the baseband processor  12  may convert signals received from the detachable, modular RF front end modules  20  into digital data that is then transmitted to edge server  30  for further processing. For example, in performing wireless transmission, the baseband processor  12  may convert binary data to input symbols (complex values representing a mapped constellation point to specify both amplitude and phase of a sinusoid for a subcarrier). For example, QAM source data may be mapped onto N orthogonal subcarriers that are “orthogonal” to each other (in an OFDM signal). The baseband processor  12  may perform digital signal processing, such as IFFT (inverse fast Fourier transform) to generate the summation of the plurality of sinusoids of different subcarriers and provide OFDM symbols in the form of I and Q digital data (forming a complex number (I + jQ) that represent an OFDM symbol). In performing wireless receiving, the baseband processor may perform the reverse process and convert I and Q digital data (forming a complex number (I + jQ) that represents an OFDM symbol) that has been received from an RF front end module  20  into a plurality of QAM data of N orthogonal subcarriers, which are then converted into N streams of data. Additional conventional processing may also be performed by the baseband processor  12  such as, for example, data scrambling, encoding, guard insertion, preamble insertion, etc., in connection with transmission, as well as the reverse processes in connection with receiving. 
     The I and Q channel digital data provided by the baseband processor  12  may be received by a selected one of the front end modules  20 , and converted into a corresponding OFDM RF signal by signal processing circuitry  22 , which is then used to drive a corresponding antenna  25  to output a corresponding electromagnetic OFDM RF signal. With respect to the transmission side (see  FIG.  3 A ), the signal processing circuitry  22  of a front end module  20  may comprise a digital to analog converter (DAC) to convert the I and Q channel digital data into corresponding I and Q analog signals. As noted, the I and Q channel digital data may form an OFDM symbol, and a sequential series of OFDM symbols may be used to generate an OFDM signal that forms a plurality of wireless links on a plurality of orthogonally spaced subcarriers about the RF carrier frequency. The signal processing circuitry  22  may comprise a local oscillator to generate an RF carrier signal and a quadrature mixer. After filtering by a low pass filter LPF, the I and Q analog signals output by the DAC may be quadrature mixed by the quadrature mixer with the RF carrier signal generated by the LO (modulated at an RF carrier frequency respectively offset by 90 degrees), with two upconverted components being summed together to provide the RF transmission signal on RF waveguide  24 . The RF front end module  20  may thus generate an OFDM (orthogonal frequency-divisional multiplexing) RF signal which is then provided to antenna  25  and transmitted wirelessly to provide a plurality of wireless communication links to user devices. 
     In performing wireless receiving, a reverse process may be performed. Antenna  25  may receive an RF electromagnetic signal which is provided as an RF electrical signal to the signal processing circuitry  22  via RF waveguide  24 . As represented in  FIG.  3 B , the RF electrical signal provided by the RF waveguide  24  may be quadrature-mixed (with signals of the RF carrier frequency that are offset by 90 degrees from one another) which are then filtered by low pass filters LPF and digitized by analog to digital converters (ADC) to extract the real and imaginary components of the OFDM symbol (the I and Q channel digital data), which may then be transmitted to the baseband processor  12  of baseband radio  10 . Other types of wireless communications may be used instead of or in addition to OFDM, such as time division multiplexing (TDM). In some implementations, the PCBS  100  may conform to LTE and the combination of the baseband radio  10  and one RF front end module  20  may correspond to an evolved base station (eNodeB or eNB) according to the LTE standard. 
     An interposer board  40  may connect the baseband processor  12  to the signal processing circuitry  22  of each RF front end module  20  to provide communications of the transmitted and received binary digital data therebetween. In some embodiments, interposer board  40  may include one or more busses  42  over which the baseband radio  10  and RF front end module  20  can transmit/receive digital data between the baseband radio  10  and RF front end module  20 . For example, referring to  FIG.  2   , a first signal path may be formed between baseband processor  12  and signal processing circuitry  22   a  of the first RF front end module  20   a  via bus  14   a , connector  50   a , bus  42   a , connector  50   c , and bus  23   a . A second signal path may be formed between baseband processor  12  and signal processing circuitry  2   ba  of the second RF front end module  20   b  via bus  14   b , connector  50   b , bus  42   b , connector  50   d , and bus  23   b . Although separate signal paths are formed between the baseband processor  12  and corresponding front end modules  20   a  and  20   b , a single shared signal path may be formed between the baseband processor  12  and multiple front end modules  20  (e.g., front end modules  20   a  and  20   b ) with address signals (or frontend selection signals) being used to select the front end module (e.g., front end modules  20   a  or  20   b ) to communicate with the baseband processor  12 . 
     In some embodiments, signal path selection may be performed in software (e.g., a virtual core on the edge server  30 ) that “mates” the RF front end modules  20  to the baseband processor  12  of the baseband radio  10  via the interposer board  40 . This process may occur when one or more RF front end modules  20  is physically swapped out (e.g., when one RF front end module  20  is physically replaced with another RF front end module  20 ). In other embodiments, the signal paths may be chosen in software operating on the edge server  30  to provide data to one or more RF front end modules  20  as defined by the user in software. In still further embodiments, signal path selection may occur automatically through the use of signal-to-noise (SNR) ratio monitoring. For example, the signal path may be changed from one RF front end module  20  to another RF front end module based on RF congestion or noise floor variables. 
     Each of the electrical connectors  50  may comprise a plug and socket connector having a first portion attached to the interposer board  40  and a second portion attached to either the printed circuit board  18  of the baseband radio  10  (as in the case of connectors  50   a  and  50   b ) or to a printed circuit board  26  of a corresponding RF front end module  20  (as in the case of connectors  50   c  and  50   d ). The interposer board  40  may thus provide a detachable electrical signal connection between the baseband radio  10  and the RF front end modules  20 , and more specifically, between the processor  12  of the baseband radio  10  and the RF front end modules  20 . For example, each of the two or more RF front end modules  20  may be detachably connected to the interposer board  40  and detachably connected to the baseband radio  10  through the interposer board  40 , providing an electrical connection between the baseband radio  10  and the two or more RF front end modules  20  and allowing communication (transmission/reception) to be exchanged between the baseband radio  40  and the two or more RF front end modules  20 . When the RF front end module  20  is detachably connected to the baseband radio  10 , the RF front end module  20  may make an electrical connection with the bus  42  of the interposer board  40 , thereby forming a communication path between the RF front end module  20  and the baseband radio  10 . In some embodiments, the interposer board  40  may further provide an electrical power connection to the two or more RF front end modules  20 , allowing power to be provided to the two or more RF front end modules  20  through the interposer board  40 . The power may be provided by an internal power source  70 . Although an interposer board  40  is used in this example to provide a detachable electrical connection, alternative structures may be used, such as plural flexible cables, each having portions of connectors attached at either end (e.g., a first cable forming bus  42   a  extending between connectors  50   a  and  50   c  and a second cable forming bus  42   b  extending between connectors  50   b  and  50   d ). 
     Edge server  30  may comprise a computer stack and may be configured to provide backend processing of the cellular network formed by PCBS  100 . Although not illustrated, the edge server  30  and/or the computer stack can include one or more of the following components: at least one central processing unit (CPU) configured to execute computer program instructions to perform various processes and methods, including the processes and methods disclosed herein, random access memory (RAM) and read only memory (ROM) configured to access and store data and information and computer program instructions, input/output (I/O) devices configured to provide input and/or output (e.g., keyboard, mouse, display, speakers, printers, modems, network cards, etc.), and storage media or other suitable type of memory (e.g., such as, for example, RAM, ROM, programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, floppy disks, hard disks, removable cartridges, flash drives, any type of tangible and non-transitory storage medium) where data and/or instructions can be stored. 
     The computer stack of the edge server  30  may host multiple Virtual Machines (“VMs”) which run software instances at the edge, thereby removing the need for connectivity to a higher echelon network for subscription services, which include, but are not limited to the following: an Evolved Packet Core (“EPC”); a situational awareness software server; a softphone application program; a voice and chat application; a streaming solution; an enhanced security layer server, providing onboard virtual private networks (VPNs); and a satellite communication (“SATCOM”) situational awareness application. These VMs may act as the control unit not only for radio operations, but also for network service operations. In addition, the edge server  30  may further include a hypervisor application that operates and monitors the VMs. 
     The situational awareness software server may include a geospatial mapping engine, originally developed for the Android Operating System, which allows for precision targeting, surrounding land formation intelligence, situational awareness, navigation, and data sharing. The softphone application program may enable Voice over Internet Protocol (“VoIP”) telephone calls from one or more computing devices. The voice and chat application may be an encrypted VoIP application, which allows users to talk to each other via the same server. The streaming solution may allow for a server/client that can stream and receive network streams. The SATCOM situational awareness application may include an encrypted web interface that enables centralized or remote monitoring and control. 
     Edge server  30  may be configured by software to form an evolved packet core (EPC) according to LTE. The software that configures the edge server  30  may be stored on one or more of the memory or storage media of the edge server  30 , and may be executed by the at least one central processing unit (CPU) of the edge server  30 . The EPC may be a framework for providing converged voice and data on a 4G LTE network. The EPC network elements may consist of the Mobility Management Entity (“MME”), Home Subscription Server (“HSS”), Serving Gateway (“S-GW”), Packet Gateway (“P-GW”), and policy and charging rules function server (PCRF server). 
     The MME module of the edge server  30  may perform security procedures such as end-user authentication and implementing ciphering and integrity protection algorithms. The MME module may also determine Quality of Service (QoS) of a particular wireless link. In some embodiments, the MME module may be responsible for selecting the RF front end module  20  through which the PCBS  100  will communicate with one or more user devices. In other embodiments, the RF front end module  20  may be selected using, for example, application layer software operating on the edge server  30 . The application layer software may monitor the RF environment via a probe, including, for example, a dormant RF front end module  20 . Monitoring the RF environment may include, for example, analyzing frequency band usage and/or the strength of signals that occupy a frequency band that is currently being used by one of the RF front end modules  20  or a frequency band that may be used by another of the RF front end modules  20 . 
     The HSS module may be a database that contains user-related and subscriber-related information. The HHS module may provide support functions in mobility management, call and session setup, user authentication and access authorization. For example, the HHS module may perform user identification and addressing (e.g., in referencing a database of mobile subscriber ISDN numbers or mobile telephone numbers), as well as determine related user profile information associate with an identified user (e.g., subscriber information such as allowed traffic class, maximum bit rate, Quality of Service, etc.). 
     The edge server  30  may communicate with baseband processor  12  via bus  14   c . For example, the edge server  30  may transmit data to and receive data from the baseband processor  12  of the baseband radio  10  via bus  14   c . Bus  14   c  may be formed on printed circuit board  18  of the baseband radio  10 , and may extend to connect to the edge server  30  (e.g., through connectors (not shown)). 
     The baseband radio  10 , the front end modules  20 , the edge server  30 , and the interposer module  40  may be located within a single housing  60 , which may encase the elements of the PCBS  100 .  FIG.  1    illustrates a base of housing  60 . Housing  60  may also include a cap (e.g., a flat plate) that connects to the base of housing  60 . The cap and the base of housing  60  may be detachably connected together with fasteners, such as by clasps or screws, allowing a user to access an internal area of the housing  60  and modify the components of the PCBS  100  (as described elsewhere herein). Antennas  25  may be provided within housing  60  or outside housing  60 , and may be connected to corresponding signal processing circuitry via the RF waveguide  24  (e.g., extending through housing  60  by connecting two coaxial cables with a coaxial connector — one shown in  FIG.  1   ). For example,  FIG.  2    illustrates an embodiment in which the antennas  25  are provided inside of housing  60  (represented by the solid line), as well as an embodiment in which the antennas are provided outside of housing  60  (represented by the dotted and dashed line adjacent to the printed circuit board  26 ). Housing  60  may be formed of a rugged material (e.g., molded epoxy resin or a metal casing) and may be environmentally sealed (e.g., waterproof). 
     An internal power source  70  may be provided within housing  60  to provide power to the components of the PCBS  100 . For example, power source  70  may provide power to baseband radio  10 , RF front end modules  20 , and edge server  30 . The power source  70  may be a primary source of power or may be a secondary source of power (e.g., a backup battery operable in response to detecting that a primary source of power outside the housing  60  is unavailable). In some embodiments, the power source  70  may be a rechargeable battery. 
     Each of the RF front end modules  20  may be physically detachably connected to housing  60 . For example, pegs (not shown) extending from the base of housing  60  (below the RF front end modules  20  in  FIG.  1   ) may extend through corresponding holes in the printed circuit boards  26  of the RF front end modules  20 . Upper portions of the pegs may correspond in size (e.g., slightly smaller in diameter) with the corresponding holes in the printed circuit boards  26  through which they extend, while lower portions of the pegs may have a larger size than the corresponding holes to support the printed circuit board  26  and provide a spacing between the printed circuit board  26  and the bottom of the base of the housing  60 . A fastener (not shown), such as a nut, may be attached to the smaller diameter pegs above the printed circuit board  26  to vertically fasten the printed circuit board in place. Horizontal movement of the printed circuit board  26  may be restricted by the pegs. 
     Each of the RF front end modules  20  may be operable at different RF carrier frequencies. Components of the RF front end modules  20  may thus be selected to operate at the RF carrier frequency of the RF front end module  20 . For example, the local oscillator LO of each RF front end module may be configured to generate a different RF carrier frequency for the upconversion and downconversion signal processing described herein. Further, RF waveguides  24  and antennas  25  may have different sizes and/or configurations to optimize transmission / reception of RF signals (as described herein) at the RF carrier frequency of the RF front end module  20 , where use of the same RF waveguides  24  and antennas  25  in another RF front end module  20  may act to filter and/or attenuate the RF signals to be transmitted/received. Because the RF front end modules  20  are detachably connected to the baseband radio  10  through, for example, interposer board  40 , each RF front end module  20  may be replaced with another RF modules  20  that operates at a different frequency band than that of the RF front end modules  20  being replaced. 
       FIGS.  4 A- 4 C  are diagrams illustrating a PCBS  100 , including two RF front end (FE) modules  20 , according to certain exemplary embodiments. In  FIGS.  4 A- 4 C , the PCBS  100  may be communicatively connected with a plurality of user devices (UDs)  420  (e.g., UD  420   a , UD  420   b , UD  420   c , and UD  420   d ) and a network  400 . 
     UDs  420  may be any type of electronic device and/or component configured to wirelessly communicate data and/or voice, many of which are known in the art. UDs  420  can include, by way of example and not limitation, client computing devices, desktop computers, laptop computers, network computers, workstations, sensors, personal digital assistants (PDA), tablet computers and/or electronic readers (e.g., iPad, Kindle, Playbook, Touchpad, etc.), telephony devices, smartphones, wireless base stations, wireless access devices, pagers, music playing devices (e.g., iPod, etc.), routers, hubs, cameras, printers, copiers, scanners, projectors, alarms, lights, home entertainment systems, audio/visual systems, home security devices, intercoms, domestic robots, appliances, HVAC systems, etc., or any component or sub-component of another UD  420  or assemblage, such as, for example, a car, a train, a plane, a boat, etc. Although not illustrated, UDs  420  can also include servers and/or databases. UDs  420  may be configured to transmit and/or receive information to and/or from other UDs  420  and/or PCBS  100  directly and/or indirectly. 
     Network  400  may be any appropriate network or other communication link that allows communication between or among one or more computing systems and/or devices, such as, for example, between two or more PCBSs  100  and/or between individual PCBSs  100  and other communication systems and/or networks. Network  400  may be wired, wireless, or any combination thereof. Network  400  may include one or more of, for example, a circuit-switched network, a packet-switched network, or any other suitable communication network or any combination thereof. In some embodiments, network  400  may include an IP Multimedia Core Network Subsystem (IMS). In some embodiments, edge server  30  may establish, maintain, and monitor the communication link(s) between the PCBS  100  and the network  400 . 
     Referring to  FIG.  4 A , in operation, a wireless cellular network may be formed with the PCBS  100  and a plurality of UDs  420  in the wireless communication cell (e.g., macrocell) formed by the PCBS  100 . The wireless cellular network may be formed using a selected one or more of the RF front end modules  20 , operating at the different RF carrier frequencies. In the example of  FIG.  4 A , a first RF front end module  20   a  may form a cellular network operating at a first LTE frequency band FB1. For example, using the first RF front end module  20   a , the PCBS  100  may establish wireless communication links with a plurality of UDs  420 , and may transmit/receive communications at the first LTE frequency band FB1 to/from each of the plurality of UDs  420 . 
     In addition, the PCBS  100  may automatically reconfigure an established cellular network to switch from one LTE frequency band to another. For example, referring to  FIGS.  4 B and  4 C , after establishing a cellular network and related wireless communication links with UDs  420  using a first RF front end module  20   a  operating at the first LTE frequency band FBI, the PCBS  100  may (a) initiate and establish new duplicative wireless links between the same UDs  420   a  to  420   d  using a second RF front end module  20   b  operating at a second LTE frequency band FB2, and (b) subsequently shutdown wireless communications (and associated wireless links) established with the first RF front end module  20   a . Handoff operations may thus be performed in a manner similar to those performed when a UD  420  moves from one cell to a neighboring cell in a conventional cellular network, however, the handoff operations performed by the PCBS  100  may be performed for UDs  420  remaining in the same cell (e.g., coverage area of the PCBS  100 ), and with respect to the same baseband radio  10 , but with respect to use of different RF front end modules  20   a  and  20   b  to replace a wireless link between PCBS  100  and UDs  420  with a newly formed wireless link. 
     For example, a first eNodeB may correspond to a first module of the baseband radio  10  and a first RF front end module  20   a  operating as described herein to process a first OFDM broadband signal (e.g., at the first LTE frequency band FB1). A second eNodeB may be implemented with a second module of the baseband radio  10  and a second RF front end module  20   b  to establish a second OFDM broadband signal (e.g., at the second LTE frequency band FB2). Handoff may be made between wireless links established using the first eNodeB to corresponding newly-established wireless links using the second eNodeB. In some examples, use of a virtual X2 interface according to LTE and its functionality may be employed within the PCBS  100  (i.e., the X2 interface and related functionality may be employed within housing  60  without interfacing with a different PCBS  100 ). Thus, switching from an existing wireless link between PCBS  100   and UDs  420  at one LTE band to a newly-established wireless link between PCBS  100  and UDs  420  at a different LTE band may be performed automatically without interrupting communications between PCBS  100  and UDs  420 . 
     In some embodiments, the transition from a first RF front end module (e.g., front end module  20   a ) operating in a first LTE frequency band to a second RF front end module (e.g., front end module  20   b ) operating in a second LTE frequency band may be performed based on one or more selection criteria. For example, the one or more selection criteria upon which a decision to select a particular LTE frequency band or transition from one LTE frequency band to another may be, for example, current or desired/expected operational conditions and current or desired/expected operational parameters. The one or more selection criteria may include, but are not limited to: geographic location (e.g., GPS data, etc.), which may be overlaid with map data (e.g., land borders, etc.); weather (e.g., overcast skies, clear skies, etc.), including actual or expected changes to weather; terrain or topography (e.g., flat topography, hilly topography, buildings, etc.) including actual or expected changes to terrain or topography; actual or projected numbers of user devices (e.g., UDs  420 ) in the communication cell; actual or projected distances between the PCBS  100  and one or more user devices (e.g., UDs  420 ); measured or calculated strength of transmitted/received signals between the PCBS  100  and one or more of the user devices (e.g., UDs  420 ); size or range of a communication cell, including desired changes to size or range of the cell; threshold signal-to-noise ratios (SNR); RF congestion predictive analysis based on real time SNR; power availability and/or power consumption associated with different LTE frequency bands; interference with other RF signals and/or external actors (e.g., network congestion, conflict with other mobile stations, jamming equipment, etc.); etc. 
     In other embodiments, a user may select an LTE band or several LTE bands in which to form a single cellular network. User selection may be performed in several ways, such as, for example, by use of a user interface (not shown) to select a corresponding mode of operation by the PCBS  100 . For example, an administrator user may input a user selection into a user interface, and the input user selection may be provided to the PCBS  100  via network  400 . As another example, an initial RF front end module  20  may be preselected and data corresponding to the preselected RF front end module  20  may be stored in memory of the edge server  30 . User selection may be made based on one or more of the selection criteria discussed above. 
     In some examples, the PCBS  100  may be configured to operate using a bandwidth less than its maximum bandwidth. For example, half or more of the RF front end modules  20  in a given PCBS  100  may be kept dormant, and related OFDM broadband communications provided in LTE bands of the dormant RF front end modules  20  may be left unused until a handoff event occurs. When a handoff event is determined to be appropriate, after the handoff, a new subset of the RF front end modules  20  (e.g., half or more) may be kept dormant. In this way, signature reduction of the PCBS  100  may be provided to reduce chances of detection, which may be of significant importance to warfighters in a battlefield environment. 
     RF front end modules  20  that are dormant to prevent transmitting an OFDM broadband signal (e.g., Tx dormant) may be operational for receiving and monitoring RF of the Tx dormant RF front end module  20 . When operating in this Tx dormant manner, although no wireless links may be established with the Tx dormant front end module  20 , the RF signal received and processed by the Tx dormant front end module  20  may be analyzed to evaluate a signal-to-noise ratio (SNR) in a SNR floor listening mode. Should the SNR floor suddenly rise to a new level, it may indicate that a jamming event is taking place to jam communications of the PCBS  100  (with respect to the operation of other RF front end modules  20  at other LTE bands). Thus, in response to detecting an increase of the SNR floor to a new level (e.g., a certain threshold, such as a predetermined percentage increase over the originally detected SNR), the PCBS  100  may automatically perform handoff operations from established wireless links using a first front end module and a first LTE band (e.g., front end module  20   a  operating in the first LTE frequency band FB1, as illustrated in  FIGS.  4 A- 4 C ) to newly established corresponding wireless links using a second front end module and a second LTE band (e.g., front end module  20   b  operating in the second LTE frequency band FB2, as illustrated in  FIGS.  4 A- 4 C ), and terminate the original wireless lines using the first front end module and the first LTE band (e.g., front end module  20   a  operating in the first LTE frequency band FBI, as illustrated in  FIGS.  4 A- 4 C ). 
       FIG.  5    is a flowchart  500  illustrating an exemplary connection and communication process using PCBS  100  in a mobile communication system, according to certain example embodiments. 
     Referring to  FIGS.  4 A and  5   , the edge server  30  of PCBS  100  may receive instructions and/or condition information (step  505 ). The instructions and/or condition information may be received by the edge server  30  of the PCBS  100 . Instructions may include, for example, commands from an administrator user to transition to a different frequency band (e.g., transition from a first frequency band in which the PCBS  100  is currently communicating with one or more UDs  420  to a second frequency band). Such instructions may be received via a user interface (not illustrated). The user interface may be physically connected to PCBS  100  or may be communicatively connected to PCBS  100  through, e.g., network  400 . 
     Condition information may be received from one or more external sources and/or from one or more internal processes. For example, external sources may provide edge server  30  with current location information (e.g., GPS data) or a weather forecast. In addition, external sources (e.g., administrator user) may provide edge server  30  with new operational parameters or conditions. For example, the administrator user may provide the edge server  30  with information about an upcoming change in the geographic location in which the PCBS  100  will operate. As another example, the administrator user may provide the edge server  30  with information about other PCBSs  100  that may be expected to operate within the current geographic location (e.g., for deconfliction purposes). Condition information provided from the one or more external sources may be received via network  400 . 
     In some embodiments, condition information may be provided from one or more processes operating on edge server  30 . For example, processes operating on the edge server  30  may evaluate a SNR and any changes thereto (e.g., elevation of SNR floor, as discussed above). As another example, the situational awareness software server may provide geospatial mapping data, surrounding land formation data, navigation data, etc. As a further example, end point connected devices (e.g., drones, end point data collection systems, etc.) may provide condition information. 
     Next, one of the RF front end modules  20  may be identified to form a first wireless connection between PCBS  100  and UDs  420  (step  510 ). In some embodiments, the edge server  30  may make the selection of the desired RF front end module  20 . The selection may be made based on any combination of received instructions, condition information and/or stored data that is available to the edge server  30 , such as that received in step  505 . 
     Once the RF front end module  20  has been identified, instructions may be provided to select the identified RF front end module  20  (step  520 ). The instructions may be sent from the edge server  30  to the baseband radio  10 , which may then select the identified RF front end module  20  via the system’s interposer board  40 , which may include up to four separate busses  42  designed to route information to the appropriate RF front end module. 
     The selected RF front end module  20  may establish first wireless connections between the PCBS  100  and one or more UDs  420  (step  530 ). The first connections may be established according to LTE protocols. For example, referring to  FIG.  4 A , the first RF front end module  20   a  may establish first wireless connections with one or more UDs  420  according to a first LTE frequency band FB1. Once the first wireless connections are established between the selected RF front end module  20  of the PCBS  100  and the one or more UDs  420 , communications between the PCBS  100  and the one or more UDs  420  may commence. The communications may include transmission/reception of voice and data between the PCBS  100  and the one or more UDs  420  at the first LTE frequency band FB 1. Once the first connections are established, instructions and condition information may continue to be received (step  535 ). The instructions and condition information may be received by edge server  30 , as discussed above in connection with step  505 . 
     The edge server  30  may monitor and assess the received instructions and condition information (step  540 ). In some embodiments, the received or calculated condition information may be monitored and evaluated to determine if a predetermined value or set of values has been met or exceeded. For example, the edge server  30  may compare a calculated SNR with a threshold SNR value (e.g., a predetermined maximum SNR value), and may determine to transition from the first frequency band FB1 to the second frequency band FB2 when the threshold SNR value has been met or exceeded. As another example, the edge server  30  may compare received GPS data with mapping data, and may determine to transition from the first frequency band FB1 to the second frequency band FB2 if a geographic border has been crossed. 
     In further embodiments, if the administrator user inputs a desired frequency band, the edge server  30  may evaluate whether the current frequency band is the same as the desired frequency band. If the current frequency band (e.g., first frequency band FBI) is not the same as the desired frequency band (e.g., second frequency band FB1), the edge server  30  may determine to transition from the current frequency band to the desired frequency band. 
     If a decision is made not to transition from the first LTE frequency band to a second LTE frequency band (step  550 , No), transmission and/or reception may be continued through the first connection at the first LTE frequency band, and any received instructions and condition information will continue to be monitored (step  540 ). In some embodiments, the monitoring of the received instructions and condition information may be performed by the edge server  30 . 
     When a decision is made to transition from the first LTE frequency band to a second LTE frequency band (step  550 , Yes), a second RF front end module  20  may be identified to form a second wireless connection between PCBS  100  and UDs  420  (step  510 ). Once the second RF front end module  20  has been identified, instructions may be provided to select the identified RF front end module  20  (step  520 ). The selected second RF front end module  20  may establish one or more second wireless connections between the PCBS  100  and one or more UDs  420  (step  530 ). For example, referring to  FIG.  4 B , the second connection may be established between the PCBS  100  and the one or more UDs  420  using the second RF front end module  20   b . The second connection may be established according to LTE protocols. For example, the second RF front end module  20   b  may establish a wireless connection with one or more UDs  420  at the second LTE frequency band FB2. Referring to  FIG.  4 C , when the second connection is established, the first connection may be disconnected. 
     In some embodiments, although not illustrated, the second RF front end module  20   b  may not address the selection criteria and/or may not be functional, and the second RF front end module  20   b  may be replaced by a third RF front end module (not illustrated). The third RF front end module  20  may operate in a third LTE frequency band, different from the first and second LTE frequency bands. For example, the second RF front end module  20   b  may be removed from the housing  60 , and the third RF front end module may be inserted into the space previously occupied by the second RF front end module  20   b . In such embodiments, references to the second RF front end module  20   b  may refer to the third RF front end module  20 , which physically replaces the second RF front end module  20   b . 
     In still further embodiments, although not illustrated, the PCBS  100  may contain only a single first RF front end module  20   a , and this single RF front end module  20   a  may not address the selection criteria and/or may not be functional. In such embodiments, the single first RF front end module  20   a  may be replaced by a third RF front end module  20  (not illustrated). The third RF front end module  20  may operate in a third LTE frequency band. For example, the first RF front end module  20   a  may be removed from the housing  60 , and the third RF front end module  20  may be inserted into the space previously occupied by the first RF front end module  20   a . In such embodiments, references to the second RF front end module  20   b  may refer to the third RF front end module  20 , which physically replaces the first RF front end module  20   a . 
     As noted herein, the RF front end modules  20  may be detachably connected within the housing  60  and to the baseband radio  10  via the interposer  40 . Thus, the PCBS  100  may be easily modified by an operator user to replace RF front end modules  20  with different RF front end modules  20  operating in different frequency bands. In some implementations, the invention may take the form of a portable cellular base station kit. The portable cellular base station kit may comprise the baseband radio  10 , the embedded edge server  30 , and power source  70  formed within housing  60 . The housing  60  may comprise n connection slots (e.g., sets of pegs) for attaching n RF front end modules  20 , where n is a number equal to or greater than 2. Each of the connection slots may be formed to physically attach an RF front end module (attach in a removable manner, e.g.) to the housing  60  (such as described herein, such as with respect to pegs and clasps, e.g.). The portable cellular base station kit may also comprise m RF front end modules  20  (with m being an integer equal to or greater than n), with each of the m RF front end modules  20  configured to operate at a different RF carrier frequency (e.g., at a different LTE band). From the m RF front end modules, a user may select n of the m RF front end modules  20  and attach them to the housing  60  using the n connection slots. The portable cellular base station kit may also comprise a signal connector, such as interposer board  40 , to connect the RF front end modules to the baseband processor  12  to provide signal communications therebetween (as described herein). 
     For example and without limitation, the portable cellular base station kit may be provided with two or more RF front end modules  20  that respectively operate in the following LTE bands: Band 1 (1920-1980 MHz uplink, 2110-2170 MHz downlink), Band 2 (1850-1910 MHz uplink, 1930-1990 MHz downlink), Band 3 (1710-1785 MHz uplink, 1805-1880 MHz downlink), Band 4 (1710-1755 MHz uplink, 2110-MHz 2155 downlink), Band 5 (824-849 MHz uplink, 869-894 MHz downlink), Band 7 (2500-2570 MHz uplink, 2620-2690 MHz downlink), Band 8 (880915 MHz uplink, 925-960 MHz downlink), Band  10  (1710-2170 MHz), Band  12  (699-716 MHz uplink, 729-746 MHz downlink), Band  13  (777-787 MHz uplink, 746-756 MHz downlink), Band  17  (704-716 MHz uplink, 734-746 MHz downlink), Band  20  (832-862 MHz uplink, 791-821 MHz downlink), Band  25  (1850-1915 MHz uplink, 1930-1995 MHz downlink), Band  26  (814-849 MHz uplink, 859-894 MHz downlink), Band  28  (703-748 MHz uplink, 758-803 MHz downlink), Band  29  (717-728 MHz downlink), Band  30  (2305-2315 MHz uplink, 2350-2360 MHz downlink), Band  38  (2570-2620 MHz), Band  40  (2300-2400 MHz), Band  41  (2496-2690 MHz), Band  66  (1710-1780 MHz uplink, 2110-2200 MHz downlink), and Band  71  (663-698 MHz uplink, 617-652 MHz downlink). 
     In the specific examples illustrated herein, only two RF front end modules  20  are shown as being implemented as part of the PCBS  100 . However, it should be emphasized that more than two RF front end modules  20  are contemplated as being implemented as part of the PCBS  100  (and connected to the baseband radio  10  and baseband processor  12  as described herein). For example, four or more RF front end modules  20  may be removably attached to the housing  60  and have removably attached signal connections with the baseband processor  12 . Thus, a PCBS  100  may be both (a) operable with multiple RF front end modules  20  at different LTE bands using only a single baseband processor  12  of a single baseband radio  10  and (b) configurable to select the desired RF front end modules  20  in a “plug-and-play” manner. It should be apparent that the physical structure of each RF front end module  20  may be the same, such that the physical and electrical connections of an RF front end module  20  may be used without modification no matter which physical slot the RF front end module  20  is connected to within the housing  60 . 
     In some examples, PCBS  100  may provide macro-cell coverage. For example, coverage area provided by the PCBS  100  may have a range greater than two kilometers, such as within an area greater than 5 kilometers, greater than 10 kilometers and provide wireless links to user devices within a 35 kilometer range. 
     Exemplary embodiments of the disclosure provide mobile broadband communication systems with band agility. A PCBS  100  (e.g., portable and/or mountable on a vehicle) is provided with several MIMO RF front end modules operating at different RF carrier frequencies. The PCBS  100  may use a selected subset (e.g., one) of the RF front end modules to provide communication links to multiple users using standard user devices (e.g., cell phones or other handheld devices) and establish communications therebetween. Switching between the RF front end modules may be done automatically or by an operator user. Further, the MIMO RF front end modules may be detachable so that different RF carrier families may be used with the same baseband radio  10  to support use within different environments. 
     The PCBS  100  may be deployed to quickly establish a broadband communications network within a corresponding cell formed by the PCBS  100 . Connection to an access point may be unnecessary in certain implementations. 
     The PCBS  100  may be portable. For example, the PCBS  100  may be carried by a human in a backpack. The PCBS  100  may also be mounted to a vehicle, such as a truck, an unmanned aerial vehicle (e.g., a drone) or to an unmanned ground vehicle. Different physical implementations of the PCBS  100  may be achieved with the baseband radio  10 , embedded edge server  30 , and RF front end modules  20 , within different housings  60  (having different slot connections for attaching the RF front end module  20  in different configurations) and using different configurations of interposer board  40 . 
     In some embodiments, an interposer board  40  may be used, but the disclosure is not limited thereto. For example, two LTE front end modules may be attached directly to a specialized baseband card containing hardware configured to perform the same function as that of an interposer board functioning as a separate item. 
     Although not shown, the PCBS  100  can include one or more mechanisms and/or devices by which the system can perform the methods as described herein. For example, the PCBS  100  can include one or more encoders and/or decoders, one or more interleavers, one or more circular buffers, one or more multiplexers and/or de-multiplexers, one or more permuters and/or depermuters, one or more encryption and/or decryption units, one or more modulation and/or demodulation units, one or more arithmetic logic units and/or their constituent parts, etc. These mechanisms and/or devices can include any combination of hardware and/or software components and can be included, in whole or in part, in any of the components shown in the figures. 
     In one or more exemplary designs of PCBS  100 , the functions described can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored as one or more instructions or code on computer-readable medium, including the computer-readable medium described above (e.g., RAM, ROM, storage media, etc.). 
     While the disclosure has been shown and described with reference to example embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit of the disclosure.