Patent Publication Number: US-2018054823-A1

Title: Frequency translation in a virtualized distributed antenna system

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/753,288, filed on Jan. 29, 2013; which claims priority to U.S. Provisional Patent Application No. 61/592,190, filed on Jan. 30, 2012. Each of these references is hereby incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     Wireless communication systems employing Distributed Antenna Systems (DAS) are available. A DAS typically includes one or more host units, optical fiber cable or other suitable transport infrastructure, and multiple remote antenna units. A radio base station is often employed at the host unit location commonly known as a base station hotel, and the DAS provides a means for distribution of the base station&#39;s downlink and uplink signals among multiple remote antenna units. The DAS architecture with routing of signals to and from remote antenna units can be either fixed or reconfigurable. 
     A DAS is advantageous from a signal strength and throughput perspective because its remote antenna units are physically close to wireless subscribers. The benefits of a DAS include reducing average downlink transmit power and reducing average uplink transmit power, as well as enhancing quality of service and data throughput. 
     Despite the progress made in wireless communications systems, a need exists for improved methods and systems related to wireless communications. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention relate to communication networks. More particularly, embodiments of the present invention provide methods and systems related to the provision and operation of virtual distributed antenna systems (DASs). Merely by way of example, the present invention has been applied to DASs utilizing software configurable radio (SCR). The methods and systems described herein are applicable to a variety of communications systems including systems utilizing various communications standards. 
     Embodiments of the present invention relate to an interacting with frequency-restricted Base Transceiver Stations (BTS) and to a non-reciprocal series of frequency translations. Factors such as user devices, geographical locations, and frequency regulations may influence an operator&#39;s decision as to which frequencies to transmit at particular locations. In some instances, the operator may own one or more BTSs that are limited in terms of frequencies that the BTS may transmit and receive. Traditionally, an operator may then be forced to either purchase new BTS equipment (e.g., new transceiver cards) or confine the associated network to frequency bands supported by the existing BTS equipment. Embodiments provided herein allow a BTS to operate within a first frequency range and antenna in communication with the BTS to operate within a different second frequency range. For example, signals (e.g., uplink-carrier signals and/or beacons) may be transmitted from the BTS within a RF base-station frequency band, they may then be translated into a baseband frequency band as the signals are carried towards a digital remote unit (DRU), and an antenna at the DRU may translate the baseband signals to one or more RF field frequency bands different from the base-station frequency band. A converse process may occur to translate signals received at the DRU transmitted to the BTS. Thus, an operator may be able to dynamically control frequency bands associated with particular DRUs (and with particular geographic areas) even if the BTS is unable to adjust its transmission and receive frequency bands. Further, these translations may be applied to a select set of signals associated with the DRU (e.g., some or all beacon signals). Thus, it may be possible to transmit, e.g., beacons from a DRU-associated antenna within a plurality of frequency bands, even if an associated BTS is not configured to emit the signals within all of the bands. 
     According to an embodiment of the present invention, a system for communicating with wireless user devices is provided. The system includes a base transceiver station (BTS) comprising at least one sector. Each sector is configured to transmit radio-frequency (RF) signals within one or more first frequency bands. The system also includes a Digital Access Unit (DAU) coupled to the BTS and configured to receive at least some of the RF signals output by the base transceiver station and process the at least some of the RF signals. The DAU is also configured to transmit the processed signals. The system further includes at least one Digital Remote Unite (DRU) configured to receive the processed signals and translate at least one of the processed signals to one or more second frequency bands different than the one or more first frequency bands. 
     According to another embodiment of the present invention, a method for communicating with wireless user devices is provided. The method includes receiving a signal at a DAU, the signal residing within a first frequency band and processing the signal at the DAU. The method also includes transmitting the processed signal from the DAU, receiving the transmitted signal at a DRU, and converting the signal to a second frequency band different than the first frequency band. 
     According to a specific embodiment of the present invention, a method for communicating with wireless user devices is provided. The method includes receiving a plurality of beacon signals, each of the beacon signals having originated at a BTS and having been transmitted by the BTS within one or more first frequency bands and translating each of the plurality of beacon signals. The translated signals are within one or more second frequency bands, the one or more first frequency bands are different than the one or more second frequency bands, the one or more first frequency bands comprise an RF frequency, and the one or more second frequency bands comprise an RF frequency. 
     According to another specific embodiment of the present invention, a system for communicating with wireless user devices is provided. The system includes a Digital Access Unit (DAU) operable to receive at least one RF signal from a base station. The at least one RF signal is associated with a first frequency band and the DAU includes an RF input, a first mixer coupled to the RF input, and an oscillator coupled to the first mixer and operable to convert signals in the first frequency band to an intermediate frequency. The DAU also includes an A/D converter coupled to the mixer and a first FPGA coupled to the A/D converter. The system also includes a Digital Remote Unit (DRU) coupled to the DAU. The DRU includes a second FPGA, a D/A converter coupled to the second FPGA, and a second mixer coupled to the D/A converter and operable to convert signals at the intermediate frequency to a second frequency band different from the first frequency band. The DRU also includes an RF output coupled to the second mixer. The system further includes an antenna coupled to the DRU. 
     According to an alternative embodiment of the present invention, a system for communicating with wireless user devices is provided. The system can include a base transceiver station (BTS) including at least one sector. Each sector is configured to transmit radio-frequency (RF) signals within one or more first frequency bands. The system also includes a Digital Access Unit (DAU) coupled to the BTS and configured to receive at least some of the RF signals output by the base transceiver station, process the at least some of the RF signals, and transmit the processed signals. The system further includes at least one Digital Remote Unit (DRU) configured to receive the processed signals and translate at least one of the processed signals to one or more second frequency bands. The one or more second frequency bands are different than the one or more first frequency bands. 
     According to another alternative embodiment of the present invention, a method for communicating with wireless user devices is provided. The method includes receiving an input from an operator identifying a field frequency band. The method further includes virtually configuring a DRU to convert signals to the field frequency band. 
     According to yet another alternative embodiment of the present invention, a method for communicating with wireless user devices is provided. The method includes receiving a signal at a DAU. The signal resides within a first frequency band. The method further includes processing the signal at the DAU. The method also includes transmitting the processed signal from the DAU. The method further includes receiving the transmitted signal at a DRU. The method further includes converting the signal to a second frequency band. The second frequency band is different than the first frequency band. 
     According to a particular embodiment of the present invention, a method for communicating with wireless user devices is provided. The method includes receiving a plurality of beacon signals. Each of the −beacon signals originated at a BTS. Each of the −beacon signals was transmitted by the BTS within one or more first frequency bands. The method further includes translating each of the plurality of −beacon signals. The translated signals are within one or more second frequency bands. The one or more first frequency bands are different than the one or more second frequency bands. The one or more first frequency bands comprise an RF frequency. The one or more second frequency bands comprise an RF frequency. 
     Numerous benefits are achieved by way of the present invention over conventional techniques. For instance, embodiments of the present invention allow a network to effectively adapt to frequency demands placed on the network. For example, frequency bands associated with a particular DRU may be altered or expanded in response to, e.g., new types of devices accessing the DRU, new frequency regulations, new frequency use at geographical locations surrounding a location associated with the DRU, a relocation of the DRU, new BTS provisioning of the DRU, and the like. Further, the alteration or expansion may be accomplished without physically altering the network (e.g., replacing BTS equipment, installing new DRU equipment, etc.). Thus, an operator may easily and quickly adjust a frequency footprint of a network and efficiently respond to network demands. 
     These and other embodiments of the invention along with many of its advantages and features are described in more detail in conjunction with the text below and attached figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a high-level schematic diagram illustrating a wireless network system providing coverage to a geographical area according to an embodiment of the present invention; 
         FIG. 2  is a high-level schematic diagram illustrating a wireless network system providing coverage to a geographical area according to an embodiment of the present invention; 
         FIG. 3  is a high-level schematic diagram illustrating Physical Nodes in a Digital Access Unit (DAU) according to an embodiment of the present invention; 
         FIG. 4  is a high-level schematic diagram illustrating Physical Nodes in a Digital Remote Unit (DRU) according to an embodiment of the present invention; and 
         FIG. 5  is a high-level schematic diagram illustrating a DAU according to an embodiment of the present invention; and 
         FIG. 6  is a high-level schematic diagram illustrating a DRU according to an embodiment of the present invention; and 
         FIG. 7  is a high-level flowchart illustrating a method of identifying frequency-translation information according to an embodiment of the present invention; 
         FIG. 8  is a high-level flowchart illustrating a method of processing signals according to an embodiment of the present invention; 
         FIG. 9  is a high-level flowchart illustrating a-transmitting signals according to an embodiment of the present invention; 
         FIG. 10  is a high-level flowchart illustrating a-transmitting signals according to an embodiment of the present invention; 
         FIG. 11  is a high-level schematic diagram illustrating a wireless network system transmitting signals according to an embodiment of the present invention; 
         FIG. 12  is a high-level schematic diagram illustrating a wireless network system transmitting signals according to an embodiment of the present invention; 
         FIG. 13  is a high-level schematic diagram illustrating a wireless network system transmitting signals according to an embodiment of the present invention; 
         FIG. 14  is a high-level schematic diagram illustrating a computer system according to an embodiment of the present invention; and 
         FIG. 15  is a simplified flowchart illustrating a method of communicating with a wireless user device according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Wireless and mobile network operators face the continuing challenge of building networks that effectively manage high data-traffic growth rates. Mobility and an increased level of multimedia content for end users typically employs end-to-end network adaptations that support new services and the increased demand for broadband and flat-rate Internet access. One of the challenges faced by network operators is caused by the cost incurred of upgrading Base Transceiver Stations (BTS) or reconfiguring the geographical frequency plan of the network operators, such that frequency bands available to network users may be adjusted. Specifically, some BTS equipment is only able to transmit and receive signals within, e.g., one or a small number of frequency bands. Meanwhile, an operator may wish to subsequently transmit and receive signals, via antennas coupled to the BTS equipment, at different frequencies. A Distributed Antenna System (DAS) can make efficient use of the frequency-restricted hardware and can provide flexibility in repositioning the carrier frequencies and beacons of the infrastructure hardware. Applications of embodiments of the present invention may be suitable to be employed with distributed base stations, distributed antenna systems, distributed repeaters, mobile equipment and wireless terminals, portable wireless devices, and/or other wireless communication systems such as microwave and satellite communications. 
       FIGS. 1-2  are high-level schematic diagrams illustrating wireless network systems according to embodiments of the present invention. The configuration of these systems may allow the system to dynamically accommodate variations in wireless network loading and network carrier geographical reconfiguration and to further efficiently use base-station resources. 
       FIG. 1  is a diagram illustrating one wireless network system  100  that may provide coverage to a geographical area according to an embodiment of the present invention. System  100  may include a DAS, which may efficiently use base-station resources. One or more base stations  105  may be located in a central location and/or at a base-station hotel. One or more base stations  105  may include a plurality of independent outputs or radio resources, known as sectors  110 . Each sector  110  may be responsible for providing wireless resources (e.g., RF carrier signals, Long Term Evolution Resource Blocks, Code Division Multiple Access codes, Time Division Multiple Access time slots, etc.). The resources may include one or more resources that allow a wireless user mobile device to effectively and wirelessly send and receive communications over a network. Thus, the resources may include one or more resources, such as those listed above, that allow a signal to be encoded or decoded in a manner to prevent the signal from interfering with or being interfered with by other wireless signals. 
     Base stations  105  may include hardware constraints that limit the resources that it may provide. For example, sectors  110  of base station  105  may include a channel card, which constrains the sectors to only providing RF carrier signals within one or more specific frequency bands. 
     Each sector may be coupled to a software-configurable radio (SCR) (which may also be referred to as a software-defined radio (SDR)) based digital access unit (DAU)  115 , which may interface the sector  110  (and thus base station  105 ) with digital remote units (DRUs)  120 . The coupling may represent a physical coupling. For example, DAU  115  may be connected to sector  110  and/or DRU  120  via a cable, a link, fiber, a high-speed optical fiber link, an RF cable, an optical fiber, an Ethernet cable, microwave line of sight link, wireless link, satellite link, etc. In some instances, DAU  115  is connected to sector  110  via an RF cable. In some instances, DAU  115  is connected to one or more DRUs via an optical fiber or Ethernet cable. An associated sector  110  and DAU  115  may be located near each other or at a same location. DAU  115  may convert signals (e.g., to different frequency bands); control routing of data and/or signals between sectors and DRUs; and/or provision sector resources across DRUs. For example, a DAS network may include router tables (e.g., sent to DAUs  115  by server  130 ) that identify specific base stations  105  which are to communicate with and/or allocate resources to specific DRUs  120  and that further identify paths (e.g., via one or more DAUs  115 ) that will enable such communication and/or allocation. Router tables may further identify frequency translations to be performed at one or more locations along the path (e.g., at a DAU receiving and/or transmitting signals directly to a sector; and/or at an end-path DRU). That is, the router tables may identify path positions at which frequency translations should be performed and/or the frequency translations that should be performed at those locations. DAU  115  may generate and/or store traffic statistics, such as a number of communications, calls, network-access sessions, etc. between sector  110  and one or more DRUs  120 . 
     Each DAU  115  may be coupled to a plurality of digital remote units (DRU)  120 . The plurality of DRUs  120  may be coupled to the DAU  115  through, e.g., a daisy-chain (indirectly coupling a DAU with one or more DRUs) and/or star configuration (directly coupling a DAU to multiple DRUs).  FIG. 1  shows an example of daisy-chain configurations, wherein a DAU couples to a first DRU directly (e.g., direct connection from DAU  1  to DRU  1 ), a second DRU indirectly (e.g., indirect connection from DAU  1  to DRU  2  through DRU  1 ), a third DRU indirectly (e.g., indirect connection from DAU  1  to DRU  3  through DRUs  1  and  2 ), etc.  FIG. 1  also shows an example of star configurations, wherein a DAU couples to multiple DRUs directly (e.g., direct connections from DAU  1  to DRU  1  and DRU  23 ). 
     Each of the DRUs can provide coverage within a geographical area physically surrounding the DRU. DRUs  120  may be strategically located to efficiently provide combined coverage across a larger geographical area (a “cell”  125 ). For example, DRUs  120  may be located along a grid, and/or coverage areas associated with adjacent DRUs  120  may be barely overlapping. A network may include a plurality of independent cells that span a total coverage area. 
     Each cell  125  may be assigned to a sector  110 .  FIG. 1 , for example, shows an embodiment in which Sector  1  provides resources to Cells  1  and  8 , Sector  2  to Cells  2  and  10 , and Sector  3  to Cells  3  and  4 . An associated sector may provide each DRU with resources, such as RF carriers, resource blocks, etc. In one embodiment, each of a plurality of sectors  110  is associated with a set of “channels” or frequency ranges. The set of channels associated with each sector  110  may be different from a set of channels associated with other sectors  110  in base station  105 . In some instances, channels associated with one or more particular sectors  110  (and/or with one or more base stations  105 ) are fixed. A network may be configured such that neighboring cells  125  are associated with different channels (e.g., by being associated with different sectors  110 ), as shown in  FIG. 1 . This may allow channels to be reused across multiple cells without the risk of creating interference. 
     An uplink signal may be received at a DRU  120 , e.g., from a cell phone. The received signal may be within a “field” frequency band or channel (e.g., a particular RF band, such as the cellular band). The signal may be translated at the DRU  120  from the field frequency band to a baseband frequency band. The translated signal may be transmitted (e.g., via an optical fiber and through any intervening DAUs  115  and DRUs  120 ) to a DAU  115  coupled to a sector  110 , and the DAU  115  may further translate the signal from the baseband frequency band to a base-station frequency band (e.g., a same or different RF band, such as the PCS band). The DRU  120  may incorporate unique information associated with the DRU  120  into the signal that it transmits to the DAU  115 , such that it may be determined that the uplink data in the signal was received by the particular DRU  120 . 
     Conversely, a downlink signal may be received at a DAU  115  from a sector  110 . The downlink signal may be within the base-station frequency band (e.g., a particular RF band). The DAU  115  may translate the signal from the base-station frequency band to a baseband frequency band. The translated signal may be transmitted (e.g., via an optical fiber cable) to a target DRU  120 . Any other DAUs and/or DRUs in the path to the target DRU  120  are involved in passing the translated signal to the target DRU. At the target DRU  120 , the translated signal may be further translated from the baseband frequency band to the field frequency band (e.g., a same or different RF band). The signal may then be transmitted, e.g., to the cell phone. Thus, both DAU  115  and DRU  120  may include a multi-directional signal converter, such that, e.g., RF signals may be converted to optical signals and optical signals to RF signals. Disclosed DAS architecture enables various base-station signals to be transported simultaneously to and from multiple DRUs  120 . PEER ports may be used for interconnecting DAUs  115  and interconnecting DRUs  120 . 
     Thus, base station  105  may be involved in bi-directional communications with user devices. Additionally or alternatively, base station  105  may transmit uni-directional communications to user devices. For example, beacons may be sent from a sector  110 , via one or more DAUs  115  and one or more DRUs  120  to a user device. The beacon may include a signal including information as to which resources are provided by the sector  110  and thus, which resources are available to a user device within a geographic area associated with the DRU  120  transmitting the signal. For example, the beacon may identify a frequency band available for bi-directional signal communications in a geographical area associated with a DRU  120 . 
     Sector resources (e.g., available frequency bands) may be dynamically re:provisioned amongst DRUs  120 , e.g., via Flexible Simulcast. Each individual data packet (e.g., included in a downlink or uplink signal) may be provided with a unique identity to which DRU  120  it is associated with. The DAUs  115  may be interconnected, as shown in  FIG. 1 , to allow transport of data among multiple DAUs. This feature provides the unique flexibility in the DAS network to route signals between the sectors  110  and the individual DRUs  120 . 
     DAU communications, routing tables or functions, switches and/or frequency translations may be partly controlled by one or more servers  130 . The servers  130  may be in communication with one or more DAUs  115  and/or one or more DRUs  120 . For example, the servers  130  may be physically or wirelessly coupled to DAUs  115  and wirelessly coupled to DRUs  120 . Using information received from the one or more servers  130 , DAUs  115  can dynamically route signals and provision resources to desired DRUs. Thus, DRUs  120  may be dynamically assigned (e.g., via software control) to sectors  110 . 
     For example, DRUs  1 - 7  in Cell  1  may initially all be assigned to Sector  1 . ( FIG. 1 .) Subsequently, DRU  5  may be assigned to Sector  3  and DRU  6  may be assigned to Sector  4 . In such instances, signals to DRU  6  may pass from Sector  2  through DAU  2  and through DAU  1 . (Conversely, signals may pass from DRU  6  through DAU  1  and DAU  2  to Sector  2 .) Similarly, signals to DRU  5  may pass from Sector  3  through DAU  3 , through DAU  2  and through DAU  1 . In this manner, a sector may be indirectly connected with a larger subset of DRUs in a network or with all DRUs in a network. 
     Further, server  130  may communicate frequency-translation information to DAUs  115 . The information may identify, e.g., a frequency translation to occur at a DAU  115 , a DAU  115  that is to perform the frequency translation, a frequency band defining signals to be received at a DAU  115 , and/or a frequency band in which signals transmitted from the DAU  115  should reside. For example, in  FIG. 1 , server  130  may send information to DAU  1  that Sector  1  operates in the cellular band. DAU  1  may then configure a DAU physical node to translate signals received from Sector  1  from the cellular band to a baseband (for optical transmission), and to translate signals received from a DRU  1 - 7  from the baseband to the cellular band. 
     Server  130  may also communicate (e.g., via a wireless network) frequency-translation information to one or more DRUs  120 . The information may identify, e.g., a frequency translation to occur at a DRU  120 , a DRU  120  that is to perform the frequency translation, a frequency band defining signals to be received at a DRU  120 , and/or a frequency band in which signals transmitted from the DRU  120  should reside. For example, in  FIG. 1 , server  130  may wirelessly send information to DRU  1  that the DRU is to operate in the PCS band. DAU  1  may then configure a DRU physical node to receive PCS signals from user devices, translate user-device signals from the PCS band to a baseband (for optical transmission), and to translate signals received from DAU  1  from the baseband to the PCS band. 
     DAUs  115  may be configured to control a gain (in small increments over a wide range) of downlink and uplink signals transported between the DAU  115  and a base station sector  110  (or base stations) connected to that DAU  115 . This configuration allows a flexibility to simultaneously control the uplink and downlink connectivity of a path between a particular DRU (or a group of DRUs via the associated DAU or DAUs) and a particular base station sector. If, e.g., a DRU  120  is reassigned from one sector  110  to another  110 , DAUs  115  may gradually adjust the gain of signals to allow for a soft hand-off between the sectors (e.g., thereby preventing a call from being dropped). 
     DAUs  110  may be physically and/or virtually connected. For example, in one embodiment, DAUs  110  are connected via a cable or fiber (e.g., an optical fiber, an Ethernet cable, microwave line of sight link, wireless link, or satellite link). In one embodiment, a plurality of DAUs  110  are connected to a wireless network, which allows information to be transmitted from one DAU  110  to another DAU  110  and/or allows information to be transmitted from/to a plurality of DAUs  110 . 
     As shown in  FIG. 2 , a load-balancing system may include multiple base stations (or multiple base station hotels)  105 . Different base stations  105  may be associated with the same, or different frequency bands. Base stations  105  may be interconnected, e.g., to serve a geographic area. The interconnection may include a direct connection extending between the base stations (e.g., a cable) or an indirect connection (e.g., each base station connecting to a DAU, the DAUs being directly connected to each other). The greater number of base stations may increase the ability to add capacity for a given cell. Base stations  105  may represent independent wireless network operators and/or multiple standards (WCDMA, LTE, etc.), and/or they may represent provision of additional RF carriers. In some embodiments, base station signals are combined before they are connected to a DAU, as may be the case for a Neutral Host application. In one instance, as shown in  FIG. 2 , sectors from BTS  1  are directly coupled to the same DAUs and/or DRUs that are directly coupled to sectors to BTS N. In some other instances, one or more sectors from different BTS may be directly coupled to DAUs not shared by sectors of one or more other DAUs. Load balancing may or may not be applied differently to the different base stations  110 . For example, if DRU  5  is reassigned from Sector  1  to Sector  2  in BTS  1 , it may or may not be similarly reassigned in BTS N. 
     Referring to  FIG. 2  and by way of example, DAU  1  receives downlink signals from BTS  1 , Sector  1 . DAU  1  translates the signals (e.g., RF signals to optical signals) and an optical fiber cable transports the desired signals to DRU  1 . The optical cable transports all the optical signals to DRU  2 . The other DRUs in the daisy chain are involved in passing the optical signals onward to DRU  7 . DAU  1  is networked with DAU  2  to allow the downlink signals from BTS  1 , Sector  2  to be transported to all the DRUs in Cell  1 . DAU  1  receives downlink signals from BTS Sector N, Sector  1 . DAU  1  translates the signals (e.g., RF signals to optical signals) and the optical fiber cable transports the desired signals to DRU  1 . The optical cable transports all the optical signals to DRU  2 . The other DRUs in the daisy chain are involved in passing the optical signals onward to DRU  7 . The additional base stations provide the capability to add capacity for Cell  1 . 
     As described above, a DAS may thus include one or more frequency-transition points, at which a signal is translated from an initial frequency band to a translated frequency band. This may allow an RF signal to be translated into an optical signal to quickly and efficiently transport the signals. As described above, both uplink and downlink signals may undergo two translations: one at a DRU and one at a DAU. An uplink signal may be translated from a field frequency band to a baseband frequency band to a base-station frequency band, and a downlink signal may undergo an opposite series of translations. A Physical Node of a DAU or DRU may translate a signal. 
       FIG. 3  shows a high-level schematic diagram illustrating a physical node  350  in a DAU. As shown, physical node  350  may process both downlink and uplink signals, which may be possible due to the downlink and uplink signals operating at different frequencies. Physical node  350  may process a received downlink signal  300 ′ to produce a downlink output  340 ′ and may further process a received uplink signal  340  to produce an uplink output  300 . However, in some embodiments, distinct physical nodes  350  may process uplink and downlink signals. 
     A downlink signal  300 ′ may be received by the physical node  350  (e.g., from a sector  110  of a base station  105 ). The received signal may not be isolated, e.g., from uplink signals. Therefore, the received signal may be processed by diplexer  305 . Diplexer  305  may filter signal  300 ′/ 300  to isolate downlink signals  300 ′ for processing. The isolated downlink signal is transmitted to mixer  306 , which mixes the isolated downlink signal with a reference signal produced by oscillator  308 . By controlling spectral properties of the reference signal, the downlink signal may be translated to a desired frequency band (e.g., translating a downlink signal from a base-station frequency band to a baseband frequency band or to an intermediate frequency band). The combined signal may be converted from an analog signal to a digital signal by analog-to-digital converter  307 . The converted signal may be transmitted from DAU physical node  350  to a chip or field-programmable gate array (FPGA)  320 , which may process and/or route the signal. The FPGA may, e.g., route the signal and/or performing signal processing, such as digital filtering. The processed signal may be converted from an electrical signal to an optical signal by a small form factor pluggable unit (SFP)  330 . The optical signal may then be transmitted, e.g., via an optical fiber to a DAU  115  or DRU  120  coupled to a DAU hosting the physical node. 
     An uplink signal  340  (e.g., an optical signal) may also be received by SFP  330  (e.g., from a DRU  120  or DAU  115  coupled to the instant DAU via an optical fiber). SFP  330  may include a photo diode and may convert the uplink signal  340  from an optical signal to an electrical signal. The electrical signal may be processed (and/or routed) by a chip or FPGA  320  and then received by DAU physical node  350 . The digital-to-analog converter  309  may convert the received signal from a digital signal to an analog signal. The analog signal may be transmitted to mixer  310 , which mixes the isolated signal with a reference signal produced by oscillator  311 . By controlling spectral properties of the reference signal, the uplink signal may be translated to a desired frequency band (e.g., translating an uplink signal from a baseband frequency band to a base-station frequency band). The combined signal may be amplified by amplifier  312 , and optionally processed by a circulator  313 . The signal may then be transmitted through diplexer  305  to a base-station sector  110  (e.g., via an RF cable). 
       FIG. 4  shows a high-level schematic diagram illustrating a physical node  450  in a DRU. Again, physical node  450  may process both downlink and uplink signals, which may be possible due to the downlink and uplink signals operating at different frequencies. Physical node  450  may process a received downlink signal  400 ′ to produce a downlink output  440 ′ and may further process a received uplink signal  440  to produce an uplink output  400 . However, in some embodiments, distinct physical nodes  450  may process uplink and downlink signals. 
     A downlink signal  400 ′ may be received by SFP  430  (e.g., from another DRU  120  or from a DAU  115 ). The received signal may be an optical signal. SFP  430  may include a photo diode and may convert the downlink signal  400 ′ from an optical signal to an electrical signal. The electrical signal may be processed (and/or routed) by FPGA  420  and then received by the DRU physical node  450 . A digital-to-analog converter  407  may convert the received signal from a digital signal to an analog signal. The analog signal may be transmitted to mixer  406 , which mixes the isolated signal with a reference signal produced by oscillator  408 . By controlling spectral properties of the reference signal, the uplink signal may be translated to a desired frequency band (e.g., translating a downlink signal from a baseband frequency band to a field frequency band). The signal may then be transmitted through diplexer  405  to an antenna (e.g., via an RF cable) to wirelessly transmit the signal to a user device (e.g., a cellular phone). 
     An uplink signal  440  may also be received by physical node  450  (e.g., from an antenna wirelessly receiving signals from a user device). The received signal may not be isolated, e.g., from uplink signals. Therefore, the received signal may be processed by diplexer  405 . Diplexer  405  may filter signal  440 ′/ 440  to isolate uplink signals  440  for processing. An amplifier  412  may process the isolated uplink signal The amplified signal may be transmitted to mixer  410 , which mixes the isolated uplink signal with a reference signal produced by oscillator  411 . By controlling spectral properties of the reference signal, the uplink signal may be translated to a desired frequency band (e.g., translating an uplink signal from a field frequency band to a baseband frequency band). The combined signal may be converted from an analog signal to a digital signal by analog-to-digital converter  409 . The converted signal may be transmitted from the DRU physical node  450 , e.g., to FPGA  420 , which may process and/or route the signal. The processed signal may be converted from an electrical signal to an optical signal by an SFP  430 . The optical signal may then be transmitted, e.g., via an optical fiber to a DAU  115  or DRU  120  coupled to a DRU hosting the physical node. 
     Thus, DAU physical node  350  and DRU physical node  450  may each include one or more frequency translators. In the depicted embodiments, the frequency translators included a mixer (e.g., mixer  306 ,  310 ,  406  or  410 ) and an oscillator (oscillator  308 ,  311 ,  408  or  411 ). In  FIGS. 3 and 4 , separate frequency translators were provided for the uplink and downlink processing streams and generally had reciprocal functions across the two streams. 
     As described, the frequency translators in the DAU physical node  350  may serve to convert signals between a base-station frequency band and a baseband frequency or intermediate frequency band. The frequency translators in the DRU physical node  450  may serve to convert signals between a baseband frequency band and a field frequency band. The base-sector and field frequency bands may include RF bands (e.g., the 800 band, cellular band, PCS band, 700 MHz band, 1.49 GHz band, AWS band, BRS/EBS band, etc.). In some instances, the base-station frequency band and the field frequency band associated with any given path are the same, and in some instances they are different. As illustrated in  FIG. 4 , multiple DRU physical nodes may be present in a DRU, enabling transmission at multiple bands from a single DRU. 
     A system may be configured such that an operator may control frequency translations occurring at a DAU and/or DRU. For example, an operator may identify a frequency translation via a computer coupled via a server that wirelessly communicates with the DAU and/or DRU. In one instance, one or more frequency translators are configurable, such that, e.g., the translation occurring at a given frequency translator may be adjusted by an operator. Thus, for example, an output of an oscillator (oscillator  308 ,  311 ,  408  or  411 ) may be adjustable and not fixed. In one instance, which physical nodes are active is configurable. For example, each physical node may be configured to perform particular frequency translations, and one or more select nodes may be activated based on frequency-translation objectives. 
     As illustrated in  FIG. 3 , the signal presented to the DAU from the BTS is illustrated as downlink signal  300 ′, which is received at the DAU physical node  350 . After frequency translation using mixer  306  and A/D conversion using ADC  307 , the digital signal is presented to the FPGA  320 . The signal transmitted to the DRU is illustrated as downlink output  340 ′. At the DRU, the received signal is illustrates as received downlink signal  400 ′. After processing by FPGA  420 , the DRU physical node  450  converts the signal to an analog signal using DAC  407  and then uses mixer  406  to frequency translate the signal to the desired frequency band (e.g., 1900 MHz as illustrated in  FIG. 12 ). Thus, using the mixers illustrated in  FIGS. 3 and 4 , it is possible to frequency translate the signal from a first frequency band used by the BTS (e.g., 850 MHz) to a second frequency band used by the DRU (e.g., 1900 MHz, 2100 MHz, or the like). Frequency translation for the uplink signals (e.g., from 1900 MHz to 850 MHz) is provided using mixers  410  (e.g., translation from 1900 MHz to an intermediate frequency or baseband frequency) and  310  (e.g., translation from the intermediate frequency or baseband frequency to 850 MHz) as will be evident to one of skill in the art. 
       FIG. 5  illustrates components of a DAU  500  according to an embodiment of the invention. DAU  500  may include one or more FPGAs  505  (e.g., a router), which may process signals and/or direct traffic between various ports (e.g., LAN Ports, PEER Ports and the External Ports). DAU  500  may include one or more ports  515  and  520  that may, e.g., enable DAU to connect to the Internet and/or a Host Unit or a server  525  (e.g., Server  130 ). Server  525  may at least partly configure the DAU, control frequency translations of the DAU (e.g., by activating select physical nodes  510  or altering frequency translations occurring at physical nodes  510 ) and/or control the routing of the signals between various FPGA ports. Server  525  may be, e.g., at least partly controlled by a remote operational control  530  (e.g., to set re-assignment conditions, identify assignments, store assignments, input network configurations, receive/collect/analyze network usage, etc.). 
     DAU  500  may include one or more physical nodes  510 . Physical nodes  510  may include configurations and/or operations similar to those described with respect to physical node  350  shown in  FIG. 3 . Different physical nodes  510  may be used for different operators, different frequency bands, different frequency translations, different channels, different base stations, etc. As described above, a physical node  510  may process both downlink and uplink signals (e.g., combining them via a duplexer) and keep the signals separate. Inclusion of multiple physical nodes  510  in a single DAU  500  may allow a DAU to process multiple types of signals simultaneously and/or dynamically adjust the types of signals that it is configured to process. 
     The physical nodes  510  may be coupled to FPGA  505  by one or more first-end ports  535 . Each physical node  510  may include one, two, or more ports, such as first-end ports, each of which may allow signals (e.g., RF signals and/or signals from/to a sector) to be received by or transmitted from DAU  500 . In some embodiments, a plurality of physical nodes  510  each includes a Downlink port  512  and an Uplink port  513 . In some embodiments, a physical node  510  may also include an additional Uplink port, e.g., to handle a diversity connection. Output ports (e.g., Downlink port  512  and Uplink port  513 ) may be coupled to one or more ports (e.g., RF pots) of a base station. Thus, DAU  500  may be physically coupled to a base station. 
     FPGA  505  may include one or more second-end ports  540 , which may couple DAU  500  to one or more DRUs or DAUs (e.g., via an optical fiber, Ethernet cable, etc.). The second-end ports  540  may include LAN or PEER ports. Second-end ports  540  may be configured to send and/or receive signals, such as digital and/or optical signals. In one embodiment, the second-end ports  540  are connected (e.g., via an optical fiber) to a network of DAUs and DRUs. The network connection can also use copper interconnections such as CAT 5 or 6 cabling, or other suitable interconnection equipment. 
     FPGA  505  may encode signals for transportation over the optical link as well as decodes the optical signals from the optical link. The DAU can monitor traffic on the various ports and either route this information to a server or store this information locally. 
     The DAU may be connected to the internet network, e.g., using IP. An Ethernet port  520  may be used to communicate between the Host Unit  525  and the DAU  500 . The DRU may connect directly to the Remote Operational Control center  530  via the Ethernet port  520 . 
       FIG. 6  illustrates components of a DRU  600  according to an embodiment of the invention. DRU  600  may include one or more FPGAs  605  (e.g., a router), which may process signals and/or route signals. The FPGA may direct data between select ports (e.g., between LAN and PEER ports to the selected External ports). DRU may include a network port  610 , which may allow DRU  600  to couple (via an Ethernet Switch  615 ) to a (e.g., wireless) network. Through the network, DRU  600  may then be able to connect to a computer  620 . Thus, a remote connection may be established with DRU  600 . 
     FPGA  605  may be configured by a server, such as server  130 , server  525 , a server connected to one or more DAUs, and/or any other server. The FPGA  605  may direct data streams (e.g., the downlink data stream from the LAN and PEER ports to the selected External D ports and the uplink data stream from the External U ports to the selected LAN and PEER ports). 
     Network port  610  may be used as a Wireless access point for connection to the Internet. Thus, a remote computer wireless access point may be able to connect to the Internet. The Internet connection may, e.g., established at the DAU and Internet traffic may be overlaid with the data transport between the DRUs Physical Nodes and the DAU Physical Nodes. 
     DRU  600  may include one or more physical nodes  625 , which may be connected to FPGA  605  (e.g., via external ports). Physical nodes  625  may include configurations and/or operations similar to those described with respect to physical node  450  shown in  FIG. 4 . Different physical nodes can be used for different operators, different frequency bands, different channels, different base stations, etc. Inclusion of multiple physical nodes  625  in a single DRU  600  may allow a DRU to process multiple types of signals simultaneously and/or dynamically adjust the types of signals that it is configured to process. 
     Each physical node  625  may include one, two, or more ports, such as first-end ports  630 , each of which may allow signals (e.g., RF signals and/or signals from mobile devices) to be received by or transmitted from DRU  500 . In some embodiments, a plurality of physical nodes  625  each include one or more ports configured to send/receive signals (e.g., RF signals) from/to DRU  600 . The ports may include, e.g., a Downlink port  627  and an Uplink port  628 . In some embodiments, an additional Uplink port exists for handling a diversity connection. Physical node ports (e.g., Downlink output port  627  and Uplink output port  628 ) may be connected to one or more antennas (e.g., RF antennas), such that signals may be received from and/or transmitted to, e.g., mobile wireless devices. 
     FPGA  605  may include one or more second-end ports  635 , which may couple DRU  600  to one or more DAUs or DRUs. Second-end ports  635  may include LAN or PEER ports, which may (e.g., physically) couple DRU  600  to one or more DAUs or DRUs via an optical fiber. 
       FIG. 7  illustrates a method  700  of configuring a communication system to dynamically adjust frequency bands in operation according to some embodiments of the invention. At  705 , a frequency band for communication signals is identified. The frequency band may be associated with particular types of communications (e.g., bi-directional uplink/downlink communications or uni-directional beacon communications). The frequency band may be associated with one or more particular DRUs, one or more particular base stations or base-station sectors, and/or one or more geographic coverage areas. The frequency band may be identified based on input received from an operator. For example, the operator may have entered the input into a computer in communication with a server  130 , e.g., based on its connection with the Internet or a direct physical connection between the computer and the server  130 . The input may have included, one or more lower bounds and one or more upper bounds of a frequency range or a frequency-band shorthand identifying a well-known frequency band (e.g., the 800 band, cellular band, PCS band 700 MHz band, 1.49 GHz band, AWS band, BRS/EBS band). In some instances, the frequency band is at least partly or completely non-overlapping with a frequency in which a base-station associated with the communication operates. 
     At  710 , one or more end-paths DRU is identified. The end-path DRUs may include all DRUs communicating with a base station, all DRUs communicating with a base-station sector, a particular DRU (e.g., identified by an operator via input to a computer), a DRU associated with a geographical coverage area (e.g., identified by an operator via input to a computer), etc. 
     At  715 , frequency-translation information is sent to the DRU. The frequency-translation information may include an identification of physical nodes that should be activated/de-activated at the DRU, a frequency translation that the DRU should perform, a field frequency band, etc. The frequency-translation information may be based on the frequency band identified at  705  and a baseband frequency band. In some instances, the frequency-translation information is further based on a base-station frequency band. The frequency-translation information may be wirelessly sent to the DRU. 
       FIG. 8  illustrates a method  800  of configuring a communication system to dynamically adjust frequency bands in operation according to some embodiments of the invention. At  805 , frequency-translation information (e.g., such as frequency-translation information sent at  715  of method  700 ) is received at a DRU. The information may be received over a wireless network. 
     At  810 , select physical nodes are activated based on the information. In some instances, the information may identify which nodes to activate. In some instances, the DRU determines which nodes to activate based on the information. For example, the information may identify a frequency translation that is to occur at the DRU, and the DRU may identify physical-node translating capabilities and determine which physical nodes may accomplish the translation objectives. Frequency translations occurring at particular physical nodes may or may not be adjusted based on the information. 
     At  815 , signals are processed through the activated physical nodes. The signals may include, e.g., downlink signals, uplink signals and/or beacon signals. Different types of signals may undergo different processing and may be processed by different physical nodes. 
       FIG. 9  is a simplified flow chart illustrating a method  900  of configuring a communication system to dynamically adjust frequency bands in operation according to some embodiments of the invention. At  905 , a frequency translation to be performed at an end-path DRU is identified. For example, an operator may enter input identifying a frequency band to be associated with a particular DRU, a particular geographic coverage area associated with a DRU, a particular base-station sector or a particular base station. The input may include an indication of a well-known band (e.g., the 800 band, cellular band, PCS band 700 MHz band, 1.49 GHz band, AWS band, BRS/EBS band), bounds on a range, etc. The frequency translation may be identified based on a known baseband frequency band, which will define signals received by the DRU. The frequency translation may be specific to a particular type of communication (e.g., uplink/downlink communications, bi-directional communications, communications associated with a particular operator, etc.). This selectivity may be identified by operator input (e.g., specifying that the frequency translation is only to be performed for bi-directional communications involving a DRU) or may be identified by a system (e.g., determining that frequency-band selections entered by a particular operator would not affect frequency translations of communications associated with other operators). 
     At  910 , the end-path DRU is configured. For example, the DRU may receive information about the frequency translation identified at  905 . The DRU may activate select physical nodes and/or adjust frequency translations occurring with select physical nodes (e.g., by adjusting reference signals contributing to mixing). In some instances, uplink and downlink processing streams of the DRU are configured in a reciprocal manner, such that a frequency translation occurring in the uplink processing stream is the opposite of that occurring in the downlink-processing stream. 
     Method  900  continues with the receipt of uplink signals ( 915 ) and/or downlink signals ( 940 ). At  915 , an uplink signal is received (e.g., via an RF cable) from an antenna at the end-path DRU. At  920 , the uplink signal is converted from a field frequency band to a baseband frequency band. Proper conversion may depend upon the configuration of the DRU performed at  910 . The uplink signal may be further processed (e.g., to convert it to an optical signal). At  925 , the signal is transmitted (e.g., via an optical fiber) to a destination DAU (e.g., a DAU directly coupled to a destination base station). The transmission may involve transmitting the signal through one or more intermediate DRUs and/or one or more intermediate DAUs. At  930 , the signal is converted from the baseband frequency band to a base-station frequency bad at the end-path DAU. The signal may be further processed (e.g., to convert it from an optical signal). At  935 , the signal is transmitted (e.g., via an RF cable) to a base station. 
     At  940 , a downlink signal is received (e.g., via an RF cable) from a base station at a DAU (e.g., directly coupled to the base station). At  945 , the downlink signal is converted from a base-station frequency band to a baseband frequency band. The downlink signal may be further processed (e.g., to convert it to an optical signal). At  950 , the signal is transmitted (e.g., via an optical fiber) to an end-path DRU (e.g., a DRU coupled to an antenna that will transmit the signal to a user device). The transmission may involve transmitting the signal through one or more intermediate DAUs and/or one or more intermediate DRUs. At  955 , the signal is converted from the baseband frequency band to the field frequency band. The conversion (and thus the field frequency band) may depend upon the configuration of the DRU performed at  910 . The signal may be further processed (e.g., to convert it from an optical signal). At  960 , the signal is transmitted (e.g., via an RF cable) to an antenna, which may then transmit the signal to a user device. 
       FIG. 10  is a simplified flow chart illustrating a method  1000  of configuring a communication system to dynamically adjust frequency bands in operation according to some embodiments of the invention. At  1005 , one or more frequency translations to be performed at an end-path are identified. For example, an operator may enter input identifying one or more frequency bands to be associated with a particular DRU, a particular geographic coverage area associated with a DRU, a particular base-station sector or a particular base station. The input may include an indication of one or more well-known bands (e.g., the 800 band, cellular band, PCS band 700 MHz band, 1.49 GHz band, AWS band, BRS/EBS band), bounds on a range, etc. The frequency translations may be identified based on a known baseband frequency band, which will define signals received by the DRU. The frequency translation may be specific to a particular type of communication (e.g., beacon communications, uni-directional communications, communications associated with a particular operator, etc.). This selectivity may be identified by operator input (e.g., specifying that the frequency translation is only to be performed for uni-directional communications involving a DRU) or may be identified by a system (e.g., determining that frequency-band selections entered by a particular operator would not affect frequency translations of communications associated with other operators). 
     At  1010 , the end-path DRU is configured. For example, the DRU may receive information about the one or more frequency translations identified at  1005 . The DRU may activate select physical nodes and/or adjust frequency translations occurring with select physical nodes (e.g., by adjusting reference signals contributing to mixing). 
     At  1015 , a beacon signal is received (e.g., via an RF cable) from a base station at a DAU (e.g., directly coupled to the base station). At  1020 , the beacon signal is converted from a base-station frequency band to a baseband frequency band. The downlink signal may be further processed (e.g., to convert it to an optical signal). At  1025 , the signal is transmitted (e.g., via an optical fiber) to an end-path DRU (e.g., a DRU coupled to an antenna that will transmit the signal to a user device). The transmission may involve transmitting the signal through one or more intermediate DAUs and/or one or more intermediate DRUs. At  1030 , the signal is converted from the baseband frequency band to a field frequency band. The conversion (and thus the field frequency band) may depend upon the configuration of the DRU performed at  1010 . The signal may be further processed (e.g., to convert it from an optical signal). At  1035 , the signal is transmitted (e.g., via an RF cable) to an antenna, which may then transmit the signal to a user device. 
     In some embodiments, signals are transmitted and received at a plurality of frequency bands, even if, e.g., the signals are associated with a same BTS, sector or operator. For example, an antenna coupled to a single DRU may transmit different beacons (e.g., originating at a same sector) within different frequency bands (e.g., the cellular band and the PCS band). This may allow user devices scanning for signals within each range to detect the beacons. The beacons may communicate which frequency bands would support transmission of uplink and downlink signals to and from the user device. As another example, an antenna coupled to a single DRU may transmit at least some beacons in a first frequency band (e.g., the PCS band) and may receive uplink signals and transmit downlink signals in another frequency band (e.g., the PCS band). As another example, one or more frequency bands associated with beacon signals transmitted by an antenna coupled to a first DRU may be different from one or more frequency bands associated with beacon signals transmitted by an antenna coupled to a second DRU, e.g., even if the signals are associated with a same sector or BTS. As another example, one or more frequency bands associated with uplink/downlink signals received/transmitted by an antenna coupled to a first DRU may be different from one or more frequency bands associated with uplink/downlink signals received/transmitted by an antenna coupled to a second DRU, e.g., even if the signals are associated with a same sector or BTS. Further, an operator may be able to dynamically adjust frequency bands for transmitting and/or receiving select types of signals without needing to manipulate any hardware (e.g., instead interacting with a network-connected graphical user interface to identify the virtual adjustment). 
     It should be appreciated that the specific steps illustrated in  FIGS. 7-10  provide particular methods according to an embodiment of the present invention. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments of the present invention may perform the steps outlined above in a different order. Moreover, the individual steps illustrated in  FIGS. 7-10  may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. 
     Methods shown in  FIGS. 7-10  or elsewhere described may be performed by a variety of devices or components. For example, some processes may be performed solely or partly by one or more DRUs. Some processes may be performed solely or partly by a remote computer, e.g., coupled to one or more DAUs. In some embodiments, shown or described process may be performed by multiple devices or components (e.g., by one or more DAUs, one and one or more DRUs, by a DRU and a remote server, by a DAU and a remote server, etc.). 
       FIG. 11  is a high-level schematic diagram illustrating a wireless network system transmitting signals according to an embodiment of the present invention. For example, the depicted frequency translation may be performed in a Virtualized DAS Network. BTS  105  is connected to DAU  115  (e.g., via an RF cable). BTS  105  operates in a base-station band, which in this instance, is shown as being a Cellular Band at 850 MHz as illustrated by signals  1100 . The signals transmitted from BTS  105  include an Uplink and Downlink carrier as well as one or more Beacons. DAU  115  translates the signals to baseband or an intermediate frequency prior to transportation (e.g., over optical fibers) to DRUs  120  (DRU  1  and DRU  2 ). As described above, the path from BTS  105  to each DRU  120  may include one or more intermediate DAUs  115  and/or one or more intermediate DRUs  120  not shown in  FIG. 11 . 
     At DRUs  1  and  2 , signals received from DAU  115  are translated from the baseband or intermediate frequency band to one or more frequency bands as illustrated by signals  1150 . In the depicted embodiment, the uplink and downlink signals are in a same band as illustrated by signals  1100  and  1150 , but at least some Beacons are transitioned between bands. Further, while all beacons in signals  1100  resided within a same band, beacons in signals  1150  reside in different bands. The beacons can be transmitted at whatever desired frequency the operator requests. This provides the DAS infrastructure with the flexibility of repositioning beacons at frequencies different from those in the base-station frequency band, and further allows an operator to transmit beacons originating from a single base-station frequency band in multiple different bands. These features may enable legacy BTS equipment with limited Transceiver Cards to operate in geographical environments where the cellular infrastructure may use multiple carrier frequencies. 
     An example of a scenario where this functionality can be utilized is when a user enters the geographic space of DRU  120  but the user is communicating in the PCS Band. The Beacons in the PCS band will tell the customers phone to shift the call to the cellular band so that a soft hand-off can be established. This feature is enabled despite the fact that the BTS  105  does not have a Transceiver operating in the PCS Band. The DAS Network has provided this capability by frequency translating the Beacons. 
       FIG. 12  illustrates a high-level schematic diagram illustrating a wireless network system transmitting signals according to an embodiment of the present invention. The depicted frequency translation may be performed in a Virtualized DAS Network. BTS  105  is connected to a DAU  115  (e.g., via an RF cable). BTS  105  operates in a base-station frequency band, which is depicted as being (for an example) the Cellular Band. Base-station signals  1200  may include an Uplink and Downlink carrier as well as one or more beacons. In some implementations, multiple BTSs can be connected to one DAU, which provides multiple RF inputs suitable for connection to multiple BTSs operating at different frequency bands. An example of such an implementation is illustrated by optional BTS  107 , which, in addition to BTS  105 , is coupled to DAU  115 . The use of multiple BTSs, which can be operated by different operators, enables the signals from multiple operators to be transported by the systems described herein. 
     DAU  115  translates the signals from the base-station frequency band to a baseband frequency band and transmits the signals (e.g., over an optical fiber) to one or more DRUs  120 . As described above, the signals may be transmitted through one or more intermediate DAUs and/or one or more intermediate DRUs before arriving at destination DRU  1  or DRU  2 . Each DRU  120  may translate the received signals from the baseband frequency band to one or more field frequency bands. The field-frequency-band signals may then be transmitted via an antenna to user devices. 
     As in  FIG. 11 , the DRU-translated signals  1250  include multiple beacons in different frequency bands as compared to their initial base-station frequency band. Further, in this illustration, uplink and downlink signals are also translated into a frequency band (the PCS band) different than the base-station frequency band (the cellular band). Thus, an operator may use legacy BTS equipment with limited Transceiver Cards and may functionally operate in variety of frequency bands outside the limits of the Transceiver Cards. This functionality may be utilized, e.g., when a customer enters the geographic space of DRU 1  and the customer is communicating in the PCS Band. The customer can be easily handed-off to BTS  105  since it is virtualized as a PCS BTS. This feature is enabled despite the fact that the BTS  105  does not have a Transceiver operating in the PCS Band. The DAS Network has provided this capability by frequency translating the Traffic Channels and Beacons. 
       FIGS. 11-12  show embodiments in which the same translations are performed at DRU  1  and DRU  2 . In other embodiments, different translations may be performed at different DRUs. 
     Referring to  FIG. 12 , in an embodiment, a three-sector Cellular BTS may be virtualized as a three-channel Cellular BTS. The DAS Network facilitates the virtualization of the BTS  105  using independent frequency translation of the sectored Carriers. This feature can be extended to a larger order sectored BTS. The sectors have independent Transceiver cards but operate at the same carrier frequency. Traditionally BTS  105  would have geographically separated the Sectors using directional antennas. In an embodiment, the DAS Network virtualizes the BTS by frequency translating the individual sectors onto distinct carrier frequencies as illustrated. 
     As described herein, embodiments enable the use of legacy base stations operating at a first frequency by translating the first frequency to a second frequency suitable for communication through equipment operating at the second frequency. As illustrated in  FIG. 12 , legacy BTS  105  is operating in the cellular band at 850 MHz, only providing RF outputs in this band. As new frequencies have been made available for communications traffic, it is desirable to utilize the legacy BTS, but to communicate in bands other than the cellular band at 850 MHz. BTS  105  is transmitting both uplink and downlink carriers in the 850 MHz band as well as beacons  1 - 4  in this same band. DRU  1   120  is transmitting uplink and downlink carriers in the 1900 PCS band as illustrated by translated signals  1250 . In order to notify mobile devices in the vicinity of DRU  1  that DRU  1  is operating at 1900 MHz, beacons  4 ,  1 - 2 , and  3  are provided in the cellular band at 750 MHZ, the cellular band at 850 MHz, and the AWS band at 2100 MHz, respectively. Accordingly, mobile devices operating in these bands on adjacent BTSs or DRUs can utilize the beacons to determine that a transfer should be made to operating at 1900 MHz in communication with DRU  1 . Beacons can also be provided in the transmission band (e.g., 1900 MHz). 
     Thus, as illustrated in  FIG. 12 , DAU  115  and DRU  1   120  are utilized to perform frequency translation to the second frequency (i.e., the PCS band at 1900 MHz) and to place beacons in the various bands as appropriate. As illustrated, the uplink carrier and the downlink carriers are frequency translated as well as the beacons. It should be noted that although  FIG. 12  illustrates DRU  1  as operating at a single translated frequency (i.e., the PCS band at 1900 MHz), this single frequency operation is not required by embodiments of the present invention. Rather, DRU  1  could be in communication with additional BTSs through DAU  115 , enabling operation at additional bands (e.g., up to or more than 4 bands). 
     Embodiments described herein may provide a high degree of flexibility to manage, control, enhance and facilitate radio resource efficiency, usage and overall performance of the distributed wireless network. This advanced system architecture enables specialized applications and enhancements including, but not limited to, flexible simulcast, automatic traffic load-balancing, network and radio resource optimization, network calibration, autonomous/assisted commissioning, carrier pooling, automatic frequency selection, radio frequency carrier and beacon placement, traffic monitoring, and/or traffic tagging. Embodiments of the present invention can also serve multiple operators, multi-mode radios (modulation-independent) and multiple frequency bands per operator to increase the efficiency and traffic capacity of the operators&#39; wireless networks. 
       FIG. 13  is a high-level schematic diagram illustrating a wireless network system transmitting signals according to an embodiment of the present invention. As illustrated in  FIG. 13 , a three sector base station  105  is used with three sectors that transmit at the same frequency (i.e., 850 MHz) as illustrated by signals  1340 . All sectors operate in the same frequency band, but include different content. By converting the frequencies of the signals from the sectors using the DAUs (e.g., DAU 1 ), the carrier frequencies of the signals transmitted by DRU  1   120  can be translated to different frequencies. As illustrated by signals  1350 , three downlink carriers F 1 , F 2 , and F 3  are transmitted from DRU 1  in the 850 MHz cellular band, whereas a single uplink carrier at F 1  was transmitted by sectors  1 - 3 . Similar frequency translations for the uplink carriers (e.g., F 1 , F 2 , and F 3  translated to F 1 ) can be performed. In some implementations, digital signal processing in the FPGA of the DRU could be used to perform the illustrated frequency translation rather than by varying the oscillators in the DRU. 
       FIG. 14  is a high level schematic diagram illustrating a computer system  1400  including instructions to perform any one or more of the methodologies described herein. One or more of the above-described components (e.g., DAU  115 , DRU  120 , server  130 , server  525 , computer  620 , etc.) may include part or all of computer system  1400 . System  1400  may also perform all or part of one or more methods described herein.  FIG. 14  is meant only to provide a generalized illustration of various components, any or all of which may be utilized as appropriate.  FIG. 14 , therefore, broadly illustrates how individual system elements may be implemented in a relatively separated or relatively more integrated manner. 
     The computer system  1400  is shown comprising hardware elements that can be electrically coupled via a bus  1405  (or may otherwise be in communication, as appropriate). The hardware elements may include one or more processors  1410 , including without limitation one or more general-purpose processors and/or one or more special-purpose processors (such as digital signal processing chips, graphics acceleration processors, and/or the like); one or more input devices  1415 , which can include without limitation a mouse, a keyboard and/or the like; and one or more output devices  1420 , which can include without limitation a display device, a printer and/or the like. 
     The computer system  1400  may further include (and/or be in communication with) one or more storage devices  1425 , which can comprise, without limitation, local and/or network accessible storage, and/or can include, without limitation, a disk drive, a drive array, an optical storage device, solid-state storage device such as a random access memory (“RAM”) and/or a read-only memory (“ROM”), which can be programmable, flash-updateable and/or the like. Such storage devices may be configured to implement any appropriate data stores, including without limitation, various file systems, database structures, and/or the like. 
     The computer system  1400  might also include a communications subsystem  1430 , which can include without limitation a modem, a network card (wireless or wired), an infrared communication device, a wireless communication device and/or chipset (such as a Bluetooth™ device, an 802.11 device, a WiFi device, a WiMax device, cellular communication facilities, etc.), and/or the like. The communications subsystem  1430  may permit data to be exchanged with a network (such as the network described below, to name one example), other computer systems, and/or any other devices described herein. In many embodiments, the computer system  1400  will further comprise a working memory  1435 , which can include a RAM or ROM device, as described above. 
     The computer system  1400  also can comprise software elements, shown as being currently located within the working memory  1435 , including an operating system  1440 , device drivers, executable libraries, and/or other code, such as one or more application programs  1445 , which may comprise computer programs provided by various embodiments, and/or may be designed to implement methods, and/or configure systems, provided by other embodiments, as described herein. Merely by way of example, one or more procedures described with respect to the method(s) discussed above might be implemented as code and/or instructions executable by a computer (and/or a processor within a computer); in an aspect, then, such code and/or instructions can be used to configure and/or adapt a general purpose computer (or other device) to perform one or more operations in accordance with the described methods. 
     A set of these instructions and/or code might be stored on a computer-readable storage medium, such as the storage device(s)  1425  described above. In some cases, the storage medium might be incorporated within a computer system, such as the system  1400 . In other embodiments, the storage medium might be separate from a computer system (e.g., a removable medium, such as a compact disc), and/or provided in an installation package, such that the storage medium can be used to program, configure and/or adapt a general purpose computer with the instructions/code stored thereon. These instructions might take the form of executable code, which is executable by the computer system  1400  and/or might take the form of source and/or installable code, which, upon compilation and/or installation on the computer system  1400  (e.g., using any of a variety of generally available compilers, installation programs, compression/decompression utilities, etc.) then takes the form of executable code. 
     It will be apparent to those skilled in the art that substantial variations may be made in accordance with specific requirements. For example, customized hardware might also be used, and/or particular elements might be implemented in hardware, software (including portable software, such as applets, etc.), or both. Further, connection to other computing devices such as network input/output devices may be employed. 
     As mentioned above, in one aspect, some embodiments may employ a computer system (such as the computer system  1400 ) to perform methods in accordance with various embodiments of the invention. According to a set of embodiments, some or all of the procedures of such methods are performed by the computer system  1400  in response to processor  1410  executing one or more sequences of one or more instructions (which might be incorporated into the operating system  1440  and/or other code, such as an application program  1445 ) contained in the working memory  1435 . Such instructions may be read into the working memory  1435  from another computer-readable medium, such as one or more of the storage device(s)  1425 . Merely by way of example, execution of the sequences of instructions contained in the working memory  1435  might cause the processor(s)  1410  to perform one or more procedures of the methods described herein. 
     The terms “machine-readable medium” and “computer-readable medium,” as used herein, refer to any medium that participates in providing data that causes a machine to operate in a specific fashion. Computer readable medium and storage medium do not refer to transitory propagating signals. In an embodiment implemented using the computer system  1400 , various computer-readable media might be involved in providing instructions/code to processor(s)  1410  for execution and/or might be used to store such instructions/code. In many implementations, a computer-readable medium is a physical and/or tangible storage medium. Such a medium may take the form of a non-volatile media or volatile media. Non-volatile media include, for example, optical and/or magnetic disks, such as the storage device(s)  1425 . Volatile media include, without limitation, dynamic memory, such as the working memory  1335 . 
     Common forms of physical and/or tangible computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, punchcards, papertape, any other physical medium with patterns of holes, a RAM, a PROM, EPROM, a FLASH-EPROM, any other memory chip or cartridge, etc. 
       FIG. 15  is a simplified flowchart illustrating a method of communicating with a wireless user device according to an embodiment of the present invention. The method  1500  includes receiving an analog RF signal from a BTS at a DAU ( 1505 ). The analog RF signal includes a downlink carrier associated with a first frequency band. As an example, the first frequency band could be a cellular band at 850 MHz, which is the frequency band at which the BTS operates. In other embodiments, the BTS could operate in another frequency band, for example, 700 MHz, 900 MHz, 1900 MHz, or the like. 
     The method also includes converting the analog RF signal to a digital signal using one or more elements of the DAU ( 1510 ). The digital signal is then transported, for example, over a fiber connection, to a DRU ( 1515 ). The digital signal is converted to an analog signal and frequency converted to a second frequency band ( 1520 ). The downlink signal, now at the second frequency band (i.e., the analog signal in the second frequency band), is broadcast using an antenna coupled to the DRU ( 1525 ). Uplink signals follow an analogous path in the upstream direction. 
     In some embodiments, the beacons that were present in the first frequency band received from the BTS are frequency translated into other frequency bands, which can be different from the second frequency band. 
     It should be appreciated that the specific steps illustrated in  FIG. 15  provide a particular method of communicating with a wireless user device according to an embodiment of the present invention. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments of the present invention may perform the steps outlined above in a different order. Moreover, the individual steps illustrated in  FIG. 15  may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. 
     According to an embodiment of the present invention, a method for communicating with wireless user devices is provided. The method includes receiving an input from an operator identifying a field frequency band and virtually configuring a DRU to convert signals to the field frequency band. As an example, virtually configuring the DRU can include identifying physical nodes of the DRU to process signals. Additionally, the input may also include a type of signal to be converted. Moreover, the input can indicate a particular DRU, of a plurality of DRUs, that is to be virtually configured. 
     The embodiments described herein may be implemented in an operating environment comprising software installed on any programmable device, in hardware, or in a combination of software and hardware. Although embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. 
     It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.