Patent Publication Number: US-11665069-B2

Title: Power management for distributed communication systems, and related components, systems, and methods

Description:
PRIORITY APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/731,773, filed Dec. 31, 2019, which is a continuation of U.S. application Ser. No. 16/281,333, filed Feb. 21, 2019, now U.S. Pat. No. 10,530,670, issued Jan. 7, 2020, which is a continuation of Ser. No. 13/687,457, filed Nov. 28, 2012, now U.S. Pat. No. 10,257,056, issued Apr. 9, 2019, the entire contents of which are incorporated by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The technology of the disclosure relates to managing power in remote units in a distributed communication system. 
     TECHNICAL BACKGROUND 
     Wireless communication is rapidly growing, with ever-increasing demands for high-speed mobile data communication. As an example, so-called “wireless fidelity” or “WiFi” systems and wireless local area networks (WLANs) are being deployed in many different types of areas. Distributed antenna systems communicate with wireless devices called “clients,” which must reside within the wireless range or “cell coverage area” in order to communicate with an access point device. One approach to deploying a distributed antenna system involves the use of radio frequency (RF) antenna coverage areas, also referred to as “antenna coverage areas.” Because the antenna coverage areas each cover small areas, there are typically only a few users (clients) per coverage area. 
     One type of distributed antenna system for creating antenna coverage areas includes distribution of RF communications signals over an electrical conductor medium. Another type of distributed antenna system, called “Radio-over-Fiber” or “RoF,” utilizes RF communications signals sent over optical fibers. Both types of systems can include head-end equipment coupled to a plurality of remote units (RUs), which may include an antenna and may be referred to as a remote antenna unit or RAU, or simply RU. The RUs can each include RF transceivers coupled to an antenna to transmit RF communications signals wirelessly, wherein the RUs are coupled to the head-end equipment via the communication medium. The antennas in the RUs also receive RF signals (i.e., electromagnetic radiation) from clients in the antenna coverage area. The RF signals are then sent over the communication medium to the head-end equipment. In RoF systems, the RUs convert incoming optical RF signals from an optical fiber downlink to electrical RF signals via optical-to-electrical (O/E) converters, which are then passed to the RF transceiver. The RUs also convert received electrical RF communications signals from clients via the antennas to optical RF communications signals via electrical-to-optical (E/O) converters. The optical RF signals are then sent over an optical fiber uplink to the head-end equipment. 
     The RUs contain power-consuming components, such as the RF transceiver, to transmit and receive RF communications signals and thus require power to operate. In the situation of an optical fiber-based distributed antenna system, the RUs may contain O/E and E/O converters that also require power to operate. In some installations, the RU may contain a housing that includes a power supply to provide power to the RUs locally at the RU. The power supply may be configured to be connected to a power source, such as an alternating current (AC) power source, and convert AC power into a direct current (DC) power signal. Alternatively, power may be provided to the RUs from remote power supplies. The remote power supplies may be configured to provide power to multiple RUs. It may be desirable to provide these power supplies in modular units or devices that may be easily inserted or removed from a housing to provide power. Providing modular power distribution modules allows power to more easily be configured as needed for the distributed antenna system. For example, a remotely located power unit may be provided that contains a plurality of ports or slots to allow a plurality of power distribution modules to be inserted therein. The power unit may have ports that allow the power to be provided over an electrical conductor medium to the RUs. Thus, when a power distribution module is inserted in the power unit in a port or slot that corresponds to a given RU, power from the power distribution module is supplied to the RU. 
     RUs may also provide wired communication ports or provide other services, each of which may require power consumption at the RU. The cumulative effect of all the power consuming components at the RUs may exceed the power provided from the remote power supply. When the power requirements exceed the available power, the RU may shut down and provide no services or may have other disturbances in the operation of the RU. 
     SUMMARY OF THE DETAILED DESCRIPTION 
     Embodiments disclosed in the detailed description include power management techniques in distributed communication systems. Related components, systems, and methods are also disclosed. In embodiments disclosed herein, services within a remote unit of the distributed communication system are selectively activated and power consumption is measured. From at least two measurements, a maximum power available may be calculated and compared to power requirements of the remote unit. 
     In this regard in one embodiment, a remote unit for use in a distributed communication system is disclosed. The remote unit comprises a first power input configured to receive a first power signal from a power distribution module through a first power medium. The remote unit also comprises a power sensor configured to measure power from the first power input. The remote unit also comprises a control system configured to activate services in the remote unit selectively such that at least two power consumption levels are generated. The control system is also configured to measure, using the power sensor, power levels at the first power input. The control system is also configured to calculate a maximum available power for the remote unit. 
     In this regard, in a further embodiment, a method of managing power in a remote unit of a distributed communication system is disclosed. The method comprises activating services in the remote unit selectively such that at least two power consumption levels are generated. The method also comprises measuring, using a power sensor, power levels at each of the two power consumption levels. The method also comprises calculating a maximum available power for the remote unit. 
     Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein. 
     The drawings illustrate various embodiments, and together with the description serve to explain the principles and operation of the concepts disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1    is a schematic diagram of an exemplary distributed antenna system; 
         FIG.  2 A  is a partially schematic cut-away diagram of an exemplary building infrastructure in which the distributed antenna system in  FIG.  1    can be employed; 
         FIG.  2 B  is an alternative diagram of the distributed antenna system in  FIG.  2 A ; 
         FIG.  3    is a schematic diagram of providing digital data services and radio frequency (RF) communication services to remote units (RUs) or other remote communications devices in the distributed antenna system of  FIG.  1   ; 
         FIG.  4    is a schematic diagram of an exemplary power distribution module that is supported by an exemplary power unit; 
         FIG.  5    is a schematic diagram of an exemplary distributed communication system employing a power management module according to an exemplary embodiment of the present disclosure; 
         FIG.  6    is a flow chart of an exemplary process used by a power management module according to  FIG.  5   ; and 
         FIG.  7    is a schematic diagram of a generalized representation of an exemplary computer system that can be included in the power distribution modules disclosed herein, wherein the exemplary computer system is adapted to execute instructions from an exemplary computer-readable media. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all embodiments are shown. Whenever possible, like reference numbers will be used to refer to like components or parts. 
     Embodiments disclosed in the detailed description include power management techniques in distributed communication systems. Related components, systems, and methods are also disclosed. In embodiments disclosed herein, services within a remote unit of the distributed communication system are selectively activated and power consumption is measured. From at least two measurements, a maximum power available may be calculated and compared to power requirements of the remote unit. 
     While the concepts of the present disclosure are applicable to different types of distributed communication systems, an exemplary embodiment is used in a distributed antenna system and this exemplary embodiment is explored herein. Before discussing an exemplary power management system, exemplary distributed antenna systems capable of distributing radio frequency (RF) communications signals to distributed or remote units (RUs) are first described with regard to  FIGS.  1 - 3   . It should be appreciated that in an exemplary embodiment the remote units may contain antennas such that the remote unit is a remote antenna unit and may be referred to as an RAU. 
     In this regard, the distributed antenna systems in  FIGS.  1 - 3    can include power units located remotely from RUs that provide power to the RUs for operation. Embodiments of power management modules in a distributed communication systems, including the distributed antenna systems in  FIGS.  1 - 3   , begin with  FIG.  4   . The distributed antenna systems in  FIGS.  1 - 3    discussed below include distribution of radio frequency (RF) communications signals; however, the distributed antenna systems are not limited to distribution of RF communications signals. Also note that while the distributed antenna systems in  FIGS.  1 - 3    discussed below include distribution of communications signals over optical fiber, these distributed antenna systems are not limited to distribution over optical fiber. Distribution mediums could also include, but are not limited to, coaxial cable, twisted-pair conductors, wireless transmission and reception, and any combination thereof. Also, any combination can be employed that also involves optical fiber for portions of the distributed antenna system. 
     In this regard,  FIG.  1    is a schematic diagram of an embodiment of a distributed antenna system. In this embodiment, the system is an optical fiber-based distributed antenna system  10 . The distributed antenna system  10  is configured to create one or more antenna coverage areas for establishing communications with wireless client devices located in the RF range of the antenna coverage areas. The distributed antenna system  10  provides RF communication services (e.g., cellular services). In this embodiment, the distributed antenna system  10  includes head-end equipment (HEE)  12  such as a head-end unit (HEU), one or more remote units (RUs)  14 , and an optical fiber  16  that optically couples the HEE  12  to the RU  14 . The RU  14  is a type of remote communications unit. In general, a remote communications unit can support wireless communications, wired communications, or both. The RU  14  can support wireless communications and may also support wired communications through wired service port  40 . The HEE  12  is configured to receive communications over downlink electrical RF signals  18 D from a source or sources, such as a network or carrier as examples, and provide such communications to the RU  14 . The HEE  12  is also configured to return communications received from the RU  14 , via uplink electrical RF signals  18 U, back to the source or sources. In this regard in this embodiment, the optical fiber  16  includes at least one downlink optical fiber  16 D to carry signals communicated from the HEE  12  to the RU  14  and at least one uplink optical fiber  16 U to carry signals communicated from the RU  14  back to the HEE  12 . 
     One downlink optical fiber  16 D and one uplink optical fiber  16 U could be provided to support multiple channels each using wave-division multiplexing (WDM), as discussed in U.S. patent application Ser. No. 12/892,424 entitled “Providing Digital Data Services in Optical Fiber-based Distributed Radio Frequency (RF) Communications Systems, And Related Components and Methods,” incorporated herein by reference in its entirety. Other options for WDM and frequency-division multiplexing (FDM) are disclosed in U.S. patent application Ser. No. 12/892,424, as well as distributed digital data communications signals, any of which can be employed in any of the embodiments disclosed herein. 
     The optical fiber-based distributed antenna system  10  has an antenna coverage area  20  that can be disposed about the RU  14 . The antenna coverage area  20  of the RU  14  forms an RF coverage area  38 . The HEE  12  is adapted to perform or to facilitate any one of a number of Radio-over-Fiber (RoF) applications, such as RF identification (RFID), wireless local-area network (WLAN) communication, or cellular phone service. Shown within the antenna coverage area  20  is a client device  24  in the form of a mobile device as an example, which may be a cellular telephone as an example. The client device  24  can be any device that is capable of receiving RF communications signals. The client device  24  includes an antenna  26  (e.g., a wireless card) adapted to receive and/or send electromagnetic RF signals. 
     With continuing reference to  FIG.  1   , to communicate the electrical RF signals over the downlink optical fiber  16 D to the RU  14 , to in turn be communicated to the client device  24  in the antenna coverage area  20  formed by the RU  14 , the HEE  12  includes a radio interface in the form of an electrical-to-optical (E/O) converter  28 . The E/O converter  28  converts the downlink electrical RF signals  18 D to downlink optical RF signals  22 D to be communicated over the downlink optical fiber  16 D. The RU  14  includes an optical-to-electrical (O/E) converter  30  to convert received downlink optical RF signals  22 D back to electrical RF signals to be communicated wirelessly through an antenna  32  of the RU  14  to client devices  24  located in the antenna coverage area  20 . 
     Similarly, the antenna  32  is also configured to receive wireless RF communications from client devices  24  in the antenna coverage area  20 . In this regard, the antenna  32  receives wireless RF communications from client devices  24  and communicates electrical RF signals representing the wireless RF communications to an E/O converter  34  in the RU  14 . The E/O converter  34  converts the electrical RF signals into uplink optical RF signals  22 U to be communicated over the uplink optical fiber  16 U. An O/E converter  36  provided in the HEE  12  converts the uplink optical RF signals  22 U into uplink electrical RF signals, which can then be communicated as uplink electrical RF signals  18 U back to a network or other source. 
       FIG.  2 A  provides further exemplary illustration of how a distributed antenna system can be deployed indoors.  FIG.  2 A  is a partially schematic cut-away diagram of a building infrastructure  50  employing an optical fiber-based distributed antenna system. The system may be the optical fiber-based distributed antenna system  10  of  FIG.  1   . The building infrastructure  50  generally represents any type of building in which the distributed antenna system  10  can be deployed. As previously discussed with regard to  FIG.  1   , the distributed antenna system  10  incorporates the HEE  12  to provide various types of communication services to coverage areas within the building infrastructure  50 . 
     For example, as discussed in more detail below, the distributed antenna system  10  in this embodiment is configured to receive wireless RF signals and convert the RF signals into RoF signals to be communicated over the optical fiber  16  to multiple RUs  14 . The distributed antenna system  10  in this embodiment can be, for example, an indoor distributed antenna system (IDAS) to provide wireless service inside the building infrastructure  50 . These wireless signals can include cellular service, wireless services such as RFID tracking, Wireless Fidelity (WiFi), local area network (LAN), WLAN, public safety, wireless building automations, and combinations thereof, as examples. 
     With continuing reference to  FIG.  2 A , the building infrastructure  50  in this embodiment includes a first (ground) floor  52 , a second floor  54 , and a third floor  56 . The floors  52 ,  54 ,  56  are serviced by the HEE  12  through a main distribution frame  58  to provide antenna coverage areas  60  in the building infrastructure  50 . Only the ceilings of the floors  52 ,  54 ,  56  are shown in  FIG.  2 A  for simplicity of illustration. In the example embodiment, a main cable  62  has a number of different sections that facilitate the placement of a large number of RUs  14  in the building infrastructure  50 . Each RU  14  in turn services its own coverage area in the antenna coverage areas  60 . The main cable  62  can include, for example, a riser cable  64  that carries all of the downlink and uplink optical fibers  16 D,  16 U to and from the HEE  12 . The riser cable  64  may be routed through a power unit  70 . The power unit  70  may also be configured to provide power to the RUs  14  via an electrical power line provided inside an array cable  72 , or tail cable or home-run tether cable as other examples, and distributed with the downlink and uplink optical fibers  16 D,  16 U to the RUs  14 . For example, as illustrated in the building infrastructure  50  in  FIG.  2 B , a tail cable  80  may extend from the power units  70  into an array cable  82 . Downlink and uplink optical fibers in tether cables  84  of the array cables  82  are routed to each of the RUs  14 , as illustrated in  FIG.  2 B . Referring back to  FIG.  2 A , the main cable  62  can include one or more multi-cable (MC) connectors adapted to connect select downlink and uplink optical fibers  16 D,  16 U, along with an electrical power line, to a number of optical fiber cables  66 . 
     With continued reference to  FIG.  2 A , the main cable  62  enables multiple optical fiber cables  66  to be distributed throughout the building infrastructure  50  (e.g., fixed to the ceilings or other support surfaces of each floor  52 ,  54 ,  56 ) to provide the antenna coverage areas  60  for the first, second, and third floors  52 ,  54 , and  56 . In an example embodiment, the HEE  12  is located within the building infrastructure  50  (e.g., in a closet or control room), while in another example embodiment, the HEE  12  may be located outside of the building infrastructure  50  at a remote location. A base transceiver station (BTS)  68 , which may be provided by a second party such as a cellular service provider, is connected to the HEE  12 , and can be co-located or located remotely from the HEE  12 . A BTS is any station or signal source that provides an input signal to the HEE  12  and can receive a return signal from the HEE  12 . 
     In a typical cellular system, for example, a plurality of BTSs is deployed at a plurality of remote locations to provide wireless telephone coverage. Each BTS serves a corresponding cell and when a mobile client device enters the cell, the BTS communicates with the mobile client device. Each BTS can include at least one radio transceiver for enabling communication with one or more subscriber units operating within the associated cell. As another example, wireless repeaters or bi-directional amplifiers could also be used to serve a corresponding cell in lieu of a BTS. Alternatively, radio input could be provided by a repeater, picocell, or femtocell. 
     The distributed antenna system  10  in  FIGS.  1 - 2 B  and described above provides point-to-point communications between the HEE  12  and the RU  14 . A multi-point architecture is also possible as well. With regard to  FIGS.  1 - 2 B , each RU  14  communicates with the HEE  12  over a distinct downlink and uplink optical fiber pair to provide the point-to-point communications. Whenever an RU  14  is installed in the optical fiber-based distributed antenna system  10 , the RU  14  is connected to a distinct downlink and uplink optical fiber pair connected to the HEE  12 . The downlink and uplink optical fibers  16 D,  16 U may be provided in a fiber optic cable. Multiple downlink and uplink optical fiber pairs can be provided in a fiber optic cable to service multiple RUs  14  from a common fiber optic cable. 
     For example, with reference to  FIG.  2 A , RUs  14  installed on a given floor  52 ,  54 , or  56  may be serviced from the same optical fiber  16 . In this regard, the optical fiber  16  may have multiple nodes where distinct downlink and uplink optical fiber pairs can be connected to a given RU  14 . One downlink optical fiber  16 D could be provided to support multiple channels each using wavelength-division multiplexing (WDM), as discussed in U.S. patent application Ser. No. 12/892,424, incorporated herein by reference in its entirety. Other options for WDM and frequency-division multiplexing (FDM) are also disclosed in U.S. patent application Ser. No. 12/892,424, any of which can be employed in any of the embodiments disclosed herein. 
     The HEE  12  may be configured to support any frequencies desired, including but not limited to US FCC and Industry Canada frequencies (824-849 MHz on uplink and 869-894 MHz on downlink), US FCC and Industry Canada frequencies (1850-1915 MHz on uplink and 1930-1995 MHz on downlink), US FCC and Industry Canada frequencies (1710-1755 MHz on uplink and 2110-2155 MHz on downlink), US FCC frequencies (698-716 MHz and 776-787 MHz on uplink and 728-746 MHz on downlink), EU R &amp; TTE frequencies (880-915 MHz on uplink and 925-960 MHz on downlink), EU R &amp; TTE frequencies (1710-1785 MHz on uplink and 1805-1880 MHz on downlink), EU R &amp; TTE frequencies (1920-1980 MHz on uplink and 2110-2170 MHz on downlink), US FCC frequencies (806-824 MHz on uplink and 851-869 MHz on downlink), US FCC frequencies (896-901 MHz on uplink and 929-941 MHz on downlink), US FCC frequencies (793-805 MHz on uplink and 763-775 MHz on downlink), and US FCC frequencies (2495-2690 MHz on uplink and downlink). 
       FIG.  3    is a schematic diagram of another exemplary optical fiber-based distributed antenna system  90  that may be employed according to the embodiments disclosed herein to provide RF communication services. In this embodiment, the distributed antenna system  90  includes optical fiber for distributing RF communication services. The distributed antenna system  90  in this embodiment is comprised of three (3) main components. One or more radio interfaces provided in the form of radio interface modules (RIMS)  92 ( 1 )- 92 (M) in this embodiment are provided in HEE  94  to receive and process downlink electrical RF communications signals prior to optical conversion into downlink optical RF communications signals. The RIMs  92 ( 1 )- 92 (M) provide both downlink and uplink interfaces. The processing of the downlink electrical RF communications signals can include any of the processing previously described above in the HEE  12  in  FIGS.  1 - 2 A . The notation “1-M” indicates that any number of the referenced component, 1-M may be provided. The HEE  94  is configured to accept a plurality of RIMS  92 ( 1 )- 92 (M) as modular components that can easily be installed and removed or replaced in the HEE  94 . In one embodiment, the HEE  94  is configured to support up to eight (8) RIMs  92 ( 1 )- 92 (M). 
     With continuing reference to  FIG.  3   , each RIM  92 ( 1 )- 92 (M) can be designed to support a particular type of radio source or range of radio sources (i.e., frequencies) to provide flexibility in configuring the HEE  94  and the optical fiber-based distributed antenna system  90  to support the desired radio sources. For example, one RIM  92  may be configured to support the Personal Communication Services (PCS) radio band. Another RIM  92  may be configured to support the 700 MHz radio band. In this example, by inclusion of these RIMs  92 , the HEE  94  would be configured to support and distribute RF communications signals on both PCS and LTE  700  radio bands. RIMS  92  may be provided in the HEE  94  that support any frequency bands desired, including but not limited to the US Cellular band, Personal Communication Services (PCS) band, Advanced Wireless Services (AWS) band, 700 MHz band, Global System for Mobile communications (GSM)  900 , GSM  1800 , and Universal Mobile Telecommunication System (UMTS). RIMS  92  may be provided in the HEE  94  that support any wireless technologies desired, including but not limited to Code Division Multiple Access (CDMA), CDMA200, 1×RTT, Evolution-Data Only (EV-DO), UMTS, High-speed Packet Access (HSPA), GSM, General Packet Radio Services (GPRS), Enhanced Data GSM Environment (EDGE), Time Division Multiple Access (TDMA), Long Term Evolution (LTE), iDEN, and Cellular Digital Packet Data (CDPD). RIMS  92  may be provided in the HEE  94  that support any frequencies desired referenced above as non-limiting examples. 
     With continuing reference to  FIG.  3   , the downlink electrical RF communications signals are provided to a plurality of optical interfaces provided in the form of optical interface modules (OIMs)  96 ( 1 )- 96 (N) in this embodiment to convert the downlink electrical RF communications signals into downlink optical RF communications signals  100 D. The notation “1-N” indicates that any number of the referenced component 1-N may be provided. The OIMs  96  may be configured to provide one or more optical interface components (OICs) that contain O/E and E/O converters, as will be described in more detail below. The OIMs  96  support the radio bands that can be provided by the RIMS  92 , including the examples previously described above. Thus, in this embodiment, the OIMs  96  may support a radio band range from 400 MHz to 2700 MHz, as an example, so providing different types or models of OIMs  96  for narrower radio bands to support possibilities for different radio band-supported RIMs  92  provided in the HEE  94  is not required. Further, the OIMs  96  may be optimized for sub-bands within the 400 MHz to 2700 MHz frequency range, such as 400-700 MHz, 700 MHz-1 GHz, 1 GHz-1.6 GHz, and 1.6 GHz-2.7 GHz, as examples. 
     The OIMs  96 ( 1 )- 96 (N) each include E/O converters to convert the downlink electrical RF communications signals to downlink optical RF communications signals  100 D. The downlink optical RF communications signals  100 D are communicated over downlink optical fiber(s) to a plurality of RUs  102 ( 1 )- 102 (P). The notation “1-P” indicates that any number of the referenced component 1-P may be provided. O/E converters provided in the RUs  102 ( 1 )- 102 (P) convert the downlink optical RF communications signals  100 D back into downlink electrical RF communications signals, which are provided over downlinks coupled to antennas  104 ( 1 )- 104 (P) in the RUs  102 ( 1 )- 102 (P) to client devices  24  (shown in  FIG.  1   ) in the reception range of the antennas  104 ( 1 )- 104 (P). 
     E/O converters are also provided in the RUs  102 ( 1 )- 102 (P) to convert uplink electrical RF communications signals received from client devices through the antennas  104 ( 1 )- 104 (P) into uplink optical RF communications signals  100 U to be communicated over uplink optical fibers to the OIMs  96 ( 1 )- 96 (N). The OIMs  96 ( 1 )- 96 (N) include O/E converters that convert the uplink optical RF communications signals  100 U into uplink electrical RF communications signals that are processed by the RIMs  92 ( 1 )- 92 (M) and provided as uplink electrical RF communications signals. Downlink electrical digital signals  108 D( 1 )- 108 D(P) communicated over downlink electrical medium or media (hereinafter “medium”)  110 D are provided to the RUs  102 ( 1 )- 102 (P), separately from the RF communication services, as well as uplink electrical digital signals  108 U( 1 )- 108 U(P) communicated over uplink electrical medium  110 U, as also illustrated in  FIG.  3   . Power may be provided in the downlink and/or uplink electrical medium  110 D and/or  110 U to the RUs  102 ( 1 )- 102 (P). 
     In one embodiment, up to thirty-six (36) RUs  102  can be supported by the OIMs  96 , three RUs  102  per OIM  96  in the optical fiber-based distributed antenna system  90  in  FIG.  3   . The distributed antenna system  90  is scalable to address larger deployments. In the illustrated distributed antenna system  90 , the HEE  94  is configured to support up to thirty six (36) RUs  102  and fit in 6U rack space (U unit meaning 1.75 inches of height). The downlink operational input power level can be in the range of −15 dBm to 33 dBm. The adjustable uplink system gain range can be in the range of +15 dB to −15 dB. The RF input interface in the RIMs  92  can be duplexed and simplex, N-Type. The optical fiber-based distributed antenna system can include sectorization switches to be configurable for sectorization capability, as discussed in U.S. patent application Ser. No. 12/914,585, and entitled “Sectorization In Distributed Antenna Systems, and Related Components and Method,” which is incorporated herein by reference in its entirety. 
     In another embodiment, an exemplary RU  102  may be configured to support up to four (4) different radio bands/carriers (e.g. ATT, VZW, TMobile, Metro PCS: 700LTE/850/1900/2100). The RUs  102  and/or remote expansion units may be configured to provide external filter interface to mitigate potential strong interference at 700 MHz band (Public Safety, CH51,56); Single Antenna Port (N-type) provides DL output power per band (Low bands (&lt;1 GHz): 14 dBm, High bands (&gt;1 GHz): 15 dBm); and satisfies the UL System RF spec (UL Noise Figure: 12 dB, UL IIP3: −5 dBm, UL AGC: 25 dB range). 
     As further illustrated in  FIG.  3   , a power supply module (PSM)  118  may provide power to the RIMs  92 ( 1 )- 92 (M) and radio distribution cards (RDCs)  112  that distribute the RF communications from the RIMS  92 ( 1 )- 92 (M) to the OIMs  96 ( 1 )- 96 (N) through RDCs  114 . In one embodiment, the RDCs  112 ,  114  can support different sectorization needs. A PSM  120  may also be provided to provide power to the OIMs  96 ( 1 )- 96 (N). An interface  116 , which may include web and network management system (NMS) interfaces, may also be provided to allow configuration and communication to the RIMs  92 ( 1 )- 92 (M) and other components of the optical fiber-based distributed antenna system  90 . A microcontroller, microprocessor, or other control circuitry, called a head-end controller (HEC)  122  may be included in HEE  94  to provide control operations for the HEE  94 . 
     RUs, including the RUs  14 ,  102  discussed above, contain power-consuming components for transmitting and receiving RF communications signals. In the situation of an optical fiber-based distributed antenna system, the RUs  14 ,  102  may contain O/E and E/O converters that also require power to operate. As an example, a RU  14 ,  102  may contain a power unit that includes a power supply to provide power to the RUs  14 ,  102  locally at the RU  14 ,  102 . Alternatively, power may be provided to the RUs  14 ,  102  from power supplies provided in remote power units. In either scenario, it may be desirable to provide these power supplies in modular units or devices that may be easily inserted or removed from a power unit. Providing modular power distribution modules allows power to more easily be configured as needed for the distributed antenna system. 
     In this regard,  FIG.  4    is a schematic diagram of an exemplary power distribution module  130  that can be employed to provide power to the RUs  14 ,  102  or other power-consuming DAS components, including those described above. In this embodiment, the power distribution module  130  may be the power unit  70  previously described above to remotely provide power to the RUs  14 ,  102 . The power unit  70  may be comprised of a chassis or other housing that is configured to support power distribution modules  130 . The power distribution module  130  may include a power supply unit  132  that has a plurality of outputs  134 ,  136 . The output  134  may be connected to a port  138 . In an exemplary embodiment, the port  138  is a multi-connector port configured to accommodate a conventional plug such as a CAT 5 or CAT 6 plug and includes conductive elements configured to carry power. 
     The output  136  may have a reduced voltage relative to output  134  (e.g., 12 V compared to 56 V) and be coupled to a fan  140  with associated fan monitor  142  and fan alarm  144 . The port  138  may further include conductive elements  146  configured to carry return signals from the RU  14 ,  102 . While  FIG.  4    illustrates an exemplary power distribution module  130 , it should be appreciated that other power supply configurations may be used with embodiments of the present disclosure. 
     The power distribution module  130  provides power to the RU  102  through the electrical medium  110  shown in  FIG.  3   . As illustrated in  FIG.  5   , the electrical medium  110  has a resistance R LINE    149  which dissipates power thereby reducing the power that is available at the RU  102 . The present disclosure provides, in exemplary embodiments, systems and techniques through which the power available at the RU  102  may be calculated and appropriate remedial action (if any) taken. In particular, in an exemplary embodiment, an alarm may be generated so that correction may be made. One such alarm may be a local light being illuminated. An alternate alarm may be a report via a management or telemetry channel to a central management system. In another exemplary embodiment, the RU  102  may prioritize services provided by the RU  102  to prevent the RU  102  from shutting down or having other anomalous and undesired operational behavior. In still another alternate embodiment, the resistance value R LINE  may be reported to a central facility for future planning purposes. That is, the system operators may review the R LINE  value when evaluating whether a potential upgrade is feasible at a particular RU  102 . For example, if R LINE  is high and there are already several services at a particular RU  102 , then it may not be practical to add a service to that RU  102  unless an additional power source is provided. 
     In this regard, the RU  102  includes a microprocessor or microcontroller  150  and a power sensor  152 . The power sensor  152  includes a current sensor  154  and a voltage sensor  156 . The microcontroller  150  selectively activates services  158 ( 1 )- 158 (N) through switches  160 ( 1 )- 160 (N). The services  158 ( 1 )- 158 (N) may include cellular services such as those enumerated above, radio frequency communication services, WiFi, Ethernet, location based services, and the like. The services  158 ( 1 )- 158 (N) may be embodied in separate modules, separate circuit boards, antennas, or the like. As these services are conventional, further explanation of them is omitted. 
     In an exemplary embodiment, the existence of the switches  160 ( 1 )- 160 (N) allows for the RU  102  to calculate available power. The process for such calculation is set forth with reference to  FIG.  6    and process  170 . The process begins when the services are installed in the RU  102  (block  172 ). Note that installation of services may be a new installation of a new RU  102  or an additional service being added to an existing and previously deployed RU  102 . In an exemplary embodiment, power will have been disconnected from the RU  102  or not yet have been attached. Accordingly, the power is connected to the RU  102  (block  174 ). 
     With continued reference to  FIG.  6   , the microcontroller  150  opens the switches  160 ( 1 )- 160 (N) so that no service  158  is active (block  176 ). Stated another way, the microcontroller  150  deactivates all services by opening all the switches  160 . The microcontroller  150  then measures, using the power sensor  152 , the power level at this first power consumption level (block  178 ). In particular, the power sensor  152  measures the voltage and current when there are no services active. Power is still consumed by at least the microcontroller  150 . The microcontroller  150  then closes at least one switch  160  to activate at least one service  158  (block  180 ). More services  158  may be activated as desired. The microcontroller  150  measures the power level at this second power consumption level (block  182 ). From the two measurements, the microcontroller  150  may calculate the maximum power available at the RU  102  (block  184 ). The calculation is a function of two equations with two unknowns and becomes a routine solution. 
     In an exemplary embodiment, the power in the first state is defined by the following equation:
 
 V   PS   =I   RAI#1   *R   LINE   +V   RAU#1   [equation 1]
 
     And the power in the second state is defined by the following equation:
 
 V   PS   =I   RAI#2   *R   LINE   +V   RAU#2   [equation 2]
 
     In equations 1 and 2, V PS  is the power supplied by the power supply module  130  and is initially unknown (i.e., the first variable). V RAU  and I RAU  are known from the measurements of the current sensor  154  and the voltage sensor  156 . R LINE  is the wire resistance of the electrical medium  110  and is initially unknown (i.e., the second variable). However, since there are two equations with two unknowns, it is possible to solve for V PS  and R LINE . Once V PS  and R LINE  are known, I RAU[MAX]  (the current at maximal power conditions) and P RAU[MAX]  (the maximum available power at the RU  102  input) can easily be calculated.
 
 I   RAU[MAX]   =P   o[MAX]   /V   PS   [equation 3]
 
     where P o[MAX]  is the maximum power allowed by the power supply. Then the voltage that reaches the RU  102  in maximum power conditions is calculated as follows:
 
 V   RAU[@PS−MAX]   =V   PS   −I   RAU[MAX]   *R   LINE   [equation 4]
 
     Thus, the maximum power is calculated as follows:
 
 P   RAU[MAX]   =I   RAU[MAX]   *V   RAU[@PS−MAX]   [equation 5]
 
     Returning to  FIG.  6   , the microcontroller  150  can compare the maximum power available to the expected power demands of the existing services  158 ( 1 )- 158 (N) (block  186 ). If the answer to the comparison is positive, that there is enough power, then the RU  102  may operate normally (block  188 ). If, however, the answer is negative, that the power required by the services  158 ( 1 )- 158 (N) exceeds the maximum available power, then the microcontroller  150  may take remedial action (block  190 ). 
     In exemplary embodiments, remedial actions include reducing transmission power of one or more of the services  158 ( 1 )- 158 (N), shutting off completely one or more of the services  158 ( 1 )- 158 (N), or generating an alarm. As noted above, the calculated R LINE  may also be reported and saved for future planning purposes. 
     In an alternate embodiment, the power supply output voltage V PS  may be known (from direct measurement, prior calculations, or the like) in which case only a single equation is needed to solve for the unknown variable R LINE . Having to solve for only one variable means that only one equation is needed. Thus, measurements may be made with no services active or with only one (or some other predetermined number (e.g., only equation 1 or equation 2 would be needed to solve for R LINE )) service active and then the maximum power can be calculated. 
       FIG.  7    is a schematic diagram representation of additional detail regarding an exemplary computer system  400  that may be included in the power distribution module  130  or the RU  102 . The computer system  400  is adapted to execute instructions from an exemplary computer-readable medium to perform power management functions. In this regard, the computer system  400  may include a set of instructions for causing the microcontroller  150  to enable and disable the services  158 ( 1 )- 158 (N), as previously described. The RU  102  or power distribution module  130  may be connected (e.g., networked) to other machines in a LAN, an intranet, an extranet, or the Internet. The RU  102  or power distribution module  130  may operate in a client-server network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. While only a single device is illustrated, the term “device” shall also be taken to include any collection of devices that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein. The microcontroller  150  may be a circuit or circuits included in an electronic board card, such as a printed circuit board (PCB) as an example, a server, a personal computer, a desktop computer, a laptop computer, a personal digital assistant (PDA), a computing pad, a mobile device, or any other device, and may represent, for example, a server or a user&#39;s computer. 
     The exemplary computer system  400  in this embodiment includes a processing device or processor  402 , a main memory  414  (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM), etc.), and a static memory  406  (e.g., flash memory, static random access memory (SRAM), etc.), which may communicate with each other via the data bus  408 . Alternatively, the processing device  402  may be connected to the main memory  414  and/or static memory  406  directly or via some other connectivity means. The processing device  402  may be a controller, and the main memory  414  or static memory  406  may be any type of memory. 
     The processing device  402  represents one or more general-purpose processing devices such as a microprocessor, central processing unit, or the like. More particularly, the processing device  402  may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor implementing other instruction sets, or processors implementing a combination of instruction sets. The processing device  402  is configured to execute processing logic in instructions  404  for performing the operations and steps discussed herein. 
     The computer system  400  may further include a network interface device  410 . The computer system  400  also may or may not include an input  412  to receive input and selections to be communicated to the computer system  400  when executing instructions. The computer system  400  also may or may not include an output  422 , including but not limited to a display, a video display unit (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)), an alphanumeric input device (e.g., a keyboard), and/or a cursor control device (e.g., a mouse). 
     The computer system  400  may or may not include a data storage device that includes instructions  416  stored in a computer-readable medium  418 . The instructions  424  may also reside, completely or at least partially, within the main memory  414  and/or within the processing device  402  during execution thereof by the computer system  400 , the main memory  414  and the processing device  402  also constituting computer-readable medium  418 . The instructions  416 ,  424  may further be transmitted or received over a network  420  via the network interface device  410 . 
     Further, as used herein, it is intended that terms “fiber optic cables” and/or “optical fibers” include all types of single mode and multi-mode light waveguides, including one or more optical fibers that may be upcoated, colored, buffered, ribbonized and/or have other organizing or protective structure in a cable such as one or more tubes, strength members, jackets or the like. The optical fibers disclosed herein can be single mode or multi-mode optical fibers. 
     Many modifications and other embodiments of the embodiments set forth herein will come to mind to one skilled in the art to which the embodiments pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. For example, the distributed antenna systems could include any type or number of communications mediums, including but not limited to electrical conductors, optical fiber, and air (i.e., wireless transmission). 
     Therefore, it is to be understood that the description and claims are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.