Patent Publication Number: US-2019182901-A1

Title: Systems and methods for noise floor optimization in distributed antenna system with direct digital interface to base station

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 15/645,791 entitled “SYSTEMS AND METHODS FOR NOISE FLOOR OPTIMIZATION IN DISTRIBUTED ANTENNA SYSTEM WITH DIRECT DIGITAL INTERFACE TO BASE STATION” and filed on Jul. 10, 2017 which is a continuation of U.S. patent application Ser. No. 14/506,145 entitled “SYSTEMS AND METHODS FOR NOISE FLOOR OPTIMIZATION IN DISTRIBUTED ANTENNA SYSTEM WITH DIRECT DIGITAL INTERFACE TO BASE STATION” and filed on Oct. 3, 2014 (now Issued U.S. Pat. No. 9,750,082) which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/887,703 filed on Oct. 7, 2013, all of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Distributed Antenna Systems (DAS) are used to distribute wireless signal coverage into buildings or other substantially closed environments. The antennas are typically connected to a radio frequency (RF) signal source, such as a service provider&#39;s base station. Various methods of transporting the RF signal from the RF signal source to the antenna have been implemented in the art. 
     SUMMARY 
     A signal interface unit for a distributed antenna system includes a channelized radio carrier interface configured to communicate an uplink channelized radio carrier for a radio frequency carrier to a channelized radio carrier base station interface; an antenna side interface configured to receive an uplink digitized radio frequency signal from the distributed antenna system communicatively coupled to the antenna side interface; and a signal conversion module communicatively coupled between the channelized radio carrier interface and the antenna side interface and configured to convert between the uplink digitized radio frequency signal and the uplink channelized radio carrier at least in part by adjusting at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of the channelized radio carrier base station interface. 
    
    
     
       DRAWINGS 
       Understanding that the drawings depict only exemplary embodiments and are not therefore to be considered limiting in scope, the exemplary embodiments will be described with additional specificity and detail through the use of the accompanying drawings, in which: 
         FIG. 1  is a block diagram of an exemplary embodiment of a distributed antenna system; 
         FIGS. 2A-2D  are block diagrams of exemplary embodiments of signal interface units used in distributed antenna systems, such as the exemplary distributed antenna system in  FIG. 1 ; 
         FIG. 3  is a block diagram of an exemplary embodiment of an antenna unit used in distributed antenna systems, such as the exemplary distributed antenna system in  FIG. 1 ; 
         FIGS. 4A-4C  are block diagrams of exemplary embodiments of RF conversion modules used in antenna units of distributed antenna systems, such as the exemplary antenna unit in  FIG. 3 ; and 
         FIG. 5  is a flow diagram illustrating one exemplary embodiment of a method of making a distributed antenna system appear as a radio head in a digital radio system. 
     
    
    
     In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the exemplary embodiments. Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific illustrative embodiments. However, it is to be understood that other embodiments may be utilized and that logical, mechanical, and electrical changes may be made. Furthermore, the method presented in the drawing figures and the specification is not to be construed as limiting the order in which the individual steps may be performed. The following detailed description is, therefore, not to be taken in a limiting sense. 
     The embodiments described below describe a distributed antenna system and components within the distributed antenna system including at least one signal interface unit communicatively coupled to at least one antenna unit through a distributed switching network. In other embodiments, the signal interface unit is directly coupled with the antenna unit or is included with the antenna unit in a single device. The signal interface unit is communicatively coupled to at least one external device, such as a base station, through a backhaul network. In exemplary embodiments, the signal interface unit is at least one of a Common Public Radio Interface (CPRI) base station interface, an Open Base Station Architecture Initiative (OBSAI) base station interface, and an Open Radio Interface (ORI) base station interface. The signal interface acts as a translator to translate uplink and downlink signals between an external device and the distributed antenna system. The translator adjusts attributes of the uplink and downlink signals and reports characteristics in such a way as to cause the antenna system to look like a single radio head to the external device. 
     In exemplary embodiments, the antenna unit is multi-standard and capable of receiving at least one signal and converting it to radio frequency (RF) and transmitting it using at least one antenna. In exemplary embodiments, the antenna unit is not specific to a number of channels or an air protocol and does not necessarily require any hardware change when channels are added or removed, or a new modulation type or air protocol is used. In exemplary embodiments, a plurality of signal interface units convert a plurality of external device signals received from a plurality of external devices and representing individual channels into a single radio system signal that is transported through the distributed switching network to at least one antenna unit that converts the single radio system signal into radio frequency (RF) signals and transmits them using at least one antenna. In exemplary embodiments, the at least one antenna unit includes a single digital/analog convertor and a single RF converter that can up-convert the entire radio system signal into RF spectrum having various channels. 
     In exemplary embodiments, the external device signals are channelized signals. As described herein, channelized signals are specific to a particular channel. In exemplary embodiments, the channelized signals are baseband data, such as channelized in-phase (I) and quadrature (Q) data in I/Q pairs. The channelized signals are not positioned relative to one another and require additional baseband conversion before RF conversion and transmission can be performed. Specifically, if a system communicated the channelized signals to an antenna unit, additional processing would be required at the antenna unit to convert the channelized signals before RF conversion and transmission. 
     In contrast, radio system signals are not specific to a particular channel and may include a number of different channels. The radio system signals represent either digitized or analog spectrum and are one step closer to RF signals than the channelized signals. In exemplary embodiments, the radio system signal is at an intermediate frequency that maps to a large portion of RF spectrum including a number of channels. In exemplary embodiments, the radio system signals can simply be up-converted from the intermediate frequency to radio frequency and transmitted at an antenna unit as described below. Thus, the antenna units do not need the capability of processing channelized signals before RF conversion and transmission. Accordingly, in these exemplary embodiments it doesn&#39;t matter what channels are sent to the antenna units. In exemplary embodiments, the antenna unit communicates with subscriber units using a first set of channels at first frequencies and a second set of channels at second frequencies. In exemplary embodiments, the antenna unit communicates using different modulation and/or radio access technologies simultaneously. 
       FIG. 1  is a block diagram of an exemplary embodiment of a distributed antenna system  100 . Distributed antenna system  100  includes at least one signal interface unit  102  (including signal interface unit  102 - 1 , optional signal interface unit  102 - 2 , and any amount of optional signal interface units  102  through optional signal interface unit  102 -A), at least one antenna unit  104  (including antenna unit  104 - 1  and any amount of optional antenna units  104  through optional antenna unit  104 -B), and an optional distributed switching network  106 . 
     Each signal interface unit  102  is communicatively coupled to a corresponding external device  108  directly or through a corresponding optional backhaul network  110 . Each external device  108  is configured to provide signals to be transported through the distributed antenna system  100  to each corresponding signal interface unit  102 . In the forward path, each signal interface unit  102  is configured to receive signals from at least one external device  108 . Specifically, signal interface unit  102 - 1  is communicatively coupled to external device  108 - 1  through backhaul network  110 - 1 , optional signal interface unit  102 - 2  is communicatively coupled to optional external device  108 - 2  through optional backhaul network  110 - 1 , and optional signal interface unit  102 -A is communicatively coupled to optional external device  108 -A through optional backhaul network  110 - 1 . In exemplary embodiments, the optional backhaul networks  110  include one or more intermediary devices positioned between the signal interface unit  102  and its corresponding external device  108 . 
     Each signal interface unit  102  is also communicatively coupled to the distributed switching network  106  across a communication link  112 . Specifically, signal interface unit  102 - 1  is communicatively coupled to the distributed switching network  106  across communication link  112 - 1 , optional signal interface unit  102 - 2  is communicatively coupled to the distributed switching network  106  across communication link  112 - 2 , and optional signal interface unit  102 -A is communicatively coupled to the distributed switching network  106  across communication link  112 -A. As described in more detail below, each signal interface unit  102  is configured to convert signals from the external device  108  to which it is communicatively coupled into a downlink radio system signal and further configured to communicate the downlink radio system signal to the distributed switching network  106  (either directly or through other components of the distributed antenna system  100 ) across a respective communication link  112 . 
     In exemplary embodiments, at least one signal interface unit  102  is configured to convert the signals from the external device  108  at least in part by digitally adjusting at least one downlink attribute of the downlink digitized radio frequency signal to comply with requirements of the external device. In exemplary embodiments, this digital adjustment is made based on knowledge about the performance characteristics and/or topology of the at least one antenna unit  104  and/or the distributed switching network  106 . In exemplary embodiments, this digital adjustment occurs at the bit level. In exemplary embodiments, the requirements of the external device are received at the signal conversion module from the external device interface. In exemplary embodiments, the external device interface is one of a Common Public Radio Interface (CPRI) external device interface, an Open Base Station Architecture Initiative (OBSAI) external device interface, and an Open Radio Interface (ORI) external device interface. 
     In exemplary embodiments, the at least one downlink attribute includes a power level, gain, noise floor, and/or delay. In exemplary embodiments where the at least one downlink attribute includes a delay, delays to individual antennas within the distributed antenna system  100  are detected, additional delay is added to the downlink delays for all except the longest delays to normalize and/or equalize the delays in the distributed antenna system  100 , and the combined delay-equalized signal is presented to the external device as if it were a single signal with a single delay value. 
     Similarly in the reverse path, in exemplary embodiments each signal interface unit  102  is configured to receive uplink radio system signals across a respective communication link  112  from distributed switching network  106 . Each signal interface unit  102  is further configured to convert the received uplink radio system signal to signals formatted for the associated external device  108  and further configured to communicate the signals formatted for the associated external device  108  to the associated external device  108  directly or across the optional backhaul network  110 . 
     In exemplary embodiments, at least one signal interface unit  102  is configured to convert the received uplink radio system signals to signals formatted for the associated external device  108  at least in part by digitally adjusting at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of the external device. In exemplary embodiments, this digital adjustment is made based on knowledge about the performance characteristics and/or topology of the at least one antenna unit  104  and/or the distributed switching network  106 . In exemplary embodiments, this digital adjustment occurs at the bit level. In exemplary embodiments, adjusting the at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of the external device includes scaling the uplink noise floor of the uplink digitized radio frequency signal to make the uplink noise floor comply with requirements for uplink noise floor of the channelized radio carrier base station. In exemplary embodiments, the requirements of the external device are received at the signal conversion module from the external device interface. In exemplary embodiments, the external device interface is one of a Common Public Radio Interface (CPRI) external device interface, an Open Base Station Architecture Initiative (OBSAI) external device interface, and an Open Radio Interface (ORI) external device interface. 
     In exemplary embodiments, the at least one uplink attribute of the uplink digitized radio frequency signal includes a power level, delay, and/or uplink noise floor. In exemplary embodiments where the at least one uplink attribute includes a power level, gain, and/or noise floor, the uplink gains from individual antennas are scaled by a factor of 1/N, where N is the number of antennas belonging to that simulcast group. The individual amplitude-adjusted signals are then combined into a composite uplink signal and the summed signal is scaled so that either the composite signal level or the composite noise floor matches what the external device expects to see from a single antenna. The combined gain-equalized signal is presented to the external device as if it were a single signal with a single gain and/or noise floor value. In exemplary embodiments where the at least one uplink attribute includes a delay, delays to individual antennas within the distributed antenna system  100  are detected, additional delay is added to the uplink delays for all except the longest delays to normalize and/or equalize the delays in the distributed antenna system  100 , and the combined delay-equalized signal is presented to the external device as if it were a single signal with a single delay value. 
     In exemplary embodiments, optional distributed switching network  106  couples the plurality of signal interface units  102  with the at least one antenna unit  104 . In other embodiments, the at least one antenna unit  104  is directly coupled to the at least one signal interface unit  102 - 1 . Distributed switching network  106  may include one or more distributed antenna switches or other components that functionally distribute downlink radio system signals from the signal interface units  102  to the at least one antenna unit  104 . Distributed switching network  106  also functionally distributes uplink signals from the at least one antenna unit  104  to the signal interface units  102 . In exemplary embodiments, the distributed switching network  106  can be controlled by a separate controller or another component of the system. In exemplary embodiments the switching elements of the distributed switching network  106  are controlled either manually or automatically. In exemplary embodiments, the routes can be pre-determined and static. In other exemplary embodiments, the routes can dynamically change based on time of day, load, or other factors. 
     In exemplary embodiments, the downlink radio system signal is a digital signal. In exemplary embodiments, the downlink radio system signal is an analog signal that contains at least one individual channel that is positioned within a set of spectrum that reflects its eventual location within radio frequency spectrum. Said another way, the channel in each downlink radio system signal is at a different frequency than the other channels to which it may be aggregated in the distributed switching network  106 . Thus, when multiple downlink radio system signals are aggregated together, the individual channels do not overlap each other and all channels can be upconverted together to radio frequency spectrum simultaneously. In exemplary embodiments, the downlink radio system signal is a digital signal through some of the distributed switching network and is converted to an analog signal at an intermediary device positioned within the distributed switching network. 
     Each antenna unit  104  is communicatively coupled to the distributed switching network  106  across a communication link  114 . Specifically, antenna unit  104 - 1  is communicatively coupled to the distributed switching network  106  across communication link  114 - 1  and optional antenna unit  104 -B is communicatively coupled to the distributed switching network  106  across communication link  114 -B. In exemplary embodiments, some or all of the antenna units  104  receive a single downlink radio system signal from the distributed switching network  106  or directly from a signal interface unit  102 . In exemplary embodiments, some or all of the antenna units  104  include components configured for extracting at least one downlink radio system signal from an aggregate downlink radio system signal and components configured for aggregating at least one uplink radio system signal into an aggregate uplink radio system signal as well as at least one radio frequency converter configured to convert between at least one radio system signal and at least one radio frequency band and at least one radio frequency antenna  116  configured to transmit and receive signals in the at least one radio frequency band to at least one subscriber unit  118 . In exemplary embodiments, the downlink radio system signal is an aggregate of multiple downlink radio system signals each with a channel positioned within a set of spectrum that reflects its location within the RF spectrum. In exemplary embodiments having multiple downlink radio system signals aggregated together, the individual channels can be converted to the at least one radio frequency band signal simultaneously. 
     In the downstream, each antenna unit  104  is configured to extract at least one downlink radio system signal from the downlink aggregate radio system signal. Each antenna unit  104  is further configured to convert the at least one downlink radio system signal into a downlink radio frequency (RF) signal in a radio frequency band. In exemplary embodiments, this may include digital to analog converters and oscillators. Each antenna unit  104  is further configured to transmit the downlink radio frequency signal in the radio frequency band to at least one subscriber unit using at least one radio frequency antenna  116 . In a specific exemplary embodiment, antenna unit  104 - 1  is configured to extract at least one downlink radio system signal from the downlink aggregate radio system signal received from the distributed switching network  106  and further configured to convert the at least one downlink radio system signal into a downlink radio frequency signal in a radio frequency band. Antenna unit  104 - 1  is further configured to transmit the downlink radio frequency signal in a radio frequency band using a radio frequency band radio frequency antenna  116 - 1  to at least one subscriber unit  118 - 1 . In exemplary embodiments, antenna unit  104 - 1  is configured to extract a plurality of downlink radio system signals from the downlink aggregate radio system signal received from the distributed switching network  106  and configured to convert the plurality of downlink radio system signals to a plurality of downlink radio frequency signals. In exemplary embodiments with a plurality of radio frequency signals, the antenna unit  104 - 1  is further configured to transmit the downlink radio frequency signal in at least one radio frequency band to at least one subscriber unit  118 - 1  using at least one radio frequency antenna  116 - 1 . In exemplary embodiments, the antenna unit  104 - 1  is configured to transmit one downlink radio frequency signal to one subscriber unit  118 - 1  using an radio frequency antenna  116 - 1  and another radio frequency signal to another subscriber unit  118 -D using another radio frequency antenna  116 -C. In exemplary embodiments, other combinations of radio frequency antennas  116  and other components are used to communicate other combinations of radio frequency signals in other various radio frequency bands to various subscriber units  118 , such as but not limited to using multiple radio frequency antenna  116  to communicate with a single subscriber unit  118 . 
     Similarly in the reverse path, in exemplary embodiments each antenna unit  104  is configured to receive uplink radio frequency signals from at least one subscriber unit  118  using at least one radio frequency antenna  116 . Each antenna unit  104  is further configured to convert the radio frequency signals to at least one uplink radio system signal. Each antenna unit  104  is further configured to aggregate the at least one uplink radio system signal into an aggregate uplink radio system signal and further configured to communicate the aggregate uplink radio system signal across at least one communication link  114  to the distributed switching network  106 . In exemplary embodiments, antenna units  104  multiplex uplink signals in different bands onto the same interface for communication to the next upstream element. In other exemplary embodiments (such as example embodiments implementing diversity processing), the antenna unit  104  aggregates (i.e. sum/combine) uplink signals in an intelligent manner. In exemplary embodiments, each uplink radio system signal contains a channel that is positioned within a set of spectrum that reflects its location within the RF spectrum. Thus and even though the uplink radio system signals that are aggregated will overlap in frequency spectrum, the individual channels themselves from the aggregated uplink radio system signals do not overlap each other when multiple uplink radio system signals are aggregated together. 
     In exemplary embodiments, a master reference clock is distributed between the various components of the distributed antenna system  100  to keep the various components locked to the same clock. In exemplary embodiments, a master reference clock is provided to at least one external device  108  via at least one signal interface unit  102  so that the external device  108  can lock to the master reference clock as well. In other exemplary embodiments, the master reference clock is provided from at least one external device  108  to the distributed antenna system  100  via at least one signal interface unit  102 . In exemplary embodiments, the master reference clock is generated within a component of the distributed antenna system  100 , such as a signal interface unit  102 , an antenna unit  104 , or somewhere within the distributed switching network  106 . 
     In exemplary embodiments, the communication links  112  and/or the communication links  114  are optical fibers and the communication across the communication links  112  and/or the communication links  114  is optical. In these embodiments, an electrical to optical conversion occurs at the antenna units  104  and/or at an intermediary device within the optional distributed switching network  106 . In other embodiments, the communication links  112  and/or the communication links  114  are conductive cables (such as coaxial cable, twisted pair, etc.) and the communication across the communication links  112  and/or the communication links  114  is electrical. In exemplary embodiments, the communication across the communication links  112  and/or the communication links  114  is digital. In exemplary embodiments, the communication across the communication links  112  and/or the communication links  114  is analog. In exemplary embodiments, any mixture of optical, electrical, analog, and digital communication occurs across the communication links  112  and the communication links  114 . In exemplary embodiments, an antenna unit  104  may include functionality to convert between digital and analog signals. 
       FIGS. 2A-2D  are block diagrams of exemplary embodiments of signal interface units  102  used in distributed antenna systems, such as exemplary distributed antenna system  100  described above. Each of  FIGS. 2A-2D  illustrates a different embodiment of a type of signal interface unit  102 , labeled  102 A- 102 D respectively. 
       FIG. 2A  is a block diagram of an exemplary embodiment of a signal interface unit  102 , general signal interface unit  102 A. General signal interface unit  102 A includes signal conversion module  202 , external device interface  204 A, antenna side interface  206 , optional processor  208 , optional memory  210 , and optional power supply  212 . In exemplary embodiments, signal conversion module  202  is communicatively coupled to an external device  108 A through the external device interface  204 A. Signal conversion module  202  is also communicatively coupled to at least one communication link  112  by antenna side interface  206 . In exemplary embodiments, the communication link  112  is an optical communication link across a fiber optic cable, though it can also be other types of wired or wireless links in other embodiments. In exemplary embodiments, the signal conversion module  202  and/or portions of the external device interface  204 A and/or the antenna side interface  206  are implemented using optional processor  208  and optional memory  210 . In exemplary embodiments, the optional power supply  212  provides power to the various elements of the signal interface unit  102 A. 
     In the downlink, the external device interface  204 A is configured to receive downlink radio system signals from the external device  108 A. The signal conversion module  202  is configured to convert the received downlink radio system signals to a downlink radio system signal. In exemplary embodiments, the signal conversion module  202  and/or the antenna side interface  206  converts the radio system signal from electrical signals to optical signals for output on communication link  112 . In other embodiments, the radio system signal is transported using a conductive communication medium, such as coaxial cable or twisted pair, and the optical conversion is not necessary. The antenna side interface  206  is configured to communicate the downlink radio system signal on communication link  112 . 
     In exemplary embodiments, the signal conversion module  202  is further configured to adjust a downlink attribute of the downlink radio system signal based on differences in attributes and/or performance characteristics of the external device  108 A and the general signal interface unit  102 A and/or distributed antenna system  100 . In exemplary embodiments, the signal conversion module  202  adjusts at least one of these downlink attributes based on requirements set by the external device  108 A and knowledge about the attributes and/or performance characteristics of the distributed antenna system  100 &#39;s effect on the downlink signals. This enables the distributed antenna system  100  to distribute downlink radio system signals to at least one antenna unit  104  that will then be broadcast to at least one subscriber unit  118  and appear as if it were transmitted directly from a radio head connected to the external device  108 A. This enables the distributed antenna system  100  to appear transparent to the at least one subscriber unit  118  in the downlink. 
     In exemplary embodiments, the at least one downlink attribute of the downlink radio system signal includes a power level, gain, noise floor, and/or delay. In exemplary embodiments where the at least one downlink attribute includes a delay, delays to individual antennas within the distributed antenna system  100  are detected, additional delay is added to the downlink delays for all except the longest delays to normalize and/or equalize the delays in the distributed antenna system  100 , and the combined delay-equalized signal is presented to the external device  108 A as if it were a single signal with a single delay value. 
     In exemplary embodiments, the downlink radio system signal is specific to a particular channel and requires additional baseband conversion before radio frequency conversion and transmission can be performed. In exemplary embodiments, the downlink radio system signal is not specific to a particular channel and does not require additional baseband conversion before radio frequency conversion and transmission can be performed. In exemplary embodiments, the downlink radio system signal contains an individual channel that is positioned within a set of spectrum that reflects its eventual location within radio frequency spectrum. In exemplary embodiments, the downlink radio system signal interface is communicatively coupled with an intermediary device that aggregates the downlink radio system signal with at least one other downlink radio system signal before being transmitted to at least one antenna unit  104 . In exemplary embodiments, the individual channels within the downlink radio system signal and the at least one other downlink radio system signal do not overlap and can be upconverted together simultaneously to radio frequency spectrum. 
     In the uplink, antenna side interface  206  is configured to receive an uplink radio system signal from communication link  112 . In exemplary embodiments where communication link  112  is an optical medium, the antenna side interface  206  and/or the signal conversion module  202  is configured to convert the uplink radio system signal between received optical signals and electrical signals. In other embodiments, the radio system signal is transported using a conductive communication medium, such as coaxial cable or twisted pair, and the optical conversion is not necessary. The signal conversion module  202  is further configured to convert the uplink radio system signal to uplink signals. External device interface  204 A is configured to communicate the uplink signals to the external device  108 A. 
     In the uplink of exemplary embodiments, the signal conversion module  202  is further configured to adjust an uplink attribute of the uplink radio system signal based on differences in attributes and/or performance characteristics of the external device  108 A and the general signal interface unit  102 A and/or distributed antenna system  100 . In exemplary embodiments, the signal conversion module  202  adjusts at least one of these uplink attributes based on requirements set by the external device  108 A and knowledge about the attributes and/or performance characteristics of the distributed antenna system  100 &#39;s effect on the uplink signals. This enables the distributed antenna system  100  to receive uplink radio system signals from at least one antenna unit  104  that were received from at least one subscriber unit  118  and appear as if it were received directly at a radio head connected to the external device  108 A. This enables the distributed antenna system  100  to appear transparent to the at least one external device  108 A in the uplink. 
     In exemplary embodiments, the at least one uplink attribute of the uplink radio system signal includes a power level, gain, uplink noise floor, and/or delay. In exemplary embodiments where the at least one uplink attribute includes a power level, gain, and/or noise floor, the uplink gains from individual antennas are scaled by a factor of 1/N, where N is the number of antennas belonging to that simulcast group. The individual amplitude-adjusted signals are then combined into a composite uplink signal and the summed signal is scaled so that either the composite signal level or the composite noise floor matches what the external device  108 A expects to see from a single antenna. The combined gain-equalized signal is presented to the external device  108 A as if it were a single signal with a single gain and/or noise floor value. In exemplary embodiments where the at least one uplink attribute includes a delay, delays to individual antennas within the distributed antenna system  100  are detected, additional delay is added to the uplink delays for all except the longest delays to normalize and/or equalize the delays in the distributed antenna system  100 , and the combined delay-equalized signal is presented to the external device  108 A as if it were a single signal with a single delay value. 
     In exemplary embodiments, the uplink radio system signal contains an individual channel that is positioned within a set of spectrum that reflects its previous location within radio frequency spectrum. In exemplary embodiments, the general signal interface unit  102 A is communicatively coupled with an intermediary device that separates the uplink radio system signal from an aggregate uplink radio system signal received from at least one antenna unit  104  and including at least one other uplink radio system signal. In exemplary implementations, the individual channels within the uplink radio system signal and the at least one other uplink radio system signal do not overlap and can be downconverted together simultaneously from radio frequency spectrum. In exemplary embodiments, the uplink radio system signal is not specific to a particular channel and does not require any baseband processing when converted from radio frequency, while the uplink data may be specific to a particular channel and require baseband processing when being converted from radio frequency. 
     In exemplary embodiments, an optional signal interface unit clock unit is communicatively coupled to an external device clock unit of the external device  108 A. In exemplary embodiments, a master reference clock is provided to the external device clock unit of the external device  108 A from the signal interface unit clock unit of the signal interface unit  102 A. In other exemplary embodiments, a master reference clock is provided from the external device clock unit of the external device  108 A to the signal interface unit clock unit of the signal interface unit  102 A. In other exemplary embodiments, a network interface clock unit is not coupled directly to an external device clock unit of the external device  108 A to provide the master reference clock to the external device  108 A. Instead, a signal interface unit clock unit provides the master reference clock to the signal conversion module  202  and the master reference clock is embedded in an upstream signal from the signal conversion module  202  to the external device  108 A. In particular, uplink signals can be clocked using the master clock, such that the master clock is embedded in the uplink signals. Then, an external device clock unit extracts the master clock from uplink signals and distributes the master clock as appropriate in the external device  108 A to establish a common clock with the distributed antenna system  100  in the external device  108 A. In exemplary embodiments where the master reference clock is provided from an external device  108 A to the distributed antenna system  100 , the master reference clock can be embedded in the downlink radio system signals by an external device clock unit so that the downlink radio system signals communicated from the external device  108 A to the signal conversion module  202  can be extracted by a signal interface unit clock unit and distributed as appropriate within the signal interface unit  102 A and the distributed antenna system  100  generally. 
       FIG. 2B  is a block diagram of an exemplary embodiment of a type of signal interface unit  102 , channelized radio carrier signal interface unit  102 B. Channelized radio carrier signal interface unit  102 B includes a signal conversion module  202 , a channelized radio carrier external device interface  204 B, the antenna side interface  206 , the optional processor  208 , the optional memory  210 , and the optional power supply  212 . Channelized radio carrier signal interface unit  102 B includes similar components to general signal interface unit  102 A and operates according to similar principles and methods as general signal interface unit  102 A. The difference between channelized radio carrier signal interface unit  102 B and general signal interface unit  102 A is that the channelized radio carrier signal interface unit  102 B is a more specific embodiment that interfaces with a channelized radio carrier base station unit  108 B using a channelized radio carrier external device interface  204 B. Further the channelized radio carrier signal interface unit  102 B includes a signal conversion module  202  that converts between channelized radio carrier signals and the radio system signals used for transport in the distributed antenna system  100  network. 
     In the downlink, the channelized radio carrier external device interface  204 B is configured to receive downlink channelized radio carrier signals from the channelized radio carrier base station unit  108 B. The signal conversion module  202  is configured to convert the received downlink channelized radio carrier signals to a downlink radio system signal. In exemplary embodiments, the signal conversion module  202  and/or the antenna side interface  206  converts the radio system signal from electrical signals to optical signals for output on communication link  112 . In other embodiments, the radio system signal is transported using a conductive communication medium, such as coaxial cable or twisted pair, and the optical conversion is not necessary. The antenna side interface  206  is configured to communicate the downlink radio system signal on communication link  112 . 
     In exemplary embodiments, the signal conversion module  202  is further configured to adjust a downlink attribute of the downlink radio system signal based on differences in attributes and/or performance characteristics of the channelized radio carrier base station unit  108 B and the channelized radio carrier signal interface unit  102 B and/or distributed antenna system  100 . In exemplary embodiments, the signal conversion module  202  adjusts at least one of these downlink attributes based on requirements set by the channelized radio carrier base station unit  108 B and knowledge about the attributes and/or performance characteristics of the distributed antenna system  100 &#39;s effect on the downlink signals. This enables the distributed antenna system  100  to distribute downlink radio system signals to at least one antenna unit  104  that will then be broadcast to at least one subscriber unit  118  and appear as if it were transmitted directly from a radio head connected to the channelized radio carrier base station unit  108 B. This enables the distributed antenna system  100  to appear transparent to the at least one subscriber unit  118  in the downlink. 
     In exemplary embodiments, the at least one downlink attribute of the downlink radio system signal includes a power level, gain, noise floor, and/or delay. In exemplary embodiments where the at least one downlink attribute includes a delay, delays to individual antennas within the distributed antenna system  100  are detected, additional delay is added to the downlink delays for all except the longest delays to normalize and/or equalize the delays in the distributed antenna system  100 , and the combined delay-equalized signal is presented to the channelized radio carrier base station unit  108 B as if it were a single signal with a single delay value. 
     In exemplary embodiments, the downlink channelized radio carrier data is specific to a particular channel and requires additional channelized radio carrier conversion before radio frequency conversion and transmission can be performed. In exemplary embodiments, the downlink radio system signal is not specific to a particular channel and does not require additional channelized radio carrier conversion before radio frequency conversion and transmission can be performed. In exemplary embodiments, the downlink radio system signal contains an individual channel that is positioned within a set of spectrum that reflects its eventual location within radio frequency spectrum. In exemplary embodiments, the downlink radio system signal interface is communicatively coupled with an intermediary device that aggregates the downlink radio system signal with at least one other downlink radio system signal before being transmitted to at least one antenna unit  104 . In exemplary embodiments, the individual channels within the downlink radio system signal and the at least one other downlink radio system signal do not overlap and can be upconverted together simultaneously to radio frequency spectrum. 
     In the uplink, antenna side interface  206  is configured to receive an uplink radio system signal from communication link  112 . In exemplary embodiments where communication link  112  is an optical medium, the antenna side interface  206  and/or the signal conversion module  202  is configured to convert the uplink radio system signal between received optical signals and electrical signals. In other embodiments, the radio system signal is transported using a conductive communication medium, such as coaxial cable or twisted pair, and the optical conversion is not necessary. The signal conversion module  202  is further configured to convert the uplink radio system signal to uplink channelized radio carrier signals. Channelized radio carrier external device interface  204 B is configured to communicate the uplink channelized radio carrier signals to the channelized radio carrier base station unit  108 B. 
     In the uplink of exemplary embodiments, the signal conversion module  202  is further configured to adjust an uplink attribute of the uplink radio system signal based on differences in attributes and/or performance characteristics of the channelized radio carrier base station unit  108 B and the channelized radio carrier signal interface unit  102 B and/or distributed antenna system  100 . In exemplary embodiments, the signal conversion module  202  adjusts at least one of these uplink attributes based on requirements set by the channelized radio carrier base station unit  108 B and knowledge about the attributes and/or performance characteristics of the distributed antenna system  100 &#39;s effect on the uplink signals. This enables the distributed antenna system  100  to receive uplink radio system signals from at least one antenna unit  104  that were received from at least one subscriber unit  118  and appear as if it were received directly at a radio head connected to the channelized radio carrier base station unit  108 B. This enables the distributed antenna system  100  to appear transparent to the at least one channelized radio carrier base station unit  108 B in the uplink. 
     In exemplary embodiments, the at least one uplink attribute of the uplink radio system signal includes a power level, gain, uplink noise floor, and/or delay. In exemplary embodiments where the at least one uplink attribute includes a power level, gain, and/or noise floor, the uplink gains from individual antennas are scaled by a factor of 1/N, where N is the number of antennas belonging to that simulcast group. The individual amplitude-adjusted signals are then combined into a composite uplink signal and the summed signal is scaled so that either the composite signal level or the composite noise floor matches what the channelized radio carrier base station unit  108 B expects to see from a single antenna. The combined gain-equalized signal is presented to the channelized radio carrier base station unit  108 B as if it were a single signal with a single gain and/or noise floor value. In exemplary embodiments where the at least one uplink attribute includes a delay, delays to individual antennas within the distributed antenna system  100  are detected, additional delay is added to the uplink delays for all except the longest delays to normalize and/or equalize the delays in the distributed antenna system  100 , and the combined delay-equalized signal is presented to the channelized radio carrier base station unit  108 B as if it were a single signal with a single delay value. 
     In exemplary embodiments, the uplink radio system signal contains an individual channel that is positioned within a set of spectrum that reflects its eventual location within radio frequency spectrum. In exemplary embodiments, the channelized radio carrier signal interface unit  102 B is communicatively coupled with an intermediary device that separates the uplink radio system signal from an aggregate uplink radio system signal received from at least one antenna unit  104  and including at least one other uplink radio system signal. In exemplary implementations, the individual channels within the uplink radio system signal and the at least one other uplink radio system signal do not overlap and can be downconverted together simultaneously from radio frequency spectrum. In exemplary embodiments, the uplink radio system signal is not specific to a particular channel and does not require any channelized radio carrier processing when converted from radio frequency, while uplink channelized data is specific to a particular channel and requires channelized radio carrier processing when being converted from radio frequency. 
     In exemplary embodiments, an optional network interface clock unit is communicatively coupled to an external device clock unit of the channelized radio carrier base station unit  108 B and a master reference clock is provided as described above with reference to  FIG. 2A . 
       FIG. 2C  is a block diagram of an exemplary embodiment of a type of signal interface unit  102 , baseband signal interface unit  102 C. Baseband signal interface unit  102 C includes a signal conversion module  202 , a baseband external device interface  204 C, the antenna side interface  206 , the optional processor  208 , the optional memory  210 , and the optional power supply  212 . Baseband signal interface unit  102 C includes similar components to general signal interface unit  102 A and operates according to similar principles and methods as general signal interface unit  102 A. The difference between baseband signal interface unit  102 C and general signal interface unit  102 A is that the baseband signal interface unit  102 C is a more specific embodiment that interfaces with a baseband base station  108 C using a baseband external device interface  204 C. Further the baseband signal interface unit  102 C includes a signal conversion module  202  that converts between baseband signals and the radio system signals used for transport in the distributed antenna system  100  network. 
     In the downlink, the baseband external device interface  204 C is configured to receive downlink baseband signals from the baseband base station  108 C. The signal conversion module  202  is configured to convert the received downlink baseband signals to a downlink radio system signal. In exemplary embodiments, the signal conversion module  202  and/or the antenna side interface  206  converts the radio system signal from electrical signals to optical signals for output on communication link  112 . In other embodiments, the radio system signal is transported using a conductive communication medium, such as coaxial cable or twisted pair, and the optical conversion is not necessary. The antenna side interface  206  is configured to communicate the downlink radio system signal on communication link  112 . 
     In exemplary embodiments, the signal conversion module  202  is further configured to adjust a downlink attribute of the downlink radio system signal based on differences in attributes and/or performance characteristics of the baseband base station  108 C and the baseband signal interface unit  102 C and/or distributed antenna system  100 . In exemplary embodiments, the signal conversion module  202  adjusts at least one of these downlink attributes based on requirements set by the baseband base station  108 C and knowledge about the attributes and/or performance characteristics of the distributed antenna system  100 &#39;s effect on the downlink signals. This enables the distributed antenna system  100  to distribute downlink radio system signals to at least one antenna unit  104  that will then be broadcast to at least one subscriber unit  118  and appear as if it were transmitted directly from a radio head connected to the baseband base station  108 C. This enables the distributed antenna system  100  to appear transparent to the at least one subscriber unit  118  in the downlink. 
     In exemplary embodiments, the at least one downlink attribute includes a power level, gain, noise floor, and/or delay. In exemplary embodiments where the at least one downlink attribute includes a delay, delays to individual antennas within the distributed antenna system  100  are detected, additional delay is added to the downlink delays for all except the longest delays to normalize and/or equalize the delays in the distributed antenna system  100 , and the combined delay-equalized signal is presented to the baseband base station  108 C as if it were a single signal with a single delay value. 
     In exemplary embodiments, the downlink baseband data is specific to a particular channel and requires additional baseband conversion before radio frequency conversion and transmission can be performed. In exemplary embodiments, the downlink radio system signal is not specific to a particular channel and does not require additional baseband conversion before radio frequency conversion and transmission can be performed. In exemplary embodiments, the downlink radio system signal contains an individual channel that is positioned within a set of spectrum that reflects its eventual location within radio frequency spectrum. In exemplary embodiments, the downlink radio system signal interface is communicatively coupled with an intermediary device that aggregates the downlink radio system signal with at least one other downlink radio system signal before being transmitted to at least one antenna unit  104 . In exemplary embodiments, the individual channels within the downlink radio system signal and the at least one other downlink radio system signal do not overlap and can be upconverted together simultaneously to radio frequency spectrum. 
     In the uplink, antenna side interface  206  is configured to receive an uplink radio system signal from communication link  112 . In exemplary embodiments where communication link  112  is an optical medium, the antenna side interface  206  and/or the signal conversion module  202  is configured to convert the uplink radio system signal between received optical signals and electrical signals. In other embodiments, the radio system signal is transported using a conductive communication medium, such as coaxial cable or twisted pair, and the optical conversion is not necessary. The signal conversion module  202  is further configured to convert the uplink radio system signal to uplink baseband signals. Baseband external device interface  204 C is configured to communicate the uplink baseband signals to the baseband base station  108 C. 
     In the uplink of exemplary embodiments, the signal conversion module  202  is further configured to adjust an uplink attribute of the uplink radio system signal based on differences in attributes and/or performance characteristics of the baseband base station  108 C and the baseband signal interface unit  102 C and/or distributed antenna system  100 . In exemplary embodiments, the signal conversion module  202  adjusts at least one of these uplink attributes based on requirements set by the baseband base station  108 C and knowledge about the attributes and/or performance characteristics of the distributed antenna system  100 &#39;s effect on the uplink signals. This enables the distributed antenna system  100  to receive uplink radio system signals from at least one antenna unit  104  that were received from at least one subscriber unit  118  and appear as if it were received directly at a radio head connected to the baseband base station  108 C. This enables the distributed antenna system  100  to appear transparent to the at least one baseband base station  108 C in the uplink. 
     In exemplary embodiments, the at least one uplink attribute includes a power level, gain, uplink noise floor, and/or delay. In exemplary embodiments where the at least one uplink attribute includes a power level, gain, and/or noise floor, the uplink gains from individual antennas are scaled by a factor of 1/N, where N is the number of antennas belonging to that simulcast group. The individual amplitude-adjusted signals are then combined into a composite uplink signal and the summed signal is scaled so that either the composite signal level or the composite noise floor matches what the baseband base station  108 C expects to see from a single antenna. The combined gain-equalized signal is presented to the baseband base station  108 C as if it were a single signal with a single gain and/or noise floor value. In exemplary embodiments where the at least one uplink attribute includes a delay, delays to individual antennas within the distributed antenna system  100  are detected, additional delay is added to the uplink delays for all except the longest delays to normalize and/or equalize the delays in the distributed antenna system  100 , and the combined delay-equalized signal is presented to the baseband base station  108 C as if it were a single signal with a single delay value. 
     In exemplary embodiments, the uplink radio system signal contains an individual channel that is positioned within a set of spectrum that reflects its eventual location within radio frequency spectrum. In exemplary embodiments, the baseband signal interface unit  102 C is communicatively coupled with an intermediary device that separates the uplink radio system signal from an aggregate uplink radio system signal received from at least one antenna unit  104  and including at least one other uplink radio system signal. In exemplary implementations, the individual channels within the uplink radio system signal and the at least one other uplink radio system signal do not overlap and can be downconverted together simultaneously from radio frequency spectrum. In exemplary embodiments, the uplink radio system signal is not specific to a particular channel and does not require any baseband processing when converted from radio frequency, while uplink channelized data is specific to a particular channel and requires baseband processing when being converted from radio frequency. 
     In exemplary embodiments, an optional network interface clock unit is communicatively coupled to an external device clock unit of the baseband base station  108 C and a master reference clock is provided as described above with reference to  FIG. 2A . 
       FIG. 2D  is a block diagram of an exemplary embodiment of a type of signal interface unit  102 , Common Public Radio Interface (CPRI) signal interface unit  102 D. CPRI signal interface unit  102 D includes a signal conversion module  202 , a CPRI external device interface  204 D, the antenna side interface  206 , the optional processor  208 , the optional memory  210 , and the optional power supply  212 . CPRI signal interface unit  102 D includes similar components to general signal interface unit  102 A and operates according to similar principles and methods as general signal interface unit  102 A. The difference between CPRI signal interface unit  102 D and general signal interface unit  102 A is that the CPRI signal interface unit  102 D is a more specific embodiment that interfaces with a CPRI base station  108 D using a CPRI external device interface  204 D. Further, the CPRI signal interface unit  102 D includes a signal conversion module  202  that converts between CPRI signals and the radio system signals used for transport in the distributed antenna system  100  network. 
     In the downlink, the CPRI external device interface  204 D is configured to receive downlink CPRI signals from the CPRI base station  108 D. The signal conversion module  202  is configured to convert the received downlink CPRI signals to a downlink radio system signal. In exemplary embodiments, the signal conversion module  202  and/or the antenna side interface  206  converts the radio system signal from electrical signals to optical signals for output on communication link  112 . In other embodiments, the radio system signal is transported using a conductive communication medium, such as coaxial cable or twisted pair, and the optical conversion is not necessary. The antenna side interface  206  is configured to communicate the downlink radio system signal on communication link  112 . 
     In exemplary embodiments, the signal conversion module  202  is further configured to adjust a downlink attribute of the downlink radio system signal based on differences in attributes and/or performance characteristics of the CPRI base station unit  108 D and the CPRI signal interface unit  102 D and/or distributed antenna system  100 . In exemplary embodiments, the signal conversion module  202  adjusts at least one of these downlink attributes based on requirements set by the CPRI base station unit  108 D and knowledge about the attributes and/or performance characteristics of the distributed antenna system  100 &#39;s effect on the downlink signals. This enables the distributed antenna system  100  to distribute downlink radio system signals to at least one antenna unit  104  that will then be broadcast to at least one subscriber unit  118  and appear as if it were transmitted directly from a radio head connected to the CPRI base station  108 D. This enables the distributed antenna system  100  to appear transparent to the at least one subscriber unit  118  in the downlink. 
     In exemplary embodiments, the at least one downlink attribute includes a power level, gain, noise floor, and/or delay. In exemplary embodiments where the at least one downlink attribute includes a delay, delays to individual antennas within the distributed antenna system  100  are detected, additional delay is added to the downlink delays for all except the longest delays to normalize and/or equalize the delays in the distributed antenna system  100 , and the combined delay-equalized signal is presented to the external device as if it were a single signal with a single delay value. 
     In exemplary embodiments, the downlink baseband data is specific to a particular channel and requires additional baseband conversion before radio frequency conversion and transmission can be performed. In exemplary embodiments, the downlink radio system signal is not specific to a particular channel and does not require additional baseband conversion before radio frequency conversion and transmission can be performed. In exemplary embodiments, the downlink radio system signal contains an individual channel that is positioned within a set of spectrum that reflects its eventual location within radio frequency spectrum. In exemplary embodiments, the downlink radio system signal interface is communicatively coupled with an intermediary device that aggregates the downlink radio system signal with at least one other downlink radio system signal before being transmitted to at least one antenna unit  104 . In exemplary embodiments, the individual channels within the downlink radio system signal and the at least one other downlink radio system signal do not overlap and can be upconverted together simultaneously to radio frequency spectrum. 
     In the uplink, antenna side interface  206  is configured to receive an uplink radio system signal from communication link  112 . In exemplary embodiments where communication link  112  is an optical medium, the antenna side interface  206  and/or the signal conversion module  202  is configured to convert the uplink radio system signal between received optical signals and electrical signals. In other embodiments, the radio system signal is transported using a conductive communication medium, such as coaxial cable or twisted pair, and the optical conversion is not necessary. The signal conversion module  202  is further configured to convert the uplink radio system signal to uplink CPRI signals. CPRI external device interface  204 D is configured to communicate the uplink signals to the CPRI base station  108 D. 
     In the uplink of exemplary embodiments, the signal conversion module  202  is further configured to adjust an uplink attribute of the uplink radio system signal based on differences in attributes and/or performance characteristics of the CPRI base station  108 D and the CPRI signal interface unit  102 D and/or distributed antenna system  100 . In exemplary embodiments, the signal conversion module  202  adjusts at least one of these uplink attributes based on requirements set by the CPRI base station  108 D and knowledge about the attributes and/or performance characteristics of the distributed antenna system  100 &#39;s affect on the uplink signals. This enables the distributed antenna system  100  to receive uplink radio system signals from at least one antenna unit  104  that were received from at least one subscriber unit  118  and appear as if it were received directly at a radio head connected to the CPRI base station  108 D. This enables the distributed antenna system  100  to appear transparent to the at least one CPRI base station  108 D in the uplink. 
     In exemplary embodiments, the at least one uplink attribute includes a power level, gain, uplink noise floor, and/or delay. In exemplary embodiments where the at least one uplink attribute includes a power level, gain, and/or noise floor, the uplink gains from individual antennas are scaled by a factor of 1/N, where N is the number of antennas belonging to that simulcast group. The individual amplitude-adjusted signals are then combined into a composite uplink signal and the summed signal is scaled so that either the composite signal level or the composite noise floor matches what the CPRI base station  108 D expects to see from a single antenna. The combined gain-equalized signal is presented to the CPRI base station  108 D as if it were a single signal with a single gain and/or noise floor value. In exemplary embodiments where the at least one uplink attribute includes a delay, delays to individual antennas within the distributed antenna system  100  are detected, additional delay is added to the uplink delays for all except the longest delays to normalize and/or equalize the delays in the distributed antenna system  100 , and the combined delay-equalized signal is presented to the CPRI base station  108 D as if it were a single signal with a single delay value. 
     In exemplary embodiments, the uplink radio system signal contains an individual channel that is positioned within a set of spectrum that reflects its eventual location within radio frequency spectrum. In exemplary embodiments, the CPRI signal interface unit  102 D is communicatively coupled with an intermediary device that separates the uplink radio system signal from an aggregate uplink radio system signal received from at least one antenna unit  104  and including at least one other uplink radio system signal. In exemplary implementations, the individual channels within the uplink radio system signal and the at least one other uplink radio system signal do not overlap and can be downconverted together simultaneously from radio frequency spectrum. In exemplary embodiments, the uplink radio system signal is not specific to a particular channel and does not require any baseband processing when converted from radio frequency, while uplink channelized data is specific to a particular channel and requires baseband processing when being converted from radio frequency. 
     In exemplary embodiments, an optional network interface clock unit is communicatively coupled to an external device clock unit of the CPRI base station  108 D and a master reference clock is provided as described above with reference to  FIG. 2A . 
       FIG. 3  is a block diagram of an exemplary embodiment of an antenna unit  104  used in distributed antenna systems, such as exemplary distributed antenna system  100  described above. The antenna unit  104  includes a signal multiplexing module  302 , at least one radio frequency (RF) conversion module  304  (including RF conversion module  304 - 1  and any amount of optional RF conversion modules  304  through optional RF conversion module  304 -C), network interface module  306 , optional Ethernet interface  308 , optional antenna unit clock unit  310 , optional processor  312 , optional memory  314 , and optional power supply  316 . In exemplary embodiments, signal multiplexing module  302 , at least one RF conversion module  304 , and/or the network interface module  306  are implemented at least in part by optional processor  312  and optional memory  314 . In exemplary embodiments, optional power supply  316  is used to power the various components of the antenna unit  104 . 
     In exemplary embodiments, signal multiplexing module  302  receives at least one downlink radio system signal from at least one signal interface unit  102  through the distributed switching network  106 . In exemplary embodiments, the at least one downlink radio system signal is received through the network interface module  306 . In exemplary embodiments where the downlink radio system signal is an optical signal, the network interface module  306  converts the downlink radio system signal from an optical format to an electrical format. In exemplary embodiments, more input lines and/or more network interface module  306  are included in the antenna unit  104 . In exemplary embodiments, the signal multiplexing module  302  splits apart an aggregate downlink radio system signal into at least one downlink radio system signal that is sent to RF conversion module  304 - 1  for eventual transmission as a radio frequency on radio frequency antenna  116 - 1 . In exemplary embodiments, the signal multiplexing module  302  splits apart the aggregate downlink radio system signal into a plurality of downlink radio system signals that are sent to a plurality of RF conversion modules  304  for eventual transmission as radio frequency signals at radio frequency antennas  116 . 
     In exemplary embodiments, signal multiplexing module  302  receives at least one uplink radio system signal from at least one RF conversion module  304 . In exemplary embodiments, the signal multiplexing module  302  receives a plurality of uplink radio system signals from a plurality of RF conversion modules  304 . In exemplary embodiments, the radio system signal multiplexing unit aggregates at least one uplink radio system signal received from an RF conversion module  304 - 1  with another uplink radio system signal received from another RF conversion module  304 . In exemplary embodiments, the signal multiplexing module  302  aggregates a plurality of uplink radio system signals into a single aggregate uplink radio system signal. In exemplary embodiments, the aggregate uplink radio system signal is provided to network interface module  306  which converts the aggregate uplink radio system signal from electrical signals to optical signals before communicating the aggregate uplink radio system signal to the distributed switching network  106  through the distributed switching network  106 . In other embodiments, the aggregate uplink radio system signal is communicated as electrical signals toward the distributed switching network  106 . In exemplary embodiments, the aggregate uplink signal is converted to optical signals at another place in the distributed antenna system  100 . 
     In exemplary embodiments, the optional Ethernet interface  308  receives a downlink radio system signal from the signal multiplexing module  302  and converts it to Ethernet packets and communicates the Ethernet packets with an internet protocol network device. The optional Ethernet interface  308  also receives Ethernet packets from the internet protocol network device and converts them to an uplink radio system signal and communicates it to the signal multiplexing module  302 . In exemplary embodiments having the optional Ethernet interface  308 , a corresponding external device  108  that is an Ethernet interface interfaces with a signal interface unit  102  that is an Ethernet interface. 
     In exemplary embodiments, the optional antenna unit clock unit  310  extracts the master reference clock from the downlink radio system signal and uses this master clock within the antenna unit  104  to establish a common time base in the antenna unit  104  with the rest of the distributed antenna system  100 . In exemplary embodiments, the optional antenna unit clock unit  310  generates a master reference clock and distributes the generated master reference clock to other components of the distributed antenna system  100  (and even the external devices  108 ) in the upstream using the uplink radio system signal. 
       FIGS. 4A-4C  are block diagrams of exemplary embodiments of RF conversion modules  304  used in antenna units of distributed antenna systems, such as the exemplary antenna unit  104  described above. Each of  FIGS. 4A-4C  are block diagrams of exemplary embodiments of RF conversion module  304 , labeled RF conversion module  304 A- 304 C respectively. 
       FIG. 4A  is a block diagram of an exemplary RF conversion module  304 A including an optional radio system signal conditioner  402 , a radio frequency (RF) converter  404 , an optional RF conditioner  406 , and an RF duplexer  408  coupled to a single radio frequency antenna  116 . 
     The optional radio system signal conditioner  402  is communicatively coupled to a signal multiplexing module  302  and the RF converter  404 . In the forward path, the optional radio system signal conditioner  402  conditions the downlink radio system signal (for example, through amplification, attenuation, and filtering) received from the signal multiplexing module  302  and passes the downlink radio system signal to the RF converter  404 . In the reverse path, the optional radio system signal conditioner  402  conditions the uplink radio system signal (for example, through amplification, attenuation, and filtering) received from the RF converter  404  and passes the uplink radio system signal to the signal multiplexing module  302 . 
     The RF converter  404  is communicatively coupled to either the signal multiplexing module  302  or the optional radio system signal conditioner  402  on one side and to either RF duplexer  408  or the optional RF conditioner  406  on the other side. In the downstream, the RF converter  404  converts a downlink radio system signal to downlink radio frequency (RF) signals and passes the downlink RF signals onto either the RF duplexer  408  or the optional RF conditioner  406 . In the upstream, the RF converter  404  converts uplink radio frequency (RF) signals received from either the RF duplexer  408  or the optional RF conditioner  406  to an uplink radio system signal and passes the uplink radio system signal to either the signal multiplexing module  302  or the optional radio system signal conditioner  402 . 
     The RF duplexer  408  is communicatively coupled to either the RF converter  404  or the optional RF conditioner  406  on one side and the radio frequency antenna  116  on the other side. The RF duplexer  408  duplexes the downlink RF signals with the uplink RF signals for transmission/reception using the radio frequency antenna  116 . In exemplary embodiments, the downlink and uplink signals within a radio frequency band are distinct in spectrum and are separated in a frequency using a Frequency Division Duplexing (FDD) scheme. In other embodiments, either or both of the downlink and uplink signals within the radio frequency band are separated in time using a Time Division Duplexing (TDD) scheme. In exemplary embodiments, downlink and uplink signals within a radio frequency band overlap in spectrum and are separated in time using a Time Division Duplexing (TDD) scheme. 
       FIG. 4B  is a block diagram of an exemplary RF conversion module  304 B including an optional radio system signal conditioner  402 , an RF converter  404 , and an optional RF conditioner  406  coupled to a downlink radio frequency antenna  116 A and an uplink radio frequency antenna  116 B. RF conversion module  304 B includes similar components to RF conversion module  304 A and operates according to similar principles and methods as RF conversion module  304 A described above. The difference between RF conversion module  304 B and RF conversion module  304 A is that RF conversion module  304 B does not include RF duplexer  408  and instead includes separate downlink radio frequency antenna  116 A used to transmit RF signals to at least one subscriber unit and uplink radio frequency antenna  116 B used to receive RF signals from at least one subscriber unit. 
       FIG. 4C  is a block diagram of an exemplary RF conversion module  304 C- 1  and exemplary RF conversion module  304 C- 2  that share a single radio frequency antenna  116  through an RF diplexer  410 . The RF conversion module  304 C- 1  includes an optional radio system signal conditioner  402 - 1 , an RF converter  404 - 1 , an optional RF conditioner  406 - 1 , and an RF duplexer  408 - 1  communicatively coupled to RF diplexer  410  that is communicatively coupled to radio frequency antenna  116 . Similarly, the RF conversion module  304 C- 2  includes an optional radio system signal conditioner  402 - 2 , an RF converter  404 - 2 , an optional RF conditioner  406 - 2 , and an RF duplexer  408 - 2  communicatively coupled to RF diplexer  410  that is communicatively coupled to radio frequency antenna  116 . Each of RF conversion module  304 C- 1  and  304 C- 2  operate according to similar principles and methods as RF conversion module  304 A described above. The difference between RF conversion modules  304 C- 1  and  304 C- 2  and RF conversion module  304 A is that RF conversion modules  304 C- 1  and  304 C- 2  are both coupled to a single radio frequency antenna  116  through RF diplexer  410 . The RF diplexer  410  diplexes the duplexed downlink and uplink signals for both RF conversion module  304 C- 1  and  304 C- 2  for transmission/reception using the single radio frequency antenna  116 . 
       FIG. 5  is a flow diagram illustrating one exemplary embodiment of a method  1100  of making a distributed antenna system appear as a radio head in a digital radio system. Exemplary method  500  begins at block  502  with receiving uplink digitized radio frequency signals for a radio frequency carrier from the distributed antenna system at a signal interface unit. 
     Exemplary method  500  proceeds to block  504  with converting the uplink digitized radio frequency signals to an uplink channelized radio carrier at the signal interface unit at least in part by adjusting at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of a channelized radio carrier base station interface communicatively coupled to the signal interface unit. In exemplary embodiments, the requirements of the channelized radio carrier base station interface are received at the signal conversion module from the channelized radio carrier base station interface. In exemplary embodiments, the at least one uplink attribute of the uplink digitized radio frequency signal includes a power level, a gain, a delay, and/or an uplink noise floor. In exemplary embodiments where the at least one uplink attribute includes a power level, gain, and/or noise floor, the uplink gains from individual antennas are scaled by a factor of 1/N, where N is the number of antennas belonging to that simulcast group. The individual amplitude-adjusted signals are then combined into a composite uplink signal and the summed signal is scaled so that either the composite signal level or the composite noise floor matches what the external device expects to see from a single antenna. The combined gain-equalized signal is presented to the external device as if it were a single signal with a single gain and/or noise floor value. In exemplary embodiments where the at least one uplink attribute includes a delay, delays to individual antennas within the distributed antenna system  100  are detected, additional delay is added to the uplink delays for all except the longest delays to normalize and/or equalize the delays in the distributed antenna system  100 , and the combined delay-equalized signal is presented to the external device as if it were a single signal with a single delay value. In exemplary embodiments, adjusting the at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of the channelized radio carrier base station interface includes scaling the uplink noise floor of the uplink digitized radio frequency signal to make the uplink noise floor comply with requirements for uplink noise floor of the channelized radio carrier base station interface. 
     Exemplary method  500  proceeds to block  506  with communicating the uplink channelized radio carrier for the radio frequency carrier from the signal interface unit to the channelized radio carrier base station interface. In exemplary embodiments, the uplink channelized radio carrier includes I/Q pairs. 
     Any of the processors described above may include or function with software programs, firmware or other computer readable instructions for carrying out various methods, process tasks, calculations, and control functions, described herein. These instructions are typically stored on any appropriate computer readable medium used for storage of computer readable instructions or data structures. The computer readable medium can be implemented as any available media that can be accessed by a general purpose or special purpose computer or processor, or any programmable logic device. Suitable processor-readable media may include storage or memory media such as magnetic or optical media. For example, storage or memory media may include conventional hard disks, Compact Disk-Read Only Memory (CD-ROM), volatile or non-volatile media such as Random Access Memory (RAM) (including, but not limited to, Synchronous Dynamic Random Access Memory (SDRAM), Double Data Rate (DDR) RAM, RAMBUS Dynamic RAM (RDRAM), Static RAM (SRAM), etc.), Read Only Memory (ROM), Electrically Erasable Programmable ROM (EEPROM), and flash memory, etc. Suitable processor-readable media may also include transmission media such as electrical, electromagnetic, or digital signals, conveyed via a communication medium such as a network and/or a wireless link. 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiments shown. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof. 
     EXAMPLE EMBODIMENTS 
     Example 1 includes a signal interface unit for a distributed antenna system, comprising: a channelized radio carrier interface configured to communicate an uplink channelized radio carrier for a radio frequency carrier to a channelized radio carrier base station interface; an antenna side interface configured to receive an uplink digitized radio frequency signal from the distributed antenna system communicatively coupled to the antenna side interface; and a signal conversion module communicatively coupled between the channelized radio carrier interface and the antenna side interface and configured to convert between the uplink digitized radio frequency signal and the uplink channelized radio carrier at least in part by adjusting at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of the channelized radio carrier base station interface. 
     Example 2 includes the signal interface unit of Example 1, wherein adjusting the at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of the channelized radio carrier base station interface includes digitally adjusting the at least one uplink attribute. 
     Example 3 includes the signal interface unit of any of Examples 1-2, wherein adjusting the at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of the channelized radio carrier base station interface includes digitally scaling an uplink gain of the uplink digitized radio frequency signal. 
     Example 4 includes the signal interface unit of any of Examples 1-3, wherein the signal conversion module is further configured to convert between the uplink digitized radio frequency signal and the uplink channelized radio carrier by converting between two distinct framing structures. 
     Example 5 includes the signal interface unit of any of Examples 1-4, wherein the signal conversion module is further configured to convert between the uplink digitized radio frequency signal and the uplink channelized radio carrier by converting from a digitized representation of radio frequency spectrum into a baseband channelized representation of the radio frequency spectrum. 
     Example 6 includes the signal interface unit of any of Examples 1-5, wherein the requirements of the channelized radio carrier base station interface are received at the signal conversion module from the channelized radio carrier base station interface. 
     Example 7 includes the signal interface unit of any of Examples 1-6, wherein the signal interface unit is configured to adjust characteristics reported to the channelized radio carrier base station interface based on the requirements of the channelized radio carrier base station interface. 
     Example 8 includes the signal interface unit of any of Examples 1-7, wherein the at least one uplink attribute of the uplink digitized radio frequency signal includes at least one of a power level, a gain, a delay, and an uplink noise floor. 
     Example 9 includes the signal interface unit of any of Examples 1-8, wherein adjusting the at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of the channelized radio carrier base station interface includes scaling an uplink noise floor of the uplink digitized radio frequency signal to make the uplink noise floor comply with requirements for uplink noise floor of the channelized radio carrier base station interface. 
     Example 10 includes the signal interface unit of any of Examples 1-9, wherein the uplink channelized radio carrier includes I/Q pairs. 
     Example 11 includes the signal interface unit of any of Examples 1-10, wherein the distributed antenna system is a digital distributed antenna system that communicates digitized radio frequency signals between the signal interface unit and an antenna unit where the digitized radio frequency signals are converted to radio frequency signals and transmitted to a subscriber unit. 
     Example 12 includes the signal interface unit of any of Examples 1-11, wherein the distributed antenna system communicates the digitized radio frequency signals between the signal interface unit and the antenna unit across a wired medium. 
     Example 13 includes the signal interface unit of any of Examples 1-12, wherein the distributed antenna system is a hybrid distributed antenna system that communicates digitized radio frequency signals between the signal interface unit and an intermediary device, converts between digitized radio frequency signals and analog signals at the intermediary device, and communicates the analog signals from the intermediary device to an antenna unit where the analog signals are converted to radio frequency signals and transmitted to a subscriber unit. 
     Example 14 includes the signal interface unit of any of Examples 1-13, wherein the distributed antenna system communicates the digitized radio frequency signals between the signal interface unit and the intermediary device across a wired medium. 
     Example 15 includes the signal interface unit of any of Examples 1-14, wherein the distributed antenna system communicates the digitized radio frequency signals between the intermediary device and the antenna unit across a wired medium. 
     Example 16 includes the signal interface unit of any of Examples 1-15, wherein the channelized radio carrier interface is further configured to receive a downlink channelized radio carrier for a second radio frequency carrier from a channelized radio carrier base station interface; wherein the antenna side interface is configured to communicate a downlink digitized radio frequency signal from the antenna side interface to the distributed antenna system; and wherein the signal conversion module is further configured to convert between the downlink channelized radio carrier and the downlink digitized radio frequency signal at least in part by adjusting at least one downlink attribute of the downlink digitized radio frequency signal to comply with requirements of the channelized radio carrier base station interface. 
     Example 17 includes a signal interface unit for an antenna system, comprising: an external device interface configured to communicate a first uplink signal to an external device; an antenna side interface configured to receive a second uplink signal from an antenna unit communicatively coupled to the antenna side interface; a signal conversion module communicatively coupled between the external device interface and the antenna side interface and configured to convert from the second uplink signal to the first uplink signal at least in part by digitally adjusting at least one uplink attribute of the second uplink signal received from the antenna side interface to comply with requirements of the external device. 
     Example 18 includes the signal interface unit of Example 17, wherein adjusting the at least one uplink attribute of the second uplink signal received from the antenna side interface to comply with requirements of the external device includes digitally scaling an uplink gain of the second uplink signal. 
     Example 19 includes the signal interface unit of any of Examples 17-18, wherein the signal conversion module is further configured to convert between the second uplink signal and the first uplink signal by converting between two distinct framing structures. 
     Example 20 includes the signal interface unit of any of Examples 17-19, wherein the signal conversion module is further configured to convert between the second uplink signal and the first uplink signal by converting from a digitized representation of radio frequency spectrum into a baseband channelized representation of the radio frequency spectrum. 
     Example 21 includes the signal interface unit of any of Examples 17-20, wherein the external device interface is a baseband signal interface unit. 
     Example 22 includes the signal interface unit of any of Examples 17-21, wherein the external device interface is at least one of a Common Public Radio Interface (CPRI) external device interface, an Open Base Station Architecture Initiative (OBSAI) external device interface, and an Open Radio Interface (ORI) external device interface. 
     Example 23 includes the signal interface unit of any of Examples 17-22, wherein the requirements of the external device are received at the signal conversion module from the external device interface. 
     Example 24 includes the signal interface unit of any of Examples 17-23, wherein the signal interface unit is configured to adjust characteristics reported to the channelized radio carrier base station interface based on the requirements of the channelized radio carrier base station interface. 
     Example 25 includes the signal interface unit of any of Examples 17-24, wherein the at least one uplink attribute of the uplink digitized radio frequency signal includes at least one of a power level, a gain, a delay, and an uplink noise floor. 
     Example 26 includes the signal interface unit of any of Examples 17-25, wherein adjusting the at least one uplink attribute of the second uplink signal received from the antenna side interface to comply with requirements of the external device includes scaling the uplink noise floor of the second uplink signal to make the uplink noise floor comply with requirements for uplink noise floor of the external device. 
     Example 27 includes the signal interface unit of any of Examples 17-26, wherein the first uplink signal includes I/Q pairs. 
     Example 28 includes the signal interface unit of any of Examples 17-27, wherein the antenna side interface is communicatively coupled to an antenna unit and receives the second uplink signals from the antenna unit; and wherein the antenna unit converts received radio frequency signals from a subscriber unit to the second uplink signals. 
     Example 29 includes the signal interface unit of any of Examples 17-28, wherein the antenna side interface receives the second uplink signals from the antenna unit across a wired medium. 
     Example 30 includes the signal interface unit of any of Examples 17-29, wherein the antenna side interface receives the second uplink signals from an intermediary device positioned between the antenna side interface and the antenna unit. 
     Example 31 includes the signal interface unit of Example 30, wherein the antenna side interface receives the second uplink signals from the intermediary device across a wired medium. 
     Example 32 includes the signal interface unit of any of Examples 30-31, wherein the intermediary device receives analog signals from the antenna unit, converts the analog signals to the second uplink signals, and communicates the second uplink signals to the antenna side interface. 
     Example 33 includes the signal interface unit of any of Examples 30-32, wherein the intermediary device receives the analog signals from the antenna unit across a wired medium. 
     Example 34 includes the signal interface unit of any of Examples 17-33, wherein the external device interface is further configured to receive a first downlink signal from an external device; wherein the antenna side interface is configured to communicate a second downlink signal from the antenna side interface to the distributed antenna system; and wherein the signal conversion module is further configured to convert between the first downlink signal and the second downlink signal at least in part by digitally adjusting at least one downlink attribute of the second downlink signal to comply with requirements of the external device. 
     Example 35 includes a method for making a distributed antenna system appear as a radio head in a digital radio system, comprising: receiving an uplink digitized radio frequency signal for a radio frequency carrier from the distributed antenna system at a signal interface unit; converting the uplink digitized radio frequency signal to an uplink channelized radio carrier at the signal interface unit at least in part by adjusting at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of a channelized radio carrier base station interface communicatively coupled to the signal interface unit; communicating the uplink channelized radio carrier for the radio frequency carrier from the signal interface unit to the channelized radio carrier base station interface. 
     Example 36 includes the method of Example 35, wherein adjusting the at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of the external device includes digitally adjusting the at least one uplink attribute. 
     Example 37 includes the method of any of Examples 35-36, wherein adjusting the at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of the external device includes digitally scaling an uplink gain of the uplink digitized radio frequency signal. 
     Example 38 includes the method of any of Examples 35-37, wherein converting the uplink digitized radio frequency signal to an uplink channelized radio carrier further includes converting between two distinct framing structures. 
     Example 39 includes the method of any of Examples 35-38, wherein converting the uplink digitized radio frequency signal to an uplink channelized radio carrier further includes converting from a digitized representation of radio frequency spectrum into a baseband channelized representation of the radio frequency spectrum. 
     Example 40 includes the method of any of Examples 35-39, wherein the requirements of the channelized radio carrier base station interface are received at the signal conversion module from the channelized radio carrier base station interface. 
     Example 41 includes the method of any of Examples 35-40, further comprising adjusting characteristics reported to the channelized radio carrier base station interface based on the requirements of the channelized radio carrier base station interface. 
     Example 42 includes the method of any of Examples 35-41, wherein the at least one uplink attribute of the uplink digitized radio frequency signal includes at least one of a power level, a gain, a delay, and an uplink noise floor. 
     Example 43 includes the method of any of Examples 35-42, wherein adjusting the at least one uplink attribute of the uplink digitized radio frequency signal received from the distributed antenna system to comply with requirements of the channelized radio carrier base station interface includes scaling the uplink noise floor of the uplink digitized radio frequency signal to make the uplink noise floor comply with requirements for uplink noise floor of the channelized radio carrier base station interface. 
     Example 44 includes the method of any of Examples 35-43, wherein the uplink channelized radio carrier includes I/Q pairs. 
     Example 45 includes the method of any of Examples 35-44, wherein the distributed antenna system is a digital distributed antenna system that communicates digitized radio frequency signals between the signal interface unit and an antenna unit where the digitized radio frequency signals are converted to radio frequency signals and transmitted to a subscriber unit. 
     Example 46 includes the method of any of Examples 35-45, wherein the distributed antenna system communicates the digitized radio frequency signals between the signal interface unit and the antenna unit across a wired medium. 
     Example 47 includes the method of any of Examples 35-46, wherein the distributed antenna system is a hybrid distributed antenna system that communicates digitized radio frequency signals between the signal interface unit and an intermediary device, converts between digitized radio frequency signals and analog signals at the intermediary device, and communicates the analog signals from the intermediary device to an antenna unit where the analog signals are converted to radio frequency signals and transmitted to a subscriber unit. 
     Example 48 includes the method of any of Examples 35-47, wherein the distributed antenna system communicates the digitized radio frequency signals between the signal interface unit and the intermediary device across a wired medium. 
     Example 49 includes the method of any of Examples 35-48, wherein the distributed antenna system communicates the digitized radio frequency signals between the intermediary device and the antenna unit across a wired medium. 
     Example 50 includes the method of any of Examples 35-49, wherein the channelized radio carrier base station interface is part of a base band unit of a base station. 
     Example 51 includes the method of any of Examples 35-50, wherein the channelized radio carrier base station interface is at least one of a Common Public Radio Interface (CPRI) base station interface, an Open Base Station Architecture Initiative (OBSAI) base station interface, and an Open Radio Interface (ORI) interface; and wherein the downlink channelized radio carrier signal is formatted according to at least one of a Common Public Radio Interface (CPRI) standard, an Open Base Station Architecture Initiative (OBSAI) standard, and an Open Radio Interface (ORI) standard. 
     Example 52 includes the method of any of Examples 35-51, wherein the downlink digital radio frequency signal contains a digital representation of the radio carrier positioned within a set of spectrum that reflects its eventual location within radio frequency spectrum. 
     Example 53 includes the method of any of Examples 35-52, further comprising receiving a downlink channelized radio carrier for a second radio frequency carrier from the channelized radio carrier base station interface at the channelized radio carrier interface; communicating a downlink digitized radio frequency signal from the antenna side interface to the distributed antenna system; and converting between the downlink channelized radio carrier and the downlink radio frequency signal at the signal conversion module at least in part by adjusting at least one downlink attribute of the downlink digitized radio frequency signal to comply with requirements of the channelized radio carrier base station interface. 
     Example 54 includes a method of conforming uplink signals to requirements of an external device, comprising: receiving a first uplink signal from an antenna unit at an antenna side interface of a signal interface unit; converting the first uplink signal to a second uplink signal at the signal interface unit at least in part by adjusting at least one uplink attribute of the first uplink signal received from the antenna unit to comply with requirements of an external device communicatively coupled to the signal interface unit; and communicating the second uplink signal from an external device interface of the signal interface unit to the external device. 
     Example 55 includes the method of Example 54, wherein adjusting the at least one uplink attribute of the first uplink signal received from the antenna side interface to comply with requirements of the external device includes digitally adjusting the at least one uplink attribute. 
     Example 56 includes the method of any of Examples 54-55, wherein adjusting the at least one uplink attribute of the first uplink signal received from the antenna side interface to comply with requirements of the external device includes digitally scaling an uplink gain of the second uplink signal. 
     Example 57 includes the method of any of Examples 54-56, wherein converting the first uplink signal to a second uplink signal at the signal interface unit further includes converting between two distinct framing structures. 
     Example 58 includes the method of any of Examples 54-57, wherein converting the first uplink signal to a second uplink signal at the signal interface unit further includes converting from a digitized representation of radio frequency spectrum into a baseband channelized representation of the radio frequency spectrum. 
     Example 59 includes the method of any of Examples 54-58, wherein the external device interface is a baseband signal interface unit. 
     Example 60 includes the method of any of Examples 54-59, wherein the external device interface is at least one of a Common Public Radio Interface (CPRI) external device interface, an Open Base Station Architecture Initiative (OBSAI) external device interface, and an Open Radio Interface (ORI) external device interface. 
     Example 61 includes the method of any of Examples 54-60, further comprising receiving the requirements of the external device at the signal conversion module from the external device interface. 
     Example 62 includes the method of any of Examples 54-61, further comprising adjusting characteristics reported to the external device based on the requirements of the external device. 
     Example 63 includes the method of any of Examples 54-62, wherein the at least one uplink attribute of the first uplink signal includes at least one of a power level, a gain, a delay, and an uplink noise floor. 
     Example 64 includes the method of any of Examples 54-63, wherein adjusting the at least one uplink attribute of the second uplink signal received from the antenna side interface to comply with requirements of the external device includes scaling the uplink noise floor of the second uplink signal to make the uplink noise floor comply with requirements for uplink noise floor of the external device. 
     Example 65 includes the method of any of Examples 54-64, wherein the second uplink signal includes I/Q pairs. 
     Example 66 includes the method of any of Examples 54-65, further comprising converting uplink radio frequency signals into the first uplink signals at the antenna unit. 
     Example 67 includes the method of any of Examples 54-66, wherein receiving the first uplink signals from the antenna unit at an antenna side interface occurs across a wired medium. 
     Example 68 includes the method of any of Examples 54-67, wherein receiving the first uplink signals from the antenna unit at the antenna side interface includes receiving the first uplink signals from an intermediary device positioned between the antenna side interface and the antenna unit. 
     Example 69 includes the method of Example 68, wherein receiving the first uplink signals from the intermediary device positioned between the antenna side interface and the antenna unit occurs across a wired medium. 
     Example 70 includes the method of any of Examples 68-69, further comprising reviving analog signals from the antenna unit at the intermediary device, converting the analog signals to the first uplink signals at the intermediary device, and communicating the first uplink signal from the intermediary device to the antenna side interface. 
     Example 71 includes the method of any of Examples 68-70, further comprising receiving the analog signals from the antenna unit at the intermediary device across a wired medium. 
     Example 72 includes the method of any of Examples 54-71, further comprising receiving a first downlink signal from an external device; communicating a second downlink signal from the antenna side interface to the distributed antenna system; and converting between the first downlink signal and the second downlink signal at the signal conversion module at least in part by digitally adjusting at least one downlink attribute of the second downlink signal to comply with requirements of the external device.