Selective multichannel amplification in a distributed antenna system (DAS)

Embodiments of the disclosure relate to selective multichannel amplification in a distributed communication system. In this regard, a remote antenna unit (RAU) in the distributed communication system receives downlink digital signals associated with downlink channels having respective downlink channel bandwidths. The RAU digitally scales the downlink digital signals based on respective digital scaling factors to generate scaled downlink digital signals having a substantially equal channel power density in the downlink channels. By digitally scaling the downlink digital signals to provide the substantially equal channel power density in the downlink channels, it is possible to provide substantially uniform radio frequency (RF) coverage range across the downlink channels, thus helping to improve overall RF coverage and user experience in a coverage area of the distributed communication system.

BACKGROUND

The disclosure relates generally to a distributed antenna system (DAS) and more particularly to techniques for amplifying multiple wireless channels in a DAS.

Wireless customers are increasingly demanding digital data services, such as streaming video signals. At the same time, some wireless customers use their wireless communications devices in areas that are poorly serviced by conventional cellular networks, such as inside certain buildings or areas where there is little cellular coverage. One response to the intersection of these two concerns has been the use of DASs. DASs include remote units configured to receive and transmit communications signals to client devices within the antenna range of the remote units. DASs can be particularly useful when deployed inside buildings or other indoor environments where the wireless communications devices may not otherwise be able to effectively receive radio frequency (RF) signals from a signal source.

In this regard,FIG. 1illustrates distribution of communication services to remote coverage areas100(1)-100(N) of a DAS102, wherein ‘N’ is the number of remote coverage areas. These communication services can include cellular services, wireless services, such as RF identification (RFID) tracking, Wireless Fidelity (Wi-Fi), local area network (LAN), wireless LAN (WLAN), wireless solutions (Bluetooth, Wi-Fi Global Positioning System (GPS) signal-based, and others) for location-based services, and combinations thereof, as examples. The remote coverage areas100(1)-100(N) may be remotely located. In this regard, the remote coverage areas100(1)-100(N) are created by and centered on remote antenna units (RAUs)104(1)-104(N) connected to a head-end equipment (HEE)106(e.g., a head-end controller, a head-end unit (HEU), or a central unit). The HEE106may be communicatively coupled to a signal source108, for example, a base transceiver station (BTS) or a baseband unit (BBU). In this regard, the HEE106receives downlink communications signals110D from the signal source108to be distributed to the RAUs104(1)-104(N). The RAUs104(1)-104(N) are configured to receive the downlink communications signals110D from the HEE106over a communications medium112to be distributed to the respective remote coverage areas100(1)-100(N) of the RAUs104(1)-104(N). In a non-limiting example, the communications medium112may be a wired communications medium, a wireless communications medium, or an optical fiber-based communications medium. Each of the RAUs104(1)-104(N) may include an RF transmitter/receiver (not shown) and a respective antenna114(1)-114(N) operably connected to the RF transmitter/receiver to wirelessly distribute the communication services to client devices116within the respective remote coverage areas100(1)-100(N). The RAUs104(1)-104(N) are also configured to receive uplink communications signals110U from the client devices116in the respective remote coverage areas100(1)-100(N) to be distributed to the signal source108. The size of each of the remote coverage areas100(1)-100(N) is determined by the amount of RF power transmitted by the respective RAUs104(1)-104(N), receiver sensitivity, antenna gain, and RF environment, as well as by RF transmitter/receiver sensitivity of the client devices116. The client devices116usually have a fixed maximum RF receiver sensitivity, so that the above-mentioned properties of the RAUs104(1)-104(N) mainly determine the size of the respective remote coverage areas100(1)-100(N).

In a non-limiting example, the RAUs104(1)-104(N) are configured to wirelessly distribute the downlink communications signals110D to the client devices116based on long-term evolution (LTE) technology. In this regard, the downlink communications signals110D may occupy different LTE channels of respective bandwidths. For example, a first LTE channel occupies a respective bandwidth of five megahertz (5 MHz) while a second LTE channel occupies a respective bandwidth of twenty megahertz (20 MHz). In this regard, if the downlink communications signals110D are transmitted in the first LTE channel and the second LTE channel with a power level P, a channel power density of the first LTE channel is P/(5 MHz), while a channel power density of the second LTE channel will be P/(20 MHz). In this regard, the first LTE channel has a higher channel power density than the second LTE channel. As a result, the downlink communications signals110D transmitted in the first LTE channel may achieve a longer coverage range than the downlink communications signals110D transmitted in the second LTE channel. As such, it may be desirable to transmit the downlink communications signals110D in both the first LTE channel and the second LTE channel with similar coverage range.

No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.

SUMMARY

Embodiments of the disclosure relate to selective multichannel amplification in a distributed antenna system (DAS). In this regard, a remote antenna unit (RAU) in the DAS is configured to receive a plurality of downlink digital signals associated with a plurality of downlink channels having respective downlink channel bandwidths. The RAU is configured to digitally scale the downlink digital signals based on respective digital scaling factors to generate a plurality of scaled downlink digital signals having a substantially equal channel power density in the downlink channels. By digitally scaling the downlink digital signals to provide the substantially equal channel power density in the downlink channels, it is possible to provide substantially uniform radio frequency (RF) coverage range across the downlink channels, thus helping to improve overall RF coverage and user experience in a coverage area of the RAU in the DAS.

In one embodiment, an RAU in a DAS is provided. The RAU comprises a plurality of channel circuits. The plurality of channel circuits is configured to receive a plurality of downlink digital signals at a plurality of signal power levels to be communicated in a plurality of downlink channels having a plurality of downlink channel bandwidths, respectively. The plurality of channel circuits is also configured to digitally scale the plurality of downlink digital signals based on a plurality of digital scaling factors determined according to the plurality of downlink channel bandwidths to generate a plurality of scaled downlink digital signals having a substantially equal channel power density in the plurality of downlink channels.

In another embodiment, a method for digitally scaling a plurality of downlink digital signals in an RAU in a DAS is provided. The method comprises receiving the plurality of downlink digital signals at a plurality of signal power levels to be communicated in a plurality of downlink channels having a plurality of downlink channel bandwidths, respectively. The method also comprises digitally scaling the plurality of downlink digital signals based on a plurality of digital scaling factors determined according to the plurality of downlink channel bandwidths to generate a plurality of scaled downlink digital signals having a substantially equal channel power density in the plurality of downlink channels.

In another embodiment, a DAS is provided. The DAS comprises a central unit. The DAS also comprises a plurality of RAUs. The plurality of RAUs is configured to receive a plurality of downlink digital communications signals from the central unit. The plurality of RAUs is also configured to provide a plurality of uplink digital communications signals to the central unit. One or more RAUs among the plurality of RAUs each comprises a plurality of channel circuits. The plurality of channel circuits is configured to receive a plurality of downlink digital signals at a plurality of signal power levels to be communicated in a plurality of downlink channels having a plurality of downlink channel bandwidths, respectively. The plurality of channel circuits is also configured to digitally scale the plurality of downlink digital signals based on a plurality of digital scaling factors determined according to the plurality of downlink channel bandwidths to generate a plurality of scaled downlink digital signals having a substantially equal channel power density in the plurality of downlink channels.

DETAILED DESCRIPTION

Embodiments of the disclosure relate to selective multichannel amplification in a distributed antenna system (DAS). In this regard, a remote antenna unit (RAU) in the DAS is configured to receive a plurality of downlink digital signals associated with a plurality of downlink channels having respective downlink channel bandwidths. The RAU is configured to digitally scale the downlink digital signals based on respective digital scaling factors to generate a plurality of scaled downlink digital signals having a substantially equal channel power density in the downlink channels. By digitally scaling the downlink digital signals to provide the substantially equal channel power density in the downlink channels, it is possible to provide substantially uniform radio frequency (RF) coverage range across the downlink channels, thus helping to improve overall RF coverage and user experience in a coverage area of the RAU in the DAS.

Before discussing exemplary aspects of selective multichannel amplification in a DAS that includes specific aspects of the present disclosure, a brief overview of a conventional RAU without the capability of digitally scaling downlink digital signals based on respective downlink channel bandwidths is first provided in reference toFIGS. 2A-2C. The discussion of specific exemplary aspects of selective multichannel amplification in a DAS starts with reference toFIG. 3A.

In this regard,FIG. 2Ais a schematic diagram of an exemplary conventional RAU200configured to generate a combined downlink digital signal202based on a plurality of downlink digital signals204(1)-204(N). The conventional RAU200includes a channel identifier and router206configured to receive a downlink digital communications signal208and split the downlink digital communications signal208into the downlink digital signals204(1)-204(N). The conventional RAU200includes a digital combiner210configured to combine the downlink digital signals204(1)-204(N) to generate the combined downlink digital signal202. The conventional RAU200also includes a broadband digital-to-analog converter (DAC)212configured to convert the combined downlink digital signal202into a downlink analog RF signal214. The conventional RAU200further includes a power amplifier (PA)216configured to amplify the downlink analog RF signal214to generate a downlink RF communications signal218. The digital combiner210receives the downlink digital signals204(1)-204(N) at respective signal power levels P1-PNand generates the combined downlink digital signal202at a total signal power level PC, as further illustrated inFIG. 2B. For the convenience of illustration, the downlink digital signal204(1) and the downlink digital signal204(N) are referenced hereinafter as non-limiting examples.

In this regard,FIG. 2Bis a schematic diagram providing an exemplary illustration of the respective signal power level P1of the downlink digital signal204(1), the respective signal power level PNof the downlink digital signal204(N), and the total signal power level PCof the combined downlink digital signal202ofFIG. 2A. Common elements betweenFIGS. 2A and 2Bare shown therein with common element numbers and will not be re-described herein.

With reference toFIG. 2B, the downlink digital signals204(1),204(N) may be communicated in respective downlink channels of different downlink channel bandwidths. For example, the downlink digital signal204(1) may be communicated in a respective downlink channel having a downlink channel bandwidth BW1of five megahertz (5 MHz). The downlink digital signal204(N) may be communicated in a respective downlink channel having downlink channel bandwidth BWNof twenty megahertz (20 MHz). In a non-limiting example, the downlink digital signals204(1),204(N) have the same signal power level P1, PNof approximately negative thirty-five decibel-milliwatts (−35 dBm). Accordingly, the total signal power level PCof the combined downlink digital signal202is approximately negative thirty-two decibel-milliwatts (−32 dBm).

A respective channel power density of the downlink digital signal204(1) is proportionally related to the respective signal power level P1and inversely related to the downlink channel bandwidth BW1. Likewise, a respective channel power density of the downlink digital signal204(N) is proportionally related to the respective signal power level PNand inversely related to the downlink channel bandwidth BWN. In this regard, since the downlink digital signals204(1),204(N) are at the same signal power level P1, PNof approximately −35 dBm, the respective channel power densities of the downlink digital signals204(1),204(N) will depend inversely upon the downlink channel bandwidths BW1, BWN, respectively. As a result, the respective channel power density of the downlink digital signal204(1), which is associated with the downlink channel bandwidth BW1of 5 MHz, will be higher than the respective channel power density of the downlink digital signal204(N), which is associated with the downlink channel bandwidth BWNof 20 MHz.FIG. 2Cis a schematic diagram providing an exemplary illustration of the respective channel power densities of the downlink digital signals204(1),204(N) ofFIG. 2B.

As illustrated inFIG. 2C, the respective channel power density of the downlink digital signal204(1) is higher than the respective channel power density of the downlink digital signal204(N) due to the difference between the respective downlink channel bandwidths BW1, BWN. As a result, the downlink digital signal204(1) could potentially reach a distance farther than the downlink digital signal204(N). However, in some deployments, it may be necessary to configure the conventional RAU200to provide uniform RF coverage across multiple downlink channels associated with different downlink channel bandwidths. As such, it may be desirable to transmit the downlink digital signals204(1)-204(N) in associated downlink channels with a substantially equal channel power density.

In this regard,FIG. 3Ais a schematic diagram of an exemplary RAU300configured to digitally scale a plurality of downlink digital signals302(1)-302(N) based on a plurality of digital scaling factors F1-FNto generate a plurality of scaled downlink digital signals304(1)-304(N) having a substantially equal channel power density in a plurality of downlink channels CH1-CHN. The RAU300includes a plurality of channel circuits306(1)-306(N) configured to receive the downlink digital signals302(1)-302(N) at a plurality of signal power levels P1-PNto be communicated in the downlink channels CH1-CHN, respectively. The downlink channels CH1-CHNcorrespond to a plurality of downlink channel bandwidths BW1-BWN, respectively. In a non-limiting example, the signal power levels P1-PNof the downlink digital signals302(1)-302(N) are substantially equal. As such, according to previous discussion inFIG. 2B, channel power densities D1-DNof the downlink digital signals302(1)-302(N) in the downlink channels CH1-CHNare inversely related to the downlink channel bandwidths BW1-BWN. Since the downlink channel bandwidths BW1-BWNof the downlink channels CH1-CHNmay be different, the channel power densities D1-DNof the downlink digital signals302(1)-302(N) in the downlink channels CH1-CHNcould be different as a result. Hence, to be able to provide uniform RF coverage in a coverage area served by the RAU300, it may be necessary to digitally scale the downlink digital signals302(1)-302(N) to generate the scaled downlink digital signals304(1)-304(N) having the substantially equal channel power density in the downlink channels CH1-CHN.

In this regard, the digital scaling factors F1-FNcan be determined based on the downlink channel bandwidths BW1-BWN, as shown in the equation (Eq. 1) below.

Accordingly, the channel circuits306(1)-306(N) are configured to digitally scale the downlink digital signals302(1)-302(N) based on the digital scaling factors F1-FN. In this regard, each of the channel circuits306(1)-306(N) is configured to mathematically multiply magnitudes of digital samples representing a respective downlink digital signal among the downlink digital signals302(1)-302(N) by a respective digital scaling factor among the digital scaling factors F1-FN. For example, if the downlink digital signal302(1) includes one hundred digital samples having one hundred respective magnitudes, the channel circuit306(1) will multiply each of the one hundred respective magnitudes by the digital scaling factor F1to generate the scaled downlink digital signal304(1). The digital scaling performed by the channel circuits306(1)-306(N) can cause the scaled downlink digital signals304(1)-304(N) to have a plurality of scaled signal power levels P′1-P′Nthat is proportional to the downlink channel bandwidths BW1-BWNof the downlink channels CH1-CHN. As a result, it is possible for the scaled downlink digital signals304(1)-304(N) to have the substantially equal channel power density in the downlink channels CH1-CHN. The RAU300includes a digital combiner308configured to combine the scaled downlink digital signals304(1)-304(N) to generate a combined downlink digital signal310at a combined signal power level PC. In a non-limiting example, the digital scaling performed by the channel circuits306(1)-306(N) can cause the combined signal power level PCto substantially equal each of the signal power levels P1-PNof the downlink digital signals302(1)-302(N).

To further illustrate effects of the digital scaling performed by the channel circuits306(1)-306(N),FIGS. 3B and 3Care discussed next. For the convenience of illustration,FIGS. 3B and 3Care discussed using the downlink digital signal302(1) and the downlink digital signal302(N) as non-limiting examples.

FIG. 3Bis a schematic diagram providing an exemplary illustration of the scaled channel power levels P′1, P′Nas a result of digital scaling. Common elements betweenFIGS. 3A and 3Bare shown therein with common element numbers and will not be re-described herein.

For the purpose of illustration, it is assumed that the downlink channel bandwidth BW1of the downlink channel CH1is 5 MHz and the downlink channel bandwidth BWNof the downlink channel CHNis 20 MHz. As such, according to the equation (Eq. 1) above, the digital scaling factor F1and the digital scaling factor FNwill be twenty percent (20%) and eighty percent (80%), respectively. It is further assumed that the signal power level P1of the downlink digital signal302(1) and the signal power level PNof the downlink digital signal302(N) are both −35 dBm. Accordingly, the channel circuit306(1) digitally scales the downlink digital signal302(1) based on the digital scaling factor F1to generate the scaled downlink digital signal304(1) at the scaled signal power level P′1, which is approximately negative forty-two decibel-milliwatts (−42 dBm). Likewise, the channel circuit306(N) digitally scales the downlink digital signal302(N) based on the digital scaling factor FNto generate the scaled downlink digital signal304(N) at the scaled signal power level P′N, which is approximately negative thirty-six decibel-milliwatts (−36 dBm). As illustrated inFIG. 3B, the combined signal power level PCof the combined downlink digital signal310is approximately −35 dBm, which is approximately equal to the signal power levels P1, PN.

By digitally scaling the signal power levels P1, PNto the scaled signal power levels P′1, P′Nbased on the digital scaling factors F1, FN, the channel power densities D1, DNof the scaled downlink digital signals304(1),304(N) will be substantially equal, as illustrated inFIG. 3C. In this regard,FIG. 3Cis a schematic diagram providing an exemplary illustration of the channel power densities D1, DNof the scaled downlink digital signals304(1),304(N) ofFIG. 3A. As illustrated inFIG. 3C, the channel power densities D1, DNof the scaled downlink digital signals304(1),304(N) are substantially equal. As a result, the scaled downlink digital signals304(1),304(N) are able to provide substantially uniform RF coverage in the coverage area served by the RAU300ofFIG. 3A.

With reference back toFIG. 3A, the RAU300includes a broadband DAC312configured to receive and convert the combined downlink digital signal310into a downlink analog RF signal314. The RAU300also includes a power amplifier316configured to receive and amplify the downlink analog RF signal314to generate a downlink RF communications signal318.

The RAU300can be configured to digitally scale the downlink digital signals302(1)-302(N) according to a process. In this regard,FIG. 4is a flowchart of an exemplary process400that can be performed by the RAU300ofFIG. 3Ato digitally scale the downlink digital signals302(1)-302(N) based on the digital scaling factors F1-FN.

According to the process400, the channel circuits306(1)-306(N) in the RAU300receive the downlink digital signals302(1)-302(N) at the signal power levels P1-PNto be communicated in the downlink channels CH1-CHNhaving the downlink channel bandwidths BW1-BWN, respectively (block402). Next, the channel circuits306(1)-306(N) in the RAU300digitally scale the downlink digital signals302(1)-302(N) based on the digital scaling factors F1-FNdetermined according to the downlink channel bandwidths BW1-BWNto generate the scaled downlink digital signals304(1)-304(N) having the substantially equal channel power density in the downlink channels CH1-CHN(block404).

With reference back toFIG. 3A, the channel circuits306(1)-306(N) include a plurality of digital channel processing units320(1)-320(N), respectively. The digital channel processing units320(1)-320(N) receive the digital scaling factors F1-FN, respectively. The digital channel processing units320(1)-320(N) are configured to digitally scale the downlink digital signals302(1)-302(N) based on the digital scaling factors F1-FNto generate the scaled downlink digital signals304(1)-304(N) having the substantially equal channel power density in the downlink channels CH1-CHN. The channel circuits306(1)-306(N) include a plurality of digital upconverters322(1)-322(N), respectively. The digital upconverters322(1)-322(N) are configured to digitally upconvert the scaled downlink digital signals304(1)-304(N) into respective downlink transmission frequencies.

The RAU300also includes a channel identifier and router324. In a non-limiting example, the channel identifier and router324can be implemented using a Field Programmable Gate Array (FPGA). In another non-limiting example, the channel identifier and router324can be implemented as an embedded software system employing a central processing unit (CPU), storage, and memory. In another non-limiting example, the channel identifier and router324can be implemented in the same physical FPGA or embedded system as other components, such as the digital channel processing units320(1)-320(N). The channel identifier and router324can be configured to receive a downlink digital communications signal326. The channel identifier and router324splits the downlink digital communications signal326into the downlink digital signals302(1)-302(N) and routes the downlink digital signals302(1)-302(N) to the channel circuits306(1)-306(N), respectively.

In a non-limiting example, the channel identifier and router324receives the downlink digital communications signal326in common public radio interface (CPRI) format. The channel identifier and router324can be configured to examine control fields in CPRI frames conveyed in the downlink digital communications signal326to determine the downlink channels CH1-CHN. The channel identifier and router324then splits the downlink digital communications signal326into the downlink digital signals302(1)-302(N) based on the downlink channels CH1-CHN.

With continuing reference toFIG. 3A, the RAU300may be communicatively coupled to a power scaling controller328, which may be a FPGA, a CPU, a microprocessor, or a microcontroller. In a non-limiting example, it is possible to provide the power scaling controller328in the RAU300. The power scaling controller328is configured to determine the downlink channel bandwidths BW1-BWNof the downlink digital signals302(1)-302(N). The power scaling controller328is also configured to determine the digital scaling factors F1-FNbased on the downlink channel bandwidths BW1-BWN, respectively. The power scaling controller328is also configured to provide the digital scaling factors F1-FNto the channel circuits306(1)-306(N) in the RAU300.

In a non-limiting example, the power scaling controller328receives the downlink digital communications signal326, which is configured to be distributed to the RAU300, in the CPRI format. In this regard, the power scaling controller328examines the control fields in the CPRI frames conveyed in the downlink digital communications signal326to determine the downlink channel bandwidths BW1-BWNof the downlink channels CH1-CHN.

In another non-limiting example, the power scaling controller328is communicatively coupled to a management database330configured to store configuration information determined by a management module332. The management module332, which may be provided inside or outside the RAU300, is responsible for configuration and ongoing management of the RAU300. The management module332provides, for example, a management interface to enable management of the RAU300by an operator. The management interface may be, for example, a human controlled graphical user interface (GUI). Alternatively, the management interface may be, for example, an electronic interface using a scheme such as Simple Network Management Protocol (SNMP) or various automation schemes. The management module332stores functional parameters obtained via the management interface in the management database330.

The functional parameters managed via the management module332may include, for example, activating and deactivating the RAU300, or controlling various configuration parameters. These configuration parameters may include, for example, a specification of the number of channels that the RAU300will amplify and the downlink channel bandwidths BW1-BWN(in, for example, quanta of 100 kiloHertz (Khz)) that the downlink channels CH1-CHNutilize. The functional parameters stored in the management database330may be utilized by the power scaling controller328to determine the downlink channel bandwidths BW1-BWNof the downlink channels CH1-CHN. In addition, the functional parameters stored in the management database330may be utilized by the digital channel processing units320(1)-320(N) to digitally scale the downlink digital signals302(1)-302(N) based on the digital scaling factors F1-FN.

Upon determining the downlink channel bandwidths BW1-BWNof the downlink channels CH1-CHN, the power scaling controller328calculates a total downlink channel bandwidth BWTOTAL(BWTOTAL=Σi=1i=NBWi) of the downlink digital signals302(1)-302(N). The power scaling controller328then determines a digital scaling factor F1for each of the downlink digital signals302(1)-302(N) according to the equation (Eq. 1) above.

The power scaling controller328may determine the digital scaling factors F1-FNaccording to a process. In this regard,FIG. 5is a flowchart of an exemplary process500that the power scaling controller328may employ to determine the digital scaling factors F1-FNofFIG. 3A. With reference toFIG. 5, the power scaling controller328determines the downlink channel bandwidths BW1-BWNof the downlink channels CH1-CHNassociated with the downlink digital signals302(1)-302(N) (block502). As previously discussed, the power scaling controller328may determine the downlink channel bandwidths BW1-BWNbased on the control fields in the CPRI frames conveyed in the downlink digital communications signal326and/or functional parameters stored in the management database330. The power scaling controller328sets a pointer i to one (1) (block504). By setting the pointer i to one (1), the power scaling controller328is set to start from the downlink channel CH1among the downlink channels CH1-CHN. Next, the power scaling controller328computes the total downlink channel bandwidth BWTOTALof the downlink channel bandwidths BW1-BWN(block506). As previously discussed, the total downlink channel bandwidth BWTOTALequals a sum of the downlink channel bandwidths BW1-BWN(BWTOTAL=Σi=1i=NBW1).

The power scaling controller328then selects a downlink channel bandwidth BWi(1≤i≤N) among the downlink channel bandwidths BW1-BWNof a downlink channel CHi(1≤i≤N) among the downlink channels CH1-CHN(block508). The power scaling controller328then computes a digital scaling factor F1(1≤i≤N) for the downlink channel CHi(1≤i≤N) (block510). The power scaling controller328then increases the pointer i by one (1) (i=i+1) (block512). The power scaling controller328then checks whether the pointer i equals N (block514). If the pointer i is less than N, the power scaling controller328returns to block508to compute a next digital scaling factor. Otherwise, the power scaling controller328ends the process (block516).

With reference back toFIG. 3A, the digital channel processing units320(1)-320(N) can be configured to digitally scale the downlink digital signals302(1)-302(N) according to a process. In this regard,FIG. 6is a flowchart of an exemplary process600that the digital channel processing units320(1)-320(N) in the RAU300ofFIG. 3Amay perform to digitally scale the downlink digital signals302(1)-302(N). For the convenience of discussion, the digital channel processing unit320(1) configured to digitally scale the downlink digital signal302(1) is referenced herein as a non-limiting example. It shall be appreciated that the process600can be employed by any of the digital channel processing units320(1)-320(N) in the RAU300.

According to the process600, the digital channel processing unit320(1) performs policy-independent scaling on the downlink digital signal302(1) based on a policy-independent scaling factor (block602). In a non-limiting example, the policy-independent scaling can help reduce magnitude (e.g., amplitude) of the downlink digital signal302(1) to prevent gain compression in the power amplifier316ofFIG. 3A. Next, the digital channel processing unit320(1) performs digital scaling by mathematically multiplying the magnitudes of digital samples representing the downlink digital signal302(1) by the digital scaling factor F1(block604). In a non-limiting example, it is possible to perform the policy-independent scaling (block602) and the digital scaling (block604) in a single scaling operation based on a combined scaling factor. In this regard, the combined scaling factor may be determined by multiplying the policy-independent scaling factor with the digital scaling factor F1.

With reference back toFIG. 3A, the downlink digital signals302(1)-302(N) include a plurality of in-phase (I) sample signals334(1)-334(N) and a plurality of quadrature (Q) sample signals336(1)-336(N), respectively. In this regard, the channel circuits306(1)-306(N) receive the I sample signals334(1)-334(N) and the Q sample signals336(1)-336(N) as the downlink digital signals302(1)-302(N). Accordingly, the channel circuits306(1)-306(N) are configured to digitally scale the I sample signals334(1)-334(N) based on the digital scaling factors F1-FNto generate a plurality of scaled I sample signals338(1)-338(N), respectively. The channel circuits306(1)-306(N) are also configured to digitally scale the Q sample signals336(1)-336(N) based on the digital scaling factors F1-FNto generate a plurality of scaled Q sample signals340(1)-340(N), respectively.

Subsequently, the digital upconverters322(1)-322(N) digitally upconvert the scaled I sample signals338(1)-338(N) and the scaled Q sample signals340(1)-340(N) into the respective downlink transmission frequencies. The digital combiner308combines the scaled I sample signals338(1)-338(N) to generate a combined downlink I sample signal342. The digital combiner308also combines the scaled Q sample signals340(1)-340(N) to generate a combined downlink Q sample signal344.

In a non-limiting example, the RAU300further includes an I-Q combiner346coupled to the digital combiner308. The I-Q combiner346is configured to combine the combined downlink I sample signal342and the combined downlink Q sample signal344to generate the combined downlink digital signal310. The broadband DAC312converts the combined downlink digital signal310into the downlink analog RF signal314.

With continuing reference toFIG. 3A, in a non-limiting example, the I-Q combiner346can also be configured to include a mixer that performs functions of the broadband DAC312. In this regard, the I-Q combiner346is able to convert the combined downlink digital signal310into the downlink analog RF signal314.

In one non-limiting example, the RAU300may include a plurality of the power amplifier316and/or a plurality of the digital combiner308. As such, each power amplifier316amplifies a particular range of frequencies. Each of the channel circuits306(1)-306(N) may be coupled to a respective digital combiner308according to the downlink channels CH1-CHN. In this manner, each of the downlink channels CH1-CHNis amplified by a respective power amplifier316.

In another non-limiting example, the RAU300may include a plurality of the broadband DAC312coupled directly to the channel circuits306(1)-306(N), respectively. In this regard, the broadband DAC312receives and converts the scaled downlink digital signals304(1)-304(N) into respective downlink analog RF signals. As such, the digital combiner308may be replaced by an analog combiner disposed between the broadband DAC312and the power amplifier316.

FIG. 7is a schematic diagram of an exemplary DAS700provided in the form of an optical fiber-based DAS that includes a plurality of the RAU300ofFIG. 3Aconfigured to digitally scale the downlink digital signals302(1)-302(N) based on the digital scaling factors F1-FN. The DAS700includes an optical fiber for distributing communications services for multiple frequency bands. The DAS700in this example is comprised of three (3) main components. A plurality of radio interfaces provided in the form of radio interface modules (RIMs)702(1)-702(M) are provided in a head-end unit (HEU)704to receive and process downlink digital communications signals706D(1)-706D(R) prior to optical conversion into downlink optical fiber-based communications signals. The downlink digital communications signals706D(1)-706D(R) may be received from a base station (not shown) as an example. The RIMs702(1)-702(M) provide both downlink and uplink interfaces for signal processing. The notations “1-R” and “1-M” indicate that any number of the referenced component,1-R and1-M, respectively, may be provided. The HEU704is configured to accept the RIMs702(1)-702(M) as modular components that can easily be installed and removed or replaced in the HEU704. In one example, the HEU704is configured to support up to twelve (12) RIMs702(1)-702(12). Each RIM702(1)-702(M) can be designed to support a particular type of radio source or range of radio sources (i.e., frequencies) to provide flexibility in configuring the HEU704and the DAS700to support the desired radio sources.

For example, one RIM702may be configured to support the Personalized Communications System (PCS) radio band. Another RIM702may be configured to support the 800 megahertz (MHz) radio band. In this example, by inclusion of the RIMs702(1)-702(M), the HEU704could be configured to support and distribute communications signals on both PCS and Long-Term Evolution (LTE)700radio bands, as an example. The RIMs702may be provided in the HEU704that support any frequency bands desired, including but not limited to the US Cellular band, PCS band, Advanced Wireless Service (AWS) band, 700 MHz band, Global System for Mobile communications (GSM)900, GSM1800, and Universal Mobile Telecommunications System (UMTS). The RIMs702(1)-702(M) may also be provided in the HEU704that support any wireless technologies desired, including but not limited to Code Division Multiple Access (CDMA), CDMA200, 1×RTT, Evolution—Data Only (EV-DO), UMTS, High-speed Packet Access (HSPA), GSM, General Packet Radio Services (GPRS), Enhanced Data GSM Environment (EDGE), Time Division Multiple Access (TDMA), LTE, iDEN, and Cellular Digital Packet Data (CDPD).

The RIMs702(1)-702(M) may be provided in the HEU704that support any frequencies desired, including but not limited to US FCC and Industry Canada frequencies (824-849 MHz on uplink and 869-894 MHz on downlink), US FCC and Industry Canada frequencies (1850-1915 MHz on uplink and 1930-1995 MHz on downlink), US FCC and Industry Canada frequencies (1710-1755 MHz on uplink and 2110-2155 MHz on downlink), US FCC frequencies (698-716 MHz and 776-787 MHz on uplink and 728-746 MHz on downlink), EU R & TTE frequencies (880-915 MHz on uplink and 925-960 MHz on downlink), EU R & TTE frequencies (1710-1785 MHz on uplink and 1805-1880 MHz on downlink), EU R & TTE frequencies (1920-1980 MHz on uplink and 2110-2170 MHz on downlink), US FCC frequencies (806-824 MHz on uplink and 851-869 MHz on downlink), US FCC frequencies (896-901 MHz on uplink and 929-941 MHz on downlink), US FCC frequencies (793-805 MHz on uplink and 763-775 MHz on downlink), and US FCC frequencies (2495-2690 MHz on uplink and downlink).

With continuing reference toFIG. 7, the downlink digital communications signals706D(1)-706D(R) are provided to a plurality of optical interfaces provided in the form of optical interface modules (OIMs)708(1)-708(N) in this embodiment to convert the downlink digital communications signals706D(1)-706D(R) into downlink optical fiber-based communications signals710D(1)-710D(R). The notation “1-N” indicates that any number of the referenced component1-N may be provided. The OIMs708(1)-708(N) may be configured to provide a plurality of optical interface components (OICs) that contain optical-to-electrical (O/E) and electrical-to-optical (E/O) converters, as will be described in more detail below. The OIMs708(1)-708(N) support the radio bands that can be provided by the RIMs702(1)-702(M), including the examples previously described above.

The OIMs708(1)-708(N) each include E/O converters to convert the downlink digital communications signals706D(1)-706D(R) into the downlink optical fiber-based communications signals710D(1)-710D(R). The downlink optical fiber-based communications signals710D(1)-710D(R) are communicated over a downlink optical fiber-based communications medium712D to a plurality of remote antenna units (RAUs)714(1)-714(S). A plurality of RAUs among the RAUs714(1)-714(S) are provided as the RAU300ofFIG. 3Aconfigured to digitally scale the downlink digital signals302(1)-302(N) based on the digital scaling factors F1-FN. The notation “1-S” indicates that any number of the referenced component1-S may be provided. RAU O/E converters provided in the RAUs714(1)-714(S) convert the downlink optical fiber-based communications signals710D(1)-710D(R) back into the downlink digital communications signals706D(1)-706D(R), which are provided to antennas716(1)-716(S) in the RAUs714(1)-714(S) to client devices (not shown) in the reception range of the antennas716(1)-716(S).

RAU E/O converters are also provided in the RAUs714(1)-714(S) to convert uplink digital communications signals718U(1)-718U(S) received from the client devices through the antennas716(1)-716(S) into uplink optical fiber-based communications signals710U(1)-710U(S). The RAUs714(1)-714(S) communicate the uplink optical fiber-based communications signals710U(1)-710U(S) over an uplink optical fiber-based communications medium712U to the OIMs708(1)-708(N) in the HEU704. The OIMs708(1)-708(N) include O/E converters that convert the received uplink optical fiber-based communications signals710U(1)-710U(S) into uplink digital communications signals720U(1)-720U(S), which are processed by the RIMs702(1)-702(M) and provided as the uplink digital communications signals720U(1)-720U(S). The HEU704may provide the uplink digital communications signals720U(1)-720U(S) to a base station or other communications system.

Note that the downlink optical fiber-based communications medium712D and the uplink optical fiber-based communications medium712U connected to each RAU714(1)-714(S) may be a common optical fiber-based communications medium, wherein for example, wave division multiplexing (WDM) is employed to provide the downlink optical fiber-based communications signals710D(1)-710D(R) and the uplink optical fiber-based communications signals710U(1)-710U(S) on the same optical fiber-based communications medium.

The DAS700further includes the power scaling controller328ofFIG. 3Aconfigured to determine the digital scaling factors F1-FNbased on the downlink channel bandwidths BW1-BWN. In a non-limiting example, the power scaling controller328is provided as an independent entity in the DAS700. In another non-limiting example, the power scaling controller328is provided in the HEU704.

The DAS700ofFIG. 7may be provided in an indoor environment, as illustrated inFIG. 8.FIG. 8is a partial schematic cut-away diagram of an exemplary building infrastructure800in which the DAS700ofFIG. 7can be employed. The building infrastructure800in this embodiment includes a first (ground) floor802(1), a second floor802(2), and a third floor802(3). The floors802(1)-802(3) are serviced by an HEU804to provide antenna coverage areas806in the building infrastructure800. The HEU804is communicatively coupled to a base station808to receive downlink communications signals810D from the base station808. The HEU804is communicatively coupled to a plurality of RAUs812to distribute the downlink communications signals810D to the RAUs812and to receive uplink communications signals810U from the RAUs812, as previously discussed above. The downlink communications signals810D and the uplink communications signals810U communicated between the HEU804and the RAUs812are carried over a riser cable814. The riser cable814may be routed through interconnect units (ICUs)816(1)-816(3) dedicated to each of the floors802(1)-802(3) that route the downlink communications signals810D and the uplink communications signals810U to the RAUs812and also provide power to the RAUs812via array cables818.

FIG. 9is a schematic diagram representation of additional detail illustrating an exemplary computer system900that could be employed in a control circuit, including the power scaling controller328and the digital channel processing units320(1)-320(N) ofFIG. 3Afor determining the digital scaling factors F1-FNand performing digital scaling based on the digital scaling factors F1-FNin the RAU300. In this regard, the computer system900is adapted to execute instructions from an exemplary computer-readable medium to perform these and/or any of the functions or processing described herein.

In this regard, the computer system900inFIG. 9may include a set of instructions that may be executed to predict frequency interference to avoid or reduce interference in a multi-frequency DAS. The computer system900may be connected (e.g., networked) to other machines in a LAN, an intranet, an extranet, or the Internet. While only a single device is illustrated, the term “device” shall also be taken to include any collection of devices that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein. The computer system900may be a circuit or circuits included in an electronic board card, such as a printed circuit board (PCB), a server, a personal computer, a desktop computer, a laptop computer, a personal digital assistant (PDA), a computing pad, a mobile device, or any other device, and may represent, for example, a server or a user's computer.

The exemplary computer system900in this embodiment includes a processing device or processor902, a main memory904(e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM), such as synchronous DRAM (SDRAM), etc.), and a static memory906(e.g., flash memory, static random access memory (SRAM), etc.), which may communicate with each other via a data bus908. Alternatively, the processor902may be connected to the main memory904and/or the static memory906directly or via some other connectivity means. The processor902may be a controller including the power scaling controller328and the digital channel processing units320(1)-320(N) ofFIG. 3A, as an example, and the main memory904or the static memory906may be any type of memory.

The processor902represents one or more general-purpose processing devices, such as a microprocessor, central processing unit, or the like. More particularly, the processor902may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor implementing other instruction sets, or other processors implementing a combination of instruction sets. The processor902is configured to execute processing logic in instructions for performing the operations and steps discussed herein.

The computer system900may further include a network interface device910. The computer system900also may or may not include an input912, configured to receive input and selections to be communicated to the computer system900when executing instructions. The computer system900also may or may not include an output914, including but not limited to a display, a video display unit (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)), an alphanumeric input device (e.g., a keyboard), and/or a cursor control device (e.g., a mouse).

The computer system900may or may not include a data storage device that includes instructions916stored in a computer-readable medium918. The instructions916may also reside, completely or at least partially, within the main memory904and/or within the processor902during execution thereof by the computer system900, the main memory904and the processor902also constituting computer-readable medium. The instructions916may further be transmitted or received over a network920via the network interface device910.