Systems and methods for providing isolation for antennas in a wireless communication system

Isolation for antennas in a wireless communication system is achieved between transmit and receive paths for a multiple input multiple output (MIMO) antenna array by separating a first transmit path from an associated receive path to be matched with a second transmit path and matching the first receive path with the second receive path. It is expected that the two transmit paths operate on sufficiently different frequencies that there is minimal interference there and the additional spacing from the transmit path to the receive path will reduce interference therebetween without increasing a footprint of the antenna array.

BACKGROUND

The technology of the disclosure relates to improving isolation between uplink and downlink channels at a wireless transceiver.

Wireless communication is rapidly growing, with ever-increasing demands for high-speed mobile voice and data communication. Information is embedded in an electromagnetic signal generally within the radio frequency range of the electromagnetic spectrum. This electromagnetic signal is transmitted from a transmitter, through a first antenna, across any intervening space, to a second receiver through a second antenna. In many instances the transmitter is actually a first transceiver and the receiver is actually a second transceiver and signals are exchanged bi-directionally. Depending on point of view, one such signal may be considered an uplink signal, and the other signal may be considered a downlink signal.

In the early days of wireless communication there was generally perceived to be ample room within the electromagnetic spectrum for many such signals to coexist without interference between signals. As the complexity of the signals has increased, in part due to the increasing amounts of information placed into the signals, the electromagnetic spectrum has become relatively crowded, particularly in the radio frequency range. Accordingly, uplink signals are typically relatively close in frequency to downlink signals for bi-directional communication.

To help isolate uplink signals from downlink signals at a transceiver, there are currently a variety of solutions. One such solution is a time-based approach (e.g., time division multiplexing) that prevents simultaneous use of uplink frequencies and downlink frequencies. While effective, this approach has fallen out of favor as more information is sent in each direction making simultaneous use of the frequencies almost a requirement. Another solution is the use of a duplexer that provides isolation between uplink and downlink frequencies. An exemplary conventional transceiver100using a duplexer is illustrated inFIG. 1.

In particular, the transceiver100includes a transmit (Tx) path102where a signal104to be transmitted enters a field programmable gate array (FPGA) circuit106for processing and is passed through a digital-to-analog converter (DAC)108and an amplifier110to a duplexer112. From the duplexer112, the converted, amplified signal104is passed to an antenna116and transmitted. The transceiver100further includes a receive (Rx) path118. Signals are received at the antenna116, passed through the duplexer112, through an amplifier120and an analog-to-digital (ADC) converter122to the FPGA106for processing to become a receive signal124.

At its simplest, a duplexer is a device that allows bi-directional (i.e., duplex) communication over a single path. In the transceiver100, the duplexer112isolates the receiver portion from the transmitter portion while permitting them to share a common antenna. In radio frequency communication, transmit and receive signals typically occupy different frequency bands, and so the duplexer112may have frequency selective filters. Modern communication often uses nearby frequency bands, so the frequency separation between transmit and receive signals is relatively small.

While duplexers may be effective at providing desired isolation, as the frequencies get closer and, particularly in the frequencies of interest, the cost of such duplexers has increased to levels that are not commercially practical. For example, such elements may cost around sixty to ninety U.S. dollars. For high frequency broadband duplexers, that cost may readily exceed one hundred U.S. dollars, and in some cases exceed three hundred U.S. dollars. Such costs are generally perceived to be unacceptable within most commercial industries.

A third solution is the use of interference cancellation calculations that may be performed in an FPGA circuit cooperating with a multiple input/multiple output (MIMO) antenna array such as illustrated inFIG. 2. In particular, a transceiver200may include an FPGA202that controls four antennas204(1)-204(4). Antennas204(1)-204(2) handle MIMO stream A, and antennas204(3)-204(4) handle MIMO stream B. For MIMO stream A, the antenna204(1) acts as the antenna for a transmit path206(1), and the antenna204(2) acts as the antenna for a receive path206(2). The transmit path206(1) includes a DAC208and an amplifier210. Similarly, the receive path206(2) has an ADC212and an amplifier214. Further, a tap216is associated with the antenna204(1) and provides a signal to an interference cancelation circuit218within the FPGA202. Likewise, for MIMO stream B, the antenna204(3) acts as the antenna for a transmit path220(1), and the antenna204(4) acts as the antenna for a receive path220(2). The transmit path220(1) includes a DAC222and an amplifier224. Similarly, the receive path220(2) has an ADC226and an amplifier228. Further, a tap230is associated with the antenna204(3) and provides a signal to an interference cancelation circuit232within the FPGA202. The interference cancelation circuits218and232operate to subtract or otherwise remove the transmit signal from the received signal of the respective paths. This subtraction is done because the signal emanating from the transmit antennas204(1),204(3) may be received at the receive antennas204(2),204(4). By subtracting such received signals, the original received signal may be restored.

MIMO antenna arrays necessarily physically space antennas from one another to help isolate signals. While effective, as the number of antennas increases, the size penalty that the physical separation requires becomes impractical. This complexity is exacerbated when there is a dual band requirement for the MIMO antenna array, such as may occur in a distributed communication system (e.g., a centralized radio access network (cRAN) or distributed antenna system (DAS)). Such a situation is illustrated inFIG. 3, where a cRAN300has a digital routing unit (DRU)302coupled to a low band baseband unit (BBU)304and a high band BBU306. Both the low band BBU304and the high band BBU306handle (at least) two data streams (MIMO A and MIMO B) each having an uplink (UL) and a downlink (DL) component. Thus, for the low band BBU304, there is data stream DL MIMO A, which goes from the low band BBU304, through the DRU302to a low band section308(1) of a transceiver system310. As with the transceiver200ofFIG. 2, the DL MIMO A goes to an FPGA312and is sent through a DAC314and an amplifier316before transmission from an antenna318. UL signals are received at an antenna320, provided to an amplifier322, converted in an ADC324, and then provided to the FPGA312. The UL signals are then passed to the low band BBU304. Similarly, the DL MIMO B goes to the FPGA312and is sent through a DAC326and an amplifier328before transmission from an antenna330. UL signals are received at an antenna332, provided to an amplifier334, converted in an ADC336, and then provided to the FPGA312. The UL signals are then passed to the low band BBU304. As noted by signals I1and I2, the signals transmitted from the antenna318may impinge on the antennas320and332. Likewise, the signals13and14from the antenna330may impinge on the antennas320and332. To reduce this interference, there is a tap338that collects information about the signal being sent from the antenna318and a tap340that collects information about the signal being sent from the antenna330. These taps338and340feed interference cancelation circuits342and344, respectively, which calculate an offset in a fashion similar to the transceiver200, albeit taking into account both possible interfering signals.

With continued reference toFIG. 3, for the high band BBU306, the DL MIMO A goes to an FPGA346in high band section308(2) of the transceiver system310and is sent through a DAC348and an amplifier350before transmission from an antenna352. UL signals are received at an antenna354, provided to an amplifier356, converted in an ADC358, and then provided to the FPGA346. The UL signals are then passed to the high band BBU306. Similarly, the DL MIMO B goes to the FPGA346and is sent through a DAC360and an amplifier362before transmission from an antenna364. UL signals are received at an antenna366, provided to an amplifier368, converted in an ADC370, and then provided to the FPGA346. The UL signals are then passed to the high band BBU306. As noted by signals15and16, the signals transmitted from the antenna352may impinge on the antennas354and366. Likewise, the signals17and18from the antenna364may impinge on the antennas354and366. To reduce this interference, there is a tap372that collects information about the signal being sent from the antenna352and a tap374that collects information about the signal being sent from the antenna364. These taps372and374feed interference cancelation circuits376and378, respectively, which calculate an offset in a fashion similar to the transceiver200, albeit taking into account both possible interfering signals.

It should be appreciated that the calculations done by the interference cancelation circuits342,344,376, and378may become more complex as the MIMO array expands past two bands or more than two antenna pairs. This complexity may add latency or otherwise impact performance and ultimately may become impractical as a solution.

Various industries have wrestled with the problem of signal isolation, but one industry that is seeing heavier use, and thus beginning to direct more attention to this issue, is in, as alluded to in the discussion ofFIG. 3, distributed communication systems. An exemplary distributed communication system may be a distributed antenna system (DAS) within a building that provides wireless connections to mobile terminals within the building in places where an outside signal may be blocked or where traffic dictates that a small cell may be appropriate.

One approach to deploying a wireless communication system involves the use of radio frequency (RF) antenna coverage areas, also referred to as “antenna coverage areas.” Antenna coverage areas can have a radius in the range from a few meters up to twenty meters as an example. Combining a number of access point devices creates an array of antenna coverage areas. Because the antenna coverage areas each cover small areas, there are typically only a few users (clients) per antenna coverage area. This allows for minimizing the amount of RF bandwidth shared among the wireless system users. It may be desirable to employ optical fiber to distribute communication signals. Benefits of optical fiber include increased bandwidth.

One type of distributed antenna system for creating antenna coverage areas includes distribution of RF communication signals over an electrical conductor medium, such as coaxial cable or twisted pair wiring. Another type of distributed antenna system for creating antenna coverage areas, called “Radio-over-Fiber,” or “RoF,” utilizes RF communication signals sent over optical fibers. Both types of systems can include head-end equipment coupled to a plurality of remote units (RUs), which may include an antenna and may be referred to as a remote antenna unit or RAU. Each RU provides antenna coverage areas. The RUs can each include RF transceivers coupled to an antenna to transmit RF communication signals wirelessly, wherein the RUs are coupled to the head-end equipment via the communication medium. The RF transceivers in the RUs are transparent to the RF communication signals. The antennas in the RUs also receive RF signals (i.e., electromagnetic radiation) from clients in the antenna coverage area. The RF signals are then sent over the communication medium to the head-end equipment. In optical fiber or RoF distributed antenna systems, the RUs convert incoming optical RF signals from an optical fiber downlink to electrical RF signals via optical-to-electrical (O-E) converters, which are then passed to the RF transceiver. The RUs also convert received electrical RF communication signals from clients via the antennas to optical RF communication signals via electrical-to-optical (E-O) converters. The optical RF signals are then sent over an optical fiber uplink to the head-end equipment.

While some RUs are simple antennas that merely bring an existing cellular-type service into an area with poor reception (e.g., inside large buildings), other RUs may be more robust and may actually act as a fully functional cell (e.g., a picocell, femtocell, microcell, or the like) with registration, hand-off, and other traditional cellular functions. Still other RUs may act as some form of hybrid with some, but not all functions of a traditional cell, but more functionality than a simple antenna.

An exemplary distributed communication system is provided with reference toFIG. 4to provide additional context. In this regard,FIG. 4illustrates distribution of communication services to remote coverage areas400(1)-400(N) of a wireless distribution system (WDS, also referred to herein as a distributed communication system, a distributed antenna system (DAS), or wireless communication system (WCS))402, 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 (WiFi), local area network (LAN), and wireless LAN (WLAN), wireless solutions (Bluetooth, WiFi Global Positioning System (GPS) signal-based, and others) for location-based services, and combinations thereof, as examples. The remote coverage areas400(1)-400(N) are created by, and centered on, remote units404(1)-404(N) (sometimes these may be low power remote units (LPR), but are more commonly referred to herein as just a remote unit (RU) or remote antenna unit (RAU)) connected to a central unit406(e.g., a digital routing unit (DRU) a head-end controller, a head-end unit (HEU), or the like). The central unit406may be communicatively coupled to a signal source408, for example, a base transceiver station (BTS) or a baseband unit (BBU). The communicative coupling may be wireless (e.g., such as through a cellular network) or over a wire-based/fiber-based system (e.g., such as through some form of telephony network backbone or the Internet). When the signal source408is a BBU, the signal source408may communicate with the central unit406, which may be a DRU, using digital communication protocols such as the common public radio interface (CPRI). In this regard, the central unit406receives downlink communication signals410D from the signal source408to be distributed to the remote units404(1)-404(N). The remote units404(1)-404(N) are configured to receive the downlink communication signals410D from the central unit406over a communication medium412to be distributed to the respective remote coverage areas400(1)-400(N) of the remote units404(1)-404(N). In a non-limiting example, the communication medium412may be a wired communication medium, a wireless communication medium, or an optical fiber-based communication medium. While wireless is possible, exemplary aspects of the present disclosure are well-suited for situations where the medium is a physical conductor (electrical, optical, or some other waveguide (e.g., a wireless microwave system may still use a microwave waveguide)). Each of the remote units404(1)-404(N) may include an RF transmitter/receiver (not shown) and a respective antenna414(1)-414(N) operably connected to the RF transmitter/receiver to distribute wirelessly the communication services to client devices416within the respective remote coverage areas400(1)-400(N). The remote units404(1)-404(N) are also configured to receive uplink communication signals410U from the client devices416in the respective remote coverage areas400(1)-400(N) to be distributed to the signal source408. The size of each of the remote coverage areas400(1)-400(N) is determined by an amount of RF power transmitted by the respective remote units404(1)-404(N), receiver sensitivity, antenna gain, and RF environment, as well as by RF transmitter/receiver sensitivity of the client devices416. The client devices416usually have a fixed maximum RF receiver sensitivity, so that the above-mentioned properties of the remote units404(1)-404(N) mainly determine the size of the respective remote coverage areas400(1)-400(N).

With reference toFIG. 4, the central unit406may include electronic processing devices, for example an FPGA, a digital signal processor (DSP), and/or a central processing unit (CPU), for processing the downlink communication signals410D and the uplink communication signals410U. Likewise, each of the remote units404(1)-404(N) also employs electronic processing devices for processing the downlink communication signals410D and the uplink communication signals410U. Further, the communication medium412is only able to carry the downlink communication signals410D and the uplink communication signals410U up to a maximum bandwidth. Collectively, the processing capabilities of the electronic processing devices in the central unit406, the processing capabilities of the electronic processing devices in the remote units404(1)-404(N), and the maximum bandwidth of the communication medium412provide the system resources available in the WDS402. In practice, the remote units404(1)-404(N) and the client devices416may each have a transceiver with frequency isolation concerns.

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 OF THE DETAILED DESCRIPTION

Embodiments disclosed in the detailed description provide isolation for antennas in a wireless communication system. Related components, systems, and methods are also disclosed. In embodiments disclosed herein, isolation between transmit and receive paths for a multiple input/multiple output (MIMO) antenna array is improved by separating a first transmit path from an associated receive path to be matched with a second transmit path and matching the first receive path with the second receive path. It is expected that the two transmit paths operate on sufficiently different frequencies such that there is minimal interference there, and the additional spacing from the transmit path to the receive path will reduce interference therebetween without increasing a footprint of the antenna array.

In one exemplary aspect of the disclosure, a distributed communication system is disclosed. The distributed communication system comprises a central unit. The distributed communication system also comprises a first remote unit coupled to the central unit through a first communication medium. The first remote unit comprises a MIMO antenna array. The MIMO antenna array comprises a first transmit antenna configured to transmit a first downlink signal in a first frequency band. The MIMO antenna array also comprises a second transmit antenna configured to transmit a second downlink signal in the first frequency band. The MIMO antenna array also comprises a first receive antenna configured to receive a first uplink signal in a second frequency band different than the first frequency band. The MIMO antenna array also comprises a second receive antenna configured to receive a second uplink signal in the second frequency band. The distributed communication system also comprises a second remote unit coupled to the central unit through a second communication medium.

An additional embodiment of the disclosure relates to a remote unit. The remote unit comprises a MIMO antenna array. The MIMO antenna array comprises a first transmit antenna configured to transmit a first downlink signal in a first frequency band. The MIMO antenna array also comprises a second transmit antenna configured to transmit a second downlink signal in the first frequency band. The MIMO antenna array also comprises a first receive antenna configured to receive a first uplink signal in a second frequency band different than the first frequency band. The MIMO antenna array also comprises a second receive antenna configured to receive a second uplink signal in the second frequency band.

An additional embodiment of the disclosure relates to a method for communicating with wireless mobile terminals through a distributed communication system. The method comprises routing a first downlink signal in a first frequency band to a first remote unit. The method also comprises routing a second downlink signal in a second frequency band to a second remote unit. The method also comprises receiving a first uplink signal in the first frequency band at the second remote unit. The method also comprises receiving a second uplink signal in the second frequency band at the first remote unit.

Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and the claims hereof, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are merely embodiments, and are intended to provide an overview or framework to understand the nature and character of the claims.

DETAILED DESCRIPTION

Embodiments disclosed in the detailed description provide isolation for antennas in a wireless communication system. Related components, systems, and methods are also disclosed. In embodiments disclosed herein, isolation between transmit and receive paths for a multiple input/multiple output (MIMO) antenna array is improved by separating a first transmit path from an associated receive path to be matched with a second transmit path and matching the first receive path with the second receive path. It is expected that the two transmit paths operate on sufficiently different frequencies such that there is minimal interference there, and the additional spacing from the transmit path to the receive path will reduce interference therebetween without increasing a footprint of the antenna array.

While it should be appreciated that uplink and downlink are relativistic terms, for the purposes of the present disclosure, a downlink path is considered to be the transmission path and an uplink path is considered to be the receive path. The terms downlink/transmit path are used interchangeably as are the terms uplink/receive path.

Thus, exemplary aspects of the present disclosure physically interleave the downlink paths in a first band with the uplink paths of a second band such that uplink and downlinks of the same band and same stream are physically separated from one another by sufficient distance to reduce possible interference to acceptable levels.

In this regard,FIG. 5illustrates a centralized radio access network (cRAN)500that has a digital routing unit (DRU)502coupled to a low band baseband unit (BBU)504that operates in a first frequency band and a high band BBU506that operates in a second frequency band higher than the first frequency band. Both the low band BBU504and the high band BBU506handle (at least) two data streams (MIMO A and MIMO B) each having an uplink (UL) and a downlink (DL) component. Thus, for the low band BBU504, there is data stream DL MIMO A, which goes from the low band BBU504through the DRU502to a first remote unit508. The DL MIMO A goes to an FPGA512, and is sent through a digital-to-analog converter (DAC)514and amplifier516before transmission of a downlink signal from an antenna518in the first frequency band. Unlike the cRAN300ofFIG. 3, the antenna for UL MIMO A is not immediately proximate the antenna518. Rather, the closest antenna520corresponds to a low band DL MIMO B path, which is also transmitting a downlink signal in the first frequency band. Specifically, the DL MIMO B goes to the FPGA512, and is sent through a DAC522and an amplifier524before transmission from the antenna520. Because the antenna520is also a transmitting antenna, any signal from the antenna518is not likely to interfere with the signals on the antenna520. In fact, rather than have any received low band signals at the first remote unit508, the uplink paths are high band paths. Specifically, a high band uplink signal is received at an antenna526and passed through an amplifier528and an analog-to-digital converter (ADC)530to the FPGA512before being passed to the high band BBU506as UL MIMO A. Likewise, a second high band uplink signal is received at an antenna532and passed through an amplifier534and an ADC536to the FPGA512before being passed to the high band BBU506as UL MIMO B. Having low band signals from the antennas518,520impinge on the antennas526,532is readily addressed through relatively normal (and relatively inexpensive) filter techniques because of the spread between the high band and the low band frequencies.

Similarly, for the high band BBU506, there is data stream DL MIMO A, which goes from the high band BBU506through the DRU502to a second remote unit538. The DL MIMO A goes to an FPGA540and is sent through a DAC542and amplifier544before transmission from an antenna546. Likewise, the DL MIMO B goes to the FPGA540, and is sent through a DAC548and an amplifier550before transmission from an antenna552. Because the antenna552is also a transmitting antenna, any signal from the antenna546is not likely to interfere with the signals on the antenna552. Similar to the first remote unit508, rather than have any received high band signals at the second remote unit538, the uplink paths are low band paths. Specifically, a low band uplink signal is received at an antenna554and passed through an amplifier556and an ADC558to the FPGA540before being passed to the low band BBU504as UL MIMO A. Likewise, a second low band uplink signal is received at an antenna560and passed through an amplifier562and an ADC564to the FPGA540before being passed to the low band BBU504as UL MIMO B. Having high band signals from the antennas546,552impinge on the antennas554,560is readily addressed through relatively normal (and relatively inexpensive) filter techniques because of the spread between the high band and the low band frequencies.

As intimated by the discussion ofFIG. 5, exemplary aspects of the present disclosure split the uplink and downlink signals at a particular band across different remote units to achieve physical separation that reduces or eliminates interference from the transmitting antennas. This process is summarized in the flowchart of process600set forth inFIG. 6. In particular, the process600starts by determining the high band and low band streams (block602). The process600continues by sending downlink high band signals to a first remote unit (block604) and sending downlink low band signals to a second remote unit spaced apart from the first remote unit (block606). Likewise, the process600continues by receiving uplink high band signals from the second remote unit (block608) and receiving uplink low band signals from the first remote unit (block610).

To further explicate what sort of spacing is sufficient,FIG. 7provides a graph700that illustrates a distance (y-axis) in meters (m) versus frequency (x-axis) in gigahertz (GHz) recommended distance between remote unit pairs. Thus, for example, at one (1) GHz, a separation of under 1.5 m is appropriate as noted generally at point702.

It should be appreciated that while the present disclosure has been presented in the context of a distributed communication system, it may be possible to scale the concepts herein to smaller scales. While the spacing of 1.5 m is impractical in a mobile terminal, it is possible that at different frequencies, aspects of the present disclosure are capable of being implemented in a mobile terminal.

Additionally, while the cRAN500is a dual-band, two stream, two remote unit system, it should be appreciated that the present disclosure can be scaled up to accommodate more streams as illustrated inFIG. 8where a system800includes a first remote unit802and a second remote unit804. In this example, there are four streams in a dual-band environment. All four high band transmit streams806(1)-806(4) are present in the first remote unit802with the four low band receive streams808(1)-808(4). Likewise, the four low band transmit streams810(1)-810(4) and the four high band receive streams812(1)-812(4) are present in the second remote unit804.

FIG. 9is a schematic diagram of an exemplary non-contiguous wireless distributed communication system (WDCS)900in the form of a non-contiguous distributed antenna system (DAS)901. The DAS901in this example is an optical fiber-based DAS. The non-contiguous DAS901in this example is comprised of three (3) main components. One or more radio interfaces provided in the form of radio interface modules (RIMs)902(1)-902(T) are provided in a central unit904to receive and process downlink electrical communication signals906D(1)-906D(S) prior to optical conversion into downlink optical communication signals. The downlink electrical communication signals906D(1)-906D(S) may be received from a base station (not shown) as an example. The downlink electrical communication signals906D(1)-906D(S) can each include one or more subcarrier sets of a cell radio, wherein each subcarrier set is comprised of one or more subcarriers (e.g., radio channels). The RIMs902(1)-902(T) provide both downlink and uplink interfaces for signal processing. The notations “1-S” and “1-T” indicate that any number of the referenced component, 1-S and 1-T, respectively, may be provided.

With continuing reference toFIG. 9, the central unit904is configured to accept the plurality of RIMs902(1)-902(T) as modular components that can easily be installed and removed or replaced in the central unit904. In one embodiment, the central unit904is configured to support up to twelve (12) RIMs902(1)-902(12). Each RIM902(1)-902(T) 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 central unit904and the non-contiguous DAS901to support the desired radio sources. For example, one RIM902may be configured to support the Personal Communication Services (PCS) radio band. Another RIM902may be configured to support the 700 MHz radio band. In this example, by inclusion of these RIMs902, the central unit904could be configured to support and distribute communication signals, including those for the communication services and communication bands described above as examples.

The RIMs902(1)-902(T) may be provided in the central unit904that support any frequencies desired, including, but not limited to, licensed 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. 9, the downlink electrical communication signals906D(1)-906D(S) may be distributed to a plurality of optical interfaces provided in the form of optical interface modules (OIMs)908(1)-908(W) in this embodiment to convert the unlicensed and/or licensed downlink electrical communication signals906D(1)-906D(S). The notation “1-W” indicates that any number of the referenced component 1-W may be provided. The OIMs908(1)-908(W) may be configured to provide one or more 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 OIMs908(1)-908(W) support the radio bands that can be provided by the RIMs902(1)-902(T), including the examples previously described above.

The OIMs908(1)-908(W) each include E-O converters910(1)-910(W) to convert the downlink electrical communication signals906D(1)-906D(S) into downlink optical communication signals912D(1)-912D(S). The downlink optical communication signals912D(1)-912D(S) are communicated over downlink optical fiber communication medium914D to a plurality of remote units provided in the form of remote antenna units916(1)-916(X). A selective router circuit918can be provided to selectively block certain subcarrier sets and/or subcarriers in the downlink optical communication signals912D(1)-912D(S) distributed to the respective remote antenna units916(1)-916(X) based on subcarriers associated with the respective remote antenna units916(1)-916(X). The remote antenna units916(1)-916(X) are arranged non-contiguously to each other based on their supported cell radio. The notation “1-X” indicates that any number of the referenced component 1-X may be provided. O-E converters920(1)-920(X) provided in the remote antenna units916(1)-916(X) convert the downlink optical communication signals912D(1)-912D(S) back into the downlink electrical communication signals906D(1)-906D(S), which are provided to antennas922(1)-922(X) in the remote antenna units916(1)-916(X) to user equipment (not shown) in the reception range of the antennas922(1)-922(X).

E-O converters924(1)-924(X) are also provided in the remote antenna units916(1)-916(X) to convert uplink electrical communication signals926U(1)-926U(X) received from user equipment (not shown) through the antennas922(1)-922(X) into uplink optical communication signals912U(1)-912U(X). The remote antenna units916(1)-916(X) communicate the uplink optical communication signals912U(1)-912U(X) over an uplink optical fiber communication medium914U to the OIMs908(1)-908(W) in the central unit904. The OIMs908(1)-908(W) include O-E converters928(1)-928(W) that convert the received uplink optical communication signals912U(1)-912U(X) into uplink electrical communication signals930U(1)-930U(X), which are processed by the RIMs902(1)-902(T) and provided as uplink electrical communication signals930U(1)-930U(X). The central unit904may provide the uplink electrical communication signals930U(1)-930U(X) to a source transceiver, such as a cell radio provided as base station or other communication system. The selective router circuit918may be configured to selectively block certain subcarrier sets and/or subcarriers in the uplink electrical communication signals930U(1)-930U(X) distributed to the respective remote antenna units916(1)-916(X) based on subcarriers associated with the respective remote antenna units916(1)-916(X). Note that the downlink optical fiber communication medium914D and uplink optical fiber communication medium914U connected to each remote antenna unit916(1)-916(X) may be a common optical fiber communication medium, wherein for example, wave division multiplexing (WDM) may be employed to provide the downlink optical communication signals912D(1)-912D(S) and the uplink optical communication signals912U(1)-912U(X) on the same optical fiber communications medium.

FIG. 10Ais a schematic diagram of an exemplary mobile telecommunication environment1000(also referred to as “environment1000”) that includes exemplary macrocell radio access networks (RANs)1002(1)-1002(M) (“macrocells1002(1)-1002(M)”), a shared spectrum RAN1003, and an exemplary small cell RAN1004located within an enterprise environment1006. The shared spectrum RAN1003(also referred to as “shared spectrum cell1003”) includes a macrocell in this example and supports communication on frequencies that are not solely licensed to a particular mobile network operator (MNO) and thus may service user equipment (UE)1008(1)-1008(N), which are communication devices, independent of a particular MNO. The UEs1008(1)-1008(N) may be mobile UEs (e.g., cellular phones or mobile devices) that can communicate wirelessly. For example, the shared spectrum cell1003may be operated by a third party that is not an MNO and wherein the shared spectrum cell1003supports citizens broadband radio service (CBRS) or unlicensed spectrum. The mobile telecommunication environment1000is configured to service mobile communication between a UE1008(1)-1008(N) to a MNO1010. When a macrocell1002(1)-1002(M), shared spectrum RAN1003, or small cell RAN1004services communication with a UE1008(1)-1008(N), such macrocell1002(1)-1002(M), shared spectrum RAN1003, or small cell RAN1004is considered a “source RAN.” A source RAN for a UE1008(1)-1008(N) is a RAN or cell in the RAN in which the UEs1008(1)-1008(N) have an established communication session with the exchange of mobile communication signals for mobile communication. Thus, a serving RAN may also be referred to herein as a serving cell. For example, the UEs1008(3)-1008(N) inFIG. 10Aare being serviced by the small cell RAN1004, whereas UEs1008(1),1008(2) are being serviced by the macrocells1002(1)-1002(M). The macrocells1002(1)-1002(M) are MNO macrocells in this example. In this example, each of the macrocells1002(1)-1002(M), shared spectrum RAN1003, and small cell RAN1004include a transmitter circuit T configured to transmit a communication signal to a UE1008(1)-1008(N) and a receiver circuit R configured to receive communication signals from the UE1008(1)-1008(N). Each of the macrocells1002(1)-1002(M), shared spectrum RAN1003, and small cell RAN1004also include a processor circuit P (e.g., a microprocessor, micro-controller, other control circuit) communicatively coupled to the transmitter circuit T and the receiver circuit R for processing communication signals and performing other processing for signaling.

With continuing reference toFIG. 10A, the mobile telecommunication environment1000in this example is arranged as a Long Term Evolution (LTE) system as described by the Third Generation Partnership Project (3GPP) as an evolution of the standards Global System for Mobile communication/Universal Mobile Telecommunications System (GSM/UMTS). It is emphasized, however, that the aspects described herein may also be applicable to other network types and protocols. The mobile telecommunication environment1000includes the enterprise environment1006in which the small cell RAN1004is implemented. The small cell RAN1004includes a plurality of small cell radio nodes1012(1)-1012(C). Each small cell radio node1012(1)-1012(C) has a radio coverage area (graphically depicted in the drawings as a hexagonal shape) that is commonly termed a “small cell.” A small cell may also be referred to as a femtocell, or using terminology defined by 3GPP as a Home Evolved Node B (HeNB). In the description that follows, the term “cell” typically means the combination of a radio node and its radio coverage area unless otherwise indicated.

The size of the enterprise environment1006and the number of cells deployed in the small cell RAN1004may vary. In typical implementations, the enterprise environment1006can be from 50,000 to 500,000 square feet and encompass multiple floors, and the small cell RAN1004may support hundreds to thousands of users using mobile communication platforms such as mobile phones, smartphones, tablet computing devices, and the like shown as the UEs1008(3)-1008(N). However, the foregoing is intended to be illustrative and the solutions described herein can be typically expected to be readily scalable either upwards or downwards as the needs of a particular usage scenario demand.

InFIG. 10A, the small cell RAN1004includes one or more services nodes (represented as a single services node1014inFIG. 10A) that manage and control the small cell radio nodes1012(1)-1012(C). In alternative implementations, the management and control functionality may be incorporated into a radio node, distributed among nodes, or implemented remotely (i.e., using infrastructure external to the small cell RAN1004). The small cell radio nodes1012(1)-1012(C) are coupled to the services node1014over a direct or local area network (LAN) connection1016, as an example, typically using secure IPsec tunnels. The services node1014aggregates voice and data traffic from the small cell radio nodes1012(1)-1012(C) and provides connectivity over an IPsec tunnel to a security gateway (SeGW)1018in an Evolved Packet Core (EPC) network1020of the MNO1010. The EPC network1020is typically configured to communicate with a public switched telephone network (PSTN)1022to carry circuit-switched traffic, as well as for communicating with an external packet-switched network such as the Internet1024.

The environment1000also generally includes an Evolved Node B (eNB) base station, or “macrocell”1002. The radio coverage area of the macrocell1002(1)-1002(M) is typically much larger than that of a small cell where the extent of coverage often depends on the base station configuration and surrounding geography. Thus, a given UE1008(3)-1008(N) may achieve connectivity to the EPC network1020through either a macrocell1002or small cell radio node1012(1)-1012(C) in the small cell RAN1004in the environment1000.

A general principle in environment1000inFIG. 10Ais that a serving RAN (e.g., an eNB in such system) provides a measurement configuration to the UEs1008(1)-1008(N) to “point” the receiver of the UEs1008(1)-1008(N) to find other systems (e.g., neighboring cells) transmitting at a specified frequency(ies) (e.g., at 1900 MHz, 2500 MHz) according to the measurement configuration that the UE1008(1)-1008(N) should measure. The measurement of communication signals of other RANs by the UE1008(1)-1008(N) at specified frequencies is performed for a variety of purposes, including inter-frequency mobility and inter-frequency measurements. The UE1008(1)-1008(N) can find these communication systems and perform actions, such as cell selection in the idle mode and sending of measurement reports (e.g., Measurement Report Messages (MRMs)) in the active mode. These measurement reports can be used by the serving RAN (e.g., MNO macrocells1002(1)-1002(M), shared spectrum cell1003, small cell RAN1004) to, for example, trigger handovers or to gather information about neighboring cells through Automatic Neighbor Relation (ANR) discovery. For example, the MNO macrocells1002(1)-1002(M) may use the MRMs for cell reselection to cause a UE1008(1)-1008(N) to be serviced by a different cell controlled by the MNO, such as the small cell RAN1004for example, for optimizing communication. This measurement report information is delivered in user mobile communication device-specific radio resource control signaling messages to serviced UEs1008(1)-1008(N) that indicate to the UE1008(1)-1008(N) the appropriate measurement configuration parameters. In these measurement configuration parameters, there are specific instructions about what frequencies the serviced UE1008(1)-1008(N) should measure. The information measured by the UEs1008(1)-1008(N) is then reported back to the serving RAN.

With continuing reference toFIG. 10A, the MNO macrocells1002(1)-1002(M), the shared spectrum cell1003, and the small cell RAN1004may be neighboring radio access systems to each other, meaning that some or all can be in proximity to each other such that a UE1008(3)-1008(N) may be able to be in communication range of two or more of the MNO macrocells1002(1)-1002(M), the shared spectrum cell1003, and the small cell RAN1004depending on the location of UE1008(3)-1008(N). If a UE1008(1)-1008(N) serviced by the small cell RAN1004as a source RAN moves into the communication coverage area of a neighboring macrocell1002(1)-1002(M), the source RAN, detecting a weaker communication signal from the UE1008(1)-1008(N), initiates a handover command (i.e., request) to the neighboring macrocell1002(1)-1002(M) as a “target RAN.” The small cell RAN1004may be aware of the EARFCN of the MNO macrocells1002(1)-1002(M) as part of its configuration or an ANR discovery process discussed above. Similarly, if a UE1008(1)-1008(N) serviced by the shared spectrum cell1003as a source RAN moves into the communication coverage area of a neighboring macrocell1002(1)-1002(M), the source RAN initiates a handover command (i.e., request) to the neighboring macrocell1002(1)-1002(M) as a “target RAN.” The target RAN has a target coverage area overlapping a source coverage area of the source RAN in this example. The shared spectrum cell1003may be aware of the EARFCN of the MNO macrocells1002(1)-1002(M) as part of its configuration or an ANR process discussed above.

A UE1008connected to the environment1000will actively or passively monitor a cell in a macrocell1002(1)-1002(M) in an access network in the communication range of the UE1008as the UE1008moves throughout the environment1000. As shown inFIG. 10B, such a cell is termed the “serving cell.” For example, if a UE1008is in communication through an established communication session with a particular small cell radio node1012(1)-1012(C) in the small cell RAN1004, the particular small cell radio node1012(1)-1012(C) will be the serving cell to the UE1008, and the small cell RAN1004will be the serving RAN. The UE1008will continually evaluate the quality of a serving cell as compared with that of a neighboring cell1026in the small cell RAN1004, MNO macrocells1002, and/or the shared spectrum cell1003, as shown inFIG. 10B. A neighboring cell1026is a cell among the small cell RAN1004, MNO macrocells1002, and/or the shared spectrum cell1003that is not in control of the active communication session for a given UE1008, but is located in proximity to a serving cell to a UE1008such that the UE1008could be in communication range of both its serving cell and the neighboring cell1026. Each of the small cell radio nodes1012(1)-1012(C), the macrocells1002(1)-1002(M), and the shared spectrum cell1003can identify themselves to a UE1008using a respective unique Physical Cell Identity (PCI)1028(1)-1028(M),1030,1032(1)-1032(C) (e.g., a public land mobile network (PLMN) identification (ID) (PLMN ID)) that is transmitted over a downlink UE1008. Each of the small cell radio nodes1012(1)-1012(C), the MNO macrocells1002(1)-1002(M), and the shared spectrum cell1003can assign a physical channel identity (PCI) that allows the UE1008to distinguish adjacent cells. As such, the PCIs1028(1)-1028(M),1030,1032(1)-1032(C) are uniquely assigned among neighboring cells1026, but can be reused across geographically separated cells.

FIG. 11is a schematic diagram representation of additional detail regarding an exemplary computer system1100. The exemplary computer system1100in this embodiment includes a processing device or processor1102, a main memory1104(e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM), etc.), and a static memory1106(e.g., flash memory, static random access memory (SRAM), etc.), which may communicate with each other via the data bus1108. Alternatively, the processing device1102may be connected to the main memory1104and/or static memory1106directly or via some other connectivity means. The processing device1102may be a controller, and the main memory1104or static memory1106may be any type of memory.

The processing device1102represents one or more general-purpose processing devices such as a microprocessor, central processing unit, or the like. More particularly, the processing device1102may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor implementing other instruction sets, or processors implementing a combination of instruction sets. The processing device1102is configured to execute processing logic in instructions1116for performing the operations and steps discussed herein.

The computer system1100may further include a network interface device1110. The computer system1100also may or may not include an input1112to receive input and selections to be communicated to the computer system1100when executing instructions. The computer system1100also may or may not include an output1114, 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 system1100may or may not include a data storage device that includes instructions1116stored in a computer-readable medium1118. The instructions1116may also reside, completely or at least partially, within the main memory1104and/or within the processing device1102during execution thereof by the computer system1100, the main memory1104and the processing device1102also constituting computer-readable medium1118. The instructions1116may further be transmitted or received over a network1120via the network interface device1110.

Unless specifically stated otherwise and as apparent from the previous discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing,” “computing,” “determining,” “displaying,” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data and memories represented as physical (electronic) quantities within the computer system's registers into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission, or display devices.

The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatuses to perform the required method steps. The required structure for a variety of these systems will appear from the description above. In addition, the embodiments described herein are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the embodiments as described herein.

It is also noted that the operational steps described in any of the exemplary embodiments herein are described to provide examples and discussion. The operations described may be performed in numerous different sequences other than the illustrated sequences. Furthermore, operations described in a single operational step may actually be performed in a number of different steps. Additionally, one or more operational steps discussed in the exemplary embodiments may be combined. Those of skill in the art will also understand that information and signals may be represented using any of a variety of technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips, that may be references throughout the above description, may be represented by voltages, currents, electromagnetic waves, magnetic fields, or particles, optical fields or particles, or any combination thereof.