Patent ID: 12232097

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a novel Reconfigurable Distributed Antenna System that provides a high degree of flexibility to manage, control, re-configure, enhance and facilitate the radio resource efficiency, usage and overall performance of the distributed wireless network. An embodiment of the Reconfigurable Distributed Antenna System in accordance with the present invention is shown inFIG.1. The Flexible Simulcast System100can be used to explain the operation of Flexible Simulcast with regard to downlink signals. The system employs a Digital Access Unit functionality (hereinafter “DAU”). The DAU serves as an interface to the base station (BTS). The DAU is (at one end) connected to the BTS, and on the other side connected to multiple RRUs. For the downlink (DL) path, RF signals received from the BTS are separately down-converted, digitized, and converted to baseband (using a Digital Down-Converter). Data streams are then I/Q mapped and framed. Specific parallel data streams are then independently serialized and translated to optical signals using pluggable SFP modules, and delivered to different RRUs over optical fiber cable. For the uplink (UL) path optical signals received from RRUs are deserialized, deframed, and up-converted digitally using a Digital Up-Converter. Data streams are then independently converted to the analog domain and up-converted to the appropriate RF frequency band. The RF signal is then delivered to the BTS. An embodiment of the system is mainly comprised of DAU1indicated at101, RRU1indicated at103, RRU2indicated at104, DAU2indicated at102, RRU3indicated at105, and RRU4indicated at106. A composite downlink input signal107from, e.g., a base station belonging to one wireless operator enters DAU1at the DAU1RF input port. Composite signal107is comprised of Carriers 1-4. A second composite downlink input signal from e.g., a second base station belonging to the same wireless operator enters DAU2at the DAU2RF input port. Composite signal108is comprised of Carriers 5-8. The functionality of DAU1, DAU2, RRU1, RRU2, RRU3and RRU4are explained in detail by U.S. Provisional Application Ser. No. 61/374,593, entitled “Neutral Host Architecture for a Distributed Antenna System,” filed Aug. 17, 2010 and attached hereto as an appendix. One optical output of DAU1is fed to RRU1. A second optical output of DAU1is fed via bidirectional optical cable113to DAU2. This connection facilitates networking of DAU1and DAU2, which means that all of Carriers 1-8 are available within DAU1and DAU2to transport to RRU1, RRU2, RRU3and RRU4depending on software settings within the networked DAU system comprised of DAU1and DAU2. The software settings within RRU1are configured either manually or automatically such that Carriers 1-8 are present in the downlink output signal109at the antenna port of RRU1. The presence of all 8 carriers means that RRU1is potentially able to access the full capacity of both base stations feeding DAU1and DAU2. A possible application for RRU1is in a wireless distribution system is e.g., a cafeteria in an enterprise building during the lunch hour where a large number of wireless subscribers are gathered. RRU2is fed by a second optical port of RRU1via bidirectional optical cable114to RRU2. Optical cable114performs the function of daisy chaining RRU2with RRU1. The software settings within RRU2are configured either manually or automatically such that Carriers 1, 3, 4 and 6 are present in downlink output signal110at the antenna port of RRU2. The capacity of RRU2is set to a much lower value than RRU1by virtue of its specific Digital Up Converter settings. The individual Remote Radio Units have integrated frequency selective DUCs and DDCs with gain control for each carrier. The DAUs can remotely turn on and off the individual carriers via the gain control parameters.

In a similar manner as described previously for RRU1, the software settings within RRU3are configured either manually or automatically such that Carriers 2 and 6 are present in downlink output signal111at the antenna port of RRU3. Compared to the downlink signal110at the antenna port of RRU2, the capacity of RRU3which is configured via the software settings of RRU3is much less than the capacity of RRU2. RRU4is fed by a second optical port of RRU3via bidirectional optical cable115to RRU4. Optical cable115performs the function of daisy chaining RRU4with RRU3. The software settings within RRU4are configured either manually or automatically such that Carriers 1, 4, 5 and 8 are present in downlink output signal112at the antenna port of RRU4. The capacity of RRU4is set to a much lower value than RRU1. The relative capacity settings of RRU1, RRU2, RRU3and RRU4and can be adjusted dynamically as discussed in connection withFIG.7to meet the capacity needs within the coverage zones determined by the physical positions of antennas connected to RRU1, RRU2, RRU3and RRU4respectively.

The present invention facilitates conversion and transport of several discrete relatively narrow RF bandwidths. This approach allows conversion of only those multiple specific relatively narrow bandwidths which carry useful or specific information. This approach also allows more efficient use of the available optical fiber transport bandwidth for neutral host applications, and allows transport of more individual operators' band segments over the optical fiber. As disclosed in U.S. Provisional Application Ser. No. 61/374,593, entitled “Neutral Host Architecture for a Distributed Antenna System,” filed Aug. 17, 2010 and also referring to FIG. 1 of the instant patent application, Digital Up Converters located within the RRU which are dynamically software-programmable as discussed hereinafter can be reconfigured to transport from the DAU input to any specific RRU output any specific narrow frequency band or bands, RF carriers or RF channels which are available at the respective RF input port of either DAU. This capability is illustrated inFIG.1where only specific frequency bands or RF carriers appear at the output of a given RRU.

A related capability of the present invention is that not only can the Digital Up Converters located within each RRU be configured to transport any specific narrow frequency band from the DAU input to any specific RRU output, but also the Digital Up Converters within each RRU can be configured to transport any specific time slot or time slots of each carrier from the DAU input to any specific RRU output. The DAU detects which carriers and corresponding time slots are active. This information is relayed to the individual RRUs via the management control and monitoring protocol software discussed hereinafter. This information is then used, as appropriate, by the RRUs for turning off and on individual carriers and their corresponding time slots.

Referring to FIG. 1 of the instant patent application, an alternative embodiment of the present invention may be described as follows. In a previous description of FIG. 1, a previous embodiment involved having downlink signals from two separate base stations belonging to the same wireless operator enter DAU1and DAU2input ports respectively. In an alternative embodiment, a second composite downlink input signal from e.g., a second base station belonging to a different wireless operator enters DAU2at the DAU2RF input port. In this embodiment, signals belonging to both the first operator and the second operator are converted and transported to RRU1, RRU2, RRU3and RRU4respectively. This embodiment provides an example of a neutral host wireless system, where multiple wireless operators share a common infrastructure comprised of DAU1, DAU2, RRU1, RRU2, RRU3and RRU4. All the previously mentioned features and advantages accrue to each of the two wireless operators.

As disclosed in U.S. Provisional Application Ser. No. 61/374,593, entitled “Neutral Host Architecture for a Distributed Antenna System,” filed Aug. 17, 2010 and also referring to FIG. 1 of the instant patent application, the Digital Up Converters present in the RRU can be programmed to process various signal formats and modulation types including FDMA, CDMA, TDMA, OFDMA and others. Also, the Digital Up Converters present in the respective RRUs can be programmed to operate with signals to be transmitted within various frequency bands subject to the capabilities and limitations of the system architecture disclosed in U.S. Provisional Application Ser. No. 61/374,593, entitled “Neutral Host Architecture for a Distributed Antenna System,” filed Aug. 17, 2010. In one embodiment of the present invention where a wideband CDMA signal is present within e.g., the bandwidth corresponding to carrier 1 at the input port to DAU1, the transmitted signal at the antenna ports of RRU1, RRU2and RRU4will be a wideband CDMA signal which is virtually identical to the signal present within the bandwidth corresponding to carrier 1 at the input port to DAU1.

As disclosed in U.S. Provisional Application Ser. No. 61/374,593, entitled “Neutral Host Architecture for a Distributed Antenna System,” filed Aug. 17, 2010 and also referring to FIG. 1 of the instant patent application, it is understood that the Digital Up Converters present in the respective RRUs can be programmed to transmit any desired composite signal format to each of the respective RRU antenna ports. As an example, the Digital Up Converters present in RRU1and RRU2can be dynamically software-reconfigured as described previously so that the signal present at the antenna port of RRU1would correspond to the spectral profile shown inFIG.1as110, and also that the signal present at the antenna port of RRU2would correspond to the spectral profile shown inFIG.1as109. The application for such a dynamic rearrangement of RRU capacity would be e.g., if a company meeting were suddenly convened in the area of the enterprise corresponding to the coverage area of RRU2. Although the description of some embodiments in the instant application refers to base station signals107and108as being on different frequencies, the system and method of the present invention readily supports configurations where one or more of the carriers which are part of base station signals107and108and are identical frequencies, since the base station signals are digitized, packetized, routed and switched to the desired RRU.

Another embodiment of the Distributed Antenna System in accordance with the present invention is shown inFIG.2. As disclosed in U.S. Provisional Application Ser. No. 61/374,593, entitled “Neutral Host Architecture for a Distributed Antenna System,” filed Aug. 17, 2010 and also as shown inFIG.2the Flexible Simulcast System200can be used to explain the operation of Flexible Simulcast with regard to uplink signals. As discussed previously with regard to downlink signals and by referring toFIG.1, the uplink system shown inFIG.2is mainly comprised of DAU1indicated at201, RRU1indicated at203, RRU2indicated at204, DAU2indicated at202, RRU3indicated at205, and RRU4indicated at206. In a manner similar to the downlink operation explained by referring toFIG.1, the operation of the uplink system shown inFIG.2can be understood as follows.

The Digital Down Converters present in each of RRU1, RRU2, RRU3and RRU4are dynamically software-configured as described previously so that uplink signals of the appropriate desired signal format(s) present at the receive antenna ports of the respective RRU1, RRU2, RRU3and RRU4are selected based on the desired uplink band(s) to be processed and filtered, converted and transported to the appropriate uplink output port of either DAU1or DAU2. The DAUs and RRUs frame the individual data packets corresponding to their respective radio signature using the Common Public Interface Standard (CPRI). Other Interface standards are applicable provided they uniquely identify data packets with respective RRUs. Header information is transmitted along with the data packet which identifies the RRU and DAU that corresponds to the individual data packet.

In one example for the embodiment shown inFIG.2, RRU1and RRU3are configured to receive uplink signals within the Carrier 2 bandwidth, whereas RRU2and RRU4are both configured to reject uplink signals within the Carrier 2 bandwidth. When RRU3receives a strong enough signal at its receive antenna port within the Carrier 2 bandwidth to be properly filtered and processed, the Digital Down Converters within RRU3facilitate processing and conversion. Similarly, when RRU1receives a strong enough signal at its receive antenna port within the Carrier 2 bandwidth to be properly filtered and processed, the Digital Down Converters within RRU1facilitate processing and conversion. The signals from RRU1and RRU3are combined based on the active signal combining algorithm, and are fed to the base station connected to the uplink output port of DAU1. The term simulcast is frequently used to describe the operation of RRU1and RRU3with regard to uplink and downlink signals within Carrier 2 bandwidth. The term Flexible Simulcast refers to the fact that the present invention supports dynamic and/or manual rearrangement of which specific RRU are involved in the signal combining process for each Carrier bandwidth.

Referring toFIG.2, the Digital Down Converters present in RRU1are configured to receive and process signals within Carrier 1-8 bandwidths. The Digital Down Converters present in RRU2are configured to receive and process signals within Carrier 1, 3, 4 and 6 bandwidths. The Digital Down Converters present in RRU3are configured to receive and process signals within Carrier 2 and 6 bandwidths. The Digital Down Converters present in RRU4are configured to receive and process signals within Carrier 1, 4, 5 and 8 bandwidths. The respective high-speed digital signals resulting from processing performed within each of the four RRU are routed to the two DAUs. As described previously, the uplink signals from the four RRUs are combined within the respective DAU corresponding to each base station.

An aspect of the present invention includes an integrated Pilot Beacon function within the each RRU. In an embodiment, each RRU comprises a unique software programmable Pilot Beacon as discussed hereinafter. This approach is intended for use in CDMA and/or WCDMA indoor DAS networks. A very similar approach can be effective for indoor location accuracy enhancement for other types of networks such as LTE and WiMAX. Because each RRU is already controlled and monitored via the DAUs which comprise the network, there is no need for costly deployment of additional dedicated wireless modems for remote monitoring and control of pilot beacons.

An RRU-integrated Pilot Beacon approach is employed for both CDMA and WCDMA networks. Each operational pilot beacon function within an RRU employs a unique PN code (in that area) which effectively divides the WCDMA or CDMA indoor network coverage area into multiple small “zones” (which each correspond to the coverage area of a low-power Pilot Beacon). Each Pilot Beacon's location, PN code and RF Power level are known by the network. Each Pilot Beacon is synchronized to the WCDMA or CDMA network, via its connection to the DAU.

Unlike the transmit signal from a base station which is “dynamic”, the Pilot Beacon transmit signal will be effectively “static” and its downlink messages will not change over time based on network conditions.

For a WCDMA network, in Idle mode each mobile subscriber terminal is able to perform Pilot Signal measurements of downlink signals transmitted by base stations and Pilot Beacons. When the WCDMA mobile subscriber terminal transitions to Active mode, it reports to the serving cell all its Pilot Signal measurements for base stations and for Pilot Beacons. For CDMA networks, the operation is very similar. For some RRU deployed in an indoor network, the RRU can be provisioned as either a Pilot Beacon or to serve mobile subscribers in a particular operator bandwidth, but not both.

For a WCDMA network, existing inherent capabilities of the globally-standardized networks are employed. The WCDMA mobile subscriber terminal is able to measure the strongest CPICH RSCP (Pilot Signal Code Power) in either Idle mode or any of several active modes. Also, measurements of CPICH Ec/No by the mobile subscriber terminal in either Idle mode or any of several active modes are possible. As a result, the mobile subscriber terminal reports all available RSCP and Ec/No measurements via the serving base station (whether indoor or outdoor) to the network. Based on that information, the most likely mobile subscriber terminal location is calculated and/or determined. For CDMA networks, the operation is very similar to the process described herein.

A previously described embodiment of the present invention referring toFIG.1involved having a wideband CDMA signal present within e.g., the bandwidth corresponding to carrier 1 at the input port to DAU1. In the previously described embodiment, the transmitted signal at the antenna ports of RRU1, RRU2and RRU4is a wideband CDMA signal which is virtually identical to the signal present within the bandwidth corresponding to carrier 1 at the input port to DAU1. An alternative embodiment of the present invention is one where a wideband CDMA signal is present within e.g., the bandwidth corresponding to carrier at the input port to DAU1. However, in the alternative embodiment the transmitted signal at the antenna port of RRU1differs slightly from the previous embodiment. In the alternative embodiment, a wideband CDMA signal is present within e.g., the bandwidth corresponding to carrier 1 at the input port to DAU1. The transmitted signal from RRU1is a combination of the wideband CDMA signal which was present at the input port to DAU1, along with a specialized WCDMA pilot beacon signal. The WCDMA pilot beacon signal is intentionally set well below the level of the base station pilot signal.

A further alternative embodiment can be explained referring toFIG.1which applies in the case where CDMA signals are generated by the base station connected to the input port of DAU1. In this further alternative embodiment of the present invention, the transmitted signal at the antenna port of RRU1is a combination of the CDMA signal which was present at the input port to DAU1, along with a specialized CDMA pilot beacon signal. The CDMA pilot beacon signal is intentionally set well below the level of the base station pilot signal.

An embodiment of the present invention provides enhanced accuracy for determining location of indoor wireless subscribers.FIG.4depicts a typical indoor system employing multiple Remote Radio Head Units (RRUs) and a central Digital Access Unit (DAU). Each Remote Radio Head provides a unique header information on data received by that Remote Radio Head. This header information in conjunction with the mobile user's radio signature are used to localize the user to a particular cell. The DAU signal processing can identify the individual carriers and their corresponding time slots. A header is included with each data packet that uniquely identifies the corresponding RRU. The DAU can detect the carrier frequency and the corresponding time slot associated with the individual RRUs. The DAU has a running data base that identifies each carrier frequency and time slot with a respective RRU. The carrier frequency and time slot is the radio signature that uniquely identifies the GSM user.

The DAU communicates with a Network Operation Center (NOC) via a Ethernet connection or an external modem, as depicted inFIG.5. Once a E911 call is initiated the Mobile Switching Center (MSC) in conjunction with the NOC can identify the corresponding BaseTransceiver Station (BTS) where the user has placed the call. The user can be localized within a BTS cell. The NOC then makes a request to the individual DAUs to determine if the E911 radio signature is active in their indoor cell. The DAU checks its data base for the active carrier frequency and time slot. If that radio signature is active in the DAU, then that DAU will provide the NOC with the location information of the corresponding RRU.

A further embodiment of the present invention includes LTE to provide enhanced accuracy for determining the location of indoor wireless subscribers. GSM uses individual carriers and time slots to distinguish users whereas LTE uses multiple carriers and time slot information to distinguish users. The DAU can simultaneously detect multiple carriers and their corresponding time slots to uniquely identify the LTE user. The DAU has a running data base that identifies the carrier frequencies and time slot radio signature for the respective RRU. This information can be retrieved from the NOC once a request is made to the DAU.

Referring next toFIG.7, the DAU embedded software control module and RRU embedded software control module can be better understood in connection with the operation of key functions of the DAU and RRU. One such key function is determining and/or setting the appropriate amount of radio resources (such as RF carriers, CDMA codes or TDMA time slots) assigned to a particular RRU or group of RRUs to meet desired capacity and throughput objectives. The DAU embedded software control module comprises a DAU Monitoring module that detects which carriers and corresponding time slots are active for each RRU. The DAU embedded software control module also comprises a DAU Management Control module which communicates with the RRU over a fiber optic link control channel via a control protocol with the RRU Management Control module. In turn, the RRU Management Control module sets the individual parameters of all the RRU Digital Up-Converters to enable or disable specific radio resources from being transmitted by a particular RRU or group of RRUs, and also sets the individual parameters of all the RRU Digital Down-Converters to enable or disable specific uplink radio resources from being processed by a particular RRU or group of RRUs.

In an embodiment, an algorithm operating within the DAU Monitoring module, that detects which carriers and corresponding time slots for each carrier are active for each RRU, provides information to the DAU Management Control module to help identify when, e.g., a particular downlink carrier is loaded by a percentage greater than a predetermined threshold whose value is communicated to the DAU Management Control module by the DAU's Remote Monitoring and Control function. If that occurs, the DAU Management Control module adaptively modifies the system configuration to slowly begin to deploy additional radio resources (such as RF carriers, CDMA codes or TDMA time slots) for use by a particular RRU which need those radio resources within its coverage area. At the same time, in at least some embodiments the DAU Management Control module adaptively modifies the system configuration to slowly begin to remove certain radio resources (such as RF carriers, CDMA codes or TDMA time slots) for use by a particular RRU which no longer needs those radio resources within its coverage area. Another such key function of the DAU embedded software control module and RRU embedded software control module is determining and/or setting and/or analyzing the appropriate transmission parameters and monitoring parameters for the integrated Pilot Beacon function contained within each RRU. These Pilot Beacon transmission and monitoring parameters include Beacon Enable/Disable, Beacon Carrier Frequencies, Beacon Transmit Power, Beacon PN Code, Beacon Downlink BCH Message Content, Beacon Alarm, Beacon Delay Setting and Beacon Delay Adjustment Resolution. The RRU Pilot Beacon Control module communicates with the pilot beacon generator function in the RRU to set and monitor the pilot beacon parameters as listed herein.

In summary, the Reconfigurable Distributed Antenna System of the present invention described herein efficiently conserves resources and reduces costs. The reconfigurable system is adaptive or manually field-programmable, since the algorithms can be adjusted like software in the digital processor at any time.

Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.

APPENDIX I

Glossary of Terms

ACLR Adjacent Channel Leakage RatioACPR Adjacent Channel Power RatioADC Analog to Digital ConverterAQDM Analog Quadrature DemodulatorAQM Analog Quadrature ModulatorAQDMC Analog Quadrature Demodulator CorrectorAQMC Analogy Quadrature Modulator CorrectorBPF Bandpass FilterBTS Base Transceiver System or Base StationCDMA Code Division Multiple AccessCFR Crest Factor ReductionDAC Digital to Analog ConverterDAU Digital Access UnitDET DetectorDHMPA Digital Hybrid mode Power AmplifierDDC Digital Down ConverterDNC Down ConverterDPA Doherty Power AmplifierDQDM Digital Quadrature DemodulatorDQM Digital Quadrature ModulatorDSP Digital Signal ProcessingDUC Digital Up ConverterEER Envelope Elimination and RestorationEF Envelope FollowingET Envelope TrackingEVM Error Vector MagnitudeFFLPA Feedforward Linear Power AmplifierFIR Finite Impulse ResponseFPGA Field-Programmable Gate ArrayGSM Global System for Mobile CommunicationsI-Q In-phase/QuadratureIF Intermediate FrequencyLINC Linear Amplification Using Nonlinear ComponentsLO Local OscillatorLPF Low Pass FilterMCPA Multi-Carrier Power AmplifierMDS Multi-Directional SearchOFDM Orthogonal Frequency Division MultiplexingPA Power AmplifierPARR Peak-to-Average Power RatioPD Digital Baseband PredistortionPLL Phase Locked LoopPN Pseudo-NoiseQAM Quadrature Amplitude ModulationQPSK Quadrature Phase Shift KeyingRF Radio FrequencyRRH Remote Radio HeadRRU Remote Radio head UnitSAW Surface Acoustic Wave FilterUMTS Universal Mobile Telecommunications SystemUPC Up ConverterWCDMA Wideband Code Division Multiple AccessWLAN Wireless Local Area Network