(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2012/0039254 A1
`Stapleton et al.
`(43) Pub. Date:
`Feb. 16, 2012
`
`US 20120039254A1
`
`(54)
`
`DASYCHAINED RING OF REMOTE UNITS
`FORADISTRIBUTED ANTENNASYSTEM
`
`(60) Provisional application No. 61/439,940, filed on Feb.
`7, 2011.
`
`(75)
`
`Inventors:
`
`Shawn Patrick Stapleton, Burnaby
`(CA); Paul Lemson, Woodinville,
`WA (US); Bin Lin, Coquitlam (CA)
`
`(73)
`
`Assignee:
`
`Dali Systems Co., Ltd., George
`Town Grand Cayman (KY)
`
`(21)
`
`Appl. No.:
`
`13/211,247
`
`(22)
`
`Filed:
`
`Aug. 16, 2011
`
`(63)
`
`Related U.S. Application Data
`Continuation of application No. 1 1/961.969, filed on
`Dec. 20, 2007, Continuation of application No.
`12/108.502, filed on Apr. 23, 2008, Continuation of
`application No. 12/603,419, filed on Oct. 21, 2009,
`Continuation of application No. 12/767,669, filed on
`Apr. 26, 2010, Continuation of application No. 12/928,
`931, filed on Dec. 21, 2010, Continuation of applica
`tion No. 12/928,933, filed on Dec. 21, 2010, Continu
`ation of application No. 12/928,934, filed on Dec. 21,
`2010, Continuation of application No. 12/928,943,
`filed on Dec. 21, 2010.
`
`Publication Classification
`
`(51) Int. Cl.
`(2009.01)
`H04740/00
`(52) U.S. Cl. ........................................................ 370/328
`(57)
`ABSTRACT
`The present disclosure is a novel utility of a software defined
`radio (SDR) based Distributed Antenna System (DAS) that is
`field reconfigurable and Support multi-modulation schemes
`(modulation-independent), multi-carriers, multi-frequency
`bands and multi-channels. More specifically, the present
`invention relates to a DAS utilizing one or more Daisy
`Chained Rings of Remote Units. The present invention
`enables a high degree of flexibility to manage, control,
`enhance, facilitate the usage and performance of a distributed
`wireless network such as Flexible Simulcast, automatic traf
`fic load-balancing, network and radio resource optimization,
`network calibration, autonomous/assisted commissioning,
`carrier pooling, automatic frequency selection, frequency
`carrier placement, traffic monitoring, traffic tagging, pilot
`beacon, etc. As a result, a DAS in accordance with the present
`invention can increase the efficiency and traffic capacity of
`the operators’ wireless network.
`
`
`
`53
`
`

`

`Patent Application Publication
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`Feb. 16, 2012 Sheet 1 of 8
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`US 2012/00392.54 A1
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`Patent Application Publication
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`Feb. 16, 2012 Sheet 7 of 8
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`US 2012/00392.54 A1
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`Patent Application Publication
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`Feb. 16, 2012 Sheet 8 of 8
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`US 2012/00392.54 A1
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`US 2012/00392.54 A1
`
`Feb. 16, 2012
`
`DASYCHANED RING OF REMOTE UNITS
`FORADISTRIBUTED ANTENNASYSTEM
`
`-continued
`
`RELATED APPLICATIONS
`
`0001. This application claims the benefit of the following
`U.S. patent applications, all of which are incorporated herein
`by reference:
`
`Ser. No.
`Filing Date
`Title
`not assigned yet Aug. 16, 2011 Remotely Reconfigurable
`Distributed Antenna System and
`Methods
`Daisy Chained Ring of Remote
`Units for a Distributed Antenna
`System.
`
`not assigned yet Aug. 16, 2011
`
`Ser. No.
`
`Filing Date
`
`Title
`
`60/877,035
`
`60/925,603
`
`60/925,577
`
`61/O12.416
`
`11/961,969
`
`61/041,164
`
`12/108,502
`
`61/172,642
`
`12/603,419
`
`61/288,838
`
`61/288,840
`
`61/288,844
`
`61/288,847
`
`12/767,669
`
`61/374,593
`
`61/382,836
`
`12/928,931
`
`12/928,933
`
`12/928,934
`
`12/928,943
`
`61f439,940
`
`FIELD OF THE INVENTION
`0002 The present invention generally relates to wireless
`communication systems employing Distributed Antenna Sys
`tems (DAS) as part of a distributed wireless network. More
`specifically, the present invention relates to a DAS utilizing
`one or more remotely monitored and controlled digital access
`units configured to assign particular packet transmissions to
`selected ones of a plurality of remote units, which can in some
`embodiments be configured in a daisy-chained rings.
`
`BACKGROUND OF THE INVENTION
`0003 Wireless and mobile network operators face the
`continuing challenge of building networks that effectively
`manage high data-traffic growth rates. Mobility and an
`increased level of multimedia content for end users requires
`end-to-end network adaptations that Support both new ser
`vices and the increased demand for broadband and flat-rate
`Internet access. One of the most difficult challenges faced by
`network operators is maximizing the capacity of their DAS
`networks while ensuring cost-effective DAS deployments
`and at the same time providing a very high degree of DAS
`remote unit availability.
`0004. In order to provide DAS network capacity which is
`high enough to meet short-term needs of network Subscribers
`in specific locations yet also avoid costly and inefficient
`deployment of radio resources, DAS network planners prefer
`to employ DAS architectures and solutions which provide a
`high degree of dynamic flexibility. Therefore, it would be
`advantageous for wireless network operators to employ a
`DAS solution which has a high degree of flexibility to imple
`ment dynamic rearrangements based on ever-changing net
`work conditions and subscriber needs. Also, the more future
`proof a DAS deployment can be, generally the lower its life
`cycle cost.
`0005 DAS network planners and system integrators
`employ a wide range of innovative approaches for helping to
`ensure that a particular DAS deployment is as cost-effective
`as possible. The types of costs considered by network plan
`ners and integrators include DAS deployment or DAS instal
`lation cost, as well as operational costs including mainte
`nance costs, emergency restoration costs and network
`re-arrangement costs. Rearrangement costs are particularly
`significant for indoor DAS applications, due to frequent
`changes in building use and facility needs changes. There
`fore, it would be advantageous to employ DAS systems and
`methods which are based on as few DAS transport facilities as
`possible to minimize installation and/or lease costs and have
`self-healing capabilities to avoid the need for costly emer
`gency restoration services.
`0006. In order to obtain a high degree of DAS remote unit
`availability, two primary conditions must be satisfied. First,
`the DAS remote unit itself must be inherently reliable. Sec
`
`Dec. 26, 2006
`
`Apr. 23, 2007
`
`Apr. 23, 2007
`
`Dec. 8, 2007
`
`Mar. 31, 2008
`
`Apr. 23, 2008
`
`Apr. 24, 2009
`
`Oct. 21, 2009
`
`Dec. 21, 2009
`
`Dec. 21, 2009
`
`Dec. 21, 2009
`
`Apr. 26, 2010
`
`Aug. 17, 2010
`
`Sep. 14, 2010
`
`Dec. 21, 2010
`
`Dec. 21, 2010
`
`Dec. 21, 2010
`
`Feb. 7, 2011
`
`Method For Baseband Predistortion
`Linearization in Multi-Channel
`Wideband Communication Systems
`Digital Hybrid Mode Power
`Amplifier System
`N-Way Doherty Distributed Power
`Amplifier
`Baseband Derived RF Digital
`Predistortion
`Dec. 20, 2007 A Method for Baseband
`Predistortion Linearization in Multi
`Channel Wideband Communication
`Systems
`An Efficient Peak Cancellation
`Method For Reducing The Peak-To
`Average Power Ratio in Wideband
`Communication Systems
`Digital Hybrid Mode Power
`Amplifier System
`Remotely Reconfigurable Power
`Amplifier System
`N-Way Doherty Distributed Power
`Amplifier with Power Tracking
`Dec. 21, 2009 Multi-Band Wideband Power
`Amplifier Digital Predistortion
`System and Method
`Remote Radio Head Unit System
`with Wideband Power Amplifier and
`Method
`Modulation Agnostic Digital Hybrid
`Mode Power Amplifier System and
`Method
`High Efficiency, Remotely
`Reconfigurable Remote Radio Head
`Unit System and Method for
`Wireless Communications
`Remotely Reconfigurable Power
`Amplifier System and Method
`Neutral Host Architecture for a
`Distributed Antenna System
`Remotely Reconfigurable
`Distributed Antenna System and
`Methods
`Modulation Agnostic Digital Hybrid
`Mode Power Amplifier System and
`Method
`Remote Radio Head Unit System
`with Wideband Power Amplifier and
`Method
`Dec. 21, 2010 Multi-Band Wideband Power
`Amplifier Digital Predistortion
`System and Method
`High Efficiency, Remotely
`Reconfigurable Remote Radio Head
`Unit System and Method
`for Wireless Communications
`Daisy Chained Ring of Remote
`Units for a Distributed Antenna
`System
`Neutral Host Architecture for a
`Distributed Antenna System
`
`not assigned yet Aug. 16, 2011
`
`

`

`US 2012/00392.54 A1
`
`Feb. 16, 2012
`
`ond, the transport media e.g., optical fiber, must be very
`reliable. It is well known that electronic and/or optical con
`nections themselves are a significant root cause of failure or
`reduced availability in a DAS network. Companies who
`maintain outdoor DAS networks have reported that a failure
`of outside plant optical fiber facilities is not as rare as would
`be desirable. Therefore, it would be advantageous to employ
`systems and methods which offer higher redundancy and/or
`self-healing features in the event of failure of a transport
`media connection.
`
`SUMMARY OF THE INVENTION
`0007. The present invention substantially achieves the
`advantages and benefits discussed above and overcomes the
`limitations of the prior art discussed above by providing a
`distributed antenna system responsive to one or more base
`stations and having at least one but in Some embodiments a
`plurality of Digital Access Units (“DAU’s), each operating
`to control the packet traffic of an associated plurality of Digi
`tal Remote Units (“DRU's). In embodiments employing
`multiple DAU’s, the DAU's can be daisy-chained linearly or
`in a ring configuration. Likewise, depending upon the imple
`mentation, the DRU’s associated with a given DAU can be
`configured in eithera linear or ring Daisy chain configuration.
`0008. The data received from the base stations is down
`converted, digitized and converted to baseband with the DAU.
`The data streams are then I/O mapped and framed and inde
`pendently serialized, such that multiple data streams are
`available in parallel from the DAU. In at least some embodi
`ments, the DAU communicates with the associated DRU's via
`an optical transport arrangement. It will be appreciated by
`those skilled in the art that, using the present invention, it is
`possible to configure a distributed antenna system having in
`base stations, each providing mRF outputs for transmission
`by one or more associated DAU's to o DRU’s, where the only
`limits are imposed by the technical performance specifica
`tions of the particular DAS, such as delay.
`0009. By the use of a ring configuration for connecting, in
`at least some embodiments, the DRU's and/or the DAU's,
`fault tolerance is built into the system, with resulting high
`availability. In single DAU embodiments, each DRU is acces
`sible through two paths, and therefore remains available even
`in the event of a line break. In multi-DAU embodiments,
`where the DAU’s are linearly daisy-chained, each DRU is
`accessible from multiple DRU's such that even some DAU
`failures will not prevent system operation. In embodiments
`employing a ring connection for the DAU’s, multiple paths
`exist to each DAU, and thus provide an additional level of
`fault tolerance as well as dynamic load balancing and
`resource management as discussed in greater detail hereinaf
`ter.
`0010 Thus, the configuration of the advanced system
`architecture of the present invention provides a high degree of
`flexibility to manage, control, enhance and facilitate the radio
`resource efficiency, usage, availability, and overall perfor
`mance of the distributed wireless network. The present inven
`tion enables specialized applications and enhancements
`including Flexible Simulcast, automatic traffic load-balanc
`ing, network and radio resource optimization, network cali
`bration, autonomous/assisted commissioning, carrier pool
`ing, automatic frequency selection, radio frequency carrier
`placement, traffic monitoring, traffic tagging, and indoor
`location determination using pilot beacons. The present
`invention can also serve multiple operators, multi-mode
`
`radios (modulation-independent) and multi-frequency bands
`per operator to increase the efficiency and traffic capacity of
`the operators’ wireless networks.
`0011
`Further the present invention provides a high degree
`of dynamic flexibility, Supports dynamic re-arrangements,
`and provides a low life cycle cost. This advanced system
`architecture enables deployment of DAS networks using
`fewer DAS transport facilities to reduce costs, while provid
`ing self-healing features. The present invention also offers
`redundancy and enhanced system availability.
`0012. It is an object of the present invention to provide
`Flexible Simulcast capabilities, as disclosed in U.S. Provi
`sional Application Ser. No. 61/382.836, entitled “Remotely
`Reconfigurable Distributed Antenna System and Methods.”
`filed Sep. 14, 2010, incorporated herein by reference and
`attached as Appendix A, in a high-availability ring configu
`ration using, for example, optical fibertransport. As discussed
`above, the ring configuration insures that a break in any
`optical fiber cable will not shut down the daisy-chained net
`work, because the downlink and uplink signals can be
`rerouted around the cable break to the respective DRUs.
`0013. It is a further object of the present invention to
`balance the bidirectional data rate on the optical fibers so as to
`increase the maximum achievable data rate during operation
`on the ring network of DRUs.
`0014. It is a further object of the present invention to
`provide higher transport network capacity in the event the
`data transport is asymmetrical between the downlink and
`uplink, as is typically the case for mobile broadband net
`works.
`0015. It is a further object of the present invention to
`provide an adaptive and automatic control for optimizing the
`transport media capacity on the ring.
`0016. It is a further object of the present invention to
`provide a method of Summing co-channel users uplink sig
`nals in the DRU daisy chain.
`0017 Applications of the present invention are suitable to
`be employed with distributed base stations, distributed
`antenna systems, distributed repeaters, mobile equipment and
`wireless terminals, portable wireless devices, and other wire
`less communication systems such as microwave and satellite
`communications. The present invention is also field upgrad
`able through a link Such as an Ethernet connection to a remote
`computing center.
`0018 Appendix I is a glossary of terms used herein,
`including acronyms.
`
`THE FIGURES
`0019. Further objects and advantages of the present inven
`tion can be more fully understood from the following detailed
`description taken in conjunction with the accompanying
`drawings in which:
`0020 FIG. 1 is a block diagram according to one embodi
`ment of the invention showing the basic structure and an
`example of a unidirectional, channelized downlink transport,
`one ring scenario based on having one DAU and four DRUs.
`0021
`FIG. 2 is a block diagram in accordance with an
`embodiment of the invention showing the basic structure and
`an example of a unidirectional, channelized uplink transport,
`one ring scenario based on having one DAU and four DRUs.
`0022 FIG. 3 is a block diagram in accordance with an
`embodiment of the invention showing the basic structure and
`an example of a unidirectional, channelized uplink transport,
`two ring scenario based on having one DAU and eight DRUS.
`
`

`

`US 2012/00392.54 A1
`
`Feb. 16, 2012
`
`0023 FIG. 4 is a block diagram in accordance with an
`embodiment of the invention showing the basic structure and
`an example of a unidirectional channelized uplink or down
`link transport. This example of a five ring scenario comprises
`two DAUs and twenty DRUs.
`0024 FIG. 5 illustrates an embodiment of a cellular net
`work system employing multiple DRUS according to the
`present invention.
`0.025
`FIG. 6 illustrates an embodiment of a multi-band
`system employing six different services operating in different
`frequency channels with multiple DRUs according to the
`present invention.
`0026 FIG. 7 illustrates in block diagram form the interac
`tion between the DAU embedded software control module
`and the DRU embedded software control module.
`0027 FIG. 8 illustrates in block diagram form an embodi
`ment of a DAS according to an aspect of the invention, includ
`ing daisy-chained DAU's.
`
`DETAILED DESCRIPTION OF THE INVENTION
`0028. 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 per
`formance of the distributed wireless network. FIG. 1 illus
`trates an embodiment of the Distributed Antenna System 100
`in accordance with the present invention. The system
`employs a Digital Access Unit functionality 105 (hereinafter
`“DAU). The DAU 105 serves as an interface between asso
`ciated base stations (BTS) 110A-B and a plurality of digital
`remote units (DRU) 125A-n, although only four DRU's are
`shown in FIG. 1. In the present description, “DRU will be
`used interchangeably with Remote Radio Head Unit, or
`“RRU, because of the similarity of the functions discussed
`herein, although those skilled in the art will recognize that a
`DRU communicates with a DAU, whereas an RRU commu
`nicates with a base station. In addition, those skilled in the art
`will recognize that a DAU is monitored and controlled by a
`remote network operations center (“NOC), as indicated at
`bidirectional link 115 in FIG. 1. Such links are typically
`Ethernet connections or external modems, but can be any
`form of link suitable for remote monitoring and control. The
`NOC has the capability to remotely configure the DAU
`parameter settings which in turn configures the DRU’s
`parameter settings. The NOC can request information from
`the DAUs. The DAUs can subsequently request information
`from the DRUs. The information requested includes but is not
`limited to uplink power, downlink power, optical error rate,
`gain settings, active carriers, etc.
`0029. For the downlink (DL) path, RF input signals 120A
`through 120m are received at the DAU 105 from one or more
`base station units (BTS) indicated at 110A through 110p. The
`RF input signals are separately down-converted, digitized,
`and converted to baseband (using a Digital Down-Converter)
`by the DAU. Data streams are then I/O mapped and framed
`and specific parallel data streams are then independently seri
`alized and translated to optical signals using pluggable SFP
`modules, again by the DAU 105. The independently serial
`ized, parallel data streams are then delivered to different
`DRU’s 125A-125k, typically over optical fiber cable
`arranged, in at least some embodiments, in a ring configura
`tion indicated at connection pairs 140A-145A, or, in other
`embodiments, a daisy chain configuration. In addition, each
`DAU can support a plurality of rings with associated DRU's,
`
`where the additional rings are indicated by fiber optic pairs up
`through 140O-145o. It will be appreciated by those skilled in
`the art that the number of RF inputs, DAU’s and DRU’s and
`rings is limited only by network performance factors, such as
`delay. In addition, as discussed in connection with FIG. 4
`herein, the DAS can be further extended by using a ring or
`daisy-chain of DAU’s, each of which Supports an arrange
`ment of DRU’s and rings as shown in FIG. 1.
`0030. One function of the DAU 105 is to determine the
`direction in which downlinked channels are propagated
`around the ring. As just one example, the embodiment shown
`in FIG. 1 is configured to have downlink channels A, B, C and
`D propagate in a first direction, for example clockwise, and
`channels E, F, G, and H propagate in the counter direction,
`although it will be understood that the number of channels
`propagating in each direction need not be equal, nor adjacent,
`nor sequential. Likewise, the number of channels received at
`each DRU is assigned by the DAU and need not be equal,
`adjacent or sequential, but instead will typically be any con
`figuration that optimizes network utilization.
`0031
`Referring next to FIG. 2, an embodiment of an
`uplink (UL) path in accordance with the invention can be
`better appreciated. Channels received at the antenna associ
`ated with each DRU are converted into optical signals by each
`DRU 125A-125k. Optical signals received from the DRU’s
`are de-serialized and de-framed by the DAU 105, and are also
`up-converted digitally using a Digital Up-Converter imple
`mented within the DAU 105. Each data stream is then inde
`pendently converted to the analog domain and up-converted
`to the appropriate RF frequency band, still within the DAU
`105 in the illustrated implementation, although this function
`ality can be separate. The RF signals are then delivered to the
`appropriate one of a plurality of BTS 110A-110p. As with the
`arrangement shown in FIG. 1, the direction of propagation of
`each channel is controlled by the DAU, with some channels
`propagating in a clockwise direction and others in a counter
`clockwise direction. Also as discussed in connection with
`FIG. 1, while adjacent channels are shown as propagating in
`the same direction in FIG. 2, this is not required and any
`channel can be selected to propagate in either direction.
`0032 Referring again to FIG. 1, it will be appreciated by
`those skilled in the art that, in Some implementations of a
`DAS, more than one carrier can exist in each channel, and, as
`Such, a DRU may receive a channel comprising a signal
`containing two or more carriers, or a wireless operator may
`have more than one RF carrier per channel allocated to a
`single base station. This is referred to as a "composite signal'.
`The manner in which a composite downlink signal is man
`aged by the present invention can be better understood with
`reference to FIG.1. In such instances, the DAU will receive a
`composite downlink input signal 130 from, e.g., a first base
`station 110A belonging to one wireless operator, enters the
`DAU 105 at the RF input port 120A. Composite signal 130
`comprises carriers A-D. A second composite downlink input
`signal from e.g., a pth base station 110p belonging to the same
`wireless operator enters DAU1 at the DAU1 RF input port
`120m. Composite signal 135 comprises carriers E-H. The
`functionality of the DAU 105, and DRU’s 125A-125k, respec
`tively, are explained in detail in U.S. Provisional Application
`Ser. No. 61/374,593, entitled “Neutral Host Architecture for a
`Distributed Antenna System.” filed Aug. 17, 2010, incorpo
`rated herein by reference and attached hereto as Appendix B.
`0033. One optical output of DAU 105 is fed to DRU 125A,
`viabidirectional optical cable 140A. A second optical output
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`of DAU 105 is fed via bidirectional optical cable 145A to
`DRU3. Similarly, bidirectional optical cables 150, 155 and
`160 connect DRU’s 125A-n in a ring configuration, such that
`DRU 125A connects to DRU 125B via cable 150A, DRU
`125B connects to DRU 125m via cable 150B, and DRU 125k
`connects to DRU 125C, or the kth-1 DRU, via cable 150m.
`This connection facilitates networking of DAU 105, which
`means that all of Carriers A-Hare available within DAU 105
`to transport data to DRU’s 125A-k depending on software
`settings within the networked DAU system. Depending upon
`the embodiment, the software settings within DRU 125A are
`configured either manually or automatically, Such that carri
`ers A-Hare present in the downlink output signal 155A at the
`antenna port of DRU 125A. The presence of all eight carriers
`means that DRU 125A is potentially able to access the full
`capacity of both base stations feeding DAU 105. A possible
`application for DRU125A is a cafeteria in an enterprise build
`ing during the lunch hour where a large number of wireless
`Subscribers are gathered.
`0034) DRU 125B is fed by a second optical port of DRU
`125A viabidirectional optical cable 150A. The optical cable
`150A performs the function of daisy chaining DRU 125A
`with DRU125B. As with DRU 125A, the software settings
`within DRU 125B are configured either manually or auto
`matically such that Carriers A, C, D and F are present in
`downlink output signal 155B at the antenna port of DRU
`125B. The capacity of DRU 125B is setto a much lower value
`than DRU 125A by virtue of its specific channel settings as
`controlled by DAU 105. The individual Digital Remote Units
`have integrated frequency selective DUCs and DDCs with
`gain control for each carrier. The DAU's can remotely turn on
`and off the individual carriers via the gain control parameters.
`0035. In a similar manner as described previously for
`DRU 125A, the software settings within DRU 125C are con
`figured either manually or automatically such that Carriers B
`and F are present in downlink output signal 155C at the
`antenna port of DRU 125C. Compared to the downlink signal
`155B at the antenna port of DRU 125B, the capacity of DRU
`125C, which is also configured via its software settings, is
`much less than the capacity of DRU 125B. DRU 125m is fed
`by the optical cable 150m connected to the second optical port
`of the n'-1 DRU, shown for simplicity in FIG. 1 as DRU
`125C. The software settings within DRU 125n are configured
`either manually or automatically Such that carriers A, D, E
`and H are present in downlink output signal 155D at the
`antenna port of DRU 125m. Typically, the capacity of DRU
`125m is set to a much lower value than DRU 125A, however,
`the relative capacity settings of each of DRU’s 125A-n can be
`adjusted dynamically to meet the capacity needs within the
`coverage Zones determined by the physical positions of
`antennas connected to those DRU’s. As noted above, the ring
`connection is completed by interconnecting DRU 125B and
`DRU 125n through optical cable 150B. The ring configura
`tion insures that any optical cable breaks will not shut down
`the daisy chained network. The downlink and uplink signals
`will be rerouted around the cable break to the respective
`DRUS.
`0036. The present invention facilitates conversion and
`transport of several discrete relatively narrow RF bandwidths.
`This approach allows conversion of only those multiple spe
`cific relatively narrow bandwidths which carry useful or spe
`cific information. This approach also allows more efficient
`use of the available optical fiber transport bandwidth for
`neutral host applications, and allows transport of more indi
`
`vidual 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 together with U.S.
`Provisional Application Ser. No. 61/382,836, entitled
`“Remotely Reconfigurable Distributed Antenna System and
`Methods', filed Sep. 14, 2010, both assigned to the assignee
`of the present invention, and also referring to FIG. 1 of the
`instant patent application, Digital Up Converters located
`within the DRU can be dynamically reconfigured as the result
`of commands from the NOC to transport from the DAU input
`to any specific DRU 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 in FIG. 1 where only specific frequency bands or
`RF carriers appear at the output of a given DRU. More spe
`cifically, through commands received from the NOC, the
`FPGA's in the DAU and one or more of the associated DRU’s
`can be reprogrammed or reconfigured to convert and trans
`port only the desired narrow bandwidths.
`0037. A related capability of the present invention is that
`not only can the Digital Up Converters located within each
`DRU be configured to transport any specific narrow fre
`quency band from the DAU input to any specific DRU output,
`but also the Digital Up Converters within each DRU can be
`configured to transport any specific time slot or time slots of
`each carrier from the DAU input to any specific DRU output.
`The carriers and time slots are monitored by the DAU by
`filtering the signals and performing power detection of the
`individual time slots, which information can be conveyed to
`the NOC as desired. Then, as with the Digital Up Converters,
`the Field Programmable Gate Arrays (FPGA) in the DAU or
`DRU can be dynamically reconfigured by commands
`received from the NOC in a manner analogous to software
`programmability. The DAU detects which carriers and corre
`sponding time slots are active. This information is relayed to
`the individual DRUs via the management control and moni
`toring protocol software. This information is then used, as
`appropriate, by the DRUs for turning off and on individual
`carriers and their corresponding time slots.
`0038. Data transport between the Base Station and the
`subscribers is typically asymmetrical, whereby the downlink
`data rate is higher than the uplink rate. The ring network
`configuration of Daisy Chained DRUs can exploit this data
`rate asymmetry to maximize the data transport on the optical
`fibers 150A-150m.
`0039. The present invention balances the bidirectional
`data rate on the optical fibers so as to increase the maximum
`achievable data rate on the ring network of DRUs. The indi
`vidual downlink channels are transmitted in a unidirectional
`sense along the ring network. Referring to FIG. 1, downlink
`channels A, B, C, and Dare transmitted in a clockwise sense
`around the ring of DRU’s 125A-k. On the other hand, down
`link channels E, F, G and Hare transmitted in a counterclock
`wise sense around the ring of DRU’s. Referring to FIG. 2, the
`uplink channels J, K, L and M are transmitted in a counter
`clockwise sense whereas uplink channels N, O, P and Q are
`transmitted in a clockwise sense around the ring of DRUs. If
`the downlink and uplink data rates were the same, there would
`be no advantage in the transport mechanism. However, if the
`data transport is asymmetrical between the downlink and
`uplink then a significant advantage can be gained. For
`example, for a factor of two difference between the downlink
`and uplink data rates, a 4/3 factor increase in data transport
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`Feb. 16, 2012
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`can be achieved. The larger the asymmetry between the
`downlink and uplink data rates, the larger will be the increase
`in data transport using the unidirectional channel transport
`mechanism around the ring.
`0040. Referring again to FIG. 1, a further embodiment in
`accordance with another aspect of the present invention may
`be better understood. In the event that there is a significant
`change in asymmetry between the downlink and uplink data
`rates and/or if there is a change in channel complement at the
`BTS, the Management Control module discussed in connec
`tion with FIG. 7 herein which is typically comprised within
`each DAU is able to automatically and adaptively re-allocate
`data transport resources on the clockwise direction of the ring
`and on the counter-clockwise direction of the ring to maxi
`mize the overall transport c