(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2010/0296816 A1
`Larsen
`(43) Pub. Date:
`Nov. 25, 2010
`
`US 2010O296816A1
`
`(54) FLEXIBLE DISTRIBUTEDANTENNA
`SYSTEM
`
`Tormod Larsen, Geneva, IL (US)
`(75) Inventor:
`Correspondence Address:
`MCDONNELL BOEHNEN HULBERT & BERG-
`HOFF LLP
`300 S. WACKER DRIVE, 32ND FLOOR
`CHICAGO, IL 60606 (US)
`
`(73) Assignee:
`
`(21) Appl. No.:
`
`EXTENET SYSTEMS, INC.,
`Lisle, IL (US)
`s
`12/781,881
`
`(22) Filed:
`
`May 18, 2010
`Related U.S. Application Data
`(60) Provisional application No. 61/180,462, filed on May
`22, 2009.
`
`Publication Classification
`
`(51) Int. Cl.
`(2006.01)
`H04B IO/00
`(52) U.S. Cl. ........................................................ 398/116
`(57)
`ABSTRACT
`An apparatus and method for implementing a flexible distrib
`uted antenna system (DAS) head end are disclosed. A flexible
`DAS head end includes an RF conditioning module config
`ured to be connected to one or more base station transceiver
`(BTS) devices and one or more low-power RF modules that
`are also part of the flexible DAS head end. In an example
`embodiment, the flexible DAS head end receives high-power
`digital-RF passband transmissions from its connections to the
`one or more BTS devices, and low-power digital-RF pass
`band signals from the one or more low-power RF modules.
`The low-power RF modules, in turn, can receive input base
`band signals from one or more baseband units (BBUs) in a
`wireless network, and then convert the input signals to the lo
`low-power digital-RF passband signals. The RF conditioning
`module constructs one or more Superposition RF signals from
`the passband signals, and routes and transmits them to an
`array of antenna nodes.
`
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`Patent Application Publication
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`Patent Application Publication
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`Nov. 25, 2010 Sheet 2 of 8
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`Patent Application Publication
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`Patent Application Publication
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`Patent Application Publication
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`Patent Application Publication
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`Patent Application Publication
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`Nov. 25, 2010 Sheet 8 of 8
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`US 2010/029681.6 A1
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`START
`
`
`
`AT THE RF CONDITIONING MODULE, RECEIVE ARESPECTIVE
`INPUT DIGITAL RF PHYSICAL SIGNAL WIAEACH OF ONE OR
`MORE OF A PLURALITY OF FIRST PHYSICAL INTERFACES
`
`802
`
`AT THE RF CONDITIONING MODULE, SPLITEACH RECEIVED
`RESPECTIVE INPUT DIGITAL RF PHYSICAL SIGNAL INTO A
`RESPECTIVE NUMBER OF DUPLICATE SIGNALS
`
`804
`
`AT THE RF CONDITIONING MODULE, COMBINE PARTICULAR
`DUPLICATE SIGNALS SELECTED FROM AMONG EACH OF THE
`RESPECTIVE NUMBER OF DUPLICATE SIGNALS INTO ONE OR
`MORE SUPERPOSITION RF SIGNALS
`
`806
`
`AT THE RF CONDITIONING MODULE, ROUTE ANDTRANSMIT
`THE ONE OR MORE SUPERPOSITION RF SIGNALS TO AN
`ARRAY OF REMOTE ANTENNANODES
`
`808
`
`AT THE LOW-POWER RF MODULES, RECEIVE RESPECTIVE
`BASEBAND DIGITAL OPTICAL SIGNALS WIA RESPECTIVE
`SECOND PHYSICAL INTERFACES
`
`810
`
`AT THE LOW-POWER RF MODULES, MODULATE THE RECEIVED
`RESPECTIVE BASEBAND DIGITAL OPTICAL SIGNALS TO
`RESPECTIVE RF PASSBAND SIGNALS
`
`812
`
`AT THE LOW-POWER RF MODULES, SEND THE RESPECTIVE RF
`PASSBAND SIGNALS TO THE RF CONDITIONING MODULE WIA
`COMMUNICATIVE CONNECTIONS TO THE PLURALITY OF FIRST
`PHYSICAL INTERFACES
`
`814
`
`FIG. 8
`
`

`

`US 2010/029681.6 A1
`
`Nov. 25, 2010
`
`FLEXBLE DISTRIBUTED ANTENNA
`SYSTEM
`
`RELATED APPLICATION
`0001. This Application claims the benefit of priority to
`U.S. Provisional Application 61/180,462 filed May 22, 2009,
`which is hereby incorporated by reference herein.
`
`BACKGROUND
`0002. A wireless communication system typically pro
`vides one or more forms of wireless access to mobile access
`devices, enabling them to engage in Voice and data commu
`nications with other devices—both wired and wireless—op
`erating in or connected to the system, and to partake invarious
`other communication services provided or Supported by the
`system. The communication path from a mobile access
`device. Such as a cellular telephone, personal digital assistant
`(PDA), or an appropriately equipped portable computer, for
`instance, to one or more other communication endpoints gen
`erally traverses a radio frequency (RF) air interface to a base
`transceiver station (BTS) or other form of access point, and on
`into a core transport network via a base station controller
`(BSC) connected to a mobile switching center (MSC) or to a
`packet data serving node (PDSN). The MSC supports prima
`rily circuit Voice communications, providing interconnectiv
`ity with other MSCs and PSTN switches, for example. The
`PDSN Supports packet data communications, providing inter
`connectivity with packet-data networks, such as the Internet,
`via other packet-data Switches and routers.
`0003. In a cellular wireless system, the BTS, BSC, MSC,
`and PDSN, among possibly other components, comprise the
`wireless access infrastructure, also sometimes referred to as
`the radio access network (RAN). A RAN is usually arranged
`according to a hierarchical architecture, with a distribution of
`multiple BTSS that provide areas of coverage (e.g., cells)
`within a geographic region, under the control of a smaller
`number of BSCs, which in turn are controlled by one or a few
`regional (e.g., metropolitan area) MSCs. As a mobile device
`moves about within the wireless system, it may hand off from
`one cell (or other form of coverage area) to another. Handoff
`is usually triggered by the RAN as it monitors the operating
`conditions of the mobile device by way of one or more signal
`power levels reported by the device to the RAN.
`0004 As the demand for wireless services has grown, and
`the variety of physical environments in which wireless access
`is provided becomes more diverse, the need for new topolo
`gies and technologies for coverage has become increasingly
`important. At the same time, alternative methods of wireless
`access, including WiFi and WiMax, are becoming more ubiq
`uitous, particularly in metropolitan areas. Consequently, tra
`ditional cellular service providers are looking for ways to
`integrate different types of wireless access infrastructures
`within their core transport and services networks. In addition,
`as wireless access infrastructures of different service provid
`ers tend to overlap more and more within Smaller spaces, the
`ability to share common infrastructure offers cost and opera
`tional benefits to network owners and operators.
`
`SUMMARY
`0005. A particular architectural challenge facing the wire
`less access infrastructure is to provide adequate coverage in
`locations where RF signals do not reach or penetrate, and on
`a relatively fine geographic scale, using equipment that is
`
`physically unobtrusive. One solution to emerge is a distrib
`uted antenna system (DAS), which subdivides and distributes
`the radio transmitter/receiver functionality of the BTS among
`a number of Smaller, lower-power antenna nodes. The nodes
`can be deployed so as to provide coverage within underserved
`structures (e.g., in buildings) or over terrain where deploy
`ment of traditional cell towers is impractical or not permitted.
`In what is referred to herein as the 'standard DAS architec
`ture' (or just DAS for short), the radio and antenna subsystem
`of a “traditional BTS is replaced with a DAS“headend' unit
`that splits the input RF signal into separate signal portions and
`routes them as digital-optical signals to Small, remote antenna
`nodes via fiber optic transmission links. Each node then trans
`mits only its RF signal portion. The DAS head end also
`receives signal portions from the remote nodes, and combines
`them for relay back into the network. The DAS head end
`receives its input from one or more traditional BTSs. More
`specifically, the traditional BTS includes an RF modulation
`subsystem (RF module) that converts the input baseband
`signals from the network into passband signals on RF carri
`ers. The output of the RF module is then connected to the
`input of the DAS via a high-power (e.g., 20W), digital link. In
`the reverse direction, RF signals received via the digital link
`are down-converted in the BTS to baseband for transmission
`into the network. The interface between the RF module and
`the DAS head end is same as that between the RF modulation
`Subsystem and the radio/antenna Subsystem of a traditional
`BTS. As such, multiple BTSs from multiple service providers
`can be connected to single DAS head end, thus allowing them
`to share a common access infrastructure.
`0006. In an alternative DAS architecture, encoded base
`band signals are routed from a baseband unit (BBU) to remote
`“radio heads” where the signals are modulated to appropriate
`RF carriers for radio transmission to mobile devices. The
`baseband links between the BBU and the remote radio heads
`are low-power (e.g., a few mW), fiber-optic lines that support
`communications according to one or another open interface
`protocols developed for decentralizing BTS operation. Each
`remote radio head includes a remote digital-to-RF module
`that functions analogously to the RF module of the traditional
`BTS. For the purposes of the discussion herein, the alternative
`DAS architecture shall be referred to as the “remote radio
`head” (RRH) architecture.
`0007 Each form of DAS architecture has advantages and
`disadvantages. Consequently, service providers must weigh
`tradeoffs when evaluating decisions to deploy one or the
`other. The RRH architecture largely eliminates the need for
`costly, high-power RF conversion in the traditional BTS by
`distributing encoded baseband signals directly to the remote
`radio heads. Moreover, the network input to the BBU is not
`restricted only to circuit-cellular data, but admits other forms
`of network traffic and protocols, including WiFi, WLAN, and
`other types of native packet data transport. However, each
`baseband link from the BBU to a particular remote radio head
`can generally support only one transport technology at a time
`(e.g., CDMA, GSM, WiFi, etc.), and each node can generally
`modulate a given incoming link to just one RF carrier for any
`one configuration of the given link. In addition, each remote
`radiohead incorporates a dedicated remote RF module. Thus,
`even though each RF module is relatively inexpensive com
`pared with that of a traditional BTS, the number of RRH RF
`modules in any given deployment scales directly with the
`number of remote nodes. Finally, a single BBU supports one
`
`

`

`US 2010/029681.6 A1
`
`Nov. 25, 2010
`
`service provider at a time, since each baseband link can be
`configured for only one carrier frequency and one transport
`technology at a time.
`0008. The DAS architecture has its own tradeoffs. The
`head end of the standard DAS architecture includes an RF
`conditioning module that can split and distribute multiple
`input RF signals from one or more networks or service pro
`viders’ traditional BTSs, and then route the separate signals to
`the different nodes according to coverage topologies (e.g.,
`cells and/or sectors) specified by the service providers. Thus
`the DAS head end supports diverse deployment topologies of
`remote nodes. In addition, since each RF input is the output of
`the RF module of a source BTS, the DAS head end and remote
`nodes can accommodate multiple carriers and cellular trans
`port technologies in concurrent transmissions, thereby
`achieving concurrent sharing of radio resources. The RF con
`ditioning module can also load balance the power delivered
`among the remote nodes based on the traffic load at each
`node. However, the standard DAS architecture still requires
`each source BTS to include an expensive RF module, and to
`support a high-power digital interface to the DAS head end.
`Further, the physical distance of this interface link is limited,
`unless some form of repeater is employed. In addition, the
`transport technologies Supported are limited to those of tra
`ditional BTSS, making integration with native packet-based
`transport more difficult.
`0009. The distinct approaches offered by the two DAS
`architectures present service providers and network operators
`with a set of “either-or of solutions, none of which may fully
`and simultaneously address challenges Such as diversity of
`transport technologies, common access infrastructure, and
`Versatility of coverage configurations, among others.
`0010. A more versatile DAS architecture is needed to
`address these and other challenges of configuring and deploy
`ing wireless access infrastructures. Accordingly, various
`embodiments of the present invention provide a flexible DAS
`that can: Support a wide and expandable array of transport
`technologies from the network side; or Support concurrent
`processing, transmission, and reception of communications
`according to Some, or any or all of the relevant technologies;
`or Support simultaneous RF transmission and reception on
`different RF carriers; or support versatile and diverse cover
`age topologies among a distribution of antenna nodes; or
`incorporate intelligent routing of signals to antenna nodes,
`and Support load balancing among the antenna nodes; or
`enable different service providers to share a common wireless
`access infrastructure; or some combination of Some or all of
`the forgoing.
`0011
`Hence, in one respect, embodiments of the present
`system provide an apparatus comprising: a radio frequency
`(RF) conditioning module having a plurality of first physical
`interfaces and being configured to: receive a respective input
`digital RF physical signal via each of one or more of the
`plurality of first physical interfaces, split each received
`respective input digital RF physical signal into a respective
`number of duplicate signals, combine particular duplicate
`signals selected from among each of the respective number of
`duplicate signals into one or more Superposition RF signals,
`and route and transmit the one or more Superposition RF
`signals to an array of remote antenna nodes to which the
`apparatus is configured to be communicatively coupled; and
`one or more low-power RF modules each having a commu
`nicative connection to one of the plurality of first physical
`interfaces, and each configured to: receive a respective base
`
`band digital optical signal via a respective second physical
`interface, modulate the received respective baseband digital
`optical signal to a respective RF passband signal, and send the
`respective RF passband signal to the RF conditioning module
`via the communicative connection to the one of the plurality
`of first physical interfaces as one of the respective input
`digital RF physical signals.
`0012. In another respect, embodiments of the present sys
`tem provide an apparatus comprising: a radio frequency (RF)
`conditioning module having a plurality of first physical inter
`faces; one or more low-power RF modules each having a
`communicative connection to one of the plurality of first
`physical interfaces; a processor, and machine logic execut
`able by the processor to cause the apparatus to: receive a
`respective input digital RF physical signal via each of one or
`more of the plurality of first physical interfaces of the RF
`conditioning module, at the RF conditioning module, split
`each received respective input digital RF physical signal into
`a respective number of duplicate signals, at the RF condition
`ing module, combine particular duplicate signals selected
`from among each of the respective number of duplicate sig
`nals into one or more Superposition RF signals, at the RF
`conditioning module, route and transmit the one or more
`Superposition RF signals to an array of remote antenna nodes
`to which the apparatus is configured to be communicatively
`coupled, at a given one of the one or more low-power RF
`modules, receive a baseband digital optical signal via a
`respective second physical interface, at the given one of the
`one or more low-power RF modules, modulate the received
`respective baseband digital optical signal to an RF passband
`signal, and at the given one of the one or more low-power RF
`modules, send the RF passband signal to the RF conditioning
`module via the communicative connection to the one of the
`plurality of first physical interfaces as one of the respective
`input digital RF physical signals.
`0013. In yet another respect, embodiments of the present
`system provide, in an apparatus comprising (i) a radio fre
`quency (RF) conditioning module having a plurality of first
`physical interfaces and (ii) one or more low-power RF mod
`ules each having a communicative connection to one of the
`plurality of first physical interfaces, a method comprising: at
`the RF conditioning module, receiving a respective input
`digital RF physical signal via each of one or more of the
`plurality of first physical interfaces; at the RF conditioning
`module, splitting each received respective input digital RF
`physical signal into a respective number of duplicate signals;
`at the RF conditioning module, combining particular dupli
`cate signals selected from among each of the respective num
`ber of duplicate signals into one or more Superposition RF
`signals; at the RF conditioning module, routing and transmit
`ting the one or more Superposition RF signals to an array of
`remote antenna nodes to which the apparatus is communica
`tively coupled; at a given one or more of the one or more
`low-power RF modules, receiving a respective baseband digi
`tal optical signal via a respective second physical interface; at
`the given one or more of the one or more low-power RF
`modules, modulating the received respective baseband digital
`optical signal to a respective RF passband signal; and at the
`given one or more of the one or more low-power RF modules,
`sending the respective RF passband signal to the RF condi
`tioning module via the communicative connection to the one
`of the plurality of first physical interfaces as one of the respec
`tive input digital RF physical signals.
`
`

`

`US 2010/029681.6 A1
`
`Nov. 25, 2010
`
`0014. These as well as other aspects, advantages, and
`alternatives will become apparent to those of ordinary skill in
`the art by reading the following detailed description, with
`reference where appropriate to the accompanying drawings.
`Further, it should be understood that this summary and other
`descriptions and figures provided herein are intended to illus
`trate the invention by way of example only and, as such, that
`numerous variations are possible. For instance, structural ele
`ments and process steps can be rearranged, combined, dis
`tributed, eliminated, or otherwise changed, while remaining
`within the scope of the invention as claimed.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0015 FIG. 1 is an example of a wireless communication
`system in which embodiments of a flexible DAS head end
`could be deployed.
`0016 FIG. 2 illustrates an example deployment of a stan
`dard DAS architecture.
`0017 FIG. 3 is an example block diagram of a standard
`DAS head end.
`0018 FIG. 4 illustrates an example deployment of an RRH
`architecture.
`0019 FIG. 5 is an example block diagram of a BBU in an
`RRH architecture.
`0020 FIG. 6 is an example block diagram of a flexible
`DAS head end.
`0021
`FIG. 7 is an example block diagram of a flexible
`DAS head end that includes a smart antenna interface.
`0022 FIG. 8 is a flowchart illustrating a method of opera
`tion of a flexible DAS head end.
`
`DETAILED DESCRIPTION
`0023 The present invention will be described by way of
`example with reference to wireless access technologies
`including Code Division Multiple Access (CDMA), UMTS,
`GSM, WiFi, and WiMax, although the invention is not limited
`to these technologies. CDMA and GSM are typically
`deployed in cellular wireless communication systems, and
`generally encompass a number of related technologies that
`collectively and/or individually support both circuit-cellular
`communications, including Voice and circuit-based packet
`communications, and native packet-data communications.
`For the purposes of the discussion herein, a “CDMA family of
`protocols' shall be taken to apply to all such technologies.
`Examples of protocols in the family include, without limita
`tion and of one or more versions, IS-95, IS-2000, IS-856, and
`GSM, among others. Native packet-data wireless protocols
`and technologies, include, without limitation WiFi, WiMax,
`WLAN, and IEEE 802.11, some or all of which may be
`interrelated. The term "wireless Ethernet' is also sometimes
`used to describe one or another of these protocols or aspects
`of these protocols.
`0024 FIG. 1 shows an example wireless communication
`system owned and/or operated by a service provider in which
`an example embodiment of a flexible DAS could be deployed.
`A wireless access device 102 is communicatively connected
`to the system by way of an RF air interface 103 to a BTS 106,
`which in turn is connected to a BSC 108. The RF air interface
`103 is defined and implemented according to one or more of
`a CDMA family of protocols. The BSC is connected to an
`MSC 110 for circuit-cellular communications, and via a
`packet control function (PCF) 114 to a PDSN 116 for packet
`data communications. The MSC is connected to a PSTN 112,
`
`thus providing a communication path to landline circuit net
`works. The connection to the PSTN 112 is also intended to
`represent trunk connections between the MSC 110 and other
`circuit Switched, including (without limitation) local
`exchange Switches, interexchange Switches for long-distance
`services and interconnections with other carriers’ networks,
`and other MSCs both in the carrier's network and other car
`riers’ networks.
`0025. As indicated, the PDSN 116 is connected to a
`packet-switched network 118, which could be the Internet or
`a core packet transport network that is part of the wireless
`communication system. A computer 120 is also shown being
`connected to the packet network 118, and the wireless device
`102 could engage in communications with the computer 120
`via a path such as the one just described. It will be appreciated
`that, although not shown, other communication devices, as
`well as communication and application servers could be con
`nected in one way or another to the network 118. In addition,
`the network 118 may comprise other equipment including,
`without limitation, routers, Switches, transcoding gateways,
`security gateways and firewalls, and other components typi
`cal of a communication and transport network.
`0026. Also shown in FIG. 1 is a second wireless access
`device 104, which is connected to the wireless communica
`tion system via the air interface 105 to a WiFi access point
`122. The access point is in turn connected to a router 124.
`which then connects to network 118. Although not shown for
`the sake of brevity, it will be appreciated that this connection
`could include other packet routing/processing elements. The
`access device 104 could also engage in communications with
`one or more communication endpoints via the physical path
`shown in the figure. The detailed protocols and methods for
`establishing communications between either of the devices
`102 or 104 and other devices and communication endpoints in
`the network are well-known, and not discussed further herein.
`0027. It should be understood that the depiction of just one
`of each network element in FIG. 1 is illustrative, and there
`could be more than one of any of them, as well as other types
`of elements not shown. The particular arrangement shown in
`FIG. 1 should not be viewed as limiting with respect to the
`present invention or embodiments thereof. Further, the net
`work components that make up a wireless communication
`system Such as the system 100 are typically implemented as a
`combination of one or more integrated and/or distributed
`platforms, each comprising one or more computer proces
`sors, one or more forms of computer-readable storage (e.g.,
`disks drives, random access memory, etc.), one or more com
`munication interfaces for interconnection between elements
`and the network, and operable to transmit and receive the
`communications and messages described herein, and one or
`more computer Software programs and related data (e.g.,
`machine-language instructions and program and user data)
`stored in the one or more forms of computer-readable storage
`and executable by the one or more computer processors to
`carry out the functions, steps, and procedures of the various
`embodiments of the present invention described herein. Simi
`larly, a communication device, such as the example access
`devices 102 and 104, typically comprises a user-interface, I/O
`components, a communication interface, a tone detector, a
`processing unit, and data storage, all of which may be coupled
`together by a system bus or other mechanism.
`
`

`

`US 2010/029681.6 A1
`
`Nov. 25, 2010
`
`1. Distributed Antenna System Architectures
`0028 a. Standard DAS Architecture
`0029. A network 200 in FIG. 2 illustrates a high-level view
`of an implementation of a distributed antenna system accord
`ing to an example configuration of a standard architecture. By
`way of example, the DAS implementation in this illustration
`is shown as providing a common access infrastructure for two
`service providers (labeled “Service Provider 1 and “Service
`Provider 2'). As shown, in the network of Service Provider 1,
`MSC 202, is connected to a BSC 204, which in turn is con
`nected to a BTS 206 and BTS 210. The BTS 206 is a tradi
`tional BTS, having a high-power digital radio connection 207
`to an antenna tower 208. In practice, a digital connection 207
`carries a signal with a power of roughly 20 watts (W), and is
`commonly implemented as a coaxial cable between the BTS
`and an RF transmission component that transmit the RF sig
`nal via antenna elements at or near the top of the tower. The
`broadcast signal generally has a power level similar to that of
`the input (i.e., roughly 20W).
`0030 The coverage area provided by the BTS (including
`the transmitting antennas) is typically a cellor cell sectors. By
`way of example, the BTS 206 (in conjunction with the
`antenna tower 208) is sectorized, such that it provides three
`sectors (labeled “Sector 1. “Sector 2,” and “Sector 3’). An
`access device then communicates on a connection via one or
`more of the cells or sectors of a BTS in accordance with one
`or more of a family of CDMA protocols. For instance, under
`IS-2000, each cell or sector will be identified according to a
`locally unique identifier based on a bit offset within a 16-bit
`pseudo-random number (PN). An access device operating
`according to IS-2000 receives essentially the same signal
`from up to six sectors concurrently, each sector being identi
`fied and encoding transmissions according its so-called PN
`offset. The details of such communications are well-known in
`the art and not discussed further here.
`0031 Signals received from access devices connected via
`the antenna tower 208 are transmitted back to the BTS 206 via
`the connection 207.
`0032 Unlike the BTS 206, which supplies the antenna
`tower 208, the BTS 210 is connected instead to a DAS head
`end 222 via a digital RF connection 211. The digital connec
`tion 211 is the same type of signal and physical interface as
`the connection 207. However, rather than supplying a single
`transmission tower, the DAS head end 222 splits and distrib
`utes the input signal from the BTS among several Smaller and
`remote antenna nodes 224-1, 224-2, 224-3,..., 224-N, where
`N is a positive integer. As describe in more detail below, the
`connections from the DAS head end 222 to each of the remote
`nodes 224-1, 224-2, 224-3, . . . , 224-N are made via low
`power digital-optical links 221-1, 221-2, 221-3, ..., 221-N,
`respectively. Hatch marks interrupting each of the links 221
`are meant to represent the remoteness of each node's location
`with respect to the DAS head end. The remote nodes could be
`distributed throughout one or more buildings, or across a
`residential area or Small down-town locale or village where a
`larger antenna tower is impractical and/or impermissible
`according local Zoning ordinances, for instance.
`0033. The combination of signals then transmitted from
`the remote nodes 224-1, 224-2, 224-3, ..., 224-N provides
`the same signals that would be transmitted from one or more
`cells or sectors if they were connected to the BTS 210, but
`spread over a region according to the topological arrangement
`of the nodes and the splitting and routing of the input signals
`by the DAS head end (this is discussed further below). Signals
`
`received from access devices connected via one or more of the
`remote antenna nodes are received at the DAS head end,
`combined, then transmitted back to the BTS 210 via the
`connection 211, in the same way as in the traditional BTS
`(e.g., transmissions from the RF module 208 to the BTS 206).
`0034 FIG. 2 also illustrates a similar network configura
`tion for Service Provider 2. In this case, a MSC 212 is con
`nected to a BSC 214, which in turn is connected to a BTS 216
`and a BTS 220. Similarly to the BTS 206, a traditional BTS
`216 is connected to a radio transmission tower 218 via a
`high-power digital-RF connection 217. Note that for both
`traditional BTSs, the BTS units (206 and 216) are typically
`collocated with their respective RF transmission towers. As
`shown, the BTS 220 connects to a DAS head end 222 via a
`high-power digital radio connection 213, which again is the
`same type of connection as the connections 207, 211, and
`217. Because the interface between the BTS and DAS head is
`the same for both the BTS 210 of Service Provider 1 and the
`BTS 220 of Service Provider 2, both service providers can
`connect to the common DAS head end and thereby share the
`same remote antenna node access infrastructure.
`0035. While the connections 211 and 213 are of the same
`type, each carries a signal (or signals) that is (or are) specific
`to the particular service provider. For example, both service
`providers could be operating according to IS-2000, but each
`using a different RF carrier frequency. Alternatively or addi
`tionally, one carrier could be operating according to CDMA
`and the other according to GSM. Other combinations oftech
`nologies and RF carriers could be used. In addition, each
`carrier could have a different configuration of cell or sector
`identifiers. For instance, the BTS 210 could be configured for
`three sectors, while the BTS 220 could be configured for a
`single cell. Any similarities or differences between the two
`systems are incorporated into their respective signals prior to
`being modulated onto their respective carriers by their respec
`tive BTSs (210 and 220 in this example). The DAS head end
`just splits and routes the respective signals to the remote
`antenna nodes, which then transmit the various carrier signals
`concurrently. Thus, the output of the antenna nodes poten
`tially comprises a mix of CDMA technologies, RF carrier
`frequencies, and coverage area (e.g., cell or sector) configu
`ration.
`0036 FIG. 3 shows a block diagram of the example con
`figuration of the standard DAS architecture that depicts addi
`tional details, in particular of the DAS head end. It will be
`appreciated, however, that FIG. 3 is nonetheless still a sim
`plified rendering of what an actual deployment would look
`like. In this figure, certain network elements have been omit
`ted for the sake of brevity, and other are represented in an
`abbreviated form. As shown, a network 302 of the wireless
`Service Provider 1 is connected to a BTS 308 via an MSC 304
`and a BSC 306. The BTS comprises an encoder 310 con
`nected to the BSC, and also connected to an RF module 312
`via a link 311. Input from the BSC comprises baseband sig
`nals from the network delivered on a circui