(12) United States Patent
`Stratford et al.
`
`I lllll llllllll Ill lllll lllll lllll lllll lllll 111111111111111111111111111111111
`US006785558Bl
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6, 785,558 Bl
`Aug. 31, 2004
`
`(54) SYSTEM AND METHOD FOR
`DISTRIBUTING WIRELESS
`COMMUNICATION SIGNALS OVER
`METROPOLITAN TELECOMMUNICATION
`NETWORKS
`
`(75)
`
`Inventors: Scott B. Stratford, Santa Clara, CA
`(US); Simon P. S. Yeung, Cupertino,
`CA (US); Lance K. Uyehara, San Jose,
`CA (US); Robin Y. K. Young, San
`Jose, CA (US)
`
`(73) Assignee: LGC Wireless, Inc., San Jose, CA (US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 5 days.
`
`(21) Appl. No.: 10/313,900
`
`(22) Filed:
`
`Dec. 6, 2002
`
`Int. Cl.7 .................................................. H04Q 7/20
`(51)
`(52) U.S. Cl. .................... 455/561; 455/562.1; 455/560;
`455/522; 455/69
`(58) Field of Search ................................. 455/561, 560,
`455/562.1, 522, 69; 370/328, 329, 338
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,627,879 A
`5,852,651 A
`6,023,625 A
`6,112,086 A
`
`5/1997 Russell et al. ................ 379/59
`12/1998 Fischer et al. ............. 379/56.2
`2/2000 Myers, Jr. ................... 455/503
`8/2000 Wala .......................... 455/434
`
`6,374,124 Bl * 4/2002 Slabinski ................. 455/562.1
`6,522,641 Bl * 2/2003 Siu et al. .................... 370/338
`6,674,966 Bl * 1/2004 Koonen ... ... ... ... .. ... ... ... 398/70
`2002/0055371 Al * 5/2002 Arnon et al.
`............... 455/562
`2002/0187809 Al * 12/2002 Mani et al. ................. 455/561
`2003/0040337 Al * 2/2003 Ylitalo ....................... 455/562
`2003/0114103 Al * 6/2003 Dinkel et al. ................. 455/17
`2003/0162539 Al * 8/2003 Fiut et al. ................... 455/424
`* cited by examiner
`
`Primary Examiner-Edward F. Urban
`Assistant Examiner-Huy Phan
`(74) Attorney, Agent,
`or Firm-Lumen
`Property Services, Inc
`
`(57)
`
`ABSTRACT
`
`Intellectual
`
`A method for transporting wireless communication signals
`between a base station hotel and remote cell sites with
`separately digitized RF carrier signals is provided. Sepa(cid:173)
`rately digitized carriers are transmitted over a digital net(cid:173)
`work between the hotel and the remote sites, remaining in
`digital format until reaching terminal antenna units. At the
`antenna units, downlink digital signals are converted to
`analog RF signals and transmitted, while uplink analog
`signals are received and converted to digital signals. A
`corresponding system comprising a base station hotel, at
`least one remote site, and a digital data network connecting
`the hotel to the remote site is provided. The hotel includes
`a plurality of base stations and a digital hub for interfacing
`the hotel to the network. The remote site includes a set of
`antenna units connected via a local data link to a network
`access node for interfacing to the network.
`
`19 Claims, 11 Drawing Sheets
`
`1- - - - - - - - - - - - - - - - - - - - - - - - - - ,
`
`I
`I
`
`I
`I
`
`I
`I
`
`I
`I
`
`'
`'
`i Remote Site 330 !
`- - ,
`'
`~----------- ------ ---- ---- _:
`:---------------------- -- ~ -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_~ -:
`i Remote Site
`i Antenna
`i i
`i
`i
`ii
`330
`
`320
`
`Network
`---- -- ---- ------- --- ---------------- -- -- ----.
`BTS Hotel ------DigitaTH~b----. i
`300
`1l.Q
`'
`
`BTS
`
`BTS
`
`BTS
`
`DIA
`AID Network
`TX/ Interface
`RX
`
`' ' ' ' '
`
`•- ---- ---- -- ------- -- -- --- -
`
`'
`'
`'
`!
`'
`:
`'
`'
`'
`'
`J Network 360 '
`Access
`Node
`l1Q
`
`I
`l
`l
`
`I
`I
`I
`
`I
`I
`I
`
`I
`I
`I
`
`' '
`' '
`'
`'
`'
`1------------------------..I
`'
`:-------------------------:
`
`'
`'
`
`l:
`
`_______________________ ]
`-1\;;t"~;;~~------------i
`i
`Unit lli
`i
`DIA TX/RX
`:
`I ND
`: _____ ------- -- -- ----- - __ .!
`.- --- -- -- ------------- -- -- -,
`'
`'
`; Remote Site 330 !
`- - ,
`'
`t_ -- --- -- -- ------- ---- _____ :
`
`Page 1
`
`T-Mobile Ex. 1030
`
`

`

`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 1 of 11
`
`US 6, 785,558 Bl
`
`Network
`
`100
`r ______ c:_ ___________ ,
`
`...,..___~: Remote Site :
`r--~:::::::::::::::::::~ _____________ c:__!_Q~--
`
`I
`I
`
`I
`
`I
`I
`
`I
`
`Remote Site
`
`FIG. 1
`
`BTS
`
`---------------------------------------------J
`100
`·-------..!: __________ ,
`
`I
`I
`I
`I
`
`I
`I
`
`I
`I
`
`--~: Remote Site :
`
`I
`I
`, ___________________ J
`I
`I
`
`Page 2
`
`T-Mobile Ex. 1030
`
`

`

`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 2of11
`
`US 6, 785,558 Bl
`
`220
`210
`_______________________ ..!: ____________________ ,
`i
`
`Network
`
`BTS Hotel
`240
`BTS
`
`BTS
`
`BTS
`
`250
`
`260
`
`DIA
`AID Network
`Interface
`
`TX/
`RX
`
`:
`:
`:
`' ' I
`'
`-------------------------------------------J
`
`200
`________ ;: _________ _
`
`I
`I
`
`: Remote Site
`'
`:===== = = = = = = === = ====--- _.c_ ~QQ. _ -----------------
`' ' ! Remote Site
`
`I
`I
`I
`
`Network
`Interface
`
`I
`
`I
`I
`I
`
`I
`I
`
`I :
`I :
`
`I
`I
`I
`I
`
`·---
`
`FIG. 2
`
`____________ c_?_~Q
`
`I
`
`: Remote Site
`I '-------------------
`
`Page 3
`
`T-Mobile Ex. 1030
`
`

`

`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 3of11
`
`US 6, 785,558 Bl
`
`Network
`
`1--------------------------
`1
`I
`: Remote Site 330
`I t _________________________ _
`
`Remote Site
`330
`
`BTS
`
`BTS
`
`BTS
`
`DIA
`AID Network
`TX/ Interface
`RX
`
`Network
`Access
`Node
`340
`
`360
`
`:--~t~~~------------:
`
`J Unit 350
`
`I
`
`-
`
`i
`
`I
`
`FIG. 3
`
`I
`I
`l------------------------~
`
`.--------------------------
`' I
`: Remote Site 330
`
`I
`I
`~-------------------------
`
`-
`
`Page 4
`
`T-Mobile Ex. 1030
`
`

`

`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 4 of 11
`
`US 6,785,558 Bl
`
`I
`
`I
`
`-
`
`I
`
`I
`
`-
`
`I
`
`I
`
`-
`
`I
`
`I
`
`-
`
`I
`
`I
`
`Wideband RF Signal 400
`1---------------------1---------------------1---------------------1---------------------,
`i Carrier Signal i Carrier Signal i Carrier Signal ! Carrier Signal i
`:
`410
`410
`410
`410
`:
`I
`I
`I
`L---------------------L---------------------L---------------------L---------------------1
`Wideband
`AID
`
`, '
`Digitized
`Wideband RF Signal
`1---------------------,---------------------1---------------------1---------------------,
`i Carrier Signal i Carrier Signal i Carrier Signal i Carrier Signal i
`:
`430
`430
`430
`430
`:
`I
`I
`I
`'---------------------L---------------------L---------------------1---------------------1
`FIG. 4
`
`I
`
`1
`
`-
`
`I
`
`I
`
`-
`
`I
`
`I
`
`-
`
`I
`
`I
`
`-
`
`I
`
`I
`
`I
`
`I
`
`-
`
`I
`
`I
`
`-
`
`I
`
`I
`
`I
`
`I
`
`-
`
`I
`
`I
`
`-
`
`Wideband RF Signal 400
`1---------------------,---------------------1---------------------1---------------------,
`i Carrier Signal ! Carrier Signal i Carrier Signal ! Carrier Signal i
`:
`410
`410
`410
`410
`:
`I
`I
`I
`'---------- ----------'---------- ----------1---------- ----------L---------- ----------1
`Narrow(cid:173)
`Narrow(cid:173)
`Narrow(cid:173)
`Narrow(cid:173)
`band
`band
`band
`band
`AID
`AID
`AID
`AID
`• ---- - - --- -- ~ J.---- - - -- -- - -- --- - ___ , , _____ ----- ---- - ---- _ _, J- - -- - -- -- - --- - - --- - - ~ J.- - - - ----- --·
`Digitized
`Digitized
`Digitized
`Digitized
`Carrier Signal Carrier Signal Carrier Signal Carrier Signal
`440
`440
`440
`440
`Wideband RF Signal
`
`FIG. 5
`
`Page 5
`
`T-Mobile Ex. 1030
`
`

`

`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 5of11
`
`US 6, 785,558 Bl
`
`Remote Site 620
`
`BTS Hotel
`
`610
`
`Remote Site 620
`
`FIG. 6
`
`Remote Site
`710
`
`BTS Hotel
`700
`
`--
`
`Remote Site
`710
`
`FIG. 7
`
`Remote Site
`710
`
`Page 6
`
`T-Mobile Ex. 1030
`
`

`

`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 6of11
`
`US 6, 785,558 Bl
`
`Remote Site
`810
`
`Remote Site
`810
`
`BTS Hotel
`
`FIG. 8
`
`Remote Site
`810
`
`511 bits
`Header
`(BCH encoded)
`
`17 bits 12,392 bits 12,392 bits
`Data
`Rsvd Data
`Carrierl
`Carrier2
`
`r-- One SONET OC- l 2c frame ( 125 µs, 7 4,880 bits~
`
`12,392 bits
`Data
`CarrierN
`
`FIG. 9
`
`Page 7
`
`T-Mobile Ex. 1030
`
`

`

`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 7of11
`
`US 6, 785,558 Bl
`
`variable bits
`8 bits
`16 bits 8 bits
`Frame Data Destination Message
`content
`Counter type
`
`r--- Message 1
`
`variable bits
`8 bits
`8 bits
`Data Destination Message
`content
`type
`
`.. , . · · r--- Message N -----1
`
`,..
`
`Header (BCH encoding removed)
`
`.. ,
`
`FIG. 10
`
`Data for carrier 1
`. . . lan-1 I an Ian+! I ...
`Data for carrier 2
`· · · lbn-11 bn
`lbn+ll · · ·
`
`Data for carrier N
`. . . lcn-11 Cn
`lcn+J I ...
`
`FIG. 11
`
`Interleaved data for carriers 1,. .. ,N
`· ·. lan-1 lbn-J I . ·. lcn-11 an I bn 1. · · 'Cn lan+1 lbn+1 I . · .1Cn+1 I . · ·
`
`Page 8
`
`T-Mobile Ex. 1030
`
`

`

`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 8of11
`
`US 6, 785,558 Bl
`
`RF
`cross-
`connect
`
`1200
`
`1210
`RF /Digital TRX
`
`RF /Digital TRX
`1210
`
`RF /Digital TRX
`1210
`
`Digital
`Interface
`
`1220
`
`Network
`Link
`1230
`
`Digital
`Network
`
`FIG. 12
`
`Analog RF
`carrier signal
`
`Analog RF
`carrier signal
`
`RF down-
`convert
`1300
`
`AID
`
`1310
`
`RxDSP
`
`1320
`
`RF up-
`convert
`1350
`
`DIA
`
`TxDSP
`
`1330
`
`1340
`FIG. 13
`
`Digital carrier
`signal
`
`Digital carrier
`signal
`
`Page 9
`
`T-Mobile Ex. 1030
`
`

`

`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 9 of 11
`
`US 6,785,558 Bl
`
`Base
`Stations :
`
`Digital
`MUX
`
`1400
`
`1410
`Digital Formatter
`
`Digital Formatter
`1410
`
`Digital Formatter
`1410
`
`FIG. 14
`
`Digital
`Interface
`
`1420
`
`Network
`Link
`1430
`
`Digital
`Network
`
`Digital
`Network
`
`1530
`
`Network
`Link
`1500
`
`Main
`CPU
`1510
`
`High-speed
`serial link 1520
`
`High-speed
`serial link 1520
`
`High-speed
`serial link 1520
`
`local digital link
`(to radio unit)
`
`local digital link
`(to radio unit)
`
`local digital link
`(to radio unit)
`
`FIG. 15
`
`Page 10
`
`T-Mobile Ex. 1030
`
`

`

`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 10 of 11
`
`US 6,785,558 Bl
`
`local digital link
`(to NAN)
`
`High-speed
`serial link
`1600
`
`RF power
`and
`distribution
`1620
`
`RF /Digital TRX
`1610
`
`FIG. 16
`
`High-speed
`serial link
`
`Delay
`11lli2
`
`RF /Digital TRX
`l1l.Q
`
`____ __,
`
`RF /Digital TRX
`1720
`
`Delay
`11lli2
`
`RF /Digital TRX
`1710
`
`RF power
`and
`distribution
`
`I
`
`1-----L-_,~ RF /Digital TRX
`1720
`!-----------------------------------------------------------------------------------------------------·
`FIG. 17
`
`Page 11
`
`T-Mobile Ex. 1030
`
`

`

`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 11 of 11
`
`US 6,785,558 Bl
`
`RF /Digital TRX
`1840
`
`High-speed
`serial link
`1800
`
`Delay
`1810
`
`RF /Digital TRX
`1820
`
`RF /Digital TRX
`1840
`
`Delay
`1810
`
`RF /Digital TRX
`1820
`
`FIG. 18
`
`High-speed
`serial link
`1900
`
`RF /Digital TRX
`1920
`
`RF /Digital TRX
`1930
`
`J--=---.---.i
`
`RF /Digital TRX
`
`RF/Digital TRX
`1930
`FIG. 19
`
`RF power
`and
`distribution
`
`1830
`
`RF power
`and
`distribution
`
`Page 12
`
`T-Mobile Ex. 1030
`
`

`

`US 6,785,558 Bl
`
`1
`SYSTEM AND METHOD FOR
`DISTRIBUTING WIRELESS
`COMMUNICATION SIGNALS OVER
`METROPOLITAN TELECOMMUNICATION
`NETWORKS
`
`FIELD OF THE INVENTION
`
`The present invention relates generally to wireless com(cid:173)
`munication systems. More specifically, it relates to tech(cid:173)
`niques for transporting signals from a base station hotel to
`remote transmitters using optical fibers.
`
`BACKGROUND OF THE INVENTION
`
`5
`
`2
`types of traffic such as telephony and data. While there is
`capacity available for additional traffic it must be transmitted
`in a format that is compatible with the existing traffic.
`Simply applying the RF signals to the fiber in an analog
`fashion would require the use of expensive optical compo(cid:173)
`nents to optically multiplex the analog signals on to the fiber
`using some type of wavelength division multiplexing. This
`assumes that the existing network even supports wavelength
`division multiplexing which is not always the case. In
`10 addition, non-standard access equipment would be required
`to combine the optical signal carrying the RF signals with
`the optical signals containing the existing digital traffic.
`Several techniques have been proposed for the digital
`transport of cellular signals over existing switched data
`15 networks. The typical approach, such as that disclosed in
`U.S. Pat. No. 5,627,879 to Russell et al., is to digitize a
`broadband RF signal comprising several dozen RF carriers
`using a single ND converter. The digitized broadband signal
`is then transmitted to the remote sites where a D/Aconverter
`20 is used to recover the broadband analog signal containing
`the multiple RF carriers. It should be emphasized that the
`AID and D/A converters at each end of the communication
`link convert an entire broadband RF signal containing
`multiple RF carriers. U.S. Pat. No. 5,852,651 to Fischer et
`25 al. describes a similar technique. Broadband RF signals from
`different sectors may be combined with each other or may
`remain separated, but in either case ND and D/Aconversion
`is performed on the entire broadband signal associated with
`each antenna. It should also be emphasized that the conver-
`30 sion at the remote site always takes place at the remote site's
`centrally located interface to the switched network, so that
`the broadband signal is communicated in analog RF form
`between the central network interface and the various sector
`antenna transmitters and their associated antennas.
`
`Wireless communication systems, and cellular system in
`particular, are evolving to better suit the needs of increased
`capacity and performance demands. Currently cellular infra(cid:173)
`structures around the world are upgrading their infrastruc(cid:173)
`ture to support the third generation (3G) wireless frequency
`spectrum. Unfortunately, the tremendous capital resources
`required to upgrade the entire cellular system infrastructure
`inhibits the deployment of these 3G systems. It is estimated
`that up to 3 million 3G cell sites will be needed around the
`world by 2010.
`Traditionally, a cellular communications system includes
`multiple remote sites, each providing wireless service to a
`geographic service area, or cell. As shown in FIG. 1, a
`cellular base station (BTS) is normally located in each
`remote site 100, together with an antenna tower, antennas, an
`equipment room, and a number of other relevant compo(cid:173)
`nents. This traditional approach of deploying all the cell site
`equipment locally at each remote site has several drawbacks
`that contribute to the expense of the infrastructure, and
`upgrades to the infrastructure. At each remote site, a BTS 35
`room or cabinet to host the large base station equipment is
`required, as well as additional electric power supplies for the
`base station. This increases both the costs of the equipment
`at each site, as well as the costs of acquiring and renting the
`physical location for the equipment. The remote cell site 40
`equipment must be designed for future coverage and capac-
`ity growth, and upgrades to the equipment require physical
`access to the remote site.
`To mitigate these problems, some cellular systems have
`been designed with a different architecture, as shown in FIG. 45
`2. The base stations 240 for multiple remote sites 200 are
`centralized in a base station hotel 210, while the antenna
`towers and antennas remain located at various remote sites
`at a distance from the base station hotel. Separating the base
`stations 240 from the antennas, however, makes it necessary 50
`to transport RF signals between the base station hotel and the
`various cell sites that it serves, typically using signal con(cid:173)
`verters 250, network interface equipment 260, and a broad(cid:173)
`band communication network 220. When broadband fiber
`optic cables are used, RF signals from the base stations are
`converted to optical format and communicated over the fiber
`optic cable and then converted back to analog RF signals at
`the remote sites. After the optical/RF conversion, the signal
`is sent to one of several sector transmitters 230 and radiated
`over the air via the antenna to provide cellular coverage. The
`BTS hotel concept is especially valuable in metropolitan
`areas where fiber is abundant but equipment space comes at
`a premium. In these types of areas it is getting increasingly
`more difficult to deploy new cell sites due to a variety of
`factors including regulatory and space constraint issues.
`Unfortunately, a significant portion of the metropolitan
`fiber networks already are configured to carry particular
`
`SUMMARY OF IBE INVENTION
`The present invention introduces an improved technique
`for transporting wireless communication signals between a
`set of base stations in a base station hotel and a set of
`remotely located cell sites. In contrast with prior techniques
`that digitize the entire broadband RF signal associated with
`each antenna, the present invention proposes a technique
`that separately digitizes each RF carrier signal within the
`broadband RF signal. Separately digitizing each RF carrier
`has significant advantages, such as easing the dynamic range
`requirements on both the receiver and AID converter. The
`separately digitized carriers are transmitted over a digital
`network between the base station hotel and the remote sites.
`In contrast with prior techniques, however, the present
`invention provides a technique wherein the digitized carrier
`signals are not converted to analog format when they first
`arrive at the remote site, but remain in digital format as they
`are distributed within the remote site to the various antenna
`units of the remote site. In other words, the remote site AID
`55 and D/A converters are terminally located at the antenna
`units rather than positioned at an intermediate point in the
`signal transport path, such as the remote site's interface with
`the digital network.
`Because signals are transported in a purely digital form
`60 until the very end of the digital transport (i.e., all the way up
`to the antenna units), the method of the invention enjoys
`some key benefits over prior systems that use analog trans(cid:173)
`port at the remote site to distribute the RF signals to separate
`antenna units. Optical effects that limit analog systems such
`65 as attenuation, dispersion and reflection do not directly affect
`the cellular signal when digital transport is used. As a result,
`the system can send signals over much longer distances
`
`Page 13
`
`T-Mobile Ex. 1030
`
`

`

`US 6,785,558 Bl
`
`5
`
`3
`without degradation. Also, dynamic range is unaffected by
`distance since the digital samples suffer no degradation due
`to the transport process as long as reliable communications
`exist. Signal reconstruction techniques can also be used with
`digital data to ensure data integrity through the entire
`transport process. For example, error-coding algorithms can
`be used to detect and correct bit errors. These benefits apply
`to both downlink and uplink directions.
`In one aspect of the invention, a method of downlink
`wireless communication is implemented by a system com(cid:173)
`prising a base station hotel, at least one remote site, and a
`digital data network (e.g., a fiber optic network) connecting
`the hotel to the remote site. The base station hotel houses a
`plurality of base stations and a digital hub which connects
`the base stations to the digital network. The remote site has
`a set of antenna units, where transmitters and antennas are
`located, and a network access node connecting the remote
`site to the digital network. A local data link (e.g., dedicated
`fiber optics, or conventional LAN) within the remote site
`connects the antenna units to the network access node.
`In an aspect of the invention providing transport of
`downlink signals, each of the base stations generates a set of
`carrier signals, where each carrier signal comprises multiple
`information channels (e.g., multiple user signals code(cid:173)
`modulated onto a carrier frequency of the carrier signal). In 25
`some systems, a base station will generate several carrier
`signals at various distinct carrier frequencies. In addition, a
`base station may also generate several carrier signals
`intended for transmission to distinct sectors of a remote site.
`Each carrier signal is then individually digitized by the 30
`digital hub to produce a digitized carrier signal. The digi(cid:173)
`tized carrier signals are then formatted appropriately and
`communicated via a digital data network to various remote
`sites. Typically, there is a one-to-one correspondence
`between base stations and remote sites, so that a given 35
`carrier signal will be sent to a single corresponding remote
`site. In some cases, however, a base station can multicast to
`multiple remote sites, or various base stations can provide
`carrier signals to the same remote site. Once received at the
`appropriate remote site, the digital carrier signal is sent via 40
`a local digital link to an antenna unit where it is converted
`to an analog carrier signal. The analog carrier signal is then
`frequency up-converted, amplified, and transmitted from an
`antenna to subscribers assigned to the various information
`channels of the carrier signal. In systems that use 45
`sectorization, the set of carrier signals comprises carrier
`signals for each of the various sectors at a cell site.
`In another aspect of the invention, an analogous method
`of uplink communication is provided in the same system.
`According to this method, analog carrier signals are received 50
`at antenna units and separately digitized there prior to being
`transported over a local digital link to a network access node
`at the remote site. The digital carrier signal is then sent over
`the digital data network to the base station hotel. Other
`carrier signals from the same antenna unit, from other 55
`antenna units at the same remote site, or from other remote
`sites are similarly sent to the base station hotel in digital
`format. The separate digital carrier signals are then con(cid:173)
`verted to analog carrier signals and received by the appro(cid:173)
`priate base station in the hotel.
`In a preferred embodiment of the invention, the cellular
`communication system is a 3rd generation cellular system
`where each of the multiple carriers within the broadband RF
`signal uses CDMA (code division multiple access) to mul(cid:173)
`tiplex several information channels onto the same RF car- 65
`rier. In such systems, it is important to accurately maintain
`proper signal power levels. Accordingly, in order to com-
`
`4
`pensate for any signal power level distortions introduced
`during conversion and processing, the preferred embodi(cid:173)
`ment uses a power control channel to transport power
`measurement signals between the base station hotel and the
`remote sites. After the RF carrier signals have been digitally
`transported, the power measurement signals are then used to
`appropriately scale the signal power level of each RF carrier
`to compensate for any distortions.
`In systems that employ CDMA (code-division multiple
`10 access), a time-diversity technique of the present invention
`may be used as well. In the downlink, after a carrier signal
`is transported to an antenna unit, both the original signal and
`a time-delayed copy of the signal are transmitted via sepa(cid:173)
`rate antennas. This technique provides an additional diver-
`15 sity signal to the subscribers without requiring any addi(cid:173)
`tional bandwidth between the base station hotel and the
`antenna units. In the uplink, primary and diversity signals
`received at the remote site can be superimposed with a
`relative time delay and then transported as one digital signal.
`20 At the base station, the two superimposed signals are auto(cid:173)
`matically separated by the base station's RAKE receiver.
`In another aspect of the invention, the method is imple-
`mented in a cellular system using a digital hub at the base
`station hotel for performing the required AID and D/A
`conversions, signal processing, and interfacing with the
`switched data network. A similar network access node is
`used at each remote site. In the downlink direction (from the
`base station to mobile user) the digital hub digitizes the RF
`signals emanating from the base station and formats the
`digitized samples into a standard telecommunication proto(cid:173)
`col such as OC-X (OC-3, OC-12, OC-48, OC-192, etc.),
`STM-n (STM-1, STM-4, STM-16, etc.) or Gigabit Ethernet.
`The appropriate format is determined by the specific type of
`transport network deployed. Using this standard data format,
`the digital hub uses network access equipment such as an
`add/drop multiplexer to interface to the digital network. The
`digital network is then used to transport the digitized RF
`signals to the remote cell site. At the remote cell site a
`remote version of the digital hub, the network access node
`(NAN), is then used to recover the digital RF carrier signals
`from the network. After being distributed to the appropriate
`antenna radio units, the digital signals are converted to
`analog RF signals and broadcast over the air to the mobile
`users using an amplifier and suitable antennas.
`In the uplink direction, similar reciprocal functions exist.
`At the remote site the antenna units receive analog RF
`signals over the air through a receiving system that typically
`consist of an antenna, amplifiers and filters. The received
`analog signal is then down-converted, digitized and sent
`over a local data link to the remote site's NAN where the
`digital carrier signal is formatted into a standard telecom-
`munication protocol, multiplexed onto the digital network,
`and sent over the digital network to the base station hotel. At
`the base station hotel, the digital hub is used to extract the
`data from the telecom network, and convert the digitized RF
`carrier signals from the network data format back into their
`native analog RF format. Finally, the RF analog signals are
`provided to the appropriate base stations for processing. In
`most instances, the same telecommunication protocol will
`60 be used in both the downlink and uplink directions. There
`may be situations, however, (especially with asymmetric
`services and applications) where different protocols can be
`used in each direction.
`The techniques of the invention are independent of the
`specific wireless protocol (W-CDMA, CDMA-2000, GSM,
`IEEE802.llx, Bluetooth, etc.) and the protocol used over the
`telecommunications network. Preferably, the technique also
`
`Page 14
`
`T-Mobile Ex. 1030
`
`

`

`5
`provides signaling between the digital hub and the NAN
`such that control, operational, administrative and mainte(cid:173)
`nance information may be exchanged between the base
`station hotel and the remote site. This signaling can also be
`used to transport other services such as data for the support 5
`and application of location-based services.
`
`US 6,785,558 Bl
`
`6
`uplink and downlink diversity according to a preferred
`embodiment of the present invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram illustrating a first communica(cid:173)
`tion system network architecture according to the prior art.
`FIG. 2 is a block diagram illustrating a second commu(cid:173)
`nication system network architecture according to the prior
`art.
`FIG. 3 is a block diagram illustrating a communication 15
`system network architecture according to a preferred
`embodiment of the present invention.
`FIG. 4 is a diagram illustrating the technique of wideband
`digitizing according to the prior art.
`FIG. 5 is a diagram illustrating the technique of narrow- 20
`band digitizing according to a preferred embodiment of the
`present invention.
`FIG. 6 is a block diagram illustrating a point-to(cid:173)
`multipoint network architecture for a communication system
`according to a preferred embodiment of the invention.
`FIG. 7 is a block diagram illustrating a ring network
`architecture for a communication system according to a
`preferred embodiment of the invention.
`FIG. 8 is a block diagram illustrating a daisy chain
`architecture for a communication system according to a 30
`preferred embodiment of the invention.
`FIG. 9 is a diagram illustrating a digital data frame
`structure used in a preferred embodiment of the present
`invention.
`FIG. 10 is a diagram illustrating a digital data header
`structure used in a preferred embodiment of the present
`invention.
`FIG. 11 is a diagram illustrating a data interleaving
`technique used in a preferred embodiment of the present
`invention.
`FIG. 12 is a functional block diagram illustrating the main
`components of a digital hub according to a preferred
`embodiment of the present invention.
`FIG. 13 is a functional block diagram illustrating the main
`components of an RF/digital transceiver according to a
`preferred embodiment of the present invention.
`FIG. 14 is a functional block diagram illustrating the main
`components of a digital hub according to an alternate
`embodiment of the present invention.
`FIG. 15 is a functional block diagram illustrating the main
`components of a remote site network interface unit accord(cid:173)
`ing to a preferred embodiment of the present invention.
`FIG. 16 is a functional block diagram illustrating the main
`components of a remote site antenna/radio unit according to
`a preferred embodiment of the present invention.
`FIG. 17 is a functional block diagram illustrating the main
`components of a remote site antenna/radio unit having
`downlink diversity according to an preferred embodiment of 60
`the present invention.
`FIG. 18 is a functional block diagram illustrating the main
`components of a remote site antenna/radio unit having
`uplink diversity according to a preferred embodiment of the
`present invention.
`FIG. 19 is a functional block diagram illustrating the main
`components of a remote site antenna/radio unit having both
`
`DETAILED DESCRIPTION
`Preferred embodiments of the invention will now be
`described in detail with reference to the drawing figures.
`Those skilled in the art will appreciate that the following
`description of the preferred embodiments contains many
`specifics for the purpose of illustration only, and that the
`10 principles of the invention are not necessarily limited by
`these details.
`In the present description, the term "carrier signal" is used
`to mean a spectrum bandwidth that is modulated by some
`standard modulation technique to carry an information sig(cid:173)
`nal. For example, one type of carrier signal is a narrow band
`frequency carrier containing one AMPS subscriber channel
`or a few TDMAsubscriber channels. Another type of carrier
`signal is a wideband CDMA signal containing many code(cid:173)
`modulated subscriber channels. The term "channel" is used
`in the broad sense as including not only frequency channels
`as in FDMA, but also code channels such as a CDMA
`channel, time/frequency channels such as in TDMA, and
`generally any type of information channel derived by divid(cid:173)
`ing the wireless spectrum using a multiplexing technique
`25 involving frequency, time, code, space, etc. In this general
`use of the term, each channel typically corresponds one-to(cid:173)
`one with a subscriber information signal that is allocated to
`the channel.
`A block diagram of a wireless communication system
`implementing the techniques of a preferred embodiment of
`the present invention is shown in FIG. 3. A series of base
`stations (BTS) reside in a BTS hotel 300. The base stations
`are connected to a digital hub 310 that also resides in the
`BTS hotel. The digital hub 310 is connected via a digital
`35 network 320 to one or more remote sites 330. Each remote
`site has a network access node (NAN) 340 and several
`remote antenna units 350 connected to the NAN 340 by
`digital communication links 360. Downlink cellular signals
`from a base station are digitized at the digital hub 310 and
`40 sent as standard formatted data over the digital network 320
`to the NANs 340. The NANs remove the network formatting
`and send the digital signals to the antenna units 350 where
`they are converted back to RF analog signals which are then
`transmitted to wireless subscribers. In the uplink direction,
`45 the antenna units 350 receive RF transmissions from the
`subscribers. These analog RF signals get digitized then sent
`to the NAN 340 where they are formatted and sent over the
`optical fiber to the digital hub 310. The digital hub converts
`the uplink data back to analog RF signals which then get
`50 passed on to the appropriate base stations (BTS).
`RF/Digital Conversion
`The technique of the invention employs narrowband
`digitizing rather than wideband digitizing when digitizing
`cellular RF signals. In other words, each cellular carrier
`signal is separately converted from analog to digital format
`(and vice versa). Wideband digitizing and narrowband digi-
`tizing are illustrated in FIGS. 4 and 5, respectively. As
`illustrated in these figures, an RF wideband signal 400 may
`contain several distinct narrowband carriers 410 (e.g.,
`CDM