United States Patent
`(12)
`(10) Patent N0.:
`US 7,133,697 B2
`
`Judd et al.
`(45) Date of Patent:
`Nov. 7, 2006
`
`USOO7133697B2
`
`(54) TRANSLATION UNIT FOR \VIRELESS
`COMRIUNICATIONS SYSTEl“
`
`(75)
`
`.
`-
`7
`Inventors: Mano D. Judd, Rockwall, TX (US);
`(1191?“ WC (:fnmfidt’ ATlilen’CTfi (UST)5(
`0 “5y
`' ”g 959’
`e
`’0 my”
`(Us)
`
`(73) Assignee: Andrew Corporation, Westchester, IL
`(US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U-S-C- 1540”) by 450 days-
`
`(21) App1.No.:10/145,298
`.
`(22) Wed:
`
`May 14, 2002
`
`(65)
`
`Prior Publication Data
`
`US 2003/0036410 Al
`
`Feb. 20, 2003
`
`(60)
`
`Related U.S. Application Data
`.
`.
`/
`.
`.
`Prov151onal application No. 60 290,882, filed on May
`14’ 2001‘
`Int. Cl.
`(2006.01)
`H04B 1/38
`(52) U.S. Cl.
`......................
`455/561; 455/11.1; 455/560
`
`(51)
`
`5,659,879 A
`5,802,452 A
`5,812,933 A
`
`.
`,
`5,2255%: 2
`5,890,055 A
`6,047,177 A
`6,141,533 A
`6,243,5"7 Bl
`6,684,058 B1>I<
`6,690,662 131*
`
`8/1997 Dupuy ........................ 455/15
`,. 455/20
`9/1998 Grandfield et a1.
`
`....................
`. 455/16
`9/1998 Niki
`
`1nson ..........
`'
`3732843
`151333 ngdonald et 31'
`
`.. 455/16
`3/1999 Chu et 31.
`4/2000 Wiekman ......
`455/422
`
`............. 455/11.1
`10/2000 Wilson et a1.
`............. 455/426
`6/2001 Elrefaie et a1.
`
`[/2004 Karacaoglu et a1.
`..... 455/20
`2/2004 Komara ct a1.
`............. 370/342
`
`DE
`EP
`EP
`EP
`EP
`EP
`“'0
`W0
`W0
`
`FOREIGN PATENT DOCUMENTS
`40 08 165
`8/1991
`0714218 A1 * 11/1994
`0714218 A1
`5/1996
`0756392 A2 .1
`7/1996
`0 756 392
`1/1997
`1 143 554
`10/2001
`W) 97/32442
`9/1997
`WO 97/32442 A1
`9/1997
`W0 01/ 11797
`/2001
`
`’1‘ cited by examiner
`
`Primary ExamineriNay Maung
`Assistant ExamineriAngelica M. Perez
`(74) Attorney, Agent, or FirmiWood, Herron & Evans,
`L'L'P'
`(57)
`
`ABSTRACT
`
`(58) Field Of Classification Search ~~~~~~~~~~_~-~~ 455(111,
`.
`.
`435/561: 560: 7
`See application file for complete Search hlstOYY
`.
`References Clted
`U.S. PATENT DOCUMENTS
`
`g
`(“6)
`
`A translation unit for use in a wireless communications
`system comprises translation circuitry configured to be
`interfaced between an RF antenna network and a backhaul
`network. The translation circuitry is operable for translating
`the frequency of signals directly between an RF network and
`a backhaul network without conversion to audio in order to
`
`,
`,
`4 783 843 A
`4,941,200 A
`5,509,028 A
`5,604,789 A
`
`e
`e a, .....................
`5
`2
`11/1988 L H t
`1
`“5/2?
`7/1990 Leslie et 31.
`455/17
`
`4/1996 Marque-Pucheu
`. 375/211
`2/1997 Lerman ....................... 379/59
`
`y
`.
`.
`provide direct communications between a base station and a
`bad‘hmfl desnnmon‘
`
`34 Claims, 11 Drawing Sheets
`
`14a
`
`16a
`
`
`
`
`
`
`
`RF T0 uW
`11W TO RF
`AMPLIFIERS
`
`80
`
`Page 1 of 20
`
`SAMSUNG EXHIBIT 1034
`
`Page 1 of 20
`
`SAMSUNG EXHIBIT 1034
`
`

`

`US. Patent
`
`Nov. 7, 2006
`
`Sheet 1 of 11
`
`US 7,133,697 B2
`
` 3""
`
`«aw
`
`flCfi
`
`E \
`
`16a
`
`24a
`
`14a
`
`30
`
`”—5.7
`
`12a
`
`103 4“
`
`FIG. 3
`
`143
`
`163
`
`
`
`
` RFTOuW
`MNTORF
`AMPUHERS
`
`
`
`FIG. 4
`
`Page 2 of 20
`
`Page 2 of 20
`
`

`

`US. Patent
`
`Nov. 7, 2006
`
`Sheet 2 of 11
`
`US 7,133,697 B2
`
`mv
`
`
`
`mo._.<.5oozmoNabisco:
`
`
`
`$$>flmp_mEmmiImas.
`
`2,10;
`
`anem
`
`3’>3
`
`3M:
`
`om‘<z._>2
`
`me“EOHn:n:o._.um«n
`
`s$95382Ea
`
`XDE
`
`E
`
`on
`
`No
`
`mGI
`
`Page 3 of 20
`
`Page 3 of 20
`
`

`

`eehS
`
`H
`
`US 7,133,697 B2
`
`«Mwov
`
`t20mm
`
`3(mx5:—
`
`.25“E
`
`N:
`
`tnetaPS”U
`
`0N
`
`60027.,
`
`V.now
`
`mm
`
`m3
`
`Page 4 of 20
`
`Page 4 of 20
`
`
`

`

`202 92
`
`204
`
` RFFilter
`RFFilter
`
`112
`
`US. Patent
`
`Nov. 7, 2006
`
`Sheet 4 of 11
`
`US 7,133,697 B2
`
`16a
`
`102
`
`3b
`
`Page 5 of 20
`
`80a
`
`FIG.6
`
`Page 5 of 20
`
`

`

`tnetaPs”U
`
`N
`
`m
`
`202my7.we88gawe;
`
`6mm:
`
`E
`
`Aa:2&Emu:u:e“a.2:mm
`
`n
`
`US 7,133,697 B2
`
`5.z..—mL_8590N:SA.
`MVn:223EE.1:u:s”E5.:mm
`
`
`
`varwoeFor
`
`2:
`
`Page 6 of 20
`
`Page 6 of 20
`
`
`

`

`US. Patent
`
`Nov. 7, 2006
`
`Sheet 6 of 11
`
`US 7,133,697 B2
`
`
`
`FIG. 8
`
`Page 7 of 20
`
`Page 7 of 20
`
`

`

`US. Patent
`
`Nov. 7, 2006
`
`Sheet 7 of 11
`
`US 7,133,697 B2
`
` '1'
`
`z I
`
`II DC #M .I
`
`Page 8 of 20
`
`Page 8 of 20
`
`

`

`US. Patent
`
`Nov. 7, 2006
`
`Sheet 8 of 11
`
`US 7,133,697 B2
`
`
`
`$3.>VDfix.IHH
`
`mam
`
`mmobmmN«6.5%_mosmm
`
`
`
`xx’xm’xm~>x._.>xH>J.’
`
`$2528me4%4%4$38>>o._
`
`HHH
`
`
`
`Page 9 of 20
`
`Page 9 of 20
`
`

`

`tnetaPS”U
`
`N
`
`6002
`
`nf09mehS
`
`US 7,133,697 B2
`
`30.—7.,mmZmZooWmmgom
`
`
`.33mmOHomm
`
`Etc.
`
`:..9...
`
`Page 10 of 20
`
`Page 10 of 20
`
`

`

`US. Patent
`
`Nov. 7, 2006
`
`Sheet 10 0f 11
`
`US 7,133,697 B2
`
`828:.
`
`oomo:
`
`_mohmm $2528Qw‘qu{gum‘Egon.38
`
`$3
`
`EEH
`
`mmosmm
`
`mmo._.om_m
`
`XE}XE}XE}®®6®®6x
`
`Page 11 of 20
`
`Page 11 of 20
`
`
`
`

`

`US. Patent
`
`Nov. 7, 2006
`
`Sheet 11 0f 11
`
`US 7,133,697 B2
`
`om:2.
`
`8mo:
`
`sham
`
` _“.85..__§_3%Q%3mmmm3%52528I_1:E38:3“am“sum_Ex._.és.Eé.rllllllllllHIlllllllllllllllllllllllllllllllIll...I..I.|I
`
`
`
`
`
`
`
`
`
`<<o_<<o_.<<c_mOFomm10.5mmmOhomm
`
`
`
`xmxfi.Etc.xx}...
`
`Qmmqumeu
`
`Page 12 of 20
`
`—LI.
`
`030....l—I-l-Ldfl:
`
`mp.OE
`
`Page 12 of 20
`
`
`

`

`US 7,133,697 B2
`
`1
`TRANSLATION UNIT FOR WIRELESS
`COMMUNICATIONS SYSTEM
`
`RELATED APPLICATIONS
`
`This application claims the filing benefit of Provisional
`Application U.S. Ser. No. 60/290,882, filed May 14. 2001,
`entitled “Translation Unit for Wireless Communications
`System”, the disclosure of which is hereby incorporated
`herein by reference in its entirety.
`
`
`
`FIELD OF THE INVENTION
`
`This invention is directed generally to wireless commu-
`nications and more particularly to an improvement in cell
`tower electronics for such a communications system.
`
`BACKGROUND OF THE INVENTION
`
`In many wireless communication stations, such as cellu-
`lar/PCS base stations, RF communication signals are
`received by an antenna at the top of a tower, routed down to
`equipment at the base of a tower (“base station”), down-
`converted from RF, and demodulated to audio. For further
`processing, the signals are then routed back to a Mobile
`Switching Ccntcr (MSC), Ccntral Office (CO), or othcr
`facility, using another wireless communication link or using
`a wired link, such as a T1 line. This routing back to the
`MSC/CO is referred to as backhaul.
`
`About 80% of all base stations route the signals back to
`the MSC/CO via a microwave backhaul link. That is, the
`base station signals are converted to microwave backhaul.
`Morc spccifically, at the basc station, thc audio signals are
`arranged or stacked and are upconverted to IF. The signals
`are then remodulated, usually using a different modulation
`scheme, and converted to a microwave frequency. They are
`then amplified and transmitted out via a microwave antemla
`or dish. The modulation and other signal processing is
`traditionally handled at the ground level of the tower, while
`the conversion to a microwave spectrum may be handled on
`the ground or on the tower. The primary reason for this
`whole complicated loop is that the RF Cellular/PCS signals
`are spread apart in the RF band, due to frequency re-use, and
`often occupy distinct bands, like a comb. For example, in a
`typical TDMA system. total comb bandwidth is around 12.5
`MHZ. However, the microwave link bandwidths are often
`much narrower.
`In order to limit the microwave bandwidth which must be
`purchased in order to facilitate the backhaul,
`the base
`stations have had to utilize expensive modulation/demodu-
`lation equipment utilizing digital signal processing or DSP
`and other supporting circuitry at
`the base station. For
`example, the RF wireless communication signals have to be
`up/down converted and modulated/demodulated down to
`audio, and then again up/down convertcd and modulatcd/
`demodulated for the microwave backhaul and have to be
`multiplexed from the RF side with the microwave hardware.
`For microwave transmissions, the multiplexed audio streams
`are modulated/demodulated with a different modulation
`scheme, such as QAM 256, and are up/down converted with
`respect to the microwave band. The modulation hardware
`and associated DSP functions are expensive and must be
`duplicated at all base stations using microwave backhaul.
`Because the base station hardware takes a larger RF band-
`width and backhauls it over a smaller microwave bandwidth,
`the base station hardware is considered to provide a spec—
`trum compres sion mechanism. Without such spectrum com-
`
`10
`
`15
`
`20
`
`30
`
`35
`
`40
`
`45
`
`60
`
`65
`
`Page 13 of 20
`
`2
`pression, it would be necessary to purchase a greater amount
`of expensive microwave backhaul bandwidth for the back-
`haul function.
`It is therefore desirable to reduce, and even eliminate, the
`expensive modulation/ demodulation hardware associated
`with the base station and its backhaul functions. More
`specifically, it is desirable to eliminate the need for compli-
`cated DSP functions and associated hardware at the base
`station.
`
`It is further desirable to simplify the base station and
`reduce its overall construction and maintenance costs, while
`still maintaining the convenient and desirable microwave
`backhaul function.
`It
`is furthcr dcsirablc to achieve thcsc goals without
`having to purchase an increased amount of an expensive
`backhaul bandwidth from the traditional microwave back-
`
`haul spectrum.
`These goals and improvements, and other features. are
`addressed by the present invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The accompanying drawings. which are incorporated in
`and constitute a part of this specification, illustrate embodi-
`ments of the invention and, together with a general descrip-
`tion of thc invcntion given above, and thc dctailcd dcscrip-
`tion of the embodiments given below, serve to explain the
`principles of the invention.
`FIG. 1 is a schematic diagram showing a tower and base
`station in accordance with the traditional backhaul capabili-
`ties;
`FIG. 2 is a block diagram of base station hardware for
`traditional backhaul capabilities.
`FIG. 3 is a schematic diagram of a tower and base station,
`in accordance with one embodiment of the invention;
`FIG. 4 is a schematic diagram of an embodiment of the
`invention;
`FIGS. 5, 6, and 7 are block diagrams showing electronics
`in accordance with several embodiments of the invention;
`FIG. 8 is a block diagram in accordance with another
`embodiment of the invention; and
`FIG. 9 is a block diagram of one embodiment of a three
`sector system configured in accordance with principles of
`the invention.
`FIG. 10 ilustrates a block diagram of another embodi-
`ment of the invention.
`FIG. 11 illustrates a block diagram of another embodi-
`ment of the invention.
`FIG. 12 i lustrates a block diagram of another embodi-
`ment of the invention.
`
`FIG. 13 ilustrates a block diagram of another embodi—
`ment of the invention.
`
` DETAILED DESCRIPTION OF TH:
`
`LU
`
`
`
`ILLUSTRATED EMBODIMENT
`
`Referring now to the drawings, and initially 0 FIG. 1, a
`cell tower or base station and tower installation in accor—
`dance with traditional backhaul capabilities is il ustrated for
`the purposes of explaining the invention. The installation 10
`includes a tower 12 or other suitable structure, for mounting
`one or more base station antennas 14, 15 (e.g. for transmit
`and receive) well above ground level. In accordance with
`traditional backhaul in such installations, communications
`with a switching center or central office (MSC/CO) are
`accommodated through a backhaul link which in FIG. 1 is
`illustrated as a microwave backhaul link, utilizing a micro-
`
`Page 13 of 20
`
`

`

`US 7,133,697 B2
`
`3
`wave antenna 16, also mounted at or near the top of the
`tower or other structure 12. Respective cables 18 and 20
`connect the antennas 14, 15 and the backhaul link antenna
`16 to base station electronics 30 which provide the proper
`processing and interface between the RF side and the
`microwave backhaul.
`in the cellular/PCS base station
`As mentioned above,
`equipment of this type, an RF signal is utilized to commu-
`nicate with a plurality of mobile units or individual users 24.
`In this regard, the cellular or PCS signals are spread apart,
`often occupying relatively small or narrow bands in a
`comb-like fashion. To handle the trafiic, the entire comb-like
`bandwidth must be processed and backhauled, which
`includes around 12.5 MIIZ of bandwidth. Typically,
`the
`bandwidth of the microwave backhaul link using the antemia
`16 is much narrower than the 12.5 MHZ RF communication
`
`bandwidth. Accordingly, in order to utilize the backhaul link
`or antenna 16, the base station electronics 30 must perform
`all of the necessary and expensive digital signal processing
`(DSP), compression, and conversion between the RF signals
`transmitted and rcccivcd by antcnnas 14, 15 and the micro-
`wave backhaul signals transmitted and received by antenna
`16.
`
`Because of the difference in spectral efiiciency between
`the RF spectrum and the microwave backhaul spectrum,
`service providers have found it necessary to maintain the
`expensive DSP hardware at each base station site to handle
`the modulation/demodulation and compression between the
`RF and backhaul spectrums. An example may be illustrative.
`For AMPS, cellular or TDMA (IS-136), the bandwidth
`requirement can be estimated as follows:
`the cell site
`In TDMA, using k77 frequency re-use,
`spectral efficiency is arotmd 1/7><0.8 bps/Hz:0.11 bps/Hz
`without spectrum compression. (prbits per second)
`For backhaul, the bps/HZ ratio, or spectral efficiency, is
`often much higher. For example, for 256 QAM modulation,
`the efficiency is around 8 bps/HZ, which is significantly
`more spectrally efficient. Using fixed wireless access (e.g.,
`MMDS), the spectral efficiency may be 011 the order of 476
`bps/Hz, over a 6 MHZ channel. A simple per cell site
`example then, for an FDMA(AMPS) arrangement, assuming
`about 8 kbps per channel. is set forth as:
`
`5
`
`10
`
`15
`
`20
`
`30
`
`35
`
`40
`
`45
`
`FDMA (AMPS):
`
`K = 7 4)
`K = 4 —>
`
`Full
`Site Spectrum
`
`60 ch (8 kbps/ch)/12.5 E6 = 0.0384 bps/Hz
`105 ch (8 kbps/ch)/12.5 E6 = 0.0672 bps/Hz
`
`Effective RF Spectrum
`
`Site bits
`
`Backhaul @
`6 bits/HZ
`
`k = 7 12.5 MHZ
`
`60 x (30 KHZ) = 1.8 MHZ
`
`480kbps
`
`80 KHZ
`
`Therefore, the RF spectrum requires about 156 times the
`bandwidth as necessary for a backhaul spectrum. Thus, it is
`usually considered better to demodulate and compress at the
`cell-site.
`
`TDMA without demodulation and compression provides
`somewhat more favorable efi‘iciency in that the RF spectrum
`would require about 52 times the bandwidth as necessary for
`a backhaul spectrum.
`For 3G/CDMA systems, assuming a full multicarrier
`(simple translation), and about 0.5 bps/Hz and a backhaul
`efficiency of around 6 bps/Hz,
`the RF spectrum would
`require around 12 times the spectrum as necessary for a
`backhaul spectrum.
`
`60
`
`65
`
`the spectrum
`
`4
`For CDMA, assuming adjacent carriers,
`efficiency is roughly:
`0.49 bits/HZ using all 64 signals/carrier
`0.25 bits/HZ using only 32 signals/carrier.
`For fixed wireless, the spectral efficiency will improve
`even more, and it is likely that a 1:1 bps/HZ efficiency may
`be achieved between the RF system and backhaul spectrum.
`In accordance with one aspect of the present invention,
`the use of expensive modulation/demodulation and DSP
`hardware is reduced and even eliminated from the base
`station. Specifically, modulators and demodulators for con-
`verting from the RF communication band to a digital audio
`stream, and the modulator/demodulator hardware for pro-
`viding thc ncccssary compression and convcrsion between
`the RF band and the microwave backhaul spectrum are
`eliminated. In one aspect of the invention, conversion occurs
`directly between the RF spectrum and the backhaul spec—
`trum without modulation and demodulation. The conversion
`occurs completely at the base station and any modulation
`and demodulation involving expensive DSP hardware
`occurs after the backhaul, such as at a MSC. In that way, the
`DSP function (and cost) is centralized for a plurality of base
`stations at the MSC/CO. In an embodiment of the invention,
`the conversion may occur on the tower without being routed
`to basc station clcctronics on thc ground at the basc of the
`tower. The present invention may utilize an inexpensive
`backhaul spectrum to handle the complete RF spectrum.
`Alternatively, newer CDMA/3G spectral efficiencies are
`utilized for reducing the required backhaul spectrum. With
`the allocation of the LMDS (Local Multipoint Distribution
`Services) 28 GHZ band (some 1300 MHz total bandwidth),
`which is mostly unused today, and for the foreseeable future,
`a Cellular/PCS provider can obtain 12.5 or 25 MHZ of this
`1300 MHZ bandwidth, likely at the same price (or lower)
`than they currently pay for a smaller amount of the micro-
`wave backhaul spectrum. The invention recognizes that,
`using this approach. a simple RF to LMDS band (and
`visa-versa) converter at the top of the tower is the only
`significant piece of hardware that would be required. There-
`fore, the cost requirements to compress the spectrum at the
`base station location are removed.
`While one described embodiment may use the above-
`discussed PCS/cellular and LMDS bands, the invention may
`be used in other bands as well. For example, any unused
`(unlicensed) band with sufficient available bandwidth could
`be used in place of the LMDS band. Also, such a system
`could be used to facilitate a wireless backhaul
`link for
`communications systems other than PCS/cellular, i.e., using
`other RF bands.
`In describing the invention, a brief description of a
`traditional backhaul scenario is helpful.
`Referring to FIG. 2,
`the base station electronics 30
`typically include circuitry 32 for downconverting RF signals
`from the anteima 14 to an IF frequency, as well as circuitry
`34 for digitizing thc signals and dcmodulating to audio. In
`the downlink path, signals received by antenna 14 are routed
`on line 18 to an amplifier, such as an LNA 19, before being
`downconverted to IF. Also, appropriate filters (not shown)
`might be utilized for filtering the individual RF channels
`received at antenna 14 prior to downconverting each channel
`to IF. Demodulator circuitry 34 also may include digitizing
`circuitry for digitizing each channel. A digital audio data
`stream is then created for each channel and is multiplexed
`with a multiplexer (MUX) 56 to form a high speed data
`stream. Downlinked signals are then routed on line 62 to
`modulator circuitry 36 where the high speed digitized data
`stream is again modulated (usually with a different modu-
`
`Page 14 of 20
`
`Page 14 of 20
`
`

`

`US 7,133,697 B2
`
`5
`lation scheme) and upconverted to IF. The IF signals are then
`upconverted to a microwave spectrum with appropriate
`conversion circuitry 38 wherein they are amplified, such as
`with a power amp 40. A diplexer 58 is necessary for
`separating backhaul uplink/downlink signals. Utilizing
`diplexer 58,
`the signals are routed via cable 20 to the
`backhaul antenna 16 for backhauling to a MSC/CO or other
`switching center. All the circuitry for up/down conversion
`and modulation/demodulation may be located at the bottom
`of the tower. Alternatively, some of the hardware, such as the
`up/down conversion circuitry and the amplifiers might be
`located at the top of the tower proximate the antenna.
`Signals arriving from the central oflice (CO) via the
`backhaul link antenna 16 would be fed to the base station
`electronics by the cable 20, through diplexer 58 where they
`are amplified, such as with an LNA 44, and then downcon-
`verted with appropriate circuitry 42 to IF frequencies.
`Appropriate demodulator circuitry demodulates and digi-
`tizes the signals which are then routed, via line 63,
`to be
`demultiplexed by the multiplexer circuitry 56 for transmis-
`sion through antenna 15. The digitized stream of the audio
`base band is then modulated and converted to appropriate IF
`signals by modulator circuitry 46. The signals are then
`upconverted to an RF band by appropriate conversion cir-
`cuitry 48 for transmission. The signals are amplified, such as
`with a power amplifier 50, and then routed on line 18 to be
`transmitted to customers or mobile units 24.
`As noted above, the various modulation circuitry utilized
`incorporates digital
`signal processing (DSP), which is
`expensive and, for a traditional backhaul, must be incorpo-
`rated with each base station. Also, such circuitry is necessary
`for both the RF side and the backhaul side of the system.
`Lines 63 and 62 may be T1 lines, or other high capacity
`lines, which may also be utilized to route the high speed
`stream directly to an MSC/CO, as well as to a backhaul link
`16. In the present invention, the use of wireless backhaul is
`addressed. For use of the microwave antenna backhaul link
`16, the base station modulator circuitry 36 might contain
`circuitry to remodulate the signal, with a high bps/Hertz rate
`such as QAM 256, prior to upconverting the signal
`to
`microwave 38.
`Referring now to FIG. 3, in accordance with one embodi-
`ment of the invention, the expensive modulation/demodu-
`lation and DSP circuitry is eliminated from the base station.
`A system 100 includes a tower or other structure 1211 which
`mounts a base station antenna 14a for an RF wireless
`communication system and a microwave antenna or dish
`16a for a backhaul
`link to a MSC/CO. In the present
`invention, the use of the terms “switching center” or “central
`oifice” for indicating a destination for the backhaul is not
`meant to be limiting to a particular type of destination. For
`example, multiple base stations might backhaul to another
`base station where DSP and modulation circuitry is present.
`Then, after processing and modulation/demodulation, the
`signals might be further backhaulcd to a traditional MSC/
`CO. Therefore, for the purposes of the invention, the terms
`“switching center” or “backhaul destination” may also mean
`another base station or some other destination. A translation
`unit 80 is provided at or near the tower top for providing
`bi-directional upconversion and downconversion respec-
`tively between the RF band and a backhaul band (e.g.,
`microwave) used by the backhaul link antemia 16a and
`associated equipment at the MSC/CO.
`In accordance with one aspect of the present invention,
`RF signals from antenna 14a are translated directly to a
`microwave spectrum for backhaul. In one embodiment of
`the invention, a low cost microwave spectrum bandwidth is
`
`10
`
`15
`
`20
`
`30
`
`35
`
`40
`
`45
`
`60
`
`65
`
`6
`used which is similar in size to the bandwidth of the RF
`
`spectrum. In such an embodiment, the difference in spectral
`efficiency between the RF side and the backhaul side is not
`an issue, and expensive DSP circuitry for spectrum com-
`pression is not required. For example, bandwidth from a
`band, such as the LMDS band, could be utilized which
`would equal
`the spectrum or bandwidth of the signals
`handled by the RF antenna 14a. The present invention is
`particularly desirable for 3G/CDMA technology wherein the
`spectral efficiency is greater and less backhaul bandwidth
`would be necessary.
`In one embodiment, by providing essentially the same
`backhaul bandwidth, in the presently largely unused and low
`cost LMDS band, as is required for the total bandwidth of
`the RF channels. such as cellular/PCS channels, the require-
`ment for compression is eliminated and simple LMDS-to-
`RF and RF-to-LMDS frequency converters
`are used
`between the two antennas 14a and 1611, thus eliminating the
`need for base station DSP and modulatiOIL/demodulation
`
`electronics. Having eliminated the need at the base station
`for processing the signals between the antenna 14a and the
`backhaul
`link antenna 1611, digital processing and other
`processing of the signals for multiple base stations may be
`performed at the MSC/CO rather than at each base station.
`This significantly reduces the complexity and costs of the
`base station hardware and the costs of the overall systems.
`While one described embodiment
`focuses upon the
`above-discussed PCS/cellular and LMDS bands, the inven-
`tion may be used in other bands as well. For example, an
`unused (unlicensed) band with sufficient available band-
`width could be used in place ofthe LMDS band for backhaul
`purposes. Also, such a system could be used to facilitate a
`wireless backhaul link for communications systems other
`than PCS/cellular,
`i.e., using other RF bands. The chart
`below lists other bands, for example and without limitation,
`which might be substituted for the RF band (band A), and
`backhaul band (band B), in the embodiment described in
`detail herein:
`
`band A
`
`band B
`
`PCS 1900
`PCS 1900
`3G 1900
`Cellular 800
`Cellular 800
`4G
`WCS 2300
`PCS 1900
`Cell 800
`PCS 1900
`Cell 800
`PCS71900
`PCS-1900
`(Iell 800
`Cell 800
`2400 Unlicensed
`2400 Unlicensed
`5.1 UNII band
`5.1 UNII band
`5.8 UNII band
`5.8 UNII band
`PCS 1900 band
`Cell 800 band
`UMTS band 1900/2100
`UMTS band 1900/2100
`UMTS band 1900/2100
`UMTS baud 1900/2100
`UMTS band 1900/2100
`
`MMDS 2500
`MMDS 2100
`MMDS 2500
`PCS 1900
`MMDS 2500
`MMDS 2500, 2100
`MMDS 2500, 2100
`WCS 2300
`WCS 2300
`2400 Unlicensed (802.11 b band)
`2400 Unlicensed (802.11 b baud)
`5.1 GHz UNII band
`5.8 GHz UNII band
`5.1 (iH/, UNII hand
`5.8 GHZ UNII band
`MMDS 2100 band
`MMDS 2500 band
`MMDS 2100 band
`MMDS 2500 band
`MMDS 2100 band
`MMDS 2500 band
`Unlicensed 900 band (U.S.)
`Unlicensed 900 band
`MMDS 2100 band
`MMDS 2500 band
`Unlicensed 2400 band
`Unlicensed 5.1 UNII band
`Unlicensed 5.8 UNII band
`
`Page 15 of 20
`
`Page 15 of 20
`
`

`

`US 7,133,697 B2
`
`7
`
`-continued
`
`band A
`
`band B
`
`UMTS band 1900/2100
`UMTS band 1900/2100
`UM'IS 1900/2100
`DCS-1800
`DCS-900
`DCS-1800
`DCS-900
`DCS-1800
`DCS-900
`DCS71800
`DCS-900
`
`PCS-1900 band (:use the existing U.S. 3G
`infrastructure to translate Euro/Asia frequencies
`Cell-800 band
`3.5 (1H7 hand (this is a license hand; the
`European MMDS band)
`3.5 GHz
`3.5 GHz
`2400 Unlicensed (this band is unlicensed
`throughout the world: 83 MHZ wide)
`2400 Unlicensed
`5.1 GHz UNII
`5.1 GIIz UNII
`5.8 UNII
`5.8 UNII
`
`Band A frequencies are embedded in the current/original
`base station modulation and transceiver hardware, as well as
`the terminal equipment.
`DCS—1800 is currently the world GSM standard, migrat—
`
`ing to GPRS, then EDGE, then W—CDMA.
`Returning to FIG. 3, the electronics module 80, located at
`the tower top, may also include amplifiers for amplifying the
`signals to be respectively transmitted by the RF antenna 14a
`and the microwave backhaul antenna 16a, respectively, in
`addition to hardware for RF-to-LMDS and LMDS-to-RF
`frequency conversion. Module 80 is also shown in FIG. 4,
`wherein the RF-to-LMDS converter, the LMDS-to-RF con-
`verter and the amplifiers are indicated as a part of the
`electronics module 80.
`FIGS. 577 show various embodiments of the electronics
`module 80 which may be used between the RF link antennas
`14a and a microwave backhaul antenna 1611.
`In FIG. 5, a single RF antenna 14a is used for both
`transmit and receive functions, and is a passive antenna.
`Antenna 14a is coupled with a frequency diplexer 90 for
`separating the transmit and receive signals. The receive or
`uplink signals from the antenna 14a are fed through diplexer
`90 to RF—to—microwave converter circuitry which includes
`an RF filter 92, an amplifier, such as an LNA 93, RF-to-IF
`downconverter or downconversion circuitry 94, an IF filter
`96, an lF-to-microwave upconverter or upconversion cir-
`cuitry 98, and a power amplifier 100. The signal is routed
`through diplexer 102 which serves to separate receive and
`transmit signals at the microwave backhaul antenna 16a.
`The signal is then backhauled to an appropriate switching
`center directly to be processed and demodulated at the
`switching center, rather than at the base station. In that way,
`modulation and demodulation circuitry and other DSP func-
`tions may be centralized at a switching center or office,
`rather than at each base station. This results in a significant
`cost savings per base station and overall.
`The reverse, or downlink, path from the diplexer 102
`directs signals received by the backhaul antenna 16a from
`the switching center through a low noise amplifier 104, to
`microwave-to-IF downconverter circuitry 106, which places
`the signal in a form to be converted to RF and transmitted
`from the tower. An IF filter 107 filters the signal before it is
`routed to an IF-to-RF upconverter, or upconversion circuitry
`108. The RF signal is amplified by a power amplifier 110 and
`filtered by an RF filter 112 before passing through the
`frequency diplexer 90 to the RF antenna 14a.
`Another version of the electronics package 80a is illus-
`trated in FIG. 6 for use with antenna 14b, which is a
`distributed active antenna DAA, for example, of the type
`described in the co-pending application Ser. No. 09/422,418,
`
`10
`
`15
`
`20
`
`30
`
`35
`
`40
`
`45
`
`60
`
`65
`
`8
`filed Oct. 21, 1999. The antenna 14b may include separate
`transmit and receive radiating elements, or a single set of
`radiating element with a diplexer. Respective power ampli-
`fiers and low noise amplifiers for the transmit and receive
`functions are incorporated with the antenna and are located
`closely adjacent
`the radiating elements. Uplink signals
`received at the antenna 1417 are RF filtered by filter 92 and
`are fed through an RF-to-microwave upconverter 202 which
`converts directly from RF to microwave. The signal is then
`amplified by a power amplifier 100 which feeds the signal to
`the microwave backhaul antenna 16a by way of a frequency
`diplexer 102, as described above with reference to FIG. 5.
`Downlink signals received at the backhaul link antenna 16a
`are directed through an LNA 104 to a microwave-to-RF
`downconverter 204 which downconverts from the micro-
`wave backhaul spectrum directly to RF. The signals are
`filtered by RF filter 112 and forwarded to the active antenna
`141).
`In yet another embodiment, shown in FIG. 7, a distributed
`active antenna 14b (DAA) is also utilized in much the same
`fashion as described above with reference to FIG. 6, but the
`hardware utilizes a conversion step to IF before converting
`to the RF or microwave spectrum, somewhat similar to FIG.
`5. Signals from RF antenna 14b are RF filtered through filter
`92 and are delivered to an RF -to-IF downconverter 94 which
`feeds the resultant IF signal to an IF filter 96 and then to an
`IF-to-microwave converter 98. The signal from the con-
`verter 98 is routed to the diplexer 102 through a power
`amplifier 100 to be transmitted by the microwave backhaul
`antenna 16a. Working in the downlink direction, the signals
`received by the backhaul like antenna 160 are directed by the
`frequency diplexer 102 to a low noise amplifier 104 which
`amplifies the signal and feeds it
`to a microwave-to-IF
`downconverter 106. The down-converted IF signal is filtered
`through an IF filter 107, and is directed to the IF-to-RF
`upconverter 108. The signals are filtered through RF filter
`112 and forwarded to the active antenna 141).
`Referring to FIG. 8, a modular electronics package
`including the basic elements of any of the embodiments of
`FIGS. 577 is shown. In the embodiment of FIG. 8, use of a
`single passive antenna element 14a is contemplated,
`whereby a diplexer 90 is provided. As explained above with
`reference to FIGS. 577, when separate transmit and receive
`antenna elements are utilized, a diplexer 90 may be omitted.
`The remaining components include a frequency diplexer 102
`for the microwave backhaul link antenna 16a, power ampli-
`fiers 110 and 100, low noise amplifiers 93 and 104. Respec—
`tive upconverter and downconverter circuitry 302, 304 may
`take the form of the up/down converter circuits shown in any
`of FIGS. 5, 6 and 7. That is, conversion may be achieved
`through an IF stage, or directly between RF and microwave.
`Advantageously, this modular electronics package may be
`conveniently mounted on the tower, eliminating a need for
`expensive DSP and modulator/demodulator electronics in a
`ground unit and associated coaxial cable running up and
`down the tower both for the RF side and the backhaul side.
`Only a relatively simple DC power cable for DC power to
`the electronics package need be provided, and this in turn
`may be eliminated if onboard power in the form of batteries,
`rechargeable batteries, solar power, or the like is provided.
`Referring to FIG. 9, a multiple sector system for the
`receive or uplink path is shown. Respective sector antennas
`314, 316, etc. are provided (one for each of the three or more
`sectors). Each antenna is provided with a low noise amplifier
`318, 320. This system supports a total of M code division
`multiple access (CDMA) carriers per sector, With N chan—
`nels per carrier. Accordingly, multiple downconverter blocks
`
`Page 16 of 20
`
`Page 16 of 20
`
`

`

`US 7,133,697 B2
`
`9
`330 are provided with down converter subcircuits 332 for
`each of the M carriers in the sector. That is, M downcon-
`verter circuits 332 are associated with each sector antenna
`314, 316, etc. Splitter circuits 321 route the carriers to their
`respective down converter circuits 332. The downconverter
`circuits 332 may also be provided with analog—to—digital
`conversion or converters 333. Thus, a digital signal is fed to
`a digital signal processor (DSP)/demodulator block 340. In
`the system of FIG. 9, a total of MxN of the DSP/demodu-
`lator blocks 340 will be provided for each sector for han—
`dling the N channels per M carriers. All of the demodulator
`outputs are fed to a high speed digital multiplexer 350 which