(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2008/0174502 A1
`(43) Pub. Date:
`Jul. 24, 2008
`Oren et al.
`
`US 2008O1745O2A1
`
`(54) METHOD AND SYSTEM FOR EQUALIZING
`CABLE LOSSES IN A DISTRIBUTED
`ANTENNASYSTEM
`
`(76) Inventors:
`
`Yair Oren, Washington, DC (US);
`Igor Berlin, Potomac, MD (US);
`Ofer Saban, Moshav Beit Elazari
`(IL)
`Correspondence Address:
`MINTZ, LEVIN, COHN, FERRIS, GLOVSKY
`AND POPEO, PC
`ATTN PATENT INTAKE CUSTOMER NO.
`30623
`ONE FINANCIAL CENTER
`BOSTON, MA 02111
`
`(21) Appl. No.:
`
`12/016,459
`
`(22) Filed:
`
`Jan. 18, 2008
`
`Related U.S. Application Data
`(60) Provisional application No. 60/885.470, filed on Jan.
`18, 2007.
`
`Publication Classification
`
`(51) Int. Cl.
`H01O 21/00
`GOIR 29/08
`
`(2006.01)
`(2006.01)
`
`(52) U.S. Cl. ......................................... 343/703: 343/853
`(57)
`ABSTRACT
`The invention is directed to a method and system for equal
`izing the signal losses over cable runs in a Distributed
`Antenna System (DAS). In a DAS, two or more antennae are
`connected to the system by cable runs that can vary widely in
`length. As a result, the signal loss over a given cable run can
`also vary widely which can impact the design and deployment
`of the DAS and reduce antenna spacing. In addition, for a
`broadband DAS that supports many frequency bands or
`ranges using a common antenna unit, the signal losses vary
`with respect to frequency further making it difficult to equal
`ize the cable losses. According to one embodiment of the
`invention, the method and system provide for measuring and
`adjusting the signal losses of each cable run to be a predefined
`value. According to another embodiment of the invention, the
`DAS can include a hybrid passive-active antenna unit which
`includes a frequency multiplexer that separates the signal into
`frequency bands or ranges that are connected to an antenna
`element associated with a particular frequency band or range.
`Where a single frequency band needs to be amplified (or
`attenuated), a single band amplification block (SBAB) can be
`inserted in the connection between the frequency multiplexer
`and the antenna element to amplify (or attenuate) the desired
`frequency band. Where more than one frequency band need to
`be amplified (or attenuated), a multiband amplification block
`(MBAB) can be inserted in the connection between the fre
`quency multiplexer and the appropriate antenna element to
`amplify (or attenuate) the desired frequency bands.
`
`
`
`Wireless
`Terminals
`
`

`

`Patent Application Publication
`
`Jul. 24, 2008 Sheet 1 of 11
`
`US 2008/0174502 A1
`
`
`
`I '9IAI
`
`Patent Application Publication
`
`Jul. 24,2008 Sheet 1 of 11
`
`US 2008/0174502 Al
`
`
`
`
`Terminals
`Wireless
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`FIG. 1
`
`
`
`
`
`
`
`y
`
`a
`
`|
`
`|
`I
`
`
`
`
`Closets
`Remote
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`TL...
`
`
`
`
`
`
`
`
`
`
`
`
`
`| Antenna Section
`
`|
`|
`|
`|
`
`
`
`
`
`
`
`
`
`
`| =I, Coonan
`
`
`
`
`
`
`
`
`
`
`
`
`
`Closet
`Main
`
`Wireless Sources |
`
`
`
`
`
`
`
`
`
`
`Source C
`
`Source B
`
`Source A
`
`
`
`
`
`
`
`Page 2
`
`CommScope Ex. 1030
`
`

`

`Patent Application Publication
`
`Jul. 24, 2008 Sheet 2 of 11
`
`US 2008/0174502 A1
`
`
`
`Z PO?I
`
`\/ ?OunOS
`
`£ ?OunOS
`
`O ?OunOS
`
`Patent Application Publication
`
`Jul. 24,2008 Sheet 2 of 11
`
`US 2008/0174502 Al
`
`
`
`
`Antenna Section
`
`Coax and
`
`
`
`
`
`
`
`
`
`
` Source D3
`
`Source D2
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Source D1
`
`—_— Ss
`
`FIG. 2
`
`
`
`
`
`
`
`
`
`
`
`
`
`Closet
`Remote
`
`
`
`
`
`
`
`
`
`
`
`
`
`Closet
`Main
`
`
`
`
`|
`|
`t
`|
`|
`
`Source C -#q—_|
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Source B
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Source A +
`
`
`
`
`
`
`
`Page 3
`
`CommScope Ex. 1030
`
`

`

`Patent Application Publication
`
`Jul. 24,2008 Sheet 3 of 11
`
`US 2008/0174502 Al
`
`
`
`
` WCU
`
`
`
`Wiring
`
`
`
`
`338
`Closet Units
`
`
`
`
`FIG. 3
`
`
`
`
`Cable Run
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Unit
`
`
`
`
`
`
`
`
`
`
`—
`
`Closet
`
`Main
`
`From
`
`
`
`
`Aggregation
`
`—
`
`
`
`
`
`
`
`‘
`
`340
`
`Remote Closet
`
`
`
`
`
`
`
`300 —4
`
`354
`Radio Source #1
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`358
`Radio Source #3
`
`
`
`
`356
`Radio Source #2
`
`
`
`
`
`
`
`
`
`
`
`
`
`Page 4
`
`CommScope Ex. 1030
`
`

`

`Patent Application Publication
`
`Jul. 24, 2008 Sheet 4 of 11
`
`US 2008/0174502 A1
`
`
`
`9.Lf7 717 | z) +
`
`0 || 7
`
`f7 %) IAI
`
`^007
`
`Patent Application Publication
`
`Jul. 24,2008 Sheet 4 of 11
`
`US 2008/0174502 Al
`
`
`
`
`410
`
`420
`
`440
`
`
`
`
`Structure (Passive)
`Antenna Elements
`
`
`
`
`
`
`
`
`
`
`
`
`Gain Block
`
`
`
`
` RF Coupler
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`\
`
`N
`
`416
`
`414
`
`412
`
`
`
`
`\
`
`<
`<_
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`L- 430
`
`
`
`
`400 N
`
` Antenna Port
`
`
`
`Page 5
`
`CommScope Ex. 1030
`
`

`

`Patent Application Publication
`
`Jul. 24, 2008 Sheet 5 of 11
`
`US 2008/0174502 A1
`
`
`
`Patent Application Publication
`
`Jul. 24,2008 Sheet 5 of 11
`
`US 2008/0174502 Al
`
`
`
`
`
`
`
`
`
`
`
`
`
`530
`
`——
`
`>
`
`<
`
`
`
`
`
`
`
`
`
`
`
`
`516
`
`Multiplexer
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`/
`/
`J I
`
`1
`
`l
`
`
`
`
`
`
`
`
`
`
`
`
`
`DCA
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`526
`Detector
`Power
`
`
`
`
`
`
`
`524
`
`Converter
`
`Digital
`Analog to
`
`8
`
`
`
`
`
`
`
`Vv
`
`
`
`
`
`
`
`Coax
`
`To Antenna
`
`RF
`
`
`
`
`
`
`
`
`
`
`Voll
`
`RF Coupler
`
`
`
`
`
`
`Loss Equalization Block 510
`
`
`
`
`
`
`
`500 ——~s
`
`
`
`
`
`
`
`529
`
`
`
`
`
`
`
`
`
`
`Controller
`
`NN,
`
`
`
`
`
`
`
`
`
`
`
`
`FIG. 5
`
`
`
`
`
`
`
`Loss Measurement Block 520
`
`
`
`
`Page 6
`
`CommScope Ex. 1030
`
`

`

`Patent Application Publication
`
`Jul. 24, 2008 Sheet 6 of 11
`
`US 2008/0174502 A1
`
`ZZ9
`
`
`
`9 (OIH
`
`Patent Application Publication
`
`Jul. 24,2008 Sheet 6 of 11
`
`US 2008/0174502 Al
`
` 624
`
`Freq. range fry — fx
`Passive Element #2 YY
`
`
`
`
`
`
`
`
`
`622
`
`
`
`
`Freq. range fin —fir
`Passive Element #1 YY
`
`
`
`
`
`
`
`
`
`
`A 620
`
`Lo 600
`
`
`
`
`
`
`
`
`
`
`610
`
`Multiplexer
`Frequency
`
`Main
`
`
`
`
`612
`
`Coax Cable
`
`
`
`
`FIG. 6
`
`626
`
`Va
`
`
`
`
`
`
`
`
`
`
`
`
`
`Freq. range fi» — fat
`Passive Element tin
`
`
`
`
`
`
`
`Page 7
`
`CommScope Ex. 1030
`
`

`

`Patent Application Publication
`
`Jul. 24, 2008 Sheet 7 of 11
`
`US 2008/0174502 A1
`
`ZZZ
`
`
`
`
`
`Z (5) IAI
`
`Patent Application Publication
`
`Jul. 24,2008 Sheet 7 of 11
`
`US 2008/0174502 Al
`
`726
`
`
`
`
`YY
`
`Freq. range fn — fru
`Passive Element #n
`
`
`
`
`FIG. 7
`
`
`
`
`
`
`
`e
`
`
`
`
`
`
`
` 724
`
`YY
`
`Passive Element #2
`
`
`
`
`
`
`
`
`
`YY
`
`Freq. range fin —fir
`Passive Element #1
`
`
`
`
`722
`
`
`
`
`
`
`
`Lo 720
`
`Jo
`
`700
`
`
`
`
`710
`
`Multiplexer
`Frequency
`
`Main
`
`
`
`
`712
`
`Coax Cable
`
`
`
`
`Page 8
`
`CommScope Ex. 1030
`
`
`
`
`
`
`(Single Band of Interest)
`
`®
`
`°
`
`
`
`
`
`
`
` /
`
`
`
`
`
`
`
`
`
`730
`
`
`
`
`
`
`

`

`Patent Application Publication
`
`Jul. 24, 2008 Sheet 8 of 11
`
`US 2008/0174502 A1
`
`ZZ9
`
`
`
`º "OICH
`
`Patent Application Publication
`
`Jul. 24,2008 Sheet 8 of 11
`
`US 2008/0174502 Al
`
`
`
`
`YY
`
`Freq. range fis — fut
`Passive Element #n
`
`
`
`
`FIG. 8
`
`
`
`
`826
`
`
`
`
`e
`
`
`
`
` 824
`
`YY
`
`Passive Element #2
`
`
`
`(Multiple Bands of Interest)
`
`@
`
`°
`
`
`
`
`
`
`
`
` /
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`830
`
`
`
`
`
`
`
`810
`
`Multiplexer
`Frequency
`
`Main
`
`
`
`
`
`
`
`822
`
`Yr
`
`
`
`
`Freq. range fix —fir
`Passive Element #1
`
`
`
`
`
`
`
`
`
`
`Lo 820
`
`812
`
`Coax Cable
`
`Page 9
`
`CommScope Ex. 1030
`
`

`

`Patent Application Publication
`
`Jul. 24, 2008 Sheet 9 of 11
`
`US 2008/0174502 A1
`
`
`
`076
`
`6 (5) IAI
`
`»J006
`
`Patent Application Publication
`
`Jul. 24, 2008
`
`Sheet 9 of 11
`
`US 2008/0174502 Al
`
`922
`
`>
`b>
`
`Passive Element
`
`Conncction to
`
`( Band k:
`
`an k-|_—————
`
`
`
`
`Freq. Multiplexer
`
`/ 930
`
`
`
`
`Freq. Multiplexer
`
`Multiband Amplification Block (MBAB)
`
`900 —~
`
`
`
`
`
`
`
`
`
`
`
`
`SBAB
`Band m
`{
`940
`
`
`
`
`£
`
`
`
`
`SBAB
`Band 1
`
`
`
`
`
`
`
`
`
`
`( A
`
`
`
`
`
`
`
`
`
`
`A
`
`
`
`
`
`
`acacalcan
` A
`
`
`FIG. 9
`
`920
`
`10
`
`
`
`CCC Lee] 9
`
`
`
`Vv
`
`958
`
`956
`
`Vv
`
`(
`
`954
`
`Vv
`
`952
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`912
`
`<q
`4
`
`Main Freq. Multiplexer
`
`Connection to
`
`Page 10
`
`CommScope Ex. 1030
`
`

`

`Patent Application Publication
`
`Jul. 24, 2008 Sheet 10 of 11
`
`US 2008/0174502 A1
`
`
`
`SpupAAOL
`
`
`
`?uòUuòIGH QAISSbae
`
`090||
`
`
`
`TGI TI()
`
`J0X9|dnGI
`
`000 I
`
`070||
`
`TGI TQ
`
`() I "OICH
`
`

`

`Patent Application Publication
`
`Jul. 24, 2008 Sheet 11 of 11
`
`US 2008/0174502 A1
`
`
`
`09 || ||
`
`07 || ||
`
`II (DIAI
`
`Patent Application Publication
`
`Jul. 24,2008 Sheet 11 of 11
`
`US 2008/0174502 Al
`
`>
`
`
`
`
`Passive Element
`
`Towards
`
`
`
`
`1120
`
`
`
`
`
`
`
`FIG. 11
`
`
`
`
`
`
`
`1110
`
`
`
`
`
`
`
`A
`
` <
`
`
`
`
`
`
`Freq. Multiplexer
`
`Towards Main
`
`
`
`
`
`
`
`Page 12
`
`CommScope Ex. 1030
`
`

`

`US 2008/01745O2 A1
`
`Jul. 24, 2008
`
`METHOD AND SYSTEM FOR EQUALIZING
`CABLE LOSSES IN A DISTRIBUTED
`ANTENNASYSTEM
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`0001. This application claims any and all benefits as pro
`vided by law of U.S. Provisional Application No. 60/885,470
`filed Jan. 18, 2007, which are hereby incorporated by refer
`ence in their entirety.
`
`STATEMENT REGARDING FEDERALLY
`SPONSORED RESEARCH
`0002. Not Applicable
`
`REFERENCE TO MICROFICHEAPPENDIX
`0003) Not Applicable
`
`BACKGROUND
`0004. 1. Technical Field of the Invention
`0005. The present invention is directed to Distributed
`Antenna Systems and more particularly, to methods and sys
`tems for compensating for signal loss or attenuation in order
`to provide predictable signal strength at the uplink and down
`link endpoints.
`0006 Distributed Antenna Systems (“DAS) are used to
`provide or enhance coverage for wireless services Such as
`Cellular Telephony, Wireless LAN and Medical Telemetry
`inside buildings and over campuses. The general architecture
`of a DAS is depicted in FIG. 1.
`0007. A single DAS can serve a single wireless service or
`a combination of wireless services operating over multiple
`bands. With respect to each wireless service served by the
`DAS, the Aggregation Configuration of the wireless service
`can be characterized as non-aggregated or aggregated. In a
`non-aggregated configuration, there is a 1:1 relationship
`between DAS antennae and Transmitter/Receiver units for
`that wireless service. In an aggregated configuration, each
`Transmitter/Receiver unit for a given wireless service is asso
`ciated with multiple DAS antennae through a hierarchy of
`aggregation. For example, in FIG. 2, Services A, B, and C are
`aggregated and Services D1, D2, and D3 are non-aggregated.
`Typically, wireless LAN services are arranged in a non-ag
`gregated configuration when using a DAS while cellular ser
`vices are typically arranged in an aggregated configuration.
`0008. One desired characteristic of a multi-service DAS is
`that it can use a single antenna to radiate and receive the
`signals for all services and frequency bands Supported by the
`DAS. Such an antenna would need to cover (i.e. have accept
`able performance) in all frequency bands of interest and is
`commonly referred to as a Broadband Antenna. An example
`of a Supported frequency range for a DAS antenna would be
`400 MHZ-6 GHZ.
`0009. In referring to the signal flows in DAS systems, the
`term Downlink signal refers to the signal being transmitted by
`the source transmitter (e.g. cellular base station) through an
`antenna to the terminals and the term Uplink signal refers to
`the signals being transmitted by the terminals which are
`received by an antenna and flow to the source receiver. Many
`wireless services have both an uplink and a downlink, but
`Some have only a downlink (e.g. a mobile video broadcast
`service) or only an uplink (e.g. certain types of medical telem
`etry).
`
`(0010 2. Description of the Prior Art
`0011. Different DAS may use different types of cabling to
`connect the antennae units to the wiring closet: various kinds
`of coaxial cable, CAT-5/6, optical fiber, etc. Analog signals
`can become attenuated as they propagate along the cable—
`the magnitude of attenuation depends on the characteristics of
`the cable, and is generally proportional to the length of the
`cable and to the frequency of the signal.
`0012 Multi-service DAS usually use passive (i.e. un-pow
`ered) broadband antennae located, for example, in the ceil
`ings, throughout a facility, connected with broadband coax
`cabling to active components residing in wiring closets. This
`is because passive antennae are cheaper and more reliable
`than powered antennae and the introduction of power ampli
`fiers in the antenna can introduce interference between bands
`that requires the use of bulky and expensive filters to mitigate.
`
`SUMMARY
`0013. A common problem of virtually any DAS installa
`tion is that the cables connecting the different antennae to the
`wiring closet are not of equal lengths. The cable lengths may
`range from as little as 30' to as much as 300 or more. It
`follows that the power level at which a signal would be
`transmitted from an antenna connected through a 'short
`cable could be significantly higher than that transmitted from
`an antenna connected through a "long cable. For example,
`assuming certain types of coaxial cables, the difference in
`propagation loss between a 30' cable and a 300' for a signal at
`6 GHz would be more than 20 dB, and therefore a downlink
`signal launched with equal power at the wiring closet into the
`two antenna cable runs would yield a dramatically different
`power level at each and resulting in a corresponding disparity
`in coverage radius around each antenna.
`0014. One of the problems created by the disparity in
`antenna cable lengths is the varying coverage radius. As a
`result of different attenuation for both uplink and downlink,
`the effective coverage radius of eachantenna may vary widely
`depending on the length of its cable run. This variance can
`complicate the antenna location planning process and would
`typically increase the cost of the project. For signals using the
`non-aggregated configuration, where each antenna is radiat
`ing a different signal, the variation in coverage radius can
`complicate (automatic) frequency channel assignment pro
`cesses and may introduce interference.
`0015. Another problem created by the disparity in antenna
`cable lengths is narrowing of system uplink dynamic range in
`systems in aggregated configurations. One measure of the
`uplink performance of a system is its Dynamic Range. Simply
`defined, Dynamic Range is the range of power levels, lowest
`to highest, that the system can handle simultaneously. In a
`system composed of a well-designed DAS and a receiver, the
`receiver would typically have the more restricted dynamic
`range.
`0016. A more restricted dynamic range can impact the
`design and deployment as well as the cost of the DAS. Gen
`erally, the strongest uplink signal is created when the terminal
`is as close as would be physically allowed to one of the DAS
`antennas (since in this case the propagation loss in the air is
`the Smallest possible) and the weakest uplink signal is created
`when the terminal is as faraway as is physically allowed from
`its nearest DAS antenna. The difference between the stron
`gest signal and the weakest signal as described above must
`not exceed the dynamic range of the system. Since there is no
`way to limit the strongest signal coming into the system, the
`
`

`

`US 2008/01745O2 A1
`
`Jul. 24, 2008
`
`only available way is to ensure the weakest signal is not too
`weak. The way to ensure that is to decrease the distance
`between antennas, thus shrinking the maximal distance
`between a terminal and its nearest antenna. This in turn has a
`negative financial impact as more antennas may be required
`for a given coverage area. The disparity in antenna cable run
`length further exacerbates the problem, since the system
`design now needs to take into account the case where the
`weakest signal is received through an antenna with a long
`cable run while the strong signal is received through an
`antenna with a short cable run. The end result would be a
`further decrease in antenna spacing and increased project
`COStS.
`0017. It should be noted that in a DAS handling multiple
`wireless services at different frequencies, the disparity in
`propagation losses on the cable will vary by frequency band
`(i.e. be larger for high frequencies).
`0018 All of the above problems can be alleviated by
`equalizing the signal losses associated with each antenna
`cable run, Such that similar losses are experienced on every
`run. If the loss on each cable is known, attenuators and/or
`amplifiers can be used to compensate for high or low loss,
`ultimately equalizing the losses. This can be achieved by a
`manual process of measuring the length of each cable or
`directly the loss on it and installing attenuators or amplifiers
`in-line to the signal path on each cable run. However, a
`manual process is cumbersome, error-prone and would sig
`nificantly increase the labor costs of the project. It does not
`solve the above identified problems for a DAS handling mul
`tiple signals at different frequencies, each requiring a differ
`ent level of attenuation and/or amplification.
`0019. In the case that amplification functionality is inte
`grated into the antenna for one or more bands, a possible
`solution would be to include an Automatic Gain Control
`(AGC) mechanism that would ensure the downlink signal is
`radiated at a pre-set power from the antenna regardless of the
`losses in incurs in the cable run. However, this does not
`address the equalization required for the uplink, and therefore
`does not resolve the impact on uplink dynamic range. In
`addition, in Some configurations, for example, non-aggre
`gated configuration services Such as Wi-Fi, the transmitter/
`receiver (e.g. Wi-Fi access point) must be permitted to
`dynamically control the coverage radius around the associ
`ated antenna by increasing or decreasing the downlink trans
`mit power. If the DAS has constant power gain, power
`changes by the transmitter external to the DAS will be
`reflected in the coverage radius around the corresponding
`DAS antenna, as required. However, if a downlink AGC
`mechanism is implemented in the antenna, any power
`changes in the transmitter power would be compensated by
`the AGC and the intended result of dynamically changing
`coverage radius would not be achieved.
`0020. In addition, wireless services (e.g. Wi-Fi) are being
`introduced in increasingly higher frequency bands (e.g.
`WLAN at 2.4 GHz and especially 5.5 GHz). This creates
`challenges when using passive antennae because analog sig
`nals are attenuated as they propagate along the coax cable and
`the magnitude of attenuation depends on the characteristics of
`the cable, and is generally proportional to the length of the
`cable and to the frequency of the signal. For in-building DAS
`deployments, cable lengths can reach 300' or more, and the
`attenuation experienced by high frequency signals along Such
`a length of cable will significantly degrade the downlink
`power of the signal as it reaches the antenna (the uplink signal
`
`would be subject to a similar problem). The result is a sub
`stantially reduced coverage radius for that frequency band
`around the antenna and the associated increased cost to add
`more antennae.
`0021
`Introducing amplification in the antenna can com
`pensate for the losses in the cable, for both the uplink and
`downlink signals, and thus alleviate the problem. For
`example, some single-service DAS platforms use single-band
`(a.k.a. narrowband) antennae which are active, in other words
`have integrated amplifiers for the specific band being
`addressed. Further, a multi-service DAS which requires some
`bands to be amplified to overcome cable losses can be imple
`mented using a collection of separate and discrete narrow
`band antennae. However, this has significant commercial dis
`advantages in terms of cost, performance and aesthetics.
`0022. One object of the invention is to provide a DAS
`which includes a system for compensating for cable losses
`which provides for predictable coverage radii regardless of
`cable lengths and frequency, and preserves the transparency
`to transmitter power variations.
`0023. Another object of the invention is to provide a DAS
`which includes a system for automatically compensating for
`cable losses regardless of cable lengths and frequency, and
`preserves the transparency to transmitter power variations.
`0024. Another object of the invention is to provide a DAS
`which includes a system for automatically compensating for
`cable losses which provides for predictable coverage radii
`regardless of cable lengths and frequency, and preserves the
`transparency to transmitter power variations.
`0025. Another object of the invention is to provide a DAS
`which includes a system for automatically compensating for
`cable losses in both aggregated and non-aggregated configu
`rations regardless of cable lengths and frequency, and pre
`serves the transparency to transmitter power variations.
`0026. In accordance with the invention, system can
`include a loss measurement component and an equalization
`component. One or more RF measurement signals can be
`generated at one end of the cable run, for example, the end
`coupled to the antenna and used to estimate signal loss over
`the cable run. The loss measurement component can be con
`nected at the other end of the cable run, for example, in the
`wiring closet where the cable run begins and be adapted to
`receive one or more of the RF measurement signals and
`determine or estimate the cable losses for one or more of the
`RF signals, signal frequencies or signal channels based on
`one or more of the RF measurement signals received. Alter
`natively, one or more RF measurement signals can be gener
`ated at the end of the cable run adjacent the wiring closet and
`received by the loss measurement component at the end of the
`cable run adjacent the antenna unit. The equalization compo
`nent can be located at either end of the cable run and con
`nected to the loss measurement component whereby the esti
`mated cable losses can be used to equalize the losses of one or
`more cable runs to a predetermined value or to adjust the
`signal amplitude input to the antenna to be a predetermined
`value.
`0027. In accordance with the invention, the method can
`include providing a measurement signal generator, providing
`a loss measurement component and providing an equalization
`component. Generating one or more RF measurement signals
`used to estimate signal loss over the cable run by the mea
`Surement signal generator located adjacent the end of the
`cable run coupled to the antenna. Receiving one or more of
`the RF measurement signals by the loss measurement com
`
`

`

`US 2008/01745O2 A1
`
`Jul. 24, 2008
`
`ponent at the other end of the cable run, for example in the
`wiring closet where the cable run begins and determining or
`estimating cable losses for one or more RF signals, signal
`frequencies or signal channels based on one or more of the RF
`measurement signals received. Equalizing or adjusting the
`losses of one or more cable runs to a predetermined value or
`the signal amplitude input to the antenna to be a predeter
`mined value as a function of the estimated or determined
`cable losses.
`0028. In accordance with an embodiment of the invention,
`a distributed antenna system that Supports a plurality of fre
`quency band or channel connections can include a hybrid
`passive active antenna unit. The hybrid passive active antenna
`unit can include a main frequency multiplexerconnected to a
`plurality of respective antenna elements which are used to
`transmit and receive signals over the corresponding respec
`tive frequency band. Each frequency band connection can
`include a single band amplification block or a multi-band
`amplification block, depending on whether only a single fre
`quency band corresponding to an antenna section needs to be
`amplified or a whether multiple bands corresponding to com
`mon antenna section need to amplified. Each single band
`amplification block can include an uplink and downlink
`duplexerconnected to a main frequency multiplexerfor sepa
`rating and combining the uplink and downlink frequency
`bands and for feeding the uplink and downlink frequency
`bands into and receiving the uplink and downlink frequency
`band from their corresponding amplifiers according to the
`appropriate direction of the signal flow. Each multi-band
`amplification block can include frequency multiplexer blocks
`which are adapted to separate out the frequency bands that
`need to be amplified, feeding them into a single band ampli
`fication block for amplification and for combining them back
`into the frequency band connection.
`0029. The present invention can be applied to single ser
`Vice and multi-service DAS, in both aggregated and non
`aggregated configurations and to both downlink and uplink
`signal flows.
`0030 These and other capabilities of the invention, along
`with the invention itself, will be more fully understood after a
`review of the following figures, detailed description, and
`claims.
`
`BRIEF DESCRIPTION OF THE FIGURES
`0031 FIG. 1 is a block diagram of a DAS.
`0032 FIG. 2 is a block diagram of a DAS.
`0033 FIG.3 is a block diagram of a DAS according to the
`invention.
`0034 FIG. 4 is a block diagram of an antenna unit of a
`DAS according to the invention.
`0035 FIG. 5 is a block diagram of a loss estimation block
`and an equalization block according to the invention.
`0036 FIG. 6 is a block diagram of a hybrid passive active
`antenna according to the invention.
`0037 FIG. 7 is a block diagram of a hybrid passive active
`antenna according to the invention.
`0038 FIG. 8 is a block diagram of a hybrid passive active
`antenna according to the invention.
`0039 FIG. 9 is a block diagram of a multiband amplifica
`tion block for a hybrid passive active antenna according to the
`invention.
`0040 FIG. 10 is a block diagram of a Single Band Ampli
`fication Block for a hybrid passive active antenna according
`to the invention.
`
`FIG. 11 is a block diagram of a Single Band Ampli
`0041
`fication Block for a hybrid passive active antenna according
`to the invention.
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`0042. The present invention is directed to a method and
`system for compensating for cable losses in distributed
`antenna systems. In accordance with one embodiment of the
`invention, the system includes a measurement component
`adapted to receive a measurement signal having a known
`frequency and power level and for determining or estimating
`the losses of a signal transmitted at one end of the cable run
`and received at the other end of the cable run. In accordance
`with the invention, the system further includes an equaliza
`tion component adapted for receiving the information about
`the determined or estimated cable run losses and for adjusting
`the signal level to a predetermined value. Each cable run in the
`DAS can include the system according to the invention
`whereby the signal levels of each cable run can be adjusted to
`the predetermined value. In one embodiment, the signal level
`corresponding a particular service or frequency range or band
`at the connection to the antenna unit can adjusted to the same
`level for all antenna units.
`0043. In accordance with one embodiment of the inven
`tion, one or more measurement components can be located at
`the beginning of one or more cable runs, for example, in the
`wiring closet at the opposite end of the cable run from the end
`connected to the antenna elements. RF measurement signals
`can be received by the antenna elements from an RF mea
`Surement signal transmitter or input to the cable at the antenna
`end of the cable by a signal generator and communicated to
`the measurement component over each of the cable runs to be
`equalized. An equalization component can be located at the
`beginning of one or more cable runs and be controlled by an
`associated measurement component to adjust the signal loss
`over the one or more cable runs to a predetermined value.
`Alternatively, the measurement component and the equaliza
`tion component can be located at the end of the cable run
`connected to the antenna and the RF measurement signals can
`be generated and transmitted from the beginning of one or
`more cable runs, for example, from the wiring closet.
`0044. In accordance with the invention, the DAS can pro
`vide a single wireless service or multiple wireless services.
`With respect to systems providing multiple wireless services,
`the invention can provide individualized equalization for all
`or any subset of the frequency bands over which services are
`provided. The invention can be incorporated in DAS where
`the antenna unit does not include any amplification capability
`for any frequency band as well as to DAS in which the antenna
`unit includes amplification capability for one or more fre
`quency bands. The invention can use Software in its imple
`mentation and the method according to the invention can be
`Software controlled and completely automated.
`0045. In accordance with another embodiment of the
`invention, the system can include a measurement component
`and an equalization component.
`0046. The measurement component can be adapted to
`measure the signal loss on the Cable Run. The Antenna Unit
`or a component coupled to the cable run at the end connected
`to the Antenna Unit, can generate a signal at a known fre
`quency and known power level and transmit that signal over
`the uplink of the Cable Run, and having a component of the
`Wiring Closet Unit for that antenna measure characteristics of
`
`

`

`US 2008/01745O2 A1
`
`Jul. 24, 2008
`
`the received signal at the wiring closet, such as the power
`level. The difference between the known transmit power and
`the received power level would indicate the loss on the Cable
`Run for that frequency. A separate measurement can be done
`for any frequency of interest by generating a signal in that
`frequency and measuring the received power. Alternatively, a
`measurement at one frequency can be made and the result in
`combination with the known loss characteristics of the cable
`at different frequencies can be used to estimate the losses at
`other frequencies.
`0047 Equalization component can be adapted to achieve
`the equalization of losses on one or more cable runs by adjust
`ing the loss on the cable run to a pre-determined value in all
`cable runs that are to be adjusted. This can be implemented by
`incorporating again adjustment block for each frequency of
`interest at one end of each cable run, for example, in the
`Wiring Closet Unit. Based on the measurement of signal loss
`on each cable run, the correct gain setting can be applied to the
`gain adjustment block Such that the overall signal level at a
`particular location along the cable run will match the pre
`determined value. The gain adjustment block can be imple
`mented using a Digitally Controlled Attenuator (DCA),
`potentially in combination with an amplifier. Separate gain
`adjustment blocks can be provided for uplink and downlink of
`each frequency of interest. In some applications, only the
`downlink or only the uplink loss adjustment can be provided.
`0048. As shown in FIG.3, the system 300 according to the
`invention can include one or more antenna units 310, 312,
`314, 316, 318 and one or more wiring closet units (WCUs)
`330, 332,334, 336, 338 connected by a cable run 320, 322,
`324, 326,328. The Antenna Unit 310, 312,314,316,318 can
`include the antenna component or components that provide
`various functions as described herein. Antenna Units 310,
`312,314,316,318 can be deployed in the ceiling of a building
`and connected by Cable Run(s)320,322,324,326,328 to the
`Wiring Closet Unit(s) 330, 332, 334, 336, 338. The Wiring
`Closet Units 330, 332, 334, 336, 338 can be a component
`residing in the wiring closet and terminating the Cable Run
`320, 322, 324, 326, 328 to/from an Antenna Units 310, 312,
`314, 316, 318. In one embodiment, multiple Wiring Closet
`units 330, 332,334,336,338 can be integrated into a single
`physical enclosure. The Cable Runs 320, 322,324,326,328
`include the stretch of cable connecting an Antenna Unit 310,
`312,314, 316, 318 to its associated Wiring Closet Unit 330,
`332, 334, 336, 338. One or more aggregation units can be
`used to provide services that utilize an aggregated configura
`tion and Radio Source #1354, Radio Source #2356, Radio
`Source #3358, can be used to provide services that utilize a
`non-aggregated configuration.
`0049. In accordance with one embodiment of the inven
`tion, the Antenna Unit 400, as shown in FIG. 4, can have
`several functional blocks or components, including one or
`more antenna elements 410, 412, 414, 416, an activ