US007848747B2
`
`a2) United States Patent
`Wala
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,848,747 B2
`*Dec. 7, 2010
`
`
`
`(54) SYSTEM AND METHOD FOR ENHANCING
`THE PERFORMANCE OF WIDEBAND
`DIGITAL RF TRANSPORT SYSTEMS
`
`715
`(75)
`
`.
`Inventor:
`
`sys
`Philip M. Wala, Savage, MN (US)
`
`(73)
`
`tas
`.
`Assignee: ADC Telecommunications, Inc., Eden
`Prairie, MN (US)
`
`(*)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`US.C. 154(b) by 0 days.
`
`(56)
`
`References Cited
`US. PATENT DOCUMENTS
`
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`
`This patent is subject to
`claimer.
`
`a terminal dis-
`
`EP
`
`(21)
`
`Appl. No.: 12/606,755
`
`(22)
`
`Filed:
`
`Oct. 27, 2009
`
`(65)
`
`Prior Publication Data
`
`US 2010/0046641 Al
`
`Feb. 25, 2010
`
`FOREIGN PATENT DOCUMENTS
`0391597
`3/1990
`
`(Continued)
`OTHER PUBLICATIONS
`
`Grace, Martin K., “Synchronous Quantized Subcarrier Multiplexing
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`Publisher: IEEE.
`
`.
`(Continued)
`
`(63)
`
`(1)
`
`(52)
`
`(58)
`
`Related U.S. Application Data
`Continuation of application No. 11/398,879, filed on
`Apr. 6, 2006, now Pat. No. 7,610,046.
`
`Primary Examiner—Kamran Afshar
`(74) Attorney, Agent, or Firm—Fogg & Powers LLC
`
`(57)
`
`ABSTRACT
`
`Int. Cl.
`(2009.01)
`HOAW 4/00
`US. Che
`eeeeeeeeeereeeeeteees 455/424, 455/450, 455/509;
`370/347; 375/257
`Field of Classification Search .................
`455/424,
`455/560—562.1, 131, 323, 334, 502, 450-453,
`455/509; 370/395.21, 468, 310, 347, 350,
`370/304, 320, 329; 375/257, 240, 316; 398/334,
`398/58, 69, 115; 341/101—255
`See application file for complete search history.
`
`Asystem and method for enhancing the performance of wide-
`band digital RF transport systems is disclosed, which enables
`the transport of different bandwidth segments ona plurality of
`wideband channels by selecting an optimal clock sample rate
`for each bandwidth segment to be transported. Thus, the
`bandwidth segments are proportionally allocated so that an
`optimum amount of bandwidth can be transported at the serial
`bit rate.
`
`17 Claims, 2 Drawing Sheets
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`

`US 7,848,747 B2
`Page 2
`
`
`U.S. PATENT DOCUMENTS
`
`5,321,849 A
`5,339,184 A
`5,572,517 A
`5,627,879 A
`5,818,883 A
`5,898,693 A
`6,456,602 B1*
`6,728,763 Bl
`7,050,419 B2
`7,068,679 B1
`7,209,455 B2
`7,417,946 B2
`7,610,046 B2*
`7,642,939 B2*
`2002/0163937 Al
`2003/0026298 Al
`2004/0074025 Al
`2004/0101303 Al
`2004/0132474 Al
`
`6/1994 Lemson
`8/1994
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`11/1996
`Satadi
`5/1997 Russell et al.
`10/1998
`Smith et al.
`4/1999
`Vecchi et al.
`9/2002 Hwangetal. ....... 370/307
`4/2004
`Chen
`5/2006 Azenkot et al.
`6/2006 Brown et al.
`4/2007
`Yee et al.
`8/2008 Kimetal.
`10/2009 Wala ..ecccesecsecseesneeres 455/424
`1/2010 Naneviez
`341/101
`11/2002
`Svacek et al.
`2/2003
`Bisson et al.
`4/2004
`Blaustein et al.
`5/2004 Williams
`= 7/2004
`_-~Wala
`
`2004/0177153 Al
`2005/0010958 Al
`2005/0114903 Al*
`2006/0121944 Al
`2007/0071033 Al
`2008/0056192 Al
`2008/0240225 AL*
`
`Pelley
`9/2004
`1/2005. Rakib et al.
`al... 725/114
`5/2005 Ahmed et
`
`6/2006 Buscaglia et al.
`3/2007 Surek et al.
`3/2008 Strong et al.
`10/2008 Zavadsky et al. ........0. 375/240
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`wo
`WO
`wo
`
`0687084
`9115927
`0233969
`2004070582
`
`12/1995
`10/1991
`4/2002
`8/2004
`
`OTHER PUBLICATIONS
`Harvey et al., “Cordless Communications Utilising Radio Over Fibre
`Techniques for the Local Loop”, “IEEE International Conference on
`Communications”, Jun. 1991, pp. 1171-1175, Publisher: IEEE.
`
`* cited by examiner
`
`Page 2
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`CommScope Ex. 1028
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`

`

`U.S. Patent
`
`Dec. 7, 2010
`
`Sheet 1 of 2
`
`US 7,848,747 B2
`
`
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`

`U.S. Patent
`
`Dec. 7, 2010
`
`Sheet 2 of 2
`
`US 7,848,747 B2
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`

`US 7,848,747 B2
`
`1
`SYSTEM AND METHOD FOR ENHANCING
`THE PERFORMANCE OF WIDEBAND
`DIGITAL RF TRANSPORT SYSTEMS
`
`CROSS REFERENCES TO RELATED
`APPLICATIONS
`
`This application is a continuation of application Ser. No.
`11/398,879 filed on Apr. 6, 2006, entitled “SYSTEM AND
`METHOD FOR ENHANCING THE PERFORMANCE OF
`WIDEBAND DIGITAL RF TRANSPORT SYSTEMS” (cur-
`rently pending) which is hereby incorporated herein by ref-
`erence.
`
`FIELD OF THE INVENTION
`
`The present invention relates generally to the telecommu-
`nications field, and more specifically, but not exclusively, to a
`system and method for enhancing the performance of wide-
`band digital Radio Frequency (RF) transport systems.
`
`20
`
`BACKGROUND OF THE INVENTION
`
`In wireless voice and data communications, the digital
`transport of RF signals over long distances via fiber optic
`cables provides enhanced capacity, and higher performance
`distributed coverage than existing analog RF transport sys-
`tems currently being used. An example of such a digital RF
`transport system that links a digital host unit to one or more
`digital remote units to perform bi-directional simultaneous
`digital RF distribution is disclosed in U.S. Patent Application
`Publication No. 2004/0132474 A1, entitled “POINT-TO-
`MULTIPOINT DIGITAL RADIO FREQUENCY TRANS-
`PORT”, which is assigned to ADC Telecommunications, Inc.
`of Eden Prairie, Minn. and incorporated herein in its entirety.
`Notwithstanding the advantages of today’s digital RF
`transport systems over other types of RF transport systems, a
`significant problem exists in the transport of large amounts of
`digital RF bandwidth (e.g., wideband). For example, the
`existing wideband digital RF transport systems combine mul-
`tiple digitized signals and convey them in serialized form on
`a common physical layer between the transmit and receive
`devices involved. However, the problem with the existing
`digital RF transport systems is that they inefficiently transport
`equal amounts of bandwidth for different wideband channels.
`In other words, the serial bit streams on the transport layer that
`convey N wideband channels are all tied to one sample rate,
`and the system transport spectrum (RF) is sent point-to-point
`in equal bandwidth segments (e.g., 25 MHz blocks). Conse-
`quently, since many of the wideband channels have band-
`width requirements that are less (or different) than 25 MHz
`(e.g.,
`5 MHz, 10 MHz, 30 MHz, etc.), the overall bandwidths
`of existing wideband digital RF transport systems are sub-
`stantially underutilized. Therefore, a pressing need exists for
`a system and method that can enhance the performance of
`wideband digital RF transport systems, by maximizing the
`utilization of the transport bandwidth, custom tailoring the
`bandwidth allocations to specific user needs on a common
`platform, and enabling the use of lower cost transport system
`devices. As described in detail below, the present invention
`provides such a system and method, which resolves the
`above-described bandwidth underutilization problems and
`other related problems.
`
`SUMMARY OF THE INVENTION
`
`The present invention provides a system and method for
`enhancing the performance of wideband digital RF transport
`
`2
`systems, which enables the transport of different bandwidth
`segments on a plurality of wideband channels by selecting an
`optimal clock sample rate for each bandwidth segment to be
`transported. Thus, the present invention allocates the band-
`width segments proportionally so that an optimum amount of
`bandwidth can be transported at the serial bit rate. In accor-
`dance with a preferred embodiment of the present invention,
`a system for enhancing the performance of a wideband digital
`RF transport system is provided, which includes a transmit
`unit, a receive unit, and an optical transmission medium con-
`nected between the transmit unit and the receive unit. The
`transmit unit includes a plurality of wideband RF analog
`signal inputs coupled to a plurality of analog-to-digital, digi-
`tal down-converter (A/D DDC) devices. Notably, the sample
`rate of each A/D DDC device is determined by a respective
`sample clock. The digitized wideband RF signal segments at
`the outputs of the A/D DDC devices are combined and con-
`verted to a frame structure, converted to serial form, and
`transmitted on the optical transmission medium to the receive
`unit.
`A light detection device in the receive unit detects the
`serial bit stream of frames on the optical transmission
`medium, the serialized frames are converted back to the origi-
`nal frame format, and the original digitized wideband RF
`segments are reconstructed. Each digitized wideband RF seg-
`ment is coupled to a respective D/A digital up-converter (D/A
`DUC) device associated with a particular wideband RF signal
`input on the transmit side. Notably, the output sample rate of
`each D/A DUC device is determined by a respective sample
`clock, which provides the same sample rate as that of the
`associated A/D DDC device in the transmit unit. The sample
`rate of each A/D DDC device (and associated D/A DUC
`device) is pre-selected so that the transmission medium can
`transport the optimum amount of RF bandwidth at the given
`serial bit rate.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The novel features believed characteristic of the invention
`are set forth in the appended claims. The invention itself,
`however, as well as a preferred mode of use, further objectives
`and advantages thereof, will best be understood by reference
`to
`the following detailed description of an
`illustrative
`embodiment when read in conjunction with the accompany-
`ing drawing(s), wherein:
`FIG. 1 depicts a schematic block diagram of an example
`system for enhancing the performance of wideband digital
`RF transport systems, which can be used to implement a
`preferred embodiment of the present invention; and
`FIG. 2 depicts a pictorial representation of an example
`frame structure, which illustrates key principles of the present
`invention.
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENT
`
`55
`
`65
`
`With reference now to the figures, FIG. 1 depicts a sche-
`matic block diagram of an example system 100 for enhancing
`the performance of wideband digital RF transport systems,
`which can be used to implement a preferred embodiment of
`the present invention. System 100 includes a
`first communi-
`cations unit 101, a second communications unit 103, and a
`transmission (transport) medium 111 connected between first
`communications unit 101 and second communications unit
`103. For this example embodiment, first communications unit
`101 is a wideband digital RF transmit unit, second commu-
`nications unit 103 is
`a wideband digital RF receive unit, and
`transmission medium 111 is a single mode (or multi-mode)
`
`Page 5
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`CommScope Ex. 1028
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`US 7,848,747 B2
`
`3
`fiber optic cable. Although system 100 is depicted for illus-
`trative purposes as a unidirectional communications system,
`the scope of coverage of the present invention is not intended
`to be so limited, and system 100 could also be implemented as
`a bi-directional communications system (e.g., using a trans-
`ceiver on each side). Also, for this illustrative example, sys-
`tem 100 may be implemented as a point-to-point digital RF
`transport system for cellular radiotelephone voice and data
`communications, with a digital host unit (first communica-
`tions unit 101) that provides an interface between a plurality
`of base station RF ports and the fiber optic cable, and a digital
`remote unit (second communications unit 103) that provides
`an interface between the fiber optic cable and a remote
`antenna. Additionally, although the transmission medium 111
`is described as an optical transmission medium for this illus-
`trative embodiment, the present invention is not intended to
`be so limited and can include within its scope any suitable
`transmission medium (e.g., millimeter wave radio
`link,
`microwave radio link, satellite radio link, infrared wireless
`link, coaxial cable, etc.) capable of transporting a serial bit
`stream.
`For this example embodiment, first communications unit
`101 includes a plurality of input interfaces 102a-102n. Each
`input interface 102a-102n is implemented with an A/D DDC
`device, for this illustrative embodiment. An input of each A/D
`DDC device 102a-102n couples a respective analog fre-
`quency band (or channel) into the associated A/D DDC
`device. For example, each A/D DDC device 1024-1027 can
`accept an input analog frequency band (e.g., frequency band
`from a base transceiver station) at a relatively high rate, and
`digitizes and down-converts the respective frequency band to
`suitable digital real and complex (e.g., I/Q) baseband signals.
`For example, the output from each A/D converter section of
`an A/D DDC device 102a-102n can be a sequence of real
`samples, representing a
`real (positive frequency) signal
`within a designated Nyquist zone. The output from each DDC
`section can be a baseband signal (centered at zero Hz) with
`positive and negative frequencies, composed of two sample
`streams (real and imaginary components) with each stream at
`one half the sample rate of the equivalent real-valued signal.
`Notably, in the example embodiment depicted in FIG. 1,
`the input interfaces 102a-102n to communications unit 101
`are implemented with a plurality of A/D DDC devices that
`can accept a plurality of analog RF bandwidths, but the
`present invention is not intended to be so limited. In other
`embodiments, the input interfaces can be implemented with
`other types of input devices to accept other types of band-
`widths. For example, in order to accept a plurality of RF
`inputs, each input interface device 102a-102n can be imple-
`mented with a single A/D converter (no DDC) operating at IF
`(e.g., real digital output), dual A/D converters (no DDC)
`operating at baseband (e.g., complex I/Q digital output), or
`single or dual A/D converters operating at a high sample rate
`and followed by digital down-conversion (DDC) whereby the
`output is a lower sample rate representation (complex I/Q) of
`a portion of the original band. In another embodiment, each
`input interface device 102a-102n can be implemented by a
`direct digital input (typically baseband I/Q) from a digital or
`“software-defined” base station. In sum, the plurality of input
`interfaces 102a-102n can be implemented with any suitable
`input interface device(s) capable of accepting or inputting
`analog or digital wideband segments.
`For this example embodiment, each A/D DDC device
`102a-102n can be implemented as part of a modular (e.g.,
`pluggable) RF card capable of adjustable bandwidth selection
`that can be determined by user requirements. For example, in
`one embodiment, each A/D DDC device 102a-102n can be
`
`20
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`25
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`30
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`35
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`40
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`
`4
`implemented as part of an RF card that passes 5 MHz band-
`width segments. Notably, the sample rate of each A/D DDC
`device 102a-102n is determined by an associated sample
`clock 104a-104n. Therefore, by selecting a suitable sample
`rate for each A/D DDC device 102a-102n, the present inven-
`tion provides the ability to custom tailor the bandwidth allo-
`cations to specific user needs on the common transport plat-
`form being used.
`For example, one or more users may desire to transport a
`combination of one 5 MHz segment and three 15 MHz seg-
`ments from a digital host unit (e.g., first communications unit
`101) to a digital remote unit (e.g., second communications
`unit 103) via a fiber optic cable (e.g., transmission medium
`111). For a given serial bit rate on the fiber optic cable, a
`suitable sample rate may be selected for the sample clock
`104a-104n associated with each A/D DDC device 102a-102n
`to be used. For this example, assume that the 5 MHz segment
`is to be input to A/D DDC device 102a, and each of A/D DDC
`devices 1026, 102c and 102d (where “n” in this case is equal
`to 4) is designed to accept a respective one of the three 15
`MHz segments to be transported. The sample rate for sample
`clock 104a is selected to accommodate the transport of the 5
`MHz segment (band) at the given serial bit rate, and the
`sample rates for sample clocks 1045-104d are selected to
`accommodate the transport of the respective 15 MHz seg-
`ments at the given serial bit rate. In a practical application, the
`sample rates (e.g., approximately 45 Msps) of sample clocks
`1045-1044 are typically three times the sample rate of sample
`clock 104a (e.g., approximately 15 Msps) for a given serial bit
`rate on a fiber optic cable. In any event it should be readily
`understood that the present invention is not intended to be
`limited to a particular set of clock sample rates, the size of a
`frequency band that can be accepted by a specific A/D DDC
`device, the size of the frequency bands to be transported, or
`the serial bit rate for the optical transmission medium to be
`used.
`For example, a suitable clock sample rate can be selected to
`accommodate the transport of a 75 MHz segment (e.g., at 15
`times the clock sample rate used for a
`5 MHz segment) from
`the input of a particular A/D DDC device via a fiber optic
`cable at a specific serial bit rate. As another example, assume
`that each A/D DDC device 102a-102n is designed to process
`a 10 MHz band of frequencies. In this case, a suitable sample
`rate for each sample clock can be selected to accommodate
`the transport of a 10 MHz band and/or a band that is
`a multiple
`of 10 MHz (e.g., 30 MHz band at three times the sample rate
`of the sample rate used for the 10 MHz band). In other words,
`the present invention enables a user to transport just the
`required amount of bandwidth at the serial bit rate of the
`transmission medium to be used.
`For this example embodiment, the digitized output of each
`A/D DDC device 102a-102n is coupled to a mapper/framer
`device 106. Essentially, the mapper section of mapper/framer
`device 106 multiplexes together the digitized bands at the
`outputs of the plurality of A/D DDC devices 102a-102n, and
`the framer section of mapper/framer device 106 converts the
`multiplexed digitized bands into a suitable frame structure
`format. For example, in a practical application, the mapper/
`framer device 106 can construct a suitable frame structure
`that provides up to twelve (e.g.,
`5 MHz) slots per frame.
`However, it should be understood that the present invention is
`not intended to be limited to a specific number of slots per
`frame, and any suitable number of slots per frame may be
`used. In any event, the frame(s) containing the multiplexed
`band segments are coupled from mapper/framer device 106 to
`aserializer device 108, which converts the parallel frame data
`from the mapper/framer device 106 to a serial bit stream. The
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`serial data from serializer device 108 is coupled to an optical
`transmit device 110. The optical transmit device 110 pro-
`cesses and translates that data into coded light pulses that
`form a
`serial bit stream. An injection-laser diode or other
`suitable light source generates the light pulses, which are
`funneled with suitable optical lenses into the optical trans-
`mission medium (e.g., fiber optic cable) 111. For example,
`optical transmission medium 111 can be a single mode or
`multi-mode fiber optic cable. Notably, an optical transport
`medium is used for this illustrative embodiment, but the
`present invention is not intended to be so limited and can
`include within its scope of coverage any suitable transport
`medium that can convey a serial bit stream.
`For this example embodiment, second communications
`unit 103 includes a receive device 112, which includes a light
`sensitive device that detects the pulsed light signals (e.g.,
`serial bit stream of frames) on transmission medium 111,
`converts the light signals to digital signals, and conveys them
`in serial form to a deserializer device 114. Again, it should be
`understood that although a light sensitive device is used for
`this illustrative embodiment, the present invention is not
`intended to be so limited and can include within its scope of
`coverage any suitable device that can receive and/or detect a
`serial bit stream from the particular transport medium being
`used. Deserializer device 114 converts the serial frame data
`from receive device 112 to parallel frame data, which is
`coupled to
`a demapper/deframer device 116. Essentially,
`demapper/deframer device 116 demultiplexes the parallel
`frame data, and extracts the bandwidth segments from the
`demultiplexed frames. The extracted bandwidth segments are
`coupled to the inputs of the appropriate output interfaces
`118a-1187. For this illustrative embodiment, each output
`interface 118a-118x is implemented with a digital-to-analog
`(D/A) digital up-converter (D/A DUC) device. Each D/A
`DUC device 118a-118” converts the complex digital base-
`band signal to
`a real passband signal. For example, each
`digital baseband signal can be filtered, converted to the appro-
`priate sampling rate by a respective sample clock 120a-120n,
`upconverted to an appropriate frequency, and modulated onto
`an analog signal. For this example embodiment, the sample
`rate of each sample clock 120a-120n is selected to be the
`same as the sample rate of the corresponding sample clock
`104a-1047 in first communications unit 101. Thus, the analog
`bandwidth segments input to first communications unit 101
`are transported via optical transmission medium 111 as a
`serial bit stream, and reconstructed at the corresponding out-
`put in second communications unit 103.
`Notably, in the example embodiment depicted in FIG. 1,
`the output interfaces 102a-1027 of communications unit 103
`are implemented with a plurality of D/A DUC devices that
`can output a plurality of analog RF bandwidths, but the
`present invention is not intended to be so limited. In other
`embodiments, the output interfaces can be implemented with
`other types of output devices for other types of bandwidths.
`For example, in a second embodiment, in order to process a
`real digital signal at its input, each output interface 118a-1187
`can be implemented with a single D/A converter and analog
`up-conversion. In another embodiment, in order to process a
`complex digital signal at its input, each output interface 118a-
`118» can be implemented with dual D/A converters and ana-
`log up-conversion, or a DUC (e.g., digital up-conversion) and
`dual D/A converters. In sum, the plurality of output interfaces
`118a-1187” can be implemented with any suitable output
`interface device(s) capable of outputting analog or digital
`wideband segments.
`FIG. 2 depicts a pictorial representation of an example
`frame structure 200, which illustrates key principles of the
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`present invention. Essentially, the frame structure 200 shown
`in FIG. 2 illustrates how the present invention allocates band-
`width proportionally, which allows a user to maximize the
`amount of bandwidth that can be transported on the serial bit
`stream. As such, the present invention enables users to trans-
`port different bandwidths efficiently on a plurality of wide-
`band channels, instead of having to transport equal amounts
`of bandwidth inefficiently on those channels.
`Specifically, referring to this illustrative example, it may be
`assumed that four different bandwidths are to be transported
`by system 100 depicted in FIG. 1. As such, for this example,
`bandwidth A (5 MHz RF) is input to A/D DDC device 202a,
`bandwidth B (40 MHz RF) is input to A/D DDC device 2025,
`bandwidth C (25 MHz RF) is input to A/D DDC device 202c,
`and bandwidth D (5 MHz RF) is input to A/D DDC device
`202d. A respective sample clock 204a-204d inputs a unique
`sample rate to the associated A/D DDC device 202a-202d.
`The outputs from A/D devices 202a-202d are coupled to a
`mapper/framer device 206 and a
`serializer device (not
`shown), which multiplexes or combines the separate band-
`width segments (A, B, C, D) and constructs a suitable frame
`208 including the bandwidth segments for transport. For this
`example frame structure, assume that the frame rate
`is
`approximately 15 MHz, and each of the frame’s 12 slots
`includes 16 bits of digitized RF (with 14 bits of payload). The
`sample rate of sample clock 204a is selected to be approxi-
`mately 15 Msps (for 5 MHz bandwidth segments), approxi-
`mately 90 Msps for sample clock 2045 (for 40 MHz band-
`width segments), approximately 60 Msps for sample clock
`204c (for 25 MHz bandwidth segments), and approximately
`15 Msps for sample clock 204d (for 5 MHz bandwidth seg-
`ments). Thus, as illustrated by this example, the bandwidths
`in frame 208 are allocated proportionally, by transporting one
`slot for bandwidth A (5 MHz), six slots for bandwidth B (40
`MHz), four slots for bandwidth C (25 MHz), and one slot for
`bandwidth D (5 MHz).
`The description of the present invention has been presented
`for purposes of illustration and description, and is not
`intended to be exhaustive or limited to the invention in the
`form disclosed. Many modifications and variations will be
`apparent to those of ordinary skill in the art. These embodi-
`ments were chosen and described in order to best explain the
`principles of the invention, the practical application, and to
`enable others of ordinary skill in the art to understand the
`invention for various embodiments with various modifica-
`tions as are suited to the particular use contemplated.
`
`What is claimed is:
`1. A method, comprising:
`receiving a plurality of analog inputs each having an asso-
`ciated bandwidth containing an arbitrary number of
`channels;
`sampling each of the plurality of analog inputs with a
`selected sample rate, the selected sample rates selected
`based on the bandwidth of the associated one of the
`plurality of analog inputs;
`combining the samples of the plurality of analog inputs;
`converting the combined samples to a serial data stream;
`and
`transmitting the serial data stream over a communication
`medium.
`2. The method of claim 1, wherein receiving a plurality of
`analog inputs comprises receiving a plurality of analog RF
`bands from a plurality of base stations, each band including a
`number of channels.
`3. The method of claim 1, wherein sampling each of the
`plurality of analog inputs comprises:
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`converting the analog input to digital samples; and
`down-converting the digital samples.
`4. The method of claim 1, wherein combining the samples
`comprises combining the samples into slots of a frame.
`5. The method of claim 1, and further comprising:
`receiving the serial data stream over the communication
`medium;
`deserializing the serial data stream to parallel data;
`demultiplexing the parallel data; and
`converting the parallel data to reproduce the plurality of
`analog inputs.
`6. The method of claim 1, wherein the sample rate is
`proportional to the bandwidth of the associated one of the
`plurality of analog inputs.
`7. A host unit for wideband digital RF transport, the unit
`comprising:
`aplurality of inputs, each input coupled to receive a broad-
`band RF signal;
`a plurality of analog to digital converter circuits, each
`coupled to a selected one of the plurality of inputs, each
`analog to digital converter circuit generating a sample
`stream, wherein each analog to digital converter circuit
`operating at a sample rate related to a signal bandwidth
`of its associated broadband RF signal; and
`amultiplexer circuit for multiplexing together the plurality
`of sample streams into one serial bit stream at a fixed bit
`rate.
`8. The host unit of claim 7, wherein each of the plurality of
`analog to digital converter circuits comprises one of (1) a
`single analog to digital converter operating at IF, (2) a dual
`analog to digital converter circuit operating at baseband, and
`(3) an analog to digital converter operating at a high sample
`rate followed by a digital down converter.
`9. The host unit of claim 7, wherein each of the plurality of
`analog to digital converter circuits comprises a pluggable RF
`card that is programmable to pass broadband RF bandwidth
`in multiples ofa selected unit bandwidth based on the selected
`sample rate.
`10. The host unit of claim 7, wherein the multiplexer circuit
`comprises:
`a mapper that multiplexes together the plurality of sample
`streams;
`a framer, coupled to the mapper, the framer converts the
`multiplexed sample streams into slots of a frame; and
`a serializer which converts the frame into the serial bit
`stream at the fixed bit rate.
`11. A host unit for wideband digital RF transport, the unit
`comprising:
`aplurality of inputs, each input coupled to receive one of a
`direct digital input of an RF bandwidth and a broadband,
`analog RF bandwidth;
`wherein each of the plurality of inputs that receives a
`broadband, analog RF bandwidth includes an analog to
`digital converter circuit that samples the associated
`broadband analog RF bandwidth with a selected sample
`rate, the selected sample rates selected based on the
`bandwidth of the analog signal;
`amapper/framer device, an output of each input coupled to
`an input of said mapper/framer device, the mapper/
`framer device multiplexes together the direct digital
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`inputs and the sampled, broadband analog RF band-
`widths into a frame structure; and
`a serializer that serializes the output of the mapper/framer
`into one serial bit stream at a fixed bit rate.
`12. The host unit of claim 11, wherein the analog to digital
`converter circuit converts the analog signal to a digital signal
`and down-converts the digital signal.
`13. The host unit of claim 11, wherein the analog to digital
`converter circuit comprises one of (1) a single analog to
`digital converter operating at IF, (2) a dual analog to digital
`converter circuit operating at baseband, and (3) an analog to
`digital converter operating at a high sample rate followed by
`a digital down converter.
`14. A wideband digital RF transport system comprising:
`a host unit coupled to a remote unit over a transmission
`medium;
`the host unit including
`a plurality of inputs that receive a plurality of RF band-
`width segments, each segment having an arbitrary
`number of channels, each input configured to receive
`either a direct digital input of an RF bandwidth seg-
`ment or an analog RF bandwidth segment;
`a mapper/framer devi