Abstract:
A communication system comprising a network having a legacy band and an extendable frequency band, a head end, and a user end, wherein said head end processes and splits source data into multiple signals and transmits said multiple signals over multiple physical channels over said extendable frequency band, and wherein said user end containing multiple receivers and a data reconstructor receives said multiple signals and recovers said source data. Another embodiment includes a communication system comprising a network having a legacy band and an extendable frequency band, a head end; and a user end, wherein said user end processes and splits source data into multiple signals and transmits said multiple signals over multiple physical channels over said extendable frequency band and wherein said head end receives said multiple signals and recovers said source data. Other embodiments include methods of communication over a network having a legacy band and an extendable frequency band.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to communication systems and in particular to communications over cable or wired networks primary designed for transmission of television and data signals. The present invention relates to data (or signal) transfers from the one or more head ends to the one or more user ends, i.e., the “forward path” or “downstream” and from the one or more user ends to the one ore more head ends, i.e., the “return path” or “upstream”.  
       BACKGROUND OF INVENTION  
       [0002]     As the number of internet users and the popularity of transferring large sized data increases, there has been a tremendous demand for systems that can serve a higher number of users (i.e., systems with a higher “capacity”) and provide those users with larger data within a short time duration (i.e., high data transfer rate or data rate). High demand for high data transfer rate is inevitable as applications which require vast amount of data being transferred per unit time continue to emerge.  
         [0003]     Presently, in the United States, the most common communication systems that offer high data rate (“broadband” or “high speed”) to commercial internet users are digital subscriber line (“DSL”) and cable modem systems. Fiber to the home (“FTTH”) provides very high data rate, but even with the recent advances in optical technologies, the cost of bring in the connection to the house (“the last mile”) is still prohibitively higher compared to those two widely adapted technologies. Therefore, it is highly desired that the data transfer rate of the widely adapted cost effective technologies is improved.  
         [0004]     The majority of current cable systems are based on Hybrid Fiber-Coax (HFC) architecture, which provides two-way, high-speed data access to the home, business, and the like using a combination of optical fiber and traditional coaxial cable along with electrical, optical, and electro-optical elements. An HFC network is an example of a wired network, even though it has optical fibers and other components. In  FIG. 1 a  block diagram of a prior art HFC cable system is shown. Head end  101  interfaces to optical network  100 . Optical network  100  consists of optoelectronic transceiver nodes  105  and optical fiber network  106 . Optical network  100  may contain elements such as optical amplifiers, hubs, splitters, etc. which are not shown in  FIG. 1 . Transceiver nodes  105  convert downstream optical signals to electrical signals and convert upstream electrical signals to optical signals. Distribution amplifiers  107  are used to compensate for any signal losses encountered while the signals propagate through the coaxial cable network  108 . Note that distribution amplifiers  107  provide amplification to both downstream and upstream signals. The coaxial cable network  108  distributes signals to sub trees  109 , which are consist of various user ends such as cable modem (CM)  110 , set top box (STB)  112 , digital cable TV, and so on. The coaxial cable network  108  and sub trees  109  may contain other elements such as signal splitters, taps, and other elements which are not shown in  FIG. 1 . Signals generated or received by cable modem termination system (CMTS)  102  are respectively sent or received through downstream (DS)  103  or upstream (US)  104  blocks. As can be seen from  FIG. 1 , downstream (DS)  103  may split a signal into several optoelectronic transceiver nodes  111  at which the electrical signals are converted to optical signals. Similarly, the optoelectronic transceiver nodes  111  connected to upstream (US)  104  convert return-path optical signals to electrical signals and the signals may be combined at upstream (US)  104  block. In the following paragraphs and figures, those multiplicities of DS and US signals are not shown. Note that downstream (DS)  103  and upstream (US)  104  blocks may contain frequency converters.  
         [0005]      FIG. 2  depicts a prior art DOCSIS (Data Over Cable Service Interface Specification) cable modem  161  connected to hybrid fiber coax (HFC) network  150  through a coax cable  151 . The current version of US DOCSIS, version 2.0, assigns downstream spectrum to 88 MHz to 860 MHz and upstream spectrum to 5 MHz to 42 MHz. Downstream signals occupying the downstream spectrum enters the DOCSIS cable modem  161  through coax cable  151  which is connected to F-connector  152 . Diplexer  153  is a frequency selective block which consists of a high pass filter (HPF) for downstream and a low pass filter (LPF) for upstream. Diplexer  153  isolates the upstream signal path from the downstream path while allowing a common connector to be used to connect to HFC network  150 . Tuner  154  tunes to a certain channel located in the downstream spectrum and produces, after appropriate amplification, filtering, and frequency conversion, and other similar processes, either intermediate frequency (IF) or baseband output signal that is fed to the analog to digital converter (ADC) in DOCSIS cable modem element or a data re-constructor  155 . The gain of Tuner  154  is controlled by DOCSIS cable modem element  155 . The ADC produces digital signals which are subsequently demodulated, error detected and corrected. Security processing, equalization, and any other required processes may also be applied to the demodulated data. For transmission of upstream data, the data is encoded for forward error correction, modulated, and then converted to analog signal by the digital to analog converter (DAC). The DAC output signal is filtered by BPF  159 , whose intended function is to avoid undesired folding of signals to the desired transmission signal band. PA  160  amplifies the filtered signal and the amplified signal passes through the LPF portion of the diplexer  153  before the transmission signal leaves the DOCSIS cable modem  161  to the HFC network  150 . The gain of PA  160  is controlled by DOCSIS cable modem element  155 . A media access control (MAC) within a DOCSIS cable modem element  155  functions as a “master” within the DOCSIS cable modem  161 , which governs various functions such as assigning upstream frequency and time slots, compensating cable delays, adjusting upstream power level, etc. The DOCSIS cable modem element  155  may contain a memory interface to external memory  156 . A user&#39;s computer  158  is connected to the DOCSIS cable modem  161  through Ethernet PHY  157 . A newer cable modem device may include a wireless LAN interface.  
         [0006]      FIG. 3  shows the spectrum allocation (not to scale) based on DOCSIS Radio Frequency Interface Specification, SP-RFIv1.1-106-001215. In  FIG. 3  the shaded areas represent channel bandwidths, which are 6 MHz for each downstream channel and 200, 400, 800, 1600, or 3200 kHz for each upstream.  
         [0007]     Some attempts in improving data transfer rate have been made. For instance, Chapman, et al. (U.S. Published Application No. 2004/0163129) has shown a way to improve down-stream data rate for a cable system based on the DOCSIS standard. However, this reference does not support up-stream high data rate and also a significant reduction in capacity is expected if a high data rate was to be maintained for all the participating users of the system since the current DOCSIS standard allocate radio frequency (RF) spectrum for down stream only up to 860 MHz.  
         [0008]     There is also prior art technology that takes advantage of the broad band nature of an HFC network and allocates additional down stream and up stream RF bands in the approximately 1 GHz to 3 GHz frequency range which is not currently utilized. A block diagram of this type of prior art is depicted in  FIG. 4 . Frequency converter  203  up-converts an additional downstream band to approximately 1 to 2 GHz and down-converts an additional upstream band centered around 2.3 GHz to the approximately 10 to 42 MHz. Wideband amplifiers  204  and wideband passives  205  replaces existing blocks whose frequency range is limited to about 1 GHz. At the user&#39;s premise, frequency converter  206  is placed external to the user&#39;s end equipment  207  and  208 . Frequency Converter  206  down-converts the additional downstream band back to the 50 MHz to 860 MHz band and up-converts the upstream signals out of the multiple cable modems to the 2.3 GHz band. The added signals are handled by fiber node  202 , which employs wavelength division multiplexing (WDM). The optical signals are sent/received through optical fiber network  201 . At head end  200 , the upstream optical signals are converted to electrical signals and further processed to recover each data stream from the user&#39;s end equipment  207  and  208 . At head end  200 , the downstream electrical signals are converted to optical signals for transmission though the optical fiber network  201 . Even though this technology utilizes the “extended” RF spectrum and provides vastly higher capacity than the existing DOCSIS system, it does not provide users higher data transfer rate per modem.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a block diagram of a prior art cable system consists of Hybrid Fiber Coax (HFC) cable network, head end and user end equipment;  
         [0010]      FIG. 2  is an illustration of a prior art DOCSIS cable modem connected to a HFC network via a coaxial cable;  
         [0011]      FIG. 3  is an illustration of signal spectrum assigned for upstream and downstream path by US DOCSIS;  
         [0012]      FIG. 4  is an illustration of a prior art high capacity cable system utilizing frequencies above 860 MHz;  
         [0013]      FIG. 5  is an illustration of an example of a set of frequency bands added to above the legacy band;  
         [0014]      FIG. 5A  is a detailed illustration of an example of a new upstream band;  
         [0015]      FIG. 5B  is a detailed illustration of an example of a new downstream band;  
         [0016]      FIG. 6  is a block diagram of a system capable of high data rate communication while achieving high network capacity;  
         [0017]      FIG. 7  is another block diagram of a system capable of high data rate communication while achieving high network capacity;  
         [0018]      FIG. 8  is an illustration of multi-duplexer operation;  
         [0019]      FIG. 9  is an illustration of an example of high data rate receiver utilizing two receivers utilizing two different physical channel bandwidths;  
         [0020]      FIG. 9A  is a flowchart showing processes when there is a failed physical channel(s) while in communication;  
         [0021]      FIG. 9B  is another flowchart showing processes when there is a failed physical channel(s) while in communication;  
         [0022]      FIG. 10  is an illustration of an example of high data rate cable modem capable of maximally two times the data transfer rate of a legacy cable modem;  
         [0023]      FIG. 11  is an illustration of an example of high data rate digital video receiver capable of maximally three times the data transfer rate of a legacy digital video receiver;  
         [0024]      FIG. 12  is an illustration of example of a versatile high data rate set top box capable of receiving maximally three times the data transfer rate of a legacy digital video receiver, receiving and transmitting data maximally two times the data transfer rate of a legacy cable modem, and supporting legacy analog TV/VCR;  
         [0025]      FIG. 13  is an illustration of high data rate capable cable system supporting various cable equipment including legacy user ends and high data rate capable user ends. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0026]     Embodiments of the claimed subject matter can provide both high data rate and high capacity in a communication system. Not only is a high data rate for downstream possible but a high data for upstream is also possible. This can also work with low data rate if a very high system capacity is desired. An embodiment may also be used with high data rate bidirectional communication over an HFC network without incurring reduced capacity and incompatibility with the legacy cable system.  
         [0027]     In the paragraphs that follow, the term signal corresponds to a modulated waveform with data or it may consist of a modulated portion and an unmodulated portion that are used for actual transmission and reception over various mediums such as copper cable, optical fiber, air, and the like. A signal can be either an electrical signal or an optical signal and one network may be made up of two or more networks to form a single network.  
         [0028]     While maintaining high data rate communication, the capacity of embodiments of the claimed subject matter can be increased over the capacity of the traditional legacy system by utilizing the previously unused RF spectrum. No additional devices or blocks should need to be added to the users end equipment since the required RF front-end blocks are all built into user&#39;s end equipment. Legacy equipment and embodiments can coexist in a system, for instance from “legacy” type to “2×” or “3×” data-rate user end equipment provided that the system supports the maximum data rate. In the following descriptions of embodiments of the claimed subject matter, the embodiments and examples shown should be considered as exemplars, rather than as limitations of the claimed subject matter. Furthermore, reference to various features in any one ore more embodiments throughout this document does not mean that all claimed embodiments or methods must include the referenced feature.  
         [0029]     In the paragraphs that follow, data corresponds to information in numerical form that can be solely information itself or also contain redundancy or extra information that can be processed to be useful, such as for error correction and other controlling purposes.  
         [0030]     One embodiment of the claimed subject matter utilizes the cable frequency spectrum allocation shown in  FIG. 5 . While maintaining the legacy band  300  intact, two additional upstream bands ( 304  and  306 ) and one additional downstream band  305  are placed in the frequency range above the legacy band  300 , which includes upstream band 1   302  and downstream band 1   303 . The ranges of frequencies occupied by these additional bands  304 , 305 , and  306  are determined or changed by a system architect considering required data rate improvement, capacity, ease and cost of implementation, and the like. Note that the individual physical channel widths, whether for upstream or downstream, can be the same as those of the legacy system or the widths can be different from those of the legacy system and varied dynamically so as to reduce network load and/or improve network reliability. For example, bands  304 , and  305  of  FIG. 5  can have channels widths shown respectively as in  FIG. 5A , and  FIG. 5B . A multiplicity of physical channels, whether for up stream or downstream, can be fixed or dynamically varied provided that the minimum guaranteed data transfer rate for a particular user is maintained. A system is normally constructed to provide a minimum guaranteed data rate to the participating users. For example, a system may be constructed so that the users are provided with 25 M bits per second (bps) under the worst-case scenario. Because the number of physical channels used for communication varies and each channel width may vary, a logical channel width, which is associated with the physical channels may also vary. Guard bands  307 , which are defined as the frequency spacing between two neighboring bands, such as shown between bands  304  and  305  and between bands  305  and  306 , are allocated in order to achieve required isolation between upstream and down stream communication.  
         [0031]     Embodiments Related to Bidirectional High Data Rate Cable Systems  
         [0032]      FIG. 6  illustrates an embodiment utilizing new band  407  placed above legacy band  406  and locations of multiple physical channels that can exist within the new band  407 . One or more physical channels associated with a high data rate logical channel can exist entirely or partially in the new band  407 , in the legacy band  406 , or in both bands  406  and  407 . In other words, downstream physical channels can be anywhere that is assigned as a downstream band and upstream physical channels can be anywhere that is assigned as an upstream band. If one or more downstream signals are sent over physical channels in the new band  407 , one or more frequency converters  403  up convert the downstream signals to physical channels in the new band  407 . If upstream signals are received from physical channels in the new band  407 , one or more frequency converters  403  down convert the upstream signals to one ore more physical channels in the legacy band  406  or in a band whose highest frequency component can be processed by the high data rate capable head end  400 . In other words, the bandwidth of the upstream portion of new band  407  does not need to be the same as that of the upstream portion of the legacy band  406  provided that the high data rate capable head end  400  is capable of processing the down-converted upstream portions of the new band  407 . Embodiments can be used so that upstream signals are down converted to a band in which interference signals such as ingress, impulse nose, or/and common mode distortion can be avoided or in which the detrimental effect of such interference signals can be mitigated. Similarly, the bandwidth of the downstream portion of the new band  407  does not need to be the same as that of the bandwidth of the downstream portion of the legacy band  406  provided high data rate capable cable user end equipment  408  is capable of processing the bandwidth of downstream portion of the new band  407 . To avoid RF related issues, multi-duplexer  410 , which is a block made up with multiple frequency selective components (i.e. filters) can be inserted before the mixing process takes place in the one or more frequency converters  403 . Multi-duplexer  410  will be described in detail in later section.  
         [0033]     Fiber node  402  utilizes wavelength division multiplexing (WDM) to assign “colors” to information carrying signals. WDM may not be necessary if multiple fibers each are carrying a certain wavelength of light. By placing the frequency converter  403  external to the high data rate capable head end  400 , an arrangement can be made so that the high data rate capable head end  400  has to deal with signals inside or in the close vicinity of the legacy band  406  and hence no hardware upgrades are needed for the high data rate capable head end  400 , optical fiber network  401 , and fiber node  402 . The high data rate capable head end  400  contains one or more fiber nodes, which may use WDM, that convert the upstream optical signals back to electrical signals and convert the downstream electrical signals to optical signals. The high data rate capable head end  400  may contain other features/functions such as one or more frequency converters, filters, signal splitters/combiners, analog to digital converter(ADC)s, digital to analog converter (DAC)s, and other blocks, features, and/or functions (implemented in either hardware or software) that can be used to process signals and data.  
         [0034]     In embodiments wherein high data rate communications are desired, high data rate capable head end  400  creates and assigns one ore more high data rate logical channels to one or more physical channels to help manage the flow of high data rate upstream and downstream communications. One or more signals may be sent in parallel, through one or more physical channels, but not necessarily simultaneously over the high data rate capable HFC network  409 . As is the case for a prior art HFC network, the high data rate capable network  409  may contain elements such as optical amplifiers, hubs, splitters, etc. which are not shown in  FIG. 6 .  
         [0035]     In an embodiment wherein the high data rate capable head end  400  sends out data bearing signals over one or more physical downstream channels, high data rate capable user end equipment  408  receives and demodulates the down stream signals. The demodulated data are then signal processed and combined to recover the high data rate downstream data. If required, data buffer or cache memory may be used for temporary data storage. Any necessary processing of recovering, or reconstructing the original source data from the received downstream signals may be done by a single stage defined as a data re-constructor.  
         [0036]     In embodiments for transmission of high data rate upstream from high data rate capable user end equipment  408 , data is first split and signal processed. After permission for transmission is granted by the high data rate capable head end  400 , modulated (and frequency up converted, if necessary) upstream signals are sent via one or more upstream physical channels that are assigned by the high data rate capable head end  400 . The high data rate capable head end  400  receives and demodulates the upstream signals sent over the high data rate capable HFC network  409  and head end  400  signal processes to recover the high data rate upstream data. High data rate capable head end  400  may also contain data buffer or cache memory for temporary data storage. The multiplicity of physical channels may be configured to help reduce communication latency.  
         [0037]     In order to reduce the effect of burst errors, which occur frequently in practice, spreading of data over time, commonly known as interleaving can be used for both downstream and upstream data. Forward error correction (FEC) is very effective on errors that are spread apart in time.  
         [0038]     Note that broadband distribution amplifiers  404  and broadband passives  405 , for example splitters/combiners, taps, and the like, may need to be inserted to replace those of legacy HFC network to support the added high frequency bands. With existing technologies, the maximum frequency response of these broadband blocks can be up to 5 to 10 GHz.  
         [0039]      FIG. 7 . illustrates another embodiment in which up and down frequency conversions are taking place at high data rate capable head end  502 . High data rate capable head end  502  consists of one or more high data rate capable CMTS  501 , up/down converters  500 , frequency selective blocks (e.g., multi-duplexer)  503 , and optical nodes  504 . In comparison to the previous embodiment, this embodiment may facilitate the transition to a high data rate capable service since up and down frequency conversion processes are not done by a frequency converter deployed in high data rate capable HFC network  512  but rather by a high data rate capable head end  502  located at a service provider. High data rate capable HFC network  512  consists of optical fiber network  505 , optical node  506 , wideband bidirectional amplifiers  507 , wideband passive elements  508 , and other necessary elements/features not shown in  FIG. 7 . As in the previous embodiment, high data rate capable user end equipment  511  may contain one or more frequency converters.  
         [0040]     Embodiment Illustrating a Multi-Duplexer  
         [0041]     A multi-duplexer is defined as a multi-port block whose signal that enters or leaves the common port is separated by frequency selective stages (i.e. filters) in one ore more prescribed ways. As illustrated in  FIG. 8 , multi-duplexer  600  is shown with two downstream bands and three upstream bands. Multi-duplexer  600  can be implemented with a set of inductive/capacitive elements (lumped or/and distributed), semiconductor integrated circuits, dielectric material filters, surface acoustic wave (SAW) filters, piezoelectric filters, ceramic filters, coupled cavities, crystal filters, Microelectromechanical (MEM) filters, or any combinations of the aforementioned. Multi-duplexer  600  may also contain switch elements for signal flow controlling purposes. Multi-duplexer  600  separates the frequency bands and provides high isolation between upstream and downstream paths. With the appropriate frequency planning, that is, with the proper selection of downstream and upstream band locations and associated guard bands, multi-duplexer  600  can be used by those skilled in the art to help mitigate other RF related impairments such as image/spurious mixing, non-linear effects that causes composite triple beat (CTB), composite second order (CSO), cross modulation (XMOD), and spurious signal emissions, and the like. For example, designing an upstream filter with center frequency of 1.7 GHz and bandwidth of 60 MHz and a downstream filter with center frequency of 2 GHz and bandwidth of 80 MHz is relatively easier, assuming the same isolation, than designing an upstream filter with center frequency of 1.9 GHz and bandwidth of 60 MHz and a downstream filter with center frequency of 2 GHz and bandwidth of 80 MHz because the filter pass bands of the former case are much farther apart.  
         [0042]     Embodiments Illustrating Uses with Non-Legacy Communication Techniques  
         [0043]     New spectrums placed in the frequency range, that were previously not used, pave the way for non-legacy communication techniques (e.g., non-DOCSIS or non-previous DOCSIS based in the case of communication over a HFC network.) These techniques include spectrum efficient modulation schemes and/or more advanced multiple access techniques which can be used without affecting existing technologies that are used in a legacy band. Examples of those non-legacy techniques may include Orthogonal Frequency Division Multiplexing (OFDM), multi carrier code division multiple access (MC-CDMA), and Hybrid FDMA/CDMA (FCDMA). Other advances may include techniques that allow the inclusion of more data into a single channel. It should be apparent to one skilled in the art that the current legacy techniques do not have to be permanently used for communication through the legacy band, rather, a gradual transfer to more advanced techniques would be desirable for communication through the legacy band utilizing proper planning involving both the legacy bands and the new bands.  
         [0044]     Transmission and reception of signals at higher frequency often impose more stringent performance requirements on the RF component blocks. Examples of the most stringent requirement include the low noise figure (NF) required for the downstream and upstream RF blocks. If this instance, instead of implementing the blocks with high performance semiconductor processes which are often not cost effective, narrower channel bandwidth can be used to reduce the effect of thermal noise. For example, instead of using the traditional 6 MHz downstream channel width, a 4 MHz downstream channel width may be used and the resultant substitution would reduce the downstream tuner NF requirement by 10log(6/4)=1.72 dB. Thus, if a tuner with a 4 MHz channel bandwidth is used with a tuner with a 6 MHz channel bandwidth, the resulting maximum data rate will not be two times the previous legacy system utilizing 6 MHz channel bandwidth data rate, but rather 1.67 times the legacy system provided that other pertinent parameters remain the same.  
         [0045]     This example is shown in  FIG. 9  wherein receiver  700  consists of duplexer  701  which separates legacy band Dn 1  and new band Dn 2 , 4 MHz channel bandwidth tuner  702  which may include an additional down converter, 6 MHz channel bandwidth tuner  703 , and data reconstructor  704  which performs demodulation, signal processing, and data combining to recover the data sent. The reduced channel width results in lower data rate transmission per channel. However, with more advanced techniques such as OFDM, it may be possible to achieve high data rate even with a narrow channel width. Nevertheless, the use of multiple physical channels for communication, as described in this present specification, can yield very high data rate even when a narrow channel width is used for each channel because the number of multiplicity can be arbitrarily increased as long as the implementation efforts remain reasonable.  
         [0046]     Embodiments Illustrating Improved Communication Reliability  
         [0047]     The use of multiple physical channels can be used to improve communication reliability. For instance, if one or more of multiple downstream paths becomes non-functional, the remainder of the one or more still functioning downstream channels can still be used so that the subscriber continues to receive downstream data. If a failure is detected, the receiver can acknowledge the sender by using one or more upstream channels and send a signal that the failure has occurred. In embodiments of the claimed subject matter, the sender could be either a head end or a user end, depending on the direction of communication. Similarly, a receiver could be either a head end or a user end, depending on the direction of communication. The sender may in turn processes the data accordingly to maintain communication with the remaining channels. The failed channel may be recoverable by such processes as the re-initialization of the hardware associated with the channel. If the failed channel cannot be recovered, a new channel can be assigned to the failed channel. Once the sender recognizes that the failed channel has either been recovered or that a new channel has been successfully assigned to the failed channel, the sender reassembles the data and resumes transmission using the full number of channels. If the failed channel is non-recoverable, the sender may continue sending data using the remaining channels at a reduced data rate.  
         [0048]      FIG. 9A  and  FIG. 9B  depict two possible scenarios after a channel failure is detected. In the first illustration  FIG. 9A , the failed channel is reset before the sender makes the choice between dropping the failed channel or resuming communication with the full number of channels. In the second illustration, the procedures described above are completed. Prior art that uses single physical channel per upstream or downstream communications, such as a DOCSIS based cable modem or a DOCSIS based digital set top box, require, when encountering a channel failure, a hardware replacement or a hardware reset which results in the temporary cessation of communication in order to resume communication.  
         [0049]     Embodiments Illustrating a High Data Rate Capable Cable Modem  
         [0050]      FIG. 10  is a block diagram of an embodiment designated as high data rate capable cable modem  800 . This particular embodiment has double the legacy data rate (2×) downstream and double the legacy data rate (2×) upstream capability. The F-connector  804  is connected to the high data rate capable HFC network through a single coaxial cable  803 . No external frequency conversion unit is required as all the required blocks are integrated into the modem.  
         [0051]     Multi-duplexer  805  separates the Dn 1  legacy downstream band in legacy band  801 , the Dn 2  new downstream band in new band  802 , the Up 1  legacy upstream band in legacy band  801 , and the Up 2  new upstream band in new band  802  from each other. Multi-duplexer  805  also may provide high isolation between the upstream and downstream paths. The characteristics of the multi-duplexer  805 , such as pass bandwidths, out of band rejections, and the like, can be set such that there would be mitigation of other RF related impairments such as image/spurious mixing, non-linear effects that causes composite triple beat (CTB), composite second order (CSO), cross modulation (XMOD), and spurious signal emissions.  
         [0052]     In this embodiment, down-converter  806  takes one or more signals from one of the outputs of multi-duplexer  805 , whose spectrum lies only around Dn 2  in new band  802 , and frequency converts the signals to band Dn 2 ′ with the appropriate intermediate frequency (IF). The IF is selected so that the bandwidth of the downstream portion of new band  802  lies within, or close to legacy band  801  so that legacy tuners  807  can be reused and hence no high cost or high performance tuner is needed. Each of the legacy tuners  807  can be packaged into various forms, for example, each tuner  807  can be packaged into a small module that can be plug into an electrical socket without soldering so that replacement of failed unit can be easily accomplished. In this embodiment, the down-converted band, Dn 2 ′ does not need to occupy the whole legacy downstream band, rather it only exists within or close to the legacy band so that legacy tuner  807  can operate. Embodiments may include a bandwidth of the downstream portion of new band  802  that is less than that of legacy band  801  so that linearity requirements of the downstream blocks are reduced. Legacy tuner  807  may produce intermediate frequency (IF) signals or I/Q baseband signals to data reconstructor  809  that follows. Down-converter  806  may be implemented as a set of discrete components or/and as an integrated circuit (IC) in various semiconductor processes such as bipolar junction transistor, silicon-germanium (SiGe), gallium arsenide (GaAs), or/and complementary metal-oxide semiconductor (CMOS). Down-converter  806  may include or consist of one or more of the following: a frequency converter, a local oscillator which is typically implemented as a frequency synthesizer utilizing phase-locked loop (PLL), a fixed gain, a variable gain amplifier, and other stages such as impedance matching or filtering. Legacy turner  807  may also include the down-conversion functionality.  FIG. 10  illustrates an embodiment of a typical portioned system. The degree of amplification or gain of legacy tuner  807  and/or down-converter  806  are individually controlled by data reconstructor  809 .  
         [0053]     Data reconstructor  809  performs demodulation, modulation, encoding, decoding, equalization, media access control (MAC), and any other signal processing required. Data reconstructor  809  includes one or more ADCs that take outputs from legacy tuners  807  and produce digital signals which are subsequently demodulated and signal processed. In the aforementioned embodiments, the functional “boundary” between legacy tuner  807  and data reconstructor  809  can vary. For instance, legacy tuner  807  may contain A/D conversion elements and output unprocessed data to data reconstructor  809 .  
         [0054]     The demodulator&#39;s demodulation capability may be changed “on the fly”. For instance, the demodulator may demodulate a 256 QAM signal and after a software request, it may demodulate a 8 VSB signal. Similarly, data reconstructor  809  may dynamically support various multiple protocols. The data recovered from multiple physical channels are combined to recover the original source data that was being sent. For transmission of signals that are carrying high data rate data, the data is first split, individually encoded, modulated, and then converted to analog signals by one or more digital to analog converters (DACs). The modulators can be I/Q modulators or digital modulators whose output signal is ether at intermediate frequency (IF) or at radio frequency (RF). The modulator&#39;s modulating capability may also be changed “on the fly”. For instance, the modulator may modulate a 64 QAM signal and after a software request, it may produce a QPSK OFDM signal. In embodiments of the claimed subject matter, the frequency ranges of signals from the modulators do not need to be identical. The bands may be partially overlapped or even separated if the interactions between the bands cause unwanted effects such as spurious signal generation, degraded modulation quality, and the like.  
         [0055]     Certain upstream or downstream channels that may not usable due to undesired interactions between the multiple paths can be avoided by having a lookup table and avoiding these problematic channels or by using dynamically, pre-determined in the design phase, or set/reset during operation “clean,” clearer or non-failing channels. Data reconstructor  809  may be implemented in various semiconductors processes and it may contain memory  810  and/or communication interface blocks  811 .  
         [0056]     BPF  812 , 815  provides filtering on the signals from the modulators. BPF  812 , 815  can be eliminated if adequate filtering can be done within data reconstructor  809 . Up-converter  813  up converts the signal within band Up 2 ′ to the new upstream band, Up 2 . Up-converter  813  can take signal at intermediate frequency (IF) or baseband signal. An I/Q modulation is used for the latter case. Up-converter  813  may be implemented as a set of discrete components or/and as an integrated circuit (IC) in various semiconductor processes such as bipolar junction transistor, silicon-germanium (SiGe), gallium arsenide (GaAs), or/and complementary metal-oxide semiconductor (CMOS) and it may consist of one or more of the following components: a frequency converter, a local oscillator which is normally implemented as a frequency synthesizer utilizing phase-locked loop (PLL), an amplifier, and any other stages such as impedance matching or filtering. The variable gain power amplifier can also integrate the up-conversion process.  FIG. 10  is an illustration of an embodiment of a portioned system.  
         [0057]     PA  814  and  816  amplify the incoming signals and the degree of amplification or gain of the stages are individually controlled by data reconstructor  809 . The amplified signals are passed through the upstream portions of the multi-duplexer  805  where they then leave high data rate capable cable modem  800  and proceed to the high data rate capable HFC network. User&#39;s computer  817  can be connected to high data rate capable cable modem  800  through either by wireless or wired interface.  
         [0058]     Embodiments Illustrating Uses with a High Data Rate Capable Digital TV/Set Top Box  
         [0059]      FIG. 11  depicts another user end embodiment in which high data rate data such as high definition TV (HDTV) data or TV over IP data is sent via a means of modulated RF and optical carrier signals over the high data rate capable HFC network  904 . At the head end  900 , the high data rate data is split into three data streams by serial to parallel converter/data splitter  901 . Each data stream modulates a carrier signal by modulator  902  and then is up-converted, if needed, to RF signals by up converter  903 . One modulator element may provide modulation and up-conversion on the multiple data streams. In one embodiment, one of the up conversions is done to the legacy band and the rest of the up conversions are up converted to the one or more new bands. Another embodiment may include up converting all the signals to the one or more new bands, leaving the legacy band intact. This latter example may be desirable if one wishes to maintain a legacy analog TV channel assignment. The former example may be advantageous in that it can support subscribers with legacy user end equipment (e.g., 1× data rate equipment).  
         [0060]     At high data rate capable cable digital TV/set top box  908 , the RF signal passes through element  905  which may be implemented as a band-pass filter bank or a multi-duplexer with the upstream ports properly terminated. Tuner bank  906  tunes to the logical channel which has associated multiple physical channels and Tuner bank  906  frequency converts/amplifies/filters out the signals as needed. Tuner bank  906  gains are individually controlled by data reconstructor  907 . As in the previous embodiment, each tuner in tuner bank  906  can be packaged into various forms. For instance, each tuner can be packaged into a small module that can be plug into an electrical socket without soldering so that replacement of failed unit can be easily accomplished. Data reconstructor  907  performs demodulation, equalization, error detection/correction, security check, data combining, and any other required processes. The data reconstructor  907  may also contain video codec functionality and one ore more interfaces to data storage devices. Again, the functional “boundary” between tuner bank  906  and Data reconstructor  907  can vary. For instance, tuner bank  906  may contain A/D conversion elements and output unprocessed data to data reconstructor  907 . The recovered high data rate HDTV data is displayed on HD display  909 .  
         [0061]     The HD display  909  can be either external or part of to the high data rate capable digital TV/set top box  908 . If the HD display  909  is external to high data rate capable digital TV/set top box  908 , the HD display  909  can be connected to the high data rate capable digital TV/set top box  908  via a wireless or wired interface. The tuner bank  906  can be used in such ways that a viewer can view a channel that is different from the main channel being displayed (i.e., a picture in picture feature) or a viewer may record a channel different from the main channel being displayed (i.e., background recording).  
         [0062]     Embodiments Illustrating a High Data Rate Capable Versatile Set Top Box  
         [0063]      FIG. 12  depicts another embodiment, termed a high data rate capable versatile set top box  1000 , in which high data rate capable cable modem (with 2× upstream/2× down stream capabilities) is combined with high data rate (3×) capable digital TV STB functionality. In this embodiment, multi-duplexer  1001  accepts a RF signal from a high data rate capable network and separates the downstream bands to Dn 1  (legacy downstream band), Dn 2  (new down stream band  1 ), and Dn 3  (new downstream band  2 ) in the frequency domain. Multi-duplexer  1001  also accepts upstream signals and separates upstream bands to Up 1  (legacy upstream band) and Up 2  (new upstream band). Multi-duplexer  1001  provides the required isolation between the upstream and the downstream signals. Signal splitter  1002  takes a signal and outputs two or more split signals. Signal splitter  1002  can be implemented as a passive and/or active block and signal splitter  1002  can be placed before or after one ore the down-conversion stages, depending on RF performance tradeoffs. One or more signal splitters  1002  may feed a set of channels in legacy band to legacy TV/VCR  1006 . The legacy tuners  1007  that are connected to the video demodulator element  1008  may be configured so that picture-in-picture viewing or/and background recording is possible. In this embodiment, data reconstruction capability is built into high data rate capable video element  1008  and/or cable modem element  1009 . As in the previous embodiments, each of legacy tuners  1007  can be packaged into various forms. For instance, each tuner can be packaged into a small module that can be plug into an electrical socket without soldering so that replacement of failed unit can be easily accomplished. A system controller element, such as a micro processor, MPU  1003  may be used for managing and controlling the overall system. High definition (HD) display  1004  is connected to the high data rate capable video element  1008  and it can be either external to or part of high data rate capable versatile set top box  1000 . If the HD display  1004  is external to high data rate capable versatile set top box  1000 , the HD display  1004  can be connected to the high data rate capable versatile set top box  1000  via a wireless or wired interface. User&#39;s computer  1005  can be either external or integrated into high data rate capable versatile set top box  1000 . If user&#39;s computer  1005  is external to high data rate capable versatile set top box  1000 , user&#39;s computer  1005  can be connected to the high data rate capable versatile set top box  1000  through a wireless or wired interface. Data recovered from the high data rate capable cable element  1009  can be viewed on the HD display  1004  using application software such as a Web browser, an email client, or a media player installed on user&#39;s computer  1005 . User&#39;s computer  1005  may be controlled by a keyboard (either wired or wireless), a mouse (either wired or wireless), and/or other various controlling/interface devices. The high data rate capable versatile set top box  1000  may also have an operating system independent from the operating system installed on user&#39;s computer  1005 .  
         [0064]     Embodiments Illustrating the Coexistence of Various High Data Rate Capable Equipment with Various Legacy Equipment.  
         [0065]      FIG. 13  illustrates a situation in which various high data rate capable equipment coexist with legacy equipment. A set of high data rate capable head ends  1104  connects to data sources such as satellite TV  1100 , terrestrial TV  1101 , internet  1102 , and other content providers  1103 . A set of high data rate capable head ends  1104  interfaces with high data rate capable HFC network  1105  and high data rate capable HFC network  1105  provides and receives signals to/from a set of user ends consist of various high data rate capable equipment and legacy equipment  1106 .  
         [0066]     When a user end first participates with high data rate capable HFC network  1105 , it goes through a number of initialization steps. For example, these steps include channel acquisition, ranging, downloading of operational parameters, and registration with the head end. In the initialization processes, the user end supplies its information including the type of equipment being used (e.g., 2× downstream/2× upstream) to the head end so that the head end can keep track of types of the user end equipment and the number of each that are connected to the network.  
         [0067]     To facilitate the initialization process, all or some of user ends joining high data rate capable HFC network  1105  may first register as legacy user end equipment. Only after the head end is communicated the type of the equipment being used and the type of service the user wish to subscribe to, minimum and maximum communication data rates and types of communication and protocol are determined and communication can be commenced at a proper rate. The user information can be stored for future use in a memory block, such as flash memory, which resides within the high data rate capable user end. In some embodiments, users of high data rate capable user ends can choose to receive and/or send data at a low data rate, such as when the end user would receive a reduced fee. The user end could also choose to receive and/or send data at a low data rate during peak system hours when usage rates may be higher. In such embodiments, the change of minimum data rate can be done “on demand” by one or more head end sending control signals and disabling some of multiple receive/transmit blocks in the high data rate capable user ends.  
         [0068]     Similarly, some users of high data rate capable user ends may prefer not to subscribe to some services that the content/service provider offers. An example is a situation wherein a user prefers not to view one or more movie channels. By allocating the movie channels to a new band, the high data rate capable user end can effectively block those un-needed channels. It can also accomplish this by disabling one or more of the receive paths.  
         [0069]     For example, entire Dn 3  band in  FIG. 12  can be assigned for movie channels. For users who wish not to view the channels, the down converter and the following tuner stages are disabled. This disabling and enabling of blocks can be done “on demand” by communicating with head end, and therefore, no field personnel need to be sent to the customer&#39;s premise to manually block or enable one or more channels. In one embodiment, a user could purchase a cable modem which supports the legacy system and the new system as described in this specification. The user could elect to pay the standard rate for the legacy system or the increased or premium rate to access the advanced system. The system could also allow a user to “roam” into the legacy band if the new advanced system is not available for some reason. This system would be analogous to a cell phone user a cell phone with a dual mode capability such as digital and analog, wherein the user roams into an analog band if he or she is not in a digital zone.  
         [0070]     An “on demand” feature using the flexibility and expandability of high data rate capable head end set  1104  and high data rate capable HFC network  1105  may benefit the content/service provider&#39;s business as well. With a sufficiently high frequency response and network capacity of high data rate capable HFC network  1105  established, high data rate capable head end can be configured/upgraded to support future higher multiplicity or improved communications without discarding services for legacy or “old” high data rate capable user ends. In this way, the service provider is able to retain the “old” legacy system subscribers while at the same time add new subscribers to both the old system and the new improved “premium” system. This would result in much higher return on investment compared to re-building an existing HFC network every time an upgrade is required due to new features. This will also lead to a decrease in system downtime and an increase in customer retention and satisfaction.  
         [0071]     Embodiments Illustrative Uses with Non-Cable and Wireless Systems  
         [0072]     Embodiments of the claimed subject matter can be used with other communication systems such a cellular phone system, a wireless local area network (LAN) system, and a satellite communication system. For example, some existing cellular phone systems use 900 MHz and 2 GHz band. One or more new bands in the unused frequency or unlicensed bands can also be added to the one or more bands that are currently being utilized in a existing communication system.  
         [0073]     Unlike the propagation through coaxial cables and optical fibers, propagation through the “air” at high frequency may incur problems such as high loss, multi-path phenomena, and the like which would add technical challenges to the system.  
         [0074]     However, future technological advances in areas such as digital signal processing, semiconductor devises, antenna design, and other areas may help make it economically feasible to design and operate a communication system capable of offering features such as high data rate, high capacity, and increased reliability using embodiments of the claimed subject matter.  
         [0075]     Another embodiment can use an added band to send and/or receive redundant data and this additional band can be used for other improvements such as to implement diversity and therefore, to improve the quality of the communications. Future advances in communication technologies may result in elimination of one or more intermediate elements or steps in embodiments of the claimed subject matter.