Abstract:
A communication system (and corresponding method of operation) provides a physical-line-based and transparent information transfer facility to distributed information receivers, whilst supporting such transfer for both first packaged data derived from sampling a real-time signal such as a telephone signal and second packaged data originating from a broadband digital data service. Respective actual transfer requirements are ascertained for the first and second packaged data. Next, transferring of the first packaged data is temporally positioned in first time slots that maintain real-time transferring of the first packaged data relative to the real-time signal. Finally, second packaged data are temporally positioned in intermediate intervals between successive first time slots, whilst transferring both the first and second packaged data items along the physical line in a deterministic manner within a single channel facility whilst foregoing encapsulation thereof in an overall frame.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates broadly to a method and apparatus for providing a physical-line-based and transparent information transfer facility to distributed information receivers. More in particular, the invention relates to a fiber-based transfer facility for multiple private homes and similar types of premises that come as being connected in parallel to central but nevertheless distributed offices.  
           [0003]    2. State of the Art  
           [0004]    Present day has seen private homes, small offices and the like being provided with multiple information services that compete with each other for the limited interconnection bandwidth available. Such information services include voice or telephone, a broadband data service such as Internet, Cable Television (CATV), and possibly others. Such information services are typically provided over separate and distinct physical line interfaces. A particular user may select among various different provider entities for receiving a particular single service.  
           [0005]    A cost-saving approach that provides such information services through a single physical channel interface, such as a copper wire or optical fiber, has been recognized as useful. However, such approaches typically require encapsulation of the information for the multiple services in a complicated frame structure. Such encapsulation has significant overhead associated with the encoding and decoding of the information into the frame structure, which adds to the cost of these approaches.  
         SUMMARY OF THE INVENTION  
         [0006]    The inventors have recognized a requirement for a transparent path in that the various information signals, even if they travel together over the same physical line, are presented in their own native formats at both ends of the physical transfer link. In that case, the link will behave in such manner that each particular service will only see a “simple wire”. In particular, the inventors have conceived and practiced an organization wherein no encapsulation in an overall frame with the associated encoding and decoding overhead would be necessary.  
           [0007]    Various aspects of the concept of the invention are as follows:  
           [0008]    All applicable telecommunication services are supported in their native formats, while the end user needs no set-top boxes or other interfacing hardware.  
           [0009]    The signals are presented to the central office in their native formats, which allows direct interfacing of an arbitrary selection among various service providers to a particular user. In many situations, the central office will serve a particular precinct or neighborhood.  
           [0010]    The transparent transport system will offer maximum performance for each data signal type. The service provider may independently decide on policy regarding performance levels.  
           [0011]    An autonomous distributed management system is feasible. No externally controlled scheduling hardware is needed, and auto-discovery of actual topology is feasible.  
           [0012]    Even without an overall frame for transfer control, the transfer remains deterministic, in that necessary buffering length and/or delay can always be calculated in advance.  
           [0013]    Although prior art has recognized the necessity for combined transfer of various data services to the consumer premises, the present inventors have arrived at a remarkably low-cost and straightforward solution.  
           [0014]    In consequence, amongst other things, it is an object of the present invention to provide a transparent, straightforward, low-cost, and unencumbered transfer scheme for the “fiber to the home” and similar single physical-line system concepts, that will guarantee most or all of the above aspects of the concept.  
           [0015]    In accord with these objects, which will be discussed in detail below, a communication system and corresponding method of operation provides a physical-line-based and transparent information transfer facility to distributed information receivers, whilst supporting such transfer for both first packaged data derived from sampling a real-time signal such as a speech-at-a-distance-signal and also for second packaged data originating from a broadband digital data service. The information transfer is accomplished by ascertaining respective actual transfer requirements for the first and second packaged data. The first packaged data items are temporally positioned at respective first time instants that maintain real-time transferring of the first packaged data relative to said real-time signal whilst foregoing encapsulation thereof in an overall frame, and thus transferring the first packaged data items along said physical line in a deterministic manner within a single channel facility. The second packaged data are temporally positioned in intermediate intervals between successive said first packaged data items subject to availability of a sufficient actual transfer interval for transferring second packaged data items in a deterministic manner.  
           [0016]    The invention also relates to a transmitting apparatus, a receiving apparatus, and system that are arranged for implementing the information transfer methodology described herein.  
           [0017]    Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a diagram of a multi-home communication environment;  
         [0019]    [0019]FIG. 2 is a pictorial illustration of an optical communication gateway in a home;  
         [0020]    [0020]FIG. 3 is a more specific diagram of facilities in a central office and a particular home;  
         [0021]    [0021]FIG. 4 is a block diagram of a part of the environment of FIG. 3;  
         [0022]    [0022]FIG. 5 is a first preferred embodiment of the setup in a central office;  
         [0023]    [0023]FIG. 6 is a second preferred embodiment of the setup in a central office and in a home, respectively;  
         [0024]    [0024]FIG. 7 is a combination embodiment of FIGS. 5 and 6;  
         [0025]    [0025]FIG. 8 is a timing diagram illustrating the multiplexing of voice and data frames;  
         [0026]    [0026]FIG. 9 is a timing diagram illustrating an exemplary arrangement of transferring multiple voice channels; and  
         [0027]    [0027]FIG. 10 is a diagram illustrating an alternate embodiment of an information transfer system in accordance with the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]    Now, various aspects of the invention will implement the transparent path concept through appropriate development details, as follows:  
         [0029]    A multiplexing technique that combines the asynchronous (e.g., Internet) data packets and the synchronous/real-time sampled data such as voice data on a single wavelength, by enclosing the voice data in an Ethernet packet that is appropriately prioritized. This is done so that synchronous delivery of the voice is guaranteed without unduly burdening the bandwidth available for the asynchronous broadband channel.  
         [0030]    An Ethernet addressing scheme will allow the communication gateways on either end of the fiber to communicate with each other without the need to exchange handshake information. This is done by changing the six-byte Ethernet address of the various devices from nn:nn:nn:xx:xx:xx into nn:nn:nn:xx:xx:xy. Here, the “nn” part is a three byte organizationally unique identifier assigned by a central authority, such as IEEE. Generally, the “xx” part is a three-byte serial number to be assigned by an apparatus vendor. Now, according to an amending feature of the present invention, “y” is a four-bit or hexadecimal item that identifies a particular voice line of a multiple voice line unit. The receiver needs only discern the particular value of “y” in a packet to find the voice channel in question. Two opposing gateways will then communicate by ignoring the serial numbers, apart from the value of “y”. This fully conforms to the Ethernet standard in that such packets are never propagated outside of the transparent path system of the invention.  
         [0031]    The fibers can be organized on patch panels in multiple layers, such as by grouping them by hundreds in a manner that allows customers to sign up in a random order while being patched to communication gateways (cf. FIG. 2) in an orderly manner. Such approach will allow the scaling up of the central office through increasing the number of communication gateways along with more customers signing up, instead of having to install one separate communication gateway for each potential customer from the start.  
         [0032]    [0032]FIG. 1 is a diagram of a multi-home communication environment. Various service providers  20 ,  22 ,  24  that may be remote, are shown at left, such as representing the Internet, a voice line from a terrestrial switched telephone network or another voice channel provider, or a cable television feed. These sources feed in a possibly customized interconnection scheme each one of a set of optical communication concentrator cells  30 A,  30 B, . . . ,  30 E, . . . , that collectively constitute optical communication concentrator  28 . Each cell is assigned to a respective one of communication gateways  32 A,  32 B, . . . ,  32 D in the various homes at right, through a respective dedicated glass fiber  34 A,  34 B, . . . ,  34 D. The Central Office through optical communication concentrator  28  may be serving an appreciable number of customers, such as from a few tens to several thousands or more. The distance covered by glass fibers or copper-based cables  34 A, . . . is limited by the properties of such physical-lines.  
         [0033]    [0033]FIG. 2 is a pictorial illustration of an optical communication gateway  40  in a home. The block  40 , that may have a size of several inches only, is connected to a dedicated input fiber  48  that represents one of fibers  34 A, . . . in FIG. 1. In many homes the block will be fixed at some appropriate standard location according to national practice, such as in a utility closet. For each appropriate service, the block will have an output plug  42 ,  44 ,  46 , that will be specific to the service in question and cannot be used for any other service. Persons skilled in the art will know such dedicating. As shown, the services provided are TV, Telephone and Internet.  
         [0034]    [0034]FIG. 3 is a more specific diagram of facilities in a central office and in a particular home, respectively. At left, Central Office  82  is fed by digital data such as a 100 MB/s Ethernet facility  50 , Telephone facility  52  that may have one or more analog telephone lines through a switch not shown, or rather an ISDN facility, and furthermore a broadband analog television signal, with a frequency band such as 50-800 MHz, through a CATV head-end  54 . Facilities  50  and  52  are connected to input block  56  and digitized if appropriate, and subsequently multiplexed in multiplexer  58 . Next, the digital signals will be collectively ( 60 ) transferred through an appropriate carrier in case of a metal-based cable, or within a single-wavelength interval in case of an optical fiber  62  that is connected to home  80 . At the home side, demultiplexer  64  will demultiplex Ethernet and telephone signals, and convert the latter through D/A back to analog. Furthermore, block  66  will restructure the telephone information to an analog signal stream for user output, and also output the Ethernet data for immediate user application, if appropriate.  
         [0035]    A similar procedure may be followed for transfer in the opposite direction from the “home” back to the Central Office, as pertaining to telephone and data. Note that in particular, Ethernet is full-duplex. Also various protocols to be disclosed hereinafter more in detail as pertaining to the transfer from the Central Office to the home, may be followed likewise for the transfer in the opposite direction from the home to the Central Office. For brevity, the two-way usage of line  62  has not been shown.  
         [0036]    The broadband and generally multichannel TV signal from head-end  54  is distributed over an appropriate first number of outputs  68 , and if appropriate, after amplification in amplifier  70 , over further numbers of outputs  72  that each feed a particular home through an appropriate physical line. Various TV channels at respective different frequencies may be received at a particular home. The transfer of the TV channels through fiber channel  62  will however generally be on one or more different frequency bands from the data emanating from element  58 , and will therefore be received on one or more different band passed filter receivers  74 , with linear amplification in element(s)  76  if appropriate. Next, coaxed video will output to a user screen device not shown for simplicity. This completes the description of the necessary facilities  78  provided in user home  80 . The various TV channels use one fiber or other physical-line together with the data/telephone. If necessary, of course a separate physical-line could be provided therefor.  
         [0037]    [0037]FIG. 4 is a block diagram of a transmitter part of the environment of FIG. 3. First, the transfer requirements for Ethernet  50  and telephone  52  are ascertained in functional blocks  81 ,  83 , respectively. Next, through interaction block  84  that evaluates these respective requirements, the voice packages are placed on line  62  according to express needs that will maintain the real-time character at the receiving side. Furthermore, the Ethernet data packages are interspersed with the voice packages in such manner that the voice packages will get no inappropriate delay, but the data packages will get as much throughput as feasible. The receiver side will recognize voice and data packages and allow entrance thereto through switches  86 ,  88 , respectively. Furthermore, receiver/converting means  90 ,  92 , will respectively convert voice data back to analog voice for user output, and receive the Ethernet data packages for further application by a user.  
         [0038]    [0038]FIG. 5 is a first preferred embodiment of the transfer setup in a central office. For a bi-directional operation, a similar setup will then be present at the “home” side. The packaged voice samples are received through input  52 . Termination of transfer of such voice package to output line  62  triggers clock  94 , that will count back from an expected maximum delay to the next voice package, to eventually arrive at zero value. The currently expected delay value is then sent to block  81  that again evaluates the transfer requirements of the next Ethernet package. If the latter will fit before the next voice package, the Ethernet package will be transferred indeed. If the latter will not fit before such next package, the Ethernet data package will be delayed. At the receiver side (not shown), various telephone and data packages will be routed to the associated target without referencing to any other transfer category. The advantage of this set-up is that voice will be transferred immediately without any delay; on the other hand, an incurred disadvantage will however be that the delaying of data will effectively lower the system transport bandwidth. When a plurality of different-length Ethernet packages is presently waiting, a selection or choice thereamong may be made to maximize data traffic, for example by transferring those packages out of sequential order, if a later package would fit before the next voice package, whereas an earlier data package would not.  
         [0039]    [0039]FIG. 6 is a second preferred embodiment of the transmitting setup in a central office. Here, an Ethernet package received on input facility  50  will be detected by device  96 , and the detection signal sent on line  97  to buffer  98  that has a total length corresponding to the fixed maximum duration of a data packet. A telephone package arriving subsequently will then be stored in buffer  98 . Upon subsequent termination of the Ethernet package transfer, the signal on line  97  will say so, and cause buffer  98  to start outputting of the stored voice data. In consequence, buffer  98  may both receive and also output voice signals at the same time and thereby have effectively a variable length. Note that the internal organization of buffer  98  has not been shown.  
         [0040]    At the receiver side, the Ethernet data are received in facility  92  in much the same way as in FIG. 4. The voice data will be received in buffer  100  that may have the same physical length as buffer  98 . If required, buffer  100 , just like buffer  98 , can be set to bring about a variable delay to the voice package in such manner that the currently accumulated delay by buffers  98 ,  100  is always the same. This has been symbolized by the (variable) input tap on buffer  100 . Therefore, in the setup of FIG. 6, the transfer bandwidth is raised with respect to the arrangement of FIG. 5, at a price of a uniform delay of the voice packages.  
         [0041]    It is feasible to design a trade-off between the two solutions in FIGS. 5 and 6. In this respect, FIG. 7 illustrates a combination embodiment of these two Figures. In this embodiment, the maximum voice delay in buffer  112  may be made equal to one half of a data package maximum, whilst data transmission will be allowed when one half of a maximum interval between two successive voice packages is still left as measured by element  110 . The receiving side in FIG. 7 corresponds to FIG. 6, except for the shorter physical length of the receiving buffer (not shown). Note that also here, the process is completely deterministic. Other fractional sizes of the buffer  112  than one half (½) of the length of the buffer  98  in FIG. 6 could be feasible as well, such as ¼ or ¾.  
         [0042]    At a Fast Ethernet line speed of 100 Mbit/sec, the maximum Ethernet packet of 1522 Bytes will last only about 122 microseconds, so voice buffering of only one Byte for a voice stream of 8000 Bytes per second would be sufficient. At a Standard Ethernet line speed of 10 Mbits/sec, the maximum waiting time would be 1.2 msec, so a 10 byte buffer would be necessary.  
         [0043]    [0043]FIG. 8 illustrates a temporal example of the multiplexing of voice and data frames. The voice signal may be 8-bit sampled at about 8 kHz, collected in groups of e.g. 32 bytes, and wrapped up in Ethernet frames, which are then padded to the minimum Ethernet data field length of 46 bytes. The link is point-to-point, with only one sender station and one receiver station. No collisions can occur, so the link is run in a full duplex manner; the only particular aspect is that the sender has two data sources, one with data per se, and one with “voice” data. If by way of example, voice frames are sent at a rate of 0.250 kHz or a mutual distance of 4 ms, the occurrence of a next voice frame is exactly predictable. If absence of voice will cause a transient pause in the stream of voice packets, only the first packet upon resumption of the voice cannot be predicted, which will cause only an unperceivable interference.  
         [0044]    In a recurrent stream of voice packets, it will show immediately whether a “data” packet (of which the maximum length is 1522 bytes as per the Ethernet standard) will fit before the “next” voice packet. If not, it will have to wait. In a more advanced implementation, a short data packet following a longer data packet frame that is waiting can be sent first, if the shorter frame could be sent before the arrival of the next voice packet. In the Figure, the lightly hatched voice frames are being sent periodically. Data frame “a” shown in white can be transmitted upon arrival, whereas darker hatched data frame “b” is delayed until transmittal is allowed as shown through “c” in white.  
         [0045]    [0045]FIG. 9 illustrates an exemplary temporal arrangement of transferring multiple voice channels ch  1 , ch  2 . Here, they are synchronized at the transmitter side in order not to overlap in time. Again, the interval between two successive voice packets (from a single, or rather from multiple telephone channels) can be used for transferring a data packet. In certain situations, the presence of multiple voice channels will shift the optimum of the trade-off between voice buffering (FIG. 6) and data buffering (FIG. 5). Anyway, the receiving end should know to which voice channel or telephone line a particular frame belongs. The label in question can be put inside the frame&#39;s data field, but other solutions are feasible as well. Note that the intervals between the voice packets of FIG. 9 are represented in their own scale that should not be compared with FIG. 8.  
         [0046]    [0046]FIG. 10 illustrates a different view of the transfer pathway concept. At left are the service providers that connect to the transparent pathway. In fact, they need no longer worry how to get their services in the homes, and can concentrate on their core business. In fact, their physical connection pattern to a particular physical-line mimics the situation at the user&#39;s premises, so that the connection in the central office may be termed a virtual representation of that user&#39;s site.  
         [0047]    Now, the present invention has hereabove been disclosed with reference to preferred embodiments thereof. Persons skilled in the art will recognize that numerous modifications and changes may be made thereto without exceeding the scope of the appended Claims. In consequence, the embodiments should be considered as being illustrative, and no restriction should be construed from those embodiments, other than as have been recited in the Claims. It is noted in this respect that a real-time signal may be another signal than a voice signal, e.g. a real-time video signal. The latter may be relevant in case were feed-back is required. Examples of such situations are gaming via the Internet and a physician doing surgery at a location remote from the patient.