Abstract:
A method and system are disclosed for enabling full-service communications between a full-service cable modem termination system (fsCMTS) and a plurality of full-service cable modems (fsCMs) for a conventional two-way hybrid fiber-coax (HFC) cable television network. Full-service communications include data, voice and video. Video includes broadcast quality MPEG-2 transport packet streams and Internet Protocol media streams. A multi-channel full-service media-access-control (fsMAC) coordinates the access to the shared upstream and downstream channels. Several MAC management messages are defined to enable a multi-channel full-service MAC domain to facilitate sharing of an arbitrary number of channels and to enable packet-by-packet true seamless channel change. Multiple upstream channels can be used in various ways to best optimize the use of the spectrum for meeting the quality-of-services needed by different services.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a divisional application of U.S. patent application Ser. No. 10/122,828, entitled “Full-Service Broadband Cable Modem System,” filed Apr. 15, 2002, which is a continuation of provisional application filed on Apr. 14, 2001, Ser. No. 60/283,842, both of which are incorporated herein by reference in their entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to “last mile” broadband digital communications systems capable of delivering full-service of voice, video and data to residential and commercial premises. More particularly the invention relates to the field of improvements in the media access control (MAC) protocol of a full-service cable modem system that uses multiple downstream and upstream channels.  
       BACKGROUND OF THE INVENTION  
       [0003]     For the last few years, cable modem systems based on data-over-cable service interface specifications (DOCSIS) have been accepted as a “last mile” high-speed data solution for the consumers.  
         [0004]     A two-way Hybrid Fiber-Coax (HFC) cable network is an infrastructure capable of supporting multiple overlaying networks, viz. analog or digital video service, high-speed data, and telephony service. Each of these services use different band of the available spectrum in the downstream and upstream directions, and each service has its own operations and provisioning infrastructure. At customer premises, a full-service subscription requiring multiple boxes of customer premises equipment (CPE) such as a set top box, a telephone network interface unit, and a cable modem. These overlaying services are inefficient in terms of increasing the cost of operations and the cost of consumer ownership.  
         [0005]     Convergent Network  
         [0006]     It is therefore highly desirable to have a converged network, capable of delivering voice, video and data in a unified communications infrastructure.  
         [0007]     Although later versions of data-over-cable media-access-control (MAC) have quality-of-service (QoS) capability by using polling, the protocol essentially is based on sharing an upstream and a downstream channel. Switching users among channels is complex and slow.  
         [0008]     Moreover, the cable modem has severe limitations when it comes to supporting digital video services. Conventional digital video (broadcast or video on demand) requires more stringent bit-error-rate than data services. High bit rate of approximately 20 Mbps per HDTV movie channel is required, significantly impacting the capacity of the other services since they reside in the same downstream channel.  
         [0009]     Upstream Limitations  
         [0010]     The upstream bandwidth of a HFC network is limited by the amount of available spectrum in the upstream in a “sub-split” HFC cable plant which is between 5 to 42 MHz in North America. Because of ingress interference, a good portion of the spectrum is not suitable for wide-band (e.g. 3.2 MHz or 6.4 MHz per channel) and higher-order modulations (e.g. 16, 32, or 64 QAM) to achieve a high capacity for the upstream channel in use. If a 6.4 MHz channel is used, only 6.4/(42−5)=17% of the upstream spectrum is used. The other 83% of the spectrum (in particular for frequencies below 10 MHz) is often unused. Conventional data-over-cable MAC is quite limited in handling multiple channels, in increasing the capacity, and providing the quality of service (QoS) required by different services.  
         [0011]     Moreover, since each upstream channel must support the packets generated by different services with different QoS requirements, it is very difficult to achieve high channel utilization under dynamically changing traffic conditions. In particular, the overhead of the MAC management packets such as bandwidth request and initial calibration can be significant and will complicate the scheduling efficiency of the cable modem termination system (CMTS).  
         [0012]     The conventional data-over-cable MAC protocol relies on some form of polling to achieve QoS goal of meeting bandwidth, latency and jitter requirements. For a polling interval of 2 ms, each upstream channel requires about 270 Kbps of downstream bandwidth for the MAC operation. This represents a significant amount of bandwidth taken from the downstream channel. Therefore, scalability of using multiple upstream channels in conventional data-over-cable is quite limited.  
         [0013]     Broadcast Quality Digital Video  
         [0014]     Although the HFC network has sufficient bandwidth to support delivery of a full spectrum of services including data, telephony and video, these services currently are separate infrastructures, each being provisioned by a service provider. As a result, these are sub-optimal usage of the HFC spectrum and costly duplication of equipment at the head end and at customer premises. Voice-over-IP enables convergence of voice and data. However, video service remains using a separate infrastructure.  
         [0015]     Therefore, there is an unmet need for a unified communication system that can provide the full need of broadband Internet access, IP telephony, broadcast quality digital video over the same HFC system.  
         [0016]     Therefore, there is an unmet need for a MAC that can be used to implement a full-service cable modem system to fulfill the full potential of a HFC network for delivery voice, video and data cost-effectively to the home and the business.  
         [0017]     It will be realized after the detailed description of the invention how to overcome the limitations of conventional cable modem systems by the novel MAC and system architecture. A highly efficient and scalable access method that can be used to deliver simultaneously interactive digital video, telephony and high speed internet access as well as interactive gaming shared by a large number of users. The MAC fully utilizes the upstream and downstream spectrum enabling service providers economically deploy the services without a forklift upgrade to the HFC cable plant currently deployed for conventional cable modem service. The unified full-service communication system will reduce the cost of providing three separate provisioning systems for video, data and voice, simplify head end equipment and at the same time reduce the number of on-premises equipment from three to one.  
         [0018]     It is an object of the present invention to overcome the disadvantages of the prior art.  
       BRIEF SUMMARY OF THE INVENTION  
       [0019]     This and other objects are achieved by the present invention. In accordance with the present invention a full-service cable modem (fsCM) system  100  capable of delivering video, data and voice over a two-way hybrid fiber-coaxial cable network is described.  
         [0020]     A high-capacity, high-efficiency multi-channel full-service MAC, capable of supporting multiple upstream and downstream channels, enables the fsCM system  100  to deliver a full spectrum of services presently requiring multiple delivery systems. The video can be a combination of high-quality broadcast MPEG-2 movie or IP video streams, with the required quality of service.  
         [0021]     Further, multiple channels can be used to multiplex packets of all types, enabled by a true seamless channel change described in this invention, thereby maximizing statistical multiplexing gain. Packet-by-packet channel switching enables fast recovery from a channel failure, as required by a high-availability fault-tolerance cable modem system.  
         [0022]     The fsCM system  100  consists of, according to the preferred embodiment, illustratively two downstream channels (DCPC and DPC 1 ), two upstream payload channels (UPC 1  and UPC 2 ), three upstream control channels (UCC 1 , UCC 2 , UCC 3 ) that connect a fsCMTS  102  in the head-end and a plurality of fsCMs  106  at subscriber sites.  
         [0023]     The fsCM  106  uses the DCPC for delivering downstream MAC management messages as well as for payloads (MPEG-2 TS or IP packets) and the DPC 1  for downstream payload channel to deliver high quality MPEG-2 video or IP packets.  
         [0024]     The present invention further includes downstream MAC management messages Multi-channel Bandwidth Allocation MMAP  900  and fsMAC Domain Channels Descriptor MDCD  1000  to enable the fsCMTS  102  to allocate upstream transmission to any of the multiple upstream channels on a packet-by-packet basis, and allows a multiple-channel MAC domain to be changed quickly to adapt to changing traffic on the network.  
         [0025]     The methods and apparatus described herein implement a novel and unique facility that provides for efficient access of a full-service cable modem network capable of simultaneously servicing the communication needs of internet access, telephony, interactive and on-demand digital video to a large number of users over a conventional HFC network. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  is a block diagram illustrating an embodiment of the full-service Cable Modem System  100 ;  
         [0027]      FIG. 2  is a block diagram of the full-service cable modem  106 ;  
         [0028]      FIG. 3  is a diagram illustrating the channel frequency plan for an example full-service cable modem system;  
         [0029]      FIG. 4  is a block diagram illustrating the structure of Synchronization SYNC message  500 ;  
         [0030]      FIG. 5  is a block diagram illustrating the structure of Calibration Request CREQ message  600 ;  
         [0031]      FIG. 6  is a block diagram illustrating the structure of Calibration Response CRSP message  700 ;  
         [0032]      FIG. 7  is a block diagram illustrating the structure of Bandwidth Request BREQ message  800 ;  
         [0033]      FIG. 8  is a block diagram illustrating the structure of the Multi-channel Bandwidth Allocation MMAP message  900 ;  
         [0034]      FIG. 9  is a block diagram illustrating the structure of the fsMAC Domain Channels Descriptor MDCD message  1000 ;  
         [0035]      FIG. 10  is a flow diagram illustrating of the fsCM initialization; and  
         [0036]      FIG. 11  is a flow diagram illustrating the upstream transmission process using contention BREQ  800 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0037]     Refer to  FIG. 1  for a preferred embodiment of a multi-channel fsCM system  100 . An fsCMTS  102 , typically located at a head end  101 , is connected to the fiber-part of a two-way HFC network  104  through an electrical to fiber interface (not shown). A remotely located fsCM  106  is connected to a coax  402  part of the HFC  104 . The downstream spectrum (typically 50 to 850 MHz) is divided into typically 6 MHz channels in the downstream for NTSC cable systems. The upstream spectrum typically ranges from 5 to 42 MHz in North America, and the upstream channel bandwidth varies typically from 160 KHz to 6.4 MHz. The architecture and topology of a modern two-way HFC cable plant are known in the art and will not be repeated here.  
         [0038]     In this example, also referring to  FIG. 3 , there are two downstream channels: the downstream control and payload channel DCPC  147  and the downstream payload channel DPC 1   137 , and the five upstream channels: the upstream control channels UCC 1   174 , UCC 2   176 , UCC 3   178  and the upstream payload channels UPC 1   182  and UPC 2   184 . The exemplified channel frequencies are illustrated in  FIG. 3 , in which channel center frequencies for the DCPC  147 , the DPC 1   137 , the UCC 1   174 , the UCC 2   176 , the UCC 3   178 , the UPC 1   182  and the UPC 2   184  correspond to f1, f2, f3, f4, f5, f6, f7 respectively. The center frequencies for the DCPC  147  and the DPC 1   137  are controlled by corresponding frequency-agile up-converters  146  and  136 . The UCCs  174 ,  176  and  178  channel center frequencies and channel bandwidths are controlled by a burst transmitter  194 . The UPCs  182  and  184  center frequencies and channel bandwidths are controlled by another burst transmitter  196 . Illustratively, the UCCs use narrower channel bandwidths and robust modulation schemes such as QPSK or BPSK that can be located in the noisier portion of the upstream spectrum. The “cleaner” part of the upstream spectrum is normally used by the UPCs so that higher order of modulations such as 16 to 64 QAM can be used reliably for higher throughput for payloads. In an alternative embodiment, a single upstream frequency-agile programmable burst transmitter can multiplex the transmission of control and payload bursts.  
         [0039]     Through an IP network interface  122 , the fsCMTS  102  is connected to a video server  108  via a communication path  120  for digital video services, to a managed Internet backbone  112  for connection to a Public Switched Telephone Network PSTN  113 , or other voice-over-IP networks for telephony services, to an Internet backbone  114  for high-speed data services, and to an Intranet IP network  116  for access to provisioning and network management servers as part of the fsCMTS system operation. The IP network interface is also connected to the video server  108  for providing IP connectivity for video-related network management and illustratively, for upstream traffic generated by set-top boxes  530 .  
         [0040]     Digital video traffics, generated by the video server  108 , packetized into MPEG-2 transport streams TS  150 ,  152  are combined with fsCMTS MAC messages  131  and  160  including Synchronization SYNC  500 , Calibration Request CREQ  600 , CRSP  700 , BREQ  800 , the Multi-channel Bandwidth allocation MMAP  900 , the fsMAC Domain Channels Descriptor MDCD  1000  and IP payload packets  154  and  155  in downstream transmitters  132 ,  142 , which are outputted to downstream modulators  134 ,  144  respectively. The intermediate frequency outputs of the modulators  134 ,  144  are up converted to the desired center frequencies by up converters  136  and  146  respectively. The radio frequency RF outputs of the up converters  136  and  146  are then transmitted through the HFC plant  104  into downstream receivers  470 ,  420  of fsCMs  106  via the coax  402  portion of the HFC  104 .  
         [0041]     The downstream modulators  134 ,  144  typically are specified to comply with ITU J83 Annex A, B, or C depending on nationality. Other modulation and forward error correction (FEC) formats are possible.  
         [0042]     IP packets  154  and  155 , and MAC management packets  131  and  160  are encapsulated in MPEG2-TS using a unique packet identifier PID (1FFE hexadecimal for data-over-cable) before transmitting downstream.  
         [0043]     The time base in the fsCMTS  102  and in the remote fsCMs  106  are synchronized by periodically sending a captured time-stamp value of a time-stamp counter  130  driven by a time-stamp frequency source  128 . The time-stamp value is encapsulated in a MAC management message (SYNC  500 ), which is in turn encapsulated into a MPEG2-TS and multiplexed with the other TS before delivering to the downstream modulator  134 . The method of synchronization using time-stamped message is known in the art.  
         [0044]     The SYNC  500  is transmitted in all downstream channels so as to enable seamless switching of downstream channels.  
         [0045]     The Downstream Control and Payload Channel DCPC  147  carries MAC management messages including a MMAP  900  and MDCD  1000  which are essential for the multi-channel MAC operation and their significance will be understood when they are described in detail below.  
         [0046]     A full-service MAC (fsMAC) has two parts: a fsMAC-CM  192  and a fsMAC-CMTS  124 , which are located in the fsCM  106  and fsCMTS  102  respectively. The fsMACs role is to co-ordinate the dispatch of downstream IP packets and fsMAC management messages; another role is to co-ordinate the efficient and orderly transmission of upstream bursts using the two upstream burst transmitters  194  and  196 .  
         [0047]     One of the transmitters  194  is used for transmitting fsMAC management packets such as calibration and bandwidth requests. The other transmitter  196  is for transmitting payload of IP packets  199  received from a CPE interface  197 .  
         [0048]     More specifically, the transmitter  194  is used to transmit bursts to UCC 1   174 , UCC 2   176  or UCC 3   178  using burst profiles communicated to fsMAC-CM  192  by fsMAC-CMTS  124  by sending down the MDCD  1000 . Similarly, the transmitter  196  is used to transmit bursts to UPC 1   182  or UPC 2   184  using other burst profiles. The fsCM  106  learns the characteristics of burst profiles by listening to the MDCD message  1000  and uses the burst profile and time to transmit by decoding the MMAP message  900 .  
         [0049]     At the fsCMTS  102 , corresponding to these transmitters in the fsCM  106 , there are matching frequency-agile programmable burst receivers  172  and  180  that will tune, demodulate and recover the packets received. These packets (including collision detection information, if any) will be inputted to the fsMAC-CMTS  124 .  
         [0050]     Full-Service Cable Modem Detail  
         [0051]      FIG. 2  is a block diagram illustrating an embodiment of the fsCM  106 . The RF signal enters the fsCM  106  via the coax  402 . The RF is divided into two paths by RF splitter  404 . Each RF path after the splitter is connected to diplex filters  410 ,  460 . Diplex filer  410  passes high frequency downstream RF signal  412  to the DPC 1  downstream receiver  420 , whose output is a MPEG-2 transport stream TS 1   422  into a packet identifier (PID) de-multiplexing unit  424 . De-multiplexing unit  424  separates the data-over-cable TS  426  from the conventional audio/video/data TS  423  by examining the PID value. Data-over-cable TS  426  is identified by a value of 1FFE (hexadecimal). The audio/video/data TS  423  associated with a program (e.g. movie) is directed to a conventional MPEG-2 decoder  428  for generating audio/visual signals. Outputs from the decoder  428  can be of digital television DTV  430 , or standard analog video signal  434  (composite video or NTSC modulated RF) for connection to conventional television receivers or video monitors.  
         [0052]     Alternatively, the TS  423  can interface to a digital set-top box using IEEE 1394 (not shown), or other high-speed connections. Another alternative is to send the MPEG-2 audio/video/data TS  476  to the fsMAC-CM  192 , where the TS is encapsulated in IP (MPEG-2 over IP) and forwarded to a home network  508  via CPE interface  504 . The digital set-top box  530  attached to the home network  508  can decode the MPEG-2 TS.  
         [0053]     Another RF path  405  passes through diplex filter  460  that outputs a RF signal  462 , which is tuned to the channel DCPC  147  and processed by the second downstream receiver  470 , whose output is another MPEG-2 transport stream TS  472 , which is inputted to the PID de-multiplexing unit  424 , which in turn separates the data-over-cable TS  426  from the audio/video/data TS  473 .  
         [0054]     Data-over-cable TS  426  and  476  are processed in a downstream processing unit  502  to recover data-over-cable packets, consisting of MAC messages and IP payload packets, before entering a fsMAC-CM. MAC messages are processed by the fsMAC-CM  192 . IP payload packets are forwarded to CPE devices attached to the home network  508 , subjected to filtering rules by the CPE interface  197 , which is illustratively, an Ethernet network interface. Specifically, IP packets are subjected to filtering rules in the packet forwarding engine within the CPE interface  197  using bridging or routing rules. The IP packets are forwarded to a CPE devices such as a personal computer  514 , an Internet Appliance  512 , Multimedia Terminal Adaptor (MTA)  516  for voice-over-IP telephone  518 , FAX machine  522 , video conferencing terminal  520  and other media streaming services using the home networking infrastructure  508  (e.g. 10/100 Base-T Ethernet, USB, HPNA, Wireless LAN, HomePlug etc.)  
         [0055]     Upstream IP packets from CPE devices  512 ,  514 ,  516 ,  530  are subjected to filtering by the packet forwarder within the CPE interface  197 , and then are queued at upstream processing unit  506 . There are two upstream burst transmitters in this embodiment: the Upstream Control Channel (UCC)  194  and the Upstream Payload Channel (UPC)  196 . Each of the two transmitters consists of FEC encoder, modulator, frequency agile digital up converter, RF front-end, etc. to enable upstream burst transmissions in any channel in the upstream spectrum, according to the stored burst profiles sent from the fsCMTS  102 .  
         [0056]     Upstream MAC management burst packets  498  are sent to UCC channel transmitter  194 , which outputted as RF burst signal  490  to the diplex filter  460 . Payload IP packets  488  emerges from an upstream processing unit  506 , accordingly processed by the UPC burst transmitter  196 , whose output burst RF signal  480  is coupled to the diplex filter  410  and emerges as a RF signal  405 , which is coupled to the HFC coax  402  by splitter  404 , traveling upstream to the head end  101  where the fsCMTS  102  is located.  
         [0057]     Now the signal flow of the fsCM system  100  between the fsCMTS  102  and fsCM  106  has been described. The following further description will show how the fsMAC-CMTS  124  and fsMAC-CM  192  coordinate the multiple access transmission of upstream bursts. The essential MAC management messages SYNC  500 , MDCD  1000 , MMAP  900 , CREQ  600 , CRSP  700 , BREQ  800  are described first and then the fsMAC protocol details will follow.  
         [0058]     Full-Service MAC Management Messages  
         [0059]     SYNC Message  
         [0060]      FIG. 4  is a block diagram of the SYNC MAC message  500  structure. The SYNC MAC message  500  includes a MAC management header  582 , a time stamp snapshot  584  capturing the sampled value of time stamp counter  130 , a fsMAC domain identifier  586 , and a downstream channel identifier  588 . A description of the fields of the SYNC message  500  is shown in Table 1. However, fewer or additional fields could also be used in the SYNC message  500 .  
                         TABLE 1                           SYNC MESSAGE 500            fsMAC Field Parameter   Description of the Field Parameter               Message Header 582   This field allows fsCM-MAC 192 to           uniquely identify and process the           SYNC management message 500.       Time stamp snapshot 584   This field           contains the sampled value of time           stamp counter 130.       fsMAC domain identifier   This field uniquely identifies the       586   fsMAC domain as defined by MMAP           message           900.       Downstream Channel identifier   This field uniquely identifies the       588   downstream channel to which fsMAC           messages are transmitted.                    
         [0061]     CREQ Message  
         [0062]      FIG. 5  is a block diagram of the calibration request (CREQ) MAC message  600  structure. The CREQ MAC message  600  includes a MAC management header  602 , a fsCM service identifier  604 , a fsMAC domain identifier  606 , a downstream channel identifier  608 , a fsCM Ethernet MAC address  610 , a fsCM type  612 , and a pre-equalizer training sequence  614 .  
         [0063]     A description of the fields of the CREQ message  600  is shown in Table 2.  
         [0064]     However, fewer or additional fields could also be used in the CREQ message  600  in other embodiments.  
                         TABLE 2                           CREQ MESSAGE 600            Field Parameter   Description of Field Parameter               fsMAC Message Header 602   This field allows fsCM-MAC 192 to           uniquely Header 602 identify and           process the CREQ message 600.       fsCM service identifier (SID) 604   This field uniquely identify the           service flow associated with the           fsCM 106 within the fsMAC domain           identified by fsMAC domain ID 606.       fsMAC domain identifier   This field uniquely identifies the       (MAC ID) 606   fsMAC domain as defined by MMAP           message 900.       DCPC channel identifier 608   This field uniquely identifies the           downstream control and payload           channel (DCPC) into which fsMAC           messages are transmitted.       Ethernet MAC address 610   This field contains the 48-bit           Ethernet MAC 610 address associated           with the fsCM 106.       FsCM type 612   This field contains information           about the type and version of the           fsCM 106.       Pre-equalizer training   This field contains pre-equalizer           training sequence 614 sequence(s)           for the fsCM 106 transmitters           194, 196.                  
 
         [0065]     CRSP Message  
         [0066]      FIG. 6  is a block diagram of the calibration response MAC message  700  structure. The CRSP MAC message structure  700  includes a MAC management header  702 , a fsCM service identifier  704 , a fsMAC domain identifier  706 , an upstream channel identifier  708 , a timing adjustment  710 , a frequency adjustment  712 , a transmit power adjustment  714 , transmitter pre-equalizer tap coefficients  716 , and a re-assigned fsMAC domain identifier  718 .  
         [0067]     A description of the fields of the CRSP message  700  is shown in Table 3. However, fewer or additional fields could also be used in the CRSP message  700  in other embodiments.  
                         TABLE 3                           CRSP MESSAGE 700            Field Parameter   Description of Field Parameter               fsMAC Message Header 702   This field allows fsCM-MAC 192 to           uniquely identify and process the CRSP message 700.       fsCM service identifier (SID)   This field uniquely identify the service flow       704   associated with the fsCM           106 within the fsMAC domain identified           by fsMAC domain ID 706.       fsMAC domain identifier (MAC   This field uniquely identifies the fsMAC domain       ID) 706   as defined by MMAP message           900.       Upstream channel identifier   This field identifies the upstream channel CRSP       708   700 is responding to.       Timing adjustment 710   This field contains information for fsCM 106           to adjust its local clock to           synchronize with that of the fsCMTS           102.       Frequency adjustment 712   This field contains information for fsCM 106           to adjust its upstream transmitter center           frequency to within the receiving           frequency range of the fsCMTS receiver           172 or 180.       Transmit power adjustment 714   This field contains information for fsCM 106           to adjust its transmitter power amplifier           gain to the correct level.       Transmit pre-equalizer tap   This field contains information for fsCM 106       coefficients 716   to adjust its transmitter pre-equalizer           to the new parameters.       Reassigned fsMAC 718   This field contains information (if present)           domain identifier about a new fsMAC domain           identifier, which fsCM 106 will associate           with after receiving this message.                  
 
         [0068]     BREQ Message  
         [0069]      FIG. 7  is a block diagram of the bandwidth request (BREQ) MAC message  800  structure, which includes a fsMAC message header  802 , a fsCM service identifier  804 , a fsMAC domain identifier  806 , a framing header type  808 , and an amount requested  810 .  
         [0070]     A description of the fields of the BREQ message  800  is shown in Table 4. However, fewer or additional fields could also be used.  
                         TABLE 4                           BREQ MESSAGE 800            Field Parameter   Description of Field Parameter               FsMAC Message Header 802   This field allows fsCM-MAC 192 to uniquely identify           and process the BREQ message 800.       fsCM service (SID) 804   This field uniquely identify the service           flow identifier associated with the fsCM 106           within the fsMAC domain identified by fsMAC domain           ID 806.       fsMAC domain (MAC ID) 806   This field uniquely identifies the fsMAC domain           as identifier defined by MMAP message           900.       Framing header type 808   This field contains the header type information           for fsCMTS to take into consideration           of the MAC frame header overhead           when allocating bandwidth for the requesting fsCM.       Amount requested 810   This field contains amount of payload           bandwidth (excluding MAC header overhead)           requested by fsCM. E.g. number of bytes or number           of time slots such as mini-slots.                  
 
         [0071]     MMAP Message  
         [0072]      FIG. 8  is a block diagram of the multi-channel bandwidth allocation MAC message (MMAP)  900  structure, which includes a fsMAC management message header  902 , a fsMAC domain identifier  904 , a list of broadcast grants  906 , a list of unicast grants  908 , and a list of pending grants  910 .  
         [0073]     A description of the fields of the MMAP message  900  is shown in Table 5. However, fewer or additional fields could also be used.  
                         TABLE 5                           MMAP MESSAGE 900            Field Parameter   Description of Field Parameter               fsMAC Message 902   This field allows fsCM-MAC 192 to uniquely           Header identify and process the MMAP message           900.       fsMAC domain   This field uniquely identifies the fsMAC domain       identifier 904       Broadcast grants 906   This field contains the bandwidth grants for           the contention area that bandwidth requests are           transmitted from any fsCM in the fsMAC domain.           Table 6 gives an example of the broadcast           grants.       Unicast grants 908   This field contains the bandwidth grants           address to an           individual fsCM. Table 7 gives and example of           unicast grants.       Pending grants 910   This field contains a list of pending grants           for those BREQs that are successfully received           by the fsCMTS, but the grants are deferred to           the later MMAP 900. Table 8 gives an example of           pending grants.                  
 
         [0074]     Table 6 
                         TABLE 6                           Broadcast grants 906 example            Broadcast Grants   Description of Field Parameter               Number of broadcast   =2 in this example       grants       Service ID   (Start of 1 st  broadcast grant). This field           contains the SID of the broadcast address for           all fsCMs.       Grant type   Bandwidth request BREQ 800       Upstream channel ID   This field contains the channel ID to which the           broadcast grant is allocated.       Burst profile ID   This field identifies the burst profile of the           BREQ 800.       Back-off start and   This field contains the back-off window of the       End values   chosen contention resolution algorithm.       Length of payload   BREQ 800 burst payload data length in bytes       data in bytes       Number of bursts   Number of BREQ 800 bursts for this grant.       Transmission start   Start transmission time of the first BREQ 800       time   burst.       Service ID   (Start of 2.sup.nd broadcast grant). This field           contains the SID of a broadcast address for a           group of fsCMs.       Grant type   Bandwidth request BREQ 800.       Upstream channel ID   This field contains the channel ID to which the           broadcast grant is allocated       Burst profile ID   This field identifies the burst profile of the           BREQ 800.       Back-off start and   This field contains the back-off window of the       End values   chosen contention resolution algorithm in this           example       Length of payload   BREQ 800 burst payload data length in bytes.       data in bytes       Number of bursts   Number of BREQ 800 bursts for this grant.       Transmission time   Start transmission time of the first BREQ 800       start   burst.                  
 
         [0075]     Table 7 
                         TABLE 7                           Unicast grants 908 example            Unicast Grants   Description of Field Parameter               Number of Unicast grants   3 in this example.       SID-1   (Start of 1 st  unicast grant). This field           contains SID of fsCM-1.       Grant type   Variable length payload packet       Upstream channel ID   This field contains the channel ID to which           the unicast grant is allocated.       Burst profile ID   This field identifies the burst profile for           packet.       Burst framing header type   This field contains framing header type to           enable fsCMTS to calculate the overhead           needed for the burst.       Length of payload data in   Burst payload data length in bytes.       bytes       Transmission start time   Start transmission time of the first BREQ           800 burst.       SID-2   (Start of 2 nd  unicast grant). This field           contains SID of fsCM-2.       Grant type   Constant bit rate (CBR).       Upstream channel ID   This field contains the channel ID to which           the unicast grant is allocated.       Burst profile ID   This field identifies the burst profile for           this burst.       Burst framing header type   This field contains framing header type to           enable fsCMTS to calculate the overhead           needed for the burst.       Length of payload data in   Burst payload data length in bytes.       bytes       Grant interval   This field contains the time interval           between two adjacent grants.       Transmission start time   Start transmission time of the burst.       SID-3   (Start of 3.sup.rd unicast           grant). This field contains SID of fsCM-3.       Grant type   Dedicated channel       Upstream channel ID   This field contains the channel ID to which           the unicast grant is allocated.       Length of payload data in   Burst payload data length in bytes.       bytes       Grant duration   This field contains the time for which the           dedicated channel can be used.       Transmission start time   Start transmission time of the first burst.                  
 
         [0076]     Table 8 
                             TABLE 8                           Pending grants 910 example                Pending Grants   Description of Field Parameter                       Number of broadcast grants   =2 in this example.           SID-a   This field contains the SID of the               pending grant for fsCM-a.           SID-b   This field contains the SID of the               pending grant for fsCM-b.                      
 
         [0077]     MDCD Message  
         [0078]      FIG. 9  is a block diagram of the fsMAC domain channel descriptor (MDCD) MAC message structure  1000 , which includes a MAC message header  1002 , a fsMAC domain identifier  1004 , an accept new fsCM registration flag  1006 , number of downstream channels  1008 , number of upstream channels  1010 , downstream channel change count  1012 , upstream channel change count  1014 , a list of downstream channel identifiers and Type-Length-Values (TLVs)  1026 , a list of upstream channel identifiers and TLVs  1028 , and a list of upstream burst profile identifiers and TLVs  1030 .  
         [0079]     A description of the fields of the MDCD message  1000  is shown in Table 9. However, fewer or additional fields could also be used.  
                         TABLE 9                           MDCD MESSAGE 1000            Field Parameter   Description of Field Parameter               fsMAC Message Header 1002   This field allows the fsCM-MAC 192 to           uniquely identify and process the MDCD message 1000.       fsMAC domain identifier   This field uniquely identifies the fsMAC       1004   domain as defined by MMAP message 900.       Accept-new-fsCM-   This field contains a flag bit which when       registration flag 1006   set, indicating the fsMAC domain is           accepting new fsCM 106 registration.       Number of downstream   This field contains N number of downstream       channels 1008   channels in the fsMAC           domain.       Number of upstream   This field contains M number of upstream       channels   channels in the fsMAC domain.       1010       Downstream channel change   This field contains a count of changes in       count 1012   downstream channel configuration. If this           field is different than the count in the           previous MDCD message 1000, fsCMs 106 in the           fsMAC domain must update its downstream           channel configuration to the current MDCD           message 1000.       Upstream channel change   This field contains a count of changes in       count 1014   upstream channel configuration. If this           field is different than the count in the           previous MDCD message 1000, fsCMs 106 in the           fsMAC domain must update its upstream           channel configuration to the current MDCD           message 1000.       List of downstream   This field contains a list of N downstream       channel identifiers and   channel identifiers and the associated TLVs       TLVs 1026   defining the channel parameters. Table 10           shows an example of a list of 2 downstream           channels.       List of upstream channel   This field contains a list of M upstream       identifiers and TLVs 1028   channel identifiers and the associated TLVs           defining the channel parameters. Table 11           shows an example of a list of 5 upstream           channels.       List of upstream burst   This field contains a list of X upstream       profile identifiers and   burst profile identifiers and the associated       TLVs 1030   TLVs defining the burst parameters. Table 12           shows an example of a list of 3 burst           profiles.                  
 
         [0080]    
       
         
               
             
               
             
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 10 
               
             
             
               
                   
               
               
                   
               
               
                 Downstream channel identifiers and TLVs 1026 example 
               
             
          
           
               
                 Number of 
               
             
          
           
               
                 downstream channels = 2 
                 TLV encoding 
               
             
          
           
               
                 Downstream channel 
                 Length 
                 Value 
                 Type 
                   
               
               
                 parameter type 
                 (1 byte) 
                 (1 byte) 
                 (L bytes) 
                 Description 
               
               
                   
               
             
          
           
               
                 Downstream channel identifier 
                 1 
                 1 
                 01 
                 01: (Channel ID) 
               
               
                 Downstream channel type 
                 2 
                 1 
                 1 
                 1: (DCPC) 
               
               
                 Center frequency 
                 3 
                 4 
                 f1 
                 Hz 
               
               
                 Symbol rate 
                 4 
                 1 
                 0 
                 0: (5.056941 M 
               
               
                   
                   
                   
                   
                 symbols/sec) 
               
               
                 FEC 
                 5 
                 1 
                 1 
                 1: (J83 Annex 
               
               
                   
                   
                   
                   
                 B) 
               
               
                 Modulation 
                 6 
                 1 
                 0 
                 64 QAM 
               
               
                 Interleave depth (I, J) 
                 7 
                 2 
                 16, 8 
                 Latency = 0.48 ms 
               
               
                 Downstream channel 
                 1 
                 1 
                 02 
                 02: (Channel 
               
               
                 identifier 
                   
                   
                   
                 ID) 
               
               
                 Downstream channel type 
                 2 
                 1 
                 2 
                 2: (DPC1) 
               
               
                 Center frequency 
                 3 
                 4 
                 f2 
                 Hz 
               
               
                 Symbol rate 
                 4 
                 1 
                 1 
                 1: (5.360537 M 
               
               
                   
                   
                   
                   
                 symbols/sec) 
               
               
                 FEC 
                 5 
                 1 
                 1 
                 1: J83 Annex B 
               
               
                 Modulation 
                 6 
                 1 
                 1 
                 256 QAM 
               
               
                 Interleave depth (I, J) 
                 7 
                 2 
                 128, 1 
                 Latency = 2.8 ms 
               
               
                   
               
             
          
         
       
     
         [0081]    
       
         
               
             
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 11 
               
             
             
               
                   
               
               
                   
               
               
                 Upstream channel identifiers and TLVs 1028 example 
               
             
          
           
               
                 Number of 
                   
               
               
                 upstream channels = 5 
                 TLV encoding 
               
             
          
           
               
                 Upstream 
                 Type 
                 Length 
                 Value 
                   
               
               
                 channel parameter type 
                 (1 byte) 
                 (1 byte) 
                 (L bytes) 
                 Description 
               
               
                   
               
             
          
           
               
                 Upstream channel 
                 1 
                 1 
                 10 
                 10 
               
               
                 identifier 
               
               
                 Upstream channel type 
                 2 
                 1 
                 0 
                 0: (UCCI) 
               
               
                 Center frequency 
                 3 
                 4 
                 f3 
                 Hz 
               
               
                 Symbol rate 
                 4 
                 1 
                 0 
                 0: (640K 
               
               
                   
                   
                   
                   
                 symbols/sec) 
               
               
                 Upstream channel 
                 1 
                 1 
                 11 
                 Channel ID = 11 
               
               
                 identifier 
               
               
                 Upstream channel type 
                 2 
                 1 
                 1 
                 1: (UCC2) 
               
               
                 Center frequency 
                 3 
                 4 
                 f4 
                 Hz 
               
               
                 Symbol rate 
                 4 
                 1 
                 2 
                 2: (320K 
               
               
                   
                   
                   
                   
                 symbols/sec) 
               
               
                 Upstream channel 
                 1 
                 1 
                 12 
                 Channel ID = 12 
               
               
                 identifier 
               
               
                 Upstream channel type 
                 2 
                 1 
                 2 
                 2: (UCC3) 
               
               
                 Center frequency 
                 3 
                 4 
                 f5 
                 Hz 
               
               
                 Symbol rate 
                 4 
                 1 
                 3 
                 3: 640K 
               
               
                   
                   
                   
                   
                 symbols/sec 
               
               
                 Upstream channel 
                 1 
                 1 
                 13 
                 Channel ID = 13 
               
               
                 identifier 
               
               
                 Upstream channel type 
                 2 
                 1 
                 3 
                 3: (UPC1) 
               
               
                 Center frequency 
                 3 
                 4 
                 f6 
                 Hz 
               
               
                 Symbol rate 
                 4 
                 1 
                 6 
                 6: 5.12 M 
               
               
                   
                   
                   
                   
                 symbols/sec 
               
               
                 Upstream channel 
                 1 
                 1 
                 14 
                 Channel ID = 14 
               
               
                 identifier 
               
               
                 Upstream channel type 
                 2 
                 1 
                 4 
                 4: (UPC2) 
               
               
                 Center frequency 
                 3 
                 4 
                 f7 
                 Hz 
               
               
                 Symbol rate 
                 4 
                 1 
                 6 
                 6: 5.12 M 
               
               
                   
                   
                   
                   
                 symbols/sec 
               
               
                   
               
             
          
         
       
     
         [0082]    
       
         
               
             
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 12 
               
             
             
               
                   
               
               
                   
               
               
                 Upstream burst profile identifiers and TLVs example 
               
             
          
           
               
                 Number of 
                   
               
               
                 upstream burst 
               
               
                 profiles = 3 
                 TLV encoding 
               
             
          
           
               
                 upstream burst 
                 Type 
                 Length 
                 Value 
                   
               
               
                 parameter type 
                 (1 byte) 
                 (1 byte) 
                 (L bytes) 
                 Description 
               
               
                   
               
             
          
           
               
                 Burst identifier 
                 1 
                 1 
                 11 
                 Burst 
               
               
                   
                   
                   
                   
                 profile 1 
               
               
                 Modulation 
                 2 
                 1 
                 0 
                 0 = QPSK 
               
               
                 Preamble length 
                 3 
                 2 
                 64 
                 64 bytes 
               
               
                 FEC code word (k) 
                 4 
                 1 
                 78 
                 13 bytes 
               
               
                 FEC error correction 
                 5 
                 1 
                 6 
                 T = 2 bytes 
               
               
                 (T) 
               
               
                 Scramble seed 
                 6 
                 2 
                 35 
                 Seed = 00110101 
               
               
                 Inter-burst guard time 
                 7 
                 1 
                 5 
                 5 symbols 
               
               
                 burst identifier 
                 1 
                 1 
                 12 
                 Burst 
               
               
                   
                   
                   
                   
                 profile 2 
               
               
                 modulation 
                 2 
                 1 
                 0 
                 0 = QPSK 
               
               
                 Preamble length 
                 3 
                 2 
                 64 
                 64 bits 
               
               
                 FEC code work (k) 
                 4 
                 1 
                 78 
                 78 bytes 
               
               
                 FEC error correction 
                 5 
                 1 
                 6 
                 T = 6 bytes 
               
               
                 (T) 
               
               
                 Scramble seed 
                 6 
                 2 
                 35 
                 Seed = 00110101 
               
               
                 Inter-burst guard time 
                 7 
                 1 
                 5 
                 5 symbols 
               
               
                 burst identifier 
                 1 
                 1 
                 13 
                 Burst 
               
               
                   
                   
                   
                   
                 profile 3 
               
               
                 Modulation 
                 2 
                 1 
                 0 
                 0 = 64 QAM 
               
               
                 Preamble length 
                 3 
                 2 
                 64 
                 128 bits 
               
               
                 FEC code work (k) 
                 4 
                 1 
                 78 
                 256 bytes 
               
               
                 FEC 
                 5 
                 1 
                 6 
                 T = 10 
               
               
                 error correction (T) 
                   
                   
                   
                 bytes 
               
               
                 Scramble seed 
                 6 
                 2 
                 35 
                 Seed = 00110101 
               
               
                 Inter-burst guard time 
                 7 
                 1 
                 5 
                 5 symbols 
               
               
                   
               
             
          
         
       
     
         [0083]     Full-Service Cable Modem System Operation  
         [0084]     For this exemplified embodiment, the fsCMTS sets up the fsCM domain comprising:  
         [0085]     Two downstream channels:  
         [0086]     1. The DCPC  147  is the broadcast channel for all the fsCMs within the fsCM domain, and is configured to ITU-T J83 Annex B standard with 64 QAM modulation and at a center frequency of f1 Hz in the downstream spectrum as shown in  FIG. 3 . This channel is primarily used for data-over-cable MAC management messages, IP traffic and to a less extent, MPEG-2 video delivery.  
         [0087]     2. The DPC 1   137  is the broadcast channel for all the fsCMs within the fsCM domain, and is configured to be ITU-T J83 Annex B standard with 256 QAM modulation and at a center frequency of f2 Hz in the downstream spectrum as shown in  FIG. 3 . This channel is primarily used for broadcast quality MPEG-2 movie delivery, but also carries IP packets.  
         [0088]     Three upstream control channels:  
         [0089]     1. The UCC 1   174  used for contention bandwidth requests for all or a group of said fsCMs, is configured to operate at 640 Ksymbols/sec with QPSK modulation and at a center frequency of f3 Hz in the upstream spectrum as shown in  FIG. 3 .  
         [0090]     2. The UCC 2   176  used for contention calibration and maintenance for all or a group of said fsCMs, is configured to operate at 320 Ksymbols/sec with QPSK modulation and at a center frequency of f4 Hz in the upstream spectrum as shown in  FIG. 3 .  
         [0091]     3. The UCC 3   178  used for Aloha contention, pay-per-view or video-on-demand request burst for all or a group of said fsCMs, is configured to operate at 640 Ksymbols/sec with QPSK modulation and at center frequency of f5 Hz in the upstream spectrum as shown in  FIG. 3 .  
         [0092]     Two upstream payload channels:  
         [0093]     1. The UPC 1   182 , intended primarily for voice-over-IP CBR traffic for all or a group of said fsCMs, is configured to operate at 5.12 Msymbols/sec with 16 QAM modulation and at a center frequency of f6 Hz in the upstream spectrum as shown in  FIG. 3 .  
         [0094]     2. The UPC 2   184  is intended primarily for high-speed data and media streaming traffic for all or a group of said fsCMs  106  is configured to operate at 5.12 Msymbols/sec with 16 QAM modulation and at a center frequency of f7 Hz in the upstream spectrum as shown in  FIG. 3 .  
         [0095]     When the fsCMTS  102  is operational, the following MAC management messages are broadcast periodically to all the fsCMs  106  to establish a fsCM domain, in the HFC  104  via the DCPC  147 :  
         [0096]     1. SYNC  500 , typically sent every 150 to 250 ms,  
         [0097]     2. MDCD  1000 , typically sent every 1 to 2 seconds, and  
         [0098]     3. MMAP  900 , typically sent every 2 to 10 ms.  
         [0099]     SYNC  500  establishes network-wide clock synchronization of the fsCMTS  102  and the fsCMs  106  using a conventional time-stamp methodology which is known in the art. The MDCD  1000  establishes the fsMAC domain using the fsMAC domain identifier  1004 . The MDCD  1000  also contains the parameters needed by the fsCMs  106  to join the fsMAC domain by setting up the channel and burst profiles. The MMAP  900  contains information about upstream transmission opportunities on a specific channel, using a specific burst profile, a duration of the transmission time, and at a specific start time to transmit. The MMAP  900  also contains upstream transmission opportunities, typically once every 1 to 2 seconds, for the fsCM  106  that wishes to join the network to transmit the CREQ  600  to adjust its ranging offset, center frequency, transmitter power level, and transmitter pre-equalizer coefficients etc. as part of the initialization process. Once initialized, the fsCM  106  starts to use the contention-based CREQ  600  to request transmission of payload packets.  
         [0100]     Full-Service Cable Modem Initialization  
         [0101]     Referring to  FIG. 10 , a fsCM initialization flow diagram  1100  is entered at a block  1102  when the fsCM  106  is powered up or reset. In a block  1104 , the DCPC receiver  470  at the fsCM  106  is continuously searching for a valid DCPC channel. The DCPC is considered to be valid if MPEG-2 TS with a valid data-over-cable PID (e.g. 1FFE hexadecimal) is found. Once found, block  1106  is entered to search for the valid MDCD  1000 . In the MDCD  1000 , the flag  1006 , if set, signifies that the DCPC is accepting the new fsCM  106  registrations, and a block  1110  is entered. If the flag  1006  is not set, signifying the MDCD  1000  is not taking in new registrations, the fsCM  106  will exit the block  1106  and enter a block  1104  for searching for another valid DCPC.  
         [0102]     In the block  1110 , all the parameters in the MDCD  1000  are accepted by the fsCM  106 . The fsMAC domain identifier  1004  will be used to match the fsMAC domain identifier  586  in the SYNC  500  in block  1114 . If the valid SYNC  500  is received, the fsCM  106  will synchronize its time base with the fsCMTS time base. The fsCM  106  initializes the other downstream and upstream channels, the burst profiles, based on information received in the MDCD  1000  and enters a block  1116 .  
         [0103]     In the block  1116 , the fsCM  106  monitor the MMAP  900  for broadcast calibration grant as shown in Table 6. In this example, the second broadcast grant is for CREQ  600 . In the block  1116 , if a CREQ  600  grant is received, a block  1118  will be entered, and the fsCM  106  will construct a calibration burst based on the burst profile, and length of payload information in the received broadcast grant  906 .  
         [0104]     In a block  1120  the CREQ  600  burst will then be transmitted at the specified upstream channel at the specified transmission start time (subject to back-off based on the back-off start and end values specified in the grant using exponential back-off algorithm). If a calibration response the CRSP  700  is received by the fsCM  106  in a block  1122 , the initial calibration is successful and a fine calibration block  1124  is entered. If no CRSP  700  is received in the block  1122 , after a pre-determined time-out, a block  1116  will be entered and the CREQ  600  process will be retried (not shown).  
         [0105]     In a block  1124 , the fsCMTS  102  will do fine calibration on each of the upstream channels in the fsCM domain by sending a periodic unicast fine calibration grant to the fsCM  106  for each upstream channel. In the block  1124  the fine-calibration process is complete after receiving the CRSP  700  from the fsCMTS  102  and after the fsCM  106  has adjusted its upstream channel parameters ranging offset, frequency, power level, and pre-equalizer coefficients etc. These parameters will be saved in the fsCM  106  upstream channel profiles and they will be used to configure the channel before a burst transmission. After fine calibration, a block  1126  is entered. The fsCM  106  completes the modem registration process and becomes operational in a block  1128 .  
         [0106]     Transmission Using Bandwidth Request  
         [0107]     Referring to  FIG. 11 , which is a flow diagram of packet transmission using contention-based bandwidth request  1200 . In a block  1204 , one or more packets are queued up at the fsCM  106 . In a block  1206  the fsMAC-CM  192  chooses one or more of packets to transmit. The number of bytes of payload and header type (e.g. short, long or concatenated) are determined. In a block  1208 , the fsCM  106  waits until the MMAP  900  is received with the broadcast grant  906  (example in Table 6). Entering a block  1210 , the fsCM  106  uses the back-off start and end values to calculate the initial back-off of burst transmission (any back-off algorithm will work and is well-known in the art). If the back-off algorithm determines the transmission opportunity is beyond the current grant, the fsCM  106  will defer the transmission to the next MMAP  900 ; otherwise, referring to Table 6, 1st broadcast grant, the fsCM  106  calculates the BREQ  800  burst transmission start time based on: 
 
(Transmission start time)+
 
(Burst duration calculated and based on the length of 
 
payload and header in bytes and burst profile)×number of 
 
burst deferred calculated by the back-off algorithm). 
 
         [0108]     BREQ  800  will be transmitted at the calculated time at the channel specified by the upstream channel ID. A block  1212  is entered and the fsCM  106  waits for the unicast grant  908  or the pending grant  910  in the next MMAP  900 . The next MMAP  900  is received in a block  1218  and is checked for the unicast grant  908  with a service identifier corresponding to the one in the original BREQ  800  in a block  1220 . The unicast grant  908  will have the necessary information (channel profile, header type, and burst profile) to assemble a burst in a block  1226  and transmit the burst at the specified upstream channel at the specified transmission start time (subject to backoff) in a block  1228 . If in the block  1220 , no unicast grant  908  is received for the BREQ  800 , the MMAP  900  is checked for existence of the pending grant  910 .  
         [0109]     In a block  1224 , if there is a pending grant for the fsCM  106 , the block  1218  is entered to wait for the next MMAP  900 . If in the block  1224 , there is no pending grant for the fsCM  106  in the MMAP  900 , the BREQ  800  is considered lost or collided, and the block  1208  is entered to retry the BREQ  800  transmission.  
         [0110]     True Seamless Channel Change  
         [0111]     In a conventional data-over cable system, a conventional cable modem termination system (CMTS) may direct a cable modem (CM) to change its upstream channel for traffic load balancing, noise avoidance, or failed channel backup. The procedure for performing a channel change is as follows. When the CMTS determines to move a CM from the currently assigned upstream channel to another, it sends a channel change request message to the CM. In response, the CM transmits a channel change response message on the currently assigned channel to signal its readiness to use the new channel. After switching to the new channel, the CM typically performs recalibration of transmitter parameters such as ranging offset, power level, frequency and pre-equalizer coefficients before the CM can use the new channel. Such a channel switching mechanism can be very time-consuming and can take seconds or more because a complete re-calibration is often required.  
         [0112]     According to this invention, a true seamless channel change can be achieved in the fsCM system  100 . True seamless channel change means on a packet-by-packet basis, each CMTS-directed cable modem burst transmission can be at any one of the upstream channels, configured with any one of the burst profiles as defined by the fsCMTS domain  1004  in the fsMAC message MDCD  1000 .  
         [0113]     The fsCM  106  joins a fsCM domain accepting new registrations in the MDCD message  1000 , which also contains fields for a list of downstream channels with channel profile parameters  1026 , a list of upstream channel parameters and channel profile parameters  1028 , and a list of burst profile parameters  1030 . These profile parameters are uniquely identified within the fsMAC domain using downstream, upstream and burst identifiers. These parameters are stored in the fsCM, together with the channel calibration parameters for each channel as a result of calibration request/response process.  
         [0114]     When an upstream transmission grant is received from the MMAP message  900 , the grant contains sufficient information about transmission channel identifier, burst profile, size of granted and header type etc. to form an upstream burst to be transmitted at the exact start time specified in the same MMAP message  900 . Thus the channel change is immediate and truly seamless.  
       ALTERNATIVE EMBODIMENTS  
       [0115]     One skilled in the art can take advantage of the multi-channel fsMAC in different variations for further optimization. Examples are:  
         [0116]     Use all downstream channels for IP packet streams, if MPEG-2 video not being needed, to further boost the downstream capacity for additional users, or for IP media streaming.  
         [0117]     Use a single upstream control channel for channel calibrations and bandwidth requests.  
         [0118]     Define different upstream payload channels, such as CBR channels, dedicated channels to achieve quality of service and capacity goals.  
         [0119]     Although the teachings of the invention have been illustrated herein in terms of a few preferred and alternative embodiments, those skilled in the art will appreciate numerous modifications, improvements and substitutions that will serve the same functions without departing from the true spirit and scope of the appended claims. All such modifications, improvement and substitutions are intended to be included within the scope of the claims appended hereto.