Mixed DOCSIS 1.0 TDMA bursts with SCDMA transmissions on the same frequency channel

• US 6,459,703 B1
• Filed: 06/21/1999
• Issued: 10/01/2002
• Est. Priority Date: 06/21/1999
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Terayon Communications Systems Incorporated (Motorola Solutions, Inc.)
• Inventors: Rakib, Selim Shlomo, Lind, Paul Alan, Grimwood, Michael
• Primary Examiner(s): Vincent, David
• Assistant Examiner(s): Sam, Phirin
• Application Number:
  US09/337,167
• Time in Patent Office: 1,198 Days
• Field of Search: 370/468, 370/229, 370/441, 370/442, 370/251, 370/252, 370/270, 370/294, 370/295, 370/302, 370/351, 370/352, 370/353, 370/358, 370/400, 370/420, 370/458, 370/436, 370/437, 370/478, 370/479, 370/480, 370/498
• US Class Current: 370/442
• CPC Class Codes: H04J 3/1694 Allocation of channels in TDM/TDMA networks, e.g. distributed multiplexers Passive Optical Networks H04Q11/0062

Abstract

A method for allowing upstream channels having the same multiplexing type but different symbol rates or the same symbol rates but different multiplexing types to be transmitted on the same frequency band without interfering with each other. In particular, a method for allowing DOCSIS 1.0 TDMA only cable modems to coexist on a digital data delivery distributed system with advanced PHY TDMA or SCDMA mode cable modems without the need for modification of the DOCSIS 1.0 cable modems or the need for the DOCSIS 1.0 modems to transmit on a different frequency. The method comprises: using a plurality of upstream channel descriptor messages transmitted from said central modem to said distributed modems to define a plurality of different upstream logical channels sharing the same frequency band, each said logical channel having either a different symbol rate but the same multiplexing type or the same multiplexing type but a different symbol rate, said upstream channel descriptor messages assigning each of said distributed modems to logical channels appropriate to the symbol rate and modulation type of said distributed modem; and, scheduling transmission bursts on each said logical channel by transmitting a bandwidth award and scheduling message for each logical channel each of which defines and controls which distributed modems on the logical channel to which the bandwidth award and scheduling message can transmit and when they can transmit, said bandwidth award and scheduling messages being coordinated by said central modem so that there is never any overlap in time between transmission bursts on different logical channels sharing the same frequency band.

Claims

1. A process for transmitting multiple upstream logical channels of data on one or more physical channels, each physical channel comprising one carrier wave having a center frequency, logical channel having one of a plurality of different multiplexing types or symbol rates and having a bandwidth according to its symbol rate, and being transmitted from one of a plurality of distributed modems to a central modem, comprising:

using a plurality of upstream channel descriptor messages transmitted from said central modem to said distributed modems to define a plurality of upstream logical channels with one upstream channel descriptor message defining each said logical channel in terms of at least its center frequency and symbol rate and which one of at least two different multiplexing types are to be used for data bursts transmitted on said logical channel, said upstream channel descriptor messages defining upstream physical and upstream logical channels transmitted on said various physical channels, said upstream logical channels having the same or different multiplexing types and the same or different symbol rates such that all said logical and physical upstream channels can at least partially or fully overlap in bandwidth, where bandwidth is defined as the range of frequencies around the center frequency of the physical channel upon which said upstream logical channel is transmitted extending from a low frequency rolloff of the Fourier spectrum of said logical channel to a high frequency rolloff of the Fourier spectrum of said logical channel;

scheduling transmission bursts on each said logical channel by specified distributed modems by transmitting to all distributed modems a separate bandwidth award and scheduling message for each logical channel, each said bandwidth award and scheduling message specifying which distributed modem or modems can transmit on the logical channel to which the bandwidth award and scheduling message applies and also specifying when each said distributed modem can transmit so as to prevent overlaps in time between transmissions on logical channels that at least share the same bandwidth with other logical channels and so as to prevent any overlap in bandwidth between selected logical channels.

2. A process for transmitting digital data in a distributed system comprising a central transceiver coupled by a shared transmission medium to a plurality of different types of remote transceivers some of which are capable of time division multiple access transmission mode (hereafter TDMA mode) and others of which can transmit using synchronous code division multiple access only or are multimode capable in that they can transmit in either time division multiple access mode or synchronous code division multiple access mode (hereafter SCDMA mode) comprising:

establishing separate TDMA only and SCDMA only logical channels at one or more symbol rates to be transmitted on one or more physical channel carrier waves that share said transmission medium and which have the center frequencies thereof set so as to allow at least some or all of said logical channels to share the same bandwidth, establishing of said logical channels being accomplished using separate channel descriptor messages each of which defines the characteristics of the logical channel to which the channel descriptor message pertains; and

avoiding interference between bursts sent on different logical channels by sending a separate bandwidth award and scheduling message for each TDMA only and each SCDMA only logical channel to define which said remote transceivers may transmit and when they may transmit so that there is never any overlap between bursts on different logical channels that at least partially overlap in bandwidth but which allow overlap in time between bursts on logical channels which do not overlap in bandwidth.

3. A process for communication of digital data in a distributed system comprised of a head end transceiver coupled by a shared cable television transmission media to a plurality of Data Over Cable System Interface (hereafter referred to as DOCSIS) 1.0 and advanced PHY cable modems such that higher symbol rate time division multiplexed (hereafter TDMA) and synchronous code division multiplexed (hereafter SCDMA) communications can be made from said advanced PHY cable modems to said head end transceiver using the same bandwidth as is used by said DOCSIS 1.0 cable modems without the necessity for any changes to said DOCSIS 1.0 cable modems comprising:

1) establishing at least one separate time division multiplexed only (hereafter TDMA only) logical channel for said DOCSIS 1.0 cable modems and at least one synchronous code division multiplexed only (hereafter SCDMA only) logical channel for said advanced PHY cable modems and at least one time division multiplexed only logical channel at a faster symbol rate than said DOCSIS 1.0 cable modems are capable of, establishment of each said logical channel accomplished using a separate upstream channel descriptor message for each said logical channel, said upstream channel descriptor messages establishing said logical channels for said DOCSIS 1.0 cable modems and said TDMA only and SCDMA only logical channels for said advanced PHY cable modem s on physical channels having center frequencies established by said upstream channel descriptor messages such that all said logical channels for said DOCSIS 1.0 modems at least partially overlap in bandwidth with the bandwidth of said TDMA only and SCDMA only logical channels for said advanced PHY cable modems;

2) avoiding collisions between bursts by cable modems of different types transmitting on different logical channels by establishing separate and nonoverlapping TDMA and SCDMA regions in said logical channels established in step 1 by using a separate MAP message for each logical channel which defines when cable modems assigned to said logical channel can transmit, and coordinating all said MAP messages such that there is never any overlap in time between bursts transmitted on different logical channels that at least partially share the same bandwidth.

4. A process comprising:

receiving upstream bandwidth request messages from Data Over Cable System Interface (hereafter referred to as DOCSIS) 1.0 and advanced PHY remote cable modems in a distributed digital data communication system coupling said remote cable modems to a head end cable modem, each said remote cable modem having a service identifier or SID, each said bandwidth request message containing the SID of the cable modem that sent it;

using the SID of each bandwidth request message and a lookup table to determine whether each remote cable modem which sent the bandwidth request message is a DOCSIS 1.0 modem or advanced PHY modem;

making bandwidth awards to one or more of said remote cable modems that made bandwidth requests using any bandwidth management scheme;

determing the number of center frequencies of one or more channels to be created in the band of frequencies reserved for digital data transmission;

determining from said bandwidth awards whether it is necessary to establish one or more time division multiplexed (hereafter TDMA) burst only logical channels for DOCSIS 1.0 modems along with a synchronous code division multiplexed (hereafter SCDMA) only burst logical channel for advanced PHY modems and a time division multiplexed burst only logical channel for advanced PHY modems to share the bandwidth of said band of frequencies reserved for digital data transmission;

establishing each necessary logical channel and each necessary physical channel by generating and transmitting to said remote cable modems an upstream channel descriptor (hereafter UCD) message for each said logical channel, said UCD message defining the symbol rate and center frequency of each said logical channel and also defining which advanced PHY remote cable modems will transmit in TDMA mode and which will transmit in SCDMA mode, each UCD message also defining which remote cable modems are assigned to transmit in each said logical channel as well as the symbol rate and the center frequency of the physical channel upon which said logical channel is to be transmitted;

composing and transmitting to said remote cable modems a MAP message for each said logical channel by using the SIDs of each remote cable modem assigned to said logical channel which has been assigned bandwidth and mapping minislots corresponding to the bandwidth assignment to that SID in the MAP message, each MAP message for a TDMA only logical channel defining TDMA regions and silent intervals, and each MAP message for an SCDMA only logical channel defining SCDMA regions and silent intervals, and wherein the silent intervals in said MAP messages for each of said logical channels that share bandwidth with any other logical channel are established so as to prevent collisions between bursts on the different logical channels that share bandwidth.

5. A process for transmitting digital data in a distributed system comprising a central transceiver coupled by a shared transmission medium to a plurality of remote transceivers all of which use time division multiple access transmission mode (hereafter TDMA) but some of which transmit at a first symbol rate and others of which transmit at a second symbol rate, comprising:

establishing a first TDMA only logical channel dedicated to transmissions at said first symbol rate and a second TDMA only logical channel dedicated to transmissions at said second symbol rate, both said first and second logical channels which at least partially share the same bandwidth, said establishing of first and second logical channels carried out using a separate upstream channel descriptor message for each logical channel, the upstream channel descriptor message for said first logical channel defining the characteristics thereof and assigning only remote transceivers that transmit at said first symbol rate thereto, the upstream channel descriptor message for said second logical channel defining the characteristics thereof and assigning only remote transceivers that transmit at said second symbol rate thereto; and

sending a separate bandwidth award and scheduling message for each of said first and second logical channels to define and control which said remote transceivers assigned to each said logical channel may transmit and when they may transmit by establishing a first set of TDMA only intervals (hereafter referred to as TDMA regions) in said first TDMA only logical channel during which only TDMA transmissions at said first symbol rate may be made by remote transceivers specified in said bandwidth award and scheduling message which are configured to transmit TDMA bursts at said first symbol rate, and establishing a second set of TDMA only intervals in said second TDMA only logical channel during which only TDMA transmissions at said second symbol rate may be made by remote transceivers which are configured to transmit TDMA bursts at said second symbol rate and which are identified in the bandwidth award and scheduling message for said second logical channel, said bandwidth award and scheduling messages establishing said first and second sets of TDMA intervals such that there is never any overlap in time between any TDMA only interval in said first set when bursts at said first symbol rate are being transmitted and any TDMA only interval in said second set when bursts at said second symbol rate are being transmitted.

6. A cable modem termination apparatus having conventional design except that a computer therein is programmed to implement a process to carry out the following steps:

receive upstream bandwidth requests from DOCSIS 1.0 and advanced PHY modems containing identifiers of said modems, hereafter referred to as SIDs each modem having a unique SID, and looking up the type of modem each modem is from its SID;

make bandwidth awards to various SIDs based upon any bandwidth allocation scheme;

generate and transmit to said modems a plurality of upstream channel descriptor messages which define a number of logical channels adequate to fulfill the requiremenst of said bandwidth awards, each of which defines the center frequency of the carrier signal that is to implement one physical channel, and which also defines the symbol rate and multiplexing type for a single logical channel to be transmitted on said carrier, two or more of said upstream channel descriptor messages defining different logical channels to be transmitted on the carrier frequency or frequencies defined in said upstream channel descriptor message so as to share bandwidth between logical channels carrying higher symbol rate traffic and logical channels carrying lower symbol rate traffic, said upstream channel descriptor messages also defining which modems are to transmit on which logical channels and defining which advanced PHY modems are to transmit using time division multiplexed bursts and which advanced PHY modems are to transmit using synchronous code division multiplexed bursts;

using said bandwidth awards and the information from said upstream channel descriptor messages defining said logical channels, build a table of SIDs for each logical channel and assign intervals for transmission for each SID such that modems having different multiplexing types or different symbol rates do not ever transmit simultaneously on logical channels that share bandwidth, and such that modems having the same multiplexing type but different symbol rates do not ever transmit simultaneously on logical channels that share bandwidth; and

building a MAP message for each logical channel from said table of SIDs and transmitting the MAP messages to said modems to control when each modem transmits; and

maintaining an upstream minislot count in an upstream minislot counter in said cable modem termination apparatus and transmitting data downstream to said modems such that they can keep local minislot counters in each modem synchronized with the count of said upstream minislot counter.

7. Any cable modem termination system (hereafter CMTS) which has circuitry for performing and/or a computer programmed to perform the following functions:

1) receive bandwidth requests from different transceivers which transmit at different symbol rates and/or using different multiplexing types;

2) make bandwidth awards in accordance with any bandwidth allocation scheme;

3) sending downstream to said transceivers a plurality of upstream channel descriptor messages that define the transmission characteristics of a corresponding plurality of different upstream logical channels, at least some of said different upstream logical channels to be transmitted in the same frequency band with overlapping bandwidth such that unless some control is excercised by said CMTS, transmissions from different transceivers will collide;

4) sending downstream data in said upstream channel descriptor messages that control which transmission characteristics are to be used by transceivers which have programmable transmission characteristics and which have been assigned by said upstream channel descriptor messages to specified logical channels;

5) sending downstream mapping messages which define which transceivers can transmit on specified logical channels and when they can transmit such that no collisions occur between transmissions on different logical channels transmitted in the same frequency band which have overlapping bandwidth;

6) maintaining an upstream minislot count of upstream minislots or timeslots in said CMTS apparatus and transmitting data or other signals from said CMTS apparatus to said transceivers that can be used by said transceivers to keep upstream minislot counts kept in each transceiver synchronized with said upstream minislot count in said CMTS apparatus; and

7) configuring a receiver in said CMTS apparatus correctly at the correct times to receive and recover the data of bursts transmitted by different transceivers at times specified by said downstream mapping messages and transmitted using assigned logical channels and transmission parameters assigned by said CMTS apparatus via said upstream channel descriptor messages.

8. An advanced PHY transceiver for use as one of a plurality of distributed transceivers which carry out bidirectional digital data communications with a headend or common transceiver and which has receiver circuitry to receive one or more upstream channel descriptor messages defining the transmission characteristics said transceiver is supposed to use when it transmits bursts of data and to receive one or more MAP messages defining when, in terms of upstream minislot numbers, said transceiver can transmit on a logical channel specified in an upstream channel descriptor message, and having a configurable transmitter coupled to said receiver circuitry which is configured to transmit on a frequency and using parameters defined according to data in an upstream channel descriptor message that assigned said transceiver to a particular upstream logical channel, said transmitter using data received from said headend transceiver including said upstream channel descriptor messages and said MAP message(s) to transmit upstream bursts to said headend transceiver and to keep said transmissions synchronized to and contained within the upstream minislot boundaries of the minislots assigned to said transceiver by said MAP messages for upstream transmissions said upstream minislot boundaries defined by an upstream minislot counter in said headend transceiver corresponding to the upstream logical channel on which said transceiver is assigned to transmit such that said transmissions arrive at said headend transceiver during the appropriate minislots assigned by said MAP message(s) and such that no collisions occur with transmissions by other transceivers on other logical channels that have bandwidth which overlaps the bandwidth of the logical channel upon which said transceiver transmits.

9. A process for sharing bandwidth between different logical channels of transmitted data in the same band of frequencies assigned for transmissions of digital data upstream to a headend transceiver by a plurality of distributed digital data transceivers having at least one advanced PHY SCDMA transceiver which transmits using synchronous code division multiplexed multiplexing (hereafter SCDMA) and with a high symbol rate so as to consume a first bandwidth and at least one advanced PHY TDMA transceiver which transmits using time division multiplexed multiplexing (hereafter TDMA) at a symbol rate which consumes approximately the same bandwidth as said advanced PHY SCDMA transceiver(s), and at least one DOCSIS 1.0 transceiver which transmits using TDMA multiplexing at a second lower symbol rate so as to consume less bandwith than said advanced PHY SCDMA transceiver(s), comprising:

keeping a local upstream counter in each transceiver synchronized with an upstream counter in said headend transceiver such that transmissions which are scheduled to be transmitted by any said transceiver during specific intervals defined based upon data from said upstream counter in said headend transceiver may be transmitted at the proper time so as to arrive at said headend transceiver during the specified intervals;

defining a plurality of different upstream logical channels within the same band of frequencies and some or all of which may overlap in bandwidth, said definition accomplished by sending from said headend transceiver on a downstream data path to said distributed transceivers an upstream channel descriptor message for each said upstream logical channel, each said upstream channel descriptor message defining at least a center frequency for a radio frequency carrier upon which data of said upstream logical channel is to be transmitted and a symbol rate which defines the bandwidth of said upstream logical channel and a multiplexing type to be used on said logical channel, each said upstream channel descriptor message also defining which distributed transceivers are assigned to said upstream logical channel, said upstream channel descriptor messages defining at least one logical channel for transmissions by said advanced PHY SCDMA transceiver(s), and at least one logical channel for said advanced PHY TDMA transceiver(s) and at least one logical channel for said DOCSIS 1.0 transceivers, said center frequencies and symbol rates of said logical channels being such that at least said logical channels for said advanced PHY SCDMA and advanced PHY TDMA transceivers overlap in bandwidth with each other and at least partially overlap in bandwidth with said logical channel for said DOCSIS 1.0 transceivers; and

sending a bandwidth award and scheduling message for each logical channel which defines which transceivers can transmit and when they can transmit in terms of intervals defined by particular counts by said upstream counter in said headend transceiver such that each transceiver knows exactly when it can transmit and for how long on the logical channel assigned to said transceiver, said bandwidth award and scheduling messages controlling said transmission intervals on the various logical channels with bandwidth that at least partially overlap so that there are no collisions between bursts on the same logical channel or on different logical channels with overlapping bandwidth.

10. A process for sharing bandwidth in the same band of frequencies for transmissions upstream to a headend transceiver by a plurality of distributed digital data transceivers of different multiplexing types and symbol rates, said plurality of distributed digital data transceivers having transmitters at least one of which transmits using any first type of multiplexing (hereafter referred to as a first type transceiver) and with a high symbol rate so as to consume a first bandwidth, and at least one of which transmits using said second type of multiplexing (hereafter referred to as a second type transceiver) and transmits at a second lower symbol rate so as to consume less bandwith than said first type transceiver, comprising:

keeping a local upstream counter in each transceiver synchronized with an upstream counter in said headend transceiver such that transmissions which are scheduled to be transmitted upstream by any of said plurality of distributed digital data transceivers at one or more times defined based upon counts of said upstream counter in said headend transmitter can be transmitted at the proper time so as to arrive at said headend transceiver during the specified interval(s);

defining a plurality of different logical channels within the same band of frequencies by sending from said headend transceiver on a downstream data path to said distributed transceivers an upstream channel descriptor message for each said logical channel each of which defines for the logical channel to which it pertains at least a center frequency for a radio frequency carrier upon which data of said logical channel is to be transmitted and a symbol rate which defines the bandwidth of said logical channel and a multiplexing type to be used for transmission on said logical channel and which assigns specific ones of said distributed digital data transceivers to said logical channel, said upstream channel descriptor messages defining at least one logical channel for said first type transceivers and at least one logical channel for said second type transceivers, and wherein said center frequencies and symbol rates are defined such that said logical channels for said first type transceivers and said second type transceivers have overlapping bandwidth, but if more than one logical channel is defined for transceivers of said second type, said logical channels for said second type transceivers do not have to overlap in bandwidth with each other; and

sending a bandwidth award and scheduling message for each logical channel which defines which transceivers can transmit and when they can transmit in terms of intervals specified based upon counts from said upstream counter in said headend transceiver such that each transceiver is controlled by said headend transceiver to transmit only during specified intervals so as to avoid collisions between bursts transmitted by said first and second type transceivers on logical channels with overlapping bandwidth.