throbber
(12) United States Patent
`Hwang et al.
`
`(161616111616;
`(45) Date of Patent:
`
`US 6,590,893 B1
`Jul. 8, 2003
`
`US006590893B1
`
`(54) ADAPTIVE TRANSMISSION SYSTEM IN A
`NETWORK
`
`(75) Inventorsi Chien-Meen Hwallg, San Jose, CA
`(Us); Eugen Gersholl, San 105% CA
`(US); Maged F. Barsoum, Sunnyvale,
`EAWS); Hclglglnjgng?hall% H h
`upemno’
`(
`)>
`“01 ' “yn ’
`San Jose, CA (US); Fred Berkowitz,
`Palo Alto, CA (US); Bin Gu0, Fremont,
`CA (US)
`
`(73) Assignee: Legerity, Inc., Austin, TX (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`USC 154(b) by 0 days.
`
`(21) Appl NO . 09/286 997
`
`.
`
`..
`
`,
`
`5,426,643 A * 6/1995 Smolinske et a1. ....... .. 375/354
`5,477,550 A * 12/1995 Crisler et al. ............. .. 714/748
`5,666,383 A * 9/1997 Huang et al.
`375/219
`5,910,970 A * 6/1999 Lu . . . . . . . . . . . . . .
`. . . .. 375/222
`6,134,274 A * 10/2000 Sankaranarayanan et al.
`375/
`254
`6,157,612 A * 12/2000 Weerackody et al. ..... .. 370/215
`6,415,410 B1 * 7/2002 Kaneiva etal. .......... .. 714/749
`
`_
`_
`* cited by examiner
`
`Primary Examiner—Salvatore Cangialosi
`(74) Attorney, Agent, or Firm—McDermott, Will & Emery
`
`(57)
`
`ABSTRACT
`
`A network node con?gured for transmitting and receiving
`data to and from other netWork nodes is able to adapt the
`transmission rate based on the netWork conditions. The node
`initially transmits the data to a receiving node at a ?rst rate.
`If the data is not received error-free, the node is able to
`reduce the number of data bits of the current packet that are
`being transmitted and to increase the amount of redundant
`data. The node repeats the process until error-free transmis
`.
`.
`.
`sion is obtained.
`
`Apr‘ 7’ 1999
`(22) Filed:
`(51) Int. Cl.7 ................................................. .. H04J 3/06
`(52) US. Cl. ...................................... .. 370/354; 370/389
`(58) Field of Search ............................... .. 370/354, 403,
`370/543, 389, 506; 375/222, 254; 714/749
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,661,657 A * 4/1987 Grenzebach et al. ...... .. 375/359
`
`17 Claims, 5 Drawing Sheets
`
`5
`:
`'
`
`:
`:
`5
`i
`:
`
`—>
`_.
`DIFF.
`ENCDR+ IFFT
`
`‘9
`
`\
`14
`
`/
`12
`
`OUT
`-
`PARJ ~>AFE
`SER.
`
`/
`18
`
`1
`16
`
`DIFF.
`DECDR
`FFT —> 8‘
`SLCR
`
`I
`26
`
`\
`28
`
`v
`
`5
`:
`;
`:
`:
`E
`5
`E
`i
`
`CSCO-1013
`Cisco v. TQ Delta
`Page 1 of 12
`
`

`
`U.S. Patent
`
`Jul. 8, 2003
`
`5f01¢I.Ce.hS
`
`US 6,590,893 B1
`
`
`
`Pm?‘&OEntFGE
`
`Page 2 of 12
`
`

`
`U.S. Patent
`
`Jul. 8, 2003
`
`5f02¢I.Ce.hS
`
`US 6,590,893 B1
`
`Page 3 of 12
`
`

`
`U.S. Patent
`
`Jul. 8,2003
`
`Sheet 3 0f5
`
`US 6,590,893 B1
`
`3 .QE
`
`E58”.
`
`0 mew
`
`< O 0
`
`6.2 Q2
`
`mew
`
`Q1 .
`
`EEEEE
`
`mm .QE
`
`um .61
`
`om .GI
`
`3|
`
`CHANNEL
`
`at 2.:
`
`O O
`
`0 O
`
`O O O
`
`Page 4 of 12
`
`

`
`U.S. Patent
`
`Jul. 8,2003
`
`Sheet 4 0f 5
`
`US 6,590,893 B1
`
`TRANSMITTER
`CONTROLLER
`
`32: RECEIVER
`
`CONTROLLER
`34
`
`20\
`
`TRANSMITTER
`CONTROLLER
`
`I
`
`RECEIVER
`CONTROLLER
`44
`
`\CHANNEL 40
`
`FIG. 4
`
`Page 5 of 12
`
`

`
`U.S. Patent
`
`Jul. 8,2003
`
`Sheet 5 of5
`
`US 6,590,893 B1
`
`TRANSMITTER CONTROLLER 200
`ADDS CRC CODE TO END
`'4
`OF DATA PACKET
`I
`TRANSMITTER ENCO DES
`DATA PACKET
`
`202
`
`Y
`TRANSMIT TIME WORK,
`DATA AND CRC CODE
`
`204
`
`DATA
`RECEIVED
`AT DESTINATION
`WITHOUT ERRORS
`
`208
`DESTINATION
`NODE XMITTER
`CONTROLLER
`XMITS ACKNOW.
`SIGNAL
`
`210
`
`SIGNAL RECEIVED
`FROM DESTINATION
`NODE
`
`YES
`
`CURRENT
`PACKET TRANS.
`PREDETERM.
`NUMBER
`
`TRANSMITTER CONTROLLER 214
`TAKES PREDET. # OF BITS OF
`CURRENT PACK.
`I
`XMITTER CONT. ADDS CRC
`CODE AND REDUNDANT DATA
`
`216
`
`I
`TRANSMITTER ENCODES DATA 21a
`PACKET AND ADDS TIME MARK
`___—I
`
`FIG. 5
`
`Page 6 of 12
`
`

`
`US 6,590,893 B1
`
`1
`ADAPTIVE TRANSMISSION SYSTEM IN A
`NETWORK
`
`TECHNICAL FIELD
`
`The present invention relates to network communications
`and more particularly, to an adaptive transmission system
`used in a netWork.
`
`BACKGROUND ART
`Modern society continues to create exponentially increas
`ing demands for digital information and the communication
`of such information betWeen data devices. Local area net
`Works use a netWork, cable or other media to link stations on
`the netWork for exchange of information in the form of
`packets of digital data. A typical local area netWork archi
`tecture uses a media access control (MAC) enabling netWork
`interface cards at each station to share access to the media.
`Most conventional local area netWork architectures use
`media access controllers operating according to half-duplex
`or full-duplex Ethernet (ANSI/IEEE standard 802.3) proto
`col and a prescribed netWork medium, such as tWisted pair
`cable.
`These architectures have proven quite successful in pro
`viding data communications in commercial applications.
`HoWever, these common local area netWork architectures
`require installation of specialiZed Wiring and use of speci?c
`Wiring topologies. For example, the most popular netWork
`protocols, such as Ethernet, require special rules for the
`Wiring, for example With regard to quality of Wire, range of
`transmission and termination.
`Due to the success of the Internet and the rapid decreases
`in the prices of personal computers and associated data
`equipment, a demand has arisen for data communications
`betWeen a limited number of devices Within relatively small
`premises, typically a residence or small business. While
`existing local area netWorks can serve the purpose, in such
`installations, the cost of installing physical netWork Wiring
`satisfying the rules for the particular protocol can be pro
`hibitively expensive.
`Most existing buildings, including residences, include
`some existing Wiring, for phones, electrical poWer and the
`like. Proposals have been made to communicate data using
`such existing infrastructure. This reduces the costs of Wiring
`for the netWork, but the existing Wiring raises a variety of
`issues regarding transport of high-speed digital signals.
`For example, efforts are underWay to develop an archi
`tecture that enables computers to be linked together using
`conventional tWisted pair telephone lines. Such an
`arrangement, referred to herein as a home netWork
`environment, provides the advantage that existing telephone
`Wiring in a home may be used to implement a home netWork
`environment Without incurring costs for substantial neW
`Wiring installation. HoWever, any such netWork must deal
`With issues relating to the speci?c nature of in-home tele
`phone Wiring, such as operation over a media shared With
`other services Without interference from or interfering With
`the other services, irregular topology, and noise. With
`respect to the noise issue, every device on the telephone line
`may be a thermal noise source, and the Wiring may act much
`like an antenna to pick up disruptive radio signal noise.
`Telephone lines are inherently noisy due to spurious noise
`caused by electrical devices in the home, for example
`dimmer sWitches, transformers of home appliances, etc. In
`addition, the tWisted pair telephone lines suffer from turn-on
`transients due to on-hook and off-hook and noise pulses
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`2
`from the standard telephones coupled to the lines, and
`electrical systems such as heating and air conditioning
`systems, etc.
`An additional problem in telephone Wiring netWorks is
`that the signal condition (i.e., shape) of a transmitted Wave
`form depends largely on the Wiring topology. Numerous
`branch connections in the tWisted pair telephone line
`medium, as Well as the different associated lengths of the
`branch connections, may cause multiple signal re?ections on
`a transmitted netWork signal. Telephone Wiring topology
`may cause the netWork signal from one netWork station to
`have a peak-to-peak voltage on the order of 10 to 20
`millivolts, Whereas netWork signals from another netWork
`station may have a value on the order of one to tWo volts.
`Hence, the amplitude and shape of a received pulse may be
`so distorted that recovery of a transmit clock or transmit data
`from the received pulse becomes substantially dif?cult.
`At the same time a number of XDSL technologies are
`being developed and are in early stages of deployment, for
`providing substantially higher rates of data communication
`over tWisted pair telephone Wiring of the telephone netWork.
`XDSL is used herein as a generic term for a group of
`higher-rate digital subscriber line communication schemes
`capable of utiliZing tWisted pair Wiring from an office or
`other terminal node of a telephone netWork to the subscriber
`premises. Examples under various stages of development
`include ADSL (Asymmetrical Digital Subscriber Line),
`HDSL (High data rate Digital Subscriber Line) and VDSL
`(Very high data rate Digital Subscriber Line).
`Consider ADSL as a representative example. For an
`ADSL-based service, the user’s telephone netWork carrier
`installs one ADSL modem unit at the netWork end of the
`user’s existing tWisted-pair copper telephone Wiring.
`Typically, this modem is installed in the serving central
`office or in the remote terminal of a digital loop carrier
`system. The user obtains a compatible ADSL modem and
`connects that modem to the customer premises end of the
`telephone Wiring. The user’s computer connects to the
`modem. The central office modem is sometimes referred to
`as an ADSL Terminal Unit—Central Office or ‘AT U-C’. The
`customer premises modem is sometimes referred to as an
`ADSL Terminal Unit—Remote or ‘ATU-R’. The ADSL
`user’s normal telephone equipment also connects to the line
`through a frequency combiner/splitter, Which is incorporated
`in the ATU-R. The normal telephone signals are split off at
`both ends of the line and processed in the normal manner.
`For digital data communication purposes, the ATU-C and
`ATU-R modem units create at least tWo logical channels in
`the frequency spectrum above that used for the normal
`telephone traf?c. One of these channels is a medium speed
`duplex channel and the other is a high-speed doWnstream
`only channel. TWo techniques are under development for
`dividing the usable bandWidth of the telephone line to
`provide these channels. One approach uses Echo Cancella
`tion. Currently, the most common approach is to divide the
`usable bandWidth of a tWisted Wire pair telephone line by
`frequency, that is to say by Frequency Division Multiplexing
`(FDM).
`FDM uses one frequency band for upstream data and
`another frequency band for doWnstream data. The doWn
`stream path is then divided by time division multiplexing
`into one or more high-speed channels and one or more loW
`speed channels. The upstream path also may be time
`division multiplexed into corresponding loW speed channels.
`The FDM data transport for ADSL services utiliZes dis
`crete multi-tone (DMT) technology. A DMT signal is basi
`
`Page 7 of 12
`
`

`
`US 6,590,893 B1
`
`10
`
`15
`
`4
`continue to reduce the number of bits sent and increase the
`amount of redundancy data until an error-free transmission
`occurs.
`According to one aspect of the invention a device is
`con?gured to transmit and receive data over a communica
`tions medium. The device includes a transmitter con?gured
`to transmit a ?rst packet comprising bits of data. The device
`also includes a receiver con?gured to receive an acknoWl
`edgement signal from a destination node indicating that the
`?rst packet Was received Without errors. The transmitter is
`further con?gured to transmit a second packet comprising a
`?rst plurality of portions, When the acknoWledgement signal
`is not received. The ?rst plurality of portions each include
`the same predetermined bits of the ?rst packet.
`Another aspect of the present invention provides a method
`of transmitting data from a netWork node. The method
`includes transmitting a ?rst packet comprising bits of data.
`The method also includes receiving an acknoWledgement
`signal from a destination node When the ?rst packet Was
`received Without errors. The method further includes trans
`mitting a second packet comprising a ?rst plurality of
`portions, When the acknoWledgement signal is not received
`Within a preset period of time. The plurality of portions each
`include the same predetermined bits of the ?rst packet.
`Other advantages and features of the present invention
`Will become readily apparent to those skilled in this art from
`the folloWing detailed description. The embodiments shoWn
`and described provide illustration of the best mode contem
`plated for carrying out the invention. The invention is
`capable of modi?cations in various obvious respects, all
`Without departing from the invention. Accordingly, the
`draWings are to be regarded as illustrative in nature, and not
`as restrictive.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`Reference is made to the attached draWings, Wherein
`elements having the same reference numeral designations
`represent like elements throughout.
`FIG. 1 is a block diagram of a conventional transmitter
`and receiver using discrete multi-tone technology.
`FIG. 2 is a block diagram illustrating a transmitter and
`receiver utiliZing DMT according to an embodiment of the
`present invention.
`FIGS. 3a—3a' schematically illustrate the constellation
`points associated With the transmission and reception of data
`using the transmitter/receiver of FIG. 2, according to an
`embodiment of the present invention.
`FIG. 4 is a block diagram of a pair of nodes used in a
`netWork in accordance With an embodiment of the present
`invention.
`FIG. 5 is a How diagram illustrating the method for
`transmitting data according to an embodiment of the present
`invention.
`
`3
`cally the sum of N independently quadrature amplitude
`modulated (QAM) signals, each carried over a distinct
`carrier frequency channel. The frequency separation
`betWeen consecutive carriers is 4.3125 KHZ With a total
`number of 256 carriers or tones (ANSI). An asymmetrical
`implementation of this 256 tone-carrier DMT coding
`scheme might use tones 32—255 to provide a doWnstream
`channel of approximately 1 MHZ analog bandWidth. In such
`an implementation, tones 8—31 are used as carriers to
`provide an upstream channel of approximately 100 kHZ
`analog bandWidth. Each tone is QAM to carry up to 15 bits
`of data on each cycle of the tone Waveform (symbol). An
`example of a conventional DMT-based system is illustrated
`in FIG. 1.
`The existing DSL systems provide effective high-speed
`data communications over tWisted pair Wiring betWeen
`customer premises and corresponding netWork-side units,
`for example located at a central of?ce of the telephone
`netWork. The DSL modem units overcome many of the
`problems involved in data communication over tWisted pair
`Wiring. HoWever, for a number of reasons, the existing DSL
`units are not suitable to providing local area netWork type
`communications Within a customer’s premises. For
`example, existing ADSL units are designed for point-to
`point communication. That is to say, one ATU-R at the
`residence communicates With one ATU-C unit on the net
`Work end of the customer’s line. There is no Way to use the
`units for multi-point communications. Also, the existing
`ADSL modems tend to be quite complex, and therefore are
`too expensive for in-home communications betWeen mul
`tiple data devices of one customer.
`As described above, multi-point netWorks using conven
`tional technology are not suitable for in-home use.
`Additionally, even conventional multi-point netWorks
`requiring specialiZed Wiring and having predetermined
`topologies often suffer from poor signal quality betWeen tWo
`or more nodes in the netWork.
`For example, the medium connecting tWo particular nodes
`may be of poor quality resulting in drastic signal attenuation
`and phase distortion. The attenuation and distortion often
`lead to data errors When transmitting the data over such a
`medium. Prior art systems often retransmit the data When
`errors occur. HoWever, When the errors are caused by the
`communications medium or the netWork layout, simply
`retransmitting the data often results in another erroneous
`transmission.
`
`25
`
`35
`
`45
`
`SUMMARY OF THE INVENTION
`
`There is a need for an arrangement that provides an
`adaptive data transmission system for use in a netWork.
`There is also a need for an arrangement that provides an
`adaptive data transmission system for use in a netWork
`employing discrete multi-tone technology.
`These and other needs are met by the present invention,
`Where a data transmission device used in a netWork node
`includes a transmitter portion and a receiver portion. The
`transmitter transmits a data packet to a receiving node.
`When the data is received Without errors, the receiving node
`transmits an acknowledgement signal to the transmitting
`node and the transmitting node is ready to transmit the next
`packet. HoWever, When an error in transmission occurs, the
`transmitting node is able to retransmit a portion of the data,
`along With at least one redundant copy of the portion. If at
`least one of the redundant data portions is received Without
`errors, an acknowledgement is sent back to the transmitting
`node. If errors still occur, the transmitting node is able to
`
`55
`
`BEST MODE FOR CARRYING OUT THE
`INVENTION
`The present invention Will be described With the example
`of a netWork node in a multi-point netWork using discrete
`multi-tone (DMT) technology. A description Will ?rst be
`given of an exemplary DMT-based netWork, folloWed by the
`arrangement for providing an adaptive transmission system.
`It Will become apparent, hoWever, that the present invention
`is also applicable to other types of netWorks.
`
`65
`
`NETWORK ARCHITECTURE OVERVIEW
`FIG. 2 illustrates an exemplary system in Which the
`present invention may be advantageously employed. Net
`
`Page 8 of 12
`
`

`
`US 6,590,893 B1
`
`5
`work nodes 10 and 20 are nodes, e.g., personal computers,
`in computer network 100. Each node is capable of trans
`mitting and receiving data over channel 40. Channel 40 may
`be a twisted pair telephone line or another medium used to
`transmit data. In FIG. 2, a detailed transmitter 11 is shown
`in network node 10 and a detailed receiver 21 is shown in
`network node 20. It should be recognized, however, that
`each node 10 and 20 includes both the transmitter and
`receiver circuitry. Additionally, although not shown, other
`network nodes may be connected to nodes 10 and 20 in a
`ring topology, star topology or any other network topology.
`According to the exemplary embodiment of the invention,
`network 100 in FIG. 2 utiliZes DMT-based technology to
`transmit data over channel 40. The present invention how
`ever departs from conventional DMT technology by utiliZ
`ing a differential coder 12 to encode an input bit stream into
`a predetermined number of tones. According to the exem
`plary embodiment, differential coder 12 uses 256 tones to
`encode the input bit stream. In alternative con?gurations,
`differential coder 12 may utiliZe other numbers of tones to
`encode the bit stream, based on the particular network
`requirements. Additionally, as described previously, in a
`DMT-based system utiliZing 256 tones, each tone is capable
`of transmitting up to 15 bits of data on the tone waveform.
`According to the exemplary embodiment of the present
`invention, each tone is used to transmit two bits of data,
`which corresponds to four constellation points. However, in
`alternative con?gurations the present invention may trans
`mit other numbers of bits per tone.
`The differential coder 12 overcomes the drawbacks asso
`ciated with a home network environment by utiliZing a
`reference tone encoded with a reference bit pattern, before
`transmitting the input data stream. In alternative
`con?gurations, a sequence of reference tones, e.g., up to 256
`tones, may be encoded with a reference bit pattern. Trans
`mitter 11 modulates the reference tone(s) to carry the
`predetermined bit pattern over channel 40. For example,
`assume that bit pattern “00” is the predetermined bit pattern.
`The reference tone is then quadrature amplitude modulated
`to carry bit pattern “00”. After processing by differential
`coder 12, the bit pattern “00” is represented by constellation
`point A in the complex plane shown in FIG. 3a. The
`constellation point represents the amplitude and phase of the
`signal at that particular tone.
`The Inverse Fast Fourier Transform (IFFT) block 14,
`receives the tone information and converts the frequency
`domain-based tone information into a time domain-based
`waveform and outputs the time domain waveform to
`parallel-to-serial converter 16. A guard-band cyclic pre?x
`may be applied between the IFFT block 14 and the parallel
`to-serial converter 16 to transmit a pre?x before the actual
`reference bits. The pre?x data is discarded at the receiver 21,
`thereby eliminating the effects of intersymbol interference
`(ISI) associated with the start of the transmission. Parallel
`to-serial converter 16 converts the data to a serial format for
`analog front end
`block 18. AFE block 18 then
`transmits the data over channel 40 to node 20.
`At node 20, AFE block 22 receives the line signal and
`performs ampli?cation, ?ltering and digitiZing. The signal is
`then fed into serial-to-parallel converter 24. After the data is
`converted to a parallel format, FFT block 26 computes the
`amplitude and phase information of the reference tone.
`Differential decoder and slicer 28 then decodes the ref
`erence signal, represented by constellation point B in FIG.
`3b. Next, the transmitter 11 transmits the actual input bit
`stream representing the data from network node 10 destined
`
`6
`for network node 20. For example, assume the current bit
`stream being transmitted from node 10 to node 20 is bit
`pattern “01”, which is illustrated by constellation point C in
`FIG. 3c.
`The receiver 20 receives the encoded carrier tone and
`processes the signal information using AF E block 22, serial
`to-parallel converter 24, FFT block 26 and differential
`decoder and slicer block 28. After processing, the tone
`information is represented by constellation point D in FIG.
`3d. The receiver 21 includes logic to compare the received
`point D with the previous received point B to determine the
`phase relationship between the points. Referring to FIG. 3d,
`the phase relationship between points B and D is 90 degrees,
`with point D leading point B. Using this information, the
`decoder and slicer block 28 assumes that the transmitted
`data bits encoded via the second carrier tone is 90 degrees
`out of phase with the reference data bits. In this example, the
`reference data bit pattern was “00”, and a bit pattern leading
`“00” by 90 degrees maps to bit pattern “01”, as shown in
`FIG. 3a. Therefore, the decoder and slicer block 28 in this
`example determines that the data bits transmitted with the
`second tone correspond to “01”.
`In the manner described above, the transmitting node 10
`uses a reference tone encoded with a reference bit pattern at
`the beginning of every data packet. The phase distortion
`between the reference tone and the subsequent tone is then
`used to determine the value of the data associated with the
`?rst tone. Each successive tone is processed in a similar
`manner by comparing the phase relationship between the
`constellation point associated with the tone with the previ
`ous constellation point. By assuming that every constellation
`point will have the same degree of amplitude attenuation and
`phase distortion, the present invention is then able to deter
`mine the value of the data transmitted on each tone without
`knowing the particular channel characteristics.
`Advantageously, the present invention is able to decode
`transmitted data without the use of an equaliZer to reverse
`the effect of amplitude attenuation or phase distortion asso
`ciated with poor quality wiring.
`In the exemplary embodiment, since a known reference
`bit pattern is transmitted before each packet of data as a new
`reference, any receiving node is able to determine the values
`of the subsequent received data bits in that packet.
`Advantageously, the system for transmitting/receiving data
`of the present invention is usable for different paths employ
`ing different channels in network 100.
`The present invention, as described above, may be advan
`tageously employed in a multi-point network. In such
`networks, a sending signal is transmitted only when there is
`data that needs to be transmitted. In accordance with an
`embodiment of the present invention, the transmitting node
`transmits a predetermined time mark to identify the begin
`ning of a packet. In the exemplary embodiment, the time
`mark consists of one cycle of a sinusoidal waveform. The
`receiver node then matches received patterns with the pre
`de?ned time mark pattern to identify the start of the packet,
`and thus begin decoding the received packet. In alternative
`con?gurations, the time mark may be several cycles of a
`sinusoidal waveform or any other predetermined waveform.
`Additionally, a predetermined transmitting node identi?er
`may also be transmitted after the time mark for identi?cation
`purposes. An exemplary node ID may consist of pulse
`amplitude modulated (PAM) sinusoidal waveforms unique
`to each network node.
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`ADAPTIVE TRANSMISSION
`As described above, the network nodes in network 100 are
`able to transmit and receive data over channel 40 without
`
`Page 9 of 12
`
`

`
`US 6,590,893 B1
`
`7
`knowing the particular channel characteristics. The present
`invention is also able to adapt the transmission rate based on
`the particular channel characteristics. For example, if the
`channel characteristics of channel 40 are poor and the
`receiving node is unable to receive the transmitted data
`Without errors, the transmitting node is able to adapt the
`transmission rate to ensure that error-free data is received.
`FIG. 4 is a block diagram of netWork nodes 10 and 20, in
`accordance With an embodiment of the present invention.
`Network node 10 includes transmitter controller 32 and
`receiver controller 34 and netWork node 20 includes trans
`mitter controller 42 and receiver controller 44. These
`transmitter/receiver controllers of nodes 10 and 11, as
`described in detail beloW, enable the present invention to
`optimiZe the data transmission rate, based on the particular
`operating conditions of channel 40. The transmitter and
`receiver circuitry of FIG. 2 are not depicted in nodes 10 and
`20 of FIG. 4 in order not to unduly obscure the thrust of the
`present invention.
`FIG. 5 is a How diagram illustrating the method for
`providing an adaptive transmission system in accordance
`With an embodiment of the present invention. At step 200,
`transmitter controller 32 appends a cyclic redundancy check
`(CRC) code at the end of a packet of data to be transmitted
`over channel 40. For an Ethernet packet, the CRC code is
`included With the packet and therefore step 200 is skipped.
`In alternative con?gurations, other error check codes may
`also be utiliZed.
`Node 10 then encodes the data packet and CRC code at
`step 202. Next, at step 204, node 10 transmits the predeter
`mined time mark along With the data stream and CRC code
`over channel 40. According to the exemplary embodiment of
`the invention, the time mark is a PAM sinusoidal signal one
`period in duration, optionally folloWed by node ID infor
`mation. The time mark information is transmitted at the start
`of each packet of data. The time marks essentially acts as a
`signal to alert the receiving node 20 that the data stream
`folloWs.
`When node 20 receives the data step 206, the receiver
`controller 44, illustrated in FIG. 4, checks the received data
`and CRC code to determine Whether the data Was received
`Without errors. If the receiver controller 44 determines that
`the data Was received Without errors, the transmitter con
`troller 42 of node 20 transmits the predetermined time mark
`back to the transmitting node 10 as an acknoWledgement
`signal, at step 208. Alternatively, any other prede?ned
`acknoWledgement signal may be used. When the receiving
`node 20 determines that the data Was received With errors at
`step 206, the receiving node does not transmit the acknoWl
`edgement signal.
`Next, at step 210, the receiver controller 34 of transmit
`ting node 10 Waits a predetermined period of time for the
`acknoWledgment time mark from node 20. When the
`acknoWledgement time mark is received in the predeter
`mined period of time at step 210, the process returns to step
`200 for the transmission of a neW packet. If the acknoWl
`edgment time mark is not received in the predetermined
`period of time, at step 210, the transmitting node 10 assumes
`that the data packet Was received With errors or Was lost.
`Next, at step 212, the transmitter controller 32 of node 10
`determines Whether the current packet has been transmitted
`a predetermined number of times. According to the exem
`plary embodiment of the invention, the predetermined num
`ber is three. HoWever, in alternative con?gurations, the
`predetermined may be any other number including one. If
`the current packet has not been transmitted the predeter
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`mined number of times, the process returns to step 204
`Where the current packet along With the time mark is
`retransmitted.
`Next, assume that the current packet has been retransmit
`ted the predetermined number of times Without an acknoWl
`edgement signal from receiving node 20. The transmitter
`controller 32 of node 10 then reduces the effective data rate
`by transmitting only a portion of the current data packet,
`along With at least one redundant copy of the portion. More
`speci?cally, at step 214, the transmitter controller 32
`retrieves a ?rst predetermined number of bits at the head of
`the current data packet. For example, suppose the original
`data packet Was 8 bits in length consisting of 11010001. At
`step 214, the transmitter controller retrieves only the prede
`termined number of bits from the beginning of this packet.
`Further assume in this example that the predetermined
`number of bits is four. In this situation, the transmitter
`controller 32 retrieves bits “1101”, i.e., the ?rst four bits of
`the current packet.
`Next at step 216, the transmitter controller 32 appends the
`appropriate CRC code to the end of the neW bit pattern. The
`transmitter controller 32 also provides at least one redundant
`copy of the neW bit pattern and CRC code, after the ?rst
`CRC code. In the example described above, and assuming
`that the number of redundant copies is one, the transmitter
`controller 32 Would provide the folloWing bit pattern for
`encoding: 1101(CRCcode)1101(CRCcode). HoWever, in
`alternative embodiments, the number of redundant copies of
`the ?rst bit pattern Would generally be limited only by the
`bandWidth of the channel.
`Next, the transmitting node 10 encodes the neW data
`packet, at step 218, and transmitter controller 32 adds the
`time mark at the beginning of the packet to indicate the start
`of the packet. The process then returns to step 204.
`The processes at steps 204—210 are the same as described
`previously With an exception at step 206. At step 206, the
`receiver controller 44 determines Whether any one of the
`redundant data patterns in the packet has been received
`Without errors. For example, assume that the receiver con
`troller 44 determines that the second group of bits, 1101 in
`the example described above, Was received Without errors,
`based on the CRC code information. The receiving node 20
`at step 208 Would then transmits an acknoWledgement time
`mark to transmitting node 10. Advantageously, a single
`reception of error-free data associated With any one of the
`redundant patterns enables the present invention to be more
`robust and to operate in conditions Where conventional
`systems are unable to operate.
`The processes at steps 212—218 continue until the receiver
`node 20 receives a group of data bits Without errors and
`sends the acknoWledgement signal to the transmitting node
`10. Each time the process reaches step 214, the transmitter
`controller 32 reduces the number of bits of the current packet
`being transmitted and increases the number of redundant bit
`patterns.
`According to the exemplary embodiment of the invention
`illustrated in connection With FIG. 2, assume that the ?rst
`packet utiliZes 256 carrier tones to transmit 512 bits of data
`as a data packet. The ?rst time the process reaches steps
`214—218, the transmitting node 10 may transmit the ?rst 256
`bits of the 512 bits. In this case, the ?rst 128 tones are QAM
`to carry the ?rst 256 bits. The next 128 adjacent to

This document is available on Docket Alarm but you must sign up to view it.


Or .

Accessing this document will incur an additional charge of $.

After purchase, you can access this document again without charge.

Accept $ Charge
throbber

Still Working On It

This document is taking longer than usual to download. This can happen if we need to contact the court directly to obtain the document and their servers are running slowly.

Give it another minute or two to complete, and then try the refresh button.

throbber

A few More Minutes ... Still Working

It can take up to 5 minutes for us to download a document if the court servers are running slowly.

Thank you for your continued patience.

This document could not be displayed.

We could not find this document within its docket. Please go back to the docket page and check the link. If that does not work, go back to the docket and refresh it to pull the newest information.

Your account does not support viewing this document.

You need a Paid Account to view this document. Click here to change your account type.

Your account does not support viewing this document.

Set your membership status to view this document.

With a Docket Alarm membership, you'll get a whole lot more, including:

  • Up-to-date information for this case.
  • Email alerts whenever there is an update.
  • Full text search for other cases.
  • Get email alerts whenever a new case matches your search.

Become a Member

One Moment Please

The filing “” is large (MB) and is being downloaded.

Please refresh this page in a few minutes to see if the filing has been downloaded. The filing will also be emailed to you when the download completes.

Your document is on its way!

If you do not receive the document in five minutes, contact support at support@docketalarm.com.

Sealed Document

We are unable to display this document, it may be under a court ordered seal.

If you have proper credentials to access the file, you may proceed directly to the court's system using your government issued username and password.


Access Government Site

We are redirecting you
to a mobile optimized page.





Document Unreadable or Corrupt

Refresh this Document
Go to the Docket

We are unable to display this document.

Refresh this Document
Go to the Docket