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`US007269208B2
`
`c12) United States Patent
`Mazzoni et al.
`
`(IO) Patent No.:
`(45) Date of Patent:
`
`US 7,269,208 B2
`Sep.11,2007
`
`(54) DEVICE FOR SENDING/RECEIVING
`DIGITAL DATA CAPABLE OF PROCESSING
`DIFFERENT BIT RATES, IN PARTICULAR
`IN A VDSL ENVIRONMENT
`
`(75)
`
`Inventors: Simone Mazzoni, Grenoble (FR);
`Helene Came, Grenoble (FR)
`(73) Assignee: STMicroelectronics SA, Montrouge
`(FR)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 873 days.
`10/088,387
`Jul. 11, 2001
`
`( *) Notice:
`
`(21) Appl. No.:
`(22) PCT Filed:
`
`(86) PCT No.:
`
`PCT/FR0l/02243
`
`§ 371 (c)(l),
`(2), ( 4) Date:
`
`Jul. 16, 2002
`
`(87) PCT Pub. No.: WO02/07324
`
`PCT Pub. Date: Jan. 24, 2002
`
`(65)
`
`Prior Publication Data
`
`US 2003/0021338 Al
`
`Jan. 30, 2003
`
`(30)
`
`Foreign Application Priority Data
`
`Jul. 18, 2000
`
`(FR)
`
`................................... 00 09409
`
`(51)
`
`Int. CI.
`(2006.01)
`H04B 1/38
`(2006.01)
`H04L 5116
`(52) U.S. CI. ...................................................... 375/219
`(58) Field of Classification Search ................ 375/219,
`375/222, 259,377; 714/701, 702, 761, 762,
`714/763
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PA1ENT DOCUMENTS
`4,559,625 A * 12/1985 Berlekamp et al .......... 714/701
`5,751,741 A * 5/1998 Voith et al .................. 714/758
`5,764,649 A * 6/1998 Tong .......................... 714/701
`5,912,898 A * 6/1999 Khoury ...................... 714/701
`6,956,872 Bl * 10/2005 Djokovic et al. . .......... 370/505
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`
`0856949
`
`8/1998
`
`OTHER PUBLICATIONS
`
`Veithen et al., A 70MB/S Variable-Rate DMT-Based Modem for
`VDSL, IEEE International Solid State Circuits Conference, IEEE
`Inc. New York, US, vol. 42, Feb. 1999, pp. 248-249, XP000862325.
`Patent Abstracts of Japan, vol. 1997, No. 02, Feb. 28, 1997 & JP
`08265177 Oct. 11, 1996.
`
`* cited by examiner
`
`Primary Examiner-David C. Payne
`Assistant Examiner-Nader Bolourchi
`(74) Attorney, Agent, or Firm-Lisa K. Jorgenson; Allen,
`Dyer, Doppelt, Milbrath & Gilchrist, P.A.
`
`(57)
`
`ABSTRACT
`
`A device for sending/receiving digital data is capable of
`processing different bit rates from a group of predetermined
`bit rates. The device may include a channel coding/decoding
`stage including an interleaver, a deinterleaver, and a memory
`whose minimum size is fixed as a function of the maximum
`bit rate of the group of predetermined bit rates. The memory
`may have a first memory space assigned to the interleaver
`and a second memory space assigned to the deinterleaver.
`The size of each of the two memory spaces may be set as a
`function of the bit rate actually processed by the device.
`
`15 Claims, 7 Drawing Sheets
`
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`
`
`CommScope, Inc.
`IPR2023-00066, Ex. 1005
`Page 1 of 14
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`

`

`U.S. Patent
`
`Sep.11,2007
`
`Sheet 1 of 7
`
`US 7,269,208 B2
`
`FIG.1
`
`TO
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`CommScope, Inc.
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`

`

`U.S. Patent
`
`Sep.11,2007
`
`Sheet 2 of 7
`
`US 7,269,208 B2
`
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`CommScope, Inc.
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`

`

`U.S. Patent
`
`Sep.11,2007
`
`Sheet 3 of 7
`
`US 7,269,208 B2
`
`FIG.3
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`
`CommScope, Inc.
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`

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`FIG.4
`
`CommScope, Inc.
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`

`

`U.S. Patent
`
`Sep. 11, 2007
`
`Sheet 5 of 7
`
`US 7,269,208 B2
`
`FIG.6
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`
`CommScope, Inc.
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`

`

`U.S. Patent
`
`Sep.11,2007
`
`Sheet 6 of 7
`
`US 7,269,208 B2
`
`FIG.7
`
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`CommScope, Inc.
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`

`

`U.S. Patent
`
`Sep.11,2007
`
`Sheet 7 of 7
`
`US 7,269,208 B2
`
`FIG.8
`
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`CommScope, Inc.
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`

`

`US 7,269,208 B2
`
`1
`DEVICE FOR SENDING/RECEIVING
`DIGITAL DATA CAPABLE OF PROCESSING
`DIFFERENT BIT RATES, IN PARTICULAR
`IN A VDSL ENVIRONMENT
`
`FIELD OF THE INVENTION
`
`The present invention relates to the field of teleconnnu(cid:173)
`nications, and, more particularly, to transmitters and receiv(cid:173)
`ers for data connnunication lines. Moreover, the invention
`relates to sending and receiving digital data that can have
`different bit rates, and to choosing the capacity of memory
`means used by interleaving and deinterleaving processes
`effected within send/receive devices capable of processing
`different bit rates.
`
`BACKGROUND OF THE INVENTION
`
`The present invention may advantageously be applied to
`a very high rate digital subscriber line (VDSL) environment
`or system, for example, though the invention may also be
`used in other applications. That is, the invention applies to
`a digital connnunication system linking an operator and
`users via very high bit rate transmission lines. Thus, the
`invention applies more particularly to send/receive devices, 25
`usually referred to as modems, at the operator and user ends
`of a transmission line.
`Those skilled in the art will appreciate that a VDSL
`communication system is capable of delivering synnnetrical
`services and asynnnetrical services. A service is synnnetrical
`if the bit rate of information exchanged between the operator
`and the user in both transmission directions (i.e., from the
`operator to the user and from the user to the operator) is
`exactly the same. A service is asymmetrical if the bit rate of
`information sent in one transmission direction is different
`from the bit rate of information sent in the other transmission
`direction.
`The processes of interleaving and deinterleaving data sent
`and received by a modem necessitates the use of memories.
`For a modem intended to operate at a predetermined bit rate,
`the memories must have a capacity that depends on that bit
`rate.
`
`2
`( e.g., all the synnnetrical or asynnnetrical services offered
`by the VDSL communication system).
`The device according to the invention may include a
`coding/decoding stage (generally referred to by those skilled
`in the art as a "channel coding/decoding stage") including
`interleaving means and deinterleaving means. The interleav(cid:173)
`ing and deinterleaving means include a memory whose
`minimum size is fixed as a function of the maximum bit rate
`of the group of predetermined bit rates ( e.g., the highest
`10 asynnnetrical bit rate in the case of a VDSL system). The
`memory also has a first memory space assigned to the
`interleaving means and a second memory space assigned to
`the deinterleaving means. The size of each of the two
`memory spaces is set as a function of the bit rate actually
`15 processed by the device. In the context of the present
`invention, the term "bit rate" as associated with a memory
`capacity or memory space is a global bit rate, i.e., the sum
`of the send and receive bit rates.
`It is therefore possible to considerably reduce the size of
`20 the memory means required for the interleaving and deinter(cid:173)
`leaving means implemented within a modem. The modem
`may be used either at the operator end or at the user end, and
`it is capable of processing a number of different and sym-
`metrical or asynnnetrical bit rates.
`The transmitted data stream may be protected from trans-
`mission channel noise by a Reed-Solomon coding algo(cid:173)
`rithm, which is well known in the art. To make the Reed(cid:173)
`Solomon coding more efficient, the coding means may be
`coupled to the interleaving means to distribute in time errors
`30 introduced by the transmission channel. These errors often
`occur in bursts and affect several successive bytes, which
`can reduce the correction capacity of the Reed-Solomon
`code in isolation (generally eight bytes per packet). The
`interleaving means may then interleave the bytes temporally
`35 by modifying the order in which they are transmitted, which
`achieves the temporal distribution of the errors.
`More specifically, the channel coding/decoding stage may
`include Reed-Solomon coding/decoding means of length N
`(where N=240 bytes, for example). The interleaving means
`40 are then adapted to effect convolutional interleaving of I
`branches with i-1 blocks of N bytes. The deinterleaving
`means are adapted to implement convolutional deinterleav(cid:173)
`ing with I' branches ofi'-1 blocks ofM' bytes. I and I' are
`sub-multiples of N, and i and i' are the current relative
`45 indexes of the branches. The size in bytes of the first
`memory space is equal to Ix(I-l)xM/2, and the size in bytes
`of the second memory space is equal to I'x(I'-l)xM'/2. The
`sizes of the two memory spaces are set by I, I', Mand M'.
`Using convolutional triangular interleaving (and, conse-
`50 quently, convolutional triangular deinterleaving) instead of
`other conventional types of interleaving is particularly ben(cid:173)
`eficial because it reduces latency generated by the memory.
`Convolutional triangular interleaving requires a much
`smaller memory, which reduces latency. Latency is a pri-
`55 mordial and decisive criterion for any VDSL connnunication
`system.
`The memory may be a random access memory, such as a
`dual-port memory, for example. The interleaving means and
`the deinterleaving means may respectively include first
`60 addressing means and second addressing means. The first
`and second addressing means may each include a first
`counter defining the relative index i or i' of a branch, and a
`second counter defining the number of bytes in a block and
`incremented each time that the first counter reaches its
`65 counting limit value. Moreover, the first and second address(cid:173)
`ing means may also include a third counter defining the
`current index of a block in the branch with index i or i' and
`
`SUMMARY OF THE INVENTION
`
`An object of the invention is to provide a send/receive
`device (i.e., modem) architecture which requires a reduced
`quantity of memory.
`Yet another object of the invention is to provide such an
`architecture which can be used at the operator end or at the
`user end of a transmission line (i.e., which is fully inter(cid:173)
`changeable between sending and receiving).
`Still another object of the invention is to provide such an
`architecture which is adaptable, particularly in terms of the
`memory capacity of the interleaving and deinterleaving
`means, to suit a number of different bit rates selected from
`a predetermined group of bit rates.
`These and other objects, features, and advantages are
`provided by a memory means whose size is optimized for a
`global (send+receive) bit rate, which can be shared between
`the interleaving means and the deinterleaving means, and
`whose memory allocation can be reconfigured in accordance
`with the bit rate actually processed by the send/receive
`device (modem). The invention therefore provides a device
`for sending/receiving digital data that is capable of process(cid:173)
`ing different bit rates from a group of predetermined bit rates
`
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`US 7,269,208 B2
`
`3
`incremented each time that a block contains M or M' bytes,
`and intermediate calculation means calculating the address
`of each branch in the memory from the content of the first
`counter.
`The first addressing means may further include first
`address determination means adapted to determine succes(cid:173)
`sive read and write addresses in the memory of data suc(cid:173)
`cessively delivered to the interleaving means. The first
`address determination means determine the addresses from
`values supplied by the intermediate calculation means, the
`second and third counters and the parameter M.
`The second addressing means may further include second
`address determination means adapted to determine succes(cid:173)
`sive read and write addresses in the memory of data suc(cid:173)
`cessively delivered to the deinterleaving means. The second 15
`address determination means determine the addresses from
`values supplied by the intermediate calculation means, the
`second and third counters, the parameter M', and the size of
`the first memory space. This is so that the first unoccupied
`address in the memory can be determined.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`4
`kbit/s, for example, and the fastest symmetrical service S6
`has a bit rate of 362x64 kbit/s.
`With the VDSL system, the operator can also provide
`asymmetrical services Al-A6. These are services with dif(cid:173)
`ferent information bit rates in the user to operator direction
`(uplink direction) and in the operator to user direction
`( downlink direction). The first asymmetrical service Al has
`a bit rate in the uplink direction of32x64 kbit/s, for example,
`and a bit rate in the downlink direction of 100x64 kbit/s. The
`10 asymmetrical service having the highest global information
`bit rate (uplink bit rate+downlink bit rate) is the service A6.
`The bit rate of the service A6 in the uplink direction is equal
`to 32x64 kbit/s and in the downlink direction is equal to
`832x64 kbit/s.
`The send/receive device according to the invention can
`therefore be installed at the user end or at the operator end
`and is capable of processing all the above services, as
`described in more detail hereinafter. Even so, the capacity of
`the memory assigned to the interleaving/deinterleaving
`20 means may need to be chosen in accordance with the
`maximum bit rate of the services offered, here the bit rate of
`the highest asymmetrical service ( service A6). Furthermore,
`the parameters of the memory space of that memory may
`need to be set in accordance with the service actually
`25 processed by the device.
`The internal architecture of the operator terminal TO from
`FIG. 1 will now be described in more detail. It should be
`understood that everything described hereinafter with
`respect to the operator terminal TO is equally valid for the
`30 terminal TU. The terminal TO includes a send system and a
`receive system both connected to the transmission line LH,
`as shown in FIG. 2. The terminal TO includes a channel
`coding/decoding stage ETC including a channel coding unit
`CC in the send system and a channel decoding unit DCC in
`the receive system.
`The channel coding unit CC includes Reed-Solomon
`coding means whose structure and function are known to
`those of skill in the art. The Reed-Solomon coding means are
`associated with the interleaving means. In conjunction with
`subsequent interleaving, the Reed-Solomon coding can cor(cid:173)
`rect bursts of errors introduced by the transmission channel.
`Reed-Solomon coding is applied individually to each of the
`data packets delivered to the input of the coding unit CC.
`Reed-Solomon coding adds a number of parity bytes to
`45 the bytes of the packets received and can therefore correct a
`number of erroneous bytes. It is assumed here, by way of
`example, that the Reed-Solomon code used is an RS (240,
`224) code with a correcting power of 8. This notation means
`that the Reed-Solomon coding means are applied to packets
`50 of 224 bytes, to which they add 16 parity bytes, to form a
`Reed-Solomon coded word whose length is 240 bytes. This
`makes it possible to correct up to eight erroneous bytes.
`Errors introduced by the channel, which often occur in
`bursts affecting several successive bytes and can therefore
`55 exceed the correction capacity of the Reed-Solomon code in
`isolation, may be distributed temporally. To do so, the bytes
`are temporally interleaved by modifying the order in which
`they are transmitted. This improves the efficacy of the
`Reed-Solomon coding.
`The information delivered to the output of the channel
`coding stage ETC is delivered to a modulation unit BM
`whose structure is known in the art and which effects
`quadrature modulation, for example. Then, after various
`standard processes have been effected in a send unit EM,
`which includes an interface to the transmission line LH, the
`modulated signal is transmitted over the transmission line
`LH.
`
`Other advantages and features of the invention will
`become apparent upon examining the following detailed
`description of non-limiting embodiments of the invention
`and the accompanying drawings, in which:
`FIG. 1 is a schematic block diagram of a communication
`system in accordance with the invention linking two send/
`receive devices;
`FIG. 2 is a more detailed schematic block diagram show(cid:173)
`ing the internal architecture of a send/receive device accord(cid:173)
`ing to the invention;
`FIG. 3 is a schematic block diagram of the internal
`architecture of a coding/decoding stage of the device shown 35
`in FIG. 2;
`FIGS. 4 and 5 are schematic diagrams showing the theory
`of convolutional triangular interleaving and deinterleaving
`of the present invention;
`FIG. 6 is a schematic block diagram of the internal 40
`architecture of the interleaving and deinterleaving means of
`a send/receive device according to the invention;
`FIG. 7 is a schematic block diagram of an embodiment of
`first addressing means associated with the interleaving
`means; and
`FIG. 8 is a schematic block diagram of an embodiment of
`the second addressing means associated with the deinter(cid:173)
`leaving means.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`An application of the invention to a VDSL communica(cid:173)
`tion system will now be described, although the invention is
`not limited to this application. Referring to FIG. 1, two
`send/receive devices TO and TU according to the invention
`are shown, which may be referred to more simply as
`terminals or modems. One of these terminals, e.g., the
`terminal TO, is at the operator end. The other terminal TU
`is at the user end. The two modems are linked by a very high 60
`bit rate communication line LH.
`The VDSL communication system enables the operator to
`provide symmetrical services, typically six symmetrical
`services Sl-S6. That is, the information bit rates in the two
`transmission directions (i.e., from the operator to the user 65
`and from the user to the operator) are exactly the same. The
`service Sl with the lowest bit rate has a bit rate of 32x64
`
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`US 7,269,208 B2
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`5
`Similarly, the receive system of the terminal TO includes
`at its input a receive unit ER including a receive interface to
`the transmission line LH which effects standard processing.
`The modulated signal delivered to the output of the receive
`unit ER is demodulated in a demodulator unit BDM. The 5
`demodulated signal is then delivered to the channel decod(cid:173)
`ing unit DCC. The latter unit includes deinterleaving and
`Reed-Solomon decoding means.
`The internal architecture and the operation of the inter(cid:173)
`leaving and deinterleaving means will now be described in 10
`more detail with more particular reference to FIGS. 3-8. As
`shown in FIG. 3, and as already explained, the interleaving
`means MET follow the Reed-Solomon coding means CRS,
`and the deinterleaving means MDET precede the Reed(cid:173)
`Solomon decoding means DCRS. As shown diagranimati- 15
`cally in FIGS. 4 and 5, the interleaving and deinterleaving
`are convolutional triangular interleaving and deinterleaving.
`There are I branches of i-1 blocks of M bytes for interleav(cid:173)
`ing and I' branches of i'-1 blocks of M' bytes for deinter(cid:173)
`leaving.
`As explained in more detail hereinafter, the parameters I,
`M, I' and M' can be modified, e.g., by software, and are
`delivered by control means MCD (see FIG. 3). The control
`means MCD may also be implemented in software. These
`parameters define the sizes of the respective memory spaces 25
`assigned to the interleaving means and to the deinterleaving
`means. This is done according to the bit rate of the infor(cid:173)
`mation sent by the terminal TO (parameters I and M) and the
`bit rate of the information received by the terminal TO
`(parameters I' and M').
`The interleaving means therefore include I parallel
`branches BRi (numbered from Oto I-1, for example) which
`are implemented with a delay increment of M per branch (M
`represents the maximum number of bytes of a block BKj
`with indexj). Each branch can be considered as a delay line, 35
`the length of the branch with index i (where i varies in the
`range from Oto I-1) being equal to ixM bytes. In FIG. 4, by
`way of example, I=7.
`Accordingly, the first block of M bytes (having the index
`0, for example) is not interleaved and is delivered unmodi- 40
`fled to the output of the interleaving means. The next block
`of M bytes (index 1) is delivered to the input of the branch
`BRl, and so on up to the seventh block of M bytes (index
`6), which is delivered to the branch BR6. The cycle then
`begins again with the blocks of bytes with indices from 7 to 45
`13. The preceding blocks of bytes are either delivered to the
`output of the interleaving means or moved forward by one
`block BKj in the branch concerned.
`The deinterleaving means associated with the interleaving
`means MET, and which are consequently incorporated into 50
`the user terminal TU, have a structure analogous to that
`which has just been described for the interleaving means.
`Yet, the indices of the branches are reversed so that the
`longest interleaving time-delay corresponds to the shortest
`deinterleaving time-delay. The deinterleaving means MDET 55
`incorporated in the operator terminal TO have I' branches,
`the branch with index i' having a length equal to i'xM' bytes.
`For simplicity, the situation in which I'=I is shown in FIG.
`5. However, if the service is an asymmetrical service, I and
`I' are generally different, of course, and likewise M and M'. 60
`In hardware terms, as shown diagranimatically in FIG. 6, the
`interleaving means and the deinterleaving means include
`common memory means MM, e.g., a dual-port random
`access memory. The memory space of the memory MM is
`then divided into a first memory space ES Ml assigned to the 65
`interleaving means MET, and a second memory space ESM2
`is assigned to the deinterleaving means MDET.
`
`6
`The interleaving means also include first addressing
`means MADl receiving the parameters I and M. The
`deinterleaving means also include second addressing means
`MAD2 receiving the parameters I' and M'. The structure of
`the addressing means is described in more detail hereinafter
`with reference to FIGS. 7 and 8. The minimum size of the
`memory MM is set by the maximum bit rate that the
`send/receive device can process. The maximum bit rate is, of
`course, the sum of the uplink bit rate and the downlink bit
`rate.
`In this example, the maximum bit rate is that of the largest
`asymmetrical service A6. An example of the capacity of the
`memory MM and of the values chosen for the parameters I,
`M, I' and M' for an asymmetrical service A6 and an RS (240,
`224) Reed-Solomon code with a correction power of 8
`bytes/word may be as follows when the transmission lines
`are disturbed by an impulsive noise with a duration of 0.25
`ms.
`In the downlink direction, the maximum bit rate is equal
`20 to 832x64 kbit/s. The number of bits affected by noise is
`consequently equal to the product of that bit rate by the
`duration of the impulsive noise, which yields a number of
`bits affected by noise equal to 13,312 (1,664 bytes). Given
`the correcting power of the Reed-Solomon code (here 8), the
`number nrs of Reed-Solomon words needed to correct 1,664
`bytes subject to noise is equal to 1,664/8, i.e. 208. The size
`of the memory space needed to store this maximum bit rate
`is then equal to Nxnrs/2, where N is the size of the
`Reed-Solomon code (here 240). The resulting memory
`30 space size is therefore equal to 24,960 bytes.
`The bit rate in the uplink direction is equal to 32x64
`kbit/s. A similar calculation shows that the number of bits
`affected by noise is equal to 512, and that nrs=8. The
`memory size to be provided for the uplink direction is
`therefore equal to 1,920 bytes. The minimum size of the
`memory MM is therefore 26,880 bytes.
`The parameters I, I', Mand M' can be determined from the
`above capacities. More particularly, the size of the first
`memory space needed to implement triangular convolu(cid:173)
`tional interleaving with I branches of i-1 blocks of M bytes
`is equal to Ix(I-l)xM/2. Similarly, the size of the second
`memory space ESM2 required to support the uplink bit rate
`is equal to I'x(I'-l)xM'/2. Also, I and I' must be sub(cid:173)
`multiples of the size N of the Reed-Solomon code.
`Since Ix(I-l)xM/2 must be equal to 24,960, it is possible
`to choose 1=40 and M=32. Similarly, because I'x(I'-1 )xM'/2
`must be at least equal to 1,920, it is possible to choose I'=24
`and M'=7. This requires a slight increase in size to 1,932 to
`facilitate the implementation. The final size of the memory
`MM is therefore equal to 26 892 bytes.
`The above calculation of I, M, I' and M' for the asym(cid:173)
`metrical service A6 can be applied in an analogous manner
`to the other services of the VDSL system. A table of values
`for the parameters I, M, I' and M' can therefore be stored in
`the coding/decoding stage. When the modem is installed at
`the end of the line, and depending on the service actually
`provided by the operator, the control means MCD may
`retrieve the corresponding values of I, M, I' and M' from the
`stored table. These values are delivered to the addressing
`means MADl and MAD2, the structure of which is
`described in more detail with reference to FIGS. 7 and 8.
`As shown in FIG. 7, the first addressing means include a
`first counter CTl delivering the relative index i of a branch
`BRi at the timing rate of a clock signal. The index i is
`delivered to intermediate calculation means MCI that deter(cid:173)
`mine the address adbs of the branch BRi in the first memory
`space. More specifically, the address adbs is equal to ix(i-
`
`CommScope, Inc.
`IPR2023-00066, Ex. 1005
`Page 11 of 14
`
`

`

`US 7,269,208 B2
`
`7
`1 )/2. The means MCI can be easily implemented using
`multipliers, dividers and subtractors.
`The first counter CTI has a counting range equal to I and
`therefore counts from 0 to I-1, for example. The means
`MDl further include a second counter CT2 which delivers
`a current value m equal to the current number of bytes in
`each block BKj of a branch BRi. The counting range of the
`counter CT2 is equal to M. In other words, m can vary from
`0 to M-1, for example. The second counter CT2 is incre(cid:173)
`mented by one unit each time that i=I-1.
`The means MDAl further include a third counter CT3
`which delivers the index j of the block BKj within the branch
`with index i. The counting range of the counter CT3 is equal
`to i. In other words, j varies from 0 to i-1, for example. The
`third counter CT3 is incremented each time that a block 15
`contains M bytes, and therefore in this example each time
`that the counter CT2 reaches the value M.
`The means MDAl further include first address determi(cid:173)
`nation means MDl which determine the read address ar in
`the memory and the write address aw in the memory. More 20
`precisely, the read address ar is equal to (adbs+j)xM+m. The
`write address aw is then simply equal to the read address but
`delayed by one cycle of the clock signal. Again, the means
`MDl can be easily implemented using adders and multipli-
`=·
`For example, a small auxiliary dual-port memory with a
`capacity of (I-1 )xM bits can be used to store the value of the
`index j delivered by the third counter CT3, which is incre(cid:173)
`mented every M clock cycles. Every M clock cycles, the
`value of j corresponds to the ith branch in the auxiliary 30
`memory, after which the counter CT3 is incremented and the
`new value is rewritten at the same address.
`The second addressing means MDA2 that deliver the read
`address ar' and the write address aw' in the second memory
`space of the memory MM have a structure similar to that just 35
`described for the first addressing means MDAl. Only the
`differences between the means MD Al and the means MDA2
`are described herein. The first counter CTlO delivers the
`relative index i' of a branch. This time i' varies in the range
`ofl'-1 to 0. The intermediate calculation means MCI deliver 40
`the address of each branch adbs' using a formula analogous
`to that used to calculate the address, but substituting i' for i.
`The second counter CT20 defines the number m' of bytes
`in a block and is incremented each time that the counter
`CTlO reaches its counting limit value, in this example when 45
`i' reaches the value 0. In this example, the second counter
`CT20 varies in the range from Oto M'-1. The third counter
`CT30 defines the current index j' of a block in the branch
`with index i'. It varies in the range from 0 to i'-1 and is
`incremented each time that a block contains M' bytes, i.e., 50
`when the second counter CT20 reaches the value M'.
`The second addressing means MDA2 include second
`address determination means MD2 which determine the
`write address aw' and the read address ar'. However, the
`second address determination means MD2 must allow for 55
`the size OF of the first memory space ESMl, which is
`defined by equation (1) below:
`
`OF~Jx(I-l)xM/2,
`
`and may be stored in a register, for example. For uplink
`interleaving, the addresses of the memory MM vary in the
`range of Oto OF-1.
`The first unoccupied address in the memory MM there(cid:173)
`fore has the value OF. The means MD2 then calculate the
`read address ar' from equation (2) below:
`
`ar'~OF+M'x(adbs'+j)+m'.
`
`(2)
`
`~
`
`8
`The write address aw' is equal to the read address and is
`available on the next clock pulse.
`Of course, everything just described here for the terminal
`TO applies to the terminal TU with deinterleaving means
`with I branches and interleaving means with I' branches. For
`the user terminal TU it is then necessary to substitute I' for
`I, and vice versa, and M' for M, and vice versa, in the
`foregoing description. It would equally be possible to use a
`single-port memory in place of a dual-port memory by
`10 adopting a clock signal having twice the frequency.
`That which is claimed is:
`1. A device for sending and receiving digital data that is
`capable of processing different bit rates from a group of
`predetermined bit rates, the device comprising:
`a chamiel coding/decoding stage comprising
`an interleaver,
`a deinterleaver,
`a shared memory having a minimum size based upon a
`maximum bit rate of the group of predetermined bit
`rates and having a first memory space assigned to
`said interleaver and a second memory space assigned
`to said deinterleaver, a size of each of the first and
`second memory spaces being set as a function of the
`bit rate actually processed by the device,
`a Reed-Solomon coder/decoder connected to said inter(cid:173)
`leaver and said deinterleaver and having a length N,
`and
`said interleaver providing convolutional interleaving of
`I branches with i-1 blocks of M bytes, and said
`deinterleaver providing convolutional deinterleaving
`with I' branches of i'-1 blocks ofM' bytes, with I and
`I' being sub-multiples ofN and i and i' being current
`relative indexes of the branches.
`2. The device according to claim 1 wherein the size of the
`first memory space is equal to Ix(I-1 )xM/2 bytes, the size of
`the second memory space is equal to I'x(I'-l)xM'/2 bytes,
`and the sizes of the first and second memory spaces are set
`by I, I', Mand M'.
`3. The device according to claim 1 wherein said inter(cid:173)
`leaver and said deinterleaver respectively comprise a first
`addressing device and a second addressing device, said first
`and second addressing devices each comprising:
`a first counter defining the relative index i or i' of a branch
`and having a counting limit value;
`a second counter defining a number of bytes in a block
`and incremented each time that said