US006005876A
`6,005,876
`(114) Patent Number:
`United States Patent 55
`Cimini, Jr. et al.
`[45] Date of Patent:
`Dec. 21, 1999
`
`
`[54] METHOD AND APPARATUS FOR MOBILE
`DATA COMMUNICATION
`
`[75]
`
`Inventors: Leonard Joseph Cimini, Jr., Howell;
`Nelson Ray Sollenberger, Tinton Falls,
`both of N.J.
`;
`.
`[73] Assignee: AT&T Corp, New York, N-Y.
`
`[21] Appl. No.: 08/718,718
`[22]
`Filed:
`Sep. 24, 1996
`[51]
`Tint. C1.o iiccieeeecccssseecsesssseesssssneesssessees HO04J 3/12
`[52] U.S. Cheee 370/525; 370/203; 375/200;
`375/260
`[58] Field of Search ..cccscseseuseneneene 370/208, 320,
`370/335, 342, 468, 525, 526, 203, 522,
`375/200, 203, 260
`
`[56]
`
`.
`References Cited
`U.S. PATENT DOCUMENTS
`.
`8/1995 Gitlin et ab. eects 370/342
`5,442,625
`oe ohoes ose . u seeteeneeneeseeneereeeeses 370/319
`antz et al..
`307,
`5734646
`3/1998 Tetal.
`.
`.. 370/335
`
`
`5/1998 Sato ........
`ws 370/335
`5,751,705
`7/1998 Schneider oe. eeeeeeteeeneee 370/335
`5,781,541
`
`5,781,583
`5,805,575
`5,867,478
`
`7/1998 Bruckert et al. wees 375/206
`
`9/1998 Kamin, Jr. eee
`ceeeeeeeeceee 370/335
`2/1999 Baum et al. wee eeeeeeeee 370/203
`
`OTHER PUBLICATIONS
`
`M. Sawahashi and F. Adachi, Multicarrier 160AM trans-
`mission with diversity reception, Mar. 14, 1996, Electronic
`Letters, vol. 32, No. 6, pp. 522-523.
`Lauterbach, Thomas, Bosch, Robert, Using Eureka 147 for
`Mobile Multimedia, Feb., 1996, Mobile Communications
`International, pp. 53-58.
`Primary Examiner—Ajit Patel
`Assistant Examiner—Bob A Phunkulh
`57
`ABSTRACT
`7]
`A high-speed wireless transmission system is employable in
`a macro-cellular environment. In the system multiple trans-
`mit antennas are employed. Multiple carrier tones are used
`to transmit the data. The carrier tones can be assigned to the
`respective transmit antennas in such a mannerasto provide
`each antenna with a subset of carrier tones with each subset
`being spread over the transmission spectrum. In addition,
`operation is enhanced by providing Reed-Solomon coding
`.
`.
`:
`of the data across consecutive time intervals.
`
`13 Claims, 5 Drawing Sheets
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`U.S. Patent
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`Dec.21, 1999
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`Sheet 1 of 5
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`U.S. Patent
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`Dec. 21, 1999
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`Sheet 2 of 5
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`6,005,876
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`U.S. Patent
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`Dec.21, 1999
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`Sheet 3 of 5
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`U.S. Patent
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`Dec.21, 1999
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`U.S. Patent
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`Dec.21, 1999
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`Sheet 5 of 5
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`6,005,876
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`1
`METHOD AND APPARATUS FOR MOBILE
`DATA COMMUNICATION
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates to a method and apparatus
`for facilitating mobile data communication, such as high
`speed data. The invention is specifically related to a new
`arrangement for assigning carrier tones to a plurality of
`antennas and a coding technique to provide reliable, high-
`speed wireless access to mobile users in macrocells.
`As more and more people come to rely on wireless
`communication and as Internet usage becomes more popular
`as well,
`it becomes desirable to provide the ability for
`mobile wireless users to have multimedia access such as to
`
`the Internet. However, effective multi-media access requires
`a high-speed communication capability such as,
`for
`example, a bit rate of 1 to 2 Mbps.
`It is currently knownto provide a wireless data system
`with high bit rates over a short distance such as in a wireless
`LAN environment. A co-pending provisional U.S. patent
`application, entitled CLUSTERED OFDM WITH TRANS-
`MITTER DIVERSITY AND CODING (USS. Provisional
`Application No. 60/011,601, filed Mar. 8, 1996), describes a
`technique for providing such a high bit rate wireless LAN.
`In that technique an input data stream is encodedto allow for
`error/erasure correction in a receiver. Then, a multicarrier
`(or multitone) signal is formed. For multicarrier, the basic
`idea is to divide the transmitted bandwidth into many narrow
`subchannels that are transmitted in parallel. Each subchan-
`nel is then modulated at a very low rate to avoid significant
`intersymbol
`interference (ISI). The disclosed method
`employs Orthogonal Frequency Division Multiplexing
`(OFDM) a multiplexing technique described in for example,
`“Data Transmission by Frequency-Division Multiplexing
`Using the Discrete Fourier Transform” by Weinstein et al.,
`IEEE Trans. Commun. Technol. Vol. COM-19, No. 5, Octo-
`ber 1971, pp. 628-634 and “Multicarrier Modulation for
`Data Transmission: An Idea Whose Time Has Come,” by
`Bingham, IEEE Commun. Mag., Vol. 28, No. 5, May 1990,
`pp. 5-14. In the method disclosed in the provisional appli-
`cation groups of adjacent tones are clustered together and
`separate clusters are providedto different ones of a plurality
`of separate independent antennas. A single receive antenna
`is then used to demodulate the OFDM signal with conven-
`tional techniques.
`Amobile data system has particular problems which limit
`the ability to provide high speed multi-media access. The
`main impairments encountered in a mobile radio environ-
`ment are delay spread, doppler and path loss as represented
`by reduced received signal power. Delay spread refers to the
`fact that because the signal will experience a wireless path
`that will have different impacts on different frequenciesit is
`likely that
`the entire signal will not be received at
`the
`receiver at the same instant in time. A delay will be intro-
`duced. The delay spread in the macrocellular environment
`could be as large as 40 usec which could limit the data rate
`to about 50 Kbaudif no measuresare taken to counteract the
`resulting ISI. In the 2 GHz PCSbandsthe doppler rate could
`be as high as 200 Hz(i.e., a mobile unit moving at about 67
`mph). Furthermore, the received signal poweris inversely
`related to the data rate such that, for example, at a data rate
`of 1Mbaud (approximately 50 times that of a typical voice
`circuit) there is a shortfall of at least 15 dB in received power
`compared to cellular voice services and this creates a link
`budget problem. Thus, without any system modification the
`coverage and performance of such systems will be severely
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`limited. In fact, in the present wireless systems that cover a
`wide area with mobile receivers, bit rates of 10 to 20 Kbps
`have been achieved. Therefore, it is desirable to adapt the
`wireless transmission systems to facilitate high-speed data
`communications.
`
`SUMMARYOF THE INVENTION
`
`The present invention achieves the desired high-speed
`wireless transmission by modifying the system to correct for
`the effects of delay spread and path loss. The present
`invention proposes an asymmetric service: a high-speed
`down link (for example 1 to 2 Mbps peak data rates, or
`more) and a lower bit rate lower uplink (for example
`50-100Kbs). This would alleviate the problem ofincreasing
`power consumption at the mobile terminal to overcome the
`15 dB shortfall in received power. Nonetheless, it should
`still be sufficient for most applications, such as Web
`browsing, voice access, e-mail, and interactive computing.
`Furthermore, the present invention provides an Orthogo-
`nal Frequency Division Multiplexing (OFDM) system that
`has narrow enough subchannels and sufficient guard period
`to minimize the effects of delay spreads as large as 40 usec.
`To overcome the 15 dB shortfall
`in link-budget,
`the
`present invention provides transmit antenna diversity and
`coding across frequencies. In one example the base station
`has four transmit antennas. Each antenna is assigned to
`transmit a subset of the total number of tones. A particular
`subset is composed of a plurality of widely spaced tones
`covering the entire transmission bandwidth. As a conse-
`quence a subset of tones on a second antenna will include
`tones between those transmitted on the first antenna. Alter-
`
`natively each subset of tones for a given transmit antenna
`can include widely spaced clusters of tones, e.g., two or
`three adjacent tones, which cover the entire transmission
`bandwidth. Spreading the tones over the transmit antennas
`randomizes the fading across the OFDM bandwidth.
`The coding is also selected to help reduce the link-budget
`problem. The digital data are encoded using Reed-Solomon
`(R-S) encoding where symbol words within R-S codewords
`are created by time-grouping modulation symbols that are
`consecutive in time. The encoding uses a combination of
`erasure correction, based on signal strength, and error cor-
`rection.
`
`When the tone antenna assignment technique and the
`coding operation are combined the link-budget problem is
`substantially alleviated.
`In alternative embodiments the mobile station may
`include receive antenna diversity. Also, the assignment of
`tones to the transmit antennas can be arranged such that the
`same tone is transmitted simultaneously by two or more
`antennas. In yet another modification the tones assigned to
`a given antenna can be changed overtime so that the effect
`of any negative correlation between a given tone and a given
`transmission path from a transmit antenna to a receive
`antenna can be minimized.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIGS. 1(A) and 1(B)respectively illustrate possible con-
`figurations of a transmitter and a receive station in a wireless
`LAN environment.
`
`FIG. 2 illustrates a possible frequency characteristic of a
`given transmission path from one transmission antenna to
`one receive antenna.
`
`FIG. 3 illustrates in block diagram form an embodiment
`of the present invention.
`7
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`6,005,876
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`3
`FIG. 4 illustrates a graphical representation of a second
`aspect of the present invention.
`FIG. 5 illustrates, in block diagram form, a more detailed
`embodiment of the present invention.
`FIG. 6 illustrates how the embodiment of the present
`invention operates to improve upon link budget shortfalls.
`DETAILED DESCRIPTION
`
`An example of a wireless transmission system in a LAN
`environment such as described in the above-referenced
`provisional application is illustrated in FIG. 1(A)-(B). A
`data bit stream is provided to an encoder 101 which pro-
`duces a plurality of symbols. In this instance the encoder
`produces NxM symbols. N tonesare assigned to each of M
`antennas, e.g., 104,.. . 104,,. The first N tones are provided
`to IFFT (Inverse Fast Fourier Transformers) 102, while the
`Mth group of N tones is provided to IFFT 102,,. Each group
`of tones is provided to RF circuitry (e.g.,
`filter and
`amplifier), e.g., 103,
`.
`.
`. 103,, and then passed on to its
`respective transmit antenna 104. The total numberof tones
`(NxM)equals the total numberofcarriers in the multicarrier
`OFDM configuration. The carriers are spread out over the
`transmission spectrum.
`Graphical representations are provided adjacent to each
`antenna 104, to 104,, to illustrate that a given antenna is
`assigned a particular cluster of adjacent tones or carrier
`frequencies. Each cluster is part of a very localized portion
`of the overall transmission spectrum.
`The M clusters of tones are transmitted from the M
`
`transmit antennas simultaneously and received by the
`receive antenna 110. As can be seen from the adjacent
`graphical representation,
`the antenna receives all of the
`clusters nearly simultaneously.
`The antenna provides the received multicarrier signal to
`RFcircuitry 111 which then providesthe processed signal to
`FFT 112. The resultant data corresponds to the NxM sym-
`bols produced by the encoder 101 in FIG. 1(A) and the
`decoder 113 receives these symbols and provides as an
`output
`the data bit stream. What
`is not shown in the
`graphical representation is that the receive antenna 110 may
`receive different frequencies at different strengths. In the
`mobile environment multi-path propagation may pose a
`significant problem for such a configuration such that certain
`of the frequencies may be so seriously faded as to have
`essentially dropped out.
`It is considered that the channel from one of the transmit
`antennas to the receive antenna can be different from the
`channel
`from another
`transmit antenna to the receive
`
`antenna. These are considered separate and distinct paths.
`Eachpath has its own frequency response characteristic. For
`instance, as illustrated in the graphical representation of
`FIG. 2, a first path may more successfully transmit frequen-
`cies in the range of f, while having more difficulty trans-
`mitting frequencies in the range of f, and f,. Thus,
`the
`inventors recognized that for a numberoftones in the region
`of f, (or f,) if those tones are clustered together and are the
`sole cluster provided along antenna 1, then the signal from
`antenna 1 will either be difficult to detect at the receiver or
`
`will likely contain many errors due to the path’s character-
`istics.
`
`To remedy this problem the inventors propose to provide
`a spreading out of the carrier tones across the transmission
`spectrum. This will counteract any frequency dependence
`that a particular path might have by optimizing the chances
`that each path will substantially transmit useful and correct
`information.
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`As illustrated in a first embodiment of the present inven-
`tion shown in FIG. 3, a sequence of data bits is provided to
`a modulator 301 that creates a modulator symbol. The
`modulator symbols are grouped, encoded and subsequently
`decomposed by elements 302, 303 and 304 as will be
`described in further detail later. The resultant data stream is
`converted to a parallel stream of data by serial-to-parallel
`converter 305. As an example, 120 symbols of data are
`provided in parallel (X, to X,,.). Where the symbols are
`QPSK modulated each consists of two bits. Other modula-
`tors can be used to create either symbols such as 8-PSK
`symbols. A distributor receives this 120 parallel symbol
`block of data. Each of the 120 symbols corresponds to one
`of 120 carrier tones to be used in the multi-carrier OFDM
`configuration. The distributor can send clusters of symbols
`to each of M IFFTs (307, to 307,,,). In the present example
`the distributor sends groups of five symbols corresponding
`to five carrier tones to each of the IFFTS. In the present
`example it 1s proposed that M=4 so that there are four
`transmit antennas (309, to 309,,) providing four separate
`paths to a single receive antenna. The distributor therefore
`provides thirty symbols of the 120 symbols to each of the
`transmit antennapaths. It does so in five-symbolclusters that
`are spread outoverthe entirety of the transmission spectrum,
`1.¢., IFFT 307, receives symbols at X, to X4, X29 to X54, Xag
`to X44... X4o9 to X494. Similarly, the remaining IFFTs also
`receive clusters of symbols assigned to carrier tones thatare
`spread over the transmission spectrum. Therefore, as shown
`in the graphical representations associated with antennas
`309, and 309,, in FIG. 3, the first antenna sends out six
`clusters of tones. These tones are spread over the entire
`transmission spectrum. As can be seen the six clusters
`transmitted by antenna 309,, are interleaved with the clus-
`ters transmitted by 309,. Although not shown,the clusters
`for 309, and 309, (where M=4)are also interleaved with the
`clusters of tones to be transmitted on the other antennas.
`
`In summary then, the problem of the frequency depen-
`dence of a given path from one antenna to the receive
`antenna and the path’s susceptibility to adversely affecting
`the overall transmission characteristic whenit only transmits
`a cluster of the multiple carrier tones, are overcome by
`providing a subsetof the carrier tones to each of the antennas
`wherethe subset for a given antennais spread overthe entire
`transmission spectrum. As a consequence, not all of the
`tones on a given antenna are adjacent to one another. In fact,
`where tones on antenna 1 are not adjacent to one another
`(e.g., tone for X, and tone for X59), there are intermediate
`tones which are supplied by different ones of the transmit
`antennas.
`
`Modifications to this arrangement may be desirable. For
`instance, in the example described abovethe distributor 306
`receives 120 symbols and divides them amongfour trans-
`mitters. Each cluster within a subset of tones can be con-
`stituted by a single tone rather than a group of adjacent
`tones. Thus, one possible modification to the arrangementof
`FIG. 3 would assign the tones corresponding to symbols Xp,
`X4, Xg, X42, X46 etc. to antenna 1 and the tones for symbols
`X,, Xs, Xo, X15, etc. to antenna 2 and so on. This arrange-
`ment should achieve a substantially similar result in that the
`improvementarises from the spreading out of the tones for
`a given antenna over the entire transmission spectrum and
`interleaving the tones carried by various ones of the anten-
`nas.
`
`In another modification to improve received signal
`strength at the receiver it might be appropriate to send the
`same signals on multiple transmitters. In this instance, it is
`conceivable to employ, for example, eight transmit antennas
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`6,005,876
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`5
`where each antenna is separate and distinct and thus pro-
`vides different paths each having their own characteristics.
`Then, the same configuration as described with respect to
`FIG. 3 could be employed with the change being that the
`same output stream provided to 309, could also be provided
`to another antenna so that two transmit antennas would be
`responsible for transmitting symbols Xp to Xy, X59 to X54
`and so on. This could improve the overall receive charac-
`teristics.
`
`In yet another modification to this design it is possible to
`vary the tone assignment amongthe transmit antennas. As an
`example, should the path associated with transmit antenna
`309, have characteristics which are adverse to the tones for
`symbols X, to X, this problem can bealleviated by rotating
`the assignment of the clusters of tones among the various
`antennas. Therefore, in a first instance a first block of 120
`symbols might be assigned in the mannerillustrated in FIG.
`3. A second block could be transmitted with a different set
`
`of tone assignments,e.g., 309, receiving tones for symbols
`X15 to X49, X35 tO Xzo, etc. This changing of the assignment
`of tones to a given transmit antenna assists in avoiding
`potential adverse impacts of a given antenna’s transmission
`characteristic upon any of the carrier tone or tone clusters.
`This could be accomplished by inserting a switching
`arrangement between the IFFT’s (307,-307,,) and the RF
`circuitry so that the IFFT’s are alternately assigned to the
`respective antennas.
`Ofcourse, one of ordinary skill in the art would recognize
`that given this description of various modifications to the
`first embodiment of FIG. 3 that combinations of these
`
`the
`modifications would also be possible. For example,
`rotation of carrier tones among transmit antennas could also
`be performed whentransmitting individual tones rather than
`clusters of tones.
`
`6
`frequency overthe three consecutive time periods. Thus, for
`example, R-S,, would be comprised of frequency f, at time
`t,, £, at time t, and f, at time t,. The actual construction of
`these Reed-Solomon symbols and code words are described
`in relation to FIGS. 3 and 5.
`
`As illustrated in FIG. 3, the modulator symbols at the
`output of the modulator are provided to a symbol grouper
`302. An example of a sequence of data bits is shown at 51
`in FIG. 5. In one more specific embodimentof the present
`invention the modulator 301 is a serial QPSK (Quadrature
`Phase Shift Key) modulator. In this embodiment the modu-
`lator converts a block of 360 data bits into 180 2-bit symbols
`(d, to d,7.). Each R-S symbolis six bits in length, thus three
`QPSKsymbols can be grouped to form a single R-S symbol.
`In accordance with the inventors’ discovery regarding time
`grouping of symbols as illustrated in FIG. 4, three symbols
`consecutive in time rather than frequency can be grouped
`together to form the R-S symbol. For instance, where there
`are 180 2-bit symbols there are three blocks of sixty 2-bit
`symbols: dy to ds, at transmission time t,, dgg to dy, at
`transmission time t,, and d,5, to d,7, at transmission timet;.
`Thus, a grouping in time of three 2-bit symbols to create an
`R-S symbol could be effected by grouping symbols do, deg
`and d,,,.. The R-S coding shown in FIG. 3 would result in
`three sets of forty R-S symbols with each set containing 20
`data symbols and 20 parity symbols. The decomposer 304
`would then reconfigure the QPSK symbols within the R-S
`wordsin timeto create time blocksof transmission symbols,
`€.2.,
`Zo tO Zsq, Zeq tO Z449, aNd Z459 to Z179. A serial to
`parallel converter 305 takes the symbol stream and creates
`a parallel configuration of 120 symbols at a time. A dis-
`tributor 306 then divides the 120 symbols among the mul-
`tiple transmit antennas in accordance with the carrier tone
`assignment for that given antenna in accordance with the
`discussions above.
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`Thus, in this exemplative arrangementthere are 120 tones
`The inventors also recognize that the way the coding is
`with a 160 usec block size and a 40 usec guard. This results
`done can have a positive influence on the worderror rate to
`in subchannels that are spaced by 6.25 kHz, block rates of
`thereby further address the link budget problem.
`In
`5 kbaud, andatotal rate of 600 kbaud or equivalently
`particular, the inventors have selected Reed-Solomon (R-S)
`channel bit rates of 1.2 Mbps for QPSK.
`encoding. In an example of such an encoding scheme each
`R-S symbolis constituted by six bits of information and the
`The combination of the coding technique with the assign-
`mentof tones to the various transmit antennas has shown an
`R-S block is constituted by a predetermined number of R-S
`symbols with a certain subset of those symbols being
`ability to substantially overcome the link budget problem
`described above. As shown in FIG. 6 where R-S encoder
`directed to data symbols and the remaining being directed to
`parity symbols. As is known, whetherthere is one bit of an
`provides 40 symbol words each word including 20 parity
`R-S symbol whichis in error or whether there are multiple
`symbols with 20 time grouped data symbols, a desired word
`bits of the R-S symbols that are in error, it takes two parity
`error rate WER of 1% requires less than 8.5 dB signal to
`symbols to correct each R-S symbol in error unless the
`noise ratio rather than the 17 to 20 dB which is typically
`location of the R-S symbolthat is in error is known. In the
`required for cellular systems. This represents about a 9 dB
`latter circumstance such an R-S symbol is considered an
`reduction in the link budget shortfall discussed above. This
`erasure and only one parity symbol is necessary to correct
`significantly improvesthe ability to transmit high speed data
`in the wireless environment.
`such an error. To enhance the through-put of data it is
`In connection with the actual error detection at
`desirable to keep the number of parity symbols low.
`However, to accomplish this goalit is beneficial to construct
`the R-S data symbols in a manner that maximizes the
`concentration of errors, ie., rather than spreading out data
`bit errors over multiple symbolsit is desirable to increase the
`likelihood that those bits that will be in error will be in the
`same R-S symbol.
`The inventors have determined that the optimum way to
`concentrate these bit errors is to group the modulator sym-
`bols in time rather than by frequency. As shown in the
`example of FIG. 4, there are three blocks of multicarrier
`signals shownat different times each with a time width of
`200 microseconds. The frequenciesf, to f, correspond to the
`multicarriers over the transmission spectrum. The inventors
`discovered that it
`is beneficial to construct a given R-S
`symbol, for example R-S,, from three symbols of the same
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`receiver end, and with a goal in mind of maximizing the use
`of the parity symbolsit is possible to designate a percentage
`of the parity symbols as being related to correcting erasures
`and the remaining being directed to correcting errors. For
`example, where there are 20 parity symbolsit is possible to
`correct ten erasures (one symbolper erasure) andfive errors
`(two symbols per error). To accomplish this end in a given
`R-S word the algorithm can designate that the ten least
`powerful R-S symbols can be treated as erasures and cor-
`rected as such. Thenfive additional errors could be corrected
`if they exist in any of the remaining R-S symbols. Other
`criteria for estimating that an erasure has occurred can be
`employed such as measuring the bit error rate or using an
`“inner code”(an error detection code) to detect where errors
`occur,
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`The exemplative embodiments illustrated in FIGS. 3 and
`5 can be constructed using well known components. First,
`the R-S encoder can be constituted by the Reed-Solomon
`Error Correction Device sold by Advanced Hardware Archi-
`tectures of Washington State.
`
`The signal processing functions can be implemented in a
`DSP which provides IFFTs as is well known. The time
`grouping and decomposing can be implemented using buff-
`ers. For example, to group-in-time a buffer could store 120
`2 bit symbols and then those symbols could be read out in
`a predetermined time order. Similarly for the decomposer
`the R-S code words could be stored in a buffer and the
`
`individual 2-bit symbols within the code word could be read
`out in a predetermined order. Also, the distributor can take
`the form of a de-multiplexerin that it takes the symbols from
`the Serial/Parallel converter and passes selected symbols to
`selected IFFTs which is simply the dividing up of informa-
`tion between channels, a common demultiplexing function.
`
`the
`To further enhance the receiving characteristics at
`mobile station, it is possible to employ multiple antennas,
`e.g., two. The signals from the two antennas can then be
`combined so as to further reduce the likelihood that any
`significant number of the carrier tones is insufficiently
`received.
`
`In the foregoing the Applicants have described twotech-
`niques which can be employed in connection with the
`wireless transmission of data to increase bit rate, namely the
`assignment of carrier tones to multiple transmit antennas
`with the carrier tones assigned to any one antenna being
`spread over the transmission spectrum and a particular type
`of coding technique. These two aspects can be employed
`separately or they can be combined together to further
`improve the achievable bit rate.
`Whatis claimedis:
`
`1. A method for high-speed wireless transmission of data
`over a transmission spectrum comprising the steps of:
`
`creating a stream of data;
`encoding said stream of data to create a plurality of
`symbols, wherein said step of encoding includes the
`substeps of,
`grouping said data in said stream to create multi-bit
`coding symbols, each coding symbol containing a
`plurality of modulation symbols grouped in time,
`and
`generating a code word from a plurality of coding
`symbols, said code word corresponding to a Reed-
`Solomon code,
`assigning each of said plurality symbols to one of a
`plurality of carrier tones;
`providing eachofsaid carrier tones to oneofa plurality
`of transmission antennas, in such a waythat each
`antenna receives a subset of said plurality of carrier
`tones and each subset of said plurality of carrier
`tones includesat least two carrier tones not adjacent
`to one another in the transmission spectrum and
`having at least one carrier tone therebetween that is
`provided to another one of said plurality of trans-
`mission antennas; and
`simultaneously transmitting the subsets of carrier tones
`from said plurality of transmission antennas.
`2. The method of claim 1 wherein in one subset of said
`plurality of carrier tones the carrier tones are uniformly
`distributed over the transmission spectrum.
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`3. The method of claim 1 wherein in one subset of said
`
`plurality of carrier tones the carrier tones are distributed over
`the transmission spectrum in a non-uniform manner.
`4. The method of claim 1 wherein at least two subsets of
`
`said plurality of carrier tones on separate antennas include
`the same carrier tones.
`
`5. The method of claim 1 wherein for a given one of
`plurality of transmission antennas a first subset of carrier
`tones at a first time and a second subset of carrier tones at
`a second time include different carrier tones.
`
`6. A method for high speed wireless transmission of data
`over a transmission spectrum comprising the steps of:
`creating a stream of digital data;
`groupingsaiddigital data in said stream to create multi-bit
`coding symbols, each coding symbol containing a
`plurality of modulation symbols grouped in time;
`generating a code word from a plurality of coding
`symbols, wherein said step of generating generates a
`Reed-Solomon code;
`assigning each of said modulation symbols to one of a
`plurality of carrier tones; and
`providing each of said carrier tones to one of a plurality
`of transmission antennas; and
`transmitting said plurality of carrier tones from said
`plurality of transmission antennas.
`7. The method of claim 6 wherein each of said plurality
`of transmission antennas is provided with a plurality of
`carrier tones.
`
`8. A high-speed wireless transmission system that
`includes a plurality of transmission antennas, the system
`comprising:
`a modulator that receives a data stream and creates a
`
`plurality of modulated symbols;
`an encoder coupled to said modulator and that receives
`said plurality of modulated symbols and outputs
`encoded words;
`a splitter coupled to said encoder and that receives said
`code words as input and assigns modulated symbols in
`said code wordsto the plurality of transmission anten-
`nas;
`
`a transmitter coupled to said encoder and that receives
`coded symbols assigned to an antenna associated with
`said transmitter and that provides a data transmission
`signal
`including a plurality of non-adjacent carrier
`tones to the associated transmission antenna;
`wherein said plurality of non-adjacent carrier tones com-
`prises a subset of a plurality of carrier tones and
`wherein at least one carrier tone that is between non-
`adjacent carrier tones of said subset
`is assigned to
`another one of said plurality of transmission antennas.
`9. System of claim 8 wherein said modulated symbols are
`assigned to the plurality of transmitters in a manner to
`provide a uniform distribution of symbols over the trans-
`mission bandwidth.
`
`10. The system of claim 8 wherein said modulated sym-
`bols are assigned to the plurality of transmitters in a manner
`to provide a randomized distribution of symbols over the
`transmission bandwidth.
`11. A high-speed wireless transmission system that
`includes a plurality of transmission antennas, the system
`comprising:
`a modulator that receives a data stream and creates a
`
`plurality of modulated symbols;
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`6,005,876
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`9
`an encoder coupled to said modulator and that receives
`said plurality of modulated symbols and outputs
`encoded words;
`a splitter coupled to said encoder and that receives said
`code words as input and assigns modulated symbols in
`said code wordsto the plurality of transmission anten-
`nas;
`
`a transmitter coupled to said encoder and that receives
`coded symbols assigned to an antenna associated with
`said transmitter and that provides a data transmission
`signal
`including a plurality of non-adjacent carrier
`tones to the associated transmission antenna;
`
`10
`wherein said plurality of non-adjacent carrier tones com-
`prises a subsetof carrier tones including two clusters of
`adjacent carrier tones.
`12. The system of claim 11 wherein said modulated
`symbols are assigned to the plurality of transmitters in a
`manner to provide a uniform distribution of symbols over
`the transmission bandwidth.
`13. The system of claim 11 wherein said modulated
`symbols are assigned to the plurality of transmitters in a
`manner to provide a randomized distribution of symbols
`over the transmission bandwi