(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2006/0067415 A1
`Mujtaba
`(43) Pub. Date:
`Mar. 30, 2006
`
`US 20060067415A1
`
`(54) METHOD AND APPARATUS FOR
`INCREASING DATA THROUGHPUT IN A
`MULTIPLE ANTENNA COMMUNICATION
`SYSTEM USINGADDITIONAL
`SUBCARRIERS
`
`(76) Inventor: Syed Aon Mujtaba, Watchung, NJ
`(US)
`Correspondence Address:
`Ryan, Mason & Lewis, LLP
`Suite 205
`1300 Post Road
`Fairfield, CT 06824 (US)
`(21) Appl. No.:
`11/223,757
`
`(22) Filed:
`
`Sep. 9, 2005
`Application Data
`Related U.S.
`
`(60) Provisional application No. 60/608,472, filed on Sep.
`9, 2004.
`
`Publication Classification
`
`(51) Int. Cl.
`H04K L/10
`
`(2006.01)
`
`(52) U.S. Cl. .............................................................. 375/260
`
`(57)
`
`ABSTRACT
`
`Methods and apparatus are provided for increasing data
`throughput in a multiple antenna communication system
`using additional Subcarriers. The multiple antenna commu
`nication system includes at least one legacy system employ
`ing an N point fast Fourier transform (FFT) within a
`bandwidth, BW. Data is transmitted using an N point
`inverse FFT within the bandwidth, BW, wherein N is
`greater than N, and Subcarriers associated with the N point
`inverse FFT are employed to transmit the data. Data can also
`be transmitted using an N point inverse FFT within a
`bandwidth, BW, wherein N is greater than N and the
`bandwidth, BW, is greater than the bandwidth, BW; and
`subcarriers associated with the N point inverse FFT are
`employed to transmit the data, wherein the employed Sub
`carriers includes one or more additional Subcarriers at outer
`edges of the bandwidth, BW, relative to the legacy system
`and one or more additional subcarriers near DC relative to
`the legacy system.
`
`
`
`-20cBc
`
`-29
`-58
`
`-29 -27-26
`-56 -54 -52
`
`-1 MHz
`
`-9 MHz
`
`O
`
`Hz
`M
`
`
`
`-20B
`+26 +27 +28-29 -INDICES FOR 64
`+52 +54 +56-58-INDICES FOR 128
`I+9 MHz
`+ 1 MHz
`
`------------------------------------------------------------------------------------ases--e.
`
`-57 (EDGE OF THE PASSBAND)
`
`+57 (EDGE OF THE PASSBAND)
`
`Exhibit 1012
`Panasonic v. UNM
`IPR2024-00364
`Page 1 of 9
`
`

`

`Patent Application Publication Mar. 30, 2006 Sheet 1 of 5
`
`US 2006/0067415 Al
`
`LYYoTLOLA
`
`
`
`QNISSI00Ud
`
`og)JeeSSSSSSSSSSSSSSSe‘1|I||TeLglONY4IAVTRGINI||ayANYS/dONIddsONaNO3S43000N3|!ON!crOMos702104|{,I[----
`=eYILIINSNVEL|sor
`
`
` (NG||¥300030BHAVANwyyyKA}any9/sINowd44!L
`TIGNV3Ud|_|||I!Iid¥N30193AON3Y
`
`WoonenaY3NII034)
`ON06081OL091c6I
`
`'|'|
`
`Exhibit 1012
`
`Panasonic v. UNM
`
`IPR2024-00364
`Page 2 of 9
`
`Exhibit 1012
`Panasonic v. UNM
`IPR2024-00364
`Page 2 of 9
`
`
`
`

`

`Patent Application Publication Mar. 30, 2006 Sheet 2 of 5
`
`US 2006/0067415 A1
`
`
`
`
`
`Exhibit 1012
`Panasonic v. UNM
`IPR2024-00364
`Page 3 of 9
`
`

`

`Patent Application Publication Mar. 30, 2006 Sheet 3 of 5
`
`US 2006/0067415 A1
`
`
`
`ihn, 11;ZHW 6+
`
`
`
`Exhibit 1012
`Panasonic v. UNM
`IPR2024-00364
`Page 4 of 9
`
`

`

`Patent Application Publication Mar. 30, 2006 Sheet 4 of 5
`
`US 2006/0067415 Al
`
`oor
`
`bYOlA
`
`094»STNOT
`QQ+—»=======areAALTWPTYTTTTT£9t
`
`
`(ze-WVTHN1)ewTow|SisAeayINT4d1004anaquay ~---------------}-------------++--------f=3-282-----f8=====tt"794
`
`
`Saas=-NOL|----------------------§--2ag
`
`
`ZHNOZINIdLO04ZHHOZ
`
`
`(z¢+1¥TINN1)(z¢+1¥TINN1)aetnINTYd1004ZHNOZINTd1003ZHNOZ
`
` 07Oz?olV
`_ESINOLCSINOLTIONSE)Loc4
`
`
`
`NOLLS1HSINOL£SADVOTI]|b7-c1y
`NOLJS1HSINOL$$ADVOIT
`
`cnoltmmati}
`
`+Q9-
`
`Exhibit 1012
`
`Panasonic v. UNM
`
`IPR2024-00364
`Page 5 of 9
`
`Exhibit 1012
`Panasonic v. UNM
`IPR2024-00364
`Page 5 of 9
`
`
`

`

`Patent Application Publication Mar. 30, 2006 Sheet 5 of 5
`
`US 2006/0067415 Al
`
`
`
`-_—_—_—_——————%98=821/01)=AON3IOLI]————>
`
`NOJOS7p'9st9°0 0¢Sf
`SINOLTWLOL821“NOLTINN30|“S3NOLSLOTId¥‘S3NOLVIVOO11TWAUAINTGa¥nd
`
`
`
`
`
`TOGNAS
`
`
`
`+ 49/=(gz1/oll)+(2°2/9'9)=AON3IOLI3TY3IAQ———H
`
`as’
`
`GOLA
`
`
`
`+—%G/=79/8"=AONIOL443——~
`
`SLOMd7‘SINOLVIVO8sft@TOSNASNOIOStZ¢
`SINOLW1OL79“4NOLTINN90|WAYJINTaNYNd0‘SINOL
`
`
`
`
`
`=—%09=(79/8r)«(7/25)=AONSIOIIITWY3IAO—~
`
`Exhibit 1012
`
`Panasonic v. UNM
`
`IPR2024-00364
`Page 6 of 9
`
`Exhibit 1012
`Panasonic v. UNM
`IPR2024-00364
`Page 6 of 9
`
`

`

`US 2006/0067415 A1
`
`Mar. 30, 2006
`
`METHOD AND APPARATUS FOR INCREASING
`DATA THROUGHPUT IN A MULTIPLE ANTENNA
`COMMUNICATION SYSTEM USING ADDITIONAL
`SUBCARRIERS
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`0001. The present application claims priority to U.S.
`Provisional Patent Application Ser. No. 60/608,472, filed
`Sep. 9, 2004, incorporated by reference herein.
`
`FIELD OF THE INVENTION
`0002 The present invention relates generally to multiple
`antenna wireless communication systems, and more particu
`larly, to techniques for transmitting data on Subcarriers in a
`multiple antenna communication system.
`
`BACKGROUND OF THE INVENTION
`0003 Multiple transmit and receive antennas have been
`proposed to provide both increased robustness and capacity
`in next generation Wireless Local Area Network (WLAN)
`systems. The increased robustness can be achieved through
`techniques that exploit the spatial diversity and additional
`gain introduced in a system with multiple antennas. The
`increased capacity can be achieved in multipath fading
`environments with bandwidth efficient Multiple Input Mul
`tiple Output (MIMO) techniques. A multiple antenna com
`munication system increases the data rate in a given channel
`bandwidth by transmitting separate data streams on multiple
`transmit antennas.
`0004. In the current IEEE 802.11a/g standard, for
`example, each channel is 20 MHz wide and there are 64
`possible subcarriers within each 20 MHZ channel. Of the 64
`possible subcarriers, however, only 48 tones are employed to
`carry data in the 802.11 standard. It is noted that twelve
`tones are not used at all, including one blank tone at DC (0
`MHz), and four pilot tones are employed that do not carry
`any user information. Thus, only 75 percent of the available
`Subcarriers are employed to carry user data.
`0005. A number of techniques have been proposed or
`Suggested for further increasing the data throughput in
`multiple antenna communication systems. For example, a
`channel bonding technique has been proposed that increases
`the channel bandwidth to 40 MHz and the number of
`subcarriers to 128. When the 802.11a standard is extended in
`such a two-fold manner to provide a 40 MHZ channel
`bandwidth, it would likewise be expected to double the
`number of Subcarriers that are employed to carry user
`information from 48 to 96 subcarriers. A need exists, how
`ever, for an ever greater improvement in efficiency and
`throughput. A further need exists for methods and apparatus
`for increasing throughput in a multiple antenna communi
`cation system using additional Subcarriers.
`
`SUMMARY OF THE INVENTION
`0006 Generally, methods and apparatus are provided for
`increasing data throughput in a multiple antenna communi
`cation system using additional Subcarriers. The multiple
`antenna communication system includes at least one legacy
`system employing an N point fast Fourier transform (FFT)
`within a bandwidth, BW. According to one aspect of the
`invention, data is transmitted using an N point inverse FFT
`
`within the bandwidth, BW, wherein N is greater than N:
`and subcarriers associated with the N point inverse FFT are
`employed to transmit the data. Additional Subcarriers, rela
`tive to the legacy system, can be employed at outer edges of
`the bandwidth, BW, or near DC. For example, N can be a
`64 point inverse FFT within the bandwidth, BW, equal to
`20 MHz, and N can be a 128 point inverse FFT within the
`bandwidth, BW.
`0007 According to another aspect of the invention, data
`is transmitted using an N point inverse FFT within a
`bandwidth, BW, wherein N is greater than N and the
`bandwidth, BW, is greater than the bandwidth, BW; and
`subcarriers associated with the N point inverse FFT are
`employed to transmit the data, wherein the employed Sub
`carriers includes one or more additional Subcarriers at outer
`edges of the bandwidth, BW, relative to the legacy system
`and one or more additional subcarriers near DC relative to
`the legacy system. For example, N can be a 64 point inverse
`FFT within the bandwidth, BW, equal to 20 MHz, and N,
`can be a 128 point inverse FFT within the bandwidth, BW.
`equal to 40 MHz.
`0008. A more complete understanding of the present
`invention, as well as further features and advantages of the
`present invention, will be obtained by reference to the
`following detailed description and drawings.
`BRIEF DESCRIPTION OF THE DRAWINGS
`0009 FIG. 1 is a schematic block diagram of a conven
`tional 802.11a/g transceiver;
`0010 FIG. 2 illustrates the current subcarrier design in
`accordance with the IEEE 802.11a standard;
`0011 FIG. 3 illustrates a subcarrier design in accordance
`with the present invention;
`0012 FIG. 4 illustrates a number of potential subcarrier
`designs 400 for 40 MHz; and
`0013 FIG. 5 evaluates the efficiency of a 64 point FFT
`and a 128 point FFT in 20 MHz.
`DETAILED DESCRIPTION
`0014. According to one aspect of the present invention,
`the total number of possible subcarriers used in 40 MHz is
`increased to 128 or 256 subcarriers. An implementation in
`accordance with the present invention optionally includes
`both 128 subcarriers and 256 subcarriers and leaves the
`choice to vendors or network managers. According to
`another aspect of the present invention, a transmission
`scheme is provided to increase the system throughput by
`increasing the number of Subcarriers that are user to carry
`user information.
`0015 FIG. 1 is a schematic block diagram of a conven
`tional 802.11a/g transceiver 100. At the transmitter side 105,
`the information bits are first encoded at stage 110 and then
`frequency interleaved at stage 120. The encoded and inter
`leaved bits are then mapped onto Subcarriers (tones) at stage
`130 and form a frequency domain OFDM signal. The
`frequency domain OFDM signal is translated to the time
`domain by an inverse Fourier transform (IFFT) during stage
`130. At stage 140, the data is serialized and a guard interval
`is added to each OFDM symbol. Finally, a preamble includ
`ing training and signal fields is added during stage 145 at the
`beginning of each packet.
`
`Exhibit 1012
`Panasonic v. UNM
`IPR2024-00364
`Page 7 of 9
`
`

`

`US 2006/0067415 A1
`
`Mar. 30, 2006
`
`0016. At the receiver side 150, the received signal is
`initially processed by the RF front end 155, and then the
`serial data is parallelized and the guard interval is removed
`at stage 160. The time domain signal is translated to the
`frequency domain using an FFT 170 and the subcarriers are
`demapped to encoded and interleaved bits. Meanwhile, the
`preamble is processed at stage 165. The interleaved bits are
`deinterleaved at stage 180 and decoded at stage 190 to
`provide the transmitted information bits.
`0017 FIG. 2 illustrates the current subcarrier design 200
`in accordance with the IEEE 802.11a standard. As shown in
`FIG. 2, each 20 MHZ channel 210 has 64 possible subcar
`riers, -32 through +32, with each Subcarrier having a
`bandwidth of 312.5 kHz. The channel 210 includes a “flat
`passband region 220. 52 subcarriers, -26 through +26, are
`actually employed by the IEEE 802.11a standard, as indi
`cated in FIG. 2 by the arrow at each subcarrier, including
`four (4) subcarriers that are utilized as pilot tones (the pilot
`tones do not carry user information). Thus, Subcarriers -27
`through -32 and +27 through +32, as well as one blank
`subcarrier at DC (0 MHz), are not employed in the 802.11a
`standard. Generally, subcarriers -27 through -32 and +27
`through +32 were blanked out to ease the filter design.
`0018) If the subcarrier design of FIG. 2 were extended to
`a 128 point FFT within the same 20 MHz spectral mask of
`the 802.11a standard, having 128 subcarriers, for example,
`it would be expected that 104 subcarriers, -52 through +52.
`would actually be employed, including eight (8) Subcarriers
`as pilot tones.
`0.019 According to one aspect of the present invention,
`however, a transmission scheme is provided to increase the
`system throughput by increasing the number of Subcarriers
`that are used to carry user information. FIG. 3 illustrates a
`subcarrier design 300 in accordance with the present inven
`tion. In the exemplary design 300 shown in FIG. 3, a 128
`point FFT is employed in each 20 MHZ channel 310, where
`the FFT samples the spectrum at twice the rate of the
`configuration shown in FIG. 2 (64 point FFT). The symbol
`time for 128 point FFT in 20 MHz is 2x3.2 us (6.4 us).
`0020. A transceiver 100 in accordance with the present
`invention increases the number of Subcarriers that are used
`to carry user information, relative to an IEEE 802.11a
`implementation. In one exemplary implementation of the
`present invention, all the available subcarriers in the “flat'
`passband region 320 from -.9 MHz to +9 MHZ are employed
`to carry user information or to serve as a pilot tone. In this
`manner, all “tone indices' between -57 to +57 on a 128 FFT
`scale are used (i.e., a total of 114 tones out of 128 tones in
`the 20 MHZ channel). If the number of pilot tones is
`maintained at four (4), which is sufficient in 20 MHz, 110
`tones can be employed to carry user information. The DC
`tone, and optionally additional tones adjacent to the DC
`tone, are nulled, in a known manner. Thus, 110 tones are
`available for data transport (assuming one null tone). In this
`manner, the efficiency of the OFDM symbol can be
`increased from 60% to 76%, as discussed further below in
`conjunction with FIG. 5.
`0021. In an exemplary implementation where 64-QAM
`encoding is employed by the transceiver 100 with 6 coded
`bits/tone, 4.5 information bits are carried per tone, with a
`rate, R, equal to 3/4. Thus, in an implementation where 110
`tones are employed for data transport (assuming one null
`tone), the maximum data rate can be expressed as follows:
`
`110:45
`495
`is a = 72 = 68.75 Mbps
`Max Data Rate =
`
`assuming a guard interval, GI, equal to 0.8 us. Compared to
`54 Mbps, which would have been achieved with 48 tones in
`20 MHz, the increase in the maximum data rate is 27%.
`0022 FIG. 4 illustrates a number of potential subcarrier
`designs 400 for 40 MHz. As shown in FIG. 4, a first
`conventional subcarrier design 410 in accordance with the
`IEEE 802.11a standard that employs two independent adja
`cent 20 MHZ channels 415-1 and 415-2. As discussed above
`in conjunction with FIG. 2, the legacy Subcarrier design
`employs 52 subcarriers (i.e., tones) in each 20 MHZ channel
`415-1 and 415-2. There are six null tones on a first end of
`each 20 MHZ channel and five null tones on the second end
`of each channel. Thus, there are 11 Subcarriers separating
`each adjacent channel.
`0023. A second subcarrier design 420 in accordance with
`the proposed IEEE 802.11n standard provides a 40 MHz
`design that employs two independent adjacent 20 MHz
`channels 425-1 and 425-2. The proposed 802.11n design 420
`employs 56 subcarriers in each 20 MHZ channel. The
`proposed 802.11n design 420 recaptures two additional
`Subcarriers on each side of each channel. The proposed
`802.11n design 420 employs tones -60 through +60, with 7
`null tones near DC, for a total of 112 used tones. There are
`thus four null tones on a first end of each 20 MHZ channel
`and three null tones on the second end of each channel.
`There are seven Subcarriers separating each adjacent channel
`in the 802.11n proposal.
`0024. According to another aspect of the invention, a
`subcarrier design 430 is provided for 40 MHz. As shown in
`FIG. 4, the 40 MHz subcarrier design 430 also spans from
`tones -60 through +60, providing an extra four tones on the
`outer edges of the band. In addition, the present invention
`reclaims three additional tones near DC that were kept null
`in design 420. The high throughput (HT) 20 MHz tone
`format has only 1 DC null. Thus, the total tone expansion
`provided by the present invention is eight, bringing the total
`number of data tones to 114, and the total number of used
`tones to 120. It is noted that this leaves seven tones in the
`transition band between adjacent 40 MHZ channels. This
`separation is identical to that between two adjacent 20 MHz
`channels. However, the Q factor of the filter has doubled.
`0.025 FIG. 5 evaluates the efficiency of a 64 point FFT
`and a 128 point FFT in 20 MHz. As shown in FIG. 5, a 64
`point FFT 510 demonstrates an overall efficiency of 60%
`and a 128 point FFT 520 demonstrates an overall efficiency
`Of 76%.
`0026. While the present invention has been illustrated in
`the context of a 128 point FFT employed in each 20 MHz
`channel 310, the present invention can be extended to a 256
`point FFT, as would be apparent to a person of ordinary skill
`in the art, based on the present disclosure. In a 256 point FFT
`implementation, the spectrum is sampled at four times the
`rate of the configuration shown in FIG. 2 (64 point FFT).
`0027. It is to be understood that the embodiments and
`variations shown and described herein are merely illustrative
`
`Exhibit 1012
`Panasonic v. UNM
`IPR2024-00364
`Page 8 of 9
`
`

`

`US 2006/0067415 A1
`
`Mar. 30, 2006
`
`of the principles of this invention and that various modifi
`cations may be implemented by those skilled in the art
`without departing from the scope and spirit of the invention.
`I claim:
`1. A method for transmitting data in a multiple antenna
`communication system, wherein said multiple antenna com
`munication system communicates with at least one legacy
`system employing an N point fast Fourier transform (FFT)
`within a bandwidth, BW, said method comprising:
`employing an N point inverse FFT within said band
`width, BW, wherein N is greater than N; and
`employing Subcarriers associated with said N. point
`inverse FFT to transmit said data.
`2. The method of claim 1, wherein additional subcarriers
`are employed at outer edges of said bandwidth, BW,
`relative to said legacy system.
`3. The method of claim 1, wherein said subcarriers
`associated with said N. point inverse FFT include additional
`Subcarriers near DC relative to said legacy system.
`4. The method of claim 1, wherein N is a 64 point inverse
`FFT within said bandwidth, BW, equal to 20 MHz, and N,
`is a 128 point inverse FFT within said bandwidth, BW.
`5. The method of claim 1, wherein said legacy system
`employs a total number of populated subcarriers N said
`method further comprising the step of employing a total
`number of populated subcarriers N., where N, is
`greater than N.
`6. The method of claim 1, wherein said legacy system
`employs a number of pilot subcarriers Nils said method
`further comprises the step of employing a number of pilot
`Subcarriers Nis, where Nils, is equal to Nils
`7. A transmitter that transmits data in a multiple antenna
`communication system, wherein said multiple antenna com
`munication system communicates with at least one legacy
`system employing an N point fast Fourier transform (FFT)
`within a bandwidth, BW, said transmitter comprising:
`an N point inverse FFT operating within said bandwidth,
`BW, wherein N is greater than N, wherein subcar
`riers associated with said N. point inverse FFT are
`employed to transmit said data.
`8. The transmitter of claim 7, wherein additional subcar
`riers are employed at outer edges of said bandwidth, BW,
`relative to said legacy system.
`9. The transmitter of claim 7, wherein said subcarriers
`associated with said N. point inverse FFT include additional
`Subcarriers near DC relative to said legacy system.
`10. The transmitter of claim 7, wherein N is a 64 point
`inverse FFT within said bandwidth, BW, equal to 20 MHz,
`and N is a 128 point inverse FFT within said bandwidth,
`BW.
`11. A method for transmitting data in a multiple antenna
`communication system, wherein said multiple antenna com
`munication system communicates with at least one legacy
`system employing an N point fast Fourier transform (FFT)
`within a bandwidth, BW, said method comprising:
`employing an N point inverse FFT within a bandwidth,
`BW, wherein N is greater than N and said band
`width, BW, is greater than said bandwidth, BW; and
`employing Subcarriers associated with said N. point
`inverse FFT to transmit said data, wherein said
`
`employed Subcarriers includes one or more additional
`subcarriers at outer edges of said bandwidth, BW,
`relative to said legacy system and one or more addi
`tional Subcarriers near DC relative to said legacy sys
`tem
`12. The method of claim 11, wherein N is a 64 point
`inverse FFT within said bandwidth, BW, equal to 20 MHz,
`and N is a 128 point inverse FFT within said bandwidth,
`BW, equal to 40 MHz.
`13. The method of claim 11, wherein said legacy system
`employs a total number of populated subcarriers N said
`method further comprising the step of employing a total
`number of populated subcarriers N., where N, is
`greater than N
`14. A method for receiving data in a multiple antenna
`communication system, wherein said multiple antenna com
`munication system communicates with at least one legacy
`system employing an N point fast Fourier transform (FFT)
`within a bandwidth, BW, said method comprising:
`employing an N point inverse FFT within said band
`width, BW, wherein N is greater than N; and
`employing subcarriers associated with said N. point
`inverse FFT to receive said data.
`15. The method of claim 14, wherein additional Subcar
`riers are employed at outer edges of said bandwidth, BW,
`relative to said legacy system.
`16. The method of claim 14, wherein said subcarriers
`associated with said N. point inverse FFT include additional
`Subcarriers near DC relative to said legacy system.
`17. The method of claim 14, wherein N is a 64 point
`inverse FFT within said bandwidth, BW, equal to 20 MHz,
`and N is a 128 point inverse FFT within said bandwidth,
`BW.
`18. A method for receiving data in a multiple antenna
`communication system, wherein said multiple antenna com
`munication system communicates with at least one legacy
`system employing an N point fast Fourier transform (FFT)
`within a bandwidth, BW, said method comprising:
`employing an N point inverse FFT within a bandwidth,
`BW, wherein N is greater than N and said band
`width, BW, is greater than said bandwidth, BW; and
`employing Subcarriers associated with said N. point
`inverse FFT to receive said data, wherein said
`employed Subcarriers includes one or more additional
`subcarriers at outer edges of said bandwidth, BW,
`relative to said legacy system and one or more addi
`tional Subcarriers near DC relative to said legacy sys
`tem
`19. The method of claim 18, wherein N is a 64 point
`inverse FFT within said bandwidth, BW, equal to 20 MHz,
`and N is a 128 point inverse FFT within said bandwidth,
`BW, equal to 40 MHz.
`20. The method of claim 18, wherein said legacy system
`employs a total number of populated subcarriers N said
`method further comprising the step of employing a total
`number of populated subcarriers N
`where N, is
`pop
`greater than N
`
`Exhibit 1012
`Panasonic v. UNM
`IPR2024-00364
`Page 9 of 9
`
`