Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.163 Filed 07/20/22 Page 1 of 28
`
`Exhibit 6
`
`

`

`( 12 ) United States Patent
`Li et al .
`
`US 10,771,302 B2
`( 10 ) Patent No .:
`( 45 ) Date of Patent :
`* Sep . 8 , 2020
`
`US010771302B2
`
`( 54 )
`
`CHANNEL PROBING SIGNAL FOR A
`BROADBAND COMMUNICATION SYSTEM
`( 71 ) Applicant : Neo Wireless LLC , Wayne , PA ( US )
`( 72 ) Inventors : Xiaodong Li , Kirkland , WA ( US ) ;
`Titus Lo , Bellevue , WA ( US ) ; Kemin
`Li , Bellevue , WA ( US ) ; Haiming
`Huang , Bellevue , WA ( US )
`( 73 ) Assignee : Neo Wireless LLC , Wayne , PA ( US )
`Subject to any disclaimer , the term of this
`( * ) Notice :
`patent is extended or adjusted under 35
`U.S.C. 154 ( b ) by 0 days .
`This patent is subject to a terminal dis
`claimer .
`( 21 ) Appl . No .: 15 / 953,950
`Apr. 16 , 2018
`( 22 ) Filed :
`( 65 )
`Prior Publication Data
`Mar. 21 , 2019
`US 2019/0089566 A1
`Related U.S. Application Data
`( 63 ) Continuation of application No. 14 / 321,615 , filed on
`Jul . 1 , 2014 , now Pat . No. 9,948,488 , which is a
`( Continued )
`
`Int . Cl .
`H04L 12/26
`H04L 27/26
`
`U.S. Cl .
`CPC
`
`( 2006.01 )
`( 2006.01 )
`( Continued )
`
`H04L 27/2626 ( 2013.01 ) ; H04B 1/707
`( 2013.01 ) ; H04B 1/711 ( 2013.01 ) ;
`( Continued )
`Field of Classification Search
`CPC
`( Continued )
`
`HO4L 12/26
`
`( 51 )
`
`( 52 )
`
`( 58 )
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.164 Filed 07/20/22 Page 2 of 28
`
`( 56 )
`
`CN
`CN
`
`5,909,436 A
`6,771,706 B2
`
`References Cited
`U.S. PATENT DOCUMENTS
`6/1999 Engstrom et al .
`8/2004 Ling et al .
`( Continued )
`FOREIGN PATENT DOCUMENTS
`
`4/2003
`1407745 A
`1445949 A 10/2003
`( Continued )
`
`OTHER PUBLICATIONS
`Extended European Search Report received for counterpart Euro
`pean Patent Application No. 18196596.3 , dated Feb. 20 , 2019 ( 8
`pages ) .
`
`( Continued )
`
`Primary Examiner — Dimitry Levitan
`( 74 ) Attorney , Agent , or Firm — Volpe and Koenig , P.C.
`
`( 57 )
`ABSTRACT
`In a broadband wireless communication system , a spread
`spectrum signal is intentionally overlapped with an OFDM
`signal , in a time domain , a frequency domain , or both . The
`OFDM signal , which inherently has a high spectral effi
`ciency , is used for carrying broadband data or control
`information . The spread spectrum signal , which is designed
`to have a high spread gain for overcoming severe interfer
`ence , is used for facilitating system functions such as initial
`random access , channel probing , or short messaging . Meth
`ods and techniques are devised to ensure that the mutual
`interference between the overlapped signals is minimized to
`have insignificant impact on either signal and that both
`signals are detectable with expected performance by a
`receiver .
`
`36 Claims , 18 Drawing Sheets
`
`1002
`
`MC
`
`MC
`
`SS
`
`MS 1
`
`1004
`
`

`

`US 10,771,302 B2
`Page 2
`
`Related U.S. Application Data
`continuation of application No. 13 / 861,942 , filed on
`Apr. 12 , 2013 , now Pat . No. 8,767,522 , which is a
`continuation of application No. 13 / 347,644 , filed on
`Jan. 10 , 2012 , now Pat . No. 8,428,009 , which is a
`continuation of application No. 12 / 975,226 , filed on
`Dec. 21 , 2010 , now Pat . No. 8,094,611 , which is a
`continuation of application No. 10 / 583,229 , filed as
`application No. PCT / US2005 / 003518 on Jan. 27 ,
`2005 , now Pat . No. 7,864,725 .
`
`( 60 ) Provisional application No. 60 / 540,586 , filed on Jan.
`30 , 2004 , provisional application No. 60 / 540,032 ,
`filed on Jan. 29 , 2004 .
`
`( 2006.01 )
`( 2006.01 )
`( 2006.01 )
`( 2011.01 )
`( 2011.01 )
`( 2006.01 )
`
`( 51 ) Int . CI .
`H04L 5/00
`H04L 25/03
`H04L 27/00
`H04B 1/707
`H04B 1/711
`H04L 25/02
`( 52 ) U.S. CI .
`H04L 5/0007 ( 2013.01 ) ; H04L 5/0028
`CPC
`( 2013.01 ) ; H04L 25/03834 ( 2013.01 ) ; H04L
`27/0008 ( 2013.01 ) ; H04L 27/0012 ( 2013.01 ) ;
`H04L 27/2602 ( 2013.01 ) ; H04L 27/2647
`( 2013.01 ) ; H04L 5/0016 ( 2013.01 ) ; H04L
`25/0228 ( 2013.01 ) ; H04L 27/2607 ( 2013.01 ) ;
`H04L 27/2655 ( 2013.01 )
`Field of Classification Search
`USPC
`370/241 , 252 , 310 , 328 , 330 , 464 , 532
`See application file for complete search history .
`
`( 58 )
`
`H04W 28/18
`370/330
`H04B 1/713
`370/342
`HO4B 1/707
`370/335
`
`( 56 )
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`7,274,652 B1
`7,873,009 B2 *
`8,102,832 B2 *
`8,363,691 B2 *
`2001/0021182 A1
`2002/0159422 A1
`2003/0072255 Al
`2003/0179776 Al
`2004/0085946 Al
`2004/0171357 A1
`2004/0264600 Al
`2006/0114815 Al
`2006/0245409 Al
`2008/0304551 Al
`2011/0211617 Al
`2011/0299474 Al
`2012/0106513 Al
`
`9/2007 Webster et al .
`1/2011 Larsson
`1/2012 Agrawal
`1/2013 Hasegawa
`9/2001 Wakutsu
`10/2002 Li et al .
`4/2003 Ma et al .
`9/2003 Sumasu et al .
`5/2004 Morita et al .
`9/2004 Lobinger et al .
`12/2004 Kao et al .
`6/2006 Hasegawa et al .
`11/2006 Korpela et al .
`12/2008 Li et al .
`9/2011 Li et al .
`12/2011 Li et al .
`5/2012 Li et al .
`
`FOREIGN PATENT DOCUMENTS
`
`CN
`WO
`
`1452326
`2003058881 A2
`
`10/2003
`7/2003
`
`OTHER PUBLICATIONS
`European Telecommunications Standards Institute , Digital Video
`Broadcasting ( DVB ) ; Framing structure , channel coding and modu
`lation for digital terrestrial television , ETSI EN 300 744 V1.5.1
`( Jun . 2004 ) .
`IEEE Standard for Local and metropolitan area networks ; Part 16 :
`Air Interface for Fixed Broadband Wireless Access Systems
`Amendment 2 : Medium Access Control Modifications and Addi
`tional Physical Layer Specifications for 2-11 GHz , IEEE Std .
`802.16a - 2003 ( Apr. 1 , 2003 ) .
`* cited by examiner
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.165 Filed 07/20/22 Page 3 of 28
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 1 of 18
`
`US 10,771,302 B2
`
`( frequency )
`
`Channel
`
`
`
`Subcarriers for subchannel 3
`
`Subcarriers for Subchannel 2
`
`Subcarriers for Subchannel 1
`
`3
`
`2
`
`1
`
`
`
`Silent subcarriers
`
`
`
`Pilot subcarriers
`
`S 1 2 3 2 2 3 1 2 1 3 2 1 0 2 1 3 3 3 2 2 3 2 1 3 0 2 1 1 3 5
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.166 Filed 07/20/22 Page 4 of 28
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 2 of 18
`
`US 10,771,302 B2
`
`n + 4
`
`no 3
`
`
`
`Time slots
`
`n + 2
`
`FIG . 2
`
`n + 1
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.167 Filed 07/20/22 Page 5 of 28
`
`sjeuueyoans
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 3 of 18
`
`US 10,771,302 B2
`
`timeslot # 6
`
`timeslot # 5
`
`timeslot # 4
`
`SP2
`
`timeslot # 3
`
`timeslot # 2
`
`316
`
`312
`
`frane # i + 1
`
`314
`
`subframe # 4
`
`subframe # 3
`
`subframe # 2
`
`310
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.168 Filed 07/20/22 Page 6 of 28
`
`Frame ( 20ms ) frame #
`
`Subframe ( 5ms ) subframe # 1
`
`800 us
`
`timeslot # 1
`
`
`Period 1 * SP2 : Special Period 2
`* SP1 : Special
`
`SP1
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 4 of 18
`
`US 10,771,302 B2
`
`UL slot # 2 T | UL slot # 3
`
`UL slot # 11 UL slot # 2
`
`UL slot # 1
`
`SP2
`
`DL slot # 5
`
`SP ?
`
`DL slot # 4
`
`UL slot # 1
`
`
`
`Example Configuration 1 : Symmetric ( 3 DL slots , 3 UL slots )
`
`
`
`Example Configuration 2 : Asymmetric ( 4 DL slots , 2 UL slots )
`
`DL slot # 4
`
`
`
`Example Configuration 3 : Asymmetric ( 5 DL slots , 1 UL slots )
`
`subframe ( 5ms )
`
`DL slot # 3
`
`DL slot # 3
`
`FIG . 4
`
`DL slot # 1 DL slot # 2 DL slot # 3 | SP2
`
`DL slot # 2
`
`DL slot # 1 | DL slot # 2
`
`DL slot # 1
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.169 Filed 07/20/22 Page 7 of 28
`
`SP1
`
`SP1
`
`SP1
`
`4.12
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 5 of 18
`
`US 10,771,302 B2
`
`GP
`
`GP2
`
`
`
`OFDM symbol # 8
`
`
`
`
`
`Spread spectrum signal #j
`
`GP
`
`
`
`not synchronized
`
`synchronized
`
`FIG . 5
`
`
`* GP1 : Guard Period 1 * GP2 : Guard
`Period 2
`
`512
`
`
`
`OFDM symbol # 2
`
`510
`
`timeslot # 1
`
`
`
`Time Slot ( 800 us )
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.170 Filed 07/20/22 Page 8 of 28
`
`
`
`
`
`Spread spectrum signal #k
`
`
`
`symbol # 1 OFDM symbol ( 100us ) OFDM
`
`
`
`GP1
`
`514
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 6 of 18
`
`US 10,771,302 B2
`
`MC signal
`
`SS signal
`
`***
`
`?
`
`FIG . 6
`
`$ 1 2 3 2 2 3 1 2 1 3 2 1 2 1 3 3 3 2 2 3 2 1 3 p 21 p 13 s
`
`doo
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.171 Filed 07/20/22 Page 9 of 28
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 7 of 18
`
`US 10,771,302 B2
`
`
`
`-SS signal
`
`MC signal
`
`subchannel n
`
`* # xaxsa
`
`DURUMEAK
`
`subchannel i
`
`C YOY
`
`YOXSAVANOZ
`
`subchannel 1
`
`subchannel k
`
`FIG . 7
`
`subchannel ]
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.172 Filed 07/20/22 Page 10 of 28
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 8 of 18
`
`US 10,771,302 B2
`
`G2
`
`
`
`Tx power control
`
`830
`
`DIA
`
`820
`
`FIG . 8
`
`810
`
`1 M
`
`
`
`
`
`
`
`Multi - Carrier Transmitter Signal Processing
`
`1
`
`Stic
`Parallel to Serial ( P / S )
`Add cyclic prefix
`
`IDFT
`Serial to Parallel ( S / P )
`
`1
`
`1
`
`1
`
`
`
`www ******
`
`G1
`
`X
`
`S ( t ) ss
`
`Pulse shaping
`
`attenuator
`
`spreading
`
`
`
`
`
`Spread Spectrum Transmitter Signal Processing
`
`
`
`
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.173 Filed 07/20/22 Page 11 of 28
`
`W M M
`
`F1
`
`1
`
`1
`
`E 3 3
`
`3 1
`
`1
`
`1 1 $ 3
`
`1
`
`!
`
`#
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 9 of 18
`
`US 10,771,302 B2
`
`AGC
`
`ro
`
`930
`
`920
`
`I
`
`2
`
`5
`
`1 1
`
`FIG . 9
`
`c * ( t )
`
`910
`
`MC Synchronization Circuit
`
`
`
`
`
`Multi - Carrier Receiver Processing
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.174 Filed 07/20/22 Page 12 of 28
`
`Serial to Parallel ( S / P )
`Remove cyclic prefix
`
`Parallel to Serial ( P / S )
`
`Pre processing
`
`correlator
`
`Peak Detector
`Further Processing
`
`
`
`Spread Spectrum Receiver Processing
`
`
`
`
`
`} 3 $ 3 2 $
`
`1
`
`1
`
`1 1
`
`!
`
`1
`
`. 1
`
`I 3 5
`
`5
`
`4
`
`$ ?
`
`$
`
`5 R
`
`!
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 10 of 18
`
`US 10,771,302 B2
`
`ZOOL
`
`MCk
`
`SS
`
`MC
`
`k
`
`MS ;
`
`poate
`
`bestaat
`
`1004
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.175 Filed 07/20/22 Page 13 of 28
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 11 of 18
`
`US 10,771,302 B2
`
`1110
`
`FIG . 11
`
`MCmi
`
`mk
`SS
`
`MC
`
`MC
`
`MS ;
`
`1
`
`SIN
`
`;
`
`BS
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.176 Filed 07/20/22 Page 14 of 28
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 12 of 18
`
`US 10,771,302 B2
`
`
`
`
`
`Cancelling the interfering SS signal
`
`AGC
`
`X
`
`1220
`
`*
`
`0
`
`0
`
`5
`
`5
`
`1
`
`1
`
`Serial to Parallel ( S / P )
`Remove cyclic
`prefix
`
`FFT
`Parallel to Serial ( PIS )
`
`Decision directed signal
`recovery
`
`SS detection
`
`FIG . 12
`
`Pre processing
`
`1210
`
`MC Synchronization Circuit
`
`
`
`
`
`Multi - Carrier Receiver Processing
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.177 Filed 07/20/22 Page 15 of 28
`
`3
`
`$ 3 1
`
`2
`
`11
`
`.
`
`L
`
`1 1
`
`0 2 $
`
`3
`
`3
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 13 of 18
`
`US 10,771,302 B2
`
`( time )
`
`1306
`
`1304
`
`1308
`
`
`
`
`
`Spread spectrum signal #p
`
`MC symbol ( or slot )
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.178 Filed 07/20/22 Page 16 of 28
`
`
`
`
`
`Spread spectrum signal #n
`
`1302
`
`FIG . 13
`
`
`
`
`
`Spread spectrum signal #m
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 14 of 18
`
`US 10,771,302 B2
`
`MC signal
`
`SS signal
`
`
`
` *** DA ** a ****
`
`FIG . 14
`
`subchannel n
`
`subchannel i
`
`CEDONI
`
`ac
`
`subchannel 1
`
`a .
`
`subchannel k
`
`subchannel
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.179 Filed 07/20/22 Page 17 of 28
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 15 of 18
`
`US 10,771,302 B2
`
`1502
`
`1506
`
`1504
`
`MC control signal
`
`1
`
`3
`
`3
`3
`}
`
`DW ZHWOL
`
`FIG . 15
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.180 Filed 07/20/22 Page 18 of 28
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 16 of 18
`
`US 10,771,302 B2
`
`1506
`
`LEAL
`
`3
`
`3
`3
`3
`
`3
`
`]
`3
`
`10MHZ ( MC )
`
`:)
`
`1
`
`ETDYR
`ONIC
`
`:
`.
`: 1
`:
`!
`
`1
`
`3
`
`5.68 or 7.68MHz ( SS )
`
`. 16
`
`Facebook
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.181 Filed 07/20/22 Page 19 of 28
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 17 of 18
`
`US 10,771,302 B2
`
`1702
`
`BS
`
`
`
`040404015 **
`
`SS
`
`MC mile
`
`MS
`
`02
`
`MC
`
`MS
`
`MS
`
`FIG . 17
`
`1704
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.182 Filed 07/20/22 Page 20 of 28
`
`

`

`U.S. Patent
`
`Sep. 8 , 2020
`
`Sheet 18 of 18
`
`US 10,771,302 B2
`
`Frequency
`
`1
`
`m
`
`Channel Response in Frequency ( Frequency
`Selectivity )
`
`1804
`
`1802
`
`Case 2:22-cv-11408-TGB ECF No. 10-7, PageID.183 Filed 07/20/22 Page 21 of 28
`
`**
`
`**
`
`X podpogokooo
`
`X
`
`& 2 X
`
`X X
`
`Time
`
`Channel Response in Time
`
`
`
`Max delay spread , Tysk
`
`

`

`US 10,771,302 B2
`
`5
`
`10
`
`15
`
`1
`CHANNEL PROBING SIGNAL FOR A
`BROADBAND COMMUNICATION SYSTEM
`
`2
`FIG . 6 is an illustration of MC signals overlaid with DSSS
`signals in the frequency domain where the power level of the
`DSSS signal is much lower than that of the MC signal .
`FIG . 7 is same as FIG . 6 wherein not all MC subchannels
`CROSS - REFERENCE TO RELATED APPLICATION
`are occupied .
`( S )
`FIG . 8 illustrates a transmitter structure of MC and DSSS
`This application is a continuation of U.S. patent applica
`overlay system .
`tion Ser . No. 14 / 321,615 ( now U.S. Pat . No. 9,948,488 ) ,
`FIG . 9 illustrates a receiver structure of MC and DSSS
`filed Jul . 1 , 2014 , which is a continuation application of U.S.
`overlay system .
`patent application Ser . No. 13 / 861,942 ( now U.S. Pat . No.
`FIG . 10 illustrates examples of communications between
`8,767,522 ) , filed Apr. 12 , 2013 , which is a continuation
`a base station and multiple mobile stations transmitting
`application of U.S. patent application Ser . No. 13 / 347,644
`DSSS and MC signals .
`( now U.S. Pat . No. 8,428,009 ) , filed Jan. 10 , 2012 , which is
`FIG . 11 illustrates a mobile station sending DSSS signals
`a continuation application of U.S. patent application Ser . No.
`to its current serving base station , or other base stations .
`12 / 975,226 ( now U.S. Pat . No. 8,094,611 ) , filed Dec. 21 ,
`FIG . 12 illustrates using interference cancellation tech
`2010 , all of which are incorporated herein by reference . U.S.
`nique to cancel interfering DSSS signal in a composite
`patent application Ser . No. 12 / 975,226 is a continuation
`signal to obtain a clearer MC signal .
`application of U.S. patent application Ser . No. 10 / 583,229
`FIG . 13 illustrates a DSSS signal and a MC signal fully
`( now U.S. Pat . No. 7,864,725 ) , filed Aug. 27 , 2008 , which
`is the National Stage Application of International Applica- 20 overlaid or partially overlaid at MC symbol or slot boundary
`tion No. PCT / US2005 / 003518 , filed Jan. 27 , 2005 , which
`in time domain .
`claims the benefit of U.S. Provisional Patent Application No.
`FIG . 14 illustrates a DSSS signal with a high Peak to
`60 / 540,586 , filed
`Jan. 30 , 2004 , and of U.S. Provisional
`Average Ratio in frequency domain causing strong interfer
`Patent Application No. 60 / 540,032 , filed on Jan. 29 , 2004 .
`ence to certain MC subcarriers .
`FIG . 15 illustrates using spectrum nulls in DSSS signal to
`protect an MC control subchannel .
`BACKGROUND
`FIG . 16 illustrates spectrum control for DSSS signal using
`simple sub - sampling method .
`A direct Sequence Spread Spectrum ( DSSS ) system is
`FIG . 17 illustrates examples of communications between
`inherently capable of supporting multi - cell and multi - user
`access applications through the use of orthogonal spreading 30 a base station and multiple mobile stations transmitting both
`codes . The initial access of the physical channel and fre
`DSSS and MC signals .
`quency planning are relatively easier because of interference
`FIG . 18 illustrates a typical channel response in the time
`averaging in a DSSS system . It has been widely used in
`and frequency domains . By estimating the peaks of a chan
`some existing wireless networks . However , a DSSS system
`nel response in the time domain , the channel profile in the
`using orthogonal spreading codes , may suffer severely from 35 frequency domain can be obtained .
`the loss of orthogonally in a broadband environment due to
`multi - path propagation effects , which results in low spectral
`DETAILED DESCRIPTION
`efficiency
`In broadband wireless communications , Multi - Carrier
`A broadband wireless communication system where both
`( MC ) technology is drawing more and more attention 40 the Multi - Carrier ( MC ) and direct Sequence Spread Spec
`because of its capability . An MC system such as an Orthogo
`trum ( DSSS ) signals are intentionally overlaid together in
`nal Frequency Division Multiplexing ( OFDM ) system is
`both time and frequency domains is described . The system
`capable of supporting broadband applications with higher
`takes advantage of both MC and DSSS techniques to miti
`spectral efficiency . An MC system mitigates the adverse
`gate their weaknesses . The MC signal is used to carry
`effects of multi - path propagation in wireless environments 45 broadband data signal for its high spectral efficiency , while
`by using cyclic prefixes to extend the signal period as the
`the DSSS signal is used for special purpose processing , such
`data is multiplexed on orthogonal sub - carriers . In effect , it
`as initial random access , channel probing , and short mes
`converts a frequency selective channel into a number of
`saging , in which signal properties such as simplicity , self
`parallel flat fading channels which can be easily equalized
`synchronization , and performance under severe interference
`with simple one - tap equalizers . The modulator and the 50 are of concern . In the embodiments of this invention both the
`demodulator can be executed efficiently via the fast Fourier
`MC and the DSSS signals are distinguishable in normal
`transform ( FFT ) with much lower cost . However , MC operations and the interference between the overlaid signals
`systems are vulnerable while operating in multi - user and
`is insufficient to degrade the expected performance of either
`signal .
`multi - cell environments .
`Unlike a typical CDMA system where the signals are
`designed to be orthogonal in the code domain or an OFDM
`BRIEF DESCRIPTION OF THE DRAWINGS
`system where the signals are designed to be orthogonal in
`frequency domain , the embodiments of this invention over
`FIG . 1 illustrates a basic structure of a multi - carrier signal
`in the frequency domain , made up of subcarriers .
`lay the MC signal , which is transmitted without or with very
`FIG . 2 illustrates a radio resource being divided into small 60 low spreading , and the DSSS signal , which is transmitted at
`a power level lower than that of the MC signal .
`units in both frequency and time domains .
`FIG . 3 illustrates a frame structure of an exemplary
`In accordance with aspects of certain embodiments of this
`OFDM system .
`invention , the MC signal is modulated on subcarriers in the
`FIG . 4 illustrates three examples of a subframe structure
`frequency domain while the DSSS signal is modulated by
`in the exemplary OFDM system .
`65 the information bits or symbols in the time domain . In some
`FIG . 5 illustrates slot structure of the OFDM system and
`cases the information bits modulating the DSSS sequence
`the overlay system .
`are always one .
`
`25
`
`55
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`US 10,771,302 B2
`
`Data Rate
`Modulation
`Coding rate
`IFFT / FFT size
`OFDM symbol duration
`Guard interval
`Subcarrier spacing
`System sampling rate ( fs )
`Channel spacing
`
`3
`4
`One subframe 312 consists of six time slots 314 and two
`This invention further provides apparatus and means to
`special periods 316 , which serve transition time from down
`implement the mentioned processes and methods in a broad
`link to uplink and vise versa . The six time slots in one
`band wireless multi - access and / or multi - cell network , using
`subframe can be configured as either uplink or downlink
`advanced techniques such as transmit power control , spread
`5 slots symmetrically or asymmetrically .
`ing signal design , and iterative cancellation .
`FIG . 4 illustrates three examples of a subframe structure
`The mentioned MC system can be of any special format
`in an OFDM system : one symmetric configuration 412 and
`such as OFDM or Multi - Carrier Code Division Multiple
`two asymmetric configurations 414 , each with differing
`Access ( MC - CDMA ) . The presented methods and apparatus
`number of uplink ( UL ) and downlink ( DL ) slots . FIG . 5
`can be applied to downlink , uplink , or both , where the
`duplexing technique can be either Time Division Duplexing 10 illustrates a slot structure of an OFDM system and an
`( TDD ) or Frequency Division Duplexing ( FDD ) .
`overlay system . One 800 us time slot 510 is comprised of 8
`Various embodiments of the invention are described to
`OFDM symbols 512 , which are overlaid by DSSS signals
`provide specific details for thorough understanding and
`514 in the time domain . Two guard periods GP1 and GP2 are
`enablement ; however , the aspects of the invention may be
`allocated for the DSSS signal 514 .
`practiced without such details . In some instances , well- 15
`known structures and functions have not been shown or
`TABLE 1
`described in detail to avoid unnecessarily obscuring the
`Uplink system parameters
`essential matters .
`Unless the context clearly requires otherwise , throughout
`2 , 4 , 8 , 16 , 24 Mbps
`the description and the claims , the words “ comprise , ” “ com- 20
`QPSK , 16 - QAM
`prising , " and the like are to be construed in an inclusive
`1/8 , 1/4 , 1/2 , 3/4
`1024
`sense as opposed to an exclusive or exhaustive sense ; that is
`100 us
`to say , in the sense of “ including , but not limited to . ” Words
`11.11 us
`using the singular or plural number also include the plural or
`9.765625 kHz
`singular number respectively . Additionally , the words 25
`11.52 MHz
`10 MHz
`“ herein , ” “ above , ” “ below ” and words of similar import ,
`when used in this application , shall refer to this application
`Detailed Description of a MC and DSSS Overlay System
`as a whole and not to any particular portions of this
`FIG . 5 illustrates the overlay of the MC and DSSS signals ,
`application . When the claims use the word “ or ” in reference
`to a list of two or more items , that word covers all of the 30 where the DSSS signal overlaps with the MC signal in the
`following interpretations of the word : any of the items in the
`time domain . The overlaid signal can be aligned at the
`list , all of the items in the list and any combination of the
`boundary of MC slot or MC symbol when they are synchro
`nized ( for example , DSSS signal #k in FIG . 5 ) . It can also
`items in the list .
`be not aligned when they are not synchronized ( for example ,
`Multi - Carrier Communication System
`The physical media resource ( e.g. , radio or cable ) in a 35 DSSS signal #j in FIG . 5 ) . In one embodiment , the DSSS
`multi - carrier communication system can be divided in both
`signal is placed at the period of cyclic prefix of the OFDM
`the frequency and time domains . This canonical division
`symbol .
`provides a high flexibility and fine granularity for resource
`FIG . 6 is an illustration of MC signals overlaid with DSSS
`sharing
`signals in the frequency domain where the power level of the
`The basic structure of a multi - carrier signal in the fre- 40 DSSS signal is much lower than that of the MC signal . The
`quency domain is made up of subcarriers . Within a particular
`subcarriers in a subchannel are not necessarily adjacent to
`spectral band or channel , there are a fixed number of
`each other in the frequency domain . FIG . 7 is similar to FIG .
`6 wherein not all MC subchannels are occupied . It illustrates
`subcarriers . There are three types of subcarriers :
`a scenario where some MC subchannels are not energized .
`1. Data subcarriers , which contain information data ;
`2. Pilot subcarriers , whose phases and amplitudes are pre- 45
`In another embodiment , the MC signal is modulated on
`determined and made known to all receivers and which
`subcarriers in the frequency domain while the DSSS signal
`are employed for assisting system functions such as
`is modulated in either the time domain or the frequency
`estimation of system parameters ; and
`domain . In one embodiment the modulation symbol on the
`3. Silent subcarriers , which have no energy and are used for
`DSSS sequence is one and the sequence is unmodulated .
`guard bands and DC carrier .
`FIG . 8 illustrates a transmitter structure 800 of an MC and
`FIG . 1 illustrates a basic structure of a multi - carrier signal
`DSSS overlay system , wherein the MC signal and DSSS
`in the frequency domain , made up of subcarriers . The data
`signal are added together prior to Digital to Analog ( D / A )
`subcarriers can be arranged into groups called subchannels
`conversion 830. In FIG . 8 , the top branch 810 is an OFDM
`to support scalability and multiple - access . The carriers
`transmitter and the bottom branch 820 is the spread spec
`forming one subchannel are not necessarily adjacent to each 55 trum transmitter . In the MC transmitter , the S / P buffer
`other . As depicted in FIG . 1 , each user may use part or all
`converts the sequential inputs into parallel outputs , which
`are in turn inputted to the inverse discrete Fourier transform
`of the subchannels .
`FIG . 2 illustrates a radio resource being divided into small
`( IDFT ) . The outputs from the IDFT are the time domain
`units in both frequency ( subchannels ) and time domains
`signals , which are converted from parallel to sequential
`( time slots ) . The basic structure of an MC signal in the time 60 signals after a cyclic prefix is added . Adding the prefix can
`domain is made up of time slots to support multiple - access .
`also be performed after the P / S conversion . In the spread
`An Exemplary MC System
`spectrum transmitter , the DSSS sequence is modulated by
`An OFDM system is used in the system as a special case
`the information bits or symbols and the modulated signals
`of an MC system . The system parameters for the uplink
`will undergo pulse - shaping filtering so that the signal spec
`under consideration are listed in Table 1. FIG . 3 illustrates 65 trum meets specified criteria .
`a frame structure of a suitable OFDM system . In this system ,
`A digital attenuator ( G1 ) is used for the DSSS signal to
`a 20 ms frame 310 is divided into four 5 ms subframes 312 .
`adjust its transmitted signal level relative to the MC signal .
`
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`US 10,771,302 B2
`
`45
`
`( 2 )
`
`5
`6
`In one embodiment , the DSSS signal is power controlled
`The two signals are overlaid in the digital domain before
`such that Pss is well below the noise level , N.
`converting to a composite analog signal . A second analog
`On the other hand , the SINR for the DSSS signal is
`variable gain ( G2 ) is used subsequent to the D / A converter
`830 to further control the power level of the transmitted
`' ss = Pss / ( N + I + Pmc )
`SINR'S
`( 5 )
`signal . When the MC signal is not present , both G1 and G2 5
`Denoting the spreading factor for the DSSS signal as KSF ,
`will be applied to the DSSS signal to provide sufficient
`the effective SINR for one symbol after despreading is :
`transmission dynamic range . G2 can be realized in multiple
`circuit stages .
`SINR'S ' ss = Pss * KsF / ( N + I + PMC )
`( 6 )
`FIG . 9 illustrates a receiver structure 900 of an MC and
`SINR'ss must be high enough to meet the performance
`DSSS overlay system . A composite signal is processed by a 10
`requirement when detecting or decoding the information
`MC receiver 910 and DSSS receiver 920. At the receiver
`conveyed in the DSSS signal . In one embodiment , Kse is
`side , after automatic gain control ( AGC ) , an Analog - to
`chosen to be 1000 , so that the DSSS signal is boosted with
`Digital ( A / D ) converter 930 converts the received analog
`30 dB spreading gain after despreading .
`signal to digital signal . The MC receiver basically performs
`FIG . 11 illustrates a mobile station 1110 sending DSSS
`a reverse process of the MC transmitter . The MC synchro- 15
`signals to its current serving base station or other base
`nization circuit carries out the synchronization in both time
`stations . The latter case is especially helpful in hand - off
`and frequency for the receiver to function properly . The
`processes . In this Figure , a mobile station MS , is commu
`outputs of the P / S are information bits or symbols . To detect
`nicating with a BS , using an MC signal while transmitting a
`whether a DSSS signal is present , the signal is despread with
`a matched filter or a correlator , using the access sequence , to 20 DSSS signal to BSK
`check if the correlation peak exceeds a predefined threshold .
`Power Control
`The information from the DSSS receiver 920 will then be
`As discussed above , one design issue is to minimize the
`used to decode the mobile station's signature in the case of
`power of the DSSS signal to reduce its interference with the
`initial random access ; to derive the channel information in
`MC data signal . In one embodiment , the initial power setting
`the case of channel probing ; or to decode the information bit 25 of a mobile station , TMS ( in dBm ) , is set based on path
`loss , L path ( in dB ) , and the desired received power level at
`in the case of short messaging .
`In one embodiment a rake receiver is used in the DSSS
`the base station , PBS_rx_des ( in dBm ) ,
`receiver 920 to improve its performance in a multi - path
`TMS_or = PBS_rx_des + Lpath - C1 - C2
`environment . In another embodiment , the MC signal is
`processed as if no DSSS signal is present . In yet another 30
`C ( in dB ) is set to a proper value so that the SINR of the
`embodiment , advanced interference cancellation techniques
`MC as specified in equation ( 4 ) meets its requirement . C2 ( in
`can be applied to the composite signal to cancel the DSSS
`dB ) is an adjustment to compensate for the power control
`signal from the composite signal thus maintaining almost the
`inaccuracy . Open loop power control inaccuracy is mainly
`same MC performance .
`caused by a discrepancy between an estimated path loss by
`The transmitted composite signal for user i can be repre- 35 the mobile station and the actual path loss .
`sented by :
`In one embodiment , C is set to 9 dB for MC using QPSK
`modulation with 1/2 error control coding or 15 dB for MC
`s¡ ( t ) = G_2 * [ G : , 1 * !; „ ss ( t ) + b ; * si MC ( O ) ]
`( 1 )
`using 16 QAM modulation with 1/2 error control coding . C2
`is set to 10 dB or 2 dB depending on whether the mobile
`where bi is ( when there is no MC signal and is 1 when an
`MC signal is present . Similarly , G , is 0 when there is no 40 station is under open loop power control or closed loop
`power control . Power control for the DSSS signal also eases
`DSSS signal and varies depending on the power setting of
`the spectrum mask requirement for the DSSS signal because
`the DSSS signal relative to the MC signal when a DSSS
`the DSSS signal level is much lower than that of the MC
`signal is present . G ; , 2 is used to control the total transmission
`signal .
`power for user i . The received signal can be represented by :
`With total power offset of C1 + C2 subtracted from an
`initial transmission power of the DSSS signal , the spreading
`factor of the DSSS signal needs to be set high enough ( e.g. ,
`512 ( 27 dB ) or higher ) so that the DSSS signal can be
`detected in normal conditions . This requires a sufficient
`50 number of bits of the A / D converter at the base station , for
`example , 12 bits .
`where M is the total number of mobile station actively
`In one embodiment , the D / A converter at the mobile
`communicating with the current base station , N is the
`station uses 12 bits , among which 8 bits are targeted for the
`Gaussian noise , and I is the total interference from all the
`MC signal ( assuming 3 bits are reserved for MC peak to
`mobile stations in current and other base stations .
`average consideration ) . Thus , there are enough bits left for
`55
`Denoting the received power of the MC signal as P
`Mc and
`the DSSS signal even with significant attenuation relative to
`the received power of the DSSS signal as Pss , the signal to
`the MC signal .
`interference and noise ratio ( SINR ) for the MC signal is :
`Canceling the Interference of DSSS Signal to the MC Signal
`In one embodiment , the base station employs interference
`( 3 )
`SINRMC = PMC ( N + 1 )
`60 cancellation techniques to cancel the DSSS interference to
`when the DSSS signal is not present ; and is
`the MC signal . FIG . 12 illustrates a system for using an
`interference cancellation technique to cancel an interfering
`SINR'Mc = Pud ( N + I + PSS )
`( 4 )
`DSSS signal in a composite signal to obtain a clearer MC
`when the DSSS signal is present . The system is