Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
OCT 13 '~3 1~3:40 SPENCEæ,F~NK~CCHNEI~E~W~aH~ P.3.~1?
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~0 ~2/20179 PCT/~1~9~/008~1
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D a~D ;~ANGE~ ~OR ~HE D~ u~N~rTA~ ~4I~UI~OM
oY ~ a~EL ~R~D8~I8~ Y8~
'rhe inv~n~ion x~ia~ to a digit;~ odulation me~ho~ and
ar! arr~rlgç~e~}t ~or a ~nulti-~h~nnel tran~ is~io~ syste~
Whic~ d~a s~rea~ i~ d~t~cibut~d to a plurality o~
c:arriers ~at l~e~ adjac~nt tu one another in th~3 fr~uer~c:y
~m~in4
o m~ in ratltio~ i~ us~d, among ot:h~;rs, i~ th2 ~O~DM t~:tsda~
ort~sgç~nal ~r~ cy div~ n mult~pl~xin~ ~eth~d e~ployed
in dis~i al radioO
~n ~ mul~l-chan~ aodula~ on ~et~ or digi1:a~ da~a
~an~is~ion, the data s~rea~ to be tra~s~nitted i~
di~ribut~d to a nu~er o~ sub-c:arEier~ ~or exampl~, sev~al
.
hm~r~d1,, ~hich are 21dj~oe~ ~o one ano~:her in ~h~ f~eg~l3ncy
do31~in, with ~h~ ~pe~:tra of t~a~ sub-carr~ ~rs po~3~3ib~ o
~erlappin~ Wit~ thi& ~ann~r of proceeding, ~ data rat~
tr~ itted in ~ach sub-carrier which i lower ~y order~; o~
2 0 mag~aitud~ ~han th~ origlnal d~ rate so that th~ 83~01
OCT 13 'g:~ 10:4; SPENCET;~,FRf~NK&SC~ E'~ SH~, 2109211 P.4~17
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duration is corr~pondir~gly lengthened~ ~hi~ h~ ~n
`.! advant~ge30u~ eff2~ if e¢hoQs app~ar i~ the trans~ls~ion
channel. ~y suitably ~ixing th~ nuT~ber c2 sub-c~arriers, a
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lt~-~hannc~l modula~ion ~ethod ~an ~lways be de~ d so
that t~ bol cluration 1~ long ~ompared tca the m~xim.lm ~cho
delay ~ime o ~e expe~ted~
The ~ nf luena~ c~ e~hoe~ can be completely el ila~nated,
~or e~ple, in that the syml~ols are no~ nfi~itted in
i~nedia ~ ~ucc~88loll but; I;ha~ ~ prol:ection period is jpravid~d
10 be~ween every ~o suc:c~ sive sy~ol~ which the echo~s of
t~e ~ir~'c tr~mi~ted sym~ol die ou~.
m~ en~ine~ring c~f ~ ~aulki-~h~nnel ~o~ulation method
~3~ imol~a~ a aon~iguratlon, for ~xample, ~s a d~gital ~et~c~d,
rhaps a~; a pr~gr~ in at l~ast one mic:roproce~sor with
. lS: whlch the ~ra~it ~ n~ calc:ulated at ~e trans~i~ting
;:$ n~l in tha c~aplex base ban~ or at an in~rmediate freg~len~
thcd~ known ~ro~ the a~alcg technol~ hi$ tran~DIif
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ig~al ~:z~ 'chen b~ put into thB carrier ~re~ncy po~ition.
.
o~rQs~orld~gly~ na~l is initially receive~ ~y t~e
r6ac~iver in an ~ g ~ode, is then converted down to the
a~ band or ~o ~n iI~termedia~e ~re~uency and is then
: proc~d f~rther in a digital mod~.
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OCT 13 '93 10:41 ~ENOER,FRflNK&SCHrK IDEP/WF`JSHo P.5/17
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,j' The ~ulti-~hannel modulation signal is ~ompo~ed o~ time-
~requency ~lot~ The time ~o~ are formed ~y ~e di~crete
~y~bol clo~k, the ixe~uen~y ~lot~ by the sub-aarrier
~ reguency ~pacing. rf m~a~ures ar~ taXen to c:ombat echc~23,
s ~or xa~ple, the abov~-mentioned protection p~riod, the
$n~1uQncQ o~ the radio ahannel in each time-~e~u~ncy ~o~ is
mani~est ~n attenuation and a ph~e ~hift. A~tenuation and
ph~ hi~t ar~ gener~lly ~ariable in tima ~nd fr~qu~ncy.
~;. Pre~ bly the known phase ~o~ula~ion is employed as ~he
0 ~odulatlon method::for a ~ub-carrie~ of the multi~ahannel
signal. To this er~ he Y~riou5 data ~bols are ~epraduced
on different phase sh~pes ~of ~he~ ~ans~it signal~ For
. . .
da3l~0dulat~csn, ~h~ chann~ peci~io phase shi~t then acts as
~ an in~er~ere~ce value whl~h ~ust be a~pensat~ by mean~ of
,~ 15 su~able ~easures~ :
: Known methods are the di~erential de~odula~ion ~nd the
iff~rential pr~coding. In ~he~e method, tho data are not
trarumitt~d in t;:he p~as~ o~ a sym1~ol b~t in the phase
;.,
ai~re~enc~ o~ tvo ~u~ iYe æy~ol~. In a multi-ch~
'; 20 method, dif~erential de~odul~tion and precoding are pe~fo~med
'~ s~p~rately in each ~ub-caxrier.
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2 1 ~ ~ 2 ~ ~ 23930 341
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~ Differential precoding takes place in the transmitter
; (Figure la) and differential demodulation takes place in the
receiver (Figure lb).
The multiplication of complex numbers corresponds to an
addition of their phases, the formation of the conjugate complex
number corresponds to the inversion of the sign of the phase.
The letter "D" in Figures la and lb identifies a delay by one
symbol; the * symbol identifies the conjugate complex component.
Differential demodulation and precoding are based on
the assumption that the channel specific phase shift does not
change from one symbol to the next. In time variable radio
channels, however, this assumption is frequently not met,
particularly if multi-channel methods are involved with their
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relatively long symbol duration. Transmission errors occur here
even in the noise-free state.
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~ ; The principle that is a duplicate of time differential
s~ modulation is frequency differential modulation. The frequency
differential modulation is based on the assumptio~ that the
channel specific phase shift from-one sub-carrier to the next
does not change.~ The time differential modulation and the
:
~ frequency differential modulation are described in "Philips
.. . .
~esearch ~eports + SuppIements", No. 4, pages 91098 ~1973).
~` It is therefore the object of the invention to provide
a modulation method and an arrangement for a multi-channel
transmission system with which the transmission quality of the
signals of unsteady radio channels is improved.
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2 1 0~211 23930-341
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This is accomplished by the characterizing features of
patent claims 1 and 2. A further embodiment is de~ined in
claim 3.
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OCT 1~ ~g3 10:42 SPENCER,FI~PNK~SCHr~IrlER,'Il~SH~ D, ,~17
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1~0 9ZJ20179 PC~EP~OO~1
~ odi~ents of the invention will now be described with
re~erenc~ to 3chematic drawing ~i~ureC.
Figure 2 ~how~ co~pon~nts o~ an ~ml30dimen'c of an
.~, arrange~ent at th~ transmitting end ~d an arr~ngement at the
3 5 r-c~iving ~nd, ~ach ha~ing several ~ carrier~i ..., k-l, k,
l~tl, . . ~, inluding a mllltip~ ier at both the transmi~t~ng end
and the ~eaeivin~ ~nd ~or linkirlg the d~ta af r~specti~e
adjacent uib-aarrler~. ~n ~he tran~ ter, fo~ examp~e~ the
~u}tlplied data of #Ub-¢arrier~ k-l and k are ~ed to the
~10 ~ultiplier of sub~ arrier k+l and are multipl~ed with the
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data or ~ carrier k~ t the rece~ving end, ~his ~ignal
o~ ~ub-carr~e~ k~l is ~ultlplied with ~e aon~ug~te complex
s~gnal o~ sub-carrier k.: This m~thod is a~lled fxequenay
di~erenti~ odulation.
~ ~ Th~ ~hod r-al~;z~d~ with this arrange~ent Ls ~ased on
the a~ou~ption ~hat the ~hannel ~peci~ic pba~e s~i~t does not
ahAnge ~rom one au~-c~rier to the next. This a~aumption is
imilar to th~ in the~known differential ~odul~tion, except
; that freguency inv~riance has taken th~ place o~ ~i~e
~2Q invarianc~. Howe~r r, particularly in multi-chanrt,el
mo~ulatiorl m~thods, th~ ~:a~ts,r is fr~ntly mor~ likely ~o
sxis~ ir~e the long ~;y~c~l du~tion corre~posld~; ~o
fregu~ncy ~pacing ~n the ~ carrier~.
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~T 13 '~3 10:42 SPEI~CER~F~NK~SCHNEIl:;ER~ lSH~, P.8~17
2109211
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In a ~u~t~er e~odiment according to Fig~lre 3, an
a~range~nt ia 6hown at ~e ~rans~itter and rec:eiver ~n which
éimely ;uaae~ e data ~ ; af a ~ a~rier a~; well a~
,
dat~ ~ro~ ad~ac~nt ~ub-~arrier~ are linked t~gether. For
5 exa~ple, in sub~ a~er k~1 o~ ~e transmit~er, d~ta tha~ ~re
transmit~ed in ~h~ pha~e di~rence o~ two su~c~e~siv~ d~ta
~;~bols are fed to a multiplier together with ~he multiplied
da~ of sub-carriers k-l and k. In the receiver, t;his
~ultiplied complex~ signal of sub-carrier k+l i~ ltiplied
3 wîth t~e aon~ugat~ ~o~aplex s~gnal of ~ arrie~ ~. Together
;
h ~e a~n~ug~te o~plex ti~e-delayed ~ignal, ~hi~
i~z ~ultlpl~ed sl~n~l :ls ~h~n fed ~o a fu~hcr ~ul~lplie~. In
~: the ~tran~QLtter, ~he signa~ of the 3ub-~arriers are
inltially di~f-ren~ially and :th2n ~requ~nc:y differentially
15 ~ pre~:oded wi~h ~his: doù~le differential modulation and are
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th-n de311odula~d ~n;~he~r ceiver, ~irst differentially and
h~n f~quenc:y d~er~ntially. The dou~le di~erential
:
~odul~tlon ~y al~so be per or~ned at t~e tran~itter a~d ~t
',3~ . ~ t;he rea~r ~ir~t by a frequenc:y differential ~od~lation and
20 ~h~n ~y a dif~eren~lal ~odulati~n.,
Compar~ld to th~ conventiona~ difr~r~ntial m~dul~t~ n and
also comp~red to the fre~uon y diff~tr~n~ial ~o~ulat~on, th~
double di~ferential l~odulation o~er~ the de~isive advantage
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CICT 13 '93 10 43 SPENOE2~FRfWK~iSCH~EID~R~ Ho P.9~.7
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that it neithe~ re~uires the as~u:mption o~ ~ ti~e in~r~rianaenor of a ~reque~y ~nvarianae o~ ~e channel ~pecific: ph~e
-, ~ift but app~ox~tes ~he ahannel our~e ~h~pe over ti~e and
~re~u~ncy by way o~ a~ plane~ In radio channel~, thi~
5 approxi~ation i~ clearly better than Em approxim~tion by way
;, o~ a pha~- curv~ tha~t i~ cons~ant ov~r tim~ and fr~ ncy,
i, respectively.
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