ETSI TS V8.4.0 ( )

Transcription

1 TS V8.4.0 ( ) Techncal Specfcaton Dgtal cellular telecommuncatons system (Phase 2+); Modulaton (3GPP TS verson Release 1999) GLOBAL SYSTEM FOR MOBILE COMMUNICATIONS R

2 1 TS V8.4.0 ( ) Reference RTS/TSGG Q8R3 Keywords GSM 650 Route des Lucoles F Sopha Antpols Cedex - FRANCE Tel.: Fax: Sret N NAF 742 C Assocaton à but non lucratf enregstrée à la Sous-Préfecture de Grasse (06) N 7803/88 Important notce Indvdual copes of the present document can be downloaded from: The present document may be made avalable n more than one electronc verson or n prnt. In any case of exstng or perceved dfference n contents between such versons, the reference verson s the Portable Document Format (PDF). In case of dspute, the reference shall be the prntng on prnters of the PDF verson kept on a specfc network drve wthn Secretarat. Users of the present document should be aware that the document may be subject to revson or change of status. Informaton on the current status of ths and other documents s avalable at If you fnd errors n the present document, send your comment to: edtor@ets.fr Copyrght Notfcaton No part may be reproduced except as authorzed by wrtten permsson. The copyrght and the foregong restrcton extend to reproducton n all meda. European Telecommuncatons Standards Insttute All rghts reserved.

3 2 TS V8.4.0 ( ) Intellectual Property Rghts IPRs essental or potentally essental to the present document may have been declared to. The nformaton pertanng to these essental IPRs, f any, s publcly avalable for members and non-members, and can be found n SR : "Intellectual Property Rghts (IPRs); Essental, or potentally Essental, IPRs notfed to n respect of standards", whch s avalable from the Secretarat. Latest updates are avalable on the Web server ( Pursuant to the IPR Polcy, no nvestgaton, ncludng IPR searches, has been carred out by. No guarantee can be gven as to the exstence of other IPRs not referenced n SR (or the updates on the Web server) whch are, or may be, or may become, essental to the present document. Foreword Ths Techncal Specfcaton (TS) has been produced by 3rd Generaton Partnershp Project (3GPP). The present document may refer to techncal specfcatons or reports usng ther 3GPP denttes, UMTS denttes or GSM denttes. These should be nterpreted as beng references to the correspondng delverables. The cross reference between GSM, UMTS, 3GPP and denttes can be found under

4 3 TS V8.4.0 ( ) Contents Intellectual Property Rghts...2 Foreword...2 Foreword Scope...5 1a References...5 1b Abbrevatons Modulaton format for GMSK Modulatng symbol rate Start and stop of the burst Dfferental encodng Flterng Output phase Modulaton Modulaton format for 8PSK Modulatng symbol rate Symbol mappng Start and stop of the burst Symbol rotaton Pulse shapng Modulaton...9 Annex A (nformatve): Change hstory...10 Hstory...11

5 4 TS V8.4.0 ( ) Foreword Ths Techncal Specfcaton has been produced by the 3 rd Generaton Partnershp Project (3GPP). The contents of the present document are subject to contnung work wthn the TSG and may change followng formal TSG approval. Should the TSG modfy the contents of the present document, t wll be re-released by the TSG wth an dentfyng change of release date and an ncrease n verson number as follows: Verson x.y.z where: x the frst dgt: 1 presented to TSG for nformaton; 2 presented to TSG for approval; 3 or greater ndcates TSG approved document under change control. y the second dgt s ncremented for all changes of substance,.e. techncal enhancements, correctons, updates, etc. z the thrd dgt s ncremented when edtoral only changes have been ncorporated n the document.

6 5 TS V8.4.0 ( ) 0 Scope The modulator receves the bts from the encrypton unt, see GSM [1], and produces an RF sgnal. The flterng of the Rado Frequency (RF) sgnal necessary to obtan the spectral purty s not defned, nether are the tolerances assocated wth the theoretcal flter requrements specfed. These are contaned n GSM [4]. 1a References The followng documents contan provsons whch, through reference n ths text, consttute provsons of the present document. References are ether specfc (dentfed by date of publcaton, edton number, verson number, etc.) or non-specfc. For a specfc reference, subsequent revsons do not apply. For a non-specfc reference, the latest verson apples. In the case of a reference to a 3GPP document (ncludng a GSM document), a non-specfc reference mplctly refers to the latest verson of that document n the same Release as the present document. [1] GSM 01.04: "Dgtal cellular telecommuncaton system (Phase 2+); Abbrevatons and acronyms". [2] GSM 05.01: "Dgtal cellular telecommuncaton system (Phase 2+); Physcal layer on the rado path General descrpton". [3] GSM 05.02: "Dgtal cellular telecommuncaton system (Phase 2+); Multplexng and multple access on the rado path". [4] GSM 05.05: "Dgtal cellular telecommuncaton system (Phase 2+); Rado transmsson and recepton". 1b Abbrevatons Abbrevatons used n ths specfcaton are lsted n GSM [1] 2 Modulaton format for GMSK 2.1 Modulatng symbol rate The modulatng symbol rate s 1/T = 1 625/6 ksymb/s (.e. approxmately ksymb/s), whch corresponds to 1 625/6 kbt/s (.e kbt/s). T s the symbol perod. 2.2 Start and stop of the burst Before the frst bt of the bursts as defned n GSM [3] enters the modulator, the modulator has an nternal state as f a modulatng bt stream consstng of consecutve ones (d = 1) had entered the dfferental encoder. Also after the last bt of the tme slot, the modulator has an nternal state as f a modulatng bt stream consstng of consecutve ones (d = 1) had contnued to enter the dfferental encoder. These bts are called dummy bts and defne the start and the stop of the actve and the useful part of the burst as llustrated n fgure 1. Nothng s specfed about the actual phase of the modulator output sgnal outsde the useful part of the burst.

7 6 TS V8.4.0 ( ) dummy bts tal bts 3 tal bts dummy bts Output phase The useful part 1/2 bt 1/2 bt The actve part Fgure 1: Relaton between actve part of burst, tal bts and dummy bts. For the normal burst the useful part lasts for 147 modulatng bts 2.3 Dfferental encodng Each data value d = [0,1] s dfferentally encoded. The output of the dfferental encoder s: d ˆ = d d 1 ( d {0,1}) where denotes modulo 2 addton. The modulatng data value α nput to the modulator s: 2.4 Flterng α = 1 2d$ ( α { 1, + 1}) The modulatng data values α as represented by Drac pulses excte a lnear flter wth mpulse response defned by: where the functon rect(x) s defned by: t g ( t) = h( t) * rect T rect t = 1 for t T T T < 2 t rect = 0 T otherwse and * means convoluton. h(t) s defned by: 2 t exp 2 2 2δ T h( t) = (2π ). δt

8 7 TS V8.4.0 ( ) ln(2) where δ = and BT = πBT where B s the 3 db bandwdth of the flter wth mpulse response h(t). Ths theoretcal flter s assocated wth tolerances defned n GSM [4]. 2.5 Output phase The phase of the modulated sgnal s: ϕ ( t' ) = α πh t' T g( u) du where the modulatng ndex h s 1/2 (maxmum phase change n radans s π/2 per data nterval). The tme reference t' = 0 s the start of the actve part of the burst as shown n fgure 1. Ths s also the start of the bt perod of bt number 0 (the frst tal bt) as defned n GSM [2]. 2.6 Modulaton The modulated RF carrer, except for start and stop of the TDMA burst may therefore be expressed as: 2Ec x( t' ) =. cos(2π f0 t' + ϕ( t' ) + ϕ0 ) T where E c s the energy per modulatng bt, f 0 s the centre frequency and ϕ 0 s a random phase and s constant durng one burst. 3 Modulaton format for 8PSK 3.1 Modulatng symbol rate The modulatng symbol rate s 1/T = 1 625/6 ksymb/s (.e. approxmately ksymb/s), whch corresponds to 3*1 625/6 kbt/s (.e kbt/s). T s the symbol perod. 3.2 Symbol mappng The modulatng bts are Gray mapped n groups of three to 8PSK symbols by the rule where l s gven by table 1. s = e j2πl / 8

9 8 TS V8.4.0 ( ) Table 1: Mappng between modulatng bts and the 8PSK symbol parameter l. Modulatng bts Symbol parameter l d 3,, d 3+1, d 3+2 (1,1,1) 0 (0,1,1) 1 (0,1,0) 2 (0,0,0) 3 (0,0,1) 4 (1,0,1) 5 (1,0,0) 6 (1,1,0) 7 Ths s llustrated n fgure 2. Q (d 3, d 3+1, d 3+2 )= (0,0,0) (0,0,1) (1,0,1) (0,1,0) (0,1,1) (1,1,1) (1,1,0) (1,0,0) I Fgure 2: Symbol mappng of modulatng bts nto 8PSK symbols. 3.3 Start and stop of the burst Before the frst bt of the bursts as defned n GSM [3] enters the modulator, the state of the modulator s undefned. Also after the last bt of the burst, the state of the modulator s undefned. The tal bts (see GSM 05.02) defne the start and the stop of the actve and the useful part of the burst as llustrated n fgure 3. Nothng s specfed about the actual phase of the modulator output sgnal outsde the useful part of the burst. 9 tal bts 9 tal bts Output phase The useful part 1/2 symbol 1/2 symbol The actve part Fgure 3: Relaton between actve part of burst and tal bts. For the normal burst the useful part lasts for 147 modulatng symbols

10 9 TS V8.4.0 ( ) 3.4 Symbol rotaton The 8PSK symbols are contnuously rotated wth 3π/8 radans per symbol before pulse shapng. The rotated symbols are defned as sˆ = s e j3π / Pulse shapng The modulatng 8PSK symbols ŝ as represented by Drac pulses excte a lnear pulse shapng flter. Ths flter s a lnearsed GMSK pulse,.e. the man component n a Laurant decomposton of the GMSK modulaton. The mpulse response s defned by: where S( t) 3 + = S( t T ), for 0 t 5T c0 ( t) = 0 0, else t sn( π g( t ) dt ), for 0 0 t 4T π = sn( π g( t ) dt ), for 2 0 0, else t 4T 4T < t 8T and The base band sgnal s g( t) 1 t = 5T /2 t 3T /2 Q(2π 0.3 ) Q(2π 0.3 2T ) T loge (2) T loge (2) Q t) τ = e 2π t ( dτ. y ( t') = sˆ c0 ( t' T + 2T ) The tme reference t' = 0 s the start of the actve part of the burst as shown n fgure 3. Ths s also the start of the symbol perod of symbol number 0 (contanng the frst tal bt) as defned n GSM [2]. 3.6 Modulaton The modulated RF carrer durng the useful part of the burst s therefore: x ( t') = 2E T s Re j( 2π f0t ' +ϕ0 ) [ y( t') e ] where E s s the energy per modulatng symbol, f 0 s the centre frequency and ϕ 0 s a random phase and s constant durng one burst.

11 10 TS V8.4.0 ( ) Annex A (nformatve): Change hstory SMG SPEC VERS NEW_VE PH SUBJECT S R97 converson to Release 97 EN S R99 Introducton of 8PSK for EDGE S30b R99 Correcton of mstake for range alpha-sub- n Clause Fgure 3 replaced (as t was corrupted) G R99 Correcton of symbol perod notaton G R99 Correcton of Tmng Algnment for GMSK and 8-PSK Sgnals Date TSG # TSG Doc. CR Rev Subject/Comment Old New G03 GP A009 Correcton of symbol perod notaton G05 GP A010 Correcton of Tmng Algnment for GMSK and 8-PSK Sgnals G07 GP A012 Correcton of tal bts for 8PSK normal burst

12 11 TS V8.4.0 ( ) Hstory Document hstory V8.1.0 October 2000 One-step Approval Procedure OAP : to V8.1.2 February 2001 Publcaton as EN V8.2.0 January 2001 Publcaton V8.3.0 June 2001 Publcaton V8.4.0 November 2001 Publcaton