(pdf file)

Récents Travaux sur le CDMA Optique!
Philippe Gallion et al "
pour le Consortium CEM2 Montpellier, ENSIL & ENST, "
CDMA Marcoussis, 25 Oct 2005"2"
Le Consortium !
CEM2 Montpellier, ENSIL & ENST!
!!CEM2 Montpellier "
"!Yves MOREAU"
"!Guillaume PiLLE"
!!ENSIL "
"!Jean Michel DUMAS"
"!Christelle AUPETIT-BERTHELEMOT"
"!Anne JULIEN-VERGONJANNE"
!!ENST"
"!Philippe GALLION "
"!Catherine LEPERS"
"!Mounia LOURDIANE"
"!Ihsan FSAIFES"
!!Avec le soutien de"
"!CNRS"
"!France Télecom R&D (Philippe GUIGNARD)"

CDMA Marcoussis, 25 Oct 2005"3"
Outline"
1.!Le CDMA en RF"
2.!Le CDMA en Optique, Pourquoi ? Comment ?"
3.!Les Codes Optiques 1D et 2D"
4.!Les Implémentations «Tout Optique » "
!!Temporelle par Réseaux de Bragg"
!!Spectrale par Optique intégrée"
5.!Les Implémentations Electrique/0ptique "
Conclusion"
CDMA Marcoussis, 25 Oct 2005"4"
Outline"
1.!Le CDMA en RF"
2.!Le CDMA en Optique, Pourquoi ? Comment ?"
3.!Les Codes Optiques 1D et 2D"
4.!Les Implémentations «Tout Optique » "
!!Temporelle par Réseaux de Bragg"
!!Spectrale par Optique intégrée"
5.!Les Implémentations Electrique/0ptique"
Conclusion"

CDMA Marcoussis, 25 Oct 2005"5"
t
f
t
f
t
f
t
f
Attribution de
fréquence
FDMA
Radiodiffusion
Etalement
de spectre
TDMA
Saut de fréquence
GSM (Europe)
1ms X 200kz
Accés multiple par
code
CDMA
IS95 CDMA (USA)
Sharing 2 Increasingly Rare Resources:!
Time and Frequency"
"!Allocation bidimensionnelle aléatoire et dynamique"
"!Signature (code) spectrale et temporelle"
CDMA Marcoussis, 25 Oct 2005"6"
Une Origine Hollywoodienne"
!!Actrice Hedy Lamar et George
Antheil"
!!Brouillage du guidage radio des
torpilles par des sauts de fréquence"
!!Brevet en 1941"

CDMA Marcoussis, 25 Oct 2005"7"
Initial CDMA Motivation"
!!Spread spectrum technique developed for the military"
"!Resistance to jamming"
"!Low probability of intercept"
!!“Civil” Properties"
"!Resistance to multi-path effect (selective fading)"
"!Multi-user interference turns to AGWN for a large number of it"
"!Opening of unlicensed Band (Trojan Horse)"
"!Software resource allocation"
"!Fair resource sharing"
"!Cell size adaptation"
!!Today applications"
"!Cellular mobile systems (IS95)"
"!Wireless local Area Networks (WLAN…)"
CDMA Marcoussis, 25 Oct 2005"8"
Data sequence"
t"
t"
Code sequence
user #1"
t"
CDMA transmitted
signal"
Bipolar Code Sequence"
1 –1 1 1 1 –1 –1 1 –1 -1"
t"
Unipolar Code Sequence"
1 0 0 0 0 0 1 0 0 1 0 0 "
t"
Antipodal Signal On Off Keying Signal
Time Domain CDMA Principle"
!!Bit duration is divided in L time slots (chips)"
"! TB is the bit duration"
"! Tc is the chip duration"

CDMA Marcoussis, 25 Oct 2005"9"
Excess bandwidth is not (necessarily)
wasted"
!!Channels sharing the same spectrum are simultaneously used"
!!No intrinsic gain using hard (single user) decision"
"!No area gain in the Time-Frequency space"
"!Repartition of resource shortage effects between users"
!!Number of users may be improved by soft (multi user) decision"
"!Other users are considered as signals"
"!Their contributions must be larger than others noise"
"!Decision on chips is mandatory"
!!Total number of users : "
"!Equals the allowed number active of users by using deterministic
code attribution"
"!Larger, by using random code attribution (Overbooking)"
CDMA Marcoussis, 25 Oct 2005"10"
Today CDMA Doubts in RF"
!!Near/far field effects leading to power divergence"
!!High density operation questioned"
!!Qualcomm patent monopole"
!!Is it a future for UMTS ??"
"!Price"
"!200 000 subscribers in France 200kbit/s"
"!Killed by WiFi (Hot spots) and WiMax (WMAN i.e. wireless ADSL) ? "
!!Chinese 3G"
"!Required by only voice applications, "
"!Do not (exactly) use it (TD-SCDMA)"
!!4G ??"
"!OFDM (Multicarrier MC) ? "
"!MC-CDMA ??"