D-AMPS - Digital Advanced Mobile Phone System, Code division multiple access

Digital Advanced Mobile Phone System (D-AMPS)is a digital version of Advanced Mobile Phone Systems (AMPS), the original analog standard for cellular phones.
D-AMPS combines time division multiple access (TDMA) and frequency division multiple access (FDMA).
It adds TDMA to get three channels per AMPS channel, thus tripling the number of calls on a channel.

1. GSM
PDC
cdmaOne
TDMA
(IS-136)
GPRS
EDGE
cdma2000
3G
Today 2G
19.2kbps
2000 evolved 2G
64--115kbps
3G
115--384kbps | 0.384--2Mbps
IMT-2000
Capable Systems
New SpectrumExisting Spectrum
TDMA/
GPRS
TDMA/
EDGE
Evolution to 3G

2. Difference from Wired Networks
Higher loss-rates due to interference
–
emissions of, e.g., engines, lightning
Restrictive regulations of frequencies
–
frequencies have to be coordinated, useful frequencies are almost all
occupied
Lower transmission rate
Higher delays, higher jitter
–
connection setup time with GSM in the second range, several hundred
milliseconds for other wireless systems
Lower security, simpler active attacking
–
radio interface accessible for everyone, base station can be simulated, thus
attracting calls from mobile phones
Always shared medium: secure access mechanisms

3. Wireless Access: Range of Operation of Different
Techniques
Mbit/s
1 10 1000,1
O
u
t
d
o
o
r
Fixed
Walk
Vehicle
I
n
d
o
o
r
Fixed/
Desktop
Walk
Mobility
UMTS
W-LAN
IEEE 802.11a
HyperLAN2
Bluetooth
G
S
M
,

I
S
-
9
5
,

D
-
A
M
P
S
W BB- LAN
Wide Area Network (WAN)
- Coverage
Local Area Network (LAN)
- Hot Spots - high speed
Personal Area Network (PAN)
- Connectivity, cable replacement
New frequency
allocations needed
Reference to S.R. Treves (Alcatel) presentation in Mobicom’01.Rome Italy

4. Current Situation

Wireless coverage in most highly populated
areas

Insufficient coverage, low system capacity,
and low bandwidth

Numerous overlapping, but incompatible
wireless system as the obstacles for inter-
system roaming.

5. Effects of Portability
Power consumption
–
Limited computing power, low quality displays, small disks due to limited
battery capacity
CPU: power consumption
Transceiver power consumption
–
Loss of data
–
Higher probability, has to be included in advance into the design (e.g., defects,
theft)
Limited user interfaces
–
compromise between size of fingers and portability
–
integration of character/voice recognition, abstract symbols
Limited memory
–
limited value of mass memories with moving parts
–
flash-memory as alternative

6. IMT-2000 radio interfaces

7. AMPS is an analog cellular phone
system using FDMA.
Note

8. Cellular bands for AMPS

9. AMPS reverse communication band

10. Second-generation cellular phone systems

11. D-AMPS
D-AMPS, or IS-136, is a digital cellular
phone system using TDMA and FDMA.

12. Rules for Efficient Multiple
Access 
Three laws

Know the channel

Minimize interference to others

Mitigate interference received from others

Requirements of wireless multiple access

Channel measurement

Channel control and modification

Multiple user channel isolation

13. Why CDMA?

Higher capacity

Improved performance in multipath by diversity

Lower mobile transmit power = longer battery life

Power control

Variable transmission rate with voice activity detection

Allows soft handoff

Sectorization gain

High peak data rates can be accommodated

Combats other-user interference = lower reuse
factors

14. IS-95 (CDMA ONE) forward transmission
IS-95 is a digital cellular phone system
using CDMA/DSSS and FDMA.

15. IS-95 (CDMA ONE) reverse transmission

16. cdma2000 Uplink Frame Structure
CRC
encoder
tail bits
Convolutional
or Turbo Coder
symbol
repetition
symbol
puncture
block
interleaver
modulation
symbol
C
channel
bits
Bits/
Frame
16
40
80
172
350
744
1512
3048
6120
CRC bits
6
6
8
12
16
16
16
16
16
tail
bits
8
8
8
8
8
8
8
8
8
Data Rate
kbps
1.5
2.7
4.8
9.6
19.2
38.4
76.8
153.6
307.2
Code
Rate
1/4
1/4
1/4
1/4
1/4
1/4
1/4
1/4
1/2
Repeats
16
8
4
2
1
1
1
1
1
Delete
1 of 5
1 of 9
none
none
none
none
none
none
none
Symbols
1536
1536
1536
1536
1536
3072
6144
12288
12288
Radio Configuration 3
C.S.0002-A-1 Fig 2.1.3.1.1.1-8

17. cdma2000 Uplink Modulator
C
C
C
A
B


d

d

d
c

)cos(t
c

)sin(t
c
Ilong,
c
Qlong,
c
+
+
+
+

+
_
s
u
m
s
u
m
1
Dw
Cw
2

S
w
1
Sw
Primary
Traffic
Secondary
Traffic 1
Secondary
Traffic 2
Control
Pilot
pulse
shape
pulse
shape

18. cdma2000 Downlink Frame Structure
Other similar tables in specification.
Bits/
Frame
21
55
125
267
552
1128
2280
4584
9192
20712
CRC bits
6
8
10
12
16
16
16
16
16
16
tail
bits
8
8
8
8
8
8
8
8
8
8
Data Rate
kbps
1.8
3.6
7.2
14.4
28.8
57.6
115.2
230.4
460.8
1036.8
Code
Rate
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
Repeats
8
4
2
1
1
1
1
1
1
1
Delete
none
none
none
none
none
none
none
none
none
2 of 18
Symbols
576
576
576
576
1152
2304
4608
9216
18432
36864
Radio Configuration 9
CRC
encoder
tail bits
Convolutional
or Turbo Coder
symbol
repetition
symbol
puncture
block
interleaver
modulation
symbol
channel
bits
W

19. cdma2000 1X DL Modulation
Processing
+
long
code
long
code
mask
0  1
1  -1
channel
gain
fwd pwr
ctrl gain
p
o
w
e
r

c
o
n
t
r
o
l
s
y
m
b
o
l

p
u
n
c
t
u
r
e
D
E
M
U
X
decimate
pwr ctrl
bit pos
I/Q scrambling
bit extract
power
control
bits
puncture
timing
800 Hz
W
YQ
YI
C.S.0002-A-1 Fig 3.1.3.1.1.1-18
modulation
symbol
rate

20. cdma2000 1X Downlink Modulation
I channel
pilot PN
Q channel
pilot PN
Walsh code
QOF code
I
Y
Q
Y





pulse
shape
pulse
shape
+
+
+
-
)cos(t
c
)sin(t
c

other
channels
other
channels
p
h
a
s
e


r
o
t
a
t
e

f
o
r

Q
O
F
QX
I
X

21. cdma2000 3X DL Modulation
Processing
+
long
code
long
code
mask
0  1
1  -1
channel
gain
fwd pwr
ctrl gain
p
o
w
e
r

c
o
n
t
r
o
l
s
y
m
b
o
l

p
u
n
c
t
u
r
e
D
E
M
U
X
decimate
pwr ctrl
bit pos
I/Q scrambling
bit extract
power
control
bits
puncture
timing
800 Hz
W
YQ1
YI1
modulation
symbol
rate
YQ2
YI2
YQ3
YI3

22. cdma2000 3X Downlink Modulation
same as below
same as above
output
carrier 1
output
carrier 2
output
carrier 3
YQ1
YI1
YQ2
YI2
YQ3
YI3

23. W-CDMA Versus cdma2000
Parameter W-CDMA cdma2000
Carrier spacing 5 MHz 3.75 MHz
Chip rate 4.096 MHz 3.6864 MHz
Data modulation BPSK FW – QPSK; RV - BPSK
Spreading Complex (OQPSK) Complex (OQPSK)
Power control frequency 1500 Hz 800 Hz
Variable data rate implement.Variable SF; multicode Repet., puncturing, multicode
Frame duration 10 ms 20 ms (also 5, 30, 40)
Coding Turbo and convolutionalTurbo and convolutional
Base stations synchronized?Asynchronous Synchronous
Base station acquisition/detect3 step; slot, frame, codeTime shifted PN correlation
Forward link pilot TDM dedicated pilot CDM common pilot
Antenna beam forming TDM dedicated pilot Auxiliary pilot

24. cdma2000 vs WCDMA

Chip rate

Coherent Pilot Channels

Transmit Diversity

Underlying Network

Single Carrier versus Multicarrier
Spreading

Cell Site Synchronization