1. TD-SCDMA Principle and Development Dr. Shihe Li e-mail: lish@pub
TD-SCDMA Principle and Development Dr. Shihe Li Datang MobileCo

2. Contents
Back ground
Principle of TD-SCDMA
Developing
Conclusion

3. History of Mobile Communication
Early period: from early 50’s:
Military application
Without system concept
Analog voice and signaling
Single BS operation
Concept of cellular in 70’s
Cellular concept
Frequency Reuse
The 1 G: Analog system in 80’s
Different standard in each country
The 2G: Digital system in 90’s
GSM/CDMA(IS-95)
Universal standard
Duplex is 1G/2G: FDD
Cellular Concept

4. Mobile Network ___1st generation
OAM BS
PSTN
Mobile SW
HS or MS

5. Mobile Network ___2nd generation
OAM
ACU BS
PSTN
Mobile SW
With data
HS or MS
PDN
BSC

6. Mobile Network ___3rd generation
OAM
ACU
Node_B
PSTN
Mobile SW
Circuit and Packet UE
PDN
RNC
Internet

7. CN and Radio Access Network: Radio Access:
Slow progress, from 1G to 3G, circuit switch take the same technology
Need longer period to stable
Low revenue and high profit (3% of market in mobile, but high margin)
Radio Access:
Fast change technologies
Key issue in mobile system and user terminals
Main part in equipment market, mobile communications
IMT-2000 asked proposal for RTT
3 main stream standards are 3 different Radio Transmission Technology

8. Basic Requirement for RTT
Contents of Physical layer
Multiple access technology
Duplexing
Frame structure
Data multiplexing
Modulation
Channel coding/Interleaving
Signal detection
Antenna technologies
Random access
Cell search
Handover
Other key technologies
Q&S
BER requirement for different service in different environment
Spectrum efficiency
Quantities of services provided in unit bandwidth
Complexity – cost
E&M compatibility
Interference to other system
Reject interference from other systems

9. One Generation per 10 years
Widely application
Standard
4G？
Product Development
R/D
3G(CDMA)
2G(TDMA)
1G (FDMA)

10. What is Multiplex means
Multiple users share a same frequency band
Possible way for multiple access
Frequency Division Multiple Access (FDMA)
Separating user by different carrier frequency
Most popular way to be used in all mobile system
Time Division Multiple Access (TDMA)
Separating user by different time slot in same carrier frequency
Common used in digital system
Code Division Multiple Access (CDMA)
Separating user by different code in same time and carrier frequency
Wide adopted in 3G technology
Space Division Multiple Access (SDMA)
Separating user by different location (direction) in same time, code, and carrier frequency
Future technology based on smart antenna

11. Frequency Plan
Both FDMA and TDMA need frequency plan__Interference in adjacent carrier
Frequency re-use factor
FDMA: same carrier shall be separated by two cells: re-use factor = 11
TDMA: same carrier shall be separated by one cells: re-use factor = 7
CDMA: Adjacent cell can use same carrier, re-use factor = 1

12. Spectrum Efficiency for voice services in 1/2G systems
1G FDMA(TACS)
2 x 25kHz for 1 voice ch., frequency re-use factor=11
Spectrum efficiency=1/0.05/11=1.8ch/cell/MHz
2G TDMA(GSM)
2 x 200kHz for 8 voice ch., frequency re-use factor=7
Spectrum efficiency=8/0.4/7=2.8ch/cell/MHz
2G CDMA(IS-95)
2 x 1.25MHz for 20 voice ch., frequency re-use factor=1
Spectrum efficiency=20/2.5/1=8ch/cell/MHz
Theoretically, if all code can be used, the spectrum efficiency may reach 64/2.5/1=25.8ch/cell/MHz, which is nearly 14 times of FDMA and 8 times of TDMA.

13. Basic CDMA concept
Spectrum Spreading is a technology used in military communication since 60’s
Basic concept
Spreading code: Walsh code, it is an orthogonal code when synchronized
CDMA is a self-interference system:
Multiplex interference: between code channels
Multi-path and Doppler
Interference from other system and users in adjacent cell
Near-far effect
Capacity of a CDMA system is limited by total interference level

14. Basic CDMA IS-95 concept IS-95 is a FDD CDMA system
Operated in AMPS frequency band (taking BW of 41 AMPS carriers)
Chiprate Mcps
Carrier separation 1.23MHz
Channel code and interleaving
Spreading factor: 64
Studying in late 80’ for public mobile communication, the mainly contributions by Qualcomm are as follows
Two sets of code: short code (Walsh) for distinguish user in the cell and long code (PN code) for distinguish cell
Strict up-link power control: to overcome near-far effect
Receiver: Rake receiver to overcome multi-path
Macro-diversity and soft-handover: to enhance capacity and handover without interrupt (suitable for data transmission)
Variable rate voice coder to enhance capacity

15. Capacity in CDMA system: General situation
Basic consumption:
Ideal power control, received power level from each active UE is the same: Eb
User distribution: uniform
When N users are active, then the interference from the same cell will be (N-1)Eb. The total interference from the adjacent cells (1st and 2nd layers) will be the same as that from the same cell.
required Eb/N0≤lg(SF)+Eb/(N0+2*(N-1)Eb)~ lg(SF)-lg(2N)
N≤(10lg(SF)-Eb/N0)/2
Reduce interference

16. Technologies related to capacity
Macro diversity
UE get down-link from 2 to 3 BSs
Each BS may transmit less power, less interference to enhance down-link capacity about 2 dB
Power control
Power control error: usually 2 to 3 dB
Because of fast fading and multi-path
Capacity loss: 2dB

17. The possible way to improve CDMA system
Variable code rate (by Qualcom in IS-95)
Based on voice performance, reduce coding rate.
May double capacity (half interference) for CDMA
Key IPR for Qualcom
Useless in Data service
Smart Antenna (by TD-SCDMA)
Most efficient tech
Capacity enhance by N times (N is the number of antenna elements)

18. Basic concept of Duplex
Fdown
Fup
Duplex: communication between UE and BS simultaneously
Traditional tech: divided by frequency: FDD
Time Division Duplex (TDD) is from data communication
From end of 80’s, TDD started to use in voice communication (CT2, DECT, etc.)
From 3G, TDD become one duplex in RTT t
Down link data
Up link data
TSdown TSup t

19. Comparison between FDD & TDD
Items
FDD
TDD
Transmission Ppeak/ave
Continuous, low
Burst, high
Receiving sensitivity
high (BW=datarate)
low (BW>datarate)
Comm distance in same Pmax
Long
Short
Number of carrier f
2, down and up separation by frequency
1, down and up separation by time
Wave propagation in down- and up-link
different
Same at the same time
Need duplexer in transceiver
Yes in UE
Two antennas in BS
None in UE
One antenna in BS
Asymmetric data
Some spectrum resource may not be used
All spectrum resource can be used

20. Main Feature in TDD Duplex
Spectrum flexibility: do not need paired frequency
Same carrier frequency in both Down- and Up-link, symmetric propagation performance suitable for smart antenna, pre-Rake, open loop power control and other technologies
Support asymmetric data services, by adjusting different numbers of slots in up- and/or down-link
It may use of different bandwidth for asymmetric services in FDD, but it could not be flexible
Low cost: Do not ask high isolation between Tx and Rx path, one may design single IC for RF transceiver in UE

21. Main Shortage for TDD t Higher peak/average tx power ratio for UE
FDD: continuous transmit
TDD: only one TS work, the extra ratio will be 10lgM, M is the number of TS
Higher requirement for transmitter and PA.
Lower sensitivity for receiver
Bandwidth: the total chiprate
Data rate: limited by number of TS
Sensitivity loss: 10lgM.
Discontinue operation
Less communication distance, half nearly
Difficult for high speed moving. t

22. How to overcome the shortages?
The shortage of TDD leads to:
TDD can only be used in Micro- and Pico-cell
TDD can only support slow moving
Possible way to overcome the shortages
Smart antenna: increase sensitivity and EPRI
Smart antenna plus Joint detection: improve performance in fast fading (multi-path in high speed moving)

23. Wave Propagation Loss ITU Model Indoor: L= 30lgd + 54.35 (n=1)
Loos
(dB)
100
110
120
130
140
150
160
170
180
Pedestrian
Vehicular
2GHz
900MHz
ITU Model
Indoor: L= 30lgd (n=1)
30lgd (n=2)
30lgd (n=3) dB
where n is the number of floors
d is the distance in meter
Pedestrian: L=40lgd +30lgf + 49
=40lgd + 148dB
Vehicular: L= 40( h)lgd- 18lgh +21lgf +80
=35.2lgd+122.7dB
where f is frequency in MHz (2GHz);
h is the hight of BS antenna over average roof level in meter(30m);
d is the distance in kilometer.
D= k 3k 10km

24. Radio Resource f
code t

25. Capacity in CDMA system: General situation
Basic consumption:
Ideal power control, received power level from each active UE is the same: Eb
User distribution: uniform
When N users are active, then the interference from the same cell will be (N-1)Eb. The total interference from the adjacent cells (1st and 2nd layers) will be the same as that from the same cell.
Itotal = 2(N-1)Eb>>N0, N0is thermal noise
Required Eb/(Itotal +N0)≈ Eb/(Itotal ) ≤lg(SF)-lg(2N)
N≤(10lg(SF)-Eb/ (Itotal + N0))/2
For QPSK modulation and R=1/3 coding, Required Eb/(Itotal +N0)≈ 3.1dB(0.3) for BER of 1x10-3
Or N≈SF/4

26. Capacity in CDMA system: General situation
Basic consumption:
Ideal power control, received power level from each active UE is the same: Eb
User distribution: uniform
When N users are active, then the interference from the same cell will be (N-1)Eb. The total interference from the adjacent cells (1st and 2nd layers) will be the same as that from the same cell.
If the antenna of BS with beamformed pattern, then only a part of interference will be inter demodulator.
Eb/N0≤lg(SF)+Eb/(N0+(2*(N-1)Eb)/m)~ lg(SF)-lg(2N/m)
N≤m(10lg(SF)-Eb/N0)/2
m means coverage anger/beam width

27. Basic concept of Smart Antenna
When the main incident ray from a user k has an incident anger of , then the received signal at the i-th element will be alejl , l means the l-th ray
Then the total received signal will be  wi(ejdicos  alejl )
Separate it by code
Find receiving weight W
Get DOA
Combine received signal (up-link beamforming
Down-link beamforming  di

28. Features of Smart Antenna
Increase receiving sensitivity
Increase EIRP
Reduce Interference
Increase Capacity of system
Reduce cost of BS
Increase reliability of BS

29. Up-link synchronization
Establish of synchronization
Open loop estimate the distance to BS.
Send UpPTS
Find error
Adjustment Tx timing
Maintenance of synchronization
Close loop
Open loop

30. Features of synchronous CDMA
In multi-path condition, ideal synchronization can not be reached
One can do is synch for the main ray, and takes the other ray as interference or noise
The main feature is to sync all up-link signals in the same time slot, simplify data procession

31. Basic concept of SR
Antenna and
Feed cable
Multi- band and multi-standard in mobile communication
Each standard ask different equipment design
Compose of a radio equipment:
Antenna and cable: wideband
RF transceiver: different bandwidth
BB digital signal processor
Ctrl and I/O: switch and MCU
The most active technology: in BB DSP
Software radio (SR): by using SW in general DSP/FPGA to replace ASICs
Advantages of SR:
Save developing time and cost, reduce risk
Easy to up-grade of technology, upgrade SW only
Suitable for using new technologies
RF sub-system
BB digital signal
processing
Ctrl and interface

32. Key point in SR design
BB DSP complexity: technologies to be used (Rack receiver or Joint detection?)
Present capacity of DSP/FPGS:
For BS, the most powerful DSP is less than 1000MIPS, and FPGA is about 200gates
For UE, DSP will be 3/400MIPS only (power consumption limitation)
Sampling rate and accuracy:
Single antenna or multiple antenna
Bandwidth (chip-rate)
This is why TD-SCDMA takes 1/3 of chip-rate for WCDMA
Algorithm to be developed
Suitable for DSP or FPGA?
Complexity and accuracy?
Low cost consideration: have to lower than developing and using ASIC

33. Why do not use Soft-handover
Points to considering
Advantage of Soft-handover
All code channel is used for services, have no more DL channel for macro-diversity
Overcome shortages of Soft handover
Do not need macro-diversity for capacity
Difficult to use two receivers for macro diversity
Possibility
Smart antenna for UE location
Synchronous CDMA
RNC

34. Baton Handover Measurement: Find target BS:
DwPTS only
List strength of measured pilot and report to BS until one reaches HO threshold
Find target BS:
Send UpPTS
Enter close loop synch with the target BS
Record new timing for UL synch with the target BS
Open-loop synch with target BS
Find the change of DL timing of target BS
Renew UL timing
Excuse HO
System decision
DL transmission by two BS
Switch to target BS
Excuse measurement

35. Narrow Bandwidth Flexible for allocation Suitable for software radio
Especial for private network
Suitable for software radio
Smart antanna
Joint detection
Synchronous CDMA
Future development: wide-band TD-SCDMA for different applications
5MHz MHz
1.6MHz

36. Single carrier frequency
Wave Propagation
Fading;
Multi-path;
Doppler;
etc.
Wave Propagation depends on frequency, environment, time, and etc. In mobile communication, it is varied.
In TDD, up-link and down-link takes the same carrier frequency, the wave propagation performance will be nearly the same if the TDD period is short enough.
Advantages of one carrier frequency:
BS can get the up-link propagation from the received signal from one user
Then BS can assume down-link has the same performance as up-link, and some technologies are easy to use such as
Beamforming for smart antenna
Pre-rack receiver
For UE, the open-loop power control will has much higher accuracy

37. Highest spectrum efficiency
Spectrum efficiency is one of most important issue in 3G
TD-SCDMA can use all code channel, reaches wolsh limitation.
For data services, TD-SCDMA can provide 3x16 pairs of symmetric channels
When voice coding is 12.2kbps, 3GPP asks to provide one voice channel by using of 2 code channels, the spectrum efficiency is 3x8/1.6=15/MHz/cell
When voice coding is 8kbps, the spectrum efficiency is 3x16/1.6=30/MHz/cell
For WCDMA, (3 for 12.2kbps and 6 for 8kbps coding rate) its spreading efficient is the lowest one in 3G standards.
For data services, the calculation and definition is varied, but TD-SCDMA is always the highest one.
The spectrum efficiency will double when smart antenna is used in FDD modes

38. All environment
In traditional understanding, TDD can only use in micro- or pico-cell environment
TD-SCDMA has overcome the shortage in TDD mode, by using of smart antenna technology, it can be used in all environment
system
Sensitivity
Max comm. distance
Operation level
Max cell radius
WCDMA
-117dBm(voice）
-99dBm(384kbps)
3.7km
2.1km
-111dBm(Voice）
-93dBm(384kbps)
2.5km
1.4km
TD-SCDMA
-113dBm(Voice）
-110dBm(384kbps)
4.5km
3.8/5.9 km
-107dBm(Voice）
-104dBm(384kbps)
3.0km
2.6/4km

39. Low cost solution Cost for 3G equipment Smart antenna reduce cost
CN/RNC/UE will be nearly the same for each standard
Cost for Node_B is varied with technology
Smart antenna reduce cost
ACU and etc. will be the same cost
The most expensive part is linear power amplifier
Smart antenna can use a group small PA to replace the expensive HPA
Now BS for IS-95 and WCDMA is much expensive than GSM, but we’ll provide BS with lower price than GSM.

40. Contents
Back ground
Principle of TD-SCDMA
Development
Conclusion

41. Development Face to next generation : Beyond 3G or 4G IP network
TDD, narrow and wide band TDD, 1.6MHz to 5MHz to 10/20MHz of band width
Smart antenna,
much efficient algorithm/FDD application/Smart antenna for UE
Software Defined Radio
Hardware platform/System structure/Algorithm
High speed package data transmission
Higher modulation scheme
Other coding technologies
IP network

42. Products From standard to commercial products TD-SCDMA products team
Core Network: Siemens; Putian; ZTE; Huawei; etc
Radio Access Network
RNC: Datang Mobile; UT starcom; Huawei; etc
Node_B: Siemens; Putian; Datang Mobile; etc UE
Chipset: Commit; T3G; etc
UE: many companies
TD-SCDMA Industrial Alliance

43. Development: system 2004 Products for large scope commercial trial
2003
Field Trial
Commercial products
development
System integration test
Node_B tester
2004
Products for
large scope
commercial
trial
2001
First call between
FTMS And Node_B
2000
Field Trial MS
2002
Demo TD-SCDMA
System integration test
Field trial
1999
Coop with Siemens
Node_B based on
GSM network

44. Development: Chipset for UE
End 2003: first chipset
Mid 2004: Multiple UE providers ready
2003
T3G
(TDM/Philips/Sumsong)
2002
Commit
(TDM/Putian/TI/
Dbtel/Nokia/LG/etc)
2003
Other companies:
RTX
National Semiconductor
Spreadtrum
………..
02-03
ST Micro
2000-
DTM
Field trial MS

45. Conclusion TD-SCDMA RTT is now accepted by more and more people
Strong supported by government
155MHz spectrum
TD-SCDMA Industrial Alliance
Key project in 10th 5 year plan
In 2003, standard will become products
In 2004, Commercial trial
After 2005, world wide application

46. Thanks