1. Coding Methods in CDMA

2. Coding Methods in CDMA Barker Code Pseudo-noise code Walsh code
Scrambling code
Channelization code
Carrier Modulation code

3. Barker code Barker code of length n= 11
(+1,-1,+1,+1,-1,+1,+1,+1,-1,-1,-1)
Used in IEEE
Strong autocorrelation
The absolute value of the inner product of a vector multiplied with itself should be large.
Barker code c11 has 6 1s and 5 0s

4. Pseudo-noise code (PN code)
Autocorrelation characteristics
A code appearing random like noise but is actually not random
Used to generate one or multiple sequences
PN codes useful for soft handover

5. Soft handover in CDMA
A second BTS added for the users on the edge of a cell and new PN code used in new cell for soft handover.
GSM - separate operate frequencies in adjacent cells to avoid inter-cell interference.
CDMA- adjacent cells use same set of carrier and chipping frequencies but different codes.
Each cell has distinct pseudo-noise code offsets.

6. M-sequences (maximum length sequences) code
Code generated by using m small length shift registers
The feedback generates a large number of sets, each set having m sequences
Example: a set of 15 registers (m = 15) can be used to generate a set of (215 – 1) sequences
Application as scrambling code

7. Linear feedback shift register (LFSR)

8. Generator Polynomial
GQ = z15 + z12 + z 11 + z10 + z6 + z5 + z4 + z3 + 1.
A generator polynomial must have at least first term zn present if the degree of the polynomial is n and last term z0 = 1
GQ = { }
Can be written as (15,12,11,10,6,5,4,3,0)
Initial State Vector
Starting sequence should not be 0.
{ }

9. Gold Codes WCDMA uses Gold codes
Created from two M-sequence codes M1 and M2.
M1 and M2 are added Modulo 2
Different M1 and M2 are created by just using different starting registers.

10. Orthogonal Codes
When there is no effect of interference between the two sets of signals on the received output
Require synchronization between the transmitter and receiver
Do not show a strong autocorrelation property

11. Orthogonal Code Zero cross-correlation
Cross-correlation refers to the product of the ith symbol in two codes and the sum of products for all values of i

12. Synchronization
Instant of the received first bit of coded symbols and first bit of generated code for extracting symbols are in the same phase

13. Best codes Optimized codes which enable significant correlation
Do not cause significant interference among the different channels

14. Three coding schemes in CDMA
Orthogonal codes almost zero cross correlation
and are used in identifying the user, user channel, and carrier.
Long M-sequence PN codes have strong autocorrelation and are used in synchronizing and detecting the user channel signals.
Short PN codes also have strong autocorrelation and are used in synchronizing and detecting the user carriers.

15. Walsh Codes Used in IS-95 cdmaOne 64 × 64 matrix
All pairs of rows orthogonal
Generated from a matrix called the Hadamard matrix

16. Walsh Code Pilot channel─ W0, zero-th row Walsh code = {0, 0, …,0,0}
Synchronization channel─ W32, 32nd row
Walsh code = {0, 0, …,0,0} all 0s for first half columns elements and {1,1,..., 1,1} all ones for next half elements
Paging channel - W1, 1st row Walsh code = {0, 0, …,0,0} all 0s for first half columns elements and {1,1, .., 1,1} all ones for next half elements
Traffic channels - W2–31, 33–63

17. W0 and W2 orthoganilty
0th row in the 8 ×8 matrix Walsh code W0 = {0, 0, 0, 0, 0, 0, 0, 0}
2nd row Walsh code W2 = {0, 0, 1, 1, 0, 0, 1, 1}
The codes can be rewritten as {–1, –1, – 1, –1, –1, –1, –1, –1} and {–1, –1, +1, +1, –1, –1, +1, +1}
Σ pi . qi = 0

18. Scrambling Codes A scrambling code can be a PN Msequence code
Must exhibit strong autocorrelation property
To support large number of users and user channels.

19. Channelization Codes
Channelization code has a short length sequence and must exhibit the orthogonality property
It is used for differentiating among different channels during CDMA transmission.
Walsh codes used for channelization due to their orthogonality property

20. Carrier Modulation Codes
Short PN codes
Orthogonal phase modulation is in time-space
To synchronize the carriers of different base stations
Orthogonal code or PN code modulation (spreading) in code-space
To identify the multiple user channels

21. Development of mobile telecommunication systems
Universität Karlsruhe
Institut für Telematik
Mobilkommunikation
SS 1998
Development of mobile telecommunication systems
CT0/1
FDMA
AMPS
CT2
NMT
IMT-FT
DECT
IS-136
TDMA
D-AMPS
EDGE
IMT-SC
IS-136HS
UWC-136
TDMA
GSM
GPRS
PDC
IMT-DS
UTRA FDD / W-CDMA
HSPA
IMT-TC
UTRA TDD / TD-CDMA
CDMA
IMT-TC
TD-SCDMA
IS-95
cdmaOne
IMT-MC
cdma2000 1X EV-DO
cdma2000 1X
1X EV-DV
(3X) 1G 2G
2.5G 3G
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller

22. 3G Technologies

23. 3G Technologies 3G wireless communications standard
First 3G system was deployed in Japan in 2001.
Defined by the recommendations of the International Telecommunication Union (ITU)
Below 3G─ Data rates lower than kbps are considered
2G systems only provide speeds ranging from 9.6 kbps to 28.8 kbps
3G technologies ─ High quality of service and high data rate support for multimedia (audio, pictures, text, and video) transfer

24. UMTS (Universal Mobile Telecommunication System
Data rates – 100 kbps to 2 Mbps
It combines CDMA for bandwidth efficiency and GSM for compatibility.

25. WCDMA Supports data rates of 2 Mbps or higher for short distances
384 kbps for long distances

26. WCDMA-FDD WCDMA access is either FDD or TDD (time division duplex)
WCDMA-FDD Also referred to as UTRAFDD (universal (or sometimes UMTS) terrestrial radio access-frequency division duplex)
FDD separates reverse link (called uplink in GSM) and forward link (called downlink in GSM) frequencies

27. WCDMA-FDD 1.920–1.980 GHz for uplink 2.110–2.170 GHz for downlink
Each 5 MHz bandwidth
Wider than the 1.25 MHz of the IS-95 (2G CDMA) system

28. Protocol Layers between the WCDMA MS and BTS

29. Physical Layer Physical layer Uu radio interface
Supports asynchronous transmission
Can also support synchronous transmission

30. Data-link layer MAC
Controls the flow of packets to and from the network layer
Ciphering function
Sends and receives data from control and user plane service access points at the radio link control (RLC) layer and sends it to the physical layer

31. Network layer above the RLCs
Provides access to multiple services such as BMC (broadcast and multicast control protocol) for the user applications
PDCP (packet data convergence protocol) for the user applications

32. Application Layer GMM (GPRS mobility management)
CC [call (connection) control]
• MM (mobility management)
• SM (session management)
• SS (supplementary service)
• SMS (short message service)
• User Applications

33. WCDMA Chipping rate used in WCDMA is 3.84 Mchip/S
Multirate transmission
Certain types of data need to be transmitted at fast rates and some (power-control data and SMS text) require slow transmission rates.
A single code is used when transmitting small data rate signals.
Multiple codes are used when transmitting large data rate signals.
Gold codes, S(2) and Walsh codes