1. Smart Antenna and MC-SCDMA Next Generation Technologies for Wireless Broadband Guanghan Xu, CTO Navini Networks
September 19, 2018
April,

2. Outline
Comparative Analysis of CDMA, OFDM, and MC-SCDMA
Comparative Analysis of Smart Antennas vs Conventional Antennas
Comparative Analysis of TDD vs. FDD
Optimal Integration of Technologies to Create a Broadband
Solution
Field Trial Results of the Integrated Technologies

3. Wireless Broadband Challenges
Path Loss (Link Budget)
14.4Kbps to 1Mbps
= 69 times or 18dB more power
Multipath Fading
Intercell Interference t F1 F1 F1 F1 F1 F1
Suburban F1
Free space
Time Domain F1 F1
City
Rural
Mixture of Broadband
& Narrowband (voice) f
Frequency Domain km

4. OFDM Multiple Access
OFDM offers very good immunity to multipath issues.
FFT is very efficient in channelization NlogN instead of O(N2).
OFDM needs much higher fade margin requiring higher signal levels and complex coding.
OFDM has high peak to average ratio that impacts link budget due to large PA backoff.
OFDMA is difficult to reliably transmitting narrowband data or voice due to the spectrum nulls. Frequency hopping does smooth out the probability of hitting the nulls.
OFDM is susceptive to intercell interference in the N=1 deployment while all the neighboring cells are fully loaded.
Transmitted OFDM Spectrum f
Received OFDM Spectrum
Signal Threshold f

5. Conventional CDMA + + +
Transmitted CDMA
Spectrum
Received CDMA
Spectrum
Interference
Signal f f
Frequency Domain
Frequency Domain
Code 1
Code 2
Code 3
Code 4
CDMA (1XEVDO, EVDV & WCDMA) all have asynchronous CDMA uplink.
Due to high spreading gain, CDMA (1X and WCDMA) signals are more resistant to intercell interference which enables N=1 deployment.
Since each code has sufficient bandwidth, signal fading is marginal.
Due to high intercode or intracell interference, the link budget is adversely impacted leading to the cell breathing effect.
The high intracell interference also considerably reduces the capacity or throughput of the system.

6. Synchronous CDMA (SCDMA)+
Code 1
Code 2
Code 3
Code 4
Symbol Period
Synchronous CDMA (SCDMA) can maintain code orthogonality and its multipath interference or intercode interference is minimized.
Due to the spreading gain, the SCDMA signals are also more resistant to intercell interference which enables N=1 deployment.
Since each code has sufficient bandwidth, signal fading is marginal.

7. Multipath Effect to SCDMA
Multipath Channel of User 1 + + + + + +
Multipath Channel of User 2 + + +
Symbol Period
Other User Interference
Self Interference
User 1 Signal
User 2 Signal
Code 1
Code 2
Code 3
Code 4

8. Joint Detection for SCDMA
Joint detection is the solution to effectively handle the multipath in multi-user CDMA systems.
Joint detection is computationally expensive and its complexity is O(N2L), where N is the spreading factor and L is the channel length.
Increasing N leads to more resistence to signal fading and the ability to assign lower data rates to handle the mixture of narrowband and broad applications
Increase N does increase the complexity of joint detection quadratically.
Wide bandwidth (1.2288Mcps for IS-95 or 1X, 3.84Mbps for WCDMA) also leads to small chip periods or relatively increases L which will increase the complexity and degrade the performance.

9. Optimal Tradeoff: MC-SCDMA
WCDMA
Best on signal fading
Worst on multipath interference
Good on intercell interference
OFDM
Best on multipath interference
Bad on intercell interference
Worst on signal fading f f
MC-SCDMA
Optimal tradeoff among multipath interference, intercell interference, and signal fading

10. Subcarrier Arrangement
5MHz
Subcarrier spacing =500KHz
Chip rate = 400kcps
Chip period = 2.5us

11. Maintain Sync in Mobility
Mobile speed 250KM/hour
Worst case movement distance in 10ms is 0.69M
Time of arrival change = 0.69/3x108 = 2.3ns.
Time of arrival change for one second is 200ns
For chip period of 2.5us, the time of arrival change is only 1/12.5 chip.

12. Competitive Analysis SUI Propagation Model (IEEE802.16)
SUI Channel model index
Tap 1
Tap 2
Tap3 1
0 ms, 0 dB
0.4 ms, -15 dB
0.8 ms, -20 dB 2
0.5 ms, -12 dB
1 ms, dB 3
0.5 ms, -5 dB
1 ms, dB 4
2 ms, -4 dB
4 ms, dB 5
5 ms, -5 dB
10 ms, -10 dB 6
14 ms, -10 dB
20 ms, -14 dB

13. Downlink Performance of WCDMA, 1X, MC-SCDMA
100% loaded W/O JD
100% loaded w/ JD
MC-SCDMA has at least 4 times improvement in performance.
25% loaded
50% loaded
100% loaded
25% loaded
50% loaded
100% loaded
Sprint Model Index

14. MC-SCDMA has at least 4 times improvement in performance.
Simulations of Uplink Performance of Best Case WCDMA, 1X, SCDMA Technologies
WCDMA 1X
MC-SCDMA
100% loaded W/O JD
100% loaded w/ JD
MC-SCDMA has at least 4 times improvement in performance.
25% loaded
50% loaded
100% loaded
25% loaded
50% loaded
100% loaded
SUI Model Index

15. Fade Margins of OFDM vs MC-SCDMA
32 tones or 32 codes in 500KHz bandwidth
for SUI model 4
Reliability
OFDM
SCDMA
SCDMA Joint Detection
95%
13dB
7dB
8dB
99%
20dB
9dB
11dB
95% reliability
99% reliability
The fade margin for OFDM with 99% reliability is about 10dB
more than MC-SCDMA.

16. Comparison among WCDMA/1X, OFDM, & MC-SCDMA
With respect to intercell interference, MC-SCDMA has similar performance as WCDMA/1X and outperforms OFDM significantly due to spreading gain.
With respect to intercode interference, MC-SCDMA with low complexity joint detection has similar performance as OFDM and outperforms WCDMA/1X significantly in the presence of multipath.
With respect to signal fading, MC-SCDMA with low complexity joint detection has similar performance as WCDMA/1X and outperforms OFDM significantly in the presence of multipath.
With respect to mixture of narrowband and broadband, the MC-SCDMA performs similarly as WCDMA and has the similar low complexity as OFDM (leveraging FFT).

17. Adaptive Antenna Array
Conventional
Smart
Antenna
Power Distribution
Legacy
RF System
Power Distribution
Patented
Smart Antenna
Software
Low Capacity
High Capacity
Signal
Interference from other users
High Complexity
128W
Signal
Interference from other users
Low Complexity
2 W
Power Level
Power Amplifier Module
Power Level
Power Amplifier

18. Link Budget Advantages
Conventional
2 Watts + 0 dB Gain
Adaptive Phased Array
2 Watts + 18 dB Gain
Same scale, same terrain, same clutter, same location

19. Interference Nulling
Desired Signal 1
Desired Signal 2

20. Interference Nulling Desired Signal 1 Lost Desired Signal 2 Lost
I/C=18dB
I/C=15dB
Desired Signal 1 Lost
Desired Signal 2 Lost

21. Interference Nulling
Simple CDMA with a Single Antenna

22. Interference Nulling
Simple Beamforming

23. Interference Nulling
Interference Nulling

24. Interference Nulling Example
Signal Without Interference
Actual Signal Measured at 2.4GHz
BTS Receive
Period
BTS Transmit
Period

25. Interference Nulling for N=1 Deployment
Simulation Assumptions:
3 sectors linear array with 8 elements
Each sector has 10 simultaneous users each has the same data rate

26. FDD vs TDD
Frequency division duplex (FDD) requires at least MHz guard band between up and down streams to make the duplexer feasible.
>30MHz
Unusable
Spectrum
Up/down
stream
Down/up
stream
Duplexer filtering
Profiles

27. FDD vs TDD Summary of FDD Advantages:
Guard time of TDD fundamentally limits the communication distance while FDD does not have such a restriction.
TDD may not be backward compatible to existing FDD wireless communication systems such as cellular phones.
FDD has 3dB more link budget than TDD in uplink link budget for symmetric separation.
Summary of TDD Advantages:
Flexibility of selecting a carrier for providing services.
Flexibility of providing dynamic asymmetric services for both uplink and downlink.
Exploitation of full benefits of smart antenna technologies leading to high capacity, high performance, and low cost.

28. Optimal Integration of Smart Antennas, MC-SCDMA, and TDD
Smart Antennas with TDD
Smart uplink and smart downlink (same carrier frequencies)
Smart Antennas with MC-SCDMA
Simple smart antenna algorithms and robust performance
Low complexity joint detection algorithms
TDD and MC-SCDMA
Simple open-loop power control scheme for mobile communications
Smart Antennas + TDD + MC-SCDMA
Require simple signaling protocol
Multiple antennas lead to high redundancy
Can localize the terminal and predict handoff

29. Baton Handoff Location based handoff Baton handoff
Determine distance from uplink synchronization
Determine direction-of-arrival (DOA) from smart antennas Determine the terminal location from DOA and distance
Location based handoff Baton handoff
Downlink
Uplink
Close to base station
Far from base station
Downlink
Uplink q
Handset
Antenna Array

30. Base Station
Antenna installation on 30m PCS tower
Outdoor cabinet

31. Frequency Planning E2: 2608-2614MHz F2: 2614-2620MHz E3: 2620-2626MHz
Frequency Reuse

32. Outdoor Tests
Omni antenna used for drive test, CPE located inside car

33. Indoor Tests

34. Test Items in the Trials
Technology
Beamforming Gain Stability (Up and Down Link)
C/I Comparative Performance (Up and Down Link)
Effectiveness of Interference Rejection Technology
Product and Network Deployment
Data Rates vs Distance
Coverage Prediction Accuracy
Service Level Agreement Stability Across System Load Levels
System Stability with Large Number of Simultaneous Users
System Stability with under High User Contention Load
CPE Portability (Roaming) Between Cells
System Recovery Speeds
Cell Coverage Stability Across System Loads
Quality of Service/Grade of Service
10) Indoor Penetration Loss

35. Beam Pattern
Many beam patterns suggests high levels of multipath during data rate tests
This multipath is exploited by adaptive antennas.
This multipath would severely degrade conventional systems.

36. Beamforming Results Average Downlink beamforming gain was 21 dB
92% of Non Line Of Site (NLOS) locations had a downlink beamforming gain of 18dB or better

37. Drive Test Result of One of Six BTS Sectors

38. Prediction vs Field Measurement

39. FTP Raw Downlink Data Rates