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www.huawei.com
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Security Level: Internal
WiMAX Principle and Key Technology
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Foreword
WiMAX ( Worldwide Interoperability for Microwave Access )
WMAN (Wireless Metropolitan Access Network) technology Multiple Broadband Services
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Contents
1. OFDM/OFDMA Principle
2. Key Technologies of WiMAX
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Contents
1. OFDM/OFDMA Principle
1.1 OFDM Principle
1.2 OFDMA Principle
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Evolution of FDMA SystemSingle Carrier
OFDM :
Orthogonal Frequency Division Multiplexing
frequency
Multi-carrier
frequency
OFDM
frequency
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Principle
Convert one high speed serial data into several low speed
parallel data
Generate several orthogonal sub-carriers
Modulate low speed parallel data onto different sub-carriers
Realization of OFDM
0,ns
1, Nns
NN
f0
fN-1
P/SIFFT
0,ns
1, Nns
N N
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
High spectral efficiency
Overcome frequency selective fading
Overcome the multi-path interference
Simple channel estimation
Easy to combine with other technologies
OFDM Characteristics
High requirements of time synchronization
High sensitivity to frequency delay
High PAPR (Peak to Average Power Ratio)
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Overcome Frequency Selective Fading
Fading
Transmit Signal Received Signalff
P(f) P(f)
BroadbandSystem
BroadbandSystem
NarrowbandSystem
NarrowbandSystem
Fading
Transmit Signal Received Signalff
P(f) P(f)
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Multi-path Environment
Received
signal
Transmitted
signal
time
time
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Overcome the Multi-path Inference
In OFDM system, the multi-path interference can be reduced by adding CP
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Importance of Time Synchronization
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Importance of Frequency Synchronization
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Contents
1. OFDM/OFDMA Basic Principle
1.1 OFDM Principle
1.2 OFDMA Principle
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
What’s OFDMA?(1) OFDMA: Orthogonal Frequency Division Multiple Access
All carriers are divided into several groups (sub-channels)
Coding, modulation and amplification are set separately for each
sub-channel based on channel conditions
Different sub-channels can be allocated to different users at the
same time
Frequency
Time
OFDM OFDMA
Ou
tput
Pow
er
Frequency
OFDM OFDMA
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Frequency
Subcarrier-N
Subcarrier-1
Time Bandwidth
Subcarrier-2
Subcarrier-3
Subcarrier-4
Guard Time
OFDM Slot/FrameIFFT
IFFT
IFFT
S1 S2 S3 S4 S5 S6 S7SN
SN+1 SN+2 SN+3 SN+4
OFDM Symbol (FTT duration) S2N
OFDMA is the foundation of 4G!OFDMA is the foundation of 4G!
What’s OFDMA?(2)
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Contents
1. OFDM/OFDMA Basic Principle
2. Key Technologies in WiMAX System
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Contents
2. Key Technologies in WiMAX system
2.1 Communication Model 2.2 Channel Coding 2.3 AMC 2.4 HARQ 2.5 Multiple Antennas
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Common Communication Model
Source decoding
Source
coding Interleaving
deinterleaving
Modulation
Demodulation
Transmitting
Receiving
Radio channel
Deinterleaving &channel deco
ding
Channel coding & interleaving
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
WiMAX Communication Model
FEC ModulationMapping
Randomization IFFTCyclicPrefixInterleave
DL PHY Process
UL PHY Process
RemoveCyclicPrefix
FFTFreq.
Domain Equalizer
De-MapSymbols
Decoder
De-Randomization
De- Interleave
Data toMAC layer
Data from MAC layer
RFTX
baseband
RF RX(Timing &FrequencyCorrection etc)
baseband
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Contents
2. Key Technologies in WiMAX system
2.1 Communication Model 2.2 Channel Coding 2.3 AMC 2.4 HARQ 2.5 Multiple Antennas
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Definition :
A technique which combines of error detection, error correcting, rate
matching, interleaving and so on
Purpose:
Reduce the probability of error
Reduce the required signal-to-noise ratio
Coding Efficiency : k/n
Coding Types in 802.16e:
CC (Convolutional Coding) : 1/2 , 2/3 , 3/4 , 5/6
CTC (Convolutional Turbo coding) : 1/2 , 2/3 , 3/4 , 5/6
Channel Coding
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Questions
Does the coding mode with higher coding efficiency
must be better than a lower one?
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Contents
2. Key Technologies in WiMAX system
2.1 Communication Model 2.2 Channel Coding 2.3 AMC 2.4 HARQ 2.5 Multiple Antennas
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
AMC
Adaptive Modulation and Coding
Purpose:
To select the suitable modulation and coding modes
according to different channel qualities
AMC
16QAM QPSK64QAM
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Modulation Modes in 802.16e Constellation of QPSK/16QAM/ 64QAM
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Modulation and Coding Mode in WiMAX
Supported Modulations and Codings
Modulation TypesDL UL
QPSK 、 16QAM 、 64QAM
QPSK 、 16QAM 、64QAM
CC (Convolutional Code) 1/2, 2/3, 3/4, 5/6
1/2, 2/3, 3/4, 5/6
CTC (Convolutional Turbo Code) 1/2, 2/3, 3/4, 5/6
1/2, 2/3, 3/4, 5/6
Repetition x2, x4, x6 x2, x4, x6
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Questions Please calculate the effective information bits per symbol
with different modulation and coding modes.
For example:
QPSK1/2, the effective information bits per symbol=2*1/2=1bit
How is about the 16QAM3/4 and 64QAM1/2?
If the AMC decision is wrong, what will happen?
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Contents
2. Key Technologies in WiMAX system
2.1 Communication Model 2.2 Channel Coding 2.3 AMC 2.4 HARQ 2.5 Multiple Antennas
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
HARQ (Hybrid Automatic Repeat reQuest)
A combination of ARQ and FEC
Types of ARQ:
SAW: Stop-and-wait
GBN: Go-Back-N
SR: Selective Repeat
Types of HARQ:
Type I
Type II(IR)
Type III
What is HARQ ?
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Performance of HARQ
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Improve the transmission reliability and system throughout
Reduce the average re-transmission and data transmission
delay
HARQ decreases the sensitivity of instantaneous channel
quality change
Combination with AMC, decreases the wrong decision
because of the feedback delay or the wrong feedback
decoding
Characteristics of HARQ
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Contents
2. Key Technologies in WiMAX system
2.1 Communication Model 2.2 Channel Coding 2.3 AMC 2.4 HARQ 2.5 Multiple Antennas
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Contents2.5 Multiple Antennas
2.5.1 MIMO
2.5.2 AAS
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
MIMO : Multiple input and multiple output
What is MIMO?
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Diversity mode ( Matrix A ) Transmit the same data in different antennas Enhance the capacity indirectly The number of receiving antenna can be less than the number of tra
nsmitting antennas
Spatial Multiplexing mode (Matrix B) Transmit different data in different antennas Enhance the capacity directly The number of receiving antenna can not be less than the number o
f transmitting antennas
Working Mode of MIMO
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
MIMO in 802.16e
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Contents
2.5 Multiple Antennas
2.5.1 MIMO
2.5.2 AAS
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
AAS: Adaptive/Advanced Antenna System
What is AAS?
Omni antenna Directional antenna AAS
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Switched Beam Antennas
Cell is covered by some fixed beams
Types of AAS
Adaptive Antenna
Arrays
Beam can trace the
user’s position
automatically
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Increase the SNR and the sensitivity of BS
Decrease the error bit of system
Decrease the system interference
Enhance the coverage
Improve the spectrum efficiency by adopting the SDMA technology
Improvement to performance
Thank youwww.huawei.com
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