AMC+Edge英文基础知识

1、1,Adaptive Modulation and Coding,Dec. 3, 2013,Basic principles, Techniques and Applications,Outline,Introduction of Adaptive Modulation and Coding Adaptive Transmission System Adaptive Techniques Application of Adaptive Modulation and Coding,2,Outline,Introduction of Adaptive Modulation and Coding A

2、daptive Transmission System Adaptive Techniques Application of Adaptive Modulation and Coding,3,Introduction of Adaptive Modulation and Coding,Adaptive Modulation and Coding (AMC): Change modulation and coding relative to the Channel State Information (CSI) Parameters to adapt: Constellation size Tr

3、ansmit power Instantaneous BER Symbol time Coding rate/scheme Optimization criterion: Maximize throughput Minimize average power Minimize average BER,4,Main Applications of AMC,High Speed Downlink Packet Access (HSDPA) Wireless Local Area Networks (WLAN) Worldwide Interoperability for Microwave Acce

4、ss (WiMax, 802.16) 3GPP Long Term Evolution (LTE, 3.9G),5,Outline,Introduction of Adaptive Modulation and Coding Adaptive Transmission System Adaptive Techniques Application of Adaptive Modulation and Coding,6,Adaptive Transmission System,7,System model,Outline,Introduction of Adaptive modulation an

5、d coding Adaptive Transmission System Adaptive Techniques Application of Adaptive modulation and coding,8,Adaptive Techniques,Rate Control Fixing symbol rate，using multiple modulation schemes or constellation sizes Fairly easy, used in current systems, such as GSM, IS-136 EDGE or 802.11a, et. al. Fi

6、xing the modulation, changing the symbol rate Varying signal bandwidth is impractical and complicates bandwidth sharing. Power Control Adapting the transmit power alone is generally used to compensate for SNR variation due to fading. To maintain a fixed bit error probability, or a constant received

7、SNR. The power adaptation thus inverts the channel fading so that the channel appears as an AWGN channel to the modulator and demodulator.,9,Adaptive Techniques,Error Control Adapt the instantaneous BER subject to an average BER constraint. Not an adaptive technique, since the transmitter does not a

8、dapt to SNR. Error probability is typically adapted along with some other form of adaption such as constellation size or modulation type. Coding Control In adaptive coding different channel codes are used to provide different amounts of coding gain to the transmitted bits. Adaptive coding can be imp

9、lemented by multiplexing together codes with different error correction capabilities. An alternative technique to code multiplexing is rate-compatible punctured convolutional (RCPC) codes.,10,Adaptive Techniques,Hybrid techniques Adapt multiple parameters of the transmission scheme, including rate,

10、power, coding, and instantaneous error probability. Joint optimization of the different techniques is used to meet a given performance requirement. Rate adaption is often combined with power adaptation to maximize spectral efficiency.,11,Outline,Introduction of Adaptive modulation and coding Adaptiv

11、e Transmission System Adaptive Techniques Application of Adaptive Modulation and Coding AMC for multi-user EDGE,12,Application of AMC,13,AMC for multi-user Downlink transmission format is adapted to different SNR Users with high SNR: use MQAM (large M) + high code rates Users with low SNR: use BPSK

12、+ low code rates Different user get a different rate,ADC for multi-user,14,ADC for multi-user,15,AMC for multi-user Lower data rates are achieved by using a small constellation such as QPSK and low rate error correcting codes such as rate 1/2 convolutional or turbo codes. The higher data rates are a

13、chieved with large constellations such as 64QAM and less robust error correcting codes, for example rate 3/4 convolutional, turbo, or LDPC codes.,ADC for multi-user,16,AMC vs Shannon Limit,Optionally turbo-codes or LDPC codes can be used instead of simple block/convolutional codes in these schemes,O

14、utline,Introduction of Adaptive modulation and coding Adaptive Transmission System Adaptive Techniques Application of Adaptive modulation and coding AMC for multi-user EDGE,17,Introduction of EDGE,EDGE = Enhanced Data rates for GSM (or Global) Evolution EDGE包括EGPRS和ECSD EGPRS是对GPRS的增强，对系统的影响主要包括： 在R

15、F层采用了8PSK调制方式，极大提高了单信道的速率 对链路层RLC/MAC做了修改，并且定义了更完善和链路控制算法,18,Key techniques of EDGE,8-PSK 调制解调 多种编码方式（MCS19) 链路质量控制（LQC） 链路自适应（LA） 递增冗余重传（IR）,19,GMSK and 8PSK Modulation,20,与GMSK相同的符号率，但比特率可提高三倍 符号率： 270.833 ksymb/s 时隙比特率： GMSK：0 22.8 kbit/s 8PSK： 0 69.6 kbit/s,GPRS与EDGE信道编码,21,链路质量控制（LQC） 所谓链路质量控制，就是指在数据传输过程中通过改变调制方式和编码方式，动态地适应无线传输环境，以达到提高链路质量的方法。EDGE采用了一套精心设计的、高效的链路质量控制算法，定义二种链路质量控制模式，链路适配LA（link adaption） 和增量冗余IR（Incremental Redundancy）。 LQC特点 估算链路质量 选择MCS 分割,Link Quality Control (