成都信息工程学院现代通信原理电子课件第十一章 通信新技术（OFDM、MIMO）.ppt

Multiple-Input-Multiple- Output (MIMO) Systems Basic principles, Algorithms and Networking Applications Topics Motivations for the development of MIMO systems MIMO System Model and Capacity Studies Design Criterion for MIMO Systems (Diversity Vs Spatial Multiplexing) Some actual architectures based on these criterion MIMO-OFDM Networking Applications: MAC protocol for MIMO PHY layer Conclusions Aspirations High data rate wireless communications links with transmission rates nearing 1 Gigabit/second (will quantify a “bit” shortly) Provide high speed links that still offer good Quality of Service (QoS) (will be quantified mathematically) Aspirations (Mathematical) of a System Designer High data rate Antenna Configurations Single-Input-Single-Output (SISO) antenna system MIMO Antenna Configuration Use multiple transmit and multiple receive antennas for a single user Data Units Will use the following terms loosely and interchangeably, Bits (lowest level): +1 and -1 Symbols (intermediate): A group of bits Packets (highest level): Lots and lots of symbols Shannon’s Capacity (C) Given a unit of BW (Hz), the max error-free transmission rate is C = log2(1+SNR) bits/s/Hz Define R: data rate (bits/symbol) RS: symbol rate (symbols/second) w: allotted BW (Hz) Spectral Efficiency is defined as the number of bits transmitted per second per Hz R x RS bits/s/Hz W As a result of filtering/signal reconstruction requirements, RS ≤ W. Hence Spectral Efficiency = R if RS = W If I transmit data at a rate of R ≤ C, I can achieve an arbitrarily low Pe Spectral Efficiency Spectral efficiencies of some widely used modulation schemes MIMO System Model Types of Channels Fading Channels Fading refers to changes in signal amplitude and phase caused by the channel as it makes its way to the receiver Define Tspread to be the time at which the last reflection arrives and Tsym to be the symbol time period Channel Matrix H In addition, assume slow fading M