8:MIMO II:Capacity and Multiplexing Architectures ireless oundations System Question Should one blindly overlay MIMO technology on CDMA universal reuse systems? These systems operate at low SINR. MIMO gain is mainly receive antenna power gain. Having multiple transmit antennas may not be necessary. Interesting implication on the uplink:expensive to have many antennas at the mobile. However mobile antennas are useful for the downlink. They can also be used to suppress out-of-cell interference and provide diversity. Fundamentals of Wireless Communication,Tse&Viswanath 11
8: MIMO II: Capacity and Multiplexing Architectures Fundamentals of Wireless Communication, Tse&Viswanath 11 System Question • Should one blindly overlay MIMO technology on CDMA universal reuse systems? • These systems operate at low SINR. • MIMO gain is mainly receive antenna power gain. • Having multiple transmit antennas may not be necessary. • Interesting implication on the uplink: expensive to have many antennas at the mobile. • However mobile antennas are useful for the downlink. • They can also be used to suppress out-of-cell interference and provide diversity
8:MIMO Il:Capacity and Multiplexing Architectures ECS Wireless F oundations Transceiver Architecture:V-BLAST AWGN coder w[m] rate R x[m] 文y[m .: H(m] Joint decoder : AWGN coder rate Rm Can get the performance gain by sending independent coded streams at each of the Tx antennas and joint ML decoding. ·Is this surprising? Question: How to get the d.o.f.gain even when streams interfere with each other? Fundamentals of Wireless Communication,Tse&Viswanath 12
8: MIMO II: Capacity and Multiplexing Architectures Fundamentals of Wireless Communication, Tse&Viswanath 12 Transceiver Architecture: V-BLAST • Can get the performance gain by sending independent coded streams at each of the Tx antennas and joint ML decoding. • Is this surprising? • Question: – How to get the d.o.f. gain even when streams interfere with each other?
8:MIMO Il:Capacity and Multiplexing Architectures Vireless oundations Interference Nulling Focusing on Tx antenna 1: y=h1x1+∑hc+w i≠1 Simple strategy:null out the interference from other antennas. Fundamentals of Wireless Communication,Tse&Viswanath 13
8: MIMO II: Capacity and Multiplexing Architectures Fundamentals of Wireless Communication, Tse&Viswanath 13 Interference Nulling Focusing on Tx antenna 1: Simple strategy: null out the interference from other antennas
8:MIMO Il:Capacity and Multiplexing Architectures EECS Wireless Foundations Receiver Architecture 1: Bank of Decorrelators Decorrelator for stream I Decorrelator for stream 2 y(m] Decorrelator for stream n Fundamentals of Wireless Communication,Tse&Viswanath 14
8: MIMO II: Capacity and Multiplexing Architectures Fundamentals of Wireless Communication, Tse&Viswanath 14 Receiver Architecture I: Bank of Decorrelators