長庚大學無線通訊實驗室 MIMO - A solution for advanced wireless access 指導老師：黃文傑 博士 學生：吳濟廷

OUTLINE Introduction Fundamentals of MIMO system Channel Capacity of MIMO system compares to SIMO and MISO Conclusion

Single-Input Multi-Output Conventional transceiving scheme (fixed beam) Smart antenna (focused beam) ~ uplink Reduce interference/extended coverage range Small battery size

Multi-Input Single-Output Transmit diversity Easier in reality Smart antenna ~ downlink

Multi-Input Multi-Output Multi-Input Multi-Output scheme Utilize the space-time signal processing to obtain the maximum gain

MIMO The use of multiple antenna at both ends of a wireless link Has the ability to exploit the multi-path scattering Good solution for bandwidth hungry wireless applications Frequency and time processing are at limits

Fundamentals of MIMO Multi-path rich environment in antenna array => Independent fading Extended to both ends => independent path

Fundamentals of MIMO Increasing spectral efficiency N times Linear increasing between capacity and antenna elements N Tx antennas N Rx antennas N parallel channels

Channel capacity SISO x(t) h(t) y(t) x(t): transmitted signal y(t): received signal h(t): channel response n(t): noise (AWGN,  2 ) y(t) = h(t) x(t) + n(t) Signal to noise ratio : Channel capacity :

MIMO channel coefficients x(t) h(t) y(t) ….. …... where i = transmit antenna # j = receive antenna # N Tx antenna N Rx antenna

Receive diversity Channel capacity : [bit/(Hz·s)] H=[ ] total Tx power average Rx power

Transmit diversity Channel capacity : [bit/(Hz·s)] Capacity increases logarithmically with number of transmit antennas total Tx power average Rx power

MIMO (2Tx-2Rx) x(t) h(t) y(t) ….. …... Channel capacity : total Tx power average Rx power

Channel capacity Matrix rank has relation to channel # Gain = eigenvalue of HH* => GG* In order to creat n parallel channel => matrix G must be at least rank n Rx antenna # Tx antenna #

ill-conditioned High rank has to be derived by independent fading Can’t guarentee decorrelation in rich multipath environment Lowest gain

MIMO channel capacity Each individual channel capacity Overall MIMO channel capacity Capacity increases linearly with number of antennas min(, )

Conclusion MIMO could provide capacity increasement linearly with antenna # MIMO could combine other techniques to arise gain (space-time code,BLAST)