Precoding and Bandlimited Signals 2.6 2001/06/20 2004/01/07 10:09:28.728 US/Central Behnaam Aazhang aaz@ece.rice.edu Dinesh Rajan dinesh@ece.rice.edu Mohammad Jaber Borran mohammad@ece.rice.edu Behnaam Aazhang aaz@ece.rice.edu Shawn Stewart mrshawn@alumni.rice.edu Roy Ha rha@rice.edu intersymbol interference ISI maximum likelihood sequence detector precoding A description of various ways to deal with the problem of intersymbol interference which occurs in bandlimited channels.

Precoding The data symbols are manipulated such that y k k T a k u 0 ISI ν k T

Design of Bandlimited Modulation Signals Recall that modulation signals are X t n a n s t n T We can design s t such that u n T large n 0 zero or small n 0 where y k T a k u 0 n a n u k T n T ν k T (ISI is the sum term, and once again, n k .) Also, y n T s g h opt n T The signal s t can be designed to have reduced ISI.

Design Equalizers at the Receiver Linear equalizers or decision feedback equalizers reduce ISI in the statistic y t

Maximum Likelihood Sequence Detection y k T n a n k T n T ν k T By observing y T , y 2 T , … the date symbols are observed frequently. Therefore, ISI can be viewed as diversity to increase performance.