Delay-Spread ISI Immune Communications: Guard Interval 2/6 No guard interval insertion F = 1/T Symbol occupancy FT = 1 No symbol rate loss Still some ISI which can be reduced by reducing F, or equivalently, increasing T = 1/F or equivalently, increasing the number of subcarriers N = w/F ISI immune communications Perfectly ISI immune communications T = 1/F+Tg FT > 1 Symbol rate loss Symbol rate loss reduced by reducing F, or equivalently increasing N Geneva, Switzerland, 18 September 2013 16