Delay Spread(cont.)
Table shows the typical delay spread that can occur in various environments. The
maximum delay spread in an outdoor environment is approximately 20usec, thus
significant inter symbol interference can occur at bit rates as low as 25kbps.
Environment or cause Delay Spread Maximum Path Length Difference
Indoor (room) 40nsec - 200nsec 12m - 60 m
Outdoor 1usec - 20usec 300m - 6km
Inter-symbol interference can be minimized in several ways. One method is to reduce
the symbol rate by reducing the data rate for each channel (i.e. split the bandwidth into
more channels using Orthogonal Frequency Division Multiplexing). Another is to use a coding
scheme which is tolerant to inter-symbol interference such as CDMA.