Compare DSSS and FHSS

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written 7.1 years ago by

• modified 5.6 years ago

DSSS	FHSS
Def:- PN sequenceof large bandwidth is multiplied with narrow band information signal.	Def:- Data bits are transmitted in different frequency slots which are changed by PN sequence.
Chip rate = $\frac{1}{T_c}$	Chip rate(R_c) = max($R_P , R_S$)
Application with large multipath delays: DS represents a reliable mitigation method as such system render all multipath signal copies that are delayed by morethan one chip time from direct signal as invisible to the receiver.	FH system can provide the same mitigation only if the hopping rate is faster than symbol rate and if the hopping bandwidth is larger.
For commercial applications implementation of DSSS radios with large gap can also be costly due to need of high speed circuits.	Implementations of FHSS radio can be costly and complex due to need of high speed frequency synthesizers.

Error will appear in pairs in DEPSK.

Consider given information system d(t) = 1 0 1 1 0 1

b(t) = 1 1 0 1 1 0 transmitted b(t)

b(t) = 1 1 0 1 1 0 received without any error

b(t - $T_b$) = 0 1 1 0 1 1

d(t) = b(t) $\oplus$ b(t - $T_b$) = 1 0 1 1 0 1

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