| FH systems use a radio carrier that “hops” from frequency to frequency in a pattern known to both transmitter and receiver |
DS systems use a carrier that remains fixed to a specific frequency band. |
| A,broad,slice,of,the,bandwidth,spectrum,is,divided,into,many,possible,broadcast frequencies. |
The data signal is spread onto a much larger range of frequencies (at a much lower power level) using a specific encoding scheme. |
| Frequencies are randomize |
Frequency is constant |
| Data is constant |
Data are randomize |
| Resistance to noise |
Less resistant to noise |
| Limited throughput (2-3 Mbps @ 2.4 GHz) |
Much higher throughput than FH (11 Mbps) |
| Systm,generate wideband signals controlled by commanding the carrier frequency,(frequency hopping) |
Syestem,generate wideband signals controlled by the code is direct carrier,modeulation (direct sequence) |
| Frequency-hopping,devices,use,less,power,and,are,cheaper |
Performance of DS-CDMA systems is usually,better and more reliable. |
| FHSS are significantly less sensitive to Bluetooth interference. |
Though bandwidth efficiency decreases; reliability, integrity and security increase. |
| FHSS systems operate with SNR (Signal to Noise Ratio) of about 18 dB |
DSSS systems, because of the more efficient modulation technique used (PSK), can operate with SNR as low as 12 dB |
| FHSS spreads the signal by hopping from one frequency to another across a bandwidth of 83 Mhz. |
DSSS spreads the signal by adding redundant bits to the signal prior to transmission which spreads the signal across 22 Mhz |
| To some other receiver, FHSS appears to be a short-duration impulse noise. Thus, the data security increases |
To,some other receiver, DSSS appears as low-power, wideband noise and is,rejected. |
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