anatomy of radio lan onno w. purbo [email protected]
TRANSCRIPT
Comparisons DS modem more complicated, MAC
in DS much simpler. FH appears to be cheaper. BW sharing, DS tends to have
lower overhead on the air. DS vs. FH = religion war …
Diversity Diversity
Redudancy in the system to overcome noise and to increase the reliability of the system.
Antenna Diversity
Sensitivity Defined as
Point at 3% packet loss (400 byte packet in Gaussian channel).
7 dB worse if we use Raleigh channel + antenna diversity.
Normally –80 dBm, better –90 dBm.
Multi-rate system Better throughput more
bandwidth. The higher the signalling rate, the
shorter the distance.
IEEE 802.11a (OFDM) Orthogonal Frequency Division
Multiplex (OFDM). Using equalization in post
processing, overcome delay spread.
OFDM is pre-processing technique. Use in 5Ghz UNII Band.
Interference & Noise Fading
Variation in time. Microwave oven & other interferer. Forward Error Correction (FEC)
Not effective, better retransmit the packet.
Delay Spread