CS742: Advanced Internet: Global Data Communications

Measurement

Fog computing
using cloud computing for main computing workload, but put task that require more responsive calculation on the edge

• section

• package

• frame

• ACM Digital Library

• IEEE Xplore

• SpingerLink

• Science Direct(ELSEVIER)

• Wiley

• Taylor & Fracis

Decibels

Power ratios

10:1 = 10dB
1:1 = 0dB
100:1 = 20dB
1000:1 = 30dB
1:10 = -10dB

Approximately

1.25:1 = 1dB
2:1 = 3dB
4:1 = 6dB
8:1 = 9dB
1:4 = -6dB
32:1 = 15dB

Voltage ratios

10:1 = 20dB
1:1 = 0dB
100:1 = 40dB
1000:1 = 60dB
1:10 = -20dB

Approximately

2:1 = 6dB
4:1 = 12dB
8:1 = 18dB
1:4 = -12dB
32:1 = 30dB
1.4:1 = 1.5:1 = 3dB

example:
47527:1 this can be round up to 50000:1
which is $100,000\div 2 = 10^{5} * 2^{-2} = 50-3 dB = 47 dB$

• dBm, power compared to 1mW in dB

Feedline

• connect devices and their antenna

Antennas

• gain in dBi or dBd
• directionality
• polarization
• reciprocal
• Aperture

$path\ loss = \frac{(4\pi r)^{2}}{\lambda}$

$path\ loss(dB) = 10 \log_{10} \frac{(4\pi r)^{2}}{\lambda}$

$P_{RX} = \frac{P_{T}G_{T}G_{Rx}\lambda^{2}}{(4\pi r)^{2}}$