Sine wave: y = A sin(2πf t), t = time in seconds, f =
frequency in Hertz (cycles/sec), A = amplitude
Square wave: y = sin(2πf t) +
1/3 sin(2π(3f)t) + 1/5 sin(2π(5f)t) + 1/7
sin(2π(7f)t) + ...
Decibels: 10 log10 Pout/Pin
| decibels |
ratio |
| 10 dB |
10× |
| 20 dB |
100× |
| 3 dB |
2× |
| 5 dB |
~ 3× |
| 6 dB |
4× |
| 7 dB |
5× |
Nyquist: C = 2B log2 M
Shannon: C = B log2 (1+SNR)
B = bandwidth, C = max data rate, M = # of signal levels, SNR = signal-to-noise ratio
Thermal noise: N0 = kT, T in Kelvins, N0
in Watts/Hz, k = 1.38 x 10-23 J/K; channel noise = N0 × band_width
NRZ: 0=high, 1=low
NRZI: 0 = no transition, 1 = transition
Manchester: NRZI alternating with transitions due to the clock signal
Bipolar-AMI: 0-bit = signal level of 0, 1-bit = alternating positive and negative signal levels for successive 1-bits
B8ZS: same as bipolar, but 0000 0000 is replaced by 000+−0−+ or 000−+0+−, depending on whether previous 1-bit was + or −.
HDLC:
RR: ACK, Receiver Ready for more
RNR: ACK, Receiver not ready for more
RR-P: poll packet sent by sender to elicit Receiver’s current RR/RNR
TDM
DS0: 64kbps voice line
DS1: 24 DS0’s plus 1 bit
DS2: 4 DS1’s plus bit-stuffing (pulse-stuffing) room
DS3: 7 DS2’s / 28 DS1’s, plus bit/pulse stuffing room
STS-1: 51.84 Mbps
STS-N: N × STS-1, exactly
GRCA(T,tau): Avg time T between packets, tau = variation
Suppose current cell is expected at time tat, and actually arrives at t
Case 1: t < tat - tau (too EARLY): NONCONFORMING; do not change tat
Case 2: t >= tat - tau: CONFORMING; newtat = max(t,tat) + T