ECEN4533 Data
Communications
Lecture #18 21 February 2011
Dr. George Scheets
ECEN4533 Data
Communications
Lecture #19 23 February 2011
Dr. George Scheets
ECEN4533 Data
Communications
Lecture #20 25 February 2011
Dr. George Scheets
255 point zero mean discrete
time
White Noise waveform
(Adjacent points are independent)
Autocorrelation Estimate
of zero mean
Discrete Time White Noise
255 point Noise
Waveform
(Low Pass Filtered White Noise)
Autocorrelation Estimate of Low Pass Filtered White Noise
Autocorrelation in ATM Cell
Stream
Each cell slot randomly On or Off (Empty)
Autocorrelation in ATM Cell
Stream
On & Off bursts average 20 cells
Queue Size: σ2
= 5.8 vs σ2 = 2.9
ρ = 0.99
Queue Size: Correlated vs
Uncorrelated
σ2 = 4.93 & ρ = 0.99
Statistical Multiplexed Packet Switch
Exponentially Distributed
Inter-Arrival Time
(Not a good fit to real world traffic)
Exponentially Distributed
Packet Length
(Somewhat decent fit to real world traffic)
Classical M/M/1 Queuing Theory