Scheduling and sequencing, del 3

Question 1

Four characteristics of queuing systems (waiting line systems):

Answer 1

• The manner in which customers arrive
• The time required for service
• The priority determining the order of service
• The number and configuration of servers in the system

Question 2

Describe the arrival of customers and arrival pattern

Answer 2

It is often a random event, random variable. The pattern is a poisson processs

Question 3

Describe poisson process

Answer 3

• Non-negative
• Discrete
• Typically not suitable when lambda >20

Rule of thumb: Normal distrb. Approx.. Poisson when lambda >= 12

Question 4

Describe service time and service time pattern

Answer 4

Service time is also a random variable, and the pattern is exponential distribution.

Question 5

How can we describe various queuing systems?

Answer 5

By three part code of the form A/B/k where Symbols used for A and B are:

M = Markov distributions (poisson / exponential)
D = deterministic (constant)
G = general distribution (with a known mean and variance)

Question 6

Vad står A/B/k för?

Answer 6

A = arrivals pattern
B = service times pattern
k = antal servers som jobbar med identisk service rates

Question 7

Vad är detta för system som refereras till? M/M/k

Answer 7

ett system där arrivals händer enligt Poisson distribution, service times följer en exponentiell distribution och det finns k servers som jobbar med identisk service rates

Question 8

Beskriv M/M/1 queuing system

Answer 8

Single channel
* Poisson arrival-rate distribution
* Exponential service-time distribution
* Unlimited maximum queue length
* Infinite calling population
* Examples: Single-window theatre ticket sales booth, Single-scanner airport security station