TECHNICAL UNIVERSITY OF CRETE

DEPARTMENT OF ELECTRONICS & COMPUTER ENGINEERING

Laboratories of Telecommunications and Information & Computer Networks

THESIS TITLE 

“Energy-Conserving Access Protocols for Transmitting Data in Unicast and Broadcast Mode”

 Papadimitriou Ioannis

  Supervisor : Prof. Paterakis Michael

Select Committee : Prof. Maras Andreas Prof. Triantafyllou Panagiotis

AIDC (Automatic Identification & Data Capture) systems  

    Very large number of tags

    Small-size and low-cost tags

 Repeated recharge/replacement of battery not feasible 

1. Introduction 1 / 1

Problem of energy saving

2. Problem Definition 1 / 1

Unicast/Broadcast packets from base station to tags Requirements :              Minimization of packet delays             Energy conservation Approach :

             Wake-up schedule at tags (“pseudo-random”)             Transmission (of packets) scheduling strategy

3. Metrics 1 / 1

Average total (Unicast/Broadcast) packet delay E(D)

Quotient of standard deviation to average total

(Unicast/Broadcast) packet delay σD / E(D)

Throughput of an algorithm

(Maximum arrival rate of packets λmax)

4. Broadcasting Case 1 / 6

Algorithms’ description :

A) FCFS (First Come First Served)

Examination of packets according to their “age”

Worst performing algorithm – Wasted slots

Analytical performance evaluation

B) FCFS-NES (First Come First Served with No Empty Slots)

No wasted slots (examination of next packet)

4. Broadcasting Case 2 / 6

Algorithms’ description (cont’d) :

C) MDFm (Most Destinations First)m

Examination of m oldest packets

Transmission of the one with most destinations awake

Better usage of each time slot

D) (DxW)m

Examination of m oldest packets

Transmission of the one with maximum DxW, where

D : number of packet’s destinations, W : the “age” of packet

Better usage of each time slot + fairness

4. Broadcasting Case 3 / 6

Algorithms’ description (cont’d) :

E) P-MDFm and P-(DxW)m (Preemptive MDFm and (DxW)m)

Modified versions of MDFm and (DxW)m

While examining the m oldest packets, if one is found that can be

transmitted to all tags that have not received it yet, then this

packet is selected for transmission during the current slot

No additional delay for a packet that can be deleted from base

station’s queue

4. Broadcasting Case 4 / 6

0

100

200

300

400

500

0.045 0.05 0.055 0.06 0.065 0.07 0.075 0.08 0.085λ ( p a c k e t s / s l o t )

Avg.

Tot

al D

elay

per

Pac

ket (

slot

s)

20

25

30

35

40

45

50

55

60

0.01 0.015 0.02 0.025 0.03 0.035 0.04

λ ( p a c k e t s / s l o t )

Avg.

Total

Dela

y per

Pac

ket

(slot

s)

F C F SF C F S - N E SM D FD x WP - M D FP - D x W

Experimental results:

Average total packet delay (slots) vs. λ (packets/slot)

          

Figure 4.1

(N=500 , p=0.3 λmax , FCFS = 0.051164 )

4. Broadcasting Case 5 / 6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08λ ( p a c k e t s / s l o t )

Sta

ndar

d D

evia

tion

/ Avg

. Tot

al D

elay

pe

r P

acke

t

F C F SF C F S - N E SM D FD x WP - M D FP - D x W

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.1 0.3 0.5

p

Thro

ughp

ut (p

acke

ts/s

lot)

F C F SF C F S - N E SM D FD x WP - M D FP - D x W

Experimental results (cont’d):

Quotient of standard deviation to average total packet delay

vs. λ (packets/slot)

Throughput of an algorithm λmax (packets/slot) vs. p

Figure 4.2 Figure 4.3

4. Broadcasting Case 6 / 6

Table 4.1

λ E(D) E(D)

0.01 22.7259976 m=2 23.00567503 0.015 24.19113293 m=2 24.81310925

0.02 25.83446155 m=2 26.90916624 0.025 27.93081583 m=2 29.37240403

0.03 30.14109566 m=2 32.1312979 0.035 33.70370171 m=2 35.790351

0.04 37.25655934 m=2 39.86206528 0.045 41.77802122 m=3 45.81274952

0.05 49.08870276 m=3 51.54672355 0.055 57.49063054 m=4 60.83074876

0.06 68.83096612 m=7 71.46693149 0.065 84.95033986 m=7 86.80265565

0.07 106.1375847 m=19 107.7482882 0.075 130.949096 m=35 134.6145136

0.08 175.3448291 m=42 179.926471 0.085 252.4292312 m=78 260.5292946

m

The parameter m:For the algorithms MDFm, (DxW)m, P- MDFm, and P- (DxW)m there is an optimum value of m for each value of λ (giving the minimum average total delay), which increases with λ.(Table 4.1 : algorithm P-(DxW)m , maximum improvement 9%)

5. Mixed case Unicasting-Broadcasting 1 / 6

Percentage of Broadcast packets higher than Unicast

Higher priority for Unicast packets

Uniform distribution for destinations of Unicast packets

5. Mixed case Unicasting-Broadcasting 2 / 6

Algorithms’ description :

A) FCFS (First Come First Served)

Unicast/Broadcast packets stored in common buffer

Packets are examined according to their “age”

Worst performing algorithm – Wasted slots

Analytical performance evaluation

B) FCFS-NES (First Come First Served with No Empty Slots)

Unicast/Broadcast packets stored in common buffer

No wasted slots (examination of next packet)

5. Mixed case Unicasting-Broadcasting 3 / 6

Algorithms’ description (cont’d) :

C) 2L-(FCFS-NES) (Two Lists – First Come First Served with No Empty Slots)

Two different buffers for Unicast/Broadcast packets

Higher priority for Unicast packets

FCFS-NES algorithm is applied to Broadcast list of packets

D) 2L-[P-(DxW)m] (Two Lists – Preemptive (DxW)m)

Two different buffers for Unicast/Broadcast packets

Higher priority for Unicast packets

P-(DxW)m algorithm is applied to Broadcast list of packets

5. Mixed case Unicasting-Broadcasting 4 / 6

10

100

1000

0.01 0.03 0.05 0.07 0.09 0.11 0.13 0.15λ ( p a c k e t s / s l o t )

Avg.

Tot

al D

elay

per

Bro

adca

st

Pack

et (s

lots

)(lo

garit

hmic

sca

le)

F C F S

F C F S - N E S

2 L - ( F C F S - N E S )

2 L - ( P - D x W )

1

10

100

1000

0.01 0.03 0.05 0.07 0.09 0.11 0.13 0.15λ ( p a c k e t s / s l o t )

Avg.

Tot

al D

elay

per

Uni

cast

Pa

cket

(slo

ts)

(loga

rithm

ic s

cale

)

F C F S

F C F S - N E S

2 L - ( F C F S - N E S )

2 L - ( P - D x W )

Experimental results:

Average total Unicast packet delay (slots) vs. λ (packets/slot)

(Ν=500 , p=0.5 , Χ=0.3)

Average total Broadcast packet delay (slots) vs. λ (packets/slot)

 Figure 5.1 Figure 5.2

5. Mixed case Unicasting-Broadcasting 5 / 6

0.5

0.7

0.9

1.1

0.01 0.03 0.05 0.07 0.09 0.11 0.13 0.15

λ ( p a c k e t s / s l o t )

Stan

dard

Dev

iatio

n / A

vg.

Tota

l Dela

y per

Uni

cast

Pa

cket

F C F S

F C F S - N E S

2 L - ( F C F S - N E S )

2 L - ( P - D x W )

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.01 0.03 0.05 0.07 0.09 0.11 0.13 0.15λ ( p a c k e t s / s l o t )

Stan

dard

Dev

iatio

n / A

vg. T

otal

De

lay

per B

road

cast

Pac

ket

F C F S

F C F S - N E S

2 L - ( F C F S - N E S )

2 L - ( P - D x W )

Experimental results (cont’d):

Figure 5.3 Figure 5.4

Quotient of standard deviation to average total Unicast packet

delay vs. λ (packets/slot)

Quotient of standard deviation to average total Broadcast packet delay

vs. λ (packets/slot)

5. Mixed case Unicasting-Broadcasting 6 / 6

1

10

100

1000

0.01 0.03 0.05 0.07 0.09 0.11 0.13 0.15

λ ( p a c k e t s / s l o t )

Avg.

Tot

al D

elay

per

Pac

ket

(slo

ts)

(loga

rithm

ic s

cale

)

F C F S

F C F S - N E S

2 L - ( F C F S - N E S )

2 L - ( P - D x W )

0

0.05

0.1

0.15

0.2

0.25

(0.1,0.1) (0.1,0.2) (0.1,0.3) (0.2,0.1) (0.2,0.2) (0.2,0.3) (0.3,0.1) (0.3,0.2) (0.3,0.3)

p , X

Thro

ughp

ut (p

acke

ts/s

lot)

F C F S

F C F S - N E S

2 L - ( F C F S - N E S )

2 L - ( P - D x W )

Experimental results (cont’d):

Average total packet delay (slots) vs. λ (packets/slot)

E(D)=X*E(Du)+(1-X)*E(Db)

Throughput of an algorithm λmax (packets/slot) vs. (p , Χ)

  Figure 5.5 Figure 5.6