From Outage Probability to ALOHA MAC Layer Performance Analysis in - - PowerPoint PPT Presentation

▶

Oct 01, 2023 207 likes •485 views

From Outage Probability to ALOHA MAC Layer Performance Analysis in Distributed Wireless Sensor Networks MEA. Seddik 1 , 2 , V. Toldov 2 , 3 , L. Clavier 1 , 3 , N. Mitton 2 1 IMT Lille-Douai, 2 Inria, 3 IRCICA USR CNRS 3380 WCNC18, 16 Apr,

SLIDE 1

From Outage Probability to ALOHA MAC Layer Performance Analysis in Distributed Wireless Sensor Networks

MEA. Seddik1,2, V. Toldov2,3, L. Clavier1,3, N. Mitton2

1IMT Lille-Douai, 2Inria, 3IRCICA USR CNRS 3380

WCNC’18, 16 Apr, Barcelona, Spain

1/27

SLIDE 2

Outline

Introduction: Wireless Sensor Networks (WSNs) Problem Statement & Outage Probability Slotted-ALOHA with Channel Reservation and Without Interferences Slotted-ALOHA with Channel Reservation and Interferences Experimental Analysis and Main Result

2/27

SLIDE 3

Introduction: Wireless Sensor Networks (WSNs)

3/27

SLIDE 4

Nowadays, WSNs are everywhere!

◮ Environmental applications. ◮ Home applications. ◮ Medical applications, etc.

4/27

SLIDE 5

LIRIMA PREDNET Project

◮ Even Rhinos need smartphones!

5/27

SLIDE 6

Challenges behind WSNs

◮ Keep the network up for several years (5-10 years). ◮ Generally the deployed architectures are distributed

⇒ Interferences! (partially responsible for the loss of energy).

6/27

SLIDE 7

To face these challenges

Two directions are natural:

◮ Use different sources of energy (solar for example). ◮ Optimizing the hardware and the software.

The software concerns essentially:

◮ The physical layers. ◮ The Medium Access Control (MAC) Layer.

In this work, we study:

◮ The influence of the MAC layer on the network performance. ◮ In particular, we address the following question:

How many channels do we need to achieve high performance distributed wireless sensor network?

7/27

SLIDE 8

Problem Statement & Outage Probability

8/27

SLIDE 9

MAC Protocol: Slotted-ALOHA

◮ Multiple nodes and a unique BTS. ◮ Distributed access policy ⇒ the nodes make the decision

(randomly) to transmit on their own (e.g. Slotted-ALOHA MAC protocol). Multiple nodes could choose the same channel ⇒ Interferences!

9/27

SLIDE 10

Interferences quantification: Outage Probability

The probability that the signal-to-interference-plus-noise-ratio (SINR) is less than a given threshold τ > 0, Op = P{SINR < τ}, where, SINR(o, r) = S(o, r)/(I(o) + N0).

10/27

SLIDE 11

Assumptions

◮ Πλ ⊂ R2 Homogeneous Poisson Point Process (HPPP)

spacial distribution of the nodes with density λ.

◮ The wireless channel consists of path loss attenuation with

no fading: ∀Xi ∈ Πλ, Pi = PeXi−α, where α, Pe > 0.

◮ The Medium Access Control strategy is a Slotted-ALOHA,

the communicating nodes have a density λ∗ s.t. λ∗ = 2Ts T 1 Nc λ.

11/27

SLIDE 12

Expression of Op

Proposition

The Outage probability for Slotted-ALOHA MAC protocol is given by the following expression: OpSA ≡ lim

N→+∞

1 N

IΣj

α >

ξ (λ∗π)α/2 (1) where I. is the indicator function, ξ = r−α

− N0

Pe and Σj

α = log

1 − Uj −α/2 +

+∞

 −kW0  − 1 k exp   log

(1 − Uj

k)k!

     

−α/2

12/27

SLIDE 13

Slotted-ALOHA with Channel Reservation and Without Interferences

13/27

SLIDE 14

MAC Protocol Description: Slotted-ALOHA with Channel Reservation (SACR)

Assuming N ∼ Poiss(µ =

Nn NtsNfc ), the reservation probability is

Rp = P{N = 0} = e−µ

14/27

SLIDE 15

SACR Strategy Illustration

15/27

SLIDE 16

Communicating Node States Modeling: Markov Chain

16/27

SLIDE 17

Communicating Node States Modeling: Markov Chain

Given its transition matrix Γ, the distribution over states is given by a stochastic row vector π s.t. π(k+1) = π(k)Γ and so π(k) = π(0)Γk, thus π∞ = π(0) limk→∞ Γk. In particular the success transmission likelihood is given by Txi =

k→∞ Γk

(1,4i)

17/27

SLIDE 18

Communicating Node States Modeling: Markov Chain

5 10 15 20 25 30 35 40 0.2 0.4 0.6 0.8 1 Number of nodes Txi’s

Tx1 Tx2 Tx3 Tx4 Fail

Figure 1: Curves of Txi’s.

18/27

SLIDE 19

Slotted-ALOHA with Channel Reservation and Interferences

19/27

SLIDE 20

When interfering nodes in the out range of the BTS

OpX0>R = P

Σα >

ξ (λ∗π)α/2

X0 > R
,

where R denotes the range of the BTS.

20/27

SLIDE 21

When interfering nodes in the out range of the BTS

10 20 30 40 0.2 0.4 0.6 0.8 1 Number of nodes Tx1

With interference Without interference

Figure 2: Comparison of the transmission success likelihood after one trial with no interfering nodes (in blue) and with interference (in black).

21/27

SLIDE 22

Experimental Analysis and Main Result

22/27

SLIDE 23

Experiment using Fit-IoT-Lab platform

23/27

SLIDE 24

Experiment details

Density of nodes λ = 1.7 · 10−6 Attenuation coeff. α = 2.2 Noise power N0 = −100dBm

Trans. power

Pe = 25dBm SINR thresh. τ = −10dB

Dist. node

r = 50m

Numb. nodes

Nn = 40

Numb. channels

Nc = 5

Numb. time-slots

Nts = 4

24/27

SLIDE 25

Theory vs Experiments

5 10 15 20 25 30 35 40 0.2 0.4 0.6 0.8 1 Number of nodes Tx1

Experimental Tx1 (5 experiments) Mean of Experimental Tx1 Theoretical Tx1

Figure 3: Comparison between the theoretical transmission likelihood and its practical estimation for 20 channels. Best view in color.

25/27

SLIDE 26

Main result: How many channels do we need to a achieve high performance distributed wireless sensor network?

20 40 60 80 100 50 100 150 NfcNts = 80 Nn = 60 Number of nodes Number of channels

Tx1 = 0.93 Tx1 = 0.97 Tx1 = 0.98 Tx1 = 0.99

Figure 4: Transmission success likelihood in terms of number of nodes in the network and number of channels assuming the presence of interfering nodes in the out range of the BTS.

26/27

SLIDE 27

Thank you for your attention!

27/27