Spatial Locality inPocket Switched Networks

June 21st, 2016

Tekenate E. Amah*, Maznah Kamat*, Kamalrulnizam Abu Bakar*, Waldir Moreira†,¥, Antonio Oliveira-Jr‡, and Marcos A. Batista§

The 10th IEEE WoWMoM Workshop on Autonomic and Opportunistic Communications (AOC 2016) Coimbra, Portugal

*Dept. of Computer Science, Faculty of Computing, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia | †COPELABS, University Lusófona, Lisboa, Portugal | ¥PPGMO, Federal University of Goiás, Catalão, Brazil | ‡INF, Federal University of Goiás, Goiânia, Brazil | §IBiotec, Federal University of Goiás, Catalão, Brazil

Agenda

Introduction

Motivation

Methodology

Results

Towards locality aware PSN routing

Conclusions and Future work

Introduction

Ubiquitous portable handheld devices Portable handheld devices form the center of human communication today

1

Store Carry Forward (SCF) communication Communication via short-range wireless interfaces, user movement and opportunistic encounters

2

Pocket Switched Networks (PSNs) = Handheld devices + SCF Opportunistic networks formed by user devices for non-real-time communications

3

Presents a scalable and resource efficient solution for data transfer Urban: connecting major infrastructure | Developing regions: providing non-real-time connectivity

4

Motivation

User movement exhibits spatial locality Users show preference to certain geographical locations or districts more than others

1

Locality affects encounter and data transfer opportunities Lower locality presents more encounter opportunities, and vice versa

2

PSN routing strategies depend on encounter opportunities There is need to understand the impact of locality on routing performance in PSNs

3

The impact of locality on point-to-point communication in PSNs How does locality affect PSN routing and how can such routing benefit from locality awareness?

4

Methodology The Helsinki city area in the Opportunistic Network Environment (ONE) Simulator 3 scenarios: locality is increased by including more overlapping districts

Small scenario Low locality: 1 district

Medium scenario Medium locality: 4 districts

Large scenario High locality: 16 districts

Methodology

Simulation parameters

Parameter

Total simulation time (days)

Warm up period (days)

Wireless interface

Transmission range (m)

Transmission rate (Mbps)

Buffer size (Mb)

Value(s)

5

1

Bluetooth

10

2

100

Message size (Mb)

Message TTL (days)

Number of nodes

Ave. meg generation/node

0.5 to 1

1

19, 76 & 304

1 msg/hr

Results

Average delivery ratio

• Delivery ratio decrease • Unlimited replication increases

buffer overflow • Lower delivery ratio for destinations farther away

• Spraying mitigates the ‘slow start’ phase

Average overhead ratio

• Overhead ratio increase • Increased locality requires more

replicas to reach destinations • Unlimited replication increases

overhead • Spraying controls the number of

replicas

Average delivery delay

• Delay increase (except SnF) • Transitivity in the ‘focus’ phase

(in SnF) reduces delay • Transitivity incurs storage

overhead

Towards Locality-aware PSN Routing

PRoPHET-LA

• Highly active nodes forward messages traversing multiple

regions • Others forward messages within

their home region • PRoPHET-LA decreases average overhead by 57%

SnF-LA

• The optimal value of L varies over different degrees of locality • The value of L for a message

depends on the home proximity, p, of the source-destination pair • SnF-LA varies L according to

L = 2(p+1)

PRoPHET-LA2

• PRoPHET-LA2 nodes maintain only encounter information for neighbours from their home

region • 11% less delivery ratio, 84%

less overhead and 5% less delay, with 88% less encounter

information stored

Conclusions and Future Work

Performance degradation

PSN routing performance decreases over higher locality

Storage overhead

Storage overhead increases with network size

Locality awareness

Locality awareness complements existing routing strategies

Next steps

A measure for locality

A study of the concepts of locality

Validation of the synthetic movement scenarios

Effects of locality on routing fairness and energy consumption

Thank you

Acknowledgement: Thanks are due to Fundação de Amparo à Pesquisa do Estado de Goiás (FAPEG) and PNPD/CAPES.