Village Communication Network
Leveraging on Fibre to the Village
Researcher: Vishal Sevani
Faculty: Bhaskaran Raman, Abhay Karandikar
TCOE IITB
Researcher: Jyoti Purohit
Faculty: Ashok Jhunjhunwala
TCOE IITM
Motivation: Rural Broadband Scenario
Tablet
(Aakaash)
House
Fibre optic
access
close to
village:
~5km
Community
centre
Tablet
(Aakaash)
School
Village: 2-3km
diameter
Need: cost effective last mile connectivity
Applications: rural education, healthcare, IT services
Solution Choices
• Running cables
High cost
• WiMAX, LTE
High cost
Requirement of tall
tower
High power
consumption
• Wi-Fi based network
License free band
Low equipment cost
Low power
consumption: <10W,
solar power possible
Long-Distance WiFi versus WiFi Mesh
High cost of tall tower
Hidden terminal issues
Fault tolerance issues
“On the Feasibility of the Link Abstraction in (Rural) Mesh Networks”, D.
Gokhale, S. Sen, K. Chebrolu, and B. Raman, INFOCOM 2008
Insight: outdoor mesh network links can be stable, TDMA MAC feasible
Solution Choices
• Running cables
High cost
• WiMAX, LTE
High cost
Requirement of tall
tower
High power
consumption
• Long-distance WiFi
High cost of tower
• Wi-Fi based multi-hop
mesh network
License free band
Low equipment cost
Low power
consumption: <10W,
solar power possible
Low cost installation on
light poles, roof-tops
Self configurable
Potential to enable
“sustainable village
franchise” model
Solution Approach: WiFi Mesh
(1) Low-cost commodity WiFi hardware
(2) WiFi-PHY based link
Fibre optic
access
close to
village:
~5km
(3) Multi-hop
mesh network
running
TDMA-based
LiT MAC
Tablet
(Aakaash)
House
Community
centre
Tablet
(Aakaash)
School
Village: 2-3km
diameter
Technical Challenges and Solution
• Commodity Wi-Fi has CSMA/CA
• Poor performance in multi-hop mesh
• Poor throughput, delay: cannot support realtime applications
• Solution: TDMA-based MAC called LiTMAC
– Light-weight TDMA MAC
Accomplishments
• Implementation of TDMA based LiTMAC
protocol for WiFi-PHY based mesh network
– Modifications to open source ath9k driver
– Testing and bug-fixing of LiTMAC implementation
– Code runs stably for long durations of time
– Implementation of the per-hop ack: performance
improvement in presence of wireless packet losses
• Ported the software on the low cost Ubiquiti
bullet M2HP platform
• Testing the solution in lab setting & test
deployment
Performance Evaluation Setup
LitMAC WiFi
Ethernet
Root
LitMAC WiFi
Infra1
Ethernet
CSMA
WiFi
LitMAC WiFi
Infra2
Ethernet
Ethernet
CSMA
WiFi
Aakash
Tablet
Infra3
Aakash
Tablet
CSMA
WiFi
Aakash
Tablet
Performance Results
Aakash 1
Aakash 2
Aakash 3
3.72 Mbits/s
3.54 Mbits/s
3.49 Mbits/s
UDP
4.15 Mbits/s,
throughput,
4.09 Mbits/s
4.10 Mbits/s,
3.812ms,
3.653ms,
3.549ms,
0%
0.047%
0%
TCP
throughput
jitter,
packet loss
Future Work
• Other features in LiTMAC implementation
– Ease of configuration of various LiTMAC parameters
– Dynamic routing, dynamic scheduling
• Identify solar-power solution for the WiFi nodes
• Detailed field deployment evaluation of LiTMAC
in rural settings
• Identify any modifications required in LiTMAC to
further improve the efficiency
• With LiTMAC code, run pilot commercial
network, in co-operation with ISP to provide
broadband Internet connectivity