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

House Tablet (Aakaash) 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 Tablet (Aakaash) School Community centre 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 real time 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 LitMAC WiFi LitMAC WiFi Ethernet Root Infra1 Ethernet Infra2 Ethernet Infra3 Ethernet CSMA WiFi CSMA WiFi CSMA WiFi Aakash Tablet Aakash Tablet Aakash Tablet

Performance Results

Aakash 1 Aakash 2 Aakash 3 TCP throughput

3.72 Mbits/s

UDP throughput,

4.15 Mbits/s,

jitter, packet loss

3.812ms, 0% 3.54 Mbits/s 4.09 Mbits/s 3.653ms, 0.047% 3.49 Mbits/s 4.10 Mbits/s, 3.549ms, 0%

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