Amalinda Gamage

Publications | Talks | Teaching | Service

Hi, I'm Amalinda from Sri Lanka 🇱🇰. ආයුබෝවන්! (āyubōwan!)— Wishes you a long and prosperous life in Sinhalese.

I am fortunate to be a PhD student advised by Professor. Mo Li. I joined NTU Singapore in 2017. Prior to that, I was an assistant lecturer to SLIIT and UNIVOTEC in Sri Lanka. I'm a also an elected member of The Institution of Engineers, Singapore (IES), the Singapore signatory to the Washington Accord.

Central to my interests is Wireless Communication. Specifically, physical layer tricks that enhance the co-existance & fairness of LPWANs. My current work is focused on bringing improvements to LoRa— a low-power LOng RAnge communication protocol for the Internet of Things. My interests also deeply span across several closely related fields. These involve having fun with UNIX systems, networking tricks and software defined radios.

The absent ability to perform carrier-sense on off-the-shelf LoRa end devices has impeded studies and implementations of the suitable Carrier-Sense Multiple Access (CSMA) schemes for LoRa. Currently, the LoRa networks, including those organized in an ad-hoc manner or by following the LoRaWAN specification, adopt an ALOHA media access control (MAC) mechanism to access communication mediums defined by radio frequency and the spreading factor (SF) of the chirp spread spectrum (CCS) modulation. Although ALOHA allows a simple network implementation, it is not competent with keeping up with the increasing demand of IoT devices added to the ISM band. For this reason, even though devices may conform to channel usage limitations (e.g., 0.1% or 1% duty cycle in Europe), the ALOHA-based LoRa networks will have degraded network performance due to massive collisions when the numbers of end devices grow sharply in this era of IoT.

In addition to the conference publicatiom, the TOSN extention looks into the following—

1. Quantifying limitations of RSS-CSMA for LoRa.
2. Highliting why LMAC enhances low SNR capabilities.
3. Interoperability considering gradual adoption and co-existance of CSMA with ALOHA.
4. Regulatory implications & workarounds.

Project Website | MobiCom 5min pitch

Long Range (LoRa) is a Low-power Wide-area Network technology designed for the Internet of Things. In recent years, it has gained significant momentum among industrial and research communities. Patented by Semtech, LoRa makes use of chirp spread spectrum modulation to deliver data with promises of long battery life, far-reaching communication distances, and a high node density at the cost of data rate. In this article, we conduct a series of experiments to verify the claims made by Semtech on LoRa technology. Our results show that LoRa is capable of communicating over 10km under line-of-sight environments. However, under non-line-of-sight environments, LoRa’s performance is severely affected by obstructions such as buildings and vegetations. Moreover, the promise of prolonged battery life requires extreme tuning of parameters. Last, a LoRa gateway supports up to 6,000 nodes with PRR requirement of >70%. This study also explores the relationship between LoRa transmission parameters and proposes an algorithm to determine optimal settings in terms of coverage and power consumption under non-line-of-sight environments. It further investigates the impact of LoRa Wide-area Networks on energy consumption and network capacity along with implementation of a LoRa medium access mechanism and possible gains brought forth by implementing such a mechanism.

In areas where the habitats of elephants and humans are rapidly encroaching on each other, real-time monitoring of the elephants’ locations has the potential to drastically improve the co-existence of elephants and humans, resulting in reduced deaths in both groups. However, as tagging (using GPS collars) elephants to obtain such location information is difficult and costly, it is important to ensure very long lifetimes of the tags, which can only be achieved using energy harvesting.
In this paper, we present a kinetic energy harvester that uses magnetic levitation and ferro fluid bearings to generate energy from an elephant’s movements. In order to determine the feasibility of using this kinetic energy harvester for powering the tags on elephants, we obtained real acceleration data collected from an Asian elephant over a 10 day period, and this data was then used to tune the system to maximize the harvested energy. Using experimentally validated analytical and simulation models, and the actual elephant acceleration data, we find that our prototype can generate 88.91J of energy per day. This energy is not only sufficient to power the tags to acquire and transmit locations 24 times a day to a distance of 114km (line of sight), but provides a surplus of at least 35.40J, which can be used to increase the frequency of position updates or to support alternative communication options such as GPRS. Therefore, this shows the viability of long-term tracking of elephants.