Page 95 - Kaleidoscope Academic Conference Proceedings 2021

Connecting physical and virtual worlds

to replace the batteries weekly. 2) The functionality of the
nodes in LPWAN is limited. The computational and storage
capabilities of the nodes in LPWAN are very weak and require
special attention in the system design.

Figure 2 – Prototype structure of experimental node

1) Node. This node is used for Bluetooth communication
between LPWA wireless communication modules and
Figure 1 – System architecture smartphones, etc. A BLE microcomputer and a commercially
available microcomputer were used. After running the
The goal of the points transfer system is the points
validation phase, we plan to run with only the LPWA module
payment implemented in normal day/disaster situations.
and the BLE microcomputer to reduce power consumption.
The objective of this paper is to optimize the packets
2) Payment operation terminal. The payment operation
transmission for the ledger-based points transfer system
terminal is planned to be installed in a smartphone, but
in LPWAN. From a technical point of view, this paper
considering the complications such as review and price, we
provides distributed storage in a traceable manner and focuses
first developed a payment terminal using a commercially
on how to build a lightweight point transfer system in a
available microcomputer with a touch screen. The terminal
resource-constrained LPWAN network with a distributed
also has Bluetooth communication capability to communicate
ledger to ensure tamper-proof transaction data and improve
with distributed ledger nodes.
system trustworthiness. Figure 1 shows that a large number of
nodes with LPWA communication capabilities are installed in 3) Tag. For the private key tag, we built a prototype using
the corresponding areas, and these nodes are also used as relay a commercially available microcomputer with low power
terminals for storage/management and payment processing consumption and Bluetooth communication capabilities to
of the distributed ledger. When an operation such as a store the account ID and encryption key. It can communicate
payment request is performed on the user’s smartphone, the with a smartphone to send an encrypted account ID or with a
request is sent to the node as a ledger operation request node to check the balance.
and forwarded to the nearby nodes. Each node determines
whether it is a legitimate request by comparing it with its 4. SOLUTIONS: OPTIMIZING PACKET
own recorded ledger, and if it is legitimate, it broadcasts TRANSMISSION
it along with a ledger update proposal. Each node that
receives them determines whether the update proposal is 4.1 Previous work
appropriate by using a majority vote, and updates it if it
is. Even if unsuccessful, the update result is returned to
the customer’s smartphone. Payment is proven by showing
successful points transfers, the user can receive goods and
services. For example, if it is deployed in shopping areas,
etc., and nodes are set up in each participating store, it is
possible to operate local currency (points) without installing
a server to manage the whole system. We have also included
in the system design the use of "tags" to store private keys
to prove the legitimacy of accounts. With this mechanism,
even people without smartphones can make payments through
simple authentication.

Based on the system architecture in Figure 2, we designed
the experimental device that miniaturizes the hardware
and performs communication using LPWAN, which mainly
consists of three parts: node, payment operation terminals
and tags. Figure 3 – Ledger operation for LPWAN [3]

– 33 –