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This research aims to develop a system that integrates the IEEE 802.11 network and LoRa WAN in developing a wireless sensor network (WSN) in an area without public communication infrastructure. The sensor nodes were developed using ESP 8266 Node MCU with embedded IEEE 802.11 module and the sink was developed using Raspberry Pi minicomputer with LoRa module. The frames sent by sensor nodes were classified into regular data and critical data. The sensing data is forwarded by the sink to the nearest location with internet access using LoRaWAN according to their priority. Each node sent its regular frames with an interarrival time that varies from 30 seconds to 3 minutes and critical frames with an interarrival time of 1 to 5 seconds. The result shows that the delay of the network sending solely regular frames varies from 16.4 s to 602 and the delay of the network sending solely critical frames varies from 0.32 t0 1 s. When some nodes in the network send the regular frames and the other nodes send the critical frames, the delay of the regular frames drops to 1.25-1.75 s. The packet delivery rate of the system is 100%.

Visual cryptography (VC) technique encodes an image into two or more shares that appear random in human eyes. In the decryption section, the pixels in the shared images are combined to obtain the information contained in the original image. This study applies visual cryptographic techniques to graysle and color images for user authentication in online transactions using the VC2,2 scheme. The server computer encodes the CAPTCHA image into two shared images that are sent to the user through different channels or applications. To authenticate himself, the user performs an XOR operation on both share images, identifies the information contained in the CAPTCHA and sends it to the server. In encryption test, histogram of the share image has a different pattern from the original image. The description test shows the decrypted image in this study visually has a better quality than the binary image has better quality than binary images.

Internet of Things (IoT) is the interconnection of several devices that have specific tasks such as sensing and control. The services in the system can be in the form of one device - one service, many devices - one service, one device -many services, and many devices - many services. A communication protocol is agreed upon by the devices in the IoT system to ensure the success of data transactions. These protocols include MQTT, HTTP, AMQP, XMPP, Web Shocket, and COAP. This study compares the performance of the COAP and HTTP protocols in consideration of the number of transactions and energy consumption. The scenario used is to send RSSI data and battery level. The scenarios also use two modes of transmission power:14dBm and 20dBm. The results show that the COAP protocol is 25 times more efficient than the HTTP protocol for a 20dBm transmit power scenario, while for a transmit power of 14dBm COAP is 61 times &nbsp, Internet of Things (IoT) merupakan interkoneksi beberapa perangkat yang memiliki tugas tertentu misalnya penginderaan dan control. Layanan dalam sistem tersebut tersebut dapat berupa satu perangkat satu layanan, multi perangkat satu layanan, satu perangkat multi layanan, dan multi perangkat multi layanan. Sebuah protokol komunikasi disepakati oleh perangkat dalam sistem IoT untuk menjamin keberhasilan transaksi data. Protokol tersebut antara lain MQTT, HTTP, AMQP, XMPP, Web Shocket, dan COAP. Penelitian ini meembandingkan unjuk kerja protokol COAP dan HTTP dalam hubungannya dengan jumlah transaksi dan konsumsi energi. Skenario yang digunakan adalah dengan melakukan pengiriman data rssi dan level daya baterai. Pengujian dilakukan dengan membedakan daya transmisi perangkat sebesar 14dBm dan 20dBm. Hasil pengujian, protokol COAP lebih hemat 25 kali dari protokol HTTP untuk scenario daya transmit sebesar 20dBm sedangkan untuk daya transmit sebesar 14dBm COAP lebih hemat 61 kali dibandingkan dengan protokol HTTP.

The IEEE 802.15.4 protocol defines the medium access control layer of Zigbee, a widely implemented WSN technology. This protocol implements both the guaranteed time slot (GTS) scheme, where note request for slot(s) to transmit their packets collision-free and the contention-based scheme where nodes randomly draw a back-off counter to win channel access. This paper analyzes the performance of both schemes in WSNs when an event is detected and the packet arrival rate of the network increases using packet delivery ratio(PDR), network throughput and packet latency as the quality of service parameters. We consider various network densities (4, 9 and 16 nodes within a common transmission range). Simulations using Castalia 3.2 shows the GTS scheme has better PDR and latency than the contention-based scheme in the 4 and 9 nodes network. However, in a dense network (16 nodes), when the packet arrival rate increases, the contention-based scheme outperforms the GTS scheme.

This study modeled the interference between the Lora system signal in the AS2 frequency band and a non-Lora radio signal. Two Lora devices operate on uplink and downlink at a frequency of 923.2MHz to send and receive data on the bandwidth of 125KHz, 250KHz, and 500KHz. The interference generator device is composed of a single board computer installed by the RPITX application. In addition, there is a GNU-Radio application to monitor data and signal transmission levels. Signal quality tests (RSSI, SNR, and time-on-air(ToA)) were carried out under line-of-sight (LOS) conditions and used reference distances of 1m and 4m. The ToA test shows that the greater the bandwidth, the smaller the ToA value, while the change in distance does not affect the ToA. The RSSI test shows that the change in distance affects the RSSI value more significantly than the change in bandwidth. The presence of an interference signal does not significantly affect the RSSI value. SNR testing shows that the greater the bandwidth, the smaller the SNR and significantly decreases when interference occurs. &nbsp