Low Power Wide Area Network (LPWAN) is designed for low-bandwidth, low-power, long-distance, large-scale connected IoT applications and realistic for networking in an emergency or restricted situation, so it has been proposed as an attractive communication technology to handle unexpected situations that occur during and/or after a disaster. However, the traditional LPWAN with its default protocol will reduce the communication efficiency in disaster situation because a large number of users will send and receive emergency information result in communication jams and soaring error rates. In this paper, we proposed a LPWAN based decentralized network structure as an extension of our previous Disaster Information Sharing System (DISS). Our network structure is powered by Named Node Networking (3N) which is based on the Information-Centric Networking (ICN). This network structure optimizes the excessive useless packet forwarding and path optimization problems with node name routing (NNR). To verify our proposal, we conduct a field experiment to evaluate the efficiency of packet path forwarding between 3N+LPWA structure and ICN+LPWA structure. Experimental results confirm that the load of the entire data transmission network is significantly reduced after NNR optimized the transmission path.

The TAT system compresses the bandwidth of picture signals into about 1/2 by using variable subsampling with 2 or 3 subsampling modes. In this paper, a new variable subsampling scheme with many modes is proposed for higher compression. We call it the pyramidal TAT. In the proposed scheme, the basic 2-modes TAT is applied to the pyramidal representation of the picture. The pyramid used here is the complementary pyramid we proposed before. Variable subsampling with very many modes is easily done and a wide range of compression ratios are achieved with the pyramidal TAT. It is effective at compression ratios higher than 2 : 1 compared to the conventional TAT system.