Distributed Ledger Technologies are one of the pillars of future technologies, prognozing to have a great impact to many aspects of our lives, including social, economic, juristic, security and many others. Bitcoin is still the most popular blockchain currency, but the opportunities to use Distribute Ledger Technologies are much more wide, outperforming financial applications as most known and popular. Besides blockchains, there are also other architectures of Distributed Ledger Technologies. This paper observes and analyses one technology as a very strong alternative to blockchains: hashgraphs, which are promising to outperform blockchains, but also tangles. Basis of their architecture and functionality will be explained and directions and prognosis of the further development will be given. The main paper contribution is a comparison of a hashgraph technology to its concurrent architectures, i.e. blockchains and tangles, considering different segments and different properties that define a quality of Distributed Ledgers.

Connected devices in IoT as well as the smartwatch market are getting more and more popular every year. The main mode of communication in IoT is an easy-to-use MQTT protocol suitable for devices with limited resources and battery power. Tizen is used for platforms such as mobile devices, smartwatches, TVs and even Linux kernel-based IoT devices. In this paper, we explain how MQTT protocol, Tizen operating systems and their architecture work, and suggest one possible implementation of a MQTT protocol for Smartwatches based on the Tizen operating system. We list the types of Tizen applications, develop a native application, and suggest possible future upgrades and appliances in IoT.

Blockchains are established as the most widely used P2P distributed application for Distributed Ledger Technologies. Nevertheless, their successful existence, especially known due to the cryptocurrency of Bitcoin, gets more and more competitors. One of those competitors is IOTA, which is based on a tangle or a Directed Acyclic Graph architecture. This paper stresses potentials of such architecture,especially in future IoT applications. In particular, few of the most import security issues are analyzed.

The main problem dealt with in this paper is the creation of a protocol for improved QoS-aware mobility management support in cellular all-IP networks, whereby we propose a new algorithm for QoS-aware mobility management, based on multidimensional QoS metrics. An analytical framework for performance evaluation was presented as well. The proposed algorithm for QoS-aware dynamic MAP selection relies on multidimensional QoS metrics, defined in QoS-preference spaces of the mobile node and QoS-ability spaces of MAP candidates, in the decision-making process. The metric is chosen to achieve the desired QoS level through three parameters: bandwidth, delay, and reliability, while retaining the balance of MAP's loads in the entire network. For purposes of performance evaluation of the proposed model, we used: algorithm convergence, traffic class distribution by MAP's, and handover delay. Results showed that the standard deviation for each component of the QoS-ability vector is two orders of magnitude smaller than the deviation in the static MAP selection scenario. We achieved a total handover delay decrease from 20 ms to several hundred milliseconds, by simplifying DAD procedures preserving the simplicity of architecture.