The Time Slotted Channel Hopping (TSCH) Medium Access Control (MAC) has been introduced in the recent IEEE 802.15.4e amendment to improve energy efficiency and reliability of short range wireless communications in industrial applications. However the joining phase can take very long time due to the operation of TSCH and beside being a problem in the deployment phase it may become a relevant source of energy consumption. To overcome this issue the present contribution investigates the problem of acquiring the first synchronization in a TSCH network from several points of view: (i) two novel mechanisms are proposed and implemented in real motes to speed up joining operations; (ii) for each of them, the average joining time is analytically modeled with closed form expressions as a function of node density, communication reliability, and beacon transmission frequency; (iii) the effectiveness of these novel algorithms and the accuracy of their models are experimentally validated in different scenarios.

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Virtual Reality/Augmented Reality applications are getting increasingly popular and new services are emerging in a diverse set of fields such as entertainment, art, e‐health, and smart factories. 360° videos are an advancement of classical two‐dimensional videos giving the user the impression of being immersed at the center of a scene that can be explored freely and dynamically by simply turning the head to a given region of interest (RoI). Providing a high Quality of Experience to users when streaming 360° videos over the Internet is particularly challenging due to the very high bandwidth requirements. In this letter, a scaling technique to reduce bandwidth requirements to stream omni‐directional videos is presented. An experimental investigation of the proposed approach has shown that it is possible to obtain a reduction of the required bitrate up to around 50% while gracefully degrading visual quality far from the RoI.

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