Duty-Cycle-Based Pre-Emption Protocol for Emergency Networks

This paper proposes a new duty-cycle-based protocol for transmitting emergent data with high priority and low latency in a sensor network environment. To reduce power consumption, the duty cycle protocol is divided into a listen section and a sleep section, and data can only be received when the receiving node is in the listen section. In this paper, high-priority transmission preempts low-priority transmission by distinguishing between high-priority preamble and low-priority preamble. However, even when a high priority transmission preempts a low priority transmission such that the high priority transmission is received first, if the sleep period is very long, the delay may be large. To solve this problem, the high priority short preamble and high priority data reduce receiver sensitivity and increase coverage through repeated transmission. If there are several receiving nodes within a wide coverage, the receiving node that wakes up first can receive the transmission, thus reducing the delay. The delay can also be further reduced by alternately reducing the sleep cycle of one node among the receiving nodes that can receive it. This paper shows that emergent data can be transmitted effectively and reliably by reducing the delay of high-priority data to a minimum through the use of preemption, coverage extension, and an asymmetric sleep cycle.

On Edge Caching in Satellite–IoT Networks

<div>The implementation of the Internet of Things (IoT) is mostly done through cellular networks which do not cover the whole world. In addition, the explosive growth of global Internet access demand introduces the need for integrating satellites with cellular IoT networks for coverage extension and backhaul offloading. Operating hybrid satellite-IoT (SIoT) networks, however, might incur excessive service latency and high satellite bandwidth consumption. To tackle these issues, edge caching technology has been considered in SIoT. This article reviews existing research on edge caching-based SIoT networks with illustrative performance evaluation. Various caching design criteria with a focus on two-tier cache-enabled SIoT are discussed. In addition, open research problems on edge caching in SIoT are identified as future research directions and opportunities.</div>

On Edge Caching in Satellite–IoT Networks

<div>The implementation of the Internet of Things (IoT) is mostly done through cellular networks which do not cover the whole world. In addition, the explosive growth of global Internet access demand introduces the need for integrating satellites with cellular IoT networks for coverage extension and backhaul offloading. Operating hybrid satellite-IoT (SIoT) networks, however, might incur excessive service latency and high satellite bandwidth consumption. To tackle these issues, edge caching technology has been considered in SIoT. This article reviews existing research on edge caching-based SIoT networks with illustrative performance evaluation. Various caching design criteria with a focus on two-tier cache-enabled SIoT are discussed. In addition, open research problems on edge caching in SIoT are identified as future research directions and opportunities.</div>

Two-Tier Cache-Aided Full-Duplex Hybrid Satellite–Terrestrial Communication Networks

Enabling global Internet access is challenging for cellular-based Internet of Things (IoT) due to the limited range of terrestrial network services. One viable solution is to deploy IoT over satellite systems for coverage extension. However, operating a hybrid satellite-terrestrial network (STN) might incur high satellite bandwidth consumption and excessive service latency. Aiming to reduce the content delivery latency from the Internet-connected gateway to the users, this work proposes a wireless two-tier cache-enabled model with full-duplex transmissions where content caches are deployed at the satellite and ground station. A closed-form solution for the successful delivery probability (SDP) of the files is derived considering the requested content distributions and channel statistics. Then, the SDP performance under common caching policies can be conveniently evaluated. The results are also used to optimize cache placement under caching capacity constraints. Numerical results demonstrate the performance improvements of the proposed system over those of single-tier cache-aided and half-duplex transmission systems.

Two-Tier Cache-Aided Full-Duplex Hybrid Satellite-Terrestrial Communication Systems

<pre>Enabling global Internet access is challenging for cellular-based Internet of Things (IoT) due to the limited range of terrestrial network services. One viable solution is to deploy IoT over satellite systems for coverage extension. However, operating a hybrid satellite-terrestrial network (STN) might incur high satellite bandwidth consumption and excessive service latency. Aiming to reduce the content delivery latency from the Internet-connected gateway to the users, this work proposes a wireless two-tier cache-enabled model with full-duplex transmissions where content caches are deployed at the satellite and ground station. A closed-form solution for the successful delivery probability (SDP) of the files is derived considering the requested content distributions and channel statistics. Then, the SDP performance under common caching policies can be conveniently evaluated. The results are also used to optimize cache placement under caching capacity constraints. Numerical results demonstrate the performance improvements of the proposed system over those of single-tier cache-aided and half-duplex transmission systems. </pre>

Two-Tier Cache-Aided Full-Duplex Hybrid Satellite-Terrestrial Communication Systems

<pre>Enabling global Internet access is challenging for cellular-based Internet of Things (IoT) due to the limited range of terrestrial network services. One viable solution is to deploy IoT over satellite systems for coverage extension. However, operating a hybrid satellite-terrestrial network (STN) might incur high satellite bandwidth consumption and excessive service latency. Aiming to reduce the content delivery latency from the Internet-connected gateway to the users, this work proposes a wireless two-tier cache-enabled model with full-duplex transmissions where content caches are deployed at the satellite and ground station. A closed-form solution for the successful delivery probability (SDP) of the files is derived considering the requested content distributions and channel statistics. Then, the SDP performance under common caching policies can be conveniently evaluated. The results are also used to optimize cache placement under caching capacity constraints. Numerical results demonstrate the performance improvements of the proposed system over those of single-tier cache-aided and half-duplex transmission systems. </pre>