International Journal of Satellite Communications and Networking最新文献

With 3GPP Release-17, global 5G standards now support non-terrestrial mobile networks comprising radio access network, terminals, and core network. This enables multi-vendor interoperability as well as interoperability with 3GPP-compliant 5G systems. This paper describes the key features enabling the NG-RAN architecture defined for 5G to support non-terrestrial networks. Starting from a general overview of NG-RAN and of the new paradigms of NTN, we introduce the NTN functionality in NG-RAN specifications with respect to feeder link switchover, cell handling, terminal registration, and OAM aspects. We also discuss different scenarios combining satellite access with 3GPP-defined core networks. We also describe some further enhancements expected to be seen in the next 3GPP release (Rel-18). We believe current and upcoming 3GPP work for NTN represents a solid basis on which 5G satellite networks can be built in the upcoming future.

For the first time, 3GPP considered in Release-17 the introduction of mobile satellite service (MSS) frequency bands for 3GPP user equipment (UE) direct connectivity with satellites and had to consider the coexistence in adjacent bands with terrestrial networks (TNs). This paper will further explain the most challenging and the main surprising outcomes of this work, which opened new market opportunities for both terrestrial and nonterrestrial stakeholders. 5G New Radio nonterrestrial networks (NTNs) for satellite communications are representing a major breakthrough in the history of telecommunication for the capability of reuniting two different types of services, that is, terrestrial and nonterrestrial, by reusing the same waveform and potentially the same type of terminal. One of the major conclusions of the 5G NR NTN 3GPP work in Release-17 was that NTN UE could reuse the current requirements of the TN UE. For this reason, the same terminal can connect to both TNs and to nonterrestrial satellite constellations. Consequently, the market is not fragmented and therefore there will be a real opportunity for both terrestrial and satellite operators to increase the coverage and the quality of the service all over the world. This is one of the most important breakthroughs that 3GPP Release-17 work was able to justify because it clearly shows that satellite connectivity using 5G NR technology is not only for dedicated satellite 5G NR UE with a higher power class. On the other hand, the 3GPP work also shows that the satellite connectivity does not require a dedicated satellite waveform, because 5G NR waveform based on CP-OFDM (for downlink) and DFT-s-OFDM (for uplink) is sufficient. Another important finding is that TN can coexist with NTN on adjacent channels with relaxed ACIR requirements for the tested simulation scenarios. In fact, the satellite 5G NR requirements are lower when compared with terrestrial base station (BS) requirements from previous 3GPP releases. The satellite ecosystem tremendously changed after these findings, and both satellite and terrestrial stakeholders now see a potential market opportunity.

Rain cell size distribution that provides an insight into the modelling of effective slant path length and also imperative for site diversity studies are carried out for a tropical inland location, Tirupati (13.6°N, 76.3°E), India. Rain cell size distribution obtained from 5 years (2013–2015 and 2017–2018) of Parsivel disdrometer measurements is observed to follow the power law. Reduction factor that accounts for the inhomogeneity of the rain along the propagation path for the region of study is modified in terms of the rain cell size distribution of the area. Slant path rain attenuation, a major propagation impediment at Ku and Ka-band links, is then studied using the results from the regional rain characteristics by modifying the CCIR 564-4 report. The attenuation results are compared with Garcia-Lopez, Excell, Bryant, and Ramachandran models while considering the ITU-R P. 618-13 as the standard model.

In delay-tolerant networks (DTN), node connection time and message transmission time are two important influencing factors that can improve the delivery rate. In this paper, we first define a new concept called communication capability (CC) and then apply this concept to the delivery predictability formulation in Prophet and improve it. Then, in Prophet, the selection of relay nodes relies only on the delivery predictability and ignores the caching and forwarding capability of the node. Therefore, we combine delivery predictability, buffering, and forwarding capability to develop a new adaptive relay node selection strategy. Subsequently, we define two metrics called message priority (MP) and message strength (MS). The node forwards messages sequentially based on message priority and discards messages based on message strength. Finally, we present a probabilistic routing algorithm based on node communication capability and message strength (CAMS). The simulation results show that compared with traditional routing algorithms, the CAMS can effectively improve the message delivery rate, reduce the overhead ratio, and keep average hop counts low.

Satellite's communication system is used to communicate under significant distance and circumstances where the other communication systems are not comfortable. Since all the data are exchanged over a public channel, so the security of the data is an essential component for the communicating parties. Both key exchange and authentication are two cryptographic tools to establish a secure communication between two parties. Currently, various kinds of authentication protocols are available to establish a secure network, but all of them depend on number–theoretical (discrete logarithm problem/factorization assumption) hard assumptions. Due to Shor's and Grover's computing algorithm number theoretic assumptions are breakable by quantum computers. Although Kumar and Garg have proposed a quantum attack-resistant protocol for satellite communication, it cannot resist stolen smart card attack. We have analyzed that how Kumar and Garg is vulnerable to the stolen smart card attack using differential power analysis attack described in He et al and Chen and Chen. We have also analyzed the modified version of signal leakage attack and sometimes called improved signal leakage attack on Kumar and Garg's protocol. We have tried to construct a secure and efficient authentication protocol for satellites communication that is secure against quantum computing. This is more efficient as it requires only three messages of exchange. This paper includes security proof and performance of the proposed authentication and key agreement protocol.

Communication payload architecture has changed from a conventional single broad beam to a large number of spot beam forms to meet the ever-increasing data rate demand. Owing to the large telecommunication requirements of the user, current generation satellites are equipped with a large number of transponders/beams. Due to the increased number of payload beams, performance evaluation and validation time increases during all stages of the satellite integration process. Also, satellite testing in thermal–vacuum (TVAC) conditions is hugely cost-intensive. Under such circumstances, the conventional test setup established for multibeam payload characterization presents limitations and increases overall measurement time. The paper proposes a novel switch matrix (SWM) based architecture for integrated multibeam payload characterization at payload input and output to significantly reduce effective uplink and downlink transmission line chains required for RF characterization without compromising overall measurement accuracy. We have developed a Telecommand and Telemetry (TCTM) simulator system for closed-loop automated switching of switches in SWM to reduce human intervention and ensure safety aspects of payload. We present the SWM approach for two classes of high throughput satellites (HTS), namely, symmetrical and asymmetrical architectures. The results show that the proposed approach is robust and advantageous in overall RF performance, reduction in the number of interfaces, electromagnetic interference and electromagnetic susceptibility (EMI/EMC) considerations, electrical integrity, and ground test setup complexity compared with conventional characterization philosophy.

Because the GEO belt is becoming more and more crowded every day, controlling the number of satellites in the same control box is becoming more common. There are different kinds of collocation strategies to control more than two satellites in the same box, such as (1) eccentricity and inclination separation or (2) longitude separation. TURKSAT has been using option (1) for a long time. In this paper, we demonstrated TURKSAT on-orbit experience to show mainly radial distances between the satellites. The motivation of this study is to demonstrate how often the satellites are becoming behind of each other, which can be used for RF colocation analysis. Most of the cases the worst case for RF interference analysis between two collocated satellites is having zero distance in normal and tangential but having a radial distance only. In this study, based on the radial distance thresholds, the noninterfered link availability is also shown.