Optical Guidance System /OGS/ for rendezvous and docking Final report

Optical guidance system for Apollo rendezvous and dockin

Microwave vs optical crosslink study

The intersatellite links (ISL's) at geostationary orbit is currently a missing link in commercial satellite services. Prior studies have found that potential application of ISL's to domestic, regional, and global satellites will provide more cost-effective services than the non-ISL's systems (i.e., multiple-hop systems). In addition, ISL's can improve and expand the existing satellite services in several aspects. For example, ISL's can conserve the scarce spectrum allocated for fixed satellite services (FSS) by avoiding multiple hopping of the relay stations. ISL's can also conserve prime orbit slot by effectively expanding the geostationary arc. As a result of the coverage extension by using ISL's more users will have direct access to the satellite network, thus providing reduced signal propagation delay and improved signal quality. Given the potential benefits of ISL's system, it is of interest to determine the appropriate implementations for some potential ISL architectures. Summary of the selected ISL network architecture as supplied by NASA are listed. The projected high data rate requirements (greater than 400 Mbps) suggest that high frequency RF or optical implementations are natural approaches. Both RF and optical systems have their own merits and weaknesses which make the choice between them dependent on the specific application. Due to its relatively mature technology base, the implementation risk associated with RF (at least 32 GHz) is lower than that of the optical ISL's. However, the relatively large antenna size required by RF ISL's payload may cause real-estate problems on the host spacecraft. In addition, because of the frequency sharing (for duplex multiple channels communications) within the limited bandwidth allocated, RF ISL's are more susceptible to inter-system and inter-channel interferences. On the other hand, optical ISL's can offer interference-free transmission and compact sized payload. However, the extremely narrow beam widths (on the order of 10 micro-rad) associated with optical ISL's impose very stringent pointing, acquisition, and tracking requirements on the system. Even if the RF and optical systems are considered separately, questions still remain as to selection of RF frequency, direct versus coherent optical detection, etc. in implementing an ISL for a particular network architecture. These and other issues are studied

Spiking Neural Networks for Inference and Learning: A Memristor-based Design Perspective

On metrics of density and power efficiency, neuromorphic technologies have the potential to surpass mainstream computing technologies in tasks where real-time functionality, adaptability, and autonomy are essential. While algorithmic advances in neuromorphic computing are proceeding successfully, the potential of memristors to improve neuromorphic computing have not yet born fruit, primarily because they are often used as a drop-in replacement to conventional memory. However, interdisciplinary approaches anchored in machine learning theory suggest that multifactor plasticity rules matching neural and synaptic dynamics to the device capabilities can take better advantage of memristor dynamics and its stochasticity. Furthermore, such plasticity rules generally show much higher performance than that of classical Spike Time Dependent Plasticity (STDP) rules. This chapter reviews the recent development in learning with spiking neural network models and their possible implementation with memristor-based hardware

Low-Latency Infrastructure-Based Cellular V2V Communications for Multi-Operator Environments With Regional Split

[EN] Mobile network operators are interested in providing Vehicle-to-Vehicle (V2V) communication services using their cellular infrastructure. Regional split of operators is one possible approach to support multi-operator infrastructure-based cellular V2V communication. In this approach, a geographical area is divided into non-overlapping regions, each one served by a unique operator. Its main drawback is the communication interruption motivated by the inter-operator handover in border areas, which prevents the fulfillment of the maximum end-to-end (E2E) latency requirements of fifth generation (5G) V2V services related to autonomous driving. In this work, we enable a fast inter-operator handover based on the pre-registration of the users on multiple operators, which substantially reduces the handover time to guarantee maximum E2E latency values of 100 ms in non-congested scenarios. To further reduce the latency of time-critical services to always less than 70 ms, even with the handover interruption time, while providing a latency around 20 ms in the majority of locations, we propose to complement the former technique with a mobile edge computing approach. Our proposal consists in the localization of application servers and broadcasting entities in all the base stations, to avoid the communication through the core network, together with the use of a new set of nodes in the base stations of cross-border areas called inter-operator relays, to minimize the communication latency between operators. Based on analytic and simulation results, it is demonstrated that the proposed techniques are effective to support low-latency infrastructure-based cellular V2V communications in multi-operator environments with regional split.The work of S. Roger was partially supported by the Spanish Ministry of Science, Innovation and Universities through grant number RYC-2017-22101.Martín-Sacristán, D.; Roger, S.; Garcia-Roger, D.; Monserrat Del Río, JF.; Spapis, P.; Zhou, C.; Kaloxylos, A. (2021). Low-Latency Infrastructure-Based Cellular V2V Communications for Multi-Operator Environments With Regional Split. IEEE Transactions on Intelligent Transportation Systems. 22(2):1052-1067. https://doi.org/10.1109/TITS.2019.29620971052106722