Downlink uplink12/29/2023 Only in a few studies, the error during the SIC is regarded. This assumption is not reasonable for the wireless communication. However, researchers mostly assume that the SIC process is error free. Also, the power allocation and user clustering algorithms are based on maximising this achievable Shannon rate. The outage performances are obtained by comparing the targeted data rates (quality of service) of users with the achievable maximum Shannon rate. Most of these studies approach all these problems by considering Shannon capacity theorem. Due to this potential, NOMA has been studied largely in the last years in terms of outage performance, power allocation, user clustering and system capacity. In, researchers first proposed the NOMA for future cellular network and demonstrated its potential in terms of capacity and user-fairness compared to OMA schemes. This NOMA principle is based on superposition coding (SC) at the transmitter and successive interference cancellation (SIC) at the receivers. In contrast to OMA, NOMA simultaneously serves multiple user equipments on the same resource blocks by splitting users into power domain. The conventional orthogonal multiple access (OMA) schemes serve to the multiple users by assigning them into different radio resources, e.g. NOMA achieves high spectral efficiency and supports dense networks by allowing the users to share same radio resources. To fulfil these targets, non-orthogonal multiple access (NOMA) is highly recommended and investigated by the researchers. The future radio access networks (5G and beyond) are to support very high rate, ultra-low latency, massive connections and very high mobility applications. The numerical results are depicted to reveal the effects of error during SIC process on the performance for various cases such as power allocation for downlink and channel quality difference for uplink. Then, the derived expressions are validated by simulations. Besides, they derive one-degree integral form exact BER expressions and closed-form approximate expressions for uplink NOMA. In this study, for the first time in the literature, the authors derive an exact closed-form bit error rate (BER) expressions under SIC error for downlink NOMA over Rayleigh fading channels. On the other hand, the interference among users may not be completely eliminated in the SIC process due to the erroneous decisions in the receivers usually caused by channels. The main drawback of NOMA techniques is the interference among users due to the its non-orthogonal access nature, that is usually solved by interference cancellation techniques such as successive interference cancellation (SIC) at the receivers. Therefore, researchers in academia and industry have been recently investigating the error performances and capacity of NOMA schemes. Non-orthogonal multiple access (NOMA) is a strong candidate for next generation radio access networks due to its ability of serving multiple users using the same time and frequency resources. IET Generation, Transmission & Distribution.IET Electrical Systems in Transportation.IET Cyber-Physical Systems: Theory & Applications.IET Collaborative Intelligent Manufacturing.CAAI Transactions on Intelligence Technology. ![]() And if you can't generate a narrow beam, you hit many satellites rather than just one, and this kills the overall network capacity. If you make an antenna array small, you simply can't generate a narrow beam. To get a narrow beam, you need a lot of antennas with a spacing that relates to the frequency in use. There's a lot of information in the SpaceX FCC filings about beam sizes and so forth.Īs for whether you'll see a Starlink antenna in a phone or laptop: no, that won't happen. The same principle is used by modern WiFi routers - it's why they have a lot of antennas - except SpaceX will use considerably more antennas than a WiFi router does and each antenna will be much smaller. As you're sending a beam in only one direction, you need a lot less power. It's similar to using a big dish, but easier to track quickly. The effect is you send a narrow beam only in the direction of the satellite. As the satellite moves, the timings of the waves are adjusted constantly, to maintain alignment at the satellite. The rough idea is you send the same signal to all the antennas, but adjust the timing slightly, so the different transmitted waves all align at the satellite, and no-where else. This is a pizza-box sized two-dimensional grid of antennas. They plan to use what is known as a phased array antenna.
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