[I'MTech] The rise in the number of connected devices will lead to increased congestion of frequencies available for data circulation. Non-Orthogonal Multiple Access (NOMA) is one of the techniques currently being studied to improve the hosting capacity of networks and avoid their saturation
To access the internet, a mobile phone must exchange information with base stations, devices commonly known as relay antennas. These data exchanges operate on frequency sub-bands, channels specific to each base station. To host multiple connected device users, a channel is attributed to each user. With the rise in the number of connected objects, there will not be enough sub-bands available to host them all.
To mitigate this problem, Catherine Douillard and Charbel Abdel Nour, telecommunications researchers at IMT Atlantique, have been working on NOMA: a system that places multiple users on the same channel, unlike the current system. “Rather than allocating a frequency band to each user, device signals are superposed on the same frequency band,” explains Catherine Douillard.
“The essential idea of NOMA involves making a single antenna work to serve multiple users at the same time,” says Charbel Abdel Nour. And to go even further, the researchers are working on the Power-Domain NOMA, “an approach that aims to separate users sharing the same frequency on one or more antennas, according to their transmitting power,” continues Catherine Douillard. This system provides more equitable access to spectrum resources and available antennas across users. Typically, when a device encounters difficulties in accessing the network, it may try to access a resource already occupied by another user. However, the antenna transmitting power will be adapted so that the information sent by the device successfully arrives at its destination, while limiting ‘disturbances’ for the user.
Superposing multiple users on the same resource will cause problems in accessing it. For communication to work, the signals sent by the machine need to be received at sufficiently different strengths, so that the antennas can identify them. If the signal strengths are similar, the antennas will mix them up. This can cause interference, in other words, information jamming phenomena, which can hinder the smooth playing of a video or a round of an online game.
Interference: an intrinsic problem for NOMA...
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by Pierre-Hervé VAILLANT