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Exploiting code division multiplexing with decentralized multiuser detection in the satellite multibeam forward link
Author(s) -
De Gaudenzi Riccardo,
Alagha Nader,
Angelone Martina,
Gallinaro Gennaro
Publication year - 2017
Publication title -
international journal of satellite communications and networking
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.388
H-Index - 39
eISSN - 1542-0981
pISSN - 1542-0973
DOI - 10.1002/sat.1215
Subject(s) - computer science , precoding , payload (computing) , throughput , multiuser detection , channel (broadcasting) , telecommunications link , multiplexing , fading , time division multiple access , communications satellite , mimo , computer network , real time computing , electronic engineering , telecommunications , satellite , code division multiple access , wireless , engineering , network packet , aerospace engineering
Summary In recent years, the need for increased satellite throughput has been tackled by extending the number of satellite beams thus allowing a higher spectrum reuse and peak throughput. However, the satellite antenna size and the number of simultaneous beams that can be generated onboard over a given coverage region cannot grow beyond certain limits because of payload accommodation constraints. The next step being pursued to increase the system throughput resides in extending the frequency reuse among the loaded beams and to mitigate the effects of the increased co‐channel interference through more advanced digital signal processing. This can be achieved in 2 different ways. The first one, which received a large attention in recent years, is to centrally mitigate the multibeam channel cross talk by exploiting precoding techniques at the gateway. The second approach, less investigated in the past, is to put in place decentralized multiuser detection (MUD) at the user terminal side. The precoding approach has the advantage of concentrating the extra processing complexity at the gateway, but it requires nonstandard payloads or accurate payload calibration techniques and periodic channel estimation reporting from the user terminal. Instead, the decentralized approach can operate in combination with existing payloads and does not require any terminal's periodic channel estimate reporting to the gateway. Only the signal‐to‐noise plus interference variations due to possible fading as for conventional adaptive coding and modulation shall be reported. One of the main barriers to the decentralized MUD approach so far was the demodulator complexity. Some simplified approach for conventional frequency/time division multiplexing schemes has been recently published, and its applicability to the forward link investigated. In this paper, we investigate the possible advantages deriving from the adoption of direct‐sequence code division multiplexing associated with affordable complexity of the MUD at the user terminal side. It is shown that the proposed MUD scheme can be practically implemented and provides sizeable advantages compared to current state‐of‐the‐art when the traffic is not evenly distributed among the beams, ie, when a subset of beams has a higher load than the others.