35 research outputs found
Performance Analysis of SSK-NOMA
In this paper, we consider the combination between two promising techniques:
space-shift keying (SSK) and non-orthogonal multiple access (NOMA) for future
radio access networks. We analyze the performance of SSK-NOMA networks and
provide a comprehensive analytical framework of SSK-NOMA regarding bit error
probability (BEP), ergodic capacity and outage probability. It is worth
pointing out all analysis also stand for conventional SIMO-NOMA networks. We
derive closed-form exact average BEP (ABEP) expressions when the number of
users in a resource block is equal to i.e., . Nevertheless, we analyze the
ABEP of users when the number of users is more than i.e., , and derive
bit-error-rate (BER) union bound since the error propagation due to iterative
successive interference canceler (SIC) makes the exact analysis intractable.
Then, we analyze the achievable rate of users and derive exact ergodic capacity
of the users so the ergodic sum rate of the system in closed-forms. Moreover,
we provide the average outage probability of the users exactly in the
closed-form. All derived expressions are validated via Monte Carlo simulations
and it is proved that SSK-NOMA outperforms conventional NOMA networks in terms
of all performance metrics (i.e., BER, sum rate, outage). Finally, the effect
of the power allocation (PA) on the performance of SSK-NOMA networks is
investigated and the optimum PA is discussed under BER and outage constraints
Threshold-based Selective Cooperative-NOMA
In this letter, we propose threshold-based selective cooperative-NOMA
(TBS-C-NOMA) to increase the data reliability of conventional cooperative-NOMA
(C-NOMA) networks. In TBS-C-NOMA, the intra-cell user forwards the symbols of
cell-edge user after successive interference canceler (SIC) only if the
signal-to-interference plus noise ratio (SINR) is greater than the
pre-determined threshold value. Hence, the data reliability of the cell-edge
user is increased by eliminating the effect of the error propagation. We derive
closed-form end-to-end exact bit error probability (BEP) of proposed system for
various modulation constellations. Then, the optimum threshold value is
analyzed in order to minimize BEP. The obtained expressions are validated via
simulations and it is revealed that TBS-C-NOMA outperforms C-NOMA and full
diversity order is achieved
Derivation of the closed-form BER expressions for DL-NOMA over Nakagami-m fading channels
NOMA is as a strong candidate for the Future Radio Access Network (FRA) due
to its potential to support massive connectivity and high spectral efficiency.
However, the most important drawback of NOMA is the error during Successive
Interference Canceller (SIC) is implemented because of the inter-user
interferences. In this paper, we derive closed-form exact Bit-Error Rate
expressions for Downlink(DL) NOMA over Nakagami-m fading channels in the
presence of SIC errors. The derived expressions are validated by the computer
simulations. It is shown that the m parameter still represents the diversity
order like as OMA systems. Besides, the BER performances of users for NOMA have
substantially depended on the power allocation coefficient.Comment: 26.IEEE Signal Processing and Communications Applications
Conference,Izmir,Turke
Kürzeste Wege im Wikipedia-Linkgraph
Diese Arbeit beschäftigt sich mit unterschiedlichen Beschleunigungstechniken zur Suche kürzester Pfade in einem Graph. Im Gegensatz zu klassischen Weganfragen wird jedoch kein geographischer Graph als Datenquelle genutzt, sondern der manuell extrahierte Wikipedia-Linkgraph. Um eine Vergleichsgrundlage für Beschleunigungsalgorithmen zu erhalten, wird eine Auswertung der Breitensuche als Basis geschaffen. Zur optimalen Auswahl eines Beschleunigungsalgorithmus ist es unabdingbar, ein grundlegendes Verständnis über die Struktur des Graphen zu erhalten. In Folge dieser Untersuchung und einer Vorstellung unterschiedlicher Beschleunigungsalgorithmen wird das Transitknotenkonzept, welches in der Arbeit von Bast u.a. [BFM+07] vorgestellt wurde, auf den Wikipedia-Linkgraph angewandt. Um das Konzept auf einen nicht geographischen Graph anwenden zu können, wird nach der Arbeit von Eisner/Funke [EF12] die Suche nach einer passenden Transitknotenmenge als Hitting-Set-Problem formuliert. Die Qualität der ausgewählten Transitknoten wird mit unterschiedlichen Konstruktionen zur Transitknotenbestimmung verglichen und die verschiedenen Lösungen werden anhand der vorhergehenden Untersuchung der Graphstruktur erklärt. Schlussendlich wird gezeigt, warum die verschiedenen Konstruktionen der Transitknotenmenge schlechte Ergebnisse liefern, wodurch das Transitknotenkonzept angewandt auf den Wikipedia-Linkgraph fehlschlägt