access scheme
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2022 ◽  
pp. 102610
Author(s):  
Abubakar Sadiq Sani ◽  
Elisa Bertino ◽  
Dong Yuan ◽  
Ke Meng ◽  
Zhao Yang Dong

2021 ◽  
Vol 63 ◽  
pp. 103020
Author(s):  
Wei-Yang Chiu ◽  
Weizhi Meng ◽  
Christian D. Jensen

2021 ◽  
Author(s):  
Syed Agha Hassnain Mohsan ◽  
Moqbel Ali Mohammed Hamood ◽  
Syed Muhammad Tayyab Shah ◽  
Alireza Mazinani

Abstract A novel downlink cooperative non-orthogonal multiple access (DC-NOMA) scheme is proposed in this paper to achieve higher performance in the spectral efficiency compared to the classical NOMA schemes. The communication system consists of one base station and two users (e.g., strong user and weak user). In down link phase, the base station transmits a superimposed signal to both users, and in the cooperative phase, the weak user sends its decoded message to the strong user. The main idea is how the weak user can help the strong user to improve the performance of both users. This occurs by enabling the weak user to perform a cooperative transmission with the strong user during the cooperative phase. The outage probability, outage throughput, and diversity order are derived and analyzed. Numerical results are provided to show that the spectral efficiency gain achieved through our proposed scheme is better than the conventional cooperative NOMA schemes.


Sensors ◽  
2021 ◽  
Vol 21 (23) ◽  
pp. 7974
Author(s):  
Wisnu Murti ◽  
Ji-Hoon Yun

Multi-link operation is a new feature of IEEE 802.11be Extremely High Throughput (EHT) that enables the utilization of multiple links using individual frequency channels to transmit and receive between EHT devices. This paper aims to illustrate enhanced multi-link channel access schemes, identify the associated coexistence challenge, and propose solutions. First, we describe the multi-link operation of IEEE 802.11be and how the asynchronous and synchronous channel access schemes facilitate multi-link utilization. Next, we describe the design variants of the synchronous channel access scheme and demonstrate the associated coexistence challenge. Subsequently, we propose four features to address this challenge by assigning penalties to multi-link devices (repicking a backoff count, doubling the contention window size, switching to another contention window set, and compensating the backoff count) as well as five coexistence solutions derived from combinations of these features. Comparative simulation results are provided and analyzed for dense single-spot and indoor random deployment scenarios, demonstrating that the throughput and latency gains of multi-link operation differ between schemes. At the same time, we investigate the coexistence performance of multi-link operation with and without the capability of simultaneous transmission and reception and demonstrate that the proposed solutions mitigate the coexistence problem. In particular, compensating the backoff count achieves the highest coexistence performance among the proposed solutions, with a marginal throughput decrease of multi-link devices. A metric for evaluating both the throughput and latency gains and the coexistence performance of a multi-link channel access scheme using a single value is also proposed.


Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Hongnan Xu ◽  
Chaoyue Liu ◽  
Daoxin Dai ◽  
Yaocheng Shi

Abstract By leveraging mode-division multiplexing (MDM), capacity of on-chip photonic interconnects can be scaled up to an unprecedented level. The demand for dynamic control of mode carriers has led to the development of mode-division multiplexing switches (MDMS), yet the conventional MDMS is incapable of directly accessing an individual lower-order mode that propagates in a multi-mode bus waveguide, which hinders its scalability and flexibility. In this paper, we propose and demonstrate the first direct-access MDMS as a novel platform for scalable on-chip multi-mode networks. At first, the highly efficient mode exchangers are developed for TE0–TE2 and TE1–TE2 mode swap, which are then employed to realize the direct-access mode add-drop multiplexers with high performances. The direct-access MDMS is then achieved based on the proposed mode add-drop multiplexers, which can be used for dynamically adding and dropping any selected mode carrier in a three-channel MDM. Moreover, the novel direct-access scheme is also adopted to simultaneously harness wavelength and mode carriers, leading to a wavelength/mode-hybrid multiplexing system with an enhanced link capacity of twelve channels. To further verify the utility of the MDMS, a multi-mode hubbed-ring network is constructed, where one hub and three nodes are organized within a ring-like multi-mode bus waveguide. The reconfigurable network traffic of 6 × 10 Gbps data streams are obtained by using three eigen modes as signal carriers. The measurement results show low bit-error rates (<10−9) with low power penalties (<3.1 dB).


2021 ◽  
Author(s):  
Jingchao Liang ◽  
Jun Wu ◽  
Bin Tan ◽  
Haoqi Ren ◽  
Zhifeng Zhang

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