scholarly journals Inter-Relay Interference Mitigation for Chirp-Based Two-Path Successive Relaying Protocol

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3346 ◽  
Author(s):  
Kwang-Yul Kim ◽  
Yoan Shin
Keyword(s):  
Spectral Efficiency ◽  
Spread Spectrum ◽  
Cross Correlation ◽  
Interference Mitigation ◽  
Data Rate ◽  
Transmission Performance ◽  
High Data ◽  
Single Relay ◽  
The Internet Of Things ◽  
Degree Of Similarity

Since the chirp spread spectrum (CSS) system is considered as a communication technology for the Internet of things (IoT), long-range communication and a high data rate are required. In wireless communications, in order to increase spectral efficiency and to extend transmission coverage, a two-path successive relaying (TPSR) protocol has been proposed. Thus, in order to improve transmission performance of the CSS system, in this paper we apply the TPSR protocol to the CSS system. However, since the TPSR protocol is successively relaying data, the spectral efficiency may be limited due to inter-relay interference (IRI). Hence, we propose a multiple linear chirp-based IRI mitigation method for the CSS-based TPSR protocol. In the proposed scheme, the cross-correlation coefficient (CCC) has been derived mathematically according to a separating bandwidth in a given total bandwidth. Then, one separating bandwidth that guarantees the transmission performance is allocated to the primary relay by considering a single relay CCC (SR-CCC) and another separating bandwidth that guarantees the orthogonality from the primary relay is allocated to the secondary relay by considering the inter-relay CCC (IR-CCC). Since the IR-CCC means a degree of similarity between these two relays, it is possible to mitigate the IRI effect within the same bandwidth by allocating orthogonal separating bandwidths to each relay. Simulation results show that the proposed scheme can improve the transmission performance by mitigating the IRI effect even in high IRI environments. Consequently, we expect that the proposed scheme can extend the transmission coverage and increase the data rate of the CSS system.

scholarly journals An Unbalanced QPSK-Based Integrated Communication-Ranging System for Distributed Spacecraft Networking

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5803
Author(s):  
Na Zhao ◽  
Qing Chang ◽  
Hao Wang ◽  
Zhibo Zhang
Keyword(s):  
Phase Shift ◽  
Spread Spectrum ◽  
Power Distribution ◽  
Satellite System ◽  
Data Rate ◽  
Phase Shift Keying ◽  
Distribution Factor ◽  
High Data ◽  
Shift Keying ◽  
Integrated Communication

The spacecraft tracking telemetering and command (TT&C) system plays an essential role in celestial and terrestrial networks, requiring relative ranging and communication, particularly in satellite formation flying networks and distributed spacecraft networks. To achieve precious ranging and high-data-rate communication in a Master/Slave satellite architecture, an integrated communication-ranging system (ICRS) is introduced. ICRS is based on the inter-satellite spread spectrum ranging and spread/non-spread spectrum communication modulated by unbalanced quadrature phase shift keying (UQPSK). In both uplink and downlink, the in-phase (I) branches and the quadrature (Q) branches undertake the tasks of ranging and communication, respectively. In addition, a global navigation satellite system (GNSS) like signal is adopted in I branches for the sake of better ranging accuracy, and binary phase shift keying (BPSK) modulation is employed in Q branches for a higher data rate. Therefore, the key point of the ICRS design is the power resource allocation between two branches via the selection of a suitable power distribution factor (PWDF). Simulation results demonstrate the good performance of the proposed approach in ranging error and bit error rate (BER). In addition, a reasonable PWDF is recommended. Furthermore, the influence of clock offset is also taken into consideration.

Design improvement to reduce noise effect in CDMA multiple access optical systems based on new (2-D) code using spectral/spatial half-matrix technique

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Mohanad Alayedi ◽  
Abdelhamid Cherifi ◽  
Abdelhak Ferhat Hamida ◽  
Mohamed Rahmani ◽  
Yousef Attalah ◽  
...  
Keyword(s):  
Multiple Access ◽  
Cross Correlation ◽  
High Capacity ◽  
Data Rate ◽  
System Capacity ◽  
Optical Systems ◽  
Two Dimensional ◽  
Code Construction ◽  
High Data ◽  
Code Division Multiple

AbstractThis paper presents for non-coherent Optical Code Division Multiple Access (OCDMA) systems a new optical code namely Two-Dimensional Half Spectral/Spatial Zero Cross Correlation (2D-HSSZCC) code based on a One-Dimensional Zero Cross Correlation (1D-ZCC) code already developed using block matrices characterized by a high capacity. The results of simulation show that the use of the new (2D-HSSZCC) code eliminates totally the Multiple Access Interferences (MAI) due to the zero cross correlation flexibility, and less complexity of the code construction which produces a very low bit error rate of closely (4×10−18) at 1 Gbps for four users with a low power source of −12.60 dBm to reach a high data rate and high number of simultaneous users upper to closely 149, save an effective power around −1.35 dBm, −3.3d Bm compared between those provides by (Two-Dimensional dynamic cyclic shift (2D-DCS) code and Two-Dimensional Dimensional Diluted Perfect Difference (2D-DPD) and (1D-ZCC) code, and increase the cardinality percentage upper to 1.58, 2.19, 2.33 and 3.9 times comparing to (2D-DCS) code, 2D-DPD code, 1D-ZCC code and Two-Dimensional Flexible Cross Corelation/Modified Double Weight (2D-FCC/MDW) code. On the other hand, 2D-HSSZCC code is comparied with other codes which has it same property namely Two-Dimensional zero cross correlation/multi diagonal (2D-ZCC/MD) and (2D-MD) codes where the increased percentage in system capacity was 1.38 and 1.05 times, respectively. Finally, the results obtained in part 1 (with Matlab software) were confirmed and validated with the Optisystem software, the proposed system gave a better BER minimum value around 10−21 and a maximum value of the Q factor of around 9.4 at 622 Mbps of data rate when the number of simultaneous users increases.

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