This paper proposes a two-way relay network with multiple relays based on generalized carrier index differential chaos shift keying (GCI-DCSK), which operates without any channel state information (CSI) or the locations of the relays. A maximum-minimum decision threshold distance (MMTD) relay selection strategy is used to select the best relay for the network, where the effects of both the location of the relays and channel states of the links are considered. Based on the probability of selecting the best relay, both the approximate expressions for the bit error rate (BER) and outage probability are derived. Simulation results show that the BER of the network is lower compared to a bidirectional single-relay network based on traditional DCSK. Finally, compared with round robin (RR) and global positioning system (GPS) strategies, MMTD not only achieves better BER performance but also has lower hardware overheads.

With the rapid proliferation of intelligent terminals and exponential growth in mobile data traffic, existing wireless networks must significantly improve their spectral efficiency to meet current demands. Device-to-device (D2D) and Full-duplex (FD) communication are promising technologies for addressing low spectrum resource utilization and high data traffic demand. While introducing FD technology can greatly enhance the total data rate of D2D-aided cellular networks (CNs), it also brings about serious interference. We analyze the maximum and optimal number of D2D links (DLs) activations that a single channel can support, determining the proportion of half-duplex (HD) mode and FD mode in DLs by optimizing system throughput. Monte-Carlo simulation results show that we can determine the maximum and optimal number of active DLs while finding an optimal mode access ratio to achieve better total data rates. This value is influenced by various factors such as signal-to-interference-plus-noise ratio (SINR) threshold parameters and number of D2D users (DUs).

Software-defined networking (SDN) is a network virtualization technology that realizes flexible network control by software operation using an SDN controller. There is an approach to formulate a packet flow allocation problem as a mathematical optimization problem and solve it. Intermediate solutions output from a mathematical optimization solver can be used to allocate packet flow routes before the optimal solution is obtained. At the time of a network reconfiguration, the overhead of the packet flow allocation occurs. Therefore, we need to select intermediate solutions that improve network resource utilization while suppressing overhead. This paper proposes a packet flow allocation method that applies intermediate solutions considering reconfiguration overhead in the network environment where the traffic amount changes dynamically. We devise a policy that takes into account both overhead and network congestion ratio, which is used in the proposed method. The proposed method is compared to the benchmark policies. The benchmark policies include one that does not use intermediate solutions and one that applies intermediate solutions each time without considering any overhead. Numerical evaluations show that the proposed method reduces the time-averaged network congestion ratio while reducing overhead compared to the benchmark policies.

Containers are the technology used by Linux to isolate execution environments. By distributing a container image, which is a collection of files contained in the container, users use an execution environment that includes the necessary files and libraries. However, container images are tens to hundreds of megabytes in size and require many network resources to be transferred. Especially in low-bandwidth network environments like edge computing, frequent image updating will be difficult and increase the network cost. The approach has been proposed to transfer only updated files but cannot provide smaller updates for partially updated files. In this paper, we propose D4C. D4C reduces the data size required for image updates using delta encodings. Delta encodings reduce data size and finish updating quickly, but generating and applying deltas is a time-consuming operation. We propose a delta generation approach by merging existing deltas to provide requested deltas as fast as we can. Also, D4C provides a dedicated file system called Di3FS. Di3FS applies deltas lazily and it enables container images to be available without applying all deltas. We confirmed that D4C can reduce the data size required to update container images by up to 95% and provide about 10x faster updating than the state-of-the-art approach. D4C’s merge-based delta generation approach can provide required deltas over 60x faster than generating deltas on-demand. Furthermore, benchmarks with PostgreSQL and PyTorch showed that D4C did not influence their performance.

In conventional multiband base station antennas, the beam direction is the same for all shared frequency bands; however the electrical length of the antenna becomes shorter and the beam width becomes wider in the lower frequency bands. Therefore, adjacent areas experience increased interference in the low-frequency band. To solve this problem, a three-dimensional phase shifter has been proposed that can tilt the beam direction of the 1.5 GHz band from that of the 2.0 GHz band by applying a composite right-handed/left-handed (CRLH) transmission line to an antenna that shares the 1.5 GHz and 2.0 GHz bands. In this paper, we propose a frequency dispersive phase shifter (FDPS) that can double the phase advance compared to the conventional structure and can be constructed in a planar structure. Using an electromagnetic field simulator based on the finite element method (FEM), we clarify the structure to realize the circuit parameters. We also design a matching element that matches 50 Ω. Furthermore, we apply the designed FDPS with 5 series-connected unit cells to a 16-element array antenna consisting of 4-element subarrays, and show that the beam direction at 1.5 GHz tilt up to 8.8 degrees when the tilt angle is set to 5 degrees at 2.0 GHz. The validity of the design is verified by a prototype.

Currently, the fifth generation (5G) new radio (NR) wireless system has been widely deployed due to its higher throughput, lower latency and massive machine communications abilities compared with the conventional fourth generation (4G) system. To achieve these features, 5G systems can be either operated at sub-6G frequency, or millimeter wave band for the available bandwidth resources. It is well-known that the channel attenuation degradation at millimeter wave band is more seriously than the sub-6G frequency. Therefore, to facilitate the coverage requirement, the physical cell identification (PCI) number of 5G was doubled from 4G to support the small cell architecture. Besides, a vehicle to everything (V2X) sidelink communication is also supported by 5G to achieve higher throughput and lower latency capabilities. For both the NR and V2X, the functions of cell identification and the signal synchronization are conducted via the same Primary Synchronization Signal (PSS) and the Secondary Synchronization Signal (SSS). Therefore, how to fast and accurate achieve the signal synchronization and acquire the cell identification to facilitate the low latency requirement become serious issues. In this paper, a fast signal synchronization and cell identification method is proposed via using the well-known Fast Fourier Transform (FFT). Combined with the overlapped FFT signal processing and the features of m-sequence, the required computational complexity of signal synchronization and cell identification of the proposed method can be greatly reduced more than 92% compared with the correlation-based method and can be applied directly to both NR downlink and V2X sidelink scenarios.

This paper considers an appropriate beam selection method in downlink massive multiple-input multiple-output (mMIMO) analog beamforming (BF) with non-orthogonal multiple access (NOMA) based on intra-beam superposition coding. To obtain a sufficient system-level throughput gain by employing NOMA in downlink mMIMO with analog BF, it is essential to select beams where each beam has many appropriate users that are to be non-orthogonally multiplexed while mitigating the interference among simultaneously selected beams. In addition, analog BF with NOMA suffers from limited channel state information since the feedback interval of the signal-to-noise power ratio (SNR) of candidate beams from users is longer than the scheduling interval. We propose a beam selection method based on an angle-domain beam grouping (ADG), which utilizes a beam group that contains multiple neighboring-angle beams. ADG selects beams that are appropriate for applying NOMA by considering the neighboring beams as well as the candidate beam itself during the beam selection process. ADG is also effective in reducing inter-beam interference by setting the neighboring beams to non-selectable beams. Furthermore, we propose a method that reuses the signal-to-interference and noise power ratio (SINR) measured for user-scheduling and transmission-rate control every beam-update interval into the beam selection. This SINR reuse method further improves the system throughput since the beam selection accuracy over time is improved. Computer simulations show that the proposed methods significantly improve user fairness while maintaining the system efficiency compared to the conventional methods, that they are especially effective when the beam update interval is long, and that the system throughput is significantly improved when using NOMA.

The waveform designed using the method of Strong Signal Masking Direct Sequence Spread Spectrum (SSM-DSSS) signal has satisfying anti-interception capabilities, but the power cost of strong signal is high. To reduce the required power cost of strong signal, a new design method for anti-interception waveform is proposed, which combines the strong signal masking technology with the variable parameter spread spectrum hopping technology. The low power useful signal is designed using the variable parameter spread spectrum hopping technology, which can eliminate the cyclostationary characteristics of the direct sequence spread spectrum signal, and then the strong power signal is used to mask the low power useful signal, finally the designed anti-interception signal is produced. The interception factor and interception probability are used to evaluate the anti-interception performance of the designed waveform. The simulation results show that the designed waveform has smaller interception factor and lower interception probability than the SSM-DSSS waveform, which can reduce the required power of the strong signal while ensuring better anti-interception performance.

The application of Reconfigurable Intelligent Surface (RIS) technology in underground coal mines provides innovative solutions for enhancing mine safety and operational efficiency. This paper proposes a signal detection scheme for RIS channels in mines, utilizing adaptive filtering algorithms to design the RIS reflection array. By iteratively updating the reflection coefficient matrix, we minimize the mean square error between the error signal and the actual received signal. To accurately estimate the RIS channel in mines, we construct a minimum mean square error (MMSE) objective function based on pilot signals, providing a closed-form solution. At the receiving end, we employ a parallel interference cancellation (PIC) algorithm combined with space-time processing techniques to improve signal detection accuracy. Experimental results indicate that under ideal Rayleigh channel conditions, the PIC algorithm based on the RIS system can effectively reduce the BER of signals propagating within the tunnel, When SNR = 6 dB, the BER with RIS assistance is 3.77 × 10^-2. Additionally, compared to higher-order QAM modulation, the system exhibits better error performance under lower-order QAM modulation. Furthermore, the performance of the system is further enhanced under OFDM-64QAM modulation; with RIS assistance, the BER using the PIC method is 7.44 × 10^-4, meeting the fundamental communication requirements for underground operations. This research is significant for improving mine communication performance in complex multipath and electromagnetic interference environments and lays a theoretical and practical foundation for the application of 6G technology in mine environments.

The functions of location information and data communication were developed separately in conventional system designs. For example, the Global Positioning System (GPS) provides geo-location information for devices or receivers while terrestrial wireless communication systems, such as fifth generation (5G) wireless networks, provide qualified communication services within the deployed coverage. However, with the fast development of joint service requirements, the issue of using integrated sensing and communication (ISAC) to efficiently and flexibly utilize limited resources in accordance with changes to the environments has become a critical problem for the future sixth generation (6G) wireless communications. One possible architecture for the 6G wireless systems, i.e., a non-terrestrial network (NTN), is to merge the operations of conventional terrestrial wireless systems with aerial platforms such as unmanned aerial vehicles (UAV) and low earth orbit (LEO) satellites to have the advantages of ubiquitous, scalable, and flexible services for future communication requirements. In this paper, an integrated environment sensing and efficient energy consumption or green communication via adopting shadowing properties of the deployed regions is proposed. With the proposed method, a terrestrial base station (BS) or a UAV can be aware of the deployed environments and use the shadowing features to determine the proper transmitted power. It can satisfy green communication requirements and avoid unnecessary energy waste. The proposed integrated method was evaluated using computer simulations to demonstrate the anticipated performance. Results show that with the proposed method, NTN can have the ability to sense the environment and reduce unnecessary energy waste significantly.