Orthogonal Space-Time Bluetooth System for IoT Communications

In this study, we investigate reference signal (RS) transmission schemes that aim to efficiently support coordinated multi-point (CoMP) transmission by providing improved channel estimation accuracy so that transmission parameters can be appropriately chosen on a cellular network. First, we investigate typical scenarios for transmission parameter selection with the widely used CoMP transmission and precoding schemes aligned with those considered for Long Term Evolution (LTE)-Advanced systems. Second, we investigate an RS transmission scheme that can provide accurate channel estimation even with severe inter-cell interference. Finally, we verify the performance benefit of the investigated scheme by a multi-cell link level evaluation. The results obtained indicate: 1) the investigated scheme improves block error rate performance compared to conventional schemes for fixed modulation and coding schemes (MCSs) allocation with a better precoding control accuracy on the LTE-Advanced system downlink and 2) the investigated scheme provides a throughput performance gain compared to conventional schemes for adaptive MCS allocation and coordinated beamforming.

In this paper, based on the characteristics of multilevel codes (MLC) and space-time block codes (STBC), a concatenation scheme (MLC-STBC) combining MLC and STBC is presented over Rayleigh fading channels. The unequal error protection (UEP) of MLC-STBC in Rayleigh fading channels for image transmission is investigated. Furthermore, taking 8ASK modulation as the example, a non-uniform signal constellation for realizing UEP of MLC-STBC is designed. Both theoretical analysis and computer simulation show that MLC-STBC scheme is a high rate and high power efficiency scheme, UEP is its inherent character and non-uniform signal constellation can improve its UEP ability. Its UEP character can enhance the transmission quality in the same bandwidth over a Rayleigh fading channel. MLC-STBC is an excellent scheme for image transmission.

The evolution of wireless communication toward 6G has intensified the demand for MIMO-OFDM systems that deliver higher spectral efficiency, robust interference handling, and adaptive performance under dynamic conditions. The rapid fluctuation of traffic patterns and channel states has created persistent challenges for conventional optimization strategies. These limitations have often constrained throughput, increased latency, and reduced the reliability of high-density 6G environments. The present study addressed this gap by integrating a reinforcement learning framework that has enabled autonomous decision processes for power allocation, beamforming, and subcarrier mapping. An agent interacted with the channel environment, evaluated the reward based on instantaneous signal quality, and adapted the transmission strategy through repeated exploration that has refined action selection. The method employed a deep Q-learning architecture that extracted real-time channel features and updated the policy based on cumulative rewards. The system used an iterative training cycle that improved convergence stability and prevented premature policy saturation. Experimental simulations using an 8×8 MIMO configuration with 256-QAM modulation and 128–256 subcarriers show that the reinforcement learning-enhanced system achieves spectral efficiency of 6.8–7.2 bps/Hz and reduces the bit-error rate to 1.8–1.5×10-3. Total power consumption decreases to 3.32–3.30 W, while the learning agent converges within 700–780 episodes. Compared to PSO-based resource allocation, DNN channel estimation, and DQL power allocation, the proposed method improves spectral efficiency by up to 1.0 bps/Hz, reduces BER by up to 25%, and lowers power consumption by 2–3%. These results indicate that the proposed framework delivers adaptive, high-throughput, and energy-efficient performance under dynamic 6G channel conditions.

본 논문에서는 wireless body area network(WBAN) 채널을 분석하기 위해 실제 채널을 측정하고, 그것의 통계적 특성들을 조사하였다. On-/off-body 채널에서, 인체의 움직임을 고려하기 위해 대표적인 움직임들을 같이 측정하여 그 분석 결과들을 비교하였다. 또한, 세 종류의 신호 전송 기법을 제한된 Outage 확률을 가질 때 최소 소비 전력을 분석하여, 이론적인 총 전력 소비를 계산하였다. 그리고 채널 측정 데이터들을 통해 이론과 실제의 차이를 분석하였다. 본 논문의 결과로 협력 통신을 통하여 전송 효율을 높일 수 있음을 알 수 있으며, 센서 노드의 부착 위치와 움직임이 신호 전송 전력에 어떠한 영향을 미치는지 확인할 수 있다. This paper presents the real channel measurements and investigates their statistical characterization in wireless body area network(WBAN). In on-/off body channel, the measurements are performed with some representative human movements for considering human movements. Moreover, three signal transmission schemes with outage constraint are studied for getting total power consumption in each transmission scheme. Using the real channel measurements, between theoretical and realistic simulation are compared. This paper shows that power efficiency is improved through cooperative communication, and how much position of sensor node and human movement affect signal transmission power.

A nonreciprocal‐amplified scheme for signal transmission is proposed in a coupled rotation‐cavity system, where the two cavities rotate with opposite directions, and an optical parametric amplifier (OPA) is attached to one cavity. The coupling between cavities can effectively compensate and enhance the frequency shift of the Sagnac effect, and a perfect nonreciprocity can be achieved. Owing to the introduction of an OPA medium, eigenvalues of the dynamic matrix exhibit exceptional points (EPs), and the amplified‐nonreciprocal transmission can be obtained around EPs.

In recent times, cooperative communication has been considered as the most developing stage in wireless communication because of its enabling technology for efficient spectrum use and its low power consumption. In this paper, we derive a novel and simple expression of cooperative communication which can overcome the unwanted effects of wireless channel on the message received at the destination which is nearly the same as the theoretical value. In cooperative communication, the three nodes (source, relay, and destination) system, where information transfers between the source and the destination through the selected relay is available in node. The node which is selected should maximize cooperation benefits for the whole system. By applying the technique which is discussed in the paper, we can reduce the error or save the transmit power by which, in turn, we can improve the performance of the network. This paper focuses on the performance of BER using DF relay over the Rayleigh fading channel by using the number of signals received at destination with assistance from the MATLAB tool.

The dirty paper channel model indicates that lossless precoding is theoretically possible at any signal-to-noise ratio (SNR). In this paper, we propose a transmission scheme for dirty-paper coding using Low density parity check (LDPC) codes and compare the performance between Gaussian and Rayleigh fading channels. The simulation results show that LDPC codes are good coding schemes over Gaussian channel using LDPC-DPC transmission scheme in multiuser communication systems.

Wireless communications have become an essential component of modern factory operations. Compared with wired communications, wireless communications can flexibly adapt to physical layout changes and movement of machines and human operators. However, wireless communications are more susceptible to influences from the surrounding environment, interference from other wireless systems and changes in signal strength due to changes in the physical environment. This requires the development of smarter communication systems that can guarantee the reliability of wireless links. In particular, the reliability of wireless links for time-sensitive communications is an important issue. This paper examines a scenario with mixed traffic of video and digital assembly tool in a factory which results in congestion where they merge at a wireless link, with increase in latency due to long waits in the wireless transmission queue. A method for traffic control at a bridge before the wireless link is proposed that balances packet delivery time (PDT) for the video streams and a new measure of block delivery time (BDT) for the digital tools. Analysis and simulations are used to show that traffic shaping with adjustable transmission weights can be effective for tuning the tradeoff between PDT of video streams and BDT of tool data. An example is presented that achieves 75% reduction of PDT for video packets to 5ms while keeping the BDT of tool data below 150ms.

In this paper, the bit error rate (BER) performance of multiuser multiple-input multiple-output (MIMO) systems over Rayleigh fading channels is studied, and corresponding asymptotic performance is analyzed. Based on the asymptotic analysis at high signal to noise ratio (SNR), using the probability density functions (PDF) of the instantaneous channel power gain, the diversity gain and coding gain of the system with transmit antenna selection (TAS) scheme and space-time block coding (STBC) scheme are derived, respectively. As a result, the same full diversity gain is achieved for two transmission schemes, but their coding gains are different. With the obtained diversity gain and coding gain, the asymptotic BER expressions for two transmission schemes are respectively derived, which are in good agreement with the corresponding simulation results. The results show that the multiuser MIMO system with TAS scheme has better BER performance than that with STBC scheme due to higher coding gain.

In this letter we investigate the relaying strategies for multihop transmission in wireless networks over Rayleigh fading channels. Theoretical analysis reveals that equally allocating power among all transmitters and placing relays equidistantly on the line between source and destination are optimal in terms of outage capacity. Then equal time duration for the transmission of each hop is also proved to be optimal. Furthermore, the optimum number of hops is also derived and shown to be inversely proportional to the signal-to-noise ratio (SNR). Numerical simulations agree well with the reported theoretical results.

This paper considers the joint optimization of the source and channel coders over a Rayleigh fading channel. The system being investigated consists of a vector quantizer (VQ) whose output indices are mapped directly into points in the modulation signal space. The modulation signal is then transmitted over a Rayleigh fading channel. A decoder based on a nonlinear estimator is used to reconstruct the source signal from the received signal samples and from the channel state information (CSI). The paper presents an iterative algorithm that jointly optimizes the vector quantizer and the modulation signal set using as optimality criterion the minimum mean-square error (MSE) between the original and the reconstructed signals. It is shown that a jointly optimized system based on average channel characteristics significantly outperforms a reference system based on a VQ designed for the given source and a standard QAM modulation signal set. >

We introduce a new space-time signal processing scheme that uses both transmitter diversity technique and beamforming technique for code-division multiple access (CDMA) systems. The introduced scheme achieves the diversity gain over Rayleigh fading channel through the transmitter diversity technique, and the signal-to-noise ratio (SNR) gain by the beamforming technique. Bit error rate (BER) analyses are given each of the three cases in which the transmitter diversity, beamforming and introduced combined scheme are used, in the frequency-flat Rayleigh fading channel. The analytic results are shown to coincide with the Monte-Carlo simulation results. We show that the combined scheme is more robust to the channel correlation and the speed of mobile than the diversity and beamforming scheme. Furthermore, the combined scheme gives a reduced multiple-access-interference because of its beamforming capability.

In this letter, we introduce a Multi-Code Multi-Packet Transmission (MCMPT) scheme for wireless Code Division Multiple Access (CDMA) ad hoc networks to increase the performance, in terms of the expected forward progress, by considering varying channel conditions in the Rayleigh fading channels. We develop an analytical model to examine the maximum expected progress per hop and optimum number of parallel transmission in MCMPT. Numerical results show that adaptive MCMPT considering varying channel conditions achieves significant progress improvement over the nonadaptive Conventional Packet Transmission (CPT) in a slow Rayleigh fading channel.

In this paper, we propose a general method to analyze the achievable rate and to characterize the optimal power-allocation (PA) scheme for a wide range of half-duplex single-relay amplify-and-forward (AF) protocols over Rayleigh fading channels in high and low signal-to-noise-ratio (SNR) regimes. These include one-way (OW) dual-hop AF (DHAF) systems, OW nonorthogonal AF (NAF) systems, and two-phase two-way AF (2P TWAF) systems using either fixed-gain (FG) or variable-gain (VG) amplification coefficients. At high-SNR regimes, our main idea is to exploit the capacity of a two-branch maximal-ratio combining (MRC) system to obtain tight yet simple approximations to the achievable rates. In low-SNR regions, we use a simple approximation to the logarithm to compute the asymptotic achievable rates. For all considered AF protocols, the closed-form approximations are tight and easy to analyze since they involve only the exponential integral. Then, using the derived approximations, we analytically quantify the asymptotic PA schemes among the nodes to achieve the maximum rate and the sum rate for OW and TW schemes, respectively. The OW and TW protocols of interest are finally compared with the direct transmission (DT) scheme. Although OW relaying is inferior in terms of capacity in high- and low-SNR regimes, the 2P TW system might become advantageous in terms of sum-rate performance at high SNRs under the right channel conditions.

Wireless links are characterized by fluctuating quality leading to variable packet error rates which are orders of magnitude higher than the ones of wired links. Therefore, it is of paramount importance to investigate the limitations of using 5G wireless links for internet of things (IoT) applications. 5G wireless links in IoT need to assure determinism of process flows via realtime communication anytime and anywhere, which is an utmost requirement for multiple verticals like automotive, industrial automation and aerospace. Based on a space-time approach, in this work, we provide novel definitions of wireless link availability and reliability, assuming a number of access points (APs) and end points (EPs) deployed over a fixed area. Our objective is to analyze the availability of a service in both domains. In the space domain, we characterize spatially available areas consisting of all locations that meet a performance requirement with confidence. In the time domain, we propose a channel allocation scheme accounting for the spatial availability of a cell. To emphasize the incurred space-time performance trade-offs, numerical results are presented, also highlighting the effect of different system parameters on the achievable link availability and reliability.