Dynamic Sensitivity Control Research Articles

Interference-Aware Two-Level Differentiated Transmission for Improving Downlink Spatial Reuse in Dense WLANs.

In this study, we address the problem of downlink throughput degradation in dense wireless local area networks (WLANs) based on the IEEE 802.11ax standard. We demonstrate that this problem essentially results from the asymmetric characteristic of carrier sense multiple access between downlink and uplink transmissions in infrastructure WLANs, and it is exacerbated by a dynamic sensitivity control algorithm that aims to improve spatial reuse (SR) in IEEE 802.11ax. To solve this problem, we propose the interference-aware two-level differentiation mechanism consisting of the dual channel access (DCA) and supplemental power control (SPC) schemes. The proposed mechanism introduces a new measure called a spatial reusability indicator, which roughly estimates the signal-to-interference ratio from the received signal strength of beacon frames. Based on this measure, stations (STAs) are classified into the following two categories: spatial reusable STAs (SR-STAs) and non-spatial reusable STAs (NSR-STAs). Because SR-STAs are more robust to interference than NSR-STAs, the DCA scheme prioritizes transmissions to SR-STAs over those to NSR-STAs by using differentiated carrier sensing thresholds. Moreover, the SPC scheme selectively increases the transmission power to NSR-STAs to compensate for transmission failure due to interference. By combining the SPC and DCA schemes, the proposed mechanism effectively differentiates the downlink transmissions to SR-STAs and NSR-STAs in terms of channel access and transmission power, and it can boost the possibility of successful SR. The proposed mechanism can be easily implemented in IEEE 802.11ax without any complex calculation or significant signaling overhead. Moreover, we provide a practical guideline to determine appropriate parameter values for use in the proposed mechanism. The extensive simulation results obtained in this study confirm that the proposed mechanism increases the downlink throughput by more than several times without decreasing the overall throughput, compared to the existing mechanisms, and it maintains fairness between SR-STAs and NSR-STAs in terms of the ratio of successful transmission.

A Deep Q-Network Approach to Optimize Spatial Reuse in WiFi Networks

The proliferation of IEEE 802.11 or WiFi networks, and the explosive growth in traffic demands call for solutions to maximize the capacity of WiFi networks. Hence, maximizing the spatial reuse of WiFi networks is critical as doing so allows multiple concurrent transmissions. In this respect, a critical network parameter, Clear Channel Assessment (CCA) threshold, plays a vital role as it dictates whether a node is allowed to transmit after sensing the channel. In this paper, we propose to use Deep Q-network (DQN) under two learning patterns to select the CCA threshold of devices. We further consider Transmit Power Control (TPC) in conjunction with CCA threshold selection to improve the capacity of a WiFi network. The simulation results show that our approach is capable of selecting the optimal CCA threshold for each device. As a result, the average throughput is 62.4% higher than that of a legacy Dynamic Sensitivity Control (DSC) algorithm.

Evaluation of HARQ for improved link efficiency within dense IEEE 802.11 networks

The progressive adoption of Wi-Fi networks in commercial verticals (dense deployments in buildings, robotics control, gaming) is leading to densification, which demands improvements in reliability and performance guarantees (improved throughput with low latency). Based on these requirements, the IEEE 802.11 working group aims to develop a new amendment called IEEE 802.11be. Hybrid Automatic Repeat Request (HARQ), an enhanced link adaptation and retransmission protocol, is one of the leading candidate features introduced in the IEEE 802.11be. HARQ has the potential to be used in any Wi-Fi configuration (number of antennas, use of MIMO, or channel bandwidth, etc.). In this work, HARQ Chase Combining is modeled in the ns-3 simulator. This new simulation code has been designed and developed considering a contribution to developing the future IEEE 802.11be simulator model within ns-3. Through extensive simulations, we demonstrate the potential advantages of introducing HARQ in dense deployments, particularly for stations amid a large number of contending stations that make transmission attempts simultaneously. Based on the insightful results, we indicate HARQ as a remedy to alleviate the side effects of Dynamic Sensitivity Control (DSC) technique proposed to improve spatial reuse (i.e., combined throughput increase of approx. 18 % and a decrease of 4 % in error rate for the spatial reuse method). To the best of our knowledge, this is the first and novel comprehensive evaluation of HARQ under extremely heavily loaded Wi-Fi conditions.

Analysis of EMC problems with the purpose of developing an effective method of WLAN design on the basis of information systems considering electromagnetic

The article analyzes the scope, technologies and principles of wireless local area networks, which allowed to mark the “bottlenecks” of these technologies, which need special attention when designing: the problem of hidden node; mutual interference between neighboring cells (intrasystem EMC); intersystem interference; providing QoS for responsible applications; expansion of wireless local area networks; the impact of network deployment features. The methods used to solve EMC problems in wireless local area networks are shown and their efficiency is analyzed: the mechanism of access to the transmission medium; IEEE 802.11e (QoS) standard; additional standards designed to reduce the impact of interference (802.11 h and k); coding and modulation. It is shown that the accounting of intrasystem and intersystem interference should be carried out in the early stages of design of wireless local area networks. It is shown that the existing mechanisms of access to the transmission medium are designed to organize the conflict-free operation of transceivers within a single access point and are vulnerable to interference created by transmission stations of neighboring access points. The dynamic sensitivity control algorithm is aimed at partially solving this problem, however, the main disadvantage of the DCC algorithm proposed for use in Wi-Fi 6 is that stations located near access points have a higher probability of access to the environment due to a higher signal level. Relative to electromagnetic interference, which leads to a shorter detection range of the carrier. That requires the development of advanced mechanisms to control the sensitivity of the service area of access points. Based on the analysis, a conclusion is made about the need to develop a methodology for designing wireless local area networks based on information systems, taking into account electromagnetic interference. Which will reduce the time of their design and increase the efficiency of their further operation.

Development of an advanced algorithm for sensitivity control of the service area of the IEEE 802.11ах Standards

The article examines the technical features of the new 802.11ax standard, which for convenience has been assigned the abbreviation Wi-Fi 6. These include: support for 2.4 and 5 GHz bands; OFDMA support; joint work of MU-MIMO and OFDMA; Target Wake Time function. OFDM technology divides data channels into multiple subcarriers, providing higher connection and network reliability. In 802.11ax, the number of subcarriers quadruples due to the long OFDM guard interval. This will help increase the network coverage, and, accordingly, the speed of Wi-Fi 6 by 11%. With channel widths up to 160 MHz, 802.11ax provides incredible connection speeds. Thus, 802.11ax increases performance by simultaneously transmitting up to 8 data streams to multiple clients simultaneously. In addition, Wi-Fi 6 supports the MU-MIMO option for the output channel, when one antenna transmits data to one subscriber. A study of the effectiveness of the IEEE 802.11ax standard, that is, BSS Color, and the effect of the service area overlap threshold in various cases was carried out. An improved algorithm for controlling the sensitivity of setting the threshold for overlapping service areas both at access points and at mobile stations is proposed, which does not require significant changes at the MAC level. An advanced sensitivity control algorithm adjusts coverage overlap based on the observed interference level and the received signal strength from the respective receiver. The improved sensitivity control algorithm was compared to dynamic sensitivity control, an algorithm that was first proposed to clean up the channel and was also used in Wi-Fi 6 to adjust the coverage threshold overlap. The improved sensitivity control algorithm has been shown to outperform the aforementioned schemes (up to 47% in terms of increased throughput) in most simulated cases, while maintaining fairness among users. On the other hand, the improved sensitivity control algorithm increases the transmission capabilities of mobile stations (roughly the same probability for all users in the service area), which also leads to a higher level of contention. However, user contention can be controlled by other means specially designed to deal with it, such as channel flush threshold and contention window size.

On Performance Evaluation of Dynamic Sensitivity Control Techniques in Next-Generation WLANs

Dynamically adapting carrier sensing range, also known as dynamic sensitivity control (DSC), could be an attractive proposition for improving the spatial reuse in dense wireless local area networks. This paper shows the promise and pitfalls of a DSC technique proposed in the IEEE 802.11ax standard and highlights a solution to mitigate these issues. An analytical framework is also presented for the performance evaluation of DSC techniques.

Measuring Environmental Quantum Noise Exhibiting a Nonmonotonic Spectral Shape

Understanding the physical origin of noise affecting quantum systems is important for nearly every quantum application. Quantum noise spectroscopy has been employed in various quantum systems, such as superconducting qubits, NV centers and trapped ions. Traditional spectroscopy methods are usually efficient in measuring noise spectra with mostly monotonically decaying contributions. However, there are important scenarios in which the noise spectrum is broadband and non-monotonous, thus posing a challenge to existing noise spectroscopy schemes. Here, we compare several methods for noise spectroscopy: spectral decomposition based on the Carr-Purcell-Meiboom-Gill (CPMG) sequence, the recently presented DYnamic Sensitivity COntrol (DYSCO) sequence and a modified DYSCO sequence with a Gaussian envelope (gDYSCO). The performance of the sequences is quantified by analytic and numeric determination of the frequency resolution, bandwidth and sensitivity, revealing a supremacy of gDYSCO to reconstruct non-trivial features. Utilizing an ensemble of nitrogen-vacancy centers in diamond coupled to a high density $^{13}$C nuclear spin environment, we experimentally confirm our findings. The combination of the presented schemes offers potential to record high quality noise spectra as a prerequisite to generate quantum systems unlimited by their spin-bath environment.