Алгоритм выбора параметров передачи видеопотока в сетях Wi-Fi
Proceedings of International Wireless Communications and Mobile Computing Conference (IWCMC) 2016
Proceedings of Wireless Communications and Networking Conference (WCNC) 2016
While celebrating the 21st year since the very first IEEE 802.11 “legacy” 2 Mbit/s wireless Local Area Network standard, the latest Wi-Fi newborn is today reaching the finish line, topping the remarkable speed of 10 Gbit/s. IEEE 802.11ax was launched in May 2014 with the goal of enhancing throughputper-area in high-density scenarios. The first 802.11ax draft versions, namely D1.0 and D2.0, were released at the end of 2016 and 2017. Focusing on a more mature version D3.0, in this tutorial paper, we help the reader to smoothly enter into the several major 802.11ax breakthroughs, including a brand new OFDMAbased random access approach as well as novel spatial frequency reuse techniques. In addition, this tutorial will highlight selected significant improvements (including PHY enhancements, MUMIMO extensions, power saving advances, and so on) which make this standard a very significant step forward with respect to its predecessor 802.11ac
Ubiquitous densification of wireless networks has brought up the issue of inter- and intra-cell interference. Interference significantly degrades network throughput and leads to unfair channel resource usage, especially in Wi-Fi networks, where even a low interfering signal from a hidden station may cause collisions or block channel access as it is based on carrier sensing. In the paper, we propose a joint power control and channel time scheduling algorithm for such networks, which significantly increases overall network throughput while maintaining fairness. The algorithm is based on branch-and-bound global optimization technique and guarantees that the solution is optimal with user-defined accuracy.
Для передачи по mesh-сети потоковых данных, предъявляющих высокие требования к качеству обслуживания, удобно использовать описанный в стандарте IEEE 802.11s механизм MCCA детерминированного доступа к среде. При использовании этого механизма станции резервируют для своих передач определенные периодически повторяющиеся интервалы времени, тем самым получая бесконкурентный доступ к каналу связи. Однако, чтобы обеспечить успешную доставку данных в условиях помех, необходимо устанавливать дополнительные резервирования под повторные попытки передачи. В работе построена аналитическая модель процесса передачи неординарного потока по многошаговым беспроводным сетям с помощью механизма MCCA. Модель позволяет определить наибольший период резервирований, при котором выполнены требования на время доставки и долю потерянных пакетов.
Proceedings of 16th International Conference on Next Generation Wired/Wireless Advanced Networking
To avoid collisions in Wi-Fi networks, access points (APs) - acting as coordinators - got the ability to use centralized contention-free channel access, e.g. HCCA, which supports parameterized QoS. However, the growth of WLANs population raises a problem of coordination between APs. As a solution to this problem, IEEE 802.11aa introduces the HCCA TXOP Negotiation mechanism, which allows APs to agree in advance on periodic time intervals used by each AP for contentionfree channel access. The paper studies the efficiency of such a mechanism, focusing on developing a model, which allows selecting appropriate reservation parameters to minimize channel resource consumption while transmitting several flows with given QoS requirements.
In Wi-Fi networks, preliminary channel reservation protects transmissions in reserved time intervals from collisions with neighboring stations. However, making changes in established reservations takes long time spent on negotiating changes with neighboring stations and dissemination of information about these changes. This complicates serving of Variable Bit Rate (VBR) flows which intensity varies with time, what leaves no choice but to reserve some additional time for handling data bursts and packet retransmissions (caused by random noise and interference from remote stations). In the paper, we consider a more flexible approach when bursts and retransmissions are handled by some random access method while a constant part of an input flow is served in preliminarily reserved intervals. We build a mathematical model of a VBR flow transmission process with this heterogeneous access method and use the model to find transmission parameters which guarantee that Quality of Service requirements of the flow are satisfied at the minimal amount of used channel time.