Downlink channel access performance of NR-U: Impact of numerology and mini-slots on coexistence with Wi-Fi in the 5 GHz band

Coexistence between cellular systems and Wi-Fi gained the attention of the research community when LTE License Assisted Access (LAA) entered the unlicensed band. The recent introduction of NR-U as part of 5G introduces new coexistence opportunities because it implements scalable numerology (flexible subcarrier spacing and OFDM symbol lengths), and non-slot based scheduling (mini-slots), which considerably impact channel access. This paper analyzes the impact of NR-U settings on its coexistence with Wi-Fi networks and compares it with LAA operation using simulations and experiments. First, we propose a downlink channel access simulation model, which addresses the problem of the dependency and non-uniformity of transmission attempts of different nodes, as a result of the synchronization mechanism introduced by NR-U. Second, we validate the accuracy of the proposed model using FPGA-based LAA, NR-U, and Wi-Fi prototypes with over-the-air transmissions. Additionally, we show that replacing LAA with NR-U would not only allow to overcome the problem of bandwidth wastage caused by reservation signals but also, in some cases, to preserve fairness in channel access for both scheduled and random-access systems. Finally, we conclude that fair coexistence of the aforementioned systems in unlicensed bands is not guaranteed in general, and novel mechanisms are necessary for improving the sharing of resources between scheduled and contention-based technologies

PUMA-TCS - a new MAC layer protocol with QoS support

W ostatnich latach obserwujemy rosnącą potrzebę zapewnienia odpowiedniej jakości świadczonych usług w lokalnych sieciach bezprzewodowych. W tym celu opracowany został standard IEEE 802.11e. Niestety, jak pokazują badania naukowe, nie jest on pozbawiony wad. W prezentowanej pracy zaproponowano nowy protokół o nazwie PUMA-TCS (Priority Unavoidable Multiple Access with Traffic Category Support) pozwalający na lepsze różnicowanie ruchu oraz większe gwarancje świadczenia usług z określoną jakością. W pracy zawarto również wyniki badań oraz analizę porównawczą obu protokołów, przeprowadzonych przy użyciu wybranych symulatorów sieci bezprzewodowych, co pozwoliło wskazać zalety oraz wady badanych metod dostępu.There is a growing interest in QoS provisioning for wireless local area networks in recent years. Because of this, the IEEE 802.11e standard was introduced. Unfortunately, a few research papers show, that it has a number of serious flaws. The presented work describes a new protocol called PUMA-TCS (Priority Unavoidable Multiple Access with Traffic Category Support), that allows for better than IEEE 802.11e traffic differentiation and QoS guarantees. Research results and comparative analysis of protocols using selected simulators are also included in the paper. This allows to reveal a pros and cons of both channel access schemes

SDN@home: A method for controlling future wireless home networks

Recent advances in wireless networking technologies are leading toward the proliferation of novel home network applications. However, the landscape of emerging scenarios is fragmented due to their varying technological requirements and the heterogeneity of current wireless technologies. We argue that the development of flexible software-defined wireless architectures, including such efforts as the wireless MAC processor, coupled with SDN concepts, will enable the support of both emerging and future home applications. In this article, we first identify problems with managing current home networks composed of separate network segments governed by different technologies. Second, we point out the flaws of current approaches to provide interoperability of these technologies. Third, we present a vision of a software-defined multi-technology network architecture (SDN@home) and demonstrate how a future home gateway (SDN controller) can directly and dynamically program network devices. Finally, we define a new type of flexibility enabled by SDN@home. Wireless protocols and features are no longer tied to specific technologies but can be used by general-purpose wireless SDN devices. This permits satisfaction of the requirements demanded by home owners and service providers under heterogeneous network conditions

CADWAN \u2013 A Control Architecture for Dense Wi-Fi Access Networks

The growing demands of ubiquitous computing are leading towards the densification of wireless access networks. The challenges of high density deployments can be addressed by network- wide centralized control. To this end we propose CADWAN \u2013 a Control Architecture for efficient management of Dense Wi-Fi Access Networks. Its main advantages are: flexibility (it supports software- defined wireless networking), scalability (it uses a three-tier optimization framework), and extendibility (it exploits a unified control interface with support for heterogeneous devices). Furthermore, CADWAN is complementary to ongoing developments in IEEE 802.11, especially 802.11ax

Using self-deferral to achieve fairness between Wi-Fi and NR-U in downlink and uplink scenarios

Wireless networks operating in unlicensed bands generally use one of two channel access paradigms: random access (e.g., Wi-Fi) or scheduled access (e.g., LTE License Assisted Access, LTE LAA and New Radio-Unlicensed, NR-U). The coexistence between these two paradigms is based on listen before talk (LBT), which was, however, designed for random access. Meanwhile, scheduled systems require that their transmissions start at the beginning of a slot boundary. Synchronizing this boundary to the end of LBT usually requires transmitting a reservation signal (RS) to block the channel. Since the RS is a waste of channel resources, we investigate an alternative self-deferral approach (gap-based access) using analytical and simulation models. We put forth a proposal to employ only self-deferral, treat the gap mechanism as a partial backoff, and adjust the contention window (CW) settings to the number of coexisting nodes. We demonstrate that this approach not only ensures fairness in Wi-Fi/NR-U coexistence but also avoids wasting radio channel resources and improves aggregate network throughput. Furthermore, we show that the proposed approach outperforms RS-based access and provides significant throughput and fairness gains. Finally, we implement a long short-term memory-based (LSTM) regression model to predict those Wi-Fi/NR-U CW settings which lead to coexistence fairness

Providing QoS Guarantees in Broadband Ad Hoc Networks

This paper presents a novel QoS architecture for IEEE 802.11 multihop broadband ad hoc networks integrated with infrastructure. The authors describe its features, including MAC layer measurements, traffic differentiation, and admission control. The modules required by the network elements as well as their integration are also presented. Additionally, the paper presents results which validate its correct operation and prove its superiority over plain IEEE 802.11. The authors are convinced that the proposed solution will provide QoS support for a variety of services in future mobile ad hoc networks

The Risks of WiFi Flexibility: Enabling and Detecting Cheating

Flexibility is an important paradigm for future WiFi networks. However, it also opens the possibility for diverse methods of cheating, which users can perform to increase their throughput. Therefore, it is important to develop the necessary tools to mitigate such efforts. In this paper we first discuss the risks of flexibility in terms of misbehaviour. We then propose an architecture to detect misbehaviour and react by punishing the cheaters. The proposed architecture utilizes advanced passive monitoring, flexible WiFi software, and appropriate reasoning to detect cheating. We validate its performance and discuss means of punishmen

Implementation of access point of IEEE 802.11 standard with QoS support

W artykule zaprezentowano sposób implementacji mechanizmów zapewniania jakości świadczonych usług w projektowanym punkcie dostępu do sieci bezprzewodowej standardu IEEE 802.11. Zaprezentowano trzy sposoby zapewnienia QoS: dla warstwy łącza danych (przy użyciu funkcji EDCA standardu IEEE 802.11), dla warstwy sieciowej (przy użyciu dyscyplin kolejkowych) oraz schemat łączony Użycie tych mechanizmów w punkcie dostępu do sieci bezprzewodowej umożliwi zarówno poprawę jak i kontrolę jakości świadczenia usług w sieciach standardu IEEE 802.11.The paper is related to the implementation of mechanisms for providing QoS in access point based on IEEE 802.11 standard. Three different methods for providing QoS are showed: for the data link layer (using IEEE 802.11 function), for the network layer (using queuing disciplines), and for the both mentioned layers (using hybrid solution). These mechanisms allow for improving and proper control of services provisioning in IEEE 802.11 wireless local area networks

Practical analysis of IEEE 802.11b/g cards in multirate ad hoc mode

In multirate ad hoc networks, mobile stations usually adapt their transmission rates to the channel conditions. This paper investigates the behavior of IEEE 802.11b/g cards in a multirate ad hoc environment. The theoretical upper bound estimation of the throughput in multirate ad hoc networks is derived. The measurement scenarios and obtained results are presented. For result validation the theoretical and experimental values are compared. The achieved results, presented in the form of figures, show that cards manufactured by independent vendors perform differently. Therefore, choosing the optimum configuration, according to the user's requirements, is possible