Andrey I. Lyakhov

A survey on IEEE 802.11ah

We study carefully the IEEE 802.11ah draft standard published in July 2014.We overview use cases of .11ah, especially related to smart cities scenarios.We describe in details novel mechanisms and explain why they are needed in .11ah. Smart technologies play a key role in sustainable economic growth. They transform houses, offices, factories, and even cities into autonomic, self-controlled systems acting often without human intervention and thus sparing people routine connected with information collecting and processing. The paper gives an overview of a novel Wi-Fi technology, currently under development, which aims to organize communication between various devices used in such applications as smart grids, smart meters, smart houses, smart healthcare systems, smart industry, etc.

Flexibility of Routing Framework Architecture in IEEE 802.11s Mesh Networks

The fundamental challenges in wireless multihop networks design are the problems of routing and hidden stations. Defining mesh networking, IEEE 802.11s amendment addresses both issues. It includes a routing protocol and novel deterministic channel access method, called MCCA, complementing random access traditional in IEEE 802.11 networks. The routing framework architecture allows extending or even replacing the default routing protocol for specific niche application, but it is not flexible enough to take advantage of using both traditional random access and novel deterministic access, as we show in this paper. Proposed flexibility enhancements are illustrated to bring benefits for the network performance.

Interference, Even with MCCA Channel Access Method in IEEE 802.11s Mesh Networks

IEEE 802.11s draft defining mesh networking includes two channel access methods: mandatory EDCA and optional MCCA. It is known that random access with EDCA, designed for ad hoc and infrastructure modes, is weak in multihop case because of the hidden stations effect. In contrast, by means of channel reservation and advertisement of set up reservations MCCA combats against the effect, provides more coordinated channel access and comes as a solution when better QoS is desired. In this paper, we draw readers attention to the hidden stations effect again and show that the interference caused by transmissions of ACK frames by hidden stations is not combated with MCCA. We evaluate the effect with a simulation model and propose a solution which is compatible with IEEE 802.11 and may be implemented in the framework of MCCA. Also, we discuss the issue of the interference coming out of MCCA advertisement horizon and propose a solution which appear to require more flexibility than provided by the current IEEE 802.11s draft.

What's new for QoS in IEEE 802.11?

Two amendments to IEEE 802.11 have recently been published: 802.11aa and 802.11ae. Both enhance Quality of Service (QoS) provisioning in Wi-Fi networks by providing support for multicast transmission, enhanced audio video streaming, coping with inter-network interference, and improved prioritization of management frames. The proposed solutions either extend mechanisms already existing in the standard or introduce new ones. Therefore, it is important for researchers to understand the new functionalities. To this end we provide the first description of these latest mechanisms: we present the motivation behind them, explain their design principles, provide examples of usage, and comment on compatibility issues. Finally, we identify new research challenges related to the two new amendments.

QoS support for bursty traffic in noisy channel via periodic reservations

The growth of the number of devices working at the same area, overlapping networks and multihop data transmission degrade the efficiency of contention based channel access. A number of deterministic channel access methods introduced in recent Wi-Fi standards allow to reserve a set of periodical time intervals, during which a single station can access channel without contention. Providing collision free transmission, these methods are favourable for real-time multimedia traffic which demands high quality of service (QoS). However, QoS provisioning for multimedia transmission is significantly complicated by the bursty nature of multimedia traffic and random noise inherent to wireless channels. In this paper, we propose an analytical model of multimedia transmission via periodic reservations considering both multimedia traffic bursty nature and random noise. The model can be used to find reservation parameters which allow to meet QoS requirements while transmitting multimedia data.

Wireless Groupcast Routing with Palette of Transmission Methods

We study the problem of wireless groupcast routing when multiple transmission methods are available. The paper is inspired by GroupCast with Retries (GCR) methods appeared in IEEE 802.11aa in 2012. The paper contributes with comparative analysis of GCR methods in a wireless multihop network from the groupcast routing perspective. It also addresses the issue of possible benefit for a routing protocol to account for this palette of transmission methods.

Analytical study of link management in IEEE 802.11s mesh networks

Efficient link management is important for mesh networking. The links opened between neighbor STAs should be stable and ensure high probability of packet delivery. Various approaches of link management are usually compared by simulation. The core contribution of this paper is original link management efficiency criteria and an analytical model of decision-making process of link management in IEEE 802.11s, which are used to improve network performance.

Multicast qos support in ieee 802.16

Multicast is a very popular bandwidth-conserving technology exploited in many multimedia applications. However, the existing IEEE 802.16 spec. provides no error recovery mechanism (ARQ) for multicast traffic. ARQ absence in wireless networks unreliable by their nature leads to frequent packet losses, which is inappropriate for most of multimedia applications. In the paper, we propose new reliable multicast mechanism supporting multimedia QoS (packet loss ratio, latency and throughput) in IEEE 802.16 Wireless Metropolitan Area Networks (WMANs). This mechanism is based on the concept of multiple ACK-leaders, i.e. multicast recipients responsible for acknowledging data packets. We develop accurate analytical models of the mechanism with various leader selection schemes, and use the models to study optimize the schemes. Numerical results show that the proposed mechanism can be easily tuned to meet specific QoS requirements of multimedia or any other multicast applications.

QoS-aware streaming with HCCA TXOP negotiation in overlapped Wi-Fi networks

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 requirements1.

Study of the group-based approach to disseminate control information in wireless networks

Various networking protocols disseminate much control information. An important task is to reduce the amount of such information in order to free channel resources for user data. In the paper, we study a novel group-based approach for dissemination of control information introduced in the latest version of the IEEE 802.11 standard. The key idea of this approach is to join various pieces of information into a small number of groups and send differential updates related only to those groups which content is changed. However, the group management algorithm (GMA) which directly affects the performance of such an approach is not specified. We consider a simple GMA, develop an analytical model to estimate the amount of sent control information, and show that this amount is significantly less than for the classical full dump approach.