The study of indicators of quality of service in local wireless networks

Content

Introduction

The last decade has been characterized by the rapid development of wireless data transmission networks. This primarily relates to local and city networks, where the use of wireless technologies provides flexibility in the network architecture, including mobility support, rapid design and low implementation costs. The growth in the number of users of wireless networks, as well as the volume of transmitted data, led to the emergence of new high-speed technologies. For ten years, the transmission speed in local and urban wireless networks has grown from 1–2 Mbit/s to 50–70 Mbit/s. Wireless devices with speeds up to 500 Mbps are expected to appear soon. To date, the most popular technologies for building high–speed local and city wireless networks are Wi–Fi (IEEE 802.11 standard) and WiMAX (IEEE 802.16 standard).

Modern wireless protocols should provide not only high–speed data transmission, but also high–quality delivery of voice and video information in the presence of electromagnetic interference, inevitable in local and urban wireless networks. Quality is understood as the achievement of certain performance indicators and reliability when transmitting information over a wireless network. The latest versions of wireless standards have introduced a number of QoS mechanisms. However, a detailed study of the effectiveness of these mechanisms is required, for which it is necessary to develop new methods for evaluating the performance and reliability of data transmission.

1. Relevance

The effectiveness of the operation of any data transmission networks depends to a large extent on the network level algorithms implemented in them, that is, the routing method, load limiting techniques, and transmission of service information.

The total number of such algorithms is large enough, which is caused by a variety of requirements for information exchange, features of transmitted data streams and capabilities of hardware and software.

Each protocol has its own advantages and disadvantages. We can confidently state the fact that ideal routing algorithms have not yet been created, and apparently their appearance is not expected in the foreseeable future.

2. Goals and objectives of the study

The aim of the work is to study the quality indicators of wireless networks of IEEE 802.11 standard. A comparison of networking architectures is needed. Analysis of existing mesh network protocols and comparison of quality indicators to select the optimal one for building certain tasks.

Main tasks:

  1. Architecture choice
  2. Analysis of existing protocols
  3. Protocol Comparison
  4. Protocol Modeling
  5. Modeling for a specific task

3. Choosing a Network Architecture

The analysis of existing methods for constructing a network architecture.

3.1 Standalone Access Points

In the case of the Autonomous Wi–Fi network architecture, the solution is a set of unconnected access points, each of which is configured and maintained independently. Therefore, the complexity of servicing a network built in this way grows linearly, and sometimes exponentially, with an increase in the number of devices. Hence, networks with autonomous architecture, as a rule, have not been designed large for a long time. Usually it is not more than 3–5 Wi–Fi Access Points. There are some exceptions that facilitate the creation of slightly larger networks, for example, access point clustering technology. But such an architecture in any case does not have full–fledged management of radio resources and so on, because there is no single center. It all comes down to simplifying the task of configuring a Wi–Fi network.

A certain development of the autonomous architecture was pseudo–centralized solutions in which in a relatively small group of access points one of the group stands out as the controller of this group. In fact, such a mini–controller can perform many functions of a full–fledged Wi–Fi network controller. But do not forget that the same processor of a typical access point performs both the actual tasks of wireless access and the tasks of controlling radio resources, security, and interference of the entire group of access points. The scaling of such solutions is, of course, small.

3.2 Network management with a controller

It should be noted right away that the Wi–Fi controller is not a router. This is a network administration device and, as the name implies, wireless access points. At the same time, a special boundary device that protects the controller itself and allows users to access the public network is called a router or a firewall.

The ability to create large–scale wireless Wi–Fi networks, ensuring the convenience and security of their administration – all this is possible thanks to the network architecture using a Wi–Fi controller.

The main functions of the Wi–Fi controller

Basic functions such as automatic search, setting up Wi–Fi access points, updating the software of connected access points are the responsibility of the Wi–Fi controller.

The controller has the ability to act as a DHCP server, performing the automatic issuance of IP addresses. He also analyzes the range of Wi–Fi networks, automatically adjusting the power of all wireless access points, from time to time updating the data on the air.

3.3 Intelligent Access Points – Wi–Fi–mesh

Mesh topology

Figure 1 – Mesh topology

(animation: 7 frames, 5 cycles of repetition, 12.9 kilobytes)

Mesh systems are made up of modules. All modules in Mesh systems are the same and equal to each other. There is no main device to which additional modules are connected. And the main difference is that these modules (within the same system) can very quickly connect to each other over a wireless network and distribute Wi–Fi to large areas. We can supply one module, and its work, in principle, will not be any different from the work of a regular Wi–Fi router. But if we need, we put another exactly the same module, plug it into a power outlet, and in just 30 seconds they connect to each other and start working in pairs.

Long range Wi–Fi network. It is due to the modular system. For example, we installed one module of some Wi–Fi Mesh system, and it turned out that in your back rooms, on other floors, in the courtyard, in the garage, or somewhere else Wi–Fi does not catch. We just buy one more or several modules and turn them on in the zone of stable signal reception from the first module. They connect and expand the Wi–Fi network. Their work is different from a pair of Wi–Fi router + repeater.

Add modules – expand Wi–Fi network. And most importantly, without loss of speed, performance, malfunctions, etc. These devices are designed for this, therefore, everything works very stably. Moreover, if one of the modules crashes out of the network, the system automatically restores the connection by connecting through other modules.

Seamless wifi. Wi–Fi Mesh systems create a true seamless Wi–Fi network. The network is really one in the range of all installed modules. When you move around the house, or around the apartment, the device is connected to the module with the best signal. And most importantly, at the time of switching to another module, the Internet connection does not disappear. Even if you communicate through some kind of messenger, there will be no breaks. File uploads will not be interrupted.

Mesh network coverage

Figure 2 – Mesh network coverage

(animation: 21 frames, 5 cycles of repetition, 97 kilobytes)

High speed Wi–Fi network and stable connection. All new Wi–Fi Mesh systems of two, or tri–band. With AC standard support. They give out Wi–Fi networks at 2.4 GHz and 5 GHz.

When a router is not enough (in terms of Wi–Fi network coverage), the best solution is to install a repeater. You can use another router that can work in Wi–Fi network amplification mode, or additional access points that connect to the main router via cable, which is not always convenient. An ordinary repeater also clones the settings of the main Wi–Fi network, and we seem to have one wireless network, but in the router + repeater bundle there are two big minuses compared to modular Wi–Fi networks.

Speed difference when passing through multiple devices

Figure 3 – Speed difference when passing through multiple devices

  1. The repeater cuts about half speed. And if two repeaters or more are installed? Modules of Mesh systems are interconnected without loss of speed. Well, if you used a Wi–Fi network in which there are repeaters, then you probably know how unstable this network is. Repeaters can disconnect, lose connection to the main network, or create problems when connecting devices.
  2. Repeaters do not create a seamless Wi–Fi network. You can only build a real seamless Wi–Fi network using the Wi–Fi Mesh system. Yes, after installing a regular repeater, one Wi–Fi network is displayed on the devices. But at the moment when the device switches between the router and the repeater – the connection is disconnected and the Internet connection is lost for a while. Switching between the Mesh modules of the system occurs without disconnection.

4. Mesh–protocols

Mesh networks are currently undergoing a period of rapid development. New routing protocols appear, old ones are improved.

Moreover, the development is carried out both by large companies and groups of enthusiasts. In mesh networks, two routing approaches – proactive and reactive – predominate. There are also quite effective hybrid schemes.

To understand the benefits of mesh networks, you need to compare them with single–hop networks. For example, in traditional 802.11 wireless networks, multiple clients are connecting to connect directly to the access point. Such networks are called single–node. For a multisite network, any device with wireless capabilities is capable of operating both a router and an access point.

In the case when several devices in a single–node network try to use the network simultaneously, virtual traffic jams may appear that slow down its operation. As the opposite is true for mesh networks, many devices can connect simultaneously through different nodes, but network performance characteristics will not necessarily degrade. For shorter data transmission distances in a network with a mesh topology, it is possible to reduce the influence of interference and implement simultaneous transmission over spatially separated information streams. Table 1. summarizes the differences between traditional WLANs and mesh networks.

  traditional WLAN Wireless Mesh Networks
destination designed for indoor use and cover buildings or small open spaces. designed to cover large open spaces, mainly in places with a missing lan structure
structure cable transmission lines constructed according to the star topology or hub wireless transmission lines based on point-to-point connections between access points
benefits do not require separate power supplies easy installation
simplicity and low cost of implementation allows you to deploy networks outside buildings
reuse existing lan structure do not require lan infrastructure

Table 1 – Differences between traditional WLAN and Mesh networks

Another important difference between mesh networks and other types of wireless networks is its topology. As already mentioned, mesh–networks have a hierarchical structure, and by this they are unique in its kind. Mesh networks use three levels:

The high mobility of mesh networks allows them to be used in specific situations, for example, to create a communication system between key objects of urban infrastructure. The advantages of this implementation are obvious: all mobile objects have the ability to be in touch regardless of their location, speed of movement, etc. A quick alert in such a network will provide a quick response, and therefore a higher level of security.

4.1 Protocol Comparison

Currently, the most popular protocols for organizing Wi–Fi Mesh networks are:

  B.A.T.M.A.N. cjdns Netsukuku DTN OSPF
Yggdrasil Hyperboria
auto address assignment no yes yes no no
auto conf. routing yes yes yes yes partially
distributed routing yes yes yes yes partially
networking no yes no no no
ipv4/6 v4/6 v6 v4 v4/6 v4
network traffic encryption íåò yes no no no
auto tuning yes yes no yes yes
development finished active active active finished
resource consumption low low high low low
overlay mode no yes no no no
linux kernel integration yes no no no yes
support 
unix\linux\openwrt yes yes yes yes yes
windows no in developing no no no
mac os x yes yes yes yes yes

Table 2 – Comparative table of Mesh protocols.

Conclusions

In this paper, we analyzed the architecture of building Wi–Fi networks. Analysis of the routing protocol used to build mesh networks. A comparison of the protocols is made.

Note

When writing this essay, the master's work is not yet completed. Planned completion date: May 2020. Full text of the work and materials on the topic can be obtained from the author or his manager after that date.

List of sources

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