Description of devices.

The main problem with seamless roaming is the fact that the decision to change the access point is always made by the device, and not by the AP itself or the central controller. A seamless roaming mechanism is such a mechanism in which the loss of transmitted data that occurs at the time of switching from point to point is minimal or equal to zero, and the TCP / IP stack of the client operating system does not even notice the fact of the switch. Such a mechanism is important in the operation of delay and loss sensitive applications such as voice over radio (Voice over Wireless), streaming video, large amounts of data, and in general all cases where the TCP protocol is not able to "digest" temporary loss of data transmission channel. If setting up automatic switching to networks with a high signal level on laptops and desktop computers is not so important (due to the stationary use of such devices), then wearable electronics will face difficulties. There are several ways to solve this problem.

A special application for Android and its analogues for IOS « WiFi Jumper» "https://play.google.com/store/apps/details?id=com .goramart.wifijumper .The main idea is that the application scans nearby wifi points and if there is a point to which it is possible to connect (Password or public network), then when the threshold value in dbi is reached (Set by the user), it automatically switches to network with a strong signal.

Benefits: Price, no extras required. equipment does not require installation. Ideal for a small home with two or more hotspots and few wearables.

Disadvantages: Household access points that work independently from each other will force the client to complete a full authorization cycle when moving from one point to another. This is fraught with serious delays in the transmission of useful traffic, especially when using centralized user bases and, as a result, — broken connections. it is necessary to drive in all access points manually, in places where the signal level is unstable, there may be constant transitions, which will negatively affect the stability of the network. In public networks (for example, in shopping centers with wifi coverage, additional authorization is required and therefore, even when reconnecting, the network is lost. Which is not convenient for the user

To build a full-fledged seamless wifi network (Seamless roaming), there are several solutions. They consist of a central controller that manages access daughters (it can be any router or virtual machine installed, for example, on a server in the office), or they have distributed intelligence. Below is an example of building a network on Uni fi controllers

Connecting a point is relatively easy. Plus, the system supports PoE (Power over Ethernet) technologies, and when buying Ubiquiti TOUGHSwitch PoE, you can use only an Ethernet wire. The idea is that the device sees the access points as a whole: as one large access point and, accordingly, there is no connection interruption. Up to a hundred such devices can be combined into a single network. The cost starts from about 500eu for one antenna. Read more at http://www.ubnt.su/reviewUniFi.htm

Several companies have similar solutions: Mikrotik (http://www.ubnt.su/ solutions/inner/besshovnyj-rouming-mikrotik.htm) Dlink and some others.

Advantages: Relatively low cost. from 1500eu for a set that allows you to cover up to 100 sq. meters of area. Easy installation, (usually mounted on the ceiling) Concise appearance. Ability to use existing controllers. Relatively simple program to learn.

Disadvantages: Encryption issues may arise when building a corporate network. You will need to run at least an Ethernet cable to the ceiling. To install the device. If it is not possible to purchase a PoE device, you will also need to lay a power cable. When programming devices, you still need to understand the commands to know how to register an IP address. The software is not yet very advanced points can sometimes freeze. It is necessary to be able to draw and load into the program a floor plan on a scale, and develop a scheme for installing access points for continuous coverage.

Professional solution from large companies. For example Cisco Juniper Wireless

http://www.juniper.net/us/en/products-services/wireless/

The principle of operation is approximately the same, but the difference is in the protocols. If solutions from Unifi are more autonomous controller inyou perform the function of distributing the Internet. That controller here is fully customizable. You can select the operating mode of the power consumption of each point. Set them to turn on by time. Set up an encryption mechanism and many other things necessary for the corporate segment.

The main disadvantage is the complicated setup procedure and the price (about $ 30,000)

Conclusions:

1. For a simple transition between two points, for example, in a large apartment for wearable electronics (Android, Ios devices), a program is enough. (if there are few devices)

2. For a large house with a lot of devices or a small office, you can use Unifi, Microtik, etc.

3. For large objects where quality is important and the issue of price plays a secondary role, it is necessary to use a solution from large companies.

Articles