Smart Wi-Fi: Wi-Fi Performance

author: Alejandro Gandara

SMART WI-FI: WI-FI PERFORMANCE I

Do you know how is the real speed connection of a Wi-Fi network?

This article belongs to a monographic series about the importance of good Wi-Fi performance, which constitutes a fundamental advance in connectivity and a key infrastructure for digital transformation.

Undoubtedly, Wi-Fi wireless technology has become the most widely used means of global Internet access. The fast spread of Wi-Fi —at the expense of cable connections (few people today worry about connecting a cable to ensure their Internet connection), especially in the home and business environment— has brought about a series of important changes in how, where and when people access the Internet.

In recent years, the spread of Wi-Fi use has led to a revolution in the wireless communications sector, becoming a strategic element for operators and access providers. If we take a look at one of the Wi-Fi Alliance latest reports, the value of this market will increase from 1.96 billion dollars to 3.47 billion dollars in 5 years, from 2018 to 2023. That is, the growing demand for wireless networks for better connectivity, productivity and critical operations, makes Wi-Fi a fundamental technology in the technological, economic and social scene.

Among the key factors that drive this growth we can highlight:

  • the massive digitisation of all kinds of current services where operators have an important business focus;
  • the spread of personal mobile devices and the adoption of the BYOD (Bring Your Own Device) business policy;
  • the growth of the number of connected devices at homes or Smart Home devices (Internet of Things or IoT), reaching about 50 devices per home in 2022;
  • new services with a higher capacity demand, such as 4K / 8K, virtual and augmented reality or videoconferencing;
  • and large-scale projects such as free European Wi-Fi, which will mean a 16% increase in the annual growth rate of Wi-Fi hotspots by 2020.

Figure 1. Wi-Fi milestones in the last 20 years.

Therefore, it is not just about the fact that most people use Wi-Fi as Internet access technology, but also the fact that the way they use it has also changed. Nowadays, people do not only connect to the Internet through a computer to check the news in the newspaper, but they also control the temperature of their house with their own voice, they talk on the phone through a Smart Watch or watch 4K movies on demand from a Smart TV.

Wi-Fi technology

Since Wi-Fi first appearance in 1999, this technology has undergone several important changes in order to meet the needs that have emerged over the past 20 years. It is true that the devices, which have come out thanks to this technology, have been adapted to enable the maximum usage of the current standard (including transmission and reception technology with multiple antennas for several simultaneous users, known as MU-MIMO for its acronym), but the new services and devices, especially those that are part of the IoT, require new formulas and operating mechanisms to reach the necessary and controlled convergence of the “everything connected”.

In this regard, this year 2019 the latest Wi-Fi update, known as version 6 or 802.11ax, has come out. Since 2013, when Wi-Fi 5 (802.11ac) appeared, a release capable of adapting to the new evolution of wireless connectivity was not defined.

Figure 2. Wi-Fi Technology evolución. | Source: Intel

As we can see in Figure 2, Wi-Fi technology has evolved until reaching higher speeds for a greater number of users and devices. This has been posible, mainly, thanks to changes in frequency bands (2.4 GHz vs 5 GHz), the increase in bandwidth (reaching 160 MHz), the creation of new high-order modulation schemes (which have stricter restrictions), and the increase in the number of data transmission streams. It is basically an evolution similar to that of the mobile phone radio access network, but over a longer period of time: better frequency bands (LTE 800), aggregation of different bands (Carrier Aggregation), several transmission streams for each user (MU-MIMO + beamforming), etc.

Figure 3. MU-MIMO in new generation routers.

At this point, it is important to understand the concept of Wi-Fi connection speed to really know how the user experience is going to be when connected to the Internet. The speeds we see in each standard definition are a reference to the maximum speed (at a physical level), that is, the maximum speed at which the devices can have a communication with the router, in the best situation.

For this, it is necessary to know the specifications of both ends of the communication, those of the router and those of the device. Usually, routers include in their definition the number of bands in which they can operate (2 or 3) and the maximum speed they can reach depending on the spatial transmission capacity (MIMO) and bandwidth.

As an illustration, we will use an example, which we will develop throughout the article:

Example: A router that is compatible with Wi-Fi 5 (ac), tri-band, MIMO 3×3, 80 MHz and AC3200 specification, means that it operates in 2.4 GHz band and in the two existing 5 GHz bands with their respective maximum speeds for MIMO 3×3 at 80 MHZ. This would be: 600 Mbps (2.4) + 1300 Mbps (5G) x 2 = 3200 Mbps.

Figure 4. Table of possible link speeds for “N” and “AC” standards. | Source: WirelessLAN Professionals

On the other hand, the devices have a similar definition, since each of its bands have a maximum capacity, as indicated in the table of physical speeds that we can see in Figure 4. However, nowadays, the differentiating element is in the spatial transmission capacity  (MIMO) of the devices. While there are already routers with MIMO 4×4 (for example, AC5300 – 1000 Mbps [2.4G] + 2 x 2166 Mbps [5G]), most current smartphones only have MIMO 2×2, thereby this fact limits the maximum transmission capacity to half.

Plus, for now, routers cannot operate in all bands at the same time, so it is impossible to reach that maximum speed.

Example: Taking the case of the example, if we connect to one of the 5GHz bands we will only have 1300 Mbps of maximum physical speed. If we connect through a Smartphone with MIMO 2×2, the capacity will be reduced to 867 Mbps (see Figure 4) in the best situation. In addition, if we are at a moderate distance from the router, we normally won’t be able to use the best possible modulation, since this is only offered when you are extremely close to the access point. The most realistic thing in this situation is to think that we will be using a 64-QAM modulation a few meters from the router, therefore, the maximum expected speed will be 650 Mbps (see Figure 4).

On the other hand, since air is a shared medium, wireless technology also provides a series of mechanisms to manage error control, broadcasts, access collisions and legacy device management, among others. All this control data means an overhead in the network of around 45%, so only 55% of the data sent or received is effective information.

Example: With this, and following the example, the connection real speed is 357 Mbps. Plus, if we consider other important factors such as interferences, caused by other users or other stations, the speed will be even lower. So, to sum up, 357 Mbps is the maximum speed that the user could obtain at best, out of the (theoretical) 1300 Mbps we saw at the beginning.

In the case of a 3×3 MIMO device and following the same premises, the maximum real speed that could be obtained in this case will be 536 Mbps.

Figure 5. Router Asus RT-AC5300 with MIMO 4×4

With the arrival of Wi-Fi 6, these and other limitations are trying to be improved in order to achieve higher transmission rates and, therefore, higher speeds. But it does not only means an improvement in speed, this new standard is also aimed at satisfying the transmission and consumption requirements of IoT devices, increasingly present in our daily lives.

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Author: Alejandro Gandara

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