Fleet of Foot

In the history of wireless networks, many innovations have already been exaggerated by providers as a major breakthrough yet, in the end, did not really meet the expectations of users. In the case of WiFi 6, however, the expectations are justified. The 802.11ax specification is the first WiFi standard developed with the premise that it will overtake wired as the primary means of connecting terminal devices to the network – in the office or on the shop floor. (See the "WiFi 6 Goals" box.)

The earlier WiFi generations were designed for occasional use and less for downloading large data volumes. The 802.11ac specification (WiFi 5) certainly made WiFi networks faster, but in reality, this variant only partially improved an outdated concept and increased transmission speed.

Every WiFi user has certainly connected to a WiFi access point (AP) at some time at a conference center, in a football stadium, or in another public space. Everything works fine until the moment the speaker starts their presentation or the spark fails to fly between the onstage musicians and the audience, prompting many people to open up private communication channels (email, Snapchat, Twitter, WhatsApp, Facebook, etc.). All of a sudden, the WiFi that had worked so well before is extremely slow and becomes unusable.

The causes of WiFi problems do not always lie in the speed of the system. The 802.11ac Wave 2 specification (WiFi 5) now provides speeds around the gigabit mark. This bandwidth should be sufficient for most applications. The bigger problem that WiFi networks face can best be described as "congestion." Wireless networks are comparable to highways: Normally, the capacity of multilane highways is sufficient for free-flowing traffic. However, if an extremely large number of people try to use the same freeway routes at the same time (e.g., to get to a large event), the bandwidth of the route is not sufficient to transport the cars efficiently, inevitably leading to traffic congestion. If many people try to access the WiFi network and communicate simultaneously, a temporary overload also occurs.

The WiFi 6 standard, based on the successful practical solutions provided by Long-Term Evolution (LTE) technology, promises to solve the congestion problem. WiFi 6 is expected to be ratified in the middle of 2020, with additional features (including operation in the 6GHz band) certified over the next couple of years, although some commercial pre-standard products are already available today.

Who Should Use WiFi 6?

All companies currently using WiFi 4 (802.11n) or older WiFi standards are candidates for an upgrade. Market analysis firm ZK Research estimates that up to 49 percent of all companies are still using WiFi 4 somewhere on their corporate networks [1]. This technology is almost a decade old and has reached the end of its performance and reliable lifetime. These customers should skip WiFi 5 (802.11ac) and directly deploy WiFi 6. An intermediate step to WiFi 5 would probably result in another WiFi upgrade in two to three years. In contrast, the direct upgrade to WiFi 6 promises to include at least five years' worth of updates.

WiFi 6 Is Far Faster

The products based on the 802.11ax standard work about four to 10 times faster than the WiFi standards used so far, because WiFi 6 has more and wider transmission channels that significantly increase throughput. (See Table 1 for the specifications of various WiFi standards.) Assuming the speed is increased fourfold when using 160MHz channels, the speed of a single WiFi 6 stream is 3.5Gbps. The equivalent WiFi 5 connection would be a transfer speed of 866Mbps.

In a 4x4 multiple in/multiple out (MIMO) environment, WiFi 6 devices achieve a maximum total capacity of 14Gbps. A wireless client that supports two or three streams in parallel can easily accommodate them in a 1Gbps connection. If the channel width is reduced to 40MHz, which can happen at any time in crowded radio fields, only a single 802.11ax stream of around 800Mbps with a total capacity of 3.2Gbps would be available. Regardless of the channel size, the new WiFi 6 specification provides an enormous increase in transmission speed and overall capacity.

Fewer Data Jams

LTE products use a technology called orthogonal frequency-division multiplexing access (OFDMA). In previous WiFi versions, the transmission channels remained open until the data transmission was completely terminated, which is comparable to queues at a ticket counter. The waiting customers can only move forward when the ticket counter is free. In the case of the WiFi process based on multiuser MIMO (MU-MIMO), this means four ticket counters and four lines (one per sales counter). The next person waiting in line can only be served when a desk becomes free, which reduces the time each person has to wait for service, thus increasing the speed of the system.

The OFDMA method splits each channel into hundreds of smaller subchannels (Figure 1). Each of these subchannels uses a different frequency. The signals are then encoded orthogonally and stacked accordingly. In the ticket booth analogy, you have to imagine a counter clerk who is able to serve several customers simultaneously. While the employee is going through the process of taking payment for a ticket, they can already start serving the next customer. Instead of alternately listening to the respective messages transmitted over the radio medium, OFDMA allows up to 30 clients to share each channel.

Figure 1: WiFi 6 offers increased efficiency at high data rates for short data packets.

OFDMA also improves in terms of efficiency as the number of users increases, because the available airtime – the time the radio medium is available to the user for transmission – can be used in a far more effective way. Of course, this presupposes that a significant proportion of terminals are WiFi-6-compatible. To achieve noticeably higher throughput, perhaps 30 percent of the terminals need to support the new standard. From a network perspective, the transmission path appears less congested than with WiFi 5. Another advantage is that the 2.4 and 5GHz bands can be combined, giving users even more channels for data transmission. The WiFi 6 specification also uses quadrature amplitude modulation (QAM) coding, which ensures that the packets transmitted can contain even more data. The OFDMA mechanism also enables granular Quality of Service (QoS), which allows applications with high bandwidth requirements or delay-sensitive requirements specifically to be prioritized in both the uplink and downlink directions.

Many users believe that by increasing the transmission power at the access point, better range and higher data rates are possible. However, because of the typically lower transmission power of end devices, this is not true in most cases. If the end devices are not able to acknowledge received packets with a comparable signal level, the access point assumes poor signal quality and thus reduces the data rate. To achieve maximum data rates requires symmetry between the received signal strengths to circumvent this problem. However, increased sensitivity of access point antennas only helps to a limited extent to compensate for the different transmission powers.