1G, 2G, 3G, 4G, 5G

The G in 5G means it's a generation of wireless technology. While most generations have technically been defined by their data transmission speeds, each has also been marked by a break in encoding methods, or "air interfaces," which make it incompatible with the previous generation.

1G was analog cellular. 2G technologies, such as CDMA, GSM, and TDMA, were the first generation of digital cellular technologies. 3G technologies, such as EVDO, HSPA, and UMTS, brought speeds from 200kbps to a few megabits per second. 4G technologies, such as WiMAX and LTE, were the next incompatible leap forward, and they are now scaling up to hundreds of megabits and even gigabit-level speeds.

5G brings three new aspects to the table: greater speed (to move more data), lower latency (to be more responsive), and the ability to connect a lot more devices at once (for sensors and smart devices).

The actual 5G radio system, known as 5G-NR, won't be compatible with 4G. But all 5G devices, initially, will need 4G because they'll lean on it to make initial connections before trading up to 5G where it's available.

4G will continue to improve with time, as well. The Qualcomm X24 modem, which will be built into most 2019 Android flagship phones, will support 4G speeds up to 2Gbps. The real advantages of 5G will come in massive capacity and low latency, beyond the levels 4G technologies can achieve.

That symbiosis between 4G and 5G has caused AT&T to get a little overenthusiastic about its 4G network. The carrier has started to call its 4G network "5G Evolution," because it sees improving 4G as a major step to 5G. It's right, of course. But the phrasing is designed to confuse less-informed consumers into thinking 5G Evolution is 5G, when it isn't.

Verizon's home service, which is a nonstandard form of 5G, has led its competitors to claim that it's not really 5G. But given that it offers multi-gigabit wireless speeds and will be swiftly transitioned over to the standard version

 

How 5G Works

Like other cellular networks, 5G networks use a system of cell sites that divide their territory into sectors and send encoded data through radio waves. Each cell site must be connected to a network backbone, whether through a wired or wireless backhaul connection.

5G networks will use a type of encoding called OFDM, which is similar to the encoding that 4G LTE uses. The air interface will be designed for much lower latency and greater flexibility than LTE, though.

5G networks need to be much smarter than previous systems, as they're juggling many more, smaller cells that can change size and shape. But even with existing macro cells, Qualcomm says 5G will be able to boost capacity by four times over current systems by leveraging wider bandwidths and advanced antenna technologies.

The goal is to have far higher speeds available, and far higher capacity per sector, at far lower latency than 4G. The standards bodies involved are aiming at 20Gbps speeds and 1ms latency, at which point very interesting things begin to happen.

What's the Frequency?

5G primarily runs in two kinds of airwaves: below and above 6GHz.

Low-frequency 5G networks, which use existing cellular and Wi-Fi bands, take advantage of more flexible encoding and bigger channel sizes to achieve speeds 25 to 50 percent better than LTE, according to a presentation by T-Mobile exec Karri Kuoppamaki. Those networks can cover the same distances as existing cellular networks and generally won't need additional cell sites. Sprint, for example, is setting up all of its new 4G cell sites as 5G-ready, and it'll just flip the switch when the rest of its network is prepared.

The real 5G innovation is happening at higher frequencies, known as millimeter wave. Down in the existing cellular bands, only relatively narrow channels are available because that spectrum is so busy and heavily used. But up at 28GHz and 39GHz, there are big, broad swathes of spectrum available to create big channels for very high speeds.

Those bands have been used before for backhaul, connecting base stations to remote internet links. But they haven't been used for consumer devices before, because the handheld processing power and miniaturized antennas weren't available. Millimeter wave signals also drop off faster with distance than lower-frequency signals do, and the massive amount of data they transfer will require more connections to the landline internet. So cellular providers will have to install more, smaller, lower-power base stations rather than use existing powerful macrocells to offer the multi-gigabit speeds that millimeter wave networks promise.