This chapter is from the book
This chapter is from the book
This chapter is from the book
Pulling Some Gs
If you’re a mobile phone user (and you are, of course), then you’ve probably heard talk about something called 3G, and maybe even something called 4G. Each “G” is a generation of technology, which means we’re currently in the middle of the third generation and moving into the fourth. Let me explain.
1G
Before the age of digital mobile networks, all cell phones broadcast analog signals. In the U.S., this meant using the Advanced Mobile Phone System (AMPS) standard, which operated in a range of frequencies between 824MHz and 894MHz, dubbed the 800MHz band.
This type of analog transmission was the first generation of cellular phone technology, or what some refer to as 1G. Because analog phones could transmit only analog voice data, not digital data, they couldn’t be used to access the Internet or transmit text messages. Fortunately, there were more Gs to follow.
2G
Moving past the analog age, the cell-phone carriers needed to cram more calls into each frequency they were assigned. The way to do that was to move beyond inefficient analog signals into more efficient digital ones. That is, the original analog voice signal is digitized into a series of 0s and 1s; the resulting digital signal is then compressed and transmitted across the assigned frequency band.
NOTE
Because of the digitization and compression, a digital system can carry about ten times as many calls as an analog one.
In this second generation of cellular transmission (dubbed 2G, of course), several competing standards came into play, and different cellular carriers adopted different standards. There are two of these standards used in the United States:
- Code Division Multiple Access (CDMA). This standard operates in the same 800MHz band used by the previous analog transmissions and is employed by Sprint and Verizon.
- Global System for Mobile Communications (GSM). This standard operates in the 1,900MHz band and is used by AT&T and T-Mobile.
That’s just in the United States, of course. Other standards and frequency bands are used in other countries.
NOTE
CDMA and GSM are mutually exclusive technologies. A CDMA phone will not work on a GSM network, and vice versa.
2G networks and phones could also be used to transmit non-voice data. This ushered in the era of text messaging, in the form of Short Message Service (SMS) and, later, Multimedia Message Service (MMS). It also enabled access to the Internet, for email, web browsing, and the like.
NOTE
SMS transmits text-only messages. MMS transmits text messages with multimedia attachments (photo, video, and so on).
3G
The next generation of cellular transmission was developed with the smartphone in mind. So-called 3G networks feature increased bandwidth and transfer rates that better accommodate the transfer of digital data necessary for Internet access and the use of web-based applications.
How much faster is 3G? A lot. Today’s 3G networks boast transfer speeds up to 2Mbps; in contrast, 2G phones can only transfer data at around 144Kbps. That’s a 13-fold increase in speed, more or less, if you’re doing the math.
Just as with 2G digital networks, there are several different 3G standards in use in the U.S. (and a few more in use overseas):
- CDMA2000 is an evolution of the previous CDMA standard. It’s used by Sprint and Verizon.
- Universal Mobile Telecommunications System (UMTS) is an evolution of the GSM standard used by AT&T and T-Mobile.
If you use your smartphone for anything other than voice calls and text messages, you need to be on a 3G network. In those areas where you’re forced to use a 2G connection, accessing the Internet is painfully slow. In this respect, 3G is the de-facto minimum requirement for using a smartphone today.
4G
Now, we get to the fourth generation of cellular networking. Carriers are just starting to roll out 4G networks, and suppliers are just starting to produce 4G smartphones. 4G promises data transmission rates in excess of 1Gbps, which is more than 30 times the rate of 3G networks. (That should make it a lot easier to watch streaming video on your iPhone!)
Naturally, competing 4G standards are in play. Look for the following protocols used by U.S. carriers:
- Long Term Evolution (LTE). This standard promises data download rates to mobile users up to 300Mbps. It’s used by AT&T and Verizon.
- Evolved High Speed Packet Access (HSPA+). This standard promises data download rates up to 168Mbps, although current rates top out at 42Mbps. It’s used by T-Mobile.
- Worldwide Operability for Microwave Access (WiMax). This standard promises data download rates of 128Mbps. It’s used by Sprint.
To put all these Gs into perspective, see Figure 4.2. This chart compares the data-transmission (download) rates of 2G, 3G, and 4G networks. (Remember, 1G was analog, not digital, and thus couldn’t transmit non-voice data.) There’s been a lot of improvement over the years!
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Figure 4.2. Comparing 2G, 3G, and 4G data download speeds.