When you’re in the market for a new smartphone, you’ll note there are a lot of acronyms included on the sales card: CDMA, GSM, 3G, 4G, LTE, and so on.
Perhaps most vital to the future usability of the cell phone is 4G and LTE. To start things simply, the “G” means generation, so in “4G,” the company selling the device is referring to the fact that it supports the fourth generation of mobile data technology, which is defined by the International Telecommunication Union-Radio (ITU-R), the United Nations’ official agency for information and communication technologies.
LTE, on the other hand, stands for “long term evolution,” which applies more generally to the idea of improving wireless broadband speeds to meet ever-increasing demand.
Third-generation mobile networks, or 3G, came to the U.S. in 2003. With minimum consistent Internet speeds of 144 kbits/s, 3G was supposed to deliver “mobile broadband.” However, there are now so many varieties of 3G that a “3G” connection can get you Internet speeds anywhere from 400 kbits/s to four times that (UMTS TDD).
4G was introduced (or I should say was first talked about) in 2008 as a successor to 3G. At that time, the ITU-R applied a set of standards. When these standards were announced, they talked of data speeds that were unheard of in the real world. Speeds like 100 Mbits/s. That’s because they weren’t meant to immediately usher in a whole new era of network capabilities but, rather, they were to help developers achieve new benchmarks for mobile technologies; a pathway, if you will. In reality, there are so many technologies called “4G,” and so many ways to implement them, that the term is almost meaningless.
I think of 4G LTE networks as providing at least 10 Mbits/s data downstream and half of that upstream. Some are said to have 50 Mbits/s “peak” speeds. Some say that their speed is 100 Mbits/s, but their average speed is just 12 to 15 Mbits/s, download. So the confusion continues.
By the way, if your phone is mostly for voice use, you don’t need 4G; stick with a cheaper 3G phone that will still operate with all your carriers’ cell towers. And, if you live in an area that doesn't have 4G coverage, there's no advantage to a 4G phone. In fact, you may have serious battery life problems if you buy an LTE phone and don't disable 4G LTE, because the radio's search for a non-existent signal may drain your battery quickly.
LTE is a general term covering a number of “pathways” to cellular advances. When the ITU-R set the minimum speeds for 4G, they were believed to be somewhat unachievable. So, LTE was created to formalize the technology being used in pursuit of these faster standards, and thereby allowing a device to be marketed as superior to its 3G predecessor.
From a technical standpoint, two key improvements led to LTE being formally recognized as a better service than 3G: orthogonal frequency division multiplex (OFDM) and multiple-input, multiple-out (MIMO). The former is a transmission technique that uses a high quantity of closely spaced carriers that are modulated with lower data rates. In short, it’s a spectral efficiency scheme that allows for higher data rates, while also permitting more than one user to share a channel.
OFDM has also been adopted in the Wi-Fi arena, where standards like 802.11a, 802.11n, 802.11ac, DAB Digital Radio, plus DVB Digital Video Broadcast make use of it. It does usually require more battery power because the power amplifier needed is more sophisticated.
MIMO is a technique using multiple antennas at the transmitter and receiver. MIMO uses complex digital signal processing to set up multiple data streams on one channel. The earliest LTE networks launched were immediately able to support 2×2 MIMO in both the downlink and uplink.
MIMO uses the multipath signal propagation that is present in all terrestrial communications. Rather than providing interference, these paths can be used to your advantage. Having more than one antenna, and using the processing power available at either end of the link, they can use the different paths between the two entities to improve the signal-to-noise ratio and, thus, data rates.
But has there been any actual improvement in downlink speeds? The answer is yes, when compared to 3G networks. When you compare what’s being called 4G networks and LTE networks, they are probably the same thing. Look for the combination 4G LTE and the data speed of a particular cell operator. And that data is often hard to read in their advertising lingo. Your best bet is to look for independent test results that cover your specific city or region. LTE is available in more major areas than ever before, but it’s still not everywhere in the sense that 3G is. And, 3G phones and plans are still often cheaper.
But, how do we get to even faster speeds? Experts believe it’ll be by way of carrier aggregation, as used in LTE-Advanced. This practice lets operators treat multiple radio channels in different or the same frequency bands as though they’re one. This produces faster speeds and aids bandwidth-dependent applications like streaming HD video and mobile game playing. Chip makers like Qualcomm believe that the aggregation of two signals could very well double download speeds to about 150 Mbits/s. In the future, there could be aggregation across more than two channels, and even up to five.
The 3rd Generation Partnership Project (3GPP) unites seven telecommunications standards development organizations (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC) and provides their members with a stable environment to advance the technologies. LTE-Advanced is a standard from 3GGP. It should be deployed by 2018 and will yield:
Increased peak data rate, DL 3 Gbps, UL 1.5 Gbps
Higher spectral efficiency, from a maximum of 16 bits/s/Hz in R8 to 30 bits/s/H in R10
Increased number of simultaneously active subscribers
Improved performance at cell edges
The main new functionalities introduced in LTE-Advanced are Carrier Aggregation, enhanced use of MIMO techniques, and support for Relay Nodes (RN).
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