The 4G Network

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By Unknown April 3, 2011 04:41

MIMO devices use multiple antennae to enhance signal strength and speed. Photo courtesy of tomsguide.com.

Does your phone take five minutes to send a thirty-second video? Are you sick of waiting 25 minutes for a 20 minute TV episode to buffer on your iPad? Perhaps an upgrade to the 4G wireless networks would do the trick. The question remains, though: does this new technology actually make a difference?

4G, or fourth generation, wireless standards are set by the International Telecommunication Union (ITU), requiring specific speeds and services. Despite what is advertised on television, no networks currently meet these official standards, but at least some of these networks will be able to roll out full 4G capabilities within a year or two.

A full understanding of the shift to 4G requires some background knowledge on wireless standards. Wireless telecommunications began in the 1980s with 1G, which handled cellular phone calls. This technology used analog voice encoding, whereas 2G, introduced in the 1990s, advanced to digital encoding of calls. 2G technology expanded mobile capabilities beyond simply calling, with the introduction of features such as short message service (SMS), or text messaging. Typical speeds were around 10 kilobits per second (kbps). Intermediate generations, called 2.5G and 2.75G, increased data transfer speeds to around 100 kbps and offered Internet access.

There were two principal types of 2G technologies used to handle multiple users: time division multiple access (TDMA) and code division multiple access (CDMA). TDMA allowed users to share a frequency channel by dividing it into “time slots.” Customers would take turns using the channel in rapid succession. CDMA allowed users to share a channel by using differently coded signals. This is analogous to pairs of people in a room communicating to each other in different languages. CDMA became more dominant under 3G standards (implemented by 2000), which provided video calls, mobile TV, and minimum data rates of 200 kbps. Recent expansions of 3G technologies, such as T-Mobile’s HPSA+ network (advertised as 4G), have improved average data rates to 28 Mbps.

So the reality is that 4G actually is much faster – it just isn’t here yet. According to the ITU, 4G peak data rates will go from 100 Mbps for “high mobility” connections (highway speed) up to 1Gbps for “low mobility” connections (pedestrian speed). This is a huge improvement – speeds will be faster by at least an order of magnitude. Additionally, 4G is an all-IP standard, unlike 3G, meaning that 4G will be more compatible with internet capabilities.

What led to this massive change? “Technology has really moved on,” explains Associate Professor of Electrical Engineering Edmund Yeh. Yeh has worked on communications networking for over a decade and his research has affected 4G standards in a meaningful way. He has contributed notably to dynamic resource allocation (DRA), designing some of the algorithms implemented in DRA prototypes. Essentially, DRA optimizes the power use and data rates of different users sharing a wireless channel. The system allocates resources based on the amount of the data transferred, the channel quality, and the wireless traffic. DRA is one of many innovations that make 4G standards so fast.

Another important advancement is orthogonal frequency-division multiple access (OFDMA), which has replaced CDMA as a means to handle multiple users. In short, OFDMA spreads signals over several orthogonal (non-interfering) frequencies, which helps mitigate frequency-specific fading in wireless channels. Also significant is the switch to multiple-input and multiple-output (MIMO) technology, originally developed in the 1990s. MIMO technology uses multiple antennae to both send and receive signals, substantially improving signal strength and speed. Turbo codes, which help correct errors, and equalization, which adapts to channel degradation, improve the reliability of 4G networks as well.

Evidently, there is a lot of technology behind 4G that you probably have not heard of. However, you might be familiar with AT&T or Verizon’s Long Term Evolution (LTE) or Sprint’s Worldwide Interoperability for Microwave Access (WiMax) networks. Unfortunately, these are only transition networks, but they will soon evolve into fully-fledged 4G networks, possibly within the next year. On the bright side, these networks already include many of the 4G upgrades; LTE, for instance, already uses OFDMA.

4G networks will have dramatically higher speeds, improved reliability, and expanded coverage. What does this mean for you? Well for one, you’ll be able to buffer movies and shows in a fraction of the current time. You will also be able to access the Internet through your laptop while traveling in a car, and you will not have to stand still to video chat on your phone. But what is really amazing is that, other than signing up for a new wireless plan, we will not have to do a thing to reap these benefits. 4G, the future of wireless, will come to us.

The current T-Mobile HSPA+ 4G coverage spans most of the United States.

Unknown
By Unknown April 3, 2011 04:41