Understanding 3G Technology


The mobile connections are becoming the successor of dial-up, in the sense that they are available virtually anywhere, given even in the most remote areas where other methods of access are not available. They are also the joy of those who need a continuous connection anywhere to work or keep in touch with family and friends. The main driver for the popularity is the availability of 3G connections, which (at least in areas of good coverage) offer an option of bandwidth usage.

As in the case of GSM, which supports the use of GPRS and EDGE, UMTS (Universal Mobile Telecommunications System) offers two access modes, which are used according to availability, reception quality and the mode supported by the device.

The most basic is the W-CDMA (Wideband Code Division Multiple Access) (not to be confused with CDMA, which is the standard of the competing GSM), which offers transmission rates up to 384 kbits, both for download and for upload. Although, on paper, be close to the value offered by EDGE 236.8 kbits, in practice, the WCDMA offers much better latency times and a connection that is much more usable. A good example of the difference is the use of VoIP applications, which are almost unusable on EDGE, due to the lag in transmission, but flow satisfactorily in WCDMA.

Then HSDPA (High-Speed Downlink Packet Access), a protocol that reduces latency and improves the download rate of the network significantly. Using HSDPA as the transport protocol, UMTS supports rates of 1.8, 3.6, 7.2 and 14.4 megabits, according to the implementation used by the carrier (version of 7.2 megabits is the most common). Naturally, the actual speed varies with the signal quality and the number of users connected to the same broadcast station, but it is always much higher than in WCDMA.

The major problem is that the HSDPA works well only relatively in short distances, reducing the transmission rate. Another limitation is that only HSDPA increases the download rate, without doing anything about the upload, which remains at the only 384 kbits, as well as WCDMA.

HSDPA is considered as a 3.5G protocol and (on most devices) you can check which system is being used simply by looking at the connection icon. A “3.5G” indicates that you are using HSDPA, a “3G” that is WCDMA in use, an “E” being used – EDGE and a “G” if you’re in an area where only the old GPRS is available.

On Mobile Phones, you will notice that the 3.5G icon only appears while the unit is transmitting data. That’s because it actually uses the HSDPA only while the connection is active. The rest of the time, it toggles back to WCDMA, to save energy, causing the icon back to “3G”.

A side effect of UMTS is that it brought back the issue of using different frequencies in different parts of the world. In the U.S., frequencies of 850 and 1900 MHz and in Europe it is900 and 2100 MHz, in India, 900 and 1800 MHz are used, in accordance with state and operator used.

Note that only the national version supports both frequencies used here. During the time of launch of mobile phones, many bought the European version (that supports the 2100 MHz band, but not the 850 MHz) only to find that they could not use it in conjunction with the 3G or in the various states where band of 850 MHz is used.

As you can see, it seems that the band of 1800 MHz predominate in India, it is not advisable to invest in equipment in the American version, which only support 850 and 1900 MHz. In the absence of a tri-band model, the best choice are the European versions (900 and 2100 MHz).

In addition to disrupt the lives of users, this confusion of frequencies is also not good for manufacturers, who are required to produce different versions of the same devices. This has led to an increase in the production of tri-band models, capable of operating at three frequencies (850/1900/2100MHz). They must become more common since the second generation of 3G handsets, solving the impasse.

As with ADSL and other forms of access, high rates of UMTS may be limited by operator according to plan. This allows increasing the number of subscribers supported within a given frame and adds the possibility to charge more by the planes faster.

In conclusion, HSUPA (also called EUL), an updated standard that complements the best download rates of HSDPA with improvements also upload rates, ranging from 730 kbps (on HSUPA category 1) up to 5.76 megabits according to the implementation. Why be just an extension of UMTS and not a new 3G standard, the investments required to migrate the networks are relatively small, since it only replace some equipment on the towers and resize the routing structure, without requiring the licensing of new tracks substitution frequencies or antennas.

HSUPA is already supported on a lot of devices. It is important to emphasize that the HSDPA and HSUPA are two standards that are complementary, not competing. HSDPA improves download rates compared to WCDMA, HSUPA improves while upload rates. According to the equipment used, operators can support both standards, offering much faster upload as download, or only support HSDPA.

In India, the only operator to have used HSUPA (in early 2002) was BPL (Now Known as Vodafone), and the service was localized only to Mumbai. And as there is so much demand for better upload rates as there is for faster downloads, most of the mobile service providers has started to offer the 3G services which has also helped to increase the use of cloud services in India like iCloud, Dropbox and eNlight on mobile devices.


Understanding  HSDPA (High Speed Downlink Packet Access)

HSDPA, which can translate to package high speed, is a technology used in mobile broadcasting, and has made it possible to download more data faster in third generation mobile networks. This protocol is designed for mobile phones that has improved the speed and capacity of existing networks to more efficiently manage the spread spectrum signals. There is a variant called HSRP + using the spectrum more efficiently, allowing higher peaks of diffusion and less delays in data transmission. This difference between the two technologies has resulted in over the second version of third generation networks that are used. The main advantage of HSRP on older technologies is the improvement in communication protocols or rules, which facilitates the movement of the voice packets and data between mobile devices and radio stations.

Many engineers are working to improve communications speed, the amount of data per channel, the number of channels, error detection and methods for encoding and decoding data. As a result of the HSDPA protocol and its enhanced version, users can download all kinds of faster services. An example could be downloading a movie or music video, where you will notice a more fluid and less stops when loaded into the buffer when compared to previous technologies. The truth is that, HSDPA is a combination of other protocols that already existed, and has a high average traffic of 14 megabits per second, and nearly 6 megabits upstream.

What it does is, improve the bandwidth of the WCDMA protocol to increase the transmission rate, the shared transmission channel shorten the time interval between transmission and improving modulation and signal amplitude. The enhanced HSDPA + version makes better use of the spectrum, which gives us 56 megabits to 22 megabits upstream. One of the best things about it is that it is compatible with virtually all protocols of the Internet. This is especially interesting when it comes to IP networks.

A structure of IP network performs more direct connections in mobile broadcast networks, which helps to reduce the cost of moving data from one place to another and also reduces latency, which are delays in processing information. This process is transparent to us, but if it is not sufficiently well, what we notice in the delivery of this information (data). The result is that the connection is lost and the response time is much better. And HSDPA + release technologies are based on the GSM mobile communication system, which is used worldwide. Therefore, this protocol will still be in use for some time, which will improve in the future.


3 Responses

  1. abhishek

    thanks for informative article. most of us know little about these smart phones and hardwares functioning. i still not understand lets say we have three frequency bands, so is it something like that 3g is going to preferably use a special band from these?

  2. Matt Darcey

    Hi Pravin, you’ve shared a nice article. Understanding 3G is a huge topic and it got my attention. It’s good to know many unknown things about 3G and the full form of HSDPA.

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