CDMA Phone: What is it? Two-standard phone CDMA + GSM

The CDMA standard is not as popular as everyone known and loved by GSM operators. However, it has its advantages and advantages. Therefore, when buying a new cell phone, it is worth paying special attention to CDMA-GSM phones. This will be the best option.

What is it?

Code Division Multiple Access - this is the abbreviation of this communication standard. It means the use of multiple channels with code division. At the same time during a telephone conversation, personal data and the voice itself are transmitted through separate channels and at different frequencies. In addition, for the data transmission itself, more space is provided than with the GSM standard.

What is CDMA phone? This is a gadget that provides services such as a direct city and mobile number, the exchange of packet data and the transmission of messages with a speed of up to 2.3 Mbps. The CDMA principle consists in some expansion of a certain spectrum of an information signal. For this, two methods are used: a direct sequence and jumps in frequency. In the first case, the main carrier frequency changes its value in a certain range. In this case, the receiver operates according to the same algorithm. This ensures the allocation and processing of a specific channel. The direct sequence method uses noise-like signals. Each separate signal is modulated by a unique code that extends the spectrum of the information signal itself.

What is GSM?

A lot more is known about the main competitor of CDMA. It is actively used in the work of domestic cellular networks. The GSM standard uses TDMA technology and is based on the frequency division algorithm of the channel. There are as many as four ranges:

• Single-band . Used extremely rarely.
• Dual-band . Here telephones are tied to a certain region.
• Three-band . The standards are 900/1800/1900, and also 850/1800/1900.
• Four-band . Such functionality provides almost all new smartphones.

There is one feature in GSM devices that the CDMA phone can not boast. What it is? The presence of an additional SIM-card. With its help, you can easily and quickly change the operator.

History of technology

Despite the prospects and safety, this standard is not used so often. And many ask the following question: "CDMA phone - what is it?". Its history began in the 30s of the last century.

In the USSR, the famous academician Ageev DV was engaged in relevant research. In 1935 he published his own work "Code division of channels". The brochure did not become a bestseller; More related to future developments. But soon this topic was picked up by other well-known scientists. So the initial basis for further development of CDMA technology was created.

Already in the late 1950s the US used this standard for military purposes. And only in the 80's the technology was declassified and presented to the world. Adapt it was able to Dr. Irwin Marc Jacobs. Later, he even created his own firm Qualcomm, engaged in satellite communications, telephony and cellular systems.

Thanks to this American since 1992, a new standard has been actively introduced around the world. And since 1996 CDMA-GSM-phones have become equally used. At that time about 24 countries of the world participated in the project.

CDMA standards

Despite the fact that this technology unites the principle of action, it has several directions. Actually, the CDMA system uses certain sets of channels with a width of 1.23 MHz. In this case, the voice itself is encoded at a speed of 8.55 kbit / s. Sometimes this data stream is cut to 1.2 kbps. This standard uses the simplest Nokia CDMA phones. Their plus is in reliability and quality.

The CDMAOne standard exists in the temporary IS-95a, IS-95b, and J-STD-008 models. The declared signal speed here is from 9.6 kbit / s to 115.2 kbit / s. There were network data back in 1995 in America. Now the standard is quite common in Asia. In Russia, it is allowed to provide only fixed fixed-line services for such a system.

The CDMA2000 standard is the successor to CDMAOne. It almost completely corresponds to the generation of 3G. Another of its features and value lies in the fact that it is on the basis of this standard that new systems of cellular operators are developed.

WCDMA standard

It is widely distributed in Japan. This technology is used in high-speed transmission of various multimedia, video conferencing and Internet access. China is also a leader in the use of such networks, but along with WCDMA TD-SCDMA and CDMA-2000 networks are advancing here.

Speaking of the principle of operation, it can be said that this is also a multiple access system with code division of existing channels and direct expansion of the spectrum of action. At the same time, the stream speed reaches 384 kbit / s, and the bandwidth is up to 5 MHz. This is achieved through multicode combinations and the use of a variable spreading factor.

The main advantage of this communication standard is that it does not have a global time reference and GPS. Therefore, it can work independently of the city or country in which it is located. This is also the difference between CDMA GSM phones (including Odessa, which is covered by this network).

Another significant factor in favor of this standard is its air interface. It works in such a way that it's easy to use not only multi-user reception, but also intelligent tuning of the necessary adaptive antennas. This contributes to a significant increase in coverage and throughput.

CDMA-450

The introduction of this system was the impetus to the development of new generation cellular networks. The plus of this standard is that all frequency ranges of mobile cellular systems can be fully used here. It is already beginning to actively use CDMA-phones (Ukraine is also in the coverage zone).

Such networks provide a long range of communication. That's why operators do not need to build a lot of stations. In the field of providing mobile Internet there are also a number of advantages over the usual GSM-operators. EV-DO technology provides broadband access at speeds up to 2.4 Mbps.

To transmit data by this system is much safer, because Here we use a special encryption algorithm and cryptographic authentication of all mobile terminals. The technology in question will also be useful for ordinary citizens. This is explained by the fact that during the operation of the stations, the radiation power is 11 times less than that of GSM networks.

From all of the above, it is quite natural to ask why in Russia and the CIS CDMA-450-phones are unpopular? The reasons, as it turned out, are several:

• Lack of special equipment.
• There is no diversity in the offered models and brands of CDMA-phones.
• Lack of roaming.

Advantages of the CDMA standard

This technology is quite new. And it is much inferior to that used by cellular operators GSM. She has undeniable advantages:

• Confidentiality and security of personal information. Due to the encoding technology used, the user is almost completely protected from various fraudulent actions. In addition, there is completely eliminated extraneous noise and the possibility of parallel conversations.
• Less energy consumption. Due to the optimized data transfer, CDMA-450 phones spend battery power much more slowly. This can allow manufacturers to create models that are much more compact and ergonomic.
• There are practically no interrupted conversations. In CDMA phones, the throughput of calls is significantly increased, busy and parallel lines are eliminated.
• Extended network activity zone. CDMA uses completely different telecommunication technologies, which allow to significantly increase the coverage area.
• Additional services . It can be the transmission of operational important data and messages, identification of any subscriber, etc.

That is why a growing number of users are choosing a CDMA phone. What it is? The opportunity to get all the benefits right away!

Disadvantages of CDMA

Despite the obvious advantages over the GSM standard, they are actively using these networks only in America. Europe is just beginning to get acquainted with this technology. Among the shortcomings that hamper the rapid and confident promotion of CDMA to the masses, we can distinguish the following:

• The cost . Despite quite tolerable tariffs for direct urban numbers, these phones cost more than GSM-analogues.
• Repair . Due to the fact that such gadgets are not common in the world, spare parts are difficult to find. In addition, not all are familiar with the technology of repair.
• No base stations on the CDMA phone. What it is? These are such telecommunication points that provide coverage of the network.

Two-standard phones

As can be seen from the article, both CDMA and GSM have their strengths and weaknesses. And our man well, it's just vital to use everything at once. That's why the dual-standard CDMA-GSM phone was invented. It combines all the advantages of both systems.

What is he like? This is quite an ordinary mobile phone with an improved battery that can withstand more calls and conversations. By design and functionality, it almost does not differ from standard relatives.

Such cellular phones have become more popular recently. Therefore, gradually all the world's mobile brands began to produce separate lines of dual-standard gadgets.

For example, CDMA-450-phones are actively promoted by Skylink. Also in various stores you can find models of Nokia, Huawei, Pantech, HTC and many others.

Features of dual-standard phones

In addition to the functional contact book, where one subscriber can be assigned 4 or more numbers at once, as well as several electronic addresses, CDMA-GSM-cellular has several more significant differences:

1. These are predominantly monoblocks. Although recently you can find sliders or cots.
2. Almost all phones support microSD.
3. Cell phones are equipped with a camera of at least 2Mp. Of course, with the growth of popularity, the line of phones on the market is also developing. In the competition include more and more new manufacturers, developing a design, adding technical capabilities and characteristics, etc.

In general, these models are standardized to the usual smart phones and phones. Manufacturers try to create them in the usual design and with the same set of functions. In some cities CDMA phones are increasingly used. Odessa, for example, how the port center provides an opportunity to use all models. Inside the country of choice, of course, less.