The CDMA standard is not as popular as the well-known and loved by GSM operators. However, it has its advantages and benefits. Therefore, when buying a new cell phone, you should pay special attention to CDMA-GSM phones. This will be the best option.
What is it?
Code Division Multiple Access - this is how the abbreviation of this communication standard is decrypted. It refers to the use of multiple code division channels. 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, more space is provided for data transfer than with the GSM standard.
CDMA phone - what is it? This is a gadget that provides services such as a direct landline and mobile number, packet data exchange and messaging at speeds up to 2.3 Mbps. The principle of CDMA is a certain extension of a certain spectrum of the information signal. Two methods are used for this: direct sequence and frequency jumps. In the first case, the main carrier frequency changes its value in a certain range. In this case, the receiver works according to the same algorithm. This ensures the selection and processing of a specific channel. The direct sequence method uses noise-like signals. Moreover, each individual signal is modulated by a unique code, expanding the spectrum of the information signal itself.
What is GSM?
Much more is known about the main competitor of CDMA. It is he who is actively used in the work of domestic cellular networks. The GSM standard uses TDMA technology and is based on the frequency division multiplexing algorithm. There are as many as four ranges:
- Single band . Used extremely rarely.
- Dual band . Here, phones are tied to a specific region.
- Three-band . The standards used are 900/1800/1900, as well as 850/1800/1900.
- Quad band . Almost all new smartphones are provided with such functionality.
There is one feature of GSM devices that a CDMA phone cannot boast of . What is this The presence of an additional SIM card. With its help, you can easily and quickly change the operator.
History of technology
Despite the promise and safety, this standard is not used as often. And many are asking the following question: “CDMA phone - what is it?”. Its history began back in the 30s of the last century.
In the USSR, the distinguished academician D.V. In 1935, he published his own work, Code Division of Channels. The brochure did not become a bestseller. More relevant to future developments. But soon this topic was picked up by other famous scientists. So the initial base was created for the further development of CDMA technology.
Already in the late 50s in the United States used this standard for military purposes. And only in the 80s was technology declassified and introduced to the world. Dr. Irwin Marc Jacobs was able to adapt it. Later, he even created his own company, Qualcomm, engaged in satellite communications, telephony and cellular systems.
Thanks to this American since 1992, the new standard has been actively introduced around the world. And since 1996, CDMA-GSM phones have been used equally. Moreover, at that time about 24 countries of the world participated in the project.
CDMA Standards
Despite the fact that this technology combines 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 trimmed to 1.2 kbps. This standard is used by the simplest Nokia CDMA phones. Their plus is in reliability and quality.
The CDMAOne standard exists in the temporary models IS-95a, IS-95b and J-STD-008. The claimed signal speed here is from 9.6 kbit / s to 115.2 kbit / s. Network data appeared back in 1995 in America. Now the standard is quite common in Asia. In Russia it is allowed to provide only fixed-line telephony services through such a system.
The CDMA2000 standard is the successor to CDMAOne. It almost completely corresponds to the 3G generation. Another of its features and value is that it is on the basis of this standard that new systems of mobile 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 also promoted here.
If we talk about the principle of action, we can say that this is also a multiple access system with code division of existing channels and direct expansion of the spectrum of action. In this case, the flow rate reaches 384 kbit / s, and the bandwidth is up to 5 MHz. This is achieved through multi-code combinations and the use of a variable expansion coefficient.
The main advantage of this communication standard is that it does not have a global time reference and GPS. Therefore, it can work regardless of the city or country in which it is located. The same is the difference between CDMA GSM phones (Odessa is also covered by this network).
Another significant factor in favor of this standard is its air interface. It works so that you can easily use not only multi-user reception, but also the 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 for the development of a new generation of cellular networks. The advantage of this standard is that all frequency ranges of mobile cellular communication systems can be fully used here. It is already being actively used by CDMA-phones (Ukraine is also in the coverage area).
Such networks provide a large communication range. That is why operators do not need to build many 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.
Transferring data with this system is much safer, because it uses a special encryption algorithm and cryptographic authentication of all mobile terminals. The technology under consideration will be useful for ordinary citizens. This is due to the fact that during the operation of the stations, the radiation power is 11 times less than from GSM networks.
From all of the above, a completely logical question arises as to why CDMA-450 phones are unpopular in Russia and the CIS? The reasons, as it turned out, are several:
- Lack of special equipment.
- There is no variety in the proposed models and brands of CDMA-phones.
- Lack of roaming.
CDMA Benefits
This technology is quite new. And it is much inferior to that used by mobile operators GSM. She has undeniable advantages:
- Confidentiality and security of personal information. Thanks to the applied coding technology, the user is almost completely protected from various fraudulent activities. In addition, extraneous noise and the possibility of parallel conversations are completely eliminated here.
- Lower power consumption. Thanks to optimized data transfer, CDMA-450 phones consume battery power much more slowly. This may allow manufacturers to create models that are much more compact and ergonomic.
- Virtually no interrupted conversations. In CDMA telephones, the call throughput is significantly increased, busy and parallel lines are eliminated.
- Extended network coverage. CDMA uses completely different telecommunication technologies that can significantly increase its coverage area.
- Additional services . This can be the transmission of operational important data and messages, the identification of any subscriber, etc.
That is why an increasing number of users are choosing a CDMA phone. What it is? The opportunity to get all the benefits at once!
Disadvantages of CDMA
Despite the clear advantages over the GSM standard, these networks are actively used only in America. Europe is just starting to get acquainted with this technology. Among the disadvantages that interfere with the rapid and confident promotion of CDMA to the masses, the following can be distinguished:
- Cost . Despite quite reasonable tariffs for direct city numbers, such phones are more expensive than GSM-analogues.
- Repair . Due to the fact that such gadgets are not common in the world, spare parts are quite difficult to find. In addition, not everyone is familiar with the repair technology.
- Lack of base stations on a CDMA phone. What it is? These are telecommunication points that provide network coverage.
Dual standard phones
As can be seen from the article, both CDMA and GSM have their own strengths and weaknesses. And our man, well, it is simply vital to use everything at once. That is why a dual-standard CDMA-GSM phone was invented. It combines all the advantages of both systems.
What is he like? This is a very ordinary mobile phone with an improved battery, which is able to withstand a greater number of calls and conversations. In design and functionality, it is practically no different from standard relatives.
Such cell phones have recently become increasingly popular. Therefore, gradually, all global mobile brands began to produce separate lines of two-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 4 or more numbers can be assigned to one subscriber at once, as well as several email addresses, CDMA-GSM-cellular has some other significant differences:
- These are mainly monoblocks. Although recently, you can find sliders or clamshells.
- Almost all phones support microSD.
- Cell phones are equipped with a camera of at least 2MP. Of course, with the growing popularity, the line of phones on the market is developing. More and more manufacturers are involved in the competition, design is being developed, technical capabilities and characteristics are added, etc.
In general, these models are standardized for familiar smartphones and phones. Manufacturers try to create them in a familiar design and with the same set of features. In some cities, CDMA phones are increasingly being used. Odessa, for example, as a port center provides the opportunity to use all models. There are, of course, fewer domestic choices.