Talk about the advantages of China Unicom compared to China Mobile: the more, the better~~

I despise the above buildings

Which one is better, China Unicom or China Mobile, depends on my personal opinion

I agree with China Unicom. China Unicom is not as good as before. Well, my family lives on top of a mountain. There is almost no mobile network here, and even if it is, it is not very good. However, China Unicom's network is full. This shows that China Unicom's network is no worse than China Mobile's. There are dead spots everywhere. The sun shines during the day. What about the places that cannot be reached?

Besides, China Unicom now also supports various services, including GPRS, QQ, etc.

Let’s talk about fees. China Mobile deducts fees at random, while China Unicom There is no such problem. The call charges are the same as those of China Mobile. There are also some cards that are lower than the charges of mobile phones. It is also cheaper when you buy the card.

Then they say the service attitude and China Mobile will send you text messages at every turn. The phone bill is less than 20 yuan, etc., as if someone owes him money. When calling the customer service number, the tone of the service desk is blunt and cold, and the problem is not solved very well. Sometimes the call cannot be connected when calling 10086. But China Unicom is different, the tone is easy-going , there are no text messages such as the phone bill is less than 20 yuan, etc., only one text message will be sent to you every week to tell you how much it cost, how much balance is left, and the phone call can be answered.

Let’s talk about environmental protection and health. Everyone knows that when two GSM mobile phones talk to each other to a certain extent, the radiation emitted can boil an egg.

Unicom CDMA mobile phones are green and environmentally friendly, and satellites are used for signal reception, transmission and validation time. Generally Generally speaking, there are very few places where CDMA cannot be used. Unless you are in a secret room, underground, on an airplane, or if there is a problem with your mobile phone, you can generally maintain a good signal, a low call drop rate, and clear voice. It also has strong confidentiality. Low radiation and other characteristics.

CDMA is the English abbreviation of Code Division Multiple Access. It is a new and mature technology developed on spread spectrum communication technology, a branch of digital technology. wireless communication technology. The principle of CDMA technology is based on spread spectrum technology, that is, the information data with a certain signal bandwidth that needs to be transmitted is modulated with a high-speed pseudo-random code with a bandwidth much larger than the signal bandwidth, so that the bandwidth of the original data signal is expanded, and then modulated by the carrier and combined Send it out. The receiving end uses exactly the same pseudo-random code to perform correlation processing with the received bandwidth signal, and replaces the broadband signal with a narrowband signal of the original information data, that is, despreading, to achieve information communication.

There are many classification methods for mobile communication systems. For example, according to the nature of the signal, it can be divided into analog and digital; according to the modulation method, it can be divided into frequency modulation, phase modulation, and amplitude modulation; according to the multi-access connection method, it can be divided into frequency division multiple access (FDMA), time division multiple access ( TDMA) and code division multiple access (CDMA). The GSM mobile phone networks currently used by China Unicom and China Mobile use a combination of FDMA and TDMA. GSM has great advantages over analog mobile phones. However, the spectrum efficiency is only three times that of the analog system and the capacity is limited. The voice quality is also difficult to reach the level of wired phones. The highest TDMA terminal access rate can only reach 9.6kbit/s; TDMA system does not have soft handover function, so calls are easily dropped, affecting service quality. Therefore, TDMA is not the best wireless access for modern cellular mobile communications, and CDMA multiple access technology is fully suitable for the large capacity, high quality, comprehensive services, soft handover, etc. required by modern mobile communications networks, and is being increasingly used. Favored by operators and users.

The emergence of CDMA technology stems from human demand for higher quality wireless communications. During the Second World War, CDMA technology was researched and developed due to the needs of the war. Its original intention was to prevent the enemy from interfering with one's own communications. It was widely used in military anti-interference communications during the war, and was later updated by Qualcomm in the United States into commercial cellular. Telecommunications technology. In 1995, after the first CDMA commercial system was put into operation, many theoretical advantages of CDMA technology were tested in practice, and it was rapidly promoted and applied in North America, South America, Asia and other places. Many countries and regions around the world, including Hong Kong, South Korea, Japan, and the United States, have built CDMA commercial networks. In the United States and Japan, CDMA has become the main domestic mobile communication technology. In the United States, 7 out of 10 mobile communication operating companies choose CDMA. By April this year, 60% of South Korea's population became CDMA users.

In the 28th Olympic Games hosted by Australia, CDMA technology played an important role.

According to statistics from the World CDMA Development Group, the number of CDMA users at the end of 1996 was only 1 million; by March 1998, it had grown rapidly to 10 million; in September 1999, it exceeded 40 million; in 2000, it exceeded 50 million. As mankind enters the 21st century, CDMA, as the mobile communication method in the new century, will develop in an all-round way.

CDMA technology advantages

1. Clear voice

CDMA uses advanced spread spectrum technology and digital voice coding technology to greatly reduce call noise. The system's vocoder can dynamically adjust the data transmission rate and select different levels of transmission based on appropriate thresholds. At the same time, the threshold value changes according to the change of background noise, so that even when the background noise is large, you can get better call quality and there is almost no noise when making calls. Especially in a noisy background, the other party can hear your voice clearly.

2. Low radiation

The power of ordinary mobile phones (GSM and analog mobile phones) can generally be controlled below 600 milliwatts, and the advent of CDMA mobile phones has brought people "green" "The dawn of mobile phones, because compared with GSM mobile phones, the transmission power of CDMA mobile phones is still less than a small fraction of it. The maximum transmission power of the CDMA system is only 200 milliwatts. The power of ordinary calls can be controlled at a few tenths of a milliwatt. Its radiation effect is negligible and has no adverse effects on health. Reducing the transmission power of base stations and mobile phones will greatly extend the talk time of mobile phones, which means that the lifespan of batteries and mobile phones will be longer, and it will protect the environment, so it is called a "green mobile phone".

3. Low call drop rate

The base station is the guarantee for mobile phone calls. When the user moves to the edge of the base station coverage, the base station should automatically "switch" to protect you, otherwise Will drop the call. The base station coverage when the CDMA system is switched is "single coverage-dual coverage-single coverage", and it automatically switches to the adjacent relatively idle base station. That is to say, when it is confirmed that the mobile phone has moved to the separate coverage area of ??another base station, It is disconnected from the original base station to ensure that the mobile phone will not drop calls.

4. The clock is accurate

Since CDMA uses global synchronization technology, the normal operation of the system can be ensured by receiving global positioning information. In addition, CDMA can also automatically provide users with an accurate clock without the need for users to adjust it themselves. Accurate local time information is clear at a glance, providing convenience for business people who frequently travel across time zones.

The reason why its clock is accurate is that CDMA uses the accurate Global Positioning System (GPS). Currently, the Global Positioning System (GPS) is the best choice for this clock reference. GPS is an antenna navigation system composed of 24 satellites orbiting the earth. Its advantages are global coverage, high system clock accuracy, and not susceptible to electromagnetic storms and low-frequency interference sources. As a backup, the long-range navigation (LORAN-C) system is also a good choice. This system uses ground wave propagation technology and also has the characteristics of accurate clock, not affected by ionospheric changes, small attenuation, stable phase and amplitude, etc., thus Guaranteed the possibility of accurate clock.

5. Good confidentiality

When customers use mobile phones, they often worry that their mobile phones will be monitored or stolen by others. However, in order to eavesdrop on the call, the code address must be found. Every time a CDMA mobile phone user makes a call, the system will randomly assign any code to the mobile phone user among 2 to the 42nd power. There are 4.4 trillion possible permutations. It is simply easy to crack the password or eavesdrop. Unthinkable. Moreover, the spread spectrum communication technology used by CDMA makes communications inherently confidential, and the probability of messages being intercepted on the air channel is almost zero.

In addition, the call protection measures such as authentication, digital format, and spread spectrum processing of the CDMA system can provide the best confidentiality features to prevent eavesdropping during the communication process and theft of mobile phone passwords.

6. Other advantages

High connection rate

Everyone who surfs the Internet has experience. It is easier to find a time to surf the Internet when there are fewer people, so there is less network congestion. Connected. The same goes for making cell phone calls.

CDMA originated from the military anti-interference system, in which the "processing gain" parameter is much higher than that of other systems; in addition, the CDMA signal occupies the entire frequency band, which is almost 7 times the ordinary narrowband modulation efficiency. Therefore, overall, for the same The bandwidth of the CDMA system is 4 to 5 times that of the GSM system. Network congestion is greatly reduced, and the connection rate is naturally high.

Wide coverage

After the first phase of China Unicom’s CDMA network is opened, the total capacity will reach more than 15.15 million doors. The network will cover more than 300 cities in 31 provinces (cities) and autonomous regions across the country. In addition, China Unicom is currently one of the few companies in the world that operates both CDMA and GSM networks. It can provide international roaming services in countries and regions that use CDMA such as South Korea, Japan, and Mexico where GSM networks cannot roam. GSM/CDMA dual-mode mobile phones will be launched soon. By then, China Unicom, which has two networks at the same time, will further demonstrate the characteristics and advantages of global roaming.

Future multimedia technology

Compared with GPRS, which also belongs to the 2.5th generation, CDMA2000 1X is more advanced and mature in carrying new services. The mobile multimedia communication function based on this technology allows users to freely receive and send rich multimedia information including voice, data and dynamic images anytime, anywhere.

Because, in the future, CDMA technology will support multiple simultaneous calls or data transmission on a broad wireless spectrum. Each voice, fax, data or video transmission is assigned a specific code that both the sending and receiving ends of the network can recognize so that the transmitted information can be reassembled at the receiving end. Its wide spectrum makes it more resistant to interference and multipath propagation in urban environments, making it an ideal choice for multiple access systems.