Today, 2002, a fashion technician who followed the trend does not understand SMS, and the mobile dream network established by the SMS is simply an unimaginable thing. Short messages, mobile dreams have no doubt that has become an important keyword that affects the communications industry, IT industry and our ordinary people in 2001.
Since you have to know SMS, then we need to have a basic understanding of the core technology of this industry - SMS short message. Because this not only makes us carefully understand the industry, but also determines what can be available in this industry, what users can get.
The SMS Service (SMS) is a wireless application that delivers short information on a mobile network. It is a process of saving and transferring information on a mobile network. The first short message in the world is to send success to the mobile phone through the PC in the GSM network in the UK Vodafone in 1992.
Like voice transmission and fax, SMS service is the main telecommunications service provided by GSM digital cellular mobile communication network, which transmits the wireless control channel, complete storage and forwarding function, and the amount of information for each short message via the short message service center. Limited to 140 eight groups.
Information (plain text) sent from the sender (plain text) is stored in the Short Message Center (SMS) and then forwards to the destination user terminal. This means that even if the receiver terminal cannot instantly receive information due to shutdown or other reasons, the system can still save the information and resend it later.
So, what can SMS service?
If you use the English text, you can send 160 characters (because the English characters use 7-bit encoding, 140 bytes can be encoded 160 characters).
If you use it to send a Chinese text, you can send 70 Chinese characters. Of course, you can also mix in Chinese and English.
Similarly, you can also use binary information below 140 bytes (such as ringtones or mobile phone boot screens)
Of course, if your phone supports EMS (Strengthening Short Replenishment Services), you can send a mixture of images that contain text text, simple graphics, black and white pictures to compatible EMS.
Compared with traditional voice services, SMS services have the following advantages:
1.SMS is transmitted by signaling channels, does not occupy a separate channel, so the transmission and reception of this information can be simultaneously performed with speech, data, and fax services on the GSM network without any interference to each other.
2. SMS can also support domestic and international roaming, allowing mobile users to send short messages to any other mobile user using the GSM system using SMS services.
3. The PCS network based on GSM, CDMA and TDMA also supports SMS, so we said that SMS is a veritable global mobile data service.
4. SMS uses feedback function. If the user is willing, you can obtain information reporting of each information sending results by setting the system.
5. The price is low. A short message 160 bytes of data volume and the space occupied by a speech call for about 1 second are substantially equal.
However, it is also advantageous, the shortcomings of SMS services are also obvious:
1. The monotonicity of the information itself. Short messages can only transmit pure text information, graphics, and sound files, and cannot transmit mixed information.
2. The length of information is limited. Since each SMS information cannot exceed 160 bytes, SMS must cut the information multiple times for a slightly long email or SMS service such as news, and the SMS must be sent multiple times, and the cost is high.
3. Data transfer rate and delay. Because SMS uses a low speed signaling channel, this channel is shared by multiple transmission, so the speed is relatively slow.
In order to solve the above shortcomings of SMS services, there is already a new generation of multimedia SMS launch, there are currently two protocols, EMS and higher MMS.
EMS is an abbreviation of Enhanced Message Service, an enhanced information service, and SMS upgrade. Compared to SMS, EMS is the advantage of send text messages like SMS, you can also send information such as simple images, sounds, and animations, and can still run on the original SMS running network, send ways and operations. no difference. This standard belongs to an open type, any third-party company or individual interested in EMS can develop application software and services on this platform. However, a decisive factor that restricts EMS development is that Nokia, which is the world's largest mobile phone manufacturer, does not support EMS, but supports higher MMS. MMS is the abbreviation of MultiMedia Messaging Service, Chinese intention is a multimedia SMS, is one of the highest standards developed by SMS technology. Using him, you can also send a message that combines text, image, animation or ringtone, and the capacity is from 30,000 BYtes. . Unlike EMS, the MMS can instantly use the mobile phone within the phone or to send the peripheral equipment such as taking a photo or admission sound. Not like EMS limits, you can only use the items in the mobile phone. The function is strong, and natural is also high for the system. MMS is born for 3G, currently used on the 2.5G GRPS, with this year China Mobile Push GRPS, MMS is also immediately a hot spot in the industry.
However, for the current, the author does not look at MMS. First, the mobile phone that supports MMS is too small to give full play to the color screen mobile phone of MMS feature, which means that users are small, users are less income, and the SMS service provider is now sticker. It is of course not easy, even It will not be made with fullness; second, MMS also requires transmission rate to reach 384kbit / s even in GPRS, so that early requirements of MMS can be taken. The GRPS currently opened in China seems to be far from this rate, which must cause the transmission speed to decline, the transmission time is greatly extended, and the user is not good for MMS; the third, the most important thing, current China Mobile in GRPS The tariff policy of the upper price (except for the surprising surprises) make MMS to send large capacity information, MMS will become a killer of the money.
It is these reasons, so the author believes that MMS and EMS are only in the short-term, as our ordinary users, or old-fashioned China Mobile's "mobile dream network" and Unicom's similar service.
