Talking about 3G( 1)
3G (the third generation) is a specification developed by the International Telecommunication Union for the third generation mobile communication technology (the first generation is analog cellular and the second generation is digital PCS). 3G digital cellular technology promises to increase the bandwidth: when the equipment is stationary or moving at pedestrian speed, it is as high as 384kbit/s,128kbit/s in cars and 2M bit/s in fixed applications.
GSM (Global System for Mobile Communications) is an open and non-proprietary system, and it is the dominant cellular technology in the world today. GSM uses a variant of Time Division Multiple Access (TDMA) protocol. The data is digitized and compressed, and then sent through a channel with two other user data streams, each with its own time slot. It works in 900 MHz or 1800 MHz and 1900 MHz frequency bands.
Another so-called second generation wireless air interface is CDMA (Code Division Multiple Access). CDMA is a form of multiplexing, which allows multiple signals to occupy a transmission channel, thus optimizing the use of available bandwidth. This technology is used in cellular telephone systems in 800 MHz and 1.9 GHz bands.
Current circuit-switched GSM networks use multi-slot high-speed circuit-switched data (HSCSD) upgrade to transmit data at 9.6kbit/s or as high as 43.2K/s.. The 3G version of GSM, Wideband Code Division Multiple Access (WCDMA), provides higher data speed. WCDMA can support mobile voice, image, data and video communication up to 2Mbit/sec (local access) or 384Kbit/sec (wide access). The input signal is digitized and transmitted in a coded spread spectrum mode within a frequency range. Compared with the 200 KHz wide carrier of narrowband CDMA, a 5 MHz wide carrier is used.
In fact, 3G technology is also applicable to all standards under consideration, including CDMA2000 in the United States. CDMA2000 can support mobile data communication with the speed ranging from 144 kilobits/second to 2 megabits/second. The deployment is in the planning stage.
Packet Radio Service (GPRS) based on GSM has been very popular in Europe, and now it is being popularized in the United States. Through GPRS, the data stream is decomposed into data packets, rather than a continuous stream of GSM circuit-switched networks. Compared with GSM, packetized GPRS provides an "always-on" connection. In GSM, if users occupy a channel and do not transmit data or voice, they need to pay. GPRS is the core of mobile Internet capability commitment, and it transmits voice, video and data to users at a speed as high as115kbit/sec. In Europe, mobile phones equipped with GPRS are expected to be put on the market in early 2002.
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Talking about 3G( 1)
3G (Third Generation) is a specification developed by the International Telecommunication Union for the third generation mobile communication technology (the first generation is analog cellular phone, and the second generation is digital personal communication service). 3G digital cellular phone technology promises to increase the bandwidth: 384Kbps when the device is stationary or walking at this speed, 128Kbps in the car and 2Mbps in the fixed application.
GSM (Global Communication) is a non-proprietary open system, which is the dominant cellular telephone technology in the world. GSM adopts a variant of TDMA protocol. After being digitized and compressed, the data is sent on the channel together with two other user data streams, and each data stream has its own time slot. It works in 900MHz or 1800MHz and 1900MHz frequency bands.
Another so-called second-generation wireless skywave interface is CDMA (Code Division Multiple Access). It adopts the form of multiplexing, allowing many signals to occupy only one transmission channel, optimizing the use of available bandwidth. This technology is used in cellular telephone systems in 800MHz and 1900MHz bands.
At present, the data transmission rate of circuit-switched GSM network is 9.6Kbps. With the upgrade of multi-gap high-speed circuit-switched data (HSCSD), the data transmission rate can reach 43.2Kbps, and 3G of GSM can provide higher data rate to WCDMA. WCDMA can support mobile voice, image, data and video communication rates up to 2Mbps (local access) and 384Kbps (wide access). The input signal is digitized and transmitted in a frequency range by code spread spectrum. Compared with the 200kHz wide carrier of narrowband CDMA, it uses the 5MHz wide carrier.
In fact, 3G technology can be equally applied to all standards under consideration, including CDMA2000 in the United States. CDMA2000 can support mobile data communication with the speed ranging from 144Kbps to 2Mbps. It is currently in the planning stage.
GPRS (packet radio service based on GSM), which is very popular in Europe, is also being introduced into the United States. Using GPRS, the data stream is divided into data packets, rather than a continuous stream of GSM circuit-switched networks. Packet GPRS provides an "always-on" connection, while for GSM, as long as you occupy the channel, you have to pay for both data transmission and voice transmission. GPRS is the core of the promised mobile Internet function, providing users with voice, video and data at the highest rate of 1 15Kbps. In Europe, it is expected that by the beginning of 2002, mobile phones with GPRS function will enter the mass market.
Computer English Translation -VoiceXML
Speech XML(2)
Designing a voice application includes providing data transmitted by telephone, building call flow and enabling prompts and grammar. VoiceXML provides a set of general rules as a flexible basis, but it is up to the designer to create a suitable process and personality for the voice system.
Just as HTML content is interpreted by a browser and visually presented on the Web, VoiceXML must be understood or interpreted by a voice browser in order to be presented on the phone. The voice browser acts as a gateway between the call and the Internet connection. It interprets VoiceXML codes and manages conversations between callers and VoiceXML content located on the website.
The voice browser software also maintains calls, provides voice prompts equivalent to URLs, and downloads audio interactive pages.
VoiceXML-based applications using voice browsers provide flexibility, which benefits both callers and content providers. Callers can use rotary phones or the latest wireless phones and get the same service. Content providers can choose to install voice browsers on their facilities or outsource them to application service providers, operators or service bureaus. Like the current visual network model, it is necessary to balance the ease of implementation, flexibility, cost and other factors.
Today, companies build services on voice-based network content by providing telephone access and interactive audio format data display. Se business hosts voice applications to provide better scalability, maintenance and support, while allowing content providers to focus on their core business.
Many obvious and subtle factors come together to make VoiceXML's Web model stand out. Many people think that Voi ceXML's extensive industry support is its most obvious advantage. Other factors, such as recent improvements in text-to-speech quality, mean that information can be presented in audio format immediately without the time and expense of recording voice. Looking at the development of the Web, it is obvious that the adoption of a common content presentation format-HTML has promoted the development of the Web. The VoiceXML standard has a similar promise for voice.
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Speech XML(2)
The design of voice application program includes the data expression of telephone submission, the establishment of call flow and the realization of prompt and grammar. VoiceXML provides a general rule set as the basis of flexibility, but the process and personality of establishing a suitable voice system depend on the designer.
Just as the content of HTML is interpreted by a browser and visually expressed on a website, VoiceXML must be understood or interpreted by a voice or voice browser before it can be expressed by telephone. The voice browser acts as a gateway between the call and the Internet connection. It explains the code of VoiceXML and manages the conversation between callers and VoiceXML content on the website.
Voice browser software can also maintain calls, express voice prompts equivalent to URL and download web pages for audio interaction.
Using voice browsers, VoiceXML-based applications provide flexibility, which is beneficial to both callers and content providers. Callers can get the same service with the old dial-up phone or the latest wireless phone. Content providers can choose to put voice browsers on their own devices or outsource them to application service providers (ASP), telecom operators or service companies. For the current visual Web model, we must make a compromise among the factors such as easy realization, flexibility and cost.
Nowadays, many companies base their business on voice-based website content, provide telephone access and provide data expression in interactive audio format. These services, including voice applications, provide greater scalability, easier maintenance and support, and allow content providers to focus on their core business.
Many obvious subtle factors combine to make the VoiceXML website model surface. Many people regard VoiceXML's extensive support in the industry as its most obvious advantage. Other factors, such as the recent improvement in the quality of text-to-speech conversion, mean that information can be expressed in audio format immediately without the cost and time of recording. Looking back on the development of the website, it is obvious that ——HTML, a universal content expression, has promoted the development of the website. VoiceXML standard is expected to provide the same prospect for voice.
Kiw.com/forum-108-1.html, there are related ones on this website ~ I won't post them one by one ~, open them yourself.