Network Communication and Printing and Publishing (4)

Another Internet technology at the Berkeley National Laboratory Lab is the development of Mbone (Multicast backbone). This technique is mainly used for video conferencing and can be applied to the transmission of large digital files. Mbone does not transmit large amounts of data to separate routers. Instead, it packages data on the network and does not block any router.
The University of California Union (composed of several branches of the University of California) is installing and debugging a new network system for CalREN-2. Its data transmission rate will reach 2.5Gbps. Its transmission speed is sufficient to transmit all the contents of the 30-volume encyclopedia in one second. All fiber optic systems and computer equipment are supplied by Pacific Bell, Qwest, GTE, Northern Telecom and Cisco. Some funds are provided by the National Science Foundation. The foundation funds many of the Internet's technological developments.
CalREN-2 is a trial name. Some people call it Internet-2. The advanced networking technology tested and developed on the CalREN-2 network will be used to connect universities across the United States. There is no doubt that advanced network technology will also be applied to the commercial Internet and the World Wide Web.
Some telecommunications companies are also building a backbone network to solve Intenet's crowded traffic. With a lot of investment in Internet infrastructure research, the situation will surely get better.
ADSL with transmission speed up to Mbps
In the early 1990s, some people thought that the data transmission limit of twisted pair has already arrived and it is impossible to improve anything. Copper shaft cable will be replaced by fiber optic cable. However, it has been proved that the DSL (Digital Subscriber Line) based on T1 and ISDN makes full use of the ability of the copper shaft cable to transmit data. With its incredible increase in transmission speed, the key is to develop a frequency bandwidth that is not used in DSL.
In POTS (Plain Old Telephone Service), the bandwidth requirement of the voice does not exceed 4 KHz. In fact, the noise bandwidth after the interference limit is 3.3 KHz. Without interference, copper shaft cables can carry higher frequencies. This is the basis of ADSL, or asynchronous DSL. ADSL uses 4 KHz to 2.2 MHz to transmit data. In a twisted pair cable, the transmission rate of this frequency range reaches 9 Mbps (upload) to 800 Kpbs (downstream). The reason why asynchronous is called is that the upload and download rates are different. Unlike standard modems or ISDN, ADSL is always connected and dialing is not necessary.
ADSL's powerful features allow it to transfer data from the far end of the remote to the user at Mbps. The data transmission rate depends on the phone node and distance that the user arrived at. Nowadays, the slowest transmission rate of ADSL is downstream 1.5Mbps and uploading 16Kpbs. A modem and a splitter are needed at the receiving end. The splitter separates the sound in the data stream. 8Mbps and 800 Kbps ADSL modems are already on the market.
Some factories and telecommunications companies have launched a system called Lite for ADSL. It does not require the installation of a speech separation box at the user. Together these companies have organized a consortium called the Universal ADSL Working Group (UAWG). Lite is also called Universal ADSL. At the end of 1998, ITU issued the standard G.Lite based on UAWG technology functions.
Lite ADSL has a download rate of 1.5 Mbps and an upstream rate of 512 Kpbs. The telephone company is eager to bring Lite ADSL to market. Because the technical staff of the telephone company do not have to go to the on-site instruction, the user can connect to the network. All users need a Lite modem. This product is already on the market now.
Lite ADSL is based on technology developed by Aware. Chip and modem manufacturers such as Lucent Technologies and Analog Devices are applying Aware's technology to their ADSL modems.
Western American companies launched the ADSL promotion campaign called MegaBit Service DSL in many cities. This ADSL service charges between $40 and $80 per month. Other telecommunication companies, such as Bell South, GIE, Pacific, Bell, and WorldCom, have announced the availability of ADSL services. AOL is using Agilent's ADSL trial.
Long-distance transmission is often slow in any network transmission. ADSL is a major technological breakthrough. It will play an extremely important role in opening the digital workflow.
The widespread application of ADSL like ISDN is just around the corner. The price-performance ratio of ADSL will bring data transmission to a new and higher level. And this is exactly what we need.
We are waiting for ADSL trials. It provides extremely low cost for T1 and high speed transmission.
Wireless networks and direct satellite handsets have brewed a vast market for countless communications. Wireless communication services are involved in mobile computers and even office computer networks. Wireless LAN has appeared. In colleges and businesses, there is a trend toward wireless campus networks and wireless LANs. In Silicon Valley, some companies have used wireless communications to access the Internet.
Computer chip developers have integrated wireless communication capabilities into many processors. IBM and Intel are developing an open-access processor called Bluetooth for wireless connectivity. More and more wireless products, such as modems, printers, and other computer peripherals are on the market. Level One Communications of California launched a wireless T1/ISDN receiver.
With the wide range of radio bands for commercial and public interest applications. Wireless communication is now enough to compete with traditional communication lines, cables, and fiber optic networks. Winstar Communications launched a wireless voice-video-data network in Washington DC. It is a two-way network that provides on-demand network bandwidth.
In the area of ​​prepress and printing, wireless networks have still not been taken seriously. Even some of its advantages are self-evident to some companies. Some prepress and printing companies use wireless satellites to connect their networks. Renting satellite communications connections is still relatively expensive, but costs have dropped dramatically. Companies such as Motorola, Loral and Teledisc plan to launch near-Earth satellite systems with data transmission rates of up to 400 Mbps. The direct satellite network is expected to become a viable and affordable networking technology in the next decade. (Finish)