通信英文文献翻译-英语论文

通信英文文献翻译-英语论文内容摘要：

A packet is accumulated. in a router’ s memory, then sent on to the next router. With circuit switching, the bits just flow through the wire continuously. The storeandforward technique adds delay. Another difference is that circuit switching is pletely transparent. The sender and receiver can use any bit rate, format, or framing method they want to. The carrier does not know or care. With packet switching, the carrier determines the basic parameters. A rough analogy is a road versus a railroad. In the former, the user determines the size, speed, and nature of the vehicle。 in the latter, the carrier does. It is this transparency that allows voice, data, and fax to coexist within the phone system. A final difference between circuit and packet switching is the charging algorithm. With circuit switching, charging has historically been based on distance and time. For mobile phones, distance usually does not play a role, except for international calls, and time plays only a minor role(., a calling plan with 2020 free minutes costs more than one with 1000 free minutes and sometimes night or weekend calls are cheaper than normal).With packet switching, connect time is not an issue, but the volume of traffic sometimes is. For home users, ISPs usually charge a flat monthly rate because it is less work for them and their customers can understand this model easily, but backbone carriers charge regional works based on the volume of their traffic. The differences are summarized in . 通信英文文献翻译 Item Circuit Switched Packet Switched Call setup Required Not needed Dedicated physical path Yes No Each packet follows the same route Yes No Packets arrive in order Yes No Is a switch crash fatal Yes No Bandwidth available Fixed Dynamic Time of possible congestion At setup time On every packet Potentially wasted bandwidth Yes No Storeandforward transmission No Yes used in detail. THE MOBILE TELEPHONE SYSTEM The traditional telephone system(even if it some day gets multigigabit endtoend fiber) will still not be able to satisfy a growing group of users :people on the go .People now expect to make phone calls from airplanes ,cars ,swimming pools ,and while jogging in the park .Within a few years they will also expect to send and surf the Web from all these locations and more consequently ,there is a tremendous amount of interest in wireless telephony .In the following sections。