tailieunhanh - MC và các hệ thống phổ Bá P5

The deregulation of the telecommunications industry, creating pressure on new operators to innovate in service provision in order to compete with existing traditional telephone service providers, is and will be an important factor for an efficient use of the spectrum. It is certain that most of the information communicated over future digital networks will be data rather than purely voice. Hence, the demand for high-rate packet-oriented services such as mixed data, voice, and video services, which exceed the bandwidth of conventional systems, will increase. Multimedia applications and computer communications are often bursty in nature | 5 Applications Introduction The deregulation of the telecommunications industry creating pressure on new operators to innovate in service provision in order to compete with existing traditional telephone service providers is and will be an important factor for an efficient use of the spectrum. It is certain that most of the information communicated over future digital networks will be data rather than purely voice. Hence the demand for high-rate packet-oriented services such as mixed data voice and video services which exceed the bandwidth of conventional systems will increase. Multimedia applications and computer communications are often bursty in nature. A typical user will expect to have an instantaneous high bandwidth available delivered by his access provides when needed. It means that the average bandwidth required to deliver a given service will be low even though the instantaneous bandwidth required is high. Properly designed broadband systems instantly allocate capacity to specific users and given a sufficiently large number of users take advantage of statistical multiplexing to serve each user with a fraction of the bandwidth needed to handle the peak data rate. The emergence of internet protocol IP and asynchronous transfer mode ATM networks exemplifies this trend. As the examples given in Table 5-1 show the average user rate varies for different multimedia services. Generally the peak data rate for a single user is required only for short periods high peak-to-mean ratio . Therefore the data rate that will be supported by future systems will be variable on demand up to a peak of at least 25 Mbit s in uplink and downlink directions delivered at the user network interface. It may be useful in some systems to allow only lower data rates to be supported thereby decreasing the overall traffic requirement which could reduce costs and lead to longer ranges. The user s demand for high bandwidth packet-oriented services with current delivery over .