在一个带宽为3 KHz、没有噪声的信道，传输二进制信号能够达到的极限数据数率为(14)。一个带宽为3 KHz、信噪比为30 dB的信道，能够达到的极限数据传输率为(15)。上述结果表明，(16)。根据奈奎斯特第十定理，为了保证传输质量，达到3 Kb/s的数据传输率需要的带宽为(17)。

 在一个无限带宽的无噪声信道上，传输二进制信号，当信号的带宽为3 KHz时，能达到的极限数据传输率为(18)Kb/s。

(70)

(71)

(69)

(68)

In low-speed network, it is usually adequate to wait for congestion to occur and then react to it by telling the source of packets to slow down. In high-speed networks, this approach often works poorly, because in the(71)between sending the notification and notification arriving at the source, thousands of additional(72)may arrive. In ATM network , a major tool for pre- venting(73)is(74)control. When a host wants a new virtual(75), it must describe the traffic to be offered and the service expected.

(66)

(64)

(65)

(63)

For each blank, choose the best answer from the four choices and write down on the answer sheet.

  (66) is a six bytes OSI layer 2 address which is burned into every networking device that provides its unique identity for point to point communication.

  (67) is a professional organization of individuals in multiple professions which focuses on effort on lower-layer protocols.

  (68) functions with two layers of protocols. It Can connect networks of different speeds and can be adapted to an environment as it expands.

  (69) is the popular LAN developed under the direction of the IEEE 802.5.

  (70) is the popular backbone technology for transmitting information at high speed with a high level of fault tolerance which is developed under the direction of ANSI.