网络系统设计过程中,物理网络设计阶段的任务是( )。
A.依据逻辑网络设计的要求,确定设备的具体物理分布和运行环境
B.分析现有网络和新网络的各类资源分布,掌握网络所处的状态
C.根据需求规范和通信规范,实施资源分配和安全规划
D.理解网络应该具有的功能和性能,最终设计出符合用户需求的网络
The traditional way of allocating a single channel among multiple competing users is to chop up its (1) by using one of the multiplexing schemes such as FDM (Frequency
Division Multiplexing). If there are N users, the bandwidth is divided into N equal-sized portions, with each user being assigned one portion. Since each user has a private frequency (2), there is no interference among users.When there is only a small and constant number of users, each of which has a steady stream or a heavy load of (3), this division is a simple and efficient allocation mechanism. A wireless example is FM radio stations. Each station gets a portion of the FM band and uses it most of the time to broadcast its signal.However, when the number of senders is large and varying or the traffic is (4), FDM presents some problems. If the spectrum is cut up into N regions while fewer than N users are currently interested in communicating, a large piece of valuable spectrum will be wasted. If more than N users want to communicate, some of them will be denied (5) for lack of bandwidth.„„
(1)A.capability
B.capacity
C.ability
D.power
(2)A.band
B.range
C.domain
D.assignment
(3)A.traffic
B.date
C.bursty
D.flow
(4)A.continuous
B.steady
C.bursty
D.flow
(5)A.allowance
B.connection
C.percussion
D.percussion