题目内容
In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet. Microwave communication uses high-frequency (26) waves that travel in straightlines through the air. Because the waves cannot (27) with the curvature of the earth, they can be (28) only over short distance. Thus, microwave is a good (29) for sendingdata between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or (30) . These can be installed on towers, high buildings, and mountain tops.
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The purpose of the requirements definition phase is to produce a clear, complete, consistent, and testable (6) of the technical requirements for the software product. During the requirements definition phase, the requirements definition team uses an iterative process to expand a broad statement of the system requirements into a complete and detailed specification of each function that the software must perform and each (7) that it must meet. The starting point is usually a set of high level requirements from the (8) that describe the project or problem. In either case, the requirements definition team formulates an overall concept for the system and then defines (9) showing how the system will be operated publishes the system and operations concept document and conducts a system concept review(SCR). Following the SCR, the team derives (10) require merits for the system from the high level requirements and the system and operations conceptusing structured or object-oriented analysis, the team specifies the software functions and algorithms needed to satisfy each detailed requirement.
In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet. Microwave communication uses high-frequency (26) waves that travel in straightlines through the air. Because the waves cannot (27) with the curvature of the earth, they can be (28) only over short distance. Thus, microwave is a good (29) for sendingdata between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or (30) . These can be installed on towers, high buildings, and mountain tops.
In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet. Spread spectrum simply means that data is sent in small pieces over a number of the (16) frequencies available for use at any time in the specified range. Devices using (17) spread spectrum(DSSS) communicate by (18) each byte of data into several parts and sending them concurrently on different (19) . DSSS uses a lot of the available (20) , about 22 megahertz(MHz).
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