2023年12月15日发(作者：)

1、Digital networks may consist of one or more routers that route data to the correct

user. An analogue network may consist of one or more switches that establish a

connection between two or more users.

2、The EDA tools allow two tasks to be performed: synthesis, in other words the

translation of a specification into an actual implementation of the design: and

simulation, in which the specification or the detailed implementation can be exercised

in order to verify correct operation.

3、DSP can be divided into two catagories,fixed point and floating point. These refer

to the format used to store and manipulate numbers within the devices. Fixed point

DSPs usually represent each number with a minimum of 16 bits, floating point DSPs

typically use a minimum of 32 bits to store each value.

4、The area served by mobile phone systems is divided into small areas known as cells.

Each cell contains a base station that communicates with mobiles in the cell by

transmitting and receiving signals on radio links. The transmission from the base

station to a mobile is typically referred to as downstream, forwardlink, or downlink.

The corresponding terms for the transmission from a mobile to the base are upstream,

reverse-link, and uplink. Each base station is associated with a mobile switching

center that connects calls to and the base to mobiles in other cells and the public

switched telephone network.

practice，the selected interval thickness is usually a compromise between the need

for a thin interval to maximize the resolution and a thick interval to minimize error.

6、The fact that under certain conditions a continuous-time signal can be completely

recovered from a sequence of its samples provides a mechanism for representing a

continuous-time signal by a discrete-time signal.

g stretches or re-shapes an object in an image, while morphing transforms

one image into another. These transformations may be accomplished by marking

control points, control lines, or triangles in source image and choosing their new

positions in a destination image. The transition between source and destination images

is the accomplished by smoothly transforming not only the control element locations,

but also their colors. T he locations and colors of pixels not explicitly marked as

control elements are determined by the locations and colors of the control elements

that are nearest.

basic types of signals will be considered: continuous-time signals and

discrete-time signals. In the case of continuous-time signals the independent variable

is continuous, and thus these signals are defined for a continuum of values of the

independent variable. On the other hand, discrete-time signals are defined only at

discrete times ,for these signals ,the independent variable takes on only a discrete set

of values

9、Provided these pulses were regenerated before they become impaired beyond

recognition, then it would be possible, in principle, to transmit the signal over

infinitely long distance with no deterioration, expect the approximation inherent in

converting an analogue signal into a digital signal and back again.

10、There are device control services that modify the behavior and modes of a

Bluetooth device, transport control services that create, modify and release traffic

bearers (channels and links), and data services that are used to submit data for

transmission over traffic bearers.

11、Transmission involves sending the digitally coded voice signal from one location

to another, while switching consists of establishing the desire connection between two

voice channels which carry digital signals.

12、This includes segmentation of L2CAP SDUs into more manageable PDUs and

then the fragmentation of PDUs into start and continuation packets of a size suitable

for the control buffers, and management of the use of controller buffers to ensure

availability for channels with quality of service commitments

13、The progress made in recent years both at home and abroad in the development of

apparatus capable of generating ultra-high-frequency electromagnetic waves whose

wave length is a few centimeters has opened up a wholly new field of research in

which for the first time the dimensions of one’s apparatus are of the same order of

magnitude as the wave length of the generated or received waves.

14、The software is instructions for the computer. A series of instructions that

performs a particular task is called a “program”. The two major categories of software

are “system software” and “application software”. System software is made up of

control programs such as the operating system and database management system.

Application software is any program that process data for the user (spread sheet, word

processor, etc.)

15、Worms—a worn is a small piece of software that uses computer networks and

security holes to replicate itself. A copy of the worm scans the network for another

machine that has a specific security hole. It copies itself to the new machine using the

security hole, and then starts replicating from there, as well

16、Due to the absence of start and stop bits the data transfer rate is quicker although

more errors will occur as the clocks will eventually get out of sync, and the receiving

device would have the wrong time that had been agreed in the protocol for

sending/receiving data, so some bytes could become corrupted by losing bits.

17、The relationship, which is called Ohm’s law, can be expressed mathematically by

means of the following formula: Current=electromotive force/resistance, where I is

measured in amperes, E in volts, and R in ohms. This means that the greater the

electromotive force is, the greater will be the current; and the greater the resistance,

the smaller the current.

18、In packet switching, it requires an explicit label(destination address) on the header

of each packet to associate it with its destination node, while the position of the packet

in time does not correspond to any channel information.

19、The Bluetooth core system, defined by Bluetooth specification, is a common

service layer protocol which covers four lower layers in seven layer protocol. Service

discovery protocol and the overall profile requirements are defined by generic access

profile.

20、How optical fibers work can be explained by Snell’s Law, which states that the

ratio of the sine of the angle of incidence to the angle of refraction is equal to the

ration of the propagation velocities of the wave in the two respect media.

21、The increase in noise, can in principle, be compensated for by increasing the

signal power S, but again this has the disadvantage that a channel’s increase in signal

power is another channel’s increase in interference and hence noise.

22、To avoid this confusion, any violation pulse is of opposite polarity to the

preceding mark pulse, whether genuine or a violation, is forced into violation by the

insertion of a “parity” pulse substituted for the first zero immediately following the

preceding mark

23、Under certain conditions, a continuous signal can be completely represented by

and recoverable from a sequence of its values, or simples, at points equally spaced in

time.

24、This arrangement resulted in some saving in terms of the number of components;

however, the design of the shared codec with a sufficiently low line-to-line crosstalk

and noise, as well as the required high speed in a fully integrated from represented a

very different design problem.