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M Wireless communication

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M ij(Wireless Communication)Ai `Hj gdCMB Wireless communication (radio communication) (Wireless Communication), (as road transport) is a telecommunications use the line. AP (Wireless)B The radio just for short (Wireless) sometimes called. LM wire

MTOLyALpgdbPHSdgipRadio CommunicationRadiocommunicationBjA gB Because the concept of a wide range of communications, cellular phones and PHS are widely used by radio to like (in English or Radio Communication Radiocommunication is equivalent.) Not only have to be included one by the light and sound . iA MBj (Especially in light of what, in the name of optical wireless communication.)

Contents

[ W ] j History

[ W ] dM Telegraph

[ W ] db Phone

[ W ] Features

B Have the following characteristics.

  • P`AIgB The maximum amount of information transmitted per unit of time is determined by the height and width of the frequency principle.
  • `G Is transmitted to the space;
    • `H~KvB There is no need to construct a line as a transmission line.
    • gUAMeB Because of diffusion, it is easy to multi-way communication. ApDKB Also, it is also suitable for broadcast.
    • dgi WQB znOV A dq@@BjWQeB Something else happens and radio (the source of interference. Objects outside the Earth and sun, and the motor and electronics.) Susceptible to interference by.
    • dg`rA`OTB To be in the middle of the propagation of radio waves and can be intercepted by third parties the information to be transmitted. iAOpAiuBj (This type of modulation used and hard to restore the information by third parties, and often is to take steps such as encryption information to the first place.)

[ W ] LMr Comparison with wireless communication

MsMAn_MsALMMIB The immensely YORAZARU to communicate if you do a wireless mobile communication, when you try to communicate between the fixed points are not, and choice of wireless or wired communications. vp[IqALMpAMAMpAMMB The cost of allqBERE to the point for each case, if the wire is to be given the cost of shipment depending on the length of the line, in the case of wireless communication, according to the accumulated costs of transmission facilities which will be in long-distance communication in the side of a rather cheap and wireless communication. ALM@piMjMmAMAXM@yM@gMm@ALM@B On the other hand, if the wire is used on a switch for the exchange line (in the same network) for many to establish a communication, in the case of wireless communication, the individual machines send is taken, the method of establishing communication to distinguish between the frequency and modulation and the receiver, and that number is greater than the number of switching equipment for wireless communications. @M@yM@iiAKv[ij_rA 1990NidCMT[rXOqAMN_I_iANZX|Cg\BjxLMB Price of the transmitter and receiver and the transmitters (or to other devices, including the price you need in each case) in comparison to the general theory is very difficult, the 1990 price up to around age If the premiseqBERE to provide telecommunications services in the situation, starting and ending point of the communication (which can be described as an access point to the line.) higher density of the wire is not cheap It is said.

AKw\dbfB As this example, the hierarchy of its telephone network lines that once. seiANZX|CgjMLMAzs{MMB Each household in the city (access point) and communication between the local exchange and wireless communication was, the way to communicate long-distance switching stations and other prefectures across the wireless station has been replaced. mMArIAANZX|CgxAUIRAMiIDB This is a communication network connecting the local exchange, long distance or a relatively low density of access points, because it is discrete, had a price advantage because of better radio communication . A1990NAgNA t@Co[eMvAdbMMt@CoLMuB However, since 1990's, the frequency and stringency, it was due to very low-capacity communications by fiber-optic long-distance telephone communication has been replaced by optical fiber and communication cable from the wireless communication. dd iNTT jxXSAp{AeiARB Corporation feeding (now NTT) from the tower was a lot of branches, which are missing dish Recently, such a reason. AASMpAeiuB However, instead of the current towers are often placed in a separate antenna for mobile communications.

[ W ] A See also


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