【 Weak current College 】 wireless LAN technology on a

1. What is wireless network?

Generally, the so-called Wireless, as the name suggests is the use of radio waves as the transmission of information, and application level, it with the wired network uses completely similar, the two biggest difference lies in the transmission of information media. In addition to this, because it is wireless, both in hardware installation or use of mobility than the cable network to many advantages.

2. wireless network with wired networks, there are those who benefits?

To use its mobility, convenience, and the cable network, the cost, it can save a considerable wiring costs, costs that are basically modified interior space is flexible.

3. wireless network effects on the human body have anything?

For wireless networks transmitting power than the average of the cellular phone to faint, wireless network transmission power about 20 ~ 70mW and transmitting power cell phones cell phone about 200mW, and using way nor like a mobile phone in direct contact to the body in General, less security on considerations.

4. If you want to structure a wireless network, the most basic of equipment needs to have those?

General set up a basic wireless network is equipped with a wireless network card and a bridge (AP), so will be able to cope with the wireless mode, the existing wired infrastructure to share network resources.

5. wireless network will be used to interfere with or affect the operation of other devices?

Basically, the wireless network is using the frequency band is part of the high frequency range ISM2.4GHz, daily life, or Office, etc. with the electrical equipment does not interfere with each other, because of the frequency difference, and the wireless network itself has a total of 12 channels available for adjustment, natural disturbance phenomena do not have to worry about.

6. What is ISM band?

ISM band, divided into industries (902-928MHz), scientific research (2.42-2.4835GHz) and medical (5.725-5.850GHz)---by United States Federal Communications Commission (FCC) allocation of having to permit radio frequency band (power cannot be more than 1W). Recently (1997.1) approved for wireless LAN (WLAN) is a medical band.

7. What is a spread-spectrum (SpreadSpectrum)?

Spread spectrum technology is divided into 「introduction frequency hopping technology "and" direct sequence 」. While the two technologies is in the second world war the army use of technology, it is hoped that in the worst war environment, still able to maintain a communication signal of stability and security. For a non-specific receivers, arising beating SpreadSpectrum signals on it, only be impulse noise. So on the whole is a more secure communication technologies.

8. What is the frequency hopping (Frequency-HoppingSpreadSpectrum)?

Frequency-hopping technology (Frequency-HoppingSpreadSpectrum; FHSS) in sync, and at the same time to accept both ends to a specific type of narrowband carrier to transmit signals for a non-specific receivers, FHSS beats produced by signals on it, only be impulse noise. The signal is FHSS may be designed to avoid noise or One-to-Many distinct channels and the frequency hopping signals must comply with the requirements of the FCC, to use more than 75-hopping signals, and frequency-hopping to the next maximum interval (DwellTime) to 400ms.

9. What is a direct sequence spread spectrum (DirectSequenceSpreadSpectrum)?

Direct sequence spread spectrum (DSSS DirectSequenceSpreadSpectrum;) is the original signal "1" or "0", with more than 10 chips to represent the "1" or "0" position, allowing the original higher power, narrower frequency becomes more broadband low-power frequency. Each bit use how many chips called Spreadingchips, a higher Spreadingchips can increase resistance to noise, and a lower SpreadingRation can increase the number of users. Basically, in DSSS SpreadingRation is quite low, e.g. in almost all 2.4GHz WLAN product are less than 20 SpreadingRation. In IEEE802.11 standard, its SpreadingRation only 11, but the FCC's regulations must be greater than 10, and, best of SpreadingRation around about 100.

10. wireless networks can cover the extent of?

General wireless networks can cover the scope appropriate to the environment is open or not, if no external antenna, in the field of vision and of about 250M, if in the case of half-open space, there is a compartment of the region, about 35 ~ 50M around, of course, if the external antenna, a distance of up to more distant the relationship to the gain of the antenna itself, therefore depends on the customer needs to be planned.

11. wireless network to use confidentiality?

Basically GEMPLEX of wireless network technologies-DSSS system itself has the function of anti-eavesdropping, plus information on encryption (WEP40bits) of dual protection, so its security is quite comprehensive.