YDI Wireless WL2400-ISA Wireless LAN Card with Amplifier User Manual FOR CARD
YDI Wireless Wireless LAN Card with Amplifier FOR CARD
Contents
- 1. USER MANUAL FOR CARD
- 2. USER MANUAL FOR AMPLIFIER
- 3. revised amp manual
- 4. revised card manual
USER MANUAL FOR CARD















![13APPENDIX ABrief Technical Description of the IEEE 802.11 Standard802.11 is the standard for Wireless Local Area Networks (WLAN's) developed by theInstitute of Electrical and Electronics Engineers (IEEE). It can be compared to the802.3 standard for Ethernet wired LANs. The goal of this standard is to tailor a model ofoperation in order to resolve compatibility issues between manufacturers of WLAN equipmentmanufacturers. The YDI WL2400 models comply with standard for DSSS for use with BPSKmodulation at a 2 Mbps data rate.The Media Access Control (MAC) under 802.11 is composed of several functional blocks.These include mechanisms to provide contention and contention-free access control on avariety of physical layers. The functions within the MAC are independent of data rates orphysical characteristics.The fundamental access method of the 802.11 MAC is known as Carrier Sense MultipleAccess with Collision Avoidance, or CSMA/CA. This technique works by a "listen before talkscheme". This means that a station wishing to transmit must first sense the radio channel todetermine if another station is transmitting. If the medium is not busy, the transmission mayproceed. The CSMA/CA scheme implements a minimum time gap between frames from agiven user. Once a frame has been sent from a given transmitting station, that station mustwait until the time gap is up to try to transmit again. Once the time has passed, the stationselects a random amount of time (called a back off interval) to wait before "listening" again toverify a clear channel on which to transmit. If the channel is still busy, another back off intervalis selected that is less than the first. This process is repeated until the waiting time approacheszero and the station is allowed to transmit. This type of multiple access ensures judiciouschannel sharing while avoiding collisions.This scheme allows automatic medium sharing between several devices with compatible radiodata link characteristics [i.e. the Physical Level (PHY)]. This access method is attractivebecause it provides spectral efficiency as well as asynchronous data transfer. FrequencyDivision Multiple Access (FDMA) and Code Division Multiple Access (CDMA) schemes wouldnot be adequate because they require bandwidth used by the modulation scheme. StrictTDMA would not work well because it requires synchronization. Thus CSMA/CA, which maybe thought of as a version of TDMA, is better suited to this application.The Physical Level (PHY) under 802.11 includes diffused infrared (DFIR), Direct SequenceSpread Spectrum (DSSS), and Frequency Hopping Spread Spectrum (FHSS). Both spreadspectrum techniques are used in the 2.4 GHz band because of wide availability in manycountries and lower hardware costs in comparison to the higher microwave frequencies.](https://usermanual.wiki/YDI-Wireless/WL2400-ISA.USER-MANUAL-FOR-CARD/User-Guide-52281-Page-16.png)