Aerohive AP120 Hardware Reference Manual

Also see for BR200-WP: Operating instructions

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Aerohive AP120 Hardware Reference Manual Manual pdf 119 page image

Hardware Reference Guide 117MIMOrecipient’s receive antennas obtain streams from all the transmit antennas. In fact, due to multipath, theyreceive multiple streams from each transmit antenna. The receive antennas pass the spatial streams to thedigital signal processors in their RF chains, which take the best data from all the spatial streams andreassemble them into a single data stream once again (see Figure 8).Figure 8 2x2 MIMO (2 transmit antennas x 2 receive antennas)In previous 802.11 standards, access points and clients each employed a single set of components, or RFchain, for transmitting or receiving. Although two antennas are often used for diversity, only the one with thebest signal-to-noise ratio is used at any given moment, and that antenna makes use of the single RF chainwhile the other antenna remains inactive. A significant improvement that MIMO introduces is to permit eachantenna to have its own RF chain and for all antennas to function simultaneously. For the AP340, forexample, you can connect up to three antennas per radio and configure the radio to use two or threetransmit chains and two or three receive chains. 1 Using two or three transmit and receive chainssimultaneously increases the amount of data that can flow across the WLAN and accelerates theprocessing of that data at each end of the wireless link.Another major aspect of MIMO is how it turns multipath signals from a curse to a boon. As a radio signalmoves through space, some objects reflect it, others interfere with it, and still others absorb it. The receivercan end up receiving multiple copies of the original signal, all kind of muddled together. However, thedigital signal processors in the multiple receive chains are able to combine their processing efforts to sortthrough all the received data and reconstruct the original message.Furthermore, because the transmitter makes use of multiple RF chains, there is an even richer supply ofsignals for the receive chains to use in their processing. To set the transmit and receive RF chains for a radioprofile, enter the following commands:radio profile transmit-chain { 2 | 3 }radio profile receive-chain { 2 | 3 }There are two sets of antennas—three antennas per set—that operate concurrently in two differentfrequency ranges: 2.4 GHz (IEEE 802.11b/g/n) and 5 GHz (IEEE 802.11a/n). Using two different frequencyranges reduces the probability of interference that can occur when numerous channels operate within thesame range. Conceptually, the relationship of antennas and radios is shown in Figure 9 on page 118.1. The convention for presenting the configuration of transmitting and receiving MIMO RF chains is TxR. Forexample, an AP radio functioning in access mode might be configured to use two RF chains fortransmitting and three for receiving. In that case, its configuration can be presented as "2x3". In general,the number of receive antennas is equal to or greater than the number of transmit antennas.TransmitantennasDigital signalprocessorsRF chains RFsignals(multipath object)ReceiveantennasDigital signalprocessorsRF chains802.11n wireless clientwith two antennasAP340 using twoantennasDataReassembleddata

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BR200-WP AP170 AP350 1U HiveManager AP110 AP120 AP121 AP141 AP320 AP330 AP340 BR100 BR200 HiveManager SR2024

Aerohive AP120 Hardware Reference Manual

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