Hi,
This is from the 225 datasheet.
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AP-225 and IAP-225 - 2.4-GHz (600 Mbps max) and 5-GHz (1.3 Gbps max) radios, each with 3x3 MIMO and three integrated omnidirectional downtilt antennas.
• AP-224 and IAP-224 - 2.4-GHz (600 Mbps max) and 5-GHz (1.3 Gbps max) radios, each with 3x3 MIMO and three combined, diplexed external antenna connectors.
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With 3x3 in 802.11n QAM-64, that max theoritical throughput is 450 Mbps which is the standard.
AP 225 has the turbo QAM feature. With 3x3 and turbo QAM (i.e QAM-256) the max theoritical throughput is 600 Mbps.
For more details about throughput, spatial streams, modulations, etc you can check http://mcsindex.com/