Performance study of MIMO-OFDM platform in narrow-band sub-1 GHz wireless LANs

Using multiple antennas at the transceivers has become a necessity in high data rate wireless communication systems. Multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) has been adopted as a mandatory modulation scheme in the upcoming IEEE 802.11ah standard. IEEE 802.11ah will specify carrier frequencies for Wireless Local Area Networks (WLANs) operating in the sub-1 GHz band. This is challenging for MIMO-OFDM in sub-1 GHz because of limited bandwidth. Thus building a prototype will provide necessary information to understand this new scenario. We build a prototype in order to test and validate modifications to physical layer (PHY) and media access control (MAC) for narrow-band data transmissions. We present here, in detail, the steps to build a real-time MIMO-OFDM testing platform that is useful for evaluating narrow-band sub-1GHz transmission characteristics. We analyzed potential MIMO-OFDM implementations and conducted extensive measurements on our platform in order to verify the required system enhancements. This paper gives a hands-on account of designing and testing a sub-1 GHz WLAN platform.