Impact of spatial expansion on channel estimation accuracy in HT and VHT wireless LAN systems

The IEEE 802.11n is a high throughput (HT) wireless LAN standard that supports multiple input, multiple output orthogonal frequency division multiplexing (MIMO-OFDM) technology with maximum of 4 transmitting and 4 receiving antennas. This technology has been extended to 8 transmitting and 8 receiving antennas in upcoming very high throughput (VHT) wireless LAN standard, IEEE 802.11ac. Spatial expansion (SE) is a transmit diversity scheme used to map fewer space time streams to more transmit antennas to obtain spatial diversity. One of the key tasks at the receiver in such MIMO-OFDM systems is the channel estimation. We discuss a technique to improve the accuracy of channel estimation and the impact of SE on it. We compare the performance of the improved channel estimation technique with different antenna configurations of SE using simulations.