Use of Long Training Field (LTF) of 802.11 standard In 802.11a/n the preamble part has L-LTF(Legacy-Long Training Field) and HT-LTF(High Throughput-Long Training Field). I want to clarify my understanding of these two fields:


Are the only difference between these 2 fields are the number of subcarriers used and the symbols used?
This field is mainly used for Channel estimation. What method is used to do this estimation (say on our home wifi router), is it LS/MMSE/MLS or any other in 802.11a and n? If possible can you explain how is it determined?
I'm not to familiar with the HT-LTF, but OFDM channel est. is done as follows:

rx'd long training symbol ($LTF_{rx}$) is the tx'd LTF ($LTF_{tx}$) convolved with the channel:

$$LTF_{rx}(n) = \sum_{m=-\infty}^{\infty}h(m)LTF_{tx}(n-m)$$

translate this to frequency domain:

$$LTF_{rx}(w) = H(w) LTF_{tx}(w)$$

and the channel inverse is then: 

$$H(w)^{-1} = \frac{LTF_{tx}(w)}{LTF_{rx}(w)}$$