Uplink Frame Utilisation

Most of our installs have pretty good Downlink stats - 64QAM+.

However, we struggle to get great modulations on the Uplink unless subscribers are really close / environment really clean.

As a result, we find our uplink frame utilisation often spiking up to close to 100%.

My question is, does thes impact the overall downlink capactiy of the AP?

Secondly, how are people achieving decent Uplink modulations?

We started out using 450d's but now use mostly integrated radios with reflector dish as these seem to give us slightly better readings.