Designing a PtMP Wireless VOIP & Data network over 802.11a

Hi,
I want to design a wireless network working on 802.11a (5GHZ). I have 2 AP’s and about 20 CPE’s on same frequency.
I want my network to support the best VOIP service and data transfer between my 20 CPE’s. And i want my cpe’s to adapt to the ap frequency automatically and to connect to the ap with the best signal.
Hardware used : RouterBoard (Mikrotik) and Ubiquity radio cards.
Can any one specify for me the modes for the ap and clients to be used regarding (wds, connect list, fire wall, ques, Qos…)
I want to choose the best for my system.

  1. What is the ap mode
  2. What is the cpe mode
  3. Do i use wds
  4. do i use connect list
  5. how to use firewall or Qos for VOIP
    I don’t want to use nstream

Thanks