With an addition of an access point, the cellphone won't receive the packet from the note directly anymore?
-and-
all the packets go to the access point and he forwards it to the phone?
In essence, the same question, but you are correct. Both the notebook and cellphone will communicate with the AP. The AP would pass traffic from one client device to another (unless it is configured to prevent client to client traffic).
I've seen analogies between access point with switch, but one of the latter goals is to replace the CSMA/CD, but, from what I get, CSMA is still the access channel method, whether it is an ad hoc or infrastructure mode. I am confused.
Your question isn't really clear, but it seems like you are either asking about the AP/switch and media access method and/or why would you want to introduce an AP in between devices when they can talk directly.
Let me start by clarifying that an AP is much more like a hub than a switch when it comes to media access. An AP is a L2 device (like a switch) because of the bridging functionality of the AP. You are correct that CSMA/CA applies both to ad-hoc and infrastructure modes of operation. However using an AP in infrastructure mode provides a number of advantages over ad-hoc mode.
First, in ad-hoc mode, each client must form an ad-hoc connection to each other client. So if you have 20 devices communicating among themselves, each device would have to form a connection to the other 19. With an AP, each client would only have to form a connection to the AP itself.
Second, the AP is the bridge to the wired network (or client devices on a different frequency range - 2.4GHz to 5GHz). If any of the wireless devices need to connect to a device on the wired network (or a different frequency range), something needs to provide that bridge.
Third, the AP provides additional functionality and coordinates the use of the channel by the clients. Ad-hoc networks are generally pretty basic connections and don't provide much more than connectivity.
