@NAJIV

1) When pairing two or more CPE610 with a single AP (PtMP scenario), the decision to use a CPE510 as the AP depends on the angle the two (or more) CPE610s are located. Thus, it can make sense to use a CPE510 if the CPE610 are at different locations exceeding the narrow antenna beam width angle of only 9º for a CPE610 on the AP side.

If we speak of PtP links, the decision to use two CPE610 in one place and two CPE510 in another place depend solely on the distance: CPE510 can only cover a smaller distance compared to CPE610 (actual distance depends on the region you are in and many other environmental parameters). But the wider antenna beam width of a CPE510 is more susceptible for interferences when lots of foreign APs are around.

2) Using CPE610 rather than CPE510 wil not necessarily increase bandwidth, but could avoid interferences which then can lead to a somewhat better bandwidth. It depends on too many environmental parameters to make such a decision w/o knowledge of the environment (which can, BTW, change over time). However, both devices are N300 devices which means the maximum (theoretical) wireless throughput is 300 Mbps according to the 802.11n standard.

3) Indeed, aligning two CPE610 can become the more difficult the longer the distance is. OTOH, only CPE610 can cover very long distances.

4) Signal strength does not depend on which CPE is client and which one is AP nor does it depend on the direction of traffic. The signal strength determines how strong the signal is on the receiver's side.

Both CPEs are always receivers (for the other station) and both CPEs are always senders (again for the other station), albeit not at the same time. Thus, signal strength is independent of the current direction of electromagnetic waves or data flow. If you reduce signal strength on one station only, the link will break down completely since replies from the opposite station can't find their way back.

5) Yes, you're wrong: AP and client mode doesn't influence up- or download badnwidths. Once a client has successfully connected to an AP, data flows in both directions.

Strictly speaking, the »speed« of electromagnetic waves is always the same for each wireless device, it's nearly the speed of light. What makes a difference is the bandwidth and therefore the throughput of a device which determines the amount of data which can be transferred. There is no such thing as »fast« EM waves or »slow« EM waves, they always travel at the same speed.

In wireless networks you always try to achieve the maximum possible throughput to allow the CPE to acquire the channel only for the shortest possible time to give the remote CPE an opportunity to acquire the channel for sending back data. That's called »AirTime« a device needs to acquire. But you can not influence the actual WiFi rate the clients negotiate with an AP dynamically. If there are interferences, they will negotiate a smaller WiFi rate even if they had a better rate before, thus dynamically reducing throughput.

Regarding AirTime: when CPE #1 is sending, CPE #2 must listen to the stream and can't send a signal itself. That's called »half-duplex« mode: only one CPE can send data at any given time (nowadays techniques such as MU-MIMO allow wireless connections from more senders at the same time, but let's ignore that for the sake of simplicity, the basic principle still remains). When both stations are sending, the EM waves will collide in the air corrupting the data they transport and transmission must be repeated again.

6) For a PtP link it doesn matter which CPE is the AP and which is the client. It just matters for the initial wireless connection. After this connection has been achieved, the link can be used to send data in both directions. There is no single »sender« and »receiver«, both stations are always sending and receiving over time.

7) Signal strength need to be the same for a certain distance to allow EM waves to travel through the air. Air is an obstacle for electromagnetic waves, too, as are trees, walls, rain, snow, etc.). Due to those obstacles the EM waves lose strength on their way through the air.

So, yes, both the client and the AP always need the same high gain antennas. That's the reason why a CPE can't connect to a cheap WiFi router / can't supply smartphones over very long distances, albeit the remote WiFi device can probably receive the CPE's SSID, but can't itself connect to the CPE.