I saw that, the ePMP1000 access point only transmit/receive on one frequency carrier. Thus, if I have much subscriber modules and it will may overlap each other. According to the ePMP1000 specs, one access point can support 128 subcriber module.
In this scenario, How to solve the interference problem ?
The ePMP system employs a channel access method called TDMA to allow multiple clients to use a shared medium... even if the clients overlap, each client will get it's own time slice and will only 'talk' when the AP signals it's ready to receive data. This is different from native WiFi systems that use an access method called CSMA, where if you have clients that overlap each other, they may interfere with each other because they will both try to talk to the AP at the same time and it will cause a re-transmit of the data.
The 128 subscriber count represents a best case scenario and/or maximum theoretical limit. Supporting this many subscribers and having happy subscribers are two different things. As you add subscribers to your AP, you'll want to monitor a number of factors (bandwidth usage, client SnR, frame utilization, etc) to ensure that you have enough capacity and that your subscribers are happy.
Assuming that you have a clean channel and subscribers that are installed with good signals, your "project with 1 AP and 8 SM" should be quite easy to accomplish using ePMP but will ultimately depend on what sort of bandwidth you're trying to deliver to each SM.
Unlike a GSM mobile system, the timeslot allocation is dynamic depending on which SMs have data to send/receive. In GSM systems, one timeslot is allocated for voice and upto 4 allocated for data (GPRS/EDGE). In the case of ePMP, there is no such concept of voice or data timeslots. Everything is data and IP based and the allocation is much more dynamic. On average ePMP is able to serve up to 7 SMs in one frame but it really depends on data demand independently on Uplink and Downlink and the number of subscribers concurrently needing to transmit/receive data. Overall, an ePMP AP can have 120 SMs registered to it and moving data, although this is not common in real world deployments.
And yes, you can set the MCS indivdually at each SM. However, this setting only applies for the Uplink data (from the SM to the AP).
Each frame is 2.5ms or 5ms long (this is configurable on the AP). 2.5ms gives you lower latency but 5ms gives you at least 10% more throughput.
Typical field deployments are 30-40 SMs although we have cases where customers have deployed 100+ SMs in thier network. That said, many deployments exist with 10 or less SMs as ePMP is low cost and can be quickly deloyed to new towers where there isnt a lot of density.
I'm sure our community members will chime in on the typical size of a sector. That will be more valuable for you than Cambium's recommendation.
When I went for the Cambium training in Edmonton, there were operators there with 60 to 90 clients connected to thier Access Points. They were only offereing the clients 2 to 5 mbit plans, but they were VERY pleased with the performance. They both had migrated from UBNT, and they said that ~20 clients per AP was OK, and ~30 was pushing it for them on UBNT and they were able to double or triple that with Cambium.
Of course, everyone's mileage will vary - I'm sure there are Cambium operators with 40 clients connected to an AP who consider that their max too. But these were a couple real-world people in a Rural ISP who reported that they had 60-90 clients connected to their AP's with good results.