Slowdown over the network

RouterOS Wireless Networking
1

I noticed some strange slowdowns on my Mikrotik network
The customer reports me that it doesn’t download more than 15Mbps
So 'I tried to do some tests using the TCP BWTest and I noticed the slowdowns

The CPE has a signal on the sector -58/-58 (NV2 protocol dual polarity)
All 1100AHx2 handle only the internal BGP routes (no Firewall, no queues, no more)
TEST1: from CPE to BTS1 arrival to 32Mbps
TEST2: from CPE to BTS2 arrival to 33Mbps
TEST3: from CPE to BTS3 arrival to 15Mbps
TEST4: from BTS1 to BTS3 arrival to 200Mbps

The RB1100AHx2 are usually free as CPU usage (obviously when launching the TCPTest gets up)
Why did I’ve this bandwidth decrease going through the last two BTS? (behaviour of Test3)
scheme.jpg
testResults.png

2

What is the CPU load on CPE during BTest?
It is probably maxing out… BTest is quite heavy for a RB43x.

3

Ccustomer with his pc see performance that I see using BWTest in TCP mode (15Mbps)
CPE is a RB911G-5HPnD and during the test cpu usage is about 20-25%
On the 1100AHx2 is about 50% (ok ..one core at 100%) but why on BTS3 is the half of previous BTS, if the routerboard model is always the same?

And also between the BTS1 and BTS3 is 200Mbps TCP

4

I tried to set the “/queue interface” to “multi-queue-ethernet-default” on all 1100AHx2 but nothing happen.
Does anyone have any idea?