Help with Router Settings

[Kiwi1961]

I have been liaising with AppleCare about a lag issue I am having from my Late 2013 iMac to Apple TV when using mirroring.
Apple have run diagnostics on the performance of my iMac and are aware that I have a D6300 wifi DSL Modem Router.

The settings they have found are as follows:

5Ghz

RSSI: -36 dBm

Noise: -95 dBM

Channel: 157 (5GHz, 80 MHz)

PHY Mode: 802.11ac

TX Rate: 88 Mbps

They have asked me to request assistance from Netgear in order to get my network working at the speeds it should be working at (for 802.11ac mode). I am not eligible for Netgear support as my product was bought more than 90 days ago in October 2014,
My Internet provider is Westnet and I am using the latest version of Yosemite 10.10.3

Could anyone on this Forum advise what Setting changes I need to make to my Modem Router to get it working at speeds that it should be working when in 802.11ac mode ?

[Fairytail]

Check the WMM and make sure it is enabled on the routers page. Try changing channels and make sure the mode is set to the highest.

[Kiwi1961]

Thanks for your advice
WMM is enabled on the routers page
Mode is set to the highest or the channels page
Any suggestion on which Channel to use ?
Any other suggestions ?

[Babylon5]

Sorry but I’m not familiar with iMACs, can you tell me what type of WiFi device it is fitted with, is it an AC capable device, what is the manufacturer / model number?

You say you have a ‘Lag’ issue, can you put any numbers to that please? Are you sure it’s lag and not throughput, or even dropped connections? Can you describe the symptom in a little more detail please?