Optimal WiFi CPE configuration for Apartment Buildings
Q: We are delivering high speed ethernet broadband to residents of an Urban high-rise apartment building, and want to offer WiFi router option to residentail customers. What is the best way to design a standard wireless configuration that maximised wireless performance for all customers?
1. First of all, to get maximum possible throughput, you need 40MHz channel width.
I suggest to avoid channel1 (2412MHz) since most production wifi devices are set to that channel out of the box. Channel 11 (2462) is a good selection, since all client devices (even international manufacture) will be supported. Select the extension channel below the primary, thus your wireless service will operate between 2432 to 2472MHz.
This will allow the AP to avoid activity from devices using channel 1 (2412) and share politely with other devices operating on channel 11 (2462) and 7 (2442mhZ) – BUT BE AWARE that any other APs or stations operating on any other channel (2,3,4,5,6,8,9,10,12,&13) will be treated as pure noise that will do nothing but reduce the maximum possible bandwidth of the wireless network.
2. The next thing to do, (to avoid causing interference to neighboring networks) is to keep the transmit power relatively low. Keeping tx low will avoid interference to neighboring networks, and (hopefully) avoid encouraging the neighbors to turn up their transmitters to cause interference to your networks. For a typical small 1 or 2 bedroom apartment with AP deployed in a relatively central location, TX EIRP of 21dBm or less should be satisfactory with low interference/noise floor. With 2.5dBi antennas, 17dBm tx power setting (in conjunction with ‘manual tx power’ setting above) should be sufficient. For smaller apartments, lower tx output will suffice. Remember that most client devices will adjust tx power as AP signal weakens, thus a lower AP tx will usually result in higher Client tx power. Thoughtful settings at the AP will result in a well tuned match between AP and Client
3. ACK timeout is automatic for routerOS, which allows the AP to automatically adjust packet timeouts for clients over long distances. When all stations are indoors, it is sensible to keep the ACK timeouts as short as possible, thus reducing ‘wait time’ before an unreplied packet is considered lost. This will result in faster overall throughput especially when there is some background noise and interference. Setting ‘indoors’ distance applies that result.
4. MIMO operation – multi-in-multi-out allows the wireless transmitters to transfer data simultaneously on multiple antennas, thus effectively doubling throughput. Note, however, that in order to completely DOUBLE the throughput, antennas must be aligned with their polarities at right angles in order to maximise the channel separation. Also, the client antennas must be similarly aligned, and almost exactly parallel to the AP. Although perfect alignment will deliver optimum results, dual chain operation certainly delivers performance benefit even in less than ideal alignment.
5. Guard interval is a break in the comms signal interval used to allow clients to synchronise with the AP. A long guard interval will give clients a better chance to detect the break, but can also be a waste of cycles that might otherwise be used to transfer actual data. Although shorter guard interval results in faster maximum throughput, many wireless client devices (namely apple and many android wifi clients) are not fast enough to deal with short guard intervals, and therefore will perform poorly when short guard interval is set.
6. Last of all, choose aes type encryption algorithm over tkip. Many wireless client devices (again apple in particular) do not perform well with tkip enbabled.
I hope the info is useful to you – for further information and background reading, I recommend that you familiarise yourself with these similar topics:
- Proximity is King: Dispelling two myths of public access WiFi service delivery.
- Tuning outdoor wireless network performance: 5 basic rules to making the most from class license equipment
- How fast?: what is the maximum wireless link speed you can expect?