Turn Your Head, Not your Tablet! Wifi Polarization
I bet I got your attention with that headline! This is going to be a brief but hopefully useful article on little known aspect of wireless WiFi networks that impacts reception quality on tablets. First, a bit of introduction.
The Basics
WiFi is a radio communication system. There is a transmitter and a receiver. Like any radio, antennas are used to radiate the electromagnetic (radio) signal. The antenna on the access point (wireless router) is sometimes visible, but in many models it is built internally to the case. On the clients, whether it is a laptop, tablet, phone, is completely hidden from view.
Polarization
The radio signal is like a sine wave travelling through space. The sine wave can travel one of two different ways: horizontal or vertical. Think of it as a thin sheet of paper with the sine wave drawn on it, held either horizontally or vertically.
For WiFi access points, the standard is vertical meaning the sine waves go up and down. It is critical that the same polarization be used in the receiver. In the case of WiFi, it was designed for use with laptops. Laptops always have their screen vertically so that is where the antenna is usually placed. Its vertical placement means that it aligns nicely with the vertical polarization used in the access point and life is good.
Houston, We Have a Problem!
Life was good until tablets came around with those cute commercials showing how you rotate them as you wish to better match the screen to your application. Well, no one bothered to talk to the RF (radio) engineers about the above antenna alignment. Unlike a laptop, when you rotate the tablet, you rotate the whole device. An antenna which was vertically polarized in the portrait orientation, becomes horizontally polarized when you rotate the device 90 degrees. This spells disaster from signal strength point of view as now the energy that is captured is the intersection of those two sheets of paper or just a sliver! The loss can be as much as 20 dB! Here is a picture showing the problem:
Theory and Practice
We have a rather long house with the access point at one end, and our living room at the other end. On my iPad 2 the problem is quite apparent. Held vertically, I get 2 bars on the WiFi meter. Rotate the tablet 90 degrees to portrait and the signal goes to one bar and often to zero, completely losing reception! This may explain why some people complain about WiFi reception and others do not.
Access Points
Given the above, it is critical that you orient your access points as designed. If the device is supposed to be vertical, be sure to use it vertically. Do not place the box horizontally or vice versa. You will lose significant range otherwise (although it would align with any horizontally held clients).
A Solution
There is one exception to the above problems which is a product from a company called Ruckus. They make a special access point with an array of antennas that it dynamically selects based on the clients it is trying to talk to. Because of the orientation of its antennas, it is able to accommodate with devices in both horizontal and vertical polarization, solving this problem. The round looking box in the above picture is that device actually. The little green PC Boards are the antennas. It is an expensive solution to be sure. But it is a nice solution to getting far better reception in larger homes and of course accommodating these new computing devices.
Short of that solution, if you are in borderline reception areas be sure to keep your iPad or tablet in vertical position.
I bet I got your attention with that headline! This is going to be a brief but hopefully useful article on little known aspect of wireless WiFi networks that impacts reception quality on tablets. First, a bit of introduction.
The Basics
WiFi is a radio communication system. There is a transmitter and a receiver. Like any radio, antennas are used to radiate the electromagnetic (radio) signal. The antenna on the access point (wireless router) is sometimes visible, but in many models it is built internally to the case. On the clients, whether it is a laptop, tablet, phone, is completely hidden from view.
Polarization
The radio signal is like a sine wave travelling through space. The sine wave can travel one of two different ways: horizontal or vertical. Think of it as a thin sheet of paper with the sine wave drawn on it, held either horizontally or vertically.
For WiFi access points, the standard is vertical meaning the sine waves go up and down. It is critical that the same polarization be used in the receiver. In the case of WiFi, it was designed for use with laptops. Laptops always have their screen vertically so that is where the antenna is usually placed. Its vertical placement means that it aligns nicely with the vertical polarization used in the access point and life is good.
Houston, We Have a Problem!
Life was good until tablets came around with those cute commercials showing how you rotate them as you wish to better match the screen to your application. Well, no one bothered to talk to the RF (radio) engineers about the above antenna alignment. Unlike a laptop, when you rotate the tablet, you rotate the whole device. An antenna which was vertically polarized in the portrait orientation, becomes horizontally polarized when you rotate the device 90 degrees. This spells disaster from signal strength point of view as now the energy that is captured is the intersection of those two sheets of paper or just a sliver! The loss can be as much as 20 dB! Here is a picture showing the problem:
Theory and Practice
We have a rather long house with the access point at one end, and our living room at the other end. On my iPad 2 the problem is quite apparent. Held vertically, I get 2 bars on the WiFi meter. Rotate the tablet 90 degrees to portrait and the signal goes to one bar and often to zero, completely losing reception! This may explain why some people complain about WiFi reception and others do not.
Access Points
Given the above, it is critical that you orient your access points as designed. If the device is supposed to be vertical, be sure to use it vertically. Do not place the box horizontally or vice versa. You will lose significant range otherwise (although it would align with any horizontally held clients).
A Solution
There is one exception to the above problems which is a product from a company called Ruckus. They make a special access point with an array of antennas that it dynamically selects based on the clients it is trying to talk to. Because of the orientation of its antennas, it is able to accommodate with devices in both horizontal and vertical polarization, solving this problem. The round looking box in the above picture is that device actually. The little green PC Boards are the antennas. It is an expensive solution to be sure. But it is a nice solution to getting far better reception in larger homes and of course accommodating these new computing devices.
Short of that solution, if you are in borderline reception areas be sure to keep your iPad or tablet in vertical position.
