Monday, July 16, 2012

How to Choose a Wireless N Router

This is a simplified guide for choosing a wireless n router. I've simplified some of the terms and concept for those who are not into networking and just want to buy a decent router.

What is 802.11 WiFi Standard?

Before we discuss the types of router in the market, we will discuss what is 802.11 and what is the difference between b router, g router and n router. 802.11 is the wireless protocol standard specified by IEEE. The letters appended behind is standard describes it characteristics of the router
  1. a 802.11 a router uses a 5GHz radio that supports a data transfer rate of 54Mbps
  2. a 802.11 b router uses 2.4GHz radio and supports a data transfer rate of 11Mbps
  3. a 802.11 g router uses 2.4GHz radio and supports a data transfer rate of 54Mbps
  4. a 802.11 n router supports 2.4GHz radio and/or 5GHz radio and supports a data transfer rate of 75Mbps and up to 600Mbps (600Mbps is in theory, most router supports up to 450Mbps)

Types of Router in the Market

There are few types of wireless router in the market. They are:

Wireless 802.11-b/g Router
This router uses 2.4GHz radio and supports specification of 802.11-b/g. This is the previous generation router that should be compatible with most wireless device.

Wireless 802.11-n Router
This router uses 2.4GHz radio and supports specification of 802.11-b/g/n

Dual Band Wireless 802.11-n Router
This router uses 2 radio, a 2.4GHz and 5GHz radio. It supports 802.11-b/g/n. However only one radio can be turn on at one time. This type of router provides you the flexibility to switch to 5GHz radio, which is less congested, when all your device is capable of transmitting in 5GHz radio.   

Dual Band Wireless 802.11-n Router (Simultaneous radio)
This router uses 2 radio, a 2.4GHz and 5GHz radio. It supports 802.11-b/g/n. This router uses 2.4GHz and 5GHz radio at the same time. This router has the best option. It allows your router to operate both radio at the same time, so that the data throughput of your 802.11n capable device will not be affected by legacy device.   


What is 802.11n?

Channel Bonding
As mentioned earlier, 802.11n supports data transfer rate from 75Mbps to 600Mbps. How does 802.11n achieve such a high transfer rate? First, 802.11n uses the concept of channel bonding. 802.11n router uses the main radio channel and an additional adjacent channel to double the data transfer rate. A single channel uses a bandwidth of 20MHz. Using channel bonding, the bandwidth of a single channel is 2x20MHz, thus the data transfer rate will be 2x75Mbps = 150Mbps.  In setting up a 802.11n router, you use a channel width of 20MHz for a single channel and you use 40MHz to double the data rate.

Multiple Input - Multiple Output (MIMO)
Second, 802.11n uses the concept of Multiple Input - Multiple Output (MIMO) by using multiple transmitting and receiving antenna. 802.11n can supports up to 4 antennas. Using 1 antenna on a single data stream will give you data transfer rate of 75Mbps.  Using 2 antennas will give you two data streams (the actual term is spatial stream) and your data rate will be double. Most advance router supports up to 3 antennas. Please note that to use MIMO, your wireless device should also support MIMO with the same number of antennas.

Antenna and Spatial Stream
A standard 802.11n router supports up to 2 antennas. In the technical specification you will notice the antenna configuration as 2x2:2. The first number is the maximum transmitting antenna, the second number is maximum receiving antenna and the last number is the maximum spatial stream (data stream). 2x2:2 indicate that this router supports a maximum to 2 antennas with a maximum of 2 data stream. Some manufacturer add an additional antenna to improve data reliability. Therefore, some router specification has 2x3:2.

Data Transfer Rate (speed) for 802.11n
Combining the channel width with MIMO, you will get the following data transfer rate.


Data Transfer Rate Channel Width
Antenna/Data Stream 20MHz 40MHz
1 75Mbps 150Mbps
2 150Mbps 300Mbps
3 225Mbps 450Mbps


Factor to Consider While Choosing a n-Router

A. Wireless Capabilities of Your Device
The first thing you should do is to list all the wireless device you are using and those that you are going to buy. Most of the older wireless-n device, mobile phone and tablets supports only 1 antenna.

Listed below is some popular device for your consideration:
Legacy device
Kindle Keyboard - support 802.11g at 2.4Ghz.
iPhone (iPhone 3 & 3GS) - support 802.11g at 2.4Ghz

802.11n capable device
iPhone (iPhone 4 & 4s) - support 802.11n at 2.4Ghz (iPhone does not support 5Ghz radio). Supports only 20Mhz data frequency and single antenna (1 data stream). Maximum data transfer rate of 65Mbps.
iPad (All models) - support 802.11n at 2.4Ghz or 5Ghz. Supports only 20Mhz data frequency and single antenna (1 data stream). Maximum data transfer rate of 65Mbps.
2009/2010 Mac Mini - support 802.11n at 2.4Ghz or 5Ghz. Supports 40Mhz with a maximum transfer rate of 130Mbps. 
All 802.11n capable laptop - it is impossible to list all device but most laptop supports 40Mhz channel which gives you a maximum of 150Mbps.

I find it difficult to search for the wireless capabilities of each device including tablets and laptop. Device manufacturer don't give additional information other than mentioning their device is 802.11n capable. Some older laptop supports only 2.4GHz radio. You need to Google a lot to find out the wireless capabilities of your device. Good luck.

B. Which Radio to Use
There is no difference in data transfer rate between 2.4Ghz and 5Ghz radio. However, there are some advantages and disadvantages in using them.

2.4GHz radio has longer range and further reach. It can penetrate wall and obstacles well. However, this radio band is quite congested and very susceptible to interference if there are a lot of device using this radio. In addition, the channels of 2.4GHz radio overlap each other easily. Thus, it is not ideal to use 40MHz channel width. If you live in a big house and your neighbor is quite far from you, then using 2.4GHz is more suitable.

5GHz radio has shorter range and it cannot penetrate obstacle very well. This radio is more ideal if you live in an apartment where your neighbor is just a few feet away. Furthermore, 5GHz radio is more suitable for 40MHz wide channel and there are few overlap channel.

Ultimately, it depends on the capabilities of your device. If all of you device supports 5GHz, then you should choose a router that support 5GHz radio.

C. Which Channel Width to Use (20Mhz or 40Mhz)
If your main wireless device is mobile phone and tablets then 20Mhz channel is good enough since most of them do not support 40MHz. However, if you own a recent laptop or mac mini that is not wired then you should consider using 40MHz.

All of the device I owned has only 1 antenna. The mobile and tablets supports only 20MHz but the laptops and mac mini is capable of 40MHz wide channel.

D. Backward Compatibility
Although all routers is backward compatible, but mixing 802.11g and 802.11n device is not ideal. According to some networking expert, running you router in mixed mode will reduce the data rate of your 802.11n capable device.

E. Internet Bandwidth
If you have only a single wireless laptop that supports 802.11n and you need to access the Internet via wireless, you would not benefit from the speed even if both your router and laptop supports up to 3 antenna. You need to consider the speed of the Internet. Most broadband data rate ranges from 30Mbps to 50Mbps. The more expensive broadband plan might gives you a maximum of 100Mbps. Furthermore, the Internet speed also depend on the web hosting server and its bandwidth.

If you have a single laptop, an iPad and iPhone, you can save the trouble by sticking to a g-router. You can get the cheapest n-router if your current router is broken.

You can only benefit from 802.11n wireless capabilities when you are transferring data between a wireless laptop and a home server or transferring data between 2 wireless laptop.

Router Analysis

Dual Band Wireless 802.11-n Router (Simultaneous radio)
This is the most expensive type of router. However, it allows you to use 2.4GHz radio for older device, tablets and mobile phones and at the same time use 5GHz radio for wireless-n capable device separately. You can configure 40MHz channel on the 5GHz radio. Please note that power consumption will be higher using 2 radios simultaneously.
 
Dual Band Wireless 802.11-n Router
This dual band router only allows you to select one radio at one time. This allows you flexibility to use 2.4GHz radio and you can switch to 5GHz radio when you phase out the older device. If you are not sure of the range and reliability of your wireless-n device you can experiment with the two radios and select the more appropriate radio based on your environment.

If you are upgrading from an older 802.11g router, you can achieve simultaneous radio by operating both router at the same time. You configure your older g-router to use 2.4GHz radio and you configure the new router to use 5Ghz radio. 

Wireless 802.11-n Router
This is the most basic n-router that runs only 2.4GHz radio. You can still use 40MHz if your environment is not congested with devices that use 2.4GHz radio. If your old router is broken and you need a cheap replacement router that is capable of 802.11n, this router might be suitable for you.


Further Information

For further details, please check out the following:
IEEE 802.11n-2009 at Wikipaedia

*****

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.