A 802.11n Wi-Fi network connection supports up to 300 Mbps of rated (theoretical) bandwidth under best case conditions. Unfortunately, an 802.11n link will sometimes operate at much lower speeds (150 Mbps and below).
For an 802.11n connection to run at its maximum speed, Wireless N broadband routers and network adapters must be linked and running in a channel bondingmode.
802.11n and Channel Bonding
In 802.11n, bonding utilizes two adjacent Wi-Fi channels simultaneously to double the bandwidth of the wireless link compared to 802.11b/g.
The 802.11n standard specifies 300 Mbps theoretical bandwidth is available when using channel bonding. Without it, about 50% of this bandwidth is lost (actually slightly more due to protocol overhead considerations), and 802.11n equipment will generally report connections in the 130-150 Mbps rated range in those cases.
Channel bonding substantially increases the risk of interfering with nearby Wi-Fi networks due to the increased spectrum and power it consumes.
Setting Up 802.11n Channel Bonding
802.11n products normally do not enable channel bonding by default but instead run in traditional single channel mode to keep the risk of interference low. Both the router and wireless N clients must be configured to run in a channel bonding mode together to achieve any performance benefit.
The steps to configure channel bonding vary depending on the product. Software will sometimes refer to single channel mode as 20 MHz operation (20 MHz being the width of a Wi-Fi channel) and channel bonding mode as 40 MHz operation.
Limitations of 802.11n Channel Bonding
802.11n equipment can ultimately fail to run in the maximum (300 Mbps) performance range for these reasons:
- Some 802.11n gear cannot support channel bonding. For example, this mode of wireless signaling is government regulated in certain countries, such as the UK.
- If the 802.11n network includes any 802.11b/g clients, performance of the entire network may be negatively affected, depending on the router's capabilities. Because 802.11b/g clients do not support channel bonding, these must be set up properly with a mixed mode Wireless N router to minimize performance impact.
- Interference from other 802.11n networks nearby can prevent a Wireless N router from sustaining channel bonded connections. In fact, some Wireless N routers automatically fall back to single channel operation when they detect wireless interference on the channels.
As with other networking standards, applications running on an 802.11n network will typically see substantially less actual bandwidth than the rated maximums imply even with channel bonding in place. A 300 Mbps rated 802.11n connection will often yield 200 Mbps or less of user data throughput.
Single Band vs. Dual Band 802.11n
Some Wireless N routers - so-called N600 products - advertise support for 600 Mbps speeds. These routers do not provide 600 Mbps of bandwidth on a single connection but rather 300 Mbps channel bonded connections on each of the 2.4 GHz and 5 GHz frequency bands.