Using Wireless G and Wireless N Devices on a Home Network
As wireless technologies evolve, it is important to understand some issues that could occur when upgrading your home network, computers, and other wireless devices from 802.11g to 802.11n standards.
An 802.11n wireless connection provides enough speed, range, and reliability to support streaming HD videos while simultaneously listening to digital music files, engaging in VoIP (Voice over IP) phone calls, and playing multi player online games, but only if the router and the rest of the network also support those speeds.
To take advantage of the newest 802.11n technology, the computer, other wireless devices, and the WLAN router or access point must be 802.11n compliant. If you have an 802.11n router but the devices connected to your wireless network are 802.11g compliant, the speed of the network will reflect the 802.11g connection.
Wireless network standards
Wireless local area network (WLAN) devices can use different wireless standards (such as IEEE 802.11a, 802.11b, 802.11g or 802.11n). Each standard provides a wide range of connection speeds, bandwidths, channels, and security measures. There are some compatibility issues when using 802.11g and 802.11n devices on the same WLAN.
The 802.11g standard attempts to combine the best of older standards, is backwards compatible with 802.11b devices, and supports bandwidth up to 54 Mbps. To increase the wireless range, 802.11g uses the 2.4 Ghz frequency. It also provides a fast maximum speed for home users, and supports a reliable signal range that is not easily obstructed.
The 802.11n standard is designed to improve wireless technology and is backwards compatible with 802.11g. An important feature in the 802.11n standard is the amount of bandwidth supported by utilizing multiple wireless signals and antennas instead of only one. The 802.11n connections support up to 300 Mbps, provide a larger wireless range due to increased signal intensity, and offer more resistance to signal interference from outside sources.
A wireless Access Point (AP) is a relay between a wireless client (such as a notebook or printer equipped with a WLAN adapter) and a network access device (such as a DSL modem or a VDSL router). A wireless router, such as the kind most often found in home networks, is simply the physical union of two separate pieces of hardware: an AP and a network access device. For larger, more complex networks, APs are physically separated from the network access device and connected to them by Ethernet cables.
For the following examples, the term AP means the device that manages wireless connections on the network. The term client means a computer, a printer, or other wireless enabled device that connects to the AP.
An AP can affect your notebook's bandwidth and connection speed as follows:
If the client and the AP use the same wireless standard, then the maximum throughput the client can ever achieve on the network is equal to the AP's maximum throughput. For example, if the AP uses 802.11n, then its maximum throughput is 300 Mbps. If a client wants to connect at that speed, then it must be equipped with a WLAN adapter that also supports 802.11n.
If a client uses a slower or older standard than the AP, then the client's maximum throughput is limited by its own wireless adapter's maximum throughput. For example, If a client's WLAN adapter uses 802.11g (maximum throughput of 54 Mbps) and it connects to an AP that uses 802.11n (maximum throughput of 300 Mbps), then the client can only ever connect at a maximum throughput of 54 Mbps.
If a client uses a faster or newer standard than the AP, the maximum throughput is limited by the AP. For example, if the client's WLAN adapter uses 802.11n (maximum potential throughput of 300 Mbps) and it connects to an AP that uses 802.11g (maximum throughput of 54 Mbps), then the client can only ever connect at a maximum throughput of 54 Mbps.
Often an AP will have a router attached to it which is hardwired to the Internet or a local area network. If that router has a higher wired throughput than wireless throughput, then the client's maximum throughput is equal to its wireless throughput. For example, if both the client and the AP have a wireless throughput of 300 Mbps (802.11n) and the wired throughput is 1000 Mbps (Gigabit Ethernet), then the client can achieve a maximum throughput of 300 Mbps with the network beyond the AP.
On the other hand, if the router attached to the AP has a lower wired throughput than the AP's wireless throughput, then client's maximum throughput is equal to the wired throughput. For example, if both the client and the AP have a wireless throughput of 300 Mbps (802.11n) but the wired throughput is 20 Mbps (DSL), then client can achieve a maximum throughput of 20 Mbps with the network beyond the AP.
If there are multiple wireless clients, most APs will detect the device with the oldest standard and throttle back all connections to that slower speed. Newer APs may detect both the 802.1g and 802.1n connections and communicate with each device at its best speed. See the documentation that came with your AP for instructions on how to determine its throughput, and its configuration options.
Remember: The slowest link in the network chain sets the limit on your client's maximum throughput.
Actual throughput vs. maximum throughput
Tests on notebooks equipped with an 802.11n WLAN adapter indicate that the computer's actual throughput is lower than what was described in the specifications. This is because the specified throughput is the maximum throughput physically possible barring all outside interference and using raw data that is free of any network overhead.
Actual throughput tends to be lower because the networks overhead, such as link management, quality of service, error detection and correction, will always reduce the maximum throughput. With wireless networks, you also have to factor in signal degradation if the client device is too far from the access point, and interference from other devices in the area, such as cordless telephones which often operate on the same radio bands as the clients.
Generally speaking, a device can typically achieve 60% of its specified throughput rate. So, an 802.11n wireless adapter that can potentially achieve a maximum throughput of 300 Mbps is more likely to achieve an actual throughput of 130 Mbps (or less).
Sharing bandwidth with multiple clients
When multiple computers and wireless clients share a single connection, either through the same access point or router, the total amount of available bandwidth gets divided by the devices. For example, on a wireless network, when one person plays video games while another streams a movie, and yet another tries to surf the net, the total amount of bandwidth available is split between all the users. This can have a significant impact on your client's throughput.
Likewise, when your computer is connected wirelessly to a public hotspot or a corporate network, the computer's throughput is reduced because you are sharing bandwidth with everyone else on the network.
Wireless security and network performance
Any time you are connected to a wireless network you should use a security protocol to protect your data. The 802.11n standard requires you to use WPA2 authentication with AES encryption or no security at all in order to fully utilize 802.11n speeds. Choosing other wireless security algorithms, such as WEP or WPA which were popular with 802.11g, or TKIP encryption methods, can dramatically reduce performance to 802.11g levels.
To view or configure your notebook's wireless security:
- Click Start , click Control Panel , and then double-click Network and Sharing Center .
- In the Network and Sharing Center , select Manage wireless networks .
- Right-click the wireless connection that you are currently using and select Properties .
- In the Properties window, select the Security tab. This is where you can view your wireless security settings or configure them according to the security information provided by your network administrator or ISP.
- When you are finished, click OK to save your settings and close the window.
Multiple input, multiple output (MIMO)
The 802.11n standard allows for dual signals to transmit and receive data, but only if a wireless adapter has two antennas. This type of configuration is called Multiple Input, Multiple Output (MIMO). Each signal allows a maximum throughput of 150 Mbps, so two antennas together allow a total maximum throughput of 300 Mbps. Note that this is not necessarily the actual throughput. In some wireless adapter configurations, there may be two antennas but transmitting data is limited to one antenna (150 Mbps) while receiving data utilizes both antennas (300 Mbps).
If you do not think an 802.11n client is achieving true 802.11n speeds, check its specifications to see if it has a MIMO configuration.
Wireless bandwidths and frequencies
All wireless devices operate over either the 20 MHz bandwidth (802.11a, 802.11b, 802.11g, and 802.11n), or the 40 MHz bandwidth (802.11n). These two bandwidths are further divided into three frequency bands: 2.4 GHz, 3.6 GHz, and 5.0 GHz. Moreover, each band allows a specific number of channels. When a wireless client connects to an access point, it connects to a specific channel on a specific frequency and bandwidth.
There are a number of bandwidth and frequency-related issues that can affect a client's throughput on a wireless network. The most common issues are:
- If an 802.11n device is allowed to operate in the 40 MHz bandwidth, it will achieve its highest possible throughput. This allows each antenna (see Multiple input, multiple output for more) to transmit and receive up to 150 Mbps.
- If an 802.11n device is forced to operate in the 20 MHz bandwidth, then its throughput is cut in half, allowing each antenna to transmit and receive only up to 75 Mbps.
- If possible, an 802.11n client should also operate in the 5.0 GHz frequency range, although using the 2.4 GHz range does not necessarily result in performance issues.
In an area where a large number of APs are transmitting on the same bandwidth and frequency there will be a high level of interference. This is especially true if the APs are also transmitting on the same channel. This can cut down the effective range of each channel, introduce a higher rate of data corruption, and generally slow down network speeds.
If an AP is dual-band but not dual-antenna, and if it is configured to allow devices using a range of wireless standards on the same network (such as 802.11b/g/n), then the connections will probably use the lowest common denominator. If an 802.11n client connects to an 802.11b/g/n AP, it may only see 802.11b speeds, or 802.11g speeds if there are no 802.11b clients connected at the time.
Each country has its own laws pertaining to which radio channels wireless devices may and may not use. As such, an AP could automatically restrict its bandwidth and frequency depending on its physical location. Although your client is properly configured to achieve its maximum throughput, the local AP is intentionally throttling the connection.
For best performance, make sure your wireless adapter device driver is up to date. An out of date driver, a missing driver, or a generic driver may affect throughput if it inadvertently applies the wrong configuration settings to the wireless adapter.
To verify the current version of the wireless adapter device driver and install an updated driver, do the following:
- Click Start , right-click Computer , select Properties , and then click Device Manager .
- In the Device Manager window, double-click the Network adapters entry to expand the list.
- Right-click the wireless adapter and select Properties .
- In the Properties window, select the Driver tab and click the Update Driver button.
- In the Update Driver Software window, select Search automatically for updated driver software .
- Windows will search online for any updates to the wireless adapter driver. It will display a message if The best driver software for your device is already installed , or it will display on-screen instructions if the driver can be upgraded.