Symptoms:

• what is link rate and transfer speed

The wireless link rate is sometimes called the physical layer (PHY) rate. It is the maximum speed that data can move across a wireless link between a wireless client and a wireless router.

User activities like file transfer and web content browsing happen at the application layer. The rate obtained at the application layer will be much lower than the physical layer rate. In fact, a link rate of "300 Mbps" usually corresponds to 50 to 90 Mbps speed on the TCP/UDP layer.

Example:

Transfer Rate (Link Rate) in the Properties of the Wireless Network Connection = 130Mbps

Corresponding Real File Transfer Speed = 4.76MB/s = 38.1Mbps

(Note that b means bit and B means byte. There are 8 bits in each byte. This distinction applies to related units of measure,for instance, KB/sec is kilobytes per second, and Mbps is megabits (millions of bits) per second.)

The reasons for the big difference between the "link" and actual rates include:

1. High overhead involved in wireless connections (lots of bits used for communicating background technical information other than the actual data you are trying to send or receive)
2. Data retransmission (due to the inherent unreliability of a wireless connection).

Link Rates:

Different wireless clients negotiate different link speeds with the wireless router, based on the wireless modes, distance, and noise level (the level of interference from other wireless transmissions).

To get IEEE 802.11n speed, both the wireless router and wireless client have to support 11n mode. If either the wireless router or the wireless client can support only 11a or 11g, the link rate would be a maximum of 54 Mbps, and the actual data transfer speed would be about 22 Mbps.

The most common 11n maximum link rates are 150 Mbps and 300 Mbps. In some new 11n products, more antennas are added so they can support up to 450 Mbps.

The link rate is directly related to wireless signal strength. The signal strength is at its maximum (100% or close to 100%) when the wireless client is close to the wireless router. In this location, the client would get the optimal link rate. As the wireless client goes farther away from the wireless router, its signal strength is reduced, and the link rate goes down as well, until no connection is possible.

If some wireless clients constantly get low signal strength and moving them closer to the wireless router is not an option, you can buy a NETGEAR wireless extender to put in the middle of the wireless router and those wireless clients. The extender will boost the wireless signal.

Note: For a 2.4 GHz wireless network, given its sensitivity to interference, the Wi-Fi Alliance mandates that the wireless router can be set by default to only to a maximum 150 Mbps link rate. This mandate is to ensure that the router is neighbour-friendly and does not generate too much wireless interference (noise) into the neighbours' networks. You can set the router to 300 Mbps if you wish, but that is likely to result in a loss of effective wireless range.