Dot11 technology has evolved rapidly with the focus to improve the speed of wireless communication. Below is the 802.11 life cycle along with the corresponding nomenclatures and rates.
| Technology | Modulation | Supported Frequency bands | MIMO | Max. no of Spatial Streams | Rate (Mbps) |
| 802.11 | FHSS,DSSS | 2.4 GHz | 1,2 | ||
| 802.11b | HR/DSSS | 2.4 GHz | 1,2,5.5,11 | ||
| 802.11a | OFDM | 5 GHz | 6,9,12,18,24,36,48,54 | ||
| 802.11g | ERP | 2.4 GHz | 6,9,12,18,24,36,48,54 | ||
| 802.11n | 64 QAM | 2.4 GHz, 5 GHz | MIMO | 4 | Max. to 600 Mbps |
| 802.11ac | 256 QAM | 5 GHz | MU-MIMO | 8 | Max to 7 Gbps |
| 802.11ax | 1024 QAM OFDMA | 2.4 GHz, 5 GHz | MU-MIMO | 8 | 9.6Gbps |
Basic Rates are speeds at which management frames, multicast and broadcast frames and transmitted. Management frames and broadcast frames are transmitted at the lowest basic rate and multicast frames are transmitted at the highest basic rate.
Basic rates listed is usually a subset of supported rate list. This rate decides if a client can associate to the AP or not.
Note: Unless a client station is not able to communicate with all the configured basic rates, it will not be able to associate to the AP or join the BSS.
Supported Rates are speeds at which unicast data frames are transmitted.
After the client station associates to an AP, it can use any of the supported rate to transmit data to the AP and receive data from AP. However, 802.11 station should support at least one rate from the AP supported rate list.
When a client device connects to the wireless network, it connects at rate from one of these supported rates called data rate or connection speed. This should not be confused with the throughput
Scenario Examples –
- If the lowest basic rate is set to 1 Mbps, then any clients that support 1Mbps can associate to this AP. 802.11b-only client will support this rate and associate to it. 802.11g-only client being backward compatible will also be able to associate to it.
- If the lowest basic rate is set to 11 Mbps, then 802.11b and 802.11g should connect.
- If lowest basic rate = 12 Mbps, then 802.11b client will not connect. However, 802.11g and 802.11a clients should be able to associate.
Another important term related to rates is DRS (Dynamic Rate Switching). As the dot 11 station moves near/away from the access point, the rate at which wireless frames are transmitted should shift up/down respectively.
Below is a demonstration of DRS for 802.11b wireless transmission with permitted rates: 1, 2 ,5.5, 11 Mbps. The data rate for the client is the lowest (i.e. 1 Mbps) when it is the farthest from the AP and rate is the highest = 11 Mbps when it is the closest to the AP.
Reference:
- CWNA Official Study Guide
- CWAP Official Study Guide
Home 