IEEE 802.11a
IEEE 802.11a is an extension of the IEEE 802.11 standard for the 5 GHz frequency band (≈ 5.2 GHz to ≈ 5.8 GHz). WLANs according to 802.11a achieve a maximum gross data rate of 54 Mbit / s.
802.11a uses the OFDM modulation method for data transmission . This technology was later also applied to the 2.4 GHz ISM frequency band - this resulted in the competing extension IEEE 802.11g. In the EU, the use of 802.11a with higher radiated powers ( EIRP ) or use outdoors is tied to the simultaneous support of 802.11h . Then 802.11a also allows a longer range than 802.11b / g , despite the greater signal attenuation due to the higher transmission frequencies.
History and Distribution of 802.11a
The IEEE 802.11a extension was ratified in 1999, and the first products came onto the market in 2001. Because of the legal restrictions on the use of the frequency band at 5 GHz, wireless networks based on 802.11a / h are much less common. The end devices are also more expensive than pure 802.11b / g devices due to the additional techniques of dynamic frequency selection (DFS) and control of the transmission power (TPC) . However, this disadvantage disappears more and more when using dual-band terminals that can transmit in both bands at the same time in accordance with IEEE 802.11a / b or IEEE 802.11a / b / g.
Since the ISM frequency band at 2.4 GHz is heavily used by Bluetooth , microwave ovens, baby monitors and many other applications, the low spread of 802.11a / h can also be seen as an advantage. Wireless networks based on 802.11a / h are often significantly more reliable and less prone to interference due to the rarely used frequency band and dynamic frequency selection (DFS). Due to the high permitted transmission power of 802.11a / h of maximum 1.0 W EIRP with automatic frequency selection, transmission power control and low utilization of the 5 GHz frequency band, 802.11a / h is particularly suitable for setting up point-to-point radio bridges in the Outdoor use.
Compatibility with other WLANs
Because a different frequency band is used, wireless networks based on IEEE 802.11a / h are not compatible with WLANs based on IEEE 802.11b / g. However, there are numerous dual-band devices on the market that can handle both frequency bands at the same time.
Bit rates
The extension provides for bit rates of up to 54 Mbit / s (6, 9, 12, 18, 24, 36, 48 and 54 Mbit / s). Compatible hardware must support at least the bit rates 6, 12 and 24 Mbit / s.
Frequencies / channels
| Channel number | Frequency ( GHz ) | Allowed in |
|---|---|---|
| 36 | 5.180 | EU , USA , Japan |
| 40 | 5,200 | EU , USA , Japan |
| 44 | 5.220 | EU , USA , Japan |
| 48 | 5.240 | EU , USA , Japan |
| 52 | 5.260 | EU , USA |
| 56 | 5.280 | EU , USA |
| 60 | 5,300 | EU , USA |
| 64 | 5.320 | EU , USA |
| 100 | 5,500 | EU |
| 104 | 5.520 | EU |
| 108 | 5,540 | EU |
| 112 | 5.560 | EU |
| 116 | 5,580 | EU |
| 120 | 5,600 | EU |
| 124 | 5.620 | EU |
| 128 | 5,640 | EU |
| 132 | 5.660 | EU |
| 136 | 5,680 | EU |
| 140 | 5,700 | EU |
| 149 | 5.745 | United States |
| 153 | 5.765 | United States |
| 157 | 5.785 | United States |
| 161 | 5.805 | United States |
| 165 | 5.825 | United States |
Transmission power
For operation with high transmission powers and for use outside of buildings in Europe, the 802.11h extension is required, which is supposed to guarantee the operation of WLANs in the 5 GHz frequency band via the transmission power control (TPC) and dynamic frequency selection (DFS) capabilities without disrupting military radars, satellite and location services.
| Frequency band in GHz | maximum EIRP transmission power over the entire range | Spectral radiant power density | additional restrictions |
|---|---|---|---|
| 5.15 ... 5.25 channels 36,40,44,48 |
200 mW (23 dBm EIRP) | 0.25 mW per 0.025 MHz | only in buildings |
| 5.25 ... 5.35 channels 52,56,60,64 |
200 mW (23 dBm EIRP) | 10 mW per 1.0 MHz | only in buildings with DFS and TPC |
| 5.470… 5.725 channels 100–140 |
1000 mW (30 dBm EIRP) | 50 mW per 1.0 MHz | with DFS and TPC |
| 5.755… 5.875 channels 149–165 |
4000 mW (36 dBm EIRP) | FBWA - only commercial, public / mandatory registration |
As part of a revision of the underlying ETSI standard 301 893, the regulations regarding 802.11h with and without TPC or DFS will be uniformly regulated across Europe from January 1, 2006.
Comparison of the IEEE standards
| Surname | released | Frequency [GHz] |
Modulation / multiplex method |
Range [m] | |
|---|---|---|---|---|---|
| in the house (approx.) depending on the walls |
outdoors (approx.) including a wall |
||||
| 802.11 | 1997 | 2.4 | FHSS - GFSK , DSSS - DBPSK / DQPSK | 20th | 100 |
| 802.11a | 1999 | 5 | OFDM - BPSK / QPSK / QAM | 35 | 120 |
| 802.11b | 1999 | 2.4 | DSSS - CCK | 38 | 140 |
| 802.11g | 2003 | 2.4 | OFDM - BPSK / QPSK / QAM | 38 | 140 |
| 802.11y | 2008 2 | 3.6 | like 802.11a | 50 | 5000 |
| 802.11n | 2009 1 | 2.4 / 5 | MIMO - OFDM - BPSK / QPSK / QAM | 70 | 250 |
| 802.11ac | 2013 | 5 | |||
- swell
Web links
-
IEEE Standard 802.11a-1999 (R2003) (Engl.)
(PDF, 23 kB) - Official Journal of the European Union (PDF) Decision of the EU Commission of July 11, 2005 on the harmonized use of radio frequencies in the 5 GHz bands for the introduction of wireless access systems including local radio networks (WAS / Wireless LANs) (PDF)
Individual evidence
- ↑ The transmission power here does not mean the (usually adjustable) transmission power of the transmitter, but the transmission power of the combination of transmitter and antenna. This is only the same if the antenna does not have antenna gain . See also EIRP .
- ↑ http://www.bundesnetzagentur.de/cae/servlet/contentblob/32264/publicationFile/2533/FundstelleId11239pdf.pdf
- ↑ ETSI 301 893 (current and outdated versions). Retrieved December 1, 2014 .