Editing Orthogonal frequency-division multiplexing (section)

===OFDM system comparison table===
Key features of some common OFDM-based systems are presented in the following table.
{| class="wikitable"
|-
! Standard name
! [[Digital Audio Broadcasting|DAB]] [[Eureka 147]]
! [[DVB-T]]
! [[DVB-H]]
! [[Digital Terrestrial Multimedia Broadcast|DTMB]]
! [[DVB-T2]]
! [[IEEE 802.11a]]
|-
! Year ratified
| 1995
| 1997
| 2004
| 2006
| 2007
| 1999
|-
! Frequency range of <br />today's equipment (MHz)
| {{nowrap|174–240}}, {{nowrap|1,452–1,492}}
| {{nowrap|470–862}}, {{nowrap|174–230}}
| {{nowrap|470–862}}
| {{nowrap|48–870}}
|
| {{nowrap|4,915–6,100}}
|-
! Channel spacing, <br />''B'' (MHz)
| 1.712
| 6, 7, 8
| 5, 6, 7, 8
| 6, 7, 8
| 1.7, 5, 6, 7, 8, 10
| 20
|-
! FFT size, {{nowrap|k {{=}} 1,024}}
| Mode I: 2k<br />Mode II: 512<br />Mode III: 256<br />Mode IV: 1k
| 2k, 8k
| 2k, 4k, 8k
| 1 (single-carrier)<br />4k (multi-carrier)
| 1k, 2k, 4k, 8k, 16k, 32k
| 64
|-
! Number of non-silent subcarriers, ''N''
| Mode I: 1,536<br />Mode II: 384<br />Mode III: 192<br />Mode IV: 768
| 2K mode: 1,705<br />8K mode: 6,817
| 1,705, 3,409, 6,817
| 1 (single-carrier)<br />3,780 (multi-carrier)
| 853–27,841 (1K normal to 32K extended carrier mode)
| 52
|-
! Subcarrier modulation scheme
| {{Frac|π|4}}-DQPSK
| QPSK,<ref name="QPSK">4QAM is equivalent to QPSK</ref> 16QAM, 64QAM
| QPSK,<ref name="QPSK" /> 16QAM, 64QAM
| 4QAM,<ref name="QPSK" /> 4QAM-NR,<ref>NR refers to Nordstrom-Robinson code</ref> 16QAM, 32QAM, 64QAM
| QPSK, 16QAM, 64QAM, 256QAM
| BPSK, QPSK,<ref name="QPSK" /> 16QAM, 64QAM
|-
! Useful symbol <br />length, ''T<sub>U</sub>'' (μs)
| Mode I: 1,000<br />Mode II: 250<br />Mode III: 125<br />Mode IV: 500
| 2K mode: 224<br />8K mode: 896
| 224, 448, 896
| 500 (multi-carrier)
| 112–3,584 (1K to 32K mode on 8&nbsp;MHz channel)
| 3.2
|-
! Additional guard <br />interval, ''T<sub>G</sub>''/''T<sub>U</sub>''
| 24.6% (all modes)
| {{Frac|1|4}}, {{Frac|1|8}}, {{Frac|1|16}}, {{Frac|1|32}}
| {{Frac|1|4}}, {{Frac|1|8}}, {{Frac|1|16}}, {{Frac|1|32}}
| {{Frac|1|4}}, {{Frac|1|6}}, {{Frac|1|9}}
| 1/128, 1/32, 1/16, 19/256, 1/8, 19/128, 1/4 <br />(for 32k mode maximum 1/8)
| {{Frac|1|4}}
|-
! Subcarrier spacing, <br /><math display="inline">\Delta f = \frac{1}{T_U} \approx \frac{B}{N}</math> (Hz)
| Mode I: 1,000<br />Mode II: 4,000<br />Mode III: 8,000<br />Mode IV: 2,000
| 2K mode: 4,464<br />8K mode: 1,116
| 4,464, 2,232, 1,116
| 8 M (single-carrier)<br />2,000 (multi-carrier)
| 279–8,929 (32K down to 1K mode)
| 312.5 K
|-
! Net bit rate, <br />''R'' (Mbit/s)
| 0.576–1.152
| 4.98–31.67 <br />({{abbr|typ.|typically}} 24.13)
| 3.7–23.8
| 4.81–32.49
| Typically 35.4
| 6–54
|-
! [[Link spectral efficiency]], <br />''R''/''B'' (bit/s·Hz)
| 0.34–0.67
| 0.62–4.0 ({{abbr|typ.|typically}} 3.0)
| 0.62–4.0
| 0.60–4.1
| 0.87–6.65
| 0.30–2.7
|-
! Inner [[forward error correction|FEC]]
| [[Convolutional code|Conv. coding]] with equal error protection code rates: <br />{{Frac|1|4}}, {{Frac|3|8}}, {{Frac|4|9}}, {{Frac|1|2}}, {{Frac|4|7}}, {{Frac|2|3}}, {{Frac|3|4}}, {{Frac|4|5}}

Unequal error protection with avg. code rates of: <br />~0.34, 0.41, 0.50, 0.60, and 0.75
| [[Convolutional code|Conv. coding]] with code rates: <br/>{{Frac|1|2}}, {{Frac|2|3}}, {{Frac|3|4}}, {{Frac|5|6}}, or {{Frac|7|8}}
| [[Convolutional code|Conv. coding]] with code rates: <br/>{{Frac|1|2}}, {{Frac|2|3}}, {{Frac|3|4}}, {{Frac|5|6}}, or {{Frac|7|8}}
| [[Low-density parity-check code|LDPC]] with code rates: <br/>0.4, 0.6, or 0.8
| [[LDPC]]: {{frac|1|2}}, {{frac|3|5}}, {{frac|2|3}}, {{frac|3|4}}, {{frac|4|5}}, {{frac|5|6}}
| [[Convolutional code|Conv. coding]] with code rates: <br/>{{Frac|1|2}}, {{Frac|2|3}}, or {{Frac|3|4}}
|-
! Outer [[forward error correction|FEC]]
| Optional [[Reed–Solomon error correction|RS]] (120, 110, {{nowrap|t {{=}} 5}})
| [[Reed–Solomon error correction|RS]] (204, 188, {{nowrap|t {{=}} 8}})
| [[Reed–Solomon error correction|RS]] (204, 188, {{nowrap|t {{=}} 8}}) + MPE-FEC
| [[BCH code]] (762, 752)
| [[BCH code]]
| {{n/a|None}}
|-
! Maximum travelling <br />speed (km/h)
| 200–600
| 53–185, varies with transmission frequency
|
|
|
|
|-
! Time [[bit interleaving|interleaving]] <br />depth (ms)
| 384
| 0.6–3.5
| 0.6–3.5
| 200–500
| Up to 250 (500 with extension frame)
|
|-
! [[#Adaptive transmission|Adaptive transmission]]
| {{n/a|None}}
| {{n/a|None}}
| {{n/a|None}}
|
| {{n/a|None}}
|
|-
! [[Multiple access method]]
| {{n/a|None}}
| {{n/a|None}}
| {{n/a|None}}
|
| {{n/a|None}}
|
|-
! Typical [[source coding]]
| 192&nbsp;[[kbit/s]] [[MPEG2]] Audio layer 2
| 2–18&nbsp;Mbit/s Standard – HDTV H.264 or MPEG2
| H.264
| Not defined (video: MPEG-2, H.264, H.265 and/or [[Audio Video Standard|AVS+]]; audio: [[MPEG-1 Audio Layer II|MP2]] or [[Dynamic Resolution Adaptation|DRA]] or [[Dolby AC-3|AC-3]])
| H.264 or MPEG2 (audio: AAC HE, Dolby Digital AC-3 (A52), MPEG-2 AL 2)
|
|}