RF Basic Background: 2.4G and 5G Band

03/26/2020 39 People found this article helpful 489,451 Views

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There are currently five widely adopted standards for 802.11 wireless network. There are 802.11a, 802.11b, 802.11 g, 802.11n, and 802.11ac. 802.11ac is the newest and highest capacity standards, while older client devices may not be able to utilize the newer standards. Following table lists the main characters for these five wireless standards.

802.11(X)	802.11a	802.11b	802.11g	802.11n	802.11ac
Standard Approved	1999	1999	2003	2009	2013
Frequency Band	5 GHz	2.4 GHz	2.4 GHz	2.4/5 GHz	5 GHz
Channel Width	20 MHz	20 MHz	20 MHz	20/40 MHz	20/40/80/160 MHz (160M is optional)
Non-Overlapping Channels	24	3	3	3/24	24
MIMO/SISO	SISO	SISO	SISO	4x4 MIMO	8x8 MIMO
Data Rate	54Mbps	11Mbps	54Mbps	600Mbps (3x3, 40MHz)	1.3Gbps (3x3, 80MHz)
Compatibility	802.11a	802.11b	802.11b/g	802.11a/b/g/n	802.11a/b/g/n/ac

2.4G Band Channels
5G Band Channels
2.4G vs 5G (Pro's and Con's)
- ?RF interference??
- Radio frequency barriers

2.4GHz Band Channels

In 802.11b/g/n 2.4Ghz radio band, there are 11 22MHz wide separate channels but only three channels (1, 6, and 11) are non-overlapping . APs and STAs operating in one of these three channels don't interfere with APs and STAs running in the other two channels.

#	Channel	Frequency (GHz)	Location	Comments
1	1	2.412	North America	North America: C#1-#11 Europe: C#1-#13 Japan: C#1-#14 (802.11bg: #14 only)
2	2	2.417	North America
3	3	2.422	North America
4	4	2.427	North America
5	5	2.432	North America
6	6	2.437	North America
7	7	2.442	North America
8	8	2.447	North America
9	9	2.452	North America
10	10	2.457	North America
11	11	2.462	North America

2.4G Band Channel List

Five possible combinations of non-overlapping channels for 2.4G band. The red color set in the below picture is recommended. Therefore, to deploy more APs, you are required to try hard to utilize channel 1, 6, and 11. Howerver, for 802.11n 2.4G? when using 40MHz channel width, only one AP can be deployed. Hence, 40 MHz operation in the 2.4 GHz band should be avoided.

2.4G Channel map

5GHz Band Channels

In 802.11a/n/ac 5Ghz radio band, there are 24 20MHz wide separate channels and 23 channels are non-overlapping in North America. APs and STAs operating in one of these channels don't interfere with APs and STAs running in the other channels. However, due to possible interference with radar systems, only the top four (Indoor Only) and buttom five (North America) channels are commonly used. For the rest 15 channels, the Dynamic Frequency Selection (DFS) is must applied.

DFS monitors the region frequency of the radar signals. If radar signal is detect on the channel which AP is using, DFS will block the transmission on the channel and randomly switch to another channel to avoid the interference with the region radar system.

#	Channel	Frequency (GHz)	Location	Comments
1	36	5.180	Indoor Only	North America:C#1-#24 Europe: C#1-19 Japan: C#1-#19
2	40	5.200	Indoor Only
3	44	5.220	Indoor Only
4	48	5.240	Indoor Only
5	52	5.260	DFS Required
6	56	5.280	DFS Required
7	60	5.300	DFS Required
8	64	5.320	DFS Required
9	100	5.500	DFS Required
10	104	5.520	DFS Required
11	108	5.540	DFS Required
12	112	5.560	DFS Required
13	116	5.580	DFS Required
14	120	5.600	DFS Required
15	124	5.620	DFS Required
16	128	5.640	DFS Required
17	132	5.660	DFS Required
18	136	5.680	DFS Required
19	140	5.700	DFS Required
20	149	5.745	North America
21	153	5.765	North America
22	157	5.785	North America
23	161	5.805	North America
24	165	5.825	North America

5G Band Channel List

5G Channel map

In 5 GHz band, higher data rates (wider channel width) means fewer available channels. With 802.11a, there are a total of 24 non-overlapping channels available, but with 802.11ac, achieving the maximum data rate will reduce the number of non-overlapping channels to two for 80MHz and only one for 160 MHz wide (including DFS).

	Including DFS		Excluding DFS
Channel Size	North America	Europe	North America	Europe
40MHz	8

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RF Basic Background: 2.4G and 5G Band

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