2.4 GHz vs. 5 GHz

This is a guest post that originally appeared on CWNP.com – the post generated a LOT of comments, so I thought I would pull it out of “the valut” and re-publish here at WiFiJedi.com

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I recently ran a poll on my blog (WiFiJedi.com) about frequency band utilization for 802.11n deployments.  Here are the results:

In what frequency band do you plan to deploy 802.11n?

  • 2.4 GHz = 17%
  • 5 GHz = 12%
  • Both (2.4 GHz and 5 GHz) = 18%
  • Not sure – why does it matter? = 8%
  • No plans to deploy 802.11n = 45%

Personally, I found the results surprising for two reasons.  First, I was surprised by the large number of respondents who said they have no plans to deploy 802.11n.   I wonder what factors are keeping them from deploying 802.11n?  Price?  Security? Reliability? Scalability?

Second, I was surprised by the low number of respondents who chose a pure 5 GHz 802.11n deployment.   I believe there are numerous advantages to deploying WLANs in the 5 GHz band, especially when it comes to 802.11n.

Consider the following:

Number of Available Channels

There are only three non-overlapping channels in the 2.4 GHz frequency band.  Channels 1, 6, and 11.  There are 23 non-overlapping channels between the 5GHz lower, middle, and upper bands.

Total Capacity

Because there are many more non-overlapping channels in the 5 GHz range, it can deliver greater total capacity.  802.11g networks offer 54 Mbps of capacity on each of the three non-overlapping channels in the 2.4 GHz spectrum.  This equates to a total capacity of 162 Mbps.  802.11a has the same speed, 54 Mbps, but offers a total of 1.24 Gbps of capacity across its 23 non-overlapping channels.  This holds true for 802.11n networks as well.  With speeds of 150 Mbps per channel, there are 450 Mbps of 802.11n capacity with 2.4 GHz use and 3.45 Gbps of capacity with 5 GHz use.

Interference

The 2.4 GHz frequency band is crowded with interfering devices.  Other Wi-Fi access points, microwave ovens, cordless phones, Bluetooth devices, baby monitors, etc. all make for a noisy environment. This degrades the overall signal-to-noise ratio (SNR).  The 5 GHz band is considerably cleaner in most areas – see for yourself with a spectrum analyzer!

Channel Planning

With nearly 8 times the number of channels to chose from in the 5 GHz band, planning is far simpler than in the 2.4 GHz band.  I realize that most enterprise grade solutions have some sort of auto-channel or automatic radio management feature to assist with this, but co-channel interference remains a concern, especially in tight spaces or high-density environments.  The additional choices in 5 GHz minimizes the possibility that two APs will utilize the same channel in the same areas.

Channel Bonding

Sure, some organizations need to support legacy devices in the 2.4 GHz spectrum.  However, I don’t think it makes sense to deploy 802.11n networks in this band.  One of the main technical improvements available in 802.11n is channel bonding.  There is only space for one bonded channel in the 2.4 GHz band which, if utilized, would increase the probability of co-channel interference and make channel planning even more complex.

Conclusion

Last week, at the Gartner Mobile & Wireless Summit in Chicago, Michael King and Timothy Zimmerman gave a presentation on Next-Gen WLANs.  In their presentation, they said that 802.11n networks are faster, cheaper, more secure, more reliable, and better managed than the wired infrastructure deployed in most enterprises today. Additionally, they said enterprises should align networking investments to an all-wireless office.  I agree with them.  But to maximize your chance of success, do it in 5 GHz.


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6 comments so far

  1. Mikael R. on

    Planning on only deploying .11n on one band depends on your equipment choice, use cases, and environment. If it’s possible to deploy .11n in both bands, do so. There are benefits to all just by deploying .11n. Those that posted that they weren’t planning on .11n deployments at all apparently lack the education on the physical, logical, and monetary benefits of the technology (not really a surprise there) which just spells “job security” for me and my teams. Some things never change…

  2. Proder on

    Mikael R. wrote: “If it’s possible to deploy .11n in both bands, do so. There are benefits to all….”

    Deploying only in 5GHz is neighbor-friendly. Deploy in both bands and you can be sure to destroy the networks of adjacent organizations using G-band.

    I guess you meant there are benefits to all…OF MY OWN CLIENTS. To hell with everyone else’s, right? Nice guy….

  3. Mike on

    I was also suprised people aren’t moving to .11n. In regards to 5ghz vs 2,4ghz:

    It depends on your environment. For most people, it’s about speed. However, 5 Ghz doesn’t have the range that 2.4 Ghz does, but none of the wifi manufacturers is going to tell you the dirty little secret are they?

    So if you are far enough away a 5 Ghz connection at 2.5 bars is actually slower than a 2.4 Ghz connection at 5 bars. Shhhh.. we need to sell product, so please keep pushing 5Ghz and dual band to the masses who don’t know any better. 5 Ghz is good but it has diminishing returns as you get futher away. How about writing a blog about that?

  4. I wish the choice of 5Ghz hardware was little broader. Consumer electronics manufacturers are not in any hurry to tell the end users about what kind of band their products support.

  5. [...] 4 has 802.11n, but not the “awesome” 802.11n which is better: 802.11n 2.4 ghz or 5 ghz? 802.11n 2.4 ghz vs. 5 ghz iphone 802.11, iphone, [...]

  6. [...] Generally, 802.11n is better than 802.11g. It offers much faster data transfer, though fewer devices support it than the g standard. As more devices use 802.11n, the g standard will eventually go the way of 820.11b and become an old, legacy protocol. 802.11g functions only on the 2.4 GHz band, while 802.11n can be deployed on either the 2.4 GHz or the 5 GHz range, and that is the newest big question in Wi-Fi setup. [...]


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