Archive for the ‘wireless interference’ Tag

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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