Archive for the ‘802.11n’ Category
OK. If you have been following my blog (here or over at Computerworld), you’ll notice that I am really starting to incorporate a lot of video into my posts. So far, I have found that one of the easiest & most effective ways to include video is to interview someone else. However, I now realize that turn-about is fair play.
The fine folks at CWNP had a little fun by asking me what I though about their recent Certified Wireless Analysis Professional (CWAP) beta course.
I told them about one mantra I hold about wireless networking… that the packets never lie. Then they took some liberties with my response. 🙂
See for yourself:
Oh, it’s all in good natured fun. That is, if you can stand seeing & hearing me more than 10 times in under 5 minutes… In all seriousness though, I had a great time at the CWAP beta course and learned a ton from all the real brains in the room.
If you want to read CWNP’s original post with the video montage, you can view it here: https://www.cwnp.com/index/cwnp_wifi_blog/cwapbeta-round-up-the-packets-never-lie
Today was the 2nd day in the CWAP (Certified Wireless Analysis Professional) beta course. Today’s material was a lot more hand-on / lab type exercise in capturing and analyzing traffic. From what I could tell, there were three main tools used by the course attendees:
They all seem to have their pros and cons, and they all seem to cost about the same amount of money (especially if you want to do multichannel packet capture on ~3 channels). Which tool do you prefer? Why?
The course contains an enormous amount of detail, such as the exact length (in microseconds) for slot times for each PHY type as well as a discussion on the application of that detail (i.e. how do the different slot times affect WLAN performance with and without QoS enabled).
Again, I thought one of the most valuable things were the networking opportunities with the other attendees and the sidebar conversations. A colleague (and good friend) of mine, Ken Hall, was even inspired to sign up for a Twitter account (@wifiscubaguy) to continue the interaction outside of this course / classroom. His account will definitely be on my next list of #WirelessWednesday mentions.
Tomorrow is the last day of the course. From what I know, we are covering a lot of 802.11n concepts, as well as spectrum analysis, which should be a blast.
I try to advertise my speaking engagements so that if you are in the area, you can stop by and introduce yourself. I love meeting others that share my passion for wireless networking and security. However, one complaint that I hear is “you never give a presentation near where I live”.
Well, here is your opportunity. This Wednesday, June 2nd, I am giving an online presentation. It is a webinar in conjunction with TribalNet and goes live at 2pmEST/11amPST. TribalNet is an industry resource for technology professionals in the Native American industry. I will be presenting “Designing for 802.11n Wi-Fi Deployments”. You don’t need to be a member to join the webinar – the link to register is below.
Link to pre-register: http://www.tribalnetonline.com/webinars.php
I hope that I will “see” many of you online this Wednesday!
I received a following set of questions via email and thought that rather than only respond to the one individual, but post it on WiFiJedi.com for general consumption.
Here’s what I received:
I have recently done a deployment where the customer is using 802.11n in both 2.4 and 5 GHz range. I have configured a WLan with that is providing coverage for all the radios including a/b/g/n on a 4402 controller in WiSM Module. The clients are also unable to run on all the radios. Everything is working fine, but we are seeing clients that have been connected to either a 2.4ghz radio or 5ghz radio, tend to switch between them when running for a while. I am trying to understand this scenario, since there is no setting on the controller that I can find would allow the preference of the radio. we are currently running the latest 6.0 code on the WLCs. Secondly the data rates are set to 24Mbps or higher for both radios, that means 802.11b is not allowed. The client machine was sitting at one position for 24hrs that means the user was not moving around hence the roaming should not be involved I think. Lastly we did the survey for 802.11a coverage and I don’t think there is any issue with the coverage, since it connects to 802.11a at excellent. The question really is that once the client connects to 802.11a on excellent and is running on that radio for an hour perfectly and the user is not moving at all why is it that it switches itself to 802.11g and then again to 802.11a?? I wanted to get your opinion as if do you know any bugs or vulnerabilities by having both radios enable?
And here is my response:
Thank you for your message. Unfortunately, at this time most/all of the roaming decisions are made by the stations (laptops, etc.) and not the infrastructure (Access Points and WLAN Controllers). The IEEE is devising a standard to change this, but it will take some time.
What type of stations are you using? Are they laptops, or something else such as handheld scanners, Voice-over-WiFi phones, etc? If they are laptops, are they Windows or Macintosh? If you are using Windows based laptops, you may be able to set a preference for 5 GHz within the client driver. For example I have an Intel 4965 AGN adapter — if I right-click on my wireless adapter and select “properties”, then click “configure” I can select the Wireless mode to be 802.11a/n only. I can also set the roaming aggressiveness so that it roams less frequently. Macintosh computers have a natural preference for 2.4 GHz and it is more difficult to encourage them to connect to something at 5 GHz – in a case like that, you may consider adding a 5 GHz SSID on its own VLAN. Again, these roaming decisions are made by the station, so your best bet is to look at the laptop settings to see what you can tweak.
One other potential “gotcha” that came to mind was how you enabled 802.11g only. The data rates have to be carefully managed for full interoperability between the station and the infrastructure. There are two types of data rates – the “basic” rates and the “supported” rates. The basic rates should include all 802.11g rates, even below 24 Mbps (therefore you should double-check that the basic rates include 6,9,12, and 18 Mbps). The requirements for supported rates are less strict.
The Burton Group and Xirrus are offering a FREE educational webinar today (Wednesday, Dec 2nd) on the newly ratified IEEE wireless standard, 802.11n. I delivered the Xirrus portion of this presentation at INTEROP New York a couple weeks ago, so I can tell you it’s packed with great information. 🙂
“802.11n: Lessons Learned from the First 1,000 Xirrus Installations”
Date: Wednesday, December 2, 2009
Time: 11:00 am PT / 2:00 pm ET / 7:00 pm UK
Paul DeBeasi, Senior Analyst, Burton Group
Kurt Sauter, Director of Product Marketing, Xirrus
The webinar is posted on the Xirrus webinars page: http://www.xirrus.com/library/webinars.php
You can use the below to register:
This webinar will discuss:
• Features that the first generation 11n products provide
• Site Survey Issues
• Performance Expectations
• Network and Architecture Considerations
• Client Device Considerations
• Security Issues
• Overall Recommendations
The webinar will be archived on the Xirrus website, and anyone will be able to listen/view after the live event.
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
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.
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.
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!
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.
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.
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.
There was no public outrage for the lack of a “Super Tuesday Poll” on WiFiJedi.com last week.
However, as “they” say… the show must go on. Here is this week’s poll: