By Jim Geier, Wireless-Nets, Ltd.
I've been experimenting lately with wireless clients having 802.11 power-save mode enabled and different access point beacon intervals. By increasing the beacon interval, clients will sleep longer and save battery power. To get a better idea of the savings, I ran some tests with the beacon interval set to 100 milliseconds (the default) and up to 5 seconds. I found beacon intervals at 1 second provide approximately 14 percent increase in battery life. Beacon intervals set beyond 1 second increased battery very slightly. So, it's probably worth setting the beacon interval out to around 1 second for clients implementing power-save mode. Just be certain that the longer beacon intervals don't negatively impact roaming.
Wednesday, July 30, 2008
Monday, July 28, 2008
Wireless Network Industry Report
By Jim Geier, Wireless-Nets, Ltd.
I just posted an extensive wireless network industry report, which explains the technologies, issues, vendors/products, and tends/outlooks for wireless PANs, LANs, MANs, and WANs. This report provides a good overview for anyone research various elements of the wireless network industry. Click here to download the report.
I just posted an extensive wireless network industry report, which explains the technologies, issues, vendors/products, and tends/outlooks for wireless PANs, LANs, MANs, and WANs. This report provides a good overview for anyone research various elements of the wireless network industry. Click here to download the report.
Friday, July 25, 2008
Cisco to discuss 802.11n performance results via Internet TV broadcast
By Jim Geier, Wireless-Nets, Ltd.
The true throughput performance of 802.11n implementations is difficult to assess without thorough testing. Cisco recently announced an Internet TV broadcast that will have representatives from Cisco, Intel, and key customers in healthcare and education who will discuss their approach and best practices for delivering high performance mobile computing with 802.11n Draft 2.0 wireless networking and mobility technologies. The discussion will highlight (1) Cisco and Intel sharing performance results from extensive testing of 802.11n technologies and (2) IT professionals from Southeast Alabama Medical Center and a university describing their business needs and technical considerations for deploying 802.11n, as well as their performance testing results. An interactive Q&A will follow.
This event is scheduled for Tuesday, July 29, 2007, 11:00 a.m. – Noon Pacific Time
You can access Cisco's broadcast on the specified date/time at the URL below:
http://tools.cisco.com/cmn/jsp/index.jsp?id=75959
The true throughput performance of 802.11n implementations is difficult to assess without thorough testing. Cisco recently announced an Internet TV broadcast that will have representatives from Cisco, Intel, and key customers in healthcare and education who will discuss their approach and best practices for delivering high performance mobile computing with 802.11n Draft 2.0 wireless networking and mobility technologies. The discussion will highlight (1) Cisco and Intel sharing performance results from extensive testing of 802.11n technologies and (2) IT professionals from Southeast Alabama Medical Center and a university describing their business needs and technical considerations for deploying 802.11n, as well as their performance testing results. An interactive Q&A will follow.
This event is scheduled for Tuesday, July 29, 2007, 11:00 a.m. – Noon Pacific Time
You can access Cisco's broadcast on the specified date/time at the URL below:
http://tools.cisco.com/cmn/jsp/index.jsp?id=75959
Migrating to 802.11n in the enterprise
By Jim Geier, Wireless-Nets, Ltd.
802.11n is a stable standard with client radios and access points widely available, so now is the time to consider migrating your wireless LAN to 802.11n. Learn some valuable tips on designing and deploying 802.11n networks from a tutorial I just posted in the technical resources section of my website.
802.11n is a stable standard with client radios and access points widely available, so now is the time to consider migrating your wireless LAN to 802.11n. Learn some valuable tips on designing and deploying 802.11n networks from a tutorial I just posted in the technical resources section of my website.
Wednesday, July 23, 2008
Wireless System Architecture: How Wireless Works – free chapter download
By Jim Geier, Wireless-Nets, Ltd.
I just posted Chapter 1, Wireless System Architecture: How Wireless Works, from my book, Wireless Networks – First Step. You can download this chapter free-of-charge. The chapter provides a very basic overview of how wireless systems work (good for someone just getting started in the wireless industry).
I just posted Chapter 1, Wireless System Architecture: How Wireless Works, from my book, Wireless Networks – First Step. You can download this chapter free-of-charge. The chapter provides a very basic overview of how wireless systems work (good for someone just getting started in the wireless industry).
Monday, July 21, 2008
Cordless phone impacts on Wi-Fi networks
By Jim Geier, Wireless-Nets, Ltd.
Some cordless phones operating in the 2.4GHz band offer potential RF interference to Wi-Fi networks. Actual interference depends on the way the phone operates. In this tutorial, I share with you what I found last week when testing multiple 2.4GHz cordless phones. I had an opportunity to do some Wi-Fi interference testing with several Plantronics 2.4GHz cordless phones. I found that the cordless phones, when ever switched on (with or without a dial tone), would always transmit a 10MHz wide signal in the 2.4GHz ISM band, which is roughly 90MHz wide. I could clearly see from a spectrum analyzer that turning on a second phone would produce another 10MHz wide signal in an unoccupied part of the band. Apparently, the phones would search for the least congested area and tune its transmitter to that frequency. With a fairly clean spectrum, with no Wi-Fi or Bluetooth devices operating, I could turn on six of the phones, which filled approximately two thirds of the spectrum. Based on the way that the phones were operating, the use of cordless phones (at least the Plantronics model I tested) will reduce the capacity for supporting Wi-Fi signals. Because a Wi-Fi access point uses one third of the spectrum, the operation of six phones would leave enough room for a single access point. If there is a need for operating nine phones, however, in the same general area as an access point, then interference between the access point and the phones (the three using a frequency that overlaps with the access point) will occur. The result is distorted voice heard over the phone when talking to someone and probably a much higher frame retransmission rate at the access point. Thus, it’s a good idea to investigate whether there are any cordless phones in operation where you’re planning to deploy a Wi-Fi network. Keep in mind, however, that the various cordless phone models operate differently. I’ve found through other testing that some even use frequency hopping spread spectrum, which distributes RF signals over the entire 2.4GHz band. This leaves no room for Wi-Fi access points.
Some cordless phones operating in the 2.4GHz band offer potential RF interference to Wi-Fi networks. Actual interference depends on the way the phone operates. In this tutorial, I share with you what I found last week when testing multiple 2.4GHz cordless phones. I had an opportunity to do some Wi-Fi interference testing with several Plantronics 2.4GHz cordless phones. I found that the cordless phones, when ever switched on (with or without a dial tone), would always transmit a 10MHz wide signal in the 2.4GHz ISM band, which is roughly 90MHz wide. I could clearly see from a spectrum analyzer that turning on a second phone would produce another 10MHz wide signal in an unoccupied part of the band. Apparently, the phones would search for the least congested area and tune its transmitter to that frequency. With a fairly clean spectrum, with no Wi-Fi or Bluetooth devices operating, I could turn on six of the phones, which filled approximately two thirds of the spectrum. Based on the way that the phones were operating, the use of cordless phones (at least the Plantronics model I tested) will reduce the capacity for supporting Wi-Fi signals. Because a Wi-Fi access point uses one third of the spectrum, the operation of six phones would leave enough room for a single access point. If there is a need for operating nine phones, however, in the same general area as an access point, then interference between the access point and the phones (the three using a frequency that overlaps with the access point) will occur. The result is distorted voice heard over the phone when talking to someone and probably a much higher frame retransmission rate at the access point. Thus, it’s a good idea to investigate whether there are any cordless phones in operation where you’re planning to deploy a Wi-Fi network. Keep in mind, however, that the various cordless phone models operate differently. I’ve found through other testing that some even use frequency hopping spread spectrum, which distributes RF signals over the entire 2.4GHz band. This leaves no room for Wi-Fi access points.
Friday, July 18, 2008
Video surveillance over Wi-Fi networks on the rise
By Jim Geier, Wireless-Nets, Ltd.
The use of Wi-Fi video cameras are being used in more and more surveillance applications. For example, London's city of Westminster is cracking down on people violating parking privileges (see related news story). More and more cities worldwide are also starting to take advantage of Wi-Fi video cameras to keep an eye on various illegal activities, such as vandalism and drug dealing. This offers a very good justification for municipalities to deploy city-wide Wi-Fi networks.
The use of Wi-Fi video cameras are being used in more and more surveillance applications. For example, London's city of Westminster is cracking down on people violating parking privileges (see related news story). More and more cities worldwide are also starting to take advantage of Wi-Fi video cameras to keep an eye on various illegal activities, such as vandalism and drug dealing. This offers a very good justification for municipalities to deploy city-wide Wi-Fi networks.
Wednesday, July 16, 2008
VoWLAN System Components – free chapter download
By Jim Geier, Wireless-Nets, Ltd.
I just posted Chapter 2, VoWLAN System Components, from my book, Deploying Voice over Wireless LANs. You can download this chapter free-of-charge. The chapter provides an overview of VoWLAN applications and details on how to assess the cost benefits of deploying voice over wireless networks.
I just posted Chapter 2, VoWLAN System Components, from my book, Deploying Voice over Wireless LANs. You can download this chapter free-of-charge. The chapter provides an overview of VoWLAN applications and details on how to assess the cost benefits of deploying voice over wireless networks.
Monday, July 14, 2008
The fight between WiMAX and Wi-Fi
By Jim Geier, Wireless-Nets, Ltd.
Wi-Fi hasn’t had a competitor since the days of HiperLAN, which was a relatively good wireless LAN technology that lost the fight against 802.11-standardized product proliferation a few years ago. For some time, Wi-Fi also won a bout against Bluetooth, which clearly fits now as a wireless PAN technology, not wireless LAN. Mobile WiMAX, however, is offering some new competition to Wi-Fi. The 802.16-2005 standard, sometimes referred to as 802.16e, provides fixed and mobile wireless MAN access in both licensed and unlicensed spectrums. Fixed WiMAX solutions have been available and certified for a while now. Mobile WiMAX, though, is relatively new. The competition between mobile WiMAX and Wi-Fi is currently focused in the outdoor environment, not indoors. Sprint is installing mobile WiMAX in many of the larger cities within the U.S. within licensed spectrum that Sprint paid big bucks to acquire. Sprint will be selling mobile access to WiMAX along with their existing services. Clearwire is also pushing mobile WiMAX. Unlicensed WiMAX will not likely be available for quite some time because of mobile WiMAX’s inability to provide effective RF interference rejection. There’s too much potential of RF interference in the unlicensed bands, such as 2.4GHz and 5GHz, to work properly without interference rejection. Thus, vendors are holding off on unlicensed mobile WiMAX for now (at least in the U.S.). So, will mobile WiMAX compete heavily with Wi-Fi in the outdoor market? Many municipalities have either installed or are in the process of installing Wi-Fi mesh systems. Wi-Fi hardware is relatively inexpensive, and it works in unlicensed spectrum, making it easier to proliferate. As a result, Wi-Fi will likely be around for a while.
Wi-Fi hasn’t had a competitor since the days of HiperLAN, which was a relatively good wireless LAN technology that lost the fight against 802.11-standardized product proliferation a few years ago. For some time, Wi-Fi also won a bout against Bluetooth, which clearly fits now as a wireless PAN technology, not wireless LAN. Mobile WiMAX, however, is offering some new competition to Wi-Fi. The 802.16-2005 standard, sometimes referred to as 802.16e, provides fixed and mobile wireless MAN access in both licensed and unlicensed spectrums. Fixed WiMAX solutions have been available and certified for a while now. Mobile WiMAX, though, is relatively new. The competition between mobile WiMAX and Wi-Fi is currently focused in the outdoor environment, not indoors. Sprint is installing mobile WiMAX in many of the larger cities within the U.S. within licensed spectrum that Sprint paid big bucks to acquire. Sprint will be selling mobile access to WiMAX along with their existing services. Clearwire is also pushing mobile WiMAX. Unlicensed WiMAX will not likely be available for quite some time because of mobile WiMAX’s inability to provide effective RF interference rejection. There’s too much potential of RF interference in the unlicensed bands, such as 2.4GHz and 5GHz, to work properly without interference rejection. Thus, vendors are holding off on unlicensed mobile WiMAX for now (at least in the U.S.). So, will mobile WiMAX compete heavily with Wi-Fi in the outdoor market? Many municipalities have either installed or are in the process of installing Wi-Fi mesh systems. Wi-Fi hardware is relatively inexpensive, and it works in unlicensed spectrum, making it easier to proliferate. As a result, Wi-Fi will likely be around for a while.
Friday, July 11, 2008
Many products now 802.11n (draft 2) certified
By Jim Geier, Wireless-Nets, Ltd.
802.11n is taking off as more and more vendors release products and gain Wi-Fi certification based on the 802.11n (draft 2) standard. Click here to see a current list of Wi-Fi 802.11n certified products.
802.11n is taking off as more and more vendors release products and gain Wi-Fi certification based on the 802.11n (draft 2) standard. Click here to see a current list of Wi-Fi 802.11n certified products.
Wednesday, July 9, 2008
WEP gets help from AirTight Networks
By Jim Geier, Wireless-Nets, Ltd.
For a number of years, we’ve certainly been aware of the security vulnerabilities of using 802.11 WEP (wired equivalent privacy) as a method of encrypting data frames traversing 802.11 networks. WPA (Wi-Fi Protected Access) is a much better alternative, but the problem is that WPA is not available in all devices. In addition, it’s sometimes difficult to get WPA working well across client radios and access points made by different manufacturers. As a result, WEP is sometimes our only option for securing wireless LAN connections for the next few years. The common thought is that “at least WEP is better than nothing.” Airtight, however, has recently announced a new tool that helps guard WEP mechanisms against hackers. You might consider this for implementations where only WEP is available, and you need some added protection. Refer to the AirTight press release for more details.
For a number of years, we’ve certainly been aware of the security vulnerabilities of using 802.11 WEP (wired equivalent privacy) as a method of encrypting data frames traversing 802.11 networks. WPA (Wi-Fi Protected Access) is a much better alternative, but the problem is that WPA is not available in all devices. In addition, it’s sometimes difficult to get WPA working well across client radios and access points made by different manufacturers. As a result, WEP is sometimes our only option for securing wireless LAN connections for the next few years. The common thought is that “at least WEP is better than nothing.” Airtight, however, has recently announced a new tool that helps guard WEP mechanisms against hackers. You might consider this for implementations where only WEP is available, and you need some added protection. Refer to the AirTight press release for more details.
Monday, July 7, 2008
VoWLAN Applications and Benefits – free chapter download
By Jim Geier, Wireless-Nets, Ltd.
I just posted Chapter 1, VoWLAN Applications and Benefits, from my book, Deploying Voice over Wireless LANs. You can download this chapter free-of-charge. The chapter provides an overview of VoWLAN applications and details on how to assess the cost benefits of deploying voice over wireless networks.
I just posted Chapter 1, VoWLAN Applications and Benefits, from my book, Deploying Voice over Wireless LANs. You can download this chapter free-of-charge. The chapter provides an overview of VoWLAN applications and details on how to assess the cost benefits of deploying voice over wireless networks.
Thursday, July 3, 2008
Tips for testing municipal mesh networks indoors
By Jim Geier, Wireless-Nets, Ltd.
Most municipal Wi-Fi networks are designed and hopefully installed to provide signal coverage inside approximately 70 percent of residences and businesses, at least near an exterior wall of the facility. It’s possible to go without permission inside some of the businesses, such as hotel lobbies and restaurants, but how do you get inside private residences? I’m currently verifying the signal coverage of a moderately-sized municipal Wi-Fi network, and we came up with a fairly good approach: simply post an advertisement in the local newspaper asking for volunteer residents to open their doors to the test team. We got a surprisingly large number of volunteers! What we learned, though, is to limit testing to daylight hours. It’s very difficult to find the homes at night, even with a GPS. Also, be ready to answer a lot of questions from the residents. Think ahead about how you’re going to response to questions such as: How good is my signal? (I don’t recommend answering that one); When will the network be ready for use?; How will I know if I have signal coverage once it’s ready for use?
Most municipal Wi-Fi networks are designed and hopefully installed to provide signal coverage inside approximately 70 percent of residences and businesses, at least near an exterior wall of the facility. It’s possible to go without permission inside some of the businesses, such as hotel lobbies and restaurants, but how do you get inside private residences? I’m currently verifying the signal coverage of a moderately-sized municipal Wi-Fi network, and we came up with a fairly good approach: simply post an advertisement in the local newspaper asking for volunteer residents to open their doors to the test team. We got a surprisingly large number of volunteers! What we learned, though, is to limit testing to daylight hours. It’s very difficult to find the homes at night, even with a GPS. Also, be ready to answer a lot of questions from the residents. Think ahead about how you’re going to response to questions such as: How good is my signal? (I don’t recommend answering that one); When will the network be ready for use?; How will I know if I have signal coverage once it’s ready for use?
Wednesday, July 2, 2008
How Wi-Fi roaming really works
By Jim Geier, Wireless-Nets, Ltd.
We all want Wi-Fi roaming to be seamless, but that just isn’t always the case. To get a better idea of what happens when a Wi-Fi client roams, I did some testing to see what the packets and protocols really do. The actual handoff from one access point to another is generally fast, but the overall roaming process can add lots of latency to wireless applications. For details, see a tutorial that I just posted in the technical resources section of my company’s website.
We all want Wi-Fi roaming to be seamless, but that just isn’t always the case. To get a better idea of what happens when a Wi-Fi client roams, I did some testing to see what the packets and protocols really do. The actual handoff from one access point to another is generally fast, but the overall roaming process can add lots of latency to wireless applications. For details, see a tutorial that I just posted in the technical resources section of my company’s website.
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