Category: Wireless Networking

Feature Article – Understanding the 802.11n high-bandwidth wireless network

Introduction

Now that the 802.11n high-bandwidth wireless-network standard has been declared a final standard, the price of 802.11n-compatible wireless-network hardware will come down to more affordable levels. This will lead to you considering upgrading your wireless network to 802.11n whenever the time is right to renew your home-network IT hardware.

The 802.11n access point

This works in a different manner to the 802.11a/b/g access points we are so used to. Basically, these units use a “multiple in, multiple out” methodology with “front-end diversity”. They will typically have two or three aerials with each aerial serving a particular transceiver. Some units may have an aerial serving a receiver as well as the two aerials serving two transceivers. It is totally different from “antenna diversity” which is used on most 802.11b/g routers and access points, where one transceiver works with two aerials, choosing whichever has the best signal strength.

These access points and the network client devices that connect to them also make use of “constructive multipath” to improve their quality of reception.This is different from the “destructive multipath” often experienced with FM radio and analogue television. Here, signals picked up as reflected signals are mixed with signals received by line-of-sight and “worked out” as a data stream.

The premium-priced 802.11n access points will be typically dual-band in which they can work on the existing 2.4GHz band or the newer 5GHz band. Some of this equipment may be able to work on both bands, as though there are two access points in one box.

Access Point Types

Single Band

These access points use a single access point that is set up to work on one band, typically 2.4GHz, but some of them work on 5GHz as an “add-on” access point.

Dual Band, Single Radio

These access points are like a single-band access point but can be set by the user to work on either 2.4GHz or 5GHz, but not both of the bands.

Dual Band, Dual Radio

These access points, sometimes described as “simultaneous dual-band”, are effectively two 802.11n access points in one box with one working on 2.4GHz and the other working on 5GHz.

Access Point Operating Modes

Primary Operating Modes

A typical 802.11n access point can be configured to work in one of two primary operating modes – a “compatibility” mode or an “N-only” mode.

Compatibility Mode

This mode, known as Mixed Mode or G-compatible mode allows 802.11g wireless network hardware to work from the same access point alongside 802.11n equipment. The limitation with this mode is that the wireless network works to a “worst-case” scenario with throughput that doesn’t hit the standards for an 802.11n segment. You will still have the larger coverage and service reliability with the 802.11n equipment and this benefit may pass through to 802.11g equipment

N-only Mode

This mode allows the access point to work only with 802.11n equipment and gives the equipment full wireless throughput as well as the full reliability of the standard.

Wideband vs Standard Channels

802.11n access points can run their channels as either “standard” 20MHz channels or 40MHz wideband channels which can yield higher throughput. The wideband channels also make use of a “standard” channel as a “base” channel for the double-width channel.

The preferred method of operation is that a 2.4GHz access point works on “standard” channels and most such access points will be set to have this kind of behaviour by default. But you can run these access points on the wideband channels with the limitation of poorer compatibility with 802.11g devices. If you are running a 2,4GHz access point in a manner to be compatible with regular 802.11g devices, it would be a good idea to stick to “standard” channels. If you are running 5GHz access points, you can get away with using the wideband channels and I would prefer setting up a 5GHz 802.11n extended-service-set to work this way.

The number of streams a device can handle

An 802.11n wireless device will typically be rated as being a single-stream, dual-stream or multiple-stream device. This relates to how many streams of data the wireless device can handle. All Wireless-N (802.11n) access points and routers will typically be either a dual-stream type or a multiple-stream type in the case of premium devices. Similarly, laptops with integrated Wireless-N capability; and add-on Wireless-N products will typically be dual-stream devices.

The main class of devices that will handle only one stream will be primarily-battery-powered devices like smartphones, WiFi VoIP phones, and WiFi-enabled digital cameras / portable media players because the single-stream ability won’t be intensive on these devices’ internal battery resources. Similarly, the idea of a single-stream Wireless-N network interface will also appeal to applications where size or cost do matter.

Other points to know

Best practice with dual-band equipment

If you are running dual-band equipment, especially dual-band dual-radio equipment, it would be a good idea to use the 5GHz band as N-only mode, while 2.4GHz works as compatibility mode. If you are running dual-band single-radio equipment, you will need to use older 2.4GHz equipment to run an 802.11g service set with the dual-band single-radio equipment on 5GHz N-only mode.

Use of aftermarket antennas

You can use external aftermarket antennas (aerials) with 802.11n equipment as long as all of the antennas are of the same type. This may work well if you replace the omnidirectional whip aerials with stronger omnidirectional ones. Then you may have to space the aerials further apart for the front-end diversity to work properly The main difficulty you will have is using directional aerials, in which case you may need to look for directional aerials optimised for 802.11n setups.

As well, if you are running dual-band dual-radio equipment, you will have to use antennas that can work on the 2.4GHz and 5GHz bands rather than antennas optimised for the 2.4GHz bands.

Shaping your 802.11n wireless network – the ideal upgrade path for your wireless network

I will be talking of WiFi networks that work on a particular technology and with a unique SSID and security parameter set as an “extended-service-set”. This allows me to cover setups where there are multiple access points working with a particular configuration.

You may be tempted to construct a multiple-access-point extended-service-set with an 802.11g access point and an 802.11n access point working in “compatibility mode” connected by an Ethernet or HomePlug wired backbone. The simple answer is "don’t”. You will end up with your wireless network having reliability problems especially as devices roam between the different access points and switch operating modes.

The simple answer would be to run different extended-service-sets with at least one access point for each WiFi technology. They are set up with different ESSIDs (such as SSID for the G cloud and SSID-N for the N cloud) with the wireless stations choosing between the different ESSIDs. The only thing they can have that is common is the WPA security parameters, and a common wired backbone which can be Gigabit Ethernet or HomePlug AV.

This could be achieved through deploying an existing 802.11g router that is set up as an access point and working on “SSID-G” and one channel while a newer 802.11n router working as the Internet “edge” is set to “N-only: or “compatibility” mode in the case of a single-band 2.4GHz unit, and set to “SSID-N” and a different channel.

As you evolve your wireless network, you may want to work towards establishing a 2.4GHz 802.11n “compatibility-mode” extended-service-set and a 5GHz N-only extended-service-set. You then upgrade your portable computers to work with dual-band 802.11n network interfaces or add dual-band 802.11n network adaptors to your existing equipment. The 5GHz extended-service-set will come in handy for high-throughput activity like video streaming and related applications while the 2.4GHz extended service set can work well with voice applications, smartphones, Internet radio and similar applications where throughput doesn’t matter.

If you are upgrading a wireless hotspot to 802.11n, it would be preferable to make sure your hotspot’s extended-service-set is on the 2.4GHz band and operating in “compatibility” mode so that customers can still use their existing 802.11g hardware on the wireless hotspot.

Some issues may occur with dual-band networks where the 5GHz extended-service-set may not cover the same area as the 2.4GHz extended-service-set. This is because the 5GHz band is of a higher frequency and shorter wavelength than the 2.4GHz band and is best demonstrated by AM radio stations being receivable at a longer distance compared to FM radio stations. It can be rectified by deploying a dual-band single-radio access point working on the 5GHz band in to the 5GHz extended-service-set as an infill access point.

Conclusion

Once you understand the 802.11n wireless standard and what it can and cannot do, you can make sure that you get the best out of the new standard while gaining the maximum mileage out of the existing wireless-network hardware.

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802.11n – now ratified as a standard

IEEE finally approves 802.11n | The Register (UK)

802.11n: Ratified at last | Wi-Fi Planet

IEEE Ratifies 802.11n | WiFi Networking News

The Fine Points of Optional Wi-Fi 802.11n Certification | Wi-Fi Networking News

My Comments On This Evolution Of The Standard

Ever since 802.11n came about as a wireless standard, the equipment that was working to the standard was working to a draft version of the standard. This may have been acceptable for networks which weren’t critical to a business’s operations, because of the doubt associated with last-minute changes that could affect hardware compatibility. In some cases, this could also mean that an 802.11n segment may not work properly unless the equipment was based on the same chipset.

Now that the standard is final, enterprises can become confident about deploying 802.11n wireless network segments with cost-effective heterogenous equipment setups. As well, the cost of establishing an 802.11n wireless-network segment will reduce now that manufacturers can confidently sell more equipment at varying price ranges.

Existing 802.11n draft-standard segments

But what does this mean for networks based around existing 802.11n draft-standard hardware? Could they work properly with final-standard hardware with as much as draft-standard hardware being “flashed” to final-standard specifications. The compatibility issue raised in this question has been through the new revisions being declared optional rather than mandatory.

Support for single-stream 802.11n devices

The most popular benefit of the new standard would be the ability to support single-stream 802.11n station devices. This concept allows a device to have one transceiver rather than the two or three that is part of the standard. It is mainly brought about because of a need to have battery-operated devices like smartphones and VoIP WiFi handsets as part of the 802.11n wireless network and the single-stream 802.11n network adaptors can fulfil this need without draining the device’s battery too quickly.

The access points can provide full bandwidth to these single-stream devices without forfeiting bandwidth to other devices simply through the use of one dedicated stream for each of the devices. It then may be like providing the wireless equivalent of a “switched” Ethernet connection or ADSL-based broadband connection to this class of devices.

This factor has been improved with the ability for access points to be tested for three streams. This may allow for access points and routers to be differentiated on wireless-network performance levels as well as functionality levels.

Conclusion

The goal has been achieved for 802.11n to be a real wireless-network standard that complements the high-throughput Internet services and the multimedia networks of today.

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Quick “extended service set” setup routines for WiFi access points

Why a quick setup routine for WiFi access points (or client devices capable of operating as access points)?

It makes it simple for one to extend or improve wireless coverage by adding access points to an existing “extended service set” with a wired backbone. This includes mitigating microwave-oven interference to computer equipment being used in the kitchen by using an access point tuned to Channel 1 installed there. Increasingly this functionality will become more relevant with WiFi-based VoIP cordless phones and come in to its own with location-based WiFi security and home-automation applications. It will also allow a device with built-in Ethernet or HomePlug network connectivity as well as a WiFi client functionality (which typically covers most WiFi-enabled devices) to become a low-power WiFi access point thus making it easy to expand the wireless network by providing infill coverage.

This is achieved by enrolling the device as a client device of the wireless network, then if the device is connected to the same Internet gateway that is visited by the wireless network via the wired network, it sets itself up as an access point with the same SSID and security data as the master access point. It then avoids users having to re-enter network data and make mistakes in setting up multiple-access-point wireless networks.

Methods

Semi-automatic operation – without WPS on master AP

  1. User: Connect to new AP via Ethernet or HomePlug
  2. User: At Web UI for new access point:
    1. Select AP – quick setup
  3. New Access Point: AP becomes wireless client bridge, direct link to host
  4. New Access Point: AP presents list of SSIDs that it can receive and their security status (open or secure)
  5. User: Clicks on SSID matching their home network’s SSID or enters home network’s SSID (for hidden SSID networks), then enters WEP/WPA-PSK key as applicable when the new AP locks on to the desired AP
  6. New Access Point: Perform DHCP test to see if it can find the gateway
    1. If successful, offer to set up as AP, gain MAC of gateway & BSSID of master (& other) APs on SSID,set WEP/WPA-PSK parameter
  7. New Access Point: If user OKs with setting up as AP for network, then switch to AP mode, self-tune to vacant frequency, remain dormant
  8. New Access Point: Once gateway is discovered through Ethernet / HomePlug interface (backbone detect), activate AP mode.

Automatic operation – with WPS on master AP

  1. User: Select Access Point mode, then invoke WPS on new and master AP (PBC “push-push” method)
  2. New Access Point: new AP gains WiFi details through WPS as if it is a client
  3. New Access Point: become wireless client bridge on these details until connected to wired backbone
  4. New Access Point: detect wired backbone (via Ethernet, HomePlug), self-tune, become AP with WPS “peer” status

Limitations

Some details may not be able to be conveyed to the new access point, especially if the access point is of lesser capability than the master access point. This may be of concern when extending the coverage of a wireless hotspot and want to enforce client-computer isolation at the access point. The client-computer isolation functionality should be achieved at the link-layer level by the hotspot gateway router thus allowing for media-independent client isolation. It can then cater for hotspots that use wired media (Ethernet, HomePlug, MoCA TV-aerial cabling) to extend WiFi coverage or connect computers supplied by themselves or their guests to their Internet service.

Similarly there may be issues with setting up a multi-LAN wireless network where there is a VLAN set up on the wired network and multiple SSIDs that are radiated by the same access point. This kind of setup describes a “private” LAN segment and a “public” or “guest” LAN segment

Conclusion

Once the WiFi equipment vendors look at using “quick-setup” methods for WiFi access points, this can allow home and small-business users, especially those with limited computer skills, to set up their wireless networks to suit their needs more easily.

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SmallNetBuilder – Small Network Help – 802.11n Headed for September Ratification

 SmallNetBuilder – Small Network Help – 802.11n Headed for September Ratification

Cited text from SmallNetBuilder article

SmallNetBuilder has learned from a reliable source that the final issues in 802.11n have been resolved in this week’s meeting of the IEEE TGn in Montreal.

The draft standard is now expected to successfully pass through the final steps required for a ratification as a final standard in September. This is four months earlier than the currently published January 2010 date.

The key issue holding up the standard has been the mechanisms to be used to prevent interference between 802.11n and Bluetooth devices.

My Comments on this stage for 802.11n

Once this standard is ratified, most of us can now buy 802.11n-compliant wireless-network hardware while being sure it will work with other manufacturers’ equipment.

But the main issue with this ratification is whether most hardware manufacturers will roll out firmware for existing draft-specification 802.11n hardware that is in the field. This is of importance whenever newer final-specification hardware is deployed, because there could be compatibility issues between the different versions of the standard.

A good step to go about this is to go to manufacturers’ Websites and look for upgrade packages for any 802.11n hardware. In the case of laptops, use the laptop manufacturer’s Website or “quick-update” routine to check for updates for the wireless-network subsystem. If you run an “n-box” or other equipment serviced by your Internet service provider, check with the provider if there is new firmware in the pipeline for the hardware. This may be dependent on whether the device’s manufacturer is rolling out compatible firmware for provider-distributed devices.

In some cases, you may need to run your 802.11n wireless network segment on a “mixed” setup which observes best compatibility with 802.11g devices even if the segment is running only with “n” devices.

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Use of WiFi technology for safety and security

Ekahau Enhances Staff Safety of Hospital Psychiatric Wards

My comments on this issue

The Ekahau press release that is linked to from this article details the use of a WiFi-based staff badge that can be used to locate particular staff members in the hospital’s psychiatric ward and deliver messages to them.  But the feature that drew me to this device was the remote panic-alarm functionality that sends its signal via the hospital’s WiFi network.

Any panic-alarm or medical-alert system that is deployed in the home typically requires a transmitter and receiver working on a dedicated frequency, in a similar manner to garage-door openers.  If they are monitored by an external agency, the devices then transmit their alert signal to the monitoring station via a dedicated telephone or cellular circuit.

Now there is a different reality being brought about with cost-effective Internet service provided to WiFi-based wireless home networks in many households. This has included the concept of providing telephone and multi-channel television service through the same pipe, all thanks to the magic of IP-based packet networks. The classic circuit-based signalling methods used by these alarm devices are becoming less relevant in the packet-based signalling. Similarly, most users will want to benefit from the infrastructure that is laid down in a home network, such as the establishment of a multi-access-point WiFi network with a HomePlug-based backbone to cover a difficult house.

The Ekahau setup could be scaled back to allow an alarm installer or broadband Internet provider to sell a similar system in to the home. Any moveable sensor like a medical-alert pendant could make use of the existing WiFi network for transferring its data to the monitoring facility. It could then lead to e-mail and / or text (SMS) messaging if the device is triggered. Similarly, the unit could be used to deal with “wandering” behaviour that can be part of dementia-related illnesses by alerting if the person goes out of range of the WiFi network. As well, such systems could support local monitoring through the use of a local server device, thus providing their output through a Web page, platform-specific “widget” or desktop application.

This setup may appeal to broadband providers who want to gain more “average revenue per unit” by reselling basic security services as part of their package. It could also be a way of achieving a legitimate upgrade path for currently-deployed building security systems, especially in the context of the “switched-on” Internet-enabled home.

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Bluetooth 3.0 with High Speed Transfer – What does this mean?

Bluetooth Special Interest Group press release

WiFi Planet article on Bluetooth 3.0

My Comments

Bluetooth has hit the “big 3” by introducing a high-throughput version of its wireless personal network specification. This same technology used for sending pictures or phone-number data between mobile phones in the same space or streaming sound between mobile phones and car handsfree kits can do such things as wirelessly transferring one’s music library between a laptop computer and an MP3 player or “dumping” the contents of a digital camera to a computer.

It primarily allows data streams conforming to the Bluetooth protocols to be transmitted over the 802.11b/g WiFi network just by using the media-transfer levels of that specification. This takes advantage of the fact that a lot of the smartphones and the laptop computers have Bluetooth and WiFi wireless technology built in to them; and that premium MP3 players like the Apple iPod Touch will offer WiFi and Bluetooth on the same device. This is a situation that will become more common as chip manufacturers develop “all-in-one” WiFi / Bluetooth radio chipsets. For applications requiring a small data stream, the device just engages a single Bluetooth transceiver with the regular Bluetooth stack, which can save on battery power.

Intel had developed “My WiFi” which is a competing standard for a personal area network based on the WiFi technology with the devices using the full list of protocols and standards applicable to regular LAN applications. The idea was to have the laptop “split” its wireless-network ability into a client for a WiFi LAN and a very-low-power access point for a WiFi LAN which is the personal area network. At the moment, this technology is limited to laptops based on the Centrino 2 platform and requires that the laptop, being a general-purpose computer, becomes a “hub” device for the personal area network. But what could happen could be that other WiFi chipset vendors would license this technology and implement it into their designs, which could extend it towards other applications.

This would lead to a highly-competitive space for technologies that connect the wireless personal area network together, especially if the primary device of the network is a laptop computer. It could also incite manufacturers of devices like digital still and video cameras to include WiFi and Bluetooth in to these devices.

Who knows what the future will hold for the wireless personal area network.

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WiFi tops poll for best technological innovation of last decade – Telegraph

 

WiFi tops poll for best technological innovation of last decade – Telegraph

What has WiFi been about especially for the home IT environment?

One major way WiFi has benefited the home IT environment is the increased sale of laptop computers (http://www.australianit.news.com.au/story/0,24897,24851973-15306,00.html?referrer=email) over desktop computers. This typically would manifest in a home computing environment consisting of one or more laptop computers that have built-in WiFi wireless ability. The network – Internet “edge” device in this environment would be a wireless router that brings the Internet to these laptops via WiFi wireless. In some countries, the standard provider-supplied “customer premises equipment” for Internet service would be equipped with WiFi wireless capability.

Increasingly, nearly every printer manufacturer is running at least one residential-tier multi-function printer equipped with network ability, typically with WiFi network access. This means that the printer can be located in one position wherever the user desires and print documents from their laptop. There also is the increasing number of “Internet radios” or “i-Radios” that use WiFi to bring Internet radio streams to the speakers in these sets.

This may not be strictly a home-IT environment issue but the number of “hotspots” and “hotzones” that are part of public places is now increasing. These WiFi-based public networks are allowing for anywhere computing.

This has also caused most current-model mobile phones and PDA devices to be equipped with WiFi wireless thus allowing for cost-effective portable Web browsing and, increasingly, DLNA-driven music management and playback. These phones will eventually lead to WiFi being another mobile-telephone network usually in the form of fixed-mobile communications for example.

There have been attempts to “kill the goose that laid the golden egg” by limiting WiFi or making it unpopular. It has mainly been based on the “electromagnetic waves being dangerous to people” theory being propagated as part of junk science, but real scientific tests have proven that the RF emissions yielded by typical WiFi and Bluetooth setups none or very little detrimental effect on people.

Even without this article, I would certainly agree that WiFi has become an important computer technology for all IT scenarios.

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802.11r – the new wireless-networking standard

In August-September 2008, there has been a fair bit of talk in the IT press about the new IEEE 802.11r standard for wireless networks. It isn’t a new waveband or transmission standard for these networks.

Instead it is an improved method of handling the “handover” procedure when a wireless-network client moves between two access points in a multi-access-point network. The idea behind this is to make the handover process hard to notice if you are using a multimedia service which works with streamed audio or video like VoIP or audio / video streaming. The same feature will also benefit multi-machine multi-player gaming such as Internet-hosted online gaming because everything that is part of the game is kept in sync, thus making sure that you can “frag” the opponent there and then. With current technology, if you move between different access points while using a multimedia service, you will notice an obvious “glitch” because of the requirement to re-associate with the network when in the new access point’s area.

The improvement is based on a “work-ahead” procedure where the client will log in with access points of the same “extended service set” while utilising the current access point. Then it will “switch over” to whichever access point has the best signal, thus avoiding unnecessary glitches.

The main issue with this technology, like any new standard being introduced, is how it can work with existing networks and equipment. As well, there is the issue of an upgrade path for existing equipment. In the first situation, would 802.11r-based clients be able to achieve the fast handover with wireless networks that work with current technology and would 802.11r-based access points work with existing WiFi clients. This also includes wireless networks where some access points may be 802.11r-enabled and some may be on existing technology. This would typify operating environments where a gradual roll-out is implemented because there will be an initial price premium for newer equipment being equipped with 802.11r and it would still wouldn’t be cost-effective to replace all access points at the same time. This brings me to what will be discussed in the next paragraph regarding existing equipment.

The second situation would determine what is needed to be done to an existing network to roll out the new technology. Could this be achieved through a firmware or software upgrade on existing equipment or would it require totally-new equipment to be deployed? This issue would be very pertinent when it comes to small wireless networks where one of the access points is built in to a wireless router that is on the network-Internet edge. It also would encompass most outdoor access points and, of course, those HomePlug-based wireless access points like the Netcomm NP-290W / Solwise PL-85PEW which I have mentioned about in this blog.

This issue may not be exposed in the small-network space because the typical small wireless network is based around only one access point — the one built in to the router at the network’s “edge”. But as I have mentioned in this blog about setting up multi-access-point wireless networks which have an Ethernet or HomePlug wired backbone as a way of extending the wireless network or conquering wireless-network reception difficulties, the issue of the 802.11r “fast-handover” technology will have to be exposed to this class of network. This is important if the network is being used for VoIP, streamed IP-based multimedia or online-gaming “frag-fests”.

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