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LANCOM FAQ on 802.11n wireless LAN

What is IEEE 802.11n?

IEEE 802.11n is the latest wireless LAN standard and offer much higher speeds and significant improvement in range and signal coverage. The 802.11n devices currently on the market achieve speeds of 300 Mbps, where the preceding standard 802.11 a/g offered just 54 Mbps. The standard itself goes further still: Even today it defines a further doubling of speeds to 600 Mbps for future generations of hardware-and that with full backwards compatibility.

Further detailed information is available from the LANCOM tech-paper "WLAN - 802.11n in Overview".

How does IEEE 802.11n work?

The improvements with the 802.11n standard are based on a series of extensions and new technologies including MIMO ("Multiple Input, Multiple Output"), packet aggregation, and doubled channel bandwidths. All of this is explained in detail in the tech-paper "WLAN - 802.11n in Overview".

What does ratification of the IEEE 802.11n standard mean?

Many products which conform to the IEEE 802.11n draft standard are available on the market or are installed already. Ratification of the standard means that there is now greater reliability of planning and investment protection for existing installations. In particular for existing installations, full compatibility between the 802.11n-draft standard and the ratified standard means that there is no need of an upgrade. Another aspect is that the coming generation of WLAN hardware will offer further increases in speed while maintaining full backwards compatibility. The standard specifies other technologies, which are not yet available in today's hardware. One example is beam forming, which will provide further improvements to the speed of wireless LANs.

When will the IEEE 802.11n standard be publicly available?

Ratification took place on September 14, 2009. The 560-page document is due for publishing in mid October 2009 and will be available at a charge for download from the IEEE Web site.

What makes IEEE 802.11n so important?

The technology behind 802.11n is an enormous breakthrough for the WLAN market. For the first time WLAN performance exceeds that of Fast Ethernet connections, and reliability is improved over the former standards.

Are the IEEE 802.11n-draft and 802.11n standards compatible with one another?

IEEE 802.11n-draft products are fully compatible with the ratified standard. Interoperability in both directions is assured.
All products confirmed by the WiFi Alliance as Draft-2.0 verified may use the "802.11n Interop" logo without further testing.

The WiFi Alliance tests differ only marginally from the draft-2.0 tests (optional items only!), and no changes are to be made to the baseline requirements of its 802.11n certification program.
http://www.wi-fi.org/news_articles.php?f=media_news&news_id=835

Can LANCOM products which conform to 802.11n draft 2.0 be upgraded to the 802.11n standard?

Full interoperability and compatibility between draft 2.0 and the 802.11n standard mean that all LANCOM 802.11n draft products are fully compatible to the final IEEE 802.11n standard. There is no need to upgrade any existing installations. All of the obligatory components and many of the standard's optional software components have already been implemented in the current versions of LCOS. These new functions are available from LANCOM with the usual free LCOS updates.

What does this mean for existing or planned installations? Should we be waiting for the new, fully 802.11n-compatible devices?

No, installations and rollouts are unaffected and can continue as planned. Full compatibility to the draft-2.0 version of the final standard means that today's LANCOM products are already compatible to the ratified standard.

Is existing 802.11a/b/g equipment compatible to 802.11n access points?

Yes, older WLAN clients can continue to be operated unchanged and without loss of performance. In practice, a slight improvement in performance may be expected as 802.11a/b/g clients also benefit from the improved features provided by MIMO access points.

How is the performance in a network with a mix of 802.11a/b/g clients and new 802.11n clients?

Other than with the transition from 11 Mbps to 54 Mbps WLAN technologies, the combined operation of 802.11a/g and 802.11n clients only gives rise to a very slight performance loss from the additional overhead in "compatibility mode". The overall data transfer rate of the WLAN network is approximately divided up into portions corresponding with the speed of each of the WLAN clients.

Does 802.11n benefit me if I continue to operate a 2.4-GHz WLAN network only?

Clearly yes. Former b/g clients profit only to a small extent, but 802.11n clients operating at 2.4 GHz with the usual bandwidth of 20 MHz benefit from 3.5 times the performance and a significantly longer range. This makes 802.11n access points ideal for setting up and expanding purely 2.4-GHz WLAN networks.

What is MIMO?

The most important new technology used in IEEE 802.11n is named "Multiple Input, Multiple Output", which is abbreviated as "MIMO". MIMO technology employs multiple antennas to transmit different data streams between access points and clients. At LANCOM, two data streams ("spatial streams") are distributed between 3 senders and receivers each. This method allows greater volumes of data to be transmitted in a given time.

What is the meaning of information such as 2x3 or 3x3?

"N x M" describes a MIMO system. Whereas "N" is the number of transmitters and transmitting antennas, "M" represents the number of receivers and reception antennas. For existing WLAN installations that are to be migrated to 11n, the following strategies can be followed:

What are the 40-MHz channels and channel bundling?

Channel bundling involves the combination of two 20-MHz channels to form one 40-MHz channel, the result of which is an effective data rate that is more than doubled.The LANCOM "Super A/G" extensions offered a "108-Mbps Turbo Mode" on the basis of 54-Mbps WLAN technology, but this setting was fixed and excluded equipment from operating in other modes. In contrast to this, it is possible to simultaneously operate 20-MHz clients and 40-MHz clients in parallel. For each client and each access point, a setting determines whether 40-MHz channels are to be operated along with the 20-MHz channels. However, in the 2.4-GHz band just 3 non-overlapping channels are available, and so the operation of this feature is only worthwhile in the 5-GHz band with its 19 channels. Not all WLAN clients support 40-MHz channel widths at 2.4 GHz.

When is the best time to switch to IEE 802.11n APs?

Right now! 802.11n-based networks offer enormous advantages over former standards. New perspectives open up to enterprises which install a high-performance, robust wireless network offering massive practical benefits.

What migration strategy does LANCOM Systems recommend?

For new networks, we recommend that IEEE 802.11n access points be incorporated immediately. For existing WLAN installations that are to be migrated to 11n, the following strategies can be followed:
Exchange of individual units: Replace the access points at locations with high levels of WLAN traffic. This gives you migration at those locations where you profit the most from the performance improvement. This is a pragmatic and cost-conscious approach to migration particularly for 2.4 GHz WLAN networks.
Install a 5-GHz overlay network: With this approach the new access points can either be employed only where top WLAN performance is required, or ideally over the entire area of network coverage. Older clients are then served by the older access points in the 2.4-GHz band and the new 11n clients enjoy all of the advantages of the new standard at 5 GHz. Instead of doubling the number of access points, it can be more cost effective to install a dual-band WLAN network: Old WLAN access points are exchanged against new dual-radio, dual-band access points such as the LANCOM L-315agn dual Wireless. One of the access point's radio modules operates in the 2.4-GHz band to serve conventional WLAN clients (802.11b and 802.11g), while the second radio module operates simultaneously in the 5-GHz band exclusively for the new 802.11n clients. Older clients continue to be served in the 2.4-GHz band and the new 11n clients enjoy all of the advantages of the new standard at 5 GHz.

Do I have to convert my entire LAN infrastructure to Gigabit Ethernet?

Even though the advertising quotes data rates of up to 300 Mbps, the effective rates are more in the order of 80 – 130 Mbps. What's more, this net data rate is only achievable in pure 11n environments where AP and clients are 11n-capable. In the case of a mixed environment, the net throughput rates are generally below the 100 Mbps limit of the Fast Ethernet standard.

Can PoE be used to supply power to LANCOM 802.11n access points?

The LANCOM 802.11n access points L-305agn Wireless, L-310agn Wireless and L-315agn dual Wireless conform to the 802.3af standard. Even at full performance—and with the L-315agn dual Wireless that includes operating both radio modules simultaneously—they can be very neatly supplied with power via the network cable from standard PoE switches.

Which IEEE 802.11n-compatible products does LANCOM have to offer?

As of September 2009, the LANCOM range of 802.11n-compatible products includes the following:

  • LANCOM L-305agn Wireless
  • LANCOM L-310agn Wireless
  • LANCOM L-315agn dual Wireless
  • LANCOM 1811n Wireless
  • LANCOM 1821n Wireless
  • LANCOM OAP-310agn Wireless

Access points of the L-300 series are for indoor use. The LANCOM L-305agn and L-310agn Wireless are equipped with Gigabit Ethernet interfaces, whereby the L-305agn features an internal antenna and the L-310agn has connectors for external antennas. Thus the L-305agn is well suited to environments where the WLAN installation should be optically understated, whereas the L-310agn with its external antenna connectors is suitable for areas with challenging radio-coverage conditions, or for P2P links. Our dual-radio indoor model, the LANCOM 315agn dual Wireless, has two radio modules which can be operated simultaneously, one as a 54-Mbps a/g module, the other as a 300 Mbps a/g/n module.

The LANCOM 1811n and 1821n Wireless are two professional WLAN routers with VPN, whereby the 1821n has an integrated ADSL2+ modem.

With the OAP-310agn Wireless, LANCOM offers an outdoor access point for infrastructure applications or point-to-point connections.

What net data rates can be achieved by LANCOM access points with the 300-Mbps WLAN module?

Maximum net data rates for wireless LANs are, in ideal scenarios, approximately half the nominal gross data rate. Devices with the 300-Mbps WLAN module and Gigabit Ethernet interface currently support up to 130 Mbps. Fast-Ethernet interfaces with 100 Mbps are generally sufficient for access points considering the speeds typically available under normal working conditions.

Precise information on the dependencies on protocols and WLAN configurations is available in the LANCOM tech-papers "WLAN – 802.11n Indoor Performance" and "WLAN – 802.11n Outdoor Performance".

Does the LANCOM L-300 series support beam forming?

No. Beam forming (i.e. electronic modification of the antenna radiation characteristics) is not yet supported by the hardware. The antennas are designed to be omni-directional in order for all of the antennas to receive and combine the signals simultaneously (MIMO principle).

Is IEEE 802.11n also suitable for outdoor applications?

Yes, the specialized polarization-diversity antennas with the LANCOM OAP-310agn Wireless and the LANCOM L-310agn provide two "spatial streams" to support the full performance of 802.11n. LANCOM has drafted a detailed tech-paper on the subject on Outdoor WLAN with 802.11n. This is available for free download from the LANCOM Web site.

Are the new IEEE 802.11n access points supported by the LANCOM WLAN Controllers?

Yes, the 11n access points are supported as of Controller software version LCOS 7.28. The strengths of the LANCOM "Smart Controller" architecture truly come into play when combined with the fast 802.11n access points. It provides full 11n performance because the payload data is not forced to travel via the Controller.

How widespread is IEEE 802.11n?

According to the WiFi Alliance, over one million products with WLAN modules supporting the various 802.11 standards are sold each day (!).
Market researchers from ABI Research expect the sales of products based on the 802.11n standard to be double those of 802.11g products as early as 2010.
http://www.abiresearch.com/press/...




LANCOM has drafted a detailed Techpaper on the subject on Outdoor WLAN with 802.11n. This is available for download from the LANCOM Web site for free.