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Cabling for 802.11n Scott D. Thompson President, Oberon, Inc.

Learn about cabling requirements for enhanced wireless data rates and connectivity with IEEE 802.11n technology. Understand signaling, data throughput, infrastructure bandwidth, TIA guidelines, and more for efficient WLAN deployment.

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Cabling for 802.11n Scott D. Thompson President, Oberon, Inc.

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  1. Cabling for 802.11n Scott D. Thompson President, Oberon, Inc. .

  2. IEEE 802.11n DEFINITION • “n” is a proposed amendment to the IEEE 802.11 Standard • Uses advanced signal processing (Multiple Input/Multiple • Output and beamforming) and advanced over the air modulation and coding methods to achieve unprecedented wireless data rates • Many client devices and access points from leading vendors are “n” ready • May operate in the 2.4 GHz band and 5 GHz band • In mixed mode deployments, 802.11n performance will be degraded somewhat by 802.11 a/b/g clients, but may improve connectivity performance of 802.11 a/b/g clients .

  3. “SIGNALING” DATA RATE vs. DATA THROUGHPUT “Signaling” data rate: Over the air modulation rate commonly used to specify the product Data throughput: effective Ethernet throughput at the connector .

  4. “SIGNALING” DATA RATE vs. DATA THROUGHPUT In Practice .

  5. “SIGNALING” DATA RATE vs. DATA THROUGHPUT The difference is that the wireless connection has more packet overhead and lower bit density in the signaling And remember- Wireless access points are (somewhat)like Ethernet hubs - They share a collision domain, and they are half duplex. .

  6. TYPICAL PRODUCT DATA RATE Vendors Claim >100Mb/s data throughput rates per radio, > 200 Mb/s for two radios. SO…. requires cabling for 1000Base-T (Gigabit Ethernet) versus 100Base-TX (Fast Ethernet). CAT5e or better, & will be less tolerant of cabling errors Is the AP,switch, and/or controller port 1000Base-T (gigabit) capable? .

  7. INFRASTRUCTURE BANDWIDTH What is the uplink bandwidth required when aggregating multiple APs? (using an over-subscription factor of 20, for example) 960 Mb/s ea. 48 X (200 Mb/s) 20 (over-subscription factor) = 480 Mb/s Controller A 48 port switch Controller B 480 Mb/s 200 Mb/s ea. peak . AP 2 AP 48 AP 3 AP 1 AP 4

  8. TIA GUIDELINES FOR CABLING Telecommunications Systems Bulletin TSB-162 Telecommunications Cabling Guidelines for Wireless Access Points (APs) provides guidelines on the topology, design, installation, and testing of cabling infrastructure for supporting wireless local area networks (WLANs) in compliance with the ANSI/TIA/EIA-568-B.2 and TIA-569-B standards for supporting wireless LAN in customer premises. TSB-162 was created by the TIA TR-42 engineering committee and released in March of 2006. TSB-162 is not a standard, but rather contains technical material that may be useful to industry and users. *Cabling Installation & Maintenance March, 2006 .

  9. TIA GUIDELINES FOR CABLING TSB-162 states that cabling should be installed and performance tested per existing 568-B.2 standards. Determination of exact cell size and placement of the AP is outside the scope of the TSB (perform a site survey or simulation) TSB-162 include wall-mount above the drop ceiling, wall-mount below the drop ceiling, and in-grid ceiling mount. Telecommunications Enclosures (TEs) can be mounted in a ceiling panel to provide locked security or aesthetics for APs .

  10. CELL SIZE The TSB includes an example of a 60-foot by 60-foot square cell structure This agrees reasonably well with vendor recommendations for 3,000 sq. ft. “cell” sizes to support wireless voice over IP AP Lmax=13 m (42 ft) Hmax=80 m (262 ft) TR X=18.3 m (60 ft) TO r=13m (42 ft) Patch=6m (20 ft) 3,600 sq.ft. square cell . EQUIPMENT (switch)

  11. TIA 569-B Telecommunications Pathways Telecommunications Enclosure (TE) may be used to enclose APs The use of suspended ceiling space for horizontal connection points may be acceptable, provided that the space is accessible without moving building fixtures, equipment or heavy furniture Access to the TE shall be controlled against unauthorized access Cables that enter the TE shall be protected from sheath abrasion and conductor deformation by means of grommets, bushings and suitable cable management hardware A TE should serve an area not greater than 3,600 sq. ft. A minimum of 3” clear vertical space shall be available above the ceiling tiles for horizontal cabling and pathway .

  12. POWER OVER ETHERNET • Most vendor wireless access points can be powered by IEEE 802.3af PoE. There are some exceptions, requiring 802.3at (PoE Plus) • 802.11n products typically require close to 12.95 W if both radios used .

  13. OTHER CONSIDERATIONS • - Although 802.11n is capable of providing coverage over large areas, recommend using the same density of access points used in 802.11 a/b/g network • This is consistent with TIA standards, vendor recommendations, and anticipates applications requiring a higher signal to noise ratio than data .

  14. COAX CABLING TO ANTENNAS • - 802.11n access points may require three to six antennas • Some access points have non-detachable or integrated antennas • - Ideally, antennas are unobstructed by ceiling tiles and other objects • Antennas should be spaced about • 4” apart (2.4 GHz), and 2” apart • (5GHz) or greater. Beyond that, • there is not a need to “space • in increments of a wavelength” • Use suitably rated coax such as • UL Type CL2P .

  15. INSTALLING IN THE “PLENUM” • vs. THE AIR HANDLING SPACE • - Ideal location for access point is in the ceiling, but…… • National Electric Code (NEC) regarding the plenum used for environmental air……. • Article 300.22(b) “Equipment and devices shall be permitted within such ducts or plenum chambers only if necessary for their direct action upon, or sensing of, the contained air” • NEC Article 100 defines plenum as “A compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system”. • NEC article 300.22(c) “The space over a hung ceiling used for environmental air-handling purposes is an example of the type of other space to which this section applies”, (Air-handling space as opposed to a plenum space) .

  16. N.E.C. COMPLIANCE • NEC article 300.22(C)(2) “Electrical equipment with a metal enclosure, (or otherwise listed) shall be permitted to be installed in such other space unless prohibited elsewhere in this Code”. • NEC article 300.23 “cables, race-ways and equipment installed behind panels, including suspended ceiling tiles, shall be arranged and secured so as to allow removal of panels and access to the equipment.” .

  17. PREPARING FOR THE FUTURE • - Cable for the future. Faster wireless standards in the works, but nothing eminent • Gigabit Ethernet to the AP probably adequate for some time into the future • In Healthcare, the Joint Commission has established rules for mitigating the spread of infectious disease and contaminants- limiting access to the air-handling space. TIA tech. committee TR-42 Health care facility cabling task group. • Department of defense installations, & other government agencies may require access point to be locked up • Consider other RF services such as RFID, asset location, cellular, etc. • RF cables- 802.11n has provisions for up to 8 antennas! .

  18. www.oberonwireless.com .

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