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Technology Stocks : LAST MILE TECHNOLOGIES - Let's Discuss Them Here -- Ignore unavailable to you. Want to Upgrade?

To: axial who wrote (11066)	4/20/2001 8:09:55 AM
From: Peter Ecclesine	Read Replies (2) \| Respond to of 12823

Hi Jim, There are three sets of rules in the US for unlicensed outdoor transmitters, depending on frequency and service. ISM (2.45GHz and 5.8GHz) allows unlimited transmit antenna gain, however every 3dB of antenna gain over the nominal 6dB must be accompanied by a 1dB reduction in transmit power. Receivers can have unlimited antenna gain. U-NII band 2, 5.25GHz-5.35GHz, has a 1W eirp limit and U-NII band 3, 5.725GHz=5.825GHz has a 4W eirp limit. There are also rules on antenna connectivity. There are a couple of new antenna technologies that pertain, MIMO and steered beam. Multiple Input, Multiple Output antenna configurations are legal under U-NII rules, and will help in multipath-limited environments. Steered beam (e.g. MetaWave) increases the directionality of signals, and so can take advantage of the ISM transmit antenna gain rule. IEEE 802.11a's 64QAM needs about 21dB S/N for flat fading and 27dB S/N for Raleigh fading. PBCC or other turbo coding can be applied to OFDM to change the S/N by about 2dB. The gain is real. The FCC will propose new ISM rules May 10th, and it will be an interesting IEEE 802.11/15/16 meeting May 14-18. petere