Reasons for the SignalMAX Product Range Improvement

The ParkerVision (PRKR) SignalMax router/card pair gives as much as 100% open field range improvement over cheap commodity 802.11b/g routers and cards. This is a 6.0 dB improvement. Furthermore, compared to the Pre-N equipment from Belkin, the SignalMax is about 35% (or 2.7 dB) better in open field range (note that SignalMax was not nearly as good in bit rate or range as the Pre-N for indoor environments).

How does PRKR get this improvement?
Is this performance improvement due to PRKR D2D technology?  No.  In fact, the reasons for longer range of PRKR cards have nothing to do with D2D technology.  The PRKR information presented here is quoted directly from their September 4, 2003 FCC filing (demonstrating that their D2D technology complies with 802.11 standards) which is found at: https://gullfoss2.fcc.gov/prod/oet/forms/blobs/retrieve.cgi?
attachment_id=375611&native_or_pdf=pdf

1. PRKR cards use an external low-noise pre-amplifier
1. PRKR cards use an external low-noise amplifier
2. Cards based on Airgo chips (such as the Belkin Pre-N) also use external low-noise pre-amplifier which results in gains similar for the PRKR card.
3. Cheap cards use fully integrated single-chip CMOS transceivers, with internal (i.e. CMOS) low-noise preamplifiers, which result in a loss of about 2.0 dB in receiver sensitivity when compared to an external low-noise preamp (as used by the PRKR cards).  For about $0.50 more, the cheap cards could improve their sensitivity by another 2.0 dB.  Their manufacturers, however, are concerned about eroding prices and rapid technology obsolescence, that they are usually do not invest in improvements.
2. PRKR cards transmit more (1.6 to 4.4 times) raw power:
1. PRKR cards transmit 132 mW (page 4 of their FCC filing)
2. Cards based on Airgo chips (such as the Belkin Pre-N) transmit only 50 mW (as confirmed by Airgo).  Therefore, the PRKR card has a net gain of 4.2 dB over the Belkin owing only to raw transmitted power which has nothing to do with D2D technology.
3. Cheap cards transmit 30 to 80 mW. This is a gain for PRKR of 2.2 dB over a 80 mW card, and a gain of 6.4 dB over a 30 mW card.
3. PRKR cards use high gain antennas:
1. PRKR cards use a Skycross antenna having a gain of 2.15 dB (http://www.skycross.com/wirelessdataantennas.asp).
2. Cards based on Airgo chips (such as the Belkin Pre-N) use a patch antenna (to reduce costs) with a gain of about -0.4 dB.  Therefore, the PRKR card has an antenna net gain over the Pre-N card of 2.1dB+0.4dB=2.5 dB, which has nothing to do with D2D technology.
3. Cheap cards use even cheaper types of antennas (such as printed antennas) which typically have gains ranging from -1 to 0 dB.  This is a gain for the PRKR card of 2.1 dB to 3.1 dB over the cheap cards.
4. PRKR cards use TWO antennas connected to TWO receivers:
1. PRKR cards use two antennas (true diversity) which results in an average gain of 3 dB (it's statistical - sometimes less, sometimes more). Also the PRKR router appears to sends all traffic over each antenna - in sequence. This already results in a statistical gain of 3 dB (i.e. it is another form of transmit diversity), but at a very significant bit-rate reduction. Note that the receiver and transceiver diversity don't sum, since one is either transmitting or receiving but not both. In any case, these techniques result in an average gain about 3 dB
2. Cards based on Airgo chips (such as the Belkin Pre-N) also use diversity which results in similar gains to the PRKR card. 
3. Cheap 802.11 cards do not use diversity (to save on duplicate components).  Therefore the PRKR card has a gain of 3 dB over the cheap cards.

Summing all of the gains, we would expect that the PRKR SignalMax router/card pair to have the following range improvements over:

• Cards based on Airgo chips (e.g., Belkin Pre-N):

0 + 4.2 + 2.5 + 0 = 6.7 dB

• Cheap 802.11 cards: 

maximum of 2.0 + 6.4 + 3.1 + 3.0 = 14.5 dB
minimum of 2.0 + 2.2 + 2.1 + 3.0 =  9.3 dB

Since we in real testing, we and others observe about a 2.7 dB gain in range over the Belkin Pre-N, we can conclude that the SignalMax receiver is about 6.7- 2.7 = 5.0 dB LESS sensitive than the Airgo receiver!