This Frequently Asked Questions list reviews the
background of wireless LAN sensitivity and range and then examines
specific claims of the ParkerVision SignalMAX product. The internals
of the SignalMAX and the NetGear routers are compared, and the
internals of the SignalMAX and the Belkin Pre-N cards are compared.
For
the SignalMAX product, the use of multiple receivers connected
to multiple antennas in the router and the use of redundant traffic
paths to the PCMCIA card can easily explain all of the improvement
observed in the tests. These are applicable to any competitor willing
to pay the higher component cost and suffer the reduced bitrate
resulting from these techniques. Moreover, these are unrelated
to D2D technology, as described in ParkerVision’s white papers. The
current SignalMAX products do not clearly demonstrate any inherent
advantage of D2D.
Basic Questions
Q |
|
How does ParkerVision increase the range of SignalMAX? |
A |
|
ParkerVision increases range in three ways:
- They use an external low noise amplifier to increase
the sensitivity of their D2D IC. Thus the shipping ParkerVision
products are not, in fact, “direct to digital” at
all: they use an external, analog low-noise preamp in front
of the the D2D receiver.
- For the WR1500 product, Parker uses multiple receivers
connected to multiple antennas. They use diversity techniques
to maximize the received signal. [5].
Note that another form of diversity (MIMO) is also used
by Belkin on their Pre-N, which gains both range and bitrate,
as compared to the ParkerVision approach which significantly
reduces the bitrate and increases range.
- In addition, the WR1500 product is designed to have redundant
transmit paths (as described in ParkerVision patent #6,647,250).
The redundancy increases product range at the expense of
a significant decrease in data rate.
|
Q |
|
How does D2D technology relate to WLAN range and sensitivity? |
A |
|
ParkerVision seem to be relying on everything but D2D to
improve SignalMax range and sensitivity. There is no evidence
that D2D technology has greater sensitivity than other IC technologies.
ParkerVision has never published the noise floor data for any
of their receivers. The use of an external low-noise preamp,
the use of multiple receivers connected to multiple antennas
in the router and the use of redundant traffic paths to the
PCMCIA card can easily explain all of the improvement observed
in the tests. These are applicable to any competitor willing
to pay the higher component cost and suffer the reduced bitrate
resulting from these techniques.. |
Q |
|
Do ParkerVision WLAN products have 20dB better sensitivity than other products? |
A |
|
No. Other chipsets on the market are significantly better
than the IEEE 802.11 standard (Infineon, Maxim 2820, Atheros).
The Infineon and Maxim chips are 16 and 17dB more sensitive
than the IEEE specification and the Atheros chipset reaches
a 20 dB improvement by doing additional data encoding (which
also reduces the data rate) [2]. |
Q |
|
Is the ParkerVision
sensitivity improvement due to their avoidance of the traditional
superheterodyne architecture? |
A |
|
No. Superheterodyne receivers can be as sensitive as the
ParkerVision D2D architecture. Many companies have moved away
from the superheterodyne architecture because it requires many
filters and is not ideal for digital integration, not because
it lacks sensitivity [7,8].
The Horizons HZ1500 card with ParkerVision D2D technology uses
a low noise amplifier (Infineon BGA622 in the Horizon card)
to improve the sensitivity of the ParkerVision 2000TR IC. The
ParkerVision WR1500 also uses low noise amplifiers in front
of their 2000TR ICs. |
Q |
|
Are Parker WLAN products more highly integrated than other products? |
A |
|
No. The WR1500, implemented with D2D technology, has over
twice as many ICs in its RF path as NetGear’s WLAN
router. |
Q |
|
Are Parker WLAN
products more cost effective to manufacture? |
A |
|
No. The WR1500 has over twice as many ICs in its RF path
as NetGear’s WLAN router. Also, The WR1500 uses separate
digital and RF printed circuit boards whereas the NetGear
has only a single board (about the size of the ParkerVision
RF board) for both. |
Q |
|
Is the ParkerVision
sensitivity improvement due to a better antenna? |
A |
|
Possibly. ParkerVision uses a neat little patch antenna
(see picture on left) that appears to be more sensitive (i.e.
have gain) and which is certainly more expensive than all
three of the printed antennas on the Belkin Pre-N card (see
picture on right). We will investigate this point further.
Again, a better antenna has nothing to do with D2D technology.
The more interesting question, however, is: if ParkerVision
has more sensitive receiver technology then why do they use
a higher sensitivity antenna? Couldn’t they simply
use a printed antenna to save costs? |
Horizon D2D HZ1500 Antenna (blue) Belkin
Pre-N Antennas (printed)
Q |
|
How does the
ParkerVision board design compare to competitors? |
A |
|
Clean design in the PCMCIA card but significantly behind
the state-of-the-art in the router. |
Horizon D2D HZ1500 Card Showing Layout
Belkin Pre-N Card Showing Layout
ParkerVision WR1500 low frequency interface
ParkerVision WR1500 RF board. Two D2D chips are visible on the RF
board
References
[1] Communication Systems, McGraw-Hill,
1975
[2] Atheros extended range white paper http://www.atheros.com/pt/atheros_XR_whitepaper.pdf
[3] Harris Spread Spectrum paper http://www.sss-mag.com/pdf/shortpn.pdf
[4] Introduction to Spread Spectrum
Communications, Prentice-Hall, 1995
[5] The RF Transmission Systems Handbook,
CRC Press, 2002
[6] Atheros white paper on Range http://www.atheros.com/pt/atheros_range_whitepaper.pdf
[7] Maxim 2280 http://www.maxim-ic.com/appnotes.cfm/appnote_number/3179
[8] Smith, Multi-Band, Multi-Mode
Architectures, IEEE MTT-S Workshop, 2003
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