RE: stds-802-16-tg4: Need for RF input to TG4 PHY specs
Demos and others,
Thanks for the dialog. Please see my comments added below (*DA:)
Drayt
-----Original Message-----
From: Kostas, Demos [mailto:dkostas@adaptivebroadband.com]
Sent: Thursday, May 03, 2001 12:23 PM
To: 'Drayt Avera'; Stds-802-16-Tg4@Ieee. Org
Subject: RE: stds-802-16-tg4: Need for RF input to TG4 PHY specs
Thanks for taking the initiative on the interference issue so that we can
get clarification and then we can move to Specification. From what you
wrote a number of items are not clear. To assure that all have an
understanding and that the understanding is common I will raise some
questions on your list of interference items, and your replies hopefully
will assist in getting a common understanding on what we are after.
1) Need specs for the expected interference conditions or protection
requirements. In 802.11a minimal adjacent channel specs are specified, and
I would think we would need greater interference protection. Some possible
specs to add:
minimum adjacent channel protection (about 40dB?) vs. channel bandwidth
selected alternate adjacent channel protection
TBD MHz blocking (jamming protection) max expected receiver level (in-band
and out of band)
Q1 your phrase "expected interference" is not clear of which one you mean:
-Interference Requirements from other Wireless HUMAN based systems
- Interference Requirements form non-Wireless HUMAN based FWA systems e.g.,
existing PMP and PP FWA systems
- Interference Requirements from WLANs/RLANs e.g., 802.11a/Hiperlan/2,
802.15,...
- Interference Requirements form Terrestrial Radar Systems
- Interference Requirements from other; e.g. other FCC Part 15 devices...
*DA: I was referring to all of these in that we need to define what
acceptable levels of interference we want to operate in. This could be
organized in terms of signal level or link availibility. There may also be
some cases where 802.16.4 systems will not operate due to excessive cost.
Q2 Is your phrase "minimum adjacent channel protection" from interference
to be interpreted as the FCC Part 15 adjacent channel interference
requirements as a minimum or are you proposing more stringent adjacent
channel interference requirements?
*DA: The FCC limits are requirements for transmitter radiation and do not
specify the quality of the receiver. I think that for an outdoor device
deployed in a cellular fashion, the adjacent channel protection should be
increased. Most systems use a SAW filter which can easily acheive 40dB,
however, I do not know if this is adequate.
Q3 Jamming protection from what device to what device?
*DA: I was thinking about ISM band devices (pt-pt or pt-multipt), but there
could be other sources such as military radar, etc.
____________________________________________________________________________
________-
2) Transmit or receive linearity requirements should be specified. The
receiver linearity will impact the system design for near/far issues. On
the transmit side, maybe an EVM measurement under standard conditions
(similar to 802.11a) make more sense.
Q1 What is an EVM measurement?
*DA: Error Vector Magnitude- It is a measure of constellation accuracy. I'm
just not sure how to measure the EVM on an OFDM signal with many carriers.
Q2 Do you mean Transmit and receive linearity requirements? Why "or" if we
specifying an interoperability Standard?
*DA: I agree that "and" is better.
__________________________________________________________________________
3) Need to determine a sensitivity requirement. Depending on the
interference and linearity requirements it should be around 5-6dB. What SNR
is required for the various modulation methods? I think a table of minimum
sensitivity vs. channel bandwidth would be most appropriate.
Q1 What is your definition of sensitivity? Is it the minimum SNR that
assures some performance or is it the sensitivity that permits accurate
detection that some other device/system is using the channel and thus the
channel should not be assigned as it will impair the incumbent Wireless
HUMAN device/ or another non-Wireless HUMAN device that is primary in that
band?
*DA: My definition is the minimum signal level to receive a defined bit
error rate under some standard test condition.
____________________________________________________________________________
______________________
4) Adjustment range for power control and any Rx AGC including response
characteristics and resolution. There were some previous responses showing
around 30-40dB, and it would be good to discuss the calculations that anyone
has done. 802.11a has requirements for the Tx flatness of +/-2dB.
Q1 Is this power control range vary with Channel BW of the Wireless HUMAN
device? i.e. is it to be the same for 20 MHz and 10MHz systems
*DA: I would think it would be the same unless required to be different due
to the regulatory or dynamic range requirements. Do you think it needs to
be the same or different?
Q2 How relevant is the power control of 802.11a to the FWA Wireless HUMAN
device as 802.11a is a LAN function and Wireless HUMAN device is a MAN
function device?
*DA: I think the near/far and fading conditions create the need for the link
to adjust dynamically. Some of the adjustment range could be made static
(set at installation) if it helps make things simpler or cheaper.
_______________________________________________________________________-
5) Tx flatness: are the 802.11a requirements good enough?
Q1 What is Tx flatness definition? and how such requirement affected by MAN
vs. LAN function?
*DA: The current 802.11a spec has spectral tone flatness requirements of
+/-2dB to +2/-4db, depending on the tone. Other BWA specs I have seen had
stringent specs for flatness across the channel. I see no reason to make
the requirement any tighter than the 802.11a spec.
______________________________________________________-
12) Do you see most systems being 1 or 2 box solutions? If 2 boxes, should
add some recommended practice for standardization.
Q1 Please define 1 or 2 box solutions.
*DA: RF and modem combined in 1 box vs outdoor RF frontend and indoor modem.
_______________________________________________________
In general here is an issue related to the FCC RO itself. Ideally our
Specification should encourage interference reduction techniques such as
Efficient modulation/coding maximizing bits/Hz/dBm
Directional antennas (e.g. allowing 23 dBi antennas on the UNII SU reduces
SU-to-SU interference).
*DA: I tend to think of antennas as something that is vendor selected
depending on the final application. Are you suggesting an antenna
requirement?
Regards
Demos
Dr. Demosthenes J. Kostas
Director, Industry Standards
Adaptive Broadband Corporation
3314 Dartmouth Ave
Dallas, TX 75205 USA
tel: 214 520 8411
fax: 214 520 9802
-----Original Message-----
From: Drayt Avera [mailto:davera@rf-solutions.com]
Sent: Thursday, May 03, 2001 7:17 AM
To: Stds-802-16-Tg4@Ieee. Org
Subject: stds-802-16-tg4: Need for RF input to TG4 PHY specs
TG4 Team,
Here are some items which need to be addressed in the TG4 spec. Let's get a
dialog started and try to solidify some numbers prior to the meeting in a
few weeks.
1) Need specs for the expected interference conditions or protection
requirements. In 802.11a minimal adjacent channel specs are specified, and
I would think we would need greater interference protection. Some possible
specs to add:
minimum adjacent channel protection (about 40dB?) vs channel bandwidth
selected
alternate adjacent channel protection
TBD MHz blocking (jamming protection)
max expected receiver level (in-band and out of band)
2) Transmit or receive linearity requirements should be specified. The
receiver linearity will impact the system design for near/far issues. On
the transmit side, maybe an EVM measurement under standard conditions
(similar to 802.11a) make more sense.
3) Need to determine a sensitivity requirement. Depending on the
interference and linearity requirements it should be around 5-6dB. What SNR
is required for the various modulation methods? I think a table of minimum
sensitivity vs channel bandwidth would be most appropriate.
4) Adjustment range for power control and any Rx AGC including response
characteristics and resolution. There were some previous responses showing
around 30-40dB, and it would be good to discuss the calculations that anyone
has done. 802.11a has requirements for the Tx flatness of +/-2dB.
5) Tx flatness: are the 802.11a requirements good enough?
6) Should we have a Clear Channel Assessment (CCA) type function and a
threshold to transmit?
7) TDD and FDD coexistence strategy. Are most of you are headed towards
TDD?
8) Phase noise requirement: Is this buried in the EVM measurement? It
would be simpler to specify it directly.
9) Are there any group delay requirements (absolute or variation)?
10) Some misc items need to be addressed:
temp range: same as 802.11a but add Type 4= -40 to +85C
Tx and Rx antenna port impedance=50ohms
11) What hooks are needed for frequency diversity/MIMO, etc... TJ, are you
including these in the future enhancements section?
12) Do you see most systems being 1 or 2 box solutions? If 2 boxes, should
add some recommended practice for standardization.
Let's get a dialog going and I'll try to provide a coordinated input to the
PHY spec.
Regards,
Drayt