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From: Youssef
Abdelilah [mailto:youssefa@earthlink.net] Hello Itzik, Thank you again for you feedback. I would like to ask some more questions
just so I can get some understanding of your answers. Please find some of the question right
below your kind answers to the original Questions. Please read the text below and you will
find the questions right after the arrows and below your answers. Thank you again in advance for your
feedback. Best regards, Youssef From: Itzik Kitroser
[mailto:itzikk@runcom.co.il] Hello Youssef, Please find some answers from Itzik. From: Youssef
Abdelilah [mailto:youssefa@earthlink.net] Thank you Any input on the other questions or
anyone from 802.16 or 802.16e group. Thank you in advance 2.The
largest and smallest time for RTG (Receiver - Transmitter Gap) between two
consecutive frames. This is really depends on you specific implementation
and system parameters (such as frame size and number of symbols within a
frame). Probably you will not require more than one OFDM/OFDMA symbol as an
upper bound. For example, if you look at the profile section,
you will find requirements for subscriber side RTG (SSRTG) will not
to exceed 50 us for TDD and 100 us for H-FDD. <<<< (question): If all 42 symbols can be used for DL in TDD, without TTG (RX-TX gap)
the frame length will be 4.8 msec (42 * 115.2 usec) instead of 5 msec. Even in
that case, the gap between frame will be RTG only as described above? If
so, wouldn’t it cause the network sync problem? Or, even though all the
42 symbols are used, there still will be TTG portion in the frame? 3. Each
SS (Subscriber Station) or MS (Mobile Station) have to process only specific DL
bursts (i.e., not all DL bursts)? This depends on your operational mode. Basically the SS/MS
should decode all DL bursts which is capable, this means less and equal to its
modulation/coding rate parameters. In addition, in OFDMA, you can provide a
list of CIDs for each DL burst allocation (i.e., DL-MAP IE) such that the
mobile user will be able to decode only the relevant bursts. This can help the
power consumption of the MS. -- If so,
what parameters that PHY can expect from the above layer and also, what are the
range of the parameters? Please look at the above answer. 4. In
each DL_MAP_IE of WMAN-OFDMA, information of the size and the location of each
logical DL burst are provided as following 4 parameters, 'OFDMA_Symbol Offset',
'subchannel offset', 'No. OFDMA symbols', and 'No. subchannels'. Though it's
not clear, we assume that 'No. subchannels' indicates the number of subchannels
corresponding to one symbol (i.e., not whole number of subchannels in a burst).
What is the maximum value of those parameters for the system we described
above? The no. subchannels parameter indicated the number of
subchannels for a specific allocation. The combination of these parameters
basically provide a rectangular allocation within the DL frame for a specific
DL-Burst. From the BS side, there is no limit, so theoretically, the BS
can allocate one rectangle with specific profile. In practice this is a
combination of requirements such as how many profiles to allocate (because we
want to maximize the system throughput), power boosting, etc. The
problem that I see is that if we take the maximum as the largest number from
the bits, one DL burst can take whole frame. Thus, I am wondering if there is
any rule to regulate the burst size beyond those parameter expression. This is exactly the task of the scheduler and what makes
one's system more efficient than other's :-) <<<<<<(QUESTION) Basically, in WMAN-OFDMA DL, there are two types of
mendatory subchannel allocations, PUSC & FUSC. In DL PUSC, one slot is defined as ‘2 symbols
& 1 subchannel’ and in DL FUSC, it is defined as ‘1 symbol
& 1 subchannel’. Thus, if ‘No. subchannels’ is indeed
defined as “The no. subchannels parameter indicated the number of
subchannels for a specific allocation” not as per symbol, then I have another question about it. In WMAN-OFDMA
DL_MAP_IE from 802.16-2004/Cor1/D5, the number of subchannels is defined in 6
bits while the number of symbols is defined in 7 bits. The point that I am
confused at with his definition is that the maximum size of burst is limited
with the number of subchannels in FUSC (which is 64 subchannels). In FUSC,
there will be 16 subchannels per one OFDM symbol, thus it means, the max size
of DL burst will take only 4 symbols in total (assuming whole subchannels per
symbol are used for only one user)? To rephrase my question, can I ask
the definition of ‘No. subchannels’ again just to make sure if it
indicate the ‘number of total subchannels within one burst allocation ‘
or it is the ‘number of subchannels per OFDM symbol’? If it is the
‘number of subchannels per symbol’, then the burst size can be
derived (in # of slots) as (No.subchannels X No. OFDM symbols) in FUSC
and (No. Subchannels X (No. OFDM symbols/2)) in PUSC; or if it the
‘number of subchannels in the DL burst’, the the burst size (in #
of slots) would be N0.subchannels in FUSC with the constraint of N0. OFDM
symbols = No. subchannels and in PUSC with the constraint of No. OFDM symbols =
No. Subchannels/2. 5.
(This question is somewhat related to the question 3 & 4) Is it possible
that whole DL subframe can be assigned to a single user Yes ? If so, the whole information for the
single user can be put into one single burst or have to be in multi-bursts This depends on specific requirements/possibilities of the
scheduler and characteristics of the traffic for the user. Regards, Youssef From: Zion Hadad
[mailto:zionh@RUNCOM.CO.IL] All the 42 in case of Broadcasting only
(as far as the Phy) From: Youssef
Abdelilah [mailto:youssefa@EARTHLINK.NET] Dear all, Target
System: WMAN-OFDMA with 10 MHz bandwidth, frame period of 5 ms, TDD mode, 1024
fixed FFT points, and 42 symbols in a frame. Questions: 1. The
sizes for DL subframe and UL subframe in one TDD frame are supposed to be given
to PHY layer from the above layer (it is written in the spec); what is the
worst case for the DL subframe size. In other words, among 42 symbols in a
frame what would be the largest number of symbols that can be assigned to DL
subframe. 2. The
largest and smallest time for RTG (Receiver - Transmitter Gap) between two
consecutive frames. 3. Each
SS (Subscriber Station) or MS (Mobile Station) have to process only specific DL
bursts (i.e, not all DL bursts)? -- If so,
what parameters that PHY can expect from the above layer and also, what are the
range of the parameters? 4. In
each DL_MAP_IE of WMAN-OFDMA, information of the size and the location of each
logical DL burst are provided as following 4 parameters, 'OFDMA_Symbol Offset',
'subchannel offset', 'No. OFDMA symbols', and 'No. subchannels'. Though it's
not clear, we assume that 'No. subchannels' indicates the number of subchannels
corresponding to one symbol (i.e., not whole number of subchannels in a burst).
What is the maximum value of those parameters for the system we described
above? The
problem that I see is that if we take the maximum as the largest number from
the bits, one DL burst can take whole frame. Thus, I am wondering if there is
any rule to regulate the burst size beyond those parameter expression. 5. (This
question is somewhat related to the question 3 & 4) Is it possible that
whole DL subframe can be assigned to a single user? If so, the whole
information for the single user can be put into one single burst or have to be
in multi-bursts? Thank you, Youssef Abdelilah |