doc.: ieee 802.22-07-0300r1 submission june 2007 chang-joo kim, etrislide 1 [proposed burst...
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June 2007
Chang-Joo Kim, ETRI
Slide 1
doc.: IEEE 802.22-07-0300r1
Submission
[Proposed Burst Allocation MethodRelating to DS/US-MAP]
IEEE P802.22 Wireless RANs Date: 2007-07-05
Authors:
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Name Company Address Phone email Chang-Joo Kim ETRI Korea +82-42-860-1230 cjkim@etri.re.kr
Myung-Sun Song ETRI Korea +82-42-860-5046 mssong@etri.re.kr
Gwang-Zeen Ko ETRI Korea +82-42-860-4862 gogogo@etri.re.kr
Sung-Hyun Hwang ETRI Korea +82-42-860-1133 shwang@etri.re.kr
Jung-Sun Um ETRI Korea +82-42-860-4844 korses@etri.re.kr
June 2007
Chang-Joo Kim, ETRI
Slide 2
doc.: IEEE 802.22-07-0300r1
Submission
Abstract
In this presentation, we propose the burst allocation (burst mapping) method for WRAN system, which is related to DS and US MAP design. In order to develop the best burst allocation method, several features should be considered as follows,
•Required bit size of DS/US-MAP IE
•Time diversity gain
•Decoding latency till delivering to MAC
•A bundle of 7 OFDMA symbols for US burst
•Contention-based burst in US (Ranging/BW Request/UCS notification, CBP)
June 2007
Chang-Joo Kim, ETRI
Slide 3
doc.: IEEE 802.22-07-0300r1
Submission
Required Bit Size of DS/US-MAP IE
• The linear allocation only needs to define the length of the burst, on the other hand, the rectangular allocation needs to define the start point and end point of the burst.
• Though, in case of linear allocation, a CPE (or a BS) should trace the history of the length for foregoing CPEs, it may not a big burden to each CPE.
• In the point of the required bit size, a linear allocation is more fascinating than a rectangular allocation.
June 2007
Chang-Joo Kim, ETRI
Slide 4
doc.: IEEE 802.22-07-0300r1
Submission
Time Diversity Gain
• If the terminal has a high mobility, such as 802.16e, we have to consider the diversity effect in the time direction.
• In that case, it is desirable to allocate the burst in the time direction first (i.e., linear-horizontal scheme).
• However, in the case of fixed WRAN system, it seems that there is no rationale to follow the allocation method same as 802.16e.
• For WRAN system, it is possible to allocate the burst in the frequency direction first (i.e., linear-vertical scheme) without any deterioration.
June 2007
Chang-Joo Kim, ETRI
Slide 5
doc.: IEEE 802.22-07-0300r1
Submission
Decoding Latency till Delivering to MAC
• To minimize the decoding latency as much as possible– Allocate the burst using the linear-vertical scheme
– Or allocate the burst using the rectangular scheme so that it occupy a reasonable time and frequency area
• When the burst is allocated using the linear-horizontal scheme in the time direction first using only length, the decoding latency could be drastically increased, particularly in the downstream in which more OFDM symbols could be allocated.
June 2007
Chang-Joo Kim, ETRI
Slide 6
doc.: IEEE 802.22-07-0300r1
Submission
Worse Case of Decoding Latency
• For Burst 2 of DS sub-frame, though the length of burst is small, the decoding latency is large.
US sub-frame(smallest US burst portion on agiven subchannel = 7 symbols)
Fra
me P
ream
ble
FCH
DCD/U
CD, DS/
US-
MAP
DCD/U
CD, DS/
US-
MAP
TTG RTG
Burst 6AM
C s
ubch
annel
s
Ranging/ BWrequest/ UCSnotification
Burst 17
Burst 18
Burst 19
AM
Csu
bch
annel
s
DS sub-frame(smallest=7 symbols)
Burst 7
Burst 8
Div
ersi
ty s
ubch
annel
s
tim
e bu
ffer
tim
e bu
ffer
Coe
xist
ence
win
dow
Burst 1
Burst 7
Div
ersi
ty s
ubch
annel
s26 to 31 symbols for cyclic prefixes from 1/ 4 to 1/ 32
60 s
ubch
anne
ls
Burst 1
Burst 3
Burst 2
June 2007
Chang-Joo Kim, ETRI
Slide 7
doc.: IEEE 802.22-07-0300r1
Submission
A Bundle of 7 OFDMA Symbols for US Burst
• In upstream, the number of OFDMA symbols allocated to a CPE needs to be at least 7 to access sufficient pilot carriers for best channel estimation.
• Therefore, each row of the subchannels within the burst should include at least 7 OFDMA symbols.
• In case that US sub-frame contains 7 to 13 OFDMA symbols, all OFDMA symbols can be included to only one burst.
• In case that US sub-frame contains more than 14 OFDMA symbols, the OFDMA symbols can be divided into several burst.
June 2007
Chang-Joo Kim, ETRI
Slide 8
doc.: IEEE 802.22-07-0300r1
Submission
Hybrid Burst Mapping in Upstream
• To reduce the decoding latency, the burst should be allocated by the bundle of 7 OFDMA symbols.
• On the other hand, if a CPE needs to transmit at maximum EIRP, the coverage of CPE will be larger if it uses more OFDMA symbols in time and less subchannels in frequency so that the power per subchannel can be maximized.
• So we propose the hybrid burst mapping as follows,– For latency-sensitive burst, the burst will be allocated in terms of at least 7
OFDMA symbols width
– For power-sensitive burst, the burst will be allocated in full width of US sub-frame.
• In hybrid burst mapping, the type of Diversity subchannel can be identified by using 2 bits in US-MAP IE.
June 2007
Chang-Joo Kim, ETRI
Slide 9
doc.: IEEE 802.22-07-0300r1
Submission
Segmentation for Latency-Sensitive Burst
• An US sub-frame can be divided into several segment in terms of at least 7 OFDMA symbols width.
• Each burst can be defined within the segment.
• If the total OFDMA symbols within US sub-frame excluding CBP packet are not divided into 7, total_OFDMA_symbols % 7 are included to the last segment.
– If the total OFDMA symbols within US sub-frame excluding CBP packet are X, then X = 7*Y+Z=7*(Y-1)+(7+Z), here, Z<7. Thus, there are (Y-1) segment with 7 OFDMA symbols width and 1 segment with (7+Z) OFDMA symbols width in the time direction. The segments are sequentially located from left to right in the time direction.
– For example, if the total number of OFDMA symbols of US sub-frame excluding CBP packet (X) are 16, there are 1 segment with 7 OFDMA symbols width and 1 segment with 9 OFDMA symbols width in the time direction.
June 2007
Chang-Joo Kim, ETRI
Slide 10
doc.: IEEE 802.22-07-0300r1
Submission
Contention-Based Burst in US
• A rectangular burst would be allocated for the function of Ranging, BW Request, and UCS notification
• At the end of US sub-frame, the CBP packet would be transmitted for self-coexistence with rectangular shape
June 2007
Chang-Joo Kim, ETRI
Slide 11
doc.: IEEE 802.22-07-0300r1
Submission
Proposed Partition of Subchannel Zone
• AMC and Diversity zones are divided in the frequency domain with the rectangular shape.
• After identifying the AMC zone using DS-MAP, the rest excluding the AMC zone is assigned to the Diversity zone.
• The AMC subchannel starts from the next OFDMA symbol of the FCH, DS/US-MAP, and DCD/UCD. – The CPE have to know the range of AMC subchannel from the
DS-MAP. If AMC subchannel start from the following the preamble symbol, the CPE would not know the information on subcarrier de-allocation of Diversity subchanel, at least for the first frame within superframe.
• The rest subchannel(s) in the header field will be allocated to the Diversity subchannel for data transmission.
June 2007
Chang-Joo Kim, ETRI
Slide 12
doc.: IEEE 802.22-07-0300r1
Submission
Partition of Subchannel Zone (Cont’d)Fr
ame
Prea
mbl
e
TTG RTG
AMC subchannelsfor data transmission
Ranging/ BW request/ UCS notification
AMC subchannels for data transmission
DS sub-frame(smallest=7 symbols)
tim
e bu
ffer
tim
e bu
ffer
Coe
xist
ence
win
dow
US sub-frame(smallest US burst portion on a given subchannel = 7 symbols)
26 to 31 symbols for cyclic prefixes from 1/ 4 to 1/ 32
60 s
ubch
anne
ls
1 OFDMA symbol
1 subchannel
Div
ersi
ty s
ubch
anne
ls f
or h
eade
r tr
ansm
issi
on
Diversity subchannels for data transmissionusing full width of US sub-frame
Diversity subchannels for data transmissionusing segment of US sub-frame
Diversity subchannelsfor data transmission
June 2007
Chang-Joo Kim, ETRI
Slide 13
doc.: IEEE 802.22-07-0300r1
Submission
Proposed Burst Structure(In case that US sub-frame contains 7 to 13 OFDMA symbols)
US sub-frame(smallest US burst portion on a given
subchannel = 7 symbols)
Fram
e Pr
eam
ble
FCH
DCD/U
CD, DS/
US-
MAP
Burs
t 1
DCD/U
CD, DS/
US-
MAP
Burs
t 2
TTG RTG
Burst 12
AM
C s
ubch
annel
s
Ranging/ BW request/UCS notification
Burst 11
Burst 12
Burst 13
AM
Csu
bch
annel
s
DS sub-frame(smallest=7 symbols)
Burst 13
Burst 14
Div
ersi
ty s
ubch
annel
s
tim
e bu
ffer
tim
e bu
ffer
Coe
xist
ence
win
dow
Burst 1
Div
ersi
ty s
ubch
annel
s
26 to 31 symbols for cyclic prefixes from 1/ 4 to 1/ 32
60 s
ubch
anne
lsBurs
t 11
Burst 2
Burst 3
1 OFDMA symbol
1 subchannel
Burst 10
June 2007
Chang-Joo Kim, ETRI
Slide 14
doc.: IEEE 802.22-07-0300r1
Submission
Proposed Burst Structure(In case that US sub-frame contains more than 14 OFDMA symbols)
Fram
e Pr
eam
ble
FCH
DCD/U
CD, DS/
US-
MAP
Burs
t 1
DCD/U
CD, DS/
US-
MAP
Burs
t 2
TTG RTG
Burst 6
AM
C s
ubch
annel
s
Ranging/ BW request/ UCS notification
Burst 17
Burst 18
Burst 19
AM
Csu
bch
annel
s
DS sub-frame(smallest=7 symbols)
Burst 7
Burst 8
Div
ersi
ty s
ubch
annel
s
tim
e bu
ffer
tim
e bu
ffer
Coe
xist
ence
win
dow
Burst 1
Div
ersi
ty s
ubch
annel
s
US sub-frame(smallest US burst portion on a given subchannel = 7 symbols)
26 to 31 symbols for cyclic prefixes from 1/ 4 to 1/ 32
60 s
ubch
anne
ls
Burs
t 5
Burst 2
Burst 3
1 OFDMA symbol
1 subchannel
more than 7 OFDMA symbols
Burst 4
Burst 5
Burst 16
June 2007
Chang-Joo Kim, ETRI
Slide 15
doc.: IEEE 802.22-07-0300r1
Submission
Proposed Modification of US-MAP IE
June 2007
Chang-Joo Kim, ETRI
Slide 16
doc.: IEEE 802.22-07-0300r1
Submission
Conclusions
• We propose to use only length (i.e., linear scheme) for DS and US burst allocation.
• For Diversity subchannel, the DS and US burst are allocated by using linear-vertical scheme and linear-horizontal scheme within burst, respectively.
• For AMC subchannel, the DS and US burst are allocated by using linear-vertical scheme within burst.
• We propose the hybrid burst mapping for both latency-sensitive and power-sensitive burst.
• Each upstream burst has to contain at least 7 OFDMA symbols at each row of subchannel.
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