Doc.: IEEE 802.22-07-0300r1 Submission June 2007 Chang-Joo Kim, ETRISlide 1 [Proposed Burst Allocation Method Relating to DS/US-MAP] IEEE P802.22 Wireless.

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 [email protected]

Myung-Sun Song ETRI Korea +82-42-860-5046 [email protected]

Gwang-Zeen Ko ETRI Korea +82-42-860-4862 [email protected]

Sung-Hyun Hwang ETRI Korea +82-42-860-1133 [email protected]

Jung-Sun Um ETRI Korea +82-42-860-4844 [email protected]

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.