Pn Planning

Samsung Proprietary & Confidential 1

WiBro PN Planning

May. 19. 2006.

SAMSUNG Electronics Co.,Ltd.

Samsung Proprietary & Confidential 2 2004, Samsung Electronics, Proprietary and Confidential

Cell Planning Parameters in WiBro (1/2)

The following six parameters should be allocated in each cell

Preamble PN code indexPN code is used for preamble modulationDelivered through the first downlink symbol (preamble) in every frameNumber of PN code: 114

IDcell IDcell is used for subchannel permutation and subcarrier

randomization Delivered through Preamble PN codeNumber of IDcell: 32

SegmentSegment is used for preamble modulation, subcarrier randomization,

and subchannel renumbering Delivered through Preamble PN codeNumer of segment: 3


Cell Planning Parameters in WiBro (2/2)

The following six parameters should be allocated in each cell

DL_PermBaseDL_PermBase is used for subchannel permutation, subcarrier

randomization, and cluster renumberingDelivered through DL_MAP messageNumber of DL_PermBase: 32

UL_PermBaseUL_Permbase is used for subchannel permutation and ranging code

generationDelivered through UL_MAP messageNumber of UL_PermBase: 70

PRBS_IDPRBS_ID is used for subcarrier randomization and subchannel

renumberingDelivered thorugh DL_MAP messageNumber of PRBS_ID : 3


Cell Specific Functions in WiBro (1/2)

Preamble Modulation Initial cell search, acquisition, and synchronization

Related Parameters: Preamble PN code, IDcell, segment

Subcarrier Randomization (Scrambling)Randomization of constellation of modulation

Related Parameters: IDcell, DL_PermBase, segment, PRBS_ID

Ranging code generation Generates cell specific uplink ranging code set

Related Parameters: UL_PermBase


Cell Specific Functions in WiBro (2/2)

Subchannel PermutationSubcarrier mapping to subchannelDownlink Permutation

Related Parameters: IDcell, DL_PermBase

Uplink PermutationRelated Parameter: UL_PermBase

Cluster Renumbering / Subchannel RenumberingEnhances diversity of PUSC subchannel permutation

Related Parameters: DL_PermBase, PRBS_ID


Preamble Modulation (1/2)

Outline The first symbol of the downlink is the preamblePreamble subcarriers are modulated using boosted BPSK by a specific preamble PN code in each cellUsed for initial cell search, acquisition, and synchronization

Preamble PN codeNumber of PN codes: 114A preamble PN code contains information of IDcell and segment number

…


Preamble Modulation (2/2)

Preamble is associated with IDcell & segmentPreamble PN index has the following relationship with IDcell & segment

For PN index 0 ~ 95– PN index = segment ⅹ 32 + IDcell

For PN index 96 ~ 113– PN index = 96 + IDcell – segment = IDcell modulo 3

There are three carrier sets for preamblePreamble occupies one of the three carrier setSegment determines carrier set in which preamble is transmitted

Importance of Preamble PN codeIn case of PN code duplication

If adjacent cells use the same preamble PN code, the initial cell search and acquisition can be impossible

Association with IDcell and segment numberOnce a mobile detects preamble, it can extract IDcell and segment of the

cell from the preamble Preamble PN code allocation should consider IDcell and segment


Subcarrier Randomization (Scrambling) (1/2)

OutlinePurpose of Subcarrier Randomization

The constellation of modulation is randomized by a cell specific PRBS (pseudo random binary sequence)

Polynomial for PRBS generator is X11 + X9 + 1 Initial vector of PRBS is determined by

Downlink: IDcell (or DL_PermBase) and segment number (or PRBS_ID)

Uplink: IDcell and Frame number

PRBS Generator PRBS Initialization Vector

b0…b4: IDcell in the 1st DL zone DL_PermBase in other DL zones IDcell in UL

b5…b6: segment + 1 in the first DL zone PRBS_ID in other DL zones 0b11 (all ones) in UL

b7…b10: 0b1111 (all ones) in DL four LSB of Frame Number in UL


Subcarrier Randomization (Scrambling) (2/2)

Number of PRBSDownlink: 96 (32 IDcell or DL_PermBase ⅹ 3 segment or PRBS_ID)Uplink: depends on the Frame number operation scheme

512 PRBS possibleNumber of uplink PRBS may reduce to 32 if frame number is

synchronized among cells

Importance of subcarrier randomization In case of PRBS duplication

If adjacent cells use the same PRBS, their randomization pattern becomes identical

Thus, pilot estimation can be seriously damaged


Ranging code generation (1/2)

OutlineRanging

Mobile performs ranging for initial access, handover, and BW requestContention based ranging with cell specific ranging codes

Ranging codeEach cell generates 256 ranging codes according to PRBS generatorPolynomial for PRBS generator is X15 + X7 + X4 + X1 + 1 Initial vector of PRBS is determined by

– 001011 + UL_PermBase

PRBS Generator


Ranging code generation (2/2)

Number of PRBS70 (UL_PermBase)

Importance of ranging code generation In case of PRBS duplication

If adjacent cells use the same PRBS, their ranging codes set becomes identical

When a mobile tries ranging to a cell, another cell may hear the ranging code and respond

System malfunction may occur


Subchannel Permutation (1/2)

OutlineEach subchannel is composed of 48 data subcarriers

Subcarriers are randomly selected from the pool of subcarriers in order to minimize subchannel collision between cells

Subchannel permutation determines the rule of subcarrier mapping to subchannel

Subchannel permutation in Downlink FUSC

DL_PermBase (or IDcell) determines subchannel permutation rule Number of DL_PermBase (or IDcell): 32

However, effective number of subcarrier permutation depends on FFT size

Effective permutation of FUSC is 16 in 1024 FFT (since Nsubchannels = 16)

subcarrier(k,s): subcarrier index of subcarrier k in subchannel snk ps : defined in IEEE 802.16e standardNsubchannels : depends on FFT size


Subchannel Permutation (2/2)

Subchannel permutation in Uplink PUSC

UL_PermBase determines subchannel permutation ruleNumber of UL_PermBase: 70

However, effective number of subcarrier permutation depends on FFT size

Effective permutation of PUSC is 35 in 1024 FFT (since Nsubchannels = 35)

Importance of subchannel permutationIn case of Permutation duplication

If adjacent cells use the same subchannel permutation, packet error may increase due to the subchannel collision between cells

Tile(s, n) : tile index of subcarrier n in subchannel sPt : defined in IEEE 802.16e standardNsubchannels: depends on FFT size


Design Principle (1/2)

Parameters to be designedPreamble PN code indexIDcellSegmentDL_PermBaseUL_PermBasePRBS_ID

Design Principle Reuse distance should be maximized for every parameterPreamble PN code, IDcell, and segment number should be considered concurrently

Preamble PN code contains IDcell and segment IDcell and segment has significance on WiBro system

DL_PermBase and PRBS_ID is similar with IDcell and segmentUL_PermBase is independent of other parameters


Design Principle (2/2)

IssuesIDcell

IDcell is not RAS parameter, but sector parameterSectors of the same RAS must have different IDcell

SegmentSectors of the same RAS is recommended to have different segment

DL_PermBaseConsideration of effective number of DL_PermBase is recommended

UL_PermBaseUL_PermBase is recommended to have difference value from IDcell It reduces damage of IDcell duplication or UL_PermBase duplication

between adjacent sectors

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