pn planning
TRANSCRIPT
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
Samsung Proprietary & Confidential 3 2004, Samsung Electronics, Proprietary and Confidential
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
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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
Samsung Proprietary & Confidential 5 2004, Samsung Electronics, Proprietary and Confidential
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
Samsung Proprietary & Confidential 6 2004, Samsung Electronics, Proprietary and Confidential
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
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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
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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
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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
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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
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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
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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
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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
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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
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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