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Spreading Code Allocation Code Allocation Algorithm chooses the correct spreading code depending on the TFC typeC 2 (0)=(1,1,1,1) C1 (0)=(1,1) C 2 (1)=(1,1,-1,-1) C 0 (0)=(1) C 2 (2)=(1,-1,1,-1) C1 (1)=(1,-1) C 2 (3)=(1,-1,-1,1) C 3 (0)=(…) C 3 (1)=(…) C 3 (2)=(…) C 3 (3)=(…) C 3 (4)=(…) C 3 (5)=(…) C 3 (6)=(…) C 3 (7)=(…)
Code Order 0 (SF 1)
Code Order 1 (SF 2)
Code Order 2 (SF 4)
Code Order 3 (SF 8)
The codes are layered from 0 to 11 according to the Spreading Factor (SF) Cm(n): The code order, m, and the code number, n, designates each and every code in the layered orthogonal code sequences In DL code order 2 to 8 (SF 4 to 512) are available In UL code order 2 to 7 (SF 4 to 256) are available7© NOKIA 30/11/2003 RANPAR Version 1.1
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Spreading Code AllocationExample Ordinary downlink speech channel, requires 30 ksps physical capacity (AMR 12.2– 4.75 kbit/s). The code order is 8, which means there are 128 chips to illust
rate one symbol (2n, n=7). If the requested channel is 120kbit/s (including DPCCH and channel coding) data channel, then the type of code is 6. Spreading code cycle depends on the symbol rate.
Code Order 9 8 7 6 5 4 3 2
Channel symbolrate (ksps) 15 30 60 120 240 480 960 1920
Channel bitrate (kbps) 7.5 15 30 60 120 240 480 960
SF 512 256 128 64 32 16 8 4
DPDCH bits/frame 40 160 340 600 1400 2880 6080 12480
8
© NOKIA
30/11/2003 RANPAR Version 1.1
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Spreading Code Allocation A code is always allocated from the optimum location in the code tree. It makes the allocated codes and the codes in the branches below and above the allocated code unavailable Code tree will fragment quickly if releases is not re-arranged Re-arrangements in the code tree is done by reallocating the codes in better locations
The above code tree has 4 codes of equal order. The best locations are in the same branch and very close to one another. The badly located codes are released and optimally reallocated allowing the use of upper layer codes9© NOKIA 30/11/2003 RANPAR Version 1.1
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CodeTreeOptimisation
The parameter indicates if rearrangement can be applied to a specific cell.range: 0 (optimisationnot used), 1 (optimisationused)default:1;
CodeTreeOptTimer
The parameter defines the timer value that triggers code treeoptimisation, if it is not triggered otherwise.range:1 ... 65535 s, step 1 s
default:3600 s; 1 ... 65535 s, step 1 s