WCDMA3G UpLkAllocOVSF

Pin Outputs

Notes/Equations

1. This model is used to generate single or multiple OVSF sequences as spreading codes for uplink transmission. The OVSF sequence family has a tree-structure; the length of each OVSF sequence varies for multi-rate transmission. The maximal length of these spreading sequence output tokens are produced for each output. The output sequence at the first signal must be a spreading sequence for DPCCH.
2. Layered OVSFs are generated from the recursions:

   C 0 (0) = 1
   
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   .
   .
   

   All OVSF sequences of the same layer are orthogonal to each other. From each OVSF sequence C_n (m), two additional OVSF sequences ( C_n+1 (2m) and C_n+1 (2m+1)) are generated. These two sequences are not orthogonal to the sequence from which they are generated-the mother sequence. However, the other 2ⁿ − 2 sequences are orthogonal to this mother sequence. So the sequences generated from a mother sequence cannot be used as spreading codes if this mother sequence is applied.
   In uplink transmission, the spreading codes allocation for DPCCH and DPDCHs applies.

   • The DPCCH is always spread by code C₈ (0) = C_ch,256,0
   • When only one DPDCH is to be transmitted, DPDCH₁ is spread by code C_ch,SF,k where SF is the spreading factor of DPDCH₁ and k = SF_d,1/4
   • When more than one DPDCH is to be transmitted, all DPDCHs have spreading factors equal to 4. DPDCH_n is spread by the code C_ch,n = C_ch,4,k, where k = 1 if , k = 3 if , k = 2 if .

   Since the cycle of a spreading code is one symbol in length as defined in [1], the cycle of a spreading code of the same chip rate is different according to the symbol rate. And, the number of spreading codes available differs according to the symbol rate. The relationship between symbol rate, spreading code cycle and the number of spreading codes is presented in the following table.
   

   Spreading Code Rates for 3.84 Mcps Chip Rate

   Condition	Symbol Rate
   	15	30	60	120	240	480	960
   Spreading code type	8	7	6	5	4	3	2
   Spreading code length	256	128	64	32	16	8	4
   Number of spreading codes	256	128	64	32	16	8	4

References

1. 3GPP Technical Specification TS 25.213 V3.0.0 "Spreading and modulation (FDD)," October 1999.
2. Koichi Okawa and Fumiyuki Adachi, "Orthogonal Multi-Spreading Factor Forward Link for Coherent DS-CDMA Mobile Radio," in Proc. 47th IEEE VTC'97, Phoenix, May 1997
3. Liu Tie and Xiang Haige, "A Improved Multi-rate Scheme for DS-CDMA System" (in Chinese), in Journal of China Institute of Communications, Vol. 19, pp.24-28, March 1998