The invention concerns a method of finding the power parts of the code of a CDMA (Code Division Multiplex Access signal that is transmitted. CDMA signals are used particularly in third-generation cellular phone standards, for example in a standard in Specification “3G TS 25.211 V3.3.0 (2000-06) 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical Channels and Mapping of Transport Channels onto Physical Channels (FDD), Release 1999.” Please see Pages 17 and 18 of the above-mentioned standard for the timing relevant to this invention in particular.
Various problems occur in finding and showing the power parts of the different orthogonal codes transmitted at the same time, and they will be described briefly below using FIGS. 1 to 3.
FIG. 1 shows a tree with branches for producing various orthogonal codes in order to give a better understanding of the invention. It shows various code classes, CC, which have different spreading factors SF. The spreading factor SF identifies in how many chips (transmission units) a symbol will be spread. The codes in a certain code class CC are orthogonal to one another, i.e., linearly independent when overlapped. This is also true of codes in different code classes, if the codes in code classes higher or lower on the same branch of the tree are not used. This is explained by the example in FIG. 1.
In the scheme 1 for producing different orthogonal codes shown in FIG. 1, the procedure is that the code of the lower code class is repeated once at each branch point and in one branch again unchanged and in the other branch repeated inverted. This way, 16 orthogonal codes in code class CC4 can be produced with the spreading factor SF=16. The 16 codes in code class CC4 can all be used at the same time. But in many transmissions, it is not necessary to use a spreading factor of SF=16, so codes in lower code classes are used. But codes in a lower code class cannot be used that are in the tree under an active code in a higher code class, since the codes would then not be orthogonal. For example, if code 0011110011000011 in code class CC4 is used, codes 00111100 in code class CC3and 0011 in code class CC2 and code 00 in code class CC1 cannot be used, since they would not be orthogonal to code 0011110011000011. But if the power of all codes in code class CC3is determined, for example, an alias power (apparent power) occurs for the non-active code 00111100 which is produced by the active code 0011110011000011 in code class CC4.
FIG. 2 shows the timing behavior of the different channels. There is a difference between a pilot channel CPICH (Common Pilot Channel) and several transmission channels DPCH (Dedicated Physical Channel). All CPICH and DPCH channels use different orthogonal codes, which do not necessarily have to be from the same code class and thus generally have different spreading factors. The pilot channel CPICH and the dedicated physical channels DPCH are broken down into different time slots, Slot 0, Slot 1, . . . , Slot 14.
As can be seen in FIG. 2, the slots of each dedicated physical channel DPCH are shifted in relation to the pilot channel CPICH in steps of 256 chips, whereby the maximum timing offset is one frame.
The power within one channel is changed by the “closed loop power control” at the beginning of a pilot sequence, which is cross-hatched in FIG. 3. Depending on the slot format, the pilot sequences are of different lengths (between 1 and 8 symbols, in some so-called “compressed modes” even 16 symbols). The length of the pilot sequence also changes depending on the spreading factor SF. Thus, the power in the individual dedicated physical channels DPCH is changed at different times, even if the timing offset of the respective dedicated physical channels DPCH is zero in relation to the pilot channel CPICH. The times when the power in the dedicated physical channels DPCH changes thus depends, on one hand, on the length of the pilot sequence used in that dedicated physical channel DPCH and, on the other, the timing offset of that dedicated physical channel in relation to the pilot channel CPICH.
A certain CPICH slot is selected to find and show the power parts of a certain code in a certain code class CC (a so-called CDP diagram). The power of the individual dedicated physical channels DPCH can change anywhere in the slot. The power can also change at several places within the slot if several active codes in a higher code class are mapped in an inactive code in a certain code class. For example, if the codes in code class CC3in FIG. 1 are studied, code 01011010 in code class CC3is not active, but codes 0101101001011010 and 0101101010100101 in code class CC4 are active, so these codes in code class CC4 are mapped in code 01011010 in code class CC3.
If the conditions explained in FIGS. 1 and 2 are not considered, it leads to incorrect, distorted power values when finding the power parts.