P-CPICH scrambling code collision detection
A method permits a UE receiver to detect and report to the network a scrambling code collision (i.e., two neighbor cells transmitting with the same scrambling code while timing is aligned). The UE receiver decodes the PCCPCH's physical channel with all the associated broadcast information while a scrambling code collision at the UE is present. The UE reports SFN-SFN information to the network, to insure the UE mobility and then prepare the handover to a new detected cell. This process and a respective apparatus are usable in the presence of MIMO and further improve the detection of the scrambling code collision in the presence of MIMO.
1. A method for decoding a Primary Common Control Physical Channel, PCCPCH, the method comprising:
monitoring by a user equipment, UE, a scrambling code transmitted by a target cell;
synchronizing with a neighbor cell by the UE, to acquire a slot and frame timing of the neighbor cell;
detecting and flagging, by the UE, a scrambling code collision between the target cell and the neighbor cell;
checking, by the UE, that broadcast information of the target cell has been applied for decoding the PCCPCH; and
if the broadcast information of the target cell has been applied, reconstructing, by the UE, a transmitted PCCPCH sequence to create a new pilot channel estimation to be used for computing a channel estimation based on the reconstructed PCCPCH sequence of the target cell,
wherein a channel estimation of a Primary Common Pilot Channel, P-CPICH, and the channel estimation based on the reconstructed PCCPCH sequence of the target cell are combined in order to compute a channel estimation of a newly appearing cell with a colliding scrambling code, and
an algorithm for combining the channel estimation of the P-CPICH and the channel estimation based on the reconstructed PCCPCH sequence of the target cell includes subtracting the channel estimation of the P-CPICH and the channel estimation based on the reconstructed PCCPCH sequence of the target cell to which defined weights are applied, respectively.
2. The method according to claim 1 , wherein the algorithm further comprises a filtering operation.
3. The method according to claim 1 , wherein the defined weights and filters are configured to be able to change over time according to a function of specific parameters including one or more of a speed estimation, a noise estimation and a delay spread estimation.
4. The method according to claim 1 , wherein the reconstruction of the transmitted PCCPCH sequence is performed by starting from a hard decision at an output of a Viterbi decoder.
5. The method according to claim 1 , wherein the reconstruction of the transmitted PCCPCH sequence is performed by using a soft decision extracted from a Viterbi metrics as basis.
6. The method according to claim 1 , wherein the reconstruction of the transmitted PCCPCH sequence is performed by using a previously decoded PCCPCH sequence saved in a memory.
7. The method according to claim 1 , wherein the channel estimation based on the reconstructed PCCPCH sequence of the target cell is computed using an algorithm.
8. The method according to claim 1 , further comprising using the computed channel estimation based on the reconstructed PCCPCH sequence of the target cell for equalizing input I, Q data and decoding a PCCPCH.