Synchronization channel noise power estimation
Apparatus and method to process a pilot channel and a synchronization channel to obtain a combined noise estimate of the pilot channel and the synchronization channel that is synchronized to the pilot channel. The combined noise estimation is processed to determine a first noise component for a period when both the pilot channel and the synchronization channel are present. Then, the combined noise estimate is processed to determine a second noise component for a period when only the pilot channel is present. Next, the second noise component is subtracted from the first noise component to derive a noise estimation for the synchronization channel. The technique may be applied to the Common Pilot Channel (CPICH), and the Synchronization Channel (SCH) defined in a 3 rd Generation Partnership Project standard specification.
1. An apparatus comprising:
a first symbol processing module coupled to receive a first pre-defined number of symbols of a slot of a downlink common pilot channel that has multiple slots, in which the first symbol processing module accumulates over the first pre-defined number of symbols to obtain a first average noise estimation over the first pre-defined number of symbols for the slot, wherein the first average noise estimation includes noise effects of a synchronization channel that is present during a time period synchronized to the first pre-defined number of symbols; and
a second symbol processing module coupled to receive subsequent N number of symbols of the slot following the first pre-defined number of symbols of the slot, in which the second symbol processing module accumulates over the N number of symbols of the slot of the downlink common pilot channel to obtain a second average noise estimation, wherein the second average noise estimation does not include the noise effects of the synchronization channel; and
a third processing module to subtract the second average noise estimation from the first average noise estimation to derive a noise estimation for the synchronization channel.
2. The apparatus of claim 1 , wherein first two symbols of the slot are used as the first pre-defined number of symbols.
3. The apparatus of claim 1 , wherein the downlink common pilot channel is a Common Pilot Channel (CPICH), and the synchronization channel is a Synchronization Channel (SCH) defined in a 3 rd Generation Partnership Project standard specification.
4. The apparatus of claim 1 , wherein the synchronization channel is present for approximately 1/10 of a duration of the slot of the downlink common pilot channel.
5. The apparatus of claim 3 , wherein the first pre-defined number of symbols is first two symbols of each slot of CPICH and the N number of symbols are remaining symbols of each slot of CPICH.
6. A method comprising:
processing a first pre-defined number of symbols of a slot of a downlink common pilot channel that has multiple slots, in order to accumulate over the first pre-defined number of symbols to obtain a first average noise estimation over the first pre-defined number of symbols for the slot, wherein the first average noise estimation includes noise effects of a synchronization channel that is present during a time period synchronized to the first pre-defined number of symbols;
processing subsequent N number of symbols of the slot following the first pre-defined number of symbols of the slot, in order to accumulate over the N number of symbols of the slot of the downlink common pilot channel to obtain a second average noise estimation, wherein the second average noise estimation does not include the noise effects of the synchronization channel; and
processing to subtract the second average noise estimation from the first average noise estimation to derive a noise estimation for the synchronization channel.
7. The method of claim 6 , wherein when processing, first two symbols of the slot are used as the first pre-defined number of symbols.
8. The method of claim 7 , wherein when processing, N number of symbols are remaining symbols of the slot.
9. The method of claim 8 further comprising applying the derived noise estimation for the synchronization channel to a signal component that is transmitted during a period that the downlink common pilot channel and synchronization channel are transmitted to compensate for additional noise introduced by the synchronization channel when the synchronization channel is present.
10. The method claim 9 , wherein the downlink common pilot channel is a Common Pilot Channel (CPICH), and the synchronization channel is a Synchronization Channel (SCH) defined in a 3 rd Generation Partnership Project standard specification.
11. The method of claim 10 further comprising adjusting for a timing offset between SCH and a signal component of a Dedicated Physical Channel (DPCH) defined in a 3 rd Generation Partnership Project standard specification and compensating for noise power in SCH overlapping the DPCH signal component to calculate a signal-to-noise ratio (SNR).