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Methods and apparatus are described for estimating a gain offset between two channels in a communication system. The gain offset arises from the system's transmission of signals on the two channels at different powers. The estimated gain offset is used for determining a set of complex channel estima

Methods and apparatus are described for estimating a gain offset between two channels in a communication system. The gain offset arises from the system's transmission of signals on the two channels at different powers. The estimated gain offset is used for determining a set of complex channel estimates.

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What is claimed is: 1. A method in a receiver of determining a gain offset between transmission channels in a communication system, comprising the steps of: receiving a first signal transmitted through a first channel in the communication system; receiving a second signal transmitted through a seco

What is claimed is: 1. A method in a receiver of determining a gain offset between transmission channels in a communication system, comprising the steps of: receiving a first signal transmitted through a first channel in the communication system; receiving a second signal transmitted through a second channel in the communication system; deriving a first set of channel estimates from samples derived from the first signal; deriving a second set of channel estimates from samples derived from the second signal; and determining the gain offset based on the first and second sets of channel estimates, wherein each of the channel estimates is a model of a respective one of the first and second channels, and includes one or more channel tap coefficients. 2. The method of claim 1, wherein the first and second channels are pilot channels. 3. The method of claim 1, wherein the first and second channels are a Dedicated Physical Channel (DPCH) and a Common Physical Pilot Channel (CPICH), respectively, in a Wideband Code Division Multiple Access (WCDMA) system. 4. A method in a receiver of determining a set of complex channel estimates for a transmission channel in a communication system, comprising the steps of: receiving a first signal transmitted through the transmission channel; receiving a second signal transmitted through a second transmission channel; deriving a first set of channel estimates from samples derived from the first signal; deriving a second set of channel estimates from samples derived from the second signal; determining a gain offset based on the first and second sets of channel estimates; and determining the set of complex channel estimates based on the gain offset and the first and second sets of channel estimates, wherein: each of the channel estimates in the first set of channel estimates is a model of the transmission channel, and includes one or more channel tap coefficients; and each of the channel estimates in the second set of channel estimates is a model of the second channel, and includes one or more channel tap coefficients. 5. The method of claim 4, wherein the gain offset is determined using a second-order equation. 6. The method of claim 4, wherein the gain offset gML is determined using the following equation: α is a scale factor based on a spreading factor such that α=(sf/256)(nD/nC), where sf is the spreading factor used for symbols of the transmission channel, 256 is the spreading factor used for symbols of the second channel, and nD and nC are, respectively, the numbers of symbols coherently summed to get the first set of channel estimates ĥiD and the second set of channel estimates ĥiC, and σei2 is an estimated noise variance parameter. 7. The method of claim 6, wherein the complex channel estimate hiML is determined using the following equation: where: α is a scale factor based on a spreading factor such that α=(sf/256)(nD/nC), where sf is the spreading factor used for symbols of the transmission channel, 256 is the spreading factor used for symbols of the second channel, and nD and nC are, respectively, the numbers of symbols coherently summed to get the first set of channel estimates ĥiD and the second set of channel estimates ĥiC. 8. The method of claim 6, wherein the complex channel estimate is determined by performing a linear combination of the first and second set of channel estimates based on the gain offset. 9. A method in a receiver of determining a set of complex channel estimates for a transmission channel in a communication system, comprising the steps of: receiving a first signal transmitted through the transmission channel; receiving a second signal transmitted through a second transmission channel; deriving a first set of channel estimates from samples derived from the first signal; deriving a second set of channel estimates from samples derived from the second signal; determining a gain offset based on the first and second sets of channel estimates; and determining the set of complex channel estimates based on the gain offset and the first and second sets of channel estimates, wherein the gain offset gML is determined using the following equation: α is a scale factor based on a spreading factor such that α=(sf/256)(nD/nC), where sf is the spreading factor used for symbols of the transmission channel, 256 is the spreading factor used for symbols of the second channel, and nD and nC are, respectively, the numbers of symbols coherently summed to get the first set of channel estimates ĥiD and the second set of channel estimates ĥiC,and σei2 is an estimated noise variance parameter. 10. The method of claim 9, wherein the complex channel estimate hiML is determined using the following equation: where: α is a scale factor based on a spreading factor such that α=(sf/256)(nD/nC), where sf is the spreading factor used for symbols of the transmission channel, 256 is the spreading factor used for symbols of the second channel, and nD and nC are, respectively, the numbers of symbols coherently summed to get the first set of channel estimates ĥiD and the second set of channel estimates ĥiC. 11. The method of claim 9, wherein the complex channel estimate is determined by performing a linear combination of the first and second set of channel estimates based on the gain offset. 12. A method in a receiver of determining a set of channel estimate gains for a transmission channel in a communication system, comprising the steps of: receiving a first signal transmitted through the transmission channel; receiving a second signal transmitted through a second transmission channel; deriving a first set of channel estimates from samples derived from the first signal; deriving a second set of channel estimates from samples derived from the second signal; determining a gain offset based on the first and second sets of channel estimates; determining a set of channel estimate gains based on the gain offset and the first and second sets of channel estimates; and associating the set of channel estimate gains with channel estimate phases of one of the first and second sets of channel estimates, wherein: each of the channel estimates in the first set of channel estimates is a model of the transmission channel, and includes one or more channel tap coefficients; and each of the channel estimates in the second set of channel estimates is a model of the second channel, and includes one or more channel tap coefficients. 13. The method of claim 12, wherein the associated channel estimate phase is the one of the first and second sets of channel estimates being from a high-power channel. 14. The method of claim 13, wherein the associated channel estimate phase is the one of the first and second sets of channel estimates being from a Dedicated Physical Channel (DPCH) channel in a Wideband Code Division Multiple Access (WCDMA) system. 15. An apparatus in a receiver for determining a gain offset between transmission channels in a communication system, the apparatus comprising: means for receiving a first signal transmitted through a first channel in the communication system; means for receiving a second signal transmitted through a second channel in the communication system; means for deriving a first set of channel estimates from samples derived from the first signal; means for deriving a second set of channel estimates from samples derived from the second signal; and means for determining the gain offset based on the first and second sets of channel estimates, wherein each of the channel estimates is a model of a respective one of the first and second channels, and includes one or more channel tap coefficients. 16. The apparatus of claim 15, wherein the first and second channels are pilot channels. 17. The apparatus of claim 15, wherein the first and second channels are a Dedicated Physical Channel (DPCH) and a Common Physical Pilot Channel (CPICH), respectively, in a Wideband Code Division Multiple Access (WCDMA) system. 18. An apparatus in a receiver for determining a set of complex channel estimates for a transmission channel in a communication system, the apparatus comprising: means for receiving a first signal transmitted through the transmission channel; means for receiving a second signal transmitted through a second transmission channel; means for deriving a first set of channel estimates from samples derived from the first signal; means for deriving a second set of channel estimates from samples derived from the second signal; means for determining a gain offset based on the first and second sets of channel estimates; and means for determining the set of complex channel estimates based on the gain offset and the first and second sets of channel estimates, wherein: each of the channel estimates in the first set of channel estimates is a model of the transmission channel, and includes one or more channel tap coefficients; and each of the channel estimates in the second set of channel estimates is a model of the second channel, and includes one or more channel tap coefficients. 19. The apparatus of claim 18, wherein the gain offset is determined using a second-order equation. 20. The apparatus of claim 18, wherein the gain offset gML is determined using the following equation: α is a scale factor based on a spreading factor such that α=(sf/256)(nD/nC), where sf is the spreading factor used for symbols of the transmission channel, 256 is the spreading factor used for symbols of the second channel, and nD and nC are, respectively, the numbers of symbols coherently summed to get the first set of channel estimates ĥiD and the second set of channel estimates ĥiC, and σei2 is an estimated noise variance parameter. 21. The apparatus of claim 20, wherein the complex channel estimate hiML is determined using the following equation: where: α is a scale factor based on a spreading factor such that α=(sf/256)(nD/nC), where sf is the spreading factor used for symbols of the transmission channel, 256 is the spreading factor used for symbols of the second channel, and nD and nC are, respectively, the numbers of symbols coherently summed to get the first set of channel estimates ĥiD and the second set of channel estimates ĥiC. 22. The apparatus of claim 20, wherein the complex channel estimate is determined by performing a linear combination of the first and second set of channel estimates based on the gain offset. 23. An apparatus in a receiver for determining a set of complex channel estimates for a transmission channel in a communication system, the apparatus comprising: means for receiving a first signal transmitted through the transmission channel; means for receiving a second signal transmitted through a second transmission channel; means for deriving a first set of channel estimates from samples derived from the first signal; means for deriving a second set of channel estimates from samples derived from the second signal; means for determining a gain offset based on the first and second sets of channel estimates; and means for determining the set of complex channel estimates based on the gain offset and the first and second sets of channel estimates, wherein the gain offset gML is determined using the following equation: α is a scale factor based on a spreading factor such that α=(sf/256)(nD/nC), where sf is the spreading factor used for symbols of the transmission channel, 256 is the spreading factor used for symbols of the second channel, and nD and nC are, respectively, the numbers of symbols coherently summed to get the first set of channel estimates ĥiD and the second set of channel estimates ĥiC, and σei2 is an estimated noise variance parameter. 24. The apparatus of claim 23, wherein the complex channel estimate hiML is determined using the following equation: where: α is a scale factor based on a spreading factor such that α=(sf/256)(nD/nC), where sf is the spreading factor used for symbols of the transmission channel, 256 is the spreading factor used for symbols of the second channel, and nD and nC are, respectively, the numbers of symbols coherently summed to get the first set of channel estimates ĥiD and the second set of channel estimates ĥiC. 25. The apparatus of claim 23, wherein the complex channel estimate is determined by performing a linear combination of the first and second set of channel estimates based on the gain offset. 26. An apparatus in a receiver for determining a set of channel estimate gains for a transmission channel in a communication system, the apparatus comprising: means for receiving a first signal transmitted through the transmission channel; means for receiving a second signal transmitted through a second transmission channel; means for deriving a first set of channel estimates from samples derived from the first signal; means for deriving a second set of channel estimates from samples derived from the second signal; means for determining a gain offset based on the first and second sets of channel estimates; means for determining a set of channel estimate gains based on the gain offset and the first and second sets of channel estimates; and means for associating the set of channel estimate gains with channel estimate phases of one of the first and second sets of channel estimates, wherein: each of the channel estimates in the first set of channel estimates is a model of the transmission channel, and includes one or more channel tap coefficients; and each of the channel estimates in the second set of channel estimates is a model of the second channel, and includes one or more channel tap coefficients. 27. The apparatus of claim 26, wherein the associated channel estimate phase is the one of the first and second sets of channel estimates being from a high-power channel. 28. The apparatus of claim 27, wherein the associated channel estimate phase is the one of the first and second sets of channel estimates being from a Dedicated Physical Channel (DPCH) channel in a Wideband Code Division Multiple Access (WCDMA) system.