Patent Application
20070242641
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:
Preferred embodiments of the present invention will now be described in detail with reference to the annexed drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for the sake of clarity and conciseness.
The present invention provides a rake reception apparatus and method for simultaneously on-line performing multi-path search and PI-demodulation in a power-on state to reduce the time for which a mobile terminal wakes up a sleep state in a mobile communication system, thereby reducing power consumption and increasing a waiting time of the mobile terminal.
To this end, the present invention adds a PI demodulator to the existing rake receiver. The PI demodulator is constructed so as to demodulate a PI as soon as multi-path search is performed, thereby reducing the time for which the terminal wakes up from the sleep state.
Referring to
The rake receiver 720 controls demodulating an RF-processed multi-path signal received from the RF processor 710. The rake receiver 720 roughly includes a searcher 721, a PI demodulator 723, a plurality of fingers 727-1˜727-N, a controller 725 and a combiner 729.
The searcher 721 simultaneously checks several hypotheses to increase a detection speed of a multi-path signal. For each hypothesis, a local scrambling code has a different phase difference with respect to a received signal, and the phase difference of each hypothesis, i.e. a size of the hypothesis being checked, has a regular interval as shown in
The searcher 721, as shown in
The channelization code generator 721a generates a channelization code. The descrambler 721b descrambles scrambling codes having different phases with an allocated multi-path signal. That is, the descrambler 721b correlates a received signal to the local scrambling code. The accumulator 721c accumulates the descrambled signal for a time corresponding to a specific length, for multi-path detection. The energy calculator 721d calculates energy using the value complex-accumulated by the accumulator 721c. As shown in
The PI demodulator 723 multiplies and accumulates a channelization code of a PICH for an interval where a PI is located, for every hypothesis being checked by the searcher 721. Because the value accumulated for each hypothesis in the searcher 721 includes phase information of a CPICH, the PI demodulator 723 performs channel compensation by multiplying the accumulated value by the corresponding accumulated PI value. Assuming that a multi-path signal has a time delay corresponding to each hypothesis, the channel-compensated value is a PI value synch-demodulated in the corresponding path. However, it cannot be known whether the multi-path signal actually exists in the position where the hypothesis appears. Therefore, it is preferable to combine the corresponding demodulated PI values only for the hypotheses that are determined to have multi-path signals.
The PI demodulator 723 includes a channelization code generator 723a, a multiplier 723b, a PI accumulator 723c, a channel compensator 723d, a decider 723e, an adder 723f, and a PI combiner 723g.
In the PI demodulator 723, the channelization code generator 723a generates a channelization code. The multiplier 723b multiplies the signal descrambled by the descrambler 721b in the searcher 721 by the channelization code output from the channelization code generator 723a. The multiplier 723b multiplies scrambling codes having different phases by the received signal to simultaneously check several time hypotheses, and a phase difference of each hypothesis has a regular interval as shown in
A phase of a scrambling code used for check of each hypothesis is determined by the controller 725. As shown in
In
The channel compensator 723d performs synch demodulation on the PI using the accumulation result on a CPICH in the accumulator 721c included in the searcher 721 and the accumulation result of the PI accumulator 723c. That is, because the value accumulated for each hypothesis in the searcher 721 includes phase information of the CPICH, the channel compensator 723d performs channel compensation by multiplying the accumulated value by the corresponding accumulated PI value. Assuming that a multi-path signal has a time delay corresponding to each hypothesis, the channel-compensated value is a PI value synch-demodulated in the corresponding path.
The decider 723e determines validity of the currently checked path by applying a threshold to the energy for each hypothesis, calculated in the searcher 721. The decider 723e determines, as a valid path, only the hypothesis having energy exceeding a valid path threshold, and allows the PI combiner 723g to combine the corresponding demodulated PI. The threshold is set by the controller 725.
The PI combiner 723g combines the PI demodulation results only when the valid path is determined.
The controller 725 controls the searcher 721 to check several hypotheses (phases) using the signals in the adjacent time interval where the PI is located. The controller 725 provides location information of the PI in a correlation interval of each hypothesis being checked by the searcher 721, to the PI accumulator 723c, and determines whether a paging channel is received, depending on a report on the combination result of the PI combiner 723g.
According to the second embodiment of the present invention, as shown in
The detector 721e detects multi-path signals using the energy values of several hypotheses, received from the energy calculator 721d, and reports the detected multi-path signals to the controller 725.
If several upper multi-path signals detected by the detector 721e exceed a threshold determined by the controller 725, the detector 721e directly delivers the detected multi-path signals to the decider 723e in the PI demodulator 723 regardless of the report to the controller 725.
The decider 723e, shown in
Therefore, because the multi-path search result is directly delivered to the PI demodulator, the multi-path search and PI detection operations can be simultaneously performed.
The controller 725 receives a report on the result obtained by combining only the accumulated PI values of the hypotheses which are determined to be valid as a multi-path signal, from the PI combiner 723g, and determines whether a PCH is received, from the result. If it is determined that a PCH is transmitted to the terminal, the controller 725 performs finger allocation using the multi-path detection result of the searcher 721, allows the rake receiver 720 to receive the PCH, and returns back to the sleep state if it is determined that the PCH is not transmitted.
The DRX mode terminal wakes up from the sleep state only at the time the PI is transmitted, and then monitors the PI. However, because there is a high possibility that a position of a multi-path signal has changed during the sleep state, the terminal, if RF power is turned on, simultaneously performs a multi-path search operation 1110 and a PI demodulation operation 1120 in a searcher in advance of PI detection. After simultaneously performing the multi-path search operation 1110 and the PI demodulation operation 1120, the terminal performs a finger allocation operation 1130 and a PCH demodulation operation 1140 after its RF power is turned off.
Referring to
The searcher 721 performs a multi-path search operation in step 1203. At the same time, the PI demodulator 723 performs a PI demodulation operation for each path in step 1205.
The decider 723e in the PI demodulator 723 determines in step 1207 validity of the currently checked path by applying a threshold to the energy value for each hypothesis, calculated by energy calculator 721d in the searcher 721, as described in the first embodiment of the present invention. The possibility of combination in the PI combiner 723g is determined depending on the validity decision.
In addition, the decider 723e in the PI demodulator 723 determines in step 1207 the possibility of the currently checked path by applying a threshold to the energy for each hypothesis, detected as several upper values by the detector 721e in the searcher 721, as described in the second embodiment of the present invention.
If it is determined that combination is impossible, since there is no paging information for the terminal the controller 725, turns off in step 1209 the digital modem and the RF part and returns to the sleep state. However, if the combination is possible, the PI combiner 723g combines the corresponding demodulated PI values only for the hypothesis having the energy exceeding a threshold. The threshold is set by the controller 725.
The controller 725 receives in step 1213 a report on the result obtained by combining only the accumulated PI values of the hypotheses which are determined to be valid as a multi-path signal, from the PI combiner 723g, and determines whether a PCH is received, from the result. If it is determined that a PCH is transmitted to the terminal, the controller 725 performs finger allocation using the multi-path detection result of the searcher 721, and allows the rake receiver 720 to receive the PCH.
As is apparent from the foregoing description, because the multi-path search result is immediately delivered to the PI demodulator, the multi-path search and PI detection operations can be simultaneously performed.
In addition, the DRX mode terminal can simultaneously performs multi-path search and PI detection after waking up from the sleep state and providing power to the RF processor, thereby avoiding the finger allocation operation necessary for the PI detection and thus reducing the interval for which the RF processor should be powered on.
Further, because operations of the fingers and the combiner in the rake receiver are not needed for PI demodulation, both the power necessary for signal processing of the RF processor and the power necessary for digital signal process of the modem are reduced, thus contributing to an increase in a waiting time of the terminal.
While the invention has been shown and described with reference to a certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-33707 | Apr 2006 | KR | national |
