Gain control method for the initial cell searching in TD-SCDMA mobile communication system
View Patent ↗The present invention discloses a gain control method used at the initial cell searching by the user terminal in TD-SCDMA mobile communication system. At each carrier frequency, the user terminal firstly receives and records the data of a plurality of subframes transmitted from a base station when the receiver is set at the maximum gain; searchs the DwPTS positions by using the time window decision method; performs the succeeding steps of the initial cell searching subsequently when the DwPTS positions can be obtained; judges whether the receiver is in saturation when the DwPTS positions can not be obtained; decreases the receiver gain by a large step and receives and records the data of a plurality of subframes transmitted from the base station if the receiver is in saturation; and determines that there is no base station for working at the present carrier frequency if the receiver is not in saturation. The above initial cell searching procedures are repeated until the receiver is not in saturation any more. The ADC of user terminals can finish the initial cell searching under the condition of less dynamic range by using the present invention.
1. A gain control method for an initial cell searching in TD-SCDMA mobile communication system, said gain control method comprising:
Step A: a user terminal receiving data in the maximum receiving gain at a selected carrier frequency;
Step B: recording the received data of a plurality of subframes;
Step C: determining a DwPTS position of each received subframe by using a time window decision method;
Step D: performing a succeeding procedure of the initial cell searching and returning to execute Step A subsequently when the DwPTS positions of the most received subframes can be determined, and executing Step E when the DwPTS positions of the most received subframes can not be determined; and
Step E: judging whether a receiver is in saturation, wherein, returning to execute Step A subsequently when the receiver is not in saturation, and decreasing the receiving gain by a step length and returning to execute Step B subsequently when the receiver is in saturation.
2. A gain control method for the initial cell searching in TD-SCDMA mobile communication system as defined in claim 1 , wherein
after said method returning to execute Step A subsequently in Step D and Step E, Step A re-selects another carrier frequency from all possible carrier frequencies until each possible carrier frequency is selected and then ends the initial cell searching.
3. A gain control method for the initial cell searching in TD-SCDMA mobile communication system as defined in claim 1 , wherein
in Step D, judging whether the DwPTS positions whose number exceeds half of the total number of DwPTS positions in the received subframes are determined so as to determine that the DwPTS positions of the most received subframes can be determined; and in Step D, judging whether the DwPTS positions whose number exceeds half of the total number of DwPTS positions in the received subframes are not determined so as to determine that the DwPTS positions of the most received subframes can not be determined.
4. A gain control method for the initial cell searching in TD-SCDMA mobile communication system as defined in claim 3 , wherein
said DwPTS positions whose number exceeds half of the total number of DwPTS positions in the received subframes are determined continuously or at intervals.
5. A gain control method for the initial cell searching in TD-SCDMA mobile communication system as defined in claim 1 , wherein
in Step D, said determined DwPTS positions whose number exceeds half of the total number of DwPTS positions in the received subframes are considered as the DwPTS positions of subframes.
6. A gain control method for the initial cell searching in TD-SCDMA mobile communication system as defined in claim 1 , wherein
in Step E, if the receiver is judged not to be in saturation and the received signal is environmental interference, there is no base station for working at present carrier frequency.
7. A gain control method for the initial cell searching in TD-SCDMA mobile communication system as defined in claim 1 , wherein
in Step E, the receiving gain is decreased by a step length ranging from 6 dB to 24 dB.