Spread communication system and mobile station thereof

Abstract

The signal received by an antenna is input to a receiving circuit. The receiving circuit allows the existence of a perch channel in a particular frequency to be examined by frequency-converting the signal having the frequency corresponding to the frequency specification data within the signal received by the antenna based on the frequency specification data from a controlling circuit. A rectifying circuit rectifies the received signal, and outputs the integrated value of the signal value after being rectified. The integrated value is converted into a digital signal by an A/D converter, and compared with a threshold value by a comparing circuit. If the digital signal value is determined to be larger than the threshold value, a Write signal is output to a storing circuit, so that the frequency specification data output from the controlling circuit is stored in the storing circuit.

What is claimed is:  
     
         1 . A mobile station for use in a spread communication system having a particular channel for establishing synchronization, comprising: 
 a receiving unit receiving a spread signal on a particular channel;    a measuring unit measuring a strength or a correlation value of the spread signal received by said receiving unit;    a storing unit storing information about the particular channel having a signal strength or correlation value; and    a synchronization establishing unit establishing synchronization based on the information stored in said storing unit.    
     
     
         2 . The mobile station according to  claim 1 , further comprising 
 a comparing unit comparing the signal strength or correlation value, which is measured by said measuring unit, with a predetermined threshold value, and    wherein said storing unit stores information about the particular channel having a signal strength or correlation value which is larger than the predetermined threshold value.    
     
     
         3 . The mobile station according to  claim 1 , wherein the spread signal on the particular channel for establishing synchronization is transmitted over a plurality of carrier frequencies.  
     
     
         4 . The mobile station according to  claim 3 , wherein said synchronization establishing unit establishes synchronization only for a carrier frequency whose signal strength measured by said measuring unit becomes a maximum.  
     
     
         5 . The mobile station according to  claim 3 , wherein said synchronization establishing unit sequentially establishes synchronization for the spread signal on the particular channel in each carrier frequency in descending order of the signal strength measured by said measuring unit.  
     
     
         6 . The mobile station according to  claim 2 , wherein: 
 said receiving unit orthogonally demodulates a reception spread signal over a single carrier frequency among the plurality of carrier frequencies;    said measuring unit generates timing-correlational square amplitude calculation value data by calculating square amplitude calculation values of correlation values measured for the orthogonal demodulated spread signals; and    said comparing unit compares the correlational square amplitude calculation value with the threshold value.    
     
     
         7 . The mobile station according to  claim 6 , wherein said storing unit stores only timing-correlational square amplitude calculation value data exceeding the threshold value based on a result of a comparison made by said comparing unit.  
     
     
         8 . The mobile station according to  claim 6  or  7 , further comprising 
 a selecting unit for selecting timing-correlational square amplitude calculation data having a maximum correlational square amplitude calculation value from among timing-correlational square amplitude calculation value data for each carrier frequency.  
 
     
     
         9 . The mobile station according to  claim 6 , further comprising 
 a sorting unit for rearranging timing-correlation square amplitude calculation value data of all of carrier frequencies, which are generated by said measuring unit, in descending order of correlational square amplitude calculation values.    
     
     
         10 . The mobile station according to  claim 6 , further comprising: 
 a classifying unit for performing classification for a plurality of pieces of timing-correlational square amplitude calculation value data by recognizing the data to be transmitted from a same base station, if the plurality of timing-correlational square amplitude calculation value data indicating identical timing exist for each carrier frequency; and    a selecting unit for selecting only data having a largest square amplitude calculation value from among timing and square amplitude calculation value data corresponding to spread signals of each base station, which are classified by said classifying unit, wherein said synchronization establishing unit uses only data selected by said selecting unit so as to establish synchronization.    
     
     
         11 . The mobile station according to  claim 10 , further comprising 
 a sorting unit for rearranging timing-correlational square amplitude calculation value data of all of carrier frequencies, which are generated by said measuring unit, in descending order of correlational square amplitude calculation values, wherein said classifying unit performs the classification based on a sorting result of said sorting unit.    
     
     
         12 . The mobile station according to  claim 10 , wherein reception timing of the spread signal on the particular channel, which is transmitted over the plurality of carrier frequencies, is shifted by predetermined timing, the mobile station further comprising: 
 a delaying unit for delaying an output from said measuring means by the predetermined timing for each frequency;    a controlling unit for controlling said delaying unit, and for making said storing unit store timing-correlational square calculation value data where the reception timing of the spread signal on the particular channel, which is transmitted over the plurality of carrier frequencies, is cancelled; and    a determining unit for determining that signals are transmitted from a same base station if timing-correlational square calculation value data stored in said storing unit indicate identical timing.    
     
     
         13 . A base station in a spread communication system having a particular channel for establishing synchronization, comprising: 
 at least one transmitting unit varying a transmission power of a spread signal on the particular channel, and transmitting the spread signal over at least one carrier frequency;    a measuring unit measuring the number of mobile stations accommodated in a local base station, or a transmission quality of a reception signal from the mobile station; and    a controlling unit controlling the number of mobile stations accommodated in at least one frequency.    
     
     
         14 . The base station according to  claim 13 , wherein: 
 said measuring unit has a capability for counting the number of mobile stations which are currently transmitting signals; and    said controlling unit determines a transmission power of a spread signal on a particular channel in each carrier frequency depending on the number of mobile stations, which is counted by said measuring unit.    
     
     
         15 . The base station according to  claim 13 , wherein said measuring unit measures a signal-to-interference power ratio, a signal-to-(interference+noise) power ratio, an interference power, or an interference+noise power as the transmission quality.  
     
     
         16 . The base station according to  claim 15 , wherein said measuring unit uses a measurement result obtained by a unit, which is comprised by the spread communication system, measuring a signal-to-interference power ratio, a signal-to-(interference+noise) power ratio, an interference power, or an interference+noise power.  
     
     
         17 . The base station according to  claim 13 , wherein: 
 said measuring unit has a capability for grasping the number of mobile stations existing in an area covered by the base station; and    said controlling unit determines the transmission power of the spread signal on the particular channel in each carrier frequency depending on the number of mobile stations existing in the area, which is grasped by said measuring unit.    
     
     
         18 . The base station according to  claim 17 , wherein said transmitting unit sequentially switches a carrier frequency over which a particular channel spread signal whose transmission power is to be increased is carried, at predetermined time intervals.  
     
     
         19 . The base station according to  claim 13 , wherein: 
 said measuring unit comprises 
 an interference power measuring unit measuring interference powers of a plurality of upward lines, and  
 a calculating unit calculating an average value of the interference powers of the plurality of upward lines for each frequency; and  
   said controlling unit determines the transmission power of the spread signal on the particular channel for each carrier frequency depending on the average value.    
     
     
         20 . A spread communication system having a particular channel for establishing synchronization, comprising: 
 a base station having a capability for controlling a transmission power level of a spread signal portion for establishing synchronization on the particular channel; and    a mobile station having a capability for selecting a base station that the mobile station itself accesses depending on the transmission power level of a received spread signal portion for establishing synchronization on the particular channel.