Modular base station with variable communication capacity

Abstract

The present invention provides a base station architecture that is modular in configuration, lowering the initial cost of implementing a new CDMA telecommunication system for a defined geographical region while allowing for future capacity. The scalable architecture is assembled from a digital base station unit that is configured to support a plurality of simultaneous wireless calls connecting to a conventional public switched telephone network. For initial startup, two base station units are deployed for redundancy in case of a single failure. Additional base station units may be added when the need arises for extra traffic capacity. If sectorization is required, the base station units may be directionally oriented. Coupled to and remote from each base station unit are two amplified antenna modules that contain an omni-directional or an external directional antenna, a high power RF amplifier for transmitted frequencies and a low noise amplifier for received frequencies. A separate power supply module capable of supporting two base station units provides continued service in the event of a mains power outage.

What is claimed is: 
     
         1 . A code division multiple access (CDMA) base station comprising:
 circuitry configured to communicate with a number of subscriber units;   circuitry configured to transmit a plurality of synchronization signals to the subscriber units at a full power level for a discrete time interval to improve available cell capacity, wherein a different synchronization signal is transmitted in each discrete time interval;   circuitry configured to transmit a broadcast channel to the subscriber units; and   circuitry configured to receive a plurality of codes derived from the broadcast channel from a subscriber unit in an access procedure.   
     
     
         2 . The base station of  claim 1  wherein each of the synchronization signals comprises a code. 
     
     
         3 . The base station of  claim 1  wherein each of the synchronization signals is a pilot signal. 
     
     
         4 . The base station of  claim 1  further comprising circuitry configured to transmit an acknowledgement to the subscriber unit indicating that at least one of the plurality of codes was received by the base station. 
     
     
         5 . The base station of  claim 1  wherein the synchronization signals from other CDMA base stations are offset from each other by a plurality of chips. 
     
     
         6 . A method for use in a code division multiple access (CDMA) base station, the method comprising:
 communicating with a number of subscriber units;   transmitting a plurality of synchronization signals to the subscriber units at a full power level for a discrete time interval to improve available cell capacity, wherein a different synchronization signal is transmitted in each discrete time interval;   transmitting a broadcast channel to the subscriber units; and   receiving a plurality of codes derived from the broadcast channel from a subscriber unit in an access procedure.   
     
     
         7 . The method of  claim 6  wherein each of the synchronization signals comprises a code. 
     
     
         8 . The method of  claim 6  wherein each of the synchronization signals is a pilot signal. 
     
     
         9 . The method of  claim 6  further comprising circuitry transmitting an acknowledgement to the subscriber unit indicating that at least one of the plurality of codes was received by the base station. 
     
     
         10 . The method of  claim 6  wherein the synchronization signals from other CDMA base stations are offset from each other by a plurality of chips. 
     
     
         11 . A code division multiple access (CDMA) communication system, the system comprising:
 a base station configured to communicate with a number of subscriber units, to transmit a plurality of synchronization signals at a full power level for a discrete time interval to improve available cell capacity, wherein the pilot channel includes synchronization signals and a different synchronization signal is transmitted in each discrete time interval, and to transmit a broadcast channel to the subscriber units; and   a subscriber unit configured to receive the pilot channel such that each of the plurality of synchronization signals are received in a plurality of different discrete time intervals, to receive and recover information from a broadcast channel based on the at least one of the synchronization signals, and to transmit a plurality of codes in an access procedure derived from the broadcast channel.   
     
     
         12 . The system of  claim 11  wherein each of the synchronization signals comprises a code. 
     
     
         13 . The system of  claim 11  wherein each of the synchronization signals is a pilot signal. 
     
     
         14 . The system of  claim 11  further comprising the base station configured to transmit an acknowledgement to the subscriber unit indicating that at least one of the plurality of codes was received by the base station. 
     
     
         15 . The system of  claim 11  wherein the synchronization signals from other CDMA base stations are offset from each other by a plurality of chips.