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.

1. A bidirectional communication system using a CDMA air interface between a plurality of subscriber units communicating with a base station, the system comprising:
 a scalable base station configured from up to a select maximum number n of modular colocated base station units for supporting incremental communication capacity based on the number of modular base station units, each base station unit for communicating with a predefined number of subscriber units; 
 each base station unit transmitting a unique CDMA global pilot channel signal at a full power level for a discrete limited time interval which time interval is distinct from the time intervals of all other base station units in the scalable base station configuration; and 
 a plurality of subscriber units for CDMA communication with the scalable base station, each subscriber unit having means for selectively receiving global pilot channel signals from up to n modular base station units, such that reception of each global pilot channel signal is in a discrete time interval synchronized with the full power level transmission time interval of the respective global pilot channel signal which time interval is distinct from the reception of all other transmission time intervals of the global pilot channel signals. 
 
     
     
       2. The communication system according to  claim 1  where n is calculated based upon a maximum desired communication capacity divided by the capacity of a single base station unit. 
     
     
       3. The communication system according to  claim 1  wherein the scalable modular base station is configured from a selected number m of modular base station units where m<n. 
     
     
       4. The communication system according to  claim 1  where n=6. 
     
     
       5. The communication system according to  claim 1  wherein the time interval is determined by the time of day. 
     
     
       6. The communication system according to  claim 1  wherein the means for selectively receiving global pilot channels includes waking up for the discrete time interval. 
     
     
       7. The communication system according to  claim 1  wherein each modular base station unit further transmits a fast broadcast channel and a slow broadcast channel. 
     
     
       8. The communication system according to  claim 1  wherein the means for receiving global pilot channels further includes storing a relative global pilot channel signal strength received. 
     
     
       9. The communication system according to  claim 7  wherein the means for receiving global pilot channels further includes receiving the slow broadcast channel and the fast broadcast channel and deriving and storing that base station unit's communicating capacity from the slow and fast broadcast channels. 
     
     
       10. The communication system according to  claim 9  wherein a subscriber unit initiates communication with one of the modular base station units by choosing from storage the modular base station unit having the strongest global pilot signal strength. 
     
     
       11. The communication system according to  claim 10  wherein the choosing from storage further includes the communication capacity of that base station unit. 
     
     
       12. A base station for use in a bidirectional communication system using a CDMA air interface between a plurality of subscriber units communicating with the base station, comprising:
 a scalable base station configured from up to a select maximum number n of modular colocated base station units for supporting incremental communication capacity based on the number of modular base station units, each base station unit for communicating with a predefined maximum number of subscriber units at any given time; and 
 each base station unit transmitting a unique CDMA global pilot channel at a high power level for a discrete limited time interval which time interval is distinct from the time intervals of all other base station units in the scalable base station configuration. 
 
     
     
       13. A method of providing bidirectional communication using a CDMA air interface between a plurality of subscriber units communicating with a base station, the steps comprising:
 configuring from up to a select maximum number n of modular colocated base station units a scalable base station for supporting incremental communication capacity based on the number of modular base station units, each base station unit for communicating with a predefined number of subscriber units; 
 transmitting a unique CDMA global pilot channel signal from each base station unit at a full power level for a discrete limited time interval which time interval is distinct from the time intervals of all other base station units in the scalable base station configuration; and 
 selectively receiving global pilot channel signals from up to n modular base station units at a plurality of subscriber units for CDMA communication with the scalable base station, such that reception of each global pilot channel signal is in a discrete time interval synchronized with the full power level transmission time interval of the respective global channel which is distinct from the reception of all others of the global pilot channel signals. 
 
     
     
       14. A code division multiple access (CDMA) subscriber unit comprising:
 circuitry configured to receive n synchronization signals from a CDMA base station such that each of the n synchronization signals are received in n discrete time intervals, each discrete time interval for receiving a different synchronization signal;   circuitry configured to receive and recover information from a broadcast channel; and   circuitry configured to transmit at least one code in an access procedure derived from the recovered information from the broadcast channel.   
     
     
       15. The CDMA subscriber unit of claim 14 wherein each of the n synchronization signals comprises a code. 
     
     
       16. The CDMA subscriber unit of claim 14 wherein each of the n synchronization signals is a pilot signal. 
     
     
       17. The CDMA subscriber unit of claim 14 further comprising circuitry configured to receive an acknowledgement from the base station indicating that at least one of the plurality of codes was received by the base station. 
     
     
       18. The CDMA subscriber unit of claim 14 wherein the circuitry further configured to receive synchronization signals from other CDMA base station and wherein the synchronization signals from the other CDMA base stations are offset from each other by a plurality of chips. 
     
     
       19. The CDMA subscriber unit of claim 14 comprising circuitry configured to transmit a reverse link pilot signal. 
     
     
       20. A method for use by a code division multiple access (CDMA) subscriber unit comprising:
 receiving n synchronization signals from a CDMA base station by the CDMA subscriber unit such that each of the n synchronization signals are received in n discrete time intervals, each discrete time interval for receiving a different synchronization signal.   
     
     
       21. The method of claim 20 wherein each of the n synchronization signals comprises a code. 
     
     
       22. The method of claim 20 wherein each of the n synchronization signals is a pilot signal. 
     
     
       23. The method of claim 20 comprising:
 receiving and recovering information from a broadcast channel; and   transmitting a plurality of codes in an access procedure derived from the recovered information from the broadcast channel.   
     
     
       24. The method of claim 23 comprising receiving an acknowledgement from the base station indicating that at least one of the plurality of codes was received by the base station. 
     
     
       25. The method of claim 20 comprising receiving synchronization signals from other CDMA base station and wherein the synchronization signals from the other CDMA base stations are offset from each other by a plurality of chips. 
     
     
       26. The method of claim 20 comprising transmitting a reverse link pilot signal. 
     
     
       27. A code division multiple access (CDMA) base station comprising:
 circuitry configured to transmit n synchronization signals such that each of the n synchronization signals are transmitted in n discrete time intervals, each discrete time interval for transmitting a different synchronization signal; and   circuitry configured to transmit information on a broadcast channel.   
     
     
       28. The CDMA base station of claim 27 wherein each of the n synchronization signals comprises a code. 
     
     
       29. The CDMA base station of claim 27 wherein each of the n synchronization signals is a pilot signal. 
     
     
       30. A method for use by a code division multiple access (CDMA) base station comprising:
 transmitting n synchronization signals such that each of the n synchronization signals are transmitted in n discrete time intervals, each discrete time interval for transmitting a different synchronization signal.   
     
     
       31. The method of claim 30 wherein each of the n synchronization signals comprises a code. 
     
     
       32. The method of claim 30 wherein each of the n synchronization signals is a pilot signal. 
     
     
       33. A code division multiple access (CDMA) subscriber unit comprising:
 circuitry configured to receive n synchronization signals from a CDMA base station such that each of the n synchronization signals are received in n discrete time intervals, each discrete time interval for receiving a different synchronization signal; and   circuitry configured to receive and recover information from a broadcast channel;   
       wherein the receive and recover information circuitry is synchronized based on at least one of the synchronization signals. 
     
     
       34. The CDMA subscriber unit of claim 33 wherein each of the n synchronization signals comprises a code. 
     
     
       35. The CDMA subscriber unit of claim 33 wherein each of the n synchronization signals is a pilot signal. 
     
     
       36. The CDMA subscriber unit of claim 33 comprising:
 circuitry configured to transmit a plurality of codes in an access procedure derived from the recovered information from the broadcast channel.   
     
     
       37. The CDMA subscriber unit of claim 36 further comprising circuitry configured to receive an acknowledgement from the base station indicating that at least one of the plurality of codes was received by the base station. 
     
     
       38. The CDMA subscriber unit of claim 33 wherein the circuitry further configured to receive synchronization signals from other CDMA base station and wherein the synchronization signals from the other CDMA base stations are offset from each other by a plurality of chips. 
     
     
       39. The CDMA subscriber unit of claim 33 comprising circuitry configured to transmit a reverse link pilot signal. 
     
     
       40. A method for use by a code division multiple access (CDMA) subscriber unit comprising:
 receiving n synchronization signals from a CDMA base station by the CDMA subscriber unit such that each of the n synchronization signals are received in n discrete time intervals, each discrete time interval for receiving a different synchronization signal; and   receiving and recovering information from a broadcast channel; wherein the receiving information is synchronized based on at least one of the synchronization signals.   
     
     
       41. The method of claim 40 wherein each of the n synchronization signals comprises a code. 
     
     
       42. The method of claim 40 wherein each of the n synchronization signals is a pilot signal. 
     
     
       43. The method of claim 40 comprising:
 transmitting a plurality of codes in an access procedure derived from the recovered information from the broadcast channel.   
     
     
       44. The method of claim 43 comprising receiving an acknowledgement from the base station indicating that at least one of the plurality of codes was received by the base station. 
     
     
       45. The method of claim 40 comprising receiving synchronization signals from other CDMA base station and wherein the synchronization signals from the other CDMA base stations are offset from each other by a plurality of chips. 
     
     
       46. The method of claim 40 comprising transmitting a reverse link pilot signal.