Method of controlling initial power ramp-up in a CDMA system by using short codes

• US 6,490,462 B2
• Filed: 03/01/2002
• Issued: 12/03/2002
• Est. Priority Date: 06/27/1996
• Status: Expired due to Term

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Lomp, Gary R., Ozluturk, Fatih M.
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): BEAMER, TEMICA M
• Application Number:
  US10/086,324
• Publication Number:
  US 20020086696A1
• Time in Patent Office: 277 Days
• Field of Search: 455/522, 455/63, 455/67.1, 455/69, 455/70, 455/436, 455/437, 455/517, 370/318, 370/320, 370/335, 370/324, 370/331, 370/332, 370/350, 370/252
• US Class Current: 455/522
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/70753 Partial phase search
• CPC Class Codes: H04B 1/70755 Setting of lock conditions, e.g. threshold
• CPC Class Codes: H04B 1/70758 Multimode search, i.e. using multiple search strategies
• CPC Class Codes: H04B 1/7077 Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation
• CPC Class Codes: H04B 1/708 Parallel implementation
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04B 2201/7071 with dynamic control of receiver resources
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04W 52/36 with a discrete range or set of values, e.g. step size, ramping or offsets
• CPC Class Codes: H04W 52/367 Power values between minimum and maximum limits, e.g. dynamic range
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 52/60 using different transmission rates for TPC commands

Abstract

A method of controlling transmission power during the establishment of a channel in a CDMA communication system utilizes the transmission of a short code from a subscriber unit to a base station during initial power ramp-up. The short code is a sequence for detection by the base station which has a much shorter period than a conventional spreading code. The ramp-up starts from a power level that is lower than the required power level for detection by the base station. The subscriber unit quickly increases transmission power while repeatedly transmitting the short code until the signal is detected by the base station. Once the base station detects the short code, it sends an indication to the subscriber unit to cease increasing transmission power. The use of short codes limits power overshoot and interference to other subscriber units and permits the base station to quickly synchronize to the spreading code used by the subscriber unit.

Claims

1. A method for controlling transmission power during the establishment of communications between a base station and at least one subscriber unit, the method comprising:

transmitting a periodic signal from said subscriber unit at an initial predetermined power level that is lower than a power level required for detection by said base station;

repeatedly transmitting the periodic signal, each retransmission occurring at successively higher power levels;

detecting said periodic signal at said base station when a sufficient power level for detection is achieved;

transmitting a signal from said base station confirming that said periodic signal has been detected; and

wherein the periodic signal is a short code that is shorter than an access code.

2. The method of claim 1 wherein the short code is an integer multiple of the access code.

3. The method of claim 2 wherein a period of the short code length is a length of one symbol.

4. A method for controlling transmission power during the establishment of communication between a base station and at least one subscriber unit, the method comprising:

transmitting a periodic signal from said subscriber unit at an initial predetermined power level that is lower than a power level required for detection by said base station;

respectively retransmitting said periodic signal, each retransmission occurring at successively higher power levels;

transmitting a signal from said base station confirming that said periodic signal has been detected;

terminating transmission of the periodic code and maintaining the power level present when said confirmation signal is received by said subscriber unit, for initiating a next operation at said subscriber unit; and

wherein said periodic signal is a short code which is shorter than an access code which is used by a subscriber unit to access a base station.

5. The method of claim 4 further comprising said base station, upon receipt of said access code, searches for the correct phase of the access code.