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

• US 6,778,840 B2
• Filed: 08/02/2002
• Issued: 08/17/2004
• 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): Gary, Erika
• Assistant Examiner(s): BEAMER, TEMICA M
• Application Number:
  US10/210,961
• Publication Number:
  US 20020187748A1
• Time in Patent Office: 746 Days
• Field of Search: 455/434, 455/515, 455/522, 455/63, 455/67.11, 370/318, 370/320, 370/324, 370/335, 370/342
• 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 a subscriber unit, the method comprising the steps of:

transmitting a periodic short code from the subscriber unit at an initial predetermined power level, the periodic short code being entirely transmitted at the initial predetermined power level and being shorter than an access code;

repeatedly transmitting the periodic short code, each retransmission occurring at a successively higher power level, the periodic short code being entirely transmitted at each successively higher power level, prior to increasing the power level;

detecting the periodic short code at the base station when a sufficient power level for detection is achieved; and

transmitting a confirmation signal from the base station confirming that the periodic short code has been detected.

2. The method of claim 1 wherein the initial predetermined power level is lower than a power level required for detection by the base station.

3. A method for controlling transmission power during the establishment of communication between a base station and a subscriber unit, the method comprising the steps of:

transmitting a periodic short code from the subscriber unit at an initial predetermined power level, the periodic short code being entirely transmitted at the initial predetermined power level;

repeatedly retransmitting the periodic short code, each retransmission occurring at a successively higher power level, the periodic short code being entirely transmitted at each successively higher power level, prior to increasing the power level;

transmitting a confirmation signal from the base station confirming that the periodic short code has been detected; and

terminating transmission of the periodic short code and maintaining the power level present when the confirmation signal is received by the subscriber unit, for initiating a next operation at the subscriber unit wherein the next operation is the transmission of an access code, the periodic short code being shorter than the access code.

4. The method of claim 3 wherein the initial predetermined power level is lower than a power level required for detection by the base station.