Power-controlled random access

Abstract

A novel power-controlled random-access method allows a mobile station to gain fast access to the base station. At the mobile station, a composite power control command is devised after an initial access attempt. The determination of the composite command uses an open-loop power-control symbol and a closed-loop power-control symbol, to decide the action of the mobile station upon transmission of its next random-access signal. In the preferred embodiment, the composite power control command can specify different levels of increase or decrease in transmission power, and the composite power control command can specify a back-off by the mobile station. This composite power-control mechanism can help resolve collision between mobile stations accessing the same random access sub-channel and therefore maintain a low-delay in the random-access process and a high-utilization on the access-channel resource.

1 . In a code-division-multiple-access (CDMA) system employing spread-spectrum modulation comprising a base station (BS) comprising a BS-spread-spectrum transmitter and a BS-spread-spectrum receiver, and a plurality of mobile stations, each mobile station (MS) comprising an MS-spread-spectrum transmitter and an MS-spread-spectrum receiver, a method comprising the steps of: 
 computing an initial power estimate for a first access attempt by one of the mobile stations;    transmitting from the MS-spread-spectrum transmitter of the one mobile station a spread-spectrum signal signifying a first attempt to utilize a random access channel, at a power level based on the initial power estimate;    receiving one or more access attempt signals relating to the random access channel at the BS-spread-spectrum receiver;    measuring the one or more access attempt signals received by the BS spread-spectrum receiver;    computing a closed loop power control symbol specifying an extent that power of the of measured one or more received access attempt signals differs from a target power;    broadcasting a control message containing the closed loop power control symbol from the BS-spread-spectrum receiver; and    if MS-spread-spectrum receiver of the one mobile station does not detect an acknowledgement responsive to the first access attempt of the one mobile station:    (a) receiving the broadcast control message and obtaining the closed loop power control symbol;    (b) processing a signal received from the base station in the MS-spread-spectrum receiver of the one mobile station to produce an open loop power control symbol specifying an extent of a change in power for uplink transmissions regarding the random access channel;    (c) generating a power control command as a function of both the closed loop power control symbol and the open loop power control symbol; and    transmitting from the MS-spread-spectrum transmitter of the one mobile station a spread-spectrum signal signifying a second attempt to utilize the random access channel, at a power level based on the power control command.    
   
   
       2 - 16 . (canceled)