Smooth Hard Handover Method and Mobile Station Adapted For The Method

Abstract

A cellular radio communications system, method, mobile station, and base station for a smooth hard handover. Selected base stations prepare radio links for potential communication with a mobile station although only one radio link is actively used for transmission. A handover is then performed from the active radio link to one of the prepared radio links. The smooth hard handover is faster and more secure than a conventional hard handover, while requiring a less complex system architecture than a conventional soft handover.

1 - 18 . (canceled) 
     
     
         19 . A mobile station comprising:
 a receiver chain;   a transmitter chain;   wherein the receiver and transmitter chains are respectively adapted to receive and transmit radio signals over an exchangeable first radio link served by a first base station, characterized by further comprising:   a receiver chain controller that controls the receiver chain to prepare a second radio link for transceiving with a second base station, while communication continues on the first radio link, wherein the receiver chain is adapted to synchronize reception to the second base station by receiving the control information from the second radio base station over a control channel.   
     
     
         20 . The mobile station according to  claim 19 , wherein the receiver chain controller controls the receiver chain to prepare the second radio channel in response to a command received over the first radio link. 
     
     
         21 . The mobile station according to  claim 19 , wherein the receiver chain controller is adapted to select the second base station for the preparation of the second radio link based on measurements made by the mobile station on the signal strengths received from base stations neighboring the first base station. 
     
     
         22 . The mobile station according to  claim 19 , wherein the receiver chain is adapted to receive user data over the first and second radio links in parallel when the user data on the two radio links are different. 
     
     
         23 . The mobile station according to  claim 19 , wherein the receiver chain includes:
 a receiver unit that receives radio signals;   a descrambling and demultiplexing unit having an input from the receiver unit and adapted to descramble and demultiplex the first and the second radio links in parallel and to output the descrambled and demultiplexed first and second radio links separately;   a demodulation, de-spreading, and channel decoding unit having at least one input from the descrambling and demultiplexing unit that separately receives the first and second radio links and demodulates, de-spreads, and channel decodes dedicated data channels received on the first and second radio links, respectively, and provides on at least one output, base band signals of the dedicated data channels received on the first and second radio links; and   a radio link control processor unit with at least one input from the demodulation, de-spreading, and channel decoding unit that separately receives the base band signals of the data channels received on the first and second radio links, respectively, and receives control commands and forwards a command regarding the preparation of the second radio link to the receiver chain controller.   
     
     
         24 - 26 . (canceled) 
     
     
         27 . A handover method performed by a mobile station having a receiver chain and a transmitter chain, each adapted to receive and transmit radio signals over an exchangeable first radio link served by a first base station, the method comprising the steps of:
 preparing by the receiver chain, a second radio link for transceiving with a second base station while communication continues on the first radio link; and   synchronizing by the receiver chain, reception to the second base station by receiving the control information from the second radio base station over a control channel.   
     
     
         28 . The handover method according to  claim 27 , wherein a receiver chain controller controls the receiver chain to prepare the second radio link in response to a command received over the first radio link. 
     
     
         29 . The handover method according to  claim 27 , wherein the step of preparing the second radio link includes selecting the second base station by the receiver chain controller based on measurements made by the mobile station on the signal strengths received from base stations neighboring the first base station. 
     
     
         30 . The handover method according to  claim 27 , wherein the step of preparing the second radio link for transceiving with a second base station while communication continues on the first radio link includes receiving user data over the first and second radio links in parallel when the user data on the two radio links are different. 
     
     
         31 . The handover method according to  claim 30 , wherein the step of receiving user data over the first and second radio links in parallel includes:
 receiving the radio signals over the first and second radio links by a receiver unit;   forwarding the received radio signals to a descrambling and demultiplexing unit;   descrambling and demultiplexing the first and the second radio links in parallel;   forwarding the descrambled and demultiplexed first and second radio links separately to a demodulation, de-spreading, and channel decoding unit;   demodulating, de-spreading, and channel decoding dedicated data channels received on the first and second radio links, respectively;   separately forwarding to a radio link control processor unit, base band signals of the dedicated data channels received on the respectively first and second radio links; and   forwarding to the receiver chain controller, a command from the radio link control processor unit regarding the preparation of the second radio link to the receiver chain controller.