Method, System and Device for Switching a Transmission Time Interval

Abstract

A method and system for synchronized switching of a Transmission Time Interval (TTI) between at least two different TTI length values. A UE transmitting a power report, where a control node or a Base Station evaluates the report and decides, based on the evaluation, to order the UE to switch to a different TTI length. The order message comprises the number of TTIs after which a TTI switch has to occur, composed a.o. based on radio environment condition. The UE receives a TTI switch order message and replies with a single message to its serving BS with a message to switch the TTI in a synchronous way.

1 . A method in a User Equipment (UE) for synchronized switching of a Transmission Time Interval (TTI) between at least two different TTI lengths, the method comprising:
 receiving a switching message indicating that the UE is to switch from using TTIs having a first length to using TTIs having a second length; and,   in response to said switching message, switching from using TTIs having the first length to using TTIs having the second length, after a predetermined number of TTIs.   
     
     
         2 . The method of  claim 1 , wherein the method further comprises transmitting a report comprising a measured received power, and wherein the switching message is received in response to the report. 
     
     
         3 . The method of  claim 1 , wherein the method further comprises, prior to receiving the switching message, receiving a network parameter indicating an applicable number of TTIs after which a switching of TTI length is to occur, and wherein the predetermined number of TTIs is the indicated applicable number of TTIs. 
     
     
         4 . The method of  claim 1 , wherein the UE is configured with multiple carriers in the downlink transmission and wherein at least two carriers, a primary and a secondary carrier, are activated, and wherein the switching message is received by the UE via the secondary carrier. 
     
     
         5 . The method of  claim 1 , wherein the switching message sent by a serving High Speed Downlink Shared Channel (HS-DSCH) cell or a secondary serving HS-DSCH cell, comprises a predetermined order mapping indicator indicating an order for switching a short TTI length to a long TTI length or vice versa. 
     
     
         6 . The method of  claim 1 , wherein the method further comprises starting a counter counting TTIs, the value of the counter indicating when transmission with the second TTI length commences. 
     
     
         7 . A method in a Base Station (BS) for synchronized switching of a Transmission Time Interval (TTI) between at least two different TTI length values, the method comprising:
 receiving, from a User Equipment (UE), a report comprising a measured received power;   evaluating the report and deciding, based on the evaluation, to order the UE to initialize a switching from a first TTI length to a second TTI length, by transmitting a switching message indicating that the UE is to switch from using TTIs having the first length to using TTIs having the second length; and,   after transmitting the switching message, switching, for communications with the UE, from using TTIs having the first length to using TTIs having the second length, after a predetermined number of TTIs.   
     
     
         8 . The method of  claim 7 , wherein the method further comprises, prior to transmitting the switching message, sending, to the UE, a network parameter indicating an applicable number of TTIs after which a switching of TTI length is to occur, and wherein the predetermined number of TTIs is the indicated applicable number of TTIs. 
     
     
         9 . The method of  claim 7 , wherein the UE is configured with multiple carriers in the downlink transmission and wherein at least two carriers, a primary and a secondary carrier, are activated, and wherein the switching message is sent by the BS via the secondary carrier. 
     
     
         10 . The method of  claim 7 , wherein the switching message, sent by a serving High Speed Downlink Shared Channel (HS-DSCH) cell or a secondary serving HS-DSCH cell, comprises a predetermined order mapping indicator indicating an order for switching a short TTI length to long TTI length or vice versa. 
     
     
         11 . A User Equipment (UE) for synchronized switching of a Transmission Time Interval (TTI) between at least two different TTI length values, the UE being configured to deploy an actual- and a different-TTI length value, the UE comprising:
 a processing circuit comprising a processor configured to process program instructions and a memory arranged to store the program instructions and network parameters; and   an interface circuit configured to communicate with a base station (BS);   wherein the processing circuit is configured to:   receive, via the interface circuit, a switching message indicating that the UE is to switch from using TTIs having a first length to using TTIs having a second length; and,   in response to said switching message, switch from using TTIs having the first length to using TTIs having the second length, after a predetermined number of TTIs.   
     
     
         12 . The UE of  claim 11 , wherein the processing circuit is further configured to control the interface circuit to transmit a report comprising a measured received power, and wherein the switching message is received in response to the report. 
     
     
         13 . The UE of  claim 11 , processing circuit is further configured to control the interface circuit to receive, prior to receiving the switching message, a network parameter indicating an applicable number of TTIs after which a switching of TTI length is to occur, and wherein the predetermined number of TTIs is the indicated applicable number of TTIs. 
     
     
         14 . The UE of  claim 11 , wherein the processing circuit is configured to receive the switching message via the secondary carrier when the UE is configured with multiple carriers in the downlink transmission and when at least two carriers, a primary carrier and the secondary carrier, are activated. 
     
     
         15 . The UE of  claim 11 , wherein the switching message sent by a serving High Speed Downlink Shared Channel (HS-DSCH) cell or a secondary serving HS-DSCH cell, comprises a predetermined order mapping indicator indicating an order for switching a short TTI length to a long TTI length or vice versa. 
     
     
         16 . The UE of  claim 11 , wherein the processing circuit is further configured to start a counter counting TTIs, the value of the counter indicating when transmission with the second TTI length commences. 
     
     
         17 . A Base Station (BS) for synchronized switching of a Transmission Time Interval (TTI) between at least two different TTI length values, the BS comprising:
 a processing circuit comprising a processor configured to process program instructions and a memory configured to store the program instructions and network parameters; and   an interface circuit configured to communicate with one or more User Equipments (UEs);   wherein the processing circuit is configured to:   receive a report message from a UE, the report message comprising a measured received power;   evaluate the report and decide, based on the evaluation, to order the UE to initialize a switching of an actual TTI length value to a different TTI length value, by transmitting a switching message indicating that the UE is to switch from using TTIs having the first length to using TTIs having the second length; and,   after transmitting the switching message, switch, for communications with the UE, from using TTIs having the first length to using Ills having the second length, after a predetermined number of Ills.   
     
     
         18 . The BS of  claim 17 , wherein the processing circuit is configured to send to the UE, prior to transmitting the switching message, a network parameter indicating an applicable number of TTIs after which a switching of TTI length is to occur, and wherein the predetermined number of TTIs is the indicated applicable number of TTIs. 
     
     
         19 . The BS of  claim 17 , wherein the processing circuit is configured to send the switching message via a secondary carrier, when the UE is configured with multiple carriers in the downlink transmission and at least two carriers, a primary carrier and the secondary carrier, are activated. 
     
     
         20 . The BS of  claim 17 , wherein the switching message, sent by a serving High Speed Downlink Shared Channel (HS-DSCH) cell or a secondary serving HS-DSCH cell, comprises a predetermined order mapping indicator indicating an order for switching a short TTI length to long TTI length or vice versa.