Method for modulation and coding scheme selection and related network nodes and terminal devices

Abstract

This disclosure provides a method, performed in a modulation and coding scheme, MCS module of a network node, for modulation and coding scheme, MCS, selection for a link between the network node and a terminal device in an orthogonal frequency division multiple access, OFDMA, based system. The OFDMA-based system provides a plurality of sub-carriers. The method comprises obtaining channel quality indicators for the plurality of sub-carriers, and estimating a link quality over a bandwidth corresponding to the plurality of sub-carriers based on the obtained channel quality indicators. The method comprises selecting a sub-carrier out of the plurality of sub-carriers as a new sub-carrier to be used for a communication to/from the terminal device based on the determined link quality. The method comprises selecting a MCS for the new sub-carrier; and transmitting information to the terminal device, the information comprising an indication of a new sub-carrier to the terminal device.

1 . A method, performed in a modulation and coding scheme, scheme (MCS) module of a network node, for MCS selection for a link between the network node and a terminal device in an orthogonal frequency division multiple access (OFDMA) based system, providing a plurality of sub-carriers, the method comprising:
 obtaining channel quality indicators for the plurality of sub-carriers;   estimating a link quality over a bandwidth corresponding to the plurality of sub-carriers based on the obtained channel quality indicators;   selecting a sub-carrier out of the plurality of sub-carriers as a new sub-carrier to be used for a communication to/from the terminal device based on the determined link quality;   selecting a MCS for the new sub-carrier where the change of MCS is at least partly based on the difference in channel quality on the previously used sub-carriers and the sub-carriers to be used for the current packet; and   transmitting information to the terminal device, the information comprising an indication of a new sub-carrier to the terminal device.   
     
     
         2 . The method according to  claim 1 , the method further comprising using the selected MCS for the new sub-carrier to the terminal device. 
     
     
         3 . The method according to  claim 1 , wherein the information further comprises an indication of a new sub-carrier from the terminal device; and the selected MCS for the new sub-carrier from the terminal device. 
     
     
         4 . The method according to  claim 1 , wherein obtaining channel quality indicators involves receiving from the terminal device a channel quality information of a sub-carrier on which the terminal device transmits or receives, and/or on sub-carriers assigned to other terminal devices. 
     
     
         5 . The method according to  claim 4 , wherein the channel quality information includes a recommended MCS for sub-carriers on which the network node transmits and/or for the sub-carriers assigned to other terminal devices. 
     
     
         6 . The method according to  claim 5 , wherein the channel quality information from the terminal device for sub-carriers assigned to other terminal devices uses an index offset value related to the modulation and coding scheme on the same sub-carrier. 
     
     
         7 . The method according to  claim 4 , wherein the channel quality information includes information about noise limitation or information about interference limitation. 
     
     
         8 . The method according to  claim 7 , wherein, selecting an MCS comprising selecting a less robust MCS when the link is interference limited, and wherein selecting an MCS comprising selecting a more robust MCS when the link is noise limited. 
     
     
         9 . The method according to  claim 8 , wherein selecting a sub-carrier comprises changing sub-carriers for a plurality of terminal devices subjected to different interference limitations, and scheduling a first terminal device of the plurality of terminal devices, which is subjected to a relatively higher interference limitation, on a sub-carrier that has more favorable channel conditions, and adapted with less robust MCS. 
     
     
         10 . The method according to  claim 1 , wherein obtaining channel quality indicators further comprises performing implicit channel sounding by measuring interleaved pilots contained in an acknowledgement (ACK) frame. 
     
     
         11 . The method according to  claim 1 , wherein the estimated link quality comprises a signal to noise ratio (SNR), a channel gain, and/or a SNR-MCS mapping table, wherein selecting the MCS is performed using the SNR-MCS mapping table. 
     
     
         12 . A method, performed in a terminal device, for a modulation and coding scheme (MCS) selection in a link between a network node and the terminal device in an orthogonal frequency division multiple access (OFDMA) based system, providing a plurality of sub-carriers, the method comprising:
 measuring a channel quality information for the plurality of sub-carriers on which the terminal device transmits and/or receives, and/or on the sub-carriers assigned to other terminal devices;   determining a channel quality indicator for the plurality of sub-carriers based on the measured channel quality information;   determining, based on the channel quality information, a MCS recommendation to be used on a currently used sub-carrier to the network node and/or on at least one other sub-carrier to the network node; and   transmitting the determined MCS recommendation and/or the determined plurality of channel quality indicators to the network node.   
     
     
         13 . The method according to  claim 12 , the method further comprising receiving information from the network node, the information comprising an indication of a new sub-carrier to the network node. 
     
     
         14 . The method according to  claim 13 , the method further comprising transmitting to the network node on the new sub-carrier indicated in the received information using the determined MCS recommendation corresponding to the new sub-carrier as MCS for the new sub-carrier. 
     
     
         15 . The method according to  claim 12 , wherein the channel quality information includes information about noise limitation or information about interference limitation. 
     
     
         16 . The method according to  claim 15 , wherein, when the link is interference limited, determining, based on the channel quality information, a MCS recommendation comprises selecting a less robust MCS than a MCS currently used, while when the link is noise limited, determining, based on the channel quality information, a MCS recommendation comprises selecting a more robust MCS than the MCS currently used. 
     
     
         17 . The method according to  claim 1 , wherein measuring channel quality information further comprises performing implicit channel sounding by measuring interleaved pilots contained in an ACK frame. 
     
     
         18 . A network node for modulation and coding scheme (MCS) selection for a link between the network node and a terminal device in an orthogonal frequency division multiple access (OFDMA) based system, providing a plurality of sub-carriers, the network node comprising an interface, a memory module, and a MCS module, wherein the MCS module is configured to:
 obtain channel quality indicators for the plurality of sub-carriers;   estimate a link quality over a bandwidth corresponding to the plurality of sub-carriers based on the obtained channel quality indicators;   select a sub-carrier out of the plurality of sub-carriers as a new sub-carrier to be used for the communication to/from the terminal device based on the determined link quality;   select a MCS for the new sub-carrier;   transmit information to the terminal device, the information comprising an indication of a new sub-carrier to the terminal device.   
     
     
         19 . The network node according to  claim 18 , wherein the MCS module is configured to transmit further information to the terminal device, the further information comprising an indication of a new sub-carrier from the terminal device and the selected MCS for the new sub-carrier from the terminal device. 
     
     
         20 . The network node according to  claim 18 , wherein the MCS module is configured to obtain channel quality indicators by receiving from the terminal device a channel quality information for sub-carriers on which the terminal device transmits or receives, and/or on sub-carriers assigned to other terminal devices. 
     
     
         21 . The network node according to  claim 20 , wherein the channel quality information includes information about noise limitation or information about interference limitation. 
     
     
         22 . The network node according to  claim 21 , wherein, when the link is interference limited, the MCS module is configured to select a less robust MCS than a MCS currently used, while when the link is noise limited, the MCS module is configured to a more robust MCS than the MCS currently used. 
     
     
         23 . The network node according to  claim 22 , wherein the MCS module is configured to change sub-carriers for a plurality of terminal devices subjected to different interference limitations, and to schedule a first terminal device of the plurality of terminal devices, which is subjected to a relatively higher interference limitation, in a sub-carrier that has more favorable channel conditions, and adapted with less robust MCS. 
     
     
         24 . A terminal device for a modulation and coding scheme (MCS) selection in a link between a network node and the terminal device in an orthogonal frequency division multiple access (OFDMA) system, being configured with a plurality of sub-carriers, the terminal device comprises an interface, a memory module, a processing unit configured to:
 measure a channel quality information for the plurality of sub-carriers on which the terminal device transmits and/or receives, and/or on the sub-carriers assigned to other terminal devices;   determine a plurality of channel quality indicators for the plurality of sub-carriers based on the measured channel quality information;   determine, based on the channel quality information, a MCS, recommendation to be used on a currently used sub-carrier to the network node and/or on the other sub-carriers to the network node; and   transmit the determined MCS recommendation and/or the determined plurality of channel quality indicators to the network node.   
     
     
         25 . A nontransitory computer-readable storage medium comprising a computer program product for selecting a modulation and coding scheme (MCS), the computer program product comprising program code adapted to perform, when executed on a MCS module of a network node, the steps of a method for MCS selection for a link between the network node and a terminal device in an orthogonal frequency division multiple access (OFDMA) based system, providing a plurality of sub-carriers, the method comprising:
 obtaining channel quality indicators for the plurality of sub-carriers;   estimating a link quality over a bandwidth corresponding to the plurality of sub-carriers based on the obtained channel quality indicators;   selecting a sub-carrier out of the plurality of sub-carriers as a new sub-carrier to be used for a communication to/from the terminal device based on the determined link quality;   selecting a MCS for the new sub-carrier where the change of MCS is at least partly based on the difference in channel quality on the previously used sub-carriers and the sub-carriers to be used for the current packet; and   transmitting information to the terminal device, the information comprising an indication of a new sub-carrier to the terminal device.   
     
     
         26 . A nontransitory computer-readable storage medium comprising a computer program product for selecting a modulation and coding scheme (MCS), the computer program product comprising program code adapted to perform, when executed on a processing unit of a terminal, device, a method for selecting a MCS in a link between a network node and the terminal device in an orthogonal frequency division multiple access (OFDMA) based system, providing a plurality of sub-carriers, the method comprising:0
 measuring a channel quality information for the plurality of sub-carriers on which the terminal device transmits and/or receives, and/or on the sub-carriers assigned to other terminal devices;   determining a channel quality indicator for the plurality of sub-carriers based on the measured channel quality information;   determining, based on the channel quality information, a MCS recommendation to be used on a currently used sub-carrier to the network node and/or on at least one other sub-carrier to the network node; and   transmitting the determined MCS recommendation and/or the determined plurality of channel quality indicators to the network node.