Methods and apparatus for multi-carrier communication systems with adaptive transmission and feedback

Abstract

An arrangement is disclosed where in a multi-carrier communication system, the modulation scheme, coding attributes, training pilots, and signal power may be adjusted to adapt to channel conditions in order to maximize the overall system capacity and spectral efficiency without wasting radio resources or compromising error probability performance, etc.

What is claimed is: 
     
         1 . A mobile station served by a base station using Orthogonal Frequency Division Multiplexing (OFDM) and utilizing time slots in a time domain and subchannels in a frequency domain, the mobile station comprising:
 a receiver configured to receive a first control message indicating a pilot pattern out of a set of pilot patterns including a first pilot pattern and a second pilot pattern, wherein the first pilot pattern and the second pilot pattern have pilots in a same number of OFDM symbols, and further wherein the second pilot pattern has pilots in more subcarriers than the first pilot pattern; and   a transmitter configured to transmit channel quality information (CQI) to the base station;   wherein the receiver is further configured to:
 receive, in response to the transmitted CQI and in response to the indicated pilot pattern being the first pilot pattern, downlink data having pilots inserted using the first pilot pattern for a first multiple-input multiple-output (MIMO) stream; and 
 receive, in response to the transmitted CQI and in response to the indicated pilot pattern being the second pilot pattern, downlink data having pilots inserted using the second pilot pattern for a second MIMO stream. 
   
     
     
         2 . The mobile station of  claim 1 , wherein:
 all pilots of the first pilot pattern are present in a same subset of subcarriers in a subset of OFDM symbols and no pilots of the first pilot pattern are present in at least another subset of OFDM symbols, wherein the subset of OFDM symbols is different than the another subset of OFDM symbols, and   a first subset of pilots of the second pilot pattern are present in a same first subset of subcarriers in a first subset of OFDM symbols, wherein a second subset of pilots of the second pilot pattern are present in a same second subset of subcarriers in a second subset of OFDM symbols, wherein the first subset of subcarriers is different than the second subset of subcarriers, wherein the first subset of OFDM symbols is different than the second subset of OFDM symbols, and wherein no pilots of the second pilot pattern are present in at least some OFDM symbols.   
     
     
         3 . The mobile station of  claim 1 , wherein:
 the first pilot pattern has a set of subcarriers that have pilots, wherein a same number of pilots are located in each subcarrier of the set of subcarriers, and wherein each pilot of the number of pilots in each subcarrier is located in a same OFDM symbol as other pilots of the number of pilots that are located in other subcarriers of the set of subcarriers; and   the second pilot pattern has:
 a first set of pilots located in a first set of subcarriers and a first set of OFDM symbols; and 
 a second set of pilots located in a second set of subcarriers and a second set of OFDM symbols; 
   a same first number of pilots are located in each subcarrier of the first set of subcarriers, and wherein each pilot of the first number of pilots in each subcarrier of the first set of subcarriers is located in a same OFDM symbol as another pilot that is located in another subcarrier of the first set of subcarriers;   a same second number of pilots are located in each subcarrier of the second set of subcarriers, and wherein each pilot of the second number of pilots in each subcarrier of the second set of subcarriers is located in a same OFDM symbol as another pilot that is located in another subcarrier of the second set of subcarrier;   the first set of OFDM symbols are different than the second set of OFDM symbols; and   each OFDM symbol of the first set of OFDM symbols is spaced apart from each OFDM symbol of the second set of OFDM symbols by at least one symbol in time.   
     
     
         4 . The mobile station of  claim 1 , wherein a location for each pilot is defined by a specific subcarrier and a specific OFDM symbol, and further wherein:
 the first pilot pattern has pilots located in a first set of subcarriers and a first set of OFDM symbols, wherein the pilots of the first pilot pattern are located at all combinations of each of the first set of subcarriers with each of the first set of OFDM symbols; and   the second pilot pattern has pilots located in a second set of subcarriers and a second set of OFDM symbols, wherein the pilots of the second pilot pattern are located in a subset of all combinations of each of the second set of subcarriers with each of the second set of OFDM symbols.   
     
     
         5 . The mobile station of  claim 4 , wherein the first set of subcarriers consists of three non-adjacent subcarriers comprising a low subcarrier, middle subcarrier, and high subcarrier, wherein the middle subcarrier is separated from the high subcarrier and the low subcarrier by the same amount of subcarriers. 
     
     
         6 . The mobile station of  claim 5  wherein the low subcarrier is the second lowest subcarrier available to the first pilot pattern. 
     
     
         7 . The mobile station of  claim 4  wherein the first set of OFDM symbols includes a first OFDM symbol and a second OFDM symbol, where the first OFDM symbol and the second OFDM symbol are non-adjacent and separated from each other by a single OFDM symbol. 
     
     
         8 . The mobile station of  claim 4  wherein the first OFDM symbol in time of the second set of OFDM symbols has pilots on three non-adjacent subcarriers that comprise a first subcarrier, a second subcarrier, and a third subcarrier, wherein the second subcarrier is separated from both the first subcarrier and the third subcarrier by three subcarriers. 
     
     
         9 . The mobile station of  claim 8  wherein the second OFDM symbol in time of the second set of OFDM symbols has pilots on non-adjacent subcarriers, where the non-adjacent subcarriers of the second OFDM symbol do not overlap with the first subcarrier, second subcarrier, or third subcarrier used for pilots in the first OFDM symbol. 
     
     
         10 . The mobile station of  claim 9  wherein the non-adjacent subcarriers of the second OFDM symbol comprise a first non-adjacent subcarrier and a second non-adjacent subcarrier, wherein:
 the first non-adjacent subcarrier of the second OFDM symbol is located between the first and second subcarriers used for pilots in the first OFDM symbol; and 
 the second non-adjacent subcarrier of the second OFDM symbol is located between the third and second subcarriers used for pilots in the first OFDM symbol. 
 
     
     
         11 . The mobile station of  claim 10  wherein:
 the first non-adjacent subcarrier of the second OFDM symbol is separated from the first and second subcarriers used for pilots in the first OFDM symbol by a single subcarrier; and 
 the second non-adjacent subcarrier of the second OFDM symbol is separated from the third and second subcarriers used for pilots in the first OFDM symbol by a single subcarrier. 
 
     
     
         12 . The mobile station of  claim 11  wherein the third OFDM symbol in time of the second set of OFDM symbols has a pilot on the second subcarrier used for pilots in the first OFDM symbol. 
     
     
         13 . The mobile station of  claim 12  wherein the fourth OFDM symbol in time of the second set of OFDM symbols has the same amount of pilots as the second OFDM symbol and the pilots in the fourth OFDM symbol are located on the same subcarriers as the pilots in the second OFDM symbol. 
     
     
         14 . The mobile station of  claim 13  wherein pilots of the second pilot pattern that are transmitted on the same subcarrier are spaced apart by three or more OFDM symbols. 
     
     
         15 . The mobile station of  claim 1  wherein the CQI is provided on a subchannel basis. 
     
     
         16 . The mobile station of  claim 1  wherein the received downlink data has a modulation and coding scheme (MCS) based on the transmitted CQI. 
     
     
         17 . The mobile station of  claim 16  wherein a modulation of the MCS was selected from a set including QPSK, 16QAM and 64QAM. 
     
     
         18 . The mobile station of  claim 17  wherein each modulation in the set has a plurality of code rates and a code rate of the MCS was selected from the plurality of code rates for the modulation of the MCS. 
     
     
         19 . The mobile station of  claim 1 , wherein the pilot pattern specifies locations of pilots on a time-frequency grid, and wherein the time-frequency grid includes more OFDM symbols than subcarriers and the time-frequency grid includes at least 10 OFDM symbols and at least 9 subcarriers. 
     
     
         20 . A base station using Orthogonal Frequency Division Multiplexing (OFDM) and utilizing time slots in a time domain and subchannels in a frequency domain, the base station serving a mobile station and comprising:
 a transmitter configured to transmit a first control message to the mobile station indicating a pilot pattern out of a set of pilot patterns including a first pilot pattern and a second pilot pattern, wherein the first pilot pattern and the second pilot pattern have pilots in a same number of OFDM symbols, and further wherein the second pilot pattern has pilots in more subcarriers than the first pilot pattern; and   a receiver configured to receive channel quality information (CQI) from the mobile station;   wherein the transmitter is further configured to:
 transmit, in response to the received CQI and in response to the indicated pilot pattern being the first pilot pattern, downlink data having pilots inserted using the first pilot pattern for a first multiple-input multiple-output (MIMO) stream; and 
 transmit, in response to the received CQI and in response to the indicated pilot pattern being the second pilot pattern, downlink data having pilots inserted using the second pilot pattern for a second MIMO stream. 
   
     
     
         21 . The base station of  claim 20 , wherein:
 all pilots of the first pilot pattern are present in a same subset of subcarriers in a subset of OFDM symbols and no pilots of the first pilot pattern are present in at least another subset of OFDM symbols, wherein the subset of OFDM symbols is different than the another subset of OFDM symbols, and   a first subset of pilots of the second pilot pattern are present in a same first subset of subcarriers in a first subset of OFDM symbols, wherein a second subset of pilots of the second pilot pattern are present in a same second subset of subcarriers in a second subset of OFDM symbols, wherein the first subset of subcarriers is different than the second subset of subcarriers, wherein the first subset of OFDM symbols is different than the second subset of OFDM symbols, and wherein no pilots of the second pilot pattern are present in at least some OFDM symbols.   
     
     
         22 . The base station of  claim 20 , wherein:
 the first pilot pattern has a set of subcarriers that have pilots, wherein a same number of pilots are located in each subcarrier of the set of subcarriers, and wherein each pilot of the number of pilots in each subcarrier is located in a same OFDM symbol as other pilots of the number of pilots that are located in other subcarriers of the set of subcarriers; and   the second pilot pattern has:
 a first set of pilots located in a first set of subcarriers and a first set of OFDM symbols; and 
 a second set of pilots located in a second set of subcarriers and a second set of OFDM symbols; 
   a same first number of pilots are located in each subcarrier of the first set of subcarriers, and wherein each pilot of the first number of pilots in each subcarrier of the first set of subcarriers is located in a same OFDM symbol as another pilot that is located in another subcarrier of the first set of subcarriers;   a same second number of pilots are located in each subcarrier of the second set of subcarriers, and wherein each pilot of the second number of pilots in each subcarrier of the second set of subcarriers is located in a same OFDM symbol as another pilot that is located in another subcarrier of the second set of subcarrier;   the first set of OFDM symbols are different than the second set of OFDM symbols; and   each OFDM symbol of the first set of OFDM symbols is spaced apart from each OFDM symbol of the second set of OFDM symbols by at least one symbol in time.   
     
     
         23 . The base station of  claim 20 , wherein a location for each pilot is defined by a specific subcarrier and a specific OFDM symbol, and further wherein:
 the first pilot pattern has pilots located in a first set of subcarriers and a first set of OFDM symbols, wherein the pilots of the first pilot pattern are located at all combinations of each of the first set of subcarriers with each of the first set of OFDM symbols; and   the second pilot pattern has pilots located in a second set of subcarriers and a second set of OFDM symbols, wherein the pilots of the second pilot pattern are located in a subset of all combinations of each of the second set of subcarriers with each of the second set of OFDM symbols.   
     
     
         24 . The base station of  claim 23 , wherein the first set of subcarriers consists of three non-adjacent subcarriers comprising a low subcarrier, middle subcarrier, and high subcarrier, wherein the middle subcarrier is separated from the high subcarrier and the low subcarrier by the same amount of subcarriers. 
     
     
         25 . The base station of  claim 24  wherein the low subcarrier is the second lowest subcarrier available to the first pilot pattern. 
     
     
         26 . The base station of  claim 23  wherein the first set of OFDM symbols includes a first OFDM symbol and a second OFDM symbol, where the first OFDM symbol and the second OFDM symbol are non-adjacent and separated from each other by a single OFDM symbol. 
     
     
         27 . The base station of  claim 23  wherein the first OFDM symbol in time of the second set of OFDM symbols has pilots on three non-adjacent subcarriers that comprise a first subcarrier, a second subcarrier, and a third subcarrier, wherein the second subcarrier is separated from both the first subcarrier and the third subcarrier by three subcarriers. 
     
     
         28 . The base station of  claim 27  wherein the second OFDM symbol in time of the second set of OFDM symbols has pilots on non-adjacent subcarriers, where the non-adjacent subcarriers of the second OFDM symbol do not overlap with the first subcarrier, second subcarrier, or third subcarrier used for pilots in the first OFDM symbol. 
     
     
         29 . The base station of  claim 28  wherein the non-adjacent subcarriers of the second OFDM symbol comprise a first non-adjacent subcarrier and a second non-adjacent subcarrier, wherein:
 the first non-adjacent subcarrier of the second OFDM symbol is located between the first and second subcarriers used for pilots in the first OFDM symbol; and 
 the second non-adjacent subcarrier of the second OFDM symbol is located between the third and second subcarriers used for pilots in the first OFDM symbol. 
 
     
     
         30 . The base station of  claim 29  wherein:
 the first non-adjacent subcarrier of the second OFDM symbol is separated from the first and second subcarriers used for pilots in the first OFDM symbol by a single subcarrier; and 
 the second non-adjacent subcarrier of the second OFDM symbol is separated from the third and second subcarriers used for pilots in the first OFDM symbol by a single subcarrier. 
 
     
     
         31 . The base station of  claim 30  wherein the third OFDM symbol in time of the second set of OFDM symbols has a pilot on the second subcarrier used for pilots in the first OFDM symbol. 
     
     
         32 . The base station of  claim 31  wherein the fourth OFDM symbol in time of the second set of OFDM symbols has the same amount of pilots as the second OFDM symbol and the pilots in the fourth OFDM symbol are located on the same subcarriers as the pilots in the second OFDM symbol. 
     
     
         33 . The base station of  claim 32  wherein pilots of the second pilot pattern that are transmitted on the same subcarrier are spaced apart by three or more OFDM symbols. 
     
     
         34 . The base station of  claim 20  wherein the CQI is received on a subchannel basis. 
     
     
         35 . The base station of  claim 20  wherein the transmitted downlink data has a modulation and coding scheme (MCS) based on the received CQI. 
     
     
         36 . The base station of  claim 35  wherein a modulation of the MCS is selected from a set including QPSK, 16QAM and 64QAM. 
     
     
         37 . The base station of  claim 36  wherein each modulation in the set has a plurality of code rates and a code rate of the MCS is selected from the plurality of code rates for the modulation of the MCS. 
     
     
         38 . The base station of  claim 20 , wherein the pilot pattern specifies locations of pilots on a time-frequency grid, and wherein the time-frequency grid includes more OFDM symbols than subcarriers and the time-frequency grid includes at least 10 OFDM symbols and at least 9 subcarriers.