METHODS AND APPARATUS FOR MULTI-CARRIER COMMUNICATION SYSTEMS WITH ADAPTIVE TRANSMISSION AND FEEDBACK
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.
1 . A communication method employed by a transmitter in an Orthogonal Frequency Division Multiple Access (OFDMA) system, the method comprising:
receiving information characterizing a condition of a telecommunications channel;
selecting a modulation and coding scheme (MCS) for a transmission signal based on the received condition of the telecommunications channel;
selecting a training pilot pattern for the transmission signal from a plurality of distinctive training pilot patterns, wherein the training pilot pattern represents a number of training pilot symbols, amplitudes and phases of the training pilot symbols, and locations of the training pilot symbols in time, frequency, or space; and
transmitting the transmission signal in accordance with the selected MCS and training pilot pattern.
2 . The method of claim 1 , wherein the transmitter further selects the training pilot pattern based on the selected MCS.
3 . The method of claim 1 , wherein different training pilot patterns may be selected for the same selected MCSs.
4 . The method of claim 1 , wherein the transmitter further:
generates a single index value to reflect the selected MCS and the selected training pilot pattern;
generates a control information signal which conveys the selected single index value; and
transmits the control information signal.
5 . The method of claim 4 , wherein the transmitter generates the single index value from a look-up table and wherein the look-up table includes sets of an MCS and a training pilot pattern employed by the transmitter.
6 . The method of claim 1 , further comprising:
selecting a rate matching scheme having repetition or puncturing for the transmission signal, the rate matching scheme selected to maintain equal packet sizes in the transmission signal when an MCS is used with different pilot patterns.
7 . The method of claim 1 , wherein the transmission signal is transmitted using a spatial processing scheme or multiple antenna techniques.
8 . A communication method employed by a receiver in an Orthogonal Frequency Division Multiple Access (OFDMA) system, the method comprising:
receiving a signal;
measuring channel conditions, based on the received signal, wherein the measured channel conditions include: signal strength, average signal to interference plus noise ratio (SINR), variance in time, variance in frequency, variance in space, bit error rate (BER), frame error rate (FER), mean square error (MSE), or any combination thereof; and
transmitting channel quality information (CQI) reflecting the measured channel conditions to a transmitter, wherein the CQI is used by the transmitter to select a desired modulation and coding scheme (MCS) and a desired training pilot pattern out of a plurality of distinctive training pilot patterns.
9 . The method of claim 8 , wherein the receiver generates a CQI index value to reflect the CQI.
10 . The method of claim 9 , wherein the CQI index value is generated using a look-up table having sets of a modulation and coding scheme (MCS) and a training pilot pattern.
11 . The method of claim 10 , wherein the look-up table includes sets with the same MCS but different training pilot patterns.
12 . The method of claim 9 , wherein the CQI index value is transmitted to the transmitter using error protection or correction coding.
13 . The method of claim 12 , wherein the CQI index value is Gray coded.
14 . The method of claim 12 , wherein bits with higher significance in the CQI index value are protected with stronger error protection codes.
15 . The method of claim 8 , wherein multiple antenna techniques are used to receive the signal.
16 . The method of claim 8 , wherein the transmitted CQI is user-based or subchannel-based.
17 . The method of claim 8 , wherein the received signal is from the transmitter.
18 . The method of claim 8 , wherein the received signal is from a common broadcast signal or a data signal targeted to another receiver.