Scheduling for non-real-time services in orthogonal frequency division multiplex (OFDM) systems

1. In a wireless orthogonal frequency division multiplexing (OFDM) communication system, a method of scheduling non-real time data transmissions to a plurality of users, the method comprising:

(a) allocating sub-carriers among the plurality of users based on normalized channel gain values; and

(b) allocating bits of data for transmission on the allocated sub-carriers based on incremental transmission cost values.

2. The method of claim 1 wherein the sub-carrier allocation step (a) further comprises:

(a1) determining a channel gain value for each user on each sub-carrier;

(a2) calculating a fairness value for each user in the OFDM system;

(a3) normalizing each user's determined channel gain values from step (a1) with said user's calculated fairness value from step (a2); and

(a4) allocating each sub-carrier to the one user with the highest normalized channel gain value on each said sub-carrier.

3. The method of claim 2 wherein the bit allocation step (b) further comprises:

(b1) determining a maximum allowable transmit power;

(b2) initializing a total allocated transmit power value and a total number of bits allocated for transmission value to zero;

(b3) calculating an incremental cost value for transmitting one bit of data to each user on each of the sub-carrier(s) allocated to said users;

(b4) allocating to the sub-carrier with the lowest incremental cost value one bit of data for transmission to the user to whom said sub-carrier was allocated;

(b5) increasing the total allocated transmit power value by a transmit power value required to transmit the allocated bit;

(b6) increasing the total number of bits allocated for transmission value by one; and

if the total allocated transmit power value of step (b5) is less than the maximum allowable transmit power of step (b1):

(b7) repeating steps (b3) through (b6).

4. The method of claim 3 wherein the incremental cost value is the additional power required to transmit one bit of a user's data on one of the sub-carrier(s) allocated to said user, multiplied by the user's fairness factor.

5. The method of claim 2 wherein each fairness value is a measure of system resources consumed by one user versus system resources consumed by the other users during a predetermined period of time.

6. The method of claim 2 wherein each fairness value is a ratio of a system performance metric experienced by a user over a predetermined period of time versus a system performance metric expected by the users over the period of time.

7. The method of claim 6 wherein the system performance metric is data throughput rate.

8. The method of claim 6 wherein the system performance metric is bit error rate (BER) or delay.

9. A base station configured to schedule non-real time data transmissions to a plurality of users in a wireless OFDM system, the base station comprising:

means capable of allocating sub-carriers among the plurality of users based on normalized channel gain values; and

means capable of allocating bits of data for transmission on the allocated sub-carriers based on incremental transmission cost values.

10. The base station of claim 9 further comprising:

means capable of determining a channel gain value for each user on each sub-carrier;

means capable of calculating a fairness value for each user in the OFDM system;

means capable of normalizing each user's determined channel gain values with said user's calculated fairness value; and

means capable of allocating each sub-carrier to the one user with the highest normalized channel gain value on each said sub-carrier.

11. The base station of claim 10 further comprising:

means capable of determining a maximum allowable transmit power;

means capable of initializing a total allocated transmit power value and a total number of bits allocated for transmission value to zero;

means capable of calculating an incremental cost value for transmitting one bit of data to each user on each of the sub-carrier(s) allocated to said users;

means capable of allocating to the sub-carrier with the lowest incremental cost value one bit of data for transmission to the user to whom said sub-carrier was allocated;

means capable of increasing the total allocated transmit power value by a transmit power value required to transmit the allocated bit; and

means capable of increasing the total number of bits allocated for transmission value by one.