OFDM communication system with multiple OFDM symbol sizes
Techniques to use OFDM symbols of different sizes to achieve greater efficiency for OFDM systems. The system traffic may be arranged into different categories (e.g., control data, user data, and pilot data). For each category, one or more OFDM symbols of the proper sizes may be selected for use based on the expected payload size for the traffic in that category. For example, control data may be transmitted using OFDM symbols of a first size, user data may be transmitted using OFDM symbols of the first size and a second size, and pilot data may be transmitted using OFDM symbols of a third size or the first size. In one exemplary design, a small OFDM symbol is utilized for pilot and for transport channels used to send control data, and a large OFDM symbol and the small OFDM symbol are utilized for transport channels used to send user data.
1. A method of transmitting data in an orthogonal frequency division multiplexing (OFDM) communication system from a transmitter device to one or more receiver devices, comprising:
selecting a first number of one or more first OFDM symbols having a first data carrying capacity for carrying pilot data and a second number of one or more second OFDM symbols having a second data carrying capacity for carrying control data that is different from the first data carrying capacity, wherein the first OFDM symbols and second OFDM symbols have different symbol sizes;
selecting, based on a payload size of data intended for at least a first user and a second user, at least a third number of third OFDM symbols having a third data carrying capacity for user data intended for the first user and a fourth number of fourth OFDM symbols having a fourth data carrying capacity for user data intended for the second user, wherein the third OFDM symbols and fourth OFDM symbols have different symbol sizes; and
transmitting the data packet using the selected number of first OFDM symbols, the selected number of second OFDM symbols, the selected number of third OFDM symbols, and the selected number of fourth OFDM symbols,
wherein the control data transmitted on the second OFDM symbols comprises information about the third data carrying capacity and symbol size of the third OFDM symbols and the fourth data carrying capacity and symbol size of the fourth OFDM symbols.
2. The method of claim 1 , wherein the number of first OFDM symbols and the number of second OFDM symbols are selected to minimize an amount of excess data carrying capacity.
3. The method of claim 1 , wherein:
the OFDM communications system comprises a multiple-input multiple-output (MIMO) system; and
transmitting the data packet comprises transmitting the data packet using multiple antennas.
4. The method of claim 1 , wherein the third data carrying capacity of the third OFDM symbols and the fourth data carrying capacity of the fourth OFDM symbols are selected based, at least in part, on a category of data transmitted to the first and second users.
5. An apparatus for transmitting data in an orthogonal frequency division multiplexing (OFDM) communication system from a transmitter device to one or more receiver devices, comprising:
an OFDM modulator configured to select a first number of one or more first OFDM symbols having a first data carrying capacity for carrying pilot data and a second number of one or more second OFDM symbols having a second data carrying capacity for carrying control data that is different from the first data carrying capacity, wherein the first OFDM symbols and second OFDM symbols have different symbol sizes, and to select, based on a payload size of data intended for at least a first user and a second user, at least a third number of third OFDM symbols having a third data carrying capacity for user data intended for the first user and a fourth number of fourth OFDM symbols having a fourth data carrying capacity for user data intended for the second user, wherein the third OFDM symbols and fourth OFDM symbols have different symbol sizes; and
at least one transmitter configured to transmit the data packet using the selected number of first OFDM symbols, the selected number of second OFDM symbols, the selected number of third OFDM symbols, and the selected number of fourth OFDM symbols,
wherein the control data transmitted on the second OFDM symbols comprises information about the third data carrying capacity and symbol size of the third OFDM symbols and the fourth data carrying capacity and symbol size of the fourth OFDM symbols.
6. The apparatus of claim 5 , wherein the number of first OFDM symbols and the number of second OFDM symbols are selected to minimize an amount of excess data carrying capacity.
7. The apparatus of claim 5 , wherein:
the OFDM communications system comprises a multiple-input multiple-output (MIMO) system; and
the at least one transmitter is configured to transmit the data packet using multiple antennas.
8. The apparatus of claim 5 , wherein the OFDM modulator is configured to select the third data carrying capacity of the third OFDM symbols and the fourth data carrying capacity of the fourth OFDM symbols based, at least in part, on a category of data transmitted to the first and second users.
9. A program product for transmitting data in an orthogonal frequency division multiplexing (OFDM) communication system from a transmitter device to one or more receiver devices, comprising a non-transitory memory unit having codes stored thereon for:
selecting a first number of one or more first OFDM symbols having a first data carrying capacity for carrying pilot data and a second number of one or more second OFDM symbols having a second data carrying capacity for carrying control data that is different from the first data carrying capacity, wherein the first OFDM symbols and second OFDM symbols have different symbol sizes;
selecting, based on a payload size of data intended for at least a first user and a second user, at least a third number of third OFDM symbols having a third data carrying capacity for user data intended for the first user and a fourth number of fourth OFDM symbols having a fourth data carrying capacity for user data intended for the second user, wherein the third OFDM symbols and fourth OFDM symbols have different symbol sizes; and
transmitting the data packet using the selected number of first OFDM symbols, the selected number of second OFDM symbols, the selected number of third OFDM symbols, and the selected number of fourth OFDM symbols,
wherein the control data transmitted on the second OFDM symbols comprises information about the third data carrying capacity and symbol size of the third OFDM symbols and the fourth data carrying capacity and symbol size of the fourth OFDM symbols.
10. The program product of claim 9 , wherein the number of first OFDM symbols and the number of second OFDM symbols are selected to minimize an amount of excess data carrying capacity.
11. The program product of claim 9 , wherein:
the OFDM communications system comprises a multiple-input multiple-output system; and
transmitting the data packet comprises transmitting the data packet using multiple antennas.
12. The program product of claim 9 , wherein the third data carrying capacity of the third OFDM symbols and the fourth data carrying capacity of the fourth OFDM symbols are selected based, at least in part, on a category of data transmitted to the first and second users.