OFDM system and method employing OFDM symbols with known or information-containing prefixes
Systems and methods for transmitting and receiving OFDM symbols are provided which enable the otherwise wasted transmission time normally used as a prefix for each OFDM symbol to contain useful information. At the receiver, the received signal is processed to convert received OFDM symbols from a linear convolution with the channel to a cyclic convolution.
1. A method comprising:
transmitting a signal comprising a non-OFDM segment containing known and/or unknown highly reliable data and an OFDM data segment before and/or after the non-OFDM segment by transmitting a slot structure comprising in sequence:
a first data segment;
a first non-OFDM segment containing known data and/or unknown highly reliable data;
at least one second data segment;
a second non-OFDM segment containing known data and/or unknown highly reliable data;
a third data segment;
wherein at least one of the data segments is an OFDM data segment and at least one of the data segments is a CDMA data segment.
2. The method of claim 1 wherein the at least one second data segment comprises two second data segments.
3. The method of claim 2 wherein each slot is 2048 chips in duration, each of the data segments is 400 chips in duration, and each of the first and second non-OFDM segments is 224 chips in duration.
4. The method of claim 1 wherein each non-OFDM segment comprises a 64 chip MAC segment, a 96 chip pilot segment and a 64 chip MAC segment in sequence.
5. The method of claim 3 wherein each non-OFDM segment comprises a 64 chip MAC segment, a 96 chip pilot segment and a 64 chip MAC segment in sequence.
6. The method of claim 1 wherein in each slot, the first and third data segments are CMDA data segments, the at least one second data segment comprises at least one OFDM data segment.
7. The method of claim 6 wherein each slot is 2048 chips in duration, each of the data segments is 400 chips in duration, and each of the first and second non-OFDM segments is 224 chips in duration.
8. The method of claim 7 wherein each non-OFDM segment comprises a 64 chip MAC segment, a 96 chip pilot segment and a 64 chip MAC segment in sequence.
9. A transmitter comprising:
a first transmit antenna;
OFDM signal generating circuitry for generating OFDM symbols for transmission;
non-OFDM signal generating circuitry for generating non-OFDM segments;
wherein the OFDM signal generating circuitry and the non-OFDM signal generating circuitry transmit a signal comprising a non-OFDM segment containing known and/or unknown highly reliable data and an OFDM data segment before and/or after the non-OFDM segment by transmitting a slot structure comprising in sequence:
a first data segment;
a first non-OFDM segment containing known data and/or unknown highly reliable data;
at least one second data segment;
a second non-OFDM segment containing known data and/or unknown highly reliable data;
a third data segment;
wherein at least one of the data segments is an OFDM data segment and at least one of the data segments is a CDMA data segment.
10. The transmitter of claim 9 wherein the at least one second data segment comprises two second data segments.
11. The transmitter of claim 10 wherein each slot is 2048 chips in duration, each of the data segments is 400 chips in duration, and each of the first and second non-OFDM segments is 224 chips in duration.
12. The transmitter of claim 9 wherein each non-OFDM segment comprises a 64 chip MAC segment, a 96 chip pilot segment and a 64 chip MAC segment in sequence.
13. The transmitter of claim 11 wherein each non-OFDM segment comprises a 64 chip MAC segment, a 96 chip pilot segment and a 64 chip MAC segment in sequence.
14. The transmitter of claim 9 wherein in each slot, the first and third data segments are CMDA data segments, the at least one second data segment comprises at least one OFDM data segment.
15. The transmitter of claim 14 wherein each slot is 2048 chips in duration, each of the data segments is 400 chips in duration, and each of the first and second non-OFDM segments is 224 chips in duration.
16. The transmitter of claim 15 wherein each non-OFDM segment comprises a 64 chip MAC segment, a 96 chip pilot segment and a 64 chip MAC segment in sequence.