Systems and methods for high rate OFDM communications using first and second cyclic prefix lengths
Messages transmitted between a receiver and a transmitter are used to maximize a communication data rate. In particular, a multicarrier modulation system uses messages that are sent from the receiver to the transmitter to exchange one or more sets of optimized communication parameters. The transmitter then stores these communication parameters and when transmitting to that particular receiver, the transmitter utilizes the stored parameters in an effort to maximize the data rate to that receiver. Likewise, when the receiver receives packets from that particular transmitter, the receiver can utilize the stored communication parameters for reception.
1. A communications system comprising an OFDM transceiver capable of:
transmitting or receiving, over a first communication channel using a first cyclic prefix length, a first plurality of OFDM symbols that carry data bytes;
detecting a change in one or more channel conditions; and
transmitting or receiving, over a second communication channel using a second cyclic prefix length, a second plurality of OFDM symbols that carry data bytes;
wherein:
the first cyclic prefix length is shorter than the second cyclic prefix length,
the first communication channel has a shorter impulse response length than the second communication channel,
the first cyclic prefix length is based on a length of an impulse response for the first communication channel, and
the second cyclic prefix length is based on a length of an impulse response for the second communication channel.
2. The system of claim 1 , wherein a message or a management frame indicates the length of the cyclic prefix.
3. The system of claim 1 , wherein a SIGNAL field indicates the length of the cyclic prefix.
4. The system of claim 1 , wherein the transceiver selects the length of the cyclic prefix.
5. The system of claim 1 , wherein a second transceiver selects the length of the cyclic prefix.
6. The system of claim 1 , wherein the transceiver is a wireless 802.11a or a 802.11g transceiver.
7. In an OFDM transceiver, a method comprising:
transmitting or receiving, over a first communication channel using a first cyclic prefix length, a first plurality of OFDM symbols that carry data bytes;
detecting a change in one or more channel conditions; and
transmitting or receiving, over a second communication channel using a second cyclic prefix length, a second plurality of OFDM symbols that carry data bytes,
wherein:
the first cyclic prefix length is shorter than the second cyclic prefix length,
the first communication channel has a shorter impulse response length than the second communication channel,
the first cyclic prefix length is based on the length of an impulse response for the first communication channel, and
the second cyclic prefix length is based on the length of the impulse response for the second communication channel.
8. The method of claim 7 , wherein a message or a management frame indicates the length of the cyclic prefix.
9. The method of claim 7 , wherein a SIGNAL field indicates the length of the cyclic prefix.
10. The method of claim 7 , further comprising selecting, by the transceiver, the length of the cyclic prefix.
11. The method of claim 7 , further comprising selecting, by a second transceiver, the length of the cyclic prefix.
12. The method of claim 7 , wherein the transceiver is a wireless 802.11 a or a 802.11g transceiver.
13. A communications system comprising an OFDM transceiver capable of:
transmitting or receiving, over a first communication channel using a first cyclic prefix length, a first plurality of OFDM symbols that carry data bytes; and
changing from a first data rate to a second data rate by transmitting or receiving, over a second communication channel using a second cyclic prefix length, a second plurality of OFDM symbols that carry data bytes,
wherein:
the first cyclic prefix length is shorter than the second cyclic prefix length,
the first communication channel has a shorter impulse response length than the second communication channel,
the first cyclic prefix length is based on the length of impulse response of the first communication channel, and
the second cyclic prefix length is based on the length of the impulse response of the second communication channel.
14. The system of claim 13 , wherein a message or a management frame indicates the length of the cyclic prefix.
15. The system of claim 13 , wherein a SIGNAL field indicates the length of the cyclic prefix.
16. The system of claim 13 , wherein the transceiver selects the length of the cyclic prefix.
17. The system of claim 13 , wherein a second transceiver selects the length of the cyclic prefix.
18. The system of claim 13 , wherein the transceiver is a wireless 802.11a or a 802.11g transceiver.
19. In an OFDM transceiver, a method comprising:
transmitting or receiving, over a first communication channel using a first cyclic prefix length, a first plurality of OFDM symbols that carry data bytes; and
changing from a first data rate to a second data rate by transmitting or receiving, over a second communication channel using a second cyclic prefix length, a second plurality of OFDM symbols that carry data bytes,
wherein:
the first cyclic prefix length is shorter than the second cyclic prefix length,
the first communication channel has a shorter impulse response length than the second communication channel,
the first cyclic prefix length is based on the length of impulse response of the first communication channel, and
the second cyclic prefix length is based on the length of the impulse response of the second communication channel.
20. The method of claim 19 , wherein a message or a management frame indicates the length of the cyclic prefix.
21. The method of claim 19 , wherein a SIGNAL field indicates the length of the cyclic prefix.
22. The method of claim 19 , further comprising selecting, by the transceiver, the length of the cyclic prefix.
23. The method of claim 19 , further comprising selecting, by a second transceiver, the length of the cyclic prefix.
24. The method of claim 19 , wherein the transceiver is a wireless 802.11a or a 802.11g transceiver.