Mixed mode preamble for MIMO wireless communications
View Patent ↗A preamble of a frame for a multiple input multiple output (MIMO) wireless communication for a first transmit antenna of the MIMO communication includes a legacy preamble portion in accordance with a legacy wireless communication protocol. The preamble of the frame for the MIMO wireless communication for the first transmit antenna also includes a current protocol preamble portion in accordance with a protocol of the MIMO wireless communication. The preamble of a frame for at least a second antenna of the MIMO communication includes a cyclically shifted legacy preamble portion for the frame. The preamble of the frame for the MIMO wireless communication for the second transmit antenna also includes a second current protocol preamble portion in accordance with a protocol of the MIMO wireless communication.
1. A method for generating a preamble of a frame for a multiple input multiple output (MIMO) wireless communication, the method comprises:
for a first transmit antenna of the MIMO communication:
generating a legacy preamble portion for the frame in accordance with a first legacy standard wireless communication protocol, wherein the legacy preamble portion includes at least a first training sequence and a second training sequence and a signal field, wherein the signal field is generated in accordance with the legacy wireless communication protocol and includes an indication of a duration of the frame; and
generating a current protocol preamble portion for the frame in accordance with a second current standard wireless communication protocol of the MIMO wireless communication;
for at least a second antenna of the MIMO communication:
generating a cyclically shifted legacy preamble portion for the frame, wherein the cyclically shifted legacy preamble portion includes a cyclically shifted first training sequence and a cyclically shifted second training sequence and a cyclically shifted signal field, wherein the cyclically shifted first training sequence the cyclically shifted second training sequence is time-shifted with respect to the first training sequence by a fraction of duration of the legacy preamble portion, and wherein the cyclically shifted second training sequence is time-shifted with respect to the second training sequence by the fraction of duration of the legacy preamble portion, and wherein the cyclically shifted signal field is in accordance with the legacy wireless communication protocol and includes the indication of the duration of the frame; and
generating a second current protocol preamble portion for the frame in accordance with the second current standard wireless communication protocol of the MIMO wireless communication.
2. The method of claim 1 wherein the cyclically shifted signal field is time-shifted with respect to the signal field by the fraction of duration of the legacy preamble portion.
3. The method of claim 1 further comprises:
generating a double guard interval between the first and second training sequences in accordance with the legacy wireless communication protocol; and
generating a second double guard interval between the first and second cyclically shifted training sequences in accordance with the legacy wireless communication protocol.
4. The method of claim 1 , wherein the fraction of the duration of the legacy preamble portion comprises at least one of, when the legacy wireless communication protocol is IEEE 802.11a or IEEE 802.11g:
a range of plus fifty nanoseconds to plus four hundred nanoseconds; and
a range of minus fifty nanoseconds to minus four hundred nanoseconds.
5. The method of claim 4 comprises:
the first training sequence including a short training sequence; and
the second training sequence including a long training sequence.
6. A radio frequency (RF) transmitter comprises:
a baseband processing module operably coupled to convert outbound data into outbound symbol streams; and
a transmitter section operably coupled to convert the outbound symbol streams into outbound RF signals, wherein the baseband processing module is operably coupled to:
for a first transmit antenna of the MIMO communication:
generate a legacy preamble portion for the frame in accordance with a legacy standard wireless communication protocol, wherein the legacy preamble portion includes at least a first training sequence and a second training sequence and a signal field, wherein the signal field is generated in accordance with the legacy wireless communication protocol and includes an indication of a duration of the frame; and
generate a current protocol preamble portion for the frame in accordance with a current standard wireless communication protocol of the MIMO wireless communication;
for at least a second antenna of the MIMO communication:
generate a cyclically shifted legacy preamble portion for the frame, wherein the cyclically shifted legacy preamble portion includes a cyclically shifted first training sequence and a cyclically shifted second training sequence and a cyclically shifted signal field, wherein the cyclically shifted first training sequence is time-shifted with respect to the first training sequence by a fraction of duration of the legacy preamble portion, and wherein the cyclically shifted second training sequence is time-shifted with respect to the second training sequence by the fraction of duration of the legacy preamble portion, and wherein the cyclically shifted signal field is in accordance with the legacy wireless communication protocol and includes the indication of the duration of the frame; and
generate a second current protocol preamble portion for the frame in accordance with the current standard wireless communication protocol of the MIMO wireless communication.
7. The RF transmitter of claim 6 wherein the cyclically shifted signal field is time-shifted with respect to the signal field by the fraction of duration of the legacy preamble portion.
8. The RF transmitter of claim 6 , wherein the baseband processing module further functions to:
generate a double guard interval between the first and second training sequences in accordance with the legacy wireless communication protocol; and
generate a second double guard interval between the first and second cyclically shifted training sequences in accordance with the legacy wireless communication protocol.
9. The RF transmitter of claim 6 , wherein the fraction of the duration of the legacy preamble portion comprises at least one of, when the legacy wireless communication protocol is IEEE 802.11a or IEEE 802.11g:
a range of plus fifty nanoseconds to plus four hundred nanoseconds; and
a range of minus fifty nanoseconds to minus four hundred nanoseconds.
10. The RF transmitter of claim 9 comprises:
the first training sequence including a short training sequence; and
the second training sequence including a long training sequence.
11. The RF transmitter of claim 6 , wherein the legacy preamble portion is formatted in accordance with at least one of the following legacy wireless communication standards: GSM, IEEE 802.11(a), IEEE 802.11(b), IEEE 802.11(g), IEEE 802.11(j) and Bluetooth.
12. The RF transmitter of claim 11 , wherein the current protocol preamble portion for the frame is formatted in accordance with the IEEE 802.11(n) current wireless standard communication standard.