Method and apparatus for communicating symbols in a multiple input multiple output communication system using interleaved subcarriers across a plurality of antennas
A method and apparatus are provided for transmitting one or more symbols in a multiple antenna wireless communication system. Subcarriers from one or more symbols are interleaved across a plurality of antennas. The symbols may be, for example, long or short training symbols based on a single-antenna long or short training symbol, respectively, and wherein each subsequent subcarrier from the single-antenna training symbol is positioned in a training symbol for a logically adjacent antenna. One or more additional subcarriers may be inserted in at least one of the plurality of symbols to allow nulled subcarriers to be estimated using an interpolation-based channel estimation technique. The remaining portions of a header, as well as the data sequences of a packet, may also be diagonally loaded.
1. A method for transmitting one or more symbols in a multiple antenna wireless communication system, said method comprising the step of:
diagonally loading, utilizing one or more processors of said multiple antenna wireless communication system, subcarriers from said one or more symbols across a plurality of antennas in said multiple antenna wireless communication system, wherein said one or more symbols include at least one of:
long training symbols based on a single-antenna long training symbol, wherein each subsequent subcarrier from said single-antenna long training symbol is positioned in a long training symbol for a logically adjacent antenna; and
short training symbols based on a single-antenna short training symbol, wherein each subsequent subcarrier from said single-antenna short training symbol is positioned in a short training symbol for a logically adjacent antenna;
wherein a reduced number of subcarriers are inserted in said at least one of said plurality of long training symbols and wherein a first long training symbol and a second long training symbol are interchanged to position at least one non-nulled subcarrier on at least one side of a nulled subcarrier.
2. The method of claim 1 , wherein said single-antenna long training symbol is an 802.11 a/g long training symbol.
3. The method of claim 1 , wherein said single antenna short training symbol is an 802.11 a/g short training symbol.
4. The method of claim 1 , wherein said multiple antenna wireless communication system is a MIMO-OFDM system.
5. The method of claim 1 , further comprising the step of inserting one or more additional subcarriers in at least one of said plurality of symbols.
6. The method of claim 5 , where said one or more additional subcarriers are inserted to ensure that any subcarrier that was nulled by said diagonal loading is surrounded by subcarriers that are not nulled.
7. The method of claim 5 , where said one or more additional subcarriers allow nulled subcarriers to be estimated using an interpolation-based channel estimation technique.
8. The method of claim 1 , wherein said one or more symbols are a SIGNAL-field symbol.
9. The method of claim 8 , wherein said SIGNAL-field symbol includes a system type indicator.
10. The method of claim 1 , wherein a number of said long training symbols is a function of the number of transmitters.
11. The method of claim 1 , further comprising the steps of: diagonally loading a remainder of a header of a packet across said logically adjacent antennas; and diagonally loading data sequences of said packet across said logically adjacent antennas.
12. The method of claim 1 , wherein said plurality of antennas are logically adjacent.
13. The method of claim 1 , whereby a lower order receiver can interpret said transmitted diagonally loaded symbols as a normal OFDM frame.
14. A method for generating a plurality of long training symbols in a multiple antenna wireless communication system, said method comprising the step of:
diagonally loading, utilizing one or more processors of said multiple antenna wireless communication system, subcarriers from a single-antenna long training symbol across long training symbols associated with logically adjacent antennas in said multiple antenna wireless communication system, wherein each subsequent subcarrier from said single-antenna long training symbol is positioned in a long training symbol for a logically adjacent antenna;
nulling subcarriers in said plurality of long training symbols that are not diagonally loaded, utilizing said one or more processors of said multiple antenna wireless communication system; and
inserting at least one additional subcarrier, utilizing said one or more processors of said multiple antenna wireless communication system, to ensure that a nulled subcarrier has at least one subcarrier located on each side of said nulled subcarrier,
wherein said one or more additional inserted subcarriers ensures that any subcarrier that was nulled by being diagonally loaded is surrounded by subcarriers that are not nulled.
15. The method of claim 14 , wherein said single-antenna long training symbol is an 802.11 a/g long training symbol.
16. The method of claim 14 , where said at least one additional subcarrier allows nulled subcarriers to be estimated using an interpolation-based channel estimation technique.
17. The method of claim 14 , wherein a reduced number of subcarriers are inserted in at least one of said plurality of long training symbols and wherein a first long training symbol and a second long training symbol are interchanged to position at least one non-nulled subcarrier on at least one side of a nulled subcarrier.
18. A transmitter in a multiple antenna wireless communication system, comprising:
a plurality of transmit antennas,
wherein subcarriers of one or more symbols are diagonally loaded across logically adjacent antennas of said plurality of transmit antennas, said one or more symbols being long training symbols based on a single-antenna long training symbol, and each subsequent subcarrier from said single-antenna long training symbol being positioned in a long training symbol for a logically adjacent antenna,
wherein a remainder of a header of a packet and data sequences of said packet are diagonally loaded across said logically adjacent antennas, and
wherein one or more additional subcarriers are inserted in at least one of said one or more symbols, said one or more additional subcarriers being inserted to ensure that any subcarrier that was nulled by being diagonally loaded is surrounded by subcarriers that are not nulled.
19. The transmitter of claim 18 , wherein said multiple antenna wireless communication system is a MIMO-OFDM system.
20. The transmitter of claim 18 , wherein said one or more symbols are a SIGNAL-field symbol.
21. The transmitter of claim 18 , wherein:
a remainder of a header of a packet are diagonally loaded across said logically adjacent antennas; and
data sequences of said packet are diagonally loaded across said logically adjacent antennas.
22. A method for transmitting one or more symbols in a multiple antenna wireless communication system, said method comprising the steps of:
diagonally loading, utilizing one or more processors of said multiple antenna wireless communication system, subcarriers from said one or more symbols across a plurality of logically adjacent antennas in said multiple antenna wireless communication system;
diagonally loading, utilizing said one or more processors of said multiple antenna wireless communication system, a remainder of a header of a packet across said plurality of logically adjacent antennas; and
diagonally loading, utilizing said one or more processors of said multiple antenna wireless communication system, data sequences of said packet across said plurality of logically adjacent antennas;
wherein one or more additional subcarriers are inserted in at least one of said one or more symbols, said one or more additional subcarriers being inserted to ensure that any subcarrier that was nulled by being diagonally loaded is surrounded by subcarriers that are not nulled.
23. The method of claim 22 , further comprising: transmitting said subcarriers from said one or more symbols using said plurality of logically adjacent antennas in said multiple antenna wireless communication system such that each of said subcarriers are active on only one of said plurality of logically adjacent antennas at a given time.
24. A transmitter in a multiple antenna wireless communication system, comprising:
a plurality of transmit antennas for transmitting subcarriers from one or more symbols,
wherein said subcarriers from said one or more symbols are diagonally loaded across said plurality of antennas, wherein a remainder of a header of a packet is diagonally loaded across logically adjacent antennas of said plurality of transmit antennas, and data sequences of said packet are diagonally loaded across said logically adjacent antennas, and
wherein one or more additional subcarriers are inserted in at least one of said one or more symbols, said one or more additional subcarriers being inserted to ensure that any subcarrier that was nulled by being diagonally loaded is surrounded by subcarriers that are not nulled.
25. The transmitter of claim 24 , wherein
said subcarriers are transmitted such that each of said subcarriers are active on only one of said plurality of antennas at a given time.
26. A method for receiving one or more symbols on at least one receive antenna transmitted by a transmitter having a plurality of transmit antennas in a multiple antenna wireless communication system, said method comprising the step of:
aggregating, utilizing one or more processors of said multiple antenna wireless communication system, subcarriers from said one or more symbols that were transmitted such that each of said subcarriers are active on only one of said plurality of antennas at a given time, wherein said subcarriers are diagonally loaded across a plurality of logically adjacent antennas of said plurality of antennas, and wherein said one or more symbols include at least one of: a long training symbol based on a single-antenna long training symbol and a short training symbol based on a single-antenna short training symbol;
wherein one or more additional subcarriers are inserted in at least one of said one or more symbols, said one or more additional subcarriers being inserted to ensure that any subcarrier that was nulled by being diagonally loaded is surrounded by subcarriers that are not nulled.
27. The method of claim 26 , wherein said one or more symbols include at least one of
long training symbols based on a single-antenna long training symbol, wherein each subsequent subcarrier from said single-antenna long training symbol is positioned in a long training symbol for a logically adjacent antenna; and
short training symbols based on a single-antenna short training symbol, wherein each subsequent subcarrier from said single-antenna short training symbol is positioned in a short training symbol for a logically adjacent antenna.
28. A receiver in a multiple antenna wireless communication system having at least one transmitter having a plurality of transmit antennas, comprising:
at least one receive antenna; and
an aggregator for aggregating subcarriers from one or more symbols that were transmitted such that each of said subcarriers are active on only one of said plurality of antennas at a given time, wherein said subcarriers are diagonally loaded across a plurality of logically adjacent antennas of said plurality of antennas, wherein one or more additional subcarriers are inserted in at least one of said one or more symbols, said one or more additional subcarriers being inserted to ensure that any subcarrier that was nulled by being diagonally loaded is surrounded by subcarriers that are not nulled, and wherein said one or more symbols include at least one of: a long training symbol based on a single-antenna long training symbol and a short training symbol based on a single-antenna short training symbol.
29. The receiver of claim 28 , wherein said one or more symbols include at least one of:
long training symbols based on a single-antenna long training symbol, wherein each subsequent subcarrier from said single-antenna long training symbol is positioned in a long training symbol for a logically adjacent antenna; and
short training symbols based on a single-antenna short training symbol, wherein each subsequent subcarrier from said single-antenna short training symbol is positioned in a short training symbol for a logically adjacent antenna.