Adaptive downstream modulation scheme for broadband wireless access systems
View Patent ↗A system and method for adaptive modulation of downstream communication between a wireless hub and a wireless modem on a selected downstream channel is provided. The adaptive modulation allows for changing the downstream modulation on a packet by packet basis. The downstream modulation is changed by specifying modulation parameters including any of a modulation format, symbol rate, and FEC for each packet. A super frame may be utilized that includes a header that specifies different modulation parameters for each of multiple data packets associated with the super frame. The modulated transmissions are sent on fixed bandwidth channels that are specified based on the bit rate of the modulated transmission.
1. A method of preparing a packet communication, comprising the steps of:
determining a modulation scheme for each data field of a set of data fields;
placing an indication of the determined modulation schemes in a super frame header;
modulating each of the data fields according to the determined modulation schemes;
transmitting the super frame header and each of the modulated data fields; and
transmitting a list of indexes and corresponding modulation schemes prior to transmitting the super frame header and data packets
wherein said indication is an index that identifies a set of at least one of a modulation format, symbol rate, and FEC scheme to be used on the data packets.
2. The method according to claim 1 , wherein said modulation schemes are at least one of QPSK, QAM 16, and QAM 64.
3. The method according to claim 1 , wherein said step of transmitting comprises transmitting said header and data packets using OFDM.
4. A method of dynamic modulation in a communication system, comprising:
preparing a super frame header that indicates a modulation scheme of at least one data packet;
modulating the data packets according to the modulation scheme; and
transmitting the header and data packets;
receiving a status message transmitted from a receiver; and
selecting the modulation scheme based on the received status message;
transmitting a list of indexes and corresponding modulation schemes prior to transmitting the super frame header and data packets
Wherein
said indication is an index that identifies a set of at least one of a modulation format, symbol rate, and FEC scheme to be used to the data packets; and
said status message includes error count information describing a number of errors detected in transmissions received by the receiver.
5. The method according to claim 4 , wherein the modulation scheme includes at least one of a modulation format, symbol rate, and FEC scheme to be used on the data packets.
6. The method according to claim 5 , wherein said modulation scheme is one of QPSK, QAM 16, and QAM 64.
7. The method according to claim 4 , wherein said step of transmitting comprises transmitting said header and data packets using OFDM.
8. The method according to claim 4 , wherein said status message includes CNR information describing a Carrier to Noise Ratio of transmissions previously received by the receiver.
9. The method according to claim 4 , wherein the method is embodied in a set of computer readable instructions stored by computer readable media.
10. The method according to claim 9 , wherein said error count is a bit error rate detected in transmissions received by the receiver.
11. A method of receiving dynamically modulated data packets, comprising the steps of:
receiving super frame header data containing a modulation scheme used to modulate at least one data packet;
receiving the data packets;
demodulating the data packets according to the modulation scheme contained in the header data;
preparing a status message indicating a quality of transmissions received; and
transmitting the status message;
receiving a list of indexes and corresponding modulation schemes prior to receiving the super frame header and data packets
wherein said indication is an index that identifies a set of at least one of a modulation format, symbol rate, and FEC scheme to be used to the data packet; and
said status message includes error count information describing a number of errors detected in the transmissions received.
12. The method according to claim 11 , wherein the modulation scheme includes at least one of a modulation format, symbol rate, and FEC scheme to be used on the data packets.
13. The method according to claim 12 , wherein said modulation scheme is one of QPSK, QAM16, and QAM 64.
14. The method according to claim 11 , wherein said steps of receiving header data and receiving the data packets comprises receiving said header and data packets using OFDM.
15. The method according to claim 11 , wherein the method is embodied in a set of computer readable instructions stored by computer readable media.
16. A method for dynamic downstream communication in a broadband wireless access system, comprising:
transmitting a first packet from a wireless hub to a wireless modem utilizing a first downstream modulation type of a plurality of downstream modulation types;
receiving the first packet at the wireless modem;
demodulating the first packet at the wireless modem according to the first downstream modulation type;
transmitting a second packet from the wireless hub to the wireless modem utilizing a second downstream modulation type of the plurality downstream modulation types that is different than the first downstream modulation type;
receiving the second packet at the wireless modem;
demodulating the second packet at the wireless modem according to the second downstream modulation type;
transmitting a third packet from the wireless hub to the wireless modem utilizing the first downstream modulation type of the plurality downstream modulation types, wherein the third packet is transmitted prior to transmission of the second packet;
receiving the third packet at the wireless modem; and
demodulating the third packet at the wireless modem according to the first downstream modulation type; and
transmitting an in-phase pilot signal to the wireless modem for determining a carrier frequency for the wireless modem to communicate with the wireless hub.
17. The method of claim 16 , wherein the second packet is a next data packet transmitted from the wireless hub to the wireless modem after the first packet.
18. The method of claim 16 , further comprising the steps of
identifying the first downstream modulation type by reading a portion of the first packet comprising an identity of the first downstream modulation type; and
identifying the second downstream modulation type by reading a portion of the second packet comprising an identity of the second downstream modulation type.
19. The method according to claim 16 , wherein said method is embodied in a set of computer readable instructions in an electronic signal.
20. A method for dynamic downstream communication in a broadband wireless access system, comprising:
transmitting a first packet from a wireless hub to a wireless modem utilizing a first downstream modulation type of a plurality of downstream modulation types;
receiving the first packet at the wireless modem;
demodulating the first packet at the wireless modem according to the first downstream modulation type;
transmitting a second packet from the wireless hub to the wireless modem utilizing a second downstream modulation type of the plurality downstream modulation types that is different than the first downstream modulation type;
receiving the second packet at the wireless modem;
demodulating the second packet at the wireless modem according to the second downstream modulation type;
determining at the wireless modem a carrier to noise ratio of a carrier signal utilized to transmit the first packet;
transmitting the carrier to noise ratio of the carrier signal utilized to transmit the first packet from the wireless modem to the wireless hub; and
determining at the wireless hub the second modulation type based upon the carrier to noise ratio; and
transmitting an in-phase pilot signal to the wireless modem for determining a carrier frequency for the wireless modem to communicate with the wireless hub.
21. The method according to claim 20 , wherein the method is embodied in a set of computer readable instructions stored by computer readable media.
22. A method for dynamic downstream communication in a broadband wireless access system, comprising:
transmitting a first packet from a wireless hub to a wireless modem utilizing a first downstream modulation type of a plurality of downstream modulation types;
receiving the first packet at the wireless modem;
demodulating the first packet at the wireless modem according to the first downstream modulation type;
transmitting a second packet from the wireless hub to the wireless modem utilizing a second downstream modulation type of the plurality downstream modulation types that is different than the first downstream modulation type;
receiving the second packet at the wireless modem;
demodulating the second packet at the wireless modem according to the second downstream modulation type; and
transmitting an in-phase pilot signal as part of a data portion of the first packet and transmitting an in phase pilot signal as part of a data portion of the second packet, wherein the carrier frequency is determined by the wireless modem-by utilizing the in-phase pilot signal.
23. A method for dynamic downstream communication in a broadband wireless access system, comprising:
transmitting a first packet from a wireless hub to a wireless modem utilizing a first downstream modulation type of a plurality of downstream modulation types;
receiving the first packet at the wireless modem;
demodulating the first packet at the wireless modem according to the first downstream modulation type;
transmitting a second packet from the wireless hub to the wireless modem utilizing a second downstream modulation type of the plurality downstream modulation types that is different than the first downstream modulation type;
receiving the second packet at the wireless modem;
demodulating the second packet at the wireless modem according to the second downstream modulation type; and
transmitting a training packet from the wireless hub to the wireless modem; and
transmitting an in-phase pilot signal to the wireless modem for determining a carrier frequency for the wireless modem to communicate with the wireless hub.
24. A carrier signal modulated with an information signal for communicating between two wireless devices, the information signal comprising a header portion and a data portion, the header portion comprising a modulation identity portion comprising information identifying a modulation type of a plurality of modulation types utilized to modulate the data portion of the information signal;
wherein the header portion further comprises timing and synchronization for the particular information signal; and the data portion comprises a in-phase pilot signal that is capable of being utilized to determine a frequency of the carrier signal.
25. The carrier signal modulated with the information signal for communicating between two wireless devices of claim 24 wherein the data portion comprises a fixed data pattern and wherein the information signal is utilized as a training signal.
26. The carrier signal modulated with the information signal for communicating between two wireless devices of claim 24 wherein the header portion is modulated utilizing a first type of modulation and the data portion is modulated utilizing a second type of modulation different than the first type of modulation.
27. A carrier signal modulated with an information signal for communicating between two wireless devices, the information signal comprising a header portion and a data portion, the header portion comprising a modulation identity portion comprising information identifying a modulation type of a plurality of modulation types utilized to modulate the data portion of the information signal;
wherein the data portion comprises a in-phase pilot signal that is capable of being utilized to determine the frequency of the carrier signal.
28. A carrier signal modulated with an information signal for communicating between two wireless devices, the information signal comprising a header portion and a data portion, the header portion comprising a modulation identity portion comprising information identifying a modulation type of a plurality of modulation types utilized to modulate the data portion of the information signal;
wherein the data portion comprises an in-phase pilot identifying a frequency of the carrier signal and a fixed data pattern and wherein the information signal is utilized as a training signal.