Systems and methods for improving range for multicast wireless communication
Methods to optimize range of multicast signal communication in wireless communication applications that use range-enhanced techniques for directed signal communication. A multicast signal may be sent multiple times through each of a plurality of independent omnidirectional transmit antennas of a communication device to a plurality of other communication devices to improve packet error rate (PER) at a given range (i.e., SNR). More generally, the multicast message can be transmitted up to N times using up to N times using any set of N complex linearly independent N-dimensional transmit weight vectors v i , . . . , v N associated with N plurality of transmit antennas that meets the power constraint ∥v i ∥ 2 =1 , i= 0 , . . . , N− 1 , where the vector v i , is used for the ith transmission of the multicast signal.
1. A method for enabling wireless communication comprising:
receiving at a first communication device a first request-to-send (RTS) signal transmitted by a second communication device, wherein the first RTS signal requests reservation of a radio communication medium for transmission of a signal from the second communication device to the first communication device;
at the first communication device, generating a first clear-to-send (CTS) signal including information to inform communication devices of an impending transmission on the radio communication medium;
transmitting the first CTS signal from the first communication device with antenna processing parameters so as to cause a null at the second communication device but not at a plurality of other communication devices;
generating a CTS timeout, executing a back-off and sending a second RTS signal using composite beamforming (CBF);
receiving a second RTS signal transmitted by the second communication device using CBF after a CTS timeout;
transmitting a second CTS signal to the second communication device in response to the second RTS using CBF;
receiving data fragments transmitted by the second communication device using CBF; and
transmitting an acknowledgement (ACK) to the second communication device using CBF.
2. The method of claim 1 , wherein the transmitting the first CTS signal comprises using a transmit weight vector that is in the null space of H, where H represents the channel response matrix between the first communication device and the second communication device.
3. The method of claim 1 , wherein the generating a first clear-to-send (CTS) signal comprises generating at least first and second CTS packets, each of which is addressed to the first communication device, and is transmitted using a transmit weight vector that is in the null space of H.
4. The method of claim 1 , wherein the transmitting comprises transmitting the first and second CTS packets with transmit weight vectors that are linearly independent.
5. The method of claim 1 , wherein the transmitting the first CTS signal comprises processing the first CTS signal with transmit antenna weights associated with the plurality of antennas of the first communication device that optimize reception of the first CTS signal by the second communication device.
6. The method of claim 1 , further comprising transmitting the acknowledgment (ACK) signal from the first communication device to the second communication device via the plurality of antennas using transmit antenna weights associated with the plurality of antennas of the first communication device that optimize reception of the CTS signal by the second communication device.
7. A processor readable medium encoded with instructions, that when executed by a processor, perform functions [that include] comprising:
in response to a first request-to-send (RTS) signal transmitted by a second communication device and received by a first communication device, generating a first clear-to-send (CTS) signal including information to inform communication devices of an impending transmission on the radio communication medium;
processing the first CTS signal with antenna processing parameters so as to cause a null at the second communication device but not at a plurality of other communication devices using a transmit weight vector that is in the null space of H, where H represents the channel response matrix between the first communication device and the second communication device;
receiving a second RTS signal transmitted by the second communication device using composite beamforming (CBF) after a CTS timeout;
transmitting a second CTS signal to the second communication device in response to the second RTS using CBF;
receiving data fragments transmitted by the second communication device using CBF; and
transmitting an acknowledgement (ACK) to the second communication device using CBF.
8. The medium of claim 7 , and further encoded with instructions that generate at least first and second CTS signals and process the first and second CTS signals with transmit weight vectors that are linearly independent.
9. The medium of claim 7 , and further encoded with instructions to process the first CTS signal addressed to the second communication device with transmit antenna weights associated with the plurality of antennas of the first communication device that optimize reception of the first CTS signal by the second communication device.
10. The medium of claim 9 , and further encoded with instructions that, process the ACK signal with transmit antenna weights associated with the plurality of antennas of the first communication device that optimize reception of the first CTS signal by the second communication device.
11. A communication device comprising the medium of claim 7 , and further comprising:
a receiver that downconverts signals received by the plurality of antennas;
a transmitter that upconverts signals to be transmitted; and
a processor coupled to the transmitter and the receiver that processes instructions encoded on the medium.
12. An integrated circuit comprising the medium of claim 7 .