Applying code division multiplexing to a beacon channel containing data for decoding a corresponding traffic channel
View Patent ↗The present invention is generally directed to using code division multiplexing (CDM) on the beacon and traffic channels while lowering the power of the beacon channel so that it rides under the traffic channel and becomes very difficult to detect. In this way, the beacon channel can contain sensitive information for decoding the traffic channel while remaining hidden from unintended recipients. By hiding the beacon channel, the CDM technique can be particularly beneficial in adaptive waveform systems where sensitive traffic channel acquisition information is regularly transmitted to the receiver.
1. A method, performed by a transmitter, for code division multiplexing a traffic channel and a beacon channel that contains acquisition information for acquiring the traffic channel, the method comprising:
generating a code division multiplexed (CDM) traffic channel by using one or more CDM parameters to spread the bandwidth of the traffic channel;
including the one or more CDM parameters used to spread the bandwidth of the traffic channel in a beacon channel;
generating a CDM beacon channel; and
transmitting the CDM traffic channel and the CDM beacon channel to a receiver,
wherein:
the transmitting step comprises transmitting the CDM traffic channel at a first power level and the CDM beacon channel at a second power level that is less than the first power level, and
a difference between the first power level and the second power level is a function of a processing gain of the CDM traffic channel and a signal to noise ratio of the CDM beacon channel.
2. The method of claim 1 , wherein the one or more CDM parameters include a PN code seed of a PN code used to spread the bandwidth of the traffic channel.
3. The method of claim 2 , wherein the one or more CDM parameters include timing information defining when the PN code is to be applied by the receiver to the CDM traffic channel to de-spread the traffic channel.
4. The method of claim 1 , further comprising:
prior to generating the CDM traffic channel, using one or more modulation parameters to modulate the traffic channel; and
including the one or more modulation parameters in the beacon channel.
5. The method of claim 4 , wherein the one or more modulation parameters comprise one or more of:
an encryption scheme;
a forward error correction code;
a modulation scheme;
a data rate;
a carrier frequency; or
an interleaving technique.
6. The method of claim 5 , further comprising:
updating one or more of the one or more CDM parameters or the one or more modulation parameters; and
including the one or more updated parameters in the beacon channel.
7. The method of claim 1 , further comprising encrypting the beacon channel.
8. The method of claim 1 , wherein the transmitting the CDM traffic channel comprises transmitting the CDM traffic channel as a continuous stream of encoded traffic payloads constituting individual parts of a message transmission.
9. The method of claim 8 further comprising, while transmitting the CDM traffic channel, changing one or more encoding parameters by which the encoded traffic payloads are encoded.
10. The method of claim 9 , wherein the transmitting the CDM beacon channel comprises:
transmitting in the CDM beacon channel information corresponding to the encoding parameters, and
upon the changing the one or more encoding parameters, changing the information transmitted in the CDM beacon channel to correspond to the changed encoding parameters.
11. The method of claim 10 , wherein the changed encoding parameters comprise one or more of the CDM parameters.
12. A method, performed by a transmitter, for code division multiplexing a traffic channel and a beacon channel that contains acquisition information for acquiring the traffic channel, the method comprising:
generating a code division multiplexed (CDM) traffic channel by using one or more CDM parameters to spread the bandwidth of the traffic channel;
including the one or more CDM parameters used to spread the bandwidth of the traffic channel in a beacon channel;
generating a CDM beacon channel; and
transmitting the CDM traffic channel and the CDM beacon channel to a receiver,
wherein:
the CDM beacon channel is transmitted at a power level that is less than the power level at which the CDM traffic channel is transmitted, and
the power level of the CDM beacon channel is given by the equation:
P
BeaconChannel
=
P
TrafficChannel
-
(
10
log
10
(
PG
)
-
Eb
No
)
where PG is the processing gain of the traffic channel and Eb/No is the signal to noise ratio of the beacon channel.
13. A method, performed by a receiver, for extracting acquisition information from a code division multiplexed beacon channel to acquire a code division multiplexed traffic channel, the method comprising:
receiving, from a transmitter, a code division multiplexed (CDM) beacon channel that contains acquisition information for de-spreading a corresponding CDM traffic channel;
processing the CDM beacon channel to extract the acquisition information, the acquisition information including one or more CDM parameters used by the transmitter to spread the bandwidth of the CDM traffic channel;
de-spreading the CDM traffic channel using the one or more CDM parameters included in the acquisition information; and
receiving the CDM traffic channel at a first power level,
wherein:
the receiving the CDM beacon channel comprises receiving the CDM beacon channel at a second power level that is less than the first power level, and
a difference between the first power level and the second power level is a function of a processing gain of the CDM traffic channel and a signal to noise ratio of the CDM beacon channel.
14. The method of claim 13 , wherein the one or more CDM parameters comprise a PN code seed of a PN code that was used to spread the traffic channel, and wherein de-spreading the CDM traffic channel comprises generating the PN code from the PN code seed and applying the PN code to the CDM traffic channel to de-spread the traffic channel.
15. The method of claim 14 , wherein the one or more CDM parameters include timing information defining a time at which the PN code is to be applied to the CDM traffic channel to de-spread the traffic channel.
16. The method of claim 13 , wherein the acquisition information includes one or more modulation parameters used by the transmitter to modulate the traffic channel, the method further comprising:
processing the de-spread traffic channel using the one or more modulation parameters.
17. The method of claim 16 wherein the one or more modulation parameters comprise one or more of:
an encryption scheme;
a forward error correction code;
a modulation scheme;
a data rate;
a carrier frequency; or
an interleaving technique.
18. The method of claim 16 , further comprising:
at a later time, processing the CDM beacon channel to extract addition acquisition information, the additional acquisition information including one or more updated parameters of the one or more CDM parameters or the one or more modulation parameters; and
processing the traffic channel using the one or more updated parameters.
19. The method of claim 13 further comprising receiving the CDM traffic channel as a continuous stream of encoded traffic payloads constituting individual parts of a message transmission.
20. The method of claim 19 further comprising, while receiving the continuous stream of encoded traffic payloads, receiving in the CDM beacon channel changed values of one or more encoding parameters by which the encoded traffic payloads are encoded at the transmitter.
21. The method of claim 20 , wherein the changed encoding parameters comprise one or more of the CDM parameters.
22. A method, performed by a receiver, for extracting acquisition information from a code division multiplexed beacon channel to acquire a code division multiplexed traffic channel, the method comprising:
receiving, from a transmitter, a code division multiplexed (CDM) beacon channel that contains acquisition information for de-spreading a corresponding CDM traffic channel;
processing the CDM beacon channel to extract the acquisition information, the acquisition information including one or more CDM parameters used by the transmitter to spread the bandwidth of the CDM traffic channel; and
de-spreading the CDM traffic channel using the one or more CDM parameters included in the acquisition information,
wherein the power level of the received CDM beacon channel is given by the equation:
P
BeaconChannel
=
P
TrafficChannel
-
(
10
log
10
(
PG
)
-
Eb
No
)
where PG is the processing gain of the traffic channel and Eb/No is the signal to noise ratio of the beacon channel.
23. A transmitter for code division multiplexing a traffic channel and a beacon channel that contains acquisition information for acquiring the traffic channel, the transmitter comprising:
an antenna for transmitting a code division multiplexed (CDM) traffic channel and a CDM beacon channel to a receiver; and
circuitry for generating the CDM traffic channel and the CDM beacon channel by:
generating the CDM traffic channel by using one or more CDM parameters to spread the bandwidth of a traffic channel;
including the one or more CDM parameters used to spread the bandwidth of the traffic channel in a beacon channel; and
generating the CDM beacon channel,
wherein:
the circuitry is further for generating the CDM traffic channel at a first power level and the CDM beacon channel at a second power level that is less than the first power level, and
a difference between the first power level and the second power level is a function of a processing gain of the CDM traffic channel and a signal to noise ratio of the CDM beacon channel.
24. The transmitter of claim 23 , wherein the circuitry is further for generating the CDM traffic channel as a continuous stream of encoded traffic payloads constituting individual parts of a message transmission.
25. The transmitter of claim 24 , wherein the circuitry is further for:
while generating the CDM traffic channel, changing at least one of the one or more CDM parameters, and
thereafter including the changed CDM parameters in the beacon channel.
26. A receiver for extracting acquisition information from a code division multiplexed beacon channel to acquire a code division multiplexed traffic channel, the receiver comprising:
an antenna for receiving a code division multiplexed (CDM) traffic channel and a CDM beacon channel from a transmitter; and
circuitry for de-spreading the CDM traffic channel by:
processing the CDM beacon channel to extract acquisition information for de-spreading the CDM traffic channel, the acquisition information including one or more CDM parameters used by the transmitter to spread the bandwidth of the CDM traffic channel; and
de-spreading the CDM traffic channel using the one or more CDM parameters included in the acquisition information,
wherein:
the circuitry is further for receiving the CDM traffic channel at a first power level and the CDM beacon channel at a second power level that is less than the first power level, and
a difference between the first power level and the second power level is a function of a processing gain of the CDM traffic channel and a signal to noise ratio of the CDM beacon channel.
27. The receiver of claim 26 , wherein the circuitry is further for receiving the CDM traffic channel as a continuous stream of encoded traffic payloads constituting individual parts of a message transmission.
28. The receiver of claim 27 wherein the circuitry is further for:
while receiving the continuous stream of encoded traffic payloads, receiving in the CDM beacon channel a changed value of the one or more CDM parameters, and
thereafter de-spreading the CDM traffic channel using the changed value of the one or more CDM parameters.