Configurable orthogonal frequency division multiplexing (OFDM) signal and transmitter and receiver for satellite to gateway uplink and downlink communications
A modem is configurable on a satellite, user terminal or gateway generates a radio frequency (RF) signal using an orthogonal frequency division multiplexing (OFDM) protocol including a radio frame including one or more bursts. A burst of the one or more bursts includes a first portion including burst detection data, a second portion including channel characteristic estimation data, a third portion including payload data, and fourth and fifth portions including pilot data. The first portion in a time domain is included in the burst prior to the second, third, fourth, and fifth portions. The first portion can include a pseudo-random noise sequence inserted in the time domain. The same physical modem can be configured to transmit signals on an uplink or downlink between a user terminal and a satellite or on the uplink or downlink between the satellite and the gateway.
1. A modem comprising:
a transmitter configurable to transmit a first waveform from a satellite (SAT) to a satellite access gateway (SAG) at a first bandwidth and configurable to transmit a second waveform from the SAG to the SAT at a second bandwidth, the first waveform and the second waveform comprising:
a unique word configured in a first time period of a burst in a radio frame;
a channel estimation symbol configured in a second time period of the burst of the radio frame, the second time period adjacent to the first time period, the channel estimation symbol being associated with user data and covering a set of frequency resources;
a first pilot subcarrier at a first frequency in a third time period of the burst in the radio frame;
a second pilot subcarrier at a second frequency in the third time period of the burst in the radio frame; and
one or more resource blocks configured in the third time period of the burst in the radio frame and configured to use the set of frequency resources between the first pilot subcarrier and the second pilot subcarrier; and
a receiver configured to receive the first waveform or the second waveform, wherein the modem is configurable for use on the SAT or the SAG.
2. The modem of claim 1 , wherein the SAT transmits the first waveform to the SAG in a point-to-point configuration.
3. The modem of claim 1 , wherein the modem, when deployed on a SAT, is configured to transmit the first waveform on a downlink at a bandwidth of approximately 250 MHz and wherein the modem, when deployed on a SAG, is configured to transmit the second waveform on an uplink at a bandwidth of approximately 500 MHz.
4. The modem of claim 1 , wherein the first waveform and the second waveform each further comprise:
a cyclic prefix and postfix symbol;
a direct current (DC) null configured in the third time period;
a first pilot sub-band offset configured in the third time period and at a third frequency; and
a second pilot sub-band offset configured in the third time period and at a fourth frequency.
5. The modem of claim 1 , wherein the first waveform or the second waveform can be configured with respect to one or more of: a direct current (DC) null, the first pilot subcarrier and the second pilot subcarrier, a value associated with a pilot sub-band offset, a value associated with the channel estimation symbol and a value associated with a cyclic prefix and postfix symbol.
6. The modem of claim 1 , wherein the first waveform or the second waveform can be configured in one of an asynchronous mode or a semi-synchronous mode.
7. The modem of claim 1 , wherein the first waveform or the second waveform is coded and modulated using a modulating and coding scheme value.
8. The modem of claim 1 , wherein the transmitter further comprises:
a pre-compensation module that pre-compensates frequency error and sampling clock error associated with the first waveform or the second waveform.
9. The modem of claim 1 , wherein, when the modem is configured within the SAT to receive the second waveform from the SAG, the receiver:
parses a PHY packet data unit (PDU) header in the second waveform to obtain a modulation and coding scheme value and symbol data that contains a code word; and
performs compensation for one or more of a sampling frequency offset, a carrier frequency offset and a Doppler effect due to movement of the SAT.
10. The modem of claim 1 , wherein, when the modem is configured within the SAG to receive the first waveform from the SAT, the receiver:
parses a PHY packet data unit (PDU) header in the first waveform to obtain a modulation and coding scheme value and symbol data that contains a code word.
11. The modem of claim 1 , wherein the first waveform and the second waveform are both orthogonal frequency division multiplex waveforms.
12. The modem of claim 1 , wherein the first waveform and the second waveform each further comprises:
a first pilot sub-band offset configured in the third time period and at a third frequency; and
a second pilot sub-band offset configured in the third time period and at a fourth frequency.
13. The modem of claim 12 , wherein the modem, when receiving the first waveform or the second waveform, utilizes the channel estimation symbol to estimate a channel and then applies a linear phase interpolation across a frequency spectrum of the radio frame using a first group of subcarriers adjacent to the first pilot sub-band offset and a second group of subcarriers adjacent to the second pilot sub-band offset to correct for residual delay or error.
14. The modem of claim 1 , wherein the unique word comprises a set of repeated pseudo-noise sequences that are used to track a phase change over time to estimate a frequency offset for correction.
15. The modem of claim 1 , wherein the receiver comprises one or more components that correct the first waveform or the second waveform for one or more of a carrier frequency offset (CFO), a sampling frequency offset (SFO), and a Doppler effect due to SAT movement.
16. The modem of claim 1 , further comprising a gain control component for correction of one of weather impacts on the first waveform and the second waveform and a phase array loss as a function of a steering angle.
17. A modem configurable for use on a satellite (SAT) or a satellite access gateway (SAG), the modem comprising:
a transmitter and receiver configurable to modify, depending on whether the modem is configured on the SAT or the SAG, one or more of a value associated with a direct current (DC) null in a radio frame of a waveform, a value associated with pilot subcarriers in the radio frame, a value associated with a pilot sub-band offset in the radio frame, a value associated with a channel estimation symbol in the radio frame and a value of a cyclic prefix and postfix symbol in the radio frame.
18. The modem of claim 17 , wherein, when the modem is configured in the SAG, the transmitter transmits the waveform to the SAG using a 250 MHz channel bandwidth, and when the modem is configured in the SAT, the transmitter transmits a second waveform to the SAT using a 500 MHz channel bandwidth.
19. The modem of claim 17 , wherein the modem comprises parameters that are configurable depending on whether the modem is deployed in the SAT or the SAG, wherein the parameters comprise one or more of: a time-domain cyclic guard band, a resource block size, a user allocation, a radio frame size, a value associated with pilot averaging, and a modulation and coding scheme.
20. The modem of claim 17 , wherein the radio frame is configured as an orthogonal frequency division multiplex waveform.
21. The modem of claim 17 , further comprising:
a receiver configured to receive a second waveform having a structure comprising:
a unique word configured in a first time period of a burst in a second radio frame of the second waveform;
a second channel estimation symbol configured in a second time period of the burst of the second radio frame, the second time period adjacent to the first time period, the second channel estimation symbol being associated with a channel and covering a set of frequency resources;
a first pilot subcarrier at a first frequency in a third time period of the burst in the second radio frame;
a second pilot subcarrier at a second frequency in the third time period of the burst in the second radio frame; and
one or more resource blocks configured in the third time period of the burst in the second radio frame and configured to use the set of frequency resources between the first pilot subcarrier and the second pilot subcarrier.
22. The modem of claim 21 , wherein the second waveform further comprises at least one pilot sub-band offset from at least one band edge of the radio frame.
23. A modem configurable for use on a satellite (SAT) or a satellite access gateway (SAG), the modem comprising:
a processor; and
a non-transitory computer-readable medium storing instructions which, when executed by the processor, cause the processor to perform operations comprising:
modifying, depending on whether the modem is configured on the SAT or the SAG, one or more of: a bandwidth for transmitting a waveform, a direct current (DC) null in a radio frame of the waveform, pilot subcarriers in the radio frame, a first pilot sub-band offset in the radio frame, a second pilot sub-band offset in the radio frame, a channel estimation symbol in the radio frame and a cyclic prefix and postfix symbol in the radio frame; and
when the modem receives the waveform, performing error correction for one or more of: a carrier frequency offset, a sampling frequency offset, a Doppler effect on the waveform, a weather impact on the waveform, a delay in a signal, and a phase-array loss impact on the waveform.
24. The modem of claim 23 , wherein the non-transitory computer-readable medium stores additional instructions which, when executed by the processor, cause the processor to perform operations comprising:
when the modem is configured in the SAT, transmitting the waveform to the SAG using a 250 MHz channel bandwidth, and when the modem is configured in the SAT, a transmitter transmits a second waveform to the SAT using a 500 MHz channel bandwidth.
25. The modem of claim 23 , wherein the modem comprises parameters that are configurable depending on whether the modem is deployed in the SAT or the SAG, wherein the parameters comprise one or more of: a time-domain cyclic guard band, a resource block size, a user allocation, a radio frame size, a value associated with pilot averaging, and a modulation and coding scheme.
26. The modem of claim 23 , wherein the non-transitory computer-readable medium stores additional instructions which, when executed by the processor, cause the processor to perform operations further comprising:
performing error correction by first estimating a channel for the waveform via the channel estimation symbol, followed by applying a linear phase interpolation across a set of frequencies associated with the radio frame and using a first group of subcarriers adjacent to the first pilot sub-band offset and a second group of subcarriers adjacent to the second pilot sub-band offset to correct for residual errors.
27. A method comprising:
transmitting, via a modem configurable to be implemented in a satellite (SAT) or a satellite access gateway (SAG), a first waveform for use in a channel between the SAT and the SAG and on either an uplink or a downlink, the first waveform comprising:
a unique word configured in a first time period of a burst in a radio frame;
a channel estimation symbol configured in a second time period of the burst of the radio frame, the second time period adjacent to the first time period, the channel estimation symbol being associated with a channel and covering a set of frequency resources;
a first pilot subcarrier at a first frequency in a third time period of the burst in the radio frame;
a second pilot subcarrier at a second frequency in the third time period of the burst in the radio frame; and
one or more resource blocks configured in the third time period of the burst in the radio frame and configured to use the set of frequency resources between the first pilot subcarrier and the second pilot subcarrier; and
receiving, at the modem, a second waveform via the uplink or the downlink.
28. The method of claim 27 , wherein, when the channel is the uplink between the SAG and the SAT, the first waveform comprises an uplink signal that has a bandwidth of 500 MHz and when the channel is the downlink between the SAT and the SAG, the first waveform comprises a downlink signal that has a bandwidth of 250 MHz.
29. The method of claim 27 , wherein the method further comprises, prior to transmitting the first waveform, configuring by the modem one or more parameters associated with the first waveform, the one or more parameters comprising: a subcarrier spacing, a bandwidth, a time-domain cyclic guard band, a resource block size, a user allocation, a radio frame size, a channel estimation symbol, a first pilot sub-band offset, a second pilot sub-band offset, a pilot averaging approach, a direct current (DC) guard band, and a modulation and coding scheme.
30. The method of claim 29 , wherein the bandwidth is set by selecting a sampling rate with a fast Fourier transform/inverse fast Fourier transform size fixed to provide a number of subcarriers for the first waveform.
31. The method of claim 30 , wherein the subcarrier spacing for the first waveform changes as the sampling rate changes.
32. The method of claim 27 , wherein receiving the second waveform further comprises performing error correction on the second waveform to correct for one or more of a sampling frequency offset (SF0), a carrier frequency offset (CFO), a delay, an impact of weather on the second waveform, a phase array loss in the second waveform, a delay variation, and a Doppler effect due to movement of the SAT.
33. A method comprising:
configuring a modem to transmit or receive a waveform, wherein the modem is configurable to be implemented in a satellite (SAT) or a satellite access gateway (SAG), the waveform having a configuration comprising:
a unique word configured in a first time period of a burst in a radio frame;
a channel estimation symbol configured in a second time period of the burst of the radio frame, the second time period adjacent to the first time period, the channel estimation symbol being associated with a channel and covering a set of frequency resources;
a first pilot subcarrier at a first frequency in a third time period of the burst in the radio frame;
a second pilot subcarrier at a second frequency in the third time period of the burst in the radio frame;
a first pilot sub-band offset configured in the radio frame;
a second pilot sub-band offset configured in the radio frame; and
one or more resource blocks configured in the third time period of the burst in the radio frame and configured to use the set of frequency resources between the first pilot subcarrier and the second pilot subcarrier;
transmitting, via the modem, the waveform in a transmit mode; and
receiving, via the modem, the waveform in a receive mode.
34. The method of claim 33 , wherein, when the channel is an uplink channel between the SAG and the SAT, the waveform has a bandwidth of 500 MHz and when the channel is a downlink channel between the SAT and the SAG, the waveform has a bandwidth of 250 MHz.
35. The method of claim 33 , wherein the method further comprises, prior to transmitting the waveform when in the transmit mode, configuring by the modem one or more parameters associated with the waveform, the one or more parameters comprising: a subcarrier spacing, a bandwidth, a time-domain cyclic guard band, a resource block size, a user allocation, a radio frame size, a channel estimation symbol, a pilot averaging approach, a direct current (DC) guard band, and a modulation and coding scheme.
36. The method of claim 33 , wherein receiving the waveform when in the receive mode further comprises performing error correction on the waveform to correct for one or more of a sampling frequency offset (SF0), a carrier frequency offset (CFO), a delay, an impact of weather on the waveform, a phase array loss in the waveform, a delay variation, and a Doppler effect due to movement of the SAT.
37. The method of claim 36 , wherein performing error correction comprises performing a linear phase interpolation across the set of frequency resources using a first group of subcarriers adjacent to the first pilot sub-band offset and a second group of subcarriers adjacent to the second pilot sub-band offset.
38. The method of claim 36 , wherein performing error correction further comprises evaluating a repetition of the unique word to track a phase change to estimate a frequency offset.
39. The method of claim 33 , wherein receiving the waveform when in the receive mode further comprises applying gain control to correct for one or more of weather impacts on the waveform and a phase array loss in the waveform.