Dynamic configuration of a flexible orthogonal frequency division multiplexing PHY transport data frame
A base station may generate and transmit a transport stream including a sequence of frames. A frame may include a plurality of partitions, where each partition includes a corresponding set of OFDM symbols. For each partition, the OFDM symbols in that partition may have a corresponding cyclic prefix size and a corresponding FFT size, allowing different partitions to be targeted for different collections of user devices, e.g., user devices having different expected values of maximum delay spread and/or different ranges of mobility. The base station may also dynamically re-configure the sample rate of each frame, allowing further resolution in control of subcarrier spacing. By allowing the cyclic prefixes of different OFDM symbols to have different lengths, it is feasible to construct a frame that confirms to a set payload duration and has arbitrary values of cyclic prefix size per partition and FFT size per partition. The partitions may be multiplexed in time and/or frequency.
1. A method, comprising:
generating a data frame; and
wirelessly broadcasting the data frame,
wherein generating the data frame comprises:
generating a first set of orthogonal frequency domain multiplexing (OFDM) symbols; and
generating a second set of OFDM symbols,
wherein each OFDM symbol of the first set of OFDM symbols and the second set of OFDM symbols comprises a useful portion and a cyclic prefix, and
wherein generating said each OFDM symbol comprises:
converting a block of frequency domain data to time-domain samples using an inverse fast Fourier transform having a transform size to form the useful portion; and
forming the cyclic prefix by prepending to said each OFDM symbol a plurality of time-domain samples from an end of the useful portion of the OFDM symbol,
wherein generating the data frame further comprises:
forming the first set of OFDM symbols using a first transform size and a first cyclic prefix size; and
forming the second set of OFDM symbols using a second transform size different than the first transform size and a second cyclic prefix size, and
wherein the data frame comprises a plurality of parameters separately indicating the first cyclic prefix size, the second cyclic prefix size, the first transform size, and the second transform size.
2. The method of claim 1 , wherein the first cyclic prefix size is different than the second cyclic prefix size.
3. The method of claim 1 ,
wherein the frequency domain data comprises a set of useful subcarriers and a set of non-useful subcarriers; and
wherein the data frame further comprises a second plurality of parameters separately indicating a number of useful subcarriers in the first set of OFDM symbols and a number of useful subcarriers in the second set of OFDM symbols.
4. A computer program product for transmitting a variable rate transport stream, the computer program product comprising one or more non-transitory computer-readable storage devices having stored thereon computer executable instructions that when executed cause at least one processor to:
construct a payload region of a data frame, wherein samples in the payload region correspond to a first sample rate, wherein the first sample rate is selected from a plurality of sample rates;
divide the samples in the payload region into one or more partitions, wherein each of the one or more partitions comprises a corresponding set of orthogonal frequency domain multiplexing (OFDM) symbols;
embed signaling information in the transport stream that includes the data frame, wherein the signaling information comprises data indicative of the first sample rate, and a second sample rate different than the first sample rate is used for the signaling information; and
transmit the transport stream based at least in part on the first sample rate.
5. The computer program product of claim 4 , wherein the computer executable instructions, when executed, further cause the at least one processor to receive data indicative of the first sample rate from an operator of a broadcast network.
6. The computer program product of claim 4 , wherein the computer executable instructions, when executed, further cause the at least one processor to embed the signaling information in a non-payload region of the data frame.
7. The computer program product of claim 4 , wherein each partition of the one or more partitions has a corresponding value of fast Fourier transform (FFT) size for OFDM symbols associated with the one or more partitions.
8. The computer program product of claim 7 , wherein the computer executable instructions, when executed, further cause the at least one processor to, for each partition, select the FFT size for the partition and the first sampling rate to define a subcarrier spacing for the partition that satisfies a specified minimum subcarrier spacing for the partition.
9. The computer program product of claim 4 , wherein each partition of the one or more partitions has a corresponding value of cyclic prefix size for OFDM symbols associated with the one or more partitions.
10. The computer program product of claim 9 , wherein the cyclic prefix size corresponding to a partition of the one or more partitions is selected from a group consisting of: 192, 384, 512, 768, 1024, 1536, 2048, 3072, and 4096 samples.
11. An apparatus, comprising:
a processor configured to generate a data frame; and
a transmitter configured to wirelessly broadcast the data frame,
wherein the data frame comprises a first set of orthogonal frequency domain multiplexing (OFDM) symbols and a second set of OFDM symbols, each OFDM symbol in the first set of OFDM symbols and the second set of OFDM symbols comprising a useful portion and a cyclic prefix,
wherein, to generate said each OFDM symbol, the processor is further configured to:
convert a block of frequency domain data to time-domain samples using an inverse fast Fourier transform having a transform size to form the useful portion; and
form the cyclic prefix by prepending to said each OFDM symbol a plurality of time-domain samples from an end of the useful portion,
wherein the processor is further configured to form the first set of OFDM symbols using a first transform size and a first cyclic prefix size, and to form the second set of OFDM symbols using a second transform size different than the first transform size and a second cyclic prefix size, and
wherein the data frame further comprises a plurality of parameters separately indicating the first cyclic prefix size, the second cyclic prefix size, the first transform size, and the second transform size.
12. The apparatus of claim 11 , wherein the first cyclic prefix size is different than the second cyclic prefix size.
13. The apparatus of claim 11 , wherein the first transform size and the second transform size are each selected from a group consisting of: 8192, 16384, and 32768 samples.
14. The apparatus of claim 11 , wherein the first cyclic prefix size and the second cyclic prefix size are each selected from a group consisting of: 192, 384, 512, 768, 1024, 1536, 2048, 3072, and 4096 samples.
15. The apparatus of claim 11 , wherein the frequency domain data comprises a set of useful subcarriers and a set of non-useful subcarriers.
16. The apparatus of claim 15 , wherein the data frame further comprises a second plurality of parameters separately indicating a number of useful subcarriers in the first set of OFDM symbols and a number of useful subcarriers in the second set of OFDM symbols.
17. A method, comprising:
generating a data frame; and
wirelessly broadcasting the data frame,
wherein generating the data frame comprises:
generating a first set of orthogonal frequency domain multiplexing (OFDM) symbols; and
generating a second set of OFDM symbols,
wherein each OFDM symbol of the first set of OFDM symbols and the second set of OFDM symbols comprises a useful portion and a cyclic prefix, and
wherein generating said each OFDM symbol comprises:
converting a block of frequency domain data to time-domain samples using an inverse fast Fourier transform having a transform size to form the useful portion; and
forming the cyclic prefix by prepending to said each OFDM symbol a plurality of time-domain samples from an end of the useful portion of the OFDM symbol,
wherein generating the data frame further comprises:
forming the first set of OFDM symbols using a first transform size and a first cyclic prefix size; and
forming the second set of OFDM symbols using a second transform size and a second cyclic prefix size,
wherein the data frame comprises a plurality of parameters separately indicating the first cyclic prefix size, the second cyclic prefix size, the first transform size, and the second transform size, and
wherein the first cyclic prefix size is selected from a group consisting of: 16, 24, 32, 48, 96, 192, 384, 768, 1536, 3072, and 6144 samples.
18. The method of claim 17 , wherein the first cyclic prefix size is different than the second cyclic prefix size.
19. The method of claim 17 , wherein the first transform size is different than the second transform size.