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 conforms 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. An apparatus, comprising:
a processor configured to generate a data frame including a non-payload region and a payload region; and
a transmitter configured to wirelessly broadcast the data frame,
wherein the payload region of 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 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 and a second cyclic prefix size,
wherein the first cyclic prefix size is a sum of a first base cyclic prefix size and an extension size,
wherein the second cyclic prefix size is a sum of a second base cyclic prefix size and the extension size, and
wherein the first transform size is different than the second transform size.
2. The apparatus of claim 1 , 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 the end of the useful portion.
3. The apparatus of claim 1 , wherein the processor is further configured to:
determine a number of excess samples based at least on a difference between a total number of samples in the payload region and a sum of a total number of samples in the first set of OFDM symbols and a total number of samples in the second set of OFDM symbols; and
determine the extension size based on at least a ratio between the number of excess samples and a sum of a total number of OFDM symbols in the first set of OFDM symbols and a total number of OFDM symbols in the second set of OFDM symbols.
4. The apparatus of claim 1 , wherein the first cyclic prefix size is different than the second cyclic prefix size.
5. The apparatus of claim 1 , wherein the first transform size and the second transform size are each selected from the group consisting of: 8192, 16384, and 32768.
6. The apparatus of claim 1 , wherein the first base cyclic prefix size and the second base cyclic prefix size are each selected from the group consisting of: 192, 384, 512, 768, 1024, 1536, 2048, 3072, and 4096 samples.
7. A method, comprising:
generating a data frame including a non-payload region and a payload region; and
wirelessly broadcasting the data frame,
wherein the payload region of 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 generating the data frame 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 first cyclic prefix size is a sum of a first base cyclic prefix size and an extension size,
wherein the second cyclic prefix size is a sum of a second base cyclic prefix size and the extension size, and
wherein the first transform size is different than the second transform size.
8. The method of claim 7 , further comprising:
determining a number of excess samples based at least on a difference between a total number of samples in the payload region and a sum of a total number of samples in the first set of OFDM symbols and a total number of samples in the second set of OFDM symbols; and
determining the extension size based on at least a ratio between the number of excess samples and a sum of a total number of OFDM symbols in the first set of OFDM symbols and a total number of OFDM symbols in the second set of OFDM symbols.
9. The method of claim 7 , wherein the first cyclic prefix size is different than the second cyclic prefix size.
10. The method of claim 7 , wherein the first transform size and the second transform size are each selected from the group consisting of: 8192, 16384, and 32768.
11. The method of claim 7 , wherein the first base cyclic prefix size and the second base cyclic prefix size are each selected from the group consisting of: 192, 384, 512, 768, 1024, 1536, 2048, 3072, and 4096 samples.