Apparatus, and associated method, for providing open loop diversity in a radio communication system
View Patent ↗Apparatus, and an associated method, for providing transmit diversity to an open-loop MIMO communication scheme, such as a point to multipoint broadcast service in a cellular system. Multiple data streams of the broadcast data are broadcast by way of transmit diversity antennas of a sending station. The data symbols of the separate data streams are phase-shifted to be offset in phase from one another. The data streams, once the data symbols thereof are selectably phase-shifted by a phase shifter, are applied by an applier to sending nodes of the respective cells.
1. Apparatus for communicating data formed of a stream of symbols at multiple system inputs pursuant to a MIMO (Multiple Input Multiple Output) communication scheme, said apparatus communicating the stream of symbols throughout a first cell of a wireless communication system from first and second diversity antennas comprising:
a first symbol diversity creator disposed at a first cell and adapted to receive the stream of symbols, said first symbol diversity creator configured to split the stream of symbols into a first substream and a second substream, the first symbol diversity creator configured to alter the phase of the symbols of the second substream by a first phase amount resulting in a phase shifted second substream;
a first multiple-input applier configured to receive the first substream and the second substream and apply the first substream to at least the first diversity antenna and apply the second substream to at least the second diversity antenna; and
a broadcast information generator configured to broadcast information identifying phase shifting information related to phase shifting of the symbols of the second substream.
2. The apparatus of claim 1 wherein said symbol diversity creator comprises a phase shifter, which shifts the phase of the second substream by substantially 90 degrees relative to the phase of the first substream.
3. The apparatus of claim 1 wherein said symbol diversity introducer is configured to introduce diversity, in a common manner, to the stream of symbols for application to each OFDM channel of a system input of the multiple system inputs.
4. The apparatus of claim 1 further comprising a transformer adapted to inverse Fourier transform the stream of symbols before the stream of symbols is received by the first symbol diversity creator.
5. The apparatus of claim 1 further comprising:
a second symbol diversity creator disposed at a second cell and adapted to receive the stream of symbols, said second diversity creator configured to split the stream of symbols into a third substream and a fourth substream, the second symbol diversity creator configured to alter the phase of the symbols of the fourth substream by the first phase amount, resulting in a phase shifted fourth substream;
a second multi-input applier configured to receive the third substream and the phase shifted fourth substream and apply the third substream to a third diversity antenna in the second cell and apply the phase shifted fourth substream to a fourth diversity antenna in the second cell; and
wherein the phase shifted second substream and the phase shifted fourth substream are broadcast in a first manner and the first substream and the second substream are broadcast in a second manner.
6. The apparatus of claim 1 wherein the MIMO communication scheme further comprises an OFDM, Orthogonal Frequency Division Multiplexing, scheme that defines OFDM channels and wherein phase-shifting of the stream of symbols by said first symbol diversity creator comprises phase shifting symbols upon the OFDM channels.
7. The apparatus of claim 2 wherein said broadcast information generator is further adapted to receive indication of phase-shifting performed by said first symbol diversity creator.
8. The apparatus of claim 5 wherein the broadcast information generated by said broadcast information generator comprises information related to the first manner and the second manner.
9. The apparatus of claim 1 wherein said first multiple-input applier is further configured to combine said first substream and said second substream and apply said combined first and second substreams to said first and second diversity antennas.
10. The apparatus of claim 9 wherein said first multiple-input applier is further configured to apply weighting to said first substream and said second substream.
11. Apparatus for introducing transmission diversity in a data stream of symbols broadcast in an open loop PTMP, Point To Multipoint, service, by multiple broadcasting nodes having a plurality of diversity antennas, said apparatus comprising:
a first symbol diversity creator disposed at a first broadcasting node and adapted to receive the data stream of symbols, said first symbol diversity creator configured to split the data stream of symbols into a first substream and a second substream and configured to alter the phase of the data symbols of the second substream by a first phase amount resulting in a phase shifted second substream;
a first data-stream applier adapted to receive the first and second substreams, said first data stream applier configured to apply said first substream, in non-phase-shifted form, to at least a first diversity antenna at a first broadcasting node of the multiple broadcasting nodes and apply the second substream to at least a second diversity antenna at the first broadcasting node of the multiple broadcasting nodes;
a second symbol diversity creator disposed at a second broadcasting node and adapted to receive the data stream of symbols, said second diversity creator configured to split the data stream of symbols into a third substream and a fourth substream, the second symbol diversity creator configured to alter the phase of the symbols of the fourth substream by the first phase amount, resulting in a phase shifted fourth substream; and
a second data-stream applier adapted to receive the third and fourth substreams, said second data-stream applier configured to apply the third substream to a third diversity antenna in the second broadcasting node and apply the phase-shifted fourth substream to a fourth diversity antenna in the second broadcasting node.
12. The apparatus of claim 11 wherein the first phase amount further comprises a phase shift of substantially 90 degrees.
13. The apparatus of claim 11 wherein said first datastream applier is further configured to combine said first substream and said second substream and apply said combined first and second substreams to said first and second diversity antennas.
14. The apparatus of claim 13 wherein said first datastream applier is further configured to apply weighting to said first substream and said second substream.
15. The apparatus of claim 11 further comprising a broadcast information generator configured to broadcast information identifying phase shifting information related to phase shifting of the symbols of at least the second substream.
16. The apparatus of claim 11 further comprising a transformer adapted to inverse Fourier transform the data stream of symbols before the data stream of symbols is received by the first symbol diversity creator.
17. A method for communicating data formed of a stream of symbols at multiple system inputs pursuant to a MIMO, Multiple Input Multiple Output, communication scheme, said method for communicating said stream of symbols throughout a first cell of a wireless communications system, from first and second diversity antennas at a first cell, said method comprising the operations of:
splitting the stream of symbols into a first substream and a second substream;
phase-shifting symbols of the second substream relative to the symbols of the first substream by a first phase amount;
applying symbols of the first substream to at least the first diversity antenna, the first data substream formed of non-phase-shifted symbols; and
applying phase-shifted symbols of the second substream to at least the second diversity antenna; and
sending broadcast information identifying phase-shifting information related to phase-shifting of the symbols of the second sub-stream.
18. The method of claim 17 further comprising the operation of transforming the stream of symbols with an inverse Fourier transform before the operation of splitting the stream of symbols.
19. The method of claim 17 further comprising the operations of combining said first substream and said second substream and applying said combined first and second substreams to said first and second diversity antennas.
20. The method of claim 17 further comprising the operation of detecting the broadcast information at a wireless device.
21. The method of claim 17 further comprising the operation of detecting, at a wireless device, at least one of the first substream and the second substream.
22. The method of claim 21 further comprising the operation of recovering, at the wireless device, informational content of the data.
23. The method of claim 17 further communicating said stream of symbols throughout a second cell from third and fourth diversity antennas, said method further comprising:
splitting the stream of symbols into a third substream and a fourth substream at the second cell;
phase shifting symbols of the fourth substream relative to the symbols of the third substream, the phase shift applied to the fourth substream being equal to the first phase amount;
applying symbols of the third substream at least to the third diversity antenna, the third substream formed of non-phase-shifted modulation symbols;
applying the phase-shifted symbols of the fourth substream at least to the fourth diversity antenna; and
broadcasting the first substream and the third substream in a first manner and the second substream and the fourth substream in a second manner.
24. The method of claim 19 further comprising the operation of applying weighting to said first substream and said second substream.
25. The method of claim 17 wherein phase-shifting symbols of the second substream relative to the symbols of the first substream by a first phase amount further comprises phase-shifting by an amount substantially equal to 90 degrees.
26. A method for wirelessly communicating in a cell using a first and a second antenna port, comprising:
providing a first substream and a second substream;
phase-shifting symbols of the second substream relative to the symbols of the first substream by a first phase amount to generate complex-valued modulation symbols;
applying the symbols of the first substream to the first antenna port and the complex-valued modulation symbols of the second substream to the second antenna port;
generating a first time-domain OFDM signal for the first antenna port and a second time-domain OFDM signal for the second antenna port; and
sending information identifying the phase shift of the complex-valued modulation symbols.
27. The method of claim 26, wherein the first phase amount is approximately 90 degrees.
28. A computer program product encoded on a tangible, non-transitory storage medium, the product comprising computer readable instructions for causing one or more processors to perform operations comprising:
providing a first substream and a second substream;
phase-shifting symbols of the second substream relative to the symbols of the first substream by a first phase amount to generate complex-valued modulation symbols;
applying the symbols of the first substream to the first antenna port and the complex-valued modulation symbols of the second substream to the second antenna port; generating a first time-domain OFDM signal for the first antenna port and a second time-domain OFDM signal for the second antenna port; and
sending information identifying the phase shift of the complex-valued modulation symbols.
29. The computer program product of claim 28, wherein the first phase amount is approximately 90 degrees.
30. A base station, comprising: one or more processors configured to:
provide a first substream and a second substream;
phase-shift symbols of the second substream relative to the symbols of the first substream by a first phase amount to generate complex-valued modulation symbols;
apply the symbols of the first substream to the first antenna port and the complex-valued modulation symbols of the second substream to the second antenna port;
generate a first time-domain OFDM signal for the first antenna port and a second time-domain OFDM signal for the second antenna port; and
send information identifying the phase shift of the complex-valued modulation symbols.
31. The base station of claim 30, wherein the first phase amount is approximately 90 degrees.