Methods and apparatuses for phase rotation in 2 sub-carrier PI/2 binary phase shift keying communication
The present invention provides methods and apparatuses for implementation of cyclic prefix (CP) and demodulation reference signal (DMRS) in 2 sub-carrier pi/2 binary phase shift keying (BPSK) modulation in a communication system. DMRS symbols are interleaved with data-carrying symbols and configured such that they are alternatingly transmitted on different ones of the two sub-carriers. When a DMRS symbol is transmitted on one sub-carrier, the other sub-carrier may be unused. In implementing CP, phase rotations may be applied to modulation symbols, such that each concurrently transmitted pair of symbols is subjected to a same phase rotation. The phase rotation can be derived based on an average frequency of the two (e.g. adjacent) sub-carriers in use. The phase rotations can be updated recursively, and the update multiplied by a scaling factor.
1. A method for transmitting symbols in a physical resource block format in a communication system, the method comprising:
converting input data into modulation symbols, the converting comprising performing Pi/2 binary phase shift keying (BPSK) modulation on the input data;
performing a discrete Fourier transform pairwise on the modulation symbols, or on the modulation symbols combined with additional modulation symbols;
performing a phase rotation operation on symbols output by the discrete Fourier transform;
performing tone (k) modulation pairwise on phase rotated symbols output by the phase rotation operation in order to map respective ones of each pair of phase rotated symbols to respective ones of the pair of sub-carriers;
adding cyclic prefixes to symbols output by the tone (k) modulation to generate a plurality of prefixed symbols; and
transmitting the prefixed symbols using a pair of sub-carriers of the physical resource block format,
wherein the phase rotation operation comprises applying a same phase rotation to pairs of symbols that will be transmitted concurrently on each one of the pair of sub-carriers.
2. The method of claim 1 , wherein the same phase rotation is generated based on an average frequency of the pair of sub-carriers.
3. The method of claim 1 , wherein the same phase rotation for a current pair of symbols is derived in part based on the same phase rotation for an immediately prior pair of symbols plus an offset incorporating the average frequency of the pair of sub-carriers.
4. The method of claim 3 , further comprising multiplying the offset by a scaling factor.
5. The method of claim 4 , wherein the scaling factor is based on characteristics of a transmit filter used in transmitting of the prefixed symbols.
6. The method of claim 4 , wherein the scaling factor is configured to balance a peak-to-average power ratio for forward and reverse phase transitions.
7. The method of claim 1 , wherein the phase rotation is configured to compensate for cyclic prefix rotation.
8. The method of claim 1 , further comprising:
determining if a frequency of one of the pair of sub-carriers is within a predetermined range of a cut-off frequency of a transmit filter used in transmission of the prefixed symbols or reconstruction filter involved in reception of the prefixed symbols;
when the frequency is within the predetermined range, re-tuning a local oscillator generating frequencies of the sub-carriers.
9. The method of claim 1 , wherein the pair of sub-carriers are adjacent sub-carriers in the physical resource block format.
10. The method of claim 1 , wherein the physical resource block format comprises the pair of sub-carriers as well as additional sub-carriers, and wherein the additional sub-carriers are unused for transmission.
11. An electronic wireless communication apparatus for transmitting symbols in a physical resource block format in a communication system, the apparatus comprising circuitry configured to:
convert input data into modulation symbols, the converting comprising performing Pi/2 binary phase shift keying (BPSK) modulation on the input data;
perform a discrete Fourier transform pairwise on the modulation symbols, or on the modulation symbols combined with additional modulation symbols;
perform a phase rotation operation on symbols output by the discrete Fourier transform;
perform tone (k) modulation pairwise on phase rotated symbols output by the phase rotation operation in order to map respective ones of each pair of phase rotated symbols to respective ones of the pair of sub-carriers;
add cyclic prefixes to symbols output by the tone (k) modulation to generate a plurality of prefixed symbols; and
transmit the prefixed symbols using a pair of sub-carriers of the physical resource block format,
wherein the phase rotation operation comprises applying a same phase rotation to pairs of symbols that will be transmitted concurrently on each one of the pair of sub-carriers.
12. The apparatus of claim 11 , wherein the same phase rotation is generated based on an average frequency of the pair of sub-carriers.
13. The apparatus of claim 11 , wherein the same phase rotation for a current pair of symbols is derived in part based on the same phase rotation for an immediately prior pair of symbols plus an offset incorporating the average frequency of the pair of sub-carriers.
14. The apparatus of claim 13 , further comprising multiplying the offset by a scaling factor.
15. The apparatus of claim 14 , wherein the scaling factor is based on characteristics of a transmit filter used in transmitting of the prefixed symbols.
16. The apparatus of claim 14 , wherein the scaling factor is configured to balance a peak-to-average power ratio for forward and reverse phase transitions.
17. The apparatus of claim 11 , wherein the phase rotation is configured to compensate for cyclic prefix rotation.
18. The apparatus of claim 11 , further comprising:
determining if a frequency of one of the pair of sub-carriers is within a predetermined range of a cut-off frequency of a transmit filter used in transmission of the prefixed symbols or reconstruction filter involved in reception of the prefixed symbols;
when the frequency is within the predetermined range, re-tuning a local oscillator generating frequencies of the sub-carriers.
19. The apparatus of claim 11 , wherein the pair of sub-carriers are adjacent sub-carriers in the physical resource block format.
20. The apparatus of claim 11 , wherein the physical resource block format comprises the pair of sub-carriers as well as additional sub-carriers, and wherein the additional sub-carriers are unused for transmission.