Methods of transmitting pilot tones and data in spatial multiplexing transmission
View Patent ↗A method and apparatus of transmitting pilot tones and data in multi-carrier spatial multiplexing transmission is disclosed. The method includes a plurality of subscribers transmitting data to a base station through common frequency sub-carrier and symbol time tiles. Each of the multiple subscribers rotating frequency sub-carrier and symbol time locations of pilot tones within the frequency sub-carrier and symbol time tiles.
1. A method comprising:
receiving, from a subscriber device, a first set of pilot symbols in a first frequency sub-carrier and symbol time tile and a second set of pilot symbols in a second frequency sub-carrier and symbol time tile, wherein the second set of pilot symbols are rotated relative to the first set of pilot symbols;
computing a first conjugate product of the first set of pilot symbols after removing from each pilot symbol in the first set of pilot symbols a known value of the pilot symbol as transmitted;
computing a second conjugate product of the second set of pilot symbols after removing from each pilot symbol in the second set of pilot symbols the known value of the pilot symbol as transmitted; and
combining the first conjugate product and the second conjugate product to obtain separate estimates for a phase offset across tones and a phase offset across orthogonal frequency-division, multiplexing (OFDM) symbols.
2. The method of claim 1 , further comprising:
updating channel estimates for the subscriber device based on the estimated phase offset across tones and the estimated phase offset across OFDM symbols.
3. The method of claim 2 , further comprising:
decoding data received from the subscriber device based on the updated channel estimates.
4. The method of claim 2 , further comprising:
determining the updated channel estimates based on averaging the first set of pilot symbols after removing from each pilot symbol in the first set of pilot symbols the known value of the pilot symbol as transmitted.
5. The method of claim 1 , wherein combining the first conjugate product and the second conjugate product comprises:
adding the first conjugate product to the second conjugate product; and
subtracting the second conjugate product from the first conjugate product.
6. The method of claim 1 , wherein combining the first conjugate product and the second conjugate product comprises:
multiplying the first conjugate product by the second conjugate product; and
multiplying the second conjugate product by the first conjugate product.
7. The method of claim 1 , further comprising:
before combining the first conjugate product and the second conjugate product, averaging the first conjugate product with one or more other conjugate products.
8. A method comprising:
receiving, a first set of pilot symbols in a first frequency sub-carrier and symbol time tile and a second set of pilot symbols in a second frequency sub-carrier and symbol time tile, wherein the second set of pilot symbols are rotated relative to the first set of pilot symbols;
computing a first conjugate product of the first set of pilot symbols and a second conjugate product of the second set of pilot symbols; and
combining the first conjugate product and the second conjugate product to obtain separate estimates for a phase offset across tones and a phase offset across orthogonal frequency-division multiplexing (OFDM) symbols.
9. The method of claim 8 , further comprising:
updating channel estimates for a subscriber device based on the estimated phase offset across tones and the estimated phase offset across OFDM symbols.
10. The method of claim 9 , further comprising:
decoding data received from the subscriber device based on the updated channel estimates.
11. The method of claim 9 , further comprising:
determining the channel estimates based on averaging the first set of pilot symbols together after removing from each pilot symbol in the first set of pilot symbols a known value of the pilot symbol as transmitted.
12. The method of claim 8 , wherein combining the first conjugate product and the second conjugate product comprises:
adding the first conjugate product to the second conjugate product; and
subtracting the second conjugate product from the first conjugate product.
13. The method of claim 8 , wherein combining the first conjugate product and the second conjugate product comprises:
multiplying the first conjugate product by the second conjugate product; and
multiplying the second conjugate product by a conjugate of the first conjugate product.
14. The method of claim 8 , further comprising:
before combining the first conjugate product and the second conjugate product, averaging the first conjugate product with one or more other conjugate products.
15. A method comprising:
receiving, from a subscriber device, a first set of pilot symbols in a first frequency sub-carrier and symbol time tile and a second set of pilot symbols in a second frequency sub-carrier and symbol time tile;
computing a first conjugate product of the first set of pilot symbols and a second conjugate product of the second set of pilot symbols; and
combining the first conjugate product and the second conjugate product to obtain separate estimates for a phase offset across tones and a phase offset across orthogonal frequency-division multiplexing (OFDM) symbols,
wherein additional sets of pilot symbols are received in the first and second frequency sub-carrier and symbol time tiles from one or more other subscriber devices, and
wherein the additional sets of pilot symbols occupy different locations in the first and second frequency sub-carrier and symbol time tiles than those occupied by the first and second sets of pilot symbols.
16. The method of claim 15 , further comprising:
updating channel estimates for the subscriber device based on the estimated phase offset across tones.
17. The method of claim 15 , further comprising:
updating channel estimates for the subscriber device based on the estimated phase offset across tones and the estimated phase offset across OFDM symbols.
18. The method of claim 17 , further comprising:
decoding data received from the subscriber device based on the updated channel estimates.
19. The method of claim 17 , further comprising:
determining the updated channel estimates based on averaging the first set of pilot symbols together after removing from each pilot symbol in the first set of pilot symbols a known value of the pilot symbol as transmitted.