Pilot boosting and traffic to pilot ratio estimation in a wireless communication system

• US 20090041151A1
• Filed: 06/02/2008
• Published: 02/12/2009
• Est. Priority Date: 08/07/2007
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Khan, Farooq, Pi, Zhouyue, Zhang, Jianzhong, Tsai, Jiannan
• Granted Patent: US 8,369,450 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04L 1/0606 Space-frequency coding
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/005 of common pilots, i.e. pilots destined for multiple users or terminals

Abstract

Methods and circuits for assigning pilot boosting factors and calculating traffic to pilot ratios in a wireless communication system. The data to be transmitted is first modulated to generate a plurality of data modulation symbols. The plurality of data modulation symbols and a plurality of reference signal symbols are mapped into transmission resources of each of a plurality of antennas in accordance with a transmit diversity scheme. The transmission resources of each of the antennas are divided into a plurality of subcarriers in a frequency domain and a plurality of time units in a time domain. Then, a power scaling factor are assigned for data modulation symbols on each of the antennas in dependence upon power levels of the reference signal symbols to maintain a fixed power level across the plurality of antennas in each time unit. Finally, the data modulation symbols and the reference signal symbols are transmitted via the plurality of antennas in accordance with the mapping scheme and the assigned scaling factors.

Claims

1. A method for transmission, the method comprising the steps of:

mapping a plurality of data modulation symbols of a plurality of data packets and a plurality of reference signal symbols into transmission resources of a transmission antenna in accordance with a certain transmission scheme, with the transmission resources being divided into a plurality of subcarriers in a frequency domain and a plurality of time units in a time domain, and within a k-th time unit, N subcarriers being available for transmitting signals, and the N subcarriers comprising N_RS^k subcarriers for transmitting reference signal symbols, N_idle^k subcarriers that are concurrently unused, and N_data^k subcarriers for transmitting data modulation symbols;

determining bandwidth ratios between respective corresponding pairs of time units for each data packet and power ratios between respective corresponding pairs of time units for each data packet, to maintain a constant bandwidth ratio between each pair of time units across all data packets and a constant power ratio between each pair of time units across all data packets, with the bandwidth ratio η

(i,j) between an i-th time unit and a j-th time unit being established for each data packet by;

$\mathrm{\eta <br><br>}<br><br>\left(i,j\right)=\frac{N-N_{\mathrm{RS}}^i-N_{\mathrm{idle}}^i}{N-N_{\mathrm{RS}}^j-N_{\mathrm{idle}}^j},$

and the power ratio γ

(i,j) between an i-th time unit and a j-th time unit for each data packet being established by;

$\mathrm{\gamma <br><br>}<br><br>\left(i,j\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^i<br><br>N_{\mathrm{RS}}^i}{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^j<br><br>N_{\mathrm{RS}}^j}·<br><br>\frac{1}{\mathrm{\eta <br><br>}<br><br>\left(i,j\right)},$

where α

_RS^k is a power boosting factor for the reference signal symbols in a k-th time unit; and

transmitting the plurality of data modulation symbols of the plurality of data packets and the reference signal symbols via the transmission antenna by using the transmission resources, with the transmission of at least one data packet being in accordance with the determined bandwidth ratios and power ratios.

2. The method of claim 1, comprised of determining a data subcarrier traffic-to-nominal-power-spectral-density-ratio (TNPR) for each of the time units, with the data subcarrier TNPR for a k-th time unit being established by:

${\mathrm{\rho <br><br>}}_k=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^k<br><br>N_{\mathrm{RS}}^k}{N-N_{\mathrm{RS}}^k-N_{\mathrm{idle}}^k}.$

3. The method of claim 1, comprised of determining a nominal data subcarrier traffic-to-pilot-ratio (TPR) for each of the time units, with the nominal data subcarrier TPR for a k-th time unit being established by:

${\mathrm{\sigma <br><br>}}_k=\frac{1}{{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^k}·<br><br>\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^k<br><br>N_{\mathrm{RS}}^k}{N-N_{\mathrm{RS}}^k-N_{\mathrm{idle}}^k}.$

4. The method of claim 1, comprised of, when all of the N subcarriers are utilized for transmitting signals, the bandwidth ratio η

(i,j) between the i-th time unit and the j-th time unit being established for each data packet by;

$\mathrm{\eta <br><br>}<br><br>\left(i,j\right)=\frac{N-N_{\mathrm{RS}}^i}{N-N_{\mathrm{RS}}^j},$

and the power ratio γ

(i,j) between the i-th time unit and the j-th time unit for each data packet being established by;

$\mathrm{\gamma <br><br>}<br><br>\left(i,j\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^i<br><br>N_{\mathrm{RS}}^i}{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^j<br><br>N_{\mathrm{RS}}^j}·<br><br>\frac{N-N_{\mathrm{RS}}^j}{N-N_{\mathrm{RS}}^i}.$

5. The method of claim 4, comprised of, when no reference signal symbol is transmitted in the j-th time unit, the bandwidth ratio η

(i,j) between the i-th time unit and the j-th time unit being established for each data packet by;

$\mathrm{\eta <br><br>}<br><br>\left(i,j\right)=\frac{N-N_{\mathrm{RS}}^i}{N},$

and the power ratio γ

(i,j) between the i-th time unit and the j-th time unit for each data packet being established by;

$\mathrm{\gamma <br><br>}<br><br>\left(i,j\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^i<br><br>N_{\mathrm{RS}}^i}{N-N_{\mathrm{RS}}^i}.$

6. A method for transmission, the method comprising the steps of:

mapping a plurality of data modulation symbols of a plurality of data packets and a plurality of reference signal symbols into transmission resources of a plurality of transmission antennas in accordance with a certain transmission scheme, with the transmission resources being divided into a plurality of subcarriers in a frequency domain and a plurality of time units in a time domain, and within a k-th time unit, N subcarriers being available for transmitting signals via all of the plurality of transmission antennas, and the N subcarriers comprising N_RS^k subcarriers for transmitting reference signal symbols, N_idle^k subcarriers that are concurrently unused, and N_data^k subcarriers for transmitting data modulation symbols;

determining bandwidth ratios between respective corresponding pairs of time units for each data packet, and determining power ratios between respective corresponding pairs of transmission antennas in different time units for each data packet, to maintain a constant bandwidth ratio between each pair of time units across all data packets and a constant power ratio between each pair of antennas in different time units across all data packets, with the bandwidth ratio η

(i,j) between an i-th time unit and a j-th time unit being established for each data packet by;

$\mathrm{\eta <br><br>}<br><br>\left(i,j\right)=\frac{N-N_{\mathrm{RS}}^i-N_{\mathrm{idle}}^i}{N-N_{\mathrm{RS}}^j-N_{\mathrm{idle}}^j},$

and the power ratio γ

^t,s(i,j) between a t-th transmission antenna in an i-th time unit and an s-th transmission antenna in a j-th time unit for each data packet being established by;

${\mathrm{\gamma <br><br>}}^{t,s}<br><br>\left(i,j\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{i,t}<br><br>N_{\mathrm{RS}}^{i,t}}{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{j,s}<br><br>N_{\mathrm{RS}}^{j,s}}·<br><br>\frac{1}{\mathrm{\eta <br><br>}<br><br>\left(i,j\right)},$

where α

_RS^k,t is a power boosting factor for the reference signal symbols from a t-th transmission antenna in a k-th time unit; and

transmitting the plurality of data modulation symbols of the plurality of data packets and the reference signal symbols via the plurality of transmission antennas by using the transmission resources, with the transmission of at least one data packet being in accordance with the determined bandwidth ratios and power ratios.

7. The method of claim 6, comprised of determining a data subcarrier traffic-to-nominal-power-spectral-density-ratio (TNPR) for each of the transmission antenna in each of the time units, with the data subcarrier TNPR for a t-th transmission antenna in a k-th time unit being established by:

${\mathrm{\rho <br><br>}}^{k,t}=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{k,t}<br><br>N_{\mathrm{RS}}^{k,t}}{N-N_{\mathrm{RS}}^k-N_{\mathrm{idle}}^k}.$

8. The method of claim 6, comprised of determining a data subcarrier nominal traffic-to-nominal-power-spectral-density-ratio (TNPR) for transmitting each of the data packet via each of the transmission antennas in each of the time units, with the data subcarrier nominal TNPR for transmission of an m-th data packet via a t-th transmission antenna in a k-th time unit being established by:

${\mathrm{\rho <br><br>}}_m^{k,t}=\frac{1}{{\mathrm{\mu <br><br>}}_m^k}·<br><br>\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{k,t}<br><br>N_{\mathrm{RS}}^{k,t}}{N-N_{\mathrm{RS}}^k-N_{\mathrm{idle}}^k},$

where μ

_m^k is a bandwidth utilization value for transmitting the m-th data packet the k-th time unit.

9. The method of claim 6, comprised of determining a data subcarrier nominal traffic-to-pilot-ratio (TPR) for each of the transmission antenna in each of the time units, with the nominal data subcarrier TPR for a t-th transmission antenna in a k-th time unit being established by:

${\mathrm{\sigma <br><br>}}^{k,t}=\frac{1}{{\mathrm{\sigma <br><br>}}_{\mathrm{RS}}^{k,t}}·<br><br>\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{k,t}<br><br>N_{\mathrm{RS}}^{k,t}}{N-N_{\mathrm{RS}}^k-N_{\mathrm{idle}}}.$

10. The method of claim 6, comprised of determining a data subcarrier nominal traffic-to-pilot-ratio (TPR) for transmitting each of the data packet via each of the transmission antenna in each of the time units, with the nominal data subcarrier TPR for transmitting an m-th data packet via a t-th transmission antenna in a k-th time unit being established by:

${\mathrm{\sigma <br><br>}}^{k,t}=\frac{1}{{\mathrm{\sigma <br><br>}}_{\mathrm{RS}}^{k,t}}·<br><br>\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{k,t}<br><br>N_{\mathrm{RS}}^{k,t}}{N-N_{\mathrm{RS}}^k-N_{\mathrm{idle}}^k}.$

11. The method of claim 6, comprised of, when all of the N subcarriers are utilized for transmitting signals, the bandwidth ratio η

(i,j) between the i-th time unit and the j-th time unit being established for each data packet by;

$\mathrm{\eta <br><br>}<br><br>\left(i,j\right)=\frac{N-N_{\mathrm{RS}}^i}{N-N_{\mathrm{RS}}^j},$

and the power ratio γ

^t,s(i,j) between the t-th transmission antenna in the i-th time unit and the s-th transmission antenna in the j-th time unit for each data packet being established by;

${\mathrm{\gamma <br><br>}}^{t,s}<br><br>\left(i,j\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{i,t}<br><br>N_{\mathrm{RS}}^{i,t}}{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{j,s}<br><br>N_{\mathrm{RS}}^{j,s}}·<br><br>\frac{1}{\mathrm{\eta <br><br>}<br><br>\left(i,j\right)}.$

12. The method of claim 11, comprised of, when the reference signal symbols in the same time unit have the same power boosting factor, the power ratio γ

^t,s(i,i) between the t-th transmission antenna in the i-th time unit and the s-th transmission antenna in the i-th time unit for each data packet being established by

${\mathrm{\gamma <br><br>}}^{t,s}<br><br>\left(i,i\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}<br><br>N_{\mathrm{RS}}^{i,t}}{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}<br><br>N_{\mathrm{RS}}^{i,s}}.$

13. A method for data transmission in a communication system, the method comprising the steps of:

modulating data to be transmitted to generate a plurality of data modulation symbols;

mapping the plurality of data modulation symbols and a plurality of reference signal symbols into transmission resources of each of a plurality of antennas in accordance with a transmit diversity scheme, with the transmission resources of each of the antennas being divided into a plurality of subcarriers in a frequency domain and a plurality of time units in a time domain;

assigning a power scaling factor for data modulation symbols on each of the antennas in dependence upon power levels of the reference signal symbols to maintain a fixed power level across the plurality of antennas in each time unit; and

transmitting the data modulation symbols and the reference signal symbols via the plurality of antennas in accordance with the mapping scheme and the assigned scaling factors.

14. The method of claim 13, comprised of transmitting reference signal symbols and four data modulation symbols S₁, S₂, S₃ and S₄ from among the plurality of data modulation symbols over six subcarriers via four antennas in a certain timer unit, with:

a first reference signal symbol being transmitted via a first antenna over a sixth subcarrier with one-third of a total power that is available for transmission over the six subcarriers in the certain time unit, and a second reference signal symbol being transmitted via a second antenna over a third subcarrier with one-third of the total power; and

a transmission matrix with the scaling factors for the four data modulation symbols being established by;

$\begin{array}{c}T=\left[\begin{array}{cccc}{T}_{11}& T_{12}& T_{14}& T_{15}\\ T_{21}& T_{22}& T_{24}& T_{25}\\ T_{31}& T_{32}& T_{34}& T_{35}\\ T_{41}& T_{42}& T_{44}& T_{45}\end{array}\right]\\ =\left[\begin{array}{cccc}{S}_1& -S_2^{*}& 0& 0\\ 0& 0& S_3& -S_4^{*}\\ \sqrt{3/2}<br><br>S_2& \sqrt{3/2}<br><br>S_1^{*}& 0& 0\\ 0& 0& \sqrt{3/2}<br><br>S_4& \sqrt{3/2}<br><br>S_3^{*}\end{array}\right],\end{array}$

where T_ij represents the symbol transmitted on the ith antenna port and the jth subcarrier.

15. The method of claim 14, comprised of transmitting a signal containing information regarding channel gains for each of the data modulation symbols, with:

the channel gains for each of the data modulation symbols S₁ and S₂ being established by;

$g_{12}=\left(h_0^2+\frac{3}{2}<br><br>h_2^2\right)<br><br>S_i,\mathrm{for}<br><br><br><br>i=1,2;<br><br>\mathrm{and}$

the channel gains for each of the data modulation symbols S₃ and S₄ being established by;

$g_{34}=\left(h_1^2+\frac{3}{2}<br><br>h_3^2\right)<br><br>S_i,\mathrm{for}<br><br><br><br>i=3,4,$

where h₀, h₁, h₂ and h₃ are channel gains from the first antenna, the second antenna, the third antenna and the fourth antenna, respectively.

16. The method of claim 13, comprised of transmitting reference signal symbols and four data modulation symbols S₁, S₂, S₃ and S₄ from among the plurality of data modulation symbols over six subcarriers via four antennas in a certain timer unit, with:

a third reference signal symbol being transmitted via a third antenna over a sixth subcarrier with one-third of a total power that is available for transmission over the six subcarriers, and a fourth reference signal symbol being transmitted via a fourth antenna over a third subcarrier with one-third of the total power; and

a transmission matrix with the scaling factors for the four data modulation symbols being established by;

$\begin{array}{c}T=\left[\begin{array}{cccc}{T}_{11}& T_{12}& T_{14}& T_{15}\\ T_{21}& T_{22}& T_{24}& T_{25}\\ T_{31}& T_{32}& T_{34}& T_{35}\\ T_{41}& T_{42}& T_{44}& T_{45}\end{array}\right]\\ =\left[\begin{array}{cccc}\sqrt{3/2}<br><br>S_1& -\sqrt{3/2}<br><br>S_2^{*}& 0& 0\\ 0& 0& \sqrt{3/2}<br><br>S_3& -\sqrt{3/2}<br><br>S_4^{*}\\ S_2& S_1^{*}& 0& 0\\ 0& 0& S_4& S_3^{*}\end{array}\right],\end{array}$

where T_ij represents the symbol transmitted on the ith antenna port and the jth subcarrier.

17. The method of claim 13, comprised of transmitting four data modulation symbols S₁, S₂, S₃ and S₄ from among the plurality of data modulation symbols over six subcarriers via four antennas in a certain timer unit, with a transmission matrix being established by:

$\begin{array}{c}T=\left[\begin{array}{cccc}{T}_{11}& T_{12}& T_{13}& T_{14}\\ T_{21}& T_{22}& T_{23}& T_{24}\\ T_{31}& T_{32}& T_{33}& T_{34}\\ T_{41}& T_{42}& T_{43}& T_{44}\end{array}\right]\\ =\left[\begin{array}{cccc}{S}_1& -S_2^{*}& 0& 0\\ 0& 0& S_3& -S_4^{*}\\ S_2& S_1^{*}& 0& 0\\ 0& 0& S_4& S_3^{*}\end{array}\right],\end{array}$

where T_ij represents the symbol transmitted on the ith antenna port and the jth subcarrier.

18. The method of claim 13, comprised of transmitting a signal containing information regarding the ratios between the assigned scaling factors of the antennas.

19. The method of claim 13, comprised of transmitting a signal containing information regarding channel gains for each of the data modulation symbols, with the channel gains being calculated in dependence upon the assigned scaling factors of the antennas.

20. The method of claim 13, comprised of transmitting a signal containing information regarding the ratios of the total power from all of the antennas for each data modulation symbol between different time units.

21. The method of claim 13, comprised of transmitting reference signal symbols and four data modulation symbols S₁, S₂, S₃ and S₄ from among the plurality of data modulation symbols over six subcarriers via four antennas in a certain timer unit, with:

a first reference signal symbol being transmitted via a first antenna over a sixth subcarrier with two-thirds of a total power that is available for transmission over the six subcarriers, and a second reference signal symbol being transmitted via a second antenna over a third subcarrier with two-thirds of the total power; and

a transmission matrix with the scaling factors for the four data modulation symbols being established by;

$\begin{array}{c}T=\left[\begin{array}{cccc}{T}_{11}& T_{12}& T_{14}& T_{15}\\ T_{21}& T_{22}& T_{24}& T_{25}\\ T_{31}& T_{32}& T_{34}& T_{35}\\ T_{41}& T_{42}& T_{44}& T_{45}\end{array}\right]\\ =\left[\begin{array}{cccc}{S}_1& -S_2^{*}& 0& 0\\ 0& 0& S_3& -S_4^{*}\\ \sqrt{3}<br><br>S_2& \sqrt{3}<br><br>S_1^{*}& 0& 0\\ 0& 0& \sqrt{3}<br><br>S_4& \sqrt{3}<br><br>S_3^{*}\end{array}\right],\end{array}$

where T_ij represents the symbol transmitted on the ith antenna port and the jth subcarrier.

22. The method of claim 21, comprised of transmitting a signal containing information regarding channel gains for each of the data modulation symbols, with:

the channel gains for each of the data modulation symbols S₁ and S₂ being established by;

g₁₂=(h₀²+3h₂²)S_i, for i=1, 2; and

the channel gains for each of the data modulation symbols S₃ and S₄ being established by;

g₃₄=(h₁²+3h₃²)S_i, for i=3, 4,

where h₀, h₁, h₂ and h₃ are channel gains from the first antenna, the second antenna, the third antenna and the fourth antenna, respectively.

23. A method for data transmission in a communication system, the method comprising the steps of:

modulating data to be transmitted to generate a plurality of data modulation symbols;

mapping the plurality of data modulation symbols into at least one modulation layer in a multiple input and multiple output system;

mapping the plurality of data modulation symbols and a plurality of reference signal symbols into transmission resources of a plurality of transmission antennas in accordance with a precoding matrix, with one modulation layer corresponding to a selected column in the precoding matrix, and each row of the precoding matrix corresponding to an antenna from a plurality of antennas for transmitting the data modulation symbols;

assigning a power scaling factor to each of the rows in the precoding matrix in dependence upon power levels of the reference signal symbols to maintain a fixed power level across the plurality of antennas in a certain time unit; and

transmitting the data modulation symbols and the reference signal symbols via the plurality of antennas.

24. The method of claim 23, comprised of the precoding matrix being constructed based upon a Householder matrix, with the Householder matrix being established by:

$M_1=I_4-2<br><br>u_1<br><br>u_1^H/{<br><br>u_1<br><br>}^2=0.5*\left[\begin{array}{cccc}1& 1& 1& 1\\ 1& 1& -1& -1\\ 1& -1& 1& -1\\ 1& -1& -1& 1\end{array}\right],$

where u₁^T=[1 −

1 −

1 −

1].

25. The method of claim 24, comprised of transmitting two reference signal symbols and two modulation layers over six subcarriers via four antennas in the certain time unit, with:

a first reference signal symbol being transmitted over a sixth subcarrier via a first antenna by using one-third of a total power that is available for transmission over the six subcarriers, and a second reference signal symbol being transmitted via a second antenna over a third subcarrier with one-third of the total power; and

the precoding matrix being established by;

$M_1^{\mathrm{\prime <br><br>}}=0.5*\left[\begin{array}{cccc}1& 0& 1& 0\\ 1& 0& -1& 0\\ 3/2& 0& 3/2& 0\\ 3/2& 0& -3/2& 0\end{array}\right]$

with a first modulation layer corresponding to the first column of the precoding matrix, and a second modulation layer corresponding to the third column of the precoding matrix.

26. The method of claim 23, comprised of the precoding matrix being constructed based upon a Fourier matrix, with an N×

N Fourier matrix being established by;

P_N=e<sup>j2π

mn/N</sup> m,n=0, 1, . . . (N−

1).

27. The method of claim 26, comprised of transmitting two reference signal symbols and four modulation layers over six subcarriers via four antennas in the certain time unit, with:

a first reference signal symbol being transmitted over a sixth subcarrier via a first antenna by using one-third of a total power that is available for transmission over the six subcarriers, and a second reference signal symbol being transmitted via a second antenna over a third subcarrier with one-third of the total power; and

the precoding matrix being established by;

$P_4^{\mathrm{\prime <br><br>}}=\left[\begin{array}{cccc}1& 1& 1& 1\\ 1& j& -1& -j\\ 3/2& -3/2& 3/2& -3/2\\ 3/2& -j<br><br><br><br>3/2& -3/2& j<br><br><br><br>3/2\end{array}\right]$

with a first modulation layer corresponding to the first column of the precoding matrix, a second modulation layer corresponding to the second column of the precoding matrix, a third modulation layer corresponding to the third column of the precoding matrix, and a fourth modulation layer corresponding to the four column of the precoding matrix.

28. The method of claim 23, comprised of transmitting a signal containing information regarding the ratios between the assigned scaling factors of the antennas.

29. The method of claim 28, comprised of the signal containing information regarding the ratios of the total power from all of the antennas for each modulation symbol between different time units.

30. A method for decoding data in a communication system, with the method comprising the steps of:

receiving data signals, reference signals and a control signal transmitted from a transmitter via a plurality of transmission antennas, with the control signal indicating traffic to pilot ratios on respective transmission antennas;

deriving power levels on respective transmission antennas in dependence upon the traffic to pilot ratios; and

decoding the data signals in dependence upon the derived power levels on the transmission antennas.

31. A method for decoding data in a communication system, with the method comprising the steps of:

receiving data signals, reference signals and a control signal transmitted from a transmitter via a plurality of transmission antennas, with the control signal indicating power boosting factors of the reference signals;

deriving power levels on respective transmission antennas in dependence upon the power boosting factors; and

decoding the data signals in dependence upon the derived power levels on the transmission antennas.

32. A method for decoding data in a communication system, with the method comprising the steps of:

receiving data signals, reference signals and a control signal transmitted from a transmitter via a plurality of transmission antennas, with the control signal indicating nominal traffic to pilot ratios and power levels on respective transmission antennas;

deriving actual traffic to pilot ratios on respective transmission antennas independence upon the nominal traffic to pilot ratios; and

decoding the data signals in dependence upon the actual traffic to pilot ratios and the power levels on respective transmission antennas.

33. A method for receiving data, the method comprising the steps of:

receiving data signals and reference signals in a plurality of time units transmitted from a transmitter via a transmission antenna;

receiving information regarding the number of subcarriers that are available for transmission in each time units, the number of subcarriers for transmitting reference signals in each time unit, the number of subcarriers for transmitting data signals in each time unit, the number of subcarriers that are available for transmission and are not used in each time unit, and power boosting factors for the reference signals in each time unit;

determining bandwidth ratios between respective corresponding pairs of time units and power ratios between respective corresponding pairs of time units, with the bandwidth ratio η

(i,j) between an i-th time unit and a j-th time unit and the power ratio γ

(i,j) between an i-th time unit and a j-th time unit for each data packet being respectively established by;

$\mathrm{\eta <br><br>}<br><br>\left(i,j\right)=\frac{N-N_{\mathrm{RS}}^i-N_{\mathrm{idle}}^i}{N-N_{\mathrm{RS}}^j-N_{\mathrm{idle}}^j},\mathrm{and}$ $\mathrm{\gamma <br><br>}<br><br>\left(i,j\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^i<br><br>N_{\mathrm{RS}}^i}{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^j<br><br>N_{\mathrm{RS}}^j}·<br><br>\frac{1}{\mathrm{\eta <br><br>}<br><br>\left(i,j\right)},$

where N being the number of subcarriers that are available for transmission in a k-th time unit, N_RS^k being the number of subcarriers for transmitting reference signal symbols in the k-th time unit, N_idle^k being the number of subcarriers that are concurrently unused in the k-th time unit, N_data^k being the number of subcarriers for transmitting data modulation symbols in the k-th time unit, and α

_RS^k is a power boosting factor for the reference signal symbols in a k-th time unit; and

decoding the received data signals by using the determined bandwidth ratios and power ratios.

34. A method for receiving data, the method comprising the steps of:

receiving data signals and reference signals in a plurality of time units transmitted from a transmitter via a plurality of transmission antenna;

receiving information regarding the number of subcarriers that are available for transmission in each time units, the number of subcarriers for transmitting reference signals in each time unit, the number of subcarriers for transmitting data signals in each time unit, the number of subcarriers that are available for transmission and are not used in each time unit, and power boosting factors for the reference signals in each time unit;

determining bandwidth ratios between respective corresponding pairs of time units and power ratios between respective corresponding pairs of transmission antennas in different time units, with the bandwidth ratio η

(i,j) between an i-th time unit and a j-th time unit and the power ratio γ

^t,s(i,j) between a t-th transmission antenna in an i-th time unit and an s-th transmission antenna in a j-th time unit being respectively established;

$\mathrm{\eta <br><br>}<br><br>\left(i,j\right)=\frac{N-N_{\mathrm{RS}}^i-N_{\mathrm{idle}}^i}{N-N_{\mathrm{RS}}^j-N_{\mathrm{idle}}^j},\mathrm{and}$ ${\mathrm{\gamma <br><br>}}^{t,s}<br><br>\left(i,j\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{i,t}<br><br>N_{\mathrm{RS}}^{i,t}}{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{j,s}<br><br>N_{\mathrm{RS}}^{j,s}}·<br><br>\frac{1}{\mathrm{\eta <br><br>}<br><br>\left(i,j\right)},$

where N being the number of subcarriers that are available for transmission in a k-th time unit, N_RS^k being the number of subcarriers for transmitting reference signal symbols in the k-th time unit, N_idle^k being the number of subcarriers that are concurrently unused in the k-th time unit, N_data^k being the number of subcarriers for transmitting data modulation symbols in the k-th time unit, α

_RS^k,t is a power boosting factor for the reference signal symbols from a t-th transmission antenna in the k-th time unit; and

decoding the received data signals by using the determined bandwidth ratios and power ratios.

35. A wireless terminal in a communication system, comprising:

a modulation unit modulating data to be transmitted to generate a plurality of data modulation symbols;

a mapping unit mapping the plurality of data modulation symbols into transmission resources of each of a plurality of antennas in accordance with a transmit diversity scheme, with the transmission resources of each of the antennas being divided into a plurality of subcarriers in a frequency domain and a plurality of time units in a time domain; and

a power scaling unit assigning a scaling factor for each of the antennas to maintain a fixed power level across the plurality of antennas in each time unit.

36. A wireless terminal in a communication system, comprising:

a modulation unit modulating data to be transmitted to generate a plurality of data modulation symbols;

a layer generation unit mapping the plurality of data modulation symbols into at least one modulation layer in a multiple input and multiple output system; and

a precoding unit, with the precoding unit;

constructing a precoding matrix for precoding the data modulation symbols in the at least one modulation layer, with one modulation layer corresponding to a selected column in the precoding matrix, and each row of the precoding matrix corresponding to an antenna from a plurality of antennas for transmitting the data modulation symbols;

assigning a power scaling factor to each of the rows in the precoding matrix to maintain a fixed power level across the plurality of antennas in a certain time unit; and

precoding the data modulation symbols by using the precoding matrix.

37. A wireless terminal in a communication system, comprising:

at least one receiving antenna receiving data signals, reference signals and a control signal transmitted from a transmitter via a plurality of transmission antennas, with the control signal indicating traffic to pilot ratios in different time units;

a processing unit deriving power levels on the respective transmission antennas in dependence upon the traffic to pilot ratio; and

a decoding unit decoding the data signals by using the derived power levels from the transmission antennas.

38. A wireless terminal in a communication system, comprising:

at least one receiving antenna receiving data signals, reference signals and a control signal transmitted from a transmitter via a plurality of transmission antennas, with the control signal indicating power boosting factors of the reference signals;

a processing unit deriving power levels on the respective transmission antennas in dependence upon the power boosting factors; and

a decoding unit decoding the data signals by using the derived power levels on the transmission antennas.

39. A wireless terminal in a communication system, comprising:

at least one receiving antenna receiving data signals, reference signals and a control signal transmitted from a transmitter via a plurality of transmission antennas, with the control signal indicating nominal traffic to pilot ratios and power levels on respective transmission antennas;

deriving actual traffic to pilot ratios on the respective transmission antennas; and

decoding the data signals in dependence upon the actual traffic to pilot ratios and the power levels on respective transmission antennas.

40. A wireless terminal in a communication system, comprising:

a mapping unit mapping a plurality of data modulation symbols of a plurality of data packets and a plurality of reference signal symbols into transmission resources of a transmission antenna in accordance with a certain transmit diversity scheme, with the transmission resources being divided into a plurality of subcarriers in a frequency domain and a plurality of time units in a time domain, and within a k-th time unit, N subcarriers being available for transmitting signals, and the N subcarriers comprising N_RS^k subcarriers for transmitting reference signal symbols, N_idle^k subcarriers that are concurrently unused, and N_data^k subcarriers for transmitting data modulation symbols;

a processing unit determining bandwidth ratios between respective corresponding pairs of time units for each data packet and power ratios between respective corresponding pairs of time units for each data packet, to maintain a constant bandwidth ratio between each pair of time units across all data packets and a constant power ratio between each pair of time units across all data packets, with the bandwidth ratio η

(i,j) between an i-th time unit and a j-th time unit being established for each data packet by;

$\mathrm{\eta <br><br>}<br><br>\left(i,j\right)=\frac{N-N_{\mathrm{RS}}^i-N_{\mathrm{idle}}^i}{N-N_{\mathrm{RS}}^j-N_{\mathrm{idle}}^j},$

and the power ratio γ

(i,j) between an i-th time unit and a j-th time unit for each data packet being established by;

$\mathrm{\gamma <br><br>}<br><br>\left(i,j\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^i<br><br>N_{\mathrm{RS}}^i}{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^j<br><br>N_{\mathrm{RS}}^j}·<br><br>\frac{1}{\mathrm{\eta <br><br>}<br><br>\left(i,j\right)},$

where α

_RS^k is a power boosting factor for the reference signal symbols in a k-th time unit; and

the transmission antenna transmitting the plurality of data modulation symbols of the plurality of data packets and the reference signal symbols by using the transmission resources, with the transmission of at least one data packet being in accordance with the determined bandwidth ratios and power ratios.

41. A wireless terminal in a communication system, comprising:

a mapping unit mapping a plurality of data modulation symbols of a plurality of data packets and a plurality of reference signal symbols into transmission resources of a plurality of transmission antennas in accordance with a certain transmit diversity scheme, with the transmission resources being divided into a plurality of subcarriers in a frequency domain and a plurality of time units in a time domain, and within a k-th time unit, N subcarriers being available for transmitting signals via all of the plurality of transmission antennas, and the N subcarriers comprising N_RS^k subcarriers for transmitting reference signal symbols, N_idle^k subcarriers that are concurrently unused, and N_data^k subcarriers for transmitting data modulation symbols;

a processing unit determining bandwidth ratios between respective corresponding pairs of time units for each data packet, and determining power ratios between respective corresponding pairs of transmission antennas in different time units for each data packet, to maintain a constant bandwidth ratio between each pair of time units across all data packets and a constant power ratio between each pair of antennas in different time units across all data packets, with the bandwidth ratio η

(i,j) between an i-th time unit and a j-th time unit being established for each data packet by;

$\mathrm{\eta <br><br>}<br><br>\left(i,j\right)=\frac{N-N_{\mathrm{RS}}^i-N_{\mathrm{idle}}^i}{N-N_{\mathrm{RS}}^j-N_{\mathrm{idle}}^j},$

and the power ratio γ

^t,s(i,j) between a t-th transmission antenna in an i-th time unit and an s-th transmission antenna in a j-th time unit for each data packet being established by;

${\mathrm{\gamma <br><br>}}^{t,s}<br><br>\left(i,j\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{i,t}<br><br>N_{\mathrm{RS}}^{i,t}}{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{j,s}<br><br>N_{\mathrm{RS}}^{j,s}}·<br><br>\frac{1}{\mathrm{\eta <br><br>}<br><br>\left(i,j\right)},$

where α

_RS^k,t is a power boosting factor for the reference signal symbols from a t-th transmission antenna in a k-th time unit; and

the plurality of transmission antennas transmitting the plurality of data modulation symbols of the plurality of data packets and the reference signal symbols by using the transmission resources, with the transmission of at least one data packet being in accordance with the determined bandwidth ratios and power ratios.

42. A wireless terminal in a communication system, comprising:

at least one receiving antenna receiving data signals and reference signals transmitted from a transmitter via a transmission antenna in a plurality of time units, and receiving information regarding the number of subcarriers that are available for transmission in each time units, the number of subcarriers for transmitting reference signals in each time unit, the number of subcarriers for transmitting data signals in each time unit, the number of subcarriers that are available for transmission and are not used in each time unit, and power boosting factors for the reference signals in each time unit;

a processing unit determining bandwidth ratios between respective corresponding pairs of time units and power ratios between respective corresponding pairs of time units, with the bandwidth ratio η

(i,j) between an i-th time unit and a j-th time unit and the power ratio γ

(i,j) between an i-th time unit and a j-th time unit for each data packet being respectively established by;

$\mathrm{\eta <br><br>}<br><br>\left(i,j\right)=\frac{N-N_{\mathrm{RS}}^i-N_{\mathrm{idle}}^i}{N-N_{\mathrm{RS}}^j-N_{\mathrm{idle}}^j},\mathrm{and}$ $\mathrm{\gamma <br><br>}<br><br>\left(i,j\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^i<br><br>N_{\mathrm{RS}}^i}{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^j<br><br>N_{\mathrm{RS}}^j}·<br><br>\frac{1}{\mathrm{\eta <br><br>}<br><br>\left(i,j\right)},$

where N being the number of subcarriers that are available for transmission in a k-th time unit, N_RS^k being the number of subcarriers for transmitting reference signal symbols in the k-th time unit, N_idle^k being the number of subcarriers that are concurrently unused in the k-th time unit, N_data^k being the number of subcarriers for transmitting data modulation symbols in the k-th time unit, and α

_RS^k is a power boosting factor for the reference signal symbols in a k-th time unit; and

a decoding unit decoding the received data signal by using the determined bandwidth ratios and power ratios.

43. A wireless terminal in a communication system, comprising:

at least one receiving antenna receiving data signals and reference signals in a plurality of time units transmitted from a transmitter via a plurality of transmission antenna, and receiving information regarding the number of subcarriers that are available for transmission in each time units, the number of subcarriers for transmitting reference signals in each time unit, the number of subcarriers for transmitting data signals in each time unit, the number of subcarriers that are available for transmission and are not used in each time unit, and power boosting factors for the reference signals in each time unit;

a processing unit determining bandwidth ratios between respective corresponding pairs of time units and power ratios between respective corresponding pairs of transmission antennas in different time units, with the bandwidth ratio η

(i,j) between an i-th time unit and a j-th time unit and the power ratio γ

^t,s(i,j) between a t-th transmission antenna in an i-th time unit and an s-th transmission antenna in a j-th time unit being respectively established;

$\mathrm{\eta <br><br>}<br><br>\left(i,j\right)=\frac{N-N_{\mathrm{RS}}^i-N_{\mathrm{idle}}^i}{N-N_{\mathrm{RS}}^j-N_{\mathrm{idle}}^j},\mathrm{and}$ ${\mathrm{\gamma <br><br>}}^{t,s}<br><br>\left(i,j\right)=\frac{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{i,t}<br><br>N_{\mathrm{RS}}^{i,t}}{N-{\mathrm{\alpha <br><br>}}_{\mathrm{RS}}^{j,s}<br><br>N_{\mathrm{RS}}^{j,s}}·<br><br>\frac{1}{\mathrm{\eta <br><br>}<br><br>\left(i,j\right)},$

where N being the number of subcarriers that are available for transmission in a k-th time unit, N_RS^k being the number of subcarriers for transmitting reference signal symbols in the k-th time unit, N_idle^k being the number of subcarriers that are concurrently unused in the k-th time unit, N_data^k being the number of subcarriers for transmitting data modulation symbols in the k-th time unit, α

_RS^k,t is a power boosting factor for the reference signal symbols from a t-th transmission antenna in the k-th time unit; and

a decoding unit decoding the received data signal by using the determined bandwidth ratios and power ratios.