Radio communication system
A transmitting station (TS), for transmitting a plurality of symbols of a data signal in a communication system, comprises a process module (PM) arranged for adding subset of the symbols of the data signal to symbols of a predetermined signal prior to proceed to transmission of the data signal.
1. A method of operating an OFDM communication system, further comprising a transmitting station and a receiving station, comprising at the transmitting station transmitting a plurality of symbols of a data signal, a subset of the symbols of the data signal are being added to symbols of a predetermined signal prior to IFFT conversion and transmission;
said method further being characterized in that
a pattern of pilot symbols is superimposed on an OFDM data signal, whereby the pilot symbols are superimposed on only a predetermined subset of the symbols on a predetermined subset of the OFDM subcarriers, and the superimposition is carried out using a configurable weighting parameter allowing a pilot-to-data transmit power ratio to be adjusted in the symbols containing superimposed pilot symbols;
said superimposition using a configurable weighting parameter is based on the addition of a known pilot sequence p(n), onto data to be transmitted d(n) in order to generate a compound symbol defined in accordance with the formula:
y ( n )=√{square root over (ρ)}· p ( n )+√{square root over (1 −ρ· )}d( n )
with
E{p ( n )}=0 and | p ( n )| 2 =1
where parameter ρ controls the amount of power allocated to the pilot signal, or Pilot-to-Signal power Ratio (PSR), and
wherein said weighted combination is further based on a function of one or more of the following: transmitted data rate, quality of service requirements for the transmitted data, type of transmitted data, instantaneous radio channel quality, average radio channel quality, coherence time of the radio channel, coherence bandwidth of the radio channel, available transmit power of the transmitting station, or decoding capability of the receiving station.
2. The method as claimed in claim 1 , wherein in said weighted combination the subset of the pilot symbols of the data signal is multiplied by a first weighting factor prior to the addition.
3. The method as claimed in claim 2 , wherein the transmission takes place in radio frames, and wherein in said weighted combination the first weighting factor is selected so that an average transmitted power in a radio frame of the symbols containing the predetermined signal is substantially the same as an average transmitted power of the symbols containing only the data signal in the radio frame.
4. The method as claimed in claim 2 , wherein in said weighted combination the value of the first weighting factor is signaled to the receiving station by the transmitting station.
5. The method as claimed in claim 2 , wherein in said weighted combination a recommended value of the first weighting factor is signaled to the transmitting station by the receiving station.
6. The method as claimed in claim 1 , wherein in said weighted combination the symbols of the predetermined signal are weighted by a second weighting factor prior to the addition.
7. The method as claimed in claim 6 , wherein the transmission takes place in radio frames, and wherein in said weighted combination the second weighting factor is selected so that an average transmitted power in a radio frame of the symbols containing the predetermined signal is substantially the same as an average transmitted power of the symbols containing only the data signal in the radio frame.
8. The method as claimed in claim 6 , wherein in said weighted combination the value of the second weighting factor is signaled to the receiving station by the transmitting station.
9. The method as claimed in claim 6 , wherein in said weighted combination a recommended value of the second weighting factor is signaled to the transmitting station by the receiving station.
10. The method as claimed in claim 1 , wherein in said weighted combination the transmission uses orthogonal frequency-division multiplexing.
11. A transmitting station for transmitting a plurality of OFDM symbols of a data signal in a communication system, further comprising at least one receiving station, said transmitting station comprising a process module arranged for adding a subset of the symbols of the data signal to symbols of a predetermined signal prior to IFFT conversion and to transmission of said data signal,
the transmitting station further including:
means for superimposing a pattern of pilot symbols on an OFDM data signal, whereby the pilot symbols are superimposed on only a predetermined subset of the symbols on a predetermined subset of the OFDM subcarriers,
means for carrying out the superimposition using a configurable weighting parameter allowing a pilot-to-data transmit power ratio to be adjusted in the symbols containing superimposed pilot signals;
said superimposition using a configurable weighting parameter is based on the addition of a known pilot sequence p(n), onto data to be transmitted d(n) in order to generate a compound symbol defined in accordance with the formula:
y ( n )=√ρ· p ( n )+√1 −ρ·d ( n )
with
E{p ( n )}=0 and | p ( n )| 2 =1
where parameter ρ controls the amount of power allocated to the pilot signal, or Pilot-to-Signal power Ratio (PSR), and
wherein said weighted combination is further based on a function of one or more of the following: transmitted data rate, quality of service requirements for the transmitted data, type of transmitted data, instantaneous radio channel quality, average radio channel quality, coherence time of the radio channel, coherence bandwidth of the radio channel, available transmit power of the transmitting station, or decoding capability of the receiving station.
12. The transmitting station as claimed in claim 11 , wherein in said weighted combination said process module is arranged for multiplying said subset of the symbols of the data signal by a first weighting factor prior proceeding to said addition.
13. The transmitting station as claimed in claim 12 , characterized in that it is arranged for transmitting said symbols in radio frames, and wherein said process module is arranged for multiplying said subset by a first weighting factor selected in order an average transmitted power in a radio frame of the symbols containing the predetermined signal is substantially the same as an average transmitted power of the symbols containing only the data signal in the radio frame.
14. The transmitting station as claimed in claim 12 , characterized in that it is arranged for signaling the value of the first weighting factor in said weighted combination, used by said process module, to the receiving station.
15. The transmitting station as claimed in claim 11 , wherein in said weighted combination said process module is arranged to use a value of the a weighting factor recommended by the receiving station.
16. The transmitting station as claimed in claim 11 , wherein said process module is arranged to weight said symbols of the predetermined signal by a second weighting factor prior proceeding to said addition.
17. The transmitting station as claimed in claim 16 , wherein it is arranged for transmitting said symbols in radio frames, and wherein said process module is arranged for weighting said symbols of the predetermined signal by a second weighting factor selected in order an average transmitted power in a radio frame of the symbols containing the predetermined signal is substantially the same as an average transmitted power of the symbols containing only the data signal in the radio frame.
18. The transmitting station as claimed in claim 16 , characterized in that it is arranged for signaling the value of the second weighting factor in said weighted combination, used by said process module, to the receiving station.
19. The transmitting station as claimed in claim 16 , wherein in said weighted combination said process module is arranged to use a value of the second weighting factor recommended by the receiving station.
20. The transmitting station as claimed in claim 11 , wherein it is arranged for using an orthogonal frequency-division multiplexing.