OFDM diversity transmission

Abstract

In an OFDM transmission a transmission diversity technique is used without orthogonal signaling. The phases of the subcarriers received at the different antennas are compared by different techniques and then the phases of the signals for different antennas are adjusted for a subsequent transmission over the OFDM interface. The phase (and optionally amplitude) adjustment is calculated in only one (transmitting) side and no orthogonal signaling required. The number of antennas can be increased as much as necessary to get a sharper beam. The negative effects of fading and interference can be reduced so that at same time a down link transmission power can be reduced.

The invention claimed is: 
     
       1. A transmission diversity device, comprising:
 a plurality of antenna elements; 
 a plurality of processing devices respectively connected to one of the antenna elements; and 
 phase comparison and adjustment means for comparing phases of data signals received at the antenna elements and for adjusting phases of signals transmitted by the antenna elements according to the result of the comparison, 
 wherein the transmission diversity device is designed for a multicarrier transmission and individually compares the phase of each data subcarrier of the multicarrier transmission of each antenna element with a phase of a corresponding data subcarrier of at least one other antenna element and adjusts the phase subsequently for a transmission and the data subcarrier has no pilot symbols. 
 
     
     
       2. The transmission diversity device according to  claim 1 , wherein the device is designed for an OFDM transmission. 
     
     
       3. The transmission diversity device according to  claim 1 , further comprising:
 a subcarrier phase comparison dependent amplitude adjustment function. 
 
     
     
       4. The transmission diversity device according to  claim 1 , further comprising
 a means for averaging phase differences of a plurality of subcarriers respectively received at one antenna element. 
 
     
     
       5. The transmission diversity device according to  claim 1 , further comprising
 a means for frequency adjusting phase differences of the subcarriers received respectively at one antenna element. 
 
     
     
       6. The transmission diversity device according to  claim 1 , further comprising
 a means for comparing only predetermined subcarriers of different antenna elements. 
 
     
     
       7. A method for a wireless transmission diversity transmission by means of a plurality of antenna elements and a plurality of processing devices respectively connected to one of the antenna elements, comprising:
 comparing, individually, a phase of each data subcarrier of a multicarrier transmission for each antenna element of the plurality of antenna elements with a phase of a corresponding data subcarrier of at least one other antenna element of the plurality of antenna elements; and 
 adjusting the phase subsequently for a transmission wherein the data subcarrier has no pilot symbols. 
 
     
     
       8. The method according to  claim 7 , wherein the step of comparing is repeated at least twice to calculate an average value used for the step of adjusting. 
     
     
       9. The method according to  claim 7 , wherein the multicarrier transmission is a OFDM transmission. 
     
     
       10. The method according to  claim 7 , further comprising
 the step of amplitude adjustment depending on the subcarrier phase comparison. 
 
     
     
       11. The method according to  claim 7 , further comprising:
 the step of averaging the phase differences of a plurality of subcarriers respectively received at one antenna element. 
 
     
     
       12. The method according to  claim 7 , further comprising
 the step of frequency adjusting phase differences of the data subcarriers received respectively at one antenna element. 
 
     
     
       13. The method according to  claim 7 , further comprising:
 the step of comparing only predetermined subcarriers of different antenna elements. 
 
     
     
       14. The method according to  claim 7 , wherein the step of comparing comprises
 the step of correlating time domain data. 
 
     
     
       15. The method according to  claim 7 , wherein in case it is detected that at any of the antenna elements no signal or a signal with an amplitude below a predetermined threshold is received, said antenna element is not used for a transmission. 
     
     
       16. The method according to  claim 7 , wherein the method is only applied in a base station of a wireless transmission system. 
     
     
       17. A non-transitory computer readable medium and instructions in the medium to be executable by a computer for a wireless transmission diversity transmission by means of a plurality of antenna elements and a plurality of processing devices respectively connected to one of the antenna elements, said instructions comprising:
 comparing individually a phase of each data subcarrier of a multicarrier transmission for each antenna element with a phase of a corresponding data subcarrier of at least one other antenna element; and 
 adjusting the phase subsequently for a transmission wherein the data subcarrier has no pilot symbols. 
 
     
     
       18. A communication device for transmitting and/or receiving OFDM signals in a multicarrier transmission system, the communication device comprising:
 a plurality of antenna elements for receiving the OFDM signals which are transmitted by using a plurality of data subcarriers used for the transmission of said OFDM signals in the multicarrier transmission system, wherein the data subcarriers have no pilot symbols; and 
 a processing device for calculating subcarrier phases of each of said plurality of data subcarriers used for the multicarrier transmission of said OFDM signals and for adjusting each of said data subcarrier phases of said plurality of subcarriers in accordance with said calculated subcarrier phases respectively and adjusts said subcarrier phases so as to reduce a multipath fading in the multicarrier transmission system. 
 
     
     
       19. A communication device for transmitting and/or receiving OFDM signals to/from another communication device in a multicarrier transmission system, the communication device comprising:
 a plurality of antenna elements for receiving the OFDM signals which are transmitted by using a plurality of data subcarriers being used for the transmission of said OFDM signals in the multicarrier transmission system, wherein the data subcarriers have no pilot symbols; and 
 a processing device, connected to said plurality of antenna elements for calculating subcarrier phases of each of said plurality of data subcarriers used for the multicarrier transmission of said OFDM signals, so that subcarrier phases of each of said plurality of data subcarriers to be used in a subsequent communication process between said communication device and another communication device are adjusted in accordance with said calculated subcarrier phases. 
 
     
     
       20. A communication device for transmitting OFDM signals in a multicarrier transmission system, the communication device comprising:
 a plurality of antenna elements for transmitting the OFDM signals which are to be transmitted by using a plurality of subcarriers of the multicarrier transmission system, wherein said plurality of subcarriers are data subcarriers to transmit data information in the multicarrier transmission system, and the data subcarriers have no pilot symbols; 
 processing device, connected to said plurality of antenna elements, for processing said OFDM signals to be transmitted, 
 wherein said processing device receives information concerning subcarrier phases of each of said plurality of data subcarriers, and adjusts subcarrier phases of said data subcarriers to transmit said data information in accordance with said information concerning subcarrier phases. 
 
     
     
       21. A communication device for transmitting OFDM signals to receiver device in a multicarrier transmission system, the communication device comprising:
 a plurality of antenna elements for transmitting the data information as said OFDM signals to be transmitted by using a plurality of data subcarriers of the multicarrier transmission system, wherein the data subcarriers have no pilot symbols; and 
 processing device, connected to said plurality of antenna elements, for generating said OFDM signals to be transmitted by said plurality of antenna elements, 
 wherein said processing device obtains subcarrier phases of each of said plurality of data subcarriers based on the communication made between said communication device and receiver device in the multicarrier transmission system, and adjusts subcarrier phases of said data subcarriers to generate said OFDM signal in accordance with said subcarrier phases. 
 
     
     
       22. A communication device for transmitting and/or receiving OFDM signals in a multicarrier transmission system, the communication device comprising:
 a plurality of antenna elements for receiving the OFDM signals each of which is transmitted by using a plurality of subcarriers in the multicarrier transmission system; wherein said plurality of subcarriers are data subcarriers for transmitting data signals and said data subcarriers have no pilot symbols; and 
 processing device for calculating subcarrier phases of all of said data subcarriers of said OFDM signals and adjusts said subcarrier phases in accordance with said calculated subcarrier phases. 
 
     
     
       23. A communication device for transmitting and/or receiving OFDM signals in a multicarrier transmission system, the device comprising:
 a plurality of antenna elements for receiving the OFDM signals each of which is transmitted by using a plurality of subcarriers of the multicarrier transmission system, wherein said plurality of subcarriers are data subcarriers for transmitting data signals and said data subcarriers have no pilot symbols; and 
 processing device, connected to said plurality of antenna elements, for processing said received OFDM signals, 
 wherein said processing device calculates symbol vectors indicating subcarrier phases of said plurality of subcarriers of each of said received OFDM signals so that subcarrier phases of each of said plurality of subcarriers to be used in a subsequent communication process in the multicarrier transmission system are adjusted in accordance with said calculated symbol vectors. 
 
     
     
       24. A communication device for communicating data signals with another communication device in an OFDM multicarrier transmission system, the device comprising:
 a plurality of antenna elements for receiving said data signals which are transmitted by using a plurality of subcarriers being used in said OFDM multicarrier transmission system wherein said plurality of subcarriers are data subcarriers for transmitting data signals and said data subcarriers have no pilot symbols, and 
 processing device, connected to said plurality of antenna elements, for calculating subcarrier phases of said plurality of subcarriers, 
 wherein said processing device, when said communication device send data signals to said another communication device by using said plurality of subcarriers, adjusts said subcarrier phases of said plurality of subcarriers in accordance with said calculated subcarrier phases. 
 
     
     
       25. A communication device for enabling data communication with another communication device in an OFDM multicarrier transmission system, the device comprising:
 a plurality of antenna elements for receiving data signals which are transmitted by using a plurality of subcarriers being used in said OFDM multicarrier transmission system, wherein said plurality of subcarriers are data subcarriers for transmitting data signals and said data subcarriers have no pilot symbols, 
 calculator for calculating subcarrier phases of said plurality of subcarriers, and 
 transmitter, being designed to receive said calculated subcarrier phases, for performing a transmission process to transmit data signals from said communication device to said another communication device, wherein said transmitter adjusts subcarrier phases of said plurality of subcarriers used in said transmission process on the bases of said calculated subcarrier phases. 
 
     
     
       26. A communication device for transmitting and/or receiving OFDM signals in a multicarrier transmission system, the communication device comprising:
 a plurality of antenna elements for receiving the OFDM signals transmitted by using a plurality of subcarriers being used for the transmission of said OFDM signals in the multicarrier transmission system, wherein said plurality of subcarriers are data subcarriers for transmitting data signals and said data subcarriers have no pilot symbols; and 
 processing device, connected to said plurality of antenna elements, for calculating subcarrier phases of said plurality of subcarriers used for the multicarrier transmission of said OFDM signals and for adjusting said subcarrier phases of said plurality of subcarriers to be used for subsequent multicarrier transmission in the multicarrier transmission system in accordance with said calculated subcarrier phases. 
 
     
     
       27. A communication device for transmitting and/or receiving OFDM signals to/from another communication device in a multicarrier transmission system, the communication device comprising:
 a plurality of antenna elements for receiving the OFDM signals which are transmitted by using a plurality of subcarriers being used for the transmission of said OFDM signals in the multicarrier transmission system, wherein said plurality of subcarriers are data subcarriers for transmitting data signals and said data subcarriers have no pilot symbols; and 
 processing device, connected to said plurality of antenna elements, for calculating subcarrier phases of said plurality of subcarriers used in the multicarrier transmission of said OFDM signals, and for adjusting subcarrier phases of said plurality of subcarriers, to be used in a subsequent communication for sending data information from said communication device to another communication device, in accordance with said calculated subcarrier phases. 
 
     
     
       28. A wireless communication device, comprising
 circuitry configured to
 receive an OFDM signal produced from a plurality of data subcarriers each of which carries a data symbol; 
 transform the received OFDM signal into a plurality of outputs in a frequency domain using FFT; 
 generate a matrix based on the plurality of outputs; and 
 adjust a phase or an amplitude of each data symbol on each data subcarrier in the frequency domain to form a beam according to the matrix, wherein 
   the plurality of data subcarriers each have no pilot symbols.   
     
     
       29. The wireless communication device according to claim 28, wherein the circuitry is further configured to estimate a channel parameter corresponding to each of the plurality of data subcarriers. 
     
     
       30. The wireless communication device according to claim 29, wherein the circuitry is further configured to configured to calculate an average of a plurality of phase differences corresponding to the plurality of data subcarriers. 
     
     
       31. The wireless communication device according to claim 29, further comprising:
 an antenna.   
     
     
       32. The wireless communication device according to claim 31, further comprising:
 a plurality of antennas.   
     
     
       33. The wireless communication device according to claim 32, further comprising:
 a plurality of antenna multiplexers each of which is coupled to one of the plurality of antennas.   
     
     
       34. The wireless communication device according to claim 33, wherein the circuitry is included in a housing of a base station.