Source: https://patents.google.com/patent/US9954710B2/en
Timestamp: 2018-12-14 14:51:50
Document Index: 552028286

Matched Legal Cases: ['§ 120', '§ 119', 'Application No. 00', 'art, 1996', 'Application No. 2008', 'Application No. 2012', 'Application No. 2012', 'Application No. 2001', 'Application No. 2008']

US9954710B2 - Communication device for receiving and transmitting OFDM signals in a wireless communication system - Google Patents
US9954710B2
US9954710B2 US15419088 US201715419088A US9954710B2 US 9954710 B2 US9954710 B2 US 9954710B2 US 15419088 US15419088 US 15419088 US 201715419088 A US201715419088 A US 201715419088A US 9954710 B2 US9954710 B2 US 9954710B2
US15419088
US20170141940A1 (en )
This application is a continuation of and is based upon and claims the benefit of priority under 35 U.S.C. § 120 from U.S. Ser. No. 14/050,963, filed Oct. 10, 2013, which is a continuation of U.S. Ser. No. 13/105,310, filed May 11, 2011 (now U.S. Pat. No. 8,743,675) which is the continuation of U.S. Ser. No. 12/604,437, filed Oct. 23, 2009 (now U.S. Pat. No. 7,961,588) which is a continuation of U.S. Ser. No. 11/248,988 (now U.S. Pat. No. 7,633,848), filed Oct. 12, 2005, the entire contents of each of which are incorporated herein by reference. U.S. Ser. No. 11/248,988 (now U.S. Pat. No. 7,633,848), filed Oct. 12, 2005 is a continuation of U.S. Ser. No. 09/935,925 (now U.S. Pat. No. 7,085,223), filed Aug. 23, 2001. This application also claims the benefit of priority under 35 U.S.C. § 119 from European Patent Application No. 00 118 418.3, filed Aug. 24, 2000.
In wireless OFDM communication systems a communication device, as e.g. a base station, communicates with another communication device, as e.g. a mobile terminal, over a wireless communication link using OFDM signals. OFDM (orthogonal frequency division multiplex) is a multi carrier modulation method wherein information to be transmitted is mapped (e.g. by phase shift keying) onto a plurality of orthogonal subcarriers signals of different frequencies which are subsequently combined into an OFDM signal. Each subcarrier frequency defines a transmission channel in which information can be transmitted over the communication link. For more background information on OFDM it is referred, for example, to K. David, T. Benkner: “Digitale Mobilfunksysterne”, B. G. Teubner Stuttgart, 1996, S. 174-176.
The inventive solution takes benefit of the above observation (i.e. subcarrier dependence of amplitude fading) and reduces the amplitude of those subcarrier signals of the OFDM transmission signal at a particular antenna element which are expected to be subject to amplitude fading. As it is highly improbable for a transmission channel to be heavily disturbed at the same time at all antenna elements, amplitude reduction of a particular subcarrier signal being transmitted from one of the antenna elements will have—if at all—only negligible effect on the ability to reliably recover the information hidden in this particular subcarrier signal on the receiver side because the same subcarrier signal still will be transmitted from other antenna elements at normal or just slightly reduced amplitude. By giving a minor role to those subcarrier signals which, due to fading, will not reach the receiving communication device at a reasonable amplitude level, waste of useless enemy can be avoided and signal interference caused by such useless energy at other receiving communication devices can be reduced. An evaluation as to which of the subcarrier signals of the OFDM transmission signal are likely to be subject to amplitude fading and therefore should be reduced in amplitude is done by examining an OFDM reception signal sent from the communication device intended to be addressee of the OFDM transmission signal. This signal examination is done individually for each antenna element.
The amplitude adjustment factor and the phase adjustment factor for a particular subcarrier signal associated to a particular antenna element 12 may be represented by a complex weight coefficient which is applied to the respective transmission subcarrier signal. FIGS. 4a to 4c show three possibilities for generating the weight coefficient. In all three cases, the phase of the weight coefficient equals the phase determined by the channel estimation means 26 for the corresponding received subcarrier signal but has opposite sign.
The magnitude of the weight coefficient can be equal (FIG. 4a ) or proportional (FIG. 4b ) to the subcarrier magnitude determined by the channel estimation means 26. Alternatively, the magnitude of the weight coefficient can be the result of a non-linear function, such as a threshold or square function, which has the subcarrier magnitude determined by the channel estimation means 26 as its input (FIG. 4c ).
To maximize the total OFDM signal energy at the receiver, the amplitude ratio and phase at each transmitter antenna should be optimized. Now, we think about the jth subcarrier. M OFDM signals coming from M different transmitter antennas They are already weighted by value wjk. The combined signal can be written like
A j = α j ′ ⁢ α j = [ α j ⁢ ⁢ 0 * α j ⁢ ⁢ M * ] ⁡ [ α j ⁢ ⁢ 0 ⁢ α j ⁢ ⁢ M ]
(Normalization of weight vector is not necessary, because ratio between antennas and subcarriers are important).
obtain, based on a received preamble signal, a vector for adjusting a plurality of subcarrier signals;
adjust each of the plurality of subcarrier signals based on the vector;
transform the plurality of subcarrier signals into an orthogonal frequency divisional multiplexed (OFDM) signal using inverse fast Fourier transform (IFFT); and
output the OFDM signal.
6. The electronic device of claim 1, wherein the circuitry includes a processor configured to perform at least the adjusting and the transforming.
9. The electronic device of claim 1, wherein the circuitry is further configured to:
adjust each of the plurality of subcarrier signals to optimize reception power.
10. The electronic device of claim 1, wherein the vector is obtained based on a
channel property in accordance with an Eigenvector of a matrix.
obtaining, based on a received preamble signal, a vector for adjusting a plurality of subcarrier signals;
adjusting, by circuitry, each of the plurality of subcarrier signals based on the vector;
transforming, by the circuitry, the plurality of subcarrier signals into an orthogonal frequency divisional multiplexed (OFDM) signal using inverse fast Fourier transform (IFFT); and
outputting the OFDM signal.
output the OFDM signal via the plurality of antennas.
US15419088 2000-08-24 2017-01-30 Communication device for receiving and transmitting OFDM signals in a wireless communication system Active US9954710B2 (en)
EP20000118418 EP1182817B1 (en) 2000-08-24 2000-08-24 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US09935925 US7085223B2 (en) 2000-08-24 2001-08-23 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US11248988 US7633848B2 (en) 2000-08-24 2005-10-12 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US12604437 US7961588B2 (en) 2000-08-24 2009-10-23 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US13105310 US8743675B2 (en) 2000-08-24 2011-05-11 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US14050963 US9596059B2 (en) 2000-08-24 2013-10-10 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US15419088 US9954710B2 (en) 2000-08-24 2017-01-30 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US14050963 Continuation US9596059B2 (en) 2000-08-24 2013-10-10 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US20170141940A1 true US20170141940A1 (en) 2017-05-18
US9954710B2 true US9954710B2 (en) 2018-04-24
US09935925 Active 2024-01-02 US7085223B2 (en) 2000-08-24 2001-08-23 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US11248988 Active 2022-04-23 US7633848B2 (en) 2000-08-24 2005-10-12 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US11558978 Active US7414959B2 (en) 2000-08-24 2006-11-13 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US12604448 Active US7957258B2 (en) 2000-08-24 2009-10-23 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US12604437 Active US7961588B2 (en) 2000-08-24 2009-10-23 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US13105310 Active 2021-09-02 US8743675B2 (en) 2000-08-24 2011-05-11 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US14050963 Active US9596059B2 (en) 2000-08-24 2013-10-10 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US14050949 Active US9455806B2 (en) 2000-08-24 2013-10-10 Communication device for receiving and transmitting OFDM signals in a wireless communication system
US15419088 Active US9954710B2 (en) 2000-08-24 2017-01-30 Communication device for receiving and transmitting OFDM signals in a wireless communication system
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