Source: http://www.google.com/patents/US20010028637?dq=U.S.+patent+number+7,325,728&ei=Y93TTteOAe702wW6uqi1BQ
Timestamp: 2017-09-26 20:59:12
Document Index: 323593700

Matched Legal Cases: ['arts 14', 'arts 14', 'arts 14', 'art 16', 'art 16', 'art 11', 'arts 100', 'art 15', 'art 115', 'art 121', 'art 122', 'art 121', 'art 123', 'art 125', 'art 124', 'art 121', 'art 122', 'art 124', 'art 241', 'art 242', 'art 124', 'arts 122', 'art 242', 'art 241', 'arts 122']

Patent US20010028637 - Multi-carrier CDMA radio transmitting method and apparatus, and channel ... - Google Patents
A multi-carrier CDMA radio transmitting method replicates each information symbol and disposes thus-obtained information symbols along a frequency axis, multiplies the thus-obtained information symbols with a spreading code along the frequency axis, spreads the information symbols into components of...http://www.google.com/patents/US20010028637?utm_source=gb-gplus-sharePatent US20010028637 - Multi-carrier CDMA radio transmitting method and apparatus, and channel estimation method and apparatus for multi-carrier CDMA radio transmitting system
Publication number US20010028637 A1
Application number US 09/780,501
Also published as CA2335225A1, CA2335225C, CN1198417C, CN1309204C, CN1324159A, CN1610288A, EP1128592A2, EP1128592A3, US7457324, US7492794, US20060039331
Publication number 09780501, 780501, US 2001/0028637 A1, US 2001/028637 A1, US 20010028637 A1, US 20010028637A1, US 2001028637 A1, US 2001028637A1, US-A1-20010028637, US-A1-2001028637, US2001/0028637A1, US2001/028637A1, US20010028637 A1, US20010028637A1, US2001028637 A1, US2001028637A1
Patent Citations (24), Referenced by (112), Classifications (15), Legal Events (3)
US 20010028637 A1
By this method, for example, as shown in FIG. 1, by using pilot symbols () inserted into a plurality of sub-carriers f1, f2, . . . at fixed periods, amplitudes and phases of received signals for respective users are measured, and the measured values are obtained through interpolation rendered two-dimensionally in the time-axis direction and sub-carrier direction (frequency direction), and, thereby, variations in transmission channel for information symbols are estimated. Then, based on this estimation result, phase rotations of data symbols are compensated, and coherent detection is rendered. In this method, in order to reduce power consumption due to insertion of pilot symbols, the technique of interpolation is used without inserting pilot symbols into all the sub-carriers on the supposition that correlation in channel variation between respective sub-carriers is very high, and variations in transmission channel for sub-carriers into which no pilot symbol is inserted are estimated (channel estimation).
In this method, such a control is made that, for a user to which information is to be transmitted at a high transmission rate, the number of modulation levels used when information symbols to be spread are obtained through the data modulation is large, and, specifically, for exmaple, a data modulation system in a 16 QAM form, a 32 QAM form or the like is used, but, for a user to which information is to be transmitted at a low transmission rate, the number of modulation levels used when information symbols to be spread are obtained through the data modulation is small, and, specifically, for example, a data modulation system in a QPSK form, a BPSK form, or the like is used.
[0056]FIG. 1 illustrates an example in which pilot symbols are inserted, in a multi-carrier CDMA radio transmitting system in the related art;
[0057]FIG. 2 is a block diagram showing a multi-carrier CDMA radio transmitting apparatus in a first embodiment of the present invention;
[0058]FIG. 3 is a block diagram showing a specific example of a configuration of each spreading modulation part shown in FIG. 2;
[0059]FIG. 4 is a block diagram showing a first exmaple of a configuration for transmission-rate control in the first embodiment of the present invention;
[0060]FIGS. 5A and 5B illustrate relationship between the transmission rate and the number of sub-carriers assigned for spreading of each information symbol in the first example shown in FIG. 4;
[0061]FIGS. 6A and 6B illustrate possible dispositions along the frequency axis of sub-carriers used for the spreading in the first embodiment of the present invention;
[0062]FIG. 7 shows one example of a technique of generating spreading codes having orthogonal relationship;
[0063]FIG. 8 is a block diagram showing a second exmaple of a configuration for transmission-rate control in the second embodiment of the present invention;
[0064]FIGS. 9A and 9B illustrate relationship between the transmission rate and the number of sub-carriers assigned for spreading of each information symbol in the second example shown in FIG. 8;
[0065]FIG. 10 is a block diagram showing a third exmaple of a configuration for transmission-rate control in the first embodiment of the present invention;
[0066]FIGS. 11A and 11B illustrate relationship between the transmission rate and the number of sub-carriers assigned for spreading of each information symbol in the third example shown in FIG. 10;
[0067]FIG. 12 is a block diagram showing a fourth exmaple of a configuration for transmission-rate control in the first embodiment of the present invention;
[0068]FIGS. 13A, 13B and 13C illustrate an example of control of the transmission rate in the fourth exmaple shown in FIG. 12;
[0069]FIG. 14 is a block diagram showing a fifth exmaple of a configuration for transmission-rate control in the first embodiment of the present invention;
[0070]FIG. 15 shows an example of a form of control of the transmission rate in the fifth exmaple shown in FIG. 14;
[0071]FIGS. 16 and 17 show possible examples of relationship of respective sub-carriers along the frequency axis in the first embodiment of the present invention;
[0072]FIG. 18 is a block diagram showing a basic configuration of a transmitting station in a multi-carrier CDMA radio transmitting system to which a channel estimation method in a second embodiment of the present invention is applied;
[0073]FIG. 19 illustrates a first example of a form of inserting pilot symbols into respective sub-carrier components in the transmitting station shown in FIG. 18;
[0074]FIG. 20 illustrates a second example of a form of inserting pilot symbols into respective sub-carrier components in the transmitting station shown in FIG. 18;
[0075]FIG. 21 is a block diagram showing an exmaple of a configuration of a demodulating apparatus in which channel estimation according to the channel estimation method in the second embodiment of the present invention is rendered;
[0076]FIG. 22 is a block diagram showing a specific example of a configuration of a channel estimation part shown in FIG. 21;
[0077]FIG. 23 is a block diagram showing another specific example of a configuration of the channel estimation part shown in FIG. 21; and
[0078]FIG. 24 is a block diagram showing a specific example of a configuration of an adaptive weighting value estimation part used in the channel estimation part in the demodulating apparatus shown in FIG. 21.
Each of the spreading modulation parts 14(1) through 14(m) is configured as shown in FIG. 3, for exmaple. As shown in the figure, each of the spreading modulation parts 14(1) through 14(m) has a replicating circuit 141 and a multiplier 142. The replicating circuit 141 replicates the input information symbol by the number according to a spreading factor, and disposes thus-obtained information symbols along the frequency axis. The multiplier 142 multiplies each of the thus-obtained information symbols, disposed along the frequency axis, by a spreading code Ci assigned for each user (i) along the frequency axis. As a result, from the multiplier 142, spread signals of components corresponding to sub-carrier f1, f2, . . . , fk along the frequency axis are output.
In the above-mentioned exmaple, because the spreading factor in each of the spreading modulation parts 14(1) through 14(n) varies so as to change the transmission rate, the period of the spreading code Ci used should be varied accordingly. Further, when the transmission rate is changed for each set of information required by a user, it is necessary to change the period of the spreading code Ci also for each user. Accordingly, when the transmission rate is controlled by the above-mentioned method, the spreading codes having various periods are used in the multi-carrier CDMA radio transmitting apparatus. In considering a process of decoding information symbols for each user on a receiving side, it is preferable that the respective spreading codes used have orthogonal relationship with each other.
When the spreading code Ci having the period of n×m is used for spreading information symbols for a user i into components of n×m sub-carriers, and the spreading code Ck having the period of n is used for spreading information symbols for a user k into components of n sub-carriers, the respective spreading codes Ci and Ck satisfy the following formulas: ∑ x = 0 n   Ci  ( x ) × Ck  ( x ) = 0 ∑ x = 0 nxm   Ci  ( x ) × Ck  ( x ) = 0
A technique for generating the spreading codes Ci and Ck is disclosed in ‘Orthogonal forward link using orthogonal multi-spreading factor codes for DS-CDMA mobile radio (K. Okawa and F. Adachi: IEICE Trans. Commun., Vol. E81-B, No. 4, pages 777-784, April, 1998’, for exmaple. In such a technique, for exmaple, as shown in FIG. 7, from spreading codes having respective periods (2m (m=1, 2, . . . ) ) generated so as to be disposed hierarchically according to a Hadamard's series, spreading codes having predetermined positional relationship therebetween are selected as the spreading codes Ci and Ck having orthogonal relationship.
Further, similarly to the case of the above-mentioned first exmaple, sub-carriers to be assigned for spreading each information symbol may be successive along the frequency axis as shown in FIG. 6A, or may be discrete along the frequency axis as shown in FIG. 6B. Further, it is preferable that the spreading codes assigned for respective users are orthogonal to each other, as mentioned above.
In this exmaple, as shown in FIG. 12, an intermittent transmission control part 16 is provided before the serial-to-parallel converting circuit 13 in each of the signal generating circuit 100(1) through 100(n) shown in FIG. 2. The intermittent transmission control part 16, based on the transmission rate control signal from the control unit (not shown in the figure), controls timing of transfer of transmitting data, having undergone the process by the channel encoder 12 (see FIG. 2), to the serial-to-parallel converting circuit 13. When the transmission rate is to be increased, as shown in FIG. 13A, intervals of data transmission (interval between each adjacent data transmission) are shortened. Conversely, when the transmission rate is to be decreased, the intervals of the data transmission are elongated, as shown in FIGS. 13B or 13C. Thus, the information transmission rate is controlled by controlling the intervals of the data transmission.
In this exmaple, as shown in FIG. 14, the number of modulation levels of data modulation by the transmitting data generating part 11 in each of the signal generating parts 100(1) through 100(n) shown in FIG. 2 is controlled by a modulation level specifying part 15 based on the transmission rate control signal. When the transmission rate is to be increased, the number of modulation levels is increased, that is, for example, modulation of transmitting data is performed in a well-known 16 QAM (the number of modulation levels: 16) or 64 QAM (64) form. When the transmission rate is to be decreased, the number of modulation levels is decreased, that is, for example, modulation of transmitting data is performed in a well-known QPSK (4) or BPSK (2) form.
In each of the above-described examples, an IFFT (Inverse Fast Fourier Transformer) or IDFT (Inverse Discrete Fourier Transformer) unit 22 is adjusted so that respective sub-carriers used for the spreading process are orthogonal with each other along the frequency axis as shown in FIG. 16, for exmaple.
A frame (packet frame) configuration of the signal output from the multi-carrier modulation part 115 rendering the multi-carrier modulation on the symbol series, in which the information symbols and pilot symbols are combined, is as shown in FIG. 19, for example. In this example, a plurality of pilot symbols P (for exmaple, two symbols) are inserted into each of all the sub-carriers f1 f2, . . . at the same timing (the top of the frame).
As shown in FIG. 21, the demodulating apparatus includes a sub-carrier separating part 121, a pilot-symbol averaging part 122 provided for each sub-carrier component from the sub-carrier separating part 121, a delay part 123 and a compensating part 125, and a channel estimation part 124. The sub-carrier separating part 121 has a function of FFT (Fast Fourier Transform) or DFT (Discrete Fourier Transform), and separates a received signal received from a transmitting station having the configuration described above with reference FIGS. 18 into respective sub-carrier components #1, . . . , #n. Each pilot-symbol averaging part 122 extracts a plurality of pilot symbols (see FIGS. 19 and 20) included in a respective one of the sub-carrier components, averages respective channel estimation values obtained from these pilot symbols, and thus obtains a channel estimation value for the relevant sub-carrier (this channel estimation value will be referred to as an individual channel estimation value, hereinafter).
There, the weighting vector W is expressed by the following matrix: W = [ w  ( 0.0 ) 0 w  ( l - 1 , l - 1 ) w  ( l , l - 1 ) w  ( l + 1 , l - 1 ) w  ( l - 1 , l ) w  ( l , l ) w  ( l + 1 , l ) w  ( l - 1 , l + 1 ) w  ( l , l + 1 ) w  ( l + 1 , l + 1 ) 0 w  ( n , n ) ]
and, the individual channel estimation values ξ are expressed by the following matrix: ξ = [ ξ1 ξ   n ]
Further, the final channel estimation values <ξ> are expressed by the following matrix: 〈 ξ 〉 = [ 〈 ξ1 〉 〈 ξ   n 〉 ]
As shown in FIG. 23, this channel estimation part 124 includes an adaptive weighting value estimation part 241 and a weighting averaging channel estimation part 242. The adaptive weighting value estimation part 124 adaptively obtains each weighting value (of the weighting coefficient vector W) described above using a technique of MMSE (Minimum Mean Square Error), for exmaple, based on the individual channel estimation values from the averaging channel estimation parts 122(1), 122(2), . . . , 122(n) corresponding to respective sub-carriers. Then, the weighting averaging channel estimation part 242 uses the weighting coefficient vector W obtained by the above-mentioned adaptive weighting value estimation part 241, combines the respective individual channel estimation values from the respective averaging channel estimation parts 122(1), 122(2), . . . , 122(n), and, thus, renders weighting combining according to the frequency response characteristics of channels (channel states).
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U.S. Classification 370/335, 370/208
International Classification H04L27/26, H04J13/16, H04J13/18, H04J11/00, H04J13/00, H04B7/216, H04J1/00, H04L25/02, H04L5/02
European Classification H04L5/02Q1, H04L25/02C7C1A