TWI433477B - Transmitting device, receiving device, and method applicable in an orthogonal frequency division multiplexing-code division multiple access system - Google Patents

Description

Transmission device, receiving device and method for use in orthogonal frequency division multiplexing multiple code division multiple access system

The present invention is related to wireless communication systems. More particularly, the present invention relates to orthogonal frequency division multiplexing (OFDM) code division multiple access (CDMA) communication systems.

Future wireless communication networks will provide broadband services for users' wireless Internet access. These broadband services require reliable and high-rate communication with limited spectrum and inter-symbol interference (ISI) time-division (frequency selective) channels resulting from multiple attenuations. The orthogonal frequency division multiplexing system is one of the most promising solutions for several reasons. Orthogonal frequency division multi-tools have high spectral efficiency, while adaptive coding and modulation can be applied across sub-carriers. Implementation is simplified by baseband modulation and demodulation using simple circuits such as inverse fast Fourier transform (IFFT) circuits and fast Fourier transform (FFT) circuits. Since only one tap point equalizer in a multi-path environment is sufficient to provide superior robustness, a simple receiver structure is one of the advantages of an orthogonal frequency division multiplexing system. In other examples, when orthogonal frequency division multiplexing is used in conjunction with signal spreading across multiple carriers, a more advanced equalizer is required.

Orthogonal frequency division multiplexing has been adopted by several standards such as Digital Sound Broadcasting (DAB), Digital Sound Broadcasting Terrestrial (DAB-T), IEEE 802.11a/g, IEEE 802.16 and Asymmetric Digital Subscriber Line (ADSL). Orthogonal frequency division multiplexing is considered for use in the Long-Term Evolution of Wideband Coded Multiple Access (WCDMA), Partition Multiple Access 2000, Fourth Generation (4G) Wireless Systems, IEEE 802.11n, IEEE 802.16 and IEEE 802.20.

Despite all the advantages, orthogonal frequency division multiplexing has several drawbacks. One of the main drawbacks of orthogonal frequency division multiplexing is its high peak-to-average power ratio (PAPR). As the number of subcarriers increases, the peak-to-average power ratio of the orthogonal frequency division multiplexing also increases. When the high peak-to-average power ratio signal is transmitted via the nonlinear power amplifier, severe signal distortion occurs. Therefore, the orthogonal frequency division multiplexing system requires a highly linear power amplifier with power back-off. As a result, the power efficiency of the mobile device with orthogonal frequency division multiplexing is very low and the implementation of orthogonal frequency division multiplexing is limited.

Techniques for reducing the peak-to-average power ratio of orthogonal frequency division multiplexing systems have been extensively studied. These peak-to-average power ratio techniques include coding, limiting, and filtering. These methods are different in effectiveness and each has its own complexity, efficiency and spectral efficiency.

The present invention relates to an orthogonal frequency division multiplexing multiple code division multiple access system. The system includes a transmitter and a receiver. At the transmitter, the spreading and subcarrier mapping unit may extend the composite quadratic sequence (SCQS) code to extend the input data symbols to generate a plurality of chips and map each of the chips to one of the plurality of carriers. An inverse discrete Fourier transform (IDFT) or inverse fast Fourier transform unit can perform inverse discrete Fourier transform or inverse fast Fourier transform on a wafer mapped to a subcarrier, and the cyclic prefix (CP) is inserted into the orthogonal frequency division multiplexing frame. A parallel-to-serial (P/S) converter converts time domain data into a serial data stream. At the receiver, a serial-to-parallel (S/P) converter converts the received data into a plurality of received data streams, and the cyclic word header is removed from the received data. A discrete Fourier transform (DFT) or fast Fourier transform unit may perform discrete Fourier transform or fast Fourier transform and perform equalization on the received data. The despreader can despread the equalizer output to recover the transmitted data.

The present invention is applicable to wireless communication systems implementing orthogonal frequency division multiplexing and code division multiple access, such as IEEE 802.11, IEEE 802.16, long-term evolution third generation (3G) cellular system, fourth generation (4G) system, Satellite systems, digital sound broadcasting, digital video broadcasting (DVB) or the like.

Features of the invention may be incorporated into an integrated circuit (IC) or configured in a circuit comprising multiple interconnected components.

The present invention can provide an orthogonal frequency division multiplexing-dividing multiple access system with improved peak-to-average power ratio and capacity. The present invention extends the input data symbols by extending the composite secondary sequence code using a special spreading code. The extended composite secondary sequence code comprises two components; a secondary phase sequence code and an orthogonal (or pseudo-orthogonal) spreading code. The quadratic phase sequence code indicated by G is a Newman phase code (or polyphase code), a generalized sequence (GCL) and a Zadoff-Chu sequence. The secondary phase sequence is also referred to as a polyphase sequence.

To support the variable spreading factor (VSF), the sequence length of the quadratic phase sequence (or polyphase sequence) is limited to K = 2 ^k . In some special cases (such as random access channels or uplink instructions), the sequence length of the quadratic phase sequence (or polyphase sequence) can be any random integer. Given the number of such carriers in the system N = 2 ⁿ , consider the length of the N sequence is N. Next, the general Newman phase code sequence is fixed. The general Newman phase code sequence is:

More orthogonal Newman phase code sequences are created by transforming the general Newman phase code sequence. The first conversion version of the general Newman phase code sequence (or discrete Fourier transform modulation) is:

The two Newman phase code sequences with different conversions are orthogonal to each other.

An example of an orthogonal (pseudo-orthogonal) spreading code indicated by H is a Walsh-Hadamard code, which is given by:

The extended composite secondary sequence code is constructed by combining a quadratic phase code and an orthogonal (pseudo-orthogonal) spreading code. The extended composite secondary sequence code system has a 2 ^m wafer for a specific spreading factor of 2 ^m . The general quadratic phase sequence code portion of the extended composite secondary sequence code has a 2 ^m wafer, which is:

Where k = 0, 1, ..., 2 ^m -1, i = 0, 1, ..., 2 ^nm -1. The first modified version of the quadratic phase sequence code portion has a 2 ^m wafer, which is:

Wherein 1 = 0, 1, ..., N-1, k = 0, 1, ..., 2 ^m -1, i = 0, 1, ..., 2 ^nm -1.

For a specific extended composite secondary sequence code having a spreading factor of 2 ^m , the orthogonal (pseudo-orthogonal) spreading code portion of the extended composite secondary sequence code is extended by a quadrature (pseudo-orthogonal) spreading block of a spreading factor of 2 ^m One of the codes is given. For example, the h coding system is marked .

The kth wafer of the extended composite secondary sequence code c _i is constructed as the kth quadratic phase sequence code of the first conversion version of the general Newman phase code sequence and the hth orthogonal (pseudo-orthogonal) having a size of N=2 ^m The product of the kth wafer of the spreading code.

The coding group size of the extended composite secondary sequence code is determined by the coding group size of the orthogonal (pseudo-orthogonal) spreading code portion and the secondary phase sequence code portion. Regardless of the spreading factor, the coding group size of the secondary phase sequence code is fixed and determined by the number of different conversions of the system subcarrier number 2 ⁿ . The coding group size of the orthogonal (pseudo-orthogonal) spreading code depends on the spreading factor. For example, in the Walsh-Hadamard code example, the size is equal to the expansion factor of 2 ^m (0 m n ).

Different users are assigned different extended composite secondary sequence codes. In order for the receiver to distinguish between different users, the quadratic phase sequence code portion, the orthogonal (pseudo-orthogonal) spreading code portion or two of the two are different in the extended composite secondary sequence code system used by the user. The coding group of the extended composite secondary sequence code is shown in Fig. 2. When there is no multiplex, as long as the secondary phase sequence code portions are different, the different extended composite secondary sequence codes are orthogonal; or orthogonal spreading codes are used. The different extended composite secondary sequence codes are pseudo-orthogonal only when their secondary phase sequence code portions are identical and the pseudo-orthogonal spreading codes are used. In both cases, the multiple access interference (MAI) between different codes is zero or very small.

In a multi-channel fading environment, the code assigned to different users should make the difference in the partial transformation of the quadratic phase sequence code as large as possible. The codes assigned to different users should be such that if the partial transform of the two phase sequence codes of the two codes is not less than the maximum delay spread of the multiple channels, there is no multiple access interference between the two codes. Therefore, the corresponding orthogonal (pseudo-orthogonal) spreading code portions can be assigned the same. Alternatively, the quadratic phase sequence code partial transform difference can be limited to at most the multi-channel maximum delay spread. This creates full coding with full multi-access interference immunity. This can be achieved as long as the number of users in the system is only N/L, where N is the number of secondary carriers and L is the maximum delay spread of the multiple channels.

If the partial transform difference of the two-phase quadratic sequence code is smaller than the maximum delay spread of the multi-channel, the corresponding orthogonal (pseudo-orthogonal) spread code portion should be different to reduce the difference cannot be deleted by the quadratic phase sequence code partial transform difference Multiple access interference.

In this method, since the phase relationship between the orthogonal codes is further reduced by the correlation of the two secondary phase sequence codes, the multiple access interference can be reduced as compared with the conventional code division multiple access system. For interference limiting systems (such as code division multiple access), multiple access interference reduction means increased system capacity.

The orthogonal frequency division multiplexing-dividing multiple access system of the present invention comprises a transmitter and a receiver. The transmitter includes an extension and subcarrier mapping component and an orthogonal frequency division multiplexing component. The extended and secondary carrier mapping component extends the input data symbols into a plurality of chips and maps the wafer to one of a plurality of subcarriers. The orthogonal frequency division multiplexing component can perform conventional orthogonal frequency division multiplexing operation. This extension can be performed in the frequency domain, the time domain or both, which will be explained in detail as follows.

1 is a block diagram of an orthogonal frequency division multiplexing code division multiple access system 100 in accordance with a first embodiment of the present invention. System 100 includes a transmitter 100 and a receiver 150. The transmitter 100 includes a spreader 112, a serial-to-parallel (S/P) converter 114, a primary carrier mapping unit 116, an inverse discrete Fourier transform unit 118, and a cyclic prefix (CP) insertion. Unit 120, a parallel pair of serial (P/S) converters 122 and an optional mixer 124. The spreader 112 can extend the input data symbols 101 in the frequency domain using the extended composite secondary sequence code 111. The procedures for spreading and subcarrier mapping are shown in Figure 3. The spreading factor used to extend the composite quadratic sequence code c _i is 2 ^m (0 m n ). A user can use all 2 ⁿ secondary carriers in the system. Therefore, the number of data symbols that can be transmitted by a user in an orthogonal frequency division multi-frame is 2 ^nm . Each data symbol d (i) 101 by spreading code based c _i 111 extended to 2 ^m 113.2 ^m wafer by wafer 113 is then parallel to serial converter 114 is converted into parallel wafer 115 2 ^m, and each chip is The subcarrier mapping unit 116 is equally mapped to one of the subcarriers 117. The distance between each subcarrier used by the wafer of the same data symbol is 2 ^nm subcarrier. The chips of different data symbols are sequentially mapped to the secondary carriers in the system, so that the data symbols d(i) are mapped to the subcarrier 2 ^nm ‧k+i, (k=0,1,..., 2 ^m -1, i = 0, 1, ..., 2 ^nm -1).

Figure 4 shows an alternate embodiment of the spread and subcarrier mapping. Repeater 402 is used in place of spreader 112 to repeat each data symbol d(i) 2 ^m times at wafer rate. The repeated data symbols 404 are converted into 2 ^m juxtaposed symbols 407 by the tandem pair parallel converter 406, and each symbol is equally mapped to one of the 2 ^m subcarriers by the subcarrier mapping and weighting unit 408. . The distance between each subcarrier is 2 ^nm subcarrier. The chips of different data symbols are sequentially mapped to the secondary carriers in the system, so that the data symbols d(i) are mapped to the subcarrier 2 ^nm ‧k+i, (k=0,1,..., 2 ^m -1, i = 0, 1, ..., 2 ^nm -1). The symbol mapped to 2 ^nm ‧k+i of each subcarrier is weighted by the extended composite subsequence code so that the symbol on the subcarrier 2 ^nm ‧k+i is multiplied and marked as The kth wafer of the extended composite secondary sequence code.

Referring back to FIG. 1, the wafer 117 mapped to the subcarrier is fed to the inverse discrete Fourier transform unit 118 and converted into time domain data 119. The cyclic prefix is then added to each orthogonal frequency division multiplexer terminal by a cyclic prefix insertion unit 120. Time domain data 121 having a cyclic prefix is then converted to serial data 123 by a parallel pair of serial converters 122 and transmitted over the wireless channel. It should be noted that the inverse discrete Fourier transform operation can be replaced by an inverse fast Fourier transform or other similar operation, and the cyclic prefix insertion can be converted by the parallel-to-serial converter 122 in the inverse discrete Fourier transform output. The serial data is previously executed, and the cyclic prefix removal is performed before the received signal is converted by the serial-to-parallel converter 154 into a parallel data stream.

Due to the structure of the extended data, the inverse discrete Fourier transform operation system can be simplified. The output 119 of the inverse discrete Fourier transform unit 118 can be converted by a particular phase. This bit is a function of the input data subcarrier and data symbol index. Therefore, the inverse discrete Fourier transform operation can be replaced by a phase conversion calculation that does not require much calculation.

For example, suppose n/2<m n The orthogonal (pseudo-orthogonal) spreading code portion of the extended composite secondary sequence code is {1, 1, ..., 1}. Then the hth output of the inverse discrete Fourier transform unit 118 is given as follows:

Where h value meets the following conditions:

h = 2 ^nm ‧ p + i , p =0,1,...2 ^m -1, i =0,1,...,2 ^nm -1

A masking operation can be performed at the transmitter 110 and a corresponding unmasking operation at the receiver 150. The purpose of the mask is to reduce multiple access interference between cells. At the conveyor 110, the mixer 124 can multiply the material 123 by the mask code 125 prior to transmission. A corresponding unmasking operation is performed at the receiver 150. The mixer 152 can multiply the received signal 128 by the conjugate 151 of the mask code 125 to produce a demasked data stream 153.

Referring to FIG. 1, the receiver 150 includes an optional mixer 152, a serial-to-parallel converter 154, a cyclic prefix removal unit 156, a discrete Fourier transform unit 158, an equalizer 160, and A despreading spreader (including a multiplier 162, an adder 164 and a gauge 166). The time domain received data 128 is converted to a parallel data stream by the serial pair parallel converter 154, and the cyclic word header is removed by the cyclic prefix removal unit 156. These operational performances can be exchanged as explained above. The output 157 from the cyclic prefix removal unit 156 is then fed into the discrete Fourier transform unit 158 to be converted to frequency domain data 159. The equalization of the frequency domain data 159 is performed by the equalizer 160. In a conventional orthogonal frequency division multiplexing system, a simple one-drop point equalizer can be used for the frequency domain data 159 at each subcarrier. It should be noted that the discrete Fourier transform operation can be replaced by a fast Fourier transform operation or other similar operation.

Discrete Fourier transform operations can also be simplified due to extended data structure factors. The output 159 of the discrete Fourier transform unit is a data symbol that is converted by a particular phase. The phase is a function corresponding to the input data subcarrier and the data symbol index. Therefore, the discrete Fourier transform operation can be replaced by a phase conversion calculation that does not require much calculation. The way it is achieved is similar but opposite to the inverse discrete Fourier transform at the opposite transmitter side.

The equalized data is despread in the frequency domain. The output 161 at each carrier after equalization is multiplied by the multiplier 162 for the extended composite secondary sequence code used at the transmitter 110. , k = 0, 1, ..., 2 ^m -1 of the corresponding conjugate 168 of the wafer. Next, the multiply outputs 163 at all subcarriers are summed by the adder 164, and the summed output 165 is normalized by the speculator 166 with the spreading factor of the extended composite secondary sequence code to recover the data 167.

Receiver 150 can further include a block linear equalizer or a joint detector (not shown) that can process the despreader output. Any type of block linear equalizer or joint detector can be used. One of the traditional configurations of block linear equalizers or joint detectors is the minimum mean square error (MMSE) block linear equalizer. In this example, the channel matrix H is established and calculated for the secondary carrier, and the equalization is performed using the established channel matrix such that:

Where H is the channel matrix, Is the received signal in the secondary carrier, The data vector is equalized in the secondary carrier.

For the uplink operation, it is preferred to maintain a fixed envelope after the inverse discrete Fourier transform operation, which facilitates the use of efficient and inexpensive power amplifiers. In order to maintain a fixed envelope, the following conditions for a system with N = 2 ⁿ subcarriers must be met. First, the expansion factor 2 ^m is n /2 m n limit, where a The term means the smallest integer greater than a. Second, for a spreading factor of 2 ^m , only a partial orthogonal code is used in conjunction with the secondary phase sequence code to produce an extended composite secondary sequence code from which a fixed envelope can be obtained. For example, in the Newman phase code and the Hadamard code example, only the first Hadamard code group The code (2 ^m size) is used to combine the Newman phase sequence code to produce an extended composite secondary sequence code. b The term means the largest integer less than b.

As described above, as long as the number of users in the system does not exceed N/L, there is no multiple access interference and no multi-user detection (MUD) is required. When the number of users in the system exceeds N/L, there will be multiple access interference and multi-user detection may be implemented. Multiple access interference is superior to traditional code division multiple access systems with the same number of users.

Suppose there are M users in the system. The number of users detected by multiple users in the traditional code division multiple access system will be M. However, the number of users detecting multiple users in the conventional code division multiple access system according to the present invention will be M / L It is reduced by the L metric compared to the traditional code division multiple access system. In this way, the complexity of the multi-user detection operation is much lower than that of the prior art multi-user detection in the conventional code division multiple access system. Multiple antennas at the transmitter and/or receiver can also be used.

Figure 5 is a block diagram of an orthogonal frequency division multiplexing multiple code division multiple access system 500 (Multi-Carrier Direct Sequence (MC-DS) code division multiple access system) in accordance with another embodiment of the present invention. System 500 includes a transmitter 510 and a receiver 550. The transmitter 510 includes a serial-to-parallel converter 512, a complex multiplier 514, a primary carrier mapping unit 516, an inverse discrete Fourier transform unit 518, a parallel-to-serial converter 520, and a cyclic prefix insertion. Unit 522, and an optional mixer 524. If the system 500 has N=2 ⁿ secondary carriers, the N consecutive data symbols 501 of the user i are converted from the serial to the N parallel symbols 513 by the serial-to-parallel converter 512. The jth data symbol of the N-parallel data symbol 513 of the user i is denoted as d ^j (i), where j=0, 1, ..., N-1. The extended composite secondary sequence code system used by user i is labeled c _i . Each N parallel data symbol 513 is extended in the time domain using the extended composite secondary sequence code c _i 511. The spreading factor of the extended composite secondary sequence code c _i is 2 ^m (0 m n ), therefore, each data symbol 513 is expanded to a 2 ^m wafer 515 by expanding the composite secondary sequence code c _i 511.

During the duration of each wafer, one of the N data symbols d ^j (i) is transmitted on its corresponding subcarrier j. A user can use all 2 ⁿ secondary carriers in the system. Therefore, the number of data symbols that can be transmitted by a user in an orthogonal frequency division multi-frame is 2 ⁿ .

Wafer 515 is equally mapped to the subcarrier by subcarrier mapping unit 516. The wafer 517 on the secondary carrier is fed to the inverse discrete Fourier transform unit 518 and converted to time domain data 519. The time domain data 519 is converted from the parallel to the serial data 521 by the parallel-to-serial converter 520, and the cyclic prefix is added to each of the frame terminals by the cyclic prefix insertion unit 522. The data 523 with the cyclic prefix is transmitted on the wireless channel. The conventional direct sequence code multiple access operation is also performed on each subcarrier using the extended composite secondary sequence code alone, and the direct sequence code multiple access signal on the secondary carrier is transmitted in parallel using the orthogonal frequency division multiplexing structure.

The receiver 550 includes a cyclic prefix removal unit 554, a serial-to-parallel converter 556, a discrete Fourier transform unit 558, an equalizer 560, a complex rake combiner 562, and a parallel pair of serials. Converter 564. First, the cyclic prefix is removed from the received material 528 via the wireless channel by the cyclic prefix removal unit 554. The data 555 is then converted from the serial to the side-by-side data 557 by the serial pair parallel converter 556. The parallel data 557 is then fed into the discrete Fourier transform unit 558 and converted to frequency domain data 559. The frequency domain data 559 is then equalized by the equalizer 560. In a conventional orthogonal frequency division multiplexing system, a simple one-drop point equalizer can be used for each subcarrier.

After equalization, the data 561 on each carrier is recovered in the time domain by the rake combiner 562 (including the despreader). The parallel data symbols 563 generated by each of the rake combiners 562 are parallel-to-serial converted by the parallel-to-serial converter 564 to recover the transmitted data.

As in the first embodiment of FIG. 1, a masking operation can be performed at transmitter 510 and a corresponding demasking operation can be performed at receiver 550 to reduce inter-cell multiple access interference. Mixer 524 can multiply output 523 from loop prefix insertion unit 522 by mask code 525 prior to transmission. The mixer 552 of the receiver 550 can multiply the received signal 528 by the conjugate 551 of the mask code 125 used at the transmitter 510.

Figure 6 is a block diagram of an orthogonal frequency division multiplexing code division multiple access system 600 in accordance with a third embodiment of the present invention. System 600 includes a transmitter 610 and a receiver 650. The transmitter 610 includes a serial-to-parallel converter 612, a complex multiplier 614, a complex repeater 616, a complex serial-to-parallel converter 618, a primary carrier mapping and weighting unit 620, and an inverse discrete Fourier transform unit. 622, a parallel pair of serial converters 624, a cyclic prefix insertion unit 626, and an optional mixer 628. According to a third embodiment, the input data symbols are expanded twice, once in the time domain and once in the frequency domain. Assume that the total number of secondary carriers is 2 ⁿ , and the spreading factors used for time domain and frequency domain expansion are 2 ^p and 2 ^{m, respectively} . The user i N _T consecutive data symbol 601 by lines parallel to serial converter 612 is converted from serial to parallel N _T symbol 613. The N _T value is equal to 2 ^nm . The jth data symbol of the N _T parallel data symbol 613 of the user i is denoted by d ^j (i), where j=0, 1, ..., N-1. The time domain extension code 611 used by user i is marked as ( i , :). Each N _T parallel data symbol 613 is then multiplied by a time domain spreading code by a multiplier 614. ( i , :) 611 is extended in the time domain. Time domain spreading code The expansion factor of ( i , :) is defined as 2 ^p in equations (3) and (4). Each data symbol 613 is extended to 2 ^p based wafer, and the wafer 2 ^p N _T parallel stream 615 is generated.

After the time domain is extended, the frequency domain extension is performed. Wafer for each stream j (corresponding to the j-th data symbol of the N _T data symbol), the given user i, each wafer chip is N _T streams on the wafer is continuously repeated during each repeated ^m times 616, which was repeated 2 ^{The m-} pass wafer is converted to a parallel 2 ^m wafer 619 by a serial-to-parallel converter 618. The 2 ^m wafers are then sequentially mapped to 2 ^m equidistant subcarriers by subcarrier mapping and weighting unit 620. The distance between each subcarrier is 2 ^nm subcarrier. The subcarrier mapping is performed sequentially such that the repeated wafer system from the jth wafer stream is mapped to the subcarrier 2 ^nm ‧k+j, (k=0,1,...,2 ^m -1,j=0 , 1, ..., 2 ^nm -1). Prior to the inverse discrete Fourier transform operation, the wafers on each carrier at 2 ^nm ‧ k+j are marked The kth wafer weight of the extended composite secondary sequence code c _i .

A user can use all 2 ⁿ secondary carriers in the system. Therefore, the number of data symbols that can be transmitted by one user in an orthogonal frequency division multi-frame is 2 ^nm .

Figure 7 shows an alternative to frequency domain extension and subcarrier mapping in the system of Figure 6. In addition to repeating the wafer 2 ^m times, the chip 615 is subjected to a frequency domain spreading code. Direct expansion. For each wafer stream j (corresponding to the jth data symbol of the N _T data symbol), for a given user i, each of the chips 615 is extended by the multiplier 702 to extend the composite secondary sequence code for each wafer duration. 703 is a 2 ^m wafer 704, and the frequency domain extension chip 704 is converted to a 2 ^m parallel wafer 707 by a serial pair parallel converter 706. As described above, these parallel wafers 707 are then sequentially mapped by the secondary carrier mapping unit 708 to the 2 ^m equidistant subcarrier 709. The distance between each subcarrier is 2 ^nm subcarrier. The subcarrier mapping is performed sequentially such that the repeated wafer system from the jth wafer stream is mapped to the subcarrier 2 ^nm ‧k+j, (k=0,1,...,2 ^m -1,j=0 , 1, ..., 2 ^nm -1).

Referring again to FIG. 6, the wafer 621 mapped to the subcarrier is fed to the inverse discrete Fourier transform unit 622 and converted to time domain data 623. The time domain data 623 is converted from the parallel data to the serial data 625 by the parallel to serial converter 624, and the cyclic prefix is added to each of the frame terminals of the data 625 by the cyclic prefix insertion unit 626. The material 627 having the cyclic prefix is transmitted on the wireless channel.

Receiver 650 includes an optional mixer 652, a cyclic prefix removal unit 654, a tandem pair parallel converter 656, a discrete Fourier transform unit 658, an equalizer 660, and a complex time-frequency Ray The gram combiner 662 and a parallel pair of serial converters 664. On the receiver 650 side, the cyclic prefix is removed from the received material 632 via the wireless channel by the cyclic prefix removal unit 654. The data 655 is then converted from the serial to the side-by-side material 657 by the serial pair parallel converter 656. The parallel data 657 is fed to the discrete Fourier transform unit 658 and converted to frequency domain data 659. Next, the frequency domain data 659 is equalized by the equalizer 660. In a conventional orthogonal frequency division multiplexing system, a simple one-drop point equalizer can be used for each subcarrier.

After equalization, the data 661 on each carrier is recovered by the time-frequency rake combiner 662, which will be explained in detail as follows. The side-by-side data symbols 663 generated by each time-frequency rake combiner 662 are then parallel-to-serial converted by the parallel-to-serial converter 664 to recover the transmitted data.

The time-frequency rake combiner 662 is a Rex combiner that recovers the time and frequency domains at the transmitter and is extended in the time and frequency domains. Figure 8 shows a 662 example of a rake combiner. Skilled artisans should note that the time-frequency rake combiner 662 can be implemented in many different ways, and the configuration shown in FIG. 8 is provided as an example and not a limitation. Each time-frequency rake combiner 662 includes a primary carrier grouping unit 802, a despreader 804, and a rake combiner 806. For each data symbol j (j=0, 1, . . . , 2 ^nm -1) of the N _T consecutive data symbols, the subcarrier grouping unit 802 can collect the 661 2 ^nm ‧k+j on the following subcarriers, A total of 2 ^m wafers. Next, the despreader 804 can perform frequency domain despreading on the 2 ^m subcarrier. The despreader 804 includes a complex multiplier 812 that multiplies the conjugate 813 of the extended composite secondary sequence code by the collected wafer 811, and the adder 815 can be summed up by one of the multiplier outputs 814 to normalize the quilt The sum output 816 is a regulator 817. After frequency spreading in the frequency domain, the wafer on the 2 ^nth carrier becomes the wafer 818 on the N _T parallel wafer stream. To recover the jth data symbol of user i, the time domain rip combination is performed on the corresponding wafer stream 818 by the rake combiner 806.

Referring again to FIG. 6, a masking operation can be performed at transmitter 610 and a corresponding unmasking operation can be performed at receiver 650 to reduce inter-cell multiple access interference. Mixer 628 can multiply output 627 from loop prefix insertion unit 626 by mask code 630 prior to transmission. The mixer 652 of the receiver 650 can multiply the received signal 632 by the conjugate 651 of the mask code used at the transmitter 610.

For all of the above embodiments, the predetermined material vector {d(i)} (i.e., the predictive signal) can be transmitted. In this method, the uplink transmitted signal can be regarded as a random access channel (RACH) pilot or uplink pilot signal. For example, all predetermined data vectors {d(i)} of 1,{1,1,...,1} can be transmitted.

The features and elements of the present invention are described in the preferred embodiments in the preferred embodiments, and the various features and elements are not required to be further Used separately.

110, 510, 610. . . Transmitter

112. . . Spreader

123. . . data

124. . . mixer

150, 550, 650. . . receiver

151, 551, 651. . . Conjugate

165. . . Output

611. . . Time domain spreading code

662. . . Time-frequency rake combiner

804. . . Despreading spreader

812. . . Multiplier

c _i . . . Extended composite secondary sequence code

CP. . . Cyclic prefix

DFT. . . Discrete Fourier transform

IDFT. . . Inverse discrete Fourier transform

OFDM. . . Orthogonal frequency division multiplexing

P/S. . . Parallel pair

SCQS. . . Extended composite quadratic sequence

SF. . . Expansion factor

S/P. . . Tandem pair

The invention can be understood in more detail from the following description of the preferred embodiments, in which:

1 is a block diagram of an orthogonal frequency division multiplexing multiple code division multiple access system according to an embodiment of the present invention;

Figure 2 shows an encoding group of an extended composite secondary sequence code in accordance with the present invention;

Figure 3 shows the extension and subcarrier mapping in the system of Figure 1;

Figure 4 shows an alternative explanation of the extension and subcarrier mapping in the system of Figure 1;

Figure 5 is a block diagram of an orthogonal frequency division multiplexing code division multiple access system according to another embodiment of the present invention;

Figure 6 is a block diagram of an orthogonal frequency division multiplexing code division multiple access system according to still another embodiment of the present invention;

Figure 7 shows an alternative method of frequency domain extension and subcarrier mapping in the system of Figure 6;

Figure 8 is a block diagram showing an example of a time-frequency rake combiner in accordance with the present invention.

110. . . Transmitter

112. . . Spreader

123. . . data

124. . . mixer

150. . . receiver

151. . . Conjugate

165. . . Output

c _i . . . Extended composite secondary sequence code

IDFT. . . Inverse discrete Fourier transform

CP. . . Cyclic prefix

OFDM. . . Orthogonal frequency division multiplexing

P/S. . . Parallel pair

SCQS. . . Extended composite quadratic sequence

S/P. . . Tandem pair

Claims (21)

A transmitting apparatus comprising: at least one circuit, the group consisting of a combined data symbol and a spreading code and a quadrature sequence having a secondary phase sequence code, wherein the spreading code having a secondary phase sequence code has a plurality of The second sequence of phases is derived by conversion, wherein for a spreading factor of 2 ^m , the spreading code has 2 ^m wafers, and the codes used by different users are different in the secondary phase sequence code portion The at least one circuit is further configured to map the extended result to the plurality of secondary carriers, and wherein the at least one circuit is further configured to process the mapped plurality of secondary carriers and transmit the result of the processing as Radio frequency signal. The transmitting device of claim 1, wherein the second sequence is a four-phase sequence having a fixed amplitude. The transmitting device of claim 1, wherein the radio frequency signal is further derived from a third sequence. The transfer device of claim 3, wherein the third sequence reduces inter-cell interference. The transfer device of claim 3, wherein the third sequence is a mask code. The transmitting device of claim 1, wherein the orthogonal sequence is assigned to the transmitting device. The conveying device of claim 1, wherein the At least one of the circuits is further configured to use orthogonal sequences of different lengths for expansion. The transmitting device of claim 1, wherein the mapped plurality of subcarriers are transmitted as an Orthogonal Frequency Division Multiplexing (OFDM) based signal. A method applicable to an orthogonal frequency division multiplexing multiple code division multiple access system, comprising: combining a data symbol and a spreading code and an orthogonal sequence having a secondary phase sequence code by a transmitting device, wherein the secondary phase has The spreading code of the sequence code is derived by converting a second sequence having a plurality of phases, wherein the codes used by different users are different in the second phase sequence code portion; by the transmission a device, using an orthogonal sequence to extend the result of the combination; by the transmitting device, mapping the extended result to a plurality of secondary carriers; processing the mapped plurality of secondary carriers by the transmitting device; and transmitting the processed result As a radio frequency signal. The method of claim 9, wherein the radio frequency signal is a four-phase sequence having a fixed amplitude. The method of claim 9, wherein the radio frequency signal is further derived from a third sequence. The method of claim 11, wherein the third sequence reduces inter-cell interference. The method of claim 11, wherein the The three sequences are mask codes. The method of claim 9, wherein the orthogonal sequence is assigned to the transmitting device. The method of claim 9, wherein the mapped plurality of subcarriers are transmitted as an Orthogonal Frequency Division Multiplexing (OFDM) based signal. A receiving apparatus comprising: at least one circuit configured to receive a radio frequency signal and determine a data symbol from the radio frequency signal, wherein the radio frequency signal is a combination of the data symbol and a spreading code having a secondary phase sequence code, Using orthogonal sequences to extend the results of the combination, mapping the extended results to a plurality of subcarriers, and the codes used by different users are different in the quadratic phase sequence code portion, and processing the mapped plurality of times As a result of the carrier, the spreading code having the quadratic phase sequence code is derived by converting a second sequence having a plurality of phases. The receiving device of claim 16, wherein the second sequence is a four-phase sequence having a fixed amplitude. The receiving device of claim 16, wherein the radio frequency signal is further derived from a third sequence. The receiving device of claim 18, wherein the third sequence reduces inter-cell interference. The receiving device of claim 18, wherein the third sequence is a mask code. The receiving device according to claim 16, wherein The radio frequency signal is received as an Orthogonal Frequency Division Multiplexing (OFDM) based signal.