JP4494331B2 - Variable rate transmission method, reception method, variable rate transmission device, and reception device - Google Patents

Description

  The present invention relates to a variable rate transmission method in wireless communication, and in particular, a variable rate transmission method applicable to a direct spreading code division multiple access (DS-CDMA) method in mobile communication and an apparatus used therefor It is about.

  In DS-CDMA, a carrier wave is narrow-band modulated with information data (for example, two-phase phase modulation or four-phase phase modulation), and then spread with a binary spreading code sequence at a higher rate and transmitted. On the receiving side, the same binary spreading code sequence as that used for transmission is multiplied on the received signal to obtain the original narrowband modulated signal and demodulated into transmission data.

  By the way, an information rate may change during communication. In voice communication, for example, the rate is about 8 kbps, but there is also a time when there is no voice signal. At this time, even if the information rate is lowered, there is no significant deterioration in quality. In CDMA, when the information rate is low, it is important to reduce the transmission power to reduce interference given to others.

  This is because the communication quality is determined by the amount of interference. For this reason, it is important to realize a variable rate transmission method in CDMA.

  There is question transmission as a method of this variable rate. This intermittent transmission is continuous transmission at the maximum information rate, but at a low rate, the instantaneous transmission rate remains at the maximum rate and the average transmission rate is changed to the information rate by reducing the ratio of transmission time. Make equal. This is intended to reduce the amount of interference.

About this intermittent transmission, for example,
Reference 1: R.A. Padovani. , R. "Reverse link performance of IS-95 based cellular systems" IEEE Personal Communications, pp 28-34, 3rd Quarter, 1994,
Reference 2: Y. Okumura and F.M. Adachi, “Variable rate data transmission with bridging detection for coherent DS-CDMA mobile radio” IEEE electron. Lett. vol. 32, pp. 1865-1866, Sept. See 1996.

  There is continuous transmission as another variable rate transmission method in CDMA. In the variable rate transmission in the continuous transmission, the wireless instantaneous transmission rate is changed in accordance with the change in the information rate, and the transmission power is changed in accordance with the transmission rate.

  As described above, since the transmission power is changed according to the transmission rate in the continuous transmission (inversely proportional to the transmission rate), the average interference amount can be reduced in the continuous transmission as well as the intermittent transmission. .

  In CDMA technology, transmission power control is indispensable. When performing this transmission power control, the reception SIR is controlled to be equal to the target SIR based on a comparison result between a reception SIR (signal to interference ratio) measured on the reception side and a preset target SIR. (For example, see Japanese Patent Application No. 8-162972 filed by the present applicant). At this time, the SIR is measured in slot units sandwiched between pilot signals, which are known signals periodically transmitted in the received signal, and this SIR is compared with the target SIR. Based on the comparison result, a command for transmission power control is created and transmitted for reflection in transmission power control. The transmission unit of this transmission power control command is a slot unit which is a measurement unit.

  When the transmission power is changed according to the transmission rate, the reception quality is not constant if the transmission power is always used for different rates using the same target SIR. For this reason, the conventional transmission power control using the target SIR cannot be applied as it is to a transmission signal whose transmission power is changed according to the transmission rate.

  An object of the present invention is to provide a transmission method, a reception method and an apparatus for realizing the above-described variable rate transmission method by continuous transmission.

  Further, when the transmission power is changed according to the transmission rate (for example, inversely proportional to the transmission rate), the reception side can perform transmission power control that can always obtain a constant reception quality even if the rate changes. Making it possible is also an object of the present invention.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided a set of orthogonal codes having different lengths, which is at least twice the maximum information rate, depending on the rate of information to be transmitted. One is selected and multiplied with the transmission signal.

According to a second aspect of the present invention, in the transmission method according to the first aspect of the present invention, the orthogonal codes are orthogonal to each other using a matrix having a small number of dimensions based on a certain rule. A matrix having a large degree (2 ^N × 2 ^N elements, N is an integer is ≧ 1) is sequentially generated, and the row vector in the matrix having a different dimensionality is generated according to the transmission data transmission rate peak size. Choose from one.

According to a third aspect of the present invention, in the transmission method according to the second aspect of the present invention, in the selection of the orthogonal code, a row vector in a 2 ^k × 2 ^{k element} matrix that is an integer k smaller than N is further selected. When selecting as an orthogonal code, any of the already assigned row vectors in the 2 ^j × 2 ^j original matrix of integer j greater than k is the row vector that is to be selected or Does not include inverted row vectors as partial vectors.

  A fourth aspect of the present invention is the transmission method according to any one of the first to third aspects of the present invention, wherein the transmission signal is further multiplied by a spreading code sequence for spreading a spectrum, and the rate It transmits with transmission power according to.

  According to a fifth aspect of the present invention, in the transmission method according to the fourth aspect of the present invention, a known pilot symbol is periodically inserted into a data symbol corresponding to the information to be transmitted, and the pilot The rate is changed in units of frames each including a plurality of slots defined by symbols.

  According to a sixth aspect of the present invention, in the transmission method according to the fifth aspect of the present invention, the transmission power is controlled in units of the slot by a transmission power control command from the reception side.

  According to a seventh aspect of the present invention, in the transmission method according to the sixth aspect of the present invention, in the slot immediately after the rate change, the inserted pilot symbol is transmitted at a power corresponding to the previous rate changing. .

  According to an eighth aspect of the present invention, in the transmission method according to the sixth aspect of the present invention, transmission power control by the transmission power control command corresponding to at least one slot immediately after the rate changes is stopped.

  According to a ninth aspect of the present invention, in the transmission method according to the eighth aspect of the present invention, the number of slots at which the transmission power control stops is determined by transmission quality.

  According to a tenth aspect of the present invention, in the transmission method according to any one of the sixth to eighth aspects of the present invention, the inserted pilot symbol is transmitted at the same rate as the frame.

  An eleventh aspect of the present invention is the transmission method according to any one of the sixth to eighth aspects of the present invention, wherein the inserted pilot symbols are transmitted at a constant rate.

  A twelfth aspect of the present invention is a reception method for receiving a signal transmitted using the variable rate transmission method according to any one of the first to fifth aspects of the present invention, wherein the received signal is sampled at a rate of an orthogonal code. To create a received signal sample sequence, correlate the received signal sample sequence with a plurality of orthogonal codes of different lengths, compare the magnitude of the correlation value that is the result of the correlation, and calculate the maximum orthogonal code. The received signal is demodulated by multiplying the orthogonal code having the maximum correlation value and the received signal sample sequence.

  According to a thirteenth aspect of the present invention, in the receiving method for receiving a signal transmitted using the variable rate transmission method according to the sixth or eighth aspect of the present invention, the received signal is sampled and received at an orthogonal code rate. Create a signal sample sequence, correlate the received signal sample sequence with multiple orthogonal codes of different lengths, compare the magnitude of the correlation value that is the result of the correlation, determine the maximum orthogonal code, The orthogonal code having the maximum correlation value is multiplied by the received signal sample sequence, the received signal is demodulated, the received SIR value is measured corresponding to the slot of the received signal, and the received SIR value is determined by the determination of the orthogonal code. It corrects by the rate, compares the corrected received SIR value with the target SIR value, and creates a transmission power control command based on the comparison result.

  According to a fourteenth aspect of the present invention, in the reception method according to the thirteenth aspect of the present invention, the demodulation of the received signal is performed for each slot.

  According to a fifteenth aspect of the present invention, there is provided a reception method for receiving a signal transmitted using the variable rate transmission method according to the seventh aspect of the present invention, wherein a received signal is sampled at a rate of an orthogonal code. And correlate the received signal sample series with multiple orthogonal codes of different lengths, compare the correlation values that are the results of the correlation, determine the maximum orthogonal code, and Multiply the maximum orthogonal code and the received signal sample sequence to demodulate the received signal, measure the received SIR value of the pilot symbol in the slot immediately after the rate change, and support the slot in the other slots The received SIR value is measured at a time, the received SIR value corresponding to the slot is corrected at a rate determined by orthogonal code, the received SIR value of the pilot symbol is corrected at a rate before the change, and the correction is performed. Compared received SIR value and to the target SIR value, the result of the comparison, generates a transmission power control command.

  According to a sixteenth aspect of the present invention, there is provided a reception method for receiving a signal transmitted using the variable rate transmission method according to the ninth aspect of the present invention, wherein a received signal is sampled at a rate of an orthogonal code. And correlate the received signal sample series with multiple orthogonal codes of different lengths, compare the correlation values that are the results of the correlation, determine the maximum orthogonal code, and Multiplying the maximum orthogonal code and the received signal sample sequence to demodulate the received signal, measure the received SIR value of the pilot symbol at the constant rate, and use the received SIR value as the rate determined by the determination of the orthogonal code. The corrected received SIR value is compared with the target SIR value, and a transmission power control command is created based on the comparison result.

  According to a seventeenth aspect of the present invention, there is provided an orthogonal code generation unit that generates one of a set of orthogonal codes having different lengths, which is a rate at least twice the maximum information rate, according to a rate of information to be transmitted. The orthogonal code from the orthogonal code generator is multiplied with the transmission signal.

According to an eighteenth aspect of the present invention, in the transmission device according to the seventeenth aspect of the present invention, the orthogonal codes use a matrix having a small number of dimensions based on a certain rule, and the row vectors are orthogonal to each other. A matrix having a large degree (2 ^N × 2 ^N elements, N is an integer is ≧ 1) is sequentially generated, and the row vector in the matrix having a different dimensionality is generated according to the transmission data transmission rate peak size. Choose from one.

According to a nineteenth aspect of the present invention, in the transmission apparatus according to the eighteenth aspect of the present invention, in the selection of the orthogonal code, a row vector in a 2 ^k × 2 ^{k element} matrix that is an integer k smaller than N is further selected. When selecting as an orthogonal code, any of the already assigned row vectors in the 2 ^J × 2 ^J-element matrix of an integer j greater than k is the row vector to be selected or Does not include inverted row vectors as partial vectors.

  According to a twentieth aspect of the present invention, there is provided a transmission apparatus according to any one of the seventeenth to nineteenth aspects of the present invention, a spreading sequence generating unit that generates a spreading code sequence for spreading a spectrum, and the spreading sequence generating unit A multiplication unit that multiplies the transmission code signal on the transmission signal, and a transmission unit that changes transmission power in accordance with the transmission rate.

  According to a twenty-first aspect of the present invention, in the transmission apparatus according to the twentieth aspect of the present invention, a pilot symbol generation unit that periodically generates known pilot symbols is provided, and the data symbols corresponding to the information to be transmitted And the rate is changed in units of a frame composed of a plurality of slots defined by the pilot symbols.

  According to a twenty-second aspect of the present invention, in the transmission apparatus according to the twenty-first aspect of the present invention, the transmission apparatus includes a transmission power control unit that controls transmission power in units of the slots in accordance with a transmission power control command from the reception side.

  According to a twenty-third aspect of the present invention, in the transmitting apparatus according to the twenty-second aspect of the present invention, in the slot immediately after the rate changes, the inserted pilot symbol is transmitted with power corresponding to the previous rate of change. .

  According to a twenty-fourth aspect of the present invention, in the transmission apparatus according to the twenty-first aspect of the present invention, the inserted pilot symbol is transmitted at the same rate as the frame.

  According to a twenty-fifth aspect of the present invention, in the transmission apparatus according to the twenty-first aspect of the present invention, the inserted pilot symbols are transmitted at a constant rate.

  According to a twenty-sixth aspect of the present invention, in the transmission apparatus according to the twenty-second aspect of the present invention, transmission power control by the transmission power control command corresponding to at least one slot immediately after the rate changes is stopped.

  According to a twenty-seventh aspect of the present invention, in the transmission device according to the twenty-sixth aspect of the present invention, the number of slots at which the transmission power control stops is determined by transmission quality.

  According to a twenty-eighth aspect of the present invention, in a receiving apparatus that receives a signal transmitted using the variable rate transmission method according to any one of the first to fifth aspects of the present invention, the received signal is sampled at a rate of an orthogonal code. And a correlation unit that correlates a reception signal sample sequence from the sampling unit with a plurality of orthogonal codes of different lengths, and a correlation result. An orthogonal code determination unit that determines the maximum orthogonal code by comparing the magnitudes of correlation values, an orthogonal code generation unit that generates an orthogonal code determined by the orthogonal code determination unit, and an orthogonal from the orthogonal code generation unit A product unit that multiplies the code and the received signal sample sequence is provided, and the received signal is demodulated.

  According to a twenty-ninth aspect of the present invention, a receiving apparatus that receives a signal transmitted using the variable rate transmission method according to the sixth or eighth aspect of the present invention samples and receives a received signal at an orthogonal code rate. A sampling unit that creates a signal sampling sequence, a correlation unit that correlates a received signal sample sequence from the sampling unit and a plurality of orthogonal codes of different lengths, and a correlation value that is a result of the correlation An orthogonal code determination unit that determines the maximum orthogonal code by comparing the sizes, an orthogonal code generation unit that generates an orthogonal code determined by the orthogonal code determination unit, and an orthogonal code received from the orthogonal code generation unit A product product unit that multiplies the signal sample sequence, a reception SIR measurement unit that measures a received SIR value corresponding to a slot of the received signal, and a correction that corrects the received SIR value at a rate based on the determination of the orthogonal code Part and said And a comparing unit for comparing the signal SIR value and the target SIR value, the result of the comparison, generates a transmission power control command.

  According to a 30th aspect of the present invention, in the receiving apparatus according to the 29th aspect of the present invention, the demodulation of the received signal is performed for each slot.

According to a thirty-first aspect of the present invention, in a receiving apparatus that receives a signal transmitted using the variable rate transmission method according to the seventh aspect of the present invention, the received signal is sampled by sampling the received signal at an orthogonal code rate. A sampling unit that creates a sequence, a correlation unit that correlates a received signal sample sequence from the sampling unit with a plurality of orthogonal codes of different lengths, and a correlation value that is a result of the correlation. An orthogonal code determination unit that determines the maximum orthogonal code by comparison, an orthogonal code generation unit that generates an orthogonal code determined by the orthogonal code determination unit, and an orthogonal code and a received signal sample sequence from the orthogonal code generation unit And a reception SIR measurement that measures the reception SIR value of the pilot symbol in the slot immediately after the rate change, and measures the reception SIR value corresponding to the slot in the other slots. And the received SIR value corresponding to the slot at the rate determined by the orthogonal code, the correction unit for correcting the received SIR value of the pilot symbol at the rate before the change, the corrected received SIR value and the target SIR value And a comparison unit that compares the data and generates a transmission power control command based on the comparison result.

  According to a thirty-second aspect of the present invention, in a receiving apparatus that receives a signal transmitted using the variable rate transmission method according to the eleventh aspect of the present invention, a received signal is sampled by sampling a received signal at an orthogonal code rate. A correlation unit that correlates a received signal sample sequence with a plurality of orthogonal codes of different lengths, and compares the magnitude of the correlation value that is the result of the correlation to determine the maximum orthogonal code An orthogonal code determination unit, and a product unit that multiplies the orthogonal code having the maximum correlation value and the received signal sample sequence, and receives the received SIR value of the pilot symbol at the constant rate. A measurement unit, a correction unit that corrects the received SIR value at a rate based on the determination of orthogonal codes, and a measurement unit that compares the corrected received SIR value with a target SIR value. Sending To create a power control command.

  Embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of the present invention, and shows a part of baseband processing of a transmission apparatus according to a CDMA transmission method. In FIG. 1, reference numeral 105 denotes a phase modulation unit that phase-modulates a transmission information sequence that is a digital signal. A multiplier 103 multiplies the phase-modulated transmission signal by the orthogonal code generated by the orthogonal code generator 101 corresponding to the transmission rate. The multiplied transmission signal is multiplied by the multiplication unit 104 by the spreading code sequence from the spreading code sequence generation unit 102 and spread.

  The orthogonal code generation unit 101 selects an orthogonal code generated based on the rate information of the transmission signal. The bit rate of the orthogonal code generated by the orthogonal code generation unit 101 is twice the maximum transmission rate to be transmitted.

  Multiplier 103 multiplies the modulated transmission signal by an orthogonal code corresponding to the rate information. The transmission signal multiplied by the orthogonal code corresponding to the rate information is multiplied by the spreading code sequence by the multiplication unit 104 to be spread spectrum, becomes a CDMA signal, and is transmitted with transmission power controlled by the rate information.

  In FIG. 1, the orthogonal code used in the transmission method when the information rate is 1 / Q at the maximum is, for example, a sequence of 2Q binary codes in total, Q consecutive 1s and Q consecutive −1s. is there. Since the time length of this orthogonal code is equal to one information length, the bit rate of the orthogonal code is always twice the maximum information rate. The orthogonal code generated by the orthogonal code generation unit 101 will be described in detail below.

The orthogonal code generated by the orthogonal code generation unit 101 is generated based on a certain rule as shown in FIG. In FIG. 2, the matrix C ₂ is a row vector C ₂ (1) = (1,1),

いる。このようにして、Ｃ_２ｎは、図２に図示したように定義される。

Yes. In this way, C _2n is defined as illustrated in FIG.

  In the example shown here, the row vector of the generated matrix is a Walsh function.

  FIG. 3 shows the row vector of each matrix in a hierarchical structure.

The subscript of the symbol C is the matrix order. The maximum order is 64. At the lowest transmission rate, one of 64 row vectors {C ₆₄ (1),..., C ₆₄ (64)} is generated as an orthogonal code. At the double transmission rate, one of 32 row vectors {C ₃₂ (1),..., C ₃₂ (32)} is assigned as an orthogonal code. When assigning a row vector in a matrix of a certain hierarchy as an orthogonal code, a row vector in a hierarchy lower than that branch is selected so as not to include those already assigned.

That is, in selecting an orthogonal code, when a row vector in a 2 ^k × 2 ^{k element} matrix (integer k) is selected as an orthogonal code, it is in all 2 ^J × 2 ^{J element} matrices (an integer j greater than k). This means that none of the already assigned row vectors are included as partial vectors with respect to the row vector to be selected or the inverted row vector.

  FIG. 4 specifically shows the orthogonal codes generated at each transmission rate.

  FIG. 4 shows the case of an orthogonal code having a rate twice as large as the maximum information transmission rate together with a hierarchical structure as in FIG. In FIG. 4, the orthogonal codes generated in the orthogonal code generation unit 101 of FIG. 1 are indicated by point A, point B, point C, and point D. Point A is an orthogonal code for the lowest transmission rate (1/8 of the maximum transmission rate), and point D is an orthogonal code for a transmission rate (maximum transmission rate) eight times that. As shown in the figure, the orthogonal code corresponding to the point D has 2 bits for one information length.

The orthogonal code in FIGS. 1 and 4 has been described in the case of an orthogonal code having a bit rate twice the maximum transmission rate. However, the bit rate of the orthogonal code to be used may be 2 ⁿ times (n: natural number) such as 4 times or 8 times the maximum information rate.

  FIG. 5 shows an example in which the bit rate of the orthogonal code used is four times the maximum transmission rate. In FIG. 5A, the point A ′ is an orthogonal code for the lowest transmission rate (1/8 of the maximum transmission rate), and the point D ′ is an orthogonal code for a transmission rate eight times (the highest transmission rate).

  The orthogonal code corresponding to the point D ′ in FIG. 5A has 4 bits for one information length. FIG. 5B shows another example in which the bit rate of the orthogonal code used is four times the maximum transmission rate. In this way, the orthogonal code selected in each level of the hierarchy may be used so that the hierarchy shown in FIG. 5 does not include the orthogonal code of the hierarchy below the branch. For example, since the point E includes points A ″ and B ″ in the lower hierarchy of the branch, as illustrated, the point D ″ not including the points A ″ and B ″ in the lower hierarchy of the branch is illustrated. Selected.

  The transmission rate of the CDMA signal thus transmitted can be determined directly from this signal. This will be described with reference to the block diagram showing the configuration of the demodulator on the receiving side shown in FIG. FIG. 6 shows only a portion after the transmitted signal is received, converted into baseband, and converted into digital.

  In FIG. 6, reference numeral 401 denotes a multiplication unit that performs despreading by multiplying the spreading code sequence from the spreading code sequence generation unit 402. A sampling unit 403 samples at a bit rate of the orthogonal code, that is, twice the maximum information transmission rate. A correlation calculation unit 420 multiplies the above-described orthogonal code used for each transmission rate at the time of transmission to obtain a correlation. For example, when the transmission signal uses the orthogonal code shown in FIG. 4, it correlates with four orthogonal codes. The correlation calculation unit 420 includes a multiplication unit 421, an integration unit 422, a square unit 423, and an addition unit 424 for each orthogonal code, and performs the calculation for each orthogonal code in parallel, Correlation is taken. Each integrating unit 422 integrates for one information length of each information rate. Similarly, each adding unit 424 adds one information length. That is, for example, in the orthogonal code of FIG. A maximum value code selection unit 404 receives the result of the correlation calculation unit 420 and selects an orthogonal code having the maximum correlation value.

  Reference numeral 405 denotes a delay unit, and the maximum value code selection unit 404 delays the received signal until the orthogonal code having the maximum correlation value is detected. Reference numeral 407 denotes an orthogonal code generation unit that generates the orthogonal code selected by the maximum value code selection unit 404. 406 multiplies the orthogonal code by the sampled received signal. Reference numeral 408 denotes an integration unit which integrates for one information period of the corresponding information rate. A phase demodulator 410 demodulates the received signal.

  In FIG. 6, the baseband digital received signal is despread using the spreading code sequence in the multiplier 401, and the sampling unit 403 converts the spread signal to the bit rate of the orthogonal code (that is, the maximum information rate). 2). Correlation calculation section 420 prepares a set of orthogonal codes used on the transmission side, correlates each with a sample signal sequence, and maximum value code selection section 404 compares the correlation values. Then, maximum value code selection section 404 determines that the rate corresponding to the orthogonal code with the maximum correlation value is the rate of the transmitted information.

  The correlation calculation unit 420 in FIG. 6 will be described in detail. The reception sampling rate is twice the information rate Rmax. The orthogonal code 1 in the correlation calculation unit 420 corresponds to the maximum information rate, and the orthogonal code Qmax corresponds to the minimum information rate. There is an integration circuit in the correlation calculation block, but the integration time is one information length of the information rate corresponding to each, and the correlation value is obtained. The squaring unit 423 is inserted to square the correlation value. Further, there is an adder circuit, because when information is transmitted at an information rate other than the lowest information rate, a plurality of information appears in one information period of the lowest information rate. For example, when the minimum rate is 8 times the maximum rate, the adder circuit of the orthogonal code 1 adds 8 times and the adder circuit of the orthogonal code 2 adds 4 times. Then, the correlation value is compared for each information period of the lowest rate, and the code that gives the maximum value is selected. In FIG. 6, the index of this code is indicated by Q '.

  In the configuration of FIG. 6, since there is a delay in rate determination, it is necessary to delay the received signal sample sequence, and a delay unit 405 is provided to guarantee this.

  After the information rate is determined, if the correlation between the corresponding orthogonal code sequence and the received signal sample sequence is taken, the correlation value sequence becomes the received sequence.

  The orthogonal code selected by maximum value code selection section 404 is generated by orthogonal code generation section 407 and multiplied by the delayed received signal sample sequence. Thereafter, integration is performed for a period corresponding to the determined information rate.

  Since the received information series is normally phase-modulated, the phase demodulator 410 phase-demodulates the correlation value series to obtain a source data series. In this way, the transmission rate can be detected by obtaining a correlation with the orthogonal code in the receiving unit. In the above description, transmission / reception in the CDMA communication system has been described. However, the transmission rate can be detected by this orthogonal code, as a matter of course, can be used in other digital transmission / reception communication systems.

  In the DS-CDMA described in the above-described embodiments, it is generally known before the present application that communication is performed using pilot symbols. Here, the pilot symbol will be described. This pilot symbol is transmitted by inserting a known signal into a data symbol periodically. By using this known pilot symbol to estimate the transfer function of the transmission path and correcting the received data symbol, accurate demodulation is possible. The period between pilot symbols sent periodically is called a slot. The rate change described above is performed in units of frames composed of a plurality of slots.

  In this CDMA, the received signal is sampled at a rate equal to or greater than the spread code rate (chip rate) (sample) as in the process of correcting the frequency drift, that is, correcting the deviation between the transmitter and the receiver at the radio center frequency. There is a process to be performed based on the information. Normally, such processing is performed on the receiving side using a received signal of a pilot symbol portion which is a known data pattern inserted.

  In the present invention, in order to determine a rate that is changed on a frame-by-frame basis, orthogonal codes having different lengths corresponding to the data rate are multiplied on the transmission data on the transmission side. In this case, the rate is changed including the above-described pilot symbols.

  When processing such as drift correction is performed on such a received signal, the signal after being sampled by the sampling unit 403 in FIG. 6 (the signal sampled at a rate twice the symbol rate) It cannot be used for frequency drift correction. For this reason, after the rate determination result is obtained for the pilot symbol, the received signal before being sampled by the sampling unit 403 in FIG. From the above, it is used in the processing such as frequency drift correction.

  In order to accurately measure the received SIR also for information symbols other than pilot symbols, signal demodulation based on the result of rate determination (orthogonal code determination) (multiplication of the orthogonal code having the maximum correlation value and the received signal sample sequence) Product) for each slot.

  In order to perform drift correction or the like after such rate determination, it is necessary to store the received signal in a memory in order to delay the received signal by a time for which a required rate determination result is obtained. However, the memory used for such a purpose has a disadvantage that it is relatively large in a CDMA receiver (that is, sampling data based on symbol rate to store the same amount of information). (The memory capacity is required to be multiplied by the spreading factor with respect to the memory capacity for storing.

  Thus, the pilot symbol portion can always be transmitted at a constant symbol rate (usually the same symbol rate as the maximum data rate). Then, the orthogonal code corresponding to the data rate is not multiplied on the transmission side. On the receiving side, processing such as the above-described frequency drift correction can be performed using the received signal (pilot symbol) in this portion without waiting for the rate determination result to be obtained. This pilot symbol is transmitted at the same transmission power as the slot data rate.

  As described above, if the signal of the pilot symbol part is always transmitted at a constant rate, it is not necessary to discriminate the rate, and the memory for storing the information in units of the chip rate is not necessary, so that the circuit scale can be reduced.

  In this case, since the pilot symbol portion is not used for rate determination, the accuracy of rate determination is expected to be slightly lowered. However, among the transmission data symbols in a frame (or in a slot), pilot symbols Since the time ratio occupied by the portion is relatively small (usually 1/10 or less), it is considered that the influence thereof is small.

  In the case of mobile communication by CDMA, it is necessary to optimally control the power of the transmission signal on the receiving side. According to the variable rate described above, when the rate changes, the transmission power changes accordingly. In the case of such transmission, it is necessary to perform transmission power control according to the rate.

  7 and 8, when transmission at the above-described variable rate is performed, the reception quality is kept constant by matching the reception SIR (signal to interference ratio) measured at the reception side with the target SIR. Next, reception when transmission power control for controlling transmission power is applied will be described.

  FIG. 7 is a block diagram illustrating the configuration of the receiver. FIG. 8 is a diagram showing processing of a slot received by the receiver having the configuration of FIG. Further, in FIG. 7, the same reference numerals are used for the same configurations as the receiver described in FIG.

  The received signal is despread using a spreading sequence, correlated using the above-described orthogonal code using the correlation calculation unit 420, and then the maximum correlation value is maximized in the maximum value code selection unit 404. An orthogonal code is selected. Thereby, the transmission rate can be recognized on the receiving side. Using this orthogonal code, the received information sequence can be extracted by demodulating the delayed received signal. This is as described in FIG.

  Now, the despread reception signal is also input to reception SIR measurement section 450. The received SIR measurement unit 450 measures the SIR value for each received signal in slot units. The measured SIR value for each slot is corrected by the correction unit 452 based on the rate held in the rate determination result holding unit 454. The comparison unit 456 compares the corrected received SIR value corrected by the correction unit 452 with the target SIR value from the target SIR setting unit 458. The rate held in the rate determination result holding unit 454 is a rate determined for a frame using the slots received immediately before. Since the transmission rate changes for each frame composed of a plurality of slots, the rate held in the rate determination result holding unit 454 is reset every time this frame changes.

  In order to accurately measure the received SIR also for information symbols other than pilot symbols, signal demodulation based on the result of rate determination (orthogonal code determination) (multiplication of the orthogonal code having the maximum correlation value and the received signal sample sequence) Product) for each slot.

  Now, the comparison result that is the output of the comparison unit 456 is reflected in the transmission power command for the transmission side. Since the comparison result is obtained for each slot as described above, the transmission power command is transmitted for each slot.

  As time elapses, the accuracy of the rate determination result is improved, and the accuracy of the determination result in the last slot of the frame is on average best. The orthogonal code for demodulating the received information sequence described above uses the determination result in the last slot by delaying one frame by the delay unit 405.

  FIG. 8A shows a received signal when the signal transmitted at the rate of Q = 1 changes so as to be transmitted at the rate of Q = 2. In the case of transmission at a rate of Q = 2, the transmission power is reduced. FIG. 8B shows an enlarged view of the last slot of a frame transmitted at a rate of Q = 1 and the first few slots of a frame transmitted at a rate of Q = 2. FIG. 8C illustrates the timing for calculating the correlation.

  The processing when the frame changes will be described with reference to FIG.

  In FIG. 8B, attention is first focused on the first slot of the frame immediately after the rate change from the last slot of the frame before the rate change. As shown in FIG. 8 (c), the correlation calculation starts when the first slot starts. The rate is determined based on the correlation calculation result, and the received SIR value for the second slot is corrected. The correlation calculation for the second slot is continued, and the calculation result obtained so far is used for correcting the target SIR value of the third slot. Thus, since the second slot and thereafter can be compared using the received SIR value corrected by the rate, accurate transmission power control can be performed.

  However, since the rate determination result holding unit 454 is reset for each frame as described above, the rate determination result cannot be obtained in the first slot of the frame. For this reason, since correction cannot be performed according to the rate, it is not possible to accurately compare received SIR values in the first slot.

  The avoidance of this will be described. FIG. 8B shows that the pilot symbol indicated by A (the first pilot symbol of the first slot) is inserted by multiplying by a power coefficient corresponding to the immediately preceding rate. When the reception SIR value of this pilot symbol is obtained, the transmission power of this signal is at the previous rate, so that the rate obtained in the previous frame can be used for correction by the rate. In this way, it is possible to perform transmission power control by correcting the reception SIR value of the pilot symbol of the first slot and comparing the corrected SIR value with the target SIR value.

  This kind of reception control is performed when the rate determination result holding unit 454 is reset not just at the end of the frame but immediately before the rate determination result of the first slot of the next frame is obtained. This can be realized by performing correction using the previous frame rate. In this way, transmission power control corresponding to the first slot of the frame can be realized even if the transmission rate changes for each frame, using the reception SIR value of the pilot symbol.

  Further, as described above, since the accurate reception SIR comparison cannot be performed in the first slot of the frame, the transmission power control command corresponding to the first slot of the frame transmitted from the reception side is ignored on the transmission side. Thus, the transmission power control by this command may not be performed. In this case, as indicated by A in FIG. 8B, it is not necessary to use the pilot symbol of the first slot of the frame as the transmission power of the previous frame.

  It is not necessary to ignore this transmission power control command only for the transmission power command corresponding to the first slot. In the forward slot (multiple slots from the beginning of the frame) where the rate judgment accuracy is relatively poor in the frame (that is, the SIR measurement value may not be corrected correctly), the transmission power corresponding to that slot It is also possible to stop the control operation and perform transmission power control from a slot in which a certain degree of accuracy can be obtained. At this time, the number of slots for starting transmission power control in the frame is determined in consideration of final transmission quality (for example, average bit error rate).

  When measuring the SIR value of the above-mentioned received signal, it is also possible to measure the received SIR value of only the pilot signal portion transmitted at the above-described constant rate.

  In the above-described embodiment, as illustrated in FIG. 7, the configuration has been described in which the reception SIR value from the reception SIR measurement unit 450 is corrected by the determined transmission rate. In this configuration, since the change of the reception SIR value due to the transmission rate is corrected, the conventional configuration of the transmission power control based on the reception SIR value when the transmission rate is not changed can be used as it is.

  As a configuration different from the configuration in FIG. 7, it is possible to compare the received SIR with the target SIR. For example, the target SIR value may be corrected by the transmission rate and compared.

  Other embodiments are described that avoid other above-mentioned problems. As described above, when the pilot symbol to be inserted is transmitted at a constant rate, it is not necessary to perform rate determination for this pilot symbol unless the transmission power is changed according to the rate. There is no need to correct the received SIR. Therefore, when the reception SIR is measured using the pilot signal transmitted at a constant rate, the transmission power control is performed by comparing with the target SIR without correcting the value of the reception SIR of the pilot signal. be able to. In this case, the configuration for correcting the received SIR value is not required in FIG.

  As described above, the present invention can detect the rate on the receiving side without information indicating the transmission rate.

  Also, with respect to a signal transmitted at a variable rate, accurate transmission power control can be performed by using the above-described transmission power control.

It is a block diagram of a transmission part. It is a figure explaining preparation of an orthogonal code. It is a figure explaining the system of an orthogonal code. It is a figure explaining the orthogonal code to be used. It is a figure explaining the other orthogonal code to be used. It is a figure explaining the other orthogonal code to be used. It is a block diagram of a receiving part. It is a block diagram of the receiving part which measures the reception SIR of a received signal. It is a figure for demonstrating operation | movement of a receiving part.

Explanation of symbols

101, 407 Orthogonal code generation unit 102, 402 Spreading code sequence generation unit 103, 104, 401, 406, 421 Multiplication unit 105 Phase modulation unit 403 Sampling unit 404 Maximum value code selection unit 405 Delay unit 408, 422 Integration unit 410 Phase Demodulation section 420 Correlation calculation section 423 Squared section 424 Addition section 450 Reception SIR measurement section 452 Correction section 454 Rate determination result holding section 456 Comparison section 458 Target SIR setting section

Claims (16)

A variable rate transmission method,
For one communication with one receiving side where the rate of information to be transmitted changes, a plurality of orthogonal codes of different lengths that are at least twice the maximum information rate before the communication starts Steps to prepare,
Selecting one of the prepared orthogonal codes according to a rate of the information to be transmitted during the communication;
Multiplying the selected orthogonal code by a transmission signal including the information,
Each of the plurality of orthogonal codes corresponds to each possible value of the rate of the information to be transmitted. 2. The transmission method according to claim 1, wherein the orthogonal code uses a matrix having a small dimensionality based on a certain rule, and has a large degree (2 ^N × 2 ^N elements, N Is an integer ≧ 1) A variable rate characterized by sequentially generating a matrix and selecting from one of row vectors in a matrix having a different number of dimensions according to the magnitude of the transmission data transmission rate peak. Transmission method. 3. The transmission method according to claim 2, wherein in selecting the orthogonal code, an integer j greater than k is selected when a row vector in a 2 ^k × 2 ^{k element} matrix that is an integer k smaller than N is selected as an orthogonal code. That none of the already assigned row vectors in the 2 ^j × 2 ^{j element} matrix of the include the row vector you are trying to select or the inverted row vector as a subvector A variable rate transmission method characterized.   The transmission method according to any one of claims 1 to 3, wherein the transmission signal is further multiplied by a spreading code sequence for spreading a spectrum and transmitted at a transmission power corresponding to the rate. Variable rate transmission method. 5. The transmission method according to claim 4, further comprising periodically inserting known pilot symbols into data symbols corresponding to the information to be transmitted.
A variable rate transmission method, characterized in that the rate is changed in units of frames each comprising a plurality of slots defined by the pilot symbols.   6. The variable rate transmission method according to claim 5, wherein transmission power is controlled in units of the slots in accordance with a transmission power control command from the reception side.   7. The transmission method according to claim 6, wherein the inserted pilot symbols are transmitted at the same rate as the frame.   7. The transmission method according to claim 6, wherein the inserted pilot symbols are transmitted at a constant rate. A variable rate transmitter,
For one communication with one receiving side where the rate of information to be transmitted changes, a plurality of orthogonal codes of different lengths that are at least twice the maximum information rate before the communication starts An orthogonal code generation unit that generates one of the prepared orthogonal codes according to a rate of the information to be transmitted during the communication,
A product unit that multiplies the orthogonal code from the orthogonal code generation unit on the transmission signal including the information,
Each of the plurality of orthogonal codes corresponds to each possible value of the rate of the information to be transmitted. 10. The transmission apparatus according to claim 9, wherein the orthogonal code uses a matrix having a small dimension number based on a certain rule, and has a large degree (2 ^N × 2 ^N elements, N Is an integer ≧ 1) A variable rate characterized by sequentially generating a matrix and selecting from one of row vectors in a matrix having a different number of dimensions according to the magnitude of the transmission data transmission rate peak. Transmitter device. 11. The transmission apparatus according to claim 10, wherein in selecting the orthogonal code, an integer j greater than k is selected when a row vector in a 2 ^k × 2 ^{k element} matrix that is an integer k smaller than N is selected as an orthogonal code. That none of the already assigned row vectors in the 2 ^j × 2 ^{j element} matrix of the include the row vector you are trying to select or the inverted row vector as a subvector A variable-rate transmission device as a feature. The transmission device according to any one of claims 9 to 11,
A spreading sequence generator for generating a spreading code sequence for spreading the spectrum;
A product unit for multiplying a transmission signal by a spreading code sequence from the spreading sequence generation unit;
A variable rate transmission apparatus comprising: a transmission unit that changes transmission power according to a transmission rate. The transmission device according to claim 12, wherein
A pilot symbol generator for periodically generating known pilot symbols;
A variable rate transmitting apparatus characterized by being inserted into a data symbol corresponding to the information to be transmitted and changing the rate in units of frames in which a plurality of slots defined by the pilot symbols are configured.   14. The transmission apparatus according to claim 13, further comprising a transmission power control unit that controls transmission power in units of slots in accordance with a transmission power control command from the reception side.   The transmission apparatus according to claim 13, wherein the inserted pilot symbol is transmitted at the same rate as the frame.   The transmission apparatus according to claim 13, wherein the inserted pilot symbols are transmitted at a constant rate.

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