JP2006517749A - Space, time and frequency diversity in multi-carrier systems - Google Patents

Abstract

The present invention relates to a method for establishing transmission diversity using a plurality of antennas in a multicarrier communication system. The method according to the invention comprises a transmission step S10 for generating a plurality of transmission streams from one sequence of transmission symbols according to a predetermined transmission rule. In step S12, in each transmission stream, a plurality of carriers are assigned to both the frequency domain and the time domain for non-differential transmission diversity, or at least the frequency domain for differential transmission diversity. Assign multiple carriers. According to the present invention, a simple and highly applicable diversity method for transmitting and receiving data at a high transmission and reception rate while maintaining reliability is realized.

Description

  The present invention relates to transmission diversity and diversity technology in a communication system using a plurality of carriers, and more particularly, to differential space / time / frequency transmission / reception diversity and non-differential (non-differential). The present invention relates to space / time / frequency transmission / reception diversity technology.

  In a communication system using a plurality of carriers (carrier waves), a radio communication channel may be subjected to fading of a received signal due to interference caused by a plurality of communication paths. In order to reduce the influence of fading, it is possible in the prior art to adopt the transmission antenna diversity method. The basic idea of the method is that the same communication signal is transmitted through a plurality of transmission antennas, and a plurality of subchannels from each transmission antenna to the receiver are attenuated independently (in other words, all subchannels are subtracted). It is also to take advantage of the fact that the probability of simultaneous attenuation in the channel is also small.

  Here, all the transmission antennas are used at the same time in order to efficiently secure the frequency band. For this reason, preprocessing must be performed at the transmitter to ensure that multiple signals transmitted from different antennas are separated at the receiver. As is conventionally known, this can be realized by transmitting a plurality of orthogonal signals from a plurality of transmission antennas. Such an orthogonal transmission diversity method is known as a space-time block code based on an orthogonal design. However, the disadvantage of this method is that the channels need to be constant in at least one space-time block coded block.

  In addition, the channel must be flat in the frequency domain to prevent intersymbol interference. This can be realized by orthogonal frequency division multiple access (OFDM), which is a kind of multi-carrier system. In Orthogonal Frequency Division Multiple Access (OFDM), a wideband channel divided into multiple narrowbands, each using a different carrier frequency, is required to prevent intersymbol interference. A space-time block code is applied per subchannel, but the symbol length in each subcarrier is increased compared to a wideband system using a single carrier. For this reason, the condition regarding the constancy of the channel in the period in which one space-time block code is transmitted becomes more severe.

  The problem described above becomes even more important in the case of differential transmission diversity in a multi-carrier system. This is because, in the case of differential transmission diversity, information is included in the difference between two consecutive blocks, and channel uniformity is not limited to one block but required over two blocks. This is because that. However, since it is necessary to estimate a plurality of subchannels and the power of pilot symbols is distributed to a plurality of antennas, it is difficult to estimate channels in a communication system with multiple inputs and multiple outputs.

  More specifically, a transmission diversity method based on an orthogonal plan for two transmit antennas is referred to as “I simple Journal for assimilation on A sele- Issue on Signal processing for wireless Communications, 16 (8): 1451-1458, 1998 ”. In addition, the space-time block codes from the spatio-temporal block codes that generalize the number of transmitting antennas by V. Tarokh, H. Jafarkhani, and A. R. Calderbank. "Organic Designs" is published in "IEEE Transactions on Information Theory, 45 (5): 146-1467, June 1999".

  Furthermore, applying a space-time block code to orthogonal frequency division multiple access (OFDM) using a method of assigning one space-time block code for each subchannel, for example, Lou (B.Lu), One (X.Wang) ) And Lee (Y.Li) under the heading “Iterative receivers for space-time block-coded OFDM systems in dispersive fading channels” (IEEE2 Transactions1 mm2, A2) It is published in.

ジ（Ａ．Ｊ．Ｐａｕｌｒａｊ）によって提案されている空間・周波数符号化方法がある。これは、「Ｓｐａｃｅ−ｆｒｅｑｕｅｎｃｙ ｃｏｄｅｄ ｂｒｏａｄｂａｎｄ ＯＦＤＭ ｓｙｓｔｅｍｓ」という表題で、「Ｓｐａｃｅ−ｆｒｅｑｕｅｎｃｙ ｃｏｄｅｄ ｂｒｏａｄｂａｎｄ ＯＦＤＭ ｓｙｓｔｅｍｓ，ｉｎ Ｗｉｒｅｌｅｓｓ Ｃｏｍｍｕｎｉｃａｔｉｏｎｓ ａｎｄ Ｎｅｔｗｏｒｋｉｎｇ Ｃｏｎｆｅｒｅｎｃｅ（ＷＣＮＣ），ｐａｇｅｓ １−６，Ｓｅｐｔｅｍｂｅｒ ２０００」に掲載されている。この文献はまた、上掲のアラムーティの文献に開示されているように、隣接する複数のサブチャネルに亙って、空間・周波数符号として、直交計画に基づくシンボルを配置することを提案している。更に、最大周波数ダイバーシティを得るために、サブチャネルの数と等しい長さの符号語からなる空間・周波数符号を生成ずることも提案されている。

There are spatial and frequency encoding methods proposed by AJ Paulraj. This is the title “Space-frequency coded broadband OFDM systems”, and is described in “Space-frequency coded broadband OFDM systems, in Wireless Communications 6, and Network Management and Network”. This document also proposes to arrange symbols based on the orthogonal plan as spatial / frequency codes over a plurality of adjacent subchannels, as disclosed in the above-mentioned Aramuti document. . Furthermore, in order to obtain maximum frequency diversity, it has been proposed to generate a space / frequency code composed of codewords having a length equal to the number of subchannels.

  As a method for performing reception diversity in a multi-carrier system, “Space-time-frequency-coding for MIMO-OFDM systems” by Morish (M. Win) and Winters (J. Winters) In the title of “European Personal Mobile Communications Conference (EPMCC), Vienna, Australia, 2001”. This proposal includes realizing diversity using only one code by using a complex code without using an orthogonal structure.

  Another way to achieve transmit diversity is related to so-called differential transmit diversity based on orthogonal design. For the two transmit antennas, the title “A differential detection scheme for transmission diversity E” by T. V. Tarokh, H. Jafarkhani and A. R. Calderbank, “I differential detection scheme for transmission E”, on Selected Areas in Communications, 18 (7): 1169-1174, July 2000 ”. In addition, a method that generalizes this to multiple transmit antennas is described by J. Fafarani (H. Jafarkhani) and V. Tarokh in “Multitransition antenna differentials gen. on Information Theory, 47 (6): 2626-2631, September 2001 ”.

  Furthermore, the differential transmit diversity method is described by B. Hochwald and S. Sverden under the title “Differential unitary space-time modulation”, “IEEE Transactions on Communications: 204 (12:12)”. 2052, December 2000 ". In addition, there is a proposal in “IEEE Transactions on Information Theory, 46 (7): 2567-2578, November 200” by BL Hugues under the title “Differential space-time modulation”. However, compared to Talok and Jafarcani's “A differential scheme for transmission diversity; IEEE Journal on Selected Areas in Communications, 18 (7): 1169-1174, July 2000, these proposals are orthogonal. Not dependent on.

  Furthermore, “IEEE Communications Letters, 6 (6): 253-255, June 2002” includes D. Gigavi, N. Al-Dhahir, N. Al-Dhahir, A. Stamulis and Cal. In the title of "Different space-time coding for frequency-selective channels" by A. R. Calderbank, a differential space-time diversity method in a pure sense is described. This method uses orthogonal frequency division multiple access to decompose one frequency selective wideband channel into a plurality of flat attenuated narrowband channels, each having a different carrier frequency, one differential space-time per carrier. The block code is applied.

  As described above, in the multi-carrier communication system, some special time / frequency diversity methods can be applied, but these methods are complicated and have low versatility. A simple method for pure space / time diversity or pure space / frequency diversity may be applied, but this method requires that the communication channel be constant for many subcarriers over a long period of time. Is done.

  However, broadband communication channels are generally frequency selective and change over time. This becomes an important problem as the transmission symbol length in each subcarrier increases in the case of using a large number of subcarriers as proposed as a future communication system.

  In view of the above-described background, an object of the present invention is to provide a transmission / reception diversity method that is simple, highly applicable, and capable of performing high data date communication with high reliability.

  According to a first aspect of the present invention, the object of the present invention is achieved by a method for establishing space, time and frequency transmission diversity using a plurality of antennas in a multicarrier communication system. The method of the present invention includes a first step of converting a transmission symbol sequence into a plurality of transmission streams according to a predetermined variable observation and supplying the plurality of transmission streams to each of the plurality of antennas. The method of the present invention further includes, in each transmission stream, a second element that assigns elements constituting the transmission stream (transmission stream elements) to a plurality of carriers that can be used by each transmission antenna, in both frequency domain and time domain. Has steps.

  That is, the first aspect of the present invention relates to transmission diversity, and transmission symbols are distributed over consecutive transmission time slots in a plurality of subcarriers. Spatial diversity is achieved by using multiple antennas, time diversity is achieved by distributing multiple transmit stream elements across different time slots, and frequency diversity is achieved by using multiple subcarriers. The

  The advantageous effects of the present invention can relax the conditions imposed on a communication channel that is constant in the time and frequency domains. In other words, according to the method of the present invention, the condition relating to the uniformity imposed on the channel coefficient in the time domain and the frequency domain is relaxed as compared with the conventional method.

  Another advantage of the present invention is that spatial diversity can be separated from time diversity and frequency diversity. This is the basis for a very simple and effective transmit diversity method that utilizes space diversity, time diversity, and frequency diversity.

  Yet another advantage of the present invention is that delay and overall overhead are reduced as compared to conventional space-time transmit diversity methods. Since no restrictions are imposed on the method of distributing the transmission stream element in the time domain and the frequency domain, the applicability is increased, and a suitable mapping method is appropriately used regardless of the presence or absence of existing fading conditions. It is also possible to change the mapping method over time.

  According to the second aspect of the present invention, the above-mentioned object is realized by using a method for establishing differential space / time / frequency transmission diversity in a multi-carrier communication system using a plurality of transmission antennas. . In the first step, the transmission bit sequence is converted into a plurality of transmission streams according to a predetermined differential type conversion side, and supplied to the plurality of antennas. Subsequently, the transmission stream elements in each transmission stream are allocated to a plurality of carriers that can be used in each antenna with respect to frequency and time domain.

  According to the 2nd viewpoint of this invention, in addition to the advantageous effect which the invention made | formed by the 1st viewpoint show | plays, it has the effect that the differential transmission diversity method can be provided. In addition to the above-described non-differential transmission type diversity method, the diversity according to the present invention is realized as a special differential type space / frequency diversity without mapping transmission stream elements to a plurality of time slots. However, in a preferred embodiment of the differential type space / frequency diversity according to the present invention, the mapping may be performed.

  The invention according to the second aspect further has an effect that the overhead generated when a reference matrix is transmitted according to a plurality of existing differential diversity methods is significantly reduced.

  In a preferred aspect of the non-differential transmission diversity method, the predetermined conversion rule is an orthogonal design. In another preferred aspect, the predetermined conversion rule is a differential orthogonal plan.

  In a preferred embodiment of the present invention, spatial diversity is realized by direct planning and a simple synthesis step at the receiving side, while processing related to time diversity and frequency diversity is performed by using an external error correction code, for example. Can be performed on the receiving side. By performing diversity separation in this way, it is possible to simplify the system and improve versatility.

  Therefore, when system parameters (eg, number of subcarriers, modulation schemes, number of transmit antennas, etc.) change, it is necessary to modify correspondingly with multiplexed components and / or orthogonal design or differential type. Only orthogonal design.

  This point is particularly important in a highly adaptable system such as a wireless mobile communication system that is expected to appear in the future. However, the method according to the existing proposal is very complicated. An important feature of the present invention is that the conditions for channel consistency in time and frequency are significantly relaxed compared to using space-time block codes or space-frequency block codes.

  Furthermore, in the above-described differential diversity method, a method of distributing different transmission stream elements to at least one of a plurality of subcarriers and one or more time slots in each subcarrier is arbitrary. However, the only rule is that it is prohibited to assign two different transmission stream elements to the same time slot of the same subcarrier.

  In particular, in a further preferred aspect of the invention relating to the differential diversity method, the transmission stream elements are mapped continuously to subcarriers and corresponding time slots with respect to continuously consecutive orthogonal schemes. Then, mapping processing for assigning the transmission stream element to a plurality of carriers and a plurality of time slots is performed. This continuous mapping method can be applied to any transmission method using a subchannel having a two-dimensional (eg, time and frequency) correlation.

  In a third aspect, the present invention relates to a method for realizing space / time / frequency diversity reception in a multicarrier communication system.

  In a first step, a plurality of transmission streams and corresponding transmission stream elements are received at each of a plurality of antennas of a receiver. It is assumed that the transmission stream element is allocated to a plurality of carriers in the frequency domain and the time domain in order to realize space / time / frequency transmission diversity in the transmitter by the method described above. In the second step, the transmitted stream elements are demapped to output symbols in the frequency domain and the time domain. This corresponds to the reverse of the mapping performed on the transmission side. In the third step, the output symbol transmission stream is output for subsequent processing.

  A fourth aspect of the present invention relates to a method for realizing differential space / time / frequency diversity reception in a multicarrier communication system using a plurality of antennas.

  In the first step, a plurality of transmission streams and corresponding transmission stream elements are received at each of the plurality of antennas. As in the case of non-differential diversity reception, in differential diversity reception, a plurality of transmission stream elements are provided on the transmitter side at least in the frequency domain in order to realize differential spatial / frequency transmission diversity. Is assigned to a certain carrier. In the second step, a process reverse to the allocation process performed on the transmitter side, that is, a process of demapping the transmission stream element to the output symbol stream at least in the frequency domain is performed. Subsequently, in a third step, the output symbol stream is output for later processing of the receiver.

  As described above, it is obvious that the space / time / frequency diversity according to the present invention is realized not only on the transmitter side but also on the receiver side. Regardless of whether it is a non-differential type or a differential type, the same effect as that described for transmission diversity occurs on the receiver side. That is, the system design for diversity reception can be simplified and the versatility can be improved.

  In a further preferred aspect related to non-differential or differential diversity reception, the generated output symbols may be supplied to a combiner in order to estimate the transmitted symbols in a subsequent turbo detection step. Good.

  In particular, turbo feedback from a forward error correction (FEC) decoder to a space-time block code detector may be used to improve system capability and diversity level. Previously, turbo feedback from a forward error correction (FEC) decoder to a space-time block code detector could not be effective due to the orthogonality of the space-time block code. However, according to the present invention, bit-wise feedback and spatial mapping of corresponding modulation symbol bits may be performed.

  Further, information generated in turbo detection, not information on the channel estimator, which is empirically given to the soft decision space / time / frequency transmission diversity detector may be used. Forces bits to be spatially mapped to symbols in an anti-Gray modulation scheme. At this time, the constellation point of the modulation system having the minimum Euclidean distance differs in the most bits.

  The present invention is based on the gray mapping (the constellation point of the modulation scheme having the minimum Euclidean distance is different from the constellation point on the order of several bits) due to the orthogonal structure of the spatial transmission diversity method. This is based on the knowledge that even if the turbo repetition is performed, the constellation point of the modulation scheme having the minimum Euclidean distance is different from only one bit, so that it is not effective.

  The present invention is not limited to the transmission diversity scheme and the reception diversity scheme described above, and can be applied to all multicarrier systems such as OFDM and multicarrier CDMA.

  The present invention, in yet another preferred aspect, is a computer program that can be read directly from the internal memory of a transmitter / receiver, and when executed by a processor of the transmitter / receiver, the non-difference. Provided is a program composed of codes for executing dynamic diversity processing or differential diversity processing.

  That is, according to the present invention, each step of the method according to the present invention can be implemented on a computer or a processor system. As a result, for example, a computer system included in a multi-carrier communication system, or specifically a computer program used with a processor is provided.

  This program gives the functions of the present invention to computers and processors in various forms. For example, information permanently stored in a non-writable storage medium (read-only memory device such as ROM or CD-ROM, which can be read by a processor or an I / O device of a computer), writable memory Information stored in a medium (floppy disk, hard disk, or the like), or information provided to a computer or processor via a communication medium such as a communication network, the Internet, or a telephone network using a communication medium modem or other interface. Such a medium alternatively executes any aspect of the present invention when a processor readable instruction implementing the method according to the present invention is executed.

  Hereinafter, the best method for carrying out various aspects of the present invention, together with preferred embodiments thereof, will be described with reference to the drawings.

  In describing various aspects of the present invention, first, as a technical background of the present invention, a basic principle relating to a space-time block code will be described.

  FIG. 1 is a diagram for explaining a transmission antenna diversity method when a space-time block code is used for two transmission antennas.

As shown in FIG. 1, the information source generates a bit stream having the number u of bits, and supplies the bit stream to the modulation unit 12 (for example, that of 8-phase phase shift keying (8-PSK)). The modulation unit 12 maps the input bits to different transmission cycles. In the example illustrated in FIG. 1, the input bit “010” is mapped to the symbol C ₁ = 2 and the input bit “111” is mapped to the transmission symbol C ₂ = 7. The generated symbols are supplied to the space-time block coding unit 14 as transmission symbols x ₁ and x ₂ , respectively. The space-time block code unit 14 performs processing according to a generalized complex orthogonal design, that is, a matrix having x ₁ , x ₂ , −x ₂ ^* , and x ₁ ^* as elements.

In general, such an orthogonal plan is characterized by the following matrix:

Here, the number of columns n _T corresponds to the number of transmission antennas, and the number of rows P corresponds to the number of time slots.

  Thus, although the matrix B is referred to as an orthogonal plan, the synchronous reference may be used as a conversion plan. This is because, as shown in FIG. 1, the plurality of transmission symbol streams are mapped to the plurality of transmission streams supplied to the corresponding transmission antennas 16 and 18, respectively.

The component b _ij of the orthogonal design B is an element x _i of the N-value signal constellation, a complex conjugate x _i ^* , or a linear combination thereof. K symbols x _t , (t = 1,... K) are inputs to the space-time block encoder represented as the transform unit 14. The space-time block codec maps K symbols to N _T · P orthogonal plans B components b _ij according to the space-time block code mapping rule. Next, all components b _ij in the same row in the orthogonal plan B are transmitted simultaneously by _NT antennas (for example, antennas 16 and 18 in the example shown in FIG. 1).

  Further, as described above, the components in the same column of the orthogonal plan B are transmitted from the same antenna 16 or 18 using successive time slots so that the columns of the orthogonal plan represent space and the rows represent time. To do.

In the example shown in FIG. 1, the direct plan is as follows.

In the example shown in FIG. 1, one block is obtained from two 8-PSK transmission symbols. According to the 8-PSK modulation scheme, three source bits are mapped to complex constellation points x _i . The symbol c ₁ = 2 is mapped to x ₁ = j, and the symbol c ₂ = 7 is mapped to x ₁ = 1/2 ^ (1/2) −j / 2 ^ (1/2). Complex transmission symbols x ₁ and x ₂ are represented as a matrix of given orthogonal designs p * n _T = 2 * 2.

In the first time slot, the transmission symbols in the first row of the orthogonal plan are transmitted simultaneously. That is, x ₁ ⁽¹⁾ = x ₁ is transmitted from the antenna 1, and x ₂ ⁽²⁾ = x ₂ is transmitted from the antenna 2. In the next time slot, the symbol x ₂ ⁽¹⁾ = − x ₂ ^* is transmitted from the antenna 1, and x ₂ ⁽²⁾ = − x ₁ ^* is transmitted from the antenna 2.

  Due to the orthogonality of the orthogonal scheme, it is possible to perform reception diversity by a simple combination on the receiver side by similarly referring to the space-time block code or the conversion rule for the transmission symbol stream. Hereinafter, this point will be described in detail. During transmission, the channel must be constant for a period corresponding to its number of time slots, in other words, the number of rows of the space-time block code matrix (ie symbol length P = 2).

  FIG. 2 shows another example of the own space block code. The example on the left shows a case where the number of antennas is 4 and the number of time slots (assuming the transmission channel is constant) is 4. The example on the right shows a case where the number of transmission antennas is 3 and the number of time slots (transmission channel is constant) is 4.

Without being limited to the example described with reference to FIGS. 1 and 2, in the present invention, a transmission symbol is a constellation of a modulation scheme (for example, quadrature amplitude shift keying; QAM or shift keying modulation scheme; PSK, etc.). It is assumed that According to the present invention, there is no limitation on the mode of the modulation scheme. For n _T transmit antennas, the symbol x _k is mapped to n _T transmit streams according to a P * n _T- dimensional orthogonal plan (transmission rule).

In addition, it is assumed that data is simultaneously transmitted from each antenna by _NT subcarriers, and transmission is performed in a multicarrier communication system in which each subcarrier corresponds to one of a plurality of carrier frequencies. Here, the channel coefficient changes in the time domain and the frequency domain. However, the channel coefficients of consecutive time slots are associated with adjacent subcarriers.

  On the receiver side, since the channel coefficient during transmission based on the orthogonal plan is required to be constant, in the present invention, one element of the orthogonal plan is preferably allocated. Details of the allocation method will be described later. On the receiver side, the received transmission symbol is demapped by performing a process reverse to the assignment process performed on the transmitter side. Details of this will be described later.

  In describing the details of the above processing, first, as a technical background of the present invention, a channel model related to a multiple-input multiple-output (MIMO) communication channel will be described with reference to FIG.

As shown in FIG. 3, it is assumed that the multicarrier communication system has n _T transmit antennas and n _R receive antennas. In each antenna, a transmission symbol is transmitted using a plurality of subcarriers (ie, the channel is divided into n _S orthogonal subcarriers).

  Hereinafter, each transmission symbol transmitted from each subcarrier at a certain time is referred to as a transmission symbol or an orthogonal frequency division multiplexing (OFDM) symbol.

As shown in FIG. 3, the transmission branches 1, in each of the · · · _{n T,} the serial / parallel conversion unit 20-1, ···, _{20-n T} is provided, the orthogonal design element set multiple of Map to subcarrier. Then, the inverse fast Fourier transform unit 22-1, the ... _{22-n t,} the serial / parallel conversion unit 20-1, ..., an inverse Fourier transform on the output values from the _{20-n T} performed. Inverse fast Fourier transform unit 22-1, ··· _{22-n t,} the corresponding conversion result parallel-serial / conversion unit 24-1, before outputting the ··· _{24-n T,} the relevant sub-carrier To separate. Next, the antenna 1, in · · · n, the corresponding guard interval section 26-1, inserts a guard interval by ··· _{26-n T.}

As shown in FIG. 3, on the receiver side, the guard interval removal unit 28-1,..., 28-n _R removes the guard interval, which is the reverse process of the transmission side. Next, serial / parallel conversion is performed by the corresponding serial / parallel converters 30-1,..., 30-n _r to generate reception elements for each subcarrier, and the inverse high-speed performed on the transmitter side. In order to perform processing opposite to the Fourier transform, the corresponding fast Fourier transform units 21-1,. . . Supply to 32-n _R. The result of the fast Fourier transform at each receiving antenna is supplied to the corresponding parallel / serial converters 34-1,..., 34-n _R , and the output reception stream generated there is processed (ie, output bit stream). Generate).

  As shown in FIG. 3, a transfer function from each transmitting antenna to each receiving antenna may be introduced for each subcarrier propagating between the transmitter and the receiver. By introducing a transfer function, it is possible to design a multiple-input multiple-output (MIMO) channel with flat fading characteristics for use in a multi-carrier communication system.

In particular, if adding a cyclic prefix as the guard interval, it is possible to decompose parallel frequency-selective high-bandwidth channels N _s number of frequency flat MIMO channel. This is shown in the lower diagram of FIG. Here, a block of N _s * n _T symbols is transmitted from each of the n _T transmit antennas by N _s subcarriers. Hereinafter, this symbol is referred to as an OFDM symbol.

The symbol length of each subchannel is _NS times larger than in the case of a single carrier system having the same bandwidth. As will be described later, the present invention is not limited to the multiple-input multiple-output channel having the uniform frequency described above, but applied to the frequency-selective MIMO channel that is decomposed into a set of channels having uniform fading. Is possible.

  In view of the technical background of the present invention described with reference to FIGS. 1 to 3, various aspects according to the present invention will be described with reference to FIGS.

  According to the present invention, the differential transmission diversity is a method of transmitting a plurality of symbols generated according to a transmission rule (for example, orthogonal plan) to a plurality of subcarriers in each antenna based on a conversion rule based on a transformation rule. Allocate over multiple consecutive time slots to achieve diversity.

  Note that the present invention is not limited to an orthogonal plan, and any conversion method that uses a transmission symbol stream that generates a plurality of transmission streams supplied by a plurality of transmission antennas as a starting point can be applied. Is possible.

  In the present invention, any kind of allocation method for both the time domain and the frequency domain may be used. Furthermore, the same allocation method is used for all transmission antennas in order to maintain compatibility with the existing reception method used on the receiver side. All transmitting antennas on the transmitter side transmit at the same time.

  FIG. 4 is a diagram showing a configuration of an apparatus for realizing differential transmission diversity according to the present invention.

  The device 36 includes an allocation unit 38 and a transmission unit 40. The value input to the allocating unit 40 is determined by converting a transmission symbol into a plurality of transmission streams using the predetermined conversion rule described above.

  FIG. 5 is a diagram illustrating a configuration of the allocation unit 40 illustrated in FIG.

  The allocation unit 40 includes a selection unit 42 that selects one subcarrier and one time slot of a transmission element before transmission, and a mapping unit 44 that allocates each transmission element determined by the selection unit 42.

  FIG. 6 is a flowchart showing the operation of the transmission apparatus shown in FIG.

  As shown in FIG. 6, in step S10, a plurality of transmission symbols are converted into a plurality of transmission streams. In step s12, a plurality of transmission stream elements in each antenna are allocated to a plurality of subcarriers usable in each antenna in the time domain and the frequency domain. In other words, for each element in each transmission stream, the selection unit 42 selects a subcarrier related to the stream element and a corresponding time slot in the subcarrier. Subsequently, the transmission stream element is mapped by the mapping unit 44.

Moreover, transmission unit 40 shown in FIG. 4, after the mapping process, and transmits a plurality of transmission streams element, a plurality of transmit antennas 1, ..., a n _T.

  FIG. 7 shows a configuration of an apparatus for realizing non-differential transmission diversity according to the present invention. In the figure, the same components as those described with reference to FIGS. 4 to 6 are denoted by the same reference numerals.

  FIG. 7 is a diagram regarding application of non-differential transmission diversity using orthogonal design and space, time, and frequency.

As shown in FIG. 7, when a plurality of transmission symbol streams are converted into a plurality of transmission streams 1,..., _NT , an orthogonal plan B is used. The transmission symbol to be converted is generated using existing means (ie, forward error correction (FEC) encoder 46, interleaver 48, and modulation unit 50). The transmission symbol generation method is not restricted by various aspects of the present invention.

As shown in FIG. 7, the transmission unit 38, the transmitting antenna 1, and generates a plurality of transmission streams supplied to each of the · · · n _T. Prior to transmission, each transmit stream element is assigned to one subcarrier and one available time slot on that subcarrier. This assignment process is executed before the inverse fast Fourier transform, parallel / serial conversion, and insertion of the guard interval.

  As described above, various aspects for realizing the non-differential transmission diversity described above with reference to FIGS. 4 to 7 have been described. Hereinafter, aspects for realizing non-differential diversity reception on the receiver side will be described. This will be described with reference to FIGS.

  FIG. 8 shows a configuration of an apparatus for realizing non-differential diversity reception according to the present invention.

As shown in FIG. 8, it is assumed receiver, receive antenna n, and having a · · · n _R. Signals received by the receiving antennas n,... N _R are supplied to the corresponding receiving units 46-1,... 46-n _R , where a plurality of received symbol streams are generated. Each received symbol stream includes a receiving antenna n, associated with subcarriers corresponding to each of the · · · n _R. Each receiving unit 46-1, the ... _{46-n R,} the corresponding output stream corresponding demapping unit 48-1, ..., is supplied to the _{48-n R.} The demapping units 48-1,..., 48-n _R perform demapping, which is the reverse process of assigning transmission stream elements to the reception stream elements of each subcarrier on the transmitter side. Do. Subsequently, the received stream element subjected to the corresponding demapping process is supplied to the processing unit 50, and an output symbol stream is generated.

  FIG. 9 is a flowchart illustrating an operation for realizing non-differential diversity reception according to the present invention.

As shown in FIG. 9, each receiving unit 46-1 to 46-n _R generates a reception transmission stream for each subcarrier. That is, each receiving unit 46-1,... 46-n _R performs guard interval removal, serial / parallel conversion, and fast Fourier transform.

Also, as shown in FIG. 9, each demapping unit 48-1,... 48-n _R corresponds to a plurality of subcarriers and corresponding to the transmission stream element in both the frequency domain and the time domain. Demapping is performed, which corresponds to the process opposite to the process of assigning to a plurality of time slots. That is, each demapping section 48-1,... 48-n _R demaps the transmission stream element to the output symbol stream in both the frequency domain and the time domain. This corresponds to a process opposite to the allocation process performed on each antenna in the transmitter. Subsequently, in step S20, the post-processing unit 50 processes the demapped reception stream (for example, performs processing for generating a maximum likelihood estimate of the output bits).

  FIG. 10 shows a preferred embodiment of the post-processing unit 50 according to the present invention.

As shown in FIG. 10, the post-processing unit 50 includes a combiner 52, an empirical probability demapping unit 54 that performs a soft decision related to the sign bit _ck , and a deinterleaver that performs deinterleaving on the soft output. 56 and a forward error correction (FEC) decoder 58. The post-processing unit 50 further includes a first combining unit 60, an interleaver 62, and a second combining unit 64. Alternatively, the post-processing unit 50 may be configured only from the coupler 52.

  The empirical probability demapping unit 54 shown in FIG. 10 calculates the log-likelihood ratio of code bits based on the output from the combiner of the receiver. The deinterleaver 56 performs deinterleaving on the log likelihood ratio of the sign bit for decoding in the FEC decoder 58 at the subsequent stage.

この外部対数尤度情報は、インターリーバ６２に出力される。第２の合成部６４にて、インターリーバ６２からの出力は、経験的確率デマッピング部５４によって得られた対数尤度比から減算される。The FEC decoder 58 decodes the source bits. The FEC decoder 58 further converts the sign bit

The external log likelihood information is output to the interleaver 62. In the second synthesis unit 64, the output from the interleaver 62 is subtracted from the log likelihood ratio obtained by the empirical probability demapping unit 54.

ット５４へ供給される。

Supplied to the base 54.

  In the present invention, a feedback mechanism is used as a priori information not for a channel estimator but for a space / time / frequency transmission diversity detector based on a soft output. Also, constellation is performed using an external FEC code and optional turbo feedback from the FEC decoder 58 to the soft output diversity combiner.

  Therefore, regarding turbo feedback, feedback may be performed in bit units. Also, a special non-gray mapping of code bits may be used for constellation symbols of higher order modulation schemes.

  In other words, the constellation symbol mapping differs from the gray mapping in that the constellation symbol with the minimum Euclidean distance has the largest number of different bits. According to this non-gray mapping, it is possible to improve an existing space-time turbo coding method in which an improvement in detection accuracy is not expected even by turbo repetition due to orthogonality of transmission diversity.

  Various aspects of the present invention for non-differential transmit diversity and diversity reception as described above have been described with reference to FIGS. 4-10. In the following, the transmit stream elements in each transmit stream are represented in the frequency domain and time domain. The method of assigning to a plurality of carriers will be described in detail.

  As already outlined, when assigning multiple transmit stream elements to mapping to multiple carriers in the frequency and time domains, unless different transmit stream elements are assigned to the same time slot on the same subcarrier. Any method may be used.

  Those skilled in the art can easily understand that the present invention can be applied to any expression format of such an allocation method. For convenience of explanation, one of the expression formats of a method of assigning a transmission stream element to a plurality of carriers in the frequency domain and the time domain will be described.

  Here, it is assumed that a transmission symbol is expressed as a set of N transmission stream elements as follows.

Considering that the number of subcarriers is N _S, by expressed as a set of carrier indexes below, the step of selecting a carrier and a time slot is realized.

Number 4

C = {α ₁ ,. . . , Α _N }, α _i ∈1,. . . , N _s

Here, α _i represents the carrier selected for the i th transmission stream element. Time slot selection is expressed by introducing the following set of time slot indices.

Number 5

S = {β ₁ ,. . . , Β _N }, β _i ∈1,. . . , T

Here, T is the number of time slots available on each subcarrier, and β _i is the time slot selected for the i th transmission stream element.

ができる。It should be noted that such a set notation method is used for convenience of explanation, and in the present invention, any other carrier and time slot selection method for the set of transmission stream elements is used. It goes without saying that a data structure representation format may be used. An example is a method using a selected subcarrier and a linked list such as a time slot or table expression. In the case of employing the set notation described above, a method for assigning a plurality of transmission stream elements to a plurality of selected carriers in the frequency domain and time domain in the subcarrier is as follows.

Can do.

行ベクトルとして、以下の式で表される。

The row vector is expressed by the following formula.

アドとの積は、以下の式で表される。

The product with the add is expressed by the following equation.

  The conditions for prohibiting the assignment of two transmission stream elements to the same subcarrier and the same time slot by generating a dyad representing the assignment of the transmission stream element using this vector notation are different as follows: It can be expressed that the difference between two transmission stream elements is not a zero matrix.

  As shown in the following equation, the final allocation result can be obtained by superimposing all the dyads representing the allocation of the transmission stream elements to the subcarriers and the corresponding timestott.

  Using the above notation, the function realized on the receiver side can be expressed by a method different from the method using the same expression.

Ability to de-mapping the output symbol transmission stream elements from the sub-channel and the corresponding time slots, the T transmit streams elements in each of the N _S carrier and placed in a diversity reception matrix D _R at each antenna, i The carrier of the th transmission stream element t _i

信ストリームエレメントｔ_ｉのタイムスロットを、行ベクトルとして、次式で表す。

The time slot signal stream elements t _i, a row vector, expressed by the following equation.

  Using the above-described notation, non-differential transmission diversity and diversity reception will be described with reference to FIGS.

  FIG. 11 shows an example of non-differential transmission diversity according to the present invention.

  As shown in FIG. 11, in this example, non-differential transmission diversity is shown when two antennas and two subcarriers used in each antenna are used. For the transmission rule, an orthogonal design according to the matrix B is adopted.

  As shown in FIG. 11, regarding the space / time / frequency diversity allocation to the transmission stream elements, particularly, consider the following two orthogonal plans.

Also, as shown in FIG. 11, in each of n _T = 2 antennas, n _S = 2 subcarriers can be used for frequency diversity, and T = 2 time slots can be used for time diversity. It is. Consider assignment in the frequency domain and time domain over multiple carriers and multiple time slots for n = 4 transmit stream elements. The assignment shown in FIG. 11 can be expressed using the above-described carrier vector and slot vector expressed by the following equations.

  When these carrier vectors and slot vectors are applied to a set of transmission stream elements, the result is as follows.

  The result of the final diversity transmission at the first antenna is as follows.

  When the same carrier set and slot vector set are applied to the transmission stream element, the result is as follows.

  The final diversity result at the second transmit antenna is as follows.

The generated transmission diversity is assumed to be used for transmission of the corresponding transmission stream element. Hereinafter, according to the non-differential transmission diversity example shown in FIG. 11, an example of non-differential diversity reception according to the present invention will be described. Will be explained. 12 represents a plurality of receiving antennas 1,... N _R and the functions already described with reference to FIGS. Most commonly, it can be assumed that the transmit stream elements are received at the first receive antenna in the order shown below.

  The transposed vector of the carrier vector and the slot vector given on the transmission side is applied as follows.

Then, the following results are obtained for the first receiving antenna.

  The second receiving antenna is as follows.

FIG. 13 shows an example of non-differential transmission diversity according to the present invention when the number of transmission antennas n _T = 3 and the number of subcarriers N _S = 4 in each antenna. In addition, the number T of time diversity time slots in each subcarrier is 2, and N = 8 transmission stream elements are supplied to each antenna and mapped to a plurality of subcarriers and a corresponding plurality of time slots. As shown in FIG. 13, transmission stream elements are arranged based on two orthogonal plans represented by the following equations, and a plurality of corresponding transmission stream elements are distributed to a plurality of subchannels and a plurality of time slots. Think.

  In the example shown in FIG. 13, a set of carrier vectors and a set of slot vectors are as follows.

  In the first antenna, these subcarriers and time slots are applied to the transmission stream elements as shown in the following equation.

  Then, the following transmission diversity is obtained.

  Similarly, the same assignment applies to the set of transmit stream elements.

  Then, the following transmission diversity is obtained in the second antenna.

  Similarly, the same carrier vector set and the same slot vector set are applied. In other words, the transmission stream element is also assigned to the transmission stream element supplied to the third antenna.

  Then, the following diversity results are obtained.

  Similar to the examples shown in FIGS. 11 and 12, in the example shown in FIG. 13, appropriate demapping is executed on the receiver side to realize the corresponding non-differential reception diversity shown in FIG. Can do.

  In particular, FIG. 14 shows the reverse processing of transmit diversity, in which the received stream elements are rearranged in an appropriate order and supplied to subsequent processing.

  Thus, according to the above-described non-differential space / time / frequency block diversity method for the transmitter side and the receiver side, the own space block code (that is, fast fading of the communication channel) and the space / frequency block are provided. Various problems related to codes (ie frequency selectivity) can be solved. Specifically, transmit stream elements (e.g., obtained from orthogonal designs in both the frequency and time domains) are distributed in order to relax the conditions regarding channel coefficient constancy in both domains.

  Such a method of performing non-differential transmission diversity is particularly effective when the number of transmission antennas is increased and the channel coefficient is required to be constant for more transmission stream elements.

  Further, there are many means for distributing a plurality of transmission stream elements at each antenna in the time domain and the frequency domain. For example, asymmetrical assignment can be applied in which multiple transmission stream elements obtained in one conversion step are assigned in different ways.

  In addition, a method of assigning a plurality of transmission stream elements to a plurality of subcarriers and a plurality of time slots may be changed according to time. In other words, a vector related to different transmission stream elements obtained from the transmission stream symbols according to a predetermined transmission rule is changed with time.

  The non-differential type space / time / frequency transmission diversity and the corresponding diversity reception have been described above with reference to FIGS. 2 to 14. In the following, the differential type transmission diversity according to various aspects of the present invention will be described. The diversity reception will be described with reference to FIGS.

  The principle of differential transmission antenna coding based on the orthogonal design will be described with reference to FIG. Regarding the principle of differential transmission diversity, V. Tarokh and H. Jafarkhani under the title “A differential detection scheme for transnational diversity,” “IEEE Journal of the United States”. 18 (7): 1169-1174, July 2000, which is incorporated herein by reference. In addition, a generalized approach to differential transmit diversity for one or more transmit antennas is described by H. Jafarkhani and V. Tarokh in "Multiple Transient Antenna Differential from Generalized Titles". And disclosed in “IEEE Transactions on Information Theory, 47 (6): 2626-2631, September 2001”, which are incorporated herein by reference.

As shown in FIG. 15, in the differential transmit diversity performs the mapping of the transmitted bits u _k using the same orthogonal design and, for example, those described above. This mapping is a mapping to complex constellation points A _k and B _k . The vector (x _{2t + 2} , x _{2t + 1} ) is transmitted in one time slot and has a unit length as shown below.

Number 32

| X _{2t + 2} | ² + | x _{2t + 1} | ² = 1

  This condition is introduced to perform differential detection. The mapping of bits to constellation points begins with the following constellation points in an M-ary shift-shift keying (PSK) constellation:

  The following applies:

Number 34

A _k = d _{2t + 1} d (0) ^* + d _{2t + 2} d (0) ^*
B _k = −d _{2t + 1} d (0) + d _{2t + 2} d (0)

The reference symbol d (0) can be randomly selected from the M-value PSK constellation. Since log ₂ (M) bits are mapped to each of PSK symbols d _{2t + 1} and d _{2t + 1} according to an arbitrary mapping method (eg, Gray mapping), constellation points A _k and B _k are 2 · log ₂ Determined by (M) bits. An important property of this mapping is that the vectors A _k and B _k have unit lengths as represented by the following equation.

Number 35

| A _k | ² + | B _k | ¹ = 1

  As in the case of differential modulation, first, the following reference space-time block code matrix is transmitted.

The space-time block code matrix, includes a M-PSK con any symbol x ₁ and x _2, which is extracted from the constellation, for encoding the first bit, past code matrix (i.e. reference numeral matrix) You can refer to. The symbol is calculated according to the following formula.

  Therefore, the orthogonal plan is transmitted over the communication channel, which makes it possible to separate transmission symbols transmitted simultaneously from a plurality of antennas by a simple combination on the receiver side.

  In view of the general framework related to differential transmission diversity described above, FIG. 16 shows a flowchart showing an operation for realizing the differential transmission diversity according to the present invention.

This operation is performed in each of the allocation units 50-1,... 50-n _T described with reference to FIGS. In other words, the overall configuration of the transmission diversity apparatus is the same as that of the non-differential transmission diversity apparatus, but the operation is different in the differential transmission diversity.

  As shown in FIG. 16, in the first step S22, a plurality of transmission streams are generated by conversion processing. The set of input transmission bits is converted into a plurality of transmission streams, for example, according to the predetermined differential transmission rule described above.

  In step S24, a plurality of transmission stream elements generated in each antenna are allocated to a plurality of subcarriers usable in each antenna at least in the frequency domain. Subsequently, in step S26, a process of allocating a plurality of transmission stream elements to a plurality of time slots usable in each subcarrier in the time domain may be performed.

  According to the differential transmission diversity framework of the present invention, allocation is performed only in the frequency domain. In this method, reference is made to differential space / frequency transmission diversity described later. Therefore, unlike the case of non-differential transmission diversity, the present invention can also be applied to the case of allocation of only the frequency domain of transmission stream elements for differential transmission diversity.

  In addition, the present invention can also be applied to a case where transmission stream elements generated from differential transmission rules are assigned to a plurality of time slots of a plurality of subcarriers. Hereinafter, this mode is referred to as a differential space / time frequency block code.

  Hereinafter, a first example of differential space / time / diversity will be described with reference to FIG.

  Normally, in the differential space-time block code, it is assumed that the channel coefficient is constant during the transmission of two space-time block code matrices. However, if the symbol length of the transmission symbol is relatively large, the channel coefficient may not be constant during the transmission of the two space-time block code matrices.

  In order to avoid the problem that the channel changes drastically in time, different transmission symbols are assigned to the same time slot of multiple subcarriers. In other words, it is assigned to the same OFDM symbol, not the same subcarrier in the OFDM symbol sequence. In the example shown in FIG. 17, it can be seen that the transmission delay can be reduced.

  However, the communication channel needs to be approximately constant over four adjacent subcarriers. This is true when the frequency selectivity of the communication channel is low and can be realized by using a large number of subcarriers to make the subcarrier space very small.

Referring to the example shown in FIG. 17, after performing mapping according to the differential space / frequency block code in the n _T streams corresponding to the transmission antennas, simple serial / parallel conversion is performed at each transmission antenna. Thus, differential space / frequency transmission diversity can be realized. As a result, diversity reception is realized on the receiver side by performing parallel / serial demapping.

As described above, for differential type space / frequency block codes, a reference matrix can be transmitted in each OFDM symbol, but the data rate is reduced. However, as shown in FIG. 17, the sub-carrier 1 of the first _{N s} number of transmission streams element first OFDM symbol, · · · _N assigned to _S, the next _{N s} number of transmission streams element second This problem can be avoided by performing differential coding over several OFDMs, such as being assigned to a carrier N _S ,.

  In addition, as an expression method for assigning transmission stream elements to a plurality of subcarriers for differential space / time transmission diversity, the expression methods for non-differential transmission diversity and reception diversity described above can be used.

  That is, with respect to differential type space / time allocation of a plurality of transmission stream elements to a plurality of carriers, a corresponding expression can be used using the above-described carrier vector and slot vector.

  In the example shown in FIG. 17, the output from the differential space-time block encoder is expressed using the following two orthogonal designs.

As shown in FIG. 17, the number of antennas n _T 2, allocated subject to the number of time slots T 1, according to the space-frequency transmit diversity, the number of subcarriers N _S 4 and the number of transmission streams element N is 8, It has become.

Further, as shown in FIG. 17, whereas the first four transmission stream element is allocated subcarriers 1 to subcarrier N _S, the next four transmit streams elements, reverse order, i.e. sub-carrier N _S To subcarrier 1. This can be expressed as follows using a carrier vector and a slot vector.

  Here, an arrangement in which the order of the first four transmission stream elements and the next four transmission stream elements are exchanged can be expressed as follows.

  The order changing method and the allocation method to a plurality of subcarriers for the differential type spatial / frequency type transmission diversity are not limited to the above-described expressions, and in a general sense, the corresponding transmission stream elements correspond to each other. Related to allocation to subcarriers. As will be described later, each assignment is referred to as a continuous assignment. This will be explained with some examples.

  As described above, the assignment result obtained by the first antenna is expressed as follows.

  Further, the assignment result obtained by the second antenna is expressed as follows.

  In addition, demapping or equivalent de-assignment on the receiving side is the same as demapping or equivalent inverse assignment for non-differential diversity reception described above. Omitted.

  Another aspect of the present invention relates to differential space-time-frequency transmission diversity and diversity reception.

  According to the present invention, transmission stream elements based on two consecutive different orthogonal designs are distributed in both the time domain and the frequency domain in order to relax the conditions in the time domain and the frequency domain for constant channel coefficients.

  FIG. 18 is a diagram for explaining the differential type space / time / frequency transmission diversity according to the present invention.

  As shown in the figure, transmission stream elements based on one orthogonal plan are transmitted by the same subcarrier using a plurality of time slots. Differential encoding is performed in the frequency domain. That is, consecutive orthogonal plans are transmitted using two consecutive time slots in adjacent subcarriers.

  Thus, the communication channel is constant over the four OFDM symbols in differential space-time transmit diversity as usual, or over the four subcarriers in differential space-frequency transmit diversity. There is no need to be constant over two OFDM symbols in the time domain and two subcarriers in the frequency domain.

  In general, differential space / time / frequency transmission diversity can be realized using two or more OFDM symbols. When two OFDM symbols are used, it is necessary to transmit one reference matrix for every two OFDM symbols.

In the example shown in FIG. 18, the symbols x ₁ , x ₂ and x ₉ , x ₁₀ belong to a reference matrix that decreases the data rate. On the other hand, if differential space / time / frequency transmit diversity is realized by multiple OFDM symbols, the channel is required to be constant over a corresponding number of OFDM symbols.

In the example shown in FIG. 19, belongs to one of the reference matrix is only x ₁ and x _2. Also, the channel is required to be constant over four OFDM symbols whenever a transmit stream element is assigned to a new OFDM symbol. In the example shown in FIG. 18, which is the case for _{x 7} and _{x 10.}

  Furthermore, in the example shown in FIG. 18, the continuity of transmission stream assignment is represented by arrows, and successive orthogonal plans are assigned to a plurality of subcarriers and time slots highly related to the carrier.

  FIG. 19 shows a second method for realizing differential space / time / frequency transmission diversity according to the present invention.

  In the example shown in FIG. 19, the maximum requirement is that the communication channel is constant over three OFDM symbols or subcarriers, respectively, instead of the four OFDM symbols shown in FIG.

  In other words, the conditions for the constant time communication channel are shown in FIG. 18 by assigning the transmission stream elements corresponding to the subscripts 9 to 12 in the “vertical” direction represented by the broken line in FIG. It means that it will be relaxed compared to the case.

  FIG. 20 is a diagram showing a third example of realizing differential space / time / frequency transmission diversity, which is a combination of the methods shown in FIGS. 18 and 19.

  In the example shown in FIG. 20, the continuity of transmission stream elements is again represented by a broken line.

  In the example shown in FIG. 20, the communication channel is required to be constant over two transmission stream elements in the time domain and over the largest subcarrier in the frequency domain. Before and after using a new OFDM symbol, the assignment only changes so that the channel is constant over two OFDM symbols and three subcarriers, not four OFDM symbols.

される。これにより、送信ストリームエレメントの時間領域および周波数領域での分配に係る自由度が増大する。Several other mapping methods can be employed. Especially for two or more transmitters, differential type

Is done. Thereby, the freedom degree regarding distribution in the time domain and frequency domain of a transmission stream element increases.

  Furthermore, according to the differential transmission diversity, ie, the differential space / frequency or differential space / time / frequency transmission diversity, the corresponding diversity reception is similarly applied to the non-differential diversity reception described above. That is, this is realized by performing reverse demapping on the receiver side corresponding to the allocation to subcarriers in the frequency domain (and time domain) of the transmission stream performed on the transmission side.

  As described above, the present invention relates to both non-differential and differential transmit and receive diversity. What if the allocation method maps multiple transmit stream elements in both frequency domain and time domain for non-differential transmit diversity and at least in the frequency domain for differential transmit diversity? The present invention can be applied even if it is anything.

  Furthermore, the present invention can be applied to any transmission scheme in which the subchannel is correlated in two dimensions (eg, time and frequency). Furthermore, the present invention can be applied to any kind of space / time block code that requires a constant channel coefficient over one block.

  In particular, for differential transmission diversity, any continuous mapping method in which a transmission stream element based on an arbitrary differential transmission diversity scheme is mapped to at least two subcarriers and one or more time slots. The present invention can be applied to various types. In addition, the present invention can be applied to any transmission method using a subchannel having a two-dimensional (eg, time and frequency) correlation.

  Further, from the perspective of the receiver, the present invention provides a turbo detection in a way that combines an external forward error correction code with a space-time-frequency block code that includes a special non-Gray mapping of bits to constellation points. Also related.

  It is the figure which showed the basic principle which concerns on the space-time block code as a technical background of this invention.   It is the figure which showed the example of the space-time block code as a technical background of this invention.   It is the figure which showed the outline | summary of the multiple input and multiple output communication system as a technical background of this invention.   It is a schematic diagram which shows the structure of the apparatus which implement | achieves the non-differential type transmission diversity which concerns on this invention.   It is the figure which showed typically the structure of the allocation part which concerns on this invention shown in FIG.   5 is a flowchart illustrating an operation for realizing non-differential transmission diversity according to the present invention.   It is the flowchart which showed typically the structure of the apparatus for implement | achieving the non-differential transmission diversity which concerns on this invention.   4 is a flowchart schematically showing a configuration of a device for realizing non-differential type or differential type diversity reception according to the present invention.   3 is a flowchart illustrating an operation for realizing non-differential or differential diversity reception according to the present invention.   It is the figure which showed typically the structure of the post-processing part in the suitable aspect of this invention.   It is the figure which showed an example of the non-differential type | mold transmission diversity which concerns on this invention.   It is the figure which showed an example of the non-differential type diversity reception corresponding to the non-differential type transmission diversity of the present invention shown in FIG.   It is the figure which showed an example of the non-differential transmission diversity which concerns on this invention.   It is the figure which showed an example of the non-differential diversity reception corresponding to the non-differential type | mold transmission diversity of this invention shown in FIG.   It is the figure which showed the basic principle which implement | achieves the differential type | mold transmission diversity as a background art of this invention.   5 is a flowchart illustrating an operation for realizing differential transmission diversity according to the present invention.   It is a figure which shows an example of the differential type space and frequency transmission diversity which concerns on this invention.   It is a figure which shows an example of the differential type space-time-frequency transmission diversity which concerns on this invention.   It is a figure which shows another example of the differential type space-time-frequency transmission diversity which concerns on this invention.   It is a figure which shows another example of the differential type space-time-frequency transmission diversity which concerns on this invention.

Claims (56)

A method for performing space, time, and frequency transmission diversity in a multi-carrier communication system using a plurality of antennas,
Converting the transmission symbols into a plurality of transmission streams according to a predetermined conversion rule for supplying to a plurality of antennas;
Allocating transmission stream elements in each transmission stream to a plurality of carriers available at each antenna with respect to frequency domain and time domain;
Having a method.   The method of claim 1, wherein the predetermined transformation rule is an orthogonal design. The method according to claim 2, wherein the orthogonal design is set as a complex orthogonal matrix from a group including a plurality of transmission symbols, a linear combination of a plurality of transmission symbols, and a complex conjugate of a plurality of transmission symbols. .   The method of claim 3, wherein the plurality of transmission stream elements are obtained based on the orthogonal plan, and the plurality of transmission stream elements are allocated to a plurality of carriers and a plurality of time slots related to one carrier. In a multi-carrier communication system using a plurality of antennas, a method of performing differential space / time / frequency transmission diversity,
Converting the transmission bits into a plurality of transmission streams based on a predetermined orthogonal scheme to supply the plurality of antennas;
Assigning transmission stream elements in a plurality of transmission streams to a plurality of carriers available at each antenna in the frequency domain.   6. The method of claim 5, wherein a plurality of transmission stream elements in each transmission stream are further assigned to a plurality of carriers available at each antenna in the time domain.   The method according to claim 5 or 6, wherein the predetermined transmission rule is a differential orthogonal plan.   The differential orthogonal design is iteratively set as a complex orthogonal matrix from a group including a plurality of transmitted bits, a constellation point of a differential space-time block code, and at least one transmitted orthogonal design. 8. The method of claim 7, wherein:   The differential orthogonal scheme is derived from elements of the differential orthogonal scheme, and a plurality of transmission stream elements are allocated to a plurality of carriers or a plurality of time slots related to one carrier. the method of.   The method according to claim 9, wherein the transmission stream elements are mapped to at least one of a plurality of adjacent carriers and time slots continuously with respect to a plurality of consecutive orthogonal plans. Assigning the plurality of transmit stream elements comprises:
Selecting one carrier and one time slot for each transmit stream element;
Mapping each transmit stream element to the selected carrier and time slot;
The method according to claim 1, comprising: N transmission stream elements t = [t _N ,. . . , T ₁ ] in the step of selecting one carrier and one time slot,
N _S The available number of carriers, when the selected carrier to alpha _i for the i th transmission stream elements, a set of carrier indexes cookie scan

Specify
A set of time slot indices, where T is the number of slots available on each carrier and β _i is the time slot selected for the i th transmission stream element.

The method of claim 11, wherein: In the step of assigning a plurality of transmit stream elements to the selected carrier;
a carrier vector c _i represented by the following equation with the i-th transmission stream element t _i as a column vector;

A time slot vector s _i representing the i th transmission stream element t _i as a row vector according to the following equation:

The product of the transmission stream element t _i and the dyad of the carrier vector and time slot vector s _i

When,
The method according to claim 12, wherein: The final assignment result is

The method according to claim 13, wherein the method is calculated by: The number N of the transmission stream elements, the carrier index set C, and the time slot index set S change with time. 15. Method.   The method according to claim 1, wherein the mapping is performed in the same way at each antenna. 16. The method according to claim 1-15, wherein the plurality of transmission stream elements in each row of _DT are transmitted sequentially on corresponding antennas. A method for realizing space / time / frequency diversity reception in a multi-carrier communication system using a plurality of antennas,
Receiving a plurality of transmission streams and corresponding transmission stream elements at each of the plurality of antennas;
The plurality of transmission stream elements are allocated to a plurality of carriers in the frequency domain and the time domain in order to realize space / time / frequency transmission diversity in a transmitter,
In the transmitter, a process reverse to the allocation process performed in each antenna, and demapping a transmission stream element to an output symbol stream in a frequency domain and a time domain;
Providing the output symbol stream to subsequent processing. A method for realizing differential space / time / frequency diversity reception in a multi-carrier communication system using a plurality of antennas,
Receiving a plurality of transmission streams and corresponding transmission stream elements at each of the plurality of antennas;
The plurality of transmission stream elements are allocated to a plurality of carriers in the frequency domain and the time domain in order to realize differential space / time / frequency transmission diversity in a transmitter.
In the transmitter, a process reverse to the allocation process performed in each antenna, and demapping a transmission stream element to an output symbol stream in a frequency domain and a time domain;
Providing the output symbol stream to subsequent processing. Multiple transmit stream elements are assigned to multiple carriers in the time domain at the transmitter to achieve differential space, time, and frequency transmit diversity,
The method of claim 19, wherein demapping of multiple transmit stream elements to an output symbol stream in the time domain is implemented as an inverse process of assignment at the transmitter.   21. A method according to claim 19 or 20, wherein the plurality of transmit stream elements are derived from elements of the differential orthogonal design.   The method of claim 21, wherein the plurality of transmit stream elements are continuously demapped to adjacent carriers and time slots for successive orthogonal plans. The N transmission stream elements t = [t _N ,. . . , T ₁ ] in the above step of performing the demapping process,
N _S number of available carriers, when the carrier to a selected alpha _i for the i th transmission stream elements, a set of carrier indexes cookie scan

Specify
A set of time slot indices, where T is the number of slots available on each carrier and β _i is the time slot selected for the i th transmission stream element.

The method according to any one of claims 18 to 21, characterized by: In the process of demapping the plurality of transmission stream elements from different carriers and time slots to output symbols y _i ,
A step of transmission streams element T in each of the the N _S carriers, placed in diversity reception matrix D _R at each antenna,
Determining a carrier vector c _i from a set C of carrier indices and expressing the step and i-th transmission stream element t _i as a column vector by

Determining a time slot vector s _i from a set S of time slot indexes and determining the i th transmission stream element t _i as a row vector according to the following equation:

The product of the transposed carrier vector, the diversity reception matrix D _R , and the transposed slot vector

24. The method of claim 23, comprising the step of:   23. The method according to claim 18, 21 or 22, wherein the output symbols at each antenna are provided to a combiner to estimate transmission symbols for subsequent turbo detection. The turbo detection step includes
Calculating a log likelihood ratio for each of a plurality of code bits output from a combiner of the receiver;
Deinterleaving log likelihood ratios of a plurality of code bits;
Decoding the de-interleaved log-likelihood ratio to generate an empirical log-likelihood ratio of a plurality of code bits;
The log likelihood ratio of a plurality of code bits is subtracted from the a posteriori log likelihood ratio of the corresponding plurality of code bits in bit units to generate external log likelihood information,
The method according to claim 25, wherein the log likelihood information is provided to the demapping step as deductive log likelihood information after interleaving is performed.   27. The method of claim 26, further comprising subtracting the external log likelihood information from a new log likelihood value generated in the demapping step.     In the process of mapping a plurality of code bits to empirical log-likelihood ratios to modulation scheme symbols, a mapping method is used in which the number of different bits is maximized at a constellation point within the minimum Euclidean distance of the modulation scheme. 28. A method according to claim 26 or 27, wherein: An apparatus for realizing space / time / frequency transmission diversity in a multi-carrier communication system,
Multiple antennas,
A transmission unit for converting a transmission symbol sequence into a plurality of transmission streams based on a predetermined transmission rule to supply the plurality of antennas;
An apparatus comprising: an assigning unit that assigns transmission stream elements in each transmission stream to a plurality of carriers that can be used by each antenna in the frequency domain and the time domain.   30. The apparatus of claim 29, wherein the transmission unit uses an orthogonal plan as the predetermined transmission rule. The apparatus according to claim 30, wherein the orthogonal design is set as a complex orthogonal matrix from a group including a plurality of transmission symbols, a linear combination of a plurality of transmission symbols, and a complex conjugate of a plurality of transmission symbols. . The transmission unit generates the plurality of transmission stream elements from the elements of the orthogonal plan, and assigns a plurality of different transmission stream elements to a plurality of carriers and a plurality of different time slots related to one carrier. Item 32. The apparatus according to Item 31. An apparatus for realizing differential space / time / frequency transmission diversity in a multi-carrier communication system,
Multiple antennas,
A transmission unit for converting a transmission bit sequence into a plurality of transmission streams based on a predetermined transmission rule to supply the plurality of antennas;
An allocation unit that allocates transmission stream elements in each transmission stream to a plurality of carriers that can be used by each antenna in a frequency domain and a time domain.   The apparatus according to claim 31, wherein the transmission unit further allocates a plurality of transmission stream elements in each transmission stream to a plurality of carriers available in each antenna in a time domain.   The apparatus according to claim 33 or 34, wherein the predetermined differential transmission rule for the transmission unit is implemented as a differential orthogonal plan.   The differential orthogonal plan is repetitively set in the transmission unit from a group including a plurality of transmission bits, a constellation point of a differential space-time block code, and at least a transmitted plan. 36. The apparatus of claim 35.   The apparatus according to claim 36, wherein the allocating unit continuously allocates a plurality of transmission stream elements to a plurality of adjacent carriers and a plurality of time slots in a continuous orthogonal plan. The assigning unit is
A selector for selecting one carrier and time slot for each transmission stream element;
38. The apparatus according to claim 29, further comprising: a mapping unit that maps each transmission stream element to the selected carrier and time slot. The selection unit includes:
N _S The available number of carriers, when the selected carrier to alpha _i for the i th transmission stream elements, a set of carrier indexes cookie scan

Specify
A set of time slot indices, where T is the number of slots available on each carrier and β _i is the time slot selected for the i th transmission stream element.

, A set of N transmit stream elements t = [t _N ,. . . , T ₁ ] with one carrier and time slot. The demapping unit
A plurality of transmission streams element T in each of the M carriers, and placement unit to place the diversity reception matrix D _R at each antenna,
A storage unit for storing a carrier vector c _i included in a set C of carrier indexes in order to express the i-th transmission stream element t _i as a column vector according to the following equation:

A storage unit for storing a time slot vector s _i included in a set S of time slot indexes in order to represent the i th transmission stream element t _i as a row vector according to the following equation:

The product of the transposed carrier vector, the diversity reception matrix D _R , and the transposed time slot vector

An arithmetic unit for calculating
40. The apparatus of claim 39, wherein a plurality of transmit stream elements are mapped to the selected plurality of carriers and time slots using. The final assignment result is

41. The apparatus of claim 40, wherein the apparatus is determined by: 32. The apparatus according to claim 29, wherein at least one of the number N of transmission stream elements, the set C of carrier indexes, and the set S of time slot indexes varies with time. .   43. Apparatus according to any of claims 29 to 42, wherein the allocation is performed in the same way at each antenna. 45. An apparatus according to any of claims 41 to 44, wherein the elements of each row of _DT are transmitted sequentially on corresponding antennas. An apparatus for realizing space / time / frequency diversity reception in a multi-carrier communication system,
Multiple antennas,
A receiver that receives a plurality of transmission streams and a plurality of transmission stream elements corresponding to each of the plurality of antennas;
Have
The plurality of transmission stream elements are allocated to the plurality of carriers in a frequency domain and a time domain in one transmitter in order to realize space, time, and frequency transmission diversity.
A demapping unit for demapping a plurality of transmission stream elements into one output symbol stream in the frequency domain, which corresponds to a process reverse to the assignment performed in each antenna in the transmitter;
An output unit for supplying the output symbol stream to subsequent processing;
A device characterized by comprising: An apparatus for realizing differential space / time / frequency diversity reception in a multi-carrier communication system,
Multiple antennas,
A receiver that receives a plurality of transmission streams and a plurality of transmission stream elements corresponding to each of the plurality of antennas;
Have
The plurality of transmission stream elements are allocated to the plurality of carriers in a frequency domain and a time domain in one transmitter in order to realize differential space / time / frequency transmission diversity,
A demapping unit for demapping a plurality of transmission stream elements into one output symbol stream in the frequency domain, which corresponds to a process reverse to the assignment performed in each antenna in the transmitter;
An output unit for supplying the output symbol stream to subsequent processing;
A device characterized by comprising: The transmission stream element is allocated to the plurality of carriers in the time domain in order to realize differential space / time / frequency transmission diversity at the transmitter,
The apparatus according to claim 46, wherein the demapping unit demaps a plurality of transmission stream elements to an output symbol stream in the time domain as a process reverse to the allocation process in the transmitter.   The apparatus of claim 47, wherein the demapping unit demaps a plurality of transmission stream elements derived from elements of the differential orthogonal plan.   49. The apparatus of claim 48, wherein the demapping unit demaps a plurality of transmission stream elements to a plurality of adjacent carriers and time slots for successive orthogonal plans. The demapping unit
N _S number of available carriers, when the carrier to a selected alpha _i for the i th transmission stream elements, a set of carrier indexes cookie scan

Specify
A set of time slot indices, where T is the number of slots available on each carrier and β _i is the time slot selected for the i th transmission stream element.

N transmit stream elements t = [t _N ,. . . , T ₁ ] is subjected to a demapping process. The apparatus according to any one of claims 45 to 49, wherein: The demapping unit
A plurality of transmission streams element T in each of the M carriers, and placement unit to place the diversity reception matrix D _R at each antenna,
A storage unit for storing a carrier vector c _i included in a set C of carrier indexes in order to express the i-th transmission stream element t _i as a column vector according to the following equation:

A storage unit for storing a time slot vector s _i included in a set S of time slot indexes in order to represent the i th transmission stream element t _i as a row vector according to the following equation:

The product of the transposed carrier vector, the diversity reception matrix D _R , and the transposed time slot vector

An arithmetic unit for calculating
51. The apparatus of claim 50, wherein the plurality of transmit stream elements is demapped from a plurality of different carriers and time slots to output symbols y _i using.   52. The apparatus of claim 46, 47 or 51, further comprising a combiner that receives the output symbol stream at each antenna, combines the corresponding streams, and provides the output to a turbo decoder. The turbo decoder is
A demapping unit that calculates a log likelihood ratio for each of the plurality of code bits output from the combiner of the receiver;
An interleaver for deinterleaving log likelihood ratios of a plurality of code bits;
A decoder for decoding the deinterleaved log likelihood ratio to generate an empirical log likelihood ratio of a plurality of code bits;
A subtractor that generates external log likelihood information by subtracting a log likelihood ratio of a plurality of code bits from a posteriori log likelihood ratio of a corresponding plurality of code bits in bit units;
53. The apparatus according to claim 52, further comprising: an interleaver that provides the log likelihood information as deductive log likelihood information to the demapping step after interleaving is performed.   54. The apparatus of claim 53, further comprising a subtractor that subtracts the external log likelihood information from a new log likelihood value generated by demapping.   The demapping unit uses code bits mapped to symbols of the modulation scheme based on a mapping method that maximizes the number of different bits at a constellation point within the minimum Euclidean distance of the modulation scheme. 55. Apparatus according to claim 53 or 54. A computer program that can be transferred directly to the internal memory of a mobile communication terminal unit,
29. A computer program comprising software code for executing the steps according to any one of claims 1 to 28 when executed by a processor of the mobile communication terminal unit.

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