JP5414055B2 - Distributed node communication system - Google Patents

Description

  In the present invention, a node group (communication stage) composed of communication nodes having transmission / reception and relay transmission functions is arranged in multiple stages in a communication space, and a signal transmitted by a communication node is generally relayed sequentially through a plurality of communication stages. The present invention relates to a distributed node communication system to be transmitted.

A conventional wireless transmission system similar in configuration to the system of the present invention will be described. First, an example of a system called multiple input multiple output (MIMO) will be described with reference to FIG. Transmission data is sent from the transmitter TX to the receiver RX. The transmission data sequence {d} is separated into _two data sequences {d ₁ }, {d ₂ } in the transmission unit TX ₀ , converted into a radio signal by a built-in modulator, and then two transmission amplifiers AMP. Transmitted from antennas TA ₁ and TA ₂ via _T.

In the receiver RX, the received signal through the receiving amplifier AMP _R from the receiving antennas RA _1, RA _{2, 2} pieces of the received signal is sent to the demodulation unit RX _0. Assuming that the propagation matrix having the propagation constant between the transmitter and the receiver as H (h ₁₁ , h ₂₁ , h ₁₂ , h ₂₂ ), the pilot response circuits PR ₁ , PR ₂ are utilized by utilizing the transmission of the pilot signal in the training period. There replica of propagation matrix _{^ H (^ h 11, ^} h 21, ^ h 12, ^ h 22) are generated in advance and stored. Here, "^ H", "^ h", and the like represent respective alphabetic symbols with "^" at the top. Thus, in this specification, “^”, “˜” may be used as a surrogate notation for an alphabetic character accompanied by “^”, “˜”.

The signal processing unit AYZ of the demodulating unit RX ₀ analyzes the two series of received signals received in a multiplexed form after the transmission signal separated into two series is converted by the propagation matrix using the replica ^ H. Thus, the soft outputs {˜d ₁ } and {˜d ₂ } of the two series of data components are separately generated. Individual data components in these components are hard-decided by the determinator DEC, and detection values {^ d ₁ }, {^ d ₂ } of the transmission data series are generated.

  The advantage of the MIMO scheme is that the transmission capacity can be doubled even with the same transmission bandwidth by using two antennas for transmission and reception compared to a scheme using one antenna for transmission and reception. In order to obtain such advantages, it is necessary that the elements of the propagation matrix are uncorrelated with each other, the receiver obtains a replica ^ H in advance, and the received signal is analyzed by this replica ^ H. In order to make the propagation constant uncorrelated, it is necessary to set the installation interval between the transmission antennas and the installation interval between the reception antennas to be 1/2 or more of the wavelength of the carrier wave. Further, in the line-of-sight propagation environment, the correlation between propagation constants increases, so that it is difficult to separate the two sequences and the capacity cannot be increased.

As a technique for solving the above problem, there is a technique of inserting the relay stages REP ₁ and REP ₂ between the transmitter and the receiver, as indicated by the broken line frame at the lower center of FIG. As an example of such a technique, communication systems such as the following Patent Documents 1 and 2 are known.

In FIG. 16, by inserting relay stages REP ₁ and REP ₂ indicated by broken line frames on the propagation path, the output of transmitter TX is transmitted to receiver RX via _two relays REP ₁ and REP _2. The The propagation matrix H in this case is the product of the transmission side propagation matrix H _T (h _1R1 , h _2R1 , h _1R2 , h _2R2 ) and the reception side propagation matrix H _R (h _R11 , h _R21 , h _R12 , h _R22 ). Since the correlation between propagation constants is reduced even in the line-of-sight environment, signal separation in the demodulator RX ₀ is achieved. The MIMO system (hereinafter referred to as the MIMO-REP system) having such a relay stage is similar in appearance to the configuration of the present invention, but is an essentially different technique as will be described later.

JP 2005-192185 A JP 2006-148482 A

  A conventional MIMO or MIMO-REP communication system is a simple communication system between a transmitting station and a receiving station for the purpose of improving the transmission efficiency between the transmitting station and the receiving station and improving the S / N ratio. It was. Such a conventional communication system is not intended for application to ubiquitous communication and does not handle a large number of communication stations (communication nodes) arranged in a wide space. In recent years, the practical use of ubiquitous communication that enables "communication with various places at the same time" has attracted attention, but conventional communication systems have not always been well adapted to such ubiquitous communication. .

  Therefore, the present invention uses a group of communication nodes having transmission / reception and relay transmission functions as communication stages, arranges the communication stages in multiple stages in the communication space, and integrates transmission / reception timing between these communication stages. It is an object of the present invention to provide a communication system that has a high degree of freedom in communication form, can be applied to various forms of application fields, and has good adaptability to ubiquitous communication.

  In order to achieve the above object, a distributed node communication system according to the present invention stores a transmission node that transmits a radio signal, and a demodulated signal obtained by receiving the radio signal transmitted by the transmission node and demodulating the radio signal. A relay stage composed of one or more relay nodes that convert the stored demodulated signal into a radio relay signal and transmit, a reception node that receives the radio signal, a transmission start time of the transmission node and the relay node, A transmission / reception time control means for controlling the relay node and the reception start time of the reception node, and causing all relay nodes belonging to the same relay stage to perform reception start and transmission start operations at the same timing. A distributed node communication system in which one or more relay stages are arranged in a communication space between the transmitting node and the receiving node. The transmission node includes means for modulating a link identification spreading sequence with transmission data to generate a baseband transmission signal, and means for transmitting a radio signal generated by modulating a carrier wave with the baseband transmission signal It is. The relay node demodulates the received radio signal with a local carrier wave to generate a baseband received signal, and for each soft output obtained by despreading each using a link identification spreading sequence used by the previous node, And each corrected soft output is generated by performing phase correction processing for correcting the phase rotation amount of the carrier wave generated by transmission between the relay node and the relay node, and a combined corrected soft output is generated by adding the corrected soft outputs. A combined modified soft output generating means, a means for generating a baseband transmission signal by modulating a spread sequence for link identification with the combined corrected soft output, and transmitting a radio signal generated by modulating a carrier wave with the baseband transmitted signal It has a means to do. The receiving node demodulates the received radio signal with a local carrier wave to generate a baseband received signal, and for each soft output obtained by despreading each using a link identification spreading sequence used by the preceding relay node, Each corrected soft output is generated by performing phase correction processing for correcting the phase rotation amount of the carrier wave generated by the transmission between the relay node and the receiving node, and the combined soft output is obtained by adding these corrected soft outputs. A composite corrected soft output generating means for generating and means for detecting transmission data transmitted by the transmitting node by making a hard decision on the composite corrected soft output.

  The distributed node communication system of the present invention stores a transmission function for transmitting a radio signal generated by modulating a carrier wave with transmission data, and a demodulated signal generated by demodulating the received radio signal with a local carrier wave. , Comprising at least one communication node having a relay function for converting a stored demodulated signal into a radio signal for relay transmission and a receiving function for detecting transmission data using the demodulated signal, all of the communication nodes being the same The communication stage that operates at the timing of the above, and the transmission start time and the reception start time of the communication node are controlled. A distributed node communication system including a transmission / reception time point control unit to be performed and a plurality of the communication stages arranged in a communication space. The communication node demodulates the received radio signal and demodulates the demodulated signal generated by the second spreading sequence used by each communication node of the previous communication stage, with respect to each soft output. Each corrected soft output is generated by applying phase correction processing that corrects the phase rotation amount of the carrier generated by transmission between each communication node and the local communication node, and the corrected soft outputs are added together to synthesize Combined modified soft output generating means for generating corrected soft output; means for generating a first spread signal by modulating a first spreading sequence for transmitting point identification with transmission data starting from the communication node; and the first spreading Means for generating a second spread signal by further modulating the second spread sequence for transmission link identification with an output obtained by adding the signal and the combined modified soft output; and generating by modulating a carrier wave with the second spread signal Means for transmitting the received radio signal, and means for generating a received soft output signal by despreading the combined corrected soft output by the first spreading sequence used by the communication node of the counterpart station that transmitted the data to be acquired, Means for detecting transmission data transmitted by the communication node of the counterpart station by making a hard decision on the received soft output signal.

  Further, in the above distributed node communication system, the combined modified soft output generating means converts each of the demodulated signals into soft outputs obtained by despreading each of the demodulated signals by the second spreading sequence used by each communication node in the preceding communication stage. On the other hand, each corrected soft output is generated by applying a phase correction process for correcting the phase rotation amount of the carrier wave generated by transmission between each communication node in the previous stage and the local station communication node. It is preferable that the combined corrected soft output is generated by adding all corrected soft outputs except for the corrected soft output whose power is a value equal to or less than a preset threshold value.

  Further, in the above distributed node communication system, the combined modified soft output generating means converts each of the demodulated signals into soft outputs obtained by despreading each of the demodulated signals by the second spreading sequence used by each communication node in the preceding communication stage. On the other hand, each corrected soft output is generated by applying phase correction processing for correcting the phase rotation amount of the carrier wave generated by transmission between each communication node in the previous stage and the local communication node, and the voltage amplitude of the corrected soft output is generated. Preferably, the adjusted soft output is generated according to the signal-to-noise ratio included in the corrected soft output, and the adjusted soft output is added to generate the combined corrected soft output.

  Further, in the above distributed node communication system, the communication stage is arranged such that the outer communication stage adjacent to the communication stage surrounds the inner communication stage in a ring shape with respect to the inner communication stage. can do.

  In the distributed node communication system, a plurality of communication stages are sequentially arranged at a distance, and the plurality of communication stages include a communication stage having one communication node and a plurality of communication nodes. Communication stages.

  In the distributed node communication system, the communication stage includes an annular communication stage composed of a plurality of communication nodes arranged in an annular shape, and the plurality of communication stages include the annular communication. It may be arranged at a distance from each other in a direction perpendicular to a plane including the stepped ring.

  In the distributed node communication system described above, the mobile station moves along the vicinity of a curve connecting the center points of the annular communication stages, and the transmission / reception time point control means moves along with the movement of the mobile station. , Which causes all communication nodes belonging to the annular communication stage in the vicinity of the mobile station to perform reception start and transmission start operations at the same timing, and in the vicinity of the mobile station The mobile station performs transmission start and reception start operations at a timing that enables communication with a communication node in the annular communication stage, and the mobile station generates by demodulating the received radio signal. For each soft output obtained by despreading the demodulated signal by the second spreading sequence used by each communication node of the annular communication stage at a nearby position, Each modified soft output is generated by applying phase correction processing that corrects the phase rotation amount of the carrier generated by transmission between the mobile station and the local station, and a combined corrected soft output is generated based on these corrected soft outputs Modified soft output generating means; means for generating a received soft output signal by despreading the synthesized modified soft output by a first spreading sequence used by a communication node of a partner station that desires data reception; and And means for detecting transmission data transmitted by the communication node of the counterpart station by making a hard decision on the output signal.

  In the above distributed node communication system, the mobile station moves along the vicinity of the curve connecting the center points of the annular communication stages, and the adjacent annular communication in the rear that the mobile station has already passed through. Each communication node in the stage transmits an unmodulated carrier at the transmission timing assigned to the annular communication stage, and the mobile station reads out data stored by itself in response to reception of the unmodulated carrier Each of the communication nodes of the annular communication stage that transmits and receives the mobile station in the front in the moving direction of the mobile station receives the transmission data of the mobile station, and further, the proximity of the rear that the mobile station has already passed. Each communication node of the annular communication stage transmits a transmission signal including write data using a carrier wave having a frequency different from that of the unmodulated carrier wave at a transmission timing assigned to the annular communication stage. And Shin, the mobile station can be made to store the write data received in the storage means of its own station.

  Since this invention is comprised as mentioned above, there exist the following effects.

  By spreading the transmission signal of each communication node by the spread sequence for link identification, it is possible to identify and separate the link signal received from each preceding communication node. Furthermore, by providing each communication node with a function of correcting a change in carrier wave phase that occurs in the propagation process, it is possible to correct the phase rotation that has occurred in the propagation process of link signals received from a plurality of preceding communication nodes. As a result, in data transmission between a desired pair of communication nodes, the reception S / N ratio increases as the number of communication stages passed through and the number of nodes constituting each communication stage increase. Therefore, even in a space where the reception level fluctuation is large, it is possible to provide stable communication with a low error generation probability using low transmission power.

  In addition, by time-division transmission method between two or multi-phase communication stages using timing control signals, forward, reverse, forward / reverse bidirectional simultaneous transmission, or from the center to the periphery in a two-dimensional or three-dimensional space, Since a flexible network can be configured by realizing transmission in the opposite direction and the selection switching control of those transmission modes, it is possible to adapt to various communication demands assumed in ubiquitous communication.

  In addition, when applied to communication between an active tag or passive tag and a fixed communication network, a highly reliable classification delivery system by low power communication can be realized. Furthermore, if the multistage relay technology of the present invention is applied to intra-cell communication in a mobile communication system, the S / N ratio is increased by multistage relay and the same symbol component is transmitted and received many times, thereby stabilizing the base station and the mobile node. Low power communication can be realized.

FIG. 1 is a diagram showing a basic configuration of a distributed node communication system according to the present invention. FIG. 2 is a diagram showing a specific configuration of a distributed node communication system using the first spreading code and the second spreading code. FIG. 3 is a graph showing the S / N ratio characteristics of the distributed node communication system. FIG. 4 is a diagram showing the simplest communication system with one relay stage. FIG. 5 is a diagram showing a communication system configured by cascading a plurality of communication systems of FIG. FIG. 6 is a diagram illustrating an example of a communication system in a space such as a long corridor. FIG. 7 is a diagram illustrating a communication system in which a branch transmission path is added to a communication system that performs transmission in a predetermined direction. FIG. 8 is a diagram showing a communication system having a structure in which a relay stage is annularly surrounded by an outer relay stage. FIG. 9 is a diagram illustrating a signal processing process in the transmission unit and the reception unit in the communication node. FIG. 10 is a block diagram showing the configuration of the communication node. FIG. 11 is a block diagram illustrating details of the symbol transmission unit of the communication node. FIG. 12 is a diagram showing an outline of a communication system including a mobile node. FIG. 13 is a diagram illustrating the relationship between the movement position of the mobile node M and each timing. FIG. 14 is a diagram showing an outline of a communication system including a mobile node that does not incorporate a power source. FIG. 15 is a side view of the communication system of FIG. It is a figure which shows the structure of the communication system of the conventional multiple input multiple output system.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a basic structure of a distributed node communication system according to the present invention. The distributed node communication system of the present invention includes a transmission node A, a relay node B _n (n = 1, 2,..., N _s ), a relay node C _m (m = 1, 2,..., N _s ) and a reception node D. It consists of A group of relay nodes B _n (n = 1, 2,..., N _s ) is a relay stage B, and a group of relay nodes C _m (m = 1, 2,..., N _s ) is a relay stage C. Here, the number of nodes in each relay stage is represented by N _s . This is a communication system in which a signal transmitted from a transmission node A propagates sequentially in the direction of an arrow through a relay stage B and a relay stage C to a reception node D.

The transmitting node A can also be considered as a communication stage composed of a single node, and the receiving node D can also be considered as a communication stage composed of a single node. Generally speaking, these communication stages A, relay stage B, relay stage C, and communication stage D may be considered as communication stages corresponding to the k-th stage (k = 0, 1, 2, 3), respectively. it can. In Figure 1, the number of nodes N _s in each communication stage, N _s = 1 in the communication stage A, relay stages B, C in N _s = 3, and has a N _s = 1 the communication stage D. The relay stage B, may be a few the number of nodes N _s is other than 3 in C, the relay stage B, the number of nodes of C may be a different number from each other.

  Although the number of relay stages in FIG. 1 is two, generally, the number of relay stages is K−1, and K-stage relay transmission is performed by K + 1 communication stages k (k = 0, 1, 2,..., K). (K-hop transmission) can be realized. In FIG. 1, broken lines to which symbols a, b, and c are attached indicate signal transmission timing. Timing a indicates signal transmission from transmission node A to relay stage B, timing b indicates signal transmission from relay stage B to relay stage C, and timing c indicates signal transmission from relay stage C to reception node D. These are different timings. Each communication is performed via an omnidirectional transmission / reception antenna. It is assumed that the distances between the nodes are almost equal, and the attenuation of signals due to the distance between the nodes is almost equal to each other.

At timing a, the transmission node A transmits the transmission signal S _A generated by modulating the local carrier wave using the binary transmission data d _A , and the relay node B _n receives the reception signal R _Bn corresponding to the transmission signal S _A. And a received signal R _Bn is demodulated by using a local carrier (here, asynchronous reception) to generate a baseband signal, which is written in a temporary storage circuit. Next, the relay node B _n reads the stored base band signal, modulates the local carrier wave with the base band signal, generates a transmission signal S _Bn , and transmits it at timing b subsequent to timing a.

The relay node C _m receives the reception signal R _Cm corresponding to the transmission signal S _Bn and demodulates the reception signal R _Cm by using a local carrier wave to generate a baseband signal. In this case, the baseband signal is an addition output of N _s received signal components individually received from N _s preceding relay nodes B _n . Then, the addition output is written to the temporary storage circuit. Next, a local carrier wave is modulated by a signal obtained by reading the stored addition output to generate a transmission signal S _Cm , which is transmitted at timing c subsequent to timing b.

The reception node D receives the reception signal R _D corresponding to the transmission signal S _Cm . By using a local carrier wave, the received signal _RD is demodulated to generate a baseband signal. The baseband signal is an addition output of N _s received signal components individually received from N _s preceding relay nodes C _m . This addition output is an output _SD . Next, the transmission data d _A of the transmission node A included in the output _SD is detected. In this way, transmission from the transmission node A to the reception node D is performed.

Here, the system is generalized, and a case is considered where there are a plurality of transmission nodes, and these communicate with each other by a multiple access method. In this case, in order to detect only the transmitted data d _A of the sending node A by separating the transmitted data d _X other transmitting node X, it is necessary to multiplex and separation recovery is possible communication scheme. As a multiplexing communication method, there are a time division multiplexing method and a frequency division multiplexing method. Here, a code division multiplexing method is used.

In other words, the first spreading code for identifying the data start point transmission node is ξ. As shown in the following equation 1, the first spreading code ξ is a set of N sequences ξ _i (i = 1, 2,..., N) orthogonal to each other.
ξ = {ξ ₁ , ξ ₂ , ξ ₃ ,..., ξ _N } Equation 1

The transmission node A uses, for example, the first sequence ξ ₁ in the first spreading code ξ as the first spreading sequence ξ _A of the transmission node A, and modulates the sequence ξ _A with the transmission data d _A to thereby generate a spread signal. d _A ξ _A is generated as a baseband signal. The sequence ξ _A is a sequence dedicated to the transmission node A from the first spreading code ξ. Thus, each communication node is assigned a dedicated sequence from the first spreading code ξ. Further, the transmission node A generates a transmission signal S _A by modulating the local carrier wave using the baseband signal d _A ξ _A, and transmits this transmission signal S _A.

Next, a description will be given focusing on the operation of the relay stage C. The operation of the relay stage B is the same as the operation of the relay stage C. The baseband signal R ′ _Cm generated by the relay node C _m demodulating the received signal is composed of N _s complex number components R ′ _Cm / B _n . However, in this specification, “components transmitted from the relay node B _n ” are represented by the notation “/ B _n ”. The same applies to other nodes. Therefore, the baseband signal R ′ _Cm becomes an addition output ΣR ′ _Cm / B _n (addition at n = 1, 2,..., N _s ) of these complex number components.

The reception signal received by the relay node C _m is attenuated α in the process in which the first spread signal d _A ξ _A generated by the transmission node A is propagated from the transmission node A → the relay node B _n → the relay node C _m. . This received signal is amplified with an amplification degree G at the relay node _Bn . In addition, this received signal generates a phase difference between transmission and reception carriers by asynchronous reception in the propagation process of the transmission node A → the relay node B _n and the relay node B _n → the relay node C _m . Let the sum of these phase differences be the phase difference θ. The baseband signal R ′ _Cm / B _n is expressed by the following equation using the attenuation α and the phase difference θ.
R ′ _Cm / B _n = αGd _A ξ _A · exp (jθ) Equation 2

Where
exp () represents an exponential function, and j represents an imaginary unit. In addition, the display of the noise component included in the received signal is omitted here. Expression 2 can also be expressed as the following Expression 3, by dividing the complex number on the right side into a real part and an imaginary part.
R ′ _Cm / B _n = I _Cm / B _n + jQ _Cm / B _n Formula 3

In Equation 3, the relay node C _m represents a real part of the signal received from the relay node B _n I _Cm / B _n, the imaginary part as the Q _Cm / B _n. The polarities and amplitudes of the real part and imaginary part change depending on the phase difference θ. The phase difference θ takes a random value. In general, complex signal components received via a link from the relay node B _n where n ≠ m to the relay node C _m are uncorrelated with each other. Therefore, the normalized power of the received signal (ΣR ′ _Cm / B _n ) composed of the real part addition output (ΣI _Cm / B _n ) and the imaginary part addition output (ΣQ _Cm / B _n ) is the real part addition output. And the square of the imaginary part addition output.

Here, if the relay node C _m can correct the phase difference θ of the reception signal received from the transmission node A via the relay node B _n by some means, the reception signal via the different relay node B _n can be corrected. Can be made in phase, and the power of the received signal (ΣR ′ _Cm / B _n ) obtained by adding them can be maximized. Thus, the second spreading code ζ is introduced to correct the phase difference θ generated according to the link through which the transmission signal passes.

As shown in the following Expression 4, this second spreading code ζ is a set of N sequences ζ _i (i = 1, 2,..., N) orthogonal to each other. However, although the number N of the second spreading code sequences is represented by the same code as the number of the first spreading code sequences, the numbers of these sequences do not have to match each other.
ζ = {ζ ₁ , ζ ₂ , ζ ₃ ,..., ζ _N } Equation 4

  FIG. 2 is a diagram showing a specific configuration of a communication system using the second spreading code ζ in addition to the first spreading code ξ in the distributed node communication system of FIG. However, in FIG. 2, illustration of carrier modulation and carrier demodulation is omitted. Next, the communication system of FIG. 2 will be described, and the function of the second spreading code ζ will also be described.

The transmission node A is assigned a dedicated sequence ξ _A from the first spreading code ξ, and is assigned a dedicated sequence ζ _A from the second spreading code ζ. Transmitting node A, the first spread signal d _A xi] _A described above was produced as a baseband signal, by further spreading modulation a second spread sequence zeta _A, to produce a double spread modulation signal as a baseband signal. The spreading process using the second spreading code ζ is used to correct the phase rotation generated in the propagation process at the next node. The baseband transmission signal S ′ _A after the second spreading of the transmission node A is given by the following equation.
S ′ _A = d _A ξ _A ζ _A Formula 5

The relay node B _n generates a baseband received signal similar to Equation 2 by demodulating the received signal with a local carrier wave. If this is despread by the second spreading sequence ζ _A , a signal (link propagation component) propagated from the transmission node A to the relay node B _n as shown in the following equation 6 is obtained.
R ′ _Bn = α _ABn G _Bn d _A ξ _A · exp (jθ)
= I _Bn + jQ _Bn ... Formula 6

Here, the attenuation α _ABn is the attenuation due to the propagation between the nodes described above, and the amplification degree G _Bn is the amplification degree of amplification performed at the relay node B _n . The phase difference θ is the amount of phase rotation due to the propagation between the nodes. The transmitting node A transmits a pilot signal prior to actual data transmission. The relay node B _n can estimate the amount of phase rotation due to propagation between the nodes from the pilot response obtained by demodulating the received signal of the pilot signal, and can compensate for the amount of phase rotation in actual data reception.

That is, the transmission data d _A of the transmitting node A is equal to only the real component, the phase difference θ can be calculated by the following equation from the ratio of the real part I _Bn and the imaginary part Q _Bn in Formula 6.
θ = arctan (Q _Bn / I _Bn ) Equation 7

Where
arctan () represents the inverse function of the tangent function. In Expression 7, “/” is an operator indicating division. The relay node B _n obtains and stores the phase difference θ from the pilot response according to Equation 7, and can perform compensation processing of the phase difference θ on the signal indicated by Equation 6 when receiving actual data. That is, the influence of the phase difference θ can be canceled by multiplying the signal shown in Expression 6 by exp (−jθ). A phase conversion signal R ^c _Bn obtained by performing the compensation process of the phase difference θ on the signal of Expression 6 is given by the following expression.
R ^c _Bn = α _ABn G _Bn d _A ξ _A ... Formula 8

Further, if the degree of amplification G _Bn is selected so that α _ABn G _Bn = 1 with respect to the attenuation α _ABn , the phase conversion signal R ^c _Bn shown in Equation 8 becomes d _A ξ _A , and the transmission node A is the same signal as the first spread signal d _A ξ _A generated as the baseband signal. At this time, the phase conversion signal has the same voltage and the same power as the first spread signal transmitted from the transmission node A. In this communication system, the amplification degree G of the communication node on the receiving side is E (α) G = 1, where E (α) is the average value of attenuation α in all propagation paths (links) from the preceding communication node. The amplification degree G is set so as to satisfy the following relationship. Here, the function for obtaining the average value is represented by E (). The amplification degree G of all communication nodes is set in this way.

The relay node B _n stores the phase conversion signal R ^c _Bn expressed by Equation 8 in the storage circuit, and then generates the baseband transmission signal S ′ _{Bn based} on the signal read from the storage circuit. At this time, a spreading process using the second spreading sequence ζ _Bn is performed so that the next-stage node can identify the propagation path (link) starting from the relay node B _n . The second spreading sequence ζ _Bn is a sequence allocated exclusively for the relay node B _n from the second spreading code ζ. The baseband transmission signal S ′ _Bn of the relay node B _n is given by the following equation.
S ′ _Bn = α _ABn G _Bn d _A ξ _A ζ _Bn ...

Signal of Formula 9 is transmitted to the relay node C _m via a carrier wave from the relay node B _n, the relay node C _m produces a baseband received signal _R'Cm carrier wave demodulation. Relay node C _m is a baseband received signal _R'Cm / B _n is the link propagation component received from the relay node B _n can be obtained by despreading the second spread sequence zeta _Bn to the received signal. This despreading process is performed by the correlators MF _{1 to} MF ₃ in FIG. Due to the orthogonality of the second spreading code ζ, the link propagation components via each relay node B _n can be received and identified independently of each other. Baseband received signal R ′ _Cm / B _n is given by the following equation.
R ′ _Cm / B _n = α _ABn G _Bn α _BnCm G _Cm d _A ξ _A · exp (jθ)
= I _Cm / B _n + jQ _Cm / B _n Equation 10

Here, the attenuation α _BnCm is the attenuation due to the propagation between the nodes (B _n → C _m ), and the amplification degree G _Cm is the amplification degree of amplification performed at the relay node C _m . The phase difference θ is the amount of phase rotation due to propagation between the nodes (B _n → C _m ). The relay node _Bn transmits a pilot signal prior to actual data transmission. The relay node C _m can estimate the amount of phase rotation due to propagation between the nodes from the pilot response obtained by demodulating the received signal of the pilot signal, and can compensate for the amount of phase rotation in actual data reception. Compensation of the phase rotation amount of the relay node C _m is the same as the compensation operation of the relay node B _n described above.

In other words, the influence of the phase difference θ can be canceled by multiplying the signal shown in Expression 10 by exp (−jθ). The phase conversion signal R ^c _Cm / B _n obtained by performing the compensation process of the phase difference θ on the signal of Expression 10 is given by the following expression.
R ^c _Cm / B _n = α _ABn G _Bn α _BnCm G _Cm d _A ξ _A ...

The relay node C _m adds the phase conversion signal R ^c _Cm / B _n given by Equation 11 for n (n = 1, 2,..., N _s ), and uses the addition output as the combined conversion output R ^s _Cm . . The combined conversion output R ^s _Cm is given by the following equation.
R ^s _Cm = Σ _n (α _ABn G _Bn α _BnCm G _Cm ) d _A ξ _A Formula 12

In Equation 12, Σ _n represents addition for n (n = 1, 2,..., N _s ). The relay node C _m stores the combined conversion output R ^s _Cm given by Equation 12 in the storage unit, reads the combined conversion output R ^s _Cm from the storage unit at the next transmission timing, and performs a relay operation.

As described above, in this communication system, the amplification degree G of the communication node and the average value E (α) of the attenuation α in each link on the upstream side are set to have a relationship of E (α) G = 1. ing. As a result, the combined conversion output R ^s _Cm of Expression 12 can be further expressed as the following expression.
R ^s _Cm = N _s d _A ξ _A ... Equation 13

From Equation 13, the following can be understood. That is, in the communication system of the present invention, the transmission voltage d _A ξ _A transmitted from the transmission node A is amplified N _s times at the relay node C _m by passing through the relay stage B having the number of nodes N _s. Will be received. When converted to a signal power is amplified to 2 th power of N _s. The dispersion of the combined conversion output decreases with an increase in the number of nodes N _{s in} the relay stage due to the spatial diversity effect generated in the two-stage (N _s × N _s ) relay propagation process. If the value of N _s is increased, the standard deviation of the combined conversion output is reduced by the law of large numbers, and stable transmission can be realized.

The relay node C _m reads the combined conversion output R ^s _Cm stored in the storage means at the next transmission timing, performs a spreading process on the signal by the second spreading sequence ζ _Cm for link identification, and performs baseband processing. The transmission signal is S ′ _Cm . The baseband transmission signal S ′ _Cm is transmitted to the reception node D via a carrier wave. Here, although the receiving node D is the end point of transmission, in general, the number of relay stages may be further increased.

The relay node C _m not only relays information transmission starting from the transmission node A and other nodes, but can also transmit information starting from the local node. In FIG. 2, information starting from the relay node C ₁ is indicated by transmission data d _C1 . The spread signal by modulating the first spreading sequence xi] _C1 by transmitting data d _C1 is added to the synthetic transformation output R ^s _C1, further subjected to spread processing by the second spreading sequence zeta _C1, the receiving node via the carrier D Is transmitted.

The receiving node D performs the same processing as the reception operation of the relay node C _m, to create a received signal by adding the synthetic transformation output R ^s _D from each relay node C _m. The combined conversion output R ^s _D can be expressed as the following equation by the same procedure as the equation 13 is obtained.
R ^s _D = N _s ² d _A ξ _A ... Equation 14

From Equation 14, it can be seen that the voltage of the reception signal at the reception node D is amplified to the square of N _s of the voltage of the transmission signal transmitted from the transmission node A. When converted to signal power, it is amplified to the fourth power of N _s . In this way, the signal power is amplified to the fourth power of N _s by passing through two relay stages composed of N _s nodes.

Here, each link A → B _n is the phase rotation amount θ of the individual between the nodes, B _n → C _m, the C _m → D different. This phase rotation amount θ is a means for transmitting a pilot signal sequentially from the transmission node A to each link during the pilot transmission period, or a means for transmitting a pilot component (a chip component not modulated with data) included in a part of the transmission symbol. Can be measured by obtaining the pilot response for these pilot signals. Therefore, if the link signal component received by each node is corrected using this pilot response so that the phase rotation amount θ is zero, the phase-corrected despread outputs are only real components having no phase difference from each other. The signal is amplified as described above. The phase rotation amount θ is not necessarily corrected to 0, and may be corrected to a constant value other than 0.

Next, the signal-to-noise ratio (S / N ratio) characteristics of the communication system of the present invention will be examined. Consider a generalized communication system as shown in FIG. 1 and having k communication stages. Here, if the communication stage of k = 0 is the transmission node A, the communication stage of k = 1 becomes the relay stage B. Assuming that the number of nodes in each relay stage is N _s , the reception voltage in the kth communication stage is N _s ^k−1 times the transmission voltage of the transmission node A as described above. The reception power is N _s ^2k−2 times the transmission power.

Here, the S / N ratio is calculated on the assumption that noise having the same power as the signal power transmitted by the transmission node A is mixed in the relay stages B and after (k ≧ 1). In that case, the ratio (S / N) of the signal power (S) and the noise power (N) is given by the following equation.
S / N = N _s ^k−1 / (1 + N _s ⁻¹ + N _s ⁻² +... + N _s ^{−k + 1} ) Equation 15

FIG. 3 shows the S / N ratio given by Equation 15 in decibels (dB) and shows the relationship with the number k of relay stages. If the number of nodes N _s ≧ 2 in the relay stage, the increase in signal power due to the number k of relay stages is larger than the increase in noise, and the S / N ratio increases as the number k of stages increases as shown in the figure. If the number of nodes in the relay stage N _s ≧ 3, a sufficiently large reception S / N ratio can be obtained in the final stage even when the S / N ratio of transmission between the nodes is about 0 dB (in the case of Equation 15). . Therefore, it is possible to construct a system that is resistant to noise and operates with low transmission power.

Now, supplementary synthesis transform output R ^s _Cm generation method in a relay node C _m and other communications nodes (12). The phase conversion signal R ^c _Cm / B _{n in} Equation 11 varies depending on the ray wave characteristic and may be a low level signal. Since such signals have a low signal-to-noise ratio (S / N ratio), it is better not to use them. Therefore, the signal level of the pilot response is detected, and when the pilot response level is lower than a preset threshold value, it is not included in the addition processing of Expression 12. That is, a combined conversion output is generated by adding all other phase conversion signals except for the phase conversion signal in which the average power takes a value equal to or less than a preset threshold value. This is the generation method of supplement 1.

Alternatively, the following synthetic conversion output generation method may be used. The power of the signal component and the noise component in the transmission between the nodes can be obtained from the pilot response signal between the nodes, and the signal-to-noise ratio (S / N ratio) of each link is obtained. The phase conversion signal of each link, the S / N multiplied by the weight coefficient w _n such that the power proportional to the ratio, by adding the phase conversion signal corrected by the weight coefficient w _n and synthetic transformation output . That is, the combined conversion output R ^s _Cm is obtained by the following equation.
^{_{R s Cm = Σ n w n}} R c Cm / B n ··· formula 16

In Expression 16, the phase conversion signal w _n R ^c _Cm / B _n corrected by the weighting factor w _n becomes power proportional to the S / N ratio of each link. If the method for generating the combined conversion output as in Expression 16 is used, the effective S / N ratio of the communication system can be further improved from the value of Expression 15. This is the generation method of Supplement 2.

In FIG. 1, it is assumed that the transmission node A has a transmission function, the relay nodes B _n and C _m have a relay function, and the reception node D has a reception function. However, these communication nodes may all be the same node, and each node may have all functions of a transmission function, a relay function, and a reception function. In such a communication system, each communication node can transmit transmission data starting from its own node to any other communication node. The transmission may be performed directly or may be performed via a relay node.

  Instead of using the modulation by the first spreading sequence, for example, it is possible to assign a specific data transmission timing (time slot) to each communication node and realize transmission between any communication nodes by a time division method. Alternatively, an arbitrary intermediate frequency can be assigned to each communication node, and transmission between any communication nodes can be realized by the frequency division method. In these cases, there is no need for double spreading modulation by the first spreading sequence and the second spreading sequence, and only the second spreading sequence is used without using the first spreading sequence.

A one-dimensional network can be configured by connecting an arbitrary number of relay stages shown in FIG. 1 in the horizontal direction. FIG. 4 shows the simplest communication system with one relay stage. The communication system of FIG. 4 includes a transmission node A, a relay stage B, and a reception node C, and the number of nodes N _{s in the} relay stage B is six. Further, the communication nodes of the relay stage B are evenly arranged on the circumference.

Here, it is assumed that the attenuation amount between the nodes is a function of the inter-node distance d. In general, excellent transmission characteristics can be obtained when the inter-node attenuation is equal. In the communication system of FIG. 4, the inter-node attenuation can be made equal by making all the inter-node distances d equal. When the configuration of FIG. 4 is used, the inter-node distance d can be kept constant even if the number of nodes N _s in the relay stage B is an arbitrary number.

  In the communication system of FIG. 4, communication nodes in communication stage B are arranged in an annular shape. The plurality of communication stages A, B, and C are arranged at a distance from each other in a direction orthogonal to a plane including the ring of the annular communication stage B. The transmission data is transmitted in a direction intersecting the plane including the ring.

  A plurality of communication systems shown in FIG. 4 can be cascaded to form a long chain communication system as shown in FIG. Also in the communication system of FIG. 5, the inter-node distance and inter-node attenuation can all be made equal. In the communication system of FIG. 5, two-phase timings of timing a and timing b are used as the transmission timing between the nodes, and both the transmission in the right direction indicated by the solid line arrow and the transmission in the left direction indicated by the broken line arrow are performed. Can be performed simultaneously. That is, bidirectional transmission can be realized.

  In the case of bidirectional transmission by repeating such two-phase timings a, b, a, b,..., For example, one transmission data transmitted from the transmission node A passes through other nodes in this network. And the multiplicity of data stored in each node is accumulated. Therefore, after an appropriate period in which each node transmits / receives a plurality of symbols, all the information stored in the memory in each node is erased by a reset signal transmitted from the control node, and the next transmission / reception is performed again. It is necessary to provide another means for starting.

Next, FIG. 6 shows an example of a communication system in a space such as a long corridor. The communication system of FIG. 6 includes a transmission node A, relay stages B, C, D,..., And the number of nodes N _{s in} each relay stage is three. As shown in the figure, communication nodes A, B ₁ , B ₃ , C ₂ , D ₁ , D ₃ ,... Are arranged on the ceiling side, and communication nodes B ₂ , C ₁ , C ₃ , D ₂ ,. ... are arranged. The communication nodes B ₁ , B ₂ , and B ₃ are arranged so that the vertex positions of the right-angled isosceles triangle (the node B ₂ is the right-angle vertex), and the communication nodes A, B ₁ , and B ₃ are also the same shape. It is preferable to arrange so that the vertex position of the equilateral triangle (node A is a right angle vertex).

That is, in the arrangement of FIG. 6, if the distance between the ceiling and the floor is e, the distance between the communication nodes B ₁ and B _{3 on} the ceiling is 2e, and the distance d between adjacent nodes is (√2) e. ing. Here, “√2” represents the square root of 2. However, the present invention is not limited to such an arrangement. In general, even if d is further increased and the inter-step distance is increased, the communication node between the ceilings (for example, B ₁₎ if the condition even satisfied that B ₃ between) distance is 2e, can be equal to each communication node distance of the main transmission link by such an arrangement.

  FIG. 7 shows a communication system in which a branch transmission path is added to the communication system that performs transmission in a predetermined direction as shown in FIG. In the communication system of FIG. 7, by appropriately selecting the timing of the communication stage D that is a branch point, the horizontal transmission line in the figure is branched to the vertical transmission line in the figure through the branch point, or vice versa. Can be transmitted.

  FIG. 8 is a diagram showing a communication system having a structure in which a relay stage arranged in a square is annularly surrounded by similar relay stages outside the square. FIG. 8A is a plan view showing the arrangement of communication nodes, and FIG. 8B is a side view. The transmission signal can be transmitted from the central communication node A outward through the relay stages B, C, D,..., And conversely, the transmission signal can be transmitted from the outer peripheral side toward the communication node A. it can. The transmission timing is driven by multiphase timings a, b, c, d, e, f, and g. If it is sequentially driven in the forward direction as a → b → c..., transmission from the central communication node A to the peripheral communication node is performed, and if it is driven in the opposite direction, it is transmitted from the peripheral communication node G to the center. Is transmitted to the communication node A.

  Further, as shown in the side view of FIG. 8B, these communication stages are arranged three-dimensionally alternately on the ceiling side and the floor side every other stage. By doing so, it is possible to realize equidistant placement between adjacent relay stage nodes. In a communication system having such an arrangement, in transmission from a certain communication node to the next stage, effective transmission is not performed to all communication nodes in the next stage due to the distance between the nodes. However, if effective transmission is performed to two or more communication nodes in the next stage, the amplification effect by relay as described above can be obtained.

  In a communication system having each configuration as shown in FIGS. 4 to 8, if all nodes are communication nodes having all functions of a transmission function, a relay function, and a reception function, transmission between any pair of nodes is possible. A general-purpose communication system can be realized. Furthermore, if the above-described double spread modulation is used, it becomes possible to amplify and transmit a multiplexed signal including a large number of data components transmitted through multiple stages of the preceding communication stage to the adjacent stage at the same timing, Excellent multi-access communication can be realized.

  Here, for the timing control signal that indicates the timing of each node, for example, a method of relaying and supplying from one control node to each node sequentially via the relay stage can be used. By this method, each node can use almost common timing within the error range of transmission delay.

FIG. 9 is a diagram illustrating a transmission symbol generation process in the transmission unit and a reception symbol demodulation process in the reception unit in the communication node. The operation of the transmission unit TX is shown in the upper half of FIG. 9 (above the horizontal dotted line), and is shown taking the communication node C ₁ as an example. The operation of the reception unit RX is shown in the lower half of FIG. 9 (below the dotted line in the horizontal direction), and the communication node D is shown as an example.

First, the operation of the transmission unit TX will be described. The data shown in the figure is obtained by multiplying the first spreading sequence ξ _C1 (the value of each chip is −1 or 1) of the sequence length 4 chips by the data d _C1 (the value of each bit is 0 or 1). A first spread signal d _C1 ξ _C1 corresponding to (1, 0) is obtained. In the lower part of the first spread signal, a signal Nd _C1 ξ _C1 is shown as a signal obtained by repeating a portion corresponding to “1” of the first spread signal N (= 8) times on the time axis. By multiplying each chip of the second spreading sequence ζ _C1 (the value of each chip is −1 or 1) of the sequence length N (= 8) chips by the first spreading signal d _C1 ξ _C1 , the signal Nd _C1 ξ _A second spread signal d _C1 ξ _C1 ζ _C1 having the same length as _C1 is generated.

In the second spread signal d _C1 ξ _C1 ζ _C1 in FIG. 9, the hatched frame indicates the non-inverted portion of the first spread signal corresponding to the chip value “1” of the second spread sequence, and the white frame portion The inversion portion of the first spread signal corresponding to the chip value “−1” of the second spread series is shown. In addition, the time axis in the figure includes a portion that is enlarged or reduced as necessary. The correspondence of the time axis between the upper and lower stages is indicated by a broken line.

The rear g chip of this second spread signal is copied, added as a guard portion to the front side of the second spread signal, and a guarded signal is generated as a baseband transmission signal S ′ _C1 . The baseband transmission signal S ′ _C1 includes a core portion having a cycle T _c and a guard portion having a cycle T _g indicated by a vertical hatching frame (front). The baseband transmission signal S ′ _C1 is shown as a signal with the original symbol period T _s . Note that in order for the communication node C ₁ to perform the relay operation, it is necessary to add the relay signal received from the previous stage to the first spread signal before performing the second spreading processing, but here the processing relating to the relay operation is omitted. doing.

Next, the operation of the receiving unit RX in the lower part of FIG. 9 will be described. Received except for a guard portion of the guarded signal R ^g _D to generate a received signal _R'D cycle T _c. The received signal R ′ _D is enlarged and displayed in the lower part of the guarded signal R ^g _D. Prepare the received signal _R'D and a second spread signal zeta _C1 gave the same period (0), the output obtained by multiplying the second spread signal zeta _C1 (0) to the received signal _R'D, the second diffusion If integration (despreading) is performed on a chip basis of the signal, a despread output E (R ′ _D ζ _C1 (0)) is obtained. This despread output is an output corresponding to a delay of zero. In general, each despread output corresponding to the number of delay chips is generated, but the illustration is omitted here.

A phase conversion signal is generated by adding and synthesizing the outputs subjected to the above-described phase correction for each of them. Signals received over the link between the communication node C _n also generates a phase conversion signal obtained by despreading the same manner. An addition output obtained by adding the phase conversion signals that have passed through all of these links becomes a combined conversion output R ^s _D. In FIG. 9, the combined conversion output R ^s _D is shown as a signal with the original symbol period T _s . When the communication node D performs the relay operation, the combined conversion output R ^s _D is stored in the storage means as a relay storage signal and transmitted to the next stage at the next transmission timing. The communication node D can also extract and receive data from the combined conversion output R ^s _D. For example, if despreading the composite converted output R ^s _D by the first spreading sequence xi] _C1, it can be communication node C ₁ seeks soft output to d _C1 of the transmitted data d _C1.

As spreading codes shown in Equations 1 and 4, a commonly used spreading code (spreading sequence set) is used. If an orthogonal code capable of complete separation between sequences is used, an excellent operation is performed. Examples of orthogonal codes include Hadamard codes in an environment where a received symbol does not include a delayed wave, ZCZ (Zero Correlation Zone) codes, and DFT (Discrete) in an environment where a delayed wave is included.
(Fourier Transform) code is used. An M sequence that is a quasi-orthogonal code can also be used.

FIG. 10 is a block diagram showing the configuration of the communication node. In FIG. 10, reference numerals and the like are described taking the communication node C ₁ as an example. The symbol transmission unit includes five upper blocks, a first transmission unit TX-I, a second transmission unit TX-II, a first reception unit RX-I, a second reception unit RX-II, and a data detection unit DX. . Here, it is assumed that the communication node C ₁ is driven by two transmission timings a and b. The first transmission unit TX-I generates a first spread signal d _C1 ξ _C1 of transmission data starting from the communication node C ₁ and temporarily stores it in the memory by a write signal W (b) indicating the timing b. Then, the first spread signal read from the memory is sent to the next stage by the read signal R (a) indicating the next timing a.

The second transmitter TX-II spreads the transmission signal S ^s _C1 with the second spreading sequence ζ _C1 and performs carrier modulation with the carrier wave f ₀ . The first receiver RX-I demodulates the received signal with the local carrier frequency f ₀ , despreads with the second spread sequence ζ _Bn, and generates a combined conversion output R ^s _C1 that combines them. The second receiving unit RX-II stores this combined conversion output R ^s _C1 as a write signal W (b) and outputs it as a read signal R (a). For example, the data detection unit DX generates detection data ^ d _A by hard-decisioning the output despread by the first spreading sequence ξ _A used by the communication node A.

The lower part of FIG. 10 is a timing generation unit, which includes a timing control signal generator OTG, a timing generator TG, a carrier wave generator CG, and a timing control signal modulator TTX. Timing control signal generator OTG incorporates an independent frequency transmitter, as well as generating a fundamental frequency f _00, the timing control signal gamma _a, generates gamma _b. The timing generator TG generates a write signal W (b) and a read signal R (a) to the memory used in this communication node based on the output of the timing control signal generator OTG. The carrier wave generator CG generates a carrier wave frequency f ₀ and timing control signal intermediate frequencies f _a ² and f _b ² .

The timing control signal modulator TTX is a modulator of the timing control signals γ _a and γ _b and transmits a timing control signal Γ () transmitted on a band shifted from the data transmission band by intermediate frequencies f _a ² and f _b ^2. f _a ² ) and Γ (f _b ² ) are output. Here, it is assumed that the communication node C ₁ is a control node. Since the control signals Γ (f _a ² ) and Γ (f _b ² ) are sequentially transmitted to the other communication nodes via the adjacent communication nodes, all the communication nodes use substantially the same timings a and b. become able to.

When the communication node C ₁ is a general communication node other than the control node, the timing control signals Γ (f _a ¹ ) and Γ (f _b ¹ ) received from the preceding communication node as inputs of the timing control signal generator OTG are used. Added. A general communication node generates timing control signals γ _a and γ _b based on these timing control signals from the previous stage. As described above, the timing control signal is distributed from the control node to each general communication node. The reset signal can be distributed to each communication node by the same means.

FIG. 11 is a block diagram illustrating details of the symbol transmission unit of the communication node. The first transmission section TX-I, comprises a multiplier MOD as modulators, the memory M _1. The second transmission unit TX-II adds the guard part shown in FIG. 9 to the signal S ⁰ _C1 obtained by adding the transmission signal d _C1 ξ _C1 to the combined conversion output R ^s _C1, and then uses the second spreading sequence ζ _C1 . The second spreading process and carrier wave modulation by the carrier wave f ₀ are performed. This output is amplified by the power amplifier AMP _S and then transmitted.

The first reception unit RX-I includes a demodulation unit DEM, a link signal synthesis unit LSS, and a pilot response memory unit PRM. In the demodulation unit DEM, the reception input from the antenna is applied to the amplifier AMP _R. Duplexer control input C _S, the transmission signal is intended to prevent the applied to the amplifier AMP _R, at the time of transmission operation to cut off the input of the amplifier AMP _R. Demodulation by the local carrier f ₀ is performed by the multiplier MOD and the low-pass filter LPF, and a demodulated output R ′ _C1 is generated.

The link signal synthesizer LSS is composed of correlators MF _E (ζ, θ) _Bn (n = 1, 2, 3) having three phase rotation functions. Each correlator MF _E (ζ, θ) _Bn separates link signal components by despreading using the second spreading sequence ζ _Bn and then forwards each link signal output from the pilot response memory unit PRM. Correct the phase rotation using the pilot response made. These phase conversion outputs are added in the adder Σ, and a combined conversion output R ^s _C1 is generated.

In the method of generating the combined conversion output R ^s _C1 , when the above-described method of generating supplement 1 or supplement 2 is performed, the following is performed. In the case of the generation method of Supplement 1, each correlator MF _E (ζ, θ) _Bn has a predetermined threshold value in the power level P _Bn transferred from the pilot response memory unit PRM with respect to the phase conversion output. A measure is taken not to transfer the link signal corresponding to the low power level to the adder Σ. In addition, in the case of the generation method of supplement 2, these phase conversion outputs are corrected to a power level proportional to the S / N ratio of each link using a weighting factor w described later, and then transferred to the adder Σ.

The switch S shown in FIG. 11 transmits the received demodulated signal R ′ _C1 so that only the pilot signal component received in the pilot transmission period of the signal frame or the pilot period in the received symbol is transferred to the pilot response memory unit PRM. The transmission timing to the pilot response memory unit PRM is controlled. This pilot signal is added to three correlators MF (ζ _Bn ) (n = 1, 2, 3) and the subsequent phase rotation detector D (θ) corresponding to the number of input links, and the correlator The phase rotation amount is obtained by using the real part and imaginary part components of the output.

The phase rotation detector D (θ) also detects the power level P _Bn of the pilot signal by adding this correlator output to a built-in rectifier. Further, the phase rotation detector D (θ) adds the demodulated signal R ′ _C1 to the integrator operating on the data symbol base, obtains the noise power estimation value included in the data symbol from the output, and outputs it to each link. The weighting coefficient w is obtained from the corresponding S / N ratio. These outputs (θ, P, w) _Bn are accumulated and stored in a memory M ₃ having an attenuation time constant, and these pieces of information are transferred to the link signal synthesis unit LSS.

The second receiving unit RX-II stores the combined conversion output R ^s _C1 in the memory M ₂ by the write signal W (b), reads it by the read signal R (a), and transfers it to the transmission adder Σ. In the case of the example in the figure, the detection unit DX generates a soft output by despreading with the first spreading sequence ξ _A of the communication node A in the correlator MF (ξ _A ). Further, the soft output is determined by the hard decision circuit DEC, and a replica (^ d _A ) of the transmission data d _A is generated.

  Next, an embodiment in which a communication node attached to a mobile unit (hereinafter referred to as a mobile unit node) moves in a transmission network configured as shown in FIG. 1 and transmits / receives to / from each communication node on the network. Will be described. First, a case where the mobile node has a built-in power supply and can transmit by itself, that is, a case where the mobile node is an active tag will be described. FIG. 12 is a diagram showing an outline of a communication system including such a mobile node.

In FIG. 12, the communication stage B indicated by a vertically long rectangular frame is a plurality of communication nodes B _n arranged substantially in an annular shape (not necessarily an exact annular shape) like the communication stage B in FIG. It consists of Similarly, the communication stages C and D are composed of a plurality of communication nodes arranged in an annular shape. The mobile node M starts from a position M ₀ indicated by a black circle, and moves to a position M ₄ before the communication node E via each link indicated by a dotted line. The mobile node M moves from the left to the right in the figure in the approximate center of the internal space of the annular communication stage arranged in cascade.

The ring moving time zones that pass through the vicinity of the center of the communication stages B, C, and D are set as moving periods T _B , T _C , and T _D , respectively. On the other hand, here, the communication node A is a control node, and the communication node A receives four-phase timing control signals Γ (f _a ⁰ ), Γ (f _b ⁰ ), Γ (f _c ⁰ ), and Γ (f _d ⁰ ). Send. These timing control signals are sequentially relayed to the communication node E via the communication stages B, C, and D as described above, and also transmitted to the mobile node M. For example, the movement period T _B is moving in the vicinity of the mobile node M communication stage B, the mobile node M timing control signal 4 phases which each node has relayed transmission of the communication stage B Γ (f _a ¹⁾ , Γ (f _b ¹ ), Γ (f _c ¹ ), Γ (f _d ¹ ) are received. The time slots of the period _TTS after receiving these relay signals are represented by symbols a, b, c, and d, and are used for transmission between the mobile node M and the fixed node.

  Using these timing control signals, the communication node of each communication stage uses two timings assigned to the communication stage among the four-phase timings a, b, c, and d using four drive phases. To send and receive. For example, the communication node in communication stage B uses timing b for transmission and timing a for reception. Timing assigned to each communication stage is, for example, communication stage A (transmission: a, reception: none), communication stage B (transmission: b, reception: a), communication stage C (transmission: c, reception: b), communication Stage D (transmission: d, reception: c), communication stage E (transmission: none, reception: d).

FIG. 13 is a diagram illustrating the relationship between the movement position (tag position) of the mobile node M and each timing. The vertical axis on the left side of FIG. 13 indicates the timing of the four phases, but serial numbers 0 to 11 are assigned to the time slots of the timings of the four phases, and codes (a, b, c, d) indicating the four phases are assigned. A time slot number is added later. In this example, the relationship between the time slot period T _TS and the movement period T _M (T _B , T _C , T _D ) used for transmission and reception is as follows.
N _T = T _M / T _TS Expression 17

In Equation 17, N _T is the number of phases of the drive phase, and in this case, N _T = 4. If Equation 17 is satisfied, the time slot of each phase in _NT can be used once when the mobile node M passes through each communication stage. Therefore, the mobile node M can communicate with each communication stage using the multiphase timings a, b, c, and d between the fixed communication nodes. As shown by the solid line R in FIG. _{13 (M 0 → M 4)} , for example, in the movement period T _B in which the mobile node M is passed through the communication stage B, the mobile node M at timing b1 is the communication of the communication stage B The transmission signal of the node B _n can be received, and can be transmitted from the mobile node M to the communication stage B at the timing a0. In the movement cycle T _C , the mobile node M can transmit to each communication node C _m of the communication stage C at timing b5 and can receive from each communication node C _m at timing c6. In the vertical axis on the left side of FIG. 13, timing symbols used for transmission / reception in this example are underlined.

  In this manner, transmission / reception between the mobile node M and all communication nodes in the nearby communication stage is performed. In parallel with this communication, each communication node in each communication stage receives symbols received from the mobile node M at timings (a), (b), (c), and (d) shown in the upper part of FIG. Since it is always transmitted to each communication node in the next communication stage together with other received symbols not displayed, the last communication node E can receive all the symbols transmitted by the mobile node M. At this time, since the signal is amplified corresponding to the number of relay stages, the signal received first can be received with a higher S / N ratio. In this way, a communication system of a mobile body and a fixed communication stage can be realized.

Also, another mobile node M ′ following the mobile node M can communicate with a communication node at the communication stage B in a cycle T _C , for example. Further, another mobile node that moves close to the mobile node M can communicate with the same communication node with which the mobile node M communicates in the same movement cycle. For this purpose, a method such as using a transmission signal modulated by a spreading sequence different depending on the mobile node may be used.

Next, the case where the mobile node M ′ moves in the left direction from the communication node E side toward the communication node A in FIG. 12 will be described. Mobile node M'moves from the position M ₄ to the left, communication stage D, C, _T'D movement cycle of sequentially passing through the B, _T'C, and _T'B. The movement periods T ′ _D , _{T ′ C} , _{T ′ B} are shown on the right side of FIG. Since the transmission / reception timing of each communication stage supplied from the communication node A does not change, the relationship between the position of the mobile node M ′, the movement cycle, and the transmission / reception timing is indicated by a broken line L (M ′ ₄ → M ′ ₀ ) in FIG. Indicated. That is, passing transmission and reception timings in time zone _T'D communication stage D is a timing c2, d3. The transmission / reception timing used in each movement cycle is shown at the right end of the figure.

  Next, a case where the mobile node does not incorporate a power source, that is, a case where the mobile node is a passive tag will be described. FIG. 14 is a diagram showing an outline of a communication system including such a mobile node. FIG. 15 is a side view of this communication system. Also in this communication system, the communication stages B, C, D are composed of a plurality of communication nodes arranged in an annular shape. As an application example of such a communication system, a system in which an object with a tag attached is moved by a belt conveyor or the like, and movement branching control according to a destination according to information held by the tag can be considered.

The mobile node M is first moved from the initial position M ₀₀ to the position M ₀ and then moved from the position M ₀ → the position M ₁ → the position M ₂ → the position M ₃ . Data transmission between the mobile node M and the fixed communication stage is the same as the communication system shown in FIG. The timing control signal is relayed from the communication node A to the communication stages B, C, and D.

Relationship between the moving period of the time slot T _S and the mobile node M in 4-phase timing is also the same as FIG. 13. In time slot a0 to mobile node M is included in the movement period T _B which has moved to a position near M ₀ of the communication stage B, the communication node A transmits the read signal R _a0 (unmodulated carrier). Receiving this, the mobile node M transmits a response signal S _a0 including information stored in the mobile node M by a known technique. This response signal S _a0 can be received by all communication nodes in the communication stage B.

Similarly, mobile node M is moved to the position M _1, in the time slot b5 included in the movement period T _C, the communication node B _n transmits a read signal R _b5. In this case, since all the communication nodes belonging to the communication stage B transmit the read signal R _b5 , the mobile node M has a power N _s times the power received from one node (N _s : the number of nodes in the communication stage), It can be received under the space diversity effect. The mobile node M that has received this transmits a response signal S _b5 including information held by the mobile node M at this time. All nodes in the communication stage C can receive the response signal S _b5 .

  By repeating such an operation, the information transmitted from the mobile node M is received at each communication stage B, C, D, and these received signals are transmitted to the communication node E by the right direction transmission function of the fixed network. The Therefore, the communication node E can receive this response signal at a high S / N ratio by increasing the signal level for each relay stage as described above.

  Note that the write signal to the mobile node M can be transmitted by using a different intermediate frequency instead of the read signal at the above-described read signal transmission timing.

  In the present invention, as described above, a large number of wireless communication nodes are dispersedly arranged for each communication stage in a predetermined communication space, and a data transmission / reception function, a relay transmission function, and a transmission / reception timing control function are provided in each communication node. doing. The control node has a function of transmitting a two-phase or multi-phase timing control signal, and a general communication node has a relay transmission function of the timing control signal. Accordingly, it is possible to provide a multi-access communication system in which each communication node performs data transmission / reception according to the timing control signal received from the control node. In this communication system, a plurality of data transmissions between any pair of communication nodes in the network can be simultaneously performed by identifying the start node of transmission data by means of time division, frequency division, or code division.

  By spreading the transmission signal of each communication node by the spread sequence for link identification, it is possible to identify and separate the link signal received from each preceding communication node. Furthermore, by providing each communication node with a function of correcting a change in carrier wave phase that occurs in the propagation process, it is possible to correct the phase rotation that has occurred in the propagation process of link signals received from a plurality of preceding communication nodes. As a result, in data transmission between a desired pair of communication nodes, the reception S / N ratio increases as the number of communication stages passed through and the number of nodes constituting each communication stage increase. Therefore, even in a space where the reception level fluctuation is large such as a Rayleigh wave propagation environment, it is possible to provide stable communication with a low error generation probability using low transmission power.

  Since this communication system uses a spread sequence for link identification, it requires a larger number of frequency bands than a band necessary for transmission of simple binary data. However, as described above, the reception S / N ratio is extremely large in a system having a large number of nodes and relay stages. If multilevel multiphase transmission such as QAM is performed using this S / N ratio increase characteristic, it is possible to improve frequency utilization efficiency and dramatically increase communication capacity. It is possible to achieve much better characteristics than conventional methods.

  On the other hand, in the relay stage and the reception stage, the complicated interference removal process necessary for the method of removing the interference component is not required according to the principle of the MIMO method. In the system of the present invention, the input of the relay stage does not include an interference component, but includes all code division signal components by the first spreading code transmitted from each node in a multiplexed form. A receiving node desiring to receive data transmitted as a starting node by a certain node can receive the desired data by detecting a soft output obtained by despreading the received signal with the corresponding first spreading code.

  In addition, since the MIMO scheme uses non-correlation between elements of the propagation matrix, it does not function in a line-of-sight propagation environment, but the present invention has an advantage that can be applied to both a line-of-sight and a line-of-sight. In the relay transmission method using the MIMO interference cancellation function, it is necessary to install a much larger number of relay nodes than the number of transmission / reception node pairs. The present invention has no restriction on the number of nodes in the relay stage.

  In addition, the present invention uses a time division transmission method between two or multi-phase communication stages using a timing control signal, and forward, reverse, forward / reverse bidirectional simultaneous transmission, or center in a two-dimensional or three-dimensional space. Since a flexible network can be configured by realizing transmission in the opposite direction from the part to the periphery, and selection switching control of those transmission modes, it is possible to adapt to various communication demands assumed in ubiquitous communication.

  In addition, when applied to communication between an active tag or passive tag and a fixed communication network, a highly reliable classification delivery system by low power communication can be realized. Furthermore, if the multistage relay technology of the present invention is applied to intra-cell communication in a mobile communication system, the S / N ratio is increased by multistage relay and the same symbol component is transmitted and received many times, thereby stabilizing the base station and the mobile node. Low power communication can be realized.

  The distributed node communication system of the present invention has a large communication mode and can be applied to various forms of application fields. It is a communication system with good compatibility with ubiquitous communication.

A Sending node B, C Relay stage D Receiving node

Claims (9)

A transmission node (A) for transmitting a radio signal;
A relay stage composed of one or more relay nodes that receive a radio signal transmitted from the transmission node and store a demodulated signal obtained by demodulating the radio signal, and convert the stored demodulated signal into a radio relay signal and transmit the radio signal. B, C)
A receiving node (D) for receiving a radio signal;
Controls the transmission start time of the transmission node and the relay node and the reception start time of the relay node and the reception node, and starts reception and transmission at the same timing for all relay nodes belonging to the same relay stage. Transmission / reception time control means for performing the start operation,
A distributed node communication system in which one or more relay stages are arranged in a communication space between the transmission node and the reception node,
The transmission node includes means for modulating a link identification spreading sequence with transmission data to generate a baseband transmission signal, and means for transmitting a radio signal generated by modulating a carrier wave with the baseband transmission signal And
The relay node demodulates the received radio signal with a local carrier wave to generate a baseband received signal, and for each soft output obtained by despreading each using a link identification spreading sequence used by the previous node, And each corrected soft output is generated by performing phase correction processing for correcting the phase rotation amount of the carrier wave generated by transmission between the relay node and the relay node, and a combined corrected soft output is generated by adding the corrected soft outputs. A combined modified soft output generating means, a means for generating a baseband transmission signal by modulating a spread sequence for link identification with the combined corrected soft output, and transmitting a radio signal generated by modulating a carrier wave with the baseband transmitted signal With the means to
The receiving node demodulates the received radio signal with a local carrier wave to generate a baseband received signal, and for each soft output obtained by despreading each using the link identification spreading sequence used by the preceding relay node, Each corrected soft output is generated by performing phase correction processing for correcting the phase rotation amount of the carrier wave generated by the transmission between the relay node and the receiving node, and the combined soft output is obtained by adding these corrected soft outputs. A distributed node communication system comprising: a composite corrected soft output generating means for generating; and means for detecting transmission data transmitted by the transmitting node by making a hard decision on the composite corrected soft output. A transmission function for transmitting a radio signal generated by modulating a carrier wave with transmission data and a demodulated signal generated by demodulating a received radio signal with a local carrier wave are stored, and the stored demodulated signal is converted into a radio signal. Communication stages (A, B) having one or more communication nodes each having a relay function for relay transmission and a reception function for detecting transmission data using the demodulated signals, all of which operate at the same timing. , C, D) and
There is a transmission / reception time control means for controlling the transmission start time and reception start time of the communication node and causing all communication nodes belonging to the same communication stage to perform reception start and transmission start operations at the same timing. And
A distributed node communication system in which a plurality of communication stages are arranged in a communication space,
The communication node is
For each soft output obtained by despreading the demodulated signal generated by demodulating the received radio signal with the second spreading sequence used by each communication node in the preceding communication stage, Each corrected soft output is generated by applying phase correction processing that corrects the phase rotation amount of the carrier wave generated by transmission between the local communication nodes, and a combined corrected soft output is generated by adding these corrected soft outputs. A composite modified soft output generating means,
Means for generating a first spread signal by modulating a first spread sequence for transmission point identification with transmission data starting from the communication node;
Means for further modulating a second spread sequence for transmission link identification with an output obtained by adding the first spread signal and the combined modified soft output to generate a second spread signal;
Means for transmitting a radio signal generated by modulating a carrier wave with the second spread signal;
Means for generating a received soft output signal by despreading the composite corrected soft output by a first spreading sequence used by a communication node of a counterpart station that has transmitted data to be acquired; and hard-decision of the received soft output signal Thus, a distributed node communication system comprising means for detecting transmission data transmitted by the communication node of the counterpart station. The distributed node communication system according to any one of claims 1 and 2,
The combined modified soft output generation means is configured to output each demodulated signal to each soft output obtained by despreading the demodulated signal using a second spreading sequence used by each communication node in the previous communication stage and each communication node in the previous stage. Each corrected soft output is generated by performing a phase correction process for correcting the phase rotation amount of the carrier wave generated by transmission between communication nodes, and the average power of these corrected soft outputs is equal to or less than a preset threshold value. A distributed node communication system for generating the composite corrected soft output by adding all corrected soft outputs except for the corrected soft output. The distributed node communication system according to any one of claims 1 and 2,
The combined modified soft output generation means is configured to output each demodulated signal to each soft output obtained by despreading the demodulated signal using a second spreading sequence used by each communication node in the previous communication stage and each communication node in the previous stage. Each corrected soft output is generated by performing a phase correction process for correcting the phase rotation amount of the carrier wave generated by transmission between the communication nodes, and the voltage amplitude of the corrected soft output is converted to the signal pair included in the corrected soft output. A distributed node communication system that generates an adjusted soft output adjusted according to a noise ratio and generates the combined corrected soft output by adding the adjusted soft outputs. A distributed node communication system according to claim 2, comprising:
The distributed communication system, wherein the communication stage is arranged so that an outer communication stage adjacent to the communication stage surrounds the inner communication stage in a ring shape with respect to the inner communication stage. A distributed node communication system according to claim 2, comprising:
The communication stages of a plurality of stages are sequentially arranged at a distance,
The distributed node communication system, wherein the communication stages include a plurality of communication stages, and the communication node includes a plurality of communication stages. A distributed node communication system according to claim 2, comprising:
The communication stage includes an annular communication stage composed of a plurality of the communication nodes arranged in an annular shape,
A distributed node communication system, wherein the plurality of communication stages are arranged at a distance from each other in a direction orthogonal to a plane including the ring of the annular communication stage. A distributed node communication system according to claim 7,
The mobile station (M) moves along the vicinity of a curve connecting the center points of the annular communication stages (B, C, D);
The transmission / reception time control means starts reception at the same timing for all communication nodes belonging to the annular communication stage located in the vicinity of the mobile station (M) as the mobile station (M) moves. And start the transmission to the mobile station (M) at a timing at which communication with the communication node in the annular communication stage in the vicinity of the mobile station (M) is possible. And reception start operation,
The mobile station (M)
For each soft output obtained by despreading the demodulated signal generated by demodulating the received radio signal with the second spreading sequence used by each communication node of the annular communication stage in the vicinity, Each corrected soft output is generated by applying a phase correction process for correcting the phase rotation amount of the carrier wave generated by transmission between each communication node and the own station, and a combined corrected soft output is generated based on these corrected soft outputs. Synthetic modified soft output generating means for generating;
Means for generating a received soft output signal by despreading the composite modified soft output with a first spreading sequence used by a communication node of a partner station that desires to receive data; and hard-decision of the received soft output signal A distributed node communication system comprising: means for detecting transmission data transmitted by the communication node of the counterpart station. A distributed node communication system according to claim 7,
The mobile station (M) moves along the vicinity of a curve connecting the center points of the annular communication stages (B, C, D);
Each communication node of the adjacent annular communication stage behind the mobile station (M) that has already passed through transmits an unmodulated carrier wave at a transmission timing assigned to the annular communication stage,
The mobile station (M) reads and transmits data stored in the mobile station corresponding to the reception of the unmodulated carrier wave,
Each communication node in the annular communication stage adjacent to the front in the moving direction of the mobile station (M) receives the transmission data of the mobile station (M),
Further, each communication node in the adjacent annular communication stage behind the mobile station (M) that has already passed uses a carrier wave having a frequency different from that of the unmodulated carrier wave at the transmission timing assigned to the annular communication stage. Send a transmission signal containing the write data,
The mobile station (M) is a distributed node communication system in which the received write data is stored in its own storage means.

Images