CN102307074A - Communication system - Google Patents

Abstract

The present invention provides a communication system comprising a transmitting device that transmits a signal using a two-dimensional spread code spread in a time direction and a frequency direction, and a receiving device that receives the signal transmitted from the transmitting device , the transmission device has: a selection unit that selects spreading codes that are orthogonal to each other in at least one of the time direction and the frequency direction; and a transmission unit that uses the selected spreading codes to signal spreading, and sending the signal, the selected spreading codes can be divided into two or more parts respectively, in at least one direction of the time direction and the frequency direction, and the selected other spreading codes The same parts are orthogonal to each other.

Description

Communication Systems

This application is an invention patent application with the original application number 200480044600.2 (international application number: PCT/JP2004/018661, application date: December 14, 2004, invention name: spreading code distribution method, reverse spreading method, sending device, receiving device , communication device, wireless base station device and mobile terminal device).

technical field

The present invention relates to a technique for transmitting and receiving data in units of channels using a two-dimensional spreading code that spreads in the time direction and the frequency direction.

Background technique

In recent years, in the field of mobile communication, as a multi-carrier modulation method, for example, OFDM-CDMA method that combines OFDM (Orthogonal Frequency Division Multiplexing) modulation method and CDMA (Code Division Multiple Access) method Having attention. The OFDM modulation method is a modulation method with high frequency utilization efficiency using a plurality of subcarriers orthogonal to each other, and the CDMA method is a modulation method using a spread spectrum communication method with strong anti-interference. The OFDM-CDMA method combining these two methods spreads at least one of the time direction and the frequency direction using a two-dimensional spreading code capable of spreading in the time direction and the frequency direction. Such a system is described in Patent Documents 1 and 2, for example.

In mobile communications, the state of a channel transmission path varies with conditions. If the state of the transmission path deteriorates, the transmission characteristics will deteriorate or the system capacity will decrease. In the prior art described in Patent Document 1, in order to suppress deterioration of transmission characteristics or reduction of system capacity, spreading factors in the time direction and frequency direction are set on the transmission side according to the state of the channel transmission path. For example, the longer the maximum delay time on the transmission path, the smaller the spreading factor in the frequency direction is, and the deterioration of the orthogonality between spreading codes is suppressed. In addition, the higher the maximum Doppler frequency on the transmission path, the lower the spreading factor in the time direction is set, and the deterioration of the orthogonality between spreading codes is suppressed.

In the prior art described in Patent Document 1, when transmitting pilot symbols (pilot symbols) for channel estimation and the like on the transmitting side, different spreading factors are applied to each user (receiving side) depending on the state of the transmission path, Or apply the same expansion rate to multiple users.

In the former method, several spreading codes are required for the user, resulting in a reduction in the overall system capacity. Thus, the utilization efficiency of the system capacity is reduced. In addition, power corresponding to the number of users is required, so power consumption also increases.

On the other hand, in the latter method, each user performs inverse spreading with the same spreading rate, so power consumption can be relatively suppressed. However, the receiving characteristics of each user are different due to the state of each transmission path, so it is very difficult to directly determine the optimum spreading rate for each user. Therefore, it is considered that the point is to allow a plurality of users to receive data with spreading ratios corresponding to their respective transmission path states while maintaining high utilization efficiency of the system capacity.

Patent Document 1: Japanese Patent Laid-Open No. 2003-46474

Patent Document 2: Japanese Patent Laid-Open No. 2004-48117

Contents of the invention

The object of the present invention is to provide a technique capable of enabling multiple users to use the corresponding communication system while maintaining high utilization efficiency of the system capacity in a communication method using two-dimensional spreading codes such as the OFDM-CDMA method for spreading. The data is received according to the spreading rate of the respective transmission path states.

The communication system of the present invention includes a transmitting device and a receiving device, the transmitting device transmits a signal using a two-dimensional spread code spread in the time direction and the frequency direction, and the receiving device receives the signal transmitted from the transmitting device, characterized in that , the transmission device has: a selection unit that selects spreading codes that are orthogonal to each other in at least one of the time direction and the frequency direction; and a transmission unit that uses the selected spreading codes to signal spreading, and sending the signal, the selected spreading codes can be divided into two or more parts respectively, in at least one direction of the time direction and the frequency direction, and the selected other spreading codes The same parts are orthogonal to each other.

In addition, it is preferable that the spreading code divided into two or more parts each have a spreading rate smaller than an original spreading rate in at least one of the time direction and the frequency direction.

In the present invention, at least one of the time direction and the frequency direction is orthogonal to each other when despreading at least one of the time direction and the frequency direction with the original spreading rate, and at least one of the time direction and the frequency direction is smaller than the original spreading rate The two-dimensional spreading codes which are orthogonal to each other even when the spreading rates are inversely spread are selected, and the spreading codes assigned to the respective channels are determined from among the spreading codes to be selected. Since channel symbols are spread using the spread codes allocated in this way, the symbols can always be inversely spread using a plurality of spreading rates on the receiving side. In this way, an environment can be realized in which a more appropriate spreading rate can be selected according to the state of the transmission path and reverse spreading can be performed.

Since received symbols can be inversely spread using a plurality of spreading rates, a plurality of users (receiving apparatuses) can select a spreading rate based on the result of performing the inverse spreading from one channel. In addition to the results obtained by inverse spreading, focusing on other factors that affect the state of the transmission path, such as the moving speed of the receiving side relative to the symbol sending side, etc., can also dynamically perform appropriate selection (including updating) of the spreading rate at any time. As a result, inverse spreading can be performed using a more appropriate spreading rate for the channel state, and high system capacity utilization efficiency can always be maintained. In the case of notifying the transmission side of the transmission path state confirmed or estimated on the receiving side and reflecting the transmission path state on the allocation of spreading codes, it is possible to more reliably allocate the state of the transmission path to the receiving side. Appropriate extension code. Therefore, the reception characteristics obtained as a result of inverse spreading can be more reliably maintained at a high level at all times.

Description of drawings

FIG. 1 is a diagram illustrating a code domain of a two-dimensional spread code used in the present embodiment.

FIG. 2A is a diagram explaining a method of extracting part of a two-dimensional spread code (in the case of SF1×4).

FIG. 2B is a diagram explaining a method of extracting part of the two-dimensional spread code (in the case of SF4×4).

FIG. 2C is a diagram explaining a method of extracting part of the two-dimensional spread code (in the case of SF2×2).

FIG. 3 is a diagram illustrating a method of assigning two-dimensional spread codes according to the present embodiment.

FIG. 4 is a diagram illustrating two-dimensional spreading codes to be allocated to other channels when two-dimensional spreading codes are allocated to two channels.

FIG. 5 is a diagram illustrating two-dimensional spreading codes to be allocated to other channels when two-dimensional spreading codes are allocated to three channels.

FIG. 6 is a diagram illustrating the configuration of a communication device according to the first embodiment.

Fig. 7 is a diagram illustrating the configurations of a spreading code generation unit and a two-dimensional spreading unit.

Fig. 8 is a diagram (Part 1) illustrating an example of contents of a spreading code assignment table.

Fig. 9 is a diagram (Part 2) illustrating an example of contents of a spreading code allocation table.

FIG. 10 is a diagram illustrating the relationship between the channels in the spreading code allocation table shown in FIG. 8 and the code domains occupied by the two-dimensional spreading codes to which the channels are allocated.

Fig. 11 is a flowchart of spreading code allocation table creation processing.

FIG. 12 is a diagram illustrating a configuration of a communication device that communicates with the communication device shown in FIG. 6 .

FIG. 13 is a diagram illustrating the configuration of a pilot despreading unit shown in FIG. 12 .

FIG. 14 is a diagram illustrating an update unit of an expansion rate.

FIG. 15 is a diagram explaining the transition between spreading ratios accompanying the updating of the spreading ratios.

FIG. 16 is a diagram illustrating the configuration of a communication device according to the second embodiment.

FIG. 17 is a diagram illustrating a configuration of a communication device that communicates with the communication device shown in FIG. 16 .

FIG. 18 is a diagram illustrating the configuration of a communication device according to a third embodiment.

FIG. 19 is a diagram illustrating the configuration of a communication device according to a fourth embodiment.

FIG. 20 is a diagram illustrating the configuration of a transmission device according to a fifth embodiment.

FIG. 21 is a diagram illustrating the configuration of a transmission device according to a sixth embodiment.

FIG. 22A is a diagram illustrating an example of spreading ratio allocation in the sixth embodiment (in the case of SF4×1).

FIG. 22B is a diagram illustrating an example of spreading ratio allocation in the sixth embodiment (in the case of SF2×2).

FIG. 22C is a diagram illustrating an example of spreading ratio allocation in the sixth embodiment (in the case of SFN×4 (N=1, 2, 4)).

FIG. 23 is a diagram illustrating the configuration of a transmission device according to a seventh embodiment.

Detailed ways

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<First Embodiment>

FIG. 1 is a diagram illustrating a code domain of a two-dimensional spread code used in the present embodiment.

In this code domain, the maximum spreading rate is 16 in both the time direction and the frequency direction. As the spreading code, a spreading code that is inversely spread or is orthogonal even if it is inversely spread with a spreading rate different from the original spreading rate (spreading rate used for spreading on the transmitting side) in both the time direction and the frequency direction is used. This spreading code can be generated using an OVSF (Orthogonal Variable Spreading Factor, Orthogonal Variable Spreading Factor) code. The spreading code generated using this OVSF code will be specifically described before proceeding to the description of FIG. 1 .

It is well known that OVSF codes can sequentially generate codes whose code length is twice that of the following formula (1).

[Formula 1]

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 3</span>}}\\ <span\; class="notranslate">\; \&CenterDot;</span>\\ <span\; class="notranslate">\; \&CenterDot;</span>\\ {\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}& {\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}& <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}& <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\\ <span\; class="notranslate">\; \&CenterDot;</span>& <span\; class="notranslate">\; \&CenterDot;</span>\\ <span\; class="notranslate">\; \&CenterDot;</span>& <span\; class="notranslate">\; \&CenterDot;</span>\\ {\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}& <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\end{array}\right]<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

The codes generated by the formula (1) have the property of maintaining orthogonality between not only the same code length, but also between different code lengths as long as they are not derived from a tree.

A spreading code (OVSF code) for two-dimensional spreading can be expressed as C _m,k ×C _n,l . Wherein, C _{m, k} , C _{n, l} represent spreading codes in the time direction and the frequency direction, respectively. The subscripts thereof indicate a spreading rate (hereinafter also denoted as "SF") and a code number. For example, "m, j" indicates the jth spreading code with spreading rate m. Here, "x" represents the Kronecker product (direct product) of the matrix. A specific example thereof is shown below.

[Formula 2]

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}"><figure-callout\; id="3"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}">C</figure-callout></figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4,3</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="C"\; filenames="HDA0000080847050000031.png,HDA0000080847050000041.png"\; state="\{\{state\}\}"><figure-callout\; id="1"\; label="C"\; filenames="HDA0000080847050000012.png,HDA0000080847050000013.png"\; state="\{\{state\}\}">C</figure-callout></figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4,1</span>}}<span\; class="notranslate">\; =</span>\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right]<span\; class="notranslate">\; \&times;</span>\left[\begin{array}{cccc}\mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{cccc}\mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the matrix representation of the two-dimensional spreading code, the row direction (horizontal direction) is usually used as the frequency axis, and the column direction (vertical direction) is used as the time axis for representation. Multiplication is performed by the law of 2. The transpose notation is omitted in the 4x4 matrix in equation (2). This equation (2) shows that in a two-dimensional spreading code composed of spreading codes with spreading ratios of 4 in the time domain and frequency domain, each of the spread codes is composed of a total of 16 (4×4) chips. The relationship between the spreading rates in the time direction and the frequency direction in this spreading code is expressed as "SF4x4". "4" placed before "x" indicates the spreading rate in the time direction, and "4" placed thereafter indicates the spreading rate in the frequency direction. The same notation is used for other expansion ratio relationships.

Different spreading codes C _{m1, k1} × C _{n1, l1} and C _{m2, k2} × C _{n2, l2} in at least any one of the relationship of C _{m1, k1} ⊥ C _{m2, k2} and C _{n1, l1} ⊥ _{C n2, l2} Orthogonal when the relationship holds. That is, when at least any one of the time direction and the frequency direction is orthogonal, they are orthogonal as a whole.

The code domain of the spreading code generated using the OVSF code becomes a unique code domain according to the spreading rate and code number of the spreading code. Fig. 1 shows the relation of spreading codes and their code domains adopted in time direction and frequency direction respectively. For example, the two-dimensional spreading code C _8,6 ×C _4,0 occupies the corresponding code fields because the spreading code in the time direction is C _8,6 and the spreading code in the frequency direction is C _4,0 . Both the vertical axis and the horizontal axis indicate that the larger the spreading rate is, the smaller the code space occupies. This also makes the code field smaller.

In order to make not only the entire two-dimensional spread code (chip) orthogonal to each other, even if only a part is taken out, this part is also orthogonal to other two-dimensional spread codes, as long as the part you want to take out from the spread code is selected as a two-dimensional spread code code, it is only necessary to generate two-dimensional spreading codes so that they are orthogonal to each other. The selected two-dimensional spreading code corresponds to a spreading code smaller than either the original spreading rate in the time direction or the frequency direction of the two-dimensional spreading code used for spreading.

For example, the two-dimensional spreading code C _4,3 ×C _4,1 has a spreading rate of 4 in both the time direction and the frequency direction, that is, the spreading code of SF4×4. Among such two-dimensional spreading codes, as shown in FIGS. 2A to 2C , it can be considered to extract a part as spreading codes of SF1×4, SF4×1 or SF2×2. Therefore, when multiplexing a plurality of channels using two-dimensional spreading codes in which any of these partial spreading codes are orthogonal, it is only necessary to select a spreading code that fully satisfies the following three conditions.

1. Orthogonal to spreading code C _4,3 in time direction (condition 1).

2. Orthogonal to the spreading code C _4,1 in the frequency direction (condition 2).

3. Orthogonal to the two-dimensional spreading code C _2,1 ×C _2,0 in the two-dimensional area of the time direction and the frequency direction (condition 3).

FIG. 3 is a diagram illustrating a method of assigning two-dimensional spread codes according to the present embodiment. In FIG. 3 , when only the two-dimensional spreading code C _4,3 ×C _4,1 is allocated, the two-dimensional spreading codes to be allocated to other channels are represented in the code field.

In FIG. 3 , an area A4 surrounded by a dotted line is an area where the spreading code in the time direction is _C4,3 , and an area A3 surrounded by a dotted line is an area where the spreading code in the frequency direction is _C4,1 . Area A4 does not satisfy condition 1, and area A3 does not satisfy condition 2. The area A1 surrounded by a solid line is an area where the two-dimensional spreading code is C _2,1 ×C _2,0 , and condition 3 is not satisfied.

The spreading code C _4,1 in the frequency direction is generated from the spreading code C _2,0 with a spreading frequency of 2. Thus, the spreading code _C2,0 is the spreading code of the upper layer of the spreading code _C4,1 . Accordingly, the two-dimensional spread code having a code field in the area A4 can be inversely spread with a spreading rate of the spreading code C _4,3 ×C _2,0 , that is, SF4×2. Likewise, a two-dimensional spread code having a code field within the area A3 can be inversely spread using the spread code C _2,1 ×C _4,1 . The two-dimensional spread code having a code field in the area A1 can be inversely spread by either of the spread codes C _4,3 ×C _2,0 and C _2,1 ×C _4,1 .

In the area A2 indicated by oblique lines, which corresponds to the portion other than the above-mentioned area, the two-dimensional spread code C _4,3 ×C _4,1 is naturally related to the SF1×4, SF4×1 and SF2× The spreading codes of 2 (FIGS. 2A-C) are also orthogonal. It is also orthogonal to the spreading codes of SF2×4 and SF4×2.

In this way, two-dimensional spreading codes satisfying all conditions 1 to 3 can be allocated to each channel used for symbol (data) transmission.

FIG. 4 is a diagram illustrating two-dimensional spreading codes to be allocated to other channels when two-dimensional spreading codes are allocated to two channels. In FIG. 4, C _8,0 ×C _8,0 and C _8,2 ×C _8,1 are allocated as two-dimensional spreading codes. Areas B1 and B3 correspond to their code domains.

The area B2 surrounded by the solid line includes the area B1, and the condition 3 is not satisfied here. Similarly, the area B3 is included in the area B6 surrounded by the solid line, and the condition 3 is not satisfied. Condition 2 is not satisfied in the area B4 including the area B1 inside and the area B5 including the area B3 inside, respectively. Condition 1 is not satisfied in the area B7 including the area B1 inside and the area B8 including the area B3 inside, respectively. Accordingly, only two-dimensional spread codes having a code field in the hatched area B9 are allocated to other channels.

FIG. 5 is a diagram illustrating two-dimensional spreading codes to be allocated to other channels when two-dimensional spreading codes are allocated to three channels. In this FIG. 5, C _8,1 ×C _8,2 is further allocated as a two-dimensional spread code from the state shown in FIG. 4 .

In FIG. 5 , regions C1 and C2 correspond to regions B1 and B3 in FIG. 4 , respectively. The region C3 corresponds to the code region of the two-dimensional spread code C _8,1 ×C _8,2 . The area C4 that is not subject to allocation due to the area C1 is indicated by a vertical line. Similarly, the area C5 that is not subject to allocation due to the area C2 is indicated by horizontal lines, and the area C6 that is not subject to allocation due to the area C3 is indicated by oblique lines. The area C7 within the area C4 is an area that is not subject to allocation because of the areas C1 and C2. Similarly, the area C8 is excluded from the allocation target due to the areas C1 and C3, and the area C9 is excluded from the allocation target due to the areas C1 to C3. As a result, the two-dimensional spread codes having code domains in the area 10 indicated by oblique lines different from the area C6 are allocated to other channels.

Assignment of the two-dimensional spreading codes to the respective channels is performed on the transmitting side as described above. By performing such an allocation, at the receiving (user) side, the received channel symbols can not only be inversely spread using the original spreading rate in the time direction and frequency direction, but also can always use the time direction and frequency direction. Inverse spreading is performed with at least one spreading rate smaller than the original spreading rate. Therefore, it is possible to reliably perform despreading of received symbols on the receiving side using a more appropriate spreading rate according to the state of the channel. This means that received symbols can be detected (restored) with higher accuracy, that is, high reception characteristics can always be maintained.

Since the spreading rate used for inverse spreading can be changed on the receiving side, the necessity of transmitting pilot symbols for channel estimation and the like for each receiving side is avoided. Therefore, it is also possible to maintain high utilization efficiency of the system capacity at all times.

FIG. 6 is a diagram illustrating the configuration of a communication device according to the first embodiment. This communication device 60 incorporates a transmission device that distributes two-dimensional spread codes as described above. For example, it is applied to a radio base station apparatus. The communication device 60 will be described in detail below with reference to FIG. 6 .

In data (symbols) to be transmitted, there are usually pilot symbols or control data in addition to data transmitted and received between users. It is not necessary to apply different spreading rates to pilot symbols for each user, so a common spreading rate can be used for each user. After the data is temporarily stored in the buffer 612 , it is output to the multiplexing unit 601 .

The multiplexing unit 601, for example, multiplexes the input data and converts it into a data sequence for each channel. The spreading code generation unit 602 generates spreading codes in the time domain and in the frequency domain, respectively. The two-dimensional spreading unit 603 receives a spreading code from the spreading code generation unit 602 for each channel, and receives a data string from the multiplexing unit 601 for each channel. As a result, the data sequence input from the multiplexing unit 601 is spread for each channel using the input spreading code.

FIG. 7 is a diagram illustrating the configurations of the spreading code generation unit 602 and the two-dimensional spreading unit 603 .

As shown in FIG. 7 , the spreading code generating unit 602 includes: an F spreading code allocating unit 611 that generates a spreading code in the frequency direction for each channel; and a T spreading code allocating unit 612 that generates a spreading code in the time direction for each channel. Another two-dimensional spreading unit 603 has: a plurality of spreading modulation units 701 that spread and modulate data in units of channels using spreading codes in the frequency direction and time direction; An adding unit 702 that adds the spread-modulated data; and an IFFT unit 703 that receives the added data from each adding unit 702 and performs IFFT (Inverse Fast Fourier Transform). Thus, the two-dimensional spreading unit 603 outputs to the transmitting unit 604 a signal obtained by multiplexing spread-modulated data of each channel.

The transmission unit 604 places the signal input from the two-dimensional expansion unit 603 on a carrier wave, amplifies it, and outputs it. The output analog signal is transmitted via the duplexer 605 and the antenna 606 .

On the other hand, the signal received by the antenna 606 is output to the receiving unit 607 via the duplexer 605 and extracted as a digital signal. The extracted reception signal is demodulated by the demodulation unit 608 and output to the detection unit 609 and the channel estimation unit 610 . The detection unit 609 performs detection using the demodulated received signal, and outputs the result as received data. Here, it is assumed that the transmission (user) side (FIG. 12) does not perform spreading using a two-dimensional spreading code.

The channel estimation unit 610 estimates the state of the channel for each channel based on, for example, the reception level or fading of the demodulated received signal, and outputs the estimation result to the spreading factor control unit 611 . The spreading rate control unit 611 determines spreading codes to be assigned to the respective channels according to the estimation results, and causes the spreading code generation unit 602 to generate spreading codes. In addition, information (code information) indicating the assigned spreading code and its spreading rate are output to the buffer 612 as control data. This information is thus transmitted to the receiving side in the form of control data.

The spreading rate control unit 611 determines the spreading codes to be allocated to the respective channels, for example, referring to the spreading code allocation table shown in FIG. 8 or FIG. 9 . Such a table is stored in a non-volatile memory installed inside.

In FIGS. 8 and 9 , the channel with the best transmission path state (the channel for which the highest communication speed can be obtained) corresponds to data A, and the channel with the worst state corresponds to data C. Thereby, the spreading ratio control unit 611 can also refer to any one of the tables in FIG. 8 and FIG. 9 to assign an optimal two-dimensional spreading code according to the state of the transmission channel to each channel. The table shown in FIG. 8 summarizes the two-dimensional spreading codes to be assigned to each channel, and the table shown in FIG. 9 collects the two-dimensional spreading codes in the form of limiting the spreading ratio to be assigned to each channel. The tables shown in FIG. 8 and FIG. 9 are examples, and the contents thereof can be appropriately determined. For example, the respective numbers of channels (pilot channels) for transmitting pilot symbols, channels for transmitting control data (control data channels), and channels for transmitting data (data channels) and the two-dimensional spreading codes that can be assigned to these channels can be arbitrarily Decide.

FIG. 10 illustrates the relationship between the channels in the table shown in FIG. 8 and the code domains occupied by the two-dimensional spread codes to which the channels are allocated. It is clear from this FIG. 10 that all channels are orthogonal to each other. Among the channels for transmitting common pilot symbols, except for SF4x4, even if despreading is performed by any one of SF1x4, SF2x2, and SF4x1, they are orthogonal to all other channels. The same applies to the table shown in FIG. 9 . In FIGS. 8 to 10 , the spreading rate and code number of the spreading code are indicated in parentheses.

Fig. 11 is a flowchart of spreading code allocation table creation processing.

It is necessary to always secure a channel (pilot channel) for transmitting pilot symbols. Therefore, it is hoped that the code domain occupied by the pilot channel is as small as possible. The creation processing shown in FIG. 11 creates a table in consideration of this situation. For example, the processing can be executed by causing a computer (data processing device) to start a program developed for generating the table. "N" in FIG. 11 indicates the total number of pilot channels.

First, in step S1, for the pilot channel, select any spreading code from the set U of two-dimensional spreading codes with the required spreading rate, assign it to the first pilot channel, and substitute 1 into the variable n. In the subsequent step S2, it is determined whether or not the value of the variable n is equal to or less than the total number N. When the value of the variable n is larger than the total number N, the determination result is "No", and a series of processing ends here. In other cases, the determination result is "Yes", and the procedure goes to step S3.

In step S3, all code domains occupied by the allocated pilot channels are calculated. In the following step S4, all spreading codes adjacent to the calculated code field in the code space are extracted from the unassigned spreading codes belonging to the set U, and the spreading code is calculated for each extracted spreading code For all the code domains in the case of assigning to the pilot channel, the calculated spread code with the smallest code domain is allocated to the n-th pilot channel, and the value of the variable n is increased. Then return to the above step S2. As a result, two-dimensional spreading codes can be sequentially allocated to each pilot channel so that all code fields are minimized.

In this embodiment, the spreading codes assigned to channels other than the pilot channel are dynamically changed with reference to the spreading code assignment table shown in FIG. 8 or FIG. The channel's spreading code. Such a change can be performed by applying, for example, an algorithm employed in the spreading code allocation table generation process shown in FIG. 11 . In this application, for example, two-dimensional extension tables to be allocated are limited in accordance with the state of the estimated transmission path, and the two-dimensional extension table with the smallest preamble field is extracted from the limited two-dimensional extension tables and allocated.

FIG. 12 is a diagram illustrating a configuration of a communication device that communicates with the communication device shown in FIG. 6 . This communication device 1200 is, for example, a mobile terminal device carried by a user. Hereinafter, the communication device 60 assumed to be fixed will be referred to as a radio base station device, and the communication device 1200 communicating therewith will be referred to as a mobile terminal device as appropriate. Hereinafter, the mobile terminal device 1200 is simply referred to as a "mobile terminal".

The signal received by the antenna 1201 is output to the receiving unit 1203 via the duplexer 1202, and extracted as a digital signal. The extracted reception signal is subjected to FFT by an FFT (Fast Fourier Transform) unit 1204, and data is extracted for each subcarrier. The data of each subcarrier is respectively output to the pilot despreading unit 1205 , the control data despreading unit 1206 and the data despreading unit 1207 .

The pilot despreading unit 1205 despreads the pilot channel, and the control data despreading unit 1206 similarly transmits control data. The channel and data despreading unit 1207 despreads each data channel.

FIG. 13 is a diagram illustrating the configuration of the pilot despreading unit 1205 .

As shown in FIG. 13 , the pilot despreading unit 1205 has: a plurality of pilot despreading units 1301 that perform despreading with different spreading ratios for the pilot channel; The selection control unit 1302 that selects the optimum spreading rate from the result obtained by performing inverse spreading. The selection control unit 1302 outputs to the coherent detection unit 1208 a signal for coherent detection calculated from the result of despreading the pilot with an optimum spreading factor and information indicating the selected spreading factor. Only the signal for coherent detection is output to the coherent detection unit 1210 .

The radio base station apparatus 60 on the transmitting side transmits the code information and the spreading rate as control data. The control data despreading unit 1206 outputs the despreaded data to the coherent detection unit 1208 . Accordingly, these pieces of information are coherently detected and extracted by the coherent detection unit 1208 . These pieces of information are output to the spreading code generator 1209 .

The spreading code generation unit 1209 recognizes the spreading code used for inverse spreading and the spreading rate from information transmitted as control data from the transmitting side. In the data despreading unit 1207, the data is despread using the recognized spreading code and spreading rate. The data obtained by despreading is output to the coherent detection unit 1210 , and coherent detection is performed using the optimum coherent detection signal output from the selection control unit 1302 . The original data extracted by this synchronous detection is output as reception data.

Here, the method of changing the spreading rate used for pilot inverse spreading will be described in detail.

FIG. 14 is a diagram illustrating an update unit of an expansion rate. The area marked with D in the figure represents an update unit on the code space.

The spreading rate of at least one of the time direction and the frequency method can be updated. The update unit D is used to determine in which direction the spreading rate should be updated in either the time direction or the frequency direction. In the time direction, for example, the expansion rate is updated according to the amount of change for a certain period. In the frequency direction, for example, the update is performed at the same timing corresponding to the amount of change occurring in subcarriers of different frequencies. As the amount of change, phase, dispersion in magnitude of signal amplitude, dispersion in SNR (Signal-to-Noise Ratio), or the like can be employed.

Fig. 15 is a diagram explaining the transition between spreading ratios accompanying the updating of spreading ratios. Marked a to f in the figure represent the conditions under which the transition between spreading rates should be performed along the arrows marked with the marks a to f. Specifically, the conditions are as follows. Here, the amount of change in the time direction is expressed as g_SF, the amount of change in the frequency direction is expressed as h_SF, the upper limit of the allowable change amount of the expansion rate in the time direction in the application is expressed as Th(SF, U, t), and the lower limit Expressed as Th(SF, L, t), the upper limit of the allowable variation of the spreading rate in the frequency direction in the application is expressed as Th(SF, U, f), and the lower limit is expressed as Th(SF, U, f), An example of the content of each condition a to f is shown. where the expansion rate in the application is denoted as SF. The spreading rate represented by this SF is a spreading rate of SF1×4. The upper and lower limits are set in advance as thresholds.

a: Satisfy g_SF<Th(SF, L, t)

b: Satisfy g_SF>Th(SF, U, t)

c: satisfy h_SF>Th(SF, U, f)

d: Satisfy h_SF<Th(SF, L, f)

e: satisfy g_SF<Th(SF, L, t) and h_SF>Th(SF, U, f)

f: Satisfy g_SF>Th(SF, U, t) and h_SF<Th(SF, L, f)

Thus, Figure 17 shows that when the spreading rate in the application is SF2×2, when the condition e is satisfied, for example, it shifts to SF4×1, the spreading rate in the time direction is upgraded from 2 to 4, and the spreading rate in the frequency direction is changed from 2 to 4. A case of downgrading to 1. Similarly, FIG. 17 also shows that when the condition a is satisfied, the transition is to SF4×2, when the condition d is satisfied, the transition is to SF2×4, and when the condition f is satisfied, the transition is to SF1×4. The same goes for others. This transfer must only be done if there is an expansion rate at which it should be made.

Even if the expansion rate is updated as described above, reverse expansion can be performed at the optimal expansion rate. In this way, the pilot channels can also be inversely spread separately without a plurality of spreading ratios.

The transition shown in FIG. 15 may also be applied when the transmission side (radio base station) 60 performs allocation of the above-mentioned two-dimensional spreading codes to channels other than the pilot channel. In this case, the expansion rate control unit 611 may have a function of obtaining the variation g_SF, h_SF, and a function of comparing the variation g_SF, h_SF obtained by this function with each threshold value to determine the expansion rate to be transferred.

As the amount of change in the time direction, it is also possible to focus on delay spread. The smaller the delay spread, the better the state of the transmission path in the frequency direction. Therefore, when focusing on the delay spread, it is preferable to update the spreading ratio with priority given to the frequency direction as the delay spread becomes smaller. Thereby, it is possible to maintain the reception characteristic in a high state at all times.

The mobile terminal 1200 is premised on being carried by a user. The state of the transmission path also changes with the moving speed (relative moving speed with the radio base station apparatus 60 performing communication). The moving speed can also be estimated on the mobile terminal 1200 side from a change in signal reception level, fading, or the like. In this way, the expansion rate can also be updated with a focus on the movement speed. When the moving speed is small, usually a sufficient spreading rate can be obtained in the time direction, so a comparatively smaller spreading rate can be used for the spreading rate in the frequency direction. On the other hand, when the moving speed is high, the state of the transmission path in the time direction deteriorates, so it is preferable to adopt a spreading rate smaller than the original spreading rate as the spreading rate in the time direction. Alternatively, the expansion ratio may be updated by focusing on a plurality of factors among the factors.

Even if the spreading rate for inverse spreading is updated as described above, the reception characteristic can be maintained at a higher state, and the utilization efficiency of the system capacity can always be maintained at a high utilization efficiency. Information on the spreading ratio thus updated may be transmitted to the radio base station apparatus 60 .

<Second Embodiment>

In the first embodiment described above, the radio base station apparatus 60 estimates the state of the transmission path from the received signal. On the other hand, in the second embodiment, the state of the transmission path is notified from the mobile terminal to the radio base station apparatus.

Most of the configurations of the radio base station apparatus and the mobile terminal in the second embodiment are basically the same as those in the first embodiment. The action is also the same. Therefore, the same reference numerals are assigned to the parts that are basically the same as those in the first embodiment, and only the parts that are different from the first embodiment will be described.

FIG. 16 is a diagram illustrating the configuration of a communication device (radio base station device) 60 according to the second embodiment.

As described above, in the second embodiment, the status of the transmission path is notified from the mobile terminal 1200 . Therefore, the propagation path estimating unit 610 is not provided, and the separating unit 1601 is disposed at the subsequent stage of the detecting unit 609 instead.

Notification of the state of the transmission path is performed using control data. The detection unit 609 detects the data of each channel, and outputs the result to the separation unit 1601 . The separation unit 1601 extracts the data of the control data channel for notifying the state of the transmission path therefrom, and outputs the data to the spreading factor control unit 1602 . In this way, the state of the channel detected on the mobile terminal 1200 side is reflected in the assignment of the spreading code.

FIG. 17 is a diagram illustrating the configuration of a communication device (mobile terminal) 1200 according to the second embodiment.

In the second embodiment, the state of the transmission path is notified to the radio base station apparatus 60 by transmitting the spreading factor information output from the pilot despreading unit 1205 . Therefore, the spreading rate information output from the pilot despreading unit 1205 is multiplexed with data by the multiplexing unit 1701 .

The spreading rate information to be sent represents the best spreading rate information determined according to the result obtained by actually performing inverse spreading. By transmitting (feeding back) such spreading rate information, the radio base station apparatus 60 can more appropriately allocate two-dimensional spreading codes.

It is also possible to send the spreading rate information only when there is a change in the spreading rate. The selection control unit 1302 of the pilot despreading unit 1205 checks whether the spreading rate selected from the newly received pilot channel is equal to the previously selected spreading rate every time the pilot channel is received, and if not, Next output the information of the spreading rate selected from the newly received pilot channel. The spreading rate used for the despreading of the data channel is thus updated at any time as required.

Notification of the channel state to the radio base station apparatus 60 may be performed by transmitting information other than the spreading rate information described above. Specifically, it may be information on a spreading rate selected (updated) focusing on a data channel, or information on a spreading rate selected (updated) focusing on delay spread or the moving speed of the own device 1200 . It may also be a plurality of them.

<Third Embodiment>

In the first and second embodiments described above, data transmission between the mobile terminal 1200→radio base station apparatus 60 is performed without using the two-dimensional spread code. In the third embodiment, two-dimensional spreading codes are used in both bidirectional data transmissions.

FIG. 18 is a diagram illustrating the configuration of a communication device according to a third embodiment. In this communication device, communication device (mobile terminal) 1200 shown in FIG. 17 has a function of transmitting data using a two-dimensional spread code. Therefore, the same reference numerals are assigned to the parts substantially the same as those in the structure shown in FIG. 17 .

In the third embodiment, the spreading factor information output from the pilot despreading unit 1205 is directly input to the spreading code generating unit 1209 . The spreading code generation unit 1209 generates a spreading code specified by the input spreading rate information, and outputs it to the two-dimensional spreading unit 1801 and the data despreading unit 1207 . The data despreading unit 1207 performs despreading of the control data channel and the data channel using the spreading code input from the spreading code generating unit 1209 .

Another two-dimensional extension unit 1801 spreads data using the extension code output from the extension code generation unit 1209 , and outputs a signal to the transmission unit 1212 similarly to the two-dimensional extension unit 603 shown in FIG. 16 . Accordingly, the signal is transmitted through the transmitting unit 1212 via the duplexer 1202 and the antenna 1201 .

In this way, in the third embodiment, the result of despreading the pilot channel is reflected on the data transmission. Since the state of the same transmission path is significantly different depending on the direction in which the data is transmitted, it is basically not considered, so even if the side receiving the signal independently decides the spreading rate for the inverse spreading of the signal, it can be extended with an appropriate rate for inverse expansion.

<Fourth Embodiment>

The third embodiment described above is a case where a function of transmitting data using a two-dimensional spread code is installed in communication device (mobile terminal) 1200 shown in FIG. 17 . The fourth embodiment is a case where, for example, a radio base station apparatus 60 shown in FIG. 6 is equipped with a function for responding to data transmitted using a two-dimensional spread code.

FIG. 19 is a diagram illustrating the configuration of a communication device (radio base station device) 60 according to the fourth embodiment.

As a function of receiving data spread and transmitted with a two-dimensional spread code, for example, the respective units 1202 to 1210 shown in FIG. 12 can be employed. Therefore, in FIG. 19, the same reference numerals are assigned to the parts that are basically the same as those shown in FIG. 6 or FIG. 12 .

As shown in FIG. 19 , in the fourth embodiment, a signal received by the antenna 606 is output to the receiving unit 1203 via the duplexer 605 . The spreading rate information output from the pilot despreading unit 1205 is output to the spreading rate control unit 611 instead of the result obtained by the channel estimation unit 610 estimating the state of the channel. As a result, a two-dimensional spreading code optimal for the state of the transmission path estimated by the mobile terminal transmitting the data can be assigned as the two-dimensional spreading code used for data spreading.

The mobile terminal may also have the structure shown in FIG. 18 . Alternatively, the spreading rate control unit 611 may be configured to assign spreading codes based on the detection result of the coherent detecting unit 1208 instead of assigning spreading codes based on the spreading rate information input from the pilot despreading unit 1205 . In the communication device with the structure shown in FIG. 19 and FIG. 18, it may be assumed that it can communicate with another communication device having the same structure. Such communication devices also include transceivers.

<Other Embodiments>

There are various techniques for obtaining desired performance in communication technology. Here, a case of applying a typical communication technology among transmission devices mounted on, for example, radio base station device (communication device) 60 shown in FIG. 6 will be described as an embodiment other than the above. Parts that are basically the same as those in the structure shown in FIG. 6 are given the same reference numerals.

FIG. 20 is a diagram illustrating the configuration of a transmission device according to a fifth embodiment. The sending device applies diversity sending technology.

In the fifth embodiment shown in FIG. 20 , there are two two-dimensional extension units 603 , a transmission unit 604 , and an antenna 606 respectively. For example, the diversity processing unit 2001 provided for each channel outputs data (symbols) to each two-dimensional extension unit 603 . The spreading code generation unit 602 outputs the same spreading code to the respective two-dimensional spreading units 603 for the same data.

Each diversity processing unit 2001 receives data from the multiplexing unit 601 shown in FIG. 6 , converts these data into mutually orthogonal sequences, and outputs the converted data to each two-dimensional expansion unit 603 . Accordingly, each two-dimensional spreading unit 603 spreads the same data (channel) with the same spreading code, and then outputs the spread data to the transmitting unit 604 . As a result, the same signals are transmitted from the respective antennas 606 .

FIG. 21 is a diagram illustrating the configuration of a transmission device according to a sixth embodiment. The transmission device applies the diversity transmission technology by another method.

In the sixth embodiment shown in FIG. 21 , the same data is input to each two-dimensional expansion unit 603 from the multiplexing unit 601 shown in FIG. 6 . Accordingly, the spreading code generation unit 601 outputs mutually orthogonal spreading codes to the respective two-dimensional spreading units 603 for the same data. By outputting such spreading codes to the respective two-dimensional spreading units 603, the diversity processing unit 2001 shown in FIG. 20 becomes unnecessary.

In the structure shown in FIG. 21, if a plurality of users share the pilot channel (symbol), it is necessary to generate two-dimensional spread codes with a number equal to or greater than the number of antennas 606. These two-dimensional spread codes not only two-dimensionally spread The code as a whole must be orthogonal, even if a part is taken out, it is orthogonal to other spreading codes, that is, all of the above-mentioned conditions 1-3 are satisfied. For example, if the spreading code of SF4×4 is considered, as shown in FIG. 22A ~ FIG. 4) Inverse spreading or orthogonal spreading codes for any one of the spreading rates. The number of such spreading codes can be further increased by further increasing the code range or further suppressing the number of spreading rates capable of inverse spreading. A to D shown in FIG. 22A to FIG. 22C respectively represent code domains to which four spreading codes can be assigned.

FIG. 23 is a diagram illustrating the configuration of a transmission device according to a seventh embodiment. The sending device applies MIMO (Multiple Input and Multiple Output) technology.

In the seventh embodiment shown in FIG. 23 , the multiplexing unit 601 allocates data (symbols) to a plurality of sequences and outputs them to the respective two-dimensional expansion units 603 . Therefore, similar to the above-mentioned sixth embodiment, if a plurality of users share the pilot channel (symbol), it is necessary to generate two-dimensional spread codes with a number equal to or greater than the number of antennas 606, and these two-dimensional spread codes are not only two-dimensional The entire spread code is orthogonal, and even if a part is taken out, it is orthogonal to other spread codes, that is, all of the above-mentioned conditions 1 to 3 are satisfied.

Here, other embodiments in which diversity transmission technology and MIMO technology are applied are described as the fifth to seventh embodiments, but other technologies can be widely applied.

Claims (2)

1. A kind of communication system, it comprises transmitting device and receiving device, and this transmitting device uses the two-dimensional spread code that spreads in time direction and frequency direction to transmit signal, and this receiving device receives described signal that transmits from described transmitting device, It is characterized in that, The sending device has: a selection unit that selects spreading codes that are orthogonal to each other in at least one of the time direction and the frequency direction; and a transmitting unit that spreads a signal using the selected spreading code and transmits the signal, The selected spreading codes can be divided into two or more parts, which are orthogonal to the same part of the other selected spreading codes in at least one of the time direction and the frequency direction. 2. The communication system according to claim 1, characterized in that, The spreading code divided into two or more parts has a spreading rate smaller than an original spreading rate in at least one of the time direction and the frequency direction, respectively.

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