JPH11317979A - Communication channel control method in direct spread cdma communication system and base station and mobile station using this communication channel control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To greatly reduce a time untill presence of a communication channel of a base station is recognized by a mobile station in the base station, the mobile station and the communication channel control method in the direct spread CDMA mobile communication system. SOLUTION: A signal format comprises a pilot symbol 21, a control information symbol 22 and a channel presence information symbol 23. The pilot symbol 21 and the control information symbol 22 are spread by channel orthogonal short codes and long codes, and the channel presence information symbol 23 is spread only the short code corresponding to the presence of a communication channel resource available by a base station. The mobile station takes correlation with the short code of the part of the channel presence information symbol 23 to discriminate the presence of the communication channel in the base station and selects the base station.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to direct spread CDMA.
The present invention relates to a communication channel control method in a mobile communication system, and more particularly to a communication channel control method in a direct spread CDMA mobile communication system capable of notifying a mobile station of the presence or absence of a communication channel resource of a base station.

[0002]

2. Description of the Related Art Currently, next-generation mobile communication systems are being studied worldwide for the purpose of achieving high-quality and high-speed data transmission indoors or outdoors. As a promising wireless access candidate, direct spread CDMA (Code Divi
sion multiple access) system, and research and development for practical use are being conducted. The direct spread CDMA system is a system in which user information is expanded and transmitted with a spreading code of a rate much higher than the information data rate, and is transmitted by a conventional frequency division multiplexing (FDMA: Frequenc).
y Division Multiple Access method, time division multiplexing (T
As compared with the DMA (Time Division Multiple Access) system, early development is expected in that it has effects such as an increase in subscriber capacity, easy realization of variable rate transmission, and flexible cell design.

In the direct spread CDMA system, the information symbol of each user is band-expanded by an individual spreading code faster than the information symbol rate, and then the frequency and time are shared with other user signals to the radio section. Sent. The receiving side performs despreading using a spreading code corresponding to a desired information symbol, thereby separating the signal and receiving the signal. Two types of spreading codes are used: a short code having the same repetition period as the user information symbol period and a long code having a longer repetition period than the user information symbol period. The former is used for orthogonalization of each user information in a wireless area (service area), and the latter is used for reducing interference between wireless areas when a plurality of wireless areas exist.

[0004] By the way, a mobile station communicates via a radio channel of the base station, but the number of channels allocated to the base station is limited, and the mobile station calls a base station having no vacant channel. Is a call loss. In order to avoid such a call loss, it is necessary for the mobile station to determine whether or not the base station has a free channel, and the mobile station must select a base station having a free channel and make a call.

In the indoor digital mobile communication system typified by the second generation digital cordless telephone, the applicant assigns channel presence / absence information indicating whether a base station has available communication channel resources to the base station. The mobile station proposes a “method of controlling a communication channel for mobile communication” in which a mobile station selects a base station with reference to the channel presence / absence information and makes a call (Japanese Patent Laid-Open No. 7-67168).

The present invention will be specifically described. Typically,
When the radio mobile station selects any one of the plurality of base stations and requests the start of communication, the radio base station receiving the communication start request performs a predetermined procedure if there is available communication channel resources. Then, a communication path with the wireless mobile station is set and communication is started. At this time, if there is no available communication channel resource in the radio base station, a channel cannot be allocated to the calling mobile station, resulting in a call loss. In order to prevent such a call loss, in advance, the radio base station transmits channel presence / absence information indicating whether or not there is a communication channel resource that can be currently used by the radio base station in a control field of a control channel signal format. And write it to the wireless mobile station. The wireless mobile station is a method of avoiding a call loss by selecting a wireless base station based on the channel presence / absence information and calling.

[0007]

If the communication channel presence / absence information from the radio base station must be obtained in a short time, not only the call loss in the radio mobile station cannot be avoided, but also the radio In some cases, the processing performance of the mobile station is deteriorated. If the above-mentioned technique proposed above is directly applied to direct spread CDMA, the radio mobile station uses the spread spectrum used by the radio base station to receive the communication channel presence / absence information transmitted by the radio base station. The code (long code and short code) is grasped by the radio mobile station,
After despreading the broadcast signal, it is necessary to recognize the presence or absence of communication channel resources from the information symbols. At this time, if the spreading code is not known, it is necessary to identify the spreading code, and therefore, it takes a lot of time before the radio mobile station recognizes the presence or absence of the communication channel resource from the broadcast signal. .

As a result, there is a case where the presence / absence information of the communication channel of the radio base station cannot be recognized by the radio mobile station in a short time. The present invention has been made in view of the above problems, and it is intended to significantly reduce a time required for a radio mobile station to recognize the presence or absence of a communication channel of a radio base station from a signal broadcast from the radio base station. It is intended for.

[0009]

According to a first aspect of the present invention, there is provided a spread code for expanding a band of a wideband signal, wherein the spread code having a rate higher than the information rate has the same repetition rate as the information symbol period. A first spreading code having a period (a code having the same repetition period as the information symbol period is referred to as a short code) group and a second spreading code having a repetition period longer than the information symbol period (a code having a repetition period longer than the information symbol period). A direct spreading CDMA mobile communication system comprising a first spreading code of the first spreading code group and a second spreading code of the second spreading code group and transmitting a signal by double spreading. In the communication channel control method according to the above, a part of the first spreading codes of the first spreading code group may have a communication channel resource available in the base station. A base station, wherein the base station spreads a signal using the first spreading code associated with the presence or absence of the communication channel resource and transmits the spread signal to the mobile station, wherein the base station transmits the signal to the mobile station. Channel control method.

According to the first aspect of the present invention, the base station uses a spreading code associated with the presence or absence of a communication channel resource,
The mobile station notifies the mobile station of the presence / absence of the communication channel resources of the base station.Since the spread code itself is the presence / absence information of the communication channel resources, the mobile station does not need to identify the spread code, and as a result, The time required for recognizing the presence or absence of communication channel resources can be greatly reduced.

According to a second aspect of the present invention, in the communication channel control method for a direct sequence CDMA mobile communication system according to the first aspect, the first spreading code associated with the presence or absence of the communication channel resource is: A code associated with the presence of available communication channel resources at the base station and at least one code associated with the absence of available communication channel resources at the base station. I do.

According to the second aspect of the present invention, there are three cases in which only the code associated with the presence of the channel, only the code associated with the absence of the channel, or both codes are used. One of them can be selected depending on the system to be adopted. According to a third aspect of the present invention, there is provided a communication channel control method in a direct sequence CDMA mobile communication system according to the first or second aspect,
The second spreading code is masked during M symbols (M is a natural number) in which the first spreading code associated with the presence or absence of the communication channel resource is used.

According to the third aspect of the present invention, the second spreading code is masked during the M symbols in which the first spreading code associated with the presence or absence of the communication channel resource is used. Thus, the presence or absence of a correlation with the first spreading code can be easily detected. The invention described in claim 4 is a spreading code for performing band expansion on a wideband signal, wherein the spreading code having a rate higher than the information rate is a first spreading code group having the same repetition period as the information symbol period. A second spreading code group having a repetition period longer than the information symbol period, and transmitting a signal by doubly spreading with the first spreading code of the first spreading code group and the second spreading code of the second spreading code group; A first spreading code of a part of the first spreading code group is associated with the presence or absence of a usable communication channel resource in a base station, The mobile station receives the signal transmitted from the base station in which the signal has been spread using the first spreading code associated with the presence or absence of the communication channel resource, and A communication channel control method in a direct spread CDMA mobile communication system, comprising: recognizing presence / absence of channel resources of a base station from an attached first spreading code, and requesting communication to a base station having channel resources. is there.

[0014] The invention according to claim 4 is the invention according to claims 1 to 3.
It defines the mobile station side of the communication channel control method in the described direct spread CDMA mobile communication system.
The invention described in claim 5 is a spreading code for performing band expansion on a wideband signal, wherein the spreading code having a rate higher than the information rate is a first spreading code group having the same repetition period as the information symbol period. A second spreading code group having a repetition period longer than the information symbol period, and transmitting a signal by doubly spreading with the first spreading code of the first spreading code group and the second spreading code of the second spreading code group; In a base station in a direct spread CDMA mobile communication system, a part of the first spreading codes of the first spreading code group is associated with the presence or absence of available communication channel resources in the base station; A base station in a direct spread CDMA mobile communication system, characterized in that a signal is spread using a first spreading code associated with presence / absence of the signal and transmitted to the mobile station.

[0015] The invention according to claim 5 is the invention according to claims 1 to 4.
A base station using the communication channel control method in the described direct spread CDMA mobile communication system. The invention according to claim 6 is a spreading code for performing band expansion on a wideband signal, wherein the spreading code having a rate higher than the information rate is a first spreading code group having the same repetition period as the information symbol period. A second spreading code group having a repetition period longer than the information symbol period, and transmitting a signal by doubly spreading with the first spreading code of the first spreading code group and the second spreading code of the second spreading code group; Direct diffusion CDM
A In the mobile station in the mobile communication system, a part of the first spreading code of the first spreading code group is associated with the presence or absence of available communication channel resources in the base station, and the presence or absence of the communication channel resources. Receiving the signal transmitted from the base station in which the signal is spread using the associated first spreading code, the channel of the radio base station is obtained from the first spreading code associated with the presence or absence of the communication channel resource. A mobile station in a direct spread CDMA mobile communication system that recognizes the presence or absence of resources.

The invention according to claim 6 is the invention according to claims 1 to 4.
A mobile station using the communication channel control method in the direct spread CDMA mobile communication system described above.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 illustrates an example of a mobile communication system to which the present invention is applied. Radio base station 11a,
11b each communication service area (wireless zone) 12a, 1
2b are arranged to overlap each other almost completely in this example. Similarly, the radio base stations 11c and 11d
The communication service areas 12c and 12d are also arranged so as to almost completely overlap each other. Each radio base station 11
a to 11d are accommodated in the radio control station 13 and controlled independently. The wireless mobile station 14 can move within the service areas 12a to 12d and select any one of the plurality of wireless base stations 11a to 11d to which the service area belongs to perform communication.

FIG. 2 shows an example of a signal format of a control channel transmitted by the radio base station according to the present invention. The signal format includes a pilot symbol 21, a control information symbol 22, and a channel presence / absence information symbol 23, and each is spread with a short code. At this time, at least two types of short codes are prepared: a short code for channel orthogonality conventionally used and a short code corresponding to the presence or absence of communication channel resources usable by the wireless base station used in the present invention. For example,
The total number of short codes is N (N is a natural number of 3 or more), and the short code for channel orthogonal is short code number 3.
The short codes corresponding to the presence / absence of communication channel resources are denoted by short code numbers 1 and 2 (for example, when there is a channel: short code number 1, and when there is no channel: short code number 2). The short code corresponding to the presence or absence of the communication channel resource may be selected from conventionally used short codes for channel orthogonality.

In addition, the pilot symbol 21 and the control information symbol 22 are spread with a short code for channel orthogonality, and the channel presence / absence information symbol 23 is a short code corresponding to the presence / absence of a communication channel resource available to the radio base station. Spread with code. That is, the pilot symbol 21 and the control information symbol 22 are spread by a short code corresponding to one of the short code numbers 3 to N, and the channel presence / absence information symbol 23 is used to determine whether there is a communication channel resource available to the radio base station. Short code number 1 according to
Or, it spreads with short code number 2. Thereafter, the portion of the pilot symbol 21 and the portion of the control information symbol 22 are further spread by a long code and transmitted.

The radio mobile station receiving the above signal is provided with a short code detection circuit for the channel “present” of the radio base station and a short code detection circuit for the channel “absent” of the radio mobile station. FIG. 3 shows a short code detecting circuit of the channel “present” of the wireless mobile station. When a signal in which the channel presence / absence information symbol portion is spread by the short code number 1 with a channel is transmitted from the radio base station, the received channel presence / absence information symbol portion 33 and the short code number 1 (34) with the channel are transmitted. Are correlated,
When the correlation value exceeds a certain level Lc, the radio mobile station determines that there is a communication channel resource. From the radio base station,
When a signal is transmitted in which the channel presence / absence information symbol portion is spread by the short code number 2 without a channel, the received channel presence / absence information symbol portion 33 is correlated with the short code number 1 (34) having a channel. However, since the correlation value does not exceed a certain level Lc,
It does not determine that there is a communication channel resource.

FIG. 4 shows a short code detection circuit for the channel "none" shown in FIG. From the radio base station, the channel presence / absence information symbol part is changed to a short code number 2 without a channel.
When the spread signal is transmitted, the received channel presence / absence information symbol portion 43 is correlated with the short code number 2 (44) having no channel, and when the correlation value exceeds a certain level Lc, the radio signal is transmitted. It is determined that the base station has no communication channel resources. When a signal in which the channel presence / absence information symbol portion is spread by the short code number 1 with a channel is transmitted from the wireless base station,
The received channel presence / absence information symbol part 34 is correlated with the short code number 2 (44) having no channel. However, since the correlation value does not exceed a certain level Lc, it is not determined that there is no communication channel resource.

The short code according to the presence or absence of a communication channel resource that can be used by the radio base station is as follows:
Short code number 1 according to the presence or absence of communication channel resources
Alternatively, the short code number 2 is used, but in order to simplify the configuration, it may be only one short code indicating that there is a communication channel resource, or it may indicate that there is no communication channel resource. It is also possible to use only one short code.

FIG. 5 shows an example of determining whether there is a communication channel in this case. That is, an example in which only the short code number 1 is used according to the presence or absence of the communication channel resource (N02)
Then, if there is a correlation with the short code number 1, it is determined that the channel is “present”, and if there is no correlation, it is determined that the channel is “absent”. Similarly, an example using only short code number 2 according to the presence or absence of communication channel resources (N0
In 3), if there is a correlation with the short code number 2, it is determined that the channel is not present, and if there is no correlation, it is determined that the channel is present. The short code in this case is not limited to the number 1 or 2.

The radio mobile station that has detected that the radio base station has a communication channel then identifies the short code and the long code of the control channel and receives the control information symbol. Further, in the case of NO2 in FIG. 5, the radio mobile station periodically monitors the correlation of the control channel with a short code (number 1: channel exists) corresponding to the channel presence / absence symbol, and when the correlation becomes less than a certain value, the radio base station. It is determined that there is no communication channel resource, and another wireless base station transmitting the short code with the communication channel resource is searched. In this way, the wireless mobile station always makes a communication request to the wireless base station using the control channel of the wireless base station having the communication channel. Since the wireless base station requested for communication has available communication channel resources, it can immediately start communication by specifying a communication channel in response to a start request from the wireless mobile station.

FIG. 6 shows the signal processing of the radio mobile station in the case of NO2 in FIG. 5, that is, when only the short code number 1 is used according to the presence or absence of the communication channel resource. The operation is
According to FIG. 3 and FIG. In the above description, the case where the channel presence / absence information symbol 23 is not spread by the long code has been described. However, it is not always necessary to mask the channel presence / absence information symbol 23. However, without spreading by long code,
The wireless mobile station can easily detect the presence or absence of a correlation with the first spreading code.

FIG. 7 is a diagram for explaining the transmission circuit of the base station. When notifying the radio mobile station of the presence or absence of the channel resource of the radio base station, the control channel information is spread by the output of the first spreading code generation unit 50 corresponding to the presence or absence of the communication channel resource by the multiplier 57. The other control information is spread by the output of the channel orthogonal first spreading code generation unit 51.), and the output of the complex conjugate code generation unit 54 for the second spreading code, that is, the second spreading code is masked. The signal is spread by a signal, and is passed through a signal synthesizer 60 to a multiplier 61.
Are spread by the output of the second spreading code generation unit 56 to obtain a multi-channel spread modulation signal output.

The communication channel information 1 to N are spread by multipliers 58 to 59 by channel orthogonal first spreading code generators 1 to N, respectively. Are spread by the output of the second spreading code generation unit 56 to obtain a multi-channel spread modulation signal output. The timing control unit 55 controls the timing so that a desired signal is obtained. Further, the first spreading code generator 50 and the first orthogonal spreading code generator 51 for channel orthogonality corresponding to the presence or absence of the communication channel resource may be the same, for example, when a single zone configuration is adopted. good.

FIG. 8 is a diagram for explaining the receiving circuit of the mobile station. In the received spread modulation signal output, the signal appearing on the line 90 is correlated by the matched filter 70 with the output of the first spreading code replica generation unit 71 corresponding to the presence or absence of communication channel resources. The maximum value of the output of the matched filter 70 is detected by the maximum correlation output detection circuit 73, and the maximum correlation peak chip phase detection circuit 74 detects the timing of the peak value of the correlation detection output. When this output is obtained, it is determined that the received spread modulated signal output has been spread by the first spreading code corresponding to the presence / absence of communication channel resources. I can judge.

Here, a circuit for synchronizing the second spreading code after identifying that there is a communication channel resource of the base station will be described. The peak value output of the maximum correlation peak chip phase detection circuit 74 is used as a trigger to drive the second spreading code replica generator 75 to generate a second spreading code. The second spread code is further multiplied by a first spread code replica generation unit for channel orthogonal 72 by a multiplier 79, and further, a received spread modulation signal output appearing on a line 91 is multiplied by a multiplier 78, and integrated. The dump circuit 76 detects the correlation. The threshold value determination circuit 77 determines whether or not the output of the integration / dump circuit exceeds a predetermined value. If the output exceeds the threshold value, it is determined that synchronization with the second spreading code has been achieved. If the difference is equal to or smaller than the threshold value, the phase of the second spreading code replica generation unit 75 is shifted until the synchronization is established.

[0030]

According to the present invention as described above, the following various effects can be realized. According to the first and fourth aspects of the present invention, the base station notifies the mobile station of the presence / absence of the communication channel resource of the base station to the mobile station using the spreading code associated with the presence / absence of the communication channel resource. Since the code itself is information on the presence or absence of the communication channel resource, the mobile station does not need to demodulate the information on the presence or absence of the communication channel resource after identifying the spreading code for despreading. The time required for recognizing the presence or absence of resources can be significantly reduced.

According to the second aspect of the present invention, there are three cases in which only a code associated with the presence of a channel, only a code associated with the absence of a channel, or both codes are used. One of them can be selected depending on the system to be adopted. According to the third aspect of the present invention, the second spreading code is masked during the M symbols used for the first spreading code associated with the presence or absence of the communication channel resource. The presence or absence of a correlation with one spreading code can be easily detected.

According to the fifth and sixth aspects of the present invention, a base station transmitter and a mobile station receiver using the communication channel control method in the direct spread CDMA mobile communication system according to the first to fourth aspects are realized. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a mobile communication system to which the present invention is applied.

FIG. 2 is a diagram for explaining an example of a signal format of a control channel transmitted by a wireless base station.

FIG. 3 is a diagram for explaining signal processing of a received channel presence / absence information symbol portion and a short code number 1 with a channel.

FIG. 4 is a diagram for explaining signal processing of a received channel presence / absence information symbol portion and a short code number 2 without a channel.

FIG. 5 is a diagram for explaining an example of adoption of a short code and determination of presence / absence of a communication channel;

FIG. 6 is a diagram for explaining signal processing of a wireless mobile station when only short code number 2 having a communication channel resource is used.

FIG. 7 is a diagram illustrating a part of a transmission circuit of a base station.

FIG. 8 is a diagram for explaining a part of the receiving circuit of the mobile station.

[Explanation of symbols]

 11a-d Radio base station 12a-d Service area of radio base station 13 Radio control station 14 Radio mobile station 21 Pilot symbol 22 Control information symbol 23 Channel presence / absence information symbol

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshiki Fujima Inside NTT Mobile Communication Network Co., Ltd. 2-1-1 Toranomon, Minato-ku, Tokyo

Claims (6)

[Claims] 1. A spreading code for expanding a band of a wideband signal, the spreading code having a rate higher than the information rate being repeated from a first spreading code group having the same repetition period as the information symbol period and the information symbol period. A direct spreading CDMA mobile station comprising a second spreading code group having a long period and transmitting a signal by doubly spreading a signal by a first spreading code of the first spreading code group and a second spreading code of the second spreading code group. In the communication channel control method in the communication system, a part of the first spreading code of the first spreading code group is associated with the presence or absence of an available communication channel resource in the base station, A communication channel in a direct spread CDMA mobile communication system, wherein a signal is spread using a first spreading code associated with the presence or absence of channel resources and transmitted to a mobile station. Le control method. 2. The communication apparatus according to claim 1, wherein the first spreading code associated with the presence / absence of the communication channel resource is a code associated with the presence of the available communication channel resource in the base station and the communication available in the base station. The communication channel control method in a direct spread CDMA mobile communication system according to claim 1, wherein the code is at least one of codes associated with the absence of a dedicated channel resource. 3. The method according to claim 1, wherein the second spreading code is masked during M symbols (M is a natural number) using the first spreading code associated with the presence or absence of the communication channel resource. Or a communication channel control method in a direct sequence CDMA mobile communication system according to 2. 4. A spreading code for expanding a band of a wideband signal, wherein the spreading code having a rate higher than the information rate is repeated from a first spreading code group having the same repetition period as the information symbol period and the information symbol period. A direct spreading CDMA mobile station comprising a second spreading code group having a long period and transmitting a signal by doubly spreading a signal by a first spreading code of the first spreading code group and a second spreading code of the second spreading code group. In the communication channel control method in the communication system, a part of the first spreading codes of the first spreading code group is associated with the presence or absence of available communication channel resources in the base station, and the presence or absence of the communication channel resources The mobile station receives the signal transmitted from the base station in which the signal is spread using the first spreading code associated with the mobile station, and the mobile station associates the signal with the presence or absence of the communication channel resource. From the spread code, to recognize the presence of the channel resources of a base station, a communication channel control method in the direct sequence CDMA mobile communication system, characterized in that the communication request to the base station with a channel resources. 5. A spreading code for expanding a band of a wideband signal, wherein the spreading code has a higher repetition rate than the information symbol period and a first spreading code group having the same repetition period as the information symbol period. A direct spreading CDMA mobile station comprising a second spreading code group having a long period and transmitting a signal by doubly spreading a signal by a first spreading code of the first spreading code group and a second spreading code of the second spreading code group. In the base station in the communication system, a part of the first spreading code group is associated with the presence or absence of available communication channel resources in the base station, and is associated with the presence or absence of the communication channel resources. A base station in a direct spread CDMA mobile communication system, wherein the base station spreads a signal using the obtained first spreading code and transmits the spread signal to a mobile station. 6. A spreading code for expanding a band of a wideband signal, wherein the spreading code having a rate higher than the information rate is repeated from the first spreading code group having the same repetition period as the information symbol period and the information symbol period. A direct spreading CDMA mobile station comprising a second spreading code group having a long period and transmitting a signal by doubly spreading a signal by a first spreading code of the first spreading code group and a second spreading code of the second spreading code group. In the mobile station in the communication system, a part of the first spreading code group is associated with the presence or absence of a usable communication channel resource in the base station, and is associated with the presence or absence of the communication channel resource. Receiving the signal transmitted from the base station in which the signal is spread using the first spread code, and obtaining the radio base station from the first spread code associated with the presence or absence of the communication channel resource. Mobile station in a direct sequence CDMA mobile communication system and recognizes the existence of the channel resources.