JP3429675B2 - Communication channel control method in direct spread CDMA mobile communication system, and base station and mobile station using this communication channel control method - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to direct sequence CDMA.
The present invention relates to a communication channel control method in a mobile communication system, and 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 communication channel resources of a base station.

[0002]

2. Description of the Related Art Currently, next-generation mobile communication systems are being studied all over the world for the purpose of achieving high-quality and high-speed data transmission indoors or outdoors. Direct spreading CDMA (Code Divi
There is a sion multiple access) method, and research and development for practical use is being carried out. This direct sequence CDMA system is a system for transmitting the user information by expanding the band with a spread code having a very high rate compared to the information data rate, and is a conventional frequency division multiplexing (FDMA).
y Division Multiple Access) method, time division multiplexing (T
As compared with the DMA (Time Division Multiple Access) method, its early development is expected in terms of effects such as increase in subscriber capacity, easy realization of variable rate transmission, and flexible cell design.

In this direct sequence CDMA system, the information symbols of each user are band-expanded by an individual spreading code that is faster than the information symbol rate, and then the frequency and time are shared with other user signals to the radio section. Sent. On the receiving side, despreading is performed using a spreading code corresponding to the desired information symbol to separate the signal and receive 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 orthogonalizing each user information in a wireless area (service area), and the latter is used for reducing interference between wireless areas when there are a plurality of wireless areas.

By the way, the mobile station communicates via the radio channel of the base station, but the channels allocated to the base station are limited, and the mobile station makes a call to the base station having no empty channel. Will be lost. In order to avoid such a call loss, it is necessary for the mobile station to grasp whether or not the base station has a free channel and to select the base station having the free channel to make a call.

In the indoor digital mobile communication system typified by the second-generation digital cordless telephone, the applicant of the present invention provides channel presence / absence information indicating whether or not the base station has available communication channel resources for the base station. Proposes a "communication channel control method for mobile communication" in which a mobile station selects a base station with reference to this 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 wireless mobile station selects any one of a plurality of base stations and requests the start of communication, the wireless base station receiving the request to start communication performs a predetermined procedure if there are available communication channel resources. After that, the 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, channel allocation cannot be performed to the calling mobile station, resulting in a call loss. In order to prevent such a call loss, in advance, from the radio base station, the channel presence / absence information indicating whether or not there is a communication channel resource that can be used by the current radio base station is set in the control field of the signal format of the control channel. Write it in and send 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 making a call.

[0007]

If the communication channel presence / absence information from the radio base station is not acquired in a short time, the call loss in the radio mobile station cannot be avoided, and rather, the radio loss is caused due to the processing. The processing performance of the mobile station may be deteriorated. If the above-proposed technique is directly applied to the direct spreading CDMA, the wireless mobile station uses the spreading used by the wireless base station to receive the presence / absence information of the communication channel transmitted by the wireless base station. The mobile station grasps the code (long code and short code),
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 for the wireless mobile station to recognize the presence or absence of the communication channel resource from the broadcast signal. .

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

[0009]

According to a first aspect of the present invention, there is provided a spreading code for expanding a band of a wide band signal, wherein the spreading code having a speed higher than an information rate has the same repetition as the information symbol period. A first spreading code having a cycle (a code having the same repetition cycle as the information symbol cycle is called a short code) and a second spreading code having a repetition cycle longer than the information symbol cycle (a code having a repetition cycle longer than the information symbol cycle Long-code group), and a direct spreading CDMA mobile communication system for transmitting a signal by double spreading with 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 according to, the presence or absence of usable communication channel resources in the base station is a part of the first spreading codes of the first spreading code group. Correspondence, 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 signal to the mobile station. It is a channel control method for.

According to a first aspect of the present invention, the base station uses a spreading code associated with the presence or absence of communication channel resources,
The mobile station is notified of the presence or absence of communication channel resources of the base station, since the spreading code itself is the presence or absence of communication channel resources, the mobile station does not need to identify the spreading code, as a result, It is possible to significantly reduce the time required to recognize the presence / absence of communication channel resources.

According to the invention described in claim 2, in the communication channel control method in the direct sequence CDMA mobile communication system according to claim 1, the first spreading code associated with the presence or absence of the communication channel resource is: At least one of a code associated with a communication channel resource available in the base station and a code associated with no communication channel resource available in the base station To 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 in relation to the system to be adopted. The invention described in claim 3 is a communication channel control method in a direct sequence CDMA mobile communication system according to claim 1,
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. Then, it is possible to easily detect the presence or absence of the correlation with the first spreading code. A fourth aspect of the present invention is a spreading code for expanding a band of a wide band signal, wherein the spreading code having a speed higher than an information rate is a first spreading code group having a repetition period that is the same as an information symbol period. A second spreading code group having a repetition period longer than the information symbol period, and the signal is transmitted by being double-spread by the first spreading code of the first spreading code group and the second spreading code of the second spreading code group. In the communication channel control method for a direct spread CDMA mobile communication system, a part of the first spread codes of the first spread code group is associated with the presence or absence of usable communication channel resources in the base station, and the communication is performed. The mobile station receives the signal transmitted from the base station whose signal is spread using the first spreading code associated with the presence or absence of the communication channel resource, and the mobile station compares the presence or absence of the communication channel resource with the presence or absence of the communication channel resource. A communication channel control method in a direct spread CDMA mobile communication system, characterized in that the presence or absence of a channel resource of a base station is recognized from the attached first spreading code and a communication request is made to the base station having the channel resource. is there.

The invention according to claim 4 is based on claims 1 to 3.
It defines the mobile station side of the communication channel control method in the described direct sequence CDMA mobile communication system.
The invention described in claim 5 is a spreading code for band-spreading a wideband signal, wherein the spreading code having a speed higher than the information rate includes 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 the signal is transmitted by being double-spread by 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 spreading 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 usable communication channel resources in the base station, and the communication channel resources are A base station in a direct spread CDMA mobile communication system characterized by transmitting a signal to a mobile station by spreading a signal using a first spreading code associated with the presence or absence of.

The invention according to claim 5 is the invention according to claims 1 to 4.
It defines a base station using the communication channel control method in the described direct sequence CDMA mobile communication system. A sixth aspect of the present invention is a spreading code for expanding a band of a wideband signal, wherein the spreading code having a speed 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 the signal is transmitted by being double-spread by the first spreading code of the first spreading code group and the second spreading code of the second spreading code group. Direct diffusion CDM
In the mobile station in the mobile communication system A, a part of the first spreading codes of the first spreading code group is associated with the presence or absence of usable communication channel resources in the base station and the presence or absence of the communication channel resources. Receiving a signal transmitted from a base station whose signal is spread using the associated first spreading code, from the first spreading code associated with the presence or absence of the communication channel resource, the channel of the wireless base station A mobile station in a direct sequence 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.
It defines a mobile station using the communication channel control method in the described direct sequence CDMA mobile communication system.

[0017]

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. Wireless base station 11a,
11b each communication service area (wireless zone) 12a, 1
2b are arranged so as to substantially completely overlap each other, in this example. Similarly, the wireless base stations 11c and 11d
The communication service areas 12c and 12d are also arranged so as to almost completely overlap each other. Each wireless base station 11
a to 11d are housed 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 communicate with.

FIG. 2 shows an example of the signal format of the 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, which are spread with a short code. At this time, as the short code, at least two kinds of conventionally used channel orthogonal short codes and short codes corresponding to the presence or absence of communication channel resources usable by the radio base station used in the present invention are prepared. For example,
The total number of short codes is N (N is a natural number of 3 or more), and the short code for orthogonal channels is short code number 3.
The short codes corresponding to the presence or absence of communication channel resources are set to short code numbers 1 and 2 (for example, with channel: short code number 1, without channel: short code number 2). The short code corresponding to the presence or absence of communication channel resources may be selected from the conventionally used channel orthogonal short codes.

Further, the pilot symbol 21 and the control information symbol 22 are spread with a channel orthogonal short code, and the channel presence / absence information symbol 23 is a short corresponding to the presence / absence of communication channel resources usable by the radio base station. Spread by code. That is, the pilot symbol 21 and the control information symbol 22 are spread by the short code corresponding to one of the short code numbers 3 to N, and the channel presence / absence information symbol 23 is the presence / absence of communication channel resource usable by the radio base station. Depending on the short code number 1
Or spread with short code number 2. After that, the part of the pilot symbol 21 and the part of the control information symbol 22 are further spread by the long code and transmitted.

The radio mobile station which receives 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 base station. FIG. 3 shows a short code detection circuit for the channel “present” of the wireless mobile station. When a signal obtained by spreading the channel presence / absence information symbol portion with the short code number 1 with channel is sent from the radio base station, the received channel presence / absence information symbol portion 33 and the short code number 1 (34) with channel are received. Is correlated,
When the correlation value exceeds a certain level Lc, the wireless mobile station determines that there are communication channel resources. From the radio base station,
When a signal in which the channel presence / absence information symbol portion is spread by the short code number 2 without a channel is sent, the received channel presence / absence information symbol portion 33 and the short code number 1 (34) with a channel are correlated. However, since the correlation value does not exceed a certain level Lc,
It is not judged that there are communication channel resources.

The short code detection circuit for the channel "none" shown in FIG. 4 is shown. From the radio base station, enter the channel presence / absence information symbol part into the short code number 2 without a channel.
When a signal spread by is sent by, the received channel presence / absence information symbol portion 43 and the short code number 2 (44) without channel are correlated, and when the correlation value exceeds a certain level Lc, the It is determined that the base station has no communication channel resource. When a signal in which the channel presence / absence information symbol portion is spread by the short code number 1 with channel is sent from the radio base station,
The received channel presence / absence information symbol portion 34 is correlated with the short code number 2 (44) without channel, but 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 depending on the presence or absence of communication channel resources available to the radio base station is, in the above example,
Short code number 1 depending on the existence of communication channel resources
Alternatively, although the short code number 2 is used, in order to simplify the configuration, it is possible to use only one short code indicating that there is a communication channel resource, or it indicates that there is no communication channel resource. It is also possible to use only one short code.

FIG. 5 shows an example of determination of the presence / absence of a communication channel in that case. That is, an example in which only the short code number 1 is used according to the presence / absence of communication channel resources (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 the short code number 2 depending on 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 there is no channel, and if there is no correlation, it is determined that there is a channel. The short code in this case is not limited to the number 1 or 2.

The radio mobile station, which 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 wireless mobile station regularly monitors the correlation of the control channel with a short code (number 1: with channel) corresponding to the channel presence / absence symbol, and when it becomes less than a certain value, the wireless base station It is determined that there is no communication channel resource, and another radio base station transmitting the short code with communication channel resource is searched. In this way, the wireless mobile station always requests the wireless base station for communication by using the control channel of the wireless base station having the communication channel. Since the requested wireless base station has available communication channel resources, it can immediately start communication by designating the communication channel in response to the start request from the wireless mobile station.

FIG. 6 shows the signal processing of the radio mobile station in the case of NO2 of FIG. 5, that is, when only the short code number 1 is used depending on the presence or absence of the communication channel resource. The operation is
According to FIG. 3 and FIG. In the above description, the channel presence / absence information symbol 23 is not spread by the long code, but it is not always necessary to mask the channel presence / absence information symbol 23. However, if there is no long code spreading,
The wireless mobile station can easily detect the presence or absence of correlation with the first spreading code.

FIG. 7 is a diagram for explaining the transmission circuit of the base station. When notifying the wireless mobile station of the presence / absence of the channel resource of the wireless base station, the control channel information is spread by the output of the first spreading code generation unit 50 corresponding to the presence / absence of the communication channel resource in the multiplier 57 ( Note that 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 of the second spreading code, that is, the second spreading code is masked. The signal is spread by the signal combiner 60 and the multiplier 61.
Then, the output is spread by the output of the second spread code generator 56, and a multi-channel spread modulation signal output is obtained.

Further, the communication channel information 1 to N are spread by the multipliers 58 to 59 by the channel orthogonal first spreading code generators 1 to N, respectively, and passed through the signal combiner 60 to the multiplier 61. Then, the output is spread by the output of the second spread code generator 56, and a multi-channel spread modulation signal output is obtained. The timing controller 55 controls the timing so that a desired signal can be obtained. Further, the first spreading code generation unit 50 and the channel orthogonal first spreading code generation unit 51 corresponding to the presence / absence of communication channel resources may be the same, for example, in the case of having a single zone configuration. good.

FIG. 8 is a diagram for explaining the receiving circuit of the mobile station. The received spread modulation signal output, which appears 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 further 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 found that the received spread modulation 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 generation unit 75 to generate the second spreading code. This second spreading code is further multiplied by the channel spreading first spreading code replica generation unit 72 and the multiplier 79, and further, the received spread modulation signal output appearing on the line 91 is multiplied by the multiplier 78 and integrated. The dump circuit 76 detects the correlation. The threshold judgment circuit 77 judges whether the output of the integration / dump circuit exceeds a predetermined value. If it exceeds the threshold value, it is judged that the second spread code is synchronized. If it is less than the threshold value, the phase of the second spreading code replica generator 75 is shifted until the synchronization is achieved.

[0030]

As described above, according to the present invention, various effects described below can be realized. According to the inventions of claims 1 and 4, the base station notifies the mobile station of the presence or absence of the communication channel resource of the base station by using the spreading code associated with the presence or absence of the communication channel resource. Since the code itself is the communication channel resource presence / absence information, the mobile station does not need to demodulate the communication channel resource presence / absence information after identifying the spreading code for despreading. The time required to recognize the presence or absence of resources can be greatly reduced.

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 in relation to the system to be adopted. According to the invention of claim 3, 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. It is possible to easily detect the presence or absence of the correlation with the one spreading code.

According to the invention described in claims 5 and 6, a base station transmitter and a mobile station receiver using the communication channel control method in the direct sequence CDMA mobile communication system according to claims 1 to 4 are realized. be able to.

[Brief description of 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 the presence / absence of a communication channel.

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

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

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

[Explanation of symbols]

11a-d radio base stations 12a-d radio base station service areas 13 Radio control station 14 wireless mobile stations 21 pilot symbol 22 Control information symbol 23-channel presence / absence information symbol

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiki Fujima 2-10-1 Toranomon, Minato-ku, Tokyo NTT Mobile Communications Network Co., Ltd. (56) Reference JP-A-9-307951 (JP , A) JP-A-9-294291 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B ^7/ 24-7/26 102 H04Q ^7/ 00-7/38

Claims (6)

(57) [Claims] 1. A spreading code for expanding a band of a wideband signal, the spreading code having a speed higher than an information rate is repeated from a first spreading code group having the same repetition period as an information symbol cycle and an information symbol cycle. A direct spreading CDMA mobile station composed of a second spreading code group having a long period, which double spreads the signal by the first spreading code of the first spreading code group and the second spreading code of the second spreading code group and transmits the signal. In a communication channel control method in a communication system, a part of the first spreading code of the first spreading code group is associated with the presence or absence of usable communication channel resources in the base station, the base station is for the communication A communication channel in a direct spread CDMA mobile communication system characterized in that a signal is spread by 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 first spreading code associated with the presence or absence of the communication channel resource, the code associated with the availability of the communication channel resource in the base station, and the available communication in the base station. 2. The communication channel control method in a direct sequence CDMA mobile communication system according to claim 1, wherein the code is at least one code associated with the absence of a use channel resource. 3. 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. Or a communication channel control method in the direct sequence CDMA mobile communication system according to item 2; 4. A spreading code for expanding a band of a wideband signal, wherein the spreading code having a speed higher than an information rate is repeated from a first spreading code group having the same repetition period as an information symbol cycle and an information symbol cycle. A direct spreading CDMA mobile station composed of a second spreading code group having a long period, which double spreads the signal by the first spreading code of the first spreading code group and the second spreading code of the second spreading code group and transmits the signal. 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 usable 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 whose signal has been spread using the first spreading code associated with the mobile station, and the mobile station is associated 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, the spreading code having a speed higher than an information rate is repeated from a first spreading code group having the same repetition period as an information symbol period and an information symbol period. A direct spreading CDMA mobile station composed of a second spreading code group having a long period, which double spreads the signal by the first spreading code of the first spreading code group and the second spreading code of the second spreading code group and transmits the signal. In a base station in a communication system, a part of the first spreading codes of the first spreading code group is associated with the presence or absence of usable 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 sequence CDMA mobile communication system, which transmits a signal to a mobile station by spreading the signal using the obtained first spreading code. 6. A spreading code for expanding a band of a wideband signal, the spreading code having a speed higher than an information rate is repeated from a first spreading code group having the same repetition period as an information symbol period and an information symbol period. A direct spreading CDMA mobile station composed of a second spreading code group having a long period, which double spreads the signal by the first spreading code of the first spreading code group and the second spreading code of the second spreading code group and transmits the signal. In a mobile station in a communication system, a part of the first spreading codes of the first spreading code group is associated with the presence or absence of usable communication channel resources in the base station, and is associated with the presence or absence of the communication channel resources. Receiving a signal transmitted from a base station whose signal is spread using the first spread code, the wireless 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.