JP2002186025A - Spread spectrum communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spread spectrum communication system that can decrease a call discrimination time addressed to its own station and/or a discrimination time of hand-off so as to extend the service life of a battery of a mobile phone or the like. SOLUTION: In the spread spectrum communication system where communication between a base station and a mobile station is conducted by using the code division multiple access system, a page indicator channel is specified for a communication channel between the base station and the mobile station. The page indicator channel has a page indicator message 200, a page indicator message is configured such that a call bit 200a of one bit is located at least at its head and a code number bit 200b of a plurality of bits is placed after the call bit 200a, the call bit expresses the presence of a call by the mobile station and the code number bits denote a spread code number.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication system, and more particularly, to a spread spectrum communication system applicable to a CDMA mobile phone system.

[0002]

2. Description of the Related Art <Technical Background> A communication line configuration method in which a common repeater or relay base is efficiently and commonly used by many users is called multiple access. Satellite communication and land mobile communication are typical examples. In satellite communication, communication between ground stations is performed via a repeater mounted on a satellite, and in land mobile communication, communication between mobiles (also referred to as mobile stations) is performed via a base station.

The following two types are known as a multiple access system. First, a frequency division multiple access (FDMA) that assigns a specific frequency channel to each user.
The second is a time division multiple access (TDMA) method in which a specific time slot in a time frame is allocated to each user.
le Access) method.

The former method (FDMA method) separates channels according to frequency, and the latter method (TDMA method) separates channels according to time. However, both have the drawback that if all frequency channels or all time slots are occupied, even if more users access, they are rejected. Therefore, in any of the systems, it is physically impossible to perform communication of N + 1 channels or more in a system designed to have an N-channel capacity.

On the other hand, a code division multiple access (CD) that assigns a specific code, that is, a PN (Pseudo Noise) sequence or a frequency hopping pattern, to each user.
The MA (Code Division Multiple Access) system separates channels only by checking with its own code, and the signals of each user share the same frequency band,
In addition, the above two methods (F
DMA, TDMA). In the CDMA method, since multiple access is performed by SS communication (Spread Spectrum Communication), the CDMA method is sometimes called a spread spectrum (or spectrum) multiple access.

[0006] The CDMA system is based on the above-mentioned FDMA system or TDMA.
Unlike the DMA system, the number of simultaneous call users is the design value (N)
Even in the above case, rejection is not caused only by deterioration of the S / N ratio and communication quality. Therefore, since overload communication is possible and communication service can be provided to many users by effectively using limited radio wave resources, for example,
This method is very suitable for use in land mobile communication systems such as mobile phones.

One of the main standard specifications for such land mobile communication systems is “TIA / EIA / IS-9”.
5 "(mobile station-base station compatibility standard for use in dual mode wideband spread spectrum mobile phone systems). Hereinafter, when this standard is simply referred to as “I-95 standard”, according to the I-95 standard, all base stations are global positioning system (GPS).
m) operates on a common time scale (CDMA system wide time scale), which references a time scale (so-called GPS time), and the timing alignment between the base station and the mobile station is based on the broadcast channel (control) from each base station. This is performed using a pilot channel (Pilot Channel). The codes of the actual pilot channels broadcast by each base station are the same, and only the timing offset differs. Each mobile station uses a different timing offset to identify the base station with which it is communicating.

FIG. 11 is a schematic flowchart showing a communication sequence in a CDMA mobile station (hereinafter, simply referred to as a “mobile station”). The mobile station first uses a pilot channel to chip a cell or a sector. Synchronization is established (step S1), and then despreading of a synchronization sync channel (Sync Channel) is performed (step S1).
2). Despread refers to a series of operations for multiplying a received signal by a code having the same phase as a code (for example, a PN sequence) in the received signal to perform coherent demodulation. When the despreading of the sync channel is completed, a paging channel (Paging Chamber) is obtained from the demodulated sync channel data.
nnel) is acquired (step S3), and various system configuration information, for example, identification information of a cell or a sector where the mobile station is located, is acquired using the paging channel (step S4). . Then
Transition to Access State (Step S)
5) Then, the base station is notified of the identification information (own station ID) of the mobile station (step S6), and it is determined whether or not there is a call to the own station (also simply called "call") (step S7). If there is a call, the mobile station shifts to a traffic channel (Traffic Channel) (step S9), and transmits and receives data to and from the base station. If there is no call, handoff (change of the cell position or sector position of the mobile station). ) (Step S)
8) If there is a handoff, various system information is acquired again. If there is no handoff, the system waits until there is a call addressed to the own station.

In this communication sequence, step S
7 is determined by the superframe (Su
per Flame) General Page Message (General
The handoff determination in step S8 is made based on the contents of the overhead information (Overhead Information) of the paging channel.

<Details of Prior Art> Here, the details of the conventional spread spectrum communication system will be described. In general, in the spread spectrum communication system, as represented by the IS-95 standard, each transmission signal is spread by a unique code (a PN code or the like; hereinafter, referred to as a "user spreading code") over the frequency band of a communication channel. Done by Each transmitted signal shares the same frequency band of the communication channel and is separated and identified only by a unique user spreading code. The specific transmission signal can be extracted from the frequency band of the communication channel by despreading using the user spreading code associated with the specific transmission signal. That is,
If the user spreading codes are orthogonal to each other, the received signal can be correlated with a particular user spreading code, emphasizing only the desired user signal for the particular spreading code and not the remaining signals for all other users. In this manner.

In a CDMA communication system, there are several different spreading codes that can be used to spread the information signal. These codes include a pseudo noise code (PN code) and a Walsh code. A Walsh code corresponds to one row or column of a Hadamard matrix, for example, a 64 channel CDM
In the A system, specific mutually orthogonal Walsh codes can be selected from among 64 code sets in a 64 × 64 Hadamard matrix. By spreading the specific data signal using this Walsh code,
A specific data signal can be separated and identified from other data.

In the IS-95 standard system, the cells or sectors are absolutely synchronized with each other depending on the GPS time, and with respect to the downlink, the base stations are offset by a short period PN sequence called a short code or a pilot PN sequence. Separated and identified. The relationship between cells and sectors may be separated by directivity such as, for example, three sectors having different directivities in one cell, or may be separated and identified only by the offset of the PN sequence. It may be done. If there is no directivity, no distinction is made between cells and sectors.

Each downlink channel in the base station is represented by C
It is separated and identified using 64 types of Walsh codes called DMA code channels, and 64 types of code channels are multiplexed in the same radio frequency band. For the purpose of ensuring security, each user applies a long code offset unique to the user to a long-period PN sequence called a long code, and is double-separated and identified. In the uplink, a pilot PN sequence and a long code having the same offset as the pilot PN sequence and the long code used in the downlink are used. The Walsh code is used for modulation called 64th-order orthogonal modulation in the uplink.

In the CDMA code channel output from the base station, the mobile station establishes chip synchronization on the pilot channel and establishes symbol synchronization on the sync channel.
In the pilot channel, all zero symbols are spread by a pilot PN sequence having a sector-specific offset and a Walsh code 0, and spreading by a long code is not performed. Since Walsh code 0 is all zero and data, that is, symbols, are all zero, only the pilot PN sequence can be finally obtained. Using this channel, the mobile station performs sequence correlation with the pilot PN sequence using a searcher circuit such as a sliding correlator or a matched filter, and establishes chip synchronization in that sector (see step S1 in FIG. 11).

After the establishment of the chip synchronization, the mobile station attempts to receive the sync channel. Since the sync channel is different from the pilot channel only in the Walsh code (Walsh code 32), after establishing the chip synchronization of the pilot channel, the mobile station applies the orthogonal spreading code from Walsh code 0 to Walsh code 32 at the timing of the short code. Then, the sync channel despreading process is performed (see step S2 in FIG. 11).

The mobile station transmits a sync channel message (Sync Chann message) which is the only message data of the sync channel.
el Message), and receives a pilot PN offset (an offset value from a zero offset pilot PN sequence to a pilot PN sequence that is synchronized with itself).
Also, an LC (Long Code) state (a long code state after a certain time synchronized with the system time, for example, 320 ms later), a long code mask value of a paging channel, and the like are acquired (see step S3 in FIG. 11).

When the above information acquisition is completed, the mobile station receives a paging channel composed of a pilot PN sequence and seven CDMA code channels (channels from Walsh codes 1 to 7). The paging channel is also spread with a long code, and the PN sequence offset value of the long code is set to a value defined in the system by the long code mask value obtained by receiving the sync channel. Similarly, the register state of the long code generator becomes the LC code state after a certain time (for example, after 320 ms) synchronized with the system time obtained by the sink channel reception, and by enabling code generation, the sector state of the receiving sector is set. Achieve long code despreading.
In the paging channel received first after despreading, one of the seven code channels is broadcast from the base station as a primary paging channel.

The mobile station first uses the primary paging channel to first use message information called overhead information (several types of messages indicating the system configuration at a geographical point where the mobile station is located; hereinafter, "system configuration information"). ) Is received continuously (Fig. 1)
1 step S4). In this continuous reception, the standard is to prohibit the intermittent operation of the mobile station in order to complete the collection of the overhead information at an early stage.

After completing the collection of the system configuration information, the mobile station transitions to a transmission state to the base station called an access state based on the system configuration information (FIG. 11).
After setting the transmission timing and the transmission output, the own station ID is transmitted (notified) to the base station (see FIG. 1).
Step 1 of Step S6). The base station determines a superframe for notifying a general page message such as whether or not there is a call to the mobile station based on the ID unique to the user, for example, 80 ms every 5.12 s. Determined by the given algorithm. This algorithm assigns all standby users to several groups, and the same algorithm is executed on the standby user side (mobile station side). This allows the general page message to be broadcast to a specific user at a certain time from the viewpoint of the base station, and only the specific superframe needs to be received from the mobile station side.

Therefore, the mobile station only needs to receive at this point only the superframe addressed to itself (hereinafter referred to as “assigned superframe” and distinguished from a normal superframe). It is only necessary to intermittently receive only the assigned superframe of 80 ms once every 5.12 s. The period (5.12 s) is a slot cycle index (Slot Cyc) that determines the length of the slot cycle period.
le Index) is dynamically determined by exchanging a parameter between the base station and the mobile station.

The mobile station determines whether or not there is a call addressed to itself based on the contents of the general page message in the assign superframe (see step S2 in FIG. 11). Shift to a traffic channel to start (see step S9 in FIG. 11).

On the other hand, when there is no call addressed to itself and no idle handoff is performed, the mobile station receives the assign superframe again as it is, and determines the call addressed to itself based on the content of the general page message. Continue (see the “YES” branch of step S8 in FIG. 11).

When an idle handoff is performed, the position of the mobile station may change and the system configuration information may change. In this case, the overhead information must be collected again (see “NO” in step S8 in FIG. 11), but whether or not the system configuration information has changed is determined by the message sequence number (Message Sequence N) included in the general page message.
It can be determined by examining o). If the message sequence number previously received and held by the user is different from the latest message sequence number, the system configuration information has changed.

At the time of an idle handoff, the idle-off destination sector has a different paging zone from the previous sector, and the mobile station needs to know whether or not registration is necessary again. Again, the mobile station, after idle handoff,
When the scheduled allocation general page message is received and idle handoff is detected and the message sequence number is different, each overhead information is continuously received again, all information is collected, and the system of the overhead information is collected. Parameter message (System Parameter
Message), the portion indicating the number of the paging zone called “REG_ZONE_NO” is checked, and if the number is different from the number collected in the previous sector, the mobile station determines that the paging destined for itself in that sector. Even if there is, it knows that it will not be called and determines that re-registration is necessary. "REG_ZONE_N
If "O" is different, the state shifts again to a transmission state called an access state, and registration with the receiving sector is executed.

By the way, in the paging channel, in order to increase the message transmission efficiency on the base station side, encoder tail bits (Encoder Tail Bits:
(A code string of several bits added to the end of the frame) is not defined. In other words, except that a one-bit indicator bit (Indicate Bit) indicating the start and continuation of the message is placed at the beginning of each frame from the start to the end of the message, all are composed of only valid messages. . For example, in the traffic channel, in contrast, every 20 ms frame defines an encoder tail bit at the end of the frame. An encoder tail bit is a constraint length K (for example, K =
When convolutional coding such as 9) is performed, the last bit of a frame is always set to “00000000”,
When decoding, for example, when performing Viterbi decoding,
This is for enabling a decoded output to be obtained for each frame, and is necessary for decoding audio data and the like. By the way, the reason why the Viterbi decoder can output every frame by defining the encoder tail bits for each frame is, in a nutshell,
One is that it is known before decoding that the register state of the convolutional encoder is "00000000" at the beginning of the frame. The other is that the output of the convolutional encoder is "00000000" in the last 8 bits of the frame.
Are known to be output in this order.

However, in the frame structure of the paging channel, as described above, since the encoder tail bits are not defined, the register state of the convolutional encoder is unknown at the head of the target frame, and the last eight bits of the frame are used. The output of the bits is also unknown. Therefore, in order to decode a frame in Viterbi decoding of a paging channel, the preceding and succeeding frames are also required. For example, when the frame length is 20 ms, at least the preceding and succeeding frames are necessary to correctly decode the 20 ms frame. Viterbi decoding must be performed for the three frames included (that is, for 60 ms). However, the necessity of the preceding and succeeding frames is not strictly for Viterbi decoding alone. This is because data is interleaved in units of frames, and only deinterleaving processing is required for the interleaved processing units. For this reason, depending on the case where the constrained length of the convolutional code is long, and how much the estimation accuracy of the register state and the 8-bit data is required, several frames of one or more frames before and after may be required.

Further, the reception of the page message is an intermittent operation, and a few meters are required for re-establishing the chip synchronization every time from the period during which the page message is stopped to the time when it wakes up.
s is required. For example, if the boundary of the spreading process is one cycle (26.66 ms) of the pilot PN, at least +6.67 is required for despreading at the shortest.
ms before, ie 26.66 m from the required frame
Despreading must start before s. In addition, in the case of the boundary of the 26.66 ms operation, the despreading is also completed, and after despreading the next frame of the target 20 ms frame, all the processing ends when the first 26.66 ms ends. Must.
Therefore, after all, processing the symbol for 60 ms,
The despreading process will be performed for 80 ms.

[0028]

A first problem of the spread spectrum communication system based on the IS-95 standard is that it takes a long time to judge a call addressed to its own station. The second problem is that it takes time to determine handoff.
Each of these problems is a technical problem that must be solved because it prolongs data processing during standby and shortens the battery life of a mobile phone or the like.

FIG. 12 is an example of a time chart showing intermittent reception of the shortest general page message when there is no call addressed to the own station. In this figure, 20 m of the paging channel corresponds to the assignment super frame in which three 26.66 ms frames of the sync channel are consecutively arranged.
A superframe in which four s frames are consecutive is shown. In this example, the general page message is acquired in the first frame of the superframe, and the signal processing time of the own station is, as shown in FIG. This is a long time from the time when the processing time (for example, 6.66 ms) is added to the middle of the third superframe.

FIG. 13 is an example of a time chart showing intermittent reception of a general page message when there is a call addressed to the own station. In this figure, the general page message is acquired from the beginning of the first frame of the superframe to the middle of the fourth frame, and the signal processing time of the own station is, as shown in FIG.
A predetermined pre-operation processing time (for example, 6.
66 ms), and after the superframe, 1
A predetermined post-processing time (for example, 6.
66 ms).

FIG. 14 is an example of a time chart showing the intermittent reception of a general page message when overhead information is broadcast up to the inside of an assign superframe. In this figure, the overhead information extends to the third frame of the super frame, and the general page message is acquired at the timing of the fourth frame of the super frame.
After all, the signal processing time of the mobile station is as shown in C in FIG.
This is a long time obtained by adding a predetermined pre-processing / post-processing time (for example, 6.66 ms) to the total time (120 ms) of the four frames of the superframe and one frame before and after it.

FIG. 15 is an example of a time chart showing the intermittent reception of overhead information when the message sequence numbers of the general page messages are different. Although different from the above example (FIG. 14) in that the overhead information does not cover the superframe, the signal processing time of the mobile station is longer, including the general page message and the overhead information, as shown in D in the figure. It's time.

Therefore, the problem to be solved by the present invention is to shorten the call determination time and / or the handoff determination time addressed to the own station, thereby extending the battery life of a portable telephone or the like. It is to provide a spread spectrum communication system that can be used.

[0034]

According to the first aspect of the present invention,
In a spread spectrum communication system in which communication between a base station and a mobile station is performed by a code division multiple access system, a page indicator channel is defined in a communication channel between the base station and the mobile station, and the page indicator channel is a page indicator message. And the page indicator message is configured to have at least a 1-bit call bit at the beginning and a plurality of code number bits after the call bit, and use the call bit to indicate whether a mobile station is called, A spreading code number is represented using the code number bit. The invention according to claim 2 is characterized in that, in the invention according to claim 1, the code number bit becomes all zeros when the call bit indicates that there is no paging of the mobile station. The invention described in claim 3 is claim 1 or claim 2.
The invention according to any one of the above aspects, wherein the page indicator channel is convolutionally encoded with a predetermined constraint length and a predetermined coding rate and transmitted from a base station. The invention according to claim 4 is a spread spectrum communication system in which communication between a base station and a mobile station is performed by a code division multiple access system, wherein an overhead indicator channel is defined in a communication channel between the base station and the mobile station, The overhead indicator channel has an overhead indicator message, and the overhead indicator message includes at least one leading indicator bit, a message sequence number of multiple bits after the indicator bit, and a max slot cycle index broadcast from the base station. And a variable length overhead information offset whose length is determined, and the overhead information is set by the next idle slot cycle period using the indicator bit. It indicates whether or no notification is present, representing the spreading code number using the message sequence number, wherein the. According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the overhead information offset becomes all zeros when the indicator bit indicates that there is no notification of overhead information by the next idle slot cycle period. It is characterized. According to a sixth aspect of the present invention, in the fourth aspect of the present invention, the overhead indicator channel is convolutionally encoded with a predetermined constraint length and a predetermined coding rate and transmitted from the base station. It is characterized by the following. In a spread spectrum communication system in which communication between a base station and a mobile station is performed by a code division multiple access system, a communication channel between the base station and the mobile station includes a page indicator channel and an overhead indicator channel. Wherein the page indicator channel has a page indicator message and the page indicator message has at least one call bit at the beginning and a plurality of code number bits after the call bit, Is used to indicate whether a mobile station is called, the code number bit is used to indicate a spreading code number, the overhead indicator channel has an overhead indicator message, and the overhead indicator message has a small number. Both a configuration having a 1-bit indicator bits and the indicators its length at Max slot cycle index to be broadcast from a plurality of bits of the message sequence number and the base station after the bits are determined variable overhead information offset to the beginning,
The indicator bit is used to indicate whether or not the overhead information is reported by the next idle slot cycle period, and the message sequence number is used to indicate a spreading code number. In the invention according to claim 8, in the invention according to claim 7, the code number bit becomes all zeros when the call bit indicates that there is no paging of the mobile station,
The overhead information offset becomes all zeros when the indicator bit indicates that overhead information is not reported by the next idle slot cycle period. According to a ninth aspect of the present invention, in the invention according to any one of the seventh and eighth aspects, the page indicator channel and the overhead indicator channel are convolutionally coded with a predetermined constraint length and a predetermined coding rate, and the base station is provided. It is transmitted from a station.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention
This will be described with reference to the drawings, taking a mobile phone of the DMA communication system as an example.

FIG. 1 is a block diagram showing a configuration of a CDMA mobile phone. In the figure, reference numeral 1 denotes an antenna, and 2 denotes a duplexer for separating a reception signal RX and a transmission signal TX on the frequency axis so that the antenna 1 is used for both transmission and reception.
The reception system converts the antenna 1 and the duplexer 2 and the reception signal RX into an intermediate frequency to extract only the reception frequency channel, and performs AGC (Automatic Gain Control) adjustment to keep the signal level of the desired reception wave constant. A reception high-frequency unit 3 and a quadrature detection unit 4 for separating a baseband IQ signal from a desired reception wave in the reception signal TX and performing AD conversion
A CDMA demodulator 5 for executing a signal processing sequence based on the IS-95 standard to demodulate an interleaved signal stream of the received digital signal (I · Q); a deinterleaver 5 for deinterleaving the interleaved signal stream; A Viterbi decoding unit 6 for performing error correction processing of the interleaved signal stream, and a sound processing unit 8 for loudspeaker-outputting the original error-corrected signal stream from a speaker 9, and the transmission system is input from a microphone 10. An audio processing unit 8 for AD-converting and compressing the audio, a convolutional encoding unit 11 for performing error correction encoding of the compressed digital audio signal, an interleave unit 12 for performing an interleaving process on the signal after error correction encoding, and Processing unit 1 for spreading the converted signal to convert it into analog IQ signals And, the analog I · Q signal OQSP
A quadrature modulator 14 for performing modulation and AGC adjustment to adjust to a required signal level, a transmission high frequency unit 15 for power-amplifying the OQSP modulation signal to generate a transmission signal TX,
A duplexer 2 and an antenna 1 are provided. The CDMA mobile phone includes a display system such as a liquid crystal display and an operation system such as a key operation unit in addition to the illustrated components.
It is omitted in the figure.

The operation of each part of the CDMA portable telephone, especially the part handling digital signals (CDMA demodulation unit 5, deinterleave unit 6, Viterbi decoding unit 7, audio processing unit 8, convolutional code unit 11, interleave unit 12, spreading process The operation of the unit 13 and the like can be controlled by software, and the CPU 16 is a control element for that. That is, the CPU 16 executes the control program for the CDMA mobile phone designed in conformity with the I-95 standard, so that the white lines 17 to 2 with arrows at both ends in the figure are displayed.
3 through a control signal line (or bus wiring)
It controls the operations of the DMA demodulation unit 5, the deinterleave unit 6, the Viterbi decoding unit 7, the audio processing unit 8, the convolutional code unit 11, the interleave unit 12, and the spread processing unit 13, and particularly defines the operation of the CDMA demodulation unit 5. Thus, the points of the first to third embodiments described later are realized.

FIG. 2 is a block diagram showing the configuration of the CDMA demodulation unit 5. The CDMA demodulation unit 5 includes a plurality (3 in FIG.
), A synthesizer 24, and a timing extraction circuit 25. The demodulators 21 to 23 demodulate the forward traffic channels from the multipath generation source and other base stations, and demodulate the sync channels from the nearest base station in a system acquisition stage such as a power-on sequence, and combine them. The unit 24 combines the finger data from the demodulators 21 to 23 to generate combined finger data, and outputs the combined finger data to the subsequent circuit (deinterleave unit 6). The timing extraction circuit 25 includes demodulators 21 to 23
And a required timing signal to the synthesizer 24 to support the acquisition of various channels and various messages included in the channels, which will be described later. Via CP
It is controlled by a control command transmitted from U5.

<First Embodiment> FIGS. 3, 4 and 5
FIG. 3 is a diagram showing a point of the first embodiment, and FIG.
Is an air timing configuration diagram when the general page message goes out of the frame, FIG. 4 is an air timing configuration diagram when the general page message fits in the frame, and FIG. 5A is a page indicator message (Page Indicate). Message), FIG.
FIG. 5B is an example of a page indicator message when there is no call, and FIG. 5C is an example of a page indicator message when there is a call.

In the first embodiment, the point is to divide a conventional function into a page indicator channel (Page Indicate Channel) and a paging channel (FIGS. 3 and 4). It is assumed that the page indicator channel has a page indicator message 200. The page indicator message 200 includes one call bit (Call Bit) 200a, 7
Code No Bits 200
b, including an 8-bit encoder tail bit 200c (FIG. 5 (a)), and having a constraint length K = 9 and a coding rate R = 1
/ 3, and is transmitted from the base station.

When any one of the assigned waiting groups receives a call, the call bit 20
It is assumed that 0a is set to "1" and the code number bit 200b represents the Walsh code number of the paging channel (FIG. 5 (c)). In this case, the configuration of the paging channel may be the same as the conventional one, and the number corresponding to the user ID of the user who called is notified using a general page message. Note that the actual value of the code number bit 200b in FIG. 5C (“0000110” = 1)
“6” in the decimal number represents a Walsh code 6, which indicates that a general page message can be received with this Walsh code.

As described above, in the first embodiment, the call bit 20 of the page indicator message 200
0a is normally "0", but becomes "1" when any one of the assigned standby groups calls, and the code number bit 200b indicates the code number of the Walsh code of the page indicator channel. To represent. The configuration of the paging channel may be the same as the conventional configuration, and the number corresponding to the user ID of the called user may be notified by a general page message.

The frame timing and the pilot PN timing are configured to be continuous, and when the leading bit "1" is detected by the mobile station, the code number bit 200b
Is detected by hardware and the Walsh code is immediately changed to the code number indicated by the code number bit 200b from the 17th bit timing and despread, thereby receiving the paging channel.

For example, when the general page message is started after one PN roll of the short code, the Walsh code is transmitted at the timing of starting the next PN roll after despreading 16 bits of the page indicator channel. Code number bit 200
By changing to the code number indicated by b and despreading, the paging channel can be received immediately.

If the call is addressed to one's own, the system shifts to the traffic channel in the same manner as before and starts talking, and if not, the intermittent reception of the page indicator channel is started again. Just fine.

If there is no call in any of the assigned waiting groups, the call bit 200a is set to "0" to indicate no call, and only the page indicator message 200 is re-assigned at the timing of the assigned superframe. Is periodically received, so when there is no paging such as at midnight or when there are very few pagings, 1 is assigned at the timing of the assigned superframe.
Only the page indicator message 200 having a length of 6 bits needs to be received, so that unnecessary standby processing is not performed.

Further, when the call bit 200a is "0", the call number bit 200b is guaranteed to be all zero (FIG. 5 (b)). It can be used as an encoding tail bit, and can be controlled to stop the receiving operation immediately after decoding the code number bit 200b.

It is known that the register state of the convolutional coder at the start of the paging channel message is all zero, since the data of the page indicator channel and the paging channel are continuously convolved. In addition, since the data of each page indicator message 200 between each superframe is also continuously convolved, the mobile station knows that the register state of the convolutional encoder is all zero immediately after the start of receiving the target frame of the paging channel. As a result, Viterbi decoding can be started.

Therefore, according to the first embodiment,
The conventional function is divided into a page indicator channel and a paging channel.
A code length bit 200a, a 7-bit code number bit 200b, and an 8-bit encode tail bit 200c, a constraint length K = 9, and a coding rate R =
Since the bits are convolved by a 1/3 convolutional encoder and transmitted from the base station, the call bit 200 is set when no one of the assigned waiting groups has a call.
a becomes "0" to indicate that there is no paging, and there is an effect that only the page indicator message 200 needs to be periodically received at the timing of the re-assigned superframe.

That is, when there is no paging such as in the middle of the night or when the number of paging is extremely small, only the 16-bit page indicator message 200 needs to be received at the timing of the assigned superframe. There is an extraordinary effect that the actual operation time when the station waits can be greatly reduced, and the battery life can be extended.

When the call bit is "0",
Since the code number bit 200b is guaranteed to be all zero, the code number bit 20b
0b can be treated as a temporary encoding tail bit, and control can be performed so that the receiving operation is stopped immediately when the 8th bit is decoded. In this regard, the actual operation time during standby can be reduced. effective.

The frame timing and the pilot P
In the case where the N timings are configured to be continuous, the mobile station detects the code number bit 200b by hardware when detecting “1” in the first bit, and changes the Walsh code from the 17th bit timing to the code number bit. The paging channel can be received by immediately changing to the code number indicated by 200b and despreading, or, for example, the short code 1
When the general page message is started after the PN roll, after the 16 bits of the page indicator channel are despread, the Walsh code is changed to the code number indicated by the code number bit 200b at the next PN roll start timing. By performing despreading by changing to, the paging channel can be received immediately, so that even when a call is detected, the reception operation time can be shortened.

Since the data of the page indicator channel and the data of the paging channel are configured to be continuously convolved, it is known that the register state of the convolutional encoder at the start of the message of the paging channel is all zero. In addition, since the data of each page indicator message 200 between each superframe is also continuously convolved, the mobile station must ensure that the register state of the convolutional encoder is all zero even immediately after the start of receiving the target frame of the paging channel. Is known, and the Viterbi decoding can be started.

<Second Embodiment> FIGS. 6, 7 and 8
FIG. 6 is a diagram showing a point of the second embodiment, and FIG.
Is an overhead indicator message (Overhead I
ndicate Message), an air timing configuration diagram when the overhead information is broadcast in slot cycle A, and FIG.
FIG. 4 is an air timing configuration diagram in the case where the notification is made by B and B. FIG. 8A is a configuration diagram of an overhead indicator message, and FIG. 8B is an example of an overhead indicator message when overhead information is not notified by the next idle slot cycle period, and FIG. Is an example of an overhead indicator message when the reporting of overhead information is started by the next idle slot cycle period.

In the second embodiment, the point is to divide the conventional function into an overhead indicator channel and a paging channel. It is assumed that the overhead indicator channel has an overhead indicator message 300. The overhead indicator message 300 includes, in order from the top, a one-bit indicator bit 300a indicating whether or not there is broadcast of overhead information by the next idle slot cycle period. , 6-bit message sequence number 300b, and a Max Slot Cycle Indication broadcast from the base station.
ex) variable length overhead information offset (Overhead Information Offse)
t) 300c, 8-bit encoder tail bit 30
It is assumed that convolutional coding is performed with a constraint length K = 9 and a coding rate R = 1/3, including 0d.

The overhead information offset 300c is, for example, 16 × 2 when the maximum slot cycle index is “2”.
^{Max Slot Cycle Index} -1 = 63 bits to be determined as a 6-bit length, and the number of offsets of the start superframe when overhead information from the currently received allocated superframe is arranged from within the above cycle. Shall be represented.

Here, the overhead information needs to be received when idle handoff is performed. In this case, the overhead indicator channel is used only when a time base confirmation cycle for periodically confirming the necessity of updating the overhead information comes. To receive. The received message sequence number is compared with the previously received message sequence number. If the received message sequence number is different, the mobile station shifts to a paging channel and receives overhead information.

As described above, in the second embodiment, the conventional function is divided into the overhead indicator channel and the paging channel, and the overhead indicator message 300 of the overhead indicator channel is
In order from the beginning, a 1-bit indicator bit 300a indicating whether or not there is notification of overhead information by the next idle slot cycle period;
It consists of a message sequence number 300b of bits, an overhead information offset 300c whose length is determined by the maximum slot cycle index broadcast from the base station, and an encoder tail bit 300d of 8 bits. Rate R
= Convolution of bits with a 1/3 convolutional encoder.

The variable length overhead information offset 300c is, for example, 16 × 2 when the maximum slot cycle index is “2”.
^{Max Slot Cycle Index-} 1 = 63 bits is determined to be a 6-bit length, and the offset value is used to determine the start superframe when the overhead information from the currently received allocated superframe is arranged within the cycle. Indicates the offset number.

It is necessary to receive the overhead information at the time of idle handoff (handoff at the time of standby). In this case, the overhead information is only transmitted when a time base confirmation period for periodically confirming the necessity of updating the overhead information comes. Receive an indicator channel. Then, the received message sequence number is compared with the previously received message sequence number, and if different, the process proceeds to the paging channel to receive the overhead information. Note that the Walsh code of the paging channel at this time is reported in advance by another method.

Further, regarding the shift to the paging channel, if the indicator bit 300a, which is the first bit of the overhead indicator channel, is "1", the overhead information is arranged within the period defined by the maximum slot cycle index. In this case, the superframe in which the overhead information is to be arranged is indicated by the overhead information offset 300c using the number of offsets from the current received superframe.

When the indicator bit 300a, which is the first bit of the overhead indicator channel, is "0", it indicates that overhead information is not yet arranged within the period. In this case,
The overhead information offset 300c is always guaranteed to be "0" by the number of bits equal to the encoder tail bit from the beginning, and the mobile station can use the overhead information offset 300c as a temporary encoder tail bit and immediately stop the reception operation. .

That is, when it is necessary to update the overhead information, in other words, even if the message sequence numbers are different, the apparatus waits so as not to perform the operation of receiving the overhead information when the indicator bit 300a is "0". After receiving only the overhead indicator channel at the timing of its assigned superframe and confirming that the indicator bit 300a has become "1",
It is possible to start receiving the overhead information in the superframe indicated by the overhead information offset 300c received in the superframe. In this case, each message of the overhead information may be reported continuously or may be reported at intervals.

The overhead indicator channel has an overhead information offset of 3 during the period in which the overhead information is reported.
Immediately after 00c, an all-zero encoder tail bit 300d such as 8 bits is guaranteed. In a period in which no overhead information is reported, for example, 6 bits of all bits of the overhead information offset 300c are guaranteed to be all zeros, and Bit 300d also guarantees all zeros. That is, in any case, immediately after the necessary information length, known data such as all zeros of the number of bits required to converge and terminate decoding of the decoder is transmitted. Therefore, depending on whether or not the message sequence numbers match or there is no overhead information at that time, even if the receiving operation is immediately stopped, only the necessary part of the message can be reliably and reliably decoded.

Further, since the data is continuously convolved between the superframes, the mobile station starts despreading from the target frame of the overhead indicator channel and ends the despreading at the end of the target frame. It is possible to obtain the decoded output from the decoder.

Therefore, according to the second embodiment,
The conventional function is divided into an overhead indicator channel and a paging channel, and an overhead indicator message 300 of the overhead indicator channel is provided.
Are sequentially replaced by one indicator bit 300
a and a 6-bit message sequence number 300
b, an overhead information offset 300c whose length is determined by the maximum slot cycle index broadcast from the base station, and an 8-bit encoder tail bit 300d, a constraint length K = 9, and a coding rate R = 1/1. The convolutional encoder of FIG. 3 convolves the bits and indicates the offset number of the starting superframe when the overhead information from the currently allocated allocated superframe is arranged from within the above-mentioned period. In the case of "1", it can be known that the overhead information is arranged within the cycle defined by the maximum slot cycle index, and only the superframe in which the overhead information is to be arranged can be received. There is an effect that it becomes possible.

If the indicator bit 300a, which is the first bit of the overhead indicator channel, is "0", it indicates that no overhead information has been arranged within the period. In this case, the overhead information is arranged. Until is indicated, there is an effect that the intermittent reception of only the assigned standby superframe can be continued.

That is, when it is necessary to update the overhead information, in other words, even when the message sequence numbers are different, if the indicator bit 300a is "0", the standby state is set so as not to perform the operation of receiving the overhead information. Then, after receiving only the overhead indicator channel at the timing of the allocated superframe and confirming that the indicator bit 300a has become "1", the superframe indicated by the overhead information offset 300c received in the superframe is received. Reception of overhead information can be started with frames, and the useless reception operation time when the message sequence number differs on the mobile station side can be greatly reduced. There is an effect.

Further, the overhead indicator channel has an overhead information offset of 3 at a period in which the overhead information is notified.
00c, an all-zero encoder tail bit 300d such as 8 bits is guaranteed, and in a period in which no overhead information is notified, for example, 6 bits of all bits of the overhead information offset 300c are guaranteed to be all zeros. Since all zeros are also guaranteed in the tail bit 300d, even if the receiving operation is immediately stopped according to the coincidence / mismatch of the message sequence numbers and the presence / absence of the arrangement of the overhead information, only the necessary messages are received. There is an effect that decoding can be performed without any trouble.

Since the data is continuously convolved between the superframes, the mobile station starts despreading from the target frame of the overhead indicator channel, and ends despreading at the end of the target frame. Also, there is an effect that a code output from the Viterbi decoder can be obtained.

<Third Embodiment> FIGS. 9 and 10 show
FIG. 9 is a diagram showing a point of the third embodiment, and FIG.
An example in which the Walsh code of the assigned paging channel reporting the general page message is a Walsh B code, and the Walsh code of the paging channel reporting the overhead information is a Walsh D code, each of which is composed of a separate code channel. The air timing configuration diagram showing
FIG. 10 is an air timing configuration diagram showing an example in which the general page message and the overhead information are configured by a common code channel. In addition,
Each example shows an example in which the slot cycle index is fixed by the max slot cycle index and the slot cycle index is “2”.

In the third embodiment, the point is to divide a conventional function into a page indicator channel, an overhead indicator channel, and a paging channel. The page indicator channel is shown in FIG.
Similarly, the page indicator message includes, in order from the beginning, one call bit, seven code number bits, eight encoder tail bits, and a constraint length K = 9, It is assumed that convolutional coding is performed at a coding rate R = 1/3 and transmitted from the base station.

The overhead indicator channel has an overhead indicator message as in FIG. 8, and the overhead indicator message is composed of a 1-bit indicator bit, a 6-bit message sequence number, and a A variable length overhead information offset whose length is determined by the broadcasted Max Slot Cycle Index, including an encoder tail bit of 8 bits, a constraint length K = 9, and a coding rate R = 1 /
3 is convolutionally coded.

The two messages start from the head of the assigned superframe, and the timings of the messages completely overlap. The mobile station despreads at the same short code timing, and then operates to obtain a message by despreading with different Walsh codes on different routes.

As described above, in the third embodiment, the conventional function is divided into a page indicator channel, an overhead indicator channel, and a paging channel, and the page indicator messages of the page indicator channel are sequentially transmitted from the top in 1-bit call messages. Bits, a code number bit of 7 bits, and an encoder tail bit of 8 bits. The bits are convolved with a convolutional encoder having a constraint length K = 9 and a coding rate R = 1/3 and transmitted from the base station. I do. Also, the overhead indicator message of the overhead indicator channel is sequentially transmitted from the head, by 1 bit indicator bit, 6 bit message sequence number, and overhead information offset whose length is determined by the max slot cycle index broadcast from the base station. , 8 bits of encoder tail bits, and convolutional bits by a convolutional encoder having a constraint length K = 9 and a coding rate R = 1/3.

If any one of the assigned waiting groups is called, the call bit of the page indicator channel becomes "1" to indicate that there is a call.
The code number bit indicates the code number of the Walsh code of the paging channel. Also, the mobile station receives the overhead indicator channel only when the mobile station performs idle handoff and when the time base overhead information confirmation cycle comes. Then, the received message sequence number is compared with the previously received message sequence number, and if they are different, the process proceeds to the paging channel to receive the overhead information.

Therefore, according to the third embodiment,
If there is no paging and there is no idle handoff and only the time-based overhead information confirmation operation is performed, the page indicator message on the page indicator channel of the Walsh A code and the Walsh C at the timing of the allocated superframe. It can be operated to periodically receive only overhead indicator messages on the code overhead indicator channel.

Here, as shown in FIGS. 9 and 10, two messages (a page indicator message and an overhead indicator message) start from the head of the allocated superframe, and the timing of the messages overlaps. That is, the mobile station only needs to operate to despread at the same short code timing and then perform Walsh despreading with different Walsh codes on different routes to acquire the message. As described above, the page indicator message and the overhead indicator message are orthogonally spread using different Walsh codes or the like, and the frame timing is made the same, so that the operation time during standby at the mobile station side can be optimized.

[0079]

According to the first aspect of the present invention, only by checking the call bit of the page indicator message,
The presence or absence of a call can be determined, and the time for determining a call addressed to the own station can be reduced. According to the second aspect of the invention, the code number bits set to all zeros can be used as temporary encoder tail bits, and the Viterbi decoding process can be quickly performed without waiting for detection of the original encoder tail bits. Can be completed. According to the third aspect of the invention, the transmission of the page indicator channel can be performed in conformity with the code division multiple access system. According to the fourth aspect of the present invention, it is possible to determine whether or not the overhead information is reported by the next idle slot cycle cycle only by examining the indicator bit of the overhead indicator message. Shortening can be achieved. According to the fifth aspect of the present invention, the overhead information offset set to all zeros can be used as a temporary encoder tail bit, and the Viterbi decoding process can be quickly performed without waiting for detection of the original encoder tail bit. Can be completed. According to the invention described in claim 6,
The transmission of the overhead indicator channel can be performed in conformity with the code division multiple access system. According to the present invention, the presence or absence of a call can be determined only by examining the call bit of the page indicator message, and the next idle slot cycle period can be determined only by examining the indicator bit of the overhead indicator message. By this time, it can be determined whether or not the overhead information has been notified. Therefore, it is possible to achieve both a reduction in the call determination time addressed to the own station and a reduction in the handoff determination time. According to the invention of claim 8, the code number bit set to all zeros or the overhead information offset set to all zeros can be used as temporary encoder tail bits, and waits for detection of the original encoder tail bits. Without this, the Viterbi decoding process can be completed quickly. According to the ninth aspect, transmission of the page indicator channel and the overhead indicator channel can be performed in conformity with the code division multiple access system.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a CDMA mobile phone.

FIG. 2 is a block diagram illustrating a configuration of a CDMA demodulation unit 5;

FIG. 3 is an air timing configuration diagram when a general page message goes out of a frame.

FIG. 4 is an air timing configuration diagram when a general page message fits within a frame.

FIG. 5 is a diagram showing a configuration diagram of a page indicator message, an example of a page indicator message when there is no call, and an example of a page indicator message when there is a call.

FIG. 6 shows that the overhead information is changed to the slot cycle A by the overhead indicator message.
FIG. 4 is an air timing configuration diagram when the notification is made in FIG.

FIG. 7 shows that overhead information is changed to a slot cycle A by an overhead indicator message.
FIG. 4 is an air timing configuration diagram in the case where the notification is made by B and B.

FIG. 8 is a configuration diagram of an overhead indicator message, an example of an overhead indicator message when overhead information is not notified by the next idle slot cycle period, and a case in which overhead information notification is started by the next idle slot cycle period. It is a figure showing an example of an overhead indicator message.

FIG. 9 shows a Walsh code of an assignment paging channel that broadcasts a general page message is a Walsh B code, and a Walsh code of a paging channel that broadcasts overhead information is a Walsh D code, which is composed of separate code channels. FIG. 6 is an air timing configuration diagram showing an example in the case where the air timing is present.

FIG. 10 is an air timing configuration diagram showing an example in which a general page message and overhead information are configured by a common code channel.

FIG. 11 is a schematic flowchart showing a communication sequence in a CDMA mobile station.

FIG. 12 is an example of a time chart showing intermittent reception of the shortest general page message when there is no call addressed to the own station.

FIG. 13 is an example of a time chart showing intermittent reception of a general page message when there is a call addressed to the own station.

FIG. 14 is an example of a time chart showing intermittent reception of a general page message when overhead information is broadcast to the inside of an assignment superframe.

FIG. 15 is an example of a time chart showing intermittent reception of overhead information when the message sequence numbers of general page messages are different.

[Explanation of symbols]

200 page indicator message 200a call bit 200b code number bit 300 overhead indicator message 300a indicator bit 300b message sequence number 300c overhead information offset

Claims (9)

[Claims] 1. A spread spectrum communication system in which communication between a base station and a mobile station is performed by a code division multiple access system, wherein a page indicator channel is defined as a communication channel between the base station and the mobile station. The channel has a page indicator message and the page indicator message has at least one leading
A call bit and a plurality of code number bits after the call bit, indicating whether a mobile station is called using the call bit, and indicating a spreading code number using the code number bit. A spread spectrum communication system characterized by the following. 2. The spread spectrum communication system according to claim 1, wherein said code number bit becomes all zeros when said call bit indicates that there is no paging of a mobile station. 3. The spectrum according to claim 1, wherein the page indicator channel is convolutionally encoded with a predetermined constraint length and a predetermined coding rate and transmitted from a base station. Spreading communication method. 4. A spread spectrum communication system in which communication between a base station and a mobile station is performed by a code division multiple access system, wherein an overhead indicator channel is defined in a communication channel between the base station and the mobile station. The channel has an overhead indicator message, and the overhead indicator message has at least a 1-bit indicator bit, a message sequence number of a plurality of bits after the indicator bit, and a maximum slot cycle index broadcast from the base station. And a variable length overhead information offset determined by using the indicator bit, the overhead information is notified by the next idle slot cycle period. It indicates whether or not there, represents the spreading code number using the message sequence number, a spread spectrum communication system, characterized in that. 5. The spread spectrum apparatus according to claim 4, wherein said overhead information offset becomes all zeros when said indicator bit indicates that no overhead information is notified by a next idle slot cycle period. Communication method. 6. The spectrum according to claim 4, wherein the overhead indicator channel is convolutionally coded with a predetermined constraint length and a predetermined coding rate and transmitted from a base station. Spreading communication method. 7. In a spread spectrum communication system in which communication between a base station and a mobile station is performed by a code division multiple access system, a page indicator channel and an overhead indicator channel are defined as a communication channel between the base station and the mobile station. The page indicator channel has a page indicator message, and the page indicator message has at least one leading one.
Bit call bit and a plurality of code number bits after the call bit, the call bit indicates presence / absence of paging of the mobile station, the code number bit indicates a spreading code number, The overhead indicator channel has an overhead indicator message, and the overhead indicator message includes at least a first indicator bit, a message sequence number of multiple bits after the indicator bit, and a max slot cycle index broadcast from the base station. And a variable length overhead information offset whose length is determined. It indicates whether or no notification is present in Omeshon represents a spreading code number using the message sequence number, a spread spectrum communication system, characterized in that. 8. The code number bit becomes all zeros when the call bit indicates that there is no paging of the mobile station, and the overhead information offset indicates that the indicator bit indicates overhead information by the next idle slot cycle period. 8. The spread spectrum communication system according to claim 7, wherein all zeros are set when there is no data. 9. The base station according to claim 7, wherein the page indicator channel and the overhead indicator channel are convolutionally coded with a predetermined constraint length and a predetermined coding rate and transmitted from a base station. Spread spectrum communication method described in Crab.