JPH0710075B2 - Synchronization method in wireless communication system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system using a digital frame, and more particularly to a system for rapidly obtaining synchronization of the digital frame, which is applied to HDLC (High Level Data Link Control Procedure). Regarding

[0002]

BACKGROUND OF THE INVENTION The present invention relates to Japanese Patent Application No. 1-321362 (wireless communication system) and Japanese Patent Application No. 2-265014 (temporary address system in wireless communication system). In this wireless communication system, a digital code is used for wirelessly transmitting information between a wireless terminal and a base station, and the transmission procedure and frame configuration are HDLC. However, since the transmission information field is an arbitrary bit in HDLC, the frame length is not constant, but in this wireless communication system, the frame length is fixed in order to perform time division multi-channel conversion. ing. In this way, when the frame length is fixed, the pattern for synchronization appears repeatedly at a specific time period, and this can be used to obtain frame synchronization.

[0003]

However, the radio wave propagation environment in mobile radio is poor, and there is a very high possibility of causing poor synchronization. If a sync failure occurs, it is necessary to quickly recover the sync, so
If a synchronization pattern is found, it is necessary to immediately start the synchronization process. For that purpose, it is necessary to ensure that the same pattern as the synchronization pattern does not occur in the frame.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a synchronization system in a wireless communication system for rapidly obtaining synchronization of a digital frame which applies HDLC.

[0005]

As a method for solving the above problems, the transparency of data in a frame is realized by using a flag sequence which is a frame identification code used in HDLC. There is a way to do it. That is, the same bit pattern as the flag sequence “01111110” is recorded as a frame pattern.
In order to prevent this from occurring in the transmission information field, for the target transmission data in the transmission information field, the bit "0" is forcibly inserted after the five consecutive bits "1" and the reception data is received. On the side, the bit "0" next to the five consecutive bits "1" is removed. Other than the transmission information field, it is necessary to use only the pattern that guarantees this transparency.

By this method, when the flag sequence is found, it is possible to immediately identify the start or end of the frame. However, since a new "0" is inserted, the required number of bits of the transmission information field becomes insufficient. Therefore, a part of the control field and the control information transmission block in the transmission information field, that is,
The block corresponding to the D channel shall be used to implement this transparency.

[0007]

As described above, by realizing the transparency of the digital code information in the frame, the quick synchronization can be established. For this reason, it is a particularly effective method in a mobile radio system that easily causes poor synchronization. However, due to the implementation of this transparency, there are various restrictions on the digital data in the frame, and even mobile radio systems are not always limited to communications in extremely deteriorated radio wave propagation environments. Considering the above, there is a method of switching between the case where this transparency is implemented and the case where this transparency is not implemented.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a frame structure which is an embodiment of the present invention. This is an embodiment of a frame structure for wirelessly transmitting digital code information, which is an application of HDLC. It should be noted that this is a bit configuration when the in-frame data is not transparent, and when it is performed, the bit configuration is slightly different.

F is a bit and frame synchronization field, A is an address field (base station 4 bits, wireless terminal 6 bits), FC is a frame count field, and C is a control field. Field (1 bit for transparency identification),
I is a transmission information field (the last block is for transmitting control information), and FCS is a frame check and collect sequence field. The numbers at the top of the frame in FIG. 1 indicate the number of bits in each block. Other order of fields can be considered. For example, F-FC-
A-C-I-FCS-F and the like.

The time required for transmission of this frame is 500 μs
And the error correction code is a fire code (m = 4, code length
105, 94 information bits, burst error with error correction capability of 4 bits or less). The correction range of the error correction code is the entire block except the bit and frame synchronization fields. The total number of bits in one frame is 121, and the transmission rate (bit.
The rate is 242 Kbit / s. Other block codes, convolutional codes, etc. can be used as the error correction code. In this case, the code length, error correction capability, etc. are different from the above. This frame is used for transmission from the base station to the wireless terminal and from the wireless terminal to the base station. (1) Function and configuration of each block in the frame (i) Bit and frame synchronization field F This is before and after the frame and indicates the start or end of the frame. However, the end part may be omitted or replaced with another end. In this embodiment, the flag is "01111110". Others include a bit synchronization pattern (eg 1010 ...) and a frame synchronization pattern.
Combinations of codes (for example, PN code) are also possible.

(Ii) Address field A This block is originally a part for inputting the address of the partner station or its own station, but in the embodiment shown in FIG. 1, 10 bits are divided and the upper 4 bits are the base station. , The lower 6 bits are used for the wireless terminal. The distribution of the number of bits between the base station and the wireless terminal can be arbitrary according to the form of the system.

As described above, it is necessary that this field also guarantees the transparency, but in this case, the next field (FC field) may be "111". It is necessary to consider that.

(Iii) Frame Count Field FC It has a code for indicating the temporal order from an arbitrary frame which is the starting point, and this code is periodically repeated.

In this embodiment, eight time division channels are taken, and 3 bits are used for this display. This channel information is a frame for transmission from the base station to the wireless terminal.
The channel number (binary) of the frame is input to the frame at the base station device. The wireless terminal can identify the channel to be used by this information.
Although the number of time-division channels can be arbitrary, the number of bits in the frame count field needs to be capable of displaying the number of channels.

(Iv) The structure of the control unit in the control field C HDLC is as shown in FIG. In FIG. 3, N (S) is a transmission sequence number and N (R) is
Is a reception sequence number (b2 and b6 are low-order bits). S is a monitoring function bit, and this bit defines the monitoring command / response. Further, M is a modifier function bit, and this bit defines an unnumbered command / response. P / F represents a pole / final bit.

Originally, in HDLC, there are the following three types of frames.

A, I (information) frame A frame having information content to be transmitted. In addition to transmitting information, it also has the function of transmission control.

B, S (monitoring) frame A frame used for executing monitoring control of the link. It has no information section.

C, U (unnumbered) Used for frame mode setting request, response and abnormal condition reporting. Some have an information section and some do not.

Although HDLC is a transmission control procedure originally established for the purpose of data transmission between computers, the present invention intends to apply this to the transmission in a wireless link between a base station and a wireless terminal. It is a thing. The data transmitted and received here is not necessarily the information such as numbers and characters for computer processing, but voice,
It also includes encoded data for sending various images. Also, in the HDLC, the number of bits in the transmission information field is arbitrary, but in the present invention, the number of bits in the frame is fixed due to time division use of the frame, adoption of an error control code and the like. As described above, there are large differences in the purpose of use and the frame structure, and it is not always necessary to be bound by the strict rules by HDLC. Further, N (S) (transmission sequence number) included in the I frame in HDLC,
Information such as N (R) (reception order number) is not necessary in encoded data such as voice and moving images. The control information block of the transmission information section, that is, the total number of bits excluding 1 byte corresponding to the D channel is 8 bits and 64 bits, and in order to realize the data transparency of this block, a maximum of 12 bits is more.
Bit needed.

Therefore, 5 bits out of the 8 bits of the control field are used, and if there is a further shortage, 8 bits corresponding to the control information transmission block of the transmission information field, that is, the D channel are used. Add and use a bit. In addition, it is confirmed that 5 bits of the control field or 5 bits of the control field and 8 bits of the D channel corresponding block of the transmission information field are used for realizing the transparency. It is identified by the remaining bit information of the field.

Further, an identification bit indicating whether or not this frame is a frame that guarantees transparency is further added, and the control field has a total of 9 bits. This identification bit is not necessary when the frame contains only transparent data at all times.

(V) Transmission information field I The transmission information field is a bit sequence of information to be transmitted, and is composed of nine blocks each consisting of 8 bits (1 byte). . Therefore, when digital data is transmitted using all 8 channels and all 9 data blocks of the transmission information field for each channel, 8 bits × 9 blocks / 500 μs = A data transmission rate of 144 Kbit / s can be obtained.

The data transmission rate of 144 Kbit / s is
2B + D (64K) defined as an international standardized interface in the integrated digital communication network (ISDN)
bit / s × 2 + 16 Kbit / s = 144 Kbit / s). Here, one of the nine data blocks corresponds to the D channel.

As a concrete application example, in the case of a standard telephone line, the transmission rate is 64 Kbit / s. This transmission rate uses 4 consecutive 8 out of 8 channels,
This can be realized by using 32 blocks excluding the block corresponding to the D channel in the transmission information fields of the four channels. Further, by using the four blocks corresponding to the D channel, for example, control information exchange with the base station or other data transmission between the terminals can be performed.

In the case of transmitting band-compressed voice information at a transmission rate of 16 Kbit / s, it is possible to deal with one channel, and 2 Kbi corresponding to the D channel.
At t / s, other data transmission can be performed at the same time.

As described above, information transmission at a transmission rate of 144 Kbit / s or less can be realized by using any continuous channel out of the eight channels.

(Vi) Frame check and collect sequence field FCS This is a block for detecting and correcting an error in transmission, and a fire code is used in the embodiment.
This field has other fields except this FCS
The remainder obtained by dividing 94-bit information by the generator polynomial is stored.

The error correction range is all data (105 bits) for removing the bit and frame synchronization fields F,
One burst error within 4 bits can be corrected. When the in-frame data is transparent, as shown in FIG. 2, "0" is inserted in the 6th bit to form a total of 12 bits. . (2) Example of transparency of transmission information data FIG. 4 shows an example of using a control field in order to achieve the desired transmission data transparency in the transmission information field. Shown in. In this case, as described in the previous section, the transmission information field is moved by 1 bit as much as the FCS field is increased by 1 bit to 12 bits, and as a result, the control field is reduced by 1 bit. To be done. b0 is a transparency identification bit. In the case of having transparency, xx ... x of b4 to b8 or b3 to b8 are the information bits at the beginning of the transmission information field. N (S), N (R) and P / F are the same as in FIG.

As shown in FIG. 4, a bit b for identifying the presence or absence of data transparency is added to the 8 bits of the control field.
0 is added, and 1 is set when there is no transparency and 0 is set when there is transparency. "0" of bit b1 indicates that the frame is in the information transfer format. When the data of the transmission information field is not transparent, the transmission / reception sequence number (N (S), N (R), P / F) is used as necessary as shown in FIG. To be done.

When the data of the transmission information field is made transparent, "0" is inserted in b3 when the two bits of b1 and b2 are "01", and the following b4 to b8 are added. It indicates that it is used for shortage. However, FCS
Since the field is increased by 12 bits and 1 bit, only 4 bits can be used for shortage. In this case, the maximum number of "0" insertions is three, and the transparent data including the block corresponding to the D channel is set to this control field.
Fields are stored in order from the b4 bit and then the transmission information field.
It should be stored in the folder. If the addition of 3 bits is insufficient due to the inclusion of the D channel corresponding block information, the transmission shall be attempted in the next frame, and the transmission of the D channel corresponding information in that frame shall be skipped. And When the number of insertions of "0" is 3 or less and the surplus is generated at the end, "0" is stored in the rest.

When the two bits of b1 and b2 are "00", the next 6 bits of b3 to b8 and the 8 bits corresponding to the D channel of the transmission information field are transparent for 64 bits of the desired transmission information. It is used to enforce sex. Here, for the same reason as described above, 13 bits, which is 1 bit less than the sum of 6 bits and 8 bits, can be used as the shortfall. Also in this case, when the surplus finally appears, the rest is filled with "0". As described above, the data to be transmitted by the transmission information field is always scissored with "0" at the front and back, and it is possible to prevent the destruction of the transparency due to the relationship with the adjacent field.

Next, as an example in which the frame is not in the information transfer format, an embodiment of frame transparency in the case of an incoming request from the base station to the wireless terminal and a response to this is shown in FIG.
Shown in. In this case, as shown in FIG. 5, the additional bits required for transparency implementation use the unused part of the transmission information field. In the case of (a), since the use area of the transmission information field is 6 bytes and 48 bits, the maximum number of additional bits is 9 bits, and in the case of (b), the same is 3 bits.
Since the number of bytes is 24 bits, the maximum number of additional bits is 4.
Is a bit. If there are no unused bits in the transmission information field, or if there are insufficient bits, the transmission information field
It is also possible to divide the information of the field into two and transmit it in two.

In order to implement the frame check and collect sequence field FCS transparency, a "0" is inserted in the sixth bit as shown in FIG. did. On the receiving side, the sixth bit is removed (it may not be "0" due to an error occurrence), so that it can be used as it is as error detection and correction information. However, there are cases where 6 consecutive "1" patterns occur after the 7th bit, but in this case, the frame end flag always follows, so this It will be processed in the frame synchronization process.

As described above, the transmission information field I is reduced by 1 bit by the amount increased by 1 bit in the frame check and collect sequence field FCS. Figure 5
In (), the number in parentheses indicates the number of bits in each field. The last bit of the control field C is always "0" in order to prevent the transparency destruction due to the relation with the data stored in the transmission information field I that follows.

[0037]

As described above, the present invention uses a high-speed digital code in a wireless link between a base station and a wireless terminal, and its transmission procedure and frame structure are HD.
The present invention relates to a synchronization method when LC is applied mutatis mutandis.

In mobile radio, usually, non-line-of-sight communication is usually performed, and therefore radio waves have a complicated structure composed of multiple waves that have undergone many reflections, diffractions and scatterings. In such a poor propagation path, there are many troubles regarding synchronization, which is the basis of digital communication. Therefore, it is a major technical problem in digital mobile radio to make it difficult to cause poor synchronization and to recover quickly if it occurs. The present invention is one of the means for solving these problems, and greatly contributes to the digitization of mobile radio which will be in full swing in the future.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of a frame structure for wirelessly transmitting digital code information according to the present invention.

[Fig.2] Frame check and collect sequence
It is explanatory drawing for the transparency implementation in a field (FCS).

FIG. 3 is an explanatory diagram for explaining a configuration of a control field in HDLC.

FIG. 4 is an explanatory diagram for explaining an example of use of the control field according to the present invention.

FIG. 5 is an explanatory diagram showing an example of information in a frame when performing an incoming operation according to the present invention.

[Explanation of symbols]

F: bit and frame synchronization field, A: address field, FC: frame count field, C: control field, I: transmission information field, F
CS: Frame Check and Collect Sequence Field.

Claims (4)

[Claims] 1. A frame structure for wirelessly transmitting digital code information, comprising a bit and frame synchronization field, an address field, and a frame count field.
In a transmission information field that stores transmission information between a base station and a wireless terminal of a wireless communication system including a field, a control field, a transmission information field, a frame check and a collect sequence field. A synchronization method in a wireless communication system characterized in that a part of a control field is used as an area required to realize transparency of digital code information. 2. The transmission information field is provided when a part of the control field is insufficient to realize transparency of digital code information in the transmission information field for storing the transmission information. 2. The synchronization method in a wireless communication system according to claim 1, wherein the control information transmission block is used. 3. A part of the control field is used or a part of the control field and the transmission information are used to achieve transparency of the digital code information in the transmission information field for storing the transmission information. 3. The synchronization method in the wireless communication system according to claim 1, wherein whether to use the control information transmission block of the field is identified by the information of the control field. 4. A synchronization method in a wireless communication system according to claim 3, wherein the synchronization information has identification information indicating whether or not the digital code information in the frame other than the bit and frame synchronization fields is transparent. .