KR20010027925A - Structure of synchronization protocol frame for special data service in mobile network using CDMA system and method of synchronization for the same - Google Patents

Abstract

PURPOSE: A synchronous protocol frame structure for a specific data service in a mobile telephone network using a CDMA(Code Division Multiple Access) system is provided to perform a voice call and to implement a protocol for reciprocal synchronizing in a traffic channel. CONSTITUTION: A primitive traffic is composed of two pieces of SI(Synchronizing Information) and one R/A(Request/Acknowledge). Each of the SI is composed of a 16-bit length preamble sequence, a 16-bit length message type, and 96-bit length information. The 16-bit length preamble sequence has a lowest frequency rate among sequences, which are not identical with a result for source-coding messages. The 16-bit length preamble sequence has a '0000x' type, and is capable of being changed. The 16-bit length message type is capable of deciding whether a message kind is an SI or an A(Acknowledge) or an NA(Non Acknowledge), and has a lowest frequency rate.

Description

Structure of synchronization protocol frame for special data service in mobile network using CDMA system and method of synchronization for the same}

The present invention relates to a synchronous protocol frame structure and a synchronous protocol method for a special data service in a mobile telephone network using a code division multiple access (CDMA) scheme. Calls for voice calls are made, separate protocols for mutual synchronization are implemented on the traffic channels to make calls, minimizing changes to the existing PCS system, and synchronization for high-reliability and accurate data services. The present invention relates to a synchronous protocol frame structure and a synchronous protocol method for data services that can be provided.

In additionally realizing a special data service technology of a CDMA digital mobile telephone network, a technology of distributing information to each other and matching synchronization information for performing a data service function should be used. However, in the existing technology, technical measures for data service have not been carried out, and since the communication must be performed with the same data information as the counterpart caller, it is necessary to deliver its own special data to the other party and precisely synchronize the data service. Therefore, the existing PCS technology does not have a separate channel to perform this, and may not require any modification to the current method.

Accordingly, an object of the present invention is to provide a synchronization protocol frame structure and a synchronization protocol method for data service in a mobile telephone network using a CDMA scheme capable of accurately transmitting synchronization information.

A synchronization protocol frame structure for data service in a mobile telephone network using the CDMA scheme according to the present invention for achieving the above object is composed of spare bits, information bits, frame quality bits and encoding tail bits, the information bits are mixed mode In a synchronous protocol frame structure consisting of bits and raw traffic, the raw traffic is composed of two synchronization information and one receiving unit (RA), and the synchronization information most occurs among the ones that do not match the result of source coding the message. in the low frequency random number sequence, and the form is in the form of 0000 _x and a preamble sequence of 16-bit length to be changed when there is a need to change, the synchronization information that the a or the message source and coded as information that can determine whether an NA Lowest occurrence among those that do not match one result 16-bit long message type and 96-bit long information.

In addition, the synchronization protocol method for data service in a mobile telephone network using the CDMA method according to the present invention transmits a predetermined number of request acknowledgment messages to the transmitting terminal at the receiving terminal receiving the predetermined number of request messages transmitted from the transmitting terminal. Entering a data transmission mode, receiving a predetermined number of request confirmation messages transmitted from the receiving terminal, entering a data receiving mode, and receiving a request message transmitted from the transmitting terminal at the receiving terminal. If not, the receiving terminal transmits a voice, and if it fails to receive a request confirmation message from the receiving terminal after transmitting a predetermined number of last request messages from the transmitting terminal, stops the protocol to make a call in the voice call mode. Data service communication room It characterized in that made in a step of displaying that.

The amount of traffic channel information lost due to synchronization information transmission is minimized, and synchronization information should be transmitted to the receiving terminal within a maximum of 600msec. In general, the time that human can detect the noise is about 200 to 250msec, but in this synchronization scheme, since the noise is hardly transmitted to the other party, it occurs with a probability of 10 ^-60 as 600msec. The probability of failing to send synchronous information is negligible, and the probability of failing to send synchronous information to one terminal in voice call mode and the other to data service mode is negligible compared to the probability of failing to send synchronous information. Small enough to be Although the synchronization information is normally transmitted, the probability that there is an error in the transmitted synchronization information is small enough to be ignored.

1 is a block diagram of a PCS digital mobile telephone network to which the present invention is applied.

2 is a structure diagram of a primary traffic channel of a PCS system;

3 is a frame structure diagram of a synchronization protocol according to the present invention;

4 is a diagram illustrating the procedure and time of the fastest synchronization information transmission / reception protocol.

5 is a diagram illustrating a procedure and time of a general synchronization protocol.

The present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a CDMA mobile telephone network to which the present invention is applied.

The interval through which synchronization information passes in the equipment providing the data service is from MS to MS. The sections to be considered in order to prepare a motive scheme for such a data service can be divided as follows.

MS ~ MS: MS → BTS → BSC → MSC → BSC → BTS → MS

At this time, only the MS ↔ BTS section is the wireless section and the section with the most likely error. The error detection used in the PCS system is based on a cyclic redundancy code (CRC) implemented using a primitive polynomial.

The forward traffic channel frame structure of the PCS system (14,400 bps) is 1 bit reserved bits (referred to as R), as shown in Figure 2, 267 bits of information bits containing the synchronization information ( Information Bits, 12-bit Frame Quality Bits (hereinafter referred to as F) with CRC results of Information Bits, and 8-bit Encoding Tail Bits (hereinafter referred to as T). Can be divided into In addition, the information bits may be divided into 1-bit mixed mode bits (hereinafter, referred to as MM) and 266 bits of primary traffic that actually contains synchronization information.

The F bits used for the double CRC are calculated using the 12 th order raw polynomial, thus equally distributing the entire information bit space, that is, 2 ²⁶⁷ bits, with a probability of 1/2 ¹² each, which probability is not detected by CRC error. This means that 1/2 ¹² = 2.5 X 10 ^-4 . For convenience, this error is called CrcER. In other words, CrcER is the probability that there is an error that is not detected by the CRC.

In the communication between the MS and the BTS, the receiver discards the frame if there is a CRC error in the received Forward Traffic Channel frame. In other words, the normal reception of the forward traffic channel frame at the receiver means that no CRC error has occurred. However, as mentioned earlier, there is a probability that there will be an error not detected by the CRC in this frame.

Since data service synchronization information cannot be recovered even if there is an error even in one bit, it is important to detect an error that is not detected by the CRC in order to correctly transmit the synchronization information.

The next thing to consider is the Frame Error Rate (hereinafter referred to as FER). This is the probability that the receiving side discards the frame, that is, the probability of CRC error in the communication between the MS and the BTS. On a typical open air FER is known as 10 ⁻² . In other words, if 100 frames are sent, 99 is known to be normally received. In practice, however, the probability may be lower than that in the field. If the probability is p, the FER between MS and MS can be calculated as shown in [Equation 1].

FER _{MS → MS} = FER _{MS → BTS} + (1-FER _{MS → BTS} ) FER _{BTS → MS} = p + (1-p) p = 2p-p ²

Here, p is a number between 0 and 1, so it is easy to see that FER _{MS → MS} is a larger number. That is, the synchronization scheme considering only the FER between the MS and the MS may be considered. For example, in an open space, FER _{MS → MS} is 1.99 × 10 ⁻² . The BER of the PCS system is generally known as ^10-3 .

The frame structure for the synchronization scheme and the error detection method will be described. First, the frame structure for the synchronization scheme will be described. Based on the above principles, a frame structure for a synchronization protocol according to the present invention is shown in FIG. 3.

The primary traffic of 266 bits is divided into two Synchronizing Information (SI) and RA, and each SI is the same. The structure of the SI is as follows.

The 16-bit preamble sequence (PRE) is the least frequently generated sequence that does not match the result of source coding the message, and the form is set to 0000 _x and needs to be changed in the future. Allow change.

The 16-bit message type (MT) refers to information that can be used to determine whether the synchronization information is A or NA. The message type (MT) is the least frequently generated sequence that does not match the result of source coding the message. The message types by type are shown in [Table 1].

Message type value Message type 0 _x Request (R) 00FF _x Request / Acknowledge (R / A) FF00 _x Acknowledge (A) FFFF _x NonAnowledge (NA)

The 96-bit information is a 4-bit (1 to 10) long sequence number (SN) used to indicate the number of synchronization information, and the 4-bit long group (Group) GR as ID information. , Level bit (LV) which is 1 bit, ID which is 6 bit length as ID information in group, 64 bit length I as information bit, Reserved bit which is 16 bit length for reserved do.

As an error detection method for the proposed synchronization protocol, the probability of CRC error provided by the PCS system is 2.5 x 10 ^-4 , and since the synchronization information should not have 1 bit error, it is necessary to minimize such error. The proposed synchronous protocol method uses folding. Folding is a method of Exclusive-ORing two SIs of one primary traffic and checking whether all are zero. If there is an error that is not checked by the CRC, there is almost no chance of getting both 0 when Exclusive-OR of two identical SIs. Therefore, using folding can detect an error not checked by the CRC, and the probability can be calculated as follows.

Since folding is the same probability as using the exclusive-OR of two blocks as a CRC, the probability of an error when calculating the CRC using an exclusive-OR of n length l blocks is calculated. Each block is represented by A ₁ , A ₂ ,. , A _n , and the bits of each block are a _i ¹ , a _i ² , a _i ^ㅣ and BER is p, the probability that there will be an even number of errors in the i th bit of the n blocks is given by Equation 2 Can be calculated

P _error = Pr (the probability that there is an even number of errors in the i-th bit)

= _n C ₀ p ⁰ (1-p) ⁿ + _n C ₂ p ² (1-p) ^n-2 + _n C ₄ p ⁴ (1-p) ^n-4 +. + _n C _{?? n / 2 ??} p ^{?? n / 2 ??} (1-p) ^{n-?? n / 2 ??}

= ∑ _{j = 0} ^{n / 2} _n C _2j p ^2j (1-p) ^{n-2 j}

In addition, the probability that all bits are correct is as shown in [Equation 3].

P _good = _n C ₀ p ⁰ (1-p) ⁿ

Therefore, when using an exclusive-OR block of n lengths l as the CRC, the probability of an undetected error is obtained by subtracting the probability that each bit fits all from the probability that each bit has an even number of errors. Equation 4 is as follows.

Pr (the probability that there is an undetected error)

= Pr (the probability that every bit has an even number of errors)-Pr (the probability that every bit is correct)

= P _error ^l -P _good ^l

Applying this to Folding, the probability of an error not detected by Folding is given by Equation 5.

Pr (the probability that there is an undetected error)

= P _error ^l -P _good ^l

= (p ² + (1-p) ² ) ^l -((1-p) ² ) ^l

≒ 10 ^-4 ≒ 2 ^-14

Since the event that is not detected by CRC and the error that is not detected by folding in one block is an independent event, the probability is 10 ^-4 x (2.5x10 ^-4 ) = 2.5x10 ^-8 . This value is negligible in the system because it occurs once when about 100 million sync information is transmitted.

Folding uses simple Exclusive-OR, so it is not difficult to implement in software in MS and can be processed at high speed. The only problem that can be considered as folding is that the number of frames discarded due to folding increases. This is related to the number of transmission of synchronization information and the number of synchronization information actually received by the MS. However, assuming that the synchronization information is received three times, the probability that there is an error in which all three synchronization information is not checked by the CRC is 1.6x10 ^-11 . That is, if there are 10 ¹¹ calls, this error may occur about 1 time, so this case can be ignored.

The synchronization protocol method proposed using the synchronization frame will be described below.

Since the PCS mobile phone system is a full duplex, in the state of providing a special data service, the sender information and the receiver information must be different and aim to send two-way special information during initial synchronization.

And according to FER of Open Air, 49 of 50 frames can be received properly. However, this motivation scheme assumes that 3 out of 10 are properly received considering the worst case. Then, the probability that all three frames will fail to check in CRC is 1/2 ³⁶ = 1.5625x10 ^-11 . In addition, if the write Folding probability of detecting an error from CRC is not Check so close to almost one error it could not be detected in the CRC 1.5625x10 ^-11 can be detected through the Folding. Therefore, assuming that three frames out of ten frames are received, there is little chance that the three pieces of data information are broken. In addition, this probability means that this can happen about once every 10 ¹¹ calls, which is negligible in terms of the number of calls that can occur in PCS systems with special data services. The synchronization method in consideration of the synchronization frame and the error detection method as described above is as follows (see FIGS. 4 and 5).

This synchronization information transmission and reception procedure is performed in the following manner.

In the following description, the definitions of the transmitting MS and the receiving MS are as follows.

The sending MS refers to a terminal transmitting sync information R (see Table 1 for R).

The receiving MS refers to a terminal that receives the synchronization information R and transmits the R / A.

The receiving unit Rx of the sending MS correctly receives the R / A [i] and enters the data service receiving mode after (240-i * 20) msec.

The transmitter Tx of the receiving MS transmits the R / A [10] and enters the data service transmission mode after 40 msec.

The Rx of the receiving MS correctly receives A [i] and enters the data receiving mode after (240-i * 20) msec.

Tx of the transmitting MS enters the data transmission mode 40msec after transmitting A [10].

If the R sent from the sending MS does not receive at the receiving MS, the receiving MS transmits voice (cannot send R / A).

The sending MS stops the protocol if R / A does not come up to 220msec after sending the last R.

Call in voice call mode and indicate data service communication failure.

When receiving the R sent from the sending MS at the receiving MS, the message R is analyzed to determine voice communication or R / A transmission using information such as whether group communication is possible.

The receiving MS sends an R / A.

If the sending MS does not receive the R / A sent from the receiving MS, the sending MS transmits the NA.

The sending MS calls in the voice call mode and displays a data service communication failure message.

If the sending MS receives the R / A sent from the receiving MS, the sending MS sends A.

Prepare to enter data service transmission mode. That is, the data service is prepared for transmission and reception.

If the receiving MS receives NA, the Tx / Rx of the sending MS does not enter the data service transmission / reception mode, and the Rx / Tx of the receiving MS does not also enter the data service transmission / reception mode.

When the receiving MS receives A, synchronization is successful and data transmission starts.

If neither A nor NA is received, and the sending MS does not receive R / A, then the Tx / Rx of the sending MS is in voice call mode and the Rx / Tx of the receiving MS is also in voice call mode.

When the sending MS receives the R / A, the sending MS communicates in data service transmission mode and the receiving MS communicates in voice call mode. In other words, communication is impossible.

In this way, communication is impossible only if the receiving MS receives the R sent from the sending MS and receives the R / A sent from the receiving MS and the receiving MS does not receive the A sent from the sending MS. Mode, one side is in voice communication mode)

As described above, the present invention has the following effects.

Accurate synchronization information can be delivered within at least 240msec.

The probability of failing a call request with a data service function is about 10 ^-11 in the worst case, so it is easy to implement even if implemented in software, and the time required for initial synchronization is up to 600msec.

In most cases of failure of data service function request, it is possible to maintain voice call mode so that there is no difficulty in calling.

No special error correction code is used.

As an essential and effective method for performing special data service functions applicable to PCS mobile telephone networks, the modification of the currently serving PCS system is minimal and its implementation is simple.

The operation is stable and the reliability is high.

The caller does not feel uncomfortable during the synchronization time, and this synchronization protocol enables the data service call function, and enables terminal authentication between the callers.

Claims (3)

In the synchronous protocol frame structure consisting of the reserved bits, information bits, frame quality bits and encoding tail bits, the information bits are composed of mixed mode bits and raw traffic, The raw traffic consists of two synchronization information and one receiving unit (RA), and the synchronization information is a sequence having the least frequent occurrence among the inconsistent results of source coding a message, and has a form of 0000 _x . A 16-bit preamble sequence that can be changed if needed, A 16-bit long message type that is the least frequently generated sequence that does not match the result of source coding the message as information for determining whether the synchronization information is A or NA; A synchronization protocol frame structure for data service in a mobile telephone network using a CDMA scheme, characterized in that the information is 96 bits long. Entering a data transmission mode after transmitting a predetermined number of request confirmation messages to the transmitting terminal by the receiving terminal receiving the predetermined number of request messages transmitted by the transmitting terminal; Receiving a request confirmation message a predetermined number of times transmitted from the receiving terminal, entering the data receiving mode; Transmitting a voice when the receiving terminal fails to receive the request message transmitted from the transmitting terminal; If the requesting message is not received from the receiving terminal after transmitting the last request message a predetermined number of times, the calling terminal stops the protocol to call in the voice call mode and indicates that the data service communication is failed. A synchronization protocol method for data service in a mobile telephone network using a CDMA scheme. Transmitting a confirmation message from a transmitting terminal to a receiving terminal; Analyzing the request message and transmitting the request confirmation message to the transmitting terminal when the receiving terminal receives the confirmation message; If the transmitting terminal fails to receive the request confirmation message transmitted from the receiving terminal, transmitting the unacknowledged message from the transmitting terminal, calling in a voice call mode, and displaying a data service communication failure message; Entering a data service transmission mode after transmitting a confirmation message when the request terminal receives the request confirmation message transmitted from the receiving terminal; When the receiving terminal receives the unacknowledged message transmitted from the transmitting terminal, the receiving terminal does not enter a data service transmission / reception mode; When the receiving terminal receives the acknowledgment message transmitted by the transmitting terminal, starting the data service transmission with a successful synchronization; When the transmitting terminal receives the request confirmation message, the transmitting terminal communicates in the data service transmission mode and the receiving terminal enters the voice call mode, the data service in the mobile telephone network using the CDMA method Synchronization protocol method for the.