CN100391143C - Method for detecting transmission errors beyond the detection range of a cyclic redundancy check mechanism - Google Patents

Abstract

The invention provides a method for checking transmission faults which exceed a checking range of a cycle verbose checking mechanism, which is used in a receiving end of a mobile communication system and is used to check the transmission faults which exceed the checking range of the cycle verbose checking mechanism. The method comprises: temporarily storing a plurality of protocol data units (Protocol Data Unit) in turn, checking the sequence number (Sequence Number) of the protocol data units in turn, and not processing a protocol data unit and removing the protocol data unit when the sequence number of the protocol data unit is not continuous with the sequence number of the protocol data unit which is before the protocol data unit and when the sequence number of the protocol data unit is not continuous with the sequence number of the protocol data unit which is after the protocol data unit.

Description

Method for detecting transmission errors beyond the detection range of a cyclic redundancy check mechanism

technical field

The invention relates to a method for detecting transmission errors beyond the detection range of a cyclic redundant check mechanism, in particular to a method for detecting transmission errors by deleting serial numbers and discontinuous protocol data units.

Background technique

With the advent of the information age, the demand for mobile voice, data communication and various mobile services is increasing day by day. The known mobile communication systems have faced the bottleneck of insufficient communication channels and insufficient transmission rates. Therefore, the third-generation mobile communication, which can provide higher frequency spectrum utilization and higher-speed transmission services, has emerged as the times require. Compared with the existing second-generation mobile communication technology, the most fundamental difference of the third-generation mobile communication is the use of wideband code division multiple access (WCDMA) wireless access method, which is used to provide a high degree of spectrum utilization Efficiency, high coverage and high-quality, high-speed multimedia data transmission can also meet various QoS service requirements at the same time, provide flexible and diversified two-way transmission services, and provide better communication quality, effectively reducing Communication outage rate.

The WCDMA communication protocol stack can be divided into an access related part (Access Stratum, AS) and a non-access related part (Non-Access Stratum, NAS). Among them, AS includes Radio Resource Control (Radio Resource Control, RRC), Radio Link Control (Radio Link Control, RLC), Media Access Control (Media Access Control, MAC), Packet Data Convergence Protocol (Packet Data Convergence Protocol, PDCP), broadcast and multicast control (Broadcast/MulticastControl, BMC) and several sublayers with different functions. The operations of the above sub-layers are well known to those skilled in the art, and will not be repeated here. Among them, the main function of the wireless link control layer communication protocol is to provide different transmission quality processing for the third-generation mobile communication system. According to different transmission quality requirements, different cuts, transmissions, and retransmissions are performed for the transmitted data or control commands. with combination processing. In the third generation mobile communication system, four different transmission quality levels, such as conversational, streaming, interactive and background, are defined. Wireless link control uses the following three methods to cut and package packets to meet different transmission quality requirements:

1. Transparent mode (Transparent Mode, TM): According to the length of the packet, it is directly cut and divided without any other processing. It is suitable for services that require high real-time transmission, such as voice calls.

2. Unacknowledged Mode (Unacknowledged Mode, UM): In addition to cutting and packetizing, an appropriate header is added before each packet to assist the receiving end in checking the packet sequence and discarding error packets. It is suitable for services that require both real-time transmission and packet order, such as Voice over Internet Protocol (VoIP) communication, Video Phone, etc.

3. Acknowledged Mode (Acknowledged Mode, AM): In addition to cutting packets and adding packet sequence headers, the receiving end also needs to perform sequence check, duplicate detection, and retransmission processing for each packet to ensure that all packets are correct. to the receiving end. It is suitable for services that do not require high real-time transmission but high data accuracy, such as web browsing, email, file transmission and other services.

In addition, wireless link control also provides packet processing services such as flow control, packet reordering, packet encryption, and error detection to provide complete data segmentation, packetization, and transmission services.

Through wireless transmission, user data and some signaling information (Signaling Information) are susceptible to interference and errors, so they must be encrypted and protected. Network Control), through a encryption method (Ciphering Method) to encrypt the relevant data. Please refer to FIG. 1 . FIG. 1 is a schematic diagram of encryption and decryption of a known third-generation mobile communication system. At the transmission end, data such as the encryption key (Ciphering Key) CK, the count (Count) COUNT-C, the bearer identifier field (BearerIdentifier) BEARER, the direction identifier field (Direction Identifier) DIRECTION, and the length indicator field (Length Indicator) LENGTH pass through the F8 The algorithm obtains multiple keystream blocks (Keystream Block) KEYSTREAM, and the keystring block KEYSTREAM is encrypted with the plaintext (Plain Text) block PLAIN-TEXT to obtain the ciphertext (Cipher Text) block CIPHER-TEXT. The receiving end can use the same key string block as the transmitting end to decrypt the received cipher text (Cipher Text) block to obtain the plain text block. Wherein, except that the count COUNT-C is changed dynamically, other parameters are determined before the encryption phase starts, and remain fixed during the encryption phase. The length of the count COUNT-C is 32 bits, which includes two parts: the Hyper Frame Number (Hyper Frame Number) HFN and the sequence number (Sequence Number) SN. When the value that can be represented by the number of digits of the sequence number SN is exceeded, the sequence number SN will start to accumulate again from the initial value (0), and the hyperframe number HFN will be increased by 1 at the same time. For example, when the sequence number SN is represented by seven bits, that is, the sequence number SN can be counted from 0 to 127 in sequence. Once the sequence number SN exceeds 127, the hyperframe number HFN will be increased by 1, and the sequence number SN will start from 0 again. At this time, because there is no skip number, when the sequence number returns from 127 to 0, the two sequence numbers are considered continuous. The serial number SN is embedded in each Protocol Data Unit, and the initial value of the hyperframe number HFN is agreed upon by the transmitting end and the receiving end before encryption. Therefore, according to the serial number SN of each protocol data unit, the transmitting end and the receiving end accumulate the hyperframe number HFN at an appropriate time, so as to maintain the synchronization of HFN and ensure the smooth progress of encryption and decryption.

In the WCDMA communication protocol, the L1 layer below the radio link control layer includes a Cyclic Redundancy Check (CRC) mechanism to check the correctness of the received PDU. When an error is found through the cyclic redundancy check mechanism, it means that an error has occurred in the protocol data unit during transmission, so the error protocol data unit will be discarded or deleted and will not be transmitted to the upper layer. On the contrary, if there is no CRC error, the PDU received by the receiving end will be sent to the RLC layer for subsequent processing.

Generally speaking, the CRC field contains 12 or 16 bits, so there may be a transmission error in the SN field, but the CRC mechanism cannot detect the error. The above situation is called "error beyond the detection range of the cyclic redundancy check mechanism". If the sequence number SN has an error beyond the detection range of the cyclic redundancy check mechanism, the hyperframe number HFN at the transmitting end and the receiving end will be out of sync and a series of errors will occur . Taking the sequence number SN represented by seven bits as an example, if the sequence number SN of a sequence of protocol data units output by the transmission end is 0, 1, 2, 3, 4, 5..., and the hyperframe number HFN= 1. When the data block with SN=3 has a transmission error and an error beyond the detection range of the cyclic redundancy check mechanism occurs, the sequence number SN of the protocol data unit received by the receiving end is 0, 1, 2, 30, 4, 5 . . . , that is, the sequence number SN of the fourth data block whose original sequence number SN=3 becomes 30. Since the sequence number SN=30 and the sequence number SN=2 are not continuous, the transmission end of the known technology will regard the protocol data units with the sequence numbers SN=3 to 29 in the hyperframe number HFN=1 as being lost during transmission (in fact, not lost ), and when receiving the protocol data unit with sequence number SN=4, the receiving end will regard the protocol data unit with sequence number SN=4 as the protocol data unit with sequence number SN=4 in the next cycle (that is, hyperframe number HFN=2) , so add 1 to the superframe number HFN. That is to say, when the receiving end receives the protocol data unit with the sequence number SN=4, since the sequence number SN=4 is smaller than the sequence number SN=30, the receiving end will transfer the sequence number after the sequence number SN=30 in the hyperframe number HFN=1 to the next sequence number PDUs before sequence number SN=4 of the cycle (hyperframe number HFN=2) are considered lost (actually not lost). In other words, the hyperframe numbers HFN of the transmitting end and the receiving end become out of sync, and even affect all subsequent PDUs, resulting in serious errors. In order to solve the above problems, the known technology also provides a method of setting a receiving window to improve the above problems. But this method will cause the protocol data unit to be discarded by mistake. For example, if the size of the receiving window is 40, and the serial number SN of the received protocol data unit=0, 1, 2, 30, 4, 5... 30, 31, 32..., that is, the sequence number SN of the fourth PDU is wrong. But because the sequence number SN=30 still falls within the range of receiving window size 40 (2+1=3 to 3+40-1=42) compared with the sequence number SN=2, the receiving window will not convert the sequence number SN=30 The protocol data unit is deleted, but the 5th to 31st received protocol data units (sequence number SN=4 to sequence number SN=30) are mistakenly regarded as not in the range of the receiving window (30+1=31 to 31+40-1=70) , and delete it. In short, although the receive window can delete a PDU when the sequence number of the PDU falls outside the receive window, when the sequence number of an error PDU falls within the receive window, the known technology Normally received PDUs will be deleted by mistake.

Contents of the invention

Therefore, the main purpose of the present invention is to provide a method for detecting transmission errors beyond the detection range of the cyclic redundancy check mechanism, so as to improve the disadvantages of the known technology.

The present invention discloses a method for detecting transmission errors, which is used in a receiving end of a mobile communication system to detect transmission errors beyond the detection range of a cyclic redundancy check mechanism. The method includes: sequentially temporarily storing a plurality of protocol data units (Protocol Data Unit); sequentially check the sequence number (Sequence Number) of the plurality of protocol data units; and when the sequence number of a protocol data unit is not continuous with the sequence number of the previous protocol data unit of the protocol data unit, and at the When the sequence number of the protocol data unit is not continuous with the sequence number of the subsequent protocol data unit of the protocol data unit, the protocol data unit is not processed and the protocol data unit is deleted.

The present invention also discloses a method for detecting transmission errors beyond the detection range of the cyclic redundancy check mechanism, which is used in a receiving end of a mobile communication system to detect transmission errors beyond the detection range of the cyclic redundancy check mechanism. The method includes the following steps: : Temporarily store a plurality of Protocol Data Units (Protocol DataUnits) in sequence; check the sequence numbers (Sequence Number) of three consecutive Protocol Data Units in the plurality of Protocol Data Units in sequence, and set the sequence numbers of the three consecutive Protocol Data Units according to The sequence is a, b and c; check whether the values of a, b and c conform to (b-a+N) mod N+(c-b+N) mod N>=N, where N=2 ^k , k is the sequence number The number of digits, mod represents the remainder operation; and when the values of a, b and c conform to (b-a+N) mod N+(c-b+N) mod N>=N, the protocol data unit whose serial number is b is not processed And delete the protocol data unit.

Description of drawings

FIG. 1 is a schematic diagram of encryption and decryption of a known third-generation mobile communication system.

FIG. 2 is a flow chart of detecting transmission errors according to the first embodiment of the present invention.

FIG. 3 is a flow chart of detecting transmission errors according to the second embodiment of the present invention.

Detailed ways

Please refer to FIG. 2 , which is a schematic diagram of a process 20 for detecting transmission errors according to a first embodiment of the present invention. The process 20 is used in a receiving end of a mobile communication system to detect transmission errors beyond the detection range of the CRC mechanism. Process 20 includes the following steps:

Step 200: start;

Step 202: Temporarily storing multiple Protocol Data Units in sequence;

Step 204: check the sequence numbers (Sequence Number) of the plurality of protocol data units in sequence;

Step 206: When the sequence number of a PDU is not continuous with the sequence number of the previous PDU of the PDU, and when the sequence number of the PDU is not continuous with the sequence number of the subsequent PDU of the PDU , the protocol data unit is not processed and the protocol data unit is deleted;

Step 208: end.

According to the process 20, when the present invention detects that the sequence number SN of a protocol data unit is not continuous with the sequence numbers SN of the previous and subsequent protocol data units, the protocol data unit is deleted, so that the mistaken deletion of the protocol data unit and the error accumulation of the superframe number can be avoided HFN also avoids transmission errors beyond the detection range of the cyclic redundancy check mechanism. Especially for the case where the RLC operates in the unacknowledged mode, due to the requirement for real-time transmission and packet sequence, there is a special requirement for the synchronization of the hyperframe number HFN between the transmitting end and the receiving end. It should be noted that the present invention deletes a PDU only when the sequence number SN of the PDU is not continuous with the sequence numbers SN of the previous and subsequent PDUs. On the contrary, if the sequence number SN of a protocol data unit is only discontinuous with the previous or subsequent sequence number SN, the condition of deleting the protocol data unit of the present invention is not met.

For example, if the sequence number SN of a sequence of PDUs output by the transmitting end is 0, 1, 2, 3, 4, 5..., and the hyperframe number HFN=1 at this time. When a transmission error occurs and an error beyond the detection range of the cyclic redundancy check mechanism occurs, the sequence number SN of the protocol data unit received by the receiving end is 0, 1, 2, 30, 4, 5..., that is The sequence number SN of the fourth data block whose original sequence number SN=3 becomes 30. According to the process 20 of the present invention, the serial number SN=30 is not continuous with the serial number SN=2, and is also discontinuous with the serial number SN=4, so the protocol data unit with the serial number SN=30 will be deleted, and the hyperframe number HFN will not be accumulated and Maintain 1, so normal operation can be maintained, and follow-up processing.

Compared with the known technology, the present invention can detect transmission errors beyond the detection range of the cyclic redundant check mechanism, so it can avoid the error accumulation of hyperframe number HFN and avoid the error deletion of protocol data units, thereby improving the receiving efficiency and improving the performance of the known technology shortcoming.

Therefore, according to the process 20, the present invention can delete PDUs with discontinuous sequence numbers to increase receiving efficiency. However, the discontinuity of the serial numbers of the PDUs may be simply caused by block errors of the PDUs. In this case, the process 20 of the first embodiment of the present invention may delete the correct PDUs. For example, if the sequence number SN of a sequence of PDUs output by the transmitting end is 0, 1, 2, 3, 4, 5..., due to a transmission error or a block error of the PDU, the receiving end The sequence number SN of the received protocol data unit is 0, 1, 2, 30, 4, 6, 7, ..., wherein the sequence number SN of the fourth protocol data unit changes from 3 to 30, and the sequence number SN=5 The protocol data unit for is missing. At this time, according to the process 20, since the sequence number SN=30 is not continuous with the sequence numbers SN=2 and 4 before and after, the protocol data unit with the sequence number SN=30 will be deleted, and at the same time, the sequence number SN=4 is also consistent with the sequence numbers SN=2 and 6 are not consecutive, so the PDU with SN=4 will also be deleted, that is, the PDU with SN=4 will be deleted by mistake. In order to improve the above problems, the present invention also provides a method. Please refer to FIG. 3 , which is a schematic diagram of a transmission error detection process 30 according to a second embodiment of the present invention. The process 30 is used in a receiving end of a mobile communication system to detect transmission errors beyond the detection range of the CRC mechanism. Process 30 includes the following steps:

Step 300: start;

Step 302: Temporarily storing multiple Protocol Data Units (Protocol Data Units) in sequence;

Step 304: check the serial numbers (Sequence Number) of three consecutive PDUs in the plurality of PDUs in sequence, and set the sequence numbers of the three consecutive PDUs as a, b and c in sequence;

Step 306: Check whether the values of a, b and c conform to (b-a+N) mod N+(c-b+N) mod N>=N, wherein N= ^2k , k is the number of digits of the serial number, and mod represents the remainder operation;

Step 308: When the values of a, b and c conform to (b-a+N) mod N+(c-b+N) mod N>=N, do not process the protocol data unit whose serial number is b and send the protocol data unit delete;

Step 310: end.

According to the flow process 30, the present invention checks whether the values of the sequence numbers a, b and c of three consecutive PDUs conform to the formula: (b-a+N) mod N+(c-b+N) mod N>=N, When the values of a, b and c conform to the formula, the PDU with the serial number b is not processed and the PDU is deleted, so as to prevent the correct PDU from being deleted. For example, for a system using a seven-bit sequence number SN, if the sequence number SN of a sequence of PDUs output by the transmission end is 0, 1, 2, 3, 4, 5..., due to transmission errors Or the block of the protocol data unit is wrong, so that the sequence number SN of the protocol data unit received by the receiving end is 0, 1, 2, 30, 4, 6, 7, ..., wherein the sequence number of the fourth protocol data unit SN changes from 3 to 30, and the protocol data unit with sequence number SN=5 is lost. According to the process 30, for the first three serial numbers SN=0, 1, 2, because (1-0+128) mod 128+(2-1+128) mod 128=1+1=2<128, so the serial number SN=0 . For sequence number SN=2, 30, 4, (30-2+128) mod 128+(4-30+128) mod 128=28+102=130>128, so sequence number SN=2, 30, 4 meet According to the condition set in the process 30 of the present invention, the PDU with the sequence number SN=30 will be deleted. Further, for sequence number SN=2, 4, 6 (the protocol data unit of sequence number SN=30 has been deleted), because (4-2+128) mod 128+(6-4+128) mod 128=2 +2=4<128, so the condition for deleting the protocol data unit in process 30 is not met.

Compared with the process 20, the process 30 can not only avoid the erroneous accumulation of the hyperframe number HFN, but also prevent the serial number discontinuity caused by the block error of the protocol data unit, so as to improve the receiving efficiency, save the system cost, and improve the known Technical shortcomings.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (7)

1. a detection exceeds the method for the error of transmission of the verbose verification mechanism detection range that circulates, and is used in the receiving terminal of a mobile communcations system, detects the error of transmission that exceeds the verbose verification mechanism detection range that circulates, and this method includes:

Temporary in regular turn a plurality of protocol Data Units;

Check the sequence number of these a plurality of protocol Data Units in regular turn; And

When the sequence number of the last protocol Data Unit of the sequence number of a protocol Data Unit and this protocol Data Unit is discontinuous, and when the sequence number of the back protocol Data Unit of the sequence number of this protocol Data Unit and this protocol Data Unit is discontinuous, do not handle this protocol Data Unit and with this protocol Data Unit deletion.

2. the method for claim 1, wherein these a plurality of protocol Data Units protocol Data Unit that is unacknowledged mode data.

3. the method for claim 1, wherein the sequence number of two protocol Data Units is the value of the maximum expression scope of sequence number and 0 o'clock in regular turn, is considered as continuously.

4. a detection exceeds the method for the error of transmission of the verbose verification mechanism detection range that circulates, and is used in the receiving terminal of a mobile communcations system, detects the error of transmission that exceeds the verbose verification mechanism detection range that circulates, and this method includes:

Temporary in regular turn a plurality of protocol Data Units;

Check the sequence number of these a plurality of protocol Data Units in regular turn; And

The sequence number that this receiving terminal is received on transmission channel opens first protocol Data Unit of beginning be not agreement open initial value the time, and when the sequence number of the back protocol Data Unit of the sequence number of this protocol Data Unit and this protocol Data Unit is discontinuous, do not handle this protocol Data Unit and with this protocol Data Unit deletion.

5. method as claimed in claim 4, the initial value that opens of this agreement is 0.

6. a detection exceeds the method for the error of transmission of the verbose verification mechanism detection range that circulates, and is used in the receiving terminal of a mobile communcations system, detects the error of transmission that exceeds the verbose verification mechanism detection range that circulates, and this method includes:

Temporary in regular turn a plurality of protocol Data Units;

Check the sequence number of continuous three protocol Data Units in these a plurality of protocol Data Units in regular turn, and the sequence number of establishing these continuous three protocol Data Units is a, b and c in regular turn;

Whether the value of checking a, b and c meets (b-a+N) mod N+ (c-b+N) mod N＞=N, wherein N=2 ^k, k is the figure place of sequence number, mod represents remainder operation; And

When the value in a, b and c meets (b-a+N) mod N+ (c-b+N) mod N＞=N, do not handle sequence number and be the protocol Data Unit of b and with this protocol Data Unit deletion.

7. method as claimed in claim 6, this k value is 7.

Images