MXPA98008094A - Combined method of alignment of minicelda and protection of head and apparatus used by mi - Google Patents

Abstract

The present invention relates to a telecommunications system that uses an asynchronous transfer mode (ATM) protocol as a data transfer infrastructure, the information of the mini-cell header is verified, the mini-cell alignment is maintained and the utilization is improved. ATM bandwidth by inserting only a header integrity check code in each ATM cell instead of a header integrity check code for each and every mini-cell header. The header integrity verification code is determined from a combination of mini-cell headers stored in cell A

Description

HEADER AND APPLIANCE USING THE SAME The present invention relates to the transmission of telecommunication data, and more particularly to the transmission of telecommunications data in the Asynchronous Transfer Mode (ATM) protocol. More specifically, the present invention relates to an efficient method and apparatus for computing, storing and using a unique header integrity verification code common to all non-standard short cells, referred to as mini-cells, multiplexed in an ATM cell. The asynchronous transfer mode (ATM) is a standard protocol for transmitting telecommunication data within a telecommunication system (for example a cellular telecommunication network). The data is transmitted in fixed size packets called ATM cells. Each ATM cell contains a payload of 48 octets and a header of 5 octets. ATM is well known in the art and is commonly used for high bit rate applications (eg, multimedia communication); however, ATM can also be used to improve REP. 28572 Significantly, the efficiency of low bit rate applications (for example, cellular voice communication). When using ATM for low bit rate communication, such as cellular voice communication, it is often advantageous to multiplex small packets of compressed data into an ATM cell stream as illustrated by process 100 in FIG. 1. These small packets they are often referred to as "minicells." Mini cells, although typically shorter than ATM cells, are similar in that they also contain a header, usually 2 octets in length, and a payload with a fixed or variable length. In fact, the minicells can be extended over the limits of the ATM cell as illustrated by the mini-cell 101 in Figure 1. When multiplexing minicells in a sorrent ATM, the utilization of the bandwidth (BW) is improved and the costs are reduced. of transmission when the mini-cells are, in general, smaller than the ATM cells. --In a stratified communication system, the mechanism for processing this additional layer of cells, or mini cells, is referred to as an adaptation layer ATM or AALm, where "m" means "mini cell". This additional process or "layer" can be further divided into three sublayers as illustrated in Figure 2. The convergence sublayer 201 allows AALm to be interconnected with the telecommunications application. The assembly and disassembly of the sub-layer 202 inserts and extracts user data (for example, voice communication data) inside and outside each mini-cell (see also Figure 1). The multiplexing and demultiplexing of the layer 203 inserts and extracts mini cells inside and outside the ATM cells (see also figure 1). A telecommunication system that uses ATM and AALm must solve two basic problems. First, you must ensure the correctness of the header information in each mini-cell. Second, it must be able to maintain the mini-cell alignment, that is, determine where each mini-cell starts and ends within an ATM cell. To ensure the correctness of the mini-cell header information, the prior art methods typically use some kind of mini-cell header integrity (HIC) verification. These checks help detect and, in some cases, correct errors in the mini-cell header information. This can be easily accomplished by including an error detection / error correction code in the header of each mini-cell. This technique is well known in the art. For example, Góran Eneroth et al., "Minicell Protocol (ALLm) for Low Bit Rate Applications, "(February 1996), uses a 301 mini-cell header with two octets in each and every mini cell, as illustrated in Figure 3. The mini-cell header 301 includes a two-bit 302 HIC code. The two-bit HIC code maintains the integrity of the header information with a two-bit interleaved parity check. In another example, illustrated in Figure 4, Tomohiro Ishihara, "Proposal of Short Cell Format for Low Bit Rate Voice," (December 1995), uses a 401 mini-cell header of two octets in each and every mini-cell, wherein each header includes an error detection / error correction code 402 HIC. In this example, the HIC code is a five-bit cyclic redundancy code (CRC) that is capable of three-bit correction and two-bit error detection. Despite the general efficiency of the AALm technique, the state-of-the-art methods used to ensure the correctness of the mini-header information are not efficient. The main reason is that each mini-cell header must dedicate several bits to perform a header integrity check, and this takes up valuable bandwidth. Inefficiency is even more severe when mini-cell payloads are short.As mentioned before, the second concern is to maintain an appropriate mini-cell alignment. Figure 5 illustrates how the prior art methods typically handle mini-cell alignment. As shown in Figure 5, most of the prior art methods use a mini-cell start pointer 501 (MSP) at the beginning of certain ATM cells as illustrated in Figure 5. The MSP 501 identifies the position start (octet) 502 of the first complete miniature cell within cell 503 ATM. The MSP 501 typically has a length of six bits, so it can identify any of the 48 octets which constitute the standard ATM payload. A two-bit extension is also provided to verify parity. In addition, each mini-cell header contains a length indicator field (see Figure 4, reference number 403) that also has a length of six bits, which identifies the length of the corresponding mini-cell in terms of the number of octets that make up the payload. of the mini-cell. Between each MSP 501, the alignment is maintained by identifying the position of the first complete mini-cell according to MSP 501 and, subsequently, counting the octets which constitute the payload of each mini-cell according to the value represented by the length indicator in each mini-cell heading.

Like the HIC code, MSP 501 uses valuable bandwidth. If each ATM cell contains an MSP 501, the effective bandwidth is decreased by approximately 2%. If an MSP 501 is included in every sixteenth ATM cell, the amount of wasted bandwidth is reduced to almost zero. In any case, if the alignment is lost for any reason, for example, due to excessive noise in the transmission lines, the alignment can not be reassigned until the next MSP 501, if correctly received, and the entire the miniceldas between these will be lost. Therefore, despite the improvements over the standard ATM, the methods which use AALm need to further improve the bandwidth utilization by increasing the efficiency of the HIC and the mini-cell alignment.

DESCRIPTION -BREVE OF THE INVENTION An object of the invention is to provide a more efficient method and means to secure the correct mini-header header information. Another object of the invention is to provide a more efficient method and means for maintaining mini-cell alignment.

A further objective of the invention is to provide a more efficient method and means to ensure correct information of the mini-cell header and maintain the mini-cell alignment, and at the same time improve bandwidth utilization. In accordance with one aspect of the present invention, the above and other objects are obtained in a telecommunication system with a method and / or an apparatus for generating a data packet (e.g., an ATM cell) comprising the steps of generating at least one ninicle, wherein each mini-packet comprises a portion of user data (e.g., a payload) and a header; then insert at least part of at least one mini cell in the data packet; then generating a back code of header integrity checking from a combination code, wherein the combining code comprises the header from each of the mini cells that are inserted into the data packet; and then insert the header header verification code inside the data package.

According to another aspect of the invention, a method and / or an apparatus for determining the integrity of mini-cell headers in a data packet includes identifying each mini-cell header in a data packet; then determine the verification code of Header integrity based on extracted mini-header headers; subsequently identify a back code of header integrity verification stored from the data packet; then compare the stored header integrity check code with the determined header integrity check code; and finally, use a comparison result to determine the integrity in each mini-cell header in the data package. According to still another embodiment of the invention, a method and / or apparatus for maintaining mini-cell alignment in a data packet includes defining a starting position for a first complete mini-cell in the data packet; then identify a first estimate header from each mini-cell in the data packet based on the start position defined in the first full mini-packet in the data packet; then determine a header integrity verification code that is based on each estimate mini-cell heading identified first; then identify a backward header integrity check code stored from the data packet; then compare the header integrity check code determined with the back verification code of header integrity stored; and finally, use a comparison result to determine if the receiver is synchronized to the mini-cells in the data package.

DESCRIPTION -BREVE OF THE DRAWINGS The objects and advantages of the invention will be understood upon reading the following detailed description together with the drawings, in which: Figure 1 is a diagram illustrating the prior art process of mini-multiplexer in the ATM cell flow; Figure 2 is a diagram showing the stratified protocol model of the prior art for AAlm; Figure 3 is a diagram showing the basic format of a minicell in the prior art; Figure 4 is a diagram illustrating the physical relationship between a mini-cell, the mini-cell header and the ATM cell in the prior art; Figure 5 is a diagram showing an alignment method of the prior art with a mini-cell start pointer in each alternating ATM cell; Figure 6 is a diagram illustrating minicells mapped in an ATM cell and the rear code HIC occupying the last octet of the ATM cell; Figure 7 is a diagram showing the calculation of the HIC rear code based on a concentration of each minicell header in the ATM cell; Figure 8 is a state diagram illustrating receiver operation; Fig. 9 is a flow diagram showing a strategy for SYNC state receiver operation; Fig. 10 is a flow chart showing a strategy for the operation of the receiver in the search state, Fig. 11 is a flow chart showing a strategy for the operation of the state receiver PRESYNC; and Figure 12 is a diagram illustrating the typical cellular telecommunication system of the prior art (e.g., a cell phone system).

DESCRIPTION T ATITIATTIA The present invention provides a more efficient method and means for carrying out header integrity checking (HIC) for each header of mini cell in an ATM cell. The invention also provides a more efficient method and means for maintaining the alignment of the mini-cell. In one embodiment of the invention, this is accompanied by adding a unique HIC code in some easily identified part of the ATM cell in view of an HIC code in each and every mini-cell header. The unique HIC codeword will be based on the combined data in each of the mini-cell headers in the corresponding ATM cell. Therefore, the unique HIC code will be common to all minicell headers in the ATM cell. Figure 6 illustrates an ATM cell 600 having an ATM cell header 601 that is five octet in length and an ATM cell payload 602 that is 48 octets in length. According to the AALm technique described above, the minicells 603 are multiplexed in the 600 ATM cell. The mini-cells 603 may, as shown, vary in length and extension from one ATM cell to the next, as illustrated by the mini-cells 604 and 605. The difference between the ATM 600 cells and the ATM cells used in the methods of the art The above is that the 600 ATM cell includes a code 606 HIC, hereinafter referred to as a HIC back code. In a preferred embodiment of the invention, the HIC rear code 606 is one octet in length and is located in the last octet of cell 600 ATM. Of course, the length and location of the HIC back code may be different in alternative modes, without departing from the teachings of the invention. As stated above, the inclusion of the HIC back code 606 replaces the prior art practice of placing a HIC code in each and every one of the mmicelda headers. This makes the present invention more efficient in terms of bandwidth utilization when the mini cells are, in general, smaller than the ATM cells. Once the HIC code 606 back is derived and inserted into the ATM cell, can be used for minicell header error detection and correction in a manner very similar to mini-cell ATM codes that are currently used to detect and correct errors in ATM cell headers and in each individual mini-cell header, respectively. In general, the transmission source will calculate the HIC rear code based on the contents of each mini-cell header in the corresponding ATM cell and insert the result into an easily identified part of the ATM cell as described above. In one embodiment of the invention, the HIC back code can be based on the properties of cyclic codes (for example, cyclic redundancy codes). In this mode, the HIC code 606 back is calculated at first concatenate the header information from all minicells in the corresponding ATM cell. Those familiar with the art will recognize that this can be accomplished by physically creating a new code word comprising the concatenated headers copied from each mini cell in the corresponding ATM cell. Alternatively, the headers from each mini cell in the corresponding ATM cell can be processed without the need to physically build a word of new code. Through this specification, the term "combination code" will be used to designate any alternative. For example, Figure 7 illustrates the combination of the word code 700 resulting from the concatenation of mini-cell headers corresponding to the mini cells 603 and 605 in a 500 ATM cell. The word combination code 700 can be represented by a polynomial M (x) of degree m-1, where m represents the number of elements or bits in the combination word code 700. For example, if the word code 700 is 100101, you can represented by a polynomial M (x) = -X5 + X2 + 1, where the values of each element (ie, bits) are used as the coefficients for the polynomial M (x). Subsequently the back code 606 HIC is calculated as the rest of x ^ M (x) / G (x), where G (x) is a polynomial generator of degree n.

As stated above, the back code 606 HIC is calculated as the remainder of xfM (x) / G (x) and then inserted into an easily identified part of the ATM cell (for example the last octet) and transmitted with the rest of the ATM cell to a receiving entity. A receiver, at the receiving entity, then calculates the cyclic code based on the currently received mini-cell header information. If the calculated cyclic code matches the HIC rear value that has been received, the header information for all received minicells is assumed to have been transmitted and received without error. The calculation of HIC codes based on cyclic codes is well known in the art and is commonly used to perform header integrity checking for ATM cell headers as described in the International Telecommunication Union ITU-T, B-ISDN User-Networ Interface -Physical Layer Specification, Recommendation 1.432 (1993), the content of which is incorporated herein by reference. In another embodiment of the invention, the HIC back code can be used to find the mini-cell limits in an ATM cell after the mini-cell alignment has been lost. The receiver can use the HIC back code in a very similar way to the one that uses the header error control codes (HEC) In the ATM cell headers to obtain an ATM cell delineation as described in ITU Recommendation 1.432, "B-ISDN User Network Interface Physical Layer Specification", the content of the sual is incorporated herein by reference. As illustrated in FIG. 8, the receiver operates in one of the following three states: state 801 SYNC, state 802 PRESYNC, or state 803 HUNT. In Figure 9 a flow diagram of state 801 SYNC is shown. While state 801 SYNC is found, it is assumed that the receiver knows how to precisely locate the principles of each mini cell within the ATM cell. The receiver, when in the 801 SYNC state, will receive an ATM cell (from the transmitting entity) as illustrated in block 901 and calculate a rear HIC code as illustrated in block 902 based on which of the Recipients believe that the information is headed from each mini cell in the ATM cell as explained above. If, for any reason, the receiver is not properly aligned with the mini-cell headers, the HIC code calculed will most likely be incorrect (that is, it will be different from the HIC rear code stored in the ATM cell by the transmitting entity). If the receiver incorrectly calculates the HIC rear code, there is a possibility that the receiver has lost synchronization. In consequently, the transitions of the receiver to state 803 HUNT as illustrated by block 903 of decision. On the other hand, the HIC rear code is calculated correctly, the receiver extracts each of the minicells, as illustrated in block 904, and supplies them to the mini-cell assembly and to the disassembly layer 202. The receiver then updates a mini-cell start indicator (MSP), as illustrated in block 905, which indicates the starting point of the first complete mini-cell in the next ATM cell to be received. Unlike the methods of the previous terrestrial, the MSP is an internal variable and does not affect the bandwidth of the ATM connection. As mentioned before, the receiver will transition to the 803 HUNT state if an incorrect HIC back code is escaped during the SYNC state. The wrong calculation of the HIC rear code can be due to a loss of the mini-cell alignment, or bit errors in the miniselled statements. The purpose of the 803 HUNT state is to reset the alignment. While the 803 HUNT state is found, the receiver stops sending mini-caches to the assembly and disassembly layer 202 and begins searching for the location of the first complete mini-cell in the ATM cell. The receiver accomplishes this by "estimating" the starting position of the first complete mini-cell. For purposes of illustration, the receiver may begin to search in the first octet (octet number zero) in the ATM cell as illustrated in block 1001 in Figure 10, where the 48 octets in the ATM cell payload are numbered from zero to forty-seven. After the receiver calculates a rear code HIC, as illustrated in block 1002. If the receiver calculates the correct HIC rear code, the receiver will update the MSP and transition from state 803 HUNT to state 802 PRESYNC as illustrated by block 1003 of desist and blocks 1004 and 1005, respectively. As in the above, the MSP is an internal variable that contains the starting position of the first full-duplex in the next ATM-that will be supported. If the receiver calculates an incorrect HIC back code, the reseptor performs another estimate respecting the position of the first complete mini-cell in the ATM cell. The receiver accomplishes this by increasing the MSP as illustrated in block 1006. The process will be repeated until the receiver calculates the correct HIC rear code or the receiver performs a system through all of the forty-eight osteos in the useful twill of the ATM system without calculating the HIC rear code correctly. If the reseptor verifies all of the suretys and eight octets in the ATM cell without correctly calcu- lating the HIC back code, the receiver will receive the next ATM cell and a new one will begin, as illustrated by the decision block 1007 and block 1008. If the receiver correctly calculates the HIC rear code during the 803 HUNT state, the receiver makes a transition from the state 803 HUNT to the state 802 PRESYNC in the assumption of that the alignment of minicells has been restored. The purpose of the 802 PRESYNC state is to ensure that the alignment of minicells has been restored by correctly calculating the HIC back code for the next N ATMs, as illustrated in Figure 11. As stated, the receiver will make a transition from the state 803 HUNT to state 802 PRESYNC if a correct HIC rear code has been calculated. In state 802 PRESYNC, the receiver first initializes an internal counter, x, as illustrated in block 1101. Next, the next ATM cell is coated and the rear part HIC is calibrated for that ATM stamp, as illustrated by the blocks 1102 and 1103. If the receiver calculates an inverse HIC rear value, the reseptor makes a transition back to the 803 HUNT state as illustrated by the 1104 de-block and the 1105 block. However, if the receiver calculates the correct HIC back code. , MSP is updated and the internal counter x is updated, as illustrated by blocks 1106 and 1107. If the receiver collects the correct HIC rear code for the ATM cells constituting the - 1 -N, the receiver makes the transition from state 802 PRESYNC to state 801 SYNC as illustrated by decision block 1108. If an estimate of the mini-cell start point estimate is confirmed by accurately qualifying the HIC back code for N + l consecutive ATM cells (which includes the calculation during the 803 HUNT state), the probability of supplying faulty minicells to layer 202 Assembly and disassembly is represented by: (1 -2 - ") 4 where n represents the number of bits of the rear code HIC and b represents the number of bytes represented by the HIC rear code. For example, the probability of supplying any failed mini-cell to the sapa 202 assembled and disassembled, for an 8-bit HIC and a N = 1 receiver, is 2.6 * 10"D. This suggests even if the alignment has been lost. a mini-cell, the probability of actually delivering a faulty mini-cell is very small.In another embodiment of the invention, the receiver must be able to send the received mini-cells to the assembly and disassembly layer 202 while it is in the 802 state PRESYNC, however, a control flag to indicate that mini-cells can be wrong. This provides the application with the opportunity to deseshar or use the mini-cells received during state 802 PRESYNC. As stated above, the telecommunications application may, for example, be a cellular telephone system 1200 as illustrated in Figure 12, wherein each radio cell C1-C10 is served by the corresponding one of a plurality of base stations B1-B10. In reading the present invention, one of the base stations B1-B10 controls the transmission of user data (ie voice data) from several mobile units M1-M10 to the mobile switching center 1201 (MSC). In general, each of the base stations B1-B10 begins by compressing the user data into minicells as illustrated in FIG. 1. Each mini-cell has a latch. The base stations B1-B10 multiplex the miniselds into ATM slots and insert a separate HIC backbone into the ATM cell as illustrated by FIG. 6. The base stations B1-B10 calculate each HIC back code as illustrated by FIG. Figure 7. The base stations B1-B10 then transmit the ATM cells to the MSC 1201. The MSC 1201 contains a 1202 reseptor which uses only one of the HIC back codes to verify the integrity of each mmicelda header and maintain the mini-cell alignment according to figures 8-11.

The invention has been deduced with reference to a particular embodiment. However, it will be readily apparent to those skilled in the art that it is possible to encompass the invention in skew-like forms different from those of the preferred embodiment described above. This can be done without departing from the spirit of the invention. The preferred modality is merely illustrative and should not be considered restrictive in any way. The scope of the invention is given by the appended claims, instead of the presending description, and all equivalent variations will fall within the range of the claims intended to be encompassed by them. It is noted that in relation to this date, the best method known by the applicant to bring the mentioned invention to trial is the one that results from the present description of the invention. Having described the invention as above, the contents of the following are respected as property:

Claims (12)

1. A method for generating data packets in a telecommunications system, the method is characterized in that the steps of: generating at least one mini-packet, wherein the mini-packet comprises a portion of data and a header; insert at least part of at least one mini-cell in the data package; generating a backsight code for verifying the integrity of the probe from a combination code, wherein the code of combination comprises the probe of each of the mini cells that has been inserted in the data packet; and insert the back code of header integrity verification within the data package.

2. The method according to claim 1, characterized in that, the step of inserting the header header verification code inside the data packet comprises the step of: inserting the header integrity check code back to a predetermined position in the data package.

3. A method for determining the integrity of the mini-cell header in a data packet, in a telecommunication system, the method is characterized in that it comprises the steps of: identifying encapsulated mini-cell sada in the data packet; determine a header integrity verification code that is based on each identified mini-header header; identify a back code of header integrity check stored from the data packet; compare the stored header integrity check code with the determined header integrity check code; and use a comparison result to determine the integrity in each mini-cell header in the data package.

4. The method of soundness is claim 3, characterized in that the step of using a comparison result to determine the integrity of each mini-cell header in the data packet comprises the step of: detect and correct errors in at least one mini-cell header in the data package.

5. A method for maintaining the alignment of mini-cells in a data packet, in a telecommunications system, the method is characterized in that it comprises the steps of: defining a starting position for a first full mini-packet in the data packet; identify a first estimating probe of each mini-packet in the data packet based on the defined start position of the first complete mini-packet in the data packet; determine a header integrity verification code that is based on the first mini-cell header estimate identified first; Identify a back header integrity check script stored from the data packet; compare the code of the verification of integrity of the determined probe with the code behind the verification of the integrity of the stored header; and use a comparison result to determine if the system is correctly aligned with the mini cells in the data package.

6. The method of sonification with claim 5, characterized in that it further comprises the steps of: predicting a new start position for the first complete mini-packet in the data packet if the result of the comparison between the header integrity check code determined on the back stored header integrity check code indicates that the two codes are not the same; identifying a second estimate header from each mini-packet in the data packet based on the new predicted start position of the first complete mini-packet in the data packet; determine a new header integrity verification code that is based on each second minicell header of identified estimate; comparing the new probe integrity verification code determined is the rear header integrity check script to generate a second result; and use the second result to determine if the system is correctly aligned with the mini cells in the data package.

7. An apparatus for generating a data packet, in a telesomunization system, the apparatus is characterized in that it comprises: means for generating at least one mini-packet, wherein each mini-pack comprises a portion of user data and a header; means for inserting at least part of at least one mini cell in the data packet; means for generating a back code for checking header integrity from a combination code, where the combinasldn code assumes the sada's password one of the mini-cells that are inserted in the data packet; and a means for inserting the header header verification code into the data packet.

8. The apparatus according to claim 7, characterized in that the means for inserting the header header check code inside the data packet comprises: means for inserting the back code of the check integrity integrity at a predetermined position in the data package

9. An apparatus for determining the integrity of mini-cell headers in a data packet, in a telecommunication system, the apparatus is sarasterized because it comprises: means for identifying each cell header in the data packet; a means to determine the header integrity verification code that is based on each identified mini-probe sampled; a means for identifying a back code for integrity check of massed sachets from the data packet; a means to supplement the stored header integrity verification code is the determined header integrity check code; and means for using a comparison result to determine the integrity of each mmicelda header in the data packet.

10. The apparatus according to claim 9, characterized in that the means for using a comparison result to determine the integrity of each minicell packet in the data packet comprises: a means to detect and correct errors in at least one mini-cell header in the data package.

11. An apparatus for maintaining the alignment of mini cells in a data packet, in a telecommunication system, the apparatus is characterized in that it comprises: means for defining a starting position for a first complete mini-cell in the data packet; means for identifying a first estimate header from each mini-cell in the data packet based on the initial position defined in the first full mini-packet in the data packet; a means for determining the header integrity verification code that is based on each first identification probe identifier identified, - a means for identifying the stored header integrity check code of the data packet; a means for comparing the code of verification of integrity of a certain probe is the back code of verification of stored header integrity; and means to use a comparison result to determine if the system of Telecommunication is correctly aligned are the mini-packages in the data package.

12. The apparatus according to claim 11, characterized in that it additionally comprises: means for predesigning a new entry position for the first complete mini-cell in the data package if the result of the comparison between the verifisation code of the specific sachet integrity swim and the back code of the storage password verification indicates that the two codes are not equal; means for identifying a second estimation header from each mini-cell in the data packet based on the new predicted start position of the first complete mini-packet in the data packet; a means to determine a new header integrity verification code that is based on each second mini-cell heading of identified estimate; a means for comparing the determined new header integrity verification code with the back code of the header integrity check to a second result; and a means to use the second result to determine if the system is correctly aligned with the mini cells in the data package.