1、TIA DOCUMENT 1 Reaffirmed September 6,2002 Aggregation of Multiple Independent I April 1996 56 kbit/s or 64 kbit/s Channels into a Synchronized Wideband Connection TIA-619 TELECOMMUNICATIONS INDUSTRY ASSOCIATION nie Telecommunications Indudry ASFOciation represents the communications sector o Electr
2、onic Industries Alliance NOTICE TIA Engineering Standards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and o
3、btaining with minimum delay the proper product for their particular need. The existence of such Publications shall not in any respect preclude any member or non-member of TIA from manufacturing or selling products not conforming to such Publications. Neither shall the existence of such Documents pre
4、clude their voluntary use by non-TIA members, either domestically or internationally. TIA DOCUMENTS TIA Documents contain information deemed to be of technical value to the industry, and are published at the request of the originating Committee without necessarily following the rigorous public revie
5、w and resolution of comments which is a procedural part of the development of a American National Standard (ANS). TIA documents shall be reviewed on a five year cycle by the formulating Committee and a decision made on whether to reaffirm, revise, withdraw, or proceed to develop an American National
6、 Standard on this subject. Suggestions for revision should be directed to: Standards the absence of the FAW 128 octets later, detected by verifying that Bit 1 = 1 in the Fc octet; the presence of the correct frame alignment word (FAW) in the next frame. To speed the inlaal establishment of frame ali
7、gnment, an endpoint shall transmit an ai ones pattern in the Data bits of the frame on iniaal establishment of the connection until it receives the remote Alignment (A) bit set to one for two consecutive CRC octets. - - - 8 EIA TIA-619 96 = 3234600 O573834 7T8 = TIMIA-61 9 An endpoint mall begin tra
8、nsmitting an al ones pattern in the Data bits cx the frame whenever t receives an A bit set to zero in two consecutive CRC octets. Receipt of an A bit set to zero in two consecutive CRC octets indicates that the remte endpoint has lost frame alignment. 5. DESCRIPTION OF CRC4 PROCEDURE The CRC4 proce
9、dure can be used to provide an end-bend quality monitor of each 56/64 Ws channel. The four CRC bits (bit positions 4 to 7 of octet 256 )contain the CRC computed d the source location. In addition, bit3of the cameoctet, referred to as the E bit, is used to transmit a1 error indication about the recei
10、ved data in the opposite direction (.e., whether or not the previous frame was received Witti errors). The CRC4 used in these procedures is defined in CCIlT Recommendation H.221. 5.1. Computation of the CRC4 bits The CRC4 is computed from the whole 56/64 kWs channel from the previous 255 octets of t
11、he frame before the CRC4 octet. The CRC4 is therefore computed over 255 octets sMrng with the first octet of the frame (.e., the octet immediately following the CRC4 octet of the previous frame) and ending with the octet just preceding the CRC 4 octet (.e., Octet 255). The CRC-4 met is not included
12、in the CRC 4 calculation. The CRC4 computation Is performed 31.25 times per second. 5.1.1. Multiplication and division process A given CRC4 located in Octet 256 is the remainder ater multiplication by $ and then division (modulo 2) by the generator polynomial e + X+ 1 of the polynomial representatio
13、n of the 255 octets preceding the CRC octet in the frame. When representing contents of aframe as a polynomial, the first bit in the frame shall be taken as being the most significant bit. Sirnuarty Bit 4 of the CRC octet is defined to be the most significant bit of the remainder and Bit 7 is the le
14、ast significant bit of the remainder. 5.1.2. Encoding procedure Octets 1 through 255 of the frame are acted upon by the multiplication and dMsion process defined in 5.1.1. The remainder, resuiting ffom the mulplition and division process, Is inserted into the CRC 4 field 3f Octet 256 (the CRC octet)
15、 of the rart.-. The CRC is dways computed over 8 bit octets. When using 56 Ws bearer channels, bit 8 of each octet shall be forced to “1“ for consistency. Note: As described in 4.2, lor 56 kWs bearer channels, an 8th bit set io 1 is stuffed at the end of each septet before CRC encoding. This 8th bit
16、 of each octet will be stripped after CRC calculation and before transmission if 56 kWs baseband bearer channels are used 5.1.3. Decoding procedure Octets 1 through 255 of a received frame are acted upon by the multipiiin and division process, defined in 5.1.1. When using 56 kbits bearer channels, a
17、n 8th bit set to “1“ shall be added to each septet (as derived from FAW alignment) to form octets or consistency. The remainder, resulting from the multiplication and division process iscompared on a bit-by-bit basis with the CRC4 received in octet 256 of the frame. if the decoded, calculated remain
18、der equals the CRU received in Octet 256, then the checked frame is considered emf-free. t they are different, then the checked frame is considered in error. Note: As described in 4.2, CRC calculation is performed after insertion of a1 8th bit set to 1 at the end of Xh Septet. 9 5.2. Consequent acti
19、ons 5.2.1. Enabling and Disabling the CRC procedures An endpoint shall indicate that CRC procedures are being used by starting the CRC Encoding process on the transmitting end, thereby not transmitting the CRC bits asd 1s. If an endpoint supports the CRC procedure on this channel, it shall enable th
20、e CRC Decoding process when it receives a CRC Octet with the CRC bits set to avalue other than al 1s; otherwise, it shall transmit the E bit set to O and CRC set to dl 1 s. An endpoint shall indicate that CRC Encoding procedures are being disabled by setting ai CRC bits to binary 1 and setting the E
21、 bit to O. An endpoint shall disable the Decoding process when it receives three CRCoctets with CFCset to d 1s and an bit set to O. The above procedure can induce a short period of CRC errors while the endpoints start and stop CRC procedures. The actions taken in the following two sections should ta
22、ke this into account. This procedure aHows an endpoint to enable the CRC procedures on achannel by channel basis. 5.2.2. Action on bit E The E Mt of the CRC octet is set to 1 in the transmitting direction when aCRC mor is detected in the receive direction (see 5.1.3). Otherwise, it is set to zero. 5
23、.2.3. Monitoring for error performance The quality of the received 56/64 kbit/s channel can be monitored by counting the number of CRC frames in em within a period of one second. The quality of the transmitted 56/64 Ws channel can be monitored by counting the number of received E bits set to 1. The
24、threshold Iw declaring a channel out of service is left or further study and is implementation dependent. 6. DESCRIPTION OF THE INFORMATION CHANNEL The information channel is used to communicate control information between two endpoints. In dl mudes, the Information Channel occupies the entire bandw
25、idth of the Master Channel during initial parair-ter negotiation. In modes 2 and 3, the Information Channel occuplr xtet 128 of the Channel Aggregation Frame in d bearer channels during deiay equalization and throughout the duratiori of the cdl. In mode 1, the Information Channel occupies octet 128
26、of the Channel Aggregation Frame in dl bearer channels only during the initial delay equalization. In mode O, the Infomiation Channd is not present ater initial parameter negotiation. 6.1. Information Channel Frame Information channel frames are ramed with aunque ALIGNment pattern (O1 11 11 11) in t
27、he first octet. In addition, the first bit (bl) of the subsequent mets is set to one. Figure 2 shows the structure of the Infomiation Channel (IC) rame. C octets only contain seven bits of information so that a common structure can be used br 56 and 64 kWs bearer channels. In Fgure 2, Mt 8 of each o
28、ctet is depicted as having the value 1. For 64 kbit/s bearer channels, bit 8 is set to 1. For 56 kbit/s bearer channeis provided via64 Ws facilitiec, bit 8is used kw network signaling and isset to 1 for off-hook. Forthe cased56 Ws baseband bearer channels, bit 8 is not present and an overhead “octet
29、“ Vansmited over the bearer channel contains only 7 Mts. Section 4.2 describes procedures for using 56 kMVs bearer channels. 10 EIA TIA-619 96 3234600 0573836 570 TIAEIA-619 bl b2 b3 b4 b5 b6 b7 b8 ALIGN i Octet 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Figure 2: Information Channel Frame ALIGN: Alignm
30、ent octet (Octet 1, Bits 1-8) The alignment octet provides aframing mechanism for the Information channel frame. it takes aconstant value of “O1 1 1 1 1 1 1 I. Note: For 56 kWs baseband bearer channels, only the first seven bits of the ALIGN octet are transmitted (.e., O1 11 11 11. CID: Channel iden
31、tifier (Octet 2, Bits 2-7) When simuttaneously dialing N calk, the network delay in cai1 setup or each cai1 might not be uniform. Hence the incoming cdl anivd sequence at the Answering Endpoint cannot be assumed to be equal to the cdl setup sequence at the Calling Endpoint. The CID identifies each i
32、ndividual channel in the transmit direction ior each side of the connection and is used to sequence the time sbts in proper order dthe receiving end. In each endpoint, the CID value transmitted in each channel is independent of the CID value received from the other endpoint. The Calling and Answerin
33、g endpoint shall assign CID = 1 to the initial channel and shall assign CID in sequential ascending order corresponding to the relative order of the remaining channels. A value of O in the CID field indicates negotiation of parameters. The CID is a6-bit binary encoded number in the range O S- CID s
34、63. GID: Group identifier (Octet 3, Bitc 2-7) The cdl Group Identifier is used to identify the group of bearer channels associated with a particular call. The value of this parameter shall be agreed upon by both ends at the tim of establishing the master channel. The GiD negotiated on the master cha
35、nnel shall be used in al subsequent bearer channels for tMs CaH. The CID is assigned by the Answering Endpoint and is unique to this cdl at the Answering Endpoint. The Calling Endpoint uses acombination of the GID anci a local identifier to uniquely identify acdl. The value of O is reserved to indic
36、ate an unknown GiD during parameter nogotiation and channel initiation. This field contains abinary encoded number in the range O s GiD s 63 MODE: Operating mode (Octet 4, Bits 24 ) This field indicates the mode of operation desired for this call. The four modes of operation are described in 4.1 of
37、this document. 11 EIA TIA-617 76 3234600 0573837 407 D TIAE IA-61 9 Bits 234 O00 O01 o1 o o1 1 1 O0 101 110 111 operating Mode O operating Mode 1 operating Mode 2 operating Mode 3 Reserved Reserved Reserved Reserved or negotiation. Note: There is no coding for the Transparent Mode because in the Tra
38、nsparent Mode there is no Irrformation Channel. Res: Reserved (Octet 4. Bits 5-7): These bits are reserved and shall be set to 1 on transmission and shall be ignored on receipt. RMULT: Rate Multiplier (Octet 5, Bits 2-7) The Rate Multiplier field RMULT together with the Subrate Multiplier field SUBM
39、ULT contains information that uniquely defines the application rate for agiven cdl. The application rate is determined from these fields in slightly different ways depending on the Operating Mode given in the MODE field of the Infomiation Message (Octet 4, Bits 2-4). See 6.1 -1 or details. RMULTtake
40、s avalue in the range O IS RMULT s 63. SUBMULT: Subrate Multipiier(Octet 6, Bits2-4): The Rate Multiplier field RMULT together with the Subrate Multiplier fieM SUBMULT contains infomiation that uniquely defines the application rate foi a given cail. For Mode O, 1 and 2, the SUBMULT field shall be se
41、t to al binary ones on transmit and ignored on receipt. See 6.1 .l ior details. For Mode 3, SUBMULT takes avaiue in the range O s SUBMULT 5 6 or BCR = 56 Ws aml O 5 SUBMULT s 7 for 64 kbWs B C R : Bearer Channel Rate (Octet 6, Bit 5) This field indikates the data rate to use when determining how to
42、use the bearer channel. A 56 kbitis BCR mans that the channels used are based on 56 Ws multiples and a64 kWs BCR means that the channeis used are based on 64 kbit/s multiples. This field takes the fdlowing values Bit5 1 64kbisbase O 56kbisbase Res: Reserved (Octet 6, Bit 6 ): This bit is reserved an
43、d shall be set to 1 on transmWin and shall be ignored on receipt. MFG. Manufacturing D Flag (Octet 6, Bit 7): When this bit is set to 1, the Dig therefore, the SUBMULT field is required to specify the application data rate with an 8 kbitls granularity. In Modes O, 1 and 2 the SUBMULT field shall be
44、set to ai ones on transmission and ignored on receipt. Let EBR (Effective Bearer Rate) represent the effective bandwidth per network channel avaibble for the transfer of application data. EBR is deftned as the Bearer Channel Rate (ER) minus the bandwidth required to transfer the Channel Aggregation
45、overhead octets. Mode O, 1 : E8. EBR = BCR , since the Channel Aggregation overhead octets am removed before application data is transferred over the channel. Modes2and3: E9. EBR = (g)*BCR, since every 64th octet of a network channel is required for the transfer of overhead octets. The number of net
46、work channels (N) required to complete the call is then determined directly based on application data rate and effective bearer rate: ModesO, 1, 2and3: rounded up to the nearest integer. “LEBRI EIA TIA-bL9 96 3234bQU CI573841 938 = TIAEIA-619 a From the above equations it follows that Cor Modes O, 1
47、 and 2 the number of channels N required for a given call is equal io the Rate Multiplier RMULT. Only in Mode 3 is it necessary to explicitly calculate N. In the case of Mode 3, N can be calculated from RMULT and SUBMULT by substituting equation E5 or A to get RMULT*BCR +SUBMULT*8000 EBR Ell. N= Equ
48、ation Ell must be used on the receiving end of a parameter negotiation frame to determine the number of channels. 6.1.1. I. Distribution of Application Data Across the Channel Aggregation Frame. In Modes O. 1 and 2 the application data rate is only allowed to be Integer multiples of the effective be
49、arer channel rate (EBR). In Mode O and 1, EBR is the same as the bearer channel rate BCR (.e., EBR = BCR = 56 or 64 Ws). In Mode 2 EBR is BCR scaled by 63/64 (ial EBR = BCR * (6364) = 55.1 25 Ws (BCR = 56 kWs) w 63 kbit/s (BCR =64 kWs). In Modes 1 and 2 d available bandwidth is used by data (Mode 1) or data and overhead (Mode 2). In Mode 3 the application data rate (A) is allowed io be an integer multiple of 8 kbWs. To support this granularity in the applcatm data rate, only aportion of the available bandwidth in the Nth network channel is used. In Mode 3, t
