短信DCS理解.doc

特殊消息－DCS字段承载 字段来源 1、TP－DCS字段在etsi 0338协议或3gpp 23038协议里规定，也就是我们平时常说的0338协议，打开此协议你可以看到此字段虽然是一字节，但规定的值很多，含义丰富。 2、SMPP协议里的DCS字段参照etsi 0338协议里的定义。 如何理解 打开etsi 0338协议，我们可以看到其DCS分多种情况进行定义，bit7～bit4为一段，bit3～bit0为一段。我们平时常用的dcs=0/4/8其实仅仅是其中的bit3与bit2的取值。重要的导读语在下面是蓝色字体标出： SMS Data Coding Scheme The TP-Data-Coding-Scheme field, defined in GSM?03.40, indicates the data coding scheme of the TPUD field, and may indicate a message class. Any reserved codings shall be assumed to be the GSM default alphabet (the same as codepoint by a receiving entity. The octet is used according to a coding group which is indicated in bits 7..4. The octet is then coded as follows: Coding Group Bits 7..4 Use of bits 3..0 00xx General Data Coding indicationBits 5..0 indicate the following : Bit 5, if set to 0, indicates the text is uncompressedBit 5, if set to 1, indicates the text is compressed using the GSM standard compression algorithm. ( see GSM TS 03.42)Bit 4, if set to 0, indicates that bits 1 to 0 are reserved and have no message class meaning Bit 4, if set to 1, indicates that bits 1 to 0 have a message class meaning : Bit 1 Bit 0 Message Class0 0 Class 00 1 Class 1 Default meaning: ME-specific.1 0 Class 2 SIM specific message1 1 Class 3 Default meaning: TE specific (see GSM?TS 07.05?[8]) 解读： 当bit7bit6=00时： 1、如果bit5=0表示内容是非压缩方式，如果bit5=1表示内容是压缩方式，压缩方法可参见GSM TS 03.42协议。 2、如果bit4=0表示bit1bit0无其它含义，如果bit4=1表示bit1bit0有意义，其bit1bit0的几种取值也是一些比较特殊的消息，其含义在后面的详细的解释，请先在这里作一标记，后面再解惑不同的Class究竟是什么意思。 Bits 3 and 2 indicate the alphabet being used, as follows :Bit 3 Bit2 Alphabet:0 0 Default alphabet0 1 8 bit data1 0 UCS2 (16bit)?[10]1 1 Reserved 解读： Bits 3 and 2，我们测试过程中最常见的dcs=0/4/8。所以看到这里要摆脱新员工学习时的误区，不要认为ucs2编码时dcs只等于8，因为dcs字段是按比特来算的，同样dcs=24时bit3bit2也为10，也是ucs2编码，等等。 NOTE: The special case of bits 7..0 being 0000 0000 indicates the Default Alphabet as in Phase 2 0100..1011 Reserved coding groups 1100 Message Waiting Indication Group: Discard Message Bits 3..0 are coded ex