1、m 3Y04583 0082bY8 O28 m Released: July I, 1993 GSM 04.21 Version: 4.2.1 Date: April, I993 Work item No: Key words: European digital cellular telecommunication system (phase 2); Rate Adaptation on the MS-BSS interface ETSI European Telecommunications Standards Institute ETSI Secretariat: Route des Lu
2、cioles, F-O6921 Sophia Antipolis Cedex . France TP. + 33 92 94 42 O0 TF. + 33 93 65 47 16 Tx. 47 O0 40 F This is an unpublished work the copyright in which vests in the European Telecommunications Standards institute. Ali rights reserved. The information contained herein is the property of ETSI and
3、no part may be reproduced or used except as authorised by contract or other written permission. The copyright and the foregoing restriction on reproduction and use extend to ali media in which the information may be embodied. 3404583 0082647 Tb4 O. 1. 2. 3. 4. 5. 6. 7. 8. 9. Page 3 GSM 04.21 - versi
4、on 4.2.1 List of Contents: Scope References Abbreviations General Approach The RA0 Function 4.1 Asynchronous-to-synchronous conversion (RAO) 4.2 Break Signal 4.3 Overspeed/Underspeed 4.4 Parity bits The RA1 Function 5.1 Network Independent Clocking 5.1.1 Multiframe Structure 5.1.2 Encoding and compe
5、nsation The RA2 Function The RA1/RAll Function 7.1 7.2 7.3 7.4 Synchronisation 7.5 Idle Pattern Radio Interface rate of 12 kbit/s Radio Interface rate of 6 kbit/s Radio Interface rate of 3.6 kbit/s The RAll Function Support of Non-Transparent Bearer Services Annex: Stacks of rate adaptation Number o
6、f Daaes: 21 W 3404583 0082b50 78b W Page 5 GSM 04.21 - version 4.2.1 O. SCOPE This Specification defines the rate adaptation functions to be used in GSM PLMN Mobile Stations for adapting terminal interface data rates to the MS-BSS interface data rates in accordance with GSM Specification 03.10. The
7、provision of these functions will depend on the services a particular station is designed to support. Note: This Specification should be considered together with GSM Specification 08.20 (Rate Adaptation on the BSS- MSC Interface) to give a complete description of PLMN rate adaptation. 1. REFERENCES
8、This TS incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriated places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications appl
9、y to this TS only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. CCITT Rec.V.110 Support of data terminal equipments (DTEs) with V.-series type interfaces by an integrated services data network CCITT Rec.X.30 Suppor
10、t of X.21, X.2lbis and X.20bic based Data Terminal Equipment (DTEs) by an ISDN GSM 03.10 PLMN connection types GSM 05.03 Channel Coding GSM 08.20 Rate adaptation on the BSS-MSC interface 2. ABBREVIATIONS BSS BTS DTE FCS IWF L2RPDU LAPB MF MS MSC MT NIC PLMN PSTN RLP TCH TDMA Base Station System Base
11、 Transmitter System Data Terminal Euipment Frame Check Sequence Interworking Function Layer 2 Relay Protocol Data Unit Link Access Protocol Balanced Multi Frame Mobile Station Mobile Switching Centre Mobile Termination Network Independent Clocking Public Land Mobile Network Public Switched Telephone
12、 Network Radio Link Protocol Traffic Channel Time Division Multiplex Access 3404583 0082653 b32 Page 6 GSM 04.21 - version 4.2.1 . 3. GENERAL APPROACH GSM Specification 03.10 defines the PLMN connection types necessary to support the GSM PLMN data and telematic services. Within the MS there are seve
13、ral different data rate adaptation functions which are combined as shown in GSM 03.10 as part of the connection type. These functions are RAO, RA1, RA2, RA1 and RA1/RAll. The RAO, RA1 and RA2 are equivalent to those functions described in CCITT recommendation V.110. The RA1 function is similar to RA
14、1 but has a reduced bit rate output compatible with the coding scheme proposed for data services on the radio interface. The RAl/RAl is a relay function, used as indicated in GSM 03.10. 4. THE RA0 FUNCTION 4.1. Asvnchronous-to-Svnchronous Conversion (RA01 The RA0 Function is only used with asynchron
15、ous interfaces. Incoming asynchronous data is padded by the addition of stop elements to fit the nearest channel defined by (2 to the power n) times 600 bit/s. Thus both 75 bit/s and 300 bit/s user data signalling rates shall be adapted to a synchronous 600 bit/s stream. The resultant synchronous st
16、ream is fed to RA1 or RA1. asynchronous user rate S 0.6 1.2 2.4 4.8 9.6 synchronous user rate 0.6 1.2 9.6 -1 4.2. Break Sianal The RA0 shall detect and transmit the break signal in the following fashion: If the converter detects M to 2M+3 bits, all of start polarity, where M is the number of bits pe
17、r character in the selected format including start and stops bits, the converter shall transmit 2M+3 bits of start polarity. If the converter detects more than 2M+3 bits all of start polarity, the converter shall transmit all these bits as start m 3403 ooww 559 m Page 7 GSM 04.21 - version 4.2.1 pol
18、arity. The 2MI3 or more bits of start polarity received from the transmitting sides shall be output to the receiving terminal. The terminal must transmit on circuit 103 at least 2M bits stop polarity after the start polarity break signal before sending further data character. The converter shall the
19、n regain character synchronism from the following stop to start transition. 4.3. Overspeed/Underspeed A RA0 shall insert additional stop elements when its associated terminal is transmitting with a lower than nominal character rate. If the terminal is transmitting characters with an overspeed of up
20、to 1% (or 2.5% in the case of nominal speeds lower than 600 bit/s), the asynchronous-to-synchronous converter may delete stop elements as often as is necessary to a maximum of one for every eight characters at 1% overspeed. The converter on the receiving side shall detect the deleted stop elements a
21、nd reinsert them in the received data stream (circuit 104). The nominal length of the start and data elements shall be the same for all characters. The length of the stop elements may be reduced by as much as 12.5% for nominal speeds exceeding 300 bit/s to allow for overspeed in the transmitting ter
22、minal. For nominal speeds less than or equal to 300 bit/s a 25% reduction in stop element is allowed. 4.4. Parity Bits Possible parity bits included in the user data are considered as data bits by the RA0 function (and RA1 function). 4.5. Flow Control Where applicable, this function is as specified
23、in the relevant terminal adaptation function Specification (GSM 07 series). W 3404583 O082653 495 synchronous user rate I 2.4 Page 8 GSM 04.21 - version 4.2.1 Intermediate rate 8 5. THE RA1 FUNCTION This function is used to adapt between the synchronous user rates, or the output of the RA0 function
24、and the intermediate rate of 8 or 16 kbit/s. 4.8 8 r- 9.6 16 I I I A CCITT V.110 80 bits frame is constructed using the user data bits received (from the RA0 in the asynchrounous case), the values of the S bits are deduced from the R interface. Adaptation of 600 bit/s to 8Kbit/s is performed by 8 ti
25、mes consecutive duplication of each user data bit. Adaptation of 1200 bit/s to 8 Kbit/s is performed by 4 times consecutive duplication of each user data bit. Adaptation of 2400 bit/s to 8kbit/s is performed by 2 times consecutive duplication of each user data bit. Adaptation of 4800 bit/s to 8 Kbit
26、/s is performed by transmitting the bit stream with no duplication. Adaptation of 9600 bit/s to 16 Kbit/s is performed by transmitting the bit stream with no duplication (the emitting period is halfed with respect to the 4800 bit/s case). The CCITT V.110 80 bit frame shown in Figure 3 is used. The D
27、 bits are used to convey the user data and the S and X bits are used to convey channel control information according to the relevant terminal adapter function Specification. D 3404583 0082654 321 Page 9 GSM 04.21 - version 4.2.1 The E bits are used to convey the following information: i) User Data R
28、ate - El, E2, E3 (see Figure 4) ii) Network Independent Clocking - E4, E5, E6 iii) Multiframe Synchronisation - E7 The order of transmission of the 80 bit frame is from left to right and top to bottom. 5.1. Network Independent Clockinq Synchronous data signals received by the MT from the DTE at the
29、MS or by IWF from the modem on the PSTN may not be synchronised to the PLMN. The following method shall be used to enable transfer of those data signals and the corresponding bit timing information via the V.110 frames. Such a situation would exist where the signals received from the modem at the IW
30、F require its own clock or where the signals received from the DTE at the MS employs its own network independent clock. In any case, the frequency tolerance of the clocks involved is 100 ppm. 5.1.1. Multiframe Structure The transmitting end of the GSM PLMN connection shall establish a multiframe str
31、ucture utilising bit E7 consisting of four frames by setting E7 in every fourth frame to binary O. This structure is identical to the use of E7 in V.110 (and X.30) except that such a multiframe structure will exist for all user data rates. This frame synchronization will be achieved and maintained d
32、uring the entire call so that corrections for the network independent clocking by the receiving end of the GSM PLMN connection can be easily recognized and applied based on the code words (in cl,c2,c3,c4 and c5) positioned in bits E4, E5 and E6 of two consecutive V.110 frames as illustrated in figur
33、e 1. Thus, the multiframe structure allows for one 5-bit code words to be transmitted every two V.110 frames for the purposes of network independent clocking. The two code-words may be different from each other within the multiframe shown in figure 1. Frame E4 E5 E6 E7 MF Oa cl c2 1 O MF la c3 c4 c5
34、 1 MF Ob cl c2 1 1 MF lb c3 c4 c5 1 NIC Multiframe Structure Figure 1 Once Multiframe synchronization is achieved, each code word is independently evaluated to determine the compensation needed, if any. The compensation is applied as explained in section 3.1.2 in V.110 frames MF la and MF lb. Page 1
35、0 GSM 04.21 - version 4.2.1 m 3404583 0082655 268 H 5.1.2. Encodina and comisensation The V.110 transmitter will use the following 5-bit code words, as shown in figure 2, to indicate the four possible states of compensation required for network independent clocking. cl c2 c3 c4 c5 No compensation 11
36、111 Negative compensation 10010 Positive compensation of one 00100 Positive compensation of a zero 0 1 O O 1 NIC Code Words Figure 2 When negative compensation is indicated, one less user data bit than normal is transported in the affected frame (MFla or MFlb). A negative compensation shall cause th
37、e receiver to delete the user data bit occupied by bit position D25, since the transmitter sets this to binary 1 and does not utilize this position for user data. At those user data rates where the user data bit is repeated, all copies of D25 shall be discarded. When a positive compensation is indic
38、ated, one additional user data bit is transferred by means of the code word. At the receiver, a positive compensation will cause a user data bit of binary value O or 1, as indicated by the code word, to be inserted between the user data bits carried in bit positions D24 and D25 (in MFla or MFlb) of
39、the V.110 frame illustrated in figure 3. When no compensation is necessary, or when NIC is applied, the values of E4, E5, E6, E7, on the 4 multi frame scheme is Frame E4 E5 E6 E7 MF Oa 1 1 1 O MF la 1 1 1 1 MF Ob 1 1 1 1 MF lb 1 1 1 1 W 3404583 008265b LT4 W Page 11 GSM 04.21 - version 4.2.1 interme
40、diate rate 6. THE RA2 FUNCTION rate at the S interface This procedure is based on the RA2 function as specified in CCITT V.110, It is used to rate adapt to/from the intermediate rates of 8 or 16 kbit/s from/to the 64 kbit/s rate used at the S interface. It considers the 64 kbit/s stream to consist o
41、f octets, bits 1 through 8, with bit 1 being transmitted first. The procedure requires that: i) The 8 kbit/s stream occupies bit position 1; ii) The 16 kbit/s bitstream occupies bit positions (1,2); iii) The order of transmission of the bits of the subrate stream is identical before and after rate a
42、daptation, iv) All unused bits in the 64 kbit/s stream are set to binary II 1tl . 3Y04583 0082657 030 8 Page 12 GSM 04.21 - version 4.2.1 3.6 7. THE RAl/RAl FUNCTION The RA1/RAll function is used to convert between the CCITT V.110 80 bit frames produced at the 8 and 16 kbit/s intermediate rates and
43、the input rate to the channel coder function for transmission by the radio subsystem. I intermediate rate Irate at the air interface1 There are three data rates (known as Radio Interface rates) used for data transfer to the channel coder. These are 12 kbit/s, 6 kbit/s and 3.6 kbit/s, and in order to
44、 adapt the 8 and 16 kbit/s intermediate rates to these data rates, three processes are used. Firstly the 17 synchronisation bits are removed. Secondly the El, E2 and E3 bits are removed. The values of the El, E2, E3 bits are determined at the MT and the BTS based on the indication given in the llset
45、-upll message regarding the BC field Inuser rate“ (octet 6a of BC in 04.08). Thirdly, in the 3.6 kbit/s case, half the data bits are discarded. These processes result in modified CCITT V.110 frames of sizes 60,60 and 36 bits for the 12, 6 and 3.6 kbit/s data rates respectively. The resultant modifie
46、d CCITT V.110 frames for the various user data rates are shown in figures 5-9. = 3404583 0082b58 Ti7 H Page 13 GSM 04.21 - version 4.2.1 7.1. Radio Interface rate of 12 kbit/s In this case one modified CCITT V.110 60 bit frame is received/sent from/to the radio subsystem every 5ms (see GSM 05.03). T
47、he RAl/RAl function will add/subtract the 17 bit synchronisation pattern and the El,E2 and E3 bits to/from each CCITT V.110 80 bit frame as follows: The modified CCITT V.110 60 bits frame received/sent from/to the air interface at 12 Kbit/s, D1 D7 D13 D19 E4 D28 D34 D4 O D4 6 D2 D3 D8 D9 D14 D15 D20
48、 D21 E5 E6 D29 D30 D35 D36 D4 1 D42 D47 D48 D4 D5 D6 D10 D11 D12 D16 D17 D18 D22 D2 3 024 E7 D25 D2 6 S6 D3 1 D32 X D37 D38 S8 D43 D44 s9 s1 X s3 s4 D27 D33 D39 D45 is converted into the following a CCITT V.110 80 bits frame at 16 Kbit/s: O 1 1 1 1 1 1 1 1 1 O O O D1 D2 D3 D7 D8 D9 D13 D14 D15 D19 D
49、2 O D2 1 El E2 E3 D25 D2 6 D27 D3 1 D32 D33 D37 D38 D39 D43 D44 D45 O D4 D10 D16 D22 E4 D28 D34 D4 O D4 6 O O O D5 D6 s1 D11 D12 X D17 D18 s3 D2 3 D24 s4 D29 D30 S6 D35 D36 X D4 1 D42 S8 D47 D4 8 s9 E5 E6 E7 For a modified CCITT V.110 60 bit frames received from the radio subsystem, the received D, S and X bits are set to the same value as the transmitted bits. Bits El, E2, E3 are set according to the user data rate as shown in Figure 4. For modified CCITT V.110 60 bit frames transmitted over the radio subsystem, the received D, S, and X bits are set to the same v
