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1、July, 19987 -1RF100 (c) 1998 Scott BaxterCDMA Call ProcessingCDMA Call ProcessingSection FJuly, 19987 -2RF100 (c) 1998 Scott BaxterMessages in CDMAn In CDMA, most call processing events are driven by messages n Some CDMA channels exist for the sole purpose of carrying messages; they never carry user
2、s voice traffic Sync Channel (a forward channel) Paging Channel (a forward channel) Access Channel (a reverse channel) On these channels, there are only messages, continuously all of the time n Some CDMA channels exist just to carry user traffic Forward Traffic Channel Reverse Traffic Channel On the
3、se channels, most of the time is filled with traffic and messages are sent only when there is something to do n All CDMA messages have very similar structure, regardless of the channel on which they are sentJuly, 19987 -3RF100 (c) 1998 Scott BaxterHow CDMA Messages are Sentn CDMA messages on both fo
4、rward and reverse traffic channels are normally sent via dim- and- burst n Messages include many fields of binary data n The first byte of each message identifies message type: this allows the recipient to parse the contents n To ensure no messages are missed, all CDMA messages bear serial numbers a
5、nd important messages contain a bit requesting acknowledgment n Messages not promptly acknowledged are retransmitted several times. If not acknowledged, the sender may release the call n Field data processing tools capture and display the messages for studyMSG_TYPE (00000110)ACK_SEQMSG_SEQACK_REQENC
6、RYPTIONERRORS_DETECTEDPOWER_MEAS_FRAMESLAST_HDM_SEQNUM_PILOTSPILOT_STRENGTHRESERVED (0s)833125102460- 7NUM_PILOTS occurrences of this field:FieldLength (in bits)EXAMPLE: A POWER MEASUREMENT REPORT MESSAGEtJuly, 19987 -4RF100 (c) 1998 Scott BaxterMessage Vocabulary: Acquisition 1 km.= 4.1 chipsPROPAG
7、ATION DELAY SKEWS APPARENT PN OFFSETSBTSBTSAB33 Chips4 ChipsIf the phone is locked to BTS A, the signal from BTS B will seem 29 chips earlier than expected. If the phone is locked to BTS B, the signal from BTS A will seem 29 chips later than expected.July, 19987 -48RF100 (c) 1998 Scott BaxterSetting
8、 Pilot Search Window SizesnWhen the handset first powers up, it does an exhaustive search for the best pilot. No windows are used in this process. nOn the paging channel, the handset learns the window sizes SRCH_WIN_A, N, R and uses them when looking for neighbors both in idle mode and during calls.
9、 nWhen a strong neighbor is requested in a PSMM, the former neighbor pilot is now a candidate. Its offset is precisely remembered and frequently rechecked and tracked by the phone. nWindow size for actives and candidates can be small, since their exact position is known. Only search wide enough to i
10、nclude multipath energy! This greatly speeds up overall searching! nMost post- processing tools deliver statistics on the spread (in chips) between fingers locked to the same pilot. These statistics literally show us how wide the SRCH_WIN_A should be set. nNeighbor and Remaining search windows shoul
11、d be set to accommodate the maximum intercell distances which a mobile might experienceSEARCH WINDOW SETTINGS AND PROPAGATION DISTANCESWindow Size (Chips)14 (7)Datafill ValueN,R Delta Distance41.06 20 (10)40 (20)28 (14)MilesKM.5 6 7 8 9 10 11 12 13 14 1560 (30) 80 (40) 100 (50) 130 (65) 160 (80) 226 (113) 320 (160) 452 (226)1.71 1.522.44 2.123.42 3.034.88 4.557.32 6.079.77 7.5912.2 9.8615.9 12.119.5 17.127.6 24.339.1 34.355.2
