Operating Manual Vol 1 - ES Documentation

Digital Standard 3GPP W-CDMA (FDD)SMIQTiming offsetThe symbol stream can be shifted in time relative to the other channels. For this purpose a timing offsetcan be entered into the channel table, stating the range of shifting in multiples of 256 chips. Since theSMIQ does not generate infinite symbol streams like a realtime system, this offset is implemented as arotation.Example for DPCH 30 ksps, 1 time slot,Timing offset = 2 2 x 256 chips = 512 chip offset 4 data symbols shifting at a symbol rate of 30 ksps(1 symbol corresponds to 3.84 Mcps / 30 ksps = 128 chips).previously:11 11 11 11 00 01 10 11 00 10 01 11 11 01 00 01 10 11 01 00afterwards:10 11 01 00 11 11 11 11 00 01 10 11 00 10 01 11 11 01 00 01The use of the timing offset usually causes a reduction of the crest factor of the total signal, since it isnot always the same spreading chips (channelization chips) CH and scramble chips SC i /SC q ' that areapplied to the pilot sequences of the channels.DemultiplexerIn the downlink, the symbol stream is divided into two bit streams D i and D q prior to processing in thespreading unit. The symbol stream is divided by allocating bits 1, 3, 5, to 2n-1 to the in-phase bit streamD i , and bits 2, 4, 6, 2n to the quadrature bit stream D q .For the above example with timing offset:D i = 1 1 0 0 1 1 1 1 0 0 1 1 0 1 0 1 1 0 0 0Dq = 0 1 1 0 1 1 1 1 0 1 0 1 0 0 1 1 1 1 0 1(lefthand bit is always the first one in the time sequence)In the uplink, independent data are used for the two paths.PRACH/PCPCH: Preamble: signature parallel to I and QMessage part : data to I, pilot and TFCI to QDPCCH:DPDCH:All bits to I, Q always unusedAll bits are always to I or Q (dependent on channel number), the other path isunused.Power controlAfter spreading and scrambling, a channel-specific power factor p is applied to the signal. A value of –6 dBtherefore results in half the level (or ¼ power) and the following diagram (DPCH):Sq*p1Si*p-11-1Fig. 2-101Constellation diagram of a channel with –6 dB power1125.5555.03 2.176E-9