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Tech Notes

Two sets of bit delay data are presented below. 
The first is for the M5 Class modems and the second is for the M4 Class modems.
M5: PSM-4900/4900H & M5000 Bit Delays
Transmit Path
  PSM-4900 Modulator ------------ 1 User Rate Bit
    Viterbi Rate 1/2 ----------- 12 Channel Rate Bits
    Viterbi Rate 3/4 ----------- 15 Channel Rate Bits
    Viterbi Rate 7/8 ----------- 17 Channel Rate Bits
    TPC Full Rate 1/2 -------- 1094 User Rate Bits
    TPC Full Rate 3/4 --------- 573 User Rate Bits
    TPC Full Rate 7/8 --------- 482 User Rate Bits
    TPC Short Rate 3/4 -------- 208 User Rate Bits
    TPC Short Rate 7/8 -------- 164 User Rate Bits
  Reed-Solomon Encoder ---------- 8·k+10 User/IBS Mux Output Rate Bits
    + Fixed 500us Delay
  IBS Mux ---------------------- 12 User Rate Bits
Receive Path
  PSM-4900 Demodulator ---------- 1 User Rate Bit
    Viterbi Rate 1/2 ---------- 184 Channel Rate Bits
    Viterbi Rate 3/4 ---------- 186 to 188 Channel Rate Bits
    Viterbi Rate 7/8 ---------- 186 to 190 Channel Rate Bits
    TPC Full Rate 1/2 -------- 2025 User Rate Bits + Fixed 751us Delay
    TPC Full Rate 3/4 -------- 2196 User Rate Bits + Fixed 446us Delay
    TPC Full Rate 7/8 -------- 3593 User Rate Bits + Fixed 447us Delay
    TPC Short Rate 3/4 -------- 729 User Rate Bits + Fixed 218us Delay
    TPC Short Rate 7/8 ------- 1087 User Rate Bits + Fixed 290us Delay
  Reed-Solomon Decoder Depth=4 -- 32·k+(24·k·(4·D-n))/n+11 User/IBS Demux Input Rate Bits + Fixed 500us Delay
                                  where D is the smallest integer >=(n-1)/4
                       Depth=8 -- 64·k+(24·k·(4·D-n))/n+11 User/IBS Demux Input Rate Bits + Fixed 500us Delay
                                  where D is the smallest integer >=(n-1)/8
  IBS Demux --------------------- 4 User Rate Bits
  FIFO Buffer (Enabled) --------- 3 + Buffer Fill User Rate Bits
Note, Channel Rate is the Convolotional Encoder Input Data Rate for the Modulator.
      Channel Rate is the Viterbi Decoder Output Data Rate for the Demodulator.
Reed-Solomon Example 1, if n=126, k=112 and Depth=4 then
      Total R-S Encoder Delay=906 User/IBS Mux Output Bits + Fixed 500us Delay
      D=32, Total R-S Decoder Delay=3,638 User/IBS Demux Input Bits + Fixed 500us Delay
Reed-Solomon Example 2, if n=201, k=219 and Depth=4 then
      Total R-S Encoder Delay=1,618 User/IBS Mux Output Bits + Fixed 500us Delay
      D=55, The Total R-S Decoder Delay=6,465 User/IBS Demux Bits + Fixed 500us Delay
Reed-Solomon Example 3, if n=205, k=225 and Depth=4 then
      Total R-S Encoder Delay=1,650 User/IBS Mux Output Bits + Fixed 500us Delay
      D=56, The Total R-S Decoder Delay=6,549 User/IBS Demux Bits + Fixed 500us Delay
 
M4: PSM-512/2100/2100L & M4000 Bit Delays
Transmit Path
  Modulator ---------------- 8 Channel Rate Bits
  Q1650/1900 Convolutional Encoder (Qualcomm Data Sheet)
    Rate 1/2 --------------- 11 Channel Rate Bits
    Rate 3/4 --------------- 11 to 19 Channel Rate Bits
    Rate 7/8 --------------- 11 to 19 Channel Rate Bits
    Scrambler Enabled ------ 1 Channel Rate Bit
  Reed-Solomon Encoder ----- 910 User/IBS Mux Rate Bits + Fixed 300us Delay
  IBS Mux ------------------ 8 User Rate Bits
  RS/IBS Option Installed -- 5 User Rate Bits

Receive Path
  Demodulator -------------- 1 Channel Rate Bit
  Q1650/1900 Viterbi Decoder (Qualcomm Data Sheet)
    Rate 1/2 --------------- 183 Channel Rate Bits
    Rate 3/4 --------------- 183 to 191 Channel Rate Bits
    Rate 7/8 --------------- 183 to 191 Channel Rate Bits
    Descrambler Enabled ---- 1 Channel Rate Bit
  FIFO Buffer (Enabled) ---- 1 Additional User Rate Bit + number of bits set.
  Reed-Solomon Decoder ----- 3598 User/IBS Demux Rate Bits + Fixed 300us Delay
  IBS Demux ---------------- 0 User Rate Bits
  RS/IBS Option Installed -- 4 User Rate Bits
Notes:
    "User" bit rate = "Terrestrial" interface rate
    "Channel" bit rate = 
	User bit rate X (1/FEC rate) X 16/15 (if mux enabled) X 9/8 (if R-S enabled)
Example: A modem with R-S and IBS mux is running at a user rate of 128 kbps. The
    Channel bit rate is then = 128 kbps X 2 X 9/8 X 16/15 = 307.2 kbps.
    The time/channel bit is 3.3 uS. The time/user bit is 7.8 uS.
    The modulator delay is 20 channel rate bits x 3.3 uS plus 923 user rate bits x 7.8 uS
	plus 300 uS, for a total delay of 7,565.4 uS or 7.565 mS.
    Notice that the majority of delay is due to the Reed-Solomon codec.