E01.1.1.pptx

UNCLASSIFIED TDMA - Time Division Multiple Access - JTIDS/MIDS uses TDMA protocol - TDMA allows multiple users access to time slices or time slots 1 UNCLASSIFIED UNCLASSIFIED Taking Turns ‒ In TDMA - units take turns according to time ‒ Each unit transmits when programmed ‒ Burst transmissions of either 258 or 444 pulses 2 UNCLASSIFIED UNCLASSIFIED Turn Distribution 1536 time slots 12 seconds ‒ Transmit capacity varies from unit to unit ‒ C2 units need more ‒ Radar units need more ‒ More turns means more capacity 3 UNCLASSIFIED UNCLASSIFIED Epoch 12.8 minutes 98304 time slots • An epoch is the largest time unit • An epoch is 12.8 minutes • There are 98304 time slots in an epoch 4 UNCLASSIFIED UNCLASSIFIED Frames 12 seconds 1536 time slots • Times slots are grouped into basic units called frames • There are 64 frames in each epoch – All frames are normally identical – Each A0 is different • Frames have 1536 time slots and are 12 seconds in duration 5 UNCLASSIFIED UNCLASSIFIED Time Slots 12 seconds 1536 time slots A-0 B-0 C-0 • The 1536 time slots sub-divided into 3 sets (A, B and C) • Time slots are numbered 0-511 in each set 6 UNCLASSIFIED UNCLASSIFIED Time Slot Components 1536 time slots 12 seconds J S/H • Time Slot components are comprised of: – Jitter – Sync – Header – Data – Propagation D P 7 UNCLASSIFIED UNCLASSIFIED Legacy Transmission Formats Standard Double Pulse (SDP) 3 Words, Double Pulse, 258 Pulses Pack 2 Single Pulse (P2SP) 6 Words, Single Pulse, 258 Pulses Pack 2 Double Pulse(P2DP) J SH J SH SH 6 Words, Double Pulse, 444 Pulses D d P d D D P P Pack 4 Single Pulse(P4SP) SH 12 Words, Single Pulse, 444 Pulses d d d d P Extended Range j (STDP and P2SP only) 8 UNCLASSIFIED SH d d P UNCLASSIFIED Track Generation 1001 1002 1003 J3.2-1003 J3.2-1002 J3.2-1001 • The host system produces track reports (J3.2 = air track) which are sent to the JTIDS/MIDS terminal • Tracks are buffered until the time of transmission 9 UNCLASSIFIED UNCLASSIFIED Track Transmission • Tracks are transmitted in the next timeslot assigned to NPG 7 • Each track is extrapolated to the time of transmission J3.2-1003 J3.2-1003 J3.2-1002 J3.2-1002 J3.2-1001 J3.2-1003 10 UNCLASSIFIED UNCLASSIFIED Packing • Packing is based upon – The number of tracks in the buffer J3.2-1003 J3.2-1002 J3.2-1001 – The number of timeslots in the next 32 for NPG 7 32 11 UNCLASSIFIED UNCLASSIFIED Transmission Formats   The minimum number of words transmitted is 3 Packing only occurs with demand 6 { Pack 2 Single Pulse TDL J Words 3 J3.2-1003 J3.2-1002 J3.2-1001 { 12 Standard Double Pulse D { 12 UNCLASSIFIED d d Pack 2 Double Pulse D D Pack 4 Single Pulse d d d d UNCLASSIFIED Packing 3.2I, 3.2 E0, 3.2C1 J3.2-1003 J3.2-1002 J3.2-1001 Air Track updates have 2 TDL J words 3.2I, 3.2 E0 31.7 I Initial Air Track reports have 3 TDL J words No statement words have 1 TDL J word 13 UNCLASSIFIED UNCLASSIFIED Pack 2 Possibilities Pack 2 Single d dPulse { 6 J3.2-1003 J3.2-1002 J3.2-1001 Pack 2 Double Pulse D D 3 3 2 2 2 Initials Reports 3 2 1 1 3 2 2 14 UNCLASSIFIED 1 Initial – 1 Update 3 Update Reports UNCLASSIFIED Average Throughput 7 9 Track reports in 4 timeslots. 1 2 3 4 9/4 = 2.25 trks/ts 5 6 Normally there are more updates 8 9 Average > 2.5 air trks/ts Too many combinations for P4. Use 4.0; most of today's Link 16 networks are designed using 4 tracks per P4SP time slot. 15 UNCLASSIFIED UNCLASSIFIED Advanced Transmission Formats Link 16 Enhanced Throughput – Key Points • With the ever-increasing fielding of L16 systems the worldwide networks have become overloaded and unable to support all IERs (Oversubscription) • A new waveform called Link 16 Enhanced Throughput or simply (LET) will allow a higher data-rate of up to 1 Mbps 16 UNCLASSIFIED UNCLASSIFIED Advanced Transmission Formats Link 16 Enhanced Throughput (LET) provides increased throughput with no change to the spectral characteristics of Link 16 • Adds 5 variable data rates up to 10 times the highest current throughput mode of Link 16 (Packed-4 Single Pulse (P4SP)) • Recent tests data shows less impact to range and anti-jam performance loss vs. original data - LET 0 thru 1 most suitable • Limitations: – Implementation required by all participants for interoperability – Message structure in time slots reduces range and anti-jam performance from current messages to gain higher data rate 17 UNCLASSIFIED UNCLASSIFIED Advanced Transmission Formats Message Structure Data Words Bits Tracks Highest Current Mode 12 Data Words 900 bits of data 4 Tracks LET Mode 0 40 Data Words 2944 bits of data 13 Tracks LET Mode 1 61 Data Words 4416 bits of data 20 Tracks LET Mode 2 93 Data Words 6752 bits of data 31 Tracks LET Mode 3 108 Data Words 7800 bits of data 36 Tracks LET Mode 4 123 Data Words 8800 bits of data 41 Tracks 18 UNCLASSIFIED UNCLASSIFIED JTIDS Wave Format • JTIDS is a pulsed RF system – Each transmission consists of a stream of pulses • The TDMA protocol determines who transmits – Multiple participants are assigned timeslots for transmission – Units receive when not transmitting 19 UNCLASSIFIED UNCLASSIFIED TDMA • Transmitters take turns – 1536 assigned time slots (Repeating every 12 seconds) – Preprogrammed by the network load 20 UNCLASSIFIED UNCLASSIFIED TDMA Summary 12 seconds The FRAME is the basic reoccurring unit of time. 7.8125 msec The Timeslot is the basic unit of access. Transmissions consist of 72, 258 or 444 pulses. 1536 time slots 258 pulses 5 bits of data 32 Chips 6.4 usec  a 6.6 usec 21 UNCLASSIFIED Each pulse is on a different frequency. Each pulse contains 5 bits of data spread into 32 chips. UNCLASSIFIED 22 UNCLASSIFIED UNCLASSIFIED 23 UNCLASSIFIED UNCLASSIFIED 24 UNCLASSIFIED UNCLASSIFIED 25 UNCLASSIFIED UNCLASSIFIED 26 UNCLASSIFIED UNCLASSIFIED 27 UNCLASSIFIED UNCLASSIFIED 28 UNCLASSIFIED UNCLASSIFIED 29 UNCLASSIFIED UNCLASSIFIED 30 UNCLASSIFIED UNCLASSIFIED 31 UNCLASSIFIED UNCLASSIFIED 32 UNCLASSIFIED UNCLASSIFIED 33 UNCLASSIFIED UNCLASSIFIED 34 UNCLASSIFIED UNCLASSIFIED 35 UNCLASSIFIED UNCLASSIFIED 36 UNCLASSIFIED UNCLASSIFIED 37 UNCLASSIFIED UNCLASSIFIED 38 UNCLASSIFIED UNCLASSIFIED 39 UNCLASSIFIED UNCLASSIFIED 40 UNCLASSIFIED UNCLASSIFIED 41 UNCLASSIFIED UNCLASSIFIED 42 UNCLASSIFIED UNCLASSIFIED 43 UNCLASSIFIED UNCLASSIFIED 44 UNCLASSIFIED UNCLASSIFIED 45 UNCLASSIFIED UNCLASSIFIED 46 UNCLASSIFIED UNCLASSIFIED 47 UNCLASSIFIED UNCLASSIFIED 48 UNCLASSIFIED UNCLASSIFIED 49 UNCLASSIFIED UNCLASSIFIED 50 UNCLASSIFIED UNCLASSIFIED 51 UNCLASSIFIED UNCLASSIFIED 52 UNCLASSIFIED UNCLASSIFIED 53 UNCLASSIFIED UNCLASSIFIED 54 UNCLASSIFIED UNCLASSIFIED 55 UNCLASSIFIED UNCLASSIFIED 56 UNCLASSIFIED UNCLASSIFIED 57 UNCLASSIFIED UNCLASSIFIED 58 UNCLASSIFIED UNCLASSIFIED 59 UNCLASSIFIED UNCLASSIFIED 60 UNCLASSIFIED UNCLASSIFIED 61 UNCLASSIFIED UNCLASSIFIED 62 UNCLASSIFIED UNCLASSIFIED 63 UNCLASSIFIED UNCLASSIFIED 64 UNCLASSIFIED UNCLASSIFIED 65 UNCLASSIFIED UNCLASSIFIED 66 UNCLASSIFIED UNCLASSIFIED 67 UNCLASSIFIED UNCLASSIFIED 68 UNCLASSIFIED UNCLASSIFIED 69 UNCLASSIFIED UNCLASSIFIED 70 UNCLASSIFIED UNCLASSIFIED 71 UNCLASSIFIED UNCLASSIFIED 72 UNCLASSIFIED UNCLASSIFIED 73 UNCLASSIFIED UNCLASSIFIED 74 UNCLASSIFIED UNCLASSIFIED 75 UNCLASSIFIED UNCLASSIFIED How does Words becomes Pulses Each word is 70 bits + 5 bits parity 3*31 Symbols 3 TDL J WORDS MSEC STD P2SP P2DP P4SP > > > > 31/15 INTERLEAVE TSEC REED/SOLOMON EDAC 75* 31/15 = 155 155/5 = 31 CCSK 93 Pulses 93 x 2 + 72 = 258 93 + 93 + 72 = 258 93x2 + 93x2 + 72 = 444 93 + 93 + 93 + 93 + 72 = 444 CPSM 76 UNCLASSIFIED UNCLASSIFIED Terminal Process • • • • • • • • • Message encryption Error detection coding Symbol interleave CCSK encode Transmission encryption Sync and header Jitter Pulse production Frequency hop 77 UNCLASSIFIED UNCLASSIFIED Message Encryption • The MSEC crypto key provides message encryption Information Fields SDU 101010110000101….(70 bits)....011 LOC 2 + 010010101110001….(70 bits)....101 111000011110100….(70 bits).…110 parity – 10100 (5 bits) • 5 Parity Bits are added at the end of the encryption process 78 UNCLASSIFIED UNCLASSIFIED Terminal Process • • • • • • • • • Message encryption Error detection coding Symbol interleave CCSK encode Transmission encryption Sync and header Jitter Pulse production Frequency hop 79 UNCLASSIFIED UNCLASSIFIED Reed Solomon EDAC  Forward detection coding • For each15 15 bits 31 in, 31 bits come out 0 1 1 0 0 1 0 1 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 0 1 0 1 1 0 0 1 0 0 1 1 1 0 1 1 0 1 0 0 1 0 80 UNCLASSIFIED UNCLASSIFIED Reed Solomon EDAC  Forward detection coding • For each 15 bits in, 31 bits come out  Error Correction • Only 16 16 needed to regenerate the original 15 15 ? 1 ? 0 ? 1 0 ? 1 1 ? 1 ? 0 1 1 ? 0 1 ? 1 ? 0 0 ? 1 0 ? 1 0 ? 1 0 0 1 1 1 0 1 1 0 1 0 0 1 0 81 UNCLASSIFIED UNCLASSIFIED Reed Solomon Video How can you go from 31 Bits to 15 bits and achieve message integrity? 82 UNCLASSIFIED UNCLASSIFIED Terminal Process • • • • • • • • • Message encryption Error detection coding Symbol interleave CCSK encode Transmission encryption Sync and header Jitter Pulse production Frequency hop 83 UNCLASSIFIED UNCLASSIFIED Symbol Interleaving  3 words produce 93 (3 x 31) total symbols.  Interleaving make R/S more efficient by converting long erasures to short erasures.  Symbols are interleaved within each 3 word data set for transmission. } } } ERBLSQ0ZU7F3ARTSHMPN5D2CGTYZQ2K …. 1FRTYNGDJU10JNTVALPQWCTEF73D1VR L N W 84 UNCLASSIFIED C TEBDUW37GEW3P3ZME12RTQZXCBGTERF A …. UNCLASSIFIED Terminal Process • • • • • • • • • Message encryption Error detection coding Symbol interleave CCSK encode Transmission encryption Sync and header Jitter Pulse production Frequency hop 85 UNCLASSIFIED UNCLASSIFIED CCSK Encode • CCSK Code words are used for the direct sequence spreading process • Each Reed Solomon symbol’s 5 bits are represented by a unique 32 chip sequence 86 UNCLASSIFIED UNCLASSIFIED Correlate • Link 16 Radio has a slightly sub-optimal 32 chip correlate – Note: prime numbers (31) are optimal • Chips are correlated with de-spreading. 00000 00001 00010 00011 00100 00101 00110 00111 ……11110 11111 00111010011101001101110011110010 Correlation 87 UNCLASSIFIED UNCLASSIFIED Transmission Encryption • The TSEC crypto key provides transmission encryption CCSK Codeword 101010110000101….(32 bits)....011 SDU LOC 0 • It also determines jitter value and hopping + 010010101110001….(32 bits)....101 111000011110100….(32 bits).…110 88 UNCLASSIFIED UNCLASSIFIED Terminal Process • • • • • • • • • Message encryption Error detection coding Symbol interleave CCSK encode Transmission encryption Sync and header Jitter Pulse production Frequency hop 89 UNCLASSIFIED UNCLASSIFIED Packing Formats • 72 pulses are added to the data for transmission – 32 Sync, – 8 (4 x 2) time refinement – 32 ( 16 x 2) header • Jitter time is determined by the transmission crypto – P2DP and P4 have no jitter – Extended range uses reduced (1/2) jitter STD P2SP P2DP P4SP > > > > 93 x 2 + 72 = 258 93 + 93 + 72 = 258 93x2 + 93x2 + 72 = 444 93 + 93 + 93 + 93 + 72 = 444 90 UNCLASSIFIED UNCLASSIFIED Terminal Process • • • • • • • • • Message encryption Error detection coding Symbol interleave CCSK encode Transmission encryption Sync and header Jitter Pulse production Frequency hop 91 UNCLASSIFIED UNCLASSIFIED CPSM Sequence • Each R/S Symbol (5 transmission data bits) is represented by a 32 bit word • A 32 bit pseudorandom sequence is added for transmission security • The resulting 32 bit stream is used as the CPSM code 92 UNCLASSIFIED UNCLASSIFIED CPSM Chipping 10100101110010110111001100010101 SAME LOWER Frequency DIFFERENT DIFFERENT UPPER Frequency UPPER Frequency SAME Lower Frequency • There are 32 CPSM chips on each transmitted pulse • Each bit results in a change or no change in the modulation • The 5 MHz chipping rate results in 200  sec chips 93 UNCLASSIFIED UNCLASSIFIED Pulse Formation • Each pulse – 6.4 usec in duration – 6.6 usec between pulses – 3 MHz wide – CCSK 3 MHz Center Frequency 6.4 usec on 200 nsec chips 6.6 usec off In the time domain, a Link 16 Radio pulse is 6.4 usec on and 6.6 usec off. In the frequency domain, it is 3 MHz wide. 94 UNCLASSIFIED UNCLASSIFIED Pulse Width • The resulting pulse is 3 MHz wide Center Frequency – compared to 25 kHz for UHF • The pulse is referred to by the center frequency 3 MHz Frequency splash is minimized by CPSM. 95 UNCLASSIFIED UNCLASSIFIED Pulse Stream • Each transmission consists of a stream of pulses • Pulses are spaced 13 microseconds apart • Depending on packing structure, the pulse stream may contain 258 or 444 pulses (Note: RTTs only have 72) 6.4 usec on 6.6 usec off 6.4 usec (on) + 6.6 usec (off) = 13 usec 96 UNCLASSIFIED UNCLASSIFIED Terminal Process • • • • • • • • • Message encryption Error detection coding Symbol interleave CCSK encode Transmission encryption Sync and header Jitter Pulse production Frequency hop 97 UNCLASSIFIED UNCLASSIFIED Spectrum Use • Transmission consist of 72 (RTTs) , 258, or 444 pulses – Each frequency used evenly – Normally 5 or 9 times per transmission • ( 5 * 6.4 sec)/(7.8125msec) = 00.41% 1030 1090 1206 -60 db 969 14 960 Each transmission uses the entire Link 16 Radio spectrum. However, little time is spent on any one frequency. 14 1215 98 UNCLASSIFIED UNCLASSIFIED Hopping Link 16 Radio changes frequency on each pulse. • Frequency hopped It reuses the same 51 frequencies in a pseudo random order. – Pulse to pulse (~77,000 hops per second) – 51 center frequencies (3 MHz spaced) 969 MHz • 969, 972, 975…… 1209 1206 MHz – IFF notches avoided • 1030/1090 + 7 MHz 14 + 5 99 UNCLASSIFIED IFF Notches + 51 32 = UNCLASSIFIED Frequency Hopping Frequency Hopping Frequency • Each pulse is on one of 51different frequencies • All frequencies are used evenly • The pseudo-random selection sequence is called a hopping pattern Time NET = Specific Hopping Pattern 100 UNCLASSIFIED UNCLASSIFIED ANTI-JAMMING 101 UNCLASSIFIED UNCLASSIFIED Anti-Jam Equations • Anti-jam is the ability to operate within a hostile electromagnetic environment • It is achieved by: PG-(S/N)D-L – Transmitter complexity – Receiver complexity – Physical Attributes Brute Force Gt Pt (R j) 2 _____________ Gj Pj (R t) 2 Following Slides are to show you how Link 16 is jam resistant 102 UNCLASSIFIED UNCLASSIFIED Link Margin Affect on Power - It’s Relative Power! • What’s a dB anyway? RT RJ For equal ranges!! • 1000 W 3 dB 6 dB 9 dB 12 dB 15 dB 18 dB 21 dB 104 UNCLASSIFIED 2000 W 4000 W 8000 W 16 kW 32 kW 64 kW 128 kW UNCLASSIFIED Link Margin on Range • What’s a dB anyway? Gt Pt (R j) 2 S/J = _____________ Gj Pj (R t) 2 RJ RT For equal power 1000 W 21.5 db 6 dB RJ = 1/2 RT 12 dB RJ = 1/4 RT 18 dB RJ = 1/8 RT RJ = 1/12 RT • If I’m 60 miles away, he’s got to be 5 ! 105 UNCLASSIFIED UNCLASSIFIED Link 16 Anti-Jam • The following attributes contribute to Link 16 anti-jam capability: – Transmitter Complexity • Spread Spectrum • Frequency Hopping – Receiver Complexity • Reed-Solomon • Interleaving • Pulse Repetition – Physical Attributes • • • • High Power (for MIDS only) Directional Antennas Relay Message Repetition 106 UNCLASSIFIED UNCLASSIFIED Spread Spectrum SIGNAL + SPECTRUM CODE = TRANSMISSION • Each pulse contains 5 transmission bits that are distributed amongst 32 chips • The spreading code changes continuously with time (determined by the crypto) 1 + 10100 = 107 UNCLASSIFIED 1 0 1 00 UNCLASSIFIED Spread Spectrum TRANSMISSION - SPECTRUM CODE = SIGNAL Threshold 1 11 11 - 10100 = 1 Signal Level 108 UNCLASSIFIED UNCLASSIFIED Spread Spectrum TRANSMISSION - SPECTRUM CODE = SIGNAL • Jammer noise is not coherent and cancels itself - 10100 = Threshold Signal Level Threshold - 10100 = 1 Signal Level • Desired signal is coherent and adds itself 109 UNCLASSIFIED UNCLASSIFIED Correlators 10100101110010110111001100010101 DELAY DELAY X DELAY X DELAY X DELAY X DELAY X X • The receiver correlates the 32 chip sequence to determine which 5 transmission data bits were sent Threshold device 110 UNCLASSIFIED 10101 UNCLASSIFIED Frequency Hopping Frequency Hopping Frequency • Frequency hopping expands the band width used • 51 center frequencies spaced 3 MHz apart for a total of 153 MHz Time Instantaneous Hopping Rate = 76,923 hops per second 111 UNCLASSIFIED UNCLASSIFIED Reed Solomon • Error detection coding creates redundancy • (31,15) R/S coding creates 31 transmission bits for each 15 data bits Message Transmission R/S Coding 112 UNCLASSIFIED UNCLASSIFIED Reed Solomon • Jamming produces erasures and errors in the transmission bits Jammed Bits Transmission 113 UNCLASSIFIED UNCLASSIFIED Reed Solomon • Any 16 transmission bits can reconstruct the original 15 bits Jammed Bits Transmission Correlation Decoding Message 114 UNCLASSIFIED UNCLASSIFIED Reed Solomon • Error detection coding creates redundancy • (31,15) R/S coding creates 31 transmission bits for each 15 data bits Message R/S Coding Jammed Bits Transmission Correlation Decoding Message • Any 16 transmission bits can reconstruct the original 15 bits 115 UNCLASSIFIED UNCLASSIFIED Percent message errors Knife Edge Jammed Pulses 116 UNCLASSIFIED UNCLASSIFIED Double Pulse • In the standard and pack 2 double pulse format, each set of data is sent twice • Successive pulses carry the same data • Different spreading codes 117 and different UNCLASSIFIED 10110 10110 10110 10110 10110 UNCLASSIFIED Double Pulse • In the double pulse format: – Each R/S symbol (5 transmission data bits) is sent twice – Successive pulses carry the same data with different coding 10010 10010 01001110110001010100110101100110 10011010110011001001110110001010 • Different center frequencies are assigned 118 UNCLASSIFIED UNCLASSIFIED Double Pulse • Multi-path cancellation occurs when the same pulse arrives over two different paths • Double Pulse prevents multi-path fading by sending redundant data on two different frequencies 119 UNCLASSIFIED UNCLASSIFIED • Link 16 occupies a 255 MHz band width compared to 175 MHz for all UHF transmitters Military UHF (225-400 MHz) HF VHF Link 16 (960-1215 MHz) UHF 120 UNCLASSIFIED SHF EHF UNCLASSIFIED Range Ratio • Anti-jam is range improvement • Which link breaks first? RT1 RJ RT2 RT3 RJ RJ 121 UNCLASSIFIED UNCLASSIFIED Range Ratio • Relay improves the range ratio • Relay provides a geometry advantage – Moves the transmitter off the line of the jammer RT1 RJ RT2 RT3 RJ RJ 122 UNCLASSIFIED UNCLASSIFIED Total Anti-Jam • Link 16 has three dimension of randomness and redundancy • frequency • time • code • Against partial band/time jamming: • Hopping • double pulse • Reed Solomon • Against predictor/followers – pseudo random code • Spreading • Fast hopping • Jitter 123 UNCLASSIFIED UNCLASSIFIED Pulse Interference • Pulses arriving more then 6.4 usec (1 nm) later are ignored because the receiver has moved to a different frequency • Pulses arriving more than 200  sec (200 ft) later are treated as noise (jamming) • Pulses arriving less than 200 sec (200 ft) later interfere 124 UNCLASSIFIED

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