Signal Waveform Comparisons Z. Sahinoglu, I. Guvenc, P. Orlik Digital Communications and Networking Group Wednesday, June 05, 2019

Option-I One Bit The Other Bit Always Empty Always Empty Always Empty 100ns 8-chip times: 150ns 100ns 8-chip times: 150ns The Other Bit Always Empty Always Empty Always Empty 8-chip times: 150ns 100ns Enough long not to cause IFI : 100ns 8-chip times: 150ns Saturday, May 28, 2005

Coherent receivers exploit chip sequence patterns Features of Option-I Coherent receivers exploit chip sequence patterns Non-coherent receivers see in which half the energy arrives In ranging preamble, each piconet is assigned a different sequence of bits Symbol rate is 1Msps (after rate ½ code) Saturday, May 28, 2005

Example SOP preambles in Ranging with Option-I Piconet-I bit sequence: {1,0,0,1,1} Piconet-II bit sequence: {1,1,0,0,0} Saturday, May 28, 2005

Ranging Performance of Option-I Very resilient to SOP interference due to proper selection of preamble bit sequences For non-coherent radios, inter-pulse-interference due to multipath does not need to be resolved Statistical multiplexing is needed to increase SNR due to spreading bit energy over many pulses Preliminary results A train of 8-pulses EbN0 = 22dB, SIR = 0dB (randomly generated 30 symbols in the preambles of desired and interference) CM1 Integration interval: 4ns Ranging error: 3ns (72%) Better accuracy if narrower energy windows Saturday, May 28, 2005

Modulation with Option-I Additional time hopping of blocks is needed to support 2-SOP Ex: Another 160ns interval in each half of the frame When same bit waveforms are used, symbol rate needs to be halved It is still an option to use different waveforms in communication to increase symbol rates Saturday, May 28, 2005

Option-II Ts = 500ns « 11 » 2-PPM + TR base M = 2 « 01 » « 11 » 2-PPM + TR base M = 2 One bit/symbol « 01 » « 10 » « 00 » (coherent decoding possible) Saturday, May 28, 2005

Pulses (or doublets) are spread over the entire 500ns symbol duration Option-II Features Pulses (or doublets) are spread over the entire 500ns symbol duration Non-coherent decoding and ranging with this waveform has not been simulated yet Has potentially better SOP isolation than Option-I in communication mode Saturday, May 28, 2005

Option-III Criteria/Target – balance max post-despreading SNR and low auto-correlation side lobes Ternary Seq [+ - - 0 0 0 + - 0 + + + 0 + 0 - 0 0 0 0 + 0 0 - 0 - + 0 0 - - ] After Square Law & Integration in PRI Unipolar M-Seq [+ + + 0 0 0 + + 0 + + + 0 + 0 + 0 0 0 0 + 0 0 + 0 + + 0 0 + + ] In AWGN Soft output Noncoherent detection of OOK Sliding Correlator LPF / integrator BPF ( )2 ADC Sample Rate 1/Tc {1,-1} Binary Sequence Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ] Saturday, May 28, 2005

Zero autocorrelation side lobe sequences Option-III Features Zero autocorrelation side lobe sequences Under SOP interference, correlator peak is 3dB degraded in non-coherent reception due to suboptimal correlation This makes identification of weak multipath components difficult After the square-law device, the integrator integrates over the PRI (~30ns) In option-I, integration interval is 2ns or 4ns. Longer integration interval collects more noise in Longer integration interval collects more interference energy in Saturday, May 28, 2005

Recommended Architecture for Ranging with Non-Coherent Rx (No FFT routine is needed, being different from doc#0269) Energy image generation Removes interference 2-4ns Length-3 Vertical Median or Minimum Filtering 1D to 2D Conversion LPF / integrator BPF ( )2 ADC 2D to 1D Conversion with Energy Combining I will get into the details of the colored blocks in the next round !!! ZS TOA Estimator Saturday, May 28, 2005

Effect of Number of Pulses on Performance for Non-Coherent Modulation and Ranging: An Example Case 1: Single Pulse Per Symbol N = 1 s = 0 s = 1 μ1 MN0 MN0+2NsEb σ12 MN02 MN0+4N0NsEb PDF s = 0 s = 1 Transmitting one pulse with large energy Energy Energy of this pulse is NsEb μ1 Saturday, May 28, 2005

Effect of Number of Pulses on Performance for Non-Coherent Modulation and Ranging: An Example Case 2: Multiple Pulses Per Symbol N = Ns s = 0 s = 1 μ2 NsMN0 Ns(MN02+2Eb) σ22 NsMN02 Ns(MN02+4N0Eb) Transmitting many pulses with less energies PDF s = 0 s = 1 Energy Energy of each pulse is Eb, and there are Ns number of pulses μ2 Saturday, May 28, 2005

The energy per symbol can be collected in a single Effect of Number of Pulses on Performance for Non-Coherent Modulation and Ranging The energy per symbol can be collected in a single pulse (N=1), or in Ns pulses The means and variances statistics of the square-law device outputs can be observed in the absence and presence of signal The Euclidean distance between the means for s=0, and s=1 are the same for both cases (2NsEb) However, the variance term when using larger number of pulses increases Saturday, May 28, 2005

Current Status MERL is simulating Option-III according to the recommended block diagram, and will share the observations soon Preliminary Option-I results are shared on slide 5 There are still unincorporated optimization techniques to improve edge detection performance Adaptive threshold selection Search back window selection etc Saturday, May 28, 2005