May 18th 2005 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: TG4a Review of proposed UWB-IR Modulation schemes Date Submitted: 21 April 2005 Source: Philip Orlik, Andy Molisch (Mitsubishi Electric), Gian Mario Maggio (STMicroelectronics), Ian Opperman (University of Oulu) Contact: Philip Orlik Voice: +1 617 621 7570, E-Mail: porlik@merl.com Abstract: Yet another UWB waveform Purpose: To provide information for further investigation on and selection of the modulation /waveform for UWB Impulse Radio (low bit rate plus ranging) Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

IEEE 802.15.4a PHY: UWB-IR Modulation for multiple receiver types May 18th 2005 IEEE 802.15.4a PHY: UWB-IR Modulation for multiple receiver types Many slides stolen from 15-05-0217-00-004a P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

May 18th 2005 Definitions Coherent RX: The phase of the received carrier waveform is known, and utilized for demodulation Differentially-coherent RX: The carrier phase of the previous signaling interval is used as phase reference for demodulation Non-coherent RX: The phase information (e.g. pulse polarity) is unknown at the receiver -operates as an energy collector -or as an amplitude detector P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Waveform Design (1/2) Combination of BPPM with BPSK May 18th 2005 Waveform Design (1/2) Combination of BPPM with BPSK Guarantee coexistence of coherent and non-coherent receiver architectures: Non-coherent receivers just look for energy in the early or late slots to decode the bit (BPPM) Coherent and differentially-coherent receivers, in addition, understand the fine structure of the signal (BPSK or DBPSK) Principle: Non-coherent and differentially-coherent modes should not penalize coherent RX performance P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Waveform Design (2/2) Two possible realizations: May 18th 2005 Waveform Design (2/2) Two possible realizations: 1) The whole symbol (consisting of Nf frames) is BPPM-modulated 2) Apply 2-ary time hopping code, so that each frame has BPPM according to TH code Coexistence coherent/non-coherent RX: - Special encoding and waveform shaping within each frame - Use of doublets with memory from previous bit (encoding of reference pulse with previous bit) - Proposed 20ns separation between pulses - Extensible to higher order TR for either reducing the penalty in transmitting the reference pulse or increasing the bit rate (see: 15-05-0217-00-004a for detail) - Also possible the use of multi-doublets (see 15-05-0217-00-004a) P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Impulse Radio Modulation Scheme May 18th 2005 Impulse Radio Modulation Scheme Rake Receiver Finger Np Finger 2 Finger 1 Summer Pulse Gen. TH Seq BPSK symbol mapper Delay Central Timing Control Multiplexer Coherent Receiver Td Hybrid Transmitter Differentially Coherent Receiver ( )2 Non-Coherent Receiver P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Pros/Cons of RX Architectures May 18th 2005 Pros/Cons of RX Architectures Coherent + : Sensitivity + : Use of polarity to carry data + : Optimal processing gain achievable - : Complexity of channel estimation and RAKE receiver - : Longer acquisition time Differentially-Coherent (or using Transmitted Reference) + : Gives a reference for faster channel estimation (coherent approach) + : No channel estimation (non-coherent approach) - : Asymptotic loss of 3dB for transmitted reference Non-coherent + : Low complexity + : Acquisition speed - : Sensitivity, robustness to SOP and interferers P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Design Parameters Pulse Repetition Period (PRP) May 18th 2005 Design Parameters Pulse Repetition Period (PRP) Proposed range between 40ns (first realization) and 125ns (second realization) Channelization (In addition to FDM) Coherent schemes: Use of TH codes and polarity codes Non-coherent schemes: Use of TH codes (polarity codes for spectrum smoothing only) TH code length Variable TH code length; proposed range: 8-16 TH code: Binary position, bi-phase Note: For first realization, higher-order TH with shorter chip duration (multiples of 2ns) may be used P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Differential Encoding: Basics May 18th 2005 Differential Encoding: Basics b-1 b0 b1 b2 b3 b4 b5 0 0 1 1 0 0 1 Tx Bits -1 -1 +1 +1 -1 -1 Reference Polarity +1 -1 +1 -1 +1 -1 Ts P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Example Signal Waveforms for data modulation (1) May 18th 2005 Example Signal Waveforms for data modulation (1) bi-1 = 1, bi = 1 bi-1 = 0, bi = 1 bi-1 = 1, bi = 0 bi-1 = 0, bi = 0 P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Example Signal Waveforms for data modulation (2) May 18th 2005 Example Signal Waveforms for data modulation (2) Ts « 11 » 2-PPM + TR base M = 2 One bit/symbol « 01 » « 10 » « 00 » 2-PPM + 16 chips 2-ary TH code or 2-PPM + 8 chips 4-ary TH code (coherent decoding possible) Time hopping code is (2,2) code of length 8/16, can be exploited by non-coherent RX Effectively, 28 or 216 codes to select for channelization for non-coherent scheme P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Example Signal Waveforms for data modulation (3) May 18th 2005 Example Signal Waveforms for data modulation (3) Ts « 11 » « 01 » 2-PPM + TR base M = 2 (with two bits/symbol) « 10 » « 00 » 2-PPM + 16 chips 2-ary TH code (coherent decoding possible) Time hopping code is (2,2) code of length 8/16, can be exploited by non-coherent RX Effectively, 28 or 216 codes to select for channelization for non-coherent scheme P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

De-Spreading TH Codes May 18th 2005 Band Matched TH r(t) Sequence Matched Filter r(t) LNA BPF Bit Demodulation ADC Case I - Coherent TH de-spreading Band Matched TH Sequence Matched Filter r(t) Bit Demodulation b(t) soft info LNA BPF ADC Case II – Non-coherent / differential TH despreading P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Coherent Receiver: RAKE Receiver May 18th 2005 Coherent Receiver: RAKE Receiver Channel Estimation Rake Receiver Finger 1 Demultiplexer Rake Receiver Finger 2 Sequence Detector Convolutional Decoder Summer Data Sink Rake Receiver Finger Np Addition of Sequence Detector – Proposed modulation may be viewed as having memory of length 2 P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

‘Uncoded’ AWGN Performance May 18th 2005 ‘Uncoded’ AWGN Performance 1.5 dB P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

‘Uncoded’ CM8 Performance May 18th 2005 ‘Uncoded’ CM8 Performance 1 dB P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

May 18th 2005 Advantages Coherent RX gets additional benefit from coding inherent in the modulation Waveform permits polarity scrambling to reduce required back-off A single waveform for all receiver types P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Coherent view of Hybrid Modulation May 18th 2005 Coherent view of Hybrid Modulation Symbols consist of sequences of doublets that have 4 possible forms bi-1 = 1, bi = 1 bi-1 = 0, bi = 1 bi-1 = 1, bi = 0 bi-1 = 0, bi = 0 P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

May 18th 2005 Basis functions Symbols can be decomposed using several equivalent orthogonal basis functions (2-D) ( ) ( ) _ _ , , [1, 0] [1/2, 1/2] [-1, 0] [-1/2, -1/2] [0, 1] [1/2, -1/2] [0, -1] [-1/2, 1/2] P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Matched Filter Outputs (basis 1) May 18th 2005 Matched Filter Outputs (basis 1) Template signals constructed from these 2 basis functions Barker 13 applied to TR doublets bi-1 = 1, bi = 1 bi-1 = 0, bi = 1 bi-1 = 1, bi = 0 bi-1 = 0, bi = 0 P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Matched Filter Outputs (basis 2) May 18th 2005 Matched Filter Outputs (basis 2) Template signals constructed from these 2 basis functions Barker 13 applied to doublets _ _ bi-1 = 1, bi = 1 bi-1 = 0, bi = 1 bi-1 = 1, bi = 0 bi-1 = 0, bi = 0 P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Ranging Implications ( ) So what does this mean for ranging? May 18th 2005 Ranging Implications So what does this mean for ranging? Really nothing If we want to transmit a barker sequence (or something else) we can still use our receiver to “look” for the ranging symbol Basically we can use as a basis and view the compression code as a polarity code applied to the reference pulse and data pulse independently. Barker 13 = [1 1 1 1 1 -1 -1 1 1 -1 1 -1 1] Reference code = [1 1 1 -1 1 1 1 ] Data code = [1 1 -1 1 -1 -1 ] ( ) _ _ , P.Orlik, A. Molisch, G. M. Maggio; I. Opperman

Barker 13 transmission Correlator output Tx waveform May 18th 2005 P.Orlik, A. Molisch, G. M. Maggio; I. Opperman