1. Voice:[86-10-139-11895301], E-Mail:[liang_1@yahoo.com]
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Proposal on Preamble Structure for IEEE b PHY]
Date Submitted: [Jan ]
Source: [Liang Li, Liang Zhang, Yafei Tian, Chenyang Yang, Zhijian Hu, Hongyu Gu] Company: [WXZJ]
Address: [2 Xinxi St, Building D, Haidian District, Beijing, China ]
Voice:[ ],
Re: [ IEEE b ]
Abstract: [Analysis of E16 orthogonal spreading code for 868/915MHz band PHY.]
Purpose: [To encourage discussion.]
Notice: This document has been prepared to assist the IEEE P 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 P
Submission
Liang Li, WXZJ Inc.

2. Overview
This document proposals the Transceiver Structure for IEEE b working group: OQPK + Pulse Shape + (TX filter). It also suggests one E16 orthogonal code Sequence for the DSSS Spreading At same time, the document offers the simulated (TX/RX) performances of this Transceiver system at 915MHz and 868MHz bands:
Submission
Liang Li, WXZJ Inc.

3. OPSK variants reviewed in this presentation
868MHz
915MHz
Bandwidth
600KHz
1.5MHz
Chip rate
400k 1M
Bit rate
100kbps
250kbps
Spectral efficiency
Contain 99% energy in 0.79 normalized bandwidth
Contain 99% energy in 1.2 normalized bandwidth
Spreading
16-chip seq per 4bits
RF backward compatibility
QPSK+Half Sine Shape+Tx filter
QPSK+Half Sine Shape
Comments
Quasi constant amplitude and continuous phase
Constant amplitude and continuous phase
Submission
Liang Li, WXZJ Inc.

4. DSSS Sequence E16
Decimal Symbol
Binary Symbol
Chip Values 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
The spread sequence corresponding to binary symbol “0000” is used for sync
Submission
Liang Li, WXZJ Inc.

5. Transceiver at 915 MHz Band
•Key design parameters
–Summary of design requirements for the TG4b PHY
•PSD of TX signal
•Auto-correlation performance of E16 code sequence
– Auto-correlation of O-QPSK with half sine pulse shaping / I/Q modulation at 2x sampling rate
– sync in condition of frequency offset
• The Receiver Performance with propsoal
– simulation condition or system construction
– AWGN and Rayleigh channel in ideal condition
– Frame detection, synchronization, phase noise, frequency offset, sampling error, respectively (to be continued)
•Summary
Submission
Liang Li, WXZJ Inc.

6. Key Features of the Transceiver
Bit rate 250 kBit/s
16 sequences for 4 bits mapping
Each consist of 16 chips
1M chip rate per second
Center frequency is 915MHz;
Bandwidth, Pulse shape , PAPR, frequency offset
The 1st null-null bandwidth 1.5MHz;
Half-sine pulse shape;
0dB PAPR, the same MSK scheme as 15.4, constant module and continuous phase, lower out-of-band emission;
30dB lower over 2M wide bandwidth, which satisfies the state of 15.4;
Tolerated frequency offset at least 40ppm;
Support of current RF
Support 2 MHz wide channels in the USA and other countries were they are permitted
Low cost and low power consumption
Multipath fading robustness
Achieve PER<10^-2 at channels with 250ns delay spread ((Multipath channel model offer by Paul with high sampling rate);
Submission
Liang Li, WXZJ Inc.

7. PSD of TX Signal Bandwidth, Pulse shape:
The 1st null-null bandwidth 1.5MHz; Half-sine pulse shape:
The modulation offers constant modulus and continuous phase;
PSD 30dB lower at 1.5MHz from center frequency.
Submission
Liang Li, WXZJ Inc.

8. PSD of TX Signal at 915MHz with 0dB ACI
PSD after 7tap Bessel Rx filter
Submission
Liang Li, WXZJ Inc.

9. Nonlinear PA Characteristics
Submission
Liang Li, WXZJ Inc.

10. Impact of PA Nonlinearity: 2x sampling rate
(1) Tx PSD without PA
(2) Tx PSD with PA
For the constant module and continuous phase in our proposal, the Tx PSD is not affected by nonlinear PA.
Submission
Liang Li, WXZJ Inc.

11. PSD characteristic PSD of TX signal is not affected by sampling error.
Low out-of-band emission, and no need for Tx filter
Satisfies the IEEE PSD requirements
Source: IEEE Standard
Submission
Liang Li, WXZJ Inc.

12. Receiver System performance
Simulation parameters & assumptions:
Auto-correlation performance of E16 Code Sequence
250ns rms delay spread Rayleigh Channel model
O-QPSK modulation + half sine pulse
2M sampling rate (1M chips/sec)
Frequency offset from 0ppm to 40ppm
20 octets in each packet
10,000 packets for Monte-Carlo simulation
Non-coherent demodulation
With or Without SFD detection
Within No fading and Fading channels
With the Nonlinear PA
Submission
Liang Li, WXZJ Inc.

13. Simulation models –At least 10000 random channel realizations;
Discrete exponential channel model
–-Sampled version of diffuse channel model offer by Paul with 4MHz sampling rate;
–At least random channel realizations;
–PER calculated on 20 bytes PPDUs with preamble;
Submission
Liang Li, WXZJ Inc.

14. Auto-correlation of Modulated E16 Sequces
In this test, E16 spreading sequences are first OQPSK modulated and the waveform half-sine pulse shaped in 2x sampling rate and then the correlations are calculated.
Auto-correlation of modulated E16
Submission
Liang Li, WXZJ Inc.

15. AWGN: Ideal Sync. vs. Correlation Sync.
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Frame Detection: No
SFD: No
Submission
Liang Li, WXZJ Inc.

16. AWGN simulation results
The BER results are close to the theoretical curve of 16-FSK.
The sync error (using received signals correlated directly with local PN) has minimal effects on performance curves.
Submission
Liang Li, WXZJ Inc.

17. Multipath channel without Fading + Correlation Sync.
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: No
Frame Detection: No
Phase noise :No
SFD: No
Sync.: Correlation
Down sampling error: No
Submission
Liang Li, WXZJ Inc.

18. Multipath channel without Fading + Correlation Sync.
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: No
Frame Detection: No
Phase noise :No
SFD: No
Sync.: Correlation
Down sampling error: Yes
Submission
Liang Li, WXZJ Inc.

19. Multipath channel without Fading + Correlation Sync.
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: Yes
Frame Detection: No
Phase noise :No
SFD: No
Sync.: Correlation
Down sampling error: No
Submission
Liang Li, WXZJ Inc.

20. Multipath channel without Fading + Correlation Sync.
Frame Detection: No
Phase noise :YES
SFD: No
Sync.: Correlation
Down sampling error: No
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: No
Submission
Liang Li, WXZJ Inc.

21. Multipath channel without Fading + Correlation Sync.
Frame Detection: No
Phase noise :YES
SFD: YES
Sync.: Correlation
Down sampling error: No
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: No
Submission
Liang Li, WXZJ Inc.

22. Multipath channel without Fading + Correlation Sync.
Frame Detection: YES
Phase noise :YES
SFD: Yes
Sync.: Correlation
Down sampling error: No
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: No
Submission
Liang Li, WXZJ Inc.

23. Multipath channel without Fading + Correlation Sync.
Frame Detection: YES
Phase noise :YES
SFD: Yes
Sync.: Correlation
Down sampling error: Yes
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: No
Submission
Liang Li, WXZJ Inc.

24. Multipath channel without Fading + Correlation Sync.
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: Yes
Frame Detection: YES
Phase noise :YES
SFD: Yes
Sync.: Correlation
Down sampling error: Yes
Submission
Liang Li, WXZJ Inc.

25. Frequency offset Affect
Sync performance
BER performance
Synchronization is achieved by correlating local PN with received preamble impaired by frequency offset.
Frequency offset affects the sync and decoding performance significantly.
Submission
Liang Li, WXZJ Inc.

26. Multipath channel without Fading + Correlation Sync
Multipath channel without Fading + Correlation Sync. (frequency offset estimation)
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: Yes
Frame Detection: YES
Phase noise :YES
SFD: Yes
Sync.: Correlation
Down sampling error: Yes
Submission
Liang Li, WXZJ Inc.

27. Multipath channel without Fading + Correlation Sync
Multipath channel without Fading + Correlation Sync. (frequency offset estimation+0dB ACI)
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: Yes
Frame Detection: YES
Phase noise :YES
SFD: Yes
Sync.: Correlation
Down sampling error: Yes
Submission
Liang Li, WXZJ Inc.

28. Multipath channel with Fading + Correlation Sync.
Frame Detection: No
Phase noise :No
SFD: No
Sync.: Correlation
Down sampling error: No
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: No
Submission
Liang Li, WXZJ Inc.

29. Multipath channel with Fading + Correlation Sync.
Frame Detection: Yes
Phase noise :Yes
SFD: Yes
Sync.: Correlation
Down sampling error: No
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Time offset: No
Submission
Liang Li, WXZJ Inc.

30. Transceiver at 868 MHz Band
•Key design parameters
–Summary of design requirements for the TG4b PHY
•PSD of TX signal
•Auto-correlation performance of E16 code sequence
– Auto-correlation of O-QPSK with half sine pulse shaping / I/Q modulation at 2x sampling rate
– sync in condition of frequency offset
• The Receiver Performance with propsoal
– simulation condition or system construction
– AWGN and Rayleigh channel in ideal condition
– Frame detection, synchronization, phase noise, frequency offset, sampling error, respectively (to be continued)
•Summary
Submission
Liang Li, WXZJ Inc.

31. Key Features of Transceiver at 868MHz
Bit rate 100 kBit/s
Better orthogonal characteristic
16 sequences for 4 bits mappin
400k chip rate per second
Bandwidth, Pulse shape , PAPR, frequency offset
The 1st null-null bandwidth 600kHz;
<1dB PAPR,
With r=0.6 raise cosine filter, constant module and continuous phase, lower out-of-band emission;
Nearly 50dB lower over 600kHz wide bandwidth, which satisfies the state of ETSI;
Tolerated frequency offset at least 40ppm;
Multipath fading robustness
Achieve PER<10^-2 at channels with 250ns delay spread (Multipath channel model offer by Paul with high sampling rate);
Support of current RF
Support current 600kHz band available at 1% duty cycle in Europe today
Allow use of extended European bands and bands in other countries once they become available
Allow addition of additional 600 kHz channels as per current ETSI / ECC report (4/6 channels?)
Do not expect US-like wide, unrestricted bands or all egulatorydomains
Support of more flexible channel selection method to flexibly add support for more countries
Low cost and low power consumption
Submission
Liang Li, WXZJ Inc.

32. OPSK variants reviewed in this presentation
Option A. E16 for 868MHz
Option B. C8 for 868MHz
Bandwidth
600KHz
600kHz
Chip rate
400k
Bit rate
100kbps
200kbps
Spectral efficiency
Contain 99% energy in 0.79 normalized bandwidth
Spreading
16-chip seq per 4bits
8-chip seq per 4bits
RF backward compatibility
OQPSK+half sine pulse+Tx filter
Comments
<1dB PAPR
Submission
Liang Li, WXZJ Inc.

33. OQPSK + half sine pulse with Tx filter
Tx / Rx Performance at 868MHz, 600KHz bandwidth
Assumption:
E16 orthogonal code + OQPSK + half-sine pulse shaping
Tx: Tx digital raised cosine filter with r=0.6;
Rx: Synchronization performance
Receiver (Non-Rake) performance comparison based on our simulation results
In the following slides, two Tx filters will be analyzed at 2x sampling rate and 4x sampling rate, respectively.
Submission
Liang Li, WXZJ Inc.

34. PSD(dB) 0 raised cosine filter r=0.6
SUPPOSE:
1, 0.8MHz (2x)sampling rate;
2, 200kHz pass band;
3, Tx digital FIR filter;
Submission
Liang Li, WXZJ Inc.

35. Impulse response of Tx filter – raised cosine filter r=0.6
SUPPOSE:
1, 0.8MHz (2x)sampling rate;
2, 200kHz pass band;
3, Tx digital FIR filter;
Submission
Liang Li, WXZJ Inc.

36. 100kbps Data rate PSD with Tx filter
400k chip rate;
600k bandwidth;
half sine pulse shape;
Raised cosine filter
with r=0.6;
2x over sampling rate;
(0.8M sampling rate)
Submission
Liang Li, WXZJ Inc.

37. PAPR of 100kbps with Tx filter
PAPR is less than 1dB
(about 0.95dB)
The amplitudes of samples after Tx filter
Submission
Liang Li, WXZJ Inc.

38. PSD(dB) 0 raised cosine filter r=0.6
SUPPOSE:
1, 1.6MHz (4x)sampling rate;
2, 200kHz pass band;
3, Tx digital FIR filter;
Submission
Liang Li, WXZJ Inc.

39. Impulse response of Tx filter – raised cosine filter r=0.6
SUPPOSE:
1, 1.6MHz (4x)sampling rate;
2, 200kHz pass band;
3, Tx digital FIR filter;
Submission
Liang Li, WXZJ Inc.

40. 100kbps Data rate PSD with Tx filter
400k chip rate;
600k bandwidth;
half sine pulse shape;
Raised cosine filter
with r=0.6;
4x over sampling rate;
(1.6M sampling rate)
Submission
Liang Li, WXZJ Inc.

41. PAPR of 100kbps with Tx filter
PAPR is less than 1dB
(about 0.65dB)
The amplitudes of samples after Tx filter
Submission
Liang Li, WXZJ Inc.

42. Nonlinear PA Characteristics
Submission
Liang Li, WXZJ Inc.

43. Impact of PA Nonlinearity: 2x sampling rate
(2)
(1)
(1) Tx PSD without Tx filter or PA
(2) Tx PSD with Tx filter, no PA
(3) Tx PSD with Tx filter and PA
Because of aliasing at relatively low sampling rate, the signal side-lobe is susceptible to PA nonlinearity.
(3)
Submission
Liang Li, WXZJ Inc.

44. Impact of PA Nonlinearity: 4x sampling rate
(2)
(1)
(1) Tx PSD without Tx filter or PA
(2) Tx PSD with Tx filter, no PA
(3) Tx PSD with Tx filter and PA
At 4x sampling rate, the impact of PA nonlinearity is neglectable.
(3)
Submission
Liang Li, WXZJ Inc.

45. 100kbps Data rate performance
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Frame Detection: No
SFD: No
Ideal sync
With Tx filter
Submission
Liang Li, WXZJ Inc.

46. Option : COBI-C8 Spreading Sequences (Suggested from I2R)
Decimal Value
Binary Symbol
Chip Value
0000
(Root – 5C) 1
1000 2
0100 3
1100 4
0010 5
1010 6
0110 7
1110 8
0001 9
1001 10
0101 11
1101 12
0011 13
1011 14
0111 15
1111
Submission
Liang Li, WXZJ Inc.

47. Option: The Correlation Analysis” Cross-correlation Characteristics (1)
(a) cross-correlations of all 16 COBI-C8 codes
(b) cross-correlation of one COBI-C8 code
No modulation; no over-sampling (all in real numbers)
Submission
Liang Li, WXZJ Inc.

48. Option: Cross-correlation Characteristics (2)
(a) cross-correlations of all 16 COBI-C8 codes
(b) cross-correlation of one COBI-C8 code
With O-QPSK modulation; 2x over-sampling (complex domain)
Submission
Liang Li, WXZJ Inc.

49. Option: Autocorrelation Characteristics (1)
Autocorrelation of all 16 COBI-C8 sequences
No modulation; no over-sampling (all in real numbers)
Submission
Liang Li, WXZJ Inc.

50. Option: Autocorrelation Characteristics (2)
Autocorrelation of all 16 COBI-C8 sequences. O-QPSK modulation; 2x over-sampling (complex domain)
Conclusion: The Cross-Correlation is good and Autocorrelation is poor.
Submission
Liang Li, WXZJ Inc.

51. Option: The PER of Transceiver with C8 in AWGN channel
From the figures we can see that the PER performance of C8 in AWGN channel is over 6dB worse than that of E16, caused by the degradation of correlation among the non-orthogonal sequences
Submission
Liang Li, WXZJ Inc.

52. Option:     The PER performance of Transceiver with C8 in 0ns multipath fading channel
Compared with the PER in fading channel, The system with E16 have almost 5dB better than C8 system. If tx filter is added, the performance of the system with C8 will descend more. (4X over sampling)
Submission
Liang Li, WXZJ Inc.

53. App 1: OQPSK + half sine pulse without Tx filter
Tx / Rx performance at 868MHz, 600KHz bandwidth
E16 orthogonal code + OQPSK + half-sine pulse shaping
Tx: PSD, No shaping Filter;
RX: Synchronization performance
Receiver (Non-Rake) performance comparison based on our simulation results
Submission
Liang Li, WXZJ Inc.

54. 100kbps Data rate PSD 100kbps; 400k chip rate; 600k bandwidth;
half sine pulse shape;
No Tx filter;
Submission
Liang Li, WXZJ Inc.

55. 100kbps Data rate performance
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Frame Detection: No
SFD: No
Ideal sync
Submission
Liang Li, WXZJ Inc.

56. App 2: Crystal quality –chip error caused by frequency offset
Performance against frequency offset
Original target in TG4: Up to ±40ppm
Assumptions for chip clock:
PDU length 127 Byte = 8*127 bit = 1016 bit
15 bit per PSSS Symbol (32 chip)
68 PSSS Symbols with 2176 chips (Chip duration Tc= 2µs)
Results
40ppm for 2176 chips = chip error for the whole PDU
For one PSSS Symbol with 32 chips the error is about 40ppm*32 chip = 0,00128 chip
Submission
Liang Li, WXZJ Inc.

57. Crystal quality –chip error caused by frequency offset
Tx PSD without chip error, no Tx filter and PA
Tx PSD with chip error, no Tx filter or PA
PSD will not be affected with the chip error.
Submission
Liang Li, WXZJ Inc.

58. Crystal quality –chip error caused by frequency offset
Tx PSD with chip error and Tx filter, no PA
Tx PSD with chip error, Tx filter and PA
The nonlinear PA performance on TX PSD is still seriously affected by Chip error
Submission
Liang Li, WXZJ Inc.

59. Summary Tx PSD will not be affected seriously by chip error.
Chip error dose not effect the nonlinear PA performance of suggested Transceivers.
Compared with PSSS. The PSD of PSSS TX signal will be more sensitive to the chip error.
Submission
Liang Li, WXZJ Inc.

60. App 3: The features of E16 Code Sequence
Generation Principle of E16 Code Sequence
Local base sequence (to generate other 15 orthogonal sequences);
[ ];
Good auto-correlation (properties for sync, SFD, and frequency offset estimation has been considered);
Orthogonal sequences generation;
Walsh conversion (the Walsh convert matrix is shown in next slide);
There is some relation among these orthogonal sequences through Walsh conversion, and they are not irregular;
Submission
Liang Li, WXZJ Inc.

61. App 3: The features of E16 Code Sequence
Decimay
Walsh matrix 1 -1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Submission
Liang Li, WXZJ Inc.

62. App 3: The features of E16 Code Sequence
Properties of E16
Orthogonal characteristic among the 16 sequences;
They are generated by one sequence (local base sequence) through Walsh conversion;
The local base sequence is designed in consideration of sync, SFD, and frequency offset estimation;
The phase comes to 0 degree after one symbol;
The orthogonal sequences are not irregular;
There are some assured relations among the orthogonal sequences, which are introduced by Walsh conversion;
Submission
Liang Li, WXZJ Inc.

63. App 3: The features of E16 Code Sequence
Comparison with 15.4
In 15.4, the DSSS sequences are generated by shift and conjugate conversion. All the conversion can be expressed in conversion matrix. Correspondingly, the conversion matrix is Walsh matrix;
For E16, the local base sequence coded as is designed in consideration of sync, SFD, and frequency offset estimation;
All the spreading sequences coded from 0001 to 1111 are generated by converting the local base sequence of 0000;
Constant amplitude and continuous phase;
Phase comes to 0 degree after one symbol;
Code position spreading modulation;
Submission
Liang Li, WXZJ Inc.