Aug. 2004

Liang Li, VSZJSlide 1

doc.: IEEE 802.15-04-0314-02-004b

Submission

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Submission Title: [Enhanced OQPSK Modulation with Orthogonal DSSS Sequences]Date Submitted: [Aug 2004]Source: [Liang Li, Yafei Tian, Liang Zhang, Chenyang Yang, Zhijian Hu, ]

Company: [WXZJ Inc/Helicomm Inc]Address: [Building D, No.2, Shangdi XinXi Lu, Beijing, China 100085 ]Voice:[], E-Mail:[liang_1@yahoo.com]

Re: [ IEEE 802.15.4 ]

Abstract: [This contribution proposes an updated PHY for TG4b.]

Purpose: [To encourage discussion.]

Notice: This document has been prepared to assist the IEEE P802.15b. 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.

Aug. 2004

Liang Li, VSZJSlide 2

doc.: IEEE 802.15-04-0314-02-004b

Submission

Proposal for IEEE802.15.4b

• A new PHY for low-rate WPAN that employs the MSK modulation scheme with new DSSS sequences:– Keeps the present OQPSK modulation. – New DSSS sequences: 16 sequences for 4-bit

mapping.– Data rate

• >=125Kbps (915MHz Band)

• >=100Kbps (868MHz Bnad)

Aug. 2004

Liang Li, VSZJSlide 3

doc.: IEEE 802.15-04-0314-02-004b

Submission

Summary of ProposalCh #0868MHz band

Ch #1-10906 – 924 MHz band

Bandwidth 600 kHz 2 MHz

Recommended Code Set 16-chip code set (1/4 bit/chip)

16-chip code set (1/4 bit/chip)

Chip rate 400kcps 500cps

Pulse shape Half-sine pulse shape Half-sine pulse shape

Modulation O-QPSK O-QPSK

Data rate >=100 kbps >=125 kbps

Aug. 2004

Liang Li, VSZJSlide 4

doc.: IEEE 802.15-04-0314-02-004b

Submission

Spectra (915MHz Band)

-2 -1 0 1 2 3 4-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

f-fc (MHz)

PS

D (

dBm

/100

KH

z) f

or 0

dBm

Tx

pow

er

Aug. 2004

Liang Li, VSZJSlide 5

doc.: IEEE 802.15-04-0314-02-004b

Submission

Spectra (868MHz Band)

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

f-fc (MHz)

PS

D (

dBm

/100

KH

z) f

or 0

dBm

Tx

pow

er

Aug. 2004

Liang Li, VSZJSlide 6

doc.: IEEE 802.15-04-0314-02-004b

Submission

Key Features of Our Proposal• Improved DSSS sequences:

– 16 DSSS sequences for 4-bit mapping.– Each sequence consists of 16 chips instead of

32, which results in ¼ chip rate • (500Kcps) for 125kbps data rate.• (400Kcps) for 100Kps data rate

– Better orthogonal characteristics between the modulated symbols and improving the decoding performance.

Aug. 2004

Liang Li, VSZJSlide 7

doc.: IEEE 802.15-04-0314-02-004b

Submission

Key Features of Our Proposal (cont.)

• Backward compatible:– The same modulation scheme used for the

transceiver on 915 MHz and 868 MHzOQPSK + Half-sine pulse shape

– Keeps constant envelop and continuous phase.

Aug. 2004

Liang Li, VSZJSlide 8

doc.: IEEE 802.15-04-0314-02-004b

Submission

Key Features of Our Proposal (cont.)

• Lower RF requirements:– At 915MHz US Band:

• 2MHz channel separation, Total 10 channels.

• 750KHz main lobe

– At 868 MHz European Band:• 600 kHz channel channel.

• 400KHz main lobe

• Lower out-of-band emission• > 30dB depression on first lobe (915MHzband)

• >28dB depression on first lobe (868MHz bnad)

Aug. 2004

Liang Li, VSZJSlide 9

doc.: IEEE 802.15-04-0314-02-004b

Submission

Generating SequenceDecimal Symbol

Binary Symbol Chip Values

0 0 0 0 0 0 0 1 1 0 1 0 0 0 1 0 0 0 1 0 0

1 1 0 0 0 0 1 1 0 0 0 0 1 0 0 0 1 0 0 0 1

2 0 1 0 0 0 0 0 0 0 1 1 1 0 1 1 1 0 1 1 1

3 1 1 0 0 0 1 0 1 0 0 1 0 0 0 1 0 0 0 1 0

4 0 0 1 0 0 0 1 1 1 0 1 1 0 1 0 0 1 0 1 1

5 1 0 1 0 0 1 1 0 1 1 1 0 0 0 0 1 1 1 1 0

6 1 1 1 0 0 0 0 0 1 0 0 0 0 1 1 1 1 0 0 0

7 0 1 1 1 0 1 0 1 1 1 0 1 0 0 1 0 1 1 0 1

8 0 0 0 1 0 0 1 1 0 1 0 0 1 0 1 1 1 0 1 1

9 1 0 0 1 0 1 1 0 0 0 0 1 1 1 1 0 1 1 1 0

10 0 1 0 1 0 0 0 0 0 1 1 1 1 0 0 0 1 0 0 0

11 1 1 0 1 0 1 0 1 0 0 1 0 1 1 0 1 1 1 0 1

12 0 0 1 1 0 0 1 1 1 0 1 1 1 0 1 1 0 1 0 0

13 1 0 1 1 0 1 1 0 1 1 1 0 1 1 1 0 0 0 0 1

14 0 1 1 1 0 0 0 0 1 0 0 0 1 0 0 0 0 1 1 1

15 1 1 1 1 0 1 0 1 1 1 0 1 1 1 0 1 0 0 1 0

Aug. 2004

Liang Li, VSZJSlide 10

doc.: IEEE 802.15-04-0314-02-004b

Submission

Modulation

The case for symbol 0

Aug. 2004

Liang Li, VSZJSlide 11

doc.: IEEE 802.15-04-0314-02-004b

Submission

Orthogonal Characteristic

With OQPSK modulation, half-sine pulse shaping and a sampling rate of 500KHz, after spreading and modulation, the symbol “0” can be written as:

Tjjjjjjjj 111111110 s

Similarly, we can get all 16 symbols s0, s1, … s15, where

)15,,0,( 0

16

nmnm

nmn

Hm ss

Sampled at the chip rate, the transmitted symbols keep their mutual orthogonality.

Aug. 2004

Liang Li, VSZJSlide 12

doc.: IEEE 802.15-04-0314-02-004b

Submission

Performance

NC-16FSK is the results of the non-coherent demodulation of 16-FSK which uses envelope detection.

Aug. 2004

Liang Li, VSZJSlide 13

doc.: IEEE 802.15-04-0314-02-004b

Submission

Performance (cont.)

Environment SNR @1e-2 PER

AWGN 4 dB

RMS Delay Spread 100ns 22 dB

RMS Delay Spread 200ns 23 dB

10,000 packets are transmitted.

Aug. 2004

Liang Li, VSZJSlide 14

doc.: IEEE 802.15-04-0314-02-004b

Submission

Remarks

– Simulation shows the decoder having a 0.5 to 1dB improvement in BER vs. Eb/No performance over 802.15.4.

– Effective bandwidth 0.25 bit/Hz.– Lower calculation complexity– Lower requirements on RF filter– Possible to implement a full-rate (250 kbps) system

using 1M chip rate without adding any complexity and still conform to the spectrum specifications with a 2MHz channel bandwidth.