doc.: ieee 802.22-06/0234r2 submission nov 2006 david mazzarese, samsungslide 1 complex beacon...

Nov 2006

David Mazzarese, Samsung

Slide 1

doc.: IEEE 802.22-06/0234r2

Submission

Complex Beacon Simulations in AWGNIEEE P802.22 Wireless RANs Date: 2006-11-07

Name Company Address Phone email David Mazzarese Samsung Electronics

Co. Ltd. Korea +82 10 3279 5210 [email protected]

K. Sivanesan Samsung Electronics Co. Ltd.

Korea +82 10 3279 5210 [email protected]

Baowei Ji Samsung Telecom. America

USA +1-972-761-7167 [email protected]

Authors:

Notice: This document has been prepared to assist IEEE 802.22. 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 grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.22.

Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair Carl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at [email protected].>

http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf

mailto:[email protected]

mailto:[email protected]

Nov 2006


Slide 2

doc.: IEEE 802.22-06/0234r2

Submission

Abstract

Proposition of complex spreading sequences with QPSK and dual channel beacon.

Simulation results of proposed enhancements to IEEE 802.22.1 beacon design.

Summary of additional comments to the 802.22.1 draft specifications.

Nov 2006


Slide 3

doc.: IEEE 802.22-06/0234r2

Submission

Reminder of Basic ProposalTransmitter with complex spreading on dual channel

+Pilot: sync & count-down

PSDU Data

I

Q

Complex spreading

Beacon Signal

Z-1

Nov 2006


Slide 4

doc.: IEEE 802.22-06/0234r2

Submission

Dual Channel with Sync-N and Complex DSSS

• Variable N variable length PSDU• N = (PSDU in bytes)/3 - 1

1. WRAN uses sync burst to determine when the PSDU has been fully received (one cycle)2. WRAN uses sync burst to schedule future quiet periods

sync(15 bits)

sync syncN(9)

N-1 0

PSDU

IQ

One Packet = 48(N+1) symbols = 48*16*(N+1) chips

Rx

period

ANP

Nov 2006


Slide 5

doc.: IEEE 802.22-06/0234r2

Submission

Reminder of Basic ProposalAdvantages

• Transmit the sync burst and the payload in parallel– I and Q channels using QPSK modulation

• Complex spreading– Separate I and Q real spreading has lower performance

• Continuous transmission of the payload (data rate increase)– Transmit payload every 40 ms, rather than once (40 ms) every second – WRAN can start decoding the payload at any time, and finish decoding once

the counter has cycled through. Namely, no need to wait for the count down to reach zero and then decode the payload

• Adaptive counter length as the length of the payload changes– e.g. with beacon payload aggregation

Nov 2006


Slide 6

doc.: IEEE 802.22-06/0234r2

Submission

Simulation Conditions• AWGN channel• Perfect chip pulse synchronization at the receiver

– No oversampling, no inter-chip interference• Sliding-window PN sequence synchronization

– For each header, a different run and synchronization– Sliding window length = PN sequence length– Synchronize with the maximum correlation value

• Packet Error Rate (one packet = sync burst = 3 bytes)– If PN sequence synchronization fails: declare a packet error (no decoding)– If PN sequence synchronization is successful: decode the data (24 bits) and

declare a packet error if at least one bit is erroneously decoded• Exactly same power for real and complex sequences of length 8

– Symbol energy Es normalized to one (8 chips)• BPSK transmission with a real PN sequence (+1,-1)• QPSK transmission with a complex PN sequence (+1,-1,+i,-i after spreading)

Nov 2006


Slide 7

doc.: IEEE 802.22-06/0234r2

Submission

1000 packets per point

2 dB gain at 1% PER

PER of Sync Burst (Header) in AWGN

Nov 2006


Slide 8

doc.: IEEE 802.22-06/0234r2

Submission

Comparison with doc171

Note: for real spreading, Es/No = Eb/No

Nov 2006


Slide 9

doc.: IEEE 802.22-06/0234r2

Submission

Properties of the Complex PN Sequences

Seq A -1-i 1+i 1+i -1-i 1+i -1-i -1-i -1-i

Seq B -1-i -1-i 1+i 1+i -1-i 1+i -1-i -1-i

Seq C -1-i -1-i -1-i 1+i 1+i -1-i 1+i -1-i

• Further divide by the square root of 2• Any one of these 3 sequences could be used

Nov 2006


Slide 10

doc.: IEEE 802.22-06/0234r2

Submission

Correlation Properties*

* Real sequence of 22-06-0196-0000_Motorola_TG1_PHY_MAC_spec_draft

Due to the poor cross-correlations, we no longer support the use of multiple

spreading sequences

Nov 2006


Slide 11

doc.: IEEE 802.22-06/0234r2

Submission

Beacon-to-Beacon Interference

Nov 2006


Slide 12

doc.: IEEE 802.22-06/0234r2

Submission

Other Comments

1. Problem for scheduling the length of the quiet period(proposal of a solution)

2. Shortening the PSDU3. Inter-beacon communication channel4. Data aggregation

Nov 2006


Slide 13

doc.: IEEE 802.22-06/0234r2

Submission

Problem in current draft* (1)

• Count-down index allows to know when the PSDU starts being transmitted• Header (PHR) of PSDU tells the length of the PSDU

… but it is too late for the WRAN, which has already scheduled a quiet period of a certain length (e.g. minimum 40 ms), which may be different than the length of the PSDU (e.g. with aggregation)

• There should be a mechanism for the WRAN to know how long the quiet period should be, prior to scheduling the quiet period

* Thanks to a discussion with Zander

Nov 2006


Slide 14

doc.: IEEE 802.22-06/0234r2

Submission

Problem in current draft (2)Possible solution

sync(15 bits)

sync syncN(9)

N-1 0

PSDU

IQ

Rx

period

ANPsync sync

4 bursts = 10 ms

sync 0

PSDU

Rx

period

ANP

4 bursts = 10 ms

N-2 N-3

syncsync sync

1 burst ≤ 5 ms

Frame length

Index

(with FEC)

Frame length

Index

(with FEC)

Frame length

Index

(with FEC)

Nov 2006


Slide 15

doc.: IEEE 802.22-06/0234r2

Submission

Shortening the PSDU (1)Is it necessary?

PeriodicSupport VoIP

ExceptionalVoIP failure

The WRAN will need to vacate the channel anyway!

Periodic quietframes(10 ms)

Fast detectionof beacon burst

(5 ms)

Quiet timescheduling

(50 ms)

Synchronization withthe count-down

Decoding ofbeacon(40 ms)

Nov 2006


Slide 16

doc.: IEEE 802.22-06/0234r2

Submission

Shortening the PSDU (2)Sub-channel information

– Information on wireless microphone sub-channel usage• 12.5 % of minimum PSDU length

– Information that is not useful to the WRAN does not belong in the first release of the 802.22.1 standard

– The WRAN could only make limited use of sub-channel information to protect the edge of an adjacent channel• e.g. with fractional bandwidth• or power control

– WRAN only needs the index of the TV channel(s) to protect– Aggregation of sub-channel information could quickly increase

the length of the payload

Sub-channel information could be removedBut it would not sufficient to get a 10 ms beacon

Nov 2006


Slide 17

doc.: IEEE 802.22-06/0234r2

Submission

Inter-Beacon Communication Channel

We suggested to review the protocol to make sure that the scenarios described below are taken into account

• One message for de-aggregation of PSDU at the primary beacon– Required when a secondary beacon leaves the channel before the primary beacon

• One message or some protocol for transferring primary beacon operation from a primary beacon to a secondary beacon– Required when the primary beacon leaves the channel before any of the

secondary beacons

A solution has been proposed by Motorola

Nov 2006


Slide 18

doc.: IEEE 802.22-06/0234r2

Submission

Data Aggregation (1)

• Data aggregation is a feature desired by incumbents– To limit the amount of spectrum used by beacons– To avoid collisions that may impair the detectability of the beacon

• Trade-offs– Aggregating neighboring beacons that protect the same TV channel and

transmitting only one beacon on the same TV channel is desirable.

– Aggregating beacons of different TV channels into one beacon increases the WRAN detection complexity, and poses the risk of losing several microphones due to misdetection of a single beacon by the WRAN.

– Reduced protection against fast and shadow fading with only one primary protecting device (Receiver diversity may not always be available)

• Trade-off with inter-beacon interference

Nov 2006


Slide 19

doc.: IEEE 802.22-06/0234r2

Submission

Data Aggregation (2)

• Trade-offs (continued)– Careful choice of inter-beacon distance for allowing aggregation is needed– Careful aggregation protocol to deal with disappearing microphones

protected by primary and secondary beacons– Aggregation also increases the PSDU payload. It is already difficult to fit

the PSDU of one beacon of one channel in a 10msec window.

• Limiting the use of wireless microphone bandwidth resources by– Moving the centre frequency of the beacon channel closer to the edge of the

TV channel, to avoid stealing more resources than necessary from wireless microphones

– Using 2 aggregated primary beacons on the same sub-channel for diversity and distribution of the payload

• Depending on inter-beacon interference performance with a single complex sequence

Nov 2006


Slide 20

doc.: IEEE 802.22-06/0234r2

Submission

Some analysis of the Trade-offs of data aggregation strategies

• No aggregation– Transmit the whole PSDU (N bytes)

• Full aggregation– Only new additional information NX is needed at each beacon, X < 1– Aggregate PSDU N(1+X) > N per beacon

• Fully distributed aggregation (among primary beacons)– Distribute PSDU equally between 2 beacons: N(1+X)/2 < N per beacon– Not robust to loss of a beacon

• Partially distributed aggregation (among primary beacons)– Only absolutely necessary information NY is aggregated, Y < X– The other data N(X-Y) is distributed– Diversity provides the crucial data with high reliability at a single receiver– N(1+X-Y)/2 + NY = N(1+X+Y)/2 < N per beacon, if (X+Y) < 1– TG or recommended practice to decide what minimum information is NY

doc.: ieee 802.22-06/0234r2 submission nov 2006 david mazzarese, samsungslide 1 complex beacon...

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