doc.: ieee 802.22-06/0234r2 submission nov 2006 david mazzarese, samsungslide 1 complex beacon...
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doc.: IEEE /0234r2 Submission Nov 2006 David Mazzarese, SamsungSlide 3 Reminder of Basic Proposal Transmitter with complex spreading on dual channel + Pilot: sync & count-down PSDU Data I Q Complex spreading Beacon Signal Z -1TRANSCRIPT
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.
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Nov 2006
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
Slide 8
doc.: IEEE 802.22-06/0234r2
Submission
Comparison with doc171
Note: for real spreading, Es/No = Eb/No
Nov 2006
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
Slide 11
doc.: IEEE 802.22-06/0234r2
Submission
Beacon-to-Beacon Interference
Nov 2006
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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
David Mazzarese, Samsung
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