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Doc.: IEEE 802.11-06/0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 1 Overview & Architecture Error Rate Requirements Notice: This document.

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Presentation on theme: "Doc.: IEEE 802.11-06/0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 1 Overview & Architecture Error Rate Requirements Notice: This document."— Presentation transcript:

1 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 1 Overview & Architecture Error Rate Requirements Notice: This document has been prepared to assist IEEE 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 Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, 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 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 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at.http:// Date: Authors:

2 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 2 Abstract IEEE 802 Overview & Architecture General Error Rate Requirements for 802 LAN Discuss modifying O&A Error Rate Requirements

3 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 3 Wireless delivery spec is impossible to meet IEEE Std 802©-2001 Overview & Architecture 7.3 Error rates Error performance of IEEE 802 LANs and MANs is required to be as follows: b) For wireless physical media: Within a single access domain, the probability that a MAC Service Data Unit (MSDU) is not delivered correctly at an MSAP of an intended receiving MAC service user, due to the operation of the Physical layer, and the MAC protocol, shall be less than 8 x per octet of MDSU length.

4 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 4 Complication – Retry takes time If you can’t control the medium, you can control either Packet Error Rate or latency –Send a frame, wait for ACK, if not ACK’ed, repeat until dot11ShortRetry Limit = 7 or dot11LongRetryLimit = 4 or the frame is ACKed –Discard frame if RetryLimit is reached, meaning it is not delivered correctly at an MSAP of an intended receiving MAC service user –Discard frame if MaxTransmitMSDULifetime is reached, meaning it is not delivered correctly at an MSAP of an intended receiving MAC service user

5 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 5 Less than 8 in 100 million frames fail? –Failure to ACK = received PLCP header checksum error.OR. received CRC checksum error.OR. ACK frame PLCP header checksum error.OR. ACK frame CRC checksum error –Example: counters in a STA CRC checksum OK = x, CRC checksum bad = x, PLCP checksum bad = 4x –Not sure of destination of any frames with bad checksums Packets Max Retries counter Packets Aged counter

6 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 6 How to fix IEEE Std 802©-2001 Overview & Architecture requirement? 7.3 Error rates b) For [*] wireless physical media: Within a single access domain, the probability that a MAC Service Data Unit (MSDU) is not delivered correctly at an MSAP of an intended receiving MAC service user, due to the operation of the Physical layer, and the MAC protocol, shall be less than 8 x per octet of MDSU length.

7 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 7 * suggestions For [*] wireless physical media: Controlled Unshared

8 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 8 Backup slides

9 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 9 The problem If you can’t control the medium, you can control either Packet Error Rate or latency If you can’t control the medium, you can’t control both PER and latency Dot11 operation may be ‘interference-limited’ in addition to ‘noise-limited’ Dot11 operates per frame, fragment and symbol, not per data octet Dot11 uses timers and per frame counters ACK MAC frame format is at least ten octets length The specified error rate is impossible for License-Exempt operation with one octet MSDUs

10 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 10 Dot11n PPDU frame format

11 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 11 Dot11n PLCP Protocol Data Unit N SS = 4N DBPS 1 st symbol –BPSK –QPSK –16-QAM –64-QAM QAM airtime is by increments of up to 270 octets 8 x is < dropping one in ten million frames 2160 x is dropping ~21 in a million frames

12 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 12 Dot11a PPDU frame format

13 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 13 Dot11a PLCP Protocol Data Unit ModulationN DBPS 1 st 2 nd n th symbol –BPSK –QPSK –16-QAM –64-QAM –SERVICE 16 bits, CRC bits, Tail 6 bits 64-QAM airtime is by increments of up to 27 octets 8 x is < dropping one in ten million frames 216 x is dropping ~two in a million frames

14 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 14 MAC knobs for dropping MDSUs dot11MaxTransmitMSDULifetime 1-4B tus, default 512 dot11EDCATableMSDULifetime tus, default 500 dot11QAPEDCATableMSDULifetime tus, default 500 dot11RTSThreshold octets, default 3000 dot11ShortRetryLimit 1-255, default 7 dot11LongRetryLimit (> dot11RTSThreshold) 1-255, default 4

15 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 15 BSS Operation Sensitivities Slow data rates, high error rates –More power-sensitive users (dual-mode phones) –More power in the License-Exempt bands from all sources –Far/Near balance vs AP Transmit Power –One tu is 128 octets at 1 Mb/s Shorter Lifetimes, smaller RetryLimits –Why are Lifetimes greater than two beacon periods? –How many short frames fail 6 times? 7 times?

16 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 16 PHY knobs affecting MSDU delivery Modulation Coding Scheme (MCS) – modulation order and FEC code rate –BPSK/QPSK/16-QAM/64-QAM and ½, 2/3, ¾, 5/6 Transmit power and EIRP vs ‘noise’ Transmit frequency vs ‘noise’ Channel width vs ‘noise’ Choice of PLCP preamble and header (.11g/.11n)

17 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 17 CRC-32 and Fragmentation dot11FragmentationThreshold, lesser of 3000 octets or aMPDUMaxLength aMPDUMaxLength, default 4095 octets, except IR PHY 2500 PHY clauses specify minimum receiver sensitivity, typically the minimum signal level for 10% PER at 1000 octet PSDU length

18 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 18 Bit error correlation and CRC-32 protection Some PHY modes have uncorrelated single-bit errors, e.g. 1 Mb/s DSSS, FHSS Some PHY modes use coding that reduces the likelihood of undetected errored bits, others do not. Such detection in the received frame body is not specified in the PHY service specification [PHY-RXEND.indication (RXERROR) indicates PLCP header checksum error] If four single bit errors in 1500 octets are possible, then there is some likelihood CRC-32 will indicate a correct frame or fragment has been received, when it is errored.

19 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 19 IEEE Std 802©-2001 Overview & Architecture 7.3 Error rates b) For [*] wireless physical media: Within a single access domain, the probability that a MAC Service Data Unit (MSDU) is not delivered correctly at an MSAP of an intended receiving MAC service user, due to the operation of the Physical layer, and the MAC protocol, shall be less than 8 x per octet of MDSU length. c) The probability that an MSDU delivered at an MSAP contains an undetected error, due to operation of the MAC service provider, shall be less than 5 x per octet of MSDU length

20 doc.: IEEE /0635r1 Submission May 2006 Peter Ecclesine, Cisco SystemsSlide 20 References IEEE Std 802© ma-D6.0 P802.11n-D1.0


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