Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: MAC CTRB Parameters Issues Date Submitted: [9 July 2001] Source: [Mark E. Schrader] Company [Eastman Kodak Co.] Address [4545 E. River Rd., Rochester, NY 14650-0898] - PowerPoint PPT Presentation
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Nov. 14, 2001 Mark E. Schrader, Eastman Kodak Co . Slide 1 IEEE 802.15-01/328r4 Submiss ion Project: IEEE P802.15 Working Group for Wireless Personal Area Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Networks (WPANs) Submission Title: MAC CTRB Parameters Issues Date Submitted: [9 July 2001] Source: [Mark E. Schrader] Company [Eastman Kodak Co.] Address [4545 E. River Rd., Rochester, NY 14650-0898] Voice:[+1.716.781.9561], FAX: [+1.716.781.9733], E-Mail: [[email protected]] Re: [IEEE 802.15.3 MAC] Abstract: QoS based Channel Time Request Block parameters are defined mathematically. Some issues and limits of the timing are defined and briefly discussed. QoS is shown to to simple from the PNC perspective when only allocated bandwidth is important.. Purpose: Channel Time Request Block parameters toward building a QoS algorithm. Notice: This document has been prepared to assist the IEEE P802.15. 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.
Transcript
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 1
IEEE 802.15-01/328r4
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: MAC CTRB Parameters IssuesDate Submitted: [9 July 2001]Source: [Mark E. Schrader] Company [Eastman Kodak Co.]Address [4545 E. River Rd., Rochester, NY 14650-0898] Voice:[+1.716.781.9561], FAX: [+1.716.781.9733], E-Mail:[[email protected]]
Re: [IEEE 802.15.3 MAC]
Abstract: QoS based Channel Time Request Block parameters are defined mathematically. Some issues and limits of the timing are defined and briefly discussed. QoS is shown to to simple from the PNC perspective when only allocated bandwidth is important..
Purpose: Channel Time Request Block parameters toward building a QoS algorithm.
Notice: This document has been prepared to assist the IEEE P802.15. 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.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 2
IEEE 802.15-01/328r4
Submission
Document Overview
• Propose the smallest set (3) of Channel Time Request Block (CTRB) parameters usable for QoS-based requests.
• Define the parameters mathematically with variables that are usable by the channel time requestor.
• Identify issues and solutions.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 3
IEEE 802.15-01/328r4
Submission
Variable Definitions1)fd = bits per second of delivered data.
2)NB = bits of source buffer available to store the data to be communicated.
3)NMPDU = bits of the data portion of one packet of data.
4)NOH = Equivalent bits of overhead of one packet of data including: actual MAC header bits, slot guard times, PHY or PLCP overhead, etc., everything-but-data, etc. It simplifies the explanation to express this as an equivalent number of bits.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 4
IEEE 802.15-01/328r4
Submission
Definitions Continued
• NE = Channel (PHY) encoding, bits per symbol
• fs = Channel symbol rate, symbols per second.
• Tbcn = Beacon Period
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 5
IEEE 802.15-01/328r4
Submission
CTRB Parameter 1: Allocation Period
3) TAP = NB / fd
4) This is how often the NB buffer must be sent to get the desired delivered data rate fd.
5) This is the size of the source buffer divided by the desired data rate.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 6
IEEE 802.15-01/328r4
Submission
Relationships I
• We need to send NP packets over the network in order to transmit one buffer:
• NP = NB / NMPDU Assume an integer for simplicity.
• NT = NMPDU + NOH, the total number of bits that would have to be sent over the network to cover both the data and the overhead.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 7
IEEE 802.15-01/328r4
Submission
CTRB Parameter 2: GTS Time Per Allocation Period
• TGTS is the total time requested for GTS allocated in order to send one buffer of data.
• TGTS = ( NP NT / NE fS ).
• For the sending NP packets,
• of equivalent size, NT = ( NMPDU + NOH )
• with a PHY encoding of NE bits per symbol
• and a PHY symbol rate of fS.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 8
IEEE 802.15-01/328r4
Submission
Relationships 2
• 1 / ( NE fS ) is a constant as long as the symbol rate and encoding method is unchanged.
• From before: NP = NB / NMPDU
• Stating the obvious: NT and NP will also be constants if the transmit packet size and the transmit buffer size both remain constant.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 9
IEEE 802.15-01/328r4
Submission
CTRB Parameter 3: Desired (Maximum) GTS Time per Allocation Period
• TDMG defines the maximum amount of GTS time per allocation period that a DEV is capable of using. TDMGDMG > TGTS
– If there is unused bandwidth, the extra channel bandwidth can be divided up among DEVs based on what they can actually use.
– Allows channel utilization to be maximized.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 10
IEEE 802.15-01/328r4
Submission
CTRB Parameter 4: Maximum Allocation Delay
• TMAD defines an allowable time jitter to the allocation of time slots by the piconet coordinator, PNC.
• The maximum allocation delay starts before the end of the allocation period, but does not affect the PNC’s reference timing of the TAP period. It allows some variability in position of the GTS slot(s)..
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 11
IEEE 802.15-01/328r4
Submission
The TGTS (blue) time is the total amount of slot time that must be allocated by the PNC within the TMAD (green) time centered around the start of the TAP interval (vertical arrows).
TGTS
TMAD
½TMAD
TAP
TMAD
½TMAD
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 12
IEEE 802.15-01/328r4
Submission
Possible PNC Slot Allocations
TAP
TMAD
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 13
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Submission
Proposed Fragmentation Policy
• The PNC shall provide the GTS time in as few time slots as possible. The PNC may provide more GTS time than the amount requested.
• The PNC shall create at least one slot for each distinct channel time request.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 14
IEEE 802.15-01/328r4
Submission
Proposed CTRB Structure
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 15
IEEE 802.15-01/328r4
Submission
Proposed CTRB Structure
CTRB field that exists in draft D0.8
CTRB field proposed in this proposal
CTRB field proposed in document 01/485
Maximum
Allocation
Delay
2Allocation
Period
2Minimum
GTS Time
2Target
Address
Octets: 1EPS
status
1Stream
index
1EPS
Set
1 2Desired
GTS
Time
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 16
IEEE 802.15-01/328r4
Submission
Appendix 1
Comments and Issues
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 17
IEEE 802.15-01/328r4
Submission
Issue 1: QoS Restrictions to Allocation
• This is ISOC slot specification. • A request for a fixed offset from the beacon for
low power devices, etc., will require different additional parameters to indicate that the time slot position is guaranteed with respect to the beacon.
• If a QoS request defined both the a fixed delay from the beacon and a fixed rate, it would set the beacon period. Should this “super QoS” mode be allowed?
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 18
IEEE 802.15-01/328r4
Submission
TMAD and the Beacon
• If TMAD > TBCN + TGTS then the beacon will never interfere with the allocation of time slots
• If TMAD is smaller than this interval, then the following slides apply.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 19
IEEE 802.15-01/328r4
Submission
Issue 2: Beacon & CAP Delays
• Any PNC QoS strategy must take into account accommodating the beacon/CAP. The occurrence of the beacon plus the CAP could delay some or all of a member’s ISOC time slots beyond the requested interval, TAP.
• The PNC must be able guarantee a limit to the size of the beacon and the CAP or QoS policies will breakdown.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 20
IEEE 802.15-01/328r4
Submission
TAP
TMAD
Beacon
Alternative 1 Start of TAP
Alternative 2 Start of TAP
Delayed Interval
The Beacon May Upset the timing of ISOC Slots
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 21
IEEE 802.15-01/328r4
Submission
TAP Adjustment to Beacon Delay
• How should the TAP be adjusted if the beacon forces the slot allocation to be late. Should the next allocation be early according to the current TAP interval (Alternative 1), or should it be late and sync off the most recent slot allocation (blue) (Alternative 2)?
• The user could specify which alternative to use if we defined the QoS parameter switch.
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 22
IEEE 802.15-01/328r4
Submission
Appendix 2
Data Rate Driven QoS
Nov. 14, 2001
Mark E. Schrader, Eastman Kodak Co.Slide 23
IEEE 802.15-01/328r4
Submission
Requirements for Data Rate Only QoS
• The transmit buffer is large enough to accept GTS slots anywhere in the superframe.
• The amount of bandwidth only depends on the data rate required fd, the data rate available, and the amount of overhead.
• TAP / TGTS = ( fd / fs ) / ( NT / NENMPDU )
• Define TMAD = 0xFFFF, which will be a special value indicating “anywhere in CFP”.
