1. VHT Metrics Considerations
April 2008
doc.: IEEE /0465r2
April 2008
VHT Metrics Considerations
Date:
Authors:
Darwin Engwer, Nortel Networks
Darwin Engwer, Nortel Networks

2. April 2008
doc.: IEEE /0465r2
April 2008
Abstract
This presentation reviews some important considerations in the development of an analytical framework for VHT. In particular, relevant metrics are discussed.
Please view in slideshow mode to see animations.
Darwin Engwer, Nortel Networks
Darwin Engwer, Nortel Networks

3. Outline Objectives Definition Analytical Framework – Part I
April 2008
Outline
Objectives
Definition
Analytical Framework – Part I
BSS Maximum Throughput Metric (M1)
Analytical Framework – Part II
Multiple BSS Maximum Throughput Metric (M2)
Analytical Framework – Part III
Maximum BSS Throughput Metric in space (M1) …
Darwin Engwer, Nortel Networks

4. April 2008
Metrics Objectives
Devise key metrics for characterization and comparison of different wireless systems.
Darwin Engwer, Nortel Networks

5. April 2008
doc.: IEEE /0465r2
April 2008
What are metrics, and how do they differ from system measurement and performance reports?
Metrics characterize a given system in terms of the abstract entities operating in a perfect environment.
Metrics are computations that expose the capabilities of a given system.
Performance reports (TGT) are the outcomes of specific tests run on a real world implementation operating in a specific, constrained environment for a specific set of use case scenarios.
Measurement reports (802.11k) indicate the current state of an operating network implementation in the real world.
[Metrics describe what the system is capable of under ideal conditions.]
Performance reports indicate how well an implementation performs in a given scenario. These are useful on their own and also in relation to the best case values, the metrics.
Measurement reports indicate how well an implementation performs in a real world setting, in real time. These are useful on their own and also in relation to the best case values (the metrics) and the performance reports for similar scenarios.
Darwin Engwer, Nortel Networks
Darwin Engwer, Nortel Networks

6. Analytical Framework – Part I
April 2008
Analytical Framework – Part I
Consider a universe; a void with nothing in it.
In the middle of this void, place an AP with a set of associated STAs communicating with the AP.
The AP is a point of access to a non LAN of infinite capacity (through a DS and portal, not shown).
A constellation of n STAs is associated with the AP.
Each STA is attempting to exchange a maximum amount of data with an entity x on the non LAN. The entity x has infinite throughput capacity.
Darwin Engwer, Nortel Networks

7. A single AP in a void April 2008 April 2008
doc.: IEEE /0465r2
April 2008
A single AP in a void
STA AP
With a constellation of associated and active MUs.
Darwin Engwer, Nortel Networks
Darwin Engwer, Nortel Networks

8. Infrastructure BSS Maximum Throughput (M1)
April 2008
Infrastructure BSS Maximum Throughput (M1)
Now consider that collectively the AP and the set of STAs are capable of some MAXIMUM throughput.
STAs
BSS Throughput
Max 1 2 3 4 5
Note: Data is for illustration purposes only.
Darwin Engwer, Nortel Networks

9. Infrastructure BSS Maximum Throughput
April 2008
Infrastructure BSS Maximum Throughput
where,
i = index of current STA
n = number of associated and active STAs
T = throughput at MAC SAP of STA i of n
Darwin Engwer, Nortel Networks

10. Analytical Framework – Part II
April 2008
Analytical Framework – Part II
Consider a universe; a void with nothing in it.
In the middle of this void, place a set of APs with a set of associated STAs communicating with each AP.
Each AP is a point of access to a non LAN of infinite capacity (through a DS and portal, not shown).
A constellation of n STAs is associated with each AP.
Each STA is attempting to exchange a maximum amount of data with an entity x on the non LAN. The entity x has infinite throughput capacity.
The APs are collocated.
The APs operate on different channels within a set of k channels.
Darwin Engwer, Nortel Networks

11. A set of collocated APs in a void
April 2008
doc.: IEEE /0465r2
April 2008
A set of collocated APs in a void AP
STA AP
STA AP
STA
With a constellation of associated and active MUs.
Darwin Engwer, Nortel Networks
Darwin Engwer, Nortel Networks

12. Multiple Infrastructure BSS Maximum Throughput (M2)
April 2008
Multiple Infrastructure BSS Maximum Throughput (M2)
Now consider that collectively the set of APs and the associated sets of STAs are capable of some MAXIMUM throughput.
APs
ESS Throughput (Mbps)
Max
Note: Data is for illustration purposes only.
Darwin Engwer, Nortel Networks

13. Multiple Infrastructure BSS Maximum Throughput (M2)
April 2008
doc.: IEEE /0465r2
April 2008
Multiple Infrastructure BSS Maximum Throughput (M2)
where,
i = index of current STA
n = number of associated and active STAs
j = index of current AP
m = number of APs
k = number of channels
T = throughput at MAC SAP of STA i of n wrt AP j of m
(j, m, k determine number of APs on current channel)
Note that a given *system* might employ multiple bands, e.g. dual concurrent 11b + 11a.
Darwin Engwer, Nortel Networks
Darwin Engwer, Nortel Networks

14. M2 examples April 2008 802.11a 802.11b Mbps Max Max APs
ESS Throughput (Mbps)
Max
802.11a
Max
802.11b
APs
Note: Data is for illustration purposes only.
Darwin Engwer, Nortel Networks

15. April 2008
Space
The metrics M1 and M2 seek to quantify aspects of the maximum throughput capability of the system.
In doing so, the M1 and M2 metrics ignore any consideration of space (or range) of the APs wrt the STAs.
Darwin Engwer, Nortel Networks

16. Analytical Framework – Part III
April 2008
Analytical Framework – Part III
Consider a universe; a void with nothing in it.
In the middle of this void, place an AP with a set of associated STAs communicating with the AP.
The AP is a point of access to a non LAN of infinite capacity (through a DS and portal, not shown).
A constellation of n STAs is associated with the AP.
Each STA is attempting to exchange a maximum amount of data with an entity x on the non LAN. The entity x has infinite throughput capacity.
The data rate varies depending on the distance between the AP and each STA.
Darwin Engwer, Nortel Networks

17. An AP in a void, with zones at different rates
April 2008
doc.: IEEE /0465r2
April 2008
An AP in a void, with zones at different rates
STA AP
With a constellation of associated and active MUs.
Darwin Engwer, Nortel Networks
Darwin Engwer, Nortel Networks

18. April 2008
M1 in space
The M1 metric now expands from a single value to array of values, one per supported MCS, M1□.
Each value in the array represents the maximum throughput achievable using the corresponding MCS, and hence reflects the maximum throughput within an abstract range boundary.
Darwin Engwer, Nortel Networks

19. April 2008
Energy
The metric M1□ seeks to quantify one aspects of the maximum throughput capability of the system.
However, the M1□ metric ignores any consideration of the energy required to lift the bits into a space. Without this correlation the ability of a system to fill a given space with data in unknown.
Darwin Engwer, Nortel Networks

20. Energy Factor [add energy factor notes here, see file 38]
April 2008
doc.: IEEE /0465r2
April 2008
Energy Factor
[add energy factor notes here, see file 38]
When we consider energy we usually do so in terms of the transmit power (EIRP), but from a system level perspective the amount of work required to actually “lift” the bits into the space is a much more valuable metric. Work is measured in units of Watt seconds, aka Joules. …
See file 38
Darwin Engwer, Nortel Networks
Darwin Engwer, Nortel Networks

21. Latency [Add latency metric notes here] April 2008
Darwin Engwer, Nortel Networks

22. Metrics Sub-summary M1 – max BSS throughput M2 – max ESS throughput
April 2008
Metrics Sub-summary
M1 – max BSS throughput
M2 – max ESS throughput
M1□ - max BSS throughput vs MCS
M1□e – max BSS throughput vs MCS vs energy
L1 – latency metric
Given those we can begin to consider parallel communications …
Darwin Engwer, Nortel Networks

23. Direction Factor [add direction factor notes here] Uplink traffic
April 2008
Direction Factor
[add direction factor notes here]
Uplink traffic
Downlink traffic
Combination of both uplink and downlink
(show effect on the formulas)
STA-to-STA traffic
Darwin Engwer, Nortel Networks

24. Parallel Communications Metrics
April 2008
Parallel Communications Metrics
[add parallel communications metrics notes here]
How to quantify various aspects of the system when parallel communications techniques are in use.
Filling a room with data
Note that with VHT we need to move away from a device centric view and instead look at what’s happening in the air. Our objective is to maximize utilize of the air (time, space, energy and frequency).
Darwin Engwer, Nortel Networks

25. Impact of various parallel communications techniques
April 2008
Impact of various parallel communications techniques
Multi-user MIMO
Downlink metric increases by number of independent streams factor
Network coding
Metric increases by total number of bits delivered, i.e. this includes the coded data
Max value is 1.5x ??
Broadcast of group addressed data
Metrics are unaffected; same data to same recipients yields no advantage
Single hop relay
Contribution to metrics is constrained to the min() of the inputs to and outputs from the relay station.
MG ?
Darwin Engwer, Nortel Networks

26. Conclusion Metrics are helpful to quantify various approaches.
April 2008
Conclusion
Metrics are helpful to quantify various approaches.
More work is needed …
Darwin Engwer, Nortel Networks

27. References April 2008 11-07-0412-01-0wng-looking-ahead-to-future.ppt
very-high-throughput-study-group.ppt
draft-par-and-5criteria-gigabit-tg.doc
vht-vht-study-group-thoughts.ppt
vht-how-should-we-manage-the-process-for-the-proposed-vht-activity.ppt
vht-vht-possibilities.ppt
“Mobile Cooperation Usage Models”, IEEE submission, , Marc de Courville (Motorola) et al vht-mobile-cooperation.ppt
“Below 6 GHz 11VHT PAR&5C’s Proposal”, IEEE submission, , Marc de Courville, Darwin Engwer et al vht-below-6ghz-11vht-par-5c-s-proposal.ppt
“Infrastructure Mesh Broadband Wireless System: Example of Cooperative Wireless”, Intel Cooperative Wireless Workshop, , N. K. Shankaranarayanan (AT&T)
Darwin Engwer, Nortel Networks

28. Revisions r0 – 2008-04-16 For first presentation to VHT SG.
April 2008
Revisions
r0 – For first presentation to VHT SG.
r1 – s3, s10, s12, s13: Changed “ESS” to “Multiple BSS”. s8, s12, s14: Added “illustrative data only” notes. s28: Added list of revisions. s30: Added equation for c.
r2 – s8, s9, s12, s13: Clarified the BSS type as “Infrastructure BSS”.
Darwin Engwer, Nortel Networks

29. April 2008
Backup Slides
Darwin Engwer, Nortel Networks

30. Multiple BSS Maximum Throughput (M2)
April 2008
doc.: IEEE /0465r2
April 2008
Multiple BSS Maximum Throughput (M2)
where,
i = index of current STA
n = number of associated and active STAs
j = index of current AP
m = number of APs
k = number of channels
c = number of APs on channel of AP j of m APs
T = throughput at MAC SAP of STA i of n with c APs on the channel
Note that a given *system* might employ multiple bands, e.g. dual concurrent 11b + 11a.
Darwin Engwer, Nortel Networks
Darwin Engwer, Nortel Networks

31. Technology axes for VHT to consider
April 2008
Technology axes for VHT to consider
Darwin Engwer, Nortel Networks

32. Technology axes for VHT to consider
April 2008
doc.: IEEE /0465r2
April 2008
Technology axes for VHT to consider
Darwin Engwer, Nortel Networks
Darwin Engwer, Nortel Networks