1. VHT in Below 6 GHz Frequency Bands
Month Year
doc.: IEEE /xxxxr0
November 2007
VHT in Below 6 GHz Frequency Bands
Date:
Authors:
Vinko Erceg, Broadcom
VInko Erceg, Broadcom

2. November 2007
Past WLAN Evolutions
In the past, we saw presentations that discussed historical maximum PHY datarate increases going from b to a to n. Historical increases were about 5 times, except for n, for which the maximum PHY datarate increases from 54 Mbps to 600 Mbps (4 spatial streams). This is 11 times increase over a.
Vinko Erceg, Broadcom

3. Evolution to VHT: Cont’d
November 2007
Evolution to VHT: Cont’d
802.11n benefited from the recent technological advances such as MIMO and LDPC, and also wider channel bandwidth (20 MHz to 40 MHz).
Unfortunately, there were no recent significant technological advances that VHT development could benefit from.
It may not be reasonable to assume that the number of spatial stream can be extended to 8 because of the cost/power/size/practicality reasons.
To achieve at least 5 fold increase in datarate, wider bandwidth will be required, most likely much wider.
Vinko Erceg, Broadcom

4. Evolution to VHT: Cont’d
November 2007
Evolution to VHT: Cont’d
Some techniques can be used to increase aggregate throughput of the VHT system, in a scenario with multiple users and/or at MAC SAP.
These techniques will not provide maximum PHY datarate increase and may not be sufficient to enable new applications. They yield better system efficiency.
Vinko Erceg, Broadcom

5. Evolution to VHT: Cont’d
November 2007
Evolution to VHT: Cont’d
Where to allocate >= 80 MHz channel bandwidth for VHT?
At 2.4 GHz – No!
At 5 GHz – possibly, but not wider than 80 MHz, severe coexistence complications.
GHz spectrum – possibly. Now for fixed and mobile satellite systems, ITU allocation for IMT-A and 4G systems.
Vinko Erceg, Broadcom

6. Evolution to VHT: Cont’d
November 2007
Evolution to VHT: Cont’d
At < 6 GHz carrier frequencies, because of the sparse spectrum, the maximum VHT PHY datarate increase may yield a factor of 2 or slightly higher.
1.2 Gbps PHY rate, with better MAC efficiency, and better overall aggregate throughput may be achievable. Possible range extension if designed for.
Vinko Erceg, Broadcom

7. Few Questions to Think About..
November 2007
Few Questions to Think About..
Would VHT at sub 6 GHz carrier frequencies be headed for a marginal datarate, MAC, and range improvements over n system?
Based on the past, do we expect that the VHT PHY datarate should reach at least 5 fold increase to make it more attractive then the n system?
Would 2 fold max PHY datarate increase justify another standards technology development cycle that on the average lasts 5 years? What new significant applications would be enabled in this case? Would such a system gain traction over n system?
Is VHT direction pointing into considerably higher carrier frequencies (60 GHz band for example) in order to enable 5-10 fold increase in PHY datarates over n system and maybe enable new technologies, applications and services?
Vinko Erceg, Broadcom

8. November 2007
Straw poll
Do you think that 2x PHY datarate increase and aggregate throughput gains would justify development of VHT system in below 6 GHz frequency bands?
Yes: 9
No: 23
Don’t know: 53
Vinko Erceg, Broadcom