Openmoko Bug #1972: Wifi interferes with Bluetooth

[Openmoko Public Trac]

#1972: Wifi interferes with Bluetooth
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    Reporter:  Mercury                              |        Owner:  openmoko-devel
        Type:  defect                               |       Status:  new           
    Priority:  normal                               |    Milestone:                
   Component:  unknown                              |      Version:                
    Severity:  normal                               |   Resolution:                
    Keywords:  bluetooth, wifi, interference, a2dp  |    Blockedby:                
Reproducible:                                       |     Blocking:                
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Comment(by werner):

 If the throughput of WLAN is reduced by the same ratio as the throughput
 that
 BT gets, and vice versa, then things should be okay. E.g., if you measure
 the
 throughput of each alone as WLAN_solo and BT_solo, and again with both
 active
 as WLAN_shared and BT_shared, you should roughly obtain
 ~100% <= WLAN_shared/WLAN_solo+BT_shared/BT_solo <= ~200%
 for any coexistence solution.

 What coexistence in its most primitive form (and I think that's what we
 have)
 does is to make sure that they don't send at the same time. So they don't
 create situations where both try to occupy the same frequency, resulting
 in
 neither being heard, and not only this transmission being lost, but also
 more
 time lost to recovery.

 Here's a good introduction to the issue:
 http://focus.ti.com/pdfs/vf/bband/coexistence.pdf

 If you do the calculation from above on the data in that paper for a
 distance
 of 50ft, you obtain roughly 25% for WLAN and 10% for BT, resulting in 35%
 bandwidth utilization for uncoordinated sharing. (Under, I presume,
 otherwise
 ideal conditions.)

 - Werner

-- 
Ticket URL: <https://docs.openmoko.org/trac/ticket/1972#comment:3>
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