How can radio technology adapt
to difficult environments?
Robin Heydon
Senior Director, Technology
Qualcomm Technologies International, Ltd.
January 23rd 2017
Difficult Radio
Environments?
3
What is the most
difficult radio
environment?
5
6
Case Study : Bluetooth® wireless technology
Each spec adds something new to help mitigate difficult radio environments
spec version
example major features
mitigation strategy
v1.1
Basic Rate
1 Mbps
v1.2
Adaptive Frequency Hopping
avoid interference
v2.0
Enhanced Data Rate
2 Mbps / 3 Mbps
v2.1
Sniff Subrating
transmit less – reducing interference
v3.0
Enhanced Power Control
802.11 PAL
quickly adapt to changing pathloss
5 GHz
v4.0
Low Energy
increased modulation index
v4.1
Piconet Clock Adjustment
align piconet timing with interferer
v4.2
LE Data Packet Length Extension
longer packets = fewer packets
v5.0
Slot Availability Mask
LE Long Range
LE2 Rate
LE Channel Selection Algorithm #2
align piconet timing with nearby LTE bands
increased coding gain
increased symbol rate
better channel selection algorithm
7
Bluetooth Radios
Physical Layer
chips / second
symbol rate
modulation
coding
BR
1
1 bit / symbol
GFSK
FEC 2/3 & 1/3
2x EDR
1
2 bits / symbol
π/4-DQPSK
none
3x EDR
1
3 bits / symbol
8-DPSK
none
LE
1
1 bit / symbol
GFSK
none
2x LE
2
1 bit / symbol
GFSK
none
LR 500k
1
2 chips / symbol
GFSK
Viterbi
LR 125k
1
8 chips / symbol
GFSK
Viterbi +
Manchester
8
Adaptive Frequency Hopping
Find good channels / mask out bad channels
Remap good channels to bad channels
nextHop = (prevHop + hop) % 37
if nextHop in badChannels:
usedCh = goodChannels[nextHop % len(goodChannels)]
else:
usedCh = nextHop
9
Channel Selection Algorithm #2
Find good channels / mask out bad channels
Remap good channels to bad channels
random = PRNG()
if random % 37 in badChannels:
usedCh = goodChannels[random % len(goodChannels)]
else:
usedCh = random % 37
10
How do you increase range?
It is easy to transmit louder ...
+20 dBm allowed by Bluetooth spec
but not allowed in all regulatory environments
Receiver sensitivity can be increased ...
but increases power used
Coding gain can be increased ...
manchester coding / viterbi coding
11
Mesh
Alternative to “more power”...
Mesh network through multiple nodes
each node is closer to neighbours
reducing “wall” / “pathloss” issues
Must be:
self-organising
self-healing
secure
12
Security Implications
Physically insecure devices
does this have the same
“network key” as the door lock?
if I ‘hack’ this door bell, can I get
into your home?
13
Malthing
Conclusion
Interference will happen
microwave ovens should not take down the house network
Increasing power / sensitivity / coding gain can help
but may not be best solution
Reducing interference may be better approach
more devices / mesh networking / adaptive frequency hopping
Poor security implementation may be the biggest risk
15
Thank you
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