This document discusses wireless technologies and the evolution of WiFi. It begins by explaining how our prejudices are shaped by the technologies we grew up with. It then discusses Shannon's communications theory and how factors like bandwidth, signal power, noise power, and propagation characteristics determine wireless channel capacity. It reviews the characteristics of radio/TV broadcast, cellular networks, and WiFi. It notes the constraints of using unlicensed spectrum and how mesh networking is an ideal architecture. The document concludes by discussing best practices for mesh networks including using different bands for backhaul and access and coordinating transmissions.

1. Wireless Common
Sense
Shifting the Collection of Prejudices
Robert J. Berger
Internet Bandwidth Development Consulting
rberger@ibd.com
1

2. 2

3. Common sense
is the collection of
prejudices acquired by
age eighteen
- Albert Einstein
2

4. Tech You Grew Up with
Shapes your Prejudices of
Wireless Tech Capabilities
3

5. Tech You Grew Up with
Shapes your Prejudices of
Wireless Tech Capabilities
3

6. Claude Shannon’s
Communications
Theory
Shows us the Reality
beyond our prejudices
4

7. C=W log (1+S/N)
5

8. Shannon’s Theory
C=W log (1+S/N)
where; C=channel capacity (bits/second)
5

9. Shannon’s Theory
C=W log (1+S/N)
where; C=channel capacity (bits/second)
W=Bandwidth (How much Spectrum we are using)
5

10. Shannon’s Theory
C=W log (1+S/N)
where; C=channel capacity (bits/second)
W=Bandwidth (How much Spectrum we are using)
S=signal power, and N=noise power
5

11. Propagation Characteristics
& Path Loss
6

12. Propagation Characteristics
& Path Loss
• Determines how much of the signal
power gets to the receiver
6

13. Propagation Characteristics
& Path Loss
• Determines how much of the signal
power gets to the receiver
• The higher the frequency
- the less easily the signal propagates
6

14. Propagation Characteristics
& Path Loss
• Determines how much of the signal
power gets to the receiver
• The higher the frequency
- the less easily the signal propagates
6

15. Propagation Characteristics
& Path Loss
• Determines how much of the signal
power gets to the receiver
• The higher the frequency
- the less easily the signal propagates
- The more buildings, trees, hills the
more attenuation
6

16. Propagation Characteristics
& Path Loss
• Determines how much of the signal
power gets to the receiver
• The higher the frequency
- the less easily the signal propagates
- The more buildings, trees, hills the
more attenuation
• Physical Reality is such a Drag!!
6

17. Radio & TV: Broadcast
HIGH POWER &
low frequency
7

18. Radio & TV: Broadcast
HIGH POWER &
low frequency
MEGA WATTS of Power!!!
7

19. Radio & TV: Broadcast
HIGH POWER &
low frequency
MEGA WATTS of Power!!!
Spectrum in the 80 - 800 MHz range
7

20. Radio & TV: Broadcast
HIGH POWER &
low frequency
MEGA WATTS of Power!!!
Spectrum in the 80 - 800 MHz range
50Khz - 6Mhz Channel Bandwidth
7

21. Radio & TV: Broadcast
HIGH POWER &
low frequency
MEGA WATTS of Power!!!
Spectrum in the 80 - 800 MHz range
50Khz - 6Mhz Channel Bandwidth
Gets Large Channel Capacity via Power
and Significant Spectrum
7

22. Tech from the 1930’s
Very simple analog modulation
Uses spectrum inefficiently
Receiver has difficulty
rejecting noise
8

23. Cell Phones: Tiny Channel Capacity
9

24. Cell Phones: Tiny Channel Capacity
Low Signal Power & Advanced Modulation
9

25. Cell Phones: Tiny Channel Capacity
Low Signal Power & Advanced Modulation
800 - 1900Mhz a bit more difficult
propagation, but still good
9

26. Cell Phones: Tiny Channel Capacity
Low Signal Power & Advanced Modulation
800 - 1900Mhz a bit more difficult
propagation, but still good
But only requires 4kbps Channel Capacity
9

27. Cell Phones: Tiny Channel Capacity
Low Signal Power & Advanced Modulation
800 - 1900Mhz a bit more difficult
propagation, but still good
But only requires 4kbps Channel Capacity
High speed data phones will have less
coverage or need more basestations
9

28. Past Experience Does Not
Apply to WiFi
10

29. Past Experience Does Not
Apply to WiFi
Uses Unlicensed Spectrum
2.4Ghz & 5 - 6Ghz, Very Low Power
10

30. Past Experience Does Not
Apply to WiFi
Uses Unlicensed Spectrum
2.4Ghz & 5 - 6Ghz, Very Low Power
Rapid comidification & evolution -
Very low cost & advanced modulation
10

31. Past Experience Does Not
Apply to WiFi
Uses Unlicensed Spectrum
2.4Ghz & 5 - 6Ghz, Very Low Power
Rapid comidification & evolution -
Very low cost & advanced modulation
Developed “Bottoms Up” like the
Internet, not from Carriers or
Broadcasters
10

32. Unlicensed Wireless
Constraints
11

33. Unlicensed Wireless
Constraints
Original Spectrum considered “Junk Spectrum”
2.4Ghz is absorption frequency of water
5 - 6 Ghz propagates about 1/2 as well
11

34. Unlicensed Wireless
Constraints
Original Spectrum considered “Junk Spectrum”
2.4Ghz is absorption frequency of water
5 - 6 Ghz propagates about 1/2 as well
Can’t interfere, but must accept interference
11

35. Unlicensed Wireless
Constraints
Original Spectrum considered “Junk Spectrum”
2.4Ghz is absorption frequency of water
5 - 6 Ghz propagates about 1/2 as well
Can’t interfere, but must accept interference
Very low power, but lots of spectrum
11

36. Unlicensed Wireless
Constraints
Original Spectrum considered “Junk Spectrum”
2.4Ghz is absorption frequency of water
5 - 6 Ghz propagates about 1/2 as well
Can’t interfere, but must accept interference
Very low power, but lots of spectrum
Very short distance with high bandwidth
11

37. Average WiFi Link Budget
12

38. Average WiFi Link Budget
AP to Client limited by weakest link
Avg clients’ Signal Power: 15dBm
Avg AP Sensitivity 1Mbps: -94dBm
12

39. Average WiFi Link Budget
AP to Client limited by weakest link
Avg clients’ Signal Power: 15dBm
Avg AP Sensitivity 1Mbps: -94dBm
Link Budget avg client to AP:
signal power + xmit antenna gain - free space
path loss + receiv antenna gain - receive
sensitivity = Margin
12

40. Average WiFi Link Budget
AP to Client limited by weakest link
Avg clients’ Signal Power: 15dBm
Avg AP Sensitivity 1Mbps: -94dBm
Link Budget avg client to AP:
signal power + xmit antenna gain - free space
path loss + receiv antenna gain - receive
sensitivity = Margin
15dBm + 2dB - (-84) + 7dB - (-94dBM) =
34 dBm Margin at 150 Meters
12

41. Link Margin
1 Mbps 11 Mbps
51
Link Margin
45
42 40
39
37
35 34
31
28
26
24
0
5
0
75
50
25
15
12
10
Meters
13

42. Link Margin
The Free Space Loss 1 Mbps 11 Mbps
calculations are
optimistic
51
Link Margin
45
42 40
39
37
35 34
31
28
26
24
0
5
0
75
50
25
15
12
10
Meters
13

43. Link Margin
The Free Space Loss 1 Mbps 11 Mbps
calculations are
optimistic
51
Link Margin
45
Realistic distance of 39
42 40
37
a laptop to an AP is 35
31
34
~30m in the open 24
26
28
0
5
0
75
50
25
15
12
10
Meters
13

44. Link Margin
The Free Space Loss 1 Mbps 11 Mbps
calculations are
optimistic
51
Link Margin
45
Realistic distance of 39
42 40
37
a laptop to an AP is 35
31
34
~30m in the open 24
26
28
At 150 Meters, One
good tree will knock
out your link
0
5
0
75
50
25
15
12
10
Meters
13

45. Real World Constraints
14

46. Real World Constraints
WiFi originally designed for indoor LAN
14

47. Real World Constraints
WiFi originally designed for indoor LAN
WiFi CSMA does not handle large numbers of
clients accessing an AP
14

48. Real World Constraints
WiFi originally designed for indoor LAN
WiFi CSMA does not handle large numbers of
clients accessing an AP
Nearby clients and APs not associated to an
SSID can cause contention
14

49. Real World Constraints
WiFi originally designed for indoor LAN
WiFi CSMA does not handle large numbers of
clients accessing an AP
Nearby clients and APs not associated to an
SSID can cause contention
Asymmetrical Power causes client misbehavior
14

50. Real World Constraints
WiFi originally designed for indoor LAN
WiFi CSMA does not handle large numbers of
clients accessing an AP
Nearby clients and APs not associated to an
SSID can cause contention
Asymmetrical Power causes client misbehavior
Obstructions:
One Tree: 20dB One Wall: 10dB
14

51. WiFi has to Evolve
Around Limitations
15

52. WiFi has to Evolve
Around Limitations
802.11 Phy has already evolved from 1Mbps to
802.11n with 125Mpbs
15

53. WiFi has to Evolve
Around Limitations
802.11 Phy has already evolved from 1Mbps to
802.11n with 125Mpbs
Distance not really improved (but more
bandwidth for same short distance)
15

54. WiFi has to Evolve
Around Limitations
802.11 Phy has already evolved from 1Mbps to
802.11n with 125Mpbs
Distance not really improved (but more
bandwidth for same short distance)
Contention by nearby nodes not addressed yet
(802.11s may, Proprietary extensions today)
15

55. WiFi Recapitulates
Ethernet Evolution
16

56. WiFi Recapitulates
Ethernet Evolution
Originally Considered a “Toy”
16

57. WiFi Recapitulates
Ethernet Evolution
Originally Considered a “Toy”
Started out as LAN evolved to MAN
16

58. WiFi Recapitulates
Ethernet Evolution
Originally Considered a “Toy”
Started out as LAN evolved to MAN
“Good Enough” and much less expensive
16

59. WiFi Recapitulates
Ethernet Evolution
Originally Considered a “Toy”
Started out as LAN evolved to MAN
“Good Enough” and much less expensive
Designed by NetHeads, not BellHeads
16

60. WiFi Recapitulates
Ethernet Evolution
Originally Considered a “Toy”
Started out as LAN evolved to MAN
“Good Enough” and much less expensive
Designed by NetHeads, not BellHeads
Continually pushed beyond original
limitations, first by proprietary extensions,
that migrate to standards
16

61. WiFi Recapitulates
Ethernet Evolution
Still at the
Hub & Bridge
Stage Compared to
Ethernet Evolution
16

62. Mesh: Ideal Architecture
for Unlicensed Bands
17

63. Mesh: Ideal Architecture
for Unlicensed Bands
• Take advantage of
17

64. Mesh: Ideal Architecture
for Unlicensed Bands
• Take advantage of
- Limited range
51
45
42 40
39
35 37
34
31
28
24 26
0
5
0
75
50
25
15
12
10
17

65. Mesh: Ideal Architecture
for Unlicensed Bands
• Take advantage of
- Limited range
- Low Cost
components
17

66. Mesh: Ideal Architecture
for Unlicensed Bands
• Take advantage of
- Limited range
- Low Cost
components
- Good amount of
Spectrum
17

67. Mesh: Ideal Architecture
for Unlicensed Bands
• Take advantage of
- Limited range
- Low Cost
components
- Good amount of
Spectrum
- Millions of Nodes
17

68. Not Yet Near the Ideal
18

69. Not Yet Near the Ideal
Some use 2.4Ghz for
backhaul & access!
18

70. Not Yet Near the Ideal
Some use 2.4Ghz for
backhaul & access!
Uses standard 802.11
CSMA protocol
18

71. Not Yet Near the Ideal
Some use 2.4Ghz for
backhaul & access!
Uses standard 802.11
CSMA protocol
Gives great demo: Works
great unloaded
18

72. Not Yet Near the Ideal
Some use 2.4Ghz for
backhaul & access!
Uses standard 802.11
CSMA protocol
Gives great demo: Works
great unloaded
As usage grows,
contention is multiplied
& becomes unusable
18

73. Not Yet Near the Ideal
Some use 2.4Ghz for
backhaul & access!
Uses standard 802.11
CSMA protocol
Gives great demo: Works
great unloaded
As usage grows,
contention is multiplied
& becomes unusable
18

74. Today’s Best Practices for
Mesh
19

75. Today’s Best Practices for
Mesh
Use different bands for Mesh
& Access
19

76. Today’s Best Practices for
Mesh
Use different bands for Mesh
& Access
Coordinate transmissions &
directional antennas
19

77. multi-node and
DELIVERS INDUSTRYÊÂS HIGHEST THROUGHPUT,
hitecture. LOWEST LATENCY ACROSS MULTIPLE HOPS
h throughput
ess hops. Today’s Best Practices for
The award winning Access/One® Outdoor Wireless System (OWS) 3600 is the
industry’s highest highest throughput, lowest latency modular multi-radio mesh
node
Mesh
networking system. Utilizing Strix DMATM, the Access/One OWS delivers multi-
radio, multi-RF and multi-channel capabilities using
advanced algorithms to deliver high throughput over
multiple hops from the core to the edge of the network.
ver and self- Use different bandsself-tunes, self-configures and
The OWS intelligently for Mesh
healing mesh
& Access to optimize the overall performance and
self-heals
availability. The OWS architecture makes 802.11 a full
tion. duplex technology, moving traffic more efficiently
with voice,
tization.
Coordinate the network and utilizing different RF
through transmissions &
radio. directional antennas for network connectivity and
frequencies and channels
client access. RF Channels are selected dynamically,
network and making the network more resilient to interference than
tagging, with
standard mesh networks. Working closely together,
parameters Multiple Mesh Radios pluses
these features deliver higher throughput and lower
and minuses multiple hops, supporting real time
latency across
or roaming,
failover. voice, video, and data applications. The OWS scales
interface efficiently
of intuitive OWS is the most secure mesh and econ-
the network, networking systemavailable, with omically
s. the tools to authenticate users,
minimizing the number of wired
encrypt wireless traffic, and
anagement monitor network activity all termination points required in the
P, CLI over provided as standard features. network, greatly reduces deployment
/HTTPS, Secure private networks can and operating costs and the Total Cost
operate in tandem with open of Ownership (TCO). Extended
19

78. Today’s Best Practices for
Mesh
Use different bands for Mesh
& Access
Coordinate transmissions &
directional antennas
Multiple Mesh Radios pluses
and minuses
Multiple tiers of Wireless
backhaul
19

79. Today’s Best Practices for
Mesh
Use different bands for Mesh
& Access
Coordinate transmissions &
directional antennas
Multiple Mesh Radios pluses
and minuses
Multiple tiers of Wireless
backhaul
Expect < 1Mbps delivered
19

80. State of Muni-Wireless
(US Centric View)
20

81. State of Muni-Wireless
(US Centric View)
20

82. State of Muni-Wireless
(US Centric View)
First phase build-outs
20

83. State of Muni-Wireless
(US Centric View)
First phase build-outs
Significant Learning Curve
20

84. State of Muni-Wireless
(US Centric View)
First phase build-outs
Significant Learning Curve
First Generation Equipment
20

85. State of Muni-Wireless
(US Centric View)
First phase build-outs
Significant Learning Curve
First Generation Equipment
Be prepared for negative Hype Cycle
People’s expectations too high
20

86. State of Muni-Wireless
(US Centric View)
First phase build-outs
Significant Learning Curve
First Generation Equipment
Be prepared for negative Hype Cycle
People’s expectations too high
Its still very early
20

87. WiMax?
21

88. WiMax?
If WiFi recapitulates
the evolution of Ethernet;
WiMax recapitulates the
evolution of all of Ethernet’s
competitors
21

89. WiMax?
22

90. WiMax?
No real advantage when comparing unlicensed
WiMax & WiFi
22

91. WiMax?
No real advantage when comparing unlicensed
WiMax & WiFi
Licensed WiMax can be useful
(ATM was useful for some things too)
22

92. WiMax?
No real advantage when comparing unlicensed
WiMax & WiFi
Licensed WiMax can be useful
(ATM was useful for some things too)
Getting a License can be difficult & Expensive
22

93. WiMax?
No real advantage when comparing unlicensed
WiMax & WiFi
Licensed WiMax can be useful
(ATM was useful for some things too)
Getting a License can be difficult & Expensive
Very good for feeding WiFi Mesh
22

94. WiMax?
Beware of Hype
Very few deployments of “real” WiMax
No deployments of Mobile WiMax
23

95. Wireless Tech of the
Future
24

96. Wireless Tech of the
Future
• Ultrawideband
- Ultra Short Range
- 2 to 3 x bandwidth
over 802.11n
24

97. Wireless Tech of the
Future
• Ultrawideband
- Ultra Short Range
- 2 to 3 x bandwidth
over 802.11n
• 60 - 70 Ghz
- Extreme Bandwidth &
Directionality
24

98. Wireless Tech of the
Future
• Ultrawideband
- Ultra Short Range
- 2 to 3 x bandwidth
over 802.11n
• 60 - 70 Ghz
- Extreme Bandwidth &
Directionality
• Super Mesh
- 802.11s evolution?
- Short Range is good
- More Bandwidth!
24

99. Wireless Tech of the
Future
25

100. Wireless Tech of the
Future
No Silver Bullets
on the Horizon
25

101. Wireless Common
Sense
Shifting the Collection of Prejudices
Robert J. Berger
Internet Bandwidth Development Consulting
rberger@ibd.com
26