located in canton, texas - mum - mikrotik
TRANSCRIPT
Located in Canton, Texas
Handle a wide range of networking services, I handle all the wireless solutions
I have been working in the IT field for 15 years
I’ve been using Mikrotik products for the last three years
Began experimenting with Wireless N in 2009
Since the ratification of the N standard, all new construction links have utilized Wireless N
Provide an introduction to Wireless N History
Feature Highlights
Explain who will benefit from using Wireless N Pros and Cons to using it
Explain ROS settings in detail as they relate to Wireless N
Provide examples
Troubleshooting Tips
Increased throughput (up to 600 Mbps) 300 Mbps for Mikrotik
250+ Mbps of actual through-put
Increased range
1st Frequency independent standard
Added MIMO (Multiple In Multiple Out)
Added a new standard for 40MHz Channels
Added MCS (Modulation & Coding Schemes)
September 11, 2003 – TGn was formed
May 2006 – draft 1 was established
February 2007 – draft 2 was approved
June 2007 – WIFI alliance announces 802.11n draft 2 certification process
September 11, 2009 – draft 11 was approved
October 29, 2009 – Wireless N amendment to the 802.11-2007 standard was published
ROS 4.0 Beta 3 – Support for Atheros based Wireless N cards was introduced
Anyone using PTP links (regardless of the number of antenna chains)
Most new constructions PTMP, but not all older PTMP
Most indoor installations
802.11n added several new connection concepts: New outlook on antenna diversity
Spatial Multiplexing
New ways to handle 20MHz & 40 MHz Channels
The ability to change the Guard Interval
Modulation & Coding Schemes
New power management standards
New terms and acronyms
HT – High Throughput
Antenna Chain – includes the Antenna, coax, pigtail, as well as an independent transmitter and/or receiver
802.11n currently does not support WDS or nstrememodes (compatibility is in beta)
Must have upgraded ROS license to 4.x in order to use any of the Wireless N cards
MIMO Notation –
#TX Chains X #RX Chains
2x2 & 3x3
Antenna Diversity and/ or
Spatial Multiplexing
2x2 & 1x1
Antenna Diversity Only
1x1 & 3x3
Antenna Diversity Only
AP Client
2x2 2x2
15 2 64-QAM 130 270 144.4 300
MCS IndexNumber of
spatial streams
ModulationData Rate (in Mbps)
(GI = 800ns)Data Rate (in Mbps)
(GI = 400ns)
20MHz 40MHz 20MHz 40MHz
Client
2x2 1x1
MCS IndexNumber of
spatial streams
ModulationData Rate (in Mbps)
(GI = 800ns)Data Rate (in Mbps)
(GI = 400ns)
20MHz 40MHz 20MHz 40MHz
AP
7 1 64-QAM 65 135 72.2 150
Client
1x1 2x2
MCS IndexNumber of
spatial streams
ModulationData Rate (in Mbps)
(GI = 800ns)Data Rate (in Mbps)
(GI = 400ns)
20MHz 40MHz 20MHz 40MHz
AP
7 1 64-QAM 65 135 72.2 150
Client
1x1 1x1
MCS IndexNumber of
spatial streams
ModulationData Rate (in Mbps)
(GI = 800ns)Data Rate (in Mbps)
(GI = 400ns)
20MHz 40MHz 20MHz 40MHz
AP
7 1 64-QAM 65 135 72.2 150
Installing new equipment or upgrading older systems can still be advantageous over 802.11 a/b/g A connection of rate of up to 150 Mbps is possible
Approximately 125 Mbps of actual throughput
Some improvement on distance is still possible, but at the cost of throughput
802.11n handles interference better than legacy systems
WirelessCard
FormFactor
AntConnector
AntennaChains
R2N mPCI 2x U.FL 2x2 w/SM
R5nH mPCI 1x MMCX 1x1
R52N mPCI 2x U.FL 2x2 w/SM
R52n-M mPCI 2x MMCX 2x2 w/SM
R52Hn mPCI 2x MMCX 2x2 w/SM
Switched Antenna Diversity – Uses which ever antenna receives the strongest signal
Prior to 802.11n using more than 1 antenna was not possible
Multi-path propagation caused significant interference
Antenna Diversity & Maximal Ratio Combining adds signals together
DSP & MIMO techniques take advantage of multi-path propagation
01234
01234
Sends and receives different blocks of info over different Spatial Streams effectively doubling the bandwidth
Both the AP and the Client must be configured to use SM
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Antenna Chains should always be at least ½ wavelength away from each other. On the 2.4GHz band that is approximately 2.5 inches
On the 5 GHz band that is approximately 1 inch
Only beam forming uses exact spacing Adaptive beam forming has not been implemented yet
Hardware configurations to utilize beam forming are outside the scope of this presentation
Symbols are groups of individual bits
The Guard Interval is a time delay between symbols to account for the late arrival of a symbol.
A GI that is too short will cause Inter-Symbol Interference (ISI).
802.11 a/b/g radios use a GI of 800 us (nanoseconds)
802.11 n can use a GI of 400 us which increases BW by approximately 10%
Symbol B Symbol A
Symbol B Symbol A
Time
Long = 800nsAny = Best Fit
Selecting long will provide a more stable link
MCS IndexNumber of spatial
streamsModulation
Data Rate (in Mbps)(GI = 800ns)
Data Rate (in Mbps)(GI = 400ns)
20MHz 40MHz 20MHz 40MHz
0 1 BPSK 6.5 13.5 7.2 15
1 1 QPSK 13 27 14.4 30
2 1 QPSK 19.5 40.5 21.7 45
3 1 16-QAM 26 54 28.9 60
4 1 16-QAM 39 81 43.3 90
5 1 64-QAM 52 108 57.8 120
6 1 64-QAM 58.5 121.5 65 135
7 1 64-QAM 65 135 72.2 150
8 2 BPSK 13 27 14.4 30
9 2 QPSK 26 54 28.9 60
10 2 QPSK 39 81 43.3 90
11 2 16-QAM 52 108 57.8 120
12 2 16-QAM 78 162 86.7 180
13 2 64-QAM 104 216 115.6 240
14 2 64-QAM 117 243 130.3 270
15 2 64-QAM 130 270 144.4 300
Modulation & Coding Schemes
•Must select configured on the Date
Rate Tab
•MCS 0-7 uses 1 spatial stream
•MCS 8-15 uses 2 spatial streams
Disabled = 20MHz Wide
Above & Below Control = 40MHz Wide
40MHz HT channels use the adjacent channel selected by either above or below control
Both the AP & the Client must have the same values
Method of frame aggregation where multiple 802.3 frames have the headers removed and the data combined into a new 802.11 frame.
0-8192
Default is best value
Similar to AMSDU
A method of frame aggregation
AP & Clients must have the same values
Default is “best effort” -best value
Changing from default will cause problems for VOIP and streaming video
Troubleshoot 1 antenna chain at a time
MIMO configurations will hide problems
Change GI to Long
Change HW Retries from 4 to 7-10
If using MIMO do not have the antennas perfectly tuned – force seperation