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

56789

01234

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