Meshdynamics MD5, MD2 User Manual

MD4000 Product Family

Hardware Installation Instructions

Terminology

Wireless Backhaul

RELAY 1

Ethernet

Root and Relay Nodes

Mesh Networks provide long range connectivity by relaying packets from one mesh node to another, like a bucket brigade. The end of the bucket brigade terminates at the root – which connects to the Ethernet. (above) Relays connect to the root or other relay nodes to form a wirelessly linked chain.

Upstream & Downstream

Upstream implies closer to the Ethernet. The root is upstream of relay 1.

Wireless Uplinks and Downlinks. The Ethernet link is the uplink (upstream link) connection for the root. The root has is a wired uplink. Its “backhaul” is the wired network.

Relays have wireless uplinks through a upstream downlink radio. Downlink radios act like Access Points (AP) : they send out a beacon. Uplink radios act like clients – they do not send out a beacon.

A wireless radio card in the laptop can inform you of the presence of downlinks but not of uplinks. Downlinks beacon, Uplinks do not.

RELAY 2

Ethernet

ROOT

DOWNLINK

UPLINK

The uplink and downlink radios form a wireless backhaul path. AP radios operate in the 2.4GHZ band to service 11b/g clients.

802.11a wireless devices may be serviced by the 5.8G downlink.

SERVICE

RELAY

Thus, both 802.11a and 802.11b/g client access is supported. Backhaul radios operate in 5.8GHZ band to avoid interference with

the 11b/g 2.4GHZ AP radio (shown pink, right). Note: Do not use

any other modules not approved with this device other then the ones that were tested which are MD2 FCC ID: UZU-MD2 and MD5 FCC ID: UZU-MD5

To summarize, there are 4 types of “links” to Structured Mesh A wired uplink to provide Ethernet connectivity. This connects the Root node to the wired network.

A wireless downlink to provide wireless connectivity. Acts like an AP for the uplink. Typically 5.8G. A wireless uplink to connect to upstream mesh nodes. This is a “client” to the downlink. Typically 5.8G. A AP radio for clients. Typically 2.4G with support for both b and g clients.

In our standard offering, the 11a uplink, the 11a downlink and 11b/g service are 3 separate radios (Fig 2.2).

products:

The MD 4000 Product Family

The MD4000 Modular MeshTM products support up to 4 radios in a single enclosure. Slots 0, 1 house one uplink and one downlink radio operating on non-interfering channels but in the same frequency band. They are both 2.4G or both 5.8G. radios.

Note: Do not use any other modules not approved with this device other then the ones that were tested which are MD2 FCC ID: UZU-MD2 and MD5 FCC ID: UZU-MD5

Note: This two radio backhaul differs from competing mesh products. The differences are explained at: www.meshdynamics.com/WhyStructuredMesh.html

Slot 2 houses a 2.4G AP radio for client connectivity. 2.4G radios can be set to b. b and g or g only modes. Slot 3 can house a 2nd downlink, 2nd AP or a scanning radio for mobile mesh module - that form part of the meshed backhaul in dynamic infrastructure mesh networks.

The 2 Ethernet ports on each module may be used to interface to cameras for high resolution video over mesh. A 2nd (slave) module attaches via Ethernet to provide a total of 8 radios. Operating temperature range is -40 to +85 Celsius. The die cast weather proof enclosure is NEMA 67 rated.

2.4G Backhaul Products (Standard Configurations)

0 3

Uplink Downlink Service

2.4G 5.8G

2 1

MD4220 MD4320 MD4325

1. MD4220-BBxx: 2-Radio module 2.4G uplink and downlink Backhaul (BH). .

2. MD4320-BBBx: 3-Radio module 2.4G sectored BH slots 0,1 and 2.4G AP radio in slot 2.

3. MD4325-BBxB: 3-Radio module 2.4G BH, Downlink also acts as AP. A 2.4G Mobility Scanner in slot 3.

2 1

Scanner

5.8G Backhaul Products (Standard Configurations)

MD4250 MD4350 MD445 MD4458 MD4455

1. MD4250-AAxx: 2-Radio module 5.8G BH uplink and downlink Backhaul (BH).

2. MD4350-AABx: 3-Radio module 5.8G BH and 2.4G AP radio in slot 2. AP modes may be b, g, or b & g.

3. MD4452-AABA: 4-Radio module 5.8G BH and 2.4G AP radio. Second sectored 5.8G downlink in slot 3.

4. MD4458-AABB: 4-Radio module 5.8G BH and 2.4G AP radios (two) in slots 2, 3 for sectored service.

5. MD4455-AABA: 4-Radio module 5.8G BH and 2.4G AP radio in slot 2. 5.8G Scanner in slot 3

0 3

2 1

0 3

2 1

Notes:

1. All 2.4G Downlinks and APs may be configured to support b only, g only, or b & g client connectivity

2. All 5.8G Downlinks may be configured to provide 802.11a client connectivity

3. All radios interfaces may be configured to provide IEEE 802.11e differentiated Class of Service

How Far Apart Should Backhaul Radios be Placed?

Case #

For a “good signal”, the fraction of the energy from the transmitter that reaches the receiver should exceed the receiver radio’s receive sensitivity. If not, the ACK will not be sent and re-transmission occurs. Throughput then declines. The rate control software on the mesh module is sampling the link quality between its uplink and the parent downlink. If the throughput declines, it lowers the transmit rate, since transmit power and receive sensitivity improve at lower transmit rates. The throughput is thus adjusted based on signal quality.

Degradation of signal quality over distance is expressed by the free space path loss relationship:

Path_Loss = 20*log(Freq) + Decay_* 10*log(Dist) – K where

Path_loss: Path Loss in dBm Freq: Frequency in MHZ Decay : Varies based on RF environment, line of sight etc. Dist: Distance between the two mesh nodes (in meters) K: Constant.

Transmit power from the radio and antenna gains offsets this path loss. The adjusted value must then exceed the receiving radio receive sensitivity for transmissions to be “heard”. Table A1 shows backhaul distances for a 5.8G radio transmitting with 20 dBm transmit power radio and over two 8 db omni-directional antennas. Acceptable receive sensitivity is set at – 65 dBm. Decay is varied from 2.0 (rural, open space) to 2.4 (more urban settings, non line of sight, occlusions, interference). Notice how range is dramatically affected by changes in Decay.

RS (dBm) TR (dBm) Decay Ant 01 Ant 02 Freq (MHZ) Dst (m) Dst (Ft)

01 65 20 2.0 8 8 5800 461 1512

Table A1

02 65 20 2.2 8 8 5800 264 866 03 65 20 2.4 8 8 5800 166 544

Increasing antenna gain from 8 dBm to a 14 dBm panel on the downlink reduces this path loss (Table A2).

01 65 20 2.0 14 8 5800 921 3017

Table A2

02 65 20 2.2 14 8 5800 495 1622 03 65 20 2.4 14 8 5800 295 967

Panels have a less dispersed beam pattern than omni-directional antennas. Their restricted field of view also makes them less sensitive to noise in the vicinity. In very noisy settings, more radio transmit power may be needed. Two downlinks doubles transmit radio power from 20 dBm to 23 dBm. (Table A3).

Table A3

01 65 23 2.4 14 8 5800 394 1290

Range is also effectively doubled by changing from 5.8G to a 2.4G backhaul. Compare Table A4 with Table A1.

01 65 20 2.0 8 8 2400 1115 3655

Table A4

02 65 20 2.2 8 8 2400 589 1931 03 65 20 2.4 8 8 2400 346 1135

Unfortunately, the 2.4G RF space is “polluted” with multiple AP and client devices. 2.4G Backhauls are best limited to rural areas with low subscriber density and low 2.4G RF interference. If 2.4G Backhauls are critical, reduce 2.4G RF interference on the backhaul with a panel antenna and its more focused beam. The 4320 3-radio 2.4G backhaul product is intended to be used with panels on the backhaul and an omni for the 3rd 2.4G AP radio .

Suggestions

In rural areas or low client density situations, use 2.4G backhauls preferably with panels to reduce RF interference from other 2.4G devices. In all other scenarios use 5.8G Backhauls. Start with two 8 dBm 5.8G omni-directional

250m apart, with clear line of sight and no metal obstructions with 1.5m of the antennas. Increase node spacing

till throughput begins to decline – look at the heart beats shown on the NMS. For noisy 5.8G environments, reduce path loss with panels and/or double the transmit power with dual downlinks (4452).

How Far Apart Should AP Radios be Placed?

Case #

RS (dBm) TR (dBm) Decay Ant 01 Ant 02 Freq (MHZ) Dst (m) Dst (Ft)

01 65 20 2.0 8 8 5800 461 1512

Table B1

Table B2

Table B1 and B2 indicate that the range of the 2.4G radios backhaul will always exceed that of the 5.8G backhaul. The theory does not take into consideration two salient real-world differences between backhauls and AP radios:

1. Antennas are generally mounted on roof tops. The backhaul antennas generally have free space line of sight connectivity. However the antennas of the AP, also mounted on roof tops, must connect with clients on the ground. The path from AP antennas to the 2.4G client radios is often not clear line of sight. Additionally, there is significant

2.4G RF interference in urban areas. With higher decay the range is significantly reduced (Table B3).

Table B3

2. Clients on the same AP also can also create RF interference due to Hidden-Node effects. The AP has big ears (high receive sensitivity). Even though clients radios are much lower power, the AP can hear them. It also has a loud voice (high transmit power) so clients can hear it. But clients may not be able to hear each other such as when clients are on opposite ends from each other. The clients are thus “hidden”.

02 65 20 2.2 8 8 5800 264 866 03 65 20 2.4 8 8 5800 166 544

01 65 20 2.0 8 8 2400 1115 3655 02 65 20 2.2 8 8 2400 589 1931 03 65 20 2.4 8 8 2400 346 1135

01 65 20 2.6 8 8 2400 221 724 02 65 20 2.8 8 8 2400 150 492 03 65 20 3.0 8 8 2400 108 352

HIDDEN NODE EFFECT

Fig. 6.1

AP hears both Clients. But clients do not hear each other.

Radio is a shared medium: only one device should be active at any time. If clients are “hidden” from each other, then they could be talking at the same time, causing RF interference and loss of signal quality. Table B4 indicates that clients hear each other only within 100 meters .In noisy or occluded settings it could be as low as 50 meters.

RS (dBm) TR (dBm) Decay Ant 01 Ant 02 Freq (MHZ) D (m) D (Ft)

01 65 15 2.0 0 0 2400 99 326

Table B4

02 65 15 2.2 0 0 2400 65 214 03 65 15 2.4 0 0 2400 46 151

Suggestions

If omni-directional antennas are being used, select ones with down tilt. This focuses the beam downwards – where the clients. This also reduces the AP range so clients are less spread apart. The hidden node effect is thus curtailed. For noisy /occluded environments, reduce path loss with panels and/or double transmit power with dual AP radios.

Note: Range Calculation Sheet location: www.meshdynamics.com/DOWNLOADS/MDRangeCalculations.xls

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