User guide

45 Mbps Backhaul User Guide
Issue 3, December 2004 Page 15 of 113
2 Product Architecture
The 45 Mbps Backhaul consists of an identical pair of units deployed one at each end of the link. The radio link
operates on a single frequency channel in each direction using Time Division Duplex (TDD). One unit is
deployed as a master and the other as a slave. The master unit takes responsibility for controlling the link in
both directions.
The non-Line-of-Sight (NLOS) aspects of the product are provided by multi-beam space time coding, coupled
with Orthogonal Frequency Division Multiplex (OFDM) modulation with a dispersion capability of 10
microseconds in both directions.
The 45 Mbps Backhaul has been developed to operate within license exempt frequency bands, for example the
ETSI 5.8 GHz C band (5.725–5.850 GHz) and the USA 5 GHz ISM band (5.725-5.850 GHz). The 45 Mbps
Backhaul has been designed to coexist with other users of the band in an optimal fashion using a combination of
Transmit Power Control (TPC), Dynamic Frequency Selection (DFS) and Antenna beam shape.
In order to maintain link availability, the product employs adaptive modulation techniques that dynamically
reduce the data rate in severe or adverse conditions. To the data network the 45 Mbps Backhaul is implemented
as a learning bridge. A learning bridge builds up a picture 102of which addresses are connected to which port.
This means that it will not bridge a packet if it knows that the destination address is connected to the same port
on which the bridge saw the packet. Figure 5 illustrates the 45 Mbps Backhaul layer diagram.
Figure 5 45 Mbps Backhaul Layer Diagram
The 45 Mbps Backhaul functionality has been extended to encompass the IEEE 802.1q sub specification IEEE
802.1p. IEEE 802.1p allows the Ethernet packets to be extended by 4 bytes to include the IEEE 802.1q VLAN
Tag and VLAN Priority/ID with VLAN ID set to 0 and the packet priority set to 0-7. The 45 Mbps Backhaul
will forward all VLAN tagged packets regardless of the VLAN ID value. Packets with a value of Priority
greater than 0 will be given priority over other packets.
Each unit in the link is manageable through an IP connection. Standard IP protocols are utilized for all
management functions e.g. HTTP, SNMP, etc.
The 45 Mbps Backhaul is fully software upgradeable. New software images are first download from the
Motorola website http://www.motorola.com/canopy to a convenient computer. The image is then uploaded to
the ODU via the web management page described in section 6.3.4 “Software Upgrade”. The compressed image
is first loaded into RAM and check-summed. If the compressed image transfer has completed successfully the
image is decompressed and written to Flash memory. On completion of this process the unit can be rebooted to
use the newly uploaded image. Should this process fail the unit will revert to a protected compressed image
installed during manufacturing to allow the unit to be recovered.