User guide

45 Mbps Backhaul User Guide
Issue 3, December 2004 Page 39 of 113
By default the Target Receive Modulation Mode is 64QAM 7/8. The value in brackets shows the maximum
unidirectional data for the current modulation / ranging mode combination.
Maximum Transmit Power This specifies the maximum transmit power in dBm of the system, it is country
dependent and although the user can change this it will be limited to that country’s regulations.
ARQ State Automatic Repeat reQuest (ARQ) is a mechanism where packets lost due to transmission errors over
the wireless link are retransmitted rapidly. The retransmission helps to prevent TCP congestion mechanisms
from inadvertently interpreting intermittent packet loss as network congestion. ARQ must be enabled on both
ends of the Point-to-Point link for it to function.
IP Address Internet protocol (IP) address. This address is used by the family of Internet protocols to uniquely
identify this unit on a network.
Subnet Mask A subnet allows the flow of network traffic between hosts to be segregated based on a network
configuration. By organizing hosts into logical groups, subnetting can improve network security and
performance.
Gateway IP Address The IP address of a computer!/!router on the current network that acts as a gateway. A
gateway acts as an entrance!/!exit to packets from / to other networks.
Ethernet Configuration This enables the Ethernet configuration to be forced rather than auto negotiated. The
configuration should only be forced if you are having problems with auto negotiation. You must ensure that you
configure both this unit and the Ethernet port to which it is connected identically. If you force a fixed Ethernet
Configuration on the 45 Mbps Backhaul unit then you MUST also force the same fixed configuration on the
equipment to which it is connected. If you fail to force the configuration of the connected equipment, its
automatic configuration mechanisms will normally cause a duplex mismatch, and you will receive greatly
reduced throughput!
Ethernet Auto Mdix This enables/disables the Auto Medium Dependent Interface (MDI)/Medium Dependent
Interface Crossover (MDIX) capability.
Local Packet Filtering When Local Packet Filtering is Enabled, the bridge learns the source MAC addresses of
devices transmitting Ethernet packets on the local Ethernet network, and only bridges packets to the remote unit
if the destination MAC address has not been learnt as a 'local' device. When Local Packet Filtering is Disabled
the bridge does not learn the source MAC addresses of devices transmitting Ethernet packets on the local
Ethernet network, and bridges ALL Ethernet packets received to the remote unit. Local Packet Filtering should
only be disabled when external routing hardware is present.
Ethernet Compression When Ethernet compression is enabled all compressible Ethernet packets are transmitted
over the wireless link using a compressed data format. This will have the net effect of increasing wireless link
traffic throughput. Because the compression techniques used in the 45 Mbps Backhaul are CPU intensive,
compression is only applied to modulation modes BPSK 1/2, QPSK 1/2 and QPSK 2/3. The net effect of
compression is solely dependant on the individual packet compressibility (entropy). Random data will not
produce good packet compression, however ASCII text and other non random data sources will produce an
acceptable level of compressibility.
All the above attributes are non-volatile, once set they will be used by the unit even after a power on reboot. A
number of attributes, such as IP Address, Subnet Mask and Gateway IP Address will require a reboot before
they are used. If any of these attributes are changed a reboot screen appears asking the user to verify the reboot.
(see Figure 14)