User's Manual

AN-50 System User Manual
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The AN-50 system utilizes Redline’s advanced Medium Access Control (MAC) design to
provide efficient transmission of data in both PTP and PMP modes. In PMP mode, the
MAC incorporates a proprietary polling algorithm to support up to 256 individual
subscriber stations from a single base station operating in a single sector. Note that
multiple base stations can be installed on a single roof-top or tower to provide multi-
sector coverage.
A single sector AN-50 PMP implements a distributed wireless L2 switch, with one uplink
port located on the sector controller (master) distributing bandwidth to a variable number
of subscriber stations (slaves).
• Each subscriber station (or slave) is considered a separate wireless link.
• Each configured wireless link adds to the switch one slave port that is the
Ethernet port on the corresponding subscriber station. This is achieved
during provisioning.
• Each link (slave port) is assigned one ID that is used to manage both the
connection traffic and the wireless link.
• The switch supports one broadcast/multicast group called default group.
• The default group is assigned automatically to a fixed ID.
The AN-50 MAC utilizes a request/grant polling mechanism to determine which
subscriber station requires bandwidth. This is achieved by periodically polling each
subscriber station to determine if there is a request for bandwidth. If the SS requests
bandwidth then the MAC allocates the appropriate number of time slots, in both the
downstream and upstream direction, in accordance with the CIR rate limits specified for
that particular SS. The AN-50 PMP system supports 18 programmable CIR levels.
Through an external calculator the minimum Committed Information rate CIR rates
allowed for each SS can be determined. Note that a minimum CIR of 8kb/s implies
almost no CIR, and is referred to as Best Effort (BE) services.
With multiple subscriber stations vying for bandwidth, the MAC ensures that time slots
are allocated in a balanced manner, according to the different CIR levels, during periods
of over-subscription. For example, during peak times, the MAC will first deny time slot
allocations for everything above the provisioned CIR, and then reduce bandwidth in a
proportional manner to the remaining units with varying CIR levels and priorities. With
the support of CIR, the service provider can offer different grades of service to each end
user in a controlled manner based on their service level agreements or contracts