System Description

MCIL -WIPLL-SDN_R2_00 Marconi Communications Ltd. 4-1 of 4-10
BSRBSR
4.1. Base Station Radio
A BSR is the centre of a WipLL sector. It has several roles in both the MAC layer as
well as in the networking and transport layers. In the MAC layer the BSR is
responsible for synchronizing the SPRs in terms of timing, frequency hopping
sequence, authentication, and control - allowing (or not) the transmission of data
within the sector.
At the network layer the BSR performs routing functions between the base station's
Ethernet network and the wireless stations, containing a routing table that can
support up to 126 stations addresses. The transport layer at a BSR makes decisions
on how to support an application in terms of bandwidth, delays and mode of
operation.
There are two modes of operation - Pre-emptive Polling (PPMA) and Time Division
Multiple Access (TDMA). Although the WipLL BSR employs PPMA, it also
recognizes the traffic type and emulates TDMA where necessary.
The BSRs are connected to the wired backbone through a BSDU with a 10Base-T
Ethernet connection which allows a cable length of up to 100 meters.
Each of the BSRs contains two internal high gain, flat plate antennas, to support
functionality of antenna diversity which helps to overcome multi-path effects.
There are typically several BSRs at each base station site. Each BSR can cover an
azimuth angle (yaw) of 60 degrees and therefore 6 BSRs can provide a full 360
degrees coverage of the entire cell if needed. The antenna may also be tilted
vertically (pitch) to reduce interference between adjacent BSRs. The maximum
number of radios that can be connected depends mainly on the radio bandwidth
allocated to the system. 6 radios can coexist at the base-station providing as much
Chapter
4