INTRODUCTION
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2-5
COM-00-21-03 OCTOBER 2021
Version No.: A
The DLSF and ULSF may be further divided into zones that are identical across the entire
system. Zones may be able to make the network more efficient during certain conditions. For
example, an RS in the middle of the sector serving area is less susceptible to interference from
other sectors and generates less interference to the remotes of other sectors. Therefore, these
remotes may use a more aggressive frequency reuse scheme than remotes in the sector that
are located closer to the sector boundaries. The DLSF and ULSF can be partitioned into two
zones. One zone will be used for remotes at the boundaries of the sector with a less aggressive
frequency reuse scheme and the other zone will be used for remotes near the center of the
sector with a more aggressive frequency reuse scheme. This is known as fractional frequency
reuse (FFR)
2.4.1 Filtering Architecture
The Airlink Mercury radio is designed to operate over a wide range of frequencies and channel
configurations while minimizing interference. The Airlink Mercury radio can operate from 100
MHz to 1 GHz using channel sizes from 12.5 kHz to 50 KHz. At QPSK using convolution coding
(CC) rate of ½, the receiver sensitivity ranges from -114 dBm for a 12.5 kHz channel.
The Airlink Mercury radio incorporates filtering at the following stages:
●
Configurable digital filter which is embedded in the CMX 983 front-end chip
●
Base band Analog Filter which is embedded in the CMX 994 front-end chip.
The configurable digital filters are software configurable filters embedded on the Airlink Mercury.
These filters are very specific, narrow filters. When the adjacent channel interferer’s power is
greater than the Airlink signal, the gain in the receive chain needs to be reduced to avoid
saturation. The stronger the interferer, the lower the receive gain. As the receive gain is
reduced, the Airlink signal occupies a smaller portion of the analog to digital converter (ADC)
amplitude range which reduces the resolution and increases the quantization noise until a level
at which the signal can no longer be decoded.
2.5
Security Architecture Authentication and Authorization
Authentication is the act of verifying the user is who they claim to be. Authorization is the
process of giving the user permission to access a specific resource or function. Both functions
are handled by the Authentication, Authorization, and Accounting (AAA) server using multi-
factor authentication.
Airlink device authentication uses Extensible Authorization Protocol – Transport Layer Security
(EAP-TLS) with X.509 authentication. Local access to the Airlink Base Station and Remote
device is authenticated by role-based usernames and passwords. Access to a device’s memory
is read/write restricted according to roles.
Remote access to these devices is controlled via Airlink NMS and Airlink Apollo with secured
authentication SNMPv3, SFTP, and SSHv2. The Airlink NMS and Airlink Apollo (when
accessible remotely) are HTTPS and authenticated through the AAA server. The Airlink system
authenticates devices before establishing network connections. Certification is handled by the
