Funk-Electronic Piciorgros GmbH
TTS-2000A documentation
V1.20 - Page 18 of 57
5.3.1
Serving Cell Information
RDC
RDC = Radio Downlink Counter. When a radio is attached to a serving cell it is
continuously monitoring the quality of the downlink signal it is receiving from the base
station. When doing this it maintains the Radio Downlink Counter. The starting value
for this counter is announced by the cell in the RADIO_DOWNLINK_TIMEOUT field
of the cells SYSINFO messages.
If the radio is unable to decode the Access Assignment Channel (AACH) in a downlink
message, the RDC is decreased by N
×
N.210 (where N.210 is a constant which defines
the quality threshold for the MS which in the case of the TTS is set always 4, and N is
equal to the number of successive timeslots the radio is receiving and decoding, so in
the TTS this is always 1).
If the radio successfully receives and decodes the AACH in a message, the RDC shall
be increased by N but shall not be increased above the value of the announced
RADIO_DOWNLINK_TIMEOUT.
Radio downlink failure is declared when the RDC falls below 0. If this happens, the
radio will perform an immediate a cell reselection. The value of N.210 controls the
AACH message error rate threshold at which radio downlink failure occurs, so for
example, in the TTS N.210 = 4, so there is a ratio of 4 to 1 between failure and success
counting to give a decreasing RDC. This will occur when the message error rate
exceeds 20 %. Therefore, a continuous message error rate greater than 20 % will cause a
radio downlink time-out and a cell reselection.
C1 value
The C1 value is known as the Pathloss and is calculated for the serving cell by the
following formula,
C1 = RSSI – RXLEV_ACCESS_MIN - Max(0, MS_TXPWR_MAX_CELL - P
ms
)
where:
RSSI = the averaged receive signal level at the MS
RXLEV_ACCESS_MIN = the minimum permissible receive level allowed at the MS
(announced in the cells SYSINFO message, and displayed as ‘Radio Access Level’
under Network Information by the TTS)
MS_TXPWR_MAX_CELL = the maximum MS transmit power permissible in this cell
(announced in the SYSINFO message from the cell and displayed under Network
Information by the TTS)
Pms = the maximum transmit power of the radio. Since the TTS does not transmit, this
value is always assumed to be the same as the MS_TXPWR_MAX_CELL being
announced by the cell. All parameters are in dB.
