Reference Manual

Packet Data Services
19 Packet Data Services
This chapter covers packet data services, including handling of the link,
GSL, between RBS and PCU, as well as Terrestrial Link Supervision
(TLS) and Link Quality Supervision.
19.1 References
/GSM:05.02/CCITT G.821/ CCITT Blue book, rec G.821 Vol III -
Fascicle III.5 "Digital Networks, digital
sections and digital line systems"
19.2 Functions
19.2.1 Terrestrial Link Supervision for GSL
This function is used when the PDCH is activated, primarily to supervise
that a correct PCU frame synchronization is maintained downlink, and
that the received frame type is expected. The function decides when the
connection is considered lost. TLS supervision can be controlled using
a flag indicating supervision on/off, according to the cases below.
TLS on active subchannel is set on:
Terrestrial link used for PDCH traffic.
Terrestrial link supervision is active.
TLS on active subchannel is set off:
Terrestrial link used for PDCH traffic.
No supervision.
If, for an activated channel, disturbances on the link between RBS and
PCU result in a connection lost decision, a CONNECTION FAILURE
message with cause value remote PCU failure is also sent to the BSC.
This is done only when the "TLS active" flag is indicating supervision
on.
19.2.2 PCU-RBS LInk Quality Supervison
The Link Quality Supervision function evaluates and reports the
Terrestrial Channel link quality for a specified period of time.
Measurements are made on the frames received from PCU, and are
related to the 16 kbit/s link.
Just a subset of the bits are known in advance, for example,
synchronization bits. Bit error measurements are only taken on these
bits to form an equivalent set of measuring counters.
Results of measurements are added to the ACTIVE measuring counters.
19.2.3 Packet Data
Upon reception of a CHANNEL ACTIVATION message from the
BSC, the startup of the GSL is initiated.
EN/LZT 720 0008 R1A
2001-06-26
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