ZXG10-OB06 (V1.0) Integrated Outdoor GSM Base Station Technical Manual
36
Confidential and Proprietary Information of ZTE CORPORATION
•
I-frame multi-frame operation
•
UI-frame operation
I - f r a m e M u l t i - f r a m e O p e r a t i o n
The L3 message is sent in the information frame mode, which requires the
confirmation from the receiver. This mode provides a whole set of control
mechanism for error recovering and flow control. It also deals with the
establishment mechanism and release mechanism for multi-frame
operations.
Figure 16 shows I-frame structure.
F
I G U R E
1 6
–
L A P D
F
R A M E
S
T R U C T U R E
flag
Address
Control
Information
FCS
flag
SAPI
TEI
N(S)
N(R)
1
0-260
2
1
LAPD frame contains the following fields:
•
Address field: The address field contains the following two identifiers:
•
Terminal Equipment Identifier (TEI): It performs addressing for
different units through TEI in the Abis interface link.
•
Service Access Point Identifier (SAPI): In general, a unit has
multiple functional entities. The functional address SAPI identifies
the logical physical links between different functional entities. Links
of the three kinds of information are distinguished by SAPI as
below:
•
SAPI=0 represents the signaling link
•
SAPI=62 represents the O&M link
•
SAPI=63 represents the management link of the LAPD layer
•
Control field: It contains to further fields:
•
N(S) represents the sending and I-frame’s serial number, currently
sent by the sending end.
•
N(R) represents the receiving serial number, the expected sending
serial number of the next I-frame. N(R) predicts the instruction
from the receiving end.
•
Frame Check Sequence (FCS): It performs the error code detection.
