3. 1. OVERVIEW
1). V Interface
The digital interface between the access network
and the switch，including V1、V2、V3、V4、V5。
4. 2). The limitation of the V1～V4 interfaces.
V1 to V4 interfaces don’t support integrated access.
And the more important is : V1 to V4 are all not standard
interfaces, which hampers the development and use of the
V interfaces.
5. 3).THE FEATURE OF V5
the V5 interfaces are more open and standard, and it
has the ability of integrated access.
7. 5)、COMPARISON BETWEEN V5.1 INTERFACE
AND V5.2
V5.1 interface V5.2 interface
Support a PCM link Support 1-16 PCM links
Dynamic time slot
allocation and have the
The time slots at the user port
traffic concentration
and on the PCM link are
function
fixedly allocated, without the
traffic concentration function
8. V5.1 interface V5.2 interface
Has not the function of Has the function of
protecting the communication protecting the
channels communication channels (C
channels)
10. 1). Basic Concepts
Link: one 2048Kbit/s PCM system in the V5 interface.
Channel:one 64kb/s time slot in a link.
Including B channel and C channel.
11. Bearer channel (B-channel)：
the channel used to carry service
Communication channel ( C channel):
the channel used to carry signaling
12. logic C channel: Make up of by some protocol. Include
PSTN protocol, BCC protocol, Control protocol, Link control
protocol and protection protocol.
Physical C channel: The V5.2 interface has been allocated the
64Kbit/s time slots used to carry the logic C channel. TS16 is
always as the physical C channel.
13. Active physical C channel: The physical C channel
currently bearing the logic C channel.
Standby physical C channel: The physical C channel
currently bearing only the protection protocol is used as
the standby channel of the logic C channel carried on the
active physical C channel, that is, it is used to protect the
logic C channel.
14. Main link :The link has active physical C channel.
Sub-link: The link has Standby physical C channel.
18. 2). STRUCTURE Application Layer
Data Link Layer
Physical Layer
Figure: Structure model of V5 protocol
19. Application Application
Layer Layer
Data Link Data Link
Layer C channel Layer
Physical Physical
Layer Layer
B channel
Figure: PSTN call procedure through V5 interface
20. Application Application
Layer Layer
Data Link Data Link
Layer Layer
C channel
Physical Physical
Layer Layer
B channel
Figure: ISDN call procedure through V5 interface
21. 3)、Layer function description
A). Physical layer：
Providing physical transmission channels for all kinds of
messages.
The physical layer of the V5 interface is composed of
2048Kbit/s links.
22. TS 15, 16 and 31 of every 2048Kbit/s link can be used as the
physical C channel. The time slots that are not used as the
physical C channels shall be used as B-channels.
23. B). Data link layer:
Provide the transmission capability for Layer 3 message and the
data.
Including:LAPV5-EF（Encapsulation Function sub_layer）、
LAPV5-DL（Data link sub_layer）、AN frame relay sub_layer、
Mapping function sub_layer.
24. ISDN-TE
Q. PS Q.
BCC PS
Control Link Link
control
protection control
control
protection BCC
931 TN TN 931
LAPV5-DL LAPV5-DL Q.
921
Q. P Mapping Mapping
ET/L2
921 S
T LAPV5-EF
N
D16 D16
TE LC C64 C64
/64 /64
AN frame relay
25. Explanation
TE：Terminal Equipment
LC：Line Circuit
ET/L2：exchange terminal/Layer 2 functions
D16/64：16kbit/s or 64kbit/s D-channel
C64：64kbit/s communication channel
LAPV5-DL：The data link sub_layer of the V5 interface LAPV5-
EF：The encapsulating function sub_layer of the V5 interface
26. LAPV5-EF（encapsulation function sub_layer）：
Provide common encapsulation function and disassembling
function to LAPV5-DL frame.
The end-to-end information exchange of the encapsulating
functions between the AN and the LE is done in the form of
frames.
27. LAPV5-DL（data link sub_layer）：
Encapsulates the messages from layer 3 into LAPV5-DL
frame;Get out the messages of layer 3 from LAPV5-DL frame.
The data current in this sub_layer has the following frame
format.
28. Link addr(high order) byte1
Link addr(low order) byte2
Control byte3
Control byte4
Information ….
LAPV5-DL distinguishes different kinds of information
by link address. The link address consists two bytes.
29. AN frame relay sub_layer:
Accomplishing the frame multiplexing and multiplexing of the
ISDN user ports cooperating with the LAPV5-EF sub_layer.
30. LAPV5 - DL
From user port to AN:
Getting rid of the head and end labels
and check sequence from the frame and
Mapping
turn it into AN frame relay. According to
the ISDN user port,it gives the frame an
Efaddr,and then send it to mapping
AN frame
LAPV5 - EF
function sub_layer. The mapping relay
function sub_layer will map the frame to D16/64 C64
Ef sublayer in which the frame will be
encapsulated it to LAPV5-EF frame and ISDN user
sent to V5 communication channel.
31. C). Application layer
V5.2 includes 5 protocols.
Link
PSTN Control BCC Protection
control
protocol protocol protocol protocol
protocol
module module module module
module
32. A、PSTN protocol：
PSTN protocol provides the procedure relating to specific calls.
it transmits the analog line status information(such as hook off
and hook on ) through the V5 interface.
33. B、Control protocol
The control protocol of the V5 interface consists of two parts:
common control and user port control.
The common control provides the operations relating to the whole
V5 interface, such as interface start, interface provisioning and the
block/unblock of all the user ports.
34. The user port control provides the operations relating to only one
port, including all types of ports, such as PSTN user port and
ISDN user port. These ports can be blocked, unblocked, activated
and deactivated.
35. C、Link control protocol
Fulfilling below functions:
Link status(normal、blocked、out of work)
management,blocking and unblocking the links.
Confirm links at both ends of the interface.(to make sure
whether the links are available).
38. 4). V5 signaling procedure in PSTN service
A).call setup（user of AN originates a call）
User port AN LE
Off hook ESTABLISH
ESTABLISH ACK
ALLOCATION
ALLOCATION COMPLETE
Dialing tone
39. B).call release（AN user ends a call）
User port AN LE
On hook SIGNAL
DISCONNECT
DEALLOCATION
DISCONNCET ACK
DEALLOCATION COMP
