3. Power Increasing
Multiplexing interference is generated from non-orthogonal
among channels, thus power will be increased.
WCDMA Network Meeting Room
Code Channel Transmission——Talking with dialect
Channel Power——Voice while speaking
Ensure Channel Quality——Clearly listen dialogue
Increase Channel Power——Raise talking voice
Power Increasing——Every one raises talking voice
Collapse when linear scope is exceeded——Cannot even
hear
Interference out of the cell——Interference out of the room
4. Signal is “Submerged”
by the UE which is
near Base Station,
thus communication
failed
One UE can
block the
whole cell
Power
f
Far-Near Effect
5. Every UE equals with interference
to other users; far-near effect has
serious influence to system
capacity
Power
f
Power Control technology can reduce
the interference among UEs, and thus
increase system capacity
Power Control
Powe
r
f
6. •Overcomes far-near effect and fading compensation
• Reduces multiplexing interference, ensures network capacity
• Extends the use of battery
Downlink Power Control
Cell transmitting
power
Transmitting power control bit
Mobile phone transmitting power
Power Control
Command
Uplink Power Control
Power Control
7. Three Power Control Methods
Open Loop
Measures received signal level and adjust transmitting power
Closed Loop－Inner Loop
Measures SIR and compare with target SIR, sends
commands to adjust transmitting power
Closed loop power control frequency for WCDMA is1500Hz
Measured SIR>Target SIR, lower transmitting power
Measured SIR<Target SIR, increase transmitting power
Closed Loop－Outer Loop
Measures BLER, adjust target SIR
8. UE Node B
Purpose of Open Loop Power Control：Provides a
brief estimate of the initial transmitting power
Open Loop Power Control
9. UE
RNC
Outer LoopInner Loop
1500Hz
Measures SIR of
the received
signal and
compare
10-100Hz
Set SIRtar
Measures
BLER of the
received data
and compare
TPC
Set BLERtar
Node B
Closed Loop Power Control
10. Closed Loop Power Control
Inner Loop Power Control:
Fast closed loop power control, speed is1500 times/s
Performed in the physical layer between Node B and UE
One power control command for one interval (0.67ms)
Outer Loop Power Control
Service quality is determined by BLER directly, while SIR is indirectly
Relation between SIR and BLER changes with environment, which is non-
linear
Outer loop power control is brief adjustment to slow
changes（RNC to Node B）
Inner loop power control is detailed adjustment to
fast changes（Node B to UE）
11. Effectiveness of Power Control
The purpose of DL power control:
Saving power resource of NodeB, reducing interference
to other NodeB.
The purpose of UL power control:
Overcome near-far effect
At signal receiving terminal, every UE has the same SIR
(Signal to Interference Ratio).
The capacity of
WCDMA system is
determined by
power control
13. Handover
When a UE moves from the original service cell to
another, link between the original Node B and UE
will be replaced by a link between new Node B
and UE; this is called Handover.
Purpose：
To keep the service continuity when UE is moving
in different wireless coverage areas.
14. Handover
Soft Handover：
Soft handover is the channel handover among Node B coverage areas with the
same frequency
When UE Started to connect with a new cell, the connection between UE and the
original cell was not disabled. In soft handover, UE establishes wireless connection
simultaneously with more than one cell.
During handover, UE might simultaneously connect with two Node B. In the
handover process from one Node B to another, communication never disable, and
seamless handover is realized.
CDMA system has this unique handover, which can effectively improve the
handover reliability.
Hard Handover：
Hard handover happens when calling is switched from one cell to another or from
one carrier to another, and only one service channel can be used at a specific time.
Hard handover requires to disable the previous connection before starting new one,
that is to disable the connection with old service channel before connecting with new
service channel.
During hard handover, UE is only connected with one of the old and new Node B,
and short disconnection might exist when switching from one Node B to another
(Call might dropped).
16. Type of Handover
Soft Handover
Intra-Node B handover (Softer Handover)
Inter-Node B handover
Inter-RNC handover (related to Iur interface)
Hard Handover
Inter-frequency handover
Intra-frequency handover (Mandatory)
Inter-system handover（Inner GSM）
Inter-mode handover (FDD and TDD）
17. Cell Relations During Handover Control
Active set：A set of cells that connected with an
UE. User information is sent from these cells.
Monitor set ：Not included in active set, but were
monitored according to the neighbor node list that
allocated by UTRAN .
Detected set：Can be detected by UE, but not
included in either active set or monitor set.
18. Basic Flow of Handover Control (Sequence)
1. Measuring (UE)；
2. Report of measurement (UE to Node B, RNC)；
3. Judgment by handover algorithm (RNC)；
4. Execution of handover (RNC to Node B, UE).
19. Flow of Handover Control（1）
1. Measuring
RNC determines UE measurement and which physical
items to report. UE measurement parameters that required
for handover are Ec/N0 or RSCP (Received Signal Code
Power) of P-CPICH .
Usually we use Ec/N0, as Ec/N0 indicates the strength as
well as interference of the received signal.
Relation between Ec/N0 and RSCP is as follows：
Ec/N0 ＝RSCP/RSSI
Note that RSSI (Received Signal Strength Indicator) is the
broadband power in the relative channel band width.
20. Soft Handover
Inner frequency
Hard Handover
Periodically-
reported
Event-
triggered
Measurement result filtered in UE
Event judgment performed in RNC
Handover judgment performed in RNC
Measurement result filtered in UE
Event judgment performed in UE
Handover judgment performed in UE
Flow of Handover Control (2)
2. Report of measurement
Periodically-reported handover algorithm：Use
measurement result
Event-triggered handover algorithm：Use event
judgment result
21. Flow of Handover Control (3)
3. Handover Algorithm
No matter for hard handover, soft handover, Periodic
report or event triggering, all the handover algorithms
are based on event judgment according to
measurement result.
Events Defined in 3GPP Specification：
Inner-frequency soft handover events：1A~1F
Inter-frequency hard handover events：2A~2F
Inter-system handover events：3A~3D
22. Handover Events
Event1
1A：A primary frequency channel entered the reporting scope.
1B： A primary frequency channel left the reporting scope.
1C：A primary frequency channel excluded in Active Set has stronger signal than
those in Active Set.
1D：The best cell is changed.
1E：Signal of a primary frequency channel is stronger than an absolute threshold
value.
1F： Signal of a primary frequency channel is weaker than an absolute threshold
value.
Event2
2A：The best frequency is changed, and the signal quality of another frequency cell
become higher than that of the best one in Active Set.
2B：The signal quality of current frequency is lower than a specific value, while the
signal quality of another frequency is higher than the value.
2C：The signal quality of another frequency is higher than a specific value.
2D：Current frequency quality is lower than a specific value.
2E：The signal quality of another frequency is lower than a specific value.
2F： Current frequency quality is higher than a specific value.
23. Flow of Handover Control (4)
4.Handover Execution
According to handover algorithm, when handover
judgment is made based on measurement result,
handover execution will be started.
Three handover operations related to soft
handover:
1）Radio link added；
2）Radio link Removed；
3）Radio link replaced (Radio link added and removed
at the same time).
24. Handover Judgment（Cells waiting for judgment ）
Case: Event 1A
Case: Event 1B
Case: Event 1C
Case: Event 1D
Case: Event 1E
Case: Event 1F
Add the cell to radio link adding list
Add the cell to radio link removing list
Add the replaced cell to radio link removing list,
Add the triggering cell to radio link adding list
Mark the cell as best cell
Add the cell to Monitor Set
Remove the cell from Monitor Set
Handover Algorithm
25. AS_Th – AS_Th_Hyst
As_Rep_Hyst
As_Th + As_Th_Hyst
Cell 1 Connected
Event 1A
Add Cell 2
Event 1C
Replace Cell 1 with Cell 3
Event 1B
Remove Cell 3
CPICH 1
CPICH 2
CPICH 3
Time
Measurement
Quantity
T T T
Following
parameters are
required：
AS_Th:：
Macrodiversity
threshold (reporting
scope)
AS_Th_Hyst:：Lag
parameter of the
above threshold
AS_Rep_Hyst：
Replace lag
parameter
T:：Trigger timing
AS_Max_Size:：
Maximum cell
numbers in Active
Set
Example of Handover Algorithm
27. Code Resource Management
Purpose of Code Resource Planning:
In WCDMA system, two kind of codes are used, OVSF code and
scrambling code.
OVSF code is a valuable scarce resource, with one cell being
correspondent with one code table. In order to have more UEs be
able to access the system and increase system capacity, the
proper use of code resources must be taken into consideration,
thus the planning and management of downlink channel code
resources become very important.
At downlink, primary scrambling code is used to distinguish cells.
As to the scrambling code allocation for every cell, we need to
consider the correlation among scrambling codes. The best way is
to ensure the smallest cross-correlation between neighbor cells.
Location of Code Resource Planning Module in System:
Located in CRNC.
28. Functions of Orthogonal Codes
OC1, OC2
OC3, OC4
OC5, OC6, OC7
OC1 , OC2, OC3
OC1, OC2
OC1, OC2, OC3, OC4
Uplink: To distinguish different channels sent from one UE
Downlink: To distinguish different channels sent from one base station
29. Principles of Code Allocation
OVSF code is a valuable resource in CDMA system. At downlink, there
is only one code tree for many UEs (All the users are using one
scrambling code). The purpose of code allocation is to support as
much as possible UEs with as low as possible complexity. Two factors
are taken into consideration for principles of code allocation:
1）Usage
To reduce as much as possible the number of blocked low-value code
resulted from code allocation, and minimize code resources. For example,
the carrier capacity of a single-code C4,1 equals with that of a double-code
C8,1 or C8,3, and so the single-code C4,1 is the better one. Complexity
will be increased if we use multi-code, thus we need to avoid multi-code
transmission as possible as we can.
2）Complexity
Principle of being close：During code allocation and management, try to
make them being close to avoid low rate of usage.
30. SF=8
SF=32
SF=16
Features of Channelized Code
1.Premise of Code Allocation：
Ensure that no other codes were allocated on its root
path and sub-tree path;
2.Result of Code Allocation：
All the low-speed scrambling code on its sub-tree path
and the high-speed scrambling code on its root path will
be blocked;
31. Functions of PN Code
Uplink: PN code is used to distinguish different UEs
Downlink: PN code is used to distinguish different base
stations/cells
PN3 PN4
PN5 PN6
PN1 PN1
Cell Site “1” transmits using PN code 1
PN2 PN2
Cell Site “2” transmits using PN code 2
34. RAKE Receiver
As multipath signal contains information that can
be used, CDMA receiver can improve the SIR of
the received signal through multipath signal
combination.
RAKE receiver receives all the signals in multipath
through relative detectors, and combines them
together.
36. Synchronizations
follow
RAKE Branch1
RAKE Branch2
RAKE Branch M
Path choose
Z1
ZOUTZ2
ZM
Phase Control
r(t)
α1
α2
αM
At the receiving end, M independent sub-links were combined and
diversity gain was obtained. There are three kinds of combinations, such
as selecting combination, maximum combination and gain combination.
WCDMA system uses the maximum combination to obtain the best
diversity gain.
Work Principle of RAKE Receiver
37. RAKE receiving effectively overcames multipath interference, and
improves receiving performance.
RAKE Receiving
Receiver
Single-path
receiving circuit
Single-path
receiving circuit
Single-path
receiving circuit
Searching machine
Signal
computer
strength and
delay
Combination Combined
signal
tt
s(t) s(t)
40. Call Admission Control
When user initiates a call, RRM decides weather
access or deny this call according to the resource
situation.
When available system resource is enough for the
user, system will access the user, and allocate the
related resources (such as scrambling code,
channel code).
41. Process of Call Admission Control
When user initiates a call and apply for resource,
RNC will perform call admission control.
System load threshold Available capacity
Access application Added load value
Added load<Available
capacity
？
Access
Deny
yes
no
42. Load Control
System continues real-time
measurement of the cell load.
When average load surpass a
threshold value during a certain
period of time, load control will
become necessary.
The purpose of load control is to accept as many as
possible services while keep the stability of the
system, and thus realize high-efficiency performance.
43. Load Control
Load control is to take various methods to
reduce system load when system is
overloaded, and limit system load to a specific
scope, thus to ensure system stability.
Speed and location
change of mobile UE
results in the
deterioration of wireless
transmission environment.
Raising
transmission power
increased system
load
Purpose of Load Control
44. Start
Judge system load
（1）Allow switch and access
（2）Allow power increasing
（3）Increase speed
（4）Others
System load low
System overloaded
System load normal
（1）Allow switch and access
（2）Allow power increasing
（1）Stop switching
and accessing
（2）Stop power
increasing
（3）Lower the speed
（4）Handover
（Switch out）
（5）Execute call
dropping
Process of Load Control
45. Uplink Load Control
Trigger Conditions：
Uplink RTWP surpassed threshold value；
Triggered by high-priority service in admission control module
Measures to reduce load：
Fast uplink load control：Reduce the Eb/N0 target value of fast
uplink power control；
Reduce the data throughput of non-real-time group business；
Switch to another frequency；
Switch to GSM system；
Reduce the bit rate of real-time business：such as ARM voice
code；
Drop a call at controlled situations.
Measures to increase load：
Actively increase PS business load and AMR voice code speed.
46. Downlink Load Control
Triggered Conditions：
Downlink RTWP surpassed target threshold value；
Triggered by high-priority service in admission control module
Measures to reduce load：
Fast downlink load control：Reduce the Eb/N0 target value of fast
downlink power control；
Reduce the data throughput of non-real-time group business；
Switch to another frequency；
Switch to GSM system；
Reduce the bit rate of real-time business：such as ARM voice
code；
Drop a call at controlled situations.
Measures to increase load：
Actively increase PS business load and AMR voice code speed.
47. Cell respiration is
one of the load
control methods
The main purpose of cell respiration is to
allocate the load of “Hot Cells” to the
relatively light-loaded cells around, and thus
to improve the reuse of system capacity.
Cell Respiration
49. Features of WCDMA Capacity
Features of WCDMA Capacity
Capacity is soft
Meaning of soft capacity
System capacity and communication quality can be
exchanged
Different capacity for different business
While carrying hybrid business, different business
proportion and composition have different capacities.
50. User Capacity
Purpose of the technologies and network planning used
in WCDMA is to gain the best balance among the three
factors.
Features of WCDMA Capacity
54. Factors That Affect WCDMA Capacity
Factors that affect
WCDMA capacity
Functions
Power control Reduce interference, save power, increase capacity
Handover Soft handover proportion and handover algorithm affects capacity
Admission control To determine whether access or deny a user
Load control Adjust business situation and user number of current cell according to
current system load
Code resource Proper allocation of code resource can affect the accessed user
numbers
RAKE receiving Advanced base band handling technology dedicated to fast fading
Intelligent antenna Dynamically adjust antenna array beam to track users, reduce
interference, save power, expand coverage, increase capacity
Multi user detection Reduced multiplexing interference, and increased system capacity
Business categories
Business
composition
Different capacity for different business
Business composition of the cell directly affects its capacity
Cell environment,
interference
Wireless condition of the cell, including interference, UE mobility,
distribution of UE in the cell, etc., can all affect the cell capacity
