Admission control guarantees quality of service by controlling the number of users based on interference, capacity, load, and coverage. It selectively denies access requests to limit load. Congestion control resolves overload by delaying packets, removing calls, or moving users between channels. Power control aims to minimize transmit power while maintaining quality by adjusting power levels through inner-loop, outer-loop, and open-loop control. Soft/softer handover combines signals from multiple base stations or sectors to support user mobility and power control.
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Wcdma radio functionality
1. UMTS Presentation - 1
UMTS Radio Features Presentation
Praveen Gupta, MobileStack,
pgupta@mobilestack.com
2. UMTS Presentation - 2
Admission control overview
Guarantees the overall Quality of Service by controlling the
number of users
Interference
Capacity / Load
Planned load
Planned coverage
Coverage
New users blocked
above this point
User added
Admission
threshold
3. UMTS Presentation - 3
Admission control purpose & algorithm
description
Purpose:
– This algorithm selectively denies access requests in order to limit the
load.
Algorithm description:
– When new resources are required for a radio connection (Radio Link
set-up or modification), the Radio Connection Coordination algorithm
requests admission.
This requests includes parameters specifying the requested amount of
resources. Admission Control checks if the requested amount of
resources is available.
4. UMTS Presentation - 4
Characteristics of admission control
The RBS regularly reports measurements values of
transmitted power
By knowing the connections, the RNC keeps track of ASE,
RBS HW and DL code usage
Handover legs have higher priority than new calls
Different thresholds for different services
At high load, interactive users may be offered lower
datarates than under normal load conditions
5. UMTS Presentation - 5
Congestion control overview
Bitrate
Over load is resolved by:
Delaying packets
Call removal
6. UMTS Presentation - 6
Congestion control purpose & algorithm
description
Purpose: This algorithm solves overload situations. An
overload situation occurs due to fluctuations in the UL
interference and the used DL power.
Algorithm description : The algorithm is only triggered in
case of (near) overload in a cell. The algorithm acts in case
the transmitted Carrier Power measurement (DL Power)
indicates overload. It is possible to set different thresholds
for different services.
7. UMTS Presentation - 7
Example 1: Congestion control work flow
DL power or UL interference
exceeded
Restrict access
Order admission to block
Interactive users in
system?
Move user to common ch Remove user
Set timer
Wait for command
No
Allow admission
and access
Message: over-
load resolved
At overload, alter
connection with
highest DL power
Yes
Timer expired
8. UMTS Presentation - 8
Enhanced Capacity control
Admission control checks HW
resources in both UL & DL
Directed retry at call set-up to
GSM in case of admission denial
in WCDMA
Load balancing between
different frequencies
9. UMTS Presentation - 9
P(Startvalue)
Open loop
P(SIR-Target,UL)
P(SIR-Target, DL)
Closed loop
DL-TPC UL-TPC
SIR-Target,DL
BLER-Measured,DL
DL-Outer
BLER = Block Error Rate
SIR = Signal to Interferenc
TPC = Transmit Power Co
e Ratio
ntrol
loop
RNC
SIR-Target,UL
SIR-Error,UL
UL-Outer loop
Power control overview
10. UMTS Presentation - 10
Power control purpose & reason
Purpose:
The purpose is to minimize the transmit power while
maintaining the quality of radio links. There are three
different types power control:
– Inner loop power control
– Outer loop power control
– Open loop power control.
Reason:
Power control
– Maintains the quality of the connections
– Reduces power consumption
– Minimizes interference
– Improves the coverage and capacity of the system
11. UMTS Presentation - 11
Power control over time
Inner-loop power Control
(Initial Receive Power
Target)
RBS Receive Power Target
Inner-loop power Control
(Updated Receive Power Target
by Outer-loop power Control)
RBS
Receive Power
Open-loop Power Control
Access Preambles
time
DPCHRACHAccess Preambles
1500 updates/sec
The PRACH is “power controlled” by means of preamble ramping
12. UMTS Presentation - 12
Channel type switching overview
Release dedicated
channel
Random-Access
Request
Random-Access Channel
Packet Packet Packet
Dedicated Channel
TTime-out
Switch to
common
Switch to
dedicated
Random-Access
Request
User 1 User 2
13. UMTS Presentation - 13
Channel type switching purpose & reason
Purpose:
To optimize the channel usage for best effort packet switched
users (Interactive users). To determine if it is necessary to
switch UE connected substates e.g. from a common to a
dedicated channel.
Reason:
For best effort traffic for a particular user there is large
variations in time in the offered traffic (bursty nature of traffic).
It is not efficient for the air-interface to keep up resources for a
dedicated channel continuously. This function saves also
battery for connected UEs, which are not transferring data.
14. UMTS Presentation - 14
Channel rate switching
Change bit rate when moving away
from RBS:
- UL supported by UE
- DL supported in RNC
Advantage: Higher coverage and higher
capacity
Bitrate
Change of bit rate at high load
- Reduce bitrate for Interactive users
- Reduce bitrate for voice users by
changing AMR mode
Advantage: Lower blocking probability
Distance
from RBS
or
Load in
the cell
15. UMTS Presentation - 15
Adaptive Multi Rate (AMR) Rate Selection
Selection of the AMR mode
at call set up
About four combinations of
simultaneous modes
defined by the standard is
supported
The modes range from
around 4.75 kbps up to 12.2
kbps
12.2
Bit rate for a user
[kbps]
7.95
4.75
X
X
X
Distance
from RBS
or
Load in
the cell
16. UMTS Presentation - 16
Adaptive Multi Rate (AMR) Rate Control
Possible to change the AMR
mode for coverage and
capacity reasons dynamically.
The AMR switching and rate
control optimises the usage of
the air-interface by adapting
the AMR rates for coverage
and capacity reasons.
12.2
Bit rate for a user
[kbps]
7.95
4.75
Distance
from RBS
or
Load in
the cell
17. UMTS Presentation - 17
Transmit Diversity - Open loop
- Introduced to combat fading with up to 5dB gain in the downlink
On
Off
15 dB
10 dBOn
18. UMTS Presentation - 18
Open Loop Transmit Diversity
Coverage & capacity gain
– additional diversity effect -> less transmitted power -> less
interference in the system
The same information is transmitted from the two
antennas. For each antenna the information is coded in a
different way.
The total transmitted power is split between the two
antennas.
19. UMTS Presentation - 19
Open Loop Transmit Diversity
- Space-Time Transmit Diversity (STTD)
A
B
b0 b1 b2 b3
b0 b1 b2 b3
-b2 b3 b0 -b1
Antenna A
Antenna B
Channel bits
STTD encoded channel bits
for antenna A and antenna B.
The signals from the two antennas are spread and scrambled with the
same code and simultaneously transmitted
The two signals experience different fading patterns and the RAKE
receiver observes the sum of the two faded orthogonal signals
The resulting signal has a smoother fading pattern than the two original
signals
Used on all DL channels (except SCH and CPICH).
20. UMTS Presentation - 20
Open Loop Transmit Diversity
- Time Switched Transmit Diversity (TSTD)
In TSTD the transmission alternates between the antennas
Used on Synchronization Channel (SCH)
TSTD is implemented as a part of STTD
b0 b1 b2 b3
b0 b2
Antenna A
Antenna B
Channel bits
b1 b3
21. UMTS Presentation - 21
Transmit diversity - Closed-loop
Closed-loop Transmit Diversity (DPCH, PDSCH only)
– UE sends Feedback Information (FBI) Bits to the RBS over the DPCCH
– FBI bits tell the RBS how to adjust antenna gain (only mode 2) and phase (both
mode 1 and mode 2) for optimal reception at the UE
– Mode 1 supported in P4
Σ
DPCCH
DPDCH
MUX
DCH (or PDSCH)
Σ
CPICH2
CPICH1
Decode FBI
Calculate
Gains, Phases
Antenna 1
Antenna 2
• S/P Demux
• Channelization
• Scrambling
• I/Q Modulation
22. UMTS Presentation - 22
TX diversity modes mapped on physical channels
Application of Tx diversity modes on downlink physical channel types
"X" – can be applied, "–" – not applied
Physical channel type Open loop mode Closed loop
TSTD STTD Mode
P-CCPCH – X –
SCH X – –
S-CCPCH – X –
DPCH – X X
PICH – X –
PDSCH – X X
AICH – X –
CSICH – X –
23. UMTS Presentation - 23
Blossoming and wilting
The purpose of the blossoming (at cell addition) and wilting (at cell removal) is
to allow cells to be added or removed from the radio network with minimum
disturbance to the network.
RBS1 RBS2
Wilting
Blossoming
Output power gradually decreased (wilting) Output power gradually increased (blossoming)
24. UMTS Presentation - 24
Micro cell support overview
Micro
Macro
Support of micro cells to:
– cover white spots or to
– increase capacity in hot-spot areas
Advanced load sharing to increase
performance by distributing users
between different cells
The micro cell can be deployed in:
– different frequency as the macro cell
– the same frequency band as the macro cell
25. UMTS Presentation - 25
Micro cell evolution scenario
At some cell radius macrocell (i.e. roof-top antennas)
capacity growth is limited due to poor RF isolation.
Microcells can be added in same or different
frequency depending on:
– rate of traffic increase
– distance macro-hot spot
– UE velocity
Ultimately there will be a complete micro-layer
f2
f2
f2
26. UMTS Presentation - 26
Connection set-up/release description
Connection Setup and Release includes establishment and
release of control plane connections between the UE and
UTRAN, and between the UE and the Core Networks.
It also covers Radio Access Bearer establishment according
to the requested Quality of Service between a Core Network
and a UE with established signalling connection, as well as
release of existing Radio Access Bearers.
The functions consists of two subfunctions
– Signaling Connection Setup and Release
– Radio Access Bearer Setup and Release
27. UMTS Presentation - 27
Radio connection supervision
Benefit:
– Allows an efficient resource utilization
– Guarantees that users are not charged for time when they did not have network contact.
Description:
This feature continuously monitors the status of the radio connection for all connected UEs
and disconnects those for which a reasonable quality cannot be maintained and/or the contact
has been lost.
The meter for the "unacceptable quality" depends on measurements performed on up-link
physical channels as well as duration of disturbance or loss of contact. Typically the meters
are set such that the quality is considered unacceptable only when there has been no working
contact with the UE for a few seconds for DCH connected and several minutes for cell
connected.
If the quality is considered unacceptable or the UE is considered lost, the radio network will
request the deletion of all connections towards this UE. Thereby all Radio bearers and RAB's
allocated for this UE are disconnected. Logical, HW and SW resources related to these
channels/bearers are also released.
28. UMTS Presentation - 28
Soft/softer Handover overview
Algorithm
–Relative thresholds minimizes the
number of mobiles in soft handover
B A
Time
C/I
Add B Delete A
Add
margin
Drop
margin
29. UMTS Presentation - 29
Soft Handover
Soft handover essential for power control
Soft handover reception
– combines signals from RBS in the RNC
RBS 1 RBS 2
RNC
30. UMTS Presentation - 30
Softer Handover
Softer handover reception
– combines signals from two or more sectors in one RBS
RBS
31. UMTS Presentation - 31
Characteristics of soft/softer handover
RNC controls the UE measurements (i.e. what to
measure, report type, what to report and the monitoring
set)
UE measures on CPICH (Ec/No, RSCP or path loss)
UE evaluates measurements (event driven or periodic)
RNC evaluates which cells to add/replace/remove from
active set (max size is 4)
RNC executes the handover decision and provides UE
with new neighbor list
32. UMTS Presentation - 32
Paging
Purpose:
Paging enables the CN to page UEs for terminating service
request or for the UTRAN to reach the UE to trigger a UE
state transition. The function will also broadcast modified
system information to all UEs.
The following cases are handled by the paging function:
– CN originated when UE in idle mode
– CN originated when UE in connected mode.
– UTRAN originated to trigger a UE state transition.
– UTRAN originated to trigger a UE to read updated system in-
formation.
33. UMTS Presentation - 33
Cell Update
Purpose:
Using common or paging channels are important to allow an efficient
management of resources for always connected low intensity packet
traffic. The feature "Cell Update" is used to allow mobility, cell
reselection ("hard handover") and efficient paging of UE's in such
states.
Benefit:
– Support the mobility for UE's on common or paging channels.
– Provide a high success rate and efficient management of
resources for paging to CELL_PCH connected UE's (PCH is
Paging Channel).
34. UMTS Presentation - 34
URA_PCH State
Idle Mode
RRC Connected Mode
Idle
URA_PCH Cell_PCH
Cell_FACH Cell_DCH
New state called
WCDMA RAN
Registration Area
(URA_PCH State)
Benefit:
– Reduce signaling in
WCDMA RAN due to
updates of location of
moving mobiles
– Simplified paging
– Lower UE battery
consumption
36. UMTS Presentation - 36
Why GSM Interoperability - why GSM Handover?
For service and coverage
– Initially to provide “seamless service” to UMTS users
For load sharing between frequencies and Radio
Access Technologies (RAT)
– Increase capacity pool size
– GSM network full used
For fair behavior in shared network solutions
To allow access to unique bearers
37. UMTS Presentation - 37
GSM Intersystem Handover
Inter frequency measurements are needed to support inter system
handover
Compressed mode supports these measurements
– 3 different types of compressed mode
Compressed mode
time for measurementsTf = 10 ms
SF=SF0
SF=SF0/2
SF=SF0
Inter system
WCDMA
GSM
38. UMTS Presentation - 38
Compressed Mode - 3 different types
Different alternatives with different impacts
Lower spreading factor
+ Same user data rate
- Power increase
- Need to allocate a code with half spreading factor
1) Allocate code in the same code tree - remain code orthogonality
2) Allocate code in another code tree - easy to get codes
Puncturing
+ Same user data rate can be used
+ Remain on the same spreading factor (code)
- Power increase
- Weakens Forward Error Correction (FEC) coding
Higher layer scheduling
+ Power increase can be avoided
- Lower user data rate
39. UMTS Presentation - 39
Control of Inter Radio Access Technology
Cell Reselection
UMTS to GSM :
Neighbour Cell List
Quality measure
• CPICH (RSCP or CPICH Eb/N0)
For each neighbour Cell Reseletion criteria
• Serving cell quality limit to start neighbor cell measurements
• Minimum required signal level to allow selection
• Minimum required quality of to allow selection
(For FDD cells)
• Offset between serving cell and neighbor cell
• Hysteresis of the serving cell for ranking of cells
• Time to trigger cell reselection
40. UMTS Presentation - 40
BSC
RNC
Real time changes of Connection & Cell
Link adaptation and control as well as inter-system, service
based load sharing.
Based on existing and currently standardized, Iur-g,
interfaces.
Functionality for:
- Handover Control
- Admission Control
- Load Control
- Service Differentiation
Ensure full utilization of
spectrum and system at
maximum performance.
Intersystem Traffic Control
Always Best Connected
GSM/EDGE
WCDMA
Core Network
41. UMTS Presentation - 41
Load Balance GSM-UMTS
System Features for Traffic Control and Efficiency as
Function of Time
Time
• Symmetric Handover Algorithms in GSM and WCDMA
• Congestion triggered Handover from GSM to WCDMA
• System preference based Handover from GSM to WCDMA
• Coverage based Handover from WCDMA to GSM
• Cell Reselection Idle& PS
• Congestion hold-down
•Congestion triggered Handover WCDMA to GSM
•System preference based Handover from WCDMA to GSM
• Real time load Balancing, Iur-g
• O&M load Management
• Self Configuring Radio Network with
Dynamic Cell Reselection Control
Dual-mode Handset
penetration
(GSM/EDGE-WCDMA)
• Combined Configuration Management, CCM
• Service based Directed Retry
• Load Control
100%
Achieved Load-balancing Efficincy
42. UMTS Presentation - 42
Transparent message transfer
Supports the transfer of signaling and other messages between a
UE and the core network nodes, MSC and SGSN.
Basic feature required for UE signaling, e.g. for call set-up
Provides support for SMS
Description
In UMTS, the radio access network need to transfer signaling
messages (Non Access Stratum) transparently between the UE and
either of the core network domains for establishing and releasing
calls.
Such transparently transferred messages are also used for other
purposes, e.g. LA/RA updating and support SMS services.
43. UMTS Presentation - 43
System Information distribution
Allows the UE to get access to updated System Information, which in
turn is necessary for correct network behavior.
Description
The system information is regularly broadcast to the UE's on
Broadcast Channel. The information is relates to:
– Power control, both Common and dedicated channels, e.g. UL
interference
– RRC connection parameters e.g. timers and counters
– Adjacent cell configuration parameters.
– UE Measurements e.g. to support handover evaluation
– Location Area and Routing Area
– Common channel configuration
– Cell selection and re-selection
44. UMTS Presentation - 44
Node and network synchronization
Node synchronization:
The Node Synchronization function contains four sub-functions:
– Holding of and generation of node reference time in the RNC and the
RBSs,
– Measurement of phase difference between the frame reference time in
the RNC and the frame reference time in each RBS.
– A database of measured phase differences to each RBS is held, and an
estimate of the accuracy of each of the measurement.
– Supervision of drifting frame reference times in the nodes.
Generation of node reference time and phase measurement are
handled by a device, the Timing Unit (TU), present in both RNC and
RBS.
45. UMTS Presentation - 45
Node and network synchronization
Network synchronization:
The RBS and RNC internal clocks can be synchronized either to:
– the transport network or to
– an external high stability clock reference.
RBSs and RNCs both have stable clocks locked to the reference carried
over the transmission network. The clocks, besides synchronizing internal
functions in the node, also generate sync to the outgoing transmission links
and to the radio transmission.
It is possible to cascade up to 5 clocks (Nodes)
One primary and up to seven secondary synchronization reference links
can be configured for each node
The network synchronization (clock) function can be configured to be
redundant or non-redundant.
46. UMTS Presentation - 46
Integrity protection and ciphering mode control
Integrity protection handles:
– the control of integrity protection of control plane data
– co-ordination of integrity keys between different core
networks (PS and CS).
The integrity protection maintains access link data
integrity between the SRNC and UE.
Ciphering Mode Control handles:
– the control of ciphering of user plane and control
plane data
– co-ordination ciphering keys between different core
networks (PS and CS).
The ciphering is performed for secure data
confidentiality between the SRNC and UE
47. UMTS Presentation - 47
IOT certification for Iu/Iur
Iu is the most
common 3G multi-
vendor interface
Enables an
operator to choose
(several) RAN
suppliers
RAN RAN
3G CN 3G CN
Vendor-A
3G system
Vendor-B
3G system
Iu Iu
Iu Iu
48. UMTS Presentation - 48
High Speed Downlink Packet Access (HSDPA)
Requirements
– High peak data rates (8-10 Mbps)
– Higher throughput
– Lower delay
Introduction of a new High Speed Downlink Shared Channel
(part of 3GPP Rel.5)
– Exists in downlink only
– Always associated with a dedicated physical channel (DPCH) pair
DPCH
HS-DSCH
49. UMTS Presentation - 49
Mulitcode to allow bit rates >384 kbit/s
One user has more than one channelization code
One user can than have several data streams to achieve
bit rates above 384kbit/s
Data 2TFCIData 1 TPC PilotPrimary
DPCCH/DPDCH
Data 4Data 3Additional
DPCCH/DPDCH
Data NData N-1Additional
DPCCH/DPDCH
50. UMTS Presentation - 50
The use of codes in WCDMA
Single cell view:
– all mobiles need to share the same frequency carrier in WCDMA
– orthogonal codes separate between the users and between
different communication channels to one user (multi-code
operation)
Channelization codes
Network view:
– nearly orthogonal codes to distinguish between the
communication channels from different RBS’s
– One scrambling code per sector and per carrier e.g a 3x2 RBS
has 6 scrambling codes
Scrambling codes
51. UMTS Presentation - 51
Multiple scrambling codes overview
Each sector/carrier (cell) broadcasts a unique cell
ID code -> downlink scrambling code
With multiple scrambling codes -> there is more
than one downlink scrambling code per
sector/carrier (cell)
Cell #1, ID code 1
Cell #2, ID code 1
Cell #1, ID code 2
Cell #2, ID code 2
Cell #3, ID code 1
Cell #3, ID code 2
52. UMTS Presentation - 52
Multiple scrambling code benefit
Multiple scrambling codes gives more than one channelization code
tree per sector/carrier
The problem with code shortage is removed.
1
11 10
1111 1100 1010 1001
11111111 11110000 11001100 11000011 10101010 10100101 10011001 10010110
1
11 10
1111 1100 1010 1001
11111111 11110000 11001100 11000011 10101010 10100101 10011001 10010110
53. UMTS Presentation - 53
Power Scheduling
Extra capacity
can be given to
packet data users
load
time
max planned load
Load sharing in time results in a high capacity
– Continuous update of the transport format for the interactive RABs both in UL and DL
– The aim is to maximize the bit rate for the interactive users
Smooth interference levels in the system
– Optimize the usage of the radio capacity in the system e.g DL power, without exceeding
the maximum planned load