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TRANSCRIPT
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RG000012
CDMA 1X Load Control &
Channel Management Algorithm
ISSUE 1.0
RG000012
CDMA 1X Load Control &
Channel Management Algorithm
ISSUE 1.0
Course Development Room,
Wireless Product
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Course ObjectiveCourse Objective
Learn the purpose of the CDMA
1X load control
Master the means of the CDMA
1X system load control
Learn the structure of the
channel management moduleMaster the contents of the
channel management
Master the algorithm of channel
assignment
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Contents of CourseContents of Course
Chapter 1 CDMA 1X Load Control
Chapter 2 CDMA 1X Channel
Management
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Chapter 1 CDMA 1X Load ControlChapter 1 CDMA 1X Load Control
Purpose of Load ControlPurpose of Load Control
Means of Load Control
Admission Control
Means of Load Control
Load Balancing
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Purpose of Load ControlPurpose of Load Control
The CDMA 1X is an interference-restricted system whose capacity
depends on the interference it suffers
To guarantee the quality of service of the subscribers in the system, it
is necessary to control the load of the system so as to avoid the
overload and intensified interference from causing the system crash.
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Chapter 1 CDMA 1X Load ControlChapter 1 CDMA 1X Load Control
Purpose of Load Control
Means of Load ControlMeans of Load Control
Admission ControlAdmission Control
Means of Load Control
Load Balancing
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Purpose of Admission Control and Trigger
Condition
Purpose of Admission Control and Trigger
Condition
Purpose
Control the access of subscribers to the cell so as toControl the access of subscribers to the cell so as to
guarantee the running quality and resource utilization of theguarantee the running quality and resource utilization of the
systemsystem.
Trigger ConditionTrigger Condition
11The system will perform the admission control when theThe system will perform the admission control when the
MS establishes a new call in a new cell or in the case of theMS establishes a new call in a new cell or in the case of the
handoffhandoff
22The system will perform the admission control when aThe system will perform the admission control when a
new service is added during an established callnew service is added during an established call
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Principle of Admission ControlPrinciple of Admission Control
Predict the load change that the admission of the call access
request may bring to the system according to the current loadof the system and the call access requests.
Judge whether the system can run normally with the new load.
The call access request is admitted if the changed load of the
system does not exceed the restricted load that allows the
system to run normally.
Otherwise, the access request is refused
Admission control algorithmAdmission control algorithm ------ an algorithm based onan algorithm based on
load predictionload prediction
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Method of Admission ControlMethod of Admission Control
Predict the system load after the call access according to the
transmission rate that the channel assignment requestrequires .
The load of the forward channel is the ratio of the current
transmitting power to the maximal power of the BS, which canbe obtained from the load control module .
The load of the reverse channel is obtained from the empirical
formula according to the RSSI reported by the BS after themeasurement.
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Classification of Admission ControlClassification of Admission Control
Set the admission thresholds for the data service and voice
service, respectively. The admission threshold for the data
service is lower than that for the voice service.
If an emergency call or high priority call can not access the
system, then the connection of the user EXEC can be
released forcedly so that the emergency call or high priority
call can access the system.
Restrict the admission of the data service according to the
settings of the traffic model of the cell.
The admission threshold for the common voice call is lower
than the soft handoff threshold for the voice call.
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Chapter 1 CDMA 1X Load ControlChapter 1 CDMA 1X Load Control
Purpose of Load Control
Means of Load Control
Admission Control
Means of Load ControlMeans of Load Control
Load BalancingLoad Balancing
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Purpose and Precondition of Load BalancingPurpose and Precondition of Load Balancing
Purpose: Guarantee the load balancing in the system, including:
Load balancing between different carriers
Load balancing between intra-frequency cells.
Precondition:
The load of some carriers is so heavy that the communication
quality is badly affected
Some resources are in the idle state and not fully utilized.
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Classification of Load Balancing AlgorithmClassification of Load Balancing Algorithm
Load balancing (handoff) between carriers
Cell breath
Both the two load-balancing methods are based on the
load measurement.
The load balancing between carriers is prior to the cell
breath.
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Load Balancing between CarriersLoad Balancing between Carriers
Load balancing algorithm between carriers:
The load balancing between carriers refers to the load
balancing between different carriers in the same region
(mainly referring to the same sector). The algorithm is to
guarantee that the subscribers on the carrier with a heavy
load in the coverage of the same sector can be handed over
to other carriers with a sufficient residual capacity
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Cell BreathCell Breath
When the loads of the adjacent cells are different, the cell with
a heavy load will reduce the transmitting power so that the
subscribers at the border of this cell would be handed over to
other adjacent cells to realize the load control.
Cell Breath dynamically assigns the cell load so as to improve the
network coverage and increase the system capacity.
load controlmainly relies oncell breath and
handoff
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SummarySummary
Master the purpose of the load control
Master the means of load control
Master the differences between the cell breath and the load
balancing
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Contents of CourseContents of Course
Chapter 1 CDMA 1X Load Control
Chapter 2 CDMA 1X Channel
Management
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Chapter 2 CDMA 1X Channel ManagementChapter 2 CDMA 1X Channel Management
Structure of Channel ManagementStructure of Channel Management
ModuleModule
Contents of Channel Management
Radio Channel Assignment
Channel Assignment Algorithm
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Diagram of CDMA 1X Channel Management
Modules
Diagram of CDMA 1X Channel Management
Modules
Wireless
Resource table
Channel
Configuration
Channel
distribution
Channel
release
State
Maintenance
CCM
Test
interface
OSDB
Test
model
BIM OAM
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Relationship between Cell, Sector, Carrier and
Channel Element
Relationship between Cell, Sector, Carrier and
Channel Element
The relevant logic resource of the radio channel includes the
channel element pool, sector and cell.
TRX
TRX
TRX
TRX
TRX
TRX
CE Pool 1
ARFCN m
ARFCN1
CE Pool m
Sector1 Sector2
TRX
TRX
TRX
Sector n
CEs
CEs
CEs
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Logical Unit of Radio ChannelLogical Unit of Radio Channel
Channel1ARFCN1 CE Pool1Sector1Cell1
Cell2
Channel1-nARFCN2 CE Pool2
Channel1-nARFCN1 CE Pool1Sector2
Channel n
Channel2
Channel1ARFCN2 CE Pool2
Channel n
Channel2
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Chapter 2 CDMA 1X Channel ManagementChapter 2 CDMA 1X Channel Management
Structure of ChannelStructure of Channel
Management ModuleManagement Module
Contents of Channel
Management
Radio Channel Assignment
Channel Assignment Algorithm
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Contents of Channel ManagementContents of Channel Management
Configuration
Assignment
Release
Maintenance of State
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Configuration of Radio ChannelConfiguration of Radio Channel
Concept: It refers to the configuration of the forward common
channel information. The forward channel of the CDMAsystem includes the forward common channel and forward
traffic channel.
The system distinguishes forward common channels from
forward traffic channels via different Walsh codes.
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Code Resource of Forward Common ChannelCode Resource of Forward Common Channel
It refers to the specific code resource channel number
stipulated in the protocol of the forward common channels.
Except the Walsh resource occupied by the common channels,the rest of one CDMA channel can be freely assigned to the
MS as traffic channels. The assignment of the fixed code
resource of forward common channels is shown in the table.
Channel Name Walsh Code
Forward Pilot Channel W(640)
Forward Synchronous
Channel
W(6432)
Forward Paging Channel W(641)W(647)
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Chapter 2 CDMA 1X Channel ManagementChapter 2 CDMA 1X Channel Management
Structure of Channel
Management Module
Contents of ChannelContents of Channel
ManagementManagement
Radio Channel Assignment
Channel Assignment Algorithm
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Radio Channel AssignmentRadio Channel Assignment
Basic Concept and Principle
Contents
Reasons
Flow Chat
General Principle
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Concept and Principle of Radio Channel AssignmentConcept and Principle of Radio Channel Assignment
Concept: When the BS and a specific MS expect to establish
the point-to-point connection on a CDMA channel, the BSCwill assign the corresponding traffic channel resource to
transfer the service & signaling data.
Principle: According to the service type and bit raterequirement, the channel assignment submodule will decide
whether to assign channels and what channels to assign, and
determine parameters of the transmission rate and radio
configuration, with reference to the current resource state.
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Contents of AssignmentContents of Assignment
Channel Type
Radio Configuration, RC
Frame Duration
Coding Scheme
Frame Offset
Code Resource
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Channel TypeChannel Type
Basic TypeFCH, SCH.
Each MS can possess one FCH, two forward SCH (F-SCH) and two
reverse SCH (F-SCH) at most on a specific CDMA channel. During the initial establishment of a call, whether voice service or
data service, only the FCH is assigned to transfer signaling and data.
For the packet data service, SCH can be assigned to transfer data on
the basis of the established FCH when high-speed operations are
required.
The assignment of the forward and reverse FCH is symmetrical. The
forward and reverse SCH for the packet data service is asymmetrical,
where the forward SCH is used for the forward packet data service
and the reverse SCH for the reverse packet data service, and they
are assigned as required.
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Radio ConfigurationRadio Configuration
It refers to the working mode of a series of forward or reverse
channels, including the encoding & decoding types, the
modulation & demodulation mechanism. Each RC supports a
set of data rates that differ in the parameters, modulation
characteristics and spreading rates of the physical channel.
BSC assigns the RC to channels according to the rate set of the
service:
IS-95 only assign RC1 or RC2
CDMA 1X --- assign RC3 ~ RC5 to forward channels and RC3 or
RC4 to reverse channels. RC1/RC2 is compatible.
RC1~RC2IS-95A/B
RC3~RC4CDMA 1X 1X
RC5~RC6CDMA 1X 3x
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Forward Channel RC (Radio Configuration)Forward Channel RC (Radio Configuration)
RadioConfiguration
SpreadingRate
Max Data Rate*(kbps)
Effective FECCode Rate
OTDAl lowed
FEC Encoding Modulation
1** 1 9.6 1/2 No Conv BPSK
2** 1 14.4 3/4 No Conv BPSK
3 1 153.6 1/4 Yes Conv and Turbo QPSK
4 1 307.2 1/2 Yes Conv and Turbo QPSK
5 1 230.4 3/8 Yes Conv and Turbo QPSK
6 3 307.2 1/6 Yes Conv and Turbo QPSK
7 3 614.4 1/3 Yes Conv and Turbo QPSK
8 3 460.8 1/4 or 1/3 Yes Conv and Turbo QPSK
9 3 1036.8 1/2or 1/3 Yes Conv and Turbo QPSK
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Reverse Channel RC (Radio Configuration)Reverse Channel RC (Radio Configuration)
Radio
Configuration
Spreading
Rate
Max Data Rate*
(kbps)
Effective FEC
Code Rate
OTD
Al low ed FEC Encoding Modulation
1** 1 9.6 1/3 No Conv 64-ary ortho
2** 1 14.4 1/2 No Conv 64-ary ortho
3 1 153.6 1/4 Yes Conv or Turbo BPSK
(307.2) (1/2)
4 1 230.4 3.8 Yes Conv or Turbo BPSK
5 3 153.6 1/4 Yes Conv or Turbo BPSK
(614.4) (1/3)
6 3 460.8 1/4 Yes Conv or Turbo BPSK
(1036.8) (1/2)
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Frame Duration (Time Span of Interweaver)Frame Duration (Time Span of Interweaver)
FCH can support 5ms frame and 20ms frame SCH can support 20ms frame, 40ms frame and 80ms frame
Since the current MS can only support the 20ms frame, the
BSC only considers the 20ms frame when assigning channels.
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Frame OffsetFrame Offset
There are altogether 16 frame offsets available to each CDMA
channels.
The BSC lets all the branches on the channel evenly distributed
on each frame offset when assigning the frame offsets.
For the same call, keep each soft handoff branch to have thesame frame offset.
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Code ResourceCode Resource
The radio channel assignment module determines the QOF
(quasi-orthogonal function) index and Walsh code of each
forward channel.
IS-95A/B adopts the fixed-length 64-bit Walsh code while theSCH in the CDMA system adopts the variable-length Walsh code.
The Walsh code length of F-FCH is fixed (RC3 and RC5 are 64,
and RC4 is 128), and the Walsh code length of F-SCH decreases
as the channel rate increases.
The BSC guarantees that the Walsh codes assigned to the SCH
of different rates are always mutually orthogonal when
assigning the code resource. If the BSC assigns a 4-bit Walsh
code with all 0s (0000), it wi ll never assign two 8-bit Walsh
codes (00000000 and 00001111) any longer.
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Reason for Radio Channel AssignmentReason for Radio Channel Assignment
Normal call
Hard handoff Soft handoff/softer handoff
SCH assignment
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Normal CallNormal Call
When the MS originates a call request to the BS or the BS
originates a paging request to the MS to establish a call, the
radio channel resource will be applied.
From one CDMA channel, the BSC assigns the channel
resource that corresponds to the Service Option and can meet
the MS capability according to the Service Option carried in
the request message as well as the MS processing capability.
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Hard HandoffHard Handoff
When the BS requires a hard handoff of the MS to hand overto another frequency, the resource assignment will be
required on another CDMA channel.
The parameters of the channel type and frame offset of thereassigned channel source can completely be different from
those of the channel resource on the original branch. The
BSC will treat the resource like a new call when it assigns the
channel resource.
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SCH (Data Service)SCH (Data Service)
If the service is the packet data service, only FCH will be
assigned during the call establishment.
When there is heavy data traffic to be transferred, the
MS may apply for the R-SCH for the uplink data, while
the BS may apply for F-SCH for the downlink data.
The BSC will assign the SCH with a certain bit rate and
duration according to the Service Option, the capability
that the MS supports SCH and the load of the system.
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Reason for Radio Channel AssignmentReason for Radio Channel Assignment
Call
Origination
Termination
Handoff
Hard Handoff Intra BSC soft handoff
Inter BSC soft handoff
Procedure of Data Service
(DS)
DS call originated by MS
DS call originated by BSC
DS call originated by the
MS is activated
DS call originated at the
network side is activated
Burst service process in
the active state
C C
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Classification of Radio Channel AssignmentClassification of Radio Channel Assignment
Requirement of
ChannelAssignment
PCH
Assign
Handoff
CH
Assign
Burst CH
of Data
Assign
i f i C A i
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Block Diagram of Radio Channel AssignmentBlock Diagram of Radio Channel Assignment
ChannelRequest
DecidetransmissionRate
Success?
Changerate
Can ratebe changedAdmission?
Can Parabe changed
Assign Coderesource
Fail andreturn
Decide CHparameter
No
ChangeParameter
SuccessAnd return
Fail andreturn
Yes
Yes
Yes
Yes
No
No
No
P i i l f Ch l A i C ll Ch lP i i l f Ch l A i t C ll Ch l
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Principle of Channel Assignment --- Call ChannelPrinciple of Channel Assignment --- Call Channel
Available State will be high priority
To Data Service , first priority of channel is DCCH that meets the
requirement and has the least resource waste
If higher requirement , reduce the data rate of data users with
lower priori ty.
Lower rate channel can be accepted if full channel can not be
afforded
For the burst data service, centralize the existing supplemental
channel resource to assign SCCH/SCH to a subscriber.
SCH , a code as long as possible will be assigned according tothe requested traffic rate so as to save the code resource
For high service, DCCH is tried to be specialized in transmitting
signaling
Principle of Channel Assignment --- HandoffPrinciple of Channel Assignment --- Handoff
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Principle of Channel Assignment Handoff
Channel
p g
Channel
Besides the Service Option and the MS capability, there are Cell
Identifier List (Target) and IS-95 Channel Identity or IS-2000
Channel Identity in the hard handoff message. When channels
are assigned, the channel type and parameters in Channel
Identity will be more considered than the principle and method
of channel assignment.
For the channel assignment of the inter-BS soft handoff, pleaserefer to the fields of channel type and service configuration
record in the A7-Handoff Request message.
In the case of the intra-BSC soft handoff, the type and
parameters of the channel can be determined with reference to
other soft handoff branches.
Ch l R lCh l R l
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Channel ReleaseChannel Release
Reason of Channel releaseReason of Channel release
Clear callClear call
Clear original branch after a hard handoffClear original branch after a hard handoff
Clear soft handoff branchClear soft handoff branch
Normal Release ProcessNormal Release Process
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Normal Release ProcessNormal Release Process
MS BTS BSC MSC
Abis-Bts Release
Release OrderRelease Order
Release Order
Clear Command
Release Order
Abis-Remove
Abis-Remove Ack
Abis-Bts Release Ack
Clear Complete
Process of Clearing Soft Handoff Branch betweenProcess of Clearing Soft Handoff Branch between
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g
BSBS
Channel State MaintenanceChannel State Maintenance
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Channel State MaintenanceChannel State Maintenance
Three states of maintenance channel of radio channelThree states of maintenance channel of radio channel
management module:management module:
Operational StateOperational State
Administrative StateAdministrative State
Usage StateUsage State
Operational StateOperational State
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Operational StateOperational State
It indicates whether the resource has been physically installed
and started to operate, and whether it is available. Including:
Disabled: When a resource does not exist any longer, the
operational state is set as Disabled.
Enabled: When a resource is physically installed, the
operational state is set as Enabled.
Administrative StateAdministrative State
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Administrative StateAdministrative State
It indicates the usage of the enabled or disabled resource,
including:
Blocked: If the resource is shut down and no subscriber uses it,
the administrative state is Blocked.
Unblocked: When the resource is completely allowed to be used,
the resource is in the Unblocked state.
Shuttingdown: If some subscribers still use the resource after it
is shut down, the administrative state is Shuttingdown.
Usage StateUsage State
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Usage StateUsage State
It indicates whether the resource is being used at a specific
point and whether there is any extra capacity to provide for
other subscribers, including: Idle: When a resource is not used by any subscriber, the usage
state is Idle.
Active: When some subscriber is using the resource and it stillhas enough capacity to support other subscribers (the current
system load is less than the admission threshold), then the
usage state is Active.
Busy: If the resource does not have enough capacity to support
other subscribers (the current system load is greater than or
equal to the admission threshold), then the usage state is Busy.
Channel State MaintenanceChannel State Maintenance
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Channel State MaintenanceChannel State Maintenance
available block
Unavailable
Receiving
Unavailable
clear all calls
Receiving
Available Allow
assignment
Receiving
Block Stop
assignment
SummarySummary
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SummarySummary
Contents of radio channel assignment
Classification of radio channel state
Chapter 2 Channel ManagementChapter 2 Channel Management
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Chapter 2 Channel ManagementC apte C a e a age e t
Structure of Channel
Management Module
Contents of Channel
Management
Radio Channel Assignment
Channel Assignment AlgorithmChannel Assignment Algorithm
Channel Assignment AlgorithmChannel Assignment Algorithm
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g gg g
Admission control algorithm based on the load
prediction
Code resource assignment algorithm
Dynamic rate adjustment algorithm
Improved frame offset algorithm
Admission Control Algorithm Based on Load
Prediction
Admission Control Algorithm Based on Load
Prediction
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PredictionPrediction
Brief introduction of algorithm:
At the time of channel assignment, first predict the effect of
the access on the whole system according to the
characteristics of the channel to be assigned, and then decide
whether to admit the access or not.
Algorithm characteristics:
The algorithm can more effectively make use of the system
capacity and better satisfy the requirements of different
service types and subscribers with different priority levels.
Purpose of Admission ControlPurpose of Admission Control
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pp
To maintain the forward and reverse load of the system in a
safe state, it is necessary to first make an admission
judgement before the channel assignment. If the latest
assignment brings the unstability of load or even a system
crash, then the channel assignment request will be refused.
Only when the access of a new call does not bring the
deterioration of the system interference, will channels be
assigned to the new call.
Principle of Admission ControlPrinciple of Admission Control
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p
Predict the system load after the access according to the
transmission rate required by the channel assignment request.
Set admission thresholds for the data service and voice service,
respectively.
If an emergency call or high priority subscriber can not access the
system, then the connection of the user EXEC can be released
forcedly so that the emergency call or high priority subscriber can
access the system.
Set admission thresholds for the data service and voice service,
respectively.
Restrict the admission of the data service according to the settings of
the traffic model of the cell.
Code Resource Assignment AlgorithmCode Resource Assignment Algorithm
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Brief introduct ion of algorithm:
Adopt the featured code resource
assignment algorithm to rationally
assign the required forward code.
Algorithm characteristics:
Integrate the characteristics of
mult iple service types.
Make use of the code resource to the
greatest extent so as to guarantee the
balance between the capacity and the
performance of the system.
Code Resource AssignmentCode Resource Assignment
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The codes required to be fixedly assigned in the protocol are
assigned as required.
Channel in forward link can bedistinguished by Walsh Functionor quasi-orthogonal function
By default, the index of the QOFis 00. if Walsh code resourcedeficient, will be non-zero. QOFof Channel W (64, 0) can onlybe 00.
IS95 (RC1, RC2), length of Walshcode is fixed as 64.
IS2000 (RC>=3), length of Walshcode can vary within [4, 128].
The structure of Walsh code canbe obtained from the HADAMARDmatrix.
Brief Introduction of Rate Adjustment AlgorithmBrief Introduction of Rate Adjustment Algorithm
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Brief introduction of algorithm:
When the load of a pilot exceeds the rate change load
threshold, trigger the low bit rate change.
Algorithm characteristics:
When the load ratio of the system is high, via the rate change,the rate of the data service whose delay requirement is not ver
high in the cell can be reduced so as to optimize the resource
assignment and improve the system capacity.
Process of Rate Adjustment AlgorithmProcess of Rate Adjustment Algorithm
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When the load of a pilotexceeds the rate changeload threshold, trigger
the low bit rate change.`
Decrease the transmissionrate of the data service whosedelay requirement is not veryhigh in this cell and reduce the
bandwidth assignment.
When the loadrecovers normal,the changed rate
will recover.
Purpose of Rate Adjustment AlgorithmPurpose of Rate Adjustment Algorithm
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Make full use of the finite data service bandwidth of the air
interface.
Avoid the impact of the high-speed data traffic channel on the
load of the whole system.
How to meet such grand demand
with limited air interface
Make full use of the finite data bandwidthMake full use of the finite data bandwidth
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The BSC firstly assigns a fundamental channel (FCH) to each data service subscriber.
Then the BSC assigns a data buffer to each data service subscriber on the data service
processing board.
When the data size in the buffer is less than the SCH assignment threshold, only the
FCH (9.6kbps) is used. Only when the data size exceeds the SCH assignment threshold,
will the SCH (9.6 ~ 153.6kbps) be assigned so as to avoid unnecessary resource waste.
The value of the SCH assignment threshold is determined by the signaling delay from the
SCH assignment to the SCH establishment.
FCH
SCH
t
t
t1 t2 t1:deciding assign SCH
t2SCH setting up
t: Delay of SCH setting up
t
Rate Adjustment Algorithm SCH AssignmentRate Adjustment Algorithm SCH Assignment
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Dynamically assign the bit rate of the
SCH according to the data flow in the
buffer of each subscriber.
Determine the duration of the SCH
according to the total data size in the
buffer of each subscriber and the bit rate
of the assigned SCH, and dynamically
assign the duration-limited SCH.
It is the most economical
data rate and duration together meet
the through exactly.
Data Suffer
Data from PSDN
FCH +
9.619.238.476.8 or
153.6kbpsSCH
Significance of Rate Adjustment AlgorithmSignificance of Rate Adjustment Algorithm
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The data service is usually discontinuous, so the rate
adjustment algorithm can
make better use of the air interface resource;
save the transmitting power;
enable multiple subscribers to share the radio resources.
SCH of User1
t
SCH of User2
t
ProblemProblem
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How to avoid the impact of high-speed data
traffic channel on the load of the whole
system?
SolutionSolution
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Restrict the highest bit rate that can be assigned to the SCH according to the
pilot strength reported by the MS so as to guarantee the stability of the
system.
Predict the system load after different bit rates are assigned to the SCH so as
to carry out the admission control. If the system load does not permit, make
another judgement after reducing the bit rate by half. Thus the subscribers
request will not easily be refused, and meanwhile, with the system resource
permitted, the requirements of the subscribers, to the greatest extent, can be
met, so as to improve the bandwidth of the system.
BTS
Improved Frame Offset Assignment AlgorithmImproved Frame Offset Assignment Algorithm
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Brief introduction of algorithm:
For the frame offset assignment, make all the calls in one BS
evenly distributed on each frame offset and integrate the
frame offset distribution of the adjacent BS.
Algorithm characteristics:
This algorithm can more effectively make use of the frame-
offset resource, and improve the call connection rate and
handoff success ratio, compared with the traditional algorithm.
SummarySummary
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Differences and characteristics of several channel assignment
algorithms
Sum-up of the ChapterSum-up of the Chapter
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This chapter mainly introduces the structure of the
radio channel management module, contents of radio
channel assignment and reasons thereof, states of
channels, and assignment algorithms.
ReferencesReferences
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Guide to CDMA 1X Admission & Load Control
CDMA BTS Controller Technical Manual (Radio Channel
Management Part)
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