traffic allocation

NORTEL NETWORKS CONFIDENTIAL Traffic Allocation, September 2000

CDMA Traffic AllocationCDMA Traffic Allocation

CDMA RF EngineeringCDMA RF Engineering

CDMA Network EngineeringCDMA Network Engineering

Nortel Wireless SolutionsNortel Wireless Solutions

Traffic Allocation, September 2000NORTEL NETWORKS CONFIDENTIAL

Methods of Traffic Allocation

• Idle Mode

— Mobile HASHING using Channel List

— Global Service Re-Direction (GSR) using Access OverLoad Class ACCOLC(0 - 9, A - F)

• Active Mode (Call Setup)

— Multi Carrier Traffic Allocation (MCTA)


Idle Mode AllocationGSR/Channel List

• Mobile is allocated to one of the available channels (with active

Paging Channel) while in Idle Mode.

• Allocation of mobiles to the available frequencies is solely

dependent on Allocation algorithm.

• Mobile Remains on that channel while in the channel’s coverage

area (Excluding step down area).

• The two methods of allocation, GSR and HASHING (Channel List),

are Mutually exclusive to prevent ping-Pong

• Margin required between Allocation and step down sectors/BTSs


Channel List (HASHING)

• Mobile is turned on or Enters the region where more than one Paging Channel is configured.

• A Channel List message with available channels is continuously broadcasted on the Paging Channel.

• Mobile Chooses the desired channel by means of its IS-95 HASHING Function (While in Idle Mode).

• Mobile remains on that channel until it leaves the area where the additional channels are available or gets directed to the underlying channel (Step Down).

• Design Considerations— Hashing will provide a statistical even traffic distribution between carriers.

— Hashing can be used between multiple carriers (F1, F2, F3, ….etc).

— GSR is used on the border sectors to provide step down direction to underlying Frequency (for all mobiles).

— A margin is required between Channel List BTS’s and GSR Step Down Sectors to prevent Ping-Pong

— Step Down should not occur in high traffic area.


Channel List at Carrier Boundaries

Margin to prevent Ping-Pong (NO HASHING)

GSR Hand Down on Outward Facing Sectors

Channel List/ Hashing Idle Mode Allocation

F2F1

F2F1F

1

F2F1

Margin

Active Call on F2 until RTD

Idle Mode Allocation


Global Service Re-Direction (GSR)• Mobile is turned on or Enters the region where GSR for Idle Mode Traffic

Allocation is active

• GSR directs mobiles based on the Access Overload Class set within the GSR Message (a bit mapping Word (16 bits 0 - F))

• GSR Message can be broadcasted full or part time on the Paging Channel

• GSR Messages should be exclusive between different Channels

• Mobile remains on that channel until it leaves the area where the additional channels are available or gets directed to the underlying channel.

— Border sectors provides a GSR message sending all mobiles to the underlay frequency

• Design Considerations— GSR can provide a selectable (10% increment) allocation of mobiles.

— Step down GSR should not overlap with Hashing or Traffic Allocation GSR

— A margin is needed between GSR Traffic Allocation Sectors and GSR Hand Down Sectors to prevent Ping-Pong

— GSR is Sector Settable which can reduce the required Margin

— Hand Down should not occur in high traffic area


Global Service Re-Direction (GSR)

• action SendGlobalServiceRedirectionMessage on O%:CBS1:Cells1:MiniBTS443:BTSC_Uni

• t1:Root1:btSC1:FrequencyAssignment1:Sector1 (REDIRECT_ACCOLC = 0x07C0,

• RETURN_IF_FAIL = 0,

• DELETE_TMSI = 0,

• RECORD_TYPE = CDMASystemRedirection,

• CDMASystemRedirectionRecord = (

• BAND_CLASS = 1_8_2_0GHz,

• EXPECTED_SID = 4181,

• EXPECTED_NID = 1,

• CDMA_CHAN_List = (1, 0=25)

• )

• );



• ACCOLC = 0x07C0

• The interpretation of this message is as follows:

• 0 7 C 0

—0 0 0 0 | 0 1 1 1 | 1 1 0 0 | 0 0 0 0 | — 0 1 2 3 4 5 6 7 8 9 A B C D E F

— Mobiles with ACCOLC ( 5 – 9 ) will be re-directed to Channel 25.



• action SendGlobalServiceRedirectionMessage on O%:CBS1:Cells1:MiniBTS143:BTSC_Uni

• t1:Root1:btSC1:FrequencyAssignment1:Sector1 (REDIRECT_ACCOLC = 0xF800,

• RETURN_IF_FAIL = 0,

• DELETE_TMSI = 0,

• RECORD_TYPE = CDMASystemRedirection,

• CDMASystemRedirectionRecord = (

• BAND_CLASS = 1_8_2_0GHz,

• EXPECTED_SID = 4181,

• EXPECTED_NID = 1,

• CDMA_CHAN_List = (1, 0=200)

• )

• );



• ACCOLC = 0xF800

• The interpretation of this message is as follows:

• F 8 0 0

—1 1 1 1 | 1 0 0 0 | 0 0 0 0 | 0 0 0 0 | — 0 1 2 3 4 5 6 7 8 9 A B C D E F

— Mobiles with ACCOLC ( 0 - 4 ) will be re-directed to Channel 200.


GSR at Carrier Boundaries

Margin to prevent Ping-Pong NO GSR on Outward Facing Sectors

GSR Hand Down on Outward Facing Sectors

GSR Idle Mode Allocation

F2F1

F2F1F

1

F2F1

Margin

Active Call on F2 until RTD

Idle Mode Allocation


Requirements to Set Channel Listor GSR

Channel ListChannel List

• Set the channels in the “ChannelList” parameter (configurable) under the BTSC MO of every BTS that the channel list is to be enabled.

• The order of the channels must be the same across the board.

• Legacy BTS has to be re-loaded.

• Settable parameter with the Metro Per DCG.

• Each DCG can have ONLY ONE Channel List (all Carriers on the same DCG will have the same Channel List).

GSRGSR

• Send the “SendGlobalServiceRedirection” action at the specific Sector MO to turn on GSR on the specific sector. The “REDIRECT_ACCOLC” parameter controls the allocation of the mobiles.

• Settable parameter (Action ON / OFF).


Multi Carrier Traffic AllocationMCTA

• It is an algorithm that intelligently allocates traffic between all carriers available in a distinct sector during the Call Setup.

• It works with:— a single Metro Cell BTS

— a combination Legacy and Metro Cell BTSs ( max 3 carriers)

— several (3) Legacy BTSs

• Active when Co-located carriers have the same Cell Ids, Belong to the same BSC, and are available (Blossomed)

• MCTA can be co-Functional with Hashing or GSR

• Design Considerations— Provides allocation of traffic at the borders

— Is independent of Idle Mode Traffic Allocation Methods


Definitions• Capacity Estimate:

— It is the estimated number of calls that can be carried on a specific sector. It can be calculated as follows:

— Note that the Capacity Estimate is the number of CEs when there are no calls on the sector.

Linksofnumber

werOverheadPoPowerUsedHPAker_per_LinAveragePow

PowerUsedHPAdngThresholCallBlockiablePowerAvailHPA

LinkpererAveragePow

ablePowerAvailHPAavailablelinksRFofnumber

availableCodesWalshofnumber

availableCEofnumber

availablelinksRFofnumber

ofSmallesttimateCapacityEs

__

_

__

__

_____

____

___

____

:_

:Where


Definitions (cont.)

• MCTA (Capacity)Threshold— It is the number used in the determination of the “Relative Capacity”

available in the sector in which a call will be setup.

– It is a datafill entry at the AdvancedFA (PilotDatabase) MO.

– It is in units of calls

• MCTA (Frequency) Priority— It the factor used to determine the order in which the carriers should

be analyzed.

– It is a datafill entry at the AdvancedFA (PilotDatabase)MO.

– Lower values have higher priorities

• Relative Capacity:

— It is used by the MCTA algorithm when selecting a carrier. It is calculated as follow:

— Relative Capacity = Capacity Estimate - MCTA (Capacity)Threshold


MCTA algorithm

Find the preferred frequency ( F ) using the priority entries

Calculate Capacity Estimate for Each blossomed frequency in the sector

is Capacity Estimate of (F)

MCTA threshold

of F

Select frequency ( F )

Find the next preferred frequency. using the priority entries

Are there morefrequencies available?

Select the frequency with the largest Capacity Estimate (voting stage)

Y

N

Y

N

Capacity Estimate = Number

of calls that can be carried on

a specific sector

MCTA Threshold : Minimum number of calls to admit to a high priority frequency before selecting the next priority frequency


Frequency F1 F2 F3

Frequency Priority (datafill) 0 0 0

Capacity Threshold (datafill) 64 64 64

Calculated Capacity Estimate 10 12 8

is Estimate > Threshold No No No

Calculate Relative Capacity -54 -52 -56

Select highest Capacity Estimate

MCTA algorithm

Example 1: Even Traffic Distribution


Frequency F1 F2 F3




is Estimate > Threshold No Yes -

F2 is selected

MCTA algorithm

Example 2: Sequential Traffic Distribution


Frequency F1 F2 F3




is Estimate > Threshold No No No

Calculate Relative Capacity -3 -1 -58

Select highest Capacity Estimate

MCTA algorithm

Example 3: Sequential Traffic Distribution


MCTA at Carrier Boundaries

F3F2F1

F2F1F

1

Datafill: Even / Sequential

F1: FrequencyPriority = 0 CapacityThreshold = 3



Datafill: Sequential


F2: Priority = 1 CapacityThreshold = 64

Datafill: N/A Datafill: Even




F3F2F1

Moving away from core of a network

Note: The value specified for CapacityThreshold is a best estimate. This value will be re-evaluated once more field data has been collected and analyzed.



MCTA Algorithm

At call set-up, the system sends a ‘capacity request’ message to each BTS/DCG configured as a part of the MCTA cell site and Blossomed.

Each BTS/DCG responds with its Capacity Estimate in the ‘capacity response’ message.

The system then uses the Carrier Determination Algorithm (CDA) to select the best carrier.



Where does the MCTA decision take place?

All Metrocell system - the MCTA decision takes place at the metrocell itself on a DCG basis.

For multiple DCGs in 1 cellsite, the MCTA decision takes place at the SBS level.

All Legacy system the MCTA decision takes place at the SBS level.

A Metrocell - Legacy System - part of the decision takes place at the metrocell/DCG and the final decision at the SBS level.


How does it work? - Single Metro CellLocal MCTA decisionis made here per DCG.A frequency is selected

Metro Cell

BTSCall Processing

Advanced FA1MCTAPriority

MCTAThreshold

Sector

Sector

Sector

Sector

Sector

Sector

Advanced FA(2)MCTAPriority

MCTAThreshold

Reports Capacity Estimate for F1 sector , , or

Reports Capacity Estimate for F n sector , , or


How does it work? - Legacy only

MCTA decisionis made here.

A frequency is selected

SBS

Pilot Database

Sector (n): CapacityThresholdSector (n): FrequencyPriority

Reports Capacity Estimate for BTS 1

sector , , or

Reports Capacity Estimate for BTS n

sector , , or

FrequencyAssignment

Sector

Sector

Sector

Legacy (n)

BTSC

FrequencyAssignment

Sector

Sector

Sector

Legacy 1

BTSC


How does it work? - Metro Cell & Legacy

Final MCTA decisionis made here.

A Frequency is selected

SBS

Pilot Database

Sector (n): CapacityThresholdSector (n): FrequencyPriority

Metro Cell 1

Reports Capacity Estimate for Legacy

sector , , or

Reports Capacity Estimate for selected

Frequency sector , , or

BTSCall Processing

Advanced FA1MCTAPriority

MCTAThreshold

Sector

Sector

Sector

Sector

Sector

Sector

Advanced FA(2)MCTAPriority

MCTAThreshold

Reports Capacity Estimate for F1 sector , , or

Reports Capacity Estimate for F n sector , , or

Initial MCTA decisionis made here, one frequency

is selected for each Metro Cell

FrequencyAssignment

Sector

Sector

Sector

Legacy 1

BTSC


Comparison of the three Traffic Allocation schemes

F2F1GSR Hand Down

Channel List/Hashing Idle Mode Allocation

F2F1

F2F1F1 Margin to avoid

ping pong

GSR Hand Down

GSR Idle Mode Allocation

F2F1

F2F1

F1

F2F1

Margin to avoid ping pong

F2F1

F2F1F1

Moving away from core of the network

F1 only regionNo MCTA

Border SiteLoading: Sequential

Core SitesLoading: Even

F2F1

Channel List/HashingIDLE MODE

GSRIDLE MODE

MCTAACTIVE MODE Margin


Requirements to Set MCTA

• Use the same Cell Id for all carriers, for at most 3 carriers, within the same MCTA site.

• All Co-located MCTA BTS’s must belong to the same BSC.

• Set the “MCTATimeout” parameter to a value that allows enough time for the “Capacity Response” message from all BTSs to be received at the SBS. Recommended value is 100 ms.

• Set both the “CapacityThreshold” and the “FrequencyPriority” PDB parameters of each sector to a proper value dependant on the MCTA RF design.

• Set “frqvct” field (cdma_frequency_vector field) of each CDMAPART table entry of an MCTA sector to have the appropriate frequency. Once done, the MCTA OMs will be collected on per frequency basis.


MCTA and Step-DownHHO Interaction

• If MCTA is turned on at the step-down sites, then special considerations need to be made to have a successful step-down:

— MPHHO must be turned on.

— The first target BTS in the target list must be a non-MCTA BTS. The rest of the targets can be either MCTA or non-MCTA BTSs.

• If the above is not feasible, then, to have a successful step-down, MCTA must be disabled at the step-down site (i.e. use different Cell Id at the step-down site).

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