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Introduction to Introduction to Parameters for Parameters for Traffic BalanceTraffic Balance

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AJEWOLE, TIMOTHY AJEWOLE, TIMOTHY OLUWATOSIN OLUWATOSIN

(84759)(84759)GSM-NPOGSM-NPO

JUNE 14, 2005JUNE 14, 2005

Tutor: PANTHER JIZENGBAOTutor: PANTHER JIZENGBAO

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CONTENT

INTRODUCTION

CAUSES OF CONGESTION

REASON FOR TRAFFIC BALANCING

WAYS OF TRAFFIC BALANCING

OPTIMIZATION PARAMETERS

C2 CALCULATION

16-BIT RULE

TECHNICAL CASES

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INTRODUCTION

• Good afternoon Network Quality Manager, RF Planning Engineers, Representatives from Huawei…

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INTRODUCTION

• Congestion is the conflict resulted from the shortage of resources due to various reasons. The resources involved in congestion at BSS side can be divided into to two classifications: wire resource and radio resource. For example, A-Interface circuit congestion and Abis-Interface circuit congestion belong to wire resource congestion. The wire resource congestion mainly refers to A-Interface congestion and the A-Interface congestion might be accompanied with radio signaling channel congestion.

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INTRODUCTION

• The radio resource congestion mainly includes the congestions of various types of channel, such as SDCCH, TCH and AGCH.

• The radio resource congestion mainly includes the congestions of various types of channel, such as SDCCH, TCH and AGCH.

• This document introduces the fundamental knowledge, analysis of the congestion, Optimization and optimization parameters (for balancing traffic)

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1) Unreasonable LA planning.

2) Terrestrial resource unavailable

3) Traffic volume is large and the capacity expansion is needed.

4) Increase of burst traffic, location for festival gathering and the time for short messages being intensively sent etc.

5) TRX fault

6) Interference resulting in channel assignment failure

Causes of Congestion

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Why do we have to balance Traffic?

•To improve the network performance utilizing existing network resources

REASON FOR TRAFFIC BALANCING

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METHODS OF TRAFFIC BALANCE

Traffic can be balanced in two ways:

• In idle mode (C1, C2)

• In dedicated mode (Handover Parameters)

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We shall concentrate on the following optimization parameters for traffic balancing:CRO, TO, PT, and Inter-layer HO Threshold

Definition:

CRO: Cell reselection offset. It indicates the C2 value can be corrected manually. Range 0~63. Corresponding level value: 0~126db. Unit- 2dB

TO: Cell reselection temporary offset, indicating the temporary correction value of C2. It works only during the "cell reselection penalty time" period. Range 0~7. The corresponding value: 0~60db and 7 corresponds to "infinite“. 1=10dB

OPTIMIZATION PARAMETERS

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OPTIMIZATION PARAMETERS

PT: Cell reselection penalty time, a parameter to ensure the safety and validity of cell reselection Its main function is to avoid too frequent MS cell reselection. Range 0~31. The corresponding time is 20~620s, 31 is a reserve value used to change the effect of the CRO on C2.

Note:After the MS completes cell selection, the MS in idle mode starts the cell reselection process to select a better serving cell. It is C2 that determines cell reselection. The principle of MS reselection is to select the cell with the maximum C2 value as compared with the serving cell.

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C2 Calculation

• C2 calculation is as follows:

• C1= (receiving signal level - RXLEV_ACCESS_MIN) - max(MS_TXPWR_MAX_CCH - PL, 0)

• C2=C1+CRO-TO*H(PT-T)(PT <31)

• C2=C1-CRO (PT = 31)

• MS_TXPWR_MAX_CCH - PL is the maximum power output of MS

• CRO values can be 0, 1. ...63. The unit is a level value, corresponding to 0=0dB; 1=2dB; ...63=126dB.

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C2 Calculation

• TO values can be 0, 1. ...7• 0=0dB; 1=10dB; ...6=60dB; 7=Infinite

• CRO values can be 0, 1. ...63. The unit is a level value, corresponding to 0=0dB; 1=2dB; ...63=126dB.

• TO values can be 0, 1. ...7• 0=0dB; 1=10dB; ...6=60dB; 7=Infinite

• H()=0 if PT-T<0• H()=1 if PT-T>0

• PT value can be 0, 1. ...31• 0=20s; 1=40s; ...30=620s

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C2 Calculation

• T is the timer, starting from zero at the point at which the cell is placed by the MS on the list of strongest carriers. T is reset to zero whenever the cell is no longer on the list of strongest carriers. This will tend to prevent fast moving MSs from selecting the cell.

• This shows that C1 reflects the radio channel quality. The greater the C1, the better the channel quality. But the C2 value is manually corrected and can be adjusted by CRO. Thus, the C2 value can be calculated accordingly to CRO, TO, and PT so as to reselect the serving cell. For example, we can set CRO so that the C2 value of GSM1800 is greater than that in GSM900. Thus, even in cases that the signal strength in the GSM1800 cell is lower than that in GSM900, MS still can reselect GSM1800 cells as serving cell.

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C2 Calculation

• Inter-Layer HO Threshold: The threshold for inter-layer Hierarchical Handover. This threshold should satisfy the following requirement: Inter-layer HO Thrsh. Edge HO RX_LEV Thrsh. + Inter-cell HO hysteresis. Range 0~63. (-110dBm~-47dBm).

Unit: dB

• Notes: Make sure that the receiving level of the destination cell is higher than inter-layer HO threshold in hierarchical handover or load handover. Otherwise, MS hands over from large load high level cell (high priority cell) to small load low level cell (low priority cell), and MS is

disconnected as a result.

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C2 Calculation

• Inter-layer HO hysteresis: Indicates the hysteresis for inter-layer or inter-priority handover. It is used to avoid inter-layer Ping-Pong handover.

• Actual Inter-layer HO Thrsh. of serving cell = value of Inter-layer HO Thrsh. - Inter-layer HO hysteresis. Actual Inter-layer HO Thrsh. of neighboring cell = value of Inter-layer HO Thrsh. + Inter-layer HO hysteresis.

• Range 0~63. unit dB

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16 BIT RULE

• The 14th bit:The 14th bit: Hierarchical cell structure HO Hierarchical cell structure HO threshold adjustment bitthreshold adjustment bit

• Serving cell criterion:Serving cell criterion: • Receive level >= Layer HO threshold - Layer HO Receive level >= Layer HO threshold - Layer HO

hysteresis hysteresis 0. At the same time, bit 13th, 12th 0. At the same time, bit 13th, 12th and 10th—5th bits are set to 0and 10th—5th bits are set to 0

• If the above criterion is not met, then bit 14 If the above criterion is not met, then bit 14 1.1.• Example : 20-5 = 15 ( -95 dBm )Example : 20-5 = 15 ( -95 dBm )

• Neighbor cell criterion:Neighbor cell criterion: • Receive level >=Layer HO threshold + Layer HO Receive level >=Layer HO threshold + Layer HO

hysteresis hysteresis 0. At the same time, bit 13th, 12th 0. At the same time, bit 13th, 12th and 10th—5th bits are set to 0and 10th—5th bits are set to 0

• If the above criterion is not met, then bit 14 If the above criterion is not met, then bit 14 1.1.• Example : 20+5 = 25 ( -85 dBm )Example : 20+5 = 25 ( -85 dBm )

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TECHNICAL CASES

• For example, we can set CRO so that the C2 value of GSM1800 is greater than that in GSM900. Thus, even in cases that the signal strength in the GSM1800 cell is lower than that in GSM900, MS still can reselect GSM1800 cells as serving cell.

• In a dual-band network of configuration S222 it In a dual-band network of configuration S222 it was observed that sector 3 is highly congested was observed that sector 3 is highly congested about 5.0% . While congestion rate in the 1800 about 5.0% . While congestion rate in the 1800 cell from analysis is about 0%.cell from analysis is about 0%.

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TECHNICAL CASES

JudgmentData configuration showed that

Parameter(900M)

Initial Value

CRO 0

PT 0

Inter-layer HO Thresh

25

Parameter(1800)

Initial Value

CRO 5

PT 0

Inter-layer HO Thresh

25

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• We can use two approaches to balance the traffic between the 900M and 1800M.

1.) Increase the CRO of 1800M so that the C2 value of this cell can stand a chance of being selected in the candidate list.

2.) Make PT=31, in order to change the effect of the CRO on C2 for 900M. i.e. C2=C1-CRO. Which implies that bigger the value of CRO the smaller the value of C2.

You can also reduce the value of Inter-layer HO Threshold from 25 to 23 of the 1800. This will make the priority of the cell to be high.