Br10 Interference Reduction

Interference reduction

RA21616EN10GLS0 2009 Noki a Siemens Networ ks

1

Contents

1 Power control 3

1.1 Basics 4

1.2 Measurement preprocessing for power control 6

1.3 Power control decision 9

1.4 Power control execution 16

1.5 Power control for AMR calls 25

1.6 Service Dependent Power Control 26

1.7 Derived Handover Power 30

2 Frequency hopping 45

2.1 Introduction 46

2.2 Frequency hopping systems applied in SBS 52

3 Network Synchronization 71

3.1 Basics 72

3.2 Realization in the SBS 72

4 Improved Uplink Interference Cancellation 81

5 Discontinuous Transmission DTX 89

6 Channel allocation due to interference level 93

7 Exercises 99

8 Solutions 107




2



3

1 Power control



4

1.1 Basics

The objective of power control (PC) is to adapt the transmit power of the MS as well

as of the BTS to the reception conditions. For example a mobile station MS 1 located near the BTS can use a lower transmit power than a mobile station MS 2 at the edge of a cell to achieve the required uplink quality.

There are two advantages of power control:

reduction of the average power consumption (especially in the MS),

reduction of the interference experienced by co-channel (for adjacent) channel users.

Two types of power control are available:

Classic PC

Steps sizes for power control are fixed (2, 4, 6dB) independent of the actual values

for RXLEV and RXQUAL. After a power control command, the power control process is suspended for a certain time.

Adaptive PC

Steps sizes for power control depend on actual value for RXLEV and RXQUAL. The time between two power control decisions is minimized.

Power control is applied separately for the uplink and the downlink and separately for each logical channel. It can be enabled/disabled using the following flags

(administered within the PWRC object):

Specification Name DB Name Meaning

EN_MS_PC EMSPWRC Flag to disable / enable classic / adaptive (def.) uplink power control.

EN_BS_PC EBSPWRC Flag to disable / enable classic / adaptive (def.) downlink power control.

Downlink power control is not applied for downlink bursts using the BCCH frequency.



5

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T

X

P

W

R

MS 1

T

X

P

W

R

MS 2

BTS

Fig. 1 Required MS transmit pow er depending on its distance to the BTS



6

1.2 Measurement preprocessing for power control

Any control loop is based on measurements of the controlled system parameters. For

PC purposes, for each call in progress and for both links (downlink/uplink), measurements of:

received signal level

received signal quality

are carried out over each SACCH multiframe, which is 104 TDMA frames (480 ms) for a TCH and 102 TDMA frames (471 ms) for a SDCCH.

Every SACCH multiframe the MS sends in the next SACCH message block the downlink measurements on the dedicated channel (averaged over one SACCH multiframe) via the Measurement Report message to the serving TRX of the BTS.

This means that any SACCH message will report the averaged data for the previous reporting period only. The TRX performs the uplink measurements on the dedicated

channel. The measurement reports (uplink and downlink) referring to the same SACCH multiframe are used as input parameters for the Measurement Report averaging procedures, implemented within the BTS.

This means that the adjustment of the transmit power of the MS and the BTS is based on following measurement values (refer to Chapter 3.2.2 Measurement

Preprocessing for Handover):

RXLEV_DL_FULL / SUB RXLEV_UL_FULL / SUB

RXQUAL_DL_FULL / SUB RXQUAL_UL_FULL / SUB

The measurement values are preprocessed within the BTS in the same way as for the handover process, i.e. a gliding average window and a weighting of FULL and

SUB values is used. The parameters for measurement preprocessing for power control are administered in the object PWRC and are listed in the table below.

Each sample value is stored together with its weight value (see Figure2). This approach valid both for classic and adaptive PC is a newer one introduced in release BR7.0.

With this method, any window size corresponds to a fixed measurement period and the time to fill the window is always the same. For example, if the window size is n,

the time to fill the window is n*SACCH multiframe period, while with the previous method, the fi lling period is variable and it can varies between n*SACCH multiframe period, in case of all SUB measurements, and (n*SACCH multiframe period)/weight-

value, in case of all FULL measurements.

As drawback the BTS has to manage two buffers, one for the FULL/SUB samples

and the other one for the related weight value.



7

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20 20 30 30 40 41 20 20 Received power level: RXLEV Samples

SACCH frames

DTXSUB

1 2 3 4 1 2 3 4 Received quality: RXQUAL Samples

20 20 30 30 40 41 20 20

x x x 1 1 x x

A_LEV_PC

x = W_LEV_PC

Averaging windows

SUBFULLFULLFULLFULL FULL FULL

The time to fill the window

A_LEV_PC* SACCH frame durationA_QUAL_PC* SACCH frame duration

4 1 2 3 4

y 1 1 y y

A_QUAL_PC

PWRC object

PAVRQUAL- pcAverangingQual

A_QUAL_PC

W_QUAL_PC

PAVRLEV - pcAverangingLev

A_LEV_PC

W_LEV_PC

y = W_QUAL_PC

1 2 3

Fig. 2 Measurement preprocessing for power control



8

Power control correction

This mechanism is necessary to ensure full handover functionality if BS power co ntrol and frequency hopping is enabled.

Normally, if BS PWRC is enabled the MS is informed about this by a flag in the SYS_INFO. This flag makes the MS suppress measurement reports derived from the

BCCH carrier in order to avoid the measurements to be falsified by the full power part of the BCCH.

If frequency hopping is disabled - which could be the case after frequency redefinition

due to failure of a TRX - the MS may hop on the BCCH carrier only. In this case all measurement reports are suppressed (or declared not valid) by the MS which means that no handover is possible. Enabling the power control correction mechanism has the following results:

The BS PWRC flag is set to 0 in the SYS_INFO even if the parameter EBSPWRC=CLASSIC or ADAPTIVE.

The MS thus provides valid measurement reports even for the BCCH carrier.

The BTS takes care that the full power part from the BCCH carrier is correctly substracted from the measurement reports.

Parameters for measurement preprocessing power control

Specification Name

DB Name Range Meaning

A_QUAL_PC PAVRQUAL AQUALPC

1-31

(4)

Averaging window size for RXQUAL values, used for power control

decisions.

W_QUAL_PC PAVRQUAL WQUALPC

1-3

(2)

Weighting for RXQUAL_FULL values.

A_LEV_PC PAVRLEV ALEVPC

1-31

(4)

Averaging window size for RXLEV values, used for power control decisions.

W_LEV_PC PAVRLEV WLEVPC

1-3

(2)

Weighting factor for RXLEV_FULL values.

EN_BS_ PWRC_CORR

EBSPWCR TRUE (def.)/ FALSE

Power control correction in case of BS-power control and frequency hopping.



9

1.3 Power control decision

For power control decision the average values of RXLEV_UL/DL and

RXQUAL_UL/DL are compared with some preset thresholds (O&M parameters). A flow chart of the power control decision process is shown in the figure below.

The power control decision is primarily based upon the received signal quality, rather than on the received signal level. The reason behind this, is that the transmitter

power directly affects the quality of the radio link regardless of the overall received signal level, which may be dominated by co-channel interference. If the controlled variable (its average value) lies in the tolerance defined by the thresholds, then no

control action is taken, i.e. a deadband type of control response is produced. This introduces stability into the control process and guarantees an adequate speech

quality. Note, that the controlled variables involved in the algorithm are used in accordance with their coding, e.g. RXQUAL_XX = 0 corresponds to the least BER (best signal quality: BER



10

The test

RXLEV_XX > L_RXLEV_XX_P + 2 x POW_RED_STEP_SIZE

should prevent the control loop from oscillating, i.e. a power decrease decision for

quality reasons should not be followed by power increase decision for signal level reasons. Note, that the O&M parameter POW_RED_STEP_SIZE is defined in terms

of a difference between two transmit power levels. An unit power level step corresponds to a nominal 2 dB step in the variation of the transmit power. Field measurements at SIEMENS have shown that even at very low received power levels

a good quality for a radio link can be obtained with a relative high probability. Because sudden fades may deteriorate the quality very rapidly, if the above condition

is satisfied, the received power level is then compared with the corresponding lower threshold to ensure a required minimum power level on the radio link.



11

PC Decision

Process

RXQUAL_XXU_RXLEV_XX_P

Power decrease

yes

no

RXLEV_XX POW_RED_STEP_SIZE.

The maximum range for uplink power control is given by:

[13 dBm, Min (MS_TXPWR_MAX, P)] for a GSM-MS Phase 1

[5 dBm, Min (MS_TXPWR_MAX, P)] for a GSM-MS Phase 2 and

for a GSM 850 MS

[0 dBm, Min (MS_TXPWR_MAX, P)] for a DCS1800-MS and

for a PCS 1900-MS

where P is the maximum RF output power of the MS (power class) and

MS_TXPWR_MAX the maximum transmit power allowed in the respective cell. The minimum step size for transmit power adjustment is 2 dB.



17

For downlink power control the range is determined by the maximum output power PBTS of the BTS and the static reduction BS_TXPWR_RED of the BTS output power:

BS_TXPWR_MAX = PBTS - 2 * BS_TXPWR_RED

BS_TXPWR_RED = 0, 1, ... 6, Unit: 2 dB.

The range for downlink power control is then given by:

BS_TXPWR_MAX - 30 dB ... BS_TXPWR_MAX with a step size of 2 dB.

In the case of a power control decision a MS/BS Power Control message is created wherein the MS/BS is requested to adjust its transmit power level to:

REQ_TXPWR = CONF_TXPWR + POW_INCR_STEP_SIZE (Power Increase)

REQ_TXPWR = CONF_TXPWR - POW_RED_STEP_SIZE (Power Decrease)

where CONF_TXPWR is the confirmed power level used by the MS or BTS on the

concerned channel. If these values of REQ_TXPWR are not within the range for power control, the nearest value within the range is used instead.



18

Having requested a transmit power REQ_TXPWR, the power control decision process is suspended and it is waited for a confirmation that the transmit power of the MS/BTS is adjusted to requested value, i.e.

CONF_TXPWR = REQ_TXPWR.

If such a confirmation is not received within an interval of P_CONFIRM SACCH

multiframes, the power control decision process is immediately resumed using the most recently reported confirmed value.

If a confirmation is received, the power control decision process is suspended for a

certain number of SACCH multiframes given by the parameter P_CON_INTERVAL. The reason for this is to allow an observation of the effect of one power control

decision before initializing the next one; by this means the power control process is stabilized. Thus it is recommended to set

P_CON_INTERVAL > A_QUAL_PC

in terms of a number of multiframes.

The processes and time relations are illustrated in the figure below:

case 1: requested transmit power confirmed

case 2: requested transmit power not confirmed



19

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

request

TXPWR

(2)requested transmit power

not confirmed

(1) requested transmit power confirmed

CONF_TXPWR

= REQ_TXPWR

suspension of PC decision

P_CON_INTERVAL

P_CONFIRM

resume

Power Control

resume

Power Control

(2)(1)

time

Fig. 6 Timer usage in the classic power control process



20

1.4.2 Adaptive power control

The adaptive power control for circuit switched services applies increment steps, which are automatically adapted to the system's need according to the signal quality (RXQUAL) or to the signal level (RXLEV). The adaptation steps are dynamically

calculated by the system according to current radio conditions.

Calculation of the stepsize:

Fast power increase is applied, if the signal quality average is below

L_RXQUAL_XX_P and the signal level average is below L_RXLEV_XX_P.

stepsize A [dB]:=abs(RXLEV 0.5*(U_RXLEV_XX_P+ L_RXLEV_XX_P))

Fast power increase is applied, if the signal quality average is above

L_RXQUAL_XX_P and the signal level average is below L_RXLEV_XX_P.

stepsize B [dB]:=abs(L_RXLEV_XX_P RXLEV))

Fast power decrease is applied, if the signal quality average is above

U_RXQUAL_XX_P and the signal level average is above U_RXLEV_XX_P.

stepsize C [dB]:= abs(RXQUAL 0.5*(U_RXQUAL_XX_P+ L_Qual_XX_P))

RXQUAL value is considered by its C/I value in dB as well as the values for U_RXQUAL_XX_P and L_Qual_XX_P.

Standard power increase is applied, if the signal quality average is below

L_RXQUAL_XX_P and the signal level average is above L_RXLEV_XX_P.

stepsize [dB]:= POW_INCR_STEP_SIZE * 2dB;

Standard power reduction is applied, if the signal quality average is above

U_RXQUAL_XX_P and the signal level average is above U_RXLEV_XX_P.

stepsize [dB]:= POW_RED_STEP_SIZE * 2dB;

In case of a power reduction for calls using baseband hopping over the BCCH carrier

the resulting power level reduction is checked against a operator-definable absolute maximum reduction (number of 2dB steps), parameter PCMBSPXTRL.



21

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

RX QUAL

Power Increase

(bad level)

Adaptive stepsize B

Power Increase

(bad quality)

Static stepsize

Power Decrease

(good quality)

Adaptive stepsize C

7

63

RXLEV

0

U_RXQUAL_XX_P

L_RXQUAL_XX_P

L_RXLEV_XX_P

2 x POW_RED_STEP_SIZE

U_RXLEV_XX_P

Power Increase

(bad quality)

Adaptive stepsize A

Power

Decrease

(good quality)

Static stepsize

Fig. 7 Definition of the areas for the different step sizes used in the adaptive power control process



22

Additional changes in the adaptive PC process

Others improvements have been included in the adaptive PC process:

1. Updating of previous RXLEV sample values

After a power change decision, all sample values in the RXLEV averaging window are corrected by the respective power level change as if they were already received with the changed power. For MS power control new UL RXLEV samples in the

averaging window are corrected until the power change was confirmed by the MS. Thus, power control can restart soon without suspension time.

2. Automatically evaluation of the suspension time

In the classic PC, after a new power level is decided, the PC process should wait to fill the window with new samples in order to estimate the quality and received level

after the new power level has been commanded. At this purpose, two timers (PWRCONF and PCONINT) are settable.

For the adaptive PC, PCONINT delay timer is evaluated automatically, while there are no changes with respect to the usage of PWRCONF (powerConfirm).

The delay timer is started only when a power change decision is made due to quality

reasons to allow a new set of RXQUAL values to be received and evaluated since with the "adaptive" mode the level samples will be automatically corrected by the

value of the power change. Since the time needed to fill the averaging window depends on the RXQUAL window length (defined by A_QUAL_PC), the delay timer is calculated from that value and will be

RXQUAL window length * 480 [ms] for TCHs and

RXQUAL window length * 470 [ms] for CCHs.

In summary, the setting of A_QUAL_PC defines the minimum time to send two consecutive power change commands for quality reasons, while the setting of W_QUAL_PC has no influence on any reaction time.

As the delay (suspension) timer is not used when the power control decision is made

due to level and as it has automatically evaluated value in case of power control decision due to quality the value of PCONINT is not relevant for the adaptive power control.



23

Database Parameters for Power Control Execution

Specification

Name

DB Name

/Object

Range Meaning

MS_TXPWR_

MAX

MSTXPMAXx

(x=GSM, DCS, PCS)

/ BTS

2...15

015

0...15, 30,

31

Maximum TXPWR an MS may use in

the serving cell 2 = 39 dBm, 15 = 13 dBm (GSM900) 0 = 30 dBm, 15 = 0 dBm (DCS1800,

PCS1900)

Def.: 5 (GSM), 0 (DCS, PCS)

Range for uplink power control: 13 dBm ... MAX (GSM, phase 1) 5 dBm ... MAX (GSM, phase 2)

0 dBm ... MAX (DCS, PCS) MAX = Min (MS_TXPWR_MAX, P)

P: power class of the MS

BS_TXPWR_ RED

PWRRED / TRX

0...9

(6)

Static reduction of the TRX output power:

BS_TXPWR_MAX = PBTS - 2 * PWRRED

Range for downlink power control: BS_TXPWR_MAX - 30 dB ... BS_TXPWR_MAX

POW_INCR_ STEP_SIZE

PWRINCSS / PWRC

DB2 DB4

DB6 (def.)

Step size for power increase in dB.

POW_RED_ STEP_SIZE

PWREDSS / PWRC

DB2 (def.) DB4

Step size for power reduction in dB.

P_CONFIRM PWRCONF /PWRC

1...31

(2)

Maximum interval to waiting for a confirmation of the new transmit power

level. Unit: 2 TSACCH

P_CON_ INTERVAL

PCONINT / PWRC

0...31

(2)

Minimum interval between changes of the RF transmit power level (time for

suspension of a PC decision after a PC execution Unit: 2 TSACCH

PC_MAX_BS_ TX_POWER_ RED_LEV

PCMBSTXPRL / PWRC

015

(15)

Maximum BS power reduction level for calls using baseband hopping over the BCCH carrier. Unit:2dB



24

PCMBSTXPRL=0 means that no BS downlink power reduction level will be applied for the channels hopping on BCCH.

PCMBSTXPRL=15 means that there are no restrictions in the lower reduction level.

Relations to be observed:

To avoid an oscillating power control due to level the following unequations shall be

fulfilled:

POW_RED_STEP_SIZE < POW_INCR_STEP_SIZE

and

POW_INCR_STEP_SIZE < U_RXLEV_XX_P - L_RXLEV_XX_P



25

1.5 Power control for AMR calls

For AMR calls the power control is implemented basing on the same principles as for

non-AMR calls. As already stated in chapter 3 regarding the AMR call HO threshold parameters, harmonization and simplification of attributes and values related to HO and PC have been implemented since this release, i.e. the same threshold

parameters for AMR and non-AMR calls in case of PC are used too.

Database parameters for AMR Power Control are harmonized within the

Service Groups (see next section, SG11PCPARSG14PCPAR) and are the same as for non-AMR calls:

Specification Name DB Name /Object Range Meaning

L_RXQUAL_AMR_DL_P

L_RXQUAL_AMR_UL_P

LOWTQUAD

LOWTQUAU / PWRC

020

(12)

Lower quality threshold on

downlink/uplink for power increase. Unit: 1dB

U_RXQUAL_AMR_DL_P

U_RXQUAL_AMR_UL_P

UPTQUAD

UPTQUAU / PWRC

020

(17)

Upper quality threshold on

downlink/uplink for power decrease. Unit: 1dB



26

1.6 Service Dependent Power Control

The feature Service Dependent Power Control is also based on distinguishing the

fourteen CS service groups as defined in Chapter 3. This concerns Signaling services, Circuit-Switched services (CS) on Half Rate (HR), Full Rate (FR), Enhanced Full Rate (EFR), Adaptive Multi-Rate (AMR), Advanced Speech Call Items

(ASCI), Voice Broadcast Services (VBS), Voice Group Call Services (VGCS), and High Speed Circuit-Switched Data services (HSCSD).

For each service group relevant threshold parameters for Power Control can be defined individually. If parameters are not set for a service group (default value "NULL"), global parameter settings is implemented. It is possible to define specific

PC parameters for some selected service groups and leave the others unchanged.

The SG quality attributes for PC are also adapted to the new units/ranges in BR 9.0.

These parameters are part of the attribute SGxPCPAR x=1,2,16 in the object SET PWRC. The attribute is composed of 16 fields.

Example:

SG3PCPAR=CLASSIC-CLASSIC-TRUE-25-25-25-35-10-12-12-17-17-NULL-NULL

or

SG14PCPAR=CLASSIC-CLASSIC-TRUE-20-20-30-23-10-8-8-14-14-NULL-NULL

with the following meaning:

SGxPCPAR=EBSPWRS-EMSPWRC-EPRWCRLFW-LOWTLEVD-LOWTLEVU-

UPTLEVD-UPTLEVU-PCRLFTH-LOWTQUAD-LOWTQUAL-UPTQUAD-

-UPTQUAU-RDLNKTBTS-RDLNKTO.



27

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

PWRC

PWRC parameters: NAME EBPWRC EMSPWRC

SG1PCPAR SG1PCPAR

SG14PCPAR

PCMBXTSPRL

Standard settings

for all SGs that

are not activated

PWRC parameters for SG1:

enableBSPowerControl enableMSPowerControl

PCUpperThresholdQualUL

PWRC parameters for SG14:

enableBSPowerControl enableMSPowerControl

pcradioLinkTimeoutBs

Special settingsfor Service Groups that are activated

PCUpperThresholdQAMRUL

pcradioLinkTimeoutMs

Fig. 8 Principle of service dependent power control



28

Parameter Description

EBSPWRC Enable Base Station Power Control

EMSPWRC Enable Mobile Station Power Control

EPWCRLFW Enable Radio Link Failure Warning

LOWTLEVD Lower DL RXLEV Threshold

LOWTLEVU Lower UL RXLEV Threshold

UPTLEVD Upper DL RXLEV Threshold

UPTLEVU Upper UL RXLEV Threshold

PCRLFTH Threshold for Radio Link Failure Counter

LOWTQUAD Lower DL receive signal quality Threshold

LOWTQUAU Lower UL receive signal quality Threshold

UPTQUAD Upper DL receive signal quality Threshold

UPTQUAU Upper UL receive signal quality Threshold

RDLNKTBS Radio Link Timeout BS counter value:

Range 0-15, 0=4*SACCH,...15=64*SACCH (10)

RDLNKTO Radio Link Timeout MS counter value:

Range 0-15, 0=4*SACCH,...15=64*SACCH (10)



29

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fig. 9



30

1.7 Derived Handover Power

Currently the maximum TX power is used after all intercell handovers until the power

control procedure has reduced the power to a required minimum level. As a consequence higher interference level after handovers (HO) is very often the case.

The BR9.0 feature Derived Handover Power (DHP) enables BSS and mobile station

to avoid the unnecessary usage of maximum transmit (TX) power on the air interface after having performed a handover, and thereby reduce interferences.

By using a derived power (TX power before HO +security margin) during uplink and downlink handovers, the TX power can be limited to the real need.

Network operators can enable/disable the Derived Handover Power feature per

neighbor cell relationship individually for UL and DL direction and set different margins to customize the feature according to the actual needs in the cell.

The Derived HO Power feature is applicable in case of:

Scenario: Intercell/Intra BSC HO,

HO type: Better Cell HO and Mobile Speed Sensitive HO,

On the first Better Cell HO for this channel (if a HANDOVER FAILURE towards the same target cell has taken place before, DHP is not applied),

Service type: CS voice (AMR and all non-AMR calls), CS data, signaling in case of SDCCH-SDCCH handover, ASCI UL (VGCS) and HSCSD.

The benefit for an operator is a decrease of the overall interference which means the

system capacity increases in the interference limited scenarios.



31

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BTSserv BTStarget

Signaling

Traffic

Neighbor

Cell Measmnt.

Path-loss

Pathloss = f {MSdedicated mode-Measurements, System parameters}

TXpwrDL = f {Pathloss between MS and BTStarget}

TXpwrUL = f {TXpwrDL} [HO Command]

The Tx Power to be used after the HO is

mainly a function of

the momentary path-

loss on the air

interface

Fig. 10 Derived Handover Pow er feature



32

1.7.1 Optimal MS/BS transmission power calculation

When an MS performs a handover from one BTS (serving BTS) to another BTS (target BTS), it is possible for the BSS to calculate the optimal UL and DL TX power for the connection between MS and the target BTS. This is achieved by enabling the

DHP feature which calculates and applies the optimal MS and BS transmission power values in the target cell immediately after power budget handover.

Thus DHP avoids interference by avoiding unnecessary high MS and BS Power levels directly after an inter-cell handover due to better cell. T

The MS and BS power values are calculated based on:

1. Neighbor cell RXLEV and (idle TCH) UL interference measurements (MEASUREMENT REPORTs from MS and Idle TCH measurements performed by the target BTS)

2. Database parameters, which have to be carefully set after qualified estimations or field measurements.

The DHP calculation is done in the handover target BTS, after reception of the

CHANNEL ACTIVATION message for the target TCH.

For this, the INTERCELL HANDOVER CONDITION INDICATION message from the serving cell contains the averaged RXLEV values of the (2G) target cells

(RXLEVtarget).

When a target cell was selected for handover, the BSC adds the corresponding

RXLEVtarget value and a flag indicating which DHP direction (UL/DL) is enabled, to the CHANNEL ACTIVATION message that is sent towards the target BTS.

The target BTS calculates the suitable MS and/or BS transmit power and sends the

resulting MS Power value back to the BSC (DHP UL).

The BSC inserts the received MS Power value into the IE Power command in the HANDOVER COMMAND message (DHP UL).

The target BTS commands the calculated MS Power value in the SACCH layer 1 header (DHP UL) and adjusts the initial BS Power to the calculated value (DHP DL).



33

Fig. 11 Intercell HO execution steps

CHANNEL ACTIVATION ACK

INTERCELL HCI (better cell)

RXLEVtarget included for 2G target cells

DHP UL/DL

enabled?

HANDOVER COMMAND

CHANNEL ACTIVATION

BTS

calculates

MS Powerand/or

BS Power

HANDOVER COMMAND

HANDOVER COMPLETE

FACCH

SABM

FACCHUA

FACCH

HANDOVER ACCESS

FACCH

PHYSICAL INFO

FACCH

BTS

applies

calculated

BS Power and commands

MS Power in SACCH layer-1

header

HANDOVER DETECT

MS BTSserving BSC BTStarget

RXLEVtarget included

DHP UL

DHP DL

MS Power included

MS Power in IE

Power Command

MS applies

commanded

MS Power

Fig. 12 DHP Operational Sequence



34

1.7.1.1 DHP Calculation Algorithm in target BTS

To determine the optimum transmit power to be used after HO, at first the pathloss

between the MS and the target BTS must be calculated by means of the MS neighbor cells measurements.

The basic calculation of the optimum MS and BS Power in the handover target cell is

based on the assumption that uplink pathloss and downlink pathloss have the same value.

The pathloss (PATHLOSS_DL or PATHLOSS_UL) is calculated by utilizing measurements carried out by the MS in dedicated mode (neighbor cell measurements) and some system parameters as mentioned above.

The following aspects are being considered by the calculation of the optimum TX power to be used after HO within the target BTS:

RF Feeder Cables

Combiner

TMA

Transmit Diversity

Receive Diversity

Dual Band / Single BCCH

UL Interference

Neighbor Cell measurement C/I

Mobile Station TX Power Capability

Base Station maximum TX power.

The following correction factors must be estimated and configured by the operators:

Security margin (including tolerances)

Unknown DL Interference,

if a significant DL interference is expected but cannot be estimated, Derived HO

Power should be used for UL only.

Once calculated, the TX power values are used in the BTS (DL direction) and can be commanded to the MS (UL direction) as a part of the Handover Command message

that is sent from the BSC to the MS.



35

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

compo

PATHLOSS_DL

PATHLOSS_UL

PATHLOSS_DL = BSPOWERANT RXLEV_DL

PATHLOSS_UL = MSPOWER RXLEV_ULANT

Fig. 13 Components of the PATHLOSS_DL/UL calculation



36

DHP Basic MS Power Calculation Algorithm in target BTS

Basic algorithm for the calculation of the optimum MS Power in the target cell is based on assumption that the PATHLOSS_DL is equal to the PATH LOSS_UL:

PATHLOSS_DL = BSPOWER RXLEV_DL

PATHLOSS_UL = MSPOWER RXLEV_UL

and assuming that

PATHLOSS_DL = PATHLOSS_UL

the equation

BSPOWER RXLEV_DL = MSPOWER RXLEV_UL

can be re-arranged for calculation of the MS Power as follows:

MSPOWER = BSPOWER - RXLEV_DL + RXLEV_UL.

To achieve an MS Power value which reflects a real optimum under the current

conditions from RXLEV perspective, the equation terms are replaced as follows:

BSPOWER BSPOWERtarget-max = Maximum possible BS transmit power in target

cell,

RXLEV_DL RXLEV_DLtarget-mea = DL RXLEV of target cell as measured and

reported by MS,

RXLEV_UL RXLEV_ULtarget-op = Desired (optimum) RXLEV UL in target cell, =

arithmetic mean of upper and lower uplink power control RXLEV threshold , i.e.

RXLEV_ULtarget-op = (UPTLEVU+LOWTLEVU)/2.

This results in the following calculation formula:

MSPOWERRXLV = BSPOWERtarget-max - RXLEV_DLtarget-mea + RXLEV_ULtarget-op

MSPOWERRXLV = Current_Pathloss_DL + Optimum_UL_RXLEV,i.e.

the optimum MS Power (RXLEV p.o.v.) is the sum of

1. the optimum UL RXLEV as intended by the operator, represented by the middle of the Power Control Level Window which is defined by the upper and lower UL RXLEV thresholds for Power Control and

2. the current DL pathloss which the MS must overcome.



37

In addition to the RXLEV based calculations and parameters, the target channels UL C/I conditions must be considered.

For this reason, the BTS calculates an additional optimum MS Power value, that

guarantees acceptable UL C/I conditions after handover.

Of both calculates values, the BTS will select the higher one, i.e.,

MSPOWERopt = max(MSPOWERRXLV, MSPOWERC/I)

In detail, the BTS checks the following additional C/I condition

MSPOWERC/I Opt_C/I_UL + UL_Interf + (BSPOWERtarget-max - RXLEV_DLtarget-mea)

where

Opt_C/I_UL = Optimum (desired) C/I UL in target cell= arithmetic mean of upper and lower uplink power control C/I threshold, i.e. (UPTQUAU+LOWTQUAU)/2

UL_Interf = UL interference as measured by the BTS on the idle target channel

BSPOWERtarget-max = Maximum possible BS transmit power in the target cell

RXLEV_DLtarget-mea = DL RXLEV of target cell as measured and reported by MS.

The above formula

MSPOWERC/I Opt_C/I_UL + UL_Interf + (BSPOWERtarget-max - RXLEV_DLtarget-mea)

can be wtitten as

MSPOWERC/I = Opt_C/I_UL + UL_Interf + Current_Pathloss_DL

Therefore, the resulting optimum MS Power must be the sum of

1. the optimum UL C/I, represented by the middle of the Power Control C/I Window which is defined by the upper and lower UL C/I thresholds for Power Control

2. the UL signal currently interfering the target channel which the MS must drown out.




38

Additional factors related to MS Power Calculation

In addition to the above basic RXLEV and C/I related MS Power calculations, further additional factors must be considered.

One factor to be considered is the feature Transmit Diversity.If Transmit Diversity is enabled in the handover target cell (and, consequently, the CUs are combined on air via two antennas), an additional 3dB gain is achieved in the DL of the target cell.

As this gain is included in the DL value measured by the MS, but does not exist in the UL, the 3dB DL gain must be considered in the MS Power calculation by adding 3dB

to the calculation result of the basic algorithm.

In case the handover target cell is a dual band cell (Dualband Concentric or Dualband Standard Cell), the pathloss difference (PLD) between the different frequency bands is considered in addition.

For both types of cells, it may happen that the neighbor cell measurements are performed for one frequency band (e.g. GSM900 used as BCCH frequency) but the

target TCH is assigned on a TRX on the other band (e.g. DSC1800).

If this scenario applies, an estimated PLD is added to the result.

The PLD is represented by an Additional PL Dualband cell term which is defined by parameter ADDPATHLDBC (PWRC object); its default value depends on the SYSID setting and the frequency band allocation of the TRXs.

This PLD parameter is not only applied for the calculation of the optimum MS Power in the target cell, but also for the optimum BS Power.

These tolerances are considered by a DHP Security Margin which can be defined by parameter DERHOPWRSM (PWRC object), default value = 5dB.

For a correct determination of the MS Power, system tolerances in measurement and

adjustment must be considered (BTS/MS receiver accuracy tolerances and BTS/MS transmit power accuracy all dependent on conditions and RXLEV range). The DHP Security Margin is applied for the calculation of the optimum MS Power in the target cell, as well as for the optimum BS Power.

Without DHP applied, the maximum allowed transmission power the MS may apply

on the assigned handover target channel is defined by the parameter MSTXPMAXx (x=GSM, DCS or PCS depending on the used frequency band). Up to BR8.0, this value was considered for the initial MS Power after HO.

In BR9.0, it is possible to define a maximum power reduction related to the setting of

defined by the parameter MULPWRRED (PWRC object), default value = 6dB.

A corresponding parameter is also available for the DL direction (parameter MDLPWRRED.



39

DHP Basic BS Power Calculation Algorithm in target BTS

Like for the MS Power calculation case, the optimum RXLEV is assumed to be the middle of the Power Control Level Window (arithmetic mean of upper and lower PWRC level threshold).

Considering that the BS TX signal must overcome the current DL pathloss, the

optimum BS Power (from RXLEV point of view) is calculated as follows:

BSPOWERRXLV = Current_Pathloss_DL + RXLEV_DLtarget-op

BSPOWERRXLV = BSPOWERtarget-max RXLEV_DLtarget-mea + RXLEV_DLtarget-op

where

RXLEV_DLtarget-op = Desired RXLEV DL in target cell, = arithmetic mean of upper and

lower downlink power control RXLEV threshold , i.e. (UPTLEVD+LOWTLEVD)/2

BSPOWERtarget-max = Maximum possible BS transmit power in target cell


In addition to these RXLEV based calculations and parameters, the target channels DL C/I conditions must be considered.

In contrast to the UL, however, the DL interference can only be estimated.

Based on this estimation, the BTS calculates an additional optimum BS Power value,

that guarantees acceptable DL C/I conditions after handover.

Of both calculates values, the BTS will select the higher one, i.e.

BSPOWERopt = max(BSPOWERRXLV, BSPOWERC/I).

In detail, the BTS checks the following additional C/I condition

BSPOWERC/I Opt_C/I_DL + DL_Interf + (BSPOWERtarget-max - RXLEV_DLtarget-mea)

where

Opt_C/I_DL = Optimum (desired) C/I DL in target cell = arithmetic mean of upper and lower uplink power control C/I threshold, i.e. (UPTQUAD+LOWTQUAD)/2,

DL_Interf = Estimated DL interference, as defined by parameter ESTDLINT,

BSPOWERtarget-max = Maximum possible BS transmit power in the target cell,


Therefore, the formula

BSPOWERC/I Opt_C/I_DL + DL_Interf + (BSPOWERtarget-max - RXLEV_DLtarget-mea)

can be converted as follows

BSPOWERC/I Opt_C/I_DL + DL_Interf + Current_Pathloss_DL.



40

The resulting optimum BS Power must be the sum of:

1. the optimum DL C/I, represented by the middle of the Power Control C/I Window which is defined by the upper and lower DL C/I thresholds for Power Control,

2. the estimated DL Interference on the target channel which the MS must drown out,


As mentioned before, additional factors, that had to be considered for a correct calculation of the optimum MS Power in the target cell, have to be considered for the 'Optimum' BS Power calculation, too.

The following factors have to be included in addition when deriving the final 'Optimum' l BS power:

Measurement and adjustment tolerances, reflected by the DHP Security Margin, parameter DERHOPWRSM, default value = 5dB,

Path Loss Difference of Dualband Cells represented by an Additional PL Dualband cell term which is adjusted by parameter ADDPATHLDBC,

Maximum Downlink Power Reduction related to the maximum DL output power

(BSPOWERMAX) of the target cell. This reduction is represented by the parameter MDLPWRRED in the PWRC object, default value = 6dB.



41

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Br10 Interference Reduction

Documents

Transcript of Br10 Interference Reduction