Concentric & Dual Band Cells

Concentric-Dual Band
Cells
Introduction
Definition
Why Dual Band Cells?

Propagation Overview
Fading Effect
Path loss and Link Budget Calculations

Alcatel/Motorola Parameters and features

Introduction
Definition

• Enables a single Network
Operator with licenses in two or
more frequency bands to support
the use of Multiband mobiles in
all bands of the licenses

• The use of Layers to provide high
capacity with contiguous
coverage. The Outer Zone
maintains contiguous coverage
and the Inner Zone provides
higher capacity. The layers
appear as being concentric due
to Inner Zone having a reduced
coverage area when compared
with the Outer Zone.

Prepared By - Faraz Husain Concentric - Dual Band Cells

Definition (cont.)

 The idea is to split the cell area of a
normal cell into an inner and an outer
zone by operating a certain number of
carriers (inner zone carriers) at a lower
transmission power (Fig). Mobile
stations situated in the outer zone
communicate on the outer carriers.
The mobiles which are closer to the
base station preferably communicate
on the inner carriers but they can use
the outer carriers if needed.

 With this feature the operator may configure non-BCCH carriers within a cell to have
a smaller coverage area. The carriers equipped within a cell may be grouped into two
zones:

• Zone 0: Also referred to as the "outer zone", is reserved for carriers that may broadcast
at the maximum transmit level defined for the cell.
• Zone 1: Also referred to as the "inner zone", may be defined with non-BCCH carriers
transmitting lower power than the BCCH carrier, or having a tighter reuse pattern
that reduces the useful coverage area of the carrier.


Definition (Cont.)

 Concentric Cells can be implemented using one of the three
different algorithms (this is vendor dependent):
 Power Based Concentric Cells: Inner zone carriers transmit less power than
outer ones and the transitions between zones are based on absolute level thresholds.
 Interference Based Concentric Cells: Inner and outer zone carriers transmit
all the same power within and the transitions between zones are based on some interference
conditions. These interference conditions are protection margins against potential interfering
neighbours.
 Dual Band Cells: Support for the management of the cells operating in different bands
by different single band BTS’s or by the same dual band BTS. This is further divided into two
kinds
 Coincident Multiband
 Single BCCH for Dual Band cells

Since we’re using Dual Band Concentric Cells in our network, we’ll
be concentrating more on them for the rest of the workshop!


Why Dual Band Cells?
 Increasing Capacity
 Improving Grade of Service
 Relieving Congestion
 Advanced Network Management Techniques
 Efficient management of traffic required to exploit capacity gain
potential of concentric cells
 Goals
 Maximize handled capacity
 Avoid congestion
 Maintain good call quality
 Avoid unnecessary handovers
 Improved Multi-layer Network
 Best system performance through optimal choice over
 Call originations
 Traffic movement between concentric cell layers
 Generalized handover situations


Let us see how DCS is different from GSM!


Propagation Overview
Fading Effect

Higher pathloss at
1800 MHz

•Reduced interference from
Distant distant site at 1800MHz
Serving Site
Site •More aggressive reuse pattern
can be achieved
Half wavelength l at 1800 MHz
Fading rate twice as fast as 900MHz

•Diversity systems become more
important especially for slow
moving mobiles 1800 radio wave


Fading Effect

The wavelength of a radio signal
determines many of its propagation
characteristics

• Antenna elements size are typically in the
order of 1/4 to ½ wavelength

• Objects bigger than a wavelength can reflect
or obstruct RF energy

• RF energy can penetrate into a building or
vehicle if they have apertures a wavelength in
size, or larger


Antennas

Different Antenna Types

• Different antenna for each Band
• Dual antennas with four ports
• Dual Antennas with 2 ports (900
and 1800 are multiplexed )


2 Ports Antennas

•Extra Duplexers will be
needed to split 1800 signal
from 900 signal

•Duplexers will be with
different polarization to
maintain diversity


Propagation Overview (cont.)

Path Losses in 900 vs. 1800

• A little physics
– Diffraction loss and Penetration loss higher in 1800 MHz band
– 6dB minimal theoretical difference

• Path loss difference - on-street
– Path loss at 1800MHz is typically 6 - 12 dB higher
– Most probable difference in urban environment: 8 dB
– Difference is nearly distance-independent (fixed), in typical urban cells (
i.e. constant offset in “ loss per length unit ” )
– Actual difference depends on site configuration like antenna height and
antenna characteristics
– Cell radius at 1800 MHz typically 25 - 50% less compared to 900 MHz




• Path loss difference - in-building
– Additional attenuation at 1800MHz when penetrating into buildings
– High dependency of penetration loss on building structure, window size,
floor height, angle of incident waves and floor level
– Difference can be compensated with a higher ERP at the 1800 band

• Empirical measurement results
– Building penetration loss at 900MHz:
5dB to 25dB
– Average additional path loss at 1800MHz:
7dB, 4dB standard deviation




LOS dominates Non-LOS dominates
~ 150m - 300m
Receive level

6 - 8 dB
GSM 900
(dB)

>8 dB

in typical urban cells:
• difference is nearly distance-independent GSM 1800

prerequisite:
• same ERP on both bands
• equal antenna pattern

Log (Distance)



Optimisation process:

• Comparing predictions of appropriate GSM900 and GSM1800 cells for in-
building coverage level
(e.g. -68 dBm at 900Mhz / -61 dBm at 1800MHz)

• Adjusting GSM1800 antenna tilts to obtain similar footprint compared to
the appropriate GSM900 cell
– Good overlapping needed to achieve efficient traffic relief on GSM900
– Supports introduction of new multi-band features like coincident multi-band
handover or single BCCH
• Same coverage conditions (except fairly fixed offset) can be achieved
easily with dual band antennas
• Reducing Combining stages in the DCS cells to reduce the losses and use
air combining instead.



Link Budget & Path Loss

Free Space Path Loss



Link Budget Calculations


After having studied in detail the propagation
difference between GSM 900 and DCS 1800,
let us switch back to our original discussion of
Implementing the DCS in a Live network.
Lets look at some BSC and Cell Level
Parameters and then we’ll move forward to
their details.


Database Parameters
BSC Level Parameters

MOTOROLA ------------ ALCATEL

 freq_types_allowed  EN_INTERBAND_NEIGH
 mb_preference  PREFERRED_BAND
 early_classmark_sending  GSM_PHASE
 early_classmark_delay  EN_SEND_CM3
 phase2_classmark_allowed  EN_LOAD_OUTER

MSC:

Ensure phase2 signalling is enabled between BSCs and/or MSCs
(Phase 1 = Legacy MS, Phase 2 introduced around 1999 supporting features like
AMR and DCS)


Database Parameters (cont)
BSC Level Parameters – Description
MOTOROLA

 freq_types_allowed  mb_preference
Numeric value Text string

1 pgsm  The mb_preference parameter enables
2 egsm or disables the Multiband Inter-cell
3 pgsm,egsm Handover feature.
Valid Range
4 dcs1800
 0 = Disabled
5 pgsm, dcs1800
 1 = Enabled
6 egsm, dcs1800
7 pgsm, egsm, dcs1800
8 pcs1900
9 pgsm, pcs1900
10 egsm, pcs1900
11 pgsm, egsm, pcs1900
12 dcs1800, pcs1900
13 pgsm, dcs1800, pcs1900
14 egsm, dcs1800, pcs1900
15 pgsm, egsm, dcs1800,
pcs1900

MSC Requirements
 To have a working Dual-Band capability, the MSC needs to have the capability to handle
Classmark 3 IE (info element)
 CM3 info is sent by multiband MS and contains info about multiband capabilities and power
classes of the mobile in different bands
 This info is present in the MSC for the duration of the call
 In case a multiband handover needs to take place, the serving BSC needs to transmit this info to
the target BSC to inform the target BSS of the capabilities of the MS
 CM3 is important message but is only sent by the MS when requested by the MSC
 However, it is possible to send an early CM3 spontaneously using some BSS level parameters.
 This will enable a multiband MS to spontaneously send CM3 info within some specific
time during Call initializing procedure and ALSO enables the MSs to handover a call to
target BSC (external Handover) by sending CM3 info in Handover Request Message


MOTOROLA
 early_classmark_sending

The early_classmark_sending parameter specifies the following:

• Whether the BSS suppresses the early sending of the Classmark Update message to the MSC.
• Whether an MS is allowed to send an early Classmark Change message.
Valid Range
0 = Disabled across both the A-interface and the Air-interface
1 = Enabled on A-interface, disabled on Air-interface
2 = Disabled on A-interface, enabled on Air-interface
3 = Enabled across both the A-interface and the Air-interface

By Air Interface, Motorola means CM3 sending during Call Setup and by A-Interface, it means CM3
sending during External Handover

When early_classmark_sending is set to 2, the BSS does not forward classmark update messages to the MSC. This means
that the MSC does not obtain any information about the MS capabilities. However, the MSC can still make solicited requests
for classmark updates by sending a Classmark Request message to the BSS. If this is not done, the frequency capabilities of
the MS are based on the target cell frequency when multiband handovers are being performed. Therefore, after an external
handover, neighbours are reported by the BSS to the MS as follows:
Handover from GSM900 to GSM900 - only the GSM900 neighbours
Handover from GSM1800 to GSM1800 - only the GSM1800 neighbours.
External multiband capabilities will be limited, and subsequent handovers to GSM1800 cells are therefore not possible.

MOTOROLA

 early_classmark_delay

The early_classmark_delay timer specifies how long the BSS delays sending the Classmark Update message to the
MSC during Early Classmark sending.
 Valid Range
0 to 100000 milliseconds

 phase2_classmark_allowed

The phase2_classmark_allowed parameter defines the format of the classmark parameter sent to the MSC based
on GSM phases.
 Valid Range
0 = Formatted for Phase 1
1 = Formatted for Phase 2
2 = Formatted for Phase 2 with Multiband


ALCATEL

 EN_INTERBAND_NEIGH (EN_INTERBAND_HO)

This flag enables / disables the multiband operation by filtering the sending of SYSTEM INFORMATION TYPE 2ter/5ter.

 PREFERRED_BAND

Frequency band to which the multiband MS are preferentially directed.
Valid Range
0 = None
1 = GSM
2 = DCS

 GSM_PHASE

This flag indicates the GSM Phase used by the BSC to format messages towards the MSC.
Valid Range
0 = GSM Phase 1
1 = GSM Phase 2


ALCATEL
 EN_SEND_CM3
This flag enables/disables sending of "Classmark
3" IE to the MSC.
 Valid Range
0 = Disabled
1 = Enabled


ALCATEL

 EN_LOAD_OUTER (Load computation in outer zone)

 Flag to enable/disable the load computation on the outer zone of a Concentric/multiband cell instead of the load
computation on the whole cell.
Valid Range
0 = Disabled
1 = Enabled

 When enabled, the values of the parameters FREElevel_1 to FREElevel_4 need to be updated to number of TRX
considered in the load computation. EN_LOAD_BALANCE & EN_LOAD_OUTER should not be both "Enabled".


 Lets take a break. I’d advise we all take
some deep breaths….How about a
joke?!?!??!


Lets head back to the Workshop!

Now we’ll discuss the Cell Level Parameters
that are most commonly used in relation to
Dual band cells.


Cell Level Parameters

MOTOROLA ------------ ALCATEL

 frequency_type •EN_BETTER_ZONE_HO
 interband_ho_allowed •CELL_TYPE
 Inner_zone_alg
•FREQUENCY_RANGE
Thresholds: •EN_MULTIBAND_PBGT_HO
 Rxlev_dl_zone •EN_Bi-BAND_MS
 Rxlev_ul_zone
 Zone_ho_hyst Thresholds:
 Dual_band_offset •RXLEV_DL_ZONE
 Secondary_freq_type •RXLEV_UL_ZONE
•ZONE_HO_HYST_UL
Optional: •ZONE_HO_HYST_DL
 band_preference •Ping_pong_Margin
 band_preference_mode •Optional:
 multiband_reporting
•EN_PREFERRED_BAND_HO
 Ms_txpwr_max_inner
 Bts_txpwr_max_inner •PREFERRED_BAND
 Ho_pwr_level_inner •EN_BETTER_ZONE_HO
 Outer_zone_usage_level
 Pbgt_mode •BS_TXPWR_MAX_INNER
 sdcch_tch_assign_delay •MS_TXPWR_MAX_INNER
•MULTIBAND_REPORTING

Let us first discuss the parameters that
ENABLE the Dual-Band capability in both
vendors. Then we’ll discuss one by one the
Call Assignment and Inter-Zone
Handovers in Motorola and Alcatel


Cell Level Parameters -- MOTOROLA

 frequency_type
The frequency_type parameter specifies the frequency type of a cell.
Valid Range
1 = PGSM
2 = EGSM
3 = DCS 1800
4 = PCS 1900

BEWARE!!!!
intra_cell_handover_allowed
This database parameter you’ll see every now and once which you’ll confuse with enabling of Inter
Zone Handovers. This parameter has nothing to do with Inter Zone handovers. However, if a
Zone attempt to Inner Zone fails due to some reason and you really need to make a handover,
you cant initiate an emergency (Quality, Interference) Handover if intra_cell_handover_allwd is
disabled



 interband_ho_allowed

Changes or sets the allowable frequencies which a cell may handover to.
This parameter must include, at a minimum, the frequency type for the cell. For example, if the cell has a
frequency_type of pgsm, then the interband_ho_allowed parameter must include pgsm as a possible
destination frequency band for handovers

Valid Range : 1 to 11
1 = PGSM
2 = EGSM
3 = PGSM and EGSM
4 = DCS1800
5 = PGSM and DCS1800
6 = EGSM and DCS1800
7 = PGSM, EGSM and DCS1800
8 = PCS1900
9 = PGSM and PCS1900
10 = EGSM and PCS1900
11 = PGSM, EGSM and PCS1900



 Inner_zone_alg
The inner_zone_alg parameter specifies the use algorithm and the associated parameters for the inner zone of the cell.
Valid Range
0 = Disable inner zone
1 = Power based use algorithm.
The system displays prompts for:
 ms_txpwr_max_inner
 Zone_ho_hyst
 Rxlev_ul_zone
 Rxlev_dl_zone
2 = Interference based use algorithm.
The system prompts for:
 neighbor_report_timer
3 = Dual Band Cell use
The system prompts for:
 Secondary_freq_type
 Bts_txpwr_max_inner
 ms_txpwr_max_inner
 Ho_pwr_level_inner
 Zone_ho_hyst
 Rxlev_ul_zone
 Rxlev_dl_zone
 Dual_band_offset


multiband_reporting

 Every MS reports 6 best neighbors in measurement reports when in dedicated mode.
 However, in a multiband environment, to ensure that each band gets its share of MS selecting the
target band’s cell, it is possible that we reserve some positions of neighbors in the measurement
report for a particular band
 This is done using the parameter multiband_reporting
Valid Range:

0 = Normal reporting of 6 strongest neighbors
1 = Report One strongest neighbour cell, in each of the frequency bands in the neighbour cell list,
excluding the frequency band of the serving cell. The remaining positions in the measurement
report shall be used for reporting Cells in the band of the serving Cell.
2 = Report the two strongest cells, in each of the frequency bands in the neighbour cell list,
report shall be used for reporting Cells in the band of the serving Cell
3 = Report the three strongest cell, in each of the frequency bands in the neighbour cell list,
report shall be used for reporting Cells in the band of the serving Cell


Cell Level Parameters -- ALCATEL

 CELL_TYPE

Combination of CELL_DIMENSION_TYPE, CELL_LAYER_TYPE, CELL_PARTITION_TYPE, CELL_RANGE. Used for cell
default parameter template.

Valid values
CELL_DIMENSION_TYPE Single (0), Concentric (1)
CELL_LAYER_TYPE Umbrella (2), Micro (3), Umbrella, Concentric (4), Mini (5)
CELL_PARTITION_TYPE Mini Concentric (8), Micro Concentric (9), Indoor (10), Indoor, Concentric(11)
CELL_RANGE Extended Inner (6), Extended Outer (7)

 EN_BETTER_ZONE_HO

This flag enables/disables the detection of "too high level in outer zone" handover cause (cause 13).
Valid Range
0 = Disabled
1 = Enabled



 FREQUENCY_RANGE

This parameter indicates the frequency range of the cell.

Valid Range: Coded over 8 bits
0: PGSM (GSM 900), 1: DCS 1800, 2: EGSM, 3: DCS 1900, 4: PGSM-DCS1800, 5: EGSM-DCS1800, 6: GSM 850, 7..255:
for future use. The parameter shall be coded over 8 bits as a provision for future frequency bands support.



 EN_MULTIBAND_PBGT_HO

This flag enables/disables the power budget handovers Cause 12 and the traffic handovers Cause 23 between cells
belonging to different frequency bands.

Valid Range
0 = Disabled
1 = Enabled

 EN_Bi-BAND_MS
This flag enables/disables the incoming handovers of bi-band MSs from the preferred band

Valid Range
0 = Disabled
1 = Enabled
.



EN_PREFERRED_BAND_HO:

This flag enables/disables the detection of handover cause 21 (high level in neighbour cell in the preferred band).

HO Cause 21 : high level in neighbour cell in the preferred band

Traffic load is taken into account for serving and target cell. Mostly used in parallel to capturing towards preferred
band and discussion would be OOS (here S=Scope) of this workshop.


Concentric Cells – Implementation

After listing all the relevant parameters for Concentric cells, lets
switch our discussion to Channel Allocation Rules for

 TCH Assignment
 Handovers

It should be clear to you that TCH Assignments to DCS or Inner zone are always
made using the same thresholds as used for Inter-Zone (IntraCell) Handovers.
Think of TCH assignment to Inner zone as a sort of Directed Retry to Inner
Zone. We all know about Directed Retry now…don’t we? :P


Concentric Cells
Database Parameters
TCH Assignment --- Motorola

 The BSS always selects an outer zone channel for an Immediate Assignment. If there are no resources available
in the outer zone, the BSS sends an Immediate Assignment Reject. (WE Cannot AVOID SD Blocking!)
 In order to decide to assign the call to Outer zone or Inner Zone, following parameters are checked:
 Band_preference
 Band_preference_mode
 Inner_zone_alg

 If band_preference = DCS and band_preference_mode is programmed so that SD to TCH assignment is towards
Inner Zone, the decision is taken by the same algorithms used for Outer to Inner Zone Handovers.

 outer_zone usage_level: allows the operator to specify the level of traffic channel congestion which must be
reached in the outer zone prior to the use of the inner zone resources. If the operator chooses to use inner zone
resources whenever a MS is qualified, regardless of outer usage, the database parameter
outer_zone_usage_level can be set to 0.

Valid Range: 0 to 100 (Indicating the percentage of outer zone TCH usage)


Concentric Cells
Database Parameters

 Band_preference: In Motorola BSS, after having set interband_ho_allowed = 1, it may be useful to utilize our
DCS resources once the immediate assignment is completed. A preference for a particular BAND is set by the
parameter band_preference. parameter displays the frequency bands that the cell prefers to use for handovers
and specifies the destination frequency band for inter-cell handovers.
Valid range
1 (PGSM),
2 (EGSM),
4 (DCS1800),
8 (PCS1900)
16 (GSM850)

 Band_preference_mode: parameter specifies the method the system uses to program a Multiband MS with the
preferred frequency band for a given cell in the BSS. This parameter plays role for both Inner Zone Assignment
of the calls (From SD to TCH) and the Handover of the call to Inner zone.


Concentric Cells
Database Parameters
Band_preference_mode:

VALID Ranges:

Band_preference_mode = 0
 The BSS attempts to hand a Multiband MS over to the strongest neighbour that the MS reported when a
handover is required for normal radio resource reasons.

 Attempt handover to strongest preferred band neighbour on SDCCH - TCH assignment
 This is where SD_TCH_ASSIG_BAND_DELAY is used just in case one wants a delay before Preferred band
neighbors are reported for Inner Zone Assignments
 If unable to handover to preferred band TCH, cancel band preference bias for the lifetime of the current
connection
 Multiband handovers due to normal radio reasons may still occur
 The algorithm used for Assignment to Inner Zone is actually the one used for Handover to Inner Zone (will be
discussed later in the Handover part)

 Do not invoke band changes on SDCCH - TCH assignment
 Go to strongest preferred band neighbour when normal radio reason (or congestion relief) handover required
 Preferred band neighbours take priority in the neighbour list


Concentric Cells
Database Parameters

 This value combines the functions of values 1 and 2.
• This would mean to prioritise preferred band at SDCCH-TCH assignment AND when radio reason
handovers are required

 Do not invoke band changes on SDCCH - TCH assignment
 As soon as possible after TCH assignment, attempt to handover to a preferred band channel
 For normal radio reason handover, also prioritise preferred band neighbours

 This value combines the functions of values 1, 2, and 4.
 Attempt to hand to preferred band at SDCCH - TCH assignment
 As soon as possible after TCH assignment, attempt to handover to a preferred band channel
 For normal radio reason handover, also prioritise preferred band neighbours

 This value functions identically to value 5, except it is only triggered when the cell is congested.


Concentric Cells
Database Parameters


Concentric Cells
Database Parameters
HANDOVERS --- Motorola

The inner zone use algorithm must adjust for values being from two different frequency bands and convert the
primary band receive levels to an estimated value for the secondary band. This is done using the dual band offset
parameter.

RXLEVINNER = RXLEVOUTER + dual_band_offset

This offset is applied to both uplink and downlink receive levels

The calculated receive level inner value is then used in the dual band inner zone algorithm for both uplink and
downlink

RXLEV_DLINNER > rxlev_dl_zone + zone_ho_hyst + (bts_txpwr - bts_txpwr_max_inner)
RXLEV_ULINNER > rxlev_ul_zone + zone_ho_hyst + (ms_txpwr - min(ms_txpwr_max_inner,P)

Within this algorithm are database parameters that are set per cell after the
inner_zone_alg = 3 (dual band use)
rxlev_dl/ul_zone = <*> *= Range 0 to 63
zone_ho_hysteresis = <*> *= Range as defined for max_tx_bts (0 to 21)
bts_txpwr_max_inner = <*> *= Range -63 to 63
ms_txpwr_max_inner = <*> *= Range as defined for max_tx_ms (5 to 39 PGSM and
EGSM 0 to 36 DCS 1800)
P = maximum capability of the mobile in the inner zone frequency band.


Concentric Cells
Database Parameters
TCH Assignment --- Alcatel

 All SDCCH channels are in the outer zone.
 The BSC can allocate a TCH in the inner zone or in the outer zone.
 Cause 13 is checked to determine the MS location (Outer to Inner Zone Handover)

Zone Assignment:
 The 900 SDCCH is always allocated to the MS (SDCCH channels are on the 900 TRX).
 Then according to the MS location (outer zone or inner zone), a TCH is allocated in the 900 band (outer zone) or in
the 1800 band (inner zone).
 To determine the location of the mobile, cause 13 (outer zone to inner zone HO) is checked.
 If the cell is congested, it is possible to allocate the TCH in a neighboring cell (Directed Retry or Forced Directed
Retry).
 Then, according to the location of the mobile, the value of the parameter EN_BETTER_ZONE_HO, the serving
BSC of the serving and the neighboring cells the TCH is allocated in :
 The 900 band if the two cells belong to two different BSC,
 the 900 band if the two cells belong to the same BSC and EN_BETTER_ZONE_HO =disable for the neighboring cell
 The 900 band if the two cells belong to the same BSC,EN_BETTER_ZONE_HO = enable for the neighboring cell and the
MS is located in the outer zone of the neighboring cell,
 The 1800 band if the two cells belong to the same BSC, EN_BETTER_ZONE_HO = enable for the neighboring cell and
the MS is located in the inner zone of the neighboring cell.


Concentric Cells
Database Parameters

 Cause 13 (too high level on UL/DL in outer zone)
 Better condition Intra-cell Handover
 Maybe Triggered from OUTER Zone of a concentric Cell TOWARDS inners zone of the same cell


Concentric Cells
Database Parameters

 Cause 13 (too high level on UL/DL in outer zone)

 RXLEV_UL_ZONE: Uplink level threshold for inner to outer zone handover.
Valid Range:
0 to 63 (0 = -110dBm, 63 = -47dBm)

 RXLEV_DL_ZONE: Downlink level threshold for inner to outer zone handover.
Valid Range:
0 to 63 (0 = -110dBm, 63 = -47dBm)


Concentric Cells
Database Parameters

Cause 13 (too high level on UL/DL in outer zone)
 ZONE_HO_HYST_UL
UL static hysteresis for interzone HO from outer to inner – In case of multi-band cell, should take into
account the difference of propagation between GSM and DCS (difference in Propagation between
two bands is countered in Motorola by dual_band_offset)
Valid Range
-40 to 40 dB

 ZONE_HO_HYST_DL
DL static hysteresis for interzone HO from outer to inner – In case of multi-band cell, should take into
account the difference of propagation between GSM and DCS and the difference of BTS
transmission power in the two bands
Valid Range
-40 to 40 dB


Concentric Cells
Database Parameters
Cause 13 (too high level on UL/DL in outer zone)

 PING_PONG_MARGIN(0,call_ref)

Its a penalty put on cause 13 if :
 The immediately precedent zone on which the call has been is the inner zone of the serving cell
and less than T_HCP seconds have elapsed since the last handover. In this case
PING_PONG_MARGIN(0,call_ref) = PING_PONG_HCP.
 If the call was not precedently on the serving cell’s inner zone (case of intercell or intrazone
handover), or if the timer T_HCP has expired, then PING_PONG_MARGIN(0,call_ref) = 0

PING_PONG_HCP
Valid Range:
0 to 127 dB

 T_HCP
Time during which PING_PONG_HCP is applied after handover.
Valid Range:
0 to 240 Seconds

Concentric Cells
Database Parameters
HANDOVERS

And now Dual Band Handovers…….!


Concentric Cells
Database Parameters

During add_cell command, when inner_zone_alg = 3 (dual band), a series of parameters are given
as inputs which will now follow along with their descriptions

 Secondary_freq_type:
If for example, frequency_type= DCS1800, the secondary_freq_type has to be any of the other types.

Valid range
1 (PGSM),
2 (EGSM),
4 (DCS1800),
8 (PCS1900)

DUAL_BAND_OFFSET:
The inner_zone_alg has to consider other factors in order to handover multiband MSs between different frequency
bands. The factors are:
 Due to different level of combining the loss of power between the radio unit and the top of the antenna may not
be consistent across all radio units within the cell. The power difference is calculated by subtracting the secondary
band power loss from the primary band power loss.
 Due to the radio frequency propagation being weaker at 1800 MHz than at 900 MHz, propagation loss over the air
interface has got to be taken into consideration.
 These factors are accounted for in the database parameter dual_band_offset

Concentric Cells
Database Parameters
 rxlev_dl_zone parameter specifies the downlink receive level threshold that must be crossed
for a handover to take place between the outer zone and the inner zone.
Valid Range:
0 to 63 (0 = -110 dBm)

 rxlev_ul_zone parameter specifies the uplink receive level threshold that must be crossed for
a handover to take place between the outer zone and the inner zone.
Valid Range:
0 to 63 (0 = -110 dBm)

 Zone_ho_hyst parameter specifies the margin for the inner zone handover hysteresis.
Valid Range:
-63 to 63

 Bts_txpwr_max_inner parameter specifies the maximum transmit power BTS inner zone for
Dual Band cells.
Valid range -1 to 21 for PGSM, EGSM, and DCS1800. 1 step = 2dBm
-1 = 44 dBm, 0 = 42dBm, 21 = 0 dBm

 Ms_txpwr_max_inner parameter specifies the maximum power an MS can use in the inner
zone of a concentric cell.
Valid range: Depends on the system:
5 to 39 dBm (odd values only) PGSM/EGSM
0 to 30 dBm (even values only) DCS1800
0 to 30 dBm (even values only) PCS1900

Concentric Cells
Database Parameters

Dual Band Inner Zone Use Algorithms

The algos below show what conditions must exist in order to handover a call from Inner
to Outer Zone

 BTS Power Control on
rxlev_dl < rxlev_dl_zone and bts_txpwr = bts_txpwr_max_inner
Or if Power Control is off
rxlev_dl < rxlev_dl_zone

 MS Power Control
rxlev_ul < rxlev_ul_zone & ms_txpwr = min(ms_txpwr_max_inner,P)
Or if MS_PC is off
rxlev_ul < rxlev_ul_zone

 pbgt(n) > ho_margin if neighbour qualifies inter-cell handover
 If no neighbour qualifies handover MS to outer zone


Concentric Cells
Database Parameters
HANDOVERS & PC --- Motorola
 A network where Power Control is enabled, the power budget equation determines
the need for an inter-cell handover by essentially comparing the serving cell BCCH
signal strength to the neighbour cell BCCH signal strength.

 This means the signal strength in a dual band cell must come from the primary zone.

 When the call is in the secondary zone, the signal strength reported by the mobile
cannot be used in the power budget equation, because

 frequencies in the secondary band have a different propagation than frequencies in the primary
band.
 In a Power Control enabled network, the serving cell will always have the signal strength
between the PC window whereas the neighbour would report a much better level of its BCCH
(Full Power)


Concentric Cells
Database Parameters

To solve this problem, we have been provided with a smart
parameter by Motorola!
Pbgt_mode

 If pdgt_mode = 0
If the mobile is assigned to a resource on the secondary band, the mobile will use the
serving channel measurements and then subtract the dual_band_offset. This estimated
value is then inserted into the power budget equation.

 If the pbgt_mode = 1
The serving cell BCCH is included in the ba_sacch neighbour cell list of the serving cell.
The mobile will then report the serving cell signal strength for the primary band, which can
be used in the calculation of power budget for neighbours with the same frequency band.
The actual number of neighbour frequencies that can be reported on is reduced by one,
also the number of true neighbours that the MS can report on is reduced from six to five. If
pbgt_mode = 1 then the server is auto equipped as a neighbour.


Concentric Cells
Database Parameters
HANDOVERS --- Alcatel

 Cause 10, 11: UL or DL level too low in the inner zone

 Emergency HO
 Intracell handovers from inner to outer zone
• cause 10: too low level on the uplink in inner zone
• cause 11: too low level on the downlink in inner zone

 Cause 10:
AV_RXLEV_UL_HO < RXLEV_UL_ZONE
and MS_TXPWR = min (P, MS_TXPWR_MAX_INNER)

 Cause 11:
AV_RXLEV_DL_HO < RXLEV_DL_ZONE
and BS_TXPWR = BS_TXPWR_MAX_INNER


Further Reading
 Motorola
 SYS12 (Directed Retry, Congestion Relief, Power and Interference
based Concentric Cells)
 BSS Command Reference GSR 7

 Alcatel
 RFT B9 (Cause 13,10,11,21,23 Handovers and their descriptions)
 Concentric Cells – Alcatel Official Document
 Telecom Parameter Dictionary – Alcatel


Concentric & Dual Band Cells

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