4 GSM Parameter Configuration and AdjustmentWhen operators
prepare to construct a mobile communication network, they must
predict coverage according to traffic prediction and local radio
propagation environment. This guides project design of the system
and parameter configuration of radio network. The project design
includes the following aspects:l Network topology designl Selecting
the location of base station l Frequency planningl Cell parameter
configurationThe RF planning determines the coverage range of a
cell, and the serving range of the cell is determined based on the
combination of RF planning and cell parameter configuration. By
this, the MS always enjoys optimal services and maximum network
capacity at the best cell.This chapter discusses the meaning and
effect of important parameters in GSM radio communication.
Mastering the effect and impact of these parameters helps to
configure network parameters and optimize the network in later
stages.In a GSM network, abundant radio parameters are configured
according to cells or partial areas; however, the parameter
configuration might affect neighbor areas. Therefore, while
configuring and adjusting parameters, you must pay attention to the
impact of configuring parameters on other areas, especially
neighbor areas.4.1 Network and Cell ID4.1.1 Cell Global IDI.
DefinitionGSM is a global cellular mobile communication system. To
ensure that each cell corresponds to a unique ID globally, the GSM
system numbers the following items:l Each GSM network in each
countryl Each location areal Each base stationl Each cellNumbering
the previous items aims as follows:l An MS can identify the serving
network so that the MS can select a network in any environment.l
The network can obtain the precise location of the MS so that the
network can process various service requests involving the MS.l The
MS can report information about neighbor cells to the network
during calling to avoid call drop.The cell global identity (CGI) is
a major network identity parameter. CGI consists of location area
identity (LAI) and cell identity (CI). LAI includes mobile country
code (MCC), mobile network code (MNC), and location area code
(LAC).The system transmits CGI information through system
information (SI) transmitted by cell broadcast. When an MS receives
SI, it demodulates SI for CGI information. The MS judge whether to
camp on the cell according to the MCC and MNC. It also judges
whether the current location area changes to determine updating
location. While updating location, the MS reports LAI information
to the network so that the network can know the location area of
the MS.II. FormatThe CGI is MCC-MNC-LAC-CI, with details as
follows:l MCC consists of three decimal digits, ranging from 000 to
999.l MNC consists of two decimal digits, ranging from 00 to 99.l
LAC ranges from 0 to 65535l CI ranges from 0 to 65535.III.
Configuration and InfluenceAs a globally unique mobile identity,
the MCC is uniformly distributed and managed by international
telecommunication union (ITU). The MCC for China is 460
(decimal).The MNC is uniformly distributed by state
telecommunication management organs. Now two GSM networks exist in
China. The MNC for China Mobile is 00. The MNC for China Unicom is
01.The method for coding LAC is ruled by each country accordingly.
This caters for China also (refer to GSM system from Ministry of
Information Industry). At the early stage of network construction,
the LAC is coded and distributed. The LAC is seldom changed in the
later stages.The coverage areas related to the LAC is vital in the
network. You can configure it as great as possible.No special
restriction is on the distribution of CI. The CI ranges from 0 to
65535 (decimal). It must be ensured that two equivalent CIs exist
in the same location area. This is determined in the system design.
Except for special situations (such as constructing base stations),
the CI must not be changed during the system operation.IV.
PrecautionsYou must pay attention to the following aspects:l The
MNC is unchangeable.l While configuring the LAC, you must follow
related regulations. Equivalent LACs must not exist in the state
network. l Equivalent CIs must not exist in the same location
area.4.1.2 Base Station Identity CodeI. DefinitionIn a GSM network,
each base station corresponds to a distributed local color code,
called base station identity code (BSIC). When the MS receives
broadcast control channel (BCCH) carriers of two cells at the same
time, with same channel number, the MS distinguishes them by
BSIC.In network planning, the BCCH carriers of neighbor cells are
different in frequency to reduce intra-frequency interference. The
cellular communication system features that the BCCH carrier might
be reused. Therefore, the BSIC of the cells with the same BCCH
carrier must be different.The system transmits BSIC on
synchronization channel (SCH) of each cell. The effect of BSIC is
as follows: l The BSIC involves in decoding process of random
access channel (RACH) to prevent base stations from connecting to
the RACH sent to the neighbor cells by the MS by error.l After the
MS receives SCH messages, it judges that it has been synchronous to
the cell. Decoding information on the downlink common signaling
channel correctly requires training sequence code (TSC) used on
common signaling channel.GSM regulations describe TSC in eight
fixed formats, and the sequence number of them is 07. The cell BCC
determines the TSC used by the common signaling channel of a cell.
Therefore the BSIC helps inform the MS of the TSC used by the
common signaling channel of the serving cell.l In a call, the MS
must measure the level of BCCH carrier of neighbor cells and report
it to the base station according to regulations to neighbor cell
list of BCCH. Meanwhile, the MS must provide measured BSIC of the
carrier in the uplink measurement reports. When the neighbor cells
of a cell include two or more cells with the same BCCH carrier, the
base station can distinguish the cells by BSIC to avoid incorrect
handover.l In a call, the MS must measure signals of neighbor
cells, and sends measurement reports to the network. The
measurement report can contain information about six neighbor cells
only, so the MS must be controlled to report the cells actually
related to handover. The first three digits of BSIC (namely, NCC)
aims as previously mentioned. Operators control the MS to report
the neighbor cell information permitted by the serving cell NCC by
broadcast parameters NCC permitted.II. FormatThe BSIC is NCC-BCC,
with details as follows:l The NCC ranges from 0 to 7.l The BCC
ranges from 0 to 7.III. Configuration and InfluenceUsually
different GSM PLMNs use the same frequency resource, but, to some
degree, their network planning is independent. The neighbor GSM
PLMNs use different NCCs according to regulations. This ensures
that the neighbor base stations with same frequency use different
BSICs.The BCC is part of the BSIC. It helps identify different base
stations with same BCCH carrier number in the same GSM PLMN. The
values of BCC must meet the previous requirements. According to GSM
regulations, the TSC of cell BCCH carrier must be same as that of
cell BCC. The equipment providers must ensure the TSC
consistency.IV. PrecautionsThe neighbor cells or cells nearby using
the same BCCH carrier must use different BSICs. Especially when two
or more cells use the same BCCH carrier in the neighbor cell list
of a cell, theses cells must use different BSIC. Pay attention to
cells at the bordering areas between provinces and cities, and
otherwise cross-cell handover might fail and abundant mistaken
access problems might occur.4.2 Paging and Access Control
Parameters4.2.1 Number of Access Grant Reserved Blocks
(BS_AG_BLK_RES or AG)I. DefinitionThe common control channel
consists of access grant channel (AGCH) and paging channel
(PCH).For different CCCHs, each BCCH multiframe (including 51
frames) contains CCCH message blocks different number. The CCCH is
shared by AGCH and PCH. According g to regulations, partial message
blocks on CCCH are especially reserved for AGCH. This avoids that
the AGCH messages are blocked when the PCH traffic is great.The
number of parameter access grant reserved blocks (AG) refers to the
number of message blocks reserved for AGCH on CCCH in each BCCH
multiframe.II. FormatThe AG ranges from 0 to 2 when CCCH shares
physical channel (CCCH_CONF = 1) with stand-alone dedicated control
channel (SDCCH).The AG ranges from 0 to 5 when CCCH does not share
physical channel (CCCH_CONF=0) with stand-alone dedicated control
channel (SDCCH).III. Configuration and InfluenceWhen the channel
combination of the cell is fixed, the parameter AG adjusts the
ratio of AGCH and PCH in CCCH. When the PCH is idle, it can send
immediate assignment messages. The AGCH does not transmit paging
messages. Equipment operators can balance AGCH and PCH by adjusting
AG, with the following principles.The principle for AG value is
that based on no overload of AGCH, you must reduce the parameter to
shorten the time for MS to respond to paging, and to improve system
service performance. When the immediate assignment messages are
superior to paging messages to be sent, configure AG to 0.The value
of AG is recommended as follows:l AG is 1 when the CCCH and SDCCH
share a physical channel.l AG is 2 or 3 in other situations.In
network operation, take statistics of overload situations of AGCH
and adjust AG accordingly. By default the immediate assignment
messages are superior to paging messages to be sent in the network,
so you need not reserve a channel for immediate assignment
messages. In this situation, configure AG to 0.4.2.2 Frame Number
Coding Between Identical PagingFrame number coding between
identical paging is BS_PA_MFRMS (MFR for short).I.
DefinitionAccording to GSM regulations, each MS (corresponding to
an IMSI) belongs to a paging group (for calculation of paging
groups, see GSM regulation 05.02). Each paging group in a cell
corresponds to a paging subchannel. According to its IMSI, the MS
calculates the paging group that it belongs to, and then calculates
the location of paging subchannel that belongs to the paging group.
The MS only receives the signals of the paging subchannel that it
belongs to, and neglects that of other paging subchannels. In
addition, the MS even powers off some hardware of itself during
other paging subchannel to lower power cost of itself.The number of
paging channel multiframe (MFR) is the number of multiframes used
in a period of paging subchannel. The MFR determines the number of
paging subchannels that the cell PCH is divided into.II. FormatThe
MFR ranges from 2 to 9, which respectively means that the same
paging group cycles in a period of 2 to 9 multiframes.III.
Configuration and InfluenceAccording to the definition of CCCH, AG,
and MFT, you can calculate the number of paging channel in each
cell.l When the CCCH and SDCCH share a physical channel, there is
(3 - AG) MFRs.l When the CCCH and SDCCH share a physical channel,
there is (9 - AG) MFRs.According to the previous analysis, the
greater the MFR is, the more the paging channels of the cell are
(see the calculation of paging groups in GSM regulation 05.02).
Theoretically, the capacity of paging channels does not increase
with the increase of MFR. The number of buffers for buffering
paging messages on each base transceiver station (BTS) increases.
The paging messages are sent more evenly both in time and space, so
it seldom occurs that the paging messages overflow in the buffers
so call lost occurs (related to functions by equipment
providers).However, to enjoy the previous advantages, you will have
a longer delay of paging messages on the radio channels. The
greater the MFR is, the greater the delay of paging messages in the
space is, and the lower the average service performance of the
system is. Therefore, the MFR is an important parameter in network
optimization.The following principle caters for configuring MFR:The
configured strategy for buffers of each equipment provider is
different, so you must select the MFR properly so that the paging
messages do not overflow on PCH. Based on this, configure the
parameter as small as possible. In addition, you must measurement
the overflow situations of PCH periodically while the network is
running, and adjust MFR accordingly.IV. PrecautionsAny paging
message of the same location area must be sent to all cells in the
location areas at the same time, so the PCH capacity of each cell
in the location area must be equivalent or close to each other.
Otherwise, you must consider smaller PCH capacity as the evidence
for designing location area.4.2.3 Common Control Channel
Configuration (CCCH-CONF)I. DefinitionThe CCCH includes AGCH and
PCH. It sends immediate assignment messages and paging messages. In
each cell, all traffic channels (TCHs) share CCCH. According to the
TCH configuration and traffic model of the cell, the CCCH can be
one or more physical channels. In addition, the CCCH and SDCCH
share a physical channel. The combination methods for CCH are
determined by CCCH parameter CCCH_CONF.II. FormatThe CCCH_CONF
consists of three bits, with the coding methods listed in
Table:CCCH configuration codingCCCH_CONFMeaningNumber of CCCH
message blocks in a BCCH multiframe
000One physical channel for used for CCCH, not shared with
SDCCH9
001One physical channel for used for CCCH, shared with
SDCCH3
010Two physical channels for used for CCCH, not shared with
SDCCH18
100Three physical channels for used for CCCH, not shared with
SDCCH27
110Four physical channels for used for CCCH, not shared with
SDCCH36
III. Configuration and InfluenceWhen the CCCH and SDCCH share
one physical channel, the CCCH has the minimum channel capacity.
When the CCCH and SDCCH do not share a physical channel, the more
physical channels that the CCCH uses, the greater the capacity
is.The CCCH_CONF is determined by the operators based on
combination of cell traffic model and paging capacity of the
location area where a cell belongs to. It is determined in system
design, and adjusted in network expansion. According to
experiences, when the paging capacity in the location area is not
high and cell has one or two carriers, it is recommended that the
CCCH uses one physical channel and share it with SDCCH (in
combination CCCH methods). This spares a physical channel for
paging. Otherwise, the method that CCCH and SDCCH do not share one
physical channel is used.When the cell TRX exceeds 6 and CCCH
OVERLOAD occurs in the cell, it is recommended that the CCCH uses
two or more basic physical channel and does not share them with
SDCCH.IV. PrecautionsThe CCCH_CONF must be consistent with the
actual configuration of cell CCCH. In addition, you must consider
the influence on the access grant reserved blocks.4.2.4 Extended
Transmission Slots (TX_INTEGER)I. DefinitionIn a GSM network, a
random access channel (RACH) is an ALOH. To reduce the conflicting
times on RACH when an MS accesses the network, and to increase RACH
efficiency, GSM regulations (sections 3.3.1.2 of 04.08) prescribe
the compulsory access algorithm for MS. The algorithm defines three
parameters as follows:l Extended transmission slots Tl Maximum
retransmission times RETl TIt is the number of slots between two
sending when the MS keeps sending multiple channel request
messages.l SIt is related to channel combination, and is an
intermediate variable of access algorithm. It is determined by T
and CCCH configuration.II. FormatThe value of T is from 3 to 12,
14, 16, 20, 25, 32, and 50.The value of S ranges as listed in
Table:Values of STS in different CCCH combination methods
The CCCH and SDCCH does not share a physical channelThe CCCH and
SDCCH share a physical channel
3, 8, 14, 505541
4, 9, 167652
5, 10, 2010958
6, 11, 2516386
7, 12, 32217115
III. Configuration and InfluenceTo access the network, the MS
must originate an immediate assignment process. To begin the
process, the MS sends (RET + 1) channel request messages on RACH.
To reduce conflicts on RACH, the time for MS to send channel
request messages must meet the following requirements:l The number
of slots (not including slots for sending messages) between
originating immediate assignment process by MS and sending the
first channel request messages is random. Its range is {0, 1, , MAX
(T, 8) - 1}. When the MS originates the immediate assignment
process, it takes a value from the range according to even
distribution probability.l The number of slots (not including slots
for sending messages) between a channel request message and the
next is from {S, S + 1, , S + T - 1} according to even distribution
probability.According to previous analysis, the greater the T is,
the larger the range of intervals between one channel request
message and the next, and the less the RACH conflicting times is.
The greater the S is, the greater the interval between one channel
request message and the next, the less the RACH conflicting times
is, and the more efficiently the SDCCH is used. However, the
increase of T and S leads to longer time for MS to access the
network, so the access performance of the whole network declines.
Therefore you must configure T and S properly.S is calculated by MS
according to T and combination of CCH. You can configure T freely
and sends it to MS by system information. Usually, you need
configure T properly to make T + S as small as possible (to reduce
the time for MS to access the network); meanwhile you must ensure
an effective assignment of SDCCH to avoid overload (for all random
access requests, the system does not distinguish whether they are
from the same MS, but assigns a SDCCH). In operation, you can
adjust the value according to traffic measurement of cell immediate
assignment.4.2.5 Minimum Access Level of RACHI. DefinitionThe
minimum access level of RACH is the level threshold for the system
to judge whether there is a random access request.II. FormatThe
minimum access level of RACH ranges from 0 to 63 (corresponding to
110 dBm to 47 dBm).The unit is level grade value.III. Configuration
and InfluenceWhen the access burst level of RACH is greater than
the threshold, the BTS judges that there is an access request. The
BTS, together with the parameter random access error threshold,
determines whether the random access burst is valid. To configure
the parameter properly, you must combine actual sensitivity of the
base station and the parameter minimum received level permitted for
MS to access. This prevents the MS from failing in calling though
there are signals. The access burst level of RACH affects call drop
rate and access range (coverage), so you must pay attention to the
influence on access of MS.4.2.6 Random Access Error ThresholdI.
DefinitionGSM protocols prescribe that by relativity of judgment
training sequence (41 bits) the system can judge whether the
received signals are the random access signals of MS.II. FormatThe
value ranges from 0 to 255. The recommended value is 180.III.
Configuration and InfluenceThe random access error threshold
defines the relativity of training sequence. If the smaller it is,
the more errors of random access signals permitted by the network
are, the easily the MS randomly accesses the network, and the
greater the report error rate is. If the greater the random access
error threshold is, the smaller the report error rate is, and the
more difficult the access to the network is when signals are weak.
See protocol 0408, 0502.The system requires the random access error
threshold transferred by current bit of 41 bit training
sequence.9010033
10112034
12114035
14116036
16117537
17619538
19622139
22224340
24425041
089 or 25125538
The two parameters random access error threshold and minimum
access level of RACH determine the validity of random access
burst.4.2.7 Access Control Class (ACC)I. DefinitionGSM regulations
(02.11) prescribe that each GSM user (common user) corresponds to
an access class, ranging from class 0 to class 9. The access class
is stored in SIM of mobile users. For special users, GSM
regulations reserves five special access classes, ranging from
class 11 to class 15. Theses classes are prior to other classes in
accessing. Special users might have one or more access classes
(between 11 and 15), which are also stored in user SIM. Users of
class 11 to 15 are prior to that of class 0 to 9. However, the
class between 0 and 9 or between 11 and 15 does not mean
priority.The access class is distributed as follows:l Class 09:
common usersl Class 11: users for PLMN managementl Class 12: users
for security departmentsl Class 13: common business departments (in
charge of water, gas)l Class 14: emergency servicesl Class 15: PLMN
staffUsers of class 09 have its access rights catering for home
PLMN and visited PLMN. Users of class 11 and 15 have its access
rights catering for visited PLMN only. Users of class 12, 13, and
14 have its access rights catering for in the country where home
PLMN belongs to.II. FormatThe access control class consists of two
parts:l Common access control classValue range: a check option,
including class 0 disabled, , class 9 disabled.Recommended value:
all 0.l Special access control classValue range: a check option,
including class 11 disabled, , class 15 disabled.Recommended value:
all 0.If a class is configured to 1, it means that access is
forbidden. For example, a common access class is configured to
1000000000; common users excluding class 0 users can access the
network.III. Configuration and InfluenceC0C15 (excluding C10) are
set by equipment room operators. Usually these bits are configured
to 1. Proper configuration contributes to network optimization as
follow:l When installing a base station, starting a base station,
or maintaining and testing in some cells, configure C0C15
(excluding C10) to 1. In this way, different users are prevented
from accessing the network, so the installing and maintenance is
less influenced.l During busy hours of cells with high traffic,
congestion occurs, RACH conflicting time increase, AGCH traffic
overloads, and Abis interface traffic overloads. When you configure
class of some users to 1, you can reduce the traffic of the
cell.4.2.8 Maximum Retransmission Times (RET)I. DefinitionSee GSM
regulation 04.08. When an MS originates an immediate assignment
process, it sends a channel request message to the network on RACH.
The RACH is an ALOH, so the MS can send multiple channel request
messages before receiving immediate assignment messages, to
increase access success rate of MS. The maximum retransmission
times M (RET) is determined by equipment room operators, and sent
to MS by SI.II. FormatThe maximum retransmission times consists of
two bits, with the meanings listed in Table:Coding of maximum
transmission times MMmaximum transmission times
001
012
104
117
III. Configuration and InfluenceThe greater the M is, the higher
the success rate of call attempt is, and the higher the connection
rate is, but the load of RACH, CCCH, and SDCCH increase. In cell
with high traffic, if the RET is over great, overload of radio
channels and congestion occur, so the connection rate and radio
resource utilization declines sharply. If the RET is over small,
the call attempt times of MS reduces, success rate reduces, so the
connection rate reduces. Therefore, proper configuration of RET for
each cell help utilize network radio resources and improve
connection rate.For configuration of RET M, refer to the following
methods:l For areas with low traffic, such as in suburban or rural
areas, configure RET to 7 to increase the access success rate of
MS.l For areas with average traffic, such as common urban areas,
configure RET to 4.For microcell with high traffic and of apparent
congestion, configure RET to 1.4.2.9 Control Class of MS Maximum
Transmit Power (MS-TXPWR-MAX-CCH)I. DefinitionMS-TXPWR-MAX-CCH is
sent in BCCH SIs. It affects behavior of MS in idle mode. It is
also used in calculating C1 and C2, and determines cell selection
and reselection.l C1 = RLA_C - RXLEV_ACCESS_MIN -
MAX((MS_TXPWR_MAX_CCH - P), 0)l RLA_C: average received level by
MSl RXLEV_ACCESS_MIN: minimum received level permitted for MS to
accessl MS_TXPWR_MAX_CCH: maximum power level of control channel
(control class of MS maximum transmit power)l P: Maximum transmit
power level of MSII. FormatThe range of MS-TXPWR-MAX-CCH is 031.
For cells of GSM900 and GSM1800, the dBm values corresponding to
the control class are different.l In a GSM900 network, the 32
control class of maximum transmit power corresponding to 031 is as
follows:{39, 39, 39, 37, 35, 33, 31, 29, 27, 25, 23, 21, 19, 17,
15, 13, 11, 9, 7, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5}l In a
GSM1800 network, the 32 control class of maximum transmit power
corresponding to 031 is as follows:{30, 28, 26, 24, 22, 20, 18, 16,
14, 12, 10, 8, 6, 4, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
36, 34, 32}Recommended values are 5 for GSM900 and 0 for
GSM1800.III. Configuration and InfluenceMS-TXPWR-MAX-CCH determines
the power class used before MS receives power control messages. For
details, see protocol 0508. The smaller it is, the greater the
output power of MS is. The MS near the base station interferes with
neighbor channels of the cell, so the access to the network by
other MSs and communication quality are influenced. The greater it
is, the smaller the output power of MS is, and the lower the access
success rate of MS at cell borders is. You must configure
MS-TXPWR-MAX-CCH properly according to the serving range of the
cell.4.2.10 Power Offset (POWEROFFSET)I. DefinitionWhen the MS
accesses the network and before it receives the initial power
control messages, all GSM900 MSs and type 1 and type 2 DCS1800 MSs
use MS_TXPWR_MX_CCH of BCCH. If the MS_TXPWR_MX_CCH exceeds the
maximum transmit power of MS, the MS uses the closest power.The
parameter POWEROFFSET is effective to type 3 DCS1800 MSs. When the
type 3 DCS1800 MS accesses the network, it use total power of
MS_TXPWR_MX_CCH + POWEROFFSET before receiving the initial power
control message. See protocol GSM0508.II. FormatThe values of 03
correspond to 0 dB, 2 dB, 4 dB, and 6 dB. The recommended value is
2.III. Configuration and InfluenceThe greater the parameter is, the
more easily the type 3 DCS1800 MS accesses the network. A great
POWEROFFSET enables MS to access the network afar, but does not
help control cross-cell interference, so the network quality is
influenced.4.2.11 IMSI Attach/Detach AllowedI. DefinitionThe IMSI
detach means that the MS informs the network of itself work state
changing from working to non-working. Usually it refers to when the
MS powers off or the SIM is taken off MS. After receiving the
inform from MS, the network sets the IMSI as in non-working
state.The IMSI attach is opposite of IMSI detach. It means that MS
informs the network of itself work state changing to working.
Usually it refers to when the MS powers on or the SIM is put into
MS again. After the MS turns to working state again, it detects
whether the current location areas (LAI) is the same as that
recorded in MS at last.l If yes, the MS starts IMSI attach process
(this is one of location updating).l If no, the MS starts location
updating process of cross location area.After receiving the
location updating message or IMSI message from MS, the network sets
the IMSI as in working state.The parameter IMSI attach/detach
allowed (ATT) is used for informing MS of the IMSI attach/detach
process.II. FormatThe value of ATT includes YES/NO. NO means that
starting IMSI attach/detach process by MS is forbidden. YES means
that starting IMSI attach/detach process by MS is compulsory.III.
Configuration and InfluenceUsually configure ATT to YES so that the
network will not process the proceeding of the MS after the MS
powers off. This frees system resources (such as PCH).IV.
PrecautionsThe ATT of different cells in the same location area
must be the same to avoid abnormalities while the MS is called. For
example, in a cell with YES as the value of ATT, when the MS powers
off, it starts IMSI detach process. Therefore the network records
that the MS is in non-working state, so it does not page the MS. In
a cell with No as the value of ATT and the cell being different
from the one where the MS powers off, when the MS powers on again
in the cell, the MS does not start IMSI attach process. In this
situation, the MS cannot be called normally until it starts
location updating process.4.2.12 Direct Retry (DR)I.
DefinitionDuring the assignment process of call setup, congestion
might cause assignment failure. The assignment failure causes
failure of the whole call. GSM networks has a function to avoid
such failures, namely, DR. The DR is that the BSS directly assign
MS to TCH of neighbor cells. The parameter is used by system to set
whether to allow direct retry function.II. FormatThe value of DR
includes YES and NO. YES means that the system allows directional
retry. NO means that the system does not support direction retry
function.III. Configuration and InfluenceDR improves call success
rate. If conditions are ready, start DR. On the contrary, DR is
that the BSS directly assign MS to TCH of neighbor cells when
congestion occurs in the cell where the MS camps, so the MS can
originates a call in the non-best cell with lowest received level,
and extra interference might be brought about in frequency reuse
networks. Therefore, you must use the function properly according
to comprehensive network situations.4.3 Serial Parameters of Cell
Selection and Reselection4.3.1 cell_bar_accessI. DefinitionIn the
SI broadcasted in each cell, a bit indicates whether the MS is
allowed to access the network in the cell, namely,
cell_bar_access.II. FormatThe value of cell_bar_access includes 1
and 0. The value 0 indicates that MS is allowed to access the
network from the cell. The value 1 indicates that the MS is barred
to access the network from the cell. Actually whether to allow MS
to access the network from the cell is determined by both
cell_bar_access and cell_bar_qualify.III. Configuration and
InfluenceThe cell_bar_access is configured by equipment room
operators. Usually the MS is allowed to access the network from all
the cells, so cell_bar_access is configured to 0. In special
situations, the operators want some cell for handover service only,
so cell_bar_access is configured to 1 The MS usually works in
microcells (you can configure the priority of cells and reselection
parameters to enable this). When the MS is calling while moving
fast, the network force MS to hand over to the base station G. The
signals of base station G are stronger than microcell base station
in most areas. When the call terminates, the MS just camps near
base station G and at edge of microcell cells, the MS will not
reselect a cell according to GSM regulations, therefore the MS
cannot return to microcell.The capacity of base station G is
usually small, so the previous phenomenon leads to congestion of
base station G. To solve the problem, you can configure the
cell_bar_access to 1, namely, to forbid MS directly accessing base
station G. In area A, handover is allowed to base station G.IV.
PrecautionsThe cell_bar_access is used only in some special areas.
For common cells, it is configured to 0.4.3.2 cell_bar_qualifyI.
DefinitionThe cell_bar_qualify determines the priority of cells,
namely, it enables MS to select some cell by preference.II.
FormatThe value of cell_bar_qualify includes 1 and 0. The
cell_bar_qualify and cell_bar_access determine the priority state
of cells, as listed in Table 1-4.Table 7-1 Cell
prioritiescell_bar_qualifycell_bar_accessCell selection
priorityCell reselection state
00NormalNormal
01BarredBarred
10LowNormal
11LowNormal
An exception is that the cell selection priority and cell
reselection state are normal when the following conditions are
met:l The cell belongs to the PLMN which the MS belongs to.l The MS
is in cell test operation mode.l The cell_bar_access is 1.l The
cell_bar_qualify is 0.l The access control class 15 is
disabled.III. Configuration and InfluenceThe priority of all the
cells are usually configured to normal, namely, cell_bar_qualify =
0. In microcell and dualband networking, operators might want MS to
camps on the cell of some type by preference. In this situation,
the equipment room operators can configure the priority of these
cells to normal and other cells to low.During cell selection, when
the proper cells with normal as the priority is not present (proper
cells means that all parameters meet the conditions for cell
selection, namely, C1 > 0, and the cell is allowed to access),
the MS will select cells with low priority.IV. PrecautionsPay
attention to the following aspects:l When cell priority is used as
a method to optimize network, the cell_bar_qualify only affects
cell selection, without any influence on cell reselection. You must
optimize the network by combining cell_bar_qualify and C2.l During
cell selection, when the proper cells with normal as the priority
is not present, the MS will select cells with low priority.
Therefore when the level of the cell with normal priority is low,
and cells with low priority and high level are present, the MS will
access the network slowly while powering on.4.3.3 Minimum Received
Level Allowing MS to Access (RXLEV_ACCESS_MIN)I. DefinitionTo avoid
bad communication quality, call drop, and a waste of network radio
resources due to MS accessing the network at low received signal
level, GSM regulations prescribe that when an MS accesses the
network the received level must be greater than the threshold
level, namely, the minimum received level allowing MS to access.II.
FormatThe value range of RXLEV_ACCESS_MIN is from 110 dBm to 47
dBm.III. Configuration and InfluenceThe recommended
RXLEV_ACCESS_MIN needs to be approximately equal to the receiving
sensitivity of MS. The RXLEV_ACCESS_MIN affects cell selection
parameter C1, so it is important to traffic adjustment and network
optimization.For cells with over high traffic and severe
congestion, you can increase RXLEV_ACCESS_MIN. In this way, the C1
and C2 of the cells decrease, and the effective coverage range
decreases. You must not configure RXLEV_ACCESS_MIN over great,
because this might cause non-seamless coverage and complaints for
signal fluctuation. It is recommended that the RXLEV_ACCESS_MIN is
smaller than or equal to 90 dBm.IV. PrecautionsExcept for areas of
high density of base stations and of qualified coverage, adjusting
cell traffic by RXLEV_ACCESS_MIN is not recommended.4.3.4
Additional Reselection Parameter IndicatorI. DefinitionThe cell
selection and reselection by MS depends on the parameters C1 and
C2. Whether C2 is the cell reselection parameter is determined by
network operators. Additional reselection parameter indicator
(ADDITIONAL RESELECT) informs MS of whether to use C2 in cell
reselection.II. FormatADDITIONAL RESELECT consists of 1 bit. In
SI3, it is meaningless, and equipment manufacturers configure it to
N. The MS uses ADDITIONAL RESELECT of SI4. l When ADDITIONAL
RESELECT is configured to N, the meaning is: if the rest bytes of
SI4 (SI4RestOctets) are present, the MS must abstract and calculate
parameters related to C2 and related cell reselection parameter
PI.l When ADDITIONAL RESELECT is configured to Y, the meaning is
that the MS must abstract and calculate parameters related to C2
and related cell reselection parameter PI.III. Configuration and
InfluenceCells seldom use SI7 and SI8, so you can configure
ADDITIONAL RESELECT to N. When cells use SI7 and SI8, and the
parameter C2 is used in cell reselection, you can configure
ADDITIONAL RESELECT to Y.4.3.5 Cell Reselection Parameter
IndicatorI. DefinitionThe cell reselection parameter indicator
(CELL_RESELECT_PARAM_IND) is used in informing MS of whether C2 is
a cell reselection parameter and whether C2 is present.II.
FormatThe value of CELL_RESELECT_PARAM_IND includes Y and N, with
the meanings as follows:l Y: The MS must calculate C2 by
abstracting parameters from SIs of cell broadcast, and set C2 as
the standard for cell reselection.l N: The MS must set C1 as the
standard, namely, C2 = C1.III. Configuration and InfluenceThe
equipment room operators determine the value of PI. Configure PI to
Y if related cells set C2 as the standard for cell reselection;
otherwise, configure it to N.4.3.6 Cell Reselection Offset,
Temporary Offset, and Penalty TimeI. DefinitionAfter the MS selects
a cell, without great change of all the conditions, the MS will
camp on the selected cell. Meanwhile, it does as follow:l Starts
measuring signals level of BCCH carrier in neighbor cells.l Records
the 6 neighbor cells with greatest signal level.l Abstract various
SI and control information of each neighbor cell from the 6
cells.When conditions are met, the MS hands over from the selected
cell to another. This process is called cell reselection. The
conditions include:l Cell priorityl Whether the cell is barred to
accessl Radio channel level (important)When the signal level of
neighbor cells exceeds that of the serving cell, cell reselection
occurs. The channel level standard used in cell reselection is C2,
with the calculation as follows:1) When PENELTY_TIME 11111:C2 = C1
+ CELL_RESELECT_OFFSET - TEMPORARY_OFFSET * H (PENALTY_TIME -
T)Wherein, if PENALTY_TIME - T (x) < 0, the function H(x) = 0;
if x 0, H(x) = 1.2) When PENELTY_TIME = 11111:C2 = C1 -
CELL_RESELECT_OFFSETT is a timer, with 0 as the initial value. When
a cell is listed by MS in the list of cells with maximum signal
level, start T with step of 4.62ms (a TDMA frame). When the cell is
removed from the list, the associated T is reset.After cell
reselection, the T of original cell works as PENALTY_TIME. Namely,
temporary offset is not performed on the original
cell.CELL_RESELECT_OFFSET (CRO) modifies cell reselecting time
C2.TEMPORARY_OFFSET (TO) is supplemented to C2 from starting
working of T to the prescribed time.PENALTY_TIME is the time for
TEMPORARY_OFFSET having effect on C2. When PENALTY_TIME = 11111,
the MS is informed of using C2 = C1 CRO.CELL_RESELECT_OFFSET,
TEMPORARY_OFFSET, and PENALTY_TIME are cell reselection parameters.
l When the cell reselection parameter PI is 1, the MS is informed
of receiving values of three parameters on BCCH. l If PI is 0, the
MS judges that the previous three parameters are 0, namely C2 =
C1.If the C2 of a cell (in the same location area as the serving
cell) calculated by MS is greater than the C2 of the cell where MS
camps, and this lasts for over 5s, the MS reselects to camp on the
cell. If the C2 of a cell (in different location area as the
serving cell) calculated by MS is greater than the sum of C2 of the
cell where MS camps and cell reselect hysteresis, and this lasts
for over 5s, the MS reselects to camp on the cell. The interval
between two reselections is at least 15s, and this avoids frequent
cell reselection by MS.C2 is formed on the combination of C1 and
artificial offset parameters. The artificial offset parameters help
MS camp on or prevent MS from camping on some cell. This balances
the traffic of the network.II. Format1) The cell reselection offset
(CRO) is in decimal, with unit of dB. It ranges from 0 to 63, which
means 0 to 126 dB (2 dB as the step). The recommended value is 0.2)
The temporary offset (TO) is in decimal, with unit of dB. It ranges
from 0 to 7, which means 0 to 70 dB (10 dB as the step). The
recommended value is 0.3) The penalty time (PT) is in decimal, with
unit of second. It ranges from 0 to 31. The value 0 to 30 means 20s
to 620s (20s as the step). The value 31 is reserved for changing
the effect direction of C2 by CRO. The recommended value is 0.III.
Configurationa and InfluenceThe previous parameters can be adjusted
accordingly in the following three situations:1) When the
communication quality is bad due to heavy traffic or other causes,
change the parameters to enable MS not camps on the cell (the cell
is exclusive from the MS). For this situation, configure PT to 31,
so TO is ineffective. C2 = C1 CRO. The C2 is artificially lowered.
So the probability for MS to reselect the cell decreases. In
addition, the equipment room operators can configure CRO to a
proper value according to the exclusive level of the cell by MS.
The greater the exclusion is, the greater the CRO is. 2) For cells
with low traffic and equipment of low utilization, change the
parameters to enable MS to camp on the cell (the cell is prior). In
this situation, configure CRO to 020 dB according to the priority.
The higher the priority is, the greater the CRO is. TO is
configured the same as or a little greater than CRO. PT helps avoid
over frequent cell reselection, the recommended value of PT is 20s
or 40s.3) For cell with average traffic, configure CRO to 0, PT to
11111 so that C2 = C1. No artificial influence is on the cell.IV.
PrecautionsIn whatever situations, the CRO must not be greater than
30 dB, because over great CRO leads to unstable network, such as
complaints about signal fluctuation.4.3.7 Cell Reselection
Hysteresis (CRH)I. DefinitionCRH affects cell reselection of cross
location area. The MS starts cell reselection if the following
conditions are met:l The signal level of neighbor cell (in
different location area) is greater than that of the serving cell.l
The difference between the signal levels of the neighbor cell and
the serving cell must be greater than the value prescribed by cell
reselection hysteresis.The difference is based on the cell
reselection methods used by MS. If the MS reselects a cell with C2,
then compare values of C2.II. FormatCRH is in decimal, with unit of
dB. The range is 0 to 14, with step of 2 dB. The recommended value
is 4.III. Configuration and InfluenceIf the original cell and
target cell belongs to different location areas, the MS must
originate a location updating process after cell reselection. Due
to the attenuation feature of radio channels, the C2 of two cells
measured at the bordering area of neighbor cells fluctuates much,
so the MS reselect cells frequently. The interval between two
reselections is over 15s, which is rather short for location
updating. The signal flow of network increases sharply, radio
resources cannot be fully utilized. During location updating, the
MS cannot respond to paging, so the connection rate decreases.
Adjust CRH according to signal flow and coverage. When signal flow
overloads or location updating of cross location area is frequent,
the cell reselection hysteresis is increased as recommended. You
must avoid abnormal coverage due to over large location area.IV.
PrecautionsDo not configure CRH to 0 dB.4.4 Parameters Affecting
Network Functions4.4.1 Newly Established Cause Indicator (NECI)I.
DefinitionIn a GSM network, the traffic channel (TCH) consists of
full-speed TCH and half-speed TCH. When the network supports
half-speed TCH, the MS is informed of whether the area supports
half-speed TCH by NECI.II. FormatThe value of NECI includes Y and
N, with the meaning as follows:l Y means that the area support
half-speed TCH.l N means that the area cannot support half-speed
TCH.III. Configuration and InfluenceHalf-speed TCHs enable each
carrier to support more traffic channel, but you must confirm
whether the system support half-speed TCH.4.4.2 Power Control
Indicator (PWRC)I. DefinitionThe PWRC informs MS of whether to take
statistics of downlink level of BCCH carrier slot for measuring
average value when the BCCH frequency participates in frequency
hopping. The causes to configuring PWRC are as follows:l GSM
regulations allow frequency hopping channels to use BCCH (frequency
hopping not in BCCH slots) .l GSM regulations allow downlink power
control over frequency hopping channels.l The MS needs signal level
of the measured neighbor cells, so the power of each slot on BCCH
frequency is prohibited to change. The downlink power control does
not involve carrier slots for BCCH which includes the frequency
hopping.For previous causes, when the MS measures the average
downlink channel level with common methods, the measurement result
is inaccurate for power control because the average value includes
the downlink received level of BCCH carriers the power of which are
not controlled, so the measurement report is inaccurate for power
control.To avoid the influence on power control, when the MS
calculates average received level during frequency hopping, the
received level obtained from BCCH carrier slot must be removed (see
GSM regulations 05.08).II. FormatThe value of PWRC includes 0 and
1, with meanings as follows:l When PWRC is 0, the measurement
result by MS includes BCCH carrier.l When PWRC is 1, the
measurement result by MS does not include BCCH carrier.III.
Configuration and InfluenceThe PWRC is usually configured to 0.
Configure it to 1 if all the following conditions are met:l
Channels have frequency hopping on two or more frequencies.l One of
the frequency is BCCH carrier frequency.l The system uses downlink
power control.IV. PrecautionsThe value of PWRC depends actually on
the following parameters:l Whether to use frequency hopping.l
Whether the hopping frequency includes BCCH carrier.l Whether the
system uses downlink power control.4.4.3 Discontinuous Transmit of
UplinkI. DefinitionDiscontinuous transmit of uplink (DTXU) refers
to the process for MS not to transmit signals during silent period
(see description about DTX in Chapter 2).II. FormatWhether the
network allows uplink to use discontinuous transmit (DTX) is set by
equipment room operators. DTX ranges from 0 to 2, with the
following meanings:l 0: MS can use DTXU.l 1: MS must use DTXU.l 2:
MS cannot use DTXU.III. Configuration and InfluenceUsing uplink DTX
affects call quality, but it is helpful in the following aspects:l
Lower interference to radio channels.Due to this, the average call
quality of network is improved.l Cut power consumption by MSFor the
previous advantages, DTX is recommended to use.4.4.4 Discontinuous
Transmit of DownlinkI. DefintionDiscontinuous transmit of downlink
(DTXD) means the network does not transmit signals during silent
period.II. DefinitionDTXD is in string, and the range is YES and
NO. The meanings are as follows:l YES: Downlink uses DTX.l NO:
Downlink does not use DTX.III. Configuration and InfluenceUsing
downlink DTX affects call quality in a limit scale, but it is
helpful in the following aspects:l Lower interference to radio
channels.Due to this, the average call quality of network is
improved.l Reduce load of base station CPUTherefore, if possible,
you use DTX.IV. PrecautionsAccording to GSM regulations, downlink
DTX is optional. If the base station equipment supports DTXD, then
use it. However, you must ensure that voice transcoder is available
to support DTXD.4.4.5 Call Resetup AllowedI. DefinitionWhen
coverage voids cause radio link failure, consequently call drop,
the MS starts to resetup the call for recovery. Whether resetting
up the call is allowed depends on the parameter call resetup
allowed (RE). II. FormatThe values of call resetup allowed are 1
and 0, with meanings as follows:l 1: Call resetup is allowed in the
cell.l 0: Call resetup is forbidden in the cell.III. Configuration
and InfluenceWhen a connected MS passes coverage voids, call drop
occurs easily. If call resetup is allowed, the average call drop
rate (CDR) is lowered. However, call resetup takes longer time, and
most users disconnects before completion of call resetup. Therefore
call resetup is difficult to achieve, and even wastes abundant
radio resources. In a word, call resetup is disabled.4.4.6
Emergency Call AllowedI. DefinitionThe following MSs cannot enjoy
various services:l MS without SIMl MS with ACC as one of C0 to C9
and with cell_bar_accessThe parameter emergency call allowed (EC)
determines whether the MS is allowed for emergency calls, such as
police emergency call.II. FormatEC consists of 1 bit. For the MS
with ACC of C0 to C9 or without SIM, the EC is NO, meaning
emergency call forbidden. YES means emergency call allowed. For the
MS with ACC of C11 to C15, when both the access control bit and EC
are configured to forbidden, it is forbidden for emergency
calls.III. Configuration and InfluenceAccording to the GSM
regulations, the emergency number is 112, different from that in
China. The Chinese emergency call cannot function as prescribed in
GSM regulations. For international roaming users, set 112 to
answerphone to inform users of various special service numbers.
Therefore, setting emergency call must be allowed through
configuring radio parameters, namely, configure EC to 1.4.4.7 Early
Classmark Sending ControlI. DefinitionIn a GSM network, the MS
classmark marks the following aspects:l Service capacityl Supported
frequency bandl Power capacityl Encryption capacityClassmark
consists of classmark1, classmark2, and classmark3. A GSM MS. In a
GSM network, the MS reports Classmark1 or Classmark2 information
immediately after ESTIND (corresponding to L2-SABM at Um interface)
is allocated. Classmark3 (CM3) information includes power
information of various frequency band of multi-frequency MS. During
handover between different bands, the power class must be correctly
described. When the GSM system pages and transmits BA2 in different
bands, it must know the CM3 message. In GSM regulation Phase2plus,
early classmark sending control (ECSC) is added. ECSC means that by
SI the system informs MS of reporting Classmark3 after link setup.
This avoids querying process by network.II. FormatThe values of
ECSC are Y and N, with the following meanings:l Y: The MS reports
Classmark3 to the network immediately after link setup.l N: The MS
is forbidden to report its Classmark3 to network initiatively.III.
Configuration and InfluenceThe major information of Classmark3 is
for dualband network, so do as follows:l Configure ECSC to N in
single frequency GSM application areas.l Configure ECSC to Y in
dualband GSM application areas.IV. PrecautionsIn a dualband
network, configure the parameter of all cell to the same value.
Configuring the parameter to different values in one or more cells
is forbidden; otherwise, the network quality declines.4.5 Frequency
Hopping Parameters4.5.1 Frequency Hopping Sequence NumberI.
DefinitionIn a GSM network, the cell allocation (CA) means the set
of carriers used by each cell, recorded as {R0, R1, , Rn - 1}.
Wherein, Ri indicates the absolute channel number. For each
communication process, the set of carriers used by base station and
MS is mobile allocation (MA), recorded as {M0, M1, , Mn - 1}.
Wherein, Mi indicates the absolute channel number. Obviously MA is
a subset of CA.During a communication process, the air interface
uses a carrier number, one element of MA. The variable mobile
allocation index (MAI) determines an exact element of MA. According
to the frequency hopping algorithm in GSM regulation 05.02, the MAI
is the TDMA frame number (RN) or reduced frame number (RFN),
frequency hopping sequence number (HSN), and mobile allocation
index offset (MAIO). Wherein, the HSN determines two aspects:l
Track of frequency points during frequency hoppingl The
asynchronous neighbor cells using the same MA can avoid continuous
frequency collision during frequency hopping by using different
HSNs. II. FormatHSN is in decimal, ranging from 0 to 63, wherein:l
0: cyclic frequency hoppingl 163: pseudo frequency hoppingIII.
Configuration and InfluenceYou can choose any HSN in cells using
frequency hopping, but you must ensure that the cells using same
frequency group must use different HSN. The following paragraph is
an exception:In an 1X1 network, three cells under a base station
use the same frequency group, but they are synchronous cells
because of same FN. Therefore the three cells use the same HSN. You
must plan MAIO properly to avoid frequency collision of the three
cells under the same base station.4.5.2 Mobile AllocationI.
DefinitionThe mobile allocation (MA) in the GSM network indicates a
frequency set for frequency hopping. Namely, when the MA of a cell
is fixed, the communication frequency points of the cell performs
transient in the set by MA according to rules.The parameter MA
determines all the elements in MA.II. FormatMA is a set, with all
GSM frequency points as its element, namely:l For GSM900 networks:
1124 and 9751023.l For GSM1800 networks: 512885III. Configuration
and InfluenceMA is configured according to network designing
requirements.IV. PrecautionsChinese GSM networks do not cover all
available frequency bands of GSM system, so configure MA in
available frequency bands.The number of elements in each MA set
cannot exceed 63.The MA cannot include BCCH carriers.The number of
MA must not be multiples of 13 if all the following conditions are
met:l Using DTXl HSN = 0 (cyclic frequency hopping)You must avoid
SACCH to appear usually at the same frequency point.4.5.3 Mobile
Allocation Index OffsetI. DefinitionDuring communication, the air
interface uses a carrier frequency, one element of MA set. MIO
determines an exact element of MA set. According to the frequency
hopping algorithm in GSM regulation 05.02, the MAI is the TDMA
frame number (RN) or reduced frame number (RFN), frequency hopping
sequence number (HSN), and mobile allocation index offset (MAIO).
MAIO is an initial offset of MAI, and it aims to avoid multiple
channels to use the same frequency carrier in the same time.II.
FormatMAIO ranges from 0 to 63.III. Configuration and InfluenceMAIO
is configured by equipment room operators.IV. PrecautionsThe
different cells using same group of MA must use consistent
MAIO.Using different MAIOs enables different sectors in the same
location to use the same frequency group (MA) without frequency
collision.4.6 Distance Control Parameters4.6.1 Call ClearingI.
DefinitionCall clearing (CallClearing) means that the maximum
allowed distance threshold is cleared between MS and base station
in talk.II. FormatCallClearing ranges from 0 to 63, with unit of
TA.III. Configuration and InfluenceConfigure CallClearing according
to actual coverage range of a cell. Proper configuration of
CallClearing helps check whether the handover threshold of the cell
is properly defined, especially for urban cells. If the call is
frequently cleared after CallClearing threshold is defined
according to cell radium, probably the handover threshold is
improperly configured. This is due to that the MS cannot hand over
to the best server cell after exceeding designed coverage
range.Define CallClearing according to msRangeMax, namely,
CallClearing > msRangeMax.In actual network operation, call
clearing is unusually performed, because radio link fails due to
over poor coverage before call clearing. Defining CallClearing aims
to restrict the distance between MS and base station and to avoid
MSs in allowed coverage range to interfere other MSs, especially in
areas with complex landform.The cell coverage range is irregular,
so island effect might occur. For this phenomenon, define
CallClearing to clear calls in island areas.4.6.2 TA Handover
Threshold (MSRANGEMAX)I. DefintionWhen the distance between MS and
base station reaches or exceeds MSRANGEMAX, distance handover is
triggered.II. FormatMSRANGEMAX ranges from 0 to 63, with unit of
TA. The reference is 63.III. Configuration and InfluenceMSRANGEMAX
must be smaller than CallClearing, and otherwise the handover
function will be actually unavailable. While configuring
MSRANGEMAX, you must adjust the threshold of other types of
handover; otherwise ping-pong handover occurs. one occasion might
be as follows:The distance between MS and the serving cell exceeds
the threshold, but the signals of target cell are weaker than that
of original cell. Consequently the PowerBudget handover is
triggered immediately after distance handover is triggered. 4.6.3
TA Restriction (MS_BS_DIST_USED)I. DefinitionThe maximum allowed
access distance between base station and MS. If the distance
between an MS and base station exceeds the maximum allowed access
distance, the MS is forbidden to access cells.II. FormatThe range
is 0 to 63, with unit of TA. The reference is 63.III. Configuration
and InfluenceFor its configuration, refer to the method for
configuring CallClearing. Adjust the parameter to enable it
consistent with the geographic coverage range of the cell. Set a
proper threshold to filter pseudo RACH requests to avoid
unnecessary assigning SDCCH.According to tests, for
mountain-mounted base stations, the coverage and interference is
difficult to control. If you define the maximum allowed access
distance to 63, the RACH misjudgment increases (the system
demodulates interference to RACH bursts by mistake). Therefore the
radio performance and traffic measurement indexes of the cell are
affected.4.7 Radio Link Failure Process and ParametersThe radio
link failure is detected from uplink and downlink. The MS completes
downlink detection, while the base station completes uplink
detection.4.7.1 Radio Link Failure Counter (RLC or Radio Link
Timeout)I. DefinitionThe MS originates call resetup or disconnects
by force if all the following conditions are met:l The voice or
data quality is too poor to be received.l Power control and
handover cannot help to improve the quality.A disconnection by
force actually brings about a call drop, so the MS considers it a
radio link failure that the voice or data service is actually too
poor to be received. GSM regulations provide solutions to the
previous problems as follows:Set a counter S in the MS. The initial
value of S is provided at the beginning of talk, and it is the
value of the parameter radio link failure counter. S changes as
follows:l S decreases by 1 if the MS fails in decoding a correct
SACCH message when the MS should receive the SACCH message.l S
increases by 2 if the MS succeed in decoding a correct SACCH
message.S cannot exceed the value for radio link failure counter.
When S equals to 0, the MS originates call resetup or disconnects
by force.II. FormatThe step from 4 to 64 is 4, with unit of SACCH
period as follows:l For TCH, the SACCH period is 480ms.l For SDCCH,
the SACCH period is 470ms.III. Configuration and InfluenceThe value
of the parameter radio link failure counter affects CDR and
utilization of radio resources.Assume that cell A is a neighbor
cell to cell B and the bordering coverage is poor. When an MS moves
from P to Q while in talk,l If the radio link failure counter is
over small, call drop occurs before cross-cell handover.l If the
radio link failure counter is over great, the network releases
related resources until radio link expires, though the voice
quality is too poor when MS camps on cell B near P. Therefore, the
utilization of radio resources declines.Proper configuration of
radio link failure counter is important, and is related to the
actual situations. To configure radio link failure counter, refer
to the following rules:l Configure it to between 52 and 64 in areas
with over low traffic.l Configure it to between 36 and 48 in areas
with low traffic and great coverage radiuml Configure it to between
20 and 32 in areas with heavy traffic.IV. PrecautionsConfigure
radioLinkTimeout to smaller than T3109. This contributes to success
of call resetup and avoids the following situation
effectively:Before the MS releases radio resources due to
expiration, the network side completes releasing channels resources
and reallocates resources to other MSs. Therefore two MSs might use
the same slot and this causes interferences even call drop.4.7.2
SACCH Multiframe (RLTO_BS)I. DefinitionRefer to the description of
radio link failure counter. A counter is set accordingly to radio
link at base station side for managing radio link failures. The
solutions vary due to different equipment providers, but a general
method is as follows:Set a counter S in the base station. The
initial value of S is provided at the beginning of talk, and it is
the value of the parameter radio link failure expiration. S changes
as follows:l S decreases by 1 if the MS fails in decoding a correct
SACCH message when the MS should receive the SACCH message.l S
increases by 2 if the MS succeed in decoding a correct SACCH
message.S cannot exceed the value for radio link expiration of base
station. When S equals to 0, the MS originates call resetup or
disconnects by force, as shown in Figure 1-5.II. FormatRLT0_BS
ranges from 4 to 64.III. Configuration and InfluenceProper
configuration of radio link expiration of base station affects CDR
and utilization of radio resources. It is related to the actual
situations. To configure radio link failure counter, refer to the
following rules:l Configure it to between 52 and 64 in areas with
over low traffic.l Configure it to between 36 and 48 in areas with
low traffic and great coverage radiuml Configure it to between 20
and 32 in areas with heavy traffic.l Configure it to a greater
value in areas with apparent voids or where call drop occurs
frequently while the MS moves.IV. PrecautionsRLT0_BS and RLC must
be consistent.4.8 Handover and Related Parameters4.8.1 PBGT
Handover Threshold (HoMargin)I. DefinitionThe PBGT handover
threshold is power handover tolerance (handover in serving areas).
When the signal level of neighbor cell is hoMargin (dB) higher than
that of the serving cell, handover occurs. Complex radio
propagation conditions cause fluctuation of signal level. Using
handover tolerance avoids frequent handover at bordering areas. The
PBGT handover threshold is similar to HO_MARGIN (GSM 05.08).II.
FormatThe PBGT handover threshold ranges from 0 to 127,
corresponding to 64 dB to +63 dB. The reference value for suburban
areas is 68. The reference value for urban areas is 70 to 72.III.
Configuration and InfluenceThe PBGT handover threshold aims to
adjust handover difficulty properly, and to avoid ping-pong
handover. If it is configured over great, the handover is delayed
and handover is less efficient. When it is smaller than 64, the MS
hands over from the serving cell to the neighbor cell with lower
level.4.8.2 Minimum Downlink Power of Handover Candidate Cells
(rxLevMinCell)I. DefinitionIt is the minimum allowed access level
for a cell to be a neighbor cell. When the cell level measured by
MS is greater than the threshold, the BSS list the cell into
candidate cell list for handover judgment.II. FormatIt ranges from
110 dBm to 47 dBm.III. Configuration and InfluenceIt is helpful in
the following two aspects:l It guarantees communication quality.For
a common single layer network structure, the value ranges from 90
dBm to 80 dBm. l It helps allocate traffic between cells
averagely.Especially in multi-layer network structure, to maintain
MS in a network layer, you can increase the level of the cell of
the network layer (such as 70 dBm), and also decrease that in other
cells. IV. PrecautionsYou cannot configure rxLevMinCell over great
(over 65 dBm) or over small (lower than 95 dBm), and otherwise
communication quality is affected.4.8.3 Handover Threshold at
Uplink EdgeI. DefinitionIf the uplink received level keeps being
smaller than the handover threshold at uplink edge for a period,
edge handover can be performed.II. FormatIt ranges from 0 to 63,
corresponding to 110 dBm to 47 dBm. The recommended values are as
follows:l Configure it to 25 in urban areas without PBGT handover.l
Configure it to 20 in single site of suburban areas.l Configure it
to 20 in urban areas with PBGT handoverIII. Configuration and
InfluenceWhen PBGT handover is enabled, the corresponding edge
handover threshold can be lowered. When PBGT handover is disabled,
and the edge handover threshold is over low, an artificial
cross-cell non-handover occurs. Therefore call drop occurs or
intra-frequency and side interference occur due to cross-cell
talk.4.8.4 Handover Threshold at Downlink EdgeI. DefinitionIf the
downlink received level keeps being smaller than the handover
threshold at downlink edge for a period, edge handover can be
performed. II. FormatIt ranges from 0 to 63, corresponding to 110
dBm to 47 dBm. The recommended values are as follows:l Configure it
to 30 in urban areas without PBGT handover.l Configure it to 25 in
single site of suburban areas.l Configure it to 25 in urban areas
with PBGT handoverIII. Configuration and InfluenceWhen PBGT
handover is enabled, the corresponding edge handover threshold can
be lowered. When PBGT handover is disabled, and the edge handover
threshold is over low, an artificial cross-cell non-handover
occurs. Therefore call drop occurs or intra-frequency and side
interference occur due to cross-cell talk.4.8.5 Downlink Quality
Restriction of Emergency HandoverI. DefinitionIf the downlink
received quality is lower than the threshold of downlink quality
restriction of emergency handover, the quality difference emergency
handover occurs.II. FormatIt ranges from 0 to 70, corresponding to
RQ (QoS 0 to 7) x 10.The recommended value is 50.III. Configuration
and InfluenceWhen frequency hopping is enabled, the voice quality
is better with the same RQ, you can configure it to 60 or 70. When
emergency handover occurs, the intracell handover occurs first. If
there are no other candidate cells, and the intracell handover is
enabled, the intracell handover occurs.4.8.6 Uplink Quality
Restriction of Emergency HandoverI. DefinitionIf the uplink
received quality is lower than it, quality difference emergency
handover is triggered.II. FormatIt ranges from 0 to 70,
corresponding to RQ (QoS 0 to 7) x 10.The recommended value is
50.III. Configuration and InfluenceWhen frequency hopping is
enabled, the voice quality is better with the same RQ, you can
configure it to 60 or 70. When emergency handover occurs, the
intracell handover occurs first. If there are no other candidate
cells, and the intracell handover is enabled, the intracell
handover occurs.4.8.7 Uplink Quality Threshold of Interference
HandoverI. DefinitionIt is the uplink received quality threshold of
the serving cell that triggers interference handover. The
interference handover is triggered if all the following conditions
are met:l The uplink received level is higher than the uplink
received power threshold of interference handover.l The uplink
received quality is lower than the uplink quality threshold of
interference handover.When handover switch is enabled, the
interference handover occurs within the cell by preference.II.
FormatIt ranges from 0 to 70, corresponding to RQ (QoS 0 to 7) x
10.The recommended value is 50.III. Configuration and InfluenceWhen
frequency hopping is enabled, the voice quality is better with the
same RQ, you can configure it to 60 or 70. When interference
handover is triggered, select the candidates according to the
sorted result. If the serving cell ranks first and its intracell
handover is enabled, the MS selects the serving cell; otherwise it
selects the second candidate cell.4.8.8 Downlink Quality Threshold
of Interference HandoverI. DefinitionIt is the downlink received
quality threshold of the serving cell that triggers interference
handover. The interference handover is triggered if all the
following conditions are met:l The downlink received level is
higher than the downlink received power threshold of interference
handover.l The downlink received quality is lower than the downlink
quality threshold of interference handover.When handover switch is
enabled, the interference handover occurs within the cell by
preference.II. FormatIt ranges from 0 to 70, corresponding to RQ
(QoS 0 to 7) x 10.The recommended value is 50.III. Configuration
and InfluenceWhen frequency hopping is enabled, the voice quality
is better with the same RQ, you can configure it to 60 or 70. When
interference handover is triggered, select the candidates according
to the sorted result. If the serving cell ranks first and its
intracell handover is enabled, the MS selects the serving cell;
otherwise it selects the second candidate cell.IV. PrecautionsThe
interference handover quality must be better than emergency
handover quality.4.8.9 Uplink Received Power Threshold of
Interference HandoverI. DefinitionIf interference handover occurs
due to uplink quality, the serving cell must reach the minimum
uplink received power threshold. If this is met, the system judges
that uplink is interfered, so interference handover is
triggered.The interference handover is triggered if all the
following conditions are met:l The uplink received level is higher
than the uplink received power threshold of interference handover.l
The uplink received quality is lower than the uplink quality
threshold of interference handover.When handover switch is enabled,
the interference handover occurs within the cell by preference.II.
FormatIt ranges from 0 to 63, corresponding to 110 dBm to 47
dBm.The recommended value is 25.III. Configurationa and
InfluenceWhen interference handover is triggered, select the
candidates according to the sorted result. If the serving cell
ranks first and its intracell handover is enabled, the MS selects
the serving cell; otherwise it selects the second candidate
cell.4.8.10 Downlink Received Power Threshold of Interference
HandoverI. DefinitionIf interference handover occurs due to uplink
quality, the serving cell must reach the minimum downlink received
power threshold. If this is met, the system judges that downlink is
interfered, so interference handover is triggered.The interference
handover is triggered if all the following conditions are met:l The
downlink received level is higher than the downlink received power
threshold of interference handover.l The downlink received quality
is lower than the downlink quality threshold of interference
handover.When handover switch is enabled, the interference handover
occurs within the cell by preference.II. FormatIt ranges from 0 to
63, corresponding to 110 dBm to 47 dBm.The recommended value is
30.III. Configurationa and InfluenceWhen interference handover is
triggered, select the candidates according to the sorted result. If
the serving cell ranks first and its intracell handover is enabled,
the MS selects the serving cell; otherwise it selects the second
candidate cell.4.8.11 Maximum Repeated Times of Physical Messages
(NY1)I. DefinitionIn asynchronous handover process of GSM system,
when the MS receives handover messages of the network, it sends
handover access messages on the target channel. After the network
receives the message, it does as follows:1) Calculate related RF
features.2) Send physical messages (it the channel messages are
encrypted, start encryption and decryption algorithm) in unit data
to MSs.3) Start timer T3105.If the network does not receive correct
layer 2 frames sent by MS until expiration of T3105, the network
will resend the physical message and restart T3105. The maximum
times for resending physical messages is determined by the
parameter maximum repeated times of physical messages (NY1)II.
FormatNY1 ranges from 0 to 254.The recommended value is 20.III.
Configuration and InfluenceWhen the network receives the handover
access messages sent by MS, the physical channel (PCH) needs to be
synchronous. If the communication quality on channels is
guaranteed, the MS can receive physical messages correctly and send
layer 2 frames to the network.If the physical messages are sent
multiple times, and the network cannot receive layer 2 frames sent
by MS, the PCH is too poor to communicate normally. Though link is
setup after multiple trials, the communication quality is not
guaranteed. This lowers the utilization of radio resources.
Therefore configure NY1 to a smaller value.IV.
PrecautionsConfiguring NY1 is affected by T3105. If T3105 is
configured to a short value, then the NY1 needs to be increased
accordingly.If a handover trial fails before the original cell
receives the HANDOVER FAILURE message, and the T3105 of the target
cell expires for Ny times, the target BTS sends a CONNECTION
FAILURE INDICATION message to the target BSC. Though the MS might
return to the original channel, the traffic measurement counters
from multiple vendors will take statistics of connection failure.To
avoid the previous phenomenon, configure T3105 as follows:Ny *
T3105 > T3124 + delta (delta: the time between expiration of
T3124 and receiving HANDOVER FAILURE message by original BTS)4.8.12
Multiband Indicator (multiband_reporting)I. DefinitionIn a single
band GSM network, when the MS send measurement reports of neighbor
cells to the network, it needs to report the content of the six
neighbor cells with strongest signals. In a multiband network,
operators wish that MS uses a band by preference in cross-cell
handover. Therefore the MS sends measurement reports according to
signal strength and signal band. The parameter multiband indicator
indicates MS to report content of multiband neighbor cells.II.
FormatThe multiband indicator ranges from 0 to 3, with meanings as
follows:l 0: According to signal strength of neighbor cells, the MS
must report six allowed measurement reports of neighbor cells with
strongest signals and known NCC, with the neighbor cells in
whatever band.l 1: The MS must report the allowed measurement
report of a neighbor cell with known NCC and with strongest signals
at each band expect for the band used by the serving cell. The MS
must also report the neighbor cells of the band used by the serving
cell in rest locations. If there are other rest locations, the MS
must report conditions of other neighbor cells in any band.l 2: The
MS must report the allowed measurement report of two neighbor cells
with known NCC and with strongest signals at each band expect for
the band used by the serving cell. The MS must also report the
neighbor cells of the band used by the serving cell in rest
locations. If there are other rest locations, the MS must report
conditions of other neighbor cells in any band.l 3: The MS must
report the allowed measurement report of three neighbor cells with
known NCC and with strongest signals at each band expect for the
band used by the serving cell. The MS must also report the neighbor
cells of the band used by the serving cell in rest locations. If
there are other rest locations, the MS must report conditions of
other neighbor cells in any band.III. Configuration and InfluenceIn
multiband networks, it is related to traffic of each band. For
configuration, refer to the following rules:l If the traffic of
each band is approximately equal, and operators do not select a
band intentionally, you can configure the multiband indicator to 0l
If the traffic of each band is obviously different, and operators
want MS to select a band by preference, you can configure the
multiband indicator to 3.l For situations between the previous two,
configure multiband indicator to 1 or 2.4.8.13 Permitted Network
Color Code (ncc permitted)I. DefinitionDuring a talk, the MS must
report the measured signals of neighbor cells to the base station,
but each report includes only six neighbor cells. Therefore the MS
is configured to report the potential handover target neighbor
cells, instead of reporting unselectively and according to signal
level.To enable previous functions, restrict MS to measure the
cells with the fixed network color code (NCC). The NNC allowed by
parameters list the NCCs of the cells to be measured by MS. The MS
compares the measured NCC of neighbor cells and NCCs set allowed by
parameters. If the measured NCC is in the set, the MS reports the
NCC to the base station; otherwise, the MS discard the measurement
report.II. FormatThe parameter ncc permitted is a bit mapping
value, consisting of 8 bits. The most significant bit is bit 7
while the least significant bit is bit 0. Each bit corresponds to
an NCC code 0 to 7 (see GSM regulations 03.03 and 04.08).If the bit
N is 0 (N ranges from 0 to 7), the MS needs not to measure the
level of the cell with NCC of N. Namely, it only measures the
signal quality and level of the cells corresponding to bit number
of 1 in NCC and ncc permitted configuration.III. Configuration and
InfluenceEach area is allocated with one or more NCCs. In the
parameter ncc permitted of the cell, the local NCC is absolutely
and only included. If excluded, abnormal handover and call drop
occur. For normal roaming between areas, the NCC of neighbor areas
must be included in the edge cells of an area.IV.
PrecautionsImproper configuration of the parameter causes normal
handover and even call drop. The parameter only affects behaviors
of MS.4.9 Power Control and Related Parameters4.9.1 Maximum
Transmit Power of MS (MSTXPWRMX)I. DefinitionThe transmit power of
MS in communication is controlled by BTS. According to the uplink
signal strength and quality, power budget result, the BTS controls
MS to increase or decrease its transmit power.& Note:In any
situation, power control is prior to related handover for BSS. Only
when the BSS fails to improve uplink signal strength and voice
quality to the prescribed level, it starts handover.To reduce
interference between neighbor cells, the power control of MS is
restricted. Namely, the BTS controls MS to transmit power within
the threshold.MSTXPWRMX is the maximum transmit power of MS
controlled by BTS.II. FormatMSTXPWRMX ranges from 0 to 31.The dBm
values corresponding to GSM900 and GSM1800 cells are different:l
The 32 maximum transmit power control classes for GSM900 are {39,
39, 39, 37, 35, 33, 31, 29, 27, 25, 23, 21, 19, 17, 15, 13, 11, 9,
7, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5}l The 32 maximum transmit
power control classes for GSM900 are {30, 28, 26, 24, 22, 20, 18,
16, 14, 12, 10, 8, 6, 4, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 36, 34, 32}III. Configuration and InfluenceConfiguring MSTXPWRMX
helps control interferences between neighbor cells, because:l If
MSTXPWRMX is over great, the interference between neighbor cells
increases.l If MSTXPWRMX is over small, the voice quality declines
and improper handover might occur.4.9.2 Received Level Threshold of
Downlink Power Increment (LDR)I. DefinitionWhen the downlink
received level of the serving cell is smaller than a threshold, the
network must start power control to increase the transmit power of
base station and to guarantee communication quality of MS.The
received level threshold of downlink power increment defines the
downlink received level threshold. When the downlink level received
by MS is smaller than it, the base station starts power control to
increase its transmit power.The parameter N1 means that at lease N1
sampling points must be measured before starting handover
algorithm.The parameter P1 means the level of at least P1 sampling
points in N1 sampling points is smaller than the threshold
prescribed by received level threshold of downlink power
increment.II. FormatIt ranges from 110 dBm to 47 dBm.N1 ranges from
1 to 32.P1 ranges from 1 to 32.III. Configuration and InfluenceThe
received level is between 60 dBm and 80 dBm in a GSM network, so
configure received level threshold of downlink power increment to
85 dBm.N1 is related to propagation quality of radio channels
within cell coverage range. To reduce influence by attenuation,
configure N1 to between 3 and 5.Configure P1 to about 2/3 of
N1.4.9.3 Received Level Threshold of Uplink Power Increment (LUR)I.
DefinitionWhen the uplink received level of the serving cell is
smaller than a threshold, the network must start power control to
increase the transmit power of MS and to guarantee communication
quality of MS.The received level threshold of uplink power
increment defines the uplink received level threshold. When the
uplink level received by MS is smaller than it, the base station
starts power control to increase MS transmit power.The parameter N1
means that at lease N1 sampling points must be measured before
starting handover algorithm.The parameter P1 means the level of at
least P1 sampling points in N1 sampling points is smaller than the
threshold prescribed by received level threshold of uplink power
increment. II. FormatIt ranges from 110 dBm to 47 dBm.N1 ranges
from 1 to 32.P1 ranges from 1 to 32.III. Configuration and
InfluenceThe received level is between 60 dBm and 80 dBm in a GSM
network, so configure received level threshold of uplink power
increment to 85 dBm.N1 is related to propagation quality of radio
channels within cell coverage range. To reduce influence by
attenuation, configure N1 to between 3 and 5.Configure P1 to about
2/3 of N1.4.9.4 Received Quality Threshold of Downlink Power
Increment (LDR)I. DefinitionWhen the downlink received quality of
the serving cell is smaller than a threshold, the network must
start power control to increase the transmit power of base station
and to guarantee communication quality.The received quality
threshold of downlink power increment defines the downlink received
level threshold. When the downlink quality received by MS is
smaller than it, the base station starts power control to increase
its transmit power.The parameter N3 means that at lease N3 sampling
points must be measured before starting handover algorithm. The
parameter P3 means the quality of at least P3 sampling points in N3
sampling points is smaller than the threshold prescribed by
received quality threshold of downlink power increment.II. FormatIt
ranges from 0 to 7, the voice quality grade.N3 ranges from 1 to
32.P3 ranges from 1 to 32.III. Configuration and InfluenceThe
received quality is 0 to 2 of quality grade in a GSM network, so
configure received quality threshold of downlink power increment to
85 dBm.N3 is related to propagation quality of radio channels
within cell coverage range. To reduce influence by attenuation,
configure N3 to between 3 and 5.Configure P3 to about 2/3 of
N3.4.9.5 Received Quality Threshold of Uplink Power Increment
(LUR)I. DefinitionWhen the uplink received quality of the serving
cell is smaller than a threshold, the network must start power
control to increase the transmit power of MS and to guarantee
communication quality.The received quality threshold of uplink
power increment defines the uplink received quality threshold. When
the uplink quality received by MS is smaller than it, the base
station starts power control to increase transmit power of MS.The
parameter N3 means that at lease N3 sampling points must be
measured before starting handover algorithm.The parameter P3 means
the quality of at least P3 sampling points in N3 sampling points is
smaller than the threshold prescribed by received quality threshold
of uplink power increment. II. FormatIt ranges from 0 to 7, the
voice quality grade.N3 ranges from 1 to 32.P3 ranges from 1 to
32.III. Configuration and InfluenceThe received quality is 0 to 2
of quality grade in a GSM network, so configure received quality
threshold of uplink power increment to 3.N3 is related to
propagation quality of radio channels within cell coverage range.
To reduce influence by attenuation, configure N3 to between 3 and
5.Configure P3 to about 2/3 of N3.4.9.6 Received Level Threshold of
Downlink Power Decrement (UDR)I. DefinitionWhen the downlink
received level of the serving cell is greater than a threshold, the
network must start power control to decrease the transmit power of
base station and to decrease interference to radio channels.The
received level threshold of downlink power decrement defines the
downlink received level threshold. When the downlink level received
by MS is greater than it, the base station starts power control to
decrease its transmit power.The parameter N2 means that at lease N2
sampling points must be measured before starting handover
algorithm.The parameter P2 means the level of at least P2 sampling
points in N2 sampling points is greater than the threshold
prescribed by received level threshold of downlink power decrement.
II. FormatIt ranges from 110 dBm to 47 dBm.N1 ranges from 1 to
32.P1 ranges from 1 to 32.III. Configuration and InfluenceThe
received level is between 60 dBm and 80 dBm in a GSM network, so
configure received level threshold of downlink power decrement to
85 dBm.N2 is related to propagation quality of radio channels
within cell coverage range. To reduce influence by attenuation,
configure N2 to between 3 and 5.Configure P2 to about 2/3 of
N2.4.9.7 Received Level Threshold of Uplink Power Decrement (UUR)I.
DefinitionWhen the uplink received level of the serving cell is
greater than a threshold, the network must start power control to
decrease the transmit power of MS and to decrease interference to
radio channels.The received level threshold of uplink power
decrement defines the uplink received level threshold. When the
uplink level received by MS is greater than it, the base station
starts power control to decrease transmit power of MS.The parameter
N2 means that at lease N2 sampling points must be measured before
starting handover algorithm.The parameter P2 means the level of at
least P2 sampling points in N2 sampling points is greater than the
threshold prescribed by received level threshold of uplink power
decrement.II. FormatIt ranges from 110 dBm to 47 dBm.N2 ranges from
1 to 32.P2 ranges from 1 to 32.III. Configuration and InfluenceThe
received level is between 60 dBm and 80 dBm in a GSM network, so
configure received level threshold of uplink power decrement to 60
dBm.N2 is related to propagation quality of radio channels within
cell coverage range. To reduce influence by attenuation, configure
N2 to between 3 and 5.Configure P2 to about 2/3 of N2.4.9.8
Received Quality Threshold of Downlink Power Decrement (UDR)I.
DefinitionWhen the downlink received quality of the serving cell is
greater than a threshold, the network must start power control to
decrease the transmit power of base station and to decrease space
interference.The received quality threshold of downlink power
decrement defines the downlink received quality threshold. When the
downlink quality received by MS is greater than it, the base
station starts power control to decrease transmit power of MS.The
parameter N4 means that at lease N4 sampling points must be
measured before starting handover algorithm.The parameter P4 means
the quality of at least P4 sampling points in N2 sampling points is
greater than the threshold prescribed by received quality threshold
of downlink power decrement.II. FormatIt ranges from 0 to 7, the
voice quality grade.N4 ranges from 1 to 32.P4 ranges from 1 to
32.III. Configuration and InfluenceThe received quality is 0 to 2
of quality grade in a GSM network, so configure received quality
threshold of downlink power decrement to 0.N4 is related to
propagation quality of radio channels within cell coverage range.
To reduce influence by attenuation, configure N4 to between 3 and
5.Configure P4 to about 2/3 of N4.4.9.9 Received Quality Threshold
of Uplink Power Decrement (UUR)I. DefinitionWhen the uplink
received quality of the serving cell is greater than a threshold,
the network must start power control to decrease the transmit power
of MS and to decrease space interference.The received quality
threshold of uplink power decrement defines the uplink received
quality threshold. When the uplink quality received by MS is
greater than it, the base station starts power control to decrease
transmit power of MS.The parameter N4 means that at lease N4
sampling points must be measured before starting handover
algorithm.The parameter P4 means the quality of at least P4
sampling points in N4 sampling points is greater than the threshold
prescribed by received quality threshold of uplink power
decrement.II. FormatIt ranges from 0 to 7, the voice quality
grade.N4 ranges from 1 to 32.P4 ranges from 1 to 32.III.
Configuration and InfluenceThe received quality is 0 to 2 of
quality grade in a GSM network, so configure received quality
threshold of uplink power decrement to 0.N4 is related to
propagation quality of radio channels within cell coverage range.
To reduce influence by attenuation, configure N4 to between 3 and
5.Configure P4 to about 2/3 of N4.4.9.10 Power Control Interval
(INT)I. DefinitionIt takes a period from beginning of power control
to detection of effect of power control. Therefore an interval must
exist between continuous two power controls; otherwise the system
becomes unstable and even call drop occurs.The parameter power
control interval (INT) configures the minimum interval between two
continuous times of power control.II. FormatIt ranges from 0 to
31s.III. Configuration and InfluenceAccording to frame structure of
GSM network, configure INT to about 3s.IV. PrecautionsINT cannot be
smaller than 1s, and otherwise the system becomes unstable.4.9.11
Power Increment Step (INC)I. DefinitionThe INC indicates the power
increment of MS or base station in power control.II. FormatThe
range of INC is 2 dB, 4 dB, or 6 dB.III. Configuration and
InfluenceThe recommended value is 4 dB.4.9.12 Power Decrement Step
(RED)I. DefinitionThe RED indicates the power decrement of MS or
base station in power control.II. FormatThe range of RED is 2 dB or
4 dB.III. Configuration and InfluenceThe recommended value of RED
is 2 dB.
4.10 Systematic Important Timers
4.10.1 T3101I. DefinitionT3101 is the BSC timer controlling time
of immediate assignment process.II. FormatT3101 ranges from 0 to
255s. The recommended value is 3s.III. Configuration and
InfluenceIn an immediate assignment process, the BSC requires BTS
to provide SDCCH to set up signaling channel. When the BSC sends a
channel activation message, T3101 starts timing. When the BSC
re