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ZXG10 – RADIOPARAMETERS
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TOPICS FOR DISCUSSION
• NETWORK IDENTIFICATION PARAMETERS – CGI , BSIC, BCC/ NCC
• CELL SELECTION PARAMETERS
– C1 and C2
• SYSTEM CONTROL PARAMETERS
– RLT, CBA, CBQ and etc.
• NETWORK FUNCTIONAL PARAMETERS
– INTAVE, LIMITn
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NETWORK IDENTIFICATION
PARAMETERS
• As a global cellular mobile communication
system, the GSM adopts a unique numbers to
every country, networks in every country,
location area of every network and cells ofeach location area.
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ROLES OF IDENTIFICATION
PARAMETERS
Enable the MS to correctly identify the ID of thecurrent network so that it can correctly select the
network when the user (or telecom operator) wants to
access to in any conditions.
Enable the network to be real time informed of thecorrect geographical location of the MS so that the
network can normally connect various service
requests with the MS.
Enable the MS to report correctly the adjacent cellinformation during the conversation process so that
the network can hand-over the calls when necessary
to ensure the continuity of the conversation.
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CELL GLOBAL IDENTITY (CGI)
MCC LAC
Cell Global Identity
MNC
3 Digi ts 2-3 Digits Max 16 Bits
CI
Max 16 bits
LAI
Cell Global Identity (CGI)
• It is used for identifying individual cells within an
LA
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ROLES OF CGI
The CGI information is sent along the systembroadcasting information in every cell.
When the MS receives the system information, it will
extract the CGI information from it and determines whether
to camp on the cell according to the MCC and MNCspecified by the CGI.
It judges whether the current location area is changed,
then determines whether to take the location updating
process. During the location updating process, the MS willreport the LAI information to the network so that the
network is fully aware of the cell where the MS is currently
located.
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SETTING OF CGI
MCC Mobile Country Code : consists of 3decimal digits, and the value range is the decimal 000
~ 999.
MNC
Mobile Network Code
: consists of 3decimal digits, and the value range is the decimal 00~
999.
LAC Location Area Code : The range is 1-
65535. CI Cell Identity : The range is 0-65535.
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BASE STATION IDENTITY CODE (BSIC)
NCC BCC
3 Bits 3 Bits
BSIC
NCC Network/ National Color Code Value Range: 0~7
BCC Base Station Color Code Value Range: 0~7
Base Station Identity Code (BSIC)
• It enables MSs to distinguish between neighboring
base stations
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NCC and BCC ROLES
NCC: In the connection mode (during conversation), theMS must measure the signals in the adjacent cells and
report the result to the network. As each measurement
report sent by the MS can only contain the contents of six
cells, so it is necessary to control the MS so as to onlyreport the information of cells factually related to the cell
concerned. The high 3 bits (i.e. NCC) in the BSIC serve this
purpose.
BCC: The BCC is used to identify different BS using the
same BCCH in the same GSMPLMN.
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BSIC CONFIGURATION PRINCIPLE
CBA
FED
In general, it is required that Cells A, B, C, D, E and F
use different BSIC. When the BSIC resources are not
enough, the cells close to each other may take the
priority to use different BSIC.
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ROLES OF BSIC
1. Inform the MS the TSC used by the common signaling
channel of the cell.
2. As the BSIC takes part in the decoding process of the
random access channel (RACH), it can be used to
prevent the BS from mis-decoding the RACH, sent by
the MS to an adjacent cell, as the access channel of thiscell.
3. When the MS is in the connection mode (during
conversation), it must measure the BCCH level of
adjacent cells broadcasting by BCCH and report theresults to the BS. In the uplink measurement report, MS
must show BSIC of this carrier it has measured to every
frequency point.
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BA LIST (BCCH ADJACENT LIST)
When a MS is turned on, it will scan from the BA
(Adjacent cell BCCH table) it remembered when
turned off last time. The MS will first search
carriers from this table and if none is found it willturns to find any of 30 carriers with highest levels,
then try to decode BCCH carriers one by one
according to their level sequences.
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CELL SELECTION C1
When the MS is turned on, it will try to contact a
public GSM PLMN, so the MS will select a proper
cell and extract from the cell the control channel
parameters and prerequisite system messages.This selection process is called cell selection. The
quality of radio channels is an important factor in
cell selection. The GSM Specifications defines the
path loss rule C1. For the so-called proper cell,C1>0 must be ensured.
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CELL SELECTION C1
C1 = RXLEV - RXLEV_ACCESS_MIN- Max(MS_TXPWR_MAX_CCH - P ,0)
where:
RXLEV_ACCESS_MIN is the minimum received level the MSis allowed to access the network
MS_TXPWR_MAX_CCH is the maximum power level of the
control channel (when MS sending on RACH);
RXLEV is average received level; P is the maximum TX power of MS;
MAX(X, Y)=X; if X Y.
MAX(X, Y)=0; if Y X.
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C1 PATHLOSS CRITERION
All the candidate cells for MS must meet the path
loss criterion, i.e C1>0. MS will select the cell with
the maximal C1 to access and will camp on this cellunless some key conditions has changed greatly.
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RXLEV_ACCESS_MIN
In order to avoid providing unsatisfactory communicationquality and avoid the unnecessary waste of radio
resources if the MS accesses to the system (the
communication quality after the access often cannot
ensure the normal communication process) at the very
low received level, the GSM system regulates that, when
a MS is to access to a network, its receiving signal level
must be larger than a threshold level, i.e. the minimum
receiving level the MS is allowed to access to
RXLEV_ACCESS_MIN).
Default value is 0 (-110dBm).
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CELL RESELECTION C2
1. Cell Reselection (C2) is a process when MS changeits service cell in idle mode.
2. When the MS selects a cell it will begin to measure
the signal levels of the BCCH TRX of its adjacent cells,
record 6 adjacent cells whose signal levels are the
strongest and extract from them various types of
system messages and control messages of each
adjacent cell.
3. When given conditions are met, the MS will move
from the current cell into another one. This process is
called cell reselection.
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CELL RESELECTION C2
When C2 Parameter Indicator (PI) indicates YES,the MS will
get parameters [CRO(cell reselect offset), TO(temporary offset)and PT(penalty time)] , from BCCH to be used to calculate
C2(channel quality criterion), which serves as cell reselection
norm. The equation is as follows:
C2=C1+CRO-H PT-T TO, when PT≠ 31
C2=C1-CRO , when PT= 31
Where T is a timer. When a cell is recorded by MS as one of the
six strongest cells, timer starts counting, otherwise, T is reset to
zero.
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PARAMETER INDICATOR (PI)
PI is used to notify the MS whether to use C2 as thecell reselect parameter and whether the parameters
calculating C2 exist.
PI consists of 1 bit. “1”means the MS should extract
parameters from the system message broadcasting in
the cell to calculate the C2 value, and use the C2
value as the standard for cell reselect; “0” means the
MS should use parameter C1 as the standard for cellreselect (equivalent to C2=C1).
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CRO, PT AND TO
The cell reselection initiated by the radio channelquality regards C2 as the standard. C2 is a parameter
based on C1 plus some artificial offset parameters.
The artificial influence is to encourage the MS to take
the priority in accessing to some cells or prevent itfrom accessing to others. These methods are often
used to balance the traffic in the network.
In addition to C1, there are three other factors
influencing C2, namely: CELL_RESELECT_OFFSET(CRO), TEMPORARY_OFFSET (TO) and
PENALTY_TIME (PT).
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C2 TYPICAL APPLICATIONS
1. In general, it’s not expected that MS access the cells
where the traffic is very heavy or the channel quality is
very low. In this case , the PT may be set 31, making TO
invalid, so C2=C1-CRO. Because the C2 is lowereddeliberately, the possibility that the cell will be
reselected by MS is lowered greatly. The greater the
CRO, the less possibility that the cell will be reselected,
and vice versa.
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C2 TYPICAL APPLICATIONS
2. It’s expected that MS stay as much as possible in cells
where the system utilization are very low and the trafficload is light. In this case, it’s recommended that CRO
be ranged from 0 to 20dB. The greater the CRO, the
more possible the cells will be reselected ,and vice
versa. It’s also suggested that TO is equal or a littlehigher than CRO. PT, whose main role is to avoid
frequent cell reselection by MS, is generally
recommended to be set at 20 seconds or 40
seconds.(20-640).
3. For cells where the traffic is moderate, the recommended
value for CRO is zero and PT=31, thus causing C2=C1,
i. e. no artificial impact will be imposed.
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CELL SELECTION HYSTERESIS (1)
1. When a MS reselects a cell, if the old cell and the
target cell are in different locations, then the MS must
initiate a location updating process after cell
reselection.
2. Due to the fading features of the radio channel, the C2
values of two adjacent cells measured along theirborders will fluctuate greatly.
3. MS will frequently conduct the cell reselection, which
will not only increase the network signaling flow and
lead to low efficiency use of radio resources, butreduces the access success rate of the system, as the
MS cannot respond to paging calls in the location
updating process.
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CELL SELECTION HYSTERESIS (2)
4. To minimize the influence of this issue, the GSMspecifications put forward a parameter called cell
selection hysteresis (CSH), which requires that the
signal level of adjacent cell (in a different location area)
be larger than the local cell signal level, and theirdifference be larger than the value specified by the
cell selection hysteresis. In this case, the MS will start
the cell reselection.
5. The cell selection hysteresis is represented in decimal
numerals, its unit is dB, its range is 0~14, its step
length is 2dB, and its default value is 4.
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CELL RESELECTION PRINCIPLE
1. If the MS calculates that the C2 value of an adjacent cell
(Same location area) surpasses the C2 value of theserving cell and maintains for 5s or longer, the MS will
start cell reselection and access to the adjacent cell.
2. If the MS detects a cell that is not in the same location
area with the current cell, the calculated C2 valuesurpasses the sum of the C2 value of the current cell
and the cell selection hysteresis (CSH) parameter and if
it remains for 5s or longer, the MS will start the cell
reselection and access to the new cell.
3. Note that the cell reselection caused by the parameter
C2 should be originated at least at the interval of 15s so
as to avoid the frequent cell reselection by MS.
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CELL BAR ACCESS (CBA)
In the system message broadcasting in each cell, there is a bit
information indicating whether to allow the MS to access to it, which is
called cell bar access (CBA). The parameter CBA is to indicate whether
the cell bar access is set in a cell.
The parameter is represented in character string. Its value range is:
YES: the cell is barred for access
NO: the cell is not barred for access
The CBA bit is a parameter for the network operator to set. Usually all thecells are allowed to be accessed by MS , so the bit is set NO. However,
in special cases, the telecom operator may want to assign a certain cells
for handover service only, then the bit can be set YES.
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CELL BAR ACCESS (CBA)
Area A
BTS A
BTS B
BTS C
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CELL BAR QUALIFY (CBQ)
In areas where the cells overlay with each other and differ incapacity, traffic and functions, the telecom operator often
hopes that the MS can have priority in selecting some cells,
that is, the setting of cell priority. This function is set by way of
the parameter "Cell Bar Qualify" (CBQ).
YES: The cell has low priority
NO: The cell has normal priority
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CELL BAR QUALIFY (CBQ) 2
C1 and C2 States with CBA and CBQ
Configurations
CBQ CBA Cell SelectionPriority
Cell ReselectionState
No No Normal Normal
No Yes Barred Barred
Yes No Low Normal
Yes Yes Low Normal
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EXAMPLE OF CBQ SETTING
For some reasons, the traffic of Cells A and B is apparently higher
than that of other adjacent cells. To balance the traffic in the wholearea, you can set the priority of Cells A and B as low, and set the
priority of the rest cells as normal so that the traffic in the shade area
will be absorbed by adjacent cells. It must be noted that the result of
this setting is that the actual coverage of Cell A and Cell B is narrowed.However, this is different from reducing the transmitting power of Cell
A and Cell B, the latter may cause blind areas of the network coverage
and the reduction of communication quality.。
B
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RANDOM ACCESS
Random access is the process that messages being transmittedon RACH when a MS turns from “idle” to “specialized” mode.
The main parameters includes:
MAXRETRANS AC
RE (Re-establishment Enable)
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MAX RETRANS
When starting the immediate assignment process (e.g, when
MS needs location updating, originating calls or responding to
paging calls), the MS will transmit the "channel request"
message over the RACH to the network. As the RACH is an
ALOHA channel, in order to enhance the MS access successrate, the network allows the MS to transmit multiple channel
request messages before receiving the immediate assignment
message. The numbers of maximum retransmission (MAX
RETRANS) are determined by the network.
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MAX RETRANS
The MAX RETRANS is often set in the following ways: For areas (suburbs or rural areas) where the cell radius is
more than 3km and the traffic is smaller, the MAX RETRANS
can be set 11 (i.e. the MAX RETRANS is 7).
For areas (not bustling city blocks) where the cell radius isless than 3km and the traffic is moderate, the MAX RETRANS
can be set 10 i.e. the MAX RETRANS is 4).
For micro-cellular, it’s recommend that the MAX RETRANS
be set 01 i.e. the MAX RETRANS is 2).
For microcellular areas with very high traffic and cells with
apparent congestion, it’s recommend that the MAX RETRANS
be set 00(i.e. the MAX RETRANS is 1).
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ACCESS CONTROL AC
In some special conditions, the telecom operator wants to barall or part of MS from sending out the access request or paging
response request in some special areas. For example, in case
some areas are in emergency state or in case a GSM PLMN
encounters a serious fault. For this reason, GSM Specification
( 02.11 ) stipulates that each GSM subscriber (ordinarysubscriber) is allocated with an access level. The access level
ranges from 0 to 9 and is stored in the SIM card of the
subscriber. The GSM Specifications reserves 5 special access
levels for some special subscribers, which range from 11 to 15.These levels usually have higher access priority. Special
subscribers can have one or more access levels (11~15), and
their access levels are also stored in the SIM cards.
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SETTING OF AC
In the BS installation and commissioning process or in theprocess of maintaining or testing some cells, the operator
can set C0~C9 as 0 to forcedly forbid the access of
ordinary subscribers so as to reduce the unnecessary
effects on the installation or maintenance work.
In some cells with very high traffic, the congestion will occur
in busy hours. For example, the RACH conflict happens
frequently, the AGCH is overloaded and the Abis interfaceflow is overloaded. The network operator can set proper
access control parameters(C0~C15)to control the traffic
of some cells.
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RE-ESTABLISHMENT ENABLE (RE)
1. For the drop calls caused by the radio link fault, the MS can startthe call reestablishment process to resume the conversation, but
the network is entitled to determine whether the call
reestablishment is allowed or not. “0”=Yes, “1”=No.
2. In some special circumstances, the drop call may occur when the
MS goes through a blind area during the conversation. If the callreestablishment is allowed, the mean drop call rate will be
reduced. However, the call reestablishment process will occupy a
longer period of time, most of the subscribers have hung up
before the reestablishment process is over, as a result, the call
reestablishment failed to achieve its purpose and wasted manyradio resources. We recommend that the call reestablishment be
not allowed in the network except for some individual cells.
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LIMITn
1. According to GSM Specification 05.08, the BTS mustmeasure the interference levels of the upward links of all
the free channels for the purpose of providing basis for
managing and allocating radio resources.
2. Moreover, the BTS should analyze its measured results,divide the interference levels into 5 grades and report
them to the BSC. The division of the 5 interference
grades (i.e. the so-called interference bands) is set by the
operator through the man-machine interface. Theparameter "Interference band border(LIMITn)” determines
the borders of the 5 interference bands.
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LIMITn
Value Range Specified dBm Level
0 <-110 dBm
1 -110 dBm ~ -109 dBm
2 -109 dBm ~ -108 dBm
…
61 -50 dBm ~ -49 dBm
62 -49 dBm ~ -48 dBm
Default: LIMIT1:4 LIMIT2:8 LIMIT3:15 LIMIT4:25
The division of the interference bands should be favorable in describing the
interference in the system. Generally the default values are recommended. Inthe ordinary situations, the free channel interference level is smaller, so the
LIMIT1~4 value should be smaller. When apparently large interference
appears in the system, you can properly increase the LIMIT1~4 values in
order to know the exact interference.
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IMSI ATTACH/ DETACH (ATT)
1. An ATT mark should be set as YES so that the network will no longer
process the paging process for the called MS after the MS shutsdown, thus saving the processing time of the network entities and
saving lots of network resources.
2. Please note that the ATT in different cells but in the same location
area should be set the same. Because the shutdown of the MS incells where the ATT is YES will start the IMSI detach process, and
the network will record the fact that the MS is in the non-working
state and reject all the connection requests when using MS as the
called. When the MS restarts and is in the same location area (so the
location update process is not started) as when it shuts down but isin a different cell and the ATT of the cells is set as NO, so the MS will
not start the IMSI attach process, either. In this case, the MS cannot
become the called party until it starts the location updating process.
IMSI ATTACH/ DETACH (ATT)
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IMSI ATTACH/ DETACH (ATT)
The IMSI detach process is that: the MS notifies the network that it is
moving from the working state to the non-working state, or the process ofthe SIM card being taken from the MS.
When receiving the notification from the MS, the network will indicate the
IMSI subscriber to be in the non-working state, so the connection request
ending the subscriber as the called party will be rejected. The
corresponding IMSI attach process is that the MS notifies the network that
it has been in the working state , or the SIM card is re-inserted into the MS.
When the MS re-enters the working state, it will detect whether the
current LAI is the same as the LAI finally recorded in the MS. If they are the
same, the MS will start the IMSI attach process, otherwise the MS will startthe location updating process (instead of the IMSI attach process). When
receiving the location updating or IMSI attach process, the network will
indicate the IMSI subscriber being in the working state.
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CCCH_CONF
The CCCH can be one or more physical channels. The CCCH
and SDCCH can share the same physical channel. Thecombination mode of the common control channel in a cell is
determined by the CCCH_CONF
CCCH_CONF
CodingMeanings
CCCH message
blocks in one
BCCH
0 CCCH use one basic physical channel, not shared with SDCCH 9
1 CCCH use one basic physical channel, shares with SDCCH 3
10 CCCH use two basic physical channels, not shared with SDCCH 18100 CCCH use three basic physical channels, not shared with SDCCH 27
110 CCCH use 4 basic physical channels, not shared with SDCCH 36
Others Reserved
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CCCH_CONF
The CCCH_CONF is determined by the telecom operationdepartment according to the traffic model of a cell. It is often
decided in the system design period. The common configurations
in practice are the following:
If a cell has 1 or 2 TRX, we recommend that the CCCH
uses one basic physical channel and shares it with the
SDCCH
If a cell has 3 or 4 TRX, we recommend that the CCCHuses one basic physical channel but does not share it
with the SDCCH.
AGBLK
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AGBLK
Since the CCCH consists of the access grant channel
(AGCH) and paging channel (PCH), it is necessary to set
how many blocks of the CCCH information blocks are reserved
and dedicated to the AGCH. To let the MS know about the
configuration information, the system message of every cell
contains a configuration parameter, that is, the access grantreserve blocks (AGBLK).
AGBLK is represented in decimal numerals, and its value
range is:
CCCH is not combined with SDCCH: 0~7.
CCCH is combined with SDCCH: 0~2.
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AGBLK
The AGBLK setting principle is: given that the AGCH is not
overloaded, try to reduce the parameter as much as
possible to shorten the time when the MS responds to the
paging and improve the quality of service of the system.
The recommended value of AGBLK is usually 1 (when the
CCCH is combined with the SDCCH), 2 or 3 (when the
CCCH is not combined with the SDCCH).
SETTING AND IMPACT OF AGBLK
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BS-PA-MFRMS (2)BS-PA-MFRMS is represented in decimal numerals and its value
range is 2~9, its unit is multiframe 51 frames), its defaultvalue is 2
BS-PA-MFRMS
Multiframes of the same
paging group that cycle
on the paging channel2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
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PERIODIC UPDATING TIMER (T3212)
The reasons for the location update in the GSM system are
of two types: one is that the MS finds its location areachanged (with a different LAC), the other one is that the
network requires the MS to periodically update its location.
The frequency of periodic location update is controlled via
the network and the period length is determined by theparameter T3212.
In general, in areas with larger traffic and signaling flow, you
should select the larger T3212(e.g. 16 hours, 20 hours or
even 25 hours), but in areas with smaller traffic and lowersignaling flow, you can set the smallerT3212 (3 hours or 6
hours, etc.). In areas where traffic is far beyond the system
capacity, we recommend that you set T3212 as 0.
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NCCPERM
In the connection mode (during the conversation), the MS willreport the measured signals of the adjacent cells to the BS, but
each report may contain at most 6 adjacent cells, Therefore, let
the MS only report the information of the cells that may become
the hand-over target cells, do not let the MS report the information
merely according to the signal level without selection (usually donot let the MS report other GSMPLMN cells).
The above functions can be fulfilled by limiting the MS to merely
measure the cells whose NCC have been specified. The
NCCPERM lists the NCCs of cells to be measured by the MS.
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NCCPERM (2)
In general, each area is allocated with one (or
several) NCC. The NCCPERM of each cell in the area
should contain the NCC of the area, otherwise a large
number of cross-cell drop calls will occur and the cellreselection will fail. To ensure the normal roaming
between different areas, the border cells of an area
should contain the NCC of its adjacent areas
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RADIO LINK TIMEOUT (RLT)
During the MS conversation, when the downward voice (or
data) quality is degraded to be unacceptable and cannot be
improved through the RF power control or handover (i.e. the so-
called radio link fault), the MS will either start the call re-
connection or forcedly disconnect the link.
As the forced disconnection actually means a "drop call"process, the MS will regard it as a downward radio link fault
when the communication quality is unacceptable (usually the
user has to hang up). In this case, it is provided in the GSM
specifications that the MS needs a counter S to assign an initial
value--"downward radio link timeout"--. When S is counted to 0,
the MS will report the downward radio link fault.
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MBCR (1)
In the single band GSM system, when the MS reports the
adjacent cell measurement result to the network, it only needs
to report the contents of the 6 adjacent cells with the strongest
signals in a band. When multiple bands form a network, the
telecom operator often, according to the actual situation of the
network, wants the MS to access to a frequency band withpriority during the handover, so the operator hopes that the
MS will report the measurement result on the basis of not only
signal strength but signal band as well. The parameter
"multiband indication (MBCR)" is used to notify the MS that itshould report the multiband adjacent cell contents.
The value is 0-3
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MBCR (2)
0: Based on the signal strength of adjacent cells, the MS
reports the measurement results of 6 adjacent cells whosesignals are the strongest, whose NCC are known and
allowed no matter in which band the adjacent cells lie. The
default value is “0”
1: The MS should report the measurement result of anadjacent cell in each band (not including the band used by
the current service area) in the adjacent table, whose
signal is the strongest and whose NCC is already known
and allowed. It should also report in the rest position the
adjacent cells in the band used by the current service area.
If there are still rest positions, it will report the information of
the rest adjacent cells no matter in which band these
adjacent cells lie.
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MBCR (3)
2: The MS should report the measurement results of two
adjacent cells in each band (not including the band used bythe current service area) in the adjacent table, whose signals
are the strongest and whose NCC are already known and
allowed. It should also report in the rest position the adjacent
cells in the band used by the current service area. If there
are still rest positions, it will report the information of the rest
adjacent cells no matter in which band these adjacent cells
lie.
3: The MS should report the measurement results of three
adjacent cells in each band (not including the band used by
the current service area) in the adjacent table, whose signals
are the strongest and whose NCC are already known and
allowed.