Gsmoptimization 130402072333-phpapp01

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Copy Rights © LEGEND Co. 2010
Prepared by Legend Technical Team

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RF people work in either
RF Planning RF Optimization
Responsibilities
−Nominal Plan Design.
−Sites Survey.
−Validation from field.
−Set RF design (Structure, Azimuth, Height, Tilt, Cables type).
−Frequency Plan.
−Neighbor Plan.
−Sites Acceptance.
RF Planning KPIs: To provide coverage outdoor & indoor and to offer traffic with acceptable grade of service. Responsibilities
−Maintain the Network„s Accessibility KPIs.
−Maintain the Network‟s Retainability KPIs.
−Maintain the Network‟s Service Integrity KPIs.
−Study and Apply new features.
−Try to think of innovative solutions to maximize the Network capacity.
They have to maintain the performance of the Network as good as possible.
RF People

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Course Outlines:
−Planning Process and Procedures.
−Sites and Hardware Equipment.
−Technical Site Survey & Validation.
−Coverage and Capacity Dimensioning.
−Frequency and Neighbor Planning. Part I: Radio Network Planning

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What will be our concern during this part of the course?
RF Optimization
How the RF Optimization people can maintain the KPIs?
By studying the different radio network features and studying the controlling parameters of each feature and how to tune them in a smart way to achieve the target KPIs.
What are we going to study during this part of the course?
Most of the Radio Network features and their controlling parameters.
KPIs monitoring and analysis.
Trouble shooting and Tuning.
Part II- Radio Network Optimization
Course Outlines:
−Idle Mode Behavior.
−Handover.
−HCS (Hierarchical Cell Structure).
−Concentric & Multi Band Cells.
−CLS ( Cell Load Sharing).
−Frequency Hopping.
−Intra Cell Handover.
−Dynamic HR Allocation.
−Power Control.
−GSM to UMTS Cell Reselection and Handover.
−Trouble Shooting and KPIs monitoring. Part II- Radio Network Optimization

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•GSM stands for “ Global System for Mobile Communication”
•GSM
–Second Generation for Mobile System.
–Digital System.
–Efficient Use of the Spectrum.
–Speech privacy and security.
–Better resistance to interference (Introducing the frequency Hopping)
–Efficient use of the power battery (Introducing the power control)
–GSM Networks are called “PLMN: Public Land Mobile Networks” i.e. the Radio Sites are located on land, not using satellites. GSM Revision
•GSM System can work in different bands as follows:
–DCS: Digital Cellular System PCS: Personal Communication Services.
•But what do we mean by frequency Band?
•What is the DL and UL?
•Why DL is higher than UL band?
Frequency Band-Down Link
Frequency Band-Up Link
GSM 800
869  894 MHz
824  849 MHz
E-GSM (Extended GSM)
925  935 MHz
880  890 MHz
P-GSM 900 (Primary GSM)
935  960 MHz
890  915 MHz
GSM 1800 (DCS)
1805  1880 MHz
1710  1785 MHz
GSM 1900 (PCS)
1930  1990 MHz
1850  1910 MHz
GSM Revision

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•Frequency Band
–The range of frequencies which the operator is allowed to use for transmission and reception.
•Down Link and Up link bands
–DL band is the range of frequencies used by the Base station when transmitting to the MS while the UL band is the range of frequencies used by the Mobile station when transmitting to the Base Station.
GSM Revision
•Why DL band is higher than the UL band?
–As freq then attenuation with air
–Since Power BaseStation > Power MobileStation then it is wise to configure the higher frequencies that will be attenuated fast to the side that is using higher power (BTS).
GSM Revision

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 What do we mean by Multiple Access techniques?
These are the Techniques through which many MSs can access the shared media which is the air interface.
i.FDMA ( Frequency Division Multiple Access)
−Each MS is assigned a dedicated frequency through which he can talk.
ii.TDMA (Time Division Multiple Access)
−All MSs are using the same frequency but each of them will be utilizing it only over a certain period of time called Time Slot (TS)
 In GSM System we’re using TDMA over FDMA where the frequency band is divided into no. of frequencies each of which is shared among no. of MSs, where each MS will be assigned a certain TS on certain frequency.
Access Techniques
•For P-GSM (GSM 900)
–UL Band 890MHz  915MHz, DL Band 935MHz  960MHz
–Each Band is 25 MHz
–Guard Band between DL and UL is 20 MHz
–Duplex Distance = 45 MHz
–Carrier separation = 200 KHz
–No. of frequencies = 124 GSM 900 Frequency Allocation
F (MHz)
915
890
Uplink
1
2 3 4
121
122 123 124
F (MHz)
Downlink
960 935
2 3 4
121
122 123 124
890.2
890.4
890.6
935.2
935.4
935.6
200 KHz
1
1
121 121 Downlink 935 – 960 MHz
Uplink 890 – 915 MHz
GSM Revision

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•For the all GSM Bands
System
P-GSM 900
E-GSM 900
GSM(DCS) 1800
GSM(PCS) 1900
Uplink (MS  BS)
Downlink(BS MS)
890 – 915 MHz
935 – 960 MHz
880 – 915 MHz
925 - 960 MHz
1710 – 1785 MHz
1805 - 1880 MHz
1850 – 1910 MHz
1930 - 1990 MHz
Wavelength
 33 cm
 33 cm
 17 cm
 16 cm
Bandwidth
25 MHz
35 MHz
75 MHz
60 MHz
Duplex distance
45 MHz
45 MHz
95 MHz
80 MHz
Carrier separation
200 kHz
200 kHz
200 kHz
200 kHz
No. of carriers
124
174
374
299
Channel rate
270.8 kbps
270.8 kbps
270.8 kbps
270.8 kbps GSM Revision
GSM Network Architecture

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 MSC (Mobile Switching Center)
–Routing/Switching of calls between 2 end users within the GSM Network.
–Charging & Billing.
–Paging of MSs is originated from the MSC
–Access to PSTN (Public Switched Telephone Network)
–Act as a Gateway for other networks.
–Controls no. of BSCs connected to it.
Core Network (NSS: Network Switching System)
HLR (Home Location Register)
–Centralized Network data base stores and manages all mobile subscriptions.
–Example: IMSI, MSISDN, MSRN, Services subscribed/restricted for that user. IMSI,MSISDN.ppt
VLR (Visitor Location Register)
–It is co-located with the MSC.
–Stored in it a copy of the user’s profile on temporary basis.
AUC (Authentication Center)
–Provides the HLR with the authentication parameters and ciphering Keys used by the MSC/VLR to authenticate certain user. (Triplets: RAND, SRES, Kc) Authentication.ppt
EIR (Equipment Identification Register)
–Used to authenticate the user equipment through the IMEI.
IMEI = International Mobile Equipment Identification Core Network (NSS: Network Switching System)

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BSC (Base Station Controller)
–It controls the air interface, it takes the decisions based on the reports came from the MS and BTS.
–Channel Allocation.
–Controls the Handover Process.
–Dynamic Power Control.
–Frequency Hopping.
BTS (Base Transceiver Station)
–It is the Hardware equipment needed to provide the radio coverage.
–Speech Coding/Channel Coding/Interleaving/Ciphering/Burst formatting/Modulation all these are done within the BTS (RBS=Radio Base Station)
–Equipment: Cabinet, jumpers, feeders, combiners, antennas.
BSS (Base Station System)
Mobile Equipment
–Transmit the radio waves.
–Speech coding and decoding.
–Call control.
–Performance measurement of radio link.
SIM card (Subscriber Identification Module)
–Stores user addresses (IMSI, MSISDN, TMSI).
–Stores authentication key Ki, authentication algorithm A3 and ciphering algorithm A8&A5
–Stores the subscribed services.
MS (Mobile Station)

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•Over the Air Interface
–Frequency Band is divided into no. of frequencies.
–Each frequency is divided into 8 Time slots (TS)
–Each user will be assigned 1 TS.
–One time slot duration = duration of 156.25 bits
–1 Bit duration=3.7 μsec
–Time slot duration =156.25x3.69 μsec= 0.577 msec
–1 Frame = 8 TSs
–Frame duration=0.577x8= 4.616 msec
–Bit rate on the air interface is 270 Kbps, but for each user it is 33.8 Kbps
Physical channel: Time slot is called the physical channel.
Logical channel: It is the content that will be sent over the physical channel. Physical Channels vs. Logical Channels

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Logical Channels
Control Channels
Traffic Channels
Half Rate Full Rate
Synchronization Channel
Broadcast Control Channel
Frequency Correction Channel
Standalone Dedicated Control Channel
Slow Associated Control Channel
Fast Associated Control Channel
Cell Broadcast Control Channel
Broadcast Dedicated
Common
Random Access Channel
Access Grant Channel
Paging Channel Logical Channels
Full Rate Channels (FR)
–Carries user’s speech traffic or user data DL and UL.
–Each user is assigned 1 TS.
–Transmission rate is 13 Kbit/s.
Half Rate Channels (HR)
–Carries user’s speech traffic or user data DL and UL.
– 2 users will share 1 TS (physical channel), each of them will be utilizing it each frame.
–Transmission rate is 6.5 Kbit/s Traffic Channels

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These are used to carry signaling or synchronization data, they’re divided into three types:
–Broadcast Channels (BCH)
–Common Control Channels (CCCH)
–Dedicated Control Channels (DCCH)
Control Channels
i.Frequency Correction Channel (FCCH)
–Pure signal is transmitted to help the MS to lock on the frequency of the BTS and synchronize to its frequency. (DL channel)
ii.Synchronization Channel (SCH)
–Carries the TDMA frame number.
–BSIC (Base Station Identification Code) of the cell. (DL Channel)
iii.BCCH (Broad Cast Control Channel)
–LAI (Location Area Identity)
–Cell parameters (used power, Idle mode parameters,…..etc)
–List of BCCH carries of the neighbor cells i.e. “BA List” (DL Channel) BCH (Broad Cast Control Channels)

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i.Paging Channel (PCH)
–Used to inform the MS of an incoming call or sms, where the MS’s IMSI/TMSI will be sent over it. (DL channel)
ii.Random Access Channel (RACH)
–Used by the MS to ask for an SDCCH to respond to the request send on the paging channel /initiate a call/location update/IMSI attach-detach. (UL Channel)
iii.AGCH (Access Grant Channel)
–Used by the network to assign an SDCCH sub-channel for the MS. (DL channel) CCCH (Common Control Channels)
i.Standalone Dedicated Control Channel (SDCCH)
–Used for signaling purposes: call setup, location update, IMSI attach-detach
–Used to send/receive SMSs in idle mode. (DL/UL channel)
ii.Slow Associated Control Channel (SACCH)
–Always allocated in conjunction with traffic channel/SDCCH channel to transmit measurement reports.
–DL measurement reports will include commands from the network to the MS to adjust its power level.
–Information about the Time Advance.
–UL measurement reports will include information about the MS own power, received SS & Quality from serving cell and SS from neighbor cells.
–Used to send SMSs in active mode. (DL/UL channel) DCCH (Dedicated Control Channels)

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iii.Fast Associated Control Channel (FACCH)
–Used to send necessary Handover information.
–Work in stealing Mode such that 1 TCH channel is replaced by FACCH to send the HO information. (DL/UL channel)
iv.Cell Broad Cast Channel (CBCH)
–It is sent point to multi point i.e. from the cell to the mobiles attached to it, this channel may carry information about the traffic, weather reports,…etc. (DL channel) DCCH (Dedicated Control Channels)
Mapping on TS0/BCCH carrier (DL)
51 consecutive control frames = 1 Control multi frame
Where F:FCCH, S:SCH, B:BCCH, C:PCH/AGCH Mapping of Logical Channels on the Physical channels

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Mapping on TS0/BCCH carrier (UL)
TS0 in UL is reserved for the RACH, for the MS to access the system. Mapping of Logical Channels on the Physical channels
Mapping on TS1/BCCH carrier (DL)
Where D:SDCCH, A:SACCH
Mapping of Logical Channels on the Physical channels

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Mapping on TS1/BCCH carrier (UL) Mapping of Logical Channels on the Physical channels
Mapping on TS2/BCCH carrier (DL/UL) if it will be used by certain MS in active mode
26 consecutive Traffic frames = 1 Traffic multi frame
Mapping of Logical Channels on the Physical channels

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Traffic Multi Frames
–Traffic Multi Frame = 26 consecutive traffic frames (4.61msec x 26 =120msec)
Control Multi Frames
–Control Multi Frame = 51 consecutive Control frames (4.61msec x 51 =235msec)
•Super Frame
51 consecutive Traffic Multi Frames or 26 consecutive Control Multi Frames
–Super Frame = 6.12 seconds
•Hyper Frame
2048 consecutive super Frames
–Hyper Frame = 3 hours and 29 minutes nearly. TDMA Multi Frames Structure

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IMSI : International Mobile Subscriber Identity
IMSI = MCC + MNC + MSIN
MCC= Mobile Country Code (3 digits)
MNC= Mobile Network Code (2 digit )
MSIN= Mobile Subscriber Identification Number (10 digits)
Ex: IMSI = MCC-MNC-MSIN = 602-03-1234567890 where,
602  Egypt Country Code
03 Etisalat Network Code
1234567890  Mobile Subscriber Identification Number
MCC (3 digits) MNC (2 digits)
MSIN
(10 digits)

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MSISDN : Mobile Station Integrated Services Digital Network
MSISDN = CC + NDC + SN
CC= Country Code (2-3 digits)
NDC= Network Destination Code (2-3 digit )
SN= Subscriber Number ( max 10 digits)
Ex: MSISDN = CC-NDC-SN =+20-10-1234567 where,
10 Vodafone Network Code
1234567  Subscriber Number
CC (2-3 digits) NDC (2-3 digits) SN (max. 10 digits)
LAI : Location Area Identity
LAI = MCC + MNC + LAC
MCC= Mobile Country Code (2-3 digits)
MNC= Mobile Network Code (2-3 digit )
LAC= Location Area Code ( max 5 digits)
Ex: LAI= MCC-MNC-LAC = 602-01-12345 where,
01 Mobinil Network Code
12345  Location Area Code
MCC (2-3 digits) MNC (2-3 digits)
LAC
(max.5 digits)

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CGI : Cell Global Identity
CGI = LAI + CI = MCC + MNC + LAC + CI
MCC = Mobile Country Code (2-3 digits)
MNC = Mobile Network Code (2-3 digit )
LAC = Location Area Code ( max 5 digits)
CI = Cell Identity ( max 5 digits)
Ex: CGI = MCC-MNC-LAC-CI = 602-01-12345-11223 where,
01 Mobinil Network Code
12345  Location Area Code
11223  Cell Identity
MCC (2-3 digits)
MNC
(2-3 digits) LAC (max. 5 digits)
CI
(max. 5 digits)
IMEI : International Mobile Equipment Identification
IMEI = TAC + FAC + SNR + spare (15 digits)
TAC = Type Approval Code, determined by a central GSM body(6 digits)
FAC = Final Assembly Code, identified the manufacturer (2 digit )
SNR = Serial Number( 6 digits)
spare = A spare bit for future use, when transmitted by MS it is always zero.
( 1 digit)

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AUC : Authentication Center
-In the AUC the below table is stored, such that for each user there is a unique authentication key (Ki)
-On authenticating certain user, the AUC will generate the triplets: RAND,SRES,Kc
-AUC generates a random no. “RAND” and send it to the MS
-Both the AUC and the MS will use RAND + Ki and Algorithm A3 to produce the SRES(Signed Response)
-VLR will take the results from AUC and MS and if:
(SRES1)_AUC = (SRES2)_MS  then the MS is Authenticated 
User#
IMSI
Authentication Key
User1
MCC+MNC+MSIN1
Ki1
User2
MCC+MNC+MSIN2
Ki2
User3
MCC+MNC+MSIN3
Ki3
User4
MCC+MNC+MSIN4
Ki4 RAND1
Ki1
(SRES1)_AUC
A3
RAND1
Ki1
(SRES1)_MS
A3 AUC side
MS Side

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AUC : Authentication Center
-The AUC is responsible also for generating the ciphering Key (Kc) for each user.
-Kc_AUC should be equal Kc_MS, so the data encrypted by the network can be
de-ciphered by the MS.
Ciphering Process:
RAND1
Ki1 Kc_AUC
A8
RAND1
Ki1
Kc_MS
A8
AUC side
MS Side +
A5
TDMA Frame no.
Kc_AUC
Speech
+
A5
TDMA Frame no.
Kc_MS
Speech
Ciphered Speech
Network side
MS side

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•MS in Idle Mode
–Doesn’t have a dedicated channel, but able to access the Network and able to be reached by the Network.
–MS will always try to camp on the best cell based on the signal strength criterion.
–MS will continuously monitor the serving and neighbor BCCH carriers to decide which cell to camp on.
–The purpose behind studying the Idle Mode Behavior is to always ensure that the MS is camped on the cell where it has the highest probability of successful communication.

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•MS Tasks during Idle Mode
–PLMN Selection.
–Cell Selection.
–Cell Reselection.
–Location Updating.
–Monitor the Incoming Paging.
– PLMN Selection
–Cell Selection.

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•PLMN Selection Criterion
–PLMN identity is defined as “MCC+MNC” which is part of the LAI, where LAI=MCC+MNC+LAC.
MCC: Mobile Country Code - MNC: Mobile Network Code - LAC: Location Area Code
–When the MS is powered “ON”, it will check if it needs to perform a Location Update by comparing the new LAI with the old stored one.
–An MS will need to make a PLMN selection only incase:
1. MS is powered “ON” for the 1st time i.e. No PLMN was registered on before
(No Information on MCC&MNC is stored on SIM)
2.Old PLMN is not available any more (Out of coverage/Roaming)
–When the MS has to do a PLMN selection due to one of the previous cases, the selection mode will depend on the MS settings either Automatic or Manual.
–Automatic PLMN Selection Mode steps:
1.Home PLMN.
2.Each PLMN stored on the SIM card in priority order.
3.Other PLMNs have Signal Strength > -85 dBm.
4.All other PLMNs in order of decreasing Signal Strength.
–Manual PLMN Selection Mode:
1.Home PLMN.
2.All other available PLMNs and give the user the choice to select.

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 National Roaming
–If National Roaming is permitted then a MS can register on a PLMN in its home country other than its home PLMN.
–National Roaming may be allowed on a certain location areas (LAs) of the visitor PLMN.
–MS should periodically try to access back his home PLMN, but this periodic attempts will occur only on automatic selection mode.
–PLMN Selection.
–Cell Selection

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•Cell Selection Criterion
–The Cell Selection algorithm tries to find the most suitable cell in the selected PLMN and make the MS camp on.
–Cell Selection is done by the MS itself.
–During Idle Mode the Network doesn’t know the cell which the MS is camping on, it only knows the Location Area where the mobile registed himself in.
•Cell Selection Criterion MS will synchronize to the BCCH frequency and read system information (LAI,BA List,…etc) Scan RF Frequencies one by one and calculates the Average received signal strength over 3  5 seconds Tune to the RF Frequency with the highest average received signal strength
Camp on the Cell
Check if the chosen frequency is a BCCH carrier frequency or not Check if C1 > 0 or not
Check if Cell is barred or not Check if PLMN is desired or not Tune to the next higher frequency that wasn‟t tried before Yes Yes
No
Yes
No
Yes
No No

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–Scanning RF Frequencies may occur in 2 ways:
1.Normal Scanning: Scan all Frequencies in the band ex:124 freq. in GSM900 Band.
2.Stored List Scanning: Scan the Frequencies in the Idle BA list (BCCH Allocation) stored on the MS SIM before being switched off.
(BA list can have maximum 32 frequencies)
If MS found cell belongs to the desired PLMN but not suitable, the MS will start to scan the Idle BA list of this cell.
–Cell is said to be suitable if:
1.Cell belongs to the desired PLMN
If at least 30 strongest frequencies from GSM900 band were tried and no suitable
cell was found, then the MS will try another PLMN based on PLMN criterion.
2.Cell is not Barred ( CB = NO)
Some cells can be barred for access at selection and reselection or given lower
priority based on settings of parameters: CB
3.C1 > 0

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–C1 is called “Cell Selection Quantity”
–It is calculated at the MS based on the below equation:
C1 = (Received SS – ACCMIN) – max (CCHPWR-P,0)
ACCMIN  Minimum allowed DL received SS at the MS in order to access the system
CCHPWR  Maximum allowed transmitting power by the MS in the UL.
P  Maximum out put power of the MS according to its class.
N.B:
1. ACCMIN and CCHPWR are cell parameters sent to the MS at the BCCH channel.
2. If CCHPWR > P then C1 will decrease and so the Received SS should be large enough to keep C1 > 0 (May be this cell is not designed for this MS class)
3. ACCMIN, CCHPWR, P are all measured in dBm, where C1&C2 are measured in dBs
–PLMN Selection.
–Cell Selection.
– Cell Reselection

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•Cell Reselection Criterion
–After a cell has been selected, the MS will start the cell reselection measurements to know if it is better to stay on the current cell or to camp on another cell.
–Cell reselection measurements:
1.Monitors the SS (Signal Strength) of the BCCH carrier of the serving cell.
2.Monitors the SS of the BCCH carrier of all defined neighbors in the Idle BA list.
3.Continuously read system information sent on the serving BCCH carrier at least every 30 seconds.
4.Continuously read system information sent on the BCCH carrier for the six strongest neighbors at least every 5 minutes.
5.Try to decode BSIC of the six strongest neighbors every 30 seconds to assure that it is still monitoring the same cells.
–Cell reselection measurements summary
BSIC
BCCH Data (System Information)
Serving Cell
-
Every 30 Seconds
Six Strongest Neighbors
Every 30 Seconds
Every 5 Minutes

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–When Cell Reselection will occur ?
1.Serving Cell became barred ( CB = YES )
2.C1 serving cell falls below zero for more than 5 seconds.
3.MS tried to access the network through this cell unsuccessfully for the allowed no. of times defined by the parameter MAXRET
4.C2 neighbor cell ( one of the six strongest neighbors) became greater than C2 serving cell for more than 5 seconds.
5.MS detects Downlink Signaling Failure.
–What will happen when the MS needs to make cell reselection?
 The MS will camp on the cell that has the highest C2 value.
–C2 is called “Cell Reselection Quantity”
C2 = C1 + CRO – TO * H( PT – T ) where PT ≠ 31
C2 = C1 – CRO where PT = 31
0 , X < 0
Where H(x)
1 , X ≥ 0
CRO  Cell Reselection Offset, unit = 2 dB, value range = 0 to 63
TO Temporary Offset, unit = 10 dB, value range = 0 to 7
PT  Penalty Time during which TO is valid
T  Initiated from zero when the MS places the neighbor in the list of the Six Strongest

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–CRO : defines a signal strength offset to encourage or discourage MSs to reselect that cell.
–TO : defines a negative temporary offset for certain time according to settings of PT (Practically this is useful to prevent fast moving MS from camping on microcells)
– PT: If PT is set to 31, this means that a (–ve) SS offset “CRO” will be applied to this cell and it appears less favorite for cell reselection.
 Down Link Signaling Failure Algorithm
–The Algorithm of type “Leaky Bucket” and used a counter “D”, where D = 90/MFRMS
–MFRMS is a cell parameter defines the no. of multiframes between the transmission of each paging group i.e. if MFRMS=4 then a MS attached to a certain paging group will wait in sleeping mode for 4 multiframes (4*235msec) until it is up again to listen to paging.
–When the MS is up to listen to its paging group, if the message is not decoded successfully then D is decremented by 4 and if the message is decoded correctly then D is incremented by 1.
–If D reaches zero, then a Down Link Signaling Failure is detected and cell reselection took place.

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 Down Link Signaling Failure Algorithm
–Ex: Assume that MFRMS = 4
Downlink signaling failure counter is initialized: D = round(90/MFRMS)=22.
If the MS unsuccessfully decodes a paging message, then: D = D - 4 = 18.
If the MS successfully decodes a paging message, then: D = D + 1 = 19.
If D reaches zero, then a Down Link Signaling Failure is detected and
cell reselection took place.
N.B: D can’t exceed the bucket size given by round(90/MFRMS)
 CRH ( Cell Reselection Hysteresis )
–Cell Reselection between two cells lie in two different Location Areas, will be accompanied by Location Update.
–At the border between cells the Signal level may be comparable, cell reselection may occur many times accompanied by many location updating leading to huge signaling load.
–To avoid this, a parameter CRH is introduced such that a cell in another location area LA2 should have C2LA2 should greater than C2LA1 of serving cell lie in LA1 by at least CRH in order to be selected.
–If C2LA1 = 5 dB, CRH = 4 dB, then C2LA2 ≥ 9 dB in order to be selected.

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–PLMN Selection.
–Cell Selection.
– Location Updating
•Location Updating
–To make it possible for the mobile subscriber to receive a call and initiate a call whenever needed, the network must know where the MS is located whenever it moves that’s why Location Updating is needed.
–In the Idle Mode, the Network knows the location of the MS on a Location area resolution not on a cell resolution.
–There are three different types of location updating defined:
1.Normal Location Updating.
2.Periodic registration.
3.IMSI attach & IMSI detach (when the MS informs the network when it enters an inactive state)

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1.Normal Location Updating
–Initiated by the MS when it enters a cell belongs to a new Location Area (LA).
–The MS will compare the LAIold stored on the SIM with the LAInew broadcasted from the new cell and it will found them different so it’ll perform Location Update type normal.
2.Periodic Registration
–Regularly the MS should update the Network with its current location Area.
–The Network will inform the MS how often it should report the location Area he is registering himself in.
–Based on the value of the Parameter T3212 the MS will know how frequent it should make periodic registration.
–T3212 take values from 1 (6min) to 255 (25.5 Hours), default = 40 (4 Hours)
–MSC has a supervision time = BTDM+GTDM if it doesn’t hear from the MS during this period, the MSC will consider the MS implicitly detached.
–BTDM+GTDM should > T3212 , to not consider the MS detach before periodic location update is performed.

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3.IMSI Attach/Detach
–IMSI attach/detach operation is an action taken by the MS to inform the Network either it will go to inactive state (Power off) or it returned back to idle mode.
–ATT is a cell parameter that will inform the MS whether IMSI attach/detach is operational or not.
–If ATT=Yes, then before the MS will be switched off, it will send an IMSI detach request to the Network, so no paging messages will be sent to this MS while it is in this state.
–When the MS is switched on again it will send an IMSI attach request to the Network so now paging messages can be sent normally to this MS.
–PLMN Selection.
–Cell Selection.
–Monitor the Incoming Paging

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•Monitor the Incoming Paging
Let us revise the DL logical channels and their mapping:
I) BCH(Broadcast Channels): including
FCCH(Frequency Correction Channel)
SCH(Synchronization Channel) Always Mapped on TS0/C0
BCCH(Broadcast Control Channel)
II) CCCH(Common Control Channels): including
PCH(Paging Channel) Always Mapped on TS0/C0
AGCH(Access Grant Channel)
III) DCCH(Dedicated Control Channels): including
SDCCH(Stand Alone Dedicated Control Channel) May be Mapped on either
SACCH(Slow Associated Control Channel) TS1/C0 or TS0/C0
CBCH(Cell Broadcast Channel)
FACH(Fast Associated Control Channel) “ Work in Stealing mode by replacing the TCH time slot”
C
B
B B B S
F
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
F
S
F
S
F
S
F
S
F
S
I
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
49
51
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Frame 1
Frame 2
Frame 3
Frame 4
Frame 5 Frame 6 Frame 7
Default Mapping on TS0/C0 (BCH+CCCH) “Non Combined Mode”
51 TDMA Frames = 1 Control Multi-frame
B
C
C
C
C C C
C
C
C

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Default Mapping on TS1/C0 (SDCCH+SACCH+CBCH(optional))
Combination of Control channels (Different Mapping Criteria)
−Mapping on TS0/C0 is controlled by Parameter called BCCHTYPE
−BCCHTYPE = NCOMB (Non Combined, BCH&CCCH)TS1/C0 will carry SDCCH+SACCH
= COMB (Combined, BCH&CCCH&SDCCH/4) TS1/C0 will be free for TCH
= COMBC (Combined with cell broadcast channel CBCH is in use,
BCH&CCCH&SDCCH/4&CBCH)  TS1/C0 will be free for TCH

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−SDCCH may have on of the following 4 configurations based on parameter SDCCH
−SDCCH = (i) SDCCH/8 (8 SDCCH Sub-channels i.e. make call setup for 8 users)
= (ii) SDCCH/8 including CBCH (7 SDCCH Sub-channels + 1 CBCH)
 For these two cases, the BCCHTYPE=NCOMB and the mapping of the SDCCH channel is done on TS1/C0
= (iii) SDCCH/4 (4 SDCCH Sub-channels)
= (iv) SDCCH/4 including CBCH(3 SDCCH Sub-channels + 1 CBCH)
 For these two cases, the BCCHTYPE=COMB or COMBC and the mapping of the SDCCH channel is done on TS0/C0
Non Default Mapping on TS0/C0 (BCH+CCCH)
2*51 TDMA Frames = 2 Control Multi-frame

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The Table below summarizes all the previous details
Default Mapping (Non Combined)
Non Default Mapping (Combined)
BCH+CCCH on TS0/C0 and
SDCCH+SACCH+CBCH on TS1/C0
BCH+CCCH+SDCCH+SACCH+CBCH on TS0/C0
CBCH doesn't exist
CBCH exist
CBCH doesn't exist
CBCH exist
1 block for BCCH
1 block for BCCH
1 block for BCCH
1 block for BCCH
9 blocks for CCCH
9 blocks for CCCH
3 blocks for CCCH
3 blocks for CCCH
8 blocks for SDDCH
7 blocks for SDDCH
4 blocks for SDDCH
3 blocks for SDDCH
1 block for CBCH
1 block for CBCH
Paging Groups
−The MS will monitor the incoming paging in only specific times, and the rest of the time it will remain in sleeping mode.
−In this way we save the MS battery and we decrease the UL interference on the system.
−The MS will monitor the incoming paging when the “Paging Group” assigned for this MS is transmitted only.
−The CCCH block can be used by either PCH or AGCH.
−When the CCCH block is used for paging it will be called “Paging Block”
−The Paging Block consists of 4 consecutive Time slots lie in 4 consecutive frames.
−The Paging Block can be used to page 4/3/2 users according to IMSI or TMSI is used when paging the MS ( Length IMSI = 2 TS, Length TMSI = 1 TS)
−The group of users belong to the same paging block will be called “Paging Group”

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C
B
B
B
B
S
F
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
F
S
F
S
F
S
F
S
F
S
I
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
49
51
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Frame 1
Frame 2
Frame 3
Frame 4
Frame 5
Frame 6
Frame 7
Default Mapping on TS0/C0 (BCH+CCCH) “Non Combined Mode”
51 TDMA Frames = 1 Control Multi-frame
B
C
C
C
C
C
C
C
C
C
Paging Groups
−As appeared the MS will listen to paging in only specific times.
−The MS will utilize the time between the 4 TS that lie in 4 consecutive frames to make the required measurements on the neighbor cells.

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Paging Groups
−How many Paging Groups we have? This will depend on a parameter MFRMS
−MFRMS is a parameter defined per cell and it defines how frequent the paging group assigned for certain MS will be transmitted.
−MFRMS takes values from 1 to 9,
 if MFRMS=1 then the paging group assigned for certain MS will be transmitted every 1 control Multiframes=235 msec
 if MFRMS=9 then the paging group assigned for certain MS will be transmitted every 9 control Multiframes = 9*235msec=2.3 seconds.
−If MFRMS is large:
Positive Side: The MS battery life time will increase coz the MS remains in sleeping mode for longer time + paging capacity will increase.
Negative Side: Call setup time will increase coz the paging won’t be sent to the MS except when the time of its paging group came.
Paging Strategies
−Paging Strategies are controlled by parameters in the MSC.
−Setting of parameters will decide whether the paging will be local paging (within the LA) or global paging (within the MSC service area).
−Setting of parameters will decide also whether paging will be done via IMSI or TMSI.
−Using the parameters we can decide also how the second paging will be incase the first paging failed, ex: If 1st paging was local with TMSI then we can set the 2nd paging to be global with IMSI.

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•Related Feature to the Idle Mode Behavior
Adaptive Configuration of Logical Channels (ACLC)
−As we know the SDCCH channel is used for signaling i.e. call setup, while the TCH channel is used to carry real user traffic (speech/data).
−As per the GSM standards, the GOS for TCH=2% i.e. within 100 calls if 2 of them are blocked then this will be acceptable, for the SDCCH/8 the GOS=0.5% and for the SDCCH/4 the GOS=1%
−As we know in the default settings for frequency C0, TS0 is used to carry BCH+CCCH and TS1 used to carry SDCCH+SACCH, and TS2TS7 used to carry speech/data
−Now if the signaling load is high, ex: many users need to make call setup, then high blocking will occur exceeding the acceptable value = 0.5%
−To solve the blocking we have 2 ways:
i) Static configuration of a TCH TS to be used as SDCCH forever
( Now TS1&TS2 used for SDDCH+SACCH and TS3TS7 used to carry speech/data)
 But in this case we lost 1 TCH channel i.e. 5 users can talk simultaneously instead of 6
ii) Adaptive configuration of a TCH TS to be used as SDCCH/8 when there is high SDCCH utilization only
( Now TS1&TS2 used for SDDCH+SACCH and TS3TS7 used to carry speech/data, but when the utilization is back to its normal trend, TS2 will be configured back automatically as a TCH and used to carry speech/data)

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Main Controlling Parameters:
ACSTATE: Activates/Deactivates the feature on cell basis, values: ON/OFF
SLEVEL: No. of Idle SDCCH sub-channels below which the feature will work.
The conditions that should be fulfilled for the ACLC feature to work:
1) ACSTATE=ON
2)No. of Idle SDCCH sub-channels ≤ SLEVEL (Indication for high utilization)
3)No. of already defined SDCCH channels/8 < Max. allowed configuration of SDCCHs in the cell.
4)No. of Idle TCHs > 4
•Parameters Summary
SCH Parameters
Parameter Name
Value Range
Recommended Value
Unit
BSIC
NCC: 0 to 7 BCC: 0 to 7
─
─
RACH Control Parameters
Parameter Name
Value Range
Recommended Value
Unit
MAXRET
1,2,4,7
4
─
Control Channel Parameters
Parameter Name
Value Range
Recommended Value
Unit
BCCHTYPE
COMB COMBC NCOMB
NCOMB
─
SDCCH
0 to 16 (0: No SDCCH/8 configured-combined mode)
1
─
IMSI Attach/Detach Parameters
Parameter Name
Value Range
Recommended Value
Unit
ATT
Yes, No
Yes
─

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Paging Parameters and Periodic Update
Parameter Name
Value Range
Recommended Value
Unit
MFRMS
2 to 9
6
Control Channel Multi frame
AGBLK
0 or 1
0
─
T3212
0 to 255 (0: infinite-No periodic registeration)
40
6 minutes
Cell Selection and Reselection Parameters
Parameter Name
Value Range
Recommended Value
Unit
ACCMIN
− 47 dBm to −110 dBm
−110 dBm
dBm
CCHPWR
GSM900: 13 to 43 in steps of 2 GSM1800: 4 to 30 in steps of 2
GSM900: 33 dBm GSM1800: 30 dBm
dBm
CRO
0 to 63
0
2 dB
TO
0 to 7 (7:infinite)
0
10 dB
PT
0 to 31
0
CRH
0 to 14 in steps of 2
dB

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•Handover (Locating) Algorithm
–The Handover (Locating) Algorithm is the basic feature to provide mobility in the Radio Network.
–Aims At? i) Keep the continuity of a current call with acceptable quality.
ii) Cell size control in-order to decrease total interference in the system.
–Implemented where? In the BSC.
–Location process initiated when? After Hand Over (HO), Assignment or Immediate Assignment.
–Inputs to the Algorithm? Signal Strength, Quality measurements &TA for serving cell and Signal Strength measurements for neighbor cells.
–Output from the Algorithm? List of candidates which the algorithm judges to be possible candidates for HO (List of HO candidates are ranked and sorted in descending order)

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–What types of Handover (locating) algorithm we have?
i) SS & Path Loss based Algorithm: Follows the GSM specifications. HO decision is taken based on both Signal Strength (SS) and Path Loss.
ii) SS based Algorithm: HO decision is taken based on Signal Strength only and this leads to better performance.
It is less complex, uses less parameters and easy to be maintained in the Radio Network.
–The main Flow of the Handover (locating) Algorithm goes as follow:
Filtering
Basic Ranking
Urgency Conditions Handling
Initiations
Auxiliary Radio Network Features Evaluation
Organizing the List
Sending the List & Allocation Reply

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–Initiation
–Filtering.
–Basic Ranking.
–Urgency Conditions Handling.
–Auxiliary Radio Network Features Evaluation.
–Organizing the List.
–Sending the List & Allocation Reply
•Initiation of the Handover (Locating) Process/Algorithm
The Locating Process is initiated when one of the following occurs:
1.Handover: Normal, Intra Cell HO (IHO), Sub-cell change (OLUL or ULOL)
2.Assignment: Allocation of TCH channel after completing call setup on SDCCH.
3.Immediate assignment: You are assigned SDCCH to make call setup, or a TCH to make call setup on when no free SDCCH channels exist.

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–Initiation
–Filtering
–Basic Ranking.
•Filtering
−Simply it is the process of collecting the required data on Signal Strength (SS), Quality and Time Advance (TA) for serving and neighbor cells and average these consecutive measurements over a specified period to rank these cells.
−This is accomplished in two steps:
1.Measurements preparation
2.SS, Quality and TA filtering

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•Filtering
1.Measurements preparation
−Data that is measured:
−The MS can measure the SS of up to 32 neighbor frequencies but only the six strongest neighbors (which it succeeded to decode its BSIC over the last 10 seconds) are reported and considered candidates for HO.
Cell on which measurements are reported
Measured Quantity
Who makes the measurements?
Serving Cell
SS DL
MS
Quality DL (rxqual_DL)
MS
Quality UL (rxqual_UL)
BTS
TA
BTS
6 Strongest neighbor cells
SS DL
MS
•Filtering
1.Measurements Preparation
−SS measurements are delivered as integer values 0  63 corresponds to real SS from
-110 dBm  - 47 dBm
−Quality is measured based on the BER and it may be represented in two forms:
i)Integers 0 (Best)  7 (Worst)
ii)Decitransformed Quality units (dtqu) from 0 (Best)  70 (Worst)
−Time Advance (TA) is reported as values between 0  63 bit period.
N.B: If TA=1 then the MS is at nearly 0.5 km from the cell

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•Filtering
2.SS, Quality and TA filtering:
−The consecutive measurements for SS, Quality and TA are averaged in some way based on the equation of the filter used.
−We’ve 5 Types of Filters that may be used, each one has its own equation or its way to produce output results from the collected consecutive measurements:
A.General FIR filters (Finite Impulse response)
B.Recursive Straight Average filter
C.Recursive exponential filter
D.Recursive 1st order Butterworth filter
E.Median filter
•Filtering
2.SS, Quality and TA filtering:
−In addition to the way each filter use to produce output results from the consecutive measurements, each filter has what we call filter length which is the period over which measurements are considered.
−We have controlling parameters on cell basis to select the type of filter used and the length of the filter.
−Also the type of the filter used in signaling (call setup) and dedicated phases may be configured separately as we’ll see.

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–Initiation
–Filtering
–Basic Ranking
•Basic Ranking
−It is called “Basic” coz in this stage ranking is done before handling the urgency conditions and evaluation of the auxiliary radio network features.
−As mentioned earlier, two algorithms are available for basic ranking (SS&Path loss based Algorithm and SS based Algorithm) and they’re selected according to the parameter EVALTYPE
−EVALTYPE=1, SS & Path loss based Algorithm is used for basic ranking taking into consideration both Signal Strength measurements and the path loss.
−EVALTYPE=3, SS based Algorithm is used for basic ranking taking into consideration Signal Strength measurements only.

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•Basic Ranking
Basic Ranking Algorithm following the SS based Algorithm will be done on four steps:
A.Correction of Base Station output power. Common for
B.Evaluation of the minimum signal strength condition for neighbors. Both
C.Subtraction of signal strength penalties. Algorithms
D.Rank the Candidates after applying Offsets and Hysteresis.
•Basic Ranking
Basic Ranking Algorithm following the SS based Algorithm
A.Correction of Base Station output power
The location algorithm aims at making the Pure traffic frequencies to control the cell
borders and not the BCCH frequencies, coz most of the time the seized TCH Time slot will be located on a TCH frequency.
 BSPWR is a parameter to set the output power of the BCCH carrier and
BSTXPWR is a parameter to set the output power of the TCH frequencies.
Correction for the output power will done for both:
(A-i) Correction for Neighbor Cells.
(A-ii) Correction for Serving Cell.

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•Basic Ranking
(A-i) Correction for Neighbor Cells
−The MS is informed by the BCCH frequencies of the neighbors cells on which he has to perform his measurements via the Active BA list.
−SS_corrected_DLneighbor = SS_measured_DLneighbor - ( BSPWR - BSTXPWR )
•Basic Ranking
(A-ii) Correction for Serving Cell
1)TCH Time Slot (TS) is on the BCCH frequency
SS_corrected_DLservingcell = SS_measured_DLservingcell - ( BSPWR - BSTXPWR )
2)TCH TS is hopping between a BCCH frequency and a TCH frequency:
SS_corrected_DLservingcell = SS_measured_DLservingcell - ( BSPWR - BSTXPWR )/N ,
Where N is the no. of the hopping frequencies
3)TCH TS is on the OL (Over Laid sub cell)
SS_corrected_DLUnderLaid = SS_measured_DLOverLaid+ ( BSTXPWR Under Laid – BSTXPWROverLaid )

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•Basic Ranking
B.Evaluation of the minimum Signal Strength condition for Neighbors
−Not all the neighbors are allowed to be ranked!!
−The neighbor should pass the minimum signal strength condition in order to be ranked.
−SS_corrected_DLneighbor will be compared with respect to parameter called MSRXMIN,
If SS_corrected_DLneighbor ≥ MSRXMIN  this neighbor will be included in ranking
If SS_corrected_DLneighbor < MSRXMIN  this neighbor will be excluded from ranking
−If UL measurements are included then SS_corrected_ULneighbor will be compared with respect to parameter called BSRXMIN,
If SS_corrected_ULneighbor ≥ BSRXMIN  this neighbor will be included in ranking
If SS_corrected_ULneighbor < BSRXMIN  this neighbor will be excluded from ranking
•Basic Ranking
B.Evaluation of the minimum Signal Strength condition for Neighbors
−Example: Assume that a MS is connected to cell A that has five neighbors B,C,D,E&F, the MSRXMIN for all the cells is -104 dBm and the SS_corrected_DLneighbor for each cell after correcting the BTS o/p power is given in the below Table
Neighbors
SS_corrected_DLneighbor
B
-85 dBm
C
-110 dBm
D
-87 dBm
E
-70 dBm
F
-100 dBm
 Cell C will be excluded from ranking and won‟t be considered in the next stage and the MS will never HO to it

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•Basic Ranking
C.Subtraction of signal strength penalties
−Penalties or Punishments will be applied on cells that are for some reasons temporarily undesirable.
−A Penalty value will decrease the rank of some cells for certain penalty time.
−SS_punished_DL = SS_corrected_DL – Locating Penalties – HCS Penalties
−In the coming slides we’ll talk about the two types of penalties:
(C-i) Locating Penalties
(C-ii) HCS Penalties
•Basic Ranking
1) Due to HO failure: If HO to a neighbor cell failed then we’ve to apply a penalty value for some time on this neighbor so when basic ranking is done again we don’t go back to this cell.
Penalty value will be configured using parameter PSSHF (default 63 dB)
Penalty time will be configured using parameter PTIMHF (default 5 sec)

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•Basic Ranking
2) Due to Bad Quality (BQ) Urgency HO:
If a cell was abandon due to BQ, then it should have been the best cell from SS point of view so without penalties using the basic ranking we’ll be back to this cell.
Penalty value will be configured using parameter PSSBQ (default 7 dB) Penalty time will be configured using parameter PTIMBQ (default 5 seconds)
3) Due to Excessive TA Urgency HO:
Handled in the same manner like the BQ case.
Penalty value will be configured using parameter PSSTA (default 63 dB) Penalty time will be configured using parameter PTIMTA (default 30 seconds)
•Basic Ranking
(C-ii) HCS Penalties
−It is related to the HCS (Hierarchical Cell Structure) feature when a MS is detected as a fast moving mobile (If fast moving mobile feature is activated)
−A penalty will be applied on lower layer cells so in ranking we will prioritize cells in the same layer of the serving cell and cells in higher layers and in this way unnecessary HO’s are prevented ( ex: layer2 cells will be prioritized than layer1 cells)

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•Basic Ranking
D.Rank the Candidates after applying Offsets and Hysteresis
−Ranking for neighbor cells will be done after
applying Offsets and Hysteresis.
–Offset: Displace the cell border as compared to
The border strictly given by SS.
Controlling parameter: OFFSET (default: zero dB)
–Hysteresis: To reduce the risk of ping pong HO
a region for Hysteresis is applied
around the cell border.
•Basic Ranking
−If the Hysteresis value is too high there will be a risk that the MS will be connected to the cell of low SS for long time and if the Hysteresis is too low then there will be a risk that ping pong HO’s occur.
−So the applied value of Hysteresis will be variable based on the received SS of the serving cell.
−SS_corrected_DLservingcell will be compared to value HYSTSEP (default -90 dBm),
If SS_corrected_DLservingcell > HYSTSEP, then the serving cell is strong enough and high value of Hysteresis will be applied such that Hysteresis value=HIHYST (default 5 dB)
If SS_corrected_DLservingcell < HYSTSEP, then the serving cell is not strong enough and low value of Hysteresis will be applied such that Hysteresis value=LOHYST (default 3 dB)

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•Basic Ranking
SS_corrected_DLservingcell > HYSTSEP
Yes
HYST=HIHYST
Now,
Rankservingcell = SS_corrected_DLservingcell
Rankneighbor= SS_punished_DLneighbor – OFFSETneighbor – HYSTneighbor
HYST=LOHYST
Output from Basic Ranking
No
–Initiation
–Filtering
–Basic Ranking
–Urgency Conditions Handling

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•Urgency Conditions Handling
−After the Basic Ranking stage a check is made on the serving cell to know if Urgency conditions are detected or not.
−We have two types of Urgency HO:
1.Bad Quality (BQ) Urgency HO
2.Excessive Time Advance (TA) Urgency HO
−If Urgency conditions are detected then the serving cell should be abandon as fast as possible, but some of the neighbors will be removed from the candidate list and the MS will not be able to HO to them as we will see later.
−As seen before, cells that were abandon due to Urgency HO will be subjected to punishment/penalty.
−The Quality measured at the DL and UL for the serving cell will be compared with two parameters QLIMDL & QLIMUL (default 50 dtqu) and if:
rxqual_DL > QLIMDL
rxqual_UL > QLIMUL
−The Quality may drop like that as a result of Co-Channel Interference or when the SS became very low.
−When Urgency condition is detected the MS has to leave the cell and make HO to other cell, but in this case the serving cell is the one that has the highest SS so the MS has to HO to a cell of worse SS, but is the MS allowed to HO to any worse cell?
Or  Urgency HO due to BQ should be performed

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−Is the MS allowed to HO to any worse cell? No, this will be based on a parameter called BQOFFSET which will ensure that far neighbors won’t be selected.
−If Rankservingcell – Rankneighbor ≤ BQOFFSET+HYST, then this neighbor is near to the serving cell and it is not much worse than the serving cell and it can be candidate for HO.
−If Rankservingcell – Rankneighbor > BQOFFSET+HYST, then this neighbor is far from the serving cell and it will be removed from the candidate list.
−Ex: If Urgency condition is detected where Rankservingcell = -75 dBm and the neighbors: RankB = -79 dBm ,RankC = -90 dBm ,RankD = -87 dBm and BQOFFSET=5dB,HYST=0 dB
Rankservingcell – RankB =4dB<BQOFFSET= 5dB Cell B is kept in the candidate list
Rankservingcell –RankC=15dB>BQOFFSET= 5dB Cell C is removed from the candidate list
Rankservingcell – RankD = 8dB > BQOFFSET=5dB  Cell D is removed from the candidate list
2.Excessive Time Advance (TA) Urgency HO
−TA can be used as a measure for the distance between the BTS and the MS.
−If TA > TALIM (63 bit period)  Urgency HO due to TA is initiated.

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•After Basic Ranking and Evaluation of the Urgency Conditions, the Serving cell and Neighbor cells will be divided into 3 Groups
Categorization #1
Better Cell
Serving Cell
Worse Cell
–Initiation
–Filtering
–Basic Ranking
–Auxiliary Radio Network Features Evaluation

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•Auxiliary Radio Network Features Evaluation
1.Assignment to Another Cell Evaluation
2.Cell Load Sharing Evaluation
3.Over Laid/Under Laid sub-cell Evaluation
4.IHO Evaluation
5.HCS Evaluation
After these Evaluations, some candidates will be removed from the HO candidate list and
Categorization#2 will be performed.
−The Locating Algorithm may be initiated after immediate assignment to know whether it is better for the MS to take a TCH time slot on the current cell or not.
−If during the signaling phase a better cell was found after ranking, then
“Assignment to Better Cell” will be initiated.
−If during the signaling phase no better cell was found, then the MS will normally be assigned a TCH time slot on the current cell.
−If the Better/Serving cells were congested then “Assignment to Worse Cell” will be initiated if possible.

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−Is the MS allowed to take TCH time slot on any worse cell? No, this will be based on a parameter called AWOFFSET which will ensure that far neighbors won’t be selected.
−Only if Rankservingcell – Rankneighbor ≤ AWOFFSET+HYST, then this neighbor is near to the serving cell and it is not much worse than the serving cell and assignment to it can be done.
−If Rankservingcell – Rankneighbor > AWOFFSET+HYST, then this neighbor is far from the serving cell and it will be removed from the candidate list.
2.Cell Load Sharing (CLS) Evaluation
−This feature is used to reduce congestion on the serving cell.
−When CLS is activated and the load on the serving cell becomes higher than certain threshold then:
i)Valid CLS HO candidates are defined
ii)Re-calculation of their ranking values will be performed.

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2.Cell Load Sharing (CLS) Evaluation
i)Valid CLS HO candidates are defined as follow:
−Load on neighbor cells < CLS load threshold
−Internal cells: lies in the same BSC
−Same Layer
ii.Re-calculation of their ranking values will be performed
−We’re going to recalculate the Ranking values of the valid CLS neighbors with reduced Hysteresis so these worse neighbors will appear with higher SS than they really are and the MS can make HO to them and relief the congestion on the current cell.
 This feature will be discussed in details afterwards.
3.OL/UL Sub-Cell Evaluation
−The OL/UL feature provides a way of increasing the traffic capacity in a cellular network without building new sites.
−Since OL subcell serves smaller area than the corresponding UL subcell a smaller reuse distance can be used in in the OL subcell than in the under laid.
−The OL/UL evaluation may result in a recommendation to change the subcell from the one currently in use, this evaluation is based on:
DL SS, TA serving Cell, Distance to cell border, Traffic Load in the cell

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4.Intra Cell HO (IHO) Evaluation
−The IHO feature provides a way to improve the speech quality during the conservation when bad quality is detected while the SS is high.
−This is can be accomplished by changing the channel the connection is currently using within the same cell.
5.Hierarchical Cell Structure (HCS) Evaluation
−The HCS feature provides the possibility to give priority to cells that are not strongest but provide sufficient SS.
−The priority of a cell is given by associating a layer to the cell.
−We have 8 layers from layer 1 (Highly prioritized) to layer 8 (least prioritized).
−Micro cells are prioritized than Macro cells for capacity purposes.
−Cells of lower layers will be ranked higher than cells of higher layers in the HO candidate list.

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•After the Auxiliary Radio Network features evaluation some candidates may be prioritized and the order of the candidate list will be modified.
The Serving cell and Neighbor cells will be divided into 3 Groups
Categorization #2
Above S
Serving Cell (SC)
Below S
–Initiation
–Filtering
–Basic Ranking
–Organizing the List

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•Organizing the List
−The final list will contain maximum up to six neighbors + the serving cell and categorized as follows: Serving Cell (SC), Above S, Below S
−To reach the final form before sending the list the following steps will be done:
A.Removal of Candidates
B.Ordering the Candidate list based on the Current Conditions.
A.Removal of Candidates
 Some Candidates may be removed coz:
−Some Controlling timers are active and preventing HO to certain cell:
TALLOC: This timer prevents HO on a target cell for some time after assignment/HO failure due to congestion on target cell. (N.B: No penalties are applied on this cell)
TURGEN: This timer prevents HO on a target cell for some time after urgency HO failure due to congestion on target cell. (N.B: No penalties are applied on this cell)
N.B: TALLOC and TURGEN are BSC parameters (Default Values= 2 SACCH periods

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B.Ordering the Candidate list based on the Current Conditions
−Means what? Means in what order the 3 categories (Above S, S, Below S) will be arranged before sending the candidate list. This will be based on some condition flags.
−Condition flags: 1  Assignment Request Arrived
2  Assignment to Worst Cell is in use
3  Excessive TA detected
4  BQ Urgency HO
5  OL/UL Subcell load change or IHO
B.Ordering the Candidate list based on the Current Conditions
Condition flags: 1  Assignment Request Arrived 2  Assignment to Worse Cell is in use 3  Excessive TA detected 4  BQ Urgency HO 5  OL/UL Subcell load change or IHO
Case
Condition Flags
Ordering
Comment
1
2
3
4
5
1
0
x
0
0
0
Above S
Normal Case
2
0
x
0
1
0
Above S Below S
Serving Cell has BQ so it should be abandon either to the Above S or Below S cell
3
1
0
0
0
0
Above S S
An Assignment request came and the AW flag is not raised
4
1
1
0
0
0
Above S S Below S
An Assignment request came and the AW flag is raised
5
0
x
0
1
1
Above S S Below S
Serving Cell has BQ so it should be abandon but coz the OL/UL subcell change flag is raised, then the serving cell is included coz this subcell change may solve the issue with no need to go for a below worse cell

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–Initiation
–Filtering
–Basic Ranking
–Organizing the List
•Sending the List & Allocation Reply
−The resulting candidate list will form the basis on which HO will be performed.
−Empty list means that no options are better than remaining on the current cell and no HO will occur.
−The channel allocation reply may be success or failure.
−Failure may be due to congestion or signaling failure on the target cell.
−Based on the result of allocation either success/failure, some actions will be taken like applying some penalties or enabling of certain timers as we saw previously.

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•Example1:
−Assume that the o/p from the Filtering stage for the SS measurements is as below and we want to prepare the Basic Ranking Candidate list for HO:
Where,
BSPWR = BSTXPWR, MSRXMIN = -90 dBm,
Cell A was abandon due to BQ urgency HO (PSSBQ=7dB)
SS based Algorithm is in use where OFFSET=0, HYSTSEP= -90 dBm,
HIHYST= 5 dB, LOHYST= 3 dB
Cell
SS(dBm)
A
-70
B (Serving Cell)
-74
C
-78
D
-68
E
-80
F
-92
G
-95
•Solution:
A) Correction of Base Station output power:
−Since BSPWR = BSTXPWR then the current measurements will be kept as it is.
−SS_corrected_DLneighbor = SS_measured_DLneighbor
−SS_corrected_DLserving = SS_measured_DLserving
B) Evaluation of the minimum Signal Strength condition for Neighbors
−The SS for neighbors will be compared against MSRXMIN = -90 dBm
Cell F and Cell G have SS < MSRXMIN then they will be
removed from the list and can’t be candidates for HO.
Cell
SS(dBm)
A
-70
B (Serving Cell)
-74
C
-78
D
-68
E
-80
F
-92
G
-95

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•Solution:
C) Subtraction of signal strength penalties
−Since Cell A was abandon due to BQ urgency HO (PSSBQ=7dB) then it will be punished,
SS_punished_DL Cell A = SS_corrected_DL – PSSBQ = -70 – 7 = -77 dBm
−The candidate list will now be in the following form:
Cell
SS(dBm)
A
-77
B (Serving Cell)
-74
C
-78
D
-68
E
-80
•Solution:
D) Rank the Candidates after applying Offsets and Hysteresis
Since SSServing cell B = -74 dBm > HYSTSEP= -90 dBm, then it is
better to stay on the current cell and high Hysteresis will be
applied
i.e. HYST = HIHYST = 5 dB
Rankservingcell B = -74 dBm  “Serving Cell”
RankA= -77 dBm – OFFSET – HYST = -77 – 0 – 5 = -82 dBm  “Worse Cell”
RankC= -78 dBm – OFFSET – HYST = -78 – 0 – 5 = -83 dBm  “Worse Cell”
RankD= -68 dBm – OFFSET – HYST = -68 – 0 – 5 = -73 dBm  “Better Cell”
RankE= -80 dBm – OFFSET – HYST = -80 – 0 – 5 = -85 dBm  “Worse Cell”
Cell
SS(dBm)
A
-77
B (Serving Cell)
-74
C
-78
D
-68
E
-80

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•Solution:
−Now the final list according to Categorization#1 will be arranged as follows:
Categorization#1
Cell
RANK(dBm)
Category
D
-73
Better Cell
B
-74
Serving Cell
A
-82
Worse Cell
C
-83
Worse Cell
E
-85
Worse Cell
•Disconnection Criteria
−The Disconnection algorithm is not part of the locating algorithm but for completeness, the topic is treated here.
−The Disconnection algorithm manages when the connection between the MS and the Network shall be dropped when signaling failure is detected.
−The Disconnection criterion can be made in both the DL and the UL such that:
In the DL: managed by the MS and in the UL: managed by the BSC.

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•Disconnection Criteria
−In DL:
Controlled by a parameter RLINKT (max. bucket size) , when the MS couldn’t decode a SACCH message (0.48 sec), the bucket will be decreased by 1 unit, when the MS successfully decodes a SACCH message, the bucket will be increased by 2 units, if the bucket reached value = Zero then disconnection will occur, recommended value RLINKT=16
−In UL:
 The disconnection algorithm will run in the same way, the BSC will make the evaluation, and the controlling parameter is called RLINKUP, , recommended value RLINKUP=16
N.B: The bucket can’t have values larger than the max. value given by RLINKT/ RLINKUP
Algorithm Selection
Parameter Name
Value Range
Recommended Value
Unit
EVALTYPE
1 or 3
3
─
Flow Control Parameters
Parameter Name
Value Range
Recommended Value
Unit
TALLOC
0 to 120
2
SACCH period=480 msec
TURGEN
0 to 120
2

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Signal Strength based Basic Ranking Parameters
Parameter Name
Value Range
Recommended Value
Unit
HYSTSEP
−150 to 0
-90
dBm
LOHYST
0 to63
3
dB
HIHYST
0 to63
3
dB
OFFSET
−63 to 63
0
dB
Handover Failure Parameters (Signaling Failure)
Parameter Name
Value Range
Recommended Value
Unit
PSSHF
0 to 63
63
dB
PTIMHF
0 to 600
5
Seconds
Urgency Conditions Parameters
Parameter Name
Value Range
Recommended Value
Unit
QLIMUL
0 to 100
55
dtqu
QLIMDL
0 to 100
55
dtqu
BQOFFSET
0 to 63
3
dB
PSSBQ
0 to 63
7
dB
PTIMBQ
0 to 600
15
Seconds
TALIM
0 to 63
62
Bit Period (0.577msec)
PSSTA
0 to 63
63
dB
PTIMTA
0 to 600
30
Seconds
Disconnection Algorithm Parameters
Parameter Name
Value Range
Recommended Value
Unit
RLINKT
4 to 64 in steps of 4
16
RLINKUP
1 to 63
16

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•HCS Evaluation Algorithm
–HCS feature provides the ability and flexibility to give priority to cells that are not strongest but provide sufficient Signal Strength.
–The priority of a cell is given by associating an HCS layer to the cell where each cell will be belonging to an HCS band.
–The lower the layer ( and the HCS band), the priority is higher,
i.e. layer 1 has higher priority than layer 2, layer 3, layer 4, …..
layer 2 has higher priority than layer 3, layer 4, layer 5, …..
–Up to 8 layers (in up to 8 bands) may be defined, where one or several layers can be assigned to the same HCS band.
–The lower HCS bands will only include lower layers compared to a higher HCS bands.
–A mixture of small micro cells (lower layers) and large macro (higher layers) cells will achieve both high capacity and good coverage.
–Micro cells will be used for capacity issues while macro cells will be used to provide coverage, fill coverage holes and handle the fast moving mobiles.

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–With Basic Ranking only, micro cells will be ranked as the strongest server in very small area, so to let micro cells serve in an area where acceptable SS is guaranteed then HCS should be used.
−The idea with a layered cell structure is to let lower layer cells serve MSs that receive sufficient SS even if there is other cells with strongest received SS in the area.
−But how to decide if the lower layer cell has sufficient SS to be prioritized over strongest cells?
This will be according to two thresholds LAYERTHR (Layer Threshold) and HCSBANDTHR (HCS Band Threshold)
−LAYERTHR: Decides if the cell should be prioritized over stronger cells lie in the same HCS band or not.
−HCSBANDTHR: Decides if the cell should be prioritized over stronger cells from different HCS bands or not.

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−The input to the HCS Evaluation Algorithm is the Basic Ranking list we prepared from the locating process.
−The output will be in the form of two lists: HCS prioritized list (on Top) then Basic Ranking list.
−HCS prioritized list: will include cells that fulfilled the HCS conditions & rules and will be ranked according to HCS evaluation (layered ranking)
−Basic Ranking list: will include cells that didn’t fulfill the HCS conditions and will be ranked according to basic ranking rules (SS ranking)
HCS Evaluation Algorithm
HCS Prioritized Cell List
Basic Ranking List
Basic Ranking List
Input
Output
Mechanism of the HCS Algorithm

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(A) Band Evaluation: In order to be a candidate in the HCS evaluation process, then the SS of serving and neighbor cells should be greater than their band threshold ( HCSBANDTHR )
SSservingcell > HCSBANDTHRservingcell – HCSBANDHYSTservingcell
SSneigbhorcell > HCSBANDTHRneighborcell + HCSBANDHYSTneighborcell
Cells that will not fulfill the above condition will go to be sorted in the Basic Ranking list in priority order according to SS.
Cells that will fulfill the criterion will pass to the next step in the HCS evaluation.
N.B: HCSBANDTHR and HCSBANDHYST are BSC parameters.
(B) Define the strongest Cell (SS) in each Band
− Cells that passed the band evaluation in step (A) will be moved to the next step.
−In this stage, the strongest cells in each Band from SS point of view will be identified.
−Strongest cells  will pass direct to be HCS Ranked
−The rest of cells that are not strongest within the band will be moved to Step (C)

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(C) Layer Threshold Evaluation
− Cells that passed the band evaluation in step (A) and they are not strongest within their own band, their SS will be checked against the Layer threshold (LAYERTHR)
SSservingcell ≥ LAYERTHRservingcell – LAYERHYSTservingcell
SSneigbhorcell ≥ LAYERTHRneighborcell + LAYERHYSTneighborcell
Cells that will not fulfill the above condition will go to be sorted in the Basic Ranking list in priority order according to SS.
Cells that will fulfill the criterion will pass to the next step in the HCS evaluation
(D) Identify the Strongest Cells within each layer
−Now we will deal with cells that passed the band evaluation (in Step A) and they were not strongest within their own band (in Step B) and they passed the layer threshold condition (in Step C)
−Cells that are strongest within their own layer will be identified and they’ll pass direct to be HCS ranked.
−Cells that are not strongest within their own layer will be moved to the next step.

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(E) Check how many cells from each layer are allowed to pass to be HCS ranked
− Now we will deal with cells that passed the band evaluation (in Step A) and they were not strongest within their own band (in Step B) and they passed the layer threshold condition (in Step C) and they are not strongest within their own layer (in step D)
−MAXCELLSINLAYER: will identify how many cells from each layer can pass to be HCS ranked, ex: if MAXCELLSINLAYER = 2 then two cells only are allowed to pass to be HCS ranked.
−MAXDBDEVINLAYER: will identify how the next strongest cell in the layer is far from the strongest cell in the layer.
i.e. if SS_Strongest Celllayer x - SS_next strongest celllayer x ≤ MAXDBDEVINLAYER
then the next strongest cell is not weak and it will pass to be HCS ranked.
(F) Form the Final list
−Now all cells that succeeded to pass to be HCS ranked, will be sorted in ascending order according to their layer not SS (as in Basic Ranking) i.e. layer1 cells, then layer2 cells, …… and these cells will form an HCS prioritized list that will lie on Top.
−All cells that failed to pass to be HCS ranking, will go to be sorted in a Basic Ranking list and this list will lie after the HCS prioritized list

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Example:
Assume that the output from the Basic Ranking is as below, where for all cells have HCSBANDTHR = - 90 dBm, LAYERTHR = - 80 dBm,
HCSBANDHYST= LAYERHYST= 0,
MAXCELLSINLAYER = 3, MAXDBDEVINLAYER = 3
Cell
SS(dBm)
Band
Layer
G
-68
Band 8
Layer 7
E
-72
Band 8
Layer 6
B (Serving)
-73
Band 4
Layer 4
A
-74
Band 4
Layer 3
C
-75
Band 8
Layer 7
F
-75
Band 4
Layer 4
D
-95
Band 4
Layer 4
Solution: (A) Band Evaluation: In order to be a candidate in the HCS evaluation process, then the SS of serving and neighbor cells should be greater than their band threshold (HCSBANDTHR )
SSservingcell > HCSBANDTHRservingcell – HCSBANDHYSTservingcell
SSneigbhorcell > HCSBANDTHRneighborcell + HCSBANDHYSTneighborcell
HCSBANDTHRservingcell = HCSBANDTHRneighborcell = -90 dBm
HCSBANDHYSTservingcell = HCSBANDHYSTneighborcell = 0 dBm
Cell
SS(dBm)
Band
Layer
G
-68
Band 8
Layer 7
E
-72
Band 8
Layer 6
B (Serving)
-73
Band 4
Layer 4
A
-74
Band 4
Layer 3
C
-75
Band 8
Layer 7
F
-75
Band 4
Layer 4
D
-95
Band 4
Layer 4
Cell D didn‟t fulfill the condition (SS_CellD = -95 dBm < -90 dBm) so it will be out of the HCS evaluation and it will go to be sorted in the Basic Ranking list.


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Solution: (B) Define the strongest Cell (SS) in each Band
− Cells that passed the band evaluation in step (A) will be moved to the next step.
−In this stage, the strongest cells in each Band from SS point of view will be identified.
−Strongest cells  will pass direct to be HCS Ranked
−Now Cells G & B will go direct to be HCS evaluated, while cells E,A,C&F will be examined in the next steps.
Cell
SS(dBm)
Band
Layer
Comment
G
-68
Band 8
Layer 7
Strongest in Band 8 - Go direct to HCS Evaluation list
E
-72
Band 8
Layer 6
Will go to the next step: Layer Evaluation
B
-73
Band 4
Layer 4
A
-74
Band 4
Layer 3
C
-75
Band 8
Layer 7
F
-75
Band 4
Layer 4
D
-95
Band 4
Layer 4
Out of the HCS Evaluation – Back to the Basic Ranking list



Solution: (C) Layer Threshold Evaluation
− Cells E,A,C&F that are not strongest within their own band, their SS will be checked against the Layer threshold (LAYERTHR) if
SSservingcell ≥ LAYERTHRservingcell – LAYERHYSTservingcell
SSneigbhorcell ≥ LAYERTHRneighborcell + LAYERHYSTneighborcell
LAYERTHRservingcell = LAYERTHRneighborcell = - 80 dBm
LAYERHYSTservingcell = LAYERHYSTneighborcell = 0 dBm
Cell
SS(dBm)
Band
Layer
Comment
G
-68
Band 8
Layer 7
E
-72
Band 8
Layer 6
SS > LAYERTHR = -80 dBm, Will go to the next step
B
-73
Band 4
Layer 4
A
-74
Band 4
Layer 3
C
-75
Band 8
Layer 7
F
-75
Band 4
Layer 4
D
-95
Band 4
Layer 4
  

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Solution: (D) Identify the Strongest Cells within each layer
−After Cells E,A,C&F all of them passed the layer threshold condition (LAYERTHR), Cells that are strongest within their own layer will be identified and they’ll pass direct to be HCS ranked.
−Cells E&A are strongest within their own layer so they will go direct to be HCS ranked.
−Cells C&F are not the strongest within their own layer, so they will be examined in the next step to know if they can pass to be HCS ranked or not
Cell
SS(dBm)
Band
Layer
Comment
G
-68
Band 8
Layer 7
E
-72
Band 8
Layer 6
Strongest in Layer 6 - Go direct to HCS Evaluation list
B
-73
Band 4
Layer 4
A
-74
Band 4
Layer 3
C
-75
Band 8
Layer 7
Not Strongest in Layer-Will be examined in the next step
F
-75
Band 4
Layer 4
Not Strongest in Layer-Will be examined in the next step
D
-95
Band 4
Layer 4





Solution: (E) Check how many cells from each layer are allowed to pass to be HCS ranked
−MAXCELLSINLAYER: will identify how many cells from each layer can pass to be HCS In our example MAXCELLSINLAYER = 3 then three cells only are allowed to pass to be HCS ranked.
−MAXDBDEVINLAYER: will identify how the next strongest cell in the layer is far from the strongest cell in the layer.
i.e. if SS_Strongest Celllayer x - SS_next strongest celllayer x ≤ MAXDBDEVINLAYER = 3 dB
then the next strongest cell is not weak and it will pass to be HCS ranked.

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Solution: (E) Check how many cells from each layer are allowed to pass to be HCS ranked
Cell C:
Check1: Lies in layer 7 and ranked as the 2nd strongest cell in the layer and since 3 cells are
allowed to be ranked according to MAXCELLSINLAYER then Check1 is passed.
Check2: Is SS_Strongest Celllayer 7 - SS_next strongest celllayer 7 < MAXDBDEVINLAYER=3dB
SSCell G - SSCell C = -68-(-75) = 7 dB > MAXDBDEVINLAYER=3dB then Check2 failed.
Cell
SS(dBm)
Band
Layer
Comment
G
-68
Band 8
Layer 7
E
-72
Band 8
Layer 6
B
-73
Band 4
Layer 4
A
-74
Band 4
Layer 3
C
-75
Band 8
Layer 7
F
-75
Band 4
Layer 4
D
-95
Band 4
Layer 4
     
Solution:(E)Check how many cells from each layer are allowed to pass to be HCS ranked
Cell F:
Check1: Lies in layer 4 and ranked as the 2nd strongest cell in the layer and since 3 cells are allowed to be ranked according to MAXCELLSINLAYER then Check1 is passed.
Check2:Is SS_Strongest Celllayer 4 - SS_next strongest celllayer 4<MAXDBDEVINLAYER=3dB
SSCell G - SSCell C = -73-(-75) = 2 dB < MAXDBDEVINLAYER=3dB then Check2 is passed.
Cell
SS(dBm)
Band
Layer
Comment
G
-68
Band 8
Layer 7
E
-72
Band 8
Layer 6
B
-73
Band 4
Layer 4
A
-74
Band 4
Layer 3
C
-75
Band 8
Layer 7
F
-75
Band 4
Layer 4
2nd Strongest in Layer4-Go to HCS Evaluation list
D
-95
Band 4
Layer 4








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Solution: (F) Form the Final list
−Now all cells that succeeded to pass to be HCS ranked, will be sorted in ascending order according to their layer not SS (as in Basic Ranking) i.e. layer1 cells, then layer2 cells, …… and these cells will form an HCS prioritized list that will lie on Top.
−All cells that failed to pass to be HCS ranking, will go to be sorted in a Basic Ranking list and this list will lie after the HCS prioritized list
Final List
Cell
SS(dBm)
Band
Layer
Comment
A
-74
Band 4
Layer 3
HCS prioritized list
(Layer Ranking)
B(Serving)
-73
Band 4
Layer 4
F
-75
Band 4
Layer 4
E
-72
Band 8
Layer 6
G
-68
Band 8
Layer 7
C
-75
Band 8
Layer 7
Basic Ranking list (SS Ranking)
D
-95
Band 4
Layer 4
HCS Traffic Distribution Concept
−This feature is useful In order to control the traffic distribution between cells.
−If this feature is active then some cells that were prioritized due HCS ranking (layer ranking) will be removed if they already have enough traffic.
−HCSTRAFDISSTATE: Is a BCS parameter that shows if HCS Traffic Distribution is enabled within the cells in the BCS or not.
–If the HCS traffic distribution is allowed then two checks will be made:
(i)Check on the serving cell’s availability vs. parameter on cell level called HCSOUT
(ii)Check on the neighbor cells’ availability vs. parameter on cell level called HCSIN
−The Availability means: the percentage of free (non-occupied) Full Rate Time Slots.

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HCS Traffic Distribution Concept
(i)Check on the serving cell’s availability:
−If AvailabilityServingCell > HCSOUT, then this cells has too many free Time slots and it is not preferred to leave this cell.
(ii) Check on the neighbor cell’s availability:
−If AvailabilityneighborCell < HCSIN, then this cells has few free Time slots and it can’t accept HO’s due to HCS prioritization.
Mechanism of the HCS Algorithm when HCS Traffic Distribution is in use

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I) Example when HCS Traffic Distribution is enabled (AvailabilityServingCell<HSCOUT)
−After ordinary HCS evaluation we formed the below list from the previous example.
−Assume HCSOUT=50%, HCSIN=30%, Availability of Cell B (serving) = 40%
and availability of Cell F (neighbor cell) = 10% only, while all other cells have availability = 45 %
−What will be the final list form ?
Final List
Cell
SS(dBm)
Band
Layer
Comment
A
-74
Band 4
Layer 3
(Layer Ranking)
B(Serving)
-73
Band 4
Layer 4
F
-75
Band 4
Layer 4
E
-72
Band 8
Layer 6
G
-68
Band 8
Layer 7
C
-75
Band 8
Layer 7
D
-95
Band 4
Layer 4
Solution:
−Availability of Serving Cell (B) = 40% < HCSOUT (50%), then the serving cell has few free Time Slots and we can leave this cell i.e. outgoing HO from this cell is enabled.
−Availability of Neighbor Cell F=10% < HCSIN (30%), then this cell can’t accept HO’s due to HCS prioritization coz it has few free TS i.e. this cell is congested.
 This cell will be removed from the HCS prioritized list and it will be moved to the Basic Ranking List.
Final List
Cell
SS(dBm)
Band
Layer
Comment
A
-74
Band 4
Layer 3
(Layer Ranking)
B(Serving)
-73
Band 4
Layer 4
F
-75
Band 4
Layer 4
E
-72
Band 8
Layer 6
G
-68
Band 8
Layer 7
C
-75
Band 8
Layer 7
D
-95
Band 4
Layer 4

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Solution:
−The final list will be as below:
Final List
Cell
SS(dBm)
Band
Layer
Comment
A
-74
Band 4
Layer 3
(Layer Ranking)
B(Serving)
-73
Band 4
Layer 4
E
-72
Band 8
Layer 6
G
-68
Band 8
Layer 7
F
-75
Band 4
Layer 4
C
-75
Band 8
Layer 7
D
-95
Band 4
Layer 4
II) Example when HCS Traffic Distribution is enabled (AvailabilityServingCell > HSCOUT)
−If the serving cell has a channel availability above HCSOUT it is considered to be taking too little traffic so it is decided to not allow handovers out due to HCS from the cell.
− Instead, all the remaining HCS prioritized candidate cells, fulfilling the HCSIN criterion and that are in a lower layer or in the same layer as the serving cell, will be basic ranked among themselves and added to a “Prioritized basic ranked cells list” that will be put above the other basic ranked cells in the final candidate list.

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II)Example when HCS Traffic Distribution is enabled(AvailabilityServingCell>HSCOUT)
−After ordinary HCS evaluation we formed the below list from the previous example.
−Assume HCSOUT=50%, HCSIN=30%, Availability of Cell B (serving) = 60%
and availability of Cell F (neighbor cell) = 10% only, while all other cells have availability = 45 %
−What will be the final list form ?
Final List
Cell
SS(dBm)
Band
Layer
Comment
A
-74
Band 4
Layer 3
From HCS prioritized list
(Layer Ranking)
B(Serving)
-73
Band 4
Layer 4
F
-75
Band 4
Layer 4
E
-72
Band 8
Layer 6
G
-68
Band 8
Layer 7
C
-75
Band 8
Layer 7
D
-95
Band 4
Layer 4
Solution:
−Availability of Serving Cell (B) = 60% > HCSOUT (50%), then the serving cell has Too many Time slots and HO out from this cell due to HCS is not allowed.
−Availability of Neighbor Cell F=10% < HCSIN (30%), then this cell can’t accept HO’s due to HCS prioritization coz it has few free TS i.e. this cell is congested.
This cell will be removed from the HCS prioritized list and it will be moved to the Basic Ranking List.
−Cells E&G are layers 6&7 respectively i.e. they are of higher layers than the serving cells.
 These cells will be removed from the HCS prioritized list and it will be moved to the Basic Ranking List.
−Now cells A&B will be ranked according to SS  “Prioritized Basic Ranking list”
cells C,D,E,F&G will be ranked according to SS  “Basic Ranking list”

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Solution:
Final List
Cell
SS(dBm)
Band
Layer
Comment
A
-74
Band 4
Layer 3
From HCS prioritized list
(Layer Ranking)
B(Serving)
-73
Band 4
Layer 4
F
-75
Band 4
Layer 4
E
-72
Band 8
Layer 6
G
-68
Band 8
Layer 7
C
-75
Band 8
Layer 7
D
-95
Band 4
Layer 4
Solution:
−The final list will be as below:
Final List
Cell
SS(dBm)
Band
Layer
Comment
B(Serving)
-73
Band 4
Layer 4
Priotirized Basic Ranking List
A
-74
Band 4
Layer 3
G
-68
Band 8
Layer 7
E
-72
Band 8
Layer 6
F
-75
Band 4
Layer 4
C
-75
Band 8
Layer 7
D
-95
Band 4
Layer 4

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Optimizing a problematic Traffic Case:
−Assume we have the below case with 3 Macro cells (layer 4) and 1 Micro cell (layer2) and all of them belong to the same HCS band, HCSBAND 1
−One of the Macro cells carries very high traffic and it is about to congest, how could we solve this case?
Macro Cell (L4)
Macro Cell (L4)
Micro Cell (L2)
Macro Cell (L4)
Solution 1: Direct more Traffic to the Micro Cell
−We can decrease the LAYERTHR of the Micro cell (Layer 2) from -75dBm to -80dBm for example, so the micro cell will capture more traffic from the congested macro cell.

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Solution 2: Direct more Traffic to the adjacent Macro Cells
−We can increase the Layer of the congested Macro cell (Layer 4  Layer 5) so it will appear less prioritized with respect to the adjacent neighbor cells and it will offload its traffic to them.
Solution 3: Direct more Traffic to one of the adjacent Macro Cells
−We can decrease the Layer of one of the adjacent Macro cell (Layer 4  Layer 3) so it will appear more prioritized with respect to the congested cell and it will capture some of its traffic.

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Fast Moving MSs
−If cell parameter FASTMSREG is “ON” and MS made no. of HOs >NHO (default=3) in time window THO (default=30sec) then MS is considered as fast moving MS.
−The stronger cells according to Basic Ranking in all higher layers within the same system type are given priority.
−For example: 1800 candidates are in Layers 1,2&3 while 900 candidates are in Layers 4&5, if the MS is considered as fast in layer1, then candidates in layers 2&3 of higher basic ranking than the serving cell are given priority.
−Highest priority is given for the strongest cell regardless of its layer.
−To prevent HO back to lower layer cells, a penalty PSSTEMP (0 to 63) is applied for a time PTIMTEMP (0 to 600s) on all neighbor cells within the current system type and all cells in other system types.
−Parameters Summary
1  For reduced HCS functionality we have only 2 bands HCS Band1 and HCS Band2 (default)
2  For reduced HCS functionality we have only 3 layers
HCS Algorithm Control Parameters
Parameter Name
Value Range
Default Value
Recommended Value
Unit
HCSBAND
1 to 8 1
2
2
─
HCSBANDTHR
150 to 0
95
─
dBm (–ve)
HCSBANDHYST
0 to 63
2
2
dB
LAYER
1 to 8 2
2
─
─
LAYERTHR
150 to 0
75
─
dBm (–ve)
LAYERHYST
0 to 63
2
2
dB
MAXCELLSINLAYER
1 to 31
1
1
MAXDBDEVINLAYER
0 to 63
3
3
dB
HCSTRAFDISSTATE
0,1
0
1
─
HCSIN
0 to100
0
─
%
HCSOUT
0 to100
100
─
%

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•Concentric Cells (Overlaid Underlaid Subcells)
−Traffic Capacity of a cellular network can be increased by either adding more frequencies or reducing the frequency reuse distance.
−One approach is to apply a second frequency re-use pattern with a tighter frequency reuse (Overlay) on the existing pattern.
−These cells should be restricted in size, so shorter reuse distance can be accomplished without causing Co-channel/Adjacent channel interference.
−They are termed Overlaid (OL) Subcells, whereas the original cells will be called Underlaid(UL) Subcells.
−Now by having more frequencies per cell, then Network capacity is increased.

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−The fundamental idea behind the OL/UL subcells is to let the traffic close to the site to be moved to the OL subcell, while traffic close to the cell border to be moved to the UL subcell.
−In that way of treading the traffic, the frequencies in the OL subcell can have tighter frequency reuse.
−Example: Assume that cell A has frequencies: f1&f2, cell B has frequencies: f3&f4 and now cell A has increase in the traffic, so we’re going to assign cell A frequency f4 also.
−Now high Co-channel interference will occur on f4 at the border between the two cells, coz f4 is reused between two adjacent cells.

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