1. The document discusses various coverage enhancement features used in cellular networks including extended cell range, long reach timeslots, super extended cells, and smart radio concepts. 2. It provides details on the technical implementation of these features such as delayed receivers, double BCCH allocation lists, and parameters for handover control. 3. Advanced concepts like intelligent downlink diversity, interference rejection combining, and space time interference rejection combining are introduced to further improve coverage and capacity.

1. 1 © Nokia Siemens Networks
BSSPAR1: Chapter 8 Coverage Enhancement Features

2. 2 © Nokia Siemens Networks
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Module Objectives
•Describe Extended Cell Range for CS calls
•Explain parameters controlling handovers in a Extended Cell
•Explain the Long Reach Timeslot for Flexi BTS
•Explain the 105km Super Extended cell and related parameters
•Give a brief introduction to Smart Radio Concept (SRC) feature

4. 4 © Nokia Siemens Networks
Extended Cell Range
•One BCCH, Two TRX solution to extend cell radius to 70km
•Normal and Extended area served with different TRX
•BTS Type supported
•Ultra CX4.1 (with EDGE capable TRX)
•Flexi EP2.0
•Talk Family DF7.0
•Not supported by Metrosite
•Activation based on TRX licence (Flexi, Ultra) or PRFILE (Talk)

5. 5 © Nokia Siemens Networks
Normal region (frequency f1)
N-TRX (Parameter eTrxInd (ETRX) = N)
Extended region (frequency f2 except timeslot 0)
E-TRX (Parameter eTrxInd (ETRX) = E)
E-TRX
(Delayed receiver)
0 1 2 3 4 5 6 7
N-TRX
0 1 2 3 4 5 6 7
f1 f1 f1 f1 f1 f1 f1 f1
BCCH/
SDCCH
Not
Used
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH
E-RACH
SDCCH
f1 f2 f2 f2 f2 f2 f2 f2
Extended cell size
Parameter radiusExtension (EXT)
Value = 1..67km radius extension of extended cell
Value = 0 ordinary cell
Extended Cell Range (Implementation)
•BB Hopping cannot be used
•RF hopping cannot be used on E-TRXs
• One BCCH, Two TRX solution
• Receiver timing delayed on ETRX
• Transmitter timing same on NTRX and ETRX

6. 6 © Nokia Siemens Networks
Call Setup
• RACH received on N-TRX
• IMM ASS sent on N-TRX
• SDCCH on N-TRX
• RACH received on E-TRX
• IMM ASS sent on N-TRX
• SDCCH on E-TRX
Overlap area: RACH is recived on N-TRX and E-TRX. BSC filters the later one out

7. 7 © Nokia Siemens Networks
Cell Selection
MS can camp on BCCH (NTRX) independent of the distance to the BTS
RACH from MS detected on RACH or E-RACH depending on the distance to the BTS
Failure of RACH burst  Wrong cell selected
Reselection on the basis of the path loss criterion C1
Handover to due Distance (Normal area  Extended area)
maxMSDistanceHOThreshold (MAX) 0..63 TA => MAX; handover triggered to extended cell
minMSDistanceHOThreshold (MIN) 0..63 TA => MIN; handover triggered to normal cell
Adjacent Cell Parameter
hoTargetArea (HOTA) indicates type of target cell (normal or extended) ;
indicates type of transceiver from which the BSC tries to allocate a channel (normal or extended)
0 – Normal cell
1 - Allocate from N-TRX
2 – Allocate from E-TRX
3 – Allocate from TRX of the same type as source BTS
Extended Cell (Cell Selection, Handover)
•Inter-BSC HO: Only values 0, 2 are allowed for HOTA.
• External HO are made only towards Extended area if Long Reach TSL (for Flexi) is NOT in use

8. 8 © Nokia Siemens Networks
• The Double BCCH Allocation List (Double BA List) may be needed in the extended cell range solution because otherwise some legacy MSs do not work properly
• The intra-cell handover between an N-TRX and an E-TRX is performed by using a HANDOVER COMMAND message.
• Using the Handover Command requires that the BCCH frequency of the serving cell is included in the BCCH allocation list.
•This can be achieved by using the Double BA List.
Extended Cell Use of Double BA list

9. 9 © Nokia Siemens Networks
Long Reach Timeslot Flexi BTS (EP2.0)
•Currently BSC allocates external handovers only towards extended area of an extended cell  higher HO failures
•Used to determine if the MS is located in normal or extended area (of the targeted cell) in case of incoming external HO
Use of LRTCH
• BTS measures TA by scanning both LRTCH for the handover access burst
• BTS sends the ACCESS DELAY information to BSC
• ACCESS DELAY < maxMSDistanceHOThreshold MAX: Normal cell area
• ACCESS DELAY >= maxMSDistanceHOThreshold MAX : Extended cell area
• Intra-cell HO from LRTCH to TCH of N-TRX or TCH of E-TRX to free up LRTCH
•Transmission on first LRTCH only
• Reception on both LRTCH

10. 10 © Nokia Siemens Networks
Long Reach Timeslot Flexi BTS (EP2.0)
•TA value sent by BTS to MS cannot be greater than 63  BTS must send an adjusted value for TA if the MS is in extended area
If TA > 1.8 * EXT
TA (adj) = TA (meas) – 1.8*EXT
TA (adj) = TA (meas)
UL is synchronized to E-TRX
UL is synchronized to N-TRX

11. 11 © Nokia Siemens Networks
105km Super Extended Cell Introduction
•Radius extension upto 105km for Flexi BTS (EP2.0 CD1)
•BCCH serves all three cell areas
•DL of E-RACH tsl not used
•E-RACH of STRX overlaps with tsl 0 and 1 of BCCH (just like E-RACH of ETRX)
•SDCCH defined on S-TRX
•Normal and Super Extended areas do not overlap
•TA of each area measured separately from 0…63
E-TRX RXN-TRX RXf1 f1 f1 f1 f1 f1 f1 f1BCCH/NotTCH40% DelayedreceiverNormalTCHTCHTCHTCHTCHTCHTCHTCHTCHSDCCHin useSDCCHTRXE-TRXE-RACHTCHS-TRX RX80% DelayedreceiverTCHTCHTCHTCHSDCCHS-TRXE-RACHf1 f2 f2 f2 f2 f2 f2 f2f1 f3 f3 f3 f3 f3 f3 f3TCHTCHTCHRACH/

12. 12 © Nokia Siemens Networks
105km Super Extended Cell
Handover between areas
EXT
MAX
N-area: 35 km
E-area: 35 km
S-area: 35 km
SEXT SMAX
Overlap area (N/E) Overlap area (E/S)
BTS
MIN
SMIN
1.
2.
3.
4.
1. Mobile is moving in Normal area (away from BTS), TA ≥ MAX => handover to Extended area triggers
2. Mobile is moving in Extended area (away from BTS), TA ≥ SMAX => handover to Super extended area triggers
3. Mobile is moving in Super extended area (towards BTS), TA ≤ SMIN => handover to Extended area triggers
4. Mobile is moving in Extended area (towards BTS), TA ≤ MIN => handover to Normal area triggers
TRX Level
E-TRX Type = S
BTS Level
Super Radius Extension (SEXT)
Location of inner edge of super
extended area from the BTS
Range: 0, 36-70
Handover Control
MS distance HO
threshold super ext cell min (SMIN)
Range: 0…63
MS distance HO
threshold super ext cell max (SMAX)
Range: 0…63
External handovers
• Performed thru LRTCH if it is in use
• If not in use, HO to super extended
area

13. 13 © Nokia Siemens Networks
•SRC consists of :
•Downlink link enhancing feature
–Intelligent Downlink Diversity (IDD)
•Uplink enhancing features
–4-way UL Diversity (4UD)
–Interference Rejection Combining (IRC)
–High gain MHA
•Up and downlink features can also be implemented separately (except for 4UD, which is used with IDD)
•BTS Support: Ultrasite CX6.0, FlexiEDGE EP2.0
•TRX Support: EDGE-capable TRX and EDGE baseband units required
SRC Concept

14. 14 © Nokia Siemens Networks
• Improves the mobile’s receiver performance by modifying the radio channel
• BTS downlink performance is boosted up to 3-5 dB
• All timeslots are transmitted through 2 transceivers and 2 antennas
• 2nd TRX transmission is delayed and phase turned
• Also BCCH carrier is sent through 2 transmitters
• Phase hopping is used to change phasing between adjacent bursts (to decrease correlation between a main and auxiliary transmitter)
• To the BSC, the main and auxiliary TRX appear as one logical TRX
• Mobile receives both signals as standard multipath
IDD Concept Delay Diversity (DD) with Phase Hopping

15. 15 © Nokia Siemens Networks
EDGE
Transceiver
Combined
Uplink
signal
EDGE
Transceiver
Baseband
Units
Downlink
signal
RX + TX
MHA
MHA
DDU
RX div.
RX div.
RX div.+
TX aux
Masthead Amplifier compensates feeder loss and matches front end of the BTS receiver optimizing sensitivity
Very efficient Interference Rejection Combining is processed for received signals giving ultimate gain for diversity reception. IRC minimizes the effect of interfering signals in the BTS receiver.
4-way UL Diversity

16. 16 © Nokia Siemens Networks
• The noise between two branches are somewhat correlated, so the
best way of combining is Interference Rejection Combining (IRC). This
takes into account the correlation between interference branches and
removes ultimately the interference from the received signal.
• Uplink receiver diversity can be either 2- or 4-way diversity.
• In 2-way diversity the receiver combines signals from two antennas
by using Interference Rejection Combining (IRC).
• 4-way diversity is based on MRC combination of two 2-way IRC
diversity branches.
• The signals from four antennas are fed into two separate TRX. Two
pair-wise signals are combined by IRC in respective TRX and then the
signal from the auxiliary TRX is fed into the main TRX where signals
are combined using Maximum Ratio Combining
4-way uplink diversity using IRC
followed by MRC.
2-Way/4-Way UL Receiver Diversity
(IRC/MRC)

17. 17 © Nokia Siemens Networks
SRC, no MHA
SRC+MHA
combiner by-pass
SRC with Mast Head Amplifier (MHA)
SRC+MHA
SRC, no MHA
combiner by-pass, no MHA
Effective cell range:
Bypass,
No MHA
SRC,
no MHA
SRC
+ MHA
DL
UL
DL
UL
DL
UL
combiner by-pass
combiner by-pass + MHA
DL
UL
Bypass
+MHA
Balanced link defines the cell range, not only BTS TX power

18. 18 © Nokia Siemens Networks
Configuring IDD in the BSC
• Main and auxiliary TRXs connected to different antenna
• TRX is created/added to IDD configuration during TRX commissioning
• Usage of IDD and mode of IDD TRX (main/auxiliary)
• 4UD is defined in the BSC with the diversityUsed (RDIV) parameter: RDIV=Y (4-way RX diversity is used).
• If IDD is used only for boosting the BCCH carrier, the IDD TRX has to be defined in the BSC as preferred BCCH TRX

19. 19 © Nokia Siemens Networks
• STIRC is an enhancement to Interference Rejection Combining (IRC) that is implemented in NSN Flexi EDGE, EDGE UltraSite, and EDGE MetroSite BTSs
• STIRC is compatible with Smart Radio Concept for EDGE (SRC). All antenna configurations are supported. However, 4-way uplink diversity configurations provide the best performance.
• Link level simulations show interference rejection performance of GMSK channel under typical urban (TU) conditions improving on average 4 - 10 dB gain compared to IRC (for 2-way uplink diversity (2UD)) - The actual gain is network and configuration dependent
• STIRC can be enabled per sector (BTS object)
Space Time Interference Rejection Combining (STIRC)

20. 20 © Nokia Siemens Networks
• In a multiple-antenna receiver, there is a strong correlation in the interference between different branches (normal and diversity) and samples for each symbol period. Usually, the interference correlation is different from the correlation of the desired signal.
• IRC is a set of diversity combining, digital signal processing methods that removes interference by taking these cross correlations into account.
• These methods can be considered as whitening the interference (there is no correlation) between the individual branches and samples of each symbol which, if done perfectly, optimizes the performance of the receiver, in particular the bit (0/1) detection process.
• STIRC works best when there is a single dominant interferer and it is best suited for urban areas
Whitening
Whitening
Interference Rejection
Combining (IRC)
Space Time Interference
Combining STIRC
Whitening,
jointly
estimated
STIRC & IRC

21. 21 © Nokia Siemens Networks
STIRC feature control
MO Class
Abbreviated Name
Range And Step
Description
Default value
BSC - MML Name
BTS
stircEnabled
STIRC is disabled (N) (0), STIRC is enabled (Y) (1)
Defines whether the STIRC feature is used in the BTS.
Valid only for Nokia UltraSite, Nokia MetroSite and Nokia Flexi EDGE Site types.
STIRC is disabled (N) (0)
STIRC
• Licence based feature: Capacity licence based on number of STIRC enabled TRXs in the BSC
• STIRC activation on BTS level