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Presentation / Author
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
Presentation / Author
* © 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
Flexi EP2.0
Activation based on TRX licence (Flexi, Ultra) or PRFILE (Talk)
Presentation / Author
Extended region (frequency f2 except timeslot 0)
E-TRX (Parameter eTrxInd (ETRX) = E)
E-TRX
BCCH/
SDCCH
Not
Used
E-RACH
SDCCH
Extended cell size
Parameter radiusExtension (EXT)
Value = 0 ordinary cell
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
N-TRX
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH
SDCCH on N-TRX
SDCCH on E-TRX
Overlap area: RACH is recived on N-TRX and E-TRX. BSC filters the later one out
Presentation / Author
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
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
Presentation / Author
Use of Double BA list
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.
Presentation / Author
* © 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
* © 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)
Presentation / Author
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
separately from 0…63
Super Radius Extension (SEXT)
Location of inner edge of super extended area from the BTS
Range: 0, 36-70
Range: 0…63
MS distance HO
Range: 0…63
If not in use, HO to super extended area
Presentation / Author
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
Presentation / Author
* © 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
Presentation / Author
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.
Presentation / Author
(IRC/MRC)
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.
Presentation / Author
SRC, no MHA
DL
UL
Bypass
+MHA
Balanced link defines the cell range, not only BTS TX power
Presentation / Author
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
Presentation / Author
Combining (STIRC)
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)
Presentation / Author
STIRC & IRC
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
Interference Rejection
Combining (IRC)
* © Nokia Siemens Networks
STIRC feature control
Licence based feature: Capacity licence based on number of STIRC enabled TRXs in the BSC
STIRC activation on BTS level
MO Class
Abbreviated Name
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
BCCH/Not
TCH
40%
Delayed
receiver
Normal
TCHTCHTCHTCHTCH
TCHTCHTCHTCHSDCCH
TCH
TCHTCH
RACH/
EXT
MAX
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