Special Features And Dimensioning

BSSDIM: Special features and dimensioningModule Objectives
At the end of the module, the participant will be able to:
Understand the basics of DFCA and CommonBCCH and MultiBCF features
Know the interfaces that are affected by these features
Identify factors in each feature that influence the interface dimensioning
* BSSDIM-Special Features and Dimensioning
Concept and functional description
Concept and functional description
Introducing Segment in S10.5
Because of BSS 10.5 features Multi-BCF, Common BCCH and EDGE, a new Radio Network Object "Segment" is introduced
Segment equals Telecom cell
BTSs of a segment are co-located and synchronized
Segment usage is an option of its own
A BTS in a segment is a group of similar TRXs
A BTS in a segment must consist of TRXs of the same frequency band (PGSM900, EGSM900, GSM1800 / GSM800, GSM1900 separated)
A BTS in a segment must consist of TRXs of the same base station site type (Talkfamily and UltraSite separated)
OLD:
Common segment specific parameters
BSC Allows the following types of BTS combinations
Nokia Talk Family + Nokia Talk Family
Nokia Talk Family + Nokia Ultrasite
Nokia Ultrasite + Nokia Ultrasite
Nokia Metrosite + Nokia Metrosite
The maximum number of BCFs, BTSs and TRXs in one BSC is same as before:
BSC2i, 512 FR TRX, 248 BTS and 248 BCF
BSC3i, 660 FR TRX, 248 BTS and 248 BCF
When a user creates a cell which has more than one BTS (e.g. combines several BTS to one segment) and maximum number of BTSs in BSC is used, the number of separate cells must be decreased
An operator can e.g. create multiple hopping groups in a cell by gathering TRXs of one hopping group into one BTS object and have several such BTSs in a segment
EDGE and non-EDGE territories
Segment-2
DOCUMENTTYPE
Common BCCH and MultiBCF dimensioning
The main consequences of Common BCCH and MultiBCF related to dimensioning
Existence of only one BCCH per segment, i.e. it is not needed a BCCH TRX per segment
In case of EDGE and non-EDGE BTSs in the same segment, the existence of two PS territories
GPRS only territory
That are configured independently
No extra TRXSIG load is generated, but the segment with Common BCCH shall be viewed as a bigger sector, having higher load than a normal sector and hence generating higher load over TRXSIG
DOCUMENTTYPE
TypeUnitOrDepartmentHere
TypeYourNameHere
TypeDateHere
B
Segment-1
BTS-1
Non-EDGE
TRXs
BTS-2
GPRS Enabled TRX = off
One sector carries the CCCH signaling of the whole segment (sectors under the same CCCH).
Information elements to assign CS resources are sent in existing IE, therefore no extra signaling is generated on TRXSIG.
For PS services, the MS camps on the sector with BCCH and later it performs a reallocation to the target sector (within the segment). This reallocation is sent in PACCH, therefore not transmitted on TRXSIG.
(E)GPRS Territory is not exclusive for (E)GPRS traffic, but GPRS users can be allocated in this territory. However, this only will happen when GPRS territory is totally full of GPRS users (nb. TBF/TSL parameters are reached).
In addition, when a GPRS TBF is allocated in EGPRS territory, in the moment that GPRS territory is again free, GPRS TBF will be automatically reallocated to GPRS territory.
Reason for this is due to the definition of GENA and EGENA parameters:
GENA is defined at segment level, i.e., if GENA = Y, PS traffic (both GPRS and EGPRS) is allowed in the whole segment
EGENA is defined at BTS level.
How to create different GPRS and EGPRS territories?
BTS with GPRS territory: GENA = Y; EGENA = N
BTS with EGPRS territory: GENA = Y; EGENA = Y (as GENA is active, GPRS users can also be allocated in this BTS)
Little interference control
C/I > C/I target
Each connection is assigned with the most suitable radio channel (MA list, MAIO, TSL)
C/I based accurate interference control
BCCH
TRX 1
TRX 2
TRX 3
TRX 4
With DFCA the radio channel for each user can be selected individually. DFCA uses cyclic hopping in synchronized BSS so the radio channel is determined by MA list, MAIO and time slot.
DFCA estimates the CIR of each channel and the channel is selected based on CIR criteria.
DFCA and Frequency Hopping
DFCA utilizes cyclic frequency hopping
Air interface synchronisation will ensure that interference relations will still remain fixed i.e. the interfering connections will hop over the same hopping sequence in synchronization
Full benefit from frequency diversity gain
Interference diversity gain against external interference
time
freq
time
freq
Interfering connection
Both the considered MS and interferers hop into the same frequency, therefore no interference diversity
With DFCA there is no interference diversity. All the interference sources are the same for all the burst even though FH is used. The reason is cyclic hopping and the fact that the interfering MA lists are the same. Thus, every time a connection changes to the next frequency in the MA list the interfering connections do the same and keep interfering for every burst. The situation is thus very similar to the non hopping case with fixed frequencies. The difference is that with cyclic hopping there is frequency diversity gain that helps to mitigate the impact of fast fading. This frequency diversity helps both against noise (coverage limited) and against interference.
The constant and predictable interference makes it possible to utilize CIR based channel selection.
DFCA and InterBSC communication
BSCs connected via inter BSC signaling link (IP based connection)
DFCA
DFCA
IP Network
BSC – BSC connection makes it possible for DFCA to work transparently over BSC area borders.
Background Interference Matrix
MS measurement reports
CIR estimations
The latest averaged measurement report is used to determine the potential CIR towards each of the reported neighboring cells. If a near-by cell that has been found to be potentially interfering is not included in the measurement report, then the CIR for that cell is determined from the background interference matrix.
The measurement reports from other connections in the surrounding cells that are potentially interfering or can get interfered by the new connection are updated to the DFCA use every 2-5 seconds. The same applies also to the power control power reductions.
DFCA radio channel selection is based on C/I criteria
Different user classes have operator definable C/I targets and soft blocking C/I limits
DFCA supported user classes:
HSCSD
User class based CIR targets help to deal with mobiles having very different link performance in a optimum way. Basically, the mobiles with more robust link performance get channels with lower CIR than the mobiles with poorer link performance. As a result all users experience similar quality and the radio resource usage is efficient without sacrificing the connection quality of the legacy mobiles.
messages exchange on BSC-BSC Interface
DFCA is an algorithm that runs in the BSC and the main new requirement that introduces is the need for a inter-BSC Interface
BSC 1
BSC 2
In order to evaluate the interface dimensioning needs, the most important messages exchanged in the BSC-BSC interface are:
Channel Assignment: Sent to BSCs in to a multicast address every time a new channel assignment is performed by DFCA algorithm
Channel Release: Sent to same BSCs recipients of Channel Assignment message in to a multicast address every time a new channel assignment is performed by DFCA algorithm
PC and neighboring cell update: Sent to BSCs into a multicast address periodically to inform about current UL and DL Power Level reductions of each ongoing DFCA connection in a DFCA BTS
DFCA
DFCA
IP Network
Channel Assignment: Channel Release: The receiving BSC updates the DFCA Radio Resource Table of foreign cell
BSC-BSC Interface. There are two potential protocol stacks:
RNSAP+/SUA/SCTP/IP/Ethr Propietary
Channel Release 37 (bytes)
33 + Active channels * (7 + Neigh * 4) (bytes)
Also transport protocol overhead needs to be considered and added up to application layer messages
DFCA and Dimensioning
In order to know the message frequency exchange between BSC-BSC following parameters should be considered
- Nbr. of DFCA TRXs/cell
- Nbr. of users / cell
Nbr. of cells / BSC
Max Nbr. Reported neighbors
The more reported neighbors, the higher the required capacity for BSC-BSC interface is, but there is a upper limitation
% of affected cells in own BSC
E.g. if all the reported cells are covered by their own BSCs, there is no need to report anything between BSC-BSC BSC-BSC Throughput 0
Nbr. of interfering BSCs
The more interfering BSCs, the total amount of messages transmitted by one BSC is higher
Freq. of Assignments/release and PC update
Conclusions
Common BCCH and MultiBCF are features allowing to gather together BTSs of different technologies in a logic BTS or segment
Consequences on dimensioning are related to
Only 1 BCCH controlling all the BTSs
Different PS territories in the same logical BTS or segment
DFCA is a feature that allows to get benefit of Cyclic Hopping that enables to control the interference, in order to perform an intelligent channel allocation
Target is to assign the channel where interference received and produced are lower
DFCA regarding dimensioning has to pay special attention to the messages exchange in the new inter-BSC interface
DOCUMENTTYPE
TypeUnitOrDepartmentHere
TypeYourNameHere
TypeDateHere
B
Segment-1
BTS-1
Non-EDGE
TRXs
BTS-2

Documents

Special Features And Dimensioning