HCS Presentation

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Hierarchical Cell Structures Feature Description

Transcript of HCS Presentation

Page 1: HCS Presentation

Hierarchical Cell Structures

Feature Description

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Introduction

The HCS feature provides the possibility and flexibility to give priority to cells that are not strongest but provide sufficient received signal strength. The priority of a cell is given by associating a layer to the cell. Each layer is also belonging to a HCS band. The lower the layer (and HCS band), the higher the priority. The Locating algorithm is primarily based on the "best server" philosophy ( Ericsson1 and Ericsson3)HCS provides to distribute the traffic between cells by giving priorities.

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DescriptionAbility to group cells (e.g. 1800 macro cells) together and prioritize these cells toward cells belonging to another band. The result will be a largerLarger service area for the micro cells by moving the handover border from the signal strength border to a new handover border controlled by the band threshold

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Distribution of HCS Band and Layers

The Layers are grouped in HCS Band8 Layers (max) and 8 HCS BandAll 8 Layers can belong to 1 HCS Band1 Layer can Belong to 1 BandLayer 1 has higher priority than Layer 2, Layer 3, Layer 4, ...Layer 8Strategy: Serve MSs with a a lower Layer respect a Higher Layer Cells with stronger SS in the same area

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ExampleLAYERTHR: is the signal strength threshold used to rank cells in different layers within each band. It is set per cellHCSBANDTHR: defines the priority for group of layers. HCS band 1 has the highest priority. It is set per layer and BSC

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Example of applicationIn a combined GSM 900 and GSM 1800 network the cells of the different system types may have different capacity potential. In order to utilize the given capacity it is desired to deviate from the strongest server principle (Locating)

The cells for 1800 Band may be smaller than the cells for 900 band, relying on basic ranking. Sometimes they are never the strongest servers.

1800 band may have more available frequencies, it can provide more traffic capacity than the other band.

For example: HCS Stadium Configuration (Frankfurt or Kaiserlautern)

Instead of using strongest cell the traffic from dual band MSs can be directed to cells with spare capacity (1800 Band). Otherwise the larger and stronger cells (typically GSM 900) would become congested easily as the traffic from both dual band and GSM 900 single band MSs are increased. Consequently, the GSM 900 single band MSs would be often left without service while spare capacity is founded in GSM 1800 cells. The objective is to fully utilize the radio capacity while offering sufficient quality.

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HCS Algorithm Flowchart

Favorite the traffic on 1800 Band Cells using some Layers and only 1 HCSBAND

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Layer and Band Designation

Assign unique Layer for each type of cell (8 layer): picocell, microcell, macro, umbrella, hot spot, ect. Ect.Definine HCS Band and then prioritize the layers on base capacity

Best effort Methods:1. Always put higher priority on cell with low traffic respect to the

higher layer cell with more traffic2. To use a few layers initially, one for each cell type (macro, micro,

900, 1800,...) and then more layers are introduced for off-loading between the cells of the same type. This is done within only oneHCS Band (Multiple Layers in only 1 HCS Band)

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Introducing HCS in a Non-HCS Network

Introducing HCS with prioritized cell will change the behaviour of the NW in this areaBut in the rest of the NW the behaviour will mainteined compared with before HCS introduction:Assign to “Old” cells the Layer 3, and configurate the cell belonging at HCS area with Layers 2 or Layers 1 depending of traffic priority;

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Example Dual Band Network

GSM 900 & 1800 MHzOnly 1 HCS BAND, HCSBANDTHR= -95 dbmLayers: 4900 GSM Macro (Layer=8, LYTRH= -75 dBm)900 GSM micro (Layer=6, LYTRH= -75 dBm) for coverage1800 GSM macro (Layer=3, LYTRH= -75 dBm)1800 GSM micro (Layer=1, LYTRH= -75 dBm) for capacity

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Off-Load of Congestioned Cells (Single Band)

HCS is also used to off-loaded the congestioned cell

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Off-Load of Congestioned Cells (Dual Band in Co-site configuration

Also is possible to redistribute the traffic from a congestioned 900 Band to a low traffic 1800 BandThe Same LAYER for 900 and 1800 BandLAYERTHR (1800) from 75 to 80 dBm (rise the DCS coverage). A step of 5 dB at time for DCS BAND is a good rule.

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Penality for Fast moving MSsTo reduce the probability that a fast moving MSs increase the HO towards lower layer cells (too many HO in microcells and drop call for sudden reason) is implemented a penalty.Parameters involved:

PSSTEMP is the temporary signal strength penalty. It is set per cell.

PTIMTEMP is the duration of the temporary signal strength penalty. It is set per cell.

THO is the time interval for measuring number of handovers allowed (NHO ) before a mobile is considered to be a fast moving mobile. THO also defines the minimum time that an MS shall remain on a higher layer cell after a handover due to FASTMSREG . This will only be performed if the feature Handling of fast moving mobiles is activated in the cell (FASTMSREG ). It is given in seconds and set per BSC.

NHO determines how many inter-cell hadovers that should be allowed within the time period specified by THO before a mobile is considered to be a fast moving mobile. If the number of handovers exceeds NHO , the mobile is directed to a higher layer cell. It is set per BSC.

FASTMSREG is a switch for activating the mechanism that direct mobiles towards a higher layer at high handover rates. It is set per cell.

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HCS Parametrs Settings

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ConclusionsThe Mobile Operator has different area where the GSM 900 cells are congestioned respect at GSM 1800 co-site cells;In special event, like football games or concerts in the Stadiums, the unbrella cells are congestioned respect the microcells inside the Stadium;In Frankfurt city, the coverage of higher buildings, with dedicated GSM 1800 cells, also give great coverage in the street area where the coverage should be done only by umbrella GSM 900 cells;In these area is suggested an implementation of HCS feature and customized parameters settings.

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