GPRS optimisation and Network visualization Janne Myllyl T-110.456 - PowerPoint PPT Presentation

GPRS optimisation and Network visualization Janne Myllylä T-110.456

Topics •What do we need to know? •Different types of information available •Basics of GPRS capacity optimisation Janne Myllylä T-110.456

Planning •The network elements: •type specific information (e.g. family, radiation patterns) •current settings •Geographic information •Land use •Building height •Statistics •Models Janne Myllylä T-110.456

Planning •Using the information we can estimate: •Network capacities in different areas •Overall service quality •Affect of changes in the network •Problems: •Models work in a perfect world •Map information is never up-to-date or accurate •Butterfly effect Janne Myllylä T-110.456

Are there more accurate methods? •Network performance can also be measured •Field measurements •Network measurements Janne Myllylä T-110.456

Optimisation basics Optimise Nokia NetAct Analyse Provision Measure Janne Myllylä T-110.456

Measurement types •Call/Session •Radio Quality •Volume Janne Myllylä T-110.456

Field measurements + •Basically a modified cellural phone is driven on a route. •Reliable information available without much traffic volume •Vendor independent • Can measure competitors network performance - •A lot of driving around needed. •Measurement sample time is very limited Janne Myllylä T-110.456

Network measurements + •Almost all possible events are measured. •Measurements span over a longer timeperiod - •Not very standardized. Different vendors measure and collect slightly different data. •Moderate traffic volume is needed for reliable measurements. •The total amount of data is huge. Janne Myllylä T-110.456

Busy Hour •The distribution of traffic is not even. During weekdays there occurs peaks in the network usage. •Radio networks don’t generally react well to traffic increase •According to common sence: Network behaviour during the busy hour is the weakest link. •Heuristics can be used to identify the bh. Janne Myllylä T-110.456

What is visualized •Network static information •Locations & directions •Parameter values •Relations between elements Janne Myllylä T-110.456

What is visualized • There are dozens of raw measurements (Performance Indicator) that are related to GPRS performance. •User wants to see the result of a preliminary analysis based on the raw measurements (Key Performance Indicator). Janne Myllylä T-110.456

KPI •Traditional benchmarks ( BER, FER, CSR, HSR ) •(E) GPRS data related •Reliability, max probability of erroneous RLC •Throughput, amount of RLC payload •Delay, measured time between SGSN and mobile •(E)GPRS load, timeslots utilized by GPRS service •And many more Janne Myllylä T-110.456

Visualizing KPI •Snaphot of network state: •Performance of network on map •List of elements not behaving within thresholds •Trend of measurements •Time based comparison between different elements / measurements •Performance animations on map Janne Myllylä T-110.456

Network capacity balancing •In GSM network the available capacity is defined by timeslots dedicated for different services. •It is possible to dimension timeslot usage between •SDCCH •CS •PS Janne Myllylä T-110.456

Visualization of timeslot usage Janne Myllylä T-110.456

Visualizing service performance Janne Myllylä T-110.456

Visualizing cell level performance Janne Myllylä T-110.456

Effect of timeslot redimensioning 6 % The relevant analysis of CS 5 service performance need to 4 PS be continuous, since without 3 increase of total capacity SDDCH 2 timeslot dimensioning is always compromise. 1 0 3.1 10.1 17.1 24.1 Janne Myllylä T-110.456

Treatment classes •Assigning GPRS capacity for different service classes •PoC •Streaming •Corporate •MMS •Diverse DL/UL QoS requirements. Janne Myllylä T-110.456

QoS Priorisation TREC 3 TREC 2 TREC 1 TREC 0 T-110.456 GPRS Capacity and QoS Capacity Balancing Janne Myllylä Speech Capacity offered for various services Priorisation SMS �

Running out of capacity 7 Dimensioning can now 6 CS only be used to increase 5 CS performance. PS 4 SDDCH The only way to improve PS 3 performance is to increase 2 the total capacity. 1 0 3.1 10.1 17.1 24.1 Janne Myllylä T-110.456

How to increase capacity •Some of the traffic volume could be redirected to other cells •A new serving cell can be setup •TRXs can be added for the current cell(s) to increase total amount of timeslots •Impact matrix Janne Myllylä T-110.456

Impact matrix •Also known as Interference matrix •All cells whose signal has been measured in serving cells dominance area • Handover possibility •Used to determine which cells could cause interference with serving cell. Janne Myllylä T-110.456

Interference basics •The frequencies have traditionally been planned using reuse patterns and propagation models •In order to increase the traffic capacity, the channel re-use becomes tighter •Too tight use of the same and adjacent channels causes a decline of C/I � BER and FER increase, worse coding schemes Janne Myllylä T-110.456

Interference without hopping •When no hopping is used some timeslots will constantly have more problems than others. •After too much reuse performance deteriorates quickly Janne Myllylä T-110.456

Too tight reuse on map T-110.456 Janne Myllylä

Averaging behaviour •Frequency hopping may be used to average network behaviour •Main idea is to reduce continuous bad performance between mobile and bss. Janne Myllylä T-110.456

Averaged behaviour on map T-110.456 Janne Myllylä

Hopping mode: BB •In BB hopping TRX frequencies don’t change, but TRX serving the mobile phone does. •Total amount of frequencies in BB hopping is the same as the number of TRXs. •Also BCCH timeslots 1-7 are included in the hopping. Janne Myllylä T-110.456

Hopping mode: RF •In RF hopping TRX serving the mobile phone doesn’t change, but TRX frequencies do. •In RF hopping an allocation list contains frequencies that are used. •BCCH TRX is not hopping. •N channels enables 64*N different hopping sequences. •MAIO offset has as many values as allocation list has channels •HSN can be selected from 64 different sequences. Janne Myllylä T-110.456

Hopping mode comparison BB TRX-1 RF BB TRX-2 RF BB TRX-3 RF Mobile hops the same frequency pattern in both modes Janne Myllylä T-110.456

Measured performance 3.5 3 DCR 2.5 2 BB RF 1.5 1 0.5 0 EFL 1 2 3 4 5 Basically RF hopping enables a more tight channel reuse Janne Myllylä T-110.456

Extreme channel reuse •Two types of service areas inside cell: •Normal with regular reuse patterns (overlay) •Small with extreme reuse (underlay) •The same underlay frequencies are used even in neighboring cells. •Cell tries to make as much as possible of the traffic volume to use the underlay frequencies. Janne Myllylä T-110.456

Extreme channel reuse •The same traffic volume can be managed with less frequencies. •With this example situation 3 underlay TRXs could free 6 frequencies. underlay Janne Myllylä T-110.456

References 3GPP TS 25.215 V6.0.0 Physical layer – measurements 3GPP TS 23.107 V6.2.0 QoS concept and architecture Halonen, Romero, Melero: GSM, GPRS and EDGE performance Janne Myllylä T-110.456