Measurement system gives drive testing a new lease on life
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PRODUCT Focus TEST AND MEASUREMENT Measurement system gives drive testing a new lease on life Tim Brooks of PCTEL explains why a new network-measurement system improves interference management. Drive testing has always been a crucial part of wireless network planning and optimization. Regularly scheduled drive tests provide an effective means of tracking and maintainine Ö C" network performance as the network changes due to growth in traffic, addition of cells and changes in traffic patterns. Drive testing involves the measurement of signal propagation information as a function of location. This data is used throughout the network life cycle to predict coverage from proposed new cell sites, shorten network turn-up time, optimize network performance and quality, and manage interference. Drive- test figures are the most reliable way of deter- mining radio-frequency (RF) propagation and are also used to assist in network trouble- shooting. Data is also used by automatic fre- quency planning, automatic cell planning and other network optimization systems. Recently, drive-test data has been comple- mented by mobile-switch statistics. These are collected by the mobile switching centre based on measurements made by any mobile phone during normal network operation. These measurements, which include signal strength and carrier-to-interference ratio (C/T), are comprehensive and closely related to the end-user experience. Some believe that switch statistics will make drive-testing redundant, but recent developments have established that this is not the case. The CLARIFY GSM Interference Man- agement system from US-based PCTEL greatly improves drive-test performance. The system can determine C/l values down to -15 dB, which is far below the interference level. It automatically compiles an exact and measured matrix of the propagation for every sector in the network. This information can be used to determine the total channel power at a location and the power of the individual contributing base stations. The key benefit of drive testing is that it measures the actual propagation of signals from each cell site. This is almost always dif- interference V braken down into 13 component sources CLARIFY provides a breakdown of interference into component sources. This can be used to determine if the signal from one cell is causing interference in another. Here, fourspurs of interference are identified. ferent from what is predicted or expected because of reflections and clutter. During network deployment and roll-out, the focus is on achieving coverage. At this stage it is important for engineers to predict RF propa- gation in order to determine the coverage of new cells. Cells are then combined to create an effective coverage area. Managing interference Today, networks have established coverage patterns, a high density of cells and significant traffic. Interference management and con- tainment have therefore become equally, if not more, important than coverage planning. Interference management requires an under- standing of how signals propagate beyond the intended coverage area of a cell. This is because a strong carrier signal in one cell becomes an interference signal in other cells. The engineering challenge is to make changes within the network to reduce inter- ference by understanding the origin of the interfering signals. This daunting task is complicated by the fact that interference usu- ally comes from multiple sources that are dif- ficult to separate. The traditional approach is the key-up drive test, which measures the propagation from each cell site. This is done by assigning a unique channel to each cell and then dri- ving the nearby area to measure propagation and signal strength. Although relatively effec- tive in gathering the necessary information, this approach is costly and time-consuming because an individual drive is required for each cell site. Also, limitations on the amount of driving done per cell often restrict infor- mation gathering to the immediate vicinity. This is unlikely to detect signal propagation and interference in unexpected places. CLARIFY has two features that address the interference management challenge. First, by using highly sensitive radio scanners com- bined with post-processing and digital-signal- processing analysis of the measured signal, the system can detect and decode signals at -15 dB, below interference and noise levels. Second, by using techniques that identify the unique nature of signals from each cell site, CLARIFY can separate interfering sig- nals into components and identify where each component comes from. Propagation and interference patterns for many cell sites wireless europe wireless.iop.org October/November 2004
Transcript of Measurement system gives drive testing a new lease on life
P R O D U C T F o c u sTEST AND MEASUREMENT
Measurement system givesdrive testing a new lease on lifeTim Brooks of PCTEL explains why anew network-measurement systemimproves interference management.
Drive testing has always been a crucial part ofwireless network planning and optimization.Regularly scheduled drive tests provide aneffective means of tracking and maintainine
Ö C"
network performance as the network changesdue to growth in traffic, addition of cells andchanges in traffic patterns.
Drive testing involves the measurement ofsignal propagation information as a functionof location. This data is used throughout thenetwork life cycle to predict coverage fromproposed new cell sites, shorten networkturn-up time, optimize network performanceand quality, and manage interference. Drive-test figures are the most reliable way of deter-mining radio-frequency (RF) propagationand are also used to assist in network trouble-shooting. Data is also used by automatic fre-quency planning, automatic cell planningand other network optimization systems.
Recently, drive-test data has been comple-mented by mobile-switch statistics. These arecollected by the mobile switching centrebased on measurements made by any mobilephone during normal network operation.These measurements, which include signalstrength and carrier-to-interference ratio(C/T), are comprehensive and closely relatedto the end-user experience. Some believe thatswitch statistics will make drive-testingredundant, but recent developments haveestablished that this is not the case.
The CLARIFY GSM Interference Man-agement system from US-based PCTELgreatly improves drive-test performance. Thesystem can determine C/l values down to-15 dB, which is far below the interferencelevel. It automatically compiles an exact andmeasured matrix of the propagation for everysector in the network. This information canbe used to determine the total channel powerat a location and the power of the individualcontributing base stations.
The key benefit of drive testing is that itmeasures the actual propagation of signalsfrom each cell site. This is almost always dif-
interferenceV braken down into
13 component sources
CLARIFY provides a breakdown of interference into component sources. This can be used to determine if the signal from
one cell is causing interference in another. Here, fourspurs of interference are identified.
ferent from what is predicted or expectedbecause of reflections and clutter. Duringnetwork deployment and roll-out, the focusis on achieving coverage. At this stage it isimportant for engineers to predict RF propa-gation in order to determine the coverage ofnew cells. Cells are then combined to createan effective coverage area.
Managing interferenceToday, networks have established coveragepatterns, a high density of cells and significanttraffic. Interference management and con-tainment have therefore become equally, ifnot more, important than coverage planning.Interference management requires an under-standing of how signals propagate beyondthe intended coverage area of a cell. This isbecause a strong carrier signal in one cellbecomes an interference signal in other cells.
The engineering challenge is to makechanges within the network to reduce inter-ference by understanding the origin of theinterfering signals. This daunting task iscomplicated by the fact that interference usu-ally comes from multiple sources that are dif-ficult to separate.
The traditional approach is the key-updrive test, which measures the propagationfrom each cell site. This is done by assigninga unique channel to each cell and then dri-ving the nearby area to measure propagationand signal strength. Although relatively effec-tive in gathering the necessary information,this approach is costly and time-consumingbecause an individual drive is required foreach cell site. Also, limitations on the amountof driving done per cell often restrict infor-mation gathering to the immediate vicinity.This is unlikely to detect signal propagationand interference in unexpected places.
CLARIFY has two features that address theinterference management challenge. First, byusing highly sensitive radio scanners com-bined with post-processing and digital-signal-processing analysis of the measured signal, thesystem can detect and decode signals at-15 dB, below interference and noise levels.
Second, by using techniques that identifythe unique nature of signals from each cellsite, CLARIFY can separate interfering sig-nals into components and identify whereeach component comes from. Propagationand interference patterns for many cell sites
w i r e l e s s e u r o p e wireless.iop.org O c t o b e r / N o v e m b e r 2004
