GSM BASICS Which Are Indeed for a Drive Test Engineer - Copy (2)

8/12/2019 GSM BASICS Which Are Indeed for a Drive Test Engineer - Copy (2)

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GSM BASICS which are indeed for a drive test engineer

Downlink and Uplink: The uplink (MS to BTS) frequencies are in the area 890 - 915 MHz andthe downlink (BTS to MS) frequencies in the 935-960 MHz.

Downlink RF Characteristics: RxLevel, RxQual, FER, MS-TX-Power etc.

Particular frequency and Network Capacity: the more often you use a particular frequency

within your network, the more capacity you can provide by your network. You will learn more

about this topic by analyzing and implementing frequency plan (the shorter the distance, thetighter frequency planning allow more subscribers in the network)

Radio Network Capacity: depends on the number of cells on-air and the number of channels

associated with each cell. The number of channel is increased in each sector, the erlong valuewould increase which allow more subscribers in the network

Transmission hop: a combination of sending and receiving ends.

Traffic: a load due to the calls generated by the subscribers.

Erlang: is the unit of traffic; one erlang means one busy subscriber/line

Tilting: is a way of mounting the cellular antenna, there are two type of rectification tasks could

be done during your DT, up-tilting (the signal is transmitted at a positive angle) and down-tilting( the signal is transmitted at a negative angle with the horizon)

Burst: time slots are arranged in a sequence 0-7, the repetitions of this sequence is called a

TDMA frame, the information content carried in one time slot is called a burst.

Accessibility: SDCCH serviceability * TCH accessibility. Repeated short call set-ups must be

exercised to measure accessibility performance of the network.

Retainibility: it takes all type of drops into consideration, for measuring retainibility and integrity

of a network, long continuous calls must be performed by drive test

SWAP NIGHT FUNCTIONALITY TEST

Make sure you have loaded correct cell file before proceeding to collect log file

Make sure one MS is in dedicated mode( long call) to measure quality and one MS is inIdle mode to scan all BCCH frequencies and another to make short call

Measure MPD from long call + short call, Integrity; SQI from long call, RxQual fromlong call, RXLevel from Idle mode, coverage area probability from idle mode, E2E call

establishment success rate from short call



Compare the LAC ID, CI and BCCH according to your MDB and CRF of a new site

You can disable Cell File and start collecting log file when you face some sort of error inyour cell file.

When you find RxLevel and RX Qual are poor (bellow the marks) just let yourcoordinator know the findings: it may be the effect of hardware installation error.

When you face some sort of HO problem, let your coordinator know the issue and try to

find out whether all the neighbor relations are well defined or not; check site status: all

the sites are on air. Prompt force HO and moving around 100 meter could be done toidentify the real situation of your target cell.

Call termination problem due to overlay and underlay: check BCCH and let your

coordinator know the issue

Always keep an eye on radio parameter, current channel, serving neighbor, C/I and C/A

If the RxLevel bad and RxQual is also bad then HO is due to RxQual

If RxLevel is bad and RxQual is good then HO is due to RxLevel

When BSIC and frequency are same; the SQI goes negative

There won’t be any significance difference between RXLevel sub and Rxlevel full whenDTX is disabled

If you find call originating problem then click on presentation>signaling>layer3Messages>properties>event to check message type|type6|type13|NCC|Message

Type|LAC|NCC permitted|Band allocation|termination Failure

Range and threshold value of RxLevel sub ( -10dBm to -115dBm, higher is better,

threshold value -95dBm) RxQual ( 0-7, lower is better, threshold value 5) SQI (-20 to 30,

threshold value 18, higher value is better) C/I (-5 to 20, threshold value 12, higher valueis better) FER full (lower value denotes the better network ) BER actual (the lower the

value, the better the network ) RxLevel full ; a higher value represents better scenario.

Cell reselection for cells in same location area

If the C2 value of the target cell is higher than that of the serving cell and last for longer than

5 seconds, a cell reselection process will be performed and the MS tunes to the new

cell.

Cell reselection for cells in different location areas



If the C2 value of the target cell is higher than that of the serving cell by at least the value of

CRH and last for longer than 5 seconds, a location updating process and the cell

reselection process will be performed.

Cell reselections caused by C2 have a time interval of 15 seconds

If current serving cell is prohibited, or down link fails, or C1 is less than 0 continuously for

5s, cell reselection will also be triggered.

MS starts a cell reselection if the access times exceed the MAX retrans .

C2=C1+CRO-TO*H(PT-T)

When PT is not equal to 31:

C2=C1-CRO

When PT is equal to 31. Wherein:

1. Function H(x)=0, when x<0; H(x)=1, when x>0.

2. T is a timer with initial value 0. When a certain cell becomes of one of the six neighbor cells with highest

signal level, T corresponding to this cell begins to count with accuracy of one TDMA frame (about

4.62ms). When it is out of the six strongest neighbor cells, the corresponding timer is reset.

3. CRO is used for manually correct the cell reselection parameter C2.

4. The function of TO is to reduce the value of C2 from the time when timer begins to count to the time when

the value of timer reaches the stipulated PENALTY_TIME.

5. PT is the time TO acts on C2. But PT=31 is reserved as the symbol to change the CRO’s effect on C2.

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GSM BASICS Which Are Indeed for a Drive Test Engineer - Copy (2)