Drive Test Concepts

Points To be considered in Survey

n  Most populated areas.

n  Business Centers.

n  Developing areas.

What To Plan

n  No. of Sectors required.

n  Type of Antenna & Height.

n  Capacity Required.

Frequency Planning

n  Frequency Reuse Concept.

      Use of same frequency at different

      places.

n  Co Channel Interference.

n  Adjacent Channel Interference.

n  Use of Map Info.

      BSIC Planning

n  BSIC = NCC + BCC. (Base station Identity Code).

n  NCC….(NETWORK Color Code).

n  BCC….(Base Station Color Code).

      Values Range From 0…..7.

Importance of BSIC.

n   Identify the BTS.

n  Used to reduce DROP Calls during Co Channel Interference.

n  Mobile can’t understand co channel & identify no difference between same frequency signal coming from two sites & so DROP Call. BSIC is the parameter that helps the mobile to  identify the different BTS. 

Drive Test

On Field Optimization

Include four tests

n  Verification

n  Drive in dedicated mode

n  Foot print

n  Hand over test

Verification

n  MOC Test

n  MTC Test

n  SMS Test

n  GPRS Test

Drive in dedicated mode

n  Checking signal strength in the entire coverage area.

n  Checking C/I, C/A.

Foot print

n  Checking the shooting distance of each sector.

n  Results of footprints are used in predicting interference in neighboring cell due to overshoot or similar problems.

Hand over test

n  Intra cell hand over

n  Inter cell hand over

Current Channel

n  Definitions:

1. Time: It is system time of computer.
2. Cell name: It displays the name of the sector which is serving according to the cellfile that is loaded in TEMS.
3. CGI : It stands for the Cell Global Identity which is unique for every sector of the site. It consists of MCC,MNC,LAC,CI.

      MCC: Mobile Country Code 0 – 999 (e.g. 404 in India), MNC: Mobile Network Code 0 – 99 (e.g. 98 for Airtel in Gujarat) LAC : Location Area Code 0 -65535 (e.g. 5101 in Gujarat) CI: Cell Identity 0 – 65535 (e.g. 11001)   

•          Cell GPRS Support:  Tells sector is having GPRS or not. Values are  Yes or No .

•          Band : It tells in which Freq. Band mobile is operating e.g. GSM 900/ 1800.

•          BCCH ARFCN: It tells by which BCCH is the mobile station getting served.

•          TCH ARFCN: On which Traffic Freq. call is going on.

•          BSIC (Base Station Identity Code) : It is combination of  Network Color Code (NCC) (0 – 7) & Base Station Color Code (BCC) (0 – 7). e.g. 62. It is decoded by mobile on every Sync. Channel Message. 

•          Mode: It is shows in which state is mobile operating, Idle, Dedicated & Packet.

•          Time slot: On which time slot of current TCH call is going on. Viz. time slot no. of  TRX.

•          Channel Type: Type of channel mobile is getting now.  Like BCCH / SDCCH/8 + SACCH/C8 or CBCH / TCH/F +FACCH/F +SACCH/F.

•          Channel Mode : Shows mode of coding like Speech Full Rate of Half Rate.

•          Speech Codec: It shows FR for Full Rate, HR for Half Rate & EFR for Enhanced Full Rate.

•          Ciphering Algorithm : It shows ciphering algorithm used by the system to protect data for privacy. E.g. Cipher by A5/2.

•          Sub Channel Number: It is displayed at  a time when mobile is on dedicated mode at time of call setup when it is getting SDCCH at that time it shows which SDCCH it is getting out of 8 available. E.g. 2.

•          Hopping Channel :  It shows that current sector is having hopping feature or not. Values are Yes or No.

•          Hopping Frequencies : It displays no. of  freq. on which mobile is allowed to hop. viz. MA List for hopping of that sector.

•          Mobile Allocation Index Offset (MAIO): It is the number  which tells from which freq. from given MA list for sector hopping has to be started. E.g. 0 means sector will start from first freq. to hop.

•          Hopping Sequence Number (HSN) : Indicates sequence in which  frequencies are allowed to hop from the MA List. 0- 63. 0 for Cyclic Hopping, 1 – 63 random hopping sequences.

Radio Parameters

•          RxLev : Receiving level in terms of dBm that mobile is receiving from the site. Range of -30 dBm to -110dBm.

•          RxQual : Quality of voice which is measured on basis of BER. Range of RxQual 0 -7.

•          FER : Frame Erasure Rate it represents the percentage of frames being dropped due to high number of non-corrected bit errors in the frame. It is indication of voice quality in network.

•          BER Actual : Ratio of the number of bit errors to the total number of bits transmitted in a given time interval. BER is a measure for the voice quality in network.. Depending on BER RxQual is measured. E,g, BER 0 to 0.2 %   corresponds to RxQual 0. Max. BER countable and useful is up to 12.8 % which corresponds to RxQual of max. 7.

•          SQI : SQI is a more sophisticated measure which is dedicated to reflecting the quality of the speech (as opposed to radio environment conditions). This means that when optimizing the speech quality in your network, SQI is the best criterion to use. SQI is updated at 0.5 s intervals. It is computed on basis of  BER and FER. For EFR 30, FR – 21 & HR – 17 are respectively ideal values.

•          C/I : The carrier-over-interference ratio is the ratio between the signal strength of the current serving cell and the signal strength of undesired (interfering) signal components. It should be atleast > 9 .

•          MS Power Control Level : Displays range of power control from 0 to 8 depending upon network design. E.g. 0 means no power control and  1 means level that is defined by operator viz. 2 dBm less acc. To airtel.

•          DTX : Discontinuous transmission (DTX) is a mechanism allowing the radio transmitter to be switched off during speech pauses. This feature reduces the power consumption of the transmitter, which is important for MSs, and decreases the overall interference level on the radio channels affecting the capacity of the network..

•          TA : Value that the base station calculates from access bursts and sends to the mobile station (MS) enabling the MS to advance the timing of its transmissions to the BS so as to compensate for propagation delay. Value of 0 means MS in radius of 550mt. From BS.

•          RL Timeout Counter (Cur) : This parameter define the maximum value of the radio link counter expressed in SACCH blocks. Range of 4 – 64 in step size of 4. it shows current value of RLT. Decrease by 1 but increase by 2. When it reaches zero it results in normal DROP Call.

•          RL Timeout Counter (MAX) : This parameter define the maximum value of the radio link counter expressed in SACCH blocks. Range of 4 – 64 in step size of 4. it shows current value of RLT. Normally 16, 20, 24. 

•          MS Behavior Modified : This window shows current settings for the mobile station, for instance whether handover is disabled or multiband reporting enabled. 

Serving + Neighbor

n  Cell Name : Name that describes the neighboring cell as per the cellfile.

n  ARFCN : Channel number mobile receives as neighbor.

n  BSIC : BSIC of the neighboring cell.

n  RxLev : Receiving Level in dBm of neighboring cell.

n  C1 & C2 : These are the cell path loss criterion and cell reselection criteria. Valid during idle mode of mobile station.

n  C31 & C32 : GPRS signal strength threshold criterion C31 and GPRS cell ranking criterion C32. Valid both in packet idle and packet dedicated mode.