Frequency Hopping - GSM

8/12/2019 Frequency Hopping - GSM

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Frequency Hopping

Frequency Hopping is an old technique introduced firstly in militarytransmission system to ensure the secrecy of communications and combat

jamming. Frequency Hopping is mechanism in which the system changes thefrequency (uplink and downlink) during transmission at regular intervals. Itallows the RF channel used for signaling channel (SDCCH) timeslot or trafficchannel (TCH) timeslots, to change frequency every TDMA frame (4.615 ms).The frequency is changed on a per burst basis, which means that all the bits ina burst are transmitted in the same frequency.

1. Frequency Diversity

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What is Frequency Hopping?

Advantages of Frequency Hopping
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In cellular urban environment, multi-path propagation exists in most cases.Due to Rayleigh fading, short-term variations in received level are frequentlyobserved. This mainly affects stationary or quasi-stationary mobiles. For a

fast moving mobile, the fading situation can be avoided from one burst toanother because it also depends on the position of the mobile so the problemis not so serious. Frequency Hopping is able to take the advantage due tofrequency selective nature of fading to decrease the number of errors and atthe same time they are temporally spread. As a result , the decoding and de-interleaving processes can more effectively remove bit errors caused by burstsreceived whilst on fading frequencies (errors will be randomly dist ributedinstead of having long bursts of errors). This increase in effectiveness leads to

a transmission quality improvement of the same proportion.

Frame Erasure Rate reduces due to 6 dB to 8 dB gain.

Number of reports with rxqual 6 and 7 reduce.

Reported values of rxlev are more concentrated around mean.


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involved in the criterion) from hopping relative to fixed frequency operation canbe achieved.

1/3 interference: 1 dB gain

i.e. if 1 out of 3 frequencies are experiencing a continuous interference a gain

of 1 dB in C/I requirement is obtained.

Similarly,





The effective gain obtained with Frequency Hopping is due to the fact that theinterference effect is minimized and it is easier to keep it under control.


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There are two ways of implementing Frequency Hopping in a Base StationSystem, one referred as Base Band Frequency Hopping (BBH) and another as

Synthesizer Frequency Hopping (SFH). Their operation differs in the way theyestablish the Base to Mobile Station link (downlink), however there is notdifference at all between Mobile Station to Base Station link in both types of hopping. Motorola does not allow BBH and SFH to be used together on thesame site

1. Base Band Frequency Hopping

This is accomplished by routing the t raffic channel data through fixed frequencyDRCUs via the TDM highway on a timeslot basis. In this case, the DRCU wouldhave fixed tuned transmitters combined either in low loss tuned combiners orhybrid combiners.

Types of Frequency Hopping


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DRCU always transmits fixed frequency.

The information for every call is moved among the available DRCUs on a per

burst basis. (Burst of 577 s)

Call hops between same timeslots of all DRCUs.

Processing (coding and interleaving) is done by digital part associated withDRCU on which call was initially assigned.

For uplink call is always processed by DRCU on which the call was initiallyassigned.

Number of DRCUs needed is equal to the number of frequencies in thehopping sequence.

BCCH frequency can be included in the hopping sequence.

Power control does not apply to BCCH or bursts transmitting BCCHfrequency.

BCCH, timeslot 0 will never hop.

Any timeslot with CCCH will never hop.

Timeslot carrying all SDCCHs can hop.

If a network running with fixed frequency plan is switched over to BBH (BCCHincluded in MA list) without any frequency changes, significant qualityimprovement can be observed in the network. As a result drop call ratereduces in the network. Alternatively, for the existing network qualityadditional capacity can be provided. FHI can be used effectively in BBH.Further details regarding FHI planning are discussed later in the document.


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2. Synthesizer Frequency Hopping

This is accomplished by high speed switching of transmit and receive frequencysynthesizers of the individual DRCUs. As a result of dynamic nature of thetransmit frequency, broadband (hybrid) combining of the transmitters isnecessary.

DRCU changes transmitting frequency every burst.

Call stays on the same DRCU where it started.

Remote tune combiners (RTC) are not allowed.

Number of DRCUs is not related to number of frequencies in hoppingsequence.


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BCCH can be included in the hopping sequence:

If BCCH is included in the hopping sequence, timeslots 1 to 7 can not be usedto carry traffic. They transmit dummy burst when BCCH frequency is not in theburst. Whenever BCCH frequency is being transmitted in a burst by DRCU, itwill be transmitted at full power.

BCCH DRCU will never hop. It either carries traffic in timeslots 1 to 7 or ittransmits dummy bursts. Transmission and reception is done on the same timeslot and same DRCU.

Motorola allows to have NBCCH on fixed frequency hopping on the samesector.

GSM defines the following set of parameters:

Mobile Allocation (MA): Set of frequencies the mobile is allowed to hop over.Maximum of 63 frequencies can be defined in the MA list .

Hopping Sequence Number (HSN): Determines the hopping order used in thecell. It is possible to assign 64 different HSNs. Setting HSN = 0 providescyclic hopping sequence and HSN = 1 to 63 provide various pseudo-randomhopping sequences.

Frequency Hopping Parameters


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Mobile Allocation Index Offset (MAIO): Determines inside the hoppingsequence, which frequency the mobile starts do transmit on. The valee of MAIO ranges between 0 to (N-1) where N is the number of frequencies definedin the MA list . Presently MAIO is set on per carrier basis.

Motorola has defined an additional parameter, FHI.

Frequency Hopping Indicator (FHI): Defines a hopping system, made up byan associated set of frequencies (MA) to hop over and sequence of hopping(HSN). The value of FHI varies between 0 to 3. It is possible to define all 4FHIs in a single cell.

Motorola system allows to define the hopping system on a per timeslot basis.So different hopping configurations are allowed for different timeslots. This isvery useful for interference averaging and to randomize the distribution of errors.

GSM has defined an algorithm for deciding hopping sequence. The algorithm isused to generate Mobile Allocation Index (MAI) for a given set of parameters.

ARFCN: absolute radio frequency channel number

MA: mobile allocation frequencies.

GSM algorithm


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MAIO: Mobile allocation offset (0 to N-1), where N is the number of frequenciesdefined in MA.

HSN: Hopping sequence number (0-63)

T1: Super frame number (0-2047)

T2: TCH multiframe number (0-25)

T3: Signaling multiframe number (0-50)

This algorithm generates a pseudo-random sequence of MAIs. MAI along withMAIO and MA will decide the actual ARFCN to be used for the burst.


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conventional fixed frequency plan with lesser number of frequencies. This planneeds to be done very carefully as the system monitors cells based on theBCCH frequency only. Since BCCH carrier radiates continuously withoutdownlink power control, frequencies used for BCCH on one cell should not beused as hopping frequencies on other cell. The reason is to avoid continuousinterference from BCCH carriers. The benefits of hopping increase if more

frequencies are available for hopping. Generally the frequency band is dividedinto two parts, one used for BCCH frequency plan and other for hoppingfrequencies. The division of frequency band for allocation of BCCH and hoppingcarriers should be done to maintain reasonable C/I for BCCH carriers as well asto have enough frequencies for hopping.

e.g.

consider a network with 31 frequencies, using 12 frequencies for BCCH andusing 18 for hopping with 1 frequency as guard, is the ideal option. But it maynot be practically possible to plan BCCHs with 12 frequencies (4/12 reuse).Using 15 for BCCH plan and 15 for hopping frequencies is more practical. Therealways exists a trade-off between BCCH and hopping plans. Using very lessfrequencies for BCCH plan might result in poor quality on BCCH carrier and theadvantages of having quality improvement on hopping carriers may be lost.The ratio between hopping and BCCH frequencies should be decided based onthe ratio of number of BCCH and NBCCH carriers in the network.

In case of BBH, generally BCCH carrier is included in the hopping sequence.The benefits of BBH can be obtained only when most of the sites in thenetwork are having more than one NBCCH carriers. Benefits of BBH comparableto SFH can only be obtained by equipping additional hardware in order toinclude more frequencies in hopping sequence. However BBH withoutadditional hardware will result in quality improvements and provide scope of additional capacity as compared to fixed frequency plan though the benefits


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may not be as significant as seen in SFH.

2. Planning of HSN:

HSN allocation to the cells is done in random fashion. Various scenarios areexplained below:

a. MA list is same for all the cells of the s ite In this case HSN is kept samefor all the cells of the site. MAIO is used on per carrier basis to provide offsetfor starting frequency in hopping sequence and avoid hits among carriers of thesite. Practically it is possible to achieve 0% hit rate within the site, as all thecells of the same site are synchronized.

b. MA list is same for the cells of different sites In this case HSN should bedifferent for all such cells. MAIO can be same or different in this case as HSN

is different.

c. MA list is different for the cells In this case HSN planning is notimportant, as there can not be any hits between these cells.

d. HSN is set to 0 This is the case of cyclic hopping. The sequence forhopping remains same and is repeated continuously. This is not recommendedin the urban environment where frequency reuse is more. This is because the


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network is not synchronized so if there is any one hit it will result incontinuous sequence of hits. Cyclic hopping is preferred in rural environmentas it provides the maximum benefits of frequency diversity.

3. Planning of MAIO:

The benefits of MAIO planning can be best achieved only in case when sectorshaving same MA list are synchronized. For non-synchronized sectors MAIO canbe the same. In the previous version (GSR2), Motorola did not provide manualMAIO setting. It was set automatically by the system. However from GSR3onwards it is be possible to set MAIO manually. It has to be changed on acase to case basis. In cases where there are large numbers of hits, MAIOchange can be effective as it adds the offset in the hopping sequence and hit-rate can be reduced.

4. Planning of FHI:

This parameter is not specified in GSM. FHI is the Motorola defined hoppingsystem. It actually means an independent hopping system consisting of MA

and HSN. Total of 4 such hopping systems can be set in a cell.

FHI can be defined on a timeslot basis.

e.g. consider a cell with 3 carriers i.e. 2 carriers are hopping. It is thenpossible to define 4 different FHIs for 16 timeslots. That means timeslot 0 to3 of 1 carrier can have one FHI and so on.


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Benefits and Drawbacks of FHI

Separate FHI can be defined even for each carrier with separate MA list.

For a fully utilized cell, FHI can be used to control increase in hitrate duringpeak hours. This can be done by defining different MA list associated with aFHI for one of the carriers.

Main benefits of FHI can be obtained in BBH. Consider a cell with 2 carriersusing BBH with BCCH included in the hopping sequence. Timeslot 0 of BCCHwill not hop. A separate FHI (with MA list without BCCH frequency) has to bedefined for timeslot 0 of NBCCH.

Different FHIs in the same cell is not used extensively in Motorola networkswith SFH, where BCCH frequency is not included in hopping sequence.

One drawback of using FHI on timeslot basis is that it adds more complexityto the database.

5. Reuse pattern for hopping carriers:

Conventionally there are 3 main reuse patterns followed for hoppingfrequencies.


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1 X 1: It means all the cells in the network use the same frequencies forhopping.

e.g. If 15 frequencies are to be used for hopping, then every cell will have all15 frequencies in the MA list. This type of reuse is useful in urban areas,where capacity requirement is large. However there is very less planninginvolved and so less control over quality problems.

3 X 9: Three hopping groups are used in 3 sites, one per site. In this case allthe sites should be considered as omni sites for planning frequency reuse. Theadvantage of this scheme is it provides better isolation between sites usingsame hopping frequencies. The problem with this method is that, addition of new site may require frequency replan for the area.

1 X 3: This scheme is very commonly used in Motorola networks. Hoppingfrequencies are divided in 3 groups. Each cell on a site uses one group and itis repeated on all si tes. e.g. consider a network with standard orientation, allV1 sectors will use the same group and so on. It is very easy to add a site inthe network. This reuse scheme is suitable for homogeneous network withminimum overlapping areas. The problem with this scheme is in peak hoursthere may be more hits.

Loading Factor: This parameter is a deciding factor for number of carriers thatcan be equipped on a sector or a site. Number of carriers equipped on a site orsector should not be greater than 50% of the number of frequencies in the MAlist of the sector or site. This factor is a major distinguishing factor between 1x 1 and 1 x 3.


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6. Tools for simulation and drive test: Motorola uses a tool Handsem whichcan simulate SFH plan (different reuse patterns and HSN plan). Latest versionsof plaNET and Golf are supposed to support Frequency Hopping simulation.Drive test tools that display decoded layer 3 information are used for

monitoring frequency hopping networks. TEMS is one of the drive test toolsthat can be used for the purpose.


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1. Handovers: When SFH is implemented, BCCH plan is done using lessernumber of frequencies as compared to fixed frequency plan. This may result inquality degradation. However quality of hopping carriers improves thanbefore. Also, quality threshold for handovers on hopping carrier should beincreased as compared to fixed frequency plan. In the present version (GSR3),different quality threshold settings are set BCCH and NBCCH. By setting lowerquality thresholds for BCCH as compared to NBCCH, number of dropped callscan be controlled. Handover Success Rate may go down because of the BCCHreplan (less frequencies). This reduction may get compensated due toimprovement in quality of hopping carriers (improvement in TCH assignmentsuccess rate).

2. Call setup: In call setup, SDCCH hopping is also possible. There are noseparate settings required for SDCCH hopping. Since GSR3 allows control overSDCCH configuration (location of SDCCH on timeslot basis), SDCCH hoppingdepends on the location of SDCCH. In case of SFH (with BCCH not included inMA list), if SDCCHs are on BCCH carrier they will not hop whereas SDCCHs onNBCCH carriers may hop. Generally it is preferred to keep SDCCHs on BCCHcarrier as SDCCH timeslot is used continuously and it will increase interferenceon hopping carriers. Call success rate will depend on the cleanliness of BCCH

Effect of Frequency Hopping


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carriers. Call Success Rate may reduce after BCCH replan. This reduction mayfet compensated due to improvement in quality of hopping carriers(improvement in TCH assignment success rate).

3. Frame Erasure Rate (FER): FER indicates the number of TDMA framesthat could not be decoded by the mobile due to interference. This parametergives the indication of hit-rate. FER improves (gain of 6 to 8 dB) afterimplementation of frequency hopping. FER is represented in percentageterms. FER less than 10% is considered to be good. But this is a subjectiveissue and good value should be decided by doing multiple drives. In futureMotorola is planning to include FER as a statistics in the OMCR.

Implementation of Synthesiser Frequency Hopping (Mumbai Network):


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4 x 3 frequency reuse plan is used which theoretically needs 12frequencies. However it is not possible to plan Mumbai network in 12considering the terrain. So remaining 4 frequencies will be used selectively.Also there is a plan to reserve these for micro cells. BCCH plan has been made

considering quality as a major criteria. E.g. sector looking towards AltamountRoad has lesser re-used frequency.

NBCCH plan:

1 x 1 plan: all 15 or 16 frequencies in all the cells . As per loading factordefinit ion there can be 7 NBCCH carriers equipped on a site. This gives someflexibility to RF Planner to have irregular configuration on each site. E.g. 3-3-4or 3-4-3 or 4-3-3 or even 2-5-3 or 2-2-6 configuration can be used on the site.It is even possible to use 8 NBCCH carriers on a site but it will result inincrease in interference in surrounding sites . However this can be used on acase to case basis. It was decided to go for 1 x 1 after 1 x 3 implementation.

1 x 3 plan: the band is divided into 3 parts

Set 1 (S1) 32, 35, 38, 41, 44

Set 2 (S2) 33, 36, 39, 42, 45 Set 3 (S3) 34, 37,40, 43, 46


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These sets are used on a sectorwise basis. Set 1 is used preferably in sectorV1 and so on. The use of these sets is related to the orientation of thesectors, so that same set is not used on sectors looking at each other.

Since there are 5 frequencies in each sector, as per definition of loading factor,there can be only 2 NBCCH carriers equipped on each sector. 3-3-3 is the onlyconfiguration allowed in this plan. If configuration like 3-4-3 is required then 4NBCCH should be in fixed frequency mode. Use of 4th NBCCH is hoppingcarrier results in more hits on surrounding sectors that are using same MA listset. However this can be used on a case to case basis.

Other issues:

1. Previously in Area A in 129 cells (48 sites) BCCH frequency reuse wasmaximum of 9 times (average use 4.4 times). In the new BCCH plan (for SFH)frequency reuse is maximum of 12 times (average use 8.6 times). The mainreason for this is we used entire band of 30 channels for BCCH earlier.However the new BCCH plan is made just from the 15 frequencies.

2. This increase in reuse is definitely going to degrade BCCH carrier quality ascompared to present situation.

3. BCCH carrier is very important for logging on to the network or staying inthe network. Even in the present plan we have observed problems of logging

on to the network (Express towers top floor). This problem might elevate afternew plan.

4. Present version of BSS software assigns SDCCHs on BCCH carrier only.Since BCCH quality is going to degrade, option of SD location will have to bepurchased.

5. Hopping carriers will have much better call quality than present frequency


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plan. There is a possibility that the quality difference in quality on BCCH andNBBCH may be significant. TCH priority (priority to allocate TCH) option mayalso be needed.

6. It is presumed that addition of the site is very easy in SFH. It is very truefor NBCCH carriers. But the BCCH plan for new sites is more difficult.

1. Reduction of overlaps of the existing coverage of all sectors by antennaoptimisation.

2. Preparation of BCCH Plan Area wise and drive test data collection and

analysis

3. Simulation of BCCH plan using NBCCH at full power feature.

4. Implementation of BCCH plan with NBCCH in fixed frequency mode.

5. Optimisation of BCCH plan.

Planned events for implementation:


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6. Implementation of hopping plan on trial basis in Vashi BSC

7. Optimisation of Vashi BSC in 1 x 3 Hopping plan

8. Testing of features in Vashi BSC

9. BCCH Plan for the entire network and monitor for 1 week

10. Optimisation of the BCCH Plan

11. Implementtaion of 1 x 3 hopping plan in the network

12. Drive test areawise collection of drive data and anlaysis.

13. GOS monitoring and analysis .

14. Optimisation of 1 x 3 Plan

15. Enable down link DTX and monitor

16. Plan for 1 x 1 plan.

17. 1 x 1 plan in the network

18. Optimise the 1 x 1 plan

Summary of Tests conducted:

a. CellAd Drive test (subjective voice quality - Mean Opinion Score)

b. Monitoring Customer Complaints

c. Addition/Deletion of carrier

d. Addition of Site


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e. Parameter Changes MAIO/HSN

f. To try & use Guard Band

g. Install a Repeater

h. Change in MA List ( No. of Frequencies)

i. Cell Broadcast Facility

j. SDCCH Hopping

k. Enable Uplink DTX

l. Enable combined and non-combined multiframe.

m. Enable Downlink DTx

n. Combination of DTx and multiframes.

o. RCU failures after switchover to hopping.

p. NBCCH full power in hopping environment

q. Extended paging.

r. Various combinations of extended paging, DTx and combined/non-combinedmultiframe should be tried out.

Activities in SFH Implementation:


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1. The parameters and statistics be monitored at OMCR

RF Loss rate

TCH RF Loss Rate

SDCCH RF Loss Rate

Handover Failure Rate

Handover Success Rate

TCH Assignment Success Rate

Call Success Rate

Drop Call rate

Drop Call Rate per Erlang

Interference on Idle

Out_ho_cause_atmpt

2. Drive Test

Drive test should be done using Tems and CellAD or Buzzard (subjectivevoice quality measurement).

Enough samples of drive tests should be taken before after each changemade to the network (or part of the network)

FICS report should be generated to check the drive test results.


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d. Non Combined & Extended Paging No Problem Found

e. NBCCH at Full Power Quality degradation observed in

some areas but no degradation in FER.

f. 1 X 1 re use plan Some Quality improvement observed

in Vashi Bridge area

g. Change in MA List No Improvements

h. Locking of Boundary site neighbours No Improvements

i. Integration of Koperkhirane Difficulty in BCCH plan &

Ease in NBCCH Plan. Degradation in neighour sites observed

j. Downlink DTx No problems found.

k. Downlink DTx and extended paging Siemens S3+ does not do location

update.

l. Extended Paging No problems found

5. Summary of problems observed after 1 x 3 implementation:

Drive Tests:

Observations : From the drive results following are the areas that had shown Voice Quality problems.


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Area A Alta Mount Road, Walkeshwar, Chowpatty

Area B E.Moses Road, Bandra Kurla Complex, Mahim-Sion Link Rd.

Area C Band Stand, Carter Road, SV Road near Mithibai College, Western Express Highway near Domestic Airport, Powai

Area D LBS Road Near Kurla, Eastern Express Highway near Chembur.

Area E Marve Road, Vasai, Essel World

In the above areas Rx Voice Quality was in levels of 6 & 7. However the call did not drop.

TEMS Drive was repeated to check consistency of the results. In some areas consistency could not beestablished. The results are dependent on the traffic (loading) carried during the drive and also on the qualityof BCCH or the hopping carriers.

GOS Statistics:

Observation: In general, it was observed that in all the BSCs the HSR, CSR, DCR have degradedmarginally except in Powai BSC and Thane BSC, where, there was considerable degradation in HSR.

Following sectors were found to be degraded:

CSR Degradation : HSR Degradation :


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1. Flora Fountain V3 1. Cuffe Parade

2. Eros V2 2. Bandra Kurla V3

3. Santacruz V1 3.Mahim Station V1

4. Mahim Station V3 4.Vashi Sect-17 V3

5. Crawford Market V1 5.Belapur V3

6. Juhu Galli V2 6. Kalamboli V1,V3

7. D Road V1 7. Girgaum V3

8. Kings Circle V3 8. Sewree V3

9. Mira Road V3 9.Sahar V1

10.MIDC V1

11.Powai Hirmdani V1

12.Mumbra V1

13.Kalyan V1

14.Ghodbunder Road V2

15.Charkop V1

Of all the BSCs it was observed that Powai BSC has degraded considerably in HSR, CSR and DCR. Sixsectors have HSR less than 90% in this BSC.

In Thane BSC, it was observed that the HSR has gone low in 4 sectors and DCR has gone high in 2 sectors.


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Coverage Reduction:

It was observed that after implementing hopping in the network, following sectors have shown coveragereduction. This was observed during the drive tests and problem statements have been issued to check theBTS power and VSWR .

The sectors are:

1. Andheri V1

2. Bandra Causeway V2

3. IES V1 (for additional 2 carriers)

4. Thane V2

5. Thane Stn V1

6. Vashi V2

7. Kings Circle V1

8. Kalina V2, V3

9. Malad V3

Power Control in SFH :

Uplink and downlink power control is enabled in the network. No changes have been made in parametersthat were working in fixed frequency plan.


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Observation:

If there is degradation in quality the downlink or uplink power increases. But sometimes intracell handover takes place without mobile or BTS radiating at full power. Ideally downlink or uplink must radiate at full

power before any handover.

Idle Channel Interference:

Observation: In the following sectors wehave observed that the Idle Channel Interference was very highduring some parts of the peak hour. Due to this there was degradation in call success rate and SD loss factor.In case of Flora Fountain V3 the timeslots on BCCH showing high idle channel interference went out of service.

1. Goregaon V3 only on BCCH

2. Sher E Punjab V3 only on BCCH

3. JP Road V2 - both

4. Flora Fountain V3 only on BCCH

The problems gets solved after change of frequency to dummy carrier.


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Loading Problem on sites with 3 hopping carriers:

Observation: In sectors that have 3 NBCCH Carriers, it is observed that there is degradation in performance of surrounding sectors with same MA list during the peak hours. This is due to the fact that 3

NBCCHs are hopping on 5 Frequencies of the MA List. The problem observed in area near Flora FountainV2 (degradation in Eros V2) and in Santacruz Market V1 (degradation in Santacruz V1). Presently, the 3rd

NBCCH hopping carrier is converted to fixed frequency carrier. After this change the performance of thesites have improved. Still in the network following four sectors are with 3 NBCCH hopping carriers:Pancharatna V1, Opera House V3, Vashi BSC V2, Hindu Colony V3.

Carrier Additions in sites which has 3 Carriers :

Need has come to increase the number of carriers in JP Road V1 from 3 to 5. Due to the MA List of only 5carriers and also due to the loading problem, further carriers cannot be added in the 1x3 Plan. Hence we hadto resort to allocating Dummy frequencies and to put them in Fixed frequencies. Thus 1x3 hopping planrestricts carrier addition in sites that has 3-3-3 carriers.

Repeater site Visits:


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After implementation of SFH, following few repeater sites were visited to check for the coverage.

1. Heera Panna

2. Churchgate BPL Gallery

3. PH Business Centre

4. Kamats, Cuffe Parade

Observation:

There was not any degradation in signals observed in the above places. The power level and coverage werethe same as it was during the Fixed plan.

Data Call :

On drive data call was made to check the data call feature in Hopping mode. The data was tried both inMobile to Mobile calls and in Mobile to PSTN Call.

Observation:

The data call facility worked well in areas where the Rx Qual was upto 6. In areas where there were multiple6 & 7 the data call dropped.


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Also it was observed that for files of size 200KB, the data transmission takes at a speed of 8KB to 8.5KBand the data rate goes down to 5KB. Never the data is transferred at 9600KB.

Co Channel BCCH and Co Channel BSIC Care has been taken to avoid Co channel BCCH and

Co BSIC problems during implementation of SFH, it was observed that the Co channel BCCH and Co BSICof neighbours also to be avoided. This problem is not visible on field but it results in degradation in HSR.Hence as a precautionary measure, following BSIC changes were done in the network.

Downlink DTx

1. Location update tests were done in location area boundary between Sion V1 and Chunabhatti V2 (LAC122 and 123). These checks were done to check location update from Sion V1 to Chunabhatti V2 and

back. Calls were initiated and received on all the phones to check whether location update has taken place.

2. Following phones were used for testing:

Siemens S3+

Siemens S4, S4 power

Siemens S10

Sony CMDX1000


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4. Drive 4: Sion V1 BCCH non-combined, SD on NBCCH (hopping), no extended paging, DTx enabled.

- Result: No problems found

5. Drive 5: Sion V1 - BCCH combined, SD on BCCH, no extended paging, DTx enabled.

- Result: No problems found

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