OpenSignal: GSM WCDMA LTE WI-FI - 2G 3G 4G (Cell Coverage) Signal Maps

Here at telecomHall, as you already know, we share tips and interesting suggestions geared to the technical audience, people who works with Telecom and IT. But today we are going to talk about a very interesting application, but that doesn't only apply to these professionals, but to everyone that use wireless devices.
Introducing OpenSignal, an application that performs Cellular and Wi-Fi Networks data collection, and use it in building a comprehensive public map with information for all these networks around the World.

And gets it through a technique that should be increasingly exploited in other applications: the collaboration of all users, with beneficial results to all.

Then, let's go to see the application?

UMTS/GSM/LTE/CDMA/EVDO Network Monitor and Drive Test tool

This is a fieldtest/netmonitor application for UMTS/GSM/LTE/CDMA/EVDO network.

The application monitors the serving CELLID, LEVEL, QUAL, MCC, MNC, LAC, technology, cell serving time and neighbor cells CELLID/PSC and LEVEL.

LEVEL and QUAL depend on technology:
- 2G - RXLEVEL and RXQUAL
- 3G - RSCP and ECNO
- 4G - RSRP and RSRQ

Only for 4G also SNR and CQI are monitored.
The reported measurements depend on the phone and are not available on all mobiles. For example most phones do not report RXQUAL on GSM and only some report ECNO on 3G.

Multiple Reuse Pattern Technology

 Basic Principle

According to multiple reuse pattern (MRP), the carriers are divided into several groups. The carries in each group work as an independent layer, and each layer uses a different frequency reuse pattern. During frequency planning, you can configure the carriers layer by layer, with reuse aggressiveness increases layer by layer.

MRP has no special requirement on hardware. It is developed from the concept of carrier layering. That is, the available channel numbers are divided into multiple groups, and each group works as a carrier layer. According to the rules of the aggressive frequency reuse pattern, the channel numbers allocated for each layer are listed in Table:

Channel number allocation for each layer

Layer	Channel number
BCCH	n1
TCH 1	n2
TCH 2	n3
…	…
TCHm-1	nm
Note: n1 ≥ n2 ≥ n3 ≥ n4 ≥…≥nm.

For MRP, first you must divide an available band into several sub-bands. Generally, the sub-bands work as the bands for BCCH. The reasons are listed below:

Logical Channels and Channel Mapping

Introduction
In GSM divides up each ARFCN into 8 time slots.These 8 timeslots are further broken up into logical channels.
Logical channels can be thought of as just different types of data that is transmitted only on certain frames in a certain timeslot.

Different time slots will carry different logical channels, depending on the structure the BSS uses.
There are two main categories of logical channels in GSM:

Signaling Channels
Traffic Channels (TCH)

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Signaling Channels

These are the main types of signaling Channels:Broadcast Channels (BCH) - Transmitted by the BTS to the MS. This channel carries system parameters needed to identify the network, synchronize time and frequency with the network, and gain access to the network.

Common Control Channels (CCH) - Used for signaling between the BTS and the MS and to request and grant access to the network.

Standalone Dedicated Control Channels (SDCCH) - Used for call setup.

Associated Control Channels (ACCH) - Used for signaling associated with calls and call-setup. An ACCH is always allocated in conjunction with a TCH or a SDCCH.

*keep in mind, these are only categories of logical channels, they are not logical channels themselves.

The above categories can be divided into the following logical channels:

Broadcast Channels (BCH)
     Broadcast Control Channel (BCCH)
     Frequency Correction Channel (FCCH)
     Synchronization Channel (SCH)
     Cell Broadcast Channel (CBCH)

Common Control Channels (CCCH)
     Paging Channel (PCH)
     Random Access Channel (RACH)
     Access Grant Channel (AGCH)

Standalone Dedicated Control Channel (SDCCH)
     Associated Control Channel (ACCH)
     Fast Associated Control Channel (FACCH)
     Slow Associated Control Channel (SACCH)

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Let's examine each type of logical channel individually.

Broadcast Channels (BCH)

Broadcast Control Channel (BCCH) - DOWNLINK - This channel contains system parameters needed to identify the network and gain access. These paramters include the Location Area Code (LAC), the Mobile Network Code (MNC), the frequencies of neighboring cells, and access parameters.

Frequency Correction Channel (FCCH) - DOWNLINK - This channel is used by the MS as a frequency reference. This channel contains frequency correction bursts.

Synchronization Channel (SCH) - DOWNLINK - This channel is used by the MS to learn the Base Station Information Code (BSIC) as well as the TDMA frame number (FN). This lets the MS know what TDMA frame they are on within the hyperframe.

Cell Broadcast Channel (CBCH) - DOWNLINK - This channel is not truly its own type of logical channel. The CBCH is for point-to-omnipoint messages. It is used to broadcast specific information to network subscribers; such as weather, traffic, sports, stocks, etc. Messages can be of any nature depending on what service is provided. Messages are normally public service type messages or announcements. The CBCH isnt allocated a slot for itself, it is assigned to an SDCCH. It only occurs on the downlink. The CBCH usually occupies the second subslot of the SDCCH. The mobile will not acknowledge any of the messages.

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Common Control Channels (CCCH)

Paging Channel (PCH) - DOWNLINK - This channel is used to inform the MS that it has incoming traffic. The traffic could be a voice call, SMS, or some other form of traffic.

Random Access Channel (RACH) - UPLINK This channel is used by a MS to request an initial dedicated channel from the BTS. This would be the first transmission made by a MS to access the network and request radio resources. The MS sends an Access Burston this channel in order to request access.

Access Grant Channel (AGCH) - DOWNLINK - This channel is used by a BTS to notify the MS of the assignement of an initial SDCCH for initial signaling.

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Standalone Dedicated Control Channel (SDCCH) - UPLINK/DOWNLINK - This channel is used for signaling and call setup between the MS and the BTS.

Associated Control Channels (ACCH)

Fast Associated Control Channel (FACCH) - UPLINK/DOWNLINK - This channel is used for control requirements such as handoffs. There is no TS and frame allocation dedicated to a FAACH. The FAACH is a burst-stealing channel, it steals a Timeslot from a Traffic Channel (TCH).

Slow Associated Control Channel (SACCH) - UPLINK/DOWNLINK - This channel is a continuous stream channel that is used for control and supervisory signals associated with the traffic channels.

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Signaling Channel Mapping

Normally the first two timeslots are allocated to signaling channels.

Remember that Control Channel (aka signaling channels) are composed of 51 TDMA frames. On a time slot Within the multiframe, the 51 TDMA frames are divided up and allocated to the various logical channels.

There are several channel combinations allowed in GSM. Some of the more common ones are:
FCCH + SCH + BCCH + CCCH
BCCH + CCCH
FCCH + SCH + BCCH + CCCH + SDCCH/4(0..3) + SACCH/C4(0..3)
SDCCH/8(0 .7) + SACCH/C8(0 . 7)

FCCH + SCH + BCCH + CCCH

Downlink


Uplink

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BCCH + CCCH

Downlink


Uplink

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FCCH + SCH + BCCH + CCCH + SDCCH/4(0..3) + SACCH/C4(0..3)

The SACCH that is associated with each SDCCH is only transmitted every other multiframe. Each SACCH only gets half of the transmit time as the SDCCH that it is associated with. So, in one multiframe, SACCH0 and SACCH1 would be transmitted, and in the next multiframe, SACCH2 and SACCH3 would be transmitted. The two sequential multiframes would look like this:


Downlink


Uplink

You will also notice that the downlink and uplink multiframes do not align with each other. This is done so that if the BTS sends an information request to the MS, it does not have to wait an entire multiframes to receive the needed information. The uplink is transmitted 15 TDMA frames behind the downlink. For example, the BTS might send an authentication request to the MS on SDCCH0 (downlink) which corresponds to TDMA frames 22-25. The MS then has enough time to process the request and reply on SDCCH0 (uplink) which immediately follows it on TDMA frames 37-40.

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SDCCH/8(0 .7) + SACCH/C8(0 . 7)

Once again, the SACCH that is associated with an SDCCH is only transmitted every other multiframe. Two consecutive multiframes would look like this:


Downlink


Uplink

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Traffic Channels (TCH)

Traffic Channels are used to carry two types of information to and from the user:

Encoded Speech
Data

There are two basic types of Encoded Speech channels:

Encoded Speech - Encoded speech is voice audio that is converted into digital form and compressed.
    Full Rate Speech TCH (TCH/FS) - 13 kb/s
    Half Rate Speech TCH (TCH/HS) - 5.6 kb/s

Data - Data refers to user data such as text messages, picture messages, internet browsing, etc. It includes pretty much everything except speech.

    Full rate Data TCH (TCH/F14.1) - 14.4 kb/s
    Full rate Data TCH (TCH/F9.6) - 9.6 kb/s
    Full rate Data TCH (TCH/F4.8) - 4.8 kb/s
    Half rate Data TCH (TCH/F4.8) - 4.8 kb/s
    Full rate Data TCH (TCH/F2.4) - ≤2.4 kb/s
    Half rate Data TCH (TCH/H2.4) - ≤2.4 kb/s

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Traffic Channel Mapping

Time slots 2 through 7 are normally used for Traffic Channels (TCH)

Traffic Channel Multiframes are composed of only 26 TDMA frames. On each multiframe, there are 24 frames for Traffic Channels, 1 frame for a SACCH, and the last frame is Idle. Remember that a MS (or other device) only gets one time slot per TDMA frame to transmit, so in the following diagrams we are looking at a single time slot.

Full Rate Traffic Channel (TCH/FS)

When using Half-Rate Speech Encoding (TCH/HS), the speech encoding bit rate is 5.6 kb/s, so one time slot can handle two half-rate channels. In this case, one channel will transmit every other TDMA frame, and the other channel would be transmitted on the other frames. The final frame (25), which is normally used as an Idle frame, is now used as a SACCH for the second half-rate channel.

Half Rate Traffic Channel (TCH/HS)

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ARFCN Mapping

This diagram shows a sample Multiframe with logical channels mapped to time slots and TDMA frames. This is just one possible configuration for an ARFCN.
*For illustrative purposes, half of the traffic channels are full-rate and the other half are half-rate

TS0
TS1
TS2
TS3
TS4
TS5
TS6
TS7
*Remember that CCH Multiframes have 51 frames and TCH Multiframes only have 26. Their sequences will synchronize every superframe.

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Offset

Even though GSM uses a full duplex radio channel, the MS and the BTS do not transmit at the exact same time. If a MS is assigned a given time slot, both the MS and the BTS will transmit during that given time slot, but their timing is offset. The uplink is exactly 3 time slots behind the downlink. For example, if the MS was allocated a TCH on TS3, the BTS would transmit when the downlink is on TS3 and the MS is set to receive on TS3. At this point, the uplink is only on TS0. Once the uplink reaches TS3, the MS would begin to transmit, and the BTS is set to receive on TS3. At this point, the downlink would be at TS6. When the MS is not transmitting or receiving, it switches frequencies to monitor the BCCH of adjacent cells.

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Speech Data Throughput

When looking at a Time slot allocated to a TCH, you will notice that TCH does not occur on every single frame within a time slot. There is one reserved for a SACCH and one that is Idle. So, in a TCH Multiframe, only 24 of the 26 frames are used for traffic (voice/data). This leaves us with a data throughput of 22.8 kb/s.

Here is the math:

1. Calculate bits per TCH Multiframe:
We know that there are 114 bits of data on a single burst, and we know that only 24 of the 26 frames in a TCH multiframe are used to send user data.
114 bits × 24 frames = 2736 bits per TCH multiframe

So, we know that on a single timeslot over the duration of one TCH multiframe, the data throughput is 2736 bits.

2. Calculate bits per millisecond (ms):
From step one above, we know that the throughput of a single TCH multiframe is 2736 bits. We also know that the duration of a TCH multiframe is 120ms.
2736 bits / 120 ms = 22.8 bits per millisecond

3. Convert milliseconds (ms) to seconds:
Now we need to put the value into terms of seconds. There are 1000 milliseconds in a second, so we simply multiply the value by 1000.
22.8 bits/millisecond × 1000 = 22,800 bits per second (22.8 kb/s)

4. Convert bits to kilobits:
Finally, we want to put it into terms of kilobits per second, wich is the most common term for referring to data throughput. We know a kilobit is 1000 bits, so we simply divide the term by 1000.
22,800 bits/s ÷ 1000 = 22.8 kb/s

So now we see why the data throughput of a single allocated timeslot is 22.8 kb/s.

There is an easier method to come to this number:

We know that only 24 of the 26 frames carry data, so we can say that the new throughput would be 24/26 of the original throughput. If we convert this to decimal form:
     24÷26 = .9231

We know from the TDMA Tutorial that the data throughput of a single timeslot is 24.7 kb/s. Apply this 24/26 ratio to the 24.7 kb/s throughput:
     24.7 × .9231 = 22.8 kb/s

You can see that we get the same answer as above.

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A single BTS may have several Transceivers (TRX) assigned to it, each having its own ARFCN, each ARFCN having 8 time slots.

The logical channels that support signaling will normally only be on one ARFCN. All of the other ARFCNs assigned to a BTS will allocate all 8 time slots to Traffic Channels, to support multiple users.

The following diagram is an example of how a medium-sized cell might be set up with 4 TRX (ARFCNs).

Sample Medium-Size Cell

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Frequency Hopping

Each radio frequency Channel (ARFCN) is influenced differently by propagation conditions. What affects channel 23 may not affect channel 78 at all. Within a given cell, some frequencies will have good propagation in a certain area and some will have poor propagation in that area. In order to take advantage of the good propagation and to defeat the poor propagation, GSM utilizes frequency hopping. Frequency hopping means that a transceiver hops from one frequency to another in a predetermined sequence. If a transceiver hops through all of the avilable frequencies in a cell then it will average out the propagation. GSM uses Slow Frequency Hopping (SFH). It is considered slow becuase the system hops relatively slow, compared with other frequency hopping systems. In GSM, the operating frequency is changed every TDMA frame.

The main reason for using slow frequency hopping is because the MS must also change its frequency often in order to monitor adjacent cells. The device in a transceiver that generates the frequency is called a frequency synthesizer. On a MS, a synthesizer must be able to change its frequency within the time frame of one time slot, which is equal to 577 µs. GSM does not require the BTS to utilize frequency hopping. However, a MS must be capable of utilizing frequency hopping when told to do so.

The frequency hopping and timing sequence is known as the hopping algorithm. There are two types of hopping algorithms available to a MS.

- Cyclic Hopping - The transceiver hops through a predefined list of frequencies in sequential order.

- Random Hopping - The transceiver hops through the list of frequencies in a random manner. The sequence appears random but it is actually a set order.

There are a total of 63 different hopping algorithms available in GSM. When the MS is told to switch to frequency hopping mode, the BTS will assign it a list of channels and the Hopping Sequence Number (HSN), which corresponds to the particular hopping algorithm that will be used.

The base channel on the BTS does not frequency hop. This channel, located in time slot 0, holds the Broadcast Control Channels which the MS needs to monitor to determine strength measurements, determine access parameters, and synchronize with the system.

If a BTS uses multiple transceivers (TRX) then only one TRX will hold the the Broadcast Channels on time slot 0. All of the other TRXs may use time slot 0 for traffic or signaling and may take part in the frequency hopping.

There are two types of frequency hopping method available for the BTS: synthesizer hopping and baseband hopping.

• Synthesizer Hopping - This requires the TRX itself to change frequencies according to the hopping sequence. So, one TRX would hop between multiple frequencies on the same sequence that the MS is required to.
• Baseband Hopping - In this method there are several TRX and each one stays on a fixed frequency within the hopping frequency plan. Each TRX would be assigned a single time slot within a TDMA frame. For example, time slot 1 might be assigned to TRX 2 in one TDMA frame and in the next TDMA frame it would be assigned to TRX 3, and the next frame would be TRX 3. So, the data on each time slot would be sent on a different frequency each frame, but the TRXs on the BTS do not need to change frequency. The BTS simply routes the data to the appropriate TRX, and the MS knows which TRX to be on for any given TDMA frame.

Baseband Frequency Hopping

• Antenna Installation and Downtilting

When we talk about antenna then we need to understand about antenna installation and specially about antenna downtilting.lets assume that antenna installed then how you can change its position.

Its two types:

1.  left-right = its called azimuth change
2. up-down = its called tilt change.

Lets understand from start.
ANTENNA INSTALLATION

• Antenna installation configurations depend on the operators preferences.

• BTS Multiplexing Mode Huawei BSC6000

This describes how to change the BTS multiplexing mode to improve the utilization of the Abis timeslot resources. If the BTS uses the TDM transmission mode, the requirement for BTS timeslots changes when the BTS traffic increases. In this case, the BTS multiplexing mode should be changed.

BTS multiplexing mode indicates the Abis timeslot multiplexing mode of the BTS. It consists of the following seven types:

• 1:1 64 kbit/s statistic multiplexing mode
• 2:1 64 kbit/s statistic multiplexing mode
• 3:1 64 kbit/s statistic multiplexing mode
• 4:1 64 kbit/s statistic multiplexing mode
• 5:1 64 kbit/s statistic multiplexing mode
• 6:1 64 kbit/s statistic multiplexing mode

Physical 16 kbit/s multiplexing mode
The bandwidth of each E1 is 2.048 Mbit/s and is divided into 32 timeslots. The transmission rate on each timeslot is 64 kbit/s. The bandwidth of each T1 cable is 1.544 Mbit/s and is divided into 24 timeslots. There are six types of Abis timeslot objects:

Operation and Maintenance Link (OML). One BTS has one 64 kbit/s OML. The OML cannot be multiplexed with the RSL of another BTS.
Radio Signaling Link (RSL)Each TRX has one 64 kbit/s RSL. The RSL cannot be multiplexed with the OML or RSL of another BTS.
Extend Signaling Link (ESL)If the Abis timeslot assignment mode of the BTS is set to Flex, one BTS requires one 64 kbit/s ESL to transfer the Abis timeslot dynamic connection message. In 64 kbit/s statistic multiplexing mode and physical 16 kbit/s multiplexing mode, the ESL can be multiplexed only with the OML of the same BTS onto a 64 kbit/s timeslot on the same E1.
Traffic Channel (TCH)The transmission rate on the TCH is 16 kbit/s.
IdleIdle timeslots of the BTS. The rate of the idle timeslots is 16 kbit/s. The idle timeslots can be multiplexed only with the TCH in the same cabinet group.
SemiMonitoring timeslots of the BTS. The rates of monitoring timeslots are 8 kbit/s, 16 kbit/s, 32 kbit/s, and 64 kbit/s. Monitoring timeslots cannot be multiplexed with other types of timeslot objects.
When changing the BTS multiplexing mode, pay attention to the following:

If the BTS multiplexing mode is 5:1 or 6:1, the Abis timeslot assignment mode must be set to Flex Abis.
If the Abis timeslot assignment mode of a BTS must be set to Flex Abis, you should add an ESL for the BTS, and change the maximum number of RSLs that can be multiplexed with the OML.
When the BTS multiplexing mode is 4:1, if the Abis timeslot assignment mode is Fix Abis, a maximum of three RSLs can be multiplexed; if the Abis timeslot assignment mode is Flex Abis, a maximum of two RSLs can be multiplexed.
When the BTS multiplexing mode is 4:1, if the Abis timeslot assignment mode is modified from Fix Abis to Flex Abis, a redundant RSL will occupy a 64 kbit/s timeslot, thus reducing the utilization of resources. In this case, you can change the BTS multiplexing mode to 5:1 or 6:1. Therefore, more RSLs can be multiplexed onto one 64 kbit/s timeslot. This saves the system resources.
If the Abis timeslot assignment mode is Fix Abis or SemiSolid, the BTS multiplexing mode cannot be set to 5:1 or 6:1.
On the BTS cascading main link, the BTS in physical 16 kbit/s multiplexing mode cannot coexist with the BTS in other multiplexing mode.
When you change the multiplexing mode of a BTS from non-4:1 to 4:1 or from 4:1 to non-4:1, the related cell parameters are modified automatically.
When you change the multiplexing mode of a BTS from non-4:1 to 4:1, the measurement report preprocessing parameter of all the cells under this BTS is set to Yes and the sent frequency of preprocessed measurement report is set to once every second automatically.
When you change the multiplexing mode of a BTS from 4:1 to non-4:1, the measurement report preprocessing parameter of all the cells under this BTS is set to No and the sent frequency of preprocessed measurement report is set to twice every second automatically.
Multiplexing Mode :

BTS multiplexing mode indicates the Abis timeslot multiplexing mode of the BTS. The OML and RSL are signaling links. Only signaling links can be multiplexed together. Statistic multiplexing mode means that the OML and RSL use one E1 timeslot through Time Division Multiplexing (TDM). For example, 4:1 multiplexing mode means that three RSLs and one OML are multiplexed onto one 64 kbit/s timeslot.

If the BTS multiplexing mode is set to 5:1, one OML, one ESL, and two RSLs are multiplexed onto one 64 kbit/s timeslot, or five RSLs are multiplexed onto one 64 kbit/s timeslot.

If the BTS multiplexing mode is set to 6:1, one OML, one ESL, and two RSLs are multiplexed onto one 64 kbit/s timeslot, or six RSLs are multiplexed onto one 64 kbit/s timeslot.

If the BTS multiplexing mode is set to Physical 16 kbit/s, one OML (ESL) and one RSL occupy one 16 kbit/s timeslot respectively.

• TCH Drop Rate – Parameter Related

The parameter settings on the BSC side and MSC side may affect the TCH call drop rate. You should check the settings of the following parameters for a cell with a high TCH call drop rate. See Case 5: Reduction of Call Drops by Optimizing Handover Parameters and Case 12: Increase in Call Drop Rate Due to Change of TR1N on the MSC Side.
1. SACCH Multi-Frames
This parameter determines whether an uplink radio link is faulty. Each time the BTS fails to decode the measurement report on the SACCH from the MS, the counter decreases by 1. Each time the BTS successfully decodes the measurement report on the SACCH, the counter increases by 2. When the value of this counter is 0, the BTS regards the radio link as faulty. In the traffic measurement, if there are many call drops (M3101A) related to radio link failure, you can infer that the radio propagation conditions are poor. In this case, you can set this parameter to a greater value.
2. Radio Link Timeout
This parameter determines whether a downlink radio link is faulty. Each time the BTS fails to decode the measurement report sent over the SACCH by the MS, the counter decreases by 1. Each time the BTS successfully decodes the measurement report sent over the SACCH, the counter increases by 2. When the value of this parameter is 0, the BTS regards the radio link as faulty. In the traffic measurement, if there are many call drops (M3101A) related to radio link failure, you can infer that the radio propagation conditions are poor. In this case, you can set this parameter to a greater value.

3. RXLEV_ACCESS_MIN
This parameter specifies the minimum receive level of an MS to access the BSS. If this parameter is set to a too small value, some MSs with low receive levels may access the network and call drops are likely to occur. You can set this parameter to a great value to reduce the TCH call drop rate. The counters such as call setup success rate and the counters related to traffic volume, however, are accordingly affected.
4. RACH Min.Access Level
This parameter determines whether an MS can access the network over the RACH. If this parameter is set to a too small value, some MSs with low signal levels may access the network and call drops are likely to occur. You can set this parameter to a great value to reduce the TCH call drop rate. The counters such as call setup success rate and paging success rate, however, are affected.
5. Min DL Power on HO Candidate Cell and Min Access Level Offset
The sum of the values of the two parameters specifies the minimum downlink receive level of a candidate neighboring cell for a handover. If this parameter is set to a too great value, some desired cells may be excluded from the candidate cells; if this parameter is set to a too small value, an unwanted cell may become the candidate cell. Both conditions may lead to the increase of call
drops.
6. Timer T3103 series
Timer T3101 series consists of T3103A, T3103C, and T8. These timers are started to wait for a handover complete message. If the lengths of the timers are set to small values, probably no message is received when timer T3103 series expires. In this case, the BSC considers that the radio link in the originating cell is faulty. Then, the BSC releases the channel in the originating cell. Thus, call drops occur. In the traffic measurement, if many call drops are related to handovers (CM331: Call Drops on Radio Interface in Handover State), you can set this parameter to a greater value. If this parameter is set to a too great value, channel resources are wasted and
TCH congestion occurs.

7. Timer T3109
This parameter specifies the period for waiting for a Release Indication message after the BSC sends a Channel Release message to the BTS. If this parameter is set to a too small value, the link may be released before the Release Indication message is received. As a result, a call drop occurs. You can set this parameter to a greater value to reduce the TCH call drop rate. It is recommended that timer T3109 be set to 1–2 seconds longer than timer Radio Link Timeout.
8. Timer T3111
This parameter specifies the interval between the time that the main signaling link is disconnected and the time that a channel is deactivated. The purpose is to reserve a period of time for repeated link disconnections. If this timer is set to a too small value, a channel may be deactivated too early. Thus, call drops increase.

9. Timers T305 and T308
Timers T305 and T308 are used on the MSC side. Timer T305 specifies the period during which the MSC monitors the on-hook procedure. Timer T308 specifies the period during which the MSC monitors the resource release procedure. You should set the two parameters when adding BSC data. Note that the modification of the data in the timer table does not take effect. If timers T305 and T308 are set to invalid or great values, the MSC clears the call a long time after the MS hangs up. After the T3103 and Radio Link
Timeout timers expire, the number of call drops is increased and thus the TCH call drop rate is significantly affected.

10. TCH Traffic Busy Threshold
If the current channel seizure ratio exceeds the value of this parameter, the BSC preferentially assigns a half-rate channel to a dualrate-enabled call. Otherwise, the BSC assigns a full-rate channel to the dualrate-enabled call. Compared with a full-rate channel, a half-rate channel has weak antiinterference capabilities. Therefore, if a large number of half-rate channels are assigned, the TCH call drop rate increases. It is recommended that this parameter should not be set to a too small value if congestion is unlikely to
occur.

11. Call Reestablishment Forbidden
This parameter specifies whether to allow call reestablishment. In case of burst interference or radio link failure due to blind areas caused by high buildings, call drops occur. In this case, MSs can initiate the call reestablishment procedure to restore communication. To reduce the TCH call drop rate, you can set this parameter to No to allow call reestablishment. In certain conditions, allowing call reestablishment greatly reduces the TCH call drop rate. Call reestablishment lasts for a long time, and therefore some subscribers cannot wait and hang up. This affects user experience.

12. Parameters related to edge handover

When the receive level drops greatly, an edge handover cannot be performed in time in any of the following conditions: The parameter Edge HO UL RX_LEV Threshold or Edge HO DL RX_LEV Threshold is set to a small value; the parameter Inter-cell HO Hysteresis is set to a great value; the parameters Edge HO Watch Time and Edge HO AdjCell Watch Time
are set to great values; the parameters Edge HO Valid Time and Edge HO AdjCell Valid Time are set to great values. As a result, a call drop occurs. To reduce the TCH call drop rate, you can appropriately set these parameters so that edge handovers can be performed in time to avoid call drops.

13. Parameters related to BQ handover
When the signal quality deteriorates, a BQ handover cannot be performed in time in any of the following conditions: The parameters
ULQuaLimitAMRFR, ULQuaLimitAMRHR, UL Qual. Threshold, DLQuaLimitAMRFR, DLQuaLimitAMRHR, and DL Qual. Threshold are
set to great values; the parameter BQ HO Margin is set to a small value; the parameter Inter-cell HO Hysteresis is set to a great value. As a result, call drops occur. To reduce the TCH call drop rate, you should appropriately set these parameters so that BQ handovers can be performed in time to avoid call drops.

14. Parameters related to interference handover
If the parameters RXQUAL1 to RXQUAL12 are set to great values or if the RXLEVOff parameter is set to a great value, strong interference may occur. In this case, if interference handovers are not performed in time, call drops occur. To reduce the TCH call drop rate, you can appropriately set these parameters so that interference handovers can be performed in time to avoid call drops. If the parameters RXQUAL1 to RXQUAL12 are set to small values, the number of handovers due to other causes increases greatly, thus affecting the handover success rate.

15. Parameters related to concentric cell handover
A call at the edge of the overlaid subcell cannot be handed over to the underlaid subcell in any of the following conditions: In the case of a normal concentric cell, the parameters RX_LEV Threshold and RX_LEV Hysteresis are set to great values; in the case of an enhanced concentric cell, the parameter OtoU HO Received Level Threshold is set to a great value. As a result, a call drop is likely to occur. If the Call Drop Ratio on TCH on the TRX in the OverLaid Subcell (RM330a) is high, you can appropriately set these parameters so that calls at the edge of the overlaid subcell can be handed over to the underlaid subcell in time. When a call in the underlaid subcell has interference, the call cannot be handed over to the overlaid subcell if the RX_QUAL for UO HO Allowed parameter is set to Yes and the RX_QUAL Threshold parameter is set to a great value. Thus, a call drop occurs. If the Call Drop Ratio on TCH on the TRX in the Underlaid Subcell (RM330) is high, you can set these parameters properly so that the call can be handed over to the overlaid
subcell at the earliest.

16. Parameters related to power control
If the power control level and quality threshold are set to small values, call drops are likely to occur because of low signal level or bad voice quality.

17. T200 and N200
If the parameters T200 FACCH/F, T200 FACCH/H, N200 of FACCH/Full rate, and N200 of FACCH/Half rate are set to small values, data links are disconnected too early. Thus, all drops are likely to occur. If call drops occur because of T200 expiry, you can increase the values of T200 and N200 properly.

18. Neighboring cell relations
If the neighboring cells configured in the BA2 table are incomplete, call drops are likely to occur in the case of no suitable neighboring cell for handover and progressive deterioration in the voice quality. Neighboring cell relations should be configured completely on the basis of the drive test data and electronic map (for example, Nastar) to minimize the call drops due to no available neighboring cells.

19. MAIO
If frequency hopping (FH) is applied in a cell and the MAIO is set inappropriately (for example, different TRXs serving the same cell have the same MAIO), frequency collision may occur during FH. Thus, the TCH call drop rate increases.

20. Disconnect Handover Protect Timer
This parameter is a software parameter of the BSC. After receiving a DISCONNECT message from an MS, the BSC cannot hand over the MS within the period specified by this parameter. Therefore, the following case can be avoided: After being handed over to the target cell, the MS cannot be put on hook because it does not receive a release acknowledgement message. You are advised to set this parameter properly.

21. TR1N
This parameter should be set on the MSC side. It is used to avoid the retransmission of short messages. When this parameter is set to a too great value, the MSC does not send a CLEAR CMD message if the MS receives a short message during link disconnection. As a result, the MS sends the BTS a DISC message to disconnect layer 2 connection. After receiving the DISC message, the BTS sends a REL_IND message to the BSC. Then, the BSC sends a CLEAR REQ message to the MSC and the number of call drops is incremented by one.

22. Software Parameter 13 and MAX TA
When the parameter Software Parameter 13 is enabled and the parameter MAX TA is set to a too small value, the channel is released when the TA of a call exceeds the MAX TA. In this case, call drops occur. It is recommended that the parameter Software Parameter 13 should not be enabled.

23. Directly Magnifier Site Flag
If a BTS is installed with repeaters, the handover between repeaters can only be asynchronous because the distance between repeaters is long. If synchronous handovers are performed, the handovers may fail and thus many call drops occur. Therefore, when a BTS is installed with repeaters, the parameter Directly Magnifier Site Flag should be set to Yes to avoid asynchronous handovers between cells under the same BTS.

• New Tip Optimization with RQI Measurement Report

I would like to introduce you a new measurement report that involved with optimization judgement tip. In order to step forward yourself to be family with the this measurement, you must have the concept of AMR algorithm in which it has relevant closely with Radio Quality Index in the call measurement report. The Radio quality index is the dB value of C/I multiplied by 2 as form RQI = 2  *  C/I ( dBm). RQI represent the C/I values in the uplink only. We can get RQI of all Mobiles per TA and by comparing it to RLF ( Radio Link Failure) per TA that mention the RQI values in areas which suffer from high radio link failures.
RQI range of values[0--55+] = 2 * C/I range of values  [0-->30]. RQI values less than 18 (C/I =  9) indicate very bad quality and strong interference. I would give you a noted that due to BB Hopping is activated in some cell in network and according to  RQI values given on TRX level might get wrong averaged values judgement in case.

All I mention above, I think it is just a brief tip that you could get while you are in a darkness of AMR Feature. I would suggest you to read more in order to make it easy in your optimization job and future career.
Here is the measurement countet:

S4400E:Number of Measurement Reports (RQI = 0 to 1)

S4401E:Number of Measurement Reports (RQI = 1 to 2)

S4402E:Number of Measurement Reports (RQI = 2 to 3)

.  .  .  .

.  .  .  .

S4418E:Number of Measurement Reports (RQI = 45 to 55)

S4419E:Number of Measurement Reports (RQI greater than 55)

S4440E:Number of Measurement Reports with RQI