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GSM ServicesService CategoryServiceComments

TeleservicesSpeech

SMS (Short Message Full Rate 13KbpsPoint to Point & Cell Broadcast

Bearer ServicesAsynchronous DataSynchronous Data300 9600bps300 9600bps

Supplementary ServicesCall ForwardCall BarringSubscriber Busy, Not ReachableInternational & Incoming Calls

900 MHz. Up link Frequency 890-915 MHZ.

Down link Frequency 935-960 MHz

1800 MHz. Up link Frequency 1725-1780 MHZ.

Down link Frequency 1820-1870 MHz

124 carriers. There are 8 channels in each carrier. Channel separation is 200 KHz.

Ciphering modifies the contents of the eight interleaved blocks through the use of encryption techniques to the particular mobile station and base transceiver station.Two types of ciphering algorithms, called A3 and A5, are used in GSM to prevent unauthorized network access and privacy for the radio transmission respectively.

Authentication is the process of uniquely proving an identity to a certain service, network or device and the verification of the given identity. The Au C is associated with the HLR (Home Location Register) in a GSM or UMTS network. It provides authentication parameters for the authentication process such as authentication triplets in GSM or authentication vectors within UMTSA3 - Authentication Algorithm A3Authentication algorithm used in conjunction with Ki the authentication key and RAND the random number generated in the AuC (Authentication Centre) to produce the SRES (Signed Response) This variable is used by the network to authenticate a MS (Mobile Station) requesting network resources.

Equalization is the technique used to improve the redial link performance. That is to minimize instantaneous bit error rate (Inter symbol interference).since the mobile feeding channel is random and time varying, equalizers must track the time varying characteristics of the mobile channel, and thus are called as adaptive equalizers.

In reality, bit errors often occur in sequence, as caused by long fading dips affecting several consecutive bits. Channel coding is most effective in detecting and correcting single errors and short error sequences. It is not suitable for handling longer sequences. For this reason, a process called interleaving is used to separate consecutive bits of a message so that these are transmitted in a non-consecutive way. The major drawback of interleaving is the corresponding delay: transmission time from the first burst to the last one in a block is equal to 8 TDMA frame

Digitization is the process of converting information into a digital format. In this format, information is organized into discrete units of data (called bits) that can be separately addressed (usually in multiple-bit groups called bytes).

The GSM speech code transform the analog signal (voice) into a digital representation, has to meet the following criteria:A .good speech qualityB. to reduce the redundancy in the sounds of the voice

Channel coding is a method to reduce information rate through the channel and increase reliability. This goal is achieved by adding redundancy to the information symbol vector resulting in a longer coded vector of symbols that are distinguishable at the output of the channel.

Frequency reuse is a technique of reusing frequencies and channels within a communications system to improve capacity and spectralefficiency. Frequency reuse is one of the fundamental concepts on which commercial wireless systems are based that involves the partitioning of an RF radiating area (cell) into segments of a cell. One segment of the cell uses a frequency that is far enough away from the frequency in the bordering segment that it does not provide interference problems. Frequency re-use in mobile cellular systems means that each cell has a frequency that is far enough away from the frequency in the bordering cell that it does not provide interference problems. The same frequency is used at least two cells apart from each other. This practice enables cellular providers to have many times more customers for a given site license.

Cell splitting is the process of splitting a mobile cell into several smaller cells. This is usually done to make more voice channels available to accommodate traffic growth in the area covered by the original cell.

A InterfaceThis is the interface within the GSM network architecture between the BSS (Base Station Subsystem) and an MSC (Mobile Switching Centre). The interface supports standard 64Kbps channels for signalling and traffic. The primary protocols on this interface are DTAP (Direct Transfer Application Part) and BSSMAP (Base Station Subsystem Management Application Part).Abis InterfaceThe interface within the GSM architecture, between the BTS (Base Transceiver Station) and BSC (Base Station Controller). This interface is usually configured using a 16Kbps slot structure.The A1 interface Carries signaling information between the Call Control and Mobility Management functions of the MSC (Mobile Switching Center) and the call control component of the BSC (Base Station Controller).A9 InterfaceThe A9 interface carries signaling information between the BS (Base Station) and the PCF (Packet Control Function).

LAPD - Link Access Protocol on the D ChannelLink Access Protocol on the D channel is a Layer 2 protocol used on the ISDN D channel. LAPD was derived from the LAPB (Link Access Protocol Balanced) protocol and was designed to satisfy the signaling requirements of ISDN basic access. LAPD is defined in the ITU-T (International Telecommunications Union-Telecommunication Standardization Sector. The LAPD, protocol is used to convey messages between layer3 entities across the GSM radio interface. LAPDm - Link Access Protocol on the Gm ChannelLAPDm is a modified version of LAPD(Link Access Protocol in the D channel), the Data link layer protocol. The modifications make it suitable for transmission across a radio interface. It is used in GSM to support the transport of information between the mobile and the network.

Wi-Fi Protected Setup (WPS) is a standard for easy and secure establishment of a wireless home network, created by the Wi-Fi Alliance .The goal of the WPS protocol is to simplify the process of configuring security on wireless networks.

17. What is MAP? MAP - Mobile Application PartA protocol which enables real time communication between nodes in a mobile cellular network. A typical usage of the MAP protocol would be for the transfer of location information from the VLR(Visitor Location Register) to the HLR(Home Location Register).

A mobile allocation index offset (MAIO) refers a time delay separating traffic channels. When a GSM (Global System for Mobile Communications) mobile phone is served by a cell that is hopping over a set of frequencies, the separate traffic channels hop over the allocated frequencies according to a hopping sequence number (HSN). The traffic channels with the same HSN hop over the same frequencies in the same order but are separated in time by a mobile allocation index offset (MAIO).The smallest amount of interference on a site is achieved if it is possible to synchronize all channels on the site and separate the channels using the MAIO.

Frequency hopping is defined as continuous changing the frequency from one slot to another Each burst is transmitted on a different frequencyBoth mobile and base station follow the same hopping sequenceBase Band Hopping (BBH)The TCUs transmit always the same frequencyNumber of frequencies for hopping = Number of carriersSynthesiser Frequency Hopping (SFH)The TCUs change (retune) the frequency every burstNumber of frequencies for hopping > Number of carriersTCUs can hop over a range of 64 different frequencies

The average speed of mobile stations within a cell is determined or estimated using a variety of techniques. If the average speed is below a predetermined threshold, then a cyclic FH sequence is used to achieve superior frequency diversity and therefore combat small-scale fading. If the average speed is above a predetermined threshold, then a random FH sequence is used to achieve superior interference averaging and therefore combat co-channel interference

Frequency hopping is employed in frequency division spread spectrum to hide the data channels in the noise or to avoid interference from other users of the common spectrum. It is also employed in fading channels to improve the quality of the radio connection. The hopping pattern must be known both by the receiver and the transmitter. This pattern is described using a hopping sequence and identified by the HSN.

Discontinuous transmission is a mechanism that allows the radio transmitter to be switched off during speech pauses. In a normal conversation this will lead to a decrease in transmission time of about 50%. The primary functions of DTX in the up link and down link are to save battery in the mobile and to reduce the interference levels in both links

Discontinuous Reception (DRX) is a method used in mobile communication to conserve the battery of the mobile device.The mobile device and the network negotiate phases in which data transfer happens. During other times the device turns its receiver off and enters a low power stateDiscontinuous reception is employed in cellular systems to prolong the mobiles battery life. The mobile station listens only to the paging channels within its DRX group. Moreover the network will only page the mobile in that group of paging channels. Thus the mobile does not have to continuously monitor the paging channels

GSM----------9.6 Kbps

2.5 G High Speed Circuit Switched Data (HSCSD) ---------76.8 Kbps

The Erlang is a measurement of telephone traffic equivalent to 3600 seconds of telephone use. Grade of Service defines the quality of a telephone service in terms of a user receiving a network busy signal. Grade of service is the blocking for the given traffic channels.

Timing advance is a solution specifically designed to counteract the problem of time alignment. It works by instructing the misaligned MS to transmit its burst earlier or later than it normally would. In GSM, the timing advance information relates to bit-times. Thus, an MS may be instructed to do its transmission by a certain number of bit-times earlier or later related to previous position, to reach its timeslot at the BTS in right time. Maximum 63 bit-times can be used in GSM systems. This limits GSM normal cell size to 35km radius.

A Location Area is a number of cells (defined by the mobile operator) throughout which a GSM / UMTS mobile will be paged.

Location information is maintained and used by the network to locate the user for call routing purposes. The network registers the users location in a register called users HLR, which is associated with an MSC located in a PLMN to which user is subscribed. Each BSS keeps broadcasting on periodic basis the cell identities on broadcast control channels of the cells under its coverage. The mobiles within each cell keep monitoring this information. As changes in location are detected (from the last information recorded by them), they each report the new location to the BSS which then routes it the VLR of the MSC to which it is connected. The VLR sends the location information to users HLR where it is also recorded. Meanwhile, the HLR directs the old VLR to delete the old visiting location of the mobile from its database and also sends a copy of the users service profile to the new VLR. Location updating is performed by the Mobility Management (MM) protocol sub layer.

IMSI stands for International Mobile Subscriber Identity. It is the unique network identity of the GSM subscriber. TMSI stands for Temporary Mobile Subscriber Identity. TMSI is the temporary network identity of the subscriber in the visited Location Area.

MSISDN is the international ISDN no. allocated to the mobile subscriber. MSISDN should comply to the countrys ISDN numbering plan. The MSISDN number basically consists of a country code (CC), a national destination code (NDC) which specifies a PLMN within that country and a subscriber number (SN). The MSISDN number is used for dialing by a calling subscriber from PSTN/ISDN, and is used to route the call to a Gateway MSC of the GSM network. The GSM MSC then uses the MSISDN to interrogate the appropriate HLR for the rerouting information required to extend the call to the Mobile's visiting MSC.

ARFCN - Absolute Radio Frequency Channel NumberWithin the spectrum allocated for cellular mobile communications, the radio channels are identified by ARFCN. If the system is operating in FDD (Frequency Division Duplex) mode then the channel number is associated with both the uplink and downlink radio channels. Within the GSM900spectrum ARFCN 1 to 124 are used. In GSM1800, ARFCN 512 to 885 are used and in GSM1900 ARFCN 512 to 810 are used.

The Power Control is sent on the Forward Power Control Sub channel or Reverse Power Control Sub channel to signal the MS (Mobile Station) or base station to increase or decrease its transmit power.

Frequency Division Duplex is employed in radio systems to provide an up link and down link radio channel between the network and the user. The frequencies separated by a duplex spacing. Users tune between the up link and down link frequencies to transmit and receive respectively.In a Time Division Duplex system a common carrier is shared between the up link and down link, the resource being switched in time. Users are allocated one or more timeslot for up link and down link transmission. The main advantage of TDD operation is that it allows asymmetric flow which is more suited to data transmission.

To provide cellular coverage in rural areas where user density is low, the operators tend to build large cells in order to reduce the number of base station (BS) sites. This reduces the total cost of BS equipment, network installation, and maintenance. The cell range extension technique is specifically targeted to the GSM/DCS1800 for providing cost-effective countryside coverage. It is based on the use of the GSM half-rate speech codec over-the full-rate traffic channel cross the extended cell range, so that additional channel coding can be utilized to improve the error rate performance.

The term Multiple Access is used to describe a system where several users can gain access to a common transmission channel. Examples of Multiple Access systems include TDMA (Time Division Multiple Access) used in GSM, CDMA (Code Division Multiple Access) used in UMTS and CSMA/CD (Carrier Sensing Multiple Access/Collision Detection) used by Ethernet.Frequency Division Multiple Access is a technique in which multiple users of a radio system are separated in the frequency domainCode Division Multiple Access is a method for describing physical radio channels. Data intended for a specific channel is modulated with that channels code. These are typically pseudo random in nature, and posses favorable correlation properties to ensure physical channels are not confused with one another.

SDCCH (Stand Alone Control Channel) when not on a callSACCH (Slow associated control channel) When we are on a call.

Random Access Channel (RACH)

The Access Grant Channel is used to assign resources to a user requesting access to the network. These resources will include the dedicated channel to be used along with timing advance information. (OR) Response for RACH is AGCH.

Call establishment, location update and SMS.SDCCH is a duplex pt-to-pt channel which is used for signaling. It carries all signaling between the BTS and the MS when no TCH is allocated.It is used for service request , location updates, subscriber authentication, ciphering initiation, equipment validation and assignment to a TCH.

Each timeslot on a TDMA frame is called a physical channelA physical channel may carry different messages, depending on the information that is to be sent. These messages are called logical channels.

TDMA Frame: It consists of 8 bursts, time is 4.616ms. one burst is 577microsec. Multi Frame: 26 TDMA frames makes one multi frame. Time of one multi frame is 120ms.Super frame: 51 multi frames make one super frame. Time of one super frame is 420 ms.Hyper frame: 2048 super frames make one hyper frame.

Frequency correction channel FCCH continuously transmits in down link direction unmodulated carrier frequency for frequency correction of MS .

SCH is used for frame synchronization of MS and contains information about RFN(Reduced TDMA Frame Number) and BSIC. BSIC consists of NCC and BCC.

BCCH broadcasts general information about the cell like neighboring cells information, MS transmit power maximum on CCHs and local area identification.

Slow Associated Control Channel (SACCH) is a GSM signaling channel that provides a relatively slow signaling connection. The SACCH is associated with either a traffic or dedicated channel. The SACCH can also be used to transfer Short Message Service (SMS) during a call. It gives measurement reports.

PCH is used to page the MS during mobile terminated call setup. Paging messages are sent to the area where the recipient MS is located. This is the down link transport channel in UMTS that carries the PCH (Paging Control Channel). It is used to broadcast paging and notification messages in a cell.

The Cell Broadcast Channel is an additional feature of the GSM system. The channel supports part of the SMS (Short Message Service) group known as point to multi point and is intended to be used for information such as traffic and weather reports. This is a down link only channel and is mapped into the second subslot of the SDCCH (Standalone Dedicated Control Channel

Yes .BCCH is down link mode channel

Four burst delay .this is used to avoid the simultaneous transmission and reception of mobile station

Traffic multi frame contains 26 bursts. Last burst is the idle burst.13th burst is for SACCH

FACCH - Fast Associated Control ChannelThe Fast Associated Control Channel appears in place of the traffic channel when lengthy signaling is required between a GSM mobile and the network while the mobile is in call. When SACCH is not available, at that moment a stealing bit is used from the normal burst by FACCH and handover is given.

Information sent during one Time Slot (TS) is called a burst. The burst types in GSM are Normal Burst (NB), Access Burst (AB), Synchronization Burst (SB), Frequency Correction Burst (FCB) & Dummy Burst (DB).

A standing wave may be formed when a wave is transmitted into one end of a transmission line and is reflected from the other end by an impedance mismatch. VSWR is the ratio of maximum to minimum voltage in a standing wave pattern

EIRP - Equivalent Isotropically Radiated PowerThe unit of measurement of the strength of a radiated field. Typically that from a radio antenna.

The polarization of an antenna is the polarization of the wave radiated by the antenna. At a given position, the polarization describes the orientation of the electric field. Vertical and horizontal are the simplest forms of polarization and they both fall into a category known as linear polarization. However it is also possible to use circular polarization. This has a number of benefits for areas such as satellite applications where it helps overcome the effects of propagation anomalies, ground reflections and the effects of the spin that occur on many satellites. Circular polarization is a little more difficult to visualize than linear polarization. However it can be imagined by visualizing a signal propagating from an antenna that is rotating. The tip of the electric field vector will then be seen to trace out a helix or corkscrew as it travels away from the antenna. Circular polarization can be seen to be either right or left handed dependent upon the direction of rotation as seen from the transmitter.Another form of polarization is known as elliptical polarization. It occurs when there is a mix of linear and circular polarization. This can be visualized as before by the tip of the electric field vector tracing out an elliptically shaped corkscrew.

Fading is the distortion that a carrier-modulated telecommunication signal experiences over certain propagation media. A fading channel is a communication channel that experiences fading. In wireless systems, fading is due to multipath propagation and is sometimes referred to as multipath induced fading.

Rayleigh fading is caused by multi path reception. The mobile antenna receives a large number, say N, reflected and scattered waves. Because of wave cancellation effects, the instantaneous received power seen by a moving antenna becomes a random variable, dependent on the location of the antenna.

A form of radio fading caused by the existence of two or more paths between the transmitter and receiver. Delays on the reflected path may add to (strengthen) or subtract from (fade) the main path. Multi path may be overcome by using multiple receive antennas or frequency hopping

OTD - Orthogonal Transmit DiversityAn optional method of transmission of the Forward CDMA Channel that utilizes two antennas, each transmitting a fraction of the code symbols. It is used to enhance the performance in the presence of fades due to multipath propagation.

Space diversityA method of TX (Transmission) or RX(Reception), or both, in which the effects of fading are reduced by the simultaneous use of two or more antennas. Antennas should ideally be separated by one or more wavelengths.Time diversityTransmission in which signals representing the same information are sent over the same channel at different times.

OTD - Orthogonal Transmit DiversityAn optional method of transmission of the Forward CDMA Channel that utilizes two antennas, each transmitting a fraction of the code symbols. It is used to enhance the performance in the presence of fades due to multipath propagation - Auxiliary Transmit Diversity Pilot ChannelThe Auxiliary Transmit Diversity Pilot Channel is associated with the APCH (Auxiliary Pilot Channel), that is transmitted by a CDMA (Code Division Multiple Access) BS (Base Station) from the non-primary antenna when orthogonal transmit diversity is employed.FTFPCH - Forward Transmit Diversity Pilot ChannelA pilot channel transmitted by a CDMA (Code Division Multiple Access) BS (Base Station) from the non primary antenna when orthogonal transmit diversity is employed

The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading. Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels, and one protection channel for automatic use by any faded channel.

Multiple versions of the same signal are transmitted at different time instants. Alternatively, a redundant forward error correction code is added and the message is spread in time by means of bit-interleaving before it is transmitted. Thus, error bursts are avoided, which simplifies the error correction.

The basic mechanisms of propagation are Reflection, Refraction, Scattering and Diffraction

Diffraction is the spreading of waves around obstacles or squeezing through a small hole. It occurs with sound waves, light, atoms, and subatomic particles.

In electromagnetic wave propagation, the knife-edge effect or edge diffraction is a redirection by diffraction of a portion of the incident radiation that strikes a well-defined obstacle such as a mountain range or the edge of a building.The knife-edge effect is explained by Huygens-Fresnel principle, which states that a well-defined obstruction to an electromagnetic wave acts as a secondary source, and creates a new wavefront. This new wavefront propagates into the geometric shadow area of the obstacle.

Scattering is where the direction, frequency, or polarization of the wave is changed when the wave encounters discontinuities in the medium, or interacts with the material at the atomic or molecular level.

In telecommunication, free-space path loss (FSPL) is the loss in signal strength of an electromagnetic wave that would result from a line-of-sight path through free space, with no obstacles nearby to cause reflection or diffraction. Free-space path loss is proportional to the square of the distance between the transmitter and receiver, and also proportional to the square of the frequency of the radio signal.

The Fresnel Zone is the area around the visual line-of-sight that radio waves spread out into after they leave the antenna. You want a clear line of sight to maintain signal strength, especially for 2.4 GHz wireless systems. This is because 2.4 GHz waves are absorbed by water, like the water found in trees. Typically, 20% Fresnel Zone blockage introduces little signal loss to the link. Beyond 40% blockage, signal loss will become significant.

The angle between the directions, on either side of the axis, at which the intensity of the radio frequency field drops to one-half the value it has on the axis.

BandwidthBandwidth may be defined as the difference between the highest and lowest frequencies available for network signals. It is also used to describe the amount of data that can be transmitted in a fixed amount of time.3dB bandwidth:The half-power bandwidth is defined as the interval between frequencies at which the power spectral density has dropped to half power or 3 Db below the peak value. Half-power bandwidth is also called the 3Db bandwidth.Absolute bandwidth of a signal is defined as the range of frequencies over which the signal has non-zero power spectral density.A simpler and more widely accepted measure of bandwidth is first null-to-null bandwidth. the null-to-null bandwidth is equal to the width of the main spectral lobe.

SNR - Signal-to-Noise RatioThe SNR or S/N (Signal to Noise Ratio) of the amplitude of the desired signal to the amplitude of noise signals at a given point in time. SNR is expressed as 10 times the logarithm of the power ratio and is usually expressed in dB (Decibel).Front-to-Back Ratio (F/B Ratio)Front to Back Ratio of an antenna is the ratio of the gain in a specified direction, i.e., azimuth, usually that of maximum gain to the gain in a direction 180 from the specified azimuth.

Hand off / HandoverA Hand off, or Handover, is the process in which a cellular phone is handed from one cell to the next in order to maintain a radio connection with the network. The variables that dictate a handover depend on the type of cellular system. Handover due to (signalling)traffic reasons:When the capacity of a cell nears its maximum, mobile stations in the periphery of the cell may be handed over to neighbouring cell with lower traffic load. Intra cell - Intra BSC handoverInter cell - Intra BSC handoverInter cell - Inter BSC handoverInter MSC Handover

When there is an excessive delay by the MSC in assigning a handoff or when the threshold is set too small for the hand off time in the system.

The ability to select between the instantaneous received signals from a variety of base stations is called soft hand off. Systems that assign different radio channels during hand off is called hard hand off.

In synchronous handover the mobile has knowledge of the base stations timing.In synchronous handover, the handset tries to find both power and synchronization information from the base station. In asynchronous (non-synchronous) the mobile first accesses the new base station over the random access channel.

These handover are occurred when request received from emergency services like 101,108 and 100,then preference is given to them rather than normal subscriber calls.

Handover due to signal quality and strength1.When a mobile subscriber is moving during a call, he may travel from one cell to another. 2.Frequency resources of previous cells can not be used any more. 3.The mobile station is handed over to the new cell.

Mobile assisted handover (MAHO)Network assisted handover (NAHO)

Vertical handover: redistributing mobile stations from one access network to anther

Ping pong effect occurs when the MS is handed over from oe cell to another but is quickly handed backed to the original cell.

The BSC controlling the current cell makes the decision to perform a handover

The source MSC finds that the call needs to be handed over to a cell controlled by a different MSC. The source MSC and target MSC interact and then command the UT to move to the new cell. The target MSC informs the source MSC when the call has been successfully handed over. The source MSC releases the radio resources for the call. Note that the call is still routed via the source MSC.

The mobile station sends the network a query as to whether the network can support the handover by transferring the link data from the first mobile station to the second mobile station. If the mobile station is informed that the network cannot support the handover the mobile station makes the link data available to the second base station.

GMSK (Gaussian Minimum Shift Keying).BPSK requires wide band width for transmission due to signal changes phase abruptly. This can be overcome by GMSK.

PSK - Phase Shift KeyingPhase Shift Keying is a technique enabling digital information to be carried over an analogue carrier such as a radio link. The process causes the phase of the carrier wave to be manipulated in order to signify either a logical 0 or 1. There are many variations of PSK allowing greater data transfer rates to be achieved.FSK - Frequency Shift KeyingIn Frequency Shift Keying the carrier frequency is shifted between distinct frequencies. A common shift pattern is between two frequencies one representing a zero and the other a one

A QPSK (Quadrature Phase Shift Keying) modulated signal typically comprises a signal of constant frequency which can have one of four phases, each phase representing two bits. It can be generated by multiplying two binary information signals, an in-phase signal I(t) and a quadrature-phase signal Q(t), by a carrier signal at a phase of 0.degree. and 90.degree. respectively (i.e. a cosine signal and a sine signal respectively). The resulting signals are then summed to form the QPSK signal.OQPSK (Offset QPSK) is another modulation scheme where the signal Q(t) or I(t) is delayed by half a symbol when the OQPSK is modulated. In the subsequent transmitted symbol, phase shifts are restricted to a maximum of 90.degree. at a time. This gives OQPSK desirable properties over QPSK which can have phase shifts of 180.degree.

MSK - Minimum Shift KeyingMinimum Shift Keying is a form of FSK (Frequency Shift Keying) used to carry digital information on a radio carrier.

QAM - Quadrature Amplitude ModulationModulation technique using two amplitude modulated RF (Radio Frequency) carriers that are out of phase by 90 degrees. Information transfer is achieved using a mixture of phase and amplitude changes. Since noise also appears as amplitude variations QAM is prone to interference

PAM - Pulse Amplitude ModulationThis is a process of representing a continuous analogue signal with a series of discrete analogue samples. The process is used in PCM (Pulse Code Modulation) during the conversion of an analogue signal into a digital representation.PCM - Pulse Code ModulationPulse Code Modulation is a process in which an analogue signal is encoded into a digital bit stream. The analogue is first sampled, then quantized and finally encoded into a bit stream. The most common version of PCM enables one voice circuit to be represented by a 64Kbps stream. Other versions of PCM exist such as ADPCM (Adaptive Differential PCM) which enables lower bit rates to be achieved.

FDM - Frequency Division MultiplexingFrequency Division Multiplexing is a technique in which the available transmission bandwidth of a circuit is divided by frequency into narrower bands, each used for a separate voice or data transmission channel. FDM enables multiple user channels to be carried on one physical circuit.TDM - Time Division MultiplexingDigital Multiplexing technique in which two or more apparently simultaneous channels can be combined to form a bit stream by interleaving bits or bit words from different channels.OFDM - Orthogonal Frequency Division MultiplexingOFDM is a multi carrier transmission technique capable of supporting high speed services whilst still being bandwidth efficient. It achieves this by forcing multiple sub-carriers together thereby reducing the bandwidth required when compared to more traditional FDM (Frequency Division Multiplexing)methods. However, to ensure these adjacent sub-carriers do not cause excessive interference, they must be orthogonal or 90 to one another

GPRS ---------GMSK and 8PSK

EDGE ---------8PSK

Cellular networks are more often limited by problems caused by interference rather than by signal strength problems. Co-channel interference is caused by the use of a frequency close to the exact same frequency. The former will interfere with the latter, leading to the terms interfering frequency (I) and carrier frequency (C). The GSM specification recommends that the carrier-to-interference (C/I) ratio is greater than 9 decibels (dB).

Adjacent frequencies (A), that is frequencies shifted 200 kHz from the carrier frequency (C), must be avoided in the same cell and preferably in neighboring cells also. Although adjacent frequencies are at different frequencies to the carrier frequency they can still cause interference and quality problems. The GSM specification states that the carrier-to-adjacent ratio (C/A) must be larger than -9dB. Erickson recommends that higher than 3 dB be used as planning criterion

RXQUAL - Received Signal QualityIn a radio system RXQUAL indicates the average signal quality received. Its range is 0 to 7. In the GSM system the conventional quality measure (Rx Quality) is based on the pseudo bit-error rate (pseudo BER) or an estimate of the BER made before channel decoding, which is an estimate of the bit errors over the air interface.

Measurements taken over a full set of TDMA frame.Measurements taken over a subset of TDMA frame. If even one frame is not transmitted in the measurement period, then it is considered as a sub set

SQI stands for speech quality index. Its range is -22 to +30.SQI is measured by the FER.

BSIC - Base Station Identity CodeThis is a code in GSM which is broadcast on the SCH (Synchronization Channel) in order to identify the NCC (Network Colour Code) and the BCC (Base Station Colour Code).

AMR - Adaptive Multi RateA codec offering a wide range of data rates. The AMR is used to lower the codec rate as the interference increases and thus enabling more error correction to be applied. The AMR codec is also used to harmonize the codec standards amongst different cellular systems.

Handover failureSDCCH dropTCH drop

Radio link time out counter

After completion of RF survey we go for drive test for measuring radio parameters, assesses speech quality, and decodes air interface messages.

Monitors the air interface between the basestation and the test mobile station.

When camped on a cell, the mobile shall regularly search for a better cell according to the cell reelection criteria. If a better cell is found, that cell is selected. This process is identified as the C2 in the GSM system .

C1 is the path loss criterion, which is used to estimate the balance between up link and down linkC2 measurements are used to optimize and prioritize cell reelections.

GSM call re-establishment service allows a mobile station to resume a call in which the radio link has been temporarily interrupted due to interference or bad signal (which is referred to as an interrupted call). This service increases end user satisfaction and network quality perception

Short call drive test is for ACCESSIBILITY and Long call drive test is for RETAINABLITY.

Call Setup Success Rate:. Number of the unblocked call attempts (setup) divided by the total number of call attempts105. What is RSSI?RSSI - Received Signal Strength Indication is the measured power of a received signal.

RXLEV - Received Signal LevelIn a radio system RXLEV indicates the average signal strength received.RXQUAL - Received Signal QualityIn a radio system RXQUAL indicates the average signal quality received.

In digital transmission, the quality of the transmitted signal is often expressed in terms of how many of the received bits are incorrect. This is called Bit Error Rate (BER). BER defines the percentage of the total number of received bits which are incorrectly detected. Channel coding is used to detect and correct errors in a received bit stream. It adds bits to a message. These bits enable a channel decoder to determine whether the message has faulty bits, and to potentially correct the faulty bits.BER - Bit Error RateThis a variable indicating the ratio between the total number of bits received to those that were errored during transmission. This ratio is typically employed when expressing the QoS (Quality of Service) of a particular bearer.FER is useful to estimate quality under frequency hopping conditions.BER is made before channel decoding where as FER made after channel decoding.

The mobile station is used for storing information on at least one subscriber-specific base station, the cell served by the base station being the mobile subscriber's home cell, office cell or the like, and the mobile station is used for changing the determined level of the signal of at least one selected radio channel on the basis of information on the subscriber-specific base station

A method for handing over a link between a mobile station and a network from a first base station to a second base station of the network. In the case of an existing link, link data for the link are stored in the base station in question and resources of the base station are held in reserve for the link. When a link is handed over, the link data initially remain stored in the first base station and the resources of the first base station initially remain held in reserve. At a later time point the link data are deleted and the resources are freed up. The mobile station sends the network a query as to whether the network can support the handover by transferring the link data from the first mobile station to the second mobile station. If the mobile station is informed that the network cannot support the handover the mobile station makes the link data available to the second base station.