LTE Possible Dimensioning ConceptsAll-AverageThe backhaul connection shall support the aggregated average capacity of all cells. The average capacity is determined under realistic air interface conditions and multiple users per cell.All-Average/Single-PeakThe backhaul connection shall support the aggregated average capacity of all cells, while at least supporting the peak capacity of one cell.All-PeakThe backhaul connection shall support the aggregated peak capacity of all cells (non-blocking). The peak capacity is determined under ideal air interface conditions and with a single user per cell. This approach will lead to over-dimensioning, thus usually extra costs

LTE Possible Dimensioning ConceptsAll-AverageThe backhaul connection shall support the aggregated average capacity of all cells. The average capacity is determined under realistic air interface conditions and multiple users per cell.All-Average/Single-PeakThe backhaul connection shall support the aggregated average capacity of all cells, while at least supporting the peak capacity of one cell.All-PeakThe backhaul connection shall support the aggregated peak capacity of all cells (non-blocking). The peak capacity is determined under ideal air interface conditions and with a single user per cell. This approach will lead to over-dimensioning, thus usually extra costs

Affects Of The Channel In LTE MIMOTo understand the impact of the channel, lets assume that the base station receiver is facing many challenges in the same MIMO receiver that universal areas, but also must receive data simultaneously from multiple users. In terms of MIMO UM, each signal is derived from a separate UE, because each signal is completely independent channel, slightly different power levels and different time. These features can be emulated Agilent N5106A scanning a MIMO receiver (PxB), in combination with the RF signal generator.Testing:Affects of the Channel in LTE MIMOTest Configuration ENB receiver configuration differs from the UE. UE normally sends error reports in the uplink packet back to the test system and base station equipment is more likely that the appropriate demodulated output signal available.Note that the recovery of the MIMO channel separation involves several components of the signal in the presence of noise and interference. When the transmitted signals are orthogonal, but once you get a lot of signal coupling path radiation receivers can reduce the difference between the signals.Normal Operation:Affects of the Channel in LTE MIMOIn normal operation, the receiver will have to deal with complex and change the channel, but the channel fading by such means, testing is not repeatable, if you want to ensure that the basic bandwidth action is appropriate. Fading channel constructed from phase differences and simple for roads, provides deterministic signal may be designed to check the capacity limit of the receiver. Adding noise to the channel may be easily creating a control signal, wherein some subcarriers are harder than other demodulation.In order to test the dual phase line source standard RF bandwidth and transient that can be achieved by means of a common reference frequency signal and the frame synchronization is sufficient for most applications.

If necessary fading configuration such as shown offers more ways off independent constant output analog or digital tester using Agilent N5106A MIMO receiver.Direct MIMO:Affects of the Channel in LTE MIMOFor direct MIMO mapping test phase relationship between the open loop test signals do not affect the receiver, because the signals are orthogonal to connect adding twice the vector to occur. In a closed loop system, the phase of test signals must be constant when the channel is sampled, allowing the first coupling coefficients to be calculated and applied. This may require the system to be stable than phase.The number of channel condition can be used to determine the SNR required achieving a specified performance de modulator. Number state is a composite measure of performance channel. Each layer of MIMO may, in fact, different performance.

How Cross Domain Signal Analysis In LTERegarding cross domain analysis, we see that, I traditionally signal from a receiver RF section can be demodulated and Q components using analog techniques. Today, however, the down conversion signal is digitized by an ADC IF, and usually then fed into the section of the baseband demodulation and decoding.In Cross domain signal Measurement ADC output is a challenge because production is now in the digital domain. A solution is to analyze the digital bits from the ADC directly using a logic analyzer for capturing digital data. The hard part of this solution is data processing in a significant result because most applications of logical analysis does not focus on RF metric generation. Using Agilent 89601A software vector signal analysis (VSA) is a way to solve this challenge.VSA software can run on a number of Agilent spectrum analyzers for Cross domain signal analysis, oscilloscopes and logic analyzers for demodulating various modulation formats, and offers a unique way to analyze the ADC performance by being able to make traditional RF measurements directly into digital data. This approach gives a designer the ability to quantify the ADC contribution to the overall system performance and RF measurements compared to using the same measurement algorithms.If IQ RFIC has analog outputs, can be analyzed by an Agilent oscilloscope or MXA signal analyzer. If RFIC uses DigRFv3 or v4 interface, the signal can be captured by (RDX) Radio Tester Digital Domain.These analog or digital IQ signals can be analyzed with the same software 89601A VSA for Cross domain signal analysis in LTE. For developer tape hardware probes are available for analog and IQ DigRF interface. VSA software provides EVM performance measurements for verification numerical and graphic details additional useful during product development to isolate the source of signal impairments. If Gaussian noise added to the signal deterioration, a relationship can be drawn between EVM and BER cruel. Alternatively, the signals captured IC can be placed in a simulated Agilent receiver and software design for LTE. The precise design of the receiver determines the performance, so that the results can vary depending on the specific application provider.

How Cross Domain Signal Analysis In LTERegarding cross domain analysis, we see that, I traditionally signal from a receiver RF section can be demodulated and Q components using analog techniques. Today, however, the down conversion signal is digitized by an ADC IF, and usually then fed into the section of the baseband demodulation and decoding.In Cross domain signal Measurement ADC output is a challenge because production is now in the digital domain. A solution is to analyze the digital bits from the ADC directly using a logic analyzer for capturing digital data. The hard part of this solution is data processing in a significant result because most applications of logical analysis does not focus on RF metric generation. Using Agilent 89601A software vector signal analysis (VSA) is a way to solve this challenge.VSA software can run on a number of Agilent spectrum analyzers for Cross domain signal analysis, oscilloscopes and logic analyzers for demodulating various modulation formats, and offers a unique way to analyze the ADC performance by being able to make traditional RF measurements directly into digital data. This approach gives a designer the ability to quantify the ADC contribution to the overall system performance and RF measurements compared to using the same measurement algorithms.If IQ RFIC has analog outputs, can be analyzed by an Agilent oscilloscope or MXA signal analyzer. If RFIC uses DigRFv3 or v4 interface, the signal can be captured by (RDX) Radio Tester Digital Domain.These analog or digital IQ signals can be analyzed with the same software 89601A VSA for Cross domain signal analysis in LTE. For developer tape hardware probes are available for analog and IQ DigRF interface. VSA software provides EVM performance measurements for verification numerical and graphic details additional useful during product development to isolate the source of signal impairments. If Gaussian noise added to the signal deterioration, a relationship can be drawn between EVM and BER cruel. Alternatively, the signals captured IC can be placed in a simulated Agilent receiver and software design for LTE. The precise design of the receiver determines the performance, so that the results can vary depending on the specific application provider.

Power Ramping In LTEOpen loop power control together with optional power ramp-up is used during therandom access process at the beginning of the connection until more accuratecontrol information is available.Power loss due to transmission distance depends on to the increase of the distancebetween NodeB and the UE. In such a case, feedback information from another sideis not necessary for estimating power loss. This type of power loss is controlled bythe open loop power control. RACH (Random Access Channel) uses open looppower control.The Open Loop Power Control is performed by the UE, after receiving informationtransmitted on system information block in broadcast channel (BCH) and measuredthe path loss in the downlink.The NodeB broadcasts the initial transmission power level and the power step to theUE in the BCH (Broadcast channel).The UE sets the initial transmission power in the first preamble and waits for the ULgrant on PDCCH. If not acknowledged, the MS increases the preamble transmissionpower by a specified power offset step.Article Topics :

Wide Bandwidths Concept For LTE MIMOOne of the unique aspects of LTE is the support of the six channel bandwidths from 1.4 MHz to 20 MHz. To simplify system operation and roaming phones should support all these bandwidths, although effective deployment in any one area may be limited to fewer band width 20 MHz LTE is significantly larger than the widths maximum bandwidth of other cellular systems today.Therefore, when designing the recipients attention to the amplitude and phase flatness is required. Filters, amplifiers and mixers in particular must now work properly on multiple channel bandwidth.The structure of the LTE signal has a reference signal (RS) which are arranged in both frequency and time throughout the LTE signal. ENB and the UE receiver may use such signals and digital signal processing (DSP) techniques to compensate for amplitude and phase errors in the receiver linearity. Flatness needs to be tested in each supported bandwidth and the band, in particular at the band edge where the edge of the duplex filter attenuates the signal.Open Loop And Close Loop Testing In LTEHere I write short notes on how to test open loop and close loop testing in lte and what idea behind it. In open loop no any data send back and in closed loop all relevant data available to both side lets check in some detail.Open and close loop testing in LTE:Open loop test where no test receiver sends feedback information source is sufficient to prove the fundamental characteristics of the individual components in the receiver and is also a first step in validating algorithms baseband demodulation section. However, complete verification.Overall performance testing in real conditions receiver require closed loop through a channel off. Closed-loop test packets lost packets are re transmitted using incremental redundancy based on real-time information from the receiving confirmation.Modulation and coding used for transmission also based on real-time information from the receiver. This feedback can be optimized for sub bands overall bandwidth channel to enable frequency selective scheduling.This is very basic funda behindOpen loop and close loop testing in LTE for more details check my old article on open loop testing in lte and close loop testing in lte individual.Article Topics :Open loop and close loop testing in LTE, open loop, close loop, loop, lte, source, feedback, receiver, testing equipment, testing of lte, baseband, demodulation

Receiver Design For LTEThe main objective of the study is to take action for the entire measurement receiver. However, many factors can affect the performance of the receiver, such sub-blocks of receipt must be checked on the basis of the first and measurable contributions eliminate or reduce uncertainty. If using multiple receivers, it is necessary to make these measurements based on each separate receive chain before verifying the effectiveness of MIMO. Principles discussed here apply to both frequency division duplex (FDD) mode and time division duplex (TDD) access FDD. Although there are examples of a typical block diagram of a mobile radio telephone LTE is shown in Figure.

Modern receivers use the same blocks as classical models; However, today there is a higher degree of integration with unique components performing multiple functions, especially in the mobile space is at a premium (which means it will probably be fewer places where signals may be injected or observed test ).Here we focus on a subset of receiver design and testing considerations, in particular: Open and closed loop operation, wide bandwidth, signal analysis of several areas affecting the channel, and finally pre-coding and code list LTE.Article Topics :Receiver Design for LTE, Open and closed loop operation, lte receivers, division duplex, lte design, receiver, testing receiver, design receiver, lte models

Basic Test For LTE Transmitter And Receiver DesignLTE already requires fundamental changes in the base and handset and research project due to higher data rates, there is an important signal bandwidth and enhance integration and miniaturization in mobile phones, for example: Need to handle 6 different channel bandwidth from 1.4 to 20 MHz, and both frequency division duplex (FDD) and Time Division Duplex (TDD) modes. Flexible transmission systems and almost infinite combination of activities in which the structure of the physical channel has a significant impact on the performance of the RF. Elements v4 compatible multi-gigabit DIgRF handset, which removes the ability of the communication bottleneck between chips and radio frequency bands (RFICs), require cross-domain (DIGITAL IN, RF OUT) potentially communication. Digital source test must simulate both data traffic and closed protocol stack within the digital interface that controls RFIC performance. High-speed digital DigRF interface serial number should be treated as a transmission medium, where the disorder can worsen the quality of analog and degradation bit error rate (BER) and be careful connecting test equipment to avoid disrupting the flow signal. Transfer of information between handsets band RF circuits and must comply with strict time constraints. Therefore, it is important that the conditions of the test, measure the exact time each frame is sent from one chip to another and provides real-time detection of timing violations.Added to these are special challenges due to the need to support a variety of techniques including antenna diversity, MIMO and beam control.

Principle Of Power Control In LTEPower control already being applied in 2nd and 3rd generation networks has high potential for improvement of the performance of mobile networks.Main benefits are:1. It can bring down the interference in up- and downlink and hence enhances the capacity of the networks.2. Additionally it helps to keep down the uplink-power consumption, thereby increasing the stand-by time for the UE.3. Furthermore, from the EMC (Electro Magnetic Compatibility) point of view it can improve the situation considerably.Principle :The transmission power is adapted in order to achieve the desired QoS (BLER/BER). This adaptation is necessary since the propagation channel is subject to several conditions, which generally vary in space and/or time,e.g. path loss log normal fading short term fading UE speed location (outdoor, indoor, in-car) etc.Downlink power controldetermines the energy per resource element (EPRE). The term resource element energy denotes the energy prior to CP insertion. The term resource element energy also denotes the average energy taken over all constellation points for the modulation scheme applied.Uplink power controldetermines the average power over a DFT-SOFDM symbol in which the physical channel is transmitted. In contrast to UTRAN based on WCDMA however the requirements for UL power control are more relaxed as a similar near-far problem of UTRAN does not exist. Compared with UTRAN the UL power control is slower. The PUSCH and the PUCCH are subject to a combined open and closed loop power control algorithm, i.e. to control the transmission power for UL channels a combination of an open (input: pathless, sysinfo and signaling) and a closed loop (TPC) method is used.A cell wide overload indicator (OI) and a High Interference Indicator (HII) to control UL interference are exchanged over X2. An indication is given which PRBs an eNodeB scheduler allocates to cell edge UEs and hence will be most sensitive to inter-cell interference.

Which Cell Parameters Needs To Obtain In LTE?To provide the most critical information to the UEs, the eNodeB uses the BCH channel The information is sent on pre-defined time-frequency resources.This information is organized into different information blocks: The MIB, the Master Information Block. System Frame Number DL -downlink System Bandwidth Number of Transmit Antennas at eNodeB Periodicity: 4 RFs SIB1 How other SIBs are scheduled and cell accessibility Periodicity: 8 RFs SIB2: Access Info SIB3: Serving Cell info for Cell reselection SIB4: Intra-frequency neighbors SIB5: Other e-UTRA frequency SIB6: UTRA frequencyThe MIB is carried by the BCH channel.All the SIBs are carried by the DL-SCH. downlink synchronization channel

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What Is Cyclic Prefix In LTE ?The guard period after each rectangular pulse carrying the modulated data symbol is a simple and efficient method to deal with multi-path reception.The cyclic prefix (CP) simply consists of the last part of the following symbol.The size of the cyclic prefix field depends on the system and can even vary within one system. Cyclic prefixes are used by all modern OFDM systems and their sizes range from 1/4 to 1/32 of a symbol period. Most receiver structures use the cyclic prefix to make an initial estimation of time and frequency synchronization which including pre-FFT synchronization, non-data assisted synchronization forCyclic prefix in LTEA receiver typically uses the high correlation between the cyclic prefix and the last part of the following symbol to locate the start of the symbol and begin then with decoding. In multi-path propagation environments the delayed versions of the signal arrive with a time offset, so that the start of the symbol of the earliest path falls in the cyclic prefixes of the delayed symbols. As the CP is simply a repetition of the end of the symbol this is not an inter-symbol interference and can be easily compensated by the following decoding based on discrete Fourier transform forCyclic prefix in LTE.Of course cyclic prefixes reduce the number of symbols one can transmit during a time interval. This method to deal with inter-symbol interference from multi-path propagation is theoretically sub-optimal. CDMA with RAKE receiver for instance provides a much better efficiency. On the other hand non-ideal implementations of RAKE receivers also degrade system performance drastically but still require a lot of hardware capacity for the basic implementation forCyclic prefix in LTE.The rectangular pulse with cyclic prefix requires far less hardware, so the free capacity can be used to implement other performance optimization techniques like MIMO.

Implementation Margin In LTE Implementation margin is used to include non-ideal receiver effects such as channelestimation errors, tracking errors, quantization errors, and phase noise. Thisimplementation margin or sensitivity degradation can be used to apply some margin to the link budget to account for devices from other vendors that may have largertolerances from the specifications or for which the actual performance is not available. Alarger implementation margin may be assumed at the subscriber end as opposed to thebase station end. This is done to reflect the scenario where one base station canconnect to multiple subscriber devices. The subscriber devices may be obtained fromseveral different vendors, each with its own receiver design whereas the base stationwill typically be from fewer vendors.

RE Groups & CFI Control Format Indication In LTERE groups & CFI Control Format Indication in LTE is as below.RE groupsIn order to support DL control information mapping, RE-groups are defined.Four useful symbols are bundled, useful in the sense that REs carrying the cellspecific reference symbols are not available.The one cell-specific RS case is mapped in the same way as in the two cell-specific RS case .So the example sketched in the figure below applies for the one and two antenna cases. In the first symbol are six REs grouped, however only four are available as two are blocked by reference signals.

How Many LTE Downlink Transport Channel ? How Its Work?There are major four channel in LTE Downlink trasport channel. which list below with its work in short.Paging Channel ( PCH) Supports UE discontinuous reception (DRX) to enable UE power saving. Broadcasts in the entire coverage area of the cell. Mapped to physical resources which can be used dynamically also for traffic/other control channels.Broadcast Channel ( BCH ) The LTE transport channel maps to Broadcast Control Channel (BCCH). Fixed, pre-defined transport format. Broadcast in the entire coverage area of the cell.Multicast Channel ( MCH) Broadcasts in the entire coverage area of the cell. Supports MBSFN combining of MBMS transmission on multiple cells. Supports semi-static resource allocation e.g.with a time frame of along cyclic prefix.Downlink Shared Channel ( DL-SCH ) Main channel for downlink data transfer. It is used by many logical channels. Supports Hybrid ARQ. Supports dynamic link adaptation by varying the modulation, coding and transmit power. Optionally supports broadcast in the entire cell. Optionally supports beam forming. Supports both dynamic and semi-static resource allocation. Supports UE discontinuous reception (DRX) to enable UE power saving. Supports MBMS transmission.

Single And Multiple User MIMO In The Uplink SU MIMO LTESU-MIMO is within LTE, but at the time of this writing has not yet been fully identified. To implement the SU-MIMO UE require two transmitters. This is an important problem from the standpoint of cost, size and battery consumption, and for these reasons, SU-MIMO is not currently a priority for development. Moreover, increased rates of data transmission in the uplink, it may be possible to SU-MIMO is not so important since they are the downlink due asymmetric distribution of traffic.Finally, if the system is to be realized by the limited capacity of the uplink may not be practical to increase the transmission power of the UE is sufficient to achieve the desired SNR in receivers ENB.

Although the UE, typically has a transmitter in the base configuration, it is still able to maintain the new shape MIMO. Unlike the reception requires MIMO transmitters are in the same physical device or location. It follows that the uplink MIMO can be implemented with two transmitters belonging to two different UE. This creates an opportunity to increase the uplink power although the single user will not see any increase in the data rate.The fact that the transmitters are physically separate two implications. Firstly, it is not possible precoding, because the source data can not be shared between the two UEs in order to create the necessary cross-coupling of data streams. This reduces the potential gains that co-located transmitters may have had. Second, the separation of the transmitter increases the likelihood that the radio channels seen by the eNB will be uncorrelated.In fact, when the ENB should be noted that two UEs to connect to the MU-MIMO, the main criterion is the presence of de-correlated channels. Any loss of profit due to lack of pre-coding is more likely to offset gains from the best channel de-correlation; Therefore, the MU-MIMO can be a valuable method of increasing the capacity of the reverse link.Restore LTE tolerated small mistakes time and frequency. Normal operation of the uplink, each UE will adjust the frequency with sufficient accuracy as ENB.ENB also instructed the UE to adjust its timing and power, so that all signals arrive at the receiver ENB approximately at the same level and time. An antenna located in another path of the transmitting device assumes correlated. These conditions allow the scheduler to control two ENB to UE transfer data simultaneously using the same subcarriers.Multi-user MIMO involves the simultaneous transmission of codewords in layers of different UE, at the same time and frequency. Using conventional methods to ensure adequate control of RF power, and time alignment of the signals received in the eNB. Align the energy received from the UE, ENB is the most difficult to master, if the potential benefits of the ability to deliver.Single User And Multi User MIMO Codewords In LTEFigure shows how the two codewords are used for a single user in the downlink. It is also possible that the code words to be assigned to different users to create multi-user MIMO (MU-MIMO). Depending on the channel information available in the eNB, modulation and precoding layers may be different to match the performance.

Precoding choices are defined in the search, known as codebook table. Codebook is used to quantize the options available, and thus limits the amount of information fed back from the receiver to the sender. Some precoding choices are clear. For example, Codebook index (CI) 0 is a direct set of codewords to layers and CI 1 applies spatial expansion.

Table 1 shows the choices codebook for one and two layers. Note only the case in two layers employs spatial multiplexing. Precoding with a layer is limited to a displacement 0 , 90 or 180 of phase.In operation, the UE will send a message to the scheduler ENB with the index codebook that is closest to the channel, even if the system can be configured for multiple codebook values, one for each group of resource block. To use this information while it is still valid, the scheduler must respond quickly, in a few milliseconds, depending on the speed of variation of the channel. If the EU is to provide information on a more regular channels, the information will be more accurate, but the percentage of resources used to increase the signal and set more challenging on ENB.

Codeword, Layer, And Precoding In LTETerms codeword, layer, and precoding have been taken to refer specifically to LTE signals and processing. The figure shows the processing steps to which they relate. The terms used in the following ways:

Codeword:codeword represents the user data before it is formatted for transmission. One or two code words, CW0 and CW1, may be used depending on the conditions of the channel and the use case. In the most common case of a single user MIMO (SU-MIMO), two codewords are sent to a single handset UE, but less common for downlink multi-user MIMO (MU-MIMO), each codeword is sent only one UE.Layer:The term is synonymous with the current. For MIMO, the use of at least two layers. Up to four layers are allowed .The Number is always less than or equal to the number of antennas.Precoding:Precoding layer modifies signals before transmission. This can be done diversity, spatial multiplexing, or beam direction. MIMO channel conditions may favor one layer (data stream) to another. If the base station (eNB) is given channel (e.g., the information sent back from the UE), the complex may be added to counter the imbalance cross-coupling in the channel. In arrangement 2 * 2, LTE uses a single stop 1 to 3 Precoding, which improves the performance if the channel has not changed too rapidly.Eigen beamforming:(sometimes known simply as beamforming) amends the transmission signals to provide the best transportation to interference and noise ratio (CINR) out of the channel.

The MIMO Channel MatrixThe MIMO channel MatrixConsider for a moment in time, on the same frequency and channel modeling as a black box with durable internal components. If we add two completely different input signals is to be mixed with each other in a certain manner depending on the value of Z1 to Z4. If we send a signal training that is unique for each input and output measurement, we know how it was connected, so as to disconnect them.All signals, data, and training will be combined in the same way, so thats what we learned from the training signal can be applied to real data. Noise and distortion of the modulation limit, which can be used along with the ability to uncouple the outputs. The worst case would be if Z1 to Z4 are the same, when both outputs are the same and MIMO does not operate.The best case is if the outputs are equal in magnitude and opposite in phase, when theoretically double the capacity in The MIMO channel Matrix.Equation 1 The long-form version of the theorem of channel capacity can be written as shown in the following figure

Where, C = channel capacity in bits per second, B = occupied bandwidth in Hz, /N = signal to noise ratio and = a singular value of the channel matrixThe potential in the instant system capacity increase can be derived from the relationship of singular values of the channel matrix H, also known as the condition number. The condition number of The MIMO channel Matrix can also be used to indicate the increase in SNR required recovering the MIMO signal in relation to the SISO case.With the channel changing due to fading and trajectories multiple effects and Doppler frequency shift due to motion of phone, among others, the number of conditions to changes of constant frequency in the spectrum of RF channel, as is illustrated in the figure below.

Reference signals (or pilots) in places regular frequency at the output of each transmitter provides a way for recipients to estimate the channel coefficients. In general, each tube of data will not have the same performance. LTE uses feedback mechanisms known as pre-coding and make Eigen training both forms of closed-loop MIMO, in the phone to request modifications to the cross-coupling of the transmitter outputs to give the best match to the MIMO channel Matrix in channel characteristics.

Visualization Of Beam Forming In LTECurrently, beam forming is only applicable for TDD version of LTE. The time synchronous version of LTE TDD on uplink and downlink also makes the implementation of beam forming more attractive than in LTE FDD.Beam forming scheme is a signal processing technology that is used to direct radio transmission in a chosen angular direction. It is mainly based on an adaptive beam patterns that acts to make the strongest point of main-lobe of the system output always be toward the direction of the expected UE and hence reducing the overall interference level for the whole cell forBeam Forming in LTEIts algorithm is highly complex and utilizes channel state information to achieve array processing SINR gain.

Channel state information that is required includes: Fast fading channel coefficientBeam Forming in LTE Direction of arrival (DoA) of signalBeam Forming in LTE CQI informationBeam Forming in LTEChannel state information can be obtained by different way, including: Feedback from receiver Estimation from reverse link assuming channel reciprocity (particularly true for TDD)As it is based on a multiple transmit configuration, this feature can significantly improve downlink system throughput and coverage performance and also provide good user experience by offering higher data rates. The main drawback here is there is also the requirement of either 4 (44) or 8 (82) transmit path from the eNodeB side which could make this more expensive to implement.There are two type of beam forming mode defined by 3GPP, Mode 7 (Rel 8) and Mode 8 (Rel 9). Mode 7 supports only single data flow so it can mainly improve coverage but Beam Forming in LTE Mode 8 can support multiplexing dual data stream as well which means it can improve both throughput and coverage.

What And How Cell Edge Rate In LTECell Edge Rate in LTE is simple if its High then Coverage Low and if Its Low then Coverage high similar to Frequency selection. Not clear lets understand in detail.Cell Edge Rate in LTE Similar to other wireless communications systems, such as CDMA2000 EVDO, WiMAX and HSPA, the LTE features a rate layering feature. That is, the higher the required edge rate, the smaller the cell coverage radius. The lower the required edge rate, the larger the cell coverage radius.This comes about due to the fixed power offered by UE (normally 23dBm) being spread evenly to the number of RBs involved in the modulation scheme assigned, assuming there is no power control (i.e. Downlink ICIC also disabled).Some of the factors that affect the edge rate in the LTE system are as follows for Cell Edge Rate in LTE: Uplink/downlink TDD proportion MIMO schemes chosen eNodeB Power Amplifier power (affect downlink only) Number of RB used at the sector edge Modulation mode (1 of 29 coding methods) Repeated coding timesThe formula for calculating the downlink cell edge rate is as follows:Cell edge rate Phy= Number of Different data stream transmittedxNumber of Resource Block assigned to user per framexNumber of available Traffic carrying Resource Element per Resource BlockxCoding ratexModulation model level / Duration of each frameWhere, Number of Resource Block Assignedin Cell Edge Rate in LTE (a single RB is the basic resource assignment level) reflects the number of resource blocks used by user at the edge of the sector. The smaller the number of resource blocks assigned, the lower the cell edge rate. In previous version of link budget tools, receive sensitivity of a base station is defined by the bandwidth of the RB which is 180 kHz. More recent version are using per subcarrier as basis of receiver sensitivity and the conversion value is simply 10log10. RB can be assigned down to a per TTI level (1 ms duration) Number of Different data stream transmitted inCell Edge Rate in LTEis related to the number of data stream being simultaneously transmitted. Number can be ranging from 1 (SFBC) to 2 (MCW 22). In case of BF, the value should be 1 for single antenna port transmission mode 7 (port 7 or 8), and 2 streams for dual antenna port transmission mode 8 (port 7 and 8). Number of available Traffic carrying Resource Element per Resource Block inCell Edge Rate in LTEindicates the number of RE available for each resource block. In FDD system, a maximum of 3 symbols (36 Res) can be consumed per frame (10ms) for control channel signaling purposes and there is at least 6 more extra RE can be used for Downlink Reference signaling per TTI (1ms). A minimum of 1 symbol (12 Res) will be required per RB for control signaling purposes. In TDD system, due to frequency sharing and time gap requirement for switching between uplink and downlink, 6 symbols equivalent (72 Res) will be the minimum overhead requirement per TTI. Coding rateindicates the volume coding rate of the channel code. For example, the volume coding rate of QPSK1/2 is 1/2, and the volume coding rate of 16QAM3/4 is 3/4. Modulation model levelindicates the number of bits in the modulation mode. For example, the modulation mode levels of QPSK, 16QAM, and 64QAM are 2, 4, and 6 respectively. Duration of each frameindicates the frame size. As regulated by the protocols, the frame size in LTE networks is 10 ms.In the link budget for Cell Edge Rate in LTE, the settings of the uplink/downlink cell edge rates (in particular the uplink cell edge rate) will determine the final cell coverage radius. Hence, an understanding of edge coverage requirement is very critical from a network planning perspective.If Downlink ICIC is enabled, downlink power control must be enabled also (which is executed at 20ms intervals based on UE BER reported value) and edge rate calculation will be more complex and beyond the formula listed above. However, the cell edge data rate requirement will still be the single most important factor in any cell planning activities.

Okumura-Hata Model For LTEThe Hata Model for Urban Areas, also known as the Okumura-Hata model for being a developed version of the Okumura Model, is the most widely used radio frequency propagation model for predicting the behavior of cellular propagation in built up areas. This model incorporates the graphical information from Okumura model and develops it further to realize the effects of diffraction, reflection and scattering caused by city structures.Okumura model was originally built into three modes, one for urban, suburban and open areas. The model for urban areas was built first and used as the base for others The Okumura Hata model also has two more varieties for propagation in Suburban Areas and Open Areas. The original Okumura model for Urban Areas is a radio propagation model that was built using the data collected in the city of Tokyo, Japan.The model is ideal for using in cities with many urban structures but not many tall blocking structures. The model served as a base for the Hata Model and the following assumptions apply to the use of Okumura Hata model.Frequency: 150 MHz to 1500 MHz inOkumura-Hata ModelMobile Station Antenna Height: between 1 m and 10 m inOkumura-Hata ModelBase station Antenna Height: between 30 m and 200 m inOkumura-Hata ModelLink distance: between 1 km and 20 km inOkumura-Hata ModelThe traditional Okumura Hata model formula is shown below:

Penetration Loss In LTEPenetration loss in LTE indicates the fading of radio signals from an indoor terminal to a base station due to obstruction by a building. For an indoor receiver to maintain normal communications, the signal must be sufficiently strong. The indoor receiver obtains radio signals in the following scenarios for Penetration loss: The indoor receiver obtains signals from an outdoor transmitter. The transmitter and receiver are located in a same building. See Figure below

The link budget is only concerned with the scenario in which an outdoor transmitter is used and the signals penetrate only one wall.The propagation modes of electromagnetic waves are as follows: direct radiation, inverse radiation, diffraction, penetration, and scattering in Penetration loss.In areas where no indoor distributed system is deployed, electromagnetic wave signals are obtained through diffraction and scattering. Therefore, the indoor Penetration loss in LTE is related to the incident angle, building materials, terrain, and working frequency. Table below lists the penetration losses associated with typical buildings forPenetration loss.Typical building penetration lossesIn the link budget, Penetration loss in LTE values depend on the coverage scenario. Therefore, coverage target areas are classified into densely populated urban areas, common urban areas, suburban areas, rural areas, and highways. Table below lists the area classification principles.Principles for classifying coverage scenariosThe building Penetration loss in LTE ranges from 5 dB to 40 dB. In link budget, if no actual test data in the target area is available, an assumed Penetration loss in LTE value must be used. The final assumption is also highly dependent on local customer requirement.For example of Penetration loss in sophisticated Asian Metropolis like Hong Kong, Singapore and Shanghai, the indoor coverage expectation will be very high, hence requiring a high Penetration loss in LTE provisioning. On the other hand, in less developed market such as Africa and Latin America, customer expectation is lower so the Penetration loss in LTE requirement can be reduced to reduce overall cost involved.During network planning, if no actual field testing data is available, refer to the Penetration loss in LTE values listed in Table below.

LTE OFDMA And Downlink Frame Structure DetailsLTE OFDMA and Downlink Frame Structure Details Downlink OFDMA time-frequency multiplexing LTE Spectrum Flexibility and Bandwidth FDD downlink frame structure detailed TDD frame structureLTE (any OFDM/OFDMA) band is made up of multiple small spaced channels and we call each of these small channels as Sub Carrier. Space between the chhanel and the next channel is always same regardless of the system bandwidth of the LTE band. So if the system bandwidth of LTE channel changes, number of the channels (sub carriers) changes but the space between channels does not change.Q> What is the space between a subcarrier and the next sub carrier ? A> 15 KhzQ> What is the number of channels(sub carriers) for 20 Mhz LTE band ? A> 1200 sub carriers.Q> What is the number of channels(sub carriers) for 10 Mhz LTE band ? A> 600 sub carriers.Q> What is the number of channels(sub carriers) for 5 Mhz LTE band ? A> 300 sub carriers.Got any feelings about sub carriers and its relation to system bandwidth ?Now lets look at the basic units of horizontal axis which is time domain. The minimum unit of the time domain is a Symbol, which amounts to 66.7 us. Regardless of bandwidth, the symbol length does not changes.In case of time domain, we have a couple of other structures as well. The largest unit in time domain is a frame, each of which is 10 ms in length. Each of the frame consists of 10 sub frames, each of which is 1 ms in length. Each of sub frame consists of 2 slots, each of which is 0.5 ms in length.Each of slots consists of 7 symbols, each of which is 66.7 us.With this in mind, lets think about the scale in reverse direction.Q> How many symbols are there in a slot ? A> 7 symbols.Q> How many symbols in a sub frame ? A> 14 symbols.Q> How many slots are there in a frame ? A> 20 slots.Now lets look at the units which is made up of both time domain (horizontal axis) and frequency domain (vertical axis). Lets call this type of unit a two-dimensional unit.The minimum two dimensional unit is resource element which is made up of one symbol in time domain and one sub carrier in frequency domain. Another two dimensional unit is resource block(RB) which is made up of one slot in time domain and 12 sub-carrier in frequency domain. Resource Block(RB) is the most important units in LTE both for protocol side and RF measurement side.

Multi-Antenna Techniques LTE To Improve The Downlink PerformanceThere are five methods of multiple antennas have been defined for the LTE downlink to improve the performance: Receive diversity at the mobile Transmit diversity using SFBC at the eNB (evolved Node B) MIMO spatial multiplexing at the eNB, for one or two users Cyclic Delay Diversity (CDD) at the eNB, used in conjunction with spatial multiplexing Beam steering (user specific)The first two Multi-antenna Techniques LTE methods are relatively conventional diversity. The third and fourth Multi-antenna Techniques LTE methods use frequency encoding mechanisms space to spread data across multiple antennas. The diversity of cyclic delay deliberately introduced delays between the antennas to create artificial multipath. It applies more dynamically than other LTE radio systems. The techniques are applied differently depending on the type of physical sign or physical channel.Both SIMO and MISO are used in third generation (3G) cellular systems, and will be launched in LTE networks. Its purpose is to improve the integrity of the connection and to improve error rates, particularly when the connection undergoes poor SNR (for example, on the edge of a cell). Conventional beam steering arrangement introduces phase shifts in phase and amplitude to the total signal power of each transmit antenna. The intention is to concentrate the signal power in a particular direction.The same Multi-antenna Techniques LTE of applying phase and amplitude offsets can be used in the receive antennas to make the most sensitive to signals from a particular direction receiver. In LTE, the amplitude and phase of individual resource blocks is adjustable and making orientation much more flexible and user-specific beam. Beam steering not increase data rates, but has a similar diversity effect in terms of increasing the strength of the signal.The effectiveness of the orientation of the beam increases with the number of transmitting antennas, which enables the creation of a narrower beam. The possible gains with only two antennas usually not considered worthwhile Thus, beam steering by generally only considered the choice of four antennas.User Equipment (UE) diversity reception (SIMO) is mandatory for the UE. It is usually performed using maximum ratio combining. In a mobile environment, the signal from a single antenna reception level suffer fluctuations due to the different types of discoloration. With the wider bandwidth channel LTE nature can also be a frequency dependent on the level of detectable signal. By combining the received signal from two antennas, the UE can regain a stronger signal. Receive diversity provides up to 3 dB gain at low SNR in Multi-antenna Techniques LTE.

LTE MIMO Types Of Inputs And OutputsLTE MIMO input and output are used for medium between transmitters and receivers, including both RF components known as the channel. Thus, the base station with two transmitters provides two inputs to the channel, mi page, and the handset takes two strings get two out of the chains, MO part. It is only when the data is transmitted and received independently and is not simply a copy of the same data, as explained below.

Single Input Single Output (SISO)transmission is the standard in most systems, and more complex target systems is capacity, or data rate of gain, measured in relation to SISO.Single Input Multiple Output (SIMO)or receive diversity (a single transmitter, and therefore a single data stream), feeds two receiver chains. This helps the integrity of the data received, where the signal-to-noise (SNR) ratio is poor due to multipath fading. There is no gain in quality of the data, except any benefit that comes from the best ratio of error and consequent reduced retransmission.Multiple Input Single Output (MISO)is a transmit diversity technique. In LTE, Space frequency block coding (SFBC) is used to improve the resistance of signal fading conditions. Transmitters send the same data to the user base, which in different places of radio frequencies.True MIMOwith two transmitters and two receivers independent of the content of the data is also known as spatial multiplexing. Each receiver sees the channel, which is a combination of results from the transmitter. Using channel receiver calculation techniques using matrix mathematics to separate the two data streams, and demodulate the data. In ideal conditions, the volume of data will be doubled, even though it is not good premium payment requirements SNR than SISO. Almost doubling the data throughput is not reached, but specific growth data quality, can be seen.

How Non Access Stratum Procedures Works In LTEThe procedures for the Non Access Stratum, especially power management procedures are substantially similar to UMTS. Main change is that the UMTS EPS allows concatenation certain procedures to allow faster creation of connection and media.Create MME UE context, when the UE is on and attaches to the network. Assign a unique ID called SAE short temporary Mobile Subscriber Identity Temporary (S-TMSI) which identifies the context of the UE MME. This context the UE has user subscription information downloaded from HSS.Local storage of data in the MME subscription allows faster execution of the procedures, such as setting the carrier because it eliminates the need to consult HSS every time. In addition, the UE context has also dynamic information such as the list of carriers that are set and terminal capabilities. To reduce overhead in E-UTRAN and processing in the UE, all UE-related information in the access network, including wireless carriers, may be released during long periods of inactivity data.This is the state-ECM IDLE.MME kept in the UE context and information about carriers established in those periods of inactivity. To enable the network to contact an ECM IDLE UE, network updates as UE the new location whenever it comes out of the current track (TA) This is called an update tracking area.MME domain is responsible for tracking the location user, while the UE is in ECM-IDLE.When there is a need to provide data downlink at UE ECM-IDLE, MME sends a paging message to all current eNodeBs its TA and UE eNodeBs page radio interface. Upon receiving a paging message, the UE makes a call for service, leading to the displacement UE ECM connected state. Such UE-related information is created in E-UTRAN and radio bearers are restabilite.MME is responsible for restoring and updating radio bearers UE context eNodeB.This transition between the UE is called a transition-inactive to active. To speed-inactive to active transition and establishing carrier EPS support concatenation of NAS and Access Stratum (AS) bearer activation procedures.Some relations between the NAS and AS protocol is used intentionally to allow the procedure to run simultaneously rather than sequentially, as in the UMTS. For example, the procedure for determining the carrier can be carried by the network without waiting for the conclusion of safety.Security features are the responsibility of the MME for both signaling and user data. When a UE attaches to the network, mutual authentication is done between the EU network and MME / HSS. This authentication feature sets also security keys are used to encrypt carriers.

Work Details Of LTE Core Network Nodes PCRF, HSS, P-GW, S-GW, And MME In LTELTE core network also called EPC in SAE is responsible for the complete control of the UE and the creation of media. The main logical nodes LTE EPC are: PDN Gateway (P-GW) Serving Gateway (S-GW) Mobility Management Entity (MME)PCRF of LTE Core NetworkThe political control and charging rules is responsible for control policy making, as well as flow control functionality based charging enforcement function Control Policy (PCEF), which is the P-GW.PCRF provides QoS authorization (QoS class identifier [QCI] and bit rates), which decides how a particular data stream will be treated PCEF and ensure that it is in accordance with the users subscription profile.HSS of LTE Core NetworkHome Subscriber Server database subscription includes SAE users such as EPS subscribed QoS profile, as well as any restrictions on access for roaming. He also holds information on PDNs which users can connect. This could be in the form of an access point name (APN) (which is a label according to DNS naming conventions describing the access point PDN) or PDN address (indicating the subscribers IP address (es)). In addition HSS has dynamic information such as the identity of the MME user is already logged in or registered. HSS can also integrate, authentication center (AUC), which generates vectors authentication keys and security.P-GW of LTE Core NetworkPDN Gateway is responsible for allocating IP UE and the application QoS and flow based charging in accordance with the PCRF. It is responsible for filtering user downlink IP packets in different QoS-based carriers. This is done based on traffic patterns (TFTs) .P-GW performs application QoS guaranteed bit rate (GBR) bearers. It also serves as the anchor for mobility for interworking with non-3GPP technologies such as CDMA2000 and WiMAX networks.S-GW of LTE Core NetworkAll user IP packets are transferred via Gateway service, which serves as the local mobility anchor data carriers if the UE moves between eNodeBs. It retains also information carriers when the UE is at rest (known as the EPS Connection Management IDLE [ECM-IDLE]) and buffers downlink data temporarily while the MME initiates paging UE to restore carriers. In addition, S-GW performs certain administrative functions in the visited network, such as the collection of information load (ie the amount of data sent or received by the user) and lawful intercept. It also serves as a mobility anchor for interworking with other 3GPP technologies such as packet radio service (GPRS) and UMTS.MME of LTE Core NetworkMobility Management Entity (MME) is a control node that processes the signaling between the UE and CN. Protocols running between the UE and CN are known as Non-Access Stratum (NAS) protocols.

LTE Overall Architecture With EPC Network Elements And Functional Split Between E-UTRAN And EPCEPS provides the user with a PDN IP connectivity for Internet access and for the operation of services such as Voice over IP (VoIP). An EPS bearer is usually associated with a QoS. Multiple carriers may be set for a user, in order to provide different QoS flows and connectivity to different PDNs.For example, a user might be engaged in a voice (VoIP) call while simultaneously performing web browsing or FTP download. A VoIP carrier could provide the necessary QoS for the voice call while a best-effort bearer would be suitable for surfing the web or FTP session.The network must also provide for sufficient security and privacy for the user and network protection against fraudulent use.

This is achieved by means of a number of network elements which have different roles EPS. Figure EPS network elements shows the overall network architecture, including network elements and standardized interfaces. At a high level, the network is composed of NC (EPC) and E-UTRAN access network.Although NC has many logical nodes, the access network is essentially consisting of a single node, evolved NodeB (eNodeB), which connects the values. Each of these network elements interconnected via standardized interfaces that allow multi-vendor interoperability. This gives network operators the opportunity to source various network elements from different vendors.In fact, network operators can choose the physical implementation of the split or merge the logical network elements based on commercial considerations. Functional division between EPC and E-UTRAN is shown in the figure below.

Article Topics :

LTE Overall Architecture With EPC Network Elements And Functional Split Between E-UTRAN And EPCEPS provides the user with a PDN IP connectivity for Internet access and for the operation of services such as Voice over IP (VoIP). An EPS bearer is usually associated with a QoS. Multiple carriers may be set for a user, in order to provide different QoS flows and connectivity to different PDNs.For example, a user might be engaged in a voice (VoIP) call while simultaneously performing web browsing or FTP download. A VoIP carrier could provide the necessary QoS for the voice call while a best-effort bearer would be suitable for surfing the web or FTP session.The network must also provide for sufficient security and privacy for the user and network protection against fraudulent use.

How UE Switch To Service Types In LTE?The action of camping on provides access to services. The network provides different levels of service to a UE in either Idle mode or Connected mode. Three levels of services are defined:LIMITED SERVICE:emergency calls on an acceptable cell.Acceptable cell:UE may camp to obtain limited service like emergency call. The minimum set of requirements for initiating an emergency call in a UTRAN network are: The cell is not barred. The cell selection criteria are fulfilled.NORMAL SERVICE:for public use on a suitable cell.Suitable cell:UE may camp on to obtain normal service. Such a cell shall fulfill all the following requirements: The cell is part of the selected / registered / equivalent PLMN The cell is not barred The cell is not part of a forbidden registration area The cell selection criteria are fulfilled In case of a CSG cell it is part of the white listOPERATOR SERVICE:FOR OPERATORS ONLY ON A RESERVED CELL.Reserved cell:When the cell status reserved for operator use is indicated and the Access Class of the UE is 11 or 15 the UE may select/re-select this cell if in Home PLMN. Set by O&M parameter.

Barred cell:When cell status barred is indicated the UE is not permitted to select/re-select this cell, not even for limited services. This information is set by office data.Article Topics :

This is achieved by means of a number of network elements which have different roles EPS. Figure EPS network elements shows the overall network architecture, including network elements and standardized interfaces. At a high level, the network is composed of NC (EPC) and E-UTRAN access network.Although NC has many logical nodes, the access network is essentially consisting of a single node, evolved NodeB (eNodeB), which connects the values. Each of these network elements interconnected via standardized interfaces that allow multi-vendor interoperability. This gives network operators the opportunity to source various network elements from different vendors.In fact, network operators can choose the physical implementation of the split or merge the logical network elements based on commercial considerations. Functional division between EPC and E-UTRAN is shown in the figure below.

L & UL Physical Channel In LTEHow Physical channel of LTE works in UL & DL?A distinction has to made between: The Physical channel The Physical signal

The DL physical channels are: Physical DL Shared Channel (PDSCH) It is a shared channel used to carry user data, radio & core network, system information (BCH), paging message. Physical DL Control Channel (PDCCH) It is a shared signaling channel to carry the allocation of the resources (PDSCH). Physical Broadcast Channel (PBCH) It is the channel used to broadcast the system information.The UL physical channels are: Physical Random Access Channel (PRACH) It is a shared channel used for the access procedure. Physical UL Shared Channel (PUSCH) It is a shared channel used to carry user data, radio & core network, Physical UL Control Channel (PUCCH) It is a shared signaling channel in uplink to allow the UE to request resources on the PUSCH.

Evaluation Process For Cell Selection In LTES-CRITERIONThe cell selection criterion S is a pre-condition for suitable cells.The conditions for E-UTRAN, UTRAN FDD and GSM cells are listed in the figure.R CRITERION CELL RESELECTIONThe cell reselection evaluation process depends on whether Hierarchical Cell Structure (HCS) is used or not. In order to perform cell reselection UE measures and ranks the neighbor cells.For each type of neighbor cells (Intra-Frequency; Inter-Frequency; Inter-RAT, i.e. GSM) thresholds are definable. Measurements of neighbor cells will be triggered if these thresholds are reached.HIGH MOBILITY / MEDIUM MOBILITY / NORMAL MOBILITY:For faster moving UEs the procedure alters speed dependent scaling rules are applied. If the number of (different cells) cell reselections during the past time period TCRmax exceeds NCR_H, high mobility has been detected. If the number exceeds NCR_M, and not NCR_H, medium mobility has been detected.In high/medium-mobility states, a UE: multiplies Qhyst by Speed dependent ScalingFactor for Qhyst for mobility state if sent. multiplies TreselectionRAT by Speed dependent ScalingFactor for TreselectionRAT for mobility state for RAT cells. (RAT = EUTRAN, UTRAN, GERAN).

Cell reselection evaluation is performed according to the UE internal triggers or if the information on the BCCH used for the cell reselection evaluation procedure has been changed.FOR INTRA-FREQUENCY AND EQUAL PRIORITY INTER-FREQUENCY CELLS:(Re-) Selected cell is a suitable cell (e.g. fulfills the S criterion) and is the best ranked cell (has the highest R). The UE shall however reselect the new cell, only if the following conditions are met: the new cell is better ranked than the serving cell during a time interval Treselections more than 1 second has elapsed since the UE has camped on the current serving cell.The cell-ranking criterion R is defined as shown below:Note,s indicates the serving cell,n indicates the candidate cell.

FOR INTER-FREQUENCY AND INTER-RAT NEIGHBOUR CELLS:If UE camps longer than 1 sec in the serving cell and:- a higher priority neighbor fulfills (during TreselectionRAT):SnonServingCell,x > Threshhigh -> reselect neighbor cell.- no cell fulfills SnonServingCell,x > Threshhigh :SServingCell < Threshserving,low and SnonServingCell,x > Threshx,low ->reselect neighbor cell.

Step Of RRC Connection Setup In LTEWhen the UE is powered up, it has to be RRC connected to be able to exchange data and signaling with the network.After the RRC connection, the Initial network attach allows to establish all the bearers to carry the data from the UE to the gateway.

After the RRC connection, Signaling Radio Bearers (SRBs) are established. An SRB is a Radio Bearer that only carries the signaling: SRB1 carries the RRC signaling. SBR2 carries the NAS signaling, i.e. between the Core Network and the UE.

During the Initial Attach: An MME is selected. The UE is authenticated. An IP address is allocated to the UE. S-GW and P-GW are selected. Bearers are established on the S1-U, S5/S8 and on the air interface. The RRC connection is reconfigured to allow user data traffic. At the end of the Initial Attach, the UE is able to reach external networks.The RRC Connection is basically made up of 2 steps: Contention Based Random Access. Exchange of Signaling to establish the connection. When a UE requests a connection, it has no dedicated resources to reach the eNodeB. It uses an uplink common channel which is able to manage the collision between 2 UEs requesting an access at the same time.

Article Topics :eps network, LTE Overall Architecture, EPC Network Elements, E-UTRAN and EPC, access network, network elements, standardized interfaces, network operators, voip

RE groups are aligned within one symbol and occupy consecutive frequencies(subcarriers). The RE groups are addressed by the index pair (k,l) where k is the lowest number among the REs of the considered group.

How Transport Channel Work In LTE?A transport channel defines how and with what characteristics the information is transmitted. Inherited from the WCDMA, data on the transport channel is organized into Transport Blocks, TBs. A Transport block can be transmitted every TTI = 1 msThe Transport Format, TF, defines how the blocks can be transmitted: Transport block size, it depends on the MCS and the number of PRB allocated Allowed modulation scheme Antenna mapping

Note: In case of multi-antenna system, there can be 2 TBs for each TTI.Each TTI, the scheduler decides which chunk to allocate to which user. The chunks are not standardized.The following transport channels in DL have been defined by the 3GPP: Broadcast Channel (BCH)characterized by a fixed, pre-defined transport format with a robust modulation to be broadcast in the entire coverage area of the cell. Downlink Shared Channel (DL-SCH)characterized by: A dynamic link adaptation by varying the modulation, coding and transmit power support for H-ARQ (radio retransmission). Paging Channel (PCH)characterized by: Requirement to be broadcast in the entire cell. Multicast Channel (MCH)characterized by: requirement to be broadcast in the entire coverage area of the cellThe following transport channels in UL have been defined by the 3GPP: Uplink Shared Channel (UL-SCH) characterized by:support for dynamic link adaptation by varying the transmit power and potentially modulation and coding , support for H-ARQ ,support for both dynamic and semi-static resource allocation. Random Access Channel (RACH)characterized by limited control information, collision risk

Cell Selection And Reselection In LTE UETo get service from the selected PLMN, the UE performs two types of procedures:LTE cell selection and LTE cell reselectionCELL SELECTION in LTEUpon PLMN selection, LTE UE uses cell selection for fast cell searching to camp on. To receive system information LTE UE tunes to the control channels. This procedure is known as camping on the cell.The UE will then register its presence in the registration area of the chosen cell by NAS (Non Access Stratum) registration procedure. NAS registration procedure means the LTE upper layer information is transmitted from UE to CN via AS (Access Stratum). The NAS offers the E-UMTS service to the users. The cell will be decided as suitable if it fulfils the cell selection criteria.The purpose of camping on a cell is: To enable LTE UE reception of system information from the selected PLMN To allow LTE UE an RRC connection, accessing the network on the cell controlchannel. To receive paging and respond to paging messages on a tuned control channel in the registration area. The PLMN knows the tracking area of the cell in which the registered UE is camped.

CELL RESELECTION in LTEIf the UE finds a better cell, UE reselects it and camps on it. After camping on, UE monitors the system information to get the quality threshold and performsmeasurements for the cell reselection evaluation procedure. The UE evaluateswhether or not a better cell exists.The E-UTRAN controls the quality measurements for LTE cells to be reselected. The UE measurements are triggered according to the serving cell quality level and the threshold indicated in the system information. The measurement must satisfy different requirements for intra frequency, inter frequency or inter RAT (Radio Access Technology) quality estimations.Cell selection is performed in RRC idle mode. The camping on a cell in idle mode enables the UE to receive information from the LTE network. UE stays in idle mode until it transmits a request to establish an RRC connection. After receiving the RRC connection set up, the mode changes into connected mode.Article Topics :

How Many Different Methods To Combine OFDMA For Handle Multiuser System?Threre are four Different Methods to Combine OFDMA for handle Multiuser System.Plain OFDM: Normal LTE OFDM has no built-in multiple-access mechanism. This is suitable for broadcast systems like DVB-T/H which transmit only broadcast and multicast signals and do not really need an uplink feedback channel (although such systems exist too).

Packet Statistical Multiplexing:It is of course possible to combine a plain OFDM with some LTE layer 2 protocol that takes over all addressing issues. In this case all LTE receivers must listen to the same signal, decode it completely and then decide in higher layers whether to go on with it or to discard the packet. A typical example for such an approach is 802.11a/g/n, where the MAC layer on top of the physical layer (which is OFDM capable) puts LTE MAC addresses in all frames to indicate source and destination. A problem of such systems is power saving to increase standby and operation time. Normally all receivers have to listen to all packets and decode them. Power saving mode in such a system is difficult and usually not very efficient.Time Division Multiple Access via OFDM:The simplest model to implement multiple access handling is by putting a time multiplexing on top of LTE OFDM. In other words all except some system specific subcarriers go to user 1 in the first symbol period, then come user 2, user 3 and so on. After some time we repeat this multiplexing scheme. The disadvantage of this simple mechanism is, that every user gets the same amount of capacity (subcarriers) and it is thus rather difficult to implement flexible high and low bit rate services. Furthermore it is nearly impossible to handle highly variable traffic (e.g. web traffic) efficiently without too much higher layer signaling and the resulting delay and signaling overhead. The 802.11 WirelessMAN-OFDM specification form selected time division multiplexing on the LTE uplink direction as method.Orthogonal Frequency Division Multiple Access OFDMA: The term LTE OFDMA is a registered trademark by Runcom Ltd. and was introduced with 802.16 (WiMAX) Wireless MAN-OFDMA for the downlink. The basic ideas is, to assign subcarriers to users and not time. This has the advantage that a single user can easily use multiple subcarriers to increase the bit rate. With this approach it is quite easy to handle high and low bit rate users simultaneously in a single system. But still it is difficult to run highly variable traffic efficiently. The solution to this problem is to assign to a single users so called resource blocks or scheduling blocks.Such block is simply a set of some subcarriers over some time efficiently it is a combination of TDMA with plain OFDMA. The blocks can be equal sized or not and a single user can use one or more blocks. 802.16d uses such a mechanism with variable block sizes. The first OFDM symbols in each frame are used to indicate which user gets which blocks with which size. LTE EUTRAN will use a similar system, but with fixed block sizes and the assignment mechanism is not specified yet (2007-08).

What Is VSWR (Voltage Standing Wave Ratio) And How Tilting AntennaVSWR means voltage standing wave ratio which everyone knows but why it comes to calculate in Telecom? When BTS transmit any signal (LTE, CDMA, GSM, WCDMA anyone) then in radio wave transmit through cable and reach to antenna so what?Now I give you one example, Think you punch in wall and one man behind wall and does he get your punch effect NO why? Now think what is reflect by wall to him nothing. So now what different in your punch and wall isimpedancemeanswall impedance is almost 1000> to your punchso you not reflect any thing and so nothing happen with men behind wall.

This same thing in our telecom fields the impedance matching should be equal 1:1 or vey less different and the ratio of this call VSWR. now you understand why needs to tack care for BTS VSWR.Now I write some calculation for VSWR,In mobile communication systems, the VSWR of antenna is 1.5:1 at most. Assume that: ZA: input impedance of antenna Z0: nominal characteristic impedanceSo the reflection coefficient is calculated as below:

You can also represent the matching character of port with echo loss as below:If the VSWR is 1.5:1, the RL is 13.98 dB.When the input impedance of antenna is not equal to characteristic impedance, the reflected and incident waves form standing wave after overlapping on the feeder. The ratio of the maximum adjacent voltage of standing wave to the minimum adjacent voltage of standing wave is the voltage standing wave ratio (VSWR). If the VSWR is over large, the communication distance will be shortened and the reflected power will return the transmitter. As a result, the power amplifier may be burnt and the communication system will work abnormally.Down TiltThe down tilt of antenna is an important means that you can enhance the signal level of serving cell and reduce the interference with other cells. The common down tilt modes include mechanical down tilt, preset electrical down tilt, and adjustable electrical down tilt (RET antenna) as below: Mechanical down tilt: you adjust the mechanical down tilt by lowering the support. Electrical down tilt: you adjust the electrical down tilt by adjusting the phase of oscillators. After the preset electrical down tilt is sold out of the factory, the down tilt cannot be adjusted. The adjustable electrical down tilt is adjustable.You can adjust the mechanical down tilt and electrical down tilt simultaneously.my suggestion for any data network (LTE,HSD,3G,GPRS) try reduce congestion or user speed by Mechanical tilt first then try on electrical tilt because electrical tilt reduce coverage from both side (Side lobes and upper lobes) and i found it also reduce some indoor coverage by adding some resistance to antenna.now share your experience about VSWR or Tilt in comment.

How CQI, PMI And RI Reporting By UE In LTE?The UE is requested to send either periodic or a periodic reports concerning Rank indication (RI)Reports are applicable for closed- and open-loop spatial multiplexing. In case of open-loop TRI=1 corresponds to transmit diversity and TRI>1 to large delay CDD. Precoding matrix indicator (PMI)PMI reporting is relevant for spatial multiplexing (open- and closed-loop), MU-MIMO, closed-loop RANK=1 precoding. PMI and RI are confined to a subset of the codebook which is created by means of a codebookSubsetRestriction parameter. Channel quality indication (CQI)CQI may be wideband or may be related to subbands. Similar to HSPA the CQI definition is targeted at 10 % BLER whereby the overall energy per bit is nearly minimized.For the purpose of periodic reporting the PUCCH is utilized, a periodic reports are sent on the PUSCH. The latter reports are explicitly requested by setting the CQI request field in connection with an uplink grant. In case of collision the aperiodic report will be transmitted.Furthermore the scheduling mode can be frequency non-selective (periodic) or frequency selective (periodic and aperiodic).The offset is signaled by nom PDSCH-RS-EPRE-Offset.

Modulation And TB SizeA 5-bit modulation and coding scheme yields the modulation order, i.e. QPSK,16QAM or 64QAM. Implicitly the coding rate is given by a combination of the number of scheduled RBs and the signaled TB size.The determination is based on the signaled MCS Index IMCS.

By means of a 27110 table the resulting TB size can be determined. Part of thetable (for non two-layer spatial multiplex) is shown in the figure. A graphical display is shown below.Note, for two-layer spatial multiplex additionally a translation table has to be applied.In case of DCI format 1C a separate table is used.

andover Algorithm And Procedure In LTEA Handover will be initiated by a measurement report, which is sent via the Radio Resource Control (RRC) protocol. Upon the reception of this measurement report, the handover algorithm will decide whether a handover should take place.In response to the handover decision, the handover execution will be carried out using the corresponding procedures. After the handover execution, the handover algorithm will be informed, whether the handover was successful or not.The Handover procedure is composed of a number of single functions: Measurements Filtering of measurements Reporting of measurement results Hard handover algorithm Execution of handoverWhen the UE is in LTE_ACTIVE state, mobility handling takes place via network controlled handovers with UE assistance. UE assistance here simply means that the UE does measurements and reports them to the eNB to assist in the handover decision. Currently it is planed that neighbor cell measurements are based on the UEs cell detection capabilities rather than on a network supplied neighbor cell list.When the source (current serving) eNB decides to start a handover of an UE to a neighbor cell in a new (target) eNB it will contact this target eNB. This is done via the X2-AP message HANDOVER REQUEST. The message will contain the target cell for the UE, the current serving MME and SAE GW. It is task of the target eNB to allocate virtual capacity in the target cell via its admission control function.If this is done the target eNB returns part of the handover message for the UE within the X2-AP message HANDOVER REQUEST ACKNOWLEDGE. In this message also a data forwarding tunnel (TEID from target eNB) is indicated. It allows the source eNB to forward still buffered or still arriving downlink packets to the target eNB.The source eNB can now give the HANDOVER COMMAND (RRC) to the UE. The command contains the configuration for the UE in the new cell and possibly already an UL/DL resource allocation. The UE will detach from the old cell and synchronize itself to the new cell. In the mean time the source eNB can start downlink packet forwarding via X2 interface.

Once synchronization between UE and the new cell is achieved, the UE confirms the handover with RRC message HANDOVER CONFIRM. This will trigger a HANDOVER COMPLETE message of S1-AP to be sent to the MME. It simply informs the MME that now a new eNB is responsible for the UE. Thus this message will contain the IP addresses and TEIDs of the target eNB for the S1 tunnels.

The MMEs task is to send this information via GTP-C UPDATE BEARER REQUEST to the SAE GW. This will switch the traffic path now completely from SAE GW to target eNB.When the path is switched, the old eNB will get the S1-AP message RELEASE RESOURCE which will clear down all allocated resources for the UE that is alreadyin the new eNB.

How Is Basic Frame Structure In LTE ? In FDD, the DL and UL Radio Frames (RFs) are not on the same carrier. The RF frame is called Type 1 by the 3GPP. The RF length is 10 ms.

The radio frame is made up of 10 sub-frames of 1 ms. Each sub-frame is made up of 2 slots of 0.5ms.

For FDD, 10 subframes are available for downlink transmission and 10 subframes are available for uplink transmissions in each 10 ms interval. Uplink and downlink transmissions are separated in the frequency domain.A Frame structure type 2 is also defined and is applicable to TDDEach slot is made up of: 7 symbols in case of normal CP (guard time between symbols)

Tu = Useful Symbol DurationTcp = Cyclic Prefix durationTecp = Extended Cyclic Prefix duration

Since OFDM offers a better flexibility in terms of sub-frame structure and pilot allocation, there is no reason to consider the same structure as for DFT-SOFDM.

The frame structure for the type 2 frames used on LTE TDD is somewhat different. The 10 ms frame comprises two half frames, each 5 ms long. The LTE half-frames are further split into five sub frames, each 1ms long.

The subframes may be divided into standard subframes of special subframes.The special subframes consist of three fields: DwPTS Downlink Pilot Time Slot GP Guard Period UpPTS Uplink Pilot Time Stot.These three fields are also used within TD-SCDMA and they have been carried over into LTE TDD (TD-LTE) and thereby help the upgrade path. The fields are individually configurable in terms of length, although the total length of all three together must be 1ms.

CFI Control Format IndicationHow many OFDM symbols per subframe are used for PDCCH is indicated on thePCFICH.For non-MBSFN subframes and frame structure type 1 there are 1, 2 or 3 OFDMsymbols used for PDCCH if more than 10 RBs are configured in a cell, 2, 3 or 4otherwise.In order to signal the actual number 32 bits are in use. These bits are scrambled depending on the cell id and are modulated using QPSK.Mapping and precoding is possible for- single antenna port- transmit diversityThe same antenna ports as for PBCH are used and 4 symbol quadruplets aremapped to resource elements.

Difference Between DL And UL In LTEwhat is main Difference between DL and UL in LTE ?OFDMA Advantages Robust against narrow-band co-channel interference Robust against Intersymbol interference (ISI) and fading High spectral efficiency Efficient implementation using FFT Drawbacks High Peak-to-Average Power RatioThe power limitation is more problematic in UL than in DL Signal with high PAPR will limit the Tx power in UL and reduce coverage.LTE uses in UL a modified form of OFDMA process, called SC-FDMASC-FDMA = Single Carrier Frequency Division Multiple AccessSC-FDMA improves the peak-to-average power ratio (PAPR) compared toOFDMReduced power amplifier cost for mobileReduced power amplifier back-off -> improved coverage

In DL, use OFDM together with some PAPR reduction techniques (clipping and filtering, tones reservation, etc)In UL, find an alternative to OFDM combining some of OFDMs advantages, but with a PAPR equivalent to single carriers one: DFT-Spread OFDM (DFT-SOFDM), also known as Single-Carrier FDMA (SC-FDMA).OFDMA Transmitter In LTEHow OFDMA Transmitter in LTE ?

In the downlink, OFDM is selected to efficiently meet E-UTRA performance requirements. With OFDM,it is straightforward to exploit frequency selectivity of the multi-path channel with lowcomplexityreceivers.This allows frequency selective in addition to frequency diverse scheduling and one cell reuse of available bandwidth.

Furthermore, due to its frequency domain nature, OFDM enables flexible bandwidth operation with low complexity. Smart antenna technologies are also easier to support with OFDM, sinceeach sub-carrier becomes flat faded and the antenna weights can be optimized on a per sub-carrier (or block of sub-carriers) basis.

In addition, OFDM enables broadcast services on a synchronized single frequency network (SFN) with appropriate cyclic prefix design.

This allows broadcast signals from different cells to combine over the air, thus significantly increasing the received signal power and supportable data rates for broadcast services.

How Is Basic Frame Structure In LTE ? In FDD, the DL and UL Radio Frames (RFs) are not on the same carrier. The RF frame is called Type 1 by the 3GPP. The RF length is 10 ms.

The radio frame is made up of 10 sub-frames of 1 ms. Each sub-frame is made up of 2 slots of 0.5ms.

For FDD, 10 subframes are available for downlink transmission and 10 subframes are available for uplink transmissions in each 10 ms interval. Uplink and downlink transmissions are separated in the frequency domain.A Frame structure type 2 is also defined and is applicable to TDDEach slot is made up of: 7 symbols in case of normal CP (guard time between symbols)

Tu = Useful Symbol DurationTcp = Cyclic Prefix durationTecp = Extended Cyclic Prefix duration

Since OFDM offers a better flexibility in terms of sub-frame structure and pilot allocation, there is no reason to consider the same structure as for DFT-SOFDM.

The frame structure for the type 2 frames used on LTE TDD is somewhat different. The 10 ms frame comprises two half frames, each 5 ms long. The LTE half-frames are further split into five sub frames, each 1ms long.

The subframes may be divided into standard subframes of special subframes.The special subframes consist of three fields: DwPTS Downlink Pilot Time Slot GP Guard Period UpPTS Uplink Pilot Time Stot.These three fields are also used within TD-SCDMA and they have been carried over into LTE TDD (TD-LTE) and thereby help the upgrade path. The fields are individually configurable in terms of length, although the total length of all three together must be 1ms.

OFDMA Parameter For LTE How Many OFDMA Parameter for LTE? Which is OFDMA Parameter for LTE ?The width of a Sub-carrier is 15 kHz whatever the bandwidth The bandwidths are: 1.4, 3, 5, 10, 15 and 20 MHz Note that in LA1.1, only 5, 10 MHz are implemented

The symbol duration is always the same whatever the bandwidth There are 2 times more sub-carriers in 10 MHz than in 5 MHz 2 times more symbols can be sent or received at the same time. The capacity is multiplied by 2Reduced subcarrier spacing of 7.5 KHz for MBSFN operation also supported

Center subcarrier (DC subcarrier) not used to allow for direct conversion receiver implementation

For the 5 MHz, there are 512 sub-carriers of 15 kHz. The total band is 7.68 MHz. It is larger than the 5 MHz band! But only 301 sub-carriers are used (Pilot, DC, data), the other ones are guard sub-carriers: 301 Sub-ca * 15 kHz = 4.515 MHz

Flexible bandwidth allocation supported by OFDM

Still different RF filter will be required Frame structure always the same Sampling frequency is an transmitter and receiver implementation issue Sampling rate is multiple of 3.84 MHz ? single clock for multi-mode UE with WCDMA Smallest bandwidth that is supported was modified recently and needs to be updated

The symbol duration depends on the sub-carrier width.

2 Cyclic Prefixes are defined by the 3GPP: Long CP: 16.67 micro seconds Normal CP: 4.69 micro seconds Only the normal CP is supported in LA1.x The total duration of a symbol is: Useful duration + CP = 66.6 + 4.69 Total duration = 71.29

SC-FDMA Receiver Benefits In LTEDFT spreading of modulation symbols reduces PAPR In OFDM, each modulation symbols sees a single 15 kHz subcarrier (flat channel) In SC-FD-A, each modulation symbol sees a wider bandwidth (i.e. mx 180 KHz) Equalization is required in the SC-FDMA receiver

DFT-spread OFDM (DFTS-OFDM) is a transmission scheme that can combine the desired properties discussed in the previous sections, i.e.: Small variations in the instantaneous power of the transmitted signal (singlecarrier property). Possibility for low-complexity high-quality equalization in the frequency domain. Possibility for FDMA with flexible bandwidth assignment.Due to these properties, DFTS-OFDM has been selected as the uplink transmission scheme for LTE.