Lte telecommunications definition

          Long Term Evolution (LTE) is a standard for the smooth and effective transition to more advanced leading - edge technology to increase wireless data network capacity and speed. LTE is commonly used to refer to wireless broadband or mobile network technology.

          LTE is also known as "3GPP Long Term Evolution. 3GPP Third Generation Partnership Project, funded by the European Telecommunications Standards Institute operates under the brand name initials. LTE is also known as Super 3G LTE and LTE super-4G.


           LTE cellular communication standard provides a significant improvement over the old reasons, some with WiMax 4G technology (fourth generation) as well as see it.

Its architecture Internet (IP) phones and many other Internet protocols, supports Long Term Evolution sites, web browsing, VoIP and other IP-based services, in contrast to the well is based on protocols. LTE theoretical per second experimental evidence based on 300 megabits (Mbps) or higher can download the support. However, a customer service provider LTE network with other customers to share the available bandwidth is much less effective.

The service is only available in limited geographic areas of sustainable development, but telecom providers have been actively expanding its LTE services.

What is frame in gsm

          The great idea dealing with radio transmission path of the GSM system is the explosion sequence (simplified as Burst). This is a series of transfer units, including over 100 bits configuration. The sequence explosion of limited duration and occupies a limited radio spectrum. Can be described as the output of the time and frequency window. This window is called Slot. In other words, within the frequency range of the system, the central frequency of each slot is defined 200KHz (observed in terms of FDMA)? While the socket is circular, as the time progresses, which occupies 15/26ms (i.e. approximately 0.577ms) each time (observed in terms of TDMA). The periods of these slots are called slots and the duration of which is called the unit of time (defined as BP, indicating the period Burst).

         We can use a time / frequency diagram to draw the groove small rectangles having a length and a width 15/26ms than 200 kHz, as shown in the above diagram. Similarly, we can call the 200 kHz bandwidth specified in the GSM, the frequency slot, which corresponds to the radio frequency channel (i.e. RF channel) of the GSM specifications.

        The two conditions: time and sequence explosion are different to some extent in the same application. For example, the burst sequence is sometimes associated with the time-frequency "rectangular" unit and sometimes the contents. Similarly, the timing is the concept of value of time or This shows a slit in each 8 slots used periodicaly.
 
        To use a specific channel to broadcast the eruption sequence to the specified torque and frequency, ie, the specified slot. Generally, the time slots in a channel is discontinuous. 

Discontinuous transmission dtx in gsm

             Actually, at the time of the communication process, only 40% of mobile users said that time and during the rest of the time is not very useful information. All information is transmitted to the network, it's just a waste of system resources, but also a system that does not include more involvement. When the transmission of radio signals transmitted voice signal is forbidden to tackle this problem, DTX technique, GSM is used in the process. This is to reduce the level of interference and increase system capacity. In addition, this approach will also save battery mobile station and the mobile station can prolong the standby time. DTX function is not used for the data transfer will be.

           GSM system, two transmission modes: a common source. In this case, the noise transmission of sound quality Pickup: There is a discontinuous transmission mode. In this case, the mobile station transmit only voice signals. Receiving end are artificial noise.

           Artificial noise communication connection is fine when you do not speak the client that is used to notify listeners. And uncomfortable to hear is noise that has been designed as a comfortable noise.
Casual noise transmission measurement system that meets the requirements. DTX mode, only 260bit code is transmitted every 480ms, normal mode, 260bit code is transmitted every 20ms while. DTX mode, 260 bits SID (silence descriptor) frames will create. Frame, such as frame size, interleaving, will be processed by channel coding, and modulation then encrypted, and sent to 8 continuous spraying. At other times, no message.

         DTX mode is optional. However, the standard transmission will reduce a bit the DTX mode. Especially when the two ends of the mobile communication subscribers, will influence the transmission quality will be more severe as the DTX will be used twice on the same path. In addition, to implement the DTX function, the system should be able to indicate when to start the discontinuous transmission and when it stopped, and when the active DTX coder should be able detect whether the signal is a voice signal or noise signal. Therefore, the use of VAD technique. The VAD algorithm determines the output frame is all voice or background noise by comparing the measured signal energy to the threshold defined for it. The principle is the decision that should be the noise energy is always lower than the energy of voice. 

Frequency Hopping in gsm

                    When the audio signal is transmitted after processing and modulation, the technique will be used also jumping frequency, any carrier transmission varies continuously on a different time (and, of course, that the difference must comply with the principles of frequency planning).

The following factors are considered in the introduction of two frequency hopping technology:

1)  The fading process is related to frequency range, the application of frequency hopping in the system may reduce the effects of Rayleigh fading. 

2)  Due to the diversity of the intervention, in areas with heavy traffic, are restricting the ability of the cell that interference caused by frequency doubling. In addition, the system is designed to meet the demands of subscribers, and is calculated by the maximum capacity of the system on the assumption that the quality of a certain number of calls is clearly reduced due to the intervention. And low diversity exact measure around the C / I value, greater system capacity. Interference call on the average value of the level of interference caused by many other calls. Thus, the intensity of the specified overlap, the more sources of intervention, the better the performance of the system.

           The radio interface design for the GSM system with the slow pace of movement (SFH) technique. The difference between SFH and fast frequency hopping (FFH) is to change the frequency of the latter is faster than the modulation frequency. During the explosion sequence the entire transition period for the GSM system, the frequency transmitting has not changed. Therefore, it belongs to the slow frequency hopping, as shown in the chart above.
 
          The GSM system allows 64 different types of frequency-hopping sequences. There are basically two of the parameters involved in the description of them: the mobile allocation index offset (MAIO) and hopping sequence number (HSN). MAIO values ​​can be many such frequencies in the group, there are 64 different values ​​available for HSN. 

What is interleaving in gsm

          If the voice signal is modulated and sent directly after channel coding, because the state becomes the wireless communication channel, deep fading affects consecutive bit sequence and causes a high bit error rate.

         If the bits of consecutive string of addresses, or lost, the other end of the communication can not be disassembled disturbed or lost bits. To solve this problem, some technique or method to distinguish a sequence of bits are required. Thus, successive bits of the message can be sent to a decentralized manner so that the bit error should be separate. In this manner, even if errors, the errors are only one or a very short bit stream which is not followed, that the onset of full or the complete message can not be decoded block. In this case, the channel coding comes into force, and back to a few mistakes. This method is called interlacing tekniikkaa.Lomituksen method is the most effective method of encoding the dispersion few errors.

        The most important thing is to break down some of the interleaving bits (I guess is the "b" bits) to a code (suppose to be "the" bursts), burst sequences in such a way to change the relationship between adjacent bits. The higher the value of "n" is, the better is the transmitting works. However, the transmission delay is greater too. Therefore, the balance of the required relief to be associated with the channel. In the GSM system, a second interleaving is applied.

        After channel coding, the extracted bits 456 are divided into eight groups, with each group having 57 bits. This is the first interleaving, also called the internal interleaving, as shown in the above diagram. Through the first interleaving successive groups of messages are scattered. One of the burst position in two segments of speech information consists of 57 bits. It is clear that if two groups of 57 bits of information about the interleaving of the first consecutive 20 ms speech blocks are arranged in the same sequence burst, burst loss leads to a loss of 25% of the bits 20 ms speech block. And therefore, requires a two-tone interleaving blocks, called the inter-block interleaving or other interleaving.

      Let us assume that the audio section B is divided into eight categories: inter-block interleaving performed in the first four groups (B0, B1, B2, and B3), block B, and the last four groups (A4, A5, A6 and A7) to the previous audio block, so four bursts consist of: (B0, A4), (B1, A5), (B2, A6) and (B3, A7) to break the adjacency relationship between successive bits, the bits in the block to occupy the position even if the burst, when the bits of the block B to occupy a strange position to explode. For example, B0 takes a little odd to explode when A4 takes even a little bit. Similarly, to perform interleaving block of the last four groups B and the first four groups of the next block C. The second interleaving 20 ms speech block is inserted into the eight sequences of different bursts, respectively, and then sent one at a time. Although the size of the burst is lost during the transmission process, only 12.5% of each block affects the sound, and errors can be corrected by channel at the other end. In addition, the second de-interleaving for controlling the various asia.Lomittelutila is (B0, B4), (B1, B5), (B2, B6) and (B3, B7).

What is channel coding in gsm

               To check and correct errors in the transmission of redundant data and information derived from the data are added to the current so as to increase the bit rate. For voice, the length of these codes is 456 bits every 20 ms.

                The bit rate of the code stream output from the vocoder is 13 kbit / s, which is divided into several continuous segments 20ms each segment containing 260 bits. They can be classified as follows:

• Very significant 50 bits;
• 132 important pieces;
• 78 ordinary pieces

                Redundancy treatment is carried out, as shown in the diagram above.

               The block encoder is applied to three-bit redundancy code, while the excited encoder applies with double redundancy, then added 4 tail bits in the data stream.

               There are three methods of channel coding in the GSM system convolution coding, block coding and parity coding.

What is Speech Coding in gsm explain

               It works as follows: 8KHZ sampling is performed first then divided into frames of 20 ms each frame has 4 sub-frames, the duration of each sub-frame is 5ms, and the pure bitrate 13kbit / s

                The voice compression coding technique is widely used in modern digital communications systems. In this technique, a speech coder is used to simulate human vocal organs generated by a model of the speech and noise. The form of the model parameters are transmitted by the TCH channels.

                The voice coder is based on the residual excited linear prediction (REIP) coder. In addition, the long term predictor (LTP) is used to enhance the compression. LTP, the coding of the remaining data advantageous by. Vowels from the voice With 20ms as a unit of the speech coder are compressed by coding 260bits. Therefore, the code rate is 13kbps. 50 very important bits, 132 bits and 78 bits ordinary important: According to the different classes of the importance of information, the output bits can be divided into three categories. 

                In comparison with the conventional PCM line on which the encoded and transmitted voice directly (64 Kbps) 13kbps, the speech rate of the GSM system is considerably reduced. Can further reduce the more advanced voice coders in the future the rate to 6.5kbps (half-rate speech coding).