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What is AAA authentication, authorization, and accounting? Let me walk you through AAA, because when you’re managing access to a network, you need to make sure every user is verified, permitted, and monitored properly. AAA stands for Authentication, Authorization, and Accounting. These three steps work together to secure the network, and you use them all … Read more

What protocols are used in LTE architecture? Let me show you how LTE uses specific protocols to handle everything from setting up connections to securing data. When you’re working with LTE, you don’t just need the names—you need to clearly see how each one fits into the system and supports what you’re trying to do. … Read more

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 … Read more

OFDM Receiver and How it work for LTE? The receiver is like in any other radio system the more complicated part. In radio systems and of course also OFDM there are two special points a receiver has to pay attention to: time/phase and frequency synchronization. Both are crucial for the performance of the receiver. A … Read more

OFDM implementation in Detail A typical OFDM transmitter is shown on the following figure. To reduce the amount of RF hardware required for OFDM the modulation process is split into two parts. A first part uses the inverse discrete Fourier transform (IDFT) or one of its more efficient but equivalent implementations known as Inverse Fast … Read more

FDM in LTE Conventional multi-carrier operation as it is used for FDM works simply by selecting a number of center frequencies – one for each carrier to be used. The center frequencies must be spaced. In fact there is a trade-off between minimizing interference between different carriers and using the total  bandwidth efficiently. In other … Read more

The price for the optimum subcarrier spacing is the sensitivity of OFDM to frequency errors. If the receiver’s frequency is some fractions of the subcarrier spacing (subcarrier bandwidth) then we encounter not only interference between adjacent carriers, but in principle between all carriers. This is known as Inter-Carrier Interference (ICI) and sometimes also referred to … Read more

RF engineering is a trade off between: required radio spectrum (bandwidth), speed of data transmission (bit rates) and complexity of implementation. The pulse form used to modulate complex data symbols to the radio carrier frequency is the major element of this story. Over the years several pulse forms and their associated pulse shaping filters have … Read more

The state-of-the-art design of the LTE air interface is characterised by OFDMA (DL) and SC-FDMA (UL) together with MIMO. The downlink modulation is based on OFDMA (Orthogonal Frequency Division Multiple Access). OFDMA is a variant of OFDM which has the advantage that receiver complexity is at a reasonable level, it can handle scalable bandwidth requirements … Read more