LTE SC-FDMA and LTE Uplink LTE (Long-Term Evolution) utilizes a specific modulation scheme for the uplink known as Single-Carrier Frequency Division Multiple Access (SC-FDMA). SC-FDMA is a modulation and access scheme that provides advantages for uplink transmission in LTE networks. Introduction to SC-FDMA and uplink frame structure Marriage of single carrier transmission and FDMA Uplink … Read more
LTE Parameters and Downlink Modulation LTE (Long-Term Evolution) utilizes various parameters and downlink modulation schemes to optimize data transmission over the wireless network. LTE parameters and frequency bands What is OFDMA? OFDMA multiple access and downlink frame structure OFDMA transmit and receive chains Here are some important parameters and downlink modulation techniques used in LTE: … 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
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. … Read more
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 receiver gets its input from the antenna (or … Read more
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 Fourier Transform to modulate … 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
Transmitting: After being processed at the MAC layer, the downlink data is sent to the physical layer inthe format of MAC PDU. The MAC PDU arranges the data block size according to the allocation results of radio resources at the MAC layer. After the data packets are processed through the channel coding, modulation, and IFFT … Read more
OFDMA is essentially a hybrid of FDMA and TDMA: Users are dynamically assigned subcarriers (FDMA) in different time slots (TDMA) . The advantages of OFDMA start with the advantages of single-user OFDM in terms of robust multipath suppression and frequency diversity. In addition, OFDMA is a flexible multiple-access technique that can accommodate many users with … Read more