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…

Difference Between OFDM and FDM in LTE

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…

What are the Advantages of OFDMA in Wimax ?

 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…

How Reference signals Map in LTE?

For channel estimation different types of reference signals are in use: – Cell specific reference signals. – MBSFN reference signals. – UE specific reference signals CELL-SPECIFIC REFERENCE SIGNALS These signals…

SC-FDMA Receiver Benefits in LTE

DFT 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.…

UL Allocation (SC-FDMA) in LTE

SC-FDMA utilizes single carrier modulation, DFT-spread orthogonal frequency multiplexing, and frequency domain equalization. LTE uses OFDMA on the DL. It allocates DL bandwidth to the user based on resource blocks,…

Ways to transmit training symbols: preamble or pilot tones in Wimax

There are two ways to transmit training symbols: preamble or pilot tones. Preambles entail sending a certain number of training symbols prior to the user data symbols. In the case…

What is SC-FDMA and how it works in LTE?

One of the major drawbacks of an OFDMA system is, that the transformation of a complex symbol mapped sequence (e.g. BPSK, QPSK, etc.) onto a small set of subcarriers produces…

Synchronization in LTE Mobile “Switch On”

Primary and Secondary Synchronization Signals occupy 2 blocks of symbols per 10 ms (central 72 subcarriers for all channel bandwidths). An example is shown below for 72 subcarrier- (1.4 MHz)…

Inter-Carrier Interference for OFDM

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…