How 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 lowcomplexity receivers. This allows frequency selective in addition to frequency diverse scheduling and one cell reuse of available bandwidth. Furthermore, due to its … Read more
Adopting a multicarrier approach for multiple access in LTE was the first major design choice. The choice of multiple-access schemes was made in December 2005, with OFDMA being selected for the downlink, and SC-FDMA for the uplink. Both of these schemes open up the frequency domain as a new dimension of flexibility in the system, … Read more
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, rather than individual subcarriers. When the signal is a combination of subcarriers, high amplitude power peaks can occur. The base stations power amplifiers are designed … Read more
LTE OFDMA and Downlink Frame Structure Details Downlink OFDMA time-frequency multiplexing LTE Spectrum Flexibility and Bandwidth FDD downlink frame structure detailed TDD frame structure LTE (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 … Read more
The uppermost evolution track shown in Figure is that developed in the 3rd Generation Partnership Project (3GPP), which is currently the dominant standards development group for mobile radio systems and is described in more detail below. Within the 3GPP evolution track, three multiple access technologies are evident: the ‘Second Generation’ GSM/GPRS/EDGE family1 was based on … Read more
The TDMA/FDMA multiplexing is used in GSM, the information needed in the synchronization between MS and BTS is provided by FCCH+SCH. The MS determines the frequency of the BCCH carrier by searching for the frequency correction Burst transmitted via FCCH; then it finds the SCH (synchronization channel) according to the relationship between SCH and FCCH … Read more
The major basic concept concerned with the radio path transmission of the GSM system is the burst sequence (simplified as Burst). It is a string of transmission units including more than 100 modulation bits. The burst sequence has a restricted duration and seizes a restricted radio frequency spectrum. They can be described as output from … Read more
SRNC and DRNC are concepts for a connected UE. The SRNC handles the connection to one UE, and may borrow radio resources of a certain cell from the DRNC. Drift RNCs support the Serving RNC by providing radio resources A UE in connection state has at least one and only one SRNC, but can has … Read more
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 … Read more
Scheduling Principle Deployment of shared channels offers the possibility for scheduling. In this way information on varying channel conditions can be exploited to increase the overall throughput. Fast scheduling in time (1 ms) and frequency domain reduces latency and improves peak rate. Adaptive Modulation and Coding leads to higher data rates and optimizes spectral efficiency … Read more