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
OFDM Fundamental OFDM was selected for the downlink because it can Improved spectral efficiency Reduce ISI effect by multipath Provide better Protection against frequency selective fading OFDM is a scheme that offers good resistance to multipath and is now widely recognized as the method of choice for mitigating multipath for broadband wireless. It can be … Read more
UE Accessibility Verification If the best cell on the LTE frequency have banned or are protected, up to exclude This cell from cell selection list. In that case may consider UE the cell on the same frequency, if banned cell indicates (by using fields ‘ intraFreqReselection ‘ in SIB1), intra-frequency selection is not allowed for … Read more
Here I write some small notes on connection Re-Establishment procedure in LTE. In a number of cases of failure (eg failure of radio link failure of teaching RLC unrecoverable error, failure of compliance reconfiguration), the procedure for restoring EU RRC connection, provided that security is active. If security is not enabled, when one of the … Read more
Here I list out some important OFDM characters for Wimax. Let’s check it in detail. OFDM Pros and Cons: OFDM enjoys several advantages over other solutions for high-speed transmission. Reduced computational complexity: OFDM can be easily implemented using FFT/IFFT and the processing requirements grow only slightly faster than linearly with data rate or bandwidth The … Read more
Shadow fading indicates the fading brought by obstruction due to a building or a natural feature. Shadow fading changes slowly, and is thus called “slow fading”. Statistics repeatedly show that the median levels of received signals follow log-normal distribution with the time and location at a certain distance. Fading caused by location (mainly from obstruction) … Read more
Here I write on simple how guard band requirement for LTE for 2 option. Guard band requirement LTE verses GSM and guard band requirement LTE FDD verse LTE TDD Guard Band Requirement: LTE-FDD vs GSM/UMTS Configuration is simpler for FDD based systems because both LTE FDD and its neighboring technologies are based on frequency duplex … Read more
Assume that the eNodeB receiver’s IF bandwidth is Bw (unit: MHz), and the eNodeB receive noise figure is Nf (unit: dB), The equivalent noise level of the eNodeB receiver is as follows: No = –174 + 10 log (Bw) + Nf (Unit: dBm) If the demodulation carrier-to-interference ratio C/I (unit: dB) of the eNodeB receive … Read more
Orthogonal frequency division multiple access (OFDMA): Mobile WiMAX uses OFDM as a multiple-access technique, whereby different users can be allocated different subsets of the OFDM tones. As discussed in detail in Chapter 6, OFDMA facilitates the exploitation of frequency diversity and multiuser diversity to significantly improve the system capacity. Flexible and dynamic per user resource … Read more