WIMAX

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

Angular Spread and Coherence Distance calculation for Wimax Calculation Angular Spread and Coherence Distance is very easy let’s see. So far, we have focused on how the channel response varies over time and how to quantify its delay and correlation properties. However, channels also vary over space. We do not attempt to rigorously treat all … Read more

Which OFDM Parameters Used in WiMAX The  fixed and mobile versions of WiMAX have slightly different implementations of the OFDM physical layer. Fixed WiMAX, which is based on IEEE 802.16-2004, uses a 256 FFT-based OFDM physical layer. Mobile WiMAX, which is based on the IEEE 802.16e-20055 standard, uses a scalable OFDMA-based physical layer. In the … Read more

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 of OFDM, one or two preamble OFDM symbols are typical. Pilot tones involve inserting a few known pilot symbols among the subcarriers. Channel estimation in … Read more

The third assumption—that the background noise is Gaussian and uncorrelated with the transmissions—is especially suspect in a cellular MIMO system. All well-designed cellular systems are by nature interference limited: If they were not, it would be possible to increase the spectral efficiency by lowering the frequency reuse or increasing the average loading per cell. In the … Read more

Transmit spatial diversity is a newer phenomenon than receive diversity and has become widely implemented only in the early 2000s. Because the signals sent from different transmit antennas interfere with one another, processing is required at both the transmitter and the receiver in order to achieve diversity while removing or at least attenuating the spatial … Read more

Spatial multiplexing and Receive Diversity in Wimax Spatial multiplexing WiMAX also supports spatial multiplexing, where multiple independent streams are transmitted across multiple antennas. If the receiver also has multiple antennas, the streams can be separated out using space-time processing. Instead of increasing  diversity, multiple antennas in this case are used to increase the data rate … Read more

Advanced Antenna Systems,Transmit diversity and Beamforming in Wimax Advanced Antenna Systems The WiMAX standard provides extensive support for implementing advanced  multiantenna solutions to improve system performance. Significant gains in overall system capacity and spectral efficiency can be achieved by deploying the optional advanced antenna systems (AAS) defined in WiMAX. AAS includes support for a variety … Read more

QoS Mechanisms in Packet Networks There are Three Types of QoS Mechanisms in Packet Networks. Control Plane Mechanisms Data Plane Mechanisms Its Tradeoffs Control Plane Mechanisms Such mechanisms include QoS policy management, signaling, and admission control. QoS policy management is about defining and provisioning the various levels and types of QoS services, as well as … Read more

Authentication and Access Control in Wimax Access control is the security mechanism to ensure that only valid users are allowed access to the network. In the most general terms, an access control system has three elements: (1) an entity that desires to get access: the supplicant, (2) an entity that controls the access gate: the … Read more