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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 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

Adaptive Modulation and Coding (AMC) in WIMAX

Set of modulation/coding schemes QPSK, 16QAM, 64QAM distributed over one sector: SINR distribution automatic selection mechanisms Maximum throughput per sector Highest modulation scheme Lowest coding protection Mean throughput offered per sector Contribution of different modulations Average over the area AMC is a link adoption (LA) method to adapt the transmission parameters to take advantage of … Read more

Basic Modulation Techniques Wimax

Data bits modulate (modify) a carrier signal Basic modulation techniques: amplitude frequency phase. Data bits are represented over the transmission channel by SYMBOLS Symbol rate is expressed in Baud (Symbols per Second) Modulation of a carrier is used to transmit data bits efficiently over the air interface The modulation process creates modulation symbols. A modulation … Read more

Important OFDM characters for 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

Advance Future for Mobile WiMAX

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

Why Limited Frequency Resource in Wimax

The challenge to broadband wireless comes from the scarcity of radio-spectrum resources. Regulatory bodies around the world have allocated only a limited amount of spectrum for commercial use. The need to accommodate an ever-increasing number of users and offering bandwidth-rich applications using a limited spectrum challenges the system designer to continuously search for solutions that … Read more

Wimax Business requirement by Point-To-Point or Point-to-Multipoint

Applications using a fixed wireless solution can be classified as point-to-point or point-to-multipoint. Point-to-point applications include interbuilding connectivity within a campus and microwave backhaul. Point-to-multipoint applications include broadband for residential, small office/home office (SOHO), and small- to medium-enterprise (SME) markets, T1 or fractional T1-like services to businesses, and (3) wireless backhaul for Wi-Fi hotspots. Consumer … 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 or capacity of the system. Assuming a … 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 of multiantenna solutions, including transmit diversity, beamforming, and … Read more