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OFDM & Dynamic Bandwidth Allocation
Good
QoS
Figure 27: WiMAX coding and modulation schemes ensure steady signal strength over distance by decreasing throughput over range to deliver the best QoS possible
An old wisdom in the networking world goes "Bandwidth is the answer, now what was the question?". WiMAX offers a pair of mechanisms that ensure good QoS. First, the coding and modulation schemes (64-QAM/16-QAM/QPSK) ensure a steady signal strength over increasing distance. Secondly, Dynamic Bandwidth Allocation (DBA) is a mechanism that monitors the network and, when interference or other detractions to sig-nal strength occur, the base station allocates more bandwidth and power for the afflicted stream.
Spectral Efficiency
Figure 28: Beam width is a measure of a product's spectral efficiency
Spectral efficiency is the measure of the width of the signal's beam through the air. It is also the measure of the WiMAX radio's scalability. In mobile WiMAX, for example, commonly used beam widths range from 1.25 MHz to 20 MHz. Efficiency of the product is determined by how much bandwidth (measured in megabits per second in this case) can be transported over how little beam width (MHz in this case). Spectral efficiency is especially important in cases where a service provider is paying a high price for spectrum (example: 40 MHz at 2.5 GHz). With high spectral efficiency, the service provider can service more customers at a lower cost per subscriber for the spectrum in use.
WiMAX Security
Figure 29: WiMAX offers state of the art security via authentication and strong encryption
Security in WiMAX is set in the Privacy Sublayer in the MAC Layer. Per their respective specifications, fixed WiMAX (802.16-2004) uses X.509 certificates for authentication and 56-bit Digital Encryption System (DES) for encryption of the data stream. Mobile WiMAX (802.16e-2005) uses EAP for authentication and Advanced Encryption System (AES, also used by the US government) for encryption. Vendors may use variants of these. Some vendors offer 152-bit AES, which is rumored to take millions of years to crack with a consumer grade PC. Both variants use Privacy Key Management (PKM) for authentication between base station and subscriber station. While Wi-Fi may have suf-fered a bad reputation for security given early problems in the industry, WiMAX offers strong security measures to thwart a wide variety of security threats.
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Figure 27: WiMAX coding and modulation schemes ensure steady signal strength over distance by decreasing throughput over range to deliver the best QoS possible
An old wisdom in the networking world goes "Bandwidth is the answer, now what was the question?". WiMAX offers a pair of mechanisms that ensure good QoS. First, the coding and modulation schemes (64-QAM/16-QAM/QPSK) ensure a steady signal strength over increasing distance. Secondly, Dynamic Bandwidth Allocation (DBA) is a mechanism that monitors the network and, when interference or other detractions to sig-nal strength occur, the base station allocates more bandwidth and power for the afflicted stream.
Spectral Efficiency
Figure 28: Beam width is a measure of a product's spectral efficiency
Spectral efficiency is the measure of the width of the signal's beam through the air. It is also the measure of the WiMAX radio's scalability. In mobile WiMAX, for example, commonly used beam widths range from 1.25 MHz to 20 MHz. Efficiency of the product is determined by how much bandwidth (measured in megabits per second in this case) can be transported over how little beam width (MHz in this case). Spectral efficiency is especially important in cases where a service provider is paying a high price for spectrum (example: 40 MHz at 2.5 GHz). With high spectral efficiency, the service provider can service more customers at a lower cost per subscriber for the spectrum in use.
WiMAX Security
Figure 29: WiMAX offers state of the art security via authentication and strong encryption
Security in WiMAX is set in the Privacy Sublayer in the MAC Layer. Per their respective specifications, fixed WiMAX (802.16-2004) uses X.509 certificates for authentication and 56-bit Digital Encryption System (DES) for encryption of the data stream. Mobile WiMAX (802.16e-2005) uses EAP for authentication and Advanced Encryption System (AES, also used by the US government) for encryption. Vendors may use variants of these. Some vendors offer 152-bit AES, which is rumored to take millions of years to crack with a consumer grade PC. Both variants use Privacy Key Management (PKM) for authentication between base station and subscriber station. While Wi-Fi may have suf-fered a bad reputation for security given early problems in the industry, WiMAX offers strong security measures to thwart a wide variety of security threats.
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