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8/9/2019 Understanding WiMAX (Chapter 12)
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Understanding WiMAX (Chapter 12)ENE 490
MON 13:30-16:30Asst. Prof. Suwat Pattaramalai
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Understanding WiMAXSystem-Level Performance of WiMAX
Overall system performance and its dependence on various network
parameters, such as frequency-reuse pattern, cell radius, andantenna patterns, are critical to the design of a networkBroadband wireless channel and its impact on the designS stem-simulation methodolo used to enerate the s stem-level
performance results of a WiMAX networkSystem-level performance of a WiMAX network under variousnetwork configurationsDependency on network parameters, environmental parameters,
such as the multipath power-delay profile; and the traffic model,such as VoIP, FTP, and HTTPSystem-level benefits of open-loop and close-loop MIMO features
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Understanding WiMAXWireless Channel Modeling
(1st )Median pathloss models are typically linear on alogarithmic decibel scale with a slope that depend on theoverall terrain and clutter environment, carrier frequency,and antenna heights
To determine the number of base stations (BSs) requiredto cover a given area
Empirical measurements median pathloss models are theOkumura-Hata model, the COST-231-Hata model, theErceg model, and the Walfisch-Ikegami model
(2nd ) Shadow fading and various aspects of the dynamicwireless channel; terrain, foliage, and large obstructions
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Understanding WiMAX
Wireless Channel ModelingShadow fading is a large-scale variation from medianvalue and modeled as a random variable having alognormal distribution
In system design is usually account for shadowing by
adding a shadow-fading margin to link budget whichimplies that more BSs are needed to cover a given area
Outage probability is the probability that theinstantaneous shadow fade deeper than the shadow-fading margin
Typical shadow margin is 6-12dB for 90-99 percentcoverage probability
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Understanding WiMAX
Wireless Channel Modeling(3 rd) variation in signal strength over a small scale causesby multipath propagationMultipath channels modeled using tap-delay lines withnoninfinitestimal amplitude response over span of v taps
Impulse response modeled typically as Rayleigh or Ricianfading, number of taps specified by empirical data
Methodology for System-Level Simulation
Link-level simulation: single link simulation for small-scalebehavior in the channel over small time duration
System-level simulations: mutiple BSs and MSs arerequired
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Understanding WiMAX
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Understanding WiMAX
Simulator for WiMAX Networks
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Understanding WiMAX
Simulator for WiMAX NetworksEdge effect: cell lie toward the edge of simulationnetwork have missing neighbor cell size and can be sloveby using the wraparound approach for edge cell
Computation of Time-Domain MIMO channel response
Computation of Frequency-Domain MIMO channel byusing a Fourier transformation
Computation of per Subcarrier SINR calculated fromchannel response
Computation of per Subchannel Effective SINR by overallsubcarrier SINR
Link Adaptation and Scheduling by using subchannel SINR
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Understanding WiMAX
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Understanding WiMAX
Simulator for WiMAX NetworksEffective SINR is also used to determine the optimummodulation, code rate, FEC code block size, andspace/time encoding matrix for each scheduled MS
Computation of per Sector Throughput and User Data
Rate based on the size and the average number of transmissions needed for each of the FEC code blocks
Table 12.2 shows the various parameters andassumptions used for the system-level simulation results
System ConfigurationsTable 12.3 shows four configurations based on thenumber of transmit and receive antennas
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
System-Level Simulation ResultsPerformance metrics such as average user data rate,
percentilr user data rate, and cell throughput, average ULand DL throughput per sector (system capacity)
System-Level Results of Basic Configuration: MS form
factors (a handheld device with omni-directionalantennas and a desktop device with low-gain directionalantennas)Figure 12.5 and 12.6 show the probability distributions of per subchannel user DL data rate for the Ped B and Ped ATable 12.4 and 12.5 summarize the throughput per BSand the fifth and tenth percentile data rates
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
System-Level Results of Enhanced ConfigurationsFigure 12.9 and 12.10 show the average per sectorthroughput for the basic and various enhancedconfigurations
Diversity improve the average throughput of WiMAX
Closed-loop MIMO improve the average throughput
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
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Understanding WiMAX
Summary and Conclusions
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Understanding WiMAX
Summary and Conclusions
