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Performance Evaluation of WiMAX/IEEE 802.16 OFDM Physical Layer - page 26 / 107

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10­66 GHz licensed band: In this frequency band, due to shorter wave length, line of sight operation is required and as a result the effect of multipath propagation is neglected. The standard promises to provide data rates up to 120 Mb/s in this frequency band [6]. The abundant availability of bandwidth is also another reason to operate in this frequency range. Unlike the lower frequency ranges where frequency bands are often less than 100MHz wide, most frequency bands above 20GHz can provide several hundred megahertz of bandwidth [19]. Additionally, channels within these bands are typically 25 or 28 MHz wide. [6]

2­11 and

GHz licensed and

licensed

exempt

licensed exempt:In this

bands

are

addressed.

frequency bands, both licensed

Additional

physical

functionality

supports have been introduced to operate in Near LOS and NLOS environment and to mitigate the effect of multipath propagation. In fact, many of the IEEE

    • 802.16

      PHY's most advantageous capabilities are found in this frequency range. Operation in licensed exempt band experiences additional interference and co­ existence issue. The PHY and MAC address mechanism like dynamic frequency selection (DFS) to detect and avoid interference [1](for licensed exempt band). Though service provision in this frequency band is highly depends on design goals, vendors typically cite target aggregate data rates of up to 70Mb/s in a 14 MHz channel [18]

    • 3.2

      IEEE 802.16 PHY interface variants

The standard has assigned a unique name to each physical interface. They have been described below along with their supported features in brief

3.2.1 WirelessMAN­SC™

This is the only PHY speci ication defined to operate in 10­66 GHz frequency band. It employs single carrier modulation with adaptive burst pro iling, in which transmission parameters, including the modulation and coding schemes, may be tuned individually to each subscriber station (SS) on a frame by frame basis. The standard both supports Frequency Division Duplexing (FDD) and Time division Duplexing( TDD) to separate

15

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