Microwave Engineering Europe - October 2007 - (Page 40)

40 DIRECT SYNTHESIS Figure 5: RFXpress in custom mode. PLCP header The PLCP header is the second major component of the PPDU. The goal of this component is to convey necessary information about both the PHY and the MAC to aid in decoding the PSDU at the receiver. The PLCP header can be further decomposed into a PHY header, MAC header, header check sequence (HCS), tail bits and Reed-Solomon parity bits, as well as tail bits at the end of the PLCP header to return the convolutional encoder to the zero state. The Reed-Solomon parity bits are added to improve the robustness of the PLCP header. Figure 4 shows the WiMedia frame related parameters as speciﬁed in the standard. The PHY header ﬁeld is composed of 40 bits, numbered from 0 to 39. • Bits 3-7 encode the RATE ﬁeld, which conveys the information about the type of modulation, the coding rate and the spreading factor used to transmit the MAC frame body. • Bits 8-19 encode the Length ﬁeld, with LSB being transmitted ﬁrst. • Bits 22-23 encode the seed value for the initial state of the scrambler, which is used to synchronize the descrambler of the receiver. • Bit 26 encodes whether or not the packet is being transmitted in the burst mode. • Bit 27 encodes the preamble type used in the next packet if in burst mode. • Bits 28-30 are used to indicate the TF code used at the transmitter. • Bit 31 is used to indicate the LSB of the band group used at the transmitter. • All other bits which are not deﬁned are reserved for future use and set to zero. PSDU The PSDU is the last major component of PPDU. This major component is formed by concatenating the frame payload with the frame check sequence (FCS), tail bits and the pad bits, which are inserted to align the data stream on the boundary of the symbol interleaver. RFXpress allows for not only generating signals in the WiMedia conformance mode, but also to customize the frame generation for all parts of the frame. This enables the characterization of the receiver beyond the boundary conditions set by the WiMedia protocol. In RFXpress custom mode as shown in Figure 5, PPDU can be generated with PLCP preamble, PLCP header and PSDU. To test a part of the receiver, the situation might demand that only parts of PPDU be generated. RFXpress enables the generation of only PLCP preamble, only PLCP preamble and PLCP header, or Microwave Engineering Europe ● October 2007 ● www.mwee.com 034-036-038-040-042-044_MWEE.ind40 40 20/09/07 17:50:28 http://www.spinner.de http://www.spinner.de http://www.mwee.com

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Microwave Engineering Europe - October 2007 Contents Comment News CMOS RF: Si-On-Sapphire Goes Mainstream Cover Feature: New Data Protection Concept for UHF RFID Tags CMOS RF: RF Design Team Touts CMOS Spin for 3G PAs Wireless HID – Are You Following the Standard to Another “Average” Product Development? Phase Optimisation of the RF Front-End Direct Synthesis of UWB-WiMedia Signal Generation 4G Chips to Target 700 MHz Applications Femtocells Mobilize to Fight Wi-Fi in the Home Products Product Feature: AXIEM Pioneers the Future of EM Technology Calendar

Microwave Engineering Europe - October 2007

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