Table 96: Allocation Variant Field for Allocation Type = 0b00 Field Bits Definition SLF 1 Start or Length Flag AVF VF 7 ATF Variant Field Dependent on SLF Start Time or Length Flag (SLF) The Start Time or Length Flag (SLF) is used to indicate whether the ATF field specifies the CSMA START TIME or the CSMA TIME (LENGTH). SLF = 0b0 designates the CSMA Start Time. SLF = 0b1 indicates that the ATF field specifies the CSMA Length (duration). Table 97 shows the overall structure of the ATF field and these fields are used to compute the CSMA Start Time when SLF = 0b0. Table 97: Allocation Variant Field for AT = 0b000 and SLF = 0b0 Field Bits Definition SLF 1 0b0 NFC 1 Number of Frame Control Symbols (0b0 =>1; 0b1 => 2) NPL 6 Number of Payload Symbols Present CSMA START TIME = (AID+1)(84.64 + NFC*59.28 + NPL*48.52 + B2BIFS) – 79.68 The CSMA START TIME is in units of microseconds measured from the end of the corresponding Coexistence Allocation Delimiter (last non-zero sample of the HomePlug 1.0.1 Frame Control) to the start time of the PRS signaling slot of the CSMA allocation. When SLF = 0b1, the CSMA LENGTH (duration) is specified by the 7-bit ATF VF field, in multiples of 250 microseconds (see Table 98). CSMA LENGTH = AVF_VF * 250 Table 98: Allocation Variant Field for AT = 0b000 and SLF=0b1 Field Bits Definition SLF 1 0b1 AVF_VF 7 CSMA LENGTH (Duration)
Table 96: Allocation Variant Field for Allocation Type = 0b00 Field Bits Definition SLF 1 Start or Length Flag AVF VF 7 ATF Variant Field Dependent on SLF Start Time or Length Flag (SLF) The Start Time or Length Flag (SLF) is used to indicate whether the ATF field specifies the CSMA START TIME or the CSMA TIME (LENGTH). SLF = 0b0 designates the CSMA Start Time. SLF = 0b1 indicates that the ATF field specifies the CSMA Length (duration). Table 97 shows the overall structure of the ATF field and these fields are used to compute the CSMA Start Time when SLF = 0b0. Table 97: Allocation Variant Field for AT = 0b000 and SLF = 0b0 Field Bits Definition SLF 1 0b0 NFC 1 Number of Frame Control Symbols (0b0 =>1; 0b1 => 2) NPL 6 Number of Payload Symbols Present CSMA START TIME = (AID+1)(84.64 + NFC*59.28 + NPL*48.52 + B2BIFS) – 79.68 The CSMA START TIME is in units of microseconds measured from the end of the corresponding Coexistence Allocation Delimiter (last non-zero sample of the HomePlug 1.0.1 Frame Control) to the start time of the PRS signaling slot of the CSMA allocation. When SLF = 0b1, the CSMA LENGTH (duration) is specified by the 7-bit ATF VF field, in multiples of 250 microseconds (see Table 98). CSMA LENGTH = AVF_VF * 250 Table 98: Allocation Variant Field for AT = 0b000 and SLF=0b1 Field Bits Definition SLF 1 0b1 AVF_VF 7 CSMA LENGTH (Duration)
HomePlug%20GP_Specification_Ch9_HP1_0_Coexist_v1.1-Jan_23_2012%20DRAFT.docx