Table 21.15 Physical modes and transmission rates of HIPERLAN/2. Mode Modulation Coding rate R Nominal bit rate (Mbps) Coded bit rate per subcarrier Coded bits per OFDM symbol Data bit per OFDM symbol 1
BPSK
1
/
2
6
1
48
24
2
BPSK
3
/
4
9
1
48
36
3
QPSK
1
/
2
12
2
96
48
4
QPSK
3
/
4
18
2
96
72
5
16-QAM
(HIPERLAN/2
only)
9
/
16
27
4
192
108
6
16-QAM (IEEE
only)
1
/
2
24
4
192
96
7
16-QAM
3
/
4
36
4
192
144
8
64-QAM
3
/
4
54
6
288
216
21.11 Other WLAN Standards 757 Ch21-P373580.indd 757
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758 21 Wireless Local Area Networks controlled TDD/TDMA scheme, MAC frame (MF) is allowed to simultaneously
communicate via a number of DLC connections in both downlink and uplink
directions. Each MF allocates time slots for broadcast channel (BCH), frame
channel, access feedback channel (ACH), random channel (RCH), downlink (DL)
phase, uplink (UL) phase and directlink (DiL) phase. Data is grouped as PDU
trains. There are two kinds of PDU, one is long PDU (LCH PDU) of 54 bytes and
another is short PDU (SCH PDU) of 9 bytes. The PDU error ratio refers to the
error rate of LCH PDU.
21.11.2 Multimedia Access Communication — High Speed Wireless Access Network Multimedia access communication (MMAC) — high speed wireless access network
(HiSWAN) — started in Japan in 1996. It uses two frequency bands: 5 GHz for
HiSWANa and 25 GHz for HiSWANb. The HiSWAN uses the 5 GHz license-free
frequency band and is closely aligned with the HIPERLAN/2. HiSWAN uses the
OFDM physical layer to provide a standard speed of 27 Mbps and 6 to 36 Mbps
by link adaptation. However, MMAC-HiSWANa differs from the HIPERLAN/2
in radio network functions due to the differences in regional frequency planning
and regulations. Instead of dynamic frequency selection in HIPERLAN/2, carrier
sense functions of access points are mandatory in MMAC-HiSWANa. Also, inter-
access point synchronizations are specifi ed to avoid interference among access
points and to use four available channels in Japan for wide coverage. Table 21.16
summaries various WLANs.
Example 21.5 Consider the HIPERLAN/2 that uses BPSK and
R 3
/
4
codes for 9 Mbps informa-
tion transmission and 16-QAM with the same coding for the actual payload data
transmission rate of 36 Mbps. Calculate the coded symbol transmission rate per
subcarrier for each of the two modes. What is the bit transmission rate per subcar-
rier for each of the two modes?
Solution User data transmission rate per carrier with
R 3
/
4
convolution encoder
(refer to Table 21.11).
Mode I (9 Mbps)
9
10
6
48
187.5 kbps
Mode II (36 Mbps)
36
10
6
48
750 kbps
Carrier transmission rate with
R 3
/
4
convolutional encoder
Mode I
187.5
(3/4)
250 kbps
•
•
Ch21-P373580.indd 758
5/3/07 10:58:41 PM
Mode II
750
(3/4)
1000 kbps
Carrier symbol rate
Mode I (BPSK)
250 ksps
Mode II (16-QAM)
1000
4
250 ksps
Example 21.6 What is the user data rate for HIPERLAN/2 with 64-QAM modulation with
R 3
/
4
covolutional coder?
Solution Carrier symbol rate
250 ksps; bits per symbol for 64-QAM
6
User data rate
250
3
4
6
48
54 Mbps
