Wimax standards and Security The Wimax

FIGURE 1.5
HIPERLAN architecture.
data rates from 6 up to 54 Mbps, with nominal ranges operating from 100 to 300 m.

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There are four OFDM subcarrier modulation modes in HIPERLAN/2: BPSK, QPSK, 16-QAM, and 64-QAM. Mandatory error correction code specifications call for rate 1/2, constraint length k 7 convolutional code, with optional rate 9/16 and 3/4 codes for the higher data rates (27–54 Mbps).
One distinguishing feature of HIPERLAN compared to IEEE 802.11 is that it supports multiple-beam antennas (sectoring) for improved link budget per- formance and reduction in interference. This feature was included primarily for ease of integration into existing cellular infrastructure. Like IEEE 802.11, however, HIPERLAN increases or decreases data rate by changing modula- tion and coding based on PHY and MAC layer metrics (such as signal strength and packet loss ratio).

5. 
   Bluetooth
   

The Bluetooth standard [7] was ratified by an industry consortium ini- tially in 1999 to enable short-range wireless connectivity between devices such as PDAs, cellular phones, printers, and computer peripherals. It oper- ates in the 2.4 GHz ISM band with an frequency hopping spread spectrum (FHSS) waveform and has a 400 Kbps data rate (symmetric) or 700 Kbps data rate (asymmetric). The range is about 10 m with a transmitter power of about 1 mW.


Time differential T1


Time differential T3


FIGURE 1.6
Bluetooth piconet hierarchy.
Bluetooth forms piconets or associations between nodes based on a particu- lar hopping sequence. Within a piconet there is only one master node. Its clock and Bluetooth device address (BD_ADDR) are passed to slaves via frequency hop synchronization packets. The master BD_ADDR is used to calculate the sequence of frequency hops required for all devices within the piconet to fol- low to communicate. The master’s clock is used to decide which hop in the sequence is current (known as the hopping phase). All slave devices within the piconet use the differential between the master clock and their own to determine which frequency to use at any given time so they can follow the hopping sequence accurately. Each piconet operates on a unique frequency- hopping sequence within the ISM band. Figure 1.6 illustrates a basic hierarchy of a piconet.
Physical channels in Bluetooth are characterized by a single radio frequency
combined with temporal parameters and are restricted spatially. Two phys- ical channel types are used for communication between Bluetooth devices: the basic piconet channel and the adapted piconet channel. The other phys- ical channels defined within Bluetooth are used for device discovery within the Bluetooth domain (inquiry scan channel) and for establishing connection between Bluetooth devices (page scan channel).
While the Bluetooth standard has been adopted as an IEEE 802 standard (as IEEE 802.15.1), it was defined prior to standardization by IEEE 802 and has been deployed significantly as a feature of wireless cellular handsets and handset accessories such as headsets.

5.