SCHOOL OF INFORMATION AND FORMATS
Take away assignment duo on 15/11/2014
1. Explain the key features of the Low Rate Wireless Personal Area Networks (LR-WPAN) as defined in the IEEE 802.15.4 standard. (3 Marks)
Ultra-low complexity, and power for low-data-rate wireless connectivity among inexpensive fixed, portable, and moving devices.
Wireless personal area networks (WPANs) are used to convey information over relatively short distances.
WPANs are focused on a space around a person or object that typically extends up to 10m in all directions. WPANs is low-cost, low power, short range and very small size Maximum data rates allowed for each of these frequency bands are fixed as 250 kbps @2.4 GHz, 40 kbps @ 915 MHz, and 20 kbps @868 MHz. Allocated 16 bit short or 64 bit extended addresses.
Allocation of guaranteed time slots (GTSs)
Carrier sense multiple access with collision avoidance (CSMA-CA) channel access Yields high throughput and low latency for low duty cycle devices like sensors and controls. Fully “hand-shake” acknowledged protocol for transfer reliability. Low power consumption with battery life ranging from months to years. Energy detection (ED).
Link quality indication (LQI).
2.4GHz and 868/915 MHz dual PHY modes.
This represents three license-free bands: 2.4-2.4835 GHz, 868-870 MHz and 902- 928 MHz. The number of channels allotted to each frequency band is fixed at 16 channels in the 2.45 GHz band, 10 channels in the 915 MHz band, and 1 channel in the 868 MHz band.
2. The IEEE 802.15.4 standard for LR-WPAN defines only the physical layer and the media access layer. Explain why. (3 Marks)
because The Physical layer provides main two services: the Physical data service and...
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