Cooperative Clustering Protocol for Saving Energy of Mobile Devices with WLAN and Bluetooth Interfaces

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Wireless local area network (WLAN) or IEEE 802.11 is one of the most widely used wireless communication protocol. It provides sufficient bandwidth and well constructed infrastructures. When it comes to energy consumption, energy consumed is grater than 50% of the total energy consumption in hand held devices. In laptops energy consumption is up to 10 percent.

Bluetooth standard provides low power consumption, a 10'th of the WLAN power and it uses a low bandwidth of only 2 Mbps with a short range of 10 meters. In this paper we try to solve the power consumption problem in WLAN based communication systems.

WLAN specifications 802.11 was released in June 1999. Initial specification was for 2.4 GHz frequency and supported a max data rate of 1 to 2 Mbps. It provide the basis for wireless network products using the Wi-Fi brand.

What is Bluetooth?

It uses 2.4 GHz radio frequency. It focuses on replacing the short cables used to connect consumer electronic devices. It is Wireless Personal Area Network (WPAN) with a range limited to approximately 10 to 30 feet (3 m to 9.1 m). The raw data rate of 1 Mbps/723 Kbps. Bluetooth as a secondary radio to reduce the overall power consumption to provide connected channel between mobile devices and the WLAN access point (AP). In On Demand Paging and Wake on Wireless, mobile devices and the AP exchange control messages via low-power channels.

It allows a mobile device to turn off the WLAN interface when it is not being used. CoolSpots and SwitchR use Bluetooth more actively for data communication when applications demand low data rates. WLAN is powered up only when the data rate reaches the Bluetooth limit. APs have both WLAN and Bluetooth interfaces and specialized software to control them. It makes Hardware and software modifications to wireless infrastructures. CONET is based on clustering.

Problem Statement

Properties of nodes and wireless networks:

  • Each node has one WLAN interface (primary) and one Bluetooth interface (secondary).
  • There is at least one WLAN AP in the field. Each node can communicate with the AP using its WLAN interface, regardless of its location and time.
  • The WLAN APs do not have Bluetooth interfaces. This is typical for most existing wireless environments. Therefore, the previous approaches are inapplicable.
  • Each node i knows the total bandwidth required, NeedBW(t), and the free bandwidth of its Bluetooth link, FreeBW(t).
  • Each node i can measure its residual energy E(t).
  • All Bluetooth interfaces have the same communication range.


CONET has four main objectives:

  • Improving the energy efficiency of wireless networks by exploiting a secondary radio,
  • Dynamically configuring clusters to meet the bandwidth requirements of all nodes,
  • Producing well-distributed cluster heads
  • Minimizing control overhead.
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