Survey on coexistence of heterogeneous wireless networks in 2.4 GHz and TV white spaces <s> Classification by mechanisms <s> As more and more wireless devices use the 2.4 GHz radio spectrum, the coexistence of 2.4 GHz wireless devices operating in one place has become a hot topic. With low transmit power, the widely deployed IEEE 802.15.4-based networks are easily interfered with by other 2.4 GHz wireless networks, such as IEEE 802.11. IEEE 802.15.4-based wireless networks have paid great attention to the coexistence between themselves and with other non-IEEE 802.15.4 wireless networks. This problem has been further promoted by two new industry wireless standards, WirelessHART and ISA100, to meet special industry requirements. This paper surveys the studies on the coexistence between IEEE 802.11 and IEEE 802.15.4-based networks following the general analysis method of “question-analysis-solution.” Based on the survey study, we discuss about some open research issues and developments in this field. <s> BIB001 </s> Survey on coexistence of heterogeneous wireless networks in 2.4 GHz and TV white spaces <s> Classification by mechanisms <s> Coordination of co-located wireless devices is a fundamental function/requirement for reducing interference. However, different devices cannot directly coordinate with one another as they often use incompatible modulation schemes. Even for the same type (e.g., WiFi) of devices, their coordination is infeasible when neighboring transmitters adopt different spectrum widths. Such an incompatibility between heterogeneous devices may severely degrade the network performance. In this paper, we introduce Gap Sense (GSense), a novel mechanism that can coordinate heterogeneous devices without modifying their PHYlayer modulation schemes or spectrum widths. GSense prepends legacy packets with a customized preamble, which piggy-backs information to enhance inter-device coordination. The preamble leverages the quiet period between signal pulses to convey such information, and can be detected by neighboring nodes even when they have incompatible PHY layers. We have implemented and evaluated GSense on a software radio platform, demonstrating its significance and utility in three popular protocols. GSense is shown to deliver coordination information with close to 100% accuracy within practical SNR regions. It can also reduce the energy consumption by around 44%, and the collision rate by more than 88% in networks of heterogeneous transmitters and receivers. <s> BIB002
Depending on whether the decision and the coordination mechanisms are performed by a centralized entity or in a distributed fashion, the coexistence solutions can be categorized into centralized and distributed approaches. Centralized coexistence approach. In centralized approaches, the coexistence decision is performed by a central entity, which is then sent to each coexisting network. An example of centralized approach is that defined in IEEE 802.19. BIB001 19 where a mediator is designated to make the coexistence decision. Distributed coexistence approach. In distributed coexistence approaches, on the contrary, the decision is made in a decentralized fashion without relying on a central entity. An example of distributed approaches is Gap Sense, BIB002 where the coexistence is coordinated distributively via the preambles of data packets.