WiMedia's networking specification is called WiNet and can be referred to as a protocol adaptation layer (see the figure). It acts as the interface between higher-layer networking protocols and the WiMedia media access controller (MAC).WiNet defines a logical link control layer networking protocol for the WiMedia radio platform to model the behavior of an IEEE 802 network. This facilitates easy migration of applications compatible with an IEEE 802 environment to a WiMedia environment with few or no changes. For example, a TCP/IP protocol stack designed for an IEEE 802.3 (Ethernet) environment will work with a WiMedia environment. The WiNet protocol preserves the IEEE 802 headers to facilitate the design of bridges between a WiMedia network and other IEEE 802 or compatible wired or wireless networks.

Since WiNet is designed for TCP/IP, it maintains support for the routable nature of Internet applications, meaning that WiNet packets contain a device address as well as a network address. Mobile WiNet devices are designed to communicate with the Web using standard Internet routers.

WiNet is a true peer-to-peer protocol, meaning that devices may communicate with each other directly. This facilitates the creation of ad-hoc wireless personal area networks (WPANs) for mobile devices and applications. Bandwidth is not reduced by the requirement for devices to transfer date through an intermediary node, such as an access point, master or host.

In WiNet, bridging to other networks is based on IEEE 802.1D. This avoids a potential legacy issue of requiring two classes of devices: those that are bridge-aware and those that cannot operate in a bridged environment. WiNet provides control messages that allow devices to select the level of bridge-forwarding services that are desired. Bridge service requests allow a device to designate which packets should be filtered based on protocol identifiers and multicast addresses. WiNet also allows devices to omit the 802 headers for more efficient data transfer if the packets are destined for WiMedia wireless network.

Another major feature is a new advanced hibernation algorithm, which makes use of mechanisms already built into the MAC. While the MAC has an information element that announces when a device will hibernate, there is no way for a set of devices to coordinate their sleep cycles. WiNet defines a local cycle, which allows a device to announce when it will be active. It further defines a global cycle, which is used to synchronize neighbors' local cycles. This hibernation scheme allows devices to conserve power when their data transfer requirements are low.

As an added benefit, WiNet is fully complementary with 802.11 and 802.16. Consequently, it can be used to extend the local area network (LAN) and the metropolitan area network (MAN) to the WPAN space.

Alan Berkema is an engineer scientist at Hewlett Packard.

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