【正文】 outing protocols [4]. The submittee standardized a medium access protocol that was based on collision avoidance and tolerated hidden terminals, making it usable, if not optimal,for building mobile ad hoc work prototypes out of notebooks and PCMCIA and Bluetooth were some other standards that addressed and benefited ad hoc working. Open Problems Despite the long history of ad hoc working, there are still quite a number of problems that are open. Since ad hoc works do not assume the availability of a fixed infrastructure, it follows that individual nodes may have to rely on portable, limited power sources. The idea of energyefficiency therefore bees an important problem in ad hoc works. Surprisingly,there has been little published work in the area of energyefficiency of ad hoc works until fairly recently. Most existing solutions for saving energy in ad hoc works revolve around the reduction of power used by the radio transceiver. At the MAC level and above, this is often done by selectively sending the receiver into a sleep mode, or by using a transmitter with variable output power (and proportionate input power draw) and selecting routes that require many short hops, instead of a few longer hops [8]. The ability of fixed, wireless works to satisfy quality of service (QoS) requirements is another open problem. Ad hoc works further plicate the known QoS challenges in wireline works with RF channel characteristics that often 4 change unpredictably, along with the difficulty of sharing the channel medium with many neighbors, each with its own set of potentially changing QoS requirements. Reflecting the multilayer nature of ad hoc works, there are numerous attempts to improve the QoS problems from the service contracts [9] to the MAC layer. A promising method for satisfying QoS requirements is a more unified approach of crosslayer or verticallayer integration. The idea is to violate many of the traditional layering styles to allow different parts of the stack to adapt to the environment in a way that takes into account the adaptation and available information at other layers. A similar multilayer issue is that of security in ad hoc works [10]. Since nodes use the shared radio medium in a potentially insecure environment, they are susceptible to denial of service (DoS) attacks that are harder to track down than in wired works. Also, since a large portion of the work nodes will be dynamically reorganizing and forwarding packets on behalf of others, ad hoc works are particularly susceptible to the injection of bogus work control traffic. Finally, ad hoc works can he victims of specialized kinds of security attacks such as DoS attacks that cause a node to use its transceiver so much that it depletes its battery. Robots and sensors also provide new hardware capabilities ripe for new methods of enhancing ad hoc efficiency. Robots, for example,have a tight integration between the processes of movement, decisionmaking, and working that allow them to modify their actions while taking into account the effects on many different system aspects [12]. Similarly,sensors are often deployed in a way that makes their roles and capabilities redundant, suggesting new ways of bining application knowledge of delivered information with the routing layer [13]. Finally, a problem that overarches all these others is the lack of well defined and widely accepted models for RF path attenuation, mobility, and traffic. These tightly interrelated models are needed for quantif