【正文】 examples include: military solders in the field。 and temporary offices such as campaign headquarters. History The history of ad hoc works can be traced back to 1972 and the DoDsponsored Packet Radio Network (PRNET), which evolved into the Survivable Adaptive Radio Networks(SURAN) program in the early 1980s [l]. The goal of these programs was to provide packetswitched working to mobile battlefield elements in an infrastructureless, hostile environment (soldiers, tanks, aircraft, etc., forming the 3 nodes in the work). In the early 1990s a spate of new developments signaled a new phase in ad hoc working. Notebook puters became popular, as did opensource software, and viable munications equipment based on RF and infrared. The idea of an infrstructureless collection of mobile hosts was proposed in two conference papers [2,3], and the IEEE submittee adopted the term “ad hoc works.” The concept of mercial (nonmilitary) ad hoc working had arrived. Other novel nonmilitary possibilities were suggested (as mentioned in the introduction), and interest grew. At around the same time, the DoD continued from where it left off, funding programs such as the Global Mobile Information Systems(GloMo), and the Nearterm Digital Radio(NTDR). The goal of GloMo was to provide officeenvironment Ethertype multimedia connectivity anytime, anywhere, in handheld devices. Channel access approaches were now in the CSMA/CA and TDMA molds, and several novel routing and topology control schemes were developed. The NTDR used clustering and linkstate routing, and selforganized into a twotier ad hoc work. Now used by the US Army,NTDR is the only “real” (nonprototypical) ad hoc work in use today. Spurred by the growing interest in ad hoc working, a number of standards activities and mercial standards evolved in the mid to late’ the IETF, the Mobile Ad hoc Networking(MANET) working group was horn, and sought to standardize routing protocols for ad hoc works. The development of routing within the MANET working group and the larger munity forked into reactive (routes ondemand) and proactive (routes readytouse) routing 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 chall