editorial  the field of mobile computing and networking is experiencing accelerated growth with the introduction of new mobile-centric products every month. more and more service providers tailor their hardware and software products to the traveling professional needs. with the conversion and augmentation of the cellular networks to digital communication formats (such as cdpd, is-136, is-95, and gsm), it is expected that wireless data services will become accessible to a large population of users and at affordable prices. finally, the vision of personal communication services (pcs) and its spectral allocation in the u.s., coupled with the ip mobility support (rfc 2002), are two of the many driving forces behind the trends of mobile computing and networking.  mobicom '96, the second annual international conference on mobile computing and networking, took place in rye, ny, on november 10 12, 1996. mobicom is a prestigious forum for presenting and discussing progress in the field of mobile computing and networking. it is sponsored by the acm and ieee organizations. in 1996, there were all together 18 papers selected from 90 submissions, which originated from 16 countries. as most of the submissions were of very high quality, the technical program committee had a difficult choice of selecting the limited number of papers that could be accommodated. we have the pleasure of bringing to you in this issue of the wireless networks journal a selected set of nine papers that were presented at the conference.  the papers are organized roughly from the more physical layer topics to the application- oriented articles. the first paper, by lorch and smith, deals with the important issue of power preservation in mobile computing hardware. in particular, it presents a set of heuristic schemes for detecting when the cpu could be put in a low-power state, thus reducing the battery drainage. as compared with the current apple's cpu power management, the papers' results suggest improvement of about 20% in the battery lifetime, with less than 2% loss in system performance.  the second paper, by vukovic and mckown, discusses the unlicensed pcs (upcs) band, which consists of three 10 mhz bands that were recently opened by the u.s. government. although no licensing is required to operate in this spectrum, the users are supposed to comply with a set of rules, known as the upcs etiquette (u.s. code of federal regulations, title 47, part 15(d)). this paper evaluates the channel sharing effects; i.e., blocking access among competing systems.  channel assignment problem has been a subject of intensive studies in the last years, with new schemes allowing greater channel reuse. the dynamic channel allocation schemes are of particular interest, because of their ability to adapt to the spatial and temporal differing traffic demands in cellular networks. the third paper, by das, sen and jayaram, proposes a dynamic channel allocation scheme and compares its performance with other channel allocation algorithms.  synchronization and dependency relations are important issues, in the design of a distributed system. vector clocks have been traditionally used to represent casual dependencies in a distributed system. in the fourth paper, by prakash and singhal, it is claimed that vector clocks are inappropriate for a distributed mobile system implementation, mainly because of their static nature and inefficiency in a large-scale system. two alternatives to vector clocks are presented and discussed in this paper.  one of the fundamental issues in mobile systems is user location management. efficient local management strategies are of particular importance to the emerging systems because of the anticipation that the number of mobile users in the future networks will be significantly larger than in today's system. the paper by jannink, lam, shivakumar, widom and cox addresses the design and evaluation of efficient, scalable, and flexible location management techniques. in particular, a family of location management techniques is introduced and its performance is evaluated and compared with other techniques.  the internet protocol (ip) and the related tcp and upd are the communication protocols of choice for computing applications. as such, the effect of the use of these protocols in the wireless and mobile environment is of particular importance. the ietf ip mobility support addresses mobility issues in ip, allowing the mobile host to continue its internet connectivity while away from home. however, the current tcp/ip protocol suite was not designed for the wireless communication links in mind, in which capacity is at premium. the sixth paper in this issue, by degermark, engan, nordgren and pink, discusses tcp/ip header compression techniques for wireless communication. the paper especially concentrates on the new version of ip, the ipv6, in which the headers are larger to increase addressing space and functionality. this paper received the best student paper award at mobicom '96.  still on the issue of tcp for wireless communication, the seventh paper, by durst, miller and travis, suggests that the space communication environment and the mobile and wireless networks share a lot of similar characteristics. specifically, issues such as harsh propagation conditions (high error rate and link outage), requirements for low power design and small physical dimensions, and low available data rate are common to both of the environments. the paper proposes a set of extensions to tcp to cope with these problems.  the last two papers are in the area of mobile applications. the paper by joseph and kaashoek describes extensions to the rover toolkit for implementation of reliable applications for the mobile environment. in particular, the existing failure models are improved upon by considering the server failures, in addition to the client and communication failures. the extensions to the rover toolkit include both system-level and language-level support. it is suggested that these extensions impose low overhead of only a few percent in the execution time and are especially optimized for the low- bandwidth and high- latency mobile communication environment.  last but not least, the paper by abowd, atkeson, hong, long, kooper and pinkerton addresses the design of context-aware applications in the mobile environment, where the knowledge of the user's current location and history of his or her location can be used in providing improved services. in particular, the addressed mobile application in this paper is the tour guide---the cyberguide.  we believe that the papers brought here are a sample that well represents the current state-of-the-art of the mobile computing and networking area and describes the up-to-date issues being addressed by the research community these days.  zygmunt j. haas ian f. akyildiz