In the performance evaluation of a protocol for an ad hoc network, the protocol should be tested under realistic conditions including, but not limited to, a sensible transmission range, limited buffer space for the storage of messages, representative data traffic models and realistic movements of the mobile users (i.e. a mobility model). This paper is a survey of mobility models that are used in the simulations of ad hoc networks. We describe several mobility models that represent mobile nodes whose movements are independent of each other (i.e. entity mobility models) and several mobility models that represent mobile nodes whose movements are dependent on each other (i.e. group mobility models). The goal of this paper is to present a number of mobility models in order to offer researchers more informed choices when they are deciding on a mobility model to use in their performance evaluations. Lastly, we present simulation results that illustrate the importance of choosing a mobility model in the simulation of an ad hoc network protocol. Specifically, we illustrate how the performance results of an ad hoc network protocol drastically change as a result of changing the mobility model simulated. Copyright © 2002 John Wiley & Sons, Ltd.

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Simulation is the research tool of choice for a majority of the mobile ad hoc network (MANET) community. However, while the use of simulation has increased, the credibility of the simulation results has decreased. To determine the state of MANET simulation studies, we surveyed the 2000-2005 proceedings of the ACM International Symposium on Mobile Ad Hoc Networking and Computing (MobiHoc). From our survey, we found significant shortfalls. We present the results of our survey in this paper. We then summarize common simulation study pitfalls found in our survey. Finally, we discuss the tools available that aid the development of rigorous simulation studies. We offer these results to the community with the hope of improving the credibility of MANET simulation-based studies.

The ratio of women involved incomputer science from high school to graduate school has been dwindling at a startling pace over the past decade. Is there hope in sight? COMMUNICATIONS OF THE ACM October I 997/Vol 40. No. I 0 103

The pipeline shrinkage problem for women in computer science is a well-known and documented phenomenon where the ratio of women to men involved in computing shrinks dramatically from early student years to working years [19, 22, 23, 32, 42, 93, 112], also see this issue [24]. During the last decade, considerable research ensued to understand the reasons behind the existence of the shrinking pipeline and in some cases to take action to increase the numbers of women in computing. Through the work of a National Science Foundation funded project [56], ACM's Committee on Women in Computing (ACM-W) has taken a first step towards pulling this research together. A large number of articles was gathered and processed on the topic of women in computing and the shrinking pipeline. The committee created a publicly available online database to organize the references of this body of work by topic, author, and reference information. The database, constantly being updated, is accessible through ACM-W's website 〈http://www.acm.org/women〉. A final report is also available via the ACM-W website which covers current statistics on women in computing, summaries of the literature in the database, and a set of recommendations.The following discussion is a brief synopsis of a subset of the literature review as of August 2001. In addition, you can find statistics on women in computing and recommendations throughout this special issue.

An analysis of the human chromosome 22 genomic sequence shows that both Z-DNA forming regions (ZDRs) and promoter sites for nuclear factor-I (NFI) are correlated with the locations of known and predicted genes across the chromosome and accumulate around the transcriptional start sites of the known genes. Thus, the occurrence of Z-DNA across human genomic sequences mirrors that of a known eukaryotic transcription factor. In addition, 43 of the 383 fully annotated chromosomal genes have ZDRs within 2 nucleosomes upstream of strong NFIs. This suggests a distinct class of human genes that may potentially be transcriptionally regulated by a mechanism that couples Z-DNA with NFI activation, similar to the mechanism previously elucidated for the human colony stimulation factor-I promoter [Liu et al. (2001) Cell, 106, 309-318]. The results from this study will facilitate the design of experimental studies to test the generality of this mechanism for other genes in the cell.