6 IEEE Wireless Communications • October 2003 his issue of IEEE Wireless Com- munications is about the topic of merging Internet Protocol (IP) and wireless networks. In the past few years, we have witnessed great demand for mobile communications services as well as tremendous improve- ments in wireless technology. While the first generation of mobile communications systems aimed mainly to provide voice ser- vice to their mobile users using circuit- switched networks, the most recent technology, called the third-generation wireless communications, or 3G, looks for more enhanced multimedia services built on pack- et switching and IP routing, where the voice communications would ultimately share only a small part in overall services. During the period when mobile communications technology was evolving from its first generation to 3G, the Internet has also achieved great popularity; at the same time technology for high-speed access has improved dramatically. The protocols configuring the Internet stack have been modified so that high- er-speed and more reliable data transmission could be achieved. Transport protocol, network protocol, and link layer protocol have been enhanced so that new applications and services could be deployed, which in turn has increased the popularity of the Internet. After all those enhancements in Internet technology, the Inter- net has become part of people’s lives, so they want to have it ready to use not only on their desktop computers but also in their mobile devices. Wireless local area networks (WLANs) have become a popular source of mobile networking, thanks to the devel- opment of IEEE 802.11 standard family and the use of unli- censed spectrum. The achievement of WLAN in providing high-speed Internet access was so impressive that it has been accept- ed as a co-player in provision of data services for indoor users of 3G systems, and thus is being integrated in some 3G net- works. WLAN not only made it possible to bring more high- speed Internet access to palm devices, but also complemented the usual cellular services in hot spot traffic areas. WLAN is a direct extension of the wired LAN, that is, the fundamental piece of the global Internet. IP remains the main net- work protocol for the WLAN and the Internet, so when the WLAN integrates with cellular 3G systems we will need to consider how the two technologies can work together. However, merg- ing IP and wireless networks will not stay at this level. IP had great success in designing the network architecture of the Internet. The hierarchy and scalability together with sim- plicity observed in IP were the keys to its success. IP, however, always had two restrictive elements: mobility and quality of ser- vice (QoS). Using the advantages of IP in cellular networks is thus on condition that these two shortcomings of the protocol can be resolved. Especially when cellular network providers have to commit a certain level of service to their users, includ- ing bandwidth, delay, and security, the best effort service of IP will not be acceptable at all. So the main issues in merging IP and wireless cellular that have to be resolved are mobility and QoS. Mobile IP, among other solutions, was invented to ease the fixed IP address con- figuration that avoids IP moving into the mobile environment. While it has certain deficiencies, Mobile IP has been researched to resolve its prob- lems. As a result, one of the main 3G systems, cdma2000, is using enhanced Mobile IP in its core network architecture. The issue of QoS for IP networks has been researched for many years and there is still much work to be done. Integrated services (IntServ) and differ- entiated services (DiffServ) are the two main directions in providing QoS in the Internet. While each method has its own advantages and disadvantages, the Internet Engineering Task Force (IETF) is also looking at a hybrid scheme of IntServ over DiffServ to tackle the end-to-end QoS problem. For realization of a merged wireless IP network, we need first to find out how the issues of service quality and mobility can be managed. In the meantime, we also need to find out how the architecture of such an integrated network can be designed, knowing that the Internet and cellular systems have been designed and implemented by people with completely different backgrounds in computers and communications, respectively, so their inter- working will not be an easy task. Such integration, however, can be considered the first step toward next-generation net- works, where heterogeneous networks are to work together in order to provide differentiated services to users in a seamless and transparent manner. In order to elaborate state-of-the art research activities within industry and academia and provide a reference for future researchers in this field, we have put together this spe- cial issue through an open call for papers. Our call for papers, as expected, received an overwhelming response. A total of 29 papers from all around the world were submitted. These arti- cles covered different topics of QoS, routing protocols, integra- tion of IP and telephony networks, mobility management for IP and cellular networks, ad hoc networks and multihopping, radio access enhancement, and more. We could confirm that the topic is very important and is worked seriously in industry and academia all around the world. All articles went through peer reviews in order to ensure technical correctness, significance, and relevance to the special issue. We would like to thank all authors who responded to our call for papers, regardless of whether their article has been included in this issue or was rejected due to space limitations. In the latter case, we hope that their work will find the intended audience through another magazine, journal, or conference proceedings, and that the feedback pro- vided by the peer reviews will help this happen sooner and more efficiently. We would like also to express our sincere thanks to all the review- ers, who did an excellent job, not only justifying their recom- mendations to the editors, but also providing detailed and helpful suggestions to the authors on improving content and presentation. They bore on their shoulders the unexpected load of a high submission volume. It is their expertise and time that helped this issue happen. The peer review has led our special issue to comprise eight articles categorized into three separate but related groups of multihop network configuration, quality of service control, and mobility management techniques. We think these topics cover the bulk of research requirements in merg- ABBAS JAMALIPOUR PASCAL LORENZ G UEST E DITORIAL MERGING IP AND WIRELESS NETWORKS T