Special issue: WLAN/3G integration for next-generation heterogeneous mobile data networks

The recent evolution and successful deployment of Wireless Local Area Networks (WLANs) has yield a demand to integrate WLANs with third-generation (3G) cellular networks, such as GSM/GPRS, UMTS, cdma 2000, etc. The key goal of this integration is to develop heterogeneous mobile data networks, capable of supporting ubiquitous data services with very high data rates in strategic locations. The effort to develop such heterogeneous networks is linked with many technical challenges including seamless vertical handovers across WLAN and 3G radio technologies, security, 3G-based authentication, unified accounting and billing, WLAN sharing (by several 3G networks), consistent QoS and service provisioning, etc. The need to address these issues and provide timely, solid technical contributions in the area of WLAN/3G integration established the motivation behind this special issue. In response to the above demand for integrated WLAN/3G mobile data networks, this special issue aims at providing a timely and concise reference of the current activities and findings in the relevant technical fields. It is composed of seven original papers that address the key technical issues pertaining to WLAN/3G integration and propose unique technical contributions. More specifically, the first article, entitled ‘A cost-based approach to vertical handover policies between WiFi and GPRS,’ by Andrea Calvagna and Giuseppe Di Modica, proposes a new approach in taking vertical handover decisions, which are not anymore exclusively based on the knowledge of the available access networks’ characteristics, but also on higher level parameters which fall in the transport and application layers. To this extent, a model is realized and simulations are run in order to evaluate the impact of the vertical handover and its frequency on a set of typical user’s network applications/services. This approach does not lead to a single optimal handover decision function, but poses the problem to assess the impact of vertical handovers’ scheduling times, as well as their frequency, with respect to the transport level protocols used by network applications. The next article ‘Adaptive bandwidth provisioning in an integrated 3G and WLAN environment,’ by Yong-Hoon Choi, Jaesung Park, and Beomjoon Kim, describes a practical bandwidth re-provisioning scheme in an integrated 3G/WLAN environment. It investigates how to increase available bandwidth for conversational class while keeping the packet loss probability of background class below a threshold. The proposed scheme is implemented as a simple network management protocol (SNMP)-compliant Management Information Base (MIB) and deployed at Packet Data Serving Node (PDSN) equipment. The experiments conducted on 1x evolution for data and voice (1xEV-DV) test-bed show that the proposed scheme increases the bandwidth of the conversational class and guarantee adequate service quality of the background class. The third article entitled ‘A mobile peer-to-peer approach for multimedia content sharing using 3G/ WLAN dual mode channels,’ by Seung-Seok Kang and Matt W. Mutka, provides a scheme to reduce the cost to distribute multimedia content to a set of nearby mobile peers, which are called chums. One peer, called the proxy, downloads multimedia content via a telecommunication link, and distributes it (this operation is called chumcast) to the ad hoc network formed from the set of nearby peers. Each peer in the ad hoc network takes turns serving as a proxy. Every peer is associated with a server that resides in the internet. The server for the proxy, called the active server, manages peer information, schedules the next proxy, selects a set of re-broadcasting peers, and detects partitioning of the ad hoc network. With