IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 56, NO. 6, NOVEMBER 2007 3511 Minimum-Cost Data Delivery in Heterogeneous Wireless Networks Haining Chen, Student Member, IEEE, Hongyi Wu, Member, IEEE, Sundara Kumar, Student Member, IEEE, and Nian-Feng Tzeng, Senior Member, IEEE Abstract—With various wireless technologies developed over the past few years, a ubiquitous and integrated architecture is envisioned for future wireless communication. An important op- timization issue in such an integrated system is how to minimize the overall communication cost by intelligently utilizing the avail- able heterogeneous wireless technologies while, at the same time, meeting the quality-of-service requirements of mobile users. In this paper, we first identify the cost-minimization (CM) problem to be NP-hard. We then present an efficient minimum-cost data- delivery algorithm based on linear programming (LP), with var- ious constraints, such as channel bandwidth, link costs, delay budgets, and user mobility, taken into consideration. In case of insufficient bandwidth for communication with the core network, prefetch is employed to fully utilize the wireless-network capacity. If multiple routes are available, a probability-based approach is taken for CM. Extensive simulations are carried out to evaluate the proposed CM scheme. Our results show that the proposed LP approach can effectively reduce the overall communication cost, with small overhead (< 3%) for signaling, computing, and handoff. We expect that minimum-cost data delivery will become imperative for the future heterogeneous wireless networks and the emerging 4G wireless systems. Index Terms—Cost minimization (CM), heterogeneous wireless networks, linear programming (LP), quality of service (QoS). I. I NTRODUCTION W ITH VARIOUS network characteristics and commercial concerns, a number of wireless technologies have been developed over the past few years, and they are likely to coexist for many years to come. For example, the cellular systems [1]–[3] have evolved from the first-generation analog system to the second-generation digital system, and they are presently entering the era of 3G that supports not only voice but also data traffic at a speed of up to 2 Mb/s, while the 4G system is under development for achieving a data rate that is ten times higher. On the other hand, a series of complementary IEEE standards, including 802.20 [4], 802.16e [5], 802.16 [6], 802.11 [7], and 802.15 [8], have been developed or are currently under development to effect data communication in mobile and fixed broadband wireless-access networks, local- and metropolitan- Manuscript received November 24, 2005; revised December 24, 2006 and February 4, 2007. This work was supported in part by the U.S. Department of Energy (DoE) under Award DE-FG02-04ER46136, by the Board of Regents, State of Louisiana, under Contract DOE/LEQSF(2004-07)-ULL, and by the National Science Foundation CAREER Award under Award CNS-0347686. The review of this paper was coordinated by Prof. T. Hou. The authors are with the Center for Advanced Computer Studies, University of Louisiana, Lafayette, LA 70504 USA (e-mail: hxc5633@cacs.louisiana.edu; wu@cacs.louisiana.edu; sxk6124@cacs.louisiana.edu; tzeng@cacs.louisiana. edu). Digital Object Identifier 10.1109/TVT.2007.901049 area networks, and personal-area networks, respectively. In particular, 802.20 and 802.16e target at mobile broadband wireless-access networks, providing users moving at vehicular speed with a data rate from 1 to 30 Mb/s in a wide area. 802.16 offers fixed broadband wireless-access network with data rate up to 75 Mb/s, which can be allotted to T1-level connections for business customers and/or to the best effort DSL-speed connections for home customers. 802.11 supports low-mobility users in small cells, at the data rates varying from 1 to 54 Mb/s. Recently, this cost-effective technology is being deployed ag- gressively for establishing metro-scale “cellular WiFi” net- works [9] to support seamless Internet access in urban areas. In addition to aforementioned terrestrial communication systems, the satellite [10] is a vital component in the wireless system, providing global coverage and high-speed data transmission. While most of these wireless technologies are deployed independently for now, the service providers have most interest to own and operate overlaid heterogeneous wireless systems, which integrate multiple wireless technologies with partially overlapped coverage areas and provide ubiquitous network ser- vice to mobile users. For example, several mobile carriers such as Verizon, Sprint PCS, and T-Mobile are anxious to include wireless LAN (or WiFi) access among their service offerings. In order to access various wireless networks/technologies, the mobile host (MH) may be equipped with one or multiple programmable wireless-interface card(s) (e.g., based on the programmable radio technology [11], [12] or an approach similar to mobile-access router [13]), resulting in twofold flex- ibility that may enable the optimization of data delivery: 1) An MH may select one of multiple available wireless-access tech- nologies at a particular location, because one area may be covered by multiple wireless networks with different costs, data rates, and mobility-support capabilities, and 2) an MH may use different access technologies when it travels in the network and arrives at different locations covered by various wireless networks. From the standpoint of the service provider, it is an important issue to minimize the overall communication cost by intelligently using the available heterogeneous wireless technologies. In this paper, we consider a typical scenario where an MH X is involved in massive data transmission while travel- ing (or staying, as a special case). For example, MH X may participate in a large peer-to-peer (P2P) network, where the members share resources such as movie files [14], [15]. Given the large data volume and the limited link capacity, a long data- transmission time (e.g., up to hours) may be expected, during which MH X needs to serve as either a receiver or a data 0018-9545/$25.00 © 2007 IEEE Authorized licensed use limited to: IEEE Xplore. Downloaded on November 6, 2008 at 12:38 from IEEE Xplore. Restrictions apply.