A multiband mobile communication system for wide coverage and high data rate (2006)

This paper studies a multiband mobile communi- cation system to support both high data rate services and wide service coverage, using high and low frequency resources with different propagation characteristics. In the multiband system, multiple frequency bands are managed by a base station and one of the frequency bands is adaptively allocated to a terminal. By limiting the low frequency resources to a terminal not covered by the higher frequencies, the presented multiband system can provide wide coverage area for many terminals, as if all radio resources have low frequency. The numerical results show that the multiband system can support wide coverage for much larger number of terminals. It is also found that an appropriate balance of bandwidths in multiple frequencies is essential for high capacity. I. INTRODUCTION The demand for high data rate communications is growing intensively and fourth generation (4G) mobile system is ex- pected to provide high data rate services in excess of 100Mbps. The final goal of the 4G system is to satisfy the consumer's demand making successful business. To achieve this goal, efficient schemes for wireless data transmissions have been widely investigated (1)(2). In actual environments, consumers are sensitive to not only data rate but also service coverage area. A wireless system with frequent connection errors will not fascinate consumers, which results in unfavorable business condition. This tendency is seen in the past economic data between population coverage and the number of subscribers. Therefore, wide service cov- erage is essential to lead the 4G mobile system into success. In fact, there are some conflicting aspects between high data rate and service coverage issues. Generally, it is known that radio wave with lower frequency is more suitable to support non-line-of-sight (NLOS) or indoor terminals, because lower frequency associated with larger wavelength has more diffraction and better propagation characteristics in NLOS locations (3)-(7). However, most of low frequency bands, e.g. frequency below 1GHz, have been already allocated to the existing services and it seems difficult to allocate much of low frequency band to the 4G system. Therefore, it will be unavoidable to allocate higher frequency band as a main radio resource. Since the high frequency band cannot sufficiently support NLOS or indoor locations, (e.g., radio wave beyond 2GHz sometimes does not penetrate from outdoor to indoor), there is a large risk in business that consumers are not satisfied with the corresponding small coverage. So far, a network handover between heterogeneous networks has been mainly studied to make complemental relationship of service areas (9)-(13). Although the network handover techniques will be important for future wireless networks, there are some problems in toll collection, delay and control complexity in network management, and complicated selection of system combination for consumers. Therefore, a single wireles system supporting both high data rate and wide service coverage would be more attractive, although the network handover is still important with other networks.