Future Wireless communication

With rapid growth in the wireless communication, the usage of spectrum is increased. Presently there is a severe shortage of the spectrum for new applications. However, the current spectrum scarcity is largely due to the inefficient static spectrum allocations rather than the physical shortage of the spectrum.

         Recent studies of FCC, which reveal that, in some locations or at some times of a day, 70% of the allocated spectrum remains unused. This means that spectrum scarcity is not due to fundamental lack of spectrum but due to static spectrum allocations. The allocation of the spectrum currently is regulated. The spectrum bands are licensed and the sharing of bands is not allowed. This inflexible spectrum allocation policy results in the under utilization of overall spectrum.

To deal with the imbalance between spectrum scarcity and spectrum under utilization, cognitive radio (CR) technology has been proposed to improve spectrum. Cognitive radio is one critical enabling technology for future communications and networking that can utilize the limited network resources in a more efficient and flexible way. Indeed, it is already being considered as one of the key candidate technologies for the fourth-generation (4G) wireless systems.

Cognitive radio enables dynamic spectrum access techniques, where users who have no spectrum licenses, also known as secondary users, are temporarily allowed to use the unused licensed spectrum. The cognitive radio enables the usage of temporarily unused spectrum, which is referred to as spectrum hole or white space. The basic idea of CR network is that it enables the unlicensed user to use the licensed spectrum whenever it is unused. If this band is to be utilized by a licensed user, the cognitive radio user has to moves to another spectrum hole or stays in the same band.

We look forward to that cognitive radio technology will soon emerge from early stage laboratory trials and vertical applications to become a general-purpose programmable radio that will serve as a universal platform for wireless system development, much like microprocessors have served a similar role for computation. Building and deploying a network of cognitive radios is a complex task. There is a growing concern that conventional academic research in this area has reached a point of diminishing returns and that further progress in the above areas will depend on a new approach involving multi-institutional research teams working with real-world experimental deployments of cognitive radio network .

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