Waveform diversity and design: Part II - Issues for waveforms and applications

Waveform diversity and design (WDD) aspects are considered in this paper drawing relations to some of the functions between the communication system layers from the given user application through to the actual waveforms. The traditional approach to WDD was typically separated within the final waveform, which has previously been composed in a monolithic manner, in an epoch when the low capacity needs, say, associated with the traditional voice-only application coupled with a relative abundance in radio-frequency (RF) spectrum enabled this approach to be deemed satisfactory. However, in more recent times, particularly over the last decade, a wide range of issues have required a need for a reassessment of the conventional WDD approach. The factors which have motivated this need include the proliferation of user applications above the basic communications need of voice only, to a wide range of Internet services and real-time applications. This broadening of user services and applications challenges the communications design environment particularly due to the limited availability of RF spectrum. The situation is exacerbated further by the current communication user´s expectations of a wide range of variable-quality services and applications within mobile environment. WDD techniques can be used to support a breadth of communication needs by supporting the use of efficient waveform, dependent upon the given application and matching the existing communications environment. This paper, forming the second part of the two-part series, aims to demonstrate WDD within a single-antenna context, and the first part identified issues for multi-antenna systems. Features of the importance of the control and management planes are discussed, including, for example, the control loops for the purpose of enhancing performance at the service and application level through WDD techniques. A part solution within this context will employ cognitive radio (CR) especially in the efforts of maxim- sing the availability of current waveforms, and standards within commercial standards are briefly reviewed.