We provide a brief overview over the development of software-defined or reconfigurable radio systems. The need for software-defined radios is underlined and the most important notions used for such reconfigurable transceivers are thoroughly defined. The role of standards in radio development is emphasized and the usage of transmission mode parameters in the construction of software-defined radios is described. The software communications architecture is introduced as an example for a framework that allows an object-oriented development of software-defined radios. Cognitive radios are introduced as the next step in radio systems' evolution. The need for cognitive radios is exemplified by a comparison of present and advanced spectrum management strategies.

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Software-defined radio: basics and evolution to cognitive radio

Software Defined Radio (SDR) may provide flexible, upgradeable and longer lifetime radio equipment for the military and for civilian wireless communications infrastructure. SDR may also provide more flexible and possibly cheaper multi-standard-terminals for end users. It is also important as a convenient base technology for the future context-sensitive, adaptive and learning radio units referred to as cognitive radios. SDR also poses many challenges, however, some of them causing SDR to evolve slower than otherwise anticipated. Transceiver development challenges include size, weight and power issues such as the required computing capacity, but also SW architectural challenges such as waveform application portability. SDR has demanding implications for regulators, security organizations and business developers.

Software Defined Radio: Challenges and Opportunities

With growing interest in using cognitive radio (CR) technology in wireless communication systems for vehicles, it is envisioned that future vehicles will be CR-enabled. This paper discusses CR technologies for vehicular networks aimed at improving vehicular communication efficiency. CR for vehicular networks has the potential of becoming a killer CR application in the future due to a huge consumer market for vehicular communications. This paper surveys novel approaches and discusses research challenges related to the use of cognitive radio technology in vehicular ad hoc networks. We review how CR technologies such as dynamic spectrum access, adaptive software-defined radios, and cooperative communications will enhance vehicular communications and, hence, present the potential of transforming vehicle communication in terms of efficiency and safety. Our work is different from existing works in that we provide recent advances and open research directions on applying cognitive radio in vehicular ad hoc networks (CR-VANETs) focusing on architecture, machine learning, cooperation, reprogrammability, and spectrum management as well as QoE optimization for infotainment applications. A taxonomy of recent advances in cognitive radio for vehicular networks is also provided. In addition, several challenges and requirements have been identified. The research on applying CR in vehicular networks is still in its early stage, and there are not many experimental platforms due to their complex setup and requirements. Some related testbeds and research projects are provided at the end.

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Cognitive radio for vehicular ad hoc networks (CR-VANETs): approaches and challenges

In this article, based on the overview of network coupling structure between radio access technologies, the concept of joint radio resource management built onto the reference structure is introduced. In order to optimize usage of radio resource and jointly designed from the user perspective, a joint scheduling mechanism allowing traffic to be split over a tightly coupled radio network supported by an adaptive radio multihoming approach is deliberately discussed. With respect to the time-division access scheme in HIPERLAN/2, which is selected as one example of WLAN, algorithms and performance of traffic scheduling in such a radio access technology are given. The required synchronization scheme supporting traffic splitting is also introduced.

Investigation of radio resource scheduling in WLANs coupled with 3G cellular network

This chapter develops five complementary perspectives of cognitive radio architecture (CRA), called CRA-I through CRA-V, each building on the previous in capability. Architecture is driven top-down by market needs and bottom-up by available, affordable technologies. Taking the top-down perspective requires some attention to the use cases that the functions are intended to realize. This chapter therefore reviews the substantial changes in use cases that drive cognitive wireless architecture. Often technical architectures of the kind accelerate the state of practice by catalyzing work across the industry on plug-and-play, teaming, and collaboration. The thought is that to propel wireless technology from limited spectrum awareness toward valuable user awareness, an architecture is needed. The CRA articulates the functions, components, and design rules of next-generation stand-alone and embedded wireless devices and networks.

Walter H. W. Tuttlebee

Papers

Software Defined Radio