One of the key challenges of the

cognitive radio A cognitive radio (CR) is a radio that can be programmed and configured dynamically to use the best wireless channels in its vicinity to avoid user interference and congestion. Such a radio automatically detects available channels in wireless spe ...

based

wireless network A wireless network is a computer network that uses wireless data connections between network nodes. Wireless networking is a method by which homes, telecommunications networks and business installations avoid the costly process of introducing c ...

s, such as

IEEE 802 IEEE 802 is a family of Institute of Electrical and Electronics Engineers (IEEE) standards for local area networks (LAN), personal area network (PAN), and metropolitan area networks (MAN). The IEEE 802 LAN/MAN Standards Committee (LMSC) maintains ...

.22 wireless regional area networks (WRAN), is to address two apparently conflicting requirements: assuring Quality of Services (QoS) satisfaction for services provided by the cognitive radio networks, while providing reliable spectrum sensing for guaranteeing licensed user protection. To perform reliable sensing, in the basic operation mode on a single

frequency band A frequency band is an interval in the frequency domain, delimited by a lower frequency and an upper frequency. The term may refer to a radio band or an interval of some other spectrum. The frequency range of a system is the range over which i ...

(the so-called "listenbefore-talk" mode) one has to allocate Quiet Times, in which no

data transmission Data transmission and data reception or, more broadly, data communication or digital communications is the transfer and reception of data in the form of a digital bitstream or a digitized analog signal transmitted over a point-to-point o ...

is permitted. Such periodic interruption of data transmission could impair the QoS of cognitive radio systems. This issue is addressed by an alternative operation mode proposed in

IEEE 802.22 IEEE 802.22, is a standard for wireless regional area network (WRAN) using white spaces in the television (TV) frequency spectrum. The development of the IEEE 802.22 WRAN standard is aimed at using cognitive radio (CR) techniques to allow sharing ...

called Dynamic

Frequency Hopping Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many distinct frequencies occupying a large spectral band. The changes are controlled by a code known to both tra ...

(DFH) where data transmission of the WRAN systems are performed in parallel with spectrum sensing without any interruption.

References

{{reflist Wireless networking