**3.1 Physical layer**

Wireless mesh networks are capable of multiple data rates simultaneously. It is achieved with the help of various modulation techniques and coding rates. Link adaption provides adaptive error resilience. High-speed data transmission is achieved with orthogonal frequency-division multiple access (OFDMA) and ultrawideband (UWB) techniques.

Wireless communication system is provided with smart antenna for the purpose of increasing the capacity and to overcome the co-channel interference, fading, multi-antenna systems, etc. But it is tedious for designing the same for wireless mesh networks though it is available with the existing system. Unoccupied spectrum can be utilized by proper frequency planning with the help of WMN. Frequency agile/cognitive radio is used in order to utilize the unused spectrum.

As most of the radio components, RF band, various channel modulations, and access modes are programmable in such a way that it can be implemented in a software for working under cognitive radio range. It will be easier if further updating is to be carried out.

With the available physical test beds, the software platform is not much appropriate to provide desired solution. But still it can able to make advance changes in physical layer techniques which suit better for wireless communications.
