Research on the many aspects of the wireless sensor network like reliability, time, etc. has been vital from very long time. That is why the authors have reviewed the optimization techniques of quality of service techniques in wireless sensor networks. From the various research issues cross layer is the recent in which there are chances of optimization in the working of the wireless network. Cross layer is the need of the time to improve quality of metrics such as delay, time, and energy efficiency. Main problem of the wireless sensor network is that they are battery operated which gives rise to the problem of energy constraint.