Smart devices in the ubiquitous computing environment implement service/device discovery protocol that helps discovering each other and the services provided. As client device may receive multiple service description messages, it implements at its MAC layer a collision resolution mechanism to resolve the collision of messages. Effectiveness of collision resolution relies on the accuracy of detecting collision at the PHY layer. In this paper, we question the reliability of the conventional collision detection technique, which inaccuracy will affect the completeness of service/device discovery. We show that capture effect and packet reception failure can cause failure in collision detection when the conventional technique is used. We then suggest a detection technique that makes use of Manchester violation test. Implementation and evaluation of the proposed technique on low-power radios show its superiority over the conventional approach.