Since the common control channel may be subject to primary user activity, the common control channel design in cognitive radio networks encounters unprecedented challenges: cognitive radio users are unable to negotiate a new control channel when the original one is occupied by primary users.
However, since 2000, the export-led regions have encountered unprecedented challenges at global, national and local levels, including the surge of labour costs, stringent labour and environment regulation, appreciation of Renminbi and decreasing orders from the sluggish demand of the core Western markets (Yang 2007).
Since 2000, these export-led regions have encountered unprecedented challenges, particularly the rising cost of labour, which have engendered spatial relocation of labour-intensive manufacturing firms from coastal China to lower-cost locations such as inland China and neighbouring Southeast Asian countries.
Since 2000, these export-led regions have encountered unprecedented challenges, especially the rising cost of labour, land, shortage of labour, policy changes, and shrinking market demand of western advanced economies, which have engendered spatial relocation of labour-intensive manufacturing firms from China to lower-cost locations, e.g. inland China and neighbouring Southeast Asia.
As the demand for services increases under healthcare reform, substance abuse and mental healthcare providers can expect to encounter unprecedented workforce challenges and possibilities.
Holt will encounter an unprecedented challenge, however, on Monday night, when he will mediate between two hungry candidates now tantalizingly close to claiming the most powerful post on Earth.
But that delicately woven tapestry is facing unprecedented challenges.
"The Welsh economy and our constitution face unprecedented challenges.
The U.S. healthcare system is facing unprecedented challenges.
Pelagic marine predators face unprecedented challenges and uncertain futures.
And while unprecedented technological change might appear to present unprecedented challenges for leaders, that is not entirely the case.
