In this letter, we introduce a novel keys distribution optimization scheme for CP-ABE based access control. This scheme integrates roles, role hierarchies and objects grouping to accelerate keys distribution, meanwhile the CP-ABE encrypting overhead is reduced by adopting deterministic cryptographic function. Experiments show that our scheme obtains noticeable improvement over the original one, especially when the number of objects is much greater than that of users.

Power consumption has become a critical factor for embedded systems, especially for battery powered ones. Caches in these systems consume a large portion of the whole chip power. Embedded systems usually adopt set-associative caches to get better performance. However, parallel accessed cache ways incur more energy dissipation. This paper proposed a region-based way-partitioning scheme to reduce cache way access, and without sacrificing performance, to reduce the cache power consumption. The stack accesses and non-stack accesses are isolated and redirected to different ways of the L1 data cache. Under way-partitioning, cache way accesses are reduced, as well as the memory reference interference. Experimental results show that the proposed approach could save around 27.5% of L1 data cache energy on average, without significant performance degradation.

The next generation mobile communication system is required to support wideband wireless data links when terminals are moving at very high speed. In such case, accurate channel estimation is more crucial in this case. This paper presents a downlink channel estimation scheme for Multi-Input and Multi-Output (MIMO) MC-CDMA system by introducing uncorrelated and continuous pilot symbol sequence for every transmit antenna in code domain. Compared with conventional pilot aided estimation methods which insert pilots symbols in time domain, frequency domain or both of them, the proposed method can obtain more accurate channel impulse response matrix estimation in fast fading environments with much lower computation complexity and less resources exhausted. At last, we analyzed the BER performances of the scheme under a typical fast fading environment-VB and AWGN.