To address the problems that data transmission delay is high and the channel utilization rate is low in the TAB-MAC (Assisted Beamforming MAC (Medium Access Control) protocol for terahertz communication network) for present terahertz Wireless Personal Area Network (T-WPAN), an Efficient and Fast dual-channel MAC protocol for T-WPAN (EF-MAC) was proposed. A test frame was sent to the source node through destination node to reduce an acknowledgment frame, so as to reduce control overhead and test delay. And then a sending and receiving mechanism of node location information was adaptively concelled, the source or destination node obtained the location information of the other node through interaction process previously of RTS/CTS (Request To Send/Clear To Send) frame, and the position of other node had not changed, thus the location information of RTS or CTS frame could be omitted to reduce control overhead. The theoretical analysis and simulation results show that compared with TAB-MAC protocol, the proposed protocol can effectively reduce data transmission delay and improve network throughput.

To resolve the problems currently existing in access protocol for Terahertz Wireless Personal Area Network (THz-WPAN) for PicoNet Coordinator (PNC) handover process, such as imperfect PNC handover process, redundant information transmission, waste of obvious timeslot resources, an access protocol of piconet coordinator high efficient handover for terahertz wireless personal area networks called PCHEH-AP (Piconet Coordinator High Efficient Handover Access Protocol) was proposed. By using deleting the specified node redundancy information mechanism, confirming first and handover next mechanism, PNC handover adaptive slot allocation mechanism, PCHEH-AP generally regulates the PNC handover process, improves channel utilization, reduces data delay, and makes PNC handover more reasonable and efficient. The simulation results show that compared with the protocol defined by IEEE 802.15.3c and the HTLL-MAC protocol, the data delay of PCHEH-AP is reduced by at least 8.98% and the throughput of MAC layer is also increased by 3.90%.

The transmission energy consumption of nodes does not be considered in the exiting Network Coding Aware Cooperative MAC (NCAC-MAC) protocol for Ad Hoc Network, and the control message sent by the candidate cooperative relay node can not make the other candidate nodes which are not in the communication range give up competition, thus causing collision. To deal with those problems, a high efficiency Medium Access Control (MAC) protocol based on cooperative network coding High Efficiency MAC protocol based on Cooperative Network Coding (HECNC-MAC) was proposed. Three optimization schemes were carried out by the protocol. Firstly, candidate cooperative relay node need to prejudge whether the destionation can decode the packet, so as to reduce the number of competitive relay nodes and ensure that the destination node could be successfully decoded. Secondly, the transmission energy consumption of nodes should be synthetically considered when selecting the cooperative relay node. Finally, the Eager To Help (ETH) message is canceled, and the destination node sents conformation message through pseudo-broadcast. Theoretical analysis and simulation results show that in the comparison experiments with Carrier Sense Multiple Access (CSMA), Phoenix and NCAC-MAC protocols, the transmission energy consumption of nodes and the end-to-end delay of date packages can be effectively reduced, and the network throughput can be improved by HECNC-MAC.

It is difficult to express diversity policy by traditional RBAC (Role-based Access Control) management model. In order to solve the problem, an Attribute based User-Role assignment (ABURA) model was proposed. Attributes were adopted as prerequisite conditions to provide richer semantics for RBAC management policy. In distributed systems, user-role reachability analysis is an important mechanism to verify the correctness of authorization management policy. The definition of user-role reachability analysis problem for ABURA model was given. According to the characteristics of state transition in ABURA model, some reduction theorems for policy were given. Based on these theorems, user-role reachability analysis algorithm was proposed, and the algorithm got verified through examples.

Opportunistic network routing algorithm based on geographic location information in DIrection based Geographic routing scheme (DIG) has the problems of large delay and low success rate, which is due to that DIG algorithm makes the waiting time of the data in the cache too long and cannot guarantee the data-carrying node move to the destination node. To solve these problems, Geographic Routing algorithm based on Directional Data Transmission (GRDDT) was proposed. The algorithm used a new data forwarding mechanism and a more effective use of the neighbor list information, effectively avoiding the appearance of the above circumstances, so as to reduce data packet transmission delay and to improve the success rate. OPNET simulation results show that, the performance of transmission delay and success rate of GRDDDT algorithm are improved compared with DIG.

To solve the redundancy of control overhead and allocation time consumption in the address assignment algorithm of Low-Rate Wireless Personal Area Network (LR-WPAN) mesh, a High-efficiency and Low-delay Address Assignment (HLAA) algorithm for LR-WPAN mesh was proposed. By using the process of network access to realize the function of network access and address assignment, and deleting the redundant fields in the address assignment, HLAA had reduced allocation time as well as control overhead in the premise of realizing the function of address allocation. The simulation results show that compared with the original algorithm, HLAA can decrease the control overhead by 22.15%, and reduce the allocation time by 7.68%.

To realize 10Gbps level wireless access under the condition of terahertz (THz) carrier frequency, a new Medium Access Control (MAC) protocol for THz ultra-high data-rate wireless networks, MAC-T (Medium Access Control for THz) was proposed in this paper. In MAC-T, a new TDMA (Time Division Multiple Access)+CSMA (Carrier Sense Multiple Access) adaptive hybrid MAC access control mechanism and a new superframe structure were designed. Moreover, some key parameters corresponding to terahertz communications were defined. Therefore, MAC-T could make the maximum data transmission rate reach up to 10Gbps or higher. The theoretical analysis and simulation results show that MAC-T can operate normally in terahertz networks and the data rate can reach up to 18.3Gbps which is 2.16 times 5.78Gbps that IEEE 802.15.3c can achieve. Meanwhile, the average access delay of MAC-T is 0.0044s which improves about 42.1% compared with that of IEEE 802.15.3 which is 0.0076s. Thus, MAC-T can provide significant support in the research and application of terahertz ultra-high data-rate wireless networks.

With regard to the singleness of the role establishment method in the traditional cross-domain authorization management models, and the problems such as implicit promotion of privilege and the separation of duties conflict, a new cross-domain authorization management model based on two-tier role mapping was proposed. The two-tier role architecture met the practical needs of role establishment and management. On this basis, unidirectional role mapping can avoid the role mapping rings. By introducing attribute and condition, dynamic adjustment of permissions was realized. The model was formalized by dynamic description logic, including concepts, relations and management actions. In the end, the security of the model was analyzed.

For Automated Trust Negotiation (ATN) consultative process may encounter the infinite cycling problem, the causes of the cycle were analyzed and the corresponding detection algorithm was designed to find and terminate the negotiation cycle. Interdependency relationships among policies in ATN were modeled as simple graph and the model's correctness was proved. The process of calculating simple grahp's reachability matrix was analyzed and cycle detection theorem was given. The algorithm of detecting cyclic policy interdependency was designed according to the theorem. Finally, a case study verifies the feasibility of the algorithm.

According to the characteristics of wireless single-hop broadcast networks, a network coding scheme based on sliding windows named NCBSW was proposed. The scheme designed a coding window which slid in a chronological order in the matrix of data packets waiting for retransmission, and the data packets used to encode were chosen from the sliding window. Meanwhile, the scheme ensured the solvability of coded packets. The simulation results show that the proposed scheme has a better performance as compared to the retransmission approach in wireless broadcasting based on network coding (NCWBR) in terms of the number of retransmission, delay, network overhead and energy consumption.

Privilege deduction relation makes the authorization management easier, and at the same time it also causes the calculation of valid privileges more difficult. Therefore, it is important for authorization and access control to calculate deduction relations between privileges correctly and efficiently. Based on the resource hierarchy and operation hierarchy, the rule of privilege deduction was given in this paper. According to the fact that privilege query happens more frequently than privilege update, a new method of calculating deduction relations based on reachability matrix of privilege deduction was proposed. The experimental results show that the new method is more efficient than the way calculating deduction relations directly.

To detect the critical nodes that can lead to topology partition in a Mobile Ad Hoc Network (MANET), a Cross-link-tolerant Partition Detection Algorithm (CPDA) was proposed. Through utilizing the information of adjacent nodes, CPDA could eliminate the cross-links' impact on the elementary loop. Therefore, it solved the problem that the existing algorithm of Distributed Partition Detection Protocol (DPDP) based on elementary-loop could not address cross links, which improved the accuracy of detection of critical nodes. The performance results show that CPDA has no limitation on network topology and outperforms DPDP in terms of detection accuracy and overhead.