As technology processes scale up and design complexities grow, system-on-chip integration continues to rise rapidly. According to these trends, increasing test data volume is one of the biggest challenges in the testing industry. In this paper, we present a new test data compression method based on reusing a stored set with tri-state coding (TSC). For improving the compression efficiency, a twisted ring counter is used to reconfigure twist function. It is useful to reuse previously used data for making next data by using the function of feedback of the ring counter. Moreover, the TSC is used to increase the range information transmission without additional input ports. Experimental results show that this compression method improves a compression ratio and a test time on both International Symposium on Circuits and Systems'89 and large International Test Conference'99 benchmark circuits in most cases compared to the results of the previous work without a heavy burden on the hardware.

As a scan-based testing enables higher test coverage and faster test time than alternative ways, it is widely used by most system-on-chip (SoC) designers. However, since the number of logic gates is over one hundred million gates, a number of scan cells lead to excessive power consumption and it produces a low shifting frequency during the scan shifting mode. In this paper, we present a new scan shift power reduction method based on a scan chain reordering (SR)-aware X-filling and a stitching method. There is no need to require an additional logic for reducing the scan shift power, just a little routing overhead. Experimental results show that this method improves scan shift power consumption on benchmark circuits in most cases compared to the results of the previous works.

Wafer testing (wafer sort) is used in the semiconductor industry to reduce test costs. High parallelism is important to reduce test application time. However, increasing parallelism is becoming more difficult because the elements that drive test costs are increases in the pin count of the system on chip (SOC), and required automated test equipment (ATE) channels. While the need for parallelism has been growing, a reliability problem in which fault distribution causes good devices under test (DUT) to be improperly tested is becoming a concern. To achieve high parallelism and reliability, we propose a novel, massively parallel testing method using multi-root. In addition, we develop a test setup for setting the root-DUT location and the path of all DUTs. Using the proposed wafer testing method, test data can be transferred between the ATE and dies using multi-roots. The experimental results using ITC 02 SOC benchmarks show that the proposed method can reduce test costs up to 90%, and achieve nearly 94.84% test reliability without affecting yield.

In this paper, we solve the interworking problem for different user authentications between licensed BWAN and unlicensed band network when an unlicensed radio band user connects to the Internet via BWAN.

Abstract Internet access from mobile phones over cellular networks suffers from severe bandwidth limitations and high bit error rates over wireless access links. Tailoring TCP connections to best fit the characteristics of this bottleneck link is thus very important for overall performance improvement. In this work, we propose a simple algorithm in deciding the optimal TCP segment size to maximize the utilization of the bottleneck wireless TCP connection for mobile contents server access, taking the dynamic TCP window variation into account. The proposed algorithm can be used when the product of the access rate of the wireless link and the propagation time to mobile contents servers is not large. With some numerical examples, it is shown that the optimal TCP segment size becomes a constant value when the TCP window size (WS) exceeds a threshold. One can set the maximum segment size (MSS) of a wireless TCP connection to this optimal segment size for mobile contents server access for maximum efficiency on the expensive wireless link. Copyright © 2007 John Wiley & Sons, Ltd.

In this paper, we propose a multi-state based hybrid location update scheme, which integrates the time-based and the movement-based methods. In the proposed scheme, a mobile terminal updates its location after n cell boundary crossing and a time interval of T[sec]. We derive an analytical solution for the performance of the hybrid scheme with exponential cell resident time and evaluate it numerically with time-varying random walk mobility model, which we model as a multi-state Markov chain. Furthermore, we also evaluate the scheme for arbitrary cell resident times by simulation. From the numerical analysis and the simulation results, we prove that the proposed scheme significantly outperforms the time-based and the movement-based methods, when implemented alone, more accurately adapting to the time-varying user mobility

This paper presents a new low power BIST TPG scheme. It uses a transition monitoring window (TMW) that is comprised of a transition monitoring window block and a MUX. When random test patterns are generated by an LFSR, transitions of those patterns satisfy pseudo-random Gaussian distribution. The proposed technique represses transitions of patterns using the k-value which is a standard that is obtained from the distribution of TMW to observe over transitive patterns causing high power dissipation in a scan chain. Experimental results show that the proposed BIST TPG schemes can reduce scan transition by about 60% without performance loss in ISCAS’89 benchmark circuits that have large number scan inputs.

Mobile ad hoc networks (MANETs) are self-organized networks that do not rely in their operation on wired infrastructure. As in any networking technology, security is an essential element in MANET as well for proliferation of this type of networks. But supporting secure communication in MANETs proved to be a significant challenge, mainly due to the fact that the set of nodes in the network can frequently and rapidly change and due to the lack of access to the wired infrastructure. In particular, the trust model and the authentication protocols, which were developed for wired and infrastructure-based networks, cannot be used in MANETs. In this paper, we address the problem of efficient authentication of mobile users distributed in geographically large networks and we propose a new authentication scheme for this case of MANETs. The proposed scheme exploits randomized groups to efficiently share authentication information among nodes that together implement the function of a distributive certification authority (CA). We evaluate the performance of the proposed randomized groups authentication scheme based on two metrics: the total cost of the scheme's operation and its reliability. As an example of the results and as a reference point, we show that the proposed scheme achieves successful authentication when the random group size is around 10 - 12 nodes, irrespectively of the number of mobile nodes, of the number of CAs, and of the mobility model of the nodes in the network.

In this paper, we propose a modified time-based registration method and analyze the performance numerically. In the analysis, we assume Poisson call arrival distribution and exponential cell resident time. The performance of the modified time-based registration method is compared with the performance of the original time-based registration method. In the comparisons, we see that in the certain range of parameters, the modified time-based registration method has better performance.

In the virtual home environment (VHE), which was proposed to offer global roaming and personal service environment portability, user's profiles and service logic are conveyed from home network to visited network to provide services at the visited network. Because user's profiles and service logics may contain confidential information, some procedures for mutual authentication among entities for offering confidence are needed. For these issues, we propose and analyze two 3-party mutual authentication protocols adaptable to the VHE in 3G; the password based mutual authentication protocol and the mutual authentication protocol with trusted third party.

In this paper, we investigate a rekey mechanism for secure multicast group communications and relate the mechanism to the amount of disclosed information from group key exposure. We also combine cost for the disclosed information and cost for group key updates and analyze the optimum rekey interval. Using the results of the analysis in this paper, we can manage secure multicast groups efficiently with the minimal cost on the bases of number of group members, each member's security level and withdrawal rates.

We analyze a time-based update method in location management and calculate the optimal time-interval. We obtain the probability that an NIT is j rings away from the center cell. And using these values, an exact analysis is made for the time-based location management cost. From the result, when the time-based method is applied to location update, we can get the optimal time-interval which minimizes the location management cost.

We introduce a method for determining the group number of cells to page. The optimal group numbers are examined according to the input load.