64,579 research outputs found
Multi-Round Contention in Wireless LANs with Multipacket Reception
Multi-packet reception (MPR) has been recognized as a powerful
capacity-enhancement technique for random-access wireless local area networks
(WLANs). As is common with all random access protocols, the wireless channel is
often under-utilized in MPR WLANs. In this paper, we propose a novel
multi-round contention random-access protocol to address this problem. This
work complements the existing random-access methods that are based on
single-round contention. In the proposed scheme, stations are given multiple
chances to contend for the channel until there are a sufficient number of
``winning" stations that can share the MPR channel for data packet
transmission. The key issue here is the identification of the optimal time to
stop the contention process and start data transmission. The solution
corresponds to finding a desired tradeoff between channel utilization and
contention overhead. In this paper, we conduct a rigorous analysis to
characterize the optimal strategy using the theory of optimal stopping. An
interesting result is that the optimal stopping strategy is a simple
threshold-based rule, which stops the contention process as soon as the total
number of winning stations exceeds a certain threshold. Compared with the
conventional single-round contention protocol, the multi-round contention
scheme significantly enhances channel utilization when the MPR capability of
the channel is small to medium. Meanwhile, the scheme automatically falls back
to single-round contention when the MPR capability is very large, in which case
the throughput penalty due to random access is already small even with
single-round contention
A Different Look at Inward FDI into Mainland China
This paper aims to find out the relationship between inward FDI into China and China's economic development. According to the descriptive analysis of FDI data from 1980 till 2007, we firstly found that there is a sectoral and regional biased distribution with regard to the inward FDI into China; we saw that the contribution of inward FDI to China's economic development exhibits a reversed U shape (the turning point locates in the year of 2001). In order to figure out the main reason and the causal-effect relationship between inward FDI into China and China's economic growth, we used ECM and Granger Causality Test based on the data between 1978 and 2001 in the second part. We found that within this period the causal-effect relationship between China's economic development and inward FDI was bidirectional and the causal impact of China's economic development on FDI was larger than the impact of FDI on China's economic development. To discover the reason of reduced FDI contribution to China's economic development since 2001 onwards, we used the fixed-effect panel analysis based on a panel dataset consisting 31 provinces in China from 2001 to 2005. We found that inward FDI in China since 2001 onwards has negative spillover effect on China's economic development. We argue that the reason might be the duplication effect of foreign firms, negative externalities of backward, forward and horizontal relationships between foreign and domestic firms, increased welfare loss, and China's regional economic disparity.Foreign direct investment, economic growth, externalities, spillovers, China
Alliance-based Network View on Chinese Firms' Catching-up: Case Study of Huawei Technologies Co.Ltd
With China's rapid economic growth in recent years, many Chinese firms especially in high-tech industries have started to technically lead in the international market. In this study, we aim to uncover the root causes that lead to Chinese firms' catching up from network perspective. By taking Huawei Technologies Co. Ltd. as a case, we integrate absorptive capacity development and firm-level catching up into an alliances-based network framework. We found that network alliances with firms and universities complement each other at different catching up stages; and alliances-based network provides a springboard for Chinese firms to shorten catching up path. We argue that in Chinese context, impact of FDI on firms' performance comes into effect only if partnership is carried out; alliances with universities facilitate development of absorptive capacity at an early stage; Partnering with leading players stimulate R&D investment at a late stage and simultaneously enhance firm's innovation performance as well.Strategic alliances, Network, Chinese firms, absorptive capacity, catching up
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