扩频技术:历史、现状及发展

如果说,要准确地理解、认识和把握"入世"对中国经济的影响,那末,首先应该是体制变革的深远影响,然后才是部门行业的利弊得失。而这种体制性的挑战,则大体上由5个既互相联系又彼此制约的关键环节所构成。     

揭开隐藏在扩谱通信中的秘密

抗干扰、跳频数字无线电系统技术正在迅速发展,军队正努力跟上新的检测技术和截获技术。     

An empirical examination of the impact of market microstructure changes on the determinants of option bid-ask spreads

This paper examines the determinants of bid-ask spreads in the Australian Options Market before and after it switched from a quote-driven floor-traded market to an order-driven screen-traded market. This study reports that both put and call option bid-ask spreads are positively related to the option's value, its remaining term-to-maturity, its absolute hedge ratio and the volatility of returns from the underlying asset and negatively related to the level of trading activity in that option series. The study also reports that spreads are generally less when market makers are obliged to maintain continuous quotes in the market. The paper also finds that following the change in trading regime, both call and put option spreads became more sensitive to the absolute value of the option's delta. This finding is consistent with previous theoretical and empirical work from equities markets that has suggested that a switch to an electronic trading regime results in an increase in the adverse selection component of the bid-ask spread. There is also some limited evidence that suggests that the switch to electronic trading resulted in call option spreads being less sensitive to the return volatility of the underlying asset but more sensitive to the option's price.     

直扩通信系统中软件无线电的建模与实现

将扩频技术和软件无线电技术相结合在未来扩频通信的发展中占有重要的地位。基于软件无线电的思想，给出了直接序列扩频通信系统的数学模型，并对软件实现直扩系统接收机的一种设计方案进行了分析。     

Strong monotonicity in surplus sharing

Summary. We consider three new axioms for surplus sharing problems. The first is strong monotonicity which says that workers should be rewarded for increases in productivity and the second says that productive workers should receive some compensation. The third requires that the surplus sharing rule should be well defined (and continuous on) the set of threshold functions. We show that none of the standard "equitable" mechanisms satisfy any of these axioms and then present a constructive characterization of mechanisms which do. Using this we construct several new mechanisms. These are the Almost Flat mechanism, the Spread Aumann-Shapley mechanism, and the Spread Serial mechanism, which have many desirable properties.Received: 15 September 2002, Revised: 11 March 2003, JEL Classification Numbers: C71, H4.I would like to thank Hervé Moulin, Rich Mclean, Yves Sprumont and an anonymous referee for helpful comments.     

中国股票市场微观结构的特征分析——买卖报价价差模式及影响因素的实证研究

本文根据股票市场微观结构理论 ,运用高频数据对我国深圳股票市场的买卖报价价差的变动模式进行实证分析 ,同时研究股票买卖报价价差的影响因素和成因 ,并建立和检验相应的模型 ,从而揭示我国股票市场的微观结构特征。     

Bid ask spread in a competitive market with institutions and order size

Large orders, particularly from institutions, are quite common these days and hence there is interest to know if institutional trading has any bearing on the price effect associated with large trades. Recent empirical studies contradict earlier evidence of negative price effect on selling large blocks and find no price effect associated with large trades. Existing theoretical framework suggests a monotonic and increasing adverse price effect for large trades, where the motivation for a large trade is private information. We model a trading system where pure information, information-liquidity, and pure liquidity traders trade small and large sizes. The pure information traders strategically choose an order size. Institutions trade only large sizes because of their low execution costs for large trades; they are information-liquidity traders whose ability to use an information signal to determine their trades is subject to a binding liquidity constraint. We show that in such a market a separating equilibrium where trade size is informative does not exist and hence there is no price effect for large trades. Trade size may be revealing only if there is a buy sell asymmetry (large buy size is not equal to large sell size) or the corresponding price effect is asymmetric (price effect due to a large buy is not equal to that of a large sell). Further for a pooling equilibrium to exist, where trade size is not informative, the width of the market denoted by the ratio of order size (large size/small size) needs to be small, while the shallowness (inverse depth) of the market denoted by the ratio between pure information and institutional trades and the information signal needs to be stronger (higher). Our results on bid and ask prices and spread confirm recent empirical evidence on price effect of large and institutional trades found in the literature.

最小价格变动单位的减小对买卖价差日内周期性的影响——来自香港的证据

本文实证分析了香港联交所2006年降低最小价格变动单位(MPV)对股票日内买卖价差的影响。首次检验并拒绝了Foucault等(2005)提出的“收盘买卖价差假说”--他们预测在MPV降低后,收盘时买卖价差相对之前同时段会增大,并给出了若干解释。进一步的回归分析发现,MPV减少后,标准化买卖价差在开盘时变大,在收盘时则变小。这说明在降低MPV的情况下,限价指令交易者调整了他们的日内交易策略。     

基于HFA3824用于DSSS的PN序列的研究

住房抵押贷款可以分为传统的“不脱离资产平衡表”型(on-balance-sheet)和新型的“脱离资产平衡表”型(off-balance-sheet)或称之为美国风格的住房抵押贷款两种类型.资产经营融资是住房抵押贷款市场的创新发展,目前已成为一个宽泛的概念,包括了一系列的金融技术. 一般认为是指个别的缺乏流动性的资产和现金流,经过重新安排,由第三者在资产现金流的基础上提供融资,用于描述一系列广泛的商业、管理、会计目标的融资结构.     

Spread behavior around board meetings for firms with concentrated insider ownership

For a set of firms with concentrated insider ownership, we find that (a) the bidask spread changes significantly around the board meeting dates, and (b) the actual number of transactions by insiders increases following the board meetings. We also find that there is a statistically significant relationship between spread and the number of insider trades surrounding the board meeting dates. Furthermore, neither an increase in the number of insider transactions nor any significant relationship between insider trading and the spread is observed for the same set of firms around non-board meeting dates.