英语翻译Abstract—Opportunistic Spectrum Access (OSA) allowsunlicensed users to share licensed spectrum in space and timewith no or little interference to primary users,which bring newresearch challenges in MAC design.In this paper,we firstlyint

英语翻译Abstract—Opportunistic Spectrum Access (OSA) allowsunlicensed users to share licensed spectrum in space and timewith no or little interference to primary users,which bring newresearch challenges in MAC design.In this paper,we firstlyint
英语翻译
Abstract—Opportunistic Spectrum Access (OSA) allows
unlicensed users to share licensed spectrum in space and time
with no or little interference to primary users,which bring new
research challenges in MAC design.In this paper,we firstly
introduce the differences between the conventional multi-channel
MAC protocols and the MAC protocols for OSA as well as the
requirements for OSA MAC protocols,and then analyze and
compare the several MAC protocols proposed so far in the
literature.At last we give the characters of these protocols.
Keywords- Cognitive radio; opportunistic spectrum access;
dynamic spectrum access; multi-channel; MAC protocol
I.INTRODUCTION
Currently,the spectrum is allocated to licensed users with a
static manner,while the spectrum demand nowadays for GSM,
WLAN,WiMAX etc is increasing.The traditional allocation
policy faces spectrum scarcity in particular spectrum bands.
But under the observation of the Federal Communication
Commission (FCC) [1],it was shown that over 70% of the
allocated spectrum is not used at any given time even in a
crowded area where the spectral usage is intensive.The
concept of cognitive radio has been proposed to make use of
the unused spectrum at a given time and place.In cognitive
radio networks,unlicensed (secondary) users can make use of
licensed frequency bands without violating the licensed
(primary) users.In cognitive radio wireless networks,
secondary users do not have pre-assigned frequency bands but
they opportunistically search,find and operate in an available
band without constraining the primary users.In order to resolve
the scarce spectrum problem,better spectrum management
strategies should be adopted in cognitive radio wireless
networks.For unlicensed users are allowed to opportunistically
access the licensed spectrum band without or with little
interference to licensed users,the nature of cognitive radio
networks demands dynamic spectrum access.
先附上部分内容,如果可以,我将整篇文章发你邮箱.

英语翻译Abstract—Opportunistic Spectrum Access (OSA) allowsunlicensed users to share licensed spectrum in space and timewith no or little interference to primary users,which bring newresearch challenges in MAC design.In this paper,we firstlyint
译注：
首次提到大写专业名词后面都有括号,括号内是它的具体解释意义；以后原文中再提到时便采用原文中这些大写专业名词（不在重复解释）.只是为了方便使用者容易理解句子,我附加了(a) ,(b), (c) 等,原文中并没有这些符号,特此说明.
译文：
摘要--- 投机频谱的介入（OSA是投机频谱介入的缩写）允许未许可用户在时空上分享许可的频谱,完全不会对（原）主用户产生干扰或几乎不对（原）主用户产生干扰.这会在MAC(通信协议控制)的设计上引起一场新型的专题性挑战.本章中,我们首先介绍了（a)常见的多频道MAC协议,（b)适用于OSA(投机频谱的介入)的MAC协议,和（c) OSA MAC 协议的需求条件（这三者之间）的区别.然后,分析和比较了目前数种文献中所推荐的MAC协定；最后我们说明了这些协议的特点.
关键词： 感知式无线电,投机频谱的介入,动态频谱的介入,多频道,MAC协议.
1 简介
目前,频谱通常都被分配到许可的静态用户上,然而现在,GSM（全球移动通信系统）,MLAN（无线宽带）,WiMAX（无限城域网）等频道的需求却一直地在增加,传统的分配政策在某些特殊频带中面临着频谱资源匮乏.但根据联邦通讯委员会（FCC）的观察报告,人们发现70%以上已分配的频谱带在给定的时间没有被应用,即使在频谱使用集中的地方也是如此.为了充分使用在给定的时间和给定的地区未使用的频谱,我们提出感知式无线电这一概念.在感知式无线电网络中,未许可的（次要）用户可以使用许可的频带而不会妨碍许可的（原）主用户.在感知式无线电网络中,未许可的（次要）用户没有预配频带.但他们仍有机会进行搜索,找到某个运行中的频带,并对其进行操作,而不会对主用户造成遏制（或约束）.为了解决频谱不足这一问题,我们应该在感知式无线电网络中采纳较好的频谱管理策略.由于允许未许可用户利用时机介入许可的频谱带,而这不会对许可用户造成干扰或几乎不对许可用户造成干扰,所以,从感知（式）无线电网络本身（性质）而言,它需要动态频谱的介入.