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Management Information Systems provides comprehensive and integrative coverage of essential new technologies, information system applications, and their impact on business models and managerial decision-making in an exciting and interactive manner.

The twelfth edition focuses on the major changes that have been made in information technology over the past two years, and includes new opening, closing, and Interactive Session cases.

Management Information Systems provides comprehensive and integrative coverage of essential new technologies, information system applications, and their impact on business models and managerial decision-making in an exciting and interactive manner.

The twelfth edition focuses on the major changes that have been made in information technology over the past two years, and includes new opening, closing, and Interactive Session cases.

A collection of Solution Focused activities for workshops and team events. It helps readers to maximise the effectiveness of their workshops, team meetings and projects, use creative stimulating activities with confidence and precision, and create even more ideas and processes for their own situations. Facilitators and consultants from all over the world share their experience in this rich collection of Solution Focused activities for workshops and team events. Clear step-by-step instructions let you use them straight away - or adapt and combine them as you wish. This book helps you to maximise the effectiveness of your workshops, team meetings and projects, use creative stimulating activities with confidence and precision, and create even more ideas and processes for your own situations.

57 SF Activities for Facilitators and Consultants

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When you need to discover what works in the workplace, The Solutions Focus: Making Coaching and Change SIMPLE offers a powerful yet subtle way to foster positive change. With this revolutionary and practical alternative to traditional problem solving, you can learn how to envision your desired future and move swiftly toward it. The Solutions Focus details the SIMPLE plan and a unique way of working that fosters customized and organization-specific solutions for every problem. Radically pragmatic and proven in many fields, this method goes to the heart of what works for people, teams, and organizations.This second updated and extended edition provides an enhanced focus on coaching and offers fascinating and wide-ranging new case studies that illustrate how these ideas are being applied in organizations worldwide, from television companies to government agencies to individual teams. The authors show you how to identify what is working in your organization and how to amplify it by focusing on what is possible rather than what isn't. The basic principles are simple: identify what works and do more of it, and stop doing what doesn't work and try something different. Packed with field-tested tools, exercises, and case examples, The Solutions Focus will interest anyone who wants practical, innovative workplace solutions for doing more with less. Visit the Solutions Focus website at www.thesolutionsfocus.com.All good coaches focus on potential, affirmation, and solutions. This book is a must. It is simple, easy to read, and filled with illustrative examples. -Sir John Whitmore, author of Coaching for Performance A focus on solution construction is the core of great coaching. This is a beautifully crafted, elegantly simple approach to applying the power of solutions to organizations-a must-read for coaches and consultants looking for truly effective tools. -Anthony M. Grant, Director, Coaching Psychology Unit, School of Psychology, University of Sydney A classic: the most exciting and applicable approach since Fisher and Ury's Getting to Yes. The logic and ethics of the approach are refreshing and unfortunately all too rare in the corporate world where I do most of my work. It makes so much sense to identify and work with what works. -Nancy Caldwell, negotiation consultant, USA If we can learn to adopt this solutions-focused way of approaching everyday situations we will transform our work and our lives in elegant and powerful ways. The book is packed with thought-provoking case studies. I love it. -Sue Knight, author of NLP at Work CONTENTS 1 Small Changes-- and a Big Idea2 Staying SIMPLE3 Solutions not Problems4 Inbetween--The Action Is in the Interaction5 Make Use of What's There6 Possibilities-- Past, Present and Future7 Language-- Simply Said8 Every Case Is Different9 The Complete Toolkit10 Coaching Solutions11 Managers Coach Their People to Solutions12 Team Coaching13 Organized Solutions14 The Solutions Artist and Scientist15 How We Reached Here

The dean of business historians continues his masterful chronicle of the transforming revolutions of the twentieth century begun in Inventing the Electronic Century.

Alfred Chandler argues that only with consistent attention to research and development and an emphasis on long-term corporate strategies could firms remain successful over time. He details these processes for nearly every major chemical and pharmaceutical firm, demonstrating why some companies forged ahead while others failed.

By the end of World War II, the chemical and pharmaceutical industries were transformed by the commercializing of new learning, the petrochemical and the antibiotic revolutions. But by the 1970s, chemical science was no longer providing the new learning necessary to commercialize more products, although new directions flourished in the pharmaceutical industries. In the 1980s, major drug companies, including Eli Lilly, Merck, and Schering Plough, commercialized the first biotechnology products, and as the twenty-first century began, the infrastructure of this biotechnology revolution was comparable to that of the second industrial revolution just before World War I and the information revolution of the 1960s. Shaping the Industrial Century is a major contribution to our understanding of the most dynamic industries of the modern era.

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Shaping the Industrial Century represents an important extension of the framework that Alfred Chandler has developed in several seminal books published during his long and productive career...Chandler has done more than provide a case study of the evolution of the modern chemical and pharmaceutical industries. Shaping the Industrial Century is a dynamic demonstration of how strategy takes precedence over structure in determining the ongoing success or failure of an industry that has reached its mature phase.
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In Effective Supervision, Robert J. Marzano, Tony Frontier, and David Livingston show school and district-level administrators how to set the priorities and support the practices that will help all teachers become expert teachers. Their five-part framework is based on what research tells us about how expertise develops. When these five conditions are attended to in a systematic way, teachers do improve their skills:

* A well-articulated knowledge base for teaching
* Opportunities for teachers to practice specific strategies or behaviors and to receive feedback
* Opportunities for teachers to observe and discuss expertise
* Clear criteria for success and help constructing professional growth and development plans
* Recognition of the different stages of development progressing toward expertise.

The focus is on developing a collegial atmosphere in which teachers can freely share effective practices with each other, observe one another s classrooms, and receive focused feedback on their teaching strategies. The constructive dynamics of this approach always keep in sight the aim of enhancing students well-being and achievement. As the authors note, The ultimate criterion for expert performance in the classroom is student achievement. Anything else misses the point.

This short book lucidly explains the moral hazard problem that plagues large financial institutions policymakers deem too big to fail...[it] contains something of interest for everyone.--Journal of Economic Behavior and Organization

This is a valuable and comprehensive treatise on TBTF, a critically important policy issue that needs to be addressed well before another banking or financial crisis occurs. Policymakers, regulators, government officials, legislators, and private financial companies should read and heed the authors' analysis and recommendations.--Richard M. Kovacevich, Chairman, Wells Fargo

Stern and Feldman have written an important book on the too-big-to-fail problem. . . .This book deserves to be widely read in the banking regulation and supervisory world.--Frederic Mishkin in the Journa of Economic Literature

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Summary: With the wide application of the IP Phone, the speech quality of the IP Phone is paid close attention to more and more by people, become and restrict a bottleneck employed extensively of it, the existence of the phenomenon that especially the pronunciation shakes, application restricting the IP Phone in people live, work especially. Influence the IP Phone quality to mainly have 3 factors: Shake, divide into groups and delay time, packet loss. This text shook to the pronunciation in the IP Phone cause carried on detailed analysis, propose, employ pronunciation divide into groups intelligence of time delay buffer the smooth method and dispel the pronunciation and shake, provide one's own peculiar buffer cipher scheme, design philosophy, and verify simple artificial experimental analysis and result, have improved the IP Phone speech quality.

Keyword: IP Phone; Divide into groups and delay time; The pronunciation shakes; Buffer

Telephone network, broadcasting the inexorable trend that the television network, unification of three nets of data network are communication domain development in 21st century. People have already realized gradually, no matter traditional speech communication or modern data communication, may go to the unitary IP agreement finally. The speech quality in the IP Phone is to restrict a bottleneck employed extensively of it, the existence of the phenomenon that especially the pronunciation has shaken, has restricted the application in people live, work of the IP Phone even more, this text shake to pronunciation in the IP Phone issue go on, analyze, get one out of analyze the solution tentatively.

Mass analysis of pronunciation in a conversation course

Pronunciation quality problem appearing in 1.1IP telephone

Convey the speech in IP network, influence and spread factor delaying time, packet loss and shaking of mainly dividing into groups of quality.

Divide into groups delayed definition taking second as unit to begin, send the intersection of 1 b and message to the host computer B at periodic line by the host computer A, reach the host computer B receive mistiming between message these. In other words, it is correspondent to beginning to talk from the first user to the second user (listener) directly dividing into groups and delaying time Hear the mistiming between the first syllable.

Packet loss means that sent the host computer A to, but can't reach the host computer B (destination place) Grouping count account for all grouping that be sent count percentage. The percentage of packet loss may influence the quality of the speech on IP network obviously on the network. The pronunciation is originally a serial signal, in the course of sending packet data to the host computer B from the host computer A, different because of the transmission path of dividing into groups, the size of each route and flowrate of data have nothing in common with each other, cause and divide into groups and reach accepting the time in the end is different to some extent, connect with when broken when the pronunciation accepting the end and returning makes like this, this kind of phenomenon is called the speech and shaken.

1.2 solves technological analysis

In order to solve the phonetic quality problem in the IP Phone, are mainly improving and improving with the following 7 technology: The intersection of pronunciation and compression technique, echo dispel technology, noise quieting inhibit technology, speech from shake treatment technology, precedence technique of the speech, make and cut apart technology *and forward error correction technology. Here introduce the intersection of pronunciation and treatment technology *of shaking mainly.

The buffering that the ones that were mainly adopted in the pronunciation shakes and deals with shook, namely presume a buffer pool in the take over party, speech wrap up reach, entering the intersection of buffer pool and phasing out, in order to stabilize mild speed make, take speech out, decompress in buffer pool and then broadcast give listener systemming at first. This kind of buffering can handle the speech to shake in certain limit effectively, improve the tone quality. Use and shake and buffer the technical principle and is shown as in Fig. 1: In order to confirm the correct time interval breathing out the speech and wrapping up, has offered a time stamp (Time Stamp) on Baotou of RTP ,Time of production used for recording this and breathing out the bag. In sending end, IP whom gateway produce breathe out the bag A,there are 20 ms on time interval of B and B, the C one time interval; After transmission of IP network, what receive breathes out the bag on the receiving end B,C time interval turn into 30 ms; For resume original some time interval, receiving end breathe out gateway confirm that breathe out the bag according to each RTP time stamp to call the bag Correct for time interval,them it is send in the apparatus to last original 20 ms. Disappear, shake, it buffers pools to be to transmit immediately under receiving every situation that speech make, so will confirm appropriate transmitting the delayed magnitude. If delay time too long, will make the integral time delay of system very long; If delay time too short, IP speech chartered and has not arrived within the range of acceptable time, the phenomenon that the speech will still shake, the function which buffers the pool is not very obvious. The result of fetching the balance point of the two is usually to make the network of the buffer memory delay time and keep about 40 ms.

2 schemes of the problem of solving the pronunciation and shaking

2.1 thinkings of treatment shaking

The essence of Internet is a packet switching network, the IP packet is a minimum unit stored, transmitted. So, the grouping of the same information source may be transmitted to the receiving end through different routes, the time delay of reaching the receiving end is different too to divide into groups. The difference of this kind of grouping transmission delay is known as time delay to shake. The speech signal after the existence that time delay shakes causes the receive side to decode appears disconnectedly, cause the pronunciation to be distorted, so the absorption that must carry on time delay and shake is compensated. Compared with transmit data of packet network, circuit switching is the allocated channel resources because in advance, the communication subnetwork treats the data in a manner to flow, the time that namely all frame data reach the B-side from the A-end is equal, like this too on the issue to shake. At the time of the management alternative that the pronunciation in designing the IP Phone shakes, can consider as follows: Adopt intelligence buffer smooth method, namely let, receive port shake intensity make prediction, and leave the cell received in the dashpot and adopt the resisting and shaking and buffering of appropriate length, absorb and delay time, export.

As shown in Fig. 2, in phonetic actual transmission, the pronunciation is from making a start out, through a series of network equipment, while reaching the receive side, after the receiving end receives the pronunciation making a start, buffer pool its make intellectual judgement to phonetic shaky intensity automatically, according to intensity of shaking it, add a pronunciation length, absorb and delay time. But it is stochastic to delay time and shake in fact, thus it is very difficult to add and shake and absorb time delay to fix accurately, such as choosing improperly to produce" Owe " Or " Over load " Phenomenon. A kind of comparatively valid solution is to regard reducing the total break length of pronunciation burst as the foundation and decide that shakes to absorb the delayed magnitude. Think, until total disconnected length under 3 ms, go on, shake absorption control can obtain better the intersection of regeneration and pronunciation too generally. How to wrap up and come from finishing resisting and shaking the choice which buffers the magnitude meeting according to the pronunciation received, resist and shake the most important ring (this is an essential step in real-time application of an IP Phone in work, have just presumed Buffer of a constant length in the model at present) .

Design that 2.2 pronunciations shake and deal with

In the thinking before is analyzed, adopt pronunciation intelligence to buffer the smooth method. In the concrete cipher scheme like this, it is a key to buffered treatment.

Design the buffer queue on 2.2.1

A traditional one, under single the intersection of buffer and way, gather speech data, it is so full that system get for buffer to gather, there is no new buffer to refer to the telephone Voice Card, so the inner voice messaging has been lost in this period of time, at it return by speech data,in receiving the speech data to telephone Voice Cards for one yuan from network in when block data finish returning this period of time, the data that come up from the network may be lost because there is no empty buffer too.

So, can design 4 buffer queues to guarantee the phonetic continuity, prevent the pronunciation from shaking: Buffer queue of the recording, sending the buffer queue, accepting the buffer queue and playing the queue operating principle sketch of the buffer and is shown as in Fig. 3. When taken fully away and sent in a block buffer, fetching an empty buffer continues carrying on the recording from the buffer queue for the telephone Voice Card at once, while playing, when receiving a piece of speech data to take away returning from network, fetch an empty buffer to plan to receive the data conveyed from the buffer queue on the next network at once.

Buffer size design philosophy on 2.2.2

Problem solving comes besides increasing the buffer number, the system also guarantees by increasing the buffer size appropriately, imprison, send one data block as one side network, take over party gateway use certain buffer receive data of magnitude, only put the Voice Card and play the buffer to play for the Voice Card after the whole data block is received. To every data block, the transmission in the network is discontinuous, but for whole data block, his transmission is relatively serial. The greater the buffer is, the better the phonetic continuity is. Meanwhile, having brought the unfavorable factor too after increasing the magnitude of the buffer, he increased transmission delay. So in real application, must make certain equilibrium between reducing the delay and increasing the buffer size, generally speaking, fetch 1 kB as the capacity of the buffer.

The Off-The-Shelf buffer memory space allocation mechanisms mostly adopt the static method, knowing by the basic conclusion of the queuing theory, the customer waits for the space in full of ing state under most situations, but because not using partly in this space is " Have already assigned " Resource,last state that does not be utilized fully dashpot so under situations most; In addition, in terms of utilization of resources, the ideal buffer memory space distribution method should be the dynamic distribution according to need, this not only can raise the utilization factor of the dashpot well meet every traffic flow and reach characteristic dynamic variation greatly, but also can, thus guarantee the speech quality of every traffic flow, the requirement that especially the pronunciation shakes. Because of " Distribute according to need dynamically " Thought,propose this text that the spaces is dynamic for distribution method a buffer memory: Because of " Add one " Distribution according to need mechanism (ABB A) . Suppose the nodal point of the network at connection establishment stage in order that users connect assignedly (basically) Buffer the capacity as K, claim that it is this connection to admit and reach the buffer memory space dividing into groups and entering " The job piece " ; In data transfer phase, enable unable login of grouping reaching newly because the job piece has already been taken, applying in the space of additional buffer memory immediately, if permitted, the administrative supervisor assigns a capacity to be still the additional buffer memory space of K for him, the ones that are called this connection " Add one " ; Subsequently, grouping that reach at present and afterwards enter it, add piece and enter original the intersection of work and yuan, need, point out no longer only, once apply to succeed, adding one turns into a new job piece, but the original job piece turns into and only accepts the service of the system and not admits and reaches dividing into groups again " The transition piece " ,Hereafter, because follow-up reach divide into groups, enter the intersection of transition and piece this again, so he can be cleared out and released finally, then the system is the new job piece clothes. Buffer the state of one and have " The work " , " The transition " Sum " Release " 3 kinds.

2.3 experimental analysis

Utilize the artificial thought of the system to set up a mathematical model, imitate the pronunciation characteristic of IP telephone network on this basis, use the simulation software of computer conferencing, adopt the target, layering means, carry on the programming, as shown in Fig. 4.

In concrete setting-up simulation model, define the network fragment into a target, each attribute with a set of configurateds. The programming environment employs the script of C style, users can construct a network or process model with graphical user interface GUI at the same time. The nodal representative's network node or host computer in artificial network topology, organizes the node through the way that very similar to the way of the model of the ISO/OSI layer. The process is the important module in the nodal model, a process imitates network protocol or a applied behavior, can use a finite state automatic machine (FSA) To represent a process. An information source of simulation, make it in at random " 0" Sum " 1" Two states, can realize the result that the pronunciation shakes with emulation in this way, he is responsible for during when sure, send the data packet with the particular speed, miscellaneous users employ the data sent to and receive. After the destination address is set up, users employ receiving miscellaneous attribute, for example average speed, user employ every magnitude, artificial time opening, the intersection of period of transmission and duration of data packet that send, and wait for the transmissive beginning in the initial state.

And then it is Daemon that should realize, the Daemon runs with the pronunciation data packet of the end system, have recorded the time delay in the pronunciation makes an appointment, can measure the spoken message is sent out and and shake the time delay between receiving. In employing, add the function PROCESS into nodal module ') ,Come and discern the spoken message in IP packet flow, to every PATH news PROCESS entered ') Check in IntServ state table of IP whether conversation has already existed. After joining the manipulation function, once the signal is sent, IP process will be buffering message storage temporarily, and is reached the transition of state to the free status (so that the bag that he can deal with miscellaneous arrival) . Finish the intersection of QoS and foundation of passway, PROCESS as output interface ') Will send an answer signal, acknowledgement IP process.

Use the method above, has carried on emulation in conveying IP speech business. Emulation is disposed and shown as in Fig. 5, two customers send the speech business on the same periodic line, assume the business that the customer produces is similar. The pronunciation digital coding average speed used is 22 kb/s, the speed of crest value is encoded for PCM of 32 kb/s.

Shake to IP pronunciation and is shown as in Fig. 6 the artificial result.

Can obviously find through an analysis of Fig. 6: Obviously than imbed pronunciation of cipher scheme, shake, want, lighten much artificial consequential the intersection of pronunciation and phenomenon of shaking to imbed cipher scheme. Therefore can be thought, this kind of cipher scheme is feasible, have reached the design object.

Summary: The network framework of new generation taking IMS as the core is a goal of the gradual progress of the telecommunication network, it will be chosen different gradual progress routes according to factors such as network current situation, market and competitive environment of the operator,etc. how to perform and enter the network of new generation from the existing network.

Keyword: IMS, the gradual progress of the network

1.Foreword

The primitive actuator force of the gradual progress of the network comes from final user's demand for the innovative business. In terms of operator, it is to dispose the Next Generation Network (NGN) based on IMS that the flexible and open business turns into and releases the environment Primary reason. The technical basic fixed position of softswitching taking controlling and bearing the weight of separating as essential feature offers traditional long distance and 5 kinds of speech businesses in a network based on IP technology. Flexible arrangement and high integration density of softswitching are the enormous reducing that operators have brought construction cost of network and maintenance cost, but because receive the restrictions of a great deal of respects such as terminal ability, QoS, security and business interface canonicalization, comparatively mature softswitching (including fixed softswitching and 3GPP R4) at present Application too only for herein, last business it. It is far from enough to only lower costs, how increase income is the question that the operator cares about further.

IMS business, control with it, bearing the weight of the horizontal framework totally separated, concentrated user's attribute, with inserting the characteristic of having nothing to do etc., solve the problem that soft swapper also can't be solved at present on one hand, such as business interface, flexible IP multimedia provision that user's excursive support, standard are open,etc.; On the other hand, because it inserts independence, make IMS become fixed to merge the plinth of the gradual progress with the mobile network. But the factor that the gradual progress of the network needs considering is numerous, it is the state of operator's existing network to be the most master among them, and market and competitive environment which it lives in. This text has analyzed the actuator force of the gradual progress of the network at first, then provide the structure based on network of new generation of IMS, provide different routes directed against the gradual progress of different operator, different network and market terms finally.

2.Actuator force of the gradual progress of the network

IP and wireless communication technical development at full speed, have initiated the explosive growth of Internet and mobile communication. Therefore personal communication and brand-new communication amusement way that bring, are impelling the traditional telecommunication network, business and operation modal transition.

Move replacement of the fixed service, it is the main threat which the operator of fixed net faces at present, also the main reason that the operator of fixed net carries on gradual progress of the network. What has been produced this kinds of replacement that mobile communication is excursive and individualize basic reason /characteristics individualized. According to the research report of Yankee Group, 12% of the European families only use the cellular telephone at present, the Europeans up to 25% consider that does not use the fixed telephone and only use the cellular telephone in the family. The development of the market of telecommunication of our country moves and replaces the stationary overall trend too. The amount of traffic of movement of our country exceeds the traffic volume (local business) of fixed communication since 2004 . Since 2003, the mobile subscriber's number of users exceeds fixed users' number of users.

How to make the existing network perform and enter one and move network and business structure merged fixedly? This is obviously that a operator of fixed net resists and moves to the best route to replace fixedly.

In fact, regardless of fixing the Network Operator or moving the Network Operator, how be fast to it disposes new business to be whether they keep dominant key factor in market competition through flexible open operation platform. According to statistics of Light Reading, it is primary reasons why they dispose IMS that there is 41.3% business development that is investigated the operator is thought to be flexible and dispose. The traditional business network is the building up vertically of a business and a network, the business totally depends on the ability of the network, this kind of business and closely linked framework of the network lead to the fact new business development is more difficult, can't realize the business of stepping the network. The intersection of IMS and business, control with their, bear the weight of horizontal framework that separate totally, characteristics such as concentrated user's attribute, opening the canonial application interface and inserting having nothing to do,etc., have solved the drawback of the business correlated to network in the traditional network completely, has offered for operator and moved business and Application Platforms merged fixedly. Final user's demand for the brand-new multimedia business is one of the actuator force of the gradual progress of the network too. Skype, MSN, QQ,etc. is changing people's communication habit; The traditional business income drops development and arrangement forcing the operator to carry on the new business too. The value chain of the traditional telecommunication industry is simpler, the operator totally depends on providing the definite business (such as the speech for final user, message) Obtain incomes. Though broadband service and move data traffic to be becoming ripe, the intersection of fixed net and operator or mobile service operator, they all face " One bit of pipelines " (bit pipe) Pressure. In addition, it be able to be by crossing over the convenient obtaining the business of multimedia with way of the fixed and mobile network that users hope too.

, but management and profitable network framework that the operator needs one and can control, to offer the brand-new business that users expect. On the basis of IP technology, have no relations with inserting, business and controlling the sep IMS network framework to be to meet the whole new architecture of this demand.

3.Network framework of new generation on the basis of IMS

The concept of NGN has already been discussed for many years, ITU-T has defined NGN too, provides its essential feature [1 ]. At present, organize the study on NGN to be due to IMS in every great standard, though IMS is only a framework of having no relations with inserting of the aspect of business control in 3GPP [2 ], however, with content [3 ] in considering more one such as user's network, insert, core network and intercommunication on IMS foundation etc. of NGN framework of ETSI TISPAN; And the progress of ITU-T [4 ] similar research work done on NGN, one regards IMS as guiding mark, the network framework of new generation of merging different access ways has been already clear gradually. However, undoutedly, the network architecture taking softswitching as the core has played an important role in studying the road of NGN, it in network optimization, reduce cost and the intersection of PSTN and the intersection of person who replace and respect, play a positive role. With the arrangement for the network of new generation based on IMS, the whole network will present the situation of coexisting in many kinds of technology. Certainly the final gradual progress goal is still a network framework of new generation based on IMS, the framework on the basis of softswitching is only the stages of one in this gradual progress course.

Adopt the synoptic diagram of the network framework of new generation of IMS, this framework includes fixedly and moves and inserts and with the interworking function of traditional circuit switching network and other IP multimedia network. The main entity includes various call conversation controlled entities (CSCF) , media resource function entity (MRF) , user's server of home country (HSS) , user make bit function (SLF) , application server (AS) , insert boundary node while being fixed, move, insert boundary node, the intersection of intercommunication and boundary node,etc. under land.

Key CSCF includes S-CSCF, P-CSCF and I-CSCF. S-CSCF is in the central control position in IMS, is used for registration, session control and deals with, and touch off the business to the application server; P-CSCF is the first entry point that UE visits IMS; I-CSCF visits from land to entry point of the land of home country, is mainly responsible for inquiring about the FYI of home country, and distribute S-CSCF,etc. for users.

MRF offers to user and plays under the control of S-CSCF and AS, medias such as the audio mixing,etc. handle the function. It includes media's resource control function (MRFC)s The resource handle the function (MRFP) in and the media .

HSS stores all users and data correlated to business in IMS, in a situation that the network allocates a plurality of HSS, SLF offers finding out to the mechanism of HSS.

AS is used in offering the multimedia business of appreciation, including SIP AS, OSA SCS and CAMEL IM-SSF, OSA AS and CAMEL business environment (SE) It is mutual to pass SCS, IM-SSF and IMS network.

Move and insert the boundary node to used in in wireless way various, the wireless terminal such as GPRS inserted through the packet field is terminal to insert IMS core network. It includes P-CSCF and tactics decision making function (PDF) ,Among them PDF controls access to the flowrate of the core network.

Insert boundary node use for various terminal broadband and SIP terminal to insert the intersection of IMS and core network while being fixed, it includes P-CSCF function. In the fixed access network, also need resources and admit the control subsystem (RACS) And the network adheres to the subsystem (NASS) In order to offer resources to reserve, accept control, IP address allocation and management,etc. function.

The intersection of intercommunication and boundary node include among the land and other the intersection of IP and the intersection of network and node and the intersection of and circuit and the intersection of land and node of intercommunication of intercommunication. Among them include the interworking function (IWF) with the node of IP network intercommunication , the control function of interconnecting the boundry (IBCF) And interconnect the borde gateway function (IBGF) Wait for the function. IWF offers the interworking function between business used agreement and other agreements based on IP of control subsystem, IBCF controls the boundry between two networks of operator, IBGF exists on the boundry between two core networks, include translating the gateway (TrGW) Function. The land intercommunication of the and circuit is mainly by the control function of the borde gateway (BGCF) , media gateway control function (MGCF) And IMS media gateway (MGW) Realize. BGCF the intersection of IMS and land and the intersection of outside and boundary point of network, where it choose land intercommunication of and circuit, MGCF is responsible for the communication among IMS and circuit users of land, controls the media signal channel correlated to MGW, MGW is responsible for realizing the media flow intercommunication between IMS and circuit land under the control of MGCF.

Because PSTN occupies very important position in the Off-The-Shelf telecommunication network, organizes ETSI TISPAN to carry on the special definition to the gradual progress of PSTN in so the standard. Have especially defined PSTN/ISDN artificial subsystem (PES) in NGN framework of TISPAN . Most function entities of PES keep the same with function entity of IMS, only insert the gateway control function (AGCF) The exception, it uses the control protocol of the media gateway to control and insert the media gateway.

4.Different scenes of the gradual progress of the network

Gradual progress of network need consider key factor include the intersection of operator and existing state and market and competitive environment that live in of network the most, the gradual progress route of combining these two factors to the fixed net in present section, mobile network is discussed separately.

4.1. Gradual progress route of fixed net

As to a operator of fixed net, the typical starting point of the gradual progress of the network is PSTN network. The appearances of VoIP technology *and softswitching take the first step for the gradual progress of PSTN network. In China, until long-distance aspect dispose and the intersection of fixed net and intelligence turn network optimization, make important contribution softswitching. But from the viewpoint of final user, softswitching and network are intelligent (NI) Have not satisfied their demands for innovative business. This is exactly the problem that IMS should be solved too.

There can be different performing the scene of marching into the arena according to the difference between attention and market situation of the operator.

The operator is mainly concerned that faces returning PSTN networks of the net, hope to fully utilize the network resource with lower operation cost. It hopes to upgrade the network on condition that influence users' business to experience and transparent to the final user. This indicates gradual progress of the network should not need to introduce the new customer equipment, that is to say, adopt it because of CS (Call Server) PES solution. In the scheme, the new source of revenue is not the question needing considering at first. Primary task of route of this gradual progress depends on softswitching and NI, realizes network optimization, reduce construction cost of network and maintenance cost to remedy the decline of the traditional pronunciation business income. However, the simple speech business will have no growth, the growth in earnings of the operator must depend on the leading-in of the new business, IMS is the technology *bringing the new business to the operator following softswitching / NI and the income increases. Certainly, IMS can realize pronunciation and multimedia business at the same time, this is embodiment and advantage of the holding capacity of IMS multi-service.

Do not need to have a major operator that large-scale PSTN replaced on ripe market in a short time to those, dispose IMS to be most attractive to them directly. What such a operator of fixed net paid close attention to the fact is to bring arrangement that is inserted to introduce the new business to increase incomes through being large-scale and wide. A stationary IMS solution is ideal first step for these operators, and then to the treble network gradual progress that broadcasts. This is realized by introducing IMS multimedia to carry on the upgrade of the software to pre-IMS solution to accord with IMS norm. Er early target users will be those commercial users and advanced users interested in broadband service taking user as the core. After the new business that can make profits is disposed, IMS platform can be used in the smooth migration of large-scale users.

The maximum advantage of route of this gradual progress described is that the operator only disposes a IMS core network, can launch the traditional business (pass PES based on IMS) at the same time And IP multimedia business; Move IMS core network merged fixedly at the same time. Route of this gradual progress has explained from another side softswitching and NI are not the stage when can be crossed over in the course of the gradual progress of the telecommunication network too, occupy leading operator on the ripe market to those, can realize the growth of business income from PSTN to IMS more quickly directly.

4.2. Gradual progress route of mobile network

There is not a pressure at present in the large scale migration from circuit land to IMS land of the pronunciation, especially to users' speech business of those low profits. But in order to increase ARPU value, what a strong pressure that development is not the new business of the pronunciation to move the operator and face. The extra business characteristic that IMS offers will be operator's preferably choice. Meanwhile, in order to reduce construction cost of network and maintenance cost, the softswitching of movement based on that IP transmits will be disposed soon. Generally speaking IMS and moves softswitching and coexists, realizes the intercommunication of some business through the intercommunication of network between them. On long terms, the land users of the circuit will migrate to IMS land finally, but the large-scale migration will not appear in the near future.

To moving the operator, the current situations of network and business are 2G pronunciation (traditional Mobile Switching Center MSC) in initial stage of 3G disposes And the data (short message, GPRS) Network. The income mainly comes from the pronunciation (80%) ,The short message takes the majority (& gt in the data traffic; 90% of the data business incomes) ,Other data traffic are in the rise period at a high speed.

Out of reducing the consideration of CAPEX/OPEX, the first step in the gradual progress of the mobile network is to move leading-in of softswitching, such as the leading-in (3GPP R4) of 5 kinds of softswitching .

View from the point of increasing the angle of business income, 3G technical leading-in begins to offer more high bandwidth and more attractive business (such as the video) Thus increase ARPU value. But more new business must depend on IMS. Has already mentioned just as in the front, IMS realizes different business (the business, reachability, group and tabulation of send out manage, the state appears etc.) Preferably comprehensive platform. IMS can be disposed as superposing the network of existing GPRS network, in addition need to increase PDF, CSCF, HSS and IMS AS,etc.. Offer IP multimedia business according to IMS, will move first-selection of operator. Because IMS key network element and what the fixed operator IMS used are uniform at the same time, so help to move and merge the network fixedly and dispose and the business is launched.

Move the gradual progress route of the operator and is shown as in Fig. 4, the arrangement for IMS does not mean the replacement circuit land, on the contrary, in initial stage of disposing in IMS, because the speech business also can't be offered by IMS land directly, the speech business will be also undertaken by the circuit land. Only when the pronunciation becomes a part of abundant multimedia business in the migration that the pronunciation is from circuit land to IMS land, and IMS could really begin after achieving certain infiltration rate. Speaking from the technology, mobile subscriber's totally migration from circuit land to IMS land depends on IMS offers the ability of the real-time business, the only radio network to the control ability of QoS, or take the possibility of other access methods (such as WiFi and Wimax) in the operator . The majority ran the association of dealers in 5 or investment of protective circuit land of a longer time.

5.Summary

IP technology *and technical development at full speed of wireless communication, final user the intersection of network and actuator force of gradual progress to open flexible demand of business structure factor to innovative expectation, operator of business. The tactics of the gradual progress of the network are involved in operator's autogenous network state and competitive environment lived in. By the look of overall trend, on the basis of IMS central network framework of new generation being a goal framework of the gradual progress of the network. Though the final goal is totally multimedia framework based on IP, in the course of the gradual progress, in order to optimize the network and reduce the maintenance cost, will also play an important role in PSTN replace the market on the basis of calling out PES of the server and PES based on IMS,etc..

In China, the arrangement for 3G network has already begun to launch. Among them, 3G transmission net playing an important role as the basic network in the whole 3G network. On transmission of 3G, because 3G core network only needs to solve the high capacity among some definite fixed nodes and transmitting the problem, the Off-The-Shelf key transmission net is very easy to solve; And because 3G access network is covered extensively, nodes are numerous, need to solve the access that the real-time nature required higher speech business and sudden and strong high-speed data traffic at the same time, so the transmission question of 3G access network is relatively complicated.

1,3G and 3G transmissive basic conception

First two generation mobile communication ( Imitate mobile communication and digital mobile communication GSM/CDMA) Rely mainly on speech communication. The goal of 3G is besides supporting speech communication, the focal point is meeting the transportability requirement that the wideband data are being inserted.

Demonstrate very great difference compared with speech business because of the flowrate characteristic of the data traffic, and 3G standard is supporting ability and way of the data traffic in the development and change constantly in the gradual progress, this makes 3G network compare in 2G network, there are higher, more complicated requirements on transmission net.

The three major rule standards of 3G include WCDMA, cdma2000 and TD-SCDMA in the world at present. From the viewpoint of transport network, different 3G standards, it is basically similar to transmit the requirement, main difference between three kinds of network rules are in the air interface (UU) Some, the logic framework of other partial networks is basically the same.

It is mainly R99, R4 and three editions of R5 that WCDMA is more mature at present, have mainly adopted R4 in testing and try net at present. WCDMA R4 network architecture shown as in Fig. 1.

3G network can adopt different bearing the weight of technology *in different technology *at developing stage, including TDM, ATM, IP,etc.. The uncertainty of flowing into the data traffic, make TDM technology *very difficult for bearing the weight of offering a high-efficient and reliable platform of 3G business. So, up till now, 3G main application transmission interfacing takes ATM and IP as the core.

Take WCDMA R4 network as examples, in view of function, divide it for the core network (CN) And wireless access network (UTRAN or RAN) ,As shown in Fig. 2.

Core network (CN) With the wireless access network (UTRAN) RNC of China links up, and RNC controls several Node Bs, connects through being wired between RNC and Node B. So, 3G network mainly includes three following respects to the transmissive demand:

( 1) The inner business of the core network is transmitted;

( 2) Between access network and core network (namely among RNC and CN, Iu interface) Professional transmission;

( 3) The inner business of the access network is transmitted, including between RNC and Node B (Iub interface) , between RNC and RNC (Iur interface) .

The above-mentioned business transmit, include pronunciation and transmission of data traffic, can divide into the intersection of user and data flow (can interpreted as pronunciation or content of data traffic) With the control flow ' Namely communication connection establishment / control signaling of removing etc. that carries on in order to carry on pronunciation conversing, data communication) Transmission. User's data flow is called the user levels and control planes too as control flow.

Core network (CN) And wireless access network (UTRAN) The transmission net used is correspondent to the layer of backbone in the transmission net and assembled, inserted layer separately.

Compared with R99, R4 is on the radio network (UTRAN) Some and R99 is basically the same, distinguish mainly R4 has introduced the soft interchange system in the core network, have set up the core network of the unitary complete packetization. R99 the same as there are 2.5G systems nowing, speech business and data traffic reach core network in circuit transport network and divide into groups at the transport network transmitting respectively. R99 network architecture shown as in Fig. 3.

R5 was compared in R4, the master change has introduced IP multimedia subsystem (IMS) in the core network Concept,in access network (U-TRAN) Have, having defined ATM and IP two kinds of move modes, the system of R5 can choose to convey the business with any kind of ATM or IP. R5 stipulates, supports UTRAN node of IP and must pass the support to ATM/IP one pair of protocol stacks at the same time, or through the built-in / outer intercommunication module, realize the nodal intercommunication with pure ATM UTRAN. At present, 3G system of a lot of manufacturers of industry chooses to support ATM to convey at first too when supporting R5. The network architecture of R5 is shown as in Fig. 4.

Different gradual progress editions such as generalized analysis WCDMA R99, R4 and R5, we can see, as 3G technical gradual progress is developed, some changes have taken place in the speed of the data traffic, network architecture,etc., know the requirement for transmitting and producing differently.

According to transmitting the interface type, the interface type summary of WCDMA each edition is shown in Table 1.

Interface type of table 1 WCDMA every edition

R99R4R5R6/R7
IubATMATMATM/IPATM/IP
IurATMATMATM/IPATM/IP
Iu-csATMATMATM/IPATM/IP
Iu-psATMATMATM/IPATM/IP
Iu-bsATMATMATM/IPATM/IP
CNTDM,IPIP/ATMIP/ATMIP

TD-SCDMA R99, R4 and R5 edition essentially identical with WCDMA on the interface type of the access network and mode of transmission, it is very similar either to have cdma2000 and WCDMA in the requirement for transmitting, so this text takes WCDMA as examples and carries on the discussion of 3G transmission net, but a lot of conclusions are suitable for these three kinds of network systems.

2,3G requirements for transport network of metropolitan area

Now take TD-SCDMA R4 as examples to analyze.

In 3G core network (CN) China, because already process of the business has disappeared and assembled, it is relatively crude to transmit the particle, only need to solve the problem that the high capacity between some definite points has been transmitted, it adopts SDH to be way comparatively direct simple in transparent transmission, can go on the high-capacity business transmit the intersection of TDM/ATM/IP over SDH/WDM and network directly.

For moving the access network (UTRAN) ,It includes the following interface:

( 1) Iub: The interface between Node B and RNC, mainly adopt IMA E1, ATM STM-1 interface;

( 2) Iur: The interface between RNC, mainly adopt ATM STM-1;

( 3) Iu: The interface between RNC and CN, mainly adopt ATM STM-1/4.

At present, the handling capacity of RNC develops towards high-capacity direction in 3G network, RNC quantity is very limited in a city, between RNC and RNC (Iur interface) ,And RNC is connected to CN (Iu interface) ,All the transmission of 155M or 622M between several limited points, it is very easy to pass the transmission net of metropolitan area. And Node B is in the edge of the network, realizes that totally covering should usually reach more than one hundred even several hundred pieces of nodal scale in a big city, the quantity is huge and assigns the scattering, so it is keys to the whole 3G transmission network to solve the transmission between Node B and RNC. Summarizing it has the following several characteristic on requirement of the transport network of metropolitan area:

( 1) Require the transmission net to offer ATM or IMA (ATM multiplex backward) Interface, namely IMA of 2Mbit/s, ATM interface of 155Mbit/s or 622Mbit/s, preferably offers the access of ATM, assembles (statistical multiplexing) And exchange capacity;

( 2) One of the characteristics of the mobile network is the scalability, accordingly, require the above-mentioned port to offer and transmit and wide cover too, will all have the above-mentioned transmission condition at the place where the base station of the Mobile network covers;

( 3) Because the construction of 3G network does not accomplish in one move, the need that the transport network demanding to offer 3G should meet the network and dispose progressively, the initial investment is small, the expansibility is good;

( 4) 3G is technological to develop gradual progress constantly by itself, require the transport network to have better adaptability, the all right gradual progress with technical development, thus protect investment and save investment;

( 5) Because 3G should support the critical pronunciation and sudden and strong data traffic of real-time nature to transmit at the same time, so demanding to transmit the scheme can offer the ability of QoS assurance well.

The following analysis on 3G different transmission mode compares, will go on around the above-mentioned requirements.

We can learn, the above demands to be suitable for R99 too according to the comparison of R99, R5 and R4 access network of front, and adopt R5 system of ATM move mode.

3,Major 3G transmits the solution to analyze to compare

View from the point of employing more extensive transmission technically, suitable for the intersection of 3G and tetherless access it transmits characteristic transmission technology *to be as follows, mainly ATM, SDH and MSTP technology,etc.. They use the intersection of 3G and all transmission of radio network for have pros and cons.

3.1　ATM technology *

In R99 and R4 what Iub interface is adopted is ATM technology, R5 is available in theory to support ATM or IP, but hit a large number of 3G systems of industry and support ATM interface actually. If can transmit 3G business in ATM network, can give play to ATM statistical multiplexing, QoS to guarantee the co dominant. Especially adopting VP cyclic(al) ATM network can guarantee the transmission security.

Shortcoming: By the look of the Off-The-Shelf transmission resource of every operator, ready-made ATM networks do not exist on access floors of the transmission net in a large amount. If build an intact ATM network for 3G access network, it is more uneconomical to invest in the situations few, low in bandwidth of previous business of the relative 3G network, and from the development of long-term of 3G, ATM technology *is not the best solution to other business, it is not also a technical development trend.

3.2　SDH technology *

Adopt SDH it transmits advantages of maximum to be to run commercial city, have abundant SDH transmit resources each at home, it is extensive to cover. So, it is a choice of saving investment to utilize existing SDH to transmit resources and set up 3G tetherless access transmission net most.

Use the traditional SDH certain defect of bearing the weight of 3G business and still existing, because of the way to adopt ATM over SDH, just offer a transparent transmission mode for ATM, can't carry on statistical multiplexing and result in transmitting unefficiently, this kind of transparent transmission way can usually adopt two kinds of interface SDH STM-1 or E1 interface. Through becoming the problem that simple MSTP can solve transmission efficiency of SDH staging.

3.3　MSTP technology *

The multi-service transport platform MSTP technical representative has developing direction of the transmission net now, it is that the future generation based on SDH conveys the platform. Can offer MSTP TDM, ATM, IP,etc. multiple operation interface and handling capacity,can dynamic alignment ATM, IP or TDM the capacities of network according to development of the network, have better expansibility.

( 1) MSTP technology *not only can offer the traditional TDM business to transmit, can also offer complete ATM to assemble / exchange, the assembling / exchanging the function of bilaminar Ethernet;

( 2) MSTP can support functions such as VP/VC exchanging, and ATMVP ring of ATM business,etc. in theory, assembles and realizes the convergence of ATM bandwidth through the business, thus improve the utilization factor of the bandwidth of the transmission net; Use the intersection of VP and ring can offer 3G business to protect in multiple layers, thus raise safety to bear the weight of network.

Shortcoming: The problem of making the investment that MSTP exists as, because there are not a lot of to adopt the transmission ring that MSTP technology *sets up at present, some MSTP rings are relatively weak too in holding capacity to ATM, mainly showing in the following aspects:

( 1) Because in fact application is not very extensive in ATM business, many MSTP nodes have not offered ATM interface card;

( 2) Some can offer ATM MSTP of interface, the ability of the respect is very limited too that its ATM exchange, TM, QoS control,etc., if apply to 3G access network and transmit, need staging.

So, if adopted MSTP to insert the transmission net as 3G on a large scale, may need to be newly-built to transmit the ring, remain huge to make the investment. But MSTP augmentability with good technology *is that this kind of investment can be got more long-termly and utilized offering some assurance.

In sum, it is each short that have their own strong points each in various transmission technology, choose application after also needing to consider various factors synthetically in practice.

4,Conclusion

3G transmission net is an important link of the whole 3G system. Various 3G insert, transmit scheme have chief to be short to some extent respectively. We should follow the condition of the transport network of metropolitan area, 3G network and requirement for transmitting of business, consider the current situations of 3G Node B, RNC apparatus (such as interface type, density, QoS ability,etc.) synthetically ,3G network is being disposed step by step and developed the requirement of gradual progress,etc. constantly, go for design plan 3G and transmit the scheme with the practical attitude. In this course, fully utilize transmission means that the existing transport network of metropolitan area can offer, use many kinds of transmission schemes in a flexible way, equilibrate with new investment, newly build the relation between the networks, will become it on the premise of fully meeting 3G network's and business needs in assurance, reduce investment, shorten and build the periodic important way.

Summary Have explained Wireless MAN (WMAN) Principle of China BWA, have introduced the newest state of IEEE 802.16 standard formulation, and canvassed the development prospect IEEE 802.16a, IEEE 802.16e and IEEE 802.20 canonial WMAN BWA systems of future generation.

Keyword Broadband wireless access (BWA) ,Wireless MAN (WMAN) ,IEEE 802.16

Broadband wireless access (BWA) It is the most challenging part in the revolution for the wireless communication, it can solve from the access bottleneck problem of customer's network between the core networks, IEEE 802.16 is exactly new-standard the most made for realizing this one and employing. IEEE 802.16 BWA system offers various broadband signal services with the lowest cost. Within the range of Family and small enterprise, the sum Digital Subscriber Line (DSL) with the cable BWA The network carries on the competition; In the medium-sized building of scale enterprise, BWA supports the high speed to connect, will compete with fiber optic link. It can enable thousands of users in Wireless MAN (WMAN) China's shared data, speech and video service, with the increase of signal channel, bandwidth and user's needs, operator also can enable systematic dilatation.

1 BWA systematic principle

BWA canonic system includes apparatuses such as base station, subscriber station, customer terminal equipment, core network apparatus, periodic line of the minizone and drop repteater,etc., while setting up the metropolitan area network, also include infrastructure such as network management system and optical cable. Among them: The base station offers the system to SNI interface of the core network, the subscriber station offers the corresponding UNI interface according to different business demands, as base station and subscriber station do not have viewing distance (LOS) When conditioned disjunction should expand the coverage of the base station, adopt the drop repteater to relay the base station signal. The reference model of universal system [1 ] is shown as in Fig. 1.

BWA system usually adopts some multi-points (PMP) Topological structure, each base station covers a honeycomb Residential Area. Descent and adopt some to many point modes, the base station sends a message by way of broadcast of TDM; The up run adopts the point mode of dot pair, the access system by way of multiple address such as TDMA or FDMA of subscriber station. So-called " The multi-point " ,Including " The point-to-multipoint " Sum " Many point-to-multipoints (MP-MP or Mesh) " Two kinds of topological ways.

BWA canonial development in 2 WMAN

2.1　IEEE 802.16a

WMAN media access control (MAC) that IEEE 802.16 standard stipulates Layer offer foundation for BWA, but physical layer its it suitable fors to be relatively low frequency, assigned available frequency relatively narrow, and the requirement is not the horizon transmission. So, has produced IEEE 802.16 canonial revision draft IEEE 802.16a, in order to relatively solve the wireless connection problem of low frequency.

IEEE 802.16a revises partly MAC layer and physical layer of the original agreement, expands the air interface to 2GHz-11 GHz frequency band. In this frequency band, the influence that the system is declined by the rain is minor.

The physical layer of this agreement supports the following 3 interface specifications in the sky [2 ]:

(a)On the basis of the single carrier system WMAN-SC of the adaptive equalizer of frequency domain, descent and adopt TDM way, the up run adopts TDMA way;

(b)Because of OFDM technical WMAN-OFDM system, adopts 256 subcarriers, descent and adopt TDM way, the up run adopts TDMA way;

(c)Because of OFDMA technical WMAN-OFDMA system, adopt OFDM of 2 048 subcarriers.

Communication distance of BWA systematic maximum on the basis of IEEE 802.16a is 50km, can improve the coverage of the goal service area of the operator notably, the coverage of frequency is 2 GHz-11 GHz, spectrum effectiveness is up to 5 bit/ (s.Hz) ,The maximum data rate of each sector is up to 70 Mbit/s. Service quality (QoS) of the MAC layer Support different grades of service, thus the enterprise users who can support to adopt Tl type to connect at the same time, with adopting the domestic consumers that DSL type connected, still support speech and video. MAC mechanism in IEEE 802.16a offers different QoS, in order to support different demands of different applications, support adaptive modulation at the same time, equilibrate different data rate and periodic line quality effectively, can adjust the modulation method instant, realize the best data transmission. The all right bandwidth of efficient use of adaptive modulation, meet the user's needs better.

IEEE 802.16a standard represented the new prospect of wireless communication of broadband, to user should install provision by multimedia, needn't methods new to connect core network ^s wired. In addition, IEEE 802.16a integrates the technology *of the metropolitan area network and IEEE 802.11 Wireless Local Area Networks, the base station will become and connect the ideal means of hot business in Internet in wireless way, play an important role in the under-developed area of the wired infrastructure.

2.2　IEEE 802.16e

Because BWA system only supports to insert fixedly or slow speed is moved and inserted in 1EEE 802.16a, do not support the high-speed mobile service, it is sure to limit to make its application area receive. So, IEEE 802.16e of the vehicle carried migration velocity of support made on the basis of IEEE 802.16a arises at the historic moment.

IEEE 802.16e has increased in the permission bandwidth of 2 GHz-6 GHz excursively, the new interface standard in the sky put forward to WMAN access way, it adopts OFDM technology, it is not the viewing distance to improve greatly, has increased the transmission distance, it is excursive to support, has reduced the operation cost.

2.3　IEEE 802.20

In November of 2002, IEEE 802.20 was established in IEEE 802 standards committees ----Move broadband wireless access (MBWA) Work group, devoted to developing a standard for the mobile subscriber, this standard supports to carry on the wireless data transmission of the high speed in 3 GHz frequency band high-reliabilitily, expected in order to offer the high data transmission of high bandwidth up to 1 Mbit/s with the moving mobile subscriber of 250 km/h speed, make the users on the high-speed train use video conference,etc. to time responsive application.

IEEE suitable to move wireless Internet, divide into groups the intersection of IP and the intersection of data and transmissive the intersection of MBWA and system in system in 802.20 MBWA, data rate, effective number of users and spectrum effectiveness of user that it supports are greater than the existing mobile communiation system, can offer more high QoS guarantee, realize high spectrum effectiveness and smaller time delay, bring to user can with wired to connect high speed data application that the result a match for.

802.20 canonial coverage of IEEE is all worldwide like present mobile telephone system, but the transfer rate reaches Wi-Fi level, have obvious advantages more than the present mobile communication network, have advantages too compared with 3G standard.

IEEE 802.16e is similar to outwardly IEEE 802.20 [3 ], in fact there is a difference greatly between them:

(a)The intersection of IEEE and 802.16e increase excursive in the intersection of permission and bandwidth of 2 GHz-6 GHz, but IEEE 802.20 work the intersection of license and frequency band under 3.5GHz, support the intersection of metropolitan area network and the intersection of environment and lower the intersection of 250km/h and high excursive vehicle carried communication, greater than l Mbit/s in the intersection of 1.25 MHz and each mouth crest value data rate of user that bandwidth can support, spectrum effectiveness reachable 1 bit/ (s.Hz.cell) The above.

(b)The air interface of IEEE 802.20 can advance real-time data transmission in the honeycomb in range of Residential Area is 15 km or bigger WMAN, compete with traditional DSL network and cable, even can still carry on normal communication when the mobile subscriber advances at 250 km/h speed. And IEEE 802.16e is only limited to the system of the vehicle carried speed, the migration velocity of maximum that the simulation test indicates to carry on normal communication is 120km/h-150km/h.

(c)More important, IEEE 802.16e is made on the basis of existing IEEE 802.16a, but 802.20 of 1EEE were made again according to MBWA draft. IEEE 802.16e suitable for the personal digital agent (PDA) walking in user's hands Or kneetop computer, but 802.20 of IEEE are suitable for the moving system of high speed.

3 conclusions

It is the inexorable trend of development of communication to be broad band, wireless. IEEE 802.16a standard is a kind of new interface standard in the sky for WMAN access way and put forward, it adopts OFDM technology, it is not the viewing distance to improve greatly, has increased the transmission distance, have reduced the operation cost. The maximum characteristic of MBWA is high excursive, high spectrum effectiveness and high data rate, MBWA system has filled in the characteristic space between present low excursive high data rate and high excursive cellular network of IEEE 802, this solution, in order to design as the foundation and according to the best spectrum effectiveness on the basis of the access network that divides into groups, so it will offer the cost performance characteristic with better more solution than the existing mobile network including 3G system.

Bibliographical reference

1 IEEE 802.16.2,Coexistence of Fixed Broadband Wireless Access Systems.2001

2 IEEE 802.16a.IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Medium Access Control Modifications and Add itional Physicall Layer Specifications for 2 GHz-11 GHz.2003

3 Vikki Lipset,802.16e vs 802.20.Wi-Fi Planet