Chinese WiMAX Market Conclusion and Summary of the Blog..

WiMAX has an excellent opportunity to expand China’s market for fixed, portable, and mobile broadband access. Though traction in the 802.16-2004 (fixed) market will be important, the real success of WiMAX in China will depend on the much larger 802.16(e) market.

China is an increasingly active test bed and emerging market for new technologies. With its large population (1.3 billion), high rate of GDP growth (9% per year) and increasing mobile user base, China would appear to offer a wealth of opportunities for WiMAX. There is a common view that the Asia Pacific will be the key global market for WiMAX, with China being the core long term opportunity for WiMAX vendors and service providers. It is therefore no wonder that the WiMAX Forum regards China as a key strategic region for growth.

And at the same time, some Chinese Telecom vendors such as ZTE and Huawei have put a lot of effort in developing WiMAX products. What they focus on is not only market in North America, but also the big market in China itself.

On the other hand, the PHS in China is a miracle. After sizzling growth in the first half of the decade, China's PHS market is over, with a contraction expected in 2008 or 2009. The slow down occurred as operators turned their attention to laying a foundation for 3G services, expected to roll out this year or in early 2008.

WiMAX may be the next PHS. While the attitude of the Chinese Government towards WiMAX, on which spectrum will be adopted for WiMAX in China, etc., is still not very clear. For Chinese operators, since the 3G network is just about to appear, the relation between WiMAX and 3G will determine the development of WiMAX in China as well.

Whether WiMAX will succeed in Chinese market may also depend on Chinese operators and vendors' participation in the standardization procedure of WiMAX. From the IEEE 802.16 Working Group and WiMAX Forum's point of view, they are trying to encourage and absort more and more Chinese operators and vendors to join in the standardization. The finalization of the WiMAX standards are little bit prolonged awaiting for China to catch up with it. A lot of big companies such as Intel and Samsung are also trying to cooperate with Chinese companies, which also proves that they pay a lot of attention to Chinese market.

In conclusion, this blog made some analysis on the advanced techniques used in WiMAX which is proved to be a very promising network. Based on my knowledge of designing microstrip antenna, the precedure of designing a patch antenna which can be used in WiMAX mobile device is presented. IEEE802.16j, Multi-hop Relay network, as the complement of IEEE802.16, which deals with the disadvantage of Base Station coverage, has attracted a lot of attention. This standard is supposed to be approved at the end of this year. So based on my experience in joining in the sessions of this task group, the developing procedure is provided. WiMAX involves a variety of multi-media applications, such as Television and VoIP, which need high data rate. The implementation of WiMAX system in many countries, especially in China, is analysed, and the perspective and possibility of its development in China is given as well.

WiMAX Prospect in China..

In April, Yankee Group announced at WiMAX World Asia that the Chinese WiMAX market will reach 8.39 million users in 2011, almost 7 times the 1.25 million users as forecasted for 2009 (the first year of significant WiMAX development in China). Of the 8.39 million users in 2011, nomadic and portable broadband access users will lead the Chinese market, accounting for 46% of the market in 2011. Mobile broadband and low-cost fixed wireless access services will come in second and third, accounting for 43% and 11% of the market, respectively.

According to the joint research report by Yankee Group and its China-based partner, Analysys International, WiMAX in China: 2007 to 2011 Outlook and Forecast, if the Ministry of Information Industry (MII) does not embrace WiMAX and create a mobile WiMAX policy soon, the Chinese market will miss the mobile WiMAX opportunity. If this were to happen, Yankee Group and Analysys International believe it will have significant implications for Chinese vendors such as Huawei and ZTE, which are among the front-runners in mobile WiMAX development in China. MII has yet to allocate mobile spectrum, which signals to the industry that MII has not committed to mobile WiMAX development in China. The key for MII to accelerate mobile WiMAX policy development is to demonstrate to local governments how Chinese companies can benefit from mobile WiMAX.

“Embracing connectivity solutions and standards such as mobile WiMAX in emerging markets like China is critical to competing in the continuously evolving global communications industry,” said XJ Wang, vice president of Yankee Group Asia-Pacific Research. “Without China’s participation, the global WiMAX ecosystem will not be complete.”

Although the big four in China—China Netcom, China Unicom, China Mobile and China Telecom—are not rushing WiMAX deployment, Yankee Group and Analysys International find that the smaller players and other municipal WiMAX providers are pushing for an aggressive WiMAX strategy in China despite their financial challenges. Considering the important roles of these smaller players, it is recommend that key members of the WiMAX Forum invest in WiMAX deployment in China.

Note:

The people of Yankee Group are the global connectivity experts™—the leading source of insight and counsel for builders, operators and users of connectivity solutions. For nearly 40 years, Yankee Group has conducted primary research that charts the pace of technology change and its effect on networks, consumers and enterprises. Yankee Group was named Official Industry Analyst for ITU Telecom World 2006. Headquartered in Boston, Yankee Group has a global presence, including operations in North America, Europe, the Middle East, Africa, Latin America and Asia-Pacific.

WiMAX Application Strategy in China..

WiMAX Forum as an organization to push the global application of 802.16 standard device, is actively organizing the interoperability tests of devices in all large system companies. Currently, WiMAX forum memebers include Intel, Siemens, British Telecom and ZTE, Huawei in China, more than 100 companies. Based on the plan made by Intel, one of the main members of WiMAX Forum, it publishes chips in the end of 2004 and realizes outdoor installation in the beginning of 2005 and indoor installation at the end of the same year. In 2006 WiMAX chip is embedded in notebook to realize its portability. With the maturation of the standard and the support of many big companies, it is helpful the realize the large scale and low cost of WiMAX technology. WiMAX will become a very powerful element to push forward the wireless broadband market. Therefore, making corresponding WiMAX application strategy is urgent for the development of operators and China Telecom industry.

WiMAX technology application strategy must be based on the existing and planned wireless networks. Because with the advantages of large transmission distance, high data rate, data and voice high quality services, and less restrictions on conditions, especially in the areas that telephone line and cable can not cover, WiMAX is very promising. The more important thing is that WiMAX not only has the advantage of traditional wideband access based on fiber and the flexibility and mobility of wireless access, but also provides the QoS support of fulfilling voice and video service applications, which makes WiMAX technique with the tent to take the place of 3G and WiFi.

The following table 1 gives the comparison between WCDMA and WiMAX. It is obvious that WiMAX and 3G have a lot of overlapping functionality and big competition, but they focus on two quite different fields of MAN and WAN seperately. They have different markets as complement for each other in netowrk arthitecture. From the perspective of WiMAX development situation, there is no direct competition between WiMAX and 3G, because although 802.16e support mobility, it is only for the roaming between wireless access system and base station. And it is not realistic to introduce 802.16e in the near future. So after the establishment of 3G network, 802.16e technique can be used as supplement. But the concrete effect of the condition of 802.16e, especially when 3G has had substantive progress and operators and device vendors have investigated a lot in 3G. We cannot expect these operators to give 3G up, and currently HSDPA technique has already been mature, which will futher limit the development of WiMAX.

Similarly compared with WiFi, the advantages of WiMAX is more obviously. as shown in table 2. But WiFi an WiMAX solve the problems of "the last 100 meters" and "the last 1 km" separately, which make them used in different fields. WiFi can use outdoor antenna making use of WiMAX to connect directly with backbone network, but not use access point to connect with wired network and then with backbone network. This largely reduces the cost of deployment of wired network. In this way, WiFi and WiMAX can develop simutaniously as complement for each other.

Furthermore, China has large area which involves various kinds of propagation environments and service needs. Based on WiMAX features of high data rate and large coverage, mix WiMAX technique and existing WiFi and 3G, there are overall considerations, such as

1. WiFi and WiMAX networks can be constructed simutaniously to reduce the investment of wired network; In areas without WiFi, users can access directly into WiMAX for data services.


2. In areas where telephone line and fiber can hardly cover, make use of WiMAX to construct wireless networks. Based on different operators' networks, in areas with weak backbone network, make use of WiMAX broadband access services as supplement of wired broadband access.


3. After the completion of 802.16e, WiMAX can ensure high data rate access in low speed mobility. Then it becomes the powerful complement of 3G network.


4. For temperary communication and large area wireless access, such as exhibition, WiMAX can be a guarantee of access.

After all, we want to establish a mixture network of 3G/WiFi/WiMAX broadband access, multi-layers, seamless coverage, co-operating network, fulfilling the as many requirements of users, and ensuring the fast development of China communication industry.

Currently the WiMAX technology is still not very mature, there is still some uncertainty in the future of WiMAX. For example, it is not an easy case to distribute spectrum in every country. But it is for sure that WiMAX will bring big opportunity and challenge to China telecom industry. The in-depth reseach of this field will be the strong base of wide future develpment for high speed network users and providers.

Intellectual Property Rights (IPR) landscape for WiMAX

A fundamental reality of the tech world is that companies have become increasingly specialized, with each building only a small chunk of any functionality that is needed by consumers. So their products must interact with each other, but without the discipline imposed by common ownership and management. This brings us to the concept of standards, the term given to the mechanisms by which the different participants in a market communicate, coordinate, and cooperate. In the tech context it usually means a specification for organizing and transmitting information.

As of September 2006, there were more than 1,500 patents distributed among 330 companies on WiMAX technologies. Of the 23 companies that hold more than ten patents, 74% are WiMAX Forum members. Nowadays more and more products become WiMAX Forum Certified™ and additional patent holders join the Forum.

There are some key findings in the IPR research:

• As a result of the IPR and market shift, Qualcomm will likely produce WiMAX plus cellular 3G multi-mode chips.
• IPR disputes for WiMAX/4G will be a less costly concern than in cellular. The positions of IPR stake holders with respect to both current and future versions of WiMAX as it evolves towards 4G, IMT-Advanced will influence royalties.
• Trends and consolidation among smaller players indicates further acquisitions by the larger players such as Intel, Qualcomm, Samsung and Motorola, who will strongly influence the overall IPR costs.
• Qualcomm's position in 802.16e-2005 is limited but patent trends indicate a stronger position for a few areas of development that will become increasingly important: “Smart Wireless Network” topology, multimode, video multi-casting and other advances and extension fields of development will strongly impact 4G.
• Wi-Lan, an IPR corporate licensor, has early agreements for WiMAX and related licenses with Redline, Cisco and Nokia, which set early benchmarks for commercial precedents of IPR agreements. This represents the limited direct commercial or legal precedent yet available for establishing IPR licensing trends in the emerging field.
• The report reveals trends in developing technology that are critical to evolution of WiMAX and 4G LTE products and markets. These developments will help to differentiate vendors that, in turn, help decide success or failure for 4G systems and device suppliers.
• Convergence between WiMAX/802.16 plus 802.22, and 3GPP/3GPP2 cellular is taking place in core link technologies, which will increasingly be based on MIMO-OFDM/OFDMA modulation schemes. The envelope of wireless invention (IPR) is being pushed in the “enhancement” technologies including MIMO-OFDMA and smart networking methods that leverage the core link platform to greater advantage.
• Patent activity has accelerated, particularly in the areas mentioned. MIMO-OFDM/OFDMA activity has dominated recent patent application and publishing.
• A few large companies file for large numbers of patents. Many of these can be characterized, as Qualcomm has pointed out, as “fractional” or derivative patents. The report discusses how important the “numbers game” is in estimation of IPR portfolio value.
• Several “WiMAX pure plays” who have been instrumental in standards development efforts have filed comparatively few patents in 4G/WiMAX. However, being closely tied to the standards, the research evaluates the essential nature of their holdings.
• WiMAX and other applications of MIMO-OFDM based systems marks a demarcation between it and prior fields of wireless development. The “evolution” from prior cellular systems is not achieved at a wireless link interface level that is necessary for transition of a majority of prior technology patents.
• Essential patents in the field are held by a large number of companies. But some consolidation has taken place through acquisitions. Some patents have not been reassigned to the acquiring company. The research database has categorized patents based on current holders.
• Some fundamental and essential patents on OFDM and MIMO go back several years. In some cases, the companies involved in important areas of early development are not those now considered wireless telecommunications industry dominant market leaders.
• Trends in competitive product developments and projections for new products are discussed.
• Competitive positions and moves are analyzed for impact on about five years forecasting of developments.
• Prospective acquisitions, partnering, pooling, and other activity can be learned from a study and is briefly discussed in the report of the database analysis.
• The guidelines for determining fair and reasonable royalty rates for WiMAX are analyzed based on what is considered fair and reasonable for similar fields of development, particularly in context for standardsbased developments.
• “Fair and reasonable” agreements of standards groups are often contested.
• Surveys show that service providers want certainty. A reasonable cost for IPR paid in royalties or cost of goods is acceptable. Disruption of business is not desired.
• Interviews with IPR holders indicate that they want/expect reasonable compensation for R&D: either reasonable royalties or expressed in the cost of goods sold; in their position in the market.
• The WiMAX/LTE 4G Intellectual Property Rights (IPR) Policy & Market Report has identified:
  o Over 550 patents that are essential to WiMAX 4G.
  o The number of “fundamental” patents is lower than 20.
  o The total number of patents that relate directly to the field that are contained in the Maravedis database is 2,060.
  o The number of patents including related areas of OFDM such as DVB/DVB-H and FH-OFDM and related segments of wireless development such as CDMA and 802.11 related to OFDM is 3,520.

WiMAX Product Aspects..

The ultimate goal of the WiMAX Forum is to accelerate the introduction of cost-effective broadband wireless access services into the marketplace. Standards-based, interoperable solutions enable economies of scale that, in turn, drive price and performance levels unachievable by proprietary approaches, making WiMAX Forum Certified™ products cost-effective at delivering broadband services on a wide scale. Designed for carrier-class deployments as well as low-cost, license-exempt deployments, WiMAX Forum Certified™ systems deliver high-capacity service throughput (up to 36 Mbps in a 10MHz channel) and provide a range of up to five kilometers in near to non-line-of-sight conditions. The systems are scalable for up to thousands of users, and because they are interoperable, service providers will be able to purchase equipment from more than one vendor, thereby reducing the overall risk and creating a price-competitive marketplace.

For enterprises, WiMAX can provide a cost-effective broadband access alternative. Since most businesses are not zoned for cable, their only option for broadband service is from the local telco, creating a monopoly situation. The ease of deployment for WiMAX Forum Certified™ systems can benefit enterprises by bringing new competition into the marketplace and lowering prices, or by enabling enterprises to set up their own private networks. This is especially relevant for industries like gas, mining, agriculture, transportation, construction and others that operate in remote locations.
For some residential customers in suburban and rural areas (where DSL or cable modem service is not available), WiMAX can provide the ability to finally have the broadband access they need. This is particularly true in developing countries, where traditional telecom infrastructure is not readily accessible.

The first generation of WiMAX Forum Certified™ CPEs are outdoor-installable subscriber stations akin to a small satellite dish. These became available in 2005 and are priced around $500. The second generation of CPEs are indoor self-installable modems similar to a cable or DSL modem and are priced around $300. Third-generation CPEs will be integrated into laptops and other portable devices, are expected to initially cost approximately $100 and are expected to be available in 2007.

WiMAX Development in other Asian Countries..

The WiMAX Forum, an industry-led non-profit organization comprising more than 460 companies committed to promoting and certifying interoperable WiMAX products, on June 21st announced establishment of the WiMAX Forum Japan Office in conjunction with appointment of Japan Director and Vice Directors by the WiMAX Forum.

Japan plays a key role in mobile communication technologies and services and is also expected to lead next-generation mobile broadband services. The Ministry of Internal Affairs and Communications (MIC) has completed the regulatory work for the 2.5 GHz broadband wireless access and also announced the draft license policy on May 15.

Given this regulatory situation and the high demands from the Japanese member companies of the WiMAX Forum, the WiMAX Forum decided to establish the Japan Office and also appointed its director and vice directors for managing all of the WiMAX Forum activities in Japan, particularly for addressing regulatory and marketing challenges.

"I will act as local representative for the WiMAX Forum to help make mobile broadband a reality in Japan by working with equipment vendors and operators to develop interoperable telecommunication services," said Dr. Tadao Saito, WiMAX Forum Japan Director.

The WiMAX Forum Japan Office is the fourth office of the WiMAX Forum after its offices in US, China and India. The Japan Director and Vice Directors appointed by the WiMAX Forum are as follows: Japan Director Dr. Tadao Saito, Professor Emeritus at the University of TokyoVice Director of Technology Dr. Kenji Kohiyama, Professor at Keio UniversityVice Director of Operations Dr. Takashi Shono, Executive Researcher of Intel K.K.

We can see that Asian countries are taking a major part in WiMAX standard, which will also accelerate the WiMAX application globally.

WiMAX License will be Awarded soon in Taiwan..

The National Communications Commission in Taiwan said that it has received thirteen applications for the six WiMAX licenses that will be awarded next month, according to a Dow Jones report. Among the companies that applied for licenses in the frequency band 2.5 ~ 2.69 GHz included Taiwan’s largest telecom operator Chunghwa Telecom, Far EasTone Telecommunications and Taiwan Mobile. The next step in the application process is for the NCC to question each applicant’s business plan and then a final selection of qualified bidders will proceed to auction. The largest phone operator in Taiwan, Chunghwa Telecom Co, said it would invest up to US$122 million in WiMAX over the next five years, if it is awarded a license for WiMAX spectrum. According to a report in Bloomberg, Chunghwa vice president Mu-Piao Shih said in an interview that “Chunghwa is betting WiMAX.” The report also said that a WiMAX service “may help Chunghwa bolster revenue from mobile gaming and video-sharing as sales decline at the fixed-line and long-distance phone businesses.” Shih added that it would integrate any WiMAX services with its 3G network, because the “two networks complement each other.”

One of the world's bigest telecom companies, Motorola chairman and CEO Ed Zander made a 24-hour visit to Taiwan last month to discuss WiMAX initiatives and cooperation with government and local enterprise. According to the China Times, Zander said Motorola will strongly support the industrial policy of the Taiwan government, and the company will coordinate activities with the Ministry of Economic Affairs to help promote M-Taiwan. Zander also met with executives at Far EasTone Telecommunications (FET) and First International Telecom (FITel). Both companies intend to bid on the forthcoming auction of WiMAX spectrum in Taiwan, and if succesful, will be potential purchasers of Motorola’s WiMAX equipment.

WiMAX Program in Taiwan..

Now I would like to talk about the WiMAX application in Taiwan. As mentioned before, Taiwan is wanting to play a lead role in matters of adopting technology in WiMAX world. It has methodically created a delicated ecosystem to demonstrate WiMAX technology.

In recent years, Taiwan has already own largely to state sponsored incentives and ICT product manufaturing capability. Therefore it also has elevated itself in the overall global market to a enviable position. Supplying the entire range of IT products ranging from semiconductor, computer, consumer electronics and networking products, Taiwan is today considered to be the top ICT manufacture with a very successful WiFi industry enjoying more than 90% of world market share.

In the quest to identify the next generation product, Taiwan government chose WiMAX to open up another frontier in the wireless industry. In 2005, the Science & Technology Advisory Group of Executive Yuan developed a WiMAX blueprint, which states "WiMAX Technology will be a focus for th efuture of Taiwan ICT industry, and will be the preferred technology to deliver M-Service, M-Learning and M-Life in the M(Mobile)-Taiwan Program". The M-Taiwan program and WiMAX acceleration projects, which aim to develop chip set and base stations, were initiated under this blueprint. Towards this, Taiwan offers not only world class manufacturing capability, but also an entire service and application test bed, by forming its own ecosystem.

Forming a complete WiMAX system, including chipset, CPE, network elements, test labs, system integration, application, commercial operation and services, is part of the overall strategy adopted by Taiwan for development of technology. Cooperation with international players, and leveraging the strengths of its indigenous WiFi industry, Taiwan is able to speed up product development, manufacturing and marketing of WiMAX technologies.

To promote global interoperability Taiwan actively participates in international standards and promotes international collaborations. Taiwan has been working closely with the WiMAX Forum in promoting WiMAX and sharing M-Taiwan experiences.

In the short period since its inauguration, 'M-Taiwan' has undeniably achieved significant initial success. With a direct investment of $1.5 billion, Taiwan now has over 80 companies participating in the program, which strengthens the overall value chain of the industry. The early success of the M-Taiwan program proves that to support a new industry, it takes not only adequate demand, solid infrastructure and plentiful supply, but also a fair and competitive environment. The government has been mindful of this from the very inception, and thus has made substantial and meaningful investments to create a desirable and encouraging environment for participation in the program.

Taiwan is moving steadfastly with its planning of WiMAX spectrum and sticking to its original plan to issue a number of regional licenses. This will allow green-field operators to participate in the M-Taiwan program to join the ranks of established operators in providing WiMAX services. Several large scale WiMAX networks are expected to be created this year, making it easier for these networks to provide commercial services in the near future. In addition, the government is considering innovative WiMAX deployment approaches to create Wireless Cities and begin the study of using WiMAX technology for the newly inaugurated Taiwan High Speed Railway system. The M-Taiwan Program ultimately provides an effective template for any other country wanting to utilize WiMAX technology, and will essentially accelerate the WiMAX adoption process in the rest of the world.

Summary and Prospect for IEEE802.16j..

Currently more and more companies and institutions are more and more interested in the standardization of IEEE802.16j MMP, especially in Asian countries, such as China, Korea, Singapore and Japan. And many of the companies have developed WiMAX products and put them into market. Facing with the fast development of WiMAX system, nearly all the telecommunication companies are willing to participate in the future big market. Therefore participating in the standardization procedure firstly is a very important step.

While in the group of voting members, companies, such as Intel, Samsung, Motorola, etc., are playing important roles, which also proves that many big companies are paying more and more attention to the intellectural properties. This is always considered to be a right strategy in the intense competition among companies.

On the other hand, this standard was supposed to be summited this July and approved this September. While the schedule may be delayed for several months, partly because the organizer also recognized the big market in China. And most of the Chinese companies just joined in this part. This is because the 3G license is just about to be assigned by the government and most of the vendors have just signed the contracts with operators for 3G equipments. The next step for them are to develop the next generation network. So in this way, the Task Group also wants to wait for China to catch up.

The procedure of Working Group letter ballot has started. The next meeting is planned to be held in July 2007, in San Francisco, USA.. And more technical contributions and comments are supposed to appear. We hope the IEEE802.16j standard can be a very powerful complement of WiMAX for its difficulty in the legacy Base Station coverage.

Continuing Development of IEEE802.16j Standard..

• Session #48 held in March 2007, Orlando, USA

The aim of this session is to advance the development of the P802.16j Baseline Document by going through the Comments and Contributions presentation, discussion and resolution, and considering the five Guideline Documents of usage models, definitions and terminology, evaluation methodology, technical requirements and table of contents.

This time 118 comments and 146 contributions were submitted and 85 of them were accepted. Members formed into 8 groups for ad-hoc discussion, which are Frame Structure, Security, Mobility Management Sleep/Idle Mode, HARQ, Routing and Path Management, MAC PDU Construction, Measurement & Reporting and other MAC/Other PHY. Because of so many topics, the meeting schedule was quite tight.

Then members texted Proposals for the Baseline Document and scheduled towards the initial draft and WG letter ballot. And after the meeting, Technical Editors revised the baseline document, which was a further step into standardization of IEEE802.16j.

• Session #49 in May 2007, Portland, USA

The main purpose of this meeting is to advance the development of the P802.16j Baseline Document. Firstly the ad-hoc group chairs reported the results of their group discussion based on the topics mentioned above. Then members discussed about resolution of comments returned to TG from adhoc groups, and Resolution of comments deferred straight to #49. After that they reviewed the comment classification and presented technical comments. Later they dealt with editorial comments.

Later Development of IEEE802.16j Standard..

• #45 Session held in September 2006, Tremblant, Canada

Since the topics of Usage Model and Terminology were done in Session #44, the objectives of #45 meeting was focused on Evaluation Methodology, Technical Requirements and Table of Contents, and also preparing for the technical proposals towards the next meeting.

For the documents of Technical Requirements and Table of Contents, before the meeting, many companies discussed a lot about them. So these documents were submitted by a group of companies. While Samsung had their own documents. During the ad-hoc discussion time, all the companies got agreement and resulted in one document.

Most of the comments were about Evaluation Methodology. Institutions from Taiwan, companies such as Notel and Nokia made a lot of effort on it.

• Session #46 held in November 2006, Dallas, USA

Except the technical contributions, the main purpose was to consider the five Guideline Documents of Usage Models, Definitions and Terminology, Evaluation Methodology, Technical Requirements and Table of Contents in order to prepare for the draft standard towards the next meeting.

This time 156 contributions were submitted before the meeting, which proved the participation was expanded a lot. And the presentations were organized based on technical topic to topic approach. The discussion at the end of topic was also organized. In this way, the technical details were forming step by step.

• Session #47 held in January 2007, London, England

This session went through the Technical Contributions presentation and discussion, considered the five Guideline Documents of Usage Models Definitions and Terminology, Evaluation Methodology, Technical Requirements and Table of Contents, and proceeded to the “call for comments” on the baseline document towards the next meeting for the draft standard.

170 contributions were submitted on topics of Relay concepts, Security, Frame structure, Network entry, BW request, Construction & transmission of MAC PDUs, Measurement & reporting, Mobility management, Routing & path management, RRM, Scheduling & Interference control, PHY, and Evaluation methodology. Among these Frame structure and Network entry got most attention, and each of them obtained 33 contributions.

My Experience in IEEE802.16j Session #43 & #44..

• Session #43 802.16 Relay TG held in May 2006, Tel Aviv, Isreal.

The objectives of this session was to organize the TG, to have contribution presentations, to deliver Draft TG Docs. preparing for the draft Std. Proposals, along with the items shown on the 1st Call for Contributions and referring to the contribution documents, and to outline the 2nd Call for Comment and Contributions.

Contributions submitted before this session were focused on several aspects, such as Terminology, Task Group Process, Usage Scenario, Technical Requirements and Evaluation Methodology. These contributions were presented on the first day. Our group submitted a contribution about frame structure which belongs to Usage Scenario. Other companies, such as Alcatel and Notel also submitted a lot of technical contributions. While at that time, the technical contributions were too early for standardization. Some companies agreed with the design, but most of companies felt there were still problems with it. However, these detailed design normally showed the trend of the development of the technologies. On the other hand, the technical contributions were not dicussed a lot during the meeting, because the preparation of this standard was still not ready and a lot of things were not so clear as well.

On the second day, there were four ad-hoc meetings for different topics. The first one was Evaluation Methodology led by Wen Tong (from Nortel, Canada); the second one was Project Plan and Schedule led by Jae Weon Cho (from Samsung, Korea); the third one was Terminology led by Roger Peterson (from Motorola); and the fourth one was Usage Scenario and Technical Requirements led by Jerry Sydir (from Intel). It is quite obvious, Intel, Samsung and Notel were very enthusiastic with this standard and put a lot of effort on it.

The Task Group also discussed on delivering Draft TG Docs. preparing for the draft Std. Proposals, along with the items shown on the 1st Call for Contributions and referring to the contribution documents, and outlining the 2nd Call for Comment and Contributions.

• Session #44 held in July 2006, San Diego, USA.

The objectives of this session is to complete the reference document set of Usage Mode, Terminology, Evaluation Mechodology and Technical Requirements, to initiate and complete the guideline document including Table of Contents, and to draft "Call for Technical Proposal".

Before the session, Peiying Zhu (from Nortel, Canada), who had much experience in standardazition, was selected as the vice chair of the task group, which partly bacause the current chair was not quite experienced. On the other hand, we can see Notel paid a lot of attention in this standard.

This time more technical contributions appeared, but some big companies still kept silence in the central techniques and tried to make the procedure following the steps. Our group submitted a contribution on Technical Requirement about the need to distinguish high and low capability Relay Stations. Based on the ability of a Relay Station, different functions could be provided. While this comment was rejected, because most of the attendants preferred an uniform design.

Usage Model and Technical Requirements ad-hoc meetings were led by Jerry Sydir (from Intel); Terminology meeting was led by Rogger Peterson (from Motorola); and Evaluation Methodology was led by Wen Tong (from Notel); During the ad-hoc meeting, two of the most powerful companies, Intel and Samsung got agreement with a lot of things, such as technical requirements, table of contents, etc.

This time more companies and institutions joined in the session and after each meeting, there happened to be more discussions about technical details. Some groups with different intensions appeared to form..

Initiation of IEEE802.16j Standard..

From this time on, I will use several posts to talk about some of my experience in joining in the IEEE802.16j sessions. During my short working experience, I joined in two IEEE802.16j sessions, i.e. the 43th and the 44th held in Tel Aviv, Isreal, and San Diego, USA, separately.

On 802.16 Working Group closing plenary meeting of July 21st, 2005, the new study group supporters, including Mitsuo Nohara (currently the chair), Peiying Zhu (vice chair, from Nortel in Canada), Mike Hart (from Fujitsu in England), etc. exchanged the views on Mobile Multi-hop Relay Networking and had open comments and technical discussions. They supported the creation of new study group and planned future activity and schedule. The session started from #39 meeting and is chaired by Mitsuo Nohara (from a Japanese operator).

IEEE 802.16's Mobile Multihop Relay Study Group was chartered on 22 July 2005. The Study Group expired on 30 March 2006, with the approval of its Project Authorization Request (PAR) P802.16j. The development of the P802.16j project has been assigned to IEEE 802.16's Relay Task Group. The PAR addresses "Air Interface for Fixed and Mobile Broadband Wireless Access Systems - Multihop Relay Specification."

In the #39 session held in Taipei, the task group summarized the scope of proposed relay project and its main features. Participants provided contributions on ideas for usage and application scenario, i.e. Network topology and capability of RS; Principle requirements on PHY/MACprotocols in IEEE802.16 to provide multi-hop connection; ideas for spectral scenario and securityissues, and references of the technology such as IEEE802.1 bridging. They discussed and agreed on the need for clarification/revision of the concept table, the need for Common Terminology, and the call for Contributions to be issued including PAR and 5 Criteria (Scope, Purpose, Reason, etc.), and the scope of MMR task including evaluation criteria, backward compatibility.

In session #40, the contributions provided technical issues relevant to a “PAR and Five Criteria” and direction of MMR activities for high level issues such as service scenarios, network topologies, etc.

In the #41 session held in India, the contributions included comments on the “Discussion Base on Draft PAR and Five Criteria”, technical issues relevant to a Tutorial Presentation and distinctions from other IEEE 802 standards and projects such as 802.1 on Spanning Tree and Bridge, 802.11s and 802.16h. At this meeting, the PAR and 5 Criteria were completed and the participants reacted to 802.1 comments.

In session #42 in Denver, Tutorial Session, Comment resolution on 802.16j PAR & 5 Criteria, and reactions to 802.1 comments were dealt with. Until here, 802 EC endorses PAR approval. And from the next session, the Relay Task Group would start the formal meeting.

Comparing Mobile WiMAX to 1*EVDO and HSPA in 3G..

Evolution Data-Optimized (1*EVDO) and High-Speed Downlink Packet Access (HSDPA/HSPA) have evolved from 3G CDMA standards to provide data services over a network originally conceived for mobile voice services. These 3G enhancements have evolved from the 3G experiences and as a result, inherit both the advantages and limitations of legacy 3G systems. WiMAX on the other hand was initially developed for fixed broadband wireless access and is optimized for broadband data services. Since Mobile WiMAX has evolved from systme concepts initially designed for fixed wireless access, WiMAX faces the challenge of meeting the additional requirements necessary to support mobility. A point by point comparison of the attributes of Mobile WiMAX with 3G-based 1*EVDO and HSDPA/HSPA systems is useful in addressing how these technologies can meet future network requirements for mobile broadband data services.

• Common features

Several features, designed to enhance data throughput, are common to EVDO, HSDPA/HSPA and Mobile WiMAX including:

- Adaptive modulation and coding (AMC)

- Hybrid ARQ (HARQ)

- Fast schedulig

- Bandwidth efficient handoff

• Key advantages of Mobile WiMAX

Unlike the CDMA-based 3G systems, which have evolved from voice-centric systems, WiMAX was designed to meet the requirements necessary for the delivery of broadband data services as well as voice. The Mobile WiMAX physical layer is based on Scalable OFDMA technology. The new technologies employed for Mobile WiMAX result in lower equipment complexity and simpler management due to the all-IP core network and provide Mobile WiMAX systems with many other CDMA-based 3G systems including:

- Tolerance to Multipath and Self-Interference

- Scalable Channel Bandwidth

- Orthogonal Uplink Multiple Access

- Support for Spectrally-Efficient TDD

- Frequency-Selective Scheduling

- Fractional Frequency Reuse

-Fine Quality of Service (QoS)

- Advanced Antenna Technology

All the systems have adopted advanced technologies to improve data throughput. However Mobile WiMAX, is based on OFDM/OFDMA technology which is more suitable for broadband wireless data communication. In fact OFDM/OFDMA is one proposal being considered in 3GPP/3GPP2 as the solution for LTE and is generally accepted as being the basis for 4G. An OFDM/OFDMA-based systme has high granular resourece allocation, better uplink efficiency, and can support a full range of advanced antenna technologies. These capabilities offer the potential for significant spectral efficiency advantages and better QoS in both the downlink and uplink direction. Mobile WiMAX can slso dynamically adjust downlink/uplink ratio with TDD support providing greater flexibility and spectral efficiency advantages in supporting varied types of broadband traffic. In contrast, EVDO and HSPA, based on FDD, have a fixed asymmetric downlink/uplink ratio determined by the difference in downlink/uplink spectral efficiency and fixed FDD channel bandwidth. Additionally, Mobile WiMAX provides superior QoS and offers operators greater flexibility in implementing Service Level Agreements to meet varied customer requirements.

From a performance perspective, only Mobile WiMAX can transport DSL and cable-like services cost-effectively in a mobile environment. This is an essential requirement for the success of Mobile WiMAX, a technology aimed at delivering broadband mobile services ranging from real-time interactive gaming, VoIP, and streaming media to non-real-time web browsing and simple file transfers.

Other benefits of WiMAX include its open standard approach and healthy ecosystem. Hundreds of companies have contributed to the development of the technology and many companies have announced product plans for this technology. The broad industry participation with worldwide adoption of th estandard will ensure economies of scale that will help drive low cost of subscription and enable the deployment of broadband mobile services in both developed and emerging markets. With a scalable architecturem high data throughput and low cost of deployment Mobile WiMAX is a leading solution for wireless broadband services. By creating a common platform that addresses a wide range of market segments, Mobile WiMAX is well-positioned to experience a high global take rate.

Co-Existence of Mobile WiMAX and GSM in China..

Mobile WiMAX has been developed for high-speed data rate applicaitons especially in mobile environments compared with other IEEE 802 series standards. Because of scarce frequency resources, it is unavoidable to interfere the neighboring commercial mobile networks when mobile WiMAX system is deployed.

Wireless broadband targets to bring high-speed data to multitudes of people in various geographical locations where wired transmission is costly, inconvenient, or unavailable. WiMAX is one kind of technologies devoted to make broadband wireless commercially available to the market. Compared with fixed version WiMAX, mobile WiMAX, based on IEEE 802.16e amendment, is intended primarily for both stationary and mobile deployments and designed specifically to optimize performance of wireless links in the outdoor environment over the next couple of year.

Mobile WiMAX defines interoperable system profiles of base stations and terminals, which are targeted for licensed and licensed-exempt frequency bands around the world. WiMAX channel bandwidths are 1.25MHz, 5MHz, 10MHz and 20MHz, etc. Data bursts can be transmitted through either FDD or TDD mode. Furthermore, TDD mode is more attractive than FDD mode in WiMAX system because TDD mode WiMAX system will not require a pair of frequency bands. On the other hand, the frequency resources are very limited around the world and it is hard to find frequency band pairs to deploy FDD mode WiMAX system.

In China, more than 150MHz frequency bands, located in 400MHz, 1.8GHz and 2.3GHz, have been allocated to TDD mode wireless access technologies. Among these frequency bands, nearly 140MHz frequency bands are reserved to 3G TDD systems. And in the left frequency bands, only 1.8GHz frequency band is adjacent to the commercial mobile networks, DCS1800 DL, which were deployed by China Mobile and China Unicom (DCS1800 is based on GSM technology which is deployed in 1800MHz frequency band). To avoid the interference between mobile WiMAX and the existing system, it is assumed that mobile WiMAX is deployed in this frequency band, the most important thing is to do the analysis on co-existence problem.

Some research results show that the interference between these two systems is very small and no additional protection is requierd when the BSs of the two systems are not co-sited. When the BSs of the two systems are co-sited, the inter-system interference except in WiMAX UL is negligible. The WiMAX UL capacity loss due to GSM BS can be alleviated to a satisfied level through increasing either ACIR (Adjacent Channel Interference Ratio) or antenna isolation. If the method of increasing ACIR is used, the recommended value is 85dB. On the other hand, if the method of increasing antenna isolation is used, the recommended value is about 60dB. Furthermore, these two methods can be used simultaneously and the required values for ACIR and antenna isolation are lower than the above-mentioned value.

My MS Antenna Design for 3.5GHz WiMAX..

As a new system, WiMAX has it special requirements and constraints.

• It operates at high frequency (2.5/3.5/5.5GHz)-> higher signal attenuation
• Deployment needs wide transmission bandwidth (5/10MHz)->high data rates per user
• It has the need to use high-level modulation (up to 64QAM)-> high capacity and high data rate per user
• it has the dimensioning with stringent indoor penetration requirements
• According to these requirements, I designed a patch antenna working at one of the possible WiMAX frequency, i.e. 3.5GHz. The design specification is as follows:

• 50Ω transmission line
• Substrate: FR4 (Flame Resistant 4)
  -Composite of a resin epoxy reinforced with a woven fiberglass mat
  -Єr = 4.4
  -tanδ = 0.01 @ 10GHz
  -Less lossy at high frequencies
  -Absorb less moisture
  -Greater strength and stiffness
  -Highly flame resistant compared to its less costly counterpart
  -Ultra high vacuum compatible


• Height of dielectric substrate (h): 1.5mm
  -for usage in cellular phones, it is essential that the antenna is not bulky.
• Patch
  -Conducting material such as copper or gold
  -Take rectangular shape as example
  -Large bandwidth and gain

The design procedure is as follows.

Other parameters are calculated as below.

Based on the above parameters, we get the following patch antenna.
This patch antenna has its advantages and disadvantages.

Advantages:

• Light weight and low volume
• Low profile planar configuration which can be easily made conformal to host surface
• Low fabrication cost, hence can be manufactured in large quantities
• Supports both, linear as well as circular polarization
• Can be easily integrated with microwave integrated circuits
• Capable of dual and triple frequency operations
• Mechanically robust when mounted on rigid surfaces

Disadvantages:

• Narrow bandwidth
• Low efficiency
• Low gain
• Extraneous radiation from feeds and junctions
• Poor end fire radiator except tapered slot antennas
• Low power handling capacity
• Surface wave excitation

Base Station Antenna Design in WiMAX system..

To increase the capacity and coverage in broadband data communication according to the IEEE 802.16e WiMAX standard, intelligent base station antenna with beam- and nullsteering over a full circle is developed and optimised.

Conventional base station antennas in existing operational systems are either omnidirectional or sectorized. The greater part of the transmitted signal power is radiated into directions other than toward the specific user. This causes interference, reduces efficiency and the range of coverage. Especially in new broadband services as WiMAX, where the user front-end is very simple, it becomes necessary to provide every user with a specific beam offering enough gain to increase the range. It is also important to reduce interference by other users or services by means of beam forming in a way, that either the side lobe attenuation of the base station antenna array as a whole is optimised or by null steering. In rural areas a whole 360 degrees coverage around the base station is desired. This leads to the solution introduced here of circular antenna arrays, a setup which can be used for direction finding.

The antenna array consists of 8 vertical dipoles equally spaced on a ring with diameter d. This building block is vertically stacked many times to achieve enough gain in the horisontal plane. The number of side lobes and the side lobe attenuation depends on the radio d/λ which is ranged in 1/2 and 3/2. It is possible to provide m different and imdependent beams in m directions concurrently. Each dipole is fed by an amplitude and phase actuator and isolated power dividers. In principle this can also be achieved by means of a digital signal processor.

With the circular array of vertical dipoles it is possible to steer the beam in the direction of any user and to provide an optimal side lobe attenuation for m different directions simultaneously. The number of coexistent beams is only limited in practice by the capabilities of the power dividers.

It is also possible to provide a full nullsteering in every direction around the base station. This can be done by phase shifters and attenuators in the RF-region or by DSP after linear down conversion. The results are achieved by the numerical EM-solver FEKO.

With this antenna array it is possible to enhance either the coverage in rural areas or to enhance the capacity of the network.

Antenna & Interference in WiMAX

By utilizing AAS and beam steering technologies, WiMAX overcomes interference while boosting range and throughput.

Adaptive Antenna Systems (AAS) use beam-forming technologies to focus the wireless beam between the base station and the subscriber. This reduces the possibility of interference from other broadcasters as the beam runs straight between the two points.

The potential spectrum for WiMAX is 2.5/3.5/5.5 GHz among which there may be a lot of interference. One of the simplest remedies to interference is to simply change frequencies to avoid the frequency where interference occurs. Dynamic frequency selection (DFS) does just that. A DFS radio sniffs the airwaves to determine where interference does not occur and selects the open frequency to avoid the frequencies where interference occurs.

Multiple in and multiple out (MIMO) antenna systems work on the same principle. With multiple transmitters and receivers built into the antenna, the transmitter and receiver can coordinate to move to an open frequency if/when interference occurs.

Software defined radios (SDR) use the same strategy to avoid interference. As they are software and not hardware defined, they have the flexibility to dynamically shift frequencies to move away from a congested frequency to an open channel.

Authentication Authorization and Accounting (AAA) in WiMAX compared with WiFi..

After talking about the interaction between different systems, the security aspect in WiMAX shows its importance to ensure the reliability of cooperation.

Security mechanisms have already been developed maturely in WiFi system. WiMAX has some similarities with WiFi, but its security aspects are stronger than that of WiFi. The current standard for WiFi security is specified in IEEE 802.11i, while it has not been widely implemented and it is expected that 802.16 will take control of the market due to the high bandwidth and long range in addition to the security strengths. This further incorporates the possibilities for higher integrated QoS, minimum bandwidth guarantees and other performance improvements.

The main issues with WiMAX security scheme is the authentication and confidentiality. It mainly focuses on the authentication and authorization of WiMAX, since they are key components of any security solution. 802.16 security features are more promising as they are better designed as compared to those of 802.11 and the standard bodies of WiMAX have been proritizing security options from the beginning. In fact, the WiMAX standard itself incorporates more flexible and better security support than the ones in WiFi standard.

• Problems in authentication and authorization - EAP

The purpose of authentication and authorization techniques used in WiFi systems are to prevent snooping of the user ID, denial of service (DoS), offline dictionary attack, man-in-the-middle attack, authentication method down-grading attacks and breaking a weak key. The authentication protocol has to ensure information gathering about the user before choosing the protocol and to authenticate both sides equally (mutual authentication).

EAP was introduced which can offer an authentication scheme to prevent the above mentioned problems. It integrates different authentication methods to match the nature of the communication channel. These methods are advised by IEEE including EAP-PKM, EAP-MD5, EAP-OTP, EAP-GTC, EAP-TLS, EAP-SIM and EAP-AKA.

WiMAX uses two of these methods, i.e. EAP-PDM and EAP-TLS. EAP-TLS is an IETF open standard and is well-supported among wireless vendors. It offers a good deal of security, since TLS is considered the successor of the SSL (Secure Socket Layer) standard. It uses PKI to secure communication to the RADIUS authentication server, and this fact may make it seem like a daunting task to set up. So even though EAP-TLS provides excellent security, the overhead of client-side certificates may be its achilles heel.

EAP-TLS is the original standard wireless LAN EAP authentication protocol. The requirement for a client-side certificate is what gives EAP-TLS its authentication strength and illustrates the classic convenience versus security trade-off. A password tha thas been compromised is not enough to break into EAP-TLS enabled systems because the hacker still needs to have the client-side certificate. When the client-side certificates are housed in smartcards, this offers the most secure authentication solution available because there is no way to recover user's private key from a smartcard without stealing the smartcard itself. Any physical theft of a smartcard would be immediately noticed and revoked and a new smartcard would be issued.

EAP-PKM on the other hand involves both one-way and mutual authentication schemes.

• Authentication mechanisims for WiMAX

1. Security Analysis

The PKM-EAP of WiMAX has been introduced in a more robust and secure way. The following enhancements have been addressed:

- Mutual authentication is provided in PKMv2, which could avoid "Man in the Middle" attacks.

- The X.509 digitally signed certificate that is issued is unique to each SS and cannot be easily forged.

- Each service has a different SAID, if one service is compromised, the other services are not compromised.

- The limited lifetime of AK provides periodic reauthorization and key refresh, which prevents attackers from having large amount of data to perform cryptanalysis on.

- Adding a random value from the BS and SS to authorization SA is a way to prevent replay attacks.

- WiMAX security supports two quality encryptions standards- DES3 and AES, which are considered secure for the foreseeable future.

- SS can attempt to use a cached or handover-transferred Master Key and avoid a full re-authentication.

- PKM-EAP relies on the TLS (Transport Layer Security) standard which uses public key cryptography and is very costly for some wireless devices. Thus, each base station in WiMAX has a dedicated high performance security processor, which gives us a chance to implement a mutual authentication system in WiMAX. In other words, an authentication protocol can be designed in a way where most of computational procedures are done inside of the base station.

However, there are also some known issues existing in the security architecture of WiMAX. It only defines ways to protect wireless communication at the MAC layer now, but hasn't considered the threats from any attacks targeting the physical layer, for example, radio jamming, or continuously sending packets. This could result in an overwhelmed receiver, and eventually cause Denial of Service (DoS) or fast battery consumption. Despit the above shortcomings, the authentication and authorization mechanism used in WiMAX is still very promising.

• Accounting

Accounting is dealt with the management section where service is procured and delivered to the business owners and individual users. The issue is that the broadband wireless service provider needs to establish a facility-based metropolitan-area scalable, secure wireless broadband offering to be wholesaled through ISP channel partner. This is usually done by the deployment of low-cost WiMAX wireless technologies to provide broadband data services that are customized to support the access requirements of residential, small/home office, and business-class subscribers. The solution includes:

- The implementation of AAA functions using specialized wireless gateways and routers that interfaced to different back-end RADIUS servers and accounting systems.

- The configuration of 802.16-based wireless equipments are required to provide customers with broadband data services using CPE-based wireless access for end-users. WiMAX itself benefits form an urban-scale 802.16 wireless coverage without using specialized wireless access equipment.

- The configuration of 802.16 equipments provide wireless backhauls to extend telecommunication access to and from 802.16 wireless network hubs and customers.

- Enabled support for multiple security mechanism for securing and encryption wireless communication using PPTP/MPPE, L2TP/IPSec, and 802.1x security protocols.

- Installation and configuration of routers, gateways, network switches, and other equipment required to ensure scalable and reliable network infrastructures.

- Construction of internet and web services providing portal-based subscriber-management functions.

- Configuration of Windows and Linux servers to manage security policies and provide for network operating functions - DHCP, DNS, VPN and WVPN termination, routing, certificate management, web servers, and etc.

- Verification of range, functionality, and volume testing of wireless network deployments in order to validate performance and capacity models.

- Performance testing of Windows client software configurations and network-interfaces cards to ensure the supportability of multiple client configurations and equipment; Intel, Netgear, Linksys, Proxim/Orinoco, DLink, Cisco, IBM/ActionTec, etc.

- Development of specialized wireless-access-point management software using http and automated CLI-based interfaces as required enabling remote configuration and management of wireless equipment.

- Development of specialized SNMP-based network tools to optimize the pointing direction of 802.16 antennas during the installation of wireless customer premise equipment and wireles point-to-point backhauls.

- Development of web-accessible reporting tools used to provide analytical information for network performance monitoring and providing summarized usage information, or on a per-subscriber basis.

- Construction of training materials and providing training to network support staff using real-life environments that simulated various network failure and response scenarios.

In conclusion, it is obvious that WiMAX has far greater security authentication than WiFI, which indicates WiMAX has the potential to achieve greater market success than WiFi. However the perception of their safety will have to be high before they win the trust of enterprise and carrier users. The challenge is that the greater range and available bandwidth in WiMAX also increase the potential for attackers and the impovement in security schemes can also come at a price; increased processing power and the need to support public key certificates.

WiMAX Services and Interworking with 3GPP Based on IMS..

WiMAX Forum members are working with other industry groups, including the Wi-Fi Alliance, to enable seamless handoffs between multiple wireless standards, furthering the development of a cohesive wireless ecosystem. WiMAX Forum is also collaborating with groups like 3GPP on implementing IMS with WiMAX networks.

The 3GPP specifies the IP multimedia subsystem (IMS) to provide several kinds of multimedia services in UMTS Release 5 and later releases. Interworking at the service layer between 3GPP and WiMAX networks requires interworking between IMS functionality. By studying several interconnection scenarios and the main functionality of IMS, WiMAX can support different levels of services. Special attention is paid at the session negotiation level, using SIP, COPS/Go and Diameter protocols/interface to provide session negotiation with QoS and AAA (authentication authorization accounting) support.

Future mobile communication networks are evolving from traditional circuit-switched architecctures to an all-IP based structure. It is suggested that the mobile networks should be integrated by a high-bandwidth IP-based core network and a variety of wireless access technologies such as UMTS or WiMAX. Mobile terminals will be able to access different multimedia applications and advanced services while roaming across zones covered by different access technologies. Currently, 3GPP is developing a feasibility study on providing seamless service continuity between UMTS and WLAN.

Interworking between diffeernt networks can be viewed from different aspects. The most important aspect is the session negotiation level, which provides service continuity from the user perspective. At this level, the protocol used by 3GPP is Session Initiation Protocol (SIP), which is the foundation of the IMS architecture defined to support real-time multimedia services in future mobile networks.

The levels of convergence may be classified into convergence of service, network and technique. The goal is to share a service system based on interworking. Providing a uniform service experience for users, through a uniform service system, would enable customers to use different terminal devices to access heterogeneous networks, to access the same service, and to achieve common billing and session management. Service convergence is the first step of the convergence. Seamless roaming and handoff between different networks is the main problem. There are significant differences between the PHY technique of 3GPP and WiMAX.

• IMS Architecture

Within the UMTS core network, IMS is defined by the 3GPP as the component that provides support for multimedia services (e.g. voice and video) based on packet switching with QoS and the provision of AAA. The above figure shows a general view of IMS architecture. From this we can appreciate how the core network is organized in two networks: a signaling or control network and a data or transport network. The signaling network is composed of a set of call session control function nodes (CSCFs). They are signaling proxies whose task is to establish, modify and release media sessions with guaranteed QoS and AAA and charging support.

Note that user equipment (UE) gains access to the IMS via UMTS terrestrial radio access network (UTRAN), which is responsible for providing access for mobile stations and managing terminal mobility. SIP, COPS, and Diameter are the major protocols involved in this architecture.

• Interworking arthitecture and interworking level
  

1. Two interworking modes

There are two methods for WiMAX networks to interwork with other wireless networks: loose couple and tight couple. There is little difference between loose couple and existing networks; WiMAX utilizes the AAA server of 3GPP network, and data streams are not passed through the core network of 3GPP. This methods guarantees the independence of WiMAX network, however it results in high handover latency between two networks. Therefore, it is not suitable for real-time services.

In tight couple mode, the data streams of WiMAX must pass through the RNC and the core network of 3GPP, so each of the existing networks must modify their protocols, interfaces and services to meet the requirements of interworking. The BS of WiMAX connects with RNC of WCDMA or SGSN directly. The advantage of this mode is that it reduces the handoff latency and guarantees seamless handoff. If different operators own both 3G and WiMAX networks, the integration would be troublesome for the open of network interface.

2. Interworking levels

WiMAX is commonly used to transport IP packets. Thus 3GPP-WiMAX interworking should be built on the top of the IP protocol and not be limited to a specific WiMAX technology.

Different interconnection levels must be defined to represent different operational capabilities. These levels are suitable for either interworking mode.

Six interconnection levels between WLAN and 3GPP were taken into consideration., as well as the operational capabilities of each of them, based on the interconnection levels. The interworking is not limited to 3GPP and WLAN, but also includes the internetworking between 3GPP and other wireless access technologies based on IP. To maintain consistency, interworking with WiMAX networks must be based on the same model as shown in the following table.

3GPP has included the first three level s in Release 6, and the last two will be developed in future releases. The first level is the simplest and includes common billing (the customer receives just one bill for usage of both 3GPP and WiMAX services) and common customer care. It does not have any impact on either 3GPP or WiMAX architecture. The subscriber is charged on the same bill for usage of both 3GPP and WiMAX services. Customer care will be ensured independently of the connecting platform.

The second level (3GPP system-based access control and charging) includes the usage of the 3GPP access procedures (including authentication and authorization) for WiMAX users within the 3GPP domain. In addition, Wimax nodes use UMTS charging systems for charging data records generation. A subscriber may use the WiMAX Access network to access the Internet, for example, but AAA operations are handled by the 3GPP platform.

The third level extends the IMS services to the WiMAX. However, it is a matter of implementation as to whether all services are provided or just a subset of the services. This scenario lacks service continuity, so the user must re-establish the session in the new access network. Continuity is considered in this context as the ability to maintain an active service session when moving from one access network to another (e.g. between WiMAX and UTRAN) at the signaling level, without considering a transport level-related continuity issue like bandwidth or packet loss. Level 3 allows the operator to extend 3GPP system PS based services to the WiMAX network. In this scenario, an authenticated 3GPP subscriber can access 3GPP PS services through a WiMAX access network by interworking with its 3GPP PLMN (non roaming case) or with a visited 3GPP PLMN (roaming case).

The last three levels are not considered by the 3GPP in Release 6 and may be developed in future releases. The fourth level introduces service continuity, although the handover process may be perceptibel to the user (due to data losses or delays). The fifth scenario provides seamless continuity, with no noticeable service interruption greater than that perceived in intra-3GPP handovers.

3. QoS guarantee

Due to the differences in the network bandwidth, providing users with a constant level of service is not feasible. The goal of QoS guarantee is to offer suitabel quality of service in the given network, in accordance with user's QoS profiles and application require,ents. The QoS guarantee involves the task of mapping the QoS parameters from P-CSCF, GGSN, PDF, QoS negotiation, and the resource reservation methanism.

UMTS defines four classes of QoS services based on different application requirements: conversational, streaming, interactive, and background. WiMAX also defines four classes of QoS: UGS (unsolicited grant service), real-time polling service, non-real-time polling service and BE (best effort). According to the application scenario, QoS class mapping can be implemented according to the mapping relation mentioned according to the mapping relation. The conversational and streaming services of UMTS correspond to the UGS and rt-PS services in WiMAX. The interactive service can be mapped to nrt-PS and BE services in WiMAX in different application scenarios. However, the background service in UMTS has the same requirement and application scenario as the BE service in WiMAX.

QoS negotiation between session peers is performed using the SIP offer/answer model, in which each session peer offers its QoS capabilities using Session Description Protocol (SDP) descriptions in the message body.

The following figure shows the architecture of QoS-enabled interworking based on COPs.

The PCF communicates with the GGSN via the Go interface. It enables two modes of operation. In the push mode, the PCF initiates communication with the PEP and sends the decision to GGSN. In the pull mode, the GGSN initiates communication with the PCF to request a decision for a particular IP flow.

In summary, SIP is the key signaling protocol of IMS. Interworking between SIP elements of the WiMAX and CSCFs of the IMS is a key issue in reaching a high level of interworking between WiMAX and 3GPP networks. Here the overall architecture of the interworking based on IMS is represented, as well as special issues such as QoS guarantees are discussed.

The Competition between WiMAX & 3G and WiMAX Technology Development Trend..

As the fourth generation network, WiMAX system is expected to provide fixed wireless alternative to conventional DSL and Cable Internet.

The competition between WiMAX and 3G:

Before the December of 2005, WiMAX and 3G played their own roles. WiMAX focused on fixed wireless broadband, while 3G was planned to take place of 2G (GSM) mobile communicaiton. However after that, mobile communication of WiMAX standard: IEEE 802.16e came out which made the positions of WiMAX and 3G overlapping. Mobile WiMAX will firstly be used in laptops. Then the size and power will be further reduced in which way it can be used in PDA and more small size portable devices. Especially Mokia has announced that it will release WiMAX mobile phone in 2008 which shows that it is quite possible that Mobile WiMAX will be a new generation mobile communication, not only 3G in consideration.
At the same time, 3G is also trying to enhance its techniques to consolidate its domain. For example, 3G added HSDPA, HSUPA, etc. This increases the transmission speed in 3G data service and it encourages to use HSDPA in mobile devices other than mobile phones. Now there has already been HSDPA interface card for laptops. There is even built-in HSDPA when the devices are made. From this point of view, the competition between WiMAX and 3G has been quite obvious. Then which one will win the game?
As mentioned above, no matter it is WiMAX or 3G, the purpose and used techniques are identical. There is not much difference between them. In order to accelerate transmission, OFDM modulation must be used and MIMO technique must be used for sure. And the HARQ error control mechanism must be used to increase the spectrum efficience.
Except for the same improvement techniques, the implementation tempo between WiMAX and 3G is different. In all IP type and OFDM techniques, WiMAX is in front. Till now 3G still cannot realize all IP and it still has not implemented OFDM technique. As for MIMO and HARQ, 3G is in leading place. While for these two techniques, WiMAX has already included them at the end of 2005. So currently for pure ideal technology standard, WiMAX is superior to 3G.
However, the above is all the comparison of existing facts. The competition on technique has extended to the future promise. 3G field has already had many development plans, including HSDPA, HSPA+, HSOPA, 3GPP LTE, etc. In these future plans, OFDM technique is also introduced and the all IP architecture will also be used. While for WiMAX, after the completion of IEEE 802.16e, there is not very clear further technology plan.
But in 2007, WiMAX will have new behaviors which are mainly the proposals of .16j and .16m. IEEE 802.16j is the standard of Relay Station for Mobile WiMAX. The other one is a proposal for ITU-R. ITU-R is making standards taking the place of IMT-2000 and IMT-Advanced which belongs to the 4th generation mobile communication standard. WiMAX Forum expects that WiMAX techniques can appear in the new standard and at the same time make sure the copatibility of Mobile WiMAX and 4G new standard.
For IEEE 802.16j, the companies of Nortel, Fujitsu and Taiwan give a lot of contributions in the working group.

WiMAX (IEEE 802.16e) Advantages and Disadvantages!

What are the disadvantages or shortfalls of WiMAX network for a corporate network, requiring high capacity and total control over the network? Should Point to point be a better option?

Here we will talk something about disadvantages of WiMAX technology. Common misconception is that WiMAX can offer 70 Mbps in range of 70 miles (113 kilometers) with moving stations. But in practice situation is very different. It is true only in ideal circumstances with only one recipient. You could have with line-of-sight (optical visibility) speed of 10 Mbps at 10 kilometers. In urban enviroment (without optical visibility) users can have 10 Mbps at 2 kilometers. If users are moving, the speed can drop significantly. Bandwidth is shared between users in given radio sector, so if there are many users in one sector, they will have reduced speed. Users could have 2, 4, 6, 8, or 10 Mbps of shared bandwidth. The biggest disadvantage of WiMAX is still much bigger installation cost and also operational cost.So let's put on paper WiMAX advantages and disadvantages.

Advantages:

1) Single station can serve hundreds of users.

2) Much faster deployment of new users comparing to wired networks.

3) Speed of 10Mbps at 10 kilometers with line-of-sight.

4) It is standardized, and the same frequency equipment should work together.

Disadvantages:

1) Line of sight is needed for longer connections.

2) Weather conditions like rain could interrupt the signal.

3) Other wireless equipment could cause interference.

4) Multiplied frequncies are used.

5) WiMAX is very power intensive technology and requires strong electrical support.

6) Big installation and operational cost.

WiMAX also has other disadvantages. Firstly it is very expensive. Normally it is used for corporate solution which is hard and expensive to find frequency license! So its disadvantage is the spectral limitation, in other words limitation of wireless bandwidth. For use in high density areas, it is possible that the bandwidth may not be sufficient to cater to the needs of a large number of clients, driving the costs high. It has less QoS and the speed is up to 70Mbps.

So what will be the solution for higher bandwidth (BW) requirements to the corporate sector for their intra-net? No operator wants to give all his available BW at a sector to a customer. It will not be cost effective to them. Also this is about unlicensed band. Licensed frequencies are definitely hard and expensive to buy.

If we talk about one corporate network, we'd better use 5.8Ghz or other frequency and fixed network, but not WiMAX! It has much higher throughput than WiMAX, because you can use 10Mhz for channel bandwith. It is available!

May we can go for lisence free band 2.4Ghz, 5.8Ghz. For backhaul links it is better to use WiFi, which can reach high throughput (37Mbps) in Point-to-Point links. And it has low cost and ther is no paid cannon radioelectric (use ISM band).

Regardless of what the WiMAX forum is telling us, the 2.5Ghz spectrum is only functional in urban area where it can leverage reflective surfaces and where it can have good line of site in rural markets.The basic unspoken issue here is how ineffective the 2.5Ghz systems are when addressing any type foliage, those horrible little things called leaves have a tendancy to absorb all RF in that frequency, such as trees and bushes, which means that most of the East Coast. If you talk to the vendor engineers out of the reach of the marketing/sales types they will agree with the above. Wait until the FCC releases the 700Mhz spectrum and then WiAMAX makes a great deal of sense, unless the Cell Carriers win the spectrum and control it.

The last, but not lease, disadvantage of WiMAX technology is that true standards-based large mobile network deployments will probably not occur very soon. In the meantime, solutions based on EV-DO, HSDPA, and various proprietary technologies have already become available.

VoIP & IPTV Applications in WiMAX..

A fixed wireless solution not only offers competitive internet access, it can do the same for telephone service thus further bypassing the telephone company's copper wire network. Voice over Internet Protocol (VoIP) offers a wider range of voice services at reduced cost to subscribers and service providers alike. The diagram below illustrates a typical solution where a WiMAX service provider can obtain wholesale VoIP services (no need for the WiMAX service provider to install and operate a VoIP softswitch).

In residential markets, VoIP is a "must offer" service. Without the additional revenue per user , WiMAX does not offer a compelling reason to switch from other forms of residential broadband. When bundled with broadband internet access and IPTV, a WiMAX triple play becomes very attractive to residential subscribers. Given the QoS, security and reliability mechanisms built into WiMAX, sub-scribers will find WiMAX VoIP as good or better than voice services from the telephone company.

Another powerful application in WiMAX, is Internet Protocol Television (IPTV). IPTV enables a WiMAX service provider to offer the same programming as cable or satellite TV service providers. IPTV, depending on compression algorithms, requires at least 1 Mbps of bandwidth between the WMAX base station and the subscriber.

In addition to IPTV programming, the service provider can also offer a variety of video on demand (VoD) services. The subscriber can select programming a la carte for their television, both home and mobile, viewing needs. This may be more desirable to the sub-scriber as they pay only for what they want to watch as opposed to having to pay for doz-ens of channels they don't want to watch. IPTV over WiMAX also enables the service provider to offer local programming as well as revenue generating local advertising.

Television as Key Application for WiMAX..

Nowadays, various kinds of applications which need high data rate, have enter the field of WiMAX systems. This will definitely enrich the life of WiMAX users. MobiTV, Inc., the global leader in mobile and broadband television and music services, announced the Company has joined the WiMAX Forum and will be leading its Proof-of- Concept trial with the mobile WiMAX network that will span a number of Northern California cities. A representative of MobiTV has been assigned to co-chair the mobile WiMAX Application POC initiative within the forum's Applications Working Group.

"MobiTV is strongly committed to a significant and ongoing investment in research and technology development to support the very latest wireless network technologies, and our service integration with WiMAX is a true industry-first," said Dr. Phillip Alvelda, CEO, chairman and co-founder of MobiTV. "This technology is powerful two-way and interactive wireless technology that will transform the television industry."

"We are delighted to have MobiTV join the WiMAX Forum ecosystem as a key member helping drive the development of new multimedia applications that satisfy the demands for personal broadband services by consumers around the globe," said Ron Resnick, president of the WiMAX Forum. "MobiTV is a pioneer in delivering mobile television and other multimedia content, and we look forward to their contributions as the industry works to create content-rich and high-bandwidth mobile services that will be possible with mobile WiMAX Forum Certified(TM) products."

The Northern California based Proof of Concept network will provide an environment to evaluate a variety of mobile WiMAX applications, including mobile television broadcast, video-on-demand, navigation and general network access. A second Proof of Concept network will be deployed in Taipei, Taiwan under the direction of the National Taiwan University.

"We have been working in partnership with several leaders in the wireless and technology industries to support this new network solution at MobiTV," said Ray DeRenzo, vice president of business development for MobiTV. "By participating in the WiMAX Forum and helping lead the task group for mobile television, we are confident that MobiTV will contribute to the success of this standard, and more importantly the rapid deployment of this powerful technology."

WiMAX and mobile WiMAX are the latest extensions to MobiTV's portfolio of supported network technologies, with features designed to support all of the key components that make mobile television viable to consumers and carriers alike. Those key features and benefits of the MobiTV service for WiMAX and mobile WiMAX include:

• Smooth integration with, and natural extension to existing service infrastructure
• Efficient full-duplex bi-directional delivery with full transactional capabilities
• Superior data delivery performance for full-motion video (due to its advanced IP based architecture)
• Support for a combination of Unicast and Multicast delivery models for optimal network utilization
• Full interactivity; which includes m-commerce, voting and other capabilities consumers, carriers and the advertising community wants
• Targeted national, regional, and local advertising
• There are no channel line-up limitations with WiMAX
• Increased channel change speed
• Broad client device support including: mobile phones, PDAs, laptops, set top boxes and more (radios in mass market devices)
• Broad industry support and open-standards based
• Support for the rapid deployment of new applications and services (extensions to the MobiTV service) at a low incremental cost

All these properties make the Television a very promising application in WiMAX system.

Mobile WiMAX Technology and Application in Industry..

This time I will describe something about WiMAX application in industry and provide some analysis on WiMAX application progress. This part will also give some advantages and challenges for mobile WiMAX and analyze its uncertainty in China. There are mainly 3 aspects: the 3G license is till not distributed; it is harder to find the spectrum for mobile WiMAX than fixed WiMAX; the technology selection may effect the whole development of Telecommunication field in China.

• WiMAX standard series:

IEEE802.16 is also called IEEE Wireless MAN air interface standard, which works between 2~66GHz wireless spectrum. Because the provided wireless system coverage can reach as large as 50km, so 802.16 is mainly used in Metropolitan Area Network (MAN). Based on whether mobility is supported or not, 802.16 standard can be devided into fixed and mobile broadband wireless access airlink.

After the publish of 802.16e standard, the Mobile Multi-hop Relay task group of 802.16j became one of the groups with most participation in IEEE 802.16. Through mobile multi-hop relay technique, it can increase the transmission rate, extent coverage range, and achieve obtaining uniform data rate property for users in the coverage. This property is quite likely to fulfill the requirements of future 4G mobile communication technology. While IEEE 802.16 MMR SG is the only organization which puts this technique into standard. This attracts a lot of industry companies to join in and participate and it also became a new direction in 802.16 standard.

The signal of wireless network base station has shadow fading effect because of the coverage area. This makes the effective coverage shrink a lot. In order to make sure the the user signal is still continuous when there is serious shadow fading, signal relay is used to solve the problem.

The advantages of mobile multi-hop relay:

• Low cost: relay station doesn't need the support of wired-line backhaul which reduces the cost of building backhaul network greatly. And the complexity and cost of relay station is much lower than base station. So although the effect provided may not be as good as adding a cell, it is still very attractive to operator for its low cost and flexibility.

• Selective power amplification: Different from the traditional analog power amplifier to amplify all the received signal, relay station will make digital process for received signal and amplify the power depending on situation. Furthermore, because when the relay station receives the signals, the interfering signals have already been dealt with. So when relaying signals, all the power on the signals needed to be relayed. While the signals don't need to be relayed, interfering signals will not be relayed as well.

• Multi-hop increasing coverage area: many neighboring relay staions can relay signals to farther away areas.

Relay task group has decided that this standard should be realized under the condition without modifying mobile station. Then the mobile station may not be able to recoganize the existance of relay staion. This is also one of the difficulties.

Mobile WiMAX production speeds up:

WiMAX forum plays an important role in WiMAX market. The approval of this forum and other work decide the possible future development and application of WiMAX. Nowadays the main work has totally moved to wireless WiMAX and speeds up to put technology in market. The time of approval and whether it is successful has relation with when the WiMAX devices will be on the market.

The approval of fixed WiMAX devices has started from the beginning of 2006. While because the approval of mobile WiMAX was postponed, it can only start at the end of 2006.

After all, big Telecommunication vendors all around the world tend to develop 802.16e devices. Especially in China, ZTE and Huawei have already given up the plan to make fixed WiMAX devices. There are also some other big companies such as Alcatel, LG, Motorola, Nokia, Samsung, Siemens and Nortel, working hard on this system.