1 Introduction
At present, in major communication exhibitions and technical forums, two post-3G technologies-HSDPA and WiMAX are becoming the new technical focus.
In the cellular mobile communications camp, as the proportion of data services continues to increase, mobile communications are evolving toward providing wireless high-speed data services, and mobile communication equipment manufacturers have accordingly optimized the system structure to continuously increase the data transmission rate. For example, the evolution route of GSM, the transmission rate from GPRS 40kbit / s to EDGE 130kbit / s and UMTS 384kbit / s and the upcoming HSDPA3Mbit / s development, and finally achieve mobile broadband for voice and data. In another camp, some major equipment manufacturers in the industry expect to use WiMAX standard for fixed data communication (such as DSL), that is, to increase wireless mobile access function in cable communication, allowing voice communication to be transmitted through IP, and under WiMAX Adding mobility in one step of expansion will eventually enable WiMAX to achieve mobile broadband for voice and data. HSDPA and WiMAX have their own advantages in terms of standards, technical characteristics and market positioning. They also show the difference between broadband mobile communications and wireless access to broadband networks. The relationship between the two has also aroused heated discussion in the industry. Is it a competitive relationship or a complementary relationship? This article compares and analyzes the technical characteristics, standards, market development and application of the two technologies, elaborate their respective advantages, and finally Analyze and summarize the relationship between the two technologies, and put forward several problems that still need to be resolved in the practice of new technologies.
2. Technical characteristics of HSDPA
In 3G applications, the main business and income of operators will come from data services. In the data service, everyone is particularly optimistic about video streaming and background download services, but these services have very high requirements on the downlink transmission rate. However, the current WCDMA network downlink transmission rate is theoretically 384kbit / s, and the rate in the actual environment is 150-250kbit / s, which is far from meeting the requirements. Operators urgently need to increase the transmission rate. HSDPA (High Speed ​​Downlink Packet Access) is a wireless solution proposed in Release 5 of 3GPP. The theoretical transmission rate can reach 14 Mbit / s. HSDPA is naturally evolved on the 3GPP R99 / R4 network structure, and is proposed to meet the asymmetry of the uplink / downlink data services. The key technologies adopted by HSDPA include adaptive modulation coding (AMC), hybrid automatic repeat request (HARQ), separate shared channel and fast scheduling (Fast Scheduling). AMC selects the appropriate modulation and coding method according to the change of the wireless channel, so that users can achieve the highest possible data transmission rate. Different combinations of coding and modulation methods produce different transmission rates. HARQ provides accurate coding rate adjustment based on channel conditions and can automatically adapt to instantaneous channel conditions. HSDPA combines AMC and HARQ technologies to achieve better link adaptation. HSDPA technology adds a high-speed downlink shared channel (HS-DSCH), and different users share the HS-DSCH channel in time and codeword space. Scheduling algorithms control the allocation of shared resources. Scheduling is mainly based on channel conditions, while considering the amount of data waiting to be sent and the priority of the business. In order to better adapt to the rapid change of the channel, the HSDPA technology places the scheduling function unit on the NodeB instead of the RNC, and also shortens the TTI (Transmission TIme Interval) to 2ms. When using 10 types of mobile phones, the theoretical peak user rate can reach 14Mbit / s. Since HSDPA is an enhanced technology in the wireless part of the WCDMA network, there is no need to upgrade and change the equipment of the WCDMA core network. Welcome to reprint, this article comes from the electronic enthusiast network (http: //)
3. Technical characteristics of WiMAX
WiMAX is also known as the IEEE802.16a standard, which is Worldwide Interoperability for Microwave Access. It uses the 10-66GHz frequency band and is a new air interface standard proposed for microwave and millimeter wave bands. WiMAX is a wireless metropolitan area network (WMAN) technology, as a wireless extension technology for cables and DSL, to achieve wireless broadband access. At the beginning of the design, 802.16 is a broadband technology standard positioned for fixed wireless transmission. At present, the IEEE certifications that the WiMAX organization has passed are 802.16a and 802.16d (also called 802.16 2004), which do not include mobile features. And 802.16e will increase the mobility of 2-6GHz licensed frequency band on the basis of the original 802.16a. By introducing 0FDM (Orthogonal Frequency Division Multiplexing) technology, it can effectively combat the multipath effect of microwave broadband transmission, thereby ensuring 802.16e access Incoming devices can roam between base stations, thereby enabling end users to improve the previously fixed access method and have the ability of nomadic mobile roaming. Therefore, WiMAX has become a new generation of WMAN broadband wireless access standard.
4. Comprehensive comparison of HSDPA and WiMAX
Although the theoretical transmission rate of WiMAX is much greater than that of HSDPA and the theoretical coverage is larger than HSDPA, in fact, if we simply compare the transmission rate and coverage, it is very one-sided and subjective. In fact, the two are fundamentally huge. difference.
(1) Data transmission rate and coverage
HSDPA technology will eventually be able to provide a transmission rate of around 20 Mbit / s for systems using MIMO smart antenna technology on the 5 MHz band. In an ideal state, the maximum transmission rate of WiMAX technology in the range of 50km is 70Mbit / s.
(2) Mobility and network roaming
Although WiMAX provides a high transmission rate, it prefers nomadic use at fixed locations, has poor mobility, and lacks handover / roaming capabilities. However, 802.16e is a mobile WiMAX standard that adds certain mobile functions. Since the 3G / HSDPA mobile communication network was designed to support fast handover / roaming, the actual deployed wireless network can meet high-quality seamless coverage, which makes its cell radius much smaller than WiMAX, and the investment is much larger than WiMAX, which is also At present, some people claim that WiMAX is one of the reasons for the end of 3G. However, from the perspective of the technology itself, WiMAX does not yet have wide-area roaming, security features, terminal portability and other mobile features of public mobile communication networks like 3G / HSDPA, which will eventually limit its application as a public mobile communication.
(3) Maturity of technical standards
Although WiMAX technology has become a new hotspot, WiMAX-compatible devices have not yet appeared on the market. The American IEEE has not yet approved the mobile WiMAX standard-802.16e. The official approval of IEEE is expected to be at the end of 2005, and the official product may be available until 2007. According to market analysts and equipment supplier analysis and prediction, it will take years from the advent of mobile WiMAX chips to the transformation of cheap products into embedded laptops. The HSDPA standard has been determined in R5, and the basic standard has been frozen. Especially recently, various communication equipment manufacturers, including Nortel, Ericsson and Nokia, have completed some business demonstrations on HSDPA. With the continuous introduction of terminals, in With the cooperation of operators, the commercial time of HSDPA may be realized before the end of 2005.
(4) Wireless spectrum
Foreign operators have already auctioned 3G licenses, and domestic operators have also invested a lot of manpower and financial resources in the preliminary work of network construction in order to obtain 3G network frequency operation licenses. The WiMAX wireless spectrum may be free. For operators who apply for less than 3G frequencies, this is one of the reasons they favor WiMAX. However, the main problem of WiMAX is that there is no unified global frequency band, so the entire industry is currently committed to the unification of WiMAX frequency bands, at least a few limited options are formed to avoid the emergence of various spectrums in the traditional wireless broadband market 2. The situation where various structures are full, otherwise it will lead to a small market and high cost, which will affect the popularization of applications. HSDPA is a wireless enhancement technology based on the WCDMAR99 / R4 network. It still uses the WCDMA spectrum without additional spectrum resources. When the initial high-speed data traffic requirements are not high, it can also be co-carrier with R99.
(5) Market application positioning
The basic market positioning of the 3G / HSDPA network is to provide public voice and multimedia services to enable global, regional and national roaming of personal mobile terminals. The typical application of HSDPA is Internet browsing and video on demand. In the long term, WiMAX market positioning can support "last 1km" and portable broadband wireless, effectively extend WLAN connections, and is more suitable for deployment in areas where xDSL and CableModem, such as suburbs, rural areas, and edges, cannot effectively cover areas. The enhanced and improved 802.16e standard on the basis of 802.16a is more helpful for effectively extending the connection of WLAN, and the realization of walking speed has limited switching capabilities, mainly for home access and enterprise markets, with large capacity. In short, HSDPA aims to cover a wide area, while WiMAX is more targeted at core urban areas.
(6) Market development
The commercialization of HSDPA was first implemented in Asia. Operators in the United States and Europe are also discussing that HSDPA will enter the stage of commercial construction from 2006. Relatively speaking, as the leader of WiMAX, Intel believes that it will take some time for mobile 802.16e to come out, and technical tests will be conducted in the second half of 2006, so the commercialization of 802.16e version will be significantly later than HSDPA. It is also reported that South Korean fixed telephone operator KT has decided to launch the WiBro plan in April 2006, which is a commercial network based on 802.16e, and plans to cover 10 cities such as Seoul and Busan by the end of 2006, and plans to cover the whole country by 2008 84 major cities; South Korean mobile operator SKT also plans to launch the WiBro program in June 2006, which will take 4 years to bring the network to 84 cities across the country. This is undoubtedly good news for the WiMAX camp.
In addition, there is a big difference in cost between the two technical devices. HSDPA does not require any new network equipment, but only smoothly upgrades the software on the basis of the existing WCDMAR99 network; WiMAX requires brand new network equipment.
5. The relationship and prospect of the two technologies
Recently, the discussion about the dispute between WCDMA and WiMAX has become increasingly fierce. Some believe that the two are gathering together, and there will inevitably be competition. Others believe that the two are technologies in different fields that complement each other in the application market.
Those who hold a view of competitive relations believe that although there is no direct conflict between the two, HSDPA focuses on mobile data and voice services, and WiMAX focuses on wireless broadband data access for enterprise users, which is not available for enterprises and businesses. Provide broadband services in the region. However, HSDPA, which focuses on the wireless broadband access market, will have an impact on the WiMAX position. The data rate and cost advantages of WiMAX derived from IP technology are beyond the reach of HSDPA. With the increasing demand for data from mobile end users, The two must form a competitive relationship with each other. Although WiMAX requires new network equipment, the initial investment and time are longer than HSDPA, but once the network is implemented, WiMAX can provide a higher rate. The most important thing is that WiMAX is based on the IEEE802.16 standard and adopts an open mode. It has obvious cost advantages compared with 3G / HSDPA developed using traditional proprietary routes. At the same time, because of the low entry barrier of the WiMAX industry, it can quickly introduce competition . After all, the two technologies are competing for the same user group. WiMAX will definitely pose a threat to 3G / HSDPA, because both are future-oriented and provide high-speed mobile data services.
But most people believe that the two have different market positions, each with their own technological advantages, and the complementary relationship is more appropriate. HSDPA can fully support the bandwidth equivalent to WiMAX, and also has complete mobility that WiMAX can't match, as well as an extensive industry chain and end user base. Therefore, WiMAX will be mainly used as a supplement and replacement for fixed broadband access, and the complementary relationship between the two can be refined to service coverage areas, terminals, and mobility. HSDPA implements a wide coverage of macrocells to meet users' enjoyment of services in various mobile environments and achieve global roaming; WiMAX is a MAN wireless metropolitan area network, which is based on the Internet and provides nomadic mobile access through multi-point base stations. Application services, such as walking and in the office, have the advantage of higher bandwidth and better stability to connect Wi-Fi hotspot areas. In terms of terminals, HSDPA is mainly a mobile phone to support voice services; WiMAX is a PDA and a portable computer to support high-speed data services. In terms of mobility, HSDPA can support the rapid movement of users, while WiMAX only supports limited low-speed mobility in subsequent versions of 802.16e.
Although the two can complement each other, the fact that is not optimistic is that it is too early to predict the success of WiMAX. In terms of standards, the 802.16e standard has not yet been finalized, and there is still a long way to go before it is truly commercial. The WiMAX standard does not define the core network specifications, and interoperability testing between devices of various manufacturers takes time. In addition, there are many uncertainties in business operations. At the same time, WiMAX also needs a complete solution and a new constructive business model relative to Wi-Fi. If dual-mode terminals (supporting HSDPA and WiMAX) appear, the interconnection of the two networks and joint billing should also be considered.
6. Summary
All in all, because WCDMA / HSDPA already has the mobility, security, and payment infrastructure required for mobile communications, and considering the cost of network construction, user costs, and the cost of applying technology to mobile phones, HSDPA has obvious cost advantages, so HSDPA is more suitable for large-scale, full-mobile wireless high-speed data services, and WiMAX is suitable for providing high-speed and high-stability access in a low-speed environment. The two technologies have different perspectives, and there are differences in service user groups, business categories, and mobile ranges, but the two can complement each other and develop in harmony. Although there is inevitably overlap and competition in coverage and business, it is precisely because of the existence of overlapping intersections that users can be guaranteed effective communication anywhere. Welcome to reprint, this article comes from the electronic enthusiast network (http: //)
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