"CDMA2000 1xEV-DO Accelerates Mobile Wireless Access" by Vedat Eyuboglu
Первоисточник: http://techon.nikkeibp.co.jp/NEA/archive/200306/249650/
CDMA2000 1xEV-DO Accelerates Mobile Wireless Access
While most industry attention has been focused on the slow deployment of third-generation (3G) mobile wireless networks based on Wideband CDMA (W-CDMA), a more powerful, but lesser-known 3G standard called CDMA2000 1xEV-DO (1x Evolution - Data Optimized) is being deployed around the globe.
The two most anticipated capabilities of 3G systems are: 1) significantly higher packet data speeds; and 2) the introduction of new wireless networks based on IP. 1xEV-DO networks are now offering both of these capabilities.
A properly engineered 1xEV-DO network can deliver average user data rates (download) of 300-600 kbits/s. Instantaneous data rates can be as high as 2.4 Mbits/s. Such data rates are achieved using only 1.25MHz of spectrum, which is one-quarter of what is required for W-CDMA, also known in Europe as Universal Mobile Telecommunication Systems (UMTS).
What Makes 1xEV-DO Faster?
In an IP-based 1xEV-DO network, illustrated in the Fig, the radio node (RN) performs RF processing, baseband modulation/demodulation and packet scheduling. RNs are installed in cell sites either as standalone units or as channel cards integrated into existing base stations and can support hundreds of subscribers. The radio network controller (RNC), typically located in a central office, provides handoff assistance, mobility management and terminal-level security via a radius server. Each RNC can support many RNs and connects to the operator's core data network through a standard wireless router called a packet data serving node (PDSN). The element management system (EMS) allows the operator to manage the 1xEV-DO radio network.
1xEV-DO takes advantage of a series of recent advances in mobile wireless communications. These include an adaptive modulation system that allows the radio node to optimize its transmission rate based on instantaneous channel feedback received from the terminals. This, coupled with advanced turbo coding, multi-level modulation and macro-diversity via sector selection, allows 1xEV-DO to achieve download speeds that are close to the theoretical limits of the mobile wireless channel.
1xEV-DO also takes advantage of a new concept called "multi-user diversity". This allows more efficient sharing of available resources among multiple, simultaneously active data users. Multi-user diversity combines packet scheduling with adaptive channel feedback to optimize overall user throughput by serving users when their channel condition is relatively good.
IP-Based 1xEV-DO Networks
A 1xEV-DO network is clearly distinguished from other 3G networks in that it is completely decoupled from the legacy circuit-switched cellular voice network (i.e., MSC, HLR, etc). This has allowed some vendors to build their 1xEV-DO networks based entirely on IP technologies. Using IP transport between the RN and RNC lowers backhaul costs by giving the operator a wide choice in backhaul services, including frame relay, router networks, metro Ethernet or wireless backhaul. IP-based 1xEV-DO networks also take advantage of off-the-shelf IP equipment such as routers and servers and use open standards for network management. The distributed nature of IP-based network architectures also increases scalability/reliability and greatly simplifies mobility management.
Its independence from legacy circuit-switched core networks makes 1xEV-DO suitable for deployment by any wireless operator (CDMA, TDMA or GSM).
Global Standard
1xEV-DO networks have the flexibility to support both user- and application-level quality of service (QoS). User-level QoS allows the operator to offer premium services to their most demanding customers. Application-level QoS allows the operator to allocate precious network resources in accordance with the application's needs. For example, application-level QoS allows the system to apply priority to delay-sensitive traffic such as Voice over IP (VoIP). Since the airlink is the primary bottleneck in wireless access, a flexible packet scheduling capability like the one built into 1xEV-DO is required to support QoS. Combined with Diff-Serv based QoS mechanisms, flexible 1xEV-DO packet schedulers can enable QoS within the entire wireless network.
1xEV-DO is recognized as an international standard by the ITU and 3GPP2. Numerous 1xEV-DO subscriber devices are now available from multiple device vendors around the globe. These devices come in various form factors including multimedia-enabled handsets, PC cards, PDA modules and fixed wireless terminals. All 1xEV-DO devices will also support CDMA2000 1x and new devices that will be available later this year will also support GSM/GPRS.
Multi-mode 1xEV-DO terminals that support CDMA2000 1x voice, will allow subscribers to receive an incoming CDMA voice call, even when they are actively downloading from the Internet using 1xEV-DO.
Getting Deployed Globally
Existing CDMA operators can deploy 1xEV-DO by adding a channel card to their existing basestations. Since 1xEV-DO does not require a cellular switch, it is relatively low-cost to deploy even for operators who do not have a CDMA network. 1xEV-DO has already been deployed by two large CDMA operators in Korea; SK Telekom and KT Freetel. These operators are now offering a number of innovative multimedia services on 1xEV-DO, such as music/video streaming, videophone and news TV broadcast. Vesper, in Brazil, and Monet Networks in the US, have launched high-speed Internet access services based on 1xEV-DO primarily geared towards homes and small businesses.
The largest CDMA operator Verizon Wireless has recently announced plans for the first North American commercial service for mobile users in the third quarter of 2003. Similarly, KDDI, the largest CDMA operator in Japan, plans to broadly rollout its 1xEV-DO service around the same time. Many other wireless operators are currently conducting 1xEV-DO trials and some have publicly announced plans for 1xEV-DO deployments.
Complementary to Wi-Fi
Recently there has been growing interest in wireless LAN technologies, especially in 802.11, also known as Wi-Fi. Low cost of equipment and wide-availability of subscriber devices in laptops has led to a proliferation of Wi-Fi in homes for home networking and in the enterprise for in-building mobility. Many wireless and wireline operators around the world are also experimenting with Wi-Fi, and exploring the possibility of offering Wi-Fi access in public hotspots. So far, however, businesses that offer Wi-Fi in public hotspots have not been successful, partly due to limited coverage and cost of backhaul.
While it is capable of supporting high-speed Internet access with full mobility at pedestrian or vehicle speeds, 1xEV-DO is equally powerful for serving hotspots such as hotels, airports and coffee shops. Therefore, with growing adoption of 1xEV-DO, we predict the need for public Wi-Fi hot spots will decrease. However, Wi-Fi and 1xEV-DO are certain to play a complementary role, as Wi-Fi serves the enterprise and home networking markets, while 1xEV-DO provides the wide-area mobile data coverage.
Although the current implementations of 1xEV-DO are geared toward high-speed wireless data applications, with new enhancements that are being added, it is on its way of becoming an all-purpose IP-based air interface that can efficiently support any kind of IP traffic, including delay-sensitive multimedia traffic such as VoIP.
Other enhancements are also being developed for 1xEV-DO, including a much faster reverse link, with peak user rates in excess of 1 Mbit/s, and a broadcast capability to support applications such as news/music/video distribution and advertising. Advanced chipsets that support 1xEV-DO will also be able to support 1x voice and 1xEV-DO simultaneously, to allow a user to maintain a phone conversation while accessing the Internet at broadband speeds.
In summary, 1xEV-DO is on its way to becoming the wireless technology that will finally make wide-area high speed wireless Internet a reality.
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