 plans additional trials of Flash-OFDM and WiMax in 2006. Sprint Nextel expects to offer 4G services to the top 100 U.S. markets by 2008. Some countries have already begun cooperating on 4G standards. In late 2005, Japan and China signed a memorandum to work together on 4G. Japanese carrier NTT DoCoMo claims its 4G prototype phones can receive data at 100Mbps while moving and at 1Gbps while standing still; at these rates, an entire DVD could be downloaded within a minute. DoCoMo's current 3G phone network offers down- load speeds of 384Kbps and upload speeds of 129Kbps, and the company plans to have a 4G network in place by 2010. The technology behind NTT DoCoMo's high- speed phone network remains experimental, but the 4G tests used a method called Variable-Spreading-Factor Orthogonal Frequency Code Division Multiplexing (VSF-OFCDM), which increases downlink speeds by using multiple radio frequen- cies to send the same data stream. MIMO was also used to further increase data capacity (e.g., by sending data via various routes across a network); it can enable a mobile phone to receive data from more than one base station in range. 4G should support a wide range of data rates, including at least 100Mbps peak rates in full-mobility wide area coverage and 1Gbps in low-mobility local area COV- erage. The 4G vision includes asymmetrical and symmetrical services. It provides for QoS for real-time services, supports streaming audio and video, and provides an efficient transport of packet-oriented services, as well as a vision that supports Chapter 14 Wireless WANs broadcast and distribution services. It supports smart, adaptive antennas and uses an adaptive modulation or coding scheme. One of the main concerns about 4G is that the high frequency suggests that it will experience severe interference from multipath secondary signals reflecting off other objects. VSF-OFCDM is one of the proposed solutions to this problem. As an IP-based network, 4G will be rolled out using IPv6, which is gradually making its way into telecomm