ired FDD Spectrum Base Station FDD Spectrum FDD Spectrum Wireless Mobile Broadband Network Card Chipset Compact Flash Figure 15.1 An example of a Flash-OFDM network because both the forward link and the reverse link are fully scheduled. Flash- OFDM's link-layer fast retransmission mechanism reduces the required safety margin in transmission power, thereby improving capacity while supporting interactive data applications. Flash-OFDM's highly reliable link quality makes upper-layer protocols (such as TCP/IP) perform efficiently, replicating the wired environment. Many other wireless technologies have a tendency to promote inefficient use of radio resources via Internet flow control protocols. The key is Flash-OFDM's use of the wideband spread spectrum technology fast-hopped OFDM, which uses multiple tones and fast hopping to spread signals over a given spectrum band. Fast hopping enables more users for a given spectrum, and orthogonality means less interference. Flash-OFDM offers an enhancement to traditional OFDM, but it requires new equipment, including new base stations, which may offset the reduced cost per subscriber. The industry was watching closely as Flarion began trials with Nextel, and some of the preliminary data was encouraging in support of the claims of Chapter 15 WMANs, WLANs, and WPANs speed, reliability, QoS, and cost. However, the merger of Sprint and Nextel resulted in Nextel canceling the trials and any further work with Flash-OFDM. This is surprising considering that Sprint is committed to CDMA, and Qualcomm is now looking to Europe and Asia for new business partners. DMB is a new concept in multimedia mobile broadcasting service, converging broadcasting and telecommunications. It is a digital transmission system for send- ing data, radio, and TV to mobile devices such as mobile phones. Because DMB allows users to view content via mobile phones anytime, anywhere, even while moving at high speed, it is likely to change the way broadcast media is consumed, creating a new cultural trend. The move