Multi-Carrier and Spread Spectrum Systems: From OFDM and MC ...

276 ApplicationsTable 5-42 Estimated data rate in mobile environment, TDD, 10 MHz [33]Cases DL: 28 data symbols DL: 22 data symbolsUL: 9 data symbolsUL: 15 data symbolsAntenna Link Sector Spectral Sector Spectralthroughput efficiency throughput efficiencySIMO DL 8.8 Mbps 1.19 bit/s/Hz 6.6 Mbps 1.07 bit/s/HzUL 1.38 Mbps 0.53 bit/s/Hz 2.20 Mbps 0.57 bit/s/HzMIMO DL 13.60 Mbps 1.84 bit/s/Hz 10.63 Mbps 1.73 bit/s/HzUL 1.83 Mbps 0.70 bit/s/Hz 3.05 Mbps 0.79 bit/s/Hz5.4 Future Mobile Communications Concepts and Field Trials5.4.1 ObjectivesBesides the introduction of new technologies to cover the need for higher data ratesand new services, integration of the existing technologies in a common platform isan important objective of the next-generation wireless systems, referred to as IMT-Advanced.The design of a generic multiple access scheme for various wireless systems is challenging.The new multiple access scheme should (a) enable the integration of existingtechnologies, (b) provide higher data rates in a given spectrum, i.e. maximize the spectralefficiency, (c) support different cell configurations and automatic adaptation to the channelconditions, (d) provide simple protocol and air interface layers, and, finally, (e) enablea seamless adaptation of new standards and technologies in the future.Especially for the downlink of a mobile communications system, data rates of 1 Gbit/sare targeted with IMT-Advanced. Therefore, new physical layer and multiple access technologiesare needed to provide high speed data rates with flexible bandwidth allocation. Anext-generation low cost generic radio interface has to be operational in various mixed-cellenvironments with a scalable bandwidth and data rate.5.4.2 Network Topology and Basic ConceptAn adaptive and flexible concept for a cellular system based on multi-carrier transmissionhas been proposed by NTT DOCOMO. The concept has been proven by several fieldtrials. The generic architecture allows a capacity optimization with seamless transitionfrom a single-cell to a multi-cell environment.5.4.3 Experiments and Field TrialsA series of successful experiments and field trials based on innovative OFDM schemeswith challenging data rate and throughput values have been performed by NTT DOCOMO.The series of experiments and field trials ranged from 100 Mbit/s in 2002 up to about5 Gbit/s in 2006. The achieved maximum data rate in the field trials together with thecharacteristic system parameters are summarized in Table 5-43.