IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 47, NO. 1, FEBRUARY 1998 133 Modulation and Coding for Mobile Radio Communications: Channels with Correlated Rice Fading and Doppler Frequency Shift Ezio Biglieri, Fellow, IEEE, Marco Di Sciuva, and Valerio Zingarelli, Member, IEEE Abstract— We discuss the relative performance of coherent phase-shift keying (PSK), differential PSK (DPSK), and double- differential PSK (DDPSK) modulation schemes over a mobile- radio channel in which transmission is affected by additive noise, a constant carrier phase offset, a constant Doppler frequency shift, and correlated Rice fading. We first compare the performance of these schemes to assess the amount of degradation caused on each one of them by fading. Among our findings, we observe that DDPSK turns out to be less sensitive to the effects of correlated fading than the other two schemes and that in these conditions interleaving may not be beneficial. We then consider the introduction of trellis-coded modulation (TCM). The system we advocate as offering the best tradeoff between performance and complexity with the channel model assumed here includes double-differential encoding, differential detection, an open-loop Doppler phase tracking circuit, and differential decoding in addition to a simple TCM scheme. Index Terms— Fading channels, modulation/demodulation, trellis-coded modulation. I. INTRODUCTION AND MOTIVATION OF THE WORK T HE RAPID growth of mobile radio and of its applications to cellular terrestrial, cordless, paging, aeronautical, and satellite communications is pushing the international regula- tory bodies, telecommunications operators, and telecommuni- cation industry to analyze the possibility of globalization of systems and services on one side and to define architecture and characteristics of the future third-generation systems, such as the universal mobile telecommunications system [5], [13] (UMTS) and mobile broadband system [6] (MBS) on the other side. Near-term globalization means providing the users with dual- or multiple-standard terminals, viz., GSM900 and DCS1800, GSM900 and DECT, GSM900 and CDMA, or GSM900 and a mobile satellite transmission standard, etc. This would allow the user to operate his terminal in countries having different systems (for example, in Germany, where both GSM900 and DCS1800 are operational) or also to guarantee international roaming to countries with different systems (for example, from Italy to the United States). Manuscript received May 30, 1995; revised September 3, 1996. E. Biglieri and M. Di Sciuva are with the Dipartimento di Elettronica, Politecnico, Torino, Italy. V. Zingarelli is with Omnitel Pronto Italia, Ivrea, Italy. Publisher Item Identifier S 0018-9545(98)00682-3. Long-term third-generation systems, such as UMTS and MBS, imply also the possibility to use the same mobile terminal everywhere and in any environment and at any speed. UMTS offers an opportunity to exploit the 2-GHz bands with a unified and universal personal mobile telecommunications system for multioperator environments. It is a multifunction multiservice multiapplication digital system that will use end- of-the-century technology to support universal roaming and offer broadband multimedia services requiring up to 2-Mb/s throughput. It is expected to have both a terrestrial and a satellite capability with an appropriate level of commonality between them, including the radio interfaces. The main targets envisaged for UMTS are: integration of residential, office, and cellular services into a single sys- tem based on one piece of user equipment; speech quality comparable to that achieved with the current fixed network; service capability up to multimedia; separation of service provision and network operation; unique UMTS user number independent of network or service provider; capacity and capability to serve more than 50% of the population; seamless global radio coverage; radio bearer services up to 144 kb/s and further to 2 Mb/s; radio resource flexibility to allow for competition within a frequency band; high-spectrum utilization efficiency; creation of direct satellite access; use of a new global frequency band; and low-cost services and terminals. Beyond the service flexibility of the radio link, the UMTS radio system is required to provide seamless indoor/outdoor operation by using terrestrial pico and microcells in outdoor and rural areas. Due to known surface propagation properties at 2 GHz, terrestrial macrocells will not be able to provide full rural coverage. The UMTS satellite access is assumed to provide a seamless rural outdoor coverage using the satellite frequencies 1980, 2010/2170, and 2200 MHz immediately adjacent terrestrial fre- quencies and with the requirement of minimum modifications in services and user terminals. A cost-efficient implementation of the UMTS satellite component would benefit the user and create new opportunities for satellite operators to approach the emerging massive UMTS user base. At the time UMTS reaches service, asynchronous transfer mode (ATM) will be an established transmission technique. Hence, the UMTS environment must support ATM-cell trans- mission through to the user terminal. This compatibility will enable service providers to offer a homogeneous network, where users can receive variable-bit-rate services regardless 0018–9545/98$10.00  1998 IEEE