The development of digital land mobile communication techniques makes it possible to use most of the modulation techniques. This paper proposes an adaptive modulation/TDMA scheme to achieve high capacity personal multimedia communication systems. TDMA is used to cope with various bit rate for multimedia services, and the modulation scheme is selected from 1/4-rate QPSK, 1/2-rate QPSK, QPSK, 16QAM and 64QAM according to the received C/I/sub c/ (power ratio of the desired signal to the co-channel interference) and the delay spread. Computer simulation confirms that the proposed system can achieve 3.5 times higher spectral efficiency than that of the conventional QPSK systems at the outage probability of 10%, and the proposed system is also effective to improve the delay spread immunity.

Adaptive modulation/TDMA scheme for personal multimedia communication systems

A number of factors have motivated most spectrum owners to make plans to deploy upbanded second-generation cellular technologies for use in the PCS bands in the United States. However, the second-generation cellular technologies will need to be enhanced to provide third-generation services. There is interest in using the PCS and cellular spectra to broaden the market of users and the range of use of wireless beyond where it stands today, and beyond the primary applications that drove the development of the technologies being deployed. There is also interest in new technologies to improve the performance of cellular and PCS services, reduce the cost, and improve availability. This article considers evolutionary changes to IS-136 TDMA to enable it to provide a variety of PCS concepts. These evolutionary changes are presented in the form of options that would (1) provide high-quality voice service for indoor and pedestrian systems such as cellular office systems and personal base stations; (2) support enhanced-bit-rate packet wireless data access to the Internet as well as circuit data access; (3) provide smart antenna technology to improve coverage, quality, and capacity; (4) automatically assign frequencies for operation and provide for dynamic channel reconfiguration; (5) support microcellular arrangements to provide low-cost and high-capacity service in dense areas; and (6) support a future high-speed packet data access mode through a wideband system that is complementary to IS-136 TDMA and supports single-terminal operation.

The evolution of IS-136 TDMA for third-generation wireless services

This paper discusses system design strategies and performance evaluation for adaptive modulation techniques used in new and up-and-coming wireless access systems. After a brief discussion on basic modulation parameter (MP) settings as well as functionalities specific for adaptive modulation systems, this paper discusses how to design a narrowband time-division multiple-access/time-division duplex (TDMA/TDD)-based adaptive modulation system and confirms through laboratory experiments that the narrowband TDMA/TDD-based adaptive modulation system dramatically enhances system robustness to multipath fading and flexibility in throughput and transmission quality control. Next, as an extension to many fields of application for adaptive modulation, this paper discusses subcarrier-level adaptive modulation for orthogonal frequency-division multiplexing (OFDM)-based one-cell reuse broadband cellular systems. One key result is that nonsubcarrier transmit power control (TPC) applied adaptive modulation systems can achieve almost the same performance as subcarrier TPC applied adaptive modulation systems provided that the required signal-to-noise-plus-interference power ratio increment in the MP sets is designed to be sufficiently small. Finally, this paper explains the dynamic parameter controlled OFDM/TDMA system as an example of a practical scheme for one-cell reuse broadband wireless access systems. The analysis confirms that this adaptive system can achieve a spatial reuse efficiency defined by (average throughput in multicell conditions)/(average throughput in single cell conditions) of 0.8 as well as an average media access control payload throughput of about 150 Mb/s using about 100 MHz of bandwidth.

System Design Issues and Performance Evaluations for Adaptive Modulation in New Wireless Access Systems

This paper discusses system design strategies and performance evaluation for adaptive modulation techniques used in new and up-and-coming wireless access systems. After a brief discussion on basic modulation parameter (MP) settings as well as functionalities specific for adaptive modulation systems, this paper discusses how to design a narrowband time-division multiple-access/time-division duplex (TDMA/ TDD)-based adaptive modulation system and confirms through laboratory experiments that the narrowband TDMA/TDD- based adaptive modulation system dramatically enhances system robustness to multipath fading and flexibility in throughput and transmission quality control. Next, as an extension to many fields of application for adaptive modula- tion, this paper discusses subcarrier-level adaptive modulation for orthogonal frequency-division multiplexing (OFDM)-based one-cell reuse broadband cellular systems. One key result is that nonsubcarrier transmit power control (TPC) applied adaptive modulation systems can achieve almost the same performance as subcarrier TPC applied adaptive modulation systems provided that the required signal-to-noise-plus- interference power ratio increment in the MP sets is designed to be sufficiently small. Finally, this paper explains the dynamic parameter controlled OFDM/TDMA system as an example of a practical scheme for one-cell reuse broadband wireless access systems. The analysis confirms that this adaptive system can achieve a spatial reuse efficiency defined by (average throughput in multicell conditions)/(average throughput in single cell conditions) of 0.8 as well as an average media access control payload throughput of about 150 Mb/s using about 100 MHz of bandwidth.

System Design Issues and Performance Evaluations for Adaptive Modulation in New Wireless Access Systems : Wireless multicell systems able to maintain throughput close to that for single-cell operation, at the data rates and bandwidth required for future systems, now appear to be practical

Coherent trellis-coded modulation (TCM) systems employing diversity combining are analyzed. Three different kinds of combining are considered: maximal ratio, equal gain, and selection combining (SC). First, the cutoff rate parameter is derived for equal gain combining (EGG) and SC assuming transmission over a fully interleaved channel with flat slow Rayleigh fading, which permits comparison with previously derived results for maximal ratio combining (MRC). Then, tight upper bounds on the pairwise error probabilities are derived for all three combining techniques. These upper bounds are expressed in product form to permit bounding of the bit error rate (BER) via the transfer function approach. In each case, it is assumed that the diversity branches are independent and that the channel state information (CSI) can be recovered perfectly. Also included is an analysis of MRC when the diversity branches are correlated-the cutoff rate and a tight upper bound on the pairwise error probability are derived. It is shown that with double diversity a branch correlation coefficient as high as 0.5 results in only slight performance degradation.

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Performance analysis of coherent TCM systems with diversity reception in slow Rayleigh fading

Trellis-coded 16QAM/TDMA systems are proposed that have a high spectral efficiency and high transmission quality and that can support a wide variety of services. A digital pilot-symbol-aided channel sounding scheme, as well as diversity reception with maximal ratio combining, are used to compensate for fading. To further improve transmission quality, symbol interleaving and two-frequency hopping are used in the trellis-coded 16QAM/TDMA system. Computer simulation demonstrates that the bit error rate (BER) performance and the spectral efficiency of the trellis-coded 16QAM/TDMA cellular system are superior to those of /spl pi//4-QPSK/TDMA used in the American and Japanese digital cellular standards. It is also demonstrated that the trellis-coded 16QAM/TDMA with diversity, symbol interleaving, and frequency hopping can achieve a BER of about 10/sup -4/ if the delay spread is 0.1 T/sub s/. >

S. Sampei

Papers

Performance of a trellis-coded 16QAM/TDMA system for land mobile communications