Yasuhisa Nakamura

256 QAM Modem for Multicarrier 400 Mbit/s Digital Radio

This paper describes the performance of a 256 QAM modem with 400 Mbit / s transmission capacity. A variety of novel techniques are introduced as ways to achieve good performance. Key techniques include 1) an accurate 256 QAM modulator employing a new monolithic multiplier IC, 2) a carrier recovery circuit which satisfies such requirements: good phase jitter performance and no false lock phenomenon, 3) a highly stable high-level decision circuit, and 4) a forward error correcting code. As an overall modem performance, BER characteristics and signatures are presented. The equivalent CNR degradations of 1 dB(at BER of 10-4) and 2 dB (at BER of 10-9)are obtained using a single Lee-error correcting code and a seven-tap baseband transversal equalizer. The residual bit errors are decreased below the order of 10-10. The performance of a 256 QAM multicarrier modem has given prospect for the development of 400 Mbit/s digital microwave radio system.

Radio Local Distribution System for High-Speed Digital Communications

The radio local distribution system (RLDS) has been proposed to transmit various business information signals. The proposed RLDS uses a 26 GHz band and time division multiple access (TDMA). The main features of the RLDS are the use of radio equipment containing the microwave integrated circuit (MIC) and the adoption of the demand-assigned TDMA (DA/TDMA) technique. The MIC is more suitable than conventional waveguide circuits for mass production because its components are miniaturized. The DA/TDMA system, operating in a fully variable demand-assignment mode, uses simple control systems with a low bit rate. As a result, the RLDS can serve a local distribution system of high-speed digital communications both expeditiously and economically.

Advanced techniques for super multi-carrier digital microwave radio with trellis-coded 256 QAM modulation

The latest techniques for realization of an outage-free digital microwave radio (DMR) are presented. Three major techniques, trellis-coded 256 QAM (quadrature amplitude modulation) modulation, super multicarrier transmission, and microwave signal processing (MSP), are described. The BER (bit error rate) and signature characteristics of the trellis-coded 256 QAM system are simulated, and its validity as a fading countermeasure is indicated. The Viterbi-decoder LSI and effect of phase error on the TCM modem are also presented. An experiment using a 4, 8, 40-carrier 256 QAM modem showed an overall outage improvement factor of nearly 500 times due to a 40-carrier system. Lastly, the microwave signal processing technique, including IF stage (carrier) signals for DMR systems, is presented. An all-digital 256 QAM modulator was constructed and showed superior performance with no adjustment.<<ETX>>

Performance of trellis coded 256 QAM super-multicarrier modem using VLSI's for SDH interface outage-free digital microwave radio

This paper describes the performance of an outage free SDH (synchronous digital hierarchy) interface 256 QAM modem. An outage free DMR (digital microwave radio) is achieved by a high coding gain trellis coded SPORT QAM and super multicarrier modem. A new frame format and its associated circuits connect the outage free modem to the SDH interface. The newly designed VLSIs are key devices for developing the modem. As an overall modem performance, BER (bit error rate) characteristics and equipment signatures are presented. A coding gain of 4.7dB (at a BER of 10/sup /spl minus/4/) is obtained using SPORT 256 QAM and Viterbi decoding. This coding gain is realized by trellis coding as well as by increasing of transmission rate. Roll-off factor is decreased to maintain the same frequency occupation and modulation level as ordinary SDH 256 QAM modem. >

150 KGate general-purpose high-coding-gain TCM VLSIs for high-speed multi-level QAM systems

Multilevel trellis-coded QAM (quadrature amplitude modulation) VLSIs were designed and developed. These VLSIs realize a coding gain of 7.9 dB with SPORT-256 QAM. The VLSIs contain an encoder, a mapper, and a decoder for trellis-coded 16, 32, 64, 128, and 256 QAM utilizing general mapping. The VLSIs also function as a phase ambiguity rejection circuit for a recovered carrier and error pulse generator. Using small-size and low-power path memory, 150K gates are achieved utilizing two chips with die sizes of 8*11 mm/sup 2/ and 14*14 mm/sup 2/. The VLSIs realize maximum data throughput rates of 17 Mb/s (guaranteed) and 30 Mb/s. The devices are designed with BiCMOS 0.8 mu m, utilizing the HSL-FX language for functional design and ALPHA2 for layout design schemes. Experimental results on bit error rate, signature performance, and synchronization performance for phase ambiguity rejection are presented. The developed VLSIs are effective for outage-free digital microwave radio systems.<<ETX>>

High quality technologies for outage-free digital microwave radio

The authors outline the various technologies for achieving high-quality digital microwave radio relay systems. The needs, the research issues, and the current conditions are explained. The following technologies are discussed: robust modulation-demodulation technology, high-performance interference canceller, and automatic transmitting power control. In the future this technology will be applied to radio relay intervals across Japan which have severe fading, and it is anticipated that it will contribute to promoting digitalization and the higher quality of microwave routes.<<ETX>>

Multipurpose high-coding-gain 0.8- mu m BiCMOS VLSIs for high-speed multilevel trellis-coded modulation

Multilevel trellis-coded quadrature-amplitude-modulated (QAM) VLSIs were designed and developed. These VLSIs realize a coding gain of 7.9 dB with SPORT-256 QAM. The VLSIs contain an encoder, mapper, and decoder for trellis-coded 16, 32, 64, 128, and 256 QAM utilizing general mapping. Using small-size and low-power path memory, 150 K gates were achieved using two chips with die sizes of 8 mm*11 mm and 14 mm*14 mm. The VLSIs achieve a maximum data throughput rate of 17 MBd (guaranteed) and 30 MBd (typical) and dissipate only 1 W at a data rate of 17 MBd. The VLSIs also contain a phase ambiguity rejection circuit for a recovered carrier and error pulse generator. The devices are designed with a BiCMOS 0.8- mu m process rule. The experimental result of bit-error-rate (BER) performance is presented. The VLSIs are effective for outage-free digital microwave radio systems. >