This paper proposes a novel Doppler frequency shift compensation technique to achieve terrestrial and low earth orbit (LEO) satellite dual mode DS/CDMA terminals robust to high Doppler shift and multipath fading. In order to satisfy the requirements of wide dynamic range and high accuracy simultaneously, the proposed scheme employs two stage compensation scheme, i.e., coarse compensation to keep dynamic range of about 100 kHz and fine compensation to satisfy its resolution of about 30 Hz, using block demodulation technique. Computer simulation results show that the proposed scheme can sufficiently compensate for the offset frequency up to the range of about 100 kHz at the terrestrial and LEO satellite combined mobile communication systems.

This paper proposes a symbol-by-symbol-based multilevel transmit power control (MTPC) scheme for orthogonal frequency division multiplexing (OFDM) based adaptive modulation system (AMS) to achieve high quality broadband wireless transmission for high mobility terminals. In the proposed system, delay profile for each OFDM symbol is estimated by linearly extrapolating previously received delay profile information (DPI) sequence to improve tracking ability of OFDM based AMS with MTPC to the fast fading variation. Moreover, 2-branch reception diversity is applied to reduce dynamic range and variation speed of the multipath fading. Computer simulation confirms that the proposed system is effective in supporting higher mobility terminals with keeping high transmission quality.

This paper gives field experimental results on 16-ary quadrature amplitude modulation/time division multiple access (16QAM/TDMA) and trellis coded 16QAM/TDMA systems for land mobile communications in order to evaluate its capability of achieving large capacity and high quality data transmission. Pilot symbol aided space diversity and symbol timing synchronization based on maximum likelihood (ML) estimation are applied to both 16QAM/TDMA and trellis coded 16QAM/TDMA to improve transmission quality. For the trellis coded 16QAM/TDMA, trellis coding with Viterbi decoding and 2-frame symbol interleaving are further employed. The field experiments were conducted in the Tokyo metropolitan area of Japan. The results show that 16QAM/TDMA and trellis coded 16QAM/TDMA are practical modulation/access schemes for land mobile communication systems.

This paper proposes a secure distributed transmission method that establishes multiple transmission routes in space to a destination. In the method, the transmitted information is divided into pieces of information by a secret-sharing method, and the generated pieces are separately transmitted to the destination through different transmission routes using individually-controlled antenna directivities. As the secret-sharing method can divide the transmitted information into pieces in such a manner that nothing about the original information is revealed unless all the divided pieces are obtained, the secrecy of the transmitted information is greatly improved from an information-theoretic basis. However, one problem is that it does not perform well in the vicinity around the receiver. This is due to the characteristics of distributed transmission that all distributed pieces of information must eventually gather at the destination; an eavesdropper can obtain the necessary pieces to reconstruct the original information. Then, this paper expands the distributed transmission method into a two-way communication scheme. By adopting the distributed transmission in both communication directions, a secure link can be provided as a feedback channel to enhance the secrecy of the transmitted information. The generation of the shared pieces of information is given with signal forms, and the secrecy of the proposed method is evaluated based on the signal transmission error rates as determined by computer simulation.

This paper proposes a concept for a new technical field called wireless distributed network (WDN) as a strategic technical field to enable flexible networking and radio resource management (RRM) to cope with dynamic variation of spatially distributed traffic demands. As the core technical subject areas for the WDN, this paper identifies distributed networking for flexible network creation, cooperative transmission and reception for flexible link creation, and dynamic spectrum access for flexible radio resource management, and explains their technical features and challenges for constructing the WDN. This paper also discusses some already being studied application fields as well as potential future directions of the WDN applications.

This paper proposed an iterative soft interference canceller (IC) referred to as turbo equalizer for the self-coherent detection, and extrinsic information transfer (EXIT) chart based irregular low density parity check (LDPC) code optimization for the turbo equalizer in optical fiber short-reach transmissions. The self-coherent detection system is capable of linear demodulation by a single photodiode receiver. However, the self-coherent detection suffers from the interference induced by signal-signal beat components, and the suppression of the interference is a vital goal of self-coherent detection. For improving the error-free signal detection performance of the self-coherent detection, we proposed an iterative soft IC with the aid of forward error correction (FEC) decoder. Furthermore, typical FEC code is no longer appropriate for the iterative detection of the turbo equalizer. Therefore, we designed an appropriate LDPC code by using EXIT chart aided code design. The validity of the proposed turbo equalizer with the appropriate LDPC is confirmed by computer simulations.

High bit rate data transmission in land mobile communication is essential for supporting more convenient and attractive services. For such transmission, however, a means to cope with frequency selective fading is indispensable. This paper surveys recent developments in Japanese adaptive equalizers which effectively compensate for such fading, and introduces its algorithm, parameter optimization, performance, and some technical improvements in adaptive equalizing performance. We also comments on problems to be solved in the future.

This paper proposes an adaptive modulation system with a punctured convolutional code for land mobile communications to achieve high quality, high bit rate, and high spectral efficient data transmission in multipath fading environments. The proposed system adaptively controls the coding rate of the punctured convolutional code, symbol rate, and modulation level according to the instantaneous fading channel conditions. During good channel conditions, the modulation parameters are selected to increase the transmission rate as much as possible with satisfying a certain transmission quality. As channel conditions become worse, lower rate modulation parameters are applied or transmission is stopped. The performances in fading environments are evaluated theoretically and by computer simulations. The results show that the proposed system can realize higher quality transmission without the degradation in average bit rate compared to conventional adaptive modulation systems.

This paper proposes a symbol rate controlled adaptive modulation/TDMA/TDD for future wireless personal communication systems. The proposed system controls the symbol rate according to the channel conditions to achieve wide dynamic range of the modulation parameter control as well as to improve the delay spread immunity. The main purpose of the proposed system is to increase the data throughput with keeping a certain transmission quality, especially in frequency selective fading environments. For this purpose, the proposed system predicts the C/N0 (carrier power-to-noise spectral density ratio) and the delay spread separately, and selects the optimum symbol rate that gives the maximum bit rate within a given bandwidth satisfying the required BER. The simulated results show that the proposed system can achieve higher transmission quality in comparison with the fixed symbol rate transmission system in both flat Rayleigh and frequency selective fading environments. The results also show that the proposed system is very effective to achieve higher bit rate transmission in frequency selective fading environments.

This paper proposes a frequency domain nulling filter and Turbo equalizer to suppress interference in the uplink of one-cell reuse single-carrier time division multiple access (TDMA) systems. In the proposed system, the desired signal in a reference cell is interfered by interference signals including adjacent-channel interference (ACI), co-channel interference (CCI), and intersymbol interference (ISI). At the transmitter, after a certain amount of spectrum is nulled considering the expected CCI, the suppressed power due to nulling is reallocated to the remaining spectrum components so as to keep the total transmit power constant. In this process, when mitigation of ACI is necessary, after a certain amount of spectrum at both edges is nulled using an edge-removal filter, the aforementioned process is conducted. At the receiver, frequency domain SC/MMSE Turbo equalizer (FDTE) is employed to suppress ISI due to spectrum nulling process in the transmitter as well as the multipath fading. Computer simulations confirm that the proposed scheme is effective in suppression of CCI, ACI and ISI in one-cell reuse single-carrier TDMA systems.

This paper proposes a new design criterion of adaptively scaled belief (ASB) in Gaussian belief propagation (GaBP) for large multi-user multi-input multi-output (MU-MIMO) detection. In practical MU detection (MUD) scenarios, the most vital issue for improving the convergence property of GaBP iterative detection is how to deal with belief outliers in each iteration. Such outliers are caused by modeling errors due to the fact that the law of large number does not work well when it is difficult to satisfy the large system limit. One of the simplest ways to mitigate the harmful impact of outliers is belief scaling. A typical approach for determining the scaling parameter for the belief is to create a look-up table (LUT) based on the received signal-to-noise ratio (SNR) through computer simulations. However, the instantaneous SNR differs among beliefs because the MIMO channels in the MUD problem are random; hence, the creation of LUT is infeasible. To stabilize the dynamics of the random MIMO channels, we propose a new transmission block based criterion that adapts belief scaling to the instantaneous channel state. Finally, we verify the validity of ASB in terms of the suppression of the bit error rate (BER) floor.

This paper proposes iterative carrier frequency offset (CFO) compensation for spatially multiplexed Bluetooth Low Energy (BLE) signals using independent component analysis (ICA). We apply spatial division multiple access (SDMA) to BLE system to deal with massive number of connection requests of BLE devices expected in the future. According to specifications, each BLE peripheral device is assumed to have CFO of up to 150 [kHz] due to hardware impairments. ICA can resolve spatially multiplexed signals even if they include independent CFO. After the ICA separation, the proposed scheme compensates for the CFO. However, the length of the BLE packet preamble is not long enough to obtain accurate CFO estimates. In order to accurately conduct the CFO compensation using the equivalent of a long pilot signal, preamble and a part of estimated data in the previous process are utilized. In addition, we reveal the fact that the independent CFO of each peripheral improves the capability of ICA blind separation. The results confirm that the proposed scheme can effectively compensate for CFO in the range of up to 150[kHz], which is defined as the acceptable value in the BLE specification.

This paper proposes multipoint-to-multipoint (MPtoMP) real-time broadcast transmission using network coding for ad-hoc networks like video game networks. We aim to achieve highly reliable MPtoMP broadcasting using IEEE 802.11 media access control (MAC) that does not include a retransmission mechanism. When each node detects packets from the other nodes in a sequence, the correctly detected packets are network-encoded, and the encoded packet is broadcasted in the next sequence as a piggy-back for its native packet. To prevent increase of overhead in each packet due to piggy-back packet transmission, network coding vector for each node is exchanged between all nodes in the negotiation phase. Each user keeps using the same coding vector generated in the negotiation phase, and only coding information that represents which user signal is included in the network coding process is transmitted along with the piggy-back packet. Our simulation results show that the proposed method can provide higher reliability than other schemes using multi point relay (MPR) or redundant transmissions such as forward error correction (FEC). We also implement the proposed method in a wireless testbed, and show that the proposed method achieves high reliability in a real-world environment with a practical degree of complexity when installed on current wireless devices.

This paper proposes an adaptive coding rate and process gain control technique with channel activation function to realize a CDMA based radio subsystem for multi-media communication services that include two types of media, i.e., fixed size data such as the computer data and still image, and constant bit rate data such as voice and video. The proposed system achieves high throughput data transmission for the fixed size data by controlling the process gain and coding rate according to the variation of the channel. Moreover, to adopt the constant bit rate data, the proposed system also employs a channel activation technique. Computer simulation confirms that the proposed system is very effective for multi-media communication services.

The performance of the Forward Error Correction (FEC) with interleaving was evaluated by computer simulation with the field experimental data and its usefulness in land mobile communications is confirmed.

This paper proposes a multiple-input multiple-output (MIMO) eigenmode transmission technique which transmits different data streams on eigenmodes of different multi-path components while suppressing intra and inter-eigenmode interferences by means of a turbo equalization technique. This paper also evaluates the effectiveness of the proposed system in frequency selective fading conditions. Computer simulation results confirms the proposed technique is effective even in high spatial correlation cases.

This paper given an outline of the general purpose DASDSP (Development Assist System for Digital Signal Processing) which contains 8 DSP (Digital Signal Processor) boards. Each board can select external analog or digital signals and it is possible for DASDSP to perform the distributed processing. This system has a memory board for the purpose of debugging programs running in each DSP.

Research and standardization activities on FPLMTS are under way throughout the world. This paper shows recent study results on radio transmission technologies in ARIB (Association of Radio Industries and Businesses), which in the standardization organization in Japan. On-going study shows two TDMA based and four CDMA based radio transmission technologies under study. These technologies need to be further studied in detail. The proposal from ARIB is expected to be summarized around the end of the year 1996.

This paper proposes a spectrum-overlapped resource management (SORM) technique where each user equipment (UE) can ideally obtain the frequency selection diversity gain under multi-user environments. In the SORM technique for cellular systems, under assumption of adopting a soft canceller with minimum mean square error (SC/MMSE) turbo equalizer, an evolved node B (eNB) accepts overlapped frequency resource allocation. As a result, each UE can use the frequency bins having the highest channel gain. However, the SORM becomes non-orthogonal access when the frequency bins having high channel gain for UEs are partially identical. In this case, the inter-user interference (IUI) caused by overlapping spectra among UEs is eventually canceled out by using the SC/MMSE turbo equalizer. Therefore, SORM can achieve better performance than orthogonal access e.g. FDMA when the IUI is completely canceled. This paper demonstrates that SORM has the potential to improve transmission performance, by extrinsic information transfer (EXIT) analysis. Moreover, this paper evaluates the block error rate (BLER) performance of the SORM and the FDMA. Consequently, this paper shows that the SORM outperforms the FDMA.