Single-carrier frequency division multiple access (SC-FDMA) has been decided to be adopted in the uplink of the future wireless communication system. Interleaved frequency division multiple access (IFDMA), whose transmitted signal is generated in the time domain, is a candidate of SC-FDMA. The number of comb like spectrum and the spectral interval between each spectrum depend on the number of transmission data symbols Q in one IFDMA block and repetition number L. In the case of large Q and small L, large frequency diversity gain can be obtained due to the number of spectrum is increased. However, inter-chip interference (ICI) owing to the multipaths environment increases. In the multi-user environment, it is difficult to get multi-user diversity due to the decrease of the degree of freedom for channel allocation to each user with large Q and small L. On the other hand, in the case of small Q and large L, frequency diversity gain becomes smaller and ICI is decreased. Furthermore, multi-user diversity gain can be obtained due to the increase of the degree of the freedom for channel allocation. Thus, it is quite interesting to see how the parameters in IFDMA, i.e., Q and L, affect the average bit error rate (BER) performance in the multi-user environment. In this paper, we derive average BER performance of IFDMA in the multi-user environment theoretically by taking into account of frequency diversity, multi-user diversity and ICI when Q and L are changed and then average BER performance of IFDMA is compared to that of OFDM. In addition, the validity of the theoretical analysis is confirmed by computer simulation.

The uplink transmission performance, e.g., bit error rate (BER) performance, of multi-carrier-code division multiple access (MC-CDMA) is limited by the multi-access interference (MAI). Recently, we proposed a FD-PR/MC-CDMA, which uses frequency domain phase rotation and symbol mapping onto equi-distantly spaced sub-carriers. In FD-PR/MC-CDMA, multiple users can be multiplexed without causing MAI as long as the number of multiplexed users is smaller than the spreading factor devided by the maximum channel length. However, the number of users to be accommodated is limited by the length of the channel impulse response and the spreading factor. To increase the number of users or the data rate per user, the code multiplexing is effective, but this results in the performance degradation. In this paper, an iterative interference cancellation is applied to FD-PR/MC-CDMA and the impacts of the spreading factor and the length of the channel impulse response are evaluated by computer simulation.

In the orthogonal frequency division multiplexing (OFDM) the multipath exceeding a guard interval (GI) is one of obstacles for high data rate transmission. For the purpose of the interference suppression the authors have proposed the canceller algorithm naming DWCC, where the canceller operation is based on decision feedback equalization (DFE), but the performance of the canceller is still subject to the frequency selectivity since the tentative symbol detection at the deep faded subcarriers could not be reliable. In this paper turbo equalized double window cancellation and combining (TE-DWCC) is proposed. Throughout the paper, it is found that the error rate performance of TE-DWCC depends on how to incorporate the channel decoding gain from turbo equalization into DWCC. In addition, it is also shown that TE-DWCC is more compatible with the hard decision feedback (HDF) rather than the soft decision feedback (SDF) due to the ICI elimination method. Finally, by varying interference level, code rate, and decision feedback type, the performances of TE-DWCC are compared with the conventional canceller that adopts turbo equalization in the exponentially distributed slow fading channel.

In this paper, we proposed multiband received signal strength fingerprint (MRSS) based location system employing the frequency diversity of received signal strength (RSS). The enhancements of estimated accuracy contribute to the frequency diversity. This paper shows the experimental results under the area of 103 m2, we achieved the accuracy improvement over 40 percent, comparing with the singleband RF fingerprint.

To increase the data rate without signal bandwidth expansion, a combination of MC system with multiple-input multiple-output (MIMO)-space division multiplexing (SDM) is attractive. MIMO-SDM transmission performance is governed by min {Nt, Nr}, where Ntand Nrare the numbers of transmit and receive antennas, respectively. For downlink transmission, many receive antennas cannot be equipped at a mobile station due to space limitation. Therefore, the achievable data rate is limited by the number of receive antennas. In this paper, we propose a virtual MIMO-SDM for multi-carrier-code division multiple access (MC-CDMA) that can use the signals received via different propagation paths as virtual receive antennas. The equivalent number of receive antennas can be increased by a factor of the number of distinct paths of the channel. We confirm, by computer simulation, the effectiveness of virtual MIMO-SDM in a frequency-selective fading channel.

The bit error rate (BER) performance of multicode MC-CDMA severely degrades due to the inter-code interference (ICI) in a strong frequency-selective channel. In, a spreading code group construction method for MC-CDMA was proposed. The Walsh-Hadmard (WH) codes are divided into a number of code groups such that the code orthogonality can be maintained within each subgroup even in a frequency-selective channel; any code pair taken from different groups is not orthogonal. The number of spreading codes in each group is determined by the maximum time delay difference of the channel. In this paper, we point out that the number of codes in each group is not determined by the maximum time delay difference but the distribution of time delay differences among the propagation paths in the channel and thus, more orthogonal spreading codes can exist in each code group. The conditional BER is derived taking into account the interference from other code groups and the achievable downlink BER performance is numerically evaluated in a frequency-selective Rayleigh fading channel.

White LEDs were invented the 1990's. Since then they have been extensively researched and applied in various ways. Compared with conventional lighting devices, the white LED has lower power consumption, lower voltage requirements, longer lifetime, smaller size, faster response, and cooler operation. The white LED will eventually replace incandescent or fluorescent lights in offices and homes. We have proposed an indoor visible light wireless communication system that utilizes multiple white LED lighting equipment. In this system, the equipment is used not only for illuminating rooms but also for an optical wireless communication system. The system has significantly higher power levels than infrared wireless communication systems, since it also functions as the main lighting equipment. One problem is we tend to install many lighting sources on a ceiling in order to illuminate the room as evenly as possible. While the number of sources permits site diversity transmission over LOS links, the optical path difference between the multiple sources triggers intersymbol interference (ISI), which significantly degrades system performance. This paper overcomes the ISI problem by proposing an adaptive equalization system. We elucidate the most effective training sequence interval for channel estimation in a mobile environment. And we show that the adaptive equalization system with the effectual interval alleviates the influence of shadowing.

The novel frequency rotation techniques for suppressing the path interference and increasing the frequency diversity gain are proposed in uplink IFDMA system. In IFDMA, the path interference in multipath fading channel and the reduction of frequency diversity gain degrades the error rate performance, especially more significantly as the number of simultaneous access users becomes large. For suppressing the path interference and enlarging the frequency diversity gain, the frequency rotation has been proposed for down link access but it cannot be applied to the uplink due to the distortion of user frequency orthogonality. In the proposed frequency rotation, multiple users do not share the multiple frequency orthogonal channels and thus the orthogonality among the users can be maintained. The effect of the revised technique is shown by computer simulation.

Multicarrier transmission techniques (i.e., orthogonal frequency division multiplexing (OFDM) and multi-carrier code division multiple access (MC-CDMA)) are the promising candidates for wireless access technique in future cellular communication systems because of their capability to eliminate the multipath interference. Multiple-input multiple-output (MIMO)-space division multiplexing (SDM) can increase the transmission rate without bandwidth expansion. A combination of multi-carrier technique and MIMO is a promising technique. However, the transmission performance of MC-CDMA severely degrades because of the inter-code interference (ICI) arising from the orthogonality distortion owing to the frequency- selective fading. In this paper, we derive the channel capacity formula for MC-CDMA MIMO taking into account the ICI and co-channel interference (CCI) in a cellular environment. Many ICI cancellers have been proposed. The cellular channel capacity of MC-CDMA MIMO with perfect ICI cancellation is numerically evaluated and is compared to that of OFDM MIMO in a cellular environment. The impacts of the frequency-reuse factor and the number of propagation paths are also discussed. The numerical computation results show that the cellular channel capacity of MC-CDMA is larger than that of OFDM.

Recently, we proposed an iterative modified QR-decomposition based M-algorithm (QRD-M) using decoding results of cyclic redundancy check (CRC) code for OFDM MIMO multiplexing. The symbol-wise CRC decoding results are used in the transmit antenna ranking and in the modified M-algorithm. Hereafter we call this iterative QRD-M as symbol-wise iterative modified QRD-M. In this paper, to further improve the transmission performance of OFDM MIMO multiplexing, we replace the use of symbol-wise CRC decoding results by the use of bit-wise CRC decoding results. The symbol replica candidates for the transmitted symbol are re-ordered using the bit-wise CRC decoding results in the modified M-algorithm. Computer simulation results show that when 16QAM data-modulation is used, an Eb/N0reduction of about 0.6~0.7 dB can be achieved for average packet error rate (PER)=10-2compared to the symbol-wise scheme.

Interleaved frequency division multiplexing (IFDM) can achieve high diversity gain as well as can establish orthogonal frequency multiplexing by means of comb-shaped frequency spectrum. In IFDM, as the number of multiplexing users becomes large, the comb-shaped frequency spectrum should be narrow, so that frequency diversity gain is decreased. In addition, IFDM suffers from inter-path interference introduced in the transmitted signal by multipath fading channel. In this paper, the frequency spectrum rotation is proposed. In the proposed method, the comb-shaped frequency spectrum is frequency-shifted for every modulated symbol. As a result, the frequency spectrum of the frame composed of many modulated symbols is widely spread. In addition, the inter-path interference can be suppressed because the modulated symbol is orthogonal in frequency with its time-consecutive symbol. From the computer simulation, the frequency rotation can achieve the better error rate performance thanks to increasing frequency diversity gain and suppressing inter-path interference.

Interleaved frequency division multiple access (IFDM A) is frequency orthogonal multiple access scheme and acquires high frequency diversity gain. In addition, the peak to average power ratio (PAPR) of IFDM symbol is small due to the single carrier modulation and thus the nonlinear amplifier having good power efficiency can be used in the mobile station. If an IFDMA is applied to the down link access (from base station to mobile station), the power consumption can be saved. However, the interleaved frequency division multiplexing (IFDM) has not been clarified yet for down link access. In this paper, we evaluate the error rate performance and PAPR performance with using the computer simulation. We derive the advantages and the disadvantages of IFDM compared to multicarrier code division multiplexing (MC-CDM).

To increase the transmission rate without bandwidth expansion, multiple-input multiple-output (MIMO) technique has been attracting much attention. When MIMO technique is applied to a cellular system, the MIMO channel capacity is affected by the interference from neighboring co-channel cells. In this paper, we evaluate the outage probability of MIMO downlink channel capacity in a cellular system, taking into account the frequency-reuse factor, path loss exponent, standard deviation of shadowing loss, and base station (BS) transmit power. We discuss about the cellular channel capacity. Furthermore, we compare the cellular MIMO channel capacity with those of other multi-antenna transmission techniques such as space time block coded multiple-input single-output (STBC-MISO) and single-input multiple-output (SIMO). We show that the optimum frequency reuse factor is 3 irrespective of type of multi-antenna transmission scheme for the outage probability of 10 %. We also show that the cellular MIMO channel capacity is always higher than those of SIMO and MISO.

An enhanced Ultra Wideband (UWB) signaling scheme employing PSWF (Prolate Spheroidal Wave Functions)- based orthogonal chip pulses and ternary complementary code sets is proposed for Direct-Sequence (DS) UWB systems. Every information bit of each user is modulated and transmitted over a set of parallel sequences of PSWF-based orthogonal chip pulses and are further assigned to a ternary complementary code set with additional zero padding if necessary. Moreover, the ternary complementary code sets are generated to be mutually orthogonal and assigned to any pair of multiple users. Hence, the mitigation of multipath interference as well as Multiple User Interference (MUI) can be expected. Furthermore, the ternary code length can be possibly designed to be much shorter by taking advantage of the pulse and code orthogonality. Thus, the proposed transmission scheme is especially suitable for high data rate DS-UWB systems for achieving much more flexibilities. Keywords-Ultra Wideband, UWB, Prolate Spheroidal Wave Functions, PSWF, direct sequence, ternary code, S-V channel model

We propose a new receiving method for visible light communication with LED-based traffic lights using 2-dimentional image sensor receiver. First, we discuss the maximum receiver's field of view (FOV) when using the 2-dimentional image sensor and we analyzed the best vertical inclination for the proposed system. We used 2-Pulse Position Modulation (PPM) and Select Best (SB) Combining Technique. We analyzed and quantified the improvement in term of the enhancement of received signal-noise ratio (SNR) when different numbers of pixels were applied. Our results indicate that using more pixels increases the received SNR and the service area becomes wider compared to the conventional system using Avalanche Photodiode (APD) receiver. We found that the optimum number of pixels to accomplish a reliable communication system is 50 × 50. Receivable information within the service area also increases and we show that proposed system is more suitable for the Intelligent Transport Communication (ITS).

This paper proposes an IP packet loss compensation scheme with bicast and forwarding for hard handover (HO) between different base stations (BSs). The proposed scheme could reduce the control delay for HO since it previously transfers IP packet from an access router to both an old BS and a new BS before HO, i.e., cell change is performed. Furthermore, the proposed scheme could realize loss less of IP packet by forwarding the IP packet only when IP packets transferred before starting bicast are buffered in the old BS for the HO request timing. From our computer simulation results, the proposed scheme could reduce the HO control delay at 95% cumulative distribution function (CDF) by approximately 1.7 sec, 340 msec, and 170 msec compared with the conventional forwarding scheme and by approximately 300 msec, 320 msec, and 330 msec compared with the conventional bicast scheme when the maximum Doppler frequency (fdmax) is 5.55 Hz and the data rate on a wired propagation channel is 10, 50, and 100 Mbps, respectively. Therefore, we clarified that the proposed scheme is effective as an IP packet loss compensation scheme for hard HO

Maximum likelihood detection with QR decomposition and M-algorithm (QRD-M) is one of the detection methods in multiple-input multiple-output (MIMO) multiplexing. We recently proposed a Turbo coded iterative modified QRD-M with decision directed channel estimation and showed that the packet error rate (PER) performance close to the ideal channel estimation case can be obtained. In the iterative modified QRD-M, signal ranking is performed based on both received signal-to- interference plus noise power ratio (SINR) and results of cyclic redundancy check (CRC) decoding and then, signal detection is performed by modified M-algorithm based on the results of CRC decoding. In this paper, we apply irregular low density parity check (irregular LDPC) codes to the previously proposed iterative modified QRD-M. The a posteriori probability of each bit (including parity bit) is necessary for decision directed channel estimation and modified M-algorithm in the iterative modified QRD-M. Unlike Turbo decoding, the a posteriori probability of each bit can be obtained in LDPC decoding. Thus, by using LDPC codes, more accurate signal detection is possible than using Turbo codes. To achieve more powerful detection of decoding errors, CRC codes can be jointly used with parity check equation of LDPC codes. It is shown by the computer simulation that the performance of the LDPC coded iterative modified QRD-M is superior to that of the Turbo coded iterative modified QRD-M.

Maximum likelihood detection with QR decomposition and M-algorithm (QRM-MLD) is one of the detection methods in multiple-input multiple-output (MIMO) multiplexing. We recently proposed an iterative QRM-MLD with decision directed channel estimation and showed that better transmission performance can be obtained compared to that with conventional pilot assisted channel estimation. In this paper, to further improve the transmission performance while keeping computational complexity low, we modify previously proposed iterative QRM-MLD by applying cyclic redundancy check (CRC) coding. In the proposed method, transmitted signals are ranked according to their CRC check results and signal-to-interference plus noise power ratio (SINR), before performing modified QRM-MLD. The number of iterations and that of surviving symbol replica candidates in iterative channel estimation/signal detection are adaptively controlled by CRC check results. Thus, the computational complexity of the proposed method can be kept low. Computer simulation results show that the loss in the average received signal energy per bit-to-noise power spectrum density ratio Eb/N0required for the average packet error rate (PER) of 10-2is approximately 0.5 dB from full MLD with ideal channel estimation for QPSK modulation

Since Time Division Synchronous Code Division Multiple Access (TD-SCDMA) technology, one of the Time Division Duplex (TDD) standards modes of 3rd Generation Partnership Project (3GPP), adopted a lower spreading rate, 1.28 MChip/sec, it is usually referred to Low Chip Rate Time Division CDMA (LCR-TD- CDMA). Therefore its multipath diversity is not large enough due to fewer independent paths. Furthermore, it suffers from multi-user access interference (MAI) as other CDMA systems, where the influence of MAI is not small due to its small spreading factor. Our proposed solution overcomes all these shortcomings of TD-SCDMA technology. We propose an implementation of Space Time Block Coding (STBC) to introduce diversity to combat low multi-path diversity character of TD-SCDMA. We further incorporate joint transmission (JT) technique to remove MAI, and thereby improve system performance. The introduction of JT at the base station (BS) side also helps to reduce the complexity of the mobile station (MS). We use a combination of analytical and simulation methods to evaluate the performance of the proposed system. The results show significant improvement for the proposed system.

In this paper we propose a Pre-rake system with a frequency domain equalizer at multi-code transmission. The Pre-rake system has been well known technology in TDD-CDMA to make a mobile station (MS) simple. However, it still has a residual path diversity loss. To gather all the residual paths requires an additional hardware such as a rake combiner to MS. For the reason Pre/Post-rake system has already been proposed, and it could increase the performance gain comparing with a Pre-rake only system by obtaining more path diversity. In the mean time, it has been verified that the maximal ratio post-rake combiner (MRC) at time domain can be designed with a less hardware complexity with a frequency domain MRC (MRC-FDE) and its performance is almost the same without considering the power loss due to the insertion of a cyclic prefix (CP). The paper introduces Pre-rake/FDE and shows the system design and presents with the numerical performance results.

Higher transmission rates are major characteristics of fourth-generation (4G) of mobile communications. Furthermore, operating at higher frequency bands means larger distance decay. These result in larger required transmission power. This causes problems particularly for uplink communications as a typical mobile station (MS) has a limited transmission power. Multihop systems have been proposed to address this problem. In this paper, we consider the issue of random-access (RA) in the multihop systems. A two-hop mobile communication system requires a two-stage RA. In this paper, we investigate a hybrid of code division multiple access (CDMA) and slotted-ALOHA for RA. We evaluate the basic performance in multihop systems, and propose interval slots allocation (ISsA) technique. This proposed technique means that dedicated slots are only used for the hop station (HS)-base station (BS) communications at intervals. Simulations demonstrate superior throughput-delay performance of a two-stage RA multihop system, including our proposed ISsA technique.

M-ary pulse shape modulation (PSM) has been proposed for achieving a high data rate even in severe multipath fading environments, based on the orthogonality of pulse waveforms of prolate spheroidal wave functions (PSWF). With respect to the PSWF-based M-ary PSM proposal, adaptive guard-time and selective-Rake receivers with different combining fingers are also considered The BER performance of the M-ary PSM, the guard-time and the Rake combination are investigated according to Monte-Carlo simulations by using the modified IEEE 802.15.3a S-V UWB multipath channel model. The proposed guard-time scheme has been verified to be effective in overcoming the inter-pulse-interferences. Moreover, it has been found that the PSWF-based pulse waveforms behave better than the conventional Gaussian mono-pulse under multipath fading conditions.

White LED offers advantageous properties such as high brightness, reliability, lower power consumption and long lifetime. White LEDs are expected to serve in the next generation of lamps. An indoor visible-light wireless communication system using white LED lightings has been proposed from our laboratory. In the proposed system, these devices are used not only for illuminating rooms but also for a wireless optical communication system. Generally, plural lights are installed in our room. So, their optical path difference must be considered. We discuss about the influence of intersymbol interference and the difference between visible-light wireless communication and other optical wireless communication. Based on numerical analyses, we show that the system will expect as indoor communication of next generation.

In the compressing and expanding (companding) method, at the transmitter, baseband signals are compressed for reducing peak-to-average power (PAPR) and at the receiver, the received signals are expanded for removing the distortion caused by the compressing. However, since the signals are distorted by the band pass filter (BPF), the high power amplifier (HPF), and the channel fading, the distortion caused by the compressing cannot be removed by expanding the received signals. We propose the novel companding system that compensates the distortions caused by not only the compressing but also the BPF, the HPF, and the fading. From the computer simulation, we show that the proposed companding system achieves better BER than the conventional one with the same level of the spectrum in the out-of-bandwidth.

UWB is limited in short range communication because it is necessary to have a limitation on UWB transmitting power density as a rule to avoid the interference with existing narrow-band communication systems. In hence, for the UWB short range low power communication limited in range, we need a short-range, multi-hop strategy relaying the UWB signal to achieve greater range and also some improvements should be investigated to shorten the relaying-delay caused by the relay of the UWB signal. In this paper, we first focus on the need of relaying UWB signals and then investigate the use of a repeater on the relaying of the UWB signal. After considering the problem of the conventional repeater for relaying the UWB signal, in particular on the area of the coupling interference and relaying-delay, this paper proposes a short range UWB system having a simple-structured PPM UWB repeater, which can relay the PPM (pulse-position-modulation) UWB signal with a short relaying-delay in the high-speed and delay-critical UWB communication environment. And also this paper investigates the special relaying method of switching control which can make it possible that the proposed PPM UWB repeater has no coupling interference and short relaying-delay.

The pre-Rake scheme for pulse based ultrawideband (UWB) communications system is proposed in a standardized UWB channel model from IEEE 802.15 SG3a, which is based on an extensive set of indoor short-range channel measurements in this paper. The pre-Rake scheme is shown to contribute to the low-power, cost-effective UWB system designing as well as Rake combining gain. Instead of building a Rake receiver at the receiving side (e.g. portable unit), the transmitter (e.g. access point) can pre-diversity the UWB signal before transmission in the forward link estimating the channel impulse response from the reverse link. While the pre-Raked signal is convolved with the estimated channel impulse response, the function of Rake combining at the receiver is automatically performed. Monte-Carlo simulations are carried out to compare the pre-Rake with Rake results and show that pre-Rake scheme is as good as Rake combining. Then the mobile or portable unit with a conventional receiver can still achieve the diversity gain of Rake combining.

Multi-carrier code division multiple access (MC-CDMA) has been one of the candidates for the next generation wireless communication systems. In an uplink, the MC-CDMA system suffers from the different access timing, the different fading, and the different frequency offset of each active user. In this paper we analyze the effects of the frequency offset compensation with MMSE-MUD (minimum mean square error based multi-user detection) for MC-CDMA in a quasi-synchronous uplink. We consider the MC-CDMA system with two subcarrier mapping schemes, the continuous mapping scheme and the discrete mapping scheme. From our theoretical analysis and computer simulation, we show that the MMSE-MUD can compensate the different frequency offsets among users. We also show that the MMSE-MUD significantly improves the bit error rate (BER) for the MC-CDMA system with the continuous mapping scheme.

In recent years, haptics, robotic and networking technology advancements bas brought about networking of various systems. As a result, the spotlight was placed on humanitarian assistance using networks, for example, remote robotic manipulation, which allows for remote surgery and removal of hazardous materials such as landmines and explosives. Most of the research done on robotic manipulation had been carried out using a wired system. Although, there are few researches done with wireless systems, they are not developed for complicated systems such as a robot hand simulating human hand. Using a bilateral robot hand, we have simulated a wireless network through introduction of errors. The bilateral robot hand is compliance-controlled, in which position information is transmitted from the master robot hand to slave robot hand, while force information is transmitted back from the slave robot hand to the master robot hand. Errors were inserted into each of the transmitted information. By evaluating the position trace of simulation and experimental results, we have concluded the effect of errors on haptic information.

In recent years, pre-Rake combining technique has become a hot topic of research as it decreases the complexity of the portable mobile unit, while achieving the same multipath diversity effect of the Rake receiver. In practice, the error in channel estimation in pre-Rake system occurs due to time variability in mobile radio channel. In this paper, we present pre-Rake performance under imperfect channel estimation due to time variability in TDD system, depending on Doppler frequency and compare it with the ideal pre-Rake system.

MC-CDMA has attracted significant attention as one of the downlink communication methods for fourth generation mobile communication systems. However, like the other non-spreading multi-carrier systems, MC-CDMA has a peak power problem. We propose a novel peak power reduction technique for MC-CDMA using code selection at the transmitter. The transmitter selects the code shift pattern from plural preassigned code shift patterns in each user cluster to minimize the output peak power of downlink signals. The proposed technique can achieve blind code detection of the transmitting codes at the receiver. However, since the detection performance degrades if the number of users increases, a code detection error recovery technique is also considered.

White LEDs offer advantageous properties such as high brightness, reliability, lower power consumption and long lifetime. The biggest potential application for white LEDs is general illumination and lighting. Indoor wireless optical communication systems employing white LED lighting have been proposed. This system is able to offer high QoS due to the high power from this lighting equipment. However, it is difficult for existing offices and households to install the communication cable to the ceiling. An easy wiring system for optical communication using existing power-lines is proposed. This system is emitted as visible-light from LED lighting according to the transmitted signal waveform without demodulating the signal from the power-line. This system is expected to be applicable from the existing lighting easily like exchanging electric bulbs. This integrated system can have a big impact as a new signal transmission system and its economical effect can be great. The basic performance of this system is analyzed. The actual system is built and its feasibility is shown through experiments.

A dynamic intelligent hub station (DIH), a hub station that moves autonomously in a wireless home network based on Wireless 1394, is proposed in order to avoid shadowing and interference without troublesome movement of terminals. We evaluate the effect of DIH in the home environment.

Future electric lights will be composed of white LED (light emitting diodes). Indoor wireless optical communication systems utilizing white LED lights have been proposed in our laboratory and we have been studying it. Generally, plural lights are installed in our room. Therefore, their optical path difference must be considered. In this paper, the influence of optical path difference has been investigated and two approaches for this problem are introduced. One uses OOK-RZ (on-off keying, return-to-zero) coding and the other uses optical OFDM (orthogonal frequency division multiplexing). From the results of computer simulations, we have found that these approaches are feasible for wireless optical communication systems utilizing white LED lights.

MC-CDMA has attracted significant attention as one of the downlink communication methods for fourth generation mobile communication systems. However, MC-CDMA has a peak power problem as well as the other nonspread multi-carrier systems. Therefore, in this paper, we propose novel peak power reduction technique for MC-CDMA using code selection at the transmitter. In the proposed system, the transmitter selects the code from plural pre-assigned codes of each user in each symbol to minimize the output peak power of downlink signals. The proposed technique also can achieve blind code detection in the receiver using correlation of pre-assigned codes without a side information channel for informing the transmitting code to the receiver in each symbol.

Jeong and Nakagawa (2000) proposed a selection type transmit diversity scheme for TDD MC-CDMA with asymmetric modulation on a duplex channel. In the scheme, the performance degraded rapidly at a large number of users even though it showed good performance at a small number of users. In this paper, we propose a new transmit diversity scheme for the TDD MC-CDMA system using multiple antennas. Computer simulation is carried out to evaluate the system performance and the performance is compared with that of the selection type transmit diversity scheme. From the simulation results, it is found that the proposed system has a good performance at a large number of users and thus, the transmit diversity scheme should be chosen applicably at the base station according to the number of users.

As a solution to traffic congestion, ADS (Advanced Demand Signals scheme) which controls a traffic light by passing vehicles has been proposed. However it is assumed that this system correctly obtains the relative distance between each vehicle and the traffic signal through the information from vehicles. This paper discusses the application of road-to-vehicle communication and ranging system using spread spectrum technique to ADS.

We propose a new transmitter diversity. It is a combined system with path diversity gain by distributed antennas and frequency diversity gain by multicarriers. The proposed system transmits the different data using several subcarriers which are correlated, while it transmits the same data using several subcarriers which are decorrelated. It can achieve combined path and frequency diversity in a variable frequency selective fading channel. It provides high data rate services by transmitting the different data using each correlated carrier, and supports good quality by transmitting the same data on decorrelated carriers with multiple antennas. The proposed system is an effective system to achieve a multimedia service with high quality according to the channel condition. Therefore, the proposed systems are flexible enough to support a variety of video, image, voice and data services with high quality.

The vehicle information and communication system (VICS) is starting to become practicable. The infrared system of a VICS detects vehicles on the road by using optical beacons to control traffic and to supply real-time traffic information. But it needs an enormous budget because the optical beacons must be located on every lane of the road throughout the country. We propose a traffic information system using existing LED traffic lights, and focus on its visible rays and power used for traffic control, the number and location of the traffic lights, and the movement toward LED traffic lights. We design the best service area not to interfere with other service areas and analyze its basic performance such as the suitable modulation, required SNR and the amount of receivable information.

This paper proposes an anti-shadowing scheme employing site diversity combined with orthogonal frequency division multiplexing (OFDM) modulation for 60 GHz wireless LAN. In the proposed system which we name overlapped-spot diversity, multiple access points (APs) sufficiently separated on a ceiling cover a same terminal so that it can receive more than one direct LOS paths even under shadowing situation. By using OFDM modulation, multiple APs within a single cell can transmit identical information using an identical frequency band while a terminal can simply add up all the arrived signals from those APs without any specific combining technique. Our computer simulation results by means of ray-tracing showed the system with multiple APs achieves better robustness to shadowing compared to that with single AP in terms of average bit error rate and outage probability.

The authors have proposed a dual mode system for indoor mobile communication. Mobile terminals (MTs) in this system communicate with each other directly or via BSs. The former mode is regarded as ad-hoc mode and the latter, as cellular mode. The decision which mode to use is given at an MT comparing the received power level from its partner and a base station (BS). The sharing approaches of wireless resources, frequency and time, considered in the cellular structure having two tiers can be applied to this dual mode indoor system with substituting the concepts of communication modes for cellular tiers. Then the capacity can be derived. In this paper, the capacity tradeoffs between the cellular mode and the ad-hoc mode for orthogonal sharing and spread-spectrum (SS) sharing are presented.

We propose to set an OFDM adaptive array on a mobile terminal in order to collect the signals received from multi-base stations efficiently in an indoor wireless system. By doing so, the system will obtain some diversity gain when the received signals contain the same data. Moreover, when they contain different data, the mobile terminal is capable of mitigating the interferer waves and thus obtaining the desired signal. The performance of the proposed system is evaluated by computer simulations and the possibility of constructing a system without the use of frequency assignment or time assignment in wireless networks is discussed.

In this paper we present a new transmission diversity technique for a TDD-CDMA system which consists of different modulation schemes between the forward and the reverse link, where the system utilizes single carrier modulation for reverse link and multi-carrier modulation for forward link, respectively. In mobile communication systems it is desirable to make the mobile unit simple without degrading the system performance. To achieve this goal we propose a new transmission diversity technique to obtain high diversity gain without equipping any diversity functions at the mobile unit. Two types of diversity are utilized for the proposed system, that is, path diversity and antenna diversity are used for the forward link transmission. A method to determine the antenna to be transmitted is presented and computer simulation is carried out to evaluate the system performance under frequency selective fading environment.

This paper investigates the optimal access point placement in a simultaneous broadcast system using orthogonal frequency division multiplexing (OFDM) for high data rate indoor wireless LAN. We aim to determine the best combination of multiple AP placements that minimizes the average bit error rate (BER) of terminals when input information including an indoor configuration, a number of APs, and total transmission power is given a priori. Since this AP placement problem is categorized as a hard combinatorial problem with many variables and constraints, we applied a nonlinear optimization scheme called very fast simulated annealing to search for an approximate optimal solution. The simulation results demonstrate that the algorithm has been successfully applied to the AP placement problem and its effectiveness was also confirmed in comparison with a local search algorithm.

One of the most spotlighted medium access control (MAC) scheme is carrier sense multiple access with collision avoidance (CSMA/CA). This scheme, adopted by the IEEE 802.11 standard, avoids packet collision by virtual carrier sensing considered for the "hidden terminal" problem, gathering physical channel sensing. Therefore, it attains higher throughput than the other MAC scheme such as slotted ALOHA (S-ALOHA), but in increasing the number of terminals and traffic in a contention scheme, serious transmission delay occurs because of avoiding packet collision. In order to solve the above problem, we propose dividing the channel by the directivity of the sector antennas specially. It is named "directional CSMA/CA". This proposal makes channel usage efficient since many terminals can transmit their packets simultaneously. From computer simulation, it is confirmed that this scheme attains a high throughput and decreases the transmission delay, and it constructs a system with high efficiency. Moreover, at the same time, sectorization limits the paths of arriving packets, and the propagation characteristics such as delay spread are improved.

DS/CDMA suffers from ISI (intersymbol interference) caused by the multipath propagation in a frequency selective fading channel, it greatly deteriorates BER performance. Since multi-carriers have high correlations among subcarriers with one antenna, it does not have enough diversity gain. In this paper, we propose a combined system with path diversity gain of the distributed antennas and frequency diversity gain of multicarrier. The base station consists of the distributed antennas, whose multi-carriers are effective for the robustness against ISI and ICI in frequency selective channel fading, because each carrier has non-frequency selective channel fading. It is assigned to several sub-carriers for each antenna. A set of antennas are fed by a common signal with time delay processing to the de-correlated signals. It creates a path diversity effect with multi-carriers for each antenna which can be combined by a RAKE receiver. As a result, we can obtain effective combined path diversity and frequency diversity gain by the RAKE combining of distributed antennas.

We propose a wireless optical communication system with white colored LEDs for a wireless home link (WHL). The white colored LEDs have a high power output and are regarded as lamps for the next generation. In the proposed system, this device is used for a wireless home link. The proposed system is suitable for private networks such as consumer communication networks. From numerical and simulation results, it is confirmed that the proposed system is available and the problems to be solved are made clear.

A method of transmission power control (TPC) for orthogonal frequency division multiplexing direct sequence code division multiple access (OFDM-DS-CDMA), in order to compensate for power attenuation at each subcarrier, is proposed. Instead of assigning the same power levels for all-subcarriers, different transmission power levels are assigned to different subcarriers, according to the attenuation of the subcarriers. System performance, in terms of bit error rate (BER), has been evaluated by Monte Carlo simulation. The simulation results presented significant improvement; the proposed system performed much better than the system without TPC. It is shown that the each-carrier TPC performed better than all-carrier TPC, hence each-carrier TPC is more suitable for OFDM-DS-CDMA systems.

A hybrid system in which mobile terminals (MTs) themselves select whether to communicate directly or via base stations (BSs) from communication conditions, "cellular ad hoc united communication system", has been proposed by Adachi and Nakagawa (1996). It has been confirmed to have effective channel usage, especially for MTs which tend to communicate with partners which are close together, such as operational mobile robots. In this paper, the hybrid system is examined with respect to battery consumption and handoff rate. In regard to battery consumption, this system showed better performance compared with pure cellular and pure ad-hoc communication systems. Such a system may suffer from frequent handoffs. However, by the addition of a simple hysteresis characteristic, the handoff rate was held down closer to that of a pure cellular system in a multipath environment. When a closer communication condition was assumed, the hybrid system out-performed the pure cellular system.

Multipath fading in inter-vehicle communication (IVC) radio links is severe and has to be taken into account. We discuss the system performance of DS/SS (direct sequence/spread spectrum) inter-vehicle communication and ranging system under aa Rician fading channel. The communication to the vehicles is done by using spread spectrum communication, and it realizes communications in both directions. The method of ranging the distance between vehicles is realized by clocking the round-trip time of a packet with a matched filter (MF) and we evaluate the system performance from computer simulation, such as the packet error probability (PER), packet delay, ranging error, and bit error rate (BER). From the performance, it is confirmed that even under a Rician fading channel our system can keep the real time communication needed for IVC, and range the distance between vehicles precisely.

In this paper power control and sector antennas are considered for an advanced form of inter-vehicle communication (IVC), called boomerang communication, which uses direct sequence spread spectrum (DS/SS). By the combined use of power control and sector antennas, an increase in reliability in the proposed system is shown by computer simulations. With increased reliability a decrease in vehicular accidents and more intelligent traffic flow can be expected.

The performance of decision-directed phase-locked loops (PLL) for use in direct-sequence code-division multiple-access (DS-CDMA) systems is investigated in the presence of phase noise, multiuser interference, and additive white Gaussian noise (AWGN). A unified and accurate analysis of the effect of these sources of noise on the PLL is carried out based on a nonlinear model (the Fokker-Planck method) since a linear analysis yields a large deviation between analytical results and actual performance at low signal-to-noise ratios (SNR). After describing the implementation of the PLL, the steady-state probability density function (PDF) of the phase estimator error in a first-order loop is derived. It is shown that a tradeoff exists between the effect due to the phase noise, the magnitude of the multiuser interference, and the AWGN as a function of loop bandwidth. The optimal loop bandwidth minimizing the impact of these sources of noise on the PLL and the requirements on the frequency uncertainty of the carrier source for a required accuracy of the phase estimator are detailed. Numerical results of the variance of the phase estimator error are discussed for Gold codes.

We propose optical multicarrier FDM coupled with suitably applied FEC (forward error control) coding technique. The strategy of optical multicarriers is new in lightwave systems and its combination with FEC is novel. The optical multicarrier approach is effective in combating dispersion and increasing throughput whereas FEC is effective in diluting the interchannel interactions and increasing the reliability. No doubt FEC offers system reliability, but its application in lightwave systems is discouraged as it changes the system bit rate. We think that suitably applied FEC, that we refer as parallel FEC (PFEC), can solve the problem. PFEC involves the creation of additional parity check channels and their transmission in parallel with the data channels. Theoretical treatment shows that the proposed approach is promising and practical.

Multicarrier modulation has been considered as a solution to the frequency selective fading problem in high speed wireless LAN. With multicarrier modulation, high efficiency channel utilization is enabled by dynamic carrier assignment according to the demand of each terminal. Conventionally in FTDMA/DA, central station is used to assign carriers dynamically to terminals. However the system becomes large and lacks flexibility. Thus in this paper we propose a carrier assignment system without a central station, M-CSMA/RCA (multi-carrier sense multiple access with random pulse carrier assignment). In a decentralized multicarrier wireless LAN, this system can avoid packet collision by sending random pulses before transmission. This system can achieve almost the same performance against conventional centralized FTDMA/DA system in terms of delay and throughput.

Inter-vehicle communication (IVC) systems, where vehicles exchange information with each other, can decrease traffic accidents and promote smoother driving. To realize such systems, decentralized (i.e., base-station-less) network management is required because of the independent movement of vehicles. However, it is very difficult to achieve decentralized synchronization among unspecified vehicles. Therefore we propose an adaptive channel access protocol for an asynchronous communication using spread spectrum (SS), so synchronization is not required. Moreover by using the SS boomerang method, we can realize an IVC system which is adaptable to vehicle density. Such a system is very important for IVC because without an adaptable communication system, when there is high vehicle density some vehicles can not access the channel and transmit their packets reliably. From computer simulations, it was confirmed that the proposed protocol is effective in realizing adaptive communication and all vehicles can transmit their packets reliably.

A new intracell orthogonalization technique for a code division multiple access (CDMA) wireless local communication system is posed. On the forward link of the system, it is necessary to achieve high bit rate transmission and to reduce the complexity of the receiving terminal. To meet these two requirements, cyclically shifted spreading sequences are utilized. However, it is necessary to orthogonalize the multiple signals since these sequences are cross-correlated. One way of achieving orthogonalization is pre-decorrelation. However, the orthogonality does not clearly appear in a multipath fading channel because of the interchip interference caused by multipath. Therefore in this paper, pre-decorrelation is combined with multicarrier modulation. The results obtained through computer simulation show that the proposed technique can achieve orthogonality in a multipath fading channel. Also the proposed technique makes efficient forward link power control possible, and reduces intercell interference.

In this paper, a new initial sequence acquisition technique for multicarrier time division duplex (TDD) CDMA systems are proposed and evaluated on a Rayleigh fading channel. The proposed technique transmits preambles utilized for initial sequence acquisition on multiple carriers at the same time in order to achieve frequency diversity. Soft decision detection on multiple carriers is employed. The numerical results show that the proposed technique improves required Eb/N/sub o/ by more than 10 dB for the probability of correct acquisition of 0.99. The proposed technique is suitable for TDD CDMA systems since a smaller number of preamble sequences for acquisition is desirable in TDD packet transmission.

In indoor optical channels, intersymbol interference (ISI) due to the multipath propagation prevents high data rate transmission. A new optical multi-wavelength PPM (pulse position modulation) has been investigated for improving the quality of transmission. In this strategy, parallel transmission is accomplished which lowers the data rate per channel and thus reduces the effect of ISI. Furthermore, this strategy also implements a parallel coding technique in the predetermined parallel branches. This parallel coding corrects errors without changing the system data rate. The simulation results show that a combination of these methods can achieve high quality transmission without reduction of the total data rate.

This paper suggests that multicarrier modulation reduces the complexity and the delay caused by the multiuser interference cancellation process utilizing convolutional codes. For spread spectrum multiple access, multiuser interference (interference due to signals from other users) limits the performance of the communication link. To remove this interference, a multiuser interference cancellation technique which utilizes orthogonal convolutional codes has been proposed for the uplink (mobiles to a base station) of the cellular code-division multiple-access (CDMA) systems. However, this technique requires large interleavers and huge memory, or artificial multipath diversity and a RAKE system to achieve sufficient coding gain if it is applied to wireless indoor communications and fading is slow compared to the data rate. To reduce the complexity of the canceller, multicarrier modulation is employed as it provides frequency diversity gain and coding gain without the interleavers or a RAKE system. This paper shows that multicarrier modulation reduces the complexity of the canceller and still provides sufficient coding gain in order to cancel the multiuser interference. A canceller with decoding in the initial decision and multicarrier modulation improves the capacity by a factor of 1.4 as compared with a canceller without decoding.

A new multicarrier direct sequence code-division multiple-access (DS-CDMA) system is proposed. Transmitted data bits are serial to parallel converted to a number of parallel branches. On each branch each bit is direct-sequence spread-spectrum (DS-SS) modulated and transmitted using orthogonal carriers. This procedure provides the following advantages: the transmission bandwidth is more efficiently utilized, the effect of frequency selective multipath interference can be mitigated, and frequency/time diversity is achieved. The system is analyzed with both a conventional matched-filter (MF) receiver and a RAKE receiver for each carrier. The performance is compared to that of the conventional single carrier system with RAKE receiver. It is shown that the multicarrier system is able to out-perform the RAKE receiver when the system parameters are selected properly.

A pre-RAKE system is proposed for the time division duplex code division multiple access systems for portable communications. Since the up and down links are time slots on the same carrier, they have the same channel impulse response during a short period of time. Instead of building a RAKE receiver in the portable unit the base station can pre-RAKE the signal before transmission in the down link using the channel impulse response estimated from the up link. When the pre-RAKE signal is convolved with the channel impulse response, the function of the RAKE receiver is automatically performed. The mobile or portable unit can use a conventional matched filter and still achieve the diversity gain of a RAKE receiver.

Proposes a coherent detector selection diversity system for fading channels. That is, in order to cope with fading channels, this system operates to switch between two phase-locked-loops (PLLs), one with the narrow loop bandwidth B/sub L/ and the other with the wide B/sub L/ by means of error-detection code. Moreover, the proposed system does not require differential encoding. Namely, it detects the signal with its absolute phase by means of error-detection. The effectiveness of this system compared with differential PSK is verified by computer simulation in fading channels; an indoor environment with maximum Doppler frequency of 5-15 Hz.

We have proposed a multi-carrier DS-SS CDMA system that eliminates the effect of multipath fading. Instead of multipath diversity, frequency diversity is obtained. This paper presents a co-channel interference cancellation technique and applies it to the multi-carrier CDMA system. Any bit of the desired user gets interference from two bits of any other user. The interference cancellation technique first removes the interference contributed by the first interfering bit then removes all interference.

There is increasing interest in direct sequence code division multiple access (DS-CDMA) communication techniques. A modified multi-stage co-channel interference cancellation technique is proposed for asynchronous CDMA. In asynchronous CDMA a desired bit of any user is affected by co-channel interference from two bits from all other users. In the first stage of interference cancellation, by the end of the integration period of a desired bit, each interfering user would have already obtained an estimate for the earliest of its two interfering bits. Hence, the interference contributed by this bit can be rebuilt and subtracted from the conventional matched filter decision statistic of the desired bit. In the second stage, after waiting a period equals to a bit duration, the remaining bits would have been estimated using a first stage cancellation. Their interference can then be rebuilt and canceled. Also the interference that has been canceled in the first stage can be re-canceled using the estimates of the second stage of other users. This system is shown to provide a good performance. It is assumed that the received powers, delays and phases of all users are perfectly attained.

The time division duplex (TDD) mode of transmission of direct sequence spread spectrum (DS-SS) signals is proposed for systems operating in multipath channels. It is shown that the TDD systems are simpler, can facilitate efficient power control, consume less power and can operate with simpler mobile unit receivers. In the proposed TDD method, both reverse and forward links use the same frequency band and thus have a highly correlated fading pattern. The reciprocity of fading patterns of forward and reverse links provides for a non-feedback power control technique to improve system performance under multipath fading. In systems where the multipaths are created artificially by using multiple antennas, such as indoor distributed antenna systems, the characteristic of the channel as seen by each antenna can be estimated at base station. The best situated antenna can then be selected and used for transmission, creating in effect a pre-selection diversity combining system at the base station. The function of power control is still carried out at mobile units. Computer simulation results show the performance of a power controlled two-path selection diversity to be within 4 dB of static channel performance at bit error rate (BER) of 10/sup -4/.>

This special issue covers the topics: power control, multiuser receiver and joint detection, network aspects, adaptive equalisation, coding aspects, broadband CDMA systems, and optical systems.>

In the paper, the authors suggest an asynchronous microcellular CDMA system with a matrix-based multiuser interference canceler for the reverse link, in which multiuser interference is completely removed on a symbol-by-symbol basis. The linear interference cancellation scheme, whose matrix order is equal to the number of active users, does not require knowledge of their received power levels, thereby resulting in high capacity and near/far resistance. In the paper, the influence of surrounding cell interference on a given base station receiver for various propagation path loss models is also analyzed and then the system performance is investigated theoretically. Provided the normalized capacity is defined by a required SNR (=E/sub b//N/sub 0/) of 7 dB at the binary DPSK detector, the CDMA system can provide capacity per cell of 46/spl sim/54%.>

A fast frequency hopping (FFH) method which uses path-diversity combining is proposed. Diversity techniques are realized when a signal is received from diverse independent paths, each of which carries identical information but suffers from independent fading variations. The improvement of communication performance of FFH systems is possible as the delayed paths are used and path-diversity combination is realized. The advantages of this method, operating in Rayleigh fading channels are confirmed by theoretical analyses. The improvement is in order of 2/spl sim/3 dB at bit error rate (BER) of 10/sup -3/. This method can be also effective against interferences from other users in a code division multiple access (CDMA) environment. The performance of this system in a CDMA environment is evaluated by theoretical analyses and is shown to be superior to non-combining method. At BER of 10/sup -3/ the required E/sub b//N/sub 0/ of the proposed system is 5 dB lower. If E/sub b//N/sub o/ is fixed, a greater number of users can be accommodated using the proposed system.>

A digital signal processing (DSP) phase synchronizer using the method of least squares for fading channels (PS-FC) is presented. The proposed PS-FC has many characteristics which are quite different from conventional phase-locked loops (PLLs). For example, it can suppress noise using a modified method of least squares instead of a loop filter. The PS-FC can satisfy the phase tracking performance and the noise suppression performance simultaneously, which cannot be done by conventional PLLs. The pull-in range of the PS-FC is about three times as wide as that of the conventional PLL. It can estimate phase fluctuations due to fading much more accurately because of the modified method of least squares. Computer simulation shows its superior performance.>

The conventional timing extraction method for block demodulation requires a large amount of calculation, a high-speed A/D (analog/digital) converter and a large memory size. A method that overcomes these disadvantages is proposed. It calculates accurate frequency and phase of symbol timing from only two extracted spectra by using a modified discrete Fourier transform (DFT). Thus it requires less calculation than the conventional method. In addition, interpolation of stored data is used to reduce the sampling rate. As a result the method can use a slower A/D converter and has a reduced memory requirement. The lower limit of the number of samples per symbol can be reduced to about 2.5.>

A digital signal processing (DSP)-type phase synchronizer based on the method of least squares (PS-MLS) is proposed that can replace the conventional circuits for phase synchronizers, such as phase-locked loops (PLLs). The construction of PS-MLS is different from that of PLLs. The proposed PS-MLS has advantageous characteristics compared with the conventional DSP-type PLLs and can satisfy three important points of PLLs simultaneously: fast acquisition, wide pull-in range, and good noise suppression. Only two steps are required for the acquisition (in a noise-less case), the condition to accomplish synchronization is relaxed, and is equal to the sampling theorem (fi>or=2fs), and the noise suppression performance is greatly improved compared with the conventional PLL.>

An improved scheme using vertical block allocation to embed data in industrial-quality monochrome analog pictures by modulo masking is investigated. The video signal on each scan line is sampled, and a data bit is inserted into a block of three pels by a scrambling of the luminance level of only one pel in the block. The performance of the system is compared to that of a conventional system. The number of data bits embedded in an image for the proposed system is about 1.3 times as large as that of the conventional system. In addition, the SNR (signal-to-noise ratio) of the recovered image in the proposed system is increased by about 3-4 dB.>

In this paper, we propose a Modulo-PCM with Multi-Quantizer (MPCM-MQ) which has high data compression efficiency because the proposed MPCM-MQ scheme can get rid of the anomaly errors by utilizing the multiquantizer method. By using this proposed scheme, we can improve its performance by about 10 [dB] ∼ 15 [dB] (1.5 [bits/sample] ∼ 1.8 [bits/sample]) in SQNR compared with the conventional MPCM-AQF scheme.

In this paper, we describe a new speech decoder for Modulo-PCM, which greatly reduces the "anomaly errors". Therefore, the proposed decoder can extend the dynamic range at the encoder input about 1.6-1.8 times compared to the conventional MPCM decoder.

This paper describes a new digital processing Phase Lock Loop (PLL) implemented on a high performance DSP, the DSSP1. Called the Linear Digital PLL (L-DPLL), the new PLL has linearty in its phase comparison characteristics. It gives fast acquision without increase in jitter, its pull-in range is wider; and its steady state errors and sampling frequency are lower than with conventional PLLs. It also does not require Automatic Gain Control.