Noriyoshi Kuroyanagi

Very efficient frequency usage system using convolutional spread time signals based on complete complementary code

We have proposed a method for increasing the information transmission rate and the frequency usage rate based on a new method for estimating multipath channels and spread time signals convolution. We used a pilot signal and data-transmission signals in the same frequency and in the same time. For this purpose, we used the complete complementary code on approximately synchronized systems. The information transmission rate came to (1.3/k) chip/bit, where k was the QAM factor. In this paper, a new usage method for a complementary code is proposed. The new method is far simpler than the old method. By applying the proposed usage method for a complete complementary code on the above high rate information transmission method, the high rate information transmission can be realized easier.

ZCZ Codes for ASK-CDMA System

This paper presents two kinds of new ZCZ codes consisting of trios of two binary sequences and a bi-phase sequence, which can reach the upper bound on the ZCZ codes. From the viewpoint of sequence design, it is shown that they can provide the most effective ASK-CDMA system, which can remove co-channel interference.

Binary signal design for approximately synchronized CDMA systems without detection sidelobe nor co-channel interference using auto- and cross-complementary codes

For mobile cellular CDMA systems, co-channel interference in the uplink is the most serious problem, because the power control or the interference cancellation required increase the systems cost. From this view point, Suehiro (1993, 1994) proposed a method for signal design by applying the pseudo-periodic sequences concept on the periodic sequence set without cross-correlation. Using this method, we can design CDMA signals without co-channel interference when the system is approximately synchronized. Approximate synchronization is not difficult for uplink in cellular mobile systems, so this signal design method is useful. Another problem of multipath fading is also solved by the proposed method, because the filter output has no sidelobe in the small shift terms. A signal design method is proposed by using a complete complementary code. Using the proposed method, we can design binary CDMA signals for far wider shifts of without sidelobe nor co-channel interference. In fact, the length of shifts without the influence of multipath is 2/sup n/ for any n.

An algebraic approach to generate super-set of perfect complementary codes for interference-free CDMA

Summary This paper introduces an algebraic approach to generate the super-set of perfect complementary (PC) codes suitable for new generation CDMA applications, characterized by isotropic multiple access interference (MAI) free and multipath interference (MI) free properties. The code design methodology proposed in this paper takes into account major impairing factors existing in real applications, such as MAI, MI, asynchronous transmissions, and random signs in consecutive symbols, such that a CDMA system using the generated codes can insure a truly interferencefree operation. Two important facts will be revealed by the analysis given in this paper. First, implementation of an interference-free CDMA will never be possible unless using complementary code sets, such as the PC code sets generated in this paper. In other words, all traditional spreading codes working on an one-code-per-user basis are not useful for implementation of an MAI-free and MI-free CDMA system. Second, to enable the interference-free CDMA operation, the flock size of the PC codes should be made equal to the set size of the codes, implying that a PC code set can support as many users as the flock size of the code set. A systematic search has been carried out to generate the super-set of various PC codes with the help of carefully selected seed codes belonging to distinct sub-sets. This paper will also propose an implementation scheme based on multi-carrier CDMA architecture and its performance is compared by simulations with the ones using traditional spreading codes. Copyright

A ZCZ-CDMA system with high tolerance to frequency selective fading

A Quasi-synchronous CDMA system using a ZCZ code called a ZCZ-CDMA system can remove co-channel interferences, simplify hardware design, and achieve fast (less latency) transmission, due to enhancement in Frame synchronization techniques. Inter-symbol interference and co-channel interference appearing in frequency-selective Rayleigh fading channels influence the bit error rate performance. This paper proposes a ZCZ-CDMA system with block coding and channel estimation techniques to improve the performance.

Transmission efficiency of code shift keying

The authors determine the frequency utilization efficiency of code shift keying (CSK) under practical design parameters. If an ideal bit-position discriminating function for M-sequence is used, the information conveyed by one frame of M chips (the length of M-sequence) increases to log/sub 2/M bits. This is the principle of CSK. However, it is more vulnerable to noise than the conventional spread spectrum system, DS-BPSK. The authors compare the transmission capacities of CSK and BPSK under identical conditions of receiving signal power, Gaussian and interfering noise power, frequency bandwidth, and bit error rate. The result shows that CSK is capable of transmitting 2/spl sim/4.5 times the capacity of BPSK.<<ETX>>

On a ZCZ code including a sequence useful for synchronization

This paper presents a ZCZ code which are combinedly used to spread data and synchronization symbol in quasi-synchronous CDMA systems using PSK, ASK or BFSK. Furthermore a simple matched filter is presented, which calculates simultaneously correlations with arbitrary sequences in the ZCZ code.

Quadriphase M-ary CDMA signal design without co-channel interference for approximately synchronized mobile systems

Suehiro (1985) has proposed a quadriphase signal design method for the uplink of the cellular CDMA mobile communication systems. The designed signals work without co-channel interference when the systems are synchronized approximately. The designed signals are free from the influence of multipath signals within some delay. The filters for the designed signals can be realized as SAW devices. We assign plural quadriphase signals as M-ary signals for each user so that the information-transmission rate is increased. The property of without co-channel interference remains the same, but the multipath property becomes a little bit worse. The filters for M-ary signals can also be realized as SAW devices.

On BFSK-ZCZ-CDMA systems

Quasi-synchronous CDMA systems, which can remove co-channel interference by means of synchronization control and use of a ZCZ code, are useful for Short-Range Wireless communications. This paper proposes a BFSK-ZCZ-CDMA modulation system which appears more advantageous in bit-error-rate performance over multi-path fading channels than ASK or PSK modulation scheme. In this system, a balanced ZCZ code and a quasi-coherent detection with IQ separation are used. The bit-error-rate performances over AWGN and fading channels are simulated.

A ZCZ-CDMA system with BFSK modulation

A quasi-timing synchronous code division multiple access (CDMA) system called ZCZ-CDMA, which uses a set of sequences with a zero-correlation zone called ZCZ code as a spreading code, is useful for short-range wireless communications because of its excellent properties such as co-channel interference-free performance, simplified hardware design, and low transmit power as well as fast frame synchronization capability. In this paper, a ZCZ-CDMA system with binary frequency-shift keying (BFSK) modulation called BFSK-ZCZ-CDMA is proposed. This system is characterized by using a pair of balanced ZCZ codes for spreading and transmitting the two spread components over the respective keying carrier frequencies. Its bit error rate performance, compared with those of existing BPSK-ZCZ-CDMA, ASK-ZCZ-CDMA, and CDMA systems using the other spreading codes, is evaluated in theory and simulation. The bit error rate performance of the three ZCZ-CDMA systems over additive white Gaussian noise and Rayleigh fading channels are formulated. It is proved that BFSK-ZCZ-CDMA is much more robust in anti-fading performance and low transmit power in such an environment that fading distributions on the keying frequencies are independent mutually. Fading versus frequency characteristics are also investigated. Copyright