Pulse Position Modulation Code Division Multiple Access Research Articles

Performance analysis of atmospheric optical PPM CDMA systems

We propose atmospheric optical code-division multiple-access (CDMA) systems. We analyze the bit-error rate of the proposed system using pulse-position modulation (PPM) with considering the effects of the scintillation, avalanche photodiode noise, thermal noise, and multi-user interference. We show that the atmospheric optical CDMA systems can realize high-speed communications when the logarithm variance of the scintillation is small. When /spl sigma//sub s//sup 2/ is large, we need to use forward-error correction codes.

Performance analysis of indoor infrared wireless systems using PPM CDMA

AbstractIndoor infrared wireless systems using pulse position modulation (PPM) code division multiple access (CDMA) have attracted much attention, because PPM CDMA can realize random access with the same wavelength. In addition, PPM CDMA has high power efficiency. The system referred to as PPM CDMA in the field of infrared wireless communications is usually referred to as CDMA with multibits/sequence in the field of optical fiber networks. The interference probability used in the literature on infrared wireless PPM CDMA systems is not applicable, and thus the correct performance of such systems has not been clarified. In this paper, we analyze the correct performance of indoor infrared wireless PPM CDMA systems. We assume a system using APD and use Gaussian approximation for the APD output. We analyze the performance in the chip synchronous case with consideration of APD noise, thermal noise, background noise, and interference noise. We show that indoor infrared wireless PPM CDMA can realize multiple access while reducing the required transmit power, compared with systems using on‐off keying (OOK) CDMA. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 85(1): 1–10, 2002

BER performance of turbo-coded PPM CDMA systems on optical fiber

We obtain upper bounds on the bit error rate (BER) for turbo-coded optical code-division multiple-access (CDMA) systems using pulse position modulation (PPM). We use transfer function bounding techniques to obtain these bounds, so our results correspond to the average bound over all interleavers of a given length. We consider parallel concatenated coding (PCC) schemes that use recursive convolutional codes as constituent codes. We consider systems using an avalanche photodiode (APD), and treat APD noise, thermal noise, and multi-user interference using a Gaussian approximation. We compare the performance of turbo-coded systems with that of BCH-coded systems with soft-decision decoding, and that of concatenated coding systems with outer Reed-Solomon (RS) code and inner convolutional code. We show that turbo-coded systems have better performance than BCH-coded systems. We also show that concatenated systems have better performance than turbo-coded systems when the block length is small and the received laser power is somewhat large.

Optical Wireless PPM CDMA Networks Employing OC and PC Signature Codes

A hybrid pulse position modulation (PPM) code division multiple access (CDMA) optical communication system is proposed and its performance is analyzed using three different orthogonal coding schemes: optical orthogonal codes, prime codes and extended prime codes. The hybrid can usefully be exploited in optical wireless and optical fiber networks. Two types of PPM CDMA structures have been considered and analyzed. The implications of the structures and the coding schemes on the system bit rate and number of users are assessed. Original results are presented for the system error probability against the number of users using the three different orthogonal codes.

Asynchronous multirate optical wireless PPM-CDMA in an indoor non-directed diffuse channel

Asynchronous multirate pulse position modulation-code division multiple access (PPM-CDMA) is proposed for an indoor optical wireless time dispersive channel. As a signature sequence for CDMA, an optical orthogonal code (OOC) is used. The optical PPM-CDMA has advantages in that it is power efficient and provides multirate services by simply varying the modulation level for the fixed chip rate at the transmitter and sampling time at the receiver.

Hybrid ppm‐cdma systems utilizing optical orthogonal codes for indoor wireless infrared communication

AbstractAn original hybrid pulse position modulation code division multiple access (PPM‐CDMA) scheme is proposed and studied in the context of the indoor infrared communication network. The use of optical orthogonal codes (OOC) is proposed and original results are presented illustrating the improvement in bit rate achieved by utilizing PPM‐CDMA rather than on/off keying (OOK) CDMA. Results are presented for the maximum number of users that can communicate over the network at a given bit rate and it is shown that there exists an optimum PPM order, at a given number of users, that maximizes the achievable bit rate. Original results are presented for the false‐alarm errors due to the OOC cross correlations, and the optimum system operating parameters that minimize these errors are specified.

New PPM-CDMA hybrid for indoor diffuse infrared channels

An original hybrid pulse position modulation code division multiple access (PPM-CDMA) communication technique that uses optical orthogonal codes (OOCs) is proposed and studied in the context of the indoor infrared channel. At the optimum PPM order and over the range of parameters considered, the hybrid is shown to achieve more than five times the bit rate achievable using conventional on off keying (OOK) CDMA under bandwidth constraints. Original results are presented for the false alarm errors due to the OOC crosscorrelations, and the optimum system operating parameters that minimise these errors are specified.