Sharif Digital Repository

In this paper we propose and analyze the application of generalized optical orthogonal codes (GOOC) in the optical wireless local area networks (OWLAN). A system deploying GOOC can support more users and achieve better BER performance. We evaluate the system performance of GOOC noting practical constraints of OWLAN applications. We consider average and peak power limitations of free space infrared sources, arising from eye safety and device non-linearity restriction. We include the impact of various noises including background-light induced noise in system evaluation. Proper system design requires appropriate selection of GOOC code parameters. We analyze the influence of code parameters on... 

Wireless infrared optical code-division multiple access (W-OCDMA) is a new developing technique with many useful applications. Noting the limitation on power consumption and eye-safety requirements, wireless optical systems are power limited. Therefore control and efficient use of optical power is a key issue in analysis and design of these systems. Also, multi-user interference is the major source of impairment in these systems and power control is required to control and reduce this interference. Power control and the inevitable errors in its algorithms play an important role in design and implementation of these systems. In this article the authors study the uplink performance of W-OCDMA... 

The effect of thermal noise and avalanche photodiode (APD) noise in a code division multiple access (CDMA) system using generalized optical orthogonal codes (GOOC) are investigated for the first time. The modulations used are pulse position modulation (PPM) and overlapping PPM (OPPM). Double optical hardlimiter receiver structure is selected because of its efficient performance. We show that, in a system with all mentioned noise sources, known parameter values, and a bit error rate of 10-7, GOOC codes with cross correlation (λ) equal to 2 support 20 more users compared to strict OOC. We have also analyzed the spectral efficiency of the GOOC OPPM system and compared it with GOOC PPM. The... 

In this paper we propose and analyze the application of generalized optical orthogonal codes (GOOC) in the optical wireless local area networks (OWLAN). A system deploying GOOC can support more users and achieve better BER performance. We evaluate the system performance of GOOC noting practical constraints of OWLAN applications. We consider average and peak power limitations of free space infrared sources, arising from eye safety and device non-linearity restriction. We include the impact of various noises including background-light induced noise in system evaluation. Proper system design requires appropriate selection of GOOC code parameters. We analyze the influence of code parameters on... 

In this paper, we analyze the performance of a wireless infrared system with code division multiple access (CDMA) technique using optical orthogonal codes (OOCs). Performance improvement is shown when power control is applied to the system. Noting the advantages of pulse position modulation (PPM), we have used chip-level binary PPM scheme. To mention some of these advantages we can name average required power reduction and BER improvement in comparison to on-off keying (OOK). The obtained results show that power control is a mandatory part of the design in a wireless infrared system using OOC. ©2007 IEEE  

This paper analyzes the performance of generalized optical orthogonal codes (OOC) in a wireless infrared system using code division multiple access (CDMA) technique. Since the emergence of generalized OOC s, they have been analyzed in optical fiber media, in which noise can be ignored with good approximation. But in an optical wireless system which inherently suffers from intense noise sources, generalized OOC behaves differently. The main issues of an optical wireless system are intense noise sources which degrades system performance and limited available bandwidth which is caused by multipath distortion in the channel. We believe that these analyses will help the designer of an optical... 

Optical Code Division Multiple Access has recently received considerable attention in wireless infrared communication. Previously introduced algorithms for wireless indoor infrared communication such as Advanced Infrared and IEEE 802.11 infrared standard use specific media access control (MAC) layer algorithms to coordinate transmission of multiple users. In this paper, we compare the multiple access performance of OCDMA with that of these algorithms and demonstrate the relative strengths and weaknesses of each algorithm. It is demonstrated that when MAC delay is an important issue, OCDMA provides a much better performance. Furthermore, OCDMA requires no coordination between users as they... 

In this study, the authors study a fibre-optic local area network deploying optical code division multiple access technique with differential M-ary pulse position modulation (DPPM). The authors present the performance analysis of DPPM signalling using a double optical hardlimiter receiver structure considering the impairment caused by interference of other users. The analysis assumes a set of bit asynchronous transmitters employing generalised optical orthogonal codes for their DPPM signalling (GOOC-DPPM). Using mathematical analysis and simulations, the authors have demonstrated that GOOCDPPM improves both frame error probability and the maximum achievable network throughput compared with... 

Wireless infrared optical code-division multiple access (W-OCDMA) is a new developing technique with many useful applications. Noting the limitation on power consumption and eye-safety requirements, wireless optical systems are power limited. Therefore control and efficient use of optical power is a key issue in analysis and design of these systems. Also, multi-user interference is the major source of impairment in these systems and power control is required to control and reduce this interference. Power control and the inevitable errors in its algorithms play an important role in design and implementation of these systems. In this article the authors study the uplink performance of W-OCDMA... 

In this paper we study slotted ALOHA random access optical code division multiple access packet-switching networks with a chip-level receiver structure. We use generalized optical orthogonal codes (GOOCs) and the overlapping pulse position modulation (OPPM) signaling technique to improve system performance. The impact of physical layer parameters such as the GOOC cross-correlation value and the OPPM overlapping index on key performance benchmarks such as network throughput and delay are analyzed. We also study the stability of the network based on the number of backlogged users, using the expected state drift. It has been shown that using GOOC instead of strict optical orthogonal codes...