Samir A. Al-Gailani

A survey on access technologies for broadband optical and wireless networks

The bandwidth demand of telecommunication network is growing rapidly due to the increasing number of technology-intelligent end-users. The emerging optical and wireless access networks are continuously competing with each other to provide these requirements for the end-users. The optical access networks provide huge data rate and long-distance link, but it is less ubiquitous. The wireless access networks provide flexible and ubiquitous communication with a low deployment cost. However, its deployment scalability is limited by the spectrum and range limitations. The hybrid wireless optical broadband access network (WOBAN) is a powerful combination of optical backhaul and wireless front-end to contribute to a good scalability, cost effective and flexible communication system. This paper reviews the key enabling access technologies and progress advancements of these networks. The emerging optical and wireless access technologies are also presented and compared.

Evaluation of a 1 Gb/s Free Space Optic system in typical Malaysian weather

Free Space Optical (FSO) communication is increasingly growing type of communication around the world because it has capability similar to fiber optic in terms of speed and bandwidth. But FSO is more preferred compared to fiber optics communication from the point of view of time and cost of deployment. FSO can transmit data from point to point at speed of light through space and requires no licensing. Since FSO is a line of sight communication so it is vulnerable to atmospheric attenuation, so to overcome this immense problem it is necessary to precisely study the channel characteristics present between the transmitter and receiver, especially for tropical climate region like Johor Bahru (JB) Malaysia, where rain and haze attenuation are the main concern. Many studies have been carried out in the temperate climate region where the attenuation due to snow and fog are the two major problems in the placement of FSO. The study in this paper concentrates on performance of single beam FSO system under heavy rain events for a period of four months from the point of view of attenuation and BER versus link distance L. The study is based on simulation and other atmospheric losses are not included. The results from the analysis have shown that under average of maximum rain rate intensities for the period of four months in typical Malaysian weather, single beam FSO system can successfully operate for a link distance of 830m with 19 dB/km attenuation and BER of 10-9. It is also clear from this study that link distance is inversely proportional to rain intensity.

Optical frequency upconversion technique for transmission of wireless MIMO-Type signals over optical fiber

The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength.

A novel optical single-sideband frequency translation technique for transmission of wireless MIMO signals over optical fiber

The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio over fiber (RoF) technique. However multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as MIMO signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical single-sideband frequency translation (OSSB-FT) technique is proposed to solve this problem. In this paper, three wireless MIMO signals are designed to transport over a 20 km standard single mode fiber (SMF) using the OSSB-FT technique by one optical source. Each wireless MIMO signal is with a 2.44 GHz carrier frequency, 1 Gb/s data rate, and 16 quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is excluded, since each wireless MIMO signal is carried on a specific optical wavelength.

Stacked TDM-PON with colorless ONU for NG-PON

Current passive optical networks (PONs) (Gigabit PON (GPON) and Ethernet PON (EPON)) will run out of bandwidth sooner or later due to the ever increasing bandwidth demand. The aforementioned and the new next generation PON stage 1 (NG-PON1) standards (10 Gigabit-PON (XG-PON) and 10 Gigabit Ethernet-PON (10G-EPON)) are based on time division multiplexing (TDM-PON), which has its limitations such as limited bandwidth. In this paper, stacked TDM-PON architecture with four wavelengths for each direction, that is compatible with currently deployed optical distribution networks (ODNs), is proposed to meet the requirements of NG-PON stage 2 (NG-PON2). The proposed architecture has colorless optical network units (ONUs) by generating the upstream wavelengths at the optical line terminal (OLT). Four laser diodes (LDs) at the OLT for the upstream transmission are enough for all ONUs, instated of having LD or optical transmitter at each ONU, which makes a colorless and cost-effective ONU. A good performance is observed for 40 Gb/s downstream transmission and 10 Gb/s upstream transmission.

Enabling optical and wireless broadband access technologies

The bandwidth demand of the telecommunication network users are increasing from day to day. Bandwidth demand in our networks will continue to grow rapidly due to the increasing number of technology-intelligent users. Four main expectations from the users are high mobility, large data bandwidth, high quality of service (QoS), and ubiquitous coverage. The emerging optical and wireless access technologies are expected to provide these demands. Optical and wireless access networks have emerged to address two issues: channel capacity sharing fairly to the customers, and adequate capacity assignment according to service requirements. In this paper, the enabling optical and wireless broadband access technologies are presented and compared. The architectures, advantages, disadvantages, and main parameters of these access networks are discussed and reported. The hybrid wireless-optical broadband access technology is presented, which has many advantages to become the next-generation broadband access network. The concept and architecture of the hybrid wireless/optical broadband access technology are reviewed. The hybrid system developed at the Lightwave Communication Research Group (LCRG) is presented as a case study. It comprises of passive optical network in the trunk and a wireless-optical access network. The passive optical network (PON) supports a maximum data rate of 100 Gbps by using the orthogonal frequency division multiplexing (OFDM) technique in the optical access network. In the wireless access network, WiMAX IEEE 802.16m provides data rate of 1 Gbps for fixed users and 100 Mbps for mobile users.

Simultaneous provision of two MIMO wireless and baseband wired services in a single wavelength

Next-generation access networks require simultaneous provision of wired and wireless services and high data rate to meet the huge demands for mobility and multiple services. In this paper, we propose a spectral efficient radio over fiber scheme to simultaneously provide two spatial multiplexed multiple input multiple output (MIMO) wireless signals with baseband (BB) signal in one wavelength using a centralized light source. The proposed scheme can be applicable in wavelength division multiplexed passive optical network (WDM-PON). The BB signal is modulated at low extinction ratio. Using the same modulated light, the two MIMO signals that have the same career frequency are combined optically using polarization-division-multiplexing (PDM). The BER performance of 10-9 is achieved for the three signals after transmission of 20 km single mode fiber (SMF).

Scalability analysis of hybrid optical wireless access network (HOWAN)

The hybrid optical wireless access network (HOWAN) is a prestigious architecture for next generation (NG) access network. NG access networks are proposed to provide high data rate, broadband multiple services, scalable bandwidth, and flexible communication for manifold wireless end-users (WEUs). In the proposed HOWAN, the optical backhaul and the wireless front-end are implemented by using wavelength division multiplexing/time division multiplexing passive optical network (WDM/TDM PON), and WiFi wireless access technique respectively. In this paper, the scalability of the optical backhaul in terms of the number of supported APs and link reach range are analyzed. The scalability of the optical backhaul based on maximum split ratio of 1/32 for each wavelength channel and a fiber length around 23 km from the central office (CO) to the access point (AP) is analyzed with bit error rate (BER) of 10-9.

Cost-effective 2.5 Gb/s bidirectional WDM PON using single optical source at the central office

Nowadays, the bandwidth demand of the telecommunication network is growing rapidly due to the increasing number of technology-intelligent users. Optical broadband access networks have emerged to address two issues: (1) channel capacity sharing fairly to the customers, and (2) adequate capacity assignment according to service requirements. The wavelength division multiplexing passive optical network (WDM PON) is a promising solution to provide high data rate, excellent scalability, good protocol transparency and easy upgradability. In this paper, a cost-effective bidirectional WDM PON is proposed to provide symmetrical 2.5 Gb/s by using just single optical laser diode (LD) at the central office (CO). The optical frequency upconversion (OFU) technique is used to implement the proposed network. At the optical network unit (ONU), the reflective semiconductor optical amplifier (RSOA) reuses and amplifies the downlink wavelength to modulate the upstream data. The bit error rate (BER) performance and eye diagrams of the designed system are investigated.

Wireless signals transport schemes in fiber wireless systems

Next generation (NG) technologies are proposed to provide high data rate, broadband multiple services, scalable bandwidth, and flexible communication for manifold wireless end-users (WEDs). The fiber-wireless (FiWi) network is a promising network for the NG technologies, since it is a powerful combination of optical backhaul and wireless front-end. The optical backhaul of the FiWi network is a tree network connecting the central office (CO) and wireless front-end. The wireless front-end consists of access points (APs) which are widespread to penetrate multiple WEDs. There are two main schemes to transmit the wireless signals in the FiWi system: (1) baseband-over-fiber (BBOF) transmission scheme, (2) radio over fiber (ROF) transmission scheme. This paper will review and discuss the concept and architecture of the FiWi system. This review is important to report the architectures, advantages, disadvantages, and the main parameters of these transmission schemes.