Radio Over Fiber (ROF) System Design For Hospital Buildings

Answer all the questions below and present your answers in a clear and concise technical report.You have to design a Radio-over-Fibre System for a four storey hospital building that has 15 rooms per floor. The communication link is to be used for a wide variety of functions including locating physicians, requesting test results, checking patient records of patients and calling for mobile test data.

a) Show a block diagram of your designed system, justifying your selection of all the components. Clearly define all assumptions. 
b) Analyse your system performance using excel sheet to demonstrate that the link budget of the designed system meets the requirements. 
c) Implement the system in Optiwave and analyse its performance. Supplement your answer by demonstrating a solution in Optiwave.Tip: You might need to redesign your system after implementing it in Optiwave, make sure
you document this iterative process.

System Design and Block Diagram

The radio over fiber system, ROF, is designed to incorporate the fiber optic cable link in the hospital building alongside a free space radio path. The two are used simultaneously to ensure the digital communication is well-achieved. The fiber in the system with a wireless access point serves to connect users on a very high-capacity multimedia service. The system seeks to integrate the wireless radio system to the fiber optic communication technology.

The wireless signals are modulated over the optical carriers for data transmission at fiber optic light speeds. The ROF enables the centralization of the signal processing of the communication system [1]. It allows for performance and error monitoring, sharing of resources, and control and management.

The economies of scale are met as the ROF equipment tends to be relatively cheaper, smaller in size and has a simple implementation of a base station. The use of fiber guarantees higher bandwidth and it allows more users to communicate over a single channel by implementing very robust modulation techniques in the system [2]. The major costs are incurred during installation and integration within a building, thereafter, the maintenance costs are relatively affordable and can be included in the organization’s budget alongside other expenses [3].

            The ROF accommodates the passive optical network, PON, infrastructure. It is possible for one to use wavelength division multiplexing technique so as to improve the network throughput in the wireless or radio section of data transmission [4]. For a four-storey building, a designer would use the fiber optic cable to tap through all the floors.  Upon reaching the floors, one can have a local area network for each floor. The LAN should have both the wired and wireless connection. For instance, in the hallways of the hospital and the reception area, the wireless access points should be installed. All the rooms ought to have one or two LAN ports to connect to the wired internet for voice and data use especially where network hospital equipment is connected.  

Part A

System Design and Block Diagram

The design proposes the use of wireless network access point as the final component in the open regions where hospital equipment is not connected [5]. In the rooms 2 LAN ports are set to be installed for the hospital equipment connection such as the lifesaving machine or the MRI system connection, and an extra port for the patients or staff. ROF enlarges the coverage of the radio signal itself and is used to transport the radio signal from wireless devices onto the optical carrier for further distribution to other remote sections [6]. The optical fiber acts as a repeater as the connection is moved from one floor to another [7]. The design block diagram is as illustrated below,

Area

Part B

Table 1 Link Budget outline for the ROF system Design

Part C

System implementation on Optiwave and performance analysis

The system is simulated on the Optisystem simulator using two LEDs as the transmission distance is on a short range and multimode fiber optic cables are implemented. The Mach-Zender modulator is used to capture the incoming signals from the pseudo-random bit sequence. The NRX signals are mixed with the message signal before being modulated. The input comprises of 4 inputs from the 4 floors and the signals are modulated despite being at different wavelengths. The difference in wavelength enables the transmission over multimode fiber within the hospital.

When the system needs to communicate with the extranet or the internet, a single mode fiber is used and hence the message signals are multiplexed for transmission. The multiplexing is done using the Wavelength Division Multiplexing technique and amplified to give the signals a huge initial boost using the EDFA. A repeater is added by using the OADM for each floor at the inception connection point of every floor. This ensures that despite the distance a room is from the base station, the connection is still very strong and speed are more or less constant on every floor.  When a repeater is not implemented, the signal weakens and some rooms have very slow speeds of connection unlike others.

• RF Spectrum Analyzer
• The transmitted signal with noise
• The BER test and analyzer

• Eye Diagram analyzer
• System Overall Performance

Part D

Compare the performance of the designed system with simulated results

The simulated system shows all the stages required and captures the repeaters required in the stages to ensure signal strength. The Q factor is used to compare the external and internal modulation during the data transmission where the respective carrier frequencies are obtained using different fiber lengths as link ranges [8].

The simulation and design results are compared such that the following table was developed,

The simulation uses the lasers that are turned on for data transmission purposes and the noise for the photodiodes that tend to receive an optical signal from another laser by incorporating the ambient noise in addition of noise conversions. The interference and other instances of loss are well curbed in the simulation and some may not have been well factored in during the design. The design captures the key losses during transmission and the simulation takes into consideration more details on the loss factors and ensures that the designer has indicated values in all the instances [9].

The eye diagram analyzer block of the Optisystem software displays multiple traces of a modulated signal to produce an eye diagram. In downstream eye diagram we have calculate Bit error rate (BER) & Received optical power (dBm). In telecommunication, an eye pattern, also known as an eye diagram is an oscilloscope display in which a digital data signal from a receiver is respectively sampled and applied to the vertical input. While the data rate is used to trigger the horizontal sweep. It is so called because, for several types of coding the pattern looks like a series of eyes between a pair of rails. In downstream when bit error rate -4 dB than received optical power is -21 dBm.

            The Erbium doped fiber amplifier is used in amplification of the optical signals during transmission over a number of kilometers from the source point. They are quite useful as repeaters in the long-distance communication and depicts a fiber loss of up to 0.2dB per km. The optical spectrum analyzer depicts the signals presented at the receiver.  

              The NRZ coding is used in the design of the ROF on Optisystem software. It tends to suffers some form of non-linearities during the assimilation of the sine wave generator input [10]. The RZ coding tends to suffer dispersion for the shorter pulse widths. During modulation, the coding techniques demonstrate a very high-power regime which is needed in the transmission of messages from the hospital equipment with the source as plain data, video, or voice [11].

Part E

Maximum number of channels that the system can accommodate. Demonstrate the solution on Optiwave.For the uplink transmission,With connection to fiber, the channels still remain as 8 but the multiplexing improves the output.

References