ENSC 427 Project

ENSC 427: COMMUNICATION NETWORKS

Group #6

Jae Sung Park : jsp6 at sfu.ca
Sujin Tom Lee : stl9 at sfu.ca

Video and Voice Backup over Mobile WiMAX

Abstract:

Most of vehicle black boxes use their own internal auxiliary data storage device to record the images and data (such as, Global Positioning System location and speed of the vehicle) at the time the accidents happen. The saved data and video provide significant and crucial information for the road accident victims. The problem occurs when the crash is severe and the internal data storage gets destroyed. The backing up of the black box information to main server will take care of this matter. The mobile WiMax (WiBro) IEEE 802.16e supports the connection across the hotspots while the fixed WiMax IEEE 802.16d does not guarantee the connection. Mobile WiMAX offers maximum transfer rate of 10 Mbps and maximum cover range of 1 km under the movement speed of 120 km/h [1]. The specification of the mobile WiMAX suits for the network that requires the high transmission rate and the flexible mobility. We will be applying the information backups from the vehicle black box using mobile WiMAX technology.

Introduction:

Mobile WiMAX Overview

Worldwise Interoperability for Microwave Access (WiMAX) is under IEEE 802.16e standard supporting high-speed (up to 75 Mb/s) wireless Internet technology over wide area (up to 50 km) [2]. Although it covers broad area, it's a fixed system, which is not suitable for use of Internet service in a moving vehicle.

During the development of IEEE 802.16 standard for fixed WiMAX, it was decided that mounting mobility support should also be considered. Thereafter, Mobile WiMAX is developed under IEEE 802.16e standard with Orthogonal Frequency Division Multiple Access (OFDMA) as its physical layer [3]. Mobile WiMAX guarantees smooth and decent data transfer speed (10 Mb/s) for a moving vehicle (up to 120 km/h) from one base station to another with regional region service. Furthermore, the technology can be accessed through portable Universal Serial Bus (USB) that converts base station signal into Wireless Fidelity (WiFi) signal. To make it handy, the system can pre-installed inside devices [4].

Mobile WiMAX and WiMAX are both under Metropolitan Area Network (MAN) range that covers up to 50 km from base station. However, only Mobile WiMAX guarantees connection from migration between two hotspots. Since base stations control hotspots, Quality of Service (QoS) has to be implemented efficiently. Under Mobile WiMAX QoS classes, Real-Time Variable Rate (RT-VR) suits flawlessly for this project. It supports real-time applications with variable-size data packet bursts, providing better throughput by “bursting” more than one packet at a time to reduce wait time duration. An example application of RT-VR is video and audio streaming. To ensure connection between a mobile station and a base station, they must “form a unidirectional connection between their respective Media Access Control (MAC) layers” sharing same QoS parameters [3].

Handover Overview

Handover is a term that is used to describe the mechanism when connection of a mobilizing subscriber station gets transferred from a BS to another. This mechanism of handover was first adopted in IEEE 802.16e (Mobile WiMAX) in September 2005, where the “old version” IEEE 802.16-2004 only supported fixed and nomadic connections [1]. Here, fixed connection only supports stationary users in the network and nomadic connection allows movements of users only inside the cover range of a BS’s.

There are mainly two different types of handovers that are correspondingly used in various situations; Hard handover and Soft handover. In detail, the Soft handover includes Macro Diversity Handover (MDHO), and Fast Base Station Switching (FBSS). Hard handover is applied to the low speed vehicles or to the walking users while Soft handover is used for very fast-moving users with speed up to 160 km/h [6]. Since the Hard handover is the simplest mechanism among the three and the backing up of the data from moving vehicles does not require the Soft handover's high-speed supports, we will be using Hard handover through out our simulations.

In the case of Hard handover, the MS only accesses to one BS. So the connection should be ended before setting up the connection to a neighboring BS, which gives the reason why the Hard handover is also called “before-make handover”[3]. The inevitable packet drops occur during the procedure because of this behavior. The handover occurs when the SNR (Signal-to-Noise Ratio) of neighboring BS exceeds that of current serving BS [6].

Figure 1: Hard handover realization [6]

For the MDHO, both BS and MS maintain a set called “Diversity Set”. It is a list of the BS’s that the MS can communicate. When downlink is set, the entire BS’s in the list send the traffic to MS’s and combination of received data gets carried out. For uplink, the MS sends to all the BS’s in the list and selection diversity of received data is performed [6].

MDHO

Figure 2: Macro Diversity Handover [6]

Similar to MDHO, MS continuously scans the BS’s in the diversity set in (FBSS). However, MS connects with only one of the active BS and defines an “Anchor BS”. Then MS communicates only with the Anchor BS for all uplink and downlink traffic. However, the Anchor BS can be switched over to other Active BS under diversity set from frame to frame depending on parameter that MS uses to choose Anchor BS [6].

FBSS

Figure 3: Fast Base Station Switching [6]

Discussion of Future Work:

For this project, the OPNET version 15 will be used to create our model. Our model will include two WiBro base stations and three sample mobile clients being the black boxes in the vehicles. Since the vehicles move over a wide range of area, we are going using two base stations is to see how the connectivity between hotspots gets changed. The mobile clients will be configured to mobilize across two WiBro base stations and the simulation parameters of packet loss probability, end-to-end delay and throughput will be used to analyze the practicality of the WiBro network. We will be looking at the parameters when the clients cross from one base station to another. In addition, we are going to include another mobile client but in this time, to mobilize inside the transmission range of a WiBro base station. This client is used for comparison purposes and will be the base line to tell the parameter discrepancies between the comparison client and the other three simulated clients.

References:

[1] K. Han-Seok; "Introduction to WiBro (mobile WiMAX)" Seoul, Korea, Sep. 2005; [Online]. Available: http://www.apnoms.org/2005/special/SS1_3.pdf (Mar. 2012)
[2] M. Brain and E. Grabianowski; "How WiMAX Works"; [Online]. Available: http://computer.howstuffworks.com/wimax2.htm (Apr. 2012)
[3] J. Pinola and K. Pentikousis, “Mobile WiMAX”, VTT Technical Research Centre of Finland; [Online]. Available: www.ciscosystems.com/web/about/ac123/ac147/archived_issues/ipj_11-2/112_wimax.html (Apr. 2012)
[4] O. Malik; "By 2012 Koreans Will Get 1Gbps Broadband Connections"; [Online]. Available: http://gigaom.com/2009/02/01/by-2012-koreans-will-get-a-gigabit-per-second-broadband-connection/ (Apr. 2012)
[5] IEEE 802.16-2004: “Air Interface for Fixed Broadband Wireless Access Systems” October 2004
[6] Z. Becvar and J. Zelenka, “Handovers in the Mobile WiMAX”, Czech Technical University Department of Telelcommunication Engineering Technicka 2, Praha 6, 166 27, Czech Republic
[7] J. Kim, J. Lee, K. Park, J. Kim, H. Chang, G. Lim, Y. Chang, and H. Kim, “WiBro (Wireless Broadband): An 802.16d/e Simulation Model”, Telecommunication System Division, Samsung Electronics, Suwon Korea, PP. 2.
[8] W. Hrudey, "Streaming Video Content Over IEEE 802.16 / WiMAX Broadband Access", April 2008.