WiMAX-THE FUTURE OF WIRELESS NETWORKS

Transcription

1 WiMAX-THE FUTURE OF WIRELESS NETWORKS V.Nithishraj*,S.Gokul Sreram**,G.Jeyanth*** Department of Electronics and Communication Engineering, MIT Anna University Chennai. Abstract-WiMAX (world wide interoperability for microwave access) is a potential backhaul technology for the fourth generation (4G) of wireless networks. 4G provides high speed, high capacity, low cost per bit, IP based services for video data and voice (VoIP). The development of new technology should allow bridging of functions like broadband data access and VoIP. This paper will evaluate the potential of WiMAX as 4G technology; provide comparison between existing wireless technology (Wi-Fi) and WiMAX. Furthermore it presents the future applications of the latter. 1. INTRODUCTION WiMAX is a telecommunication protocol that provides fixed and mobile internet access. WiMAX forum describes WiMAX as a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL. WiMAX refers to the interoperable implementations of IEEE standard, whereas Wi-Fi refers to the implementations of standards. The further two subdivisions of the WiMAX standards are d which is for fixed WiMAX and e for mobile WiMAX. WiMAX provides an ample amount of opportunity to interconnect devices within an entire geographical area. This provides a mechanism of interconnecting devices in a large area, thereby making the devices smarter and increases the efficiency with which devices in a network communicate with each other. This finds particular application in vehicular collision prevention and hospitals in bio telemetry system, the details of which have been presented in the later sections. In short, WiMAX enables on the go connection to a metropolitan network. There is a lesser probability for disconnection, as in WiMAX each user is allocated a slot of the bandwidth which will not be shared by the other users, as a result of which each user gets a constant data rate without disruption. Several market players in India have started recognizing WiMAX as the perfect technology for the speedy rollout of mobile internet access. The rest of the paper is organized as follows: section II will present an overview of the wireless evolution. Section III describes the characteristics of WiMAX technologies. Section IV presents a comparison between Wi-Fi and WiMAX. Section V will elucidate on future applications of this technology.

2 II. OVERVIEW OF THE WIRELESS EVOLUTION The original analog and digital cellular services were invented to cut the wire on landline phone service and give regular telephone service that was mobile. But the bandwidth of data services was low. Now the cell phones double as a smart phone, messaging system, internet browser, reader and facilitate social networking. The demand for greater bandwidth has brought about intermediate generations- 2.5G,2.75G,3G,3 ¼ G(called HSDPA). 4G standards of data speeds of up to 20Mbps sufficient for HD video transmission and facilitate downloading of large files. WiMAX provides mobile broadband connectivity across cities and countries and enable data, telecommunications (VoIP) and IPTV services (triple play). Triple play service is a marketing term for provisioning of two bandwidth intensive services, high speed internet access and television and a less bandwidth demanding but more latency sensitive service, telephone, over a single broadband connection. WiMAX supports the technologies that make triple play service offerings possible such as quality of service and multicasting. Wi-Fi is a popular wireless technology of the current generation which provides localized highspeed wireless broadband access. Whereas WiMAX facilitates long range wireless access at an incessant data rates. Smart phones of the future, PC cards, USB dongles which have omnidirectional antennas are used to tap into a WiMAX network. Table 1.Mobile evolution III. CHARACTERISTICS OF WiMAX (A)SPECIFICATIONS OF WiMAX WiMAX adds support for mobility (soft and hard hand off between base stations). This is seen as one of the most important aspects of e and is the very basis of mobile WiMAX. This standard uses scaling of the FFT to the channel bandwidth in order to keep the carrier spacing constant across different channel bandwidth (typically 1.25 MHz, 5 MHz, 10 MHz or 20 MHz). Constant carrier spacing results in higher spectrum efficiency in white channels and a cost reduction in narrow channels. This is known as scalable OFDMA (orthogonal frequency division multiple access). The bands that are not multiples of 1.25 MHz defined in the standard but since the allowed FFT sub-carrier numbers are only 128,512, 1024 and 2048, other frequency bands will not exactly have the same carrier spacing which might not be optimal for implementations. Carrier spacing is KHz. WiMAX uses advanced antenna

3 diversity schemes and hybrid automatic repeat request (HARQ). It uses adaptive antenna systems and MIMO (multiple input multiple output) technology. It provides for denser sub channelization thereby improving indoor penetration. This technology introduces turbo coding and low density parity coding. It introduces downlink sub channelization allowing administrators to trade coverage for capacity or vice-versa. There is a provision for adding an extra Quality of Service Class for VoIP applications. The protocols are subdivided into two layers viz, physical layer and MAC data link layer. Physical layer uses SOFDMA (scalable OFDMA), multiple access support through MIMO.MAC data link layer provides scheduling algorithm wherein the user needs to wait only once to gain connection. Subscriber s station is offered a slot which the other users need not use. (B)VIABILITY OF WiMAX AS AN ALTERNATE TO 3G AND MIGRATION TOWARDS 4G Introduction of mobility into the WiMAX roadmap, as well as the slow and expensive roll-out of 3G in many areas of the world, has changed the picture, and WiMAX is seen as a direct challenge to some 3G operators. This section gives the answer to the Mobile carriers' burning question, how WiMAX will pose a significant threat to cellular voice and will compete with their cellular networks and migrate towards 4G. (i) Data Speed: W-CDMA can support speeds up to 100 Kbps. EVDO has download speeds up to 2.4 Mbps. The HSDPA technology enables downlink with data transmission up to 8-10 Mbps. But WiMAX supports data downlink speeds in excess of 500Kbps several kilometers from a base station. (iii) Coverage range: The voice requirement limits the W-CDMA cell size, restricting coverage to just two to three kilometers from a base station. WiMAX has a range of 4-6 miles (30 miles max). (v) Spectrum: WiMAX's genuine advantage over 3G is that it can work in either licensed or unlicensed spectrum, whereas cellular require licensed spectrum. (vi) Interference: WiMAX based on OFDM utilizes multiple channels to send and receive data, which results in less interference than 3G cellular data systems such as 1x EV-DO and HSDPA. (vii) IP connectivity: WiMAX supports ATM, IPv4, IPv6, Ethernet, and VLAN services. So, it can provide a rich choice of service possibilities to voice and data network service providers. (viii) Interoperability: The architecture shall lend itself to integration with an existing IP operator core network (e.g. DSL, cable, or 3G) via interfaces that are IP based and not operator-domain specific. This permits reuse of mobile client software across operator domains. (ix) Cost of deployment: In addition to the advantages in converging mobility, portability and fixed Internet access, the cost factor is also important for any deployment. WiMAX infrastructure is far cheaper than cellular. (xi) Standardization: The WiMAX forum works for standardization and will make sure multiple vendor solutions available. This means that the big mobile operators

4 could potentially migrate their networks with mobile WiMAX technology. (xii) Economies of scale: With standardization comes the ability to massproduce products, so research and development costs decline along with manufacturing expenses. This could pave the way for lower-cost services and will make BWA feasible for mass deployment. (xii) Limitations: WiMAX operates at high bit rate or over long distances but not both. It cannot deliver 70Mbps over 50Kms. Peer-to-Peer(P2P) and ad hoc networks, where an end user communicates to users or servers on another LAN using its access points or base station. However supports also direct ad hoc or P2P networking between end user devices without an access point, while end user devices must be in range of the base station. Feature WiMAX (802.16a) Wi-Fi (802.11b) IV.COMPARISON BETWEEN WiMAX AND Wi-Fi Primary Application Frequency Band Broadband Wireless Access Licensed/Unlicensed 2 G to 11 GHz Wireless LAN 2.4 GHz ISM WiMAX is a long range system covering many kilometers that uses licensed or unlicensed spectrum to deliver connection to a network, in most cases the internet whereas the Wi-Fi uses unlicensed spectrum to provide access to a local network. Wi-Fi runs on media access control s CSMA/CA protocol which is connectionless and connection based whereas WiMAX runs a connection oriented mac. WiMAX and Wi- Fi have quite different quality of service mechanisms. WiMAX uses a QoS mechanism based on connections between the base station and the user device. Each connection is based on specific scheduling algorithms. Wi-Fi uses contention access all subscriber station that wish to pass data through a wireless access point is competing for the access point s attention on a random interrupt basis. This can cause subscriber stations distant from the access point to be repeatedly interrupted by closer station, greatly reducing their throughput. Both (Wi-Fi) and (WiMAX) define Channel Bandwidth Radio Technology Bandwidth Efficiency Modulation FEC Encryption Adjustable 1.25 M to 20 MHz OFDM (256-channels) 25 MHz Direct Sequence Spread Spectrum <=5 bps/hz <=0.44 bps/hz BPSK, QPSK, 16-, 64-, 256-QAM Convolutional Code Reed-Solomon Mandatory- 3DES Optional- AES QPSK None Optional- RC4 (AES in i) Access Protocol Request/Grant CSMA/CA Duplexing TDD, Frequency DD (FDD), Half-Duplex FDD(H-FDD Time Division Duplexing(TDD) Table 2.comparison of Wi-Fi and WiMAX V. POSSIBLE TRENDS OF FUTURE WiMAX COMMUNICATIONS The inception of WiMAX will pose benefits in multitudinous fields like surveillance, road traffic monitoring, security, bio-

5 telemetry systems, and telecommunications and so on. Video surveillance system: Success of realtime video surveillance on public transport heavily depends on future communication technologies like WiMAX. WiMAX has emerged as an exciting technology with promises to offer high throughput and improved quality of services (QoS), key requirements for video surveillance on public transport. WiMAX however, offers limited throughput at high vehicular speeds mainly because of multipath fading that causes high bit error rate at the receiver at vehicular speeds. Figure 1. Systematic architecture of disaster system IP-Cam Video Surveillance: The way of setting up traditional analog camera is building cable lines. Through the cable lines, video data captured by CCD (Charge- Coupled Device) camera is delivered to Control Center. The setting of cable lines is limited by distance and impact by terrain and surface features. In contrast, IP cameras are relatively simple installation. Through the video server that converts analog video signals to IP-based video format, back-end storage devices or control equipment can be placed in any network. Through the network connection, the image is able to be sent back. The IP based approach enables the camera image data can be managed in a centralized way. WiMAX, with the large coverage of high-bandwidth access, is very applicable to the deployment of IP cameras, especially for avoiding the impact of topography or the place where network line is not easy to reach, such as remote home care and military surveillance. Figure 2. Simulation scenario of a real-time video surveillance system on a public train. Security Aspects: Disaster-field video and audio subsystem provides a wireless broadband device mounted on a fire man, the device integrates the video, dualdirection audio, and data. Its aim is to deliver the fire field video to commander outside and provides dual-direction talking simultaneously. Figure 3. The architecture of IP-cam WiMAX service Mobility Surveillance System: In applications where there is a need of mobile surveillance such as cash transport van safety system, police on duty recording system, and disaster field video return system, etc. a camera is mounted on the

6 vehicle. This then provides a wireless network between the camera and control room through WiMAX. future Mobile WiMAX is expected to offer full broadband mobility for all type of services and deliver the goals 4G technology. REFERENCES [1] WiMAX Forum, M-Taiwan WiMAX applications Lab (MTWAL) Open House, Hsinchu, Taiwan, June Figure 4: The architecture WiMAX Mobility Surveillance System Road Traffic Monitoring: in the current scenario not all vehicles are equipped with a wireless system. After the large scale implementation of WiMAX each vehicle can be fitted with a WiMAX transceiver so that the relative signal strength between neighboring vehicles can be monitored continuously. if one of the received signals is of immense strength, then automatic braking system can be activated in the vehicles to avoid collision. VI. CONCLUSION We all know that in 5 years, 4G should be a reality and VoIP is going to drive new revenues and business models in the decade to come. Certainly, analyses done in the paper shows that WiMAX will win the marketplace and will capitalize on this and will further support the proliferation of VoIP devices and IP-based services. At the moment combination of WiMAX with Wi- Fi has the potential to compete on a costper-megabyte level with cable and DSL. The main advantage of this combination is that the whole geographic area becomes a hot zone and leads the path towards 4G. In the [2] Westech Communications Inc, can WiMAX Address Your Applications, WiMAX Forum, Oct [3] J. Wang, Q. Chen, D. Zhang, et al, Embedded Wireless Video Surveillance System for Vehicle, Proc. of ITS Telecommunications, June [4] Y. Zhao, Design and implementation of video surveillance system based on CDMA cellular wireless networks, Proc. of Int'l Conf. on Information and Automation, June [5] J. Hou, C. Wu, Z. Yuan, et al, Research of Intelligent Home Security Surveillance System Based on ZigBee, Proc. of the Intelligent Information Technology Application Workshop, Dec [6]Iftekhar Ahmad and DaryoushHabibi., High Utility Video Surveillance System on Public Transport using WiMAX Technology,Edith Cowan University, Australia [7] IEEE e Task Group (Mobile wirelessman ), 16/tge/, last accessed April [8] John Shelper, 1G, 2G, 3G, 4G, TechColumn, April2005, [Online] Available: [9] Alex Goldman, WiMAX is wrong for urban areas, ISPPlanet, June [10] Blue print, The next bout: 3G versus BWA. [11] Sean Buckley, WiMAX Forum gears up for mobility and more, Telecommunications Americas, Horizon House Publications, Inc., Gale Group, 2005.