+ All Categories
Home > Documents > CHAPTER 1

CHAPTER 1

Date post: 05-Oct-2015
Category:
Upload: apecevsb
View: 213 times
Download: 0 times
Share this document with a friend
Description:
DWT based WIBRO-Introduction
of 8 /8
CHAPTER 1 INTRODUCTION 1.1 Introduction With the increasing of the Internet based communication requirements, not only Internet, but also the wireless cellular mobile communication is sharply increased. Accordingly, with the spread of the notebook and the personal digital assistan wireless communication network is spotlighted. WI!"# is the wireless network w connect Internet in high data rate anywhere and anytime. WI!"# is a wireless b Internet technology being de$eloped by the %outh &orean telecoms industry. Wir broadband (Wi!ro is another name for I''' )*.+ e Internet standard. WI!"# time di$ision duple-ing ( DD for duple-, orthogonal frequency di$ision multi (#/D0A for multiple access and .12034 as a channel bandwidth. WI!"# was de$i to o$ercome the data rate limitation of mobile phones and to add mobility to b Internet access. #rthogonal frequency di$ision multiple-ing (#/D0 is a multip technique that subdi$ides the system bandwidth into multiple narrowband subcar an #/D0 system, the input data stream is di$ided into se$eral parallel sub5str reduced data rate, which increase symbol duration and each sub5stream is modul transmitted on a separate orthogonal subcarrier. he increased symbol duratio of cyclic prefi- and frequency domain equali4ation impro$e the robustness of # multipath delay spread in non5line5of5sight (67#% channel. WI!"# is wireless solution that enables con$ergence of mobile and fi-ed broadb through a common wide area broadband radio access technology and fle-ible netw architecture. he WI!"# Air Interface adopts #/D0A for impro$ing the performa multipath fading channel. #/D0A is a multiple5access8multiple-ing scheme that multiple-ing operation of data streams from multiple users onto the channels, and uplink multiple accesses by means of uplink sub channels. Initially WI!"#, targeted for operation in the *.9:34 frequency band, is desig high degree of fle-ibility in order to allow ser$ice pro$iders the ability to 3owe$er due to increase in wireless broadband demands in a unfair channel and asymmetric traffic between transmitter and recei$er the use of // 8I// in # a poor %ignal to noise ratio which results in increased bit error rate. 3ence address this by suitably replacing // 8I// by DW 8IDW in #/D0A section. 6 DW Decompose signals into subbands with smaller bandwidths and slower sample
Transcript

CHAPTER 1INTRODUCTION1.1 IntroductionWith the increasing of the Internet based communication requirements, not only the wired Internet, but also the wireless cellular mobile communication is sharply increased. Accordingly, with the spread of the notebook and the personal digital assistant (PDA), the wireless communication network is spotlighted. WIBRO is the wireless network which can connect Internet in high data rate anywhere and anytime. WIBRO is a wireless broadband Internet technology being developed by the South Korean telecoms industry. Wireless broadband (WiBro) is another name for IEEE 802.16e Internet standard. WIBRO adapts time division duplexing (TDD) for duplex, orthogonal frequency division multiple access (OFDMA) for multiple access and 8.75MHz as a channel bandwidth. WIBRO was devised to overcome the data rate limitation of mobile phones and to add mobility to broadband Internet access. Orthogonal frequency division multiplexing (OFDM) is a multiplexing technique that subdivides the system bandwidth into multiple narrowband subcarriers. In an OFDM system, the input data stream is divided into several parallel sub-streams of reduced data rate, which increase symbol duration and each sub-stream is modulated and transmitted on a separate orthogonal subcarrier. The increased symbol duration and the use of cyclic prefix and frequency domain equalization improve the robustness of OFDM to multipath delay spread in non-line-of-sight (NLOS) channel. WIBRO is a broadband wireless solution that enables convergence of mobile and fixed broadband networks through a common wide area broadband radio access technology and flexible network architecture. The WIBRO Air Interface adopts OFDMA for improving the performance in multipath fading channel. OFDMA is a multiple-access/multiplexing scheme that provides multiplexing operation of data streams from multiple users onto the downlink sub channels, and uplink multiple accesses by means of uplink sub channels. Initially WIBRO, targeted for operation in the 2.3GHz frequency band, is designed with a high degree of flexibility in order to allow service providers the ability to optimize system. However due to increase in wireless broadband demands in a unfair channel and asymmetric traffic between transmitter and receiver the use of FFT/IFFT in OFDMA gives a poor Signal to noise ratio which results in increased bit error rate. Hence there is need to address this by suitably replacing FFT/IFFT by DWT/IDWT in OFDMA section. Normally DWT Decompose signals into subbands with smaller bandwidths and slower sample rates. Compute the Discrete Wavelet Transform or decompose a signal into subbands with smaller bandwidths and slower sample rates. It uses a filter bank with lowpass and highpass FIR filters. The lowpass and highpass filters are usually half-band filters designed to complement each other and similarly uses IDWT to Compute the Inverse Discrete Wavelet Transform or reconstruct a signal from subbands with smaller bandwidths and slower sample rates. This Design of a DWT based WIBRO System for Military Applications and its Performance in Fading Channels deployments with respect to cell planning, cost, radio capabilities, services, and capacity. DWT based WIBRO adapts TDD for duplexing, OFDMA for multiple access and 10MHz as a channel bandwidth. It offers an aggregate data throughput of 30 to 50 Mbit/s and covers a radius of 1-5km allowing for the use of portable internet usage. In detail, it will provide mobility for moving devices up to 120km/h compared to WLAN(Wireless Local Area Network) having mobility up to walking speed and mobile phone having mobility up to 250km/h. 1.2 Network Architecture of DWT based WiBro or Indoor DWT based WiBro network modelThe network architecture of DWT based WiBro is shown in Figure 1.1.

Figure 1.1 Network Architecture of DWT based WiBro

Functionality of ACR and RAS ACR Access Control Router Packet classification & header suppression Service flow management Traffic switching & Integration point Handover management Session information maintenance RAS interface Core network interface

RAS Radio Access Station PHY Processing and air resource scheduling MAC management message processing MAC PDU processing CID management Encryption & Decryption ACR interface

Basically, the network architecture of DWT based WiBro is the same as other IP-based networks but there is difference at the radio access network. A new RAN has been designed to enable the requirements of high data rate with mobility. RAS have the responsibility to interface between mobile and core network at the physical layer and it also controls the radio resource at the data link layer in conjunction with ACR. RAS and ACR also support link layer handoff. Indoor DWT based WiBro system is supposed to be deployed in home and office. In this case, each indoor RAS can construct its own private network (Femto cell). Usually, indoor DWT based WiBro network in home environment does not even contain ACR. The RAS of indoor DWT based WiBro takes over some essential functions of ACR instead. Also, there can exist an simplified ACR in the indoor DWT based WiBro network, namely pico-ACR, in offfice area. However, the functions of a pico-ACR are very different from those of the existing ACR in outdoor DWT based WiBro system. Therefore, if we directly apply the existing layered architecture for network management to indoor DWT based WiBro system, each RAS in home and each ACR in office should have their own DWT based WiBro.

Figure 1.2 DWT based WiBro system architecture.1.3 DWT based WiBro System Specification:Koreas Wireless Broadband (DWT based WiBro) initiative is pursuing to provide ubiquitous Internet access from various wireless devices with the mobility of up to 60km/h over a distance of several tens of kilometers in the multi-cell environment. It is launched by Korean government and several Korean companies, and the first commercial service will be opened in 2006 by a couple of service providers. The DWT based WiBro specification released by Korean Telecommunication Technology Association (TTA), is based on a subset of IEEE 802.16 standard. For the radio channel between BS and SSs, Korean government allocates 100MHz frequency bandwidth from 2.3GHz to 2.4GHz. DWT based WiBro specifies a communication channel of 9MHz bandwidth, thus, nine individual 9MHz channels are available. Over this radio channel, uplink and downlink access divides a fixed time interval, called frame. Among various physical layer schemes to organize a frame in 802.16, DWT based WiBro system only adopts Orthogonal Frequency Division Multiple Access (OFDMA) in Time Division Duplex (TDD) mode. The TDD frame length is 5 msec, and is segmented into the sequence of small fixed-duration logical units, called symbols. The frame structure is fixed as 27 symbols for the downlink subframe and 15 symbols for the uplink subframe. The detailed DWT based WiBro frame structure is depicted in Figure 1.3. (The narrow gaps between subframes are ignored.)

Figure 1.3: DWT based WiBro OFDMA TDD Frame StructureThe encoded data bits are transmitted over a set of subcarriers in wireless communications. In the DWT based WiBro specification, there are 864 subcarriers (FFT size is 1024) within 9MHz bandwidth. A set of subcarriers composes a logical transmission unit, called subchannel. While there are several different ways of constructing a subchannel from subcarriers according to the location of subchannels within subframe, the number of subchannels is 16 (in FUSC mode) in the DWT based WiBro specification. The unit symbol time of a single subchannel is defined as a slot. This slot is the logical encoding unit of wireless transmission. A bit stream is encoded into a slot, in other words, the bit stream is carried by a sub channel during the period of a symbol time. For downlink, 26 symbol times are available for logical maps and downlink bursts, while 12 symbol times are available for uplink bursts for uplink; 416 slots for downlink and 192 slots for uplink. The MAP consists of Frame Control Header (FCH), DL-MAP (downlink map), and UL-MAP (uplink map). The maps guide SSs how to decode the following data bursts. The burst is a set of actual data slots that are allocated by a BS, for either downlink or uplink. SSs are informed when and on which sub channel they need to decode data for downlink, and to encode data for uplink. The BS is responsible for organizing the maps and the bursts in every frame. The 802.16 MAC messages are transferred in each burst. The DWT based WiBro specification uses the same MAC message format as 802.16. The MAC message has user payload, 6-byte fixed MAC header, optional 4-byte CRC and optional 12-byte encryption data. There is no difference, when it comes to the functionality and the format of MAC messages, between DWT based WiBro and 802.16. In addition to the messages in 802.16d, DWT based WiBro adopts standard messages defined in 802.16e for mobility support. Hand-over mechanisms and sleep mode operations are two main features added for the mobility support. The uplink control information sub frame is a collection of special-purpose control channels and uses three dedicated symbol times in the uplink sub frame. There are four different bandwidth allocation service types; Unsolicited Grant Service (UGS), real-time Polling Service (rtPS), non-real-time Polling Service (nrtPS), and Best Effort (BE) service. They are different in how the bandwidth request and grant messages are exchanged between SS and BS. Every uplink session is mapped to one of the service types. The BS is responsible for uplink scheduling as well as downlink scheduling at the same time.1.4 Key features of DWT based WiBro: High speed internet service (indoor & outdoor) Maximize the usage over the allocated spectrum Maximize the spectral efficiency Extend the service coverage Reduce the cost per bit Low power consumption Faster handoff Easy cell planning Roaming with cellular and WLAN Much lower service charges than EV-DO Much higher-speed Internet access than EV-DO Mobile Internet access in high-speed mobile environment Much wider coverage than wireless LAN-based services Flexible sub channelization for band selection and diversity Full diversity sub channel by multiple symbol grouping Preamble for Cell differentiation with different Random sequences Pilot tone based DL and UL and Pilot-assist transmission in DL and UL OFDM symbol timing and frequency. DWT based WiBro is for the wireless high-speed broadband service able to deliver data, video and voice at speeds of up to 120 km/h. DWT based WiBro (Mobile WiMAX) provides true mobile connectivity by giving users seamless broadband connections anytime, anywhere. Portable and mobile applications include DWT based WiBro will provide broadband services to metropolitan areas not accessible by current technology as well as create broadband "hot zones" in more densely populated areas. DWT based WiBro service is being provided in Korea using 100 MHZ of frequency spectrum in the 2.3GHz band. DWT based WiBro technology can become one of the strong candidates for the 4G (4th Generation) wireless standard and DWT based WiBro in aperture between 3G and 4G. DWT based WiBro services can have potential applications in various fields e.g., Interactive services: Web Browsing, Game interface, Interactive information, Wireless Internet access, Network Game etc Streaming services: VoD, MPEG, etc. Back Ground services: FTP, E-MAIL, SMS, multicast/broadcast, MMS, Push To Talk, Real time broadcasting, Conferencing etc. Information service : Voice over Internet Protocol (VoIP), Video telephony

Figure 1.4 Wireless technology roadmap: DWT based WiBro Positioning1.5 Advantages of DWT based WiBro Provides high data rate and high speed internet service (indoor & outdoor) Maximize the usage over the allocated spectrum Maximize the spectral efficiency Extend the service coverage Reduce the cost per bit Low power consumption Faster handoff Easy cell planning Roaming with cellular and WLAN Frequency reuse is possible

Figure 1.5 Advantages of DWT BASED WIBRO

In this, we apply DWT based OFDMA technology to WIBRO system in military applications. Chapter II briefly outlines the FFT based WIBRO system architectures; Chapter III describes the multipath channel and applies DWT based WIBRO OFDMA technology to this environment; and Chapter IV provides the channel model and the BER performance evaluation.


Recommended