Wireless Metropolitan Area Networks PDF

Wireless# Guide to Wireless Communications Chapter 9 Wireless Metropolitan Area Networks Dr.Adnan Alrabea  Objectives Explain why wireless metropolitan area networks (WMANs) are needed Describe the compo...

Wireless# Guide to Wireless Communications Chapter 9 Wireless Metropolitan Area Networks Dr.Adnan Alrabea  Objectives Explain why wireless metropolitan area networks (WMANs) are needed Describe the components and modes of operation of a WMAN List the range of WMAN technologies, including FSO, LMDS, MMDS, and 802.16 (WiMAX) Explain how WMANs function Outline the security features of WMANs Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 2  What is a WMAN? Wireless metropolitan area networks (WMANs) – Provide wireless connectivity across a substantial geographical area such as a large city WMANs primary goals – Extend wired networks beyond a single location Without the expense of high-speed cable-based connections – Extend user mobility throughout a metropolitan area – Provide high-speed connections to areas not serviced by any other method of connectivity Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 3  Last Mile Wired Connections Last mile connection – Link between a customer and ISP – Most last mile connections use copper wiring Copper-based digital communications lines – Require the signal to be regenerated every 6,000 feet Last mile delivery of telephone and data lines has long been a problem for the carrier – Must be able to justify the cost of installing wired connections to remote areas Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 4  Last Mile Wired Connections (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 5  Last Mile Wired Connections (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 6  Last Mile Wireless Connections Microwaves are higher frequency RF waves – In the 3 to 30 GHz range of the electromagnetic spectrum known as super high frequency (SHF) band Microwave towers are installed roughly 35 miles (56 kilometers) apart from each other. Fixed wireless – Wireless as the last mile connection for buildings Backhaul connection – Company’s internal infrastructure connection Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 7  Baseband vs. Broadband Broadband transmission – Sends multiple signals at different frequencies. Baseband transmission – Treats the entire transmission medium as if it were only one channel – Only one signal can be set at a time Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 8  Baseband vs. Broadband (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 9  Land-Based Fixed Broadband Wireless Most are proprietary solutions or RF-based equipment – Require licensed frequency bands Solutions – Free Space Optics – Local multipoint distribution service – Multichannel multipoint distribution service Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 10  Free Space Optics Free space optics (FSO) – Optical, wireless, point-to-point, line-of-sight broadband technology – Excellent alternative to high-speed fiber-optic cable – Can transmit up to 1.25 Gbps at a distance of 4 miles (6.4 kilometers) in full-duplex mode – Uses infrared (IR) transmission instead of RF Transmissions are sent by low-powered invisible infrared beams through the open air – FSO is a line-of-sight technology Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 11  Free Space Optics (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 12  Free Space Optics (continued) Advantages of FSO – Cost – Speed of installation – Transmission rate – Security Disadvantages of FSO – Atmospheric conditions impact FSO transmissions – Scintillation Temporal and spatial variations in light intensity caused by atmospheric turbulence Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 13  Free Space Optics (continued) Disadvantages of FSO (continued) – FSO overcomes scintillation by sending the data in parallel streams (spatial diversity) From several separate laser transmitters – Dealing with fog Increase the transmit power of the signal – Signal interference – Tall buildings or towers can sway due to wind or seismic activity Affecting the aim of the beam Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 14  Free Space Optics (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 15  Free Space Optics (continued) FSO applications – Last mile connection – LAN connections – Fiber-optic backup – Backhaul Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 16  Local Multipoint Distribution Service (LMDS) Local multipoint distribution service (LMDS) – Fixed broadband technology that can provide a wide variety of wireless services High-speed Internet access Real-time multimedia file transfer Remote access to local area networks Interactive video, video-on-demand, video conferencing Telephone service – Can transmit from 51 to 155 Mbps downstream and 1.54 Mbps upstream Over a distance of up to about 5 miles (8 kilometers) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 17  Local Multipoint Distribution Service (LMDS) (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 18  Local Multipoint Distribution Service (LMDS) (continued) Frequency – Based on high frequency, low-powered signals over short distances – LMDS used the following ranges of frequencies 27.5 MHz and 28.35 MHz 29.1 MHz and 29.25 MHz 30 GHz, 31.075 GHz, and 31.225 GHz Architecture – Cells (like a cellular telephone system) – LMDS is a fixed wireless technology for buildings Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 19  Local Multipoint Distribution Service (LMDS) (continued) Architecture (continued) – Factors that determine the cell size Line-of-sight Antenna height Overlapping cells Rainfall Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 20  Local Multipoint Distribution Service (LMDS) (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 21  Local Multipoint Distribution Service (LMDS) (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 22  Local Multipoint Distribution Service (LMDS) (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 23  Local Multipoint Distribution Service (LMDS) (continued) Architecture (continued) – LMDS signals are broadcast from radio hubs that are deployed throughout the carrier’s market Area in which the LMDS provider has a license to use a certain frequency – Hub connects to the service provider’s central office Can connect to other networks, such as the Internet – Equipment at the receiving site 12- to 15-inch diameter directional antenna Digital radio modem Network interface unit Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 24  Local Multipoint Distribution Service (LMDS) (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 25  Local Multipoint Distribution Service (LMDS) (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 26  Local Multipoint Distribution Service (LMDS) (continued) Architecture (continued) – LMDS systems can use either: Time division multiple access (TDMA) Frequency division multiple access (FDMA) – Modulation techniques Quadrature phase shift keying (QPSK) Quadrature amplitude modulation (QAM) Advantages of LMDS – Cost, service area, and data capacity Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 27  Local Multipoint Distribution Service (LMDS) (continued) Disadvantages of LMDS – LMDS requires a direct line of sight between buildings – LMDS signals are susceptible to interference from rain and fog Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 28  Multichannel Multipoint Distribution Service (MMDS) Multichannel multipoint distribution service (MMDS) – Fixed broadband wireless technology similar to LMDS – Can transmit video, voice, or data signals at 1.5 to 2 Mbps downstream and 320 Kbps upstream At distances of up to 35 miles (56 kilometers) – MMDS is sometimes called wireless cable Can broadcast 300 channels – Internet access using MMDS is an alternative to cable modems and DSL service Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 29  Multichannel Multipoint Distribution Service (MMDS) (continued) Layout – MMDS hub is typically located on a high point Uses a point-to-multipoint architecture that multiplexes communications to multiple users – Tower has a backhaul connection to carrier’s network Carrier network connects with the Internet – MMDS signals can travel longer distances Provide service to an entire area with only a few radio transmitters – MMDS cell size can have a radius of up to 35 miles (56 kilometers) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 30  Multichannel Multipoint Distribution Service (MMDS) (continued) Layout (continued) – Pizza box antenna 13 by 13 inches antenna used at receiving site Aimed at the hub to receive the MMDS signal – Cable runs from the antenna to an MMDS wireless modem Modem can connect to a single computer or an LAN Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 31  Multichannel Multipoint Distribution Service (MMDS) (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 32  Multichannel Multipoint Distribution Service (MMDS) (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 33  Multichannel Multipoint Distribution Service (MMDS) (continued) Advantages of MMDS – Signal strength – Cell size – Cost Disadvantages of MMDS – Physical limitations – Frequency sharing – Security – Availability of the technology Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 34  IEEE 802.16 (WiMAX) Standard for wireless broadband metropolitan area networks 802.16 supports enhancements and extensions to the MAC protocols – Base station (BS) can communicate with another BS And also directly with subscriber stations (SS) WiMAX Forum – Promotes the implementation of 802.16 by testing and certifying equipment WiMAX stands for worldwide interoperability for microwave access Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 35  WiMAX Applications Applications – Suitable for backhaul applications for business – Last mile delivery applications – Supports simultaneous voice, video, and data transmission – Suitable for voice-over-IP (VoIP) connections – Enables vendors to create customer premises equipment (CPE) – Can also be deployed as a point-to-point network Provide broadband access to rural and remote areas Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 36  WiMAX Applications (continued) Applications (continued) – WiMAX CPE devices will support TV (video), telephone (voice), and data on the same network WiMAX MAC layer makes it easy for carriers to deploy the network Range of a WiMAX network is measured in miles Cellular phone operators can easily incorporate WiMAX networks Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 37  Standards Family Overview 802.16-2001 and 802.16-2004 standards – Define the interface specification for fixed, point-to-multipoint broadband WMANs 802.16a – Supports systems in the 2 GHz to 11 GHz band 802.16c – Provided clarifications related to performance evaluation and testing 802.16e – Defines specifications for a mobile version of WiMAX Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 38  WiMAX Protocol Stack PHY layer supports multiple frequency bands and several modulation techniques WiMAX MAC layer is connection oriented – Includes service-specific convergence sublayers That interface to the upper OSI layers WiMAX offers multiple simultaneous services through the same link – Asynchronous transfer mode (ATM), IPv4, IPv6, Ethernet, and VLAN Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 39  WiMAX Protocol Stack (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 40  WiMAX Protocol Stack (continued) PHY layer – Five variations of the PHY layer in 802.16 – First two are based on the modulation of a single carrier signal Transmission is half-duplex Each frame is subdivided into one uplink subframe and one downlink subframe Subframes are further divided into a series of time slots Burst is a data transmission to or from a single device Use time division duplexing (TDD) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 41  WiMAX Protocol Stack (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 42  WiMAX Protocol Stack (continued) PHY layer (continued) – WiMAX allows two different frequency channels Frequency division duplexing (FDD) – WiMAX can support half-duplex and full-duplex equipment – Variations of the PHY layer specified in the standard WirelessMAN-SC (single carrier) WirelessMAN-SCa (single-carrier access) – 802.16 standard also provides support for non-line-of- sight applications Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 43  WiMAX Protocol Stack (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 44  WiMAX Protocol Stack (continued) PHY layer (continued) – Additional PHY layer transmission mechanisms to support NLOS applications: WirelessMAN-OFDM – Uses TDMA WirelessMAN-OFDMA – Divides the available channel into a large number of orthogonal subcarriers – Third transmission mechanism Wireless high-speed unlicensed metro area network (WirelessHUMAN) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 45  WiMAX Protocol Stack (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 46  WiMAX Protocol Stack (continued) Modulation and error correction – 802.16 uses Forward Error Correction (FEC) – 802.16 also uses automatic repeat requests (ARQ) – 802.16 dynamically changes modulations – Latency Amount of time delay that it takes a packet to travel from source to destination device – 802.16 defines several transmission profiles Sets of predefined connection parameters – System profiles are combination of the basic profile and one of the transmission profiles Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 47  WiMAX Protocol Stack (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 48  WiMAX Protocol Stack (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 49  WiMAX Protocol Stack (continued) Range and throughput – Maximum distances achievable in a WiMAX network Depend on the frequency band used – Higher frequencies are used for: Metropolitan area line-of-sight, point-to-point, or multipoint application at very high data rates – Lower licensed frequencies will be used for: Private, line-of-sight network connections up to 10 miles (16 kilometers) Long distance links of up to 35 miles Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 50  WiMAX Protocol Stack (continued) Range and throughput (continued) – Frequencies below 11 GHz will be used for: Non-line-of-sight networks with a maximum range of up to 5 miles (8 kilometers) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 51  WiMAX Protocol Stack (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 52  WiMAX Protocol Stack (continued) MAC layer – Most wireless MAN implementations function in a point-to-multipoint basis With one BS and potentially hundreds of SSs – 802.16 MAC dynamically allocates bandwidth to individual SSs for the uplink – Advanced antenna system (AAS) : Transmits multiple simultaneous signals in different directions to stations that fall within the range – WiMAX can also take advantage of multiple in multiple out (MIMO) antenna systems Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 53  WiMAX Protocol Stack (continued) MAC layer (continued) – BS uses a 16-bit connection identifier (CID) To address a burst to a particular SS – Stations can request additional dedicated bandwidth (for QoS) – Jitter Maximum delay variation between two consecutive packets over a period of time. – WiMAX MAC protocol maintains a consistent bandwidth by using a self-correcting mechanism For granting more bandwidth to SSs Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 54  WiMAX Protocol Stack (continued) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 55  WiMAX Coexistence As the number of transmitters grows, so does interference. WiMAX is not limited to the 2.4 GHz or the 5 GHz bands U-NII band offers 12 channels and about 300 MHz of bandwidth – WiMAX signals are limited to between 30 and 35 miles – Interference may not be a serious problem Adaptive modulations, variable data rates, signal power levels, and FEC help with interference Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 56  WiMAX Coexistence WiMAX is different from technologies such as 802.11 in that it is not limited to the 2.4 GHz band or the 5 GHz band. Business users are encouraged to develop a sharing agreement when operating in the unlicensed bands service providers that expect to sell wireless connectivity to customers should consider a low-cost purchase or lease of a small amount of spectrum in the 2–11 GHz band. FCC(Federal Communications Commission) policies allow spectrum holders to resell unused spectrum to other operators. The ISM band offers approximately 80 MHz of bandwidth. U-NII band offers 24 channels and 555 MHz of bandwidth. Depending on the distance between transmitters, interference may not be a serious problem because WiMAX signals are limited to between 30 and 35 miles (approximately 48 to 56 kilometers) under ideal, line-of-sight conditions. Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 57  WMAN Security Security in WMANs is a major concern. FSO (Free Space Optics ) systems are generally considered secure – To sniff information from FSO systems is difficult Attacker must access the equipment and block only a portion of an invisible beam. LMDS and MMDS systems – RF signals can be captured by a receiver without blocking the radio signal Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 58  WiMAX Security MAC layer includes a privacy sublayer – WiMAX standard was initially designed to include very powerful security measures. Privacy sublayer provides a client/server authentication and key management protocol – Uses digital certificates. Components in the privacy sublayer – An encapsulation protocol for encrypting packet data – A privacy key management protocol that provides secure key distribution Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 59  WiMAX Security (continued) Traffic encryption key (TEK) – Security key used to encrypt the data – SS must renew the keys periodically with the BS – Default TEK lifetime is 12 hours Data encryption algorithms – 3-DES – RSA with 1024-bit key – AES with 128-bit key Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 60  Summary WMANs are a group of technologies – Provide wireless connectivity throughout an area such as a city without cable infrastructure Last mile wired connections are the link between the customer’s premises and an ISP Transmission techniques – Broadband and baseband Land-based fixed broadband wireless techniques – Free space optics (FSO) – Local multipoint distribution service (LMDS) – Multichannel multipoint distribution service (MMDS) Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 61  Summary (continued) IEEE 802.16 (WiMAX) standard introduced in 2000 – Can transmit at speeds up to 70 Mbps in the 2 to 11 GHz bands – Can also achieve 120 Mbps at short distances in the 10 to 66 GHz bands – Bring full support of mobile devices to WiMAX technology The WiMAX MAC layer is connection oriented The BS can support both half-duplex and full-duplex devices simultaneously Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 62  Summary (continued) Variations of the WiMAX PHY layers for point-to- point connections: – WirelessMAN-SC – WirelessMAN-OFDM OFDM and OFDMA in 802.16 are scalable WiMAX transmission profile – Specifies the frequency channel, bandwidth, and transmission mechanism MAC layer is the key to the intelligence and security behind WiMAX Wireless# Guide to Wireless Communications Dr.Adnan Alrabea 63