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Introduction

This paper provides guidelines for network providers on how best to take advantage of the IEEE 802.16 standard for wireless broadband equipment, which will be certified by the WiMAX Forum, to grow their business while managing risks. We begin by identifying the key challenges currently facing service providers, and providing a brief introduction to WiMAX technology. We go on to describe some of the ways in which WiMAX can help service providers meet those challenges and the main risks involved in making the move to WiMAX. We then provide detailed recommendations on how and when service providers should transition to WiMAX so as to further their business goals while minimizing the risks.

What Network Service Providers Need Most

Network service providers currently face a situation in which revenues from traditional sources are either declining or stagnating. The market for services delivered via wired infrastructure is saturated, and opportunities for growth in that market are extremely limited. By contrast, demand for services beyond the reach of wired infrastructures is potentially huge, but the wireless technology required to support the delivery of broadband to those market sectors has until now been largely proprietary and marked by either poor performance (at the low end) or prohibitive cost (at the high end).

Network service providers need a cost-effective solution that would allow them to satisfy the demand for broadband-based services beyond the reach of wired infrastructures. They need a solution with a rapid ROI and the promise of steadily increasing revenues. They need to move more quickly than their competitors in order to achieve a dominant position in these new markets. In addition, they need to minimize the risks associated with timely deployment of new wireless technologies.

WiMAX Benefits for Service Providers

Enter IEEE 802.16, or “WiMAX”—the emerging wireless standard that promises to substantially reduce the costs required to further expand the reach of broadband delivery systems while delivering performance that exceeds that of most wired technologies. WiMAX technology offers several key benefits to network service providers. It will: 

  • Allow service providers to profitably deliver high-throughput, broadband-based services like VoIP, high-speed Internet access and video to business and residential users who previously could not be economically served 

  • Facilitate equipment compatibility, allowing all of the components of WiMAX-based broadband systems to form a cohesive network, further reducing deployment and maintenance costs 

  • Facilitate equipment interoperability, allowing service providers to avoid having to commit to single vendors, diversifying vendor-dependent deployment risks 

  • Reduce the initial and incremental capital expenditures required for network expansion 

  • Provide vastly improved performance and extended range compared to existing wireless technologies 

  • Overcome many technical limitations of current wireless technology—for example, it will support service to customers that could not be economically served by legacy “line of sight” wireless technologies 

  • Allow service providers to achieve rapid ROI and maximize revenues

The potential for providers to achieve a faster ROI by deploying emerging wireless technologies than they could by deploying wired networks has been widely recognized. For example, a recent Gartner Research study describes the business advantage of emerging wireless succinctly:

“Looking at the basic pricing mode, a leased T1 line can cost $7,200 per year ($600 per month). Basic wireless point-to-point metropolitan-area network equipment ranges from $1,000 to $10,000 per unit (not including towers, additional routers, shelters, cables or installation, which can add less than $5,000 to the project), depending on speed needed. An enterprise can get a return on investment in less than a year on many systems, and in less than 18 months for most systems.“

Source: P. Redman, Research Note, Gartner Research Inc., July 2003

WiMAX Technology

The following section is excerpted from Can WiMAX Address Your Applications?, published by the WiMAX Forum

The WiMAX standard has been developed with many objectives in mind. These are summarized below:

Flexible Architecture: WiMAX supports several system architectures, including Point-to-Point, Point-to-Multipoint, and ubiquitous coverage. The WiMAX MAC (Media Access Control) supports Point-to-Multipoint and ubiquitous service by scheduling a time slot for each Subscriber Station (SS). If there is only one SS in the network, the WiMAX Base Station (BS) will communicate with the SS on a Point-to- Point basis. A BS in a Point-to-Point configuration may use a narrower beam antenna to cover longer distances.

High Security: WiMAX supports AES (Advanced Encryption Standard) and 3DES (Triple DES, where DES is the Data Encryption Standard). By encrypting the links between the BS and the SS, WiMAX provides subscribers with privacy (against eavesdropping) and security across the broadband wireless interface. Security also provides operators with strong protection against theft of service. WiMAX also has built-in VLAN support, which provides protection for data that is being transmitted by different users on the same BS.

WiMAX QoS: WiMAX can be dynamically optimized for the mix of traffic that is being carried. Four types of service are supported:

  • Unsolicited Grant Service (UGS) UGS is designed to support real-time data streams consisting of fixedsize data packets issued at periodic intervals, such as T1/E1 and Voice over IP.

  • Real-Time Polling Service (rtPS) rtPS is designed to support real-time data streams consisting of variable-sized data packets that are issued at periodic intervals, such as MPEG video.

  • Non-Real-Time Polling Service (nrtPS) nrtPS is designed to support delay-tolerant data streams consisting of variable-sized data packets for which a minimum data rate is required, such as FTP.

  • Best Effort (BE) BE service is designed to support data streams for which no minimum service level is required and which can be handled on a spaceavailable basis.

Quick Deployment: Compared with the deployment of wired solutions, WiMAX requires little or no external plant construction. For example, excavation to support the trenching of cables is not required. Operators that have obtained licenses to use one of the licensed bands, or that plan to use one of the unlicensed bands, do not need to submit further applications to the Government. Once the antenna and equipment are installed and powered, WiMAX is ready for service. In most cases, deployment of WiMAX can be completed in a matter of hours, compared with months for other solutions.

Multi-Level Service: The manner in which QoS is delivered is generally based on the Service Level Agreement (SLA) between the service provider and the end-user. Further, one service provider can offer different SLAs to different subscribers, or even to different users on the same SS. Interoperability: WiMAX is based on international, vendorneutral standards, which make it easier for end-users to transport and use their SS at different locations, or with different service providers. Interoperability protects the early investment of an operator since it can select equipment from different equipment vendors, and it will continue to drive the costs of equipment down as a result of mass adoption.

Portability: As with current cellular systems, once the WiMAX SS is powered up, it identifies itself, determines the characteristics of the link with the BS, as long as the SS is registered in the system database, and then negotiates its transmission characteristics accordingly.

Mobility: The IEEE 802.16e amendment has added key features in support of mobility. Improvements have been made to the OFDM and OFDMA physical layers to support devices and services in a mobile environment. These improvements, which include Scaleable OFDMA, MIMO, and support for idle/sleep mode and hand-off, will allow full mobility at speeds up to 160 km/hr. The WiMAX Forumsupported standard has inherited OFDM’s superior NLOS (Non-Line Of Sight) performance and multipath-resistant operation, making it highly suitable for the mobile environment.

Cost-effective: WiMAX is based on an open, international standard. Mass adoption of the standard, and the use of low-cost, mass-produced chipsets, will drive costs down dramatically, and the resultant competitive pricing will provide considerable cost savings for service providers and end-users.

Wider Coverage: WiMAX dynamically supports multiple modulation levels, including BPSK, QPSK, 16-QAM, and 64- QAM. When equipped with a high-power amplifier and operating with a low-level modulation (BPSK or QPSK, for example), WiMAX systems are able to cover a large geographic area when the path between the BS and the SS is unobstructed.

Non-Line-of-Sight Operation: NLOS usually refers to a radio path with its first Fresnel zone completely blocked. WiMAX is based on OFDM technology, which has the inherent capability of handling NLOS environments. This capability helps WiMAX products deliver broad bandwidth in a NLOS environment, which other wireless product cannot do.

High Capacity: Using higher modulation (64-QAM) and channel bandwidth (currently 7 MHz, with planned evolution towards the full bandwidth specified in the associated IEEE and ETSI standards), WiMAX systems can provide significant bandwidth to end-users.

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Orthogonal Frequency Division Multiplexing (OFDM) has been successfully applied to a wide variety of digital communications applications over the past several years and has been adopted as the wireless LAN standard. This paper presents the challenges associated with implementing OFDM for high speed wireless data communication and how Wide-band OFDM (W-OFDM), a variation of OFDM improves bandwidth and noise tolerance.

Introduction

Just what is OFDM, and what makes it better? To answer this question, we need to review some basic ideas about wireless telecommunications systems, and how OFDM fits into the overall picture.

In what follows, we will review the following concepts needed to understand OFDM; digital messages, carrier waves, modulation and multiplexing. Then we will explain OFDM and why it is used.

Messages

Wireless communications systems are used to send messages between two locations using radio waves which travel across free space. Messages of all types (voice, music, image, video, text) are usually converted to digital form and are represented as a stream of 1's and 0's called bits (binary digits). Voice messages can be represented by about 10,000 bits per second, CD quality music needs about 100,000 bits/sec, and TV quality video messages require about 1,000,000 bits per second, plus or minus. Text messages can be sent at any speed, depending on how long you are willing to wait.

Carrier Waves

Radio waves are electromagnetic waves used to carry a message over a distance. Thus radio waves are also called a carrier waves. A carrier wave looks like a sine wave, and moves like a train at the speed of light. The frequency of the carrier wave is the number of times per second that the wave train goes up and down and back up as it moves past you, and is measured in units of cycles per second or Hertz.

Carrier (electromagnetic) waves of different frequencies and wavelengths have different properties. For example, radio waves can travel through walls, but light waves cannot. Lower frequency waves tend to travel further, and can bend around corners. Higher frequency waves travel more or less only via line of sight. Thus certain parts of the radio spectrum are better suited for certain types of telecommunications. For indoor wireless communications through walls over a distance of several hundred feet, or outdoor communications over several miles mostly over line of sight with perhaps some trees in the way, carrier frequencies in the range of 1 to 5 GHz (gigahertz or billion cycles per second) are used.

Modulation

Modulation is the process whereby a carrier wave of a particular frequency is modified or modulated by the message signal, so that the modulated carrier wave can be used to carry the message over a distance. For digital messages (a stream of 1's and 0's), there are three basic kinds of modulation:

  • Amplitude Shift Keying (ASK) (digital AM) in which the amplitude of the carrier wave is modulated in step with the message signal.

  • Frequency Shift Keying (FSK) (digital FM) in which the frequency of the carrier wave is modulated in step with the message signal.

  • Phase Shift Keying (PSK) (digital PM) in which the phase of the carrier wave is modulated in step with the message signal.

ASK and PSK may also be used at the same time on one carrier, which is called Quadrature Amplitude Modulation (QAM) or Amplitude/Phase Keying (APK). The receiver is designed to receive the carrier wave, detect these amplitude and phase shifts in the carrier (demodulation), and thus retrieve the digital message.

When a carrier wave is modulated, it is no longer a single frequency but is spread out over a range of frequencies. The bandwidth of the modulated carrier wave is the range from lowest to highest frequency, with the original carrier frequency in the center. The bandwidth is approximately equal to the speed of the digital message, e.g. 10,000 Hz (10 KHz) for voice or 1,000,000 Hz (1 MHz) for video.

OFDM (Orthogonal Frequency Division Multiplexing) is a method of using many carrier waves instead of only one, and using each carrier wave for only part of the message. OFDM is also called multicarrier modulation (MCM) or Discrete Multi-Tone (DMT). We first describe Multiplexing, then Frequency Division and then Orthogonal. It is important to stress that OFDM is not really a modulation scheme since it does not conflict with other modulation schemes. It is more a coding scheme or a transport scheme.

Multiplexing

Multiplexing is a way to split a high speed digital message into many lower speed ones. A useful analogy is a highway with a toll collection point. Where each car is one bit of the message, and the number of cars passing a given point in one second is the speed of the message, which represents bits per second. The single lane highway may be split into 10 different lanes for paying tolls. At a point beside the single lane highway, the cars will pass at high speed, whereas at the toll booths, the cars will pass slowly. Thus the single high speed message (flow of cars past a point of single lane highway) is divided into many low speed messages (flow of cars past many toll booths). In a perfect system, the first car will take the first toll lane, the second car takes the second toll lane, etc. The 11th car takes the first toll lane again, and follows the first car. A multiplexer is a switch that assigns each car to one of the many toll booths.

Demultiplexing is the opposite, where many low speed messages are combined into one high speed message. Following the analogy, demultiplexing is where the many low speed messages (cars) passing slowly through the toll booth lanes are merged back into a high speed message travelling quickly on a single lane highway.

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Introduction

Orthogonal Frequency Division Multiplexing (OFDM) is a multi carrier transmission technique whose history dates back to the mid1960's. Although, the concept of OFDM has been around for a long time, it has recently been recognized as an excellent method for high speed bidirectional wireless data communication. The first systems using this technology were military HF radio links. Today, this technology is used in broadcast systems such as Asymmetric Digital Subscriber Line (ADSL), European Telecommunications Standard Institute (ETSI) radio (DAB:Digital Audio Broadcasting) and TV (DVBT:Digital Video Broadcasting---Terrestrial) as well as being the proposed technique for wireless LAN standards such as ETSI Hiperlan/2 and IEEE 802.11a. There is also growing interest in using OFDM for the next generation of land mobile communication systems.

OFDM efficiently squeezes multiple modulated carriers tightly together reducing the required bandwidth but keeping the modulated signals orthogonal so they do not interfere with each other. Any digital modulation technique can be used on each carrier and different modulation techniques can be used on separate carriers. The outputs of the modulated carriers are added together before transmission. At the receiver, the modulated carriers must be separated before demodulation. The traditional method of separating the bands is to use filters, which is simply frequency division multiplexing (FDM). Fig. 1 shows a representative power spectrum for three sub channels of a FDM system.

In a classic FDM system, the sub channels are non-orthogonal and must be separated by guard bands to avoid inter channel interference. This results in reduced spectral efficiency.

Another method to achieve frequency separation, but is more spectrally efficient than FDM is to overlap the individual carriers, yet ensuring the carriers are orthogonal is to use the discrete Fourier Transform the (DFT) as part of the modulation and demodulation schemes. This is where the name orthogonal FDM (OFDM) arises. High speed, fast Fourier transform (FFT) chips are commercially available, making the implementation of the DFT a relatively easy operation. Fig. 2 shows the spectrum of an OFDM signal with three sub carriers. The main lobe of each carrier lies on the nulls of the other carriers. At the particular sub carrier frequency, there is no interference from any other sub-carrier frequency and hence they are orthogonal. In Fig.2, the sub carriers are 300 Hz apart.

The orthogonal nature of the OFDM sub channels allows them to be overlapped, thereby increasing the spectral tightly efficiency. In other words, as long as orthogonality is maintained, there will be no inter channel interference in an OFDM system. In any real implementation, however, several factors will cause a certain loss in orthogonality.

Designing a system which will minimize these losses therefore becomes a major technical focus. Another advantage to OFDM is its ability to handle the effects of multipath delay spread. In any radio transmission, the channel spectral response is not flat. It has fades or nulls in the response due to reflections causing cancellation of certain frequencies at the receiver. For narrowband transmissions, if the null in the frequency response occurs at the transmission frequency then the entire signal can be lost.

Multipath delay spread can also lead to inter symbol interference. This is due to a delayed multipath signal presents overlapping with the following symbol. This problem is solved by adding a time domain guard interval to each band OFDM symbol. Inter carrier interference (ICI) can be width avoided by making the guard interval a cyclic extension of, the OFDM symbol. There are, however, certain negatives associated with this technique. It is more sensitive to carrier frequency offset and sampling clock mismatch than single carrier systems. Also the nature of the orthogonal encoding leads to high peak to average ratio signals: or in other words, signals with a large dynamic range. This means that only highly linear, low efficiency RF amplifiers can be used.

We present here WOFDM technology, which is less sensitive to inherent OFDM problems such as frequency offset, sample clock offset, phase noise and amplifier non-linearities. WOFDM is also able to tolerate strong multipath and fast changing selective fading by using a powerful equalization scheme combined with a forward error correction scheme.

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Introduction

Today’s heightened requirements for security, public safety, and crime prevention have created an unprecedented worldwide demand for cost-effective, flexible, and reliable video surveillance systems. 

This paper introduces the benefits of using wireless technology based on Internet Protocol (IP) for video surveillance. 

We begin by describing the benefits of IP-based networking compared to traditional Closed Circuit TV (CCTV) technology, and the benefits of wireless networking. We point out that by combining IP and wireless technologies for their video surveillance solutions, companies and organizations can realize the benefits of both. We go on to introduce some of the important technical aspects of surveillance technology, and describe the main challenges involved in delivering surveillance services—challenges that have been addressed by EION’s own wireless surveillance solutions. Next, we describe the opportunities created by the new technologies for enterprises and security companies. Finally, we describe how EION, a leader in wireless IP-based networking, is spearheading the movement to wireless IP surveillance with innovative solutions based on their best-of-breed wireless networking products.

Advantages of wireless IP video surveillance:

  • Less expensive than wired solutions

  • Can use existing IP network for video surveillance

  • Can be used to monitor remote locations

  • Can be set up, reconfigured, expanded or disassembled quickly to add video surveillance to special events

  • Video images can be transmitted over secure

  • Internet connection or private IP network for little or no cost.

  • Scalable—can be expanded at little cost without having to lay wire or cable

  • Can be integrated with solutions that provide surveillance in high-speed

Wireless IP Surveillance—the Benefits of Both IP Networking and Wireless

The trend toward using IP networks for surveillance purposes is part of a larger drive to move more and more types of services (video, voice over IP, in addition to data services) to IP. By now, the benefits of IP-based networking are probably familiar:

  • Earlier technical challenges regarding quality of service, throughput, and processing performance have been addressed, making IP a sound alternative to traditional analog and privately owned or controlled communication mediums.

  • Transmitting video, data, and voice messages over the Internet or a Virtual Private Network (VPN) costs much less than traditional alternatives, allowing enterprises to reduce their telecommunications costs, and service providers to add more subscribers and deliver more diverse services for a relatively low rate. 

The benefits of wireless communications are also widely recognized:

  • Wireless networking has allowed many companies, organizations, and even countries to make Internet access, as well as applications such as telephony widely available to both urban and remote rural areas without assuming the expense involved in laying cable lines or copper wires.

  • Wireless technology has advanced to the point where the quality of the services delivered over wireless networks is equivalent to that of wired alternatives.

Now wireless technology can be combined with IP-based networking to deliver advanced data, video, and voice services wirelessly, simultaneously achieving the benefits of both IP and wireless technology. In addition, this powerful convergence of wireless and IP is revolutionizing surveillance services as well—making cost-effective new solutions available for users and providers of video surveillance.

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