XMAX Technology

XMAX TECHNOLOGY

DRK Institute of Science & Technology

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XMAX TECHNOLOGY

CHAPTER-1 INTRODUCTION


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XMAX TECHNOLOGY 1.1Current Situation:

Wireless operators today are facing a dilemma. Customers are demanding more and more data applications to be delivered on the go. However, the operator is using scarce expensive licensed spectrum that is overburdened with delivering core voice services. Support for voice, data, location awareness, chat and other applications are required for customers that are very mobile. The operator is facing a choice of acquiring more licensed spectrum (if any is available) or losing customers due to demand for advanced services. xG Technology has a solution to this dilemma of overwhelming demand for advanced applications versus lack of spectrum. xG Technology is developing an affordable mobile voice and data cellular system that operates in free unlicensed bands using what is known as cognitive radio technology. Using cognitive (i.e., smart) radios and advanced system and signal processing capabilities, the xG system makes unlicensed spectrum communications as reliable as licensed band communications. This is made possible by effectively mitigating the interference in the congested and chaotic unlicensed bands. Another advantage of xG’s cognitive radio approach is the reduction of the RF engineering the operator needs to deploy and maintain the system.

1.1.1Cognitive Radio:

Cognitive radio (CR) is a form of wireless communication in which a transceiver can intelligently detect which communication channels are in use and which are not, and instantly move into vacant channels while avoiding occupied ones. This optimizes the use of available radio-frequency (RF) spectrum while minimizing interference to other users. A third benefit of this system is the ability to reuse all the engineering going into smartphones, tablets and laptops today. The xG system is designed to support these devices through a physical or WiFi connection. Finally, the xG system is all-IP protocol based so that it can utilize COTS (commercial off-the-shelf) infrastructure components for network connectivity, standard applications and established management interfaces.


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XMAX TECHNOLOGY

1.2 About xG Technology: xG Technology is a leading developer of innovative and disruptive communications technologies for wireless networks. Its extensive patented intellectual property portfolio covers a broad range of applications including cognitive radio networks. The company has commercialized some of these technologies to create xMax, the world’s first carrier -class cognitive radio network. xMax’s standards-based IP architecture minimizes network deployment, management and operational costs while simplifying the delivery of fixed and mobile services. Using field-proven cognitive radio technology, xMax enables the delivery of mobile services in both licensed and unlicensed bands. xMax offers unique capabilities to enterprises, utilities, government agencies and others who require advanced wireless communications to support business operations and mission critical applications.

Fig:1.1 Logo of xG

1.3 xMax Mobile Voice and Data Overview: xMax is a mobile voice and data solution from xG Technology that has been designed to address the issues raised above and more. In particular, it was designed with the following requirements in mind:

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Leverages COTS end user devices including 3G and 4G smartphones, tablets and netbooks without requiring licensed commercial frequencies. Dynamic Spectrum Access (DSA) and advanced interference mitigation to increase operational and deployment flexibility. 5g Full cognitive networking capabilities including dynamic access and optimization of available spectrum resources, as well as self-Radio Frequency (RF) planning and selforganizing. A single end-to-end IP network architecture supporting mobile voice, wideband data, real time video, chat and other apps.


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XMAX TECHNOLOGY

CHAPTER-2 xMax NETWORK COMPONENTS


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XMAX TECHNOLOGY

Fig:2 xMax cellular Network

2.xMax Cellular Architecture: The xMax mobile cellular solution leverages a standard cellular architecture – with some notable enhancements. The following are the major components of the system: xMod xAp xMSC x Monitor/x Drive


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XMAX TECHNOLOGY 2.1 xMod: The xMod is a small battery or vehicle-powered radio that bridges the COTS end user device to the wideband transport layer of the xMax system. Devices may be physically tethered or connected via secure WiFi links to the xMod. The xMod can deliver up to 3.5Mbps to the connected end user device(s) under real worl d conditions

Fig:2.1 xMod

2.2 xAP:

The xAP acts as a compact, high-performance base station and wirelessly connects to the xMod using the xMax cognitive networking waveform. Each xAP can deliver up to 14 Mbps of total user bandwidth to its associated xMods. xAPs may be deployed individually or in clusters of up to 9 xAPs to increase total throughput.

Fig:2.2 xAP


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XMAX TECHNOLOGY 2.3 xMSC: The xMSC acts as both a base station controller and aggregation point for the connected xAPs. It performsrouting and security functions, as well as proprietary mobile VoIP optimization and compression. The xMSC is typically connected to the worldwide Internet and one or more VoIP soft switches.

Fig:2.3 xMSC

2.4 xMonitor/xDrive: These software tools provide integrated and comprehensive network and element management for the xMax network, as well as mobile network throughput and coverage optimization.

Fig:2.4 xMonitor/Drive DRK Institute of Science & Technology

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XMAX TECHNOLOGY

CHAPTER-3 WORKING OF XMAX TECHNOLOGY


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3.1 End-to-end IP architecture and shared spectrum optimization: All the components of the xMax system are IP based. COTS routers and switches are used as network components. The xMax xAP supports both Ethernet and Fibre interfaces. Voice is transported as mobile-optimized Voice over IP (VoIP), enabling the entire system to operate as a data packet network – but with full voice calling features. Standard SIP signalling supports integrated COTS voice switches and gateways, or an external (cloudbased) switch/gateway service may be utilized. The air interface between the xMod and xAP is an advanced Physical Layer (PHY) featuring OFDM modulation and MIMO transmit and receive. This interface, combined with other xG innovations, was optimized to provide licensed quality service in free, unlicensed spectrum. Since this is a shared spectrum resource, implementing interference immunity and spectral efficiency was paramount for commercial applications.

3.2 Cognitive operation including DSA and interference mitigation: xMax employs advanced cognitive radio and networking techniques, including Dynamic Spectrum Access to provide reliable operation in unlicensed but interference prone spectrum. xMax’s Dynamic Spectrum Access technology is frequency agnostic and can be re-tuned to operate in TV white spaces, unlicensed or licensed commercial bands. Another benefit of xMax’s cognitive technology is that the network has the ability to self -configure and self-organize. This is planned to be further enhanced to support full meshing capabilities in future xMax product releases.

3.3 Advanced cognitive sensing, signal and multi-spatial processing: Real time RF sensing and dynamic spectrum access are the cornerstones of xMax radio technology. The commercial xMax system (slated for release in H1 2012) utilizes the 902-928 MHz and the 5.725- 5.825 GHz band for license free operation. Using these freely available bands allows the xMax system to scan over 125 channels (in release 3) for interference-free operation. Both the xAP and xMod devices are frequency agile and have several built-in capabilities to mitigate interference by first employing advanced signal/spatial processing as well as dynamically switching channels to avoid overwhelming interference or jamming.


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XMAX TECHNOLOGY

Fig:3.1 Dynamic channel selection

3.4 Advanced antenna, PHY layer and software radio design: The xMax PHY layer is designed with a proprietary 2x4 (two transmitters, four receivers per link) multiple input multiple output (MIMO) antenna and radio configuration. This MIMO system enables longer range, higher throughput and is a key enabler of the xMax interference mitigation technology. The system uses orthogonal frequency division modulation (OFDM) which is found in other state-of-the-art wireless systems such as LTE, WiMAX, WiFi and other solutions. The xMax system utilizes proprietary long OFDM symbols, which allow longer cyclic prefixes. This results in low overhead and high usable throughput (as a percentage of total over the air bandwidth). The xMax PHY supports adaptive modulation with BPSK, QPSK, QAM16 and QAM64 modes that allow the system to dynamically self-configure for the optimal combination of range, throughput and interference rejection. This combination of capabilities enables increased performance under dynamic conditions, in addition to minimizing power consumption for extended battery life and remote operation. DRK Institute of Science & Technology

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XMAX TECHNOLOGY 3.5 Interference tolerance, frequency reuse and high link reliability: By applying cognitive capabilities to enhance active interference mitigation, xMax can operate effectively under higher interference and jamming levels than competing solutions. This is critical for maximizing reliability as well as increasing the utilization of scarce spectrum resources. By enabling xMax to tolerate high levels of interference before requiring the radios to switch channels, more “gray spectrum” (spectrum containing interference or jamming) can be used in place of white spectrum (clean and interference-free spectrum). This capability increases the network’s total throughput and capacity greatly – without consuming additional scarce spectrum resources. Since the technique is primarily implemented within the receiver chain, the RF environment is not made noisier as would be the case for mitigation techniques that rely on raising the transmitter power to overcome the interferer. This technique significantly increases the system capacity of an xMax network.

Fig:3.2Spatial processing to Jamming and Interference


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CHAPTER-4 Wi-Fi


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4.1 Wi-Fi: Wireless networking, also called WiFi or 802.11 networking, is used to connect the computers at home, and some cities are trying to use the technology to provide free or lowcost Intrnet access to residents.

Fig:4.1 WiFi Network

4.2 What Is Wi-Fi? A wireless network uses radio waves, just like cell phones, televisions and radios do. In fact, communication across a wireless network is a lot like two-way radio communication. Here's what happens: 1. A computer's wireless adapter translates data into a radio signal and transmits it using an antenna. 2. A wireless router receives the signal and decodes it. The router sends the information to the Internet using a physical, wired Ethernet connection. The process also works in reverse, with the router receiving information from the Internet, translating it into a radio signal and sending it to t he computer's wireless adapter. The radios used for WiFi communication are very similar to the radios used for walkietalkies, cell phones and other devices. They can transmit and receive radio waves, and they can convert 1s and 0s into radio waves and convert the radio waves back into 1s and 0s. But WiFi radios have a few notable differences from other radios: 

They transmit at frequencies of 2.4 GHz or 5 GHz. This frequency is considerably higher than the frequencies used for cell phones, walkie-talkies and televisions. The higher frequency allows the signal to carry more data.


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XMAX TECHNOLOGY 

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They use 802.11 networking standards, which come in several flavors: 802.11a transmits at 5 GHz and can move up to 54 megabits of data per second. It also uses orthogonal frequencydivision multiplexing (OFDM), a more efficient coding technique that splits that radio signal into several sub-signals before they reach a receiver. This greatly reduces interference. 802.11b is the slowest and least expensive standard. For a while, its cost made it popular, but now it's becoming less common as faster standards become less expensive. 802.11b transmits in the 2.4 GHz frequency band of the radio spectrum. It can handle up to 11 megabits of data per second, and it uses complementary code keying (CCK) modulation to improve speeds. 802.11g transmits at 2.4 GHz like 802.11b, but it's a lot faster -- it can handle up to 54 megabits of data per second. 802.11g is faster because it uses the same OFDM coding as 802.11a. 802.11n is the newest standard that is widely available. This standard significantly improves speed and range. For instance, although 802.11g theoretically moves 54 megabits of data per second, it only achieves real-world speeds of about 24 megabits of data per second because of network congestion. 802.11n, however, reportedly can achieve speeds as high as 140 megabits per second. The standard is currently in draft form -- the Institute of Electrical and Electronics Engineers (IEEE) plans to formally ratify 802.11n by the end of 2009. Other 802.11 standards focus on specific applications of wireless networks, like wide area networks (WANs) inside vehicles or technology that lets you move from one wireless network to another seamlessly. WiFi radios can transmit on any of three frequency bands. Or, they can "frequency hop" rapidly between the different bands. Frequency hopping helps reduce interference and lets multiple devices use the same wireless connection simultaneously. As long as they all have wireless adapters, several devices can use one router to connect to the Internet. This connection is convenient, virtually invisible and fairly reliable; however, if the router fails or if too many people try to use high-bandwidth applications at the same time, users can experience interference or lose their connections.

4.3 The name Wi-Fi: The name of a popular wireless networking technology that uses radio waves to provide wireless high-speed Internet and network connections. The organization that owns the Wi-Fi (wireless fidelity) term specifically defines Wi-Fi as any "wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards."

Fig:4.2 Logo of Wi-Fi


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XMAX TECHNOLOGY 4.4 Comparison between xMax and Wi-Fi: As calculated above, the received signal power at the xMax receiver was -120.91 dBW or -90.91 dBm. The Ruckus Wireless 802.11g transceiver specifies a receiver sensitivity of only -96 dBm at 6 Mb/s. That's 5 dB less power for almost twice the data rate (6 Mb/s Vs 3.7 Mb/s), or 7.1 dB less power for WiFi compared to xMax at the same speed. Note that this comparison does not require any estimates, while the E b /N0 calculation above required that we estimate the noise temperature of the receiving system. This is because receiver sensitivity figures combine the effects of system noise and demodulator/decoder Eb /N0. It is possible that the xMax demo operated with link margin, meaning that it could have worked on a weaker signal than the one used. But one can reasonably presume that if this were the case, xG would have lowered the signal level and eliminated the margin to make its demo seem more impressive. In any event, xG Technology is the one claiming to have a new and vastly more power-efficient modulation method so it is entirely up to them to prove it. The xMax demo may impress those who haven't done the calculations and are unaware of how little power it actually takes to transmit digital data over a benign line-ofsight path. But the same demonstrated performance could have been easily achieved with just about any conventional digital modulation scheme, including an off-the-shelf WiFi transceiver, and some of these schemes already come very close to the theoretical limits. Broadcast stations use such powerful transmitters because they cannot assume line of sight paths; large margins are required to reliably overcome obstacles, fading, reflections and interference throughout their entire service areas. This is not to say there can't be any more big developments in digital radio communications; far from it! But they will not come as fundamental modulation breakthroughs from xG Technologies or anyone else. Opportunities still abound in frequency reuse, the basis of modern cellular phones; cooperative ad-hoc networking; improved spectrum sharing; better adaptivity to changing or hostile radio link conditions; improved interference mitigation; multiple-in, multiple-out (MIMO) antenna arrays; improvements in RF hardware that will let us make better use of the underutilized higher frequency bands, and in other ways but not from breakthroughs in modulation, because there won't be any more. By way of analogy, dialup modems reached their theoretical limits years ago, but Internet access speeds continue to rise thanks to cable modems, fibre deployments, radio networking, and DSL.


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XMAX TECHNOLOGY 4.5 xMax and Wi-Fi differences:

Table:4.1 Differences between Wi-Fi and xMax technology


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XMAX TECHNOLOGY

CHAPTER-5 ADVANTAGES , DISADVANTAGES & APPLICATIONS OF XMAX TECHNOLOGY


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XMAX TECHNOLOGY 5.1 Advantages: 

Quality of service (QoS) to support long ranges mobile VoIP.

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Deterministic latency on wireless links for voice packets.

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Header compression.

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Zero latency network configuration.

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Soft hand- off mechanism.

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Substantially lower capital requirements for materially more sophisticated product offering.

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No spectrum license costs.

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Exclusive service territories.

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Network capacity managed through software-defined radio system.

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Path to 4G performance with a revolutionary battery solution for user device.

5.2 APPLICATIONS: 

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The completely new mobile VoIP system that is similar to most popular VoIP service providers like skype. xMax cognitive radio cellular system represents a complete, scalable mobile wide band solution that is capable of supporting a wide range of smart phones,tablets,net books and other end – user devices. The coverage and capacity of the network can be tailored to the market and business model at hand and can be rapidly reconfigured to support new or expanded applications. xMax’s cognitive networking technology is frequency agnostic and can be adapted to a wide array of TV spaces, unlicensed frequency bands. The xMax system’s cognitive networking capability allows it to dynamically access and optimize available spectrum resources, while also enabling it to optimize its own RF plan. xMax’s end-to-end IP network architecture supports mobile voice,widwband,real time video, chat and other apps over a single integrated network, unlike typically 3G and 4G networks that require separate voice and data network equipment and transport layers.


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XMAX TECHNOLOGY 5.3 Disadvantages: 

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VoIP technology is great at saving its users money, but it does have some disadvantages – you have to be connected to a computer to use it, and VoIP calls are blocked on some networks by cellular companies concerned that they are missing out on revenues. There is also an issue with quality, as cellular networks are not designed for Internet voice traffic. US-based xG Technology has addressed these problems with its xMax system, which has been specifically designed for mobile VoIP. The network uses available free spectrum, rather than licensed spectrum and an all-IP architecture that is less expensive to operate than traditional networks. Although the test was limited in its scope, he used a phone connected to a laptop while being driven around Fort Lauderdale and reported that the voice quality was fine. There still seems to be issues to address, as the phone eventually overheated, but it seems that mobile VoIP could not be too far away.

FUTURESCOPE:

The XMAX™ technology can provide fixed, nomadic, portable solution and with OFDMA at the heart of the technology, it can also deliver mobile wireless broadband connectivity across vast open and congested areas, over many kilometres. With the XMAX™ Customer Premises Equipment, IPaXIom gives businesses, enterprise and the end customer get more options for broadband connectivity at lower cost. The XMAX™ comes with its own NMS for comprehensive and user friendly day-to-day management and support function.


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XMAX TECHNOLOGY Conclusion: From my analysis it seems that xG's xMax technology is nothing special. Despite xG's implications to the contrary, no spectacular results have been demonstrated, certainly nothing that would call into question the fundamental principles of communication theory that have been firmly established for six decades. And a reading of xG's published claims and patents belie a surprising lack of awareness of these principles. Prospective investors should be very wary.

References:     

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www.xgtechnology.com A review of Bobier's TriState Integer Cycle Modulation, added 16 May 2007 comments on MiCOM lab test of xMax, added 4 June 2007 comments on Prof. Stu Schwartz's evaluation of xMax added 6 June 2007 an analysis of xG's claims that xMax requires 3,000,000 times less power than WiFi, revised 29 June 2007 Prof. Ben Friedlander's blog on xMax and other wireless fantasies, added 21 June 2007 Comments on Patent Application 20040196910 from an engineer who wishes to remain anonymous, added 17 June 2007.


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