IBM's promotion of metrozone WiMAX leads to Texas deal
IBM has shown an increasingly keen interest, over the past few years, in the potential for its integration business in the metrozone market, and now it is set to take advantage of this sector's evolution from focusing on best effort, socially oriented networks, to providing carrier class services.ption

IEEE makes its bid to underpin harmonized 4G with 802.16m development
Standards bodies have their politics and their rivalries just like the commercial companies that fund them, and in wireless, there is an increasingly intense battle to take the driving seat for next generation standards. Bodies that once had clearly distinct remits now have overlapping spheres, thanks to convergence, yet unifying them may prove harder than making the platforms they support interoperable.

Alcatel backing boosts Sequans' place in complex WiMAX chip market
Although the amount of Alcatel's investment is undisclosed, the endorsement, and the contracts it brings, are significant to Sequans in the race by WiMAX start-ups to establish a strong enough position to survive eventual consolidation, or at least exit profitably.

4G

Ericsson deals blow to unified 4G dream by pulling out of WiMAX
The pre-4G networks are evolving on such similar paths that they will be distinguished by brand and politics, rather than core technologies. But those differences may still be just as divisive and deeply ingrained as though the various factions - WiMAX, LTE and Qualcomm's Ultra Mobile Broadband (UMB) - had chosen entirely different physical designs. Against this backdrop, the WiMAX community is necessarily on the defensive because its technology lacks the advantage of a heritage in an installed base like UMTS or GSM. So Motorola and Nortel, the companies that failed to get rich on UMTS, are keen to stress the convergence potential between WiMAX and LTE - they say the R&D overlap could be over 85%; while those with most to lose by having a viable alternative to the HSPA/LTE route - Nokia and Ericsson - have been more inclined to stress the differences, and the lack of backwards integration.

China Unicom starts work on WiMAX
China Unicom, which has been testing WiMAX for about a year, has now formally begun the construction of its network

Microsoft leads internet industry bid to dominate vacated TV spectrum

Microsoft leads internet industry bid to dominate vacated TV spectrum
It is clear that the mobile internet, once it becomes truly workable, will become a cornerstone of business and communications. What is less clear is which companies will control its evolution and so derive the maximum benefit, and this question has already resulted in an ongoing war for the driving seat, waged between the cellular community on one hand and the internet players, with their open IP, PC-oriented heritage, on the other - with the broadcast and media industries trying to carve out their own position. One of the most dramatic battles in this war could arise in the US from current lobbying over future use of the 'white space' spectrum (idle channels in the TV bands between 54MHz and 862MHz, set up to avoid interference, but now possibly to be used for internet access). A coalition led by Microsoft, and backed by most of the heavyweights of the internet industry, has submitted a device for use in this white space to the FCC for approval, signalling the determination of these players to make use of new spectrum availability to promote their own business model.

A bit more on WiMAX Samsung has also demonstrated two WiMAX-enabled products – the SPH-P9000 and the SPH-M8100, meant for the US market in the first place.

Mobile Television Meets WiMAX

What happens when you take two of the most popular technologies in the last 50 years - television and the cell phone - and bring them together? Furthermore, what if you could simplify the delivery and management of that experience through a single, global wireless broadband standard?

This week at CTIA in Orlando, Florida, a California-based company will be demonstrating television over a mobile WiMAX network. Last August, the company announced its support for mobile WiMAX and that is was working to integrate it into a broad range of emerging video and television technologies. It also offered a demonstration earlier this year at CES in Las Vegas.

"One of the things we are showing is how well suited WiMAX is for television and video," says MobiTV's CTO Kay Johansson. "WIMAX gives you true mobile internet with streaming as high as 1Mbps which delivers very good quality video to a number of devices including mobile phones, PCs and PDAs."

Antenna Design and Analysis for MIMO Communication Systems

Introduction to MIMO Antenna Design

Multiple-input multiple-output (MIMO) wireless technology uses multiple antennas at the transmitter and receiver to produce significant capacity gains over single-input single-output (SISO) systems using the same bandwidth and transmit power. It has been shown that the capacity of a MIMO system increases linearly with the number of antennas in the presence of a scattering-rich environment. This will ensure that the signals at the antennas in the array are sufficiently uncorrelated with each other. This is where antenna design comes in for MIMO systems.

The primary aim of MIMO antenna design is to reduce correlation between received signals by exploiting various forms of diversity that arise due to the presence of multiple antennas, like space diversity (spacing antennas far apart), pattern diversity (using antennas with different or orthogonal radiation patterns), polarization diversity (using antennas with different polarizations) etc. These 3 forms of diversity are pictorially represented as shown.

Previous Research

Previous research at WSIL showed the benefits of pattern diversity over space diversity. While the latter is viable only when sufficient real estate is available, pattern diversity can be utilized even in the case where space is limited – like in cellular phones or handsets. Research carried out in WSIL established that circular patch array (CPA) yields significant capacity gains over the conventional uniform linear array with the advantage of reducing the physical size of the array significantly. It was shown that collocated CPAs produce orthogonal radiation patterns, which gives excellent pattern diversity. The work also involved optimizing overall systems performance, using CEM and EM software tools, to maximize antenna theory and communication theoretic metrics for given size constraints. The output of the optimization problem was used to tune antenna array parameters (i.e., size, antenna material, feed points).

Current Research in WSIL

We are currently working towards MIMO antenna design for base stations using the IEEE 802.16e-2005 and 3GPP-LTE channel models. We aim to develop channel simulators for these standards with transmission modes like Tx-AA and D-TxAA, to analyze the performance of different antenna designs with capacity as the metric. The challenge here is to employ MIMO antenna design techniques to a cellular system, thereby extending ‘theoretical’ analysis to workable solutions.

We are also analyzing the performance of reconfigurable antenna arrays for MIMO systems, and demonstrating the impact of antenna geometry and configurations on the capacity of different transmission schemes for MIMO systems. We hope that this would lead to the development of algorithms for reconfigurable antenna arrays in MIMO systems that would switch their configuration in accordance with the channel statistics to maximize capacity.

MIMO Relay Channels

MIMO Relay Channels

Why study MIMO Relay Channels?

Relay channels will play a central role in next-generation wireless systems. If a source wants to send a message to a distant sink in a relatively dense network, it can forward the message via several intermediate nodes. This would improve overall throughput and coverage.

We can consider SISO relay channels, where each terminal employs a single antenna. Under this setup, though, there are channel conditions where the relay may not be able to assist the source in its transmission. For example, the minimum of the source-relay and relay-sink channel gains may be less than the source-sink channel gain. We can avoid this issue by considering MIMO relay channels, where each terminal employs multiple antennas. Under this setup, we can exploit the multiple antennas at the source and the relay to perform more sophisticated encoding and decoding schemes, which will lead to improved performance.

Problem Statement

Since sophisticated encoding and decoding schemes will lead to improved system performance, we first aim to use information-theoretic techniques to realize these improved gains. Once we have obtained these gains, we then want to come up with reduced-complexity approaches that will perform well. In particular, much research has focused on the case where the relay performs decode-and-forward operations. Requiring decoding at the relay, though, could be prohibitively complex, especially in a battery-limited sensor network. Instead, we aim to implement linear processing methods at the relay that will still yield good performance.

Main results and future areas of research

We have studied the MIMO relay channel where multiple antennas are employed by each terminal. Compared to SISO relay channels, MIMO relay channels introduce additional degrees of freedom that allow for partial cooperation between the transmitter and the relay. This partial cooperation is effected via precoding at the transmitter. We have derived new lower capacity bounds for both discrete memoryless relay channels and Gaussian relay channels for cases where the transmitter employs superposition coding and precoding. Our proposed lower bounds improve on a previously proposed non-cooperative lower bound.

We have also investigated MIMO relaying in a multiuser environment. Our aim is to use a fixed MIMO relay to support multiuser transmission in a cellular system. The fixed relay should employ linear processing for ease of implementation. After performing this linear processing, the relay would forward the processed output to multiple users.

We have made several contributions that reveal the value of this setup. First, we have derived upper and lower bounds on the achievable sum rate, where it is assumed that the base station performs nonlinear encoding. We want to use more practical methods to achieve the derived rates, though. To this end, we have devised a multiuser precoding scheme; in this approach, the base station employs Tomlinson-Harashima precoding (THP) along with adaptive user selection. A low-complexity user selection algorithm is presented and adaptive modulation is used to load the individual user data streams.

Our multiuser precoding strategy, which relies on QAM modulation, performs very close to our derived sum-rate upper bound. In addition, even though we do not require the relay to perform any decoding operations in our strategy, our scheme performs very close to the sum-rate achieved by decode-and-forward relaying. This illustrates the power of our practical approach.

Worldmax and Intel launch WiMAX trial

AMSTERDAM (WiMAX Day). The Dutch WiMAX operator Worldmax, a joint venture between Intel and Enertel, will begin a trial of WiMAX services this week in Amsterdam, the Dutch newspaper Het Parool reported.

The trial, which employs equipment from Motorola, will cover an area of ten square kilometres. Jeanine van der Vlist, CEO of Worldmax commented “Our system is 10 to 20 times faster than UMTS.”

If the tests in Amsterdam are successful, Worldmax intends to cover all of the Netherlands with WiMAX. However, the company only intends to work as a network provider. According to van der Vlist, “The network will be used by other partners, such as broadcasters, phone companies, video services and security.”

WiMAX sales jump to $549 million

Monday, March 19th, 2007

LONDON (WiMAX Day). The market for WiMAX equipment, such as base stations, modems and other networks fixtures, grew by 286% in 2006 with total revenue reaching $549.2 million. In a report by Infonetics Research, the strongest grow was in the fourth quarter of 2006 with total equipment sales at $226.5 million.

“2006 was a landmark year for the WiMAX industry, with service provider trials moving to service launch phase in many areas, fixed WiMAX deployments accelerating rapidly in developing countries, and mobile WiMAX products coming to market for the first time,” said Richard Webb, an analyst at Infonetics Research, in a press release.

The report also forecast that the worldwide WiMAX equipment market would increase to $5.6 billion in sales by 2010, with mobile WiMAX sales garnering $3.7 billion.

Standards

The 802.16 standard IEEE Std 802.16e-2005, approved in December 2005 follows on from IEEE Std 802.16-2004, which replaced IEEE Standards 802.16-2001, 802.16c-2002, and 802.16a-2003.

IEEE Std 802.16-2004 (802.16d) addresses only fixed systems. 802.16e adds mobility components to the standard.

IEEE 802.16e

IEEE 802.16e-2005 (formerly named, but still best known as, 802.16e or Mobile WiMAX) provides an improvement on the modulation schemes stipulated in the original (fixed) WiMAX standard. It allows for fixed wireless and mobile Non Line of Sight (NLOS) applications primarily by enhancing the OFDMA (Orthogonal Frequency Division Multiple Access).

SOFDMA (Scalable OFDMA) improves upon OFDM256 for NLOS applications by

• Improving NLOS coverage by utilizing advanced antenna diversity schemes, and hybrid-Automatic Retransmission Request (hARQ)
• Increasing system gain by use of denser sub-channelization, thereby improving indoor penetration
• Introducing high-performance coding techniques such as Turbo Coding and Low-Density Parity Check (LDPC), enhancing security and NLOS performance
• Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa
• Improving coverage by introducing Adaptive Antenna Systems (AAS) and Multiple Input Multiple Output (MIMO) technology
• Eliminating channel bandwidth dependencies on sub-carrier spacing, allowing for equal performance under any RF channel spacing (1.25-14 MHz)
• Enhanced Fast Fourier transform (FFT) algorithm can tolerate larger delay spreads, increasing resistance to multipath interference

On the other hand, 802.16-2004 (fixed WiMAX) offers the benefit of available commercial products and implementations optimized for fixed access. Fixed WiMAX is a popular standard among alternative service providers and operators in developing areas due to its low cost of deployment and advanced performance in a fixed environment. Fixed WiMax is also seen as a potential standard for backhaul of wireless base stations such as cellular, WiFi or even mobile WiMAX.

SOFDMA and OFDMA256 are not compatible so most equipment will have to be replaced. However, some manufacturers are planning to provide a migration path for older equipment to SOFDMA compatibility which would ease the transition for those networks which have already made the OFDMA256 investment. This effects a relatively small number users and operators.

HIPERMAN

The equivalent of 802.16 in Europe is HIPERMAN. The WiMAX Forum is working to ensure that 802.16 and HIPERMAN inter-operate seamlessly.

WiBro

Korea's electronics and telecommunication industry spearheaded by Samsung Electronics and ETRI has developed its own standard, WiBro. In late 2004, Intel and LG Electronics have agreed on interoperability between WiBro and WiMAX.

WiBro has South Korean government support with the requirement for each carrier to spend over US$1 billion for deployments. The Koreans sought to develop WiBro as a regional and potentially international alternative to 3.5G or 4G cellular systems. But given the lack of momentum as a standard, WiBro has joined WiMAX and agreed to harmonize with the similar OFDMA 802.16e version of the standard. What makes WiBro roll-outs a good 'test case' for the overall WiMAX effort is that it is mobile, well thought out for delivery of wireless broadband services, and the fact that the deployment is taking place in a highly sophisticated, broadband-saturated market. WiBro will go up against 3G and very high bandwidth wire-line services rather than as gap-filler or rural under-served market deployments as is often exampled as the 'best fit' markets for WiMAX.

Mobile applications

Mobile applications

Some cellular companies are evaluating WiMAX as a means of increasing bandwidth for a variety of data-intensive applications; indeed, Sprint Nextel has announced in mid-2006 that it will be investing about US$ 3 billion in a WiMAX technology buildout over the next few years.

In line with these possible applications is the technology's ability to serve as a high bandwidth "backhaul" for Internet or cellular phone traffic from remote areas back to an internet backbone. Although the cost-effectiveness of WiMAX in a remote application will be higher, it is not limited to such applications, and may be an answer to reducing the cost of T1/E1 backhaul as well. Given the limited wired infrastructure in some developing countries, the costs to install a WiMAX station in conjunction with an existing cellular tower or even as a solitary hub are likely to be small in comparison to developing a wired solution. Areas of low population density and flat terrain are particularly suited to WiMAX and its range. For countries that have skipped wired infrastructure as a result of inhibitive costs and unsympathetic geography, WiMAX can enhance wireless infrastructure in an inexpensive, decentralized, deployment-friendly and effective manner.

Technical info

WiMAX is a term coined to describe standard, interoperable implementations of IEEE 802.16 wireless networks, in a rather similar way to Wi-Fi being interoperable implementations of the IEEE 802.11 Wireless LAN standard. However, WiMAX is very different from Wi-Fi in the way it works.

MAC layer

In Wi-Fi the media access controller (MAC) uses contention access — all subscriber stations that wish to pass data through a wireless access point (AP) are competing for the AP's attention on a random interrupt basis. This can cause subscriber stations distant from the AP to be repeatedly interrupted by closer stations, greatly reducing their throughput. This makes services such as Voice over IP (VoIP) or IPTV, which depend on an essentially constant Quality of Service (QoS) depending on data rate and interruptibility, difficult to maintain for more than a few simultaneous users.

In contrast, the 802.16 MAC uses a scheduling algorithm for which the subscriber station need compete once (for initial entry into the network). After that it is allocated an access slot by the base station. The time slot can enlarge and contract, but remains assigned to the subscriber station which means that other subscribers cannot use it. The 802.16 scheduling algorithm is stable under overload and over-subscription (unlike 802.11). It can also be more bandwidth efficient. The scheduling algorithm also allows the base station to control QoS parameters by balancing the time-slot assignments among the application needs of the subscriber stations.

Physical layer

The original WiMAX standard (IEEE 802.16) specified WiMAX for the 10 to 66 GHz range. 802.16a, updated in 2004 to 802.16-2004 (also known as 802.16d), added specification for the 2 to 11 GHz range. 802.16d (also known as "fixed WiMAX") was updated to 802.16e in 2005 (known as "mobile WiMAX"). and uses scalable orthogonal frequency-division multiplexing (OFDM) as opposed to the OFDM version with 256 sub-carriers used in 802.16d. This brings potential benefits in terms of coverage, self installation, power consumption, frequency re-use and bandwidth efficiency. 802.16e also adds a capability for full mobility support. The WiMAX certification allows vendors with 802.16d products to sell their equipment as WiMAX certified, thus ensuring a level of interoperability with other certified products, as long as they fit the same profile.

Most interest will probably be in the 802.16d and .16e standards, since the lower frequencies suffer less from inherent signal attenuation and therefore give improved range and in-building penetration. Already today, a number of networks throughout the World are in commercial operation using certified WiMAX equipment compliant with the 802.16d standard.

Advantages over Wi-Fi

• The WiMAX specification provides symmetrical bandwidth over many kilometers and range with stronger encryption (TDES or AES) and typically less interference. Wi-Fi is short range (approximately 10's of metres) has WEP or WPP encryption and suffers from interference as in metropolitan areas where there are many users.
• Wi-Fi Hotspots are typically backhauled over ADSL in most coffee shops therefore Wi-Fi access is typically highly contended and has poor upload speeds between the router and the internet.
• It provides connectivity between network endpoints without the need for direct line of sight in favourable circumstances. The non-line-of-sight propagation (NLOS) performance requires the .16d or .16e revisions, since the lower frequencies are needed. It relies upon multi-path signals, somewhat in the manner of 802.11n.

Broadband Access

Broadband Access

Many companies are closely examining WiMAX for "last mile" connectivity at high data rates. This could result in lower pricing for both home and business customers as competition lowers prices.

In areas without pre-existing physical cable or telephone networks, WiMAX will, it appears, be a viable alternative for broadband access that has been economically unavailable. Prior to WiMax, many operators have been using proprietary fixed wireless technologies for broadband services.

WiMAX subscriber units are available in both indoor and outdoor versions from several manufacturers. Self install indoor units are convenient, but the subscriber must be significantly closer to the WiMAX base station than with professionally installed units. As such, indoor installed units require a much higher infrastructure investment as well as operational cost (site lease, backhaul, maintenance) due to the high number of base stations required to cover a given area. Indoor units are comparable in size to a cable modem or DSL modem. Outdoor units allow for the subscriber to be much further away from the WiMAX base station, but usually require professional installation. Outdoor units are roughly the size of a textbook, and their installation is comparable to a residential satellite dish.

Limitations

A commonly held misconception is that WiMAX will deliver 70 Mbit/s, over 70 miles (112.6 kilometers). Each of these is true individually, given ideal circumstances, but they are not simultaneously true. In practice this means that in Line of sight environments you could deliver symmetrical speeds of 10Mbps at 10Km but in Urban Environments it is more likely that 30% of installtions may be Non Line of sight and therefore Users may only receive 10Mbps over 2Km. WiMAX has some similarities to DSL in this respect, where one can either have high bandwidth or long reach, but not both simultaneously. The other feature to consider with WiMAX is that available bandwidth is shared between users in a given radio sector, so if there are many active users in a single sector, each will get reduced bandwidth. However, unlike SDSL where contention is very noticeable at a 5:1 ratio if you are sharing your connection with a large media firm for example WiMax does not have this problem. Typically each cell has a 100Mbps backhaul so there is is no contention here. On the radio side in practice many users will have a range of 2,4,6,8 or 10Mbps services and the bandwidth can be shared. If the network becomes busy the business model is more like GSM or UMTS than DSL in that it is easy to predict the capacity requirements as you sign more customers and additional radio cards can be added on the same sector to increase the capacity.

What is WiMAX?

What is WiMAX?

WiMAX is defined as Worldwide Interoperability for Microwave Access by the WiMAX Forum, formed in June 2001 to promote conformance and interoperability of the IEEE 802.16 standard, officially known as WirelessMAN. The 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 is not a technology, but rather a certification mark, or 'stamp of approval' given to equipment that meets certain conformity and interoperability tests for the IEEE 802.16 family of standards. A similar confusion surrounds the term Wi-Fi, which like WiMAX, is a certification mark for equipment based on a different set of IEEE standards from the 802.11 working group for wireless local area networks (WLAN). Neither WiMAX, nor Wi-Fi is a technology but their names have been adopted in popular usage to denote the technologies behind them. This is likely due to the difficulty of using terms like 'IEEE 802.16' in common speech and writing."

The bandwidth and reach of WiMAX make it suitable for the following potential applications:

• Connecting Wi-Fi hotspots with each other and to other parts of the Internet.
• Providing a wireless alternative to cable and DSL for last mile (last km) broadband access.
• Providing high-speed mobile data and telecommunications services (4G).
• Providing a diverse source of Internet connectivity as part of a business continuity plan. That is, if a business has a fixed and a wireless internet connection they are unlikely to be affected by the same service outage.
• Providing Nomadic connectivity.

Spectrum Allocations issues

The 802.16 specification applies across a wide swath of the RF spectrum. However, specification is not the same as permission to use. There is no uniform global licensed spectrum for WiMAX. In the US, the biggest segment available is around 2.5 GHz, and is already assigned, primarily to Sprint Nextel and Clearwire. Elsewhere in the world, the most likely bands used will be around 3.5 GHz, 2.3/2.5 GHz, or 5 GHz, with 2.3/2.5 GHz probably being most important in Asia. In addition, several companies have announced plans to utilize the WiMAX standard in the 1.7/2.1 GHz spectrum band recently auctioned by the FCC, for deployment of "Advanced Wireless Services" (AWS).

There is some prospect in the U. S. that some of a 700 MHz band might be made available for WiMAX use, but it is currently assigned to analog TV and awaits the complete rollout of digital TV before it can become available, likely by 2009. In any case, there will be other uses suggested for that spectrum if and when it actually becomes open.

It seems likely that there will be several variants of 802.16, depending on local regulatory conditions and thus on which spectrum is used, even if everything but the underlying radio frequencies is the same. WiMAX equipment will not, therefore, be as portable as it might have been - perhaps even less so than WiFi, whose assigned channels in unlicensed spectrum vary little from jurisdiction to jurisdiction.

The actual radio bandwidth of spectrum allocations is also likely to vary. Typical allocations are likely to provide channels of 5 MHz or 7 MHz. In principle the larger the bandwidth allocation of the spectrum, the higher the bandwidth that WiMAX can support for user traffic.