WIMAX TRANSMISSION POWER

As designers turn their attention to mobile WiMAX devices, they are quickly learning that there are some specific design challenges regarding power amplifiers. For Wave 2 mobile WiMAX products, the mobile device needs to efficiently deliver +23 dBm output power with high linearity from a 3.3 VDC supply.
Managing power in mobile WiMAX is quickly shaping up to be vitally important as first-generation designs are tested and deployed. One of the challenges of designing for mobile WiMAX is its long range, since WiMAX networks typically achieve coverage of about 1 km per cell.
To achieve these ranges, WiMAX must have an optimized power profile—from the base station right down to the components in the mobile device. High transmit power, then, is important. But how high can WiMAX go and what are the limitations imposed by regulatory bodies, technological limits, and usage models?
Designers of the power amplifier (PA) and those selecting PAs need to find the optimal balance between high power and high efficiency in order to ensure robust links, high data rates, and good range for their WiMAX services.
The nature of WiMAXWhat makes WiMAX challenging for designers is that it is an access technology with a unique set of constraints. As a result, power amplification circuits that were used for cellular or Wi-Fi applications cannot simply be dropped into WiMAX designs and tweaked to perform adequately.
In many ways, WiMAX can be considered a hybrid technology because it shares aspects of both cellular and Wi-Fi networks. Mobile WiMAX is very similar to cellular; it is meant to be used in highly mobile devices and it uses licensed frequency bands (so users expect high reliability). It also employs transmit power control techniques, much like CDMA cellular does.
However, it differs from cellular because it operates at much higher data rates (resulting in more stringent linearity requirements) and must simultaneously handle voice over Internet Protocol (VoIP), data, and video transmissions. Managing the bandwidth and priority of transmission for these types of services requires a quality of service (QoS) component that is not required for mobile voice alone.
On the other hand, WiMAX is also similar to Wi-Fi. For instance, it offers high data rates, uses orthogonal frequency division multiplexing (OFDM) with modulations from BPSK to 64-QAM, and is an all-IP-based network.
However, it differs from Wi-Fi because it uses a fully-scheduled service, unlike the collision-based carrier sense multiple access (CSMA) technique used by Wi-Fi. This gives WiMAX a significant advantage over Wi-Fi.
As the number of users increases in a CSMA network, overall capacity drops dramatically since each collision requires a subsequent retransmission. With a scheduled service, overall network capacity is unaffected as the number of users increases, since the basestation manages each user's access to the network efficiently.

WiMAX network coverageWi-Fi networks typically cover ranges that are measured in the tens or hundreds of meters for each access point (AP). However, WiMAX networks will achieve coverage of about 1 km per BS. In order to achieve this, mobile WiMAX networks employ a number of techniques to achieve longer range, including high transmit power, subchannelization, and adaptive modulation.
Simply put, RF power translates directly into range, so higher power equals longer range. To achieve long range, WiMAX basestations transmit at power levels of approximately +43dBm (20W), as compared to Wi-Fi APs, which typically transmit at +18 dBm (60 mW).
A WiMAX mobile station (MS) typically transmits at +23 dBm (200mW), as compared to +18 dBm (60 mW) for Wi-Fi. Cellular (CDMA) transmit powers for both the BS and MS are similar to those used in WiMAX.
However, because WiMAX uses much higher modulation orders to achieve higher throughput, WiMAX requires a much better SNR than cellular. For the mobile transmitter, high modulation orders require a PA with much better linearity and greatly complicates PA design compared to GSM or CDMA.
You might notice that there is a large difference (approximately 20 dB) between downlink power (from the BS to the MS) and uplink power (from the MS to the BS), so mobile WiMAX networks are severely uplink limited (this is also the case for cellular networks, of course).
This means that, while a mobile can easily receive transmissions from a BS, the mobile's relatively low transmit power makes it difficult for the BS to hear it.
One way to combat this mismatch is by using a technique called subchannelization, where only a subset of all of the available subchannels is used for any particular user.
In effect, each mobile concentrates its power over a smaller range of frequencies, and the net signal gain is 10*log(Ntotal/Nused), where Nused is the number of subcarriers assigned to the user, and Ntotal is the total number of subcarriers available.
For example, if a user is assigned one subchannel made up of 24 subcarriers, the net gain that is achieved relative to the BS that is transmitting on all 841 allocated subcarriers is 10*log(841/24)=15.4 dB. The other subcarriers are made available to other users, and they can use these simultaneously.
Another technique to address the link imbalance is adaptive modulation. In this case, the mobile transmits using a lower order modulation compared to the BS. For example, the mobile could transmit QPSK or 16QAM signals, while the BS transmits using 64QAM.
Because the SNR required to receive QPSK or 16QAM is lower than 64QAM, using a lower order modulation allows the MS to communicate with the BS using less transmit power (although uplink throughput is reduced, since fewer bits are transmitted per subcarrier with lower order modulation).
For example, the SNR required for QPSK-1/2 is 5 dB as compared to 10.5 dB for 16QAM-1/2 and 20 dB for 64QAM-3/4 modulation1. If the MS transmits with QPSK, the BS can tolerate 5.5 dB more link loss than with 16QAM.
When sub-channelization and adaptive modulation are combined, a network operator can effectively balance the uplink and downlink budgets, and the network will operate bi-directionally.
The downside is that when these techniques are used, the uplink throughput will be lower than the downlink throughput; subchannelization limits the number of subcarriers available for mobile transmission, and lower order modulation means that fewer bits are transmitted on each available subcarrier.

Power profile of a mobile WiMAX cellWith all of the above explanations in mind, let's examine what the transmit power profile looks like across a WiMAX cell. A common misconception is that mobile stations transmit at maximum power only at the edge of a cell, and at lower power when mobiles are closer to the BS. In reality, this is not the case; mobile stations will transmit at high powers over a range of distances.
To understand why this is the case, consider a mobile device moving from the edge of the cell directly towards the BS. When it is at the extreme cell edge, path loss will be very large, so the mobile device will be transmitting at maximum power with the most robust modulation.
As a result, uplink data rates will be relatively low. However, with the high MS transmit power and robust modulation, the BS will be able to receive transmissions from the MS, and the link is sound.
As the mobile moves closer to the BS, path loss decreases. The signal level at the BS increases, and the SNR improves, since the received signal is now farther above the noise floor.
In response, the BS may instruct the mobile to start reducing power (to minimize potential for interference between different mobile stations). However, as soon as the signal level supports a higher order modulation, the BS will instruct the mobile to switch modulations in order to increase overall network capacity.
Going back to our example comparing QPSK and 16QAM, suppose a transmitter operates at +23 dBm and it just achieves the 5 dB SNR required for QPSK when it is at the edge of the cell. As is moves closer to the BS, path loss drops, and the BS may ask the MS to reduce its transmit power.
However, as soon as the path loss has decreased by 5.5 dB, the BS will instruct the MS to switch to 16QAM-1/2, and will increase transmit power back to +23 dBm, since the MS will now be able to achieve a 10.5 dB SNR. Therefore, a mobile will typically transmit at higher powers until it is close enough to the BS to achieve 16QAM operation (or even 64QAM in many instances), at which point power is reduced. This is shown in Figure 1.
Click here for Figure 1.Figure 1: Achievable modulation versus distance with +23 dBm transmit power.

Figure 1 was derived using parameters from a WiMAX Forum whitepaper2. It shows the modulation that is achievable as a function of distance from the BS. We use the parameters in the whitepaper, so, for example, maximum available path loss is calculated assuming a 10 MHz channel bandwidth at 2.5 GHz, with 3 subchannels, and 10 dB penetration loss.
In calculating the path loss, we have assumed a COST231 suburban model at 2.5 GHz with 32 m BS height and 1.2m MS height. This analysis has assumed the presence of slow (lognormal) fading, but is somewhat simplified, since we assume a fixed 5.5 dB fade margin.
In reality, of course, fading is a random process, and closed loop power control will be used to help mitigate its effects. However, for the sake of this analysis, the conclusions are valid, as fading will simply blur the boundaries between the different modulations.
Note that the red ring, labeled QPSK-1/8 represents QPSK-1/2 modulation with a repetition factor of 4. This is the most robust modulation scheme, and it can be seen that it is indeed required at maximum range.
In our analysis, we calculate that with +23 dBm transmit power, an MS must use QPSK-1/8 for mobiles from 0.9 km to 1.35km from the BS. At closer distances, the MS is able to use higher order modulations, and network capacity is therefore increased.
For example, the MS is able to use 16QAM-1/2 modulation at distances from 0.45 to 0.6 km from the BS. Since 16QAM-1/2 modulation transmits 2 bits per symbol, while QPSK-1/8 transmits only 0.5 bits per symbol, one can see that the throughput in the green ring is 4 times higher than in the red ring.
We can also estimate the required transmit power as a function of range. At the edge of each of the zones in Figure 1, the MS will be transmitting at maximum power. It will decrease its transmit power as it moves towards the BS, until it has sufficient power to achieve the next modulation order.
At this time, it will increase transmit power again to maximize capacity.
Figure 2 shows the expected transmit power as a function of distance, showing the impact of adaptive modulation. It can be seen that transmit power is significantly reduced only once the maximum modulation order has been achieved, which in this case is 64QAM-3/4.
Click here for Figure 2.Figure 2:

Transmit power versus distance from basestation.
If the maximum modulation order was instead 16QAM-3/4, then the transmit power would be monotonically reduced once the 16QAM-3/4 rate was achieved.
It should be noted that the presence of fading will result in significant changes to this curve. In a real-life fading environment, additional margin may be required to counteract fading effects, and one would expect that transmitting at maximum power would occur less frequently.
However, the overall trend shown in Figure 2 is correct, and shows that mobile stations will be required to transmit at high powers not only at the cell edges, but also at much closer distances in order to achieve higher-order modulation.

Benefits of high powerThe benefits of higher power transmission from the mobile WiMAX terminal are significant. Consider the effect of increasing the transmit power by 40%, from +23 dBm (200mW) to +24.5 dBm (281 mW). First, it would require a larger power amplifier (PA). Assuming that losses after the PA are 1 dB, the output power from the PA must increase from 250 mW (+24 dBm) to 355mW (+25.5 dBm).
There are two benefits to transmitting at higher power. First, transmitting at this higher output power increases the maximum range. Using parameters from the WiMAX Forum 3, maximum mobile to BS distance is increased from 1.35 to 1.5 km when the output power is increased from 23 to 24.5 dBm, so that the overall coverage area increases by 23.5%.
In principle, one might expect that a network operator could deploy 23 percent fewer base stations, and realize a cost savings. However, this effect may be of only limited benefit, since many networks will have been designed with cell sizes assuming +23 dBm uplink transmit power, so cell sizes may already be fixed.
The second benefit is more significant, however. If an MS is able to transmit at higher power, then it can achieve the SNR required for higher order modulation when it is further from the BS. This improves overall network capacity, so increases overall spectral efficiency.
Figure 3 shows the modulation that is achievable as a function of distance from the BS with +24.5 dBm transmit power.
Click here for Figure 3.Figure 3:

Achievable modulation versus distance with +24.5 dBm transmit power.
In this figure, we again plot achievable modulation as a function of distance from the BS (and the dashed lines show the ranges for +23 dBm from Figure 1 for reference). Note that the maximum distance has increased from 1.35 to 1.5 km, as discussed above.
However, it is more important to note that users can now achieve higher order modulations over a wider range. For example, for 16QAM-1/2 modulation the maximum range is now 0.7 km, versus 0.6 km for +23 dBm.
As a result, each user will achieve higher throughput over a wider range, and the network aggregate capacity will be increased accordingly. With every additional user who can transmit at a higher power level, overall network capacity increases.
It is important to understand that all users would need to transmit at a higher transmit power in order to allow cell sizes to expand. However, each and every higher power user added to the network increases overall network capacity.
Finally, it is relatively straightforward to calculate the capacity increase seen by increasing transmit power from +23 to +24.5 dBm. We know how many bits per symbol can be transmitted for each modulation scheme, and we know the relative areas that can be covered for each modulation scheme, for both power levels.
When this information is used to calculate relative capacity, we find that it increases by 24% when transmit power is increased from +23 dBm to +24.5 dBm.
Even if the maximum cell size remains fixed at 1.35km when the transmit power is increased to +24.5 dBm (as would be the case if networks were rolled out assuming +23 dBm devices) the capacity still increases by 18% when devices are able to transmit at higher power.

Limitations of powerSo, now we understand why higher transmit power is important in a WiMAX network; it allows overall network throughput to increase, and in a 'greenfield' deployment, it would allow for larger cell sizes, and therefore reduce deployment costs.
So why not transmit even more power? There are three important factors that limit our ability to transmit at higher power: PA efficiency, available supply voltage, and regulatory requirements.
PA efficiencyIn PAs, efficiency is the measure of the RF power out versus the DC power in. For example, if a PA has a 10 percent efficiency, it would consume 3.55 W to transmit at +25.5dBm (355 mW). If the PA efficiency could be doubled to 20 percent, then the peak power consumption drops to 1.7W.
Today's state-of-the-art WiMAX PAs, like SiGe Semiconductor's SE7262, operate with >20 percent efficiency (See sidebar Why is PA efficiency so low for WiMAX?.)
The PA efficiency has a direct impact on battery life for mobile devices. Of course, the PA is not working all of the time, so the average power consumption will be considerably lower than the peak power consumption quoted above.
For instance, transmit duty cycles for WiMAX devices are typically about 40 percent when the MS has data to transmit. Therefore the average power consumption for a 20 percent efficiency PA will be about 680 mW if the PA is transmitting at maximum power.
Furthermore, often there will be no data to transmit, and in this case, the device will transmit very infrequently (essentially, it transmits only ranging messages to let the BS know that it is still in the cell).
In the end, however, the PA power consumption can have a significant impact on battery life, and it is important that PA efficiency is as high as possible.
Available supply voltageMobile WiMAX devices will be powered directly from the mobile station's battery, and battery supply voltages vary significantly during use. When freshly charged, the battery will operate at about 4.8V.
The supply voltage drops as the battery discharges, and the minimum practical supply voltage before the device shuts down is typically 2.7V. Most manufacturers want to use the battery for as much of this range as possible, and therefore specify that the power amplifier must faithfully deliver fully rated power at 3.3V (and occasionally 3.0 V).
Delivering high power under these conditions imposes some significant challenges. As most circuit designers know, a low supply voltage requires a high current, which implies a very low output impedance. Consequently, matching the low impedance PA output to a 50 Ohm antenna is difficult to achieve.
If higher output powers are required, the impedance becomes even lower, and it becomes increasingly difficult to achieve a good broadband match between the PA and the antenna.
Regulatory requirementsRegulatory requirements also place a serious constraint on how much power a PA can deliver. An ideal linear PA produces only the original frequency from the input signal. In real-world implementations, PA non-linearities introduce new frequencies through intermodulation distortion (IMD), and these out-of-band signals can interfere with users in adjacent channels (referred to as spectral regrowth or spectral leakage).
Regulatory bodies have imposed strict regulations on the amount of power that can be emitted out of band. For example, for mobile devices in the 2.5GHz band, the FCC specifies4 that the emissions must be below -25 dBm/MHz, measured 5.5MHz outside the device's assigned band.
Since this limit is an absolute power measurement, as output power is increased, more and more rejection of out-of-band emissions is required, and the power amplifier must be made more and more linear.
For example, when transmitting at +23 dBm with a 10 MHz channel bandwidth, achieving -25 dBm/MHz requires a net rejection of 23-10log(10)+25=38 dB rejection. Transmitting at 24.5 dBm requires 39.5 dB rejection.
Therefore, it becomes increasingly difficult to meet regulatory requirements as output power is increased. To reduce IMD distortion, the PA must operate more linearly, and the result is that PA efficiency will drop as the output power target is increased.
Recognizing the Tradeoffs Undoubtedly, higher transmit power is important for mobile WiMAX networks. Networks are currently being deployed specifying that the minimum transmit power is +23 dBm.
Each user who enters a network transmitting at powers greater than +23 dBm increases overall network efficiency. However, delivering higher transmit powers comes at a cost to power consumption. As a result, power amplifier efficiency becomes more important as higher output powers are used.

Source from Wireless Net Design Line

WIMAX DEPLOYMENTS MAP FROM WIMAXFORUM

The WiMAX Forum has announced the launch of their Interactive Deployment Database, which has information on more than 300 WiMAX deployments around the world.The site is using Google Web Map based localization map and give you able to find results by searching 802.16.e, 802.16.d, All range frequencies ( 2.1 - 5.8Ghz ), Status ( Deployed, In Deployment, License Awarded etc ), Vendors ( from Alcatel, Alvarion, Airspan, Aperto etc ).

The new Interactive Deployment Database relies upon the WCIS database offered by Informa Telecoms, and focuses upon various WiMAX operators, providing the readers with the latest data regarding the WiMAX deployments that have been made worldwide. A link to the database has been provided at the homepage of the WiMAX forum, and can be accessed at www.wimaxmaps.org.

THE ROAD TO WIMAX TV

Despite the rise in popularity of user-generated videos and other "do-it-yourself" forms of content, when it comes to authentic revenue generation, broadcast television programming is still king. The revenue it generates, regardless of whether it is distributed via ad-supported, "free-to-air" broadcasting, pay television or any other model, dwarfs that of other content types. Telcos and other communications service providers looking to leverage their IP-based networks to offer video as part of subscriber packages recognize the necessity and huge appeal this type of content has in winning and maintaining an audience share.
Similarly, mobile operators are finding that broadcast programming is the key to thriving in an increasingly competitive landscape. As growth rates from pure voice traffic flatten, they are introducing data applications, not the least of which are videos of popular broadcast network programs. Hence "mobile TV" is already proving to be a promising ARPU generator for mobile operators, with several million subscribers to such services worldwide.
Beyond the ARPU increase, mobile distribution of broadcast programming offers such new business opportunities as targeted advertising models. It's not surprising that incumbent operators are investing in infrastructure to meet the consumer expectation for "content anywhere, any time on any device."
WiMAX is emerging as one of the most promising wireless networking technologies designed to meet this demand. However, broadcast-quality video is a bandwidth hog. As an IP-based network, WiMAX faces inherent scalability problems. Each new customer requires more bandwidth, connectivity sessions grow longer and applications such as video require ever more capacity. Serving thousands of such individual "unicast" streams becomes expensive, and there is a seemingly inevitable decline in quality of service at periods of peak demand.
One way to avoid these issues, and take full advantage of WiMAX to meet consumer demand and operator interests, is to implement hybrid broadcast/multicast architecture. This type of architecture is economically feasible because TV viewers tend to aggregate around "peak" viewing times: Despite the huge explosion in the amount of content now available on many networks and the inevitable fragmentation of audiences, in most markets, the bulk of TV audiences are largely served by five to ten major channels or networks.
This is true of fixed TV viewing and is likely to be the same with mobile, with the channels or networks meeting the demand for appropriately produced programming directed at commuting periods and other times in the day or week when mobile viewing is likely to be popular. A WiMAX TV broadcast/multicast solution enables operators to offer the most popular mobile programming at quality reception over predictable bandwidth and without any risk of congestion or contention during these peak-viewing periods.
In addition to nationwide or regional TV broadcasting, WiMAX TV also enables local content insertion and "micro-broadcasting" " the efficient delivery of content within restricted areas during popular sports events or concerts, or within airports, campuses or hospitals.
While viewing habits do tend to aggregate around certain predictable times, and audiences tend to gravitate en masse toward certain shows or programs, the portable nature of mobile TV means there will be a demand for individual streams and so-called niche or long-tailed content. Meeting this demand requires using a mix of broadcast, multicast and unicast technologies.
Typically, this is done by broadcasting the most popular TV channels on bandwidth that is set aside and efficiently managed through dynamic multiplexing. Other TV channels are multicast based on the demand in each particular cell, while interactive services and niche content are serviced over unicast links. How these various services are packaged and sold to the viewers will evolve over time as the market emerges.
Making this hybrid approach to mobile video delivery successful involves not just the use of a WiMAX network itself, but the implementation of an architecture specifically optimized for WiMAX-based mobile video delivery. It is this type of architecture that can transform a typical WiMAX network into a WiMAX TV network.
An optimized WiMAX TV architecture is based on the Multicast-Broadcast Services (MBS) specification, which is part of the Mobile WiMAX (802.16e) standard. MBS supported by Mobile WiMAX (802.16e) leverages the most successful features of such technologies as DVB-H, DVB-SH, MediaFLO and 3GPP E-UTRA. It offers high data rates and coverage using a Single Frequency Network (SFN); a flexible allocation of radio resources; low mobile-station power consumption; support for datacasting in addition to audio and video streams and fast channel-switching.
The Mobile WiMAX Release-1 profile defines a toolbox for initial MBS service delivery. The MBS service can be supported by either constructing a separate MBS zone in the DL frame along with unicast service (embedded MBS) or by dedicating the whole frame to MBS (DL only) for standalone broadcast service. MBS can be accessed when MS is in idle mode to allow low MS power consumption. The flexibility of Mobile WiMAX to support integrated MBS and unicast services enables a broader range of applications. [1]
As this architecture is fully IP-based, it enables operators to use standard network and headend components, as well as their existing terminal applications. A complete infrastructure overhaul or rebuild is not necessary. In addition, the architecture is scalable over a practically unlimited number of users, flexible in content trafficking, and centrally managed and monitored.
The Single Frequency Network (SFN) architecture brings an additional gain of several dBs in the radio channel, thus improving reception quality. "Time-slicing" technology, successfully implemented in DVB-H and other broadcast standards, increases the lifetime of the terminal's battery by receiving the content in short bursts, rather then continuously. The Inter-bursts Forward Error Correction (iFEC) " developed by UDcast -- ensures perfect video quality under difficult propagation conditions, making short reception blackouts totally invisible to end-customers, such as when they are passing under a bridge or tree.
While developing WiMAX TV architecture may not involve a heavy infrastructure upgrade, it is necessary to integrate software to manage the network's operations. UDcast has recently developed three software modules designed to meet this need including a WiMax TV Manager, which ensures the management of the entire WiMAX TV network, as well as the integration of the broadcast/multicast system with content sources, service protection and interactive services. Other software modules include the WiMAX TV ASN/MBS (Mobile Base Station) Module and the WiMAX TV Base Station Module. The MBS module implements the core functions of our WiMAX Multicast-Broadcast Service Controller and ensures the correct level of synchronization of the base stations for SFN operation, plus Inter-bursts Forward Error Correction (iFEC), intra-BS handover and content time-slicing. The WiMAX TV Base Station Module enforces SFN broadcasting and time-slicing and executes procedures for local content adaptation or injection, enabling geographically addressable content distribution.
These modules demonstrate that it is feasible to use WiMAX to deliver broadcast-quality programming to mobile devices. Harnessing the power of WiMAX to enable such a service offers numerous benefits to players across all segments of the industry. IP and telecom infrastructure providers, for example, can use it as revenue-generating extension of their existing WiMAX solutions. Similarly, broadcast TV providers can use it as an innovative WiMAX extension to their existing broadcast operations, or as a direct television distribution channel to the fast-growing community of WiMAX users.
Even though new applications and models won't be discovered until operators and other users began to implement WiMAX as a mobile video delivery tool, there are emerging applications and business models for WiMAX TV today. Many operators already have the existing network infrastructure to do this " they just need to embrace the technology in order to leverage it to its maximum, revenue-generating potential.

CASE STUDY BULGARIAN TELCO PIONEERS MOBILE "TRIPLE-PLAY" SERVICES OVER WIMAX

Max Telecom uses Navini Smart WiMAX and Cisco Carrier Ethernet solutions to deliver
nationwide mobile services.
Business Challenges Max Telecom entered the telecommunications market in Bulgaria just two and a half years ago and quickly established itself as a new-generation operator by adopting the latest network and business innovations and giving subscribers industry-leading services and capabilities. The “greenfield” company is garnering international attention with its nationwide network based on mobile WiMAX™ technology. The ambition of Max Telecom is to extend its modern, highly efficient network to the entire population of the country within the next few years. The aggressive build-out has challenged the company to select technology partners that can deliver the required hand-held devices as well as help Max Telecom deliver its vision of mobile access for all services.
The company currently offers Internet access, VPNs, voice services, video, and IPTV.
Having already selected Cisco® for the core network, Max Telecom evaluated radio vendors to determine the best possible foundation to meet its goal of delivering all services using mobile WiMAX. The company simultaneously evaluated all alternatives for an efficient access/aggregation solution. To shorten time to market and keep costs low, Max Telecom decided to lease parts of the network. A third-party provides Ethernet to the home (ETTH) for access to base stations in various cities, and Metropolitan Area Network (MAN) lines to connect its headquarters with the smaller cities. To build out the mobile access network, Max Telecom looked for base station equipment and an overall architecture that could scale aggressively and
help ensure security within its leased transport environment. The company aims to cover 90 percent of the 7.5 million residents of Bulgaria by the end of this year.



The major requirements for the base station selection and overall design included:
● Controlling capital expenses and operating expenses by minimizing cell counts and
improving in-building coverage. Evolving from fixed services (desktop modems, PCs) to mobile services (handheld and embedded devices) as new 802.16e wireless broadband devices become available
● Enabling a broad range of services for competitive differentiation and to gain market share Network Solutions Aiming to pioneer mobile WiMAX services, Max Telecom focused its selection process on a rigorous evaluation of the leading WiMAX technologies. The company identified Smart Beamforming as a breakthrough that could enable its aggressive goals. This led the operator to Navini, the global leader for broadband wireless access solutions. With an established relationship with Cisco, Max Telecom also had confidence in Cisco as a partner that could enable a fast deployment. (See Figure 1.)
Figure 1. The Max Telecom 802.16e WiMAX Network



Leading-edge WiMAX Navini Smart WiMAX combines both Smart Beamforming and beamformed multiple-input multipleoutput (MIMO) technologies, two advancements uniquely combined by Navini to push the capabilities of broadband wireless networks. The unique combination doubles the data throughput for mobile WiMAX, extends the range, and enhances the signal strength. By using both Smart Beamforming and MIMO technologies, Navini offers base station and smart antenna solutions that enable data transmissions at rates up to six times faster than other WiMAX solutions. Smart WiMAX also extends coverage. In many places where standard signals cannot be received, the enhanced beamformed MIMO signal has the power and performance to break through. The results
are better mobility, higher throughput rates, and better coverage both indoor and outside. The Navini technology also enables fewer cell sites while increasing overall network capacity. “In terms of technology, Navini was clearly the best for our WiMAX deployment,” says Kroum Manoilov, chief operating officer for Max Telecom. “Now that Navini has been acquired by Cisco, we feel even better about the solution. Cisco and Navini have extensive worldwide deployment experience, and we have relied on their knowledge of the WiMAX space to help us meet our fastpaced rollout of mobile services.”
Smart WiMAX service has enabled Max Telecom to begin rolling out mobile services. The
company offers fixed and nomadic services today, and will enhance mobility when IEEE 802.16ecompliant CPE and hand-held devices are available in early 2008. Max Telecom has already built out more than 150 base stations and introduced fixed and nomadic WiMAX service to more than 10 cities.
Cisco Aggregation
The WiMAX network officially went live in October 2007, allowing transfer speeds of up to 2 megabits per second (Mbps). Max Telecom plans to increase that rate to 5 Mbps in early 2008. To aggregate traffic from the base stations, the operator decided to use Ethernet over Multiprotocol Label Switching (EoMPLS) and Hierarchical Virtual Private LAN Service (H-VPLS). This Carrier Ethernet solution allows Max Telecom to efficiently and securely tunnel all WiMAX traffic over the leased transport connections.
Max Telecom selected the Cisco Catalyst® 3750 Metro Ethernet switch for aggregating base station traffic. The Cisco Catalyst 3750 nodes are connected to Cisco 7600 Series routers (over the EoMPLS/H-VPLS network) for a complete aggregation solution. With greater intelligence at the edge, the Cisco Catalyst 3750 metro switches enable more differentiated Ethernet services and give Max Telecom hierarchical quality of service (QoS), traffic shaping, intelligent 802.1Q tunneling, VLAN mapping, and EoMPLS support. This robust feature set helps Max Telecom offer different service-level agreements (SLAs) and flexible service options.
End-to-End Solution Cisco and Navini products provide a complete mobile WiMAX solution for Max Telecom. The open, flexible design can accommodate Access Service Network (ASN) gateways as the mobile service subscriber base grows, and a full suite of features help to differentiate the carrier from the competition. End-to-end QoS, over-the-air activation, and self-provisioning contribute to a costeffective
business model and enable a growing portfolio of services.

Business Results WiMAX has fulfilled its promise and enabled Max
Telecom to rapidly and cost-effectively achieve national coverage. The Navini and Cisco solutions have created the WiMAX foundation for mobile services, and put Max Telecom in an enviable position for service innovations. As soon as mobile equipment vendors introduce new handsets and other devices, Max Telecom can give subscribers
anytime, anywhere voice over IP (VoIP) and IPTV as well as the full suite of other broadband services. The new network gives the operator a build-as-they-grow solution, with the current plans for expanding capacity for up to 100,000 subscribers by the end of 2008. To compete against larger DSL and cable players, Max Telecom has also adopted an aggressive wholesale strategy. The operator is developing relationships with LAN service providers, and will pass through its voice and other services that can be bundled with the data services from these providers. The 802.16e WiMAX network enables this business, and is also enabling Max Telecom to expand its “tripleplay”
business by teaming up with a Bulgarian satellite TV provider to bring more content to subscribers. Within the first few months after deploying the new mobile WiMAX solution, the results are promising:
● Capital expenses will come down from about US$430 per potential subscriber to less than
US$200 within three years.
● Data subscribers are expected to grow from less than 10,000 to between 50,000 and
100,000 by the end of 2008 (depending on the availability of mobile WiMAX devices).
● Scalable capacity can support more services, with plans in place for creative service
bundles. For example, Max Telecom plans to bundle mobile VoIP and broadband.
● The low operating expenses achieved with the WiMAX solution will enable differentiating
services including a free TV service (MaxTV), rebranded Google applications (mobile
MaxApps), and a mobile e-mail service (MaxMail).
“Cisco has helped us establish a very strong market position,” says Manoilov. “We have hit all of our schedule targets and are confident that our WiMAX network can help us bring exceptional service quality to our subscribers. The combination of Navini WiMAX and Cisco Carrier Ethernet technologies put us ahead of the incumbent providers and other competitors.”
For More Information To find out more about Cisco Carrier Ethernet solutions, go to: www.cisco.com/go/cedesign.
To find out more about the Navini WiMAX solutions, go to: www.cisco.com/go/wimax.

WIMAX SERVICE TARIFF PLANNING

Recently read that how you can plan your WiMax internet service tariff plans. You can go to few different ways to how to calculate it most affordable for your customers.

The per-line $ cost of WiMax is totally differrent from the Per-Line$ cost of ADSL. Yes, ADSL Costs have been recovered over 10's of years, and you dont have that much time for break-even, but WiMax per capita Capex is also very low.
- Make a 3 year model on the Capex recovery with 3 scenarios - Conservative, Realistic and Optimistic. Each model will have projected number of subscribers - at various price points. this will give you 2-3 key data points on which model looks most realist.
Once the data is right in front of you, just take a 20% dip in bandwidth costs over every year, and build data price.
Carriers also optimise throughput by reducing throttle bandwidth. Access might be 54mbps, but bandwidth is rarely close to that number, that can further optimise the OpEx.

Add a Delta of recovery exp - 20% - 40% of Opex. and see if the number is helpful.
The other disruptive way of doing it is - take a ridiculusly low price, say in a market which has 40$ per year fee, take 10$ per year. build projections on network, opex and subscribers - you might be surprised on the results.

WiMax for starter as you understand is far superior tech compared to ur adsl or other existing techs on the price front here the method i will apply to determine the price
1.what is total CAPEx involment with project (like 360 Wimax tower and other infrastructure required),
next is what is cost acquire the Bandwidth for delivery through the last mile (in this case Wimax)
now you have to price the product so that your not making loss on whole thing plus add profit in

2.Now,Bcoz ur using the the newest tech u hav many advantages over old legacy techs ,deployment is cheaper
like if u hav 360 tower u can very much cover a area of 25sq km

3.on the price there could be synergy be a premium player as ur tech is the best,target the niche market
and ask for premium payout or target the mass market and price it below asdl player and get get
paid by driving the volume and creating new market of users(this is what Indian mobile players did!)
on the pricing a lot will depend on the sourcing of your infrastructure and bandwidth.
Amortization of the cost of bandwidth + cost of BTS + cost of CPE + Marginal opex cost

Example -
- BTS (360 coverage) capacity - 'x' mbps
Wimax POP/ BTS(360 Coverage) Costs "y"
Per kbps cost = (x * 1024) / y

- Cost of CPE (if on Right to use/ Bundled model)
- CAPEX (network hardware, switching architecture, Tower, backhaul)
- Bandwidth cost - (shared model costing - typical to what ADSL does)
take all these into consideration and align your foretasted numbers with minimal margins in place to start with.

Tarrif models could have multiple variants.
To cover the capex spent on WIMAX
- One time Service charges - covers cost of CPE (if provided on rental)
- Recurring Wireless access charges - (Covers per kbps bandwidth usage cost & maintenance)

Bandwidth
- Clean bandwidth / bundled with CPE - High premium
- 1:4 , min and max throughput / bundled with CPE -

You can keep on subsidizing the price after adding bundles like VOIP and internet telephony.

MOBILE WIMAX DEPLOYMENT ALTERNATIVES

Traditionally, cellular deployments were based solely on achieving ubiquitous coverage with little consideration for capacity requirements. Since the only services offered were voice and the market was uncertain, this was a very reasonable approach. Moreover, the voice service offering is a low data rate application enabling traditional cellular networks to achieve wide outdoor and indoor coverage with a low data rate network (~10-15 kbps bandwidth depending on type of vocoder). As the customer base grew and more services offered, additional base stations were deployed and/or channels added to existing base stations to meet the growing capacity requirements. With Mobile WiMAX, however, operators will want to offer a wide range of broadband services with Quality-of-Service (QoS) support. To meet customer expectations for these types of services it will be necessary to predetermine capacity requirements and deploy accordingly at the outset. Careful deployment planning in anticipation of growing customer demands will ensure a quality user experience when the network is at its busiest.

Determining Capacity Requirements
Arriving at an accurate estimate of capacity requirements for new broadband services is not a simple exercise. One must anticipate how users will make use of the new services being offered and how often users will be actively engaged with the network. Data density, expressed as Mbps per km^2, is a convenient metric for describing capacity requirements. Determining the required data density for a specific demographic region is a multi-step process.The expected market penetration, or take-up rate, at maturity is dependent on a number of factors including the competitive situation and the services offered that distinguish one service provider from another. The service provider’s penetration may also vary within the metropolitan area since urban and dense urban residents will often have other broadband access alternatives from which to choose as compared to residents in suburban and rural areas.

Base Station Deployment Alternatives
Mobile WiMAX base station equipment will be available from many different vendors and, although all will be WiMAX compliant and meet performance and interoperability requirements, a great many different configurations will be available from which service providers can choose. The availability and timing of optional features also adds to the equipment variability. Additionally, there are different frequency bands that can be considered and varied amounts of spectrum availability within these bands. The spectrum choices will, in many cases, affect the frequency reuse factor and the channel bandwidths that can be employed in the access network.WiMAX solutions with beamforming will generally be architected quite differently from
SIMO and MIMO solutions. A typical SIMO or MIMO configuration will have power amplifiers mounted at the base of the tower to facilitate cooling and maintenance. The amplifiers in this case would have to be sized to compensate for cable losses, which can range from 2 to 4 dB depending on tower height and frequency. Beamforming solutions require good phase and amplitude control between transmitting elements and will often be architected with their power amplifiers integrated with the antenna elements in a tower-mounted array. The larger size and weight of these structures will also require more robust mounting. There is additional signal processing requirements for beamforming solutions with Adaptive Beamforming being the most computational intensive.

The selection of channel bandwidth and duplexing method can also have an economic impact on the varied WiMAX deployment alternatives. In addition the desired “worse case” UL rate will affect the UL link budget and therefore, impact the range and coverage of the base station.

Conventional cellular deployments used cell frequency reuse factors as high as seven (7) to mitigate intercellular co-channel interference (CCI). These deployments assured a minimal spatial separation of 5:1 between the interfering signal and the desired signal but required seven times as much spectrum. With technologies such as CDMA, introduced with 3G, and OFDMA, introduced with WiMAX, more aggressive reuse schemes can be employed to improve overall spectrum efficiency.

Number of Base Stations
The key metric for a quantified comparison will be the number of WiMAX base stations required to meet both capacity and coverage requirements in the varied demographic regions. The WiMAX base station is a key network element in connecting the core network to the enduser in that it determines the coverage of the network and defines the end-user experience. If too few base stations are deployed the coverage will not be ubiquitous and the end-user may experience drop outs or periods of poor performance due to weak signal levels as he moves throughout the coverage area. And since the base station investment will tend to be a dominant contributor to the total end-to-end network costs, deploying too many base stations can result in unnecessary start-up costs for the operator leading to a weaker business case.

Summing up
In the long term, the higher performance base stations with wideband channels provide a potentially more cost-effective deployment solution as measured by the number of required base stations. One might conclude that it would be worth waiting for antenna technologies such as beamforming and beamforming + MIMO and possibly even 20 MHz channels, before deploying a Mobile WiMAX network. This however, is not the case. In the early years , deployment can begin with range-limited base stations using (1x2) SIMO or (2x2) MIMO base station configurations to get ubiquitous coverage over the entire metropolitan area. These base stations can then be upgraded in the following years with beamforming and beamforming + MIMO as necessary to meet the capacity requirements in anticipation of a growing customer base. In most metropolitan area deployments this will only be necessary in the dense urban and urban areas.

WHEN BROADBAND WIRELESS AND SATELLITE SERVICES COLLIDE

The C-band frequency is used worldwide by fixed satellite services (FSS) operators to eliver TV transmissions, distancelearning, telemedicine, disaster recovery, meteorological and earth observation services, and also by certain military services. Today, there are approximately 160 geostationary satellites operating in the C-band frequency worldwide. In addition, two out of every three commercial satellites under construction will utilize C-band. The deployment of broadband wireless access (BWA) services, including WiMax, has been gaining momentum in several countries. BWA equipment, slated to operate within the 3.4-3.7 GHz ranges of the FSS extended C-band frequency, has been demonstrated to severely interfere with satellite communications operating within the C-band. Early Indications With several national administrations having designated portions of the C-band for terrestrial wireless applications, including BWA and future mobile services, massive interruptions of satellite services, radar and microwave links has occurred in those regions. Interference has also been reported in other parts of the world, including Australia, Bolivia, Fiji, Hong Kong, Indonesia, Pakistan, Kazakhstan, and Sub-Saharan Africa. Compatibility testing in areas where WiMax services are being implemented has clearly indicated the potential for significant threat to satellite services operating in Cband. A BWA field trial in Hong Kong, for example, inadvertently knocked off the TV-signal feeds to an estimated 300,000 households throughout Asia.

Taking on Spectrum Sharing The satellite industry mobilized effectively to lobby the ITU and governing organizations against sharing the 3.4-3.7 GHz ranges of the FSS extended C-band frequency spectrum. Several prominent organizations, including APSCC, the Asia- Pacific Broadcasting Union, Asia- Pacific Telecommunity, and the Global VSAT Forum (GVF),
When Broadband Wireless and Satellite Services Collide SATELLITE TRENDS The well organized “no change” lobbying campaign orchestrated by the satellite industry resulted in a landlark decision during WRC'07 to preserve the C-band srpectrum for interference- free delivery of satellite communications. Robert Ames President and CEO SUIRG, Inc. 34 APSCC Quarterly Newsletter ted position papers to the ITU while major satellite operators vigorously engaged the ITU and other regulatory administrations on this issue. In preparation for the November ITU World Radiocommunication Conference (WRC) 2007, the Satellite Users Interference Reduction Group (SUIRG), in collaboration with GVF, the U.S. Navy and several other industry organizations conducted a field test to assess whether WiMax systems would cause severe interference to satellite systems and to measure the xtent of such interference. The test was conducted in two phases in RF-quiet areas to ensure no external signals contaminated the test results.

Testing was performed using a Prodelin-provided fixed satellite service antenna, Vertex/RSI-provided LNA and a WiMax unit. The NSS 806 satellite, located at 319.5°E, was used for both phases of the test with the baseline video signal sent from a TT&C earth station in Manassas, Virginia. The FSS antenna was aligned to receive a video program channel at 3,515 MHz. Phase 1: The testing was conducted in Punta Gorda, Florida where the FSS antenna stayed at a fixed location and the WiMax transmitter, positioned at a slightly elevated level of about 3 meters, was moved to a variety of locations. The FSS receive C/N (carrier/noise) was set to a nominal 10 dB. At the receiver down-converter (D/C) output, the Bit Error Rate (BER) and digital power of the carrier were measured to establish a baseline. The WiMax transmitter and omni-directional antenna were fixed to a vehicle and set to transmit at various frequencies and power outputs. Field testers adjusted the WiMax transmitter to various frequencies and various output power levels. C/N, I/N (interference /noise), BER, and video quality results were then measured at the FSS antenna along with spectrum plots for each phase of the test. Phase 1 testing was designed to simulate a subscriber unit operating within the vicinity of an FSS antenna system. Phase 2: The second test phase was held in the Southern Maryland and Northern Virginia areas. The WiMax antenna and base station were mounted on a water tower at an elevation of 50 meters, with a down tilt angle of 8 vertical (typical of cellular tower antennas). The FSS antenna was moved to several locations transmitting at differing angles from the WiMax antenna. Before the start of Phase 2 testing the C/N, I/N, BER, and video quality results were measured at the FSS antenna along with spectrum plots for each phase of the test. These results acted as a baseline for the Phase 2 testing.




















The FSS antenna was moved varying distances and placed at differing angles relative to the fixed WiMax transmitter, with the same measurements made at each location. Field testers adjusted the WiMax transmitter to various frequencies and various output power levels, and measured the same parameters as in Phase 1. The purpose of Phase 2 testing was to provide field data relative to the distance required to meet the maximum long-term WiMax generated IN of -10 dB specified for an exclusion zone where WiMax systems could not be installed. Results the WiMax Forum provides for an interference to- noise ratio of -10 dB, whereby the WiMax signal should be at least 10 dB below the carrier noise floor. However, the findings of the field test indicate significant interference where the lowest I/N level measured at the test FSS antenna was found to be 7 dB above the noise floor. In addition, the WiMax base station and antenna used during Phase 2 have a maximum Eq uivalent Isotropic Radiated Power (EIRP) of 34 dBm. ITU studies and regulating bodies have used 44 dBm for the protection of FSS earth stations. Extrapolating the test data for defining the distance required between FSS and WiMax systems indicate an exclusion zone of 280 km, which would restrict WiMax systems to extremely remote locations. “The results identified significant levels of interference generated by the WiMax system,” said Robert Ames, President of SUIRG. “The importance of C-band services dictates urgency when dealing with this potential threat. We hope that the results of our field test will make a difference in the decision-making process for re-allocating this critical frequency for terrestrial wireless services.” The well organized “no change” lobbying campaign orchestrated by the satellite industry resulted in a landmark decision during the ITU World Radiocommunication Conference (WRC) 2007, held 22 October- 1 November in Geneva, to preserve the C-band spectrum for interference- free delivery of satellite communications. The resulting decision restricts International Mobile Telecommunications (IMT), including WiMax, from any part of the satellite C-band (3.4-4.2 GHz). The ITU table of allocations remains unchanged, with the limited number of countries in favor of change identified in an opt-in footnote. By taking this approach, the world’s regulators participating in the WRC have made it clear that the C-band is off limits for IMT and have preserved the precious spectrum for satellite communications. The WRC further restricted IMT, specifying adherence to stringent requirements for the protection of existing and future satellite services in the C-band, including transborder protection. For example, in Region 2 (the Americas and the Caribbean), there is no identification for IMT, just an upgrade through a footnote, in 14 countries of the mobile service allocation in 3.4-3.5 GHz. In Region 3, only eight countries inserted their name to the footnote identifying IMT. Only in Region 1 was there broader support from countries to be included in the footnote identifying IMT for national use.

MOBILE PHONE RADIATION AND HEALTH

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A Greenfield-type tower used in base stations for mobile telephony

Mobile phone radiation and health concerns have been raised, especially following the enormous increase in the use of wireless mobile telephony throughout the world (as of August 2005, there were more than 2 billion users worldwide). This is because mobile phones use electromagnetic radiation in the microwave range. These concerns have induced a large body of research (both epidemiological and experimental, in non-human animals as well as in humans). Concerns about effects on health have also been raised regarding other digital wireless systems, such as data communication networks.

The World Health Organization has concluded that serious health effects (e.g. cancer) are very unlikely to be caused by cellular phones or their base stations, and expects to make recommendations about mobile phones in 2007–08.

However, some national radiation advisory authorities, including those of Austria, France, Germany and Sweden recommend to their citizens measures to minimize exposure. Examples of the recommendations are:

• Use hands-free to decrease the radiation to the head.
• Keep the mobile phone away from the body.
• Do not telephone in a car without an external antenna.

However, the use of "hands-free" was not recommended by the British Consumers' Association in a statement in November 2000.

Health hazards of handsets

Calculated specific absorbed radiation (SAR) distribution in an anatomical model of head next to a 125 mW dipole antenna. Peak SAR is 9.5 W/kg over 1 mg. (USAF/AFRL).

Part of the radio waves emitted by a mobile telephone handset are absorbed by the human head. The radio waves emitted by a GSM handset, can have a peak power of 2 watts, and a US analogue phone had a maximum transmit power of 3.6 watts. Other digital mobile technologies, such as CDMA and TDMA, use lower output power, typically below 1 watt. The maximum power output from a mobile phone is regulated by the mobile phone standard it is following and by the regulatory agencies in each country. In most systems the cellphone and the base station check reception quality and signal strength and the power level is increased or decreased automatically, within a certain span, to accommodate for different situations such as inside or outside of buildings and vehicles.

The rate at which radiation is absorbed by the human body is measured by the Specific Absorption Rate (SAR), and its maximum levels for modern handsets have been set by governmental regulating agencies in many countries. In the USA, the FCC has set a SAR limit of 1.6 W/kg, averaged over a volume of 1 gram of tissue, for the head. In Europe, the limit is 2 W/kg, averaged over a volume of 10 grams of tissue. SAR values are heavily dependent on the size of the averaging volume. Without information about the averaging volume used comparisons between different measurements can not be made. Thus, the European 10-gram ratings should be compared among themselves, and the American 1-gram ratings should only be compared among themselves. SAR data for specific mobile phones, along with other useful information, can be found directly on manufacturers' websites, as well as on third party web sites.

Thermal effects

Microscope photographs of lenses incubated in organ culture
conditions for 12 days. Right frame shows Control lens with no
damage. Bottom frame demonstrates the effect of microwave radiation on bovine lens sutures for a total exposure of 192 cycles (1.1 GHz, 2.22 mW). Each cycle lasts 50 min followed by 10 min pause. In the absence of microwave radiation, the bubbles are generated by temperature increase to 39.5 °C during 4 h; see left frame. Credit: IsraCast Technology News

One well-understood effect of microwave radiation is dielectric heating, in which any dielectric material (such as living tissue) is heated by rotations of polar molecules induced by the electromagnetic field. In the case of a person using a cell phone, most of the heating effect will occur at the surface of the head, causing its temperature to increase by a fraction of a degree. In this case, the level of temperature increase is an order of magnitude less than that obtained during the exposure of the head to direct sunlight. The brain's blood circulation is capable of disposing of excess heat by increasing local blood flow. However, the cornea of the eye does not have this temperature regulation mechanism. Premature cataracts have not been linked with cell phone use, possibly because of the lower power output of mobile phones.

It has been claimed that some parts of the human head are more sensitive to damage from increases in temperature, particularly in anatomical structures with poor vasculature, such as nerve fibers.

Non-thermal effects

The communications protocols used by mobile phones often result in low-frequency pulsing of the carrier signal.

Some studies have claimed to show that mobile phone signals affect sleep patterns and possibly delay sleep onset during exposure. In another clinical study, carried out by Sweden's Karolinska Institute and Wayne State University in the US, the authors concluded their research suggested an association between RF exposure and adverse effects on sleep quality within certain sleep stages, though participants were unable to determine better than chance if they had been exposed to actual radiation or sham exposure. The UK National Health Service criticized the research because of the small sample size used, and because of the 53% of participants who reported sensitivity to mobile use, a proportion unlikely to be representative of the general population. The NHS also criticized the press for inaccurate reporting of the study.

Some researchers have argued that so-called "non-thermal effects" could be reinterpreted as a normal cellular response to an increase in temperature. The German biophysicist Roland Glaser, for example, has argued that there are several thermoreceptor molecules in cells, and that they activate a cascade of second and third messenger systems, gene expression mechanisms and production of heat shock proteins in order to defend the cell against metabolic cell stress caused by heat. The increases in temperature that cause these changes are too small to be detected by studies such as REFLEX, which base their whole argument on the apparent stability of thermal equilibrium in their cell cultures.

Swedish researchers from the University Lund, Salford, Brun, Perrson, Eberhardt and Malmgren, have studied the effects of microwave radiation on the rat brain. They found a leakage of albumin into brain via a permeated blood-brain barrier.

Genotoxic effects

Research published in 2004 by a team at the University of Athens had a reduction in reproductive capacity in fruit flies exposed to 6 minutes of 900 MHz pulsed radiation for five days. Subsequent research, again conducted on fruit flies, was published in 2007, with the same exposure pattern but conducted at both 900 MHz and 1800 MHz, and had similar changes in reproductive capacity with no significant difference between the two frequencies. Following additional tests published in a third article, the authors stated they thought their research suggested the changes were “…due to degeneration of large numbers of egg chambers after DNA fragmentation of their constituent cells …”.

In December 2004, a pan-European study named REFLEX (Risk Evaluation of Potential Environmental Hazards from Low Energy Electromagnetic Field (EMF) Exposure Using Sensitive in vitro Methods), involving 12 collaborating laboratories in several countries showed some compelling evidence of DNA damage of cells in in-vitro cultures, when exposed between 0.3 to 2 watts/kg, whole-sample average. There were indications, but not rigorous evidence of other cell changes, including damage to chromosomes, alterations in the activity of certain genes and a boosted rate of cell division.

Mobile phones and cancer

In 2006 a large Danish study about the connection between mobile phone use and cancer incidence was published. It followed over 420,000 Danish citizens over 20 years and showed no increased risk of cancer.The German Federal Office for Radiation Protection (BfS) consider this report as inconclusive.

In order to investigate the risk of cancer for the mobile phone user, a cooperative project between 13 countries has been launched called INTERPHONE. The idea is that cancers need time to develop so only studies over 10 years are of interest.

The following studies of long time exposure have been published:

• A Danish study (2004) that took place over 10 years and found no evidence to support a link.
• A Swedish study (2005) that draws the conclusion that "the data do not support the hypothesis that mobile phone use is related to an increased risk of glioma or meningioma."

• A British study (2005) that draws the conclusion that "The study suggests that there is no substantial risk of acoustic neuroma in the first decade after starting mobile phone use. However, an increase in risk after longer term use or after a longer lag period could not be ruled out."

• A German study (2006) that states "In conclusion, no overall increased risk of glioma or meningioma was observed among these cellular phone users; however, for long-term cellular phone users, results need to be confirmed before firm conclusions can be drawn."^[

• A joint study that draws the conclusion that "Although our results overall do not indicate an increased risk of glioma in relation to mobile phone use, the possible risk in the most heavily exposed part of the brain with long-term use needs to be explored further before firm conclusions can be drawn."

Other studies on cancer and mobile phones are:

• Tumour risk associated with use of cellular telephones or cordless desktop telephones, that states: "We found for all studied phone types an increased risk for brain tumours, mainly acoustic neuroma and malignant brain tumours".

• A Swedish scientific team at the Karolinska Institute conducted an epidemiological study (2004) that suggested that regular use of a mobile phone over a decade or more was associated with an increased risk of acoustic neuroma, a type of benign brain tumor. The increase was not noted in those who had used phones for fewer than 10 years.

Electrical sensitivity

Main article: Electrical sensitivity

Some users of mobile handsets have reported feeling several unspecific symptoms during and after its use; ranging from burning and tingling sensations in the skin of the head and extremities, fatigue, sleep disturbances, dizziness, loss of mental attention, reaction times and memory retentiveness, headaches, malaise, tachycardia (heart palpitations), to disturbances of the digestive system all of which can be attributed to psychological stress (e.g. Placebo, Nocebo).

Health hazards of base stations

Another area of worry about effects on the population's health have been the radiation emitted by base stations (the antennas on the surface which communicate with the phones), because, in contrast to mobile handsets, it is emitted continuously and is more powerful at close quarters. On the other hand due to the attenuation of power with the square of distance, field intensities drop rapidly with distance away from the base of the antenna. Base station emissions must comply with ICNIRP guidelines of a maximum power density of 4.5 W/m² for 900 MHz and 9 W/m² for 1800 MHz.

These guidelines are set for short term heating, which is the only understood mechanism of electromagnetic fields on biological tissue. The ICNIRP guidelines are distrusted by some scientists, such as the BioInitiative group, who report that the existing standards for public safety are inadequate to protect public health.

A 2002 survey study by Santini et al. in France found a variety of self-reported symptoms for people who reported that they were living within 300 metres (984 ft) of GSM cell towers in rural areas, or within 100 m (328 ft) of base stations in urban areas. Fatigue, headache, sleep disruption and loss of memory were among the symptoms reported. Similar results have been obtained with GSM cell towers in Spain, Egypt, Poland and Austria. It is, however, important to note that these surveys do not show statistically significant clustering or causality and those complaining of adverse symptoms may be displaying the nocebo effect, unless this is controlled in the study.

However, a study conducted at the University of Essex concluded that mobile phone masts were unlikely to be causing these short term effects in a group of volunteers who complained of such symptoms. The study has been criticised as being skewed due to drop-outs of test subjects, although electrical sensitivity lobby groups have praised the study as a whole, and these criticisms were answered by the authors.

As technology progresses and data demands have increased on the mobile network, towns and cities have seen the number of towers increase sharply, including 3G towers which work with larger bandwidths. Many measurements and experiments have shown that transmitter power levels are relatively low - in modern 2G antennas, in the range of 20 to 100 W, with the 3G towers causing less radiation than the already present 2G network. An average radiation power output of 3 W is used. The use of 'micro-cell geometries' (large numbers of transmitters in an area but with each individual transmitter running very low power) inside cities has decreased the amount of radiated power even further. The radiation exposure from these antennas, while generally low level, is continuous^.

Occupational health hazards

Telecommunication workers who spend time at a short distance from the active equipment, for the purposes of testing, maintenance, installation, etc. may be at risk of much greater exposure than the general population. Many times base stations are not turned off during maintenance, because that would affect the network, so people work near "live" antennas.

A variety of studies over the past 50 years have been done on workers exposed to high RF radiation levels; studies including radar laboratory workers, military radar workers, electrical workers, amateur radio operators. Most of these studies found no increase in cancer rates over the general population or a control group. Many positive results could have been attributed to other work environment conditions, and many negative results of reduced cancer rates also occurred.

Safety standards and licensing

In order to protect the population living around base stations and users of mobile handsets, governments and regulatory bodies adopt safety standards, which translate to limits on exposure levels below a certain value. There are many proposed national and international standards, but that of the International Commission for Non-Ionizing Radiation Protection (ICNIRP) is the most respected one, and has been adopted so far by more than 80 countries. For radio stations, ICNIRP proposes two safety levels: one for occupational exposure, another one for the general population. Currently there are efforts underway to harmonise the different standards in existence.

Radio base licensing procedures have been established in the majority of urban spaces regulated either at municipal/county, provincial/state or national level. Mobile telephone service providers are, in many regions, required to obtain construction licenses, provide certification of antenna emission levels and assure compliance to ICNIRP standards and/or to other environmental legislation.

Many governmental bodies also require that competing telecommunication companies try to achieve sharing of towers so as to decrease environmental and cosmetic impact. This issue is an influential factor of rejection of installation of new antennas and towers in communities. The safety standards in the U.S. are set by the Federal Communications Commission (FCC). The FCC has based its standards primarily on those standards established by the Institute of Electronics and Electrical Engineering (IEEE), specifically Subcommittee 4 of the "International Committee on Electromagnetic Safety".

Camouflaging towers to look like tree trunks and other more visually acceptable structures has been tried so that the usually unaesthetic towers fit better into their surrounding environment.

Lawsuits

In the USA, a small number of personal injury lawsuits have been filed by individuals against cellphone manufacturers, such as Motorola, NEC, Siemens and Nokia, on the basis of allegations of causation of brain cancer and death.^[39] Many of these cases have been decided in a federal court^{[citation needed]}, where it is required that expert testimony relating to science must be first evaluated by a judge, in a Daubert hearing, to be relevant and valid before it is admissible as evidence.

Precautionary principle

In 2000, the World Health Organization (WHO) recommended that the precautionary principle could be voluntarily adopted in this case. It follows the recommendations of the European Community for environmental risks. According to the WHO, the "precautionary principle" is "a risk management policy applied in circumstances with a high degree of scientific uncertainty, reflecting the need to take action for a potentially serious risk without awaiting the results of scientific research." Other less stringent recommended approaches are prudent avoidance principle and ALARA (As Low as Reasonably Achievable). Although all of these are problematic in application, due to the widespread use and economic importance of wireless telecommunication systems in modern civilization, there is an increased popularity of such measures in the general public. They involve recommendations such as the minimization of cellphone usage, the limitation of use by at-risk population (such as children), the adoption of cellphones and microcells with ALARA levels of radiation, the wider use of hands-off and earphone technologies such as Bluetooth headsets, the adoption of maximal standards of exposure, RF field intensity and distance of base stations antennas from human habitations, and so forth.

FDD WIMAX UNCLOAKS

From Dailywireless.org

Although the WiMax industry has kept a lid on FDD WiMax, “that cat is now truly out of the bag and is now frolicking amongst the pigeons,” says Dean Bubley of Disruptive Analysis. “I’d had some hints about this before, but I’d thought the main aim was to get WiMax working in paired-spectrum 700MHz bands in the upcoming U.S. auction.”

The WiMax Forum is making a profile for mobile WiMax that uses “paired” FDD (frequency division duplex) signalling, with separate channels for uplink and downlink. Telcos and regulators such as the ITU prefer FDD, and most of the spectrum for 3G and 4G networks requires it. WiMax standards and equipment have focussed on TDD (time division duplex), in which uplink and downlink signals have separate time slots on a single channel - but which is limited to smaller bands of spectrum.

The ITU endorsed WiMax for 2.6GHz spectrum in May 2007, but operators have expected to limit its deployment to a smaller part of this spectrum which would be designated for TDD technologies: 50MHz in the middle of the band, sandwiched between two paired 70MHz chunks for FDD.

FDD WiMax could well be pitched head-on against HSPA, EVDO, LTE and other 3G technologies in the 2.5-2.6 Ghz band, according to Bubley. But he wonders if that means that Ofcom and other regulators need to go back to the drawing boards and re-work their interference assumptions for a possible cellular/WiMax mix across the whole band.

Ericsson believes FDD is the way to go — with HSPDA/LTE — not WiMAX (video).

Spectrum auctions for combined 3G and Mobile WiMAX service is moving to high gear this year.

• New WiMAX spectrum has been licensed in Japan and New Zealand. The KDDI-led consortium Wireless Broadband Planning (WBP) and PHS operator Willcom were awarded the two Japanese 2.5GHz licences, taking 30MHz of spectrum each. WBP also includes among its investors Intel and Kyocera. WBP plans to have its 802.16e network reach nine per cent of the population by March 2009. It is aiming for 55 per cent coverage by March 2010 and 93 per cent coverage by March 2013.
• New Zealand’s December spectrum auctions resulted in Telecom New Zealand and Canada’s Craig Wireless each with 40MHz chunks of 2.5GHz spectrum. Vodafone bought 35MHz while CallPlus acquired 30MHz of the airwaves.

  CallPlus has already launched WiMAX in the Auckland area using 3.5GHz spectrum while both Telecom New Zealand and Vodafone New Zealand have been testing WiMAX. Craig Wireless, meanwhile, has now added New Zealand spectrum rights to its recently acquired holdings in Norway and Greece.

  In the simultaneous 2.3GHz auction the state-owned telecoms group Kordia walked away with 35MHz of 2.3GHz spectrum and Woosh Wireless also won 35MHz of airwaves. Woosh has announced its intention to migrate its existing wireless broadband services to WiMAX

• Hong Kong’s Office of the Telecommunications Authority said in mid-December that it intended to auction spectrum at 2.3GHz and 2.5GHz in 4Q08. About 150MHz will be reserved for operators at 2.5GHz, with roughly 90MHz of spectrum earmarked for 2.3GHz.
• Thailand’s Bangkok Post reports that the National Telecommunications Commission had granted 12 permits to test WiMAX. The 12 operators included True Move, True Universal Communication, Shin Satellite, Siemens and, perhaps surprisingly, Ericsson.
• Asia is predicted by Informa Telecoms & Media to account for 40 per cent of WiMAX subscribers worldwide in 2012, and there were further signs of WiMAX momentum in the region from Korea and India.
• Korean Mobile WiMAX pioneer Korea Telecom has now officially reported over 100,000 WiBro subscribers while a Samsung executive at CES claimed that WiBro now had 140,000 subscribers. KT plans to expand its WiBro deployments beyond Seoul to some 80 cities in 2008 and is targeting 350,000-400,000 WiBro subscribers by year-end.

  It has also teamed up with POSDATA to build a “Mobile WiMAX town” in the city of Pohang, Korea. POSDATA will provide KT with MIMO-enabled mobile WiMAX base stations, ASN-gateways, network management systems, as well as WiMAX terminals. The partners expect to launch commercial services in Q3 2008. Until now, KT has used WiMAX equipment from Samsung and LG.

• Indian telco VSNL, soon to become Tata, will launch WiMAX services in Bangalore, Delhi, Mumbai and Hyderabad this year. Later, services will be extended to 35 other cities. VSNL is supplied by Telsima, which has been running VSNL’s pilot WiMAX project in Bangalore.