A new standard for 60GHz Wi-Fi goes beyond 802.11ad wireless speed & range
A new standard for high speed multi-gigabit WiFi is emerging. Though products based on the IEEE 802.11ad (WiGig) standard have really only begun rolling out, an effort to deliver an enhancement called IEEE 802.11ay that promises to deliver faster and longer range Wi-Fi networks is gaining steam.
The up-coming 802.11ay is as an enhancement of 802.11ad in the unlicensed 60 GHz millimeter wave band of spectrum, and should be a natural upgrade. The upgrade will offer significant speed and range improvements.
802.11ay is a type of WLAN in the IEEE 802.11 set of WLANs. It will have a frequency of 60 GHz, a transmission rate of 20–40 Gbit/s and an extended transmission distance of 300–500 meters. It has also been noted that it is likely to have mechanisms for channel bonding and MU-MIMO technologies. It is expected to be released in 2017. 802.11ay will not be a new type of WLAN in the IEEE 802.11 set, but will simply be an improvement on 802.11ad.
Where 802.11ad uses a maximum of 2.16 GHz bandwidth, 802.11ay bonds four of those channels together for a maximum bandwidth of 8.64 GHz. MIMO is also added with a maximum of 4 streams. The link-rate per stream is 44Gbit/s, with four streams this goes up to 176Gbit/s. Higher order modulation is also added, probably up to 256-QAM. 802.11ay applications could include replacement for Ethernet and other cables within offices or homes, and provide backhaul connectivity outside for service providers.
What is the difference between ad and ay?
The 802.11ad standard was published in 2012 and the technology gives devices access to the unlicensed and relatively unclogged 60 GHz millimeter wave spectrum band for multimedia streaming, VR headset connectivity, computer-to-monitor wireless links and other apps that don’t require more than say 30 or 40 feet of unimpeded space. It has been adopted by chipmakers as well as vendors of routers, access points and other devices. The Wi-Fi Alliance runs a WiGig certification program for vendors, and the early 11ad gear on the market most commonly supports data transfer rates of 4.6Gbps – way faster than 802.11n and 11ac, but more limited in range and unable to penetrate solid objects.
The backwards compatible 802.11ay amendment to 802.11ad is designed to boost speeds several-fold. That initially would amount to a transmission rate of 20 to 30Gbps and a range of 33 to 100 feet with 11ay-to-11ay device setups, but once channel bonding, MIMO and other capabilities are exploited, you could be getting closer to 200Gbps and reaching distances approaching 1,000 feet, according to industry players.
11ay, as the specs are being developed, “is really allowing for a wider range of products than you’d get with ad, which has one set of data rates that everyone supports… ay has a lot more parameters to play with in channel bonding, MIMO and features at the MAC level to allow a far greater range of performance and products” according to one chipset vendor.
Other up-coming Fast WiFi standards: 802.11ax
Users should not confuse 802.11ay with 802.11ax, which will work in the 2.5 and 5 GHz bands. The lower frequency bands for 11ax will penetrate walls. 11ay will not.
What will 802.11ay be used for?
It remains to be seen how soon the high speeds of 11ay will really be needed for internal uses, as 802.11ac — including Wave 2 products — are already pretty robust. But experts say that if 11ad doesn’t quite do it for you given its distance limitations, “11ay will finally be the technology that would let you snip that Ethernet cord – you no longer have to run Ethernet cables to everyone’s desk… there’s enough wireless bandwidth in ay.”
Many are enthusiastic about 802.1ay’s potential as a fixed point-to-point or point-to-multipoint outdoor backhaul technology, especially in light of scaled back fiber rollout plans by providers like Google and Verizon in the face of extraordinary costs associated with such implementations. “I’m more bullish on using ad & ay for backhaul (instead of mesh) in the case of campus & city networks — provided that it has a useful range” according to one industry expert
But it’s possible that 802.11ay could find a role in internal mesh and backbone networks as well as for other uses such as providing connectivity to VR headsets, supporting server backups and handling cloud applications that require low latency. “I believe that eventually, there will be enterprise applications for this – but it’s probably a few years into the future, given that we will have 802.11ax fairly soon & because there’s still a lot of 5 GHz band available for that (and ac).
When will 802.11ay become reality?
The 802.11ay task group had its initial meeting in 2015 and the spec only hit the Draft 0.1 stage in January. Though it is expected to reach Draft 1.0 by July 2017, according to the IEEE task group. If that mark is hit, expect pre-standard 11ay products to start rolling out within a year of that time.
Who is behind 802.11ay?
The IEEE task force leading the 11ay work includes representatives from major equipment and chipsets vendors. The group states its goal as this: “Task Group ay is expected to develop an amendment that defines standardized modifications to both the IEEE 802.11 physical layers (PHY) and the IEEE 802,11 medium access control layer (MAC) that enables at least one mode of operation capable of supporting a maximum throughput of at least 20 gigabits per second (measured at the MAC data service access point), while maintaining or improving the power efficiency per station. This amendment also defines operations for license-exempt bands above 45 GHz while ensuring backward compatibility and coexistence with legacy directional multi-gigabit stations (defined by IEEE 802.11ad-2012 amendment) operating in the same band.”
5G radio access technology will be a key component of the Networked Society. It will address high traffic growth and increasing demand for high-bandwidth connectivity. It will also support massive numbers of connected devices and meet the real-time, high-reliability communication needs of mission-critical applications. 5G will provide wireless connectivity for a wide range of new applications and use cases, including wearables, smart homes, traffic safety/control, critical infrastructure, industry processes and very-high-speed media delivery. As a result, it will also accelerate the development of the Internet of Things. ITU Members including key industry players, industry forums, national and regional standards development organizations, regulators, network operators, equipment manufacturers as well as academia and research institutions together with Member States, gathered as the working group responsible for IMT systems, and completed a cycle of studies on the key performance requirements of 5G technologies for IMT-2020.
The Aim of 5G
The overall aim of 5G is to provide ubiquitous connectivity for any kind of device and any kind of application that may benefit from being connected. 5G networks will not be based on one specific radio-access technology. Rather, 5G is a portfolio of access and connectivity solutions addressing the demands and requirements of mobile communication beyond 2020.
The specification of 5G will include the development of a new flexible air interface, NX, which will be directed to extreme mobile broadband deployments. NX will also target high-bandwidth and high-traffic-usage scenarios, as well as new scenarios that involve mission-critical and realtime communications with extreme requirements in terms of latency and reliability.
In parallel, the development of Narrow-Band IoT (NB-IoT) in 3GPP is expected to support massive machine connectivity in wide area applications. NB-IoT will most likely be deployed in bands below 2GHz and will provide high capacity and deep coverage for enormous numbers of connected devices.
Ensuring interoperability with past generations of mobile communications has been a key principle of the ICT industry since the development of GSM and later wireless technologies within the 3GPP family of standards.
4G to 5G Evolution
In a similar manner, LTE will evolve in a way that recognizes its role in providing excellent coverage for mobile users, and 5G networks will incorporate LTE access (based on Orthogonal Frequency Division Multiplexing (OFDM)) along with new air interfaces in a transparent manner toward both the service layer and users. Around 2020, much of the available wireless coverage will continue to be provided by LTE, and it is important that operators with deployed 4G networks have the opportunity to transition some – or all – of their spectrum to newer wireless access technologies.
For operators with limited spectrum resources, the possibility of introducing 5G capabilities in an interoperable way – thereby allowing legacy devices to continue to be served on a compatible carrier – is highly beneficial and, in some cases, even vital. At the same time, the evolution of LTE to a point where it is a full member of the 5G family of air interfaces is essential, especially since initial deployment of new air interfaces may not operate in the same bands. The 5G network will enable dual-connectivity between LTE operating within bands below 6GHz and the NX air interface in bands within the range 6GHz to100GHz. NX should also allow for user-plane aggregation, i.e. joint delivery of data via LTE and NX component carriers. This paper explains the key requirements and capabilities of 5G, along with its technology components and spectrum needs.
In order to enable connectivity for a very wide range of applications with new characteristics and requirements, the capabilities of 5G wireless access must extend far beyond those of previous generations of mobile communication. These capabilities will include massive system capacity, very high data rates everywhere, very low latency, ultra-high reliability and availability, very low device cost and energy consumption, and energy-efficient networks.
MASSIVE SYSTEM CAPACITY
Traffic demands for mobile-communication systems are predicted to increase dramatically. To support this traffic in an affordable way, 5G networks must deliver data with much lower cost per bit compared with the networks of today. Furthermore, the increase in data consumption will result in an increased energy footprint from networks. 5G must therefore consume significantly lower energy per delivered bit than current cellular networks. The exponential increase in connected devices, such as the deployment of billions of wirelessly connected sensors, actuators and similar devices for massive machine connectivity, will place demands on the network to support new paradigms in device and connectivity management that do not compromise security. Each device will generate or consume very small amounts of data, to the extent that they will individually, or even jointly, have limited impact on the overall traffic volume. However, the sheer number of connected devices seriously challenges the ability of the network to provision signaling and manage connections.
VERY HIGH DATA RATES EVERYWHERE
Every generation of mobile communication has been associated with higher data rates compared with the previous generation. In the past, much of the focus has been on the peak data rate that can be supported by a wireless-access technology under ideal conditions. However, a more important capability is the data rate that can actually be provided under real-life conditions in different scenarios.
5G should support data rates exceeding 10Gbps in specific scenarios such as indoor and dense outdoor environments.
Data rates of several 100Mbps should generally be achievable in urban and suburban environments.
Data rates of at least 10Mbps should be accessible almost everywhere, including sparsely populated rural areas in both developed and developing countries.
VERY LOW LATENCY
Very low latency will be driven by the need to support new applications. Some envisioned 5G use cases, such as traffic safety and control of critical infrastructure and industry processes, may require much lower latency compared with what is possible with the mobile-communication systems of today. To support such latency-critical applications, 5G should allow for an application end-to-end latency of 1ms or less, although application-level framing requirements and codec limitations for media may lead to higher latencies in practice. Many services will distribute computational capacity and storage close to the air interface. This will create new capabilities for real-time communication and will allow ultra-high service reliability in a variety of scenarios, ranging from entertainment to industrial process control.
ULTRA-HIGH RELIABILITY AND AVAILABILITY
In addition to very low latency, 5G should also enable connectivity with ultra-high reliability and ultra-high availability. For critical services, such as control of critical infrastructure and traffic safety, connectivity with certain characteristics, such as a specific maximum latency, should not merely be ‘typically available.’ Rather, loss of connectivity and deviation from quality of service requirements must be extremely rare. For example, some industrial applications might need to guarantee successful packet delivery within 1 ms with a probability higher than 99.9999 percent.
VERY LOW DEVICE COST AND ENERGY CONSUMPTION
Low-cost, low-energy mobile devices have been a key market requirement since the early days of mobile communication. However, to enable the vision of billions of wirelessly connected sensors, actuators and similar devices, a further step has to be taken in terms of device cost and energy consumption. It should be possible for 5G devices to be available at very low cost and with a battery life of several years without recharging.
While device energy consumption has always been prioritized, energy efficiency on the network side has recently emerged as an additional KPI, for three main reasons:
Energy efficiency is an important component in reducing operational cost, as well as a driver for better dimensioned nodes, leading to lower total cost of ownership.
Energy efficiency enables off-grid network deployments that rely on medium-sized solar panels as power supplies, thereby enabling wireless connectivity to reach even the most remote areas.
Energy efficiency is essential to realizing operators’ ambition of providing wireless access in a sustainable and more resource-efficient way.
The importance of these factors will increase further in the 5G era, and energy efficiency will therefore be an important requirement in the design of 5G wireless access.
For More Information
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Two questions: “Do I need Gigabit LTE?” and “Will mobile networks support these new speeds?” The short answer to both is a resounding “Yes.”
Do I need Gigabit LTE?
There’s a common misconception that we need to address right away. Some people think that extreme speeds are only realized in ideal lab conditions, so they’re not relevant in the real world. Their argument is that current LTE devices and networks already support peak speeds of 300 Mbps or 600 Mbps, but actual speeds are lower. It follows, then, that there’s already “enough headroom” in the networks and thus the faster speeds are irrelevant.
Nothing could be further from the truth.
Here’s the thing. Gigabit LTE — and every other LTE innovation we’ve helped commercialize in the past few years — directly contributes to improving the real-world speeds that you’ll experience.
Gigabit LTE provides more consistent Internet speeds as compared to previous generations of LTE. In an extensive network simulation conducted by Qualcomm Technologies, we placed LTE devices of varying capabilities from Cat 4 to Cat 16 (the Gigabit LTE category) in the same network. The average throughput achieved by a GB LTE device was comfortably above 100 Mbps. Depending on traffic type, the average throughput could be much higher. That’s compared to around 65 Mbps for Cat 6 devices, the current baseline for many LTE devices and networks.
And these simulation results bear out in the real world. At the Sydney event, one analyst who tried the first Gigabit LTE device, reached 360 Mbps in a speed test. A real device on a live network in the middle of a very crowded tourist area — that’s the power of Gigabit LTE.
The constituent technologies that make Gigabit LTE possible — carrier aggregation, 4×4 MIMO, and 256-QAM — are engineered to allow the network to allocate many more network resources to your device simultaneously than you would get with an older LTE device. Or, alternatively, allocate fewer resources to you without diminishing the speed.
There’s an additional benefit as well. A Gigabit LTE device has four antennas in order to support 4×4 MIMO, giving it a hidden edge. In good signal conditions, you can get four streams of data that increase your speed, as compared to two streams with conventional LTE. In weak signal conditions, the additional antennas act like additional “ears” that are designed to help your Gigabit LTE device lock on to the signal from the tower, which can yield up to 70 percent faster speeds. Think about how slow LTE speeds can get in weak signal conditions. Wouldn’t this speed bump help quite a bit? A real-world study of this on T-Mobile’s network – using the Samsung Galaxy S7, which is capable of 4×4 MIMO – confirms this.
Additionally, with Gigabit LTE devices, you should be able to finish your downloads much faster, with fewer resources from the network. This can improve the capacity of the network and allow it to serve other users sooner. Not only do you enjoy faster speeds, but other people connected to the same cell tower get faster speeds as well, even if they don’t have a Gigabit LTE device.
So yes, you do need Gigabit LTE. It can improve your average, real-world speeds, give you better speeds in weak signal conditions, and allow other people to enjoy faster speeds too.
Will mobile networks support these new speeds?
Here, again, the answer is “Yes.”
Fifteen mobile operators in 11 countries intend to launch or trial Gigabit LTE in 2017. They include: T-Mobile, Sprint, and AT&T in the U.S.; EE, T-Mobile Germany, Vodafone, and Telefonica in Europe; and NTT DoCoMo, SoftBank, KDDI, and SingTel in Asia.
And, of course, Telstra’s Gigabit LTE network is already live. We expect many more to come online over the next few years. It’s important to remember that many people are hanging on to their devices for longer. So even if on day one your network doesn’t support GB LTE, there’s a good chance it may over the lifetime of your phone.
2017 will be the year of Gigabit LTE. And with the right device, power users can enjoy next-gen experiences sooner than we expected.
CableFree 10Gbps MMW links have been installed for Safe City applications
Using the latest 10Gbps Millimeter Wave wireless technology, the links connect Safe City customer sites with a full 10Gbps (10Gig-E) full duplex capacity, with no compression or slow-down.
CableFree has pioneered high speed 10 Gigabit Millimeter Wave (MMW) technology to connect sites where fibre optics are unavailable, too slow to provision, too expensive or at risk of damage. In busy cities, fibre optics is usually installed in ducts underground which are prone to disruption when digging or building works take place.
This client had already installed fibre optics for major CCTV backbones around the city. However, 3rd party building works disrupted the ducts severing the fibres, causing major outage in the network and loss of CCTV coverage – putting citizens at risk.
CableFree 10Gbps Millimeter Wave links offer an ideal alternative to fragile fibre optics: the radio units are installed on sites owned by the customer, bringing the full network under user control and management. The units are typically mounted on building rooftops well away from street-level disruption, which are easy to access, secure and defend. MMW wireless links can be installed in hours, not weeks, and at a tiny fraction of the cost of trenches and ducts for fibre optics.
Reliable operating distances of 5-8km depending on climatic region are ideal for city-scale networks. A full range of planning tools allows users to predict performance prior to purchase or installation. The E-band (70-80GHz) frequencies are available in many countries with “light license” and are uncongested, with narrow “pencil beams” allowing dense re-use of the spectrum with no interference between links or users. The narrow beams make such link are inherently secure, with proprietary signals and encoding.
For long links, the Adaptive Coding and Modulation feature enables the MMW link to dynamically adjust modulation in high rainfall conditions to ensure link uptime, capacity and range are maximised. For shorter links and long links in low rainfall regions, the links retain 10Gbps at all times.
10Gbps MMW links are a movable asset: if the network requirements change, or different sites require connecting, the links can be moved to the new sites immediately, retaining all the investment in infrastructure. For Special Events and Disaster Recovery, temporary links can be deployed using generator or alternative “off grid” (Solar + Battery) power if no AC power is available on sites. The units can be mounted on tripods or stationary vehicles as required for rapid deployment.
For mobile operators, advanced features such as IEEE 1588v2, SyncE and management are included which make CableFree MMW ideal for RAN backhaul for 4G & 5G networks. CableFree 10Gbps MMW is upgradable to 20Gbps and 40Gbps with “stacking” giving the very highest throughput in the wireless industry, comparable to fibre optic backbone networks.
For more information please visit the CableFree website or contact our expert team:
Preliminary details and information about the wireless technology being developed for 5th generation or 5G mobile wireless or cellular telecommunications systems
With the 4G telecommunications systems now starting to be deployed, eyes are looking towards the development of 5th generation or 5G technology and services.
Although the deployment of any wireless or cellular system takes many years, development of the 5G technology systems is being investigated. The new 5G technologies will need to be chosen developed and perfected to enable timely and reliable deployment.
The new 5th generation, 5G technology for cellular systems will probably start to come to fruition around 2020 with deployment following on afterwards.
5G mobile systems status
The current status of the 5G technology for cellular systems is very much in the early development stages. Very many companies are looking into the technologies that could be used to become part of the system. In addition to this a number of universities have set up 5G research units focussed on developing the technologies for 5G
In addition to this the standards bodies, particularly 3GPP are aware of the development but are not actively planning the 5G systems yet.
Many of the technologies to be used for 5G will start to appear in the systems used for 4G and then as the new 5G cellular system starts to formulate in a more concrete manner, they will be incorporated into the new 5G cellular system.
The major issue with 5G technology is that there is such an enormously wide variation in the requirements: superfast downloads to small data requirements for IoT than any one system will not be able to meet these needs. Accordingly a layer approach is likely to be adopted. As one commentator stated: 5G is not just a mobile technology. It is ubiquitous access to high & low data rate services.
5G cellular systems overview
As the different generations of cellular telecommunications have evolved, each one has brought its own improvements. The same will be true of 5G technology.
First generation, 1G: These phones were analogue and were the first mobile or cellular phones to be used. Although revolutionary in their time they offered very low levels of spectrum efficiency and security.
Second generation, 2G: These were based around digital technology and offered much better spectrum efficiency, security and new features such as text messages and low data rate communications.
Third generation, 3G: The aim of this technology was to provide high speed data. The original technology was enhanced to allow data up to 14 Mbps and more.
Fourth generation, 4G: This was an all-IP based technology capable of providing data rates up to 1 Gbps.
Any new 5th generation, 5G cellular technology needs to provide significant gains over previous systems to provide an adequate business case for mobile operators to invest in any new system.
Facilities that might be seen with 5G technology include far better levels of connectivity and coverage. The term World Wide Wireless Web, or WWWW is being coined for this.
For 5G technology to be able to achieve this, new methods of connecting will be required as one of the main drawbacks with previous generations is lack of coverage, dropped calls and low performance at cell edges. 5G technology will need to address this.
Although the standards bodies have not yet defined the parameters needed to meet a 5G performance level yet, other organisations have set their own aims, that may eventually influence the final specifications.
Typical parameters for a 5G standard may include:
SUGGESTED 5G WIRELESS PERFORMANCE
10 000 times capacity of current network
Peak data rate
Cell edge data rate
< 1 ms
These are some of the ideas being put forwards for a 5G standard, but they are not accepted by any official bodies yet.
There are several key areas that are being investigated by research organisations. These include:
Millimeter-Wave technologies: Using frequencies much higher in the frequency spectrum opens up more spectrum and also provides the possibility of having much wide channel bandwidth – possibly 1 – 2 GHz. However this poses new challenges for handset development where maximum frequencies of around 2 GHz and bandwidths of 10 – 20 MHz are currently in use. For 5G, frequencies of above 50GHz are being considered and this will present some real challenges in terms of the circuit design, the technology, and also the way the system is used as these frequencies do not travel as far and are absorbed almost completely by obstacles.
Future PHY / MAC: The new physical layer and MAC presents many new interesting possibilities in a number of areas:
Waveforms: One key area of interest is that of the new waveforms that may be seen. OFDM has been used very successfully in 4G LTE as well as a number of other high data rate systems, but it does have some limitations in some circumstances. Formats being proposed include: GFDM, Generalised Frequency Division Multiplexing, as well as FBMC, Filter Bank Multi-Carrier, UFMC, Universal Filtered MultiCarrier. Each has its own advantages and limitations and it is possible that adaptive schemes may be employed, utilising different waveforms adaptively for the 5G mobile systems as the requirements dictate. This provides considerably more flexibility for 5G mobile communications. Read more about 5G waveforms
Multiple Access Schemes: Again a variety of new access schemes are being investigated for 5G technology. Techniques including OFDMA, SCMA, NOMA, PDMA, MUSA and IDMA have all been mentioned. Read more about 5G multiple access schemes
Modulation: Whilst PSK and QAM have provided excellent performance in terms of spectral efficiency, resilience and capacity, the major drawback is that of a high peak to average power ratio. Modulation schemes like APSK could provide advantages in some circumstances. Read more about 5G modulation schemes
Duplex methods: There are several candidate forms of duplex that are being considered. Currently systems use either frequency division duplex, FDD or time division duplex, TDD. New possibilities are opening up for 5G including flexible duplex, where the time or frequencies allocated are variable according toth e load in either direction or a new scheme called division free duplex or single channel full duplex. This scheme for 5G would enable simultaneous transmission and reception on the same channel. Read more about 5G full duplex
Massive MIMO: Although MIMO is being used in many applications from LTE to Wi-Fi, etc, the numbers of antennas is fairly limited -. Using microwave frequencies opens up the possibility of using many tens of antennas on a single equipment becomes a real possibility because of the antenna sizes and spacings in terms of a wavelength.
Dense networks Reducing the size of cells provides a much more overall effective use of the available spectrum. Techniques to ensure that small cells in the macro-network and deployed as femtocells can operate satisfactorily are required.
Other 5G concepts
There are many new concepts that are being investigated and developed for the new 5th generation mobile system. Some of these include:
Pervasive networks : This technology being considered for 5G cellular systems is where a user can concurrently be connected to several wireless access technologies and seamlessly move between them.
Group cooperative relay: This is a technique that is being considered to make the high data rates available over a wider area of the cell. Currently data rates fall towards the cell edge where interference levels are higher and signal levels lower.
Cognitive radio technology: If cognitive radio technology was used for 5th generation, 5G cellular systems, then it would enable the user equipment / handset to look at the radio landscape in which it is located and choose the optimum radio access network, modulation scheme and other parameters to configure itself to gain the best connection and optimum performance.
Wireless mesh networking and dynamic ad-hoc networking: With the variety of different access schemes it will be possible to link to others nearby to provide ad-hoc wireless networks for much speedier data flows.
Smart antennas: Another major element of any 5G cellular system will be that of smart antennas. Using these it will be possible to alter the beam direction to enable more direct communications and limit interference and increase overall cell capacity.
There are many new techniques and technologies that will be used in the new 5G cellular or mobile telecommunications system. These new 5G technologies are still being developed and the overall standards have not yet be defined. However as the required technologies develop, they will be incorporated into the new system which will be defined by the standards bodies over the coming years.
FSO (Free Space Optics, Laser, Optical Wireless) Guide
Free Space Optics (FSO) communications, also called Optical Wireless (OW) or Infrared Laser, refers to the transmission of modulated visible or infrared (IR) beams through the atmosphere to obtain optical communications. Like fibre, Free Space Optics (FSO) uses lasers to transmit data, but instead of enclosing the data stream in a glass fibre, it is transmitted through the air. Free Space Optics (FSO) works on the same basic principle as Infrared television remote controls, wireless keyboards or IRDA ports on laptops or cellular phones.
History of Free Space Optics (FSO)
The engineering maturity of Free Space Optics (FSO) is often underestimated, due to a misunderstanding of how long Free Space Optics (FSO) systems have been under development. Historically, Free Space Optics (FSO) or optical wireless communications was first demonstrated by Alexander Graham Bell in the late nineteenth century (prior to his demonstration of the telephone!). Bell’s Free Space Optics (FSO) experiment converted voice sounds into telephone signals and transmitted them between receivers through free air space along a beam of light for a distance of some 600 feet. Calling his experimental device the “photophone,” Bell considered this optical technology – and not the telephone – his pre-eminent invention because it did not require wires for transmission.
Although Bell’s photophone never became a commercial reality, it demonstrated the basic principle of optical communications. Essentially all of the engineering of today’s Free Space Optics (FSO) or free space optical communications systems was done over the past 40 years or so, mostly for defense applications. By addressing the principal engineering challenges of Free Space Optics (FSO), this aerospace/defence activity established a strong foundation upon which today’s commercial laser-based Free Space Optics (FSO) systems are based.
How Free Space Optics (FSO) Works
Free Space Optics (FSO) transmits invisible, eye-safe light beams from one “telescope” to another using low power infrared lasers in the terahertz spectrum. The beams of light in Free Space Optics (FSO) systems are transmitted by laser light focused on highly sensitive photon detector receivers. These receivers are telescopic lenses able to collect the photon stream and transmit digital data containing a mix of Internet messages, video images, radio signals or computer files. Commercially available systems offer capacities in the range of 100 Mbps to 2.5 Gbps, and demonstration systems report data rates as high as 160 Gbps.
Free Space Optics (FSO) systems can function over distances of several kilometres. As long as there is a clear line of sight between the source and the destination, and enough transmitter power, Free Space Optics (FSO) communication is possible.
FSO: Wireless Links at the Speed of Light
Unlike radio and microwave systems, Free Space Optics (FSO) is an optical technology and no spectrum licensing or frequency coordination with other users is required, interference from or to other systems or equipment is not a concern, and the point-to-point laser signal is extremely difficult to intercept, and therefore secure. Data rates comparable to optical fibre transmission can be carried by Free Space Optics (FSO) systems with very low error rates, while the extremely narrow laser beam widths ensure that there is almost no practical limit to the number of separate Free Space Optics (FSO) links that can be installed in a given location.
How Free Space Optics (FSO) benefits you
FSO is free from licensing and regulation which translates into ease, speed and low cost of deployment. Since Free Space Optics (FSO) transceivers can transmit and receive through windows, it is possible to mount Free Space Optics (FSO) systems inside buildings, reducing the need to compete for roof space, simplifying wiring and cabling, and permitting Free Space Optics (FSO) equipment to operate in a very favourable environment. The only essential requirement for Free Space Optics (FSO) or optical wireless transmission is line of sight between the two ends of the link.
For Metro Area Network (MAN) providers the last mile or even feet can be the most daunting. Free Space Optics (FSO) networks can close this gap and allow new customers access to high-speed MAN’s. Providers also can take advantage of the reduced risk of installing an Free Space Optics (FSO) network which can later be redeployed.
The Market. Why FSO? Breaking the Bandwidth Bottleneck
Why FSO? The global telecommunications network has seen massive expansion over the last few years. First came the tremendous growth of the optical fiber long-haul, wide-area network (WAN), followed by a more recent emphasis on metropolitan area networks (MANs). Meanwhile, local area networks (LANs) and gigabit Ethernet ports are being deployed with a comparable growth rate. In order for this tremendous network capacity to be exploited, and for the users to be able to utilize the broad array of new services becoming available, network designers must provide a flexible and cost-effective means for the users to access the telecommunications network. Presently, however, most local loop network connections are limited to 1.5 Mbps (a T1 line). As a consequence, there is a strong need for a high-bandwidth bridge (the “last mile” or “first mile”) between the LANs and the MANs or WANs.
A recent New York Times article reported that more than 100 million miles of optical fibre was laid around the world in the last two years, as carriers reacted to the Internet phenomenon and end users’ insatiable demand for bandwidth. The sheer scale of connecting whole communities, cities and regions to that fiber optic cable or “backbone” is something not many players understood well. Despite the huge investment in trenching and optical cable, most of the fibre remains unlit, 80 to 90% of office, commercial and industrial buildings are not connected to fibre, and transport prices are dropping dramatically.
Free Space Optics (FSO) systems represent one of the most promising approaches for addressing the emerging broadband access market and its “last mile” bottleneck. Free Space Optics (FSO) systems offer many features, principal among them being low start-up and operational costs, rapid deployment, and high fiber-like bandwidths due to the optical nature of the technology.
Broadband Bandwidth Alternatives
Access technologies in general use today include telco-provisioned copper wire, wireless Internet access, broadband RF/microwave, coaxial cable and direct optical fiber connections (fiber to the building; fiber to the home). Telco/PTT telephone networks are still trapped in the old Time Division Multiplex (TDM) based network infrastructure that rations bandwidth to the customer in increments of 1.5 Mbps (T-1) or 2.024 Mbps (E-1). DSL penetration rates have been throttled by slow deployment and the pricing strategies of the PTTs. Cable modem access has had more success in residential markets, but suffers from security and capacity problems, and is generally conditional on the user subscribing to a package of cable TV channels. Wireless Internet access is still slow, and the tiny screen renders it of little appeal for web browsing.
Broadband RF/microwave systems have severe limitations and are losing favor. The radio spectrum is a scarce and expensive licensed commodity, sold or leased to the highest bidder, or on a first-come first-served basis, and all too often, simply unavailable due to congestion. As building owners have realized the value of their roof space, the price of roof rights has risen sharply. Furthermore, radio equipment is not inexpensive, the maximum data rates achievable with RF systems are low compared to optical fiber, and communications channels are insecure and subject to interference from and to other systems (a major constraint on the use of radio systems).
Free Space Optics (FSO) Advantages
Free space optical (FSO) systems offers a flexible networking solution that delivers on the promise of broadband. Only free space optics or Free Space Optics (FSO) provides the essential combination of qualities required to bring the traffic to the optical fiber backbone – virtually unlimited bandwidth, low cost, ease and speed of deployment. Freedom from licensing and regulation translates into ease, speed and low cost of deployment. Since Free Space Optics (FSO) optical wireless transceivers can transmit and receive through windows, it is possible to mount Free Space Optics (FSO) systems inside buildings, reducing the need to compete for roof space, simplifying wiring and cabling, and permitting the equipment to operate in a very favorable environment. The only essential for Free Space Optics (FSO) is line of sight between the two ends of the link.
Security and Free Space Optics (FSO)
The common perception of wireless is that it offers less security than wireline connections. In fact, Free Space Optics (FSO) is far more secure than RF or other wireless-based transmission technologies for several reasons:
Free Space Optics (FSO) laser beams cannot be detected with spectrum analyzers or RF meters
Free Space Optics (FSO) laser transmissions are optical and travel along a line of sight path that cannot be intercepted easily. It requires a matching Free Space Optics (FSO) transceiver carefully aligned to complete the transmission. Interception is very difficult and extremely unlikely
The laser beams generated by Free Space Optics (FSO) systems are narrow and invisible, making them harder to find and even harder to intercept and crack
Data can be transmitted over an encrypted connection adding to the degree of security available in Free Space Optics (FSO) network transmissions.
Free Space Optics (FSO) Challenges
The advantages of free space optical wireless or Free Space Optics (FSO) do not come without some cost. When light is transmitted through optical fiber, transmission integrity is quite predictable – barring unforseen events such as backhoes or animal interference. When light is transmitted through the air, as with Free Space Optics (FSO) optical wireless systems, it must contend with a a complex and not always quantifiable subject – the atmosphere.
Attenuation, Fog and Free Space Optics (FSO)
Fog substantially attenuates visible radiation, and it has a similar affect on the near-infrared wavelengths that are employed in Free Space Optics (FSO) systems. Note that the effect of fog on Free Space Optics (FSO) optical wireless radiation is entirely analogous to the attenuation – and fades – suffered by RF wireless systems due to rainfall. Similar to the case of rain attenuation with RF wireless, fog attenuation is not a “show-stopper” for Free Space Optics (FSO) optical wireless, because the optical link can be engineered such that, for a large fraction of the time, an acceptable power will be received even in the presence of heavy fog. Free Space Optics (FSO) optical wireless-based communication systems can be enhanced to yield even greater availabilities.
Free Space Optics (FSO) and Physical Obstructions
Free Space Optics (FSO) products which have widely spaced redundant transmitters and large receive optics will all but eliminate interference concerns from objects such as birds. On a typical day, an object covering 98% of the receive aperture and all but 1 transmitter; will not cause an Free Space Optics (FSO) link to drop out. Thus birds are unlikely to have any impact on Free Space Optics (FSO) transmission.
Free Space Optics (FSO) Pointing Stability – Building Sway, Tower Movement
Only wide-beamwidth fixed pointed Free Space Optics (FSO) systems are capable of handling the vast majority of movement found in deployments on buildings. Narrow beam systems are unreliable, requiring manual re-alignment on a regular basis, due to building movement. ‘Wide beam’ means more than 5milliradians. Narrow systems (1-2mRad) are not reliable without a tracking system
The combination of effective beam divergence and a well matched receive Field-of-View (FOV) provide for an extremely robust fixed pointed Free Space Optics (FSO) system suitable for most deployments. Fixed-pointed Free Space Optics (FSO) systems are generally preferred over actively-tracked Free Space Optics (FSO) systems due to their lower cost.
Free Space Optics (FSO) and Scintillation
Performance of many Free Space Optics (FSO) optical wireless systems is adversely affected by scintillation on bright sunny days; the effects of which are typically reflected in BER statistics. Some optical wireless products have a unique combination of large aperture receiver, widely spaced transmitters, finely tuned receive filtering, and automatic gain control characteristics. In addition, certain optical wireless systems also apply a clock recovery phase-lock-loop time constant that all but eliminate the affects of atmospheric scintillation and jitter transference.
Solar Interference and Free Space Optics (FSO)
Solar interference in Free Space Optics (FSO) free space optical systems can be combated in two ways. Optical narrowband filter proceeding the receive detector used to filter all but the wavelength actually used for intersystem communications. To handle off-axis solar energy, sophisticated spatial filters have been implemented in CableFree systems, allowing them to operate unaffected by solar interference that is more than 1 degree off-axis.
Free Space Optics (FSO) Reliability
Employing an adaptive laser power (Automatic Transmit Power Control or ATPC) scheme to dynamically adjust the laser power in response to weather conditions will improve the reliability of Free Space Optics (FSO) optical wireless systems. In clear weather the transmit power is greatly reduced, enhancing the laser lifetime by operating the laser at very low-stress conditions. In severe weather, the laser power is increased as needed to maintain the optical link – then decreased again as the weather clears. A TEC controller that maintains the temperature of the laser transmitter diodes in the optimum region will maximize reliability and lifetime, consistent with power output allowing the FSO optical wireless system to operate more efficiently and reliably at higher power levels.
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What is OFDM? (Orthogonal Frequency Division Multiplexing)
OFDM: Orthogonal Frequency Division Multiplexing, is a form of signal modulation that divides a high data rate modulating stream placing them onto many slowly modulated narrowband close-spaced subcarriers, and in this way is less sensitive to frequency selective fading.
Orthogonal Frequency Division Multiplexing or OFDM is a modulation format that is being used for many of the latest wireless and telecommunications standards.
OFDM has been adopted in the Wi-Fi arena where the standards like 802.11a, 802.11n, 802.11ac and more. It has also been chosen for the cellular telecommunications standard LTE / LTE-A, and in addition to this it has been adopted by other standards such as WiMAX and many more.
Orthogonal frequency division multiplexing has also been adopted for a number of broadcast standards from DAB Digital Radio to the Digital Video Broadcast standards, DVB. It has also been adopted for other broadcast systems as well including Digital Radio Mondiale used for the long medium and short wave bands.
Although OFDM, orthogonal frequency division multiplexing is more complicated than earlier forms of signal format, it provides some distinct advantages in terms of data transmission, especially where high data rates are needed along with relatively wide bandwidths.
What is OFDM? – The concept
OFDM is a form of multicarrier modulation. An OFDM signal consists of a number of closely spaced modulated carriers. When modulation of any form – voice, data, etc. is applied to a carrier, then sidebands spread out either side. It is necessary for a receiver to be able to receive the whole signal to be able to successfully demodulate the data. As a result when signals are transmitted close to one another they must be spaced so that the receiver can separate them using a filter and there must be a guard band between them. This is not the case with OFDM. Although the sidebands from each carrier overlap, they can still be received without the interference that might be expected because they are orthogonal to each another. This is achieved by having the carrier spacing equal to the reciprocal of the symbol period.
Traditional view of receiving signals carrying modulation
To see how OFDM works, it is necessary to look at the receiver. This acts as a bank of demodulators, translating each carrier down to DC. The resulting signal is integrated over the symbol period to regenerate the data from that carrier. The same demodulator also demodulates the other carriers. As the carrier spacing equal to the reciprocal of the symbol period means that they will have a whole number of cycles in the symbol period and their contribution will sum to zero – in other words there is no interference contribution.
One requirement of the OFDM transmitting and receiving systems is that they must be linear. Any non-linearity will cause interference between the carriers as a result of inter-modulation distortion. This will introduce unwanted signals that would cause interference and impair the orthogonality of the transmission.
In terms of the equipment to be used the high peak to average ratio of multi-carrier systems such as OFDM requires the RF final amplifier on the output of the transmitter to be able to handle the peaks whilst the average power is much lower and this leads to inefficiency. In some systems the peaks are limited. Although this introduces distortion that results in a higher level of data errors, the system can rely on the error correction to remove them.
Data on OFDM
The data to be transmitted on an OFDM signal is spread across the carriers of the signal, each carrier taking part of the payload. This reduces the data rate taken by each carrier. The lower data rate has the advantage that interference from reflections is much less critical. This is achieved by adding a guard band time or guard interval into the system. This ensures that the data is only sampled when the signal is stable and no new delayed signals arrive that would alter the timing and phase of the signal.
The distribution of the data across a large number of carriers in the OFDM signal has some further advantages. Nulls caused by multi-path effects or interference on a given frequency only affect a small number of the carriers, the remaining ones being received correctly. By using error-coding techniques, which does mean adding further data to the transmitted signal, it enables many or all of the corrupted data to be reconstructed within the receiver. This can be done because the error correction code is transmitted in a different part of the signal.
OFDM advantages & disadvantages
OFDM has been used in many high data rate wireless systems because of the many advantages it provides.
Immunity to selective fading: One of the main advantages of OFDM is that is more resistant to frequency selective fading than single carrier systems because it divides the overall channel into multiple narrowband signals that are affected individually as flat fading sub-channels.
Resilience to interference: Interference appearing on a channel may be bandwidth limited and in this way will not affect all the sub-channels. This means that not all the data is lost.
Spectrum efficiency: Using close-spaced overlapping sub-carriers, a significant OFDM advantage is that it makes efficient use of the available spectrum.
Resilient to ISI: Another advantage of OFDM is that it is very resilient to inter-symbol and inter-frame interference. This results from the low data rate on each of the sub-channels.
Resilient to narrow-band effects: Using adequate channel coding and interleaving it is possible to recover symbols lost due to the frequency selectivity of the channel and narrow band interference. Not all the data is lost.
Simpler channel equalisation: One of the issues with CDMA systems was the complexity of the channel equalisation which had to be applied across the whole channel. An advantage of OFDM is that using multiple sub-channels, the channel equalization becomes much simpler.
Whilst OFDM has been widely used, there are still a few disadvantages to its use which need to be addressed when considering its use.
High peak to average power ratio: An OFDM signal has a noise like amplitude variation and has a relatively high large dynamic range, or peak to average power ratio. This impacts the RF amplifier efficiency as the amplifiers need to be linear and accommodate the large amplitude variations and these factors mean the amplifier cannot operate with a high efficiency level.
Sensitive to carrier offset and drift: Another disadvantage of OFDM is that is sensitive to carrier frequency offset and drift. Single carrier systems are less sensitive.
There are several other variants of OFDM for which the initials are seen in the technical literature. These follow the basic format for OFDM, but have additional attributes or variations:
COFDM: Coded Orthogonal frequency division multiplexing. A form of OFDM where error correction coding is incorporated into the signal.
Flash OFDM: This is a variant of OFDM that was developed by Flarion and it is a fast hopped form of OFDM. It uses multiple tones and fast hopping to spread signals over a given spectrum band.
OFDMA: Orthogonal frequency division multiple access. A scheme used to provide a multiple access capability for applications such as cellular telecommunications when using OFDM technologies.
VOFDM: Vector OFDM. This form of OFDM uses the concept of MIMO technology. It is being developed by CISCO Systems. MIMO stands for Multiple Input Multiple output and it uses multiple antennas to transmit and receive the signals so that multi-path effects can be utilised to enhance the signal reception and improve the transmission speeds that can be supported.
WOFDM: Wideband OFDM. The concept of this form of OFDM is that it uses a degree of spacing between the channels that is large enough that any frequency errors between transmitter and receiver do not affect the performance. It is particularly applicable to Wi-Fi systems.
Each of these forms of OFDM utilise the same basic concept of using close spaced orthogonal carriers each carrying low data rate signals. During the demodulation phase the data is then combined to provide the complete signal.
OFDM, orthogonal frequency division multiplexing has gained a significant presence in the wireless market place. The combination of high data capacity, high spectral efficiency, and its resilience to interference as a result of multi-path effects means that it is ideal for the high data applications that have become a major factor in today’s communications scene.
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FSO is a line-of-sight wireless communication technology that uses invisible beams of light to provide high speed wireless connections that can send and receive voice, video, and data information. Today, FSO technology – pioneered and championed by CableFree’s optical wireless offerings – has enabled the development of a new category of outdoor wireless products that can transmit voice, data, and video at bandwidths up to 1.25 Gbps. Free Space Optics connectivity doesn’t require expensive fibre-optic cable and removes need for securing spectrum licenses for radio frequency (RF) solutions. FSO technology requires light. The use of light is a simple concept similar to optical transmissions using fiber-optic cables; the only difference is the medium. Light travels through air faster than it does through glass, so it is fair to classify FSO technology as optical communications at the speed of light.
Optical communications, in various forms, have been used for thousands of years. The Ancient Greeks used a coded alphabetic system of signalling with torches developed by Cleoxenus, Democleitus and Polybius. In the modern era, semaphores and wireless solar telegraphs called heliographs were developed, using coded signals to communicate with their recipients. In 1880 Alexander Graham Bell and his assistant Charles Sumner Tainter created the Photophone, at Bell’s newly established Volta Laboratory in Washington, DC. Bell considered it his most important invention. The device allowed for the transmission of sound on a beam of light. On June 3, 1880, Bell conducted the world’s first wireless telephone transmission between two buildings, some 213 meters (700 feet) apart. Its first practical use came in military communication systems many decades later, first for optical telegraphy. German colonial troops used Heliograph telegraphy transmitters during the 1904/05 Herero Genocide in German South-West Africa (today’s Namibia) as did British, French, US or Ottoman signals.
During the trench warfare of World War I when wire communications were often cut, German signals used three types of optical Morse transmitters called Blinkgerät, the intermediate type for distances of up to 4 km (2.5 miles) at daylight and of up to 8 km (5 miles) at night, using red filters for undetected communications. Optical telephone communications were tested at the end of the war, but not introduced at troop level. In addition, special blinkgeräts were used for communication with airplanes, balloons, and tanks, with varying success. A major technological step was to replace the Morse code by modulating optical waves in speech transmission. Carl Zeiss Jena developed the Lichtsprechgerät 80/80 (literal translation: optical speaking device) that the German army used in their World War II anti-aircraft defense units, or in bunkers at the Atlantic Wall.
The invention of lasers in the 1960s revolutionized free space optics. Military organizations were particularly interested and boosted their development. However the technology lost market momentum when the installation of optical fiber networks for civilian uses was at its peak.
FSO vendor CableFree has extensive experience in this area: CableFree developed some of the world’s first successful commercial FSO links, with world-first achievements including
World’s first commercial 622Mbps wireless link: 1997
World’s first commercial Gigabit Ethernet 1.25Gbps wireless link: 1999
While fibre-optic communications gained worldwide acceptance in the telecommunications industry, FSO communications is still considered relatively new. CableFree Free Space Optical technology from Wireless Excellence enables bandwidth transmission capabilities that are similar to fibre optics, using similar optical transmitters and receivers and even enabling WDM-like technologies to operate through free space.
How Free Space Optics / Laser Communications Work
The concept behind FSO technology is very simple. It’s based on connectivity between FSO-based optical wireless units, each consisting of an optical transceiver with a transmitter and a receiver to provide full-duplex (bi-directional) capability. Each optical wireless unit uses an optical source, plus a lens or telescope that transmits light through the atmosphere to another lens receiving the information. At this point, the receiving lens or telescope connects to a high-sensitivity receiver via optical fibre. This Free Space Optics technology approach has a number of advantages: Requires no RF spectrum licensing. Is easily upgradeable, and its open interfaces support equipment from a variety of vendors, which helps enterprises and service providers protect their investment in embedded telecommunications infrastructures. Requires no security software upgrades. Is immune to radio frequency interference or saturation. FSO Can be deployed behind windows, eliminating the need for costly rooftop rights.
Choosing Free Space Optics or Radio Frequency Wireless
Optical wireless, using FSO technology, is an outdoor wireless product category that provides the speed of fibre, with the flexibility of wireless. It enables optical transmission at speeds of up to 1.25 Gbps and, in the future, is capable of speeds of 10 Gbps using WDM. This is not possible with any fixed wireless or RF technology. Optical wireless also eliminates the need to buy expensive spectrum (it requires no FCC or municipal license approvals worldwide), which further distinguishes it from fixed wireless technologies. Moreover, FSO technology’s narrow beam transmission is typically two meters versus 20 meters and more for traditional, even newer radio-based technologies such as millimeter-wave radio. Optical wireless products’ similarities with conventional wired optical solutions enable the seamless integration of access networks with optical core networks and helps to realize the vision of an all-optical network.
Free Space Technology in Communication Networks
Free-space optics technology (FSO) has several applications in communications networks, where a connectivity gap exists between two or more points. FSO technology delivers cost-effective optical wireless connectivity and a faster return on investment (ROI) for Enterprises and Mobile Carriers. With the ever-increasing demand for greater bandwidth by Enterprise and Mobile Carrier subscribers comes a critical need for FSO-based products for a balance of throughput, distance and availability. During the last few years, customer deployments of FSO-based products have grown. Here are some of the primary network uses:
Because of the scalability and flexibility of FSO technology, optical wireless products can be deployed in many enterprise applications including building-to-building connectivity, disaster recovery, network redundancy and temporary connectivity for applications such as data, voice and data, video services, medical imaging, CAD and engineering services, and fixed-line carrier bypass.
Mobile Carrier Backhaul
Free Space Optics is valuable tool in Mobile Carrier Backhaul: FSO technology and optical wireless products can be deployed to provide traditional PDH 16xE1/T1, STM-1 and STM-4, and Modern IP Gigabit Ethernet backhaul connectivity and Greenfield mobile networks.
Front-Haul: Mobile Carrier Base Station “Hoteling”
FSO-based products can be used to expand Mobile Carrier Network footprints through base station “hoteling.” using CPRI interface. Free Space Optics with CPRI enables “front haul” networks where the remote radio heads can be separated by up to 2km from the Base station with a 1.22Gbps CPRI “native” link between them.
Low Latency Networks
Free Space Optics is an inherently Low Latency Technology, with effectively no delay between packets being transmitted and received at the other end, except the Line of Sight propagation delay. The Speed of Light through the air is approximately 40% higher than through fibre optics, giving customers an immediate 40% reduction in latency compared to fibre optics. In addition, fibre optic installations are almost never in a straight line, with realities of building layout, street ducts and requirement to use existing telecom infrastructure, the fibre run can be 100% longer than the direct Line of Sight path between two end points. Hence FSO is popular in Low Latency Applications such as High Frequency Trading and other uses.
Hybrid Resilient choices such as FSO+MMW and MMW+Radio
Our expert team has over 18 years experience in planning and deploying Gigabit Wireless Networks in over 65 countries, including indoor and outdoor wireless networks. Our team will be delighted to assist with all aspects of design, planning and deployment.
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Building a modern Gigabit Wireless Network will require choosing the appropriate technology for the precise network requirements. With wireless, there is no “magic technology” or “one size fits all” approach – a successful network deployment will consider which technologies are best suited
Choosing the correct technology for a Gigabit Wireless Network is essential to ensure you have the very best throughput, capacity and network uptime.
Ask our team of experts who will be delighted to assist in designing an choosing exactly the right products and solutions to meet your needs