TVWS - What you need to know to get started
Overview
TVWS is a license exempt technology that utilizes the frequency spectrum from roughly 400-700 MHz (low frequencies).
With the FCC ruling on the definition of high-speed broadband, it is clear to Service Providers that the 900MHz ISM band, the “go to” band for NLOS for the last decade, is now becoming extremely challenging. Beyond the technology available today, this band has only 26MHz of total spectrum that is shared between several wireless services commonly found in the residential market. This means it is not a viable solution heading into the future.
The TV White Space (TVWS) band is very effective in rural markets. In fact, the more rural the market is, the better this band performs. This is because of the nature of the band and the fact that it is shared with analog TV station services.
The TVWS band, like all bands, has its specific characteristics and introduces two significant new factors that Service Providers did not have to worry about before:
1. Interference from transmitters that are significantly more powerful than those the broadband industry is accustomed to working around.
2. A database management system to ensure all the band users behave properly.
The TV Broadcast industry runs extremely powerful transmitters at heights that can impact broadband at very long distances. As a Service Provider, you are used to contending with peers that use similar transmit power to you, so interference is present; but in the TVWS band, noise from the TV industry can actually be destructive to all available channels. This means that testing in your service area is key to understanding where and how the band can be used for your services. The good news about analog TV stations is that they are not new and the legacy broadcasters are slowly leaving the market. This means that the more rural your market is, the better the band usability will be.
The database that provides channel availability, and to which all systems need to connect, is a new element in the Service Provider business model. The TVWS band is the first band to be impacted by this database access situation, but will not be the last one. Shared spectrum is a new reality that we all must understand and learn to work with. The new CBRS band will also work with database access. There is a finite amount of spectrum accessible to all wireless users and sharing will become the standard in the future. The positive side to the database system is that, over time, it will provide a very powerful tool for predicting noise level in service areas.
Redline has been active in TVWS for years. With more radios deployed in the U.S. than any other country, we are well aware of the benefits and challenges of the band. From our engineering group to field experts, we have developed best practices and methodologies to address the usage and usability of this band in a way that will minimize our customers’ investment and ensure commercially viable deployments.
Redline had its very first field trial with this band five years ago. Since then we have done countless field trials and pilots, and have been involved in some of the largest deployments in the U.S.
The Database
Nominet is approved by FCC to operate a TV White Space Database in the USA. This database supports unlicensed radio devices to use unoccupied spectrum in the broadcast television and 600MHz bands, subject to rigorous coexistence calculations to protect certain entities using spectrum in these bands. Data describing some entities is acquired from FCC's databases. Other entities entitled to protection may register themselves via this web portal to be included in the coexistence process. More here https://usa.wavedb.com/
Channel Search
Discover channel availability at your entered location.
https://usa.wavedb.com/channelsearch/tvws
This is the column you will use Channel 14 and higher up to channel 35 but no higher:
Training
Visit the Redline training page at http://rdlcom.com/products/training-and-certification/ and watch the video on TVWS and radio configuration.
FAQ About TVWS
Note: A 10MHz channel in the TVWS band will both deliver in excess of 50Mbps for the same modulation. The TVWS radio will do it over longer distance and through more obstruction. Each channel is 6 MHz.
What are the rules around using the TVWS band?
• First off, Service Providers should make sure to review the rules thoroughly, as for any other band, to ensure their TVWS implementation abides by the FCC provision and amendment of Part 15 (FCC Document FCC-15-99A1.PDF). This document can be found on the FCC Website at the following address: https://www.fcc.gov/document/fcc- adopts-rules-unlicensed-services-tv-and-600-mhz-bands.
Really? Can you make it simple?
• You owe it to your business to stay abreast of FCC rulings as any complaints can result in you being fined.
• The ruling, as it applies to the broadband industry, is set to ensure proper power setting based on distances and elevation. The document referred to above has detailed charts on EIRP and distance.
• Generally speaking, the antenna cannot be more than 30M AGL and 250M HAAT. Most vendor are controlling the power output not to exceed the TX power limit.
• Furthermore, the database will also assist in enforcing the rules by not providing a list of available channels to radio outside of the physical installation limits.
• Again, please take the time to become familiar with the rules.
What is the license fee for the band?
• There are no licenses for the band. It is license exempt . The novelty is the database “policing” the various users of the band: TV broadcasters, broadband industry, wireless microphone, etc. These databases are certified by the FCC and every vendor gets to make a choice of with whom it wants to certify their radios. In Redline’s case, we have elected to use Nominet a database operator: https://usa.wavedb.com/
If the band is not licensed, why do I have to pay to use it?
• Nominet, like all the database operators, is a business like yours. As such they are not subsidized or otherwise funded by the government. The fee you are paying is to ensure the Nominet database is kept operational.
I want to buy your radio but will shop the database myself.
• This is not possible. The FCC certification for the radio is required to be done with the radio AND database connection. So for you to be using another database a Nominet implies that Redline would need to recertify its radio with a second database. While this is all relatively easy to say, the costs and engineering associated make this quite prohibitive.
How does this database work? What do I have to do?
• The primary function of the database is to protect the TV transmission and reception from noise pollution from the broadband industry. In this role, the database validates antenna heights and provides a list of available TV channel (White Spaces) that can be used. It will not make the channel selection nor the channel bonding decision. This
will be your responsibility and will be done on the radio Gui.
• Outside of ensuring that the network has an open port for the radios to reach the database, there is nothing else to do on your part; just point the radio to the database and click on the channel(s) you want to use.
• The radios need to have access to the internet, through your network, to reach the database. No proxy can be used.
How do I know what channel to use?
• You will do this the same way for any other license exempt product: run a spectrum sweep, identify a list
of RF positions that are acceptable then overlay this with the available TV channel from the database to pick the channel(s) best suited for your market. While it seems complicated, it is all simplified by being done from the radio Gui.
Will your radio have further reach than the other products we have worked with?
• You should not count on that. The law of physics and RF propagation work in the same way for all vendors. The RSSI and noise level will be quite similar from vendor to vendor. What you will notice thought are variations in link stability, performance and capacity.
• What this translates into is simple: Radio XYZ gave you 5Km of reach but barely any capacity. The Redline radio, the only MIMO solution on the Market, will also reach the 5Km mark but will deliver far better capacity and link margin.
• If you have already played with TVWS, share with us the TX, RSSI, antenna gain and noise level observed and we will be able to tell you what the Redline solution will deliver.
What speed will I get?
• Since NLOS performance varies for every single link, providing performance guidance can be misleading to you. We can say that in LOS, the TVWS version of our Virtual FiberTM RDL-3000 carries the same performance as our other Virtual Fiber bands in 2, 3 & 5GHz: at QAM 256 7/8 and 20MHz channel, the radio will deliver about 160Mbps aggregate. Of course, you will not likely see this in NLOS but it is quite frequent to hit QAM 64 and QAM 16 in real life. In fact, when we model RF conditions, we only pay attention to QAM 256 / 64 / 16 and ignore the lower modulations. The objective of radios is to deliver broadband services so lesser modulation is far less interesting to you. Typical measure speeds are from 10Mbps to 45Mbps download speeds. The actual speed measured will depend on the modulation and channel size the link is using.
Why is your radio getting more capacity?
• Redline’s Virtual Fiber platform is the only MIMO platform in this band. This alone provides tremendous advantage as there are 2 radio chains to work with and deal with noise/obstruction.
• Further to this, Virtual Fiber has the most advanced MIMO A implementation. This comes from the fact that Virtual Fiber is not based on a chipset and limited in development but rather Redline’s entire intellectual property. Redline owns every part of the radios “DNA” and this has been able to optimize it. In MIMO A, Redline can take advantage of STBC (Space Time Block Coding) on the TX side and MRRC (Maximal Ratio Receiver Combining) on the Rx side to achieve MIMO gain of close to 12dBi on its link budget. So, for the same RF environment, Redline gets a much higher link budget, hence more stability and capacity.
• One other unique feature of the VF radio is the use of a very linear OFDM amplifier and tight filter mask. This result in a flat power curve i.e. the radio TX does not drop with increase modulation but remains at maximum level for all modulation. In real life, this means that Redline will keep high modulation further away than any other radio, maximizing the capacity to the edge of the base station reach.
Why is Redline different?
• Simply said, there are three types of vendors in the TV White Space market today: 1 - Those that came from the serial modem and SCADA market.
• Already have radios in the band but no broadband experience.
• OFDM and wide channel operations are just not this simple to develop. Just ask any of the failed WiMax vendor from 10 years ago.
2 - The TVWS startup.
• No legacy to deal with, but building a radio from the ground up.
• Just as above, not that simple. Most turn to some form of 802.11 chipset.
• Using chipset can be limiting on the feature side as you cannot do more than what the chipset is built for.
3 - The there is Redline.
• Publicly traded, mature radio vendor.
• Virtual FiberTM is not new but the 5th generation of intellectual property.
• No chipset but dual FPGA i.e. we can make it anything we want.
• Virtual fiber exists in multiple frequencies, so development for TVWS also goes to the 2,3 & 5GHz version and vice versa. This gives Redline a much wider financial scope when undertaking development.
Should I synchronize the Ellipse base stations?
• In many instances synchronizing traffic will alleviate intra cell noise and allow higher throughput. This is especially useful when collocating Sector and /or using lesser quality antenna on sector radio. With 600MHZ frequency, OFDM transport and MIMO, the solution propagates very nicely, which can be challenging with radios in close proximity.
• Another interesting use case for synchronization is with close proximity CPEs, where wide beam antenna such as flat panel and Yagi antenna may cause self interference with one another
Can I re-use a channel on the same base station?
• While this is feasible in theory, it would require antenna with higher lobe isolation factor than currently available. From what we have seen of current antennas, it would be difficult to consider channel re-use.
How many CPE can I connect to a Sector (AP)?
• Virtual Fiber uses a connection-oriented environment and uses a scheduler to ensure all users have proper time allocation to transmit. Currently the scheduler, hence the radio, can support up to 120 simultaneous connection or CPE/client. This was done to accommodate the industrial SCADA requirement. It is doubtful that the ISP community would connect this many customer as the individual capacity would be very low.
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